Justia Federal District Court Opinions

This appeal is taken from the judgment of the United States District Court for the District of Colorado, holding claims 25-31 of the patent in suit invalid for lack of utility, unenforceable based on inequitable conduct, and not infringed.¹ The judgment of unenforceability and invalidity are reversed. The judgment of noninfringement is affirmed.

The Patented Invention

Proma Produkt-Und Marketing Gesellschaft m.b.H. is the owner of United States Patent No. 4,664,020, invention of Siegmund Kaiser (the "Kaiser patent"). Norgren Company is the exclusive licensee under the patent. (The appellants will collectively be called "Proma".)

The Kaiser patent is directed to a rodless piston-cylinder. In rodless cylinders, an internal piston is driven by pneumatic or hydraulic pressure applied to one end of the cylinder. This piston is connected to a rib that extends through a slit that runs the length of the cylinder. In use, the rib is connected to an external load; when the piston is driven toward the opposite end of the cylinder, the load is moved. If the slit through which the rib passes is not maintained in a sealed condition, air or hydraulic fluid leaks from the cylinder and pressure is lost. As Kaiser discussed in the patent, the integrity of the slit seal can be compromised in two principal ways: internal pressure from within the cylinder may widen the slit; or the external load may drive the rib against one side of the slit, also causing widening.

In the Kaiser device, longitudinal grooves run the length of the cylinder wall, parallel to and located on either side of the slit. To the rib is attached a yoke that spans the slit and moves on guides along the grooves on the cylinder. As the rib and yoke move along the cylinder, forces tending to widen the slit are counteracted by the yoke "squeezing" the slit. Figure 2 of the Kaiser patent shows yoke (11) riding in grooves (16) on the outside of the cylinder:

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