Patent ID: 6102072
Filing Date: 2000-08-15
Classification: F16K,Y10T

Abstract:
A check valve which opens when a fluid is fed forward and closes when feed of the fluid is stopped to prevent the fluid from reversing, comprising:a main valve unit and a bypass valve unit disposed in parallel;said main valve unit including an inlet passage, an outlet passage, an inclined main valve seat disposed between said inlet passage and said outlet passage having an opening, a single main valve element for opening and closing said opening of the main valve seat, and biasing means for constantly biasing said main valve element in a valve closing direction, said biasing means having such a magnitude that a valve closing force produced by said biasing means is balanced with a valve opening force exerted by the fluid flowing at a maximum flowrate through said opening toward the outlet passage when the main valve unit is fully open, so that the main valve element is held afloat in the fluid flowing past the main valve element, whereby the main valve element is substantially completely seated on the main valve seat at the moment the velocity of an inertial flow of the fluid in a discharge direction decreases to naught after the feed of the fluid has been stopped; andsaid bypass valve unit including a bypass valve seat disposed between said inlet passage and said outlet passage and having an opening, a bypass valve element linearly movable in opposite directions to open and close said opening of the bypass valve seat, and a damping device linked to the bypass valve element for damping linear movement of the bypass valve element so that the bypass valve element may gradually close the opening of the bypass valve seat in the direction of the reverse flow of the fluid after the start of the reverse flow;whereby water hammer and pressure rise due to the reverse flow occurring open stoppage of the feed of the fluid are prevented.