Prosecution Insights
Last updated: April 19, 2026
Application No. 18/910,903

PISTON RING

Non-Final OA §103§112
Filed
Oct 09, 2024
Examiner
LEE, GILBERT Y
Art Unit
3675
Tech Center
3600 — Transportation & Electronic Commerce
Assignee
Hamilton Sundstrand Corporation
OA Round
2 (Non-Final)
79%
Grant Probability
Favorable
2-3
OA Rounds
2y 6m
To Grant
89%
With Interview

Examiner Intelligence

Grants 79% — above average
79%
Career Allow Rate
1081 granted / 1376 resolved
+26.6% vs TC avg
Moderate +10% lift
Without
With
+10.4%
Interview Lift
resolved cases with interview
Typical timeline
2y 6m
Avg Prosecution
44 currently pending
Career history
1420
Total Applications
across all art units

Statute-Specific Performance

§101
0.2%
-39.8% vs TC avg
§103
44.3%
+4.3% vs TC avg
§102
36.9%
-3.1% vs TC avg
§112
13.7%
-26.3% vs TC avg
Black line = Tech Center average estimate • Based on career data from 1376 resolved cases

Office Action

§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 . The amendment filed 10/15/25 has been entered. Response to Amendment Applicant has not properly canceled claims 4 and 20 as “No claim text shall be presented for any claim in the claim listing with the status of "canceled" or "not entered" as per MPEP 1.121 (c)(4)(i). Claim Rejections - 35 USC § 112 The following is a quotation of the first paragraph of 35 U.S.C. 112(a): (a) IN GENERAL.—The specification shall contain a written description of the invention, and of the manner and process of making and using it, in such full, clear, concise, and exact terms as to enable any person skilled in the art to which it pertains, or with which it is most nearly connected, to make and use the same, and shall set forth the best mode contemplated by the inventor or joint inventor of carrying out the invention. The following is a quotation of the first paragraph of pre-AIA 35 U.S.C. 112: The specification shall contain a written description of the invention, and of the manner and process of making and using it, in such full, clear, concise, and exact terms as to enable any person skilled in the art to which it pertains, or with which it is most nearly connected, to make and use the same, and shall set forth the best mode contemplated by the inventor of carrying out his invention. Claim 1-3, 5-18, 21, and 22 are rejected under 35 U.S.C. 112(a) or pre-AIA 35 U.S.C. 112, first paragraph, as based on a disclosure which is not enabling. The disclosure does not enable one of ordinary skill in the art to practice the invention without material of the lubricant and tool steel, which is/are critical or essential to the practice of the invention but not included in the claim(s). See In re Mayhew, 527 F.2d 1229, 188 USPQ 356 (CCPA 1976). Amended claims 1 and 12 recite “such that a friction coefficient between the ring and the inner surface of the respective bore is about 0.11 when hydrodynamically lubricated.” It is clear from the current disclosure that the claimed friction coefficient is achieved by the material of the piston ring, lubricant, and tool steel. Claims 2,3,5-11, 13-18, 21, and 22 are rejected for depending on a rejected claim. 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. Claim(s) 1-3 and 5-11 is/are rejected under 35 U.S.C. 103 as being unpatentable over Rabhi (KR20190117497) in view of Tejima (US Pub. No. 2003/0178781). Regarding claim 1, the Rabhi reference discloses a pump system (Fig. 1) for an aircraft, comprising: a cylinder barrel (35) configured to rotate within a pump housing of a pump, and a plurality of pistons (3) seated within a respective bore (4) defined in the cylinder barrel, wherein each piston further includes a piston ring (15) disposed at an end thereof configured to form a hydrodynamic seal with an inner surface of the respective bore (Figs. 2-10). However, the Rabhi reference fails to explicitly disclose each respective piston ring consisting of silicon nitride. The Tejima reference, a piston ring (Para. [0165]), discloses making a piston seal of silicon nitride (Para. [0165]). It would have been obvious to one of ordinary skill in the art at the time of filing to make the piston ring of silicon nitride in the Rabhi reference in view of the teachings of the Tejima reference in order to provide decrease a friction coefficient and improve durability (Tejima, Para. [0165]). The modified Rabhi reference discloses the claimed structure and is capable of having a friction coefficient between the ring and the inner surface of the bore is about 0.11 when hydrodynamically lubricated. Regarding claim 2, the Rabhi reference, as modified in claim 1, discloses the pump (Rabhi, the 2 paragraphs preceding the description of embodiments). Regarding claim 3, the Rabhi reference, as modified in claim 2, discloses the cylinder barrel comprises: a main cylindrical body (Rabhi, main body of 35); a center recess defined within the main cylindrical body configured to seat a drive shaft therein (Rabhi, Fig. 1); and a plurality of bores (Rabhi, 4) defined in the main cylindrical body configured to allow fluid flow therethrough, each respective bore extending in an axial direction (Fig. 1), wherein the plurality of bores are spaced apart circumferentially relative to one another about the main cylindrical body radially outward of the center recess (Rabhi, Fig. 1), wherein the respective bore is one of the plurality of bores (Rabhi, Fig. 1). Regarding claim 5, the Rabhi reference, as modified in claim 2, discloses the pump is or includes a piston pump (Rabhi, Fig. 1). Regarding claim 6, the Rabhi reference, as modified in claim 6, discloses the piston pump is or includes a bent axis variable displacement piston pump (Rabhi, Fig. 1). Regarding claims 7 and 8, the Rabhi reference discloses the invention substantially as claimed in claim 1. However, the modified Rabhi reference fails to explicitly disclose the claimed number of bores. It would have been obvious to one of ordinary skill in the art at the time of filing to change the number of bores, since it has been held that mere duplication of the essential working parts of a device involves only routine skill in the art and in order to provide optimal sealing pressure. St. Regis Paper Col. V. Bemis Co., 193 USPQ 8. Regarding claim 9, the Rabhi reference, as modified in claim 1, discloses the invention substantially as claimed. However, the modified Rabhi reference fails to explicitly disclose the piston ring includes a chamfer or radius on either the outer or inner periphery of a leading edge of the piston ring. The examiner takes official notice that it would have been obvious to one of ordinary skill in the art at the time of filing to provide a chamfer or radius to the leading edge of the piston ring of the modified Rabhi reference in order to longer life to the sealing ring and to allow for scraping. Regarding claim 10, the Rabhi reference, as modified in claim 1, discloses the piston ring includes a cut therethrough (e.g. definition of a piston ring) configured to allow for thermal expansion of the piston ring. Regarding claim 11, the Rabhi reference, as modified in claim 1, discloses the piston ring being self-polishing (e.g. since the modified ring of Rabhi is made of silicon nitride). Claim(s) 12-18, 21, and 22 is/are rejected under 35 U.S.C. 103 as being unpatentable over Rabhi in view of Tejima as applied to claims 1-11, 19, and 20 above, and further in view of Charles et al. (US Patent No. 4,684,446). Regarding claim 12, the Rabhi reference, as modified in claim 1, discloses the invention substantially as claimed in claim 12. However, the modified Rabhi reference fails to explicitly disclose each piston ring comprised of between seventy-five and ninety-five volume percent silicon nitride, with the silicon nitride comprised of between one and twenty percent in glassy phase. The Charles et al. (hereinafter Charles), a sealing ring, discloses a silicon nitride sealing ring comprised of between seventy-five and ninety-five volume percent silicon nitride (Col. 2, Lines 35-54) forming a glassy phase between one and twenty percent glassy phase (Col. 2, Lines 35-54). It would have been obvious to one of ordinary skill in the art at the time of filing to provide a glassy phase in the claimed range to the modified Rabhi reference in view of the teachings of the Charles reference in order to provide an optimized sliding ring. The modified Rabhi reference discloses the claimed structure and is capable of having a friction coefficient between the ring and the inner surface of the bore is about 0.11 when hydrodynamically lubricated. Regarding claim 13, the Rabhi reference, as modified in claim 12, discloses the pump (Rabhi, the 2 paragraphs preceding the description of embodiments). Regarding claim 14, the Rabhi reference, as modified in claim 13, discloses the cylinder barrel comprises: a main cylindrical body (Rabhi, main body of 35); a center recess defined within the main cylindrical body configured to seat a drive shaft therein (Rabhi, Fig. 1); and a plurality of bores (Rabhi, 4) defined in the main cylindrical body configured to allow fluid flow therethrough, each respective bore extending in an axial direction (Fig. 1), wherein the plurality of bores are spaced apart circumferentially relative to one another about the main cylindrical body radially outward of the center recess (Rabhi, Fig. 1), wherein the respective bore is one of the plurality of bores (Rabhi, Fig. 1). Regarding claims 15, the Rabhi reference discloses the invention substantially as claimed in claim 14. However, the modified Rabhi reference fails to explicitly disclose the claimed number of bores. It would have been obvious to one of ordinary skill in the art at the time of filing to change the number of bores, since it has been held that mere duplication of the essential working parts of a device involves only routine skill in the art and in order to provide optimal sealing pressure. St. Regis Paper Col. V. Bemis Co., 193 USPQ 8. Regarding claim 16, the Rabhi reference, as modified in claim 12, discloses the invention substantially as claimed. However, the modified Rabhi reference fails to explicitly disclose the piston ring includes a chamfer or radius on either the outer or inner periphery of a leading edge of the piston ring. The examiner takes official notice that it would have been obvious to one of ordinary skill in the art at the time of filing to provide a chamfer or radius to the leading edge of the piston ring of the modified Rabhi reference in order to longer life to the sealing ring and to allow for scraping. Regarding claim 17, the Rabhi reference, as modified in claim 12, discloses the piston ring includes a cut therethrough (e.g. definition of a piston ring) configured to allow for thermal expansion of the piston ring. Regarding claim 18, the Rabhi reference, as modified in claim 12, discloses the piston ring being self-polishing (e.g. since the modified ring of Rabhi is made of silicon nitride). Regarding claim 21, the Rabhi reference, as modified in claim 12, discloses the piston ring is comprised of at least ninety volume percent silicon nitride (Charles, Col. 2, Lines 35-54). Regarding claim 22, the Rabhi reference, as modified in claim 12, discloses the piston ring is comprised of less than ten percent silicon nitride in glassy phase (Charles, Col. 2, Lines 35-54). Response to Arguments Applicant’s arguments with respect to claim(s) 1-3, 5-18, 21, and 22 have been considered but are moot because the new ground of rejection does not rely on any reference applied in the prior rejection of record for any teaching or matter specifically challenged in the argument. Conclusion Any inquiry concerning this communication or earlier communications from the examiner should be directed to GILBERT Y LEE whose telephone number is (571)272-5894. The examiner can normally be reached Monday-Friday 8am-430pm. 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, Christine Mills can be reached at (571)272-8322. 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. /GILBERT Y LEE/Primary Examiner, Art Unit 3675
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Prosecution Timeline

Oct 09, 2024
Application Filed
Jul 12, 2025
Non-Final Rejection — §103, §112
Oct 15, 2025
Response Filed
Jan 23, 2026
Non-Final Rejection — §103, §112
Mar 04, 2026
Interview Requested
Mar 19, 2026
Examiner Interview Summary
Mar 19, 2026
Applicant Interview (Telephonic)

Precedent Cases

Applications granted by this same examiner with similar technology

Patent 12595747
METHOD OF MITIGATING VIBRATIONS IN A SEAL COMPONENT
2y 5m to grant Granted Apr 07, 2026
Patent 12590545
METHOD FOR MANUFACTURING SEAL RING, METHOD FOR ASSEMBLING TURBINE, AND TURBINE
2y 5m to grant Granted Mar 31, 2026
Patent 12553520
METAL SEAL FOR DYNAMIC DOWNHOLE ENVIRONMENTS
2y 5m to grant Granted Feb 17, 2026
Patent 12546395
SLIDE RING
2y 5m to grant Granted Feb 10, 2026
Patent 12535013
GAS TURBINE ENGINE WITH CARBON/CARBON COMPOSITE PISTON SEAL
2y 5m to grant Granted Jan 27, 2026
Study what changed to get past this examiner. Based on 5 most recent grants.

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Prosecution Projections

2-3
Expected OA Rounds
79%
Grant Probability
89%
With Interview (+10.4%)
2y 6m
Median Time to Grant
Moderate
PTA Risk
Based on 1376 resolved cases by this examiner. Grant probability derived from career allow rate.

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