Patents by Inventor Hans Rudolf Keller

Hans Rudolf 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).

  • Method of and apparatus for controlling the inlet openings of central ventilation installations
    Patent number: 3990356
    Abstract: A method of and apparatus for controlling the inlet or exhaust openings of central ventilation or exhaust installations wherein air is only removed from the individual rooms or areas by means of a central exhaust ventilator when such rooms or areas are in use as well as for a certain time duration thereafter, and after expiration of such time duration the exhaust openings of the rooms or areas are automatically closed.
    Type: Grant
    Filed: February 4, 1975
    Date of Patent: November 9, 1976
    Inventor: Hans Rudolf Keller