GB1245995A - Liquid level sensing means and installations provided with such means - Google Patents

Abstract

1,245,995. Fluid-pressure servomotor systems. R. C. PEARSON. Oct. 20, 1969 [Nov.26, 1968; Jan. 15, 1969; April 23, 1969], Nos. 55938/68, 2347/69 and 20683/69. Heading G3P. The supply of liquid to a tank 2 in the Fig. to provisional Specification 55938/68 may be shut-off when the liquid enters the lower end of a U-tube 3 supplied with pulses of air. The pulses are generated by a fluidic NOR gate 5 supplied with compressed air at port 19 and provided with a delay circuit comprising a restrictor 8 and a reservoir 9 to deflect the output periodically into a line 12. The rise in pressure when liquid enters the U-tube is applied to the control port 12 of a flip-flop 14 to divert the compressed air-flow from a port 18 into a line 21 leading to the liquid filling control. Radial holes may be provided at the end of the U- tube. In the Fig. to provisional Specification 2347/69, a pair of similar pulse generating circuits reciprocate a pilot valve 13 which in turn causes reciprocation of a main valve 14 supplying U-tubes 9, 10 in the compartments of a road or rail fuel tanker through non-return valves 40. When a rise in pressure occurs in a U-tube, a diaphragmactuated valve 44 connects a line 53 supplying compressed air to the left hand side of a ram 54 to atmosphere so that the ram is operated by a spring 51 to energize a solenoid valve 58 which connects a filling pipe 5 to atmosphere and returns the liquid supply from a line 59 to a return line 61. The apparatus is supplied through a pressure regulator and lubrication unit 24 which may be filled with glycol to prevent freezing and is fitted with a reset valve 12 and a stop/start valve 20. In a modification, diaphragm-actuated ball valves are used to connect the ram to atmosphere and the pressure in the compartment to be filled is applied to both sides of a diaphragm to prevent any rise in air-pressure in the compartment from operating the filling control. In a further modification, the diaphragm-actuated valve is connected to the U- tube through a restrictor to provide a delay in automatic resetting. The restrictor may be by-passed by a non-return valve so that response time remains unaffected. The U-tube and diaphragmactuated valve may be mounted on a plate which loosely surrounds the filling pipe and rests on the man-hole flange of the compartment and a disc or plate of flat or shaped form may be used to prevent splashing or surging near the end of the tube.