GB917771A - Improvements in or relating to apparatus for dispensing mixtures of two liquids - Google Patents

Abstract

917,771. Fluid-pressure servomotor-control systems. AVERY-HARDOLL Ltd. Aug. 11, 1961 [Aug. 15, 1960; Oct. 26, 1960], Nos. 28234/60 and 36767/60. Class 135. Apparatus for dispensing a mixture of two liquids, such as petrol, in predetermined proportions comprises pumps 10, 11, Fig. 1, which deliver the liquids through flow-control valves 19, 21 and flowmeters 22, 23 to pipes 24, 25 leading to a common outlet nozzle. Each flowcontrol valve 19, 21, Fig. 3, comprises a valve closure member 49, loaded by a spring 56 towards its seat 48 and opened by the delivery from the pump acting on a surface 52, the delivery being admitted through ports (not shown) in the valve housing 47. The valve member 49 allows leakage to a control chamber 55 to allow liquid to act in a valve closing direction and the leakage from this chamber is controlled by a pilot valve formed by a hollow stem 67 co-operating with a piston member 62. The piston member 62 is loaded by a spring 64 and carries a mushroom head 59 which is smaller than the smallest end of a tapered sleeve 61 fixed to the valve member 49. When the flow through the valve reaches a predetermined value, the head 59 is moved against the spring 64 to move the piston 62 away from the stem 67 thus allowing more leakage from the chamber 55 and the valve 49 opens further, thus for a given position of the stem 67 the opening of the valve 49 depends on the flow through it, but this rate of flow depends on the position of the stem 67. By providing an adjustable path of entry to the chamber 55 the two flow-control valves may be matched. The positions of the stems 67 are adjusted by levers 43, Fig. 1. The speed of rotation of the flowmeters 22, 23 are fed through shafts 28, 35 and 29 to elements of a.differential gear 36, the sum of the speeds being transmitted through shaft 41 and bevel gears 39 to one element of the differential gear 37. A second element of the gear 37 is fed from shaft 28 through a change of speed gear-box 42 and the output of the gear 37 actuates the levers 43 to adjust the stems to maintain the required flow proportions set by the gear box 42. The gear-box is set by a knob 80 which also arranges that one or other of the electric motors 12, 13 driving the pumps is not actuated at two positions of the knob when a switch is actuated. The gearing may also actuate computers for total flow and cost.