GB2036210A

GB2036210A - Monitoring brake systems

Info

Publication number: GB2036210A
Application number: GB7847653A
Authority: GB
Original assignee: CHIA SHANG WONG
Current assignee: CHIA SHANG WONG
Priority date: 1978-12-07
Filing date: 1978-12-07
Publication date: 1980-06-25

Abstract

The operation of a brake system is monitored by mounting an electrical conductor 1 in the lining 14 of a brake shoe so as to extend on to the braking surface thereof, the conductor 1 being connected in an electrical circuit including an indicator light (15) such that electrical contact between the conductor 1 and a brake drum during a braking operation completes the circuit via the conductor effective to light or to extinguish the light to indicate proper brake engagement, the circuit being broken to indicate proper brake disengagement. The lining may also include a second conductor 2 which terminates a set distance inwardly from the braking surface when the brake shoe lining is new, and causes operation of a second indicator light (16) to indicate excessive wear of the lining (14). Conductors comprise bars interfitted and fixed by adhesive. Circuits are disclosed (see, e.g. Fig. 1). <IMAGE>

Description

SPECIFICATION Monitoring brake systems This invention relates to the monitoring of brake systems. More particularly, though not necessarily exclusively, the invention is concerned with the monitoring of the operation of a drum brake system in a vehicle, especially a motor vehicle.

In a first aspect of the present invention there is provided a method of monitoring brake system operation comprising mounting an electrical conductor in the lining of a brake shoe or the like so as to extend to or towards the braking surface thereof, and connecting the conductor in an electrical circuit including an indicator light, such the electrical contact between the conductor and a brake drum or the like during a braking operation completes the circuit via the conductor effective to light or to extinguish the indicator.

The invention provides in a second aspect thereof a brake shoe in the brake lining of which is mounted an electrical conductor which extends to or towards the braking surface thereof, the conductor being connected in an electrical circuit including an indicator light, such that electrical contact between the conductor and a brake drum during a braking operation completes the circuit via the conductor effective to light or to extinguish the indicator.

In a third aspect of the present invention, there is provided a vehicle provided with a drum brake operation monitoring system, the brake lining of at least one brake shoe of the vehicle being provided with at least ocne conductor which extends to or towards the braking surface thereof and is connected in an electrical circuit including an indicator light such that electrical contact between the conductor and the brake drum during a braking operation completes the circuit via the conductor effective to light or to extinguish the indicator.

If the conductor extends to the braking surface of the brake lining, then the circuit will be completed via the conductor each time the brake is properly engaged and will be broken each time the brake is satisfactorily disengaged.

If the conductor terminates a set distance inwardly from the braking surface of a new brake shoe lining, the circuit via the conductor would only be completed during a braking operation when the brake lining is worn down to the conductor.

Both systems may be incorporated in a single brake shoe and in both the leading and trailing shoes of each drum of a vehicle braking system.

The invention is hereinafter more particularly described by way of example only with reference to the accompanying drawings in which: Figure 1 shows a schematic diagramatic view of an entire drum brake operation monitoring system embodying the invention; Figure 2 shows part of the apparatus shown in Fig. 1 to an enlarged scale; and Figure 3 is a sectional view taken along the line 2-2 in Fig. 2.

Fig. 1 shows a drum brake in which both brake shoes are provided in their linings with two electrical conductors 1 and 2. The arrangement of the conductors is best shown in Figs. 2 and 3. Each = conductor consists of a short bar, the longer conductor bar 1 being provided with a flange 10 and the shorter bar 2 being interfitted with the first. Each bar is suitable made of carbon and is electricallt insulated from the other and from its surroundings by a high thermally resistant electrically insulating material coating (for example of mica).The shorter bar 2 is fixed to the longer bar by means of adhesive and extends forwardly towards the braking surface of the brake shoe lining terminating at a depth from that surface which is between 2/3 and 3/4 of the overall thickness of the brake lining 1 4. The longer conductor bar 1 extends to the braking surface.

Each conductor bar is electrically coupled to a conductor wire 8. These are suitably coated wires with different colours. The conductor wires pass through an insulating washer 9 which separates the flanged portion 10 of conductor bar 1 from an adjusting screw 6 through which the wires pass. The adjusting screw 6 is threadedly received in an internally threaded sleeve 5 which may be fixed directly to the body 4 of the brake shoe or, as here, when the brake shoe body has insufficient thickness, may be received threadedly in a nut 7 suitably soldered or welded to the brake shoe. The bars are held in position by the bias of a compression spring 11.

As shown in Fig. 1, the longer conductor bars 1 for each brake shoe are connected in an electrical circuit including an indicator light 15, while the shorter conductor bars 2 are connected in an electrical circuit including an indicator light 16.

When the brake pedal is pressed, the longer conductor bar 1 in each brake shoe will make contact with the confronting surface of the brake drum 1 2 to complete the circuit via the conductor bar effective, in this case, to light the indicator.

In an alternative arrangement it would be possible for the conductor bars to be connected across the indicator light 1 5 so that electrical contact between the conductor bar 1 and the confronting surface of the brake drum 1 2 will have the effect of short circuiting the indicator light which would accordingly be extinguished rather than lit as a consequence of the circuit being completed via the conductor bar.

Equally well, if the shorter conductor bar 2 should come into contact with the confronting surface of the brake drum 12, then the indicator light 1 6 will be lit. In an exactly similar way, the conductor bars 2 could be connected across the indicator light 1 6 so that the effect of the circuit being completed via the conductor bar would be to extinguish rather than to light the indicator.

The described and illustrated arrangement enables a number of simple checks to be made on the operation of the brake. If indicator 1 5 is lit when the brake pedal is pressed and is extinguished when the brake pedal is released, and indicator light 1 6 is not lit at all, then the system is operating satisfactorily and the brake lining is not excessively worn.

If indicator 1 5 should fail to be lit on pressing the pedal, then an immediate check should be made on the hydraulic system of the brake, for example for possible breakdown in the main oil hydraulic cylinder resulting from wear on its jacket or wall, leakage of oil pipes, or breakdown of an auxiliary oil hydraulic cylinder as by wear on its jacket or wall.

If the indicator 1 5 should cease to extinguish as the brake pedal is released, this suggests rust or corrosion on the wall of an auxiliary oil hydraulic cylinder or that a piston is causing a blockage and should be replaced, or that a gap adjustment screw is improperly adjusted (for example the gap is too large), so that the non-returnable piston in the system should be removed for readjustment.

If the indicator 1 6 should be lit at all, this indicates that the lining requires replacement.

Claims

1. A method of monitoring brake system operation, comprising mounting an electrical conductor in the lining of a brake shoe or the like so as to extend to or towards the braking surface thereof, and connecting the conductor in an electrical circuit including an indicator light, such that electrical contact between the conductor and a brake drum or the like during a braking operation completes the circuit via the conductor effective to light or to extinguish the indicator.

2. A method according to Claim 1, wherein said electrical conductor extends to the braking surface of the brake shoe or the like, and wherein a second electrical conductor is provided in said lining extending towards said braking surface but terminating short thereof, the second conductor being connected in a second electrical circuit including a second indicator light, such that electrical contact between said second conductor and the brake drum or the like during a braking operation completes the circuit via the second conductor effective to light or to extinguish the second indicator, whereby completion of the circuit via the first conductor effective to light or to extinguish the first indicator is indicative of normal braking operation, while completion of the circuit via the second conductor effective to light or to extinguish the second indicator is indicative of excessive braking and/or excessive wear of the lining.

3. A method of monitoring brake system operation, the method being substantially as herein before described with reference to the accompanying drawings.

4. A brake shoe in the brake lining of which is mounted an electrical conductor which extends to or towards the braking surface thereof, the conductor being connected in an electrical circuit including an indicator light, such that electrical contact between the conductor and a brake drum during a braking operation completes the circuit via the conductor effective to light or to extinguish the indicator.

5. A brake shoe according to Claim 4, wherein said electrical conductor extends to the braking surface of the brake lining, and wherein a second electrical conductor is mounted in the brake lining, which second conductor extends towards the braking surface but terminates a predetermined distance short thereof when the lining is new, said second conductor being connected in a second electrical circuit including a second indicator light, such that electrical contact between the second conductor and a brake drum during a braking operation completes the circuit via the second conductor effective to light or to extinguish the second indicator.

6. A brake shoe substantially as herein before described with reference to and shown in the accompanying drawings.

7. A vehicle provided with a drum brake operation monitoring system, the brake lining of at least one brake shoe of the vehicle being provided with at least one conductor which extends to or towards the braking surface thereof and is connected in an electrical circuit including an indicator light such that electrical contact between the conductor and the brake drum during a braking operation completes the circuit via the conductor effective to light or to extinguish the indicator.

8. A vehicle according to Claim 7, wherein said brake lining is provided with two conductors, the first of which extends to the braking surface thereof and is connected in the said electrical circuit, and the second of which extends towards the braking surface but terminates a set distance inwardly therefrom when the brake shoe lining is new, and is connected in a second electrical circuit including a second indicator light such that electrical contact between the second conductor and the brake drum during a braking operation completes the second circuit via the second conductor effective to light or to extinguish the second indicator, whereby to indicate that the brake lining is worn down to the said second conductor.

9. A vehicle substantially as herein before described with reference to and as shown in the accompanying drawings.