Insituform Technologies, Inc. v. CAT Contracting, Inc.

Insituform Technologies, Inc. (Insituform) (plaintiff) held a patent (the 012 patent) that disclosed a method for repairing underground pipes by installing a resin-filled liner. Claim 1 disclosed a method in which windows were cut in the liner and a single vacuum cup was transferred between windows to create suction, moving the resin up the liner. Claim 1 of the original application for the 012 patent did not specify the number of vacuum cups, their location, or the location of the vacuum source. The use of a single vacuum cup applied to windows along the liner was only described in dependent claim 4. The application was rejected because another patent, the Everson patent, claimed the use of a single vacuum source at the end of a tube to fill liners with resin. Insituform amended the patent application so that claim 1 included the limitations in the original dependent claims, such as the use of a single cup. Insituform noted during patent examination that the Everson method was problematic because it required large suction compressors. Claim 1 as amended directly addressed that issue by moving the suction source closer to the resin. The prosecution history raised no discussion of a multiple-cup process. Insituform sued CAT Contracting, Inc. (CAT) (defendant) in federal court for infringement of claim 1 of the 012 patent. The accused CAT process used multiple vacuum cups. The district court ruled that the CAT process infringed on claim 1 under the doctrine of equivalents. CAT appealed.