Stress relieved tool elements

{
  "publication_number": "US4076436A",
  "country": "US",
  "kind": "A",
  "title": "Stress relieved tool elements",
  "abstract": "Specially designed stress relief grooves for threaded end portions of tools and for collars on reciprocating or rotating drill string mounted tools.",
  "claims": [
    "1. A drill string mounted tool having a threaded end which is joined to an abrupt shoulder by a new and improved stress relief groove, comprising: a first partially curved groove portion descending from said threaded end to a point of minimal wall thickness where said groove is the deepest; and a second groove portion ascending from said point of minimal wall thickness to said abrupt shoulder in a series of curved segments which are joined at common tangents to provide a continuously ascending curved groove portion, each curved segment having a consecutively smaller radius of curvature from said point of minimal wall thickness to said abrupt shoulder whereby stress concentration is substantially reduced between said threaded end portion and said abrupt shoulder.",
    "2. The structure of claim 1, wherein: each curved segment is formed by a radius of curvature, wherein, from said point of minimal wall thickness to said abrupt shoulder, each radius of curvature has an origin on said preceding radius of curvature.",
    "3. The structure of claim 1, wherein: said radius of curvature of said second groove portion is substantially perpendicular to said abrupt shoulder where said second groove portion meets said shoulder.",
    "4. The structure of claim 3, wherein: said second groove portion terminates at said abrupt shoulder at the intersection of the plane of the threads of the threaded end with said abrupt shoulder.",
    "5. The structure of claim 1, wherein said first groove portion includes: a first straight inclined section originating adjacent said threaded end and extending inwardly therefrom being at substantially a 45° incline with respect to the longitudinal axis of the pipe; and a second curved section adjacent to and aligned with said first section, said second section being in tangential alignment with said first section and tangent to said point of minimal wall thickness.",
    "6. The structure of claim 5, wherein: said second curved section subtends substantially an arcuate 45° angle between said tangential alignment with said first section and said tangential alignment at said point of minimal wall thickness."
  ],
  "description_excerpt": "This is a continuation of application Ser. No. 541,642 filed Jan. 6, 1975.\n\nThe field of this invention relates to the stress relieving of drill string tools.\n\nIn oil well drilling, the drill string and tools mounted thereon are subjected to various stresses from torsional bending and longitudinal loading. Generally, downhole tools are designed to withstand such stresses for extended periods. However, stress failure continues to be a problem in downhole tools having abrupt changes in sections where stress tends to concentrate.\n\nThe present invention provides a new and improved stress relief groove to be used adjacent to and between a threaded end of a drill string mounted tool body and an abrupt shoulder on the tool body. The stress relief groove of the preferred embodiment of this invention for the drill string mounted tool body has a first partially curved groove portion descending from the threaded end to a point of minimal wall thickness and a second groove portion ascending from the point of minimal wall thickness to the abrupt shoulder in a series of curved segments which are joined at common tangents to provide a continuously ascending curved grooved portion.\n\nFurthermore, the present invention also includes a stress relieved tool element having an abrupt shoulder with a stress relief groove displaced from the abrupt shoulder for relieving stress concentrations adjacent the abrupt shoulder wherein the displacement is less than one-half the difference of the outside diameter of the tubular member and the outside diameter of the tool portion or mandrel of smaller diameter.",
  "cpc": [
    "E21B 17/042",
    "E21B 17/04",
    "F16B 7/182"
  ],
  "ipc": [
    "E21B 17/04",
    "E21B 17/042",
    "F16B 7/18"
  ],
  "assignees": [
    "Bowen Tools Inc"
  ],
  "inventors": [
    "Damon T. Slator",
    "Archie W. Peil",
    "Thomas R. Bishop"
  ],
  "filing_date": "1976-02-05",
  "publication_date": "1978-02-28",
  "grant_date": "1978-02-28",
  "priority_date": "1975-01-06",
  "application_number": "US-65544276-A",
  "family_id": "24160450",
  "cited_by_count": 46,
  "citations": [
    "US1926925A",
    "US2045520A",
    "US2110825A",
    "US2606778A",
    "DE1194349B"
  ]
}