Patent GB-1021545-A (GB)
Title: A method of and apparatus for grinding annular workpieces
IPC: B24B41/06
Filed: 1962-08-30
Abstract: 1,021,545. Grinding. ULVASNDA VERKSTADER A.B. Aug. 30, 1962 [Sept. 1, 1961], No. 33289/62. Heading B3D. A method of grinding the internal surfaces of annular workpieces in which the workpiece is held in engagement with a surface formed on a work spindle in a plane perpendicular to the central axis of the spindle by means of a rotatable plate which is carried in a stationary element is characterized in that the workpiece is caused to assume, during a first period of application, a concentric or almost concentric position in relationship to the work spindle by backing members fixing the workpiece in all radial directions, after which the position thus attained is maintained during grinding by the axial force exerted by the plate towards the said surface, and thereafter moving the backing members away from the workpiece. The work spindle 10 of a grinding machine, Fig. 1 (not shown), and Fig. 2 (not shown), is provided at its end with an anti-wear ring 12 forming a flat surface, perpendicular to the spindle axis, against which an annular workpiece 16, e.g. a ball-bearing ring, is held by a device activated by pressure medium, the device including a stationary housing 18 and a piston 20 axially movable therein. A ball bearing 24 is interposed between the housing 18 and a cylindrical portion of the piston. The piston is moved towards the work spindle, against the action of springs 32, by admitting air, through an adjustable restriction 27, to a chamber 30 at the lower side of the piston. A plate 36 is rotatably mounted by balls 38 in the piston.' A plate 40 is rotatably mounted in the plate 36 by balls 42 coacting with races on the two plates such that the plate 40 has a radial freedom of motion relative to the plate 36; the plate 40 is centred relatively to the plate 36 by an annular element 47, e.g. of resilient material. Within the plate 40 is disposed an annular element 48 carrying a pressure plate 50 having a flat surface to engage the workpiece. The plate 40 and element 48 have spherical races 54, 56 for balls 58, the centre of the races being located on the axis of the workspindle at a point above the pressure plate 50 whereby the pressure plate 50 can adjust itself to any warpage or distortion that the end planes of the workpiece may exhibit in relationship to a plane perpendicular to the axis of the work spindle. The internal surface of the workpiece is ground by a grinding wheel 62 which is reciprocated and fed radially. Non-rotatable jaws 64, 66 are provided with backing members 68, 68 and 70, 70. The jaws are movable on balls 96, 98, and are connected, so as to move simultaneously but oppositely, by a bar 84 acting on one end of a pivoted lever 86 the other end of which acts on the jaw 86; the connection may be duplicated. The jaws are urged apart by a spring 100 and are moved toward each other by compressed air acting on a piston 74 in a cylinder in a housing 78. A pin 106 axially movable in a bore in the housing 78 has a head 112 received in a chamber 110 in the jaw 64. A screw 114 adjustable in the inner end of the pin co-operates with an abutment 116 in the wall of the chamber. A spring 118 urges the join outwardly of the jaw 64. The pin 106 may be locked axially in the housing 78 by compressed air acting on a piston 120 in a cylinder in the housing 78, the piston rod co-operating with a flattened surface 128 on the pin 106. When a workpiece is inserted between the surfaces on the ends of the ring 12 and of the pressure plate 50 the backing members 68, 68 and 70, 70 are spaced from the workpiece. Air is then applied to the piston 74 to move the jaws 64, 66 toward the workpiece so that the backing members 68, 68 and 70, 70 engage the workpiece which assumes a substantially concentric position relative to the work spindle axis. Air is then applied to the piston 20 so that the pressure plate 50 is applied to the workpiece to hold it against the ring 12; at the same time the workpiece is caused to rotate with the work spindle. During the clamping of the workpiece, air is applied to the piston 120 to lock the pin 106. Pressure on the piston 74 is then exhausted, and the spring 100 moves the jaws 64, 66 away from the workpiece, the movement being limited by the engagement of the abutment 116 with the screw 114. The internal surface of the workpiece is ground to a circular configuration independent of the external surfaces 134 of the workpiece by which it was centred, so that the surfaces need not be provided with great accuracy; after the internal surface has been ground the curved ball race 136 may be treated so as to be concentric with the internal surface within very narrow tolerances. In a modification, Fig. 3 (not shown), and Fig. 4 (not shown), there is located between the plates 36, 50 a gimbal member comprising an outer ring 152 resting on the top side of the plate 36 and an inner ring 153 having a shoulder 154 engaging the plate 50. The gimbal member is further provided with a central cylindrical sleeve 156 merging at the top into a radial inwardly directed annular flange 158 and at the bottom into a radial outwardly directed annular flange 160. At diametrically opposed points the flange 158 is connected by flexible strips 162, 162 with an annular flange 164 on the inner ring 153. At diametrically opposed points, displaced 90 degrees from the previous points, the flange 160 is connected by flexible strips 166, 166 with the outer ring 152.