Master cylinder assembly for a vehicle hydraulic braking system

Abstract

In a master cylinder assembly comprising two pedal-operated master cylinders, each master cylinder comprises a pedal-operated piston of stepped outline working in a complementary stepped bore in a housing and having an inner end of smaller area carrying a first seal and an outer end of greater area carrying a second seal, a pressure space in the bore in advance of the inner end of the piston, a quick-fill chamber defined in the bore between the inner and outer ends of the piston, a normally-open recuperation valve providing communication between a reservoir for fluid and the pressure space at least when the piston is in a retracted position, and a normally-closed pressure-limiting valve assembly between the quick-fill chamber and the same or a second reservoir. The pressure-limiting valve assembly is adapted to open at a threshold value when the piston is moved in a brake-applying direction and following closure of the recuperation valve and the transfer of fluid to the pressure-space to take up the braking clearances, further movement of the piston in the same direction pressurizes fluid in the pressure space to apply the brake. The two quick-fill chambers are connected through a transfer passage so that fluid can be transferred between the two quick-fill chambers when both master cylinders are operated simultaneously at least until the said threshold value is attained.