US 5,326,159 AGranted

Quick service limiting valve for freight brake control valve device

AssigneeWestinghouse Air Brake Company

InventorsJames E. Hart, Edward W. Gaughan

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Abstract

A quick service limiting valve device for a freight brake control valve employing a primary valve in a fluid flow path via which brake pipe air is connected to the brake cylinder during a secondary phase of quick service to propagate the brake pipe reduction signal until the brake cylinder pressure acting on the limiting valve control piston effects closure of the primary valve to terminate the quick service flow of brake pipe air to the brake cylinder when a predetermined brake cylinder limit pressure is realized. A secondary valve is arranged to interrupt the brake pipe to brake cylinder flow path downstream of the primary valve in the event leakage at the primary valve causes the pressure acting on the quick service limiting valve control piston to exceed the predetermined limit pressure. Until this limit pressure is exceeded, the secondary valve is bypassed so that only the primary valve controls the brake pipe to brake cylinder flow path via the limiting valve, thereby reducing hysteresis due to friction to obtain more efficient limiting valve operation.

Claims29

Dependent claims

For a railway car equipped with a fluid pressurized brake pipe and a fluid pressure operated brake cylinder device, a quick service limiting valve device comprising:

(a) a control piston having an application zone, a cut-off zone, and a limit zone intermediate said application and cut-off zones;
(b) fluid flow path means for conducting fluid under pressure from said brake pipe to said brake cylinder device in said application zone of said control piston;
(c) a control chamber in said fluid flow path means in which said control piston is operably disposed so as to be subject to the fluid pressure effective in said control chamber;
(d) first valve means for interrupting said fluid flow path means when said control piston is in said limit zone in accordance with the fluid pressure effective in said control chamber exceeding a first predetermined value;
(e) second valve means for providing a redundant cut-off of said fluid flow path means with said first valve means when said control piston is in said cut-off zone in accordance with the fluid pressure in said control chamber exceeding a second predetermined pressure greater than said first predetermined pressure;
and
(f) said fluid flow path means including means for bypassing said second valve means when said control piston is in said application and limit zones in accordance with the fluid pressure in said control chamber being less than said second predetermined pressure.

4 more elements

For a railway car equipped with a fluid pressurized brake pipe and a fluid pressure operated brake cylinder device, a quick service limiting valve device comprising:

(a) a control piston having an application zone, a cut-off zone, and a limit zone intermediate said application and cut-off zones;
(b) fluid flow path means for conducting fluid under pressure from said brake pipe to said brake cylinder device in said application zone of said control piston;
(c) a control chamber in said fluid flow path means in which said control piston is operably disposed so as to be subject to the fluid pressure effective in said control chamber;
(d) first valve means for interrupting said fluid flow path means when said control piston is in said limit zone in accordance with the fluid pressure effective in said control chamber exceeding a first predetermined value;
(e) means for varying the rate of flow of fluid under pressure conducted from said brake pipe to said brake cylinder device via said fluid flow path means prior to said first valve means interrupting said fluid flow path means in response to movement of said control piston from said application zone toward said limit zone, as the fluid pressure effective in said control chamber increases.

2 more elements

Dependencies are inferred from the claim text.