| 摘要 |
<p>A pneumatic valve actuator for moving the valve stem of a control valve comprises an upper casing (56) and a lower casing (58) each having flanges (78, 80), a diaphragm plate operatively coupled to the valve stem, a spring arranged to bias the diaphragm plate in a first direction, a diaphragm (70) movable in conjunction movement of the diaphragm plate, an air inlet defined in the casing and arranged for attachment to an air supply source to bias th diaphragm plate in a second direction, and a ring (76) disposed between the upper flange and the lower flange and positioned to engage the outer portion of the diaphragm. The ring includes a protrusion (96) positioned to engage a surface of the outer portion of the diaphragm.</p> |
