Ex parte Burdgick
Appeal 2009004835; Appl. No. 10/317,192; Technology Center 2100
Decided November 19, 2009
Method claim 1 recited:
1. A method for establishing load limits for pipe connections to a turbine casing comprising:
a. identifying a plurality of the pipe connections as key pipe load connections on the turbine casing, wherein the key pipe load connections is a subset of all pipe load connections on the turbine casing;
b. developing transfer functions to model deformation of the turbine casing based on loads applied to the key pipe connections;
c. establishing individual load limits for each of the key pipe connections by optimizing solutions to the transfer functions, and
d. establishing a cumulative load limit for the key pipe load connections by optimizing solutions to the transfer functions.
The Examiner asserted the claim was obvious. The primary reference allegedly taught "finite element analysis and optimization of structural designs including turbine housings", but "did not provide much detail about the loading of pipes on turbine". The secondary reference allegedly taught "FEM analysis of pipe loading on pressure vessels including deformation failure and load limit determination." The Examiner then filled in the remainder of the claim using Applicant's background as Admitted Prior Art (APA), as follows:
It would have been obvious to one of ordinary skill in the art at the time of invention to modify the teaching of Oi et al. with the pipe loading analysis teachings of Meier et al. for the following reasons. Applicants have admitted (page 2, specification) that it was known to obtain pipe load limits on turbines:
 Excessive piping loads can also distort the turbine casing during turbine transient operations. Piping loads during transients, especially when cooling occurs in the pipes, tend to distort the turbine casing to reduce the clearances between the seals and buckets. If these clearances become too small, the stationary seals may "rub-out" as they scrap against the rotating buckets. Seals that rub-out do not provide effective sealing as they allow excessive steam leakage during steady state turbine operating conditions. Accordingly, excessive piping loads may damage and distort the seals between the casing and the buckets such that turbine performance is degraded.
 Piping load limits are imposed on the turbine design to avoid excessive piping loads that unduly distort the casing. In the past, these limits have been based on empirical and historical information regarding prior piping loads on similar turbine casing. It was common for piping load limits to be developed using simple calculations of the loads on the casing. Conventional turbine casing design techniques were not particularly helpful in identifying those key pipe connections that distort the turbine casing (seals) or in establishing load limits for pipe connections. Accordingly, there is a long felt need for methods to establish pipe load limits on turbine casings that avoid excessive casing distortion.
On appeal, the Applicant argued that APA did not disclose "identifying key pipe connections":
Applicant's Admission are statements in the application describing problems associated with excessive piping loads (para. 0005) and the prior art practice of developing piping load limits based on "empirical and historical information regarding prior piping loads on similar turbine casing[s]". [Para. 00061. These prior art techniques do not suggest the above highlighted steps of claim 1. Instead of suggesting the obviousness of the invention, Applicant's Admission indicates that persons of ordinary skill determined acceptable pipe loads using techniques starkly different than those recited in the method claims of this application. Applicant's Admission indicates that persons of ordinary skill would have not viewed the invention as being obvious.
In the Answer, the Examiner put forth a lengthy defense of his rationale as follows:
Note that in claim 1 that "identifying key pipe connections" is an arbitrary 'identification' of some of the connections as more important ('key') than others. This depends upon the particular design, common sense and experience of the mechanical engineer (or possibly a program written by the engineer - the claim does not specify), and intended use.
The first limitation of claim 1 only requires that certain of the pipe connections be 'identified' as key pipe connections. There is no requirement that the identification be carried out using any program or special technique; allowing for a skilled artisan to arbitrarily choose the connections based upon experience, for example, satisfies the limitation in the context of the claim.
The engineer in 'identifying' the key connections is 'identifying' the pipes which will cause the most deformation. Since the claim does not require any special technique (at least prior to step 1), the 'identification' appears to be based upon experience, and in fact is satisfied by par. 6 of the specification .... Applicants have admitted (par. 6, as specified in the rejection) that it was known to impose load limits, and that there was a long felt need to establish better techniques to identify connections. Therefore, by Applicant's admission, it was known to identify key pipe connections and pipe load limits on turbines, in the same context using, at the least, a less than better technique.
The Board reversed the obviousness rejection, finding that the Background did not teach "identifying" as claimed, and in fact taught the lack of this ability to identify:
However, we find that Appellants’ statement, although found in the Background of the Invention section, is not an “admission” but rather a statement regarding the need to identify key pipe connections. Defining a need suggests something that does not yet exist. While the above-noted statement is in the Specification’s Background section, we find that this is not enough to launch such a statement into an admission of prior art. Thus, the record does not contain evidence that supports the Examiner’s position that Appellants’ Specification admits that it was known to identify key pipe
connections. As such, we find that Appellants’ disclosure does not teach the claimed identifying step, but instead stresses the need to develop such a step. Therefore, we disagree with the Examiner that AAPA teaches identifying key pipe connections as a subset of all pipe connections. Given that the Examiner also has not shown, and we do not readily find, how the Oi, Meier, and Tsai references teach the “identifying” limitation, we cannot sustain this rejection.
My two cents: I found the Examiner's rejection to be a little unclear, because he didn't map to the claim language.
The Board treated the rejection as relying on AAPA for teaching the "identifying" feature. And it's true that the rejection didn't clearly assert that one of the other references taught that feature. So maybe that's the most plausible reading.
But the final rejection kinda reads like AAPA is used as a rationale for combining: "would have been obvious to modify .. for the following reasons. Applicants have admitted it was known". Then the Answer made it sound like the rejection relied on the knowledge of a POSITA: "engineer in 'identifying' the key connections is 'identifying' the pipes" ; "allowing for a skilled artisan to arbitrarily choose the connections based upon experience, for example, satisfies the limitation".
In the Appeal Brief, the Applicant treated the rejection as alleging that AAPA disclosed the identifying step. Guess that was the right reading, because it convinced the Board that the Examiner's rejection was flawed.
Maybe there's another takeaway here: be aware that everything you say in your Background can, and probably will, be used against you by the Examiner.