Patent ID: 6227521
Filing Date: 2001-05-08
Classification: B60T

Abstract:
A graduated release valve apparatus for a pneumatic brake system of a railcar, said railcar having a brake cylinder and a brake pipe, said graduated release valve apparatus comprising:(a) a valve body defining a piston bore, a supply passage in communication with a first end of said piston bore, a return passage in communication with a second end of said piston bore, a release passage for connecting said piston bore with such brake cylinder, and an exhaust passage for connecting said piston bore with atmosphere via an exhaust choke;(b) an inlet check valve normally closed to prevent gas from such brake pipe from flowing into said supply passage;(c) an outlet check valve normally closed to prevent gas from said return passage from flowing into such brake pipe; and(d) a piston biased in a normally closed position against said first end within said piston bore, said piston defining a passageway through which said first and second ends communicate such that (i) upon an increase in pressure within such brake pipe said inlet check valve opens causing said first end to pressurize and move said piston to an open position in which communication is established between said release and exhaust passages so that such brake cylinder vents gradually to atmosphere via said exhaust choke, and as pressure gradually equalizes between said first and second ends via said passageway, said piston returns to said normally closed position thereby discontinuing communication between said release and exhaust passages so that such brake cylinder ceases venting to atmosphere and (ii) upon a decrease in pressure within such brake pipe said outlet check valve opens causing pressure to equalize between said supply and return passages via said passageway and approximate pressure within such brake pipe.