This appeal concerns the validity of patent No. 2,807,659, a tube shield and insert designed for protecting glass electron tubes. Cool-Fin Electronics Corporation (Cool-Fin), a now defunct manufacturer of tube shields, originally sued the International Electronic Research Corporation (IERC) for violations of the antitrust laws. IERC counterclaimed that Cool-Fin had infringed its patent. The district court tried the patent issue separately and held the IERC patent invalid, reasoning that it was anticipated by the prior art under 35 U.S. C. § 102 (1970) and that it would have been obvious to one of ordinary skill in the field under 35 U.S.C. § 103 (1970). IERC appeals, and we reverse.
Tube shields are metal covers used to surround electron tubes. Following World War II, electronic equipment, especially military equipment, was notoriously unreliable due largely to breakdowns in electron tubes.1 Overheating of the tubes was a major cause. Vibration of the tubes, caused by the operation of the high-powered equipment to which the tubes were attached, was also responsible. Existing tube shields did not solve these problems. Despite expert efforts, no one had produced a reliable shield when the IERC apparatus was devised in 1952.
The patent in suit, issued in 1957, adequately remedied these deficiencies, as its commercial success confirmed. It utilizes a sheet metal insert, placed between the tube and the shield, with numerous leaf springs (flat pieces of tense metal cut out of the main sheet and appearing, aptly, like leaves) arranged in longitudinal and circumferential rows. These springs contact the glass bulb, holding it firmly in place, thereby dampening vibration. The springs provide curved contact with the tube, resulting in effective conduction of heat from the surface of the tube outward to the shield and thence to the chassis of the machinery to which the shield is secured, thus dissipating heat. The advantage of the patented device—and its alleged patentable feature—is the area contact provided by these arcuate leaf springs.
We need not discuss the prior art in detail. It is sufficient to note that there were a number of previously patented tube shields almost all of which are clearly different in conception and effectiveness from the patent in suit. The closest analogue to the IERC device is the Dickinson patent, No. 2,673,721.2 In this, a few coil springs (conventional wound wire springs) are inserted in a shield. The springs encircle the tube at its central region where the wire coils of the springs contact the tube at spaced points.
Anticipation
The trial court apparently found that the area contact concept of *662the IERC leaf spring insert was not contained within the four claims of the patent in issue—claims 3, 13, 14, and 15. Claims are to be read liberally. See, e. g., Smith v. Snow, 294 U.S. 1, 14, 55 S.Ct. 279, 79 L.Ed. 721 (1935). Drawings and specifications in the patent’s file folder history, while not available to enlarge a patent claim, can explain an ambiguity. See, e. g., Illinois Tool Works, Inc. v. Brunsing, 389 F.2d 38, 40 (9th Cir. 1968). In light of these principles, we find that claims 3 and 15 3 properly state that a novel feature of the IERC device is its use of leaf spring (area) contact.4
Alternatively, though the trial court’s findings are ambiguous, the court seems to have held that even if the area concept was incorporated in the claims, the patent was still anticipated by the Dickinson device. This was clearly erroneous. It has been oft-repeated that “anticipation is a strictly technical defense. Unless all of the same elements are found in exactly the same situation and united in the same way to perform the identical function in a prior pleaded patent, there is no anticipation.” Stauffer v. Slenderella Systems, Inc., 254 F.2d 127, 128 (9th Cir. 1957).5 There is a major element in the IERC device not present in the Dickinson apparatus: the use of leaf springs to provide area contact. That cannot be said to be a combination of the same elements in the same way. See The Barbed Wire Patent, 143 U.S. 275, 12 S.Ct. 443, 36 L.Ed. 154 (1892); Kockum Industries, Inc. v. Salem Equipment, Inc., 467 F.2d 61 (9th Cir. 1972), cert. denied, 411 U.S. 964, 93 S.Ct. 2140, 36 L.Ed.2d 684 (1973). Furthermore, there was no evidence that the Dickinson device produced similar results—-facts that would indicate similarity of operation. Indeed, all the evidence showed the IERC apparatus to produce dramatically improved results.6
Obviousness
As to obviousness, we think the trial court was also clearly in error. One of the inquiries necessary for such a finding is whether the alleged invention would be obvious to one of ordinary skill7 in the art. Graham v. John Deere Co., 383 U.S. 1, 17, 86 S.Ct. 684, 15 L.Ed.2d 545 (1966). Yet the evidence shows that others skilled in the field, no*663tably military researchers, had been unable to find a satisfactory solution to the problem of electron tube failures. This is a weighty indication that at the then level of skill as to tube covers, the patented discovery was not obvious. See Reeves Instrument Corp. v. Beckman Instruments, Inc., 444 F.2d 263, 272 (9th Cir.), cert. denied, 404 U.S. 951, 92 S.Ct. 283, 30 L.Ed.2d 268 (1971); Neff Instrument Corp. v. Cohu Electronics, Inc., 298 F.2d 82, 87 (9th Cir. 1961). Neither do the Dickinson patent’s teachings support a finding of obviousness. Although Dickinson teaches the use of springs, they are structurally distinct, are not designed to dampen vibration, and provide merely point contact with the glass tube.
Certain secondary considerations, see Graham v. John Deere Co., 383 U.S. at 17-18, 86 S.Ct. 684, support our conclusion. The IERC shield fulfilled a long-felt need. Moreover, it was an undoubted commercial success.
Left, as we are, “with the definite and firm conviction that a mistake has been committed,” United States v. United States Gypsum Co., 333 U.S. 364, 395, 68 S.Ct. 525, 542, 92 L.Ed. 746 (1948), we reverse the trial court’s ruling of invalidity.8
As to Cool-Fin’s claim to an attorney’s fee in connection with IERC’s ’108 patent counterclaim which IERC dropped and which the district court dismissed with prejudice, we do not find clearly erroneous the district court’s finding that it was not of such character as to make it an exceptional case within the meaning of 35 U.S.C. § 285 (1970).
Since the issue of whether Cool-Fin infringed the IERC patent has not been decided, we remand for further proceedings.
Reversed and remanded.