GB1343715A - Automatic positioning apparatus for printing presses - Google Patents

Abstract

1343715 Positional control VICTORY KIDDER Ltd 31 Aug 1971 [8 Sept 1970] 40551/71 Heading G1N In an apparatus for positioning plate and roller mechanisms of a printing press, the desired position is presented on a dial and converted into a voltage which is compared with a second voltage indicative of the instantaneous position of the members to provide an error signal to cause the driving of the members towards the desired position. As shown, a reference voltage derived from the output of a differential amplifier (200), Fig. 3, (not shown), having a resistance network (202) in one of its input circuits the value of which is altered by the dial, is combined with a voltage derived from a movable slide potentiometer indicative of the instantaneous position of the member. The combined signal is amplified at 54 and taken to the positive and negative inputs respectively of 2 further differential amplifiers 58, 60 to yield an output either across resistance 74 or 76 depending upon the polarity of the combined signal. The signal from amplifier 58 is adapted to gate S.C.R. 78 to enable triac 86 to enable a pneumatic or hydraulic valve to cause motion of the member in one direction, whereas that from amplifier 60 gates S. C.R. 80 and triac 94 for motion in the opposite direction. The signals are also used respectively to gate S.C.R. 104 and triac 108 and S.C.R. 114 and triac 118 to enable clutch valves on both sides of the member (the "operator" and the "gear" sides) to apply a drive, these parts of the circuits being interconnected as shown so as to move both sides of the member in one or other direction Relay contacts 120, 122 are provided which when operated remove the enabling power voltage from the valve(s). Under these conditions a remote controller may be used to supply power to a plurality of positioning stations according to a programme. The potentiometers moved by the members may have further resistances in series, Figs. 2a-2c (not shown) shunted by relay contacts which may be selectively operated in conditions when a mechanical constraint etc. necessitates modification of the feed-back signal.