AU742721B2 - Single wire brake wear and adjustment sensing system - Google Patents

Description

S F Ref: 420312

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

*99 9 9..

9 *9* 9 9 .9 .9 9 9.

9 *99 9 99 Name and Address of Applicant: Actual Inventor(s): Address for Service: Invention Title: Sanford Acquisition Company 4500 Dorr Street Toledo Ohio 43615 UNITED STATES OF AMERICA James R Clark, G Clark Fortune, LaVerne A Caron, John-Cyril P Hanisko Spruson Ferguson, Patent Attorneys Level 33 St Martins Tower, 31 Market Street Sydney, New South Wales, 2000, Australia Single Wire Brake Wear and Adjustment Sensing System The following statement is a full description of this invention, including the best method of performing it known to me/us:- 5845 -1- SINGLE WIRE BRAKE WEAR AND ADJUSTMENT SENSING SYSTEM BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brake warning system and, more specifically, to a brake warning system using a single wire connection between a plurality of types of brake condition sensors.

2. DescriDtion of the Prior Art .:•..Prior art brake wear and adjustment systems separately connect 1 each sensor to a conditioning electronics module to generate a signal to the 15 driver or mechanic that brake service is required. Many systems have been developed in the past to provide a signal to a vehicle operator to warn that brake lining wear has progressed a predetermined amount and systems have been developed to signal when the actuator travel reaches a given point. However, these systems have been generally unsatisfactory due to their complexity and/or unreliability due to the number of electrical connections because each type of sensor is connected individually to the electronics.

U.S. Patent Nos. 3,594,721; 3,716,831; 3,735,343; 3,755,774; 3,869,695 and 3,902,157 the disclosures of which are hereby incorporated by reference, disclose electronic signaling systems for the detection and notification of abnormal brake wear. One disadvantage with many of these systems is the parallel wiring configuration which results in a large number of conductors that must be used to connect the sensors with the electronic monitoring unit. Another disadvantage is that some prior art systems do not indicate when brake service is required if a short to ground fault occurs. Still another disadvantage is the fact -2that no provision is made for connecting other types of sensors in series with the brake wear sensors.

U.S. Patent No. 3,456,236 discloses a brake shoe wear indicator system where the wear sensors are connected in series to a relay which, when deenergized, closes contacts to light a bulb in a trouble alarm circuit. This concept lacks the reliability required of a brake condition alarm system because it indicates a working brake system when the light is burned out or there exists an open circuit to the bulb.

OBJECT OF THE INVENTION o It is an object of the present invention to overcome or ameliorate some of the disadvantages of the prior art, or at least to provide a useful alternative.

,SUMMARY OF THE INVENTION Accordingly in a first aspect there is disclosed herein a brake condition sensing Is system comprising: a plurality of types of brake sensors comprising at least one break wear sensor and at least one actuator travel switch; an electrical connector having a first end and a second end connecting each sensor in series with each other sensor, said first end connected to electrical ground; and 20 an indicator light having a first contact connected to said second end of said electrical connector and having a second connector connected to a source of electrical power, wherein said indicator light remains in a lit condition under normal acceptable brake function and is unlit in an abnormal unacceptable brake function.

In a second aspect there is disclosed herein a brake condition sensing system comprising: a first type of brake sensor comprising a break wear sensor; a second type of brake sensor comprising an actuator travel limit switch electrically connected in series with said brake wear sensor; and an indicator light connected to said brake wear sensor and to said actuator travel limit switch where said indicator light is energized when said brake wear sensor and said actuator travel limit switch are conductive and where said indicator light is nonenergized when at least one of said brake wear sensor and said second type of brake sensor actuator travel limit switch is nonconductive.

[R:\LIBLL] 2089.doc:caa The present invention preferably provides a reliable series type circuit for a plurality of types of brake sensors such as the electrical connection of at least one brake wear adjustment sensor and at least an actuator travel sensor at a plurality of braking units. In the preferred embodiment, a plurality of types of brake wear sensors such as a brake shoe wear sensor and a brake actuator rod position switch are fitted to each braking unit and all sensors and switches are connected in series with one another. All of these sensors are normally closed and continuity is established along a connector line as long as the brake units are in good working order. A first end of the series connector is connected to a brake condition indicator light or other type of brake condition sensing system such lo as a driver message center which in turn connected to a voltage source. The second end of the series connector is connected to ground. As long as the brake shoes are not worn to a service limit and the actuator rods travel within a prescribed range, then the indicator light remains energized. As soon as any one of the brake shoe wear sensors opens or any one of the brake actuator switches opens, then the brake condition indicator light goes out 15 thereby signalling to the operator that service is required. An open circuit fault or a burned out light would also signal that service is required.

o: The present invention preferably provides a brake sensor electrical system that uses only one conductor to connect a plurality of types of brake sensors.

The present invention preferably provides a brake sensor electrical system that energizes an indicator lamp when the braking units are within a satisfactory operating range.

°o:The present invention preferably provides a brake sensor electrical system that °indicates a need for services when an indicator lamp does not light upon application of the brakes.

The present invention preferably provides a brake sensor electrical system that indicates a need for service when an open circuit fault occurs in any one of a plurality of types of brake sensors.

BRIEF DESCRIPTION OF THE DRAWINGS A preferred embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings.

FIG. 1 is an electrical schematic of the sensor electrical circuit of the present invention; and FIG. 2 is an electrical schematic of an alternate embodiment of the sensor O electrical circuit of the present invention.

[R:\.LIBLL]I 2089.doc:caa -3a- DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT For the purpose of promoting an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated device, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.

Now referring to FIG. 1 of the drawings, an electrical schematic of the brake condition sensing system 2 of the present invention is shown. Actuator rod travel switches 4A,4B,4C,4D,4E and 4F are fitted to each of the brake actuators at each of the brake assemblies A,B,C,D,E and F and are adapted to be normally closed and conducting when the brake actuators are operating in a normal range. When any one of the brake s15 actuator rods reaches 0 [R:\LIBLL] 12089.doc:caa 4 97-A&B-053 its service travel limit, its respective travel switch opens e.g. travel switch 4A for wheel brake assembly is opened when in an over travel condition.

Brake shoe wear sensors 6A,6B,6C,6D,6E and 6F are fitted one each to respective brake assemblies A,B,C,D,E and F and are normally electrically closed when the respective brake shoes (not shown) have adequate operational thickness remaining. When any one of the brake shoes wears beyond its operational limit, the shoe wear sensor 6A,6B,6C,6D,6E or 6F opens the circuit e.g. wear sensor 6A opens when the brake shoe (not shown) in brake assembly A exceeds its service limit of wear. It should be noted that the present invention is adaptable to any type of brake condition sensor that is normally closed and then switches to an open state when an abnormal condition occurs.

Any combination of a plurality of series connected sensors can be used according to the teaching of the present invention.

The wear sensors 6A,6B,6C,6D,6E and 6F and the travel switches 4A,4B,4C,4D,4E and 4F are all connected in series by electrical conductor 8.

The first end 8A of conductor 8 is connected to an indicator lamp 10 with another side of the indicator lamp 10 connected to a voltage source 12 such as that available from the vehicle ignition switch. In place of or in addition to the indicator lamp 10, another electronic circuit could be connected to communicate the condition of the brakes to warn of a service condition. For example, an electronic driver message center could be utilized to communicate brake wear information based on the output from the brake condition sensing system 2 of the present invention. The second end 8B of the conductor 8 is attached to an electrical ground 14. The indicator lamp 10 can be one or more light emitting 25 diodes (LED) hooked in series or an incandescent light or any other type of indicator device or electrical communication device.

Thus, to check the condition of the vehicle brake assemblies A,B,C,D,E and F which includes as shown in FIG. 1, the brake shoe thickness using the thickness sensors 6A,6B,6C,6D,6E and 6F and the actuator rod travel using the travel switches 4A,48,4C,4D,4E and 4F, the operator first releases the parking brakes and the service brakes. If the indicator lamp 10 is energized, 97-A&B-053 then both the brake assemblies and the brake condition sensing system 2 are basically operational. The operator then applies the service brakes thereby activating the brake actuator and checking to see if the actuator rods exceed their travel limits thereby opening any one of the travel switches 4A,4B,4C,4D,4E or 4F. If the indicator lamp 10 continues to be energized, then the brake assemblies are fully operational. If later, while operating the vehicle, the indicator lamp 10 goes out, then the operator is notified of the need for system service.

Now referring to FIG. 2, an electrical schematic of an alternate embodiment of the brake condition sensing system 2' of the present invention is shown. The single wire conductor 8 serves to electrically connect the travel switches 4A,4B,4C,4D,4E and 4F and the brake shoe thickness sensors 6A,6B,6C,6D,6E and 6F in series (see FIG. 1) contained within wheel brake assemblies A,B,C,D,E and F. Again, any combination or type of normally closed sensors could be utilized with the brake condition sensing system 2' of the present invention. In this embodiment, the first end 8A of the conductor 8 is connected to the indicator lamp 10 where the indicator lamp 10' is also connected to electrical ground 14. The second end 88 of the conductor 8 is connected both to the power conductor 18 used to power the brake light and to the vehicle brake light 20 which is also connected to electrical ground 14.

According to this alternate embodiment of the brake condition sensing system 2' of the present invention, if one or more of the brake actuator travel switches 4A,4B,4C,4D,4E or 4F are open, then the indicator lamp 10 will 2 not light upon application of the brakes and a service condition is thereby relayed to the operator. Likewise, if one or more of the brake shoe wear sensors 6A,6B,6C,6D,6E and 6F are open, then the indicator lamp 10 will not light upon application of the brakes. This second embodiment of the brake condition sensing system 2' has an added feature over the first embodiment heretofore described, in that it will also detect electrical shorts to ground 14 of the travel switches 4A,48,4C,4D,4E and 4F or the shoe thickness sensors 6- 97-A&B-053 6A,6B,6C,6D,6E and 6F or any other shorts to ground 14 anywhere along conductor 8 upon which, the indicator lamp 10 is turned off.

Although this present invention has been described in its preferred form within a certain degree of particularity, it is understood that the present disclosure of the preferred embodiment has been made only by way of example, and that numerous changes in the detail construction in combination and arrangement of the elements may be resorted to without parting from the spirit and the scope of the invention as hereinafter claimed.

Claims (8)

1. A brake condition sensing system comprising: a plurality of types of brake sensors comprising at least one break wear sensor and at least one actuator travel switch; an electrical connector having a first end and a second end connecting each sensor in series with each other sensor, said first end connected to electrical ground; and an indicator light having a first contact connected to said second end of said lo electrical connector and having a second connector connected to a source of electrical power, wherein said indicator light remains in a lit condition under normal acceptable brake function and is unlit in an abnormal unacceptable brake function. *o Is

2. The brake condition sensing system of claim 1, wherein said brake wear sensor is normally closed and said actuator travel switch is normally closed.

3. A brake condition sensing system comprising: a first type of brake sensor comprising a break wear sensor; 20 a second type of brake sensor comprising an actuator travel limit switch electrically connected in series with said brake wear sensor; and an indicator light connected to said brake wear sensor and to said actuator travel limit switch where said indicator light is energized when said brake wear sensor and said actuator travel limit switch are conductive and where said indicator light is nonenergized when at least one of said brake wear sensor and said actuator travel limit switch is nonconductive.

4. The brake condition sensing system of claim 3, wherein said indicator light is one or more light emitting diodes.

The brake condition sensing system of claim 3 further comprising a plurality of said first type of brake sensors and a plurality of said second type of brake sensors all connected in series with one another and with said indicator lamp. [R:\LIBLL] 12086.doc:caa

6. The brake condition sensing system of claim 3 wherein said indicator means is an incandescent light.

7. The brake condition sensing system of claim 3 wherein said indicator means is at least one light emitting diode.

8. A brake condition sensing system, substantially as described herein in relation to any one of the embodiments with reference to the accompanying drawings. Dated 12 November, 2001 Sanford Acquisition Company Patent Attorneys for the Applicant/Nominated Person SPRUSON FERGUSON oo *oe 4 *•eo [R:\LIBLL]I 2086.doc:caa