Abstract:
A dose setting mechanism for a medicament delivery device is presented having a locking feature that reliably and consistently unlocks a dose injection button and concurrently a lead screw when the dose setting mechanism is transitioned from a non-activated state to an activated state. This locking feature uses dose member assembly having a rotational biasing element combined with concentric inner and outer sleeves interfacing with a locking member.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation-in-part of of U.S. patent application Ser. No. 14/449,671, filed Aug. 1, 2014, which is a continuation of U.S. patent application Ser. No. 13/896,639, filed May 17, 2013, now U.S. Pat. No. 8,827,962, which is a continuation of U.S. patent application Ser. No. 13/203,040, filed Jan. 31, 2012, now U.S. Pat. No. 8,491,536, which is a U.S. National Phase Application pursuant to 35 U.S.C. §371 of International Application No. PCT/US2010/060022 filed Dec. 13, 2010, which claims priority to Swedish Patent Application No. 0950958-9 filed on Dec. 15, 2009. The entire disclosure contents of these applications are herewith incorporated by reference into the present application. 
    
    
     TECHNICAL AREA 
     The present invention relates to a medicament delivery device comprising a dose setting function. 
     BACKGROUND 
     Medicament delivery devices such as injectors are sometimes provided with functions where a specific dose can be set by the user, which dose may be varied within a range. 
     Quite often this dose setting function is performed by turning a knob or wheel at the distal end of the device whereby it is moved in the distal direction. When performing a subsequent injection, the knob is pushed linearly in the proximal direction. One such injector is disclosed in the document U.S. Pat. No. 6,221,053 in which the distal dose knob of the injector is threaded out of a rod barrel tube as a dose is set. Thus the distance the knob is moved in the distal direction is directly related to the dose quantity to be delivered. 
     One drawback with that type of solution is that if larger doses are to be delivered the dose knob has to be moved quite a long distance in the distal direction, which means that it might be difficult for a user to push the dose knob in the proximal direction during injection. 
     SUMMARY 
     The aim of the present invention is to remedy the drawbacks of the state of the art medicament delivery devices and to provide a device by which it is possible to set a desired or required dose in a simple and intuitive way. 
     This aim is obtained by a medicament delivery device according to the features of the independent patent claim. Preferable embodiments of the invention are subject of the dependent patent claims. 
     Another aim of the present invention is to provide a dose injection button locking feature that reliably releases the dose button to an activated state when a user is ready to set a second and/or subsequent doses for injection. Failure to unlock the dose button, and concurrently the lead screw, reliably each time a dose is to be set will present a potentially dangerous situation in that a user may not be able to set and administer needed subsequent doses of medicament from the drug delivery device. The drug delivery device must be reliably unlocked after each administered dose by dialing the dose setting knob to an initial start position or to a zero dose setting causing the dose button to pop out rearwardly in the distal direction away from the outer housing of the delivery device. 
     According to a main aspect of the invention it is characterised by a medicament delivery device comprising a housing having opposite distal and proximal ends; a medicament container holder releasably connected to said housing; a medicament container arranged inside said medicament container holder; a threaded plunger rod arranged to pass through a first inner wall of the housing and arranged to act on a stopper in the medicament container; a lead screw member coaxially connected to the threaded plunger rod by co-acting first slidably-and-rotatably-locked means; wherein said device further comprises a nut coaxially connected to the threaded plunger rod by a treaded engagement between them, connected to the lead screw member by co-acting non-slidable-and-rotatable means, and connected to the housing by co-acting second slidably-and-rotatably-locked means; a primary dose member coaxially rotatable on the lead screw member when the device is in a non-activated state and connected to the lead screw member by co-acting third slidably-and-rotatably-locked means when the device is in an activated state; a locking member fixedly connected to the housing and releasably connected to the lead screw member by co-acting locking means; a first spring force means arranged between the first inner wall of the housing and the nut, wherein the first spring force means is in a pre-tensioned state when said locking means are engaged and the device is in the non-activated state; a secondary dose member rotatably connected to said primary dose member via a pinion gear; dose setting means connected to the primary dose member by co-acting fourth slidably-and-rotatably-locked means, such that when the device is to be set from the non-activated state to the activated state, the dose setting means are manually manipulated in a pre-determined direction, whereby the locking means are released and the lead screw member is distally moved a pre-determined distance by the first spring force means independent of the size of a dose to be set. 
     According to a further aspect of the invention, said primary and said secondary dose members are provided with indicia. 
     According to another aspect of the invention, the locking means comprises a proximally pointing and radial flexible lever arranged on the locking member, an annular ledge on the circumferential surface of the lead crew member, and the circumferential inner surface of the secondary dose member; such that when the first spring force means is in a pre-tensioned state, the circumferential inner surface of the secondary dose member forces the flexible lever radial inwardly in contact with the ledge; and when the dose setting means are manually manipulated, the secondary dose member is rotated to a position wherein the flexible lever is radial outwardly flexed into a longitudinal groove on the inner circumferential surface of the secondary dose member. 
     According to yet a further aspect of the invention, the locking member comprises on its distal circumferential surface a distally pointing stop member, and wherein the secondary dose member comprises on its proximal circumferential surface a first and a second proximally pointing stop members arranged to interact with the stop member of the locking member. 
     According to yet another aspect of the invention, the non-slidable-and-rotatable means comprises ratchet arms and radial inwardly directed arms on the nut, grooves on the outer circumference of wheels on the proximal end of the lead screw member, and an annular groove between the wheels, wherein the ratchet arms cooperate with the grooves for giving an audible signal when the lead screw member is rotated; and wherein the radial inwardly directed arms cooperate with the annular groove such that the lead screw member and the nut are slidably locked and rotatable in relation to each other. 
     According to a further aspect of the invention, the first slidably-and-rotatably-locked means comprises radial inwardly directed ledges on the inner surface of the proximal end of the lead screw member, and longitudinally extending grooves on the plunger rod, wherein the grooves cooperate with the radial inwardly directed ledges such that the lead screw member and the plunger rod are rotationally locked and slidable in relation to each other. 
     According to another aspect of the invention, the second slidably-and-rotatably-locked means comprises grooves on the outer circumferential side surface of the nut, and longitudinal ribs on the inner surface of the housing, wherein the grooves cooperate with the longitudinal ribs such that the nut and the housing are rotationally locked and slidable in relation to each other. 
     According to yet a further aspect of the invention, the third slidably-and-rotatably-locked means comprises splines on the outer circumferential surface of the lead screw member, and corresponding splines arranged on the inner circumferential surface of the primary dose member, wherein the splines cooperate with corresponding splines such that the lead screw member and the primary dose member are rotationally locked and slidable in relation to each other. 
     According to yet another aspect of the invention, the dose setting means comprises a clutch plate provided with a first annular ratchet, a dose setting knob provided with a second annular ratchet, and a second spring force means arranged between a second inner wall of the housing and a proximal surface of the clutch plate, such that clutch plate is distally urged and the first and the second ratchet are abutting each other, and which dose setting knob protrudes through the distal end of the housing. 
     According to a further aspect of the invention, the fourth slidably-and-rotatably-locked means comprises longitudinally extending grooves on the outer circumferential surface of the primary dose member, and radial inwardly directed protrusions on the inner surface of the clutch plate, wherein the longitudinally extending grooves cooperate with radial inwardly directed protrusions such that the primary dose member and the clutch plate are rotationally locked and slidable in relation to each other. 
     According to another aspect of the invention, the plunger rod is arranged to be proximally moved a distance corresponding to a set dose to be delivered by manually manipulating the dose setting knob when the device is in the activated state. 
     Yet another aspect of the the invention relates to reliably unlocking the dose injection button and lead screw when the dose setting mechanism transitions from a non-activated to an activated state. The dose setting mechanism includes a housing having a longitudinal axis, a lead screw positioned with the housing, and a locking member rotationally and slidably fixed to the housing, the locking member comprising a locking slot. A a dose member assembly is included in the housing having a biasing element, an inner sleeve and an outer sleeve, where the dose member assembly is arranged coaxially around the locking member and the lead screw, the biasing element is operatively engaged with the locking member and the inner sleeve, and where the inner sleeve has a radially projecting key configured to travel in the locking slot to engage the lead screw to prevent axial movement of the lead screw when the dose setting mechanism is in the non-activated state. Preferably, the locking slot maybe L-shape. 
     The biasing element may be a spring, preferably a torsional spring, that exerts a rotational force on the inner sleeve. The key on the inner sleeve can be configured to disengage from the leadscrew when the dose setting member transitions from the non-activated state to an activated state thereby releasing or unlocking the dose injection button. 
     In one particular advantageous embodiment of the dose setting mechanism, the key comprises a chamfer projecting distally and configured to engage a proximal edge of an axial rib positioned on an outer surface the lead screw such that axial movement of the lead screw in a proximal direction causes rotation of the inner sleeve. Additionally the the inner sleeve may include a radially projecting protrusion on its outer surface that engages a radially projecting rib located on an inner surface of the outer sleeve such that rotation of the outer sleeve causes rotation of the inner sleeve. 
     There are a number of advantages with the present invention. Because the lead screw, e.g. the manually operating delivery means, protrudes outside the housing with the same length independent of the set dose quantity the manual dose delivery operation is the same independent of set dose, i.e. the lead screw member has always the same position when a dose has been set. 
     Compared to the state of the art medicament delivery devices, this solution is a great advantage for the user or patient who suffers of dexterity problems. Also when not in use, the lead screw member is inside the medicament delivery device and locked. The unlocking of the lead screw member is performed when said dose setting knob is turned to an initial position, preferably a zero-dose position. 
     These and other features and advantages will become apparent from the detailed description and from the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       In the detailed description reference will be made to the accompanying drawings in which 
         FIGS. 1 a, b    are a cross-sectional view of a medicament delivery device according to the present invention; 
         FIG. 2  is an exploded view of the medicament delivery device of  FIGS. 1   a, b;    
         FIG. 3  is a detailed view of a dose-setting mechanism comprised in the present invention; 
         FIG. 4  is a further detailed view of the dose-setting mechanism comprised in the present invention; and 
         FIG. 5  is yet a further detailed view of the dose-setting mechanism comprised in the present invention; 
         FIGS. 6, 7   a ,  7   b ,  8   a , and  8   b  are cross-sectional view of different functional positions. 
         FIG. 9  is a perspective view of a possible embodiment of the present invention; 
         FIG. 10  is a partially exploded view of the embodiment shown in  FIG. 9 ; 
         FIG. 11  is a partially exploded perspective view of the dose setting mechanism of the embodiment shown in  FIG. 9 ; 
         FIG. 12  is a further exploded perspective view of the dose setting mechanism of the embodiment shown in  FIG. 9 ; 
         FIG. 13  is a close up perspective view of the locking member, lead screw and dose member of the embodiment shown in  FIG. 9 ; 
         FIG. 14  is a close up perspective view of the nut and lead screw of the embodiment shown in  FIG. 9 ; 
         FIG. 15  is a close up perspective view of the locking member and plunger rod of the embodiment shown in  FIG. 9 ; 
         FIG. 16  is a close up perspective view of the locking member, dose member and distal housing portion of the embodiment shown in  FIG. 9 ; 
         FIG. 17  are cross-sectional views of the sequence of operation of the embodiment shown in  FIG. 9 ; 
         FIG. 18  is a close up perspective and exploded view of a portion of the dose setting mechanism having a modified locking member and a dose member assembly; and 
         FIG. 19  is a close up perspective and exploded view of a portion of the modified locking member and a dose member assembly shown in  FIG. 18 . 
     
    
    
     DETAILED DESCRIPTION 
     In the present application, when the term “distal part/end” is used, this refers to the part/end of the injection device, or the parts/ends of the members thereof, which under use of the injection device is located the furthest away from the medicament injection site of the patient. Correspondingly, when the term “proximal part/end” is used, this refers to the part/end of the injection device, or the parts/ends of the members thereof, which under use of the injection device is located closest to the medicament injection site of the patient. 
     The medicament delivery device  10  according to the drawings comprises a generally elongated housing  12  having opposite distal and proximal ends. The elongated housing  12  being e.g. divided in a proximal  12   a  and a distal part  12   b.  The proximal end of the housing  12  is arranged with fastening means such as e.g. threads  14  on its inner surface, which fastening means cooperate with corresponding fastening means such as outwardly threads  16  on a distal end of a medicament container holder  18 , providing a releasable connection. Inside the medicament container holder  18  a medicament container  20  can be placed. The proximal end of the medicament container holder  18  is arranged with a threaded neck  22  for connection of a medicament delivery member such as an injection needle  24 , a mouthpiece, a nozzle or the like,  FIG. 2 . 
     When received by a user, the medicament delivery device  10  is provided with a releasably attachable protective cap  26 . At the distal end of the medicament container holder  18  a sleeve-shaped container support  28  is inserted for holding and supporting the medicament container  20  when inserted,  FIG. 2 . At the proximal end of the housing  12  a first inner wall  30  is arranged, which wall is provided with a central passage  32 ,  FIG. 1B . The central passage  32  is arranged with a distally directed tubular flange  34 ,  FIG. 1A . A threaded plunger rod  36  extends in the longitudinal direction through the central passage  32  with a proximal end adjacent a stopper  38  inside said medicament container  20 ,  FIG. 1   a.  The proximal end of the plunger rod  36  is further arranged with a plunger rod tip  40 ,  FIG. 2 . 
     The device further comprises a lead screw member  58  coaxially connected to the threaded plunger rod  36  by co-acting first slidably-and-rotatably-locked means; and a nut  44  coaxially connected to the threaded plunger rod  36  by a treaded engagement between them. The nut  44  also being connected to the lead screw member  58  by co-acting non-slidable-and-rotatable means, and to the housing by co-acting second slidably-and-rotatably-locked means. 
     The first slidably-and-rotatably-locked means comprises radial inwardly directed ledges  57  on the inner surface of the proximal end of the lead screw member  58 , and longitudinally extending grooves  42  on the plunger rod  36 ,  FIG. 2 , wherein the grooves  42  cooperate with the radial inwardly directed ledges  57  such that the lead screw member  58  and the plunger rod  36  are rotationally locked and slidable in relation to each other. 
     The non-slidable-and-rotatable means comprises ratchet arms  50  and radial inwardly directed arms  51  on the nut  44 , grooves  56  on the outer circumference of wheels  54  on the proximal end of the lead screw member  58 , and an annular groove  53  between the wheels  54 , wherein the ratchet arms  50  cooperate with the grooves  56  for giving an audible signal when the lead screw member  58  is rotated; and wherein the radial inwardly directed arms  51  cooperate with the annular groove  53  such that the lead screw member  58  and the nut  44  are slidably locked and rotatable in relation to each other,  FIG. 3 . 
     The second slidably-and-rotatably-locked means comprises grooves  52  on the outer circumferential side surface of the nut  44 ,  FIG. 3 , and longitudinal ribs on the inner surface of the housing (not shown), wherein the grooves  52  cooperate with the longitudinal ribs such that the nut and the housing are rotationally locked and slidable in relation to each other. 
     The nut  44  comprises a threaded central passage  46  which cooperates with the threads of the plunger rod  36 ,  FIG. 2 , thereby forming the threaded engagement between them. 
     The device also comprises a primary dose member  66  coaxially rotatable on the lead screw member  58  when the device is in a non-activated state and connected to the lead screw member  58  by co-acting third slidably-and-rotatably-locked means when the device is in an activated state. The third slidably-and-rotatably-locked means comprises splines  60  on the outer circumferential surface of the lead screw member  58 ; and corresponding splines  64  arranged on the inner circumferential surface of the primary dose member  66 , wherein the splines  60  cooperate with corresponding splines  64  such that the lead screw member  58  and the primary dose member  66  are rotationally locked and slidable in relation to each other,  FIGS. 2 and 3 . 
     The device further comprises: a locking member  96  fixedly connected to the housing  12  and releasably connected to the lead screw member  58  by co-acting locking means; a first spring force means  48  arranged between the first inner wall  30  of the housing  12  and the nut  44 , wherein the first spring force means is in a pre-tensioned state when said locking means are engaged and the device is in the non-activated state; and a secondary dose member  90  rotatably connected to said primary dose member  66  via a pinion gear  94 ,  FIG. 3 . 
     The device also comprises dose setting means connected to the primary dose member  66  by co-acting fourth slidably-and-rotatably-locked means, such that when the device is to be set from the non-activated state to the activated state, the dose setting means are manually manipulated in a pre-determined direction, whereby the locking means are released and the lead screw member  58  is distally moved a pre-determined distance by the first spring force means  48  independent of the size of a dose to be set. 
     The dose setting means comprises a clutch plate  74  provided with a first annular ratchet  76 , a dose setting knob  84  provided with a second annular ratchet  82 , and a second spring force means  78  arranged between a second annular inner wall  80  of the housing and a proximal surface of the clutch plate  74 , such that clutch plate  74  is distally urged and the first and the second ratchet  76 ,  82  are abutting each other, and which dose setting knob  84  protrudes through the distal end of the housing  12 ,  FIGS. 1 a    and  4 . The fourth slidably-and-rotatably-locked means comprises longitudinally extending grooves  70  on the outer circumferential surface of the primary dose member  66 , and radial inwardly directed protrusions  72  on the inner surface of the clutch plate  74 , wherein the longitudinally extending grooves  70  cooperate with radial inwardly directed protrusions  72  such that the primary dose member  66  and the clutch plate  74  are rotationally locked and slidable in relation to each other,  FIGS. 2 and 3 . The distal end of the lead screw member  58  protrudes through the dose setting knob  84 , and is at its distal end arranged with a dose injection button  86 ,  FIGS. 2 and 7   b . Outside the dose injection button  86  a spin ring  88  is rotatably arranged,  FIG. 2 . 
     The locking means comprises: a proximally pointing and radial flexible lever  102  arranged on the locking member  96 , an annular ledge  62  on the circumferential surface of the lead crew member  58 , and the circumferential inner surface of the secondary dose member,  FIG. 2 . The secondary dose member  90  is also arranged with teeth  92  arranged around its circumference, which teeth cooperate with teeth  92  on the pinion gear  94 , which is journalled in the housing as well as the locking member  96  via a locking lever bracket,  FIG. 3 . Further the primary dose member  66  is arranged with a gear segment  98 , which also cooperate with the pinion gear  94 ,  FIG. 3 . A certain part of the lead screw member  58  is arranged with the splines  60  on its outer circumferential surface,  FIG. 2 ; which splines  60  have a lesser diameter than the proximal part of the lead screw member  58 , thereby creating the annular ledge  62 ,  FIG. 2 . The locking member  96  also comprises on its distal circumferential surface a distally pointing stop member  95 , and the secondary dose member  90  comprises on its proximal circumferential surface a first  91  and a second  93  proximally pointing stop member  95  arranged to interact with the stop member  96  of the locking member,  FIG. 4 . 
     The proximal part of the primary dose member  66  and the secondary dose member  90  are arranged with a circumferential band containing numbers or indicia  68  which are used to indicate dose size through a dose window on the housing, as will be explained below,  FIG. 3 . 
     The device is intended to function as follows. When delivered to the user, the device is in the non-activated state wherein a medicament container  20  has been inserted in the medicament container holder  18  in the proximal end of the device,  FIG. 1 , the first spring force means  48  is in a pre-tensioned state and said locking means are engaged, wherein the circumferential inner surface of the secondary dose member  90  forces the flexible lever  102  radial inwardly in contact with the ledge  62 . 
     When the device is to be used the protective cap  26  is removed and the dose setting means are manually manipulated for setting the device from the non-activated state to the activated state by rotating the dose setting knob  84  counter clockwise until activating indicia as e.g. two zeros are visible through the window of the housing  12 . The rotation of the dose setting knob  84  causes the clutch plate  74  and thereby the primary dose member  66  to rotate due to the engagement between the co-acting fourth slidably-and-rotatably-locked means, and due to the connection between the first  76  and the second  82  ratchets. However, the lead screw member  58  is not rotated since the third slidably-and-rotatably-locked means  60 ,  64  are not in engagement, i.e. the splines  60  on the outer circumferential surface of the lead screw member  58  and the corresponding splines  64  arranged on the inner circumferential surface of the primary dose member  66  are not in engagement. The secondary dose member  90  also rotates due to the connection between the gear segment  98  of the primary dose member  66  and the teeth  92  of the secondary dose member  90  through the pinion gear  94 . The rotation of the secondary dose member  90  is stopped when its second proximally pointing stop member  93  abuts the distally pointing stop member  95 . This causes a longitudinal groove on the inner circumferential surface (not shown) of the secondary dose member  90  to be aligned with the flexible lever  102  whereby the flexible lever  102  is radial outwardly flexed into the groove and thereby moved out of contact with the ledge  62  of the lead screw member  58 . This causes the lead screw member  58  to move a pre-determined distance in the distal direction due to the force of the spring  48  acting on the nut  44 , which in turn is attached to the lead screw member  58 . The splines  60  on the outer circumferential surface of the lead screw member  58  and the corresponding splines  64  arranged on the inner circumferential surface of the primary dose member  68  are then engaged to each other. Because of the movement of the nut  44 , the plunger rod  36  is also moved. The distal end of the lead screw member  58  and its dose injection button  86  now protrude distally out of the housing said predetermined distance and independent of the size of the dose to be set. 
     The device is now in the activated state and ready for setting a required dose of medicament,  FIGS. 7 a    and  7   b.    
     When setting a dose, the plunger rod  36  is arranged to be proximally moved a distance corresponding to a set dose to be delivered by manually manipulating the dose setting knob  84 . The dose setting knob  84  is rotated in the clockwise direction which also rotates the primary dose member  66  clockwise indicating the dose that is being dialed. At the same time the primary dose member  66  rotates the lead screw member  58  clockwise due to the engagement between the co-acting third slidably-and-rotatably-locked means  60 ,  64 ; and the lead screw member  58  rotates the plunger rod  36  due to the engagement between the co-acting first slidably-and-rotatably-locked means, driving the plunger rod  36  through the nut  44  because of the threaded engagement between them, thereby moving the plunger rod  36  proximally. The secondary dose member  90  also rotates due to the connection between the gear segment  98  of the primary dose member  66  and the teeth  92  of the secondary dose member  90  through the pinion gear  94 . The rotation of the secondary dose member  90  is stopped when its first proximally pointing stop member  91  abuts the distally pointing stop member  95 , which indicates the maximum dose the device can deliver e.g. two indicia as e.g. a seven and a zero are visible through the dose window. In any case, the set dose is visible through the dose window of the housing. At this point the device is ready for an injection. 
     Moreover, if the user attempts to dial past the maximum dose the device can deliver or if the user attempts to dial pass the activating indicia, the connection between the first annular ratchet  76  and the second annular ratchet will function as a clutch. 
     When the dose is set, a medicament delivery member  24  is attached to the proximal end of the device, such as e.g. an injection needle. It is however to be understood that other types of medicament delivery members may be used in order to deliver a dose of medicament. The medicament delivery member  24  is then placed at the delivery site and the user presses the dose injection button  86  in the proximal direction the predetermined distance that the distal end of the lead screw member  58  and its dose injection button  86  protrudes distally out of the housing and which said predetermined distance is independent of the size of the dose to be delivered. This causes the lead screw member  58  to move in the proximal direction as well as the nut  44  and the plunger rod  36 . This proximal movement of the plunger rod  36  causes it to act on the stopper  38  of the medicament container  20  whereby a dose of medicament is expelled through the medicament delivery member  24 . When the lead screw member  58  has reached a certain distance inside the housing, the flexible lever  102  of the locking member  96  is again moved in contact with the ledge  62  of the lead screw member  58 ,  FIG. 8 . The medicament delivery member may now be removed and discarded. 
     When a subsequent dose is to be performed, the above described procedure is performed and can be repeated until the medicament container is emptied. 
     Another embodiment of the invention is presented in  FIGS. 9-19 . This embodiment  200  differs slightly in structure and operation from that of the above-described embodiments in that this version of the device allows a user to set only one preset, pre-selected or pre-determined dose setting. For example, the device  200  could be manufactured such that a single fixed dose of 5 units or 10 units is preselected and the user would not be able to dial a dose greater than or less than the one single dose. In other words, the device does not have variable dose setting functionality, instead this type of device is referred to as a fixed dose device. 
     In one possible embodiment of the fixed dose design, device  200  has a dose setting mechanism  201  shown in  FIG. 10  and in more detail in  FIGS. 11-12 . The distal part  12   a  of the elongated housing  12  contains a window  210  that allows a user to view and/or feel indicia  68  printed or otherwise located on the outer surface  66   a  of the dose member  66 . As illustrated in the figures, an arrow can be used to provide the user with a visual clue or prompt as to what direction to rotate dose setting knob  84  when the dose setting mechanism is in the activated state. The activated state is achieved when the user rotates the dose setting knob to the zero dose position, which as exemplified in the figures can be seen as the arrow or as a “0” or any other desired indicia to indicate the starting position. 
     In the non-activated state, the flexible lever  215  of locking member  96  is engaged with ledge  62  on lead screw  58 . This is best shown in  FIG. 18  where the upper figure illustrates the activated state where the dose button is moved distally outward (so-called “popped out”) from the dose setting knob  84  and housing  12   a  as a result of the axial movement in the distal direction of lead screw  58  by the biasing force exerted by biasing member  48 , shown as a compression spring.  FIG. 11  illustrates indicia  205  and  206  being aligned when the device is in the activated state with the button  86  “popped out.” The lower figure of  FIG. 18  illustrates the dose setting mechanism  201  in the non-activated state where spring  48  is compressed (pre-tensioned) by the forward or proximal movement of lead screw  58  during dose delivery. The lead screw  58  is prevented from moving distally by the engagement of lever  215  with ledge  62 , where the lever  215  is biased radially inward by the dose member  66  and in particular by the cam surface  232  on the inside surface of dose member  66 . This is best shown in  FIG. 16 . This cam surface  232  acts as a bearing surface against the outside surface of lever  215  to deflect the lever  215  inwardly so that it remains engaged with ledge  62 . 
       FIG. 16  shows the relationship of locking member  96 , dose member  66  and distal housing  12   a.  As mentioned, locking member  96  is rotationally and axially fixed relative to the housing  12   a.  This fixation is a result of the engagement of radially projecting ribs  225  on locking member  96  that engages corresponding slots  226  on the inside surface of housing  12   a.  Dose member  66  has two rotational stops  230  and  231  that engage corresponding stops  213  and  214  on the distal side of locking member  96  (see  FIG. 13 ).  FIG. 13  illustrates axial ribs  217  that engage with slots  216  on dose member  66  when the device is in the activated state. This engagement rotationally fixes the dose member  66  to the lead screw  58  such that rotation of the dose setting knob  84  causes the dose member  66  to rotate as well as lead screw  58 .  FIG. 15  illustrates the relationship of the plunger rod  36  to the lead screw  58 . In the particular embodiment shown the plunger rod  36  is shown with a non-circular cross-section having a pair of opposed flat surfaces  36   b  with threaded segments  36   a  between each flat portion  36   b.  The proximal through hole  222  of lead screw  58  is configured to match the non-circular cross-sectional shape of plunger rod  36  such that the plunger rod is rotationally fixed to the lead screw  58 , but can move or slide axially relative to the lead screw. 
     The plunger rod  36  is threadedly engaged with nut  44  through threaded through hole  46  (see  FIGS. 12 &amp; 14 ). Nut  44  is rotational fixed to the housing by the engagement of radially extending ribs  219  that cooperate with corresponding slots on the inside of the housing. These slots are longitudinal in length and are configured to allow the nut  44  to slide axially relative to the housing. The nut  44  is fixed to the proximal end of lead screw  58  through the engagement of finger  218  in radial groove  211  at the proximal end of lead screw  58 . This groove  211  is sized with sufficient axial width such that the lead screw  58  and the distal face of the nut  44  can move axially relative to each other during dose setting. During dose setting the lead screw  58  is rotated relative to nut  44 , which is rotationally fixed to the housing. The spring  48  exerts a biasing force in the proximal direction against the proximal face of the nut  44  causing two opposed distally projecting ratchet teeth  221  to engage complimentary proximally projecting ratchet teeth  220  located at the proximal end of the lead screw  58 . As the lead screw  58  is rotated the ratchet teeth  220  rotate relative to the stationary ratchet teeth  221  causing the teeth  220  to ride up and over teeth  221 . This riding up and over motion moves the lead screw axially back and forth within groove  211 . The nut is held in the groove by finger  218  (see  FIG. 12 ). 
       FIG. 17  illustrates the sequence of operation of device  200 . The top figure shows the device in a non-activated state, for example, immediately after dose delivery. Here the dose button is pushed in (i.e., not “popped out”) and the spring is in the pre-tensioned compressed state being held in this compressed state by the engagement of the flexible lever on the locking member locked with the ledge on the lead screw. The next figure shows the device in the activated state when the dose setting knob is rotated to the zero dose or starting position, e.g., where the arrow is shown in the housing window. The transition from the non-activated to the activated state causes the lead screw, plunger rod and nut to all move distally by the biasing force exerted by the spring. The spring moves these three components because the dose setting knob and dose member were rotated such that the dose member no longer biases the flexible lever inward and thus it disengages from the ledge on the lead screw. The distance these three components move is always the same distance distally as indicated by the distance between lines  300  and  305 . This moves the plunger rod off of and away from cartridge piston  20   a  by the same distance. At this point, when the device is in the activated state, a dose can be set by rotating the dose setting knob. Since the plunger rod was moved distally off the cartridge piston when the zero dose position was obtained, the axial movement of plunger rod in the proximal direction does not move (or contact) the bung. 
     Setting a dose also rotates the dose member, which then biases the flexible lever inwardly. The third figure in  FIG. 17  represents the device with a dose set. Setting the dose caused the plunger rod to screw through the nut moving proximally a distance X. To deliver the set dose the user pushes the dose button proximally which pushes the lead screw, nut and plunge rod proximally as well. These three components move proximally and as the lead screw is pushed forward proximally, the flexible levers on the locking member that is axially fixed relative to the housing, flex over the ledge on the outside of the lead screw and causes the lead screw to be locked in the original most forward or proximal position, i.e., the non-activated state. As the lever re-engages the ledge on the lead screw, the spring is returned to the pre-tensioned state. As illustrated in the bottom figure of  FIG. 17 , the plunger rod moves an additional distance X representing and proportional to the dose set. This in turn moves the cartridge piston the same distance X and thus expels that amount of medicament from the proximal end of the cartridge through the injection needle  310 . 
     An alternative to locking member  96  and dose member  66  as described above is presented in  FIGS. 18-19 , where an alternative design of the locking member  96   a  is operatively engaged with dose member  66   a  to provide a lock mechanism that reliably unlocks the dose injection button and the lead screw  58  so subsequent doses can be set, as will be further described below. Dose member assembly  66   a  comprises at least three components, a biasing element  420 , an inner sleeve  410  and an outer sleeve  400 . The biasing element is shown as a torsional spring, however, other types or designs of springs may be used. Likewise, a non-spring component could be used, for example, flexible fingers, spring washers, and the like materials can be used to provide the required rotation forces necessary to bias the key  412  to stay within the transverse portion  430   b  of the locking slot  430 . 
     The inner and outer sleeves,  410  and  400 , preferably have a circular cross-section and are concentrically positioned with respect to each other such that the outer sleeve  400  is coaxially arranged and covers the inner sleeve  410 . The outer sleeve  400  has an outer surface  402  that may contain indicia  68  as earlier described. The outer sleeve  400  also has an inner surface  406  that contains at least one radially projecting rib  404  positioned longitudinally along the inner surface  402 . This rib  404  is configured to interact with protrusion  416  on the outer surface  414  of inner sleeve  410  when the dose setting knob  84  is rotated to set a dose of medicament, which also causes outer sleeve  400  to rotate. 
     Inner sleeve  410  has an inner surface  415  that contains a radially projecting key  412  having a proximally facing stop face  413 . This stop face  413  is configured to abut the distal facing ledge  62  on lead screw  58  (see  FIG. 13 ) when the dose setting mechanism is in the non-activated state and the dose button  86  is locked in the retracted or proximal-most position. As the outer sleeve  400  is rotated to a zero dose or initial position (i.e., where the the indicia arrow shown in  FIG. 18  is moved to be visible in window  210  (see  FIGS. 9-10 ) the inner sleeve  410  and key  412  are simultaneously rotated, which moves the stop face  413  from abutment with ledge  62  thus allowing spring  48  to move the lead screw  58  distally to the activated position where the dose button is popped out in the distal direction rearwardly relative to the housing  12   a  and the dose setting knob  84 . Key  412  also has a chamfer  411  (see  FIG. 19 ) that faces distally and is configured with a sloping or camming surface that will operatively engage with a proximal projecting end face  417  (see  FIG. 14 ) in manner where axial movement of the lead screw  58  in the proximal direction, when the dose button is pushed to deliver a set dose of medicament, causes the inner sleeve  410  and key  412  to rotate against a biasing force of biasing element  420 , as described in more detail below. 
     Key  412  is configured and designed to travel within a locking slot  430  during rotational movement caused by both the rotation of outer sleeve  400  and the engagement with end face  417  of the lead screw  58 . Inner sleeve  410  is axially fixed relative to housing  12   a  and also has a connector  418 , shown as a hole  418 , or indentation, that fixedly attaches a proximal end of the biasing element  420 . Biasing element  420  is illustrated in the embodiment in  FIGS. 18 and 19  as a spring with opposing anchor posts  424  and  422 . Connector  418  is configured to accept and retain post  424  to prevent rotational movement of spring  420 . Post  422  is configured to attach to a similar connector  432  located in locking member  96   a.  Because locking member  96   a  is rotationally fixed to the outer housing  12   a  of the dose setting mechanism, the biasing element  420  exerts a rotational spring force on inner sleeve  410  such that the key  412  is biased in the locking position within the transverse portion  430   b  of locking slot  430 . Locking member  96   a  also has stops  435 ,  436 , and  437 . The stops work collectively as a device to limit the rotation of the radially projecting rib  404  to certain degrees of rotation. The degree of rotation depends on the spacing between the neighboring two stops and can be adjusted according to design needs. 
     The interaction of the key  412  with the locking slot  430  will now be described. In the non-activated state of the dose setting mechanism the key  412  is positioned within the transverse portion  430   b  of the locking member  96   a,  which itself is axially fixed relative to the dose member assembly  66   a  and housing  12   a.  In this position the lead screw is blocked by the key  412  from moving axially in the distal direction. The indicia on the outer sleeve  400  will display a dose number (as opposed to the arrow or a “0”) in the window of the housing. To activate the dose setting mechanism, a user will rotate the dose setting knob to an initial or start position in order to display the arrow or a “0”. This rotational force overcomes the rotational biasing force exerted by biasing member  420  on the inner sleeve  410 . Biasing element  420  exerts a biasing spring force to maintain key  412  against end wall  430   c  of the transverse portion  430   b.  Rotation of the outer sleeve causes the key  412  to rotate against the biasing spring force causing the key  412  to travel in the transverse portion  430   b  of locking lot  430  disengaging the key  412  from the ledge  62  of the lead screw  58 . Spring  48  expands and pushes the lead screw  58  axially in the distal direction relative to the locking member  96   a  and the dose member assembly  66   a.  The lead screw  58  has now moved distally relative the key  412  such that the end face  417  of the lead screw  58  is positioned distally from the chamfer  411 . This movement of the lead screw  58  causes the dose button to pop out of the distal end of the housing  12   a  relative to the dose setting knob placing the device in an activated state. At this point the dose setting knob can be rotated to set a fixed predetermined dose medicament, which also causes rotation of the lead screw relative to plunger rod  36 . This rotation of the dose setting knob also rotates the outer and inner sleeves  400 ,  410  and returns the key  412  to abutment with end wall  430   c  of the locking slot  430 . This rotation further causes end face  417  to align axially with chamfer  411 . The device is now ready to deliver a dose. 
     To deliver the set dose the user pushes the dose button in the proximal direction causing the lead screw to move with it axially, thus engaging end face  417  with chamfer  411  causing rotation of the inner sleeve  410  to move key  412  away from end wall  430   c  against the biasing force of biasing element  420 . As the axial rib  217  of the lead screw  58  moves past the key  412  it holds inner sleeve  410  from rotating back in response to the biasing force exerted by biasing element  420 . Once the rib  217  moves proximally out of engagement with key  412  the inner sleeve  410  is then free to rotate back to end wall  430   c  in response to the biasing force of biasing element  420 . At the end of the proximal travel of the lead screw the set dose of medicament has now been delivered. As a result of the resetting of the key  412  to abut end wall  430   c,  the device is now locked or in a non-activated state with the last set dose number shown in the housing window. To set another or subsequent dose, the user repeats the process of first unlocking the key from engagement with the leadscrew and then rotating the dose setting knob to set a dose. 
     It is to be understood that the embodiment described above and shown in the drawings is to be regarded only as a non-limiting example of the invention and that it may be modified in many ways within the scope of the patent claims.