Patents by Inventor Ernst W. Hellriegel

Ernst W. Hellriegel 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).

  • Tennis training apparatus
    Patent number: 5344138
    Abstract: An apparatus for training the overhead service in tennis. The apparatus comprises indicators of a target base area and of correct feet placement, a connecting member between the two indicators, and, optionally, a flexible connecting member between the target base area indicator and a tennis ball.
    Type: Grant
    Filed: June 14, 1991
    Date of Patent: September 6, 1994
    Inventor: Ernst W. Hellriegel