GB791242A - Improvements relating to liquid level indicators - Google Patents

Abstract

791,242. Low liquid-level indicators. ANDREWS, J. H. Dec. 16, 1955 [May 16, 1955; June 21, 1955], Nos. 14095/55 and 17946/55. Class 123(1) [Also in Group XXXVII] Means for indicating an abnormally low level of oil in, for example, the sump of a motor vehicle comprises a small internal diameter tube or probe 1. Fig. 1, which is fixed relatively to the sump and is provided with openings 3 at the minimum desirable oil level 4. The upper end of the probe terminates in an enlarged chamber 13 which is connected to a valve-less air suction pump 8 by small bore tubing 11, the latter having a branch 16 leading to an electric switch 14 which controls a signal lamp 17 and is responsive to air pressure so that its contacts close only when the pressure in. the branch is less than atmospheric, that is when the oil level is above the openings 3. In a modification, not shown, the probe 1 is fitted with an orifice-type restriction or a liquid-only non-return valve to check any withdrawal of oil by the pump 8, and the switch 14 may be incorporated in the circuits of the oil pressure or ignition warning lamps. In a further arrangement the pump 8 is dispensed with and the tubing 11, Fig. 3, with its branch 16, is connected by a capillary tube 24 to the induction manifold 23 of the vehicle engine, the other end of the tubing 11 communicating with the probe 1, having a restriction 18, through an oil trap and overflow chamber 13, a liquid-only non-return valve 25, and an oil delay chamber 26. The valve 25 and chambers 13, 26 are located within a tubular casing comprising pairs 28, 28, 29, 29, of circular metal pressings seam-welded around flanges 27, the valve body being secured to the upper pressing 29 and providing a seat 30 to co-operate with a movable valve stem 31 on the lower pressing; as shown, the lower pressing has peripheral apertures 32 and the valve body has apertures 37. The switch 14 consists of a pressure sensitive member preferably in the form of a convoluted rubber tube 38, Fig. 4, and metal blanking pieces 39, 40 with an interposed spring 49 which latter is adapted normally to connect electrically, through a contact 48 on the blanking piece 39, an insulated terminal 46 on a housing 44 for the bellows and a second terminal 50 on the pipe 41 to which the branch air pipe 16 is connected, the pipe 41 being secured to the blanking piece 40 and, through an insulating bush 43, to the housing 44. In this construction the switch opens in response to a sub-atmospheric pressure in the pipes 16, 41, but in a modification, Fig. 5 (not shown), the switch is adapted to be open normally and to close when the pressure falls in the said pipes. Probes for indicating fuel and water levels, as well as oil level, may be associated with a single suction pump.