Piezoelectric reed power supply for use in abnormal tire condition warning systems

• US 4,510,484 A
• Filed: 03/28/1983
• Issued: 04/09/1985
• Est. Priority Date: 03/28/1983
• Status: Expired due to Fees

• Current Assignee: The Pullman Company (Apollo Global Management, Inc.)
• Original Assignee: Imperial Clevite Incorporated
• Inventors: Snyder, Daniel S.
• Primary Examiner(s): Caldwell, Sr., John W.
• Assistant Examiner(s): Harding, Ellwood G.
• Application Number:
  US06/479,504
• Time in Patent Office: 743 Days
• Field of Search: 340/52 R, 340/58, 200/61.22, 200/61.23, 200/61.24, 200/61.25, 116/34 A, 116/34 B, 116/34 R, 73/146, 73/146.2, 73/146.3, 73/146.4, 73/146.8, 73/146.5, 310/311, 310/339, 310/319, 455/127, 455/343, 455/345
• US Class Current: 340/438
• CPC Class Codes: B60C 23/0411 Piezoelectric generators
• CPC Class Codes: B60C 23/04985 using straps surrounding the rims
• CPC Class Codes: H02N 2/188 adapted for resonant operation
• CPC Class Codes: H10N 30/306 Cantilevers

Abstract

A device is provided for sensing the condition of a pneumatic tire preferably of the type used on an automobile wherein the tire is mounted on a tire rim and the tire is subject to normal vibrations. The device comprises a housing, a band for mounting the housing to the tire rim, a sensor for monitoring the condition within the tire, circuitry operatively connected to the sensor for generating radio signals indicative of the tire condition, power supply operatively connected to the circuitry and a receiver for receiving the radio signals. The power supply includes a piezoelectric reed having a base portion and an end portion. The base portion is elastomerically bonded to the housing. A tuning mass member is mounted to the end portion and is configured for mating abutment against stop members which limit the flexure stroke of the piezoelectric reed and inhibit compound bending of the reed. The tuning mass member includes an outer weighted casing and an inner elastomeric portion insulating the reed from physical shocks to the outer casing and from electrical shorts across the casing. The tuning mass member is sized relative to the piezoelectric reed to obtain a resonant frequency of vibration of the power supply induced by common road vibrations during wheel operation. The reed is symmetrically configured about a radiating center line of the tire.

Claims

1. A device for sensing a condition of a pneumatic tire preferably of the type used on a motor vehicle wherein the tire is mounted on a tire rim and the tire is subject to normal wheel vibrations, said device comprising:

a housing;

a means for mounting said housing to said tire rim;

sensing means associated with said housing for monitoring a condition within the tire;

circuit means associated with said housing including a radio transmitter circuit operatively connected to said sensing means for generating radio signals indicative of said tire condition;

power supply means associated with said housing operatively connected to said circuit means, said power supply means including a piezoelectric reed having a base portion and an end portion, said base portion being fixedly attached to said housing, and a tuning mass member mounted to said end portion, said power supply further including opposed stop members spaced from said tuning mass member to permit flexure of said reed therebetween, said stop members and said tuning mass member being configured for mating abutment to inhibit compound bending of said reed during flexure; and

means for receiving said radio signals.

2. The device as claimed in claim 1 wherein said housing is mounted in a cavity of said tire rim, said piezoelectric reed being aligned along a radiating center line of said tire rim.

3. The device as claimed in claim 1 wherein said stop members comprise wall portions of said housing, said stop members being spaced from said tuning mass member to limit flexure movement of said reed to an extent to inhibit flexing stress damage to said reed.

4. The device as claimed in claim 1 wherein said tuning mass member is sized relative to said reed to provide a natural resonant frequency of said power supply means of generally 60 Hertz.

5. The device as claimed in claim 1 wherein said tuning mass member includes an inner elastomeric insulating member and an outer weighted casing, said insulating member being chemically bonded to said reed and insulating said reed from physical shocks to said outer casing.

6. The device as claimed in claim 5 wherein said outer weighted casing is compression fitted to said inner elastomeric insulating member.

7. In a device for sensing the abnormal condition of a pneumatic tire of the type used on an automobile wherein the device includes a housing fastened to the tire rim, sensing means mounted to the housing for monitoring a condition within the tire, circuit means contained in the housing and operatively connected to said sensing means for transmitting a radio signal upon sensing of a predetermined condition by said sensing means, and means for receiving said signal and indicating the condition of said tire, the improvement comprising:

a piezoelectric crystal power supply including a radially extending piezoelectric reed elastomerically mounted to said housing, said power supply further including a tuning mass member mounted to an end portion of said reed for facilitating vibration of said reed, said tuning mass member being sized relative to said reed to induce a resonant frequency vibration of said power supply, said resonant frequency being actuated upon normal operation of said automobile tire.

8. The improvement as described in claim 7 further including stop members limiting the vibration stroke of said reed and tuning mass member to within safe flexure stress levels of said reed.

9. The improvement as described in claim 8 wherein said stop members are configured for mating abutment to said tuning mass member to inhibit compound bending of said reed.