Patent GB-1516175-A (GB)
Title: Metal working machine
IPC: B24B5/10
Filed: 1975-07-22
Abstract: 1516175 Automatic control BRYANT GRINDER CORP 22 July 1975 30609/75 Heading G3N [Also in Division B3] A metal working machine comprises a workhead assembly Fig. 1, rigidly secured to the base 12, workpieces being fed to the chuck by a shoot 26 and loader mechanisms and, after grinding, being discharged by a shoot 28 to which they are fed by an unloader arm 30. The operations of the loader and unloader, and a dresser 33, are controlled by a mechanical programming mechanism 34 having a synchronous motor 36 and variable speed motor 44 selectively operable to drive a shaft 40 having cams 42, the rotation of the shaft being controlled by a sequencer 46. A digital control circuit, Fig. 9, is provided to control the motor 172 which effects the pivotal movement of the wheelslide and hence the lateral feed of the grinding wheel. A control memory 202 operates to select or excite thumb wheel switch sets 202a, 202b, &c., for setting feed end points and feedrates. The selected switch set feeds a digital position signal to a counter and direction comparator 204 and to a feedrate oscillator 206. The left-hand input to the comparator is the new position command and the right hand input is the old or current position signal. The comparator determines the direction required to equalize the signals and has an output connected to the oscillator 206. When the signals are equalized, pulses supplied to a translator 224 for the motor 172 are stopped. An encoder 226 is rotated by the motor 172 and feeds pulses to a progress counter 228 which is part of a feedback connection, the pulses stored in the counter being compared in a comparator 230 with the left-hand number in the comparator 204. The encoder pulses are also supplied to an absolute feed counter 234 to maintain an indication from the centreline of the wheel spindle, the output from the counter being compared in a comparator 238 with an absolute thumb wheel signal from a switch set 236. The end-points of switches 200a, 200b are referenced to the radius of the grinding wheel after each dressing operation, the compensation being effected by a compensation pulse source 240 which supplies pulses to the oscillator 206. The machine functions are operated by a sequence controller, Fig. 45, which has a command section 810 for generating several classes of digitally coded control signal sequences defining control and analysis steps in the grinding operation, the section having a fixed frequency clock 818 to provide basic timing signals connected through a gate 820 to a digital counter 822 and programmer 826. An output section 812 receives output codes representing functions to be performed by output generators 823, 840. An input signal generator section 814 is responsive to the performance of specific machine functions to produce signals representing performance or non-performance and transmits such signals to the control section 810 so that the sequence is advanced only when the functions have been performed. The programmer may be operated to effect a subroutine according to a signal on a line 878 applied to the counter 822.