Empty/load changeover valve for railway car

For use in a railway vehicle brake control system including a brake pipe charged to a certain chosen pressure, an auxiliary reservoir charged to the pressure carried in said brake pipe, a brake cylinder device, and a brake control valve device via which fluid under pressure is supplied from said auxiliary reservoir to said brake cylinder device and released therefrom in accordance with variation of the fluid pressure in said brake pipe, an empty/load changeover valve device mounted on one of the sprung and unsprung members of said vehicle comprising:

• (a) load sensing means engageable with the other of said sprung and unsprung members for measuring the distance therebetween to provide an empty setting and a load setting of said changeover valve device depending upon said distance being greater or less than a predetermined distance corresponding to the changeover point between said empty and load settings;
• (b) an inlet passage connected to said control valve device and an outlet passage connected to said brake cylinder device;
• (c) a valve seat between said inlet and outlet passages;
• (d) a check valve between said valve seat and said outlet passage, said check valve being engageable with said valve seat in a closed position to interrupt the supply of fluid under pressure to said brake cylinder device and disengageable therefrom in an open position to conduct the supply of fluid under pressure to said brake cylinder device;
• (e) a balance piston to which said check valve is connected having equal opposing pressure areas, one of said pressure areas being subject to the fluid pressure effective at said inlet passage;
• and
• (f) empty/load valve means for pressurizing the other of said pressure areas in said load setting of said changeover valve device to establish a fluid pressure force balance across said balance piston, and for depressurizing said other pressure area in said empty setting to establish a differential fluid pressure force across said balance piston in the direction of engagement of said check valve with said valve seat.