| 摘要 |
This invention relates to a three-position sealed ball-type brake cylinder pressure retaining valve device, for connection to the exhaust passageway of a railway car brake control valve device, having a body provided with a securing flange that has a port therein connecting the external face of the flange to a chamber in the body in which chamber a ball-type valve element is rotatably mounted by a handle movable in a plane parallel to the flange selectively to any one of its three positions. The ball-type valve element has a stepped bottomed bore extending inward from its spherical surface, in which bore is a spring-biased check valve. A leaf-type spring interposed between the ball-type valve element and the interior wall surface of the chamber in the body biases this valve element into tight seating contact with a resilient annular exhaust valve seat carried by a removable annular plug disposed in a bore connecting the chamber in the body to the exterior thereof. The ball-type valve element has therein a plurality of angularly spaced passageways and orifices opening at one end at its spherical surface and at the other end either into another passageway also opening at one end at this spherical surface or into the stepped bottom bore. These passageways and orifices, in cooperation with one another and with the check valve, are effective in three respective positions of the ball valve element to selectively provide a fast blow-down of brake cylinder pressure to atmosphere, a slow blow-down to a chosen pressure above atmospheric pressure, and a slow blow-down to atmosphere.
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