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Floating offshore drilling platform

  • US 4,117,691 A
  • Filed: 08/11/1977
  • Issued: 10/03/1978
  • Est. Priority Date: 08/11/1977
  • Status: Expired due to Term
First Claim
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1. A floating offshore drilling platform including a hollow generally circular horizontal float body tapering in thickness from its central portion to its outer periphery, said body including upper and lower walls which are inclined downwardly and upwardly, respectively, from said central portion to said outer periphery, a horizontal work platform spaced above said body and supported therefrom by upstanding supports extending and secured between said body and platform at points spaced about said central portion, said body including means defining a central vertical passage therethrough, the interior of said body spaced outwardly of and about said central portion including means defining ballast tanks which may be selectively flooded and evacuated of water, and a central upstanding tubular caisson supported at its upper end from said body about said passage and adapted at its lower end for engagement with the ocean floor, at least the lower end portion of said caisson comprising an extendable and retractable end portion thereof, said retractable end portion including selectively operable flotation means for buoying said lower end portion upwardly toward a retracted position, said flotation means including means defining a closed outer flotation chamber supported from said retractable end portion, flexible air conduit means extending downwardly along said caisson and having a lower end opening into said outer flotation chamber, and purge passage means opening inwardly of the lower portion of said outer flotation chamber and outwardly of the latter.

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