Patents by Inventor Friedhelm Keller

Friedhelm Keller 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).

  • Welding sleeve and method for its manufacture
    Patent number: 5255943
    Abstract: A welding sleeve is disclosed comprising a sleeve member of thermoplastic weldable material having a resistor wire winding at the internal surface thereof.
    Type: Grant
    Filed: May 15, 1992
    Date of Patent: October 26, 1993
    Assignee: Georg Fischer Rohrleitungssysteme AG
    Inventors: Friedhelm Keller, Dirk Petry, Helmut Hilger