the device according to the figures comprises a generally tubular outer housing 10 . in the front end of the housing , to the right in fig1 , 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 container carrier 16 is arranged . inside the container carrier a container 18 , containing medicament , is attached . container is to be interpreted as comprising syringes , cartridges , ampoules and the like . the front end of the container is arranged with attachment means 20 for attaching a needle 22 to the container . the rear end of the container 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 container with one end adjacent a stopper 32 . the rear end of the plunger is surrounded by a decoupling sleeve 34 which is snap - fitted to the container holder . the decoupling sleeve is arranged with flexible tongues 36 , fig2 , where each tongue is arranged with inwardly directed ledges . in the initial state , these ledges are positioned in a circumferential groove 37 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 of the plunger 30 and a wall part 42 of the decoupling sleeve 34 . the decoupling sleeve 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 decoupling sleeve 34 . the upper part of the arms 62 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 . further a penetration retraction spring 76 is arranged between the retraction release ring 46 and an annular ledge 78 arranged on the decoupling sleeve 34 , fig5 b . according to the invention it is further arranged with a delay mechanism , fig4 . it comprises a cap or cover 100 slidably arranged at the front end of the plunger rod 30 . a compartment 102 created by the interior of the cap and the front surface of the plunger rod is filled with a highly viscous liquid , such as grease , oil , paste and the like . the front surface of the plunger rod is further arranged with a through - hole 104 forming a passage between the compartment and the interior of the plunger rod , the function of which will be explained below . the device is intended to function as follows . when in the initial position the needle shield 12 is positioned inside the housing 10 and held in place by the protrusions 14 acting against the ledge of the housing , fig1 . the device can be delivered with a protective cap 106 inserted into the front end of the needle shield surrounding the front end of the container 18 with its container cap 78 . the protective cap is removed , whereby the container cap is also removed , and a needle 22 is attached to the container . 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 , fig5 a . 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 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 . if the device is withdrawn from the injection site the lockout sleeve and the needle shield are moved back to initial position . 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 50 , 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 . 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 decoupling sleeve 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 decoupling sleeve 34 by the protrusions 44 . thus the decoupling sleeve 34 , the plunger 30 arranged inside the decoupling sleeve , the container carrier 16 connected to the decoupling sleeve , the injection release ring 28 and the container 18 are moved forward causing a penetration of the needle into the injection site , fig6 . at a certain depth the injection release ring 28 is stopped by the engagement of protrusions on its flexible arms into slots on the needle shield 12 , which frees the flexible tongues 36 because they pass the ring due to the continued movement of the decoupling sleeve 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 37 on the plunger . the movement of the decoupling sleeve 34 , and thus the penetration , is stopped when the retraction release ring 46 contacts the retraction spring retainer 52 . 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 , fig7 . when the stopper has reached almost the front end of the container , the force of the plunger rod will act on the highly viscous liquid in the compartment 102 inside the cap 100 , the force generating a displacement of the cup 100 which in turn makes the grease , or oil , to flow through the passage 104 provided by the tip of the plunger rod , fig4 . grease viscosity and hydraulic diameter , size and shape of the opening of the plunger rod , are main parameters to tune to deliver the intended and desired functionality , the intended function being to achieve a time delay at stroke end so that displacement members of the system are not triggered before desired displacements , such as e . g . delivery of the drug , have been completed . the movement of the plunger in relation to the decoupling sleeve 34 causes the upper end of the plunger to pass the protrusions 44 of the decoupling sleeve , whereby they are capable of collapsing inwards , fig8 . the collapsing causes the retraction release ring 46 to pass the protrusions 44 and to be pushed downwards by the retraction spring 76 . this causes the container carrier 16 with the container 18 to be pulled into the housing via the decoupling sleeve 34 at near end of injection stroke , and thus the needle 22 to be retracted , fig9 . the injection is now completed and the needle is protected inside the housing . the present invention could of course be used for delaying other functions of an injection device such as a delaying mechanism arranged to delay the movement of the penetration mechanism in order to ascertain that the penetration is fully completed before the injection is triggered . 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 .
an injection device comprising a medicament container , a needle attached to the container , and a mechanism for automatic penetration of the needle , injection of medicament and withdrawal of the needle . the device operates by initiating a penetration sequence , followed by an injection sequence and followed by a withdrawal sequence . a previous sequence can trigger a subsequent sequence . the device further comprises a dampening mechanism arranged and designed to dampen the movement of the injection mechanism during an injection sequence .