Photo courtesy Caterpillar Caterpillar compact track loaders, such as the one seen here, are just one class of equipment that Doosan Bobcat alleges violates its intellectual property, but the U.S,-based rival is countersuing.. After being sued by Doosan Bobcat last December over patents for compact equipment, Caterpillar Inc., filed a new amended counterclaim on May 26, now alleging violations of Section 337 of the Tariff Act of 1930. It claims that South Korea-based Doosan Bobcat is violating Caterpillar patents and illegally importing equipment that does so. The equipment manufacturing giant seeks relief for its U.S.-based workers and operations, an investigation of Doosan Bobcat and a halt to importation of its equipment.…