Patents by Inventor David C. Johnstone

David C. Johnstone has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Patent number: 4069880
    Abstract: An excavation tool, specifically, a down-the-hole bit which reduces a formation by being impacted axially against a formation while rotating and through which a supply of fluid, such as air, is supplied through a passage in the bit to the working face thereof to blow away the material taken by the bit and wherein the working face of the bit is provided with grooves extending outwardly from the lower end of the fluid supply passage to the periphery of the bit and in communication with axial grooves formed in the bit. The provision of the grooves in the working end of the bit in communication with the axial grooves in the outer periphery of the bit greatly improves the removal of debris which accumulates at the bottom of the hole being drilled and increases the efficiency of the bit.
    Type: Grant
    Filed: May 24, 1973
    Date of Patent: January 24, 1978
    Assignee: Kennametal Inc.
    Inventors: David C. Johnstone, John F. Kita