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.

Abstract: An apparatus for detecting a pressure drop in a tire chamber of a tire-and-wheel assembly for an automotive vehicle, comprising an oscillator assembly held stationary with respect to the vehicle body structure and a resonator assembly mounted on the wheel rim of the tire-and-wheel assembly, wherein the resonator assembly comprises a resonant inductor and a resonant capacitor which are electrically connected together across a pressure-sensitive switch unit directly communicating with the tire chamber and which are positioned together with a portion of the switch unit within a protective receptacle secured to the wheel rim and wherein the resonant inductor and capacitor and the portion of the switch unit are encapsulated in a body of potting compound forming a potted resonance circuit structure within the protective receptacle, the switch unit and the resonant capacitor being positioned intermally of the resonant inductor.

Abstract: A tire inner pressure drop alarming device comprises an oscillation section mounted on a vehicle body in the vicinity of a vehicle wheel, a resonance section mounted on a peripheral portion of a tire and including a resonance coil, a signal processing and alarming section mounted on the vehicle body in spaced relation with the vehicle wheel, and a coaxial cable connecting the oscillation section and the signal processing and alarming section. The resonance coil has a major length measured in the direction of rotation and longer than a minor length of the resonance coil in a direction perpendicular to the direction of rotation. The ratio of the minor length to the major length ranges from 0.2 to 1.0.

Abstract: An alarm device for signalling a reduction of pneumatic pressure of vehicle tires comprises an oscillator 6 having coil secured to a chassis of a vehicle, and a resonator 1 secured to the peripheral portion of a wheel having a tire adjacent to the coil and consisting of a pressure switch 4 for sensing an abnormal change of tire pressure, and a resonant coil and a capacitor 5 tuned to an electromagnetic wave radiated from the oscillation coil. A signal processing device contains means for sensing a change in an oscillation condition generated in the oscillator due to a resonant condition of the resonator switched on and off in accordance with abnormal internal tire pressure and for processing a signal from the sensing means, and an alarm for generating a warning signal in accordance with the output of the signal processing device.

Abstract: This invention is concerned with a tire pressure drop alarming apparatus for signaling an abnormal pressure drop of a pneumatic tire by transforming the pressure drop into an electric signal.The apparatus comprises a resonating circuit including a resonance coil and a resonance condenser and includes a retaining body made of metal.

Abstract: A pressure sensing switch for transducing the change of pneumatic pressure to an electrical signal comprises a diaphragm made of a material having a Young's modulus E of 1.0.times.10.sup.4 -2.1.times.10.sup.4 kg/mm.sup.2, a Poisson's ratio V of 0.3, a thickness t of 0.02-0.2mm, a diameter d measured at a radially inner edge of a side wall portion being 5-10mm, a ratio of a radius or curvature R measured at a deflectable portion to a diameter d measured at the radially inner edge of the side wall portion being 2.

Abstract: An alarm device for informing reduction of pneumatic pressure of vehicle tires by sensing abnormal change of tire internal pressure of a vehicle when running by a pressure sensing switch, by converting the thus sensed abnormal change into an electric signal and by generating an alarm to an operator.

Abstract: There is described a pressure-responsive switch device particularly suitable for the detection of a pressure drop in a pneumatic tire on a vehicle wheel, wherein a contact carrying movable rod member is securely urged into a contact closing position by means of a conical compression spring to actuate a warning device whenever the internal pressure of the tire drops below a predetermined level. A permanent magnet may be mounted at the contact point of the switch to impart a quick motion thereto.