Proportioning relay valve disabled by failed front braking circuit
AssigneeAllied-Signal Inc.
InventorBruce E. Latvala
Life of this patent
Estimating the term…
Abstract
A fluid pressure braking system for a tractor-trailer combination vehicle includes a proportioning relay valve which controls communication to the rear wheel brakes of the tractor. When the tractor pulls a trailer, the proportioning control within the relay valve is disabled, but when the vehicle is operated in the "bobtail" mode without pulling a trailer a proportioned brake application is effected in which the braking pressure communicated to the rear brake actuator is a predetermined percentage of that in the front wheel braking circuit. The proportioning mechanism is also disabled when the front axle braking circuit malfunctions, so that upon loss of pressure of the front axle system, the driver effects a non-proportioned rear brake application.
Claims16
Fluid pressure braking system for a tractor-trailer combination vehicle comprising a tractor braking system, a trailer braking systems, and a pressure line communicating the tractor braking system with the trailer braking system, said tractor braking system including separate front wheel and rear wheel braking circuits, an operator-actuated brake valve for simultaneously providing service brake application effecting signals to establish a corresponding pressure level in said braking circuits, a relay valve responsive to the service brake application effecting signal provided by said operator-actuated brake valve for effecting a service brake application in said rear wheel braking circuit, said relay valve including proportioning means responsive to a predetermined pressure condition in said pressure line for establishing a proportioned fluid pressure level in said rear wheel braking circuit upon generation of said brake application effecting signal in the rear wheel braking circuit, and disabling means for disabling said proportioning means, means for communicating the pressure level in said front wheel braking circuit to said disabling means said disabling means being responsive to a decrease in the pressure level in the front wheel braking circuit below a predetermined level to disable said proportioning means to thereby assure that full braking pressure is communicated in the rear wheel braking circuit when the pressure level in the front wheel braking circuit is below the predetermined level.
Dependencies are inferred from the claim text.