Oil pressure sender with rolling diaphragm

Abstract

This pressure sender or transducer comprises a metal housing having a steel cover and containing a rolling diaphragm which is secured over a cavity in the housing to communicate at one side with fluid under pressure, such as the oil in the crankcase of an automobile. Mounted centrally in the opposite side of the diaphragm is a rigid cup, which rotatably supports one end of a reciprocable plunger which in one embodiment carries two sets of equi-angularly spaced, resilient metal wipers or contacts, four of which are slidably engaged with the cylindrical operating surface of a printed resistor, which is mounted in the closed end of the cover, and four others of which are slidably engaged with the inner peripheral surface of the cover itself. The resistor comprises a steel can having a thin layer of porcelain baked on its outer peripheral surface, and a thin, cylindrical layer of resistance material printed and baked onto the porcelain layer with one end in electrical contact with the steel can. A coiled compression spring resists movement of the plunger in one direction, but cannot apply any rotational torque to the diaphragm because the plunger is mounted for rotation relative to the diaphragm. In a second embodiment the resistor and a ground conductor are printed on the plane surface of a ceramic substrate, and are engaged slidably by two sets of fine wires carried by the plunger.