Prosecution Insights
Last updated: April 19, 2026
Application No. 18/992,746

PRECHAMBER-TYPE ENGINE

Non-Final OA §102§103§112
Filed
Jan 09, 2025
Examiner
LATHERS, KEVIN ANTHONY
Art Unit
3747
Tech Center
3700 — Mechanical Engineering & Manufacturing
Assignee
Mitsubishi Heavy Industries Engine & Turbocharger Ltd.
OA Round
1 (Non-Final)
80%
Grant Probability
Favorable
1-2
OA Rounds
2y 3m
To Grant
96%
With Interview

Examiner Intelligence

Grants 80% — above average
80%
Career Allow Rate
658 granted / 825 resolved
+9.8% vs TC avg
Strong +16% interview lift
Without
With
+16.1%
Interview Lift
resolved cases with interview
Typical timeline
2y 3m
Avg Prosecution
17 currently pending
Career history
842
Total Applications
across all art units

Statute-Specific Performance

§101
1.6%
-38.4% vs TC avg
§103
41.2%
+1.2% vs TC avg
§102
27.2%
-12.8% vs TC avg
§112
23.2%
-16.8% vs TC avg
Black line = Tech Center average estimate • Based on career data from 825 resolved cases

Office Action

§102 §103 §112
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 § 112 The following is a quotation of 35 U.S.C. 112(b): (b) CONCLUSION.—The specification shall conclude with one or more claims particularly pointing out and distinctly claiming the subject matter which the inventor or a joint inventor regards as the invention. The following is a quotation of 35 U.S.C. 112 (pre-AIA ), second paragraph: The specification shall conclude with one or more claims particularly pointing out and distinctly claiming the subject matter which the applicant regards as his invention. Claim 6 is rejected under 35 U.S.C. 112(b) or 35 U.S.C. 112 (pre-AIA ), second paragraph, as being indefinite for failing to particularly point out and distinctly claim the subject matter which the inventor or a joint inventor (or for applications subject to pre-AIA 35 U.S.C. 112, the applicant), regards as the invention. The claim recites “the fourth end” wherein no “third” end is ever recited. This creates uncertainty about how many “ends” there are and is therefore indefinite. Claim Rejections - 35 USC § 102 In the event the determination of the status of the application as subject to AIA 35 U.S.C. 102 and 103 (or as subject to pre-AIA 35 U.S.C. 102 and 103) is incorrect, any correction of the statutory basis (i.e., changing from AIA to pre-AIA ) for the rejection will not be considered a new ground of rejection if the prior art relied upon, and the rationale supporting the rejection, would be the same under either status. The following is a quotation of the appropriate paragraphs of 35 U.S.C. 102 that form the basis for the rejections under this section made in this Office action: A person shall be entitled to a patent unless – (a)(1) the claimed invention was patented, described in a printed publication, or in public use, on sale, or otherwise available to the public before the effective filing date of the claimed invention. Claim(s) 1 and 4-7 is/are rejected under 35 U.S.C. 102(a)(1) as being anticipated by Regueiro (US 6,065,441). Regarding claim 1, Regueiro discloses a prechamber-type engine (Abstract) comprising: a cylinder 14 and a cylinder head 10 (Fig.1, shown); and a piston 16 that defines a main combustion chamber between the cylinder and the cylinder head (Fig. 1, shown), wherein a pre-combustion chamber 46 that communicates with the main combustion chamber through a nozzle hole 52 is defined inside the cylinder head (Fig.1, shown), the nozzle hole extends from a prechamber-side opening toward a main chamber-side opening such that a distance between a center line of the nozzle hole and a central axis line of the cylinder is reduced (Fig. 1, the nozzle hole 52 is an angled one which moves toward the central axis), a top surface of the piston has a concave piston cavity 34 (Fig. 1, the piston includes a concave cavity 34), and in a cross-sectional view in which the central axis line of the cylinder and a center of the main chamber-side opening are present, a first end on a side far from the central axis line of the cylinder in a peripheral edge of the main chamber-side opening is located farther from the central axis line of the cylinder than a second end on a side close to the nozzle hole in a peripheral edge of the piston cavity (Fig. 1, shown passage 52 includes its peripheral edge opening into the main-chamber at a point further than the edge of the piston cavity). Regarding claim 4, Regueiro disclose the prechamber-type engine according to claim 1, wherein in the cross-sectional view, the piston cavity has an R portion that passes through the second end (Fig. 1, the cavity 34 goes from the 2nd end to an opposite end). Regarding claim 5, Regueiro disclose the prechamber-type engine according to claim 4, wherein the R portion has a deepest portion having a largest distance from the top surface of the piston to the piston cavity (Fig. 1, the deepest portion of the cavity is indicated at 40 and is further from the cylinder head). Regarding claim 6, Regueiro disclose the prechamber-type engine according to claim 5, wherein in the cross-sectional view, the piston cavity has an inclined portion that extends from the deepest portion toward a fourth end on a side far from the nozzle hole in the peripheral edge of the piston cavity such that a distance from the top surface of the piston is reduced (Fig. 1, the cavity 34 has a deeper portion 34 which then inclines upward to the portion indicated near 34 which is flat and extends to a fourth end). Regarding claim 7, Regueiro disclose the prechamber-type engine according to claim 5, wherein in the cross-sectional view, the piston cavity has a flat portion in which a distance from the top surface of the piston is constant (Fig. 1, the portion which extends away from the deepest portion 40 slants upward and then is a flat portion with a constant distance from the cylinder head). Claim Rejections - 35 USC § 103 In the event the determination of the status of the application as subject to AIA 35 U.S.C. 102 and 103 (or as subject to pre-AIA 35 U.S.C. 102 and 103) is incorrect, any correction of the statutory basis (i.e., changing from AIA to pre-AIA ) for the rejection will not be considered a new ground of rejection if the prior art relied upon, and the rationale supporting the rejection, would be the same under either status. 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. Claim(s) 1-2 is/are rejected under 35 U.S.C. 103 as being unpatentable over Regueiro. Regarding claim 2, Regueiro disclose the prechamber-type engine according to claim 1, but fails to specify wherein in the cross-sectional view, in a case where a width of the main chamber-side opening is denoted by D, and a distance between the first end and the second end in a direction orthogonal to the central axis line of the cylinder is denoted by L, L/D >0.1 is satisfied; and further wherein in the cross-sectional view, a first tangent line that is a tangent line of a far-side wall surface of the wall surfaces of the nozzle hole on a side away from the central axis line of the cylinder and that passes through the first end passes through the second end of the piston cavity at a predetermined angle of a crank angle of the prechamber-type engine in a range of 5 to 20 degrees after a top dead center. However, it would have been obvious to one having ordinary skill in the art at the time the invention was made to include such shapes/angles/ranges within the device of Regueiro since it has been held that where the general conditions of a claim are disclosed in the prior art, discovering the optimum or workable ranges involves only routine skill in the art. In re Aller, 105 USPQ 233. In this case, Regeurio discloses the slanted passage and piston constructions that are nearly identical, as shown in Fig. 1 and disclosed, to that of the instant inventions’ disclosure but simply fails to specify these exact numbers or ranges. As such, one of ordinary skill in the art could and would arrive at the best ranges and exact angles through routine experimentation. Conclusion The prior art made of record and not relied upon is considered pertinent to applicant's disclosure. Omura et al (JP H0893475 A) discloses a precombustion chamber type engine that discloses all limitations of claim 1 (Fig. 5, shown). Regueiro (US 5,417,189) discloses a precombustion chamber engine (Fig. 1, shown). Any inquiry concerning this communication or earlier communications from the examiner should be directed to KEVIN A LATHERS whose telephone number is (571)272-1050. The examiner can normally be reached M-F 10a-6p. 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, Lindsay Low can be reached at 5712721196. 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. /KEVIN A LATHERS/Primary Examiner, Art Unit 3747
Read full office action

Prosecution Timeline

Jan 09, 2025
Application Filed
Jan 05, 2026
Non-Final Rejection — §102, §103, §112 (current)

Precedent Cases

Applications granted by this same examiner with similar technology

Patent 12595772
APPARATUS AND METHOD FOR REGULATING GASEOUS FUEL PRESSURE AND MITIGATING EMISSIONS IN AN INTERNAL COMBUSTION ENGINE SYSTEM
2y 5m to grant Granted Apr 07, 2026
Patent 12595754
SLIDING MEMBER AND INTERNAL COMBUSTION ENGINE
2y 5m to grant Granted Apr 07, 2026
Patent 12595753
ROCKER ARM ASSEMBLY
2y 5m to grant Granted Apr 07, 2026
Patent 12590563
VEHICLE
2y 5m to grant Granted Mar 31, 2026
Patent 12584449
CONTROLLER FOR INTERNAL COMBUSTION ENGINE
2y 5m to grant Granted Mar 24, 2026
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
80%
Grant Probability
96%
With Interview (+16.1%)
2y 3m
Median Time to Grant
Low
PTA Risk
Based on 825 resolved cases by this examiner. Grant probability derived from career allow rate.

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