| 摘要 |
A control force input system for a balance beam pneumatic valve positioner which does not allow the controlled apparatus to make a full travel motion when the overall control signal is removed. The control force is transmitted to the balance beam or other force summing bar using a linear solenoid coupled to a control spring coupled to the balance beam. When the motive power control signal is removed from the linear solenoid, the balance beam establishes an equilibrium position based on the existing position of the linear solenoid. Split wedges are repelled from the linear solenoid when a control signal is applied, releasing the solenoid shaft for movement. Alternatively, split slides are repelled from each other when a control signal is applied, releasing the solenoid shaft bias spring. When the control signal is removed, the split wedges or split slides are biased and attracted to the solenoid, locking the solenoid shaft in position. A variation for use with a current to pressure transducer is detailed.
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