Pilot operated pressure equalising mechanism for subsurface valve

As shown, a flow tube 18, moveable within a longitudinal bore of the subsurface valve, is used to shift a pilot activator 48 within a pilot bore 50 from a closed position (Figure 8) to an open or equalising position as shown. In the open position, fluid below the valve closure member 24 is allowed to pass through a pilot passageway 58 establishing fluid communication between the pilot bore 50 and a cylinder 64 in which a pilot piston 62 is located. Exposure of the pilot piston 62 to fluid pressure from below the valve member moves the pilot piston 62 within the cylinder 64, causing an equalising plug 66 to move to an open or equalising position, establishing fluid communication from below the valve closure member 24 through an equalising passageway 92. The pressure above and below the valve closure member is then equalised through the equalising passageway prior to the opening of the valve closure member by further downward movement of the flow tube 18. Other embodiments are shown in figures 12 and 13 in which the sealing surfaces are made of pliable materials and figures 14-19 in which the pressure is equalised via an internal fluid passageway in the equalising plug.