Grinding machine and method of grinding

Abstract

A grinding machine and a method for grinding buttons of a rock drill bit are disclosed. The grinding machine has a frame and a grinding head. The grinding head has a rotatable grinding spindle. The free end of the grinding spindle is intended to drive, and to replaceably carry, a grinding cup. The grinding spindle has a first rotational axis, the grinding spindle being intended to rotate around the same as well as also around a second rotational axis. The first rotational axis of the grinding spindle is arranged to assume at least two separate positions, one of which positions is collinear with the second rotational axis and the second of which positions places the first rotational axis at an angle β with the second rotational axis.

1 . A grinding machine for grinding a button of a rock drill bit, the grinding machine comprising: 
 a frame; and    a grinding head, the grinding head including a rotatable grinding spindle,    wherein a free end of the grinding spindle drives and replaceably carries a grinding cup,    wherein the grinding spindle has a first rotational axis, the grinding spindle rotating around the first rotational axis as well as also around a second axis, and    wherein the first rotational axis of the grinding spindle is arranged to assume at least two separate positions, one of which positions is collinear with the second rotational axis.    
   
   
       2 . The grinding machine according to  claim 1 , wherein the end of the grinding spindle facing away from the free end of the grinding spindle is arranged to assume at least two separate positions, one of which positions is intersected by the second rotational axis.  
   
   
       3 . The grinding machine according to  claim 1 , wherein the end of the grinding spindle facing away from the free end of the grinding spindle can be displaced within an area that is defined by a spherical cone.  
   
   
       4 . The grinding machine according to  claim 3 , wherein the spherical cone has a cone angle of 1° to 90°.  
   
   
       5 . The grinding machine according to  claim 1 , wherein a rotation unit, which is rotatably mounted in the frame and carries the grinding spindle, is arranged to rotate around the second axis, the rotation unit comprising members for adjusting the first rotational axis of the grinding spindle in relation to the second rotational axis.  
   
   
       6 . The grinding machine according to  claim 5 , wherein the members for adjusting the first rotational axis of the grinding spindle in relation to the second rotational axis are arranged to lock the other end of the grinding spindle in a path, which substantially is described by a radius having a radius centre, and in that said radius centre substantially coincides with a radius centre of a cavity of the grinding cup.  
   
   
       7 . The grinding machine according to  claim 5 , wherein the members for adjusting the first rotational axis of the grinding spindle in relation to the second rotational axis comprise curved grooves arranged in the rotation unit and co-operating with followers arranged on a motor bracket, and in that actuators are arranged to lock the motor bracket in a desired position in relation to the grooves.  
   
   
       8 . The grinding machine according to  claim 7 , wherein a driving source for the grinding spindle is rotatably mounted in the motor bracket, so that the driving source in its entirety can rotate in relation to the motor bracket and the first rotational axis.  
   
   
       9 . The grinding machine according to  claim 1 , wherein a member for supplying flush medium to the grinding spindle is mounted on a part-of the grinding spindle that is situated outside a driving source.  
   
   
       10 . The grinding machine according to  claim 1 , wherein the grinding head is displaceable relative to the frame.  
   
   
       11 . A method for grinding the buttons of a rock drill bit by means of a grinding machine, the grinding machine including a frame; and a grinding head, the grinding head including a rotatable grinding spindle, a free end of the grinding spindle driving and replaceably carrying a grinding cup, the grinding spindle having a first rotational axis, the grinding spindle rotatable around the first rotational axis as well as also around a second rotational axis, the method comprising at least the following steps: 
 positioning the grinding cup in a starting position so that the first rotational axis of the grinding spindle substantially coincides with a centre axis of the button that is to be ground;    starting rotation of the grinding spindle around the first rotational axis and around the second rotational axis;    feeding the grinding cup toward the button until the grinding cup abuts against the button;    grinding the button under simultaneous slanting of the grinding cup, from a first position where the first rotational axis of the grinding spindle is collinear with the second rotational axis to a second position where the first rotational axis and the second rotational axis form an angle with each other; and    after a certain time of grinding, guiding the grinding cup back to the starting position.    
   
   
       12 . A grinding machine for grinding a button of a rock drill bit, the grinding machine comprising: 
 a frame;    a grinding head, the grinding head including a rotatable grinding spindle and a grinding cup at a first end; and    a positioning unit operatively connected to the grinding head at a second end of the grinding head,    wherein the grinding head and positioning unit are operatively connected to the frame to translate the grinding head and positioning unit axially along a first axis, and    wherein the second end of the grinding head is displaceable relative to the positioning unit within an area that is defined by a spherical cone.    
   
   
       13 . The grinding machine according to  claim 12 , wherein the spherical cone has a cone angle of 1° to 90°.  
   
   
       14 . The grinding machine of  claim 12 , wherein a vertex of the cone angle is the first end of the grinding head.  
   
   
       15 . A grinding machine for grinding a button of a rock drill bit, the grinding machine comprising: 
 a frame;    a grinding head, the grinding head including a rotatable grinding spindle and a grinding cup at a first end; and    a positioning unit operatively connected to the grinding head at a second end of the grinding head,    wherein the grinding head and positioning unit are operatively connected to the frame to translate the grinding head and positioning unit axially along a first axis,    wherein the second end of the grinding head is displaceable relative to the positioning unit, and    wherein the grinding head is operative over a continuum of positions from a first position in which a rotational axis of the grinding head is coincident with the first axis to a second position in which the rotational axis forms an angle with the first axis.    
   
   
       16 . The grinding machine of  claim 15 , wherein the angle is 1 to 90°.