GB2477487A

GB2477487A - Injection device

Info

Publication number: GB2477487A
Application number: GB0917786A
Authority: GB
Inventors: Clive Nicholls
Original assignee: Owen Mumford Ltd
Current assignee: Owen Mumford Ltd
Priority date: 2009-10-12
Filing date: 2009-10-12
Publication date: 2011-08-10
Also published as: GB2477487A8; GB0917786D0

Abstract

A safety arrangement for injection devices which inhibit operation of the drive mechanism when the housing is open. An injection device is described with a separable elongate housing (10, 12) for receiving in use charged syringe (24) which has a drive mechanism disposed in a rear part of the housing for expressing a dose from the syringe. The housing may be opened to allow loading or unloading of a syringe, and the drive mechanism is cocked when the housing is open. Operation of the drive mechanism is inhibited when the housing is open, for example by blocking forward movement of a drive plunger or inhibiting movement of a release trigger. In one embodiment an elongate finger (36, 40) may prevent the actuation of the drive mechanism. In a second embodiment a latch (42, 44) in combination with a keyway (48) may provide the blocking action.

Description

Iniection Device This invention relates to injection devices receiving a syringe or cartridge and having a housing which can be opened or separated into parts for loading and unloading, and which contain a drive mechanism releasable to express a dose from the syringe or cartridge. In many such devices the drive mechanism is energised or cocked when the housing is open, the syringe or cartridge is then loaded, and the housing closed ready for performing the injection. An example of such a device is disclosed in our earlier published application W094/21316.

In devices of this type there is a risk that, having cocked the drive mechanism it is inadvertently fired before the device is fully closed or reassembled.

There is a fair amount of stored energy in the cocked drive mechanism and premature firing can damage the syringe or cartridge or the mechanism, or waste the drug. In addition in some such devices which are separated into forward and rearward parts, the drive mechanism plunger projects from the front end of the rear part when fired, and so premature firing could cause injury or damage.

Although such devices often already include safety features to prevent inadvertent firing, for example requiring a compound action of maintaining a forward pressure on a hand grip whilst pushing a trigger member transversely, these actions do not address the potential difficulties described above.

We have therefore designed a safety arrangement for an injection device which inhibits operation of the drive mechanism when the housing is open.

Accordingly, in one aspect of this invention there is provided an injection device comprising: an elongate housing for receiving in use a charged syringe or cartridge with a needle at its forward end; a drive mechanism in a rear part of the housing, the drive mechanism including: a plunger movable longitudinally from a rearward to a forward position to express a dose from said syringe or cartridge, and a stored energy arrangement for propelling the plunger forward upon actuation of said drive mechanism; wherein the elongate housing may be opened to allow the loading or unloading of a syringe or cartridge, characterised i that operation of said drive mechanism is inhibited when the housing is open.

Whilst this arrangement may be used for a wide range of injection devices which can be opened to allow loading or unloading of a syringe or cartridge, for example arrangements where the housing is hinged or has a slideable flap or the like, the elongate housing conveniently comprises coupled front and rear parts that may be uncoupled to open the housing, with the drive mechanism being disposed in the rear part. The front and rear parts may be coupled by any suitable action including a releasable push fit, but it is preferred for the front and rear parts to be coupled by rotary action, for example a threaded action or a bayonet action.

Conveniently, a latch member is provided on the rear housing part, the latch member being unlatchable from the latch position from which it inhibits operation of said drive mechanism, with the coupling action of the front and rear parts unlatching the latch member.

The latch member may inhibit operation of the drive mechanism in a variety of ways, eg by blocking movement of the plunger or preventing release of a trigger mechanism that frees the plunger for movement.

Thus in one arrangement, when in its latched position the latch member may prevent movement of the plunger to its forward position, and unlatching the latch member allows said movement. The latch member may conveniently comprise an elongate finger having a rearward portion operable to block the plunger and a forward portion for being acted upon by said front housing part, the elongate finger being rockable about a transverse axis between latched and unlatched positions, and being biased towards said latched position. Two or more such latch members may be provided, the or each latch member conveniently being provided on a collar which fits inside the front end of the rear housing part.

In an alternative arrangement, said drive mechanism may be operated or triggered by moving an actuation member on said rear housing part, and said latch member may be adapted to prevent effective actuation movement of said actuation member when the latch member is latched. The latch member is conveniently rotatable between the latched and unlatched positions. Preferably the latch member has a forward abutment for being engaged and rotated as the front and rear housing parts are coupled, and a rearward key element for cooperating with a keyway formed in said actuation member.

Whilst the invention has been described above it extends to any inventive combination of the features set out above or in the following description.

The invention may be performed in various ways, and two embodiments therefore are now described by way of example only, reference being made to accompanying drawings in which; Figure 1 is a cross sectional view of existing form of an injection device described in our earlier published application W094/21316; Figure 2 is a perspective view of a device of the type of Figure 1 with the rear housing uncoupled from the front housing; Figures 3(a) and 3(b) are detailed section views on the front part of the rear housing of an injection device in accordance with this invention showing the latch fingers of the latch collar in the blocking position (Figure 3(a)) and the free position (Figure 3(b)), and Figure 4 is a detailed view on the rear part of the front housing and the forward part of the rear housing embodying another arrangement of this invention.

Referring initially to Figures 1 and 2, the injection device comprises forward housing part 10 and a rearward housing part 12 having respective internal and external threaded portions 14, 16 by which the parts may be screwed together and unscrewed to separate them. The rear housing part 12 contains a drive mechanism including a drive spring arrangement 18 which acts on a drive plunger 20 which cooperates with the piston rod 22 of a syringe 24 having a needle 26, the syringe being located in the forward part 10 of the housing. On the rear end of the rear housing 12 is a sleeve 28 capable of limited sliding movement against a spring bias from the rest position shown in Figures 1 and 2. A trigger button 30 projects through an aperture in the sleeve 28. As discussed in more detail in W094/21316, the drive mechanism is cocked by pushing the plunger 20 back against the bias of the spring arrangement 18 until it is releasably held by the trigger 30. In the position shown in Figure 1, the trigger button 30 cannot be pressed until the sleeve 28 is pushed forward.

Although this safety catch arrangement reduces the risk of inadvertent firing of the trigger it will be appreciated that, once cocked, the drive mechanism could be fired prematurely before it has been fully assembled with the front part.

Figures 3(a) and 3(b) and 4 show embodiments for inhibiting operation of the drive mechanism until after the front and rear housings have been safely coupled.

Referring initially to Figure 3, in this arrangement the front part of the rear housing 12 is provided with two circumferential slots 32 just to the rear of the threaded portion 16. A latch collar of cylindrical shell form is slid inside the front of the rear housing and has diametrically opposed latch fingers 36 that can rock resiliently about respective spaced transverse axes between a blocking position in which they block forward movement of the plunger 20, and a free position (shown in dotted lines in Figure 3(b)) in which forward movement of the plunger is unobstructed. The forward parts of the latch fingers 36 have out-turned ribs 38 that project through the slots 32 in the housing and are designed to be engaged by and pushed inwardly by the rear edge of the front housing 10 as it is screwed fully home. The rear ends of the latch fingers 36 are formed as abutments 40 for engaging the front of the plunger 20.

Thus, until the front housing part 10 is screwed fully home onto the rear housing part 12, the abutment portions 40 block forward movement of the plunger 20. However once the device has been fully assembled the abutments which retract to allow forward movement of the plunger 20.

Referring now to the embodiment of Figure 4, here the rear housing part is provided with a rotatable hollow cylindrical latch 41 mounted in the forward end of the rear housing part 12, and having forward and rearward lugs 42 and 44 respectively. The cylindrical latch 41 is biased in the counter-clockwise direction by a spring (not shown) which urges the latch to the position shown in Figure 4. The forward lug 42 is designed to be engaged by and rotated clockwise, along with the rearward lug 44 as the front housing part 10 is screwed fully home on the thread 16.

In the uncoupled position, the rear lug 44 lies adjacent to the forward edge of the sleeve 28, thereby preventing forward movement of the sleeve 28. It will be appreciated that, if the sleeve 28 is prevented from moving forwardly, this in turn will prevent firing of the mechanism because the trigger 30 is locked and cannot be released for firing. However, when the cylindrical latch 41 rotates clockwise, the rear lug 44 is rotated into alignment with a slot 48 in the sleeve 28 and so the sleeve 28 can now be shifted forwardly when required to allow the user to operate the trigger 30.

In both the above arrangements, the rotary action of coupling the front housing 10 to the rear housing 12 moves a latch from a position in which operation of the drive mechanism is inhibited to one in which operation is allowed.

Claims

CLAIMS1. An injection device comprising: an elongate housing (10, 12) for receiving in use a charged syringe (24) or cartridge with a needle (26) at its forward end; a drive mechanism (18, 20, 30) in a rear part of the housing, the drive mechanism including: a plunger (20) movable longitudinally from a rearward to a forward position to express a dose from said syringe or cartridge, and a stored energy arrangement (18) for propelling the plunger forward upon actuation of said drive mechanism; wherein the elongate housing may be opened to allow the loading or unloading of a syringe or cartridge, characterised i that operation of said drive mechanism is inhibited when the housing is open.
2. An injection device according to Claim 1, wherein said elongate housing comprises coupled front and rear parts (10, 12) that may be uncoupled to open the housing, the drive mechanism (18, 20, 30) being disposed in the rear part (12).
3. An injection device according to Claim 2, wherein said front and rear parts (10, 12) are coupled by rotary action.
4. An injection device according to Claim 3, wherein said front and rear parts (10, 12) are coupled by a threaded action (14, 16).
5. An injection device according to Claim 3, wherein said front and rear parts (10, 12) are coupled by a bayonet (axial and rotary) action.
6. An injection device according to any of Claims 2 to 5, wherein a latch member (36, 41) is provided on the rear housing part, the latch member being unlatchable from a latch position in which is inhibits operation of said drive mechanism, and wherein coupling action of the front and rear parts unlatches the latch member.
7. An injection device according to Claim 6, wherein the latch member (36) in its latched position prevents the movement of the plunger (20) to its forward position, and unlatching the latch member allows said movement.
8. An injection device according to Claim 7, wherein said latch member comprises an elongate finger (36) having a rearward portion (40) operable to block the plunger and a forward portion (38) for being acted upon by said front housing part, the elongate finger being rockable about a transverse axis between latched and unlatched positions, and being biased towards said latched position.
9. An injection device according to Claim 8, wherein said latch member (36) is provided on a collar (34) which fits inside the front end of the rear housing part (12).
10. An injection device according to Claim 6, wherein said drive mechanism (18, 20, 30) is operated by moving an actuation or trigger member on said rear housing part, and said latch member (41) is adapted to prevent effective actuation movement of said actuation member when the latch member is latched.
11. An injection device according to Claim 10, wherein said latch member (41) is rotatable between the latched and unlatched positions.
12. An injection device according to Claim 10 where the latch member (41) has a forward abutment (41) for being engaged and rotated as the front and rear housing parts are coupled, and a rearward key element (44) for being brought into alignment with a keyway (48) formed in said actuation member.