Brake system

In a brake system for a tractor unit of a tractor-trailer vehicle, having a source of pressurized fluid, a valve means for reducing the flow of pressurized fluid to a certain of said brake actuators when operating without a trailer, comprising:

• (a) a housing structure defining a plurality of ports;
• (b) flow passage means communicating an input port with an output port;
• (c) a valve member interposed in said flow passage means for reducing the flow of pressurized fluid;
• (d) valve member disabling means for rendering said valve member inoperative thereby allowing non-restricted fluid pressure flow through said flow passage means under predetermined vehicle operating conditions;
• and,
• (e) source pressure biasing means urging said valve member towards a flow reducing position.

A brake porportioning system for the tractor unit of a tractor trailer vehicle comprising:

• (a) a source of pneumatic pressure;
• (b) pneumatic pressure operated brake actuators for engaging friction brakes on the front and rear wheels of said tractor;
• (c) front and rear relay valve means for controlling the flow of pressure from the source to the brake actuators;
• (d) treadle means for generating a signal pressure in proportion to the extent of movement in an operator actuated treadle;
• (e) structure defining two flow paths, one flow path for conveying the signal pressure to the front relay valve means and the other flow path for conveying the signal pressure to the rear relay valve means;
• and,
• (f) a variable porportioning valve means disposed in one of said flow paths and responsive to trailer-attached and trailer-detached conditions, said proportioning valve means reducing the flow and application of signal pressure to one of said relay valve means so that reduced braking is effected on the rear wheels of the tractor when operating without a trailer.

A brake system for the towing unit of a vehicle having a detachable towed unit, comprising:

• (a) a source of pressurized fluid:
• (b) at least one front and one rear fluid pressure operated brake actuator for engaging wheel mounted friction brakes;
• (c) valving for controlling the flow and application of pressurized fluid from the source to said actuators, including:
• (i) treadle valve means for generating a signal pressure in proportion to the extent of treadle movement;
• (ii) relay valve means communicating with said treadle valve means and responsive to said signal pressure, such that said relay valve means provides pressurized fluid to one of said actuators in relation to treadle movement;
• (iii) variable flow proportioning means disposed in a signal pressure flow path, intermediate the treadle valve means and said relay valve means, said proportioning means responsive to towed unit detached and attached conditions, and operative to affect the flow of signal pressure to said relay valve means so that under one condition, the flow of pressurized fluid to said other actuator in a first function of treadle movement and in the second condition, the fluid pressure flow to said other actuator is a second function of treadle movement.

In a brake system for a tractor unit of a tractor trailer vehicle, having a source of pneumatic pressure, pneumatic pressure operated brake actuators for engaging front and rear wheel brakes on the tractor, and a means for connecting the system to a trailer carried brake system, a treadle operated control valve means, comprising:

• (a) a treadle valve for generating a signal pressure in relation to movement in an operator actuated treadle;
• (b) relay valve means for controlling the flow and application of pneumatic pressure from the source to the actuators;
• (c) means communicating the signal pressure from said treadle valve to said relay valve means such that pneumatic pressure is provided to at least one of said actuators in relation to the degree of treadle movement;
• and
• (d) flow proportioning means responsive to trailer-detached and trailer-attached conditions, and operative to affect the flow of signal pressure to said relay valve means such that under one condition the flow of pneumatic pressure to said other actuator is a first function of treadle movement and in the second condition, the flow of pneumatic pressure to said other actuator is a second function of treadle movement.

A brake proportioning system for the tractor unit of a tractor trailer type vehicle comprising:

• (a) a source of pressurized fluid;
• (b) fluid pressure operated brake actuators for engaging front and rear wheel brakes on said tractor;
• (c) front and rear valve means for controlling the flow of pressurized fluid from the source to the front and rear brake actuators respectively;
• (d) fluid pressure proportioning means responsive to trailer-unattached and trailer-attached conditions;
• (e) at least one flow control member in said fluid proportioning means for reducing the output pressure of one of said valve means when said fluid proportioning means is sensing one of said conditions;
• and
• (f) fluid biasing means urging said flow control member towards a position wherein the output pressure of the one valve means is reduced.

A brake proportioning system for the trailer unit of a tractor-trailer type vehicle comprising:

• (a) a source of pressurized fluid;
• (b) fluid pressure operator brake actuators for engaging front and rear wheel brakes on said tractor;
• (c) front and rear valve means for controlling the flow and application of pressurized fluid to the front and rear brake actuators respectively;
• (d) a first conduit means for conveying pressurized fluid from the tractor to a trailer brake subsystem, said conduit means being generally at atmospheric pressure when a trailer is not connected to the tractor, and at a predetermined pressure when a trailer is connected to a tractor;
• (e) fluid pressure proportioning means communicating with said first conduit means;
• (f) a flow control member in said fluid pressure porportioning means operative to reduce the output pressure of the rear valve means when the fluid pressure in said first conduit means is atmospheric;
• (g) fluid biasing means urging said flow control member towards a position that effects reduced output pressure of said rear valve means.