DETAILED ACTION
Notice of Pre-AIA or AIA Status
The present application, filed on or after March 16, 2013, is being examined under the first inventor to file provisions of the AIA .
Claim Rejections - 35 USC § 103
The following is a quotation of 35 U.S.C. 103 which forms the basis for all obviousness rejections set forth in this Office action:
A patent for a claimed invention may not be obtained, notwithstanding that the claimed invention is not identically disclosed as set forth in section 102, if the differences between the claimed invention and the prior art are such that the claimed invention as a whole would have been obvious before the effective filing date of the claimed invention to a person having ordinary skill in the art to which the claimed invention pertains. Patentability shall not be negated by the manner in which the invention was made.
The factual inquiries for establishing a background for determining obviousness under 35 U.S.C. 103 are summarized as follows:
1. Determining the scope and contents of the prior art.
2. Ascertaining the differences between the prior art and the claims at issue.
3. Resolving the level of ordinary skill in the pertinent art.
4. Considering objective evidence present in the application indicating obviousness or nonobviousness.
Claims 1 – 3, 10 are rejected under 35 U.S.C. 103 as being unpatentable over Baur, et. al. (WO 2013045041 A2), et. al., in view of Fiebig, et.al. (US2006199061A1).
Regarding Claim 1, Baur teaches a method for drying a fuel cell ([p.1]) for generating electrical energy for a consumer, in which an anode gas having a first reactant (“[p.5] During regular operation, the fuel cell 3 generates the electrical power in a manner known per se by supplying air to a cathode space 10 of the fuel cell 3 via an air feed device 11. At the same time, hydrogen is supplied from a compressed gas storage 13 to an anode space 12 of the fuel cell 3 via a valve device 14” ; in this case, the anode gas having a first reactant is gas comprising hydrogen, which here is the “first reactant”) is supplied to an anode (anode space 12), and a cathode gas having a second reactant (“[p.5.] supplying air to a cathode space 10 of the fuel cell 3 via an air feed device 11”; here, the cathode gas air, and the second reactant is oxygen) is supplied to a cathode (cathode space 10), and the reactants are converted to electricity (“[p.5.] the fuel cell 3 generates the electrical power in a manner known per se by supplying air to a cathode space 10 of the fuel cell 3 via an air feed device 11. At the same time, hydrogen is supplied from a compressed gas storage 13 to an anode space 12 of the fuel cell 3 via a valve device 14. In this case, more hydrogen is typically supplied to the anode space 12 than can be converted therein in order to be able to utilize the available active area ideally”) by means of an electrochemical reaction (see [p.5.]), the method having the following steps
flushing the cathode with the cathode gas (“[p.6.] Alternatively or additionally, it would also be possible, for example, to flush out the gas from the cathode chamber 10 by a brief operation of the air conveying device 11. This is particularly useful when water vapor is additionally formed during electrolysis due to the heat generated and there is the risk that this water vapor condenses out again and precipitates in the region of the cathode chamber.”)
However, Baur is silent as to “ b) operating the fuel cell the fuel cell with an amount of cathode gas that the second reactant is substantially consumed along the flow path by the electrochemical reaction for conversion to electricity, wherein an electric current density of the fuel cell is less than 20% of a maximum achievable electric current density of the fuel cell.”
Fiebig teaches an electrochemical cell, namely a fuel cell, and teaches “[0010] During operation of an electrochemical cell supplied with gaseous reactants, e.g., hydrogen gas as the fuel at the anode and oxygen gas (or air) as the oxidant at the cathode, organic polymer proton exchange membranes can become sufficiently dehydrated either at the anode electrocatalyst/membrane interface, the cathode electrocatalyst/membrane interface, or throughout the bulk thickness of the membrane . . . almost uniformly over the electrochemically active plane of the membrane or in localized regions of the active plane . . . this drying effect is relatively proportional to the current density experienced by the fuel cell or electrochemical gas concentrator during operation of such devices . . . [0011] A second mechanism of drying a proton exchange membrane solid polymer electrolyte in an electrochemical cell is associated with the characteristics of the anode reactant gas and cathode reactant gas (if any) introduced into the cell . . . The dehydrating effects as a result of this mechanism will be more pronounced the greater the flow rate of the dry, or partially humidified, reactant gases supplied to the electrochemical cell. Furthermore, membrane drying effects arising from this mechanism will tend to be non-uniform in the plane of the membrane and will be more pronounced at the points of introduction of the reactant gas(es) into the electrochemical cell. Therefore, the extent of drying of a proton exchange membrane in an electrochemical cell depends upon various factors, including the physical design, or structure, of the cell and the operating conditions in which the cell is used.” Fiebig at [0010 – 11]. In simplified terms, Fiebig indicates that a) current density of the fuel cell is known in the art to be “relatively proportional” to drying of the cell, and that b) the greater the flow rate of dry, dehydrated cathode gas, the greater the drying effect. In other words, this indicates that the current density and cathode gas flow rate (and thereby amount) are result effective variables which may be modified to change drying performance. Further, Fiebig teaches that in some cases excessive drying may be undesirable; this indicates that the parameters of current density and cathode gas flow rate bear upon the overall operation of the cell, providing a motivation to optimize these variables to improve operation.
One of ordinary skill in the art before the effective filing date of the claimed invention would find it obvious to modify the method of modified Braun, such that it comprises “ b) operating the fuel cell the fuel cell with an amount of cathode gas that the second reactant is substantially consumed along the flow path by the electrochemical reaction for conversion to electricity, wherein an electric current density of the fuel cell is less than 20% of a maximum achievable electric current density of the fuel cell” because Fiebig teaches the current density and cathode gas flow rate (and thereby amount/concentration) are result effective variables which may be modified to change drying performance.
Claim 1 is obvious over Braun, in view of Fiebig.
Regarding Claim 2, Claim 2 relies upon Claim 1. Claim 1 is obvious over modified Braun.
Braun teaches “Temperature sensor 18 is provided, by means of which the temperature is continuously measured and transmitted to a control unit 19. The control device 19 can correspondingly monitor the continuously measured temperature. If, when the fuel cell system 1 is at a standstill, a temperature drop below a predefined value [occurs] . . . then the control device 19 . . . carry out a drying of the fuel cell system [as modified, this corresponds to operation (b)” and subsequently “In order to produce the most homogeneous possible concentration of hydrogen and to distribute the mixture of residual gases and hydrogen remaining in the recirculation line 15 as uniformly as possible. In addition, water located in the region of the recirculation line 15 would be conveyed to the region of the anode space 12 on this occasion and could likewise be converted there by electrolysis, so that not only the fuel cell 3 itself, but also the anode recirculation can be dried. Alternatively, it would also be possible to flush the anode recirculation and the drain valve 17 with the anode recirculation [as modified, this corresponds to operation (a)]. ” Braun at [p.6]. This as modified meets the limitation of “alternately” performing the flushing and operating steps. The method for drying a fuel cell (10) according to claim 1, in that steps a) and b) are performed at least repeatedly or alternately.
Claim 2 is obvious over Braun, in view of Fiebig.
Regarding Claim 3, Claim 3 relies upon Claim 1. Claim 1 is obvious over modified Braun.
Braun teaches that its use of the temperature sensor and electrolysis-based drying is “[p.6.] In order to produce the most homogeneous possible concentration of hydrogen and to distribute the mixture of residual gases and hydrogen remaining in the recirculation line 15 as uniformly as possible” as previously noted within [p.6.]. As previously optimized in view of Fiebig, modified Braun performs step (b) of claim 1. Taken together, the process of producing the “most homogenous” and “uniform” distribution of residual gas reads upon “step b) is performed until an inhomogeneity state of a humidity distribution in the cathode (100) is compensated for.”
Claim 3 is obvious over Braun, in view of Fiebig.
Regarding Claim 10, Claim 10 relies upon Claim 1. Claim 1 is obvious over modified Braun.
Braun teaches a fuel cell system (fuel cell system 1) comprising at least one fuel cell (fuel cell 3) and a control unit (control device 19), wherein the control unit is designed to perform a method for drying a fuel cell (“[p.6.] the control device 19 will wake up the fuel cell system 1" and carry out a drying of the fuel cell system 1.”). Braun at [p.6].
Claim 10 is obvious over Braun, in view of Fiebig.
Claims 4 – 6 are rejected under 35 U.S.C. 103 as being unpatentable over Baur, in view of Fiebig, as applied to claim 1, and further in view of Kawahara, et. al. (JP 3555178 B2).
Regarding Claim 4, Claim 4 relies upon Claim 1. Claim 1 is obvious over modified Braun.
Modified Braun teaches detecting a temperature value, and performing a drying step in order to distribute the mixture of residual gases and hydrogen remaining as “uniformly as possible,” but does not teach a predetermined inhomogeneity limit value.
Kawahara teaches a fuel cell, having a humidity sensor 300, wherein, “Therefore, in the second embodiment, the electrolyte membrane 10 suddenly became dry for some reason, and the partial pressure of water vapor at the outlet side of the fuel gas channel groove 40 detected by the humidity sensor 300 dropped below the predetermined value P1. In this case, the humidity in the fuel gas flowing through the fuel gas flow channel groove 40 and the humidity in the oxidizing gas flowing through the oxidizing gas flow channel 50 can be increased, and as a result, the electrolyte membrane 10 can be reliably returned to the wet state. Thus, battery performance can be improved.” Kawahara at [p.4]. This teaches “ c) detection (3) of a dry state in which a humidity distribution in the cathode (100) has reached a predetermined inhomogeneity limit value
and/or of a homogeneity state in which a humidity distribution in the cathode
(100) has reached a predetermined homogeneity limit value, d) detection (5) of a target state in which the humidity distribution in the cathode (100) has reached a predetermined homogeneity limit value, and a humidity in the cathode (100) has reached a predetermined humidity limit value or e) monitoring (1) of the humidity in the cathode (100).
,” insofar as the predetermined value P1 is a “limit value.” Regarding homogeneity, as previously noted, Braun teaches homogeneity is preferable and that the amount of humidity is analogous to “homogeneity” within this context. Kawahara teaches a benefit to improved operation utilizing this method step.
One of ordinary skill in the art before the effective filing date of the claimed invention would find it obvious to further modify the method of modified Braun, such that it comprises the humidity sensor and adjustment of Kawahara, because Kawahara teaches a benefit to operation.
Claim 4 is obvious over Braun, in view of Fiebig, further in view of Kawahara.
Regarding Claim 5, Claim 5 relies upon Claim 1. Claim 1 is obvious over modified Braun.
Kawahara teaches a fuel cell, having a humidity sensor 300, wherein, “According to the third aspect of the present invention, when the partial pressure of water vapor at the outlet of the fuel gas passage detected by the detecting means falls below a predetermined value, the control means controls the cooling water passage . . .” Kawahara at [p.2]. This implicitly teaches the third scenario of teaches “at least one of the following steps is performed:
. . . if a target state is detected, the method is at least continued or
started at step e),” because drying only occurs below a specific target state.
Claim 5 is obvious over Braun, in view of Fiebig, further in view of Kawahara.
Regarding Claim 6, Claim 6 relies upon Claim 1. Claim 1 is obvious over modified Braun.
Kawahara teaches a fuel cell, having a humidity sensor 300, wherein, “Therefore, in the second embodiment, the electrolyte membrane 10 suddenly became dry for some reason, and the partial pressure of water vapor at the outlet side of the fuel gas channel groove 40 detected by the humidity sensor 300 dropped below the predetermined value P1. This is “at least a dry state, a homogeneity state or a target state of the cathode is determined by one of the following methods: measuring an output humidity at least at an exhaust air, an output of the cathode or at an output of an anode.”
Claim 6 is obvious over Braun, in view of Fiebig, further in view of Kawahara.
Claim 7 is rejected under 35 U.S.C. 103 as being unpatentable over Baur, in view of Fiebig, as applied to claim 1, and further in view of Yamashita, et. al. (US2008063917A1).
Regarding Claim 7, Claim 7 relies upon Claim 1. Claim 1 is obvious over modified Braun.
Regarding the terms “a dry state is dependent on a standardized water loading for a membrane of the fuel cell, wherein the dry state is in particular reached when the standardized water loading is less than a critical water loading parameter, wherein the critical water loading parameter is in particular 6, 4, or 2.5,” the “water loading,” is a numerical value, taken together with the later phrase “parameter.” Further, the critical water loading parameter is not given a special definition within the present specification at page 9, and is treated as unitless. For this reason, the analysis below treats this term as effectively arbitrary, although as will be discussed, the “dry” state of the membrane of Yamashita is from 10% of the maximum water content.
Yamashita teaches a fuel cell having an electrolyte membrane, and describes of the water content, “[0059] an electrolyte membrane with a maximum water content within the range of from 10% to 120% (preferably ranges from 20% to 45% and from 70% to 110%) is used. If the maximum water content is less than 10%, it is impossible to retain a sufficient amount of water in use as an electrolyte membrane, resulting in a defect of showing no ion conductivity.” Yamashita at [0059]. Yamashita notes “The "maximum water content" referred to herein means the amount of water which an electrolyte membrane can retain during the preparation of an electrolyte membrane-electrode assembly based on the weight of the electrolyte membrane.” Id. at [006]. In other words, 10% - 45%of the maximum water content of the electrolyte membrane is known as a standardized water loading for a membrane of a fuel cell, wherein the dry state is in particular reached when the standardized water loading is less than a critical water loading parameter. Id. Further, because 6, 4, or 2.5 are unitless values, they would be expected by one of ordinary skill in the art to be fairly close to, for example, 10% of the maximum water content.
One of ordinary skill in the art before the effective filing date of the claimed invention would find it obvious to further modify the method of Braun, such that it comprises a dry state is dependent on a standardized water loading for a membrane of the fuel cell, wherein the dry state is in particular reached when the standardized water loading is less than a critical water loading parameter, wherein the critical water loading parameter is 10%, because a prima facie case of obviousness exists where the claimed ranges or amounts do not overlap with the prior art but are merely close, wherein one of ordinary skill in the art before the effective filing date of the claimed invention would expect them to have the same properties. MPEP 2144.05(I).
Claim 7 is obvious over Braun, in view of Fiebig, further in view of Yamashita.
Claim 8 is rejected under 35 U.S.C. 103 as being unpatentable over Baur, in view of Fiebig, as applied to claim 1, and further in view of Preston, et. al. (US 20130035898 A1).
Regarding Claim 8, Claim 8 relies upon Claim 1. Claim 1 is obvious over modified Braun.
Braun is silent as to impedance.
Preston teaches “[0011] A technique for determining membrane humidification is known in the art as high frequency resistance (HFR) humidification measuring. HFR humidification measurements are generated by providing a high frequency component or signal on the electrical load of the stack so that a high frequency ripple is produced on the current output of the stack. The resistance of the high frequency component is then measured by a detector, which is a function of the level of humidification of the membranes in the stack. High frequency resistance is a well-known property of fuel cells, and is closely related to the ohmic resistance, or membrane protonic resistance, of the fuel cell membrane. Ohmic resistance is itself a function of the degree of fuel cell membrane humidification. Therefore, by measuring the HFR of the fuel cell membranes of a fuel cell stack within a specific band of excitation current frequencies, the degree of humidification of the fuel cell membrane may be determined. This HFR measurement allows for an independent measurement of the fuel cell membrane humidification, which may eliminate the need for RH sensors.” Preston at [0011]. Further, this provides the benefit of determining whether the water vapor transfer unit is operating properly or if the system is leaking. Id. at [0002]. This reads upon “when measuring an electrochemical impedance spectrum of the resistance of the fuel cell, in particular the resistance of a membrane of the fuel cell, a high-frequency resistance is determined, wherein the high- frequency resistance is the resistance above a cut-off (“[0022] The processor 44 receives an RH measurement signal from the RH sensor 42 and an HFR-based relative humidity signal from the circuit 40 that gives a representation of the humidity level of the membranes in the fuel cell stack 12 . The two values are compared in the processor 44 , and if the difference is greater than a predetermined allowable calibration value, then a potential WVT unit failure may be occurring, which can be provided to a warning device 46 , such as a light.”)
One of ordinary skill in the art before the effective filing date of the claimed invention would find it obvious to further modify the method of Braun, such that when measuring an electrochemical impedance spectrum of the resistance of the fuel cell, in particular the resistance of a membrane of the fuel cell, a high-frequency resistance is determined, wherein the high- frequency resistance is the resistance above a cut-off as in Preston, because Preston teaches a benefit to independently determining humidity and protecting against a potential failure of other sensors.
Claim 8 is obvious over Braun, in view of Fiebig, and further in view of Preston.
Conclusion
Any inquiry concerning this communication or earlier communications from the examiner should be directed to KRISHNA RAJAN HAMMOND whose telephone number is (571)272-9997. The examiner can normally be reached 9:00 - 6:30 PM M-F.
Examiner interviews are available via telephone, in-person, and video conferencing using a USPTO supplied web-based collaboration tool. To schedule an interview, applicant is encouraged to use the USPTO Automated Interview Request (AIR) at http://www.uspto.gov/interviewpractice.
If attempts to reach the examiner by telephone are unsuccessful, the examiner’s supervisor, Nicole Buie-Hatcher can be reached at (571) 270-3879. The fax phone number for the organization where this application or proceeding is assigned is 571-273-8300.
Information regarding the status of published or unpublished applications may be obtained from Patent Center. Unpublished application information in Patent Center is available to registered users. To file and manage patent submissions in Patent Center, visit: https://patentcenter.uspto.gov. Visit https://www.uspto.gov/patents/apply/patent-center for more information about Patent Center and https://www.uspto.gov/patents/docx for information about filing in DOCX format. For additional questions, contact the Electronic Business Center (EBC) at 866-217-9197 (toll-free). If you would like assistance from a USPTO Customer Service Representative, call 800-786-9199 (IN USA OR CANADA) or 571-272-1000.
/K.R.H./Examiner , Art Unit 1725
/NICOLE M. BUIE-HATCHER/Supervisory Patent Examiner, Art Unit 1725
Prosecution Insights