Abstract:
An electric hand tool is disclosed which has a gt ( 15 ), received in a housing ( 10 ), with a gear shaft ( 20 ) and also has at least one radial bearing ( 30 ) for rotary support of the gear shaft ( 20 ), the inner bearing ring ( 301 ) of the radial bearing being fixed on the gear shaft ( 20 ) and the outer bearing ring ( 302 ) of the radial bearing being fixed in a bearing box ( 31 ) disposed in the housing ( 10 ), in each case being fixed axially nondisplaceably. For simple assembly of the gt ( 15 ) without tools, the outer bearing ring ( 302 ) of the radial bearing ( 30 ) rests with a sliding seat in the bearing box ( 31 ) and is fixed by means of a clamping bracket ( 32 ) fixed to the bearing box ( 31 ).

Description:
BACKGROUND OF THE INVENTION 
   The invention relates to an electric hand tool, in particular a jackhammer or a percussion drill. 
   In a known jackhammer or percussion hammer (German Patent Disclosure DE 28 20 128 A1), the gear shaft, forming part of a layshaft gear, is received rotatably in the housing by means of two ball bearings, which with their inner bearing ring are each shrink-fitted onto one end portion of the gear shaft. The outer bearing ring of the ball bearing is press-fitted in a respective bearing box. One of the bearing boxes is embodied in the housing, and the other of the bearing boxes is embodied in an intermediate flange retained in the housing. Each bearing box has an annular shoulder, on which the outer bearing ring is placed for its positionally correct positioning in the process of press-fitting the ball bearing into the bearing box. 
   SUMMARY OF THE INVENTION 
   The electric hand tool of the invention has the advantage that because of the sliding seat, provided according to the invention, of the radial bearing in the bearing box, the gear shaft and radial bearing can be easily assembled and then, by means of the clamping bracket provided according to the invention, can be axially fixed in the housing without tools. An axial stop provided on the bearing box predetermines the positionally correct position. The clamping bracket is an inexpensive component and makes a compact design of the drive gear possible. 
   By means of the provisions recited in the further claims, advantageous refinements of and improvements to the electric hand tool defined by claim  1  are possible. 
   In a preferred embodiment of the invention, the clamping bracket is embodied spring-elastically and can be slipped onto the bearing box transversely to the axis of the gear shaft in such a way that it fits over the outer ring of the radial bearing, on one face-end annular face thereof, and the radial bearing is adapted, with its other face-end annular face, to an axial stop embodied on the bearing box. The clamping bracket that is resilient in the axial direction of the gear shaft serves as a lever during assembly and with a high axial clamping force it makes an only slight assembly force possible, since the high clamping force is attained only just before the final position of the clamping bracket is reached. For this purpose, in an advantageous embodiment of the invention, the clamping bracket has two spring-elastic bracket arms, which can be inserted axially nondisplaceably by their free end portions into two first counterpart bearings embodied on the bearing box, and also has a transverse part integrally joining the two bracket arms at the other ends of the arms; this transverse part is axially nondisplaceably fixable in a second counterpart bearing, embodied on the bearing box. 
   To generate a high clamping force, in an advantageous embodiment of the invention, the bracket arms are embodied as flat and in at least one arm portion are provided with a bulge oriented transversely to the plane of the bracket arms. 
   In an alternative embodiment of the invention, the bracket arms extend parallel to one another and each have one longitudinally extending guide rib. The guide ribs can be inserted into longitudinal grooves that extend parallel to one another and are diametrically opposite one another on the bearing box and extend transversely to the bearing axis. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention is described in further detail in the following description, in terms of exemplary embodiments shown in the drawing. Shown are: 
       FIG. 1 , a detail of a longitudinal section through a jackhammer; 
       FIG. 2 , a section taken along the line II—II in  FIG. 1 ; 
       FIG. 3 , a fragmentary perspective plan view on the clamping bracket and intermediate flange of the jackhammer in  FIG. 1 ; 
       FIG. 4 , a detail of a plan view of a modified intermediate flange of the jackhammer of  FIG. 1 , with a modified clamping bracket slipped onto it; 
       FIG. 5 , a section taken along the line V—V in  FIG. 4 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The jackhammer, shown in fragmentary form in longitudinal section in  FIG. 1 , as an exemplary embodiment for an electric hand tool in general, has a housing  10  with an inner housing shell  11  and an outer housing shell  12  as well as an intermediate flange  13 . An electric motor is received with its power takeoff shaft  14  in the interior of the housing  10  in a known manner and via a drive gear  15 , it drives a rotary sleeve  16  to rotate and drives a percussion mechanism  17  translationally. Although not further shown, the rotary sleeve  16  is coupled with a tool receptacle, in which a tool such as a percussion drill, is fastened; this drill is carried along in the direction of rotation of the tool receptacle and is capable in the tool receptacle of executing a limited reciprocating displacement motion. The percussion mechanism  17  has a reciprocating drive piston  18 , guided axially displaceably in the rotary sleeve  16 , and a beater, not shown here, which can be acted upon by the drive piston  18  via an air cushion, and which outputs its impact energy to the tool retained in the tool receptacle. A complete illustration and description of the tool receptacle with the tool and the percussion mechanism  17  are found in DE 28 20 128 A1. 
   Both the rotary pivoting motion of the rotary sleeve  16  and the translational motion of the drive piston  18  are derived from the power takeoff shaft  14  of the electric motor by means of an intermediate shaft  20 . To that end, on the power takeoff shaft  14 , a drive pinion  19  is embodied, which meshes with a gear wheel, in this case an intermediate gear wheel  22 , that is press-fitted onto the intermediate shaft  20 . The power takeoff shaft  14  is received, with its wave portion directly adjacent the drive pinion  19 , in a ball bearing  21 , which is fixed in the intermediate flange  13 . The intermediate shaft  20  supports a layshaft pinion  23  in a manner fixed against relative rotation, and this pinion meshes with a layshaft gear wheel, not shown, which in turn engages a ring gear embodied on the rotary sleeve  16 . 
   The percussion mechanism  17  is driven by the intermediate shaft  20  via a pendulum gear  24 . In the exemplary embodiment shown, the pendulum gear  24 , which is known per se, has a drive bearing  25 , embodied as a ball bearing, which is either seated in a manner fixed against relative rotation on the intermediate shaft  20  or is loosely slipped onto it and can then be connected by means of a coupling to the intermediate shaft  20  for the sake of taking over rotation. The drive bearing  25 , comprising an inner bearing body  251  and an outer bearing ring  252  with balls  253  disposed between them is placed with its inner bearing body  252  on the intermediate shaft  20  and is embodied such that the bearing axis forms an acute angle with the axis of the intermediate shaft  20 . The outer bearing ring  252  of the drive bearing  25  supports a radially protruding slaving bolt  26 , which with play engages a qb of a pivot bolt  27 . The pivot bolt  27  is retained in a bifurcated end of the drive piston  18 . The intermediate shaft  20  is rotatably supported in the housing  10  by means of two radial bearings. The radial bearing  28  shown on the left in  FIG. 1  is embodied as a needle bearing, which is received in a corresponding bearing receptacle  29  of the housing  10 . The radial bearing  30 , which has an inner bearing ring  301  and an outer bearing ring  302  with balls  303  retained between them, is press-fitted with its inner bearing ring  301  onto the intermediate shaft  20  and rests with its outer bearing ring  302  in a sliding seat in a bearing box  31  embodied in and integrally with the intermediate flange  13  and is retained axially nondisplaceably in the bearing box  31  by means of a clamping bracket  32  that is fixed to the bearing box  31  or the intermediate flange  13 . The clamping bracket  32 , embodied spring-elastically, is slipped—as can be seen in FIGS.  1 – 3 —onto the bearing box  31  or the intermediate flange  13  transversely to the axis of the intermediate shaft  20 ; the clamping bracket  32  fits over the outer bearing ring  302  on one face-end annular face and presses with its other face-end annular face against an annular shoulder  311  embodied on the bearing box  31  and acting as an axial stop. The clamping bracket  32 , which can be seen in plan view in  FIG. 2  and in perspective in  FIG. 3 , has two spring-elastic bracket arms  321 ,  322 , which on one end of the arms are joined on one end of the arms by a transverse part  323  that is integral with them. The bracket arms  321 ,  322  are embodied as flat, and to increase their clamping force, they each, in an arm portion, have one bulge  324  oriented transversely to the plane of the bracket arms. The bracket arms  321 ,  322  extend at an acute angle to one another approximately in a V, while their free end portions  321 ′,  322 ′ are oriented parallel to one another. The transverse part  323  is bent twice toward the underside on its transverse edge, forming a “U”, whose leg located at the bottom forms a rear-engagement rib  323 ′ that is integral with the transverse part  323 . 
   For firmly fastening the clamping bracket  32  to the bearing box  31  or to the intermediate flange  13 , two slotlike first counterpart bearings  33 ,  34  and one second counterpart bearing  35  embodied as an undercut are embodied on the bearing box  31  and the intermediate flange  13 , respectively. In the process of slipping the clamping bracket  32  onto the intermediate flange  13 , the free end portions  321 ′ and  322 ′ are each slipped into a respective one of the first counterpart bearings  33 ,  34 , and the first counterpart bearings  33 ,  34  axially nondisplaceably fix the bracket arms  321 ,  322 . The clamping bracket  32  is then slipped on far enough that the rear-engagement rib  323 ′, embodied on the transverse part  323 , is located immediately in front of the second counterpart bearing  35  on the underside of the bearing box  31 . The clamping bracket  32  is then pressed onto the bearing box  31  counter to the spring force of the bulges  324  and is displaced farther, until the rear-engagement rib  323 ′ engages the undercut of the second counterpart bearing  35  from behind ( FIGS. 1 and 3 ). 
   In  FIGS. 4 and 5 , a modified clamping bracket  42  is shown, for fixing the radial bearing  30  in the bearing box  31  of the intermediate flange  13 . The clamping bracket  42 , once again embodied spring-elastically, has two spring-elastic bracket arms  421 ,  422 , which on one end of the arms are integrally joined by means of a transverse part  423 . The bracket arms  421 ,  422  extend parallel to one another, and each arm has both a respective guide rib  421 ′ and  422 ′, formed by bending their longitudinal edges into a U and extending parallel to the longitudinal axis of the clamping bracket  42 , and an inward-protruding, wide spring arm  421 ″ and  422 ″, which are prestressed transversely to the plane of the clamping bracket. 
   The embodiment of the bearing box  31  in the intermediate flange  13  is modified such that instead of the counterpart bearings on the bearing box  31 , two parallel longitudinal grooves  43 ,  44  ( FIG. 5 ), diametrically opposite the axis of the intermediate shaft  20 , are provided, into which the bracket arms  421 ,  422  can be inserted with their guide ribs  421 ′,  422 ′. If the clamping bracket  42  is inserted with its bracket arms  421 ,  422  into these longitudinal grooves  43 ,  44 , the spring arms  421 ″ and  422 ″ press axially against the outer bearing ring  302  of the radial bearing  30  and press the radial bearing  30  against the annular shoulder  311 , embodied on the bearing box  31 , in the same way as in  FIG. 1 . 
   The invention is not limited to the jackhammer described. It can be employed in any electric hand tool in which a gear shaft is rotatably supported by means of a radial bearing, such as power drills, power saws, power planes, and the like.