Patent Publication Number: US-9415498-B2

Title: Hammer mechanism

Description:
RELATED APPLICATION INFORMATION 
     The present application claims priority to and the benefit of German patent application no. 10 2010 062 099.8, which was filed in Germany on Nov. 29, 2010, the disclosure of which is incorporated herein by reference. 
     FIELD OF THE INVENTION 
     The present invention is directed to a hammer mechanism. 
     BACKGROUND INFORMATION 
     A hammer mechanism having a snap die, a tool chuck drive shaft, and an impact generating shutoff unit, which has a blocking element, which is provided for the purpose of preventing an axial displacement of the snap die, has already been proposed. 
     SUMMARY OF THE INVENTION 
     The exemplary embodiments and/or exemplary methods of the present invention is directed to a hammer mechanism having a snap die, a tool chuck drive shaft, and an impact generating shutoff unit, which has a blocking element, which is provided for the purpose of preventing an axial displacement of the snap die. 
     The blocking element acts parallel to at least one force of the tool chuck drive shaft on the snap die, at least during a drilling operation. A “snap die” is to be understood in particular as an element of the hammer mechanism which transmits an impact momentum from a striker in the direction of an insertion tool during impact operation. The snap die may strike directly on the insertion tool in at least one operating state. The snap die may prevent penetration of dust through a tool chuck into the hammer mechanism. A “tool chuck drive shaft” is to be understood in particular as a shaft which transmits a rotational movement from a gear, in particular a planetary gear, in the direction of the tool chuck during rotary and/or percussion drilling operation. The tool chuck drive shaft is advantageously at least partially configured as a solid shaft. The tool chuck drive shaft may extend over at least 40 mm in the striking direction. The tool chuck drive shaft and the tool chuck may have an equal rotational speed during rotary and/or percussion drilling operation, in particular always, i.e., in particular a drivetrain between the tool chuck drive shaft and the tool chuck is free of a gear. 
     An “impact generating shutoff unit” is to be understood in particular as a unit which is provided for the purpose of allowing an operator to shut off the impact generating unit for a drilling and/or screwing operation. The impact generating shutoff unit may prevent automatic activation in particular of the impact generating unit when the insertion tool is pressed against a workpiece in a drilling and/or screwing mode. Contact pressure in a chisel and/or percussion drilling mode may cause an axial displacement of the tool chuck drive shaft. 
     The blocking element is advantageously provided for the purpose of preventing an axial displacement of the tool chuck drive shaft, the tool chuck, and/or advantageously the snap die in the drilling and/or screwing mode. “Provided” is to be understood in particular as specially configured and/or equipped. The term “parallel to a force” is to be understood in particular to mean that the tool chuck drive shaft and the blocking element cause a force on the snap die at two different positions in at least one operating state. Alternatively or additionally, the tool chuck drive shaft and the blocking element may exert a force on the tool chuck at two different positions in at least one operating state. The forces may have a component oriented in the same direction, which may be parallel to the rotational axis of the tool chuck drive shaft, from the tool chuck drive shaft in the direction toward the tool chuck. The blocking element may act directly on the snap die, however, which may particularly be at least via one tool chuck bearing. The tool chuck drive shaft may act directly on the snap die. The snap die may transmit a rotational movement from the tool chuck drive shaft to the tool chuck. Through the embodiment according to the present invention, an advantageous arrangement of an operating element of the impact generating shutoff unit may be achieved with a simple configuration. In particular, a ring-shaped operating element, which encloses the snap die or the tool chuck drive shaft, is easily implementable. In addition, little installation space is required with this configuration. 
     In another embodiment, it is proposed that the impact generating shutoff unit have a sliding guide, which is provided for the purpose of moving the blocking element, whereby low production costs and a high level of robustness may be achieved. A “sliding guide” is to be understood in particular as a device in which a bevel of an element presses the blocking element from one position into another position in the event of a movement of the element. A “bevel” is to be understood in particular as an inclined face of the element in relation to a direction of the movement. The sliding guide may have a face which axially fixes the tool chuck via the blocking element in at least one operating state. 
     Furthermore, it is proposed that the impact generating shutoff unit have a rotatably mounted operating element, whereby a particularly ergonomic operation is possible. A “rotatably mounted operating element” is to be understood in particular as an element, using which the hammer mechanism may be switched from one operating mode into another operating mode by a rotational movement of the operating element. The operating element may enclose a rotational axis of the tool chuck drive shaft. The operating element may be rotatable around an axis which is oriented parallel to the tool chuck drive shaft. 
     Furthermore, it is proposed that the hammer mechanism have a housing element, which is provided for the purpose of mounting the blocking element in a rotationally fixed manner, whereby a configuration having a particularly simple configuration is possible. The term “mount in a rotationally fixed manner” is to be understood in particular to mean that the blocking element is mounted so it is translationally movable. 
     In an advantageous embodiment of the present invention, it is proposed that the hammer mechanism have a striker, which mounts the tool chuck drive shaft so it is movable in the striking direction in at least one operating state, whereby a low weight and a small overall size are possible. In particular, the term “striker” is to be understood as an arrangement of the hammer mechanism, which is provided for the purpose of being translationally accelerated in particular during operation by the impact generating unit and delivering a momentum absorbed during the acceleration as an impact momentum in the direction of the insertion tool. The striker may be mounted so it may be accelerated in the striking direction by an air pressure or advantageously by a rocker. The striker may be unaccelerated immediately before an impact. The striker may deliver an impact momentum in the direction of the insertion tool, in particular via a snap die, to the insertion tool in the case of an impact. A “rocker” is to be understood in particular as an arrangement which is mounted movably around a pivot axis and which is provided for the purpose of delivering power absorbed on a first coupling area to a second coupling area. A “striking direction” is to be understood in particular as a direction which runs parallel to a rotational axis of the tool chuck and is oriented from the striker in the direction toward the tool chuck. The striking direction may be oriented parallel to a rotational axis of the tool chuck drive shaft. The term “mounted so it is movable” is to be understood in particular to mean that the tool chuck drive shaft has a bearing surface, which transmits bearing forces perpendicularly to the striking direction onto the striker in at least one operating state. 
     Furthermore, it is proposed that the tool chuck drive shaft at least partially penetrate the striker, whereby a tool chuck drive shaft may be provided having a particularly small mass and a small installation space requirement. In particular, the term “at least partially penetrate” is to be understood to mean that the striker encloses the tool chuck drive shaft by more than 270°, advantageously by 360°, on at least one plane, which is advantageously oriented perpendicularly to the striking direction. The striker may be fastened in a form-locked manner on the tool chuck drive shaft in a direction perpendicular to the rotational axis of the tool chuck drive shaft, i.e., mounted so it is movable in the direction of the rotational axis. 
     In addition, it is proposed that the hammer mechanism include at least one bearing, which is provided for the purpose of mounting the tool chuck drive shaft so it is axially displaceable, whereby an impact mechanism shutoff having a simple configuration is possible. A “bearing” is to be understood in particular as a device which fastens the tool chuck drive shaft in particular so it is movable at least around the rotational axis and axially displaceable in relation to a housing. “Axially displaceable” is to be understood in particular to mean that the bearing fastens the tool chuck drive shaft so it is movable parallel to the striking direction, in particular in relation to a housing. A connection of the coupling arrangement of the tool chuck drive shaft, which drives the impact generating unit, may be disengaged by an axial displacement of the tool chuck drive shaft. 
     Furthermore, it is proposed that the hammer mechanism have a planetary gear, which drives the tool chuck drive shaft in at least one operating state, whereby an advantageous transmission ratio may be achieved in a small space. Furthermore, torque limiting and multiple gear stages may be implemented with a simple configuration. A “planetary gear” is to be understood in particular as a unit having at least one planet wheel set. A planet wheel set may have a sun wheel, an annulus gear, a planet wheel carrier, and at least one planet wheel guided by the planet wheel carrier on an orbit around the sun wheel. The planetary gear may have at least two transmission ratios, which are selectable by an operator, between an input and an output of the planetary gear. 
     Furthermore, it is proposed that the snap die have a coupling arrangement, which is provided for transmitting a rotational movement to a tool chuck, whereby a particularly compact hammer mechanism may be provided. The snap die advantageously transmits a rotational movement of the tool chuck drive shaft to the tool chuck. The term “tool chuck” is to be understood in particular as a device which is provided for the purpose of directly fastening an insertion tool so it may be disengaged by an operator in particular without tools, and at least in a rotationally fixed manner. 
     Furthermore, it is proposed that the hammer mechanism include an impact generating unit and a coupling arrangement, which is connected in a rotationally fixed manner to the tool chuck drive shaft and which is provided for the purpose of driving the impact generating unit, whereby a particularly compact and high-performance hammer mechanism may be provided with a simple configuration. An “impact generating unit” is to be understood in particular as a unit which is provided for the purpose of converting a rotational movement into an impact movement of the striker, in particular a translational movement, which is suitable for rotary and percussion drilling operation. In particular, the impact generating unit is configured as an impact generating unit which appears meaningful to a person skilled in the art, but which may be configured as a pneumatic impact generating unit and/or which may particularly be configured as an impact generating unit having the rocker. 
     A “coupling arrangement” is to be understood in particular as a arrangement which is provided for the purpose of transmitting a movement from one component to another component at least by a form lock. The form lock may be configured in such a way that it may be disengaged by the operator in at least one operating state. The form lock may particularly be disengaged to switch over an operating mode, advantageously between screwing operation, drilling operation, chisel operation, and/or percussion drilling operation. In particular, the coupling arrangement is configured as a coupling which appears meaningful to a person skilled in the art, but advantageously as a claw coupling and/or a gearing. The coupling arrangement advantageously has multiple form-locked elements and an area which connects the form-locked elements. In particular, the term “rotationally fixed” is to be understood to mean that the coupling arrangement and the tool chuck drive shaft are fixedly connected to one another at least in the peripheral direction, which may be in every direction, and in particular in every operating state. In particular, “driving” is to be understood in this context to mean that the coupling arrangement transmits a kinetic energy, in particular a rotational energy, to at least one area of the impact generating unit. The impact generating unit may drive the striker using this energy. Through the embodiment according to the present invention, a particularly compact and high-performance hammer mechanism may be provided, having a simple configuration. 
     In addition, the hammer mechanism has a spur gear stage, which converts a rotational speed of the tool chuck drive shaft into a higher rotational speed for impact generation, whereby a particularly advantageous ratio between rotational speed and impact count of an insertion tool may be achieved with a simple configuration and in a space-saving way. A “spur gear stage” is to be understood in particular as an arrangement of two meshing gearwheels in particular, which are mounted rotatably around parallel axes. The gearwheels may have a gearing on a surface facing away from their axis. In particular, a “rotational speed for impact generation” is to be understood as a rotational speed of a drive arrangement, which appears meaningful to a person skilled in the art, of the impact generating unit, which converts a rotational movement into a linear movement. The drive arrangement of the impact generating unit may be configured as a wobble bearing or particularly may be configured as an eccentric element. “Converting” is to be understood here to mean that the rotational speed of the tool chuck drive shaft and the rotational speed for impact generation differ. The rotational speed for impact generation may be greater, advantageously at least twice as great as the rotational speed of the tool chuck drive shaft. A transmission ratio of the rotational speed for impact generation to the rotational speed of the tool chuck drive shaft particularly may be a non-integer number. 
     Furthermore, the hammer mechanism includes a torque limiting device, which is provided for the purpose of limiting a maximum torque which may be transmitted via the tool chuck drive shaft, whereby the operator is advantageously protected and the handheld tool may be used comfortably and efficiently for screwing. “Limiting” is to be understood in particular in this context to mean that the torque limiting device prevents the maximum torque, which is settable in particular by an operator, from being exceeded. The torque limiting device may open a connection between a drive motor and the tool chuck, which is rotationally fixed during operation. Alternatively or additionally, the torque limiting device may act on a power supply of the drive motor. 
     Furthermore, a handheld tool having a hammer mechanism according to the present invention is described. A “handheld tool” is to be understood in this context in particular as a handheld tool which appears meaningful to a person skilled in the art, but which may be a drill, a rotary hammer drill, an electric screwdriver, a drill chisel, and/or a percussion hammer. The handheld tool may be configured as a battery-powered handheld tool, i.e., in particular the handheld tool has a coupling arrangement, which is provided for the purpose of supplying a drive motor of the handheld tool with electrical power from a handheld tool battery connected to the coupling arrangement. 
     Further advantages result from the following description of the drawings. Five exemplary embodiments of the present invention are shown in the drawings. The drawings, the description, and the claims contain numerous features in combination. A person skilled in the art will advantageously also consider the features individually and combine them into meaningful further combinations. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a handheld tool having a hammer mechanism according to the present invention in a perspective view. 
         FIG. 2  shows a section of the hammer mechanism from  FIG. 1 . 
         FIG. 3  shows a coupling arrangement, a tool chuck drive shaft, a snap die, and a part of a tool chuck of the hammer mechanism from  FIG. 1 , each shown individually in a perspective view. 
         FIG. 4  shows another partial section of the hammer mechanism from  FIG. 1 , which shows an impact generating shutoff unit of the hammer mechanism. 
         FIG. 5  shows a first alternative exemplary embodiment of a snap die of the hammer mechanism from  FIG. 1  in a schematic view. 
         FIG. 6  shows a second alternative exemplary embodiment of a snap die of the hammer mechanism from  FIG. 1  in a schematic view. 
         FIG. 7  shows a third alternative exemplary embodiment of a snap die of the hammer mechanism from  FIG. 1  in a sectional view. 
         FIG. 8  shows the snap die from  FIG. 7  in a first perspective view. 
         FIG. 9  shows the snap die from  FIG. 7  in a second perspective view. 
         FIG. 10  shows a part of a tool chuck of the hammer mechanism from  FIG. 7  in a perspective view. 
         FIG. 11  shows a fourth alternative exemplary embodiment of a snap die of the hammer mechanism from  FIG. 1  in a schematic view. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a handheld tool  10   a , which is configured as a rotary hammer drill. Handheld tool  10   a  has a pistol-shaped housing  12   a . A drive motor  14   a  of handheld tool  10   a  is situated in housing  12   a . Housing  12   a  has a handle area  16   a  and a battery coupling arrangement  18   a , which is situated on an end of handle area  16   a  facing away from drive motor  14   a . Battery coupling arrangement  18   a  couples a handheld tool battery  20   a  in a way which may be electrically and mechanically disconnected by an operator. Handheld tool battery  20   a  has an operating voltage of 10.8 V, but may also have a different, in particular a higher, operating voltage. Furthermore, handheld tool  10   a  has a hammer mechanism  22   a  according to the present invention, having an externally situated tool chuck  24   a  and operating elements  26   a ,  28   a.    
       FIG. 2  shows hammer mechanism  22   a  in a sectional view. Furthermore, hammer mechanism  22   a  includes a planetary gear  30   a  and a tool chuck drive shaft  32   a . Planetary gear  30   a  drives tool chuck drive shaft  32   a  to rotate around an rotational axis during operation. For this purpose, planetary gear  30   a  has three planetary gear stages  34   a ,  36   a ,  38   a . A transmission ratio of planetary gear  30   a  between a rotor  40   a  of drive motor  14   a  and tool chuck drive shaft  32   a  is settable by an operator in at least two stages. Alternatively, a transmission ratio between drive motor  14   a  and tool chuck drive shaft  32   a  may be nonadjustable. 
     Hammer mechanism  22   a  has a torque limiting device  42   a . Torque limiting device  42   a  holds an annulus gear  44   a  of planetary gear  30   a  fixed during operation. For this purpose, torque limiting device  42   a  has fixation balls  46   a , which engage in recesses of annulus gear  44   a . A spring  48   a  of torque limiting device  42   a  exerts a force on fixation balls  46   a  in the direction of annulus gear  44   a  for this purpose. An end of spring  48   a  facing toward fixation balls  46   a  is movable in the direction of fixation balls  46   a  by an operator with the aid of one of operating elements  26   a . For this purpose, operating element  26   a  has an eccentric element. The force acting on fixation balls  46   a  is therefore settable. When a certain maximum torque is reached, fixation balls  46   a  are pressed out of the recesses and annulus gear  44   a  runs free, whereby a force transmission between rotor  40   a  and tool chuck drive shaft  32   a  is interrupted. Torque limiting device  42   a  is therefore provided for the purpose of limiting a maximum torque transmittable via tool chuck drive shaft  32   a.    
     Hammer mechanism  22   a  has an impact generating unit  50   a  and a first coupling arrangement  52   a . First coupling arrangement  52   a  is connected in a rotationally fixed manner to tool chuck drive shaft  32   a ; in fact, first coupling arrangement  52   a  and tool chuck drive shaft  32   a  are formed in one piece. Impact generating unit  50   a  has a second coupling arrangement  54   a , which is connected in a rotationally fixed manner to first coupling arrangement  52   a  in a rotary and/or percussion drilling mode. As also shown in  FIG. 3 , first coupling arrangement  52   a  is configured as molds and second coupling arrangement  54   a  is configured as recesses. In the event of an activation of the drilling mode, first coupling arrangement  52   a  plunges completely into second coupling arrangement  54   a . The coupling between first coupling arrangement  52   a  and second coupling arrangement  54   a  may therefore be disengaged by an axial displacement of tool chuck drive shaft  32   a  in the direction of tool chuck  24   a . A spring  56   a  of hammer mechanism  22   a  is situated between first coupling arrangement  52   a  and second coupling arrangement  54   a . Spring  56   a  presses tool chuck drive shaft  32   a  in the direction of tool chuck  24   a . The spring opens the coupling between first coupling arrangement  52   a  and second coupling arrangement  54   a  when impact generating unit  50   a  is shut off. 
     Hammer mechanism  22   a  has a first bearing  58   a , which fixes second coupling arrangement  54   a  in relation to housing  12   a  in the axial direction and mounts it so it is rotatable coaxially to tool chuck drive shaft  32   a . Furthermore, hammer mechanism  22   a  has a second bearing  60   a , which mounts tool chuck drive shaft  32   a  so it is rotatable around the rotational axis on a side facing toward drive motor  14   a . Second bearing  60   a  is formed in one piece with one of three planetary gear stages  38   a . Tool chuck drive shaft  32   a  has a coupling arrangement  62   a , which connects it in an axially displaceable and rotationally fixed manner to a planet wheel carrier  64   a  of this planetary gear stage  38   a . This planetary gear stage  38   a  is therefore provided for the purpose of mounting tool chuck drive shaft  32   a  so it is axially displaceable. On a side facing toward tool chuck  24   a , tool chuck drive shaft  32   a  is mounted by a tool chuck bearing  70   a  so it is rotatable together with tool chuck  24   a . Tool chuck bearing  70   a  has a rear bearing element, which is pressed in an axially fixed manner on tool chuck  24   a . Furthermore, tool chuck bearing  70   a  has a front bearing element, which mounts tool chuck  24   a  so it is axially displaceable in housing  12   a.    
     Impact generating unit  50   a  includes a spur gear stage  72   a , which converts a rotational speed of tool chuck drive shaft  32   a  into a higher rotational speed for impact generation. A first gearwheel  74   a  of spur gear stage  72   a  is formed in one piece with second coupling arrangement  54   a . During a percussion drilling operation, it is driven by tool chuck drive shaft  32   a . A second gearwheel  76   a  of spur gear stage  72   a  is formed in one piece with an impact mechanism shaft  78   a . A rotational axis of impact mechanism shaft  78   a  is situated adjacent in the radial direction to the rotational axis of tool chuck drive shaft  32   a . Impact generating unit  50   a  has two bearings  80   a , which mount the impact mechanism shaft  78   a  so it is rotatable and axially fixed. Impact generating unit  50   a  has a drive arrangement  82   a , which converts a rotational movement of impact mechanism shaft  78   a  into a linear movement. An eccentric element  84   a  of drive arrangement  82   a  is formed in one piece with impact mechanism shaft  78   a . An eccentric sleeve  86   a  of drive arrangement  82   a  is rotatably mounted on eccentric element  84   a  in relation to eccentric element  84   a , with the aid of a needle bearing. Eccentric sleeve  86   a  has a recess  88   a , which encloses a rocker  90   a  of impact generating unit  50   a.    
     Rocker  90   a  is mounted so it is pivotable on a tilt axis  92   a  of impact generating unit  50   a , specifically pivotable around an axis which is oriented perpendicularly to the rotational axis of tool chuck drive shaft  32   a . An end of rocker  90   a  facing away from drive arrangement  82   a  partially encloses a striker  94   a  of hammer mechanism  22   a . The rocker engages in a recess  96   a  of striker  94   a . Recess  96   a  is configured in a ring shape. During a percussion drilling operation, rocker  90   a  causes a force on striker  94   a  which accelerates it. Rocker  90   a  is moved sinusoidally during operation. Rocker  90   a  has a resilient configuration. It has a spring constant between eccentric sleeve  86   a  and striker  94   a  of less than 100 N/mm and greater than 10 N/mm. In this exemplary embodiment, rocker  90   a  has a spring constant of approximately 30 N/mm. 
     Tool chuck drive shaft  32   a  mounts striker  94   a  movably in striking direction  98   a . For this purpose, striker  94   a  delimits a recess  100   a . Tool chuck drive shaft  32   a  penetrates striker  94   a  through recess  100   a . Striker  94   a  encloses recess  100   a  over 360° in a plane perpendicular to recess  100   a . During operation, striker  94   a  strikes a snap die  102   a  of hammer mechanism  22   a . Snap die  102   a  is situated between an insertion tool  104   a  and striker  94   a . In an operationally ready state, insertion tool  104   a  is fastened in tool chuck  24   a . Tool chuck  24   a  mounts snap die  102   a  so it is movable parallel to striking direction  98   a . Snap die  102   a  relays impact momentum, which comes from striker  94   a  during a percussion drilling operation, to insertion tool  104   a.    
     Tool chuck drive shaft  32   a  is connected to snap die  102   a  so it is axially movable and rotationally fixed. For this purpose, snap die  102   a  delimits a recess  106   a . In an operationally ready state, tool chuck drive shaft  32   a  is partially situated in recess  106   a  of snap die  102   a . Tool chuck drive shaft  32   a  is mounted rotatably via snap die  102   a , tool chuck  24   a , and tool chuck bearing  70   a . Tool chuck  24   a  is driven to rotate via snap die  102   a . For this purpose, tool chuck  24   a  and snap die  102   a  each have a coupling arrangement  108   a ,  110   a , the coupling arrangement being provided for transmitting the rotational movement to tool chuck  24   a . Coupling arrangement  108   a  of snap die  102   a  is configured as a groove, whose main extension is situated parallel to striking direction  98   a . Coupling arrangement  108   a  extends along a radial external lateral surface of snap die  102   a . Coupling arrangement  110   a  of tool chuck  24   a  is configured as a protrusion which matches the groove. 
     Tool chuck  24   a  has an insertion tool coupling area  112   a , in which insertion tool  104   a  is fastened so it is fixed in striking direction  98   a  during a drilling or screwing operation, or in which it is fastened so it is movable in striking direction  98   a  during a percussion drilling operation. In addition, the tool chuck has a taper  114   a , which delimits a movement range of snap die  102   a  in striking direction  98   a . Furthermore, tool chuck  24   a  has a fastening ring  116   a , which delimits a movement range of snap die  102   a  against striking direction  98   a.    
     During a percussion drilling procedure, an operator presses insertion tool  104   a  against a workpiece (not shown). The operator thus displaces insertion tool  104   a , snap die  102   a , and tool chuck drive shaft  32   a  in relation to housing  12   a  in a direction against striking direction  98   a , i.e., in the direction of drive motor  14   a . The operator compresses spring  56   a  of hammer mechanism  22   a . First coupling arrangement  52   a  plunges into second coupling arrangement  54   a , whereby tool chuck drive shaft  32   a  begins to drive impact generating unit  50   a . When the operator stops pressing insertion tool  104   a  against the workpiece, spring  56   a  displaces tool chuck drive shaft  32   a , snap die  102   a , and insertion tool  104   a  in striking direction  98   a . A rotationally fixed connection between first coupling arrangement  52   a  and second coupling arrangement  54   a  is thus opened, whereby impact generating unit  50   a  is shut off. 
     Hammer mechanism  22   a  has an impact generating shutoff unit  118   a  having a blocking element  120   a , a sliding guide  122   a , and an operating element  28   a . In a drilling or screwing mode, blocking element  120   a  causes a force on snap die  102   a  which acts on snap die  102   a  in parallel to at least one force of tool chuck drive shaft  32   a . The force of blocking element  120   a  acts on snap die  102   a  via tool chuck bearing  70   a , tool chuck  24   a , and fastening ring  116   a . Due to the force of blocking element  120   a , in a drilling or screwing mode, an axial displacement of snap die  102   a  and tool chuck drive shaft  32   a  and therefore an activation of impact generating unit  50   a  are prevented. The force of tool chuck drive shaft  32   a  has a component which is parallel in action, which drives snap die  102   a  to rotate during operation. In addition, the force has a component which is parallel in action and direction, which is caused by spring  56   a  via tool chuck drive shaft  32   a  on snap die  102   a.    
       FIG. 4  shows a section oriented perpendicularly to the section of  FIG. 2  and parallel to striking direction  98   a , operating element  28   a  being situated in two different positions in the sections of  FIGS. 2 and 4 . Operating element  28   a  is configured in a ring shape. It coaxially encloses the rotational axis of tool chuck drive shaft  32   a . Operating element  28   a  is rotatably mounted. It is connected in a rotationally fixed manner to sliding guide  122   a . Sliding guide  122   a  is also configured as ring-shaped. Sliding guide  122   a  has a bevel  124   a . Bevel  124   a  connects two faces  126   a ,  128   a  of sliding guide  122   a . Faces  126   a ,  128   a  are oriented perpendicularly to striking direction  98   a . Faces  126   a ,  128   a  are situated on different planes in striking direction  98   a.    
     In a percussion drilling mode, blocking element  120   a  is situated in a recess  130   a , which is delimited, inter alia, by bevel  124   a  and one of faces  126   a . This face  126   a  is situated closer to drive motor  14   a  than the other face  128   a . Housing  12   a  has a housing element  132   a , which mounts the blocking element so it is rotationally fixed and displaceable in striking direction  98   a . At the beginning of a percussion drilling procedure, blocking element  120   a  may thus be pressed together with tool chuck  24   a  in a direction against striking direction  98   a . During a percussion drilling procedure, blocking element  120   a  does not cause any blocking force on tool chuck  24   a . During a rotation of operating element  28   a  of impact generating shutoff unit  118   a , blocking element  120   a  is moved by bevel  124   a  in striking direction  98   a . Blocking element  120   a  is held in this forward position in the drilling or screwing mode. Blocking element  120   a  thus prevents an axial displacement of tool chuck drive shaft  32   a  in the drilling or screwing mode. 
     Further exemplary embodiments of the present invention are shown in  FIGS. 5 through 11 . The following descriptions and the drawings are essentially restricted to the differences between the exemplary embodiments, reference fundamentally being able to be made to the drawings and/or the description of the other exemplary embodiments, in particular of  FIGS. 1 through 4 , with respect to identically identified components, in particular with respect to components having identical reference numerals. To differentiate the exemplary embodiments, the letter a follows the reference numerals of the exemplary embodiment in  FIGS. 1 through 4 . In the exemplary embodiments of  FIGS. 5 through 11 , the letter a is replaced by the letters b through e. 
       FIG. 5  shows a part of a hammer mechanism  22   b . A striker  94   b  of an impact generating unit  50   b  of hammer mechanism  22   b  is mounted so it is movable on a tool chuck drive shaft  32   b  of hammer mechanism  22   b . Tool chuck drive shaft  32   b  is connected to a snap die  102   b  of hammer mechanism  22   b  so it is axially displaceable and rotationally fixed. Snap die  102   b  has a coupling arrangement  108   b , which forms a rotationally fixed connection to a tool chuck  24   b  of hammer mechanism  22   b  in at least one operating state. Coupling arrangement  108   b  is situated on a side which faces toward a taper  114   b  of tool chuck  24   b . Coupling arrangement  108   b  is configured as a gearing. A sealing area  134   b  of the snap die presses without a gearing against tool chuck  24   b  and advantageously prevents penetration of dust into impact generating unit  50   b.    
     Like  FIG. 5 ,  FIG. 6  schematically shows a part of a hammer mechanism  22   c . A striker  94   c  of an impact generating unit  50   c  of hammer mechanism  22   c  is mounted so it is movable on a tool chuck drive shaft  32   c  of hammer mechanism  22   c . Tool chuck drive shaft  32   c  is connected to a snap die  102   c  of hammer mechanism  22   c  so it is axially displaceable and rotationally fixed. Snap die  102   c  has a coupling arrangement  108   c , which forms a rotationally fixed connection to a tool chuck  24   c  of hammer mechanism  22   c  in at least one operating state. Tool chuck  24   c  has an insertion tool coupling area  112   c , in which coupling arrangement  108   c  of snap die  102   c  at least partially engages. Insertion tool coupling area  112   c  is provided for the purpose of causing forces to be applied in the peripheral direction on an insertion tool during operation. In an operationally ready state, coupling arrangement  108   c  is at least partially situated inside a taper  114   c  of tool chuck  24   c . Coupling arrangement  108   c  is configured as an external hexagon. The dimensions of the external hexagon correspond to those typically had by a bit for a screwing operation. A sealing area  134   c  of snap die  102   c  presses without a gearing against tool chuck  24   c  and, in an advantageous way which may be produced cost-effectively, prevents penetration of dust into impact generating unit  50   c . In particular, a grease loss may be minimized. 
       FIGS. 7 through 10  also show a part of a hammer mechanism  22   d  as a section and in perspective. A striker  94   d  of an impact generating unit  50   d  of hammer mechanism  22   d  is mounted so it is movable on a tool chuck drive shaft  32   d  of hammer mechanism  22   d . Tool chuck drive shaft  32   d  is connected so it is axially displaceable and rotationally fixed to a snap die  102   d  of hammer mechanism  22   d . Snap die  102   d  has a coupling arrangement  108   d , which forms a rotationally fixed connection to a tool chuck  24   d  of hammer mechanism  22   d  in at least one operating state. In an operationally ready state, coupling arrangement  108   d  is at least partially situated inside a taper  114   d  of tool chuck  24   d . Coupling arrangement  108   d  is configured as a gearing having two coupling ribs which are diametrically opposite with respect to a rotational axis. Coupling arrangement  108   d  has the same shape and the same dimensions as a coupling arrangement for coupling to an insertion tool. The shape and the dimensions correspond to the SDS-Quick standard. A sealing area  134   d  of snap die  102   d  presses without a gearing against tool chuck  24   d.    
     Like  FIG. 5 ,  FIG. 11  schematically shows a part of a hammer mechanism  22   e . A striker  94   e  of an impact generating unit  50   e  of hammer mechanism  22   e  is mounted so it is movable on a tool chuck drive shaft  32   e  of hammer mechanism  22   e . Tool chuck drive shaft  32   e  is connected so it is axially fixed and rotationally fixed to a snap die  102   e  of hammer mechanism  22   e . Tool chuck drive shaft  32   e  and snap die  102   e  are formed in one piece. During an impact, striker  94   e  moves tool chuck drive shaft  32   e  and snap die  102   e  jointly in striking direction  98   e . Tool chuck drive shaft  32   e  is connected with the aid of a coupling arrangement  62   e , so it is axially displaceable and rotationally fixed, to a planetary gear stage described in the exemplary embodiment of  FIGS. 1 through 4 .