Patents by Inventor C. Donald Johnson

C. Donald Johnson 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).

  • Open-closed center hydraulic valve assembly
    Patent number: 4548229
    Abstract: A valve assembly for a pressurized fluid tool is disclosed. The valve assembly includes a spool inside a sleeve. Rotation of the sleeve by 180.degree. causes the valve to change from an open center (normally open--N.O.) to a closed center (normally closed--N.C.) condition.
    Type: Grant
    Filed: April 8, 1981
    Date of Patent: October 22, 1985
    Assignee: Harsco Corporation
    Inventor: C. Donald Johnson