(after stating the facts' as above). Guide strips for precisely the same purpose as Calkins’ were indeed old in November, 1919, when he filed his first application; they are disclosed in the Swiss patent to Cassani of 1910. They left no scope for invention, except in the form of the strips themselves. Probably Cassani assumed that the patterns might be curved, though he did not so show them, but in any case that would *68make no difference, because' bis strips were of thin metal, and to bend them was at best no more than a new use of his disclosure. But Cassani showed strips without wings, or any intervals to create a bond, and Calkins certainly made a patentable advance over what he had done; indeed, we do not understand that so much is denied.
Perhaps the nearest approach to the form of Calkins’s strips was McKnight’s, disclosed as early as 1883. That, it is true, was a patent for a pavement, apparently a street pavement; but that would scarcely in itself be a sufficient distinction, if it were all. He described a concrete pavement laid in several layers, three as it chanced, in which he wished to avoid cracks. This he sought to do by dividing into square sections the two upper layers, or- it might be all three, by straight vertical strips, which were set in the lower layer, and in some eases had horizontal wings, apparently along the whole length of the strip. The strip was set in the lower layer while it was being laid, and, as its upper edge did not reach the top of the upper layer, it could make no pattern in it, which, indeed, would not have been desirable. Moreover, the wings were not struck out of the lower half of the strip, but extended along its whole length. Even had the device been used for the same purpose as Calkins’s, we should have some doubt whether these differences were not enough; but in view of the fact that Me-Knight’s purpose and his result were quite different, structural distinctions which might be trivial become crucial.
Assuming, for argument, that the law is absolute that there can be no patent for the new use of an old thing, that is because the statute allows no monopolies merely for ideas or discoveries. If the thing itself be new, very slight structural changes may be enough to support a patent, when they presuppose a use not discoverable without inventive imagination. We are to judge such devices, not by the mere innovation in their form or material, but by the purpose which dictated them and discovered their function. Certainly the art would have waited indefinitely, in the light of all that McKnight disclosed for Cal-kins’s contribution to its advance. It will not serve now to observe how easy it was, given the suggestion, to change his invention into that of the patent in suit.
Kahn’s patent of 1912 is the best anticipation after MeKnight’s. He disclosed a metal and concrete beam, in which metal was reinforced by concrete, rather than concrete by metal. So far as his patent concerned sidewalk lights, we need not pause to describe it. His nearest approach to Calkins was in Figures 5 and 6, where he showed beams set in concrete, having tabs struck out of the metal at intervals to receive transverse connecting rods. The holes so made did indeed permit a bond between the sections of concrete created by the beams, and the similarity to Calkins’s invention arises from this fact and from the form of the wings. But the resemblance stops there. The beams were wholly unfitted for use as guide strips. They had heavy flanges at the bottom, like ordinary I-beams, and the web was of solid material. They were not designed to come to the surface of the top layer of concrete, and could not be depressed into the lower; the wings did not, and could not, serve as stops to mark off the height to which the top layer was to be filled. It was to distinguish from this patent that the change in claim 1 was made, which required the slits which formed the wings to run to the lower edge of the strip. Such a distinction was quite unnecessary, and would have been ineffectual, if it had been.
Chadbourne’s patent of 1910 was for a reinforcing grid, apparently to give tensile strength to the lower part of a concrete mass laid in different layers. The grid rested on transverse strips of metal, rising about an inch above the bottom of the lowest layer; these had bases turned horizontally to hold the strip upright," one side of which was struck out of the metal which formed the upright part, leaving a space through which the concrete could form a bond. So far as we can see, this resulted in nothing, approaching Calkins’s disclosure, for such obvious reasons that we forego their statement.
Baker’s patent was also for a street pavement, laid in sections made by dividing plates of metal. The concrete was homogeneous throughout, and there was no such problem as Calkins had to meet. The plates were set in pairs, with a separating material of asphalt or the like. They had flanges at right angles to the main body, and were set at an angle to the surface of the pavement and-to each other, so as to make a slight trench at the surface, and to flare away from each other into the body of the cement, serving as anchors. The only resemblance, and that the faintest, to Calkins’s invention, lay in the fact that there were openings in the main body of the plates to allow a bond of concrete to flow through.
The only other supposed anticipation which seems to us worth notice is Del Tureo’s. This invention was, indeed, for the same pur*69pose as Calkins’s, and the differences between them well illustrate his contribution. The guide strip, set in a wooden base, was placed in position when the lower layer was made, not forced down into it. There were no wings and no openings to lock the underlying concrete. This was the best that the art had done, and it was very far from Calkins.
Thus the case is in substance familiar enough, one in which the inventor has culled this and that out of nearby arts, and so formed a combination nowhere before existing. It has been a success; it has substantially driven out earlier cumbersome methods; it has enabled the art to do with ease what before it could only do slowly and imperfectly. The result seems to us a genuine invention, and we so hold.
Little need be said of the reissue, in view of what has gone before. The learned District Judge who tried the suit at bar was, of course, quite right in seeing no substantial change between the original patent and the reissue. Accepting the decision in the first suit, he had no choice but to hold the patent void, and our difference with him is not in that conclusion, but in his acceptance of the original holding, which went, not to'the sufficiency of the claim, but to the invention as a whole. We should, indeed, agree that there was no invention in cutting the wings through to the base of the strip, if that had been all that Calkins did; that was a mere detail of design. In fact, he had no need of a reissue at all; his original claim was quite narrow enough; his first disclosure was complete; Indeed, the new claim added nothing of substance to the old. To call the strip “thin” and “flexible” was unnecessary, since that was apparent anyway. So far as the new claim comprised the functions of the strip, it was improperly drawn, though the additions were harmless.
However, though the reissue was unnecessary,. the first patent being good enough as it stood, it did no harm if the patentee timidly chose to contract his claim. What he lost by so yielding, he lost; but it did not affect what was left. Nobody could be hurt by that but Calkins himself. Thus we find it quite unnecessary to consider the points raised over the reissue. There could be no intermediate rights acquired in the face of a valid patent adequately claimed. Nor do we understand what is meant by speaking of the decision in the first suit as a final adjudication upon the patent, good as against all, unless reversed on appeal. Such a suit is in personam; it concludes the parties, and it concludes nobody ’ else. A second suit against other parties starts afresh, and the second court is free to disregard the earlier ruling, if so advised — a common event, out of which arise nearly all patent eases that reach the Supreme Court. That under the canon, stare decisis, an earlier decision will have much weight is true enough, but each court is bound in the end to exercise an independent judgment.
Penn Electric & Mfg. Co. v. Conroy, 185 F. 511 (C. C. A. 3), was a second suit between the same parties as had litigated the first. The point was res judicata in the strict sense, and the decision has "nothing to do with the case at bar.
Decree reversed, and cause remanded, with instructions to grant a decree for the plaintiff.