breaking-down effected by force or pressure applied to side of slit

Industry

  • CPC
  • E21C27/14
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Patents Grantslast 30 patents

  • Information Patent Grant

    2420755

    • Patent number 2,420,755
    • Issue date May 20, 1947
    • E21 - EARTH DRILLING MINING
  • Information Patent Grant

    1682555

    • Patent number 1,682,555
    • Issue date Aug 28, 1928
    • E21 - EARTH DRILLING MINING

Patents Applicationslast 30 patents