Abstract: A system for indicating low tire pressure in vehicles, in which each vehicle wheel has a transmitter (100) with a unique code. A central receiver (200) in the vehicle is taught, at manufacture, to recognize the codes for the respective transmitters (100) for the vehicle, and also a common transmitter code, in the event one of the transmitters (102) needs to be replaced. During vehicle operation and maintenance, when the tires are rotated, the system can be recalibrated to relearn the locations of the transmitters. The transmitters (100) employ surface acoustic wave (SAW) devices (110). An application specific integrated circuit (ASIC) encoder (130) in each transmitter (100) is programmed at manufacture, in accordance with its unique code, to send its information at different intervals, to avoid clash between two or more transmitters (100) on the vehicle. The transmitters (100) are powered by long-life batteries.

Abstract: The diaphragm of a dual tire equalizer has an axial probe actuating or not actuating a switch in a radio frequency transmitter circuit mounted on the wheel. The transmitter sends a signal varying, depending on the condition of the switch. A radio frequency receiver on the vehicle and connected to an indicator in the driver's cab responds to the signal and issues appropriate information to the driver concerning condition of the equalizer.

Abstract: A tubular insert is adapted to be secured into an opening in the vessel and is formed with an internally threaded section adapted to receive a closure. The closure is a subassembly which includes a core hosuing having a threaded section threadedly engaging the insert and an internal threaded section and formed with a valve seat at its lower end. A core body is threadedly disposed in the housing and a valve element engages the seat with a compression spring inbetween the body and valve element. A stop is provided on the insert and retaining means are provided on the housing so that when the core housing is unscrewed, it is loosely retained in the insert indicating to everyone that the vessel is depressurized and the metal of the vessel can be heated and melted without any fear of explosion.

Abstract: A reliable indication of temperature-compensated pressure is provided from each of the wheels of a vehicle to an operator within the vehicle. A piezoresistive transducer bridge is supplied by a constant current source in one embodiment, and by a voltage of constant amplitude in another embodiment. Voltage to the bridge is reversed on a periodic basis. The use of constant current enables compensation for temperature-induced drift in transducer bridge output. The use of constant voltage enables compensation for ambient temperature, and provides an absolute, rather than a relative indication of pressure or "flatness" within the tire. Voltage polarity reversal permits compensation of amplifier offset voltage. Energy is transmitted to an from the wheel by means of a tuned circuit which is excited by a primary coil when the vehicle's engine is running.

Abstract: This tire valve comprises a brass stem having an elongate insulating sleeve over it, the sleeve being circumposed by a flanged threaded metal body which is provided with a gasket and a clamping nut to clamp the valve to the wheel. Electrically insulated from each other are a pair of contact rings held respectively against the clamping nut on the body and a second final nut contacting the stem, the rings having take-off leads. A molded rubber shroud protects the rings and holds them and an insulating spacer in proper relation.