AU781599B2

AU781599B2 - A retractable syringe

Info

Publication number: AU781599B2
Application number: AU73949/00A
Authority: AU
Inventors: Roy Tudor Brewer
Original assignee: Individual
Current assignee: Individual
Priority date: 1999-09-09
Filing date: 2000-09-11
Publication date: 2005-06-02
Anticipated expiration: 2020-09-11
Also published as: AU7394900A

Description

A RETRACTABLE SYRINGE Field of the Invention The present invention is directed towards a syringe having aretractable needle.

Background of the Invention Syringes in which the needles are able to be retracted into the syringe barrel after use are known.

Such syringes have been developed in order to reduce the risk of needle-stick injuries experienced by health professionals. Typically these earlier syringes provide means by which the syringe piston can engage the needle base at the end of the injection procedure. The piston and needle can then be withdrawn into the barrel of the syringe by the user. A disadvantage of such syringes is that in the withdrawn position, the end of the plunger extends from the open barrel of the syringe. If the end of the plunger is accidentally depressed, the needle may be pushed out of the barrel. In order to avoid this occurring complicated locking arrangements for locking the plunger in the withdrawn 1s position have been proposed. Typical locking arrangements have a twist-lock mechanism.

A further disadvantage of these syringes is that withdrawal of the plunger and needle into the syringe barrel and subsequent locking action is a two handed operation.

Thus, the ultimate safety of the syringe is subject to the method of operation of the user.

An error in operation may result in incomplete withdrawal of the needle into the barrel and/or failure to securely lock the needle within the barrel.

In order to overcome the disadvantages of the manually operable single use syringes, syringes which automatically withdraw the needle into the body of the plunger after fluid delivery.

Typically, the piston engages the base of the needle and is then withdrawn into the body of the piston. Withdrawal may be actuated by a spring or by air pressure in which case the body of the piston has an evacuated chamber.

For withdrawal of the needle and plunger to occur, the needle and plunger must be released from the syringe barrel and piston respectively. Further, the piston must be able to engage the base of the needle. There have been a number of different [R \LIBTT03721 doc hxa rt t 2 arrangements which have been proposed to provide the respective engagement and needle release means. Examples of such arrangements include rupturable membranes or frangible members which can fracture so as to release either the needle or the piston.

Other arrangements include complex claw arrangements whereby claws are deformed at the end of the depression stroke of the plunger to either release and/or engage the respective parts.

A major disadvantage of these arrangements is that they are quite complicated and include a large number of parts. This makes the syringes complicated and expensive to manufacture. However, a particular disadvantage is that the mechanism must 6perate 1o when the needle is inserted into the flesh of a patient. In the above mechanisms, a reasonable amount of force is required to rupture or deform the various parts so as to activate the withdrawal mechanism. Such force may be greater than that normally required during a normal delivery stroke of the plunger. Any increase in downwards force on the plunger at the end of fluid delivery has potential to injure or inflict pain or discomfort to a patient. Also, the necessity to use additional force at the end of an injection may be undesirable during procedures such as spinal injections.

Object of the Invention It is therefore an object of the invention to provide a syringe which may at least partially overcome the above disadvantages or provide the public with a choice.

S: 20 Summary of the Invention There is disclosed herein a hypodermic syringe having: a barrel with an open end, a base end and an internal bore; a needle assembly including a needle base member located inside the bore and releasably engaged with the base end and a needle which protrudes through the base end of the barrel; a plunger slidable within the bore, the plunger having a piston releasably engaged therewith and a chamber having air evacuated therefrom, the chamber being sealed at one end by the piston; wherein the piston includes means for engaging the needle base member such that in use when the plunger is depressed and the piston approaches the base end of the barrel, the piston can engage the needle base member, the [R \LIBTT]03721 doc.hxa needle base member is released from the base end and the piston is released from the plunger such that the piston, needle base member and needle can be forced into the chamber by atmospheric pressure, wherein the needle base member is releasably engaged with the base end of the barrel by means of a split ring movable from an engagement position to a release position.

Preferably, the needle base member has a recess which receives the split ring when the split ring is in the engagement position.

Preferably, the needle base member is spaced from the base end of the barrel and when the plunger approaches and contacts the base end, the plunger pushes the needle to base member towards the lock end of the barrel, so as to cause the split ring to move in the direction of plunger travel and allows it to expand out of the recess in the needle base "member.

Preferably, the piston is releasably engaged with the plunger by means of a split ring.

Preferably, the plunger includes means for locking the plunger to the base end of the barrel when the plunger is depressed.

Preferably, the locking means include a split ring located on the plunger, the base end of the barrel includes a radially outward extending locking projection and the split ring moves to engage the locking projection when the plunger is depressed.

ooo 20 Preferably, the split ring which locks the locking projection is the same split ring S• which releasably engages the piston and the plunger.

S•There is also disclosed herein a hypodermic syringe having: a barrel with an open end, a base end and an internal bore and a locking means at the base end; a needle assembly including a needle base member located inside the bore and releasably engaged with the base end and a needle which protrudes through the base end of the barrel; a plunger slidable within the bore and having a chamber with air evacuated therefrom, a piston releasably engaged with the plunger and sealing an end of the chamber; wherein the piston includes means for engaging the needle base member such that in use when the plunger is depressed and the piston approaches the base end of the [R \LIBTT]03721 doc hxa

I

4 barrel, the piston engages the needle base member, the needle base member is released from the base end, the plunger releases the piston and is engaged by the locking means at the base end of the barrel; such that the piston, needle base member and needle are forced into the chamber by atmospheric pressure and the plunger remains engaged with the barrel with the locking means so that it may not be removed from the bore.

Preferably, the syringe includes air inlets at the base end of the barrel.

There is further disclosed herein a hypodermic syringe including: a barrel having an internal bore surrounding a volume to receive a liquid to be injected, the bore extending to a base end; 0to a needle assembly releasably mounted in said base end and including a needle base member and a needle mounted therein, the needle communicating with said volume S•so that liquid can be injected through said needle upon a reduction in said volume; a hollow plunger slidably located within said bore and moved towards said base end to reduce said volume, the plunger providing a chamber with air evacuated therefrom and having a leading portion from which the chamber extends; a piston releasably mounted at said leading portion so as to move with the o plunger to reduce said volume, the piston sealing said chamber and receivable in said chamber upon release from said leading portion, the piston further having engaging ••means to engage the needle assembly to attach the needle assembly to the piston; 20 a release means releasably attaching the piston to the plunger; a locking means fixed to the bore and operatively associated with the plunger so Sthat upon the plunger reaching a predetermined position adjacent the base end the locking means engages the plunger to prevent movement of the plunger away from said base end beyond said predetermined position; and wherein said piston engages the needle assembly so as to be fixed thereto and said release means is activated to release said piston after said plunger is engaged by said locking means, with said piston and needle assembly caused to move into said chamber under atmospheric pressure.

Preferably, said release means includes a co-operating recess and projection, with said projection being located in said recess to attach the piston to the plunger, and (R.\LIBTT03721 .doc.hxa said projection is spaced from said recess to release the piston for movement into said chamber.

Preferably, the hypodermic further includes a retaining means mounted on said plunger and to engage said locking means to attach the plunger to the barrel.

Preferably, said retaining means moves radially outward to engage said locking means, and said projection is attached to said retaining means to move radially from within said recess.

Preferably, said retaining means and said projection are provided by a ring that is expanded radially to release said piston and to engage said locking means.

Preferably, said needle base member has a portion to be engaged by said engaging means, said portion and engaging means being a co-operating further recess and G further projection.

Preferably, said needle base member includes a stem having a further projection, and said piston includes a cavity to receive said stem and said further projection engages 15s in said recess and engages said piston to attach said needle mounting to said piston, the piston having said further recess.

Preferably, said needle base member is releasably attached to said base end by a Go.* o co-operating end recess and end projection.

""Preferably, said needle base member has said end recess and said end projection 20 extends between said end recess and said base end to releasably secure the needle base •member to said base end, with said end projection being moved radially to release said o••oo Sneedle base member.

Preferably, said needle base member is moved longitudinally of the hypodermic syringe to release said needle base member for movement with said piston.

Preferably, said end projection is a ring that moves radially upon said axial movement of said needle base member to release said needle mounting.

Preferably, said base end has an air passage to provide said atmospheric pressure.

Brief Description of the Drawing Figure 1 illustrates a schematic cross sectional view of a preferred syringe 1 of the present invention.

(R \LIBTT]03721 doc hxa Description of the Preferred Embodiment Section A of the Figure illustrates the syringe towards the completion of the fluid injection procedure. Section B illustrates the syringe at the end of the injection procedure.

The syringe 11 includes a barrel 12 having a bore. The barrel is open at one end 13. The base 14 of the barrel is adapted to retain a needle 15. The needle 15 is firmly held by a needle base member 16. The needle base member 16 is housed within an aperture 18 in the wall 19 at the base 14 of the barrel. The needle base member 16 is held in place within aperture 18 by split ring 20. The split ring 20 is located between opposed io recesses 21, 22 in the needle base member 16 and wall 19 of the barrel respectively. The recess 22 is a step expansion recess having a depth of half the cross sectional thickness of the split ring.

The needle base member includes a further recess 23, also fitted with a split ring 24. The purpose of this split ring will be described below.

When the syringe 11 is assembled, split rings 20, 24 are entered into recesses 21, 23 in the needle base member 16. The needle base member 16 and attached needle 15 are inserted into barrel 12 through opening 13 until split ring 20 is aligned with recess 21. An O ring 25 provides a fluid seal between the needle base member 16 and barrel wall 19.

The syringe 11 also includes a plunger 26. The plunger 26 has a head 27 which 20 extends from the open end 13 of barrel 12. The plunger 26 is slidable within the bore of the barrel 12. The plunger 26 has an evacuated chamber 28. The chamber 28 is sealed at ooooo* one end by a piston 29. The piston 29 is releasably attached to the plunger wall 30 by a multi-function split ring 31. An O ring 32 provides a gas and fluid seal between the plunger 26 and piston 29. A further O ring 40 provides a seal between the plunger 28 and barrel wall.

The syringe 11 is initially operated in a manner similar to conventional syringes.

The barrel is charged with a injectable fluid and the fluid is injected by depressing plunger 26. Section A illustrates the relative position of the syringe components as the plunger 26 is almost fully depressed. As the plunger is depressed further, the piston 29 meets the needle base member 16 and the base wall 19 of the barrel 12. The piston 29 has a recess 33 which is complimentary to the shape of the end 34 of the needle base member [R \LIBTT]03721 doc hxa 16. As the piston 29 is urged towards the needle base member, the recess 33 receives the end 34 of the needle base member and engages split ring 24. Split ring 24 expands within the recesses and locks the piston 29 to the needle base member 16.

Further depression of the plunger 26 forces the needle base member 16 towards s the base wall 19 of the barrel 12 as illustrated in section B. The base 36 of barrel 12 has an annular locking projection 35. As the piston 29 is depressed, split ring 31 comes into contact with radially outward extending locking projection 35. This causes the split ring 31 to fully expand which releases the piston 29 from plunger 26. Further depression of plunger 26 forces split ring 31 to engage locking projection 35 so as to effectively lock 1o the plunger 26 and barrel wall together.

Downwards pressure of the plunger 26 on the needle base member 16 pushes the needle base member into the position shown in B. Split ring is pushed downwards along se: the stepped portion of recess 21 allowing it to expand, thereby disengaging from recess 22 in the needle base member 16 and releasing the needle base member from the barrel.

15 When the piston 29 is released from the plunger 26, the piston 29 and engaged needle base member are forced into evacuated chamber 28 by air pressure. Air inlets 36 are provided in the barrel base to facilitate movement of the piston in response to the difference in air pressure. The difference in air pressure between the chamber 28 and the oo atmosphere assists in maintaining the piston 26, needle base member 16 and needle within the chamber 28.

It can be seen that in the above embodiment the needle is rapidly and Sautomatically withdrawn into the plunger body. Such withdrawal does not require two handed operation and does not rely on correct operation by the user. At the completion of the action, all components are locked together, and the needle is safely secured within the plunger body.

It can also be seen that the needle base member can be released from the barrel without requiring the rupturing or deformation of any members by force.

The split ring is under compression and it is released of part of the compression force which expands the split ring. The only force input required by the operation is that required to slide the ring along the step of the recess in the barrel wall. Typically, this force will be essentially the same as that required for movement of the plunger. In other [R:\LIBTT]03721 doc hxn words, the needle base member may be released as part of the normal downward stroke of the plunger. The other split rings operate sequentially in a similar manner to reduce the amount of force required to engage and release the various parts as compared to earlier syringes.

It will be appreciated that various changes and modifications may be made to the above embodiment without departing from the spirit and scope of the invention.

*o *o (R'\LIBrl03721.doc hxa

Claims

1. A hypodermic syringe having: a barrel with an open end, a base end and an internal bore; a needle assembly including a needle base member located inside the bore and releasably engaged with the base end and a needle which protrudes through the base end of the barrel; a plunger slidable within the bore, the plunger having a piston releasably engaged therewith and a chamber having air evacuated therefrom, the chamber being sealed at one end by the piston; wherein the piston includes means for engaging the needle base member such that in use when the plunger is depressed and the piston approaches the base end of the barrel, the piston can engage the needle base member, the needle base member is released from the base end and the piston is released from the plunger such that the piston, needle base member and needle can be forced into the °0C chamber by atmospheric pressure, wherein the needle base member is releasably engaged 5I with the base end of the barrel by means of a split ring movable from an engagement S.o position to a release position.

The syringe of claim 1, wherein the needle base member has a recess which receives the split ring when the split ring is in the engagement position.

3. The syringe of claim 2, wherein the needle base member is spaced from *0CC 20 the base end of the barrel and when the plunger approaches and contacts the base end, the S: plunger pushes the needle base member towards the lock end of the barrel, so as to cause Sthe split ring to move in the direction of plunger travel and allows it to expand out of the recess in the needle base member.

4. The syringe of claim 1, wherein the piston is releasably engaged with the plunger by means of a split ring.

The syringe of claim 4, wherein the plunger includes means for locking the plunger to the base end of the barrel when the plunger is depressed.

6. The syringe of claim 5, wherein the locking means include a [R-\LIBTT]03721 doc:hxa split ring located on the plunger, the base end of the barrel includes a radially outward extending locking projection and the split ring moves to engage the locking projection when the plunger is depressed.

7. The syringe of claim 6, wherein the split ring which locks the locking projection is the same split ring which releasably engages the piston and the plunger.

8. A hypodermic syringe having: a barrel with an open end, a base end and an internal bore and a locking means at the base end; a needle assembly including a needle base member located inside the bore and releasably engaged with the base end and a needle which protrudes through the base end of the barrel; a plunger slidable within the bore and having a chamber with air evacuated .:therefrom, a piston releasably engaged with the plunger and sealing an end of the chamber; wherein the piston includes means for engaging the needle base member such that in use when the plunger is depressed and the piston approaches the base end of the barrel, the piston engages the needle base member, the needle base member is released from the base end, the plunger releases the piston and engaged by the locking means at 1 the base end of the barrel; such that the piston, needle base member and needle are forced into the chamber by atmospheric pressure and the plunger remains engaged with the 20 barrel with the locking means so that it may not be removed from the bore.

9. The syringe of claim 8, which includes air inlets at the base end of the barrel.

A hypodermic syringe including: a barrel having an internal bore surrounding a volume to receive a liquid to be injected, the bore extending to a base end; a needle assembly releasably mounted in said base end and including a needle base member and a needle mounted therein, the needle communicating with said volume so that liquid can be injected through said needle upon a reduction in said volume; a hollow plunger slidably located within said bore and moved towards said base end to reduce said volume, the plunger providing a chamber with air evacuated therefrom and having a leading portion from which the chamber extends; [R\LIBTTrJ03721 doc hxa 11 a piston releasably mounted at said leading portion so as to move with the plunger to reduce said volume, the piston sealing said chamber and receivable in said chamber upon release from said leading portion, the piston further having engaging means to engage the needle assembly to attach the needle assembly to the piston; a release means releasably attaching the piston to the plunger; a locking means fixed to the bore and operatively associated with the plunger so that upon the plunger reaching a predetermined position adjacent the base end the locking means engages the plunger to prevent movement of the plunger away from said base end beyond said predetermined position; and wherein said piston engages the needle assembly so as to be fixed thereto and said release means is activated to release said piston after said plunger is engaged by said locking "means, with said piston and needle assembly caused to move into said chamber under •:atmospheric pressure.

11. The hypodermic syringe of claim 10, wherein said release means Is includes a co-operating recess and projection, with said projection being located in said recess to attach the piston to the plunger, and said projection is spaced from said recess to release the piston for movement into said chamber.

12. The hypodermic syringe of claim 11, further including a retaining means mounted on said plunger and to engage said locking means to attach the plunger to S 20 the barrel.

13. The hypodermic syringe of claim 12, wherein said retaining means 1moves radially outward to engage said locking means, and said projection is attached to said retaining means to move radially from within said recess.

14. The hypodermic syringe of claim 13, wherein said retaining means and said projection are provided by a ring that is expanded radially to release said piston and to engage said locking means.

The hypodermic syringe of any one of claims 10 to 14, wherein said needle base member has a portion to be engaged by said engaging means, said portion and engaging means being a co-operating further recess and further projection.

16. The hypodermic syringe of claim 15, wherein said needle base member includes a stem having a further projection, and said piston includes a cavity to receive [R \LIBTT]03721 doc hxa 12 said stem and said further projection engages in said recess and engages said piston to attach said needle mounting to said piston, the piston having said further recess.

17. The hypodermic syringe of any one of claims 10 to 16, wherein said needle base member is releasably attached to said base end by a co-operating end recess and end projection.

18. The hypodermic syringe of claim 17, wherein said needle base member has said end recess and said end projection extends between said end recess and said base end to releasably secure the needle base member to said base end, with said end projection being moved radially to release said needle base member.

19. The hypodermic syringe of claim 18, wherein said needle base member is moved longitudinally of the hypodermic syringe to release said needle base member for movement with said piston.

The hypodermic syringe of claim 19, wherein said end projection is a ring that moves radially upon said axial movement of said needle base member to release said needle mounting.

21. The hypodermic syringe of any one of claims 10 to 20, wherein said base end has an air passage to provide said atmospheric pressure.

22. A hypodermic syringe substantiates hereinbefore described with reference to the accompanying drawings. 20 Dated 12 April, 2005 ooo° Rod Tudor Brewer Patent Attorneys for the Applicant/Nominated Person SPRUSON FERGUSON [R:\LIBTT)03721 doc:hxa,