Patent GB-1320480-A (GB)
Title: Grinding machine
IPC: B24B47/20
Filed: 1972-05-23
Abstract: 1320480 Grinding TOYODA KOKI KK 23 May 1972 [3 June 1971] 24309/72 Heading B3D A grinding machine comprises a support 12 for a workpiece 18, such as a crank-shaft, a support 25 for a grinding wheel 26, feed means for effecting movement of the wheel support toward and away from the work support, sizing means 83 engageable with the workpiece to generate a signal responsive to the diameter of the workpiece, means 110 for detecting grinding resistance applied to the wheel during grinding, a timer energized during movement of the wheel support towards the workpiece and timed out after a predetermined time period, control means responsive to the sizing signal for stopping movement of the wheel support towards the work support to effect a spark-out operation before the timer is timed out, control means operable when the timer times out before the grinding resistance becomes a predetermined value in accordance with the spark-out operation to cause retraction of the wheel support and to render a succeeding operation inoperative, and control means operable when the grinding resistance becomes a predetermined value before the timer times out to render the succeeding grinding operation operative. The workpiece is mounted between pot chucks 15, 16 which are synchronously driven by a shaft 19 and mounted in headstocks 13, 14 on a table 12 slidable on a bed 11. The table is longitudinally indexable to positions determined by engagement of a pin 23 with a notched plate 21, and the workpiece is angularly indexable in the pot chucks. The grinding wheel is rotatable by an electric motor 27 and mounted on the support 25 which has a nut 28 engaged by a lead screw 29. The screw is also engaged by a nut 31 which is located in a case 31 and acted upon by fluid pressure to eliminate backlash. A piston 32 in the screw is slidable in a cylinder 38 and has a rod 48 on which is a valve 42 which when actuated during rapid advance of the support by the pistons slows the feed for shoulder grinding. The screw 29 also has a splined portion 52 engaging a member 53 to which is secured a gear 54 meshing, through an intermediate gear 57, with a gear 55 in a shaft 56. A gear 59 in the shaft meshes with a rack 68 on the rod of a piston 69 in a cylinder 70 and is integral with one part 58 of a clutch, the other part 60 of which can be engaged by fluid pressure with part 58. A feed plate 66 is adjustable on the shaft 56 and has a dog 67 for actuating a limit switch. The sizing means 83 is carried by the rod of a piston 82 slidable in a cylinder 84 and its output is fed through an amplifier 87 into a Schmitt circuit which generates first and second signals responsive to the diameter of the workpiece. The spindle 93 of the grinding wheel 26 is rotatably received with small radial clearance in bearing members 90, 91 mounted in the wheel support 25, the members having a plurality of bearing pockets 95, 96. A shoulder 94 on the spindle has a small axial clearance with side surfaces in the member 95 provided with annular grooves 99, 100. A supply of fluid pressure is supplied through restrictors 97, 98 in the pockets and grooves to radially and axially support the spindle. A pair of horizontally opposed pockets 95a, 95b are connected to respective chambers 123, 124 of a differentiator 110 which has a flexible member 112 provided with strain gauges G1, G2 connected into a bridge circuit and Schmitt circuit so as to give an output voltage when the pressure in the chambers 123, 124 is equal, i.e. when there is no load on the grinding wheel. In operation, fluid is supplied to chamber 34 to rapidly advance the grinding wheel until the dog 49 moves valve 42 and a throttle valve 39 is operative to slow the feed for shoulder grinding. At the end of shoulder grinding, a dog 50 actuates a limit switch LS2 to start a timer and to supply fluid to cylinder 71 so that piston 69 moves to effect a rough grinding feed determined by a throttle 74. During rough grinding, the dog 67 actuates limit switch LS3 which causes piston 82 to advance the sizing gauge 83 which, through the Schmitt circuit 87, produces the first signal AS1 at a predetermined size so that fluid from cylinder 71 then passes through a throttle 77 for controlling a fine grinding of the workpiece. When the workpiece is ground to the finish size, the gauge 83 and circuit 87 produces the second signal AS2 and the advance of the grinding wheel is stopped for a spark-out operation. The differentiator 110 at this time does not produce a signal since there is a pressure difference in the chambers 123, 124 because of the grinding resistance. As the grinding resistance reduces, the pressure in the chambers becomes equal and the Schmitt circuit associated therewith produces a signal to initiate retraction of the wheel. If the signal is produced before the timer times out, the control circuit is prepared for the next grinding cycle. If the timer times out before the signal is produced, indicating some inefficiency, such as a dull wheel, the control circuit is prevented from preparing for the next cycle and an alarm is sounded.