GB348691A - Hydraulic mechanism - Google Patents

Abstract

348,691. Fluid-pressure brakes. LLOYD, H. J., Thorpe Lodge, Thorpe-le- Soken, Essex, and RICHARDS, S. H., 10, Patten Road, Wandsworth Common, London. Feb. 15, 1930, Nos. 5131 and 7360. [Class 103 (i).] Hydraulic brake mechanism, in which some free movement of the parts takes place before the full power is applied comprises two pumps 7, 3, Fig. 1, of different diameters and operated by the same member, the piston 6 of the larger pump being operated through a spring 8 or the like which is at all times held compressed without the pressure being transmitted to the piston in the off position. During the first part of the movement of the pedal 5, the pressure of the comparatively large quantity of liquid displaced by the piston 6 acts through pipes 18, 19 on the pistons 21 attached to the shoes, and quickly moves them against the brake drum 31. When the liquid pressure rises to a certain point, a differential valve 23, previously held open by a spring 24 is closed, and further movement of the pedal compresses the spring 8, while the piston 2 of the small pump applies further pressure to the shoe pistons 21. In a modification, the piston 6, Fig. 2, of the large pump surrounds the smaller pump, and the differential valve is dispensed with. The lever 5 acts on the piston 6 through the smaller piston 2 and a spring 8, which is compressed when the liquid pressure produced by the larger pump rises above a certain point, and allows the smaller piston to move in its cylinder 3.