Abstract: A fluid flow valve having a body (11) with first, second and third fluid inlets (8, 18, 25), a working fluid outlet (4), a first pressure element (11) movable, under the influence of pilot pressure fluid applied to the first inlet, from a first position in which it causes closure of the second inlet, to a second position in which it causes opening of the second inlet, and a second pressure element (20) movable, in response to pressure at the fluid outlet, from a first position in which it causes closure of the third inlet (25) to a second position in which it causes opening of the third inlet, said elements (11, 20) operating in conjunction to permit an initial high volume fluid flow from the second inlet through the outlet and subsequently, with the second element causing interruption of a path between the second inlet and outlet, a high pressure fluid flow from the third inlet through the outlet. The invention embraces a vehicle braking system incorporating the aforesaid valve.

Abstract: A dual hydraulic booster assembly for a braking system of a tractor or like vehicle has a logic valve operable in a first mode to control the supply of pressure fluid for braking on one side of the vehicle to facilitate steering, and in a second mode of operation to control the supply of fluid pressure for braking on both sides of the vehicle for full vehicle retardation. A pressure amplifier valve may be provided to increase the pressure of the pressure fluid from the logic valve for braking in the second mode of operation. The logic valve and amplifier valve may be incorporated into the booster assembly to provide an integrated unit.