Communications: electrical – Land vehicle alarms or indicators – Internal alarm or indicator responsive to a condition of the...
Reexamination Certificate
1999-04-02
2001-01-16
Tong, Nina (Department: 2736)
Communications: electrical
Land vehicle alarms or indicators
Internal alarm or indicator responsive to a condition of the...
C340S447000, C073S146300, C073S146400
Reexamination Certificate
active
06175302
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a tire pressure indicator, more particularly to one including pressure gauges that have a self-generating power capability.
2. Description of the Related Art
A tire pressure indicator is to be installed in a vehicle to monitor the pressure of the tires of the vehicle. A regular tire pressure indicator is generally comprised of a set of pressure gages, each of which is mounted on a corresponding pneumatic tire of the vehicle, and a receiver device. Each pressure gauge wirelessly transmits a pressure signal to the receiver device when the pressure in the corresponding pneumatic tire is not within a predetermined normal operating pressure range. As such, the receiver device can alert the driver of the vehicle in the event of an abnormal tire pressure condition.
Since the receiver device of a known tire pressure indicator is built into an instrument panel of the vehicle, or as a separate device to be installed in the driver's compartment of the vehicle, the power source of the vehicle can be used as the power source for the receiver device. However, since the pressure gauges of the known tire pressure indicator are mounted on the tires of the vehicle, battery cells are used as the power source for the pressure gauges. The need to replace the battery cells when they run out of power inconveniences the owner of the vehicle.
In order to eliminate the aforesaid problem, the same applicant filed an application for a tire pressure indicator, which subsequently issued as U.S. Pat. No. 5,694,111. The structure of this tire pressure indicator comprises a piezoelectric type self-generating voltage means, and an LC oscillatory loop formed of a volume variable member, a magnetic core, and an induction coil. This structure of the tire pressure indicator is functional, however, the installation cost of the LC oscillatory loop is expensive.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a tire pressure indicator which has self-provided power generating means to provide the necessary working power economically.
It is another object of the present invention to provide a wireless tire pressure indicator, which eliminates radio signal transmission interference.
According to the present invention, the tire pressure indicator comprises a plurality of pressure gauges, at least one receiver circuit adapted to be installed in the vehicle to receive output signal from said pressure gauges wirelessly, and a controller. Each of the pressure gauges comprises a casing, a power supplying device, a pressure sensing unit, and a transmitter circuit. The power-supplying device comprises a self-generating voltage unit. The self-generating voltage unit comprises a spring element having a first end secured to a casing and a second end, a weight securely mounted on the second end of the spring element, and a piezoelectric unit securely mounted on the spring element. The spring element is vibrated upon motion of the respective pneumatic tire, thereby causing the piezoelectric unit to generate a voltage output to the pressure sensing unit and the transmitter circuit. The pressure sensing unit comprises a capacitor means. The capacitor means comprises a motion member, a conductive member, and a converting circuit. The motion member is made of electrically conductive material and is spaced from the conductive member at a distance. The distance between the motion member and the conductive member is changed subject to the air pressure of respective pneumatic tire, thereby causing the capacity of the capacitor means to be changed relatively. The converting circuit comprises an oscillator connected to the capacitor means such that the converting circuit detects the number of RC oscillating waves from the oscillator and converts the detected signal into a first signal indication of the pressure of the respective pneumatic tire. The transmitter circuit receives the first signal from the pressure-sensing unit, and outputs a second signal by radio. A respective receiver circuit is installed in the vehicle adjacent to each pneumatic tire. The motion member comprises a top side wall, a bottom mouth, and a bellows-like peripheral wall connected between the top side wall and the bottom mouth and defining an air chamber in communication with the bottom mouth. The bottom mouth receives air pressure from the respective pneumatic tire for moving the top side wall relative to the conductive member so as to change the capacity of the capacitor means subject to the pressure of the respective pneumatic tire.
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Bacon & Thomas PLLC
Tong Nina
LandOfFree
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