GB1021144A - Improvements in and relating to hydraulic brake fluid reservoirs - Google Patents

Abstract

1,021,144. Hydraulic brake systems. R. T. HAMILTON and W. J. GRANVILLE. Feb. 21, 1964 [Feb. 23, 1963], No. 7361/63. Headings F2E and F2F. [Also in Division H2] A brake fluid reservoir is connected internally to a source of fluid pressure to maintain the interior at a predetermined pressure above atmospheric, a warning device being provided to indicate a fall in the pressure due to loss of hydraulic fluid. The pressure source may comprise a hand-operated pump or a cylinder extending from the reservoir lid with an open end below the surface of the hydraulic fluid. In the latter case a piston is forced downwardly against the action of a spring by fluid from the clutch master cylinder, the resulting reservoir pressure being monitored by a gauge or the air pressure above the fluid operating a mechanical indicator or a pressure switch in a warning light circuit. In the embodiment shown the switch and pressure source are combined. A rod 36 slidable in the reservoir lid 2 has insulating surface 41, 42 and an intermediate conducting surface 43. The interior of the upper bellows 34 is connected by a tube 40 to a vehicle induction manifold or vacuum vessel. Loss of brake fluid permits the external atmospheric pressure on the diaphragm to overcome spring 38 and depress the rod to allow brush 44 to contact surface 43 and complete the circuit of lamp 46. In other embodiments a piston and cylinder may replace the lower bellows. In a further embodiment (Fig. 9, not shown), a brush 74 is employed as a detent to hold the piston raised against a spring. The detent is released when the lid 2 is in place, to pressurize the brake fluid.