Patent ID: 8235352

Claim:
A diaphragm valve comprising: a valve body having an inlet passage and an outlet passage; a diaphragm assembly positioned between the inlet passage and the outlet passage, the diaphragm assembly having a closed position where fluid flow from the inlet passage to the outlet passage is blocked and an open position where fluid flow from the inlet passage to the outlet passage is permitted; a bonnet having a neck defining an opening; a control chamber disposed on a control side of the diaphragm assembly and bounded at least in part by the control side of the diaphragm assembly and the bonnet; a rotatable flow control shaft extending through the opening of the bonnet, the flow control shaft being movable along a longitudinal axis relative to the bonnet between a sealed position where a seal is engaged with the neck to block fluid flow through the opening from the control chamber and a bleed position where the seal is spaced from the neck to permit fluid flow through the opening from the control chamber, a flow area between the neck and the seal increasing gradually as the flow control shaft is moved from the sealed position to the bleed position; and a stop axially moveable relative to the flow control shaft from a first position retained by the shaft to a second position retained by the shaft for limiting movement of the flow control shaft from the sealed position to the bleed position when in the first position, the stop being selectively moveable to the second position to permit movement of the flow control shaft from the sealed position to the bleed position.