Abstract: In an hydraulic system in which an hydraulic accumulator is charged with hydraulic fluid under pressure by means of an hydraulic pump which draws hydraulic fluid from a tank, and an unloader valve disposed in a supply line between the pump and the accumulator is operative to prevent the accumulator from being overcharged and to allow the pump to re-charge the accumulator should the pressure stored therein fall below a desired minimum value, the unloader valve incorporates a control valve, and a pressure responsive slave which is operated by fluid pressure under the control of the control valve.

Abstract: An automatic adjuster comprises a mechanism of adjustable length operative between a hydraulic brake piston and either a cylinder or an opposed piston. A cam journalled in the cylinder or the opposed piston serves to apply the brake mechanically (hand brake) and act as a stop for the mechanism. The adjustable length mechanism comprises two members, one of which may be the first mentioned piston in interengagement with one another through a non-reversible screw-thread connection. A reversible screw-thread connection or a reversible face cam is provided for turning one member of the mechanism relatively to the other responsively to excessive piston travel to effect adjustment.