Patents by Inventor Otmar Kramer

Otmar Kramer 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).

  • Patent number: 5469704
    Abstract: The invention relates to a hydraulic drive apparatus having a cylinder. Said cylinder comprises a piston movably mounted in a working chamber, a piston rod which is guided towards the outside through a cylinder head and a wear resistant primary seal and a leakage free secondary seal. Both said seals act between the cylinder head and the piston rod, with the primary seal being closer to the working chamber than the secondary seal. Further, a leakage oil conduit is provided between the primary seal and the secondary seal. Such a hydraulic drive apparatus is to be improved such that the cylinder will hold or maintain a load in a certain position even if the pump is switched off for a long period of time. This is achieved by providing that the leakage oil conduit can be subjected to the load holding pressure by switching a valve.
    Type: Grant
    Filed: November 18, 1993
    Date of Patent: November 28, 1995
    Assignee: Mannesmann Rexroth GmbH
    Inventor: Otmar Kramer