Worn brake lining detector

• US 3,902,157 A
• Filed: 06/01/1973
• Issued: 08/26/1975
• Est. Priority Date: 07/17/1972
• Status: Expired due to Term

• Current Assignee: Masachika Yamamoto, Yasuo Kita
• Original Assignee: Masachika Yamamoto, Yasuo Kita
• Inventors: Kita, Yasuo, Yamamoto, Masachika
• Primary Examiner(s): Caldwell, John W.
• Assistant Examiner(s): Nowicki, Joseph E.
• Application Number:
  US05/365,947
• Time in Patent Office: 816 Days
• Field of Search: 340/52A,52B,378,384E 188/1A 200/61.4
• US Class Current: 340/454
• CPC Class Codes: F16D 66/022 indicating that a lining is worn to minimum allowable thickness

Abstract

A fail-safe detector circuit for detecting a worn condition of the friction linings mounted on the brake pads of a disc brake assembly. A conductor loop project through each brake pad into the lining to a point defined as the working limit of the lining. When the lining wears down to this working limit, an alarm is energized. The conductors embedded in the linings are connected in a series circuit with a fuse and a relay coil. Connected in parallel with this series circuit is an alarm circuit consisting of the relay contacts and an alarm device. Under normal operating condition, current from a battery flows through the series circuit to energize the relay and hold open the relay contacts, so that the alarm device is not energized. When either one of the linings wears down beyond the working limit, the associated embedded conductor loop electrically engages the rotating disc of the brake assembly, thereby short-circuiting the series circuit and causing the fuse to blow and open the series circuit so that the relay coil is de-energized. Consequently, the relay switch contacts in the alarm circuit close to permit energization of the alarm device by the battery.

Claims

1. In a worn brake-lining detector circuit of the type in which an electrical conductor embedded in the lining electrically contacts a rotating braking member when the lining is worn down beyond a predetermined working limit to energize an alarm, an improved alarm circuit comprising:

a. a series circuit including a circuit breaker means connected in series with said electrical conductor and operative to interrupt said circuit in response to an overcurrent caused by electrical contact between said conductor and said braking member, b. a single electric power source coupled to said series circuit and said braking member so that electric current from said single power source normally flows through said series circuit, and c. a normally de-energized alarm device connected in a circuit parallel with said series circuit, said parallel circuit being connected to said single power source and normally having a higher impedance than said series circuit so that interruption of said series circuit causes sufficient current to flow from said single power source and through said alarm device to energize it.

2. The improved circuit as defined in claim 1 further comprising a relay switch having its normally energized operating coil connected in series with said series circuit and its normally open contacts connected in series with said alarm device, whereby interruption of said series circuit de-energizes said coil to close said contacts so that current flows from said power source and through said contacts and said alarm device to energize said alarm device.

3. The improved circuit as defined in claim 1 wherein said alarm device comprises a light-emitting diode.

4. The improved circuit as defined in claim 1 wherein said alarm device comprises a piezo-electric buzzer.

5. The improved alarm circuit as defined in claim 1 wherein said circuit breaker means is a fuse.

6. The improved alarm circuit as defined in claim 1, further comprising a resistor connected in series with both said parallel circuit and said series circuit.

7. The improved alarm circuit as defined in claim 2 wherein one side of said power source is connected to one end of said series circuit, the other end of said power source is connected to both said braking member and to the other end of said series circuit, said circuit breaker means is connected between said one side of said power source and the point at which said conductor contacts said braking member, and said coil is connected between said point and said other side of said power source.

8. The improved alarm circuit as defined in claim 7, further comprising a resistor connected between said point and said other side of said power source and in series with said coil.