Patent GB-1483476-A (GB)
Title: Grinding machine
IPC: B23Q5/22
Filed: 1974-12-02
Abstract: 1483476 Grinding CINCINNATI MILACRON HEALD CORP 2 Dec 1974 [3 Dec 1973] 52078/74 Heading B3D A grinding machine comprises a workhead slide 18 and wheelhead slide 19 mounted on a base 11, a feed mechanism, including a stepping motor 57, for producing transverse relative movement between the slides to produce a grinding cycle, a pulse generator having a first section for producing pulses at a first rate and a second section for producing pulses at a second rate which is substantially greater than the first rate, and control means for introducing pulses from the first section to the motor during a portion of the grinding cycle and for introducing pulses from the second section to the motor during another portion of the grinding cycle. As described, the machine is for grinding the inter. nal surface of roller bearing races and has a grinding wheel 24 on a spindle 23 which is rotated by a motor 15 and mounted on the wheel slide 19. Axial movement of the wheel is effected by an hydraulic cylinder 60 and longitudinal oscillation of the wheel during grinding is produced by an oscillator 50. A workhead 21 is mounted on a slide 19 movable transversely to the axis of the grinding wheel along guides 32, 33 which form self-balancing hydrostatic bearing surfaces of the type in which horizontal or vertical forces on the slide 18 do not change the thickness of the oil film supporting the slide. A block 35 of the slide is slidable relative to a lower element 31 on the base 11 of the machine and has a shaft 36 slidable in a bearing 37 in a flange of the element 31. A pair of flanges 38, 39 extend from the rear of the block and have bearings slidably receiving rods 43, 44 mounted on flanges at the rear of the element 31. The block has a recess 43 formed with vertical surfaces 46, 47. A contact member 48 adjustable by rotation of shaft 36 extends from surface 46 and a contact member 51 is fixed in surface 47. A nut 52 is mounted in block 35 and engages a screw 53, the nut and screw being of the ball type, and the screw is mounted in a bearing 54 and has a gear 55 engaged by a worm 56 driven by the stepping motor 57. A finger 58 depends from the slide 18 into the recess 43 and has plates 58, 62 for engaging the contact members 48, 51, sensing elements 61, 63 indicating when contact is effected. The Specification gives details of a circuit controlling the operation of the machine and, in particular, the stepping motor 57, in which high speed stepping, or half stepping and of high voltage switching of the motor windings. With the workhead slide 18 feeding at a certain grinding rate, a signal calls for a "dress interrupt" and the slide is moved rearwardly at high speed stopping operation so as to align a dressing apparatus 30 with the grinding wheel. A feed reset operation is effected and the pulses set to high speed operation to return the slide at high speed until a deceleration signal is received to produce low speed pulses, a counter and size signal controlling the operation. The accelerations and decelerations provide a smooth change over of feed rates. The control circuit is such that the stepping motor does not lose synchronism with the incoming pulses and grinding can be effected by "dead reckoning" counting.