Prosecution Insights
Last updated: April 19, 2026
Application No. 18/571,870

PREMIXED GAS HEATING SYSTEM FOR H2

Non-Final OA §103
Filed
Dec 19, 2023
Examiner
SHIRSAT, VIVEK K
Art Unit
3762
Tech Center
3700 — Mechanical Engineering & Manufacturing
Assignee
Ferroli S P A
OA Round
1 (Non-Final)
74%
Grant Probability
Favorable
1-2
OA Rounds
3y 0m
To Grant
99%
With Interview

Examiner Intelligence

Grants 74% — above average
74%
Career Allow Rate
781 granted / 1061 resolved
+3.6% vs TC avg
Strong +28% interview lift
Without
With
+28.5%
Interview Lift
resolved cases with interview
Typical timeline
3y 0m
Avg Prosecution
60 currently pending
Career history
1121
Total Applications
across all art units

Statute-Specific Performance

§101
0.4%
-39.6% vs TC avg
§103
45.7%
+5.7% vs TC avg
§102
25.2%
-14.8% vs TC avg
§112
23.3%
-16.7% vs TC avg
Black line = Tech Center average estimate • Based on career data from 1061 resolved cases

Office Action

§103
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 . Claim(s) 1 9, 24-26, and 29 is/are rejected under 35 U.S.C. 103 as being unpatentable over Smelcer (US 2010/0095905 A1) in view of Drift (WO 95/23315) . With respect to claim 1 9 Smelcer discloses a premixed gas heating system, comprising: a fan assembly [reference character s 52 and 54] configured to supply a premixed air-gas flow required for combustion [see Fig. 1]; a burner [reference character 42] including a plurality of holes [reference character 101 in Fig. 4, which is described as a “burner screen”, see paragraph 0055] , wherein the plurality of holes provides a free passage area defined as an area that allows the outflow of the premixed air-gas flow from a feeding chamber [reference character 82-84] upstream the burner to a combustion chamber [reference character 32] where combustion flames are generated; and a load controller [reference character 76] , configured to regulate an output load of the burner such that the heating system modulates between a minimum load and a maximum load, wherein a ratio between the maximum load and the minimum load is at least 4 [see paragraph 0047 where the turndown ratio is 25:1]. Smelcer does not disclose that a combustible gas of the premix air-gas flow contains at least 20% by volume of hydrogen , the minimum load of the heating system is set such that a combustion index ranges between 4 E06 and 6 E07, the combustion index being defined as the ratio of the minimum load over the free passage area of the burner. Drift discloses a burner system [see Fig. 14] having a burner plate [reference character 30 in Fig. 15] having holes [reference character 31]. Drift further discloses that increasing the percentage of hydrogen gas in the fuel mixture reduces the amount of CO in the exhaust [see Fig. 10], where the burner operates on 100% hydrogen gas [see Table 2] . Additionally, Drift discloses an exemplary burner plate [see Example 2 on pp. 14] that is 64mm x 46mm in area ( 0.002944m 2 or 2.9E-03m 2 ) [see pp. 13] and operates between 500-1500kW/m 2 [see “Q” in Table 2]. The plate has 39 holes of 1mm diameter which is a total area of 0.000030615m 2 (3.0E-05m 2 ) ; therefore, the combustion index is between 4.8E07 and 1.4E08 , which overlaps with the requirements of the claim . Drift discloses that this configuration provides for improved ignition without an increase in NOx formation [see pp. 14]. It would have been obvious to one of ordinary skill in the art at the time o f the filing date of the invention to modify the system taught by Smelcer by burning a fuel with a hydrogen concentration of 95%, as taught by Drift, in order to minimize CO formation [see Fig. 10 of Drift] and provide a combustion index of between 4.8E07 and 1.4E08 because this configuration provides for improved ignition without an increase in NOx formation [see pp. 14 of Drift]. With respect to claim 24 Smelcer discloses that the ratio between the minimum load and the maximum load is at least 8 [see paragraph 0047 where the turndown ratio is 25:1]. With respect to claim 25 the combination of Smelcer and Drift disclose that the combustible gas of the premix air-gas flow supplied to the burner contains at least 60% by volume of hydrogen [Drift discloses 100% hydrogen] . With respect to claim 26 the combination of Smelcer and Drift disclose that the combustible gas of the premix air-gas flow supplied to the burner contains at least 10 0% by volume of hydrogen [Drift discloses 100% hydrogen] . With respect to claim 29 Smelcer discloses that the burner has a cylindrical shape, or has a convex profile [see Fig. 4] . Claim(s) 34 is/are rejected under 35 U.S.C. 103 as being unpatentable over Smelcer (US 2010/0095905 A1) in view of Drift (WO 95/23315) . With respect to claim 34 Smelcer discloses a method for operating a premixed gas heating system capable of modulating between a minimum and a maximum load, wherein the ratio of the maximum load over the minimum load is at least 4 [see paragraph 0047 where the turndown ratio is 25:1] , the method comprising the following steps: providing a fan assembly [reference characters 52 and 54] configured to supply a premixed air-gas flow required for combustion; supplying a premix of combustible gas and air to the burner; providing a burner [reference character 42] including a plurality of holes [reference character 101 in Fig. 4, which is described as a “burner screen”, see paragraph 0055] , wherein the plurality of holes provides a free passage area defined as an area that allows the outflow of the premixed air-gas flow from an area upstream the burner to an area where combustion flames are generated; providing a load controller [reference character 76] , configured to regulate an output load of the heating system such that the heating system modulates between the minimum load and the maximum load . Smelcer does not discloses that the combustible gas of said premixed air-gas flow contains at least 20% by volume of hydrogen setting a value of minimum load such that a combustion index value is within the range between 4 E06 and 6 E07, the combustion index being defined as the ratio of the minimum load over the free passage area of the burner. Drift discloses a burner system [see Fig. 14] having a burner plate [reference character 30 in Fig. 15] having holes [reference character 31]. Drift further discloses that increasing the percentage of hydrogen gas in the fuel mixture reduces the amount of CO in the exhaust [see Fig. 10], where the burner operates on 100% hydrogen gas [see Table 2]. Additionally, Drift discloses an exemplary burner plate [see Example 2 on pp. 14] that is 64mm x 46mm in area (0.002944m 2 or 2.9E-03m 2 ) [see pp. 13] and operates between 500-1500kW/m 2 [see “Q” in Table 2]. The plate has 39 holes of 1mm diameter which is a total area of 0.000030615m 2 (3.0E-05m 2 ); therefore, the combustion index is between 4.8E07 and 1.4E08, which overlaps with the requirements of the claim. Drift discloses that this configuration provides for improved ignition without an increase in NOx formation [see pp. 14]. It would have been obvious to one of ordinary skill in the art at the time of the filing date of the invention to modify the method taught by Smelcer by burning a fuel with a hydrogen concentration of 95%, as taught by Drift, in order to minimize CO formation [see Fig. 10 of Drift] and provide a combustion index of between 4.8E07 and 1.4E08 because this configuration provides for improved ignition without an increase in NOx formation [see pp. 14 of Drift]. Claim(s) 38 is/are rejected under 35 U.S.C. 103 as being unpatentable over Smelcer (US 2010/0095905 A1) in view of Drift (WO 95/23315) . With respect to claim 38 Smelcer discloses a method for manufacturing a premixed gas heating system capable of modulating between a minimum and a maximum load, wherein the ratio of the maximum load over the minimum load is at least 4 [see paragraph 0047 where the turndown ratio is 25:1] , the method comprising the following steps: providing a fan assembly [reference characters 52 and 54] configured to supply a premixed air-gas flow required for combustion; providing a premix of combustible gas and air to the burner; providing a burner [reference character 42] including a plurality of holes [reference character 101 in Fig. 4, which is described as a “burner screen”, see paragraph 0055] , wherein the plurality of holes provides a free passage area defined as an area that allows the outflow of the premixed air-gas flow from an area upstream the burner to an area where combustion flames are generated; providing a load controller [reference character 76] , configured to regulate an output load of the heating system such that the heating system modulates between the minimum load and the maximum load wherein the minimum load is set to a predetermined reference value [80,000 BTU/ hr , see paragraph 0042] . Smelcer does not discloses that the combustible gas of said premixed air-gas flow contains at least 20% by volume of hydrogen setting a value of minimum load such that a combustion index value is within the range between 4 E06 and 6 E07, the combustion index being defined as the ratio of the minimum load over the free passage area of the burner. Drift discloses a burner system [see Fig. 14] having a burner plate [reference character 30 in Fig. 15] having holes [reference character 31]. Drift further discloses that increasing the percentage of hydrogen gas in the fuel mixture reduces the amount of CO in the exhaust [see Fig. 10], where the burner operates on 100% hydrogen gas [see Table 2]. Additionally, Drift discloses an exemplary burner plate [see Example 2 on pp. 14] that is 64mm x 46mm in area (0.002944m 2 or 2.9E-03m 2 ) [see pp. 13] and operates between 500-1500kW/m 2 [see “Q” in Table 2]. The plate has 39 holes of 1mm diameter which is a total area of 0.000030615m 2 (3.0E-05m 2 ); therefore, the combustion index is between 4.8E07 and 1.4E08, which overlaps with the requirements of the claim. Drift discloses that this configuration provides for improved ignition without an increase in NOx formation [see pp. 14]. It would have been obvious to one of ordinary skill in the art at the time of the filing date of the invention to modify the method taught by Smelcer by burning a fuel with a hydrogen concentration of 95%, as taught by Drift, in order to minimize CO formation [see Fig. 10 of Drift] and provide a combustion index of between 4.8E07 and 1.4E08 because this configuration provides for improved ignition without an increase in NOx formation [see pp. 14 of Drift]. Allowable Subject Matter Claims 20-23, 27-28, 30-33, and 35-37 are objected to as being dependent upon a rejected base claim, but would be allowable if rewritten in independent form including all of the limitations of the base claim and any intervening claims. Conclusion Any inquiry concerning this communication or earlier communications from the examiner should be directed to FILLIN "Examiner name" \* MERGEFORMAT VIVEK K SHIRSAT whose telephone number is FILLIN "Phone number" \* MERGEFORMAT (571)272-3722 . The examiner can normally be reached FILLIN "Work Schedule?" \* MERGEFORMAT M-F 9:00AM-5:20AM . 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, FILLIN "SPE Name?" \* MERGEFORMAT Steven B McAllister can be reached at FILLIN "SPE Phone?" \* MERGEFORMAT 571-272-6785 . 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. /VIVEK K SHIRSAT/ Primary Examiner, Art Unit 3762
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Prosecution Timeline

Dec 19, 2023
Application Filed
Feb 28, 2026
Non-Final Rejection — §103 (current)

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Study what changed to get past this examiner. Based on 5 most recent grants.

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Prosecution Projections

1-2
Expected OA Rounds
74%
Grant Probability
99%
With Interview (+28.5%)
3y 0m
Median Time to Grant
Low
PTA Risk
Based on 1061 resolved cases by this examiner. Grant probability derived from career allow rate.

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