Abstract:
The invention is based on a hand power tool, in particular a manually operated right angle grinding machine or a manual circular saw, with a driver mechanism ( 12 ), which can operatively connect an inserted tool ( 16 ) to a drive shaft ( 18 ). 
     The invention proposes that at least one sensor ( 10 ) can detect at least one procedural step in the changing of an inserted tool ( 16 ) and can produce a signal.

Description:
BACKGROUND OF THE INVENTION 
   The invention is based on hand power tool. 
   In order to be able to advantageously connect an inserted tool to a drive shaft of a machine tool by means of a tool holding fixture, it is known to affix the drive shaft to a locking device. 
   For right angle grinders, a locking device is known that has a locking bolt, which is guided in a housing so that it is rotationally fixed in relation to the drive shaft and which, by means of an actuating button, can be brought into engagement with a gearing that is non-rotatably connected to the drive shaft. 
   In addition, EP 0 904 896 A2 has disclosed a grinding machine tool holding fixture for a manually operated right angle grinding machine. The right angle grinding machine has a drive shaft, which has a thread oriented toward the tool. 
   The grinding machine tool holding fixture has a driver and a retaining nut. In order to install a grinding wheel, the driver is slid with a mounting opening onto a collar of the drive shaft and by means of the retaining nut, is clamped in a frictionally engaging manner to a supporting surface of the drive shaft. Oriented toward the tool and extending in the axial direction, the driver has a collar that has recesses on its outer circumference, on two radially opposing sides, which extend axially to a base of the collar. A groove extends on the outer circumference of the collar, counter to the drive direction of the drive shaft, starting from each of the recesses. The grooves are closed counter to the drive direction of the drive shaft and taper axially starting from the recesses, counter to the drive direction of the drive shaft. 
   The grinding wheel has a hub with a mounting opening, which contains two opposing tabs pointing radially inward. The tabs can be inserted axially into the recesses and then introduced circumferentially into the grooves, counter to the drive direction. By means of the tabs in the grooves, the grinding wheel is fixed in a form-fitting manner in the axial direction and is fixed in a frictionally-engaging manner by the tapering contour of the grooves. During operation, the frictional engagement increases due to the reaction forces acting on the grinding wheel, which act counter to the drive direction. 
   In order to prevent the grinding wheel from coming off when the driver is braking the drive shaft, in the vicinity of a recess on the circumference of the collar, a stopper is provided, which is supported so that it can move in the axial direction in an opening. In an operating position with the grinding wheel pointing downward, the stopper is axially deflected toward the grinding wheel by the force of gravity, closes the groove in the direction of the recess, and prevents the tabs disposed in the groove from moving in the drive direction of the drive shaft. 
   SUMMARY OF THE INVENTION 
   The invention is based on hand power tool, in particular a manually operated right angle grinding machine or a manual circular saw, with a driver mechanism, which can operatively connect an inserted tool to a drive shaft. 
   The invention proposes that at least one sensor, which is disposed in particular in the vicinity of the driver mechanism, can detect at least one procedural step in the changing of an inserted tool and can produce a signal. An operation of the hand power tool can be prevented while the inserted tool is being changed and the safety can be increased particularly by virtue of the fact that the signal can prevent an operation of the driver mechanism. A wide variety of sensors deemed appropriate by one skilled in the art can be used for the embodiment according to the invention, such as electrical, mechanical, and/or electromechanical sensors, etc., which can produce a variety of signals, such as electrical, mechanical, optical, and/or acoustic signals, etc. 
   Furthermore, preventing the driver mechanism from operating can be achieved by variety of structural embodiments, for example by means of a mechanical and/or electromechanical clutch, which can be combined with a locking device of a drive shaft. If the signal can interrupt a power supply, for example by means of an electrical sensor and a switch, then this allows the operation to be prevented with a particularly space-saving and lightweight design. 
   It can also be advantageous if a light source can be switched by means of the signal, for example a warning light, which notifies an operator of a change, or a change that has not yet been completed, and/or an illumination of the driver mechanism, which can facilitate an installation and removal of an inserted tool in dark spaces. 
   In another embodiment, the invention proposes that the inserted tool can be operatively connected to the driver mechanism by means of at least one detent element, which is supported so that it can move in opposition to a spring element and which engages in an operating position of the inserted tool and fixes the inserted tool in a form-fitting manner, and that the sensor can detect at least one position of the detent element. The form-fitting engagement can achieve a high degree of safety and can produce a simple and inexpensive tool-free quick-clamping system and the sensor can be easily integrated into it. The movement of the detent element can be detected directly or indirectly by means of a component moved by the detent element. The inserted tool can be reliably prevented from unintentionally coming loose by means of the form-fitting engagement, even when the drive shaft is being braked, during which intense braking moments can occur. Fundamentally, however, it is also conceivable that the sensor is actuated by means of a cable control and/or a lever mechanism, etc. 
   The movable support of the detent element permits a large deflection of the detent element during installation of the inserted tool, which permits a large amount of overlap between two corresponding detent elements and a particularly secure form-fitting engagement to be produced and on the other hand, permits an easily audible engagement sound to be produced, which advantageously indicates to the operator that the desired locking procedure has been completed. 
   The movably supported detent element can be embodied in a variety of forms deemed appropriate by one skilled in the art, for example an opening, projection, pin, bolt, etc., and can be disposed on the inserted tool or on the driver mechanism. The detent element itself can be movably supported in a component in a bearing, for example in a flange of the driver mechanism or in a tool hub of the inserted tool. The detent element, however, can also be embodied as connected by means of frictional engagement, form-fitting engagement, and/or materially adhesive engagement to a component movably supported in a bearing or can be of one piece with this component, for example a component supported on the drive shaft or to a tool hub of the inserted tool. 
   Furthermore, the form-fitting engagement permits an advantageous encoding to be achieved so that only specifically intended inserted tools can be fastened in the driver mechanism. The driver mechanism can be at least partially embodied as a detachable adapter piece or can be detachably connected to the drive shaft by means of frictional engagement, form-fitting engagement, and/or materially adhesive engagement. 
   The detent element can be embodied so that it can move in various directions in opposition to a spring element, for example in the circumference direction or in a particularly advantageous manner, in the axial direction, which permits the achievement of a structurally simple embodiment and a movement path that can be easily detected by the sensor. 
   A particularly inexpensive, rugged, and structurally simple embodiment can also be achieved in that the detent element can actuate an electrical switch element that constitutes the sensor. If the switch element is disposed so that it cannot rotate in relation to a rotation axis of the drive shaft or is affixed to the housing, then an additional rotating mass and an expensive set of contact connections between components that rotate in relation to each other can be avoided. At the very least, however, individual pieces can also be embodied so that they rotate, for example in the vicinity of an actuating button. 
   In another embodiment, the invention proposes that the drive shaft can be locked by means of an actuating button of a locking device in order to change the inserted tool and that the sensor can detect a position of the actuating button. Additional components can be saved and a reliable signal can be achieved. Fundamentally, however, it is also conceivable for the signal be able to lock the drive shaft electrically and/or electromagnetically, etc. 
   The invention also proposes that the actuating button is operatively connected to the drive shaft in the rotation direction and the actuating button for locking the drive shaft can connect at least one first part, which is operatively connected to the drive shaft in the rotation direction, to a second part that cannot rotate in relation to a rotation axis of the drive shaft. Having the actuating button rotate with the drive shaft during operation can reliably prevent the actuating button from being improperly used to slow down the drive shaft. A detachment of inserted tool due to an unforeseen, powerful braking moment and an associated injury risk can be reliably prevented and wear on the locking device can be reduced. 
   The embodiment according to the invention can be used in a variety of hand power tools deemed appropriate by one skilled in the art, for example eccentric grinders, oscillating grinders, brushes, drills, etc., but can be used to particular advantage in manual circular saws and right angle grinders in which uncontrollably rotating inserted tools can cause particularly serious injuries. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other advantages ensue from the following description of the drawings. An exemplary embodiment of the invention is shown in the drawings. 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 will unite them to form other meaningful combinations. 
       FIG. 1  shows a top view of a right angle grinder, 
       FIG. 2  shows a schematic cross section along the line II—II in  FIG. 1 , through a grinding machine tool holding fixture according to the invention, and 
       FIG. 3  shows a bottom view of a tool hub. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1  shows a top view of a right angle grinding machine with an electric motor, not shown, contained in a housing  42 . The right angle grinding machine can be guided by means of a first handle  44  extending the longitudinal direction and integrated into the housing  42  on the side remote from a cutting wheel  16  and by means of a second handle  48  extending lateral to the longitudinal direction and fastened to the transmission housing  42  in the vicinity of the cutting wheel  16 . 
   By means of a transmission that is not shown in detail, the electric motor can drive a drive shaft  18 , whose end oriented toward the cutting wheel  16  is provided with a driver mechanism  12  (FIG.  2 ). On a side oriented toward the cutting wheel  16 , the driver mechanism  12  has a driver a flange  50  press-fitted onto the drive shaft  18  and on a side oriented away from the cutting wheel  16 , has a driver disk  40 , which is supported so that it can be slid on the drive shaft  18  in opposition to a concentrically disposed helical spring  28 . 
   Furthermore, three pins  52 , which extend up from the supporting surface  56  in the axial direction  38  and are evenly distributed in the circumference direction  32 ,  34 , are provided for axially fixing the cutting wheel  16  in the axial direction  38  in relation to a respective disk spring  102 . At their ends oriented toward the cutting wheel  16 , the pins  52  each have a head, which has a greater diameter than the rest of the pin  52  and at an end oriented toward the driver flange  50 , have a conical contact surface  104  tapering in the axial direction  36  and a contact surface  104   a  extending parallel to the supporting surface  56 . 
   The driver a flange  50  constitutes an axial supporting surface  56  for the cutting wheel  16 , establishes an axial position of the cutting wheel  16 , and has openings  58  let into it in the vicinity of the pins  52 . In addition, three axial through bores  60  are let into the driver flange  50 , which are evenly distributed over the circumference in the circumference direction  32 ,  34 . 
   The driver disk  40  that is movably supported on the drive shaft  18  has three bolts  30  press-fitted into it one after the other in the circumference direction  32 ,  34 , which extend in the axial direction  38  toward the cutting wheel  16  and, with a part  24 , protrude up from the driver disk  40  in the axial direction  36  oriented away from the cutting wheel  16 . The helical spring  28  presses the driver disk  40  in the direction  38  toward the cutting wheel  16 , against the driver flange  50  and the driver disk is supported against this driver flange. The bolts  30  protrude through the through bores  60  and extend up from the driver flange  50  in the axial direction  38 . 
   In addition, disposed in the center on the side oriented toward the cutting wheel  16 , the driver mechanism  12  has a cup-shaped unlocking button, which is of one piece with the actuating button  22  of a locking device  20  of the drive shaft  18 . The unlocking button has three segments  62 , which are distributed evenly in the circumference direction  32 ,  34 , extending in the axial direction  36  in relation to the movably supported driver disk  40  and which reach through corresponding recesses  64  of the driver flange  50  and are secured against falling out in the axial direction by means of a snap ring  66  inside the driver disk  40 . The unlocking button is guided so that it can move in the axial direction  36 ,  38  in an annular recess  68  in the driver flange  50 . 
   The cutting wheel  16  has a sheet metal hub  70 , which is securely connected to and pressed onto a grinding device  72  by means of a riveted connection that is not shown in detail (FIG.  3 ). The tool hub could also be made of another material deemed appropriate by one skilled in the art, for example plastic, etc. The sheet metal hub  70  has bores  74 ,  76 ,  78  in succession, distributed evenly in the circumference direction  32 ,  34 , whose diameter is slightly greater than the diameter of the bolts  30 . In addition, the sheet metal hub  70  has three oblong holes  80 ,  82 ,  84  distributed evenly in the circumference direction  32 ,  34  and extending in the circumference direction  32 ,  34 , each of which has a narrow region  86 ,  88 ,  90  and a wide region  92 ,  94 ,  96  produced by means of a bore, whose diameter is slightly greater than the diameter of the heads of the pins  52 . 
   The sheet metal hub  70  has a centering bore  98 , whose diameter is advantageously chosen so that the cutting wheel  16  can also be clamped by means of a conventional clamping system to a clamping flange and a spindle nut on a conventional right angle grinding machine. A so-called backward compatibility is assured. 
   When the cutting wheel  16  is installed, the cutting wheel  16  is slid with its centering bore  98  onto a collar  54  formed onto the supporting surface  56  of the driver flange  50 , which radially centers the cutting wheel  16  with its centering bore  98 . The driver flange  50  can thus advantageously absorb radial forces produced during operation without putting strain on the unlocking button  22 . 
   Then the cutting wheel  16  is rotated until the pins  52  engage in the provided wide regions  92 ,  94 ,  96  of the oblong holes  80 ,  82 ,  84  of the sheet metal hub  70 . The sheet metal hub  70  pressing against the supporting surface  56  of the driver flange  50  causes the bolts  30  to be slid into the through bores  60  and causes the driver disk  40  to be slid axially counter to a spring force of the helical spring  28  on the drive shaft  18 , in the direction  36  oriented away from the cutting wheel  16 . The parts  24  of the bolts  30 , which protrude up from the driver disk  40  in the axial direction  36  oriented away from the cutting wheel  16 , are each slid into one of a number of pockets  26 , which are distributed in the circumference direction  32 ,  34  and are formed into a bearing cover  100 . The bearing cover  100  is screwed firmly into the transmission housing  46 . The pockets  26  cannot rotate in relation to a rotation axis of the drive shaft  18  or in relation to the drive shaft  18  itself and are closed in the rotation direction, and the drive shaft  18  is form-fittingly locked in the circumference direction  32 ,  34  by means of the driver flange  50  and the bolts  30 . 
   In the direction of the driver mechanism  12 , in a pocket  26  of the bearing cover  100 , a sensor  10  is disposed so that it cannot rotate in relation to a rotation axis of the drive shaft  18  and can detect an installation and removal of the cutting wheel  16 . When the bolt  30  is inserted into the pocket  26 , the bolt  30  actuates an electrical switch element  14  that constitutes the sensor  10 . A signal is produced, which interrupts a power supply of the right angle grinder and reliably prevents the right angle grinder or of the driver mechanism  12  from operating. 
   The pockets  26  are embodied so that they are open radially toward the inside, which can prevent them from becoming clogged with dirt and dust. The pockets  26  could also be advantageously embodied so that they are open in the axial direction  36  oriented away from the cutting wheel  16 . 
   A further rotation of the sheet metal hub  70  counter to the drive direction  34  causes the pins  52  to be slid into the arc-shaped narrow regions  86 ,  88 ,  90  of the oblong holes  80 ,  82 ,  84 . As a result, the pins  52  are slid by means of the conical contact surfaces  104  axially in the direction  38  counter to the force of the disk springs  102  until the contact surfaces  104   a  of the pins  52  overlap the edges of the oblong holes  80 ,  82 ,  84  in the arc-shaped narrow regions  86 ,  88 ,  90 . 
   When assembled, the disk springs  102 , by means of the contact surfaces  104   a  of the pins  52 , press the cutting wheel  16  against the supporting surface  56 . In lieu of several disk springs  102 , the pins can also be loaded by means of other spring elements deemed appropriate by one skilled in the art, such as helical springs or a disk spring, not shown, which extends over the entire circumference. The exemplary embodiment with the pins  52  supported so that they can move axially, is particularly suited for thick tool hubs and/or tool hubs, which can only be elastically deformed slightly. 
   In an end position or in an achieved operating position of the cutting wheel  16 , the bores  74 ,  76 ,  78  in the sheet metal hub  70  come to rest over the through bores  60  of the driver flange  50 . Due to the spring force of the helical spring  28 , the bolts  30  slide out of the pockets  26 , in the axial direction  38  toward the cutting wheel  16 , engage in the bores  74 ,  76 ,  78  of the sheet metal hub  70 , and fix this hub in a form-fitting manner in both circumference directions  32 ,  34 . When they engage, an engagement sound is produced, which is audible to the operator and indicates that the tool is ready for operation. Furthermore, when the bolt  30  comes out of the pocket  26 , the electrical switch element  14  constituting the sensor  10  is actuated and the power supply of the right angle grinder is switched back on. 
   A driving torque of the electric motor of the right angle grinding machine can be transmitted from the drive shaft  18  to the driver flange  50  in a frictionally engaging manner and can be transmitted from the driver flange  50  to the cutting wheel  16  in a form-fitting manner by means of the bolts  30 . Furthermore, a braking moment, which is directed counter to a driving torque during and after the electric motor being switched off, can be transmitted in a form-fitting manner from the driver flange  50  to the cutting wheel  16  by means of the bolts  30 . An unintentional detachment of the cutting wheel  16  is reliably prevented. The three bolts  30  distributed evenly in the circumference direction  32 ,  34  achieve an advantageous, uniform distribution of force and mass. 
   In order to detach the cutting wheel  16  from the right angle grinding machine, the unlocking button is pressed. The driver disk  40  is then slid together with the bolts  30  by means of the unlocking button or actuating button  22 , counter to the helical spring  28 , in the axial direction  36  oriented away from the cutting wheel  16 , as a result of which the bolts  30  move in the axial direction  36  out of their locked position and out of the bores  74 ,  76 ,  78  of the sheet metal hub  70 . At the same time, the bolts  30  engage with their parts  24  in the pockets  26 , as a result of which the drive shaft  18  is form-fittingly locked in the rotation direction  32 ,  34 . As with the installation of the cutting wheel, when the bolt  30  is inserted into the pocket  26 , the electrical switch element  14  constituting the sensor  10  is actuated by the bolt  30 . A signal is produced, which interrupts the power supply to the right angle grinder and reliably prevents an operation of the right ankle grinder or of the driver mechanism  12 . 
   Then the cutting wheel  16  is rotated in the driving direction  34  until the pins  52  come to rest in the wide regions  92 ,  94 ,  96  of the oblong holes  80 ,  82 ,  84  and the cutting wheel  16  can be removed from the driver flange  50  in the axial direction  38 . After the unlocking button is released, the helical spring  28  slides the driver disk  40 , the bolts  30 , and the unlocking button or actuating button  22  back into their initial positions. When the bolt  30  comes out of the pocket  26 , the electrical switch element  14  constituting the sensor  10  is actuated and the power supply of the right angle grinder is switched back on. 
   
     
       
             
           
             
             
           
         
             
                 
             
             
               Reference Numerals 
             
             
                 
             
           
           
             
                 
             
           
        
         
             
               10 
               sensor 
             
             
               12 
               driver mechanism 
             
             
               14 
               switch element 
             
             
               16 
               inserted tool 
             
             
               18 
               drive shaft 
             
             
               20 
               locking device 
             
             
               22 
               actuating button 
             
             
               24 
               part 
             
             
               26 
               part 
             
             
               28 
               spring element 
             
             
               30 
               detent element 
             
             
               32 
               circumference direction 
             
             
               34 
               circumference direction 
             
             
               36 
               direction 
             
             
               38 
               direction 
             
             
               40 
               component 
             
             
               42 
               housing 
             
             
               44 
               handle 
             
             
               46 
               transmission housing 
             
             
               48 
               handle 
             
             
               50 
               driver flange 
             
             
               52 
               pin 
             
             
               54 
               collar 
             
             
               56 
               supporting surface 
             
             
               58 
               opening 
             
             
               60 
               through bore 
             
             
               62 
               segment 
             
             
               64 
               recess 
             
             
               66 
               snap ring 
             
             
               68 
               recess 
             
             
               70 
               sheet metal hub 
             
             
               72 
               grinding device 
             
             
               74 
               bore 
             
             
               76 
               bore 
             
             
               78 
               bore 
             
             
               80 
               oblong hole 
             
             
               82 
               oblong hole 
             
             
               84 
               oblong hole 
             
             
               86 
               region 
             
             
               88 
               region 
             
             
               90 
               region 
             
             
               92 
               region 
             
             
               94 
               region 
             
             
               96 
               region 
             
             
               98 
               centering bore 
             
             
               100 
               bearing cover 
             
             
               102 
               disk spring 
             
             
               104 
               supporting surface