Note: Descriptions are shown in the official language in which they were submitted.
WO 93/14797 PCT/US93/00565
PLATEN PUMP
Field of the Invention
This invention relates to a low cost drug delivery system
useful in delivering drugs, from pliable plastic containers.
Background of the Invention
Many drugs in the healthcare field are administered to a
patient on a continuous basis. Continuous delivery of a drug
to a patient was initially achieved by placing a drug delivery
bag filled with a drug above the patient and letting gravity
force the drug from the bag into the patient. Although this
method has proven successful for many applications, its
drawbacks included (a) an unsteady flow to the patient due to
the changing height of the intravenous infusion site relative
to the drug bag, (b) the awkwardness of requiring the patient
to remain below the fluid delivery bag at all times, and (c)
the constant adjustment of a roller clamp which regulates the
flow to the patient. Electromechanical infusion pumps were
developed to mitigate these concerns. However, the utility of
such pumps was hindered by their bulky size and by their need
for a constant source of electricity. These hindrances are
especially troublesome in situations where a patient is at
home and ambulatory, thus requiring the freedom to move about.
During the past five years, a new style of apparatus has
entered the marketplace for controlled delivery of a drug
which does not require the use of an electromechanical
infusion pump, and thus is suited for the controlled delivery
of drugs to patients who are ambulatory. This new style
utilizes an inflatable latex rubber balloon housed inside a
rigid, clear plastic housing. When the devices are filled
with a drug, the latex balloon expands. An administration set
is attached to the device and thus acts as the conduit for the
drug to the patient. When the balloon is inflated by the
drug, the balloon itself becomes the driving force to transfer
the drug out of the reservoir to the patient via the drug
administration set. Controlled release of the drug at a
desired flow rate is achieved by placing an orifice of
predetermined diameter in- the drug line. These devices
SUBSTITUTE SHEET
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generally operated at a relatively high pressures ~of
approximately 10 to 15 psi. Examples of the latex balloon
system are disclosed in U.S. Patent Nos. 4,769,008 and
4,915,693 and European Patent Application 0,426,319 A2.
Although the latex balloon method of drug delivery has
certain advantages over the electromechanical infusion pump, .
the method also has its disadvantages. For example, because
the balloon expands in all directions, the shape of the ,
housing enclosing the balloon is round. This round shape does
not conform well to the patient when worn in the patient's
pocket. Furthermore, some of the latex balloon style devices
require a special machine to fill and pressurize the balloon
with a drug. Consequently, the pharmacist must~use the
special machine to load the device. Thus, there exists the
need for a safe, economical drug delivery system which could
(a) be inconspicuously and comfortably worn by the patient,
(b) allow the pharmacist to fill the drug container without
the use of a special pressurizing device, (c) allow the nurse
or patient to load the drug container into the pressurizing
device, (d) allow for reuse of parts of the system.
Summary of the Invention
There is provided in accordance with one aspect of the
present invention, an infusion pump for expelling a fluid from
a fluid reservoir. The infusion pump comprises a housing
having a chamber therein for receiving a reservoir, and a
first wall on the housing for contacting the fluid reservoir.
A second wall is movable between a first position, distanced
from the first wall to form said chamber therebetween, and a
second position relatively closer to the first wall, for
forcing fluid out of the fluid reservoir. Preferably, the
first and second walls are provided with non-planar
complementary surface configurations to minimize the change in
.the contact area between each of the first and second walls
and the fluid reservoir throughout the dispensation cycle.
The housing is provided with a loading port for inserting '
a fluid reservoir into the chamber between the first and
second walls. In one embodiment, the first wall is removably
SUBSTITUTE SHEET
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-3-
secured to the housing for installation of the first
reservoir. In an alternate embodiment, tie loading port is
disposed on the side wall of the housing so that the fluid
reservoir may be laterally inserted between the first and
second walls.
In one variation, the second wall compr~.ses ~wo.or more
distinct zones. A central region is provided for contacting
the central region on the fluid reservoir, and at least one
peripheral region is also provided, said peripheral region
movable into and out of the plane of the central region.
Preferably, the infusion pump in accordance with the
present invention is further provided with at least one spring
for biasing the second wall in the direction of the second
position to expel fluid from the fluid reservoir.
Alternatively, two, three, or more springs can be utilized.
A variety of retractors are provided for retracting the
second wall from the second position to the first position,
such as for loading a fluid reservoir within the device. Tn
accordance with one embodiment of the retractor, the retractor
comprises a lever pivotably secured to the housing. The lever
comprises a grip end for gripping by a user of the pump, and
a cam end for engaging a projection secured to the movable
wall: Lifting the grip end of the lever away from the housing
advances the projection along the cam to retract the movable
wall. Preferably, the cam comprises a friction surface for
contacting the projection, and for retaining the grip at at
least one preselected stationary position between the limits
of its range of motion.
In an alternate embodiment of the retractor, the
retractor comprises a first component having a thread thereon,
and second component having ,a complementary thread thereon for
engaging the thread on the first component, so that relative
' rotation of the first component with respect to the second
component retracts the movable wall from the second position
towards the first position. In one embodiment, the first wall
is threadably removably engaged with the housing to permit
removal thereof , for installation of a fluid reservoir between
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the first wall and the second wall, wherein threadably
engaging the first, wall back onto the housing with a fluid
reservoir therein compresses the movable wall from the second
position to the first position.
Alternatively, the retractor comprises a post secured
with respect to the movable wall, and having a threaded region
thereon, for cooperating with a complementary thread on a
rotatable key. The key is threadably engaged with the
threaded region on the post, and rotated to retract the
movable wall from the second position to the first position.
Alternatively, the retractor comprises a threaded post
extending through the housing and cooperating with a
complementary thread secured with respect to the housing, so
that rotation of the threaded post about its longitudinal axis
advances the post in an axial direction, thereby retracting
the second wall against the spring bias.
In a further embodiment of the retractor of the present
invention, the retractor comprises an axially collapsible
linkage for connecting a retractor component exposed to the
outside of the housing to the movable wall. In one aspect of
this embodiment of the present invention, 'the axially
collapsible linkage comprises a first elongate element axially
movably disposed within a second tubular element.
Alternatively, the axially collapsible linkage comprises
at least two pivotably connected links, for limiting the
maximum separation between the second wall and the retractor
component exposed to the outside of the housing-.
In accordance with a further aspect of the present
invention, there is provided an indicium of the completion
status of the dispensation cycle. In one form, the indicium
comprises a scale for evaluating the position of the movable
wall along its axis of travel. This embodiment provides the
user with a continuous expression of the current status of the
dispensation cycle. In another form, the first wall comprises
a window, and the indicium becomes visible through the window '
at the completion of the dispensation cycle.
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In accordance with a further aspect of the present
invention, the retractor comprises at least one pressure
activated expansible reservoir. In one form, the expansible
reservoir comprises at least one pneumatic cylinder having an
axial length which is movable from a first retracted position
when the cylinder is substantially empty, to a second extended
position when the cylinder is filled with a filling media such
as fluid or gas. Alternatively, the pressure activated
expansible reservoir comprises at least one bladder.
Inflation of the bladder from an empty to a full condition
compresses the movable wall from the second position to the
first position.
The present invention provides a spring housed within a
first shell and a collapsible fluid delivery bag housed within
a second shell, wherein the reception of the second shell
within the first shell compresses the spring against the fluid
delivery bag and the subsequent expansion of the spring slowly
forces fluid from the fluid delivery bag. The first and
second shells are threadably engaged to provide a mechanical
advantage to ease compression of the spring when connecting
the shells. The drug delivery system of the present invention
is preferably constructed as a platen pump. It includes a
platen positioned between the spring and the fluid delivery
bag 'to distribute the load from the spring over a
substantially flat portion of the bag. The platen is
rotatably attached to the first shell so that when the shells
are being screwed together the platen does not apply torque to
the fluid delivery bag. The fluid delivery bag used with the
platen pump of the present invention is advantageously formed
as a circular pouch.
This device allows for the use of conventional, low cost
manufacturing methods and facilitates reuse of the cylindrical
housing for multiple dose drugs such as antibiotics.
. The present invention provides a flexible generally
inelastic medication container for use with a compression pump
for compressing the container to express medication therefrom.
The container comprises first and second opposing, flexible
$UBSTITUTE SHEET
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walls which define a chamber therebetween, an elongate
seam for joining the first and second opposing walls to
enclose the chamber therebetween, the seam extending
generally in a plane through the container and defining
an outer peripheral configuration of the medication
container, and an effluent fluid flow port on the
container for providing fluid communication with the
chamber. The outer peripheral configuration of the
effluent fluid flow port is generally circular. The
medication container of the present invention is
preferably constructed of a PVC in U.S. Class 6.
Further, the walls of the medication container of the
present invention have a diameter in the range of 3.5
inches to 50 inches. In addition, when the medication
container of the present invention is full, the chamber
formed between the medication container walls has a
thickness of from about 0.5 inch to 1.0 inches and the
diameter of the planar portion of the walls in a
container full of fluid ranges from 2.4 inches to 2.8
inches. The medication container may be used in
combination with a platen pump.
According to an aspect of the present invention,
there is provided an infusion pump for expelling a fluid
from a fluid reservoir, comprising:
a collapsible reservoir having a substantially flat
central top surface area, a substantially flat central
bottom surface area, and a peripheral bottom surface area
that has a curved contour that extends from the flat
central bottom surface area towards a periphery of the
reservoir when the reservoir is substantially full of
fluid;
a housing having a chamber therein for receiving a
fluid reservoir;
a compression means;
a first wall for contacting the bottom surface area
of the fluid reservoir; and
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a second wall for contacting the top surface area of
the fluid reservoir, the second wall movable between a
first position distanced from the first wall to form the
chamber therebetween, and a second position relatively
closer to the first wall, and coupled to the compression
means to be biased by the compression means;
wherein the first wall is configured to support the
reservoir across a contact surface of the reservoir,
wherein the contact surface comprises the substantially
flat central bottom surface area and at least a portion
of the peripheral bottom surface area; and
wherein the second wall comprises a flat bottom
surface area which does not extend beyond the flat
central top surface area of the reservoir, to minimize
the change in the contact area between each of the f first
and second walls and the fluid reservoir throughout the
dispensations cycle so that the fluid is expelled from
the. reservoir at a substantially constant flow rate over
a dispensation cycle.
According to another aspect of the present
invention, there is provided an infusion apparatus
comprising:
a fluid delivery bag connected to an outlet tube,
the fluid delivery bag having a bottom side and a top
side, the bottom side having a curved contour about its
periphery and the top side having a substantially flat
central portion;
a first shell having threads and a closed end;
a second shell threadably engaged with the first
shell, the second shell having a chamber for receiving
the delivery bag, the chamber having a bottom contour
which approximates the contour of the bottom side of the
fluid delivery bag;
a conical helical spring, having a first coil end
attached to the closed end of the first shell, and a
second coil end; and
CA 02126320 2004-06-04
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a platen having a non-planar bottom surface
configuration which is complementary to the bottom
contour of the second shell and a top surface, the top
surface of the platen attached to the second end of the
helical spring, wherein the helical spring exerts a force
on the top surface of the platen and wherein the bottom
surface of the platen exerts a force on the top side of
the fluid delivery bag when the fluid delivery bag is
placed in the chamber of the second shell.
According to a further aspect of the present
invention, there is provided an infusion apparatus
comprlslng:
a fluid delivery bag connected to an outlet tube,
the fluid delivery bag having a bottom side and a top
side, the bottom side having a curved contour about its
periphery and the top side having a substantially flat
central portion;
a first shell having threads and a closed end;
a second shell threadably engaged with the first
shell, the second shell having a chamber having a bottom
contour which approximates the contour of the bottom side
of the fluid delivery bag;
a conical helical spring, having a first coil end
attached to the closed end of the first shell, and a
second small coil end; and
a platen having a non-planar bottom surface
configuration which is complementary to the bottom
contour of the second shell and a top surface, the top
surface of the platen attached to the second end of the
helical spring, wherein the helical spring exerts a force
on the top surface of the platen and wherein the bottom
surface of the platen exerts a force on the flat central
portion of the fluid delivery bag when the fluid delivery
bag is placed in the chamber of the second shell.
According to another aspect of the present
invention, there is provided an infusion apparatus
comprising:
CA 02126320 2004-06-04
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a fluid delivery bag connected to an outlet tube,
the fluid delivery bag having a top surface with a
substantially flat central portion;
a first shell having a closed end;
a helical spring attached to the closed end of the
first shell;
a second shell threadably engaged with the first
shell and having a chamber therein for holding the fluid
delivery bag between the first shell and the second
shell; and
a platen attached to the helical spring, the platen
having a non-planar bottom surface configuration which is
complementary to a bottom contour of the chamber and a
top surface, the platen for distributing a force exerted
from the spring to the substantially flat central portion
of the fluid delivery bag, wherein when the second shell
is engaged with the first shell, the helical spring
exerts force on the top surface of the platen and the
bottom surface of the platen exerts force on the fluid
delivery bag so as to force a fluid contained with the
fluid delivery bag through the outlet tube.
According to a further aspect of the present
invention, there is provided an infusion pump for
expelling fluid from a flexible reservoir comprising:
a top shell removably connected to a bottom shell,
the bottom shell having a non-planar interior bottom
surface;
a pressure plate movably connected to the top shell,
the plate having a non-planar surface complementary to
the interior bottom surface of the bottom shell, the
pressure plate and the interior bottom surface of the
bottom shell defining therebetween a variable-sized area
for accepting the fluid reservoir therein;
a shaft positioned between the top and bottom
shells, the shaft having a first end and a second end;
a first slide and a second slide slidably positioned
on the shaft;
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four arms defining a parallelogram structure
extending between the top shell, the first slide, the
second slide, and the pressure plate, the arms rotatably
connected to the top shell, the slide members and the
pressure plate, the slide members and shaft supported by
the arms between the shells; and
biasing means positioned between the first end of
the shaft and the first slide and between the second end
of the shaft and the second slide for biasing the slides
toward one another along the shaft, thereby biasing the
pressure plate through the arms, downwardly towards the
bottom shell when the top and bottom shells are
connected.
According to another aspect of the present
invention, there is provided an infusion pump for
expelling fluid from a fluid reservoir comprising:
a housing comprising a bottom member having a non-
planar inner surface and a top member removably connected
to the bottom member;
a platen member movably connected to the top member,
the platen having a non-planar engaging surface which is
complementary in shape to the inner surface;
a first arm having a first end and a second end, the
first end rotatably connected to the top member and the
second end rotatably connected to a first mounting block;
a second arm having a first end and a second end,
the first end rotatably connected to the top member and
the second end rotatably connected to a second mounting
block;
a shaft having a first end and a second end, the
shaft extending through the blocks;
a first spring extending between the first end of
the shaft and the first block and a second spring
extending between the second end of the shaft and the
second block;
CA 02126320 2004-06-04
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a third arm having a first end and a second end, the
first end rotatably connected t~o the first block and the
second end rotatably connected to the platen member; and
a fourth arm having a first end and a second end,
the first end rotatably connected to the second block and
the second end rotatably connected to the platen member,
whereby the arms form a linkage between the top member,
the blocks, and the platen member, biasing the platen
member downwardly towards the bottom member when the top
and bottom members are connected.
Further features and advantages of the present
invention will become apparent to one of skill in the art
from a: review of the Detailed Description of Preferred
Embodiments which follows, when considered together with
the attached claims and drawings.
Brief Description of the Drawings
Figure 1 is an isometric view of the infusion device
of the present invention.
Figure 2 is a partial cross-sectional view of the
infusion device of Figure 1 with the shells not engaged.
Figure 3 is a side cross-sectional view of the top
shell of Figure 2.
Figure 4 is a cross-sectional view of the infusion
device of Figure l with the shells fully engaged.
Figures 5a and 5b are a plan view and side view,
respectively, of the rotatable spring retainer used in
the infusion devices of Figure 1.
WO 93/14797 '~ ~ ~ i'~ ~ ~ ~ PGT/US93/00565
Figures 6a and 6b are ~ a plan view and side view,
respectively, of the platen used in the infusion device of
Figure 1.
Figure 7 is a plan view of the fluid delivery bag of the
present invention.
Figure 8 is an isometric view of an alternate_embodiment
of the infusion device of the present invention.
Figure 8a is a cross-sectional view of the infusion
device of Figure 8 in an open position.
Figure 8b is a cross-sectional view of the infusion
device of Figure 8 in a closed position.
Figure 9 is a top perspective view of a dual concentric
platen embodiment of the infusion pump in accordance with the
present invention.
Figure 10 is an elevational cross-sectional view of the
pump illustrated in Figure 9.
Figure 11 is an elevational cross-sectional view of the
pump illustrated in Figure 9, partway through the dispensation
cycle.
Figure 12 is an elevational cross-sectional view of the
pump illustrated in Figure 9, at the completion of the
dispensation cycle.
Figure 13 is an elevational cross-sectional view of a
multi-segment platen embodiment in accordance with the present
invention, at the commencement of the dispensation cycle.
Figure 14 is a cross-sectional elevational view of the
pump of Figure 13, partway through the dispensation cycle.
Figure 15 is a cross-sectional elevational view of the
pump illustrated in Figure 13, at the completion of the
dispensation cycle.
Figure 16 is a top plan view of a mufti-segment platen in
accordance with one aspect of the invention.
Figure 17 is a top plan view of an alternate multi-
segment platen.
Figure 18 is an elevational cross-sectional view of a
lever assisted spring retractor in accordance with the present
invention.
sussTrru-~E sr~EEr
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Figure 19 is ~n elevational cross-sectional view of the
embodiment of Figure 18, with the platen in the retracted
position.
Figure 20 is an elevational cross-sectional view of the
embodiment of Figure 18, at the commencement of the
dispensation cycle. - w '
Figure 21 is an elevational cross-sectional view of a
key-operated platen retractor in accordance with the present -
invention.
Figure 22 is an elevational cross-sectional view of the
embodiment of Figure 21, with a key in place.
Figure 23 is an elevational cross-sectional view of the
embodiment in Figure 21, at the commencement of the
dispensation cycle.
Figure 24 is an alternate embodiment of the design
illustrated in Figure 23.
Figure 25 is an elevational cross-sectional view of an
infusion pump having a collapsible platen retractor.
Figure 26 is an elevational cross-sectional view of the
pump of Figure 25, at the completion of the dispensation
cycle.
Figure 27 is an elevational cross-sectional view of an
ultra-low profile pump in accordance with the present
im~ention .
Figure 28 is an elevational cross-sectional view of the
pump of Figure 27, with the platen fully retracted.
Figure 29 is an elevational cross-sectional view of the
pump of Figure 27, at the commencement of the dispensation
cycle.
Figure 30 is an elevational view of the pump illustrated
in Figure 29.
Figure 31 is an elevational cross-sectional view of an
alternate platen retractor in accordance with the present
invention.
Figure 32 is an elevational cross-sectional view of the
retractor of Figure 31, in the fully retracted position.
Figure 33 is an elevational cross-sectional view of the
SUBSTITUTE SHEET
WO 93/14797 w ~ h ~'1 J ~ ~ PCT/US93/00565
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retractor of Figure 31, at the commencement of the
dispensation cycle.
Figure 34 is an elevational cross-sectional view of a
pneumatic platen retractor embodiment of the present
invention.
Figure 35 is a top plan view of the ,embodiment
illustrated in Figure 34.
Figure 36 is a top plan view of a flexible platen
retraction device in accordance with the present invention.
Figure 37 is an elevational cross-sectional view of the
embodiment of Figure 36.
Figure 38 is an elevational cross-sectional view of the
embodiment of Figure 36, at the completion of the dispensation
cycle.
Figure 39 is an elevational cross-sectional view of the
folding link platen retractor in accordance with the present
invention.
Figure 40 is an elevational cross-sectional view of the
embodiment of Figure 39, with a retracting key in place.
Figure 41 is an elevational cross-sectional view of the
embodiment of Figure 39, at the commencement of dispensation
cycle.
Figure 42 is an elevational view of a linkage assembly.
Figure 43 is an elevational view of an alternate linkage
assembly.
Figure 44 is an elevational cross-sectional view of an
infusion pump having a drag element in accordance with the
present invention.
Figure 45 is an elevational cross-sectional view of an
empty indicator in accordance with the present invention.
Figure 46 is an elevational cross-sectional view of the
embodiment of Figure 45, at the completion of the dispensation
cycle.
Figure 46A is an enlarged portion of an elevational
cross-sectional view of the embodiment of Figure 45, at the
completion of the dispensation cycle.
Figure 47 is a bottom plan view through the transparent
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window of the embodiment of Figure 45.
Figure 48 is a top plan view of a low-profile sliding
spring retractor embodiment of the present invention.
Figure 49 is a side elevational view of the embodiment of
Figure 48.
Figure 50 is a side elevational view of the embodiment of
Figure 48, at the commencement of the dispensation cycle.
Figure 51 is a side elevational view of the embodiment of .
Figure 48, partway through the dispensation cycle.
Figure 52 is a top perspective view of a scissor-type
biasing means in accordance with the present invention.
Figure 53 is an elevational cross-sectional view of the
embodiment of Figure 52.
Figure 54 is an elevational cross-sectional view of the
embodiment of Figure 52 , at the completion of the dispensation
cycle.
Figure 55 is an exploded view of the embodiment of Figure
52.
Figure 56 is a plot of fluid pressure versus volume.
Figure 57 is a plot of percent change in pressure versus
volume.
Figure 58 is a plot of fluid pressure versus volume.
Figure 59 is a plot of percent change in pressure versus
volume.
Figure 60 is a plot of force versus volume.
Figure 61 is a top plan view of the fluid container
embodying the present invention:
Figure 62 is a left side view of the fluid container of
Figure 61:
. Figure 63 is a front view of the fluid container of
Figure 61;
Figure 64 is a rear view of the fluid container of Figure
61:
. Figure 65 is a left side cross-sectional view of the
fluid container of Figure 61 when full of fluid; '
Figure 66 is a top plan view of an alternative embodiment
of the fluid container shown in Figure 61;
SUBSTITUTE SHEET
dV0 93/ 14797 ~' ~' '~ ~'~ ''~ '~' ~ PCT/US93/OOS65
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Figure 67 is a left side view of the alternative
embodiment shown in Figure 66;
Figure 68 is a front view of the alternative embodiment
shown in Figure 66;
Figure 69 is a rear view of the alternative embodiment
shown in Figure 66; w
Figure 70 is an other alternative
embodiment
of the fluid
container shown in
Figure 61;
Figure 71 is .a left side view of the alternative
embodiment shown in Figure 70;
Figure 72 is a front view of the alternative embodiment
shown in Figure 70;
Figure 73 is a rear view of the alternative embodiment
shown in Figure 70:
Figure 74 is a top plan vi ew of another alternative
embodiment of the fluid shown in Figure 61;
container
Figure 75 is a left side view of the alternative
embodiment shown in Figure 74;
Figure 76 is a front view of the alternative embodiment
shown in Figure 74;
Figure 77 is a rear view of the alternative embodiment
shown in Figure 74;
Figure 78 is a top plan view
of another
alternative
embodiment of the fluid shown in Figure 61;
container
Figure 79 is a left side view of the alternative
embodiment shown in Figure 78; _.
Figure 80 is a front view of the alternative embodiment
shown in Figure 78;~
Figure 81 is a rear the alternative embodiment
view of
shown in Figure 78;
Figure 82 is a top plan view
of another
alternative
embodiment of the f luid container shown in Figure 61;
Figure 83 is a left side view of the alternative
embodiment shown in Figure 82;
~ 35 Figure 84 is a top plan view
of another
alternative
embodiment of the f luid container shown in Figure 61;
SUBSTITUTE SHEET
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Figure 85 is a left side view of the alternative
embodiment shown in Figure 84:
Figure 86 is a top plan view of another alternative
embodiment of the fluid container shown in Figure 61;
Figure 87 is a left side view of the alternative
embodiment shown in Figure 86; . -. .
Figure 88 is a top plan view of another alternative
embodiment of the fluid container shown in Figure 61;
Figure 89 is a left side view of the alternative
embodiment shown in Figure 88.
Detailed Description of the preferred Embodimen s
Referring now to the figures, the infusion device of the
present invention shall be called a platen pump. The platen
pump is formed in two parts, a pressurizing portion and a
fluid containing portion. Each portion is housed in a
container or shell. A pressurizing shell 12 includes a
helical spring 14. A fluid containing shell 16 includes a
chamber 17 for housing a fluid delivery bag 18. When the
pressurizing shell 12 and the fluid containing shell 16 are
connected to form the enclosed pump, the fluid delivery bag is
pressurized by the spring 14. Fluid is thus continuously
forced out of the bag 18 through an outlet tube 20 in fluid
communication therewith. Controlled fluid flow is achieved
with a small diameter fixed orifice 46 located at or near the
end of the tube. The pump of Figure 1 is 3 1/2'° in diameter
and 1.7" high. ~ A selectively releasable clamp 34 may be
applied to the outlet tube to stop fluid flow from the pump.
Releasing the clamp restores fluid flow.
In accordance with the presently preferred embodiment of
the invention, the pressurizing means is a conical helical
coil spring 14. The spring is formed from stainless steel or
a suitable spring material. The coils of the spring are made
progressively larger so that when compressed the spring coils
can overlap to compress to a lower height than a conventional
compression spring. When the spring is expanded it takes on
a conical shape. The conical helical spring exerts the
greatest force when it is fully compressed. The force is
$US$TiTUTE SHEET
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.; , ,:.
approximated by the equation F=kx, where.k is the spring rate
and x is the distance the spring is compressed. Because it is
desirable to have the force exerted on the drug container be
nearly the same when the container is full as when it is
nearly empty, it is preferred that the free length of the
spring be several times the height of the pump. _ Thus, the
working length is but a fraction of its total free length.
This insures that the force applied by the spring is kept
within an acceptable tolerance from the beginning to the end
of the infusion. In accordance with the presently preferred
embodiment, the change in force exerted by the spring over the
course of an infusion as compared to the initial force it
exerts when compressed against a full fluid delivery bag is
less than ~20%. In accordance with the invention, the spring
length should be selected such that the change in force over
the course of an infusion is less than 200. In addition to a
conventional compression spring, this concept would apply to
a leaf spring, if it was used instead, where the deflection in
the leaf spring is but a fraction of the total possible
deflection.
A flexible cable retainer 26 encircles the spring 24 to
set its initial compressed height and also to prevent it from
expanding beyond the height of the pressurizing shell 12. In
the presently preferred embodiment, two cables 26 are used.
Thus, the spring 14 does not bear against the fluid delivery
bag when the pressurizing shell 12 is initially engaged with
the fluid containing shell 16. This makes it easy for a user
to bring the two shells together. With the spring in its
initially compressed state, the force differential between the
full position shown in Figure 4 and empty position with the
bag squeezed to a completely collapsed position is less, than
20% of the initial force in the full position. While the
conical helical coil spring is preferred, it would be possible
to make a platen pump with a leaf spring, a pressurized
bladder, a standard helical compression spring or a canister
of pressurized gas to act as the pressurizing means.
~3UBST~TIJTE SHEET
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The smallest coil of the spring is rotatably attached to
the closed end of the pressurizing shell 12. The spring is
attached to the pressurizing shell by a rotatable connector
including a spring retainer 22, an anchor pivot 28, a spring
stop 23 and a screw 31. The anchor pivot 28 is seated on a
shoulder 29 encircling a hole in the top of the pzessurizing
shell 12. The anchor pivot 28 is free to rotate on the
shoulder 29. The rotatable spring retainer 22 is mounted to .
an anchor pivot 28. The spring retainer 22 centers the spring
to the shell. A spring stop 23 clamps the end coil of the
spring to the spring retainer and prevents the spring from
dislodging from the spring. retainer 22. The screw 31 holds
the anchor pivot 28 and the spring stop 23 together. The
spring retainer 22 is sandwiched between the anchor pivot and
the spring stop.
Preferably, in the present invention, a fluid delivery
bag is pressurized to only about 5 psi which requires only
about 30 pounds of force. In order that health personnel or
the patient can pressurize the pump without assistance, the
pressurizing shell 12 and fluid containing shell 16 are
threadably engaged. In the presently preferred embodiment,
the pressurizing shell has inner helical threads 13 and the
fluid in containing shell has outer helical threads 19. By
increasing the number of threads per inch, the axial force
provided by the threads can be increased for a given torque.
The presently preferred embodiment uses four (.4) threads per
inch so that it is relatively quick and easy:to screw the
shells together to fully pressurize the pump. The threads
provide a mechanical advantages so that a modest amount of
torque can generate sufficient amounts of axial load to
compress the spring.
The platen 24 is located between the spring 14 and the
fluid delivery bag 18 when the two shells are connected. The
platen 24 distributes the pressure from the spring 14 over the
bag. The presently preferred platen is made of polycarbonate.
The platen has a bottom flat portion which extends over a.n
area no greater than a substantially flat central portion of
SUBSTITUTE SHEET
WO 93/14797 ~ ~ ~'~ pCT/US93/00565
-is-
the full fluid delivery bag. This serves to keep the
contacting surface areas fairly constant over the course of
the entire infusion to help minimize changes in pressure on
the fluid bag. The platen 24 is held against the helical coil
within the pressurizing shell 12 by the flexible restraining
cable 26. The cable 26 is preferably made from multi-strand
stainless steel. It is looped about the rotatable retainer 22
and the platen 24. Preferably, two cable loops 26 are used.
Grooves are provided in the retainer 22 and platen 24 to
accommodate the cables 26. A plastic label 36 may be adhered
to the bottom of the platen 24 and the cable 26 all rotate
freely about the axis of the pressurizing shell. Thus, when
the pressurizing shell is rotated with respect to the fluid
delivery shell to thread the two together, the pressurizing
shell turns independently of the platen 24. The platen 24
should remain stationary with respect to the fluid delivery
bag so that no torsional load is imparted on the bag. In
order to mechanically prevent twisting the fluid delivery bag
18 when the two shells are screwed together, anti-rotation
tabs can be attached to the outer edges of the platen 24. The
tabs would extend out radially to engage slots in the wall of
the fluid containing shell 16. The tabs would be guided in
the slot, thus preventing the platen from turning with respect
to the fluid containing shell. It has been found that
rotatably attaching the spring and platen to the pressurizing
shell is sufficient to avoid applying undesirable torque to
the fluid delivery bag. The tabs and slots are not required.
Because it is desirable to have a device which allows the
patient to examine the volume of fluid still retained in the
fluid delivery bag so that the patient can determine when the
bag is empty, preferred embodiments of the present invention
utilize a clear plastic window 38 in the bottom of the fluid
containing shell 16. Due to cost and safety considerations,
especially preferred embodiments of the present invention use
a clear plastic, such as polycarbonate, as the window
material. A legend such as the word "Empty" or ".E" or some
other symbol is embossed on the bottom side of the platen 24.
SUBST'ITU'TE SHEET
WO 93/14797 ~ ~ ~ ~ ~ ~ ~ PCT/US93/00565
Advantageously, the legend will be fuzzy or illegible when
viewed through the elastomeric disk and transparent window
when there is liquid in the fluid delivery bag. When the bag
has been emptied and the platen lies flat against the layers
of the bag, disk and the bottom of the chamber 17, the legend
on the platen 24 comes into focus through the bottom of the
fluid containing shell due to the transparent nature of the
fluid delivery bag and the contact clarity of the disk. This '
can be used to provide a clear indication of when the fluid
bag is empty. It has been found that a small amount of
silicone oil between the window and the disk will enhance the
clarity.
To the extent possible, it is desirable to maintain a .
relatively constant flow rate throughout an infusion with the
platen pump. In order to minimize changes in the internal
pressure within the fluid delivery bag, it is important that
the surface area of contact between the bag and the rigid
surfaces pressing against it be kept constant. In accordance
with the present invention, the bottom of the chamber 17 in
the fluid containing shell 16 is contoured to evenly support
the bottom of the bag over its entire area. Thus, the surface
contact against the bottom of the bag remains constant during
the full stroke of the platen. In the figures, a curved
contour is Shawn about the periphery of the chamber 17. The
bag 18 when filled with fluid matches this curved contour to
receive supportlover its entire area. The contour of the
chamber 17 could also be achieved with a 45° angle about the
periphery. While the bag 18 might not completely fill the
corner formed by the angle, the contour of the surface areas
should be adequate to provide substantial support and contact
with the bag's entire area.
It is also important that the contact area of the platen .
24 against the bag remain constant. Therefore, the platen 24
has a bottom flat surface which does not extend beyond a flat
central portion of the fluid delivery bag. If only the flat
portion of the platen were to act on the bag, a residual fluid
would remain in the bag about its periphery at the end of the
SUBSTITUTE SHEET
PCT/US93/(H1565
WO 93/14797
_y_
infusion. In order to more completely deliver the fluid from
the bag, the platen has a chamfered edge 40 and a recessed
outer ring 42~ These portions of the platen roughly match the
contour of the periphery of the bottom of the chamber 17. A
platen 24 with a periphery that conforms more exactly to the
contour of the chamber bottom could also be used" _Near the
end of an infusion, as the platen 24 descends towards the
chamber bottom, fluid which builds up about the periphery of
the bag 18 is pushed out by the edge 40 and the recessed ring
42.
An opening 30 is provided in the fluid-containing shell
through which the outlet tube connected to the fluid delivery
bag 18 can be extended. An outer wall 32 of the fluid
containing shell can be provided to serve as a grip. When
screwing the shells together, one hand holds the outer wall of
the pressurizing shell and the other hand holds the outer wall
32 of the fluid containing shell 16.
These two shells of the pump are circular in shape to
permit threadable engagement. Referring now to Figure 7, the
fluid delivery bag 18 for use in the platen pump is a circular
pouch connected to an outlet tube. The circular pouch,
advantageously, has no corners. Thus, the seam 44 of the bag
is uniformly stressed. To assist in achieving uniformity of
pressure in the bag, the periphery of the bag has a curved
contour when filled. The center portion of the bag is
substantially flat so that the contacting surfaces between the
platen and the bag can remain relatively constant throughout
an infusion. The bag is made from a suitable pliable
biocompatible plastic material, such as a class VI, PVC
biocompatible plastic. The bag is formed from two sheets that
are RF welded together and trimmed around their circumference.
The round shape of the bag achieves uniform stress on the
welded seam.
The outlet tube 20 is connected to the bag 18. The tube
20 may lead to a restricted orifice 46 which restrains the
flow of fluid from the delivery bag when it is pressurized.
Orifices of .004" to .008°' diameter are presen~cly
'.~3UBSTiTUTE ShIEET
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,.,:.,,
-iFf-
contemplated. In order to prevent the orifice from becoming
blocked, an optional particulate filter 48 can be inserted in
the outlet tube to stop the flow of particles which might
occlude the orifice. The orifice provides a relatively
constant fluid flow. As an alternative to the restricted
orifice, a length of tubing of known diameter, e:g._, an 18
inch length of .015" tube can be substituted. In order to
facilitate filling the fluid delivery bag, a Y-injection site
52 may be inserted into the outlet tube 20. The Y-injection
site 52 includes a latex rubber self-sealing septum 54 through
which a needle may be inserted to inject fluid into the bag.
As an alternative, a second filling port (not illustrated) may
be added to the bag.
The end of the outlet tube can be connected to a luer
adapter 50. The adapter is a threadably engaged connector.
It is designed to mate with a threadably engaged disconnect on
an IV line. In order to permit reusability of an infusion
set, the outlet tube 20 of the fluid delivery bag can be
directly connected to a second luer adapter 50 (not
illustrated) approximately 3 inches from the drug bag. A
clamp would be used on the tube between the bag and the luer
adapter 50. Fluid may be injected in through the luer adapter
50 so a Y-injection site would not be needed. When the drug
has been expended, a new drug bag may be attached to the IV
set, thus reusing the IV set for multiple doses over a 24 to
48 hour period. ~ -. .
In practicing the invention, the clamp 34 is used to
close the outlet tube on an empty drug delivery bag. A needle
pierces the septum 54 to inject fluid into the drug delivery
bag. The bag when full should have a substantially flat top
and bottom central portion when resting on a flat surface.
The needle is removed. The bag, with its permanently affixed
IV line, is placed in the chamber 17 of fluid containing shell
16 with the IV line passing through the opening 30 in the
bottom of the shell. When the upper and lower shells are
brought together, the threads should preferably engage
initially before the platen 24 pressurizes the bag. The two
SUBSTITUTE SHEET
WO 93/14797 ~ ~.~ ~ ~ ~ ~~ PCT/US93/00565
- i 9-
shells are then simply screwed together until a stop position
is reached. At this point, the drug bag is fully pressurized.
The IV output line is purged of air by opening the clamp 34
and allowing fluid to flow. Once the fluid stream ejects
slightly, the tube can be reclamped. The output line is then
connected to a catheter line or needle for administe_~ing an
infusion to a patient. Releasing the clamp initiates fluid
flow. When the legend on the platen 24 comes into focus
through the window 38 in the fluid containing shell 16, the
bag has been emptied. The output line is removed or
disconnected from the patient. The two shells are then
unscrewed and the drug container and IV line are discarded.
The pump can be reused.
Referring now to Figures 8, 8a and 8b, an alternate
embodiment of the present invention illustrated. The
numerical labels in the drawings are 100 higher than
corresponding elements in the first embodiment. When it is
desired to use a conventional rectangular drug delivery bag
188, the alternate embodiment can be used. The fluid
containing shell 116 of the alternate embodiment is provided
with a rectangular chamber to accommodate the rectangular drug
delivery bag. The fluid containing shell 116 is formed by an
upper portion 152 and lower portion 154 attached at one end by
a hinge 156. The opposite ends are connected by a latch 158
when the upper and lower portions are closed. The upper
portion 152 includes a threaded cylindrical wall 119 for
interfacing With the threaded wall 113 of the pressurizing
shell 112. The platen 124 attached to the spring 114 of the
pressurizing shell 112 is made rectangular to fit over the
substantially flat center portion of the rectangular bag.
To operate the platen pump of the alternate embodiment,
the pressurizing shell is unscrewed and loosened on the fluid
containing shell. The fluid containing shell is opened about
its hinge or sliding means. A fluid delivery bag is inserted.
The fluid containing shell is closed at its latch. The
pressurizing shell can then be screwed onto the fluid
containing shell to pressurize the drug delivery bag.
SUBSTITUTE SHEET
PCT/US93/00565
WO 93/14797
,..:.,,
_a o
In accordance with a further aspect of the present
invention, there is provided an infusion pump having a platen
which is divided into two or more segments. Preferably, each
segment is provided with an independent biasing means for
compressing each respective segment against the medication
bag. The multi-segment pressure pad of the present_invention
cooperates with the changing contour of the deflating
medication bag to maintain an improved relatively constant -
surface contact area between the platen arid the bag. As has
been previously discussed, the maintenance of a substantially
constant surface contact area has been determined by the
inventors herein to promote constant output pressure
performance.
Referring to Figures 9-12, there is disclosed a dual
concentric platen embodiment of the infusion pump in
accordance with the present invention. Infusion device 160 is
provided with a hausing 162, comprising a cover portion 164
and a base 166. As with previous embodiments, the cover 164
and base 166 are preferably formed in accordance with
conventional techniques for the production of medical device
housings, such as injection molding of thermoplastic or
thermoset polymers. Alternativeljr, any of a variety of other
techniques may be utilized, including fabrication from sheet
metal stock, as will be well understood by one of skill in the
art.
The cover 164 and base 166 can be secured together in any
of a variety of manners disclosed elsewhere 'herein. For
example, cover 164 and base 166 can be provided with
complementary surface structures such ,as male and female
engaging threads. For this purpose, base 166 is provided with
an annular, axially extending wall 170 to provide an extended
surface contact area between the base 166 and cover 164.
Alternatively, the contacting surfaces of the cover 164 and
base~166 are provided with complimentary pins and J- or L-
shaped grooves to permit a press-and-twist fit interlock. Any
of a variety of alternative interlocking structures may be
SUBS'PITUTE SHEET'
WO 93/14797 ~ ~;~ ~ ~ PCTlUS93/00565
-a~-
utilized with the.multiple segment platen embodiment of the
invention.
Depending upon the type of spring retraction structure
utilized, the base 166 and cover 164 may or may not need to be
removably connected. For example, in a side loading
embodiment, base 166 and cover 164 may be integrally formed or
permanently secured together during the manufacturing process:
In this embodiment, an opening is provided in the side wall to
permit introduction of a medication bag between the retracted
platen and base as will be discussed.
In general, base 166, annular wall 170 and cover 164
cooperate to form a chamber 172 for containing the functional
components of the infusion device 160. In the illustrated
embodiment, a first platen segment 176 is biased against a
medication bag 174 by means of a coil spring 178. Platen
segment 176 is provided with an axially extending spring guide
184, which may comprise an axially extending annular wall or
a plurality of axially extending projections. Spring guide
184 assists in maintaining the axial alignment of the spring
178 during repeated tensioning and discharge cycles of the
infusion device 160. The spring guide 184 may alternatively
be positioned on the radially interior side of spring 178, as
well as on the radial exterior or radial interior side of the
spring but depending from cap 164, as will be apparent to one
of skill in the art.
The first paten segment 176 is provided with a radially
outwardly extending annular flange 186 for cooperating with a
radially inwardly directed stop 188 on second platen segment
180. Stop 188 is axially spaced apart from the plane of
' second platen segment 180 by a support 190, as will be
discussed.
Second platen segment 180 comprises an annular ring
positioned concentrically about the first platen 176. Second
platen 180 is independently axially movable with respect to
first platen 176, and moveable from a first position spaced
apart from the plane of first platen segment 176 to a second
position substantially in the plane of first platen segment
suBSTrru-~ sHEEc
WO 93/14797 ~ ~ 2~~ ~ S z PCT/US93/00565
176. Preferably, second platen segment 180 is biased in the
direction of medication bag 174 by a second spring 182.
Although first spring 178 and second spring 182 are
illustrated as substantially cylindrical in configuration, a
comically shaped spring is also desirable for the reasons
previously discussed. In addition, alternative biasing means
such as leaf springs, pressurized bladders, canisters of
pressurized gas or the like may also be adapted for use in ..
accordance with the multi-segment platen embodiment of the
present invention.
The illustrations contained in Figures 9-11 are
simplified somewhat to highlight the multiple platen aspect of
the invention. However, a variety of additional features will
generally be incorporated into a finished device. For
example, a spring or platen retraction structure for
retracting the platen and limiting the distention of the
spring in the absence of a base 166 or fluid bag 174 is also
typically used. A variety of suitable retention structures
are disclosed elsewhere herein, or will be immediately
apparent to one of skill in the art in view of the present
disclosure. In a side loading-type embodiment, a spring
retraction structure is particularly desirable.
Fluid bag 174 is in fluid communication with the patient
by way of effluent fluid line 168. Fluid line 168 extends
through the housing 162 byway of a port 169: Modification of
the port 169 to accommodate the various relationships between
the cover 164 and base 166 will be apparent to one of skill in
the art. Alternatively, in a side loading embodiment of the
multiple segment platen pump, the port 169 is preferably
, configured in the form of a circumferentially extending slot
having a wide enough opening in the circumferential and axial
directions to accept the appropriately sized fluid bag 174.
In general, the fluid bag diameters contemplated for use
in accordance with the present invention are in the area of
from about 3.5 inches in diameter to about 5 inches' in
diameter, and from about 0.5 inches to about 1.0 inches thick.
However, infusion pumps adapted to receive other sized bags
SUBSTITUTE SHEET
WO 93/14797 . . .. . .. ., s 3 2 ~'GT/US93/(10565
-..23 -
can be readily produced in accordance with the disclosure
herein.
Figure 10 illustrates the configuration of the pump with
a relatively full medication bag 174. Second platen 180
compresses the radially exterior-most portion of bag 174
independently of the first platen 176, which provic~,es_.pressure
against the central portion of bag 174. It has been
determined by the inventors herein that the provision of this
bifurcated biasing allows a surprisingly more constant
pressure output profile compared to the use of a planar single
flat platen design.
Figure 11 illustrates the configuration of the device
when the medication bag 174 is approximately one-half empty,
and Figure 12 illustrates the device when the fluid medication
bag 174 has been substantially completely emptied.
In a dual segment platen embodiment designed far use with
a 3.5-inch diameter, 1/2 inch thick 50 cc medication bag 174,
the first platen 176 has a circular contact surface having a
diameter within the range of from about 2.2 to about 2.8
inches. The bag contact surface on second platen 180 is in
the form of an annular ring, with the width of the ring at any
one point being within the range of from about 0.4 to about
0.7 inches. The overall outside diameter across the entire
second platen 180 is approXimately equal to the exterior
diameter of the bag.
The relative extent to which the second platen 180 can
travel distally along its path of travel with respect to the
first platen 176 is limited by the axial height of the support
190. In an embodiment having a bag which is approximately
one-half inch thick when full, the length of the support 190
is about 0.4 inches.
In accordance with a further aspect of the present
invention, there is disclosed an alternate multi-segment
platen embodiment at Figures 13-17. Referring to Figure 13,
infusion pump 192 comprises a housing 194 having an upper wall
196 and lower wall 198. Upper wall 196 and lower wall 198 may
be rigidly secured with respect to one another, or removably
SUBSTITUTE SHEET
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WO 93/14797 PCT/US93/00565
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secured with respect to one another such as by threadable
engagement or other previously disclosed means.
Upper wall 196 can be substantially planar throughout the
width of the pump 192, or, as illustrated in Figures 13-15,
can have a substantially planar central region and a sloped
annular region 197. Sloped region 197 is provided on the ~ ,
interior surface with a peripheral spring guide 211, which is
preferably an integrally molded annular ring.
A chamber 200 is formed between upper wall 196 and lower
wall 198 to receive the functional components of the infusion
pump 192. A platen 202 is movably disposed between upper wall
196 and lower wall 198. Platen 202 comprises a central region
204 and a peripheral region 206. Referring to Figure 16, a
multi-segment peripheral region 206 is illustrated.
Central region 204 is biased in the direction of lower
wall 198 by at least one central spring 208. Central spring
208 is preferably maintained in position with the assistance
of central spring guide 209, which may comprise a plurality of
axially extending projections or an annular ring.
Alternatively, spring 208 can seat within an annular recess
disposed on the spring side of central region 204 of platen
202.
The peripheral region 206 is biased in the direction of
lower wall 198 by one or more peripheral springs 210.
Although each of the peripheral segments 214 can be provided
with independent biasing means, a single annular peripheral
spring 210 has been determined to perform satisfactorily in
embodiments of the present invention.
An approximation of the deflation cycle is illustrated in
Figures 13-15. At the completion of the infusion cycle, the
platen 202 is biased against the lower wall 19;8 to
substantially completely expel all of the contents of the .
fluid bag. In this embodiment, the lower wall 198 is provided
with an axially upwardly inclined peripheral zone 199, which .
is dimensioned to be complementary with the peripheral region
206 on platen 202.
SUBSTITUTE SHEET
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i~VO 93/14797 212 6 3 2 0 PCT/US93100565
-e2S-
Referring to Figure 16, each of the peripheral segments
214 on platen 202 is connected to the central region 204 by
way of a hinge 215. Hinge 215 can be provided in any of a
variety of ways, and still accomplish the objectives of the
present invention. For example, the entire platen 202 can be
formed from a sheet of material having sufficient flexibility
that the biasing forces due to central spring 208 and
peripheral spring 210 will deform the platen, as illustrated
in Figure 14. Preferably, however, the hinge 215 comprises a
relatively more flexible zone than the surrounding material of
platen 202. This may be provided, for example, by reducing
the thickness of the platen material in the region of each
hinge 215, as illustrated, for example, in Figures 13-15.
Alternatively, the central zone 204 can be formed separately
from the peripheral segments 214, and assembled thereafter
such as by mounting the central zone 204 and peripheral
segments 214 on a flexible sheet of material. reduced
thicknesses can be produced by injection molding of the
platen. Any of a variety of stamping and/or milling or
grinding techniques may also be utilized to produce an annular
groove in the material of an integrally formed platen 202.
Referring to Figure 17, there is disclosed an alternate
embodiment of the platen 202, particularly adapted for an
infusion pump designed for use in an octagonal housing.
Spring rates and lengths may be selected to complement
the respective surface areas of the central and peripheral
zones to achieve the most acceptable internal bag pressure.
Referring to Figures 18-20, there is disclosed a leverage
assisted spring retractor for loading an infusion pump 216 in
accordance with the present invention. The spring retractor
is conveniently operated by a patient actuated lever, to
retract the platen against the spring bias into the "ready"
position. The fluid medication bag may thereafter be easily
inserted either through a side opening on the device or by
removing the bottom shell.
Referring to Figure 18, infusion pump 216 is provided
with a spring retractor 218. Spring retractor 218 is op~erat.ed
SUBSTITUTE SHEET
.. . . ... . . ,: :, : v . :- ,. , y
WO 93/ 14797 1 ~ y ~ ;~ PCT/US93/OOS65
I
by lifting a patient actuated lever 220, which rotates about
a fulcrum 222 on the housing of the infusion pump 216. The
lever 220 extends through an opening 223 into the upper
housing 232, and is thereafter pravided with a ramp 224 such
as a cam or other structure having a surface for slidably
engaging a pin 230. The pin engaging surface of ramp 224 is
preferably provided with friction enhancing surface structures
such as a plurality of teeth 225. In this manner, the lever
can be released by the patient at any point throughout its
range of travel, and the teeth 225, pin 230 and curvature of
ramp 224 cooperate to retain the partially retracted lever in
position.
Pin 230 is connected to a support 228 for transferring
force to the platen 226. Although illustrated as a unitary
platen 226, the spring retractor in accordance with this
aspect of the present invention can be readily utilized with
the dual platen embodiment which has previously been
disclosed.
To facilitate lifting of the Lever 220, the lever 220
extends slightly beyond the outer periphery of the housing 232
to provide a tab 221. Alternatively, any of a wide variety of
friction enhancing or gripping surface structures can be
provided, as will be apparent to one of skill in the art.
In addition, the cam configuration is preferably such
that the lever 220 has a minor amount of free play before the
friction enhancing structures 225 engage the pin 230. In this
manner, the lever 220 can be readily lifted slightly away from
the upper housing 232 so that the patient can easily position
fingers underneath the lever 220 before retracting the lever
against the resistance provided by spring 231.
The spring retractor 218, in accordance with the present
invention, can be utilized with any of a variety of housing
structures. rr~or example, in the embodiment illustrated in
Figures 18-20, the housing comprises an upper housing 232
removably secured to a lower housing 234 by way of a plurality
of threads 236. When the lower housing 234 is threadably
removed from the upper housing 232, the combination of the
SUBSTITUTE SHEET
.__
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ramp 224, pin 230, support 228 and platen 226 operate to limit
the expansion of the spring to retain the desired
prestressing. Thus, the housing can be disassembled with the
platen either in the extended or retracted positions, and a
fluid medication bag 235 can be placed within the lower
housing 234.
Since reassembly of the lower housing 234 with upper
housing 232 is not opposed by any force from the spring 231,
any of a wide variety of securing means can be utilized in
place of the illustrated threads 236. For example, snap fit
structures, hinge and 7.atch arrangements, and the like can be
readily adapted for use. Alternatively, side installation
embodiments are also contemplated by the present inventors.
For example, the upper housing 232 and lower housing 234 can
be integrally molded, or can be secured together in a
permanent fashion following installation of the functional
components. A port (not illustrated) on the side of the
housing is then appropriately sized to receive a fluid
medication bag 235 therethrough.
The embodiment illustrated in Figures 18-20 provides a
uniquely low profile infusion pump 216, which may be readily
loaded by the patient without the use of any additional tools,
and which has a thickness of only slightly greater than the
sum of the inflated medication bag and the length of the
collapsed spring.
Figures 21-'24 illustrate a key operated platen retractor
in accordance with a further aspect of the present invention.
Referring to Figure 21, there is disclosed an infusion pump
238 having a key operated platen retractor 240 thereon.
Platen retractor 240 comprises a threaded member 242 such as
a disk, which is connected to the platen 244 by way of a
spacer 246. As will be appreciated by one of skill in the
art, the threaded element 242 may comprise either a disk
having an external thread on the circumferential surface
thereof, or an aperture bored axially through spacer 246 and
provided with a female thread for receiving a threaded key.
SUBSTITUTE SHEET
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-ay_
Referring to Figure 22, a key 248 is provided for
threadably engaging the threaded disk 242. Key 248 is
provided with an aperture extending therethrough, and having
a female thread thereon.
Threaded disk 242 operates as a stop by abutting against
a portion of the housing, thereby limiting axial expansion of -
the spring. In this manner, the spring can be prestressed as
desired. '
Preferably, the threaded disk 242 is axially movably
positioned within a well 250. Well 250 serves multiple
functions, including permitting the loaded infusion pump 238
to retain the same exterior profile as the discharged infusion
pump 238, as illustrated in Figures 23 and 21, respectively.
In addition, the lower limit of the well 250 operates as a
stop to prevent further expansion of the spring.
Additionally, threaded disk 242 can serve as a liquid level
indicator.
In use, the user inserts the key 248 into the well 250,
and rotates the key to engage the threads on disk 242.
Continued rotation of the key draws the disk axially against
the bias provided by the spring, until the platen is in the
fully retracted state. When fully retracted, the platen abuts
the lower wall of the recess 250, as illustrated in Figure 22.
At this point, the lower portion of the housing can either be
removed for installation of a fluid medication bag, or the
fluid medication bag can be installed through a lateral or
side entry port. It is therefore preferable that the distance
between the platen when fully retracted and the bottom of the
housing be slightly greater than the thickness of the filled
medication bag, so that the bag may be conveniently slidably
positioned therebetween.
Once the bag is in position, the user simply reverses the
direction of rotation of the key, and spins the key to remove
it from the threaded disk 242. Once the key is partially
backed off of the threaded disk 242, the medication bag will -
be under pressure exerted from the platen 244.
SUBSTITUTE SHEET
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Referring to Figure 24, there is disclosed a loaded and
pressurized fluid medication delivery pump 238, similar to
that illustrated in Figures 21-23, and including some
additional details. For example, the cross-sectional view of
the threads 252 reveals that the thread has a width which
changes from a relatively narrow dimension at the point of
attachment of the thread to the corresponding support
structure, to a relatively wide width at the free end of the
thread. Similarly, the channel for receiving each thread is
provided with side walls which taper towards each other in a
direction extending away from the bottom of the channel. In
this manner, the threads are provided with a full or partial
interlocking fit, which will permit the use of thinner, more
flexible construction materials for the side walls of the
housing, while minimizing the risk that plastic deformation of
the side walls under bias from the spring will cause the
threaded side walls to disengage from each other.
In addition, an annular platen guide 253 is provided to
optimize the precision of the axial travel of the platen 244
throughout the dispensation and reloading cycles. Platen
guide 253 cooperates with an annular spring guide 254. Platen
guide 253 and spring guide 254 in one preferred embodiment
comprise concentric annular flanges which are axially movable
towards and apart from each other in a telescoping fashion.
An alternate means for connecting the spacer 246 to the
platen 244 is also disclosed in Figure 24. Although the
spacer 246 may be integrally molded or otherwise formed with
the platen 244, the spacer 246 may, for manufacturing reasons,
preferably be separately manufactured and later connected to
the platen 244. This may be convenient from a manufacturing
standpoint or because of the desirability to utilize different
construction materials for the platen and the spacer 246.
For example; referring to Figure 24, the spacer 246
extends through an aperture in the platen 244. A shallow
recess 249 is provided on the medication bag side of the
platen 244, and preferably is radially symmetrically disposed
about the axis of the spacer 246. Recess 249 receives an
SUBSTITUTE SHEET
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_30 -
anchor 247 on the end of spacer 246. Anchor 247 may be an
integrally formed disk or sheet on the~end of spacer 246.
Alternatively, anchor 247 is secured to spacer 246 in a post-
forming operation, such as by spot welding, solvent bonding,
thermal bonding, or attachment by screws or other fastening
means . . - .
In a preferred embodiment, the threaded disk 242, spacer
246 and anchor 247 are all manufactured from a suitable non-
corrosive metal such as stainless steel to minimize the
occurrence of stress fatigue following repeated usage of the
infusion pump 238. As illustrated in Figure 24, anchor 247 is
preferably seated within recess 249 in such a manner that a
smooth exterior surface is provided for compressing the fluid
medication bag.
The overall thickness of the infusion pump 238 can be
reduced by incorporating a collapsible platen retractor and
restrainer. For example, referring to Figures 25 and 26,
there is disclosed an infusion pump 256 having a collapsible
platen retractor 258. Collapsible retractor 258 generally
comprises a first segment 260 which is axially movably
disposed with respect to a second segment 262. The first
segment 260 and second segment 262 are assembled in such a .
manner that they operate to limit the distal travel of the
platen as illustrated in Figure 26. In this manner, the base
of the infusion pump can be removed, and a medication bag
inserted therein', while the collapsible platenretractor 258
retains a prestress on the spring.
In the illustrated embodiment, first segment 260 is
conveniently provided in the form of a tubular body 261 having
a longitudinal axis which extends at a perpendicular to the
plane of platen 268. The tubular body 261 of first segment
260 may be integrally molded with the platen~268, or secured
thereto using conventional techniques sufficient to withstand
the forces generated by the spring for any given embodiment.
The proximal end of the tubular body 261 of first segment 260
is provided in the illustrated embodiment with a radially
inwardly directed flange 263 which operates as a limit on
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travel with respect to second segment 262, as will be
discussed.
Second segment 262 in the illustrated embodiment
comprises an elongate body portion 264 having a first end 265
a:~d a second end 266. Preferably, first end 265 comprises a
transverse element, such as a disk, extending generally in a
plane which is transverse to the longitudinal axis of body
264, and adapted for reciprocal axial motion within a recess
267 provided on the housing of infusion pump 256. The recess
267 terminates in a stop such as a radially inwardly directed
annular flange 269 for limiting travel of the disk shaped
first end 265. See Figure 26.
Similarly, the second end 266 of body 264 is provided
with an enlargement for cooperating with the flange 263 on
tubular body 261 to limit the extension of the platen 268.
Thus, second end 266 preferably comprises one or more barbs
having a ramped distal surface, and a proximally facing
shoulder to cooperate with flange 263 as is illustrated in
Figure 26. In this embodiment, second end 266 is generally in
the form of a rounded screw head, having a slot 270 extending
axially therein. This design permits- easy assembly of the
components of the invention, such that the second end 266 can
be press f it through the opening within annular flange 263 , to
provide an axially movably interlocking fit between first
segment 260 and second segment 262.
Retraction~of the platen 268 against the spring bias in
the embodiment illustrated in Figures 25-26 can be
accomplished in any of a variety of ways disclosed elsewhere
herein. For example; first end 265 can be provided with an
exterior thread, for threadably receiving a key such as that
illustrated in Figure 22. In this manner, first end 265 can
be drawn axially against the direction of force generated by
the spring, to retract platen 268 to the position illustrated
in Figure 25. At that time, a medication bag 272 is inserted
into the pump 256 such as by insertion through a lateral
opening, or by removal of the base of the pump 256. Following
introduction of the medication bag 272, the key (not
suBS~rrru-rE sHEEr
PC'f/US93/00565
WO 93/14797
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illustrated) is removed from the first end 265. As
.illustrated in Figure 25, the second segment 262 .can
thereafter be slidably collapsed within the tubular body 261
of first segment 260, to provide a sleek exterior profile of
the infusion pump 256.
Alternatively, any of the additional detraction "
structures disclosed herein can also be incorporated into the
present embodiment. "
Referring to Figures 27-29, there is disclosed an ultra
flat spring powered pump comprising at least one spring 274,
positioned within a housing 276 for biasing a platen 277
against a base wall 278 for compressing a fluid medication bag
therebetween. Platen 277 is retracted against the force of
the spring 274 by a rotatable retraction mechanism 279.
Preferably, retraction mechanism 279 comprises a threaded
shaft 280 which is rotatably linked to platen 277. This is
conveniently accomplished by providing a radially enlarged
anchor 289 on the end of shaft 280 and positioning shaft 280
through an opening in platen 278 which is too small to permit
passage of anchor 289, as illustrated.
The proximal end of shaft 280 is adapted to receive a
crank 281 to permit the patient to rotate the threaded shaft
280 to retract platen 277. In the illustrated embodiment, an
opening in the upper portion of the housing is provided with
a complementary female threaded surface for cooperating with
the threads on threaded shaft 280.
In this embodiment, the platen 277 is retracted by
rotating the threaded shaft 280 so that a medication bag 282
can be installed between the platen and the base. Thereafter,
in order to reduce the profile of the pump, the threaded shaft
280 may be rotated in a reverse direction to advance fully or
partially axially back into the medication bag 282 as ,
illustrated in Figure 29. For this purpose, medication bag
282 preferably comprises a material which will permit the
flexible deformation illustrated in Figure 29, arid the volume
of fluid contained in the medication bag 282 should be
sufficiently low in relation to the elastic limit of the bag,
SUBSTITUTE SHEET
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-.33
to accommodate the displacement illustrated in Figure 29.
Referring to Figure 30, there is disclosed an end
elevational.view of an infusion pump such as that illustrated
in Figures 27-29. As illustrated therein, a scale 283
provides an indicium of the relative status of the pump
throughout the dispensation cycle. In the illustrated
embodiment, the platen 277, or an extension of the platen 277
is visible through an opening 284 on the side of the housing.
Status indicium 285 are provided an the side of the housing
for allowing the user to roughly quantitatively evaluate the
remaining portion of the dispensation cycle.
For example, in the illustrated embodiment, the scale 283
runs from 100 to zero. This scale may represent the
percentage of remaining medication in the bag. Alternatively,
in a device which is dimensioned to accommodate a 100 cc
delivery bag, the scale could indicate remaining milliliters
of medication. In an embodiment having a single, known flow
rate and medication volume, the indicium 285 can be provided
in units of time such as hours or minutes, reflecting the
remaining time of the dispensation cycle.
Also illustrated in Figure 30 is an alternative crank
arrangement for retracting the~platen 277. Crank 286 is
pivotally attached to threaded shaft 280, so that it can be
conveniently moved from a first compact position 287 such as
during storage or use, to a second ready position 288 in which
the crank is positioned for use in retracting the platen 277.
Referring to Figures 31-33, there is disclosed an
alternate embodiment of an infusion pump having a collapsible,
segmented, platen retraction and retention structure. This
embodiment permits the use of a threaded retractor such as
that illustrated in Figures 27-29, yet permits the threaded
retractor to be reinserted into the pump to provide a
generally smooth exterior configuration, without indenting the
medication bag.
Referring to Figure 31, a first segment 290 preferably
comprises a threaded post which engages complementary threads
in an opening in the top of the pump housing, so that rotation
suBS-rn-u~ sHEEr
WO 93/ 97 ~ , . PGT/US93/00565
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of the threaded post draws the post axially through the
opening of the housing. First end 292 and second end 293 of
first segment 290 are provided with an enlargement such as a
disc-shaped stop, for reasons which have been previously
discussed, for example, in connection with the embodiments
illustrated in Figures 25-29. Similarly, second segment 291
preferably comprises a tubular element analogous in structure
and function to the segment 260 illustrated in Figure 25. In .
either embodiment, however, a variety of alternative
structures for retracting and restraining the platen such as
only partially indenting the medication bag, will be apparent
to those of skill in the art in view of the disclosure herein.
Referring to Figure 32, rotation of the threaded shaft
290 draws the platen against the bias provided by the spring,
to produce an opening for receiving a fluid medication bag.
In the illustrated embodiment, two coil springs are
illustrated in cross section. However, anywhere from about
one to about five or more springs can readily be incorporated
into a design of the present invention.
Threaded post 290 can be rotated using any of a variety
of implements, such as an allen wrench, a crank, a rotatable
nut, an electric drill, or others as will be apparent to one
of skill in the art.
The dimensions of the embodiment illustrated in Figures
31-33 can be varied throughout a considerable range, depending
upon the desired'volume of medication to be infused in a given
dispensation cycle, as well as other considerations that will
be apparent to one of skill in the art. In general, however,
the thickness of the pump along an axis parallel to the
longitudinal axis of the spring is preferably no thicker than
about 2 inches, and more preferably within a range of from
about 1.4 inches to about l.6 inches in an embodiment adapted
for receiving a 0.5-inch thick medication bag. In this
embodiment, the distance between the_retracted platen and the
base is preferably about 0.6 inch, to permit sufficient
clearance to easily install a medication bag.
SUBSTITUTE SHEET
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Preferably, as discussed in connection with Figures 27-
30,~the edge of the platen is visible through the opening 294
or other window to permit the user to assess the remaining
fluid volume in the medication bag.
Retraction of the platen in order to facilitate
introduction of a medication bag can alternatively be
accomplished through any of a variety of hydraulic or
pneumatic means. For example, referring to Figures 34 and 35,
there is provided a pneumatic lift for moving the platen from
a second distended position to a first retracted position to
facilitate introduction of a medication bag. In this
embodiment, there is provided one or more pneumatic cylinders
296 for advancing the platen against the bias provided by one
or more springs 297. Pneumatic cylinder 296 generally
comprises a housing 298 for defining a chamber 299, having at
least one movable wall 300 axially slidably disposed within
the housing 298 to enlarge or contract the volume of chamber
299. Movable wall 300 is mechanically linked to platen 302 by
a spacer 301. Movable wall 300 is provided with any of a
variety of known sealing rings or other means for providing a
seal between the movable wall 300 and housing 298.
At least one port 303 is provided on the housing for
communicating with the chamber 299. In operation, a source of
a pressurized material such as a fluid or gas is placed in
communication with port 303 and forced into chamber 299 under
sufficient pressure to advance wall 300 against the force
resulting from one or more springs 297.
In a preferred embodiment, two or more pneumatic
cylinders 296 are provided. Thus, for example, there is
disclosed in Figure 35 a top plan view of an infusion pump
having seven pneumatic cylinders 296 positioned about the
periphery of a medication bag. To facilitate retraction of
the platen by infusing pressurized fluid or gas through only
a single port 303, each of the chambers 299 of the pneumatic
cylinders 296 are in communication with each other by way of
a flow path 304.
$UBSTITUTE SHEET
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In accordance with one embodiment, four pneumatic
cylinders 296 are provided, each having an internal diameter
of about one-half inch. This provides a surface area on
movable wall 300 of approximately .196 square inches per
pneumatic cylinder, for a total of .784 square inches for the
set of four. To provide a lift of 150 pounds, assuming no -
friction, a fluid will need to be introduced into port 303 at
approximately 190 psi. By doubling the piston area to 1.57 _
square inches, such as by providing eight pistons instead of
four, the required pressure of the pneumatic fluid drops to
about 95 psi. A variety of pressure sources can be utilized,
as is discussed infra.
Alternatively, referring to Figures 36-38, there is
disclosed a pneumatic retraction embodiment in which one or
more flexible bladders are utilized to provide the force
necessary to retract the platen against the spring bias.
Thus, referring to Figure 36,, there is disclosed a top plan
view of an embodiment of the present invention having two
elongate tubular bladders 306 in communication with a fill
port 308 by way of lumen 307. As illustrated in Figures 37
and 38, inflation of the bladders 306 advances the platen
against the spring bias provided by one or more springs 309 to
provide sufficient space between platen 310 and base 311 to
accommodate a full medication bag 312.
Any of a variety of configurations for bladder 306 may be
utilized in acdomplishing the present embodiment of the
invention. In general, the bladder comprises one or more
elongate tubular bodies having a diameter which is sufficient
in its inflated state to provide a sufficient distance between
the platen 310 and base 311 to accommodate the medication bag
312. The axial length of the bladder 306 will depend upon the
size of the medication bag contemplated, together with factors
such as the maximum acceptable pump housing size, and the
maximum acceptable pressure required to retract the platen.
In general, the larger volume of bladder 306 will enable the '
use of less compressive force to retract the platen, but will
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require a larger housing as will be apparent to one of skill
in the art.
Motive force for filling the bladder 306 can be provided
in any of a variety of ways, utilizing either a fluid or a gas
medium. For example, the fill port 308 can be provided with
a luer . -connector or other conventional means for establishing
fluid communication with a conventional syringe having a
volume sufficient to inflate the bladder 306. The syringe may
be filled with water, or air, depending upon the relative
farce characteristics of the bladder and spring. In the
hospital or clinical setting, pressurized air from a house
compression system, such as is commonly available through a
wall outlet in the patient's room, can be utilized.
Alternatively, compressed C02 cartridges or other convenient
sources of pressurized air or liquid can be readily utilized.
Referring to Figures 39-41, there is disclosed a further
embodiment of the infusion pump in accordance with the present
invention. In this embodiment, retraction of the platen is
accomplished by the use of a threaded key, as has been
previously discussed, and the overall thickness of the
infusion pump is minimized through the use of a folding link
lift mechanism.
In this embodiment, infusion pump 314 is provided with
one or more springs 320 for biasing a platen 316 in the
direction of base 318, as has been previously discussed. In
order to limit the distal travel of platen 316, such as when
the base 318 is removed, and to retract the platen 316 against
the bias provided by spring 320, a retraction and retention
structure 322 is provided.
Referring to Figure 42, the retraction and retention
structure 322 generally comprises a folding linkage assembly
324. The linkage assembly 324 permits the relative movement
of proximal end 325 and distal end 326 between a first
position in which proximal end 325 and distal end 326 are
spaced apart by a predetermined maximum distance, and a second
position in which proximal end 325 and distal end 326 axe
spaced apart by a lesser distance.
SUBSTITUTE SHEET
WO 93/14797 PCT/~.1593/a85f5
the embodiment illustrated in Figure 42, linkage
-3~-
assembly 324 is provided with a first segment 327, which is
pivotably secured to the proximal end 325 such as by a pin
328. The distal end of linkage 327 is provided with a slip
joint connection with a second linkage 329. The slip joint
connection is conveniently accomplished by providing one of
the first and second linkages with an axially extending slot,
and the other of the first and second linkages with a pin 332
for extending through the slot, together with an anchor such
as a nut, soldered washer or pin for preventing removal of the
pin 332 from the slot.
The second linkage 329 is thereafter pivotabl,y connected
to the platen 316, such as by providing a proximally extending
flange on the platen 316 for pivotally engaging the distal end
of the second linkage 329.
Preferably, this embodiment is provided with a threaded
plug at the proximal end 325 of folding linkage 324, adapted
to be received within a key 330, as has been discussed in
connection with previous embodiments. Alternatively, other
retraction structures such as a lever can also be used in the
present embodiment. One function of the linkage 324 in the
threaded plug embodiment is to resist rotation of the plug
during rotation of the key. Thus, if an alternative to
linkage 324 such as a multistrand braided cable is used, some
additional registering structure should be provided to resist
rotation of the threaded plug.
In use, the threaded plug is engaged within the key 330,
and withdrawn by rotation of the key 330 to retract the platen
316 to the loaded position. While the platen is being
retracted against the spring bias, the first linkage 327 and
second linkage 329 become extended to their axial limit.
After installation of the medication bag, the key is
removed by reverse rotation with respect to the housing, and
the .linkage assembly 324 can be collapsed back into the
housing, as illustrated in Figure 41, by pressing upon the
proximal end 325. Preferably, releasable retention structures
are provided for retaining the proximal end 325 within or
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against the housing, to maintain the outer profile of the pump
at a minimum during the dispensation cycle. For example, any
of a variety of recesses and snap-fit interrelationships
between the proximal end 325 and the housing can be
incorporated, which take advantage of the plastic
deformability of the materials of the housing. . _.
In accordance with one embodiment of this aspect of the
present invention, the linkage assembly 324 is configured so
that the maximum length between the proximal end 325 and
distal end 326 is about 1.0 inches. Thus, a coil spring
having a relaxed length of about 7 inches will be permitted to
expand no more than about 1.0 inches in axial length by the
end of the dispensation cycle. Preferably, the loaded
infusion pump 314 will have a thickness of no more than about
1.2-1.6 inches, so that the collapsed distance between
proximal end 325 and distal end 326 of linkage assembly 324 is
within the range of from about .3 to about .5 inches.
Linkages 327 and 329 can be manufactured in any of a
variety of ways which will be well known to those of skill in
the art. For example, linkages 327 and 329 may be pressed or
stamped from sheet metal stock, such as aluminum or stainless
steel, and thereafter drilled or punched with the appropriate
slots and pivot holes, or may be molded from any of a variety
of plastic moldable materials having sufficient strength for
this intended application.
In one embodiment of the invention, linkages 327 and 329
are punched out of 0.1 inch thick stainless steel sheet, with
a width of about 0.25 inches and a length of about 0.6 inches.
The axial length of the slot is about 0.4 inches, and pivots
are formed using rivets, screws or the like.
In an alternate embodiment, the first and second linkages
are pivotally connected together without the use of a slip
joint. This construction may extend pivot 331 (Figure 41)
farther in a lateral direction than pivot 332 (Figure 42) when
the platen is in the retracted position and the proximal end
325 of linkage 324 is pressed back inside the housing.
Depending upon other design parameters, as will be apparent,
SUBSTITl,ITE SHEET
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- 'S~0 -
the embodiment of Figure 42 may be utilized with a relatively
smaller diameter spring 320.
As a further alternative, the linkage connection
comprises a unitary link 327', as illustrated in Figure 43.
As will be apparent to one of skill in the art, the outer
profile of an infusion pump having the linkage 327'_of Figure
43 will be relatively larger than an embodiment having a
collapsible linkage assembly. In addition, compressive force -
such as by the patient upon the threaded plug 325 in the
embodiment illustrated in Figure 43 will be additive to the
spring force, and potentially cause changes in the effluent
fluid flow rate. Thus, this embodiment, although relatively
simply to manufacture, may be desirably utilized only in
circumstances where the outer profile and compression issues
are not of concern.
The foregoing designs have been determined by the present
inventor to produce a relatively constant output profile
throughout the dispensation cycle of devices incorporating
these designs. However, even with reasonable prestressing of
the spring, output pressure generally declines over the
dispensation cycle as the spring relaxes and the pressure
contact area on the bag changes. Provision of a spring having
a higher spring constant or higher pretension can change the
starting force and ending force throughout a dispensation
cycle, but generally not appreciably flatten the output force
or contact area profile.
In a test where the internal pressure of the bag was
maintained at a constant 5 lbs./in2 while the contents were
delivered, it was found that the force applied to the bag
needed to be increased from 24 lbs. force at the beginning of
the dispensation cycle to 40 lbs. force near the completion of
the dispensation cycle. See Figure 60. .
Thus, in accordance with a further aspect of the present
invention, there is provided an element for introducing a drag
or resistance to distal travel of the platen to produce a
flattening of the output pressure profile. Preferably, the
amount of drag .on the distal movement of the platen changes
SUBSTITUTE SHEET
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WO 93/14797 ~ ~ ~ PCT/US93/(HD565
continuously over a portion or all of the dispensation cycle,
having a maximum value at the commencement of the dispensation
cycle and reaching a minimum value at some point between the
commencement and end of the dispensation cycle. Preferably,
the declining drag provided by the drag elements complements
the declining spring force throughout the dispensation cycle
in a manner that produces a substantially flat net spring and
bag contact area and force throughout the dispensation cycle.
Of the two, the changing bag contact area is a greater
negative influence than the declining spring force.
Thus, referring to Figure 44, there is disclosed an
infusion pump 334 having one or more springs 336~for biasing
a platen 338 against a medication bag 340. Platen 338 is
provided with at least one drag element 342 for contacting a
friction element 342 throughout at least a portion of its
axial length of travel. Drag element 342 can be provided in
any of a variety of forms, and can extend radially outwardly
within the plane of the platen 338, or be spaced apart axially
from the plane of the platen, such as is illustrated in Figure
44.
In the illustrated embodiment, drag element 342 comprises
an axially extending support 345, having a generally
transverse element 346 at the proximal end thereof. Element
346 engages at least one friction surface 344, which, in the
illustrated embodiment, ramps radially outwardly away from
element 346 as~ the element 346 travels in the distal
direction. Element 342 preferably comprises- a resilient
material such as a rubber or other elastomer, such as
neoprene.
Element 346 and surface 344 can take any of a variety of
configurations. For example, in the illustrated embodiment,
element 346 can take the shape of a circular disk, extending
within a generally frusto-conically shaped well, having
annular surface 344 extending around the well. Alternatively,
surface 344 can be provided on only one side or oppasing sides
of a bilaterally symmetrical element 342. Retraction of
platen 338 in the proximal direction forces element 342
SUBSTITUTE SHEET
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against surface 344, to provide a relatively tight fit, whicn
dissipates as element 342 is drawn axially in the distal
direction.
In a simplified embodiment, the interior wall of the pump
housing is ramped or stepped slightly in the radially inward
direction along all or a portion of its .interior .
circumference. This ramped or stepped region extends radially
inwardly in the proximal direction, so that the smallest _
cross-sectional area occurs at the beginning of the
dispensation cycle. At that point, the radially exterior edge
of the platen 338 frictionally engages the step or ramp to
provide a resistance to distal travel which dissipates or
disappears at some point along the distal travel of the
platen.
In general, in a stepped friction surface embodiment, the
step will extend throughout no more than about the first one
half or one third of the travel. However, the extent of
friction desired and the rate of taper or location of the
distal edge of the step will vary depending upon the spring
constant and amount of prestress, and the bag contact area,
and can be optimised for any particular embodiment through
routine experimentation by one of skill in the art.
In accordance with one embodiment of the present
invention, a drag element is constructed as shown in Figure
44. A 50 cc medication bag is inserted within the infusion
pump, and the change in spring force exerted against the bag,
as well as the drag due to the resistance element, are
measured at each 10-cc increment of fluid dispensation. The
following results are obtained:
~ TABLE 1
fill spring force output pressure drag net change output
w o dra!; element w element y dray element w drag clement
SO m1 40 lbs. +8 psi -13 lbs. t1 S psi
40 ml 39 lbs. +7 psi -11 Ibs. (1 S psi
3U ml 38 lbs. +S ~) psi -8.8 lbs. U 5 psi
20 ml 37 lbs. +4.4 psi -6.4 Ibs. t) 5 psi
10 ml 3G lbs. +2.4 psi -3.4 Ibs. 0 5 psi
tl ml 3S lbs. () psi t) Ibs. t) S psi
SUBSTITUTE St°IEET
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In accordance with a further aspect of the present
invention, there is provided an indicium of the status of the
dispensation cycle, which can be readily incorporated into any
of the previously disclosed embodiments. Referring to Figure
45, there is disclosed a fluid medication bag 348, positioned
between a platen 349 and the base 350 of an infusion pump.
Preferably, at least a portion of base 350 comprises a
transparent window 352, such as polycarbonate or clear
polypropylene, or other materials well known in the art.
Disposed between the medication bag 348 and the platen 349 is
a membrane 354, which will be discussed in detail infra.
The platen 349, or a cover for the platen,~is provided
with at least one embossed symbol 356, such as an E indicating
"empty." The embossed symbol is preferably raised from the
planar surface of the platen.
When the medication has been fully expelled from bag
348, the embossed symbol 356 is pressed by the platen 349 into
the membrane 354 and the symbol 356 embossed on the platen
becomes visible through the window 352 in the base 350 of the
infusion pump. For this purpose, membrane 354 may comprise
any of a variety of materials such as rubber or silicone:
Membrane 354 is preferably has a thickness within the range of
from about .020 inches to about .030 inches. However, the
thickness of the membrane 354 and material can be varied
considerably, depending upon~the native pigmentation,in the
membrane and compressibility under the force due.. to the
spring. The embossed letters are preferably raised to a
height of about 0.04 inches from the surface of the platen.
Referring to Figures 48 through 51, there is disclosed
an ultra low profile sliding spring retractor embodiment in
accordance with a further aspect of the present invention.
Infusion pump 360 is provided with a housing 362, having a
platen 366 contained therein which is biased in the direction
of a fluid medication bag 368 by one or more springs 364. In
the illustrated embodiment, four coil springs 364 are
provided, each having a generally conical configuration so
that the axial length of the compressed spring is no more than
SUBSTITUTE SHEET
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212~3~~
the diameter of the spring coil wire, as illustrated in Figure
50.
The platen 366 is retracted against the bias from spring
364 by one or more levers 374 movably disposed along an
inclined path such as slot 370 with respect to the housing
362. Rreferably, at least one pair of opposing lev~rs.374 and '
376 are provided, and, in the illustrated embodiment, a second
pair of levers 375 and 377 are also provided. Referring to
Figure 49, lever 374 rides in a slot 370 formed in a housing
362. Slot 370 is inclined from a first end 371 to a second
end 379 in an axial and medial direction. Similarly, lever
375 travels in slot 372, which inclines medially in the axial
direction. In this manner, the user can place a thumb on
lever 375 and a forefinger on lever 374, and compress the two
levers together to advance the platen against the spring bias.
Inclusion of a mirror image pair of levers 376 and 377 for
traveling in corresponding inclined slots (not illustrated) on
the opposite side of the housing 362, the amount of force
required to be exerted by each hand of the user is divided in
half, and provides a more convenient force distribution within
the platen pump 360.
In one embodiment of the invention, each of levers 374,
375, 376 and 377 are separately movably mounted within their
respective slots in the housing 362. For example, each lever
is integrally molded with or secured to the platen 366, and,
preferably, provided with a bearing such as a roller bearing
(not illustrated) for minimizing friction during reciprocal
travel within the corresponding inclined path of travel.
Alternatively, each opposing member of a pair of levers
are joined through the center of the device, to provide a
single post extending therethrough. For example, lever 374
and 376 can comprise opposite ends of a single shaft, which ,
extends through or adjacent to the platen 366. This design
simplifies the construction of the pump in some aspects, such
as by eliminating the torque which would otherwise occur at
bearing and or connecting of the lever to the platen 366. The
unitary post can either be permanently mounted within the
SUBSTITUTE SHEET
WO 93/14797 2 ~ ~ 6 3 2 0 PCT/US93/00565
-.~s-
housing, or removably positionable within a through lumen, so
that the posts can be removed from the unit once the
medication bag has been inserted.
In the illustrated embodiment, opposing levers 374 and
376 are opposite ends of a unitary post, and opposing levers
375 and 377 are similarly opposing ends of a unitary post.
.The posts in this embodiment extend along the medication bag
368 side of platen 366, as is illustrated in Figures 50 and
51. Figure 50 illustrates a side elevational view of an
embodiment of the invention in which the posts are retained in
the retracted position, such as for insertion of the
medication bag 368. Figure 51 illustrates a point in the
dispensation cycle of the embodiment of Figure 50, with the
posts remaining in position adjacent the platen 366.
Referring to Figure 49, the medial most extent 379 of
the path of travel for lever 374 is provided with a detest
380, for removably retaining the lever 374 at the fully
retracted position such as during loading. After each of the
levers has been advanced to the detest 380, the platen 366
will be releasably retained in the retracted position to
permit insertion of a fluid medication bag 368 between the
platen 366 and the bottom of housing 362. This can be
accomplished in any of a variety of ways disclosed Qlsewhere
herein, such as by introduction of the fluid bag 368 through
a side opening in the housing 36~, or by providing the housing
362 with a hinged bottom wall which can be opened to insert
the fluid medication bag 368. Following installation of the
bag, each lever 374 can be advanced laterally slightly out of
the corresponding detest 380, so that the never 374 is no
longer retaining the spring bias. The levers thereafter may
be withdrawn from the device, or folded at a hinge point (not
illustrated) to reduce the peripheral profile of the device.
Preferably, the angle of the path of travel of lever
374, which, in the illustrated embodiment is governed by the
angle of the slot 370 is within the range of from about 10° to
about 20° from the plane of the central region of the platen
SUBSTITUTE SHEET
. . __ _ : _. :. . , . .... ..: .:.:.. . :: .. -- .. , . r: .: : , -: ~. . -
. . . . ... ,. . ~ , .. . . ... .~... :.. . :. .. . ... . ~ . wr. ~ ~ .~ . ,.
PGT/US93/00565
,~~ _
366. As will be apparent to one of skill in the art, as the
axis of the path of travel of lever 374 approaches
perpendicular to the plane of the platen (i.e. approaches the
longitudinal axis of travel of spring 364), the leverage
obtained in advancing the platen against the spring bias
diminishes. Thus, in one embodiment, the slot. 370 could
extend at a perpendicular to the plane of the platen.
However, the patient would be required to exert a significant _
force in order to retract the platen against the spring bias.
The lower limit on the range of angels between the path
of travel of lever 374 and plane of platen 366 is governed by
several factors. The axial component of the path of travel
must be sufficient to fully retract the platen 366 so that a
medication bag 368 can be inserted. Thus, as the angle
decreases beyond a certain limit, the length of the path of
travel must be increased to obtain the same axial component,
thereby requiring a larger outer peripheral dimension of the
device. In one preferred embodiment, the housing 362 has a
length of about 5 inches and a thickness along the
longitudinal axis of spring 364 of about 0.9 inches. Slot 370
inclines at an angle of about 15° from the plane of the
central region of the platen 366, and has a length of about
2.2 inches.
In accordance with a further embodiment of the present
invention, there is provided an improved spring biased
intravenous infusion pump having a parallelogram "scissor"~
type linkage for transferring spring force to the medication
reservoir. Referring to Figure 52, the pump 400 comprises a
housing 401 which may be formed as an integral unit, or from
two or more detachably connected components as has been
previously described.
Referring to Figures 53 and 54; the preferred detachable
component housing 401 comprises a cover 402 and a base 404.
Each of the cover 402 and the base 404 contain an annular wall
442 and 444 extending in the axial direction. Complementary
threads are preferably provided on the outer surface of the
SUBSTITUTE SHEET
212~3~
WO 93/14797 PCT/US93/00565
annular wall 442 of the base 404 and inner surface of the
annular wall 444 of the cover 402,~to facilitate threadable
engagement of the cover 402 arid base 404 as has been
discussed. Alternatively, the contacting surfaces of the
cover 402 and base 404 are provided with complementary pins
and J- or L-shaped grooves to permit a press-and-twist fit
interlock. Any of a variety of alternative interlocking
structures may be utilized for the housing 401 of the
invention, as will be apparent from the previous disclosures
herein.
The cover 402 and base 404 are preferably formed in
accordance with conventional techniques for the production of
medical device housings, such as injection molding of
thermoplastic or thermoset polymers. Alternatively, any of a
variety of other techniques may be utilized, including
fabrication from sheet metal stock, as will be well understood
by one of skill in the art.
In general, base 404, annular wall 442, annular wall 444
and cover 402 cooperate to form a chamber 446 for containing
the functional components of the infusion device. In the
illustrated embodiment, a platen segment 410 is biased against
a reservoir such as a flexible medication bag 406 by means of
a spring and linkage assembly 411.
Fluid bag 406 is in fluid communication with the patient
by way of effluent fluid line 448, which extends through the
housing 401 by way of a port 450. Modification of the port
450 to accommodate the various relationships between the cover
402 and base 404 will be apparent to one of skill in the art.
A flow regulator (not illustrated) to regulate the flow of
medication is provided on fluid line 448.
In general, the fluid bag diameters contemplated for use
in accordance with the present invention are in the area of
from about 3.5 inches in diameter to about 5 inches in
diameter and from about 0.5 inches to about 1.0 inches thick.
However, infusion pumps adapted to receive other size bags can
be readily produced in accordance with the disclosure herein.
Referring to Figures 53 and 54, the platen 410
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_ y~_
embodiment designed for uss~ with a 3.8 inch diameter, one inch
thick, 100 cc. medication bag 406 has both a flat, circular
central contact surface 413, having a diameter within the
range of from about 2.4 to about 2.8 inches, and an annular
ring portion 415 which inclines away from the reservoir
contacting side of platen 410. The outside diameter of
annular ring portion 415 is generally within the range of from
about 3.4 to about 3.6 inches for use with a 3.8-inch diameter
flat medication bag 406. Medication bag 406 is approximately
3.5 inches in diameter when full. The angle of the surface of
annular ring portion 415 with respect to an extension of the
plane of central contact surface 413 is preferably-within the
range of from about 10° to about 45°, and more preferably
within the range of from about 10° to about 30°.
In general, the transition 417 between the central
contact surface 413 and the radially inwardmost extent of
annular ring portion 415 is positioned so that the circular
central contact surface 413 substantially completely covers
the planar portion on the upper surface of fluid medication
bag 406. Referring to Figure 53, medication bag 406 comprises
a generally planar upper surface, having an outer limit or
transition 407 where the peripheral region of bag 406
commences deviation from the plane of upper surface 409.
As illustrated in Figure 53, the transition point 407 on
the bag 406 is roughly coincident with the transition point
417 on the platen 410. Referring to Figure 54, the interior
surface of bottom plate 408 is configured with a complementary
nesting surface for platen 410. Preferably, platen 410
contains a guide 425 such as an annular flange extending in
the axial direction.for stabilizing the platen 410 as it
compresses the medication bag 406 against the base 404 of the
housing 401.
The platen 410 is biased towards the medication bag 406
through a linkage assembly 411. In general, linkage assembly
411 comprises one or more biasing elements having a
longitudinal axis which extends at an angle with respect to
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-y
the longitudinal axis of travel of platen 410. Preferably,
the biasing element axis extends approximately at about a
perpendicular to the axis of travel of platen 410. As is
discussed below, the biasing element preferably comprises one
or more springs having at least one concentric or parallel
spring guide such as a central shaft or tubular cover.
In the illustrated embodiment, a spring guide 414
extends along an axis which is generally perpendicular to the
axial direction of travel of platen 410. The spring guide 414
conveniently comprises a threaded metal rod having a length
within the range of from about 3.0 to about 3.4 inches, and a
diameter from about .125 inches to about .250 inches, although
variations will be readily apparent to one of skill in the
art.
'In an embodiment in which the spring guide 414 comprises
a unitary or segmented shaft having a continuous thread
extending throughout its length, a tubular sleeve may be
conveniently disposed over the portions of the threaded shaft
Which will slidably carry .other moving parts, as will be
discussed. Alternatively, the spring guide 414 can be
constructed from a generally smooth rod; having a threaded
region only on the distal ends thereof for receiving nuts 416
and 416'.
A spring stop is carried at either end of the spring
guide 414. As will be readily apparent to one of skill in the
art, any of a variety of means can be utilized for retaining
a spring under tension. For example, a nut or nut and washer
threadably engaged to the spring guide 414 is convenient, both
from a manufacturing standpoint, and due to the ability of the
manufacturer to adjust the spring tension by simply rotating
the nut.
In the illustrated embodiment, a spring stop 419 is
provided on each lateral end of the spring guide 414 for
limiting the lateral expansion of each spring. The spring
'stop 419 generally comprises a radially outwardly extending
annular flange '423, having an aperture 421 extending axially
therethrough for receiving a threaded portion of spring guide
SUBSTITUTE SHEET
WO 93/14797 PCT/US93/00565
14. Spring stop 419 also has a cross-sectional area through
212632 -
a radial plane sufficient to limit expansion of the spring.
Each spring stop 419 is preferably provided with an axially
extending tubular sleeve 418 and 418', which in the assembled
pump extends medially along the spring guide 414 and within
the spring. In the illustrated embodiment, the sleeves 418
and 418' have internal threads complementary to the thread on
spring guide 414 to securely threadably retain the spring stop _
419 in place.
In an alternate embodiment (not illustrated), the spring ,
stop 419 comprises a radially outwardly extending annular
flange 423 and an axially extending tubular sleeve 418, as in
the foregoing embodiment. However, the spring stop 419 is
held in place by a threaded nut secured directly to the spring
guide 414 on the lateral side of outwardly extending annular
flange 423. In this embodiment, the internal thread on
aperture 421 and interior wall of axially extending tubular
sleeve 418 is unnecessary. Although the use of a lateral
threaded nut is convenient from a manufacturing standpoint, it
adds to the overall lateral length of the spring guide 414,
which may be undesirable in a given embodiment.
The springs 412 and 412' are compressed between the
spring stops 419 and twa axially moveable blocks 420 and 420 ° .
In one embodiment, the springs 412 and 412° comprise music
wire having a wire diameter of approximately .085 inches.
Lower diameters such as 0.080 may also be used by increasing
the preload.
Preferably, springs 412 and 412° have a spring canstant
within the range of from about 80 lbs. per inch to 130 lbs.
per inch in a dual spring embodiment. Each spring 412 and
412° is approximately 1.7 inches long in its un-compressed
state and approximately 0.9 inches long in its fully
compressed state, shown in Figure 53, and 1/2 inch in
diameter. The sum of the axial travel of springs 412 and 412 °
is approximately 0.'7 inch between the compressed state as
shown in Figure 53 at the beginning of the dispensation cyc~.e
and the state shown in Figure 54 at the end of the
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_ 5- O _
dispensation cycle.
Blocks 420 and 420' function as medial spring abutments
to mechanically link the medial travel of the spring to the
linkage assembly 411 and platen 410. In the illustrated
embodiment, blocks 420 and 420' are generally rectangular in
exterior configuration and contain an annular .or tubular
recess 422 on the lateral side which does not go through the
entire axial length of the block 420 and 420'. The springs
412 and 412' fit into the recess 422 in each block 420 and
420'. The blocks 420 and 420' also contain an axially
extending tubular opening through the center of the block to
allow the blocks to slide axially along the spring guide 414.
Each block 420 and 420' may comprise any of a variety of
durable materials such as aluminum, stainless steel or other
metal known in the medical device arts. Preferably, however,
a strong lightweight plastic material such as Delrin,
available from DuPont is used. Polymeric blocks or coatings
are preferred, due to the~.r ability to slide relatively freely
on the spring guide 414 when biased by the springs 412 and
412' .
Each of two opposing sides of the blocks 420 and 420'
parallel to the spring guide 414 contains a block pivot 438.
The relative positioning of pivots and corresponding recesses
discussed herein can readily be reversed, as will be apparent
to one of skill in the art.
Two link arms 424 and 426 are pivotably affixed to each
pivot 438 at a first end thereof. Link arm 424 is connected
at a second end to an anchor pivot 436 which is connected to
the cover 402. Link arm 426 is connected at its second end to
a platen pivot 434 which is connected to the platen 410. Link
arms 424 and 426 form a scissor-type configuration which is a
mirror image of the configuration of link arms 428 and 430.
'Together, the four link arms 424, 426, 428 and 430 form an
adjustable parallelogram linkage, as will be understood by one
of skill in the art. Preferably, an identical parallelogram
linkage exists on the opposing vertical wall of blocks 420 and
420', as shown in Figure 55.
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Anchor pivot 436 is secured to attachment 432, which is
preferably fixed to cover 402. Platen pivot 434 is affixed to
platen attachment 440, which is preferably pivotably attached
to platen 410.
In a preferred embodiment, platen attachment 440 is
provided with an upper cam shaped profile that is.shaped and
sized to follow the path of the lower inside edge of each of
blocks 420 and 420'. Suitable cam shaped surfaces can be -
provided by either an annular, dome shaped element 440, or by
providing one or more generally parallel planer elements
having a cam shaped outer profile, as will be apparent to one
of skill in the art. Provision of a cam surface which tracks
the path of the lower inside edge of the blocks 420 and 420'
operates to limit the extent to which the plane of platen 410
is permitted to deviate from its normal position which is
generally parallel to the plane of the bottom plate 408.
Preferably, the outer surface of the cam shaped portion of
anchor 440 is sufficiently close to the path of travel of each
of blocks 420 and 420' so that the tilt of the platen is
limited no more than about 50.
As a further option on the scissor embodiment of the
present invention, a fluid level indictor 451 is provided.
See Figure 54. Fluid level indicator 451 generally comprises
a linkage 452 which is pivotably connected to a moving portion
of the scissor assembly, and also to the fluid level indicator
451. Level indicator 451 is preferably slidably mounted in a
track 454 adjacent a scale (not illustrated) and calibrated
such that the level indicator 451 and scale will indicate the
remaining fluid volume.
After a medication bag 406 has been inserted into the
base 404 and the base 404 engaged with the cover 402, the
springs 412 and 412' are at their point of highest ,
compression. As the springs 412 and 412' release force in a
direction perpendicular to the axial direction of platen
travel, the blocks 420 and 420' slide towards each other on
spring guide 414, causing the medial ends of link arms 4:.4,
426, 428 and 430 to move further apart in the axial direction.
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-53-
Through this mechanism the force exerted by the.springs 412
and 412' is transmitted through the link arms 424, 426, 428
and 430 to. the platen 410 through the platen attachment 440.
The spring force component transmitted by the link arms 424,
426, 428 and 430 to the platen 410 increases throughout the
dispensation cycle as the tension of the spring decreases so
as to maintain a surprisingly substantially constant
medication output pressure until the bag is substantially
collapsed, as shown in Figure 54. This surprising result
shown in the experiments discussed infra is desirable in
applications such as infusion of chemotherapy chemicals into
a patient over a period of time at a constant rate. The
mechanical advantage obtained by the link arms 424, 426, 428
and 430 compensates for the decrease in spring tension and the
increase in the bag contact area over the dispensation cycle.
EXPERIMENT 1
Constructincr the Pumn
A platen was constructed in accordance with the
embodiment illustrated in Figures 52-55, having springs 412
and 412' comprised of music wire having a wire diameter of
approximately .085 inch. Springs 412 and 412' had an outside
diameter of about 0.5 inches, a spring constant of
approximately 111 lbs. per inch, and were approximately 1.7
inches long in the uncompressed state and approximately
inch long in the fully compressed state, as shown in. Figure
54. The sum of~the axial travel of springs 412 and.412' was
approximately 0.7 inch between the compressed state as shown
in Figure 53 at the beginning of the dispensation cycle and
the state shown in Figure 54 at the end of the dispensation
cycle. The springs were preloaded to about 35 lbs. on each
side, and were measured to generate a total spring force of
about 160 lbs. Blocks 420 and 420' were constructed from
Delrin, available from DuPont. The length of each of the four
link arms was about 0.8 inches from pivot to pivot. The
platen and opposing wall were substantially flat to isolate
the pressure effects due to the spring biasing assembly.
EXPERIMENT 2
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.Testing the Platen Pump
A 50 cc medication bag 406 was inserted in the platen
pump of Experiment 1 and the output fluid pressure from the
medication bag 406 was measured as the volume in the
medication bag 406 decreased over the dispensation cycle.
Table I below illustrates the data accumulated_fxom this
experiment.
TABLE I
Volume Extaelled from Outr~ut Fluid
Medication Bag (cc) Pressure (psi)
0 5.0
.5 5.0
1 5.0
2 5.0
5.0
4 5.0
5 5.0
10 5.0
15 5.05
20 5.1
5.1
5.1
5.1
25 40 4.95
42.5 4.6
4.45
46 4.25
47 4.1
30 47.5 9.0
48 3.9
48.5 3.5
49 2.4
~50 0
35 The data obtained f rom the above experiment reproduced
is
in Figure 56, which plots
the volume of medication
dispelled
in cubic centimeters versus lbs/sq. in.
the output pressure in
The percent change in output pressure versus the volume
expelled is illustrated in Figure 57. Figure 57 illustrates
40 the remarkably steady output pressure of the medication
contained in medication bag 406 during the dispensation
cycle
produced by the platen pump 400.
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-ss
EXPERIMENT 3
100 cc Volume Test
In Experiment 3, the 50 cc medication bag 406 was
replaced with a 100 cc medication bag. The experiment
conducted in Experiment 2 above was repeated and the following
data was recorded.
TABLE II
Volume Expelled from Output Fluid
Medication Bact (cc) Pressure (psi)
0 5.1
5 4.6
10 4.7
4.75
15 30 4.75
40 4.6
50 4.55
60 4.4
70 4.2
20 80 3.95
g0 3.6
95 3.4
99 2.9
100 0
Figure 58 illustrates the output pressure over the
dispensation cycle. Figure 59 illustrates the percent change
in pressure over the dispensation cycle.
Increasing the volume of medication in the medication bag
406 from 50 cc to 100 cc remarkably did not dramatically
affect the change in pressure over the dispensation cycle on
the medication bag 406.
Referring to Figures 61°65, a fluid container 500 is
provided which may be readily used with any of the previously
disclosed embodiments of the platen pump. Preferably, the
fluid container 500 consists of a collapsible medication
reservoir or bag 510 in fluid communication with an effluent
fluid line 530. The effluent fluid line 530 may lead to an
administration set 540 shown in phantom in Figure 61. An
administration set is also shown in Figure 7. The effluent
fluid line 530 may be standard PVC tubing or other material
known to those skilled in the art.
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_ _ _ . , _ ~ _ _ _ ~~ ,... ......-. .~ ~... ..-, ; ,., ~ ~ r1 h a c a f i r c
t
surface 508 and a second generally opposing surface 509. The
first surface 508 and second surface 509 each have a
substantially planar central portion 512 and 513. In a
medication reservoir having a diameter of about 3.5 inches,
the generally planar central portions 512 and 513 typically
have a diameter in the range of from about 1.5 inches to about
3.0 inches, and preferably from about 2.4 inches to about 2.8 -
inches in the fully filled configuration.
. 10 A transition portion 514 surrounds the circular central
portions 512 and 513 of the first surface 508 and second
surface 509. Transition portion 514 comprises the
portion of the surface of the reservoir 510 which
deviates from the plane of first surface 508 or second
surface 509. Thus, transition 514 joins the flat
circular central portions 512 and 513 with radially
exterior-most sloping portions 516 when the medication
reservoir 510 is full as shown in Figure 62.
The radially exterior-most opposing sloping portions 516
are preferably joined at seam 520. By "seam" the present
invention also contemplates the outer peripheral edge of a
"seamless" bag such as may be produced through any of a
variety of molding or other plastic forming techniques known
in the art.
The first surface 508 and second surface 509 are
preferably formed from two sheets of a suitably .bondable,
inelastic material which exhibits suitable stability in the
presence of the intended.medication. The two sheets may be
joined at seam 520 with the use of any of a variety of joining
techniques, such as thermal bonding, solvent bonding,
adhesives or by a radio,frequency, weld. Preferably, the
medication reservoir is constructed from a PVC in U.S. Class
6 adequate for the delivery of drugs to a patient although
other materials known to those of skill in the art are
available and may be used.
As shown in Figures 63 and 65, the effluent fluid line
530 may be joined to the medication reservoir 510 through the
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use of a radio frequency weld or other bond at a joint 525.
Other means for joining the medication reservoir 510 and the
effluent fluid line 530, such as thermal bonding, solvent
bonding, adhesives or friction couplings will be readily
apparent to those of skill in the art.
Preferably, the medication reservoir 510 shown i-n Figures
61-65 has a diameter within the range of from about 3.5 inches
to about 5 inches and a height within the range of from about
0.5 inches to 1.0 inches. In general, the diameter of the bag
is influenced by the type of compression mechanism used. For
example, in the threaded clam shell embodiment of Figure 1, a
bag having a diameter of much greater than about four inches
would require a pump having too big a diameter to be
conveniently grasped by many patients. other compression
mechanisms, however, can be readily used with 5 inch, 6 inch,
or larger diameter bags. The height, or thickness of the bag
is typically governed by the desired volume and the maximum
desired diameter.
For many applications of the present invention, the fluid
container 500 preferably contains 50 cc of fluid. Although
these volumes are preferred in the present invention, other
sizes of fluid containers may be easily constructed using the
disclosure of the present invention. These varying size fluid
containers are contemplated by this disclosure.
An important aspect of the fluid container 500 is that it
is able to withstand pressures applied to it by the platen
pump disclosed herein. Further, preferably the fluid
container 500 is relatively inelastic in order to minimize the
change in pressure on. the fluid by the platen pump.
Advantageously, the disc like configuration of the present
embodiment of the fluid container 500 results in substantially
even pressure distribution throughout seam 520 when the
medication reservoir 510 and effluent fluid line 530 are in
the dispensation cycle. As discussed above, this uniform
pressure distribution minimizes the buildup of localized
stresses which could lead to a rupture of the container 5(~0.
Another advantage of the fluid container 500 is that a
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plurality of filled fluid containers 500 may be easily stored
such as in a refrigerator in a stacked configuration.
Further, when the fluid containers 500 are empty, the volume
required to dispose of them is very small because the fluid
containers 500 are flat and flexible when empty.
In addition to a fluid container with a circular outer '
profile, other shaped reservoirs may be constructed in
accordance with the disclosure of the present invention. For
example, referring to Figures 66-69, a square medication
reservoir 560 having a generally planar square top surface 562
and bottom surface 563 may be used in connection with the
various embodiments of the platen pump. In a similar fashion
to the circular medication reservoir, the top and bottom
surfaces of the square medication reservoir 560 have generally
square flat central portions, transition portions 564 and
radially exterior-most sloping portions 566. Preferably, a
high frequency weld is used to join seam 572 and attach the
medication bag 560 to the effluent fluid line 570 at a joint
568.
Referring to Figures 70-73, a diamond-shaped fluid
reservoir 561 may be provided. Further, a hexagonal fluid
reservoir 580 and 581 (Figures 74-81) with a joint 582 on one
of the sides of the hexagonal medication reservoir 580
(Figures 74-77) or a joint 583 at one of the corners of the
hexagonal medication reservoir 581 (Figures 78-81) may be
provided. Referring to Figures 82-89, fluid containers having
medication reservoirs with eight sides (586), ten sides (588),
twelve sides (590) or twenty-four sides (592) may be provided.
It is therefore intended that such changes in fluid containers
be covered by the following claims.
Of course, it should be understood that various changes
and modifications to the preferred embodiments described above
will be apparent to those skilled in the art. If the
mechanical advantages of the threads can be done without, the
pressurizing shell and fluid containing shell could be held
together by latches. As already mentioned, other methods of
pressurization may be used in place of the conical helical
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WO 93/14797
-s~-
spring. In addition, further variations of the fluid
container can be devised without departing from the present
invention. These and other changes can be made without
departing from the spirit and scope of the invention and
witi~out diminishing its attendant advantages.
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