The issue in this case is whether a combination patent on an exercise sandal is invalid for obviousness under 35 U.S.C. § 103. The District Court, after a bench trial, held the patent valid and infringed. We reverse the judgment.

Reduced to its essentials, the alleged invention consists of changing the position provided for the big toe in the sole of the sandal. A prior German patent, known as the Berkemann patent,1 taught the design of an exercise sandal that was the same in the following respects to that of the Bittner, et al., patent² in suit:

(1) a rigid sole block in the shape of the foot,3

(2) with a loose fitting strap fitting across the foot to hold the sandal on the foot, and

(3) a ridge on the sole block on which the toes rest.

The Berkemann sandal was sold to the general public at least as early as 1950, and some 25,000,000 pairs of that sandal were sold in 50 countries, including the United States, between 1950 and 1970.4

The patent in suit merely called for two changes in the Berkemann design, neither of which was new, Viz., eliminating the part of the ridge under the big toe and providing a slight depression under that toe.5

As early as 1938 Dr. Phillip R. Brachman, one of the medical experts who testified at the trial (who was originally identified as plaintiff's expert but who was called as a witness for the defendant), wrote a book6 in which he discussed the idea of a ridge for the toes and recommended that the ridge not be extended to the area under the big toe.7 A depression for the big toe anterior to the ridge is not mentioned in the Berkemann patent, but such a depression appears in the exemplification of that patent that is in evidence.

A depression for the big toe in relation to the other toes and the ball of the foot was taught as anatomically correct in the Stroup patent issued in 1951,⁸ which applied that design to the sole of a shoe. In addition, a 1941 publication by Musebeck Shoe Company entitled "Your Patient and His Feet" taught "hollow(ing) out" the insole to fit the contours of the foot, including "the ball of the great toe."

The Bittner patent is thus a combination patent, combining Berkemann with Stroup, Musebeck Shoe Company, and Brachman. It amounted to changing the Berkemann sandal by honing off the ridge under the big toe as advocated by Brachman and providing a slight depression as taught not only by the production model of the Berkemann sandal but also by the Stroup patent and the Musebeck Shoe Company book.

The district judge, although stating that he "had enough trouble deciding it wasn't an obvious modification of Berkemann,"9 made an oral finding that the modification resulted in "some anatomical, or therapeutic, orthopedic benefit, improvement." He later entered written findings10 that the modification was

a novel and useful combination of elements having a unique interdependent functional relationship, thereby affording a synergistic result which in and of itself was non-obvious, namely, the automatic separation of the great toe from the other four toes, resulting in some anatomical advantage and beneficial orthopedic or podiatric effects on the foot as well as promoting increased comfort.

The written findings also stated,

The differences between the prior art and the claim of the patent reside in the combination of a metatarsal crest which underlies the four lesser toes, but terminates short of the great toe, and a depression to receive the metatarsal head of the great toe, both features being provided in a contoured rigid sole block having a strap means as the sole means of retaining the sandal on the foot. That combination constitutes a patentable improvement over the prior art.

In addition the court found that the combination would not have been obvious to a person having ordinary skill in the art.11

Although we base our decision on another ground, we note that the evidence of the orthopedic usefulness asserted in the patent specifications for the Bittner modification is slight. The modification has little to do with the ostensible12 function of the patented sandal, which is to exercise the foot, because the exercise occurs through the gripping action of the toes to keep the sandal from falling off when the wearer is walking, and this occurs regardless of the position of the toes. The orthopedic effect asserted for the modification in the specifications is that, by providing "an anatomically correct positioning of the toes when the sandal is put on," the modification "prevent(s) the formation of crooked toes, and alleviate(s) or counteract(s) conditions such as hallux valgus." (Hallux valgus is "angulation of the great toe away from the midline of the body, or toward the other toes." Dorland's Illustrated Medical Dictionary 642 (24th ed. 1965).) The District Court's finding that the modification actually produced "some" orthopedic benefit apparently was based on the view that depressing the position of the big toe had "some" deterrent effect on its lateral movement. That effect was described by Dr. Larson, the only expert who testified specifically concerning the orthopedic benefit to be derived from the modification, as slight and having a "very small amount" of medical significance. The record is thus extremely weak on the issue of whether the alleged invention produces an orthopedic benefit of any consequence, but, even if plaintiff's proof on this point had been satisfactory, the patent could not be sustained for a reason to which we now turn.

Plaintiff concedes in its brief that "improved comfort alone would not have been sufficient" to entitle it to prevail on the obviousness issue, which we take to be a concession that honing off the ridge and providing a depression under the big toe to make the sandal more comfortable was obvious. Even without this concession, we would have no difficulty in reaching the same conclusion.

The obviousness of the combination of old elements for the purpose of promoting comfort disposes of the case. Patentability may not rest upon the discovery of a new use or a previously unnoticed advantage of an old structural element. General Electric Co. v. Jewel Incandescent Lamp Co., 326 U.S. 242, 247-249, 66 S. Ct. 81, 90 L. Ed. 43 (1945); Preuss v. General Electric Co., 392 F.2d 29, 33-34 (2d Cir.), Cert. denied, 393 U.S. 834, 89 S. Ct. 105, 21 L. Ed. 2d 104 (1968); Gould-National Batteries, Inc. v. Gulton Industries, Inc., 361 F.2d 912, 914 (3d Cir. 1965); Cf. Research Corp. v. NASCO Industries, Inc., 501 F.2d 358, 360 (7th Cir.), Cert. denied, 419 U.S. 1096, 95 S. Ct. 689, 42 L. Ed. 2d 688 (1974). Before the issuance of the Bittner patent, it would have been obvious to persons of ordinary skill in the sandal art to improve the comfort of an exercise sandal by lowering the position of the big toe pursuant to the teachings of Stroup and others. The discovery that the combination also had some orthopedic benefit would not make patentable that which was already in the public domain.

We therefore find the patent invalid for obviousness.

REVERSED.