Abstract:
A medicament injection device arranged to receive a replaceable container subassembly includes front and rear housings releasably connectable to each other. A reloadable drive mechanism is accommodated in the rear housing for acting on the plunger of a replaceable container subassembly for expelling medicament. A needle hider front is slidably arranged within the front housing. A needle shield remover is arranged to connect with a needle shield of the replaceable container subassembly and to be removably inserted into a proximal end of the front housing through the needle hider front. The needle shield remover is adapted to interact with the reloadable drive mechanism such that a user can reload the drive mechanism.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to an injection device, especially a reusable auto injector. 
       BACKGROUND OF THE INVENTION 
       [0002]    Reusable auto injectors which can be loaded with a container subassembly, such as a syringe, are known in the prior art. US- 5599309  discloses an auto injector for use with proprietary syringes. That prior art discloses a device comprising a drive member that receives the rear end of a plunger of a syringe and a trigger for releasing the drive member such that a medicament can be injected. Drawbacks with that prior art are that needle is outside the device and visible to the user after the device has been removed from the injection site and that the re-loading is complicated and time consuming. 
       SUMMARY OF THE INVENTION 
       [0003]    It is therefore an object of the invention to provide an injection device with improved user friendliness. In particular, it is an object of the present invention to provide an injection device where the needle is kept non-visible to the user at all times and that the device is easily re-loadable. This object and other objects are solved by an injection device as defined in claim  1 . This object and other objects are also solved by a method as defined in claim  15 . Preferred embodiments of the present invention are defined in the dependent claims. 
         [0004]    Thus, in accordance with an aspect of the present invention, there is provided a medicament injection device having a proximal end and a distal end and being arranged to receive a replaceable container subassembly having a medicament container with a plunger therein, a needle and a needle shield. The medicament injection device comprises a front housing and a rear housing which are releasably connectable to each other and a reloadable drive mechanism is accommodated in the rear housing for acting on the replaceable container subassembly. The reloadable drive mechanism is moveable between a cocked and an extended position and a release mechanism is provided for releasing the drive mechanism from said cocked position to said extended position. A needle hider front is slidably arranged within the front housing. A needle shield remover is arranged to connect with a needle shield of the replaceable container subassembly received in the reloadable medicament injection device, wherein the needle shield remover is arranged to be removably inserted into a proximal end of the front housing through the needle hider front. The needle shield remover, when inserted into the front housing is adapted to be used to interact with the reloadable drive mechanism accommodated in said rear housing such that a user can re-locate the reloadable drive mechanism from said extended position to said cocked position. By designing a needle shield remover and the front housing having a needle hider front such that needle shield remover together with the front housing can be used for reloading the drive mechanism, the use of the device is simplified and improved to a large extent. A user simply has to release the front housing from the rear housing, replace the needle shield remover and then turn the front housing 180 degrees and use the needle shield remover to push the drive mechanism from its proximal, extended position to its distal, cocked position. By providing a needle hider front at the proximal end of the front housing, the needle can be kept out of sight of a user. Many users prefer not to see the needle, neither during use, nor when the device is not used. 
         [0005]    In accordance with an embodiment of the medicament injection device according to the invention, a needle hider body is arranged within the front housing and the needle hider front is adjustably connected to the needle hider body by means of a threaded connection. This assures that the needle is kept out of sight at all times. 
         [0006]    In accordance with an embodiment of the medicament injection device according to the invention, the needle shield remover and the needle hider front are arranged to mate with each other such that axial movement of the needle shield remover relative to the needle hider front is allowed while rotation of the needle shield remover relative to the needle hider front is prevented. This arrangement allows a user to use the needle shield remover to adjust the axial position of the needle hider front which is connected by a threaded connection to the needle hider body by holding the front housing while turning the needle shield remover. 
         [0007]    In accordance with an embodiment of the medicament injection device according to the invention, the needle hider body is axially moveable within the front housing between a proximal end position and a distal end position and wherein a syringe guide is arranged within said needle hider body for receiving a replaceable container subassembly, said syringe guide being axially moveable between a proximal end position and a distal end position relative to the front housing and wherein a proximal end surface of the syringe guide defines a maximum insertion depth for the needle shield remover. The proximal end surface of the syringe guide defines the maximum insertion depth of the needle shield remover and acts as an abutment such that the front housing can be used to relocate the drive mechanism in the rear housing. 
         [0008]    In accordance with an embodiment of the medicament injection device according to the invention, a first biasing member is arranged between the syringe guide and the needle hider body. This first biasing member biases the syringe guide towards said distal end position and the needle hider body towards said proximal end position. The first biasing member ensures that the needle hider moves out and covers the needle as soon as the injection device is removed from the injection site such that the needle never will be visible to the patient. 
         [0009]    In accordance with an embodiment of the medicament injection device according to the invention, a resilient syringe collar is arranged at a distal end of the syringe guide, said resilient syringe collar being adapted to receive and hold a replaceable container subassembly. The resilient syringe collar, made from e.g. rubber, will make sure that the replaceable container subassembly is firmly held in place while still being replaceable. 
         [0010]    In accordance with an embodiment of the medicament injection device according to the invention, the front housing comprises internal abutment surfaces defining said proximal end positions and distal end positions for the needle hider body and the syringe guide relative to the front housing. 
         [0011]    In accordance with an embodiment of the medicament injection device according to the invention, the penetration depth of a needle of a container subassembly received in the reloadable medicament injection device is adjusted by adjusting the position of the needle hider front. The threaded connection of the needle hider front to the needle hider body is a simple solution providing an adjustable penetration depth. 
         [0012]    In accordance with an embodiment of the medicament injection device according to the invention, the needle hider front comprises indication means presenting a set needle penetration depth. The indication means can be in the form of numerals visible in a window or opening in the front housing clearly indicating the currently set penetration depth. 
         [0013]    In accordance with an embodiment of the medicament injection device according to the invention, the needle shield remover comprises flexible hook means arranged to grasp the needle shield of a replaceable container subassembly received in the reloadable medicament injection device. When the needle shield remover is inserted into the proximal end of the front housing through the needle hider front the flexible hook means will deflect over the outer surface of the needle shield and as soon as the flexible hook means passes the distal end of the needle shield they will flex back to a less biased position and the hook means, preferably provided with a fluke, or barbed element, will securely grasp the needle shield such that when the needle shield remover is pulled out of the front housing, the needle shield will be pulled off the container subassembly received in the medicament injection device. 
         [0014]    In accordance with an embodiment of the medicament injection device according to the invention, the reloadable drive mechanism comprises an axially moveable plunger rod driver and a drive spring biasing the plunger rod driver towards the proximal end position. The plunger rod driver and the rear housing comprise corresponding guide means for guiding the plunger rod driver during movement within the rear housing. By providing the drive mechanism and its components in the rear housing, and since the rear and front housings are separable, reloading of the drive mechanism is simplified. 
         [0015]    In accordance with an embodiment of the medicament injection device according to the invention, the plunger rod driver is configured to act on the plunger of the replaceable container subassembly for moving axially said replaceable container subassembly in relation to the front housing such that said needle is penetrated and said medicament is expelled through said needle. Obviously, it is understandable that the plunger rod driver is configured to act directly on the plunger when the plunger rod driver may comprise a plunger rod or indirectly through a plunger rod which is part of the container subassembly. 
         [0016]    In accordance with an embodiment of the medicament injection device according to the invention, the rear housing comprises a button blocker moveable within the rear housing between a proximal end position, in which the button blocker prevents the release mechanism from releasing the drive mechanism from said cocked position to said extended position, and a distal end position, in which the button blocker allows the release mechanism to release the drive mechanism from said cocked position to said extended position, wherein the button blocker is moved from said proximal end position to said distal end position when the needle hider body is axially moved within the front housing from said proximal end position to said distal end position. This means that the button blocker is released only when the needle hider body is pushed towards a distal end position, e.g. when the medicament injection device is pushed against a patient&#39;s skin, which ensures that the medicament injection device is not inadvertently discharged. 
         [0017]    In accordance with an embodiment of the medicament injection device according to the invention, a second biasing member is provided within the rear housing biasing the button blocker towards said proximal end position. This ensures that as soon as the plunger rod driver is pushed back to its distal end position, the button blocker will assume its proximal end position where release of the drive mechanism is prevented. 
         [0018]    In accordance with another aspect of the present invention, there is provided a method for reloading a medicament injection device according to the first aspect of the invention. There, a user removes the front housing from the rear housing having the needle shield remover arranged at the front housing through the needle hider front, and brings the proximal end of the needle shield remover in contact with a proximal end of the reloadable drive mechanism accommodated in said rear housing and subsequently moves the reloadable drive mechanism from said extended position to said cocked position by pushing said front housing and said needle shield remover axially towards said rear housing and said drive mechanism. 
     
    
     
       BRIEF DESCIRPTION OF THE DRAWINGS 
         [0019]    The invention will now be described in more detail and with reference to the appended drawings in which: 
           [0020]      FIG. 1   a  is a schematic perspective view of an embodiment of the medicament delivery device according to the invention in a disassembled state. 
           [0021]      FIG. 1   b  is a schematic perspective view of an embodiment of the medicament injection device according to the invention in an assembled state. 
           [0022]      FIG. 2   a  is a schematic exploded perspective view of an embodiment of the rear housing of the medicament injection device according to the invention. 
           [0023]      FIG. 2   b  is a schematic exploded perspective view of an embodiment of the rear housing of the medicament injection device according to the invention. 
           [0024]      FIG. 3  is a schematic perspective cross-section of an embodiment of the front housing of the medicament injection device according to the invention. 
           [0025]      FIG. 4  is a schematic perspective view of an embodiment of the front housing of the medicament injection device according to the invention. 
           [0026]      FIGS. 5   a  and  5   b  is a schematic perspective view of method steps according to the invention. 
           [0027]      FIGS. 6   a ,  6   b ,  7   a  and  7   b  are schematic perspective cross-sections of an embodiment of the medicament injection device according to the invention. 
       
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0028]    As used herein, the term “container” encompasses all types of containers suitable for injectable liquid composition. Concerning the terms “distal” and “proximal” they refer to points which are further away and closer to the injection site respectively. 
         [0029]    In a first embodiment of a medicament delivery device  100  according to the invention, as shown in  FIGS. 1   a  and  1   b , a medicament injection device  100  comprises a rear housing  101  made from e.g. thermoplastic, a front housing  102  and a replaceable container subassembly  103 , such as a syringe. The rear and front housings  101 ,  102  are connectable to each other by e.g. a twisting coupling. Typically, the front and rear housings  101 ,  102  can be connected and disconnected by a 90 degree relative twist of the housings  101 ,  102 . The replaceable container subassembly  103  may comprise a needle (not shown in  FIG. 1   a ), a medicament container  15 , a plunger  14 , a plunger rod  13  and a needle shield  11  arranged to protect users from the needle. Obviously, it is also imaginable that the container subassembly  103  lacks a plunger rod  13  and that this plunger rod is part of the device. 
         [0030]      FIGS. 2   a  and  2   b  disclose the rear housing  101  comprising the drive mechanism  108 . The drive mechanism  108  comprises a plunger rod driver  1  arranged axially moveable within the rear housing  101  between a proximal end position (shown in  FIG. 2   a ) and a distal end position (shown in  FIG. 2   b ). The proximal end position of the plunger rod driver  1  corresponds to a position where the plunger rod  13  and the plunger  14  of the replaceable container subassembly  103  have been pressed to the end of its stroke, i.e. the medicament container  15  has been emptied, and the distal end position of the plunger rod driver  1  corresponds to a position where the plunger rod  13  and the plunger  14  of the replaceable container subassembly  103  have not yet been moved, i.e. the medicament container  15  is full. The drive mechanism  108  further comprises a drive spring  2 , here in the form of a helical coil spring, which biases the plunger rod driver  1  towards its proximal end position. A release mechanism  3  for releasing the plunger rod driver  1  of the drive mechanism  108  from the distal, or cocked, position to the proximal, or extended, position is arranged at an upper surface of the rear housing  101 . The release mechanism  3  is pivotable around a pivoting axle  6  between an extended position (shown in  FIG. 2   b ) and a depressed position (shown in  FIG. 2   a ) and comprises a trigger button  4  and an abutment member  5  which abuts and interworks with the plunger rod driver  1 . In  FIG. 2   a , the release mechanism  3  has been depressed and the plunger rod driver  1  has adopted its extended, proximal end position. In this position the abutment member  5  abuts an upper surface of the plunger rod driver  1  and prevents the release mechanism  3  from pivoting back around pivot axle  6 . The design of the details imply that as long as the plunger rod driver  1  is not in its distal end position, the release mechanism  3  cannot assume its extended position but is instead locked in the depressed position. A resilient member (not shown in the figures) is provided biasing the trigger button  4  towards its extended position which means that when the interaction between the plunger rod driver  1  and the release mechanism  3  allow for it, i.e. when the abutment member  5  of the release mechanism  3  reaches recess  9  in the plunger rod driver  1 , the release mechanism  3  will assume its extended position (see  FIG. 2   b ). Adjacent, or at least near, the release mechanism  3  a status window  7  is arranged through which symbols provided on the plunger rod driver  1  are visible to indicate the status of the medicament delivery device  100 . The status window is preferably made of a transparent, or at least translucent, plastic material. The rear housing  101  can be made up of two halves which are secured to each other by means of pins or projections  8  provided at one of the halves and corresponding openings  8 ′ (not shown in  FIG. 2   a  or  2   b ) in the other halves. Obviously, other solutions are imaginable, such as tongue and groove solutions; snap catch elements; or even permanent securing with welding or gluing. Interacting guide means  10  are provided on an outer surface of the plunger rod driver  1  and an internal surface of the rear housing  101  guiding the plunger rod driver  1  during its movement within the rear housing  101 . 
         [0031]      FIG. 3  shows a cross-section of a front housing  102  provided with a replaceable container subassembly in the form of a syringe  103  and a needle shield remover  109  partially arranged at a proximal end of the front housing  102  and grasping a needle shield  11  encompassing a needle  12  of syringe  103 . The syringe  103  further comprises a plunger rod  13 , a plunger  14  and a medicament container  15 . A needle hider front  16  is provided at a proximal end of the front housing connected to a needle hider body  17  by means of a threaded connection  18 , more specifically the needle hider front  16  is provided on the needle hider body  17 . The needle shield remover  109  comprises a proximal and a distal end, wherein the distal end is arranged at the proximal end of the front housing  102  through the needle hider front  16 . The threaded connection  18  provides a user with a possibility of adjusting the penetration depth of needle  12  during use. The needle hider body  17  extends through the inside of the front housing  102  and encompasses the syringe  103 . The purpose of the needle hider body  17  and the needle hider front is to hide the needle from a user, both during and between uses of the device. The needle hider body  17  and front housing  102  are provided with corresponding abutment surfaces  20 ,  21  which define the distal and proximal end positions of the axial movement of needle hider body  17  relative to the front housing  102 . This relative axial movement in combination with the adjustability of the needle hider front  16  ensures that the needle  12  is kept non-visible at all time. A syringe guide  24  is arranged within front housing  102 , more specifically within the needle hider body  17 , axially moveable between a distal end position and a proximal end position relative to the front housing  102 . The proximal end position is defined by corresponding abutment surfaces (not shown) provided on an internal surface of the front housing  102  and on the external surface of the syringe guide  24  respectively. The abutment surfaces provided on the front housing  102  and on the syringe guide  24  will typically have to extend through openings or slots provided in the needle hider body  17  in order to connect with each other. These abutment surfaces in combination with the adjustable needle hider front  16  determine the penetration depth of needle  12  during use of the device. The needle shield remover  109  is configured to be partially inserted i.e. axially movable into the proximal end of the front housing  102  through the needle hider front  16  and through the needle hider body  17 . The axial movement of the needle shield remover when inserted into the proximal end of the front housing  102  is stopped by the interaction between the abutment surfaces of the syringe guide  24  and of the needle shield remover  109 , more specifically the proximal end of the syringe guide and the distal end of the needle shield remover  109 , while the abutment surfaces between the front housing  102  and the syringe guide  24  serve to prevent the syringe guide from moving distally relative to the front housing  102 . A resilient syringe collar  25 , typically made of rubber, is arranged at a distal end of the syringe guide  24  for receiving and holding the syringe  103 . The resilient material will securely hold the syringe in place while still allowing it to be replaced after it has been emptied. Normally, the resilient syringe collar  25  will stay in its position in the syringe guide during replacement of the syringe but can of course be exchanged if necessary. A first biasing member  19  is arranged between the syringe guide  24  and the needle hider body  17  which biases the syringe guide  24  towards its distal end position and the needle hider body  17  towards its proximal end position. The first biasing member  19  ensures that as soon as the device according to the invention is removed from the injection site, the needle hider body, and thus also the needle hider front  16 , automatically travel outwards keeping the needle  12  out of sight to a user. The front housing  102  can be made up of two halves which are secured to each other by means of pins or projections  8  (not shown in  FIG. 3 ) provided at one of the halves and corresponding openings  8 ′ in the other halves. Obviously, other solutions are imaginable, such as tongue and groove solutions; snap catch elements; or even permanent securing by welding or gluing. 
         [0032]    In  FIG. 4  the easiness of adjusting the penetration depth of needle  12  is displayed. Needle shield remover  109  is provided with axially running protrusions  23  having a corresponding shape to recesses  22  provided in the needle hider front  16 . This means that the needle shield remover  108  can be inserted axially into needle hider front  16  while any relative rotational movement between the two is prevented. By using the needle shield remover  109  as a grip element, a user can adjust the position of the needle hider front  16  relative to the needle hider body  17  by turning, thus setting the penetration depth of the needle  12  during use. The front housing  102  and/or the needle hider body  17  may be provided with means defining a number of pre-set positions which snap in place when the needle hider front  16  is turned. The needle hider front  16  is provided with digits  26  visible in a cut-out, window  29  or similar provided at the front housing  102  indicating a set penetration depth. The penetration depth can be adjusted back and forth until a desired value has been set. 
         [0033]      FIGS. 5   a  and  5   b  schematically show how the drive mechanism of the device  100  is reloaded. The front housing  102  having the needle shield remover  109  attached at its front end through the needle hider front  16  is removed from the rear housing  101  by twisting the housings 90 degrees relative to each other. Then, the proximal end of the needle shield remover  109 , is positioned abutting the drive mechanism  108  arranged in the rear housing  101  and situated in its proximal end position. Thereafter, the front housing together with the needle shield remover  109  is used to force the drive mechanism  108  towards its proximal end position where it will snap into a cocked position, ready to be used. A more detailed explanation of the functioning of the device will be provided with respect to  FIGS. 6   a ,  6   b ,  7   a  and  7   b  below. 
         [0034]      FIG. 6   a  shows the device loaded with a fresh syringe and in a cocked position, i.e. drive spring  2  is completely compressed such that the drive mechanism  108  is loaded but release mechanism  3  is prevented from releasing the plunger rod driver  1 . This is realized by the button blocker  26  reaching from a proximal part of the rear housing  101  to a distal part of the rear housing  101  where it prevents the trigger button  4  from being depressed and releasing the drive mechanism  108 . In the embodiment shown in  FIGS. 6-7 , the button blocker  26  is moveable between a proximal and a distal position defined by the openings  8 ′ provided in the rear housing  101 . Abutment member  5  of the release mechanism  3  (see also  FIGS. 2   a  and  2   b ) reaches into recess  9  of the plunger rod driver  1  and prevents it from moving forward towards its proximal end position. The needle shield remover  109  is still in place grasping needle shield  11  and it can be used to set a desirable penetration depth. In  FIG. 6   b  the needle hider front has been set in a position corresponding to maximum penetration depth and the needle shield remover  109  has subsequently been pulled out together with the needle shield  11 . The device  100  is now in position corresponding to when a user presses it against the intended injection site by which the needle hider body  17  and needle hider front  16 , have assumed the distal end position, where abutment surfaces  20 ,  21  come in contact with each other. Upon pressing the device against the injection site, the needle hider body  17  also comes into contact with the button blocker  26 . As the needle hider body  17  travels backwards, towards the distal end position, it forces the button blocker  26  axially relative to the rear housing towards a distal end position. This movement of the button blocker  26  allows the release mechanism  3  to be activated and the device  100  is now ready to start the injection. In  FIG. 7   a  the trigger button  4  has been depressed, causing the plunger rod driver  1  to be forced forwards by drive spring  2  and thereby moving the syringe  103  and syringe guide  24  towards the proximal end position of the syringe guide  24 . As the syringe  103  and syringe guide  24  move forward, needle  12  penetrates the injection site and the plunger rod  13  forces the plunger  14  forward thus emptying the content of the syringe through the opening in the needle. The force of the drive spring  2  is far more powerful than that of the first biasing member  19  which therefore is compressed when the drive mechanism  108  is released.  FIG. 7   b  corresponds to a state where a user has removed the device from the injection site after completed injection. As soon as this is done, the first biasing member  19  extends and needle hider body  17  assumes its proximal end position thus effectively hiding the needle  12  from being visible to a user. A second biasing member  27  is provided between the rear housing  101  and the button blocker  26  which, when the drive mechanism  108  is forced to its distal end position and the release mechanism assumes its extended position (see description referring to  FIGS. 2   a  and  2   b ), will force the button blocker  26  to assume its proximal end position thus preventing the trigger button  4  from being depressed. Also shown in e.g.  FIG. 6   a  is a spring guide  28  which supports and guides drive spring  2  in order to avoid buckling of drive spring  2  during compression. 
         [0035]    Finally, it is realized, that a medicament injection device according to the invention has a number of advantages over the known prior art devices. Due to the fact that the device has a completely mechanical design, reliability can be ensured at all time without being dependent on batteries or similar. The drive mechanism can in a simple and reliable manner be reloaded by using the front housing and the needle shield remover of the device itself. The needle hider front is biased and always covers the needle such that the needle never will be visible to the patient. Penetration depth can also be set in a very simple and user-friendly manner. By using the needle shield remover as a grip, also users with reduced strength and/or co-ordination will be able to do this. The indication means of the present invention will in a clear and concise manner present a set penetration depth. The set penetration depth will not have to be re-set for each injection occasion; instead the device according to the present invention provides an automatic penetration depth memory. The device is re-usable and the user can change the emptied syringe to a new in a simple manner. The device allows for a variable penetration depth and the setting of the dose can be set downwardly and upwardly until a required depth has been set. 
         [0036]    It is to be understood that the embodiments described above and in the drawings are to be regarded only as non-limiting examples of the invention and that they may be modified in many ways within the scope of the claims.