Follow the Patents: Considerable Innovation Underway in Underground Conduit

After three killer hurricanes slammed into three different areas of the U.S., and left millions without power, the question more and more Americans are asking is “Why don’t we bury all these power lines?”

The answer is short and simple: Money. It is simply too expensive an undertaking. Most new residential developments have underground power, telephone and cable wiring, and most large cities put their utility lines underground years ago, but the majority of the U.S. power grid is still above ground.

Burying power lines is not a new idea. In fact, the granddaddy patent for underground conduit dates back to 1885. One William Walter received U.S. Patent No. 323,241 for an “Underground Conduit for Cables, Electric Wires, Etc.“ It was built with bricks and mortar since plastic would not be invented for another 50 years, and used an arched roof with iron reinforcement to support the weight of ground above it. It was quite sophisticated for its time–it even included pulleys to pull cable through the conduit–and it was designed for not just power lines, but telephone cables as well as steam and gas lines.

There is considerable ongoing innovation in the area of conduits for electric power lines, and in this installment of Follow the Patents, we once again look into the future by examining the latest underground conduit-related patented technologies.

U.S. Patent No. 8,590,862 for a “Method and Apparatus for Replacing Old Underground Conduit“ is way ahead of the curve since it is ready for the time when old conduit needs to be replaced. Burying conduit for the first time is a large enough task. Digging up old conduit and replacing it would be an even grander undertaking, and this patent addresses that with a technology that lays bare the old conduit, removes it, and sets new conduit down in place of the old in a continuous process. The patent was filed by Tracto-Technik Gmbh & Co., a German manufacturer of pipe rammers and bore rigs. Not surprisingly, Tracto-Technik also filed for and received a German patent.

U.S. Patent No. 9,328,853 for a “Low EMF Compact Duct Spacer“ addresses the issue of reducing electromagnetic fields (EMF) in underground conduits. The patent creates spacers that reduce the distance needed to bury underground power cables. The spacers place the conduits adjacent to each other for maximum cancellation of both single three-phase cable installations and dual three-phase cable installations. This patent is one of three patents derived from the same patent application and is assigned to Underground Devices, Inc.

U.S. Patent No. 9,389,271 for a “Security System for Underground Conduit“ addresses an often-talked-about, but largely unaddressed issue–an attack by terrorists, criminals or nut cases on the power grid, as well as damage to underground conduit from earthquakes and other natural disasters. Filed by and assigned to Ohio University, this patent addresses identifying disruptions to underground conduit by laying a series of signal-carrying cables along different sections of the conduit. Each section of cable is configured to transmit a signal to the next section of cable when it is impacted by an exterior force. To avoid false alarms from minor movements in the earth–like a heavy truck driving by–an alert is not sent until one or more sections of the force-sensitive cable detect impact from an exterior source.

U.S. Patent No. 9,391,433 for a “Conduit Space Recovery System“ is also especially forward-thinking. It addresses removing older, no-longer used cable from an underground conduit to make room for newer-technology–greater bandwidth cabling, for example. It uses a slitting device to slice the cable open as it is pulled out of the conduit. This patent is just one property in an international patent portfolio from Taiwan-based Wesco Distribution Inc. that includes Canadian, Chinese and European patents and applications.

U.S. Patent No. 9,660,426 for “Attachments for Compact Tractor for Pulling Wire through Underground Conduits“ is the most recent of this installment’s patents having been issued in May of this year, and like the previous patent, it addresses the challenge of removing older cable from long sections of underground conduit so it can be replaced with newer-technology cabling. From independent inventor Matthew Krimple, this patent describes an attachment to a tractor that includes a boom and a dipper on the rear, and a rotatable “witch’s hat” spool assembly (a spool with a tapered shaft just like the hat the Wicked Witch of the East wore in “The Wizard of Oz”) on the front. The spool assembly is mounted on lifter arms so the spool of old cable can be lifted up and placed on a truck or trailer and carted away.

Next time: Patents have multiple purposes for the businesses to which they are assigned. In the next installment of Follow the Patents, we will address how businesses, especially electric utilities, can optimize the value of their intellectual assets.

About the author: Alec Schibanoff is vice president of IPOfferings LLC, a leading patent broker and IP consulting services firm. He can be reached at


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