| 摘要 |
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.
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