Abstract:
An injection device ( 30 ) features a housing ( 42, 52 ) for reception of a container ( 34 ) having a fluid ( 32 ) to be injected, a first element ( 94 ) for ejecting injection fluid ( 32 ) from such a container ( 34 ), and said first element ( 94 ) has an external thread ( 92 ). A metering element ( 66, 88 ) has an internal thread ( 90 ) that is in engagement with the external thread ( 92 ) of the first element ( 94 ), and said metering element ( 66 ) is rotatable, together with the first element ( 94 ), for preselection of a desired injection dose. A coupling arrangement (K 1 ) serves, during an injection operation, to create a nonrotatable connection between the first element ( 94 ) and the housing ( 42, 52 ) and thereby to block, during an injection operation, a rotation of the first element ( 94 ) relative to the housing ( 42, 52 ) but to enable a rotation of the metering element ( 66, 88 ) relative to the housing ( 42, 52 ).

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application is a section 371 of PCT/EP07/09552 filed 5 Nov. 2007, published 4 Dec. 2008 as WO-2008-145171-A1, which in turn claims priority from DE 10 2007 026 083.2 filed 25 May 2007, the contents of which are hereby incorporated by reference. 
     FIELD OF THE INVENTION 
     The invention relates to an injection device having an injection dose settable by the patient. Such injection devices must be operable in easy and self-evident fashion. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the invention to make available a novel injection device. 
     This object is achieved by providing a housing, a first element, formed with an external thread, for ejection of fluid from a replaceable container, a metering element formed with an internal thread adapted to engage with the external thread of the first element and which is rotatable with respect to the housing for setting an injection dose, and a coupling arrangement configured to block, during an injection operation, a rotation of the first element with respect to the housing but to enable a rotation of the metering element with respect to the housing, the rotation of the metering element, during an injection operation, permitting an axial displacement of the first element in a patient-proximal direction. In such an injection device, the patient can set the desired injection dose in easy and simple fashion. Such a device also has a simple configuration, which facilitates assembly thereof; its operation is also self-evident, which improves user compliance since brief instructions are sufficient to teach operation. 
    
    
     
       BRIEF FIGURE DESCRIPTION 
       Further details and advantageous refinements of the invention are evident from the exemplifying embodiments, in no way to be understood as a limitation of the invention, that are described below and depicted in the drawings. 
       In the drawings: 
         FIG. 1  is a side view of an embodiment of an injection device  30  according to the present invention, prior to an injection, in a state in which an injection dose of 10 units is set; 
         FIG. 2  is a section viewed along line II-II of  FIG. 1 ; 
         FIG. 3  is a side view of a housing part  42  that serves to receive a carpule  34  (see  FIG. 2 ) having the fluid to be injected, viewed in the direction of arrow III of  FIG. 2 ; 
         FIG. 4  is a section viewed along line IV-IV of  FIG. 3 ; 
         FIG. 5   a ) is a side view of a housing part  52  visible at the top of  FIG. 1 , viewed in the direction of arrow Va of  FIG. 5   b ); 
         FIG. 5   b ) is a section viewed along line Vb-Vb of  FIG. 5   a ); 
         FIG. 5   c ) is a side view viewed in the direction of arrow Vc of  FIG. 5   b ); 
         FIG. 6  is a side view of a metering element (graduated tube)  66  serving to display a dose that has been set, viewed in the direction of arrow VI of  FIG. 7 ; 
         FIG. 7  is a section viewed along line VII-VII of  FIG. 6 ; 
         FIG. 8  is a side view of a nut  88  effective in the context of an injection, viewed in the direction of arrow VIII of  FIG. 10 ; 
         FIG. 9  is a section viewed along line IX-IX of  FIG. 8 ; 
         FIG. 10  is a plan view of the nut, viewed in the direction of arrow X of  FIG. 8 ; 
         FIG. 11  is a section through nut  88  of  FIGS. 8 to 10  in the assembled state; 
         FIG. 12  is a plan view of the lower end of a piston rod  94  depicted in  FIG. 13 , viewed in the direction of arrow XII of  FIG. 13 ; 
         FIG. 13  is a side view of piston rod  94 ; 
         FIG. 14  is a plan view of the upper end of piston rod  94 , viewed in the direction of arrow XIV of  FIG. 13 ; 
         FIG. 15  depicts an injection sleeve  116  that is equipped with a window  130  that is effective in the context of dose display; 
         FIG. 16  is a side view of injection sleeve  116 ; 
         FIG. 17  is a section viewed along line XVII-XVII of  FIG. 16 ; 
         FIG. 18  is view of a rotary and injection knob  40  that serves for the operation of injection device  30 , viewed in the direction of arrow XVIII of  FIG. 19 ; 
         FIG. 19  is a partly sectioned side view of the rotary knob, viewed in the direction of arrow XIX of  FIG. 18 ; 
         FIG. 20  is a longitudinal section viewed along line XX-XX of  FIG. 19 ; 
         FIG. 21  is a perspective depiction of a driver  150  that serves, in the context of dose setting, to transfer a rotary motion of rotary knob  40  to metering element (graduated tube)  66 ; 
         FIG. 22  is a side view of driver  150 , viewed in the direction of arrow XXII of  FIG. 24 ; 
         FIG. 23  is a longitudinal section viewed in the direction of line XXIII-XXIII of  FIG. 22 ; 
         FIG. 24  is a plan view from above of driver  150 , viewed in the direction of arrow XXIV of  FIG. 22 ; 
         FIG. 25  is a longitudinal section through the upper part of the injection device, analogous to  FIG. 2  but with a zero injection dose and before dose setting begins; 
         FIG. 26  is a longitudinal section analogous to  FIG. 25  but after completion of an injection; 
         FIG. 27  is a plan view of a metering element (graduated tube)  166  that is provided for a disposable injection device in which carpule  34  cannot be replaced once its contents are consumed; 
         FIG. 28  is a longitudinal section viewed along line XXVIII-XXVIII of  FIG. 27 ; 
         FIG. 29  is a diagram to explain the manner of operation; 
         FIG. 30  depicts a particular aspect of piston rod  94 ; 
         FIG. 31  is a longitudinal section analogous to  FIG. 2 , in which various section planes have been plotted; 
         FIG. 32  is a section along line C-C of  FIG. 31 ; 
         FIG. 33  is a section along line D-D of  FIG. 31 ; 
         FIG. 34  is a section along line E-E of  FIG. 31 ; 
         FIG. 35  is a section along line F-F of  FIG. 31 ; and 
         FIG. 36  is an exploded depiction to facilitate comprehension. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows, at greatly enlarged scale, a pen injector  30 , viewed in the direction of arrow I of  FIG. 2 . It uses a reservoir, usually referred to as a carpule  34 , for injection fluid  32 . Located in this carpule  34  is a rubber piston  36 , and when the latter is displaced from top to bottom (in  FIG. 2 ), it presses injection fluid  32  out through an injection needle  38 . Carpule  34  is a commercially usual part and is therefore not described further. 
     In the terminology usual in medicine, the terms “proximal” and “distal” are hereinafter used as follows: 
     proximal=toward the patient; in other words, in the direction of that end of injection device  30  at which needle  38  is located; 
     distal=away from the patient, i.e. in the direction of the upper (in  FIGS. 1 and 2 ) end of device  30  at which a rotary knob  40  for setting the injection dose is located. 
     Be it noted that the terms “proximal” and “distal” are occasionally also used by medical non-professionals in the opposite sense, in which case these terms then refer to the doctor&#39;s hand. 
     A receiving part  42 , which is depicted in  FIGS. 3 and 4  and is also referred to as a carpule container, serves to receive carpule  34 . Said part has two longitudinal windows  44 ,  46  through which the fill level in carpule  34  or the axial position of piston  36  can be observed, so that the patient can estimate, with the aid of graduations printed onto receiving part  42 , the number of injection units that are still possible. Windows  44 ,  46  are not depicted in  FIGS. 1 and 2 . 
     Receiving part  42  has, at the bottom, an external thread  47  for screwing on injection needle  48 , and at the top an internal thread  48  that serves for connection to external thread  50  of an upper (in  FIGS. 1 and 2 ) distal housing part  52  that is depicted in  FIG. 5 . Said part has a window  54  that serves for reading off the injection dose that has been set, and it has a cylindrical internal opening  56  that transitions at the bottom (in  FIG. 5   b )), via a shoulder  58  that serves as an axial bearing in the context of an injection, into an opening  60  of smaller diameter in which is located a shoulder  62  that serves for axial latching of metering element (graduated tube)  66  ( FIGS. 6 and 7 ) in housing part  52 . A corresponding rolling bearing could, for example, also be used instead of shoulder  58  as an axial bearing. Metering element  66  has a plurality of functions, and could therefore also be referred to as metering sleeve  66 . 
     Metering element (graduated tube; metering sleeve)  66  is equipped on its cylindrical outer side  68  with numbers  70  to display the injection dose that has been set, and can therefore also be referred to as a graduated tube. Also located on this outer side  68  is an external thread  72  whose function will be explained below. Metering element (graduated tube)  66  transitions at its proximal end, via a shoulder  74  whose lower side  76  serves as a countermember for axial bearing  58  of  FIG. 5   b ), into a cylindrical portion  78  of smaller diameter into which, in the assembled state, radial projection  62  ( FIG. 5   b ) of housing  52  ( FIG. 5   b ) engages, as shown e.g. by  FIGS. 2 and 11 . Portion  78  is delimited at the bottom by a radially projecting collar  80  that is adjoined at the bottom by a portion  82  having a slightly smaller outside diameter. 
     The inner side of portion  78  is equipped with an axial internal spline set  84  that serves for coupling to a complementary axial external spline set  86  that is located on a nut  88  that is depicted in  FIGS. 8 to 11 . 
     This nut  88  has an internal square thread  90  that is in engagement with external thread  92  of a piston rod  94  whose shape is best inferred from  FIGS. 11 to 14 . Said rod serves in the context of an injection, as shown in  FIG. 2 , to displace rubber piston  36  in a proximal direction, i.e. downward in  FIG. 2 , in order to inject injection fluid  32  through needle  38  into a patient. For this purpose, its external thread  92  is in engagement with an internal square thread  90  (depicted in  FIGS. 9 and 10 ) of nut  88 ; and when, in the context of an injection, metering element (graduated tube)  66 , and nut  88  nonrotatably coupled to it via axial spline sets  84 ,  86 , is rotated clockwise as viewed from above, said element displaces piston rod  94 , whose rotation is blocked during an injection, downward. In that context, piston rod  94  presses, with its proximal end and with an abutment plate  96  arranged thereon ( FIG. 2 ), against rubber piston  36  and displaces it in the direction toward needle  38 , so that fluid  32  is expelled there. 
     In order to prevent rotation during injection, piston rod  94  has at its distal part  98 , which is depicted at the top in  FIG. 13 , a cross section ( FIG. 12 ) that deviates from a circular shape, and this part is in positive engagement with an opening  99  ( FIG. 18 ), complementary thereto, of rotary knob  40  ( FIG. 2 ), so that blocking the rotation of rotary knob  40  also causes blocking of the rotation of piston rod  94 , but an axial displacement is possible between rotary knob  40  and piston rod  94 . This is described in detail below. 
     As  FIGS. 9 and 11  show, nut  88  has upwardly projecting barbs  100  that are in engagement with corresponding barbs  102  at the lower end of metering element  66 . 
     As  FIG. 11  shows, a compression spring  104  is located between portion  82  and the portion having axial external spline set  86 . This spring is compressed when, after insertion of a fresh carpule  34 , internal thread  48  ( FIG. 4 ) is screwed onto external thread  50  ( FIG. 5 ), with the result that axial external spline set  86  ( FIG. 8 ) of nut  88  becomes coupled nonrotatably to axial internal spline set  84  of metering element (graduated tube)  66  (see  FIG. 11 ). 
     When a carpule  34  is replaced, spring  104  ( FIG. 11 ) pushes axial spline sets  84 ,  86  apart from one another so that nut  88  can rotate freely. This allows the doctor or patient to rotate nut  88  by hand so that piston rod  94  is displaced in a distal direction until it comes to rest against nut  88 , and space is created for the insertion of a fresh carpule  34 . 
     Nut  88  is not required for a disposable injector, and  FIGS. 27 and 28  show a simplified solution for this instance, in which a thread  174  that interacts with the external thread ( 92 ) of piston rod  94  is likewise provided in a metering element (graduated tube)  166 . 
     A sleeve-shaped element in the form of an injection sleeve  116 , which is depicted in  FIGS. 15 to 17 , is provided for engagement into external thread  72  of metering element (graduated tube)  66 . As  FIG. 2  shows, said sleeve is arranged between metering element (graduated tube)  66  and housing  52 , and has an internal thread  118  ( FIG. 17 ) that is in engagement with external thread  72  of metering element (graduated tube)  66  ( FIG. 6 ) or  166  ( FIG. 28 ), so that when injection sleeve  116  is rotated counterclockwise (as viewed from above) with the aid of rotary knob  40  in the context of dose setting, injection sleeve  116  is displaced upward on external thread  72  of metering element (graduated tube)  66 , as depicted in  FIGS. 1 and 2  for a small injection dose. The same is true analogously for graduated tube  166  of  FIGS. 27 and 28 . 
     Injection sleeve  116  has, at the top, an extension  120  having an axial internal spline set  122  that has a variety of functions: 
     a) As shown in  FIGS. 19 ,  20 ,  25 , and  26 , tube  41  is fixedly connected to rotary knob  40 , and an external spline set  146  is provided on tube  41 . Like external spline set  125  of rotary knob  40 , this set is part of two couplings K 1  and K 2  (see  FIGS. 25 and 26 ), and these couplings can be actuated by displacing tube  41  by means of knob  40 , or by means of a compression spring  167  in the latter, axially relative to injection sleeve  116 . A comparison of  FIGS. 25 and 26  shows this axial displacement. 
     It serves, in the context of an injection, to couple rotary knob  40  via coupling K 1  to injection sleeve  116  in such a way that rotation between these two parts is blocked; in other words, when the patient (after having set a dose) presses with a force F in a proximal direction onto rotary knob  40 , as shown in  FIG. 26 , injection sleeve  116  is moved in a proximal direction, in which context an axial external spline set  125  ( FIG. 25 ) provided on rotary knob  40  engages into internal spline set  122 . A rotation between injection sleeve  116  and rotary knob  40  is thereby blocked, and injection sleeve  116  is moved in a proximal direction; because of its longitudinal guidance (by grooves  53  of  FIG. 5  and projections  117  of  FIG. 15 ), it cannot rotate in housing  52 . This axial motion of injection sleeve  116  is transformed by threads  72 ,  118  into a rotary motion of metering element (graduated tube)  66  ( FIGS. 6 and 7 ). 
     This rotary motion also rotates nut  88  and thereby displaces piston rod  94  (which in this situation is prevented from rotating) in a proximal direction, so that rubber piston  36  is displaced in a proximal direction and an injection of fluid  32  takes place. 
     b) Also engaging into axial internal spline set  122  ( FIGS. 15 ,  17 , and  25 ) are two resilient ratchet members  124 ,  126  ( FIG. 18 ) that are arranged on the inner side of rotary knob  40 . They become effective in the context of dose setting, since here external spline set  125  of rotary knob  40  is not in engagement with axial internal spline set  122  of injection sleeve  116  ( FIG. 15 ), and rotary knob  40  can thus rotate relative to said axial internal spline set  122 , making it possible even for patients with poor vision to set a dose by counting the clicks generated in the context of the rotary motion. 
     The axial motion of injection sleeve  116  in the context of dose setting and injection also results in an axial displacement of window  130  ( FIGS. 15 to 17 ), which is provided in casing portion  132  of injection sleeve  116  and is delimited at the top by a thickened casing part  134  and at the bottom by a thickened casing part  136 . These thickened casing parts  134 ,  136  are guided in window  54  ( FIGS. 1 ,  2 , and  5 ) of upper housing part  52 . They move upward in window  54  in the context of dose setting and move downward in window  54  during an injection, dose  70  that is to be injected being continuously displayed in window  130  as a result of the simultaneous rotation of metering element (graduated tube)  66 . This dose display consequently decreases during an injection, and thereby indicates to the patient how much he or she still has to inject. The patient can thus constantly monitor injection progress during the injection operation, and thus knows exactly when the injection is complete as the “0” display appears in the viewing window, and he or she can therefore pull the injection needle out of his or her fatty tissue without losing injection fluid. 
     As  FIGS. 19 and 20  show, an external spline set  146  is provided on tube  41  that is connected to rotary knob  40 ; this set, like external spline set  125 , is a part of couplings K 1  and K 2  ( FIGS. 25 ,  26 ) that is actuated by an axial displacement of tube  41  (by means of knob  40  or compression spring  167  associated therewith). 
     External spline set  146  is closed off at the bottom by a plate-like flange  147 , and interacts with an internal spline set  148 , complementary to the first set, of a driver  150  that is depicted in  FIGS. 21 to 24 . As  FIGS. 21 to 24  clearly show, driver  150  has approximately the shape of a cylindrical tube  154  that is closed off at the top by a kind of flange  156  that protrudes, with a rim  158 , radially beyond tube  154 . Axial internal spline set  148  is located at the center of flange  156 . Tube  154  is equipped with a guide groove  157  that interacts with a corresponding projection  160  ( FIG. 7 ) on the inner side of metering element (graduated tube)  66  or  166  ( FIG. 28 ) so that a rotation of driver  150  (in order to set a dose) produces a corresponding rotation of metering element (graduated tube)  66 . 
     Located in rotary knob  40  is compression spring  167 , which biases rotary knob  40 , and tube  41  connected to it, in an upward direction (see  FIG. 25 ) so that upper coupling K 1  ( FIGS. 25 ,  26 ) constituted by axial external spline set  125  (of rotary knob  40 ) and axial internal spline set  122  (of injection sleeve  116 ) is opened because axial external spline set  125  is not engaging into axial internal spline set  122  of injection sleeve  116 . It thereby becomes possible to set a desired injection dose because, in this position, lower coupling K 2  ( FIG. 25 ) is closed because axial external spline set  146  ( FIGS. 19 ,  20 ; on tube  41 ) is engaging into axial internal spline set  148  ( FIG. 21 ) of driver  150 , the engagement motion being limited by flange  147 . Rim  158  of flange  156  is then braced against a shoulder  168  in the interior of injection sleeve  116  (see  FIG. 26 ). 
     In this position, when knob  40  is then rotated it rotates driver  150 , by tube  41  and axial external spline set  146  ( FIG. 20 ) located on it as well as internal spline set  148  ( FIG. 21 ), and said driver, by its groove  157 , rotates graduated tube  166 . Injection sleeve  116  is thereby displaced in a distal direction, i.e. axially upward, and window  130  along with it. Nut  88  is also rotated along with the rotation of graduated tube  66 , but this has no influence on the location of rubber piston  36 , since piston rod  94  also rotates together with nut  88  so that the former cannot change its axial location. 
     In the position as shown in  FIG. 25 , upper coupling K 1  is therefore open and lower coupling K 2  is closed, so that upon a rotation of knob  40  both piston rod  94  and nut  88  rotate in the same direction and at the same speed; and the position of piston rod  94  consequently cannot change because of course it is coupled nonrotatably, but axially displaceably, to tube  41 . 
     Injection sleeve  116  together with rotary knob  40  does, on the other hand, become displaced upward, i.e. in a distal direction, as a result of such a rotary motion, and the dose that has been set is correctly displayed in window  130 , as depicted in  FIG. 29 . 
       FIG. 26  shows the situation in the context of an injection. The patient firstly inserts needle  38  ( FIGS. 1 ,  2 ,  30 ) and then presses with a force F ( FIG. 26 ) on rotary knob  40 . He or she thereby opens coupling K 2  and closes coupling K 1 , thereby nonrotatably connecting tube  41 , and piston rod  94  guided therein (see  FIG. 2 ), to injection sleeve  116  and consequently to housing  52 , so that piston rod  94  can now no longer rotate relative to housing  52 . 
     As a result of (the patient&#39;s) force F, injection sleeve  116  is displaced downward, over the distance previously ( FIG. 25 ) selected, into the zero position, and as a result of the threaded connection between internal thread  118  of injection sleeve  116  and external thread  72  of metering element (graduated tube)  66 , rotates said graduated tube and, with it, nut  88  ( FIGS. 8 to 10 ) so that piston rod  94 , which cannot rotate, is moved by the rotation of nut  88 , and of internal thread  90  provided therein, in a proximal direction and brings about an injection, by displacing rubber piston  36  in a proximal direction by an amount equal to the dose that was set. 
     A mechanical conversion ratio can be provided in this context, i.e. a displacement of injection sleeve  116  over a preset distance D causes piston rod  94  to move a distance D/f, where f can assume values between approximately 0.5 and 2, depending on the design of the thread pitches. This enables a more accurate dose display for small injection doses, and has proven to be advantageous especially for patients having poor vision. 
       FIGS. 27 and 28  show a graduated tube  166  for a so-called disposable injection device (depicted here only in part), i.e. for an injection device in which carpule  34  (not depicted in  FIGS. 27 and 28 ) cannot be replaced. The injection device must therefore be discarded once the carpule is empty. The construction of metering element (graduated tube)  166  corresponds largely to that of metering element (graduated tube)  66  according to  FIGS. 6 and 7 , i.e. graduated tube  166  also has on its outer side  68  an external thread  72  and graduated values  70 , and internally it has a projection  160  for longitudinal guidance in a longitudinal groove  157  of driver  150  (see  FIGS. 21 to 24 ). Metering element (graduated tube)  166  of  FIGS. 27 and 28  also has at its proximal end a base  170  in which a threaded orifice  172  having an internal square thread  174  is located. Piston rod  94  is screwed with its external thread  92  into this threaded orifice  172 , similarly to what is shown in  FIG. 11 . Because, in this case, piston rod  94  cannot be returned to its position prior to the first injection once the contents of carpule  34  have been exhausted, the device must be disposed of after use. 
     Cartridge Replacement 
     In the version according to  FIG. 11 , the two housing parts  52 ,  42  are unscrewed from one another when carpule  34  needs to be replaced. The connection from metering element  66  to part  88  is thereby interrupted (by the action of compression spring  104 ) so that part  88  can be freely rotated by hand and the patient can thread piston rod  94  upward in a distal direction until it stops. Once the exhausted carpule  34  is taken out, a fresh carpule can then be inserted and, after the usual setting steps prior to the first injection, the patient can once again make injections normally. 
       FIG. 29  shows the dose setting procedure; carpule  34  and carpule container  42  are not depicted, so that the illustration is more informative. Rubber piston  36  of carpule  34  is indicated with dot-dash lines. 
     Looking in  FIG. 29   a ) from above, i.e. in a proximal direction, onto rotary knob  40 , the latter is rotated clockwise (arrow  41 ) in order to set a dose. Piston rod  94  thereby rotates, but so does nut  88  ( FIG. 11 ), so that piston rod  94  projects the same length L out of housing  52  both at a dose of zero and at any dose that can be set. Injection sleeve  116 , however, does become displaced upward out of housing  52  in the context of the setting process;  FIG. 29   b ) shows the maximum dose that can be set, the value of which may differ depending on how the device is used. The value “20” that is depicted is therefore to be understood as merely an example. 
     Dose setting is accomplished here by an axial displacement of injection sleeve  116  in a distal direction, whereas the location of plate  96  relative to rubber piston  36  does not change as the dose is set. 
     Because piston rod  94  rotates relative to rubber piston  36  as the dose is set, it is advisable to use, at proximal end  95  ( FIG. 30 ) of piston rod  94 , a plate  96  having an opening  97  in which proximal end  95  of piston rod  94  can rotate with little friction. As  FIG. 30  shows, proximal end  95  of piston rod tapers downward so that the friction there between end  95  and rubber piston  36  becomes low. 
     The actual injection, by means of axial pressure on rotary knob  40  with force F, has already been described with reference to  FIG. 26 , to which the reader is therefore referred. 
       FIG. 31  shows a longitudinal section analogous to  FIG. 2  in which four different horizontal sections C-C, D-D, E-E, and F-F are plotted. The reference characters are the same as in the preceding Figures, and this is not a disposable syringe. 
       FIG. 32  shows carpule container  42  on the outside, barbs  100  therein, then barbs  82  and spring  104 , as well as external spline set  86  of part  88  and, all the way on the inside, piston rod  94  with its external thread  92 . 
       FIG. 33  shows that tube  41  has an axial opening  99  in which part  98  ( FIGS. 12 and 13 ) of piston rod  94  is guided nonrotatably but longitudinally displaceably. This makes it possible, by pushing rotary knob  40  (see  FIG. 26 ), to connect piston rod  94  to housing  52  in such a way that tube  41  cannot rotate relative to housing  52 . 
     Three longitudinal ribs  117 , which are guided in corresponding longitudinal grooves  53  ( FIG. 5 ) of housing  52 , are provided on injection sleeve  116 . 
     A screw connection  72 ,  118  is provided between injection sleeve  116  and metering element (graduated tube)  66 . Metering element (graduated tube)  66  has three longitudinal ribs  160  that are guided in corresponding longitudinal grooves  157  of driver  150 . 
       FIG. 34  shows, on the outside, housing  52  with its three longitudinal grooves  53  in which injection sleeve  116  is guided with its three longitudinal ribs  117 . On its inner side, injection sleeve  116  is connected via threads  72 ,  118  to metering element (graduated tube)  66 , which in turn is equipped on its inner side with three longitudinal ribs  160 . 
       FIG. 35  shows section F-F of  FIG. 31 . On the outside is housing  52  in which (as shown in  FIG. 5 ) are provided longitudinal grooves  53  into which three corresponding ribs  117  of injection sleeve  116  engage. The inner side of injection sleeve  116  is connected via threads  72 ,  118  to the outer side of metering element (graduated tube)  66 . The inner side of metering element (graduated tube)  66  has three longitudinal ribs  160  that are guided in longitudinal grooves  154  of driver  150 . The latter has an internal spline set  148  that is in engagement with external spline set  146  of tube  41 . 
       FIG. 36  is an exploded view of injection device  30 , serving to facilitate comprehension. At the very top is rotary knob  40  with its spline set  125 , said knob being fixedly connected to tube  41  as shown in  FIG. 20 . The latter is equipped with external spline set  146 , which serves as part of coupling K 2  ( FIGS. 25 and 26 ). 
     Also depicted in  FIG. 36  is driver tube  150  ( FIGS. 21 to 24 ) which has on its outer side  154  three longitudinal grooves  157  (see  FIG. 35 ), only one of which is visible in  FIG. 36 . By these longitudinal grooves  157 , driver tube  150  is coupled nonrotatably, but axially displaceably, to metering element (graduated tube)  66 . Metering element (graduated tube)  66  is equipped on its inner side with corresponding longitudinal projections  160  for engagement into longitudinal grooves  157  (see  FIGS. 33 and 35 ). 
     Piston rod  94  is guided axially displaceably in tube  41  (whose cross-sectional shape is evident from  FIG. 18 ), but, by means of a non-round part  98 , it is connected nonrotatably to tube  41  so that a rotation of knob  40  also produces a rotation of piston rod  94 , whereas an immobilization of knob  40  immobilizes piston rod  94  in terms of rotation but does not prevent its axial displacement in tube  40 . 
     Internal thread  118  (see  FIGS. 15 and 17 ) of injection sleeve  116  ( FIG. 35 ) is threaded onto metering element (graduated tube)  66  that is equipped with an external thread  72 ; said sleeve is equipped on its outer side with three longitudinal projections  117  with which injection sleeve  116  is guided in a longitudinal direction in housing part  52 . Housing part  52  has for this purpose three longitudinal grooves  53  that are depicted in  FIGS. 5 ,  33 , and  35 . 
     Housing part  52  is equipped at its proximal end with external thread  50  which serves for connection to housing part  42 , which latter is depicted in  FIGS. 3 and 4  but omitted from  FIG. 36  for reasons of clarity. 
     Compression spring  167  is located in rotary knob  40  (see also  FIGS. 25 and 26 ). 
     Metering element (graduated tube)  66  is latched in a longitudinal direction in housing part  52  (see  FIG. 11 ). Spring  104  interacts with nut  88  (see  FIG. 11 ). Depicted at the very bottom of  FIG. 36  is pressure application disk  96  that, after assembly, is installed at lower end  95  of piston rod  94  (see  FIG. 30 ). 
     It is evident from  FIG. 36  that injection device  30  is made up of only a few simple parts that can be assembled very easily and are well suited for automated production. Many variants and modifications are of course possible within the context of the present invention. Normally, for example, the parts of the injection device are manufactured from injection-molded plastic, but highly stressed parts can also be manufactured from metal or from a special plastic, e.g. a plastic with glass-fiber reinforcement. These and other modifications are within the scope of the capabilities of one of ordinary skill in the art.