Patent Publication Number: US-11376368-B2

Title: Injection device

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional application of U.S. patent application Ser. No. 15/230,320, filed Aug. 5, 2016, which, in turn, is a continuation application of international patent application PCT/EP2015/000205, filed Feb. 3, 2015, designating the United States and claiming priority from German application 20 2014 001 134.6, filed Feb. 5, 2014, and the entire content of the above applications is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     An injection device in which a latching part which is connected in a rotationally fixed manner to the operating button and interacts with the injection sleeve is provided is known from WO 2013/117332 A1. When setting an amount of injection fluid to be squeezed out, the operating button is rotated in relation to the housing, and when the injection fluid is being squeezed out, is held so as to be rotationally fixed in relation to the housing and guided in the longitudinal direction of the injection device. When setting an amount of injection fluid to be squeezed out, and when the injection fluid is being squeezed out of the container, the injection sleeve is moved in the direction of the longitudinal central axis of the injection device, without being rotated in relation to the housing. On account thereof, the rotational position of the operating button in relation to the injection sleeve is modified in the case of each injection procedure. 
     A second latching installation of WO 2013/117332 A1 acts between a housing part and a dosing member. The dosing member rotates when setting the amount of an injection fluid to be squeezed out, and the dosing member rotates back when the amount of injection fluid to be squeezed out is being squeezed out. The latching installation has two latching arms which are disposed so as to be mutually opposite. Since the dosing member is rotatable about the longitudinal central axis by multiple rotations, each latching position is reached multiple times when setting the maximum dosage. 
     If and when, for example, amounts of 0.20 ml and 0.25 ml of injection fluid which are to be set for a therapy are required, then known injection devices are conceived such that dosing increments of at most 0.05 ml are settable. This means, on the one hand, that the user has to overcome a plurality of latching steps until the minimum dosage which is provided for the therapy is reached. On the other hand, the amount of injection fluid which has to be discarded during the priming procedure is comparatively sizeable in the case of a minimum fixed dosage increment of 0.05 ml, for example. Therefore, significantly smaller dosing increments would be desirable for the priming procedure. However, this leads to a significantly increased number of latching positions which have to be overcome by the user when setting the dosage. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to provide an injection device which enables a plurality of latching positions to be disposed at variable spacings. 
     An injection device defines a longitudinal center axis, a proximal direction and a distal direction. The injection device includes: a housing; a dosing member held so as to be rotatable and fixed in the housing in the direction of the longitudinal center axis; an injection sleeve held so as to be rotationally fixed in relation to the housing and displaceable in the direction of the longitudinal center axis; the dosing member being connected to the injection sleeve via a first threaded connection; the dosing member being configured to rotate in a first rotational direction in relation to the housing when an amount of injection fluid to be dispensed is being set; the injection sleeve being configured to move in the distal direction because of the first threaded connection; the dosing member being further configured to rotate in a second rotational direction counter to the first rotational direction when the amount of injection fluid to be dispensed is being pressed out; the injection sleeve being configured to move in the proximal direction because of the first threaded connection; a container configured to contain injection fluid; a dosing piston configured to press injection fluid out of the container; the dosing piston being connected to the dosing member via a second threaded connection; the dosing piston being connected to the dosing member in a rotationally fixed manner so as to rotate conjointly therewith when the amount of injection fluid to be dispensed is being set; the dosing piston being connected to the injection sleeve in a rotationally fixed manner when the amount of injection fluid to be dispensed is pressed out and, by virtue of the second threaded connection, is moved in the proximal direction; a latching unit configured to act at least when the amount of injection fluid to be dispensed is being set; and, the latching unit being configured to act between two components of the injection device which during setting of the amount of injection fluid to be dispensed, move relative to one another, wherein a set amount of injection fluid is unequivocally assigned to each relative mutual position of the two components. 
     The present invention provides that the latching installation acts between two components of the injection device wherein each relative mutual position of the two components is unequivocally assigned a set amount of injection fluid. On account thereof, the required latching positions may be disposed at variable mutual spacings. For example, an injection device which provides precisely three latching positions at 0.01 ml for the priming procedure, and at 0.20 ml and 0.25 ml for the dosages to be injected, could be provided for the exemplary therapy which has been described at the outset. Operating the injection device is significantly simplified on account thereof. Where reference is made hereunder to “the two components”, this means the two components between which the latching installation is in effect and in which case each relative mutual position is unequivocally assigned a set amount of injection fluid. 
     The latching installation advantageously has at least one latching element and at least one counter-latching element which in a latching position interacts with the latching element. 
     Advantageously, one of the two components between which the latching installation acts is the dosing member, and the other of the two components is the injection sleeve. When setting the amount of injection fluid to be squeezed out, the dosing member and the injection sleeve are moved in relation to one another in helical manner, since the dosing member performs a rotation movement, and the injection sleeve performs a movement in the direction of the longitudinal central axis of the injection device. When the injection fluid is being squeezed out, the dosing member and the injection sleeve move back from one another to their respective initial position. On account thereof, precisely one set amount of injection fluid is assigned to each relative mutual position of the dosing member and the injection sleeve. 
     It may also be provided that one of the two components between which the latching installation acts is the injection sleeve, and the other of the two components is the housing. The injection sleeve moves in the direction of the longitudinal central axis of the injection device when setting an amount of injection fluid to be squeezed out. When the injection fluid is being squeezed out, the injection sleeve moves back to the initial position thereof. On account thereof, each axial position of the injection sleeve corresponds to precisely one set amount of injection fluid. 
     The statement that the latching installation acts between the two components means that the latching installation is effective between these components, but does not mean that the latching element and the counter-latching element have to be disposed on the two components per se. Rather, the latching element and the counter-latching element may be configured on further components which likewise perform the relative mutual movement of the two components and, on account thereof, are effective between the two components. 
     It is provided that the injection device has an operating element. The operating element advantageously has a distal position in which the operating element is located when setting the amount of injection fluid to be squeezed out, and a proximal position in which the operating element is located when the amount of injection liquid to be squeezed out is being squeezed out. The distal position and the proximal position of the operating element here are positions of the operating element in relation to the injection sleeve. Advantageously, the operating element by way of a first coupling is connectable in a rotationally fixed manner to a follower or entrainer which is connected in a rotationally fixed manner to the dosing member, and by way of a second coupling is connectable to the injection sleeve. In the distal position of the operating element, the operating element by way of the first coupling is advantageously connected in a rotationally fixed manner to the entrainer. The second coupling in the distal position of the operating element is advantageously opened such that the operating element is rotatable in relation to the injection sleeve. In the proximal position of the operating element the first coupling is advantageously opened, and the operating element is rotatable in relation to the entrainer, and the operating element by way of the second coupling is connected in a rotationally fixed manner to the injection sleeve. The operating element is rotated when setting an amount of injection fluid to be set. The entrainer, the dosing member, and the dosing piston which is connected in a rotationally fixed manner to the operating element rotate conjointly with the operating element. When injection fluid is being squeezed out the operating element is connected in a rotationally fixed manner to the injection sleeve and, on account thereof, is guided in a rotationally fixed manner in relation to the housing. The entrainer conjointly with the dosing member rotates about the longitudinal central axis of the injection device, and by way of the second threaded connection moves the dosing piston in the proximal direction. On account thereof, the injection fluid is squeezed out of the container. 
     Comfortable operation results when the latching installation is effective only when setting the amount of injection fluid to be squeezed out, but not during the injection procedure. This may be achieved in a simple manner in that the latching installation is coupled to the position of the operating element, and is effective in the distal position of the operating element. In the proximal position of the operating element, the at least one latching element and the at least one counter-latching element advantageously are mutually disengaged, independently of the relative mutual position of the two components. If and when the latching installation is effective only when setting an amount of injection fluid to be squeezed out, the latching element and/or the counter-latching element may be configured so as to be asymmetrical such that a significantly higher force is required for overcoming a latching position in order to reduce the set amount of injection fluid to be squeezed out than for setting an amount of injection fluid to be squeezed out. 
     Advantageously, one of the two components between which the latching installation acts is the entrainer, and the other of the two components is the injection sleeve. A simple construction of the injection device results on account thereof. In the case of injection devices in which the operating element is rotated by fewer than one revolution in order for the maximum dosage to be reached, precisely one set amount of injection fluid is assigned to each relative rotational position of the entrainer and the injection sleeve. Advantageously, the entrainer in the direction of the longitudinal central axis is coupled to the position of the injection sleeve such that the entrainer moves conjointly with the injection sleeve in the distal direction when setting the amount of injection fluid to be squeezed out, and moves in the proximal direction when the set amount of injection fluid is being squeezed out. On account thereof, a simple construction of the first coupling which acts between the entrainer and the operating element is enabled. 
     A simple construction of the injection device results if and when at least one latching element is disposed on the one of the two components, and at least one counter-latching element is disposed on the other of the two components. In a particularly advantageous manner, the latching element and the counter-latching element, respectively, are configured so as to be integral with the respective component. A fixed connection to the respective component may also be advantageous in particular in order for the production of the component to be simplified. 
     In order for it to be achieved in a simple manner that the latching installation is effective only when setting an amount of injection fluid to be set, but not when the injection fluid is being squeezed out, it is advantageous for at least one latching element to be disposed on one latching part which is connected in a rotationally fixed manner to one of the two components, so as to be displaceable in relation to this component in the direction of the longitudinal central axis. Advantageously, at least one counter-latching element is disposed on the other of the two components. The at least one latching element in a first axial position of the latching part may advantageously come into engagement with the at least one counter-latching element. The at least one latching element, in a second axial position of the latching part, independently of the relative mutual position of the two components, is advantageously disengaged from the at least one counter-latching element. 
     A simple construction results when the position of the latching part is linked to the position of the operating element such that the latching part, in the distal position of the operating element, is located in the first axial position thereof and, in the proximal position of the operating element, is located in the second axial position thereof. The latching part is advantageously elastically biased in the direction toward the first axial position thereof, preferably by at least one spring. 
     A simple construction having a minor number of individual parts results when the latching part has at least one spring arm which biases the latching part in the direction toward the first axial position thereof. The spring arm advantageously is configured so as to be integral with the latching part such that no additional spring is required for biasing the latching part in the direction toward the first axial position thereof. 
     Advantageously, a spring which biases the dosing member in the second rotation direction acts between the injection sleeve and the dosing member. On account thereof, the dosing member is reset in the direction toward the next latching position which corresponds to the next lowest amount of injection fluid to be set, when the operating element is released between two latching positions. On account thereof, inadvertent squeezing out of an unintended amount of injection fluid is prevented in a simple manner. Since the injection sleeve in relation to the dosing member moves in the direction of the longitudinal central axis when setting an amount of injection fluid to be squeezed out, the spring advantageously is connected to the entrainer which is connected in a rotationally fixed manner to the dosing member. Advantageously, the spring by way of one end is secured to the injection sleeve, and by way of the other end is secured to the entrainer. A simple construction of an injection device which has a latching part results when the spring by way of one end is secured to the latching part, and by way of the other end is secured on the entrainer. A spring which biases the dosing member in the second rotation direction is advantageous in particular in the case of an injection device in which the latching installation thereof is only effective when setting an amount of injection fluid, but not when the latter is being squeezed out. The latching installation advantageously is configured such that to overcome the latching positions a lesser force is required for setting an amount of injection fluid to be squeezed out, than for turning back in the opposite direction. On account thereof, when the operating element is released between two latching positions, it may be ensured that the dosing member is reset only to the next lowest latching position and that this latter latching position cannot be overcome. At the same time, the spring which biases the dosing member in the second rotation direction may be conceived to be so strong that reliable turning back of the dosing member is also ensured in the case of unfavorable friction conditions and tolerances. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will now be described with reference to the drawings wherein: 
         FIG. 1  shows a side view of a first embodiment of an injection device in the zero position; 
         FIG. 2  shows a section along the line II-II in  FIG. 1 ; 
         FIG. 3  shows a side view of the injection device of  FIG. 1 , after setting an amount of injection fluid to be squeezed out; 
         FIG. 4  shows a section along the line IV-IV in  FIG. 3 ; 
         FIG. 5  shows a side view of the injection device of  FIG. 1 , after setting an amount of injection fluid to be squeezed out and displacing the operating element in the proximal direction; 
         FIG. 6  shows a section along the line VI-VI in  FIG. 5 ; 
         FIG. 7  shows a side view of the entrainer, the spring, and the latching part of the injection device of  FIGS. 1 to 6 ; 
         FIG. 8  shows a side view of the assembly in  FIG. 7 , in the direction of the arrow VIII in  FIG. 7 ; 
         FIG. 9  shows a plan view in the direction of the arrow IX in  FIG. 7 ; 
         FIG. 10  shows the fragment X of  FIG. 9 , in an enlarged illustration; 
         FIGS. 11 and 12  show perspective illustrations of the entrainer of the injection device of  FIGS. 1 to 6 ; 
         FIG. 13  shows a side view of the entrainer; 
         FIG. 14  shows a side view in the direction of the arrow XIV in  FIG. 13 ; 
         FIG. 15  shows a section along the line XV-XV in  FIG. 14 ; 
         FIGS. 16 and 17  show perspective illustrations of the latching part of the injection device of  FIGS. 1 to 6 ; 
         FIG. 18  shows a side view of the latching part of  FIGS. 16 and 17 ; 
         FIG. 19  shows a section along the line XIX-XIX in  FIG. 18 ; 
         FIGS. 20 and 21  show perspective illustrations of the operating element of the injection device; 
         FIG. 22  shows a side view of the operating element; 
         FIG. 23  shows a section along the line XXIII-XXIII in  FIG. 22 ; 
         FIG. 24  shows a view of the operating element, in the direction of the arrow XXIV in  FIG. 22 ; 
         FIGS. 25 to 27  show perspective illustrations of the injection sleeve of the injection device; 
         FIGS. 28 and 29  show side views of the injection sleeve; 
         FIG. 30  shows a section along the line XXX-XXX in  FIG. 29 ; 
         FIG. 31  shows the fragment XXXI of  FIG. 30 , in an enlarged illustration; 
         FIG. 32  shows a section along the line XXXII-XXXII in  FIG. 30 ; 
         FIGS. 33 and 34  show side views of the dosing member; 
         FIG. 35  shows a section along the line XXXV-XXXV in  FIG. 33 ; 
         FIG. 36  shows a section along the line XXXVI-XXXVI in  FIG. 33 ; 
         FIG. 37  shows a perspective illustration of a piston rod of the injection device of  FIGS. 1 to 6 ; 
         FIG. 38  shows a side view of the piston rod of  FIG. 37 ; 
         FIG. 39  shows a section along the line XXXIX-XXXIX in  FIG. 38 ; 
         FIGS. 40 and 41  show side views of a housing part of the injection device of  FIGS. 1 to 6 ; 
         FIG. 42  shows a section along the line XLII-XLII in  FIG. 41 ; 
         FIG. 43  shows a section along the line XLIII-XLIII in  FIG. 41 ; 
         FIG. 44  shows a side view of a holder of the injection device of  FIGS. 1 to 6 ; 
         FIG. 45  shows a section along the line XLV-XLV in  FIG. 44 ; 
         FIG. 46  shows an injection sleeve, a latching part, and an entrainer of an embodiment of an injection device; 
         FIG. 47  shows a section along the line XLVII-XLVII in  FIG. 46 ; 
         FIGS. 48 to 52  show perspective illustrations of the latching part of  FIGS. 46 and 47 ; 
         FIG. 53  shows a side view of an embodiment of an injection sleeve of an injection device; 
         FIG. 54  shows a section along the line LIV-LIV in  FIG. 53 ; 
         FIG. 55  shows a section along the line LV-LV in  FIG. 54 ; 
         FIG. 56  shows a side view of an embodiment of an entrainer of an injection device; 
         FIG. 57  shows a section along the line LVII-LVII in  FIG. 56 ; 
         FIG. 58  shows the fragment LVIII in  FIG. 57 , in an enlarged illustration; 
         FIGS. 59 and 60  show side views of an embodiment of an injection device after setting an amount of injection fluid to be squeezed out; 
         FIG. 61  shows a section along the line LXI-LXI in  FIG. 60 ; 
         FIG. 62  shows the fragment LXII in  FIG. 61 , in an enlarged illustration; 
         FIG. 63  shows a perspective illustration of an embodiment of a dosing member; 
         FIG. 64  shows the fragment LXIV of  FIG. 63 , in an enlarged illustration; 
         FIG. 65  shows a side view of the dosing member of  FIG. 63 ; 
         FIG. 66  shows a section along the line LXVI-LXVI in  FIG. 65 ; 
         FIG. 67  shows a side view of an embodiment of an injection sleeve; 
         FIG. 68  shows a section along the line LXVIII-LXVIII in  FIG. 67 ; 
         FIG. 69  shows a section along the line LXIX-LXIX in  FIG. 67 ; 
         FIG. 70  shows a side view of an injection device in the zero position; 
         FIG. 71  shows a section along the line LXXI-LXXI in  FIG. 70 ; 
         FIG. 72  shows a side view of the injection device of  FIG. 70  after setting an amount of injection fluid to be squeezed out; 
         FIG. 73  shows a section along the line LXXIII-LXXIII in  FIG. 72 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION 
       FIG. 1  shows an injection device  1  which has a housing  2 . The housing  2  includes an upper distal housing part  3 , and a holder  4  which is disposed on the proximal side of the upper housing part  3 . An injection needle  8  is secured to the proximal side of the holder  4 . Adjacent to the injection needle  8 , the holder  4  has a latching installation  9 , a container  5  shown in  FIG. 2  being latched thereto in the holder  4 . An operating element  6  is disposed on the distal side of the injection device  1 . As is shown in  FIG. 1 , the injection device  1  has a longitudinal central axis  50  which runs in the longitudinal direction of the injection device  1 . The upper housing part  3  has a viewing window  7  which is configured so as to be at least partially transparent. The viewing window  7  in  FIG. 1  is drawn in a schematic and non-transparent manner such that the components lying therebelow are not visible in  FIG. 1 . 
     The distal end of the injection device  1  is that end that faces away from an injection needle  8  which is held on the injection device. “Proximal” refers to that side of the injection device  1  that faces the puncture when injecting, “distal” referring to that side that faces away from the puncture. The proximal direction refers to the direction of injection, that is, the direction toward the injection needle  8 , or that direction in which the injection fluid is squeezed out of the container  5 , respectively. The distal direction refers to the opposite direction, that is, away from the injection needle  8 . 
     As is shown in  FIG. 2 , a plug  10 , a piston disk  13  of a dosing piston  11  bearing thereon, is disposed in the container  5 . The dosing piston  11  moreover includes a piston rod  12  which carries an external thread  92 . 
     An injection sleeve  17 , the external side thereof being visible through the viewing window  7  of the upper housing part  3 , is disposed in the upper housing part  3 . The injection sleeve  17  has an opening  26 , the external circumference of a dosing member  18  which is disposed within the injection sleeve  17  being visible therethrough. The dosing member  18 , which may also be referred to as a graduated tube, on the external circumference thereof carries a graduation (not visible in  FIG. 2 ) which to the operator is visible through the viewing window  7  and the opening  26 . 
     The injection sleeve  17  in the upper housing part  3  is held so as to be displaceable in the direction of the longitudinal central axis  50  and so as to be rotationally fixed in relation to the upper housing part  3 . The dosing member  18  and the injection sleeve  17  are interconnected by way of a first threaded connection  19 . An entrainer  14  which is connected in a rotationally fixed manner to the dosing member  18  is disposed within the dosing member  18 . The entrainer  14  has a circumferential groove  63 , a retaining periphery  64  of the injection sleeve  17  protruding thereinto. The retaining periphery  64  here is held with a clearance in the circumferential groove  63 . On account thereof, the injection sleeve  17  and the entrainer  14  are interlinked in the direction of the longitudinal central axis  50 . However, by virtue of the clearance, minor relative movement between the injection sleeve  17  and the entrainer  14  in the direction of the longitudinal central axis  50  is possible. 
     The dosing member  18  by way of a latching connection  71  is held in the upper housing part  3  so as to be fixed in the direction of the longitudinal central axis  50 . In the embodiment the latching connection  71  is disposed at the proximal end of the dosing member  18 . The dosing member  18  by way of a pivot bearing  21  is rotatably mounted in the upper housing part  3 . The dosing member  18  by way of a second threaded connection  22  is connected to the piston rod  12  of the dosing piston  11 . The operating element  6  by way of an entrainment portion  51  is connected in a rotationally fixed manner to the piston rod  12 . 
     The operating element  6  in  FIG. 2  is shown in the distal position  90  thereof in relation to the injection sleeve  17 . The operating element  6  by way of a first coupling  16  is connectable to the entrainer  14 . In the distal position  90  of the operating element  6 , the operating element  6  and the entrainer  14  are interconnected in a rotationally fixed manner by way of the first coupling  16 . A latching part  15  is disposed in the operating element  6 . The latching part  15  in the embodiment is configured so as to be annular, being disposed on the external circumference of the entrainer  14 . A latching installation  35  which will be described in yet more detail hereunder is formed between the entrainer  14  and the latching part  15 . The latching part  15  is connected in a rotationally fixed manner to the injection sleeve  17 . The latching part  15  is movable in the direction of the longitudinal central axis  50 , being biased by a spring  23  in the direction toward the first axial position  88  of the latching part  15 , as shown in  FIG. 2 . 
     A second coupling  20  which is opened in the zero position  28  of the injection device  1 , as shown in  FIG. 2 , is provided between the operating element  6  and the injection sleeve  17 . On account thereof, the operating element  6  is rotatable in relation to the injection sleeve  17 . No dosage is set in the zero position  28 . In the zero position  28  the injection sleeve  17  bears on a first stop  24  on the upper housing part  3 . 
     In order for an amount of injection fluid to be squeezed out to be set, the operator rotates the operating element  6  in a first rotation direction, being the clockwise direction in the embodiment. The entrainer  14  and the dosing member  18  which is connected in a rotationally fixed manner to the entrainer  14  are conjointly rotated by way of the first coupling  16 . The piston rod  12  is also conjointly rotated by way of the entrainment portion  51  of the operating element  6 . The injection sleeve  17 , by virtue of the first threaded connection  19  and of the rotationally fixed fixation of the injection sleeve  17  in the upper housing part  3 , is moved in the distal direction  30 . The entrainer  14  and the operating element  6  also move conjointly with the injection sleeve  17 . Since the entrainer  14  moves in relation to the latching part  15  which is connected in a rotationally fixed manner to the injection sleeve  17 , the latching increments of the latching installation  35  are perceivable and audible to the operator. The latching installation  35  is effective when setting an amount of injection fluid to be squeezed out. 
       FIGS. 3 and 4  show the injection device  1  in the injection position  29 , after setting an amount of injection fluid to be squeezed out. The operating element  6  here has been rotated by fewer than one full revolution in relation to the upper housing part  3 . The injection sleeve  17  in the distal direction has partially moved out of the upper housing part  3 . As is shown in  FIG. 4 , the spring  23  is not only configured as a compression spring, but additionally acts as a torsion spring. To this end, the spring  23  by way of a first end  84  is hooked to the latching part  15 , and by way of a second end  85  is hooked to the entrainer  14 . The spring  23  is tensioned when the operating element  6  is rotated in the first rotation direction. If and when the operating element  6  between two latching positions of the latching installation  35  is released by the operator, the spring  23  turns the entrainer  14  and, conjointly with the entrainer, the dosing member  18  back to the next lowest latching position, that is, to that latching position which corresponds to the next lowest envisaged amount of injection fluid. Moreover, the spring  23  biases the latching part  15  to the first axial position  88  thereof. The operating element  6  which by way of the latching part  15  is likewise biased to the distal position  90  thereof, bears on the latching part  15 . 
     In order for the set amount of injection fluid to be squeezed out, the operator has to move the operating element  6  in the proximal direction  31 , counter to the force of the spring  23  acting in the direction of the longitudinal central axis  50 . As is shown in  FIG. 4 , the operating element  6  has a stop element  32  which in the position shown in  FIG. 4  bears on a first stop  33  of the injection sleeve  17 . The stop element  32  here bears on the proximal side of the first stop  33 , being urged by the spring  23  against the first stop  33 . As is also shown in  FIG. 4 , the injection sleeve  17  has a second stop  34  which is disposed on the proximal side of the stop element  32 , in the position shown in  FIG. 4  being disposed at a spacing from the stop element  32 . As is also shown in  FIG. 4 , the injection sleeve  17  in the injection position  29  shown in  FIG. 4  also bears on a stop  25  of the upper housing part  3 , which delimits the maximum amount of injection fluid to be set. 
       FIGS. 5 and 6  show the injection device  1  after displacing the operating element  6  from the distal position  90  thereof to the proximal position  91  thereof, and prior to injection fluid being squeezed out. In the proximal position  91  of the operating element  6 , the stop element  32  bears on the second stop  34 . As is also shown in  FIG. 6 , the latching part  15  has been displaced in the proximal direction  31 , to the second axial position  89  thereof, by the operating element  6 . In this position the latching installation  35  is not active such that no latching positions can be perceived or heard when injection fluid is being squeezed out. 
     The first coupling  16  is opened in the proximal position  91  of the operating element. As a result the entrainer  14  can rotate in relation to the operating element  6 . As is also shown in  FIG. 6 , the first coupling  16  on the entrainer  14  has latching teeth  38  which in the case of a closed coupling  16  engage between the latching teeth  53  of the operating element  6 . In the case of an opened coupling  16 , the latching teeth  38  in the direction of the longitudinal central axis  50  are disposed so as to be spaced apart from the latching teeth  53 , being mutually disengaged. The second coupling  20  in the proximal position  91  of the operating element  6  is closed such that the operating element  6  is connected in a rotationally fixed manner to the injection sleeve  17  and thus also in a rotationally fixed manner to the upper housing part  3 . If and when the operating element  6  is displaced from the position shown in  FIG. 6  in the proximal direction  31 , the injection sleeve  17  by way of the stop element  32  and by way of the second stop  34  moves in the proximal direction. The dosing member  18  is rotated by way of the first threaded connection  19 . The piston rod  12  is connected in a rotationally fixed manner to the operating element  6  and, by way of the operating element  6 , in a rotationally fixed manner to the upper housing part  3 . By virtue of the rotation of the dosing member  18 , the piston rod  12  is moved in the proximal direction, on account thereof squeezing out the set amount of injection fluid from the container  5 . The entrainer  14  is entrained by the injection sleeve  17  in the proximal direction. The spring  23  is at least partially relaxed when the operating element  6  moves in the proximal direction  31 , on account thereof facilitating the injection procedure. 
       FIGS. 7 to 10  show the entrainer  14 , the latching part  15 , and the spring  23 .  FIG. 8  schematically shows the insertion fit of the two ends  84  and  85  of the spring  23  on the latching part  15  and on the entrainer  14 . The latching part  15  has longitudinal grooves  37  for the rotationally fixed connection to the injection sleeve  17 . The entrainer  14 , on the proximal cylindrical portion thereof, has longitudinal grooves  36  for the rotationally fixed connection to the dosing member  18 . This cylindrical proximal region at the distal side thereof is delimited by a periphery  48 . As is shown in  FIGS. 9 and 10 , the entrainer  14  has the inwardly protruding latching teeth  38 . The latching teeth  38  do not extend across the entire internal circumference of the entrainer  14 . Four groups of three latching teeth  38  each, which are symmetrically disposed, are provided in the embodiment. Another number or arrangement of the latching teeth  38  may also be advantageous. As is also shown in  FIGS. 14 and 15 , the entrainer  14  has an opening  47 , in each case on the proximal side of the latching teeth  38 . On account thereof, the proximal end of the latching teeth  38  may be manufactured in a simple manner in terms of production technology. The latching teeth  53  of the operating element  6 , which are shown in  FIG. 6 , in the case of an opened first coupling  16  are located in the region of the openings  47 . The spring  23  is configured as a combined compression and torsion spring, biasing the latching part  15  in the distal direction, and biasing the entrainer  14  in the rotation direction about the longitudinal central axis  50  in the direction toward the zero position  28 . 
       FIGS. 9 and 10  also show the latching installation  35  in detail. The latching installation  35  includes a latching element  43  which is configured on the latching part  15 . A counter-latching element  40  on the entrainer  14  interacts with the latching element  43 . The counter-latching element  40  is configured on a latching arm  39 , being resilient by virtue of the inherent elasticity of the material. Both the latching element  43  as well as the counter-latching element  40  in the circumferential direction are asymmetrically configured. The counter-latching element  40  has a latching flank  45 , the latching element  43  in the latching position coming to lie there behind. The further flank of the counter-latching element  40  is configured as a guide flank  46  which has a comparatively flat profile. Accordingly, the counter-latching element  40  is also asymmetrically configured, having a latching flank  45  and a guide flank  46 . When setting an amount of injection fluid to be squeezed out, the entrainer  14  conjointly with the operating element  6  is rotated in a first rotation direction. The guide flanks  46  come into mutual contact during this rotation. The guide flank  46  of the latching element  43  deflects the counter-latching element  40  in a radially inward manner such that the latching positions can be readily reached. During rotation of the operating element  6  in a second rotation direction, counter to the first rotation direction, the steep latching flanks  45  come into mutual contact. The spring  23  is advantageously conceived such that the force of the spring  23  does not suffice for the latching flanks  45  to be overcome, so that the injection device  1  is always reset to the next lowest latching position when the operating element  6  is released between two latching positions. However, a symmetrical layout of the latching elements  40  and/or  43  may also be advantageous. The latching flanks may be conceived such that the operator may overcome a latching position that has already been reached, being able to reset the operating element  6  to a lower set dosage. The latching flanks may also be conceived such that the latter is impossible. 
       FIG. 11  shows an opening  94  on the entrainer  14 , the second end  85  of the spring  23  ( FIG. 8 ) being hooked into the opening  94 .  FIGS. 12 and 13  show the configuration of the latching arm  39  which carries the counter-latching element  40 . As is also shown in  FIG. 13 , the periphery  48  delimits the circumferential groove  63 , the retaining periphery  64  of the injection sleeve  17  ( FIG. 2 ) protruding thereinto. 
       FIGS. 16 to 19  show the latching part  15 . As is shown in particular in  FIG. 19 , the latching part  15  for the rotationally fixed connection to the injection sleeve  17  has on the external circumference two longitudinal grooves  37 , disposed so as to be mutually opposite. Four latching elements  41 ,  42 ,  43 , and  44 , which are of identical configuration and are disposed at dissimilar mutual spacings on the circumference, are configured on the latching part  15  in the embodiment. The latching element  41  corresponds to the zero position, the latching element  42  is assigned to the priming position, the latching element  43  is assigned to a first dosage, and the latching element  44  is assigned to a second dosage. The latching part  15  at the distal end side  49  thereof is configured in a rounded manner. The latching part  15 , by way of this end side  49 , bears on the operating element  6 . Low friction forces result by way of the rounded configuration when the operating element  6  is being rotated in relation to the latching part  15 . 
       FIGS. 20 to 24  show the operating element  6 . As is shown in  FIGS. 20 and 21 , the entrainment portion  51  of the operating element  6 , by way of which the operating element  6  is connected in a rotationally fixed manner to the piston rod  12  ( FIG. 1 ), is configured by two arms  52  which extend in the longitudinal direction of the injection device  1 . As is shown in  FIG. 23 , the operating element  6 , in the distal region of the circumferential wall thereof, carries an internal toothing  54  which interacts with a toothing  55 , shown in  FIG. 25 , on the external circumference of the injection sleeve  17 , forming with the latter the second coupling  20 . As is shown in  FIG. 24 , the latching teeth  53  which together with the latching teeth  38  of the entrainer  14  form the first coupling  16 , are likewise not distributed across the entire circumference of the operating element  6 , but are in each case only disposed in part-regions. The latching teeth  53  and the latching teeth  38  are to be disposed such that it is ensured in every rotational position of the operating element  6  in relation to the entrainer  14  that at least one latching tooth  50  engages with at least one latching tooth  38 . As is shown in  FIGS. 23 and 24 , the stop element  32  is configured as an inwardly protruding periphery. No continuous periphery is provided in the embodiment; rather, four individual and mutually separated peripheral portions which form stop elements  32  are provided. During assembly of the operating element the stop elements  32  snap-fit behind the first stop  33  of the injection sleeve  17 . However, a continuous stop element  32  which extends across the entire circumference may also be advantageous. 
     The injection sleeve  17  is shown in  FIGS. 25 to 32 . The injection sleeve  17  is configured in the shape of a sleeve, having a distal portion  59  and a proximal portion  60  which are mutually separated by a groove  56 . The stops  33  and  34  are configured on those sides that delimit the groove  56 . The stop elements  32  of the operating element  6  protrude into the groove  56 . The injection sleeve  17  on the internal side thereof has two longitudinal webs  58 , shown in  FIG. 26 , which serve for the rotationally fixed connection to the latching part  15  and which protrude into the longitudinal grooves  37  of the latching part  15 . The opening  26  through which the outside of the dosing member  18  is visible to the operator is also shown in  FIGS. 25 and 26 . As is shown in  FIGS. 28 and 30 to 32 , the proximal portion  60  of the injection sleeve  17 , on that side that is opposite the opening  26 , has a longitudinal web  61  which is configured as an elevation on the external circumference. The longitudinal web  61  has a rectangular depression  62 . The configuration of the depression  62  is shown in detail in  FIG. 31 . 
     The depression  62  has a distal edge  86  which in the zero position  28  of the injection device  1  interacts with a distal edge  78 , shown in  FIG. 42 , on the upper housing part  3 , forming with the distal edge  78  the first stop  24 . The depression  62  has a proximal edge  87  which in the injection position  29 , shown in  FIG. 4 , which corresponds to the maximum settable amount of injection fluid to be squeezed out, bears on a proximal edge  79  of the upper housing part  3  ( FIG. 42 ), forming with the proximal edge  79  the second stop  25 . The second stop  25  delimits the maximum settable amount of injection fluid to be squeezed out. 
     As is shown in  FIGS. 42 and 43 , the upper housing part  3  has a depression  76  which is configured as an approximately rectangular longitudinal groove, a longitudinal web  77  rising therefrom. The longitudinal web  61  of the injection sleeve  17  protrudes into the depression  76 . On account thereof, the injection sleeve  17  in the circumferential direction is secured against rotating in relation to the housing  2 . The longitudinal web  77  of the upper housing part  3  protrudes into the depression  62  of the injection sleeve  17 , forming with the depression the stops  24  and  25 . The longitudinal web  77  and the depression  62  also form an anti-rotation security feature for the injection sleeve  17 . As is shown in particular in  FIG. 30 , the injection sleeve  17  in the proximal portion  60  thereof carries an internal thread  57 . 
     The dosing member  18  is shown in detail in  FIGS. 33 to 36 . The dosing member  18  on the external side thereof carries an external thread  65  which with the internal thread  57  of the injection sleeve  17  ( FIG. 30 ) forms the first threaded connection  19 . The dosing member  18 , in the region of the external thread  65 , has the graduation  66 , shown in  FIGS. 33 and 34 , which indicates to the operator the set amount of injection fluid. As is shown in  FIGS. 33 to 35 , the dosing member  18  on the proximal side thereof has latching hooks  67 . As is shown in  FIG. 42 , the upper housing part  3  has an encircling latching periphery  75 , the latching hooks  67  hooking thereinto and thus forming the latching connection  71 . As is shown in  FIGS. 34 and 35 , the dosing member  18  on the proximal side thereof has a mounting pin  70  which is mounted in a bearing sleeve  74  of the upper housing part  3  ( FIG. 42 ). On account thereof, the dosing member  18  is rotatably mounted in the upper housing part  3 . As is shown in  FIG. 35 , an internal thread  68  is disposed in the mounting pin  70 . The internal thread  68  interacts with the external thread  92  of the piston rod  12 , shown in  FIGS. 37 and 38 , and with the latter forms the second threaded connection  22 . As is shown in  FIG. 36 , the substantially sleeve-shaped dosing member  18 , on the internal circumference thereof, has a total of four longitudinal webs  69  which serve for the rotationally fixed connection to the entrainer  14 . To this end, the longitudinal webs  69  protrude into the longitudinal grooves  36  of the entrainer  14 , which are shown in  FIGS. 11 to 13 . 
     As is shown in  FIGS. 37 to 39 , the piston rod  12  on the distal side thereof has a guide portion  72  which has a rectangular cross section which in the embodiment is square. The arms  52  of the operating element  6 , which are schematically indicated in  FIG. 39 , bear on opposite longitudinal sides of the guide portion  72 , on account thereof producing a rotationally fixed connection between the operating element  6  and the piston rod  12 . The piston rod  12 , on the proximal region thereof, has a groove  73  to which the piston disk  13  is hooked ( FIG. 2 ). 
     As is shown in  FIG. 42 , the upper housing part  3 , in the proximal region thereof, has latching hooks  80  which serve for the latching connection to the holder  4  which is shown in  FIGS. 44 and 45 . The holder  4  in the distal region thereof has latching openings  81  into which the latching hooks  80  hook. Two latching hooks  80  and two latching openings  81  are shown in the embodiment. The latching installation  9  is also shown in  FIGS. 44 and 45 . The latching installation  9  is formed by two mutually opposite latching hooks  82  which latch onto the container  5 . The holder  4 , on the external circumference thereof, in the proximal region has an external thread  83  onto which the injection needle  8  ( FIG. 1 ) is screwed. 
     In the embodiment as per  FIGS. 1 to 45  the spring  23  fulfills a dual function, since the former has to both generate torque between the entrainer  14  and the latching part  15  as well as bias the latching part  15  and the operating element  6  in the distal direction. In order for the layout of the spring  23  to be simplified, separate spring elements may be provided for generating the axial force and for generating the torque. A respective embodiment is shown in  FIGS. 46 to 52 . The same reference signs are used for designating corresponding elements in all figures of the present application. An injection sleeve  97  in which a latching part  95  and an entrainer  14  are disposed is shown in  FIGS. 46 and 47 . The injection sleeve  97  has an inwardly protruding support periphery  98  on which a first end  84  of a spring  93  is secured. A second end  85  of the spring  93  is hooked to the entrainer  14 . The spring  93  serves for generating torque between the injection sleeve  97  and the entrainer  14 . Since the entrainer  14  is connected in a rotationally fixed manner to the dosing member  18 , the torque acts between the dosing member  18  and the injection sleeve  97 , biasing the dosing member  18  in the direction toward the zero position  28  of the assembly. 
     As is shown in  FIGS. 48 to 52 , the latching part  95 , on the proximal side thereof, has two spring arms  96 . In the embodiment the spring arms  96  are configured preferably from plastics so as to be integral with the latching part  95 . By virtue of the inherent elasticity thereof, the spring arms  96  bias the latching part  95  in the distal direction. Instead of the spring arms  96 , a screw compression spring or a spring element of another configuration may also be expedient for biasing the latching part  95  and the operating element  6  in the direction of the longitudinal central axis  50 . 
     A further embodiment of an injection device is shown in  FIGS. 53 to 58 , wherein only the injection sleeve  107  and the entrainer  114  are shown. The further elements which are not shown correspond to the components which are shown and described in the context of the injection device  1 . As is shown in  FIG. 54 , the injection sleeve  107 , on the internal circumference thereof, has latching elements  101 ,  102 ,  103 , and  104 . The latching elements  101 ,  102 ,  103 , and  104  establish the latching positions of the injection device  1 . As is shown in  FIG. 54 , the latching elements  101  to  104  on the circumference have dissimilar mutual spacings. The latching element  101  is assigned to the zero position, the latching element  102  is assigned to the priming position, and the latching elements  103  and  104  are assigned to a first and second amount of injection fluid to be squeezed out. 
     As is shown in  FIGS. 56 to 58 , the entrainer  114  has a latching arm  109  on which a counter-latching element  110  is configured which, for defining the latching positions, may interact with the latching elements  101  to  104 . Since the relative position of the injection sleeve  107  and of the entrainer  114  by virtue of the retaining peripheries  64  which protrude into the circumferential groove  63  is predefined, the latching installation which is formed by the latching elements  101  to  104  and the counter-latching element  110  is effective both when setting an amount of injection fluid to be squeezed out and when squeezing out the injection fluid from the container. As is shown in  FIGS. 55 and 58 , the latching elements  101  to  104  and the counter-latching element  110  in the circumferential direction are configured so as to be approximately symmetrical such that no excessive force is required in order to overcome the latching positions when the injection fluid is being squeezed out. In the case of the injection device which is shown in  FIGS. 53 to 58 , no spring is provided which biases the dosing member in the direction of the zero position. A step  108  for bearing a compression spring which acts between the injection sleeve  107  and an operating element (not shown in  FIGS. 53 to 58 ) and which biases the operating element in the distal direction is provided on the internal circumference of the injection sleeve  107 . 
     A further embodiment of an injection device  121  is shown in  FIGS. 59 to 62 . The injection device  121  has an upper housing part  123 , a latching arm  129  being configured thereon. The latching arm  129  in the embodiment is visible from the outside. However, the latching arm  129  is advantageously configured such that the former is invisible to the operator. The injection device  121  has an injection sleeve  127  which substantially corresponds to the injection sleeve  17  of the injection device  1 . However, the injection sleeve  127 , on the external side thereof, has latching elements  128  which are configured as depressions and into which a counter-latching element  130  which is configured on the latching arm  129  and which in the embodiment is configured as a latch can latch, so as to form with the latching elements  128  a latching installation  125 . As is shown in  FIG. 61 , the injection device  121  has an entrainer  124  which does not carry any latching elements or counter-latching elements. A latching part is also not provided. A spring  133  which biases the operating element  6  in the distal direction is disposed in the operating element  6 . In the embodiment, the latching installation  125  acts between the upper housing part  123  and the injection sleeve  127  both when setting an amount of injection fluid to be squeezed out, as well as when the injection fluid is being squeezed out of the container  5 . However, it may also be provided that the latching arm  129 , when the operating element  6  is being readjusted to the proximal position  91  thereof ( FIG. 6 ), is deflected such that the counter-latching element  130  cannot interact with the latching elements  128 . This is expedient in particular when the latching arm  129  is disposed not on the upper housing part  123  but on the injection sleeve  127 , the latching elements  128  being disposed on the upper housing part  123 . 
     In the case of the injection device  121  shown in  FIGS. 59 to 62 , a spring which biases the dosing member in the second rotation direction and which acts between the injection sleeve  127  and the dosing member may also be provided. As is shown in  FIG. 62 , the latching element  128  and the counter-latching element  130  in the embodiment shown are symmetrically embodied. If and when a spring is additionally provided for biasing the dosing member in the second rotation direction, it may be expedient for the latching elements to be asymmetrically configured such that dissimilar forces for overcoming the latching positions when setting and when squeezing out the injection fluid result, the additional spring in each case being able to turn back the dosing member only to the next lowest envisaged amount of injection fluid. 
     A further embodiment of an injection device  131  ( FIGS. 70  and  72 ) is shown in  FIGS. 63 to 73 . The dosing member  138  of the injection device  131  is shown in  FIGS. 63 to 66 . The dosing member  138  on the distal side thereof has a latching arm  139  which carries a counter-latching element  140 . The further construction of the dosing member  138  corresponds substantially to the construction of the dosing member  18 . As is shown in  FIG. 66 , the counter-latching element  140  in the embodiment is symmetrically configured. As is shown in  FIGS. 67 to 69 , the injection device  131  has an injection sleeve  137  which, on the internal circumference thereof, carries latching elements  141  and  142 . The latching elements  141  and  142  in the embodiment are configured as depressions. Further latching elements may be provided. It may be advantageous for the latching arm  139  to be configured on the injection sleeve  137  instead of on the dosing member  138 , and for corresponding latching elements or latching depressions to be provided on the dosing member  138 . The latching elements  141  and  142  are mutually offset both in the direction of the longitudinal central axis  50  as well as in the circumferential direction. The latching elements  141  and  142  lie on a helical path which corresponds to the thread pitch of the external thread  65  of the dosing member  138 . On account of the latching elements  141  and  142  being mutually offset both in the direction of the longitudinal central axis  50  as well as in the circumferential direction, comparatively minor spacings between the latching positions are possible. 
     The injection device  131  is shown in the zero position in  FIGS. 70 and 71 . The latching element  141  is latched to the counter-latching element  140 , forming with the latter a latching installation  135 . The injection device  131  in  FIGS. 72 and 73  is located in an injection position. The counter-latching element  140  is latched to the latching element  142 . By virtue of the symmetrical configuration of the latching elements  141 ,  142 , and of the counter-latching element  140 , the latching positions in both rotation directions may readily be bridged by the operator, so that the operator may reset the injection device  131  from an already set dosage to the zero position, without injection fluid being squeezed out. However, another asymmetrical layout of the latching elements may also be expedient. A spring which biases the dosing member  138  in the second rotation direction may also be provided between the injection sleeve  137  and the dosing member  138  in the case of the embodiments of an injection device  131  shown in  FIGS. 63 to 73 . Since the injection sleeve  137  in relation to the dosing member  138  moves not only in the circumferential direction but also in the axial direction, a set amount of injection fluid is unequivocally assigned to each relative position of the injection sleeve  137  and of the dosing member  138 , even in the case of a plurality of revolutions of the operating element  6  up to the maximum dosage. 
     It is understood that the foregoing description is that of the preferred embodiments of the invention and that various changes and modifications may be made thereto without departing from the spirit and scope of the invention as defined in the appended claims.