Abstract:
The invention is based on a hand power tool, in particular a hammer drill, with a drivable drive mechanism ( 12 ) accommodated in a housing ( 10 ) and a mechanical hammer unit ( 14 ), which is for percussion-driving a tool ( 16 ) in a tool holding fixture ( 18 ) and has a hammer ( 20 ) that can be driven in its hammering motion by a driver unit ( 22 ), which has at least one annular curved path ( 24, 26 ) with raised areas and recessed areas oriented axially toward the tool and has a feeler unit ( 28 ), which is operationally connected to the hammer ( 20 ) and which, by at least one feeler element ( 30 ), can be brought into operational connection with the raised areas and recessed areas of the curved path ( 24, 26 ). 
     The invention proposes that the feeler unit ( 28 ) has at least two feeler elements ( 30 ) that can be brought into operational connection with the curved path ( 24, 26 ).

Description:
BACKGROUND OF THE INVENTION 
     The invention is based on hand power tool. 
     DE 197 26 383 A1 has disclosed a hand power tool that defines the species, specifically an electrically driven hammer drill. The hammer drill has a rotary driven working spindle that is supported in a housing and in turn drives a tool holding fixture of a tool. The hammer drill also has a mechanical hammer unit with a hammer, which can move axially inside the working spindle embodied as a hollow shaft and can be accelerated in the axial direction, and which acts directly or indirectly on a shaft of the tool during operation. The hammer is acted on by a driver unit, which converts a rotary motion of the working spindle into an axial acceleration of the hammer. 
     The driver unit has a feeler unit that can move axially and rotates synchronously with the working spindle and that is guided with axial play between two annular curved paths, which do not rotate in relation to the working spindle and have raised areas and recessed areas oriented toward each other in the axial direction of the working spindle. The feeler unit is constituted by an annular component, which can be moved on the hammer in the axial direction, counter to a compression spring and which has a feeler element extending radially outward, which reaches through a slot in the working spindle between the curved paths and can thus bring the feeler unit into an operative connection with the curved paths. 
     For a switching on and off of the hammer unit, the curved path oriented toward the tool is supported so that it can move axially in tandem with the working spindle. If the tool is pressed against a working surface, the working spindle at the curved path oriented toward the tool is slid axially toward the curved path oriented away from the tool, counter to an idling spring embodied as a compression spring so that the feeler element comes into contact with the two curved paths during a rotating motion. The hammer unit is switched on. 
     If the tool is lifted up from the working surface, the curved path oriented toward tool and the working spindle are restored to their initial position by the idling spring. The distance between the two curved paths is thereby enlarged to such an extent that the feeler element in rotate freely between the two curved paths, without coming into contact with them. The hammer unit is switched off. 
     SUMMARY OF THE INVENTION 
     The invention is based on a hand power tool, in particular a hammer drill, with a drivable drive mechanism accommodated in a housing and a mechanical hammer unit, which is for percussion-driving a tool in a tool holding fixture and has a hammer that can be driven in its hammering motion by means of a driver unit, which has at least one curved path with raised areas and recessed areas oriented axially toward the tool and has a feeler unit, which is operationally connected to the hammer and which, by means of at least one feeler element, can be brought into operational connection with the raised areas and recessed areas of the curved path. 
     The invention proposes that the feeler unit has at least two and preferably three or more feeler elements that can be brought into operational connection with the curved path. A tilting moment on the feeler unit and the hammer can be prevented and a centering of the feeler unit on the curved path can be achieved. The efficiency can be increased and the wear can the reduced. 
     If the feeler elements have at least one sloped surface at least partly oriented in the rotation direction and/or counter to the rotation direction, the feeler elements can be advantageously guided with a minimum of wear from a recessed area of a curved path onto a raised area of the curved bath and from a raised area of the curved path into a recessed area of the curved path. A tilting contact between the feeler elements and the curved paths can be prevented. The sloped surfaces can, for example, be constituted by a concavely curving sloped surface or by a phase. 
     In order to assure a reliable engagement and disengagement of the hammer unit and to assure a reliable neutral position, when in this neutral position, a respective stop limits the movement of the feeler elements of the feeler unit in the axial direction toward at least one curved path, or when there are two curved paths, advantageously limits this movement of the feeler elements in the axial direction toward both functional curved paths. If the drive mechanism is supported in an axially mobile fashion, and if a stop is constituted by a device affixed to the drive mechanism, for example a securing ring, a shoulder formed onto the drive mechanism, or the like, then a disengaging movement of the drive mechanism can be advantageously used to correspondingly position a stop in order to limit the movement of the feeler elements of the feeler unit. 
     Another embodiment of the invention proposes that a stop is constituted by a component, which, when the hammer unit is in a hammering position, forms a part of curved path, which permits an embodiment that is particularly compact and lightweight to be produced. This can be achieved in a structurally simple manner particularly in that the component is comprised of a ring with openings, which extend in the circumference direction and are separated by struts, and in the hammering position, partial regions of the curved paths protrude through the openings, the struts plunge into recesses between the partial regions, and form a part of the curved path. 
     Instead of two curved paths between which the feeler unit is disposed, the driver unit can also be embodied with only one curved path, one whose raised areas and recessed areas are oriented axially toward the tool. The device must be balanced in such a way that the feeler unit is moved back toward the curved path by a spring and/or by the hammer rebounding off a stop surface. This permits additional components, space, and weight to be saved in comparison to a driver unit with two curved paths. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further advantages ensue from the following description of the drawings. The drawings show an exemplary embodiment of the invention. The drawings, the specification, and the claims contain numerous features in combination. One skilled in the art will also suitably consider the features individually and unite them in other meaningful combinations. 
     FIG. 1 shows a side view of a hammer drill, 
     FIG. 2 shows a sectional view of an enlarged detail II from FIG. 1, 
     FIG. 3 shows a detail of a hammer unit from FIG. 2 during hammering operation, 
     FIG. 4 shows a section along the line IV—IV in FIG. 3, 
     FIG. 5 shows a section along the line V—V in FIG. 4, and 
     FIG. 6 shows a curved path with an annular component that constitutes a stop. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 shows a hammer drill in a side view, with a drive mechanism  12  (FIGS. 2 and 3) embodied as a spindle, which can be driven to rotate in a housing  10  by an electric motor that is not shown in detail. The hammer drill has a mechanical hammer unit  14  for percussion-driving a drill bit  16 , which is held in a tool holding fixture  18 . The hammer unit  14  has a hammer  20 , which can be driven in its hammering motion by a driver unit  22  and is movably supported in the drive mechanism  12 , which is embodied as a hollow shaft. On an end oriented toward the tool holding fixture  18 , the drive mechanism  12  is supported by a needle bearing  104  that encompasses the drive mechanism. At an end oriented away from the tool holding fixture  18 , the drive mechanism  12  is supported by a ball bearing  108 , which is disposed on a plastic bearing journal  106  that is formed onto the housing  10  and extends radially inside the drive mechanism  12 , which permits space to be saved. Alternative slide bearings  104   a  and  108   a  are shown in the lower half; the slide bearing  108   a  remote from the tool holding fixture  18  is disposed on a separate metal bearing journal  106   a  that is press-fitted into the housing  10 . 
     The driver unit  22  has two annular curved paths  24 ,  26  non-rotatably situated in the housing  10 , which each have five sinusoidal recessed areas and raised areas oriented toward each other in the axial direction of the drive mechanism  12 . In principle, however, it is also conceivable for there to be a larger or smaller number of raised areas and recessed areas. Furthermore, curved paths can be used, which have different amplitudes and/or curve progressions, for example curves that also deviate from a sinusoidal form. In a hand power tool with a tool that is stationary in the rotation direction, curved paths with only one raised area and one recessed area would actually also be conceivable. 
     Between the curved paths  24 ,  26 , there is a feeler unit  28 , which can be driven to rotate. The feeler unit  28  is comprised of an annular component that has five strut-shaped feeler elements  30  extending radially outward and distributed evenly over the circumference and has two strut-shaped driver elements  52  extending radially inward (FIG.  4 ). 
     The component comprising the feeler unit  28 , with its driver elements  52  extending radially inward, reaches between two sliding rings  64  disposed on the hammer  20 . The feeler unit  28  is supported so that it can rotate between the sliding rings  64  and so that it can be moved axially on the hammer  20  by the sliding rings  64 , between two helical compression springs  54 ,  56  (FIGS.  2  and  3 ). In principle, a feeler unit and a hammer could also be non-rotatably connected to each other. The helical compression spring  54  closer to the tool holding fixture  18  is supported, in the direction oriented toward the tool holding fixture  18 , against a stop  58  formed onto the hammer  20  and acts on the feeler unit  28  in the direction oriented away from the tool holding fixture  18  by means of a sliding ring  64 . The helical compression spring  56  remote from the tool holding fixture  18  is supported, in the direction oriented away from the tool holding fixture  18 , against the hammer  20  by means of a spring support  60  and by means of a securing ring  62  fastened to the hammer  20  and acts on the feeler unit  28  in the direction oriented toward the tool holding fixture  18  by means of a sliding ring  64 . The helical compression springs  54 ,  56  are prestressed toward each other. 
     In addition, the feeler unit  28 , with its feeler elements  30  extending radially outward, reaches through slot-shaped openings  66  extending axially in the drive mechanism  12  and is form-fittingly connected in the rotation direction  32  to the drive mechanism  12 . By means of the feeler elements  30 , the feeler unit  28  remains operationally connected to the curved paths  24 ,  26  during a hammering operation. In lieu of a feeler unit that can be driven to rotate, in principle, the curved paths could also be designed so that they could be driven to rotate. 
     In order to keep the wear between the feeler elements  30  and the curved paths  24 ,  26  as low as possible, the feeler elements  30  have sloped surfaces  34 ,  36 , which are comprised of phases, oriented toward the two curved paths  24 ,  26 , in the rotation direction  32  and counter to the rotation direction  32 . 
     The drive mechanism  12  is supported so that can be moved in the axial direction along with the tool holding fixture  18 . If the hammer drill is pressed with the drill bit  16  against a working surface, the drill bit  16 , together with the tool holding fixture  18  and the drive mechanism  12 , is slid into the housing  10 , as shown in the upper half of FIG. 2 down to the center line of the drive mechanism  12 . By means of a securing ring  68  and an axial bearing  70 , the drive mechanism  12  acts in the axial direction on a cup-shaped sleeve (FIG.  3 ). The sleeve is fixed in the rotation direction in the housing  10  by means of cylindrical pins  82  and is supported so that it can slide in the axial direction (FIGS.  2  and  3 ). 
     The cup-shaped sleeve extends axially with its cup wall in the direction oriented away from the tool holding fixture  18 , and a part of the front curved path  24  is formed onto an end of the cup wall oriented toward the feeler unit  28 . A helical compression spring  72 , which is disposed in the sleeve, radially encompasses the drive mechanism  12 , and is supported, in the direction oriented away from the tool holding fixture  18 , against an annular spring plate  44  affixed to the housing, acts on the bottom of the sleeve in the direction toward the tool holding fixture  18 . By means of the drive mechanism  12 , the sleeve and along with it, a part of the front curved path  24 , is slid counter to the helical compression spring  72  until the sleeve strikes against the spring plate  44 . 
     If the sleeve is slid into its end position oriented away from the tool holding fixture  18 , partial regions  50  of the curved path  24  formed onto the end of the sleeve reach through circumferentially extending openings  48  of the spring plate  44  (FIG.  6 ). The openings  48  are separated by struts  46 , and in the end position or hammering position, plunge into recesses  74  in the cup wall of the cup-shaped sleeve, between the partial regions  50 , and form a part of the curved path  24 . 
     In the hammering position, the rotary driven feeler unit  28  comes into contact with the curved paths  24 ,  26  by means of its feeler elements  30  and drives the hammer  20  in a translatory fashion by means of the helical compression springs  54 ,  56 . The hammer  20  acts in a translatory fashion on a snap  76 , which strikes against an end of the drill bit  16  oriented toward the housing  10 . The hammer unit  14  is switched on. Depending on the design, the feeler unit  28  leaves the curved path  26 , which is oriented away from the tool holding fixture  18 , before or after a dead center of the tool. It is also possible for there to be a design in which the feeler unit  28  continuously travels on the curved path  26  in a steady state. In lieu of a stop on the drill bit  16 , it would also be conceivable for a hammer or a snap to strike directly or indirectly against a drive mechanism, a tool holding fixture, or another component viewed as suitable by one skilled in the art. 
     If the drill bit  16  is lifted up from the working surface, then by means of the sleeve bottom, the helical compression spring  72  slides the cup-shaped sleeve with the partial regions  50  of the curved path  24 , the drive mechanism  12 , and the tool holding fixture  18  with the drill bit  16  into their initial position, until the cup-shaped sleeve, with a radially outward extending collar  78  formed onto it, comes into contact with a stop  80  in the housing  10 . 
     The partial regions  50  of the curved path  24  thereby travel toward the tool holding fixture  18  through the openings  48  of the spring plate  44 , whose axial end oriented toward the feeler unit  28  constitutes a stop  38 , which, in the neutral position of the hammer unit  14 , limits the axial movement of the feeler unit  28  and its feeler elements  30  in the direction of the curved path  24  or the functional curved path  24 . 
     Along with the drive mechanism  12 , a device  42 , which is fastened to the drive mechanism  12  and is comprised of a securing ring, moves axially through the annular curved path  26 , which is oriented away from the tool holding fixture  18  and is affixed in the housing  10  axially and radially, and constitutes a second stop  40 , which limits the movement of the feeler unit  28  and its feeler elements  30  axially in the direction of the curved path  26  (FIG.  2 ). The stops  38 ,  40  reliably prevent a contact between the feeler elements  30  and the functional curved paths  24 ,  26  in the neutral position of the hammer unit  14 . 
     In the direction of the tool holding fixture  18 , the securing ring also supports a spring plate  84  for a locking spring  86 , which acts on a locking disk  88  in the direction oriented away from the tool holding fixture  18  (FIG.  2 ). With driver elements  90  oriented radially inward, the locking disk  88  engages in a form-fitting manner in the rotation direction in recesses of the drive mechanism  12  and on the side oriented away from the tool holding fixture  18 , has axially extending locking pins  92 . The locking pins  92  engage in a form-fitting manner in the rotation direction in recesses of a gear  94  that is supported in rotary fashion on the drive mechanism  12  and meshes with a pinion  102  formed onto a driveshaft  100 . In the direction oriented away from the tool holding fixture  18 , the gear  94  is supported on the drive mechanism  12  by a stop ring  96  and a securing ring  98 . 
     If an existing torque exceeds a particular value, the locking ring  18  can move out of the way in the axial direction toward the tool holding fixture  18 , counter to the locking spring  86 , the locking pins  92  can slide in the rotation direction over the recesses in the gear  94 , and a rotary drive of the drive mechanism  12  can be interrupted. 
     
       
         
               
             
               
               
             
           
               
                   
               
               
                 Reference Numerals 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 10 
                 housing 
               
               
                 12 
                 drive mechanism 
               
               
                 14 
                 hammer unit 
               
               
                 16 
                 tool 
               
               
                 18 
                 tool holding fixture 
               
               
                 20 
                 hammer 
               
               
                 22 
                 driver unit 
               
               
                 24 
                 curved path 
               
               
                 26 
                 curved path 
               
               
                 28 
                 feeler unit 
               
               
                 30 
                 feeler element 
               
               
                 32 
                 rotation direction 
               
               
                 34 
                 sloped surface 
               
               
                 36 
                 sloped surface 
               
               
                 38 
                 stop 
               
               
                 40 
                 stop 
               
               
                 42 
                 device 
               
               
                 44 
                 component 
               
               
                 46 
                 strut 
               
               
                 48 
                 opening 
               
               
                 50 
                 partial regions 
               
               
                 52 
                 driver element 
               
               
                 54 
                 helical compression spring 
               
               
                 56 
                 helical compression spring 
               
               
                 58 
                 shoulder 
               
               
                 60 
                 spring support 
               
               
                 62 
                 securing ring 
               
               
                 64 
                 sliding ring 
               
               
                 66 
                 opening 
               
               
                 68 
                 securing ring 
               
               
                 70 
                 axial bearing 
               
               
                 72 
                 helical compression spring 
               
               
                 74 
                 recess 
               
               
                 76 
                 snap 
               
               
                 78 
                 collar 
               
               
                 80 
                 stop 
               
               
                 82 
                 cylindrical pin 
               
               
                 84 
                 spring plate 
               
               
                 86 
                 locking spring 
               
               
                 88 
                 locking disk 
               
               
                 90 
                 driver element 
               
               
                 92 
                 locking pin 
               
               
                 94 
                 gear 
               
               
                 96 
                 stop ring 
               
               
                 98 
                 securing ring 
               
               
                 100 
                 driveshaft 
               
               
                 102 
                 pinion 
               
               
                 104 
                 needle bearing 
               
               
                 106 
                 bearing journal 
               
               
                 108 
                 ball bearing