Patent ID: 9321446
Filing Date: 2016-04-26
CPC Classification: B60T

Claim Text:
1. A valve for maintaining brake cylinder (BC) pressure in freight car brake equipment, comprising: a control diaphragm with a first surface area and having a source of emergency reservoir ER pressure on a first side and a source of auxiliary reservoir AR pressure on a second side; a brake cylinder feedback diaphragm with a second surface area, wherein a first side of the brake cylinder feedback diaphragm is coupled to the second side of the control diaphragm and a source of brake cylinder BC pressure is on a second side of the brake cylinder feedback diaphragm; a charging check valve coupled to the second side of the brake cylinder feedback diaphragm and moveable between a first position, where a source of brake pipe BP pressure is isolated from the source of brake cylinder BC pressure and a second position, where the source of brake pipe BP pressure is connected to the source of brake cylinder BC pressure; wherein said control diaphragm and said brake cylinder feedback diaphragm together comprise a differential relay configured to maintain brake cylinder (BC) pressure by moving the charging check valve into the second position if the force exerted on the second side of the brake cylinder feedback diaphragm falls below the differential force across the control diaphragm.