| 摘要 |
<p>A suck back valve (20) comprises an electric linear actuator (118) which displaces a suck back diaphragm (100) through a stem (96), an encoder (120) which detects a displacement amount of the linear actuator (118), and a flow amount controller (68) for controlling a pilot fluid supplied to an ON/OFF valve mechanism (26). During suck back, the actuator shaft (126) is withdrawn by a predetermined amount as measured by the encoder, and the stem (96) carrying the diaphragm follows the actuator shaft under the action of a spring 98, whereby the amount of suck back can be controlled. The flow amount controller 68, figure 2 (not shown) includes a diaphragm (78) acted on by an enclosed volume of liquid (77) where volume is varied by an electric heater (79). The encoder (120) includes an optical encoding disc (134) rotating with, but slidable along, the actuator shaft, the disc engaging a groove (136, figure 3, not shown) in a support (138) to maintain it in its axial position.</p> |
