Brakes – With condition indicator – Wear
Reexamination Certificate
1998-10-09
2001-06-26
Graham, Matthew C. (Department: 3613)
Brakes
With condition indicator
Wear
C340S454000, C073S121000
Reexamination Certificate
active
06250429
ABSTRACT:
BACKGROUND OF THE INVENTION
This application relates to a brake shoe assembly having a resistive brake lining wear sensor.
Most motor vehicles include a brake system having a set of brake shoe assemblies for retarding the rotation of the wheels of the vehicle when the brakes are applied. Typically, each brake shoe assembly includes a brake lining made of a friction material which gradually wears away during brake applications. After numerous brake applications, the brake lining wears below a critical material thickness and, therefore, must be replaced. As a result, the brake lining must be periodically inspected for excessive wear. To eliminate time-consuming and costly visual inspections of the brake lining, the prior ar t has taught several types of brake lining wear sensors for indicating when the brake lining must be replaced.
One type of brake lining wear sensor, sometimes referred to as a direct read sensor, directly monitors the material thickness of the brake lining. Although direct read sensors provide the most accurate indication of when replacement of the brake lining is necessary, prior art direct read sensors are expensive, complex, and prone to failure. Accordingly, it would be desirable to provide an inexpensive, simple, and robust direct read brake lining wear sensor.
SUMMARY OF THE INVENTION
In a disclosed embodiment of this invention, a brake shoe assembly includes a brake lining and a brake lining wear sensor. The brake lining has a predetermined thickness which gradually wears away as the brake shoe assembly is used to brake a vehicle. The brake lining wear sensor has a pair of spaced electrical conductors and an electrical resistance located across the pair of spaced conductors for indicating the thickness of the brake lining. The brake lining wear sensor is positioned to wear away concurrently with the brake lining, thereby continuously changing the electrical resistance across the pair of spaced conductors. In this manner, the electrical resistance across the pair of spaced conductors is used to determine the thickness of the brake lining.
In a first embodiment of this invention, the brake lining wear sensor includes an insulating substrate, the pair of spaced electrical conductors cohered to one surface of the substrate, and a layer of material cohered to the substrate. In this first embodiment, the layer of material provides the electrical resistance across the pair of spaced conductors.
In a second embodiment of this invention, the brake lining wear sensor includes an insulating substrate, the pair of spaced electrical conductors cohered to one surface of the substrate, and a body of material supporting the substrate. In this second embodiment, the body of material provides the electrical resistance across the pair of spaced conductors.
In a third embodiment of this invention, the brake lining wear sensor includes a substrate and the pair of spaced electrical conductors cohered to one surface of the substrate. In this third embodiment, a resistive compound is mixed in the substrate to provide an electrical resistance across the pair of spaced conductors.
In a fourth embodiment of this invention, the brake lining wear sensor includes a frame and a body of material supporting the frame. The frame includes the pair of spaced electrical conductors and a plurality of support pieces attached between the pair of spaced conductors. In this fourth embodiment, the body of material provides an electrical resistance across the pair of spaced conductors.
These and other features of the present invention will be best understood from the following specification and drawings, the following of which is a brief description.
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Carlson Gaskey & Olds P.C.
Graham Matthew C.
Lipka Pamela J.
Meritor Heavy Vehicle Systems LLC
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