Patent GB-1323887-A (GB)
Title: Logic gates
IPC: F15C5/00
Filed: 1970-05-26
Abstract: 1323887 Fluidic elements O BRYCHTA and C J CHARNLEY 20 May 1971 [26 May 1970 13 Nov 1970] 25191/70 and 54204/70 Heading G4P [Also in Divisions F2 and G3] A fluid logic gate employs an input stage comprising a number of diaphragm valves coupled together to provide the required logic function. The output stage of the gate includes two output channels, fluid pressure being high in one channel when it is low in the other. Fluid is also applied to the input stage, this fluid being obtained from fluid applied to the output stage. One form of diaphragm valve, Fig. 1, has a cavity divided by diaphragm 2. Fluid under constant pressure is applied to duct 7. In the absence of a fluid control signal at duct 5 diaphragm 2 is biased upwards and the supply fluid exhausts through duct 8. When the signal pressure at 5 exceeds the bias force the diaphragm moves down with a snap action on to the end of duct 7, so stopping fluid flow. When the control signal is removed the diaphragm snaps back to the upper position. A second form of the. valve, Fig. 2, includes an exhaust duct 16, the diaphragm permitting fluid flow from one or other exhaust duct 16, 17 dependent on its position. An AND/NAND gate, Fig. 25, having three control signal inputs 30-32, includes three valves 21-23 of the first form and one 20 of the second form. Fluid supplied to Ps passes via the upper leg of fluidic element 150 to ducts 39-41 of the first valves 21-23. In the absence of any one or more of the three inputs the fluid passes through the valves and through channel 54<SP>1</SP> to valve 20. The consequent downward position of the diaphragm of valve 20 prevents fluid from Ps flowing through the upper leg of element 150 B to exhaust via valve 20. The flow in element 150 B therefore passes to the lower leg. The high pressure in this leg represents fulfilment of the NAND function. If all three inputs 30-32 are present the diaphragm of valve 20 bows upwards allowing fluid to flow through the upper leg of element 150 B. Flow through the upper leg of element 150 A being prevented, flow from Ps passes to the lower leg, representing fulfilment of the AND function. The elements 150 A, 15 B may be replaced by elements of the type shown in Fig. 22. An OR/NOR gate, Fig. 24 (not shown), is described. This is similar to the AND/NAND gate of Fig. 25 but the valves are connected in series rather than in parallel. In an alternative arrangement, Fig. 29, a 3- input AND/NAND gate employs 3 valves as shown and a single monostable element 160. Fluid is supplied to the valves and to element 160 from source Ps. In the absence of one or more input signals at 30-32 flow from channel 60 passes to the control input 163 of element 160 resulting in flow from output 162 (NAND). If all three inputs are present there is no flow at input 163 so fluid flow reverts to output 161 (AND). A generally similar OR/NOR gate is described, Fig. 28 (not shown). Another form of AND/NAND gate, Fig. 10, employs valves in an arrangement similar to that in Fig. 25. The vents of the valves associated with the control inputs 117 are not shown in this figure but are connected to channel 125. Fluid is supplied to the valves at A and B and passes through nozzles 75 A, 75 B. The nozzles are surrounded by annular gaps 78 A, 78 B connected to output channels 79 A, 79 B. In the absence of one or more control signals fluid flows through nozzle 75 B, resulting in suction at the gap 78 B and low pressure at 79 B. This represents lack of fulfilment of the AND function. On the other hand, because the diaphragm of the left hand valve is bowed down, fluid from nozzle 75 A passes through gap 78 A and causes high pressure at 79 A, representing fulfilment of the NAND function. If all three inputs are present, pressure at 79 B becomes high and at 79 A low. An OR/NOR gate, Fig. 9 (not shown), is similar to the gate shown in Fig. 9 but the valves 30-32 are connected in series rather than in parallel. Fig. 26 illustrates a bi-stable circuit having two pairs of inputs 195-198. With the diaphragm in the position shown fluid from supply Ps flows from the upper leg of element 150 A and through the valve to vent at 193. Since fluid from Ps cannot flow through the upper leg of 150 B because of the position of the diaphragm, fluid flows from the lower leg, giving output P. If an input pressure is present at either input 197 or 198 the diaphragm willmove downwards, resulting in an output P and no output P. Fig. 30 illustrates a single input bi-stable circuit. With the diaphragm as shown flow from Ps vents via the lower leg of bi-stable element 90, giving output Po. When a pressure pulse appears at Pin it is directed via channels 17, 204 to input 174 of bi-stable 90, causing the flow from Ps to vent at 171, Po. Reverse flow through channel 203 moves the diaphragm downwards when Pin ceases, so that the circuit is prepared to switch back to the state illustrated when the next pulse Pin arrives. Figs. 15 and 22 illustrate monostable elements in which fluid flow from supply Ps normally attaches to the right hand wall of the right hand leg to exit at Pv. If Pv is progressively throttled, in the case of Fig. 15 back pressure in the channel rises. When it reaches a certain value flow switches to the left hand channel, pressure remaining high in the RH channel. When the throttling of the RH channel output is reduced there is a proportional decrease in pressure in the LH channel until, at a certain pressure in the RH channel, the flow switches back to the RH channel. In the case of Fig. 22, flow through the RH channel causes suction in the LH channel. The suction reduces to zero as the RH channel is progressively throttled, flow from Ps then passing to both Po and Pv. When Pv is closed the flow passes entirely to Po.