Patent Publication Number: US-2021187201-A1

Title: Injection device with a preselector

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is the national stage entry of International Patent Application No. PCT/EP2018/080077, filed on Nov. 5, 2018, and claims priority to Application No. EP 17200313.9, filed on Nov. 7, 2017, the disclosures of which are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates in one aspect to an injection device, such as a pen-type injector for setting and dispensing of a dose of a medicament. In particular, the disclosure relates to an injection device comprising a preselector configured to limit a maximum dose that can be set and dispensed by the injection device. 
     BACKGROUND 
     Injection devices for setting and dispensing a single or multiple doses of a liquid medicament are known. Generally, such devices have substantially a similar purpose as that of an ordinary syringe. 
     Injection devices, in particular pen-type injectors have to meet a number of user-specific requirements. For instance, with patient&#39;s suffering chronic diseases, such as diabetes, the patient may be physically infirm and may also have impaired vision. Suitable injection devices especially intended for home medication therefore need to be robust in construction and should be easy to use. Furthermore, manipulation and general handling of the device and its components should be intelligible and easy understandable. Moreover, the dose setting as well as dose dispensing procedure must be easy to operate and has to be unambiguous. 
     Typically, such devices comprise a housing including a particular cartridge holder, adapted to receive a cartridge at least partially filled with the medicament to be dispensed. Such devices further comprise a drive mechanism, usually having a displaceable piston rod which is adapted to operably engage with a piston of the cartridge. By means of the drive mechanism and its piston rod, the piston of the cartridge is displaceable in a distal direction or dispensing direction and may therefore expel a predefined amount of the medicament via a piercing assembly, which is to be releasably coupled with a distal end section of the housing of the injection device. 
     The medicament to be dispensed by the injection device is provided and contained in a multi-dose cartridge. Such cartridges typically comprise a vitreous barrel sealed in a distal direction by means of a pierceable seal and being further sealed in proximal direction by the piston. With reusable injection devices an empty cartridge is replaceable by a new one. In contrast, injection devices of disposable type are to be discarded when the medicament in the cartridge has been dispensed or used-up. 
     SUMMARY 
     The present disclosure provides an injection device with increased patient safety and comprises a mechanism that prevents unintended overdosing of a medicament. The injection device provides a limited capability to set and to dispense doses of different sizes. The injection device at least temporally provides setting and dispensing of only one or a few differently sized doses. In particular, the injection device is configured to allow and to enable repeated and multiple setting and dispensing of only a few, e.g. of two, three or four differently sized doses of the medicament. 
     The present disclosure further provides an injection device being intuitive and simple to use even for patients suffering side effects or having an impaired vision. The injection device provides a clearly visible feedback and/or mechanical or haptic feedback to a user thereby indicating that a dose of a predefined size is set and that the device is ready for starting a dispensing procedure. 
     Advantageously, a maximum size of a dose that can be dispensed or expelled from the cartridge can be limited to prevent unintended overdosing of the medicament. 
     In one aspect there is provided an injection device for setting and for injecting a dose of a medicament. The injection device comprises an elongated housing extending along a longitudinal axis and having a distal end and a proximal end. The distal end is closest to a dispensing end of the housing whereas the proximal end is located at an opposite end of the elongated housing. Typically and in use, the proximal end is provided with at least one actuator, such as a dose dial, a preselector and/or a trigger in order to set a dose and to trigger dispensing of the dose. 
     The injection device further comprises a dose tracker being at least one of translationally or rotationally displaceable relative to the housing. The dose tracker is displaceable between a zero dose positional state and a maximum dose positional state relative to the housing for setting of the dose. The positional state of the dose tracker relative to the housing is indicative of a size of the dose. In the present context a positional state includes a position of the dose tracker relative to the housing as well as an orientation of the dose tracker relative to the housing. 
     At least one of the elongated housing and the dose tracker comprises at least one tracking stop feature. The injection device further comprises a preselector displaceable relative to the housing between at least two preselection positional states thereby defining the maximum dose positional state of the dose tracker. The preselector comprises at least one preselector stop feature. The preselector stop feature is configured to mechanically engage with the at least one tracking stop feature in order to block and to impede a displacement of the dose tracker beyond the maximum dose positional state. 
     The preselector defines a maximum length of a displacement path for the dose tracker relative to the housing. The length of the displacement path correlates to the size of the dose actually set and to be dispensed during a subsequent dispensing operation of the injection device. During setting of a dose the preselector is stationary relative to the housing. It may be fixed or locked to the housing. During setting of the dose and for setting of the dose the dose tracker is displaceable relative to the housing. At the end of the dose setting procedure the dose tracker is in the maximum dose positional state that is defined by the preselection positional state of the preselector. Once the dose tracker has reached the maximum dose positional state a dispensing operation for expelling a dose of the medicament may commence or may be triggered. 
     The process of dose setting while the preselector is in a predefined preselection positional state is either conducted by the user himself or is conducted automatically. The dose tracker is displaceable from the zero dose positional state to the maximum dose positional state either under the action of a mechanical drive, such as a spring or the dose tracker is manually displaced by a user interacting with an actuator, such as a trigger or a dose dial. For dispensing of a dose the user may exert a dispensing force onto a trigger of the injection device. During dose dispensing the dose tracker returns from the maximum dose positional state to the zero dose positional state. During dispensing of a dose the dose tracker may be displaced against the action of the mechanical drive, hence against the action of the spring. 
     The interaction between the preselector and the dose tracker is beneficial for that the user does not have to take care about a setting of a correct dose. The preselector is particularly applicable with injection devices generally providing numerous different positional states for the dose tracker starting from which a dose injection procedure may commence. With the preselector the capability of the injection device to set and to dispense differently sized doses of the medicament is limited to only one dose size at a time. It is intended that the dose tracker is always displaced from the zero dose positional state to the maximum dose positional state. The mechanical interaction between the preselector stop feature and the tracking stop feature automatically limits and prevents an overdosing and hence a displacement of the dose tracker beyond the maximum dose positional state. 
     In effect, setting of a dose is provided through the interaction of the preselector and the dose tracker. The preselector defines a maximum dose without actually setting the dose whereas the dose tracker is to be displaced relative to the housing for setting of a dose without selecting or defining the size of the dose. Dose size selection is exclusively performed and conducted by the preselector. Setting of a dose of predefined size governed by the configuration of the preselector is exclusively performed and conducted by some other device component, such as a dose dial. 
     The total displacement of the dose tracker is defined by the preselection positional state of the preselector. Once the preselector is correctly positioned in a predefined preselection positional state the end user does no longer have to take care about the setting of a correct dose. This is of particular benefit in a scenario where the preselector is for instance manipulated or is exclusively configurable by authorized persons, such as caregivers. In this way a patient or user of the injection device is hindered from modifying the preselection positional state of the preselector. Movement or configuration of the preselector may require a certain tool or may require a partial disassembly of the injection device. For instance, the preselector may be covered by a cover, such as an adhesive label 
     In this way, the caregiver may be provided with the exclusive possibility to limit and to restrict a maximum size of a dose that can be set and dispensed by the injection device. 
     In examples wherein the at least one tracking stop feature is provided on the elongated housing the preselector is at least translationally fixed to the dose tracker. In particular, the preselector may be locked to the dose tracker with regard to the longitudinal direction. A longitudinal displacement or a translational displacement of the dose tracker relative to the elongated housing is then equally transferred to the preselector and vice versa. In this way the preselector moves in unison with the dose tracker. When reaching the maximum dose positional state the preselector stop feature engages with the tracking stop feature of the housing. Here, for selecting at least one of the two preselection positional states the preselector may be rotatable relative to the dose tracker for selection of the preselection positional state among a plurality of available preselection positional states. 
     In other examples, wherein the tracking stop feature is provided on the dose tracker the preselector may be translationally fixed relative to the housing. The preselector may be rotationally supported on the housing or the preselector may be rotatable or slidable along a tangential or circumferential direction of the housing. The housing may comprise a substantially tubular or cylindrical shape. Typically, the preselector is fixed to the housing with regard to the longitudinal axis. A longitudinal displacement of the dose tracker from the zero dose positional state to the maximum dose positional state then brings the tracking stop feature in engagement or in abutment with the preselector stop feature. In this way a further displacement of the dose tracker along the longitudinal axis of the injection device is effectively blocked and impeded. 
     Use of the injection device by a patient becomes safer since the injection device is preconfigured for only one predefined dose size. By means of the preselector the injection device originally configured as a variable dose size injection device can be transferred or transformed into a fixed dose injection device preconfigured to set and to dispense numerous doses of a medicament of a predefined size. 
     The preselector stop feature and the tracking stop feature may comprise mutually corresponding stop faces, e.g. extending in circumferential and/or radial direction so as to engage axially. Alternatively or additionally the preselector stop feature and the tracking stop feature may comprise mutually corresponding stop faces extending in axial direction and radial direction so as to engage circumferentially. When configured to engage axially, the mutual engagement of the preselector stop feature and the tracking stop feature provides an axial stop thereby impeding and blocking a longitudinal or axial translation of the dose tracker beyond the maximum axial dose positional state. 
     In another example at least a proximal end of the dose tracker protrudes proximally from a proximal end of the housing when in the maximum dose positional state. A longitudinal distance between the zero dose positional state and the maximum dose positional state correlates with the size of the dose. In the zero dose positional state a proximal end of the dose tracker may be located distally from a proximal end of the housing. Alternatively, the proximal end of the dose tracker may align with a proximal end of the housing. When in the maximum dose positional state and when protruding proximally from a proximal end of the housing the dose tracker or an actuator, such as a trigger operatively connected to the dose tracker, may be depressible in distal direction in order to trigger, to commence and/or to control a dose dispensing action of the injection device. 
     The dose tracker protruding proximally from a proximal end of the housing provides a rather intuitive, at least a visible or haptically discernible indication to a user, that the maximum dose positional state has been reached and that the injection device is prepared and ready for conducting a dose dispensing operation. 
     In another example the preselector is lockable relative to the housing in any of the at least two preselection positional states. The preselector may be lockable relative to the housing by means of a first locking feature provided on the preselector and by means of a second locking feature provided on the housing. For instance, the first locking feature may comprise a detent structure and the second locking feature may comprise a counter detent structure. One of the detent structure and the counter detent structure comprises a protrusion whereas the other one of the detent structure at the counter detent structure comprises numerous recesses to receive and to positionally lock the protrusion. The recesses are spaced from each other with regards to a displacement direction of the preselector between the at least two preselection positional states. The recesses may be spaced equidistantly. 
     Typically, the preselector is accessible to a user from outside the housing. The preselector may flush with an outside surface of the housing. Alternatively, the preselector may protrude from an outside surface of the housing or the preselector may be arranged in a recess of the outside surface of the housing. Eventually and for impeding unauthorized access to the preselector the preselector may be covered by a protector, such as an adhesive label or the like cover. 
     In one example the injection device further comprises a spring to urge the dose tracker in the proximal direction relative to the housing. In this way an automated dose setting can be provided. By means of the spring the dose tracker can be automatically displaced from an initial position towards and into the at least a first activation position. In a further example the injection device comprises an interlock to lock the dose tracker in the initial position relative to the housing. By means of the interlock the dose tracker can be immobilized relative to the housing at least with regard to the longitudinal or axial direction. It can be fixed to the housing by means of the interlock to prevent unintended dose setting and/or dose dispensing. 
     In a further example the injection device comprises a release member connected to one of the housing and the dose tracker. The release member is selectively engageable to the other one of the housing and the dose tracker in order to lock the dose tracker to the housing when in the zero dose positional state. The release member may be operable engaged or may be operable engageable with the interlock. The release member may be a component of the interlock. The release member may comprise a trigger or an actuator that can be actuated, i.e. depressed or dialed by a user in order to initiate an automated dose setting procedure. By means of the mutual interaction of the spring, the interlock and the at least one release member the process of dose setting can be facilitated. For setting of a dose a user only has to actuate or to depress the at least one release member so as to release the interlock. With a released interlock the dose tracker is released with regard to a longitudinal displacement. It is then free to be moved under the action of the relaxing spring. 
     The release member may comprise a first locking feature while the housing or the dose tracker may comprise a correspondingly shaped second locking feature to engage with the first locking feature of the release member. The first and second locking features may comprise or may form a positive engagement between the housing and the dose tracker. The release member may be directly attached or connected to one of the housing of the dose tracker. The release member may be also indirectly attached or connected to one of the housing and the dose tracker. The release member may be connected or integrally formed with a further component of the injection device that is operably engaged with one of the release member and the housing. 
     For releasing the dose tracker from the housing the release member is one of rotationally or longitudinally displaceable relative to the housing. The release member may be rotatable or pivotable or depressible relative to the housing with regard to the longitudinal axis, with regard to a radial direction or with regard to a tangential direction of the tubular shaped housing. 
     The release member is of particular benefit for such examples, wherein the dose tracker is automatically displaceable from the zero dose positional states to the maximum dose positional state. Here, the injection device may comprise a mechanical drive operable to displace the dose tracker from the zero dose positional state to the maximum dose positional state. Once released by the release member the dose tracker may travel or may be displaced automatically from the zero dose positional state to the maximum dose positional state under the effect of the mechanical drive. In this way a rather automated dose setting can be provided which is rather user-friendly and failure safe. 
     According to another example the release member comprises an annular ring rotationally supported at the proximal end of the housing. One of an inside surface of the annular ring and an outside surface of the dose tracker comprises at least one catch to engage with a protrusion of the other one of the inside surface of the annular ring or the outside surface of the dose tracker. For releasing the dose tracker from the housing the annular ring is intended to be rotated along a tangential or circumferential direction of the housing. In this way the at least one catch disengages from the at least one protrusion thereby liberating a displacement of the dose tracker relative to the housing. 
     In typical examples, the dose tracker is translationally supported relative to the housing. When released the dose tracker or a component connected therewith is slidably and/or rotationally displaceable from the zero dose positional state to the maximum dose positional state. 
     In another example the injection device comprises a spring having a first end operably connected to the housing and having a second end operably connected to the dose tracker for displacing the dose tracker from the zero dose positional state to the maximum dose positional state. The spring may serve and provide a mechanical drive for automatically displacing the dose tracker at least from the zero dose positional state to the maximum dose positional state. In this way the spring provides an automated dose setting as soon as a movement of the dose tracker relative to the housing is allowed or released by actuation of the release member. 
     The spring is implemented in an injection device. It provides a long-lasting, durable and failure safe mechanical drive to apply a driving force to the dose tracker during a dose setting procedure. During a dose dispensing procedure the dose tracker returns from the maximum dose positional state to the zero dose positional state. This displacement is typically conducted manually by a force exerted and provided by a user of the device. The displacement of the dose tracker from the maximum dose positional state to the zero dose positional state is to be conducted against the action of the spring. 
     In this way mechanical energy exerted to and provided to the dose tracker during dispensing of a dose is at least partially stored in the spring. For a subsequent dose setting procedure this mechanical energy may be release again. Insofar the injection device is configured for repeated use and hence for setting and dispensing of a multitude of doses of the medicament. 
     The first end of the spring may be directly connected to the housing or may be indirectly connected to the housing. The first end may be connected to a further component of the injection device, which further component is at least one of rotationally or translationally locked to the housing. In the same way also the second end of the spring may either be directly connected to the dose tracker or it may be connected to a component of the injection device that is at least one of translationally or rotationally locked to the dose tracker. 
     According to another example the spring comprises a cylindrically shaped torsion spring. The spring may enclose at least a portion of the dose tracker. Alternatively, the spring is arranged inside a hollow portion of the dose tracker. The torsion spring is configured to induce a torque to the dose tracker relative to the housing. A torsion spring is of particular benefit where the dose tracker is rotationally supported on the housing or wherein the dose tracker is threadedly engaged with the housing. 
     The first end of the torsion spring may be directly connected to the dose tracker while the second end of the torsion spring may be directly connected to the housing of the injection device. The first end of the torsion spring may be also connected to a further device component in a torque proof engagement with the dose tracker. Also, a second end of the torsion spring may be directly connected to a further device component in a torque proof engagement with the housing of the injection device. This provides an increased flexibility to integrate the torsion spring inside the housing and to integrate the torsion spring in a dose setting mechanism of the injection device. 
     According to a further example the dose tracker comprises a tracking sleeve that is threadedly engaged with the housing. The tracking sleeve may be cylindrically shaped. The tracking sleeve may be located inside the housing. When threadedly engaged with the housing the first end of the spring may be directly connected to the dose tracker whereas the second end of the spring may be directly connected to the housing. In this way and when released by actuation of the release member the dose tracker is free to rotate or to wound helically relative to the housing under the action of the spring. 
     In this way a fully automated dose setting procedure can be provided by the injection device. The end user does no longer have to take care about the dose setting process. He may only actuate the release member for that the dose setting mechanism automatically displaces the dose tracker into the maximum dose positional state. Selection or modification of the dose to be set is exclusively conducted by the preselector. The preselector remains fixed and stationary relative to the housing during dose setting as well as during dose dispensing. For setting and dispensing numerous doses of equal size the preselector may remain stationary relative to the housing. At least the preselector remains stationary with regard to a displacement direction along which the preselector has to be displaced for bringing the preselector from one preselection positional state to another preselection positional state. User interaction with the injection device may be limited to an actuation of the release member for setting of the dose and to the application of a driving force to a trigger or the like actuator of the injection device in order to trigger or to control a dose dispensing procedure. 
     In another example the tracking stop feature comprises a radial protrusion protruding from a sidewall of the dose tracker. Typically, the radial protrusion may protrude from an outside facing surface of the tracking sleeve. The radial protrusion of the tracking stop feature may comprise a radially outwardly extending protrusion when the tracking stop feature is provided on the dose tracker. When provided on the housing the radial protrusion of the tracking stop feature may comprise a radially inwardly extending protrusion. Generally, the radial protrusion may comprise a pin or a flange. 
     According to another example the preselector stop feature comprises a radial protrusion protruding from a sidewall of the preselector. The preselector may also comprise a sleeve like shape. The preselector stop feature may comprise a radially inwardly extending protrusion to engage with a radially outwardly extending protrusion of the tracking stop feature. Alternatively, the radial protrusion of the preselector stop feature may comprise a radially outwardly extending protrusion to engage with a radially inwardly extending protrusion of the tracking stop feature. 
     This applies in particular where the tracking stop feature is provided on the housing of the injection device. The radial protrusion of the preselector stop feature may comprise a pin or a flange. Typically, the at least one radial protrusion of the tracking stop feature and the at least one radial protrusion of the preselector stop feature are correspondingly or complementary shaped. They are arranged on a particular portion or section of the dose tracker or housing and the preselector such that upon reaching the maximum dose positional state the radial protrusions of the tracking stop feature and the preselector stop feature get in direct mechanical abutment thereby impeding any further displacement of the dose tracker relative to the housing in a dose incrementing direction. 
     According to another example one of the preselector stop feature and the tracking stop feature comprises at least a first groove and a second groove configured to slidably receive the radial protrusion of the other one of the preselector stop feature and the tracking stop feature. It is intended that a radial protrusion of one of the preselector stop feature and the tracking stop feature slides along only one of the first groove and the second groove of the other one of the preselector stop feature and the tracking stop feature. When the preselector is in a first of the two preselection positional state the radial protrusion slides along the first groove. When the preselector is in a second of the at least two preselection positional states the radial protrusion slides along the second groove. 
     The first and the second grooves comprise different shapes. In this way, the first and the second grooves enable and provide different relative displacement paths between the preselector and the dose tracker or the housing. Likewise, the differently shaped grooves provide different displacement path length of the dose tracker between the zero dose positional state of the maximum dose positional state relative to the preselector or relative to the housing, respectively. 
     In a further example the first groove extends parallel to the second groove. The second groove is longer than the first groove. The first groove and the second groove merge into a connecting groove. The connecting groove extends along a direction that is substantially parallel to that direction along which the preselector is displaceable between the first preselection positional state and the second preselection positional state. While in the zero dose positional state the protrusion of the tracking stop feature may be located in the connecting groove. A displacement of the preselector along the elongation of the connecting groove leads to a sliding motion of the protrusion along the connecting groove. 
     When reaching one of the at least two preselection positional state the protrusion is still in the connecting groove but is also aligned with one of the first groove and the second groove. When the preselector is in the first preselection positional state the protrusion is aligned with the first groove. When the preselector is arranged in the second preselection positional state the protrusion is aligned with the second groove. As soon a dose setting procedure is started the protrusion slides along the first groove or along the second groove depending on the preselection positional state of the preselector. 
     The first and the second groove comprise a stop for the protrusion at an end facing away from the connecting groove. Since the first and second grooves are of different length they provide different displacement paths for the radial protrusion sliding along the respective groove. In this way differently sized maximum dose positional states of the dose tracker can be provided. Once the radial protrusion reaches an end of a respective groove facing away from the connecting groove any further displacement of the dose tracker relative to the housing is effectively impeded. 
     According to another example the preselector is rotationally supported on the housing. Alternatively, the preselector is displaceable relative to the housing along a tangential or circumferential direction. The preselector may comprise a preselector sleeve. The preselector sleeve may be located at a proximal end of the housing. The preselector sleeve may be provided between a proximal portion of the dose tracker and a proximal end of the housing. The preselector may be located directly on or may be supported by the housing at a predefined distance from the proximal end of the housing. Here, the preselector may be located and arranged at a predefined distal offset from the proximal end of the housing. 
     In another example the preselector may be translationally fixed to the dose tracker but may be freely rotatable relative to the dose tracker. Here, the preselector may be in keyed engagement or may be splined to the housing, e.g. by way of one of the first and second grooves of the preselector stop feature engaged with the tracking stop feature. 
     Generally and in some examples the preselector is arrestable or fixable to the sidewall of the housing in at least two different discrete positions denoted as preselection positional states. The preselection positional states may be equidistantly arranged on the sidewall. A distance between neighboring preselection positional states is identical and corresponds to the longitudinal advancing motion of the dose tracker as the dose tracker may undergo a complete revolution relative to the housing. In this way it is guaranteed, that the tracking stop feature always exactly engages with the preselector stop feature when reaching the maximum dose positional state. 
     According to a further example the injection device comprises a trigger and a piston rod. The trigger is arranged at a proximal end of the dose tracker. The trigger may be effectively locked to the dose tracker in longitudinal direction. Hence, any displacement of the dose tracker in longitudinal direction is equally transferred to the trigger. For initiating or for triggering a dispensing procedure the trigger is depressible in a distal direction to induce a distally directed motion of the piston rod. The injection device may further comprise a dose dial that is also translationally fixed to the dose tracker. By means of the dose dial the dose setting may be conducted and/or controlled especially for injection devices that are void of a spring driven mechanical drive. 
     Typically, the injection device comprises at least one clutch by way of which the dose setting mechanism or drive mechanism can be switched between a dose setting mode and a dose dispensing mode. The clutch may be operable by a depression of the trigger relative to the housing and/or relative to the dose tracker. 
     In another example the injection device further comprises a cartridge. The cartridge comprises a barrel filled with the medicament. The barrel is sealed by a bung or piston that is axially displaceable relative to the barrel by means of the piston rod. For and during a dispensing operation the piston rod is operably engageable with the bung of the cartridge in order to displace the bung in a distal direction. Typically, a distal end of the cartridge is sealed by a pierceable membrane, such as a septum. For dispensing of the medicament the pierceable seal is penetrated by a double-tipped injection needle. A distally directed displacement of the bung induced by a correspondingly advancing piston rod therefore leads to the expelling of the dose of the medicament. 
     In the present context the term ‘distal’ or ‘distal end’ relates to an end of the injection device that faces towards an injection site of a person or of an animal. The term ‘proximal’ or ‘proximal end’ relates to an opposite end of the injection device, which is furthest away from an injection site of a person or of an animal. 
     The term “drug” or “medicament”, as used herein, means a pharmaceutical formulation containing at least one pharmaceutically active compound,
     wherein in one embodiment the pharmaceutically active compound has a molecular weight up to 1500 Da and/or is a peptide, a proteine, a polysaccharide, a vaccine, a DNA, a RNA, an enzyme, an antibody or a fragment thereof, a hormone or an oligonucleotide, or a mixture of the above-mentioned pharmaceutically active compound,   wherein in a further embodiment the pharmaceutically active compound is useful for the treatment and/or prophylaxis of diabetes mellitus or complications associated with diabetes mellitus such as diabetic retinopathy, thromboembolism disorders such as deep vein or pulmonary thromboembolism, acute coronary syndrome (ACS), angina, myocardial infarction, cancer, macular degeneration, inflammation, hay fever, atherosclerosis and/or rheumatoid arthritis,   wherein in a further embodiment the pharmaceutically active compound comprises at least one peptide for the treatment and/or prophylaxis of diabetes mellitus or complications associated with diabetes mellitus such as diabetic retinopathy,   wherein in a further embodiment the pharmaceutically active compound comprises at least one human insulin or a human insulin analogue or derivative, glucagon-like peptide (GLP-1) or an analogue or derivative thereof, or exendin-3 or exendin-4 or an analogue or derivative of exendin-3 or exendin-4.   

     Insulin analogues are for example Gly(A21), Arg(B31), Arg(B32) human insulin; Lys(B3), Glu(B29) human insulin; Lys(B28), Pro(B29) human insulin; Asp(B28) human insulin; human insulin, wherein proline in position B28 is replaced by Asp, Lys, Leu, Val or Ala and wherein in position B29 Lys may be replaced by Pro; Ala(B26) human insulin; Des(B28-B30) human insulin; Des(B27) human insulin and Des(B30) human insulin. 
     Insulin derivates 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-Y-glutamyl)-des(B30) human insulin; B29-N-(N-lithocholyl-Y-glutamyl)-des(B30) human insulin; B29-N-(ω-carboxyheptadecanoyl)-des(B30) human insulin and B29-N-(ω-carboxyheptadecanoyl) human insulin. 
     Exendin-4 for example means Exendin-4(1-39), a peptide of the sequence H-His-Gly-Glu-Gly-Thr-Phe-Thr-Ser-Asp-Leu-Ser-Lys-Gln-Met-Glu-Glu-Glu-Ala-Val-Arg-Leu-Phe-Ile-Glu-Trp-Leu-Lys-Asn-Gly-Gly-Pro-Ser-Ser-Gly-Ala-Pro-Pro-Pro-Ser-NH2. 
     Exendin-4 derivatives are for example selected from the following list of compounds:
     H-(Lys)4-des Pro36, des Pro37 Exendin-4(1-39)-NH2,   H-(Lys)5-des Pro36, des Pro37 Exendin-4(1-39)-NH2,   des Pro36 Exendin-4(1-39),   des Pro36 [Asp28] Exendin-4(1-39),   des Pro36 [IsoAsp28] Exendin-4(1-39),   des Pro36 [Met(O)14, Asp28] Exendin-4(1-39),   des Pro36 [Met(O)14, IsoAsp28] Exendin-4(1-39),   des Pro36 [Trp(O2)25, Asp28] Exendin-4(1-39),   des Pro36 [Trp(O2)25, IsoAsp28] Exendin-4(1-39),   des Pro36 [Met(O)14 Trp(O2)25, Asp28] Exendin-4(1-39),   des Pro36 [Met(O)14 Trp(O2)25, IsoAsp28] Exendin-4(1-39); or   des Pro36 [Asp28] Exendin-4(1-39),   des Pro36 [IsoAsp28] Exendin-4(1-39),   des Pro36 [Met(O)14, Asp28] Exendin-4(1-39),   des Pro36 [Met(O)14, IsoAsp28] Exendin-4(1-39),   des Pro36 [Trp(O2)25, Asp28] Exendin-4(1-39),   des Pro36 [Trp(O2)25, IsoAsp28] Exendin-4(1-39),   des Pro36 [Met(O)14 Trp(O2)25, Asp28] Exendin-4(1-39),   des Pro36 [Met(O)14 Trp(O2)25, IsoAsp28] Exendin-4(1-39),
 
wherein the group -Lys6-NH2 may be bound to the C-terminus of the Exendin-4 derivative;
 
or an Exendin-4 derivative of the sequence
   des Pro36 Exendin-4(1-39)-Lys6-NH2 (AVE0010),   H-(Lys)6-des Pro36 [Asp28] Exendin-4(1-39)-Lys6-NH2,   des Asp28 Pro36, Pro37, Pro38Exendin-4(1-39)-NH2,   H-(Lys)6-des Pro36, Pro38 [Asp28] Exendin-4(1-39)-NH2,   H-Asn-(Glu)5des Pro36, Pro37, Pro38 [Asp28] Exendin-4(1-39)-NH2,   des Pro36, Pro37, Pro38 [Asp28] Exendin-4(1-39)-(Lys)6-NH2,   H-(Lys)6-des Pro36, Pro37, Pro38 [Asp28] Exendin-4(1-39)-(Lys)6-NH2,   H-Asn-(Glu)5-des Pro36, Pro37, Pro38 [Asp28] Exendin-4(1-39)-(Lys)6-NH2,   H-(Lys)6-des Pro36 [Trp(O2)25, Asp28] Exendin-4(1-39)-Lys6-NH2,   H-des Asp28 Pro36, Pro37, Pro38 [Trp(O2)25] Exendin-4(1-39)-NH2,   H-(Lys)6-des Pro36, Pro37, Pro38 [Trp(O2)25, Asp28] Exendin-4(1-39)-NH2,   H-Asn-(Glu)5-des Pro36, Pro37, Pro38 [Trp(O2)25, Asp28] Exendin-4(1-39)-NH2,   des Pro36, Pro37, Pro38 [Trp(O2)25, Asp28] Exendin-4(1-39)-(Lys)6-NH2,   H-(Lys)6-des Pro36, Pro37, Pro38 [Trp(O2)25, Asp28] Exendin-4(1-39)-(Lys)6-NH2,   H-Asn-(Glu)5-des Pro36, Pro37, Pro38 [Trp(O2)25, Asp28] Exendin-4(1-39)-(Lys)6-NH2,   H-(Lys)6-des Pro36 [Met(O)14, Asp28] Exendin-4(1-39)-Lys6-NH2,   des Met(O)14 Asp28 Pro36, Pro37, Pro38 Exendin-4(1-39)-NH2,   H-(Lys)6-desPro36, Pro37, Pro38 [Met(O)14, Asp28] Exendin-4(1-39)-NH2,   H-Asn-(Glu)5-des Pro36, Pro37, Pro38 [Met(O)14, Asp28] Exendin-4(1-39)-NH2,   des Pro36, Pro37, Pro38 [Met(O)14, Asp28] Exendin-4(1-39)-(Lys)6-NH2,   H-(Lys)6-des Pro36, Pro37, Pro38 [Met(O)14, Asp28] Exendin-4(1-39)-(Lys)6-NH2,   H-Asn-(Glu)5 des Pro36, Pro37, Pro38 [Met(O)14, Asp28] Exendin-4(1-39)-(Lys)6-NH2,   H-Lys6-des Pro36 [Met(O)14, Trp(O2)25, Asp28] Exendin-4(1-39)-Lys6-NH2,   H-des Asp28 Pro36, Pro37, Pro38 [Met(O)14, Trp(O2)25] Exendin-4(1-39)-NH2,   H-(Lys)6-des Pro36, Pro37, Pro38 [Met(O)14, Asp28] Exendin-4(1-39)-NH2,   H-Asn-(Glu)5-des Pro36, Pro37, Pro38 [Met(O)14, Trp(O2)25, Asp28] Exendin-4(1-39)-NH2,   des Pro36, Pro37, Pro38 [Met(O)14, Trp(O2)25, Asp28] Exendin-4(1-39)-(Lys)6-NH2,   H-(Lys)6-des Pro36, Pro37, Pro38 [Met(O)14, Trp(O2)25, Asp28] Exendin-4(S1-39)-(Lys)6-NH2,   H-Asn-(Glu)5-des Pro36, Pro37, Pro38 [Met(O)14, Trp(O2)25, Asp28] Exendin-4(1-39)-(Lys)6-NH2;
 
or a pharmaceutically acceptable salt or solvate of any one of the afore-mentioned Exendin-4 derivative.
   

     Hormones are for example hypophysis hormones or hypothalamus hormones or regulatory active peptides and their antagonists as listed in Rote Liste, ed. 2008, Chapter 50, such as Gonadotropine (Follitropin, Lutropin, Choriongonadotropin, Menotropin), Somatropine (Somatropin), Desmopressin, Terlipressin, Gonadorelin, Triptorelin, Leuprorelin, Buserelin, Nafarelin, Goserelin. 
     A polysaccharide is for example a glucosaminoglycane, a hyaluronic acid, a heparin, a low molecular weight heparin or an ultra low molecular weight heparin or a derivative thereof, or a sulphated, e.g. a poly-sulphated form of the above-mentioned polysaccharides, and/or a pharmaceutically acceptable salt thereof. An example of a pharmaceutically acceptable salt of a poly-sulphated low molecular weight heparin is enoxaparin sodium. 
     Antibodies are globular plasma proteins (˜150 kDa) that are also known as immunoglobulins which share a basic structure. As they have sugar chains added to amino acid residues, they are glycoproteins. The basic functional unit of each antibody is an immunoglobulin (Ig) monomer (containing only one Ig unit); secreted antibodies can also be dimeric with two Ig units as with IgA, tetrameric with four Ig units like teleost fish IgM, or pentameric with five Ig units, like mammalian IgM. 
     The Ig monomer is a “Y”-shaped molecule that consists of four polypeptide chains; two identical heavy chains and two identical light chains connected by disulfide bonds between cysteine residues. Each heavy chain is about 440 amino acids long; each light chain is about 220 amino acids long. Heavy and light chains each contain intrachain disulfide bonds which stabilize their folding. Each chain is composed of structural domains called Ig domains. These domains contain about 70-110 amino acids and are classified into different categories (for example, variable or V, and constant or C) according to their size and function. They have a characteristic immunoglobulin fold in which two β sheets create a “sandwich” shape, held together by interactions between conserved cysteines and other charged amino acids. 
     There are five types of mammalian Ig heavy chain denoted by α, δ, ε, γ, and μ. The type of heavy chain present defines the isotype of antibody; these chains are found in IgA, IgD, IgE, IgG, and IgM antibodies, respectively. 
     Distinct heavy chains differ in size and composition; α and γ contain approximately 450 amino acids and δ approximately 500 amino acids, while μ and ε have approximately 550 amino acids. Each heavy chain has two regions, the constant region (C H ) and the variable region (V H ). In one species, the constant region is essentially identical in all antibodies of the same isotype, but differs in antibodies of different isotypes. Heavy chains γ, α and δ have a constant region composed of three tandem Ig domains, and a hinge region for added flexibility; heavy chains μ and ε have a constant region composed of four immunoglobulin domains. The variable region of the heavy chain differs in antibodies produced by different B cells, but is the same for all antibodies produced by a single B cell or B cell clone. The variable region of each heavy chain is approximately 110 amino acids long and is composed of a single Ig domain. 
     In mammals, there are two types of immunoglobulin light chain denoted by λ and κ. A light chain has two successive domains: one constant domain (CL) and one variable domain (VL). The approximate length of a light chain is 211 to 217 amino acids. Each antibody contains two light chains that are always identical; only one type of light chain, κ or λ, is present per antibody in mammals. 
     Although the general structure of all antibodies is very similar, the unique property of a given antibody is determined by the variable (V) regions, as detailed above. More specifically, variable loops, three each the light (VL) and three on the heavy (VH) chain, are responsible for binding to the antigen, i.e. for its antigen specificity. These loops are referred to as the Complementarity Determining Regions (CDRs). Because CDRs from both VH and VL domains contribute to the antigen-binding site, it is the combination of the heavy and the light chains, and not either alone, that determines the final antigen specificity. 
     An “antibody fragment” contains at least one antigen binding fragment as defined above, and exhibits essentially the same function and specificity as the complete antibody of which the fragment is derived from. Limited proteolytic digestion with papain cleaves the Ig prototype into three fragments. Two identical amino terminal fragments, each containing one entire L chain and about half an H chain, are the antigen binding fragments (Fab). The third fragment, similar in size but containing the carboxyl terminal half of both heavy chains with their interchain disulfide bond, is the crystalizable fragment (Fc). The Fc contains carbohydrates, complement-binding, and FcR-binding sites. Limited pepsin digestion yields a single F(ab′)2 fragment containing both Fab pieces and the hinge region, including the H—H interchain disulfide bond. F(ab′)2 is divalent for antigen binding. The disulfide bond of F(ab′)2 may be cleaved in order to obtain Fab′. Moreover, the variable regions of the heavy and light chains can be fused together to form a single chain variable fragment (scFv). 
     Pharmaceutically acceptable salts are for example acid addition salts and basic salts. Acid addition salts are e.g. HCl or HBr salts. Basic salts are e.g. salts having a cation selected from alkali or alkaline, e.g. Na+, or K+, or Ca2+, or an ammonium ion N+(R1)(R2)(R3)(R4), wherein R1 to R4 independently of each other mean: hydrogen, an optionally substituted C1-C6-alkyl group, an optionally substituted C2-C6-alkenyl group, an optionally substituted C6-C10-aryl group, or an optionally substituted C6-C10-heteroaryl group. Further examples of pharmaceutically acceptable salts are described in “Remington&#39;s Pharmaceutical Sciences” 17. ed. Alfonso R. Gennaro (Ed.), Mark Publishing Company, Easton, Pa., U.S.A., 1985 and in Encyclopedia of Pharmaceutical Technology. 
     Pharmaceutically acceptable solvates are for example hydrates. 
     It will be further apparent to those skilled in the art that various modifications and variations can be made to the present injection device without departing from the spirit and scope what is disclosed herein. Further, it is to be noted, that any reference numerals used in the appended claims are not to be construed as limiting the scope of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       In the following, embodiments of the drive mechanism and the injection device are described in detail by making reference to the drawings, in which: 
         FIG. 1  is illustrated of an example of an injection device, 
         FIG. 2  shows an exploded view of the components of the injection device, 
         FIG. 3  is an exemplary and simplified illustration of the injection device with the dose tracker in the zero dose positional state, 
         FIG. 4  is indicative of the device according to  FIG. 3  with the dose tracker in the maximum dose positional state, 
         FIG. 5  shows a longitudinal cross-section of some components of the injection device according to  FIG. 3 , 
         FIG. 6  shows a longitudinal cross-section of the device according to  FIG. 4 , 
         FIG. 6 a    shows a longitudinal cross-section of a modification of the device according to  FIG. 3 , 
         FIG. 6 b    shows a longitudinal cross-section of the device of  FIG. 6 a    with the clutch and the preselector shifted in distal direction, 
         FIG. 7  is illustrative of a longitudinal cross-section of another example of an injection device according to  FIG. 3 , 
         FIG. 8  shows the injection device of  FIG. 7  with the dose tracker in the maximum dose positional state, 
         FIG. 9  shows a further example of an injection device with the dose tracker in the zero dose positional state, 
         FIG. 10  shows the device according to  FIG. 9  with the dose tracker in the maximum dose positional state, 
         FIG. 11  is an exemplary illustration of another injection device with a preselector located on a housing of the injection device with the dose tracker in the zero dose positional state, 
         FIG. 12  shows the device according to  FIG. 11  with the dose tracker in the maximum dose positional state, 
         FIG. 13  is a longitudinal cross-section through a device highly similar to the device according to  FIG. 11 , 
         FIG. 14  shows the device of  FIG. 13  with the dose tracker in the maximum dose positional state, 
         FIG. 15  is a further illustration of an injection device, wherein the preselector is translationally locked to the dose tracker, 
         FIG. 16  shows the injection device according to  FIG. 15  with the dose tracker in the maximum dose positional state, 
         FIG. 17  shows a longitudinal cross-section through the device according to  FIG. 15 , 
         FIG. 18  shows a longitudinal cross-section of the device according to  FIG. 16 , 
         FIG. 19  is a perspective view of a further example of an injection device comprising a dose tracker and a preselector, 
         FIG. 20  shows the injection device according to  FIG. 19  with the dose tracker in the maximum dose positional state, 
         FIG. 21  shows the device according to  FIGS. 19 and 20  without the outer housing, 
         FIG. 22  shows the injection device according to  FIG. 21  with the preselector, 
         FIG. 23  is an isolated illustration of a release member, 
         FIG. 24  shows an interaction between the dose tracker and the release member before reaching the end of a dispensing procedure, 
         FIG. 25  is an illustration in accordance to  FIG. 24  with the dose tracker moved even closer to the zero dose positional state, 
         FIG. 26  shows the interaction of the release member and the dose tracker when reaching the zero dose positional state and 
         FIG. 27  shows the mutual interaction of the release member and the dose tracker  40  and the dose tracker in the zero dose positional state, 
         FIG. 28  is a longitudinal cross-section through the device according to  FIG. 19 , 
         FIG. 29  is illustrative of a further longitudinal cross-section through the device of  FIG. 19  rotated by 90° with regards to a longitudinal axis of the injection device, 
         FIG. 30  is exemplary of the interaction between an interlock and a release member in an initial configuration, 
         FIG. 31  shows the arrangement of  FIG. 30  with the interlock released, 
         FIG. 32  shows another example of an interaction between an interlock and a release member in an initial or interlocked configuration and 
         FIG. 33  shows the arrangement of  FIG. 32  with the interlock released. 
     
    
    
     DETAILED DESCRIPTION 
     The injection device  1  as shown in  FIGS. 1 and 2  is a pre-filled disposable injection device that comprises a housing  10  to which an injection needle  15  can be affixed. The injection needle  15  is protected by an inner needle cap  16  and either an outer needle cap  17  or a protective cap  18  that is configured to enclose and to protect a distal section of the housing  10  of the injection device  1 . The housing  10  may comprise and form a main housing part configured to accommodate a drive mechanism  8  as shown in  FIG. 2 . The injection device  1  may further comprise a distal housing component denoted as cartridge holder  14 . The cartridge holder  14  may be permanently or releasably connected to the main housing  10 . The cartridge holder  14  is typically configured to accommodate a cartridge  6  that is filled with a liquid medicament. The cartridge  6  comprises a cylindrically-shaped or tubular-shaped barrel  25  sealed in proximal direction  3  by means of a bung  7  located inside the barrel  25 . The bung  7  is displaceable relative to the barrel  25  of the cartridge  6  in a distal direction  2  by means of a piston rod  20 . A distal end of the cartridge  6  is sealed by a pierceable seal  26  configured as a septum and being pierceable by a proximally directed tipped end of the injection needle  15 . The cartridge holder  14  comprises a threaded socket  28  at its distal end to threadedly engage with a correspondingly threaded portion of the injection needle  15 . By attaching the injection needle  15  to the distal end of the cartridge holder  14  the seal  26  of the cartridge  6  is penetrated thereby establishing a fluid transferring access to the interior of the cartridge  6 . 
     When the injection device  1  is configured to administer e.g. human insulin, the dosage set by a dose dial  12  at a proximal end of the injection device  1  may be displayed in so-called international units (IU, wherein 1 IU is the biological equivalent of about 45.5 μg of pure crystalline insulin (1/22 mg). 
     As shown further in  FIGS. 1 and 2 , the housing  10  comprises a dosage window  13  that may be in the form of an aperture in the housing  10 . The dosage window  13  permits a user to view a limited portion of a number sleeve  80  that is configured to move when the dose dial  12 , e.g. in form of a dose dial button or dose dial sleeve is turned, to provide a visual indication of a currently set dose. The dose dial is rotated on a helical path with respect to the housing  10  when turned during setting and/or dispensing or expelling of a dose. 
     The injection device  1  may be configured so that turning the dosage knob  12  causes a mechanical click sound to provide acoustical feedback to a user. The number sleeve  80  mechanically interacts with a piston in the insulin cartridge  6 . When the needle  15  is stuck into a skin portion of a patient, and when the trigger  11  or injection button is pushed, the insulin dose displayed in display window  13  will be ejected from the injection device  1 . When the needle  15  of the injection device  1  remains for a certain time in the skin portion after the trigger  11  is pushed, a high percentage of the dose is actually injected into the patient&#39;s body. Ejection of a dose of the medicament may also cause a mechanical click sound, which is however different from the sounds produced when using the dose dial  12 . 
     In this embodiment, during delivery of the insulin dose, the dose dial  12  is turned to its initial position in an axial movement, that is to say without rotation, while the number sleeve  80  is rotated to return to its initial position, e.g. to display a dose of zero units. 
     The injection device  1  may be used for several injection processes until either the cartridge  6  is empty or the expiration date of the medicament in the injection device  1  (e.g. 28 days after the first use) is reached. 
     Furthermore, before using injection device  1  for the first time, it may be necessary to perform a so-called “prime shot” to remove air from the cartridge  6  and the needle  15 , for instance by selecting two units of the medicament and pressing trigger  11  while holding the injection device  1  with the needle  15  upwards. For simplicity of presentation, in the following, it will be assumed that the ejected amounts substantially correspond to the injected doses, so that, for instance the amount of medicament ejected from the injection device  1  is equal to the dose received by the user. 
     The expelling or drive mechanism  8  as illustrated in more detail in  FIG. 2  comprises numerous mechanically interacting components. A flange like support of the housing  10  comprises a threaded axial through opening threadedly engaged with a first thread or distal thread  22  of the piston rod  20 . The distal end of the piston rod  20  comprises a bearing  21  on which a pressure foot  23  is free to rotate with the longitudinal axis of the piston rod  20  as an axis of rotation. The pressure foot  23  is configured to axially abut against a proximally facing thrust receiving face of the bung  7  of the cartridge  6 . During a dispensing action the piston rod  20  rotates relative to the housing  10  thereby experiencing a distally directed advancing motion relative to the housing  10  and hence relative to the barrel  25  of the cartridge  6 . As a consequence, the bung  7  of the cartridge  6  is displaced in distal direction  2  by a well-defined distance due to the threaded engagement of the piston rod  20  with the housing  10 . 
     The piston rod  20  is further provided with a second thread  24  at its proximal end. The distal thread  22  and the proximal thread  24  are oppositely handed. 
     There is further provided a drive sleeve  30  having a hollow interior to receive the piston rod  20 . The drive sleeve  30  comprises an inner thread threadedly engaged with the proximal thread  24  of the piston rod  20 . Moreover, the drive sleeve  30  comprises an outer threaded section  31  at its distal end. The threaded section  31  is axially confined between a distal flange portion  32  and another flange portion  33  located at a predefined axial distance from the distal flange portion  32 . Between the two flange portions  32 ,  33  there is provided a last dose limiter  35  in form of a semi-circular nut having an internal thread mating the threaded section  31  of the drive sleeve  30 . 
     The last dose limiter  35  further comprises a radial recess or protrusion at its outer circumference to engage with a complementary-shaped recess or protrusion at an inside of the sidewall of the housing  10 . In this way the last dose limiter  35  is splined to the housing  10 . A rotation of the drive sleeve  30  in a dose incrementing direction  4  or clockwise direction during consecutive dose setting procedures leads to an accumulative axial displacement of the last dose limiter  35  relative to the drive sleeve  30 . There is further provided an annular spring  40  that is in axial abutment with a proximally facing surface of the flange portion  33 . Moreover, there is provided a tubular-shaped clutch  60 . At a first end the clutch  60  is provided with a series of circumferentially directed saw teeth. Towards a second opposite end of the clutch  60  there is located a radially inwardly directed flange. The clutch  60  may comprise a clutch sleeve. 
     Furthermore, there is provided a dose dial sleeve also denoted as a number sleeve  80 . The number sleeve  80  is provided outside of the spring  40  and the clutch  60  and is located radially inward of the housing  10 . A helical groove  81  is provided about an outer surface of the number sleeve  80 . The housing  10  is provided with the dosage window  13  through which a part of the outer surface of the number  80  can be seen. The housing  10  is further provided with a protrusion  63  or helical rib at an inside sidewall portion of an insert piece  62 , and the helical rib is to be seated in the helical groove  81  of the number sleeve  80 . The tubular shaped insert piece  62  is inserted into the proximal end of the housing  10 . It is rotationally and axially fixed to the housing  10 . There may be provided first and second stops on the housing  10  to limit a dose setting procedure during which the number sleeve  80  is rotated in a helical motion relative to the housing  10 . As will be explained below in greater detail, at least one of the stops is provided by a preselector stop feature  71  provided on a preselector  70 . 
     The dose dial  12  in form of a dose dial grip is disposed about an outer surface of the proximal end of the number sleeve  80 . An outer diameter of the dose dial  12  typically corresponds to and matches with the outer diameter of the housing  10 . The dose dial  12  is secured to the number  80  to prevent relative movement therebetween. The dose dial  12  is provided with a central opening. 
     The trigger  11 , also denoted as dose button is substantially T-shaped. It is provided at a proximal end of the injection device  10 . A stem  64  of the trigger  11  extends through the opening in the dose dial  12 , through an inner diameter of extensions of the drive sleeve  30  and into a receiving recess at the proximal end of the piston rod  20 . The stem  64  is retained for limited axial movement in the drive sleeve  30  and against rotation with respect thereto. A head of the trigger  11  is generally circular. The trigger side wall or skirt extends from a periphery of the head and is further adapted to be seated in a proximally accessible annular recess of the dose dial  12 . 
     To set or to dial a dose a user rotates the dose dial  12 . With the spring  40  also acting as a clicker and the clutch  60  engaged, the drive sleeve  30 , the spring or clicker  40 , the clutch  60  and the number sleeve  80  rotate with the dose dial  12 . Audible and tactile feedback of the dose being dialed is provided by the spring  40  and by the clutch  60 . Torque is transmitted through saw teeth between the spring  40  and the clutch  60 . The helical groove  81  on the number sleeve  80  and a helical groove in the drive sleeve  30  have the same lead. This allows the number sleeve  80  to extend from the housing  10  and the drive sleeve  30  to climb the piston rod  20  at the same rate. At a limit of travel a radial stop on the number sleeve  80  engages either with a first stop or a second stop provided on the housing  10  provided on the preselector  70  to prevent further movement in a dose incrementing direction  4 . A rotation of the piston rod  20  is prevented due to the opposing directions of the overall and driven threads on the piston rod  20 . 
     The last dose limiter  35  keyed to the housing  10  is advanced along the threaded section  31  by the rotation of the drive sleeve  30 . When a final dose dispensed position is reached, a radial stop formed on a surface of the last dose limiter  35  abuts a radial stop on the flange portion  33  of the drive sleeve  30 , preventing both, the last dose limiter  35  and the drive sleeve  30  from rotating further. 
     Should a user inadvertently dial beyond the desired dosage, the injection device  1 , configured as a pen-injector allows the dosage to be dialed down without dispense of the medicament from the cartridge  6 . For this the dose dial  12  is simply counter-rotated, in the dose decrementing direction  5 . This causes the system to act in reverse. A flexible arm of the spring or clicker  40  then acts as a ratchet preventing the spring  40  from rotating. The torque transmitted through the clutch  60  causes the saw teeth to ride over one another to create the clicks corresponding to dialed dose reduction. Typically, the saw teeth are so disposed that a circumferential extent of each saw tooth corresponds to a unit dose. 
     When the desired dose has been dialed the user may simply dispense the set dose by depressing the trigger  11 . This displaces the clutch  60  axially with respect to the number sleeve  80  causing dog teeth thereof to disengage. However, the clutch  60  remains keyed in rotation to the drive sleeve  30 . The number sleeve  80  and the dose dial  12  are now free to rotate in accordance with the helical groove  81 . 
     The axial movement deforms the flexible arm of the spring  40  to ensure the saw teeth cannot be overhauled during dispense. This prevents the drive sleeve  30  from rotating with respect to the housing  10  though it is still free to move axially with respect thereto. The deformation is subsequently used to urge the spring  40  and the clutch  60  back along the drive sleeve  30  to restore the connection between the clutch  60  and the number sleeve  80  when the distally directed dispensing pressure is removed from the trigger  11 . 
     The longitudinal axial movement of the drive sleeve  30  causes the piston rod  20  to rotate through the through opening of the support of the housing  10 , thereby to advance the bung  7  in the cartridge  6 . Once the dialed dose has been dispensed, the number sleeve  80  is prevented from further rotation by contact of at least one stop extending from the dose dial  12  with at least one corresponding stop of the housing  10 . A zero dose position may be determined by the abutment of one of axially extending edges or stops of the number sleeve  80  with at least one or several corresponding stops of the housing  10 . 
     The expelling mechanism or drive mechanism  8  as described above is only exemplary for one of a plurality of differently configured drive mechanisms that are generally implementable in a disposable pen-injector. The drive mechanism as described above is explained in more detail e.g. in WO2004/078239A1, WO 2004/078240A1 or WO 2004/078241A1 the entirety of which being incorporated herein by reference. 
     Compared to the injection device as described in any one of the documents WO2004/078239A1, WO 2004/078240A1 or WO 2004/078241A1 the injection device according to  FIGS. 1 and 2  is further provided with the preselector  70 . The preselector  70  is displaceable relative to the housing  10  between at least two preselection positional states in order to define a maximum 54 dose positional state of the dose tracker  50 . In the example of  FIG. 2  the dose tracker  50  may comprise a number sleeve  80  having a helical groove  81  that is in threaded engagement with the housing  10  or with the insert  62  that is fixed to the housing  10 . 
     On an outside surface of the number sleeve  80  there may be provided consecutive numbers that show up in the dosage window  13 . Selection and indication of visualization of a dose is modified with the various examples of an injection device as described hereinafter with regards to  FIGS. 3 to 29 . With the various examples as illustrated in  FIGS. 3 to 29  the number sleeve  80  provided by the dose tracker  50  is displaceable in unison with a trigger  11  relative to the housing  10  for setting as well as for dispensing of the dose of the medicament. 
     In the example of  FIGS. 3 to 6  there is provided a preselector  70  that is displaceable relative to the housing  10  between at least two preselection positional states  72  and  74 . Each preselection positional state  72 ,  74  defines a maximum dose positional state  54  for the dose tracker  50 . In the present example the preselector  70  comprises a preselector sleeve that is rotationally fixed to the tubular shaped housing  10 . 
     As shown in  FIGS. 3 to 6  the preselector  70  is provided and rotationally supported at a proximal end  42  of the housing  10 . It may be rotationally supported on a side wall  48  of the housing  10 . For selecting at least one of two available preselection positional states  72 ,  74  the preselector  70  is rotatable with regard to a rotation axis extending parallel to the longitudinal axis of the housing  10 . The preselector  70  is lockable or fixable relative to the housing  10  in any one of the at least two preselection positional states  72 ,  74 . In this way and when the preselector  70  is in a first preselection positional state the preselector is hindered and impeded against self actuated displacement relative to the housing. 
     The preselector  70  comprises a preselector stop feature  71 . The preselector stop feature  71  as illustrated in  FIG. 5  comprises a first groove  101  and a second groove  102 . The grooves  101 ,  102  are provided on an inside facing surface of the sleeve of the preselector  70 . The dose tracker  50  comprises a tracking stop feature  51 . The tracking stop feature comprises a radial protrusion  56  protruding radially outwardly from an outside surface of the dose tracker  50 . Here, the dose tracker  50  comprises a tracking sleeve  55  that is rotationally and translationally supported inside the elongated housing  10 . 
     Typically, the dose tracker  50  is in threaded engagement with the housing  10 . As illustrated in  FIG. 5  and when in the zero dose positional state the tracking stop feature  51  is located inside a connecting groove  104  interconnecting the first groove  101  and the second groove  102 . One end, e.g. a first end of the first groove  101  merges into the connecting groove  104 . A first end of the second groove  102  also merges into the connecting groove  104 . The connecting groove  104  extends at a predefined angle relative to the elongation of the first groove  101  and the second groove  102 . Typically, first and second grooves  101 ,  100  extend parallel to each other. As illustrated, the second groove  102  comprises a larger extension compared to the first groove  101 . There is also provided a third groove  103 . Also the third groove  103  extends parallel to the first groove  101  and to the second groove  102 . The third groove  103  comprises an elongation that is larger than the elongation of the second groove  102 . As shown further, the second groove  102  is located between the first groove  101  and the third groove  103 . 
     The connecting groove  104  comprises an elongation that aligns with and/or coincides with a direction of displacement of the preselector  70  when the preselector is displaced between the at least two preselection positional states  72 ,  74 . For transferring and displacing the preselector  70  from the first preselection positional state  72  as illustrated in  FIG. 3  to the second preselection positional state  74  as illustrated in  FIG. 4  the preselector  70  is rotatable relative to the housing  10 , e.g. in a counterclockwise direction. Accordingly, the connecting groove  104  extends in circumferential or tangential direction with regards to the tubular shaped housing  10  or with regards to the tubular shaped preselector  70 . 
     As further illustrated in  FIGS. 3 and 4 , the housing  10 , in particular the sidewall  48  thereof is provided with a preselection indication  43 . The preselection indication  43  comprises numerous numbers or symbols arranged along a displacement path of the preselector  70 . The preselector  70  comprises a correspondingly shaped preselection indication  75 , e.g. in form of an arrow. In each one of the provided preselection positional states  72 ,  74  the preselection indication  75  of the preselector  70  aligns with one of the preselection indications  43  of the housing  10 . 
     In an alternative implementation, the preselection indication  43  comprises a pointer or an arrow and wherein the preselection indication  75  comprises numerous numbers or symbols arranged along a displacement path of the preselector  70 . The preselection indication  75  aligning with a preselection indication  43  indicates to the user, which one of the preselection positional states  72 ,  74  is actually valid for the injection device. In the present example there may be provided three or even four preselection positional states. In a first preselection positional state the tracking stop feature  51  is in alignment with the first groove  101 . In a second preselection positional state the tracking stop member  51  is in alignment with the second groove  102 . 
     Optionally, there is provided a release member  90  that is connected to one of the housing  10  and the dose tracker  50 . It is selectively engageable to the other one of the housing  10  and the dose tracker  50  in order to lock the dose tracker  50  to the housing  10  when in the zero dose positional state  52  as illustrated in  FIG. 5 . In the present example there is further provided a mechanical energy reservoir in form of a spring  44 . The spring  44  comprises a first end  45  connected to the housing  10  and the spring  44  comprises a second end  46  connected to the dose tracker  50 . If the release member  90  is actuated in order to liberate or to release the dose tracker  50  the dose tracker  50  starts to rotate relative to the housing  10  under the action of the relaxing spring  44 . 
     As illustrated the spring  44  comprises a cylindrically wound torsion spring  47 . The spring  44  encloses at least a portion of an outside surface of the tracking sleeve  55  of the dose tracker  50 . In this way and when released the spring  44  is configured to induce a torque to the dose tracker  50 . 
     In the given preselection positional state  72 ,  74  the preselector  70  is rotationally fixed to the housing  10 . Here, the engagement of the tracking stop feature  51  with one of the grooves  101 ,  102 ,  103  provides a threaded engagement between the dose tracker  50  and the housing  10 . Since the preselector  70  is translationally or axially fixed to the housing  10  the dose tracker  50  is subject to a proximally directed displacement such that a proximal end  53  of the dose tracker protrudes from a proximal end of the preselector  70  and/or from a proximal end  42  of the housing  10  when reaching the maximum dose positional state  54  as illustrated in  FIG. 6 . 
     The amount of displacement or the length of a displacement path of the dose tracker  50  relative to the housing  10  is indicative and is directly correlated to the size of a dose actually set. The grooves  101 ,  102 ,  103  each comprise a second end facing away from the connecting groove  104 . The second end of the grooves  101 ,  102 ,  103  provides an end stop for the tracking stop feature  51 . Once the tracking stop feature  51 , presently in form of a radially outwardly extending protrusion  56 , reaches the second end of the second groove  102  as illustrated in  FIG. 6 or 8  further displacement of the dose tracker  50 ,  150  in a dose incrementing direction relative to the preselector  70  and/or relative to the housing  10  is effectively impeded and blocked. 
     Once the maximum dose positional state  54  has reached the injection device  1  is prepared and ready for a dose dispensing procedure. For this, a user has to depress the trigger  11  in distal direction as described above with regard to  FIGS. 1 and 2 . During a dispensing procedure the dose tracker  50  returns into the zero dose positional state  52 . It rotates in a dose decrementing direction  5  relative to the housing  1  in accordance and along the helical path provided by the respective grooves  101 ,  102  or  103 . When reaching the zero dose positional state  52  as illustrated in  FIGS. 3 and 5  the release member  90  reengages and positionally fixes the dose tracker  50  to the housing  10 . Thereafter, the preselector  70  may be transferred to another preselection positional state in order to vary the size of the dose if required. Otherwise, the preselector  70  remains in the present preselection positional state. A repeated release of the release member  90  will lead to another automated displacement of the dose tracker  50  from the zero dose positional state  52  to the maximum dose positional state  54 . Accordingly, another dispensing procedure may take place. 
     The implementation of the spring  44  and the automated displacement of the preselector  50  from the zero dose positional state  52  to the maximum dose positional state  54  is only optional. Alternatively and when the injection device  1  is void of such a driving spring  44  the displacement of the dose tracker  50  from the zero dose positional state  52  to the maximum dose positional state  54  is governed and conducted by manually rotating the dose dial  12  in the dose incrementing direction  4 , e.g. clockwise to the housing  10 . 
     In the example of  FIGS. 3 to 6  the dose tracker  50  may also comprise not only one but even two or more radially outwardly extending protrusion  56  that are arranged circumferentially offset, e.g. at 180°. Accordingly the preselector  70  may comprise a respective amount of grooves, e.g.  6  grooves altogether. Here, two diametrically oppositely located protrusions  56  of the dose tracker  50  may be always and simultaneously in engagement with two oppositely located grooves of the preselector  70 . 
     In the example of  FIGS. 3 to 6  the dose tracker  50  may be in threaded engagement with the housing  10  only via the tracking stop feature  51  sliding along the preselector stop feature  71  of the preselector  70 . It is generally conceivable, that the insert  62  as described in connection with  FIGS. 1 and 2  is replaced by the preselector  70 . In this way, only minor modifications have to be implemented in the injection device  1  as described in any of the documents WO2004/078239A1, WO 2004/078240A1 or WO 2004/078241A1 in order to implement a preselection of only a limited number of different dose sizes. 
     In  FIGS. 6 a  and 6 b    a modification of the device as illustrated in  FIGS. 3-6  is illustrated. Here, the injection device is equipped with a supplemental clutch  66  having a recess  67  to engage with the protrusion  56  and hence with the tracking stop feature  51  of the dose tracker  50 . The supplemental clutch  66  may comprise a clutch sleeve. The supplemental clutch  66  may comprise a tubular shaped body with a tubular-shaped sidewall  68 . The clutch  66  is attached to the housing  10 . It may be located on an outside surface of the housing  10 . It may be displaceable in longitudinal direction relative to the housing  10 . The clutch  66  is rotationally fixed to the housing  10 . The clutch  66  may be in a splined engagement with the housing  10 . Hence, the clutch  66  is hindered to rotate relative to the housing  10 . The clutch  66  may be in a longitudinally sliding and rotation inhibiting engagement with the housing  10 . 
     In the zero dose positional state  52  of the dose tracker  50  as illustrated in  FIG. 6 a    the tracking stop feature  51  of the dose tracker  50  and hence the protrusion  56  is located inside the recess  67  of the clutch  66 . The recess  67  comprises a tangential or circumferential width that substantially matches with the respective size or width of the protrusion  56 . The width or size of the recess  67  may be slightly larger than the size of the protrusion so as to enable a smooth insertion of the protrusion  56  into the recess  67 . The recess  67  is open towards the proximal direction  3 . 
     The clutch  66  is axially displaceable in distal direction  2  against the action of a spring  65 . One end of the spring  65  is engaged with the clutch  66  and the opposite end of the spring  65  is engaged with the housing  10 . The spring  65  may comprise a compression spring. It may be configured to urge or to drive the clutch  66  in and towards the proximal direction  3 . As long as the protrusion  56  is located inside the recess  67  the mutual engagement of the protrusion  56  and the recess  67  hinders the dose tracker  50  from rotating under the action of the spring  44 . 
     The position of the recess  67  matches and overlaps with the position of the protrusion  56  as the dose tracker  50  is in the zero dose positional state  52 . By depressing the clutch  66  in distal direction the recess  67  is moved in distal direction accordingly. As a consequence, the protrusion  56  is no longer retained inside the recess  67  and the dose tracker  50  becomes free to rotate under the action of the spring  44 . 
     The preselector  70  is axially engaged with the clutch  66 . It is fixed to the clutch  66  in axial or longitudinal direction. Any movement of the clutch  66  in longitudinal or axial direction equally transfers to a respective movement of the preselector  70 . The preselector  70  is rotatable relative to the clutch  66 . In any of its rotational states, the preselector  70  is rotationally fixable to the clutch and hence to the housing  10 . The preselector  70  may be in a kind of a snap-fit engagement or ratchet engagement with the housing  10  or with the clutch  66 . This allows and supports a dedicated rotation of the preselector  70  with the longitudinal axis of the injection device as an axis of rotation, so as to bring one of the groves  101 ,  102 ,  103  in axial or longitudinal alignment with the tracking stop feature  51  as the tracking stop feature is in the zero dose positional state. The rotation of the preselector  70  relative to the housing  10  and/or relative to the clutch  66  may be accompanied by an audible click sound or haptic feedback. 
     When in the zero dose positional state  52  the preselector  70  is rotatable relative to the housing  10  as well as relative to the clutch  66  in order to preselect a dose of a particular size. For instance and as illustrated in  FIG. 6 a    the second groove  102 , in particular the distal end of that groove  102 , is brought in longitudinal alignment with the recess  67  and hence with the protrusion  56  or tracking stop feature  51  located therein. 
     Since the preselector  70  is axially connected to the clutch  66 , a distally directed displacement of the clutch  66  equally transfers to a respective distally directed displacement of the preselector  70 ; and vice versa. As a consequence, the tracking stop feature  51  and hence the protrusion  56  slides out of the recess  67  and enters the preselector stop feature  71 , i.e. the groove  102 . Through this axial displacement of the preselector  70  relative to the housing  10  the protrusion  56  enters the groove  102 . The protrusion  56  is then allowed to slide along the helical path provided by the groove  102 . In this way the entire dose tracker  50  becomes subject to a proximally directed screwing motion relative to the housing  10  as it is free to rotate under the action of the spring  44  as described above in connection with  FIGS. 3-6 . 
     At the end of a dose delivery procedure during which the dose tracker  50  is moved in distal direction  2  and during which the dose tracker  50  returns into the zero dose positional state  52  the tracking stop feature  51  and hence the protrusion  56  re-enters the recess  67 . As the dose dispensing or injection procedure terminates the mutual engagement of the tracking stop feature  51  or protrusion  56  with the recess  67  hinders the dose tracker  50  from rotating. 
     In the example of  FIGS. 6 a  and 6 b    the release member  90  may be replaced by the clutch  66 . Here, the clutch  66  may provide both, an interlock  184  as well as a release member  90 . In the proximal position as indicated in  FIG. 6 a    the clutch  66  provides an interlock  184  configured to prevent a rotation of the dose tracker  50  relative to the housing  10 . In the distal position as indicated in  FIG. 6 b    the clutch  66  provides a release member  90  disengaging the interlock  184 , thus allowing and supporting a rotation of the dose tracker  50  relative to the housing  10 . 
     The clutch  66  as illustrated in  FIGS. 6 a  and 6 b    may be integrally formed with the clutch  60  as illustrated in  FIG. 2 . The clutch  66  may be a portion of the clutch  60 . In further examples the clutch  66  and the clutch  60  may be separate parts. 
     In  FIGS. 7 and 8  another example of an injection device  1  is illustrated. Identical or components compared to the example of  FIGS. 3 to 6  are denoted with identical reference numbers. Similar components compared to the example of  FIGS. 3 to 6  are denoted with respective reference numbers that are increased by 100. 
     In comparison to the example of  FIGS. 5 and 6  the example of  FIGS. 7 and 8  comprises an insert  62  that is fixed to the housing  10 . The insert  62  is typically fixed to a sidewall  48  of the housing  10 . The insert  62  is a threaded insert. The insert  62  comprises a radially inwardly extending protrusion  63 . The protrusion  63  may comprise a helical shape. It may be in threaded engagement with an outer thread or with a helical groove  81  on the outside surface of the dose tracker  150 . Also here the preselector  170  is of sleeve-like shape. It is rotationally supported at or near a proximal end of the housing  10 . The preselector  170  comprises a preselector stop feature  171 . The dose tracker  150  comprises a correspondingly shaped tracking stop feature  151 . Compared to the example of  FIGS. 5 and 6  it is the tracking stop feature  151  that comprises a first groove  101 , a second groove  102 , a third groove  103  and a connecting groove  104 . The preselector stop feature  171  comprises a radial protrusion  176 . 
     The radial protrusion  176  may protrude radially inwardly from the sleeve-shaped preselector  170 . The radial protrusion  176  is in sliding engagement with one of the grooves  101 ,  102 ,  103 ,  104 . As the dose tracker  150  is subject to a rotation due to the threaded engagement with the insert  62  the radial protrusion  176  slides along the elongation of one of the grooves  101 ,  102 ,  103 . Also here, the dose tracker  150  may comprise two or even more preselector stop features  171 , e.g. in form of two or even more radial protrusions  176  that are simultaneously engaged with a corresponding number of grooves. 
     In the zero dose positional state  52  as illustrated in  FIG. 7  the preselector stop feature  171  is slidably engaged with the connecting groove  104 . A rotation of the preselector  170  relative to the housing  10  provides an alignment of the preselector stop feature  171  with one of the grooves  101 ,  102 ,  103 . After a release of the dose tracker  50  by actuating the release member  90  the dose tracker  50  starts to rotate according to the threaded engagement with the insert  62  relative to the housing  10  and hence relative to the preselector  170 , which is rotationally fixed to the housing  10  in the respective preselection positional state. 
     As illustrated in  FIG. 8  the preselector stop feature  171 , in particular a radially inwardly extending protrusion  176  as provided on an inside facing sidewall of the sleeve-shaped preselector  170  slides along the groove  102  until it reaches a second end of the groove providing a stop for the preselector stop feature  71 . In this maximum dose positional state  54  any further proximally directed displacement of the dose tracker  50  is blocked through the mutual engagement of the protrusion  176  with the second end of the groove  102 . The mode of operation of the device according to  FIGS. 7 and 8  is comparable if not identical to the mode of operation as described in connection with the device according to  FIGS. 3 to 6 . 
     The further example of  FIGS. 9 and 10  is somehow similar to the example as described in connection with  FIGS. 7 and 8 . Also here, the dose tracker  250  comprises a tracking stop feature  251 . The dose tracker  250  comprises a tracking sleeve  255  that is in threaded engagement with the insert  62 . Also here, the preselector  270  is of sleeve-like shape. It is also longitudinally or axially fixed to the housing  10 , in particular to a sidewall  48  thereof. The preselector  270  is displaceable supported on the housing  10  or relative to the housing between at least two preselection positional states  72 ,  74 . 
     The preselector  270  comprises a preselector stop feature  271 , which is implemented as a radial protrusion  276  protruding radially inwardly from a sidewall of the preselector  270 . The correspondingly shaped tracking stop feature  251  of the dose tracker  250  is provided on an outside surface portion of the tracking sleeve  255 . The tracking stop feature  251  comprises a radially outwardly extending protrusion  256 . For setting of a dose and for transferring the dose tracker  250  from the zero dose positional state  52  to the maximum dose positional state  54  the dose tracker  250  rotates in accordance to the threaded engagement with the housing  10 . 
     The preselection positional state of the preselector  270 , hence the orientation of the preselector  270  with regard to a rotation axis thereof defines the positional state, hence the longitudinal position and/or an orientation of the dose tracker  250  relative to the housing  10  at least when the tracking stop feature  251  abuts with the preselector stop feature  271 . As illustrated in  FIGS. 9 and 10  the preselector  270  may comprise numerous preselector stop features  271 ,  272  and  273 . The various preselector stop features  271 ,  272 ,  273  all comprise a radially inwardly extending protrusion  276 . The various preselector stop features  271 ,  272 ,  273  are located at predefined positions at an inside facing sidewall portion of the preselector  270 . 
     The preselector stop features  271 ,  272 ,  273  are located at predefined and different axial and/or longitudinal positions along the elongation or along the inner circumference of the preselector  270 . The preselector stop features  271 ,  272 ,  273  may each comprise a flange protruding radially inwardly from the sidewall of the preselector  270 . The tangential or circumferential extension of the flange may be larger than the tangential or circumferential extent of the correspondingly shaped tracking stop feature  251 . The tangential or circumferential extension of the preselector stop features  271 ,  272 ,  273  is shorter than 180°, shorter than 90° or shorter than 45° with respect to the inner circumference of the preselector  270 . 
     In this way and depending on the rotational state of the preselector  270  the tracking stop feature  251  may pass by at least one of the preselector stop features  273  and  272  on its way towards the maximum dose positional state  54 . When reaching the maximum dose positional state  54  the tracking stop feature  251  axially and/or tangentially engages with the correspondingly shaped and preselector stop feature  271 . 
     In a further example as illustrated in  FIGS. 11 to 14  the preselector  370  is located and arranged at a predefined distance from the proximal end  42  of the housing  10 . As illustrated in  FIG. 13  the preselector  370  is located distally offset from a proximal end  42  of the housing  10 . Apart from that the mechanical interaction between the preselector  370  and the dose tracker  350  is substantially identical as described in connection with  FIGS. 9 and 10 . Also here, the dose tracker  350  comprises a tracking sleeve  355  that is in threaded engagement with the insert  62  and/or with the housing  10 . At or near a proximal end  53  of the dose tracker  350  there is located a dose dial  12  as well as a trigger  11  as described before in connection with  FIG. 1  or  FIG. 2 . The cross-section according to  FIGS. 13 and 14  does not exactly match with the perspective illustration of  FIGS. 11 and 12 . In  FIGS. 13 and 14  the preselector  370  is positioned distally offset from the illustration of  FIGS. 11 and 12 . However, the working principle of the device of  FIGS. 11 and 12  is schematically apparent from the cross-sections of  FIGS. 13 and 14 . 
     The example of an injection device of  FIGS. 11 to 14  is void of a spring  44  configured for automatically displacing the dose tracker  350  from the zero dose positional state  52  towards the maximum dose positional state  54 . For displacing the dose tracker  350  from the zero dose positional state  52  towards the maximum dose positional state  54  a user has to grip the dose dial  12  and to rotate the dose dial  12  along a dose incrementing direction as described above. The device according to  FIGS. 11 to 14  may be also equipped with a spring  44  as described above. 
     Also here and as described in connection with  FIGS. 9 and 10  the dose tracker  350  comprises a tracking stop feature  351  implemented as a protrusion  356  protruding radially outwardly from an outside surface portion of the tracking sleeve  355 . The preselector  370  comprises a sleeve like shape. It is located on an outside surface of the sidewall  48  of the housing  10 . 
     Alternatively, the preselector  370  could be located inside the housing  10 . It could be rotationally displaceable in an intermediate space formed between an inside facing surface of the sidewall  48  and an outside facing surface of the dose tracker  350 . The preselector  370  comprises at least one preselector stop feature  371 . In the illustrated example the preselector  370  comprises numerous preselector stop features  371 ,  372 ,  373 . The preselector stop features  371 ,  372 ,  373  each comprise a radially inwardly extending protrusion  376  in form of a pin or flange. The protrusions  376  may extend through correspondingly-shaped through openings in the sidewall  48  of the housing  10 . In another but not illustrated example the protrusion  376  are located entirely inside the housing  10 . The preselector  370  may be accessible from outside the housing  10  through a recess or a through opening provided in the sidewall  48 . 
     As already described above the preselector  370  is fixable to the housing  10  or to the sidewall  48  in any of the available preselection positional states. The protrusions  376  comprise a radially inwardly extending pin or a flange having a predefined extension in circumferential or tangential direction, e.g. as described in connection with  FIGS. 9 and 10 , so as to axially and/or tangentially engage with the correspondingly shaped protrusion  356  of the tracking stop feature  351  when the maximum dose positional state  54  of the dose tracker  350  has been reached. 
     With the further example according to  FIGS. 15-18  the preselector  470  is permanently translationally fixed to the dose tracker  450 . The preselector  470  is rotatable relative to the dose tracker  450 . As already described above in connection with  FIGS. 7-14  the dose tracker  450  is threadedly engaged with the housing  10 , e.g. via the threaded insert  62 . Also here, a spring  44  in form of a torsion spring  47  is provided in order to provide an automated displacement of the dose tracker  450  from the zero dose positional state  52  towards the maximum dose positional state  54 . 
     In the zero dose positional state the dose tracker  450  is positionally locked to the housing  10  by means of the release member  90 . In the illustrated example the preselector  470  comprises a sleeve having an inside facing surface that faces towards the outside facing surface of the sidewall  48  of the housing  10 . Hence, the preselector  470  comprises a cup-shaped receptacle to receive a proximal end  42  of the housing  10 . Other configurations are also conceivable, wherein at least a distal end of the preselector  470  is insertable into the sleeve-shaped housing  10 . 
     In the example as shown in  FIGS. 17 and 18  the preselector stop feature  471  provided on the preselector  470  comprises a radially inwardly extending protrusion  476  to engage with the tracking stop feature  451 . In contrast to the examples as described above the tracking stop feature  451  is provided on the sidewall  48  of the housing  10 . The tracking stop feature  151  comprises a first groove  101 , a second groove  102  and a third groove  103 . All three grooves  101 ,  102 ,  103  merge into a connecting groove  104  with a first end. The grooves  101 ,  102 ,  104  comprise different elongations. The grooves  101 ,  102 ,  103  extend parallel to each other. The second ends of the grooves  101 ,  102 ,  103  are located at a longitudinal offset relative to each other. 
     In this way the elongation of the groove  101 ,  102 ,  103  define the maximum dose positional states  54  of the dose tracker  450 . The tracking stop feature  451  is provided on or in an outside facing surface portion of the sidewall of the housing  10 . The preselector stop feature  471  protruding radially inwardly from an inside facing section of the sidewall of the preselector  470  is in permanent engagement with at least one of the grooves  101 ,  102 ,  103 ,  104 . In the zero dose positional state  52  as illustrated in  FIG. 17  the preselector stop feature  471 , hence the radial protrusion  476 , is located inside the connecting groove  104 . By rotating the preselector  470  relative to the housing  10  the preselector stop feature  471  can be aligned with one of the grooves  101 ,  102 ,  103 . Thereafter and upon releasing of the dose tracker for  450  by actuation of the release member  90  the spring  44  induces a rotation of the dose tracker  450 , which according to the threaded engagement with the housing  10  is subject to a helical motion relative to the housing  10 . 
     The grooves  101 ,  102 ,  103  extend parallel to the elongation of the housing  10 . They extend e.g. perpendicular to the elongation of the connecting groove  104 . Since the preselector  470  is freely rotatable relative to the dose tracker  450  but remains axially and longitudinally locked and constrained to the dose tracker  450  the preselector stop feature  471  starts to slide along the selected grooves  103  in the example of  FIG. 18  as soon as the dose tracker is subject to a longitudinal movement relative to the housing  10 . 
     The engagement of the preselector stop feature  471  with the groove  103  also prevents a rotation of the preselector  470  relative to the housing  10  during a dose setting motion of the dose tracker  450 . When reaching the maximum dose positional state  54 , the preselector stop feature  470  gets in abutment with the second end of the groove  103  by way of which a further proximally directed displacement of the preselector  470  is impeded. Due to the permanent longitudinal interlock or engagement between the preselector  470  and the dose tracker  450  any further rotation of the dose tracker  450  is impeded and prevented. 
     Since the dose tracker  450  is threadedly engaged with the housing  10  any further rotation thereof would require a further displacement in longitudinal direction relative to the housing  10 . This is effectively blocked an impeded when the dose tracker  450  is in the maximum dose positional state  54 . In the maximum dose positional state  54  as illustrated in  FIG. 18  the trigger  11  can be depressed in order to induce a dose dispensing procedure as described above. 
     Generally, the preselector may be fixed in the preselection positional states at discrete positions relative to the housing or relative to the dose tracker. The supported preselection states may correspond to consecutive and complete revolutions of the dose tracker. Alternatively or additionally it is also conceivable that the dose tracker comprises two or even three tracking stop features to engage with the preselector stop feature. Alternatively, also the preselector may comprise two or more preselector stop features to engage with the tracking stop feature. In this way the maximum dose positional state could be assigned with every half or every third revolution of the dose tracker relative to the housing. Furthermore it is conceivable, that two or more tracking stop features simultaneously engage with correspondingly shaped two or more preselector stop features. In this way the mechanical interaction and robustness of the abutment between the dose tracker and the preselector can be enhanced and increased. 
     In the further example of an injection device according to  FIG. 19  to  FIG. 29  the injection device  1  as illustrated in  FIG. 1  and  FIG. 2  serves as a basis. The injection device as shown in  FIG. 19  comprises some additional features as will be explained below in order to provide an enhanced functionality of the injection device  1  as described above. 
     As illustrated, there is provided an outer housing  100  encapsulating or accommodating the entirety of the housing  10  of the injection device  1 . On the outside of the housing  10  there is provided the dose tracker  550 . The dose tracker  550  as illustrated in  FIG. 22  comprises two components, namely a distal part  552  and a proximal part  553 . The distal part  552  and the proximal part  553  may be provided as a single-pieced or as an integrally shaped dose tracker  550 . Only for reasons of assembly of the injection device  1  the dose tracker  550  is separated into two separate components. 
     The distal part  552  and the proximal part  553  are permanently and rigidly connected to each other. They are locked with regards to the longitudinal direction (z) as well as with regard to a rotation relative to the housing  10 . A longitudinal displacement or rotational displacement of one of the distal part  552  and the proximal part  553  equally transfers to the other one of the distal part  552  at the proximal part  553 . 
     In the present example the distal part  552  comprises at least one or more elongated ribs  557  extending in longitudinal direction. The ribs  557  provide a keyed and longitudinally sliding engagement with the outer housing  100 . The outer housing  100  may comprise a correspondingly shaped longitudinal groove  107  in which the rib or ribs  557  are slidably guided. The dose tracker  550  is rotationally locked to the outer housing  100  but is translationally displaceable relative to the housing  100  in longitudinal or axial direction (z). The dose tracker  550  also comprises a tracking sleeve  555  and a tracking stop feature  551 . 
     As further illustrated in  FIG. 22  there is provided a preselector  570  with a preselector stop feature  571 . The preselector  570  comprises a sleeve rotatably supported on an outside facing surface of the dose tracker  550 . Typically, the distal part  552  and the proximal part  553  of the dose tracking sleeve are of tubular shape. As illustrated in  FIGS. 22, 28 and 29  a proximal portion of the distal part  552  is received in a receptacle at a distal portion of the proximal part  553 . In the overlapping region the distal part  552  of the proximal part  553  are mutually engaged and permanently interlocked. 
     The preselector  570  comprises an annular ring or a sleeve with a preselector stop feature  571 . As illustrated in  FIG. 22  the preselector stop feature  571  comprises numerous axial recesses in a proximal side of the preselector  570 . The recesses may form slots of different axial length or of different elongation. The preselector stop feature  571  comprises a first recess  501  and a second recess  502 . The recesses  501 ,  502  comprise different elongations in longitudinal direction as illustrated in  FIG. 22 . Both recesses  501 ,  502  are open towards the distal end and hence towards the tracking stop feature  551 . The recesses  501 ,  502  are located tangentially or circumferentially adjacent and next to each other. 
     Depending on the rotational position of the preselector  570  either the first recess  501  or the second recess  502  longitudinally aligns with the tracking stop feature  551 . Since the dose tracker  550  and hence the tracking stop feature  551  thereof can only slide in longitudinal or axial direction relative to the housing and since the preselector  570  is axially or longitudinally fixed to the outer housing  100  the distance between the tracking stop feature  551  and a proximal end of the recesses  501 ,  502  defines a maximum displacement path for the dose tracker  550  for setting of a dose. Depending on the rotational state, hence depending on the preselection positional state of the preselector  570  the maximum displacement path for the dose tracker  550  can be modified on demand. 
     The recesses or slots are configured to receive and to engage the tracking stop feature  551  protruding from an outside surface of the tracking sleeve  555 . In the present example the tracking stop feature  551  comprises a radially outwardly extending protrusion  556  integrally formed with the distal part  552  and protruding radially outwardly through a correspondingly shaped recess at a sidewall of the proximal part  553 . It may likewise be integrally formed with the proximal part  553 . 
     The radial extension of the protrusion  556  matches with the radial extension or radial position of the preselector stop feature  571 . The preselector  570  is rotatable between at least two preselection positional states as described above. In any of the preselection positional states the preselector  570  is rotationally locked to the outer housing  100 . The preselector  570  is also permanently longitudinally locked to the outer housing  110 . For instance, a proximal end  572  or edge of the preselector  570  may be in axial abutment with the outer housing  100  or with another component of the injection device, e.g. with the release member  590  that is axially fixed to the housing  100 . In this way the preselector  570  is locked to the outer housing  100  with regard to the longitudinal or axial direction. 
     The preselector  570  may be further provided with a locking feature  575  extending through a recess or a through opening of the preselector  570 . The locking feature  575  may comprise a spring biased actuator that is depressible in radial direction for temporarily releasing the preselector from the outer housing  100 . The locking feature  575  may comprise a screw or the like fastening element that requires a correspondingly shaped tool for temporarily releasing the locking feature  575  and hence the preselector  570  from the outer housing  100  in order to enable a sliding motion or rotation of the preselector  570  relative to the outer housing  100 . Depending on the selected preselection positional state of the preselector  570  a maximum dose positional state for the dose tracker  550  can be defined. 
     If the preselector  570  is in a first preselection positional state  74 , in which the first recess  501  is longitudinally aligned with the tracking stop feature  551  the maximum distance the dose tracker  550  is longitudinally displaceable relative to the outer housing  100  is shorter compared to a configuration in which the preselector is in the second preselection positional state, in which the second recess  502  is longitudinally aligned with the tracking stop feature  551 . 
     As further illustrated in  FIG. 22  there are provided numerous preselection indications  576  on an outside surface portion of the preselector  570 . One preselection indication  576  always aligns with a preselection window  130  provided in the outer housing  100 . As illustrated in  FIGS. 19 and 28  number  20  shows up in the preselection window  113  indicating to the user that a preselection of 20 units of the medicament has been pre-selected. Dialing or displacing the preselector e.g. with the second recess  502  in alignment with the tracking stop feature  551  may reveal a larger number, e.g. number  30  in the preselection window  113 . 
     The interaction between the release member  590  and the dose tracker  550  is illustrated in connection with  FIG. 23  to  FIG. 27 . The release member  590  comprises an annular ring  591  comprising numerous catches  592  at an inside facing portion thereof as illustrated in  FIG. 23 . The release member  590  comprises an annular groove  593  near a proximal end of the annular ring  591 . The groove  593  is positively engaged with a radially inwardly extending fastener  114  at the outer housing  100  as illustrated in  FIG. 29 . In this way the release member  590  is freely rotatable relative to the outer housing  100  but is permanently locked to the outer housing  100  in longitudinal direction. 
     In the sequence of  FIGS. 24 to 27  only the catches  592  and the proximal portion of the annular ring  591  are illustrated. An outer section of the annular ring  591  is cut away or faded away for illustration purpose in order to reveal the mutual engagement of the various catches  592  with radially outwardly extending protrusions  562  provided on an outside surface portion of the dose tracker  550 . As illustrated, the protrusions  562  are of a pin-shaped structure. They extend radially outwardly near a proximal end of the proximal part  553 . The catches  592  and the protrusions  562  are regularly and equidistantly arranged along the outer circumference of the dose tracker  550  and along the inner circumference of the annular ring  591 , respectively. 
     The catches  592  extend at a predefined angle relative to the longitudinal direction. Each catch  592  comprises a rather straight shaped beveled section  594  extending in distal direction into a curved section  595 . The curved section  595  extends from the beveled section  594  into the undercut section  596 . The curved section  595  may even overlap with the undercut section  596 . A free end of the undercut section  596  is located at a predefined tangential or circumferential distance from the beveled section  594 . As the protrusion  562  is displaced in distal direction relative to the release member  590  it gets in contact with the beveled section  594  and slides along the beveled section  594  until it reaches the curved section  595  as illustrated by a comparison of  FIG. 25  and  FIG. 26 . 
     The curved section  595  is shaped and describes at least half of a circle or three-quarter of a circle. It describes a circumference of a circle of about 270°. A bottom of the curved section  595  forms the distal end of the catch  592 . Due to the curved section  595  the button thereof is in longitudinal overlapping configuration with the undercut section  596 . As the protrusion  562  is displaced in distal direction and returned towards the zero dose positional state  50  the release member  590  is subject to a rotation in accordance to the extension and slope of the beveled section  594  and the curved section  595 , respectively. As the protrusion  562  reaches the bottom of the curved section  595  it has tangentially entered a free space between the undercut section  596  and the curved section  595 . 
     Releasing of the trigger  511  in the configuration as shown in  FIG. 26  may enable a small spring driven proximally directed displacement of the dose tracker  550 . But then the protrusion  562  gets in abutment with the undercut section  596 , thereby impeding any further displacement of the dose tracker  550  relative to the release member  590  and hence relative to the outer housing  100  in proximal direction. 
     For release of the dose tracker  550  the release member  590  has to be rotated in a clockwise direction. In this way, the undercut section  596  induces a slight but distinct initial distal displacement of the dose tracker  550  before the protrusion  562  enters a free space between the undercut section  596  and the beveled section  594  of the catch  592 . Due to the regular arrangement of a plurality of catches  592  and protrusions  562  the protrusions  562  and catches  592  mutually engage and disengage simultaneously. Once the protrusions  562  have disengaged from the catches  592  the dose tracker  550  is free to slide in proximal direction relative to the outer housing  100 . 
     The annular ring  591  and hence the release member  590  may be also spring biased, e.g. by a further torsion spring not further illustrated here. In this way, the release member  590  can be kept in an interlocked configuration as shown in  FIG. 27 . A releasing motion of the release member  590  may have to be conducted against the action of such a return spring. 
     As illustrated in  FIG. 21  in connection with  FIG. 28  or  FIG. 29  there is also provided a spring  44  implemented as a torsion spring  47 . The spring  44  has a first end  45  permanently connected to the dose tracker  550 , in particular to the distal part  552 . Since the dose tracker  550  is rotationally fixed to the outer housing  100  the first end  45  of the spring  44  is effectively connected to the outer housing  100  and hence to the housing  10 . In other words the first end  45  of the spring  44  is indirectly connected or coupled to the housing  10 . 
     The opposite second end  46  of the spring  44  is connected to the dose dial  12  or to a separate sleeve-shaped fastener  116  as for instance illustrated in  FIG. 21 . The fastener  116  is annular shaped and comprises a ring structure. The fastener  116  is permanently locked or attached to the dose dial  12  provided at the proximal end of the injection device. The fastener  116  may be adhesively attached to the dose dial  12 . The second end  46  of the spring  44  is connected to the fastener  116  in a torque prove way. Liberating the dose setting mechanism, e.g. by actuating the release member  590  enables a rotation of the number sleeve  80  and the rotation of the dose dial  12  will stop. As illustrated further the fastener  116  comprises a rim  117  and a recessed portion  118  on the outside surface of the fastener  116 . The rim  117  extends into the recessed portion  118  via a radial step  119  or shoulder. 
     As illustrated in  FIG. 28  the dose tracker  550 , in particular the proximal part  553  comprises a radially inwardly extending ledge or rim  558  that is in axial abutment with the step  119 . Insofar the rim  117  is in axial abutment with the rim  558 . As the spring  44  induces a dose incrementing rotation of the fastener  116  and hence of the dose dial  12  the number sleeve  80  starts to rotate relative to the inner housing  10 . Due to the threaded engagement between the insert  62  and the number sleeve  80  the number sleeve  80  and hence the dose dial  12  as well as the fastener  116  become subject to a proximally directed displacement relative to the outer housing  100 . This proximal displacement of the fastener  116  is equally transferred to the dose tracker  550  due to the mutual axial abutment and engagement between the rim  117  and the rim  558 . 
     A spring driven rotation of the number sleeve  80  therefore transfers to a longitudinal sliding and proximal displacement of the dose tracker  550  until the tracking stop feature  551  thereof engages with the preselector stop feature  571 . As illustrated in  FIGS. 28 and 29  there is provided a separate trigger  511  that covers the trigger  11  of the injection device  1 . The trigger  511  is provided and configured to cover the trigger  11 . The trigger  511  comprises a larger cross-section compared to the cross-section of the trigger  11 . The trigger  511  may be adhesively attached to the trigger  11 . The trigger  511  is configured to cover a proximal end of the outer housing  100 . 
     In  FIGS. 30 and 31  a more detailed exemplary implementation of an interlock  184  and a release member  190  is illustrated. Here, the interlock  184  comprises a first locking feature provided on the dose tracker  150  and further comprises a second locking feature provided on the release member  190 . The first locking feature is presently implemented as a catch  157  protruding radially outwardly from the dose tracker  150 . The catch  157  may be integrally formed with the dose tracker  150 . The release member  190  comprises a correspondingly shaped catch  197  protruding radially inwardly from the release member  190 . The catch  197  may be also integrally formed with the release member  190 . 
     The release member  190  is configured as a pivotable lever  191 . The lever  191  is pivotally supported on a pivot axis  192 . The pivot axis extends in tangential or circumferential direction with regard to the overall geometry of the housing  10 . The lever  191  may flush with the outside surface of the sidewall of the housing  10  in the initial configuration i as shown in  FIG. 30 . 
     The lever  191  comprises the catch  197  and a depressible end portion at an opposite end. The depressible end portion and the catch  197  are provided on opposite ends of the lever  191 . By depressing the depressible end radially inwardly the opposite end and hence the catch  197  is raised or lifted radially outwardly thus disengaging from the catch  157  of the dose tracker  150  as illustrated in  FIG. 31 . The release member  190  may be further provided with a return spring, presently not illustrated. The return spring may be arranged at the pivot axis  192  in order to return the release member  190  into the initial configuration as shown in  FIG. 48 , in which the catch  197  of the release member  190  is in axial abutment and in engagement with the correspondingly shaped catch  157  of the dose tracker  150 . 
     The catch  157  comprises an axial abutment face facing in proximal direction. The catch  197  comprises a correspondingly shaped axial abutment surface facing in distal direction. In the initial configuration as illustrated in  FIG. 30  the two abutment faces are in axial abutment thus inhibiting a proximally directed displacement of the dose tracker  150 . 
     In one embodiment the release member  190  may comprise a radially outwardly bulged portion  193  that is configured to become depressed by the user of the device. The radially raised or bulged portion  193  slightly protrudes from the outside surface of the sidewall of the housing  10 . Insofar it provides a haptic feedback to the user that this respective bulged portion  193  is configured for a radially inwardly directed depression. Once the user depresses the bulged portion  193  the oppositely located end section of the lever  191  is raised so that the mutually corresponding abutment faces  157 ,  197  get out of engagement. As the dose tracker  150  and hence the interlock  184  is liberated, the dose tracker  150  is free to rotate or to move proximally in longitudinal direction under the effect of the spring  44  as described above, e.g. in connection with  FIGS. 3 to 6 . 
     The catch  157  further comprises a beveled section  158 . The catch  197  also comprises a correspondingly shaped beveled section  198 . The beveled section  158  of the dose tracker  150  faces in distal direction  2  whereas the beveled section  198  of the release member  190  faces in proximal direction  3 . During dose delivery the dose tracker  150  is subject to a distally directed displacement, hence to the left in  FIGS. 30 and 31 . As the catch  157  approaches the initial configuration or initial axial position as indicated in  FIG. 30 , the beveled section  158  slides along the beveled section  198 . Such a sliding motion is accompanied by the release member  190  becoming lifted radially outwardly so that the outermost and inner most radial tips of the catches  157 ,  197  mutually pass by until the axial abutment faces  157 ,  197  return into an engagement configuration as shown in  FIG. 30 . 
     If the release member  190  or its lever  191  biased by a spring, the catch  197  is raised or lifted radially outwardly against the action of the respective spring. As soon as the abutment faces  197 ,  157  get in alignment the lever  191  snaps into the initial configuration i as illustrated in  FIG. 30  under the action of the spring. 
     In  FIGS. 32 and 33  a further conceivable implementation of an interlock  284  and a release member  290  is illustrated. Here, the dose tracker  250  comprises an elastic portion  256 . The elastic portion  256  may axially protrude from the dose tracker  250 . Alternatively, it may be integrated into the sidewall of the dose tracker  250 . It may be separated from a sidewall of the dose tracker along a u-shaped slit. Here, the dose tracker  250  comprises a catch  257  correspondingly shaped with a catch  297  provided at an inside facing portion of the sidewall of the housing  10 . The catch  257  comprises an axial abutment face as described above that faces in proximal direction  3 . The correspondingly shaped catch  297  of the housing  10  comprises a distally facing abutment face to engage with or to abut with the abutment face  257 . 
     The catch  257  and the catch  297  both comprise a beveled section  258 ,  298  that enable and induce a slight radially inwardly directed elastic deformation of the elastic portion  256  as the dose tracker  250  returns into the initial configuration as illustrated in  FIG. 32 . 
     The interlock  284  is formed by the mutually corresponding catches  257 ,  297  of the dose tracker  250  and the housing  10 . In order to release the interlock  284  there is provided a release member  290  in form of a depressible button  291 . The release member  290  comprises a somewhat planar-shaped or slightly bulged button  291  integrally formed with a longitudinally extending stem  292 . The stem  292  extends radially inwardly and intersect a recess or through opening in the sidewall of the housing  10 . The button  291  slightly protrudes from the outside surface of the sidewall of the housing  10 . It is radially displaceably supported on the housing  10  against the action of a spring  295 . The spring  295  is located in a recess  293  on the outside surface of the sidewall. The recess  293  comprises a bottom  294  that is recessed compared to the outside surface of the sidewall. The bottom  294  provides a support for the spring  295 . An opposite end of the spring  295  is in abutment with an underside of the button  291 . 
     An inner free end  299  of the stem  292  protrudes radially inwardly from an inside surface of the sidewall. The free end  299  is provided with lateral protrusions  296  that are separated by distance that is larger than the inner diameter of the recess of the sidewall through which the stem  292  extends. In this way, the stem  292  and the entire button  291  is hindered from getting pushed out of the housing  10  under the action of the spring  295 . 
     In an initial configuration as illustrated in  FIG. 32  the free end  299  of the stem  292  axially overlaps with the elastic portion  256  of the dose tracker  250 . By depressing the release member  290  and hence the button  291  radially inwardly, the stem  292  advances downward in the illustration of  FIG. 32  and  FIG. 33 . Since the free end  299  is in abutment with an outside surface portion of the elastic portion  256  such a depression leads to a local and radially inwardly directed deformation of the elastic portion  256 . The elastic deformation is large enough to bring the catches  297 ,  298  out of engagement so as to liberate a proximally directed displacement of the dose tracker  250 . 
     The examples of  FIGS. 30 to 33  are only exemplary for an interlock and a release member  190 ,  290  and can be generally implemented with any of the examples as illustrated in  FIG. 1  to  FIG. 29 . 
     
       
         
           
               
             
               
                   
               
               
                 List of reference numbers 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
            
               
                 1 
                 injection device 
               
               
                 2 
                 distal direction 
               
               
                 3 
                 proximal direction 
               
               
                 4 
                 dose incrementing direction 
               
               
                 5 
                 dose decrementing direction 
               
               
                 6 
                 cartridge 
               
               
                 7 
                 bung 
               
               
                 8 
                 drive mechanism 
               
               
                 9 
                 dose setting mechanism 
               
               
                 10 
                 housing 
               
               
                 11 
                 trigger 
               
               
                 12 
                 dose dial 
               
               
                 13 
                 dosage window 
               
               
                 14 
                 cartridge holder 
               
               
                 15 
                 injection needle 
               
               
                 16 
                 inner needle cap 
               
               
                 17 
                 outer needle cap 
               
               
                 18 
                 protective cap 
               
               
                 20 
                 piston rod 
               
               
                 21 
                 bearing 
               
               
                 22 
                 first thread 
               
               
                 23 
                 pressure foot 
               
               
                 24 
                 second thread 
               
               
                 25 
                 barrel 
               
               
                 26 
                 seal 
               
               
                 28 
                 threaded socket 
               
               
                 30 
                 drive sleeve 
               
               
                 31 
                 threaded section 
               
               
                 32 
                 flange 
               
               
                 33 
                 flange 
               
               
                 35 
                 last dose limiter 
               
               
                 36 
                 shoulder 
               
               
                 40 
                 spring 
               
               
                 41 
                 distal end 
               
               
                 42 
                 proximal end 
               
               
                 43 
                 preselection indication 
               
               
                 44 
                 spring 
               
               
                 45 
                 first end 
               
               
                 46 
                 second end 
               
               
                 47 
                 torsion spring 
               
               
                 48 
                 sidewall 
               
               
                 50 
                 dose tracker 
               
               
                 51 
                 tracking stop feature 
               
               
                 52 
                 zero dose positional state 
               
               
                 53 
                 proximal end 
               
               
                 54 
                 maximum dose positional state 
               
               
                 55 
                 tracking sleeve 
               
               
                 56 
                 protrusion 
               
               
                 60 
                 clutch 
               
               
                 62 
                 insert 
               
               
                 63 
                 protrusion 
               
               
                 64 
                 stem 
               
               
                 65 
                 spring 
               
               
                 66 
                 clutch 
               
               
                 67 
                 recess 
               
               
                 68 
                 sidewall 
               
               
                 70 
                 preselector 
               
               
                 71 
                 preselector stop feature 
               
               
                 72 
                 preselection positional state 
               
               
                 74 
                 preselection positional state 
               
               
                 75 
                 preselection indication 
               
               
                 80 
                 number sleeve 
               
               
                 81 
                 groove 
               
               
                 90 
                 release member 
               
               
                 100 
                 outer housing 
               
               
                 101 
                 groove 
               
               
                 102 
                 groove 
               
               
                 103 
                 groove 
               
               
                 104 
                 connecting groove 
               
               
                 107 
                 groove 
               
               
                 113 
                 preselection window 
               
               
                 114 
                 fastener 
               
               
                 116 
                 fastener 
               
               
                 117 
                 rim 
               
               
                 118 
                 recessed portion 
               
               
                 119 
                 step 
               
               
                 150 
                 dose tracker 
               
               
                 151 
                 tracking stop feature 
               
               
                 155 
                 tracking sleeve 
               
               
                 157 
                 catch 
               
               
                 158 
                 catch 
               
               
                 170 
                 preselector 
               
               
                 171 
                 preselector stop feature 
               
               
                 176 
                 protrusion 
               
               
                 184 
                 interlock 
               
               
                 190 
                 release member 
               
               
                 191 
                 lever 
               
               
                 192 
                 pivot axis 
               
               
                 193 
                 bulged portion 
               
               
                 197 
                 catch 
               
               
                 198 
                 catch 
               
               
                 250 
                 dose tracker 
               
               
                 251 
                 tracking stop feature 
               
               
                 255 
                 tracking sleeve 
               
               
                 256 
                 protrusion 
               
               
                 257 
                 catch 
               
               
                 258 
                 catch 
               
               
                 270 
                 preselector 
               
               
                 271 
                 preselector stop feature 
               
               
                 272 
                 preselector stop feature 
               
               
                 273 
                 preselector stop feature 
               
               
                 276 
                 protrusion 
               
               
                 284 
                 interlock 
               
               
                 290 
                 release member 
               
               
                 291 
                 button 
               
               
                 292 
                 stem 
               
               
                 293 
                 recess 
               
               
                 294 
                 bottom 
               
               
                 295 
                 spring 
               
               
                 296 
                 protrusion 
               
               
                 297 
                 catch 
               
               
                 298 
                 catch 
               
               
                 299 
                 free end 
               
               
                 350 
                 dose tracker 
               
               
                 351 
                 tracking stop feature 
               
               
                 355 
                 tracking sleeve 
               
               
                 356 
                 protrusion 
               
               
                 370 
                 preselector 
               
               
                 371 
                 preselector stop feature 
               
               
                 372 
                 preselector stop feature 
               
               
                 373 
                 preselector stop feature 
               
               
                 376 
                 protrusion 
               
               
                 450 
                 dose tracker 
               
               
                 451 
                 tracking stop feature 
               
               
                 455 
                 tracking sleeve 
               
               
                 470 
                 preselector 
               
               
                 471 
                 preselector stop feature 
               
               
                 476 
                 protrusion 
               
               
                 501 
                 recess 
               
               
                 502 
                 recess 
               
               
                 550 
                 dose tracker 
               
               
                 551 
                 tracking stop feature 
               
               
                 552 
                 distal part 
               
               
                 553 
                 proximal part 
               
               
                 555 
                 tracking sleeve 
               
               
                 556 
                 protrusion 
               
               
                 557 
                 rib 
               
               
                 558 
                 rim 
               
               
                 562 
                 protrusion 
               
               
                 570 
                 preselector 
               
               
                 571 
                 preselector stop feature 
               
               
                 572 
                 proximal end 
               
               
                 575 
                 locking feature 
               
               
                 576 
                 preselection indication 
               
               
                 590 
                 release member 
               
               
                 591 
                 annular ring 
               
               
                 592 
                 catch 
               
               
                 593 
                 groove 
               
               
                 594 
                 beveled section 
               
               
                 595 
                 curved section 
               
               
                 596 
                 undercut section