| 摘要 |
A hydraulic actuator for a gate valve incorporates an eddy current proximity sensor to detect a displaceable stem cap made of ferromagnetic material. The stem cap is mounted on one end of an actuating stem. The other end of the stem is coupled to a plunger having a cammed tip which meets a cam attached to the piston. The camming action moves the stem cap from a position out of proximity to a position in proximity to the eddy current proximity sensor when the piston is at the end of its stroke. The proximity sensor is mechanically coupled to the stem housing by means of a housing cap, a barrel and a sensor cap, all made of non-magnetic material. The barrel is threaded at both ends with opposing threads so the barrel can be screwed onto the housing and sensor caps at the same time, thereby drawing the housing and end caps toward each other without sensor rotation. This feature allows the proximity sensor to be positioned at the correct distance from the stem cap without damage to the sensor connector wires. Lock nuts are employed to lock the barrel in position on the housing cap and sensor cap.
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