Patent GB-1231053-A (GB)
IPC: F15B21/00
Filed: 1968-06-12
Abstract: 1,231,053. 053. Fluid logic circuits. WERK ZEUGMASCHINEN KOMBINAT "FRITZ HECKERT" KARL-MARX-STADT, VEB. June 12, 1968, No.27964/68. Heading F1P. [Also in Division G3] In a contactless pneumatic positioning system for machine control a cam 1 carried by a moving machine part traverses a nozzle block 2 defining an auxiliary cascade 2À1 and a main cascade 2.2, supplied with auxiliary air over preliminary throttles 3À1, 3.2. Nozzle 2À2 is connected over duct 4.2 to chambers 5.3 and 5.5 of pneumatic calculating amplifier 5 directly, and to chambers 5.4 and 5.6 over controllable shut-off valves 6, 7. Chambers 5.1, 5.2; 5.3; 5.4; 5.5, 5.6; are separated by force transmission membranes 8À1, 8À2, 8À3 while chambers 5-1; 5-2, 5-3; 5.4, 5-5; 5À6; are bounded by sealing membranes 9.1, 9.2, 9.3, 9.4. Nozzle 2À1 is connected over duct 4À1, threshold switch 10, AND gate 11, to store 14 direct and to store 13 through OR gate 12, which is controlled by the output cascade of calculating amplifier 5 at nozzle 15 and the preliminary throttle 16 supplied with auxiliary air; through amplifying relay 17, duct 18, and delay element 19; the duct also connecting through impulse shaper 20, OR gate 21 and store 13 to an adjusting element effecting opening of valve 6. Signals indicating changeover from fast feed to dead slow feed, are passed from relay 17 over duct 22 to the control systems and drive elements for the machine (not shown) which carries cam 1, while stopping signals are passed from relay 17 or a manual control (not shown) over the control and drive elements to duct 23, and to OR gate 21 and store 14. Chambers 5.1, 5.2 may be pressurized to P corr  to displace the cut-out point. In operation, a cut-out control pressure P s  of the main cascade is derived corresponding to a predetermined cam position lying between limiting minimum and maximum pressures P min and P max for full opening and full closing of the nozzles, and it is shown that for a uniform cut-out point 1 Ps=(P max- CP min/C) + P min where c is a constant e. g. 2. so that P max + P min - 2P s  = 0. Positioning cut-out is effected by the main cascade over nozzle 2.2, while control of shut-off valves 6, 7 to chambers 5.4 and 5À6 is effected by the auxiliary cascade over nozzle 2À1. When cam 1 approaches block 2 in the direction shown at machine fast speed, nozzles 2À1 and 2.2 are open to establish P min which is fed over 4.2 to chambers 5.3, 5.5 and over open valves 6, 7 to chambers 5.4, 5.6 of the calculating amplifier, whose output cascade pressure is less than the control pressure of relay 17. As cam 1 traverses the block, pressure increases, and nozzle 2À1 is covered to increase auxiliary pressure in duct 4À1 to operate threshold switch 10, whose output traverses open AND gate 11 to zeroize stores 13, 14, and close valves 6, 7; so that P min is stored in chambers 5.4 and 5.6. Cam 1 then leaves nozzle 2À1 and covers nozzle 2.2 so that pressure increases in duct 4.2 and chambers 5.3, 5.5 against P min in chambers 5.4, 5À6. This switches the amplifier to increase its output cascade pressure whereby relay 17 deliver an output signal over duct 22 to the central system to change over the drive elements (not shown), and the machine part carrying cam 1 from fast speed to dead slow speed, and also to operate AND gate 11 to interrupt the output signal of threshold switch 10 and open shut-off valve 6 over impulse shaper 20, OR gate 21, and store 13. The cam continues to travel in the same direction dead slow to cover nozzle 2‹2, and the main cascade pressure then increases in chambers 5.3, 5.5 and also in chamber 5.4 over open valve 6 to P max, and thereafter the signal over duct 18 closes valve 6 over delay element 19, OR gate 12, and store 13 to hold P max in chamber 5.4. Subsequently continued cam movement unmasks nozzle 2À1 and the main cascade pressure is reduced, and when this (P max - P mm reaches (P max - P min /2), amplifier 5 switches to open the output nozzle 15 on satisfaction of the equation for P s . The pressure in the output cascade falls, and amplifying relay 17 cancels output signal in ducts 18, 22 to stop the machine element drive, and imposes a signal on duct 23 to open valves 6, 7 over OR gate 21 and stores 13, 14. Static pressurization of chambers 5À1 or 5.2 with a measured valve of P corr  corrects the equilibrium of the cut-out point. A modification Fig. 2 (not shown), eliminates pressure differential errors and enables more precise control to be achieved, while a further modification Fig. 3 (not shown), utilizing plural cams and nozzle boxes in association with the circuit of Fig. 1, enables the machine part'to be controlled in similar manner to assume plural positions in bi-directional movement.