| 摘要 |
A valve comprising a body having a straight-through flow passage, a valve head moveable at an acute angle with the downstream end of the passage into and out of the passage, and a valve seat extending about the passage for cooperation with the valve head to adjust the valve over a range from the wide-open to the closed condition, the valve seat approaching the axis of the passage no more closely than does the wall of the narrowest portion of the passage upstream or downstream of the seat, whereby in the wide-open condition, the valve head is removed from the passage, the axis of the passage remains a straight line, and the cross-sectional area of the passage at the position of the seat is no less than it is at the narrowest portion of the passage upstream or downstream of the seat.
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