| 摘要 |
<p>A valve disc (4) is mounted to an opening/closing drive shaft (7) through two supports, that is, a fixed length support portion (5) provided on a side of the valve disc opposite to a side thereof facing a valve seat (3) and a variable length support portion (6). The fixed length support portion (5) comprises a fixed length arm member (5a) pivotally connected to the valve disc (4) and the opening/closing drive shaft (7). The variable length support portion (6) comprises an elastic member (6a) for providing a bias in a direction, in which a distance between both ends of the support portion (6) is decreased, a transmitting mechanism (6b, 6c) for converting a torque of the opening/closing drive shaft (7) into a working force acting in a direction, in which a distance between both ends of the support portion (6) is increased, and a stopper (6f) for regulating a distance between both ends of the support portion (6) within a range of predetermined values. When the opening/closing drive shaft (7) is rotated in a clockwise direction for valve closing, an end side (4a) of the valve disc (4) first abuts against the valve seat (3). When the opening/closing drive shaft (7) further continues to be rotated in the clockwise direction, interaction of a cam plate (6b) and a cam bearing member (6c) causes the stopper (6f) to be separated from the cam plate (6b) and an end side (4b) of the valve disc (4) to abut against the valve seat (3) overcoming a bias of the elastic member (6a), so that an entire outer peripheral surface of the valve disc (4) is firmly and uniformly pressed against the valve seat (3). Incidentally, a link mechanism in addition to a cam mechanism may be employed as the transmitting mechanism.</p> |
