WO2001072363A1

WO2001072363A1 - Retractable syringe

Info

Publication number: WO2001072363A1
Application number: PCT/AU2001/000341
Authority: WO
Inventors: Peter George Austin
Original assignee: Peter George Austin
Priority date: 2000-03-27
Filing date: 2001-03-27
Publication date: 2001-10-04
Also published as: AUPQ647100A0

Abstract

A retractable syringe is provided which has a hollow plunger (20) movable within a barrel (11) to expel fluid through a needle (34; 70) mounted at the front end of the syringe. When the plunger (20) reaches the front end of the barrel (11), a forward extension (26, 128) of the plunger (20) engages an expandable seal (42; 60) to release a spring (40) which urges the needle (34; 70) rearwardly. A rear portion (36; 74) of the needle (34; 70) dislodges a removal plug (50; 70) at the front end of the plunger (20) so that the needle (34; 70) is automatically retracted into an inner chamber (22) of the plunger (22) preventing re-use of the syringe.

Description

RETRACTABLE SYRINGE

This invention relates to syringes and is particularly concerned with providing a syringe in which the needle of the syringe is automatically retracted into the body of the syringe after the injection process is completed. There is currently significant concern within the general public and the medical profession about the problem of accidental stabbing of persons by needles of hypodermic syringes, otherwise known as "needle-stick" injuries. Such injuries can occur when needles of hypodermic syringes are exposed before and after use of the syringe, and can lead to infections of diseases, such as AIDS and Hepatitis.

In order to reduce the problem of needle-stick injuries, caps or shields for needles can be employed which are removable immediately before use of the syringe. However, it is undesirable to re-cap a needle of a syringe after use because needle-stick can occur during the re-capping operation. Also, several types of hypodermic syringes are designed for single-shot application which are intended to be thrown away immediately after use. It is undesirable for the needle of such syringes to be exposed after use.

There have previously been proposed various types of retractable syringes in which the needle of the syringe is retracted into the body of the syringe after use. However, previous proposals have often involved relatively complicated retraction mechanisms, often requiring frangible parts, which can be expensive to manufacture and which do not always function efficiently.

It is therefore desirable to provide an effective retractable syringe in which the needle is automatically retracted into the body of the syringe immediately after the injection process is completed.

It is desirable to provide a retractable syringe which has a relatively simple but effective needle retraction mechanism and which involves a relatively low cost of manufacture.

According to one aspect of the invention there is provided a retractable syringe comprising: a barrel having a front end, a rear end and defining a receptacle for containing a liquid for injection; a needle mounted at the front end of the barrel; a hollow plunger movable within the barrel from the rear end to the front end of the receptacle to expel fluid out of the barrel through the needle; said plunger having an inner chamber, an axial hole at the front end of the chamber and means blocking the axial hole; resilient means which is adapted to urge the needle in a rearward direction into the barrel; wherein said resilient means is restrained by an expandable annular member providing a seal at the front end of the receptacle of the barrel, such that when the plunger reaches the front end of the receptacle of the barrel, a forward part of the plunger engages the expandable annular member which moves along a surface at the front end of the barrel and expands to release the resilient means, whereby the axial hole is unblocked so that the needle is automatically retracted through the axial hole into the inner chamber of the plunger.

In one preferred embodiment of the present invention, the expandable annular member comprises a ring member which is engaged by at least one forwardly extending projection on a front end portion of the plunger when the plunger reaches the front end of the receptacle of the barrel. The ring member is preferably in the form of an O-ring seal which provides a seal at the front end of the receptacle of the barrel.

The O-ring seal is preferably moveable rearwardly along a surface which allows the O-ring to expand when it is engaged by the forward part of the plunger. The surface may be a tapered surface, or a stepped surface which allows the O-ring to expand when it moves past a shoulder of the stepped surface.

In an alternative embodiment of the invention, the expandable annular member comprises a split tapered collet which is engaged by the forward part of the plunger and which expands to release the resilient means when the plunger reaches the front end of the barrel. The collet is preferably movable along a tapered surface when it is engaged by the forward part of the plunger.

The needle may be mounted at the front end of the barrel by being attached to a needle holding means which is also retracted with the associated needle into the inner chamber of the hollow plunger when the resilient means is released. The needle holding means may be of tubular form received in a bore in a front end member of the barrel. Such a tubular needle holder preferably has a tubular portion for holding the needle and an enlarged rear head portion engageable with the expandable annular member. Alternatively, the needle may have an enlarged head portion at its rear end either integral with or attached to the main body part of the needle. This enables the size of the barrel to be reduced so that an effective syringe of small size can be produced for one-shot administration of drugs.

In the preferred embodiment utilising an O-ring seal as the expandable annular member, the enlarged head portion of the needle or needle holder preferably has a bevelled or tapered surface with the O-ring being positioned between the bevelled surface of the head and the surface at the front end of the barrel.

The means for blocking the axial hole at the front end of the plunger may comprise any convenient blocking means, including a frangible member, such as a membrane. However, the blocking means preferably comprises a removable plug.

The resilient means preferably comprises a spring and when the spring means is released from its compressed state by expansion of the expandable annular member, the plug is preferably dislodged into the inner chamber of the plunger by engagement of a rear end portion of the needle or the needle holding means with a front end of the plug.

Preferred embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a section through an embodiment of a retractable hypodermic syringe in accordance with the invention; Figure 2 is a section of the syringe of Figure 1 after use showing the needle retracted into the body of the syringe;

Figure 3 is a side view of a second embodiment of a retractable hypodermic syringe in accordance with the invention; Figure 4 is an exploded sectional view of the cylindrical body and plunger of the syringe of Figure 3;

Figure 5 is an exploded sectional view of the front end member, the needle holder, the retraction spring and the plug of the syringe of Figure 3;

Figure 6 is a side view of the expandable collet member of the syringe of Figure 3;

Figure 7 is an end view of the expandable collet member of the syringe of Figure 3; and

Figure 8 is a section on the line A-A of Figure 6;

Figure 9 is a section through an alternative needle for use in a retractable syringe in accordance with the invention;

Figure 10 is an exploded sectional view of the barrel and plunger of a further embodiment of a retractable syringe in accordance with the invention;

Figure 11 is a sectional view of the syringe of Figure 10 with the plunger inserted into the barrel; and Figure 12 is an enlarged view of part of Figure 11.

Figures 1 and 2 show a retractable hypodermic syringe having a hollow syringe body 10 defining a receptacle for containing a liquid for injection, a hollow plunger 20, needle holding means 30 for holding a hypodermic needle 34 (only partially shown in Figure 1), and resilient means in the form of a retraction spring 40 which is retained by an expandable annular member in the form of an O-ring seal 42 and which automatically retracts the needle holder 30 and associated needle 34 into the syringe body 10 when the plunger 20 reaches the front end of the syringe body 10.

The syringe body 10 comprises a cylindrical barrel 11, the front end of which is closed by a front end body member 12. The body also has a laterally extending rear flange 13 at the rear end of the barrel 11. The front end body member 12 has a stepped through bore 14 having a narrower front bore portion 15 and a wider rear bore portion 16. A ring retaining member 17 having a tapered forwardly facing surface 18 extends rearwardly from the rear end of the front end body member 12. The needle holder 30 has a tubular portion 32 for holding the needle 34 at its front end, and an enlarged hollow head portion 36 at the rear end of the tubular portion 32.

In the assembled state ready for use as shown in Figure 1, the tubular portion 32 of the needle holder 30 extends through the stepped bore 14 in the front end member 12 with the retraction spring 40 mounted in the wider rear bore portion 16 surrounding the tubular portion 32 of the needle holder 30. The front end of the spring 40 engages a shoulder between the narrower and wider bore portions 15 and 16, and the rear end of the spring engages a shoulder 38 on the enlarged head portion 36 of the needle holder 30. The needle holder 30 and the retraction spring 40 are retained in position by the O-ring 42 which is located between a bevelled or chamfered rear end of the enlarged head portion 36 and the front end of the tapered surface 18 of the rearward extension 17 of the front end member 12 of the syringe body.

The hollow plunger 20 has a cylindrical body portion 21, an annular front end portion 23 and a rear end portion 24 which together define an inner chamber 22 for receiving the needle holder 30 and associated needle 34. An axial hole 25 is provided in the annular front end portion 23 of the plunger, the axial hole 25 being blocked by a frusto-conical plug 50 in the assembled state of the plunger which is ready for use as shown in Figure 1. A ring seal 27 is provided in an annular recess in the front end portion 23 of the plunger to provide a seal between the plunger 20 and the cylindrical barrel 11 of the syringe body. An annular projection 26 extends forwardly from the front end portion 23 of the plunger for engagement with the O-ring 42 when the plunger 20 is moved forwardly so that its front end portion 23 reaches the front end of the syringe body. The plug 50 is of frusto-conical form having a tapered outer surface 52 and a rear projection 54.

In operation, the plunger 20 is advanced within the barrel 11 by depressing the rear end portion 24 so that the plunger 20 expels the injection fluid out of the barrel and through the needle holder 30 and needle 34.

The O-ring 42 also provides a seal at the front end of the barrel 11 around the head portion 36 of the needle holder 30 so that when the plunger 20 is advanced, the fluid is expelled into the needle 34 through the hollow head portion 36 and not around the head portion 36 into the axial bore 14 in the front end body member 12 in which the retraction spring 40 is located.

When the front end portion 23 of the plunger 20 reaches the front end of the barrel 11, the annular projection 26 on the front end portion 23 engages the O-ring 42 to expand the O-ring 42 and to push it forwardly along the tapered surface 18 and out of engagement with the enlarged head portion 36 of the needle holder 30. This releases the compressed retraction spring 40 which expands to urge the needle holder 30 and associated needle 34 rearwardly. The enlarged head portion 36 of the needle holder 30 engages the front end of the frusto-conical plug 50 which is also pushed rearwardly by the force of the retraction spring 40 into the inner chamber 22 of the plunger 20. As shown in Figure 2, a recess 28 may be provided in the rear end portion 24 of the plunger into which the rear projection 54 is pushed by the force of the retraction spring 40, so that the plug 50 is not loose to rattle around within the inner chamber 22. The force of the retraction spring 40 is sufficiently to retract fully the needle holder 30 and associated needle 34 into the inner chamber 22 within the hollow plunger. This ensures that the needle and syringe cannot be re-used.

Referring to Figures 3 to 8 of the drawings, there is shown an alternative embodiment of a retractable syringe in accordance with the invention which has several parts similar to those of the embodiment of Figures 1 and 2, and corresponding reference numerals have been applied to corresponding parts. The body 10 of the syringe of Figure 3 comprises a cylindrical barrel 11 to the front end of which a front end member 12 is mounted, eg. by a snap-fit connection comprising an internal annular projection 121 engageable in an annular recess 111 in the external surface of the barrel 11 at its front end.

As in the embodiment of Figures 1 and 2, the front end member 12 of the syringe body has a stepped through bore 14 having a narrow front bore portion 15 and a wider rear bore portion 16.

The needle holder 30 has a tubular portion 32 having a tapered front end portion 33 to which a needle (not shown) is adapted to be mounted. The needle holder 30 also has an enlarged head portion 36 at the rear of the tubular portion 32. In the assembled syringe ready for use, the tubular portion 32 of the needle holder extends through the bore 14, with the retraction spring 40 being received in the wider rear bore portion 16 with the front end of the spring 40 engaging a shoulder between the narrow and wider rear bore portions 15 and 16 and the rear end of the spring engaging a shoulder 38 on the head portion 36 of the needle holder 30.

In the embodiment of Figures 3 to 8, the spring 40, the needle holder 30 and associated needle are retained in position before and during use by an expandable annular member in the form of a split collet 60 of frusto-conical form having a tapered outer surface 62 which is received in a front end portion 112 of the cylindrical barrel 11 having a slightly forwardly facing internal tapered surface 118.

The split collet 60 like the O-ring seal 40 of Figures 1 and 2 is preferably formed from a resilient material, such as rubber or neoprene, and also provides a seal around the rear end of the head portion 36 of the needle holder 30. The expandable split collet 60 has a stepped through bore 64 having a wider front bore portion 65 and a narrower rear bore portion 66. As shown in Figure 8, the rear portion of the collet is split into three segments 68, the arrangement being such that when the collet 60 and the needle holder 30 are inserted into the front end portion 112 of the cylindrical barrel 11, the tapered surface 118 slightly compresses the segments 68 of the split collet inwardly so that the collet grips the enlarged head portion 36 of the needle holder 30, with the shoulder between the wider and narrower bore portions 65, 66 at the rear end of the collet 60 preventing rearward movement of the spring 40, needle holder 30 and associated needle relative to the cylindrical barrel 11 and front end member 12 of the syringe body 10. The hollow plunger 20 of the syringe of Figures 3 to 8 is similar to that of Figures 1 and 2 in that it has a cylindrical body 21, a front end portion 23 and a rear end portion 24 defining an inner chamber 22 for receiving the needle holder 30 and associated needle when they are urged rearwardly by the retraction spring 40. The front end portion 23 has an axial hole 25 in its front end which, in the assembled syringe ready for use, is blocked by a tapered plug 50. The plug 50 has a frusto-conical front portion 51 having a tapered outer surface 52 and a cylindrical rear portion 53. The front end portion 23 of the plunger 20 has a front part 123 of conical form terminating in an annular front end 128. In use, the plunger 20 can be moved forwardly within the cylindrical barrel 11 by depressing the rear end portion 24 of the plunger to expel fluid from the barrel 11 of the syringe through the needle holder 30 and associated needle. As shown in Figure 3, a rear end portion 13 of the syringe body 10 may have an aperture 19 extending radially inwardly for receiving a removable peg (not shown) which engages with the plunger 20 to prevent inadvertent depression of the rear end portion 24 of the plunger 20.

When the front end portion 23 of the plunger 20 reaches the front end of the cylindrical barrel 11, the projecting annular front end 128 of the plunger engages with the expandable split collet 60 to push the collet forwardly along the tapered surface 118. This causes the split collet to expand so that the shoulder between the wider and narrower bore portions 65 and 66 of the collet no longer retains the shoulder 38 on the enlarged head 36 of the needle holder 30. This releases the retraction spring 40 which urges the needle holder and associated needle rearwardly with the rear end of the enlarged head portion 36 engaging with the front end of the tapered plug 50 to push the plug 50 into the inner chamber 22 of the hollow plunger 20. The spring continues to force the needle holder 30 and associated needle rearwardly until they are completely contained within the inner chamber 22 of the hollow plunger 20.

Referring to Figure 9, there is shown an alternative form of needle for use in a retractable syringe 70 similar to the embodiment of Figures 1 and 2. The needle 70 comprises a tubular needle body 72 and a hollow enlarged head portion 74 at the rear end of the needle body 72. The enlarged head portion 74 may comprise an annular moulding of plastics material secured to the rear end of the needle body 72. Alternatively, the head portion 74 may be formed integrally with the needle body 72. The needle 70 with its enlarged head 74 is intended to replace the needle holder and associated needle 34 of Figures 1 and 2 with the tubular needle body extending through a bore in the front end member 12 of the barrel 10 which is narrower than the bore portion 15 of Figures 1 and 2, and the rear end of the retraction spring 40 abutting the forwardly facing front surface 76 of the head portion 74. The rear end of the head portion 74 has a bevelled surface 78 with the O-ring 42 being positioned between the bevelled surface 78 and the tapered surface 18 of the front end member 12 of the barrel 10 when the syringe is assembled ready for use.

A syringe with a needle 70 as shown in Figure 9 operates in the same way as the embodiment of Figures 1 and 2 with the O-ring 42 being pushed along the tapered surface 118 and expanded when engaged by the annular projection 26 on the front end of the plunger 20 to release the retraction spring 40. The released spring 40 forces the needle rearwardly so that the enlarged head portion 74 pushes the plug 50 out of the axial hole 25 into the inner chamber 22 of the plunger 10 with the needle 70 also being forced into the chamber 22 by the spring 40.

One of the main advantages of an embodiment having a needle with a unitary enlarged head as shown in Figure 9 is that it allows the size of the retractable syringe to be reduced to a size suitable for one-shot administration of a small volume of drugs in fluid form. Ref erring to Figures 10 to 12, there is shown another modified embodiment of a retractable syringe in accordance with the invention.

The syringe of Figures 10 to 12 has several components in common with those illustrated in Figures 1 to 9 and corresponding reference numerals have been applied to corresponding parts. For instance, the syringe shown in Figures 10 to 12 has a hollow syringe body 10 with a barrel 11, a hollow plunger 20 with an axial hole 25 at its front end closed by a removable tapered plug 50, a needle 70 with an enlarged heard 74 similar to that of Figure 9 a retraction spring 40 and an expandable annular member in the form of an O-ring seal 42. The syringe of Figures 10 to 12 differs from the previous embodiments mainly in that the front end portion 112 of the barrel 11 has a stepped bore 114 which retains the O-ring seal 42 instead of a smooth tapered surface. As shown in greater detail in Figure 12, the stepped bore 114 has a rear bore portion 141 of diameter just sufficiently large enough to allow the enlarged head 74 of the needle 70 to pass through, an intermediate bore portion 142 which retains the O-ring seal 42 and a forward bore portion 143 of greater diameter which allows the O-ring seal 42 to expand when it is engaged by an annular front end extension 128 of the plunger 20.

The syringe body 10 has a front end member 12 mounted to the front end of the barrel 11 and the tubular body 72 of the needle 74 extends through, and is guided for rearward axial movement into the syringe body by a bore at the front end of member 12. As shown in Figure 11, the retraction spring 40 is compressed between an inner surface of the front end member 12 and the forwardly facing surface 76 of the head 74 of the needle 70. In operation of the syringe of Figures 10 to 12, the plunger 20 is moved forwardly within the barrel 11 by depressing the rear end portion 24 to expel fluid from the barrel 11 though the enlarged head 74 and the needle 70.

When the front end portion 23 of the plunger 20 reaches the front end of the cylindrical portion of the barrel 11, the projecting front end extension portion 128 of the plunger 20 engages the O-ring 42 to push it forwardly over a shoulder 144 between the bore portions 142 and 143 to expand the O-ring 42 so that it no longer engages the enlarged head 74 of the needle 70. The shoulder 144 may be chamfered to facilitate such forward movement of the O-ring 42 when it is engaged by the front end extension portion 128 of the plunger. This releases the compressed retraction spring 40 which expands to urge the needle 70 rearwardly through the first portion 141 of the bore 114. The enlarged head portion 74 of the needle 70 engages the front end of the tapered plug 50 and the force of the expanding compression spring 40 pushes the plug 50 rearwardly and the plug 50 and needle 70 are thus retracted into the inner chamber 22 of the plunger 20. It will also be apparent from the foregoing description that a particular advantage of the present invention is the use of an expandable annular member to release the retaining means which also provides a seal at the front end of the receptacle for liquid within the barrel. The embodiments of retractable syringes described above each have relatively simple and effective needle retraction mechanisms having only a few components, and so the syringes can be manufactured at a relatively low cost.

It will be appreciated that various modifications may be made to the embodiments described above without departing from the scope and spirit of the present invention. For example, the needle 70 of Figure 9 may have an integral enlarged head portion formed by bending the ends of the needle tube outwardly so as to provide means for receiving the rear end of the retraction spring.

Claims

1. A retractable syringe comprising: a barrel having a front end, a rear end and defining a receptacle for containing a liquid for injection; a needle mounted at the front end of the barrel; a hollow plunger movable within the barrel from the rear end to the front end of the receptacle to expel fluid out of the barrel through the needle; said plunger having an inner chamber, an axial hole at the front end of the chamber and means blocking the axial hole; resilient means which is adapted to urge the needle in a rearward direction into the barrel; wherein said resilient means is restrained by an expandable annular member providing a seal at the front end of the receptacle of the barrel; the expandable annular member being engaged by a forward part of the plunger when the plunger reaches the front end of the receptacle of the barrel such that the expandable annular member moves along a surface at the front end of the barrel and expands to release the resilient means, whereby the axial hole is unblocked and the needle is automatically retracted through the axial hole into the inner chamber of the plunger.

2. A retractable syringe according to claim 1 wherein the expandable annular member is engaged by at least one forwardly extending projection on a front end portion of the plunger when the plunger reaches the front end of the receptacle of the barrel.

3. A retractable syringe according to claim 2, wherein said at least one forwardly extending projection is an annular projection.

4. A retractable syringe according to any one of claims 1 to 3, wherein the expandable annular member comprises an O-ring seal.

5. A retractable syringe according to claim 4, wherein the O-ring seal is moveable along a tapered surface which allows the O-ring to expand when it is engaged by the forward part of the plunger.

6. A retractable syringe according to claim 4, wherein the O-ring is moveable along a stepped surface which allows the O-ring to expand when it is engaged by the forward part of the plunger.

7. A retractable syringe according to claim 6, wherein the O-ring expands when it moves past a shoulder of the stepped surface.

8. A retractable syringe according to claim 7 wherein the shoulder of the stepped surface is chamfered.

9. A retractable syringe according to any one of claims 1 to 3, wherein the expandable annular member comprises a split tapered collet which expands when it is engaged by the forward part of the plunger.

10. A retractable syringe according to claim 9, wherein the collet is movable along a tapered surface which allows it to expand when it is engaged by the forward part of the plunger.

11. A retractable syringe according to any one of the preceding claims wherein the needle is attached to a needle holding means which is retracted with the needle into the inner chamber of the plunger when the resilient means is released.

12. A retractable syringe according to claim 11 wherein the needle holding means is of tubular form received in a bore in a front end member of the barrel.

13. A retractable syringe according to claim 12 wherein the needle holder has a tubular portion for holding the needle and an enlarged head portion engageable with the expandable annular member.

14. A retractable syringe according to any one of claims 1 to 10 wherein the needle has an enlarged head portion at its rear end.

15. A retractable syringe according to claim 14 wherein the enlarged head portion is integral with the main body part of the needle.

16. A retractable syringe according to claim 13 or claim 14 as appended to any one of claims 5 to 8 wherein the enlarged head portion has a bevelled surface at its rear end, with the O-ring being positioned between the bevelled surface of the head and the surface which allows the O-ring to expand.

17. A retractable syringe according to any one of the preceding claims wherein the resilient means comprises a spring which is released from a compressed state by expansion of the expandable annular member to urge the needle rearwardly.

18. A releasable syringe according to any one of the preceding claims wherein the means for blocking the axial hole at the front end of the plunger comprises a removable plug.

19. A releasable syringe according to claim 18 as appended to any one of claims 13 to 16 wherein the removable plug is dislodged into the inner chamber of the plunger by engagement of the enlarged head portion of the needle or needle holder with the front end of the plug.

20. A releasable syringe according to claim 18 or claim 19, wherein the plug is at least partly of tapered form.

21. A releasable syringe according to any one of claims 18 to 20, wherein the plug has a rear projection which is received in a recess in a rear end portion of the plunger when the plug is pushed rearwardly into the inner chamber of the plunger.

22. A syringe according to any one of the preceding claims, wherein a rear end portion of the syringe body has a radial aperture for receiving a removable peg to prevent inadvertent depression of the plunger 20 until the syringe is required for use.