Note: Descriptions are shown in the official language in which they were submitted.
CA 02571731 2006-12-21
PERISTALTIC PUMP COMPRISING A LOCKABLE REMOVABLE CASSETTE
This application is a continuation application of International Application
No.
PCT/FR2005/001524 filed on June 17, 2005, the entire disclosure of which is
incorporated
herein by reference, which claims the benefit of French Patent Application No.
04106764
that was filed June 22, 2004, the entire disclosure of which is incorporated
herein by
reference.
FIELD
The field of the disclosure relates generally to peristaltic pumps. More
specifically, the disclosure relates to cassettes that are readily attached
and detached from
the pump.
BACKGROUND
Peristaltic pumps have been known for many years, and are commonly used for
medical and research purposes. Peristaltic pumps move a liquid through a tube
without
any part of the pump ever touching the liquid. As a result, it is possible to
pump liquids,
such as blood, which are sensitive to external contamination. Typically, a
pump
comprises rotating rollers that compress a part of the flexible tube as they
move, which
propels the liquid through the tube.
For example, such a pump is described in document EP 339 857, the entire
disclosure of which is incorporated herein by reference. The flexible tube
must withstand
the compressive force while remaining leak proof. The pump in the aforesaid
document
includes removable cassettes that each include a tube and a means for securing
the
cassettes to the pump frame so that the tube is held against the rollers to
ensure good
contact between tube and rollers. The means described for securing the
cassettes include a
notch and cam arrangement which requires two hands to operate a release lever
to unlock
the cassette from the pump. Additionally, a second hand simultaneously holds
the cassette
to prevent it from jumping off of the frame. What is needed is a peristaltic
pump cassette
which may be easily mounted to and dismounted from a peristaltic pump using a
single-
hand.
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CA 02571731 2006-12-21
SUMMARY
A mechanism for mounting and dismounting a removable cassette from a
peristaltic pump is provided. The removable cassette is easily mounted to a
pump frame
of the peristaltic pump using a single-hand of a user. Additionally, a similar
motion both
mounts the cassette to the pump frame and dismounts the cassette from the pump
frame.
In an exemplary embodiment, a peristaltic pump includes, but is not limited
to, a
pump frame, a plurality of rollers configured to mount to the pump frame, an
actuator
operably coupled to move the plurality of rollers, and a cassette. The
cassette includes a
cassette frame and a cam positioned to compress a tube against the plurality
of rollers.
The cassette is mountable to the pump frame by applying pressure in a first
direction to the
cassette frame and is dismountable from the pump frame by applying pressure in
the first
direction to the cassette frame.
In another exemplary embodiment, a method of using a cassette in a peristaltic
pump is provided. A cassette frame of a cassette is positioned for mounting to
a pump
frame of a peristaltic pump. A hook is engaged in a notch to mount a first end
of the
cassette frame to the pump frame. A pin slides in a first direction to accept
a second end
of the cassette frame. The pin slides along a ramp and is held in a seat of
the ramp to
mount the cassette to the peristaltic pump.
Other principal features and advantages of the invention will become apparent
to
those skilled in the art upon review of the following drawings, the detailed
description,
and the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
Exemplary embodiments of the invention will hereafter be described with
reference to the accompanying drawings, wherein like numerals denote like
elements.
Fig. I is a perspective view of a peristaltic pump head with a cassette in a
position
to be mounted onto the pump in accordance with an exemplary embodiment.
Fig. 2 is a perspective view of the peristaltic pump head of Fig. 1 with the
cassette
mounted on the pump in accordance with an exemplary embodiment.
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Fig. 3 is a front cross sectional view of the pump head of Fig. 2, and
designated by
the line along III - III with the cassette in accordance with an exemplary
embodiment.
FIG. 4 is a front perspective view of the cassette FIG. 2 in a mounted
position.
FIG. 5 is a side perspective view of the cassette as in FIG. 2.
FIG. 6 is a larger scale view of a ramp of the cassette of FIG. 5 in
accordance with
an exemplary embodiment.
FIGS. 7-11 are partial perspective views showing the steps in mounting the
cassette to a pump frame and dismounting the cassette from the pump frame
using a pin
and a ramp in accordance with an exemplary embodiment.
FIGS. 12 and 13 are lateral views of the pin indicating the longitudinal
motion in
accordance with an exemplary embodiment.
DETAILED DESCRIPTION
While a single style of cassette has been illustrated in the figures, a
plurality of
cassettes similar in construction to that described are contemplated. For the
purposes of
this disclosure and unless otherwise specified, "a" or "an" means "one or
more."
With reference to FIGS. 1-3, a peristaltic pump head 2 of a peristaltic pump
is
shown in accordance with an exemplary embodiment. The peristaltic pump may
include
peristaltic pump head 2 and an actuator. Peristaltic pump head 2 may include a
crankcase
4, a frame 5, a plurality of rollers 16, and a removable cassette 6. Frame 5
may include a
center support 14, a front wall 10, a back wall 8, a first brace 40, and a
second brace 42.
Crankcase 4 mounts to front wall 10 and includes an axis of symmetry 18. As
used in this
disclosure, the term "mount" includes join, unite, connect, associate, insert,
hang, hold,
affix, attach, fasten, bind, paste, secure, bolt, screw, rivet, solder, weld,
and other like
terms.
In the exemplary embodiment of FIG. 1, the plurality of rollers 16 includes
eight
rollers symmetrically arranged around the axis of symmetry 18. The rollers are
mounted
in a rotating fashion on central support 14. In the exemplary embodiment of
FIG. 1, each
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roller of the plurality of rollers 16 has a spherical shape and rotates about
an axis parallel
to the axis of symmetry 18. Central support 14 rotates around the axis of
symmetry 18.
The actuator is operably coupled to rotate the plurality of rollers 16. For
example,
the actuator may include a rotor connected to the plurality of rollers through
a shaft 1 I as
known to those skilled in the art. The actuator may be any device as known to
those
skilled in the art for causing rotation of the plurality of rollers. Exemplary
actuators
include an electric motor, a servo, stepper, or piezo motor, a pneumatic
actuator, a gas
motor, etc.
Front wall 10 and back wall 8 define between them a cassette housing 12 sized
to
accommodate one or more removable cassettes 6. Front wall 10 and back wall 8
are
linked together by a first brace 40 and a second brace 42 which extend
parallel to the axis
of symmetry 7, and act as a support and locking mechanism for the removable
cassette(s)
6. With reference to FIG. 1, the removable cassette 6 is shown released from
the two
braces 40, 42. With reference to FIG. 2, the removable cassette 6 is shown
mounted to the
two braces 40, 42 for use with the peristaltic pump. A plurality of cassettes
6 may be held
in the cassette housing 12, side by side, parallel to one another, and/or in
contact with each
other. When mounted to frame 5, removable cassette 6 extends parallel to front
wall 10
and back wall 8 in a plane, which is perpendicular to the axis of symmetry 7.
With reference to FIGS. 2-5, a front perspective view of removable cassette 6
is
shown in accordance with an exemplary embodiment. Each removable cassette is
basically flat. The removable cassette 6 includes a cassette body 20. In the
exemplary
embodiment of FIGS. 2-5 the cassette body 20 has essentially an inverted U
shape formed
by a front wall 21 and a back wall 25 with a frame edge 27 extending between
the front
wall 21 and the back wall 25. A cavity 29 (shown with reference to Fig. 5) is
formed
between the front wall 21 and the back wall 25. The inverted U shape of
cassette body 20
is formed by the front wall 21 and the back wall 25 includes legs 24.
The removable cassette 6 includes a cam 30 accommodated in cavity 29. Cam 30
has an essentially flat rectangular shape with a saddle-shaped hollow formed
by a lower
edge designed to face the plurality of rollers 16. The front wall 21 and the
back wall 25
partially cover each side of cam 30.
With reference to FIG. 3, a front cross sectional view of the removable
cassette 6
mounted to frame 5 is shown in accordance with an exemplary embodiment. A
flexible
tube 22 is mounted to cassette frame 20 in a removable manner. In particular,
flexible
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tube 22 is held in slots 26. The tube 22 rests against the lower edge of cam
30. The part
of tube 22 resting against the lower edge extends between the parts of tube 22
housed in
slots 26. The removable cassette 6 includes a biasing member 32. In an
exemplary
embodiment, biasing member 32 is a blade spring. Tension on the cam 30 may be
modulated by a control knob 34 extending from an upper edge of the cassette
body 20.
The removable cassette 6 mounts to the peristaltic pump head 2 at the ends of
legs
24 adjacent to slots 26. For example, as shown in FIGS. 4 and 5, a hook 44
extends from
one of the legs 24 and is capable of engaging in a notch 46 in the second
brace 42 of frame
5. One of the legs 24 has a ramp 52 (shown with reference to FIG. 5) capable
of engaging
a pin 50 in first brace 40 of frame 5. When the removable cassette 6 is
mounted to frame
5, a shoulder 48 of the removable cassette 6 rests on an upper edge of second
brace 42.
For each cassette position, second brace 42 has a notch 46 and first brace 40
has a pin 50.
FIGS. 7-13 illustrate a pin 50 according to an exemplary embodiment. Exemplary
pins 50 have an elongated cylindrical body 55 with a head 56 at a first end of
the
cylindrical body 55 and a distal end 54 opposite head 56 of the cylindrical
body 55. The
pin 50 is rigidly or slidably encased in a rectangular parallelepiped housing
51. The distal
end 54 of the pin 50 extends beyond an inside face 53 of first brace 40. The
pin 50 and the
parallelepiped housing 51 is slidable within an aperture 60, the aperture 60
extending from
an inner face 53 of first brace 40 to a cavity 67 located within first brace
40, or near an
outer face 57 of first brace 40. The head 56 of the pin 50 resides in cavity
67 inside first
brace 40.
The aperture 60 allows the pin 50 to slide back and forth, along a
longitudinal axis
of the pin 50, while being retained within first brace 40 by a retaining clip
63. The
retaining clip 63 has a shape that is colnplementary to that of cavity 67. The
retaining clip
63 includes a fork 68 through which the distal end 54 of the pin 50 is
inserted such that the
fork 68 maintains the head 56 of pin 50 within the aperture 60. The retaining
clip 63 also
has a leaf spring 66 which exerts a force on head 56.
When a force is applied to the distal end 54 of the pin 50 in a direction
parallel to
the longitudinal axis of the pin 50, the pin 50 is pushed against leaf spring
66 and into first
brace 40 (FIG. 12). When the force is removed, the leaf spring 66 exerts a
force on the
head 56 of the pin 50 to return it to the original position (FIG. 13).
The aperture 60 allows the pin 50 to pivot freely within the aperture 60
around an
axis 64, indicated in FIGS. 11 and 13, which extends perpendicular to the
longitudinal axis
CA 02571731 2006-12-21
of the pin 50. The parallelepiped housing 51 of the pin 50 guides it as it
moves within
aperture 60.
FIGS. 5 and 6, illustrate a ramp 52 according to an exemplary embodiment. The
ramp 52 is integrally formed in an outer side of one of the legs 24. In
describing the ramp
52, it will be apparent to those of skill that the ramp is multileveled. The
ramp 52 is
integrally formed to have different levels of relief from the full depth of
the ramp 52 into
the leg 24 of the removable cassette 6. The same areas of the ramp 52 may also
be of
varying levels. For example, area 70 of the ramp 52 is angled such that it is
adjacent to
exit area 90 along facet 71, and area 70 is also flush with launching area 78
along facet 75,
despite launching area 78 being less deeply cut into leg 24 (i.e. having a
greater relief)
than exit area 90. Area 70 is more deeply cut at edge 72 than at facet 75.
Launching area
78 may also be sloped such that a point proximal to facet 71 is of higher
relief than an area
proximal to facet 72 (see FIG. 8). As such, the ramp 52 is stepped from a
"high" point of
the ramp at launching area 78 to a lower point of exit area 90, to the lowest
point along
edge 72 in area 70. Each of the successive facets 72, 73, 75, 76 along the
direction of
ramp 52 is a step down from the areas previous to the facet along the
direction of travel
along the ramp 52.
As used herein, facet is used to refer to an area that may be flush, but of a
different
plane than that of an adjacent area (e.g. FIG. 6), or to an area having a
higher or lower
relief whereby a wall separates the adjacent areas (e.g. FIG. 8).
The form and function of the various elements of the peristaltic pump 2 and a
removable cassette 6 will be more apparent using a description of a method for
mounting
and dismounting the removable cassette 6.
The hook 44 of one of the legs 24 of removable cassette 6 is engaged in the
notch
46 of the second brace 42. The ramp 52 of the removable cassette 6 is brought
into close
proximity with the distal end 54 of pin 50. As pressure is applied to the
cassette body 20,
tube 22 is compressed, and the distal end 54 of pin 50 enters the ramp 52 at
area 70. As
pressure is continuously applied, the distal end 54 of pin 50 follows a course
in which the
distal end 54 of pin 50 initially encounters facet 71 and enters launching
area 78, the
"highest" or shallowest portion of ramp 52. A wall 92 on relief area 71 aids
in guiding the
distal end 54 to the launching area 78. Pressure is continuously applied to
the cassette
body 20 until the distal end 54 encounters a wall 80 that prevents further
travel in such a
direction. As the pressure is released, the compression of tube 22 recoils the
removable
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cassette 6 in a reverse direction launching the distal end 54 over facet 72
from the
launching area onto a seating area 82 and into a seat 84, thus securing the
removable
cassette 6 within the cassette housing 12.
As the distal end 54 of pin 50 enters area 70 of the ramp 52, the contact of
the
distal end 54 with the area 70 of the ramp 52 causes the pin 50 to move in a
longitudinal
direction toward the cavity 67 of the first brace 40, thus tensioning leaf
spring 66 against
head 56 and about axis 62. As the distal end 54 moves from areas of higher
relief in the
ramp 52 to those of lower relief, the leaf spring 66 exerts a force on pin 50
causing the
distal end 54 to remain in contact with the ramp 52.
When dismounting the removable cassette 6 from the cassette housing 12 is
desired, pressure is again applied to the cassette body 20, with facet 72
preventing
"reverse" travel of the distal end 54, and encouraging "forward" travel of the
distal end 54
over facet 73, onto landing area 86 as tube 22 is compressed. A wall 88
prevents further
compression of the tube 22. As pressure is once again released, the tube 22
exerts a recoil
force in the direction opposite to the applied pressure, with the distal end
54 traveling
through exit area 90, thus dismounting the removable cassette 6 from the
cassette housing
12.
The motions required to mount and dismount removable cassette 6 from the
peristaltic pump head 2 may be performed by a single hand of a user and are
ergonomically efficient. The pivoting of the pin 50 in aperture 60 allows for
lateral travel
of the removable cassette 6 during insertion and removal. A user can pivot the
dismounted removable cassette 6 to separate the released leg 24 from the first
brace 40,
and then separate the hook 44 from the second brace 42 to remove the cassette
from its
support.
Therefore, the presently embodied removable cassette and pump frame allows the
user to mount the removable cassette 6 onto the peristaltic pump head 2 by
simply
applying pressure to the top of the removable cassette 6. The same action
allows the user
to dismount and remove the removable cassette 6. These actions can therefore
be
performed simply and quickly and, if required, one after the other or even
simultaneously
for several of the pump's cassettes.
It should be noted that these operations are accomplished without the user
ever
touching the tube. These operations use the compressibility and recoil of the
tube to
define limit positions, which prevent undue action on the tube both during
these operations
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and when the cassette is in its functional position on the pump head. In
particular, there is
no risk that the tube will be excessively stressed during these operations.
This is
particularly important to prolong the lifetime of the tube. Typically, the
lifetime of a
peristaltic pump tube is directly impacted by the pump's operation. As a
result, the
lifetime of the peristaltic pump tube may be considerably reduced if overly
stressed.
While some embodiments have been illustrated and described, it should be
understood that changes and modifications can be made in accordance with
ordinary skill
in the art without departing from the invention in its broader aspects as
defined in the
following claims. For example, the relative positions of a hook and a notch
may be
reversed such that the hook is associated with a brace and the notch is
associated with a
leg of the removable cassette and/or the relative positions of a pin and a
ramp may be
reversed such that the ramp is associated with a brace and the pin is
associated with a leg
of the removable cassette.
The foregoing description of exemplary embodiments of the invention have been
presented for purposes of illustration and of description. It is not intended
to be
exhaustive or to limit the invention to the precise form disclosed, and
modifications and
variations are possible in light of the above teachings or may be acquired
from practice of
the invention. The embodiments were chosen and described in order to explain
the
principles of the invention and as practical applications of the invention to
enable one
skilled in the art to utilize the invention in various embodiments and with
various
modifications as suited to the particular use contemplated. It is intended
that the scope of
the invention be defined by the claims appended hereto and their equivalents.
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