Patent GB-869014-A (GB)
Title: Method and apparatus for numerical control of machine tools
IPC: G05B19/4103
Filed: 1957-05-31
Abstract: 869,014. Copying-machines. GIDDINGS & LEWIS MACHINE TOOL CO. May 31, 1957 [June 5, 1956], No. 4516/59. Divided out of 869,012. Class 38 (6). [Also in Group XXII] The Specification repeats the description of the programmed control system for a milling- machine disclosed in Specification 869,013 and adds the following features:- (1) Special codes.-A multiplicity of special codes consisting of two numbers prefixed by an " X " may be entered on the original punched tape in between blocks of dimensional information. Such codes (i) determine which combination of the 5 control axes shall be used; (ii) select the time scale of the director and magnetic tape recorder; (iii) shut down the entire system; (iv) effect up to 21 miscellaneous (and largely unspecified) on/off switching operations. In all cases the effect of the " X " prefix is to momentarily release a relay in the bank 121, and this by a multiplicity of contacts effects the following: (a) the punched tape reader 120 is stopped; (b) the output of the coding matrix 122 is open-circuited; (c) the magnetic store register 125 is cleared; (d) the command clock time selector gates 126 are re-set to unit time ratio; (e) the acceleration adjust circuit 140 is prepared so that as disclosed, in Specification 869,012, the command clock 128 is slowed down to decelerate the machine-tool system before it stops; (f) a circuit to a bank of selector relays' 144 and Fig. 35 (not shown) is prepared; (g) after a 5-second delay the punched tape reader is restarted. The subsequent two numerals (before the X code set-up is cancelled by yet another code input), selectively energize interconnected relays 144 to effect any of the controls listed above. These are:-(i) axis selection. Provision is made for the machine to operate with either all 5 axes in action, or for the " A " axis with some combinations of two of the others. The appropriate 5 codes selectively energize relays 124 by which the output of the coding matrix 122 is supplied either to the full sequence of 5 magnetic stores 125, Figs.12A, 12B, 12C (not shown), or to the last three only. In the latter case (because certain axes have been omitted from the sequence), the sign and distance information for the 3 axes will not necessarily be in the normal sequence so the output lines to the decoder 132 are crossconnected by gates 131 switched by the selected relays. (ii) Director time scaling. When an increment is programmed to occupy 1 second or less of machine time, the punched tape reader would not have sufficient time to read the next block of information if the director operated at normal speed. Therefore provision is made to run the command clock 128, master clock frequency-divider 134, and magnetic tape recorder drive 98 at full, half or quarter speed. All these are selectively switched by two relays, Fig. 36 (not shown) controlled as above by the appropriate 3 codes. (iii) and (iv). On/off switching. Twenty-two different codes selectively energize corresponding outputs of the selector relays, Fig. 35 (not shown). One directly controls the starter circuits of all the equipment to effect a shut-down, the others are connected as desired by a manual switchboard, Fig. 37 (not shown), to energize or de-energize selected relays (14 are provided) by which 200 c.p.s. or 4000 c.p.s. tones can be applied to selected recording-heads (7 are provided) on the magnetic tape recorder 98. On playback, Fig. 40 (not shown), the outputs of these seven auxiliary channels are amplified, the tones selected by filters and used to energize relays which start and stop lubricating pumps &c. (2) Reversal of direction of movement.-The gates 133, Fig. 25 (not shown), which determine whether the phase-modulation of the output pulses from the director shall be such as to cause movement in one direction or the other, may be reversed in sense by a manual control, Fig. 27 (not shown) so as to reverse the direction of movement from that originally programmed. (3) Automatic acceleration limiting.-Provision is made to automatically limit the rate of change of machining speed between two blocks of time and distance information, as described in Specification 869,012.