Patent ID: 7121522

Claim:
A valve for fluids operating under differential pressure, which receives a main inlet flow and releases a main outlet flow, comprising: a main valve ( 1 , 4 , 5 , 7 , 9 ) having a main inlet ( 112 , 412 , 512 , 712 , 912 ) and a main outlet ( 113 , 413 , 513 , 713 , 913 ) for fluid; said main inlet being equipped with a main valve seat ( 114 , 414 , 514 , 714 , 914 ) over which a main plug ( 100 , 400 , 500 , 700 , 900 ) is seated, with said main plug being displaceable in an axial direction, perpendicular to a sealing plane; a control inlet ( 111 , 411 , 511 , 711 , 911 ), communicating with a pressure chamber ( 110 , 410 , 510 , 710 , 910 ), which carries the flow from upstream said main flow to said pressure chamber; a control outlet ( 121 , 421 , 521 , 721 , 921 ), communicating with said pressure chamber, for allowing total or partial release of the flow control from said pressure chamber, with said control flow being discharged at a point located downstream said main outlet flow; a secondary control valve, to regulate the control fluid in said pressure chamber, said secondary control valve being formed by an axially driven stem ( 103 , 403 , 503 , 703 , 903 ) made up of a hollow portion and an end portion, where said stem drives the relative displacement between said main plug and said main seat, with one of the ends of said end portion being located beyond a body of said valve in order to allow said end portion to be driven from the outside; said hollow portion is provided with two openings in their corresponding axial end, with said hollow portion being joint in one end to said main plug, with one of said two openings being located in the joint end to said main plug, being surrounded by said pressure chamber, and with another of said two openings being located outside said pressure chamber, from which said hollow portion goes out through an opening of said pressure chamber, being provided with a tight seal which allows axial displacement of said hollow portion; said end portion is independent from and is axially aligned with said hollow portion, with one of the ends of said end portion being provided with a secondary plug portion to obstruct said another of said two openings which is located outside said pressure chamber; an area, corresponding to said control inlet, being smaller than an area corresponding to said control outlet, so that the volume of flow through said control inlet is lower than the volume of flow through said control outlet, so that the control fluid may enter through said control inlet.