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 § 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, 2, 9-11, 14, and 15 is/are rejected under 35 U.S.C. 103 as being unpatentable over US Pre-Grant Publication 2021/0033095 to De Raeve et al. (De Raeve hereinafter) in view of US Pre-Grant Publication 2017/0306966 to Valland et al. (Valland).
Regarding claim 1, De Raeve teaches a pumping arrangement in Fig. 3, having a first multistage pump (1a) and a second multistage pump (1b), each having a housing (2) with a pump unit with an inlet (21), an outlet (22), and a plurality of impellers (31, 32 33) mounted in a torque proof manner on a pump shaft (5) having an upper drive end and a lower non-drive end, the pumps being arranged in series and having a first mechanical seal (50) with a process side facing the pump unit. De Raeve further teaches that the process side of the first mechanical seal (50) is downstream of the pump inlet of the first multistage pump to receive fluid therefrom. De Raeve teaches a balance drum (7) in each pump unit connected to the pump shaft (5) between the pump unit and the upper drive end of the shaft, the balance drums having a first side facing the pump unit and a back side. De Raeve does not teach pressure equivalence between the process side of the first seal and the suction pressure of the first multistage pump. Valland teaches another multistage pump generally, and particularly teaches that a pressure equalizing line (742) may be included to set the pressure at the process side of a mechanical seal (770) equal to process suction pressure (paragraph 42). Valland teaches that this “will provide a very stable barrier fluid pressure at the expense of slightly reduced efficiency” (paragraph 42). One of ordinary skill in the art would have found it obvious before the effective filing date of the application to provide a conduit as taught by Valland to the pump of De Raeve in order to provide stable barrier pressure therein. See below annotated versions of De Raeve Fig. 3 and Valland Fig. 7, with the De Raeve annotations showing a disposition of the pressure equalizing line of Valland in an analogous position. In this position, the claimed pressure equalization between the second multistage pump and suction side of the first multistage pump and fluid recirculation will occur according to the teachings of Valland and De Raeve due to the contiguous spaces defined by the balance and equalization lines in combination with the process side of the mechanical seal.
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De Raeve does not teach a second balance drum. Bourne teaches another pump generally, and particularly teaches that a subsea pump may be provided with two balance drums so as to improve rotor dynamics and stability (paragraph 12). Bourne further teaches that the second balance drum (8) is fixedly connected to the pump shaft between a pump unit (3) and a non-drive end (52) and has front and back sides arranged as claimed, with a second relief passage (83) and a second stator (27). One of ordinary skill in the art would have found it obvious before the effective filing date of the application to provide a second balance drum as taught by Bourne to the pump of De Raeve in order to improve rotor dynamics and stability. Thus provided at the non-drive end of at least the second pump, the second balance drum would be in at least indirect fluid communication with the pump inlet of the first multistage pump.
Finally, De Raeve as modified by Valland teaches a set of lines including the balance lines (9) of De Raeve and the pressure equalizing line (742) of Valland which combine (as shown in the annotated Fig. 7 of De Raeve above) to connect the process sides of the mechanical seals with the inlet of the first pump. Bourne teaches another balance line (9) arranged to connect a first back side (72) and a second back side (82) and wherein each back side is bounded by a drum (7/8) and a seal (531/541) as claimed herein. Bourne teaches that this enables the operation of the balance drums and the recirculation line at a desirable pressure (paragraph 71). One of ordinary skill in the art would have found it obvious before the effective filing date of the application to provide the balance lines of De Raeve in the same location relative to the balance drums of Bourne in order to allow their function at a desirable pressure in conjunction with the remaining elements of De Raeve.
Regarding claim 4, Bourne teaches that the balance line (9) is configured to connect the first back side of the second multistage pump with the second backside (82) of the second pump.
Regarding claim 5, Bourne teaches that the second drum front side is exposed to second pump inlet pressure (at 81).
Regarding claim 6, Bourne teaches a second mechanical seal (54) arranged as claimed.
Regarding claim 9, De Raeve teaches that each pump comprises a drive unit (4) and a drive shaft (not separately labeled) configured to drive the pump shaft via a coupling (8).
Regarding claim 10, De Raeve teaches that each first mechanical seal is arranged between the associated first balance drum and the drive unit.
Regarding claim 11, De Raeve teaches vertical pumps (paragraph 37).
Regarding claim 14, De Raeve teaches a pump configured for installation on a sea ground (paragraph 2).
Regarding claim 15, De Raeve teaches pumping compressible fluid in a dense state (see e.g. paragraph 8).
Regarding claim 17, as discussed above, De Raeve as modified in view of Valland (for the pressure equalizing line 742) and in view of Bourne (for the second balance drum) links the inlet pressure of the first pump to the inlet of the second pump and thereby to the first back side so as to essentially equalize those pressures.
Response to Arguments
Applicant's arguments filed 30 April 2026 have been fully considered but they are not persuasive.
In response to applicant's arguments against the De Raeve and Bourne references, one cannot show nonobviousness by attacking references individually where the rejections are based on combinations of references. See In re Keller, 642 F.2d 413, 208 USPQ 871 (CCPA 1981); In re Merck & Co., 800 F.2d 1091, 231 USPQ 375 (Fed. Cir. 1986).
In this case, applicant argues that neither De Raeve nor Bourne teaches the claimed location of the pressure equalizing line. In so arguing, the applicant has not addressed the teachings of Valland at all. Since the pressure equalizing line is taught by Valland as discussed above, the examiner is not persuaded that the combined references lack the claimed location. At most, in connecting the first pump inlet to the second pump inlet, the artisan faces only a choice of providing the pressure equalizing line on the upper (pump) side or the lower (bearing) side of the balance drum added from Bourne. At the minimum, either choice would have been obvious to try (MPEP 2143 I. E).
In view of the above, the examiner maintains that the claimed invention is obvious over the cited prior art.
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 PHILIP E STIMPERT whose telephone number is (571)270-1890. The examiner can normally be reached Monday-Friday, 8a-4p.
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If attempts to reach the examiner by telephone are unsuccessful, the examiner’s supervisor, Chelsea Stinson can be reached on 571-270-1744. The fax phone number for the organization where this application or proceeding is assigned is 571-273-8300.
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/PHILIP E STIMPERT/Primary Examiner, Art Unit 3746 11 June 2026
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