The present invention is concerned with brake apparatus for railway vehicles and particularly to such apparatus, as disclosed in copending Patent Application Ser. No. 195,149 assigned to the assignee of the present invention.
In the foregoing copending Patent Application, there is disclosed a dual-piston brake cylinder device that is arranged to provide for storage of sufficient air as necessary to develop the desired brake forces, without the need for conventional storage reservoirs. The dual pistons are tandem-connected, one being larger than the other and cooperating with the brake cylinder body to form air storage chambers on its opposite sides.
During brake release, air is supplied to these storage chambers by a control valve device that is operative in response to variations in the train brake pipe pressure. When a service brake application is initiated, the control valve device connects air from the brake pipe and also from one side of the larger piston to the opposite side of the smaller piston. A poppet valve device is provided to effect pressure equalization between the opposite chambers of the larger piston to permit movement of the dual pistons in a brake application direction under the influence of the pressure acting on the smaller piston. Once the tandem-connected pistons are in application position, the control valve releases pressure from the one side of the larger piston to establish a pressure differential thereacross and accordingly produce braking force.
During an emergency brake application, the venting of brake cylinder chamber 14 is established by an emergency sensitive valve device and controlled by an inshot valve adapted to control the emergency buildup of brake forces through a train in accordance with a predetermined brake force profile, whereby initially the brake forces produce rapid run-in of the train slack, thereafter the brake forces are held constant for a predetermined time period to assure sufficient "bunching" of the train slack, and thence restoring the rapid buildup of brake forces to preserve stopping distance.
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