Pressure-sensitive switch unit in resonator assembly of tire pressure

Abstract

A pressure-sensitive switch unit forming part of a resonator assembly for use in a tire pressure drop detecting apparatus of the electromagnetic induction type, wherein an atmospheric chamber, formed in a casing structure and hermetically isolated by a diaphragm from a pressure-acting chamber communicating with the tire chamber in a tire-and-wheel assembly, communicates with the atmosphere through contact surfaces of two or three of the component parts of the casing structure and further through a body of a gas-permeable synthetic rubber in part exposed to the atmosphere so that an atmospheric pressure is at all times introduced into the atmosphere atmospheric chamber and an ingress of water and dust into the atmospheric chamber is precluded by the body of the gas-permeable synthetic rubber.