Abstract:
An electric hand power tool has an on/off switch, an elongated switching key having a front end and a rear end and actuating the switch, a projecting blocking lever which manually sets a turning on lock out of operation, the switching key being supported turnably, the switching key having a concave curvature starting substantially centrally and extending toward the rear end, the switching key carrying the blocking lever near the rear end.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to an electric hand power tool with a switching key.  
           [0002]    Electric hand power tools with elongated switching keys are known. They can be operated with several fingers simultaneously and therefore in a force-saving and comfortable manner. They extend parallel to the longitudinal axis of the motor housing. The front end of the switching key is supported rotatably in the motor housing so that the rear end is turnable for turning on of the motor in the motor housing.  
           [0003]    The known switching keys carry a centrally projected turnable locking lever. When this blocking lever is turned then the switching key can be pressed to its turning-on position, so that then the motor of the hand power tool can be set in operation. When the blocking lever is not turned rearwardly, the switching key is not movable to its turning-on position even with application of considerable force.  
           [0004]    The outer contour of the known switching key extends flatly and is not adapted to the operator hand. After long operational time the hand power tool is therefore not convenient to operate, also since the blocking lever turned to its releasable position extends as unevenness over the contour of the switching key and thereby interferes with the operator hand. Moreover, the exposed blocking lever has a tendency to break because in rough environment operations it is not protected from impacts and strikes, in particular with frequent occurrences. If the blocking lever is broken, the hand power tool either can not be turned or can be unintentionally turned on due to failure of the turning-on lock with a considerable risk of accidents.  
         SUMMARY OF THE INVENTION  
         [0005]    Accordingly, it is an object of the present invention to provide a hand power tool which avoids the disadvantages of the prior art.  
           [0006]    More particularly, it is an object of the present invention to provide a hand power tool which has the advantage that due to the convex curvature provided on the rear end of the switching key, in particular its use over a long time, comfortable and reliable operation is provided.  
           [0007]    In keeping with these objects and with others which will become apparent hereinafter, one feature of the present invention resides, briefly stated, in an electric hand power tool which has an on- and off switch, an elongated switching key having a front end and a rear end actuating the switch, a projecting blocking lever which manually sets a turning-on lock out of operation, the switching key being supported turnably, the switching key having a concave curvature starting substantially centrally and extending toward a rear end, and the switching key carries the blocking lever near the rear end.  
           [0008]    When the hand power tool is designed in accordance with the present invention, due to the convex curvature arranged at the rear end of the switching key, during its use in particular over a long time, a comfortable and reliable operation is provided.  
           [0009]    The blocking lever can be located on the rear end of the switching key. Therefore a greater, free supporting surface of the finger of the operator is provided.  
           [0010]    The convex curvature at the rear end of the switching key can merge into a concave curvature. Therefore the operator hand can hold the switching key in a particularly reliable and comfortable manner.  
           [0011]    The blocking lever can be provided at the deepest point of the concave curvature of the switching key. Therefore, the blocking lever can be turnable comfortably by the operator hand to its release position and well protected against breaking by impacts and strikes.  
           [0012]    The concave curvature can have the recess which corresponds to a negative form or an imprint of the blocking lever. Therefore the blocking lever moves into this recess in its release position flush and improves the comfort for the operator head.  
           [0013]    The switching key in the region of its convex curvature can carry a plurality of small calotte-shaped depressions. This improves the gripping of the switching key.  
           [0014]    The blocking lever can be arranged turnably to the rear end of the switching key. Therefore an error-free operation is guaranteed.  
           [0015]    The housing outer contour in the region of the switching key can extend as a concave curvature. In this construction the rear end of the switching key extends relative to the housing further outwardly than the front end. This provides an especially comfortable, force-reducing operation of the switching key.  
           [0016]    In accordance with another feature, a raised actuation arrow can point in the turning direction of the blocking lever and is arranged near the switching key. Therefore a failure-free operation of the blocking lever and the switching key is guaranteed.  
           [0017]    The blocking lever can be curved in the same direction to the concave curvature of the switching key. Thereby the recess for insertion in the outer contour of the switching key is very small and improves the operator comfort.  
           [0018]    An important advantage of the present invention is the protected arrangement of the turning-on blocking lever in the concave “trough” of the switching key. Both its front concave region and also its rear edge extend outwardly beyond the upper edge of the blocking lever. It provides two supporting points at opposite sides in the immediate vicinity to the blocking lever, which are located higher than the upper edge of the blocking lever and therefore can take the force. Thereby in the case of mistaken actuation of the device the turning-on blocking lever is not damaged. Furthermore, due to this arrangement the blocking lever can not be actuated, for example when the device is pulled on the cable over the work bench.  
           [0019]    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  
       [0020]    [0020]FIG. 1 is a side view of an electric hand power tool in accordance with the present invention; and  
         [0021]    [0021]FIG. 2 is a plan view on a switching key with a section of the lower side of the inventive hand power tool.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0022]    [0022]FIG. 1 shows a side view of an electric hand power tool  10  formed as an angle grinder. It has, at the right side in an observation direction, a motor housing  12 , with an electric cable  13  at its rear end for power supply of a not shown motor which is received in the motor housing  12 . A transmission housing  13  is located forwardly on the electric hand power tool  10 . It contains a not shown angular transmission, with drive shaft  16  extending perpendicularly to the longitudinal axis  11  of the motor housing  12  and exiting under it from the angle transmission housing  14 .  
         [0023]    The electric hand power tool  10  at its lower side is provided with an elongated switching key  18 . It is turnable inwardly into the housing  12  in correspondence with a movement arrow  36  around a turning axis  20  located at the front end  17 .  
         [0024]    From the center of the switching key  18 , its straight extending contour  21  merges into an outwardly curved or convex contour  22 . This convex contour  22  merges at the rear end  19  of the switching key  18  into an inwardly extending or concave contour  24 , which ends at the rear end  19  above the highest point of the convex contour  22 .  
         [0025]    A blocking lever  26  is arranged near the deepest point of the convex contour  22 . In its blocking position it projects inclinedly to the left toward the longitudinal axis  11  of the hand power tool  10 , and it is flappable around its turning axis  28  to the rear end  19 .  
         [0026]    The concave curvature  24  in the region of the blocking lever  26  has a depression which corresponds to a negative form of the blocking lever  26 . The depression  23  is shown in FIG. 1 in a broken line and in FIG. 2 in a solid line. Thereby the blocking lever  26  which is turnable in direction of the actuating arrow  38  can be introduced into the outer contour of the concave curvature  24  flush. Thereby it does not interfere with the operator hand during pressing down of the switching key  18 .  
         [0027]    Moreover, the blocking lever  26  in a normal position, or in other words in the OFF position of the switching key  18 , due to its arrangement in the trough-shaped, concave depression  24 , can not be reached by mistake with shoe soles and thereby is especially secure from damages which frequently occur in construction operations. This feature is illustrated by a shown tangent  15  which contacts the both highest points of the contour of the switching key  18  over the depression  24 .  
         [0028]    At the right side as considered in the observation direction, an arresting key  30  is provided on the rear end  19  of the switching key  18 . It is pressable in direction of the movement arrow  13  into the interior of the motor housing  12  when the switching key  18  is actuated in its turning on position.  
         [0029]    When the arresting key  30  after pressing down of the switching key  18  is activated, it is held in its turning on position. Therefore the blocking lever  26  remains flapped into the contour of the concave curvature  24  and thereby there is no danger that the blocking lever  26  breaks during handling of the electric hand power tool  10  by an operator.  
         [0030]    The blocking lever  26  is curved in the same direction toward the concave depression  24 . Therefore it is introduced in the recess  32  completely flush and contour-identically, so that it can be smaller than in the case of a straight-shaped blocking lever.  
         [0031]    The switching key  18 , similarly to a golf ball, carries a calotte-shaped small depression  34  in the region of the convex curvature  22 . This improves the gripping for the operator hand in the actuating region of the switching key  18  and makes this region especially well feelable.  
         [0032]    [0032]FIG. 2 shows a bottom view of the motor housing  12  with the switching key  18 , while from FIG. 1 it can be seen especially clear how the recess  32  extends for insertion of the blocking lever  26 . The turning axis  28  of the blocking lever  26  is located in the deepest region of the concave curvature  24 .  
         [0033]    An actuating arrow  40  is provided for identification of the turning direction of the blocking lever  26 . It is located centrally in the switching key  18  and is formed as a raised formation.  
         [0034]    The present invention provides the same advantages for pressure air operating hand power tools or hand power tools operated from other sources.  
         [0035]    In a not shown embodiment of the invention, instead of the actual bodily formed rotary axis, a virtual rotary axis can be provided for turning the switching key around it. It operates so that the switching key engages the housing with its front end and is clamped in it. It is supported with elastic prestress and is turnable within a range of a gap provided by the housing shape.  
         [0036]    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.  
         [0037]    While the invention has been illustrated and described as embodied in electric hand power tool with switching key, 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.  
         [0038]    Without further analysis, the foregoing will so fully reveal the gist of the 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 this invention.