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Tight tank.

U.S. Patent 7,736,566 (June 15, 2010), "Manufacturing Process for Hydrogen Pressure Tank," Rainer Pechtold, Ingo Hermann, and Markus Lindner (GM Global Technology Operations, Inc., Detroit, Michigan, USA).

In a fuel cell system in a vehicle, hydrogen is typically stored in a compressed-gas tank under high pressure, which can be upwards of 700 bar. In one known design, the tank includes an inner plastic liner that provides a gastight seal for the hydrogen, and an outer carbon fiber composite layer that provides the structural integrity of the tank. Because hydrogen is very light and easily diffusible, the inner liner and the tank connector components, such as O-rings, must be carefully engineered in order to prevent leaks. The hydrogen is removed from the tank through a pipe. At least one pressure regulator is typically provided that reduces the pressure of the hydrogen within the tank to a pressure suitable for the fuel cell system. The most cost-effective technique for molding the plastic liner is a rotomolding process, in which plastic material is applied as a granulate to a mold shaped like the liner. But the rotomolding process is not conducive for filling small gaps, and therefore the sealing properties in the tank may be diminished. Pechtold et al. have developed a process for manufacturing a compressed-gas tank that combines injection molding and rotomolding. In a first step, a boss to be positioned in the opening of an outer structural layer of the tank is provided, and a thin portion of the liner is injection--molded to the boss, so that a channel within the boss is filled with the liner material to increase the seal integrity between the boss and the liner. Once the liner material hardens, the surface of the injection-molded liner portion is cleaned. Next, a rotomolding process molds the remaining portion of the liner to the boss. During the rotomolding process, the injection-molded portion of the liner melts to become part of the liner made during the rotomolding process.

Roger D. Corneliussen is Professor Emeritus of Materials Engineering, Drexel University, in Philadelphia, Pennsylvania, USA. He is editor of Maro Polymer Alerts and the Maro Polymer website (www. He has been active in SPE since 1962 and has served on the Board of the Philadelphia Section and as SPE Councilor. For Maro Patent Alerts, he reviews all U.S. Patents weekly, makes links to the polymer-related patents, and sends the links daily to subscribers. These patent abstracts are based on the weekly selection process. To sample Maro Patent Alerts, email a request to

The patents described here are selected on the basis of their novelty; selection does not affirm or imply the accuracy of a patent or its practical applicability.
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Title Annotation:industry PATENTS
Author:Corneliussen, Roger
Publication:Plastics Engineering
Geographic Code:1USA
Date:Oct 1, 2010
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