Patents by Inventor William Frederick Robotham

William Frederick Robotham 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: 4006334
    Abstract: This invention teaches an on/off switch design that can be used in electric power tools, where the power is normally off and further cannot be shifted on unless a switch actuating element is first manipulated through two right angle motions according to a predetermined sequence. The subject device has a normally off on/off switch and a switch actuating element that is supported to move against the switch to shift the same on. The actuating element carries a latch that normally holds it in the switch off position. The latch must first be moved laterally against the force of a biasing spring and held there to release the actuating element, and only then can the actuating element be moved at right angle to the latch releasing movement and then depressed, effective to switch the on/off switch on.
    Type: Grant
    Filed: March 17, 1975
    Date of Patent: February 1, 1977
    Assignee: McGraw-Edison Company
    Inventors: William Frederick Robotham, Larry D. Annis
  • Patent number: 3959878
    Abstract: This invention teaches a convertible portable electric tool having a common power housing and different operating tool output pieces which can be releasably secured to said power housing without the need of any tools. Each of the tool output pieces has a stationary element and a movable element supported by the stationary element. The power housing has an exposed drive element which can cooperate with and drive the movable element when the statonary element is properly positioned relative to the housing. The stationary element in turn is sized to cooperate with the housing to cover the exposed drive element and be accurately positioned and held in place against the housing. Flexible fingers cantilevered integrally from the housing have free end flexture parallel to the stationary element, and further have projections on the finger ends that interlock with the positioned stationary element to hold it operatively in place relative to the housing.
    Type: Grant
    Filed: April 2, 1975
    Date of Patent: June 1, 1976
    Assignee: McGraw-Edison Company
    Inventors: Edward A. Irelan, David W. Dorheim, William Frederick Robotham