Uncoupling valve with override feature

Abstract From the Canadian patent

Abstract of the Disclosure, An uncoupling valve for use in rail car brake systems having a pressurized supervisory pipe includes opposed piston motors which hold the valve open long enough to depressurize the supervisory pipe and cause an emergency brake application, when two cars are uncoupled accidentally. On the other hand, the valve includes a controlled source of pressure for overpressurizing one of the piston motors to hold the valve closed to prevent depressurization of the supervisory pipe when, two cars uncoupled intentionally.