U.S. patent number 3,759,425 [Application Number 05/049,008] was granted by the patent office on 1973-09-18 for piston valve syringe gun.
This patent grant is currently assigned to Cooper, McDougall & Robertson Limited. Invention is credited to Ronald Harvey David Frank Lee.
United States Patent |
3,759,425 |
Lee |
September 18, 1973 |
PISTON VALVE SYRINGE GUN
Abstract
A syringe gun suitable for dispensing liquid or semi-liquid
comprises, in combination, a barrel, a piston rod, a piston
attached to the piston rod and located within the barrel for
discharging the contents of the barrel therefrom, an inlet valve
enabling the passage of liquid or semi-liquid into the barrel, and
a discharge valve enabling the passage of liquid or semi-liquid out
of the barrel. At least one of said valves is the combination of a
chamber, an inlet orifice to the chamber, a plate within the
chamber of substantially greater cross-sectional area than that of
the inlet orifice, the plate having an inlet side and an outlet
side, a passage for liquid or semi-liquid from the inlet side of
the plate to the outlet side of the plate, and an outlet orifice
for enabling the passage of liquid or semi-liquid from the chamber.
In this valve arrangement the plate seals the inlet orifice under
pressure upon the outlet side of the plate and, in the alternative,
permits the passage of liquid or semi-liquid through the inlet
orifice, by the flexing or moving of the plate away from the inlet
orifice and through said passage to the outlet orifice by flexing
of the resilient plate or the moving of a floating plate from the
inlet orifice, and through said passage to the outlet orifice.
Inventors: |
Lee; Ronald Harvey David Frank
(Berkhamsted, EN) |
Assignee: |
Cooper, McDougall & Robertson
Limited (Hertfordshire, EN)
|
Family
ID: |
21957602 |
Appl.
No.: |
05/049,008 |
Filed: |
June 23, 1970 |
Current U.S.
Class: |
222/309;
222/387 |
Current CPC
Class: |
A61M
5/204 (20130101); G01F 11/06 (20130101) |
Current International
Class: |
A61M
5/20 (20060101); G01F 11/06 (20060101); G01F
11/02 (20060101); G01f 011/06 () |
Field of
Search: |
;222/387,309
;137/525,533 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Reeves; Robert B.
Assistant Examiner: Shannon; John P.
Claims
We claim:
1. In a syringe gun suitable for dispensing liquid or semi-liquid,
the combination of a barrel, a piston rod, a piston attached to
said piston rod and located within said barrel for discharging the
contents of said barrel therefrom, an inlet valve for enabling
passage of liquid or semi-liquid into said barrel, and a discharge
valve for enabling passage of liquid or semi-liquid out of said
barrel, wherein at least one of said valves is the combination of a
chamber, said chamber having an inlet wall and said inlet wall
defining an inlet orifice to said chamber, a resilient plate within
said chamber of substantially greater cross-sectional area than
said inlet orifice, said plate having an inlet side and an outlet
side, a passage for liquid or semi-liquid from said inlet side of
said plate to said outlet side of said plate, said inlet wall and
said plate each having a central area for enabling the sealing of
said inlet orifice and each having a peripheral area, a support
within said chamber abutting said outlet side of said plate,
whereby the peripheral area of said inlet side of said plate is
spaced apart from the peripheral area of said inlet wall, and an
outlet wall to said chamber, said outlet wall defining an outlet
orifice for enabling passage of liquid or semi-liquid from said
chamber, at least one said central area projecting beyond its own
peripheral area towards said other central area, whereby the
central area of said inlet side of said resilient plate will be
held against the central area of said inlet wall by said support to
seal said inlet orifice and will flex away from said central area
of said inlet wall under pressure upon said inlet side of said
plate to permit the passage of liquid or semi-liquid through said
inlet orifice and through said passage to said outlet orifice.
2. The combination defined in claim 1, wherein the cross-sectional
area of said plate is the same as or is less than the internal
cross-sectional area of said chamber, and wherein said plate is so
shaped as to define at least one perforation in said peripheral
area forming said passage whereby liquid or semi-liquid may pass
from said inlet side of said plate to said outlet side of said
plate.
3. The combination defined in claim 2, wherein said plate defines a
plurality of perforations in said peripheral area of said plate,
said perforations being symmetrically disposed within said plate,
whereby liquid or semi-liquid may pass from said inlet side of said
plate to said outlet side of said plate.
4. The combination defined in claim 1, wherein said inlet valve is
the combination of a chamber, said chamber having an inlet wall and
said inlet wall defining an inlet orifice to said chamber, a
floating plate within said chamber of substantially greater
cross-sectional area than said inlet orifice but smaller than the
internal cross-sectional area of said chamber, said plate having an
inlet side and an outlet side, a support within said chamber, a
passage for liquid or semi-liquid from said inlet side of said
plate to said outlet side of said plate, and an outlet wall to said
chamber, said outlet wall defining an outlet orifice for enabling
passage of liquid or semi-liquid from said chamber, whereby said
plate will seal said inlet orifice under pressure upon said outlet
side of said plate and will move from said inlet orifice under
pressure upon said inlet side of said plate to abut said support to
permit passage of liquid or semi-liquid through said inlet orifice,
and through said passage to said outlet orifice, and wherein said
discharge valve is the combination of a chamber, said chamber
having an inlet wall and said inlet wall defining an inlet orifice
to said chamber, a resilient plate within said chamber of
substantially greater cross-sectional area than said outlet
orifice, said plate having an inlet side and an outlet side, a
passage for liquid or semi-liquid from said inlet side of said
plate to said outlet side of said plate, said inlet wall and said
plate each having a central area for enabling the sealing of said
inlet orifice and each having a peripheral area, a support within
said chamber abutting said outlet side of said plate, whereby the
peripheral area of said inlet side of said plate is spaced apart
from the peripheral area of said inlet wall, and an outlet wall to
said chamber, said outlet wall defining an outlet orifice for
enabling passage of liquid or semi-liquid from said chamber, at
least one said central area projecting beyond its own peripheral
area towards said other central area, whereby the central area of
said inlet side of said plate will be held against the central area
of said inlet wall by said support to seal said inlet orifice and
will flex away from said central area of said inlet wall under
pressure upon said inlet side of said plate to permit the passage
of liquid or semi-liquid through said inlet orifice and through
said passsage to said outlet orifice.
5. The combination defined in claim 4, wherein said central area of
said inlet wall is raised as a lip, whereby said central area of
said inlet side of said resilient plate may seat against said lip
to seal said inlet orifice.
6. The combination defined in claim 4, wherein the central area of
said plate projects beyond its own peripheral area towards the
central area of said inlet wall.
7. The combination as defined in claim 1, there being means for
limiting the backward stroke of said piston to allow the entry of a
predetermined quantity of liquid or semi-liquid into said barrel
through said inlet valve.
8. The combination as defined in claim 1, wherein said inlet valve
is integral with said piston.
9. The combination defined in claim 1, wherein said passage
comprises castellations defining interposed recesses in said
support whereby when said plate abuts said support liquid or
semi-liquid may pass from said inlet side of said plate to said
outlet side of said plate by way of said recesses between said
castellations.
10. In a syringe gun suitable for dispensing liquid or semi-liquid,
the combination of a barrel, a piston rod, a piston attached to
said piston rod and located within said barrel for discharging the
contents of said barrel therefrom, an inlet valve for enabling
passage of liquid or semi-liquid into said barrel, and a discharge
valve for enabling passage of liquid or semi-liquid out of said
barrel, there being at least one ring of resilient material on the
circumference of said piston whreby an air- and liquid-tight fit is
provided between said piston and said barrel, wherein said inlet
valve is integral with said piston and is the combination of a
chamber, said chamber having an inlet wall and said inlet wall
defining an inlet orifice to said chamber, a floating plate within
said chamber of substantially greater cross-sectional area than
said inlet orifice but smaller than the internal cross-sectional
area of said chamber, said plate having an inlet side and an outlet
side, a support within said chamber, a passage for liquid or
semi-liquid from said inlet side of said plate to said outlet side
of said plate, and an outlet wall to said chamber, said outlet wall
defining an outlet orifice for enabling passage of liquid or
semi-liquid from said chamber, whereby said plate will seal said
inlet orifice under pressure upon said outlet side of said plate
and will move from said inlet orifice under pressure upon said
inlet side of said plate to abut said support to permit passage of
liquid or semi-liquid through said inlet orifice, and through said
passage to said outlet orifice.
11. In a syringe gun suitable for dispensing liquid or semi-liquid,
the combination of a barrel, said barrel having a front end and a
rear end, a piston rod, a piston attached to said piston rod and
located within said barrel for discharging the contents of said
barrel therefrom upon a forward stroke of said piston and said
piston rod, said piston having a front face and a rear face, an
inlet valve integral with said piston for enabling passage of
liquid or semi-liquid into said barrel, a discharge valve for
enabling passage of liquid or semi-liquid out of said barrel, and
means for limiting the backward stroke of said piston to allow the
entry of a predetermined quantity of liquid or semi-liquid into
said barrel through said inlet valve, said means for limiting the
backward stroke of said piston being the combination of two
mutually abutting surfaces, the one surface being on said rear face
of said piston and the other surface being on a sleeve held in a
fixed but variable disposition relative to said barrel; wherein
said inlet valve is the combination of a chamber, said chamber
having an inlet wall and said inlet wall defining an inlet orifice
to said chamber, a floating plate within said chamber of
substantially greater cross-sectional area than said inlet orifice
but smaller than the internal cross-sectional area of said chamber,
said plate having an inlet side and an outlet side, a support
within said chamber, a passage for liquid or semi-liquid from said
inlet side of said plate to said outlet side of said plate, and an
outlet wall to said chamber, said outlet wall defining an outlet
orifice for enabling passage of liquid or semi-liquid from said
chamber, whereby said plate will seal said inlet orifice under
pressure upon said outlet side of said plate and will move from
said inlet orifice under pressure upon said inlet side of said
plate to abut said support to permit the passage of liquid or
semi-liquid through said inlet orifice and through said passage and
through said outlet orifice into said barrel; and wherein said
discharge valve is the combination of a chamber, said chamber
having an inlet wall and said inlet wall defining an inlet orifice
to said chamber, a resilient plate within said chamber of
substantially greater cross-sectional area than said inlet orifice,
said plate having an inlet side and an outlet side, said inlet wall
and said plate each having a central area for enabling the sealing
of said inlet orifice and each having a peripheral area, a support
within said chamber abutting said outlet side of said plate,
whereby the peripheral area of said inlet side of said plate is
spaced apart from the peripheral area of said inlet wall, a passage
for liquid or semi-liquid from said inlet side of said plate to
said outlet side of said plate, and an outlet wall to said chamber,
said outlet wall defining an outlet orifice for enabling passage of
liquid or semi-liquid from said chamber, at least one said central
area projecting beyond its own peripheral area towards said other
central area, whereby the central area of said inlet side of said
plate is held against the central area of said inlet wall by said
support to seal said inlet orifice and under pressure upon said
inlet side of said plate will flex away from said central area of
said inlet wall to permit the passage of liquid or semi-liquid
through said inlet orifice through said passage and through said
outlet orifice.
12. The combination defined in claim 11, wherein a base member has
said rear end of said barrel firmly attached thereto, said base
member defining a bore therein, and wherein said sleeve is located
within said barrel and is held within said bore in said base
member.
13. The combination defined in claim 12, wherein said bore in said
base member is screw-threaded internally and wherein said sleeve is
screw-threaded externally, whereby rotation of said sleeve within
said bore will move said sleeve relative to said base member and to
said barrel.
Description
BACKGROUND OF THE INVENTION
This invention relates to improvements in syringe guns.
In particular the present invention relates to improvements in
multiple-dose syringe guns capable of dispensing a large number of
desirably predetermined doses of a liquid. This invention is
especially useful in the veterinary field where it is often
necessary to dose a large number of animals, for example sheep or
cattle, with a drug, vaccine or the like.
When dosing a large number of animals a substantial quantity of
liquid is required, and this may be carried in a container attached
to the operator's back or arm. The liquid is usually fed via a tube
to the syringe gun. Such a syringe gun must normally be capable of
accurately dispensing a predetermined amount of liquid on a large
number of successive occasions without leakage. Desirably it must
also be light and easy to operate, to minimise the manual effort
required by the operator; and of simple and cheap construction, so
that it can be readily constructed but be sufficiently inexpensive
to be disposable after the necessary dosing operations have been
completed. It is also advantageous if the syringe gun can be
adjusted to deliver different predetermined dosages.
Heretofore many syringe guns have employed ball valves which are
not only of complicated and therefore expensive construction but
can be inaccurate when dispensing liquids such as vaccines which
generally contain minute solid particles. These particles often
tend to lodge between the ball and its housing, and prevent or
interfere with closure, resulting in difficulties such as leakage
and inaccurate dosing.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a valve for use
in a syringe gun of simple construction which minimizes these
difficulties.
For the purposes of the present invention the term liquid includes
freely-flowing substances of a semi-liquid nature and also pastes
of a comparatively low viscosity.
Accordingly in one aspect the present invention provides a syringe
gun suitable for dispensing liquid comprising a barrel, a piston
with attached piston-rod within the barrel for discharging the
contents of the barrel therefrom, an inlet valve and a discharge
valve, at least one one of the valves comprising a chamber having
inlet and outlet orifices, a plate within the chamber of
substantially greater cross-sectional area than the inlet orifice
of the chamber, the plate sealing the inlet orifice under pressure
upon the outlet orifice side of the plate and being capable of
moving or flexing away from the inlet orifice when the pressure on
the inlet orifice side of the plate exceeds that on the outlet
orifice side to permit liquid to pass from the inlet orifice,
through the chamber and out via the outlet orifice.
In one form, at least one of the valves of the syringe gun
hereinbefore described comprises a chamber having inlet and outlet
orifices, a plate within the chamber of substantially greater
cross-sectional area than the inlet orifice of the chamber and
normally held by a support against the inlet orifice so as to seal
it, the plate being resilient such that when the pressure on the
inlet orifice side of the plate exceeds that on the outlet orifice
side the plate flexes away from the inlet orifice and liquid may
pass from the inlet orifice, through the chamber and out via the
outlet orifice but when the excess pressure is removed the plate
returns to the closed position and is held there by the
support.
The chamber and the support of the valve are most conveniently
constructed of a thermoplastic material, such as polystyrene. The
chamber of the valve is preferably of circular cross-section with
the inlet and outlet orifices centrally located at the two opposite
ends, and the orifices are themselves preferably circular holes;
the unit is then more readily constructed. The plate is preferably
of circular cross-section and maybe of any resilient material but
natural or synthetic rubber is preferred, primarily because of cost
and availability considerations.
In one embodiment the resilient plate is constructed with a raised
central portion on the inlet orifice side of greater, though not
substantially greater, cross-sectional area than the inlet orifice.
This construction is particularly advantageous in that there is
less tendency for liquid passing through the valve under pressure
to be retarded. The raised central portion of the resilient plate
is flexed away from the inlet orifice of the chamber under the
conditions hereinbefore described such that the liquid may flow
readily and quickly through the valve in the manner hereinbefore
described. Alternatively, the inlet orifice may have a raised lip
to form a valve seat and this may be used in conjunction with a
resilient plate of flat shape without a raised contral portion. The
same easy flow of liquid through the valve is obtained with this
arrangement.
The support may be in the form of stepped castellations situated on
the base of the valve chamber and of such a size that they hold the
peripheral parts of the resilient plate in position. Liquid from
the valve chamber passes through the spaces between the
castellations to the outlet orifice.
Thus in general the valve is normally closed when there is no
excess pressure on the inlet orifice side of the resilient plate by
virtue of the support. When pressure is applied, at least a portion
of the plate closing the inlet orifice flexes and liquid flows
through the inlet orifice, btween the inner wall of the chamber and
the plate through the castellated recesses, and finally flowing
through the outlet orifice. When the pressure deforming the
resilient plate is removed, the plate resumes its original shape
and any "back-flow" of liquid or air is effectively prevented. If
the liquid is one which contains minute particles, such as a
vaccine, then any particles lodged in the valve do not prevent
closure as the resilient plate deforms to allow for them and still
provides efficient closure.
In another embodiment the resilient plate within the valve chamber
is flat and is recessed at one or more points around the periphery
to permit the passage of liquid from the valve chamber into the
outlet orifice of the valve. In a preferred configuration the plate
has a plurality of such recesses and these latter are symmetrically
disposed. The plate is preferably used in conjunction with a valve
chamber wherein the inlet orifice has a raised lip which forms a
valve seat. Alternatively, when no such raised lip is present, the
resilient plate is advantageously constructed with a raised central
portion of greater, though not substantially greater,
cross-sectional area than the inlet orifice. The support holding
the plate against the inlet orifice is optionally castellated, the
castellations, when present, being of the form as hereinbefore
described. It will be understood that if such castellations are not
present the width of the support must be such that the peripheral
recesses in the resilient plate are not totally occluded thereby
and liquid may flow freely from the valve chamber through the
recesses into the outlet orifice of the valve.
In yet another embodiment the resilient plate is flat and is
pierced by one or more holes or slots to permit the passage of
liquid from the valve chamber into the outlet orifice of the valve,
the holes being located such that they are neither in communication
with the inlet orifice of the valve chamber nor totally occluded by
the support holding the plate against the inlet orifice. In a
preferred configuration the plate has a plurality of holes which
are symmetrically disposed within the plate, and for ease of
manufacture the holes are preferably of circular cross-section. The
plate is preferably used in conjunction with a valve chamber
wherein the inlet orifice has a raised lip which forms a valve
seat, when the holes are preferably located within the plate
peripheral to the area in contact with said raised lip.
Alternatively, when no such raised lip is present, the resilient
plate is advantageously constructed with a raised central portion
of greater, though not substantially greater, cross-sectional area
than the inlet orifice with the holes located peripheral to the
raised central portion. The support holding the plate against the
inlet orifice is optionally castellated, the castellations, when
present, being of the form as hereinbefore described.
The valve in the syringe gun according to the invention is
particularly suitable as a discharge valve in that the problems of
leakage and desirability of accurate dosing necessitate efficient
closure at the discharge point in the gun. In such circumstances,
it may be conveniently integral with the barrel of the syringe. The
pressure differential required to move liquid through the valve
maybe created by the discharge stroke of the piston in the syringe
barrel.
The valve the subject of the present invention may also be used as
the inlet valve for a syringe gun, when it is most conveniently
integral with, for example, the piston. The combined piston and
valve is connected to the piston-rod and is advantageously
constructed such that there are one or more rings, such as, for
example, rubber O-rings, on the circumference of the piston which
provide a tight fit with the inside of the barrel of the syringe.
When the combined piston and valve is drawn up the barrel away from
the base thereof the pressure on the outlet orifice side of the
resilient plate is reduced; the excess pressure on the inlet
orifice side of the plate causes the plate to flex away from the
inlet orifice of the valve to permit liquid to pass from a
container through the inlet orifice into the valve chamber, through
the outlet orifice and into the barrel of the syringe. It will be
appreciated that where the outlet valve of the syringe gun is also
of the type provided by the present invention, the decrease in
pressure in the barrel of the syringe consequent upon withdrawal of
the piston increases the effectiveness of the seal between the
inlet orifice and the resilient plate in the said outlet valve.
Conversely, the increase in pressure in the barrel of the syringe
consequent upon advancing the piston towards the base of the
barrel, to expel the liquid contents therefrom through the outlet
valve thereof as hereinbefore described, will increase the
effectiveness of the seal in the inlet valve between the resilient
plate and the inlet orifice.
In another form, at least one of the valves of the syringe gun
hereinbefore described comprises a chamber having inlet and outlet
orifices, a plate within the chamber of cross-sectional area less
than that of the interior of the chamber but substantially greater
than that of the inlet orifice of the chamber, the plate sealing
the inlet orifice when the pressure upon the outlet orifice side of
the plate exceeds that upon the inlet orifice side thereof and
being capable of moving away from the inlet orifice to abut a
support when the pressure upon the inlet orifice side of the plate
exceeds that upon the outlet orifice side thereof to permit liquid
to pass from the inlet orifice, through the chamber and out via the
outlet orifice. As hereinbefore described the chamber of the valve
is preferably of circular cross-section with the inlet and outlet
orifices centrally located at the two opposite ends, and the
orifices are themselves preferably circular holes. The support may
be in the form of castellations situated on the base of the valve
chamber. The inlet orifice of the chamber may have a raised lip to
form a valve seat, and the plate within the chamber may have a
raised central portion on the inlet orifice side of greater, though
not substantially greater, cross-sectional area than the inlet
orifice. The plate is preferably of circular cross-section and may,
as hereinbefore described, be recessed at one or more points around
its periphery or pierced by one or more holes or solts. In the form
described above, the valve is particularly suitable as the inlet
valve of the syringe gun, and is preferably integral with the
piston thereof. The combined piston and valve is advantageously
constructed such that there are one or more rings, such as, for
example, rubber O-rings, on the circumference of the piston which
provide a tight fit with the inside of the barrel of the
syringe.
The inlet valve for the gun may, alternatively, be of a different
construction. It has been found that particularly efficient
operation can be achieved by having, connected to the piston-rod, a
combined piston and valve formed from a plug of resilient material,
preferably natural or synthetic rubber, having a central bore and
at the outlet end a flap of resilient material which is normally
positioned so as to seal the bore but, when under liquid pressure
from a reservoir, is moved from the outlet of the bore so as to
allow liquid to pass through into the syringe barrel. The liquid
pressure may be created by the operation to fill the syringe barrel
with liquid from a reservoir in a container.
Such a combination of piston and inlet valve is particularly
advantageous since the plug of resilient material is of very simple
construction. There is no need for integers requiring screw-thread
connections or attachments, nor for a housing for the valve, nor
for a valve spring, nor for keepers which allow liquid through the
valve but retain any valve spring in position. Moreover, there is
no need for washers nor other seating components for attaching the
valve to the piston. The plug can simply be fitted directly on to
the end of the piston-rod, thereby forming itself the piston head.
There is therefore need for only one moulding operation, and simple
friction fitment is sufficient to attach it to the piston-rod.
Preferably the flap is integral with the plug and is formed by
making a lateral slit in a partially bored plug, such that the slit
and the bore meet. In this way two perfectly mating surfaces are
produced which envelope any minute particles which might lodge in
the valve.
The combined piston and valve is advantageously constructed in such
a way that there are one or more rings on its circumference to
provide a tight fit with the barrel of the syringe.
In another apsect the present invention provides the combinations
of piston and inlet valve described herein.
A most convenient method of dispersing a predetermined volume of
liquid from a syringe gun, dose determination, is to limit the
stroke of the piston to a particular length. In a further aspect
the present invention provides a dose selector which comprises
means for limiting the backward stroke of a piston in a syringe
gun, the means being in the form of two mutually abutting surfaces,
one on the external surface of the syringe piston-rod and the other
in or on the barrel of the syringe. The abutment surfaces can be
made simply by having them integral with the piston-rod and barrel,
so that they may be obtained when the main units are formed, for
example, during their moulding.
The abutment surface on the syringe piston-rod may take the form of
a projection or step which abuts a projection on the inside of the
barrel or a plate across the end of the barrel through which the
piston-rod passes. As another possibility the projection on the
piston-rod may pass through a slot in the wall of the barrel, the
length of the slot determining the dose selected.
If desired a variable dose selection can be obtained by having two
or more abutment surfaces on the piston-rod which abut one or more
movable surfaces on or in the barrel. This can conveniently be
achieved by having a square piston-rod with graduated steps on its
faces, preferably two steps, each on opposite faces. A sliding
plate abuts each of the steps as it is moved to different
positions, thereby causing the backward stroke of the piston to be
limited to a series of different lengths.
An alternative form of dose selector suitable for use in syringe
guns having at least one of the inlet and outlet valves of the type
provided by the present invention comprises means for limiting the
backward stroke of the piston, the means being in the form of two
mutually abutting surfaces, the one either on the rear face of the
piston or on the external surface of the syringe piston rod and the
other in or on a sleeve held in a fixed but variable disposition
relative to the syringe barrel.
In a preferred embodiment the rear face of the piston abuts the
face of a sleeve located within the barrel of the syringe, the rear
end of the syringe barrel being firmly attached to a base member
with the sleeve held within a bore in said base member.
In one configuration the bore in the base member is screw-threaded
internally and the sleeve is screw-threaded externally such that
rotation of the sleeve within the bore moves the former relative to
the base member and to the firmly held syringe barrel to limit the
backward stroke of the piston. In a second configuration the
opposing faces of the bore and sleeve are smooth and the base
member is in the form of a split collar, having a longitudinal slit
in a part of the wall of the bore therein and extending the whole
length thereof, and is provided with means for clamping in
apposition the two surfaces thus formed. The base member has a
recess with the aforementioned bore centrally located therein, the
internal dimensions of the bore and recess being such that when the
opposing surfaces of the base member are clamped together by the
means provided therefor, the sleeve and rear end of the syringe
barrel are firmly held within the bore and recess respectively, the
position of the sleeve relative to the base member and syringe
barrel determining the limit of the backward stroke of the piston
within the barrel. The dose dispensed from the syringe is adjusted
by changing the position of the sleeve relative to the base member
and syringe barrel whilst the clamping means applied to the base
member is temporarily released. As another possibility the base
member has a smooth bore and a longitudinal slit in a part of the
wall of the bore extending from the rear face of the base member
throughout part but not all of the length thereof, the base member
being provided with means for clamping in apposition the two
surfaces formed by the aforementioned slit. The rear end of the
syringe barrel is firmly attached to the base member concentrically
with the bore therein, the internal dimensions of the bore being
such that when the opposing surfaces of the slit in the base member
are clamped together by the means provided therefor, the sleeve is
firmly held with respect to the base member and syringe barrel.
In each of the above-described configurations the base member is
advantageously constructed with lateral projections which serve as
finger grips for holding the syringe gun.
In an alternative embodiment a projection on the external surface
of the piston rod abuts a projection on the inner surface of a
sleeve surrounding the barrel of the syringe. In one configuration
the sleeve has a longitudinal slit in a part of the wall thereof
and extending from one end thereof, said sleeve being provided with
means for clamping in apposition the two surfaces formed by the
slit. The internal dimensions of the sleeve are such that when the
opposing surfaces of the slit are clamped together by the means
provided therefor, the barrel of the syringe is firmly held within
the sleeve. The dose dispensed from the syringe is adjusted by
changing the position of the sleeve relative to the syringe barrel
whilst the clamping means applied to the sleeve is temporarily
released. The sleeve is advantageously constructed with lateral
projections which serve as finger grips for holding the syringe
gun.
The syringe barrel, piston rod, dose selector plate, base member
and sleeve hereinbefore described may be constructed of any
suitable materials such as thermoplastic materials or light metal,
and the piston rod is advantageously spring-loaded for return to
the pre-dispense position. The syringe barrel or the sleeve may be
graduated to indicate the volume of liquid to be dispensed.
In still further aspects the present invention provides a syringe
gun having any combination of inlet and discharge valves as
hereinbefore described and a dose selector also as hereinbefore
described.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described, though only by way of
illustration, with reference to the accompanying drawings in
which:
FIG. 1 is a longitudinal cross-section of a syringe according to
the invention incorporating inlet and discharge valves as
hereinbefore defined and a dose selector also as defined;
FIG. 2 is a section on the line A--A of FIG. 1 showing in greater
detail the dose selector;
FIG. 3 is an enlargement of the discharge valve of FIG. 1; and
FIG. 4 is a section on the line B--B.sup.1 of the valve shown in
FIG. 3 with the resilient plate removed.
FIG. 5 is a lateral view of a median longitudinal section of a
second syringe provided by the present invention incorporating
inlet and discharge valves as hereinbefore defined and a dose
selector also as defined;
FIG. 6 is an enlargement of the combined inlet valve and piston of
FIG. 5;
FIG. 7 is an enlargement of the discharge valve of FIG. 5; and
FIG. 8 is a plan view of a section on the line XX.sup.1 of the
valve shown in FIG. 7 with the syringe barrel removed.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
With reference to FIGS. 1 to 4, the syringe consists of a barrel 1,
piston-rod 2 having combined piston head and inlet valve 3 and
thumb pad 5. Barrel 1 has discharge valve 4 at its outlet end.
Valve 4 consists of a housing 6, inlet and outlet orifices 7 and 8
respectively and a resilient plate 9 which rests on stepped
castellations 10 having spaces 11 therebetween and is held against
inlet orifice 7 (shown in the drawing for the sake of clarity as
spaced apart from the inlet orifice). The housing 6 is integral
with a needle mount 12 and the discharge valve 4 is enclosed by a
needle lock nut 13.
Combined piston and inlet valve 3 has rings 14 on its outer surface
and a central bore 15 with a flap 16 at its discharge end.
The piston-rod 2 is provided with steps 17 and 18 and passes
through plate 19 having a rectangular hole 20. Dose selector plate
19 is attached by rivets 21 to a pair of shoulders 22 having
protuberences 23. These shoulders act as finger grips for holding
the syringe during operation.
The syringe is loaded in the following manner; pressure is applied
to thumb pad 5 so that the piston is as far into the barrel as
possible. Dose selector plate 19 is moved to a position in which it
is ready to abut either step 17 or 18. Piston 2 is now withdrawn
until step 17 (say) abuts plate 19. As the piston 2 is being
withdrawn liquid within the piston-rod (fed from a container not
shown in the drawings) flows through the central bore 15 of
combined piston and valve 3, the withdrawal causing flap 16 to
open, into the barrel 1 where it is retained ready to be
dispensed.
When it is desired to inject, pressure is applied to the thumb pad
5 and the liquid is forced against the portion of the resilient
plate 9 closing inlet orifice 7, this portion of the plate buckles
slightly and liquid flows over the plate, down into the valve
chamber, and out of outlet orifice 8. It will be understood that
the pressure of the liquid will cause flap 16 to be pressed firmly
over bore 15 thus preventing the liquid flowing back into the
piston-rod. When all the liquid has been dispensed the plate 9
resumes its original shape and closes inlet orifice 7.
With reference to FIGS. 5 to 8, the syringe gun comprises a barrel
24, the rear end of which is firmly located within a recess 25 in a
base member 26 having an internally screw-threaded bore 27
concentric with and of lesser diameter than the recess 25 and the
interior of the barrel 24. Rotatably disposed within the bore 27 is
an externally screw-threaded sleeve 28 within which is slidably
located a piston-rod 29 having an axial bore 30. Firmly attached to
the rear end of the piston-rod 29 is a thumb pad 31 and to the
other end is firmly attached a combined inlet valve and piston 32
having a rubber O-ring 33 on its circumference to provide a tight
fit with the inside of the barrel 24. The thumb pad 31 has a bore
34 continuous with the bore 30 of the piston-rod 29 and opening to
the exterior via a nipple 35; the base member 26 has lateral
projections 36 serving as finger grips for holding the syringe gun.
A spring 37 slidably surrounds the piston-rod 29 and extends
between the thumb pad 31 and the rear end of the sleeve 28 where it
is slidably located within a recess 38. The discharge end of the
barrel 24 is firmly located within a discharge valve housing 39
having a needle mount 40 integral therewith.
The combined inlet valve and piston 32 has a circumferential groove
41, wherein is firmly located the rubber O-ring 33, and a central
chamber 42 of circular cross-section within which is centrally
disposed a rubber valve disc 43, also of circular cross-section and
of lesser diameter than the chamber 42. The bore 30 of the
piston-rod 29 communicates with the chamber 42 via an inlet orifice
44 of circular cross-section and of substantially smaller diameter
than the valve disc 43 and having a raised lip 45 integral with the
piston rod 29 and forming a seat for the valve disc 43. The base of
the chamber 42 comprises flat-topped castellations 46 integral with
the body of the piston 32 with interposed recesses 47 converging to
an outlet orifice 48 of circular cross-section and leading to the
interior of the barrel 24; the distance between the tops of the
castellations 46 and the raised lip 45 is greater than the
thickness of the valve disc 43.
The discharge valve housing 39 is firmly located upon the discharge
end of the barrel 24 with a step 49 abutting the end wall thereof.
A chamber 50 within the housing 39 is of circular cross-section and
has a step 51 and an outlet orifice 52, the latter being of
circular cross-section and opening to the exterior via the needle
mount 40. Supported by the step 51 and centrally located within the
chamber 50 is a resilient rubber plate 53, of circular
cross-section and of lesser diameter than the chamber 50 and being
pierced by a plurality of circular holes 54 disposed equidistantly
from the centre of the plate 53 and located within the unsupported
portion thereof. The interior of the barrel 24 communicates with
the chamber 50 via an inlet orifice 55 of circular cross-section
and of substantially smaller diameter than the plate 53 and having
a raised lip 56 integral with the end wall of the barrel 24. The
respective heights of the step 51 and the lip 56 are such that the
plate 53 is normally held against the lip 56 and is flexed thereby
to effect a seal of inlet orifice 55 at their point of contact, the
diameter of the lip 56 being such that said point of contact lies
within the ring of holes 54 in the plate 53.
When the syringe gun is in use the unit dose dispensed therefrom is
determined by the length of the backward stroke of the piston 32
within the barrel 24, this being set by the point along the barrel
at which the rear face of the piston 32 abuts the end of the sleeve
28. Rotation of sleeve 28 within the bore 27 of base member 26
changes the position of the sleeve 28 relative to the base member
27 and to the firmly held barrel 24; the end of sleeve 28 is in
this manner brought to lie at a different point along the barrel 24
to provide for a piston stroke of a different length and hence the
dispensation of a different unit dose.
The syringe gun is loaded in the following manner. With the gun
prepared in the manner hereinbefore described to dispense a desired
unit dose, pressure is applied to thumb pad 31 so that the piston
32 is as far into the barrel 24 as possible; the piston 32 is then
withdrawn until the rear face thereof abuts the end of sleeve 28.
During this withdrawal the pressure within barrel 24 on the outlet
orifice side of valve disc 43 is reduced below that on the inlet
orifice side thereof and the valve disc 43 is held on the floor of
the chamber 42 against the castellations 46. Liquid within the bore
30 of piston-rod 29 (fed through bore 34 in thumb pad 31 from a
reservoir, not shown, attached to nipple 35) flows through inlet
orifice 44, between valve disc 43 and lip 45 into chamber 42,
around the sides of disc 43, through recesses 47 between
castellations 46 and out via outlet orifice 48 into barrel 24 where
the liquid is retained. At the same time the decrease in pressure
in barrel 24 increases the effectiveness of the seal between the
plate 53 and lip 56 in discharge valve housing 39 and any back flow
of air or liquid through inlet orifice 55 is prevented.
When it is desired to discharge the contents of the barrel 24,
pressure is applied to thumb pad 31 and the piston 32 is driven
down the barrel 24 as far as possible. As a result of the movement
of the piston 32 the pressure in barrel 24 on the inlet orifice
side of plate 53 is increased above that on the outlet orifice side
thereof to a level where at least a portion of plate 53 is flexed
away from lip 56; liquid then flows under pressure from the barrel
24 through the inlet orifice 55, between lip 56 and plate 53 into
the chamber 50, then through holes 54 to leave via outlet orifice
52. Likewise the pressure on the outlet orifice side of disc 43 is
raised above that on the inlet orifice side thereof and the disc 43
is held against lip 45 to seal inlet orifice 44 and prevent any
escape of liquid back into the bore 30 of the piston-rod 29. When
the piston 32 reaches the end of its discharge stroke the pressure
flexing the plate 53 away from the lip 56 is removed; plate 53 then
resumes its original shape and any back flow of liquid or air
through inlet orifice 55 is prevented. The syringe gun is then
ready for another operational cycle.
* * * * *