Abstract:
A medicament delivery device includes a housing with a compartment for a medicament container, an injection needle arranged to housing and connectable to the medicament container for delivering a dose of medicament, a manually operated activation mechanism, an actuation mechanism operably connected to the activation mechanism and configured to extend the injection needle, upon activation of the activation mechanism, from a first position inside the housing to a second position for penetrating a patient, a plunger rod in the housing configured to act on the medicament container for delivering a dose of medicament through the injection needle, a driver configured to acting on the plunger rod for delivering the dose, and a needle cover operably arranged in the housing between a position inside the housing and an extended position outside the housing for shielding the injection needle when the injection needle is in the second position.

Description:
TECHNICAL AREA 
       [0001]    The present invention relates to a medicament delivery device and in particular a compact and easy to use infuser. 
       BACKGROUND OF INVENTION 
       [0002]    For a number of years infusers have been used that provides the patient or user with the means of administering a drug in an easy way without the need for a medically trained person, such as a physician or nurse to handle the device. 
         [0003]    One drawback with these infusers is that they have a medicament container of a certain length as well as a plunger rod acting on said medicament container for delivering a dose of medicament, also having a certain length, whereby the total length of a device has to be at least the length of the medicament container and the plunger rod. If a drive member is used, such as for instance a drive spring, the length of the device is further increased. 
         [0004]    One way of handling this is to make at least the plunger rod shorter for not adding so much to the overall length. One solution to this is to have a flexible plunger rod, which is disclosed for example in EP 1 583 573 where the plunger rod may be bent or formed as a circle. Another solution is disclosed in EP 1 276 529 having a bendable plunger rod with a ratchet on a side surface, where the plunger rod is bent around a cogwheel, for driving the plunger rod. 
         [0005]    The drawback with these solutions is that the length might not be increased by the whole length of the plunger rod, but at least by some amount because the circle formed by the bent plunger rod also adds to the length. Further, the dimensions of the device in other directions are increased considerably by these solutions, providing a rather bulky device. 
         [0006]    The above-mentioned solutions utilize some sort of power spring wound around a shaft or the like positioned in the centre of the circle formed by the curved plunger rod. These power springs often act directly or almost directly on the curved plunger rod, such as with the device of EP 1 276 529 where the power spring acts on the cogwheel. 
         [0007]    The drawback with this drive solution is that it complicates the addition of functions such as activation mechanisms, constant injection speed mechanism, automatic stop mechanisms, just to mention a few. This is mainly because the plunger rod surrounds and thereby blocks access to the plunger drive spring without enlarging the device. 
         [0008]    Regarding the injection speed control aspect, some solutions have been devised, such as for example in EP 1 326 659 where an electric motor is utilized for driving the flexible plunger rod. Also document WO 2010/112377 discloses a device utilizing electric motors for driving and controlling the movement and speed of the plunger rod. 
         [0009]    The drawback with this is that the device has to rely on electric power in order to deliver a dose of medicament. If any batteries used are depleted, the device cannot be used at all, which may be critical for some types of drugs. 
         [0010]    Another drawback with many of the mentioned devices is that there is no feature or mechanism for handling the injection needle after completed injection. When the device is withdrawn, the injection needle completely exposed and may cause injuries to persons handling or coming in contact with the device after use. 
       BRIEF DESCRIPTION OF INVENTION 
       [0011]    In the present application, when the term “distal part/end” is used, this refers to the part/end of the device, or the parts/ends of the members thereof, which under use of the device is located the furthest away from the medicament delivery site of the patient. Correspondingly, when the term “proximal part/end” is used, this refers to the part/end of the device, or the parts/ends of the members thereof, which under use of the device is located closest to the medicament delivery site of the patient. 
         [0012]    The aim of the present invention is to remedy the drawbacks of the state of the art medicament delivery devices. This aim is obtained with a medicament delivery device according to the features of the independent patent claim. Preferable embodiments of the invention form the subject of the dependent patent claims. 
         [0013]    The medicament delivery device preferably comprises a housing having a compartment inside said housing for positioning a medicament container. The medicament container may have a number of designs that are suitable for delivering a dose of medicament when the device is activated. According to one favourable aspect, the medicament container may be arranged with a stopper that is movable by appropriate means. The medicament container may further be arranged with some connection interface to an injection needle, through which a dose of medicament may be delivered. The connection interface may for example be a septum or other type of membrane or wall that may be penetrated or pierced by a connection element, which connection element may be a pointed end of a conduit in flow communication with the injection needle. 
         [0014]    The device may further advantageously comprise a manually operated activation mechanism for activating said device in order to deliver a dose of medicament. The activation mechanism may be operably connected to a number of functions and features of the device. 
         [0015]    One such feature may be an actuation mechanism arranged to, upon activation of said activation mechanism, extend the injection needle from a first position inside said housing to a second position wherein a penetration of a patient is performed. Thus, when the device is placed on the body of a patient and the activation mechanism is operated, a penetration of the skin of the patient will be performed by the actuation mechanism, rendering the device ready for delivering a dose of medicament. 
         [0016]    In order to provide a dose of medicament from the medicament container through the conduit to the injection needle, the device is preferably provided with a plunger rod in said housing and arranged to act on the stopper of the medicament container. In order to do so, the plunger rod may be operably connected to a driver capable of acting on said plunger rod for delivering a dose of medicament. In this aspect, the driver may advantageously comprise some energy accumulating feature, which energy may drive the plunger rod. The energy accumulating feature may comprise a number of different designs such as compression springs, torsion springs, clock springs, gas springs and the like, just to mention a few. 
         [0017]    Preferably the device may comprises a needle cover operably arranged in said housing from a first position inside said housing to a second extended position outside said housing for shielding said injection needle when said injection needle is in said second position. With this solution, the injection needle may be protected when the device is removed from the body of the patient, thereby minimizing the risk of unintentional needle sticks. 
         [0018]    According to one feasible solution, the actuation mechanism may comprise a locking mechanism capable of locking said injection needle in said second position. This ensures that the penetration depth of the injection needle is maintained during the subsequent injection sequence. Thus, it is not required for the user to operate the activation mechanism after the injection needle has reached the second penetration position. 
         [0019]    Further, another favourable feature, the needle cover may comprise locking elements operably arranged to lock said needle cover in said second position. This further minimizes the risk of injuries of the injection needle since the needle cover is locked from movement. 
         [0020]    According to another favourable feature, the activation mechanism may comprise two operating elements placed on opposite sides of said device. This solution of the activation of the device is advantageous since the operating elements may be operated by one hand of the user gripping the device. According to a further favourable solution, the operating elements may comprise activation buttons, which buttons are manually depressed for activating said device. Since the buttons are placed on opposite sides of the device, the forces for depressing the buttons are directed towards each other. Thus the forces will not affect the position of the device on the body of the patient, which is an advantage during the penetration and the injection sequence, because any movement of the device when the injection needle has penetrated the body will cause pain and discomfort. 
         [0021]    According to one feasible solution, the activation buttons may be connected to said injection needle via a linkage comprised in said actuation mechanism, thereby enabling movement of said injection needle to said extended position when said buttons are depressed. The linkage thus enables movement of the injection needle in directions deviating from the movement directions of the activation buttons, for example a direction ninety degrees in relation to the activation buttons. When using a linkage, the locking mechanism of said injection needle may preferably be comprised in the linkage. 
         [0022]    In order to ascertain a smooth and more or less constant injection speed, the device may further comprise an injection speed control mechanism operatively connected to said driver. With such a mechanism, the injection speed may be chosen and controlled in a positive manner. This may be an important feature for medicament solutions that for example are painful when delivered in larger quantities quickly. The dose delivery may then be set and controlled to deliver very small quantities continuously for longer time periods. 
         [0023]    According to one feasible solution, the injection speed control mechanism may for example comprise a pallet fork acting on an escapement wheel, as well as a transmission between said drive means and said escapement wheel. This solution provides possibilities of a choosing and changing injection speeds in a wide range. The use of a transmission enables the choice of gearing those suites the delivery speed of a certain medicament. In order to provide a certain injection speed, the escapement wheel is preferably drivably connected to a drive spring. 
         [0024]    According to another preferable solution, the device may further comprise an auto-stop mechanism capable of permanently stopping said injection speed control mechanism at the end of a dose delivery sequence. Thereby it is clearly indicated to a user that the injection is completed and that the device may be removed from the patient. 
         [0025]    To further enhance the usability of the device, it may further comprise a manually operable stop mechanism capable of permanently stopping said injection speed control mechanism upon activation. This may for example be an advantage in a situation when the user for some reason has to remove the device from the body. The stop mechanism will then ascertain that no medicament is expelled from the device after removal. 
         [0026]    According to another feasible solution, the device may further comprise a manually operated pausing mechanism capable of temporarily stopping and subsequent starting of the injection speed control mechanism upon activation. This may for example be an advantage when the user has started the injection sequence but wants to pause it for some reason. The injection speed control mechanism is then stopped only temporary and may be resumed by the user. The pausing mechanism may for example by operably connected to the activation mechanism. 
         [0027]    According to another feasible solution, the device may also comprise a medicament container penetration mechanism operably connected to said activation mechanism for creating, upon activation, a communication between the medicament inside said medicament container and said injection needle. In this manner, the content of the medicament container is not affected in any way before the device is activated. Thus, the medicament container may be inserted into the device at any time without the risk of degrading the medicament, because a passage between the interior of the medicament container and the injection needle is only obtained after activation of the device. 
         [0028]    These and other aspects of, and advantages with, the present invention will become apparent from the following detailed description of the invention and from the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0029]    In the following detailed description of the invention, reference will be made to the accompanying drawings, of which 
           [0030]      FIG. 1  is a perspective view of an embodiment of a medicament delivery device, 
           [0031]      FIG. 2  is a perspective view of the device of  FIG. 1  turned 180 degrees, 
           [0032]      FIG. 3  is a perspective view of the device of  FIG. 1  with a housing part removed, 
           [0033]      FIG. 4  is a perspective view of the device of  FIG. 1  turned 180 degrees in relation to  FIG. 3  and with a housing part removed, 
           [0034]      FIGS. 5-15  are detailed views of components and mechanisms comprised in the device of  FIG. 1 , 
           [0035]      FIGS. 16-25  show different functional positions of the device during use. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0036]    The embodiment of a medicament delivery device shown in the drawings comprises a housing, which may be in two housing parts  10 ,  12 ,  FIGS. 1 and 2 . It is of course feasible that it comprises more than two housing parts. Preferably, the complete housing has a generally rectangular shape having a measure or thickness as seen along a proximal-distal axis  14  that is much less than the dimensions in the other two directions, vertical  16  and horizontal  18 . The housing is arranged with operating elements,  20   a, b  in the embodiment shown,  FIGS. 1 and 2 , as two buttons arranged on opposite side surfaces of the device. 
         [0037]    The device is arranged with a driver  50 , the function of which will be explained below. The driver comprises a shaft  24 ,  FIG. 5 , which shaft is rotatably arranged inside the housing and journalled with a distal end in a seat  26 ,  FIG. 6 , on the inner surface of the distal housing part  12 . An Allen keyhole  22  is arranged on an end surface of a shaft  24 , where the Allen keyhole  22  is accessible via an opening on the proximally directed housing surface,  FIG. 2 . A proximal end of the shaft  24  is arranged with a number of arms  28 ,  FIG. 5 , that extend in a generally circumferential direction. The free ends of the arms  28  are arranged with radially outwardly directed edges  30 . The proximal end of the shaft  24  with the arms  28  is intended to fit into a seat  32 ,  FIG. 7 , on the inner surface of the proximal housing part  10 . The seat  32  is surrounded by an annular ledge  34  having radially inwardly directed teeth  36  of a certain configuration. The teeth  36  are intended to cooperate with the free ends of the arms  28  as will be described. 
         [0038]    The driver  50  further comprises a flat spiral clock spring  38 ,  FIG. 5 , wound around the shaft  24 , wherein an inner end of the spiral clock spring  38  is attached to the shaft  24 . The spring  38  is further arranged inside a spring housing  40 ,  FIG. 5 , designed as a generally tubular part. An outer end of the spiral clock spring  38  is attached to an inner surface of the spring housing  40 . The spring housing  40  is further arranged with a sidewall  42 ,  FIG. 5 , having a central opening  44 , through which the shaft  24  can extend. On the outer circumferential surface of the spring housing  40  a ratchet  46  is arranged,  FIG. 5 . The ratchet  46  is intended to cooperate with a cogwheel  48  of the driver  50 ,  FIG. 8 . The driver  50  further comprises a shaft  52  where the cogwheel  48  is attached to one end such that the shaft  52  extends generally in the radial direction of the spring housing  40  as seen in  FIG. 8  along line  53 . The shaft  52  of the driver  50  is journalled in the proximal housing part  10  by support elements  54 ,  FIG. 7 . A second cogwheel  56 ,  FIG. 8 b   , is attached to the second end of the shaft  52 , having a generally conical shape. The second cogwheel  56  is arranged to be in contact with teeth of a third mating cogwheel  58 . The third mating cogwheel  58  is journalled on a shaft  60  having an extension generally perpendicular to the extension of the shaft  52 . Attached to the third mating cogwheel  58 , or made integral with, is a drive wheel  61  having teeth  62  around its circumference. These teeth  62  are arranged to cooperate with corresponding teeth  64  on a plunger rod  66 ,  FIG. 4 . 
         [0039]    In the embodiment shown the plunger rod  66  is of a certain configuration,  FIGS. 9 and 10 . The plunger rod  66  generally has a rectangular configuration as seen in a cross-sectional view. Further the plunger rod  66  is divided up into a number of plunger rod segments. The end of the first plunger rod segment  68  that is to be in contact with a stopper  69  of a medicament container  70 ,  FIG. 4 , is arranged with a generally circular pusher plate  72 ,  FIG. 9 , having a diameter somewhat less than the inner diameter of the medicament container  70 . The first plunger rod segment  68  has a certain length. 
         [0040]    The following plunger rod segments  74 ,  FIG. 9 , are somewhat shorter. All plunger rod segments  74  are arranged with connection elements that comprise generally vertically arranged cut-outs  76  at their distal ends,  FIG. 10 . The sidewalls of the cut-outs  76  are arranged with generally vertically directed grooves  78 ,  FIG. 10 , having a certain configuration. Further, each plunger rod segment apart from the first segment, is arranged with a proximally directed nose  80  designed to fit into the cut-out  76  of a previous plunger segment  68 . Further the nose  80  is arranged with generally vertically extending ledges  82  having similar configuration as the grooves  78  of the cut-out  76 , whereby the ledges  82  may fit into the grooves  78 . Further, the cut-outs  76  are arranged with flexible tongues  84 ,  FIG. 10 b    that engage a surface of the nose  80  of a subsequent plunger rod segment so as to lock the segments to each other. 
         [0041]    The plunger rod segments  74  are arranged in a generally vertical stack on top of each other and directed such that the nose  80  of the segments point in the same direction,  FIGS. 8 a    and  9 . The stack of plunger rod segments is held in place inside the housing by a magazine  86 ,  FIG. 9  providing side supports on three sides. The fourth side is arranged with an elongated slit  88 ,  FIG. 9 . In the slit  88  a flat band spring  90  is arranged having a first upper end attached to a fixture post  92  on the proximal housing part  10 ,  FIGS. 4 and 7 . The second lower end of the band spring  90  is arranged with a coil  94 ,  FIG. 9 , which coil  94  fits into a cavity  96  attached to a plunger rod follower  98  positioned inside the magazine  86 ,  FIG. 9 . The function of the described components will be explained below. 
         [0042]    The proximal end of the plunger rod  66  extends into a space in the device intended to accommodate the medicament container  70 ,  FIG. 4 . The space is accessible via a hingedly attached lid  100 ,  FIGS. 1 and 4 , on an upper area of the housing. Inside the space a holder or cartridge retainer  102 ,  FIGS. 3 and 4 , is arranged, on which the medicament container  70  may be placed. In that respect, the cartridge retainer is arranged with a holding portion  104 ,  FIG. 4 , in which a neck portion  105 ,  FIG. 11 , of the medicament container  70  fits. A penetration mechanism  106  is further arranged in the device. It comprises a cup-shaped element  108 ,  FIG. 11 , arranged slidable in relation to the holding portion  104  and thus the neck portion  105  of the medicament container as seen in a longitudinal direction thereof. The cup-shaped element  108  is arranged with a hollow needle or a hollow pointed spike  110  directed towards the neck of the medicament container,  FIG. 11 , intended for piercing a septum  112  of the neck portion  105  of the medicament container  70 . 
         [0043]    Further, an end surface of the cup-shaped element  108  is arranged with a ledge  114  having an inclined surface  116 ,  FIG. 12 . The ledge  114  is intended to interact with a pusher  118  of the penetration mechanism. The pusher  118  is designed as a generally elongated rod  120  provided with an inclined surface  122 ,  FIG. 12 , arranged to be in contact with the inclined surface  116  of the cup-shaped element  108 . The pusher  118  is further arranged with a compression spring  124  arranged surrounding the rod  120  and fitted between a generally radially directed ledge  126  of the rod and a seat  128  in the housing parts as seen in  FIG. 7 . Further, in an initial position as seen in  FIG. 12 , the pusher  118  with its inclined surface  122  is somewhat turned in relation to the inclined surface  116  of the cup-shaped element  108 . In this position, the ledge  126  fits into a recess  127  in the seat  128 ,  FIG. 7 , thereby locking the pusher with spring  124  compressed. Further, a generally radially extending protrusion  132  is arranged on the rod of the pusher, below a surface area  131  on the side of the pusher  118 ,  FIG. 12 . 
         [0044]    The device is further arranged with an activation mechanism  129 ,  FIG. 13 . It comprises the two operating elements  20   a  and  20   b  that in the embodiment shown are arranged as push buttons. The push button  20   a  is arranged with a protrusion  130  on its side surface,  FIG. 12 . This protrusion  130  is intended to interact with the surface area  131  as will be explained below. Further, the protrusion  130  is positioned such in relation to the protrusion  132  of the pusher that any movement of the pusher in the vertical direction is prevented even if the ledge  126  would unintentionally be moved out of the seat  128 , which might occur if the device was shaken or dropped on a hard surface. 
         [0045]    Each push button  20   a, b , is arranged with a generally U-shaped guide element  134 ,  FIGS. 4 and 13 , where the free ends of the U&#39;s of the guide elements  134  are arranged with inwardly directed ledges  136 ,  FIG. 14 . These guide elements  134  are intended to interact with guide rails  138 ,  FIG. 6 , on an inner surface of the distal housing part  12 . The guide rails  138  are arranged with a generally T-shaped cross section as seen in  FIG. 14 . 
         [0046]    Further, one of the push buttons  20   b  is arranged with an elongated rod  140 ,  FIG. 13 . The end of the elongated rod  140  is arranged with a generally cylindrical body  142 . The cylindrical body  142  is designed to fit into a tubular body  144 , which also is attached to an elongated rod  146 . The elongated rod  146  is journalled in a post  147  of the other push button  20   a ,  FIG. 13 , so as to allow rotational movement of the elongated rod  146  and the tubular body  144  in relation to the push button  20   a.    
         [0047]    The cylindrical body  142  is further arranged with a ridge  148  extending in the longitudinal direction of the cylindrical body  142 . The ridge  148  fits into a slit  150  in the tubular body  144 , such that the bodies  142 ,  144  are rotationally locked to each other while allowing longitudinal movement between them. A compression spring  149 ,  FIGS. 13 and 15 , is arranged inside the tubular body  144  acting between an end wall  152  of the tubular body  144  and an end wall  154  of the cylindrical body  142 . The cylindrical body is further arranged with grooves  156 ,  FIGS. 15 and 16 , having a certain configuration as will be described. A guide element  158 ,  FIGS. 13 and 17 , is arranged to be placed in the grooves with a pin  160 . The pin  160  is attached to a generally T-shaped body  162 , which body  162  fits into a slit  164  in the tubular body, which slit  164  is arranged generally perpendicular to the longitudinal direction of the tubular body  144 , as seen in  FIG. 13 . These components form a pausing mechanism, as will be described. 
         [0048]    An actuation mechanism  165 ,  FIG. 18 , is further arranged to the activation mechanism. The actuation mechanism  165  comprises two elongated guide rods  166 ,  FIG. 18 , arranged slidable on the guide rails  138 ,  FIG. 6 . In that respect, the guide rods  166  preferably have the same shape as the guide elements  134  when seen in a cross-section. Each guide rod  166  is arranged with a ledge  168 ,  FIG. 18 a   , extending generally transversal to the longitudinal direction of the guide rod  166 . Each ledge  168  is designed to cooperate with a generally L-shaped holding element  170 ,  FIG. 6 , where the free end is arranged with a ledge  172  arranged to grip the transversal ledge  168  of the guide rod  166  as will be described. 
         [0049]    A linkage  167  is comprised in the actuation mechanism,  FIG. 18 , wherein each guide rod  166  is further arranged with a first attachment post  174  comprising a bearing passage. A bearing shaft of an actuator arm  176  is journalled in the first attachment post  174 . The opposite end of the actuator arm  176  is provided with a bearing shaft intended to fit into a bearing passage of a second attachment post  178 . The second attachment post  178  is in turn attached to an arm  180  of a needle holder  182 . The needle holder  182  is designed with a generally cylindrical outer shape. The needle holder is arranged with a central passage through which an injection needle  184  is extending. Further, a tube  186  is attached to one end of the injection needle  184 ,  FIG. 11 . The tube  186  then connects to the spike  110 , thereby providing a passage between the spike  110  and the injection needle  184 . 
         [0050]    A needle cover  188  is further arranged to the device,  FIGS. 3 and 7 . It comprises a generally tubular body having a number of longitudinally extending ribs  190  on its outer surface,  FIG. 7 , in the embodiment shown two ribs  190  arranged on opposite sides of the needle cover  188 . The ribs  190  end a short distance from a proximal end wall  192 ,  FIG. 3 , of the needle cover  188 , which distance generally corresponds to the thickness of the proximal housing part  10 . This is due to that the proximal end of the needle cover protrudes through a passage  194  in the proximal housing part,  FIG. 7 , where proximal end surfaces of the ribs  190  abut the inner surface of the proximal housing part  10  adjacent the passage  194 . 
         [0051]    The passage  194  is further arranged with cut-outs  196 ,  FIG. 7 , having generally the same shape as the ribs  190  in a cross-sectional view. The proximal end wall  192  of the needle cover  188  is further arranged with a central passage  198 ,  FIGS. 3 and 19 , which central passage  198  is surrounded by a generally tubular element  200 ,  FIGS. 7 and 19 , extending in the distal direction. The tubular element  200  has a diameter somewhat larger than the outer diameter of the needle holder  182 , where the latter is able to slide inside the tubular part along the proximal-distal axis  14 . The tubular element  200  is further arranged with two slits  202 ,  FIG. 7 , in which the arms  180  of the needle holder  182  may be positioned. 
         [0052]    Further the needle cover  188  is also arranged with slits  204 , with a first part  204   a  open in the distal direction, where the first part  204   a  transforms into a second generally circumferential second part  204   b , which in turn transforms into a third part  204   c  generally parallel with the first part  204   a  but closed in the distal end. The needle cover  188  is further arranged with radially outwardly extending ledges  206 , 
         [0053]      FIG. 7 , one on each side of the needle cover  188  as seen in the transversal direction. Further, a longitudinally extending ledge  207 ,  FIG. 7  is provided in the distal end surface of the needle cover  188 . Arms  208  are further arranged on the inner surface of the proximal housing part surrounding the passage extending in the distal direction,  FIG. 7 . These arms are arranged with radially inwardly extending ledges  210 . Further, a needle cover spring  211 ,  FIG. 19 , is arranged between the inner surface of the end wall  192  of the needle cover  188  and the arms  180  of the needle holder  182 . Also, a needle cap  209 ,  FIG. 2 , is releasibly arranged in the central passage  198  of the needle cover  188 , surrounding the needle and keeping it sterile. 
         [0054]    The device is further arranged with an injection speed control mechanism  212 ,  FIG. 8 , that preferably is capable of providing a constant injection speed during the injection. It comprises a transmission  213 ,  FIGS. 8 a  and 8 b   , with a first cogwheel  214 ,  FIG. 8 b   , acting on the ratchet  46  on the outer surface of the spring housing  40 , where the first cogwheel  214  has a smaller diameter than the ratchet  46 . The first cogwheel  214  is attached to a second cogwheel  216  having a diameter generally corresponding to the first cogwheel but with a larger number of teeth, wherein the first and second cogwheels  214 ,  216  are rotatably arranged to a first shaft  218 . The second cogwheel  216  is in engagement with a third cogwheel  220  having a smaller diameter. The third cogwheel  220  is attached to a fourth cogwheel  222  having a larger diameter. The third and the fourth cogwheel  220 ,  222  are rotatably arranged to a second shaft  224 . 
         [0055]    The fourth cogwheel  222  is then in engagement with a fifth cogwheel  226  having a smaller diameter. The fifth cogwheel  226  is attached to a sixth cogwheel  228  having a larger diameter. The fifth and the sixth cogwheels  226 ,  228  are rotatably arranged to a third shaft  230 . The sixth cogwheel  228  is in engagement with a seventh cogwheel  232 . The seventh cogwheel  232  is attached to an eighth cogwheel  234 . The seventh and eighth cogwheels  232 ,  234  are arranged on a fourth shaft  236 . The eighth cogwheel  234  is in engagement with a ninth cogwheel  238 . The ninth cogwheel is attached to an escapement wheel  240  having a number of teeth. The ninth cogwheel  238  and the escapement wheel  240  are arranged on a fifth shaft  241 . 
         [0056]    A pallet fork  242  is arranged rotatable on a shaft  244  where the arms of the fork are arranged to act on the teeth of the escapement wheel  240 . Further an arm  246  is arranged to the pallet fork  242  where the free end of the arm  246  is arranged with two fingers  248 . These fingers are in engagement with a protrusion  250  attached on a side surface of a regulator wheel  252 . One end of a balance spring  254  is attached to the regulator wheel  252  and the other end of the balance spring  254  is attached to a housing part of the device, capable of oscillating said regulator wheel when activated. 
         [0057]    The outer circumferential surface of the regulator wheel  252  is arranged with indentations  256 . The protrusion  250  of the regulator wheel  252  is positioned such in relation to the fingers  248  that oscillation of the regulator wheel  252  will cause the pallet fork  242  to swing back and forth. A more detailed function will follow below. A locking element  258  in the form of an arm attached to the push button  20   a ,  FIGS. 3 and 13 , is arranged to fit into the indentations  256  in an initial position of the push button  20   a , as will be explained below. 
         [0058]    The device is further arranged with an auto-stop mechanism  260 ,  FIG. 20 . It comprises a beam  262  arranged with a shaft  264  journalled in a post  266  on an inner surface of the proximal housing part  10 ,  FIG. 7 . The shaft  264  is positioned generally midway along the longitudinal direction of the beam, producing two oppositely directed first and second arms  268   a ,  268   b . An end of the first arm  268   a  is arranged to be in contact with one of the ledges  206  on the needle cover  188 , as seen in  FIG. 20 . A torsion spring  270  is further wound around the post  266  and is attached with one free end  272   a  to the second arm  268   b  of the beam. The other free end  272   b  of the torsion spring  270  is attached to a fixed housing part, in the embodiment shown the cartridge retainer  102 . The second arm  268   b  extends through an opening  274  in the magazine  86 ,  FIG. 4 , having a free end that is in contact with and pushes against the plunger rod segments  74  due to the force of the torsion spring  270 , as seen in  FIG. 20 . 
         [0059]    The device is further arranged with a manually operated stop mechanism  276 ,  FIG. 21 . It comprises an actuator element  278  in the form of a button that is accessible via an opening  280  in the distal housing part,  FIG. 6 . The actuator element  278  is arranged with an arm  282  having a generally U-shaped form as seen in cross-section. The free ends of the U are arranged with inwardly directed ledges. A guide post  284 ,  FIG. 6 , attached to the inner surface of the distal housing part, is arranged to fit inside the U-shaped arm, providing guiding action of the stop mechanism when moved linearly as will be described. The stop mechanism  276  further comprises a beam  286   FIG. 21 , directed generally transversal to the arm  282 . In an initial position of the stop mechanism, an upper surface of the arm  282  is in contact with the ledge  207  of the needle cover  188  as seen in  FIG. 21 . 
       Intended Function of the Device 
       [0060]    The device is usually delivered without a medicament container. Thus, before use, a medicament container  70  has to be inserted into the device. The lid  100  at the upper end of the device is then opened, whereby the space and the cartridge retainer  102  are accessible. The medicament container  70  is then inserted with a neck portion towards the holding portion  104  of the cartridge retainer  102 . The lid is then closed. 
         [0061]    The device is now made ready. This may be done by inserting an Allen key into the hole  22  on the proximal surface of the device and turning the shaft  24  in the clockwise direction. This in turn causes the arms  28  to slide over the teeth  36  because of the direction of the arms in relation to the teeth. Because the inner end of the spiral clock spring  38  is attached to the turning shaft  24  the spiral clock spring  38  is tensioned. When the user stops turning the shaft  24 , it is locked against rotating back because of the edges  30  of the arms  28  now locking against the teeth  36 . Also, after activation of the device, the shaft  24  cannot be rotated again. The device is now ready for delivering a dose of medicament. 
         [0062]    In the initial position, the operating elements, the activation buttons  20   a ,  20   b , are in their extended position as seen in  FIGS. 3 and 4 . In this position, the locking element  258  is in engagement with the regulator wheel  252 , as seen in  FIG. 3 , whereby action of the constant speed control mechanism  144  is prevented. The balance spring  254  has been tensioned beforehand. The process up to this point may be done without the device being in contact with the patient. In order to be able to deliver a dose of medicament to the patient, the needle cap  209  is removed from the central passage  198  of the needle cover  188  and the proximal surface of the device has to be in contact with some part of the body of the patient, i.e. to releasibly attach the device to the body. This may be performed in many ways, by straps, by merely pressing it manually, but preferably the proximal surface is arranged with some sort of adhesive, like sticky tape, with which the device may be fastened to the body. One variant is to have double-sided sticky tape on the proximal surface with an outer protective layer that is peeled off before attachment. 
       Activation of the Device 
       [0063]    When the device is to be activated, the user presses both activation buttons  20   a ,  20   b  towards each other. This causes several things to be initiated. 
         [0064]    1. Connection of Medicament Container 
         [0065]    When the activation button  20   a  is moved inwards, the protrusion  130  on the activation button is moved along the surface area  131  of the pusher, thereby turning the latter around its longitudinal axis. This causes the ledge  126  to be moved out of the locking engagement with the recess  127  out of contact with the protrusion  132  of the penetration mechanism. Also the protrusion  130  is moved away from the protrusions  132  of the pusher. Thus, the pusher  118  is released and is forced upwards due to the compression spring  124 ,  FIG. 22 . This causes the inclined surface  122  of the pusher  118  to be moved in contact with the inclined surface  116  of the ledge  114  of the cup-shaped element  108  such that cup-shaped element  108  and the spike  110  is moved towards the neck of the medicament container, which in turn causes the end of the spike  110  to penetrate the septum  112 , creating a passage between the interior of the medicament container and the injection needle via the tube  186 . 
         [0066]    2. Penetration of Patient 
         [0067]    The inwards pressing of the activation buttons causes the guide elements  134  to move inwards along the guide rails  138 . The guide elements  134  will thereby also move the guide rods  166  inwards,  FIG. 23 . Due to the attachment of the needle holder  182  with the guide rods  166  via the actuator arms  176 , the needle holder  182  with its injection needle  184  will move in the proximal direction whereby the injection needle  184  will extend in the proximal direction beyond the surface of the proximal housing part, causing a penetration of the patient. The advancement of the needle holder  182  with its arms  180  will compress the needle cover spring  211 , as seen in  FIG. 23 . When the guide rods  166  have advanced inwards a certain distance inwards, the ledges  168  of the guide rods  166  will pass the ledges  172  of the holding elements  170 . This prevents the guide rods  166  from moving back outwards, and holds thus the needle holder with the injection needle in the extended position as seen in  FIG. 23 . 
         [0068]    Also, when the activation buttons are pressed inwards, the cylindrical body  142  will move inside the tubular body  144 , compressing the spring  149 . The pin  160  of the guide element  158  will move in the grooves  156  on the outer surface of the cylindrical body as seen in  FIG. 16  from a start position I. When the pin  160  reaches position II and follows the inclined surface of the groove to position III, the body  162  of the guide element will move in the slit  164 . In this position, the activation buttons are in their most depressed position and the injection needle has penetrated the patient, who may now release the buttons. This will cause the pin  160  to move to position IV, keeping the activation buttons in a rather depressed state. 
         [0069]    3. Start of Injection 
         [0070]    The inwards pressing of the activation buttons will also cause the injection to start in that the locking element  258  of the activation button  20 a is moved out of contact with the indentations  256  of the regulator wheel  252 , as seen in  FIG. 22 . The tensioned balance spring  254  will now oscillate the regulator wheel  252 , whereby the pallet fork  242  will start to oscillate back and forth due to the contact with the protrusions  250  on the regulator wheel. 
         [0071]    This in turn will cause the escapement wheel  240  to move an increment or rotational angle per time unit, thus controlling the speed. This rotational speed is then transferred through the transmission  213  to the spring housing  40 , determining the rotational speed of the spring housing  40 . However, it is the spiral clock spring  40  that causes the spring housing  40  of the driver  50  to rotate, the transmission merely regulates the rotational speed. 
       Injection Operation 
       [0072]    The rotation of the spring housing  40  will cause its ratchet  46  to move around the circumference, thereby acting on the cogwheel  48  of the driver  50 . Thus the shaft  52  will rotate as will the second conical cogwheel  56 . The rotation of the conical cogwheel  56  is transferred to the third mating cogwheel and thus the drive wheel  61 . Because the teeth  62  of the drive wheel  61  are in engagement with the teeth  64  of the first plunger rod segment  68 , the first plunger rod segment  68  is moved in the direction of the medicament container  70 , whereby the pusher plate  72  acts on the stopper  69  in the medicament container  70 . When the first plunger rod segment  68  has moved a distance towards and inside the medicament container  70 , the space behind the first plunger rod segment  68  is so large that a subsequent plunger rod segment  74  may be pushed in the vertical direction by the flat band spring  90  acting on the lowermost positioned plunger rod follower  98  in the magazine  86 . When the following plunger rod segments  74  are pushed upwards in the vertical direction, they are connected to a previous plunger rod segment in that the ledges  82  of the nose  80  of the subsequent segment fit into the grooves  78  of the cut-out  76  of the previous segment and in that the plunger rod segments are inter-locked by the flexible tongues  84 . In this manner a sequentially “building” of a continuous plunger rod  66  is performed with the segments while performing injection of medicament from the medicament container  70  through the injection needle  184  via the tube  186 . 
       Pausing of the Injection 
       [0073]    The user may pause the injection by pressing shortly at both activation buttons  20 . This will cause the pin  160  of the pausing mechanism to be moved from position IV in  FIG. 16  to position V and along the inclined surface to position VI, causing the body  162  to move further upwards in the slit  164 . When the user releases the activation buttons, the spring  149  between the cylindrical body  142  and the tubular body  144  will force the buttons outwardly to the initial start position while the pin  160  also is moved back to the start position I along the walls of the groove as seen in  FIG. 16 . The return of the activation buttons to their initial positions will in turn bring the locking element  258  in engagement with the indentations  256  of the regulator wheel  252  such that the rotation of the regulator wheel  252  is stopped. This in turn stops the spring housing  40  from rotation via the transmission, whereby the injection is stopped. 
         [0074]    The user may then resume the injection by pressing again on the activation buttons  20   a, b , whereby the locking element  258  is moved out of contact with the regulator wheel, and the sequence continues in the same manner as described above. 
       Auto-Stop Function 
       [0075]    As described earlier, the second arm  268   b  of the auto-stop mechanism  260  is resting against the plunger rod segments  74  in the magazine. However, when the injection sequence is about to end when the medicament container has been emptied, there will be a space under the plunger rod follower  98 , which has been moved upwards during the “building” of the plunger rod. Thus the second arm  268   b  is moved out of contact and the force of the torsion spring  270  will cause the beam  262  to turn around its shaft  264 , whereby the first arm  268   a  will act on the ledge  206  of the needle cover  188 ,  FIG. 24 . This will in turn cause the needle cover  208  to be turned around its longitudinal axis, which coincides with the proximal-distal axis  14 . 
         [0076]    The turning of the needle cover  188  will further cause the arms  180  of the needle holder  182  to be moved from the first part  204   a  of the slit to the third part  204   c  of the slit via the second part  204   b ,  FIGS. 12 and 25 . The turning of the needle cover  188  will cause the ribs  190  on the outer surface of the needle cover to be aligned with the cut-outs  196 ,  FIG. 24  and due to the force of the needle cover spring  211  the needle cover  188  is urged in the proximal direction. When now the device is removed from the body of the patient, the needle cover  188  will extend and surround the needle cover  188 ,  FIG. 26 . The movement of the needle cover  188  is stopped when the ledges  206  come in contact with the inner surface of the proximal housing part  10 . 
         [0077]    When in this position, the ledges  210  of the arms  208  on the inner surface of the proximal housing part  10  will engage the distal end surface of the needle cover  188 , preventing any movement of the needle cover  188  in the distal direction, thus locking the needle cover  188  in relation to the housing and the injection needle. Further, one of the ledges  206  is moved in contact with the teeth of the escapement wheel  240 ,  FIG. 27 , thereby preventing any further action or movement of the injection speed control mechanism  212 , should a user be pressing on the activation buttons. Thus the device is locked and ready to be discarded. 
       Manual Stop Function 
       [0078]    Instead of the automatic stopping of the device, it may be stopped manually by a user. This is done by pressing the actuator element  278  upwards on the distal side of the device. This causes the arm  282  to slide vertically upwards, whereby the beam  286  is also moved upwards. This upwards movement of the beam will cause the needle cover  188  to rotate due to the contact between the beam  286  and the ledge  207 , which rotation performs exactly the same functional sequence as with the automatic stop function,  FIG. 28 . Thus the needle cover  188  will be extended and locked in the extended position and the injection speed control mechanism  212  will be locked by the interaction of the ledge  206  with the escapement wheel  240 . The device may now be removed and discarded. 
         [0079]    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.