Diaphragm Valve for Irrigation Systems

A method of venting fluid in an irrigation system, the method comprising:

• providing a valve body having an inlet passage and an outlet passage;
• providing a 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;
• providing a control chamber bounded at least in part on one side by the diaphragm assembly and on the other side by a bonnet having a neck defining an opening;
• providing a flow control shaft extending through the opening and moveable inward relative to the bonnet from 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;
• and
• venting the control chamber through one or more bypass recesses when the flow control shaft is positioned between the sealed position and the bleed position.

A method of selectively permitting fluid flow in an irrigation system, the method comprising:

• providing a valve body having an inlet passage, an outlet passage and a valve seat with a central opening positioned between the inlet passage and the outlet passage;
• providing a diaphragm assembly with a control side and a fluid flow side, the diaphragm assembly having a diaphragm sealing member positioned to engage the valve seat when the diaphragm assembly is in a closed position to block flow through the central opening and between the inlet passage and outlet passage and to be spaced from the valve seat when the diaphragm assembly is in an open position to permit flow through the central opening and between the inlet passage and outlet passage;
• providing a control chamber on a control side of the diaphragm assembly, the pressure in the control chamber relative to the pressure in the inlet passage of the valve body being selectively controllable;
• shifting the diaphragm assembly from the closed position to the open position by decreasing pressure in the control chamber relative to pressure in the inlet passage to increase a flow area between the valve seat and the at least one seal to an equilibrium amount;
• and
• shifting the diaphragm assembly from the open position to the closed position by increasing pressure in the control chamber relative to pressure in the inlet passage, the shifting of the diaphragm assembly from the open position to the closed position having an end segment of travel where the flow area between the valve seat and the diaphragm sealing member decreases non-linearly.

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 flexible membrane, the membrane having an outer portion fixed relative to the valve body and an inner portion fixed relative to a diaphragm sealing member;
• an annular seat for the diaphragm assembly having a central fluid passage and a plurality of radially extending recesses on the outer surface of the valve seat spaced by intermediate surfaces;
• a control chamber disposed on a control side of the diaphragm assembly;
• a control chamber entrance passage extending from the inlet passage to the control chamber to permit flow from the inlet passage into the control chamber;
• a control chamber exit passage extending from the control chamber to permit flow from the control chamber;
• a valve to selectively permit flow through the control chamber exit passage;
• an open stage of the diaphragm valve member where the diaphragm sealing member is spaced from the seat to permit flow through the central fluid passage and between the inlet passage and outlet passage when forces due to fluid pressure in the control chamber acting on the control side of the diaphragm assembly are less than forces due to fluid pressure in the inlet passage acting on the opposite side of the diaphragm assembly;
• an intermediate sealing stage of the diaphragm assembly where the diaphragm sealing member is engaged with the intermediate surfaces of the seat and spaced from the recesses to partially block flow through the central fluid passage and between the inlet passage and outlet passage;
• and
• a final sealing stage of the diaphragm assembly where the diaphragm sealing member is engaged with the seat to block flow through the central fluid passage and between the inlet passage and outlet passage when forces due to fluid pressure in the control chamber acting on the control side of the diaphragm assembly are greater than forces acting on the opposite side of the diaphragm assembly.