Bit holder

Abstract

The invention relates to a bit holder for an earth working machine, in particular a road milling machine, having a support body onto which a holding portion having a bit receptacle, and oppositely an insertion projection, are shaped. The holding portion is terminated at the end by a wear surface, and the bit receptacle by a centering receptacle opening in bevel fashion toward the wear surface. A centering height, measured in the direction of the longitudinal center axis, between an end of the centering receptacle and the wear surface or a maximum point of a projection projecting beyond the wear surface, is designed in such a way that the ratio between the inside diameter D i of the bit receptacle and the centering height is less than 8; and/or that the centering height is greater than an axial play of a round-shank bit installable in the bit holder; and that the support body comprises, on its side facing away from the holding portion, at least two bearing surfaces that are at an angle to one another and form a bearing-surface pair. Reduced wear on the holding portion and a reduced load on the insertion projection, and thus an extension of the service life of the bit holder, are achieved.

1 - 11 : (canceled) 
     
     
         12 : A bit holder for an earth working machine, comprising:
 a support body including a holding portion and an insertion projection, the holding portion being located on a working side of the support body, and the insertion projection extending from a side of the support body opposite from the holding portion;   the holding portion including:
 a bit receptacle having a longitudinal center axis and an inside diameter; 
 a wear surface defined on an end of the holding portion facing away from the support body, the wear surface surrounding the bit receptacle and being configured for abutment of a round-shank bit or of a support element for a round-shank bit;
 a centering surface oriented obliquely to the longitudinal center axis of the bit receptacle, the centering surface connecting the bit receptacle and the wear surface and defining a centering receptacle, the centering receptacle having a centering height measured parallel to the longitudinal center axis, the centering height extending between an end of the centering receptacle facing away from the wear surface and a maximum point of projection of the wear surface, a ratio of the inside diameter of the bit receptacle to the centering height being less than 8.0; 
 
 wherein the support body includes at least one bearing surface on the second side of the support body, the at least one bearing surface extending on both sides of a center plane of the support body including the longitudinal center axis of the bit receptacle. 
   
     
     
         13 : The bit holder of  claim 12 , wherein the ratio of the inside diameter of the bit receptacle to the centering height is less than 7.5. 
     
     
         14 : The bit holder of  claim 12 , wherein the ratio of the inside diameter of the bit receptacle to the centering height is less than 7.0. 
     
     
         15 : The bit holder of  claim 12 , wherein the ratio of the inside diameter of the bit receptacle to the centering height is less than 6.5. 
     
     
         16 : The bit holder of  claim 12 , wherein the maximum point of projection surrounds the bit receptacle. 
     
     
         17 : The bit holder of  claim 12 , wherein:
 the wear surface includes a plurality of projections projecting beyond a lowest part of the wear surface by the same or differing heights; and   the centering height is defined with reference to one of the projections having a greatest height.   
     
     
         18 : The bit holder of  claim 12 , wherein:
 the wear surface includes a guidance groove defined in the wear surface and spaced away from and surrounding the centering receptacle.   
     
     
         19 : The bit holder of  claim 18 , wherein:
 the maximum point of projection is located between the centering receptacle and the guidance groove; and   the centering receptacle has a greater depth with respect to another portion of the wear surface adjacent the guidance groove than does the guidance groove.   
     
     
         20 : The bit holder of  claim 12 , wherein a transition between the centering surface and the maximum point of projection is continuous or rounded. 
     
     
         21 : The bit holder of  claim 12 , wherein a height of the maximum point of projection with respect to a lowest part of the wear surface is greater than or equal to 0.3 mm. 
     
     
         22 : The bit holder of  claim 12 , wherein the height of the maximum point of projection with respect to a lowest part of the wear surface is in a range of from 0.3 mm to 2.0 mm. 
     
     
         23 : The bit holder of  claim 12 , wherein the height of the maximum point of projection with respect to a lowest part of the wear surface is in a range of from 0.5 mm to 1.5 mm. 
     
     
         24 : The bit holder of  claim 12 , wherein the inside diameter of the bit receptacle is equal to 20 mm and the centering height is greater than 2.5 mm. 
     
     
         25 : The bit holder of  claim 12 , wherein the inside diameter of the bit receptacle is equal to 22 mm and the centering height is greater than 2.75 mm. 
     
     
         26 : The bit holder of  claim 12 , wherein the inside diameter of the bit receptacle is equal to 25 mm and the centering height is greater than 3.125 mm. 
     
     
         27 : The bit holder of  claim 12 , wherein the inside diameter of the bit receptacle is equal to 42 mm and the centering height is greater than 5.25 mm. 
     
     
         28 : The bit holder of  claim 12 , wherein the maximum point of projection is formed on the wear surface by a material-removing production method selected from the group consisting of turning, sinking and milling. 
     
     
         29 : The bit holder of  claim 12 , wherein the at least one bearing surface comprises a bearing surface pair of two bearing surfaces on opposite sides of the center plane. 
     
     
         30 : The bit holder of  claim 29 , wherein the at least one bearing surface further comprises at least one further bearing surface that is at an angle to the two bearing surfaces of the bearing surface pair. 
     
     
         31 : The bit holder of  claim 12 , wherein the centering height is greater than an axial play of a round-shank bit installed in the bit holder.