WO1997029798A1

WO1997029798A1 - Device

Info

Publication number: WO1997029798A1
Application number: PCT/GB1997/000417
Authority: WO
Inventors: Marius Van Der Merwe
Original assignee: Harwill Industries (Pty.) Limited
Priority date: 1996-02-16
Filing date: 1997-02-14
Publication date: 1997-08-21
Also published as: GB9603318D0; AU1802297A; ZA971250B

Abstract

The present invention provides a syringe for use with a unit dose cartridge, which syringe comprises: a) an axially extending body member having an axially extending bore therein adapted to receive a unit dose cartridge therein; b) a mounting at the distal end of the body carrying or adapted to carry a hollow needle member through which fluid can flow from said unit dose cartridge; c) a plunger member carrying or adapted to engage the proximal face of a piston member journalled for axial movement within the bore of a unit dose cartridge when mounted in the body member of the device, characterised in that: d) the plunger is secured to the proximal end of the syringe body by a pivotal connection whereby the plunger can be pivoted from a first position at which it lies outside the syringe body but generally parallel to the longitudinal axis of the syringe body to a second position at which the longitudinal axis of the plunger is substantially co-incident with that of the bore within the syringe body whereby the plunger can be moved axially into and within the bore of the syringe body, the pivotal connection allowing relative axial movement between the plunger and the syringe body; and e) the plunger member is provided with a groove or recess therein into which the needle of the syringe is adapted to locate so as to provide a sheath for the needle when the plunger is in its said first position; and f) a locking mechanism is provided for securing the plunger member in its said first position.

Description

TITLE: DEVICE

The present invention relates to a device, notably to a safety syringe for use with unit dose cartridges of a material to be administered to a mammal.

BACKGROUND TO THE INVENΗON:

Many medicaments and other materials, for example anaesthetics, are put up in cartridges or vials which contain a unit dose of the material. The cartridge or vial comprises a glass, metal or plastic cylindrical body having one end, its distal end, closed by a transverse rupturable bung or membrane and having a piston slidably journalled for axial movement within the axial bore of the body. The bore contains the fluid to be administered which is expelled as the piston member is moved axially within the bore from the proximal to the distal end of the bore. Such vials or cartridges will for convenience be denoted as unit dose cartridges hereinafter.

The unit dose cartridge is used in combination with a re-usable syringe which comprises an axial hollow housing having a hollow needle mounted at the distal end and having an open proximal end through which the cartridge is inserted into the axial bore of the syringe. A plunger can be inserted into the syringe bore so that its distal end enters the bore of the cartridge and bears against the piston within the cartridge . The rupturable bung or membrane of the cartridge is ruptured by being pierced by a rearward axial portion of the needle or its mount so that fluid flows from the cartridge into the bore of the needle as the piston is driven axially along the cartridge bore by depression of the plunger.

Such syringes are typically constructed so that they can be used repeatedly and this results in a complex and expensive construction. Furthermore, in order to prevent cross contamination between successive patients, the needle is usually removably mounted on the syringe body to enable the needle to be replaced between each use of the syringe. This introduces the risk of accidental stabbing of the operator during the affixing and removal of the needle. There have been many proposals as to ho to render such re-usable syringes more safe for the operator and to reduce the complexity and cost thereof. We have now devised a simple and effective form of such a safety syringe.

SUMMARY OF THE INVENTION:

Accordingly, the present invention provides a syringe for use with a unit dose cartridge, which syringe comprises: a. an axially extending body member having an axially extending bore therein adapted to receive a unit dose cartridge therein; b. a mounting at the distal end of the body carrying or adapted to carry a hollow needle member through which fluid can flow from said unit dose cartridge; c. a plunger member carrying or adapted to engage the proximal face of a piston member joumalled for axial movement within the bore of a unit dose cartridge when mounted in the body member of the device, characterised in that: d. the plunger is secured to the proximal end of the syringe body by a pivotal connection whereby the plunger can be pivoted from a first position at which it lies outside the syringe body but generally parallel to the longitudinal axis of the syringe body to a second position at which the longitudinal axis of the plunger is substantially co-incident with that of the bore within the syringe body whereby the plunger can be moved axially into and within the bore ofthe syringe body, the pivotal connection allowing relative axial movement between the plunger and the syringe body; and e. the plunger member is provided with a groove or recess therein into which the needle of the syringe is adapted to locate so as to provide a sheath for the needle when the plunger is in its said first position; and f. a locking mechanism is provided for securing the plunger member in its said first position. Preferably, the said groove or recess for receiving the needle is adapted to receive the needle by relative transverse movement of the needle and the groove or recess.

The pivotal connection between the syringe body and the plunger member can take a variety of forms. For example, it can be a hinged ring carried at the proximal end of the syringe body. The plunger is a sliding fit within the ring to allow the plunger to move axially within the bore of the syringe body when the plunger has been pivoted from its first position to its second position in register with the bore of the syringe. Preferably, the ring removably engages within the proximal end of the bore in the syringe body when the plunger adopts its second position so that the ring provides lateral support to the plunger as the plunger moves axially within the bore of the syringe body. Thus, the ring can engage in an annular groove at or adjacent the proximal end of the syringe body.

Alternatively, the pivotal connection can be achieved by means of a lug member which is pivotally mounted at the distal end of the syringe body and which carries means which engage the plunger. For example, the lug can carry a terminal ring in which the plunger is a slideable fit as described above. Or the lug can carry an axially orientated bead or the like which engages in an axial groove or recess of the plunger whereby the plunger can slide axially upon the lug member. It is preferred that the bead and the co-operating groove or recess are formed so that the plunger cannot be separated radially from the lug. Thus, the axial mouth of the groove or recess be narrower than the remainder of the groove or recess so as to provide a retaining lip for the bead carried by the lug which engages in the wider portion of the groove or recess. Preferably, the bead has a generally circular cross-section and it a snap fit past the retaining lip of the groove or recess. Alternatively, the lips of the groove can be sufficiently rigid to prevent ready radial removal of the lug from the groove, in which case either or both ends of the groove are open ended to permit axial insertion of the bead into the groove. Alternatively, the lug and the groove can have co-operating T shaped cross sections whereby the lug cannot be removed radially from the groove. In a particularly preferred embodiment of the invention, the lug has a cruciform or other non-circular aperture in the radially outward end thereof and the plunger has a corresponding cross-section so that it is a sliding fit in the aperture. Due to the non-circular shape of the aperture and the plunger cross-section, the plunger cannot readily rotate about its longitudinal axis. This enables the plunger and parts carried by it to retain their relative orientation upon the syringe body as described below.

The use of an axial groove formed in the surface or wall of the plunger to receive the bead or enlarged head of the lug member has the advantage that the groove can be extended axially to the distal end of the plunger when in its first position. The groove can then act as a sheath for the needle as described below, thus simplifying the construction and reducing the cost of the device. Alternatively, the plunger can carry at its distal end a cross member having a groove in its proximal face. As the plunger is moved into its first position, the grooved face of the cross member engages the axially extending needle at the distal end of the syringe body, and progressively bends the needle until it adopts a position substantially normal to the axis of the syringe body. The shank of the needle will then be located in the groove of the cross member which then acts as the sheath for the needle. In this case it is preferred to use the embodiment where the cross-section of the plunger and the aperture in the radial lug have non-circular, notably cruciform, shape to minimise twisting of the plunger about its longitudinal axis allowing the needle to escape from the groove in the cross member. Preferably, the cross member acts as the head of the plunger when in its second position to provide a transverse surface upon which the user presses to move the plunger axially within the syringe body. The cross member can thus be a transverse disc-like head to the plunger or a transverse arm to form a T shaped end to the plunger.

Alternatively, as stated above, the needle sheath can be provided by an axial extension to the groove or recess in which the lug/bead engage. The plunger therefore extends axially for the full length of the syringe body and the needle mounted thereon. The needle receiving portion of the axial groove can be of a different lateral and radial dimension to that portion of the groove within which the lug engages. However, it is preferred to form the groove with substantially the same cross section throughout. Where the needle extends off centre from the distal end of the syringe, for example where the needle is mounted radially adjacent the side wall of the bore in the syringe body, the plunger may be a substantially linear member, for example a simple rod with the axial groove formed in that side of the rod adjacent the body of the syringe when the plunger is in its first position.

However, in some applications, it is desirable that the needle be mounted substantially upon the longitudinal axis of the syringe to permit accurate positioning of the needle tip in confined locations such as the mouth of a patient. In this case the plunger will require to be formed with a suitable radial configuration so that the distal portion of the plunger when in its first position extends radially inwardly to encase or protect at least the tip of the needle. For example, that portion of the plunger can have one or more radially extending parallel walls which form between them a radial extension to the axial groove within which at least the tip of the needle locates so as to protect the user from accidentally stabbing with the needle tip. The walls can be shaped to conform to the external shape of the distal end of the syringe body and preferably extend for the full length of the needle to ensure that the needle is fully protected by a single side wall or sheathed between two side walls.

It is preferred to form the distal portion of the plunger when in its first position with one or more radial arms or flanges which act as an enlarged head to the plunger when in its second position. This head can also form a transverse closure to the axial groove in which the needle tip locates and thus provide further protection against exposure of the distal end of the needle before or after use. As described above, this head can carry a radial groove or recess in its proximal face into which the needle locates as it flexes to accommodate the relative transverse movement of the head as the plunger is moved into its first position.

The axial groove in the plunger or the radial groove in the transverse head of the plunger can be dimensioned such that it is a frictional fit upon the needle shaft so that needle is firmly held in the groove. This may be sufficient to provide the locking mechanism for securing the plunger in its first position. However, it is preferred to provide a positive acting member to lock the plunger in its first position, especially where the needle is flexed into a radial groove carried by the head of the plunger.

It will be appreciated that the needle enters the axial groove or radial groove by a generally transverse movement of the groove with respect to the longitudinal axis of the needle. The risk of accidental stabbing of the hand of a user is therefore reduced as compared to systems in which the needle moves axially into a groove or bore which acts as the needle sheath.

Such a locking means can take a number of forms, for example a locking ring or elastic band which is a tight fit around both the syringe body and the plunger in its first position. Such a ring can have a circumferential groove or rib which is a snap fit upon a rib or groove carried by the plunger and/or the syringe body so as to secure the ring in position. However, it is preferred to provide the locking means in the form of a second, locking, radial lug which engages an axial locking groove or recess, one carried by the plunger and the other by the syringe body. Preferably, such a locking lug and recess combination is located at a point intermediate the pivotal connection of the plunger to the syringe body and the distal end of the needle, notably at or adjacent the distal end of the syringe body, so as to minimise transverse flexing of the plunger during storage and transport. Such a locking mechanism can be engaged as a snap fit as the plunger is pressed radially against the body of the syringe. Alternatively, the engagement can require part radial and part axial relative movement between the plunger and the syringe body. For example, the plunger carries barbs or a T shaped locking lug, which engages in an axial locking recess having an open distal end and a part open radially outward face at the distal end of the syringe body. The locking lug is brought into radial register with the locking aperture as the plunger adopts its first position, with the radial shank of the barb or T in register with the axial open top of the recess. The plunger is then moved axially in a proximal direction to bring the head of the barb or T into engagement with the locking recess, the shank of the barb or T locating in the open top of the recess. The plunger is thus secured against radial movement away from the syringe body and is secured in its first position.

Preferably, the barbs in the locking mechanism are formed on the side wall(s) forming the radial extension to the axial groove in the plunger. The open topped locking recess or groove into which the barbs engage is formed in the exterior of the body of the syringe at or adjacent its distal end. It is also preferred that the barb engages in the locking groove to two different extents so that in a first extent the barb(s) can be readily disengaged from the groove, but cannot readily be disengaged from the groove when the barbs have been fully engaged into the groove. In this way, the syringe can be supplied with the plunger temporarily secured in its first position and shielding the needle tip. The barb(s) require to be released from the groove before the plunger can be pivoted to its second, operative, position and expose the needle tip for use. However, -when the barbs fully engage the groove as the plunger is returned to its first position after use, the barbs can be more permanently engaged with the groove to prevent return of the plunger to its second position, thus reducing the risk of un-authorised re-use of the syringe.

For example, the locking groove can be provided with two sets of axial ribs or recesses into which the barbs engage, one set close to the open top of the groove, the other located radially deeper into the groove. Alternatively, the locking groove can be provided with a transverse membrane which is penetrated by the barbs and traps them when the plunger is firmly depressed radially against the body of the syringe when returned to its first position after use. Alternatively, the base of the groove can be provided with a deformable surface, for example a foamed plastic or the like. This provides a resilient member in the locking groove which has to be depressed to allow the barbs to penetrate sufficiently deeply radially into the groove to engage axial ribs or grooves in the wall of the groove. The ribs and barbs only engage when sufficient radial pressure is applied to the plunger as it is returned to its first position after use to depress the deformable surface. Such constructions enable the needle to be sheathed and protected after use of the syringe in a single operation which can be performed single handedly once the plunger has been at last partially returned to its first position after use of the syringe.

The slight spring in the radial side walls projecting from the shank of the plunger to form the axial groove within which the needle is received as described above provides a snap fit action by which the locking barbs carried by the radial side walls to engage the axial locking socket or groove as described above. However, when the side walls are flexed inwardly towards one another, the barbs disengage from the groove and permit the plunger to be pivoted into its second position for use of the syringe. Since this requires a positive action by the user of the syringe, accidental release of the plunger from its first position is prevented. When the plunger is returned to its first position after use, radial pressure on the plunger forces the radial side walls deeply into the groove so that insufficient side wall is exposed to permit access thereto. This prevents disengagement of the barbs from the groove thus preventing un-authorised re-use of the syringe. Furthermore, this operation requires the operator to keep his hand and fingers radially to one side of the needle, thus further reducing the risk of accidentally stabbing himself with the needle tip as the plunger is pivoted between its first and second positions.

It will be appreciated that the locking mechanisms described above can be inverted so that the plunger shaft carries the locking groove or recess into which locking barbs or the like carried at or adjacent the distal end of the syringe body engage.

The invention can be applied to a syringe body which does not carry a needle thereon initially, in which case the invention serves to protect the user against accidental stabbing with a used needle after the syringe has been used. However, the invention is of especial benefit with syringes which are supplied with a needle already fitted to the syringe body, in which case the syringe is supplied with the plunger in its first position protecting the needle during storage and transport and during the initial stages of use of the syringe. The needle can be of any suitable type, for example a canula needle or, more usually, a conventionalhypodermic needle for administration of a fluid medicament or anaesthetic to a patient. The needle can be removably mounted on the distal end of the syringe body using any suitable conventional mounting, or can be formed integrally with the syringe body. Since the fluid to be injected is provided in a unit dose cartridge, the needle preferably extends proximally axially into the bore of the syringe body to provide means for piercing the end wall or membrane of the cartridge and thus allow fluid to flow to the needle bore. It is also preferred to form one or more axial apertures in the wall of the syringe body whereby the user can manipulate the cartridge through those apertures to assist insertion and removal of the cartridge from the syringe bore. Such apertures also enable the user visually to monitor the extent of discharge of the contents of the cartridge or the presence of blood in the cartridge during aspiration of the syringe.

The syringe of the invention thus offers a simple construction which can be produced by injection or other moulding techniques using a suitable plastic, in which case the pivotal connection between the lug and the body of the syringe can be formed as a live plastic hinge.

In operation, the syringe is preferably provided as a sterile packed unit comprising the syringe body having the needle mounted thereon and with the plunger in its first position engaging the needle in a frictional fit and with the locking barb(s) only partially engaged in the locking groove at the distal end of the syringe body. The unit dose cartridge is inserted into the axial bore of the syringe body through the open proximal end of the bore. The risk of accidental stabbing of the user by the tip of the needle is minimised because the needle is still sheathed in the axial groove in the shank of the plunger or in the radial groove in the transverse head of the plunger. Once the cartridge is in position, the locking mechanism is released and the plunger pivoted about its pivotal connection to the syringe body to bring the plunger into line with the axis of the syringe bore. In doing so, the orientation of the plunger is reversed so that the enlarged end of the plunger which had been at the distal end of the packed device now becomes the proximal end of the plunger which a user can push against to move the plunger axially within the syringe bore. The end of the plunger moves into contact with the piston within the cartridge and drives the piston axially within the cartridge to expel the contents of the cartridge through the bore of the needle. Once the plunger has been fully depressed to eject the contents of the cartridge, the plunger can be retracted, pivoted about its pivotal mounting to return to its first position at which it sheaths the used needle. The application of radial pressure to the plunger in the region of the locking groove at the distal end of the syringe body causes the locking barbs to engage fully with that groove to lock the plunger in its first position.

It will be appreciated that the cartridge may not incorporate a piston, but that this may be provided integrally with die plunger of the syringe. It will also be appreciated that it may be desirable to retract the piston in the bore of the cartridge during use in order to verify whether the needle has penetrated a blood vessel or adjacent tissue, that is to aspirate the syringe. Where the piston is provided in the cartridge bore, it may therefore be necessary to provide some form of positive engagement between the distal end of the plunger and the piston, for example a snap fit ball and socket or barb and lip arrangement, to enable the piston to be retracted for such aspiration.

The device of the invention finds widespread use wherever it is desired to use a syringe to inject material from a unit dose cartridge. The device can thus be used to inject unit doses of insulin or other medicament, but is of especial use in the administration of local anaesthetics, notably in dentistry, where the invention provides a simple safe alternative to the complex and costly metal syringes used at present. Moreover, since the syringe of the invention can be made by simple injection moulding techniques, the syringes can be one use disposable devices. However, if desired, the syringe can be made for multiple re-use, in which the invention provides a more simple construction than such syringes in present use and reduces the risk of accidental needle exposure before or after use. DESCRIPTION OF THE DRAWINGS:

The invention will now be illustrated with reference to preferred forms thereof as shown in the accompanying drawings in which Figure 1 shows the two main components of the syringe of the invention separately and an assembled syringe made from those components; Figure 2 shows in axial cross section various stages in the use of the syringe of Figure 1; Figure 3 shows in axial cross section various alternative constructions to the distal end of the unit dose cartridge and syringe of Figure 1; Figures 4 and 5 show in axial cross section an alternative form of the pivot mounting of the plunger to the syringe body; Figures 6 and 7 show in enlargement detail a locking mechanism using a socket in the syringe body and the radial side walls of the needle sheath portion of the plunger; and Figure 8 shows an alternative form of the device of Figure 1 using a groove on the proximal face of a cross member carried by the plunger to provide the needle sheath.

DESCRIPTION OF THE PREFERRED EMBODIMENT:

The syringe of the invention comprises a plastic body member 1 having an axial bore therein and axial apertures 2 in the side wall of the body member which enable a user to manipulate a medicament unit dose cartridge (30 shown in Figure 2) within the bore of the syringe body and to detect the presence of blood in the cartridge during aspiration. The distal end of the body 1 is provided with a needle 3, which can be removably mounted on a suitable luer formed in the end wall of the body 1, but can be formed integrally with body 1 as shown. At the proximal end of body 1 are radial finger flanges 4. An axially aligned circular cross section bead 5 is connected by a transversely acting live hinge 6 to the syringe body at the proximal end of the body 1 so that it can pivot about the lip of the open end of the bore in body 1. The whole of the body member can be formed by injection moulding of a suitable plastic, such as polyamide or polyester, in which case a stainless steel hypodermic needle 3 can be incorporated into the distal end of the body member 1 during the moulding operation. A plunger member comprises an axially elongated shaft 10 having an axial groove 11 formed along the length of the shaft. As shown in the detailed transverse cross section in Figure 1, groove 11 has a circular cross section within which bead 5 is a sliding fit.

In place of the bead 5 and groove 11 shown in Figures 1 and 2, the plunger 10 can be connected to the body 1 by means of a ring within which the plunger shaft is a sliding fit as shown in Figures 4 and 5. The ring 50 is connected to body 1 by the hinge 6 and plunger shaft 10 is retained in ring 50 by the radial finger flanges 12 at one and of the plunger shaft 10 and by a circumferential radially extending rib or stop 51 carried at the other end of the plunger shaft. The plunger shaft 10 is a sliding fit within ring 50 so that the shaft can move axially within the ring when the plunger is aligned with the axis of the bore in body 1 as shown in Figure 5. It is preferred to form the rib 51 as a rubber or similar O ring so that it is a sliding sealing fit within the bore of the cartridge 30 as shown in Figure 5 and provides lateral support to the distal end of shaft 1 in the bore and also provides a secondary seal within the cartridge 30. It is also preferred that ring 50 be a close fit within the proximal end 52 of the bore in body 1 so that it provides lateral support to shaft 10. If desired, ring 50 can be formed with a shoulder 53 thereto as shown in Figure 5 to assist location of the ring as a push fit within the proximal end of the bore in body 1.

In the further alternative shown in Figure 8, a radially extending arm 60 is provided at the proximal end of the syringe body 1. The arm 60 has a transverse line hinge 61 so that the radially outward portion of the arm can pivot about the hinge to adopt a radially inwardly directed position. The free end 62 of arm 60 has an enlarged portion having an axially orientated aperture therein within which is journalled the shank 63 of the plunger 64. The aperture and the shank of plunger have congruent cruciform shapes so that the plunger shaft 63 can move axially with respect to the arm 60, but cannot rotate about its longitudinal axis.

The plunger shaft 10 carries transversely extending radial finger flanges 12 at one end thereof and axially extending radial side walls 13 extending from the axial lips of the groove 11. Side walls 13 form the needle sheath when the plunger is in its first position shown in the bottom assembled drawing of Figure 1. The side walls

13 are shaped so that they follow the profile of the distal end of the body member 1 upon which the plunger is to be mounted.

As shown in the bottom drawing of Figure 1 of the assembled syringe prior to use, the plunger 10 is mounted on syringe body 1 by engaging the bead 5 in the axial groove 11 of plunger shaft 10 with the flange 12 end of the plunger shaft adjacent the distal end of body 1. The side walls 13 are located to either side of needle 3 and serve to form a sheath to at least the tip of the needle 3. Preferably, the side walls 13 extend for the full length of needle 3 as shown. The plunger 10 can be held in this first position shown in Figure 1 by a locking bead located adjacent the distal end of body 1 and engaging as a snap fit in the axial groove 11 in plunger 10. However, it is preferred to form the lip of walls 13 with external locking barbs

14 as shown in Figures 6 and 7 and to provide an axially extending locking groove or socket 15 in the distal end of body member. The locking socket 15 has an undercut axial rib 16 adjacent the bottom thereof as shown in Figures 6 and 7. Walls 13 engage in socket 15 and the locking barbs can retain plunger 10 in the position shown in Figure 6a by frictional engagement with the walls of the locking socket. The locking socket can be provided with a transverse membrane or resilient pad 17 in the base of the socket as shown in Figure 6a which will require additional radial pressure to be applied to the plunger before the locking barbs 14 can be engaged with the undercut rib 16 to provide positive retention of walls 13 in socket 15. Thus, the assembled syringe as shown in Figure 1 can be supplied with the plunger 10 releasably held in its first position as shown ready for use and after use the syringe can be disabled by returning plunger 10 to its first position and applying sufficient radial pressure to cause the locking barbs 14 to fully engage locking socket

15 so that they engage the undercut rib 16.

However, the frictional retention of plunger 10 in the position shown in Figure 1 is susceptible to accidental disengagement and it is preferred to provide locking socket 15 with two undercut ribs 16 and 18 located at two different depth within socket 15 as shown in Figure 7. Prior to use, walls 13 are located within locking socket 15 so that the locking barbs 14 engage the first undercut 16 and thus provide a positive retention of plunger 10 in its first position. Walls 13 are slightly flexible so that barbs 14 are a snap fit engagement with undercut 16, but radial pressure on the exposed portion of walls 13 causes the barbs 13 to disengage from undercut 16 as shown in Figure 7A, thus releasing plunger 10 for pivot about hinge 6. Upon return of plunger 10 to the position shown in Figure 1 after use, radial pressure applied to the plunger in the region of walls 13 causes the walls to penetrate deeply into the locking socket 15 so that locking barbs 14 engage the second undercut 18. The plunger shaft lies closely adjacent syringe body 1 and walls 13 are no longer accessible to release the barbs 14 from the undercut 18 in socket 15. The plunger is now retained against body 1 and it is virtually impossible to release it for re-use of the syringe. In this form of the locking of plunger 10 in its first position after use, the resilient pad or membrane 17 in the base of groove 15 can be omitted.

As shown in the top drawing of Figure 2, the syringe is provided in the configuration shown in the bottom drawing of Figure 1 with plunger 10 retained in its first position. A unit dose cartridge 30 is inserted into the bore in body 1. The membrane of the closure cap 32 of the cartridge is penetrated by the proximal end 7 of needle 3 which protrudes proximally into the bore of body 1 as shown in detail in Figure 3. The user can manipulate the cartridge 30 into position through the apertures 2 in the side wall of body 1. By squeezing radially inward on the side walls 13 as shown in Figure 6 or 7, the locking barbs 14 carried by the side walls 13 are released from engagement with the side walls or undercuts 16 of socket 15 so as to release plunger 10 and expose needle 3. Plunger 10 is then rotated about the hinge 6 to bring the plunger shaft into line with the axis of the bore in body 1 as shown in the middle drawing in Figure 2. Due to the sliding fit of bead 5 in groove 11, the plunger can then be moved axially so that its distal end enters the bore in body 1 and bears against the piston 31 usually provided in the cartridge 30. Needle 3 can be inserted into the skin of a patient in the usual manner and medicament injected by moving plunger 10 in the bore of body 1 by pressing on finger flange 12 as shown in the middle drawing of Figure 2.

Where it is desired to aspirate the syringe to determine whether the tip of the needle is in a blood vessel or adjacent tissue, it may be necessary to form a barbed connector 40 on the distal end of plunger 10 as shown in Figure 3B to provide a positive drive between piston 31 and plunger 10 so that the piston can be retracted to draw fluid into the bore in body 1. Any blood in the fluid can be observed through the apertures 2 in the wall of body 1 and the needle 3 withdrawn for re¬ insertion at some other point in the patient if necessary. Alternatively, as shown in Figure 3C, the distal end of plunger 10 can be provided with a piston 41 in replacement for or in addition to piston 31 of cartridge 30. Other means by which aspiration can be achieved include the provision of an axial spigot 42 around needle 7, as shown in Figure 3D, which engages the membrane 43 of the cartridge and causes the membrane to flex inwardly during the forward stroke of plunger 10. However, if the pressure on plunger 10 is reduced, this will allow membrane 43 to Tevert to its unflexed position and draw a small suction within the cartridge which is sufficient to draw blood into the clear body of the cartridge if needle 3 is located in a blood vessel.

After administrationof the medicament, plunger 10 has adopted the position shown in the middle drawing of Figure 2. The plunger is then fully retracted so that it can be pivoted about the live hinge 6 to adopt its first position as shown in the bottom drawing of Figure 2. Application of radial pressure to the exposed face of plunger 10 in the region of socket 15 will cause walls 13 to enter socket 15 sufficiently for the locking barbs 14 to engage the undercut rib 16 in locking socket 15 in the case of the assembly shown in Figure 5 or the second undercut 18 in the case of the assembly shown in Figure 7, thus locking the plunger in the position shown. This provides a sheath for needle 3 and dis-ables the syringe against re-use.

In the alternative form of the device shown in Figure 8, the plunger 64 carries a transverse head 65 at its distal end when in its first position, so that the plunger has a generally T shape. The proximal face of one arm of the transverse head of the T carries a radially extending groove 66. As the plunger is pressed radially towards the body 1 of the syringe, the needle 67 extending axially from the distal end of the body 1 engages in groove 66 in head 65. As the plunger is pressed fully home against the syringe body, the needle is bent through about 90o as shown and its shank is then located in groove 66. The head 65 is dimensioned so that the length of needle 67 is accommodated in groove 66, which thus acts as the needle sheath. Groove 66 may be formed with a narrow open top so that the needle 67 is a snap fit therein; and groove 66 may be formed with a closed radially outward end to further protect the tip of the needle.

An alternative form of mechanism for locking the plunger against the body of the syringe is also shown in Figure 8. The shank 63 of the plunger is provided with a radially inwardly directed T shaped lug 68. The distal end of syringe body 1 is provided with a corresponding T shaped recess 69. As the shank of the plunger is pressed against body 1, the lug 68 engages in recess 69. The lug 68 can have a barbed shape so that it is a radial snap fit into recess 69. Alternatively, lug 68 can have a rigid T shape and is engaged by bringing it radially into register with the open distal end of recess 69 and then moving the plunger axially so that the lug engages axially into the socket through the open distal end thereof.

Claims

CLATMS:

1. A syringe for use with a unit dose cartridge, which syringe comprises: a. an axially extending body member having an axially extending bore therein adapted to receive a unit dose cartridge therein; b. a mounting at the distal end of the body carrying or adapted to carry a hollow needle member through which fluid can flow from said unit dose cartridge; c. a plunger member carrying or adapted to engage the proximal face of a piston member joumalled for axial movement within the bore of a unit dose cartridge when mounted in the body member of the device, characterised in that: d. the plunger is secured to the proximal end of the syringe body by a pivotal connection whereby the plunger can be pivoted from a first position at which it lies outside the syringe body but generally parallel to the longitudinal axis of the syringe body to a second position at which the longitudinal axis of the plunger is substantially co-incident with that of the bore within the syringe body whereby the plunger can be moved axially into and within the bore of the syringe body, the pivotal connection allowing relative axial movement between the plunger and the syringe body; and e. the plunger member is provided with a groove or recess therein into which the needle of the syringe is adapted to locate so as to provide a sheath for the needle when the plunger is in its said first position; and f . a locking mechanism is provided for securing the plunger member in its said first position.

2. A syringe as claimed in claim 1, characterised in that the said groove or recess for receiving the needle is adapted to receive the needle by relative transverse movement of the needle and the groove or recess.

3. A syringe as claimed in claim 1, characterised in that the pivotal connection between the syringe body and the plunger member comprises a radially extending transversely hinged member carried at the proximal end of the syringe body, said hinged member having an axially orientatedaperture therein, within which aperture the plunger is a sliding fit to allow the plunger to move axially with respect to the apertured member.

4. A syringe as claimed in claim 3, characterised in that the apertured portion of the hinged member removably engages within the proximal end of the bore in the syringe body when it pivots with the plunger as the plunger adopts its second position so as to provide lateral support to the plunger when the plunger adopts its second position and as it moves axially within the bore of the syringe body.

5. A syringe as claimed in claim 1, characterised in that the pivotal connection between the plunger and the proximal end of the syringe body comprises an axially orientated bead member which mounted at the proximal end of the syringe body by means of a transverse pivot means and which engages in an axial groove or recess of the plunger, or vice versa, whereby the plunger can slide axially upon the bead member.

6. A syringe as claimed in claim 5, characterised in that the bead and groove or recess are formed so that the bead cannot be separated radially from the groove or recess.

7. A syringe as claimed in claim 5, characterised in that the recess or groove into which the needle carried by the syringe is to locate when the plunger is in its first position is provided as an axial extension of the groove or recess into which the bead member engages, and the plunger extends axially for the full length of the syringe body and the needle mounted thereon.

8. A syringe as claimed in claim 7, characterised in that the distal portion of the plunger when in its first position extends radially inwardly to encase or protect at least the tip of the needle.

9. A syringe as claimed in claim 8, characterised in that the distal portion of the plunger has one or more radially extending parallel walls which between them form a radial extension to the said axial groove within which at least the tip of the needle locates when the plunger is in its first position.

10. A syringe as claimed in any one of claims 1 to 4, characterised in that the plunger member is provided with a radially extending transverse head member at the distal end thereof when the plunger is in its first position, and the proximal face of said head member is provided with a radially extending groove or recess into which a needle carried at the distal end of the syringe body is adapted to engage as the plunger member adopts its first position.

11. A syringe as claimed in any one of the preceding claims, characterised in that the groove or recess into which the needle is adapted to engage is dimensioned such that it is a frictional fit upon the needle shaft.

12. A syringe as claimed in any one of the preceding claims, characterised in that a positive locking mechanism is provided which secures the plunger in its first position.

13. A syringe as claimed in claim 12, characterised in that the locking mechanism comprises a locking ring which is a tight fit around both the syringe body and the plunger in its first position.

14. A syringe as claimed in claim 13, characterised in that the ring has a circumferential groove or rib which is a snap fit upon a rib or groove carried by the plunger and/or the syringe body so as to secure the ring in position.

15. A syringe as claimed in claim 12, characterised in that the locking mechanism comprises a radially extending member which engages a groove or recess, one carried by the plunger and the other by the syringe body.

16 A syringe as daimed in any one of daims 12 to 15, characterised in that the locking mechanism is engaged by a snap fit mechanism.

17. A syringe as daimed in any one of daims 12 to 16, diaracterised in that the locking mechanism is located at a point intermediate the pivotal connection of the plunger to the syringe body and the distal end of the needle carried by the syringe body.

18. A syringe as daimed in any one of daims 15 to 17, characterised in that the radially extending member of the locking mechanism is provided by a side wall(s) forming the radial extension to the axial groove in the plunger and the groove into which that locking member engages is formed in the exterior of the body of the syringe at or adjacent the distal end of the syringe.

19. A syringe as daimed in dai 18, diaracterised in that, the radially extending member of the locking mechanism engages in the said groove to two different extents so that in a first extent the locking mechanism can be readily disengaged, but in the second extent it cannot readily be disengaged.

20. A syringe as daimed in dai 1 substantially as hereinbefore described with respect to and as shown in any one of the accompanying drawings.