Oil pressure sender with friction free resistor device

Abstract

The housing has a flexible diaphragm secured over a fluid pressure inlet port in one end thereof, and a cover secured over an opening in the opposite end thereof. A plunger is mounted to reciprocate in the housing between said diaphragm and said cover in response to changes in fluid pressure at the inlet. Secured in the housing beneath the cover is a ceramic chip or substrate, which has a plane surface that extends normal to the axis of the plunger. A spirally shaped resistor element is printed or otherwise formed on the face of the chip, and a conically coiled compression spring is located in the housing between the resistor element and the plunger, and in such manner that its outer convolution at the larger end thereof is engaged with the outer convolution of the spirally shaped resistor element. The smaller end of the spring is connected to the plunger to be reciprocated thereby toward and away from the resistor element. The windings or convolutions of the conical spring register with the spirally shaped convolutions of the flat resistor element, so that as the spring is pressed toward the element it progressively engages more and more of its length with the registering convolutions of the resistor element, thereby progressively shunting out more and more of the resistor from the associated indicator circuit. Conversely, as the plunger moves in the opposite direction the conical spring expands and progressively removes more and more of its length from engagement with the resistor element, thereby increasing the amount of resistance placed in the associated circuit.