WO2004082758A1

WO2004082758A1 - A syringe

Info

Publication number: WO2004082758A1
Application number: PCT/AU2004/000325
Authority: WO
Inventors: Simon Paul Clayson; Paul Leonard Clayson
Original assignee: Simon Paul Clayson; Paul Leonard Clayson
Priority date: 2003-03-17
Filing date: 2004-03-17
Publication date: 2004-09-30
Also published as: AU2003901197A0; WO2004082758A8

Abstract

A single-use syringe (10) has a needle (24) that is withdrawn into a hollow plunger (14). A needle holder (26) has a rigid element resisting the forward movement of the needle (24) and a compressible element (29) frictionally holding the needle (24) and preventing rearward movement. The needle (24) is released by applying additional pressure to the hollow plunger (14) to compress the compressible element (29). The rear (22) of the needle (24) ruptures the face (36) of the hollow plunger (14) which has a rupturable portion (34) covering an optional flexible coupling (39) for withdrawing a needle (24) into the plunger (14) after the needle (24) is released from the needle holder (26). Upon inversion of the syringe (10) the needle (24) is able to fall freely into the hollow plunger (14).

Description

A Syringe

Field of the Invention

The present invention relates to a syringe of the type used in used in human or veterinary medicine for injection of medicinal substances and/or removal of samples of blood and liquids. The present invention relates specifically,, but not exclusively,, to a single-use syringe that, after normal operation and upon inversion, provides protection from needle stick injuries after the single use of the syringe.

Background of the Invention

Millions of syringes are used around the world every year. A syringe typically comprises a substantially cylindrical hollow barrel in which a plunger slides reciprocally to facilitate filling or emptying of the syringe in normal operation. Throughout this specification, the phrase "normal operation of the syringe" refers to the actions 'of filling or emptying the syringe of a fluid. A hypodermic needle having a head or hub, a hollow cannula and a sharpened tip is typically mounted in the syringe through an opening at one end of the barrel.

With the spread of blood-borne diseases such as AIDS, discarded used syringes represent a hazard to the general public. Needlestick injuries in which a person's skin is punctured unintentionally are becoming more common. If the needle is contaminated, illness, bodily harm or even death may occur. An inadvertent needlestick injury can cause a person to undergo months of stress as they await results of testing to see if any infection has resulted.

It is also known for users of syringes such as addicts to reuse or share syringes containing contaminated fluid therein. The spread of infection by reusing syringes is a major health concern.

A number of single-use syringes which have a function that differs from the present invention have entered the marketplace with varied success. Many of the designs have needles which are automatically retracted into the syringe at the end of an injection cycle. One example is disclosed in US 5,211,629 (Pressly et al) . Pressly et al discloses a hypodermic safety syringe having a needle with an enlarged head that is held in a needle assembly. The needle assembly is provided with a spring and sacrificial support which are used to limit the travel of the plunger during normal operation of the syringe. The plunger terminates in a rupturable boot. When the sacrificial support is severed the spring is compressed. When sufficient force has been applied to the plunger such that the elastic energy stored in the depressed spring exceeds the frictional force holding the needle in the needle assembly, the needle is propelled into the hollow plunger.

Another example of a disposable syringe with an automatically retractable hypodermic needle is described in US 6,017,325 (Yerfino et al) . ^A tip of a needle capturing device positioned at the forward end of the plunger is wedged into a nipple provided at the end of the needle. The needle capture device is attached to the rear end of the plunger by means of an elastic medium such that forward movement of the plunger causes the elastic medium to be stretched. The captured needle is retracted into the plunger when by the elastic energy that has been generated in the stretched elastic medium exceeds the energy required to break a perimetral projection provided on the needle capturing device is caused to break.

The retractable syringe of US 5,984,898 (Garvin) relies on a needle assembly mounted on a needle holder which is biased rearwardly by a coil spring. The needle is held in a collet which is caused to expand only after a collapsible cap on the forward end of the plunger is punctured. When the collet has been caused to expand sufficiently, the needle holder becomes disengaged from the collet, propelling the needle into the plunger under the action of the spring.

AU 49596/90 (Caral t Batlle) describes a single-use hypodermic syringe in which the head of the plunger is shaped so as to interlock with a complimentarily shaped bushing provided on the head of the needle.

The safety syringe of EP 0413414 (Tsao) has a needle holder held in an elastic clamp connected to the inside of a barrel of the syringe by a threaded connection. The elastic clamp is provided with a pair of elastic clamping elements with flanges that engage with recesses provided in the holder. A coil spring is provided between the front end of the holder and elastic clamp. The front end of the plunger has an opening that is sealed with a cover. When the plunger is pushed towards its forward limit, the cover is pushed free to expose the opening at the end of the plunger. Simultaneously, the clamping elements are prised apart allowing the flanges to break free from the recesses. This releases the needle holder, which is then propelled into the body of the syringe by the spring force of the spring element. The plunger is simultaneously locked in its forward position in the barrel by a set of wedging rings.

In US 5,084,018 (Tsao) another mechanism for releasing a locking tip of a needle is described. The locking tip is held securely to a sliding base having an annular groove that engages with a limiting flange on an inner wall of the barrel of the syringe. As the plunger is pushed towards its forwardmost limit, a plug in the open end of the plunger is pushed inwards. At the same time, the front end of the plunger pushes against the sliding base, sliding it forward over the limiting flange and releasing the locking tip of the needle. The locking tip, together with the needle, is ejected into the hollow interior of the plunger by means of a coil spring.

One of the problems with these prior art designs is their complexity, particularly given that syringes are commonly required to be quite small. It is difficult to miniaturise the complex retraction mechanisms of such syringes and still have parts that reliably function effectively. Moreover, many of the prior art devices incorporate designs or technology that do not lend themselves economically feasible mass production.

The present invention was developed to provide a low-cost alternative to existing syringes.

It will be clearly understood that, although prior art use and publications are referred to herein, this reference does not constitute an admission that any of these form a part of the common general knowledge in the art, in Australia or in any other country.

In the statement of invention and description of the invention which follow, except where the context requires otherwise due to express language or necessary implication, the word "comprise" or variations such as "comprises" or "comprising" is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.

Summary of the Invention

According to one aspect of the present invention, there is provided a syringe comprising: a barrel having a forward end and a rearward end, the forward end of the barrel comprising a discharge opening for receiving a needle, the needle comprising a head, a hollow cannula and a sharpened tip, the forward end of the barrel further comprising a needle holder for holding the needle during normal operation of the syringe, the needle holder comprising a rigid element for resisting movement of the needle towards the forward end of the barrel, a fluid impervious barrier having an upper face directed towards the rearward end of the barrel for resisting flow of fluid into the needle holder, and a collapsible retaining means for holding at least a portion of the needle during normal operation of the syringe; and, a plunger comprising a forward end, a rearward end, and a hollow portion for receiving the needle after the needle has been released from the needle holder, the plunger being reciprocally slidable along the barrel for effecting a change in volume of a chamber so as to fill or empty the syringe, the chamber being defined between the forward end of the plunger and the upper face of the fluid impervious barrier, the forward end of the plunger further comprising a rupturable portion to facilitate release of the needle from the needle holder and a seal for restricting flow of fluid from the chamber towards the rearward end of the barrel, whereby, in use, after emptying the chamber of the syringe, the application of an additional force to the plunger in the direction of the forward end of the barrel, collapses the collapsible retaining means of the needle holder and ruptures the rupturable portion of the forward end of the plunger so as to release the needle from the needle holder, such that upon inversion of the syringe, the released needle is able to fall freely under gravity inside the hollow portion of the plunger.

Preferably, the fluid impervious barrier is the retaining means . Preferably, the forward end of the plunger further comprises a flexible coupling covered by the rupturable portion, whereby, in use, after the rupturable portion has been ruptured, the application of additional pressure to the plunger causes the flexible opening to expand so as to receive the portion of the needle retained by the collapsible retaining means such that subsequent movement of the plunger towards the rearward end of the barrel retracts the needle into the barrel of the syringe.

Preferably, the flexible coupling positively engages a portion of the needle. Preferably, the portion of the needle retained by the retaining means is the head of the needle. More preferably still, the head of the needle has a larger cross-sectional area than the cannula of the needle.

Preferably, the needle holder further comprises a compressible element in abutting contact with at least a portion of the needle for providing frictional resistance against movement of the needle towards the rearward end of the barrel during normal operation of the syringe. The compressible element is able to be depressed after the rupturable portion has been ruptured, reducing the frictional resistance holding the needle in the needle holder.

Preferably, the head of the needle further comprises at least one projection for breaking through the rupturable portion of the forward face of the plunger, the at least one projection extending outwardly from the head of the needle towards the rearward end of the barrel when the needle is received in the discharge opening of the barrel. More preferably, the projection is a serration for cutting through the rupturable portion of the plunger. More preferably still, the at least one projection or serration is one of a plurality of projections or serrations.

Preferably, the rupturable portion is a portion of the seal. The rupturable portion may equally be separate from the seal. In one embodiment, the rupturable portion is in the form of a ball element.

Preferably, the compressible element is fluid impervious and the fluid impervious barrier is a portion of the compressible element. In one embodiment, the compressible element is the collapsible retaining means.

Preferably, the syringe further comprises locking means for restricting movement of the plunger towards the rearward end of the barrel after release of the needle from the needle holder so as to render the syringe unusable for subsequent use. More preferably, the locking means comprises one or more interlocking components with a first component being provided on the plunger and a second component being provided on the barrel. More preferably still, one of the first or second components is a protrusion and the other is a recess.

Brief Description of the Drawings

The preferred embodiments of the present invention will now the described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a first preferred embodiment of the present invention with a needle loaded into the syringe and held in the needle holder;

Figure 2 is a close-up view of the forward end of the housing of the syringe of Figure 1;

Figure 3 illustrates the syringe of Figures 1 and 2 after the release of the needle from the needle holder and upon inversion of the syringe;

Figure 4 is a second preferred embodiment of the present invention with a needle loaded into the syringe and held in the needle holder;

Figure 5 is a close-up view of the forward end of the housing of the syringe of Figure 4;

Figure 6 illustrates the syringe of Figures 4 and 5 after the release of the needle from the needle holder and upon inversion of the syringe; and,

Figure 6a is a close-up view of the locking means of the syringe of Figures 4 to 6 in a locked position.

Detailed Description of the Preferred Embodiments of the Invention

Preferred embodiments of the present invention are now described in detail. It is to be understood however that the disclosed embodiments are merely exemplary of the present invention which may be embodied in various forms.

The specific structure and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to employ the present invention.

A first preferred embodiment is illustrated in Figures 1 to 3. With reference to Figure 1, there is provided a syringe 10 comprising an elongate substantially cylindrical hollow barrel 12 and a plunger 14 reciprocally slidable along the barrel 12.

The barrel 12 has a forward end 13 and a rearward end 15. The rearward end 15 of the barrel 12 is provided with tabs 17 radially extending outwardly from the barrel and positioned to facilitate gripping of the barrel 12 of the syringe 10 during use.

The forward end 13 of the barrel 12 is provided with a discharge opening 19 for receiving a needle 24. The discharge opening 19 is sized so as to provide sufficient clearance for insertion the needle 24 while at the same time allowing the needle 24 to fall freely inside the barrel 12 after the needle 24 has been released in the manner described below.

The forward end 13 of the barrel 12 is further provided with a needle holder 26 for holding the needle 24 during normal operation of the syringe 10. The needle holder 26 comprises a rigid element 28 for resisting movement of the needle towards the forward end 13 of the barrel 12 and a collapsible retaining means 31 for holding a portion of the needle 24 during normal operation of the syringe 10.

The rigid element 28 is coaxially aligned with the discharge aperture 19 and is either integrally formed as part of the barrel 12 or mounted on an inside surface 11 of the barrel 12 during assembly of the syringe 10. The rigid element 28 acts as a seat upon which the head 22 of the needle 24 rests during normal operation of the syringe 10.

The needle 24 comprises a head 22, a hollow cannula 23 and a sharpened tip 25. The needle cannula 23 and head 22 are of a conventional type provided only that the head 22 has a larger cross-sectional area than that of the cannula so as to allow the head 22 of the needle 24 to rest on the rigid element 28 of the needle holder 26. The head 22 of the needle 24 is the portion of the needle 24 that is held by the collapsible retaining means 31 in the preferred embodiments of the present invention.

The needle holder 26 further comprises a fluid impervious barrier 27 having an upper face 29 directed towards the rearward end 15 of the barrel 12. The fluid impervious barrier 27 may serve as the collapsible retaining means 31 as shown in the embodiment illustrated in Figures 4 to 6a. In this example, the fluid impervious barrier 27 may be constructed of a rubber or other elastomeric material and shaped so as to hold a portion of the needle 24 such as the head 22 of the needle 24 and stop fluid passing from the barrel 12 into the needle holder 26.

In the illustrated embodiment of Figures 1 to 3, the needle holder 26 is further provided with an optional compressible element 30 surrounding the rigid element 28 and the head 22 of the needle 24.

Depending on the size and material selection of the compressible element 30, the compressible element can perform the function of the collapsible retaining means provided only that it provides sufficient frictional resistance to hold the needle 24 in the needle holder 26 during normal operation of the syringe 10. To achieve this, the frictional resistance between the compressible element 30 and the needle 24 needs to exceed the suction force on the head 22 of the needle 24, which is generated as the plunger 14 is pulled towards the rearward end 15 of the barrel 12 as the syringe 10 is filled with fluid. It is considered a matter of routine for the person skilled in the art to determine the quantity of material to provide the requisite degree of frictional resistance depending on the specific material chosen for the compressible element.

The compressible element 30 is made of a piece of polymeric material that is itself fluid impervious. Thus, the fluid impervious barrier 27 is simply the upper face 29 of the compressible element 30. When the compressible element 30 is made of a material that is not fluid- impervious, such as a porous material or indeed when the present invention is performed without the use of a compressible element at all, a separate fluid impervious barrier 27 is needed to prevent leakage of fluid into the needle holder 26 to ensure the correct quantity of fluid delivered from the syringe 10 to a patent.

The substantially cylindrical plunger 14 has a forward end 16 and a rearward end 18 and is provided with a hollow portion 20 for receiving the needle 24 when released from the needle holder 26. The plunger 14 need not be hollow across its full cross-section nor its full length. It is sufficient that the hollow portion 20 is large enough to receive the needle 24.

Reciprocal sliding of the plunger 14 along the barrel 12 effects a change in volume of a chamber 32. The chamber 32 is in fluid communication with the needle 24. The chamber 32 is defined between the forward end 16 of the plunger 14 and the upper face 29 of the fluid impervious barrier 27 and the inner surface 11 of the barrel 12.

When the forward end 16 of the plunger 14 is brought into contact with the upper face 29 of the fluid impervious barrier 27, effectively all of the fluid in the chamber 32 has been expelled from the syringe 10. The effective volume of the chamber 32 is zero.

The forward end 16 of the plunger 14 further comprises a rupturable portion 34 and a seal 36 for retaining fluid within the chamber 32. The seal 36 encourages the passage of the fluid to and from the chamber 32 via the cannula 23 of the needle 24 by preventing the passage of fluid from the chamber 32 towards the rearward end 15 of the barrel 12.

In the illustrated embodiment of Figures 1 to 3, the rupturable portion 34 is a portion of the seal 36, typically with a reduced cross-sectional area so as to render the rupturable portion easier to break.

In the illustrated embodiment of Figure 4 to 6a where like numeral refer to like parts, the rupturable portion 34 is in the form of a ball element 39 that is separate from the seal 36. The ball element 39 is in sealing contact with the seal 36 such that fluid flow out of the chamber 32 into the hollow portion 20 of the plunger 14 is restricted. In the embodiment of Figures 4 to 6, the rupturable portion is ruptured by the needle 24 pushing on the ball element 39 which is ejected from the seal 36 into the hollow portion 20 of the plunger.

In the illustrated embodiment of Figures 1 to 3, the rupturable . portion 34 covers a flexible coupling 40 for engaging the head 22 of the needle 24. The syringe of the present invention may equally be used without a flexible coupling being provided under the rupturable portion as shown in the illustrated embodiment of Figures 4 to 6. It is sufficient to render the syringe unusable for subsequent use, that the needle 24 is released from the needle holder 26 by collapsing the collapsible retaining means 31 and causing the rupturable portion 34 to rupture.

With reference to Figures 1 to 3, after the rupturable portion 34 has been broken, the application of additional pressure to the plunger 14 causes the flexible coupling to expand so as to receive the head 22 of the needle 24. Subsequent movement of the plunger 14 towards the rearward end 15 of the barrel 12 retracts the needle 24 into the barrel 12 of the syringe 10.

It is to be clearly understood that positive engagement of the head 22 of the needle 24 is not essential to the working of the present invention. It is sufficient that the needle 24 is released from the needle holder 26.

Attached to the rearward end 18 of the plunger is a pad 42 which allows the user to move the plunger 14 towards the forward end 13 of the barrel 12 by applying a pushing force to the pad 42, typically with a thumb, with a reaction force being provided by positioning an index finger on each of the tabs 17 at the rearward end 15 of the barrel 12.

As can be seen in Figure 1, the head 22 of the needle 24 in the illustrated embodiments of Figures 1 to 3 is frustoconical and provided with tapered sides 46 whereby the cross-sectional area of the head 22 increases in the direction of the forward end 13 of the barrel 12. This preferred shape of the head 22 has two benefits. The first is that the tapered sides 46 help to direct movement of the compressible element 30 forward and away from the head of the needle to depress the compressible element 30 and facilitate the release of the needle 24 from the needle holder 26 by reducing the frictional resistance holding the needle 24 in the needle holder 26.

The second benefit is that the tapered sides 46 of the frustoconical head 22 of the needle 24 help to progressively open up the flexible coupling 40 in the forward end 16 of the plunger 14. This gradual opening of the flexible coupling 40 continues until such time as the head 22 of the needle 24 has been fully received within the flexible coupling. When the head 22 has been fully received within the flexible coupling 40, the flexible coupling 40 contracts inwardly towards the cannula 23 of the needle 24 such that upon application of a pulling force to the plunger 14, the released needle 24 is drawn inside the barrel 12.

With reference to Figure 2, the head 22 of the needle 24 is provided with a plurality of upwardly extending projections 48 in the form of serrations to assist in perforating the rupturable portion 34 of the forward end 16 of the plunger 14. A single projection or serration 48 may equally be used to break through the rupturable portion 34. A plurality of sharpened projections 48 in the form of serrations is preferred as a way of reducing the amount of additional pressure needed to effect release of the needle 24 from the needle holder 26.

The flexible coupling 40 need not positively engage the needle 24. Upon inversion of the syringe as illustrated in

Figure 3, the needle 24 is able to fall freely under gravity out of the flexible coupling 40 and into the hollow portion 20 of the plunger 14.

To assemble the syringe, the needle 24 is positioned within the forward end 28 of the barrel 12 such that the head 22 of the needle 24 sits on the rigid element 28 of the needle holder 26. The seal 36, including the rupturable portion 34, is positioned over the forward end 18 of the plunger 14 covering over the flexible coupling 40. The plunger 14 is then ready to be loaded into the barrel 12.

The use of the syringe illustrated in Figures 1 to 3 will now be described in detail. To fill the syringe 10, the plunger 14 is slid along the barrel 12 until the seal 36 rests against the upper face 29 of the fluid impervious barrier 27 of the compressible element 30. Fluid is then drawn into the syringe 10 by inserting the tip 25 of the needle 24 into a fluid and pulling the plunger 14 towards the rearward end 15 of the barrel 12. As the plunger 14 moves away from the forward end 13 of the barrel 12, the chamber of increasing volume 32 is formed and fluid is sucked under vacuum into the chamber 32 through the cannula of the needle. The barrel 12 is provided with markings to indicate the volume of fluid held in the chamber 32.

When the fluid within chamber 32 is to be discharged from the syringe 10, the plunger 14 is moved towards the forward end 13 of the barrel 12 causing the fluid to be forced through the cannula 23 of the needle 24 and out of the tip 25 of the needle 24. The seal 36 prevents passage of the fluid past the forward end 16 of the plunger 14 towards the rearward end 15 of the barrel 12.

The fluid in the chamber 32 is fully discharged from the syringe 10 when the seal 36 is brought into contact with the upper face 29 of the fluid impervious barrier 27.

After normal operation of the syringe, further depression of the plunger 14 towards the forward end 13 of the barrel

12 is required to release the needle 24 from the needle holder 26. As the plunger 14 is caused to move further towards the forward end 13 of the barrel 12, the compressible element 30 of the needle holder is depressed, reducing the frictional resistance holding the needle 24 in the needle holder 26. The head 22 of the needle 24 is restrained against movement in the direction of the forward end 13 of the barrel 12 by the rigid element 28. At the same time, the serrations 48 extending upwardly from the head 22 of the needle 24 cut through the rupturable portion

34 of the seal 36.

With reference to Figure 2, once the rupturable portion 34 has been broken, the flexible coupling 40 is no longer covered. The tapered sides 46 of the frustoconical head 22 assist in opening up the flexible coupling 40 around the head 22 of the needle 24. Once the flexible coupling 40 has passed over the largest cross-sectional area of the tapered sides 46 of the head 22, the flexible coupling 40 contracts to engage the head 22 of the needle 24. The head 22 is engaged by the flexible coupling 40 only to the extent that movement of the plunger 14 away from the forward end 13 of the barrel 12 draws the needle 24 inside the barrel 12.

Release of the elastic energy stored within the depressed compressible element 30 further assists in encouraging movement of the plunger 14 towards the rearward end 15 of the barrel 12. The amount of elastic energy stored in the depressed compressible element 30 depends on the type and quantity of elastic material used. It is to be clearly understood that it is not essential that sufficient elastic energy be stored in the depressed compressible element 30 to cause retraction of the entire needle 24 within the barrel 12 of the syringe 10. It is sufficient that the needle 24 is released from the needle holder 26 so as to render the syringe 10 inoperable for subsequent use.

Inversion of the syringe 10 as illustrated in Figure 3 causes the needle 24 to fall freely under gravity out of the flexible coupling 40 and into the hollow portion 20 of the plunger 14 whereby the user is protected from needlestick injury.

The needle 24 is safely held within the plunger 14, which can be safely disposed of. The barrel 12 may be re-used as often as desired.

A second preferred embodiment is illustrated in Figures 4 to 6a. In this embodiment, the syringe is provided with an optional locking means 50 for restricting movement of the plunger 14 towards the rearward end 15 of the barrel 12 after release of the needle 24 from the needle holder 26. The locking means 50 is used to render the syringe unusable for subsequent use.

As best illustrated with reference to Figure 6a, the locking means is provided using interlocking components with a first component 62 in the form of a protrusion being provided on the plunger 14 and a second component 64 in the form of a recess being provided on the barrel 12. The first and second components 62 and 64 in the illustrated embodiment of Figures 4 to 6 are positioned towards the rearward end of the plunger 14 and barrel 12 - Irrespectively. Each of the first and second components 62 and 64, respectively may be located anywhere along the length of the plunger 14 and barrel 12 respectively. The only proviso is that the first and second components 62 and 64 be arranged relative to each other so as to lock the plunger into the barrel after additional pressure has been applied to rupture the rupturable portion 34 of the front end 16 of the plunger 14.

The locking means 60 could equally be provided using a protrusion on the barrel and a recess on the plunger or any other suitable locking means provided only that the plunger 14 is able to slide along the axis of the barrel

12 to fill or empty the syringe 10.

The collapsible retaining means 31 in the second preferred embodiment is made of a fluid impervious material like rubber. It thus also serves as the fluid impervious barrier 27 and wraps snugly around the head 22 of the needle 24. A collapsible element such as the one used for the first preferred embodiment may also be included as part of the needle holder 26 in this second preferred embodiment.

As illustrated in Figures 4 to 6a, the head of the needle is part-spherical in the second preferred embodiment. After normal operation of the syringe 10 so as to empty chamber 32, the application of additional pressure to the plunger 14 is used to release the needle 24 from the needle holder 26. The rupturable portion 34 in the form of the ball element 39 is popped out of sealing engagement with the seal 36 at the forward end 16 of the plunger 14.

As the plunger 14 moves further towards the forward end

13 of the barrel 12, the collapsible retaining means 31 is flattened, allowing the protrusion 62 to become engaged in the recess 64, locking the plunger 14 in the barrel 12. If a compressible element (not shown) is included, it would be depressed in the manner described above for the first preferred embodiment. Inversion of the syringe 10 causes the needle 24 to fall freely under gravity into the hollow portion 20 of the plunger 14.

The plunger and barrel of the syringe would typically be moulded from conventional plastic materials. If the rigid element is made as a separate component to the barrel, the rigid element would typically be secured in position around the discharge opening by sonic welding. The compressible element is preferably formed from medical-grade rubber or elastomeric material. The term "medical grade" is used to connote that approval has been granted by an applicable regulatory authority to use the material for medical use. All parts of the syringe would typically need to be sterilisable.

Now that the preferred embodiments of the present invention have been described in detail, the present invention has a number of advantages over the prior art, including: a) the syringe is well adapted for mass use by virtue of the simplicity of the componentry and use; b) the needle holder is extremely simple in design and may be readily adapted for miniaturisation; c) the needle holder design allows for the cost of production of syringes made in accordance with the preferred embodiments to be relatively inexpensive compared to more complex prior art devices; d) the rupturable seal of the plunger can be readily replaced in the event that re-use of the plunger is required; and, e) the barrel portion of the syringe complete with needle holder can be re-used after the needle has been captured in the hollow portion of the plunger.

Numerous variations and modifications will suggest themselves to persons skilled in the relevant art, in addition to those already described, without departing from the basic inventive concepts. For example, whilst a piece of polymeric material has been used to form the compressible element of the needle holder in the illustrated embodiments, the compressible element may equally take the form of a simple helical spring or one or more leaf springs. All such variations and modifications are to be considered within the scope of the present invention, the nature of which is to be determined from the foregoing description and the appended claims.

Claims

CLAIMS :

1. A syringe comprising: a barrel having a forward end and a rearward end, the forward end of the barrel comprising a discharge opening for receiving a needle, the needle comprising a head, a hollow cannula and a sharpened tip, the forward end of the barrel further comprising a needle holder for holding the needle during normal operation of the syringe, the needle holder comprising a rigid element for resisting movement of the needle towards the forward end of the barrel, a fluid impervious barrier having an upper face directed towards the rearward end of the barrel for resisting flow of fluid into the needle holder, and a collapsible retaining means for holding at least a portion of the needle during normal operation of the syringe; and, a plunger comprising a forward end, a rearward end, and a hollow portion for receiving the needle after the needle has been released from the needle holder, the plunger being reciprocally slidable along the barrel for effecting a change in volume of a chamber so as to fill or empty the syringe, the chamber being defined between the forward end of the plunger and the upper face of the fluid impervious barrier, the forward end of the plunger further comprising a rupturable portion to facilitate release of the needle from the needle holder and a seal for restricting flow of fluid from the chamber towards the rearward end of the barrel, whereby, in use, after emptying the chamber of the syringe, the application of an additional force to the plunger in the direction of the forward end of the barrel, collapses the collapsible retaining means of the needle holder and ruptures the rupturable portion of the forward end of the plunger so as to release the needle from the needle holder, such that upon inversion of the syringe, the released needle is able to fall freely under gravity inside the hollow portion of the plunger.

2. A syringe as defined in claim 1 wherein the fluid impervious barrier is the collapsible retaining means.

3. A syringe as defined in claim 1 or 2 wherein the forward end of the plunger further comprises a flexible coupling covered by the rupturable portion, whereby, in use, after the rupturable portion has been ruptured, the application of additional pressure to the plunger causes the flexible opening to expand so as to receive the portion of the needle retained by the collapsible retaining means such that subsequent movement of the plunger towards the rearward end of the barrel retracts the needle into the barrel of the syringe.

4. A syringe as defined in claim 3 wherein the flexible coupling positively engages a portion of the needle.

5. A syringe as defined in any one of claims 1 to 4 wherein the at least a portion of the need retained by the retaining means is the head of the needle.

6. A syringe as defined in claim 5 wherein the head of the needle has a larger cross-sectional area than the cannula of the needle.

7. A syringe as defined in any one of claims 1 to 6 wherein the needle holder further comprises a compressible element in abutting contact with a portion of the needle for providing frictional resistance against movement of the needle towards the rearward end of the barrel.

8. A syringe as defined in any one of claims 1 to 7 wherein the head of the needle further comprises at least one projection for breaking through the rupturable portion of the forward face of the plunger, the at least one projection extending outwardly from the head of the needle towards the rearward end of the barrel when the needle is received in the discharge opening of the barrel.

9. A syringe as defined in claim 8 wherein the projection is a serration for cutting through the rupturable portion of the plunger.

10. A syringe as defined in claims 8 or 9 wherein the at least one projection or serration is one of a plurality of projections or serrations.

11. A syringe as defined in any one of claims 1 to 10 wherein the rupturable portion is a portion of the seal.

12. A syringe as defined in any one of claims 1 to 10 wherein the rupturable portion is a ball element.

13. A syringe as defined in any one of claims 7 to 12 wherein the compressible element is fluid impervious and the fluid impervious barrier is a portion of the compressible element.

14. A syringe as defined in any one of claims 7 to 13 wherein the compressible element is the collapsible retaining means.

15. A syringe as defined in any one of claims 1 to 14 further comprising a locking means for restricting movement of the plunger towards the rearward end of the barrel after release of the needle from the needle holder.

16. A syringe as defined in claim 15 wherein the locking means comprises one or more interlocking components with a first component being provided on the plunger and a second component being provided on the barrel.

17. A syringe as defined in claim 16 wherein one of the first or second components is a protrusion and the other is a recess.

18. A syringe substantially as herein defined ,with reference to and as illustrated in the accompanying drawings .