A pneumatic tractor-trailer brake system by which application of the trailer brakes and the tractor brakes occurs simultaneously to guard against jack-knifing. This is accomplished by connecting the pressure chamber of the relay valve on the trailer and the adjacent end of the service line with the air pressure tank on the trailer by opening a normally closed solenoid-actuated valve as a consequence of initial depression of the brake pedal. Energization of the solenoid to open this valve results from closure of the energizing circuit for the stop light on the trailer. The resulting immediate response of the relay valve pressurizes the entire trailer brake system, including the service line, sufficiently to take up any slack in the trailer brakes no later than that occurs at the tractor brakes. At the instant the brakes begin to grip, a fluid pressure actuated electric switch opens the solenoid energizing circuit. The resulting reclosure of the valve commits the trailer brakes to application simultaneously with the tractor brakes in the customary way by continued depression of the brake pedal. For brake systems equipped with automatic anti-wheel-locking means that effects its control by reducing the pressure in the pressure chamber of the relay valve, a unidirectional flow restriction in the line leading to the fluid pressure actuated switch holds the switch open and thus prevents reopening of the solenoid-actuated valve.
A brake activation system for reducing the time between the brake application of tractors and trailers utilizes a speed differential between the electrical and air signals. The application of the tractor brake actuates simultaneously a stop light circuit and the air brake systems. The electrical signals from this energized stop light circuit actuates solenoid valve which releases the air from the trailer reservoir being subsequently reduced to a predetermined low pressure level. This low pressure air reaches the trailer wheel brake chambers prior to the arrival of the brake air with high pressure overriding the low pressure air route and completing the trailer brake application.
A fluid control system for use with vehicles, in particular, trailers, includes a branch conduit which is to be connected to a pressure supply line and a control line to enable priming of the control line so that signals generated upon application of the vehicle brake pedal are more quickly transmitted to the trailer brakes. This overcomes problems associated with delay in application of the trailer brakes. An electrically operated solenoid valve controls fluid flow through the branch conduit so that upon application of the vehicle brake pedal the solenoid valve is operated to open the branch conduit to allow pressurized fluid to flow from the supply line to the control line for a predetermined time period to prime the control line. Pressurized fluid from the branch supply conduit is directed longitudinally down the control line by a longitudinally arranged outlet so that substantially all of the fluid is directed to backfill the control line. The system may be embodied in a block arrangement in which bores are drilled in a block housing and in which the branch conduit is formed by passages drilled in the block or may be formed from discrete hose sections and couplings.
An emergency brake illumination system for a trailer illuminates the trailer brake lamps upon application of the emergency brakes. The system includes a pressure switch which senses pressure in the emergency brake system. The pressure switch is electrically connected between the blue circuit and the red circuit of a seven-way connector. If a loss of pressure is sensed by the pressure switch, the switch closes and power is provided by the blue circuit to the red circuit to illuminate the brake lamps.
A braking apparatus engages the brakes of a towed vehicle and is actuated by the engaging the brake of the towing vehicle. A pivotally mounted foot pedal engaging member attaches to the floor of the towed vehicle and depresses the brake pedal of the towed vehicle when actuated. A pneumatic cylinder forces the engaging member to depress the brake pedal when air is supplied to the cylinder. Air is supplied from air brakes in the towing vehicle or from another pressurized air source. Air to the pneumatic cylinder matches the force of the towing vehicle if equipped with air brakes, or is controlled by a flow regulator and pressure regulator.
A compressed air brake system including a low pressure control circuit and a high pressure operating circuit. The control circuit is interfaced by a plurality of relay valves with the operating circuit for the direct actuation of the wheel brake cylinders with high pressure. The dual pressure arrangement results in a significant reduction in consumption of air while retaining the advantages which are common to a high pressure system.
