NZ237440A - Safety syringe: needle withdrawal by plunger created vacuum - Google Patents

Description

• 1 3 37-hJfO • Priority Ds:c(:): Cuir.jjiulo C v..!/ : . ..ri ; ';:J: JMr".

C!a?3: ^.vpa^sI^.'WS: p,> Date: ..-2-8-AUG-1995 I P IMu NEW ZEALAND PATENTS ACT, 1953 I We, ROBB PASCAL PATENT PTY. LTD., a company incorporated under the laws oT^^fte State of Queensland, Australia, 8 Eagle Street, Alderley, Queensland, Australia hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement - 1 -(followed by page la) 237££<? la FIELD OF THE INVENTION The present invention relates to a syringe, and more particularly to a safety syringe for preventing 5 contamination, fear of contamination and physical injury by "needle stick" by the syringe needle after use and/or for preventing reuse of the syringe.

BACKGROUND ART In order to minimise the risk of contamination from a 10 used syringe, it is common practice for used syringes to be deposited into heavy duty plastic bins which cannot be pierced by the needles. The bin and contents are then moved to a disposal facility at which they are incinerated. This means of disposal is of limited effect 15 as it does not eliminate "needle stick" risk between liccuic uo? • uu. . uic .iiuud a a. ~ also relatively expensive.

Numerous attempts have been made to design an acceptable syringe in which, after use, the needle is 20 withdrawn into the body of the syringe and retained there in some manner. These designs are ail directed to the same end of covering the needle after use to prevent inadvertent "needle stick" injuries with their attendant risk of cross-infection and to prevewL ;ause of the 25 syringe. In many of these prior art arrangements the withdrawal of the needle into the body is entirely manual and requires the syringe user to remember to make some deliberate relative movement, normally between the plunger and the body, to effect withdrawal of the needle into the 30 body of the syringe. Proposals have been made, as in Australian Patent Specifications 593,513, 594,634 and 35,676/89, to induce automatic withdrawal of the plunger into the body by the use of a helically coiled spring.

This necessitates the use of additional and costly parts 35 in the syringe and complicates its assembly. fg -first 8 APR 1991, 23 7 4 4 0 aspect the present invention is directed to an alternative arrangement for the automatic withdrawal of a syringe needle into the body of the syringe.

In the above proposals for automatic withdrawal of 5 the plunger they have the disadvantage that immediately the positive manual pressure holding the plunger in a depressed condition is removed the spring will immediately commence the return of the plunger to its extended condition and simultaneously commence withdrawal of the 10 needle into the body of the syringe. This could cause tissue tear and inadvertent and unwanted suction of blood into the syringe unless the operator consciously keeps the plunger depressed until the syringe is fully withdrawn from the patient's body. In a second aspect the present 15 invention provides braking means to slow at least the initial rate of withdrawal of the needle into the body of the syringe.

DISCLOSURE OF THE INVENTION According to a first aspect of the present invention 20 there is provided a syringe comprising: a body having a forward end, a rearward end, and a bore extending from the forward end to the rearward end; a needle bolder on the body proximate its forward end; a plunger having an end mounted slidably within the 25 bore of.the body, the plunger extending out of the rearward end of the body; connecting means for connecting the plunger to the needle holder on completion of an injection stroke of the plunger whereby subsequent retraction of the plunger 30 withdraws a needle mounted on the needle holder into a shielded position within the bore of the body; and energy storage means comprising a vacuum chamber defined between the plunger, the syringe body, and first and second sealing members extending between the plunger - \ . "r - \ and the syringe body, vacuum being created within the / ^ 1 c \ 12 OCT i?93 ° - <• ° / L _ _ 2 3 7 4 4 0 chamber by movement of the plunger during the injection stroke which moves the first and second sealing means relatively apart, the vacuum serving to withdraw the plunger and the needle holder after injection pressure on the plunger is removed.

The syringe according to the invention preferably also includes resilient braking means for retarding the retraction of the plunger, the resilient braking means being disposed within a space between the bore and the 10 plunger, the resilient braking means either being disposed on the body and bearing on the plunger, or being disposed on the plunger and bearing on the body, to provide a braking force sufficient to retard but not stop the retraction of the plunger.

In a preferred embodiment of the invention of the resilient braking means is formed integrally with sealing means defining one end of the vacuum chamber of the first aspect of the invention. It is preferred that the resilient braking means is moveable longitudinally of that 20 one of the body and the plunger to which it is affixed so as to alter the braking force it applies to the other of those members. This allows the withdrawal of the plunger under the action of the vacuum chamber to be prevented until the completion of injection stroke of the plunger if 25 desired.

The syringe preferably also includes stop means located on the body for arresting movement of the end of the plunger proximate the forward end of the body during only a preparatory forward stroke of the plunger so that 30 the connecting means does not connect the plunger to the needle holder on completion of the preparatory stroke, and engagement means on the plunger adapted to engage with the stop means and render it inoperative during a rearward stroke of the plunger, ^ '* 1 o ( 1 o nf.T i?93 / 23 7440 BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be further described with reference to the accompanying drawings in which; Fig. 1 is a schematic longitudinal section of a syringe in accordance with the preferred embodiment of the invention, the upper half of the section showing the syringe in a condition prior to use and the lower half of the section showing the syringe in a condition at the end □£ its injection stroke, the lower half of the section also showing an alternative mounting for the syringe Fig. 2 shows five longitudinal sectional views through a syringe according to another embodiment of the present invention; Fig. 2a shews the syringe in the condition in which it is shipped for use; rig- 2b shows the syringe in a condition ready to draw up an injectable liquid; Fig. 2c shows the syringe in a condition in which the liquid has "been drawn uc and the cose of the liquid is about to be selected with an accompanying exclusion of air from the syringe; Fig. 2d shews the syringe in a condition immediately after the injection has been given; and Fig. 2e shows the syringe in a condition after the needle has been automatically withdrawn into the syringe body; Fig. 3 is a longitudinal sectional view through one end of a narrow base syringe according to another embodiment of this invention; and Fig. 4 is a longitudinal sectional view n s s t \ 12 OCT 1793 mitko needle holder and adjacent end of the body of a wide base syringe according to another embodiment of the present invention.

BEST METHOD FOR CARRYING OUT THE INVENTION 5 The syringe shown in Fig. 1 comprises a body 2 and a plunger 4 mounted within the body 2. A needle holder 6 is mounted at the forward or inner end of the body 2 by means of an annular array of releasabls locking pawls 8 which normally engage over a shoulder 10 of the holder 5 in 10 order to pre vent retraction cf the holder 6 ir.zo the body 2. A forwardlv-projecting part 12 cf the needle holder 6 is of conventional form in order to mount a standard needle which is a friction fit on the holder. Alternatively the body 2 can mount a needle with an 15 integral holder 6b as shown in the lower part of Fig. 1, the holder 6b co-operating with the releasable pawls 8 in the same manner as the holder 6. The pawls 8 extend rearwardly from a sleeve 13 which centres the needle holder in the body 2.

The plunger 4 carries, towards its forward end, an annular travelling seal 14 in sliding contact with the inner surface of the syringe bocy 2. The seal 14 is intended to form a high quality hermetic seal and is shaped to define a series of axiallv spaced annular 25 sealing zones against the body 2. A similar high quality annular seal 16 is fixedly mounted on the body 2 towards its rear or outer end. This fixed seal 15 has on its inner surface a series of annular sealing zones which seal against the outer surface of the plunger 4. The space 18 30 defined between the two seals 14, 16 constitutes a vacuum chamber. Upon actuation of the syringe the movement of the seal 14 away from the seal 16 generates a vacuum in the vacuum chamber 18 to cause eventual withdrawal of the holder 6 or 6b together with the needl.e_.into the^Byringe 35 body 2 after use. ^ - 8 APR 1991 K- * s* , C * J ~ ^ J 11 2374^-0 0 - The forward end of the plunger 4 includes a radially-extending braking flange 20 which frictionaily engages the inner surface of the body 2 in order to prevent non-intentional retraction of the plunger 4 under the 5 influence of the vacuum created in the vacuum chamber 18. The braking flange 20 is a resilient flange defined at an outer edge of a conical wedge 22 formed at the forward end of the plunger. The conical wedge 22 is adapted to co-operate with the retaining pawls 8 for the needle 10 holder in order to release zr.e pawls 8 as will subsequently be described. The forward end of the plunger is also formed with an annular array of flexible pawls 24 arranged inwardly of the conical wedge 22. The pawls 24 are shaped to engage into an undercut groove 25 formed in 15 the head of the needle holder in order to anchor the needle holder to the plunger 4 when the plunger 4 is in its forward position.

A removable stop ring 29 is mounted in an inner annular seat formed in the inner surface of the body 2 20 rearwardly of the fixed seal 15. The stop ring 28 is a split ring which is resiliently biased to an external diameter greater than that of the inner seat. An outer seat 30 for the stop ring 28 is formed in the body 2 rearwardly of the inner sear. The stop ring 28 has, on 25 its internal surface, an annular groove 32 adapted to receive an annular rim 34 formed on the external surface of the plunger 4 towards the rear end of the plunger.

The syringe is supplied with the plunger 4 in its retracted position. In order to use the syringe, the 30 plunger 4 is pushed inwardly to expel most of the air from the fluid-receiving chamber which is defined between the forward end of the plunger 4 and the needle holder 6 or 6b. Insertion of the plunger during this phase is limited by the stop ring 28, the rear edge of which engages a 35 shoulder 36 at the outer end of the plunger 4. In this 237i+ifO limit position, the annular groove 32 in the stop ring 28 is axially aligned with, and is engaged by, the projecting annular rim 34 on the plunger body whereby the stop ring 23 is releasably connected to the plunger 4. The stop ring 23 prevents insertion of the plunger 4 to its forwardmcst position and hence prevents connection of the pawis 24 at the forward end of the plunger 4 with the groove 25 in the head cf the needle holder. The piur.cer 4 can then be retracted to craw fluid into the fluid chamber cf the syringe. It is to be noted that during this ntcce, the braking flange 20 on the plunger frictionally encages the inner wall of the body 2 in order to prevent retraction of the plunger under the influence of the vacuum generated within the vacuum chamber 13 during the insertion cf the plunger. As mentioned above, at the end of the initial insertion stroke, the step ring 23 was encaged by, and was connected to, the plunger. As the plunger is withdrawn to draw fluid into the chamber, the stop ring 23 is withdrawn with the plunger until the stop ring 23 is clear cf the inner seat. When the stop ring mcves into alignment with the outer seat 30, the inherent resilience cf the stop ring 28 enables the stop ring to expand into the outer seat 30. The increased diameter of the cuter seat 30 enables the stop ring 28 to expand to such a diameter that it disengages from the annular rim 34 on the plunger and is retained in the cuter seat, as shown in the lower half of Fig. 1. A retaining lip 37 at the outer end cf the outer seat 30 ensures that the ring 28 is retained within the seat in order to prevent accidental displacement of the ring 28 and possible jamming of the plunger.

When the required quantity of fluid has been drawn into the fluid chamber, the plunger is then depressed in order to expel air from the chamber in the usual manner and then to discharge the fluid into the patient. It is to be noted that as the plunger rea • its / 53 7It 1+6 injection stroke, the plunger is no longer subject to the influence of the stop ring 23 which is new in its larger diameter outer seat 30 and this enables the plunger to be moved into its fully forwards ccndition for discharge of 5 substantially the entire contents of the fluid chamber.

During the injection stroke, vacuum again builds up in the vacuum chamber 18, the effect cf this vacuum being resisted by the braking fiance 20 which fricticnally engages the inner surface of the syringe bccy. 10 As the plunger nears the end cf its injection stroke, that is beyond the stop position previously defined by the presence of the stop ring 23 when in its inner seat, the conical wedge 22 contacts the retaining pawls 3 in order to deflect these pawls outwardly beyond the retaining 15 shoulder 10 on the needle holder and into engagement with the inner surface of the syringe body as shewn in the lower half of fig. 1. At the same time, the pawls 24 at the plunger move into snap-engagement in the undercut groove 26 in the head of the needle holder in order to 20 connect the needle holder with the plunger. The rear ends 8a of the retaining pawls 3 constitute shear knives which, when the pawls 8 are deflected outwardly by the wedge 22, lie against the inner surface of the syringe body in order to contact the braking flange 20 and to 25 deflect the flange 20 inwardly and rearwardly by plastic deformation of the flange, thereby reducing or removing the frictional contact between the braking flange 20 and the syringe body. When manual pressure is removed from the rear end of the plunger and with the braking action of 30 the braking flange 20 removed or reduced consequent on its plastic deformation, the vacuum generated in the vacuum chamber 18 during the injection stroke acts to withdraw the plunger and thus the needle holder and needle which is now attached to the plunger. In the withdrawn position of 35 the plunger, the needle is enclosed fully within 9 plunger body with no portion of the needle exposed for accidental contact. The needle holder is a relatively-loose fit on the pawls 24 so that the axis of the needle holder and needle can incline relative to the syringe body 5 whereby the tip of the needle will lie to one side of the syringe body and will be prevented by the sleeve 13 from accidental extension from the body. The sleeve 13 .nay also comprise a central iris structure held open by the needle holder when in its operative position. As seen as 10 the needle holder is withdrawn by the plunger, the iris structure contracts or closes in order to close the central aperture of the sleeve 13 and thereby to prevent any access to the interior of the syringe body. syringe, the syringe can be disposed cf in a conventional plastic bag. The absence cf exposure of the needle also assists in preventing the spread of infection by contaminated needles. body 100 and a plunger 101. A needle holder 102 is mounted at the forward or inner end cf the body 100. The needle holder 102 has at its forward end a cylindrical boss 103 inclined slightly to the longitudinal axis of the syringe body 100. A needle 104 is disposed cn the 25 boss 103 and is held in place thereon by a conventional U-lock fitting 105. Due to the inclination of the boss 103 the needle 104 is also inclined to the longitudinal axis of the body 100. The needle holder 102 has a bore 106 extending longitudinally through it and 30 communicating at one end with an undercut recess 107, adapted to engage with a suitably shaped protuberance on the plunger as will be hereinafter described, and at the other end with the needle 104. A flange 108 on the needle holder 102 surrounding the underc "" fes As no part cf the needle is exposed after use of the The syringe shown in Figs. 2a to 2e comprises a behind an annular rib 109 on the 3 3 7U0 body 100. A plurality of triangular sprags 111 project inwardly from the forward end of the body 100 and engage about the circumference of the needle holder 102. The engagement of the flange 108 cf the needle holder 102 with 5 the annular rib 109 of the bccy 100 and the engagement of the sprags 111 about the circumference of the needle holder 102 serve to securely locate the needle holder at the forward end of the body 130 until it is released therefrom by engagement with the plunger as will be 10 hereinafter described.

The body 100 defines a substantially cylindrical bcre 110 extending from the annular rib 109 which retains the needle holder 102 in place at the forward end of the body 100 to a second annular rib 113. Rearwardly of the 15 annular rib 113 the body 100 increases in internal diameter through a frusto-conical zone 114 to a substantially cylindrical zone 115. The cylindrical zone 115 is directly connected to a second cylindrical zone 116 of slightly increased internal diameter which in 20 turn is connected to a tapering zone 117 which tapers outwardly in diameter to the free end 113 of the body 100. Between the zones 116 and 117 the body is formed integrally with an annular collar 113. This collar 118 is moulded extending rearwardly of the junction 25 between the two zones 116 and 117 and is then turned ever to lie within zone 116, forming an inwardly directed annular abutment. The free end 110 of the body 100 is moulded integrally with a pair of diametrically opposed stop members 121 joined by a thin flexible ring 122. The 30 stop members 121 and ring 122 are also moulded integrally with, and extended rearwardly of, the body 100 and are then turned over to lie within the zone 117.

A resilient annular braking and sealing member 123 is positioned within the zones 115 and 116 of the body 100. 35 The member 123 includes a pair of <n 3-7/ / A a- y / if -f annular sealing lips 124 sliding radially inwardly from the member 123 and adapted to sealinaly engage about the plunger 101. Rearwardly cf the lips are three braking ribs 125, which could in another embodiment of the 5 invention be replaced by rows cf bosses which may serve the same purpose. The braking ribs are adapted to apply a braking force to the plunger 101. The radially outer surface of the member 123 carries at its forward end a circumferential rib 125. In the initial configuration of 10 the syringe the member 123 is positioned with the rib 126 abutting against the forward end of the collar 119. The collar 118 then surrounds the member 123 and serves to compress the braking ribs 125 against the plunger 101. with a pair of outwardly extending finger grips 112 disposed in diametric opposition about the body 100.

The plur.cer 101 includes an elongate shaft 127 and at its forward end a radially extending sealing flange 128 in sealing engagement with the here 110 of the body 100. At 20 its forward free end the plunger 101 is formed with a protuberance 129 adapted to engage with the recess 107 in the needle holder 102. The protuberance 129 and recess 107 are so dimensioned that on engagement of the protuberance 129 in the recess 107 an inwardly directed 25 flange 131 will be pivoted inwardly and fcrwardly by contact with the protuberance 129 which will cause the flange 108 on the needle holder to be pivoted rearwardly and inwardly to free the flange 108 from the annular rib 109 on the bore of the body 100.

The rearward end of the plunger 101 is forced with an enlarged head 132 which head 132 includes at its forward end a radially outwardly extending flange 133. The enlarged head 132 on the plunger 101 is preferably formed by heat reforming the rearward 5nd of the_ glunger after The rearward end of the syringe body 100 is formed the sealing and braking member 53 7U0 12 - the stem 127 cf the plunger 101.

In use the syringe is shipped in conditions depicted in Fig. 2a. The plunger 101 is in its fully retracted position and the braking and sealing member 123 is 5 surrounded by the collar 113 such that the braking ribs 125 are urged firmly against the shaft 127 of the plunger 101.

In order to draw an injectable fluid into the syringe the plunger 101 is depressed to the position, shown in 10 Fig. 2b. The plunger 101 is depressed until it is stopped by the engagement cf the fiance 133 on the head 132 of the plunger 101 with a pair of inwardly directed recesses 134 in opposed faces of the stop members 121. This engagement occurs when the prctruberance 129 on the forward end cf 15 the plunger 101 is closely adjacent but net engaged with the undercut recess 107 in the needle holder 102. Subsequent retraction cf the plunger 101 will draw an injectable liquid, into which the needle has been inserted, into the body 100 cf the syringe. Such 20 retraction will also shear the thin connection between the stop members 121 and the body 100 of the syringe. The dose of liquid in the syringe may then be adjusted, and air removed from the syringe, by depression of the plunger 101. The braking fcrce applied to the shaft 127 25 of the plunger 101 is at this point sufficient to resist movement of the plunger 101 relative to the body 100 under the influence cf the vacuum created between the braking and sealing member 123 and the sealing flange 128 as the plunger 101 is depressed into the body 100. Thus movement 30 of the plunger 101 relative to the body 100 will only occur by manual application of force to the plunger 101 by the person using the syringe.

When an injection is to be given the needle is inserted into the patient in a conventional manner. This 35 insertion is facilitated by the inclilh'^^^of A l l, 84PA?"9/~) / / I 13 537440 needle 104 relative to the body 100 cf the syringe as the body 100 is disposed at a mere convenient angle to the skin of the patient, at least in the case of intravenous injections, than would be the case if the needle 10 4 was 5 in axial alignment with the body 100 of the syringe. The plunger 101 is then depressed to inject the liquid into the patient. At the end of the plunger stroke the protruberance 129 will engage with the undercut recess 107 of the needle holder 102, as the earlier removal cf the 10 stop members 121 now allows the plunger 101 to be fully depressed. The engagement cf the prctrucerance 129 with the undercut recess 107 causes the flange 103 cn the needle holder 102 to be drawn radially inwardly free cf the circumferential groove 109 in the bedv 100. As the 15 protruberance 129 is entering the undercut recess 107 so the flange 133 cn the head of the plunger 10i engages the rearward end of the braking and sealing member 123 pushing it into zone 115 of the syringe body 100 free of collar 118. The braking and sealing member 123 can expand 20 radially within the zone 115 so that the braking pressure on the shaft 127 of the plunger 101 is reduced. When the syringe is withdrawn from the patient the vacuum created between the braking and sealing member 123 and the sealing flange 108 will be sufficient to slowly draw the 25 plunger 101 back into the body 100 cf the syringe. The plunger 101 will also draw the needle holder 102, now freed from engagement with the body 100, and the needle 104 into the body. As the needle holder 102 is drawn into the body the free ends of the triangular 30 sprags 111 will spring radially inwardly to form an iris precluding egress of the needle 104 outwardly from the now open forward end of the syringe body 100.

The vacuum pressure created in the syringe body 100 will be sufficient to draw the needle 104 fully into the 35 body 100 behind the iris formed by tfri^tr-i-aiigular 237440 14 sprags 111, and to engage radially outwardly directed fingers 135 on the shaft 127 of the plunger 101 behind at least the forwardmost one of sealing lips 124. Any subsequent use of the syringe is prevented firstly by the 5 fact that the needle 104 is trapped within the body 101 by the sprags 111 and the inclination of the needle 104 and secondly by the fact that any depression cf the plunger 101 will cause fingers 135 to drag the braking and sealing member 123 into the frustcccnical zone 114 cf the 10 body where the braking ribs *115 cf the braking and sealing memoer 123 will be caused to tightly bind against the shaft 127 of the plunger 101.

The arrangement of Fig. 3 shows the application cf the present invention to a narrow bore syringe which would 15 typically be used for giving an injection of about 1ml of liquid to a patient. In this case the construction and operation of the syringe is as has been described with reference to Figs. 2a to 2e except that the vacuum pressure is created between the braking ar.d sealing 20 member 123 and an additional sealing flange 135 mounted cn the shaft 127 of the plunger 131 intermediate its ends. A step 137 on the shaft 127 causes the sealing flange 135 to move downwardly of the bore 110 as the plunger is depressed creating a vacuum between the sealing lips 124 25 and the flange 136. This vacuum will draw the flange 136 rearwardly when the injection has been completed anc the flange 136 will carry the plunger 101 and the needle 104 rearwardly with it.

The arrangement cf Fig. 4 shows the needle holder 102 30 positioned in a wide bore syringe. in this case the arrangement is as described with reference to Figs. 2a to 2e except that the sprags 111 do not need to be moulded so as to spring inwardly to form an iris upon withdrawal of the needle holder into the body 100 as the inturn^d. . 35 flanges 139 and 138 are sufficient to prevent thei K 12 OCT 1993 needle 104 from being re-extended from the syringe once it has been drawn into the body 100.

The embodiments of the invention are given for the purpose of example only and are not intended to limit the 5 broad scope of the present invention as defined by the claims. The needle holder 102 could if desired be held in place in the body 100 of the syringe by a friction fit without the need for the rib 109. Similarly the braking ribs 125 could be replaced by other configuration of means 10 adapted to apply a braking effect between the plunger 101 and the syringe body 100.

Claims (12)

23 7440 - 16 - WHAT///.'" CLAW! !S GLAIM3♦~

1. A syringe comprising: a body having a forward end, a rearward end, and a bore extending from the forward end to the rearward end; 5 a needle holder on the body proximate its forward end; a plunger having an end mounted slidably within the bore of the body, the plunger extending out of the rearward end of the body; connecting means for connecting the plunger to the 10 needle holder on completion of an injection stroke of the plunger whereby subsequent retraction of the plunger withdraws a needle mounted on the needle holder into a shielded position within the bore of the body; and energy storage means comprising a vacuum chamber 15 defined between the plunger, the syringe body, and first and second sealing members extending between the plunger and the syringe body, vacuum being created within the chamber by movement of the plunger during tht- injection stroke which moves the first and second sealing means 2 0 relatively apart, the vacuum serving to withdraw the plunger and the needle holder after injection pressure on the plunger is removed.

2. A syringe as claimed in claim 1 wherein the first sealing member is carried by the plunger 25 within the bore proximate the end of the plunger, and the second sealing member is carried by the body within the bore proximate the rearward end of the body.

3. A syringe as claimed in claim 1 or claim 2 wherein the syringe further includes resilient braking means for 30 retarding the retraction of the plunger, the resilient braking means being disposed within a space between the bore and the plunger, the resilient braking means either being disposed on the body and bearing on the plunger, or being disposed on the plunger and bearing on the body, to 35 provide a braking force sufficient to retard but not stop L. !% , ! ^ 4 T- 12 OCT 1753 2 3 7 4 4 0 - 17 - the retraction of the plunger.

4. A syringe as claimed in-claim 3 wherein the braking means includes means adapted-to bear against corresponding means on the body such that relative movement therebetween 5 alters the braking force.

5. A syringe as claimed in claim 4 wherein the bore comprises zones of different internal diameter and the resilient braking means comprises a resilient cylindrical member having engagement means resiliently bearing against 10 the plunger to exert the braking force, the resilient cylindrical member being longitudinally moveable within the zones of different internal diameter so as to alter the braking force on the plunger.

6. A syringe as claimed in any one of claims 1 to 5 15 wherein the syringe further includes stop means located on the body for arresting movement of the end of the plunger proximate the forward end of the body during only a preparatory forward stroke of the plunger so that the connecting means does not connect the plunger to the 2 0 needle holder on completion of the preparatory stroke, and engagement means on the plunger adapted to engage with the stop means and render it inoperative during a rearward stroke of the plunger.

7. A syringe as claimed in claim 6 wherein the bore 25 forms an inner surface of the body and the stop means comprises an abutment formed on the inner surface of the body and wherein the engagement means is adapted to engage with the abutment during the preparatory forward stroke, and the abutment means being sheared from the body upon 30 the rearward stroke of the plunger.

8. A syringe as claimed in any one of claims 1 to 7 wherein the connecting means comprises a protuberance at the end of the plunger and a complementary undercut recess in the needle holder. c , ^ \ ^ i 35

9. A syringe as claimed in claim 8 wherein the needled * \ \ 12 OCT S993" 23 74 4 0 18 holder is retained in the body by a radially extending flange on the needle holder engaged with complementary engagement means within the bore, the flange being 5 released from the complementary engagement means upon connection of the protuberance to the undercut recess.

10. A syringe as claimed in any one of claims X to 9 wherein the body includes a plurality of pivotable fingers within the bore proximate the forward end of the body, the 10 plurality of pivotable fingers pivoting radially inward so as to form an iris to substantially occlude the forward end of the body when the needle holder is drawn into the bore.

11. A syringe as claimed in any one of claims 1 to 10 15 wherein a needle is disposed on the needle holder at an angle to a longitudinal axis of the body.

12. A syringe substantially as hereinbefore described with reference to the accompanying drawings. DATED THIS V'-2A W DAY OF ' \9 ^ ^ A..!. PA.T' & SON PEH ' AGENTS FOR TH£ APPLICANTS O ^ . r