GB1305205A - - Google Patents

Abstract

1305205 Sensing and controlling liquid levels GRESHAM AND CRAVEN Ltd 19 March 1970 [11 April 1969] 18653/69 Heading G1H [Also in Division F1] A liquid level sensing element includes a float 1 moveable by the liquid, means 2 operatively linking the float to a valve 4 in a valve chamber 8 and a fluid-flow path 13 from the valve chamber to an otherwise closed chamber in the float through a one way valve 9 and said link means 2. The float may thus be constructed of an inert material such as stainless steel which would make it too heavy to act as a float if it had to be made with walls strong enough to resist outside pressure. The valve chamber 8 in use is connected to a source of fluid under pressure through a filter 23 and choke 20 and the back pressure (high or low when the outlet 5 is closed or opened by valve 4) is used for controlling purposes. An ejector operated displacement pump 48 uses two of these elements 36, 35, for sensing low and high liquid levels in tank 49. The source of fluid pressure supplies air to the sensing elements and on a suction stroke through valve 31 in the position shown to the ejector 41. Suction of ejector 41 draws air out of tank 49 through valve 31 and liquid in via valve 54. Upper level sensor 35 is arranged so that lifting its float closes its outlet; the resulting back pressure moves valve 31 to its alternative position in which the pressure is cut off from the ejector, the ejector is cut off from the tank ending the suction stage and a bleed of compressed air leaks to the tank forcing liquid out via valve 55. When the float of the lower element drops, its outlet port is closed and the back pressure in 37 moves the valve 31 to its alternative position, there being no back pressure in line 38, the float of element 35 having dropped to open its outlet when the liquid level in 49 started to fall. A new suction stage then begins.