GB2441972A

GB2441972A - Automatic Needle Withdrawal from Patient

Info

Publication number: GB2441972A
Application number: GB0621559A
Authority: GB
Inventors: Henry Kirby; Bruce Roser
Original assignee: Cambridge Biostability Ltd
Current assignee: Cambridge Biostability Ltd
Priority date: 2006-09-19
Filing date: 2006-10-31
Publication date: 2008-03-26
Also published as: GB0618294D0; WO2008034743A1; EP2200685A1; GB0621559D0

Abstract

An injector comprising a container for containing a medication, a piston arranged to move in the container to expel the medication, a needle (4) for delivering the expelled medication into a patient, an operating means designed to push the needle into the patient and operate the piston, a single spring-action means (8), and a release mechanism (7A&7B) for operating the spring-action means, wherein the release mechanism, which may be a ramp or catch mechanism, is caused to be automatically released by a final movement of the piston, and/or operating means, during expulsion of medication, thereby withdrawing the needle from the patient after delivery of the medication.

Description

An Injector The present invention relates to an injector device and

more particularly, but not exclusively, to an injector for the administration of medicinal, therapeutic or diagnostic substances.

The ubiquitous traditional syringe suffers from two significant problems. The first is that once used, the syringe's exposed needle poses a hazard until destroyed; and secondly, to ensure that the dose is administered correctly and to minimise discomfort to the patient, those who administer vaccines and other medicaments by syringe, require training in their correct use.

The later problem is particularly significant in the organisation of an emergency response to incidents such as a viral outbreak (e.g. a variant of Avian Influenza) or a biological attack. In such cases, it is likely that the response would involve, inter alia, the need for mass vaccination of the proximate population to the outbreak within a very short time frame, such as a few days. It is thought that such a vaccination program would be impeded potentially to the point futility by the inability to fmd a sufficient number of skilled persons to deliver the number of vaccinations needed within the required time frame.

Consequently, there is a drive to develop a safety injector wh ich can be used by persons having little or preferably, no training and which can reliably administer the correct dosage with the minimum degree of discomfort to the patient.

An example of an existing approach of a safety syringe to counter the above problems is described in patent specification WO 03/095003. The injection device employs a series of snap-tabs which arc designed to break, in sequence, so as to regulate the separate steps of the injection process. Although demonstrated with some success, the design suffers from the vulnerability that, having broken the first tab, it is not inevitable that the process will continue smoothly and uninterrupted to the end. Each tab requires a successively larger force to break meaning that user is likely to experience a series of spurs' of resistance. This may result in the action stopping part-way if the force onto the housing is not consistently large enough. Such a jerky action is likely to be unsettling to a patient and may cause greater physical discomfort particularly as the design requires the yielding of a final tab after administration of the substance to activate a needle withdraw mechanism which may cause the needle to be present in the patient for longer than is necessary.

The Inventors have endeavoured to overcome the above problems by looking towards an alternative method to control the action of an injector which is not reliant on force to snap a tab.

The invention provides an injector comprising: a container for containing a medication; a piston arranged to move in the container to expel the medication; a needle for delivering the expelled medication into a patient; an operating means designed to push the needle into the patient and operate the piston; a spring-action means for withdrawing the needle from the patient after usc; and a release mechanism for operating the spring-action means; characterised in that the release mechanism is caused to be released by a final movement of the piston, and/or operating mechanism, during expulsion of a final portion of medication.

It is preferable that the injector's release mechanism includes a catch or groove mechanism, in fact this feature is itself thought to be novel in a injector and thus there is provided an injector comprising: a container for containing a medication a piston arranged to move in the container to expel the medication; a needle for delivering the expelled medication into a patient; an operating means designed to push the needle into the patient and operate the piston; a spring-action means for withdrawing the needle from the patient after use; and a release mechanism for operating the spring-action means; characterised in that the release mechanism is a ramp or catch mechanism caused to be released by a movement of the piston, and/or operating mechanism.

In a preferred embodiment the release mechanism includes a resiliently deformable member arranged so that the final movement of the piston causes deformation of the resiliently deformable member. This in turn causes release of the release mechanism and that this deformation is preferable caused by abutment of the deformable member against the container for containing the medication.

It is additionally favoured that the deformable member has at least two flexible limbs which are arranged so as to radially deform towards one another and so to release the mechanism. Ills further preferable that the member is arranged so that until the release mechanism is released, the member acts to transmit the force or movement from the operating means to the piston.

In another favourable embodiment the resiliently deformable member and the piston arc formed as a single integrated component.

The invention will now be described by way of example with reference to the following drawings in which: Figures 1 and 1A are cross sectional views through perpendicular planes of an injector device according to the invention illustrated in its pre-injection configuration; Figures 2 and 2A are cross sectional views of the injector of figure 1 shown at a first stage of the operation at which point the needle has been deployed but before the medicament has been dispensed.

Figures 3 and 3A are cross sectional views of the injector in which the medicine has been partially dispensed.

Figures 4 and 4A are cross sectional views of the injector as the needle recoil mechanism is being released; Figures 5 and SA arc cross sectional views of the injector after the needle recoil mechanism has been released; and Figure 6 is a perspective view of an actuator and plunger formed as a single component.

Referring firstly to Figure 1, there is shown an injector having an open ended tubular main body I with a collet (conical flange) I A on the inside surface of its base and an orifice defined in the base of the main body 1 at the centre of the collet IA. Defined on the inside wall is a downwardly facing lip lB located approximately half way up the main body 1 and parallel beading 1 C and I D substantially near the top of the main body 1. The outer surface of the base supports an adhesive layer 1C protected by a release sheet (not shown).

A cap 2 having two tubular sections of different internal diameters is located with the wider diameter section housed within the main body I and held in a pre-dispensing position by a bead 2A sandwiched between beading lC and ID of the main body. The two tubular sections of the cap 2 are joined so as to define a downwardly facing step 2B.

Housed within the main body 1 is a syringe formed from a barrel 3, defining a flange 3A, a hypodermic needle 4 and a plunger 5 with a seal 6, arranged to move within the barrel 3 and administer the substance held within it. The barrel 3 has a narrowed opening widening by means of a downwardly facing lip 3B on the inside of the barrel 3. The plunger's 5 outer surface defines a peripheral beading 5A, the plunger being arranged so that in the pre-dispensing position the beading 5A abuts on top of lip 3B. An upper portion of the plunger 5 is bisected by a longitudinal groove into which is an actuator 7 is supported. The actuator 7, formed from a single piece, defines two resiliently flexible limbs which extend upwards and each terminates with an enlarged head defining an upwardly facing lip 7B on the outer edge. Along the outer edges of limbs are upwardly facing lips 7A. Both lips 7A & 7 B stand proud of the outer surface of plunger 5. The tip of the needle 4 is secured into a needle seal 8. A coil spring 8 sits around the collet lÀ and needle 4 and between the base of the main body 1 and the flange 3A. The spring 8 biases the syringe so that the lips 7B of the actuator 7 abut a corresponding lip 2B of the cap 2.

To administer the substance the release sheet is removed and the base of the main body I placed onto a patient's skin. The adhesive IC helps to secure the injector so as to prevent the possibility of movement of the base across the skin during administration. The substance is administered by exerting pressure onto the top of the cap which forces the bead 2A to pass over beading 1 C and 1 D. The downward movement of the cap 2 is transmitted through to the plunger 5 via the actuator 7. This is in turn transmits the movement via the abutment between lips 5A and 3B to the barrel 3 and needle 4 causing the needle 4 to pierce through the base of the needle seal 8, through the orifice in the base of main body 1 and into the patient's skin. The barrel 3 continues to move downwardly until it abuts the top of the collet 1A. Further pressure on the cap 2 caus es lip 5A associated with the plunger to pass over bead 3B allowing the plunger to move downwards through the barrel causing the medicament to be pushed through the needle 4 and into the patient. As the plunger 5 draws to the end of its stroke, as seen in Figure 3, the graduated lip 7A is forced against the inside wall of the barrel 3 causing the limbs of the actuator 7 to close together. Continued movement of the plunger 5 downwards continues to close of the limbs until, at the point shown in Figure 4, the lips 7B completely disengage with the step 2B. The compressed spring 8 recoils causing the barrel 3, needle 4, plunger 5 and actuator 7 to be propelled upwards. The cap 2 is prevented from similar movement upwards by the engagement of the lip 2A which having passed over the ramped portion of lip I B during the down stroke of the piston 5, abuts against is stepped face.

Consequently, the actuator 7 and portion of the barrel 3 homes inside the cap 2 as can be seen in Figure 5.

In the above example, all parts except the coil spring 9 and needle 4 are made from various types of synthetic plastics materials.

It is favourable that the beading IC, 1 D and 2A be of such a size and design that the forcc required to release the bead 2A from its home position between beading 1 C and 1 D is large enough that, once released, the subsequent momentum is sufficient to cause all the above described movements without additional force being required. Or expressed in another way, it is difficult for the person administering the substance to stop the operation before the needle recoil has been released. It is important that the beading 5A creates enough resistance in combination with fluid resistance that the plunger 5 does not move within the barrel 3 until the barrel 3 engages the collet 1A. This ensures that all the substance contained within the barrel 3 is administered upon the needle 4 reaching the correct depth.

It should be appreciated that the above described embodiment is but example which falls within the scope of the invention. F or example, rather than the actuator having a ramped lip 7A the whole of the outside edge of the limp may be ramped thus causing a more gradual and perhaps smoother action.

The limbs may not be resiliently deformable and be separate from the actuator having movement restricted by a ratchet or other mechanism.

Indeed the actuator may take other forms other than the wishbone' shape illustrated, such as a resiliently deformable clip or collar. In such as embodiment, the clip or collar may be located so as to circumvent the syringe can could be deformed by contact with a protrusion on the inside of the main body so as to release the clip.

In an alternative embodiment; the actuator 7 and the plunger 5 are replaced with a single integrated piece 8, illustrated in Fig 6, which defmes a single flexible arm. This simplified design in creases the reliability of the device by reducing the possibility of jamming caused if the cap 2 depresses in a skewed fashion causing the arms to be released at separate times. It otherwise operates in a similar manner as to the separate actuator and piston as described in the main embodiment.

Claims

Claims 1. An injector comprising: a container for containing a

medication; a piston arranged to move in the container to expel the medication; a needle for delivering the expelled medication into a patient; an operating means designed to push the needle into the patient and operate the piston; a spring-action means for withdrawing the needle from the patient after use; and a release mechanism for operating the spring-action means characterised in that the release mechanism is caused to be released by a final movement of the piston, and/or operating mechanism, during expulsion of a fmal portion of medication.
2. An injector according to Claim 1 characterised in that the release mechanism comprises a catch mechanism.
3. An injector according to Claim 1 or 2 characterised in that the release mechanism includes a resiliently deformable member arranged so that the final movement of the piston causes deformation of the resiliently deformable member releasing the release mechanism.
4. An injector according to Claim 3 characterised in that the resiliently deformable member is arranged so it is deformed by abutment against the container for containing medication.
5. An injector according to any Claims 3 or 4 characterised in that the resilient deformable member has a resiliently flexible limb defining a lip arranged so that before the final movement of the piston the lip abuts a corresponding lip associated with the operating means preventing release of the release mechanism.
6. An injector according to Claims 3-5 characterised in that resiliently deformable member is arranged between the operating means and piston so that it acts as to transmit movement of the operating means to the piston until the release mechanism, is released.
7. An injector according to Claims 3 or 4 characterised in that resiliently deforinable member has at least two limbs which are arranged so as to radially collapse towards each other.
8. An injector according to Claims 3 to 7 characterised in that the resiliently deformable member and piston are formed as a single integrated piece.
9. An injector comprising: a container for containing a medication; a piston arranged to move in the container to expel the medication; a needle for delivering the expelled medication into a patient; an operating means designed to push the needle into the patient and operate the piston; a spring-action means for withdrawing the needle from the patient after use; and a release mechanism for operating the spring-action means characterised in that the release mechanism is a ramp or catch mechanism caused to be released by a movement of the piston, and/or operating mechanism.