Patent GB-1449630-A (GB)
Title: Apparatus for controlling the movement of a machine tool carriage
IPC: B24B49/04
Filed: 1973-12-27
Abstract: 1449630 Automatic movement control FORTUNA WERKE MASCHINENFABRIK AG 27 Dec 1973 [27 Dec 1972] 59886/73 Heading G3N In the control of machine tool (grinding machine or lathe) carriage movement, pulses derived from rotation of the carriage feed screw change the content of a counter, feed screw movement being arrested either in response to a signal from a workpiece measuring device, or, should the device fail, in dependence on the counter content, whereupon the counter is reset to control reverse movement of the carriage, until a final count state is reached. When reversal is instigated by the measurement signal, the counter is reset to a content distinct from the original content. As shown; carriage 2 supporting wheel 1 for grinding workpiece 3; push button arrays 20, 21 are used to provide BCD digits of a number representing the amount by which the workpiece radius is to be reduced, with a safety allowance, to BCD counter stages 17, 18, an amount corresponding to change of wheel size due to dressing being set in array 22 for transfer to stage 19. Following a dressing, wheel 1 undergoes fine feed into workpiece 3 as pulses provided by pulse generator 10 decrease the content of stages 17-19 by counting stage 19 to zero, whence via link F-G, stage 18 is counted to zero, whence, via divider 23, stage 17 is counted towards zero, operation of start command 24 having enabled, via signals E, transfer of the BCD numbers from arrays 20-22 to stages 17-19. (i) Grinding cycle with workpiece measurement. Before the content of the counter reaches zero, and when the workpiece attains its desired diameter, measurement unit 16, via units 32, 40, stops the feed and operates reversing switch 12. After a dwell period due to the time constant of monostable 40 during which spark-out occurs, counters 17 and 18 are reset, counter 19 not being reset, and the motor 8 is actuated in reverse, pulses from 10 decreasing the content of counter stages 17 and 18, a signal, at zero counter content, via units 32, 38 and 36 causing the motor to stop, with wheel 1 retracted just sufficiently for a new workpiece to be inserted, reversing switch 12 again being operated preparatory to the next cycle. (ii) Grinding cycle without a measurement signal, the measurement unit having failed. Fine feed forward takes place until the counter content is zero, whence the signal from G, stage 17 via units 38, 32, 40 stops the feed and actuates the reversing switch. In this case all stages 17-19 are reset and their content reduced to zero during the reverse fine feed. Stage 19 receives only zeroes from array 22 after the first fine feed following wheel dressing, during which it contained the amount by which the wheel was dressed. The feed stopping signal, being present in conjunction with a signal from limit switch 29 of a coarse feed, operates an alarm lamp 44. Motor 8 is controlled by thyristor rectifier 11, whose control pulses are provided by continuous oscillator 35. Alternatively, it may be a stepping motor. A coarse feed comprising double acting hydraulic cylinders 5, whose piston 7 acts as the leadscrew unit, as well as direction control valve 14 and pump 13 may be provided, fine forward feed being preceded by forward movement of piston 7, the coarse feed also acting to retract the carriage in conjunction with the fine reverse feed. If the feed line of carriage 2 is not perpendicular to the workpiece axis, each pulse from generator 10 represents a given change only in the component of motion transverse to the workpiece axis. The control circuit may be embodied in electro-mechanical, or fluid logic form. The counter stages may increase in content from zero, to predetermined values to control the fine feeds.