Abstract:
An operating mode switch for setting at least one operating mode in a hand-held power tool, comprising an adjustment ring rotatable manually around its axis and movable into at least one rotational position which activates an operating mode, and a locking device controlled by the adjustment ring and engaging in the adjustment ring, the locking device being configured such that in the at least one rotational position of the adjustment ring it automatically falls into a locking position which locks the adjustment ring in position, while the engagement ring is engageable from the at least one rotational position by manually rotating the adjustment ring.

Description:
CROSS-REFERENCE TO A RELATED APPLICATION  
       [0001]     The invention described and claimed hereinbelow is also described in German Patent Application DE 102005059182.5 filed on Dec. 12, 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  
       [0002]     The present invention is based on an operating mode switch for setting at least one operating mode in a hand-held power tool, in particular for selectively turning the “impact drilling” mode on or off in an impact drill.  
         [0003]     With a known impact drill with an operating mode switch for selecting several operating modes (DE 100 06 641 A1), the operating mode switch includes two adjustment or switching rings which are located next to each other on the machine housing and are designed such that one switching ring, in two consecutive setting positions, selects the “impact drilling on/off” mode, and the other switching ring selects the “drill” mode” and the “screw” mode, and, in the “screw” mode, the disengagement torque or rotational torque of a safety clutch is specified via several setting positions. A blocking or disengagement device is coupled with both switching rings, which blocks the safety clutch in the “impact drilling” and “drill” modes. The disengagement device is deactivated in the third setting position of the first setting ring for selecting the “screw” mode, and the disengagement torque or rotational torque of the safety clutch is determined by the coupling spring, the preload of which is adjustable using the second switching ring.  
       SUMMARY OF THE INVENTION  
       [0004]     Accordingly, it is an object of the present invention to provide an operating mode switch for setting at least one operating mode in a hand-held power tool, which eliminates the disadvantages of the prior art.  
         [0005]     In keeping with these objects and with others which will become apparent hereinafter, one feature of the present invention resides, briefly stated, in an operating mode switch for setting at least one operating mode in a hand-held power tool, comprising an adjustment ring rotatable manually around its axis and movable into at least one rotational position which activates an operating mode; and a locking device controlled by said adjustment ring and engaging in said adjustment ring, said locking device being configured such that in the at least one rotational position of said adjustment ring it automatically falls into a locking position which locks said adjustment ring in position, while said adjustment ring is engageable from said at least one rotational position by manually rotating said adjustment ring.  
         [0006]     When the operating mode switch is designed in accordance with the present invention it has the advantage that the locking device ensures the functionality of the hand-held power tool in the selected operating mode—which is activated using the setting ring—despite vibrations, handling errors, and other external influences, e.g., accidental rotation of the setting ring caused by circumstances in the operating environment. This is particularly significant for the “impact drilling” mode, since considerable impact-related vibrations are produced in this case, which cause the unsecured setting ring to rotate, thereby resulting in malfunction.  
         [0007]     According to an advantageous embodiment of the present invention, the locking device includes at least one recess located in a sliding track formed in the adjustment ring, and an axially displaceable, non-rotatably held locking element designed to at least partially engage in the recess in a form-fit manner and which bears against the sliding track with an axially directed spring force. This design of the locking device is simple and robust, and it ensures reliable locking quality.  
         [0008]     According to an advantageous embodiment of the present invention, the locking element is designed as a sliding wedge which is acted upon by a compression spring and includes a wedge angle pointing toward the sliding track. This recess is triangular, with a triangular angle corresponding to the wedge angle. By adjusting the wedge angle of the sliding wedge and adapting the triangular angle of the triangular recess accordingly, it is possible to adapt the manual force required to disengage the locking device to the customer&#39;s preference and to attain an optimum between locking quality and ease of use.  
         [0009]     The novel features 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  
       [0010]      FIG. 1  shows an exploded view, in sections, of a hand-held power tool with an operating mode switch in accordance with the present embodiment, and  
         [0011]      FIG. 2  shows a section of a schematized top view of the operating mode switch with locking device in accordance with the present embodiment.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0012]     With the hand-held power tool shown in an exploded view, in sections, in  FIG. 1 , it is possible to switch to three different operating modes, i.e., the “impact drilling on/off” mode, the “drill” mode, and the “screw” mode, using an operating mode switch composed of two adjustment rings. In the “screw” mode, it is possible to preselect various starting torques. If this torque is exceeded, a safety clutch is activated, and the screwing tool cannot be driven.  
         [0013]     The section of the hand-held power tool shown in  FIG. 1  shows a guide sleeve  11  which is fixedly connected with the front region of a machine housing (not shown here) which accommodates an electric motor and a gearbox. A tool spindle (not shown here) is rotatably supported in guide sleeve  11 , and operating mode switch  10  is located on guide sleeve  11 . Operating mode switch  10  includes a setting ring for the “drill” and “screw” modes—and only one threaded ring  13  is shown—and a setting ring  12  with which the “impact drilling” mode can be engaged and disengaged.  
         [0014]     Setting ring  12  has a two-component design and is composed of a manually holdable outer ring  121  and an inner ring  122 . Inner ring  122  is rotatably supported on guide sleeve  11  and is rotatably connected with outer ring  121 . Rotatable threaded ring  13  bears against the inner surface of inner ring  122  and can be rotated using the setting ring (not shown here) for the “drill” and “screw” modes. Inner ring  122  has two control curves  14  on its front side. Only control curve  14  is shown in  FIG. 1 . Two control cams, which are not shown in  FIG. 1 , are positioned on both control curves  14  such that, when setting ring  12  is rotated into its “impact drilling” position, the control cams each run up onto a blocking element  15 .  
         [0015]     Both blocking elements  15  are guided on guide sleeve  11  in an axially displaceable manner and are pressed via compression springs  16  against control curve  14  of inner ring  122  and threaded ring  13 . When the control cams run onto blocking elements  15 , the latter are pushed back against the force of compression spring  16  and block the safety clutch in this position. In this rotational position of setting ring  12 , an actuating unit—which is not shown here—switches on the impact mechanism.  
         [0016]     To ensure reliable positioning and holding of setting ring  12  at least in its rotational position in which the “impact drilling” mode is selected, a locking device  17  controlled by setting ring  12  is provided, which engages in setting ring  12  and, in fact, in inner ring  122  of setting ring  12 , and it designed such that, in the rotational position of setting ring  12  for the “impact drilling” mode, it automatically falls into a locking position which locks setting ring  12  in position, and the locking position can be disengaged by manually rotating setting ring  12  out of the rotational position for the “impact drilling” mode.  
         [0017]     To this end, locking device  17  includes at least one recess  18  located in control curve  14  of inner ring  122 , and an axially displaceable, non-rotatably held locking element  19  designed to at least partially engage in the at least one recess  18  in a form-fit manner and which bears against the control curve  14  with axially directed spring force. In the exemplary embodiment shown in  FIGS. 1 and 2 , locking element  19  is a sliding wedge  21  which is acted upon by a compression spring  20  and has a wedge angle which points toward setting ring  12 . Sliding wedge  20  is held in an axially displaceble manner in a guide groove  22 —which extends in the axial direction—on guide sleeve  11 .  
         [0018]     A blind hole  23  is formed in groove end  221  of guide groove  22  pointing away from setting ring  12 . One end of compression spring  20  is preferably accommodated in a form-fit manner in blind hole  23 . Compression spring  20  bears against hole base  231  of blind hole  23  and against the end of sliding wedge  21  facing away from the wedge angle. Compression spring  20  is slid onto a mounting peg  24  which projects out of the end of sliding wedge  21  facing away from the wedge angle. Recess  18  is designed triangular in shape with a triangle tip pointing in the axial direction, the triangle tip having a triangular angle which corresponds to the wedge angle of sliding wedge  21 , so that sliding wedge  21  can engage in recess  18  via its wedge angle, at least partially, and in a form-fit manner.  
         [0019]     If setting ring  12  is located in any rotational position in which it has switched off the impact mechanism for the “impact drilling” mode, sliding wedge  21  is pressed via its wedge angle by compression spring  20  against control curve  14  on inner ring  122 . Setting ring  12  can be easily rotated in the circumferential direction, and it is only necessary to overcome the frictional force between the tip of sliding wedge  21  and control curve  14 . If, when setting ring  12  is rotated manually, it reaches its rotational position in which it activates the impact mechanism, recess  18  reaches the region of sliding wedge  21 , and the latter falls—via action of compression spring  20 —into recess  18 , thereby locking setting ring  12  relative to its rotation in the circumferential direction.  
         [0020]     To switch off the “impact drilling” mode, setting ring  12  is rotated back manually. Due to the resultant rotational motion of inner ring  122 , via one triangular surface of triangular recess  18 , sliding wedge  21  is pushed back via its wedge flank against the force of compression spring  20  until the wedge tip of sliding wedge  21  rests against control curve  14  again. A greater amount of manual force is therefore required to disengage the “impact drilling” mode.  
         [0021]     It is also possible, of course, to lock setting ring  12  in both rotational positions, i.e., also in the “impact drilling off” rotational position, using locking device  17 . To this end, it is only necessary to provide an additional recess  25  ( FIG. 1 )—which is offset by an angle of rotation—in control curve  14  in inner ring  122 .  
         [0022]     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 types described above.  
         [0023]     While the invention has been illustrated and described as embodied in an operating mode switch for setting at least one operating mode 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.  
         [0024]     Without further analysis, the foregoing will so fully reveal the gist of reveal present invention that others can, by 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 the invention.