Patents by Inventor Keith Drummond Stevens

Keith Drummond Stevens 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).

  • Pulse controllers
    Patent number: 4119898
    Abstract: A controller for a series electric motor is described of the type comprising means for applying D.C. pulses to the motor and means for controlling the mark/space ratio of the pulses applied to the motor. The current through the motor is sensed and the maximum mark/space ratio which may be applied to the motor is reduced when the motor current is below a predetermined limit to avoid overspeed in light load conditions.
    Type: Grant
    Filed: December 22, 1976
    Date of Patent: October 10, 1978
    Assignee: Cableform Limited
    Inventors: John Morton, Keith Drummond Stevens