U.S. patent application number 15/193378 was filed with the patent office on 2016-10-20 for apparatus for delivering foam.
The applicant listed for this patent is BTG INTERNATIONAL LMIITED. Invention is credited to Julian Richard DIXON, Christopher John HURLSTONE, Stuart Brian William KAY, Andrew Gordon POCOCK.
Application Number | 20160303328 15/193378 |
Document ID | / |
Family ID | 29764452 |
Filed Date | 2016-10-20 |
United States Patent
Application |
20160303328 |
Kind Code |
A1 |
KAY; Stuart Brian William ;
et al. |
October 20, 2016 |
APPARATUS FOR DELIVERING FOAM
Abstract
Apparatus, e.g. a syringe, for dispensing foam includes means
for ensuring that only foam of adequate quality is dispensed. In
use, the syringe may be filled from a pressurised canister which
generates foam e.g. for therapeutic use in treating varicose veins.
An initial quantity of foam dispensed from the canister may be of
inadequate quality in which case it should not be used: the syringe
includes means to ensure that this initial quantity of foam is
diverted to a waste port or to an internal waste chamber e.g.
located in the syringe plunger. Foam dispensed after the initial
quantity of poor quality foam is stored in the main barrel of the
syringe ready for administration to a patient in need of
treatment.
Inventors: |
KAY; Stuart Brian William;
(Cambridgeshire, GB) ; HURLSTONE; Christopher John;
(Cambridgeshire, GB) ; DIXON; Julian Richard;
(Cambridgeshire, GB) ; POCOCK; Andrew Gordon;
(Cambridgeshire, GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
BTG INTERNATIONAL LMIITED |
London |
|
GB |
|
|
Family ID: |
29764452 |
Appl. No.: |
15/193378 |
Filed: |
June 27, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14878588 |
Oct 8, 2015 |
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15193378 |
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13137796 |
Sep 14, 2011 |
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14878588 |
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10581513 |
Aug 2, 2006 |
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PCT/GB2004/005086 |
Dec 3, 2004 |
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13137796 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B01F 2215/0034 20130101;
B01F 13/04 20130101; A61M 5/385 20130101; B01F 15/00954 20130101;
A61M 5/3129 20130101; B01F 5/0694 20130101; A61M 39/24 20130101;
A61M 2005/3114 20130101; B01F 5/0682 20130101; B01F 13/0023
20130101; B01F 15/00993 20130101; A61M 2005/3123 20130101; B01F
3/04446 20130101; B01F 13/002 20130101; A61M 2202/04 20130101; A61M
5/31511 20130101; A61M 5/2053 20130101; A61M 5/3137 20130101 |
International
Class: |
A61M 5/315 20060101
A61M005/315; A61M 5/38 20060101 A61M005/38; B01F 15/00 20060101
B01F015/00; B01F 3/04 20060101 B01F003/04; B01F 5/06 20060101
B01F005/06; B01F 13/00 20060101 B01F013/00; A61M 39/24 20060101
A61M039/24; A61M 5/31 20060101 A61M005/31 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 3, 2003 |
GB |
0327957.7 |
Claims
1-11. (canceled)
12. A syringe for dispensing foam comprising: (a) a syringe plunger
having a front end and a back end; (b) a syringe barrel having a
nozzle and a bore to receive the plunger; and (c) wherein the
plunger includes a foam inlet at the back end and a foam outlet at
the front end, which inlet and outlet are in communication with
each other.
13. A syringe as claimed in claim 12 further comprising a one way
valve permitting flow of foam into the inlet.
14. A syringe as claimed in claim 12 wherein the foam outlet is
located adjacent the nozzle.
15. A syringe as claimed in claim 12 wherein the foam outlet is
provided in a projection that extends into a bore of the nozzle
when the plunger is in a fully depressed state.
16. An apparatus for dispensing foam comprising a syringe as
claimed in claim 12 and a waste foam container having an inlet with
a connector of complementary form to the nozzle of the syringe.
17. An apparatus as claimed in claim 16 wherein the waste foam
container has flexible walls and is substantially empty before foam
is dispensed into it.
18. An apparatus as claimed in claim 17 wherein the flexible walls
are inextensible.
19. An apparatus as claimed in claim 16 wherein the waste foam
container is rigid.
20. An apparatus as claimed in claim 19 wherein the waste foam
container comprises a vent.
21. An apparatus as claimed in claim 20 wherein the vent is a
simple hole.
22. An apparatus as claimed in claim 20 wherein the vent is a
hydrophobic vent.
23. A kit for providing a syringe full of foam, the kit comprising
an apparatus as claimed in claim 16 together with a source of
foam.
24. A kit as claimed in claim 23 wherein the source of foam is a
pressurised canister containing liquid to be foamed and gas under
pressure.
25. A method of dispensing foam using an apparatus as claimed in
claim 16 comprising the steps of: (a) connecting a source of foam
to the plunger foam inlet, unless a source is supplied already so
connected; (b) with the plunger fully depressed, generating a
substantially continuous flow of foam from the said source and
allowing an initial quantity of foam to flow from the plunger inlet
through the plunger foam outlet and thence to exit from the syringe
nozzle; and (c) without interrupting the flow of foam from the
source, blocking the syringe nozzle and causing the plunger to move
back such that foam starts to fill the syringe barrel.
26. A method as claimed in claim 25 wherein a waste foam container
is attached to the syringe nozzle.
27. A method as claimed in claim 26 wherein a waste foam container
may be filled or substantially filled with the initial quantity of
foam, and may provide automatically the syringe nozzle blocking
step when so filled or substantially filled.
Description
[0001] The present invention relates to apparatus for delivering
and to methods for filling such apparatus, e.g. from a source of
foam such as a pressurized canister which generates foam by passing
liquid and gas through a fine mesh. The invention is suitable in
particular for a precision foam such as a sterile clinical grade
therapeutic foam, e.g. for the treatment of varicose veins.
[0002] WO 00/72821 describes apparatus and methods for generating a
foam for treatment of varicose veins. In one of the embodiments
described in that patent application, foam is generated by
pressurising a sclerosant liquid and a physiological gas in a
canister and releasing the mixture through a mesh whereby a stable
foam is produced suitable for injection into varicosed blood
vessels in sclerotherapy treatment. An apparatus is described which
incorporates a three-way valve attached to the outlet of the foam
generating canister. The first portion of foam generated by the
canister tends to be of poor quality, and the valve allows this
foam to be diverted to waste. The valve may then be switched over
to feed foam to a syringe for use in treatment. The disclosure of
WO 00/72821 is incorporated herein by reference.
[0003] A number of technical problems have been identified in the
course of further development of the canister based system
described in WO 00/72821. These include the following. [0004] 1.
When the three-way valve is switched from the waste position to the
fill position, there is a momentary dead time when the valve is
closed to both outlet ports and flow is completely obstructed. When
the valve is fully set to the fill position and the flow
re-commences, the foam is initially of poor quality the canister
has effectively re-started its delivery of foam. [0005] 2. In a
delivery device, such as a syringe, for administering foam to a
patient, there is normally a dead space. In the case of a syringe,
this is within the bore of the luer connector on the syringe. As
foam is directed from the valve to the syringe and pushes the
plunger of the syringe back, a large bubble tends to form adjacent
the plunger, which may become incorporated within the foam and
undermine its quality. [0006] 3. It is desirable to be able to
inspect the foam and to determine when consistent, good quality
foam is being generated, so as to check that foam with the correct
properties is being directed into a patient's vein. In the
apparatus described in WO 00/72821, the foam is observable in a
transparent tube communicating between the canister and valve unit
(ref 35 in FIGS. 10 and 11). A difficulty with this is that the
foam which is observed is some way back from the foam being
delivered. Therefore it is possible to observe adequate quality
foam in the tube and still be delivering inadequate quality foam to
the syringe. [0007] 4. The waste foam from tube 38 is not
contained. [0008] 5. The use of a relatively long tube 35 joining
the canister to the valve is wasteful, since a quantity of foam
sufficient to fill the tube will always be wasted. [0009] 6. The
system is somewhat dependant on the skill of the operator to
consistently produce a syringe full of good quality foam.
[0010] Although these problems have been discussed above in
connection with the system described in WO 00/72821, they may be
applicable to other systems for generating and dispensing foam of
various sorts, where a uniform foam product having consistent,
predetermined properties is required. The contents of WO02/41872,
which also relates to this field, is incorporated herein by
reference.
[0011] A number of solutions to some or all of these problems have
been devised. Some of these are described in a simultaneously filed
patent application in the name of the applicant; these solutions
relate in the main to features of a dispensing device which
connects the foam source to a syringe, the syringe being the
delivery device from which foam will ultimately be delivered for
use. A number of solutions are described in the present
application, which solutions are based more on modifications to the
design of a syringe.
[0012] According to a first aspect of the invention, a syringe for
dispensing foam comprises: [0013] (a) a syringe plunger having a
front end and a back end; [0014] (b) a syringe barrel having a
nozzle and a bore to receive the plunger; [0015] (c) wherein the
plunger includes a foam inlet at the back end and a foam outlet at
the front end, which inlet and outlet are in communication with
each other; and [0016] (d) a one way valve permitting flow of foam
into the inlet.
[0017] Preferably the plunger foam outlet is located adjacent the
syringe nozzle. The plunger outlet may be provided in a projection
from the seal end which projection extends into a bore of the
syringe nozzle when the plunger is in a fully depressed state.
[0018] Also according to the first aspect of the invention, an
apparatus for dispensing foam comprises a source of foam (e.g. a
pressurised canister adapted for generating foam) and a syringe as
described above. Preferably the source of foam includes an outlet
of complementary form to the foam inlet of the plunger, and adapted
to make a seal with the foam inlet.
[0019] Also according to the first aspect of the invention, an
apparatus for dispensing foam comprises a syringe as described
above together with a waste foam container having an inlet with a
connector of complementary form to the nozzle of the syringe. The
waste foam container preferably has flexible walls (e.g. is a film
or foil bag) and is substantially empty/airless before foam is
dispensed into it. If the container is a flexible bag, the walls of
the bag are preferably inextensible. The waste container may
alternatively be rigid, in which case a vent is desirable which may
take the form of a simple hole or alternatively a "hydrophobic
vent", i.e. a vent having a filter of some sort which will allow
gas but not liquid to pass.
[0020] Also according to the first aspect of the invention, an
apparatus for dispensing foam comprises a source of foam, a syringe
and a waste container as described above. The syringe, foam source
and waste container may be supplied as a kit of separated elements,
or two or more of these elements may be supplied ready
assembled.
[0021] A method of dispensing foam according to the first aspect of
the invention and using the above described apparatus comprises the
steps of: [0022] (a) connecting the foam source to the plunger foam
inlet (unless the source is supplied already so connected); [0023]
(b) with the plunger fully depressed, generating a substantially
continuous flow of foam from the said source and allowing an
initial quantity of foam to flow from the plunger inlet through the
plunger foam outlet and thence to exit from the syringe nozzle; and
[0024] (c) without interrupting the flow of foam from the source,
blocking the syringe nozzle and causing the plunger to move back
such that foam starts to fill the syringe barrel.
[0025] The method preferably comprises attaching a waste container
to the syringe, or alternatively providing a syringe with a waste
container fitted to it as described above. In this event, the waste
container may be filled or substantially filled with the said
initial quantity of foam in step (b) above, and may provide
automatically the said syringe nozzle blocking step when so filled
or substantially filled.
[0026] The syringe for dispensing foam as described may
additionally comprise a waste container within an internal chamber
defined by the plunger (or the internal plunger chamber or a part
thereof may constitute the waste container), the container being in
communication with the plunger foam inlet and having an outlet in
communication with the plunger outlet. Preferably, the
communication between the waste container outlet and the plunger
outlet is via a pressure sensitive valve. The waste container may
have the optional features described above, i.e. may have flexible
walls or rigid walls and, if the latter, desirably has a vent which
is either a hydrophobic vent or a small hole.
[0027] The invention also encompasses a syringe plunger for such a
syringe, having the features described in the preceding
paragraph.
[0028] The invention also encompasses such a syringe, together with
a source of foam either in assembled form or in kit form.
[0029] With this syringe, the method of dispensing foam comprises:
[0030] (a) connecting the foam source to the plunger foam inlet
(unless the source is supplied already so connected); [0031] (b)
generating a substantially continuous flow of foam from the said
source and allowing an initial quantity of foam to flow from the
plunger inlet into the waste container such as to fill or
substantially fill the waste container; and [0032] (c) causing foam
to flow from the plunger inlet to the plunger outlet and thence
through the syringe nozzle for use.
[0033] Preferably, step (c) includes the step of causing sufficient
back pressure to build up in the waste container to open the
pressure sensitive valve thereby allowing flow of foam through the
waste container outlet.
[0034] According to a second aspect of the invention, a syringe for
dispensing foam comprises: [0035] (a) a syringe plunger having an
internal waste chamber with an inlet; and [0036] (b) a syringe
barrel having a nozzle and a bore to receive the plunger; wherein
the plunger inlet is in communication with the syringe nozzle.
[0037] Preferably the internal waste chamber is provided with a
vent which may either be a hydrophobic vent or a hole or some other
means for allowing sir to escape whilst substantially preventing
foam from escaping from the chamber. The chamber may have one or
more flexible walls and may be substantially empty/airless in its
initial state prior to filling with foam. In the latter case, the
flexible chamber may be contained within a space defined by rigid
walls of the plunger, in which case it may be preferable to have
vents in the said rigid walls to allow air between the chamber
walls and the said rigid plunger walls to escape when the chamber
is filling with foam.
[0038] In an alternative arrangement, the waste chamber may simply
comprise a bag located behind the face of the plunger, but with an
inlet through the front face of the plunger whereby the bag
communicates with the main chamber of the syringe. The bag is
preferably inextensible.
[0039] The inlet to the chamber is preferably adjacent the syringe
nozzle when the plunger is in its fully depressed state. The
chamber may be substantially cylindrical with substantially rigid
walls, in which case it may be defined by an end wall adjacent the
syringe nozzle when the plunger is depressed, in which end wall the
said inlet is located. Alternatively, the chamber may have no end
wall, in which case the chamber comprises a back wall remote from
the syringe nozzle and a cylindrical wall.
[0040] The second aspect of the invention also encompasses a
syringe as defined above together with a source of foam, e.g. a
pressurized canister adapted for generating foam, either in
assembled form or in kit form.
[0041] A method of dispensing foam according to the second aspect
and using a syringe as defined above may comprise the steps of:
[0042] (a) connecting a syringe as defined above to a source of
foam or alternatively providing an assembly comprising a source of
foam having an outlet connected to the syringe nozzle; and [0043]
(b) dispensing a continuous flow of foam into the syringe from the
source; [0044] (c) whereby the flow of foam initially enters the
waste chamber such that foam fills or substantially fills the said
waste chamber, and [0045] (d) the flow of foam subsequently pushes
the syringe plunger back in the syringe barrel and starts to fill
the syringe.
[0046] According to a third aspect of the invention a syringe for
dispensing foam comprises: [0047] (a) a syringe barrel comprising a
cylindrical side wall and a front end wall in which is located a
syringe nozzle; and [0048] (b) a syringe plunger having an end face
which seals against an interior surface of the cylindrical side
wall of the syringe; [0049] (c) wherein the side wall of the barrel
is provided with an outlet at a position remote from the
nozzle.
[0050] Preferably the end face of the syringe plunger, or a portion
of it, makes an oblique angle with the longitudinal axis of the
syringe barrel.
[0051] A waste container may be fitted to the outlet or connected
to it via tubing. The waste container may have substantially rigid
walls or may have one or more flexible walls. A hydrophobic vent or
a vent hole may be provided in a wall of the waste container.
[0052] The third aspect encompasses an assembly or a kit comprising
two or more of: a syringe as described above, a waste container as
described above and a foam source (e.g. a pressurized canister
adapted for generating foam).
[0053] The third aspect of the invention encompasses a method of
using the apparatus described above comprising the steps of:--
[0054] (a) connecting a syringe as defined above to a source of
foam or alternatively providing an assembly comprising a source of
foam having an outlet connected to the syringe nozzle, with the
syringe plunger drawn back such that the syringe nozzle and syringe
outlet communicate; and [0055] (b) dispensing a continuous flow of
foam into the syringe from the source; [0056] (c) whereby foam
flows into the syringe and fills or substantially fills it, with an
initial portion of the foam being directed out of the syringe
outlet to waste.
[0057] Preferably, a waste container is fitted to the syringe
outlet or connected to it by tubing, or such an arrangement is
provided ready assembled. Also, preferably the syringe is held in a
vertical orientation to help the exit of bubbles to waste. This
helps large bubbles to rise and be ejected before too much foam is
wasted.
[0058] Once it is determined that the foam passing out of the
outlet is of substantially consistent, acceptable quality, the flow
of foam from the generator is stopped and the plunger depressed to
seal off the outlet from communication with the syringe nozzle. The
waste chamber and the source may then be disconnected and the
syringe full of foam is ready for use.
[0059] If the end face of the plunger is formed obliquely, this
helps prevent dead spots in the flow of foam from the source to the
outlet, thus helping to ensure that all or substantially all the
poor quality foam is removed from the syringe without too much
wasting of good foam. If there is any poor quality foam retained in
the syringe, it is likely to be in the vicinity of the plunger
face, e.g. if the foam is stiff or if the syringe is held vertical
or at least with the nozzle pointing downwards at an angle
throughout the procedure. Having the plunger face at an oblique
angle to the end wall of the syringe barrel means that the syringe
is never completely emptied of foam, and any poor foam will be
retained in the space formed between the end wall of the barrel and
the oblique face of the plunger.
[0060] The sequence of operation may thus be: [0061] 1.
Continuously dispense foam into the syringe with the plunger drawn
back past the side outlet until all or substantially all foam of
poor quality (either from the start up phase of the foam source or
due to air pockets in the syringe or in any system interposed
between the syringe and the source) has been driven out of the
outlet. [0062] 2. Before disconnecting the syringe from the source
of foam, cease generating or dispensing foam into the syringe.
[0063] 3. Push the plunger past the side outlet. [0064] 4.
Disconnect the foam source.
[0065] Further features and details of the invention will be
apparent from the following description and from the accompanying
drawings in which:--
[0066] FIG. 1 is a schematic sectional view of a first embodiment
of syringe and
[0067] FIG. 2 is a schematic sectional view of a second embodiment
of syringe and system;
[0068] FIG. 3 is a schematic sectional view of a third embodiment
of syringe and system;
[0069] FIG. 4 is a schematic sectional view of a fourth embodiment
of syringe and system;
[0070] FIG. 5 is a schematic sectional view of a fifth embodiment
of syringe and system;
[0071] FIG. 5a is a schematic sectional view of a modified version
of the fifth embodiment;
[0072] FIG. 6 is a sectional view of a sixth embodiment of syringe
and system; and
[0073] FIG. 7 is a sectional view of a pressurized canister for
generating foam, which canister forms part of the first to sixth
embodiments.
[0074] Referring firstly to FIG. 1, a system is shown for filling a
syringe with a clinical grade foam made with a sclerosant liquid,
e.g. 1% polidocanol solution, for injection into varicose veins.
The canister 40 shown schematically in FIG. 1 is shown in more
detail in the sectional view of FIG. 7. A dip tube 44 communicates
with an internal valve 42 which functions in a conventional way to
open the canister when it is depressed. Mounted on top of the valve
is a stack of mesh elements 43 communicating with a canister nozzle
41, the whole mesh stack arrangement being slidably mounted such
that the canister nozzle 41 may be depressed to open the valve
42.
[0075] The canister 40 contains sclerosant liquid as described
above, together with a gas mixture comprising carbon dioxide and
oxygen at 3 bar gauge pressure.
[0076] The syringe 1 comprises a barrel 10 which has a front end
wall 13 in which is located a conventional luer nozzle 11, a
cylindrical side wall 14 and an opening 15 at the back end. Finger
grips 12 are located at the back and as is conventional. Received
within an internal bore 16 of the barrel 10 is a plunger 20 with a
seal formation 21 at the front end thereof which seals with the
bore 16 of the barrel as is conventional.
[0077] The plunger 20 of formed of a plastics moulding having a
front end wall 22 and a cylindrical wall 23. The back end of the
plunger moulding has no wall but has a resilient plug 24 fitted
therein. Located in the resilient plug 24 is an inlet 25 which
includes a one way valve 26 of conventional design. Extending
within the plunger 20 is a tube 27 which communicates between the
inlet 25 and an outlet 28 in the front end wall 22 of the plunger
20. The outlet 28 is located such that it is in registry with the
bore of the luer nozzle 11 when the plunger is folly received into
the barrel 10.
[0078] The inlet 25 is designed to make a seal with the nozzle 41
of a pressurized canister 40 for generating foam. As described
above, foam is dispensed when the canister nozzle 41 is depressed,
thereby opening the internal valve 42 in the canister 40, and
propelling gas and liquid through a stack of mesh elements 43 and
out of the nozzle 41 as foam.
[0079] Fitted onto the front end of syringe is a waste container
50. The waste container comprises a flexible bag 51 of e.g. of
inextensible film or foil. The container 50 is equipped with a
rigid tube 52 communicating with the interior of the bag 51, with
the walls of the bag sealed around the tube 52. The outer end of
the tube 52 is formed as a female luer connector 53.
[0080] In operation, the syringe, with the plunger 20 in the fully
depressed position as shown in FIG. 1, is fitted to the canister by
inserting the canister nozzle 41 into the complementarily-formed
plunger inlet 25. A waste container 51 is then fitted to the
syringe nozzle 11 so as to seal around the nozzle.
[0081] The syringe 1 is then pushed towards the canister 40 by
applying force to the syringe finger grips 12, whereby the canister
nozzle 41 is pushed in so as to activate the canister valve and
generate a flow of foe from the canister. Foam flows from the
canister 40 into the inlet 25, past the valve 26, through the tube
27, out of the plunger outlet 28 and then out of the syringe nozzle
11 and into the waste container 50.
[0082] Pressure an the syringe towards the canister is maintained
so that the flow from the canister 40 is continuous. The initial
portion of this flow consists of foam of inconsistent and poor
quality; this foam is fed into the container 50 as described above,
together with air from the tube 27 in the plunger and from the luer
nozzle 11, and from any other dead spaces in the system. This air
may become incorporated in the foam in which case the quality of
the foam may be affected; whether or not this happens, the air is
dispensed from the syringe nozzle 11 into the waste container
50.
[0083] The flexible walls of the waste container, which is
initially substantially airless, allow it to expand as foam enters,
until it can hold no more foam. As foam continues to flow from the
canister 40, a back pressure is built up which soon becomes
sufficient to overcome the friction between the plunger seal 21 and
the inner surface 16 of the syringe barrel 10. The plunger 20 then
moves back and the syringe barrel fills with substantially
homogeneous, good quality foam.
[0084] The walls of the syringe barrel 10 are transparent, which
allows the quality of the foam to be checked by the user. The user
may be looking for homogeneity, bubble size, density or stiffness,
all of which may be discerned to some degree by the naked eye: when
the bubbles are microscopic, the foam may take on a smooth, white
appearance. The volume of the waste container is about 10% of that
of the syringe and this has been determined to ensure that both the
initial quantity of poor foam together with any trapped air in the
system can be dispensed into the container before the waste
container becomes full. The visual check on the contents of the
syringe could therefore be dispensed with, but is nevertheless
desirable to ensure nothing has gone wrong.
[0085] Once a sufficient quantity of foam has been dispensed into
the syringe, pressure on the canister nozzle is released, thereby
shutting off the flow of foam. The waste container 50 may than be
removed and the foam-filled syringe is ready for use. Use of the
syringe 1 involves dispensing foam down a line to a cannula
inserted into the venous system of a human patient. When the
plunger 20 is depressed to dispense foam, it will be appreciated
that the one way valve 26 on the plunger inlet 25 prevents flow of
foam back out of the inlet.
[0086] A modification to this system is to provide a valve 54 in
the tube 52 of the waste container 50. At the start of the filling
process, this valve 54 is open; when foam is being delivered, the
user may determine from visual inspection that the foam in the
syringe is of acceptable quality even though the bag 51 is not yet
full. In this case, the user may shut off the valve 54 so that the
plunger starts to move back and the syringe to fill.
[0087] In another modification, the waste container 50 could
comprise a rigid vessel, in which case a vent would be provided to
allow displaced are to be exhausted as foam entered the
container.
[0088] A second embodiment is shown in FIG. 2. Reference numerals
for parts corresponding to parts of the first embodiment
correspond, with the series starting at 101. In the second
embodiment, the waste container 150 is incorporated within the
plunger 120.
[0089] The syringe barrel 110 and its various parts are the same as
for the first embodiment. The plunger 120 is almost the same as
that of the first embodiment as regards its external features,
except that it has a small vent hole 130 in its cylindrical side
wall--the operation of this feature will be described below. The
inlet 125, fitted with a one-way valve 126, communicates with a
waste container 150 located within a cavity in the plunger defined
by the plunger walls 122, 123 and plug 124. The canister 140, shown
schematically in FIG. 2, is the same as that of the first
embodiment and the same as that shown in FIG. 7. The waste
container 150 comprises an elongate bag 151 extending the length of
the plunger. The inlet 125 is aligned so as to direct foam along
the length of the bag 151 and thus fill the bag from the end 155
furthest from the inlet.
[0090] Adjacent the inlet 125 is a burst seal 156 in the wall of
the bag 151. The burst seal 156 communicates with a tube 127, also
located within the plunger, and which communicates in turn with an
outlet 128 analogous to the outlet 28 in the first embodiment. In
FIG. 2, the outlet 128 is shown as being slightly to one side of
the syringe nozzle 111; alternatively, and preferably, the nozzle
111 and outlet 128 are in registry with each other.
[0091] The volume of the bag 151 is about 5-10% of the volume of
the syringe barrel when the plunger is fully back. In use, similar
to the first embodiment, the syringe is pressed against the
canister with the canister nozzle 141 fitted to the inlet 125,
whilst the plunger 120 is in its fully depressed state as shown.
Foam is then dispensed from the canister 140, through the nozzle
125 and into the bag 151. The jet of foam issuing from the canister
nozzle 125 passes down to the end 155 of the bag 151 and the bag
fills from this end. As the bag fills from its initially airless
state, it displaces air around it in the cavity defined in the
plunger this is released through the vent 130 in the side wall of
the plunger. In a modification, the tube 157 extends from the
nozzle 125 and terminates at the blind end of the bag 151. This
allows "bad" foam to accumulate distal to the pressure break valve
156, so that when the break valve 156 is broken, only good quality
foam flows through the tube 127 to the outlet 128.
[0092] Once the bag 151 is full of foam, the quality of foam being
dispensed from the canister is consistently good. The volume of the
bag is such that the inlet end of the bag will contain good foam.
Any dead spaces in the inlet 125 and the canister nozzle 141 are
now filled with good quality foam. However, the tube 127 still
contains air.
[0093] At this point continued generation of foam by the canister
causes a back pressure to build up in the waste bag 151, sufficient
to burst the seal 156 on the bag. The flow of foam is then diverted
through the opening created by bursting the seal 156 and then into
the tube 127. Foam at the inlet end of the bag may be displaced and
may pass into the tube 127, but as discussed above this foam will
be of good quality.
[0094] Foam passing into the tube 127 drives out air from the tube
and then passes out through the outlet 128 and syringe nozzle 111.
When the user observes foam exiting the syringe nozzle 111, he or
she puts a syringe nozzle cap 102 on the luer nozzle 111 to block
the flow. The plunger then moves back and the syringe fills.
[0095] As with the first embodiment when the syringe is full,
generation of foam is stopped and the canister removed. Before
delivering foam from the syringe into a patient, the nozzle cap 102
is removed. As with the first embodiment, the valve 126 prevents
foam flowing back out of the inlet 125 when the plunger is
depressed to deliver foam through the nozzle 111.
[0096] The second embodiment is not the preferred one, since the
user still needs to expel a small quantity of waste foam from the
nozzle of the syringe and, preferably, to monitor this foam to
ensure its quality. However, the majority of the waste foam is
contained and the arrangement is neater than that of the first
embodiment since the bag is contained within the plunger.
[0097] A third embodiment is shown in FIG. 3. Again, similar parts
are designated by numbers corresponding to those used in the
descriptions of the first and second embodiments, the series
starting at 200. The canister 240 is identical to that of the first
and second embodiments, as shown in more detail in FIG. 7.
[0098] This embodiment is similar in most respects to the second,
the waste container being rigid rather than flexible. The waste
container 250 is an annular shape extending for most of the length
of the plunger as shown in the Figure, apart from a flat
cylindrical portion 257 at the inlet end. The container 250 is
defined by the end and side walls 222, 223 and the bung 224 of the
plunger, together with a central rigid tubular portion 227 of the
plunger.
[0099] In the front end wall 222 of the plunger 220 are located
hydrophobic vents 229. These are composed of a fine mesh or porous
material such as a porous PTFE film. Their purpose is to allow air
to pass through but not liquid (or foam).
[0100] Located in the region of the inlet end of the plunger 220 is
a burst seal 256 which seals the interior of the container 250 from
the interior of the tubular portion 227.
[0101] In use, the third embodiment works in an analogous manner to
the second embodiment. Foam is generated by the canister when the
syringe is pressed against it to depress the canister nozzle 241 in
order to actuate the canister valve (see FIG. 7). Foam flows from
the canister into the inlet 225 and is carried by its own momentum
to the front end of the waste container 250, air being displaced
through the hydrophobic vents 229.
[0102] Foam builds up in the container until it is full, the
container being sized such that the foam in the region of the inlet
225 is of good quality. A back pressure accumulates and bursts the
seal 256, allowing foam to pass down the central tube 227.
[0103] The remainder of the operation of the third embodiment is
exactly as described for the second embodiment. This embodiment is
not preferred, for similar reasons to those explained above in
connection with the second embodiment. In addition to those issues,
in the third embodiment the hydrophobic vents may became blocked
with foam and prevent air escaping from the waste container
250.
[0104] A fourth embodiment is shown in FIG. 4. As before, reference
numerals designating similar parts correspond, but with the
sequence starting at 301. In this embodiment, unlike the first to
third described above, the syringe is filled from the front,
through the main syringe nozzle 311.
[0105] The barrel 310 of the syringe 301 is identical to that of
previous embodiments, and is conventional. The canister 340 is
identical to that of the first to third embodiments, as shown in
FIG. 7.
[0106] A tubular connector 345 is provided to make a sealing
connection between the canister nozzle 341 and the syringe luer
nozzle 311. One end 346 of the connector is adapted to receive the
canister nozzle 341 whilst the other is formed as a female luer
connector 347 to fit the luer nozzle 311 of the syringe.
[0107] The plunger 320 is formed conventionally with a rear flange
331 to assist manual actuation, whilst the shaft 332 of the plunger
is formed, also conventionally, with a cruciform section. At the
front and of the plunger 320, a waste container 350 is located. The
container 350 is defined by a relatively short cylindrical side
wall 323, a front end wall 322 and a rear end wall 333. An inlet
aperture 334 is provided in the front end wall 322 which is in
registry with the syringe nozzle 311 when the plunger 320 is in its
fully depressed position. Hydrophobic vents 329 are provided in the
rear end wall 333 of the container 350. The external cylindrical
surface of the container forms a seal with the internal surface 316
of the barrel 310. The front end face 322 of the container is
equivalent to the front face of the plunger in the other
embodiments.
[0108] In use, the syringe nozzle 311 is connected to the canister
nozzle 341 by means of the connector 345 as shown in FIG. 4. The
syringe is pressed against the canister 340, thereby causing foam
to be generated by the canister as previously described in
connection with the other embodiments. The foam flows into the
syringe nozzle 311 and then into the waste container 350. Air in
the waste container is displaced out though the hydrophobic vents
329 whilst foam is retained in the container.
[0109] The volume of the waste container is about 10% of that of
the syringe. Once full, as with previous embodiments, it is
reasonably certain that the foam will be of consistant, acceptable
quality. At this point pressure will build in the syringe as foam
continues to be generated by the canister. The plunger 320 will be
pushed back and the syringe filled. It is possible that a little of
the foam in the waste container 350 will leak out of the inlet
aperture 334 into the main chamber of the syringe. However, the
foam adjacent the inlet of the container 350 will be good quality
foam and therefore this is not too important.
[0110] Once the syringe is full, all that is required is to stop
the generation of foam and detach the syringe, which is ready for
use.
[0111] Referring now to FIG. 5, a fifth embodiment is shown which
is similar in most respects to the fourth. As before, reference
numerals designating similar parts correspond, but with the
sequence starting at 401. In this embodiment, a flexible waste bag
451 is provided within a chamber 458 of the syringe plunger
420.
[0112] The barrel 410, connector 445 and canister 440 are identical
to the fourth embodiment described above. The plunger 420 is also
identical to that of the fourth embodiment except for the front end
of the plunger 420 which houses a waste container bag 451. The
front of the plunger 420 is formed, similar the fourth embodiment,
as a short hollow cylinder having a cylindrical side wall 423,
front end wall 422 and rear end wall 433. In the front end wall is
provided an inlet 434 which communicates a waste bag 451 located in
a chamber 458 defined by the walls 422, 423, 433. The waste bag 451
is in a substantially collapsed state so that it contains little or
no air. Provided in the rear end wall 433 of the chamber 458 are
vent holes 429.
[0113] In use, the fifth embodiment operates almost identically to
the fourth. Instead of entering a rigid waste container, foam from
the canister enters a flexible waste bag 451 which, as it fills,
displaces air from the chamber 458 through vents 429. When the
waste bag is full, the syringe plunger is pushed back and the
syringe fills with consistant, good quality foam. As with the
fourth embodiment, once the syringe is full the canister is shut
off and the syringe simply detached for use.
[0114] A modification of the fifth embodiment is shown in FIG. 5a,
which illustrates only the syringe (the other elements being the
same as for FIG. 5). The syringe comprises a conventional syringe
barrel 410. The plunger 480 has a rear flange 481 to assist
application of pressure by hand. The shaft of the plunger comprises
four parallel shaft members 482. The front end of the member
comprises an and wall member 483 with a sealing region 484 around
its periphery for sealing against the internal surface 416 of the
barrel. In the centre of the end wall is an inlet 485 which, when
the plunger is depressed fully, is in registry with the luer nozzle
411 of the syringe.
[0115] Extending from the rear face of the plunger 480 is a boss
486 through which extends the inlet 485. The boss 486 terminates in
a flange 487 around which an airless waste bag 451 is retained.
[0116] The operation of this modification is exactly the same as
that of the fifth embodiment.
[0117] A sixth embodiment is shown in FIG. 6. The system shown
comprises a canister of identical design to the first to fifth
embodiments and shown in detail in FIG. 7. Also provided is a
connector 545 of identical design to the connector described above
in connection with the forth and fifth embodiments.
[0118] As before, reference numerals designating similar parts
correspond, but with the sequence starting at 501.
[0119] In this embodiment, an additional luer nozzle 515 is
provided in the side wall 514 of the syringe barrel 510, towards
the rear of the syringe, for dispensing waste foam. In all other
respects the syringe barrel 510 is conventional and the same as in
the other embodiments.
[0120] The plunger 520 has a conventional rear flange 531 and shaft
532 of cruciform section, as in the fourth and fifth embodiments.
The end wall 522 of the plunger makes a seal 521 with the interior
surface 516 of the barrel 510 as is conventional, but the wall is
inclined at an oblique angle to the longitudinal axis of the
syringe 501.
[0121] In use, the syringe is pressed against the canister as
previously described and foam is dispensed into the syringe with
the plunger in the fully depressed position (not the position shown
in the Figure). Although not shown in the Figure, it will be
appreciated that when the plunger is fully depressed, there will
still be a space defined between the face of the plunger and the
interior of the end wall of the syringe barrel. The initial poor
quality foam will enter this space, but will not fill it since air
will be trapped in the space. Once a back pressure has built up,
the plunger 520 will move back and the syringe fill with foam.
[0122] When the plunger reaches the position shown in FIG. 6, it
will stop moving back since the foam will have a low resistance
path into the waste bag 551 which is substantially airless in its
initial state. The poor quality foam initially dispensed into the
syringe will be the first to pass into the waste bag, assisted by
the inclined face of the plunger.
[0123] After a quantity of foam has been dispensed into the waste
bag 551, the syringe is filled exclusively with consistent, good
quality foam. The user may determine that this state has been
reached by observing the foam through the transparent walls of the
syringe barrel 510. Alternatively or in addition the user may wait
until the waste bag is full at which point a back pressure will
build up which the user may fl on the syringe plunger as it starts
to move.
[0124] However this state is determined, the user then shuts off
the canister, moves the syringe plunger the few millimetres
necessary to close the second luer 515, then removes the canister
and waste bag. The syringe full of foam is then ready for use.
[0125] In a modification of this embodiment, the waste container
described above, with a predetermined volume, is omitted. The
principle of waste foam, exiting a nozzle on the side of the
syringe barrel applies whether a container is attached or not; it
is therefore possible to omit it or to provide some other form of
container which is not designed to fill and provide a back pressure
indicating that sufficient foam has been wasted. In this
modification, the user simply determines by observation when all
the foam in the syringe barrel is of adequate quality, or
alternatively wastes foam for a predetermined time, and then stops
generation of foam and proceeds as before.
* * * * *