Abstract:
The present invention relates to a method of operating an injection device, which device comprises a medicament cartridge and a needle attached to said cartridge, means for automatic penetration of needle, injection of medicament and withdrawal of needle, comprising the steps of initiating a penetration sequence, followed by an injection sequence and followed by a withdrawal sequence, wherein a previous sequence triggers a subsequent sequence, and wherein the subsequent sequence is triggered before the previous sequence has ended.

Description:
TECHNICAL FIELD  
       [0001]     The present invention relates to an injector, and in particular an injector having several automatic functions.  
       BACKGROUND OF THE INVENTION  
       [0002]     There are many injectors on the market where the aim is to have high degrees of functionality and automatic features, such as in connection with penetration, injection, setting of dose, priming and covering of the needle after use. At the same time there is a demand on robustness, repeatability and reliability regarding the function, which sometimes might be difficult to meet when dealing with complex multi functions involving many interacting components. When there further are demands on low production costs, especially for devices that are to be used only once, the picture becomes even more complex.  
         [0003]     There are in the patent literature numerous solutions to injection devices, the bulk of which never enter the market due to that they do not meet the demands in one way or the other. There is therefore a continuous search for solutions that provide the desired functions that at the same time fulfill the functional and/or economical demands.  
         [0004]     Many devices having multi-functions that work in sequence, such as for example penetration, followed by injection, followed by withdrawal, have a subsequent sequence triggered at the end of a previous sequence, for example when the needle has reached full penetration depth, the injection sequence is triggered.  
         [0005]     The drawback with this solution, especially when several components are interacting with each other in order to perform the sequences and the triggering of them, is that the tolerance and functional demands are increased in order to ensure that the subsequent sequence is really triggered at the end of the previous sequence. Should there be a tolerance error or a mismatch between two interacting components for triggering a subsequent sequence, the previous sequence will come to an end without triggering the next sequence. This may lead to a fatal situation if for example the injection of medicament is not performed.  
         [0006]     In view of cost efficiency, high tolerance demands in order to achieve the desired chain of functions, are not advantageous, in particular when mass-producing injection devices.  
       BRIEF DESCRIPTION OF THE INVENTION  
       [0007]     The aim of the present invention is to provide an injector that fulfils the demands that are put on such devices both regarding functionality, reliability and low cost.  
         [0008]     According to a main aspect of the invention it is characterized by the features of claim  1 . Further advantageous features are subject of the dependent claims.  
         [0009]     The present invention is characterized by a method of operating an injection device, which device comprises a medicament cartridge and a needle attached to said cartridge, means for automatic penetration of needle, injection of medicament and withdrawal of needle, comprising the steps of initiating a penetration sequence, followed by an injection sequence and followed by a withdrawal sequence, wherein a previous sequence triggers a subsequent sequence, and wherein the subsequent sequence is triggered before the previous sequence has ended.  
         [0010]     The advantage with the method according to the present invention is for one that a subsequent sequence of operation of the injector is not triggered at the end of a previous sequence. This provides an increased reliability regarding ensuring that a subsequent sequence is triggered by a previous sequence, without increasing the tolerance and functional demands on the interacting components.  
         [0011]     The triggering of a subsequent sequence may preferably in an end range of movement of components performing the previous sequence.  
         [0012]     The solution provides a cost effective multi-function device comprising a safe and reliable chain of sequences, thus ensuring that the user receives a proper dose of medicament each time the device is used.  
         [0013]     These and other features and advantages with the present invention will become apparent from the following detailed description and the drawings 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]     In the following detailed description, reference will be made to the drawings, of which  
         [0015]      FIG. 1  is a longitudinal cross-section of an embodiment of the present invention,  
         [0016]      FIGS. 2-3  are exploded views of the injector of  FIG. 1 ,  
         [0017]      FIGS. 4-9  show different functional steps of the device of  FIG. 1 .  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0018]     The device according to the figures comprises a generally tubular outer housing  10 . In the front end of the housing, to the right in  FIG. 1 , a generally tubular needle shield  12  is arranged slidably in the outer housing. When in the non-extended position the needle shield is held in place by protrusions  14  on the outer surface co-operating with ledges (not shown) on the inner surface of the housing. Inside the needle shield in the front area of the device a syringe carrier  16  is arranged. Inside the syringe carrier a syringe  18 , containing medicament, is arranged. The syringe is prevented from moving forward by a circumferential ledge  20 . The front end of the syringe is arranged with attachment means for attaching a needle  22  to the syringe. The rear end of the syringe is seated with its flange  24  in a holder  26 . Adjacent the holder an injection release ring  28  is arranged, which will be described in more detail below. A plunger  30  extends into the syringe with one end adjacent a stopper  32 . The rear end of the plunger is surrounded by an activation housing  34  which is snap-fitted to the syringe holder. The activation housing is arranged with flexible tongues  36 , where each tongue is arranged with inwardly directed ledges. In the initial state, these ledges are positioned in a circumferential groove  38  on the plunger  30 . The tongues and ledges are held in this position by the injection release ring  28 . Inside the plunger an injection spring  38  is arranged compressed between a front wall  40  of the plunger  30  and a wall part  42  of the activation housing  34 . The activation housing is further arranged with outwardly extending protrusions arranged on flexible arms  44 . Abutting the protrusions is a retraction release ring  46 , which will be described closer below. A spring  48 , hereafter named penetration spring, is arranged between the retraction release ring  46  and a penetration sleeve  50 . At the front end of the penetration sleeve, a retraction spring retainer  52  is snap fitted with the penetration sleeve  50  by outwardly directed protrusions  54  having a straight part and a ramped part, extending into recesses  56  of the sleeve. Outside the penetration sleeve a lockout sleeve  58  is arranged. At the rear part of the lockout sleeve  58  recesses  60  are arranged adjacent flexible arms  62  of the penetration sleeve, which arms are arranged with outwardly extending protrusions  64  as well as inwardly extending ledges  66 . In the initial position these ledges are in contact with a wall of a circumferential groove  68  on the plunger. The upper part of the arms is further arranged with inclined surfaces  70  At the upper end of the housing an activation button  72  is slidably arranged, having inwardly extending parts  74 , which are arranged with inclined surfaces facing the inclined surfaces  70  of the arms  62 .  
         [0019]     The device is intended to function as follows. When in the initial position the needle shield  12  is pushed inside the housing  10  and held in place by the protrusions  14  acting against the ledge of the housing,  FIG. 4   b.  The device is delivered with a protective cap  76  inserted into the front end of the needle shield surrounding the front end of the syringe  18  with its syringe cap  78 . The protective cap is removed, whereby the syringe cap is also removed, and a needle  22  is attached to the syringe. The needle shield  12  is then pushed manually forward until the protrusions  14  of the needle shield enter a recess  80  on the inner surface of the housing  10 ,  FIG. 5   b.  The protrusions have such a configuration that they are able to slide over the ledge when the needle shield is extended but prevent a pushing in of the needle shield when they have entered the recess. The forward movement of the needle shield pushes a protective needle cap  90  off the needle.  
         [0020]     The device is now ready to use. The user places the end of the needle shield  12  against the injection site and presses the push button  72 . The pressing of the needle shield  12  causes it to move a short distance inwards until the protrusions  14  of the needle shield abut the upper wall of the recess  80 . This movement causes the lockout sleeve  58  to be moved the same short distance since the upper end of the needle shield  12  in the extended position is in contact with the lower end of the lockout sleeve  58 .  
         [0021]     If the device is withdrawn from the injection site the lockout sleeve and the needle shield are moved back to initial position.  
         [0022]     The movement of the lockout sleeve causes its recesses  60  to be positioned outside of the outwardly extending protrusions  64  of the arms  62  of the penetration sleeve  58 , which enables the button  72  to be depressed whereby the inclined surfaces of the inwardly extending parts act on the inclined surfaces  70  of the arms  62 , causing them to move radially outwards. This is not possible when the lockout sleeve  58  has not been moved since the protrusions of the arms then abut the inner surface of the lockout sleeve.  
         [0023]     When the arms move radially outwards the inwardly directed ledges  66  of the arms  62  are moved out of contact with the circumferential groove  68  of the activation housing  34  which then is moved forward by the penetration spring  48  acting on the retraction release ring  46  which is held in place relative the activation housing  34  by the protrusions  44 . Thus both the activation housing  34 , the plunger  30  arranged inside the activation housing, the syringe carrier  16  connected to the activation housing, the injection release ring  28  and the syringe  18  arc moved forward causing a penetration of the needle into the injection site,  FIG. 6 .  
         [0024]     At a certain depth the injection release ring  28  is stopped by the engagement of protrusions on its flexible arms into slots on the shield, which frees the flexible tongues  36  because they pass the ring due to the continued movement of the activation housing  34 . The freeing of the tongues cause them to flex outwards radially, whereby the inwardly directed ledges are moved out of contact with the groove  38  on the plunger  30 . The movement of the activation housing  34 , and thus the penetration, is stopped when the retraction release ring  46  contacts the retraction spring retainer  52 .  
         [0025]     However the plunger is now free to move by the force of the injection spring  38 , whereby it pushes on the stopper  32  and an injection is performed. The movement of the plunger in relation to the activation housing  34  causes the upper end of the plunger to pass the protrusions  44  of the activation housing, whereby they are capable of collapsing inwards.  
         [0026]     The collapsing causes the retraction release ring to pass the protrusions  44  and to be pushed downwards by the retraction spring  48 . This causes the syringe carrier  16  to be pulled into the housing via the retraction spring retainer at near end of injection stroke, and thus the needle to be retracted,  FIG. 7 . The injection is now completed and the needle is protected inside the housing.  
         [0027]     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 within the scope of the patent claims.