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Valve seat retraction method and apparatus

  • US 4,718,444 A
  • Filed: 12/04/1986
  • Issued: 01/12/1988
  • Est. Priority Date: 12/04/1986
  • Status: Expired due to Term
First Claim
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1. In a valve assembly having:

  • a housing with axially spaced inlet and outlet ports, a housing interior region disposed between said inlet and outlet ports, and an access opening disposed proximate said interior region;

    a removable cover for sealingly closing said access opening;

    a ball valve member disposed in said interior region for controlling flow between said inlet and outlet ports and selectively removable from said interior region through said access opening; and

    at least one retractable annular valve seat having a forward end urged axially by a resilient bias force into slidable sealing engagement with said valve member;

    means for selectively retracting said valve seat away from said valve member comprising;

    a substantially convex camming surface defined as a radially outward-facing surface of said valve seat, said camming surface subtending a cam angle with a reference plane oriented perpendicular to flow through said valve assembly, said cam angle increasing as a function of axial displacement from said forward end of said valve seat;

    at least one threaded retraction port defined through said housing and extending radially inward from outside said housing to a location in said interior region juxtaposed with said camming surface of said valve seat at an axial position rearward of said forward end when said valve member and said valve seat are in sealing engagement;

    selectively removable sealing means for sealing said one retraction port during operation of said valve assembly; and

    first retraction tool means adapted for radial insertion into said interior region through said one retraction port when said sealing means is removed from said retraction port, said retraction tool means having a distal end and a threaded shaft portion for threadedly engaging said threaded retraction port, said distal end being oriented to contact said camming surface and forcefully axially displace said valve seat from said valve member as said distal tool end is increasingly extended radially into said housing interior region, whereby the cam angle at the point of contact between said camming surface and said distal tool end changes and becomes smaller as the radial insertion of said retraction tool means increases and said distal end slides along the camming surface.

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