Patents by Inventor Dennis P. Graham

Dennis P. Graham 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).

  • Twistlock operating mechanism
    Patent number: 4630856
    Abstract: Twistlocks of a container spreader are operated and controlled by hydraulic cylinders and interlock valves connected in series. Interlock valves block the flow of fluid through the cylinders when insertion of the twistlocks in their mating connectors is incomplete. Parallel fluid ports at the inlet and outlet of the cylinders permit the inlet and outlet to be connected, at the ends of the hydraulic cylinder's piston stroke, to compensate for different volume requirements of the hydraulic cylinders.
    Type: Grant
    Filed: January 31, 1985
    Date of Patent: December 23, 1986
    Assignee: Hyster Company
    Inventors: Jan A. Peeters Weem, David E. Krueger, Dennis P. Graham