AU2005201528B2 - A retractable syringe - Google Patents

Description

S&F Ref: 653305AUD1

AUSTRALIA

PATENTS ACT 1990 COMPLETE

SPECIFICATION

FOR A STANDARD

PATENT

Name and Address of Applicant: Actual Inventor(s): Address for Service: Invention Title: Roy Tudor Brewer, Australian Citizen, of 109 Capper Street, Gayndah, Queensland, 4625, Australia Roy Tudor Brewer Spruson Ferguson St Martins Tower Level 31 Market Street Sydney NSW 2000 (CCN 3710000177) A retractable syringe The following statement is a full description of this invention, including the best method of performing it known to me/us:- 5845c O A RETRACTABLE

SYRINGE

Field of the Invention _The present invention is directed towards a syringe having a retractable needle.

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

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 The piston and needle can then be withdrawn into the barrel of the syringe by the user. A disadvantage of such syringes is that in the withdrawn position, the end of the plunger extends from the open barrel of the syringe.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 In order to avoid this occurring complicated locking arrangements for locking the plunger in the withdrawn position have been proposed.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

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

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

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

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

Typically, the piston engages the base of the needle and is then withdrawn into the body of the piston.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

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

Other arrangements include complex claw arrangements whereby claws are deformed at 00 5 the end of the depression stroke of the plunger to either release and/or engage the respective parts.

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

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

Summary of the Invention There is disclosed herein a hypodermic syringe including: a barrel having an internal bore surrounding a volume to receive a liquid to be injected, the bore extending to a base end; a needle assembly releasably mounted in said base end and including a needle base member and a needle mounted therein, the needle communicating with said volume so that liquid can be injected through said needle upon a reduction in said volume; a hollow plunger slidably located within said bore and moved towards said base end to reduce said volume, the plunger providing a chamber and leading portion from which the chamber extends; R\l 1FTT103721 div.doc:hxa 1 a piston releasably mounted at said leading portion so as to move with the 2 plunger to reduce said volume, the piston being receivable in said chamber and being urged into said chamber, the piston further having engaging means to engage the needle assembly to attach the needle assembly to the piston upon the needle assembly projecting 00 5 inwardly of the piston; a release means releasably attaching the piston to the plunger; and wherein said needle assembly includes a catch member that radially expands to engage Ct the engaging means so as to be fixed thereto, and said release means is activated to (release said piston after said needle assembly is fixed to said piston so that said piston and needle assembly move into said chamber.

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

Preferably, said needle base member has said catch member, said piston includes a recess engaged by said catch member.

Preferably, said needle base member includes a stem having said catch member, and said piston includes a cavity to receive said stem.

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

Preferably, said needle base member has said end recess and said end projection extends between said end recess and said base end to releasably secure the needle base member to said base end, with said end projection being moved radially to release said needle base member.

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

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

Preferably, said piston sealing closes said chamber, and said chamber has air evacuated therefrom so that said piston is urged into said chamber so that upon release of ra.. ITprT1O7,div d-rehx the piston with respect to the plunger the piston is moved into the chamber under the 2 influence of atmospheric pressure.

Preferably, said base end has an air passage to provide said atmospheric pressure Brief Description of the Drawing Figure 1 illustrates a schematic cross sectional view of a preferred syringe 1 of the present invention.

Description of the Preferred Embodiment SSection A of the Figure illustrates the syringe towards the completion of the fluid injection procedure. Section B illustrates the syringe at the end of the injection procedure.

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

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

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

The syringe 11 also includes a plunger 26. The plunger 26 has a head 27 which extends from the open end 13 of barrel 12. The plunger 26 is slidable within the bore of the barrel 12. The plunger 26 has an evacuated chamber 28. The chamber 28 is sealed at one end by a piston 29. The piston 29 is releasably attached to the plunger wall 30 by a multi-function split ring 31. An O ring 32 provides a gas and fluid seal between the IRTT1n 721di dc:hxa plunger 26 and piston 29. A further O ring 40 provides a seal between the plunger 28 and barrel wall.

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

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

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

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

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

It can be seen that in the above embodiment the needle is rapidly and automatically withdrawn into the plunger body. Such withdrawal does not require two handed operation and does not rely on correct operation by the user. At the completion of rR:\LIBTT]03721 div.doc:hxa 1 the action, all components are locked together, and the needle is safely secured within the 2 plunger body.

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

The split ring is under compression and it is released of part of the compression force which expands the split ring. The only force input required by the operation is that required to slide the ring along the step of the recess in the barrel wall. Typically, this force will be essentially the same as that required for movement of the plunger. In other 0words, the needle base member may be released as part of the normal downward stroke of the plunger. The other split rings operate sequentially in a similar manner to reduce the amount of force required to engage and release the various parts as compared to earlier syringes.

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

11 1-11A1 ~n~hu

Claims (8)

1. A hypodermic syringe including: a barrel having an internal bore surrounding a volume to receive a liquid to be injected, the bore extending to a base end; 00 5 a needle assembly releasably mounted in said base end and including a needle base member and a needle mounted therein, the needle communicating with said volume N so that liquid can be injected through said needle upon a reduction in said volume; t a hollow plunger slidably located within said bore and moved towards said base end to reduce said volume, the plunger providing a chamber and leading portion from which the chamber extends; a piston releasably mounted at said leading portion so as to move with the plunger to reduce said volume, the piston being receivable in said chamber and being urged into said chamber, the piston further having engaging means to engage the needle assembly to attach the needle assembly to the piston upon the needle assembly projecting inwardly of the piston; a release means releasably attaching the piston to the plunger; and wherein said needle assembly includes a catch member that radially expands to engage the engaging means so as to be fixed thereto, and said release means is activated to release said piston after said needle assembly is fixed to said piston so that said piston and needle assembly move into said chamber.

2. The hypodermic syringe of claim 1, wherein said release means includes a co-operating recess and projection, with said projection being located in said recess to attach the piston to the plunger, and said projection is spaced from said recess to release the piston for movement into said chamber.

3. The hypodermic syringe of claim 1 or 2, wherein said needle base member has said catch member, said piston includes a recess engaged by said catch member.

4. The hypodermic syringe of claim 3, wherein said needle base member includes a stem having said catch member, and said piston includes a cavity to receive said stem. rn.\ TTTn '17)IdV nr'hya The hypodermic syringe of any one of claims 1 to 4, wherein said Sneedle base member is releasably attached to said base end by a co-operating end recess and end projection.

6. The hypodermic syringe of claim 5, wherein said needle base member 00 5 has said end recess and said end projection extends between said end recess and said base N,1 end to releasably secure the needle base member to said base end, with said end projection being moved radially to release said needle base member.

7. The hypodermic syringe of claim 6, wherein said needle base member is moved longitudinally of the hypodermic syringe to release said needle base member for 0to movement with said piston.

8. The hypodermic syringe of claim 7, wherein said end projection is a ring that moves radially upon said axial movement of said needle base member to release said needle mounting.

9. The hypodermic syringe of any one of claims 1 to 8, wherein said piston sealing closes said chamber, and said chamber has air evacuated therefrom so that said piston is urged into said chamber so that upon release of the piston with respect to the plunger the piston is moved into the chamber under the influence of atmospheric pressure. The hypodermic syringe of any one of claims 1 to 9, wherein said base end has an air passage to provide said atmospheric pressure. Dated 12 April, 2005 Roy Tudor Brewer Patent Attorneys for the Applicant/Nominated Person SPRUSON FERGUSON r-\1 IRTT1Y721 divdoc:hxa