Patent GB-1088581-A (GB)
Title: Improvements in and relating to grinding machines
IPC: B24B49/04
Filed: 1964-06-02
Abstract: 1,088,581. Grinding. LANDIS TOOL CO. June 2, 1964 [June 6, 1963], No. 22691/64. Heading B3D. A machine for grinding non-cyclindrical workpieces comprises a transducer type gauge having a work engaging element arranged to engage only the large diameter portion of the workpiece, characterized by the fact that the oversize large diameter portion actuates said gauge to open an electric circuit and when the larger diameter portions of the work are ground to the desired size, the circuit remains closed, and further characterized in that the transducer circuit is adjustable to effect a slight change in the diameter at which the size signal is given. 30 More particularly, a machine for grinding non- cylindrical workpieces having two angularly spaced portions of substantially the same radius comprises (i) A grinding wheel support; (ii) Means for advancing and retracting said wheel support relative to a workpiece; (iii) A grinding wheel rotatably mounted on said wheel support; (iv) A work support having means for rotatably supporting a workpiece in operative relation with said grinding wheel including a work drive spindle; (v) A gauge movable into and out of contact with said workpiece; (vi) An electric circuit for controlling said advancing and retracting means; (vii) A first means operable when one of said portions is ground to size to close a part of said electric circuit; and (viii) A second means to complete closure of said circuit when the other portion of said workpiece is to size to retract said wheel support. In a machine for grinding automatic pistons, a grinding wheel 15 is carried by a support 11 slidable on a base 10. The support 11 is advanced for a grinding operation by a feed screw 132 operated by a hand wheel 130; power operation is by a rack 140 actuated by a piston 141. Incremental feed is effected by a reversible ratchet 150 connected to the feed screw 132 and operated clockwise by a pawl 152 actuated by a piston 153; the extent of feed is determined by a stop 170 held by a piston 175 in the path of a stop surface 171 on a plate 172. The feed screw 132 is actuated counterclockwise by a pawl 160 actuated by a piston 161. The feed mechanism may have a gear ratio such that feed increments correspond to the increments of size adjustment. Work spindle 40 is rotatable in a cradle 31 pivoted at 22 on a support 30. The spindle 40 carries a diaphragm chuck 47 having jaws 39 which grip the rigid head of a piston workpiece W at angularly spaced positions corresponding to slots separating the head from the skirt portions, so that any deformation of the head by the jaws is not transmitted to the skirt portions. A workpiece is pushed into the chuck by a ram 100 moved endwise by a lever 102, the ram having a pair of locating pins 101 engaging corresponding holes in the workpiece to ensure proper angular positioning of the workpiece. The spindle 40 also carries a master cam 41. Follower 42 is rotatably mounted on an arm 43 pivotally supported by a shaft 45 rotatably mounted in a support 46. A plate 50 adjustably attached to the arm 43 by screws 51 passing through a slot 52 has mounted on its upper end one end of a leaf spring 55, the relative position of the spring 55 and the shaft 45 determining whether a positive or an inverted master cam is used. The other end of the spring 55 is attached to a lug 23 on the cradle 31. A stiffening member 56 is attached to the spring 55 to prevent buckling. A leaf spring 57 is attached at its ends to the member 56 and to the lug 23. A rod 61 mounted on a lug 62 on the support 46 carries a spring 60 acting against the lug 23 and reacting against a washer 67 and nuts 65, 66 by which the spring force urging the master cam against the follower may be adjusted. Precise vertical adjustment of the plate 50 is effected by adjusting screws 70, 71 in a bracket 72 attached to the arm 43. A spring 80 connected between the bracket 72 and the support 46 urges the follower against the master cam. A feeler 110 pivotally mounted on the underside of a gauge 112 is attached to a variable differential transformer or transducer having means for varying the size of workpieces to conform to assembly requirements. The gauge 112 is mounted on a pivoted arm 113 operated by piston 116 in cylinder 117. Movement of gauge 112 towards the workpiece is limited by shoe 120 arranged to ride on cylindrical guide member 121, whereby gauge 112 is held in predetermined relation to spindle 40 and workpiece W and feeler 110 is prevented from contacting the minor diameter of the workpieces. When the workpiece has been ground so that contact with the feeler is discontinued the gauge 112 and grinding wheel support 11 are retracted while the minor diameter of the workpiece is adjacent the grinding wheel. At the end of the grinding operation the work spindle 40 stops in an approximate position which is short of the desired predetermined angular work-receiving position. The spindle is then rotated slowly by a positioning device comprising a piston 180 connected to rotate a gear segment 182 meshing with a pinion 183 driving through a one-way clutch a pulley 187 connected by belt 184 to the spindle 40. A member 185 on the spindle 40 has a stop surface 186 engaged by stop pawl 190 to stop the spindle 40 in the desired position. The pawl 190 is movable between operative and inoperative positions by a piston 191. Actuators 48, 49 on the work spindle 40 actuate limit switches 11 LS and 7 LS at each rotation of the work spindle. After a finished workpiece has been removed from the machine an unground workpiece is dropped from the loading shoot in a predetermined angular position so that the workpiece is in proper relation to the master cam, any slight error in this angular position being corrected on engagement of the pins on the ram with corresponding holes in the workpiece as the ram pushes the workpiece into operative relation with the chuck. The chuck clamps the workpiece and workpiece rotation begins. The feed mechanism advances the grinding wheel for a grinding operation, at a predetermined point in which the gauge is applied to the workpiece, contacting it only on the portions being ground, i.e. the major diameters. When the major diameter of the workpiece engages the gauge, the gauge contact is opened so long as the workpiece is oversize. A proximity switch is actuated simultaneously with opening of the gauge contact. Final approach of the grinding wheel for finish grinding is by increments in timed relation with workpiece rotation, the increments being timed to occur while the minor diameter of the workpiece is passing the grinding wheel. When the workpiece is to size, the gauge contact remains closed and coacts with the proximity switch to stop the grinding operation by retracting the grinding wheel. Workpiece rotation is then stopped and the work head indexed to proper angular position to receive the next workpiece after removal of the finished workpiece.