## Facts

- Steve Stumbo owned U.S. Patent No. 5,628,338 covering a portable, collapsible hunting blind with fabric walls supported by a foldable frame.
- The asserted claims required a “closable vertical opening” for entry/exit located at a side edge or vertical corner of the blind.
- Eastman Outdoors, Inc. and Ameristep Corporation sold hub-style collapsible blinds that used a triangular zippered opening on a side wall created by diagonal zipper paths.
- Stumbo sued for patent infringement, alleging literal infringement and infringement under the doctrine of equivalents.
- The dispute turned on construction of “closable vertical opening” and whether the accused triangular openings fell within (or were equivalent to) the claimed opening.

## Issues

1. How should “closable vertical opening” be construed: a straight, slit-like vertical opening at a side edge/vertical corner, or any opening with a vertical component including triangular openings?
2. Under the correct construction, did the accused blinds literally infringe?
3. If not, did the accused blinds infringe under the doctrine of equivalents, or would that theory improperly extend the claim to cover prior art?

## Decision

- The Federal Circuit affirmed summary judgment of noninfringement for defendants.
- The court upheld the construction of “closable vertical opening” as a slit-like opening running straight up and down (perpendicular to the horizon) at a side edge or vertical corner.
- Under that construction, the accused triangular side-wall openings did not literally infringe.
- The court also affirmed no infringement under the doctrine of equivalents because the triangular openings were not equivalent under the function–way–result analysis and because the equivalents theory would ensnare prior art.

## Legal Principles

- Claim terms are construed in view of the intrinsic record, including the specification and drawings; claim context can support a structural, narrowing construction.
- Summary judgment of noninfringement is appropriate when, after claim construction, the accused structure’s relevant features are undisputed and fall outside the claim as a matter of law.
- The doctrine of equivalents is limited: an asserted equivalent must satisfy equivalence (often evaluated by function–way–result), and claim scope cannot be expanded through equivalents to cover subject matter that would encompass prior art.

## Conclusion

The court affirmed that the patent’s “closable vertical opening” required a straight, slit-like vertical opening at a side edge or corner, making the defendants’ triangular side-wall door openings noninfringing both literally and under the doctrine of equivalents, particularly where an equivalents theory would reach prior art.


Stumbo v. Eastman Outdoors, Inc., 508 F.3d 1358 (Fed. Cir. 2007)