Ex Parte Lee et al

Patent Trial and Appeal BoardSep 21, 2012

11602421 (P.T.A.B. Sep. 21, 2012)

UNITED STATES PATENT AND TRADEMARK OFFICE ____________________ BEFORE THE PATENT TRIAL AND APPEAL BOARD ____________________ Ex parte CHING-PANG LEE, KEVIN SAMUEL KLASING, PAUL HADLEY VITT, and BRIAN DAVID KEITH ____________________ Appeal 2010-006216 Application 11/602,421 Technology Center 3700 ____________________ Before: JENNIFER D. BAHR, LINDA E. HORNER, and JOHN C. KERINS, Administrative Patent Judges. BAHR, Administrative Patent Judge. DECISION ON APPEAL Appeal 2010-006216 Application 11/602,421 2 STATEMENT OF THE CASE Ching-Pang Lee et al. (Appellants) appeal under 35 U.S.C. § 134 from the Examiner’s decision rejecting claims 11, 12, and 28. The Examiner indicated that claims 1-10 are allowable and objected to claims 13-24 and 29-31 as depending upon a rejected base claim. Claims 25-27 have been canceled. We have jurisdiction under 35 U.S.C. § 6(b). We REVERSE. The Claimed Subject Matter Claims 11 and 28, reproduced below, are illustrative of the claimed subject matter. 11. A turbine blade comprising an airfoil tip having a pressure- side first rib joined to a suction-side second rib at opposite leading and trailing edges and spaced transversely apart to include a trifurcate tip baffle extending chordally between said leading and trailing edges to define triple tip pockets. 28. A turbine blade comprising an airfoil having a trifurcate tip baffle defining a triforial tip cavity bounded by opposite tip ribs. Evidence The Examiner relied on the following evidence in rejecting the claims on appeal: Eiswerth Lee US 4,390,320 US 5,997,251 Jun. 28, 1983 Dec. 7, 1999 Rejections Appellants request our review of the rejection of claims 11, 12, and 28 under 35 U.S.C. § 103(a) as unpatentable over Eiswerth and Lee. OPINION The Examiner found that Eiswerth discloses a turbine blade comprising an airfoil tip (tip cap 30) having a pressure side first rib (radially Appeal 2010-006216 Application 11/602,421 3 tallest rib 32a) joined to a suction side second rib (radially shortest rib 32c) at opposite leading and trailing edges (upstream edge 14 and downstream edge 15) and spaced transversely apart to include a tip baffle (next tallest rib 32b) extending chordally between the leading and trailing edges. Ans. 3. The Examiner found that Eiswerth’s tip baffle is not a trifurcate tip baffle extending chordally to define triple tip pockets (claim 11) and does not comprise first, second, and third legs integrally joined together at corresponding central ends between the ribs and having opposite ends integrally joined to the ribs (claim 12), and that Eiswerth lacks a trifurcate tip baffle defining a triforial tip cavity (claim 28). Id. The Examiner found that Lee teaches a tip baffle having “at least 3 pockets 38 defined by ribs 36 and 60 to reduce the tip leakage flows” and thus “meets the requirement of a triforial tip cavity.” Id. The Examiner further found that “Lee shows first, second and third legs joined together at central ends.” Id. The Examiner determined it would have been obvious to “modify the tip baffle of Eiswerth, with the teaches [sic, teachings] of Lee, by providing a trifurcate tip baffle for the purpose of further reducing tip leakage flow.” Ans. 3-4. More specifically, the Examiner explained “[t]he ribs 36 of Lee ‘251 would easily be extended from the center rib of Eiswerth as taught and still maintain their function, to prevent leakage from the pressure side to the suction side of the tip of the blade (column 3, line 61 to column 4, line 7).” Ans. 7. Appellants argue that, given the disparate structures of the tip caps of Eiswerth and Lee, there is insufficient evidence in the record to establish that reduced tip leakage would be a predictable result of the modification Appeal 2010-006216 Application 11/602,421 4 proposed by the Examiner. App. Br. 11-12, 14-15. For the reasons that follow, we agree with Appellants. Lee discloses the configuration of squealer ribs 36 and channel ribs 60 as a means of reducing tip leakage flows in place of the more conventional squealer tip including “a continuous peripheral end wall . . . surrounding and projecting outwardly from an end cap on the outer end of a turbine blade which closes a cooling air chamber in the interior of the blade.” Col. 1, ll. 21-25; col. 3, ll. 59-60. According to Lee, this conventional type of squealer tip results in rubbing interference between the rotating blade tips and the surrounding stationary shroud, which heats the blade tips, causing excessive wear or damage to the blade tips and the shroud. Col. 1, ll. 35-38. Eiswerth, on the other hand, discloses a rotor blade tip cap 30 comprising a plurality of ribs, including a pressure side radially tallest rib 32a and a suction side radially shortest rib 32c joined to one another at the upstream and downstream edges 33 and 34, and at least one intermediate next tallest rib 32b disposed between and connected to the ribs 32a and 32c at the upstream and downstream edges 33 and 34, to provide an effective close-clearance seal between the radially outer end of the rotor blade and the shroud. Figs. 2, 4; col. 2, ll. 54-62; col. 4, ll. 49-52; 6, ll. 2-18. Thus, Lee and Eiswerth disclose two different approaches to reducing tip leakage flow between the rotor blade tip and the shroud. It is not readily apparent that providing squealer ribs 36 extending transversely between Eiswerth’s ribs 32a and 32c would further reduce tip leakage flow as asserted by the Examiner. Moreover, the addition of such squealer ribs transversely between the stepped ribs of Eiswerth’s cap tip 30 would seemingly interfere with the stepped arrangement for successive wearing Appeal 2010-006216 Application 11/602,421 5 away of the abrasive material on Eiswerth’s ribs described by Eiswerth. Col. 5, l. 66 – col. 6, l. 29. See App. Br. 23. In light of the above, the proposed combination of Eiswerth and Lee on which the Examiner’s rejection of claims 11, 12, and 28 is predicated lacks rational underpinnings. We do not sustain the rejection. DECISION The Examiner’s decision rejecting claims 11, 12, and 28 is reversed. REVERSED mls