Patent GB-1438305-A (GB)
Title: Machine tool having rest apparatus
IPC: B24B47/20
Filed: 1973-11-20
Abstract: 1438305 Grinding TOYODA KOKI KK 20 Nov 1973 [29 Nov 1972] 53821/73 Heading B3D A machine tool comprises drive means for rotating a workpiece W supported on workpiece supporting means 38, at least one machining tool 14, such as a grinding wheel, carried by tool slide means 13, first feed means 20, 33 for moving the tool slide towards and away from the workpiece, rest apparatus located on the opposite side of the workpiece from the tool slide and having an engaging finger 45a for supporting the workpiece during machining, and second feed means 43, 51 for moving the rest apparatus towards and away from the workpiece. First control means controls the first and second feed means to move the tool slide and rest apparatus towards and away from the workpiece. Sizing device means 54 measures a dimension of the workpiece and generates an output corresponding to the dimension. Second control means effects a temporary stop of the tool slide means at a given moment, and third control means controls the second feed means 51 so as to move the engaging finger in a direction of the workpiece during the momentary stop through a predetermined distance in co-operation with the sizing device means to forcedly shift the workpiece towards the machining tool, the workpiece continuing to be machined while the tool slide means is momentarily stopped. Fourth control means controls a movement of the engaging finger in the direction of the workpiece synchronously with a movement of the tool slide means at the same speed after the forced shifting by the third control means. The machining is thus effected independently of wear of the engaging finger. As described, the machine tool is a grinding machine having a wheel 14 belt driven from a motor 16 and mounted on the tool slide 13 which is movable along guide ways 12 on a bed 10. The tool slide has a nut 23 engaged by a lead screw rotatable in, but axially fast with, a piston 21 movable in a cylinder 20 on the bed. A gear 24 on the screw is connected by gearing 29 ... 34 to a stepping motor 33. The workpiece W is mounted between head and tail stocks on a swivel table 38 carried by a traverse table 36 slidable along guideways 35 on the bed by an hydraulic cylinder 39. The bed also carries a base 41 for a rest body 43 which is movable towards and from the workpiece by an hydraulic cylinder 43 of the second feed means. A pair of rods 44a, 44b are slidably mounted in the body, rod 44a having a finger 45a for engaging the workpiece, and rod 44b engaging a pivotally mounted arm 46 to engage a finger 45b with the workpiece. The rods are engaged by screws 48a, 48b of opposite hand which are interconnected by gears 49a, 49b driven by a second stepping motor 51 of the second feed means. The sizing device 54 has upper and lower feelers 55, 56 connected to a differential transformer to produce an output proportional to the diameter of the workpiece In operation, a start signal applied to a main control circuit 59 caused the supply to the hydraulic cylinder 20 to effect a rapid advance of the wheel slide until a limit switch LS1 is actuated at point A, Fig. 5, so that pulses are supplied at a rapid rate to the stepping motor 33 for a rough feed rate. The pulses are also supplied to an up-down counter 62 to enable a digital display of the position of the wheel slide by an indicator 64. When the number of pulses equals a value preset in a switch 60, a coincidence circuit 61 effects a momentary stop at point B and the body 42 of the rest apparatus is advanced to the workpiece at point H and the feelers 55, 56 engage the workpiece. The body advances to operate a limit switch LS3 and start a timer which, after a short interval, produces a single pulse to render a memory circuit 58 conductive and store an output signal from the sizing device 54 and which causes a train of pulses to be supplied to motor 51 so that the engaging fingers 45a, 45b press the workpiece against the grinding wheel which is thereby ground during the momentary stop of the tool slide 13, the output from the sizing device 54 decreasing and being compared with the stored signal. When the difference reaches a preset value a Schmitt circuit produces a synchronized start signal to advance the wheel slide 13, point C, and the engaging fingers 45a, 45b, point J. Rough grinding continues to points D, K, a mensuration control circuit produces a fine grind signal AS1, whereby a conversion circuit 65 reduces the frequency of the pulses supplied to the motors 33, 51 for fine grinding to points E, L whereupon the mensuration circuit produces a size complete signal AS2 to stop advance of the wheel slide 13 and engaging fingers for a spark-out to points F, M.