Patent GB-952065-A (GB)
Title: Method and apparatus for grinding
IPC: B24B49/04
Filed: 1960-05-24
Abstract: 952,065. Grinding. HEALD MACHINE CO. May 24, 1960 [Nov. 25, 1959], No. 18247/60. Heading B3D.  A method of grinding the surface of a workpiece comprises the steps of advancing a first abrasive surface into contact with the surface of the workpiece, removing the first abrasive surface from contact with the surface of the workpiece and advancing into contact with the surface of the workpiece a second abrasive surface, removing the abrasive surfaces from the workpiece, removing the workpiece and replacing it with an unfinished workpiece while dressing the second abrasive surface at a point removed from the workpiece area. An internal grinding machine has grinding wheels 12, 13 on a spindle 11 rotated by a wheelhead motor 19 mounted on a wheelhead table 21. The table 21 is movable, in the direction of the axis of the spindle 11, on a base 22, the motion being effected by a piston 44 in a cylinder 43. A cylinder 46 has a piston 47 with a rod 48 co-operating with an ear extending downwardly from the table 21. The cylinder 46 is provided with a solenoid valve 61 and a screw 64 permits adjustment of the contact between the rod and the ear. A workhead table 23 is mounted on ways 24 for movement transversely of the axis of the spindle 11. The table 23 has a bridge 25 through which the table 21 extends and on the upper part of the bridge is a workhead 26 in which is rotatably mounted a hollow drive spindle 27 provided with a pulley 28 by which it is driven and with a drive platen 15 pressing against one end of a workpiece 16, e.g. the outer race of a tapered roller bearing, the other end of the workpiece being contacted by a pressure member 20 comprising rolls on a yoke to which is connected a cylinder 59 also connected to an ejection mechanism. A supporting shoe 29 extending from the workhead 26 contacts the outer cylindrical surface of the workpiece 16. A dresser 31 carrying a diamond 14 is mounted on the workhead table 23. Movement of the workhead is effected by a feed-screw 32 mounted on the base and passing through a nut 33 mounted in the workhead table 23 and connected thereto by a back-off cylinder 58. The feed screw has at its outer end a gear 34 meshing with a rack 35 on a feed piston 36 slidable in a bore 37 formed in a feed-box 38. Also connected to the outer end of the feed-screw 32 is a disc 39 with cams 41, 42. A loading shoot 49 contains unfinished workpieces which are released at a suitable time by an escapement mechanism 51. An air gauge 17 is located within the tapered bore 18 of the workpiece. The gauge 17 is mounted on an arm 52 pivoted at 53 and connected to the rod 55 of a piston in a cylinder 54 provided with a solenoid valve 56. A stop-feed mechanism 65 within the feed-box 38 has a peg 67 which can be projected into the bore 37 in position to be engaged by the end of the feed piston 36. The mechanism 65 has a piston 68 with an inclined surface engaging the inner end of the peg 67 to move it outwardly, against a spring 71, when the piston is moved, against a spring 69, under the control of a solenoid valve 72. The control system includes a hand throttle 74, a pilot valve 75 associated with a reverse valve 76, a sequence valve 77 (with rough adjusting knob 78, finish adjusting knob 79 and dress adjusting knob 81), a runout solenoid valve 82, a dresser solenoid valve 83, a sparkout solenoid valve 84, a transfer valve 85, a stopvalve 86, a feed pressure regulating valve 87, a table stop-and-start solenoid valve 88, a loading solenoid valve 89, a relief valve 91, an accumulator 94, a solenoid valve 96, a pump 97 connected to a check valve 92 for supplying the system with pressure fluid, and a check valve 93 connected to a sump tank. A solenoid valve 99 regulates the flow of oil from the feed-box 38, the energization of the valve coil being under the supervision of a load control 101. Operation.-(1) The workpiece is loaded into the machine and both wheels are dressed by the diamond. Both wheels 12, 13 are out of contact with the workpiece. The gauge cylinder 54 is connected, by the solenoid valve 56, to exhaust. The solenoid valve 99, which is a bypass to the feed side of the feed piston 36 during the rapid in-feed, is closed. The solenoid valve 72 connects the cylinder 65 to exhaust. The solenoid valve 61 connects the cylinder 46 to pressure. (2) Rapid infeed. The valve 99 is open, permitting very fast feed. When the wheel 12 contacts the workpiece current builds up in the wheelhead motor 19 which current is measured by the load control 101, similar to that in U.S.A. Specification 2,722,648, and effects termination of rapid infeed.  (3) Plunge for rough grind. The wheel 12 is in contact with the workpiece. The metoring valve associated with the knob 78 of the sequence valve 77 regulates the feed rate. (4) Sparkout. A gauging control 105 associated with the air gauge 17 determines when the proper point in the plunge has been completed and energizes the solenoid valve 72, thus extending the peg 67 into the path of the feed piston 36 to stop feed at that point. (5) Back-off. When the bore has been enlarged so that deflection in the spindle is relieved, the gauging control 105 de-activates the solenoid valve 72 to retract the peg 67 ; feed does not recommence, being prevented by stopvalve 86. The workhead is retracted until the wheel clears the workpiece surface and the solenoid valve 61 is actuated, connecting the cylinder 46 to exhaust and causing the spindle to move longitudinally so that the wheel 13 enters the workpiece bore. (6) Finish grind with reciprocation. Feed is continued under control of the finish metering knob 79 along with reciprocation of the table 21 until the gauge 17 indicates that the workpiece has reached the finished size. At that time the cylinder 58 will be energized, thus withdrawing the workpiece away from the wheel and the table cylinder will be energized on a long stroke to move the spindle and abrasive wheels out of the workpiece.  The cycle starts again with the ejection of the finished workpiece and the insertion of another unfinished workpiece into the machine.