Is that Patented Design Really New?

United General Supply sued Rural King alleging Rural King sold products infringing three design patents, one of which is D577,520 (the ‘520 patent) for a chair back.


The claimed chair back has 5 slats, the center slat being wider than the lateral pairs. The claimed design also includes a longer upper horizontal bar and a shorter lower horizontal bar extending behind the slats. The remaining part of the chair shown in figure 9 is in broken lines and therefore not claimed. The accused Rural King product is shown in the color photo and looks pretty close to the claimed design.

One might ask, “is that patented design new?” or “Doesn’t this five slat design exist in the prior art?” And that’s what every defendant in a patent infringement asks and searches to answer. Because if the design is in the prior art, then the patent is invalid and the defendant wins. However, don’t just look at the slats. You must consider the upper and lower horizontal bars that are claimed.

But even as to the slats, the prior art cited by the patent examiner in the ‘520 patent does not get close enough to the claimed design. Below are figures from some of the patents cited by the Examiner during the prosecution of the ‘520 patent.



None of the figures above show a chair back with a wide center slat and smaller lateral slats.

Defendants look beyond the prior art cited during the prosecution of the patent. They search US and foreign patents and patent applications, as well as non-patent prior art to try to invalidate the patent.

Yet, design patent scope is often quite narrow. That means small changes may be sufficient to distinguish the prior art. And therefore invalidating design patents based on the prior art can be challenging.

If Rural King is to succeed it will need to deal with the ‘520 patent as well as U.S. D597,352 which is directed to the rocking chair frame. The ‘352 patent, shown below, provides more details and may be harder to attack.


Citation: United General Supply Co., Inc. v. Rural King Administration, Inc., No. 2:18-cv-02004 (C.D.Ill 2018).