A SYRINGE

Abstract: A syringe (1) comprising a barrel (2) having an outer sheath (3) and an inner sheath (4). The outer sheath (3) has a nozzle (5) and the inner sheath also has a nozzle (6) which corresponds and fits into the nozzle (5). A needle (7) is attachable to the nozzle (6). A plunger (9) is located partly within the barrel (2) and is used to administer a drug. After the drug is administered the plunger (9) interlocks with the inner sheath (4) and as the plunger (9) is withdrawn, so is the inner sheath (4) and hence the needle (7) is retracted to be within the outer sheath (3). After the needle (7) is retracted the outer sheath (3) and inner sheath (4) are interlocked thus preventing the syringe (1) from being used again as well as locking the needle (7) in a retracted position within the outer sheath (3).

Description: A SYRINGE The present invention relates to syringes and in particular, to a syringe which is only able to be used once and is able to be disarmed. BACKGROUND ART It is the modern practice in medicine to dispose of used syringes an needles after only one operation. This practice has arisen due to possibl contamination of the needle and syringe when administering to a patient. Such a practice is strictly adhered to by medical practitioners and other ancillary staff in medical institutions. Therefore, the main proble in this regard in relation to hospitals and the like 1s not whether the syringes are used more than once but whether the syringes are disposed of correctly. In this case responsible users of the syringes ensure that the syringes are correctly disposed of. Also with the advent of increased use of Intravenous drugs by drug addicts, repeated use of syringes by such users, and even several drug users using the same needle, is unhygienic and tends to lead to the spread of infectious diseases, in particular hepatitis and AIDS. It has been noted that education and free distribution of syringes and needles is one way of overcoming the possibility of the spread of such infectious diseases. However, it has been acknowledged that these schemes are only successful up to a point, whereby it is possible for the syringes to be used more than once and for more than one person thus increasing the risk of the spread of such diseases. The needle exchange programmes which have been initiated require that a syringe be returned before another one issues, and are safer if the syringe has been disabled and/or disarmed for safe disposal thereof. OBJECT OF THE INVENTION It is an object of the present invention to provide a syringe which can only be used once and/or is able to be disarmed which substantially overcomes or ameliorates the abovementioned disadvantages. DISCLOSURE OF THE INVENTION According to one aspect of the present invention there is disclosed syringe comprising a barrel having an outer sheath and an inner sheath, said inner sheath having a cavity for a drug to be drawn therein and being able to move reciprocatingly along the longitudinal axis of said outer sheath and having a needle attached to one end thereof and having an opening at both ends with a plunger having a piston, a stem and a base wit at least part of said stem being located within one end of said outer shea and within one end of said inner sheath, stop means to prevent said plunger being totally removed from said outer sheath, a first engaging and locking means to engage and lock said plunger with said inner sheath and a second engaging means to engage said inner sheath to said outer sheath wherein after use of said syringe after said plunger empties the drug from the cavity within said inner sheath, the first engaging means engages and locks said plunger to said inner sheath whereby as the plunger is withdrawn the Inner sheath is also withdrawn thus withdrawing the needle into within said outer sheath, wherein said second engaging and locking means engages and locks said outer sheath and said inner sheath in a position whereby said needle is located wholly within said outer sheath. BRIEF DESCRIPTION OF THE DRAWINGS One embodiment of the present invention will now be described with reference to the drawings in which: Fig. 1 is a plan view of the syringe of a preferred embodiment, Fig. 2 is a sectional view A-A of the syringe of Fig. 1, Fig. 3 is a sectional view C-C of the syringe of Fig. 2, Fig. 4 is a sectional view D-D of the syringe of Fig. 2, Fig. 5 is a sectional view B-B of the syringe of Fig. 1, Fig. 6 is a sectional view A-B of the syringe of Fig. 1, and Fig. 7 is a perspective view of the syringe of the preferred embodiment. BEST MODE OF CARRYING OUT THE INVENTION The syringe 1 of the preferred embodiment has a barrel 2 having an outer sheath 3 and an inner sheath 4. The outer sheath 3 has a nozzle 5. and likewise the inner sheath 4 has a nozzle 6 which has a friction fit within the interior of the nozzle 5. A needle 7 also has a friction fit in an aperture 8 in the nozzle 6 of the inner sheath 4. A plunger 9 is similar to a plunger of a standard syringe, and comprises a piston 10, a stem 11 and a base 12. A pair of locking ribs 13 are located midway on the stem 11 along two of the four radial portions 14 of the stem 11 as seen in Fig. 5. A pair of integral safety locks 15 and a pair of stops 23 are located adjacent the locking ribs 13 on the stem 11 to prevent accidental plunger lock before use. The safety locks 15 are formed on the inner sheath 4 being joined by a thin piece of plastics material 25 which is able to be deformed. The inner sheath 4 prior to use as illustrated in Fig. 2 fits within the outer sheath 3. The inner sheath 4 has a shoulder 16 which fits within a shoulder 17 of the outer sheath 3. The location of the shoulders 16 and 17 is approximately midway along the outer sheath 3. The pair of safety locks 15 are seen in Fig. 2 to be resting against the pair of stops 23 whereby the plunger 9 is not able to be moved in a downwards direction. A pair of resilient protruding fingers 24 are located on the stem 11 of the plunger 9 to interact with the safety locks 15. Thus the safety locks 15 and stops 23 prevent accidental movement of the plunger prior to use which may lock mechanism of syringe 1. As Illustrated in F1g. 3, a pair of plunger locks 18 are located at the interior end 19 of the inner sheath 4. The plunger locks 18 are to interact with the locking ribs 13 after use of the syringe 1. Both the plunger locks 18 and the locking ribs 13 are made of resilient material. A sealing cap 20 is located at the other end 21 of the outer sheath 3 of the barrel 2. The sealing cap 20 is integrally moulded with the body of the syringe 1 and is welded to the body during assembly. A pair of locking hooks 22 are located within the outer sheath and protrude upwardly, whereby and the locking hooks 22 are to interact with the interior end 19 of the inner sheath 4 to prevent movement therebetween. The syringe 1 is illustrated as ready for use in Fig. 2 whereby the inner sheath 4 and outer sheath 3 are in a position where the needle 7 is exposed, the plunger 9 is ready to draw in a drug. Initially the plunger 9 is drawn in an upwards direction thus drawing in the drug into the barrel 2. Due to the air gap between the piston 10 and the nozzle 6, a small amount of air is mixed with the drug when drawn into the barrel 2. The usual practice is that the air is expelled prior to injection. As the plunger 9 is drawn in the upwards direction, the fingers 24 interact with the safety locks 15 thus deforming the thin piece of plastics material 25 which joins the safety locks 15 and inner sheath 4. The safety locks are plastically deformed and are not able to lock the downward movement of the plunger 9 after deformation. Once the syringe 1 is ready for use, the plunger 9 is pressed in a downwards motion thus expelling the drug in the barrel 2. As illustrated in Fig. 3, the locking ribs 13 interact with the plunger locks 18 of the inner sheath 4. In the position illustrated in Fig. 3, the locks have not yet interacted, however, with a greed factor point just prior to the locking of the plunger to the barrel, in unauthorised use of the syringe, in particular with illegal drugs, it is envisaged that the plunger 9 will be further forced in a downwards motion to thereby lock the locking ribs 13 with the plunger locks 18. Once these locking ribs 13 and plunger locks 18 have locked together, when the plunger 9 is pulled in a upward motion the inner sheath 4 is also pulled in an upward motion thus retracting the needle 7 into the interior of the outer sheath 3. The syringe 1 is now able to be disposed of safely due to the covering of the needle thus helping to prevent needle stick. The syringe 1 is also disarmed in that it cannot be used again. However, it is desirable that the needle 7 be locked in the retracted position as illustrated in F1g. 4, and hence by further upward movement of the plunger 9, the locking hooks 22 lock with the other end 21 of the inner sheath 4 thus preventing any movement of the inner sheath 4 within the outer sheath 3. The syringe as well as being disarmed is thus able to be disposed of safely. The foregoing describes only one embodiment of the present invention, and modifications obvious to those skilled in the art can be made thereto without departing from the scope of the present invention.

Claims: CLAIMS 1. A syringe comprising a barrel having an outer sheath and an inner sheath, said inner sheath having a cavity for a drug to be drawn therein and being able to move reciprocatingly along the longitudinal axis of said outer sheath and having a needle attached to one end thereof and having an opening at both ends with a plunger having a piston, a stem and a base with at least part of said stem being located within one end of said outer sheath and within one end of said inner sheath, stop means to prevent said plunger being totally removed from said outer sheath, a first engaging and locking means to engage and lock said plunger with said inner sheath and a second engaging means to engage said inner sheath to said outer sheath wherein after use of said syringe after said plunger empties the dru? from the cavity within said inner sheath, the first engaging means engages and locks said plunger to said inner sheath whereby as the plunger is withdrawn the inner sheath is also withdrawn thus withdrawing the needle into within said outer sheath, wherein said second engaging and locking means engages and locks said outer sheath and said inner sheath in a position whereby said needle is located wholly within said outer sheath. 2. A syringe according to claim 1 wherein said first engagement means comprises at least one protrusion on said stem which engages and locks with a corresponding resilient member on said inner sheath. 3. A syringe according to claim 1 wherein said second engagement means comprises at least one protrusion on said inner sheath which engages with a corresponding resilient hook means on said outer sheath. 4. A syringe according to claim 1 wherein a second stop means is provided to prevent the plunger from being interlocked with said inner sheath prior to the use of said syringe. 5. A syringe according to claim 4 wherein said second stop means comprises at least one barrier on said plunger which interacts with at least one safety lock on said inner sheath. 6. A syringe according to claim 5 wherein said at least one safety lock is a resilient member which is connectable to said inner sheath by a plastically defor able connection member which is deformed by the movement of a deforming means located on the stem of the plunger when the plunger is retracted, thus allowing the plunger to be interlocked with the inner sheath after use of the syringe. 7. A syringe according to claim 6 wherein said deforming means comprises at least one finger member attached to said stem of said plunger, and as the finger member passes the safety lock, the deformable connection member is forced outwardly and is plastically deformed. 8. A syringe substantially as described with reference to the drawings.

Inventors: WHITLEY KEVIN, WHITLEY, KEVIN
Applicants: WESTERN MED PROD PTY LTD, WESTERN MEDICAL PRODUCTS PTY LIMITED
Application year: 1990
Main classification: A61M5
IPC codes: A61M5