US Patent 7497000 Method for repairing a collapsed duct section

The present invention is an apparatus and method for repairing a collapsed underground duct for a fiber cable. A head is inserted into the duct until the collapsed section is sensed. Power, such as hydraulic or pneumatic pressure of electric potential, is applied to the head, actuating an expansion member that engages the duct wall and applies a force to it, forcing it to a non-collapsed state. The head may be fed through the non-collapsed duct by applying air pressure behind it, forcing through the duct until it encounters the collapsed section.