Patent Law

Ex Parte Framatome

By Alloy Comprising

On Dec. 12th, 1999, Reexamination No. 90/005,589 of U.S. Patent No. 5,940,464 was requested by Westinghouse Electric Company. On May 12, 2006, the Board of Patent Appeals and Interferences decided Ex parte Framatome ANP, upholding rejections of claims 1-4 as being obvious over U.S. Patent No. 4,649,023 to Sabol et al. assigned to Westinghouse Electric Company.

Understanding claim 1 is sufficient. Claim 1 recited,

A tube of zirconium-based alloy for constituting all or the outside portion of cladding for a nuclear fuel rod or of a guide tube for a nuclear fuel assembly, made of a zirconium-base alloy containing, by weight,0.8% to 1.8% niobium, 0.2% to 0.6% tin, and 0.02% to 0.4% iron, plus inevitable impurities, and having a carbon content controlled to lie in the range of 30 ppm to 180 ppm, a silicon content in the range 10 ppm to 120 ppm, and an oxygen content in the range 600 ppm to 1800 ppm."

In comparison, Sabol disclosed a range of alloys having 0.5-2.0% Nb, up to 1.5% Sn and up to about 0.25 of a third element such as iron, and Sabol's only exemplary embodiment had 0.9-1.1% Nb, 0.9-1.1% Sn, 0.09-0.11% Fe, 120 ppm of carbon, 1000-1600 ppm of oxygen and 80 ppm of silicon.  Accordingly, Sabol clearly anticipated each range of claim 1 except Sn.

In upholding the rejection of claim 1-4 as being obvious in view of Sabol, the Board reasoned at page 6,

Although Sabol does not expressly describe an example of a zirconium alloy comprising amounts of niobium, tin, iron, carbon, silicon and oxygen within the ranges recited in claim 1, Sabol does describe a zirconium alloy comprising amounts of niobium, tin and iron which overlap the claimed ranges.  See In Re Wertheim, 541 F.2d 257, 267, 191 USPQ 90, 100 (CCPA 1976) (where the difference between the claimed invention and the prior art is overlapping ranges, the appellant must show that the particular ranges are critical).  Sabol also indicates that a zirconium alloy in accordance with the disclosed invention would contain amounts of carbon, oxygen and silicon within the ranges of carbon, oxygen and silicon recited in appellant's claim 1... The examiner correctly points out that the phrase "up to" includes zero. Answer at 4. This range (up to 1.5%) encompasses the range of tin recited in claim 1 (0.2% to 0.6%).  However, the appellant argues that the teachings of Sabol as a whole would have led one of ordinary skill in the art away from the tin concentration recited in claim 1... The appellant argues that this passage would have suggested to one of ordinary skill in the art that an amount of tin below one percent should be avoided.  We disagree... nothing in Sabol suggests that an amount of tin as low as 0.6% would not provide the desired corrosion resistance.

To summarize, the Board deduced (1) "up to 1.5%" includes zero, (2) prima facie obvious because 0 to 1.5% overlaps with 0.2 to 0.6%, and (3) Sabol does rebut prima facie obviousness because Sabol does not suggest that low tin content would not work.  Without equating up to with zero, the Board could not have relied upon the case law on overlapping ranges.

Appellant then on July 12, 2006 filed a request for rehearing pursuant to 37 CFR 41.52, and argued,

According to the Board, the statement in Sabol that the amount of tin in the disclosed zirconium alloy may be "up to 1.5 percent tin" establishes a tin range of 0.0 percent to 1.5 percent and therefore is sufficient to establish a prima facie case of obviousness that is not rebutted by Sabol... With all due respect, the Board incorrectly read the phrase "up to 1.5 percent tin" when it agreed with the Examiner that such a phrase supports a Sabol alloy having no tin.  However true as a general matter it may be that a statement "up to X," when interpreted in isolation, supports a range of 0.0 to X, that interpretation is inappropriate for the phrase "up to 1.5 percent" in Sabol.  When viewed in light of Sabol as a whole, this phrase does not specify a specific lower limit of zero percent for the tin concentration; it instead merely specifies that the upper limit is 1.5 percent.  Indeed, the contention by the Examiner in the Answer that, on account of this phrase, Sabol fully supports a zirconium alloy that completely omits tin is undermined... (T)he entire Sabol specification requires every Sabol alloy to include tin, and... tin, according to Sabol, must be present to improve corrosion resistance, it makes no sense to say that providing no tin in the alloy would achieve the desired corrosion resistance... Thus, the statement "up to 1.5 percent tin" cannot be rigidly interpreted in a way that ignores the context provided by Sabol.

Since Sabol does not support a lower tin limit of 0.0 percent, the question then becomes what lower limit is in fact supported by Sabol...  Given that the phrase "up to 1.5 percent tin" does not established in Sabol a range of 0.0 to 1.5 percent tin, it is not the case that Sabol establishes a prima facie case of obviousness, since there is no evidence in Sabol establishing an overlap with the claimed tin range.  Therefore, the burden in not on Appellants to show that Sabol does not suggest an amount of tin below 1.0 percent.

Unfortunately, on July 12, 2007, the Board declined to address the merits of this argument, stating "Appellant did not present this argument in its (Appeal) Brief.  Therefore it is not entitled to consideration on rehearing."

Regardless, Appellants arguments are interesting.  The issue is burden of proof.  If successful, there would have been no overlapping ranges to establish obviousness by rule of law, then there would have been no need for the Appellant to show that Sabol teaches away.  Instead, the silence of Sabol would have worked for instead of against the Appellant.

Full post as published by Benefit of Hindsight on October 20, 2008 (boomark / email).