GB2341805A - A hypodermic syringe with retracting needle - Google Patents

Abstract

A safety syringe with a retractable needle mounting is disclosed, having a barrel 4 with a nozzle 8 on which a needle 10 can be mounted and a plunger 6 movable within the barrel. The area 14 of the barrel adjacent the nozzle is weakened. The contents of the syringe barrel are expelled by depressing the plunger 6, but means 20 on the plunger enables it to selectively engage with the nozzle 8. Subsequent return of the plunger 6 into the syringe barrel 4 results in the weakened barrel area being broken and the nozzle with attached needle is withdrawn into the body of the syringe barrel. Detent means to lock the plunger in the barrel may be provided.

Description

2341805 ASyringe The present invention relates to syringes.

Most syringes consist of a barrel with a plunger at one end and, at the other, a nozzle to which a hollow needle can be attached. Modern syringes are disposable plastic instruments that are pre-sterilized and packed in sealed bags and are intended for just a single use for injecting fluid into, or withdrawing from, a body cavity, blood vessel or tissue.

One of the biggest problems with modern disposable syringes is the safe disposal thereof, particularly in view of the fact that approximately five million syringes are used each day in the UK alone.

One major drawback is the incidence of needle-stick injuries to the user causing pain, possible sickness and transmission of diseases such as HIV and Hepatitis B. The incidence of needle-stick injuries has also led to an increase in the number of claims for compensation from health workers.

In the United States alone up to 800,000 needle-stick injuries are reported each year, and this leads to compensation in the region of one billion dollars a year.

A further drawback is that used syringes are often illegally taken and sold to drug users, further causing the transmission of disease.

New syringe designs have been proposed to alleviate the occurance of needle-stick injuries.

In one known design the syringe is prefilled. However, many drugs cannot be stored in plastics, therefore the syringe must be made of a non reactive material, for example glass, leading to an increase in the unit cost.

Also, a syringe containing a particular dosage and needle type must be selected for a specific use. It is not possible to charge the syringe with the required amount or attach a needle of the correct length/bore to match a particular task. This leads to a proliferation in the number of syringes needing secure, possibly refrigerated storage and also to waste if a particular syringe is not used before the use by date of the drug therein.

In a further design the drug to be injected is provided in a cartridge which slots into the barrel of the syringe. However, the syringe must be specifically adapted to hold the cartridge and in order to discharge the contents of the cartridge a metal plunger is required, further adding to the unit cost and complexity of the syringe design.

-3 Although, the above designs may help reduce the incidence of re-use of the syringe, the incidence of needle-stick injury remains. In a further syringe design the needle is retractable into the syringe body after use by way of a retracting mechanism in the form of a metal spring. By effectively shrouding the needle, the incidence of needle-stick injuries is reduced.

However, the mechanism is complex and therefore the unit cost is high.

Also, this type of syringe is fitted with a permanent needle of a fixed size.

It is therefore not possible to attach a needle of a required size for the task in hand. Furthermore, the metal spring may react with the medicine causing degradation contamination of the medicine It is an object of the present invention to overcome or alleviate the above described drawbacks.

In accordance with one aspect of the present invention there is provided a syringe comprising a barrel having a nozzle for attachment of a needle, and a plunger moveable within the barrel to draw fluid into and expel fluid out of the barrel through the nozzle, the end of the barrel adjacent the nozzle having a weakened area, and engagement means being provided on the plunger for selectively engaging the nozzle and drawing the nozzle and a needle attached thereto wholly into the syringe barrel by breaking through the weakened end of the barrel when the plunger is drawn -4 up the barrel of the syringe.

This has the advantage that once the syringe has been discharged, the needle can be drawn into the barrel to allow safer disposal of the syringe with a reduced incidence of needle-stick injuries. Also, since the movement of the needle into the barrel also causes the syringe to break, this prevents further use of the syringe, and thereby the spread of disease.

Preferably, the weakened area is a series of grooves and/or an area of reduced thickness in the material of the barrel. This has the advantage of being a simple means of producing the required breakage of the syringe after use. This has the advantage that the syringe can be manufactured using the same cheap materials such as plastics as the known syringe, keeping the unit cost low. The grooves and/or area of reduced thickness can be included in the forming process when the syringe is produced by standard production techniques, for example injection moulding with a very small alteration to the usual process. Alternatively, the grooves and/or area of reduced thickness can be added to the base of the syringe after production.

The means for engagement may be a male member on the foot of the plunger. This once again has the advantage that it can simply be added to a standard syringe with only a minor alteration to the production process.

The male member may simply be adapted for a press-fit within the nozzle and/or needle when the plunger has been fully descended into the barrel and any fluid therein has been expelled. In order to improve the mating between the nozzle, the male member may have a roughened surface, a corresponding surface may be provided on the interior of the nozzle or needle.

In a preferred embodiment the nozzle has an inwardly projecting shoulder, and the male member is adapted to hook under the shoulder when the plunger is rotated. This has the advantage that the plunger lifts the nozzle and needle into the barrel and lends additional force to break through the weakened area. Alternatively the shoulder may be provided in the needle.

The male member may be a barbed member for engagement with a corresponding socket in the nozzle. The barbed member can thereby cut into the nozzle to provide a permanent connection between the nozzle/needle and plunger.

In a further embodiment the male member is provided on the nozzle and/or needle for engagement with the plunger, for this purpose the plunger may carry a corresponding socket.

The barrel may be provided with detent means for engagement with the plunger once the needle has been drawn into the barrel. This prevents accidental movement of the plunger which may cause the needle to protrude from the barrel, thereby further reducing the incidence of needle stick injuries By way of example only, specific embodiments of the present invention will now be described, with reference to the accompanying drawings, in which:

Fig. 1 is an exploded view of a syringe constructed in accordance with one embodiment of the present invention; Fig. 2 is an end view of the syringe body of Fig 1; and Figs. 3 to 5 show the operation of the syringe of Fig. 1.

Referring to Fig. 1 a syringe 2 comprises a syringe barrel 4 and a syringe plunger 6.

-7 A nozzle 8 at the base 10 of the barrel 4 is shaped to receive thereon a needle 10 as best illustrated in Figs. 3 to 5. The interior of the nozzle 8 is provided with a shoulder 12. The base end 14 of the barrel 4, has a plurality of grooves 16 encircling the nozzle 8 and also extending radially outwardly therefrom along the surface 14, (as best illustrated in Fig. 2).

The grooves 16 form a weakened area in the surface 14.

The base end of the plunger 6 is provided with a head 18 which in use, as the plunger 6 descends into the barrel 4, as best illustrated in Fig.

3, pushes fluid in the barrel 4 out through the nozzle 8. The end of head 18, opposite the end 14 of the barrel 4 has an outwardly extending projection 20 which is adapted to engage the shoulder 12.

As best illustrated in Figs. 3 to 6, once the contents of the barrel 4 are expelled by the user depressing the plunger 6, the user depresses the plunger 6 a little further whilst at the same time twisting the plunger 6 in order that the projection 20 passes through opening 22 and engages the opposite side 24 of the shoulder 12. The user then pulls on the plunger 6 in order to move it back up through the barrel 4 whereby the shoulder 20 forces the nozzle 8 and the needle attached thereto up into the barrel 4.

This is achieved because the force of projection 20 on the shoulder 22 breaks the weakened area 16. This opens the end 14 to allow the nozzle 8 and the needle 10 to be drawn into the barrel 4. By this means the needle 10 is shrouded by the barrel 4, and the syringe is no longer usable because the end 14 has been broken.

Detent means (not illustrated) can be provided at the upper end 5 of the barrel 4 which engage the head 18 in the fully retracted position of the plunger, thereby retaining the needle 10 within the barrel 4 and preventing the plunger 6 being accidentally depressed with consequential protrusion of the needle from the barrel.

Although a shoulder and projection have been described as being as the engagement means between the nozzle and plunger, the means of engagement could instead be a barbed member engaging a serrated edged opening or bore with a push-fit connection. Alternatively, the engagement could be by a tight-fit between a socket and male member.

Although grooves have been described as providing the weakened area in surface 14, the weakened area could alternatively be provided by one or more areas of reduced thickness rendering the surface 14 more easily broken by the drawing of the needle into the barrel.

Although means for engaging the plunger have been described on the -9interior surface of the nozzle, such means may alternatively be provided on the needle adjacent the nozzle.

Claims (8)

Claims

1. A syringe comprising a barrel having a nozzle for attachment of a needle, and a plunger moveable within the barrel to draw fluid into and expel fluid out of the barrel through the nozzle, the end of the barrel adjacent the nozzle having a weakened area, and engagement means being provided on the plunger for selectively engaging the nozzle and drawing the nozzle and a needle attached thereto wholly into the syringe barrel by breaking through the weakened end of the barrel when the plunger is drawn up the barrel of the syringe.

2. A syringe according to claim 1, wherein the weakened area is a series of grooves.

3. A syringe according to claim 1 or claim 2, wherein the weakened area is an area of reduced thickness in the material of the barrel.

4. A syringe according to claim 1, 2 or 3, wherein the engagement means is a male member. ')o

5. A syringe according to any one of the preceding claims wherein the engagement means is adapted for a press-fit with the nozzle and/or needle.

6. A syringe according to any one of the preceding claims wherein the engagement means has a roughened surface.

7. A syringe according to any one of the preceding claims, wherein the engagement means comprises a barbed member for engagement with a corresponding socket in the nozzle.

8. A syringe according to any one of the preceding claims, comprising detent means to lock the plunger in the barrel once the needle has been drawn into the barrel.