GB1341297A - Method and apparatus for grinding a curved periphery of a workpiece - Google Patents

Abstract

1341297 Grinding BRYANT GRINDER CORP 19 April 1971 [24 March 1970] 22514/71 Heading B3D An apparatus for grinding a non-circular workpiece 34 which has a major axis and a minor axis comprises a workhead having a holding means 30 adapted to grip the workpiece and rotate it about a central axis O, the holding means being mounted on a workspindle 45 journalled in a workspindle housing 44, an X cam 48 and a Y cam 50 journalled for rotation on a cam-shaft 52 parallel to the workspindle and rotating in timed relation therewith, a grinding wheel 22 to contact the workpiece surface 36 at a first or contact point spaced from the central axis, and a pair of X and Y cam followers 60, 62 attached to the housing and kept in contact with the X and Y cams, respectively, the X cam follower 60 moving the workpiece in an X direction towards and away from the grinding wheel, and the Y cam follower 62 imparting pivoting movement to the housing about a second point 61 on workhead, the second point being located at a distance S from the centre axis O not less than the minor radius of the workpiece nor greater than the major radius on a line from the central axis to the first point. The cams control the movement of the workpiece so that the linear speed of the contact between the grinding wheel and the surface 36 of the workpiece is substantially constant and to eliminate the effect of change in diameter of the grinding wheel due to wear. The workpiece, 34, such as a cam or a "Wankel" engine cylinder, is held by fluid operated fingers 32 on a chuck 30, and its internal surface 36 is ground by a wheel 22 on a spindle 28, the wheel being trued by a dresser 24. The chuck is carried by the spindle 45 which is rotatable in the housing 44, the housing being laterally movable in opposed hydrostatic bearings 46 in the workhead housing 54. The workspindle housing 44 is supported by a pivot 61 at the end of a bellcrank lever 58 which is mounted on a pivot 56 on the housing 54 and acted upon by an hydraulic cylinder 66 to press the X cam follower 60, which is also mounted on the shaft of pivot 61, against the X cam 48. The housing 44 is movable in the Y direction about the pivot 61 by the Y cam follower 62 which is mounted on a shaft 63 on the housing and is urged against the Y cam 50 by an hydraulic cylinder 68 acting on the housing. The cams 48, 50 are mounted on the shaft 52 which is rotated by a wheel 70 engaging a worm 71 on a shaft 76 rotated by a belt drive 74. The shaft 76 is connected by a flexible coupling 80 to a ball spline 82 in which a splined shaft 84 is slidable. The splined shaft 84 is connected by a constant velocity universal joint 86 to a worm 73 engaging a wheel 72 keyed on the workpiece spindle 45 to effect synchronous rotation of the cam-shaft 52 and spindle 45; alternatively because the workpiece is symmetrical, the cam-shaft may be rotated at twice the speed of the workpieee spindle. During grinding, the cams move the workpiece as it is rotating so that as points 2, 3, 4 &c. of the surface 36 is ground, the grinding wheel centre is at points V 2 , V 3 , V 4 &c., respectively, each point having co-ordinates X 2 , Y 2 , X 3 , Y 3 , X 4 , Y 4 , respectively. The distance X can be corrected by a distance Xc to compensate for changes in the wheel diameter due to wear so that the wheel centre is at points W 2 , W 3 , W 4 &c.