This application relates to packaging a temperature sensing brake lining wear indicator in a brake shoe assembly and to a unique temperature sensing brake lining wear indicator. 
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 art has taught several types of brake lining wear indicators for indicating when the brake lining must be replaced. 
One type of brake lining wear indicator, sometimes referred to as a temperature sensing brake lining wear indicator, monitors the temperature of the brake lining to determine the thickness of the brake lining material.  Often, prior art temperature based indicators experience material homogenization and heat transfer problems when embedded in a brake shoe assembly.  Accordingly, it would be desirable to package a temperature sensing brake lining wear indicator in a brake shoe assembly so as to overcome the shortcomings of the prior art.  A unique temperature sensing brake lining wear indicator designed to overcome the shortcomings of the prior art would also be desirable. 
In a disclosed embodiment of this invention, a brake shoe assembly includes a backing plate and a brake lining.  The brake lining has an interface surface abutting the backing plate and a wear surface for contacting a vehicle.  A pair of temperature sensors are positioned adjacent to the interface surface and spaced unequal distances from the wear surface for determining the thickness of the brake lining.  The pair of temperature sensors may be embedded directly in the brake lining or encapsulated in one of a plurality of housing embodiments packaged in the brake lining. 
In accordance with the teachings of the present invention, a brake shoe assembly having a unique brake lining temperature sensor assembly is also disclosed.  The brake shoe assembly includes a backing plate and a brake lining.  The brake lining has an interface surface abutting the backing plate and a wear surface for contacting a vehicle.  The unique temperature sensor assembly includes a body of material having a proximate end positioned adjacent to the backing plate and a distal end for contacting the vehicle concurrently with the wear surface of the brake lining.  A heat pipe, disposed within the body of material, extends from the distal end toward the proximate end.  A first electrical conductor is attached to the heat pipe to form a first thermoelectric junction.  A second electrical conductor is attached to the heat pipe to form a second thermoelectric junction spaced from the first thermoelectric junction.  The heat pipe provides a thermal communication path from the distal end of the sensor body to the first and second thermoelectric junctions.  In this manner, heat waves or fronts, produced when the distal end of the sensor body contacts the vehicle, are transmitted quickly through the heat pipe from the distal end of the sensor body to the first and second thermoelectric junctions and used to determine the thickness of the brake lining. 
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.