Pressure monitor system

• US 20020117005A1
• Filed: 01/24/2002
• Published: 08/29/2002
• Est. Priority Date: 07/28/1999
• Status: Active Grant

• Current Assignee: Transense Technologies Plc
• Original Assignee: Transense Technologies Plc
• Inventors: Beckley, John, Vile, David
• Granted Patent: US 6,715,355 B2
• Time in Patent Office: Days
• US Class Current: 73/702
• CPC Class Codes: B60C 23/0408 transmitting the signals by non-mechanical means from the wheel or tyre to a vehicle body mounted receiver
• CPC Class Codes: B60C 23/0494 Valve stem attachments positioned inside the tyre chamber
• CPC Class Codes: G01L 17/00 Devices or apparatus for measuring tyre pressure or the pressure in other inflated bodies
• CPC Class Codes: G01L 9/0025 with acoustic surface waves

Abstract

A pressure monitoring system comprises a first chamber (11) and a second chamber (12) separated by a diaphragm. The diaphragm carries respective SAW devices on the respective sides thereof, the SAW devices having different resonant frequencies. Variations in pressure within the second chamber (12) relative to the pressure within the first chamber (11) will cause deflection of the diaphragm and the resulting changes in resonant frequency of the SAW devices can be analyzed to indicate the pressure differential between the chambers. As illustrated, the pressure-measuring device is incorporated within a valve assembly for a vehicle tire. When the vehicle tire is inflated the inflation pressure is trapped within the first chamber (11) as a reference. Any subsequent loss of pressure from the second chamber (12), e.g. as a result of a puncture, will cause deflection of the diaphragm and a corresponding output from the SAW devices.

Claims

1. A pressure monitoring system comprising a first pressure chamber and a second pressure chamber separated by a diaphragm, a first SAW device having a first resonant frequency mounted on one side of the diaphragm and a second SAW device having a second resonant frequency mounted on the other side of the diaphragm, the first chamber being arranged to be pressurised to a predetermined pressure Pand to remain at that pressure and the second chamber being arranged to initially be pressurised to a pressure P₂ equal to pressure P₁ but being subject to change over time, whereby if the pressure P₂ in the second chamber falls or rises relative to the pressure P₁ in the first chamber, the diaphragm will deflect so one side thereof is subject to tension and the other side thereof is subject to compression, the first and second SAW devices being arranged to sense this deflection by sensing said tension and compression and hence provide an output indicative of the change of the pressure P₂ in the second chamber relative to the pressure P₁ in the first chamber.

2. A pressure monitoring system as claimed in claim 1 in which the diaphragm comprises one or more layers of a piezoelectric material.

3. A pressure monitoring system as claimed in claim 1 or 2 in which the first chamber is provided with a first one-way valve which prevents air leaving the chamber.

4. A pressure monitoring system as claimed in claim 1, 2 or 3 comprising processing means arranged to subtract the output of the first SAW device from the output of the second SAW device, or vice versa, to provide an indication of the pressure differential between the first and second chambers.

5. A pressure monitoring system as claimed in claim 4 in which the processing means is arranged to generate a warning signal when a pressure differential greater than a given level is detected.

6. A pressure monitoring system as claimed in any preceding claim comprising a transponder for providing wireless communication between the system and a remote sensor.

8. An inflation valve comprising a pressure monitoring system as claimed in any preceding claim.

9. An inflation valve as claimed in claim 8 comprising a pressure monitoring system as claimed in claim 3 or any claim dependent thereon, having a second one-way valve through which inflation air is provided and having a release mechanism which may be actuated to prevent flow of air therethrough in the opposite direction.

10. An inflation valve as claimed in claim 9 in which the first on-way valves also has a release mechanism to permit air to escape from the first chamber, the first and second one-way valves being interconnected so actuation of the release mechanism of the second one-way also actuates the release mechanism of the first one-way valve.

11. An inflation valve as claimed in claim 8, 9 or 10 comprising a metal insert to function as an aerial.

12. An Inflation valve as claimed in any of claims 8-11 which comprises the inflation valve for a pneumatic tyre.

13. An inflation valve as claimed in claim 12 when connected to a pneumatic tyre.

7. A pressure monitoring system substantially as herein before described with reference to the accompanying drawings.