WO2009095689A1

WO2009095689A1 - Power unit

Info

Publication number: WO2009095689A1
Application number: PCT/GB2009/000271
Authority: WO
Inventors: Barry Peter Liversidge
Original assignee: Barry Peter Liversidge
Priority date: 2008-02-01
Filing date: 2009-02-02
Publication date: 2009-08-06
Also published as: GB0801875D0

Abstract

A power unit suitable for incorporation within a medical injection device such that when released, the injection device is operated fully automatically, to perform an injection. The power unit has a unitary elongate component (10) of moulded plastics material and having first and second portions (11, 12) with a frangible neck (13) therebetween and a pre-loaded spring (22) urging apart the first and second portions. Breaking the neck (13) allows the spring to separate the first and second portions of the component (10) such that one of those portions may drive some other component such as the piston of a syringe.

Description

POWER UNIT

This invention relates to a power unit including a pre-charged drive means and arranged so the energy of the power unit may be released when required. In its preferred aspects, the invention concerns a power unit which may be used in a medical injection device so that when the energy of the pre- charged drive means is released, the power unit thereafter operates the injection device fully automatically, in order to perform an injection.

Springs pre-charged with energy are frequently used in power units, such that the spring may release its stored energy when some other device is to be powered. For example, in GB2093122A there is described an oil pump having a spring to discharge a measured dose of oil, a mechanical lock being employed to hold the spring in its charged condition. The lock includes a lock member which must be moved out of the path of the pump component driven by the spring. Unfortunately, the load imparted by the spring on the component and bearing on the lock member will restrict the ease with which the lock member may be moved out of the way of the component, so that significant force is required to move that lock member and release the component - and in this case a solenoid is used for this purpose.

A further problem with known forms of power unit for use with injection devices is that it may be possible to release the energy of the spring inadvertently and so before the device powered by the unit is ready. In the case of a medical injection device including such a power unit, this could mean that a medicament contained within the device is discharged prematurely so leading to waste and much more importantly to an intended patient not receiving the medicament. In the case of the treatment of anaphylactic shock with a single-use injection device, this could have fatal consequences for the patient in the event that no second injection device is available.

It is a principal aim of the present invention to provide a power unit which, in a preferred embodiment, is suitable for incorporation in a single-use injection device in order to allow the performance of an injection by the energy of the power unit, when released. A further aim is that the force required to cause the power unit to release its stored energy is not dependent upon the magnitude of the stored energy.

According to this invention, there is provided a power unit comprising a unitary elongate component defining first and second portions spaced along the length of the component, a dividing zone provided between the first and second portions, and pre-loaded drive means arranged to generate a separating force on said first and second portions, whereby division of the component at the dividing zone allows relative separating movement of the first and second portions, under the action of the drive means. It will be appreciated that the power unit is a single-shot device, able to operate only once since the release of the energy of the pre-loaded drive means requires division of the unitary elongate component at the dividing zone. Such a device should be relatively simple and so cheap to manufacture, in order that it may simply be thrown away when the energy of the drive means has been released.

Though it would be possible to effect division of the component so that the first and second components are separated in a variety of different ways, such as by cutting through the dividing zone for example with a guillotine, the preferred form of the device has a dividing zone in the form of a weakened region which can be divided by breaking through the material forming that zone. Thus, the dividing zone may be a region of reduced cross-sectional area formed as a neck extending along the length of the elongate component with the first and second portions to the two sides respectively of that neck.

Conveniently, the elongate component comprises a unitary plastics material moulding in the form of a rod, with the dividing zone being frangible by way of a force applied laterally to one of the portions, relative to the length of the rod so as to break through the dividing zone.

In a preferred arrangement of power unit, the pre-loaded drive means comprises a helical coil spring surrounding the elongate component and acting in compression on the two portions thereof. One of those portions may be formed as a push rod for driving a member of some other device (such as the piston of a syringe, when the power unit is used within an auto-injection device) and the other portion may be formed as an operating button which may be thrust laterally relative to the one portion, to break the dividing zone.

The spring of the power unit may bear on one portion of the elongate component, there being a sleeve surrounding and engaged by the spring so as to bear on the other portion of the elongate component. On division of the elongate component, the one portion and sleeve will be driven apart by the spring.

This invention extends to a medical injection device whenever incorporating a power unit of this invention as described above. When so incorporated, the movement of one of the portions may initially drive the needle of a syringe into tissue at an injection site and then may drive the piston or plunger of the syringe so as to expel medicament out of the needle of the syringe. This sequential action is possible in view of the hydraulic resistance to expulsion out of the needle of medicament in the syringe.

By way of example only, two specific embodiments of power unit of this invention will now be described in detail, reference being made to the accompanying drawings in which:-

Figure 1 is a side view of the first embodiment of power unit of this invention, in a loaded condition, ready for use;

Figure 2 is an isometric view of the power unit of Figure 1 ;

Figure 3 is a side view of the power unit of Figures 1 and 2, but following the use thereof;

Figure 4 is an isometric view of the used power unit of Figure 3; Figure 5 is an axial section through the second embodiment of power unit of this invention, in a loaded condition ready for use;

Figure 6 is an isometric view of the power unit of Figure 5;

Figure 7 is an axial section through the second embodiment, but following the use thereof; and Figure 8 is an isometric view of the used power unit of Figure 7. Referring initially to Figures 1 to 4, the first embodiment of power unit of this invention comprises an elongate component 10 comprising a moulded plastics material rod divided into first and second portions 11 and 12 by a neck 13 constituting a weakened zone between the portions. The first portion 11 comprises a push rod 14 having an end face 15 for bearing on some other member (not shown). The push rod has a cruciform cross-section but could be of any shape appropriate for the situation in which the power unit is to be used. The end region of the push rod 14 remote from end face 15 has an enlarged section 16 with a flange 17 extending around that enlarged section, where the section joins the push rod 14. The enlarged section also has a cruciform cross- sectional shape.

The second portion 12 comprises an operating button 19 including a part-spherical form 20 adjoining the neck 13 and a slightly conically-flared form 21 extending axially away from the part-spherical form 20. A generally helical coil spring 22 has one end bearing on the flange 17 and the other end engages the part-spherical form 20 of the operating button 19. As best seen in Figures 1 and 3, that other end of the spring has the end turns of a reduced diameter as compared to the remainder of the spring, such that the greater length of the spring may freely be passed over the part-spherical form 20 but those last few turns must be resiliency sprung over that part-spherical form. Once done, and as shown in Figures 1 and 2, the spring will be in a pre-loaded condition acting between the first and second portions 11,12 of the elongate component 10. Provided the spring rate and the material of the spring is appropriately selected, that pre-load will be insufficient to drive the reduced diameter turns of the spring over the part-spherical form 20.

Figures 1 and 2 show the power unit in its pre-loaded condition, ready for use. Typically, the power unit will be positioned in some other device having a member against which the end face 15 of the push rod 14 bears, the part-spherical form 20 of the second portion 12 being received in an aperture in a second member of the device such that the form 20 may exert a force thereon. When the first and second members of the device are to be moved apart to allow that device to function, a lateral force is applied to the operating button 19 thereby to break the frangible neck 13 connecting together the first and second portions 11 ,12 of the elongate component 10. Once broken, the spring force acting on the flange 17 and part-spherical form 20 drives the first and second portions apart, as shown in Figures 3 and 4, so imparting relative movement on the first and second members of the device, with which the power unit is engaged.

A typical application for the power unit as described above may be in an auto-injector for the performance of medical injections, where the push rod 14 is used to drive the piston of a syringe in order to expel medicament therefrom, with a reaction being taken up by a member of the auto-injector having an opening for receiving the operating button but engaged with the part-spherical form thereof.

The second embodiment of power unit is shown in Figures 5 to 8. Like parts with those of the first embodiment are given like reference numbers; those parts will not be described again here. The second embodiment differs from the first embodiment in that a sleeve 25 is slidably received over flange 17 and the device uses a spring 26 having all of its turns of the same diameter. The sleeve has an inwardly-directed lip 27 at the end thereof adjacent the second portion 12 and the end of the spring remote from flange 17 bears on that lip, rather than on the part-spherical form 20. There is an axial hole into the sleeve defined by the lip 27, the diameter of the hole being slightly smaller than the diameter of the part-spherical form 20 such that the sleeve can be moved to the position illustrated in Figures 5 and 6 only by springing that lip over the part-spherical form. To assist this, the edge of the lip is given a conical form, flaring outwardly in the direction internally of the sleeve 25.

The power unit of Figures 5 to 8 is assembled by dropping the spring 26 over the operating button 19 and then sliding the sleeve 25 to that part- spherical form 20, whereafter the lip 27 of the sleeve is sprung over the form 20 so as to engage that form from the side nearer the enlarged section 16 of the first portion 11 ; this is shown in Figure 5. When the power unit is to be used to exert a force on two members of some other device, the operating button 19 is pressed laterally to break the neck 13 as described in relation to the first embodiment. The part-spherical form 20 will tend to roll around the lip 27 so facilitating the breaking of the plasties material forming the neck 13. Once broken through, the spring will relatively separate the first and second portions 11 ,12 of the elongate component 10, as shown in Figures 7 and 8, so allowing the power unit to cause relative separation of the members of the device within which the power unit is incorporated.

With the first embodiment, that other device must have a member against which the part-spherical form 20 may bear, in order to allow the power unit to exert a separating force on the members of that device. The power unit of Figures 5 to 8 is easier to deploy since the device within which the power unit is incorporated merely has to have a member with a surface against which the sleeve 25 may bear, with the operating button 19 extending through an opening in that surface.

Claims

1. A power unit comprising a unitary elongate component defining first and second portions spaced along the length of the component, a dividing zone provided between the first and second portions, and pre-loaded drive means arranged to generate a separating force on said first and second portions, whereby division of the component at the dividing zone allows relative separating movement of the first and second portions, under the action of the drive means.

2. A power unit as claimed in claim 1 , wherein the dividing zone comprises a weakened zone relative to the remainder of the elongate component.

3. A power unit as claimed in claim 2, wherein the weakened zone comprises a region of reduced cross-sectional area.

4. A power unit as claimed in claim 3, wherein the weakened zone is in the form of a neck extending along the length of the elongate component, separating the first and second portions thereof.

5. A power unit as claimed in any of the preceding claims, wherein the dividing zone is frangible thereby to effect division of the component and allow separation of the first and second portions.

6. A power unit as claimed in any of the preceding claims, wherein the elongate component comprises a unitary plastics material moulding.

7. A power unit as claimed in claim 6, wherein the elongate component is in the form of a rod of a moulded plastics material and the dividing zone is breakable by a force applied laterally to one of the portions, relative to the length of the rod.

8. A power unit as claimed in any of the preceding claims, wherein the drive means comprises a helical coil spring surrounding the elongate component and acting between the two portions thereof.

9. A power unit as claimed in claim 8, wherein the helical coil spring is preloaded to act in compression between the first and second portions.

10. A power unit as claimed in claim 8 or claim 9, wherein one of the portions of the elongate component is formed as an operating button for division of the elongate component, the spring acting directly on the operating button.

11. A power unit as claimed in claim 8 or claim 9, wherein one end of the spring acts on one portion of the elongate component and the other end of the spring acts on a sleeve surrounding the spring, the sleeve bearing on the other portion of the elongate component.

12. A power unit as claimed in claim 11 , wherein the sleeve has an end wall defining a central opening, said other end of the spring bearing on the end wall and the end wall bears on the other portion of the elongate component.

13. A power unit as claimed in claim 12, wherein the surface of the other portion of the elongate component against which the end wall of the sleeve bears is rounded so as to act as a fulcrum for division of the component by a lateral force applied to the other portion.

14. An auto-injector device whenever incorporating a power unit according to any of claims 1 to 13.