Electrical warning system for vehicular brake installations

Claim 2

A brake system comprising: a pair of fluid-operated brake networks including substantially concurrently actuatable master-cylinder chambers and respective sets of wheel brakes communicating therewith; an electric source; switch means including a pair of fluid-responsive switches each operatively connected with a respective one of said networks and included in a respective circuit connected across said source; electrical warning means bridged across said circuits for energization upon the development of a differential in the current flow through said circuits upon failure of hydraulic pressure in one of said networks for indicating such failure, each of said circuits including a respective resistance connected in series with a respective one of said switches across said source, said resistances being of substantially equal value, said electrical warning means including an indicator lamp, a relay having contacts connected in circuit with said indicator lamp, said resistances being formed by respective coils of said relay effective in opposite senses upon substantially concurrent operation of said switches whereby said contacts remain open, but individually effective upon the failure of one of said switches to close said contacts; and manually actuatable retaining means for maintaining said electrical warning means energized upon restoration of said brake networks to an operative condition upon an actuation of the electrical warning means indicative of pressure failure in either of said networks.

Claim 3

The brake system defined in claim 1, further comprising time-delay means connected with said electrical warning means for delaying operation of said electrical warning means for a period sufficient to ensure operation of both said switches when neither network is defective.

Claim 4

A brake system comprising: a pair of fluid-operated brake networks including substantially concurrently actuatable master-cyliNder chambers and respective sets of wheel brakes communicating therewith; an electric source; switch means including a pair of fluid-responsive switches each operatively connected with a respective one of said networks and included in a respective circuit connected across said source; electrical warning means bridged across said circuits for energization upon the development of a differential in the current flow through said circuits upon failure of hydraulic pressure in one of said networks for indicating such failure, each of said circuits including a respective resistance connected in series with a respective one of said switches across said source, said resistances being of substantially equal value, said electrical warning means including an indicator lamp, a relay having contacts connected in circuit with said indicator lamp, said resistances being formed by respective coils of said relay effective in opposite senses upon substantially concurrent operation of said switches whereby said contacts remain open; but individually effective upon the failure of one of said switches to close said contacts; and a lamp connected in series with said coils across said source.

Claim 5

A brake system comprising: a pair of fluid-operated brake networks including substantially concurrently actuatable master-cyliNder chambers and respective sets of wheel brakes communicating therewith; an electric source; switch means including a pair of fluid-responsive switches each operatively connected with a respective one of said networks and included in a respective circuit connected across said source; electrical warning means bridged across said circuits for energization upon the development of a differential in the current flow through said circuits upon failure of hydraulic pressure in one of said networks for indicating such failure, each of said circuits including a respective resistance connected in series with a respective one of said switches across said source, said resistances being of substantially equal value, said electrical warning means including an indicator lamp, a relay having contacts connected in circuit with said indicator lamp, said resistances being formed by respective coils of said relay effective in opposite senses upon substantially concurrent operation of said switches whereby said contacts remain open; but individually effective upon the failure of one of said switches to close said contacts; and a lamp connected in series with said coils across said source.

Claim 6

The brake system defined in claim 3 wherein one of said resistances is constituted by said brake lamp.

Claim 7

The brake system defined in claim 1, further comprising a test switch triggerable by the vehicle operator and connected between said source and said electrical warning means for temporarily operating same independently of said fluid-responsive switches.

Claim 8

The brake system defined in claim 1, further comprising a brake-fluid reservoir communicating with said chambers, a liquid-level-responsive switch connected between said source and said electrical warning means for operating same independently of said fluid-responsive switches upon fall of the brake-fluid level in said reservoir below a predetermined point.

Claim 9

The brake system defined in claim 1, further comprising a brake pedal shiftable through a predetermined stroke and adapted to operate said networks, said switch means further including a mechanical switch operatively connected with said brake pedal and effective upon displacement thereof through a major portion of said stroke beyond that required for normal pressurization of both said networks upon failure of one of said networks, said electrical warning means including an indicator lamp connected in series with said mechanical switch across said source, and a diode connected in series with said mechanical switch and with said brake lamp.

Claim 10

A brake system comprising: a pair of fluid-operated brake networks including substantially concurrently actuatable master-cylinder chambers and respective sets of wheel brakes communicating therewith; an electric source; switch means including a pair of fluid-responsive switches each operatively connected with a respective one of said networks and included in a respective circuit connected across said source; electrical warning means bridged across said circuits for energization upon the development of a differential in the current flow through said circuits upon failure of hydraulic pressure in one of said networks for indicating such failure; a brake lamp; a brake pedal shiftable through a predetermined stroke and adapted to operate said networks, said switch means including a mechanical switch operable by said brake pedal and connected in series with said brake lamp, said fluid-responsive switches being connected in series with said mechanical switch; and means operatively connecting said mechanical switch with said brake pedal for closure of said mechanical switch only upon application of sufficient brake force to said pedal to effect normal actuation of both said fluid-responsive switches in the absence of a defect in one of said networks; said electrical warning means including an indicator lamp, a relay having contacts in series with said indicator lamp and said source, and mechanical means engaGeable with the relay armature for retaining said contact means in a closed position upon energization of said relay, but manually releasable to de-energize said relay.

Claim 11

A brake system comprising: a pair of fluid-operated brake networks including substantially concurrently actuatable master-cylinder chambers and respective sets of wheel brakes communicating therewith; an electric source; switch means including a pair of fluid-responsive switches each operatively connected with a respective one of said networks and included in a respective circuit connected across said source; electrical warning means bridged across said circuits for energization upon the development of a differential in the current flow through said circuits upon failure of hydraulic pressure in one of said networks for indicating such failure; a brake lamp; a brake pedal shiftable through a predetermined stroke and adapted to operate said networks, said switch means including a mechanical switch operable by said brake pedal and connected in series with said brake lamp, said fluid-responsive switches being connected in series with said mechanical switch; and means operatively connecting said mechanical switch with said brake pedal for closure of said mechanical switch only upon application of sufficient brake force to said pedal to effect normal actuation of both said fluid-responsive switches in the absence of a defect in one of said networks; said electrical warning means including an indicator lamp, a relay having contacts in series with said indicator lamp and said source, and mechanical means engaGeable with the relay armature for retaining said contact means in a closed position upon energization of said relay, but manually releasable to de-energize said relay.