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Anderson v. International Engineering and Manufacturing Inc.

November 02, 1998


Before Newman, Circuit Judge, Skelton, Senior Circuit Judge, and Michel, Circuit Judge.

The opinion of the court was delivered by: Newman, Circuit Judge.

Appealed from: United States District Court for the District of Minnesota Judge John R. Tunheim

Lynn J. Anderson and Koronis Parts, Inc. ("Anderson"), owners of reexamined United States Patent No. B1 4,758,055 ("the '055 patent") entitled "Snowmobile Stud," filed suit in the United States District Court for the District of Minnesota, alleging infringement by appellees, five snowmobile track makers. Anderson moved for summary judgment of infringement, and appellees moved for summary judgment of invalidity on the ground that Anderson impermissibly broadened the '055 claims upon reexamination. The court granted appellees' motion, stayed further proceedings, and entered final judgment of invalidity. *fn1 We affirm the judgment.


The invention of the '055 patent relates to a method of inserting and securing small pointed studs into snowmobile tracks. The studs provide additional traction, of particular advantage at high speeds on ice.

The snowmobile tracks of the '055 patent are made of flexible, resilient material. In installing the studs so that the pointed ends protrude outwardly from the track, it is important to achieve a smooth surface on the inside of the track that is in contact with the snowmobile's drive mechanism. According to the description of the preferred embodiment in the specification of the '055 patent, when the stud is installed into the track the stud head is gripped by a tool and held at the sides of the head as the stud is drawn into the track by action of a tightening nut. When the top surface of the stud head is drawn substantially even with the resilient inside surface of the track, the tool is automatically disengaged from the stud head by contact with the resilient track; the stud head can no longer be gripped by the tool, the head is free to rotate and the nut can not be further tightened, signaling that the installation is complete. This tightening action is illustrated in the following figures of the '055 patent:

Figure 9

Figure 10

Figure 9 depicts the stud (10) before it is secured to the resilient track (25), with the stud head (14) gripped by a tool (34), ready for installation. A metal cleat (30) that is wider than the stud head rests against the outer surface of the track, and when the lock nut (20) is tightened the cleat prevents it from becoming embedded in the track. Tightening the nut draws the stud head into the track, as shown in the partially assembled view of Figure 10, until the resiliency of the track causes the tool to disengage from the stud head. The stud then becomes free to rotate, and further turning of the lock nut has no tightening effect. This rotation avoids undue compression of the track and irregularities in the inner surface of the track.

The issue on motion for summary judgment was whether the claims, original and reexamined, encompass a system in which the tool continues to grip the stud head after it is drawn completely into the track, such that instead of automatic disengagement the tool is manually removed. In appellees' system the tool is held so that it grips and follows the head as it is drawn into the resilient track, and retains its grip on the head until it is manually disengaged by the installer. Anderson states that the reexamined claims clarify that his system does not require automatic disengagement of the tool when the stud is fully installed; on this claim interpretation the claims would be infringed by the appellees' snowmobile stud assembly systems.

According to appellees, if the claims as modified on reexamination are read broadly enough to reach appellees' systems, as Anderson argues, the claims were impermissibly enlarged and are invalid. Thus the dispositive question is whether the original claims have the meaning sought by Anderson for the reexamined claims. If the original claims, correctly construed, encompass a system that does not automatically disengage the stud head from the tool, then the claims were not impermissibly broadened on reexamination. But if the original claims are limited to automatic disengagement of the tool by action of the resilient track, then on Anderson's interpretation of the reexamined claims they are broadened in scope, contrary to 35 U.S.C. §305.


At issue are reexamined claims 1-6 and 12. Claim 1, the only independent claim, is directed to the entire track assembly. Portions relevant to the installation of the stud follow:

"1. A single snowmobile stud assembly for attachment to a flexible resilient snowmobile track of predetermined thickness for engaging ice, by using a tool, said resilient snowmobile track having an inner surface ...

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