Abstract:
The present invention relates to an injection device comprising a housing, a resilient member adapted to provide a force in the axial direction of the injection device for ejecting a dose from the injection device. The injection device further comprises a dose setting member operatively connected to a dose indicator barrel positioned within the housing, the dose setting member and the dose indicator barrel being movable relative to each other and cooperating to set the dose to be ejected from the injection device. The dose indicator barrel undergoes, during dose setting, a combined rotational and translational movement within the housing and relative to the housing.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a 35 U.S.C. §371 national stage application of International Patent Application PCT/EP2005/011288 (published as WO 2006/045529), filed Oct. 20, 2005, which claimed priority of European Patent Application 04077901.9, filed Oct. 21, 2004; this application further claims priority under 35 U.S.C. §119 of U.S. Provisional Application 60/626,250, filed Nov. 9, 2004. 
     FIELD OF THE INVENTION 
     The present invention relates to an injection device having an internally positioned dose indicator barrel adapted to display a dose of medicament to be ejected from the injection device. 
     BACKGROUND OF THE INVENTION 
     Various types of injection devices have been described over the years. However, injection devices formed as pen-type injection devices have attracted special attention over recent years. 
     For example, EP 0 338 806 discloses pen-like syringe incorporating a dose metering device. The pen is provided with a cap rotatable, with respect to a pen body, to a position representing the dose of medicament (for example insulin) to be injected. The rotation loads a torsion spring, which is prevented from unwinding by co-operating teeth. When the dose is to be injected, a trigger slide is moved to the left causing the toothing to come out of engagement. This disengagement allows the spring to unwind. The unwinding of the spring causes a drive sleeve, drive gear and a drive plunger to rotate. The drive plunger is formed with a quick pitch screw thread so that its rotational movement is accompanied by an axial movement which causes medicament to be discharged from a cartridge and injected through a needle. 
     EP 0 338 806 is based on a torsion spring. However, by applying a linear spring the axial movement of an integrated dose metering device could be made independent of the pitch screw threads on the plunger and the integrated dose metering device would be capable of rotating more than one revolution following a helical pattern. 
     U.S. Pat. No. 6,673,035 discloses a medical injector and medicament loading system for use therewith. The medicament loading system includes cap for a medicament cartridge. The cap has a post for causing movement of the cartridge stopper toward the seal when the cap engages the medicament cartridge to thereby eliminate adhesion between the medicament chamber and the stopper. The medical injector according to the present invention includes the medicament loading system, i.e. a cartridge assembly, a needle free syringe assembly, and a power pack assembly. 
     WO 02/053214 relates to a dose setting and expelling device comprising a drive member and a dose setting mechanism which simultaneously sets a given dose and stores the energy necessary for subsequently driving the drive member in order to expel a dose of medicine from an injection device. According to WO 02/053214 the dose setting mechanism allows adjustment in both directions, such that a given set dose can be reduced or cancelled by reversing the input motion, typically by rotating a setting member in a backward direction. Thus, WO 02/053214 discloses a simple dose setting and reverse mechanism. However, it is a disadvantage of the arrangement suggested in WO 02/053214 that the axial movement of an integrated dose metering device is dependent on the pitch screw threads on the plunger. 
     It is an object of the present invention to provide an injection device where the axial movement of the dose metering device is independent of the pitch of the threads on the plunger. 
     It is a still further object of the present invention to provide an injection device with a dose metering device allowing larger read-outs compared to known systems. 
     SUMMARY OF THE INVENTION 
     The above-mentioned objects are complied with by providing, in a first aspect, an injection device comprising
         a housing,   a resilient member adapted to provide a force in the axial direction of the injection device, the force being necessary for ejecting a dose from the injection device, and   a dose setting member operatively connected to a dose indicator barrel positioned within the housing, the dose setting member and the dose indicator barrel being movable relative to each other and cooperating to set the dose to be ejected from the injection device,
 
wherein the dose indicator barrel, during dose setting, undergoes a combined rotational and translational movement within the housing and relative to the housing. The dose indicator barrel ( 4 ) may engage a threaded portion of the housing ( 8 ).
       

     In a first embodiment of the present invention, the dose setting member may engage the dose indicator barrel and the injection device may further comprise
         a piston rod having a threaded outer surface with a drive track arranged in a longitudinal direction of the outer surface of the piston rod,   a drive member engaging at least part of the drive track of the piston rod and having a threaded inner surface cooperating with a threaded portion arranged on an outer surface of the dose indicator barrel, the drive member being adapted to drive and rotate with the piston rod during ejection of a dose from the injection device,
 
wherein the housing has a threaded portion cooperating with the threaded outer surface of the piston rod so that rotation of the piston rod results in an axial movement of the piston rod.
       

     The drive track arranged in the piston rod may be an indentation in the longitudinal direction of the piston rod. Alternatively, it may also be a planar surface or two opposing planar surfaces as illustrated in for example  FIG. 2 . 
     In a second embodiment of the present invention, the dose setting member may engage the dose indicator barrel and the injection device may further comprise
         a piston rod having a threaded outer surface with a track arranged in a longitudinal direction of the outer surface of the piston rod,   a drive member having a threaded portion cooperating with the threaded outer surface of the piston rod, and having a threaded inner surface cooperating with a threaded portion arranged on an outer surface of the dose indicator barrel, the drive member being adapted to rotate relative to the piston rod during ejection of a dose from the injection device,
 
wherein the housing engages at least part of the track of the piston rod so that rotation of the drive member results in an axial movement of the piston rod.
       

     In a third embodiment of the present invention, the injection device may further comprise
         a piston rod having a threaded outer surface with a drive track arranged in a longitudinal direction of the outer surface of the piston rod,   a resilient member housing being at least partly defined by the dose indictor barrel in combination with a main member, the dose indicator barrel and the main member being movable in relation to each other, the main member having a threaded portion cooperating with the threaded outer surface of the piston rod,   a drive member operatively connected to the main member via a toothing so that the drive member is movable in relation to the main member during dose setting but rigidly connected to the main member during ejection of a dose from the injection device, the drive member engaging at least part of the drive track on the outer surface of the piston rod,
 
wherein the housing has a threaded portion cooperating with the threaded outer surface of the piston rod so that rotation of the piston rod by the drive member results in an axial movement of the piston rod.
       

     In the third embodiment, the injection device may further comprise an intermediate part engaging the dose setting member and the main member of the resilient member housing, the intermediate part being adapted to provided a biasing force to the drive member in a direction towards the toothing. 
     In a fourth embodiment of the present invention, the injection device may further comprise
         a piston rod having a threaded outer surface with a drive track arranged in a longitudinal direction of the outer surface of the piston rod,   a resilient member housing being at least partly defined by the dose indictor barrel and a main member,   a drive member operatively connected to the main member via a toothing in such a way that the drive member is movable in relation to the main member during dose setting but rigidly connected to the main member during ejection of a dose from the injection device, the drive member having threaded portion cooperating with the threaded outer surface of the piston rod,
 
wherein the housing engages at least part of the track of the piston rod so that rotation of the drive member results in an axial movement of the piston rod.
       

     The injection device according to the first and third embodiments may further comprise a locking member adapted to fixate the piston rod in such a way that no relative rotation of the piston rod and the housing is possible when the locking member is in its locking position. The injection device may further comprise a release button adapted for releasing the locking member from its locking position. The release button may be positioned in the distal half of the length of the injection device. 
     The injection device according to the second and fourth embodiment may further comprise a locking member adapted to fixate the drive member in such a way that no relative rotation of the drive member and the housing is possible when the locking member is in its locking position. The injection device may further comprise a release button adapted for releasing the locking member from its locking position, the release button being adapted to be released by a user of the injection device. The release button may be positioned in the distal half of the length of the injection device. 
     The resilient member may comprise a spring, such as a helical spring. The helical spring may be arranged coaxially with the piston rod. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will now be described with reference to the accompanying figures wherein 
         FIG. 1  is a cross sectional view of an injection device according to a first embodiment of the present invention, 
         FIG. 2  is a cross sectional view of an injection device according to a second embodiment of the present invention, 
         FIG. 3  is a cross sectional view of an injection device according to a third embodiment of the present invention, and 
         FIG. 4  is a cross sectional view of an injection device according to a fourth embodiment of the present invention. 
     
    
    
     While the invention is susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and will be described in detail herein. It should be understood, however, that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims. 
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  is a cross-sectional view showing half of an injection device  1  according to a first embodiment of the present invention. The injection device  1  comprises a dose setting member  2  being adapted to rotate about a centre axis of the injection device  1 . It further comprises a dose indicator barrel  4 , a threaded piston rod  5 , a drive member  6  adapted to move the piston rod  5  along the centre axis, a helical spring  7  extending along and concentrically with the centre axis, and a housing  8 . 
     The dose setting member  2  engages the dose indicator barrel  4  via a key/keyway connection. The key/keyway connection ensures that rotation of the dose setting member  2  about the centre axis causes rotation of the dose indicator barrel  4  about the centre axis, and advice versa. Furthermore, the key/keyway connection ensures that the dose setting member  2  and the dose indicator barrel  4  are slidably movable in relation to each other in a direction which is substantially parallel to the centre axis. 
     Similarly, the drive member  6  engages the outer threaded portion of the piston rod  5  via a threaded portion of the drive member. 
     The dose indicator barrel  4  is provided with a threaded portion  9  which engages a threaded portion  10  of the drive member  6 . 
     The injection device  1  is further provided with a locking member  11  which may be switched between a locking state and an unlocking state. When the locking member  11  is in its locking state (as shown in  FIG. 1 ) it prevents the drive member  6  from rotating about the centre axis. On the other hand, when the locking member  11  is in its unlocking state, the drive member  6  is free to rotate about the centre axis. The dose setting member  2  is connected to the housing  8  via a toothing connection  3 . The toothing connection  3  allows the dose setting member  2  and the housing  8  to be rotationally movable in relation to each. However, the helical spring  7  provides an axial force to the dose setting member  2  and thereby to the toothing so that the dose setting member  2  stays in a set position. 
     The injection device of  FIG. 1  is preferably operated in the following manner. 
     When a dose is to be set, the locking member  11  is switched to its locking state. In most cases, the locking state is the default position of the locking member  11 . The user then causes the dose setting member  2  to rotate about the centre axis by turning a protruding part  12  of the dose setting member  2 . Due to the key/keyway connection between the dose setting member  2  and the dose indicator barrel  4 , the dose indicator barrel  4  is also caused to rotate about the centre axis. Since the threaded portion  9  of the dose indicator barrel  4  engages the threaded portion  10  of the drive member  6 , this rotation forces the dose indicator barrel  4  in a direction parallel to the centre axis and towards the protruding part  12  of the dose setting member  2 . Thus, the dose indicator barrel  4  performs a sliding movement along the key/keyway connection between the dose setting member  2  and the dose indicator barrel  4 . This movement causes the helical spring  7  to be compressed, thereby storing energy in the spring  7 . Thus, the dose is set without causing any changes to the outer appearance of the injection device  1 , including an outward movement of the dose setting member  2 . 
     The dose indicator barrel  4  is provided with a set of numerals (not shown). As the dose indicator barrel  4  moves towards the protruding part  12  of the dose setting member  2 , these numerals will be sequentially visible through a window  13  in the drive member  6 , thereby indicating the dose which has been set. In order for the user of the injection device to view the numerals on the dose indicator barrel  4 , the housing  8  is equipped with a belt-like window aligned with the window  13  in the drive member  6 . 
     When the desired dose has been set, a needle (not shown) positioned opposite the protruding part  12  of the dose setting member  2  is inserted into a desired body part of the user. Then the locking member  11  is switched to its unlocking state, thereby allowing rotation of the drive member  6  about the centre axis. Due to the energy stored in the compressed helical spring  7 , the dose indicator barrel  4  is forced towards its initial position, i.e. away from the protruding part  12  of the dose setting member  2 . Via the threaded portion  10  and the threaded portion  9  of the dose indicator barrel  4 , the drive member  6  is thereby caused to rotate about the centre axis, and due to a key/keyway connection between the housing  8  and the piston rod  5 , the piston rod  5  will perform an axial movement away from the protruding part  12 , thereby causing the desired and set dose to be ejected from the injection device  1 . 
     Alternatively, the drive member  6  may comprise a key/keyway connection with the piston rod  5 . Thus, the threaded portion of the drive member  6  will in this case be replaced by the key/keyway connection between the drive member  6  and the piston rod  5 . In this case the piston rod  5  will rotate about the centre axis when the locking member  11  is switched to its unlocking state. The rotational movement causes the piston rod  5  to be moved in a direction parallel to the centre axis and away from the protruding part  12  of the dose setting member  2 . The reason for this being that the threaded outer surface of the piston rod  5  engages a threaded portion of the housing  8 . This movement will cause a dose to be ejected from the injection device  1 . 
     When the dose has been ejected, the various parts of the injection device  1  are again in their initial position, except for the fact that the piston rod  5  has been moved in a direction away from the protruding part  12  of the dose setting member  2  due to the dose having been ejected. Even further, the angular position of the drive member  6  has changed whereby the “new” zero point has been angularly shifted relative to the housing  8 . Thus, the injection device  1  is now ready for setting a new dose. 
       FIG. 2  is a cross-sectional view showing half of an injection device  1  according to a second embodiment of the present invention. This embodiment is similar to the embodiment shown in  FIG. 1 , and like parts have therefore been provided with like reference numerals. Thus, the injection device  1  shown in  FIG. 2  also comprises a close setting member  2  being adapted to rotate about a centre axis of the injection device  1 . It further comprises a dose indicator barrel  4 , a threaded piston rod  5 , a drive member  6  adapted to rotationally drive the piston rod  5  about the centre axis, a helical spring  7  extending along and concentrically with the centre axis, and a housing  8 . 
     The dose indicator barrel  4  engages a main member  15  via a key/keyway connection similar to the one described above. The drive member  6  is connected to the main member  15  via a toothing connection  19  allowing the drive member  6  and the main member  15  to be rotationally movable in relation to each. However, the helical spring  7  provides an axial force to the main member  15  and thereby to the toothing  19  so that the dose setting member  2  stays in a set position. An intermediate member  16  engages the dose setting member  2  via a key/keyway connection. It is also operationally connected to the main member  15  in such a way that when the intermediate member  16  rotates about the centre axis the main member  15  also rotates about the centre axis and vice versa. Finally, the main member  15  engages the threaded portion of the piston rod  5 . 
     The dose indicator barrel  4  is provided with a threaded portion  9  which engages a threaded portion  17  of the housing  8 . 
     The injection device  1  is further provided with a locking member  11  which may be switched between a locking state and an unlocking state. When the locking member  11  is in its locking state (as shown in  FIG. 2 ) it prevents the piston rod  5  from rotating about the centre axis. On the other hand, when the locking member  11  is in its unlocking state, the piston rod  5  is free to rotate about the centre axis. 
     The drive track  21  arranged in the piston rod may be an indentation or groove in the longitudinal direction of the piston rod. Alternatively, it may also be a planar surface or two opposing planar surfaces. 
     The injection device  1  of  FIG. 2  is preferably operated in the following manner. 
     When a dose is to be set, the locking member  11  is switched to its locking state which may be the default position of the locking member  11 . The user then causes the dose setting member  2  to rotate about the centre axis by turning an outer part  18  of the dose setting member  2 . The outer part  18  of the dose setting member  2  is a part which is positioned on the outside of the housing  8  as illustrated in  FIG. 2 . Due to the connections between the various parts of the injection device  1  described above, the rotation of the dose setting member  2  about the centre axis causes the intermediate member  16 , the main member  15  and the dose indicator barrel  4  to be rotated about the centre axis. The drive member  6  is not rotated due to the toothing connection between the drive member  6  and the main member  15 . Since the threaded portion  9  of the dose indicator barrel  4  engages the threaded portion  17  of the housing  8 , and due to the main member  15  engaging the threaded part of the piston rod  5 , the dose indicator barrel  4  and the main member  15 /intermediate member  16  will be moved towards each other. This causes the helical spring  7  to be compressed, thereby storing energy in the spring  7 . Thus, as it is the case in the embodiment shown in  FIG. 1 , the dose is set without causing any changes to the outer appearance of the injection device  1 . 
     The dose indicator barrel  4  is provided with a set of numerals (not shown). As the dose indicator barrel  4  moves away from the outer part  18  of the dose setting member  2 , these numerals will be sequentially visible through a window  13  in the housing  8 , thereby indicating the dose which has been set. 
     When the desired dose has been set, actions similar to the ones described above in connection with  FIG. 1  are performed. However, when the locking member  11  is switched to its unlocking state the following happens. The piston rod  5  is now free to rotate about the centre axis. Due to the energy stored in the helical spring  7 , the dose indicator barrel  4  and the main member  15 /intermediate member  16  will be forced away from each other. Due to the threaded portion  9  engaging the threaded portion  17  of the housing  8 , the dose indicator barrel  4  is thereby rotated about the centre axis in a rotational direction which is opposite to the direction in which it was rotated when the dose was set. This, in turn, will cause the main member  15 , the intermediate member  16  and the dose setting member  2  to rotate about the centre axis in the same direction. Due to the toothing connection between the main member  15  and the drive member  6 , the drive member  6  is also caused to rotate about the centre axis, and due to the key/keyway connection between the drive member  6  and the piston rod  5 , the piston rod  5  is also caused to rotate about the centre axis. The threaded part of the piston rod  5  engages a threaded portion  14  of the housing  8 . Therefore the rotational movement causes the piston rod to be moved in a direction parallel to the centre axis and away from the outer part  18  of the dose setting member  2 , thereby causing the desired and set dose to be ejected from the injection device  1 . 
     As described above, the injection device  1  is now ready for setting a new dose. 
     Alternative embodiments are shown in  FIGS. 3 and 4 . Compared to the second embodiment shown in  FIG. 2 , the intermediate member  16  has been omitted whereby the mechanical design of the injection device has been significantly simplified. In  FIGS. 3 and 4  the main member  15  is operatively connected to drive member  6  via toothing  19 . In  FIG. 3  the threaded outer surface of the piston rod  5  engages with a threaded portion  14  of the housing  8 , whereas in  FIG. 4  the threaded outer surface of the piston rod  5  engages with a threaded portion  20  of the drive member  6 . 
     Thus, in the embodiment shown in  FIG. 1  as well as in the embodiment shown in  FIG. 2 , the ejection of the dose is actually effected by the energy stored in the helical spring  7  when setting the dose, and the only effort required from the user of the injection device  1  in order to cause the ejection is the switching of the locking member  11  from its locking state to its unlocking state. This is very easily done and an ejection can therefore be caused even by persons having reduced motoric skills or reduced finger strength, such as children, elderly people or disabled people.