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EP-4736913-A2 - AUTO INJECTOR WITH IMPROVED FUNCTIONALITY

EP4736913A2EP 4736913 A2EP4736913 A2EP 4736913A2EP-4736913-A2

Abstract

The invention relates to an auto injector, by which a fixed dose of a medicament can be injected as self-treatment, and by which needle exposure to an accessible position, injection of the medicament and retraction of the needle to an inaccessible position is automatically performed as a continuous sequence, after the auto injector is triggered. The auto injector includes a syringe assembly (1), a driver (7) and a screw (6). Either: the screw (6) and the driver (7) are rotationally connected, so that they rotate together but are allowed to telescope relatively, and the screw (6) is rotated in an expelling thread engagement (19/39) causing the screw (6) to move towards the needle end; or the screw (6) and the driver (7) are engaged in an expelling thread engagement thread engagement and the movement of the plunger is the result of a rotational movement of the driver (7) relative to the screw (6) in the expelling thread engagement. The syringe assembly (1) and the driver (7) during exposure of the needle are engaged in an exposure thread engagement (21/27) and the axial movement of the syringe assembly (1) during exposure of the needle is a result of relative rotational movement between the syringe assembly (1) and the driver (7).

Inventors

  • MOELLER, CLAUS SCHMIDT

Assignees

  • Shaily Engineering Plastics Limited

Dates

Publication Date
20260506
Application Date
20190330

Claims (4)

  1. An auto injector defining a main axis and comprising: a housing (2), of which one end is the "needle end"; a syringe assembly (1) comprising a cartridge (10) with a hollow needle and a plunger and the medicament to be injected; a first spring means (14); a driver (7); a screw (6); and a trigger (4) adapted to initiate functional sequences of the auto injector after activation; wherein the syringe assembly (1) is rotationally secured relative to the housing (2) but is allowed to move axially relative to the housing (2); wherein the functional sequences include moving the syringe assembly (1) in one direction to expose the needle to an accessible position, expelling the medicament out through the needle, and moving the syringe assembly (1) in the opposite direction to retract the needle to an inaccessible position; wherein the screw (6) during injection is adapted to move the plunger in the cartridge (10) to expel the medicament by means of the first spring means (14) and via the driver (7); and wherein the first spring means (14) is a torsional spring rotating the driver (7) during exposure of the needle and expelling of the medicament; CHARACTERIZED in that : either: the screw (6) and the driver (7) are rotationally connected, so that they rotate together but are allowed to telescope relatively, and the screw (6) is rotated in an expelling thread engagement (19/39) causing the screw (6) to move towards the needle end; or: the screw (6) and the driver (7) are engaged in an expelling thread engagement thread engagement and the movement of the plunger is the result of a rotational movement of the driver (7) relative to the screw (6) in the expelling thread engagement; and in that the syringe assembly (1) and the driver (7) during exposure of the needle are engaged in an exposure thread engagement (21/27) and that the axial movement of the syringe assembly (1) during exposure of the needle is a result of relative rotational movement between the syringe assembly (1) and the driver (7).
  2. An auto injector according to claim 1, characterized in that the driver (7) is engaging the housing (2) in a retraction thread engagement (25/31) at least during expelling of the medicament, and that the second thread engagement (25/31) in the end of the expelling of medicament disengages, so that the driver (7) and the syringe assembly (1) by means of a second spring means (13) is moved away from the needle end to the position where the needle is inaccessible.
  3. An auto injector according to claim 2, wherein the pitch of the threads in the exposure thread engagement (21/27) is higher than the pitch of the threads in the retraction thread engagement (25/31).
  4. An auto injector according to any preceding claim, characterized in that the length and position of the thread on the screw (6) is arranged such that rotation of the screw (6) in the expelling thread engagement does not move the plunger in the cartridge (10) during exposure and retraction of the needle.

Description

Field of invention The invention relates to an auto injector, by which a fixed dose of a medicament can be injected as self-treatment, and by which needle exposure to an accessible position, injection of the medicament and retraction of the needle to an inaccessible position is automatically performed as a continuous sequence, after the auto injector is triggered. Background for the invention Through the last two decades the use of auto injectors has increased significantly every year as they have the benefit that they allow patients to take their medication without involving a doctor or a nurse. Automated needle insertion, injection and needle retraction is state of the art for this type of auto injectors and new auto injectors enters the market regularly. As users of this type of auto injectors often are first time users, it is essential that the auto injectors are easy to use, smooth in operation and reliable, but unfortunately this is not the case for many auto injectors on the market. For a first time user the act of injection a medicament into his own body can be very stressful, and it is therefore very important that the auto injector is easy to understand and to handle, as the stressful situation can lead to an incorrect use of the auto injector with a risk of mistreatment. It is also important that the injection is carried out smoothly, with the correct injection speed and without accompaniment of high and scarring noises, to prevent that the injection is painful or unnecessarily scarring. And last the auto injectors should work every time to prevent that this type of auto injectors are being associated with uncertainty and misbelief. The most common problems with auto injectors is non-intuitive handling and complicated instructions, expelling of medicament beginning before the needle is inserted to the correct depth, too fast injection of the medicament, and after retraction of the needle it is loud noises when the auto injector shifts from one functional sequence to another, and malfunction of the auto injector, especially related to the retraction of the needle. Description of the related art The patent field for auto injectors is very crowded, but the documents WO9535126, EP0516473, WO2005115509, WO2005115511, WO2005115513, WO2005115516, WO2007066152, WO2008005315, WO2011101377, EP2468329 and EP2129416 give a good description of the prior art in the field. Some of these will be further described hereafter. In WO2005115516 an auto injector comprising a housing adapted to receive a syringe with a hollow needle is described. The housing includes means for biasing the syringe from an extended position in which the needle extends from the housing to a retracted position in which the needle is contained within the housing. The auto injector further comprises a compressible spring, a drive acted upon by the spring and in turn acting on the syringe to discharge its contents through the needle, a decoupling mechanism, activated when the drive has been advanced to a nominal decoupling position, to allow a first component of the auto injector to move relative to a second component, a release mechanism, activated when the said first component has reached a nominal release position relative to the second, to release the syringe from the action of the spring, whereupon the biasing means restores the syringe to its retracted position, and a highly viscous fluid is damping the movement of the said first component relative to the second, so that the release of the syringe is delayed after the activation of the decoupling mechanism to allow the remaining contents of the syringe to be discharged before the syringe is released for retraction. In WO2008005315 another auto injector for providing a subcutaneous injection of a substance into a user is described, comprising a housing, a syringe with a barrel portion holding the substance and with a needle attached movably disposed in the housing, and a plunger for sealing the barrel portion and selectively applying pressure to the substance to force the substance through the needle, a syringe actuation component for first moving the syringe towards the first end of the housing such that the needle is exposed and for subsequently applying pressure to the plunger, and a compressible spring for biasing the syringe actuation component towards the proximal end of the housing, the spring disposed between a flange on the syringe actuation component and the distal end of the housing. Both of the described auto injectors make use of compression springs for insertion and retraction of the needle and for injection, which in turn requires a number of couplings and locking/unlocking features to shift between the different operational sequences, and which therefore increases the risk of a malfunction. Secondly both auto injectors push on the plunger to move the syringe forward, which increases the risk of starting the injection before the needle is fully inserted. Furthermore, compr