Brakes – With condition indicator – Electrical
Patent
1986-01-28
1987-08-11
Reger, Duane A.
Brakes
With condition indicator
Electrical
340 52B, F16D 6600
Patent
active
046855408
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a signal transmitter for monitoring a brake lining, especially in a disc brake for motor vehicles, comprising a casing which, when installed, is positioned opposite a brake member at decreasing spacing as the wear of the brake lining progresses and which contains electrical contacts and leads the switching states of which are adapted to be changed at certain wear and/or heating of the brake lining.
A known signal transmitter of this kind (DE-OS No. 2 144 466) is installed in a brake shoe provided for this purpose in a brake lining with a recess of greater diameter which is open toward the corresponding brake disc and with a coaxially adjacent recess of smaller diameter. The recess of smaller diameter extends also through a backplate carrying the brake lining. The casing of the signal transmitter is substantially cylindrical, passes through both recesses, and includes a flange which faces the brake disc and is located in the recess of greater diameter. The two ends of the casing each comprise a closure of an insulating ceramic composition. A wire loop is embedded in the front closure facing the brake disc and lies approximately in the plane of the flange. A pair of wires extend from the loop and through the rear closure to the outside where they form contacts for plug connectors. A bimetal spring is secured to the inside wall of the casing within the front closure and has a free end with a contact in the space between the two closures. A contact at one of the two wires is associated with this contact such that these two contacts are positioned opposite each other at a spacing at normal temperature. When the temperature rises, the bimetal spring deflects until the contacts finally touch each other, closing a circuit, whereby overheating of the brake lining is indicated. When the brake lining is worn considerably but not yet completely, the brake disc slowly wears off a front layer of the front closure until it reaches the wire loop so that a circuit is closed by the brake disc and thereby a signal is emitted during braking indicating the advanced wear of the lining. When the brake disc has entirely destroyed the wire loop upon continued wear of the lining, a closed circuit is interrupted, and this may be utilized to emit a permanent signal.
This known signal transmitter is relatively expensive and yet usually unsuitable for renewed use upon exchange of the brake lining because it is largely destroyed in the course of normal wear of the brake lining.
It is, therefore,the object of the invention to develop a signal transmitter of the kind specified initially such that it can be produced at low cost and be reusable.
This object is met, in accordance with the invention, in that a plug is guided in the casing for displacement from an inoperative position in parallel with the direction of wear of the brake lining and adapted to be pressed further into the casing by the brake member mentioned and, in a terminal position, holds at least one of the contacts in a switching position which differs from the inoperative position.
If the signal transmitter according to the invention is subjected to wear at all, this occurs at the plug which is exchangeable as such so that the signal transmitter can be continued to be used upon replacement of the corresponding brake lining.
If the signal transmitter according to the invention like the known signal transmitter specified initially, is equipped with a heat sensitive switch, such as a bimetal switch, it is convenient to place the heat sensitive switch in a front portion of the signal transmitter facing the brake disc.
In a first embodiment the signal transmitter is arranged like the known signal transmitter described such that an end face of its casing is disposed opposite a rotating brake body, especiallly a brake disc. In this case the invention preferably is developed further in that the casing is fixed to a stationary brake carrier, has its opposed end face disposed opposite an extension of a backplate carrying the lining, and the plug is adapted to
REFERENCES:
patent: 3674114 (1972-07-01), Howard
patent: 3716113 (1973-02-01), Kobayashi et al.
patent: 3975706 (1976-08-01), Kato
patent: 4374375 (1983-02-01), Allori et al.
Rath Heinrich B.
Schemmel Winfried
Lucas Industries Public Limited Company
Reger Duane A.
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