| 摘要 |
A valve lock for locking a valve spindle in a selected position corresponding to the valve being for example fully open or fully closed. The lock has a housing which is mounted on the valve body and a hub which engages and rotates with the valve spindle relative to the housing. A latch is provided between the housing and the hub, the latch being actuatable by a key to assume a latched condition in which rotation of the hub relative to the housing is permitted in one direction but prevented in the other direction. A spindle position indicator is coupled by a transmission to the hub so as to be displaced as a result of rotation of the spindle, thereby to indicate the spindle position relative to the valve body. The spindle position indicator prevents actuation of the latch by the key except when the spindle is in the selected position as represented by the spindle position indicator. The spindle position indicator is locked in the predetermined orientation corresponding to the selected spindle position when the latch has been actuated by the key. The transmission incorporates a slip clutch which enables rotation of the hub in one direction if the spindle position indicator is locked in the predetermined orientation and sufficient torque is applied to the spindle engaging member to cause the clutch to slip. As a result the selected position can be reset simply by locking the spindle position indicator and then rotating the hub to a reset position. |
