Abstract:
The invention describes a supplementary handle for a power tool, including a grip element and a clamping device for detachable fastening of the handle to a housing of a power tool, the clamping device including a clamping screw in such a way that by rotation of the grip element, the clamping device can be clamped to a housing of a power tool, and the grip element has at least a first axial partial element and a second axial partial element, and the first partial element is embodied rigidly relative to the clamping device, and the second partial element is embodied rotatably relative to the clamping device.

Description:
REFERENCE TO FOREIGN PATENT APPLICATION  
       [0001]     This application is based on German Patent Application No. 10 2006 041 069.6 filed 1 Sep. 2006, upon which priority is claimed.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The invention relates to a handle for a power tool, and more particularly to a supplementary handle for a power tool.  
         [0004]     2. Description of the Prior Art  
         [0005]     Numerous electric tools, such as right-angle sanders, power drills and drill hammers, are equipped with a supplementary handle. To prevent vibration that occurs in operation of the electric tool from being transmitted to the user via the supplementary handle, supplementary handles are usually provided with vibration-damping means.  
         [0006]     From the prior art, supplementary handles are known which have a clamping device, such as a taut band or a clamping ring, for securing the supplementary handle to the housing of a power tool. For instance, in German Patent Disclosure DE 41 32 058 A1, a handle for handheld power tools is described that has a clamping ring. The clamping ring is clamped to a housing of a power tool by means of a screw. To that end, the screw thread is screwed into the grip sleeve of the handle, and the clamping ring contracts upon rotation of the grip sleeve.  
         [0007]     For tightening and loosening the handle in DE 41 32 058 A1, the entire grip sleeve is accordingly used. This has the advantage that the user can exert major torque for tightening and loosening. On the other hand, a handle of this kind has the disadvantage that under certain conditions, such as major vibration in operation of the power tool, the handle may loosen by itself or in some other way unintentionally.  
       SUMMARY OF THE INVENTION  
       [0008]     The invention is based on a handle for a power tool, which includes a grip element and a clamping device for releasably securing the handle to a housing of a power tool. The clamping device has a clamping screw, which can be screwed into a receptacle in the grip element in such a way that by rotating the grip element, the clamping device can be clamped to a housing of a power tool.  
         [0009]     According to the invention, the grip element has at least one first axial partial element and one second axial partial element. The two axial partial elements, disposed in contact with one another in the axial direction, together form the grip element that can be grasped by the user of the power tool. The first partial element is embodied rigidly relative to the clamping device, while the second partial element is embodied rotatably relative to the clamping device. Unlike in the handle known from the prior art, according to the invention it is not the entire grip element but only a partial element of the grip element that is embodied rotatably relative to the clamping device. For securing the handle to a housing of a power tool, it is therefore not the entire grip element that is rotated relative to the clamping device, but only the rotatably mounted partial element.  
         [0010]     In a preferred embodiment, the first partial element is embodied as longer than the second partial element. In particular, the first, rigid partial element forms a grip element region that is oriented toward the clamping device. Conversely, the rotatable partial element is disposed on the end of the grip element facing away from the clamping device.  
         [0011]     Dividing the grip element into one rigid and one rotatable partial element, and in particular a rigid longer partial element and a rotatable shorter partial element, has the advantage that the user&#39;s hand on grasping the grip element is holding the longer, rigid partial element. The handle according to the invention does not involve the risk that by simply grasping the grip element, the handle can come loose from the power tool. Unintentional loosening can thus be reliably prevented, since the user has to actuate the rotatable and in particular shorter partial element with enough force to loosen the handle from the power tool. If the handle according to the invention is used as a supplementary handle, it for instance prevents the following situation: The user of the power tool lets the main handle go with one hand, while with the other hand he continues to firmly hold the supplementary handle. In a supplementary handle of the prior art, it is then possible for the power tool to slip away and for the screw connection between the grip element and the clamping device to be undone. In the supplementary handle of the invention, this slipping, away of the power tool with simultaneous loosening of the screw connection is no longer possible, since the user is holding the rigid partial element firmly in his hand.  
         [0012]     Especially preferably, the length of the first, rigidly embodied partial element amounts to at least two-thirds the length of the grip element. If the length of the rigid, first partial element amounts to essentially two-thirds, and the rotatable, second partial element essentially amounts to one-third of the total length of the grip element, then on the one hand adequate safety is attained, since the user&#39;s hand is essentially grasping the rigid partial element. If when the main handle is let go the power tool should slip and at that time be held only by the hand on the supplementary handle, there is no risk that the slippage will undo the screw connection between the clamping device and the grip element. On the other hand, a length of one-third for the second, rotatable partial element makes convenient and also sufficiently firm tightening of the grip element possible, since over this length, the user is capable of exerting a sufficiently high torque for tightening or loosening.  
         [0013]     The clamping device of the handle of the invention preferably has a taut band. However, the clamping device may also be a one-piece or multiple-part clamping ring. This version of the clamping device will not be described further here, since it is not the subject of the invention. As an example, see DE 41 32 058 A1, in which a one-piece clamping ring is described. A two-part clamping ring is known for instance from German Utility Model DE 79 27 713 U1.  
         [0014]     The handle according to the invention is especially suitable as a supplementary handle for a power tool, such as a power drill or drill hammer.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]     The invention will be better understood and further objects and advantages thereof will become more apparent from the ensuing detailed description of preferred embodiments, taken in conjunction with the drawings, in which:  
         [0016]      FIG. 1  shows a power tool with a supplementary handle according to the invention;  
         [0017]      FIG. 2  shows the supplementary handle with a taut band as its clamping device;  
         [0018]      FIG. 3  is an exploded view showing partial components of a supplementary handle with a two-part clamping ring as the clamping device; and  
         [0019]      FIG. 4  is a sectional view showing the supplementary handle of  FIG. 3  in the installed state. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0020]     In  FIG. 1 , a power tool  12  such as a power drill or percussion drill is shown. The power tool  12  includes a tool receptacle  52 , which can be driven via a drive unit not shown in further detail, and a main handle  54  disposed on a side of the power tool  12  facing away from the tool receptacle  52 . Along a bore axis  22  of the power tool  12 , a supplementary handle  32  is disposed upstream in the axial direction  28  of the tool receptacle  52 . The supplementary handle  32  represents a preferred embodiment of the handle of the invention. The supplementary handle  32  is located on a spindle neck  44  of the power tool  12 . The supplementary handle  32  includes both a clamping device  10  and a grip element  65 . By means of the clamping device  10 , the supplementary handle  32  can be secured to the spindle neck  44  of the power tool  12 .  
         [0021]      FIG. 2  shows as an example a supplementary handle  32  with a taut band  15  as its clamping device  10 .  
         [0022]      FIGS. 3 and 4  show a two-part clamping ring  16  as the clamping device  10 ; it includes a first component  34  and a second component  36 . The invention will now be described in further detail in terms of the embodiment of  FIGS. 3 and 4 . The clamping device  10  has a fastening means  18  for attaining the positive-engagement connection in the circumferential direction of the fastening axis and a fastening means  24  for attaining a positive-engagement connection in the axial direction  28  of the fastening axis. Fastening means corresponding to the fastening means  18 ,  24  for attaining the positive-engagement connection in the circumferential direction of the fastening axis and the positive-engagement connection in the axial direction of the fastening axis are provided (not shown) on the spindle neck  44 .  
         [0023]     The first component  34  of the supplementary handle  32  includes a grip means  64  and a semicircular receiving means  66  for receiving the spindle neck  44  of the power tool. The receiving means  66  is embodied integrally with the grip means  64  and is open on a side facing away from the grip means  64 . For securing the supplementary handle  32  to the spindle neck  44  of the power tool in the circumferential direction of the fastening axis, the receiving means  66  of the first component  34  has the fastening means  18 . The fastening means  18  is formed by recesses  48 , spaced uniformly apart from one another, that are disposed in the circumferential direction on a side of the receiving means  66  toward a receiving region  70 . The recesses  48  extend along the fastening axis over a portion of the semicircular receiving means  66 . For securing the supplementary handle  32  in the axial direction of the fastening axis, the receiving means  66  has the fastening means  24  for attaining a positive-engagement connection in the axial direction of the fastening axis, and this means is formed by a riblike fastening element  50  and is press-fitted into the receiving means  66 . The riblike fastening element  50  embodied as a bolt protrudes into the semicircular receiving region  70  of the receiving means  66 . A main lengthwise direction of the riblike fastening element  50  is oriented perpendicular to the fastening axis. The riblike fastening element  50  is formed by a stamped sheet-metal part.  
         [0024]     The second component  36  includes a portion  74 , which is intended for engagement with the inside of the first component  34 , and a circular receiving means  76 , for receiving the spindle neck  44  of the power drill and/or percussion power drill. The portion  74  and the circular receiving means  76  are embodied in one piece. The receiving means  76  forms a circular receiving region  78 , which has a circle diameter that is equal to the circle diameter of the first component  34 . The second component  36  has the fastening means  18  for attaining a positive-engagement connection in the circumferential direction. The recesses  48  extend along a portion  56  of the receiving means  76  of the second component  36  in the circumferential direction, and in the installed state, the portion  56  having the recesses  48  makes a transition to the recesses  48  of the first component  34 .  
         [0025]     For the positive interengagement of the first component  34  and the second component  36  of the supplementary handle  32 , a portion surrounded by the grip means  64  of the first component  34  is provided with a hollow space on the inside (not shown) that is intended for receiving the second component  36 . The second component  36  is embodied in slotted form in the portion  74 , in a region of the receiving means  76  toward the portion  74 , so that a positive engagement with the inside of the first component  34  is made possible. A slotted region  84  of the second component  36  is oriented perpendicular to the fastening axis. Upon mounting of the supplementary handle  32  on the spindle neck  44  of the power tool the second component  36  is introduced, perpendicular to the fastening axis and with the portion  74  leading, into the semicircular receiving region  70  and then into a hollow space  82  in the first component  34 . In the process, the second component  36  is introduced so far into the first component  34  that essentially a complete circle diameter of the second component  36  is preserved. The circle diameter of the receiving region  78  is adapted to a cross section of the spindle neck  44 , so that the supplementary handle  32  an be guided virtually without play on the spindle neck  44 . In order to keep the second component  36  in position relative to the first component  34  as the supplementary handle  32  is being attached to the spindle neck  44 , the first component  34  and the second component  36  are screwed together via a screw connection, not shown in detail.  
         [0026]     For clamping the first component  34  to the second component  36 , the supplementary handle  32  includes a third component  86 . The first component  34  forms the first axial partial element  68 , and the third component  86  forms the second axial partial element  69  of the grip element, so that the two partial elements  68 ,  69 , disposed axially against one another, form the grip element  65 . For that purpose, the third component  86  includes a grip means  88 , which is introduced rotatably into the first component  34  and is screwed together with the second component  36  via a screw, threaded rod, or the like, that serves as a clamping screw  90 . For that purpose, the portion  74  of the second component  36  includes a recess  92 , with a nut  94  placed in the recess  92 . The nut  94  has a torsion preventing means and is incorporated by positive engagement into a plastic wall of the portion  74  of the second component  36 . In addition, in the hollow space  82  in the first component  34  there is a spring  96 , which is disposed around the clamping screw  90  of the third component  86  and which is prestressed in the installed state of the supplementary handle  32 . If by rotation of the third component  86  the screw connection with the second component  36  loosens, a spring force of the spring  96  causes the second component  36  to be forced out of the first component  34 , causing the riblike fastening element  50  to come loose from the groovelike recess in the spindle neck  44 , and the supplementary handle  32  can be removed from the spindle neck  44  of the power tool  12 .  
         [0027]     It can be seen from  FIG. 4  that the first partial grip element  68  is embodied as longer than the second partial grip element  69 , so that unintentional undoing of the screw connection is virtually impossible, since the user of the power tool, for using it in the conventional way, grasps the supplementary handle  32  with his whole hand over the entire length of the grip element  65 . However, this means that the user&#39;s hand primarily grasps the first, longer axial partial element  68 . Since the second axial partial element  69  forms the shorter partial element and is further disposed on the free end, oriented counter to the clamping device  10 , of the grip element  65 , only one or at most two fingers of the user&#39;s hand, and specifically the little finger and possibly the ring finger, grasp the second axial partial element  69 . If the user wishes to undo the screw connection, he must instead grasp the grip means  88  or second partial grip element  69  and rotate it with sufficient force.  
         [0028]     The foregoing relates to preferred exemplary embodiments of the invention, it being understood that other variants and embodiments thereof are possible within the spirit and scope of the invention, the latter being defined by the appended claims.