Alarm device for informing reduction of pneumatic pressure of vehicle tires

• US 4,275,377 A
• Filed: 06/18/1979
• Issued: 06/23/1981
• Est. Priority Date: 06/20/1978
• Status: Expired due to Term

• Current Assignee: Bridgestone Tire Company Limited (Bridgestone Corporation), Mitaka Instrument Company Limited
• Original Assignee: Bridgestone Tire Company Limited (Bridgestone Corporation), Mitaka Instrument Company Limited
• Inventors: Nishino, Hiroshi, Matsuda, Akira, Iwasaki, Motoaki, Yasuda, Shigeo, Goshima, Norio
• Primary Examiner(s): Caldwell, Sr., John W.
• Assistant Examiner(s): Nowicki, Joseph E.
• Application Number:
  US06/049,830
• Time in Patent Office: 736 Days
• Field of Search: 340/58, 200/61.22, 200/61.25, 73/146.5
• US Class Current: 340/448
• CPC Class Codes: B60C 23/0428 using passive wheel mounted resonance circuits

Abstract

An alarm device for signalling a reduction of pneumatic vehicle tire pressure comprises an oscillator 6 having an oscillation 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 oscillation coil and consisting of a pressure switch 4 for sensing an abnormal tire pressure change and a resonance coil and a capacitor 5 tuned to an electromagnetic wave radiated from the oscillation coil. A signal processing device contains a 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. The latter comprises a signal input section 21 having a desired number of input terminals, a signal processing section 22 having an arithmetic circuit connected to the signal input section, a resettable latch circuit 30,32, and an alarm section 23 operated by the output of the latch circuit whereby an alarm signal is not generated at normal internal pressure and during stops of the vehicle.

Claims

1. In an alarm device for signalling a reduction of the pneumatic pressure of vehicle tires including an oscillator (6) having an oscillation coil secured to a chassis of a vehicle;

a resonator (1) secured to a peripheral portion of a wheel having a tire adjacent to the oscillation coil and including a pressure sensing switch (4) responsive to an abnormal change of the pneumatic pressure of said vehicle tire, a resonant coil and a capacitor (5) which are tuned to an electromagnetic wave radiated from the oscillation coil;

a signal processing device (3) containing means for sensing a change in an oscillation condition generated in the oscillator due to a resonant condition in the resonator switched on and off in accordance with abnormal internal pressure of the tire and for processing a signal sensed by the sensing means; and

an alarm means for generating a warning signal in accordance with the output of the signal processing device;

the improvements characterized by;

the signal processing device including a signal input section (21) having a desired number of input terminals, a signal processing section having an arithmetic circuit connected to the signal input section and comprising an AND gate (24) and an OR gate (25) connected in parallel with each other and each having the same number of input terminals as the number of output terminals of the signal input section and individually connected thereto, a delay circuit (27) having first and second input terminals connected to outputs of the AND gate and the OR gate, a first latch circuit (30) having a second input terminal connected to an output of the delay circuit and a plurality of latch elements equal in number to the output terminals of the signal input section and having first input terminals individually connected thereto, a second latch circuit (32) having a first input terminal connected to the output of the delay circuit and consisting of a single latch element, and an alarm reset circuit (29) connected to a third input terminal of the first latch circuit, to a second input terminal of the second latch circuit, and to a third input terminal of the delay circuit, respectively, and having a switch (28) for resetting an alarm signal, and an alarm section operated by outputs of the first and second latch circuits, whereby an alarm signal is not generated at normal internal pressure and during stops of the vehicle.

2. An alarm device as claimed in claim 1, wherein the alarm section comprises a photocoupler (33) and a relay (34) connected to the output of the second latch circuit to generate and display an alarm at a remote place.

3. An alarm device as claimed in claim 1, wherein the signal processing section further comprises a switch (26) for canceling the input of the pressure reduction sensed signal provided between the signal input terminal of the signal input section and the OR gate of the signal processing section.