Ex Parte Zhang et al

Patent Trial and Appeal Board

Aug 23, 2013

11695236 (P.T.A.B. Aug. 23, 2013)

UNITED STATES PATENT AND TRADEMARKOFFICE
UNITED STATES DEPARTMENT OF COMMERCE
United States Patent and Trademark Office
Address: COMMISSIONER FOR PATENTS
P.O. Box 1450
Alexandria, Virginia 22313-1450
www.uspto.gov
APPLICATION NO. FILING DATE FIRST NAMED INVENTOR ATTORNEY DOCKET NO. CONFIRMATION NO.
11/695,236 04/02/2007 Yan Zhang GP-308872-FCAR-CHE 2313
104102 7590 08/23/2013
BrooksGroup
48685 Hayes
Shelby Township, MI 48315
EXAMINER
WALLS, CYNTHIA KYUNG SOO
ART UNIT PAPER NUMBER
1726
MAIL DATE DELIVERY MODE
08/23/2013 PAPER
Please find below and/or attached an Office communication concerning this application or proceeding.
The time period for reply, if any, is set in the attached communication.
PTOL-90A (Rev. 04/07)

UNITED STATES PATENT AND TRADEMARK OFFICE
________________

BEFORE
THE PATENT TRIAL AND APPEAL BOARD
________________

Ex parte YAN ZHANG,1
Hubert A. Gasteiger, and Steven R. Falta
________________

Appeal 2012-005778
Application 11/695,236
Technology Center 1700
________________

Before HUBERT C. LORIN, JEFFREY T. SMITH, and MARK NAGUMO,
Administrative Patent Judges.

NAGUMO, Administrative Patent Judge.

DECISION ON APPEAL
Yan Zhang, Hubert A. Gasteiger, and Steven R. Falta (“GM”) timely
appeal under 35 U.S.C. § 134(a) from the final rejection2 of claims 1-6,
12-18, 20, 21 and 23-26. We have jurisdiction under 35 U.S.C. § 6.
We affirm.

1 The real party in interest is listed as General Motors Co. (hereinafter,
“GM).” (Appeal Brief, filed 22 September 2011 (“Br.”), 4.)
2 Office action mailed 25 April 2011 (“Final Rejection”).
Appeal 2012-005778
Application 11/695,236

2
OPINION
A. Introduction3
The subject matter on appeal relates to methods of shutting-down and
starting-up a fuel cell stack, particularly in a vehicle in cold weather.
According to the 236 Specification, at temperatures below 0°C, the
temperature of a fuel cell stack in an automobile used for short trips “might
not reach above 0°C using the waste heat of the chemical reaction.”
(Spec. 9 [0027].) At sub-freezing temperatures, water from the normal
operation of the fuel cell could freeze and the ice could accumulate in the
void volume of the cathode, preventing operation of the vehicle.
(Id. at 9-10 [0027].) The inventors seek exclusive patent protection for a
process of heating the fuel cell stack above a purge temperature greater
than 0°C before shutting down so the voids in the cathode electrode can be
purged using a gas so they do not become plugged with ice.
(Id. at 10 [0027].) In some embodiments, the process further includes a step
of starting the fuel cell stack when the temperature is below 0°C, in which
the fuel cell is operated under a load in excess of that required by the
operator, in order to heat the fuel cell rapidly at least past the freezing point.
Claim 1 is representative and reads:
A method of operating a fuel cell stack comprising:
(a) upon requesting shutdown of the fuel cell stack,
measuring a stack temperature of the fuel cell stack;

3 Application 11/695,236, Method of starting up a fuel cell under conditions
in which water may freeze, filed 2 April 2007. The specification is referred
to as the “236 Specification,” and is cited as “Spec.”
Appeal 2012-005778
Application 11/695,236

3
(b) comparing the stack temperature to a predetermined
purge temperature and either
(1) shutting down the fuel cell stack if the stack
temperature is greater than the predetermined purge
temperature or
(2) continuing to operate the fuel cell stack to draw a
load to heat up the fuel cell stack until the stack
temperature exceeds the predetermined purge
temperature and
thereafter shutting down the fuel cell stack [if the stack
temperature is below the predetermined purge temperature][4],
the predetermined purge temperature being above 0°C;
(c) after the fuel cell stack is shut down, purging water from
the fuel cell stack so that the cathode of the fuel cell stack is
free of ice, the purging water comprising blowing a gas
through the fuel cell stack; and
(d) starting the fuel cell stack when the stack temperature is
below 0°C and
drawing a load on the fuel cell stack ranging
from 75 percent of the maximum to the maximum load
that the fuel cell stack is capable of responding to,
wherein the maximum load is limited by fuel cell
system constraints and wherein the load drawn is
greater than that requested by an operator of the fuel
cell stack to drive primary and auxiliary devices and
continuing to draw the load in an amount greater than that
requested by the operator at least until the stack
temperature is above 0°C.
(Claims App., Br. 27; some paragraphing and indentation added.)

4 The bracketed text (entered in the Amendment filed 27 September 2010)
appears to be extraneous, and we so treat it, without deciding the issue,
which has not been raised between the Examiner and GM. We assume it
will be dealt with appropriately in the event of further prosecution.
Appeal 2012-005778
Application 11/695,236

4
Claim 20, the only other independent claim, is similar, but lacks
step (d). (Claims App., Br. 29.)5
The Examiner maintains the following grounds of rejection:6
A. Claims 1-6, 12-14, 17, 18, and 21 stand rejected under
35 U.S.C. § 103(a) in view of the combined teachings of
Aso,7 Yu,8 and Takahashi.9
A1. Claim 25 stands rejected under 35 U.S.C. § 103(a) in view of
the combined teachings of Aso, Yu, Takahashi, and
Margiott.10
B. Claims 20, 23, 24, and 26 stand rejected under
35 U.S.C. § 103(a) in view of the combined teachings of Yu
and Takahashi.
B1. Claim 25 stands rejected under 35 U.S.C. § 103(a) in view of
the combined teachings of Yu, Takahashi, and Aso.

5 Claim 20 does not include the anomalous text noted supra, 3 n.4, in
claim 1.
6 Examiner’s Answer mailed 6 December 2011 (“Ans.”).
7 Takeshi Aso, Fuel cell system and control method, WO 2004/102720 A1
(2004); The Examiner relies, without objection, on U.S. Patent Application
Publication 2006/0088738 A1 (27 April 2006), the U.S. National stage of
the WO application, for cites.
8 Paul Taichiang Yu and Frederick T. Wagner, Method of using H2 purge
for stack startup/shutdown to improve stack durability, U.S. Patent
Application Publication 2006/0046106 A1 (2 March 2006).
9 Naoki Takahashi, Fuel cell stack defrosting, U.S. Patent Application
Publication 2005/0238934 A1 (2005).
10 Paul R. Margiott et al., U.S. Patent 6,093,500 (2000).
Appeal 2012-005778
Application 11/695,236

5
B. Discussion
Findings of fact throughout this Opinion are supported by a
preponderance of the evidence of record.
Initially, we find that GM only presents arguments for the separate
patentability of claims 1 and 20, and further, that the arguments for the
patentability of claims 1 and 20 are substantially the same. (Br. 21, ll. 2-4.)
All claims thus stand or fall with claim 1.
GM argues that the Examiner erred in finding that the combined
teachings of Yu and Takahashi teach or suggest the required shut-down
phase (steps (a) and (b) of claim 1). (Br. 16; see also the findings of fact
SF1-SF28 at Br. 21-25.) More particularly, GM argues that Yu does not
teach measuring the temperature of the stack, and that Yu “does not disclose
any particular restriction on the temperature of the fuel cell stack 12[11]
during shut-down or purging with H2 and air.” (Id. at 16, 2d full para.)
GM argues further that Takahashi does not describe a shut-down procedure,
but rather a method of defrosting a fuel cell stack operated below the
freezing point. Takahashi does not, in GM’s view, describe or suggest
measuring the fuel cell stack temperature upon a shut-down request, or
comparing the measured temperature to a predetermined purge temperature
as part of a shut-down procedure. (Id. para. bridging 16-17.) The
temperature Tc, above which there is no likelihood of water vapor
condensing to liquid water or ice, is not, in GM’s view, equivalent to the

11 Throughout this opinion, for clarity, labels to elements are set in bold font,
regardless of their presentation in the original document.
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Appeal 2012-005778
Application 11/695,236

7
completion temperature Tc is attained. (Ans., para. bridging 6-7, discussing
the Takahashi method described at [0031]-[0045], cited by GM (Br. 24-25,
SF18-SF22.) The Examiner finds that Yu discloses preventing stack freeze
by purging all the water vapor and liquid out of the stack via the introduction
of air. (FR 3, last para, citing Yu 2 [0017]; Ans. 6, ll. 4-6 (same).) The
Examiner reasons that it would have been obvious “to add a controller of
Takahashi to the shutdown procedure of Yu for the benefit of purging the
water above zero degrees as required by Yu during shutdown.” (Ans. 7.)
GM’s arguments are not persuasive of harmful error in the Examiner’s
rejections. First, despite detailed findings regarding Yu (Br. 22-23,
SF8-SF16), and denials that “Yu discloses particular restrictions” on the
temperature during shut-down (Br. 16, 2d full para.), GM appears to have
overlooked the teaching by Yu, cited by the Examiner, that during stack
shutdown, “[t[]he introduction of air purges all the water vapor and liquid
out of the stack for preventing stack freeze” (Yu 2 [0017], penultimate
sentence; emphasis added.) Thus, we have no difficulty finding that the
routineer would have been prompted by both Yu and Takahashi to remove
the water produced at the cathode during the normal operation of the fuel
cell to prevent freezing at sub-0°C temperatures. Takahashi’s teaching of
monitoring the stack temperature until the “defrost completion temperature,”
Tc, would suggested—if such a suggestion were necessary—that such
monitoring would improve the efficiency of the process by running the
blower 11 and heating the cell no longer than necessary. Thus, GM’s
statement of fact, SF23, that “[i]n the Takahashi method, the defrosting
completion temperature Tc is not used to prepare the fuel stack 1 for
Appeal 2012-005778
Application 11/695,236

8
purging,” although technically accurate, is misplaced. The routineer would
have recognized, from the teachings of Takahashi if not from their own
experience, that the purging taught by Yu would occur more efficiently at
higher stack temperatures. It is the teachings of the references as a whole
that must be evaluated in evaluating the obviousness vel non of the claimed
process.
We have no difficulty finding on this record that the routineer would
have had the motivation to apply such teachings to the shut-down processes
taught by Yu when confronted by the need to operate at sub-freezing
temperatures. The temperature measurements, fuel cell stack heatings, and
gas purgings recited in the claims would have been routine implementations
of applying purging gas in a manner similar to that taught by Takahashi to a
shut-down of Yu’s fuel cell system under sub-zero freezing temperature
conditions. GM has not directed our attention to any credible evidence in
the record that the level of ordinary skill is so low that the explicit teachings
GM demands as evidence of obviousness would have been required.
As we have already found, GM has not raised further substantive
issues regarding the combination with Aso. Moreover, GM has not raised
arguments for patentability based on so-called secondary considerations
such as unexpected results or commercial success.
We therefore affirm the rejections maintained by the Examiner.
Appeal 2012-005778
Application 11/695,236

9
C. Order
We affirm the rejections of claims 1-6, 12-18, 20, 21, and 23-26.
No time period for taking any subsequent action in connection with
this appeal may be extended under 37 C.F.R. § 1.136(a).
AFFIRMED
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