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 .
Priority
Acknowledgment is made of applicant’s claim for foreign priority under 35 U.S.C. 119 (a)-(d). The certified copy has been filed in parent Application No. JP2022-037609, filed on March 10, 2022.
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 non-obviousness.
Claims 1-3 are rejected under 35 U.S.C. 103 as being unpatentable over Mitzutani U.S. Pub. No. 20070059584 A1, March 15, 2007 (hereinafter “Mitzutani”) in view of Shibata et al. EP 2862616 A2, September 22, 2016 (hereinafter “Shibata”).
Regarding claim 1, Mitzutani discloses a silicon carbide honeycomb filter (paragraph 0032) constituted by honeycomb segments (2, 3) (paragraphs 0002, 0029; fig. 3) each comprising cell walls (partition wall 6, fig. 1) forming cells defining pluralities of flow paths/passages longitudinally extending between both end surfaces (paragraphs 0025, 0038), plugs sealing end surfaces of said cells alternately in a checkerboard pattern (paragraph 0030), and an outer peripheral wall(figs. 1-2), bonding material layers filling lattice gaps between said honeycomb segments for bonding them (paragraph 0039), and a skin layer (coating material 4) covering the bonded honeycomb segments (paragraph 0037; fig. 3). Mitzutani discloses the wall thickness of 310 µm but fails to disclose that the thickness of said outer peripheral wall being more than 1.5 times and 9 times or less that of said cell walls.
However, Shibata discloses a honeycomb structure having a thickness of the cell walls (133) of 0.18 mm, and the thickness of the outer walls was 0.35 mm (paragraph 0346).
Thus, Shibata teaches an outer peripheral wall approximately 1.94 times as thick as the partition walls, and the disclosed thickness falls within the claimed range. Therefore, it would have been obvious to one of ordinary skill in the art at the time of the invention to use Shibata’s peripheral-wall-to-partition-wall thickness relationship in Mitzutani’s honeycomb segments to increase segment handling strength and resistance to chipping and damage while retaining the known thin porous call walls required for filtration.
Regarding claim 2, Mitzutani fails to disclose that the thickness of said cell walls is 0.17-0.31 mm. However, Shibata discloses a silicon-carbide honeycomb fired body having porous cells defining exhaust-gas flow cells and expressly discloses that the thickness of the cell walls is 0.18 mm (paragraphs 0321 and 0346). The disclosed thickness of 0.18 mm falls within the claimed range. It would have been obvious to one of ordinary skill in the art at the time of the invention to form the cell walls of Mizutani’s silicon-carbide honeycomb segment with the thickness taught by Shibata because Shibata identifies that thickness as suitable for silicon-carbide wall-flow filter.
Regarding claim 3, Mitzutani fails to disclose a cross section of said honeycomb segment in a plane perpendicular to the flow path direction, the cross-section areas of introducing cells whose outlet-side end surfaces are sealed are larger than those of discharging cells whose inlet-side end surfaces are sealed. However, Shibata discloses a silicon carbide wall-flow honeycomb filter having exhaust-gas introduction cells that are open at the exhaust-gas introduction side and plugged at the exhaust-gas emission side, and exhaust gas emission cells having the opposite plugging arrangement (paragraph 0008). Shibata further discloses employing introduction and emission cells having different cross-sectional areas to control exhaust-flow resistance, particularly accumulation and pressure loss (paragraph 0008-0009, 0038-0044).
It would have been obvious to one of ordinary skill in art at the time of the invention to employ Shibata’s known asymmetric cell configuration in Mizutani’s segmented silicon-carbide filter such that the introducing cells have a larger cross-sectional area than the discharging cells. Shibata teaches that the cell cross-sectional area is selected to control the respective inflow, flow-through, particulate-layer, and outflow resistances and thereby maintain a low-pressure loss during particulate accumulation (paragraph 0038-0042).
Allowable Subject Matter
Claims 4-12 are allowed.
The prior art of record does not disclose the claimed silicon-carbide honeycomb filter having the particular external configuration of the individual honeycomb segments and the resulting arrangement of the bonding material free spaces. Independent claim 4 requires, that each honeycomb segment have an octagonal cross-sectional shape formed by providing a linear chamfer at each of the four corners of an underlying quadrilateral, such that four first outer peripheral walls corresponding to the sides of the quadrilateral alternate with four second outer peripheral walls corresponding to the chamfered portions. Claim 4 further requires the segments to be arranged so that the second outer peripheral walls face one another at intersections of the lattice-shaped gaps and define vacant spaces that are not filled with bonding material.
Mitzutani (U.S. Pub. No. 20070059584 A1) in view of Shibata et al. (EP 2862616 A2) fails to disclose that each individual segment has the recited chamfered-octagonal external cross section; the four chamfer walls of adjacent segment face one another at a lattice intersection; and those facing chamfer walls collectively define a bonding-material free vacant space at the intersection. Salmona et al (U.S. Pub. No. 20130055694 A1) discloses that corners of inlet or outlet cells may be chamfered or rounded (paragraphs 0020, 0033) and discusses octagonal cell configurations, but identifies a quadrangular shape as a preferred shape of each structure in a segmented filter. Salmona fails to disclose forming each segment itself as the claimed chamfered octagon or arranging four segment chamfer walls to define the claimed vacant space.
Furthermore, the prior art fails to teach the claimed dimensional relationship of the vacant spaces, including the recited space ratio, defined by the relationship between the maximum diameter of the vacant space and the width of the lattice-shaped gap, as well as the claimed range of the space ratio. The dependent claims (claims 5-12) further recite additional limitations concerning the proportion of lattice intersections containing vacant spaces, the dimensional relationship between the outer peripheral walls and the cell walls, the geometry of the chamfered corner portions, and the relative cross-sectional area of the introducing and discharging cells. These additional limitations are likewise not taught by the prior art in combination with the allowable subject matter of independent claim 4.
Conclusion
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/M.N.E./Examiner, Art Unit 1776
/Jennifer Dieterle/Supervisory Patent Examiner, Art Unit 1776
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