Patent GB-1348458-A (GB)
Title: Grinding machines
IPC: B24B53/00
Filed: 1972-09-07
Abstract: 1348458 Trueing WARNER & SWASEY CO 7 Sept 1972 [24 Sept 1971] 41552/72 Heading B3D A grinding machine includes a base 10, a grinding wheel 23 on a slide 20, work support means 14, 16, means for feeding the wheel 23 towards a workpiece W, wheel trueing means 66, means 115 for advancing the slide 20 to compensate for trueing, and control means for periodically actuating the trueing means 66 after a number of workpieces have been ground in sequence, the number decreasing progressively as the wheel diameter is reduced. The slide 20 may be advanced by means of a rapid traverse piston 36 acting on a feed screw 24 in a feed nut 30 of the slide 20, a fine feed being provided by rotation of the screw 24 coupled by a sleeve 25 to a shaft 52, rotatable by means of a gear connection to a rack piston 61, or a hand feed wheel 45 acting through a gear train 48-51. The pistons 36, 61 are actuated by a common fluid pressure source governed by a solenoid operated valve V1, the workpiece W being ground to size under the control of an in-process gauge G or a timer T. At the end of a grinding cycle, the slide 20 is retracted by the piston 36, and a rod 164 integral with the piston 36 actuates a limit switch LS4, sending an impulse to a counter 166 for summing the grinding operations. A trueing tool 72 is advanced by a pair of alternately fluid actuated ratchet pistons 82, 84 whose ratchet wheel 86 drives a feed screw 71, the tool 72 being traversed across the wheel 23 by a piston 94, with a follower 90 engaging a form bar 88 to provide the required profile. A cable 100 connected to the shaft of the wheel 86 actuates rheostat means 104 for controlling the speed of a wheel drive motor M to maintain a substantially constant surface speed, and the fluid pressure is also led to a rack piston 127, arranged to rotate the shaft 52 through gears (not fully shown) to cause the screw 24 to effect the compensating movement of the nut 30. Trueing frequency control.-At each trueing action, a valve V3 is arranged to effect a reciprocation of a rack piston 142 in a cylinder 140 fixed to the base 10. The return stroke is limited by engagement of a rod 143 of the piston with a stop bracket 162 of the slide 20, and the stroke varies from zero with a new wheel 23 to a maximum when the wheel 23 is about to be replaced. The piston 142 drives an inner member 152 of a one way overrunning clutch mechanism 150, so arranged that the inward strokes of the piston 142 act to turn a rotary cam disc 158 bearing a dog 160, which at each complete revolution of the disc 158 actuates a switch LS3. As the slide 20 is further advanced with successive trueing operations, the stroke of the piston 142 increases and the switch LS3 is operated with increasing frequency, producing a series of pulses which are fed to the counter 166 along with those from the switch LS4. Each LS3 pulse adds, in effect, one " workpiece " to the counted number and since trueing is effected each time the summation reaches a preset limit, the number of actual grinding operations between trueing strokes decreases as the proportion of pulses due to the switch LS3 rises, resulting in the required increase in trueing frequency.