Well tool anchoring mechanism with improved slip release

  • US 5,148,866 A
  • Filed: 09/27/1991
  • Issued: 09/22/1992
  • Est. Priority Date: 09/27/1991
  • Status: Expired due to Term
First Claim
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1. In a well tool with a set of slips carried within a cage slidably mounted on a mandrel for said slips to move within said cage radially from retracted positions into radially extended positions by the wedging action of a frustoconical setting head sliding between the mandrel and the slips so as to force the latter to gripping engagement with the inside of a well casing to anchor the tool against upwardly acting forces in the well, and a shoulder on said mandrel engageable with said cage to lift said cage off said setting head for releasing said slips to free the tool for upward movement within the well, the improvement comprising a plurality of windows formed within said cage and spaced circumferentially from each other around said mandrel, said slips protruding through said windows for movement between said retracted and extended positions with each of said slips having a toothed outer surface for gripping engagement with the casing wall and a primary release shoulder formed thereon beneath said toothed outer surface, said windows each including a lower edge engageable with said primary release shoulder when said cage is lifted by said shoulder on said mandrel and in turn lifting said slips free from said casing wall for movement into said retracted positions, and a plurality of circumferentially spaced slots formed through said cage with one each of said slots being associated with and located above each of said windows, each one of said slips including a secondary release shoulder formed thereon above said toothed outer surface and projecting in a radial direction outwardly from said cage into the one of said slots associated with said one slip, said slots further each having a lower ledge spaced from the edge of the one of said associated windows a selected distance whereby said ledge engages said secondary release shoulder in the event of deformation occurring between said primary release shoulder and said lower edge when pulling said mandrel upwardly to release said slips.

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