Patent GB-938898-A (GB)
Title: Apparatus for recording a working programme in a memory device and for controlling a machine in accordance with this programme
IPC: G05B19/425
Filed: 1961-04-17
Abstract: 938,898. Electric selective signalling systems; programmed control of machine tools. MASCHINENFABRIK HEID A.G. April 17, 1961 [May 30, 1960], No. 13755/61. Classes 38 (6) and 40 (1). In a machine-tool control system, pulses from a programming tape representing increments of movement are supplied to one input of a reversible counter the other input of which is connected to a pulse transmitter associated with the driven machine element, the output of the counter is used to control the means for driving the machine element and switch means is provided whereby different outputs of the counter may be made operable so as to vary the sensitivity of the follow-up system at different speeds and avoid hunting. Recording the programme.-Leads used during recording are shown as full lines in Fig. 1. Input switches S supply frequencies f1- f4 signifying movement left, right, up or down to discriminator D and over lead 21 to be recorded on magnetic tape M. Discriminator D and switching unit Sch supply the appropriate command signals to driving units I, II for machine-tool 12, and pulse transmitters I<1>, II<11> associated therewith supply a burst of frequency f6 or f7 over leads 24, 25, 26 to tape M for each increment of movement in the x or y direction. In this manner a complete programme is recorded as a test workpiece is machined. An additional frequency f5 is used to control drive units I, II so as to drive tool 12 at a fast speed during setting up operations, this frequency being recorded in the appropriate parts of the programme. Play-back.-Leads used during play-back are shown as broken lines in Fig. 1. The directioncontrol frequencies f1-f4 are used to control units I, II as during recording. The pulses from transmitters I<1>, II<1> are supplied via flip-flops F:F. to the respective reversible counter ZI, ZII over leads 36, 37, and at the same time pulses of frequencies f6, f7 derived from tape M and converted to D.C. are supplied over leads 32, 33 to the other inputs of counters ZI and Zn. The " 1 " state of these counters remains in the central stage when the position of the machine tool is synchronized with the programme. In one embodiment, stages 0 to Œ4, Fig. 7, are connected to respective gates 0<11> to Œ4<11> each of which is included in a different speed control circuit. As the " 1 " state in the counter progresses further from stage 0, so the speed of tool 12 is progressively increased or decreased until the " 1 " state is brought back to stage 0. At high speeds, however, i.e. when frequency f is recorded in the programme, a relay is operated to change over contacts g4-g9, whereupon a speed correction control only becomes operative when the. error registered in the counter reaches Œ4, thus reducing the sensitivity of the system and avoiding hunting. In another embodiment, Fig. 6 (not shown), stages - 1, 0 + 1 are disconnected and stages Œ2 or Œ5 are all connected to a common decrease or increase speed control circuit. At high speed operation, relay contacts disconnect stages Œ2 to Œ4 so that speed control is only effected if the error reaches Œ5 increments. Each high-speed setting-up operation is concluded by a low-speed operation so that any errors registered in the counters during the high-speed movement can be eliminated. Errors which are not eliminated at the end of a run remain registered in the appropriate counter and are taken into account during the next run in the same direction. Errors registered during a run in one direction, e.g. to the left, would normally be wrongly compensated if a subsequent run was made in the opposite direction, e.g. to the right, and to avoid this a relay is arranged to reverse the connections 32, 36 or 33, 37 in Fig. 1 when the frequencies f1 or f2 and f3 or f4 occur. Alternatively the output connections of the counters may be reversed for runs in opposite directions.