Patents by Inventor Fritz Marggraff

Fritz Marggraff 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).

  • Boat with a raisable and lowerable keel
    Patent number: 4690089
    Abstract: A boat with a raisable and lowerable keel is proposed, which can be constructed as a swivel, lifting or ballast drop keel. The keels are fixed to tensioning members either directly or via cables. The tensioning members can be spiral springs, which run in the lifting keel box and are guided in the interior of the lifting keel to the lower end thereof. If the lifting keel is lowered, the spiral springs are tensioned, so that only relatively limited forces are required for raising by means of a spindle (FIG 1).
    Type: Grant
    Filed: January 21, 1986
    Date of Patent: September 1, 1987
    Inventor: Fritz Marggraff