Abstract:
A device for the dosed administration of a fluid product including a housing, a conveying device for the product, a drive element influenced by the selection of a product dose, a coupling input member coupled to the drive element, a coupling output member coupled to the conveying device, a retaining device which maintains the coupling elements in a maintaining position uncoupled from each other, wherein at least one of the coupling elements is displaceable by a coupling movement from the maintaining position into a coupling state, and wherein a driving force of the drive element causes a delivery movement of the conveying device via the coupling elements.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation of International Application No. PCT/CH2005/000713, filed on Nov. 30, 2005, which claims priority to German Application No. DE 10 2004 063 647.8, filed on Dec. 31, 2004, the contents of both of which are incorporated in their entirety herein by reference. 
    
    
     BACKGROUND 
     The present invention relates to devices for dispensing, delivering, injecting, infusing or administering substances, and to methods of making and using such devices. More particularly, it relates to a device for administering a fluid product in doses. The device may be an injection apparatus, e.g., an injection pen. 
     Injection apparatus are known for example from diabetes therapy, administering growth hormones or osteoporosis preparations. Such apparatus should guarantee that the correct dosage is administered, yet should be simple and convenient to operate, two requirements which are particularly important when the user administers the relevant product him/herself. 
     An injection apparatus known from WO 01/10484 comprises a conveying and dosing means comprising a piston rod, a drive member and a two-member coupler consisting of a coupler input member and a coupler output member. The drive member is in threaded engagement with a casing of the injection apparatus and is coupled to the coupler output member via the coupler input member. The coupler output member is in another threaded engagement with the piston rod. The piston rod is guided axially and linearly by the casing, such that it is secured against rotating. For setting a dosage, the user rotates the drive member which, due to its threaded engagement with the casing,  30  then extends in the proximal direction, out of the casing. During this combined translational and rotational movement, the drive member slaves the coupler input member. The coupler input member is linearly guided on the coupler output member, such that it is secured against rotating, and together with the drive member forms a ratchet which allows the drive member to rotate relative to the coupler input member in one direction only. Once the desired dosage has been set, the user delivers it by pressing the drive member in the distal direction, into the casing. Due to the threaded engagement with the casing, the translational movement of the drive member is superimposed with a rotational movement which is transferred onto the coupler output member via the coupler input member. The rotational movement of the coupler output member advances the piston rod and therefore delivers the product. However, correcting a dosage which has been set too high proves awkward, for if the desired dosage has been exceeded while setting, the drive member has to be rotated up to a position corresponding to the maximum dosage. The coupler input member which is slaved during the combined translational and rotational movement of the drive member pushes against a translational stopper of the coupler output member when the drive member is in its maximum dosage position. Pulling further on the drive member releases the ratchet, and the arrangement consisting of the drive member and the coupler input member can be moved back in order to set the correct dosage. For correcting, the drive member has to be moved back into its ratchet engagement with the coupler input member. 
     While the drive force to be introduced into the conveying and dosing means for delivering still has to be manually applied in the injection apparatus of WO 01/10484, a conveying and dosing means follows from WO 02/053214 A1 which uses a drive spring for generating the drive force, wherein said drive spring is tensed by the setting the dosage and releases its stored energy during delivery. A spring which is wound around an axis in a spiral serves as the drive spring, the windings of which lie adjacently along the axis. Due to the coupling between the drive spring and the piston rod, only a fixedly predetermined dosage can be set. 
     SUMMARY 
     It is an object of the present invention to provide a device for administering a fluid product which is simple and secure to operate, and advantageously enables the dosage to be corrected simply and securely. 
     In one embodiment, the present invention comprises a device for the dosed administration of a fluid product comprising a housing, a conveying device for the product, a drive element influenced by the selection of a product dose, a coupling input member coupled to the drive element, a coupling output member coupled to the conveying device, a retaining device which maintains the coupling elements in a maintaining position uncoupled from each other, wherein at least one of the coupling elements is displaceable by a coupling movement from the maintaining position into a coupling state, and wherein a driving force of the drive element causes a delivery movement of the conveying device via the coupling element. 
     In some embodiments, the present invention relates to a device for administering a fluid product which comprises a casing comprising a reservoir. The reservoir can itself form a container for the product or can accommodate a container for the product, for example an ampoule. The device also includes a conveying means for the product, a drive member and a coupler for coupling and decoupling the conveying means and the drive member. A piston and a piston rod which acts on the piston in an advancing direction can in particular form the conveying means, wherein the piston rod presses loosely against a rear side of the piston, but in principle can also be connected to the piston by means of an extendable connection or can be formed integrally with the piston. 
     The conveying means is charged with a drive force by the drive member to deliver a settable product dosage. The drive member is influenced by the setting of the dosage, either because it forms a dosing member itself, by which the product dosage can be set, or because setting the product dosage moves it into a particular position or elastically tenses it in accordance with the product dosage set. In the latter case, the drive member is loaded with energy, in accordance with the product dosage set, which it stores and releases when triggered. Correspondingly, the drive member can be operable by introducing the drive force manually via the drive member, or it can be triggered and, when triggered, releases the energy previously absorbed and stored. As a drive member which can be triggered, it need not necessarily be tensed or otherwise loaded by setting the dosage, but can also for example be formed as an electric motor which is triggered and switched off again by a switch set in accordance with the dosage. 
     The coupler couples the drive member to the conveying means in a coupler engagement to transfer a drive force of the drive member for delivering the product onto the conveying means. In a decoupled state, it decouples the conveying means from the drive member, such that manipulations to the drive member or acting on the drive member, such as for example setting or correcting a dosage, cannot influence the conveying means. 
     The coupler consists of at least two coupler members, of which a coupler input member is coupled to the drive member and a coupler output member is coupled to the conveying means. At least one of the coupler members can be moved into the coupler engagement, and at least one of the coupler members—not necessarily the same one—can be moved out of the coupler engagement. 
     In some embodiments of the present invention, the device also includes a holding means, holder or holding fixture which holds the coupler members in a holding position, decoupled from each other. Correspondingly, at least one of the coupler members can be moved by a coupler movement from the holding position into the coupler engagement. In the holding position, the flow of forces between the coupler members is interrupted. In the coupler engagement, by contrast, the drive force of the drive member can be transferred onto the conveying means via the coupler members and causes a delivery movement of the conveying means. 
     The engaging elements of the relevant coupler members, which in the coupler engagement interlock with each other in a positive lock or, as applicable, are merely pressed against each other in a frictional lock, are retracted from each other in the holding position. The coupler members themselves can in fact contact each other, even in the holding position, but their engaging elements are not in contact in the holding position. In some preferred embodiments, the coupler members—which are in the coupler engagement in their coupled state—are completely retracted from each other in their decoupled state. 
     In some preferred embodiments, the holder or holding means is or includes a restoring member which acts counter to the coupler movement with an elastic restoring force. Instead of holding the coupler in its decoupled state by an elastic force, as in some preferred embodiments, the holding means could also act in a positive lock by fixing the at least one coupler member performing the coupler movement on the casing or on a structure which is fixedly connected to it at least with respect to the coupler movement, in a releasable positive lock. 
     In the coupled state of the coupler, the coupler input member and the coupler output member can be directly in coupler engagement with each other. In one development, however, the coupler includes a coupler intermediate member, via which the coupler input member is coupled to the coupler output member in the coupler engagement. In some preferred embodiments, the coupler engagement is established between the coupler input member and the coupler intermediate member. The coupler intermediate member is in an engagement—in which the drive force can be transferred—with the coupler output member, even in the holding position of the coupler members, i.e. in the decoupled state. Advantageously, it can be moved relative to the coupler output member in said engagement, in and counter to the direction of the coupler movement. 
     In a further development, the coupler output member is fixed on the casing in the holding position of the coupler members, such that it cannot perform any movement which would cause a delivery movement of the conveying means. The coupler output member has to be deliberately released, directly connected with delivering the product. It is advantageous if the fixation on the casing part is released by performing the coupler movement. The coupler engagement is established in a first phase during a path portion travelled during the coupler movement, and the fixation on the casing is released in a subsequent, second phase, advantageously against the cited elastic restoring force of the holding means. Advantageously, the coupler output member is fixed on the casing in the holding position of the coupler members via the coupler intermediate member. The blocking engagement which exists for this purpose between the coupler intermediate member and the casing or a structure connected to it is expediently released by performing the coupler movement. It is advantageous if the coupler intermediate member can be moved in the direction of the coupler movement, out of the blocking engagement, since such a mobility allows the coupler intermediate member to simply be slaved, for example pressed out of the blocking engagement, during the coupler movement. The blocking engagement can be a positive-lock engagement and/or a frictional-lock engagement. 
     In a first variant, the restoring member acts on the at least one coupler member performing the coupler movement via the coupler intermediate member and holds it in the holding position. In a second variant, the restoring member acts directly on the at least one coupler member performing the coupler movement, the coupler input member, and is for example supported, for charging, on the casing or on a structure which is fixedly connected to the casing with respect to the coupler movement or on the coupler output member. 
     In some preferred embodiments in which the drive force is manually applied, the coupling between the drive member and the conveying means established by the coupler members is formed such that the drive movement of the drive member is reduced. The path distance travelled by the drive member for a delivery process of a particular dosage, i.e. the total path distance of the drive movement, is longer in such embodiments than the path distance of the delivery movement of the conveying means caused by this. 
     The coupler output member is in engagement with the conveying means, e.g., a threaded engagement, but in an alternative embodiment can in principle also be coupled indirectly to the conveying means via intermediate members to deliver the product. In preferred threaded engagements, a rotational movement of the drive member is converted into a translational movement of a conveying member of the conveying means. The threaded engagement is advantageously not self-locking, such that the conveying member can be axially moved by a force exerted, in the direction of the threaded axis, on the conveying member which can be translationally moved in the threaded engagement. 
     In some preferred embodiments, the coupler input member is in engagement with the drive member, but alternatively can in principle also be coupled to the drive member via intermediate members. The coupling can be a purely positive lock or a purely non-positive lock. It may be formed as a positive and non-positive lock and as a threaded engagement, e.g., in which the coupler input member and the drive member are in engagement with each other. The threaded engagement is advantageously not self-locking, such that the drive member can be axially moved in the threaded engagement by a drive force acting, in the direction of the threaded axis, on the drive member. 
     In embodiments in which the coupler input member is rotationally driven in a first threaded engagement, and the coupler output member drives a conveying member translationally via another, second threaded engagement or in a second threaded engagement directly with the conveying member, the two threaded engagements form a reducing gear which reduces the path distance of the drive movement to a shorter path distance of the delivery movement. In some preferred embodiments, the reduction measures at least 2:1 or 3:1. The reduction can advantageously be reached solely by the different pitches of the two threaded engagements or spindle drives. Thus, for example, the pitch can measure 60° in the first threaded engagement and 17° in the second threaded engagement. 
     Although the drive member can simultaneously also form a dosing member of the device, on which the user sets the dosage, preferred embodiments of a device in accordance with the present invention include a dosing member in addition to the drive member. The dosing member is coupled to the drive member, e.g., purely mechanically, such that a dosing movement of the dosing member also causes a dosing movement of the drive member. The dosing movement of the drive member is counter to the drive force applied by or via drive member during delivery. The device has a dosage display for displaying the product dosage set. The display can be an acoustic display and/or a tactile display and/or an optical display. The dosage display is coupled to the dosing member such that a movement which the dosing member performs when the product dosage is being set causes a change in the product dosage displayed. In the holding position of the coupler members, the dosing member and/or the dosage display is/are decoupled from the conveying means. The decoupling enables the dosage to be set and, as applicable, corrected in the decoupled state, without having a feedback effect on the conveying means. 
     In a preferred embodiment, the coupling between the dosage display and the drive member remains extant in the coupler engagement, such that as delivery progresses, a drive movement of the drive member, counter to the dosing movement, is progressively reset in the same way. If administering is impacted or prematurely aborted, whether deliberately or erroneously and unknowingly, the dosage display thus displays the remainder of the dosage set which has not yet been delivered. This can for example be advantageous when the dosage set is larger than what is still available. 
     If, as is preferred in some embodiments, a dosing member is provided in addition to the drive member, the drive member and the dosing member are advantageously decoupled from each other in the coupler engagement, such that during the drive movement of the drive member, no manipulations can be performed on the dosing member which would have a feedback effect on the drive member. 
     In some preferred embodiments, the drive member drives the coupler input member rotationally, a spiral spring can in particular form the drive member. The spiral spring is wound around a rotational axis of the rotational movement, wherein at least one outer spring winding surrounds an inner spring winding. The spring exhibits a zero pitch with respect to the rotational axis all over. Using the spiral spring can save on axial length, in particular as compared to the springs from the prior art, the windings of which are arranged axially next to each other. One of the two ends of the spiral spring, e.g., its radially inner end, is connected, such that it is secured against rotating, to the coupler input member. The other end, e.g., the radially outer end, is connected, such that it is secured against rotating, to the casing. The coupler input member advantageously forms a reel on which the spiral spring is wound. When setting the dosage, the coupler input member is rotated about the rotational axis, which tenses the spiral spring. A suitable rotational block, for example a ratchet, ensures that the coupler input member can only be rotated in one direction. The rotational block is releasable to be able to correct an incorrectly set dosage. If the rotational block is released, then the worst which can happen if the device is operated erroneously is that the coupler input member is rotated too far back due to the effect of the tensed drive spring. Since the coupler engagement, which couples the coupler input member to the coupler output member, has not yet been established when the dosage is being set, since the coupler members are being held in the holding position, such operational errors cannot affect the conveying means. 
     In some preferred embodiments, the coupler movement is an axial stroke movement. If a piston and a piston rod form the conveying means, the stroke movement is performed in the advancing direction of the piston and the piston rod. If the drive force rotationally drives the coupler input member, which rotationally drives the coupler output member via the coupler engagement, advantageously about a rotational axis pointing in the advancing direction, then the coupler members between which the coupler engagement is formed can in particular be provided with engaging elements which in the coupler engagement co-operate as grooves and springs which can be shifted axially with respect to each other, or can be formed as teeth or more e.g., conical teeth, axially facing each other. Although, for example, a single tooth and a single tooth gap are in principle sufficient for the coupler engagement, at least one of the coupler members forming the coupler engagement may be formed with teeth encircling the rotational axis. In some preferred embodiments, each of the two coupler members for the coupler engagement comprise circumferential teeth or a suitable textured area. The same applies to engaging elements formed as grooves and springs or formed otherwise. Irrespective of the shape of the coupler areas, the coupler engagement is formed such that slip does not occur in the coupler engagement. 
     To obtain a slim, compact injection apparatus, the piston rod and the drive member or the piston rod and the coupler input member—the piston rod, the drive member and the coupler input member—should be arranged co-axially with respect to each other. One of these members should surround at least one other member; in some preferred embodiments, all three members are arranged nested. It is also advantageous if the coupler output member is also arranged co-axially with respect to the piston rod and/or the coupler input member, wherein it can surround the piston rod or, as applicable, be surrounded by the piston rod. 
     The embodiments and the features described herein are advantageous to injection apparatus which comprise the coupler in accordance with the present invention but not necessarily the feature of the holding means and the feature or function of holding in the holding position. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows an embodiment of an injection apparatus in accordance with the present invention, in a perspective view; 
         FIG. 2  shows the injection apparatus of  FIG. 1  with the coupler open, in a longitudinal section; 
         FIG. 3  shows the injection apparatus of  FIG. 1  with the coupler closed; 
         FIG. 4  shows a detail from  FIG. 2 ; 
         FIG. 5  shows a detail from  FIG. 3 ; 
         FIG. 6  shows the injection apparatus of  FIG. 1  after a dosage has been set; 
         FIG. 7  shows the injection apparatus of  FIG. 1  after a reservoir has been emptied; 
         FIG. 8  shows a decoupling member and a casing part of the injection apparatus of  FIG. 1 ; 
         FIG. 9  shows a distal portion of the injection apparatus of  FIG. 1  while the casing parts are being detached; 
         FIG. 10  shows the distal portion with the casing parts connected; 
         FIG. 11  shows another embodiment of an injection apparatus in accordance with the present invention, with the coupler open, in a longitudinal section; 
         FIG. 12  shows the injection apparatus of  FIG. 11 , with the coupler closed, in a different longitudinal section; 
         FIG. 13  shows a detail from  FIG. 11 ; 
         FIG. 14  shows a detail from  FIG. 12 ; 
         FIG. 15  shows the injection apparatus of  FIG. 11 , after a dosage has been set; 
         FIG. 16  shows the injection apparatus of  FIG. 11 , after the reservoir has been emptied; 
         FIG. 17  shows the injection apparatus of  FIG. 11 , with the casing parts detached from each other; 
         FIG. 18  shows a detail from  FIG. 17 ; 
         FIG. 19  shows another embodiment of an injection apparatus in accordance with the present invention; 
         FIG. 20  shows a proximal part of the injection apparatus of  FIG. 19 , with the coupler open; 
         FIG. 21  shows the injection apparatus of  FIG. 19 , with the coupler closed; 
         FIG. 22  shows the proximal part of the injection apparatus of  FIG. 19 , when correcting the dosage; 
         FIG. 23  shows the proximal part of the injection apparatus of  FIG. 19 , after the reservoir has been emptied; 
         FIG. 24  shows a blocking member and a stopping member of the injection device of  FIG. 19 . 
     
    
    
     DETAILED DESCRIPTION 
     With regard to fastening, mounting, attaching or connecting components of the present invention, unless specifically described as otherwise, conventional mechanical fasteners and methods may be used. Other appropriate fastening or attachment methods include adhesives, welding and soldering, the latter particularly with regard to the electrical system of the invention, if any. In embodiments with electrical features or components, suitable electrical components and circuitry, wires, wireless components, chips, boards, microprocessors, inputs, outputs, displays, control components, etc. may be used. Generally, unless otherwise indicated, the materials for making the invention and/or its components may be selected from appropriate materials such as metal, metallic alloys, ceramics, plastics, etc. 
       FIG. 1  shows an injection apparatus of a first embodiment of the present invention. The injection apparatus comprises a first casing part  1  and a second casing part  4  which are detachably connected to each other. The casing parts  1  and  4  are screwed to each other. The injection apparatus is formed as a slim injection pen. The casing part  1  serves to accommodate a container  2  filled with a fluid product and in this sense forms a reservoir, and the casing part  4  serves as a bearer for a dosing and drive means, a dosing member  18  of which can be seen. The casing part  4  is breached or has on opening in the region of the dosing member  18 , such that a user has direct access to the dosing member  18 . The dosing member  18  is mounted such that it can be rotated about a central longitudinal axis of the apparatus, and formed as a sleeve which is ribbed on its outer circumference so as to be user-friendly. A dosage display  20  can also be seen, which is laterally placed through a breach in the shell of the casing part  4 . 
       FIG. 2  shows the injection apparatus in a longitudinal section. The container  2  is accommodated in the casing part  1 . In the container  2 , a piston  3  is accommodated such that it can be moved in an advancing direction V. The piston  3  seals the container  2 , fluid-proof, at its proximal end. Advancing the piston  3  in the advancing direction V displaces and delivers product through an outlet of the container  2 , e.g., through an injection needle protruding into the outlet and fastened to the distal end of the casing part  1  by means of a needle holder. The container  2  may be formed in the manner of conventional ampoules. The casing part  1  directly forms a container holder; in the exemplary embodiment, an ampoule holder. The proximal end of the casing part  1  protrudes into the casing part  4  and is screwed to the casing part  4 . 
     The casing part  4  accommodates a piston rod  15  and the dosing and drive means which is formed as a dosing and drive mechanism. In a dosing and drive line, the dosing and drive means includes a drive member  5  and a coupler comprising components  6 - 11  which in a coupled state, i.e. in a coupler engagement, couples the drive member  5  to the piston rod  15 . The piston rod  15 , together with the piston  3 , forms a conveying means. In the coupled state, coupler members  6 - 10  transfer a drive force exerted on the drive member  5  onto the piston rod  15 . No coupler engagement exists in  FIG. 2 , such that the piston rod  15  is decoupled from the drive member  5 . In this decoupled state, the user can set the product dosage to be administered, by a dosing movement of the dosing member  18 ; in the exemplary embodiment, a rotational movement. 
     The drive member  5  is sleeve-shaped. On its shell outer area, it comprises a thread about a threaded axis R pointing in the advancing direction V. Via this thread, the drive member  5  is in threaded engagement with a coupler input member  6 . The coupler input member  6  is also sleeve-shaped and provided with a corresponding inner thread for the threaded engagement. The thread pitch in the threaded engagement is large enough that self-locking cannot occur. The dosing member  18  surrounds the coupler input member  6  and is connected to the coupler input member  6  such that it is secured against rotating and cannot be moved axially. The piston rod  15  protrudes into the drive member  5  and the coupler input member  6 . 
     The piston rod  15  is provided with an outer thread over its axial length. Via the outer thread, it is in threaded engagement with a coupler output member  9  which is provided with a corresponding inner thread. These two threads also exhibit a thread pitch which prevents self-locking in the threaded engagement. In some embodiments, the thread pitch is less than the thread pitch in the threaded engagement between the drive member  5  and the coupler input member  6 . A coupler sleeve  8  is connected to the coupler output member  9  such that it is secured against rotating and cannot be moved axially. The coupler sleeve  8  and the coupler output member  9  can be regarded as an integral component with respect to the movements between the drive member  5  and the piston rod  15 ; however, to accommodate an equalizing spring  17 , they are embodied in two parts and fixedly connected to each other. The coupler output member  9  and the coupler sleeve  8  are mounted in the casing part  4  such that they can be rotated about the threaded axis R of the coupler output member  9  but cannot be moved axially. In the threaded engagement, the piston rod  15  protrudes through the coupler output member  9  and protrudes into the coupler sleeve  8 . The equalizing spring  17  is clamped between a proximal end of the coupler sleeve  8  and a proximal end of the piston rod  15  and acts on the piston rod  15  in the advancing direction V as a pressure spring. The equalizing spring  17  presses onto the piston rod  15  via a disc  15   a  which is supported such that it can be rotated on the piston rod  15  and forms a flange of a sleeve placed onto the piston rod  15 . 
     The piston rod  15  is linearly guided in and counter to the advancing direction V in a linear guide  4   a , such that it cannot be rotated relative to the casing part  1 . The drive member  5  is also linearly guided relative to the casing part  4  such that it can be moved in and counter to the advancing direction V, for which purpose the casing part  4  directly forms a linear guide  4   b.    
     The threaded axis of the piston rod  15  forms the main movement axis of the device. It forms a rotational axis R for the rotational drive movement of the coupler input member  6  and, via the coupler intermediate member  7 , the coupler output member  9 . It forms both threaded axes. It also forms the translational axis for the piston rod  15  and the drive member  5 . 
     The coupler also includes a coupler intermediate member  7  and a restoring member  10  which is formed as a pressure spring and charges the coupler intermediate member  7  with an elasticity force acting counter to the advancing direction V. The restoring member  10  is clamped between the coupler output member  9  and the coupler intermediate member  7 . 
     If no force acting in the advancing direction V is exerted on the drive member  5 , the restoring member  10  ensures, via the coupler intermediate member  7 , that the coupler engagement is released. This state is shown in  FIG. 2 . The coupler input member  6  is pressed in the advancing direction V until it abuts against the coupler intermediate member  7 , and is pressed into a proximal end position by the restoring member  10  via the coupler intermediate member  7 . By means of the coupler intermediate member, the restoring member  10  holds the coupler input member  6  in a holding position relative to the coupler output member  9  and the coupler sleeve  8  fastened to it. The restoring member  10  and the coupler intermediate member  7  thus form a holding means, acting in a non-positive lock, for the coupler input member  6 . 
       FIG. 3  shows the injection apparatus in a coupled state. A coupler engagement exists between the coupler input member  6  and the coupler sleeve  8 . For the coupler engagement, the coupler input member  6  and the coupler sleeve  8  form engaging elements which, in the coupler engagement, establish a rotationally secured connection between the two members  6  and  8  about the threaded axis R pointing in the advancing direction V. The engaging elements co-operate as grooves and springs or toothings which are formed parallel to the advancing direction V and evenly distributed about the threaded axis R. 
       FIGS. 4 and 5  show the region of the coupler engagement in detail.  FIG. 4  shows the apparatus in the decoupled state and  FIG. 5  shows the apparatus in the coupled state.  FIG. 4  thus corresponds generally to  FIG. 2 , and  FIG. 5  to  FIG. 3 . 
     In the decoupled state, the coupler input member  6  is retracted from the coupler sleeve  8  counter to the advancing direction V, such that the coupler input member  6  can be freely rotated relative to the coupler sleeve  8  and therefore the coupler output member  9  fixedly connected to it. The coupler output member  9  is simultaneously connected, such that it cannot be rotated, to the casing part  4  via the coupler sleeve  8 , the coupler intermediate member  7  and a decoupling member  11 . For this rotationally secure coupling, the coupler intermediate member  7  is provided with engaging elements  7   b  on an inner area radially facing the coupler sleeve  8 , and the coupler sleeve  8  is provided with corresponding engaging elements  8   b . For the rotationally secured engagement with the decoupling member  11 , the coupler intermediate member  7  is provided with engaging elements  7   a  on an outer circumferential area, and the decoupling member  11  is provided with radially facing engaging elements  11   a  on a shell inner area which, in the decoupled state, interlock with each other—like the engaging elements  7   b  and  8   b —in the manner of grooves and springs or teeth parallel to the advancing direction V. The coupler intermediate member  7 , in its rotationally secured engagement with the coupler sleeve  8  and its rotationally secured engagement with the decoupling member  11 , can be moved axially in and counter to the advancing direction V, wherein the engagement with the decoupling member  11  is released when it moves in the advancing direction V. 
     If the drive member  5  is operated by exerting a pressure force on a triggering element  16  in the advancing direction V, the drive member  5  and the coupler input member  6  together complete an axial coupler stroke of length X. In this drive stroke movement or coupler movement, the coupler input member  6  pushes the coupler intermediate member  7  in the advancing direction V, against the restoring elasticity force of the restoring member  10 . In the course of the stroke movement, the engaging elements  6   a  and  8   a  pass into engagement with each other, while the coupler intermediate member  7  simultaneously moves relative to the decoupling member  11  until it passes out of the rotationally secured engagement with the decoupling member  11 . The coupler intermediate member  7  remains in the rotationally secured engagement with the coupler sleeve  8 . The coupler movement is limited by a stopper of the triggering element  16  on the coupler sleeve  8 ; in the exemplary embodiment, on its proximal facing area ( FIG. 3 ). 
       FIG. 5  shows the injection apparatus in the coupled state. The engaging elements  6   a  and  8   a  are axially superimposed, such that the coupler engagement is established as a rotationally secured engagement between the coupler input member  6  and the coupler sleeve  8 . The engagement between the coupler intermediate member  7  and the decoupling member  11  is not released until the coupler engagement is securely established. 
     For setting the dosage, the user rotates the dosing member  18 , which locks in easily releasable locking positions. The dosing member  18  is connected to the coupler input member  6  such that it is secured against rotating and also cannot be moved axially, such that the latter rotates with it. The drive member  5  guided linearly in and counter to the advancing direction V at  4   b  is moved, by the dosing movement of the coupler input member  6 , in the proximal direction and then protrudes out of the casing part  4 . The axial dosing path of the drive member  5  follows from the rotational angle by which the dosing member  18  is rotated and the thread pitch in the threaded engagement between the drive member  5  and the coupler input member  6  which abuts against the coupler intermediate member  7  in the advancing direction V and against the casing part  4  counter to the advancing direction V. 
       FIG. 6  shows the injection apparatus with the container  2  still completely filled, after a first dosage has been set. In this state, the user penetrates the skin with the injection needle, for a subcutaneous injection. Once the injection needle has been placed, the user operates the drive member  5  by pressing it in the advancing direction V, into the casing part  4 . In the first portion of the drive movement, coupler movement or coupler stroke X, the drive member  5  slaves the coupler input member  6 , against the elastic restoring force of the restoring member  10 , until the coupler engagement with the coupler sleeve  8  is established and the rotationally secured engagement between the coupler intermediate member  7  and the decoupling member  11  is released. As soon as the coupler sleeve  8  and together with it the coupler output member  9  can freely rotate about the common threaded axis R, the coupler stroke X is complete and a delivery stroke follows as the second portion of the drive movement. During the delivery stroke, the drive member  5  is pressed further in the advancing direction V. Since the coupler input member  6  cannot perform any further movement in the advancing direction V once it abuts axially against the coupler intermediate member  7 , it rotates—in the threaded engagement with the drive member  5  which is guided such that it is secured against rotating—about the common threaded axis R. When rotated in the coupler engagement, the coupler input member  6  slaves the coupler sleeve  8 , which slaves the coupler output member  9 . The coupler sleeve  8  is held in the casing part  4 , together with the coupler output member  9 , such that it cannot be moved axially. The rotational movement of the coupler output member  9  advances the piston rod  15 , via the threaded engagement with the piston rod  15  and its rotationally secured linear guide at  4   a , and thus causes the delivery movement of the piston rod  15  and together with it the piston  3 . As soon as the injection button  16  passes into abutting contact against the coupler sleeve  8  in the course of the drive and delivery movement ( FIG. 3 ), the delivery process is complete. 
     If the user takes the pressure off the triggering element  16 , then the restoring member  10  moves the coupler input member  6 , via the coupler intermediate member  7 , back to the holding position retracted out of the coupler engagement, as shown in  FIGS. 2 and 4 . The coupler input member  6  and together with it the drive member  5 , the dosing member  18  and the dosage display  20 , are decoupled from the coupler output member  9  and thus from the piston rod  15  by the retracting movement of the coupler input member  6 . On the other hand, the piston rod  15  is again connected to the casing part  4 , such that it is secured against rotating, via the returning coupler intermediate member  7  and decoupling member  11 . 
       FIG. 7  shows the injection apparatus at the end of a final delivery which has emptied the container  2 . 
     For exchanging the emptied container  2 , the casing part  1  is detached from the casing part  4  e.g., by a screwing movement. When the casing parts  1  and  4  are detached, the decoupling member  11  is automatically moved relative to the casing part  4 , counter to the direction of the coupler movement of the coupler input member  6 ; in the exemplary embodiment, counter to the advancing direction V. The casing part  4  mounts the decoupling member  11  accordingly. The axial path which the decoupling member  11  thus travels relative to the casing part  4  is as long as the coupler stroke X, such that once the casing parts  1  and  4  have been detached, the decoupling member  11  lying axially opposite the coupler input member  6  blocks it, and the coupler input member  6  can no longer be moved in the advancing direction V, at least not into the coupler engagement with the coupler sleeve  8 . Blocking the coupler input member  6  in the disengaged position prevents the coupler output member  9  from being able to pass into a rotationally secured connection with the casing part  4  and so prevent the piston rod  15  from retracting. In other words, it ensures that the piston rod  15  can be retracted into the casing part  4 , without being blocked. 
       FIG. 8  shows the decoupling member  11  and the first casing part  1  in a perspective view. The decoupling member  11  is a sleeve part and comprises, in a distal portion, three engaging elements  12  protruding radially inwards and, in a proximal portion, a fixing element  13  protruding radially outwards. 
       FIG. 9  shows the casing part  1  and a connecting portion of the casing part  4 , wherein the hidden decoupling member  11  is shown by a broken line. For its decoupling function, the decoupling member  11  is accommodated in the connecting portion of the casing part  4  such that it can be rotated and moved axially. Its relative mobility is determined by an axial guide  4   e  and a circumferential guide  4   c , along which the fixing element  13  moves in succession when the casing part  1  is detached from the casing part  4 . The circumferential guide  4   c  extends at a right angle to the axial guide  4   e , in the circumferential direction about the screw axis. It is formed as a breach or cavity in the casing part  4 . 
     The decoupling member  11  is in a guiding engagement with the casing part  1 . For the guiding engagement, one guiding curve  1  a per engaging element  12  is formed on a shell outer area of the casing part  1  and guides the engaging element  12  and thus the decoupling member  11  when the casing parts  1  and  4  are detached. Another guiding curve la, spaced in parallel, guides the decoupling member  11  accordingly, when the casing parts  1  and  4  are connected ( FIG. 10 ). In a distal portion, the guiding curve la runs obliquely, i.e. at a pitch, with respect to the screw axis of the screw connection between the casing parts  1  and  4 , such that in the relative rotation between the casing parts  1  and  4 , required for detaching them, the engaging element  12  performs an axial movement of the decoupling member  11  relative to the casing part  4  counter to the advancing direction V, sliding along the guiding curve  1  a, until the fixing element  13  reaches the axial height of the circumferential guide  4   c . The pitch measures about 45° and is constant. In principle, it can be selected from the entire range larger than 0° and smaller than 180° and, as applicable, can also be variable, as long as the relative movement required for detaching the casing parts  1  and  4 —in the exemplary embodiment, a screwing movement—causes a movement of the decoupling member counter to the coupler movement X to be performed by the coupler input member for coupling. A distal portion of the guiding curve  1   a  runs axially, such that when the casing parts  1  and  4  are screwed further apart, the fixing element  13  is moved along the circumferential guide  4   c . In the course of this relative circumferential movement between the decoupling member  11  and the casing part  4 , the fixing element  13  slides over a fixing element  4   d  in the region of the circumferential guide  4   c . The fixing element  4   d  is formed as a cam on a strip portion of the casing part  4 . The strip portion acts as a spiral spring which is fixedly clamped on both sides and elastically gives when the fixing element  13  moves over the fixing element  4   d , in order to then spring back again into its initial position and form a releasable locking engagement for the decoupling member  11 . In the locking position, the fixing element  13  abuts the fixing element  4   d  in one circumferential direction and in the other circumferential direction abuts a collar formed in the circumferential guide  4   c  and is thus fixed in both circumferential directions. 
       FIG. 9  shows the two casing parts  1  and  4  and the decoupling member  11 , after its fixing element  13  has been moved behind the fixing element  4   d  of the casing part  4 . The decoupling member  11  is in the releasable locking engagement with the casing part  4  via the fixing elements  4   d  and  13  and in this way is axially fixed on the casing part  4  such that it is secured against rotating. In the locking position shown in  FIG. 9 , the decoupling member  11  blocks the coupler input member  6  and thus ensures that the drive member  5  and the piston rod  15  are decoupled. As soon as the decoupling member  11  has reached the locking position, its engaging element  12  moves out of the guiding engagement with the guiding curve  1   a  when the casing parts  1  and  4  are screwed further apart. The guiding curve  1   a  is shaped accordingly. 
     When the casing parts  1  and  4  are screwed together again, they are centered with respect to the circumferential direction by co-operating centering elements, such that the engaging element  12  of the decoupling member  11  passes into engagement with the guiding curve  1   a again. As soon as the guiding engagement has been established, further screwing together automatically moves the decoupling member  11  out of the locking engagement of the fixing elements  4   d and  13  until it again assumes the same position relative to the casing part  4  as in  FIG. 10  and  FIGS. 2 to 7 ; this corresponds to the operational position of the decoupling member  11 . 
     While or before screwing together, the piston rod  15  is simply retracted into the casing part  4 , which—due to the released coupler engagement, causes a rotational movement of the coupler output member  9 . 
     The dosage display  20  of the first exemplary embodiment is coupled to the drive member  5  via a display coupling member  21  and the coupler input member  6 . The display coupling member  21  is connected to the coupler input member  6  such that it is secured against rotating, by being able to move on the coupler member  6  and relative to it in and counter to the direction of the coupler movement X, forming a ring in the exemplary embodiment. Conversely, the display coupling member  21  can be rotated with respect to the casing part  4  about the rotational axis R, but is held such that it cannot be moved axially relative to the casing part  4 . The display coupling member  21  circumferentially comprises teeth, which in the exemplary embodiment re formed as a conical teeth, via which it is in engagement with a gear of the dosage display  20  to introduce the dosing movement and also the drive movement into the gear. 
       FIGS. 11 to 18  show an injection apparatus of a second exemplary embodiment. The injection apparatus of the second embodiment exhibits some modifications as compared to the apparatus of the first embodiment with regard to the coupling and decoupling of the drive member  5  and the piston rod  15 . The drive member  5  and the piston rod  15  themselves, and how they co-operate in principle when coupling and decoupling, has however remained the same. Functionally identical components are provided with the same reference numbers as in the first embodiment. In order to indicate modifications, the relevant components are provided with the same reference numbers, but apostrophised. 
       FIG. 11  shows the injection apparatus in its resting state, in which the drive member  5  is decoupled from the piston rod  15 . The first casing part  1  is covered by a protective cap  37  which is connected to the casing part  4  and removed for administering the product. Unlike the first embodiment, the coupler engagement is established and released between the modified coupler input member  6 ′ and the modified coupler intermediate member  7 ′. 
       FIG. 12  shows the injection apparatus of the second embodiment in its coupled state, which is established by charging the triggering element  16  and therefore the drive member  5  and the coupler input member  6 ′ with a drive force acting in the advancing direction V. However, as in corresponding  FIG. 3  of the first embodiment above, no dosage has yet been selected or only a small dosage of a few units for priming. The protective cap  37  has been replaced by a casing part  38  which is placed onto the casing part  4  and snapped onto it. The casing part  38  mounts a needle protection  39 , in the form of a needle protecting sleeve, such that it can be elastically moved counter to the advancing direction V. When the injection needle (not shown) is injected, the needle protection  39  springs counter to the advancing direction V, into the casing part  38 ; in a reversal of this movement, the needle penetrates through a distal opening of the needle protection  39 . 
       FIGS. 13 and 14  show the region of the coupler engagement in detail, wherein  FIG. 13  stands for the decoupled state and  FIG. 14  stands for the coupled state. Unlike the first embodiment, the engaging elements  6   a  and  7   c  between which the coupler engagement is established exhibit an inclination with respect to the advancing direction V. In the exemplary embodiment, the engaging elements  6   a  and  7   c  are each formed in the manner of a conical toothed ring encircling the threaded axis of the piston rod  15 , wherein the coupler input member  6 ′ forms its engaging elements  6   a  on its distal end as an inner cone, and the coupler intermediate member  7 ′ forms the engaging elements  7   c  on its proximal end as an outer cone. The conical engaging areas are congruent to each other and lie directly opposite each other, axially facing, with the clear distance X. Instead of being conical, the coupler areas could also be shaped to be congruently convex/concave or to have another suitable shape. 
     Unlike the first embodiment, the coupler intermediate member  7 ′ can be moved axially and is in engagement with the coupler output member  9 , such that it is secured against rotating, in any axial position. It is again formed as a sleeve part and mounted on the coupler output member  9  such that it can be slid axially. For this purpose, it penetrates through the coupler sleeve  8 ′ which is axially slit accordingly, which however is not visible in the figures. The rotationally secured connection is created in a positive lock via engaging elements formed as axially linear toothings. The restoring member  10 ′, which is the same in its embodiment and installation but reduced with regard to its function, is tensed between the coupler output member  9  and the coupler intermediate member  7 ′, as in the first embodiment, and charges the latter with an elasticity force, counter to the advancing direction V. In the decoupled state, in which the coupler input member  6 ′ is retracted from the coupler intermediate member  7 ′ counter to the advancing direction V, as shown in  FIG. 13 , the restoring member  10 ′ presses the coupler intermediate member  7 ′ into the rotationally secured engagement with the decoupling member  11 ′. The corresponding engaging elements are again indicated as  7   a  and  11   a . The engaging elements  7   a  and  11   a  are also formed as conical toothed or suitably textured rings. The engagement between the coupler intermediate member  7 ′ and the decoupling member  11 ′ can alternatively be in a purely frictional lock. In this case, the engaging elements  7   a  and  11   a  comprise mutually facing congruent frictional areas; these could be the mutually facing conical areas. 
     Another modification exists in the dosing member  18 ′. Unlike the dosing member  18  of the first embodiment, the dosing member  18 ′ cannot be moved relative to the casing part  4  in the direction of the coupler movement X, the axial direction. Instead, the coupler input member  6 ′ is again connected to the dosing member  18 ′ such that it is secured against rotating, but such that it can be moved axially. The rotationally secured engagement between the coupler input member  6 ′ and the dosing member  18 ′ exists in the decoupled state of the drive member  5  and the piston rod  15  and is released in the course of the coupler stroke X, namely directly before the rotationally secured connection between the coupler output member  9  and the casing part  4  is released. For this engagement, the coupler input member  6 ′ and the dosing member  18 ′ are provided with engaging elements  6   b  and  18   a  which are formed on shell areas, radially facing each other, of the two members  6 ′ and  18 ′ in the manner of grooves and springs. With respect to the rotationally secured connection between the coupler input member  6 ′ and the dosing member  18 ′, reference may also be made to  FIGS. 11 and 12 . The rotationally secured connection exists in the decoupled state shown in  FIG. 11 , and is released in the coupled state shown in  FIG. 12 . 
     Another difference with respect to the first embodiment exists with regard to the holding means. In the second exemplary embodiment, the restoring member  10 ′ has no effect which separates the coupler members  6 ′ and  9  from each other. The holding means of the second embodiment includes a restoring member  14 , a supporting structure  6   c  and the dosing member  18 ′. The restoring member  14  charges the coupler input member  6 ′, via the supporting structure  6   c , with an elastic restoring force which counteracts the coupler movement X of the coupler input member  6 ′. In the direction of the coupler movement X, which coincides with the advancing direction V, the restoring member  14  is supported on the dosing member  18 ′ which forms a supporting collar for this purpose. The supporting structure  6   c  is connected to the coupler input member  6 ′ such that it cannot be moved in or counter to the direction of the coupler movement X. It is formed as a short sleeve with an outer flange on which the restoring member  14  is supported. Counter to the direction of the coupler movement X, the supporting structure  6   c  abuts with respect to the casing part  4 . The coupler movement X moves the coupler input member  6 ′, against the elastic restoring force of the restoring member  14 , into the coupler engagement with the coupler intermediate member  7 ′. As in the first embodiment, the restoring member  14  is formed as a pressure spring charged with a pressure force in the direction of the coupler movement X. 
     The mode of operation of the modified coupler, comprising components  6 ′- 11 ′ and  14 ,′ is the same as the coupler of the first embodiment. Thus, in the decoupled state, the coupler output member  9  is connected, such that it is secured against rotating, to the casing part  4  via the coupler sleeve  8 ′, the coupler intermediate member  7 ′ and the decoupling member  11 ′. Operating the injection button  16  and consequently performing the coupler stroke X ( FIG. 11 ) establishes the coupler engagement, in the second embodiment between the coupler input member  6 ′ and the coupler intermediate member  7 ′. In the first phase of the coupler stroke X, the engaging elements  6   a  and  7   c  interlock with each other, such that the coupler input member  6 ′ is connected, such that it is secured against rotating, to the coupler output member  9  via the coupler intermediate member  7 ′ and the coupler sleeve  8 ′. Only once the rotationally secured engagement has been established is the coupler intermediate member  7 ′ moved out of engagement with the decoupling member  11  ′ by the coupler input member  6 ′ pressing in the advancing direction V, such that the coupler output member  9  can freely rotate about the threaded axis R formed with the piston rod  15  and the coupler engagement is completely established. 
       FIG. 14  shows the injection apparatus in its coupled state, i.e. in the coupler engagement.  FIGS. 15 and 16  generally correspond to  FIGS. 6 and 7  showing the first embodiment, such that reference can be made to these. 
       FIG. 17  shows the injection apparatus of the second embodiment while the reservoir  2  is being exchanged. Once the reservoir  2  has been emptied, as shown in  FIG. 16 , the casing part  1  is detached from the casing part  4 , which moves the decoupling member  11 ′ into the decoupling position. This function fully corresponds to that of the decoupling member  11  of the first embodiment, such that reference can be made to the explanations of that embodiment and to  FIGS. 8-10 . 
     In the state shown in  FIG. 17 , the casing part  1  is already accommodating the new reservoir  2 . In order to connect the casing part  1  to the casing part  4 , the casing part  1  can be moved towards the casing part  4  using the piston  3  which proximally seals the reservoir  2 . The piston rod  15  which freely protrudes out of the casing part  4  is moved back by the pressing piston  3  in the threaded engagement with the coupler output member  9  which can be freely rotated but is axially fixed. Due to the rotationally secured linear guide  4   a , which in the second embodiment is formed by a coupler receptacle which is inserted into the casing part  4  such that it is secured against rotating, the piston rod  15  completes an axial linear movement when retracted, while the coupler output member  9  freely rotates, together with the coupler sleeve  8 ′, about the common threaded axis. Instead of moving the piston rod  15  back, pressing against the piston  3 , the piston rod  15  can also be moved back beforehand by pressing directly on its plunger. 
       FIG. 18  shows the coupler region, with the decoupling member  11 ′ situated in the decoupling position, in detail. The function of the decoupling member  11 ′ corresponds to that of the first embodiment, namely blocking the coupler input member  6 ′ in the retracted axial position. 
     The dosing movement and the drive movement are also introduced into a gear of the dosage display  20 ′ via the coupler input member  6 ′ and a display coupling member  22  in the second embodiment. The display coupling member  22  is also connected to the coupler input member  6 ′, such that it is secured against rotating, and cannot be moved relative to the casing part  4  in and counter to the direction of the coupler movement X. 
       FIGS. 19 to 24  show a third exemplary embodiment of the injection apparatus, in which during administering, the drive force for delivering the product is not applied manually but rather by a drive member  25  formed as a drive spring. The drive member  25  is tensed by setting the dosage to be administered. The spring energy absorbed when setting the dosage is released when the apparatus is triggered and converted into advancing the piston rod  15 . 
       FIG. 19  shows the injection apparatus of the third embodiment, complete with the assembled casing part  38  and the needle protection  39  accommodated in it such that it can be slid counter to the advancing direction V, against the force of a restoring spring. 
       FIGS. 20 and 21  show the casing part  4  with the components of the injection apparatus accommodated in it;  FIG. 20  in a resting state, comparable to the preceding embodiments, in which the dosage can be set, and  FIG. 21  in the coupler engagement. Unless stated differently below, reference is made in particular to  FIGS. 20 and 21 . 
     The drive member  25  is a spiral spring acting as a torsion spring, comprising spring windings which encircle the threaded axis R of the threaded engagement between the coupler output member  9  and the piston rod  15 . The spring windings are arranged one over the other, radially with respect to the threaded axis R; they exhibit a zero pitch with respect to the threaded axis. An inner end of the spring windings is fastened to the coupler input member  6 ′, and an outer end is fastened to a supporting structure  26  which is connected to the casing part  4  such that it can be moved in the direction of the coupler movement X but is secured against rotating. On the other hand, the supporting structure  26  is connected to the coupler input member  6 ′ such that it cannot be moved in and counter to the direction of the coupler movement X. The coupler input member  6 ′ can be rotated about the threaded axis R relative to the supporting structure  26 . Another supporting structure  6   d  is connected to the coupler input member  6 ′ such that it cannot be moved in and counter to the direction of the coupler movement X. The coupler input member  6 ′ and the supporting structure  6   d  are formed integrally. The drive member  25  is axially enclosed by the supporting structures  6   d  and  26 . 
     The functionality of the coupler corresponds to that of the second embodiment, such that the same reference signs are used for the coupler members  6 ′- 10 ′ and the decoupling member  11 ′. Unlike the coupler of the second embodiment, however, the coupler sleeve  8 ′ in that embodiment has been omitted. The coupler intermediate member  7 ′ is directly in an engagement with the coupler output member  9  which transfers the rotational drive movement of the coupler input member  6 ′ onto the coupler output member  9 . 
       20 ″ indicates a dosage display which is coupled to the coupler input member  6 ′ via a display coupling member  23  and, like the display coupling members  21  and  22  of the other embodiments above, is connected to the coupler input member  6 ′, such that it is secured against rotating. The display coupling member  23  cannot be moved in and counter to the direction of the coupler movement X relative to the casing part  4 . As in the first and second embodiments above, the rotationally secured connection of the display coupling member  23  exists both in the decoupled and in the coupled state of the device. 
     For setting the dosage and during storage, to prevent the coupler input member  6 ′ from the rotational drive movement and to hold the drive member  25  in its tensed state, a rotational block is formed between the coupler casing  6 ′ and the casing part  4 . In the holding position of the coupler members  6 ′,  7 ′ and  9  shown, the rotational block exists between a first blocking member  24  and a second blocking member  34 . The blocking member  24  is connected to the coupler input member  6 ′, such that it is secured against rotating. The blocking member  34  is connected to the casing part  4 , such that it is secured against rotating but can be moved in and counter to the direction of the coupler movement X relative to the casing part  4  and the coupler input member  6 ′. The facing areas of the blocking members  24  and  34 , which contact each other in the blocking engagement, form a ratchet which allows a rotational movement of the coupler input member  6 ′ which tenses the drive member  25 , and prevents a rotational movement in the opposite direction. 
       FIG. 24  shows the coupler input member  6 ′ together with the blocking member  24  mounted on it, such that it is secured against rotating, the display coupling member  23  connected to the coupler input member  6 ′, such that it is secured against rotating, and a connecting part  33  connected to the input member  6 ′ such that it cannot be moved. The display coupling member  23  forms a units counting ring of the dosage display  20 ″ and is suitably coupled to a tens counting ring in order to display the dosage set. On a proximal facing side facing the blocking member  34 , the blocking member  24  is provided with blocking teeth  24   a  which are arranged evenly about the axis R and, in the blocking engagement, co-operate with counter teeth of the blocking member  34 , to form the rotational block with respect to the drive movement. For a second function connected with dosing and delivery, a shell outer area of the blocking member  24  is provided with a thread  24   b , the threaded axis of which coincides with the threaded axis R of the piston rod  15 . A stopping member  27  engages with the thread  24   b . The stopping member  27  is guided such that it can be linearly moved parallel to the threaded axis R; in the exemplary embodiment, in an axial groove on the inner shell area of the casing part  4 . The blocking member  24  forms a rotational stopper  24   c  for the stopping member  27 , which limits the drive movement of the coupler input member  6 ′ which advances the piston rod  15 . It forms another rotational stopper  24   d  for the stopping member  27 , which determines the maximum dosage which can be delivered and set. Another stopping member  27  is arranged on the other side of the threaded axis R, opposite the stopping member  27  which can be seen in the view in  FIG. 23 , and co-operates in the same way with two other rotational stoppers  24   c  and  24   d . The thread  24   d  is double-threaded. The stopping members  27  simultaneously abut against the respectively assigned rotational stoppers  24   c  and  24   d , as can be seen in the cross-sectional representation in  FIG. 23  for the rotational stoppers  24   c . The rotational stoppers  24   c  determine a zero dosage position and the rotational stoppers  24   d  determine a maximum dosage position. 
     In the third embodiment, the holding means is formed in a third variant. It includes a restoring member  19 , as well as the display coupling member  23  and the blocking member  24 . The restoring member  19  is supported on the casing part  4  via the display coupling member  23  in the direction of the coupler movement X and on the blocking member  24  counter to the direction of the coupler movement X. The restoring member  19  presses the blocking member  24  until it abuts against the connecting part  33 . Since the connecting part  33  is connected to the coupler input member  6 ′ such that it cannot be moved in and counter to the direction of the coupler movement X, the restoring member  19  thus exerts an elastic restoring force, acting counter to the direction of the coupler movement X, on the coupler input member  6 ′ via the blocking member  24  and the connecting part  33 , said elastic restoring force holding the coupler input member  6 ′ in the holding position retracted out of the coupler engagement. It again acts as a pressure spring. The blocking member  24  is a sleeve part comprising an outer shell forming the thread  24   b , an inner shell serving to mount it on the coupler input member  6 ′ such that it is secured against rotating, and a base which connects the two shells and on which the blocking teeth  24   a  are formed. The restoring member  19  protrudes into the blocking member  24  which is cup-shaped in this way, and is supported on the base of the blocking member  24 . 
     The restoring member  19  presses the blocking member  24  not only until it abuts against the connecting part  33 , but also until it abuts against the casing part  4 . Abutting in this other way prevents the blocking member  24  from being able to move counter to the direction of the coupler movement X beyond the holding position assumed in  FIG. 20 . The blocking member  24  can thus be moved relative to the coupler input member  6 ′, against the restoring elasticity force of the restoring member  19 , in the direction of the coupler movement X. Conversely, the coupler input member  6 ′ can be moved counter to the direction of the coupler movement X relative to the blocking member  24  abutting against the casing part  4 . 
     The equalizing spring  17 , tensed between the piston rod  15  and the connecting part  33 , supports the restoring member  19  in its function of holding the coupler input member  6 ′ in the holding position. The equalizing spring  17  could in principle replace the restoring member  19  for retracting the coupler members  6 ′,  7 ′ and  9 . In some preferred embodiments, however, it is weak enough that, at least once it has been partially relaxed, it can no longer hold the coupler members  6 ′- 9  in the holding position, and thus can no longer hold the coupler in the decoupled state. 
     A triggering element  28  is provided for triggering the drive member  25 . The triggering element  28  can be moved translationally relative to the casing part  4  in the direction of the coupler movement X—the advancing direction V and/or distal direction—and rotationally about the rotational axis R of the coupler input member  6 ′, which coincides with the threaded axis R of the piston rod  15 , and is guided in these two movements by the casing part  4 . The translational movement in the distal direction establishes the coupler engagement between the coupler input member  6 ′ and the coupler intermediate member  7 ′ and releases the rotational block between the blocking members  24  and  34 , which triggers the drive member  25 , i.e. delivery. The translational movement in the advancing direction V is therefore also referred to in the following as the triggering movement. 
     In another function, the triggering element  28  forms the dosing member of the third embodiment. Via multiple intermediate members, the rotational movement of the triggering element  28  relative to the casing part  4  sets the product dosage which can be delivered by the next delivery process. This movement is also referred to in the following as the dosing movement. From the zero dosage position, which is shown in  FIG. 20  and determined by the stopping members  27  abutting the rotational stoppers  29   c  of the blocking member  24  which limit the drive movement of the coupler input member  6 ′, the dosage can be set by rotating the triggering element  28  in the direction of the rotational direction arrow indicated, the dosing direction. The rotational dosing movement of the triggering element  28  is transferred onto the coupler input member  6 ′ via an inner part  29 —which is connected to the triggering element  28  such that it is secured against rotating and shifting or is formed integrally with it—and the connecting part  33 . For transferring, the inner part  29  and the connecting part  33  are in an engagement with each other, such that they are secured against rotating, and the connecting part  33  is connected to the coupler input member  6 ′, such that it is secured against rotating. For securing against rotating, the inner part  29  and the connecting part  33  are provided with inner teeth  29   a  and outer teeth  33   a  which interlock with each other in the resting state of the apparatus and can be axially shifted with respect to each other. 
     The triggering element  28  is arranged in the proximal end region of the casing part  4  so as to be user-friendly. Its outer sleeve part surrounds the casing part  4 . A base of the triggering element  28  forms a proximal end of the injection apparatus. For setting the dosage, the triggering element  28  can be operated as a turning button and is ribbed on its outer shell area for this purpose. For triggering, it can be operated as a push button. During the dosing movement, the triggering element  28  locks with the casing part  4  in discrete rotational angular positions corresponding to the dosage units. 
     A stopper element  29   b  facing a proximal facing area of the connecting part  33  projects radially inwards from the inner part  29 . In the resting state of the apparatus, a clear distance remains between the connecting part  33  and the stopper element  29   b , said clear distance being just large enough that the rotational block between the inner part  29  and the connecting part  33  is released during the triggering movement of the triggering element  28 , before the stopper element  29   b  terminates the relative movement of the triggering element  28  relative to the connecting part  33  by an abutting contact. 
     The second blocking member  34  is tensed in the blocking engagement with the blocking member  24  by a blocking spring  31 . For this purpose, the blocking spring  31  is supported in the direction of the coupler movement X on the blocking member  34  and counter to the coupler movement X on a casing part  30  which is fixedly connected to the casing part  4 . Another spring  32 , arranged between the inner part  29  and the blocking member  34 , tenses the triggering element  28  relative to the blocking member  34  into a proximal end position. The blocking member  34  is axially guided, such that it is secured against rotating, by the casing part  4 . The casing part  4  forms a distal and a proximal stopper for the mobility of the blocking member  34 . 
     In the resting state shown in  FIG. 20 , the user sets the dosage by rotating the triggering element  28  in the dosing direction. During this rotational dosing movement, the triggering element  28  slaves the connecting part  33  via the rotational block  29   a,    33   a , and the connecting part  33  for its part slaves the coupler input member  6 ′ which thus completes the same rotational dosing movement as the triggering element  28 . Rotating the coupler input member  6 ′ tenses the drive member  25 . In engagement with the thread  24   b  of the blocking member  24 , the stopping member  27  migrates from the stopper  24   c  of the thread  24   b  which determines the zero dosage, in the direction of the stopper  24   d  which determines the maximum dosage ( FIG. 24 ). 
     The injection apparatus also offers a convenient way of correcting the dosage, as is clear from a comparison of  FIGS. 20 and 22 . If the user has inadvertently set too high a dosage, he/she can correct the dosage by rotating the coupler input member  6 ′ back. For correcting the dosage, the user pulls the triggering element  28  in the proximal direction. This retracting movement of the triggering element  28  is indicated in  FIG. 22  by an arrow, as is the rotational direction for correcting. In the resting state of the apparatus, the inner part  29  and the blocking member  34  are in a slaving engagement with respect to a movement in the proximal direction. The corresponding slaving means are indicated as  29   c  and  34   a . The slaving means  29   c  formed by the inner part  29  and the slaving means  34   a  formed by the blocking member  34  grip behind each other and form a latch for the retracting movement of the triggering element  28 . Pulling on the triggering element  28  thus also moves the blocking member  34  in the proximal direction, against the force of the blocking spring  31 , thus releasing it from the blocking engagement with the blocking member  24  which abuts against the casing part  4 . As soon as the rotational block is released, the user can correct the dosage by means of a reverse rotational movement of the triggering element  28  and the still extant rotationally secured engagement between the inner part  29  and the connecting part  33 . As soon as the user releases the triggering element  28 , it snaps back in the distal direction together with the blocking member  34  due to the effect of the blocking spring  31 , and the blocking member  34  thus snaps back into the blocking engagement with the blocking member  24 . During the reverse rotational movement, the user expediently continues to hold the triggering element  28  fast, which is facilitated by the rotational angular locking positions of the triggering element  28 . In principle, however, the user can also let it snap back and re-dose, as applicable. 
     Once the desired dosage has been set, the apparatus is placed onto the skin at the desired administering location, and the injection needle is injected. For injecting the needle, the triggering element  28  takes on another function, for which purpose it is coupled to the needle protection  39  ( FIG. 19 ). 
     In a first phase of injecting, the user presses the injection apparatus against the skin, such that the needle protection  39  is moved in the distal direction relative to the casing part  38 . However, this first part of the movement of the needle protection  39  does not yet expose the injection needle; rather, its tip remains short of the needle protection  39 . In this first phase of the injecting process, the needle protection  39  abuts against a resisting element, such that it cannot be moved further in the distal direction relative to the casing part  38 . While continuing to exert pressure on the injection apparatus in the direction of the skin, the user presses the triggering element  28  in the proximal direction. In the course of this first phase of its triggering movement, the triggering element  28  releases an abutting contact between the needle protection  39  and the resisting element, such that the injection apparatus, and together with it the injection needle, are moved relative to the needle protection  39  in the direction of the skin, and the injection needle injects. With respect to the function of the triggering element  28  for injecting the needle, reference may be made to the patent application entitled “Attachment Module for an Injection Device Comprising an Engagement Control for a Needle Covering Element” owned by the owner of the present application. 
     As soon as the injection needle has been subcutaneously placed, the drive member  25  can be released and the product delivered by pressing further onto the triggering element  28 . In the second phase of the triggering movement of the triggering element  28 , which follows the injection phase, the triggering element  28  and therefore the inner part  29  is pressed further in the distal direction relative to the connecting part  33 , against the pressure of the spring  32 , such that the rotational block  29   a ,  33   a  is released. The triggering element  28  can rotate idly. As soon as the rotational block  29   a,    33   a  has been released, the stopper element  29   b  passes into abutting contact with the connecting part  33 . In the third phase of the triggering movement which then follows, the triggering element  28  presses the connecting part  33  and therefore the coupler input member  6 ′ via the stopper element  29   b , in the direction of the coupler movement X; in the exemplary embodiment, in the advancing direction V. Due to the effect of the spring force of the blocking spring  31 , the blocking member  34  follows this movement until it abuts against the casing part  4 . Before the blocking member  34  reaches the abutting position, the coupler input member  6 ′ passes into the coupler engagement with the coupler intermediate member  7 ′. The coupler input member  6 ′ presses the coupler intermediate member  7 ′ out of the frictional-lock blocking engagement with the decoupling member  11 ′, against the force of the restoring member  10 ′. Once the blocking engagement between the conical areas of the two members  7 ′ and  11 ′ has been released and the coupler engagement therefore completely established, the blocking member  34  abuts the casing part  4 . In the final phase of the triggering movement which then follows, the triggering element  28  presses the blocking member  24  out of the blocking engagement with the blocking member  34  via the connecting part  33 . 
     As soon as the rotational block formed by the blocking members  24  and  34  is released, the rotational drive movement of the coupler input member  6 ′ is initiated due to the drive force of the drive member  25  and is transferred onto the coupler output member  9  via the coupler engagement. Because it is guided,—such that it is secured against rotating—in the linear guide  4   a , the piston rod  15  is moved—in the threaded engagement with the coupler output member  9 —in the advancing direction V, and product is delivered. This delivery movement is terminated by the stopping member  27  abutting the stopper  24   c  of the blocking member  24  which determines the zero dosage. 
       FIG. 21  shows the injection apparatus when a zero dosage or a small priming dosage is set, in the coupled state after the rotational block  24 ,  34  has been released, i.e. after the triggering element  28  has completely performed the triggering movement. If, advantageously, pressure is continuously exerted on the triggering element  28 , the triggering sequence described above progresses automatically, from injecting to completely delivering the dosage set. 
       FIG. 23  shows the injection apparatus after the container  2  has been emptied. The casing part  1  has already been removed from the casing part  4 . The piston rod  15  assumes its most distal position. The decoupling member  11 ′ blocks the coupler input member  6 ′ in the position retracted from the coupler intermediate member  7 ′. The functionality of the decoupling member  11 ′ corresponds to that in the other exemplary embodiments. Unlike the other embodiments, however, the casing part  1  and the decoupling member  11 ′ are not directly in a guiding engagement with each other, but rather via an adaptor structure  36 . The adaptor structure  36  is a sleeve in the casing part  4  which is fixed in and counter to the direction of the coupler movement X in the connecting portion, but can be rotated about the central longitudinal axis R of the casing part  4 . The adaptor structure  35  forms a guiding curve  36   a  either as a cavity on or a breach in its shell area facing the decoupling member  11 ′. The guiding curve  35   a  exhibits the course of a threaded portion. The length measured over the circumference and the pitch of the guiding curve  35   a  measured with respect to the central longitudinal axis of the casing part  4  are dimensioned such that the decoupling member  11 ′ is moved into the decoupling position shown in  FIG. 21  by a quarter to a half revolution of the adaptor structure  35  relative to the decoupling member  11 ′. For generating the axial movement, the decoupling member  11 ′ engages via its engaging element  12  with the guiding curve  35   a . In this respect, reference is made to the statements regarding the first embodiment. 
     When connecting the casing parts  1  and  4 , the adaptor structure  35  forms a linear guide for the casing part  1 . The casing part  1  is inserted into the adaptor structure  35 , wherein a slight frictional lock and correspondingly a sliding guide for the casing part  1  exists. The casing part  1  cannot be rotated about the central longitudinal axis of the casing part  4  relative to the adaptor structure  35 . The engagement, which is rotationally secured accordingly, is established right at the beginning of inserting the casing part  1  into the adaptor structure  35 . Once the casing part  1  has been inserted until it abuts against the casing part  4 , i.e. once the coupler is accommodated at  4   a , the casing part  1  is rotated relative to the casing part  4  and slaves the adaptor structure  36  during this rotational movement, until the engaging element  12  of the decoupling member  11 ′ abuts the end of the guiding curve  36   a . The rotational movement of the casing part  1  is not possible until its axial abutting position, for which purpose a rotational block acting up until the abutting position can also be formed between the casing parts  1  and  4 . 
     The movement of the decoupling member  11 ′ caused in the guiding engagement exhibits an axial length which is greater than the length X of the complete coupler movement. In its decoupling movement, the decoupling member  11 ′ presses the coupler input member  6 ′ beyond its holding position as assumed in the resting state, and blocks it in said decoupling position. In this forced decoupling movement, the coupler input member  6 ′ slaves the triggering element  28  via the stopper element  29   b . Via the latch between the slaving means  29   c  and  34   a , the blocking member  34  is also slaved, against the force of the blocking spring  31 , and moved out of the blocking engagement. The blocking member  24  cannot follow the blocking member  34 , since it is abutting against the casing part  4 . Detaching the casing parts  1  and  4  thus releases the rotational block by means of the decoupling mechanism which the casing parts  1  and  4  form with the decoupling member  11 ′ via the adaptor structure  35 . If the coupler input member  6 ′ has not yet assumed the zero dosage position, it is rotated now at the latest into the zero dosage position by the drive member  25 , and the dosage display  20 ″ is zeroed. In this respect, reference may again be made to the advantage of the coupling between the dosage display  20 ″ and the coupler input member  6 ′, namely that for each delivery, the dosage display  20 ″ is reset in accordance with the delivered dosage. If, one time, the dosage set was not delivered, for example because the injection process was aborted or the container  2  no longer contained the complete dosage set, the user can read this from the dosage display  20 ″ which is then only partially reset. 
     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 forms and steps disclosed. The embodiments were chosen and described to provide the best illustration of the principles of the invention and the practical application thereof, and to enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the 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.