| 摘要 |
A backup pneumatic emergency control valve for an electro-pneumatic brake system for a railroad freight car comprising an emergency portion of a standard AB type freight brake control valve device without the service portion. In the absence of a service portion in which the release function of an emergency brake application is normally provided, the emergency portion is modified to achieve this release function in one embodiment by venting the inshot valve control chamber to which brake cylinder pressure is typically connected via the high pressure spool valve during brake pipe recharge following an emergency brake application; and in another embodiment by replacing the accelerated emergency release check valve with a plug to isolate brake cylinder pressure in a backdump passage from the brake pipe and venting the check valve cavity to provide a means of exhausting brake cylinder pressure via the backdump passage when the backdump spool valve is moved to release position by the emergency piston during brakepipe recharge following an emergency brake application.
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