Abstract:
A device for producing a fluid jet suitable for hygienic requirements in mechanical wound cleaning, including removal of biological tissue, may include a drive casing with a drive and a pump module with a pump casing which can be detachably joined. The drive casing may include a positive-locking element and the pump casing may include a positive-locking counter-element. The positive-locking element may interact with the positive-locking counter-element so that the pump casing is imposed a pivotal motion relative to the drive casing until reaching a final position. In final position the pump casing may be connected to the drive casing and a drive element may be connected to an associated drive counter-element. Drive element and drive counter-element may be arranged eccentric to a pivot axis of the pivotal motion and may be formed so a positive-locking connection arises between the drive element and drive counter-element due to the pivotal motion.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of priority to European patent application No. 15186573.0, filed Sep. 23, 2015, which is incorporated herein by reference in its entirety as though fully set forth herein. 
         [0002]    TECHNICAL FIELD 
         [0003]    The present invention relates to a device for producing a fluid jet, in particular for the removal of biological tissue. 
         [0004]    BACKGROUND 
         [0005]    Devices for producing a water jet for the treatment of biological tissue are known from EP 1 924 305 131, WO 2007/031304 A1, U.S. Pat. No. 7,553,318 132 and WO 01/97700 A2. The present invention in particular relates to the debridement by way of a water jet. With debridement, the wound is cleaned for promoting wound healing, also scab and overgrowths are commonly removed. The aforementioned publications show the efforts in the expert industry to propose solutions for performing this debridement by use of a water jet. Another document originating from the present applicant is given by EP 1 296 601 131. 
         [0006]    With equipment that is used in hospitals and in particular in the mechanical treatment of wounds, there is a need to form certain components used in the treatment with a fluid jet such that they are disposable products or can at least be sterilized. On the other hand, certain components of a device for producing a fluid jet, for example, at least the electric drive of a pump, can effectively not be sterilize and are also commonly too expensive to be designed as disposable products. 
         [0007]    The present invention seeks to provide a device for producing a fluid jet which can be produced economically and in a simple manner while satisfying the above requirements. 
       BRIEF SUMMARY 
       [0008]    To solve this problem, the present invention proposes a device having the features of claim  1 . The device according to the invention has a drive casing in which a drive is provided. This is commonly an electrically powered drive. The drive casing accommodates this electric drive and usually comprises control elements for switching on and off and for actuating the drive. Furthermore, the device according to the invention has a pump module. This pump module comprises a pump casing as well as a mechanism within the pump casing which is adapted to pressurize and convey fluid supplied to the pump casing. The pump casing can comprise, for example, at least one piston communicating with inlet and outlet openings or the fluid so as to suck in said fluid at the inlet opening and discharge it at the outlet opening at an increased pressure. The pump casing can comprise valves for directed conveyance of the fluid. The pump casing itself can have a relatively simple design and be configured as a disposable member, in particular as a plastic member. Preferably all components of the pump module are designed to be made of plastic. 
         [0009]    A modular design of the device is proposed with the present invention in Which the pump casing on the one hand and the drive casing on the other hand can be detachably joined. 
         [0010]    According to the invention, the drive casing has at least one positive-locking element. The pump casing has a positive-locking counter-element interacting with this positive-locking element when joining the pump casing and the drive casing. The positive-locking element and the positive-locking counter-element there interact until a final position is reached such that the pump casing is imposed a pivotal motion relative to the drive casing until the pump casing has reached its final position. The final position of the pump casing is that position in which the pump casing is connected to the drive casing and at least one drive element of the drive provided, on the drive casing is connected to an associated drive counter-element of the pump module. The drive element and the drive counter-element are there arranged eccentric to a pivot axis of a pivotal motion that is imposed to the pump module relative to the drive casing when joining the drive and the pump module. The configuration of the drive element and the drive counter-element is such that a positive-locking connection between the drive element and drive counter-element arises due to the pivotal motion imposed until the final position has been reached. 
         [0011]    It is with the present invention ensured that joining the pump module and the drive necessarily results in a positive-locking connection of the respective elements for driving the pump. The drive element is there coupled to the drive, while the drive counter-element is regularly connected directly or indirectly to a piston which pressurizes the fluid in a cylinder of the pump module. 
         [0012]    The device according to the invention can therefore be easily handled. Even without technical expertise, joining the drive casing and the pump module results in the two drive elements of the device necessarily being drivingly coupled and accordingly being in operative connection to each other. The guidance between the drive casing and the pump module effected by the positive-locking element and the positive-locking counter-element there prevents incorrect operation. 
         [0013]    The positive-locking element and the positive-locking counter-element preferably form a bayonet lock which first imposes an axial motion upon the pump casing that is relative to the drive casing. This axial motion is an axial motion relative to a substantially cylindrical recess. At the end of this axial motion, a pivotal relative motion is imposed by interaction of the positive-locking element and the positive-locking counter-element and extends substantially perpendicular to the axial motion. It is by the second part of the pivotal motion, which is determined by the bayonet lock, also ensured that the connection between the pump module and the drive casing is secured. Catch mechanisms or projections common for bayonet locks can there be provided which prevent accidental reverse rotation of the pump module relative to the drive casing. In the embodiment presently discussed, the recess can be defined by the pump casing in which a projection of the drive casing engages. However, it is in view of a compact design preferable to provide the recess on the drive casing. The drive element is there preferably exposed in the recess, however, is preferably received within the recess. The drive element accordingly usually does not project beyond the recess in the longitudinal direction, which is usually the direction of movement of the drive element, toward the exterior. In this embodiment, the pump module is configured such that the pump casing is at least in part insertable into the recess. 
         [0014]    According to a preferably embodiment of the present invention, the pump casing has a recess in which the drive counter-element is exposed. For insertion into a recess formed in the drive casing, the pump casing preferably comprises a sleeve section which encloses the drive counter-element and forms the positive-locking counter-element. Also in this embodiment, a drive counter-element is at least predominantly with its outwardly exposed connection end located within the recess, which is hereinafter referred to as the pump recess, so that this connection end of the drive counter-element, though being protected within the pump casing, is also exposed within the pump casing. 
         [0015]    According to a preferable embodiment of the present invention, the recess and/or the pump casing is/are at least in part designed to be rotationally symmetrical. The rotationally symmetrical design pertains in particular to an enveloping surface, for example, at inner circumferential surface sections of the recess and/or outer circumferential sections in particular of the sleeve section of the pump casing. The positive-locking elements or the positive-locking counter-elements are commonly within or outside this enveloping surface. The rotationally symmetrical configuration gives rise to guide surfaces which guide at least the axial motion when joining the pump module and the drive casing. This axial motion is commonly a motion that is directed parallel to the center longitudinal axis of the recess or of a substantially cylindrical sleeve section, respectively. While the rotationally symmetrical enveloping surface performs the axial motion, the interaction of the positive-locking element and positive-locking counter-element indeed also causes axial guidance, but in particular forced guidance of the pivotal motion until the final position has been reached. 
         [0016]    According to a preferred embodiment of the present invention, the positive-locking element and the positive-locking counter-element form a guide that during joining defines a unique orientation of the pump casing relative to the drive easing. A configuration is there in particular intended which fulfills a poka-yoke function and thereby defines that the pump casing can be joined in only a single position, possibly in two positions rotated by 180°, relative to the drive casing due to the interaction of the positive-locking and the positive-locking counter-element. Several positive-locking elements and positive-locking counter-elements can there be provided on the circumference of the recess and/or a sleeve section and each be assigned exactly to each other so that the respectively associated pairs of positive-locking elements and positive-locking counter-elements necessarily must be made to overlap in order to enable joining the pump module with the drive casing. This configuration as well reliably prevents faulty joining of the pump casing and the drive casing and thereby inadequate mechanical coupling of the drive element and drive counter-element. 
         [0017]    According to a preferred development of the present invention, the positive-locking element and the positive-locking counter-element are configured such that the pump casing when joining and at the end of the axial motion is pivotable relative to the drive casing by an angle of between 10° and 90°, preferably by an angle of 25-35°, i.e. 30°±5°. Such pivotability can usually be achieved by the user without the hand holding the pump casing changing the grip and is thereby realized in a comfortable manner. The joining action can thereby be performed comfortably and with one hand. 
         [0018]    According to a preferred embodiment of the present invention, the drive element is a drive pusher. The drive counter-element is preferably formed integrally as part of a pump piston. In other words, the drive counter-element is formed by the pump piston. It is understood that the part of the piston in a cylinder used for pumping is commonly accommodated inside the pump casing, whereas the other free end of the pump piston on the drive side forms the drive counter-element. The guide formed by the drive element and the pump piston between the pump module and the drive casing is in the axial direction there configured such that the drive element abuts an abutment surface of the pump piston before the final position has been reached. This configuration ensures that the drive element and the drive counter-element after joining the pump casing and the drive casing bear against each other in the axial direction. The drive pusher with its abutment surface there preferably bears against the counter-surface of the pump piston before joining the drive casing and the pump module in the axial direction has been completed. In other words, the abutment surface during, axial joining, strikes against the counter-surface. The drive element and the drive counter-element thereby at least at the face sides bear against each other. This bearing is achieved at least when the final position has been reached. This bearing can preferably also be effected prior to the final position being reached. The remaining axial displacement motion between the pump module and the drive casing is then compensated by an axial relative motion of the pump piston and/or the drive pusher so that the relative position of the drive element and the drive counter-element does not change despite an axial joining motion. This increases security so that the drive element at the end of the axial joining motion at the end side securely bears against the pump piston. 
         [0019]    For simplifying the configuration, the drive piston is commonly on the drive side held axially immovable, whereas the drive counter-element associated with the pump module is mounted axially displaceable. 
         [0020]    In view of the forced positive-locking connection due to a pivotal motion between the pump casing and the drive casing taught by the invention, it is in a preferred embodiment of the present invention proposed that the drive element or the drive counter-element comprise a hammerhead and the respectively other of the two elements an adapted hammerhead seat for engaging over the hammerhead. The hammerhead seat is there matched to the configuration of the hammerhead such that the pivotal motion at the end of the joining motion, i.e. after completion of the relative axial motion and in the framework of the pivotal motion, leads to the hammerhead seat in a positive-locking manner engaging over the hammerhead, and both elements of the drive are thereby connected to each other on both sides in the axial direction in a positive-locking manner. An alternating axial motion of the drive element thereby necessarily also leads to a corresponding alternating motion of the drive counter-element after the pump module has reached the final position and the drive has been switched on. 
         [0021]    It is in view of exact axial coupling by way of a positive-locking connection of the drive element and drive counter-element according to a preferred development of the present invention proposed to provide the element forming the hammerhead seat in a rotationally fixed manner. The element forming the hammerhead seat can be rotatably supported and in particular when the hammerhead itself is formed rotationally symmetrical so that its orientation relative to the hammerhead seat does not affect the quality of the positive-locking connection to be produced in the context of the joining. 
         [0022]    To further increase security against incorrect joining, it is according to a further preferred development of the present invention proposed to provide the hammerhead seat with a claw engaging over the hammerhead. The claw engaging over the hammerhead there causes axial fixation of the drive element and the drive counter-element. Fixation within this meaning, however, can also be understood to be a configuration in Which a cyclic axial motion of the drive element is at times not completely transferred to the drive counter-element, as both allow for a certain axial play. Any such play leading to the two elements knocking, however. Which results in undesirable noise and wear in particular with a high-frequency drive, is to be avoided. The hammerhead seat is usually designed such that it receives the hammerhead within itself substantially without axial play. According to the preferred development presently discussed, however, the claw being provided according to the embodiment also forms a stop. This stop is effective before the final position has been reached and interacts with the hammerhead provided that the latter is located at the same height as the claw in such a way that pivoting is in the final position prevented. In other words, the interaction of the hammerhead and the stop prevents the final position from being reached. The stop acts in a pivoting motion of the pump module relative to the drive casing, thereafter it acts radially. 
         [0023]    A drive device of the previously discussed device for producing a fluid jet is by itself considered as being essential to the invention and protected in an independent claim. According thereto, the drive unit has a drive which is provided in a drive casing. The drive casing comprises at least one positive-locking element with which the pump module previously mentioned can be affixed to the drive casing. The fixation is there done in a positive-locking manner, preferably in the manner described above by way of a bayonet lock. The drive easing is further provided with a recess. Exposed in this recess is a drive element of the drive. The drive element is arranged eccentric relative to a center longitudinal axis of the recess. Since the recess of the drive casing is to allow the pump module being at least partially inserted into the recess to pivot, the recess is commonly formed with a rotationally symmetrical inner circumferential surface. The same applies to the portion of the pump module introduced into the recess. This portion is commonly formed as a cylindrical section having a circular outer circumferential surface. It is due to this configuration possible to insert the pump module at least in part into the recess of the drive casing and to connect it in a positive-locking manner by pivoting. 
         [0024]    The drive element comprises a positive-locking mechanism for the positive-locking connection of the drive element to a drive counter-element of the pump module by pivoting the pump module about the center longitudinal axis. The positive-locking mechanism is formed such that the drive element of the drive unit is connected to a drive counter-element of the pump module when pivoting the pump module about the center longitudinal axis of the recess for positive-locking fixation of the pump module at the drive casing by way of the positive-locking element. In the pump module according to the invention, the preferably positive-locking counter-element for fixation of the pump module at the drive casing and the positive-locking mechanism for connecting the drive element and the drive counter-element are accordingly each located eccentric to the center longitudinal axis of the recess. The drive unit according to the invention provides the possibility of forced coupling of both the pump module as a whole as well as the drive element of the drive unit to the associated drive counter-element of the pump module by an even pivotal motion. 
         [0025]    The pump module of the previously discussed device for producing a fluid jet specified in a further independent claim is also by itself considered as being essential to the invention. This pump module has a pump casing with at least one positive-locking counter-element with which the pump module can be fixed at a drive casing of a drive. The pump casing is further configured as being adapted for the insertion into a recess of the drive casing and for this purpose has a corresponding cylindrical section. The cylindrical section is typically formed with a rotationally symmetrical outer circumferential surface and in the manner of a fitting adapted to the dimension of the recess. The pump module further has a drive counter-element which is disposed eccentric to a center longitudinal axis of the cylindrical section. The drive counter-element is provided with a positive-locking counter-mechanism fur coupling the drive counter-element to a drive element of the drive exposed in the recess in a positive-locking manner by pivoting the pump module about the center longitudinal axis of the cylindrical section. This pivotal motion takes place during the positive locking fixation of the pump module to the drive casing by way of the positive-locking element of the pump casing. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0026]    Please gather further details and advantages of the present invention from the following description of an embodiment in combination with the drawing, in which 
           [0027]      FIG. 1  shows a perspective view of an embodiment of a device for producing fluid jet; 
           [0028]      FIG. 2  shows the detail of  FIG. 1  in an enlarged representation without the pump module; 
           [0029]      FIG. 3  shows the detail of  FIG. 2  in a top view; 
           [0030]      FIG. 4  shows a top perspective view of an end portion of the pump module shown in  FIG. 1 ; 
           [0031]      FIG. 5  shows an face side top view of the end portion shown in  FIG. 4 ; 
           [0032]      FIGS. 6 a - c    show a sequence of steps for joining the pump module. 
           [0033]      FIG. 7  shows a perspective partially transparent side view of the pump module of the embodiment; 
           [0034]      FIGS. 8 a - d    show semi-sectional views of the drive element and the drive counter-element of the embodiment and their position relative to each other during joining; 
           [0035]      FIG. 9 a - c    show partially sectional top views of the interacting ends of the drive element and the drive counter-element and their relative position when pivoting during the joining process; and 
           [0036]      FIG. 10  shows a perspective partially transparent side view. 
       
    
    
     DETAILED DESCRIPTION 
       [0037]      FIG. 1  shows a perspective side view of an embodiment of a drive unit  1  with a drive provided in a drive casing  2  which is an electric drive. A holder  4  protrudes from drive casing  2  for holding a fluid bag. Exposed on drive casing  2  are also various control elements  6  which serve to actuate the drive and to switch the drive on and off Reference numeral  8  denotes a substantially cylindrical recess in which a pump module designated with reference numeral  10  is inserted and which projects beyond recess  8 . Pump module  10  comprises a pump casing  12  composed of two casing shells. As illustrated in  FIGS. 2, and 3 , drive casing  2  has lugs  16  that protrude inwardly into recess  8  and are embodiments of positive-locking elements of the present invention. Four lugs  16  are presently provided distributed on the circumference. The lug identified by reference numeral  16 . 4  has a smaller radial extension and a smaller extension in the circumferential direction than the other lugs  16 . 1  to  16 . 3 . Exposed in recess  8  are further drive elements in the form of drive pushers  18  which are connected to the drive provided within drive casing  2  and driven cyclically to and fro in the longitudinal direction. Drive pushers  18  form an abutment surface  20 . Two drive pushers  18  are presently provided. A C-shaped claw  22  in a top view projects over abutment surface  20  and forms a hammerhead seat  24  between itself and abutment surface  20 . The respective details are clearly marked in particular in  FIG. 8   a.    
         [0038]    A seal made of rubber-elastic material is in  FIGS. 1 and 2  marked with reference numeral  25  and extends between the outer side of drive casing  2  and an opening toward the recess. Recess  8  is formed by a cup that is associated with the drive and encloses both drive pushers  18 . This cup is subjected to certain vibrations that arc caused by the drive. Seal  25  prevents direct transmission of these vibrations to drive casing  2 . 
         [0039]    As is shown in particular in  FIGS. 4 and 5 , pump module  10  comprises grooves  26  that are marked with reference numeral  26  and extend in the axial direction relative to cylindrical pump casing  12  and which by way of example form positive-locking counter-elements within the meaning of the present invention. These grooves  26  are provided on the outer circumference of pump casing  21  strictly extending in the axial direction. The groove marked with reference numeral  26 . 4  has a smaller radial depth and a smaller width in the circumferential direction and is formed adapted for precise reception of the smaller lug  16 . 4 . Due to the interaction of in particular smaller lug  16 . 4  with smaller groove  26 . 4 , a biunique orientation of pump casing  12  is defined during joining, i.e. when inserting pump casing  12  into recess  8 . Pump casing  12  can be inserted only at an angle perpendicular to a final position offset by  30  shown in  FIG. 6 c   . This pivoted position is illustrated in  FIGS. 6 b  and 9 a   . Reference numerals  28  in  FIG. 9 a    there illustrate two hammerheads which are provided at free ends of each one pump piston  30  and each form an embodiment of a drive counter-element within the meaning of the present invention. Hammerhead  28  projects beyond an end-side cylinder section  32  of each pump piston  30  that has a smaller diameter than the remainder of pump piston  30 . Hammerhead  28  defines the face side, connection side end of pump piston  30  and forms a counter-surface  34  to abutment surface  20 . 
         [0040]    As is illustrated in particular by  FIG. 4 , as transverse groove  36  branches off from an inwardly end of groove  26 . Groove  26  accordingly together with transverse groove  36  forms a guide for a bayonet lock with the respective lug  16  to first perform an axial insertion motion which then comes to an end when lugs  16  abut against the inside lower end of grooves  26 , to thereafter be pivoted in a pivotal motion into transverse groove  36  and thereby be axially locked. In the final position on the end side abutting transverse groove  36 , a catch projection can be active which forms an anti-rotation lock between pump module  10  and drive casing  2  so that pump module  10  is secured in its final position. 
         [0041]    Lugs  16  shown in  FIG. 3  are not of identical configuration. Identical are instead only lugs  16 . 1  and  16 . 2  for which the associated grooves are formed adapted accordingly. Lug  16 . 4  is in its circumferential extension less wide than lugs  16 . 1  to  16 . 3 . It is associated with a correspondingly narrow groove  26 . Corresponding groove  26  accordingly fits together only with lug  16 . 4 , whereby a unique orientation between pump module  10  and recess  8  is determined. 
         [0042]    Drawn in  FIG. 4  is further a catch and switch projection  37  within transverse groove  36  which is exposed in transverse groove  36  and formed fixedly on pump casing  12 . This catch and switch projection  37  is associated with a switch  39  provided centrically in lug  16 . 2 . Switch  39  is preloaded in a radial direction inwardly relative to recess  8  and interacts accordingly with catch and switch projection  37 . Only actuation of this switch by catch and switch projection  37  gives rise to the possibility of driving drive pusher  18 . If pump module  10  is accordingly not connected in the prescribed manner to drive unit  1 , then the drive unit can not be operated. In addition, drive casing  2  and pump casing  12  are provided with mutually associated, preferably electronic lock and key mechanisms. For example, an RFID tag can be provided on pump casing  12  which is recognized by a reading unit that is provided on drive casing  2 . Only in the presence of a respective RFID tag is drive pusher  16  released by a logic unit provided in drive casing  2 , 
         [0043]      FIGS. 6 a  to  c    illustrate the insertion of pump module  10  into recess  8 . As already mentioned above, pump module  10  is first pivoted by 30° in the counterclockwise direction relative to the final position to make lugs  16  coincide with grooves  26  (see  FIG. 6 a   ). The pivoted position is visualized by a division plane that is provided between two casing elements forming pump casing  12 . In this relative orientation, pump module  10  can now be inserted into recess  8 . This axial insertion motion is guided by lugs  16  which engage in grooves  26  formed to correspond thereto, in the representation according to  FIG. 6 b    this axial insertion, which is in  FIG. 6 b    illustrated by a straight arrow, of pump casing  12  is completed. Pump casing  12  is now inserted fully into recess  8 . Thereafter, the pump casing is pivoted by 30° in a clockwise direction, as indicated by the arrow in  FIG. 6 c   . After this pivotal motion by 30°, pump module  10  has reached its final position. The final position is indicated to the user by a directional arrow  40  which is provided on the outer periphery of pump casing  2  and is in the final position aligned with a position indicator  41  provided on drive casing  2 . The directional arrow also indicates the direction of insertion for pump casing  2  into recess  8 . 
         [0044]    As the previously discussed figures illustrate, drive pushers  18  are exposed within recess  8  but are covered entirely by the latter circumferentially and thereby cased in a protected manner. Only cylindrical recess  8  provides access to drive pushers  18 . 
         [0045]    Similarly, pump casing  2  comprises a pump recess  42  which is enclosed by a sleeve section  44  of pump casing  12  marked with reference numeral  44  and forms grooves  26 ,  36  on its outer circumferential surface. The pump pistons with their connection end project slightly axially beyond sleeve section  44 , but are otherwise received within sleeve section  44  and accessible only axially through the opening of pump recess  42 . 
         [0046]    When joining pump casing  12  and drive casing  2 , drive pushers  18  and pump pistons  30  are approached to each other, as is illustrate by  FIGS. 8 a  and 8 b   . Due to the axial guidance of Jugs  16  in grooves  26 , counter-surface  34  formed by hammerhead  28  is at least in part located above the abutment surface formed by drive pusher  18  (cf.  FIG. 9 a   ). A progressive axial motion ultimately causes pump piston  30  to bear with the end side against abutment surface  20 , and even when the alternately axially moved drive pushers  18  project at different distances into recess  8 , as this is implied by the representation of  FIGS. 8 a  to  d   . With increasing proximity of pump casing  12  to drive casing  2 , no further relative axial motion arises thereafter between the pair of drive element  18  and pump piston  30  shown in  FIGS. 8 a  to  d    at the top. According to another axial displacement motion of pump casing  12  relative to drive casing  2  illustrated in  FIGS. 8 b , 8 c    and  8   d,  lower pump piston  30  finally with its counter-surface  34  finally abuts against abutment surface  20  of associated drive pusher  18 . 
         [0047]    The respective hammerhead  28  of the tow pump pistons  30  is there located in an eccentric position relative to the center of drive pusher  18 , which is shown in  FIG. 9 a   . Pump casing  12  is typically after the axial abutment of both pump pistons  30  against drive pushers  1 . 8  displaced by a further minor distance axially relative to drive casing  2 , so that it is ensured that an axial abutment of pump piston  30  is always reliably achieved against drive pusher  18  until the axial final position has been reached when joining pump module  10  and drive easing  2 , before pump module  10  is pivoted relative to the drive casing. The configuration is certainly to be such that reliable abutment of pump piston  30  against drive pusher  18  is after completion of the axial insertion motion obtained in every possible position of drive pusher  18 , even in a position of drive pusher  18  being, in the lowest position within recess  8 . 
         [0048]    After this axial final position has been reached, pump module  10  is then pivoted clockwise. Hammerheads  28  being disposed eccentric to the center of this pivotal motion are thereby—as illustrated in  FIGS. 9 a  to 9 c   —with their counter-surface  34  in a sliding, manner on abutment surface  20  displaced relative to drive pusher  18 , namely in a plane extending perpendicular to the direction of insertion. The previously eccentric arrangement of pump pistons  30  relative to drive pushers  18  according to  FIG. 9 a    via an intermediate position shown in  FIG. 9 b    thereafter approaches the final position shown in  FIG. 9 c   . In this final position, lugs  16  abut against stops which are farmed by transverse grooves  36 . Pump casing  12  is commonly locked against drive casing  2 . Pump pistons  30  are arranged substantially concentric to drive pushers  18 . Each claw  22  engages over the associated hammerhead  28 . Hammerhead  28  is by engagement of hammerhead seat  24  comprising claw  26  held in an axially positive-locking manner. Hammerhead seat  24  is typically matched axially exactly to the height of hammerhead  28  so that a play-free axial positive-locking connection between drive pusher  18  and pump piston  30  arises. As shown in  FIGS. 9 a - c   , catch and switch projection  37  is located at a free end of a spring, arm  14  formed by pump casing  12  which snaps into a locking depression formed by lug  16 . 2  (cf.  FIG. 9 ). 
         [0049]    Detaching pump module  10  is done in the opposite direction. Here as well, respective hammerheads  28  are by pivoting first made to disengage from hammerhead seats  24 . Pump module  10  can then be extracted from recess  18 . This motion is guided by the interaction of lugs  16  with axial grooves  26 . 
         [0050]      FIG. 10  illustrates a lock of the embodiment shown which prevents that the pivotal motion to the final position can be performed when hammerheads  28  are insufficiently engaged. Because claw  22  with its outer contour forms a stop  50  which acts radially, i.e. interacts with hammerhead  28  when pump casing  12  is pivoted, as shown in  FIG. 10 , and accordingly prevents a pivotal motion according to  FIGS. 9 a  to 9 c   . Such pivotal motion can theoretically be possible when lugs  16  have reached the lower end of longitudinal grooves  26 , i.e. When pump casing  12  is fully inserted into recess  8 , a pump piston  30 , however, is not held in the forwardly position projecting in the direction of drive easing  2 , for example due to manual displacement of pump piston  30 . Incorrect mounting of pump module  10  to drive casing  2  is accordingly avoided by this radial stop  50 . This stop  50  is only active as long as hammerhead  28  is in the axial direction, i.e. the direction of insertion, located at the same height as stop  50 , i.e. claw  22 , and has not yet been moved to the level of hammerhead seat  24 . 
         [0051]    As is evident, hammerheads  28  are formed to be rotationally symmetrical. Pump piston  30  can then be supported freely rotatable at pump casing  12 . In contrast, drive pushers  18  are mounted to drive casing  2  in a rotationally fixed manner so that the C-shaped opening of claws  22  is aligned such that the pivotal motion of pump module  10  relative to the final position due to the eccentric arrangement of drive pushers  18  and pump pistons  30  relative to the pivot axis of this pivotal motion, but with the same radius about this center, leads to a forced reception of cylinder sections  32  of respective pump pistons  30 . 
         [0052]    As it arises from the above general description, the drive unit has a rotationally symmetrical recess for receiving as likewise rotationally symmetrical cylindrical section Which is in the specific embodiment formed by sleeve  44 . This section  44  is basically received in the manner of a fitting within recess  8  and held thereby. Only positive-locking elements  16  or positive-locking counter-elements  26 ,  36 , respectively, engage above or behind the cylindrical surface. Pump module  10  is there pivotally guided and supported within recess  8 . The pivot axis of this pivotal motion there forms the center longitudinal axis of recess  8  or the center longitudinal axis of cylindrical section  44 , respectively. Due to the eccentric arrangement of drive element  18  and drive counter-element  30 , respectively, relative to the center longitudinal axis and the relative arrangement of drive element  18  relative to drive counter-element  30  after the axial final position has been reached and before pivoting for positively locking pump module  10  to drive casing  2 , a forced positive-liquid [sic] coupling between drive element  18  and drive counter-element  30  in the frame work of the pivotal motion causes [sic]. Claw  22  of pump piston  30  configured as a drive device there forms the positive-locking mechanism of the drive unit. The positive-locking counter-mechanism provided for this is in the embodiment shown formed by hammerhead  28 .