Switching system

1,129,736. Programmed control of machine tools. STARKSTROM-ANLAGENBAU KARLMARX STADT VEB. April 7, 1967, No. 15997/67. Heading G3N. In a numerical control system for operating and processing machines a distance governed transport feed-rate selection, within a range of pre-set preliminary coincidence points is effected through coincident point set OR-elements and feed-rate determining AND-gates interconnected through negators. As shown, when a programmed movement is initiated preliminary coincidence points, A, B, corresponding to particular difference values, from a comparator between the actual and the required position values, are present as L signals at one input of each of OR-gates O1 02. When a transport feed rate Fl is called in through input a of an AND-gate Ul the machine past is moved at this feed-rate until the first preliminary coincidence point A is reached, at which the L signal from OR- gate O1 is cancelled. The feed-rate F1 is then cancelled and a feed-rate V1 initiated through a negator N and an AND-gate U2 enabled by the OR-gate 02. At the second preliminary coincidence point B the L signal from OR-gate 02 is cancelled, thus cancelling feed-rate V1, and initiating a feed-rate 5, through a negator N2, by an AND-gate U3. At the desired position HK, a L signal, through a negator N3, cancels the AND- gate U3 to terminate the movement of the part. For rapid return feed, an X signal to the OR-gate O1 is fed to a second input of the OR-gate 02 and to the AND- gate Ul for the feed-rate F1. The signal X continues over the entire distance to the desired position. The system can be modified to enable the order of the transport actions to be changed by intercalating further OR-gates between the negators and associated feed-rate AND-gates. The number of feed-rates can be increased or reduced by connecting further AND-gates in parallel with the feedrate AND-gates.