Abstract:
The present invention relates to an injection device comprising a generally elongated tubular housing, a syringe containing medicament and having a needle, a needle shield slidably arranged to the housing and protruding a distance outside the front end of the housing, a plunger arranged to act on the syringe and a pre-tensioned drive member arranged the drive the plunger, characterized in that it comprises radially acting holding elements capable of releasably holding the plunger, axially acting actuator elements connected to the needle shield and capable of releasably locking the holding elements and axially acting activator elements capable of releasing the holding elements from the actuator elements have when the needle shield and the actuator elements has moved axially a certain distance due to that injection device has been placed against an injection site.

Description:
TECHNICAL FIELD  
       [0001]     The present invention relates to an injector for administering drugs in a safe and reliable way.  
       BACKGROUND OF THE INVENTION  
       [0002]     The handling and safety aspects of injector devices, having a certain degree of automatic functions, as well as immediate accessibility in emergency situations are issues that attract a lot of attention when developing this type of device.  
         [0003]     A few of these devices have safety aspects like a two-step operation before the injection is activated in order to avoid unintended activation, for example if the user comes in contact with the trigger button before the injector is placed at the injection site. However many of these solutions are rather bulky and rely also on many components acting in co-operation and in sequence, one trigging another, which may lead to a mal-function, or that the device becomes complicated, hence not user friendly.  
         [0004]     One device utilising a high degree of automation is described in the document WO 02/74774. The device is an auto-injector whereby the injection can be activated by a push button, i.e. penetration and injection, but only when the front end of the injector is pressed against the injection site. It is designed as a kind of two-step operation where the order has to be: pressing the injector at the site and then depressing the button. Any other order of sequence will not result in an activation of the device. This ensures that the injector cannot be accidentally activated by merely pushing the button nor even pushing the button and then pressing the front end.  
         [0005]     Even though the device according to WO 02/74774 has proved to function well and displays a high degree of safety and user-friendliness there is always a desire for improvements of such devices, among them being the design of the mechanism in order to simplify the manufacture and assembly in order to reduce costs but at the same time maintain or even improve the reliability of the function of the device.  
       SHORT DESCRIPTION OF THE INVENTION  
       [0006]     The aim of the invention is to provide an injection device which is uncomplicated and easy to use, which is safe both before, during and after use and which displays a high degree of functionality.  
         [0007]     According to one aspect of the invention, an injection device is provided comprising a generally elongated tubular housing, a container containing medicament and having a needle attached to the container, a needle shield slidably arranged to the housing and protruding a distance outside the front end of said housing, a plunger arranged to act on said container and a pre-tensioned drive means arranged to drive said plunger, characterised in that it comprises radially acting holding means capable of releasably holding said plunger, axially acting actuator means connected to said needle shield and capable of releasably locking said holding means and axially acting activator means capable of releasing said holding means from said actuator means when said needle shield and said actuator means has moved axially a certain distance because the injection device has been placed and pressed against an injection site.  
         [0008]     According to another aspect of the invention it is characterised in that said holding means comprises generally radially extending inwards directed ledges and that said plunger comprises a groove, with mutual shapes as for the ledges to fit into said groove and that said ledges are arranged at the ends of flexible tongues.  
         [0009]     According to a further aspect of the invention it is characterised in that it comprises a locking means capable of locking said activator means until said actuator means has moved axially a certain distance.  
         [0010]     Preferably said locking means comprises hooks arranged on said activator means co-operating with fixedly arranged stop means and that said actuator means comprises means for displacing said hooks in relation to said stop means upon movement of said actuator means.  
         [0011]     The injector according to the present invention comprises a number of radially and axially co-acting means in order to obtain a compact and yet reliable injecting device with rather few components. This implies that the holding means are acting to hold and lock the pre-tensioned plunger radially which is a safe way to lock and store the device pre-tensioned for long periods until use. As a benefit the user does not have to arm the device before use. The holding means are held in place by the axially slidable actuator means, preferably a sleeve, which in turn is connected to the needle shield. Thus the movement of the needle shield, when pressing the device against an injection site axially moves the actuator sleeve axially in relation to the holding means, but not so much that the holding means is released from the plunger. This step of releasing the plunger is performed by the activator means, for example a push button at the end of the device, which moves the holding means axially in relation to the actuator sleeve until the holding means is released and the plunger is released to act on the container.  
         [0012]     The axial movement in order to release the holding means is thus performed both by the actuator sleeve but also by the holding means. There is thus a two-step operation in order to activate an injection. For enhancing the safety of the device it is designed so that the operation of the device is performed in a pre-determined sequence.  
         [0013]     The needle shield is further provided with a spring that urges needle shield to an extended position surrounding the needle when the device is withdrawn from the injection site after the injection, and locking means for locking the needle shield in that extended position in order to avoid accidental needle sticks after injection and subsequently after disposal. The device may be provided with means for delivering a subsequent dose, whereby the needle first has to be removed and replaced. In order to enable this the needle shield can be released by a separate release mechanism in order to push it backwards, or with a separate tool, thereby exposing the needle so that it can be replaced.  
         [0014]     The device may also be arranged for replaceable containers, i.e. when one container is emptied, the patient replaces it with a new container.  
         [0015]     The mechanism of the injector of the present invention is designed such that an injection is only activated when first the injector is pressed against the injection site and then the activator (e.g. a button) is pressed or activated. It is not possible to press the activator first and then press the injector against an object to activate an injection nor is it possible to perform these steps simultaneously. Also if the injector is removed from an injection site before the activator is pressed, the injector is reset to its original locked state. This ensures a very high degree of safety in handling the device and prevention of faulty or not performed injections.  
         [0016]     These and other aspects of and advantages with the present invention will become apparent from the following detailed description and from the accompanying drawings. 
     
    
     SHORT DESCRIPTION OF THE DRAWINGS  
       [0017]     In the following detailed description of the invention, reference will be made to the accompanying drawings, of which  
         [0018]      FIG. 1A  is a cross-sectional side view of one embodiment of the auto-injector according to the invention,  
         [0019]      FIG. 1B  is an enlarged view of  FIG. 1A  showing a locking part-of an actuator means of the device,  
         [0020]      FIG. 1C  is an enlarged view of a part of an activator means of the device,  
         [0021]      FIG. 2A  is a cross-sectional view of the front part of the auto-injector according to  FIG. 1 ,  
         [0022]      FIG. 2B  is a cross-sectional view of the front part where the section is taken 90° in relation to the section of  FIG. 2A ,  
         [0023]      FIG. 3  is an exploded view of the front part shown in  FIGS. 2A  and B,  
         [0024]      FIG. 4A  is a cross-sectional view of the rear part of the auto-injector according to  FIG. 1 ,  
         [0025]      FIG. 4B  is a cross-sectional view of the front part where the section is taken 90° in relation to the section of  FIG. 4A ,  
         [0026]      FIG. 5  is an exploded view of the rear part shown in  FIG. 4 ,  
         [0027]      FIG. 6A , B are side views of an actuating means comprised in the device according to  FIG. 1 ,  
         [0028]      FIG. 7  is a cross-sectional view of a holding means comprised in the device according to  FIG. 1 ,  
         [0029]      FIG. 8A , B cross-sectional views of the device when it has been pressed against an injection site, where the section of  FIG. 8B  is taken 90° in relation to  FIG. 8A ,  
         [0030]      FIG. 8C  is a detailed view of the activation means of the device,  
         [0031]      FIG. 9A , B are cross-sectional views of the device when penetration has started, where the section of  FIG. 9B  is taken 90° in relation to  FIG. 9A ,  
         [0032]      FIG. 9C  is a detailed view of the position of the actuator means during this phase,  
         [0033]      FIG. 9D  is a detailed view of the activator means during this phase,  
         [0034]      FIG. 10A , B are cross-sectional views of the device when injection has started, where the section of  FIG. 10B  is taken 90° in relation to  FIG. 10A ,  
         [0035]      FIG. 11A , B are cross-sectional views of the device when injection is completed, where the section of  FIG. 11B  is taken 90° in relation to  FIG. 11A ,  
         [0036]      FIG. 12A , B are cross-sectional views of the device when injector is removed from the injection site, where the section of  FIG. 12B  is taken 90° in relation to  FIG. 12A ,  
         [0037]      FIG. 12C  is a detailed view of the actuator means, and  
         [0038]      FIG. 12D  is a detailed view of activator means. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0039]     The embodiment shown in the drawings comprises a front part  10 ,  FIGS. 2-3  and a rear part  60 ,  FIGS. 4-5 .  
         [0040]     The front part  10  comprises a generally tubular front body  12  having elongated openings  14  for viewing a syringe  16 ,  FIG. 1 , and a somewhat narrowing front end. The rear end is arranged with annular recesses  18  on the inner surface. Inside the front body a needle shield  20  is slidably arranged. The needle shield is generally tubular with a first front part  22  having a certain diameter and a second rear part  24  having a diameter larger than the front part, where these parts are joined by an intermediate conical part  26 ,  FIG. 3 . Two elongated grooves  28  are arranged along the needle shield, on opposite sides of the needle shield, also for viewing the syringe. On the inner surface of the conical part a circumferential ledge  30  is arranged. At the rear end of the needle shield two openings  32  are arranged opposite each other, where each opening is arranged with somewhat inwardly projecting, flexible, tongues  34 .  
         [0041]     Further a syringe carrier  36  is arranged inside the needle shield in the form of a generally tubular body. The front part of the syringe carrier is arranged with a neck portion  38  of lesser diameter. Adjacent the neck portion cut-outs  40  have been made on either side to form guide surfaces. These surfaces cooperate with corresponding shapes of the inner surface of the needle shield in order to obtain a stop means against rotation of the syringe carrier relative the needle shield. The rear end of the syringe carrier is arranged with two rearwardly directed tongues  42  where each tongue is arranged with an opening  44  and an inwardly directed ledge  46  on the rear edge of each opening. The syringe carrier is further arranged with radially directed flanges  48  on its inner surface in order to obtain a space between the syringe carrier wall and a syringe to be placed inside.  
         [0042]     At the front end of the front part a needle protection cap grabber  50  is arranged. It is inserted into the front part of the needle shield and held there by friction. Inside the cap grabber a metal ring  52  is arranged with sharp pointed tongues  54  directed somewhat inwards and towards the front end.  
         [0043]      FIG. 4-5  shows the rear part or power unit  20  of the injector according to  FIG. 1 . It comprises a plunger  60  formed as a tube and with an outer diameter somewhat smaller than the inner diameter of the syringe body to be used. The plunger  60  is arranged with a circumferential groove  62  with a certain width. Inside the plunger a helical compression spring  64  is arranged and inside the spring a spring guide  66  is placed. Adjacent the groove of the plunger a holding member  68  is arranged. It comprises a ring-shaped body  70   FIG. 7 , having an annular ledge  72  arranged around its circumference and a number of flexible tongues  74  directed towards the rear of the power unit, to the left in the figures. Each tongue  74  is arranged with inwardly directed ledges  76  arranged and shaped as to fit into the groove  62  of the plunger. Each tongue is further arranged with reinforcing ribs  78  on the outer surfaces.  
         [0044]     Surrounding the plunger is an activator  80  with a mainly tubular shape. Its front end, to the right in the figures, has an inclined transition surface  82  which meets with a band-shaped part  84  with enlarged diameter. On the inner surface adjacent the transition surface an annular inwardly directed ledge  86  is arranged, with a shape as to fit into the groove  62  of the plunger. A number of longitudinally directed cut-outs  88  are arranged at the front part of the actuator so as to form flexible tongues  90 . The activator is further provided with two stop ledges  92  directed radially outwards from the outer surface on either side. Between the stop ledges two flexible tongues  94  are arranged on the outer surface. Each tongue is arranged with an outwardly directed hook  96  at the outer end and a protrusion  98 , with an inclined surface  99 , a distance along each tongue. The upper end of the activator is arranged with an end wall  100 . An activator button  102  is attached to the upper end of the activator having two tongues  104  attached to its outer edge and directed towards the front of the device.  
         [0045]     Outside the activator an actuator sleeve  110  is slidably arranged, also of a generally tubular form. It comprises a front end with a conical part  112  ending in a ledge  114  on its outer surface. At a distance from the ledge a first annular ring  116  is arranged the outer surface. A second annular ring  118  is also arranged a further distance from the ledge. The rear end of the actuator sleeve is arranged with two oppositely arranged cut-outs  120  of a generally rectangular shape where the widths correspond to the width of the stop ledges  92  of the actuator. A compression spring  122 , hereafter named needle shield spring is surrounding the actuator sleeve.  
         [0046]     The previously named components of the power unit are housed in a rear housing  124  of a generally tubular shape, where the front end of the rear housing has a somewhat lesser diameter, corresponding to the inner diameter of the rear end of the front body and provided with a number of annular protrusions  126  which are intended to fit into the corresponding annular recesses  18  on the inner surface of the front body  12 . Inside the rear housing an annular ring  128  is arranged, which ring is provided with a circumferential ledge  130  with a shape corresponding to the hooks of the actuator. Adjacent the annular ring  128  and in the vicinity of the tongues  104  of the activator button when placed in the housing  124  are arranged inclined surfaces  132 , the function of which will be described below.  
         [0047]     The function of the injector according to the invention will now be described in connection with the  FIGS. 8-11 .  
         [0048]     When assembling the injector the front and the rear parts are assembled individually. As regards the power unit the plunger is held against the force of the compression spring in that the inwardly directed ledges  86  of the tongues  90  of the activator are situated in the groove  62  of the plunger  60  and that the actuator sleeve  110  prevents the tongues  90  from moving outwards. Further the ledges  76  of the holding member are also arranged in the groove  62 ,  FIG. 1B . The hooks  96  of the activator are adjacent the circumferential ledge  130  as a second safety means should the tongues  90  move out of the groove of the plunger. In this position, if the activator button is depressed, it can only move a very short distance inwards together with the actuator  80  until the hooks engage the circumferential ledge.  
         [0049]     A syringe is placed in the front end and a rear part is attached to the front part wherein the protrusions  126  fit into the recesses  18 . At the same time the tongues  34  of the needle shield  20  fit behind the ledge  114  of the actuator sleeve  110  and the ledges  42  of the syringe carrier  36  pass behind the annular ledge  72  of the holding member  68 . The needle protection cap grabber  50  is inserted into the front end of the device. The device is now ready for use.  
         [0050]     When an injection is to be performed the needle protection cap grabber is pulled out of the injector. This causes the sharp pointed tongues  54  to be pushed into the rubber needle protection cap and remove it from the needle. The front end of the injector is then pressed against the injection site and the somewhat projecting front end of the needle shield is pushed into the housing,  FIG. 8 , against the force of the compression spring  122  acting between the second annular ring  118  of the actuator sleeve and a ledge  136  arranged inside the housing  124 . The upper end of the needle shield is in contact with the first annular ring  116  of the actuator sleeve  110  and its movement causes the sleeve to move backwards, to the left in the figures, whereby a part of the band-shaped part  84  is situated outside the front part of the sleeve. The upper edge of the actuator sleeve will then come in contact with the inclined surface  99  of the tongues  94  on the actuator  80  whereby the hooks  96  are moved inwards and are free to pass inside the circumferential ledge  130 .  
         [0051]     The next step is to activate the penetration and injection. Should the user however remove the injector from the injecting site the compression spring  122  will push the actuator sleeve  110  and thereby the needle shield  20  back to its original position and a press on the button will not cause the device to fire. When activating the penetration and injection, the user merely depresses the activator button,  FIG. 9 . This causes the activator to be moved to the right in the figures whereby the hooks  96  pass inside the circumferential ledge  130  and the band-shaped part  84  completely out of the actuator sleeve. The resilient properties of the tongues  90  of the activator causes the ledges  86  to move out of the groove  62  of the plunger, which then is free to move due to the spring  64 . During the movement of the plunger, the ledges  76  of the holding member  68  are also moved out of the groove because the arms  74  of the holding member are no longer held in place by the band-shaped part of the activator.  
         [0052]     The force of the compression spring urges the plunger to push on the stopper of the syringe. But because of the friction between stopper and container wall and incompressibility of liquid in the syringe and the very small flow passage through the needle, the force will push the syringe forward, to the right in the figures, and thereby penetrate the skin of the patient,  FIG. 10 . The penetration stops when the front surface of the syringe carrier surrounding the neck portion abuts a ledge  138 ,  FIG. 9B , arranged inside the front part. The force from the compression spring now moves the stopper inside the syringe and the liquid medicament is injected into the patient until the stopper reaches the inner front end of the syringe. When the plunger has moved this distance, its rear end has passed the ledges  86  of the activator and the tongues are moved inwards,  FIG. 11C . Because the compression spring is also acting on the activator, the activator is moved inside the actuator sleeve. Because of this and because the needle shield spring is acting on the actuator sleeve it is urged forward, to the right in the figures. When now the injector is removed from the injection site, the force of the needle shield spring pushes the actuator sleeve and thus the needle shield connected to it forward, whereby the needle shield is pushed out of the front end of the injector and surrounds the needle. The movement of the actuator sleeve causes the band-shaped part  84  of the actuator  80  to pass ribs  140  arranged on the inner surface of the actuator sleeve,  FIG. 12 . These ribs prevent any attempts to push the needle shield back into the injector because the ribs will abut the front end of the band-shaped part  84  of the actuator  80 . The needle shield is thus locked, which prevents unintentional needle sticks.  
         [0053]     As a safety measure, it is not possible to first press the activator button  102  and then press the injector against an injection site and release a penetration/injection action because the depression of the activator button causes the hooks  96  to engage the circumferential ledge  130 . Because of the inclined surfaces between the hooks  96  and the circumferential ledge  130  it is not possible to push the tongues  104  inwards by the actuator sleeve  110  acting on the inclined protrusions on the tongues. In order to release a penetration/injection action, the injector has to be pressed first against an injection site in order to be able to depress the activator button and release the plunger.  
         [0054]     It is to be understood that the embodiment described above and shown in the drawings is to be regarded as a non-limiting example of the invention and that it is defined be the patent claims.