Patents by Inventor Peter J. Ellefson

Peter J. Ellefson 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).

  • Gradient density filter
    Patent number: 5472600
    Abstract: A gradient density filter made from sheets of blown polypropylene microfibers where the microfibers of at least one of the sheets have an effective fiber diameter less than that of the other sheets is described. This filter is especially useful in solid phase extraction processes, particularly those where biological fluids are being analyzed.
    Type: Grant
    Filed: February 1, 1995
    Date of Patent: December 5, 1995
    Assignee: Minnesota Mining and Manufacturing Company
    Inventors: Peter J. Ellefson, David A. Wells