Ex Parte Logan

Patent Trial and Appeal Board

Dec 4, 2012

11457880 (P.T.A.B. Dec. 4, 2012)

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.
11/457,880 07/17/2006 Victor W. Logan GP-308178-GAPR-CHE 7923
65798 7590 12/04/2012
MILLER IP GROUP, PLC
GENERAL MOTORS CORPORATION
42690 WOODWARD AVENUE
SUITE 200
BLOOMFIELD HILLS, MI 48304
EXAMINER
MARKS, JACOB B
ART UNIT PAPER NUMBER
1729
MAIL DATE DELIVERY MODE
12/04/2012 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 VICTOR W. LOGAN
____________________

Appeal 2011-007708
Application 11/457,880
Technology Center 1700
____________________

Before CHUNG K. PAK, CHARLES F. WARREN, and
CATHERINE Q. TIMM, Administrative Patent Judges.

TIMM, Administrative Patent Judge.

DECISION ON APPEAL

STATEMENT OF CASE
Appellant appeals under 35 U.S.C. § 134 from the Examiner’s
decision to reject claims 10-13, 15, 16, and 181. We have jurisdiction under
35 U.S.C. § 6(b).
We REVERSE.
The claims are directed to a fuel cell system. Claim 10 is illustrative:

1 The Examiner has withdrawn the rejection of claims 14 and 17 (Ans. 3).
Claim 15 remains rejected but depends from claim 14.
Appeal 2011-007708
Application 11/457,880

2
10. A fuel cell system comprising:
a fuel cell stack including an anode input and an anode
output;
a bleed valve for periodically bleeding anode exhaust gas
from the anode output; and
a controller for controlling the bleed valve, said
controller
[1] determining the partial pressure of nitrogen in
the anode exhaust gas,
[2] calculating the partial pressure of water vapor
and hydrogen in the anode exhaust gas,
[3] calculating the gas mole fraction of the
nitrogen, the water vapor and the hydrogen in the anode
exhaust gas using the partial pressure of the nitrogen, the
water vapor and the hydrogen,
[4] determining a desired valve coefficient using
the gas mole fraction of the nitrogen, the water vapor and
the hydrogen in the anode exhaust gas, and
[5] determining when to open and close the bleed
valve using the desired valve flow coefficient.
(Claims App. at Br. 22 (clause indenting and numbering added).)
The Examiner rejects claim 10 under 35 U.S.C. § 112, ¶ 1 as lacking
enablement. The Examiner further rejects claims 10, 15, 16, and 18 under
35 U.S.C. § 103(a) as obvious over Iio2 in view of Callahan3; and claims 11-
13 as obvious those references further in view of ISA4.

2 Iio, WO 2004/105169 A1, pub. Dec. 2, 2004. The Examiner relies upon
US 2007/0009772 A1, pub. Jan. 11, 2007 as the English language
Appeal 2011-007708
Application 11/457,880

3
For the reasons that follow, we determine that the preponderance of
the evidence does not support the rejections.
OPINION
ENABLEMENT
The Examiner rejects claim 10 as lacking enablement because
“applicant does not sufficiently describe the relationship between the valve
flow coefficient and the anode exhaust composition for one of ordinary skill
in the art to use the invention.” (Ans. 4.) According to the Examiner,
“undue experimentation by one of ordinary skill in the art would be required
for determining how to calculate the valve flow coefficient and the desired
flow rate based on the anode exhaust gas composition.” (Ans. 4-5.)
Appellants contend “paragraphs [0020]-[0031] of the specification
describe in detail each of the steps associated with calculating the desired
valve flow coefficient, which is used to determine when to open and close
the bleed valve.” (Br. 11.)
The initial question is whether the Examiner has advanced acceptable
reasoning inconsistent with enablement such that the Examiner’s burden of
proof is met. In re Strahilevitz, 668 F.2d 1229, 1232 (Fed. Cir. 1982). Once
this burden is met, the burden shifts to Appellant to show that one of
ordinary skill in the art could have practiced the claimed invention without
undue experimentation. Id. Ultimately, all the evidence must be considered
in view of the Wands factors to determine whether a preponderance of the

equivalent. As Appellant does not object the the Examiner’s use of the
U.S.C document, we also relied on and cite to the U.S. document.
3 Callahan et al., US 2006/0003204 A1, Jan. 5, 2006.
4 ISA-S75.01-1985, Flow Equations for Sizing Control Valves, (1995)
Appeal 2011-007708
Application 11/457,880

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evidence supports the Examiner’s conclusion of enablement. In re Wands,
858 F.2d 731, 737 (Fed. Cir. 1988).
To determine whether the Examiner advanced acceptable reasoning,
we first consider what Appellant’s Specification would have conveyed to the
ordinary artisan keeping in mind that the Specification need not convey that
which is already known and available to one of ordinary skill in the art. See
In re Howarth, 654 F.2d 103, 105 (CCPA 1981) (“An inventor need not,
however, explain every detail since he is speaking to those skilled in the
art.”)
Appellant’s Specification describes a hydrogen fuel cell with an anode
recirculation loop 20 (Spec. ¶ [0015]; Fig. 1). The anode exhaust is
recirculated in order to reuse hydrogen (Spec. ¶ [0006]). Because some
nitrogen from the air permeates the membrane electrode assemblies (MEAs)
between the electrodes of the stacks, the recirculating hydrogen becomes
diluted with the cross-over nitrogen (Spec. ¶ [0007]). To prevent excess
nitrogen from affecting the performance of the fuel cell, it is necessary to
periodically bleed the anode exhaust gas to reduce the amount of nitrogen
being recirculated (Spec. ¶ [0016]).
According to Appellant’s Specification:
During the nitrogen bleed, the valve 26 is controlled to divert a
portion of the anode exhaust gas from the recirculation loop to
an exhaust line 28. It is beneficial to adapt the recirculation rate
of the anode gas to the fuel cell load and the hydrogen feed gas
flow to support proper water management and to reduce
parasitic loads on the fuel cell system.
(Spec. ¶ [0016].)
The control strategy is shown in Figure 3, reproduced below:
App
App

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Appeal 2011-007708
Application 11/457,880

6
[0016] (portion reproduced above)). In the context of the Specification as a
whole, particularly, paragraphs 16 and 19, it appears that determining the
stoichiometry setpoint and calculating the hydrogen bleed flow based on
stack load were known in the art. The Examiner provides no convincing
evidence or reasoning indicating otherwise.
Appellant’s invention is directed toward the next two algorithm boxes
shown in Figure 3, i.e., boxes 68 and 70 (Spec. ¶ [0033]). To complete the
calculation of box 68, the controller 34 uses a mathematical nitrogen
pressure model to estimate the gas composition of the anode exhaust gas in
line 20 (Spec. ¶ [0019]). To complete the calculation of box 70, the
controller uses an inverse valve model to calculate a desired valve flow
coefficient Cv needed to bleed the anode recirculation gas at a flow rate that
achieves a desired anode stoichiometry (id.). The controller 34 then controls
the bleed valve 26 to obtain the desired valve flow coefficient Cv (box 72 of
Fig. 3; Spec. ¶¶ [0019] and [0033]).
Paragraphs 20-22 of the Specification discuss the calculation of box
68 and disclose how the gas mole fraction of the nitrogen, water vapor, and
hydrogen in the anode exhaust gas is calculated using the calculated partial
pressure of the nitrogen, a calculated partial pressure of the water vapor, and
an assumption that the remaining partial pressure is due to hydrogen (Spec.
¶¶ [0020-22]).
At paragraphs 23-29, the Specification derives and describes
equations for calculating the valve flow coefficient Cv (equations (12) and
(13) at Spec. ¶ [0029]). Those equations (equations (12) and (13)) require
the input of specific gravity (Sg) (id.). Specific gravity Sg is calculated using
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Application 11/457,880

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the mole fractions of nitrogen, water vapor, and hydrogen previously
calculated (Spec. ¶¶ [0022] and [0025] at equation (5)).
The evidence supports Appellant’s contention that determining a
desired valve coefficient Cv using the gas mole fractions of the nitrogen,
water vapor, and hydrogen in the anode exhaust gas is merely a matter of
inputting the previously calculated gas mole fractions to calculate the
specific gravity (Sg) variable of equations (12) and (13) (Br. 11-13). There
is no undue experimentation with regard to “determining a desired valve
coefficient using the gas mole fraction of the nitrogen, the water vapor and
the hydrogen in the anode exhaust gas” as recited in claim 10.
Nor is there support for the Examiner’s conclusion that there is no
enablement for “determining when to open and close the bleed valve using
the desired valve flow coefficient” (Ans. 15). The Specification discloses
setting the duty cycle of the valve 26 to the ratio of the desired valve flow
coefficient Cv to the full valve flow coefficient Cv-valve. The disclosure
appears consistent with enablement in the face of lack of evidence or
reasoning to the contrary.
With regard to the Examiner’s reasoning that there is no enabling
disclosure supporting “determin[ing] the partial pressure of nitrogen, which
is used to calculate the partial pressures of hydrogen and water” (Ans. 15),
we agree with Appellant that there is no requirement in the claim that
nitrogen partial pressure be used to calculate the partial pressures of
hydrogen and water (Reply Br. 5-6). The claim language only requires
“determining the partial pressure of nitrogen in the anode exhaust gas,
calculating the partial pressure of water and hydrogen in the anode exhaust
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Application 11/457,880

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gas.” The Specification discloses how to calculate the nitrogen partial
pressure using equation (1), how to calculate the water vapor partial pressure
using temperature and assuming 100% humidity, and how to calculate the
hydrogen partial pressure from the total pressure minus the other partial
pressures (Spec. ¶¶ [0020-22]).
We do not sustain the rejection of claim 10 as lacking enablement.

OBVIOUSNESS
To reject claims 10-13, 15, 16, and 18, the Examiner relies on Iio in
view of Callahan alone or in view of further prior art (Ans. 7-13).
All of the claims require a controller “determining a desired valve
coefficient using the gas mole fraction of the nitrogen, the water vapor and
the hydrogen in the anode exhaust gas,, and determining when to open and
close the bleed valve using the desired valve flow coefficient.” (See claim
10.)
The Examiner acknowledges that Iio does not disclose the above
recited control requirements (Ans. 8). The Examiner finds that Callahan
discloses controlled pulsed purging, and that purging should be based on the
composition of the anode gas flow (Ans. 8, citing Callahan, ¶ [0006]). The
Examiner further finds that “[t]he use of a controlled pulsed purge rate
would inherently require the use of a valve flow coefficient” (Ans. 8-9).
As a first matter, we agree with Appellant that Callahan does not
teach “calculating the gas mole fraction of the nitrogen, the water vapor and
the hydrogen in the anode exhaust gas using the partial pressure of the
nitrogen, the water vapor and the hydrogen” as required by claim 10.
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Application 11/457,880

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Callahan explains that, in the prior art, the rate of purging, i.e. the rate of
opening and closing the purge valve or its duty cycle, was typically
determined during initial testing of fuel cell models on the basis of the
density of current being produced (Callahan, ¶ [0003]). Callahan instead
provides a purge control responsive to actual conditions in the anode fuel
flow (Callahan, ¶ [0006]). According to Callahan, the purge is “responsive
to actual gas composition of the anode gas flow.” (Id.) Control over the
purge valve may be determined as a function of the pressure rise across
recycle pump 20 (Callahan, ¶ [0020-21]). This measured pressure rise is
related to the hydrogen flow (Callahan, ¶ [0008]). Callahan states:
In accordance with one aspect of the invention, a
function of fuel recycle blower speed(s) and recycle gas
temperature (T) or load current (I), provides a calculated,
estimated pressure rise, which is compared with the actual
measured pressure across the recycle blower, the error thereof
being used to alter or trim the load current signal used to
control the fuel purge valve.
(Callahan, ¶ [0008].)
According to Callahan, a pressure rise that is greater than the
estimated pressure rise indicates that there are more inerts (nitrogen) in the
fuel recycle stream than there should be (Callahan, ¶ [0021]). An actual
pressure rise that is less than the estimated pressure rise means there is more
hydrogen in the fuel recycle than is normal (Callahan, ¶ [0021]).
Callahan determines pressure differentials, but Callahan does not
calculate the gas mole fractions or use those gas mole fractions to determine
a desired valve coefficient.
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Application 11/457,880

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With regard to the Examiner’s finding that “[t]he use of a controlled
pulsed purge rate would inherently require the use of a valve flow
coefficient, whereby the rate of flow through the purge valve is controlled by
opening and closing the valve” (Ans. 8-9), we do not agree that this finding
provides an adequate basis to support the rejection. Even if the use of a
valve flow coefficient were itself inherent, the Examiner does not provide
reasonable evidence tending to show that using the gas mole fractions to
determine the desired valve coefficient would have been inherent or
suggested by the prior art.
The additional evidence used to reject claims 11-13 does not cure the
deficiencies discussed above. We do not sustain either of the obviousness
rejections.
CONCLUSION
We do not sustain the Examiner’s rejections.
DECISION
The Examiner’s decision is reversed.

REVERSED
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