WO2007019647A1

WO2007019647A1 - A hypodermic syringe

Info

Publication number: WO2007019647A1
Application number: PCT/AU2006/001196
Authority: WO
Inventors: Stephen Francis Goodall; Robert Warring Geddes; Paul Joseph Fabre; Stephen Duddy; Michael Steven Buffinton; James Troy Collins Iii; Nathan Anderson Pollock
Original assignee: Analytica Limited
Priority date: 2005-08-19
Filing date: 2006-08-18
Publication date: 2007-02-22

Abstract

A syringe (10) that includes a body (11) to receive a needle assembly (12). The body (11) includes a cylinder (13) having an internal bore (14) that receives a piston assembly (15). In use of the syringe (10), a spring (25) propels the needle (13) to the interior of the syringe (10) when the syringe (10) has been used, to reduce the risk of a needle stick injury.

Description

A HYPODERMIC SYRINGE

Technical Field

The present invention relates to hypodermic syringes and more particularly to syringes that retract the needle into the body of the syringe after use

Background of the Invention

The safe disposal of sharp medical instruments is of a prime concern to healthcare professionals such as doctors and nurses. For example, a particular problem is the safe disposal of needles. An accidental puncture (needle stick) can result in the healthcare professional contacting a serious disease such as Acquired Immune Deficiency Syndrome and Hepatitis.

A wide variety of methods are proposed to inhibit accidental needle injuries including withdrawing the needle after use into the interior of the syringe. Such arrangements are described in International Patent Publications WO92/18186,

WO91/10461, WO01/17594 and WO2005/0589399 as well as USA Patents 5000736 and 5125898.

The syringes of the abovementioned patent publications suffer a number of disadvantages including the needle and the needle mounting being supplied and fixed to the body of the syringe thereby making it necessary to provide a significant range of syringes with different needle sizes and gauges. A further disadvantage is that upon the piston completing its stroke a significant volume of liquid is retained in the syringe.

A still further disadvantage is that during normal operation of these syringes, when air is being expelled from within the syringe with the purpose of then operating the syringe to draw liquid into the syringe, the needle mounting can be inadvertently engaged and the syringe rendered inoperative (retraction prematurely activated).

Object of the Invention

It is the object of the present invention to overcome or substantially ameliorate at least one of the above disadvantages. Summary of the Invention

There is disclosed herein a syringe including: a hollow body having a forward end and a rear end, and a cylindrical bore, the forward end being adapted to engage a needle mounting to secure a needle to the body; a piston assembly slidably located in the bore and operatively associated therewith to substantially enclose a variable volume chamber to receive a liquid to be injected through the needle, said assembly including a plunger having a forward end, a rear end and a longitudinal axis, a needle engaging member mounted in the plunger for longitudinal movement relative thereto from the plunger forward end toward the plunger rear end, the needle engaging member being adapted to engage the needle mounting when the engaging member is moved to adjacent the body forward end so as to be secured to the needle mounting, with said engaging member being urged to move from the plunger forward end toward the plunger rear end, a catch device releasably securing the engaging member to the plunger so that the engaging member is located adjacent the plunger forward end with the catch device being operated to release the engaging member for movement from the plunger forward end toward the plunger rear end when said engaging member is fixed to said mounting; and wherein said piston assembly further includes a seal connecting said plunger and engaging member when said engaging member is secured to said plunger by said catch device.

Preferably, said seal is attached to said plunger so as to move therewith and permit sliding movement of said member relative to said seal when said sliding member is released from said plunger by operation of said catch device.

Preferably, said seal is attached to the forward end of said plunger and has a central aperture through which said engaging member passes. Preferably, said seal is resiliently deformable.

Preferably, said body has an annular surface at the body forward end facing toward the body rear end, said surface being engaged by said seal when said piston assembly has said chamber at a minimum volume, with further forward movement of said piston assembly reducing the longitudinal length of said seal.

Preferably, said engaging member has a forward end and a rear end, and a head extending forwardly of the engaging member forward end, said head being adapted to engage the needle mounting to secure the needle mounting thereto.

Preferably, said plunger is hollow so as to provide a passage within which said engaging member is to be located.

Preferably, said catch device is a projection on said engaging member and a recess in said plunger, with said projection being removed from said recess to release the engaging member for movement relative to the plunger.

Preferably, said seal includes an annular passage within which the plunger projects, with movement of the plunger into said annular passage providing for engagement of the engaging member with said mounting. There is also disclosed herein a syringe including: a hollow body having a forward end and a rear end, and a cylindrical bore, the forward end being adapted to engage a needle mounting to secure a needle to the body; a piston assembly slidably located in the bore and operatively associated therewith to substantially enclose a variable volume chamber to receive a liquid to be injected through the needle, said assembly including a plunger having a forward end, a rear end and a longitudinal axis, a needle engaging member mounted on the plunger for longitudinal movement relative thereto from the plunger forward end toward the plunger rear end, the needle engaging member being adapted to engage the needle mounting when the engaging member is moved adjacent to the body forward end so as to be secured to the needle mounting, with said engaging member being urged to move from the plunger forward end towards the plunger rear end, a catch device releasably securing the engaging member to the plunger so that the engaging member is located adjacent the plunger forward end with the catch device being operated to release the engaging member for movement from the plunger forward end toward the plunger rear end when said engaging member is fixed to said mounting; and wherein said plunger assembly further includes a seal connecting the plunger and said bore, with said seal having a forward portion located at a predetermined position when said volume is at a minimum, with said plunger being movable further forward after the seal forward portion is in said predetermined location to thereby enable said engaging member to engage the needle mounting.

Preferably, said plunger moves relative to said seal to provide for the further forward movement. Preferably, said plunger slidably enters said seal to provide for the further forward movement. hi an alternative preferred form said seal is resiliently deformed and/or compressed to provide for the further movement of said engaging member to engage said mounting. There is further disclosed herein a needle assembly for mounting on a syringe adapted to retract the needle assembly into the syringe by a needle mounting engaging member movably mounted in the syringe, said needle assembly including: a cap that is manipulated to secure the assembly to the syringe, the cap having a longitudinal passage; a needle mounting locating in said passage; a needle attached to said needle mounting and projecting therefrom forwardly beyond the cap; and a catch assembly releasably securing the needle mounting in said passage, the catch assembly being operable upon engagement with the engaging member when said engaging member is engaged with said mounting to release the needle mounting and needle.

Preferably, said catch device includes a neck portion that is expanded by engagement with the engaging member to release the needle mounting. Preferably, said catch device is a plurality of fingers that are resiliency urged apart to release said mounting.

In an alternative preferred form, said catch device includes a resilient ring connecting the needle mounting and cap to secure the needle mounting to the cap, with said ring being displaced to release the needle mounting.

Preferably, said ring is displaced forwardly to release the mounting.

Preferably the ring is exposed to be engaged by the needle mounting engaging member.

Brief Description of the Drawings Preferred forms of the present invention will now be described by way of example with reference to the accompanying drawings wherein:

Figure 1 is a schematic sectioned side elevation of a syringe; Figure 2 is a schematic sectioned enlarged view of portion of the syringe of Figure 1; Figure 3 is a schematic sectioned side elevation of a second syringe;

Figure 4 is a schematic sectioned enlarged view of portion of the syringe of Figure 3;

Figure 5 is a schematic sectioned side elevation of a third syringe; Figure 6 is a schematic sectioned enlarged view of portion of the syringe of Figure 5;

Figure 7 is a schematic sectioned side elevation of a third syringe; Figure 8 is a schematic enlarged view of portion of the syringe of Figure 7; Figure 9 is a schematic sectioned side elevation of a fourth syringe; Figure 10 is a schematic sectioned enlarged view of portion of the syringe of Figure 9;

Figure 11 is a schematic sectioned side elevation of portion of a fifth syringe; and

Figure 12 is a schematic sectioned side elevation of a sixth syringe. Detailed Description of the Preferred Embodiments

In Figures 1 and 2 of the accompanying drawings there is schematically depicted a syringe 10 having a longitudinal axis 58. The syringe 10 includes a body 11 that receives a needle assembly 12. The needle assembly 12 is formed separately from the body 11 and attached thereto just prior to use.

The body 11 includes a cylinder 13 having an internal cylindrical bore 14. Received by the bore 14 is a piston assembly 15 that includes a plunger 16 that extends outwardly of the rear of the cylinder 13 so that the extremity 17 is exposed so that it may be gripped by a user to cause longitudinal movement of the plunger 16 relative to the bore 14. In that regard it should be noted the cylinder 13 has a flange or projections 18 that enable a user to cause longitudinal movement of the plunger 16 relative to the cylinder 13.

The piston assembly 15 further includes a needle gripping member 19 releasably secured to the forward end of the plunger 16 by means of a catch device including a flange 20. The flange 20 has an annular depression 21 that receives an annular projection 22 of the member 19 so that the member 19 is releasably held thereby. One extremity of the member 19 has a head 23, while the plunger 16 has a radially inwardly extending flange 24 that in cooperation with the head 23 maintains a spring 25 in a compressed state. Accordingly the spring 25 urges the member 19 rearwardly, that is, in the direction of the arrow 26.

The piston assembly 15 sealingly engages the bore 14 by including a resilient seal 27. The seal 27 sealingly engages the bore 14 and further includes an annular cavity 28 that receives a forwardly projecting annular flange 29 that is part of the plunger 16. The cavity 28 is curved inwardly toward the axis 58 so that the flange 29 moves the seal 27 away from the member 19 as the flange 29 moves into the cavity 28. The flange 29 has an annular projection 30 that is received within an annular recess 31 so that the seal 27 is moved with the plunger 16 during normal movement of the plunger 16. However upon the seal 27 reaching its forward limit and engaging the surface 32 of the cylinder 13, and upon sufficient force being applied to the extremity 17, the projection 30 moves from within the recess 31 so that the flange 29 may progress into the cavity 28. That is, there is forward movement of the member 19 relative to the cylinder 13 after the seal 27 has completed its forward travel. Located between the seal 27 and the surface 33 is a variable volume chamber that receives the liquid to be injected. Accordingly with use of the seal 27 this chamber is reduced to essentially zero volume when the seal 27 engages the surface 32, yet further forward movement of the member 19 is obtainable by continuing to apply pressure to the extremity 17. This further forward movement of the member 19 causes the member 19 to engage the mounting 34 while causing the mounting 34 to be released from the cap 35 so that under the influence of the spring 25, the member 19 with the mounting 35 attached thereto is propelled rearwardly into the interior chamber 36 of the plunger 16. hi that regard the plunger 16 is cylindrical in configuration and is hollow so as to provide the chamber 36.

In the above construction, the seal 27 has a central aperture 94 within which the member 19 is slidably engaged so as to provide sealing contact therewith. When the member 19 is released, the member 19 slides through the aperture 94 to be located in the chamber 36.

The cap 35 has a thread engaging portion 37 that engages the internal thread 38 of the cylinder 13 adjacent the leading portion 39 of the cylinder 13. The cap 15 has a longitudinally extending passage 40 into which the needle 33 projects and within which the needle mounting 34 is located. The passage 40 is at least partly provided by a rearwardly projecting member 41. The member 41 is hollow so as to provide at least portion of the passage 40, and terminates at its inner extremity with a neck 42 through which a leading head 43 of the member 19 passes when the flange 29 is moving forwardly relative to the seal 27. Ultimately the head 43 passes a tapering portion 44 to engage behind a radially extending surface 45. Accordingly the head 43 is inhibited from being withdrawn from within the passage 40. More particularly the surface 45 is part of the needle mounting 34 so that the head 43 is engaged within and maintained within the mounting 34.

The member 19 adjacent the head 43 has a frusto-conical length 46 that causes the member 41 to expand radially to thereby release the mounting 34 thus the member 41 acts as a catch assembly to relatively secure the mounting within the cap 35. Accordingly with the head 43 engaged with the mounting 34, and the mounting 34 released from the cap 35, the spring 25 propels the member 19 rearwardly (in the direction of the arrow 26) together with the mounting 34 and needle 33 attached thereto.

A seal 47 connects the mounting 34 with the cap 35. The above described preferred embodiment has the advantage of reducing the amount of liquid retained in the syringe 10 at the end of operation thereof.

In the embodiment of Figures 3 and 4, the seal 27 of the previous embodiment has been modified. In this example, the seal 27 includes an annular wall 48 that resiliently deforms to enable further forward movement of the member 19 so that the member 19 engages the mounting 34 and releases the mounting 34 from the cap 35. hi this embodiment the member 50 has longitudinal extending slots 49 so that the mounting

34 has rearwardly extending fingers 99 that have barbs 51 that engage the head 43. The head 43 engages the barbs 51 to cause resilient deformation of the fingers 50 so that the head 43 can eventually pass the barbs 51 so as to be engaged thereby. In particular the barbs 51 engage behind the annular abutment surface 52 of the head 43 so that the head

43 is captively located within the mounting 34.

The seal 48 has an annular flange 53 that engages behind an annular flange 54 of the plunger 16 so as to be attached thereto.

When the piston assembly 15 reaches the forward end of its travel, that is, when the seal 27 engages the surface 32, further pressure applied to the extremity 17 causes resiliently deformation of the seal 27 by deformation of the wall 48 so that member 19 can travel further forward. In the above described preferred embodiment, the member 19 passes through the seal 27 so as to be sealingly connected thereto. Li particular the seal 27 has a forward annular lip 55 that sealingly engages the member 19 and slides therealong so as to sealing engage the member 19. When the member 19 is propelled rearwardly into the chamber 36, the member 19 moves from engagement with the lip 55, with the mounting 34 and needle 35 also passing through the seal 27.

In this embodiment, the plunger 16 has an annular projection 56 that is located behind the head 23 to retain the member 19 attached to the plunger 16. However upon the seal 27 engaging the surface 32, and further pressure being applied to the extremity 17, the head 23 passes the projection 56 by resilient deformation of the plunger 16 in the vicinity of the projection 56. This then releases the member 19 for movement in the direction of the arrow 26. To aid in resilient deformation of the plunger 16 in the vicinity of the projection 56, the plunger 16 is longitudinally slotted so as to have a plurality of slots 57 that are longitudinally extending and angularly spaced about the longitudinal axis 58 of the plunger 16.

The plunger 16 has a forwardly projecting annular ramp surface 102 that engages the lip 55 to aid in lifting the lip 55 from the member 19 when the seal 27 is deformed.

In the embodiment of Figures 5 and 6, again the seal 27 is modified. In this embodiment the seal 27 has a generally forward annular lip 59 that engages the surface 32, and an annular wall 60 that is resiliently deformed when the lip 59 engages the surface 32 and pressure is continued to be applied to the extremity 17. Accordingly the member 19 can again travel forward to engage the needle mounting 34.

In this embodiment, the member 19 is hollow and has two generally parallel annular flanges 61 that engage a projection 62 of the plunger 16. Upon the lip 59 engaging the surface 32 and pressure still applied to the extremity 17, the projection 62 moves past the flanges 61 to release the member 19 for rearward movement under the influence of the spring 25. Although the member 19 is hollow, it is closed at its forward end by a plug 63 and has a forwardly projecting annular flange 64 provided with an annular barb 65. The barb 65 engages an annular projection 66 on the inner end of the needle mounting 34. The needle mounting 34 is maintained in position attached to the cap 35 by a resilient seal 67. The seal 67 engages within an annular recess 68 of the mounting 34 to retain the mounting 34 in position. However upon the member 19 being released from the plunger 66 and with the member 19 engaged with the mounting 34, the spring 25 applies sufficient force to the member 19 to release the mounting 34 from the seal 67.

The plug 23 has a forwardly projecting conical projection 103 that engages the inner end of the needle 33 to prevent any further liquid being delivered through the needle 33 when the piston assembly 12 stroke has been completed.

In the embodiment of Figures 7 and 8, again the seal 27 is modified. In this embodiment the seal 27 has a resiliently deformable annular wall 69 that resiliently deforms upon the lip 58 engaging the surface 32 with pressure still being applied to the extremity 17. In this embodiment, the seal 27 has an annular recess 70 that receives an annular flange 71 of the plunger 16.

In this embodiment, the needle mounting 34 is modified so as to have a plurality of rearwardly projecting fingers 72 that engage behind an annular barb 73 of the member 19. Again the member 19 is hollow but closed by a plug 74. The annular barb 73 is part of an annular flange 75 of the plunger 16.

The needle mounting 34 is sealing connected to the cap 35 by means of a seal 76, with the mounting having an annular recess 77 that receives an annular projection 78 of the cap 35. When the fingers 72 are resiliently deflected inwardly by the flange 75 and engaged behind the barb 73, and the annular projection 56 moves past the head 23 by pressure applied to the extremity 17, the spring 25 applies sufficient force to the needle mounting 34 to move the needle mounting past the projection 78 so that the needle mounting 34 and needle 33 are moved rearwardly with the plunger 16. In the embodiment of Figures 9 and 10, the seal of Figures 7 and 8 is again used. However in this embodiment, the needle mounting 34 is retained in the cap 35 by means of resilient fingers 79. The resilient fingers 79 are moved resiliently radially outwardly by a ramp surface 80 upon movement of the member 19 to resiliently deform the seal 27. Additionally the member 19 has its head 43 engaged behind resilient fingers 81 so as to be captively located with respect to the needle mounting 34. Again the fingers 81 have barbs 82 that engage behind the head 43 so that the head 43 is captively located.

In operation of the syringe 10, the plunger 16 is progressed forwardly until the seal 27 engages the surface 32. Thereafter continued pressure applied to the extremity 17 causes resilient contraction (compression) of the seal 27 so that the member 19 moves forwardly to be captively located with respect to the mounting 34. This movement also releases the mounting 34 by radial outward deflection of the fingers 79. Accordingly the mounting 34 is released from the cap 35 and is attached to the forward end of the member 19. Further pressure applied to the plunger 16 causes the annular projection 56 to move past the head 23. This then releases the member 19 so that the spring 25 will propel the member 19 rearwardly with the mounting 34 and needle 33 attached thereto.

In the embodiment of Figure 11, yet again the seal 27 is modified. In this embodiment the seal 27 has an annular recess 53 within which an annular flange 54 is located. The seal 27 has a resilient longitudinal generally cylindrical wall 83 and a forward lip 84 that both slidably and sealingly engages a forwardly projecting annular flange 85 of the member 19. The member 19 is hollow but is closed at one extremity by means of a plug 95.

The member 19 has rearwardly projecting fingers 86 that act as "pawls" and engage an annular barb 87 so that the mounting 34 can be secured to the member 19. This engagement takes place upon resilient deformation of the wall 83 to provide for further forward movement of the member 19 to engage the mounting 34. Upon the mounting 34 being secured to the member 19, the projection 56 is moved past the projection 23 to release the member 19 from the plunger 16. Thereafter the spring 25 propels the member 19 rearwardly into the plunger 16 together with the mounting 34 and needle 33.

The mounting 34 is retained in the cap 35 by means of a clip assembly including a resilient seal ("O" ring) 88 engaged in an annular recess 89 of the mounting 34. The resilient ring 88 acts as a retaining ring and is forwardly displaced by engagement with the forward portion 97 of the member 19 to release the needle mounting 34 from the cap 35. In Figure 11, the seal 88 is depicted as retaining the mounting 34 attached to the cap 35. hi the embodiment of Figure 12, the member 19 has forwardly projecting resilient fingers 90 that engage an annular barb 91 of the mounting 34. The fingers 90 resiliently deform to pass over the barb 91 to engage there behind so that the mounting 34 becomes captively located with respect to the member 19. Upon the head 23 passing the projection 56, the member 19 is released. A seal 92 is located in an annular recess 93 of the mounting 34 to retain the mounting 34 in position, hi this embodiment, the seal 27 is again modified but is resiliently compressed to provide for further forward movement of the member 19 so that the fingers 90 can move past the annular barb 91.

In this embodiment, the member 19 also has a leading portion 97 that engages the seal 92 to displace the seal 92 forward to release the mounting 34 from the cap 35. In Figure 12, the seal 92 is depicted in the release position, that is releasing the mounting 34. When the seal 92 is in the release position, the fingers 90 are displaced forward so as to have barbs 98 thereof displaced behind the barb 91 so as to engage the barb 91 when the spring 25 pushes the member 19 back into the chamber 36. hi the above described preferred embodiments, when the variable volume chamber 100, that is for example the chamber existing between the forward end of the seal 27, such as the lip 95, and the surface 32, is at its minimum. The piston assembly 12 can then be moved rearwardly in the direction of the arrow 26 to increase the volume of the chamber 95. Liquid is then drawn into the chamber 95. When the liquid is to be expelled, the piston assembly 12 is moved forward toward the needle 33. When the seal 27 engages the surface 32, the chamber 95 is virtually reduced to zero. That is, the maximum amount of liquid has been delivered by the syringe 10. Thereafter the member 19 moves forward relative to the seal 27 either by the plunger 16 sliding into the seal 27 or by resilient deformation/compression of the seal 27 so that the needle mounting 34 may be engaged. This arrangement has a number of advantages including minimising the volume of liquid retained in the syringe 10 after operation, while allowing normal operation of the syringe, that is, to move the piston assembly forward to expel air from within the syringe and then to move the piston assembly rearward to draw liquid into the syringe 10 without having the member 19 engage the mounting 34. Thereafter when the liquid is expelled via the needle 33, the mounting 34 can be engaged by applying further pressure to the extremity 17 to cause the further forward movement of the member 19, that is, by the plunger 16 entering the seal 27 (as in the embodiment of Figures 1 and 2) or alternatively by resilient deforming/compressing the seal 27 as in the embodiments of Figures 3 to 12.

Claims

CLAIMS:

1. A syringe including: a hollow body having a forward end and a rear end, and a cylindrical bore, the forward end being adapted to engage a needle mounting to secure a needle to the body; a piston assembly slidably located in the bore and operatively associated therewith to substantially enclose a variable volume chamber to receive a liquid to be injected through the needle, said assembly including a plunger having a forward end, a rear end and a longitudinal axis, a needle engaging member mounted in the plunger for longitudinal movement relative thereto from the plunger forward end toward the plunger rear end, the needle engaging member being adapted to engage the needle mounting when the engaging member is moved to adjacent the body forward end so as to be secured to the needle mounting, with said engaging member being urged to move from the plunger forward end toward the plunger rear end, a catch device releasably securing the engaging member to the plunger so that the engaging member is located adjacent the plunger forward end with the catch device being operated to release the engaging member for movement from the plunger forward end toward the plunger rear end when said engaging member is fixed to said mounting; and wherein said piston assembly further includes a seal connecting said plunger and engaging member when said engaging member is secured to said plunger by said catch device.

2. The syringe of claim 1, wherein said seal is attached to said plunger so as to move therewith and permit sliding movement of said member relative to said seal when said sliding member is released from said plunger by operation of said catch device.

3. The syringe of claim 2, wherein said seal is attached to the forward end of said plunger and has a central aperture through which said engaging member passes.

4. The syringe of claim 1, 2 or 3, wherein said seal is resiliency deformable.

5. The syringe of anyone of claims 1 to 4, wherein said body has an annular surface at the body forward end facing toward the body rear end, said surface being engaged by said seal when said piston assembly has said chamber at a minimum volume, with further forward movement of said piston assembly reducing the longitudinal length of said seal.

6. The syringe of anyone of claims 1 to 5, wherein said engaging member has a forward end and a rear end, and a head extending forwardly of the engaging member forward end, said head being adapted to engage the needle mounting to secure the needle mounting thereto.

7. The syringe of anyone of claims 1 to 6, wherein said plunger is hollow so as to provide a passage within which said engaging member is to be located.

8. The syringe of anyone of claims 1 to 7, wherein said catch device is a projection on said engaging member and a recess in said plunger, with said projection being removed from said recess to release the engaging member for movement relative to the plunger.

9. The syringe of anyone of claims 1 to 8, wherein said seal includes an annular passage within which the plunger projects, with movement of the plunger into said annular passage providing for engagement of the engaging member with said mounting.

10. A syringe including: a hollow body having a forward end and a rear end, and a cylindrical bore, the forward end being adapted to engage a needle mounting to secure a needle to the body; a piston assembly slidably located in the bore and operatively associated therewith to substantially enclose a variable volume chamber to receive a liquid to be injected through the needle, said assembly including a plunger having a forward end, a rear end and a longitudinal axis, a needle engaging member mounted on the plunger for longitudinal movement relative thereto from the plunger forward end toward the plunger rear end, the needle engaging member being adapted to engage the needle mounting when the engaging member is moved adjacent to the body forward end so as to be secured to the needle mounting, with said engaging member being urged to move from the plunger forward end towards the plunger rear end, a catch device releasably securing the engaging member to the plunger so that the engaging member is located adjacent the plunger 5 forward end with the catch device being operated to release the engaging member for movement from the plunger forward end toward the plunger rear end when said engaging member is fixed to said mounting; and wherein said plunger assembly further includes a seal connecting the plunger and said bore, with said seal having a forward portion located at a predetermined position when

I₀ said volume is at a minimum, with said plunger being movable further forward after the seal forward portion is in said predetermined location to thereby enable said engaging member to engage the needle mounting.

11. The syringe of claim 10, wherein said plunger moves relative to said seal to provide for the further forward movement. is

12. The syringe of claim 11, wherein said plunger slidably enters said seal to provide for the further forward movement.

13. The syringe of claim 10, wherein said seal is resiliently deformed and/or compressed to provide for the further movement of said engaging member to engage said mounting.

20 14. A needle assembly for mounting on a syringe adapted to retract the needle assembly into the syringe by a needle mounting engaging member movably mounted in the syringe, said needle assembly including: a cap that is manipulated to secure the assembly to the syringe, the cap having a longitudinal passage; 25 a needle mounting locating in said passage; a needle attached to said needle mounting and projecting therefrom forwardly beyond the cap; and a catch assembly releasably securing the needle mounting in said passage, the catch assembly being operable upon engagement with the engaging member when said engaging member is engaged with said mounting to release the needle mounting and needle.

15. The needle arrangement of claim 13, wherein said catch device includes a neck portion that is expanded by engagement with the engaging member to release the needle mounting.

16. The needle assembly of claim 13 or 14, wherein said catch device is a plurality of fingers that are resiliently urged apart to release said mounting.

17. The needle assembly of claim 13 or 14, wherein said catch device includes a resilient ring connecting the needle mounting and cap to secure the needle mounting to the cap, with said ring being displaced to release the needle mounting.

18. The needle assembly of claim 17, wherein said ring is displaced forwardly to release the mounting.

19. The needle assembly of claim 17, wherein the ring is exposed to be engaged by the needle mounting engaging member.

20. A syringe substantiates hereinbefore described with reference to Figures 1 and 2, Figures 3 and 4, Figures 5 and 6, Figures 7 to 10, or Figures 11 and 12.