Patents by Inventor Hubertus Augustinus Leonardus Maria De Graaf

Hubertus Augustinus Leonardus Maria De Graaf 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: 5639183
    Abstract: A method for installing a tubular cable-duct around a cable buried in the ground includes steps of freeing a portion of the buried cable from the ground in a forward longitudinal direction of the cable, starting from a free end of the buried cable, and advancing a foremost end of the cable-duct and subsequent portions of the cable-duct in the forward longitudinal direction of the cable over the portion of the cable freed from ground, starting from the free end of the cable. The advancing step includes the sub-steps of exerting pulling forces on the cable with a pulling device engaging the free end of the buried cable in a direction which is substantially opposed to the forward longitudinal direction of the cable, and exerting pushing forces with a pushing device engaging the cable-duct in a direction which is substantially opposed to the direction in which the pulling forces are exerted.
    Type: Grant
    Filed: October 31, 1995
    Date of Patent: June 17, 1997
    Assignee: Koninklijke PTT Nederland N.V.
    Inventors: Willem Griffioen, Cornelis Casparus Van Bijsterveld, Hubertus Augustinus Leonardus Maria De Graaf