Note: Descriptions are shown in the official language in which they were submitted.
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FLUID HANDLING DEVICES, IN PARTICULAR FOR MEDICAL USE
This invention relates to fluid handling devices, such as medical syringes,
in which a plunger is used to deliver fluid from a barrel of the device via a
needle.
For safety reasons, e.g. to avoid needle stick injuries, it is desirable that
the needle is retracted into the barrel following delivery of the fluid. Our
prior
European Patent No. 776225 discloses a fluid handling device provided with a
needle
l0 retraction mechanism of this type.
The present invention seeks to provide a fluid handling device having a
simplified needle retraction mechanism.
According to the present invention there is provided a fluid handling
device comprising a barrel for containing fluid to be delivered through a
needle, a
needle-mounting hub at one end of the barrel, a biasing element arranged to
urge the
hub inwardly of the barrel, a stop element blocking inward movement of the hub
into
the barrel, a hollow plunger which is movable within the barrel to deliver
fluid from the
barrel via the needle and has at its forward end a portion which is severable
in response
to movement of the plunger over the final part of, or at the conclusion of,
its delivery
stroke to allow retraction of the needle-mounting hub into the hollow plunger,
the hub
and the stop element being formed as plastics mouldings in such a way that the
stop
element is axially captive with the hub and the plunger being arranged to
disengage the
stop element and the hub during said final part of, or at the conclusion of,
the delivery
stroke to allow the biasing element to drive the needle into the hollow
plunger.
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The stop element may incorporate an integral seal, e.g. a lip seal, which
may be annular so as to encircle the stop element.
The stop element and the hub may have interengaged formations at the
location of the moulding interface which are caused to separate from one
another
during said final part of, or at the conclusion of, the delivery stroke of the
plunger.
The stop element and the hub may alternatively or additionally be at least
partially united, e.g. partially fused, together at the moulding interface,
the arrangement
being such that the connection is fractured or broken during said final part
of, or at the
conclusion of, the delivery stroke.
The hub may be elongate and may have a central bore for reception of the
needle.
The needle-receiving bore may be of reducing cross-section.
The hub may be produced with some degree of draft, i.e. so as to be of
reducing cross section in a direction of travel of the plunger during its
delivery stroke.
The biasing element may be a helical spring, usually a compression spring,
which may be arranged in encircling relation with the hub. One end of the
spring may
coact with a forward end of the barrel or an end cap attached to the main body
of the
barrel and the opposite end of the spring may coact with the hub at a location
inwardly
of the forward end of the barrel.
The forward end of the plunger may comprise a rim portion and a central
blocking portion, the latter forming said severable portion.
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The arrangement may be such that, during the final part of or at the
conclusion of the plunger delivery stroke, the rim portion of the plunger is
arranged to
engage the stop element while the hub is arranged to engage the blocking
portion, the
engagement between the two sets of components being effective to free the hub
from
the stop element and to free the blocking portion from the rim portion at
least to the
extent necessary to allow the hub to enter the interior of the plunger.
Preferably the hub is freed from the stop element before the blocking
portion is at least partially freed from the rim portion; however, if desired
the blocking
l0 portion may be freed first or alternatively the hub and the blocking
portion may be
freed substantially simultaneously.
The arrangement may be such that the hub and stop element are united
together by the moulding process to afford a well-defined threshold at which
they break
15 away from one another in response to the application of force to the stop
element in the
course of operating the plunger.
Preferably one of the components (hub and stop element) is produced as a
plastics moulding in a mould having moulding surfaces defined, in part, by the
other
20 component, i.e. moulding of one component being effected with the other
component
in situ.
The two portions may be of plastics materials having different chemical
compositions and/or characteristics or they may both be of substantially the
same or a
25 similar plastics material.
The hub and stop element may be capable of being broken away from each
other without deformation of either of the two portions and, to this end, the
moulding
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interface may be shaped so that no deformation of either component occurs when
breaking one from the other.
Alternatively, the hub and the stop element may be interlocked with each
other so that some deformation of at least one of the parts occurs when
effecting the
break.
At the moulding interface, an annular surface of one of the components
may be have a configuration complementary with an annular surface of the other
component.
The annular surfaces may be cylindrical or of other configuration, e.g.
conical.
Z5 At the moulding interface, the components may intimately contact each
other with a degree of fusion bonding consistent with securing fracture
preferentially at
the interface region during the break.
The assembly of the hub and stop element may include a detent
arrangement acting between the components. The detent arrangement may be
provided
at or in the vicinity of said moulding interface. For example, the hub and the
stop
element may, by virtue of the mould design, have interengaging formations
which lock
the components together to prevent separation, and at least one of the
formations may
be resiliently deformable to allow the disengagement of the formations on
application
of sufficient loading to the stop element relative to the hub.
Resistance to separation of the two components may additionally or
alternatively be afforded by the nature of the interaction between material or
materials
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of the hub and the stop element at the moulding interface. For instance, there
may a
shrink type fit between the components at the moulding interface obtained by
material
shrinkage during cooling following the moulding process.
As a further addition or alternative to the detent arrangement and/or shrink
type fit mentioned above, resistance to separation may be provided by fusion
bonding
between the components at the moulding interface. Such fusion bonding may
range
from relatively weak, e.g. as a result of some degree of diffusion of material
from one
component across the moulding interface into the other component, through to
l0 relatively strong.
Depending on the nature of interaction desired between the hub and the
stop element at the moulding interface, the material or materials from which
said
portions are produced may be selected so as to secure the desired extent of
fusion
bonding, if any. For example, if negligible fusion bonding is desired, the
materials
employed will usually differ in chemical and/or physical characteristics and
will be
such that no significant diffusion of material takes place across the moulding
interface
as a result of the moulding process. Similarly the materials can be
appropriately
selected to obtain the desired degree of fusion bonding where there is a
requirement to
2o develop a fusion bond at the moulding interface.
In the latter case for example, the hub and the stop element may be
composed of the same material 'so that significant fusion of the material
takes place
between the two components.
The width of the moulding interface and hence the zone of contact
between the two components may be selected with regard to the required
effectiveness
of the seal and/or with regard to the resistance to separation of the
components required
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at said interface. For instance, a given degree of resistance may be secured
by a
relatively narrow interface where the components axe strongly fusion bonded
together
whereas a wider interface may be required if resistance is afforded by
shrinkage andJor
a weak fusion bond.
Irrespective of how the hub and the stop element are coupled together, the
arrangement may be such that the resistance to separation of the two parts is
greater
with respect to forces applied in one direction compared with forces applied
in the
opposite direction.
Where one part is moulded in advance of the other and the second part is
then moulded with the first part in situ, the first part to be moulded may
have a higher
heat distortion temperature than the second part so that the first part is not
deformed
during moulding of the second part.
The stop element and the hub may advantageously be formed in a two-
shot moulding process in which one component, e.g. the hub, is initially
formed and
located so that an annular surface thereof forms a boundary surface of the
mould cavity
in which the other component is produced so that, during formation of the
second
component, an annular surface of the latter is conformed with the annular
surface of the
first component.
The manner of coupling together the hub and the stop element as referred
to in the preceding paragraphs may also be employed to couple together the rim
portion
and the blocking portion, e.g. as disclosed in our International Patent No.
GBOO104573,
the entire disclosure of which is incorporated herein by this reference.
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Other aspects of the invention include a needle-mounting hub assembly
produced as a two-shot moulding and comprising a hub and a stop element
captive with
the hub, and a method of manufacturing such an assembly.
The invention will now be described by way of example with reference to
the accompanying drawings in which:
Figure 1 is a side view of a syringe which may embody features of the
present invention;
1o
Figure 2 is a fragmentary sectional view of the syringe showing the
plunger approaching the final part of its delivery stroke;
Figure 3 is a similar view to that of Figure 2 but with the plunger shown at
i5 its point of initial contact with the crown associated with the needle-
mounting hub;
Figure 4 is similar view to that of Figure 2 at the conclusion of the plunger
delivery stroke and showing the needle undergoing retraction into the
2o hollow plunger; and
Figure 5 is detail view of the needle-mounting hub and crown.
Referring now to the drawings, the disposable medical syringe 10
25 comprises a hollow barrel 12, from the rear of which (upper end as viewed
in Figure 1)
protrudes a plunger 14. A seal 15 is mounted on the plunger to ensure a fluid
tight seal
with the internal wall of the barrel. The barrel 12 includes an end cap 12A
including a
cylindrical section 16 which is engaged with a annular collar 1 ~ of the main
body of the
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barrel 12 and a generally conical section 20. The end cap 12A may be
permanently
bonded to the main body of the barrel 12 or it may be releasably attached
thereto. A
needle-mounting hub 22 is accommodated within the end cap 12A and is encircled
by a
spring 24 which engages at its forward end with a flange 26 of the conical
section 20
and at its rear end with a radial shoulder 28 on the hub 22 and serves to bias
the hub 22
and needle 30 inwardly relative to the barrel 12.
The hub 22 is of generally cylindrical configuration and has an axial bore
32 for reception of the needle 30. The bore 32 may be a throughboxe as
illustrated. The
to bore 32 is of tapering configuration to allow the needle to be fitted to
the hub as a
press-fit or by spin-welding either before or after the end cap 12A has been
assembled
to the main body of the barrel.
Rearward movement of the hub and needle assembly is prevented by a
stop element in the form of a crown 34 which is carried by hub 22 and is
received
within the annular collar 18. The crown 34 is of generally cylindrical
configuration and
comprises a forward portion 36 incorporating an integral annular lip seal 38
and a
reduced diameter portion 40. As shown in Figure 5, prior to insertion into the
annular
collar 18, the lip seal flares outwardly as shown in Figure 5 and is
resiliently flexible so
2o that, on insertion into the collar, it is deflected radially inwardly so as
to bear against
and make sealing engagement with the inner surface of the collar 18. At its
forward
end, the collar 18 includes a lead-in portion 42 to facilitate insertion of
the crown 34.
The hub and crown are produced as plastics mouldings by two-shot
moulding which serves to integrate the two components and render them captive
with
each other so that they effectively constitute a one-piece component designed
to
fracture at the interface between the hub and the crown when subjected to a
predetermined forwardly directed axial force. In addition, the assembly of hub
and
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crown incorporates the lip seal 38 which may be integral with the crown since
the latter
can be moulded from polyethylene for example. In this way, needle mounting and
sealing at the forward end of the barrel is considerably simplified compared
for
example with the arrangement disclosed in our prior European Patent No.
776225. At
the interface between the hub and crown, the components may have interfitting
formations, e.g. mating frusto-conical surfaces, which may determine at least
in part the
force needed to separate the two components.
The plunger 14 is hollow and has a closed trailing end. The forward end of
to the plunger is arranged to receive a closure assembly comprising an insert
52 which
engages firmly in the plunger to form an end wall of the plunger while
defining an
aperture 54 which is sufficiently large to allow the needle 30 and hub 22 to
pass
through during needle retraction.
The insert 52 comprises a rim portion 55 fitted with a forwardly projecting
blocking portion 56 of generally frusto-conical configuration so that the
blocking
portion 56 closes and seals the aperture 54. The blocking portion 56 and rim
portion 55
seal the forward end of the plunger to prevent ingress of liquid into the
plunger interior
from the interior of barrel 12.
The rim and blocking portions 55, 56 are also formed as plastics
mouldings by two-shot moulding so that the two portions 55 and 56 are
integrated and
captive with each other. A closure assembly of this form is disclosed in
International
Patent Application No.GB00/04573 (the entire contents of which are
incorporated
herein by this reference) and the design of these components may be as
described and
illustrated therein. The rim and blocking portions 55, 56 are coupled together
in such a
way that they can be separated from each other in response to the application
of a
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predetermined axial force as described in International Patent Application No.
GB00/04573.
Although the hub 22 and crown 34 and also the rim and blocking portions
55, 56 may have interengaging formations at the interface between them such
that these
formations render the respective components captive to one another and
contribute to
the resistance to separation of the components, such interengaging formations
are not
essential as long as sufficient resistance to separation at the interface is
available, e.g.
as described below. Whether or not such formations are provided, it will be
appreciated
1o that the "force-to-break" or allow the components to separate from each
other can be
tailored according to requirements by appropriate design of features such as
the angle
of the interface between the two parts and/or the surface texture present at
the interface
and/or extent of the interface.
In accordance with a preferred feature of the invention, each assembly
comprising parts 22, 34 and 55, 56 respectively is produced by a two-shot
moulding
process, for instance a first stage in which the inner part 22, 56 is produced
followed by
a second stage in which the outer part 34, 55 is moulded onto the inner part
22, 56
thereby connecting the two parts together, e.g. through the interengaging
formations (if
2o present) and/or through a zone of intimate contact which sealingly engages
the two
parts with each other at the moulding interface. Two-shot moulding technology
may be
carried out for instance using a mufti-stack moulding machine such as
available from
Milacron Inc of Cincinnati, Ohio, USA in which a two-sided pivoting centre
platen
allows two simultaneous moulding operations to be carried out. The process
starts with
a preform injected into cavities on one mould face. The mold opens, the centre
platen
swivels through 180 degrees in a vertical plane, locks into position, the mold
closes,
and a second material component is inj ected. At the same time, another pre-
form is
injected into the opposite mould face of the centre platen. In this way, a
preforrn and a
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completed part are injection-moulded simultaneously during each cycle of
operation
using two plastic melts which may be the same material, similar or different
materials.
A two-shot moulding machine is also disclosed in US-A-6139305.
To prevent the inner and outer parts 22, 34 and 55,56 welding together
inseparably during the moulding process, the two parts may be moulded using
materials
which are compatible with each other and have different characteristics.
However,
some degree of fusion bonding between the rim and closure parts may be
desirable, e.g.
to ensure sealing and, where desired, to play a role in predetermining the
loading
1o necessary to break the blocking portion away from the rim portion.
The closure assembly in Figures 2 to 4 is shown fitted into the forward
end of the plunger 6; however, in an alternative embodiment, the rim portion
may be
formed integrally with at least the forward end portion of the plunger so that
the
plunger and rim portion can be produced as a single moulding. For example,
both the
plunger and rim portion may be made from a plastics material such as
polyethylene or
polypropylene. In this case, the other end of the plunger may be closed by an
end cap.
The parts 22, 34 and 55, 56 may be held captive to one another by
interengaging formations (as illustrated for parts 22, 34) which may act as a
detent-type
arrangement. However, instead of or in addition to such a detent-type
arrangement, the
parts may be rendered captive to one another as a result of some degree of
fusion or
bonding of the materials at the interface and/or by virtue of an interference
or shrink
type fit between the parts at a zone of contact, e.g. as illustrated in Figure
3 of
International Patent Application No. GB00/04573. The shrink fit may be
obtained
during the moulding process by moulding the outer part 34, 55 around the inner
part 22,
56 and exploiting material shrinkage on cooling to secure the interference
fit. Where
the inner part is held captive in this way, there is not necessarily any
significant fusion
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bonding between the materials although, if desired, the materials) may be
selected sa
that such fusion bonding is present, e.g. as a result of some degree of
diffusion of
material between the two parts.
When the hub and crown are assembled as shown in Figure 2, the
rearward end of the lip seal 3 ~ engages a shoulder 44 while the reduced
diameter
portion 40 of the crown projects beyond an annular end wall 46 of the main
body of the
barrel 12 for co-operation with the forward end of the plunger 14 as described
below.
Likewise, the blocking portion 56 is arranged for entry into the opening
defined by the
1o crown 34 to contact the rearward end of the hub 22.
In operation, as the plunger 14 is displaced inwardly into the barrel 12, the
contents of the barrel are delivered through the needle. As the plunger
approaches
completion of its stroke, the condition shown in Figure 3 is reached in which
the rim
portion 55 is in contact with, or about to contact, the rearward end of the
crown 34
while the blocking portion S6 is in contact with, or about to contact, the
rearward end
of the hub 22. By appropriate design of the components, the axial force
developed by
continued displacement of the plunger to the completion of its stroke (see
Figure 4)
results in the connections between the parts 22, 34 and 55, 56 being broken,
e.g.
2o fractured, freeing the hub 22 from the crown 34 and freeing of the blocking
portion 56
from the rim portion 55.
More specifically, the rim portion 55 displaces the crown 34 forwardly
while engagement between the hub, which is blocked from forward movement by
the
forward end of the portion 12A, and the blocking portion 56 exerts a
rearwardly
directed force on the latter. Under these conditions, once the connections
rendering
parts 22, 34 and 55, 56 captive with one another are broken, the spring 24 is
no longer
restrained and becomes effective to propel the hub through the crown, through
the
aperture created by freeing of the blocking portion 56 and into the interior
of the
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plunger thereby concealing the needle and avoiding the risk of needle stick
injury once
the contents of the syringe have been delivered. Freeing of the hub and the
blocking
portion may occur substantially simultaneously or in sequence, freeing of the
hub first
being currently preferred. The forces required to effect freeing of the hub
and the
blocking portion may be readily tailored to requirements by for example
appropriate
selection of the dimensioning/configuration of the components, tuning of the
two-shot
moulding process etc.
In the course of being displaced by the rim portion 55, the extent of travel
l0 of the crown 34 is such that the lip seal 38 remains in sealing contact
with the internal
surface of the collar 18. Although the hub may be of generally cylindrical
configuration, it is desirable to produce it with a draft (i.e. of reducing
cross-section
from its trailing end towards its forvVard end) so as to facilitate easy ej
ection and
prevent binding of the spring against the peripheral surface of the hub. The
hub may be
manufactured so that, when assembled as shown in Figure 2, there is a small
clearance
between the shoulder 28 and the adjacent end wall of the end cap 12A thereby
eliminating any risk of the hub/crown hub connection being broken during
assembly of
the syringe (i.e. because of tolerance variations in the length of the hub).
This clearance
is taken up as when the rim portion of the plunger initially contacts and
begins to
2o displace the crown.
From the foregoing, it will be seen that the present invention as embodied
in the illustrated syringe results in a much simplified design compared with
that of
European Patent No. 776225. Advantages that can be realised include the
following:
better control of the release force needed to separate the hub from the
crown since the two-shot moulding can be tuned to requirements;
the possibility of increasing the diameter of the spring to allow a shorter,
more robust design;
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an integral lip seal rather than an "O" ring seal which reduces the risk of
premature firing and low pressure failures;
a shorter travel of the crown with reduced risk of accidental firing when
expelling air;
reduced tolerance dependency;
greater control of the timing/sequencing of the needle retraction process;
simplified assembly since the hub/crown/lip seal effectively comprises a
single component;
redesign of the end cap 12A to enable easier moulding;
1o possibility of needle insertion into the hub after the latter has been
installed, thereby reducing the risk of needle damage;
hub design permits press-fit or spin-weld needle fixation;
ullage can be reduced and be more consistent; and
higher locking force (inserting needle into vials etc) as the hub and crown
are moulded in one piece.
Whilst endeavouring in the foregoing specification to draw attention to
those features of the invention believed to be of particular importance, it
should be
understood that the Applicant claims protection in respect of any patentable
feature or
2o combination of features disclosed herein and/or shown in the drawings
whether or not
particular emphasis has been placed on such feature or features.
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