Patent Description:
Safety syringes typically include some form of safety mechanism to protect healthcare workers from a hypodermic needle of the syringe after it has been injected into a patient. Exemplary safety syringes may include a sheath for covering the needle after use of the syringe. Other exemplary syringes may cause the needle to retract within the barrel of the syringe.

Safety syringes may be broadly split into 'active' and 'passive' safety syringes. Active safety syringes typically require some action by a user of the syringe to engage the safety mechanism and/or deploy the sheath. Such action may be taken after removal of the needle from the patient, or may be taken during removal of the needle from the patient. Passive safety syringes typically engage the safety mechanism and/or deploy the sheath without any specific action by the user, that is, without any action other than that usually taken to use the syringe.

An auto-injector is a device for receiving a syringe and for driving a syringe plunger of the syringe into a barrel of the syringe without any force being applied by the user. Typically, an auto-injector includes a plunger driver and a drive spring that are arranged to provide a force to drive the syringe plunger into the barrel. The drive spring and plunger driver may be activated by operation of a button or other release mechanism on the auto-injector. A safety auto-injector may be one which includes a shroud that may be deployed to a position covering a needle of a syringe received within the auto-injector before and after use of the syringe. The shroud of the auto-injector may be deployed under a force applied by a shroud spring.

The force applied by a drive spring typically depends on the viscosity of the drug in the barrel. The more viscous a drug is, the greater the force the drive spring has to apply upon firing. The manual priming of an auto-injector with a high force drive spring can therefore be challenging if the force required to prime it is too high for a typical user of the auto-injector.

<CIT> describes an autoinjector comprising a main body for receiving a syringe and a hinged lid. Opening of the door to allow insertion of a syringe results in compression of a main drive spring.

An improved auto-injector and method for priming thereof is required.

According to the invention there is provided an auto-injector for receiving and operating a syringe, the auto-injector comprising: a housing for receiving the syringe, the housing comprising a main body and a door operable into a first position and a second position, wherein the syringe is receivable within the housing when the door is in the first position; wherein the door is configured to couple to: (i) a first plunger driver for priming thereof on a first movement of the door, the first plunger driver comprising a first spring; and (ii) a second plunger driver for priming thereof on a second movement of the door, the second plunger driver comprising a second spring; the first and second plunger drivers being configured on activation of the auto-injector to drive a plunger forward within the auto-injector to operate the syringe received within the auto-injector. The autoinjector is further configured such that:.

The priming of the auto-injector is made easier by dividing the priming into first and second movements to reduce the force required to complete each movement. Optionally, the first spring comprises a compression spring, and/or the second spring comprises a tension spring.

Optionally, the main body and the door are connected by a hinge, and the auto-injector is provided with a charging link between the main body and the door, wherein the connection of the charging link to the main body and/or the connection of the charging link to the door is a slidable connection configured to slide when the door moves between the first and second positions, the charging link being configured to couple to the first and second plunger drivers for priming thereof on the respective first and second movements of the door. Optionally, the syringe is receivable within the main body of the housing when the hinged door is in the first position.

Optionally, the main body and the door are connected by a sliding means, and the auto-injector is provided with a charging link between the main body and the door, wherein the connection of the charging link to the main body and/or the connection of the charging link to the door is a slidable connection configured to slide when the door moves between the first and second positions, the charging link being configured to couple to the first and second plunger drivers for priming thereof on the respective first and second movements of the door.

Optionally, the first position of the door is the open position, the second position of the door is the closed position, the first movement of the door is an opening movement, and the second movement of the door is a closing movement.

Optionally, the connection of the charging link to the door is fixed and the connection of the charging link to the main body is slidable.

Optionally, the connection of the charging link to the door is positioned at a point up to a half, up to a third, or up to a quarter of the length of the door from the hinge of the door.

Optionally, the main body and the connection of the charging link to the door are configured such that a maximum angle between the plane of the main body and the charging link during: (i) the first movement of the hinged door; and (ii) the second movement of the hinged door is up to <NUM> degrees.

Optionally, the force required for priming of the first plunger driver is less than the force required for priming of the second plunger driver.

Optionally, a combined driving force of the first and second plunger drivers is in the range from <NUM>-<NUM> Newtons.

Optionally, the charging link comprises a shuttle configured to travel along a shuttle guide to provide a slidable connection of the charging link to the main body.

Optionally, the shuttle comprises a first priming portion coupled to the first plunger driver and configured to travel along the shuttle guide in a first direction on the first movement of the door for priming the first plunger driver.

Optionally, the main body and/or the first priming portion comprises a latch configured to retain the first priming portion in position after the first movement of the door.

Optionally, the first plunger driver is primed under compression and is connected between the main body and the first priming portion.

Optionally, the shuttle comprises a second priming portion configured to travel along the shuttle guide in a second direction opposite the first direction on the second movement of the door for priming the second plunger driver.

Optionally, the charging link is configured to retain the second priming portion in position after the second movement of the door.

Optionally, the second plunger driver is primed under tension and is connected between the first priming portion and the second priming portion.

Optionally, the charging link is connected to the second priming portion.

Optionally, the first and second priming portions are configured to travel together along the shuttle guide on the first movement of the door, and are separable such that the second priming portion separates from the first priming portion and travels along the shuttle guide on the second movement of the door.

Optionally, the shuttle guide is coupled to the first and second plunger drivers such that movement of the first and second plunger drivers follows a path determined by the shuttle guide.

Optionally, the shuttle guide comprises a rod passing through the first plunger driver and passing through an aperture in the shuttle.

Optionally, the auto-injector comprises a ratchet operable during the second movement of hinged door to prevent movement of the door in the direction of the first position by a force exerted by the second plunger driver.

Exemplary embodiments are disclosed herein with reference to the accompanying drawings, in which:.

Generally, disclosed herein are exemplary methods and apparatus for auto-injectors. The term "auto-injector" is used herein and may be considered to encompass both an auto-injector and a safety auto-injector, as appropriate. The auto-injectors may be configured to receive and operate a standard syringe (i.e. not a safety syringe) and/or a safety syringe.

In the following embodiments, the terms "forward" and "front" refer to the patient facing end of the injection device or component thereof. In other words, the front end of the injection device is the end proximal to the injection site during use. Likewise, the term "rear" refers to the non-patient end of the injection device assembly or component thereof. In other words, the term "rear" means distant or remote from the injection site during use. Further, the term longitudinal is used to encompass a direction along or parallel to a longitudinal axis of the injection device.

Features of the exemplary arrangements disclosed herein are described as being "coupled" to other features. This term encompasses any coupling that results in the coupled features moving together in any direction, whether that be on a <NUM>:<NUM> basis or on some geared basis. The term "coupled" also encompasses any one of a connection between features, an abutment of one feature against another and an engagement of one feature with another, and such coupling may be direct or may be indirect, i.e. with a third feature therebetween.

In general terms, the invention is directed to assisting the priming of an auto-injector by using both the opening and closing movement of the auto-injector for priming thereof. An auto-injector may be considered primed when the plunger driver is in a configuration suitable to move the plunger of a syringe and thereby deliver medication using the auto-injector. A user may prime a plunger driver of an auto-injector by applying a force to the plunger driver. This may be done, for example by opening and closing a door of the auto-injector. Methods and apparatus disclosed herein use a force applied by a user when opening and closing the door to prime the plunger driver. In some arrangements, the plunger driver may comprise a plurality of biasing members (e.g. springs), one or more of the plurality being primed on opening of the door and one or more of the plurality being primed on closing of the door.

<FIG> show an exemplary auto-injector <NUM> for receiving and operating a syringe (not shown) during various stages of priming and firing.

The auto-injector <NUM> comprises a housing that further comprises a plurality of component parts. In the configuration of <FIG>, the housing comprises a main body <NUM> and a hinged door <NUM>. The hinged door <NUM> is operable between an open position and a closed position. The hinged door <NUM> is in its closed position in <FIG>. A syringe (not shown) is receivable within the housing, for example, in the main body <NUM>, when the hinged door <NUM> is in the open position.

The main body <NUM> and hinged door <NUM> are connected at a hinge <NUM>. The door <NUM> is therefore rotatable relative to the main body <NUM>. In <FIG>, the hinge is located at the rear end of the main body <NUM> and the hinged door <NUM>. In other arrangements, the hinge <NUM> may be positioned at locations further forward on one or both of the hinged door <NUM> and the main body <NUM>.

At least one charging link <NUM> is connected between the main body <NUM> and the hinged door <NUM>. <FIG> show an exemplary auto-injector having two charging links <NUM>. A connection <NUM> of the charging link <NUM> to the main body <NUM> is a slideable connection configured to slide on movement of the hinged door <NUM> between its open and closed positions. A connection <NUM> between the hinged door <NUM> and the charging link <NUM> is fixed with respect to its position on the hinged door <NUM>. The connection <NUM> between the charging link <NUM> and the hinged door <NUM> is rotatable. The connection <NUM> is at a point on the hinged door <NUM> where when the hinged door <NUM> is open the connection <NUM> is rearward of the hinge <NUM> and when the hinged door <NUM> is closed the connection <NUM> is forward of the hinge <NUM> i.e. the connection <NUM> rotates about the hinge during opening and closing of the hinged door <NUM>. In other arrangements, the connection <NUM> may be slidable and/or the connection <NUM> may be positionally fixed.

Optionally, the hinged door <NUM> comprises gripping features, which in the example shown comprise ergonometric handles <NUM>. The gripping features may include any features that allow greater purchase for a user when pulling the hinged door <NUM> open and/or pushing the hinged door <NUM> closed. For example, the gripping features might include any type of handle, lip, flange or gripping surface for a user to open and/or close the hinged door <NUM>.

The auto-injector <NUM> further comprises a first plunger driver <NUM>. The first plunger driver <NUM> is configured to drive a plunger of a syringe received within the auto-injector <NUM> forwards to dispense a fluid from the syringe. In the example provided in <FIG>, the first plunger driver <NUM> comprises at least one spring or other biasing member, which may be a tension spring, a compression spring or a torsion spring but in the example shown comprises a spring, which in this case is a compression spring.

The connection <NUM> is configured to couple to the first plunger driver <NUM> for priming thereof on an opening movement of the hinged door <NUM>. That is, in the example shown in <FIG>, upon opening the hinged door the slidable connection <NUM> slides rearward along the main body <NUM>, thereby compressing the compression spring of the first plunger driver <NUM>. The first plunger driver <NUM> may comprise a spring or a plurality of springs. As described below, the charging link <NUM> may comprise a shuttle <NUM> configured to travel along a shuttle guide <NUM> to provide the slideable connection of the charging link <NUM> to the main body <NUM>.

The charging link <NUM>, through its connections <NUM>, <NUM> to the main body <NUM> and hinged door <NUM> converts the arc shaped movement of the hinged door <NUM> as it opens into a linear force (in this example in a rearward direction) on the first plunger driver <NUM> to prime it. The positioning of the connection <NUM> of the charging link <NUM> to the hinged door <NUM> and/or the length of the charging link <NUM> determine the level of mechanical advantage provided by this mechanism and can thereby make it easier for a user to prime the first plunger driver <NUM> during the opening movement of the hinged door. The longer the charging link <NUM> and the closer the connection <NUM> is positioned to the hinge <NUM>, the shallower the maximum angle the charging link <NUM> forms with the main body <NUM> during the opening and/or closing movements of the hinged door <NUM>. A shallower angle results in a greater mechanical advantage and allows the first plunger driver <NUM> to be primed more easily. This permits higher force springs to be used in the first plunger driver <NUM>. It is noted, however, that there is a trade-off between having a shallow angle to increase mechanical advantage and having a steeper angle to increase the amount of rearward translation of the connection <NUM>, but a decreased mechanical advantage.

<FIG> shows the hinged door <NUM> of the auto-injector <NUM> moving from a closed position to an open position. As the hinged door <NUM> moves in an arc, the connection <NUM> follows a path that ensures the angle between the charging link <NUM> and the main body provides a predetermined mechanical advantage during the opening movement.

<FIG> shows the hinged door <NUM> of the auto-injector <NUM> in an open position. In the open position, a space in the main body <NUM> is provided into which a syringe (not shown) can be loaded. One or more internal support structures <NUM> may optionally be provided with which the syringe can be secured.

In the example provided in <FIG>, the auto-injector <NUM> further comprises a second plunger driver <NUM>, which may comprise a spring or a plurality of springs. In exemplary arrangements, the second plunger driver <NUM> comprises two springs. The two springs are tension springs.

The slidable connection <NUM> of the charging link <NUM> to the main body <NUM> is configured to couple to the second plunger driver <NUM> for priming thereof on a closing movement of the hinged door <NUM>. The second plunger driver <NUM> may optionally be positioned in a different plane of the main body <NUM> to the first plunger driver <NUM>. In the example provided, the second plunger driver <NUM> is positioned in a plane below the first plunger driver <NUM>. By positioning the second plunger driver <NUM> in a different plane, the available space in the main body <NUM> for placing the syringe is increased. Further, the length of the charging link <NUM> is increased by extending it to the different plane.

As described above, during the opening movement of the hinged door <NUM>, the charging link <NUM> is pulled in a rearwards direction by the hinged door <NUM> acting through the charging link's connection <NUM> to the hinged door <NUM>. In turn, the charging link <NUM> through its slidable connection <NUM> to the main body slides along the main body in a rearwards direction to compress the compression spring of the first plunger driver <NUM>. This primes the first plunger driver <NUM>. Not only does the movement of the charging link in a rearwards direction prime the first plunger driver <NUM>, but it also translates the second plunger driver <NUM> rearwardly without priming it. In the example provided in <FIG>, the second plunger driver <NUM> slides with the charging link <NUM> in a rearwards direction without the tension springs being put under tension. The opening movement of the hinged door <NUM> thus only primes one of the two plunger drivers <NUM>, <NUM>.

<FIG> shows a perspective view of an underside of the auto-injector <NUM> when the hinged door <NUM> is in its open position. As can be seen in <FIG>, the compression spring of the first plunger driver <NUM> is in a primed, compressed state whereas the two tension springs of the second plunger driver <NUM> are in an un-primed, un-tensioned state.

<FIG> shows the auto-injector <NUM> during the closing movement of the hinged door <NUM>. As the hinged door <NUM> closes, the charging link <NUM> is pushed in a forward direction by the hinged door <NUM> acting through the connection <NUM>. At the same time, the slideable connection <NUM> slides in a forward direction and pulls a first end of the tension spring of the second plunger driver <NUM> forward. A second end of the tension spring is retained in position and the second plunger driver <NUM> is therefore primed. The first plunger driver <NUM> is maintained in its primed state. In the example provided in <FIG>, the first plunger driver <NUM> is maintained in its primed state with a latch configured for this purpose.

As was the case when priming the first plunger driver <NUM>, the charging link <NUM>, through its connections <NUM>, <NUM> to the main body <NUM> and hinged door <NUM> convert the arc shaped movement of the hinged door <NUM> as it closes into a linear force (in this example in a forward direction) on the second plunger driver <NUM> to prime it. The positioning of the connection <NUM> of the charging link <NUM> to the hinged door <NUM> and/or the length of the charging link <NUM> determine an amount of mechanical advantage provided by this mechanism and can thereby make it easier for a user to prime the device during the closing movement of the hinged door <NUM>.

As is the case with the opening movement of the hinged door <NUM> described above, the positioning of the connection <NUM> of the charging link <NUM> to the hinged door <NUM> and/or the length of the charging link <NUM> determine the level of mechanical advantage provided by this mechanism and can thereby make it easier for a user to prime the second plunger driver <NUM> during the opening movement of the hinged door. The longer the charging link <NUM> and the closer the connection <NUM> is positioned to the hinge <NUM>, the shallower the maximum angle the charging link <NUM> forms with the main body <NUM> during the opening and/or closing movements of the hinged door <NUM>. A shallower angle results in a greater mechanical advantage and allows the second plunger driver <NUM> to be primed more easily. This permits higher force springs to be used in the second plunger driver <NUM>, or a combined higher force of a plurality of springs.

Thus, in exemplary arrangements the connection <NUM> may be positioned, for example, at a point up to a half, up to a third, up to a quarter, or up to a smaller fraction of the length of the hinged door <NUM> from a hinge of the hinged door <NUM>. The smaller the fraction, the greater the mechanical advantage. For example, a connection at a point up to a quarter of the length of the hinged door <NUM> will provide a greater mechanical advantage over a connection that is half way along the hinged door <NUM> from hinge <NUM>.

The main body <NUM> and the connection <NUM> of the charging link <NUM> to the hinged door <NUM> are configured such that a maximum angle between the plane of the main body <NUM> and the charging link <NUM> during the opening movement and/or closing movement of the hinged door <NUM> is up to <NUM> degrees. Typically, the maximum angle of the charging link <NUM> will be achieved when the hinged door <NUM> is perpendicular to the main body <NUM>. Other maximum angles are possible, for example, the maximum angle may be up to <NUM> degrees, <NUM> degrees or <NUM> degrees.

<FIG> shows the auto-injector <NUM> after activation. The first plunger driver <NUM> and second plunger driver <NUM> are configured upon activation of the auto-injector <NUM> to drive a plunger forward within the auto-injector <NUM> to operate a syringe received within the auto-injector <NUM>. In the example of <FIG>, the compression spring of the first plunger driver <NUM> and the two tension springs of the second plunger driver <NUM> work together to provide the forward force necessary to cause a drug in the mounted syringe to be injected into a patient.

The plunger of the syringe may be coupled to the first and second plunger drivers <NUM>, <NUM> to achieve this. Auto-injectors described herein divide the priming movement into two separate, lower force movements: the opening and the closing of the hinged door. In this way an injection force applied by the plunger drivers to the plunger can be high, for example in the range of <NUM>-<NUM> Newtons. The maximum force a user needs to apply at any point to prime the plunger drivers may be lower, for example in a range of <NUM>-<NUM> Newtons. Preferably the maximum force a user needs to apply at any point to prime the plunger driver is between <NUM> and <NUM> Newtons, and even more preferably the force a user needs to apply at any point to prime the plunger drivers is <NUM> Newtons. In contrast, in known devices the maximum drive spring strength is typically limited to the force a user can reasonably apply during a single priming movement.

The contribution the first plunger driver <NUM> makes to the injection force need not be (but can be) equal to the contribution made by the second plunger driver <NUM>. In one configuration, as it is typically easier for a user to apply a higher force on a closing movement the hinged door <NUM> as they can use their palm to push the door closed, the second plunger driver <NUM> may provide a greater driving force than the first plunger driver <NUM>. In this case, the force required for priming of the first plunger driver <NUM> is less than the force required for priming of the second plunger driver <NUM>.

Further optional features and components will now be described with reference to <FIG>.

The charging link <NUM> may be coupled to a shuttle <NUM>. The shuttle <NUM> may be slidable along the main body <NUM> and configured to travel along a shuttle guide <NUM>. The connection <NUM> may be between the charging link <NUM> and the shuttle <NUM> and may be rotatable. In some arrangements, the shuttle <NUM> provides the slideable connection of the charging link <NUM> to the main body <NUM>.

The shuttle <NUM> comprises a first priming portion <NUM> and a second priming portion <NUM>. The first plunger driver (e.g. compression spring) <NUM> is connected at a first end to the main body and at a second end to the first priming portion <NUM>. The second plunger driver (e.g. tension springs) is connected at a first end to the first priming portion <NUM> and at a second end to the second priming portion <NUM>. The first and second priming portions <NUM>, <NUM> are configured to travel along the shuttle guide <NUM> together towards the hinge <NUM> upon opening of the hinged door <NUM>. As the compression spring of the first plunger driver <NUM> is connected between the main body <NUM> and the first priming portion <NUM>, this motion primes the first plunger driver <NUM>. As the tension springs of the second plunger driver <NUM> are connected between the first and second priming portions, this movement does not prime the second plunger driver <NUM>.

The main body <NUM> and/or the first priming portion <NUM> may comprise a latch configured to retain the first priming portion <NUM> in position on the shuttle guide <NUM> after opening of the hinged door <NUM>. The first and second priming portions <NUM>, <NUM> are separable after opening of the hinged door <NUM>. This separated state is shown in <FIG>. The second priming portion <NUM> is configured to travel along the shuttle guide <NUM> away from the hinge <NUM> upon closing of the hinged door <NUM>. Because the tensions springs are connected between the first and second priming portions <NUM>, <NUM>, as the second priming portion <NUM> travels forward the tension springs of the second plunger driver <NUM> are primed.

Upon firing, caused for example by pressing the front end of the auto-injector <NUM> on a patient's skin or via some other firing mechanism, the separated first priming portion <NUM> is released from its latch and travels forward along the shuttle guide <NUM> under the combined force of the first plunger driver <NUM> and second plunger driver <NUM>. In the example of <FIG>, the compression spring pushes and the tension springs pull the first priming portion <NUM> of the shuttle <NUM> in a forward direction. As shown in <FIG>, the shuttle guide <NUM> is coupled to the first and second plunger drivers <NUM>, <NUM> such that movement thereof follows a path determined by the shuttle guide <NUM>. In the example of <FIG>, the shuttle guide comprises a rod passing through the first plunger driver <NUM> and passing through an aperture in the shuttle <NUM>.

The auto-injector <NUM> may also comprise a shroud at least partially covering and extending forwards beyond a forward end of a needle of the syringe when the syringe is fitted within the auto-injector and before use. When present, the shroud may be configured, upon rearward movement thereof, for example caused by pressing of the shroud onto a patient's skin, to release the latch and fire the device. Other firing mechanisms envisaged include side or rear buttons.

The auto-injector <NUM> may also comprise a ratchet operable during the closing movement of the hinged door <NUM> to prevent movement of the hinged door in the opening direction by a force exerted by the second plunger driver <NUM>. With reference to <FIG>, as the door is moved to its closed position and the second plunger driver <NUM> becomes primed, the second plunger driver <NUM> exerts an opposing force against the closing hinged door <NUM>. If a user does not maintain a force on the hinged door <NUM> during closing before it is fully closed, it will spring back open. The ratchet prevents this from happening by permitting movement of the hinged door <NUM> in a closing direction but preventing it in the opening direction. The ratchet is configured to become operable only after the user has opened the door for the first time so that it does not interfere with a user's ability to open the hinged door <NUM> in order to load the syringe into the main body <NUM>.

The skilled person will be able to envisage other assemblies, auto-injectors and features thereof without departing from the scope of the appended claims. In particular, it is noted that one or more features included in one or more drawings may be integrated into auto-injectors shown in other drawings, as will be appreciated by the skilled person.

Although the present invention has been described with reference to a hinged door it may be understood that other door configurations are possible. For example the main body and door may have a slideable connection as illustrated in the example auto-injector <NUM> of <FIG>. Such an auto-injector <NUM> will function in the same way as described previously with reference to Figures <NUM> to <NUM>. The main body <NUM> and door <NUM> may be connected by any suitable means, for example a projection from the door <NUM> may be received within the main body <NUM>. As was the case in the example configurations of <FIG>, a charging link between the main body and door may be provided. The charging link may be configured to slide when the door <NUM> is moved between the first and second positions as shown in the transition between <FIG> and <FIG>. The charging link may be configured to couple to the first and second plunger drivers of the auto-injector <NUM> for priming thereof on a respective first and second movement of the door to achieve the advantages described herein.

Claim 1:
An auto-injector (<NUM>) for receiving and operating a syringe, the auto-injector comprising:
a housing for receiving the syringe, the housing comprising a main body (<NUM>) and a door (<NUM>) operable into a first position and a second position, wherein the syringe is receivable within the housing when the door (<NUM>) is in the first position;
wherein the door is configured to couple to:
(i) a first plunger driver (<NUM>) for priming thereof on a first movement of the door, the first plunger driver comprising a first spring;
characterised in that
the door is further configured to couple to:
(ii) a second plunger driver (<NUM>) for priming thereof on a second movement of the door (<NUM>), the second plunger driver comprising a second spring;
the first and second plunger drivers being configured on activation of the auto-injector to drive a plunger forward within the auto-injector to operate the syringe received within the auto-injector, and
wherein the first position of the door (<NUM>) is the open position,
wherein the second position of the door (<NUM>) is the closed position,
wherein the first movement of the door (<NUM>) is an opening movement, and
wherein the second movement of the door (<NUM>) is a closing movement.