GB716958A - Improvements in or relating to liquid level gauges - Google Patents

Abstract

716,958. Electric control systems. NATIONAL RESEARCH DEVELOPMENT CORPORATION. March 17, 1952 [March 19, 1951], No. 6580/51. Class 40 (1). A liquid level indicator includes a variable electrical resistance, which comprises at least one electrical element 12 extending within, or as part of, an elongated hollow 11 which is adapted to be resiliently collapsed under the pressure of liquid into which it extends, the length of the element 12 which is electrically effective at any time depending on what proportion of the length of the body 11 is collapsed. The body 11 is insulating and may be of rubber or polythene, and the element 12 is a strip of resistive material, e.g. carbon-treated paper secured to the body wall. On collapsing of the body 11, the strip 12 is contacted in the collapsed part by a second strip 12 which may be resistive or conductive, e.g. copper. Various modifications are described. The strips 12 may serve to bridge two V-section body parts, thus forming part of the hollow body, or the strips 12 may both be conductive, a central rod carrying a resistance winding. Alternatively the winding may be dispensed with, the rod be conductive, and the strips 12 resistive. Again, the strips 12 may be replaced respectively by a stranded conductor 18 and by a zig-zag resistance 19 which is bowed transversely, see Fig. 8, or two stranded resistances may be each enclosed between two arms of a central conductive element of cruciform cross-section. A further embodiment differs from those previously described in that two conductive strips are not secured to the body wall, but are resiliently secured at their top ends, a central rod supporting a resistance helix. Finally, see Fig. 9, one electrical element 20 only may be used, comprising a resistance helix the coils of which are inclined to the horizontal to contact each other on collapse of the body. The body is preferably vented.