Load responsive air brake control valve for providing continuously

Abstract

A braking force control valve responsive to the load on a vehicle has a three-part body with a central bore with a spring-biased proportioning spool disposed within the central bore and with a pair of side control chambers for receiving air when the spool is displaced. The spring bias on the spool is controlled by a plunger, the position of which is controlled by the load on the car via a load-sensing arm. The valve may be mounted either so that the position of the plunger is determined by lading itself or variably by the load weight. The body has an inlet port which is connected to the braking air source and an outlet port connected to the brake cylinder. The passage of air from the inlet port to the outlet port is controlled by the proportioning spool, which is urged from a closed position in which it prevents passage of air from the inlet port to the outlet port by the spring pressure applied thereto and is urged into such closed position by the pressure of the air in the control chambers. Thus, the pressure of the air supplied to the outlet port is a continuously variable proportion of the pressure of the air supplied to the inlet port. A check valve permits air to be exhausted from the control chamber side of the spool and the brake cylinder when the supply of air to the inlet port is discontinued.