Patent Description:
Injection devices, such as auto-injectors, are known in the art for dispensing a medicament to the injection site of a patient. Such injection devices often comprise a body and a cap, a needle syringe located in the body and the cap removably attached to the body to shield the needle of the needle syringe. To dispense the medicament, the cap is first removed from the body to expose the needle. The needle is then inserted into the body of the patient at the injection site to dispense the medicament.

It is important to prevent access to the needle after the injection has occurred. A moveable needle sleeve and locking means can be provided to ensure that the needle is covered after the medicament has been dispensed and that access to the needle is restricted; this prevents the sharp needle from causing injury and can also act as an indicator that the injection device has already been used.

<CIT> discloses a safety device for a pre-filled syringe comprising a hollow support body to retain the pre-filled syringe therein, a hollow needle shield that is slidable relative to the support body and guiding means for guiding the movement of the needle shield relative to the support body. The guiding means comprise a deflectable flexible arm, a guide pin and a guide track. The deflectable flexible arm extends essentially parallel to a central axis of the safety device. The guide pin extends radial from the flexible arm. The guide track guides the guide pin within and along the guide track when the needle shield is slid relative to the support body.

It is an object of the present invention to provide an improved injection device.

According to a first embodiment there is an injection device comprising: a housing; a carrier disposed within the housing for holding a syringe that has a needle at one end; a needle sleeve located within the housing and being axially moveable with respect to the housing between an extended position and a retracted position; a biasing element configured to bias the needle sleeve towards the extended position; the injection device comprising a locking mechanism configured to lock the needle sleeve in the extended position after use of the injection device, the locking mechanism comprising; a first locking member provided on and projecting from the carrier; and a second locking member comprising a deflectable arm provided on the needle sleeve and moveable between a relaxed position and a deflected position; wherein the housing includes an inwardly projecting boss which engages the second locking member and moves the second locking member into the deflected position as the needle sleeve is moved to the retracted position; the first and second locking members configured such that the first locking member is out of engagement with the second locking member when the second locking member is in the deflected position; and the first and second locking members configured such that the second locking member blocks the first locking member when the second locking member is in the relaxed position and the needle sleeve is in the extended position, thereby preventing movement of the needle sleeve back into the retracted position.

Preventing the movement of the needle sleeve back into the retracted position may improve the safety of the device as access to the needle can be restricted once the injection has occurred. This may also act as an indicator that the injection device has already been used, furthermore it can avoid accidental injury. The mechanism as described above may be particularly beneficial when a syringe with a short needle is required.

'Short' when referred to in this specification may refer to a needle length of less than about <NUM>, typically as an example about <NUM>, however it can be appreciated that the injection device described in this specification can also be used for a needle length greater than or equal to <NUM>. The length of the needle can be measured from the distal end of the syringe glass to the tip of the needle.

The terms distal and proximal as used herein refer to directions relative to the injection device. The term "distal" refers to a location that is relatively closer to a site of injection, and the term "proximal" refers to a location that is relatively further away from the injection site.

There are a number of benefits to using a short needle in an injection device; the overall size of the device is reduced in comparison to devices with longer length needles, the injection time can be improved, more viscous fluids can be injected, storage loads and stopper impact forces can be reduced and a thinner gauge needle can be used without compromising the injection time. A thinner gauge needle may also mean that there is less pain for a user and could be particularly beneficial in paediatric applications.

In one embodiment the needle sleeve may extend further out from the housing in the extended position than in the retracted position. In a further embodiment the needle sleeve may be moveable between three positions, a start position, the retracted position and the extended position, wherein the needle sleeve may extend further out from the housing in the extended position than in the start position, and may extend further out from the housing in the start position than in the retracted position.

In one embodiment, the needle sleeve is retractable beteween the housing and the carrier.

In one embodiment the deflectable arm may have a first end fixedly attached to the rest of the needle shield and a second, free end remote from the first end.

The injection device being moveable between three positions may aid the priming of the locking mechanism to be carried out during assembly of the device by machinery as opposed to manually. However it can be appreciated that the locking mechanism could be primed by a user before they actuate the injection device. For those who are elderly or infirm, or for those who are in a rush or require easier actuation of the device, simplification of actuating the injection device by priming the locking mechanism during the assembly stage is desirable.

In one embodiment, the first locking member comprises a protrusion.

In one embodiment when the needle sleeve is in the start position the deflectable arm may be in the relaxed position and the first locking member may be disposed distally of the free end of the deflectable arm.

The or each arm may be deflectable circumferentially. However, a skilled person will recognise that in other embodiments the or each arm may be deflectable in an alternative direction, for example, being deflectable radialy or tangentially.

In one embodiment the first and second locking members may be axially aligned when the second locking member is in the relaxed position but are out of axial alignment when the second locking member is in the deflected position. This may enable the first locking member to move past the second locking member when the second locking member is in the deflected position, this can provide a means for the second locking member to engage the first locking member in the start position but also to block the second locking member when the second locking member is in the relaxed position.

In one embodiment the deflectable arm may be deflectable laterally with respect to the axial direction of the injection device when the second locking portion is engaged by the inwardly projecting boss of the housing. Lateral deflection of the deflectable arm may aid simple assembly due to the alignment of particular components but also may enable the second locking member to engage with the first locking member when the second locking member is in the relaxed position.

The second locking member may be a pair of deflectable arms, it may be a single deflectable arm which is biased against a surface of the needle sleeve or alternative component. It can be appreciated that the second locking member may also be a pair of pivotable arms, the arms can be rigid and comprise a series of joints. There may also only be one pivotable arm biased against a fixed surface of the injection device, for example a surface of the needle sleeve. The second locking member may be directed in a proximal direction; however it can be appreciated that the second locking member may also be directed in a distal direction. The deflectable arm may be substantially linear and the free end of the deflectable arm may extend in a distal direction.

It may be beneficial for the second locking member to be a pair of deflectable arms; the equal force of each deflectable arm in the relaxed position on the first locking member may hold or block the first locking member more easily.

In one embodiment, the or each arm may be deflectable circumferentially with respect to the housing. However, a skilled person will recognise that in other embodiments the or each arm may be deflectable in an alternative direction, for example, being deflectable radialy or tangentially with respect to the housing.

In one embodiment the injection device may further comprise a removable cap. One advantage of the cap is that it may shield the needle when not in use, helping to ensure that the needle remains sterile before use. The cap may also reduce the risk of accidental actuation of the injection device, for example when the device is dropped. When the cap is on the device, interlocking portions of the cap may engage with corresponding interlocking portions on the needle sleeve preventing accidental depression of the needle sleeve before the cap is removed.

In one embodiment the first locking member can comprise a T shaped boss projecting from the carrier. The first locking member may have a relative narrow portion and a relative wider portion, the first locking member may be at least substantially rigid. The boss may project inwardly or outwardly of the carrier, inward being towards the central axis of the injection device.

A T shaped boss may be advantageous to the performance of the locking mechanism. The head of the T may be easily held or blocked by the second locking member while still being able to move past the second locking member when the second locking member is in the deflected position. A T shaped boss can also be easily manufactured to be part of the carrier.

In one embodiment the inwardly projecting boss of the housing may be tapered or shaped like an arrow head, pointing in a distal direction. It can be appreciated however that any shape which can forcibly move the second locking member of the needle sleeve into the deflected position may be suitable.

A tapered or arrow like shape to the inwardly projecting boss may enable the inwardly projecting boss to gradually force the second locking member into the deflected position and gradually release the second locking member into the relaxed position. This gradual movement between positions can provide less force on the second locking members and reduce the likelihood of damage or elastic deformation.

In one embodiment the first locking member may comprise at least one rigid portion and the second locking member may comprise at least one flexible portion. The combination of rigid and flexible portions can also provide less force on the locking mechanism and reduce the likelihood of damage or elastic deformation to the locking mechanism.

In one embodiment the injection device may further comprise a syringe having a needle at one end. The syringe may contain a medicament.

In one embodiment, the injection device may be an auto-injector.

In one embodiment there is a method of assembling an injection device which may comprise the following steps:insert a syringe having a needle into the carrier; move the needle sleeve relative to the housing in a proximal direction of the device to a first assembly position wherein the inwardly projecting boss of the housing engages the second locking member of the needle sleeve and moves the second locking member from the relaxed position into the deflected position;.

Enabling the priming of the locking mechanism to be carried out during assembly of the device by machinery as opposed to manually may be beneficial for those who are elderly or infirm, or for those who are in a rush or require easier actuation of the device. The needle sleeve being in the start position may simplify actuation of the injection device for a user.

The method may comprise inserting the carrier into a sub-assembly comprising the housing and needle sleeve into an intermediate position before moving the needle sleeve relative to the housing into the first assembly position, and subsequently moving the carrier further within the housing is a distal direction to the second assembly position after the needle sleeve have been moved into the first assembly position.

In one embodiment the second locking member may have two deflectable arms; the deflectable arms may each have a first end fixedly attached to the rest of the needle sleeve and a second end which is free. In the second assembly position the first locking member may be disposed between the two arms.

A drug delivery device, as described herein, may be configured to inject a medicament into a patient. For example, delivery could be sub-cutaneous, intra-muscular, or intravenous. Such a device could be operated by a patient or care-giver, such as a nurse or physician, and can include various types of safety syringe, pen-injector, or auto-injector. The device can include a cartridge-based system that requires piercing a sealed ampule before use. Volumes of medicament delivered with these various devices can range from about <NUM> to about <NUM>. Yet another device can include a large volume device ("LVD") or patch pump, configured to adhere to a patient's skin for a period of time (e.g., about <NUM>, <NUM>, <NUM>, <NUM>, or <NUM> minutes) to deliver a "large" volume of medicament (typically about <NUM> to about <NUM>).

The delivery devices described herein can also include one or more automated functions. For example, one or more of needle insertion, medicament injection, and needle retraction can be automated. Energy for one or more automation steps can be provided by one or more energy sources. Energy sources can include, for example, mechanical, pneumatic, chemical, or electrical energy. For example, mechanical energy sources can include springs, levers, elastomers, or other mechanical mechanisms to store or release energy. One or more energy sources can be combined into a single device. Devices can further include gears, valves, or other mechanisms to convert energy into movement of one or more components of a device.

The one or more automated functions of an auto-injector may each be activated via an activation mechanism. Such an activation mechanism can include one or more of a button, a lever, a needle sleeve, or other activation component. Activation of an automated function may be a one-step or multi-step process. That is, a user may need to activate one or more activation components in order to cause the automated function. For example, in a one-step process, a user may depress a needle sleeve against their body in order to cause injection of a medicament. Other devices may require a multi-step activation of an automated function. For example, a user may be required to depress a button and retract a needle sleeve in order to cause injection.

According to some embodiments of the present disclosure, an exemplary drug delivery device <NUM> is shown in <FIG>. Device <NUM>, as described above, is configured to inject a medicament into a patient's body. Device <NUM> includes a housing <NUM> which typically contains a reservoir containing the medicament to be injected (e.g., a syringe) and the components required to facilitate one or more steps of the delivery process. Device <NUM> can also include a cap assembly <NUM> that can be detachably mounted to the housing <NUM>. Typically a user must remove cap <NUM> from housing <NUM> before device <NUM> can be operated.

As shown, housing <NUM> is substantially cylindrical and has a substantially constant diameter along the longitudinal axis A-A. The housing <NUM> has a distal region D and a proximal region P. The term "distal" refers to a location that is relatively closer to a site of injection, and the term "proximal" refers to a location that is relatively further away from the injection site.

Device <NUM> can also include a needle sleeve <NUM> coupled to housing <NUM> to permit movement of needle sleeve <NUM> relative to housing <NUM>. For example, needle sleeve <NUM> can move in a longitudinal direction parallel to longitudinal axis A-A. Specifically, movement of needle sleeve <NUM> in a proximal direction can permit a needle <NUM> to extend from distal region D of housing <NUM>.

Insertion of needle <NUM> can occur via several mechanisms. For example, needle <NUM> may be fixedly located relative to housing <NUM> and initially be located within an extended needle sleeve <NUM>. Proximal movement of needle sleeve <NUM> by placing a distal end of needle sleeve <NUM> against a patient's body and moving housing <NUM> in a distal direction will uncover the distal end of needle <NUM>. Such relative movement allows the distal end of needle <NUM> to extend into the patient's body. Such insertion is termed "manual" insertion as needle <NUM> is manually inserted via the patient's manual movement of housing <NUM> relative to needle sleeve <NUM>.

Another form of insertion is "automated," whereby needle <NUM> moves relative to housing <NUM>. Such insertion can be triggered by movement of needle sleeve <NUM> or by another form of activation, such as, for example, a button <NUM>. As shown in <FIG>, button <NUM> is located at a proximal end of housing <NUM>. However, in other embodiments, button <NUM> could be located on a side of housing <NUM>.

Other manual or automated features can include drug injection or needle retraction, or both. Injection is the process by which a bung or piston <NUM> is moved from a proximal location within a syringe <NUM> to a more distal location within the syringe <NUM> in order to force a medicament from the syringe <NUM> through needle <NUM>. In some embodiments, a drive spring (not shown) is under compression before device <NUM> is activated. A proximal end of the drive spring can be fixed within proximal region P of housing <NUM>, and a distal end of the drive spring can be configured to apply a compressive force to a proximal surface of piston <NUM>. Following activation, at least part of the energy stored in the drive spring can be applied to the proximal surface of piston <NUM>. This compressive force can act on piston <NUM> to move it in a distal direction. Such distal movement acts to compress the liquid medicament within the syringe <NUM>, forcing it out of needle <NUM>.

Following injection, needle <NUM> can be retracted within needle sleeve <NUM> or housing <NUM>.

Retraction can occur when needle sleeve <NUM> moves distally as a user removes device <NUM> from a patient's body. This can occur as needle <NUM> remains fixedly located relative to housing <NUM>. Once a distal end of needle sleeve <NUM> has moved past a distal end of needle <NUM>, and needle <NUM> is covered, needle sleeve <NUM> can be locked.

As the locking of the needle sleeve is based on a relative movement between the housing or needle and the needle sleeve, the length of the needle needs to be taken into account when considering a suitable locking mechanism. There are a number of benefits to using a short needle in an injection device; the overall size of the device is reduced in comparison to devices with longer length needles, the injection time can be improved, more viscous fluids can be injected, storage loads and stopper impact forces can be reduced and a thinner gauge needle can be used without compromising the injection time. A thinner gauge needle may also mean that there is less pain for a user and could be particularly beneficial in paediatric applications.

'Short' when referred to in this specification refers to a length of less than about <NUM>, typically as an example about <NUM>, however it can be appreciated that the device described below can also be used for a needle length greater than or equal to <NUM>. The length of the needle <NUM> can be measured from the distal end of the syringe <NUM> glass to the tip of the needle <NUM>.

Referring now to <FIG>, an injection device <NUM> according to a first embodiment of the invention is shown. The injection device <NUM> is in the form of an auto-injector <NUM> that has similar features to the auto-injector <NUM> described above in relation to <FIG>, with like features retaining the same reference numerals. The device <NUM> has a carrier <NUM> comprising a receiving end <NUM> for receiving a syringe, and a needle end <NUM>, through which a needle <NUM> of the syringe protrudes when received in the carrier <NUM>. The receiving end <NUM> is larger than the needle end <NUM>, the needle end <NUM> further comprising cut out portions <NUM>, and carrier sections <NUM> tapering towards a distal end of the carrier. The carrier <NUM> further comprises a first locking member <NUM> which consists of at least one substantially rigid boss or protrusion <NUM>. This carrier boss <NUM> has a body portion <NUM> and a head portion <NUM>, however it can be appreciated that only the head portion is required, the head portion <NUM> is substantially T shaped and the body portion <NUM> being substantially linear. However it can be appreciated by a personal skilled in the art that the head portion <NUM> could be any alternative shape, for example but not limited to an arrow head shape, a V shape, an arc or hook shape. The body portion <NUM> can also be non-linear.

For the assembly of the injection device <NUM> the carrier <NUM> is inserted into a sub assembly comprising the needle sleeve <NUM> and the housing <NUM>. It can be appreciated that the carrier, needle sleeve and housing are all assembled as part of the same stage. The needle sleeve <NUM> comprises needle sleeve legs <NUM> and cut away portions <NUM>. The needle sleeve <NUM> further comprises a second locking member <NUM> comprising a pair of deflectable arms <NUM> attached to each other by a strut <NUM>. The strut is then coupled to the rest of the needle sleeve <NUM> by three supports <NUM>. The deflectable arms <NUM>, strut <NUM> and supports <NUM> can all be integrally formed with the needle sleeve <NUM>, it can also be appreciated that these may be any combination of separate parts coupled to one another. The deflectable arms may be coupled directly to the needle sleeve <NUM> and no further struts <NUM> or supports <NUM> may be required. There may also be more or less than three supports <NUM>, or more or less than one strut <NUM> depending on the structural properties required from the second locking member <NUM>. The needle sleeve <NUM> can have a pair of second locking members <NUM> disposed on opposite sides of the needle sleeve <NUM>.

The deflectable arms <NUM> have a first end <NUM> fixedly attached to the rest of the needle sleeve <NUM> and a second, opposite end <NUM> extending from the first end in a proximal direction. The second end <NUM> is free and not attached to the rest of the needle shield other than via the first end <NUM>. The deflectable arms also have an intermediate part <NUM> which can be straight, bent inwards towards eachother or comprise a further joint.

The housing <NUM> further comprises an inwardly projecting boss <NUM> located towards a distal end of the housing <NUM>. The inwardly projecting boss <NUM> can be tapered pointing towards a distal end of the injection device <NUM>. The inwardly projecting boss <NUM> may be integrally formed with the housing <NUM>, however it can be appreciated that the inwardly projecting boss <NUM> may be a separate component coupled to the housing <NUM>. The inwardly projecting boss <NUM> is to engage with the second locking member <NUM>, forcibly moving the deflectable arms <NUM> apart, opening the space between the two deflectable arms into a deflected position as shown in <FIG>. This engagement between the second locking member <NUM> of the needle sleeve <NUM> and the inwardly projecting boss <NUM> of the housing can be actuated by the needle sleeve <NUM> being moved in a proximal direction with respect to the housing <NUM>. When the inwardly projecting boss <NUM> is not engaged with the second locking member <NUM> then the second locking member is in a relaxed position as shown in <FIG>.

When the second locking member <NUM> is in a deflected position as shown in <FIG> the first locking member <NUM> and in particular the carrier boss <NUM> is able to move past the free ends <NUM> of the deflectable arms <NUM>. When the second locking member <NUM> is in a relaxed position the head portion <NUM> of the first locking member is unable to pass the free ends <NUM> of the deflectable arms <NUM>. In a relaxed position either the head portion <NUM> is trapped between the deflectable arms <NUM> of the second locking member <NUM> and is restricted from axial movement in a proximal direction past the deflectable arms <NUM> or the head portion is stopped by the free ends <NUM> of the deflectable arms <NUM> of the second locking member and restricted from axial movement in a distal direction past the deflectable arms <NUM>. The movement described above is relative to the housing.

To assemble the device <NUM> the needle sleeve is inserted into the housing and the syringe <NUM> is inserted into the carrier <NUM>. The carrier <NUM> and syringe <NUM> are advanced to an intermediate position within the housing <NUM>, an intermediate positon being less than fully inserted into the device and can be known as a first assembly position. The needle sleeve <NUM> is then moved in a proximal direction with respect to the housing <NUM> pushing the deflectable arms <NUM> towards the inwardly projecting boss <NUM> opening the second locking member <NUM> into the deflected position. The carrier <NUM> can then be moved further in the distal direction, the carrier boss <NUM> being able to pass the deflectable arms <NUM> as they are opened by the inwardly projecting boss <NUM>. This can be known as the second assembly position and can be the final assembled position for the carrier <NUM> and syringe. It can however be envisaged that the intermediate position is not required and the carrier <NUM> can be fully inserted at the same time as the needle sleeve <NUM> has been depressed and the deflectable arms <NUM> are in the deflected position. The rest of the device is then assembled, such as the insertion of a drive assembly into the housing to prepare the device for use. The drive assembly comprises a plunger <NUM>, a drive spring <NUM> and a housing end <NUM>. The drive spring <NUM> is arranged to push the plunger <NUM> acting on the piston <NUM> into the syringe <NUM> to force medicament through the needle <NUM> during use of the injector device <NUM>. The plunger <NUM> and piston <NUM> may be separate components or a single component.

During assembly the plunger is rotated as it is inserted into the device either manually or by a suitable assembly tool and a plunger boss <NUM> engages with a needle sleeve rib <NUM> on the needle sleeve legs <NUM> as can be seen in <FIG>. The needle sleeve <NUM> is held in a retracted position while the drive assembly is inserted and then let go, when the it is let go the needle sleeve <NUM> moves in a distal direction, however the engagement between the plunger boss <NUM> and the needle sleeve rib <NUM> during the assembly and priming of the device prevents the needle sleeve <NUM> from fully extending into the extended position. The contact between the plunger boss <NUM> and the needle sleeve rib <NUM> also prevents downward rotation of the plunger in this position. When the needle sleeve <NUM> is depressed or moved into the retracted position for an injection the plunger is able to rotate further and the plunger boss <NUM> disengages with the rib <NUM>, the needle sleeve is then free to move into the extended position and the plunger is free to move distally under the force of the drive spring to dispense the medicament.

It can be appreciated that the needle sleeve can be held in the start position by alternative means, for example the needle sleeve could engage with protrusions or retractible parts of the housing. The retractible parts being retracted by an actuator after an injection has occurred. Furthermore the needle sleeve can be held in the start position by a further component such as a collar located at a distal end of the device, the needle sleeve comprising protrusions which engage with slots in the collar, the collar rotating as an injection occurs in a similar manner to the plunger <NUM> during the assembly stage to release the needle sleeve into a fully extended position once the injection is complete. It can be appreciated that a person skilled in the art can determine a number of alternative methods to simply catch and release two components.

When the device <NUM> is fully assembled the needle sleeve <NUM> is released or moved in a distal direction disengaging from the inwardly projecting boss <NUM> into a start position, the head portion <NUM> of the carrier boss <NUM> remains distally of the free ends <NUM> of the deflectable arms <NUM> and the needle sleeve is not fully extended due to the engagement with the plunger <NUM> described above. This arrangement means the device is now assembled and primed for use by a user.

To use the device <NUM>, the cap <NUM> is removed from the rest of the device, in particular from the housing <NUM>, however it can be appreciated that the device <NUM> may not have a cap assembly or it may have already been removed. The cap also reduces the risk of accidental actuation of the injection device, for example when the device is dropped. As can be seen in <FIG> when the cap <NUM> is on the device, a locking boss <NUM> on the cap <NUM> may engage with corresponding cut outs <NUM> on the needle sleeve <NUM> preventing accidental depression of the needle sleeve <NUM> before the cap <NUM> is removed. As the cap <NUM> is removed the locking boss <NUM> is able to elastically deform into a stepped portion <NUM> of the housing <NUM>, releasing the locking boss <NUM> from the needle sleeve cut outs <NUM>. After the cap is removed the needle is then inserted into the body of the patient at the injection site to dispense a medicament, the needle sleeve <NUM> being depressed in a proximal direction in the process from the start position to the retracted position. During this process the needle sleeve <NUM> is moved in a proximal direction against a biasing force of a biasing means, for example a spring <NUM>, into the retracted position. In the retracted position the second locking portion engages with the inwardly projecting boss <NUM>, the inwardly projecting boss is shaped to push against the deflectable arms, moving the second locking portion into the deflected position wherein the two deflectable arms deflect laterally of the central axis of the device from a proximal to a distal end. The spring biases the needle sleeve <NUM> in a distal direction and towards the extended position. However it can be appreciated that the biasing means could be an alternative for example a bellows or compressed foam, or the sleeve could be moved into the extended position by a magnetic attraction or repelling means.

In the extended position the first locking member is not engaged with the second locking member and the head portion <NUM> is on a proximal side of the deflectable arms, the second locking portion is in a relaxed position and the spring <NUM> pushes the needle sleeve <NUM> into the extended position. When the needle sleeve is in the extended position, after an injection has occurred, if the needle sleeve <NUM> is depressed or moved in a proximal direction then the second locking member abuts the head portion <NUM> of the carrier boss <NUM> preventing axial movement in a proximal direction of the needle sleeve <NUM> in relation to the carrier <NUM>. If a force is applied to the needle sleeve <NUM> in the proximal direction when the needle sleeve is in the extended position then the load is resolved through the interface between the free ends of the deflectable arms <NUM> and the carrier boss <NUM>. This mechanism can improve the safety of the device asthe mechanism effectively locks the needle sleeve <NUM> in the extended position enclosing the needle <NUM>, ensuring that a user cannot access the needle <NUM> after injection is complete.

It can be appreciated that the second locking member may comprise only one deflectable arm located against a surface of the needle sleeve <NUM>, it may also comprise a deflectable member of an alternative shape for example a cup shaped deflectable member with a corresponding T shaped head portion <NUM> or any alternative deflectable member with a correspondingly shaped head portion <NUM>. There are a number of alternative deflectable or flexible members or arms which can trap and block a rigid carrier boss as described above.

The deflectable members and arms can be made of a flexible material, however they may also include joints, pivots or hinges to deflect and can therefore be flexible or substantially rigid.

It can be appreciated that the carrier boss <NUM> can have flexible properties in that it may be the shape of the carrier boss <NUM> when engaged with the second locking member <NUM> which causes it to be trapped and stopped by the deflectable arms.

Exemplary insulin derivatives are, for example, B29-N-myristoyl-des(B30) human insulin; B29-N-palmitoyl-des(B30) human insulin; B29-N-myristoyl human insulin; B29-N-palmitoyl human insulin; B28-N-myristoyl LysB28ProB29 human insulin; B28-N-palmitoyl-LysB28ProB29 human insulin; B30-N-myristoyl-ThrB29LysB30 human insulin; B30-N-palmitoyl- ThrB29LysB30 human insulin; B29-N-(N-palmitoyl-gamma-glutamyl)-des(B30) human insulin; B29-N-(N-lithocholyl-gamma-glutamyl)-des(B30) human insulin; B29-N-(ω-carboxyheptadecanoyl)-des(B30) human insulin and B29-N-(ω-carboxyhepta¬decanoyl) human insulin. Exemplary GLP-<NUM>, GLP-<NUM> analogues and GLP-<NUM> receptor agonists are, for example: Lixisenatide / AVE0010 / ZP10 / Lyxumia, Exenatide / Exendin-<NUM> / Byetta / Bydureon / ITCA <NUM> / AC-<NUM> (a <NUM> amino acid peptide which is produced by the salivary glands of the Gila monster), Liraglutide / Victoza, Semaglutide, Taspoglutide, Syncria / Albiglutide, Dulaglutide, rExendin-<NUM>, CJC-<NUM>-PC, PB-<NUM>, TTP-<NUM>, Langlenatide / HM-11260C, CM-<NUM>, GLP-<NUM> Eligen, ORMD-<NUM>, NN-<NUM>, NN-<NUM>, NN-<NUM>, Nodexen, Viador-GLP-<NUM>, CVX-<NUM>, ZYOG-<NUM>, ZYD-<NUM>, GSK-<NUM>, DA-<NUM>, MAR-<NUM>, MAR709, ZP-<NUM>, ZP-<NUM>, TT-<NUM>, BHM-<NUM>. MOD-<NUM>, CAM-<NUM>, DA-<NUM>, ARI-<NUM>, ARI-<NUM>, Exenatide-XTEN and Glucagon-Xten.

Claim 1:
An injection device (<NUM>) comprising:
a housing (<NUM>);
a carrier (<NUM>) disposed within the housing (<NUM>) for holding a syringe (<NUM>) that has a needle (<NUM>) at one end;
a needle sleeve (<NUM>) located within the housing (<NUM>) and being axially moveable with respect to the housing (<NUM>) between an extended position and a retracted position;
a biasing element (<NUM>) configured to bias the needle sleeve (<NUM>) towards the extended position;
the injection device (<NUM>) comprising a locking mechanism configured to lock the needle sleeve (<NUM>) in the extended position after use of the injection device (<NUM>), the locking mechanism comprising;
a first locking member (<NUM>) provided on and projecting from the carrier (<NUM>); and
a second locking member (<NUM>) comprising a deflectable arm (<NUM>) provided on the needle sleeve (<NUM>) and moveable between a relaxed position and a deflected position;
wherein the housing (<NUM>) includes an inwardly projecting boss (<NUM>) which engages the second locking member (<NUM>) and moves the second locking member (<NUM>) into the deflected position as the needle sleeve (<NUM>) is moved to the retracted position;
the first and second locking members (<NUM>, <NUM>) configured such that the first locking member (<NUM>) is out of engagement with the second locking member (<NUM>) when the second locking member (<NUM>) is in the deflected position; and
the first and second locking members (<NUM>, <NUM>) configured such that the second locking member (<NUM>) blocks the first locking member (<NUM>) when the second locking member (<NUM>) is in the relaxed position and the needle sleeve (<NUM>) is in the extended position, thereby preventing movement of the needle sleeve (<NUM>) back into the retracted position.