Patent GB-1205746-A (GB)
Title: Fluid pressure control systems
Inventor: WARBRICK JOHN CHRISTOPHER
IPC: F15C3/12
Filed: 1966-10-20
Abstract: 1,205,746. Hydraulic brakes. DUNLOP CO. Ltd. 19 Oct., 1967 [20 Oct., 1966], No. 46901/66. Heading F2F. [Also in Division G3] An amplifier applying hydraulic pressure to a braking system is controlled by a signal pressure from a wheel driven pump to prevent skids. The signal pressure source causes variation of output pressure in direct and accurate proportion to the signal pressure value which is modified by feedback derived from the difference in pressure across a restrictor R. An inlet line 109, 108, 105, Fig. 1, terminates in an emitter jet 104, in a beam 101 supported on trunnions 102 and supplies a pair of receiver cups connected to outlet unions. At each end of the beam two opposed pairs of signal pads are provided, the four pads at the upper end of the beam receiving signal pressures while the four pads at the lower end are connected so that opposed pads in each receive upstream and downstream pressures from the same restrictor. A vent for spill flow is provided in the chamber 100 enclosing the beam. The swinging beam may be replaced by a rotor having a pair of emitters 175, Fig. 6, connected to a common supply line to co-operate with a pair of misaligned receiver nozzles 164 each of which supplies a restrictor. The upstream and downstream pressures from each restrictor are applied to opposite sides of each of a pair of vanes on the rotor while opposed signal pressures are oppositely applied to a further four vanes. Rotor movement is limited by a pair of adjustable stops 165 and is damped by oil retained in concentric grooves of adjacent faces of the rotor and casing. An emitter jet 180, Fig. 9, may be formed in a block carried on a flexible steel supply tube and have depressions to receive jets from feed-back and signal nozzles 186 . . . 189. A further nozzle 198 receives a feed-back signal from an output line which is parallel with the line 185 and supplied by a tube constrained to move in unison with the tube 181 to compensate for rate or gravitational effects. To reduce the effects of vibration the system may be mass balanced. In Fig. 12, a slidable spool 201 is subjected through end bores 207 to signal and feed-back pressures which exhaust through radial bores 206. Input and output lines 204, 205 are in slight misalignment and connected by a waisted portion 202 of the spool. A linear drop or lamina restrictor R may be arranged in series with a square law or turbulent flow type R2 as shown in Fig. 13, so that PαS<SP>2</SP>. Reversing the positions of the restrictors produces the relationship Pα#S. Amplifiers similar to that of Fig. 13 may be connected in parallel to feed a third restrictor providing differential forces for operation of a further amplifier when the product or quotient of two signals is required. Fig. 17 includes two containers, such as polythene pipes, downstream of the restrictors to give a linear relation between pressure and contained volume so that the pressure in the container is a measure of the integral of the control signal when the latter controls the flow rate. A similar circuit may be used to obtain a pressure drop across the restrictors which is proportional to the rate of change of signal. If the movement of the emitter beam is damped the relationship PO = (K/C)   # Pidt may be obtained when C is the damping constant and PO and Pi are the input and output pressures. To obtain an output which may be represented graphically by a series of slopes, a summing amplifier is provided for each slope while operation of the emitter beam at predetermined pressure may be produced by the pressure drop across series-connected linear and square law restrictors which are applied in opposition to the beam. A similar arrangement may be used to compensate for temperature changes.