Abstract:
A hand-held power tool damping unit has a damping element which is configured for producing friction between an output unit and a drive unit for driving the output unit, wherein damping element includes at least one annular segment.

Description:
CROSS-REFERENCE TO A RELATED APPLICATION 
   The invention described and claimed hereinbelow is also described in German Patent Application DE 102005047602.3 filed on Oct. 5, 2005. This German Patent Application, whose subject matter is incorporated here by reference, provides the basis for a claim of priority of invention under 35 U.S.C. 119(a)-(d). 
   BACKGROUND OF THE INVENTION 
   The present invention is directed in particular to a hand-held power tool damping unit with a damping element. 
   A hand-held power tool damping element is made known in DE 197 30 198 B4. It is integrated in a shaft coupling that includes a first coupling part, which is non-rotatably connected with a drive shaft, and a second coupling part, which is non-rotatably connected with an output shaft. The coupling parts can be rotated relative to each other, within the limits of circumferential backlash. The hand-held power tool damping unit includes a friction element, which serves to produce a moment of friction when the two coupling parts move relative to each other. The friction element is formed by a spring wire, which is inserted in the second coupling part and is pressed such that it bears against the first coupling part. 
   SUMMARY OF THE INVENTION 
   The present invention is directed, in particular, to a hand-held power tool damping unit with a damping element, which is provided for producing friction between an output unit and a drive unit for driving the output unit. 
   It is provided that the damping element includes at least one annular segment. In this context, “friction” is understood to mean, in particular, a force that counteracts a relative motion between the output unit and the drive unit, and which occurs at a contact point at which the drive unit and the output unit are in contact with each other. The damping element can be designed as part of the output unit and/or the drive unit, and preferably includes a rubbing surface, with which it bears against the drive unit or the output unit. In this context, an annular segment refers to a segment that extends, at least partially, along a circumferential region, and/or preferably has a curved region. By way of the annular segment, a large rubbing surface can be attained using a simple design, and a moment of friction with a distinct effect on the rubbing surface can be created. 
   An inventive hand-held power tool damping element is suited, in particular, for use in a self-blocking blocking device, which is provided for blocking a transfer of a torque from the output unit to the drive unit. To this end, this blocking unit provides circumferential backlash of the output unit relative to the drive unit, which is used, e.g., to wedge wedging elements. Due to this circumferential backlash, if damping means were not provided in the partial load region, a distinct, metallic noise would be produced, which is eliminated by the damping element. 
   It is also provided that the damping element includes at least one annular supporting element for supporting the annular segment. As a result, the damping element can be installed easily and automatically. In addition, free installation space between the central axis and the inner contour of the annular supporting element can be used advantageously for further parts, e.g., for an oscillating spindle in the case of an impact drill. The supporting element can be designed as a single component, or it can include several annular pieces, which are brought together during assembly. 
   If the damping element includes several annular segments, which are located in the circumferential direction of the annular supporting element, a large rubbing surface and a symmetrical generation of moments of friction can be advantageously attained. 
   In a further embodiment of the present invention, the damping element includes at least one fastening element, by way of which an advantageous stability of the damping element can be attained. The damping element can be fastened to the output unit or the drive unit. 
   In this context, it is provided that the hand-held power tool damping unit includes at least one receiving means, which is provided for producing a form-fit connection in interaction with the fastening element. As a result, particularly easy assembly can be attained. 
   When the hand-held power tool damping unit includes at least one securing element, which is provided for securing the fastening element in its fastening position, an undesired loosening of the damping element, e.g., when it is stressed during operation of a hand-held power tool, can be advantageously prevented. 
   In a further embodiment of the present invention, it is provided that the annular segment is designed as a spring element. In the installed state, the annular segment can bear, preloaded, against the drive unit or the output unit with a rubbing surface, by way of which a high moment of friction can be generated on the rubbing surface. The spring element is preferably composed of an elastic metal or plastic. 
   The present invention is furthermore directed to a hand-held power tool damping unit with a damping element, which is provided for producing friction between an output unit and a drive unit for driving the output unit. 
   It is provided that the damping element is provided for pulling the drive unit and the output unit toward each other. By way of the damping element, a contact force of the output unit and the drive unit on each other can be generated, by way of which large rubbing surfaces can be attained without any additional components, therefore resulting in low wear. Furthermore, large normal forces can be realized, without the need to provide additional support for the output unit and/or the drive unit. In addition, a force which tends to separate the output unit and the drive unit can be advantageously counteracted. 
   In this context, it is provided that the damping element includes at least one spring element, which is provided for pulling the drive unit and the output unit toward each other. As a result, a simple and low-cost configuration of the damping element can be attained. In addition, or as an alternative thereto, it is feasible that the output unit and the drive unit are pulled toward each other by a magnetic force. 
   It is furthermore provided that the damping element includes at least one annular segment, and the spring element is designed integral with the annular segment. By way of the annular segment, which advantageously bears, preloaded, against the drive unit or the output unit with a rubbing surface, a high moment of friction—in addition to the attraction force—can be generated on the rubbing surface using the spring element. 
   In an advantageous refinement of the present invention, the hand-held power tool damping unit includes a bevel, against which the annular segment is pressed and bears, in a loaded state. This bevel, which is preferably a surface of the output unit or the drive unit, advantageously forms an angle with a central axis of the output unit or the drive unit. The bevel can be designed, e.g., in the form of a conic surface. By way of the bevel, a return force of the annular segment perpendicular to the central axis can be advantageously redirected, so that this return force has a component that is directed parallel to the central axis. 
   Further advantages result from the description of the drawing, below. An exemplary embodiment of the present invention is shown in the drawing. The drawing, the description and the claims contain numerous features in combination. One skilled in the art will also advantageously consider the features individually and combine them to form further reasonable combinations. 
   The novel features of which are considered as characteristic for the present invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows a hand-held power tool with a motor unit, a drive spindle, and a transmission unit in accordance with the present invention, 
       FIG. 2  shows a spindle locking device of the hand-held power tool, in accordance with the present invention, 
       FIG. 3  shows the drive spindle, an element of the transmission unit with internal toothing, and an annular damping element with annular segments in accordance with the present invention, 
       FIG. 4  shows the damping element in accordance with the present invention, and 
       FIG. 5  shows the damping element, a star, and wedging rollers of the spindle locking device placed on the star in accordance with the present invention. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  shows a hand-held power tool  10  designed as a cordless screwdriver. It includes a housing  12 , a motor unit  14 , a drive spindle  16 , and a tool fitting  18 , which is non-rotatably coupled with drive spindle  16 . Drive spindle  16  is oriented in an axial direction  20 . A motor shaft  22  is coupled with drive spindle  16  via a transmission unit  24  designed as a planetary gearset. Transmission unit  24  is also provided with a spindle locking device  26 . This device, the design and mode of operation of which are described with reference to  FIG. 2 , allows drive spindle  16  to be driven freely by motor unit  14 , but it prevents torque from being transmitted by drive spindle  16  via transmission unit  24  to motor shaft  22 . As a result, a tool can be replaced, in particular, with a high amount of operating comfort. 
   The mode of operation of the spindle locking device  26  is shown in  FIG. 2 . Drive spindle  16  is shown in a top view in  FIG. 2 . A star  30 , which is non-rotatably connected with drive spindle  16 , is located on one end  28  of drive spindle  16  ( FIG. 3 ). During operation of hand-held power tool  10 , star  30  is driven to rotate by motor unit  14  via a drive unit  32  designed as a driving element. Three parts,  32 . 1 ,  32 . 2 , and  32 . 3 , of drive unit  32  are shown in the figure. Drive unit  32  and star  30  are enclosed by an outer ring  34 , which is attached to housing  12 . Spindle locking device  26  includes wedging elements, which are designed as wedging rollers  36   a ,  36   b , and are accommodated in receiving areas  38  of star  30 . 
   In addition, circumferential backlash is provided between star  30  and drive unit  32 . Star  30  is movable relative to drive unit  32  within the range of this circumferential backlash. The circumferential backlash is labeled as a half angle of rotation α/2 in the figure. 
   It is assumed that drive unit  32  is driven by motor unit  14  to rotate in the clockwise direction. Based on the configuration shown in  FIG. 2 , drive unit  32  rotates relative to star  30 , until surfaces  40   a  of drive unit  32  each contact an outer surface  42   a  of one of the wedging rollers  36   a . After contact is made, rotation of star  30  and drive spindle  16  in the clockwise direction is driven by drive unit  32 . When drive unit  32  rotates in the counterclockwise direction, each of the surfaces  40   b  of drive unit  32  contacts an outer surface  42   b  of one of the wedging rollers  36   b  and drives star  30  to rotate in the counterclockwise direction. 
   It is now assumed that drive spindle  16  is driven to rotate in the counterclockwise direction by an operator who wants to replace the tool. Star  30  rotates within the range of the circumferential backlash relative to drive unit  32  and outer ring  34 . When this motion occurs, wedging rollers  36   b  become wedged in constrictions  44   b  formed by an outer surface  46  of star  30  and an inner contour  48  of outer ring  34 . This wedging prevents star  30  from rotating further. When star  30  rotates in the clockwise direction, wedging rollers  36   a  become wedged in constrictions  44   a.    
     FIG. 3  shows drive spindle  16 , which is guided through a spindle bearing  49 ; star  30 , which is non-rotatably connected with drive spindle  16 ; drive unit  32 , which is designed as a driving element, and outer ring  34 . End  28  of drive spindle  16  is designed in the shape of a square. Other form-fit elements can be used, however, which satisfy the geometric and mechanical requirements. An internal gear  50  with inner toothing of transmission unit  24  is non-rotatably coupled with drive unit  32 . 
   To prevent an undesired noise from occurring during operation of hand-held power tool  10 —which is due to the circumferential backlash of spindle locking device  26 —hand-held power tool  10  is provided with a hand-held power tool damping unit. It includes a damping element  52 , which is provided to produce friction with drive unit  32 . Damping element  52  is non-rotatably connected with star  30  and forms therewith an output unit  54 , which is non-rotatably connected with drive spindle  16 . Damping element  52  includes an annular supporting element  56  (see  FIG. 4 ), on which several annular segments  58  are integrally formed. Each of these is designed in the shape of a clamp, and they are located in the circumferential direction of annular supporting element  56 . To fasten damping element  52  to star  30 , damping element  52  is provided with fastening elements  60  designed as arms (see also  FIG. 4 ). The hand-held power tool damping unit is provided with receiving means  62 , which are formed by recesses in star  30 , and in which the arms are accommodated (see  FIG. 5 ). Each of these fastening elements  60  includes an end designed in the shape of an arm wraparound  64 , which, in the installed state, is snapped into a wraparound  66  of one of the receiving elements  62 . To prevent arm wraparounds  64  from sliding out of wraparounds  66  of receiving means  62  when loads are placed on hand-held power tool  10 , the hand-held power tool damping unit is provided with securing elements  68 , which are formed by ribs of drive unit  32 , which are shown in  FIG. 2 . Arm wraparounds  64  of fastening elements  60  of damping element  52  are also shown in  FIG. 2 . Damping element  52  is therefore positioned, fastened, and secured on star  30  concentrically and axially around a central axis  69 . 
   An attraction force is produced between output unit  54  and drive unit  32 . To this end, annular segments  58  of damping element  52  are designed as spring elements, in the form of springs subjected to bending, and the hand-held power unit damping unit has a bevel  70 , against which annular segments  58  are pressed and bear, in a preloaded state. This bevel  70  is formed by an inner surface of drive unit  32 , which forms an angle with central axis  69 . Via the bearing of annular segments  58  in the preloaded state, a return force is produced at contact points  72 , where annular segments  58  touch bevel  70 . The return force has a component in axial direction  20 . Via this component, an attraction force is produced between drive unit  32  and output unit  54 . 
   Furthermore, when damping element  52  moves relative to bevel  70 , a moment of friction is produced at contact points  72 , which counteracts this relative motion. When, during operation of hand-held power tool  10 , rotation of drive unit  32  by motor unit  14  is braked in a stepwise manner or abruptly, torques of drive unit  32  and output unit  54  differ momentarily, so that a relative motion of drive unit  32  and output unit  54  occurs within the range of the circumferential backlash, and spindle locking device  26  is activated. A moment of friction is produced at contact points  72 , and the relative motion is braked. A noise that is produced when wedging rollers  36   a ,  36   b  become wedged, or when drive unit  32  contacts wedging rollers  36   a ,  36   b  is therefore prevented. 
   Damping element  52  is shown separately in a perspective view in  FIG. 4 . 
     FIG. 5  shows damping element  52 , which is fastened to star  30 . Fastening elements  60  are each located in a receiving means  62  of star  30 . Receiving elements  62  also serve to support the torque of damping element  52 . Wedging rollers  36   a ,  36   b  of spindle locking device  26  in receiving areas  38  are located on star  30 . 
   Assembly is described with reference to  FIGS. 3 and 5 . In a first assembly step, star  30  is placed on end  28  of drive spindle  16 . Next, damping element  52  is fastened to star  30  by sliding fastening elements  60  into receiving elements  62  until the arm wraparounds  64  snap into wraparounds  66 . Wedging rollers  36   a ,  36   b  are then each slid into one of the receiving areas  38 . Drive unit  32  is then slid in axial direction  20 , until surface  74  of drive unit  32  contacts a surface  76  of star  30 . When this sliding motion occurs, annular segments  58  reach bevel  70  of drive unit  32 . Annular segments  58 , which are designed as spring elements in the form of springs subjected to bending, are bent continually. After drive unit  32  contacts star  30 , annular segments  58  bear, preloaded, against bevel  70 . They exert a return force at contact points  72 , which has a component in axial direction  20  and, by way of which, an attraction force is produced between drive unit  32  and output unit  54 . 
   It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the type described above. 
   While the invention has been illustrated and described as embodied in a hand-held power tool, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention. 
   Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, be applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention. 
   What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims.