Charging cut-off valve arrangement for microprocessor-based electropneumatic locomotive brake control system

A brake pipe charging cut-off arrangement for a microprocessor-based locomotive brake control system comprising:

• (a) a source of fluid under pressure;
• (b) a brake pipe;
• (c) regulator means between said source of fluid pressure and said brake pipe for controlling the pressure of fluid carried in said brake pipe in accordance with a certain chosen pressure;
• (d) charging cut-off valve means having an open position for providing fluid pressure communication between said regulator means and said brake pipe, and a closed position for interrupting fluid pressure communication therebetween;
• (e) selector means for establishing said open and closed positions of said charging cut-off valve means, in accordance with a desired controlling or non-controlling mode of operation of said locomotive;
• (f) microprocessor means for providing electric power to said regulator means and said selector means, said selector means comprising:
• (i) a lead and a trail electropneumatic valve device each having a supply port to which said fluid pressure source is connected and a delivery port communicated with said supply port in an energized condition thereof and to atmosphere in a de-energized condition thereof;
• and
• (ii) switch means for connecting electric power from said microprocessor means to either one of said lead and trail electropneumatic valve means, while concurrently cutting off electric power from said microprocessor means to the other of said lead and trail electropneumatic valve means to establish said controlling and non-controlling modes of locomotive operation, said lead electropneumatic valve device being energized in said controlling mode of operation and said trail electropneumatic valve device being energized in said non-controlling mode;
• (g) bias means for urging said charging cut-off valve means toward said closed position, so that in the absence of electric power at said regulator means and both said lead and trail electropneumatic valve devices, fluid pressure communication between said brake pipe and said regulator means is interrupted;
• and
• (h) sensing means for maintaining said charging cut-off valve means in said open position in opposition to said bias means in accordance with loss of electric power from said microprocessor when said locomotive is in a controlling mode of operation.