Gillette Co.'s patent suit against rival Schick-Wilkinson Sword was dealt a sharp blow from a federal judge in Boston, who ruled Thursday that the razor giant's patent suit seeking to block Schick from selling its four- bladed Quattro razor has "no reasonable likelihood of success" on its infringement claim.

In the ruling, U.S. District Judge Patti B. Saris denied Gillette's request for a preliminary injunction that could pull Quattro from the market. Quattro hit store shelves in September. The decision doesn't mean the end of the case; Gillette says it intends to follow it through to trial.

...The patent referred to three blades, but Gillette lawyers argued that the patent's language didn't restrict it to only three blades.

Judge Saris appeared not to buy that line of reasoning. "No amount of creative numbering ... can avoid the plain language regarding blade configuration in Claim 1 that excludes from its literal scope the possibility that the accused razor unit contain four blades," she wrote in the ruling.

In her ruling, Judge Saris dissected the innards of Gillette's patent, determining in essence that Gillette's use of the word "third" in defining a razor blade nearest one end of the cartridge, and "first" defining a blade nearest the other, precluded that same cartridge from having a fourth blade.

Paul McGowan, a patent attorney and editor in chief of the Litigation Stock Report newsletter, says Gillette could appeal that point to the Federal Circuit, but the process could drag on for a year or two. "It's not a good sign, frankly, " says Mr. McGowan, who has followed the case.

Schick's next move is likely to file a motion for summary judgment asking Judge Saris to rule without a trial, says Scott Marrs, a patent attorney at the Houston firm of Beirne Maynard & Parsons LLP. "They are certainly down but not out," Mr. Marrs says of Gillette. Still, he adds, "this is a significant blow to their case."