| 摘要 |
<p>In one embodiment, a mains pressure valve has a body ( 10 ) and a main valve component ( 17 ) which is movable to effect opening and closing of the mains pressure valve. A flow controller ( 36 ) is disposed downstream of the main valve component and has a downstream end. At least one air vent ( 38 ) is provided downstream of the downstream end of the flow controller ( 36 ) and the vent is shielded from the downstream end of the flow controller ( 36 ). In another embodiment, there is a main chamber ( 12 ) within which the main valve component ( 17 ) moves, the main chamber having a control portion ( 40 ). A bypass passageway ( 13 ) has an upstream end ( 35 ) from the control portion ( 40 ) of the main chamber and a downstream end ( 46 ). A control valve ( 42 ) controls the flow through the by-pass passageway ( 13 ) to control the operation of the mains pressure valve. The downstream end ( 46 ) of the bypass passageway ( 13 ) is downstream of the flow controller ( 36 ). In a further embodiment, an upstream portion of the bypass passageway ( 13 ) is defined within a manifold ( 25 ).</p> |
