DETAILED ACTION
Response to Amendment
The Amendment filed 04/20/2026 has been entered. Claim 1 remains pending in the application and is presented for examination on the merits.
Claim Interpretation
Note that the limitation “for pressure piping” of claim 1 is an intended use limitation that does not impart any structural limitations to the claimed steel pipe. “If the body of a claim fully and intrinsically sets forth all of the limitations of the claimed invention, and the preamble merely states, for example, the purpose or intended use of the invention, rather than any distinct definition of any of the claimed invention’s limitations, then the preamble is not considered a limitation and is of no significance to claim construction.” See MPEP §2111.02 (Il).
Regarding the limitation of “the steel pipe being subjected to autofrettage” of claim 1, this is a product-by-process limitation. MPEP § 2113 states that “even though product-by-process claims are limited by and defined by the process, determination of patentability is based on the product itself. The patentability of a product does not depend on its method of production. If the product in the product-by-process claim is the same as or obvious from a product of the prior art, the claim is unpatentable even though the prior product was made by a different process”. In this instance, the claimed processing limitation of the steel pipe being subjected to autofrettage results in compressive residual stresses which could be achieved by other processes.
The term “critical internal pressure” is interpreted in light of the instant specification, which recites “an internal pressure to be a limit up to which no fracture due to fatigue occurs at an inner surface of the steel pipe (hereinafter, referred to as "critical internal pressure")” ([0012]).
Claim Rejections - 35 USC § 103
The text of those sections of Title 35, U.S. Code not included in this action can be found in a prior Office action.
Claim 1 is rejected under 35 U.S.C. 103 as being unpatentable over “Paris fatigue life modeling of pressure vessel service simulation tests” of Underwood (as cited in IDS mailed 10/05/2023) in view of “ASTM A723/A723M-18 Standard Specification for Alloy Steel Forgings for High-Strength Pressure Component Application” of ASTM.
Regarding claim 1, Underwood teaches pressure vessel service simulation tests (Abstract). Underwood teaches the pressure vessels are ASTM A723 steel (Abstract, “Introduction” section, 2nd paragraph, reads on claimed steel) and an autofrettaged gun tube pressure vessel (Fig. 1, Abstract, and “Introduction” section; steel autofrettaged gun tube pressure vessel reads on claimed steel pipe for pressure piping, the steel pipe being subjected to autofrettage; one of ordinary skill in the art understands and a tube and a pipe both have similar geometries and an outer and inner diameter).
Underwood therefore reads on the limitation a steel pipe for pressure piping, the steel pipe being subjected to autofrettage of claim 1.
Underwood teaches a pressure vessel made of A723 steel with a yield strength of 1140 MPa, an inner radius of 79 mm, an outer radius of 155 mm, a yield pressure of 802 MPa, and a fatigue pressure of 700 MPa (pages 2-3, Table 1, yield pressure is an autofrettage pressure as explained in the paragraph before the “Residual Stress Plots” subsection).
Underwood therefore reads on the limitation wherein when an outer diameter of the steel pipe is denoted by D (mm), an inner diameter of the steel pipe is denoted by d (mm), and a yield stress of the steel pipe is denoted by σy (MPa) of claim 1.
The inner radius of 79 mm and outer radius of 155 mm of Underwood are equivalent to an inner diameter of 158 mm, an outer diameter of 310 mm, and dividing the outer and inner diameters results in a D/d ratio of 1.96, which meets the claimed limitation of D/d is 1.2 or more.
Underwood therefore reads on the limitation D/d is 1.2 or more of claim 1.
Regarding the residual stress, Underwood teaches the pressure vessel has a residual stress of -687 MPa (Table 2, the residual stress is the near-bore compressive autofrettage hoop stress as explained in “Stresses for Fatigue Life Calculation” subsection; reads on claimed residual stress after autofrettage).
While Underwood does not explicitly disclose the values of Formulas (i)-(v), using the values for the outer diameter of 310 mm, inner diameter of 158 mm, and yield stress of 1140 MPa of Underwood in the given formulas, the resulting values are F: -0.68, A is 6.02, and C is -4.04. Using these values in Formula (v) gives:
-848.69 MPa ≤ σi1 ≤ -617.23 MPa
which fits the expected residual stress of -687 MPa of Underwood. While Underwood does not explicitly state the residual compressive stress of the vessel is at the inner surface of the tube, one of ordinary skill in the art understands the residual stresses of Underwood and the claimed invention to be comparable since they are both autofrettaged steel pipes. One of ordinary skill in the art further understands autofrettage applies residual stress at the inner surface of the vessel.
Underwood therefore reads on the limitation of an estimated value σi1 (MPa) of a residual stress at an inner surface of the steel pipe after the autofrettage satisfies Formula (v) of claim 1.
Regarding the critical internal pressure, Underwood teaches a pressure vessel made of A723 steel with a yield pressure of 802 MPa, and a fatigue pressure of 700 MPa (page 2, Table 1, yield pressure is an autofrettage pressure as explained in the paragraph before the “Residual Stress Plots” subsection). Underwood teaches yield pressure is the internal pressure at which yielding first occurs at the inner radius and fatigue pressure is that used in the service simulation fatigue tests (page 2, paragraph below Table 1). While Underwood does not explicitly disclose a “critical internal pressure”, the fatigue pressure of Underwood is interpreted as a pressure at which no fracture due to fatigue occurs and is therefore analogous to the claimed “internal pressure”. The fatigue pressure of 700 Mpa of Underwood reads on the claimed internal pressure.
Underwood therefore reads on the limitation wherein the critical internal pressure of the steel pipe is 300 MPa or more of claim 1.
Underwood teaches the pressure vessels are ASTM A723 steel (Abstract, “Introduction” section, 2nd paragraph) and a yield strength of 1140 MPa, but does not explicitly disclose a tensile strength. It would have been obvious to one of ordinary skill in the art before the effective filing date of the invention to refer to the ASTM A723 standard referenced by Underwood to find a relevant tensile strength value for the steel of Underwood.
ASTM teaches a standard specification for alloy steel forgings for high-strength pressure component application (Title) and is considered analogous art. ASTM teaches minimum tensile requirements for various class of alloys of A723 steels (Table 2). While ASTM A723 does not include a class with a yield strength of specifically 1140 MPa, ASTM teaches an A723 steel with a tensile strength of 1240 MPa will have a minimum tensile strength of 1310 MPa. A tensile strength of 1310 MPa will be used as a conservative estimate for the tensile strength of the steel of Underwood.
While Underwood does not explicitly disclose the values of Formulas (I) and (II) of the instant invention, calculating their values using the values of Underwood for the outer diameter of 310 mm, inner diameter of 158 mm, and tensile strength of 1310 MPa of Underwood in view of ASTM in the given formulas results in values of Formula (II): α = 0.95 and therefore Formula (I): IP ≥ 549.83 MPa. Since Underwood teaches a fatigue pressure of 700 MPa, the fatigue pressure of Underwood satisfies Formula (I).
Usui therefore reads on the limitation wherein the steel pipe for pressure piping has a critical internal pressure satisfying Formula (1) shown below of claim 1 and
Although Underwood teaches a residual stress after autofrettage, Underwood does not explicitly disclose what the residual stress is in the outer surface of the pipe after autofrettage or any residual stresses after autofrettage and halving the steel pipe. While Underwood does not explicitly disclose these properties nor the distance “t”, one of ordinary skill in the art would reasonably expect the values to be present even if they are not explicitly measured or disclosed given the overlap in composition (steel), structure (D/d ratio of 1.2 or more), an estimated value σi1 (MPa) of a residual stress at an inner surface of the steel pipe after the autofrettage satisfies Formula (v), as described above, and critical internal pressure. Absent any clear and convincing evidence and/or arguments to the contrary, one of ordinary skill in the art would expect the pressure vessel of Underwood to possess the claimed measured values of residual stress. A prima facie case of obviousness has been properly established herein. As the Patent Office does not possess the laboratory facilities to test any differences in the claimed invention versus that of the reference, the burden shifts to applicant to demonstrate otherwise.
Underwood therefore reads on all the limitations of claim 1.
Response to Arguments
Applicant’s arguments, see page 5, filed 04/20/2026, with respect to the rejection of claim 1 under 35 U.S.C. 103 have been fully considered and are persuasive. Therefore, the rejection has been withdrawn. However, upon further consideration, a new ground of rejection is made in view of “Paris fatigue life modeling of pressure vessel service simulation tests” of Underwood.
Conclusion
Applicant's amendment necessitated the new ground(s) of rejection presented in this Office action. Accordingly, THIS ACTION IS MADE FINAL. See MPEP § 706.07(a). Applicant is reminded of the extension of time policy as set forth in 37 CFR 1.136(a).
A shortened statutory period for reply to this final action is set to expire THREE MONTHS from the mailing date of this action. In the event a first reply is filed within TWO MONTHS of the mailing date of this final action and the advisory action is not mailed until after the end of the THREE-MONTH shortened statutory period, then the shortened statutory period will expire on the date the advisory action is mailed, and any extension fee pursuant to 37 CFR 1.136(a) will be calculated from the mailing date of the advisory action. In no event, however, will the statutory period for reply expire later than SIX MONTHS from the date of this final action.
Contact Information
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/M.A./Examiner, Art Unit 1733
/REBECCA JANSSEN/Primary Examiner, Art Unit 1733
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