| 摘要 |
A relay valve provides an initial pressure advance in a trailer brake with minimal hysteresis, the advance being adjustable. A retroactive piston (12) is subjected to the pressure introduced by way of a triple valve (17, 30, 31) operated by the control piston (8). The pistons (12, 8) have approximately the same external diameters. An adjustable stop (29) provided in the control piston (8) is initially ineffective so that the control piston (8) responds rapidly so as to change over the control valve in the braking sense, and thereby provide the initial advance. However, after a predetermined pressure has been exceeded in output chamber (14), the retroactive piston (12) moves to abut the adjustable stop (29), whereupon the advance in the braking of the trailer is terminated and the valve thereafter operates conventionally with small hysteresis. <IMAGE> |
