Abstract:
The invention relates to a hand-held power tool for predominantly percussively driven tool attachments, in particular hammer drills and/or a chisel-action hammers. The power tool has a percussion axis and an intermediate shaft that is parallel to the percussion axis and which has a first stroke generating device having a first stroke element for a percussion drive. Additionally, at least one additional second stroke generating device having at least one second stroke element is provided for driving a counter oscillator that is arranged on or about the intermediate shaft and can be driven by the intermediate shaft. A phase displacement that is different from zero and that is unequal to 180° takes place between a movement of the first stroke element and a movement of at least one second stroke element.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a 35 USC 371 application of PCT/EP2008/065707 filed on Nov. 18, 2010. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a hand-held power tool. 
     2. Description of the Prior Art 
     DE 198 51 888 has already disclosed a hand-held power tool for percussively driven insert tools, in particular a rotary hammer and/or chisel hammer, which has an air cushion impact mechanism with an impact axis and an intermediate shaft parallel thereto, with the excitation sleeve of the air cushion impact mechanism being driven by means of a stroke producing device embodied in the form of a wobble drive. The wobble drive includes a wobble plate with a wobble pin formed onto it, which is supported on a drive sleeve by means of a wobble bearing in such a way that the rotation of the intermediate shaft sets the wobble pin into an axial deflecting motion by means of a raceway of the bearing elements that is provided on the drive sleeve and tilted at an angle in relation to the intermediate shaft. Due to reactions of the air cushion impact mechanism, which are caused among other things by mass forces acting on the excitation sleeve, oscillations are produced in the hand-held power tool. These oscillations are transmitted to the housing of the hand-held power tool in the form of vibrations and from there, are transmitted to an operator via the handle of the hand-held power tool. In order to reduce the mass forces, the hand-held power tool of DE 198 51 888 has a counterweight embodied in the form of a counter-oscillator that is driven by means of a second wobble pin formed onto the wobble plate diametrically opposite from the first wobble pin. The diametrically opposed arrangement of the wobble pins produces a phase shift Δ of 180° between the axial deflecting motions of the wobble pins. The mass forces produced by the oscillating deflecting motion of the excitation sleeve are particularly powerful at the dead-center positions, i.e. in the vicinity of the maximum speed changes that occur, as a result of which their compensation is particularly effective with a phase shift Δ of the counter-oscillator of 180° relative to the deflecting motion of the excitation sleeve. 
     In addition to the mass forces, so-called aerodynamic forces that also excite oscillations occur in air cushion impact mechanisms, among other things due to cyclically changing pressure ratios in the air cushion of the air cushion impact mechanism. Particularly with very lightly constructed excitation sleeves, the aerodynamic forces can even outweigh the mass forces. The maximum of the aerodynamic forces is reached by the compression of the air cushion, typically between 260° and 300° after the front dead center of the axial motion of the excitation sleeve. DE 10 2007 061 716 A1 has disclosed a rotary hammer in which a second wobble pin is formed onto the wobble plate, but in this case encloses an angle not equal to 180° in relation to the first wobble pin for driving the excitation sleeve. This arrangement achieves a phase difference Δ not equal to 180° between a deflection of the excitation sleeve by the first wobble pin and the deflection of a counter-oscillator by the second wobble pin. By suitably selecting the angle orientation, it is possible to optimize the action of the counter-oscillator relative to both oscillation-producing forces, i.e. the mass forces and the aerodynamic forces. The arrangement according to DE 10 2007 061 716 A1, however, is characterized by a sharp limitation on installation space since the counter-oscillator must be situated in the vicinity of the optimum angular position of the second wobble pin, as a result of which the air cushion impact mechanism and required bearing elements limit the available installation space. Furthermore, the second wobble pin executes a nonlinear, complex motion, thus requiring complex bearings to accommodate the wobble pin in the counter-oscillator. 
     In addition to the wobble drives of air cushion impact mechanisms known from DE 198 51 888 and DE 10 2007 061 716, there are also known air cushion impact mechanisms in which the piston of the impact mechanism is driven by means of a crank drive. These are particularly known in the form of crank drives in which the piston is connected to a crank disk by means of a connecting rod and driven thereby. 
     ADVANTAGES AND SUMMARY OF THE INVENTION 
     The hand-held power tool to the invention has the advantage that in terms of its phase position, the motion of the counter-oscillator can be matched in a particularly effective way to the effective oscillation-exciting forces resulting from the mass forces and aerodynamic forces. 
     The separate drive of the counter-oscillator also achieves the advantage that the counter-oscillator can be accommodated in the machine housing in an advantageous way in terms of installation space without requiring particularly complex bearings. 
     A compact embodiment of a hand-held power tool according to the invention is achieved by means of having the at least one additional second stroke producing device be driven by the intermediate shaft. 
     A particularly effective drive of the counter-oscillator is achieved through a phase shift Δ not equal to 90°. Preferably, the phase shift Δ between the motion of the first stroke element and the motion of the second stroke element lies between 190° and 260°. In a particularly preferred embodiment, the phase shift Δ lies between 200° and 240°. 
     A particularly effective embodiment of the counter-oscillator has at least one counter-oscillator mass, which is guided along a linear or nonlinear movement path, in particular along a straight line or arc. 
     A compact and simultaneously effective embodiment of the counter-oscillator has a center-of-gravity path situated close to the impact axis. In a particularly preferred fashion, the center-of-gravity path is oriented parallel to, preferably coaxial to, the impact axis. 
     In a preferred modification of the hand-held power tool according to the invention, the second stroke producing device is equipped with a clutch device. This allows the second stroke producing device to be coupled to the first stroke producing device for co-rotation. In particular, it is thus possible for the second stroke producing device to be activated only in selected operating states of the hand-held power tool. For example, the second stroke producing device can be advantageously deactivated in an idle state of the hand-held power tool. 
     In a preferred embodiment, the clutch device is embodied in the form of a meshing clutch. In a particularly preferred form, an axial movement path is provided between an engaged state and a disengaged state. 
     In a particularly advantageous embodiment, a stroke of the stroke element of the second stroke producing device changes in linear fashion along the movement path. As a result, the amplitude of the motion of the counter-oscillator can be embodied in a particularly easy-to-adjust fashion. 
     In another modification of the hand-held power tool according to the invention, the second stroke producing device has an additional deflecting element. Preferably, the additional deflecting element is able to drive a second counter-oscillator. Depending on the position of the additional deflecting element relative to the stroke element of the second stroke producing device, the motion of the additional deflecting element has a second phase shift Δ A  that in particular differs from the phase shift Δ. 
     In a particularly efficient embodiment of a hand-held power tool according to the invention, the first stroke producing device is embodied in the form of a first crank drive. The crank drive here includes at least one connecting rod and one crank disk. An eccentric pin is provided on the crank disk. The connecting rod engages with the eccentric pin. As a result, the connecting rod functions as a first stroke element. 
     An effective and compact driving of the crank drive is possible by means of a first bevel gear, which is situated on the intermediate shaft. In this case, the intermediate shaft is able to drive the first bevel gear in rotary fashion. 
     A second bevel gear is advantageously provided, which is situated on a bevel gear shaft. The bevel gear shaft advantageously extends perpendicular to the intermediate shaft. The second bevel gear is connected to the bevel gear shaft for co-rotation and can be driven to rotate by the first bevel gear. 
     In a particularly compact embodiment, the eccentric disk with the eccentric pin is situated on the bevel gear shaft. The crank disk can be driven by being connected, preferably detachably, to the bevel gear shaft for co-rotation. 
     In a preferred embodiment of a hand-held power tool according to the invention, the second stroke producing device is embodied in the form of a second wobble drive. This second wobble drive includes at least one second drive sleeve that supports a second raceway, a second wobble bearing, and a second wobble plate with a wobble pin situated on it. 
     In another preferred embodiment of a hand-held power tool according to the invention, the second stroke producing device is embodied in the form of a cam drive. In particular, the cam drive, which deflects at least one additional stroke element and is embodied in the form of a cylindrical cam drive with a curved track situated on a circumference surface. The additional stroke element deflects the counter-oscillator along the curved track. 
     In a preferred modification, the cam drive is embodied in the form of an end-surface cam drive or in the form of a cam drive equipped with a surface profile. A pressing element acts on the counter-oscillator so that the counter-oscillator can be pressed against the surface profile and deflected so that it follows the surface profile. 
     In another preferred embodiment of a hand-held power tool according to the invention, the second stroke producing device is embodied in the form of a connecting rod drive in which the counter-oscillator is operatively connected to the intermediate shaft by means of a connecting rod. 
     In a preferred modification of the hand-held power tool according to the invention, a motion sequence of the second stroke element has a time behavior that differs from a sinusoidal shape. A time behavior that differs from a sinusoidal shape can be advantageously used to adapt the motion sequence of the counter-oscillator to a time behavior of the oscillation-exciting effective forces. 
     In another preferred modification of the hand-held power tool according to the invention, a deflection of the first stroke element has a first frequency. A deflection of the second stroke element has a second frequency, in particular one that differs from the first frequency. In a particularly preferred embodiment, the second frequency is in particular approximately half the first frequency. This advantageously achieves an additional degree of freedom for adapting the motion of the counter-oscillator to the time behavior of the oscillation-exciting effective forces. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments of the invention are shown in the drawings and will be described in greater detail in the description that follows. 
         FIG. 1   a  is a side view of a first exemplary embodiment, 
         FIG. 1   b  shows a section through the exemplary embodiment according to  FIG. 1   a  (line T-T), 
         FIG. 1   c  shows a section through the exemplary embodiment according to  FIG. 1   c  (line U-U), 
         FIGS. 2   a  through  2   d  each show a depiction of the stroke producing devices from  FIG. 1   a  in different phases of the motion, 
         FIGS. 3   a  and  3   b  each show a perspective depiction of an alternative counter-oscillator as a second exemplary embodiment, 
         FIG. 4   a  is a perspective schematic depiction of a third exemplary embodiment, 
         FIG. 4   b  is a perspective schematic depiction of a fourth exemplary embodiment, 
         FIG. 4   c  is a perspective schematic depiction of a fifth exemplary embodiment, 
         FIG. 4   d  is a perspective schematic depiction of a sixth exemplary embodiment, 
         FIG. 5   a  is a schematic side view of a modification of the exemplary embodiment from  FIG. 1   a , constituting a seventh exemplary embodiment, 
         FIG. 5   b  is a schematic side view of another modification of the exemplary embodiment from  FIG. 1   a , constituting an eighth exemplary embodiment, 
         FIG. 6  is a schematic side view of a ninth exemplary embodiment, 
         FIG. 7  is a schematic side view of a tenth exemplary embodiment, 
         FIG. 8   a  is a schematic side view of a modification of the exemplary embodiment from  FIG. 7 , constituting an eleventh exemplary embodiment, 
         FIG. 8   b  shows a section through the exemplary embodiment according to  FIG. 8   a  (line A-A), 
         FIG. 8   c  is a schematic depiction of the phase relationship between the motions of the stroke elements according to the exemplary embodiment from  FIG. 8   a.    
         FIG. 9  is a schematic side view of a twelfth exemplary embodiment, 
         FIG. 10  is a schematic side view of a thirteenth exemplary embodiment, 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1   a  shows a side view of a subregion of a rotary hammer  1  as an example of a hand-held power tool according to the invention. The rotary hammer  1  has a machine housing  2 , not shown here, which encloses a drive motor, not shown here, and a transmission region  3 . The transmission region  3  is accommodated by an intermediate flange  21  via which it is connected to a subregion of the machine housing  2  supporting the drive motor. The transmission region  3  had a transmission device  4  via which a hammer tube  5  can be coupled to the drive motor so that the hammer tube  5  can be driven to rotate. The hammer tube  5  is situated in the transmission region  3  and is supported in rotary fashion in the intermediate flange  21 . The hammer tube  5  in this case extends along a machine axis  6  away from the intermediate flange  21 . By means of the transmission device  4 , a torque produced by the drive motor is transmitted to the hammer tube  5 . The transmission device  4  here can also be spoken of as a rotary drive of the hammer tube  5 . 
     To drive the hammer tube  5  in rotary fashion, the transmission device  4  has an intermediate shaft  7  that is situated parallel to the machine axis  6  in the transmission region  3  of the machine housing  2 , beneath the hammer tube  5 . The intermediate shaft  7  is rotationally decoupled from the machine housing  2  by means of a plurality of bearing devices  8 . An output gear  10  embodied in the form of an output spur gear  10   a  is situated in a subregion  9  of the intermediate shaft  7  remote from the drive motor and is connected to the intermediate shaft  7  for co-rotation. A driven spur gear  11  is situated on the hammer tube  5  and meshes with the output spur gear  10   a . The driven spur gear  11  is operatively connected to the hammer tube  5  via an overload safety clutch  12 . If the torque acting on the driven gear  11  is below a threshold torque of the overload safety clutch  12 , then the driven gear  11  is connected to the hammer tube  5  for co-rotation. The torque acting on the driven gear  11  is thus transmitted to the hammer tube  5 . 
     At one end of the hammer tube  5 , a tool holder  5   a  is provided, into which insert tools, not shown here, can be inserted. In this case, the tool holder  5   a  is connected to the hammer tube  5  for co-rotation. The torque acting on the hammer tube is therefore transmitted to the insert tool by the tool holder  5   a.    
     In typical rotary hammers, e.g. of the kind known from DE 198 51 888 C1 and DE 10 2007 061 716 A1, the tool holder  5   a  also produces a limited axial mobility of the insert tool along a tool axis or impact axis defined by a longitudinal span of the insert tool. Typically, the tool axis or impact axis and the machine axis  6  are oriented coaxial to each other so that the term “impact axis  6 ” is used synonymously with the term “machine axis  6 ” in the text below. 
     In addition to the rotary drive of the hammer tube, the transmission device  4  can also drive an air cushion impact mechanism, not shown in detail here, e.g. of the kind known from DE 198 51 888 C1 and DE 10 2007 061 716 A1. In air cushion impact mechanisms of this kind, a piston situated in axially movable fashion inside the hammer tube  5  can be set into an oscillating axial motion so that pressure modulations are produced in a pneumatic spring provided between the end surface of the piston oriented toward an interior of the hammer tube  5  and an end surface of an impact element oriented toward this end surface of the piston, which impact element is likewise situated in axially movable fashion inside the hammer tube  5 . As a result, the impact element is accelerated along the impact axis  6 . 
     If the piston moves toward the tool holder, the impact element is accelerated until it strikes an end region of the insert tool. As a result, the impetus of the impact element is transmitted to the insert tool in the form of a hammering impetus. 
     The transmission device  4  according to the invention from  FIG. 1   a  includes a first stroke producing device  13  embodied in the form of a wobble drive  13   a . The wobble drive  13   a  in this case is situated with a first drive sleeve  14  in a region  15  of the intermediate shaft  7  oriented toward the drive motor. The drive sleeve in this case is preferably connected to the intermediate shaft  7  for co-rotation. A first raceway  16 , not shown here, is provided on the drive sleeve  14 . The raceway  16  in this case is embodied as circular and is tilted in an impact plane containing the impact axis  6  and the intermediate shaft  7  by an angle W 1  that is greater than zero and less than 180° and particularly preferably, lies between 45° and 135°. A wobble bearing  17 , not shown here, which is preferably embodied in the form of a ball bearing, is situated on this first raceway  16 . The wobble bearing  17  includes at least one, but preferably two or more bearing elements  18 , which are preferably embodied in the form of balls. The raceway  16  and the wobble bearing  17  are shown most clearly in  FIG. 1   c . A wobble plate  19 , which includes the bearing elements  18  of the wobble bearing  17 , is situated around the wobble bearing  17 . A wobble pin  20 , not shown here, is situated on, preferably formed onto, the wobble plate  19 . The wobble pin  20  extends away from the intermediate shaft  7  toward the impact axis  6 . Its front end, not shown here, is accommodated in a swivel bearing that is provided at the rear end of the piston of the air cushion impact mechanism. 
     A rotary motion of the intermediate shaft  7  sets the drive sleeve  14  into rotation together with the raceway  16  provided thereon. The wobble bearing  17  is restrictively guided with its bearing elements  18  on the raceway  16  so that the wobble plate  19  is in fact rotationally decoupled from the intermediate shaft  7 , but is set into a wobbling motion by the restrictive guidance. As a result of the wobbling motion, the wobble pin  20  executes an oscillating axial motion in the direction of the impact axis  6 . The wobble pin  20  here functions as a first stroke element  20   a  of the first stroke producing device  13 . The oscillating axial motion of the wobble pin  20  is transmitted via the swivel bearing to the piston of the air cushion impact mechanism. 
     The transmission device  4  according to the invention from  FIG. 1   a  also has a second stroke producing device  23 , which in the present exemplary embodiment, is embodied in the form of a second wobble drive  23   a . The second wobble drive  23   a  is shown most clearly in  FIG. 1   c . The second wobble drive  23   a  in this case is situated on the intermediate shaft  7 , at an end surface of the first wobble drive  13   a  oriented away from the drive motor. The design and principle function of the second wobble drive  23   a  are equivalent to those of the above-described first wobble drive  13   a . In particular, the second wobble drive  23   a  has a second drive sleeve  24  with a second raceway  26 ; the second drive sleeve  24  is preferably coupled to the intermediate shaft  7  for co-rotation. In addition, a second wobble bearing  27  is provided with bearing elements  28  that are guided along the second raceway  26  and encompassed by a second wobble plate  29 . The wobble plate  29  in this case has a second wobble pin  30 . The second raceway  26  in this case is tilted in the plane containing the impact axis  6  and the intermediate shaft  7  by an angle W 2  that is greater than zero and less than 180° and particularly preferably lies between 45° and 135°. In relation to the first wobble pin  20 , the second wobble pin  30  is rotated out from the impact plane by a rotational offset angle WV in the circumference direction of the intermediate shaft  7 , as shown in  FIG. 1   b . The second wobble drive  23   a  is adapted to structural boundary conditions in the machine housing  2  through selection of the rotational offset angle WV. In addition, the rotational offset angle WV prevents a possible collision of the first wobble pin  20  with the second wobble pin  30  during operation of the transmission device  4 , even with large strokes of the wobble pins  20 ,  30 . 
     The end of the wobble pin oriented away from the second wobble plate  29  is accommodated in a counter-oscillator  31 . The counter-oscillator  31  can be equipped with a receiving swivel bearing  32 , as depicted in  FIG. 1   c , for a low-friction accommodation of the wobble pin  30 . In the embodiment shown here, the counter-oscillator  31  is essentially embodied as a counter-oscillator mass  33 . The counter-oscillator mass  33  in this case is embodied in the form of a cylindrical mass component. In the first exemplary embodiment, the counter-oscillator  31  is situated in an axially movable fashion on the side of a sleeve-shaped section  22  of the intermediate flange  21 . The sleeve-shaped section  22  is provided with a receiving groove  36  for this purpose, in which the cylindrical counter-oscillator mass  33  is accommodated. The counter-oscillator  31  is embraced by a guide element  34 , as is shown in  FIG. 1   b . In the present example, the guide element  34  is detachably fastened to the sleeve-shaped section  22  by means of screw connections. The person skilled in the art is also aware of other fastening possibilities such as clamped, detent-engaged, riveted, soldered, or welded connections that can be used to advantage here. The guide element can also be situated for example in the surrounding machine, housing  2 . By means of the guide element  34  and the receiving groove  36 , the counter-oscillator  31  is guided along a linear path, in particular a straight path parallel to the impact axis  6 . It can, however, also be advantageous to guide the counter-oscillator  31  on the other path forms, in particular along an arc or other nonlinear path forms such as parabolic, elliptical, or hyperbolic paths. Selecting the most suitable path form for each respective intended use should present no difficulty to the person skilled in the art. 
     In the present exemplary embodiment, the first drive sleeve  14  and the second drive sleeve  24  are connected to each other for co-rotation. In this case, an orientation angle WO in the circumference direction of the intermediate shaft  7  between the first raceway  16  and the second raceway  26  is selected to set a rotational position of the raceways relative to each other. In the present preferred embodiment of a hand-held power tool according to the invention, the orientation angle WO is equal to the rotational offset angle WV of the second wobble pin  20 . This is shown, among other things, in  FIG. 1   b . The relative rotational position and the angles W 1  and W 2  of the first and second wobble pin  20 ,  30  yields a phase shift Δ between the oscillating axial motions of the two wobble pins  20 ,  30 . 
     Different connecting techniques can be used to produce a connection for co-rotation. 
     For a form-locked connection, at its end oriented toward the second drive sleeve  24 , the first drive sleeve  14  can be provided with detent elements such as a spur gearing, a gearing on the outer circumference surface, or similar shapes. On the other hand, the second drive sleeve  24  is provided with corresponding receiving elements with which the detent elements engage, particularly during assembly of the transmission device  4 , to produce a form-locked connection. 
     A nonpositive, frictional engagement can be produced, for example, by means of a press fit between the first drive sleeve  14  and the second drive sleeve  24 . In addition to this simple nonpositive, frictionally engaged connection, more complex connections, for example including an additional connecting element such as a connecting sleeve, can also possibly be included. 
     In addition to the form-locked and/or nonpositive, frictionally engaged connections, the person skilled in the art also knows other connecting techniques such as gluing, soldering, or welding that can be used to advantage depending on the circumstances. 
     In a preferred, particularly inexpensive form, the first drive sleeve and the second drive sleeve can also be manufactured of one piece. In particular, the sintering technique or metal injection molding (MIM) can be used for this. 
     It can also be advantageous, however, if the connection for co-rotation is embodied as detachable, in particular axially detachable. Possible embodiments are shown in  FIGS. 10   a  and  10   b  and described in connection therewith and are included here by reference. 
     During operation of the rotary hammer  1 , the oscillating axial motions of the piston and/or impact element and/or insert tool produce inertial forces when a change occurs in the respective motion state of the piston and/or impact element and/or insert tool, based on their masses. These inertial forces are referred to hereinafter as mass forces. In particular, a change in the motion state of the piston sometimes produces very powerful mass forces. In addition to the kinematic values of the motion sequence such as the instantaneous accelerations, the mass forces depend in particular on the mass of the piston and therefore on its geometry and the material used. 
     The mass forces act directly on the piston, the impact element, and the hammer tube and excite them to oscillate. Particularly with a sinusoidal motion sequence of the piston, the accelerations at the dead-center positions of the axial motion of the piston are relatively high so that the mass forces demonstrate a pulse-like time behavior and particularly powerful oscillation excitations occur. Because of its direct connection to the motion sequence of the piston, the time behavior is synchronous to the motion state of the piston. 
     In order to reduce the mass forces of the above-described air cushion impact mechanism, the counter-oscillator  31  is preferably deflected in antiphase to the oscillating axial motion of the piston. In terms of pure mass forces, a phase shift Δ of 180° advantageously prevails between the oscillating axial motion of the piston and the oscillating axial motion of the counter-oscillator  31 . In addition to a mass of the counter-oscillator mass  33 , the stroke of the oscillating axial motion of the counter-oscillator  31  constitutes a parameter for matching a reducing action of the counter-oscillator  31  to the respective air cushion impact mechanism. 
     As already described at the beginning, however, mass forces are not the only oscillation-exciting forces at work in air cushion impact mechanisms. Instead, the so-called aerodynamic forces have a considerable influence on an excitation of oscillations. Particularly with an increasing hammering power of the rotary hammer with a simultaneous mass reduction of the moving components such as the piston, the aerodynamic forces assume a dominant role in the excitation of oscillations. As explained above, due to fluid mechanical effects, the aerodynamic forces are subject to a phase shift in relation to the oscillating axial motion of the piston, which typically lies in the range between 260° and 300° after a front dead center FDC of the oscillating axial motion of the piston. With the counter-oscillator  31  according to the invention, it is easily possible to optimally select and adjust the phase shift Δ between the oscillating axial motion of the piston and the oscillating axial motion of the counter-oscillator  31 . In real air cushion impact mechanisms, the balancing of the phase shift Δ takes into account a chronological behavior of the oscillation-exciting effective forces, which are composed of the mass forces and aerodynamic forces. Preferably, the phase shift Δ lies between 190° and 260°. In a particularly preferred embodiment, the phase shift Δ lies between 200° and 240°. 
       FIGS. 2   a  through  2   d  show an example of the sequence of the oscillating axial motions of a piston  38  and the counter-oscillator  31  and therefore of the first wobble pin  20  and second wobble pin  30 , using one case as an example. The figures here show different movement phases. In  FIG. 2   a , the piston  38  is situated in its front dead center, which is labeled “impact drive FDC 0°”. At this time, the counter-oscillator  31  is situated to the front of its rear dead center, which is labeled “counterweight RDC”. In  FIG. 2   b , the piston  38  is on its way to its rear dead center (labeled “impact drive RDC 180°”) while the counter-oscillator  31  has now reached its rear dead center. In  FIG. 2   c , the piston  38  has reached its rear dead center, while the counter-oscillator  31  is still moving toward its front dead center (labeled “counterweight FDC”). Only after the piston  38  has already traveled part of the way to the front dead center as shown in  FIG. 2   d  does the counter-oscillator  31  reach its front dead center and reverse its movement direction. 
     The parameters of counter-oscillator mass, stroke of the counter-oscillator  31 , and phase shift Δ constitute optimization parameters that depend on the respective air cushion impact mechanism and can be mathematically and/or experimentally determined. 
     A preferred modification provides an additional linking element, not shown here, on the second wobble plate  29  of the second wobble drive  23   a . The additional linking element in this case is preferably situated on, preferably formed onto, the wobble plate  29  at a circumference angle WA in relation to the second wobble pin  30 . This linking element is preferably used to drive in particular a second counter-oscillator. 
       FIGS. 3   a  and  3   b  show perspective views of a modification of the above-described embodiment of a hand-held power tool according to the invention that constitutes a second exemplary embodiment. The reference numerals of parts that are the same or function in the same manner have been increased by 100 in these figures. 
       FIG. 3   a  shows a counter-oscillator  131  which has three counter-oscillator masses  133   a ,  133   b ,  133   c  connected to one another by means of a bracket-shaped connecting element  135 . In the embodiment shown here, the counter-oscillator  131  is composed of two predominantly mirror-symmetrical halves to facilitate assembly. The halves are screwed to each other during assembly. Analogous to the first exemplary embodiment, a receiving swivel bearing  132  is provided in the counter-oscillator mass  133   a  and accommodates the second wobble pin  130  of the second wobble drive  123 . The counter-oscillator  131  is arranged around the sleeve-shaped section  122  of the intermediate flange  121  and supported on it in axially movable fashion. To that end, the sleeve-shaped section  122  has receiving grooves  136   a ,  136   b ,  136   c  in which the cylindrical counter-oscillator masses  133   a ,  133   b ,  133   c  are accommodated. Analogous to the first exemplary embodiment, the counter-oscillator  133   a  is secured to and guided on the sleeve-shaped section  122  by means of a guide element  134 . In terms of their masses and their positioning, the counter-oscillator masses  133   a ,  133   b ,  133   c  of the second exemplary embodiment are designed so that the counter-oscillator  131  has a centrally situated center of gravity M. 
     This center of gravity M is situated so that it essentially lies on the impact axis  106 . In an oscillating axial motion of the counter-oscillator  131 , the center of gravity M describes a center-of-gravity path that is essentially parallel to, preferably coaxial to, the impact axis  106 . 
     The center-of-gravity path of the counter oscillator  131  permits the counter oscillator  131  to counteract the oscillation-exciting effective forces in a particularly effective way since these effective forces act directly on components of the rotary hammer  101 , e.g. the piston of the air cushion impact mechanism, which are primarily situated in a cylindrically symmetrical fashion around the impact axis  106  in a known way so that their center-of-gravity paths likewise extend parallel to, primarily even coaxial to, the impact axis  106 . 
     In addition to the three-element embodiment of a counter-oscillator  131  described here, other embodiments of counter-oscillators are known to the person skilled in the art, which permit a counter-oscillator center-of-gravity path that is primarily coaxial to the impact axis  6 . In particular, the form and number of counter-oscillator masses  133   a ,  133   b ,  133   c  connected to one another can differ from the embodiment shown here. In an advantageous modification, the counter-oscillator  131  can be embodied in the form of a sleeve-shaped component. Furthermore, modifications of the counter-oscillator  131  shown here can be achieved by differently dividing them into differing halves or other subelements and/or differently attaching them to each other. 
       FIG. 4   a  is a schematic, perspective view of a third exemplary embodiment of a transmission device  204  according to the invention. The reference numerals of parts that are the same or function in the same manner have been increased by 100 in this figure. Of the transmission device  204 ,  FIG. 4   a  shows only the first and second stroke producing devices  213 ,  223  that are situated in the region  215  of the intermediate shaft  207  oriented toward the drive motor; in lieu of the intermediate shaft  207 , only an intermediate shaft axis  207   a  is shown. The stroke producing devices in this exemplary embodiment are embodied in the form of a first wobble drive  213   a  and a second wobble drive  223   a . The first wobble drive  213   a  in this case is embodied in the way known from the preceding exemplary embodiments, rendering its description unnecessary here. 
     The third exemplary embodiment differs from the preceding exemplary embodiments through a modification of the second wobble drive  223   a . Two output pins  237   a ,  237   b  are provided on the second wobble plate  229 . These output pins  237   a ,  237   b  are laterally connected to, preferably formed onto, the wobble plate  229  in its circumference direction. The output pins  237   a ,  237   b  extend in a bow shape around a piston  238  of the air cushion impact mechanism that is connected to the first wobble pin  220 . In the embodiment shown, the output pins  237   a ,  237   b  are mirror-symmetrical in relation to the impact plane, which includes the impact axis  206  and the intermediate shaft axis  207   a . It can also be advantageous, however, to deviate from this symmetry. At their ends oriented away from the wobble plate  229 , the output pins  237   a ,  237   b  are connected to, preferably embodied of one piece with, a pin head  240  that supports an output element  239 . The output element  239  is operatively connected to the counter-oscillator  231 . In particular, the output element  239  can be accommodated—in a fashion similar to that of the already known second wobble pin  30 ,  130 —in a receiving swivel bearing  232  provided in the counter-oscillator mass  233 . Due to this arrangement, the oscillating axial motion of the counter-oscillator  231  is situated in the impact plane. This arrangement makes it unnecessary to rotationally offset a stroke of the second wobble drive  223  in relation to the impact plane. This simplifies tuning and can be advantageous in terms of available space. By contrast with the first two exemplary embodiments, in the third exemplary embodiment, the phase shift Δ between the oscillating axial motion of the piston  238  triggered by the first wobble pin  220  and the oscillating axial motion of the counter-oscillator  231  is determined solely by an angular difference between the angles W 1  and W 2 . The function of the third exemplary embodiment corresponds to that of the first embodiment, whose description is included here by reference. 
       FIG. 4   b  shows a fourth exemplary embodiment that is a modification of the third exemplary embodiment from  FIG. 4   a . The depiction here is analogous to the depiction in  FIG. 4   a . The discussion here will concentrate solely on modifications since the basic design and function correspond to those of the third exemplary embodiment. 
     By contrast with the design of the third exemplary embodiment, the second wobble plate  229  of the second wobble drive  223   a  has an output pin  237   a  on only one side. The output pin  237   a  in this case is bow-shaped. Its end oriented away from the wobble plate  229  is attached to the pin head  240 , which supports the output element  239 . In this embodiment as well, the counter-oscillator  231  is situated in the impact plane, above the piston  238 . The function of the fourth exemplary embodiment corresponds to that of the first embodiment, whose description is included here by reference. 
       FIG. 4   c  is a combination of the second exemplary embodiment from  FIG. 3   a  and the third exemplary embodiment from  FIG. 4   a , constituting a fifth exemplary embodiment. The depiction here is analogous to the depiction in  FIG. 4   a . The discussion here will concentrate solely on modifications since the basic design and function correspond to those of the third exemplary embodiment. 
     By contrast with the third exemplary embodiment, the counter-oscillator  231  of the fifth exemplary embodiment corresponds in design to that of the counter-oscillator  131  known from the second exemplary embodiment. The receiving swivel bearing  232  in the counter-oscillator  231  is provided in the middle counter-oscillator mass  233   b  since analogous to the counter-oscillator  231  in exemplary embodiments three and four, this bearing is situated in the impact plane beneath the pin head  240 . Due to its three-element embodiment, the center of gravity M of the counter-oscillator is located centrally between the counter-oscillator masses  233   a ,  233   b ,  233   c . Suitable selection of the counter-oscillator masses yields a form of the center-of-gravity path that is largely coaxial to the impact axis in an oscillating axial motion of the counter-oscillator. 
     In a way similar to the one already described in conjunction with the second exemplary embodiment, the person skilled in the art can select forms of the counter-oscillator  231  that differ from the embodiment shown here. 
       FIG. 4   d  is a modification of the third exemplary embodiment from  FIG. 4   a , constituting a sixth exemplary embodiment. The depiction here is analogous to the depiction in  FIG. 4   a . The discussion here will concentrate solely on modifications since the basic design and function correspond to those of the third exemplary embodiment. 
     In the sixth exemplary embodiment, the pin head  240  of the two output pins  237   a ,  237   b  is itself embodied as a counter-oscillator mass  233 . The pin head  240  therefore functions as a counter-oscillator  231 . Due to a swiveling motion of the output pins  237   a ,  237   b  triggered by the wobble plate  229 , the counter-oscillator in the present instance executes a swiveling motion in the impact plane. The counter-oscillator is in particular guided on an arc-shaped path. 
     In another modification, alternative to or in addition to the counter-oscillator  231  of the sixth exemplary embodiment, a guide pin  241  can be situated on, in particular formed onto, the pin head  240 . This guide pin  241  is preferably oriented away from the wobble plate  229 . In addition, a counter-oscillator  231 , not shown here, that includes a slotted link  242  can be situated on the guide pin  241 . The guide pin  241  protrudes into this slotted link  242  and transmits the oscillating axial motion of the pin head  240  to the counter-oscillator  231  in which the slotted link  242  is provided. An exemplary embodiment of a slotted link  242  is shown in  FIG. 8   b.    
     Other advantageous embodiments of a second stroke producing device  23  according to the invention, embodied in the form of a second wobble drive  23   a ,  123   a ,  223   a  can be composed, among other things, of combinations of both the individual features of the exemplary embodiment described above and features of wobble drives known to the person skilled in the art. 
       FIG. 5   a  shows a schematic side view of a modification of the exemplary embodiment from  FIG. 1   a , constituting a seventh exemplary embodiment. The reference numerals of parts that are the same or function in the same manner are preceded by an 8 in this figure. 
     This figure depicts stroke producing devices  813 ,  823  embodied in the form of a first and second wobble drive  813   a ,  823   a , in a modification based on the exemplary embodiment known from  FIG. 1   a . In this embodiment, only the first drive sleeve  814  is connected to the intermediate shaft  807  for co-rotation. The second drive sleeve  824  is axially movable and can freely rotate on the intermediate shaft  807 . In this case, a clutch device  873  embodied in the form of a meshing clutch  872  is provided between the first drive sleeve  814  and the second drive sleeve. An axial movement along a movement path V brings the clutch device  872 ,  873  into an activated or engaged state so that the second drive sleeve  824  is then connected to the first drive sleeve  814  for co-rotation. 
     In the embodiment shown here, at least one, but preferably two or more clutch elements  874  are provided on the side of the first drive sleeve oriented toward the second drive sleeve  824 . On the side of the second drive sleeve  824  corresponding to this side, at least one, but preferably two or more counterpart clutch elements  875  are provided, to which the clutch elements  874  can be coupled in order to produce a rotational connection between the first drive sleeve  814  and the second drive sleeve  824 . To that end, the counterpart clutch elements  875  are brought into engagement with the clutch elements  874  through an axial movement of the second drive sleeve  824 . The person skilled in the art is aware of an extremely wide variety of embodiments that can be used for the concrete embodiment of the clutch elements  874  and the counterpart clutch elements  875  that correspond to them. For example, end-surface or circumferential gearings and counterpart gearings can be used. It is also conceivable to provide clutch devices  873  with clutch elements such as balls and ball receptacles, to name just two known embodiments. 
     Through the integration of a clutch device  872 ,  873 , it is possible to embody the driving of the counter-oscillator  831  so that it can be switched by means of the second wobble drive  823   a . In particular, it is conceivable for the driving of the counter-oscillator  831  to be deactivated when the rotary hammer  801  is in an idle state. Only when performing a work task, particularly one in which the insert tool is percussively driven, is the driving of the counter-oscillator  831  manually or automatically switched into the operative state. 
       FIG. 5   b  shows a schematic side view of a modification of the exemplary embodiment from  FIG. 5   a , constituting an eighth exemplary embodiment. The embodiment of a meshing clutch  872  shown here is in particular already known from DE 10 2004 007 046 A1, whose description is explicitly included herein by reference. At the end of the intermediate shaft  807  oriented away from the drive motor, an axially movable shifting sleeve  876  is provided, which has a conically tapering shifting wedge  877  at its end oriented toward the second drive sleeve  824 . In this embodiment, the second drive sleeve  824  is supported in freely rotating fashion on the intermediate shaft  807 . To that end, it has a through bore  878  with a receiving diameter that opens in conical fashion in both directions along the intermediate shaft  807  and each opening has a different cone angle. The side of the through bore oriented toward the shifting sleeve  876  has a cone angle that corresponds to that of the shifting wedge  877 . 
     In an idle state of the rotary hammer  801 , the shifting sleeve  876  is held in a disengaged position by means of a return element  879 , which is embodied here in the form of a spring element  880 . The idle state in this case is defined such that in this state, the insert tool contained in the tool holder  805   a  is not pressed against a work piece. Because the shifting sleeve  876  is positioned in the disengaged state, the shifting wedge  877  is not engaged with the conical receiving diameter that corresponds to it. As a result, the second driving sleeve  824  is not rotationally connected to the intermediate shaft. In addition, the raceway  826  provided on the second driving sleeve  824  is situated in a rest state that is tilted by 90° in relation to the intermediate shaft  807  so that the counter-oscillator  831  is therefore also not subjected to any deflection. If the insert tool is now pressed against a work piece, then the shifting sleeve  876  is slid axially toward the second drive sleeve  824  and the shifting wedge  877  comes into engagement with the corresponding receiving diameter. On the one hand, this produces a rotational connection between the second drive sleeve  824  and the intermediate shaft  807 . On the other hand, with a continued sliding of the shifting wedge, the angle W 2  of the raceway  826  becomes more sharply inclined relative to the intermediate shaft  807 , thus increasing a stroke of the second wobble pin  830 . In this case, the cone angle of the other receiving diameter limits the maximum possible angle W 2 max. 
     The following exemplary embodiments of a hand-held power tool according to the invention demonstrate examples with alternative second stroke producing devices of the type that can be advantageously used in the context of the invention: 
       FIG. 6  shows a schematic side view of a rotary hammer  601  with a transmission device  604  according to the invention. The reference numerals of parts that are the same or function in the same manner are preceded by a 6 in this figure. 
     The transmission device  604  has a first stroke producing device  613  in the form of a crank drive  613   b.    
     A first bevel gear  685  is situated at the end of the intermediate shaft  607  oriented toward the drive motor and can be driven to rotate by the intermediate shaft  607 . To that end, the first bevel gear  685  is connected, preferably detachably, to the intermediate shaft  607  for co-rotation. In the direction toward the impact axis  606 , a second bevel gear  686  is situated above the intermediate shaft  607 . The second bevel gear  686  is situated on a bevel gear shaft  687  and is preferably connected to it for co-rotation. In a preferred embodiment, the bevel gear shaft  687  extends toward the impact axis  606 , perpendicular to the intermediate shaft  607 . The second bevel gear  686  can be driven to the rotate by the first bevel gear  685 . In this way, a rotating motion of the intermediate shaft  607  is transmitted via the first and second bevel gears  685 ,  686  to the bevel gear shaft  687 . 
     At an end of the bevel gear shaft  687  oriented toward the impact axis  606 , a crank disk  688  is provided. This crank disk  688  is connected, preferably detachably, to the bevel gear shaft  687  for co-rotation so that a rotating motion of the bevel gear shaft  687  can be transmitted to the crank disk  688 . An eccentric pin  689  is situated on, preferably formed onto, a radially outer region of the crank disk  688 . The eccentric pin  689  is engaged by a connecting rod  690 , preferably by one end of the rod. At the other end, the connecting rod  690  is operatively connected to the piston  638  of the air cushion impact mechanism. Preferably, a receiving swivel bearing is provided for this purpose in the piston  638  and the connecting rod  690  engages in this bearing. 
     During operation, the crank disk  688 —and therefore the eccentric pin  689  situated on it—is set into a rotating motion. In an axial direction along the impact axis  606 , the eccentric pin  689  and the connecting rod  690  engaging it execute an oscillating axial motion that is transmitted to the piston  638 . 
     The person skilled in the art is aware of many modifications to the crank drive  613   b  schematically outlined here, which in connection with the present invention, can yield advantageous embodiments of a hand-held power tool according to the invention. In particular, the crank drive  613   b  can be advantageously supplemented with a clutch device that operates between the bevel gear shaft  687  and the second bevel gear  686  or between the bevel gear shaft  687  and the crank disk  688 . In addition, the second bevel gear  686  and the crank disk  688  can be embodied of one piece. In particular, the eccentric pin  689  can be situated directly on the second bevel gear  686 . 
     The transmission device  604  includes a second stroke producing device  623  in the form of a wobble drive  623   a  that is already known from the foregoing description. It will therefore not be discussed in detail at this point. The above-described modifications of the wobble drive  623   a  can also be transferred to the embodiment of the present exemplary embodiment. 
     The counter-oscillator  631  therefore behaves analogously to the embodiment known from  FIG. 1   a . In this exemplary embodiment, a phase shift Δ is set by selecting the angle W 2  of the raceway  626  of the wobble drive  623   a , taking into account the circumference angle WE of the eccentric pin  689  on the crank disk  688 . 
       FIG. 7  is a schematic side view of a rotary hammer  301  with a transmission device  304  according to the invention, constituting a ninth exemplary embodiment. The reference numerals of parts that are the same or function in the same manner are preceded by a 3 in this figure. 
     The transmission device  304  has a first stroke producing device  313  embodied in the form of a crank drive  313   b  that is already known from the above-described embodiment. Its description there is included here by reference. 
     The second stroke producing device  323  for driving a counter-oscillator  331  is embodied in the form of a cam drive  323   b . In this case, the second stroke producing device  323 ,  323   b  has a cam cylinder  343  that is situated on the intermediate shaft  307  in its region  309  oriented away from the drive motor and is preferably connected to the intermediate shaft  307  for co-rotation. A curved track  344  is provided on an outer circumference surface of the cam cylinder  343 . The curved track has an axial course  345  that varies in the circumference direction of the cam cylinder  343 . In particular, the axial course  345  can be comprised of a circular path that is tilted by an angle W 3  in relation to the intermediate shaft. Other path forms, in particular nonlinear path forms such as spiral paths, sinusoidal paths, and similar path courses, however, can possibly be advantageous. 
     In the embodiment shown here, the curved track  344  is embodied in the form of a groove provided in the outer circumference surface of the cam cylinder  343 . It is also possible, however, to manufacture a curved track  344  by means of suitable molded or formed-on features. It is also conceivable to manufacture the curved track  344  by encasing or wrapping the cam cylinder with a sleeve element, which is manufactured in a flat arrangement and supports a curved profile. It is then possible, for example, for the sleeve element to be produced by means of stamping and then for it to be rolled into a sleeve. The person skilled in the art is also aware of other methods to accomplish this. 
     The counter-oscillator  331  has a guide element  346 , for example a guide ball  346   a  or a guide pin  346   b , which is situated on the side of the counter-oscillator oriented toward the cam cylinder. In this case, the guide element  346  is in a predominantly fixed radial position in relation to the cam cylinder  343 . The guide element  346  engages in the curved track  344  and is guided by it. 
     During operation, the cam cylinder  343  is driven to rotate by the intermediate shaft  307 . As a result, the guide element  346  is deflected along the axial course  345  of the curved track  344  so that this can be referred to as an oscillating axial motion. In this exemplary embodiment, a phase shift Δ is set by selecting a rotational position of the curved track  344 , taking into account the circumference angle WE of the eccentric pin  389  on the crank disk  388  of the first stroke producing device  313 ,  313   b.    
     Typically, the axial motion of the guide element  346  repeats after one full rotation of the cam cylinder  343 . The counter-oscillator  331  thus behaves analogously to the embodiment known from  FIG. 1   a . However, it is also possible to provide curved tracks  344  that deviate from this relationship. In particular, the repetition of the axial motion can be an integral multiple or an integral fraction of a rotation of the cam cylinder  343 .  FIGS. 8   a  through  8   c  show an example of this, the description of which is included here by reference. 
     The oscillating axial motion of the guide element  346  sets the counter-oscillator  331  into an oscillating axial motion. Through a suitable selection of the angle W 3  and/or the axial course  345  of the curved track  344 , it is possible to set a desired phase shift □ between the first wobble pin  320  and the guide element  346  functioning as a stroke element  330   a  of the second stroke producing device  323 ,  323   b . As a result, the counter-oscillator  331  functions in a fashion analogous to that of the preceding exemplary embodiments. The ability to select the axial course  345  of the curved track  344  provides this exemplary embodiment of a transmission device  304  according to the invention with an additional degree of freedom for optimally matching the oscillating axial motion of the counter-oscillator to the time sequence of the oscillation-exciting effective forces, a degree of freedom which can be advantageously used for further oscillation reduction. In particular, the selection of the curved track  344  or axial course  345  makes it possible to produce a movement profile of the counter-oscillator  331  that differs from a sinusoidal shape that is typical of oscillating motions. 
       FIG. 8   a  shows a schematic side view of a modification of the exemplary embodiment from  FIG. 7 , constituting a tenth exemplary embodiment. The reference numerals of parts that are the same or function in the same manner are preceded by a 9 in this figure. 
     The transmission device  904  has a first stroke producing device  913  embodied in the form of a crank drive  913   b  that is already known from the foregoing description. Its description there is included here by reference. 
     The second stroke producing device  923 ,  923   b  has a cam cylinder  943  that is situated on the intermediate shaft  907  in its region  909  oriented away from the drive motor and is preferably connected to the shaft for co-rotation. A curved track  944  is provided on an outer circumference surface of the cam cylinder  943 . In the embodiment shown here, the curved path  944  is embodied in the form of a reverse-action crisscrossing spiral track  981 . In particular, the spiral track  981  has two respective rotations in each direction. The guide element  946  provided on the counter-oscillator mass  933  is embodied in the form of a rail slider  982 , which is shown most clearly in  FIG. 8   b . In the embodiment shown here, the rail slider  982  has at least two guide elements  983 , which are preferably embodied in the form of balls. The guide elements  983  are situated in freely rotating fashion on a support element  984  and are spaced apart from each other in the circumference direction of the cam cylinder  943 . During operation, the cam cylinder  943  rotates at the same speed as the intermediate shaft  907 . By means of the spiral track  981 , the axial deflection of the counter-oscillator  931  by means of the rail slider  982  occurs at a reduced speed. In other words, the oscillating axial motion of the second stroke element  30   a  that drives the counter-oscillator occurs with a second, in this case reduced, frequency F 2  as compared to a first frequency F 1  of the oscillating axial motion of the first wobble pin  920 .  FIG. 8   c  shows a schematic stroke/time graph for the deflections of the piston and counter-oscillator that correspond to this exemplary embodiment. 
     As has already been indicated in the description of several of the preceding exemplary embodiments, there are other possibilities for influencing a second frequency F 2  of the second stroke producing device  923 . Other possibilities for modifying the exemplary embodiments shown here are also known to those skilled in the art. 
       FIG. 9  shows a schematic side view of a rotary hammer  401  with a transmission device  404  according to the invention, constituting an eleventh exemplary embodiment. The reference numerals of parts that are the same or function in the same manner are preceded by a 4 in this figure. 
     The transmission device  404  has a first stroke producing device  413  in the form of a crank drive  413   b  that is already known from the foregoing description. Its description there is included here by reference. 
     The second stroke producing device  423  for driving a counter-oscillator  431  is embodied in the form of an end-surface cam drive  423   c . The end-surface cam drive  423   c  has a cam plate  450  that is situated on an end surface perpendicular to the intermediate shaft  307 , is oriented away from the drive motor, and has a surface profile  449 . It can therefore also be referred to as a cam drive  423   c . In particular, the surface profile  449  has an axial course  451  that varies in the circumference direction of the cam plate  450 . 
     The counter-oscillator  431  is oriented away from the drive motor and is situated axially in front of the intermediate shaft  307 , in particular in front of the cam plate  450  in the machine housing  402 . The counter-oscillator  431  here has a pressing element  452  that prestresses the counter-oscillator mass  433  of the counter-oscillator  431  axially in the direction toward the cam plate  450 . The pressing element  452  in the present case is embodied in the form of a prestressed helical spring  452   a . The end of the helical spring  452   a  oriented away from the transmission device rests against a support element  454  affixed to the machine housing  302 . Its opposite end rests against a support ring  455  provided on a counter-oscillator mass  433 . In this connection, the person skilled in the art is also aware of other pressing elements  452  such as elastomer elements or other spring elements that can be advantageously used in the context of the invention. Support and assembly elements that differ from the form shown here can also be advantageous for the assembly of the pressing element  452 . 
     During operation, this prestressing action presses the counter-oscillator mass  433  against the surface profile  449 . The end of the counter-oscillator mass  433  oriented toward the cam plate has a contact element  453  that is pressed against the surface profile in an outer radius region of the cam plate  450 . If the intermediate shaft  407  drives the cam plate  450  to rotate, then the counter-oscillator mass  433  is axially deflected by the contact element  453  serving as a stroke element  430   a  of the second stroke producing device  423 ,  423   c . Because of the axial course  451  that repeats with a rotation of the cam plate  450 , the counter-oscillator  431  executes an oscillating axial motion. In this exemplary embodiment, a phase shift Δ is set by selecting a rotational position of the cam profile  449 , taking into account the circumference angle WE of the eccentric pin  489  of the first stroke producing device  413 ,  413   b.    
     It is thus possible by means of the cam profile  449 , in particular the axial course  451 , to selectively influence the chronological course of the axial motion. In particular, it is possible to produce movement profiles that deviate from a sinusoidal form that is typical for oscillating motions. It is also possible to provide multiple deflections per rotation of the cam plate  450 , depending on the cam profile  450 . 
       FIG. 10  shows a schematic side view of a rotary hammer  501  with a transmission device  504  according to the invention, constituting a twelfth exemplary embodiment. The reference numerals of parts that are the same or function in the same manner are preceded by a 5 in this figure. 
     The transmission device  504  has a first stroke producing device  513  in the form of a crank drive  513   b  that is already known from the foregoing description. Its description there is included here by reference. 
     The second stroke producing device  523  for driving a counter-oscillator  531  is embodied in the form of a connecting rod drive  523   d . A drive plate  556  is situated on the part  509  of the intermediate shaft  507  oriented away from the drive motor and can be driven to rotate by means of the intermediate shaft  507 . In the present example, the first bevel gear  585  is embodied in the form of a drive plate  556 . A swivel joint  557  is provided in a radially outer region, on an end surface of the drive plate  556 . One end of a connecting rod  558  is operatively connected to the drive plate  556  by means of this swivel joint  557 . At its other end, the connecting rod  558  is provided with a second swivel joint  559 , which operatively connects the connecting rod  558  to the counter-oscillator mass  533  of the counter-oscillator  531 . The counter-oscillator  531 , in particular the second swivel joint  559 , is situated spaced radially apart from the intermediate shaft axis  507   a . Preferably, the counter-oscillator mass  533  is guided so that it can move axially along a path. In a particularly preferred way, this path is a straight line parallel to the impact axis  506 . 
     During operation, the intermediate shaft  507  drives the drive plate  556  to rotate, as a result of which the connecting rod  558  follows the rotary motion via the first swivel joint  557 . Due to the axial guidances of the counter-oscillator mass  533 , the motion of the connecting rod  558  at the second swivel joint  559  is transmitted in the form of an oscillating axial motion to the counter-oscillator mass  533 . The counter-oscillator  31  therefore behaves in a fashion analogous to the already known embodiments. 
     In this exemplary embodiment, a phase shift Δ is set by means of a circumference angle WU at which the first swivel joint  557  is situated on the drive plate  556  and by means of the position of the second swivel joint  559  relative to the first swivel joint  557 . It is necessary here to take into account the circumference angle WE of the eccentric pin  589  of the first stroke producing device  513 ,  513   b.    
     Modifications of this embodiment of a transmission device according to the invention are produced, among other things, in the embodiment of the swivel joints  557 ,  559  and/or of the connecting rod  558 . In addition, the counter-oscillator mass  533  can be embodied in a multitude of ways. In particular, the person skilled in the art can easily identify other advantageous combinations of the above-described exemplary embodiments. 
     In a particularly preferred modification, an adjusting device that acts on the raceway  26  of the second drive sleeve  24  is provided, which goes beyond the stroke adjustment for the stroke element  30   a  of the second stroke producing device  23  known from the first exemplary embodiment. It can therefore be advantageous for the adjusting device to adjust the rotational position of the raceway of the second drive sleeve  24  and therefore the phase shift Δ for the oscillating motion of the stroke element  30   a  of the first stroke producing device  13 . To that end, the shifting wedge could be asymmetrically embodied and either manually or by means of an actuator, could be changed in its rotational position relative to the machine housing  2 , in particular the impact plane. The person skilled in the art is aware of other ways to implement such an adjusting device. In particular, such an adjusting device can also be advantageously used in second stroke producing devices  23  that are embodied in the form of cam drives, end-surface cam drives, connecting rod drives, crank drives, or rocker arm drives. In these cases, a rotational position of the cam cylinder  343 , the cam plate  450 , the drive plate  556 , or the eccentric pin  663  can be varied by means of the adjusting device. 
     In another preferred modification of a transmission device according to the invention, a bearing device  8  is provided between the first stroke producing device  13  and the second stroke producing device  23 . The bearing device  8  in this case is affixed to the machine housing  2 . This bearing device  8  is used to support the intermediate shaft  7  in rotary fashion in the machine housing  2 . 
     The foregoing relates to the preferred exemplary embodiments of the invention, it being understood that other variants and embodiments thereof are possible within the spirit and scope of the invention, the latter being defined by the appended claims.