Chemistry: electrical current producing apparatus – product – and – With pressure equalizing means for liquid immersion operation
Reexamination Certificate
1999-03-01
2001-07-31
Maples, John S. (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
With pressure equalizing means for liquid immersion operation
C429S006000, C429S006000
Reexamination Certificate
active
06268077
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
This application is related to U.S. Pat. No. 6,127,058, by Pratt et. al., entitled “Planar Fuel Cell,” and assigned to Motorola, Inc.
TECHNICAL FIELD
This invention relates in general to devices that deliver electric power to handheld electrical devices, and more specifically, to a portable power supply utilizing a fuel cell to convert a fuel to electricity.
BACKGROUND
In fuel cells, electrical energy is produced by reacting a fuel with an oxidant in the presence of a catalyst. A typical fuel cell consists of a fuel electrode (anode) and an oxidant electrode (cathode), separated by an ion-conducting electrolyte. The electrodes are connected to a load (such as an electronic circuit) by an external circuit conductor. In the circuit conductor, electric current is transported by the flow of electrons, whereas in the electrolyte it is transported by the flow of ions, such as the hydrogen ion (H
+
) in acid electrolytes, or the hydroxyl ion (OH
−
) in alkaline electrolytes. At the anode, incoming hydrogen gas ionizes to produce hydrogen ions and electrons. Since the electrolyte is not an electronic conductor, the electrons flow away from the anode via the external circuit. At the cathode, oxygen gas reacts with the hydrogen ions migrating through the electrolyte and the incoming electrons from the external circuit to produce water as a byproduct, which is then typically extracted as a vapor. One well-known type of fuel cell includes a “membrane-electrodeassembly” (MEA) which is typically a thin, proton-transmissive, solid polymer membrane electrolyte having an anode on one of its faces and a cathode on the opposite face. The MEA is sandwiched between a pair of electrically conductive elements which serve as current collectors for the anode and cathode, and contain appropriate channels and/or openings therein for distributing the fuel cell's gaseous reactants over the surfaces of the respective anode and cathode catalysts. One such MEA and fuel cell is described in U.S. Pat. No. 5,272,017. In practice, a number of these unit fuel cells are normally stacked or ‘ganged’ together to form a fuel cell stack or assembly. The individual cells are electrically connected in series by abutting the anode current collector of one cell with the cathode current collector of its nearest neighbor in the stack.
For portable electrical equipment requiring up to about 100 Watts of electrical power, batteries have been the only choice. From toys to laptop computers, batteries provide power for a limited amount of time and then have to be either recharged or replaced. In theory, fuel cells have the same consumer friendly general properties as batteries—giving quiet electrochemical power and can also be ‘recharged’ chemically although not by electrical means. However, the real advantage of fuel cells lies in their long lifetime and their use of liquid or gas rather than the solid ‘fuels’ used in conventional batteries. The efforts of the prior art have essentially been focused on improvements in fuel cell stacks, and much of this effort has resulted in smaller stacks that were created by miniaturizing many of the mechanical parts in the stack. However, even the smallest stacks are still prohibitively large for use with handheld portable electrical equipment, such as two-way radios, cellular telephones, laptop computers, and cordless power tools, to name but a few. Little, if any effort has been expended to reduce the size of the various other components required to support a fuel cell, namely the fuel storage, the interconnections (hoses, clamps, etc.) and the regulators. Thus, even the smallest, state-of-the-art devices are still as large as a shoe box. It would be a significant addition to society if a truly small portable power supply could be created, using fuel cell technology, to unlock the true potential of portable electric devices. For example, even the best electrochemical batteries can only power a laptop computer or a cellular telephone for, at most, one day, whereas 30 days would be a much more useful capacity.
REFERENCES:
patent: 5514486 (1996-05-01), Wilson
patent: 5595834 (1997-01-01), Wilson et al.
patent: 5759712 (1998-06-01), Hockaday
patent: 5962155 (1999-10-01), Kuranaka et al.
patent: 5976725 (1999-11-01), Gamo et al.
patent: 6057051 (2000-05-01), Uchida et al.
patent: 6194092 (2001-02-01), Ohara et al.
Kelley Ronald J.
Landreth Bobby Dean
Muthuswamy Sivakumar
Pennisi Robert W.
Pratt Steven D.
Dorinski Dale W.
Maples John S.
Motorola Inc.
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