Briggs & Stratton has filed a counterclaim in U.S. District Court in Omaha against Beatrice lawn mower maker Exmark Manufacturing, which sued the Wisconsin company and Schiller Grounds Care Inc. in May alleging their mowers infringe on its patents.

In the filing Thursday in U.S. District Court in Omaha, Briggs & Stratton Power Products Group seeks a declaration from the court that it has not infringed Exmark's patent "either directly, indirectly, literally, or under the doctrine of equivalents." Briggs & Stratton also alleges the claims of its patent are invalid.

The ‘863 Patent, at issue, covers multiblade mowers equipped with baffles between blades that allow the mower to be converted from a mulching to a side-discharge mower.