Prosecution Insights
Last updated: August 15, 2026
Application No. 19/100,420

MULTI-ROW PROPELLER (MRP) WITH CO-ROTATING BLADES

Final Rejection §102§103
Filed
Jan 31, 2025
Priority
Aug 03, 2022 — provisional 63/370,314 +1 more
Examiner
SEABE, JUSTIN D
Art Unit
3745
Tech Center
3700 — Mechanical Engineering & Manufacturing
Assignee
Virginia Polytechnic Institute and State University
OA Round
2 (Final)
72%
Grant Probability
Favorable
3-4
OA Rounds
1y 4m
Est. Remaining
96%
With Interview

Examiner Intelligence

Grants 72% — above average
72%
Career Allowance Rate
565 granted / 787 resolved
+1.8% vs TC avg
Strong +24% interview lift
Without
With
+24.5%
Interview Lift
resolved cases with interview
Typical timeline
2y 11m
Avg Prosecution
34 currently pending
Career history
823
Total Applications
across all art units

Statute-Specific Performance

§101
1.8%
-38.2% vs TC avg
§103
49.1%
+9.1% vs TC avg
§102
19.1%
-20.9% vs TC avg
§112
26.2%
-13.8% vs TC avg
Black line = Tech Center average estimate • Based on career data from 787 resolved cases

Office Action

§102 §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 . Response to Arguments Applicant's arguments filed June 3rd, 2026 have been fully considered but they are not persuasive. Applicant argues Bogert does not disclose the first centerline of the first blade and a second centerline of the second blade intersect with a helical line that extends along the rotation axis of the hub, and that the Examiner is relying on inherency without identifying the specific blades mapped to the first/second blade and the specific helical line; additionally, Applicant argues Bogert shows only discrete stages or rows of blades with no helical pattern between them. These arguments are not persuasive. Bogert discloses angular and axial offset directly from the Figures and the Figures were cited as the teaching. The rejection therefore does not solely rely on inherency for the teachings. The Office Action explicitly cited Figures 3-4 and then explained why these Figures show and teach the claimed invention. Collectively from Figures 3-4, the center row of blades defines the first row, and the aft/downstream row of blades defines the second row; the center row has a first blade (blade extending vertically downward) and the aft row has a second blade (blade extending downward to the right). Because these two blades are at different angular positions about the rotation axis (as seen in Figure 4) and at different axial positions along the rotation axis (as seen in Figure 3), the angular and axial offset are directly disclosed in the Figures and don’t rely on inherency. Given that the two blades are positioned at different angular locations and different axial locations on a cylindrical or conical hub surface, a helical curve on that surface passing through both centerline positions necessarily exists. This is not probabilistic or speculative, but a consequence of cylindrical geometry. Two points on a cylinder that differ in both circumferential and axial coordinate define a unique helical path connecting them. This is particularly true with respective to the blades on Bogert because the blades of different rows are positioned between the respective angular positioning: first row of blades positioned at the ~6:00, ~10:00, and ~2:00 position; the second row of blades positioned at the ~8:00, 12:00, and 4:00 position. Each blade in the respective row of blades is separated by ~60 degrees, and the other row of blades fits inside of that ~60 degree separation. It is the combination of the axial offset and the circumferential offset that allows for the geometric helical pattern to exist. The claims should be amended to more limit how this helical relationship between the respective rows of blades is structured and how the respective blades are aligned in sequence. The rejections are maintained. Claim Rejections - 35 USC § 102 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. (a)(2) the claimed invention was described in a patent issued under section 151, or in an application for patent published or deemed published under section 122(b), in which the patent or application, as the case may be, names another inventor and was effectively filed before the effective filing date of the claimed invention. Claims 1-7, 9, 11-12, and 16-19 are rejected under 35 U.S.C. 102(a)(1) or 35 U.S.C. 102(a)(2) as being anticipated by Bogert (US 2242642). Regarding claim 1, Bogert discloses a propulsion device, comprising: a hub having a curved surface extending around and along a rotation axis of the hub (Figures 3-5, hub unlabeled); and two or more rows of blades (8) extending radially outward from the curved surface and comprising a first row of blades having a first blade and a second row of blades having a second blade (Page 2, Col. 1, lines 7-10), the second blade being angularly and axially offset from the first blade on the curved surface (Figures 3-4), wherein a first centerline of the first blade and a second centerline of the second blade intersect with a helical line that helically extends along the rotation axis of the hub, the first blade and the second blade collectively forming a helical pattern of blades that projects radially outward from the curved surface along the helical line (the angular/axial offset and helical pattern: Bogert discloses that the hub has a steadily enlarged diameters from aft forward, meaning the blade rows are positioned at different axial locations; this has an implicitness that the blade rows would have angular offset (staggered arrangement) to provide proper blader coverage during rotation and avoid interference between rows. When multiple blade rows are arranged with angular and axial offset on a hub, the blade centerlines inherently intersect with a helical line extending along the rotation axis because of the cylindrical shape of the hub, and the blades collectively form a helical pattern). Regarding claim 2, Bogert discloses the propulsion device according to claim 1 above. Bogert further discloses the two or more rows of blades and each blade of the two or more rows of blades rotate at a same rotational rate and in a same rotational direction about the rotation axis during rotation of the propulsion device (blade rows share the same mounting on a singular shaft, and therefore all blades rotate at the same rate and in the same direction). Regarding claims 3-4, Bogert discloses the propulsion device according to claim 1 above. Bogert further discloses the first blade has a first leading edge and the second blade has a second leading edge, and wherein the first leading edge and the second leading edge are facing in a same rotational direction about the rotation axis (for propeller to function, the blades must have their leading edges oriented to face the incoming flow, and since the blades are the same rotational direction, they face the same direction). Regarding claim 5, Bogert discloses the propulsion device according to claim 1 above. Bogert further discloses the first blade and the second blade each comprise a discrete blade that is individually coupled to the curved surface, the curved surface being a single continuous surface (see figures 2-3, blades are discrete and individually coupled to the single continuous surface of the hub). Regarding claim 6, Bogert discloses the propulsion device according to claim 1 above. Bogert further discloses the first blade and the second blade each has a different blade angle with respect to a rotation plane that is normal to the rotation axis (“the pitch of each row of blades should increase from forward aft, in order that each separate propeller or each separate row of blades should perform its share of the propulsive work”). Regarding claim 7, Bogert discloses the propulsion device according to claim 1 above. Bogert further discloses each row of the two or more rows of blades comprises an equal number of blades (the figures illustrate propeller configurations where each row has an equal number of blades). Regarding claim 9, Bogert discloses the propulsion device according to claim 1 above. Bogert further discloses each blade of the two or more rows of blades has a same geometry (Figure 4). Regarding claims 11-12 and 16, Bogert discloses the propulsion device according to claim 1 above. Bogert further discloses each row of the two or more rows of blades comprises a uniform angular distribution of blades about the rotation axis, each row of the two or more rows of blades comprises a same uniform angular distribution of blades about the rotation axis (see the Figures, angular spacing/distribution of the blades around the circumference/rotational axis is uniform), and at least one blade of the two or more rows of blades has a blade angle that is different from at least one other blade of the two or more rows of blades (“the pitch of each row of blades should increase from forward aft, in order that each separate propeller or each separate row of blades should perform its share of the propulsive work”). Regarding claims 17-19, Bogert discloses A propulsion device, comprising: a first hub having a first row of blades (8) extending radially outward from a first curved surface of the first hub, the first row of blades comprising a first blade, the first curved surface extending around and along a rotation axis of the propulsion device; and a second hub having a second row of blades (8) extending radially outward from a second curved surface of the second hub (see Figure 3 which shows multiple hubs and each with their respective rows of blades extending radially outward, each of the hubs having a curved surface), the second row of blades comprising a second blade that is angularly and axially offset from the first blade as measured from the rotation axis, the second curved surface extending around and along the rotation axis, wherein a first centerline of the first blade and a second centerline of the second blade intersect with a helical line that extends helically along the rotation axis, the first blade and the second blade collectively forming a helical pattern of blades that projects radially outward from the first curved surface and the second curved surface along the helical line (the angular/axial offset and helical pattern: Bogert discloses that the hub has a steadily enlarged diameters from aft forward, meaning the blade rows are positioned at different axial locations; this has an implicitness that the blade rows would have angular offset (staggered arrangement) to provide proper blader coverage during rotation and avoid interference between rows. When multiple blade rows are arranged with angular and axial offset on a hub, the blade centerlines inherently intersect with a helical line extending along the rotation axis, and the blades collectively form a helical pattern, each blade of each of the first row of blades and the second row of blades rotate at a same rotational rate and in a same rotational direction about the rotation axis during rotation of the propulsion device (blade rows share the same mounting on a singular shaft, and therefore all blades rotate at the same rate and in the same direction), and a leading edge of each blade of each of the first row of blades and the second row of blades is facing in a same rotational direction about the rotation axis (for propeller to function, the blades must have their leading edges oriented to face the incoming flow, and since the blades are the same rotational direction, they face the same direction). 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. Claims 8 and 13 are rejected under 35 U.S.C. 103 as being unpatentable over Bogert (US 2242642) in view of Checkley (US 1717663). Bogert discloses the propulsion device according to claim 1 above. Bogert fails to teach at least one row of the two or more rows of blades comprises a number of blades that is different from at least one other row of the two or more rows of blades and at least one row of the two or more rows of blades comprises a uniform angular distribution of blades about the rotation axis that is different from at least one other row of the two or more rows of blades. Checkley teaches a propulsion device comprising at least one row of two or more rows of blades, wherein at least one row comprises a number of blades that is different from at least one other row (Figures 1-2), and at least one row of the two or more rows of blades comprises a uniform angular distribution of blades about the rotation axis that is different from at least one other row of the two or more rows of blades (Figure 2). It would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to modify the propulsion device of Bogert such that at least one row of the two or more rows of blades comprises a number of blades that is different from at least one other row of the two or more rows of blades and at least one row of the two or more rows of blades comprises a uniform angular distribution of blades about the rotation axis that is different from at least one other row of the two or more rows of blades as taught by Checkley for the purposes of optimizing the fluid flow by having the front propeller break up the fluid while subsequent rows handle the pre-conditioned flow, thereby maximizing pushing power through the additional blade area. Claim 10 is rejected under 35 U.S.C. 103 as being unpatentable over Bogert (US 2242642) in view of Smith (US 8770941). Bogert discloses the propulsion device according to claim 1 above. Bogert fails to teach at least one blade of the two or more rows of blades has a geometry that is different from at least one other blade of the two or more rows of blades. Smith teaches a multi-set impeller of propeller wherein at least one set of blades may have the same or different sizes, or the same or different plane angles, compared to at least one blade of the adjacent set of blade rows (abstract). It would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to modify the propulsion device of Bogert such that at least one blade of the two or more rows of blades has a geometry that is different from at least one other blade of the two or more rows of blades as taught by Smith for the purposes of adjusting different blade geometries between sets to optimize performance of the fluid flow conditions at each axial position along the hub. Claim 14 is rejected under 35 U.S.C. 103 as being unpatentable over Bogert (US 2242642) in view of Nojiri (US 4514146). Bogert discloses the propulsion device according to claim 1 above. Bogert fails to teach at least one row of the two or more rows of blades comprises a nonuniform angular distribution of blades about the rotation axis. Nojiri teaches a propulsion device wherein pairs of forward and rearward blades (5, 6) can be arranged at different spacings (Col. 3, Lines 9-18). Additionally, there can be a nonuniform angular distribution (Figure 5). It would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to modify the propulsion device of Bogert such that at least one row of the two or more rows of blades comprises a nonuniform angular distribution of blades about the rotation axis as taught by Nojiri for the purposes of preventing decreases in efficiency by optimizing the mutual interference between adjacent blades. Claim 15 is rejected under 35 U.S.C. 103 as being unpatentable over Bogert (US 2242642) in view of Pien (US 4306839) or Mehus (US 3606579) or Ogawa (US 5078632). Bogert discloses the propulsion device according to claim 1 above. Bogert fails to teach each blade of the two or more rows of blades has a same blade angle. Pien teaches a propulsion device with two sets of radially extending blades. The blade sets are configured to that outer portions of the blades are equispaced and lie substantially in a common plane of propeller rotation. The blade angle of the respective sets have the same angle relative to the rotation plane. Mehus teaches a propulsion device having main blades and auxiliary blade which are in distinct rows, each having the same blade angle (“the pitch angle of said auxiliary blades being at least equal to the pitch angle of the main blade). Ogawa teaches a propulsion device with a first set of blades (3) and a second set of blades (10) and they have the same blade angles: the subblades are arranged at regular intervals on the rearward surface of the boss with the angles being the same in Figure 4C. It would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to modify the propulsion device of Bogert such that each blade of the two or more rows of blades has a same blade angle as taught by Pien or Mehus or Ogawa for the purposes of reducing negative pressure zones and improving overall efficiency. Claim 20 is rejected under 35 U.S.C. 103 as being unpatentable over Bogert (US 2242642) in view of Pien (US 4306839). Bogert discloses a method of improving propulsion efficiency, the method comprising: rotating a propulsion device, the propulsion device comprising a hub (Figures 3-4) having two or more rows of blades (8) that extend radially outward from a curved surface of the hub and comprise a first row of blades having a first blade and a second row of blades having a second blade, the second blade being angularly and axially offset from the first blade on the curved surface, the first blade and the second blade collectively forming a helical pattern of blades that extends helically along at least a portion of the curved surface the angular/axial offset and helical pattern: Bogert discloses that the hub has a steadily enlarged diameters from aft forward, meaning the blade rows are positioned at different axial locations; this has an implicitness that the blade rows would have angular offset (staggered arrangement) to provide proper blader coverage during rotation and avoid interference between rows. When multiple blade rows are arranged with angular and axial offset on a hub, the blade centerlines inherently intersect with a helical line extending along the rotation axis, and the blades collectively form a helical pattern). Bogert fails to teach altering a first direction of a fluid flow over the first blade by a first amount and a second direction of the fluid flow over the second blade by a second amount that is less than the first amount based on rotating the propulsion device; and increasing an efficiency of the propulsion device based on altering the second direction of the fluid flow over the second blade by the second amount. Pien teaches a propulsion device with different inflow fields (differential flow alteration: “loading on forward and aft propeller blades is not equalized because they operate different inflow fields since one is axially ahead of the other”). Thus the upstream blades alter the flow, and the downstream blades encounter the pre-altered flow (i.e., the second blade experiences less flow direction change because the first blade already altered it). It would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to modify the method of Bogert such that altering a first direction of a fluid flow over the first blade by a first amount and a second direction of the fluid flow over the second blade by a second amount that is less than the first amount based on rotating the propulsion device; and increasing an efficiency of the propulsion device based on altering the second direction of the fluid flow over the second blade by the second amount as taught by Pien for the purposes of improving efficiency through reduced kinetic energy in the slipstream. Conclusion THIS ACTION IS MADE FINAL. 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 nonprovisional extension fee (37 CFR 1.17(a)) 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 mailing date of this final action. Any inquiry concerning this communication or earlier communications from the examiner should be directed to JUSTIN D SEABE whose telephone number is (571)272-4961. The examiner can normally be reached Monday-Friday, 9:00-5:30. 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, Nathaniel Wiehe can be reached at 571-272-8648. 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. /JUSTIN D SEABE/Primary Examiner, Art Unit 3745
Read full office action

Prosecution Timeline

Jan 31, 2025
Application Filed
Jan 27, 2026
Non-Final Rejection (signed) — §102, §103
Mar 05, 2026
Non-Final Rejection mailed — §102, §103
Jun 03, 2026
Response Filed
Jun 18, 2026
Final Rejection mailed — §102, §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

3-4
Expected OA Rounds
72%
Grant Probability
96%
With Interview (+24.5%)
2y 11m (~1y 4m remaining)
Median Time to Grant
Moderate
PTA Risk
Based on 787 resolved cases by this examiner. Grant probability derived from career allowance rate.

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