the drawings depicts one exemplary embodiment of an auto - injector in accordance with the present invention . the depicted auto - injector has a casing “ c ” comprised of a front casing part 1 and a rear casing part 2 , wherein the two casing parts are joined together by a connection 3 . if the auto - injector is a refillable auto - injector , the connection 3 is releasable , for example , it may comprise a threaded connection . if , however , the auto - injector is a disposable , the connection 3 can be fixed , for example , by a fused connection , adhesive connection or latching connection . on the left in the figures , a needle protecting tube 4 can be seen which can be shifted axially in the front casing part 1 , as will be described in more detail below . a sliding sleeve 5 which can be shifted axially is guided in the needle protecting tube 4 via its front end and in the front casing part 1 via a flange 6 formed on its rear end . the sliding sleeve 5 accommodates an ampoule - like active agent container 7 , in the interior of which a piston 8 can be shifted axially with the aid of a piston rod 9 , for the purpose of delivering the active agent . at its front end , the active agent container 7 is provided with an injection needle 10 . a locking member in the form of a locking sleeve 24 is mounted externally on the sliding sleeve 5 . at least one locking tongue 25 protrudes elastically outwards from the locking sleeve 24 and in the operational state in accordance with fig1 abuts an inner heel 27 of the needle protecting tube 4 . a cavity 26 which is formed in the needle protecting tube 4 and into which the locking tongue 25 protrudes is connected to the heel 27 . the function of the locking sleeve 24 and the locking tongue 25 will be set forth further below . a guiding sleeve 11 is arranged in the rear casing part 2 , such that it can be shifted axially . a driving part 12 , which protrudes backwards out of the guiding sleeve 11 and abuts an end flange of the guiding sleeve 11 via latching projections 13 , is situated in the guiding sleeve 11 . the driving part 12 contacts the piston rod 9 and is biased against it by a driving spring 14 . in fig1 , the auto - injector is depicted in its latched position . this position is useful for the delivery , shipment , sale or storage of the auto - injector since it secured against being intentionally or unintentionally activated and is protected from contamination . a needle protecting cap 15 on the side of the injection needle 10 serves this purpose and has an outer sleeve 16 reaching over the front casing part 1 and the needle protecting tube 4 and an inner sleeve 17 reaching over the injection needle 10 and the front end of the active agent container 7 which encloses it , forming a seal , and thus ensures that the injection needle 10 is clean and sterile . in addition , the attached needle protecting cap 15 also secures the auto - injector against being intentionally or unintentionally triggered , by preventing the needle protecting tube 4 from being touched or shifted . a securing cap 18 , which comprises a securing pin 19 in its centre , is placed on the rear end of the auto - injector , on the right in the figures . the securing pin 19 protrudes between the latching projections 13 of the driving part and thus reliably prevents an injection from being triggered . in order to prepare the auto - injector for use , the needle protecting cap 15 and the securing cap are removed . it is clear that when the needle protecting cap 15 is removed , a tensile force is exerted on the active agent container 7 as a result of the static friction between the inner sleeve 17 and the active agent container 7 . consequently , the active agent container 7 must be prevented from leaving its position ( e . g ., being undesirably moved or pulled forward ) in the auto - injector when the needle protecting cap 15 is removed . for this purpose , a latching sleeve 20 is mounted in the front casing part such that it cannot move axially and at least one latching tongue 21 is arranged on the latching sleeve 20 . three latching tongues 21 are preferably provided in one embodiment , arranged or distributed symmetrically around the circumference of the latching sleeve . as fig1 clearly shows , the free end of the latching tongue 21 abuts the flange 6 of the sliding sleeve 5 and thus prevents the sliding sleeve 5 from being pulled forwards together with the active agent container 7 arranged in it . fig2 shows the auto - injector after the needle protecting cap 15 and the securing cap 18 have been removed as described above . the latching member 20 is still in the latching position and the latching tongue 21 prevents the active agent container 7 , comprising or carrying the injection needle 10 , from being slid forward . in addition , at the then open end , the needle protecting tube 4 creates a distance which prevents the injection needle 10 from being touched or at least makes it difficult to touch the injection needle 10 . the needle protecting tube 4 is held in this position by the force of a spring 22 which is clamped between the rear end of the needle protecting tube 4 and the rear casing part 2 . fig3 shows the auto - injector in a position which it assumes when it is pressed onto the skin of a patient but has not yet been triggered . the needle protecting tube 4 has been shifted backwards into the casing as compared to the position of fig2 , compressing the spring 22 , such that the tip of the injection needle 10 is then situated slightly above the skin of the patient . fig3 also shows that the needle protecting tube 4 shifted backwards has forced the latching tongue 21 outwards , which then exposes the flange 6 of the sliding sleeve 5 . as compared to fig2 , it can be seen that a flange 23 formed internally in the rear part of the needle protecting tube 4 then abuts the front facing side of the guiding sleeve 11 . it should be noted that the needle protecting tube still protrudes out of the front casing part 1 by a remaining amount at the front . however , as compared to fig1 and 2 , it should be clear that the needle protecting tube 4 has slid the locking sleeve 24 some distance backward on the sliding sleeve 5 . fig4 shows the auto - injector at the moment of triggering . proceeding from the state depicted in fig3 , the user has pressed the auto - injector slightly harder onto the skin , such that the needle protecting tube 4 has been shifted into the casing by the remaining amount mentioned above , wherein the flange 23 has shifted the guiding sleeve 11 backwards in the rear casing part 2 by the remaining amount and the latching projections 13 have been moved into the region of a triggering ring 28 arranged in the rear end of the rear casing part 2 . the triggering ring 28 has contacted and / or pressed the latching projections 13 , formed on elastic arms of the driving part , far enough against each other that they are then pulled through the end opening of the guiding sleeve 11 by the force of the driving spring 14 . the force of the driving spring 14 then acts , unobstructed , on the piston 8 via the piston rod 9 , the piston 8 in practice abruptly increasing the hydraulic pressure in the active agent container 7 . this pressure slides the active agent container forwards , such that the injection needle 10 penetrates into the skin of the patient . since the diameter of the passageway in the injection needle 10 is comparatively small , at most a very small amount of the active agent can exit the injection needle 10 in this short period of time between triggering and the injection needle 10 penetrating into the skin . the injection stroke is complete when the flange 6 of the sliding sleeve 5 abuts the end of the needle protecting tube 4 and / or the end of the locking sleeve 24 . fig5 and 6 show the auto - injector in the position in which the injection needle 10 is inserted or injected , wherein fig5 shows the operational state at the beginning of delivering the active agent and fig6 shows the state of the auto - injector after the active agent container 7 has been completely emptied . when the operational state in accordance with fig6 has been reached , the user retracts the auto - injector in order to remove the injection needle 10 from his skin . fig7 shows the operational state after the injection needle 10 has been removed from the skin of the patient . the needle protecting tube 4 was shifted back into its initial state by the force of the spring 22 as soon as the auto - injector was lifted from the skin of the patient . it then mainly serves to substantially cover the injection needle and protect the user and other persons from injuries from the injection needle 10 . consequently , the needle protecting tube 4 must be prevented from being shifted relative to the injection needle 10 such that the injection needle 10 protrudes out of the needle protecting tube 4 . this task is accomplished by the locking tongue 25 , which is formed in the locking sleeve 24 . while the needle protecting tube 4 , as mentioned , has been shifted forwards by the spring force , the locking sleeve 24 maintains its position on the sliding sleeve 5 as a result of a latch tongue 29 formed on the sliding sleeve 5 , which then protrudes into a cavity of the locking sleeve 24 in the position in accordance with fig7 and thus fixes it in place on the sliding sleeve 5 . as can clearly be seen in fig7 , the free end of the locking tongue 25 at the rear end of the needle protecting tube 4 then protrudes into its path . thus , the needle protecting tube 4 cannot be retracted without the locking sleeve 24 , the sliding sleeve 5 and the active agent container 7 together with the injection needle 10 , being shifted backwards relative to the front casing part 1 and the rear casing part 2 , against the force of the driving spring 14 . thus , the injection needle 10 maintains its relative position with respect to the needle protecting tube 4 and the injection needle 10 and is reliably prevented from being intentionally or unintentionally touched . this solution has the advantage that the axially directed force to be absorbed by the locking tongue 25 never exceeds the force of the driving spring 14 , irrespective of how hard one presses against the front end of the needle protecting tube 4 . fig8 to 11 show another embodiment of an auto - injector in accordance with the present invention . in these figures , identical elements and elements having substantially the same function are denoted using the reference numerals from fig1 to 7 . in this embodiment , the latching tongue 21 is guided by means of surfaces on the latching tongue 21 and the sliding sleeve 5 , the surfaces running or extending obliquely with respect to the longitudinal axis of the auto - injector . the latching tongue 21 for latching the active agent container or the sliding sleeve 5 and the locking tongue 25 for latching the needle protecting tube 4 are also both arranged on the latching sleeve 20 . in some preferred embodiments , the latching tongue 21 and the locking tongue 25 are formed integrally with the latching sleeve 20 . in some embodiments , multiple latching tongues 21 and locking tongues 25 can be provided on the latching sleeve 20 . fig8 shows a latching member in the form of a latching sleeve 20 which comprises a latching tongue 21 which comprises a surface 30 running or extending obliquely with respect to the longitudinal axis of the auto - injector , on its facing side . the tip of the oblique surface 30 abuts the outer side of the latching tongue 21 . the sliding sleeve 5 comprises a cavity 31 into which the latching tongue 21 protrudes in the latching position . the edge of the cavity 31 opposite the oblique surface 30 of the latching tongue 21 comprises an oblique surface 30 ′ which runs or extends generally parallel to the oblique surface 30 of the latching tongue 21 . ( in some embodiments , an oblique surface could be provided directly on the active agent container 7 , such that the sliding sleeve 5 can be omitted .) the two oblique surfaces 30 and 30 ′ come to rest on each other . the needle protecting tube 4 is at least partially arranged between the latching sleeve 20 and the sliding sleeve 5 , wherein the latching tongue 21 protrudes through a cavity in the needle protecting tube 4 into the cavity 31 of the sliding sleeve 5 . a part 32 of the needle protecting tube 4 overlaps the abutting point of the oblique surfaces 30 and 30 ′, such that the latching tongue 21 is locked in the latching , latched or lacked position . in fig8 , a locking tongue 25 is also arranged on the sliding sleeve 5 , on the side opposite the latching tongue 21 . the locking tongue 25 protrudes into a cavity opposite it , in the needle protecting tube 4 . fig9 , generally analogous to fig3 , shows the auto - injector in a release position in which the needle protecting tube 4 is slid into the casing “ c ”. in this position , the part 32 of the needle protecting tube 4 has been retracted from the overlapping area of the oblique surfaces 30 and 30 ′. the latching tongue 21 can then be moved into the cavity 31 of the needle protecting tube 4 . the movement can be caused by a bias on the elastic latching tongue 21 . in some preferred embodiments , however , the latching tongue 21 is slid outwards into the cavity by the pressure exerted by the driving spring 14 , which acts on the oblique surface 30 . fig1 , generally analogous with fig5 , shows the auto - injector in a position in which the active agent container 7 is advanced relative to the casing “ c ” and the injection needle 10 is injected into a tissue . the sliding sleeve 5 has been advanced together with the active agent container 7 in a distal direction along the latching sleeve 20 , wherein the latching tongue 21 comes to rest in the cavity 31 of the needle protecting tube 4 . fig1 , generally analogous with fig7 , shows the auto - injector in a position in which the needle protecting tube 4 surrounds the injection needle 10 after the auto - injector has been removed from the surface of the tissue . in this embodiment , the locking tongue 25 is likewise arranged on the sliding sleeve 5 . this enables a component to be omitted in the auto - injector . when the needle protecting tube 4 is advanced , the locking tongue 25 grips behind the end edge of the needle protecting tube 4 , such that the needle protecting tube 4 is secured against retracting relative to the active agent container 7 or the sliding sleeve 5 . when pressure is applied to the needle protecting tube 4 in the proximal direction , the needle protecting tube 4 shifted together with the sliding sleeve , the active agent container 7 and the injection needle 10 , relative to the casing “ c ”. in the foregoing description , embodiments of the present invention , including preferred embodiments , have been presented for the purpose of illustration and description . they are not intended to be exhaustive or to limit the invention to the precise form disclosed . obvious modifications or variations are possible in light of the above teachings . the embodiments were chosen and described to provide the best illustration of the principals of the invention and its practical application , and to enable one of ordinary skill in the art to use the invention in various embodiments and with various modifications as are suited to a particular use contemplated . all such modifications and variations are within the scope of the invention as determined by the appended claims when interpreted in accordance with the breadth they are fairly , legally , and equitably entitled .
in an elongated casing , an active agent container connected to an injection needle can be shifted axially by a spring force . auto - injectors which are sold or distributed filled and with the springs tensed have to be provided with a needle protecting cap to ensure the sterility of the injection needle . when such a needle protecting cap is removed as preparation for using the auto - injector , a tensile force can be exerted on the active agent container . therefore , the active agent container comprising the injection needle must be prevented from being undesirably pulled forwards . at least one latching tongue prevents the active agent container from being prematurely shifted with respect to the casing , by abutting a flange arranged on a sliding sleeve which accommodates the active agent container . when the auto - injector is placed onto a person &# 39 ; s skin , a needle protecting tube is shifted into the casing , forcing the latching tongue away from the flange and , thus , freeing the travel path for needle movement .