Auxiliary stabilizer valve for VX vent valve

A vent valve device for locally venting a railway car brake pipe when an emergency rate of reduction of the fluid pressure carried in said brake pipe is initiated, comprising;

• (a) a housing having an inlet port to which said brake pipe is connected, a vent port, a first chamber communicated with said inlet port, and a second chamber;
• (b) flow restrictor means via which fluid pressure communication is provided between the first and second chambers for establishing a predetermined pressure differential therebetween when said brake pipe pressure is reduced at an emergency rate;
• (c) vent valve means for establishing fluid pressure communication between said inlet port and said vent port in accordance with said predetermined pressure differential being established between said first and second chambers;
• (d) nullifier valve means in parallel with said flow restrictor means between said second chamber and said brake pipe for establishing fluid pressure communication between said second chamber and said brake pipe in bypass of said flow restrictor means in response to said nullifier valve means being predetermined pressure differential from being established in response to an emergency rate of reduction of said brake pipe fluid pressure and for automatically resetting to interrupt said fluid pressure communication between said second chamber and said brake pipe when the fluid pressure effective in said second chamber is less than a predetermined value;
• and
• (e) said nullifier valve means comprising:
• (i) a body fixed to said housing;
• (ii) a bore in said body having an open end and a closed end;
• (iii) a first passage at least partly in said body connecting said bore with said brake pipe;
• (iv) a second passage at least partly in said body connecting said bore with said second chamber;
• (v) a piston valve in said bore having an actuating stem projecting from said open end of said bore externally of said body, said piston valve cooperating with said bore at said closed end thereof to form an actuating chamber, said piston valve having an actuated position in which fluid pressure communication is established between said first and second passages and said actuating chamber, and a de-actuated position in which said first and second passages are cut off from said actuating chamber by said piston valve;
• and
• (vi) spring means for biasing said piston valve toward said de-actuated position.