Patent GB-1386970-A (GB)
Title: Fluidic systems
IPC: F15C1/00
Filed: 1972-01-20
Abstract: 1386970 Fluid regulation BOWLES FLUIDICS CORP 20 Jan 1972 2853/72 Heading G3H In a fluidic circuit comprising an anolog fluidic amplifier providing a fluid output signal as a function of a fluctuating fluid input signal, the transfer function or gain is variable by a command signal generated in separate control means in dependence on the fluid input signal and on a second fluctuating fluid signal that does not of itself constitute an input to the analog amplifier. The fluctuations of the second signal are differently phased from those of the input signal at least part of the time. The second signal may be the integral or derivative of the fluid input signal or originate from an independent source. In the embodiment of Fig. 1, input signal A is integrated at capacitor 11 to provide a signal representative of the average pressure of signal A. This signal and the input signal A are supplied to control nozzles 17, 13 of amplifier 15 to produce outputs which may be used as gain command signals in analog amplifiers 39, 49 each receiving the input signal A direct. Integrating capacitors 35, 47 and a maximum pressure selector unit 31 are included in the circuitry. Signal #A of Fig. 1 may be used in further circuitry, Fig. 2 (not shown), in which the frequency of fluctuations of an input signal from its average is used to provide a gain command signal. The circuitry includes, in flow series, a proportional amplifier (61), a fluidic bistable element (77), a fluidic logic inverter (87), a fluidic slip resolver (95) and a digital-to-analog converter (103) the output from which is supplied as a gain command signal to analog amplifier (107). In Figs. 3 and 4 (not shown), two input signals A and B are supplied to respective sections of the circuit. In each section the input signal A or B is delivered directly to a respective differentiator through one inlet and via a delay element through a second inlet. The outputs of the differentiators are fed to further fluidic devices to produce outputs dependent on signals derived from both inputs A and B for use for gain command purposes. Alternatively, the outputs of the Fig. 4 embodiment may be fed to a fluid logic circuit comprising a number of AND and OR gates, Fig. 5 (not shown), to provide digital indications representing the conditions whereby input signals A and B have amplitudes which are diverging or converging, the outputs from the circuit being usable as gain command signals. Alternatively, they may be used as gating signals in a bistable buffer amplifier 346 of a further fluid circuit shown in Fig. 6b, wherein signals generated in the Fig. 4 circuit are supplied as control signals to amplifiers 313, 325 to produce outputs which are fed to maximum pressure selector units 330, 338 which, in turn, discharge to bistable elements 335, 349. The outputs of the latter are supplied to an amplifier circuit 359 receiving the input signals A and B at control passages 361, 363 and having output passages 370, 372. In use, gain is varied in the amplifier circuit 359 by the various command signals received thereby, by varying the flow impedence of passages 374, 376 or by varying the pressure of power stream issuing from nozzle 360. In Fig. 7 (not shown), four input signals W,X and Y,Z are supplied in pairs to a respective OR gates (383, 393) which discharge to two counters (397, 399), the difference between the counts of which are monitored by a digital comparator (401) and converted to an analog signal by converter 403 for use as a gain command signal in an amplifier receiving, e.g., signals W,X as the input signals. Another circuit, Fig. 8 (not shown), has an amplifier (411) receiving an input signal S and a bias signal to derive an output signal which is delivered directly and indirectly through a delay (418), to a differentiator (419) having three output passages the signal from any one of which may be used for gain command purposes. In a final circuit, Fig. 9 (not shown), an input signal A is supplied directly, and indirectly through a delay (447), to the control nozzles of an amplifier (443) the outputs of which are supplied directly, and indirectly through delays (459, 467), to pairs of control nozzles of a second amplifier whose outputs are similarly supplied to a third amplifier, thereby generating signals which are first, second and third derivatives with respect to time of signal A and which may be used as gain command signals.