Brake wear indicator system

• US 4,298,857 A
• Filed: 02/01/1980
• Issued: 11/03/1981
• Est. Priority Date: 02/01/1980
• Status: Expired due to Term

• Current Assignee: Ford Motor Company
• Original Assignee: Ford Motor Company
• Inventors: Lindre, Jaan, Robins, Ronald F.
• Primary Examiner(s): Waring, Alvin H.
• Application Number:
  US06/117,898
• Time in Patent Office: 641 Days
• Field of Search: 340/52 A, 340/52 B, 200/61.4, 200/61.41, 200/61.44, 188/1 A
• US Class Current: 340/454
• CPC Class Codes: F16D 66/024 Sensors mounted on braking members adapted to contact the brake disc or drum, e.g. wire loops severed on contact
• CPC Class Codes: F16D 66/027 Sensors therefor

Abstract

A brake wear indicator system includes a brake pad having a support plate, a layer of friction material secured thereto and an electrical contact assembly which extends through the support plate to project into the layer of friction material and which comprises two terminal portions electrically insulated from each other and a connecting portion which electrically connects the terminal portions and is located wholly within the layer of friction material. The connecting portion is arranged to be exposed and abraded after prolonged abrasion of the friction material by contact with a braking surface whereby electrical contact between the terminal portions is broken. The contact assembly is connected to an electrical indicator circuit which produces a first warning signal when the layer of friction material has become abraded sufficiently to allow electrical contact between the connecting portion of the associated braking surface, and a second warning signal when the connecting portion has become sufficiently abraded to break the electrical connection between the terminal portions of the contact assembly.

Claims

1. A motor vehicle brake warning system including a brake pad comprising:

a layer of friction material having a face operably engageable to a braking surface;

signal means operably embedded in said friction material for producing a first warning signal when the layer of friction material has abraded a predetermined amount and a second distinctive warning signal when the layer of friction material has further abraded beyond said predetermined amount;

said signal means comprising;

an electrical contact embedded in part into the layer of friction material such that said electrical contact comes in contact with an electrically grounded braking surface when said layer of friction material has abraded said predetermined amount and said brake pad is applied to said braking surface;

an electric circuit connectable to said electrical contact and being actuated when said electrical contact comes into contact with said braking surface to produce said first signal;

said electrical contact comprising;

two terminal portions electrically insulated from each other;

a connecting portion electrically connecting the two terminal portions;

said connecting portion being located wholly embedded within said layer of friction material such that said connecting portion comes into contact with the braking surface when said brake pad is applied to said braking surface after said layer of friction material has abraded a predetermined amount to produce said first signal, and said connecting portion becomes totally abraded when said layer of friction material has further abraded beyond said first predetermined amount to electrically disconnect said first terminal portion from said second terminal portion to produce said second signal.

2. A brake warning system as defined in claim 1 wherein said electric circuit comprises a test switch and an indicator such that the indicator is actuated either when the test switch is closed, or when the connecting portion of the contact assembly makes contact with the braking surface to produce said first signal, and the indicator remains deactuated by the closure of the test switch when the connecting portion is totally abraded to produce said second signal.

3. A brake pad comprising:

a support plate with an aperture therethrough;

a layer of friction material secured to said support plate and having a face engageable to a braking surface;

an electrical contact assembly extending through said aperture of said support plate and connected to said support plate;

said electrical contact assembly includes two electrically insulated terminal portions extending through said support plate an integral connecting portion electrically connecting said terminal portions;

said connecting portion extending into a plane intersecting the layer of friction material and substantially parallel to the face engaging the braking surface such that upon a predetermined amount of abrasion of said face of the layer of friction material, said connecting portion comes in contact with said braking surface when said pad is applied to said braking surface to close a first electric circuit connectable to said electrical contact assembly and produce a first signal, and upon a further amount of abrasion of said braking surface beyond said predetermined amount, said connecting portion becomes totally abraded to electrically disconnect said terminal portions to electrically disconnect said first terminal portion from said second terminal portion to produce a second signal.

4. A brake pad as defined in claim 3, wherein said connecting portion being located wholly embedded within said layer of firction material.

5. A brake pad comprising:

a support plate with an aperture therethrough;

a layer of friction material secured to said support plate and having a face engageable to a braking surface;

an electrical contact assembly extending through said aperture of said support plate and connected to said support plate;

said electrical contact assembly includes two electrically insulated terminal portions extending through said support plate an integral connecting portion electrically connecting said terminal portions;

said connecting portion extending into a plane intersecting the layer of friction material and substantially parallel to the face engaging the braking surface such that upon a predetermined amount of abrasion of said face of the layer of friction material, said connecting portion comes in contact with said braking surface when said pad is applied to said braking surface, and upon a further amount of abrasion of said braking surface beyond said predetermined amount, said connecting portion becomes totally abraded to electrically disconnect said terminal portions;

the contact assembly comprising;

a block of electrically conductive material bifurcated to form said two terminal portions by a slot extending therein with said integral connecting portion spanning the slot;

a sheet of insulating material positioned in said slot between the terminal portions and projecting laterally from the block;

said aperture through said support plate having opposing recesses sized to receive the projecting ends of said sheet of insulating material.

6. A brake pad as defined in claim 5, wherein said connecting portion being located wholly embedded within said layer of friction material.