Patent ID: 6371156
Filing Date: 2002-04-16
Classification: G05D,Y10T

Abstract:
A pilot valve for a control valve in a main flow line, comprising:an inlet fluid chamber in fluid communication with fluid to be controlled in the main flow line on one side of the control valve; an outlet fluid chamber in fluid communication with the main flow line on an opposite side of the control valve; a first control fluid chamber in fluid communication with one side of a pressure surface in the control valve; a second control fluid chamber in fluid communication with an opposite side of a pressure surface in the control valve; a diaphragm disposed inside the outlet fluid chamber and movable in response to an outlet fluid pressure between a lockup position and a flow position; a passage formed in the pilot valve establishes fluid communication between the inlet fluid chamber and the first control fluid chamber; an insert defining a valve seat positioned between the inlet fluid chamber and the second control fluid chamber; a slidable valve body supported for movement with the diaphragm, the valve body having a central passage with a lower end in fluid communication with the first control fluid chamber and an enlarged valve portion, wherein the passage is unobstructed and the enlarged valve portion engages the insert valve seat when the diaphragm is in the lockup position, and the enlarged valve portion is spaced from the insert valve seat and the passage is blocked when the diaphragm is in the flow position; a stationary collar defining an orifice establishing fluid communication between the outlet fluid chamber and the second control fluid chamber; a stationary stop member defining a valve seat positioned between the outlet fluid chamber and an upper end of the central passage; and a movable collar supported for movement with the diaphragm and defining an orifice, the movable collar engaging the stationary stop member valve seat to cut off flow through the movable collar orifice when the diaphragm is in the lockup position, and the movable collar engages the stationary collar to cut off flow through the stationary collar orifice when the diaphragm is in the flow position.