Hydraulic brake system for trailers connected with mechanically braked towing vehicles

Claim 1

A hydraulic brake system for a trailer which is attached to a towing vehicle having non-hydraulic brake means, particularly mechanical brake means, and a mechanical linkage for actuating said brake means with a variable force, said brake system comprising a brake having a brake cylinder; a source of pressurized fluid; a valve assembly interposed between said cylinder and said source; a valve assembly interposed between said cylinder and said source; first signal generating means arranged to furnish first signals whose characteristics are indicative of the magnitude of said force; second signal generating means arranged to furnish second signals whose characteristics are indicative of the fluid pressure in said cylinder; regulator means connected with said first and second signal generating means and being operative to actuate said valve assembly in response to said signals so that the fluid pressure in said cylinder is related to the magnitude of said force, said first signal generating means comprising a first transducer actuated by said linkage and arranged to furnish to said regulator means first electric signals whose intensity is proportional to the magnitude of said force and said second signal generating means comprising a second transducer responsive to fluid pressure in sayd cylinder and arranged to furnish to said regulator means second electric signals whose intensity is proportional to said pressure; a reservoir for fluid; and a consumer of pressurized fluid, said valve assembly having an inlet connected with said source, a first outlet connected with said consumer, a second outlet, a brake line connecting said second outlet with said cylinder, a third outlet connected with said reservoir, a distributor valve having a valve member movable between a plurality of positions to thereby control the flow of fluid between said inlet and said outlets, control valve means connected with and actuatable by said regulator means to effect the movements of said valve member between said positions and to change the fluid pressure in said cylinder, one-way valve means provided in said brake line to prevent the flow of fluid from said cylinder to said second outlet, and a return line connecting said reservoir with said brake line intermediate said one-way valve means and said cylinder, said control valve means including a portion provided in said return line and actuatable by said regulator means to permit the flow of fluid from said cylinder to said reservoir in response to decreasing intensity of said first signals.