Patent Description:
Injection devices are shown in <CIT> and <CIT>. These devices employ a drive spring and some form of release mechanism that releases the syringe from the influence of the drive spring once its contents are supposed to have been discharged, to allow it to be retracted by a return spring.

<CIT> describes an injection device comprising means for adjusting the amount of substance to be expelled from a container. <CIT> describes an injection device having a sleeve which projects from an exit aperture and can be depressed to release a locking mechanism. <CIT>) describes an autoinjector with active agent container latching. <CIT>) describes an autoinjector with a re-usable firing mechanism.

Generally, the return spring is relatively weak, since its restoring force must be overcome by the drive spring, even while the drive spring is doing work on the various components of the injection device and the syringe during an injection cycle. This may give rise to a problem when the injection device is used with sealed hypodermic syringes, which typically have a hermetically sealed cover, needle shield or "boot" that covers the hypodermic needle and maintains the sterility of the syringe contents. Naturally, it is necessary to maintain the sterility of the syringe contents up to the point of administration, which devices that are designed to be disposable, as many will be, means that the boot must be removed with the syringe inside the injection device.

Typically, the action required to remove the boot from the syringe is simply to pull the boot away from the syringe, which requires a force in excess of 20N. This is significantly greater than the restoring force of the return spring, so the syringe will be pulled out of the injection device as the boot is removed and, when the boot comes away, it will snap back into place. This is not the best way to handle the syringe. The shock could damage it, the needle could be damaged and there may be problems re-engaging the syringe with those components of the injection device designed to act upon it. Even in cases where there is no return spring, for example where the syringe is held in place by friction with components of the injection device, the problem will still arise of relocating the syringe onto those components of the injection device designed to act upon it.

Moreover, there is a problem with having the syringe generally moveable in a direction out of the injection device. Accidental activation of the drive spring by mechanical failure of the drive spring's release mechanism (e.g. a trigger) can occur, for example by dropping the device on a hard surface. This accidental activation could cause the syringe to be extended unintentionally out of the device and its contents to be ejected. This could expose the needle of the syringe and increase the risk of inadvertent ski puncturing and/or infection.

The injection device of the present invention is designed to deal with the aforementioned problems.

Thus, the syringe carrier and syringe are locked in place within the injection device until such time that the device is actuated by activation of the release mechanism. This prevents damage to the syringe and its contents. Moreover, this assists in preventing accidental activation of the injection device, for example by dropping the injection device on a hard surface.

According to one embodiment of the invention, the aperture may comprise:.

This arrangement provides a secure and effective locking mechanism for preventing movement of the syringe carrier via the release mechanism, in addition to the release mechanism's function of retaining the drive in an unactuated position until such time that the release mechanism is activated.

The invention will now be described by way of example with reference to the accompanying drawings, in which:.

<FIG> is a right-side view of an injection device <NUM> according to the present invention. The injection device <NUM> has a housing <NUM>, a cap <NUM> which is removable from a proximal end <NUM> the housing <NUM> and a trigger button <NUM>. Other parts of the device will be described in greater detail below.

<FIG> is a perspective view of the injection device <NUM> according to the present invention with the cap (not shown) removed from its end. The end of the housing <NUM> has an exit aperture <NUM>, from which the end of a sleeve <NUM> can be seen to emerge.

<FIG> is a perspective view of the cap <NUM> of the injection device <NUM> according to the present invention. The cap <NUM> has a central boss <NUM> that fits within the sleeve <NUM> when the cap <NUM> is installed on the housing <NUM>.

<FIG> is an exploded right-side view of the components of the injection device <NUM> according to the present invention and <FIG> is a right-side view of the assembled components of the injection device <NUM> according to the present invention without the housing <NUM> or cap <NUM>.

As illustrated, the injection device <NUM> comprises a hypodermic syringe <NUM> of conventional type, including a syringe body <NUM> terminating at one end in a discharge nozzle, specifically a hypodermic needle <NUM>, and at the other in a flange <NUM>. The conventional plunger that would normally be used to discharge the contents of the syringe <NUM> manually has been removed and replaced with a drive element (referred to below as the second drive element <NUM>) that contacts a bung <NUM> in the syringe <NUM>. The bung <NUM> constrains a drug (not shown) to be administered within the syringe body <NUM>. Whilst the syringe illustrated is of hypodermic type, this need not necessarily be so. Transcutaneous or ballistic dermal and subcutaneous syringes may also be used with the injection device of the present invention.

As illustrated, the injection device <NUM> includes a return spring <NUM> that biases the syringe <NUM> from an extended position in which the needle <NUM> extends from the aperture <NUM> in a case nose 112a of the housing <NUM> to a retracted position in which the needle <NUM> is contained within the housing <NUM>. The return spring <NUM> acts on the syringe <NUM> via a syringe carrier <NUM>. The syringe <NUM> is moveable along a longitudinal axis <NUM> of the injection device <NUM> which extends centrally along the length of the injection device <NUM> from the exit aperture <NUM> at its proximal end <NUM> to a distal end <NUM>.

Contained within the housing at its distal end <NUM> is an actuator, which here takes the form of a compression drive spring <NUM>. Drive from the drive spring <NUM> is transmitted via a multi-component drive <NUM> to the syringe <NUM> to advance it from its retracted position to its extended position and discharge its contents through the needle <NUM>. The drive <NUM> accomplishes this task by acting directly on the drug and the syringe <NUM>. Hydrostatic forces acting through the drug and, to a lesser extent, static friction between the bung <NUM> and the syringe body <NUM> initially ensure that they advance together, until the return spring <NUM> bottoms out on the syringe carrier <NUM> or meets some other obstruction (not shown) that retards its motion.

<FIG> is an exploded perspective view of the multi-component drive <NUM>. The multi-component drive <NUM> between the drive spring <NUM> and the syringe <NUM> consists of three principal components. A drive sleeve <NUM> takes drive from the drive spring <NUM> and transmits it to a delay piston <NUM> on a first drive element <NUM>. This in turn transmits drive to the second drive element <NUM>.

As will be seen from <FIG>, the first drive element <NUM> includes a hollow stem <NUM>, the inner cavity of which forms a collection chamber <NUM> in communication with a vent <NUM> that extends from the collection chamber <NUM> through the end of the stem <NUM>. The second drive element <NUM> includes a blind bore <NUM> that is open at one end to receive the stem <NUM> and closed at the other. As will be appreciated, the bore <NUM> and the stem <NUM> define a fluid reservoir within which a damping fluid is contained.

The trigger button <NUM> is provided on the side of the housing <NUM> which, when in an engaged position with a proximal end <NUM> of the drive sleeve <NUM>, serves to retain the drive spring <NUM> in a compressed state by contact between locking surface 102b and the drive sleeve <NUM> when the button <NUM> is in an unactuated position. The trigger button <NUM> can pivot on the housing <NUM> via pivot 102a. When downwards pressure is applied to the trigger button <NUM> at an activation surface 102c (i.e. pressure directed into the housing <NUM>), the locking surface 102b moves upwards in a direction away from the longitudinal axis <NUM>. In this actuated position of the button <NUM>, the locking surface 102b is decoupled from the drive sleeve <NUM>, thereby allowing the drive sleeve <NUM> to move relative to the housing <NUM> towards the exit aperture <NUM> under the influence of the drive spring <NUM>.

The sliding sleeve <NUM> is moveable from its extended position (as shown in <FIG>) where it protrudes out of the exit aperture <NUM> into a retracted position in the case nose 112a of the housing <NUM>. The sliding sleeve <NUM> is connected to a button lock element <NUM> which has resilient arms <NUM> which bias the sliding sleeve <NUM> into its extended position in which its end protrudes from the end of the case nose 112a. Thus, application of pressure to the end of the sliding sleeve <NUM>, for example by pressing the end of the sliding sleeve <NUM> against tissue, causes it to move into its retracted position into the housing <NUM>; release of the pressure causes the sliding sleeve <NUM> to move into its extended position under bias from the resilient arms <NUM> acting against a side wall of the housing <NUM>. The button lock element <NUM> has a button lock protrusion <NUM> which contacts with the end of a trigger button protrusion 102d on the trigger button <NUM> when the sliding sleeve is in its extended position. The trigger button protrusion <NUM> extends in a direction which is generally parallel to the longitudinal axis <NUM> of the injection device <NUM>. The button lock protrusion <NUM> extends in a direction which is generally perpendicular to the longitudinal axis <NUM> towards the trigger button protrusion 102d. The trigger button protrusion 102d has an aperture 102e which can move over the top of the button lock protrusion <NUM> when the button lock element <NUM> has been moved away from the exit aperture <NUM> (i.e. when the sliding sleeve <NUM> has been moved into the exit aperture <NUM> into its retracted position). In this position, the trigger button <NUM> can be moved into its deactivated position by rotating the trigger button <NUM> about the pivot 102a in the direction of the pressure applied to the pressure surface 102c. Thus, the button lock element <NUM> and the sliding sleeve <NUM> act together to lock the trigger button <NUM> in its activated position (i.e. the locking surface 102b contacts the end of the drive sleeve <NUM> preventing it from moving towards the exit aperture <NUM> under the bias of the compressed drive spring <NUM>).

When the sliding sleeve <NUM> has been moved into a position in which it is retracted into the housing <NUM> (i.e. into its unlocked position) and the trigger button <NUM> has been rotated into its deactivated position, the operation of the device <NUM> is then as follows.

Initially, the drive spring <NUM> moves the drive sleeve <NUM>, the drive sleeve <NUM> moves the first drive element <NUM> and the first drive element <NUM> moves the second drive element <NUM>, in each case by acting through flexible latch arms 132a, 134a, 134b. The second drive element <NUM> moves and, by virtue of static friction and hydrostatic forces acting through the drug (not shown), moves the syringe body <NUM> and syringe carrier <NUM> against the action of the return spring <NUM>. The return spring <NUM> compresses and the hypodermic needle <NUM> emerges from the exit aperture <NUM> of the housing <NUM>. This continues until the return spring <NUM> bottoms out or the syringe body <NUM> meets some other obstruction (not shown) that retards its motion. Because the static friction between the second drive element <NUM> and the syringe body <NUM> and the hydrostatic forces acting through the drug (not shown) to be administered are not sufficient to resist the full drive force developed by the drive spring <NUM>, at this point the second drive element <NUM> begins to move within the syringe body <NUM> and the drug (not shown) begins to be discharged. Dynamic friction between the second drive element <NUM> and the syringe body <NUM> and hydrostatic forces acting through the drug (not shown) to be administered are, however, sufficient to retain the return spring <NUM> in its compressed state, so the hypodermic needle <NUM> remains extended.

Before the second drive element <NUM> reaches the end of its travel within the syringe body <NUM>, so before the contents of the syringe have fully discharged, the flexible latch arms 134a, 134b linking the first and second drive elements <NUM>, <NUM> reach a constriction <NUM> provided on a latch actuator element 137a which is fixed to the end of the syringe carrier <NUM>. The constriction <NUM> moves the flexible latch arms 134a, 134b inwards from the position shown in <FIG> to a position at which the flexible latch arms 134a, 134b no longer couple the first drive element <NUM> to the second drive element <NUM>, aided by the bevelled surfaces on the constriction <NUM>. Once this happens, the first drive element <NUM> acts no longer on the second drive element <NUM>, allowing the first drive element <NUM> to move relative to the second drive element <NUM>.

Because the damping fluid is contained within a reservoir (not shown) defined between the end of the first drive element <NUM> and the blind bore <NUM> in the second drive element <NUM>, the volume of the reservoir will tend to decrease as the first drive element <NUM> moves relative to the second drive element <NUM> when the former is acted upon by the drive spring <NUM>. As the reservoir collapses, damping fluid is forced through the vent <NUM> into the collection chamber <NUM>. Thus, once the flexible latch arms 134a, 134b have been released, the force exerted by the drive spring <NUM> does work on the damping fluid, causing it to flow though the constriction formed by the vent <NUM>, and also acts hydrostatically through the fluid and through friction between the first and second drive elements <NUM>, <NUM>, thence via the second drive element <NUM>. Losses associated with the flow of the damping fluid do not attenuate the force acting on the body of the syringe to a great extent. Thus, the return spring <NUM> remains compressed and the hypodermic needle remains extended.

After a time, the second drive element <NUM> completes its travel within the syringe body <NUM> and can go no further. At this point, the contents of the syringe <NUM> are completely discharged and the force exerted by the drive spring <NUM> acts to retain the second drive element <NUM> in its terminal position and to continue to cause the damping fluid to flow though the vent <NUM>, allowing the first drive element <NUM> to continue its movement.

Before the reservoir of fluid is exhausted, the flexible latch arms 132a linking the drive sleeve <NUM> with the first drive element <NUM> reach another constriction (not shown) within the housing <NUM>. This constriction moves the flexible latch arms 132a inwards from the position shown to a position at which they no longer couple the drive sleeve <NUM> to the first drive element <NUM>, aided by bevelled surfaces on the constriction. Once this happens, the drive sleeve <NUM> acts no longer on the first drive element <NUM>, allowing them to move relative each other. At this point, of course, the syringe <NUM> is released, because the forces developed by the drive spring <NUM> are no longer being transmitted to the syringe <NUM>, and the only force acting on the syringe will be the return force from the return spring <NUM>. Thus, the syringe <NUM> is now returned to its retracted position and the injection cycle is complete.

All this takes place, of course, only once the cap <NUM> has been removed from the end of the housing <NUM>. The end of the syringe is sealed with a boot <NUM>. The central boss <NUM> of the cap that fits within the sleeve <NUM> when the cap <NUM> is installed on the housing <NUM> comprises a retainer element <NUM> which is fixed into the boss <NUM>. The retainer element <NUM> comprises resilient protrusions 125a which are directed away from the exit aperture <NUM>. These resilient protrusions 125a deform as the cap <NUM> is inserted onto the housing <NUM> over a needle shield or rubber boot <NUM>. The protrusions 125a then grip the boot <NUM> tightly so that the ends of the protrusions are slightly embedded in the boot <NUM> which might be made from rubber. This means that, as the cap <NUM> is pulled off the housing <NUM>, the boot <NUM> is pulled away from the syringe <NUM> with the cap <NUM>.

<FIG> also shows a syringe lock protrusion <NUM> located on the button <NUM> at its distal end which is proximal to the end which is located nearest to the aperture <NUM>. The syringe lock protrusion <NUM> extends in a generally perpendicular direction (with respect to the longitudinal axis <NUM>) into the injection device <NUM> towards the longitudinal axis <NUM>.

<FIG> illustrates a distal end of the button <NUM> in greater detail. As can be seen, the syringe lock protrusion <NUM> comprises an aperture <NUM> which includes a first portion 171a and a second portion 171b. The first and second portions 171a, 171b overlap with each other and have different cross-sectional areas as will be seen from <FIG>. The first portion 171a has an edge 171c.

<FIG> shows how the button <NUM> is integrated with the injection device <NUM> of the present invention.

The case nose 112a comprises a case nose slot <NUM> located towards the distal end of the housing <NUM>. The case nose slot <NUM> extends about a substantial proportion of the circumference of the case nose 112a and extends through the case nose 112a. The case nose slot <NUM> does not extend round the case nose 112a on a section of its circumference which faces towards the button <NUM>. The length of this section about the circumference of the case nose 112a corresponds to the overlap between the first and second portions 171a, 171b of the syringe lock protrusion <NUM>. The width of the case nose slot <NUM> (in a direction along the longitudinal axis <NUM>) is slightly more than the thickness of the edge 171c of the syringe lock protrusion <NUM>.

The syringe carrier <NUM> comprises a syringe carrier slot <NUM> located towards the distal end of the syringe carrier <NUM>. The syringe carrier slot <NUM> extends about a substantial proportion of the circumference of the syringe carrier <NUM> and extends through the syringe carrier <NUM> (although this is not absolutely necessary). The syringe carrier slot <NUM> does not extend round the syringe carrier <NUM> on a section of its circumference which faces towards the button <NUM>. The length of this section about the circumference of the syringe carrier <NUM> corresponds to the overlap between the first and second portions 171a, 171b of the syringe lock protrusion <NUM>. As with the case nose slot <NUM>, the width of the syringe carrier slot <NUM> (in a direction along the longitudinal axis <NUM>) is slightly more than the thickness of the edge 171c of the syringe lock protrusion <NUM>.

In the unactuated position of the button <NUM> (as shown in <FIG>), the first portion 171a of the syringe lock protrusion <NUM> surrounds the case nose slot <NUM> and the syringe carrier slot <NUM>. In addition, the edge 171c of the syringe lock protrusion <NUM> extends through the case nose slot <NUM> into the syringe carrier slot <NUM> so that the syringe carrier <NUM> is locked to the button <NUM> and cannot move along the longitudinal axis <NUM>. This prevents the syringe <NUM> and syringe carrier <NUM> moving towards the exit aperture <NUM> when the cap <NUM> is removed or through accidental activation of the injection device <NUM>, for example by dropping it on a hard surface.

When the button <NUM> is moved to its actuated position, the edge 171c of the first portion 171a of the syringe lock protrusion <NUM> moves out of the syringe carrier slot <NUM> so that the second portion 171b of the syringe carrier protrusion <NUM> surrounds the syringe carrier <NUM>, but does not engage with the syringe carrier slot <NUM>. In this way, the syringe carrier <NUM> is no longer locked to the button <NUM> and can move along the longitudinal axis <NUM>. Thus, the syringe <NUM> will extend under bias from the drive spring <NUM> along the longitudinal axis <NUM> because activation of the button <NUM> (by applying force to its pressure surface 102c) will have released the drive cylinder <NUM> from its contacting position against the locking surface 102b, thereby permitting the multi-component drive to move towards the exit aperture <NUM>, along with the syringe <NUM> and syringe carrier <NUM>.

Thus, the syringe <NUM> and syringe carrier <NUM> are prevented from moving longitudinally until the time that the button <NUM> is actuated. Of course, this also requires that the sliding sleeve <NUM> has also been moved into its retracted position, thereby releasing the button lock element <NUM> from its locked position against the button <NUM>.

Claim 1:
An injection device (<NUM>) comprising:
a housing (<NUM>) adapted to receive a syringe (<NUM>) having a discharge nozzle (<NUM>), the syringe being moveable in the housing along a longitudinal axis between a retracted position in which the discharge nozzle is contained within the housing and an extended position in which the discharge nozzle of the syringe extends from the housing through an exit aperture (<NUM>);
an actuator (<NUM>);
a drive (<NUM>) adapted to be acted upon by the actuator (<NUM>) and in turn act upon the syringe to advance it from its retracted position to its extended position and discharge its contents through the discharge nozzle;
a release mechanism comprising a trigger button (<NUM>) adapted, in an engaged position, to prevent the actuator (<NUM>) acting on the drive (<NUM>) and, in a disengaged position, to permit the actuator (<NUM>) to act on the drive (<NUM>);
a syringe carrier (<NUM>) adapted to support the syringe as it is advanced; and
characterised by
a locking mechanism (<NUM>) between the syringe carrier and the release mechanism to inhibit movement of the syringe carrier (<NUM>) and syringe (<NUM>) towards the exit aperture when the trigger button (<NUM>) is in its engaged position, wherein the locking mechanism comprises a protrusion (<NUM>), located on the trigger button (<NUM>) at its distal end which is proximal to the end which is located nearest to the aperture (<NUM>), the protrusion (<NUM>) extending in a perpendicular direction with respect to the longitudinal axis (<NUM>) into the housing towards the longitudinal axis (<NUM>),
wherein the protrusion (<NUM>) engages the syringe carrier (<NUM>) in the engaged position of the trigger button (<NUM>) and is disengaged from the syringe carrier (<NUM>) in the disengaged position of the trigger button (<NUM>).