The patent claims were directed to a system for handling and positioning sections of well casing, which line a well bore to facilitate removal of oil or gas. Because of their size and weight, moving and positioning casings manually can be dangerous. The invention provided a remote-controlled boom for lowering and positioning casings from a distance. The boom had jaws at one end for engaging a casing and was hydraulically movable in an up-and-down "pivoting" motion and in a side-to-side "yawing" motion. A piston and cylinder subassembly, which in the preferred embodiment operated against a lift plate beneath the boom, facilitated these motions. Frank's Casing Crew & Rental Tools, Inc. v. Weatherford Int'l Ltd., Case Nos. 03-1519, -1563 (Fed. Cir., Nov. 30, 2004).
The claims at issue recited "means for selectively pivoting said boom about said horizontal axis to raise and lower the second end of said boom which carries said jaws, and to elevate said boom to a location where it extends in a generally vertical direction." The parties agreed that the limitation was in "means-plus-function" format, governed by §112, ¶6. The parties also agreed that its function was "selectively pivoting said boom about said horizontal axis to raise and lower the second end of said boom which carries said jaws, and to elevate said boom to a location where it extends in a generally vertical direction."
At issue was whether the corresponding structure included the lift plate. The plaintiff asserted that the structure included only a piston and cylinder subassembly for pivoting the boom. Anything additional, according to the plaintiff, would constitute "improperly imported structure unnecessary to perform the recited function." However, the defendant argued that the structure must also include the lift plate, which was disclosed in the preferred embodiment of the invention. The Court turned to the prosecution history, specification and other claims for its answer.
During prosecution of the parent case, the applicant had distinguished his invention from a prior art reference that disclosed a cylinder attached under the boom for the lifting function. The applicant argued that "the spatial and positioning limitation [of the prior art reference] is overcome in the present invention by connecting [the cylinder which lifts the boom] not directly to the boom, but by connecting it indirectly to the boom through securement" to the lifting plate. The Federal Circuit affirmed the district court’s holding that the prosecution history of the parent case "amounted to a disclaimer" of the "below-mounted and directly-attached lifting means."
The Court also noted that while the specification on occasion referred to the piston and cylinder subassembly without mentioning the lift plate, the only embodiment showing use of the piston and cylinder subassembly disclosed a direct connection to a lift plate. Additionally, the Court referred to other claims in the patent, directed to the yawing function, noting that a device could not perform yawing without a lift plate under the boom. Although the claims at issue did not recite "yawing," the Court recognized the principle that related claims should be interpreted consistently.
The Court concluded that the "means for selectively pivoting" must include a lift plate under the boom. As the accused device did not include a lift plate located under the boom, the Court held that it did not infringe under either §112, ¶6 or the judicially created doctrine of equivalents.
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