But the court, when acting upon other cases, has not given a patentee even this period of two years from the date of the original patent to enlarge his claims by reissue so as to protect his real invention, for in the case of Coon v. Wilson, 113 U. S. 268, 28 L. ed. 963, a reissue with an enlarged claim was held to be void, although the application for the reissue was filed less than four months after the issue of the original patent; and in the case of Yale Lock Mfg. Co. v. Berkshire Nat. Bank, 135 U. S. 342, 34 L. ed. 168, the reissue with an enlarged claim was held to be void, although the application for the reissue was filed only thirteen days after the issue of the original patent.

These late decisions of the Supreme Court as to the period within which a reissue with an enlarged claim should be applied for are not only at variance with the earlier decisions of the same court as we have previously shown (93), but are in conflict with the reasonable dictum of a former Chief Justice (Taney) of the same court, who, while holding that a patentee should apply within a reasonable period for the reissue of a patent that was defective by an error which arose from inadvertence, accident, or mistake, also held that the period should be "within a reasonable time after he discovered it." Knight v. Baltimore & O. R. Co., Taney, 106.

§ 102. Reasonable Period for Reissue.

It is no doubt in accordance with equitable considerations that a patentee who knowingly permits others to use a part of his original invention which has not been claimed in his original patent, and does not apply for a reissue within a reasonable period after such knowledge has come to him, should be held to have forfeited his

right to a reissue with an enlarged claim covering the part so unclaimed in the original patent. But the question still remains, what is such reasonable period? The law (§ 4886) as to the effect of a public use of an invention before the application for a patent is filed, fixes the period within which the application must be filed at not exceeding two years from the first public use. By analogy it may seem reasonable to the courts that a period of two years would be a reasonable period within which a reissue with an enlarged claim must be applied for; but if that is to be the period, it should not date from the date of issue of the original patent, but, like that of public use before the application for the original patent, should date from the first public use by an unauthorized party of the unclaimed part of the invention of the patentee subsequently grasped by the enlarged claims of the reissue. Such first public use by another party might happen years after the grant of the original patent, and it is not at all likely that it would occur to any patentee that his patent was inoperative to protect his whole real invention until such public use of it was made by another.

To fix the period even at two years from the date of first public use by a party unauthorized by the patentee would in many cases be unjust to the latter, because the best counsel he can employ may advise him that his original claim is operative and sufficient without reissue; and yet the court may take a contrary view; so that the patentee may not be able to ascertain whether a reissue with an enlarged claim is or is not required to make his patent operative to protect his full invention until after an action under the patent has been had and a decision rendered by the court of last resort.

§ 103. Reasonable Period for Reissue with Reduced

Claims.

What would be a reasonable period within which an application must be filed for the reissue of a patent with an enlarged claim is not necessarily reasonable for a reissue with a reduced claim; because in the latter case it is as a general rule impracticable to know whether the claims of the original patent are or are not too broad in scope until either a suit under it has been prosecuted and evidence has been put in as to the previous state of the art, or often until a decision has been rendered by a court of last resort, because the patentee and his counsel may be of the opinion that the claim when properly construed is not too large in scope, while the court may decide to the contrary.

In the case of a disclaimer it has been held that a disclaimer applies to a cause in suit, even if filed after all the testimony in such suit has been taken, and that the suit may be proceeded with (Tuck v. Bramhill, 6 Blatchf. 95); and although a patent cannot be reissued during the pendency of a suit, it certainly would not be reasonable that a patentee should be expected to reduce the scope of his claims until a reasonable period after it has been shown that his original claims are too broad and include more than he invented. What such reasonable period may be must depend upon the circumstances of each particular case, and cannot equitably be fixed by rule.

104. Equitable Right of a Manufacturer before Reissue to Continue to Manufacture Subsequently.

It has been urged that when a patentee has failed to claim in his original patent the full invention which he made, and when another party, unauthorized by the

patentee prior to the reissue of the patent with an enlarged claim, has engaged in the manufacture of articles containing only the part of the invention unclaimed in the original patent but reclaimed in the reissue, it is not equitable that such other party should have his business stopped by the reissue, and that the reissue with the enlarged claim should be void because it was delayed until after such other party commenced manufacturing. This objection is in substance the same as the proposition that the part of the invention unclaimed in the original patent is dedicated to the public; but assuming that the proposition is equitable as respects the party who has innocently engaged in the manufacture prior to the reissue, does it follow that it is equitable to the patentee as respects the rest of the public? We think that it should not be so held. When an inventor permits another party to use his invention prior to filing his application for a patent (that is for the original patent) it has been held that such permit amounts in substance to a license to such party, permitting him to continue to use the invention subsequent to the grant of the patent. McClurg v. Kingsland, 42 U. S. 1 How. 202, 11 L. ed. 102. In like manner, it would appear to be equitable that a patentee who by delay in applying for a reissue with an enlarged claim permits another party to engage innocently in the manufacture of an article which does not infringe the original patent, but embodies only the part of the invention unclaimed therein and subsequently grasped by the enlarged claim of the reissue, should be held to have licensed such other party to manufacture, use and vend for use the unclaimed part of the invention, and to continue to do so after the reissue. But as respects all other parties, the reissue

patent should be held operative and valid. Such a construction of the law would be equitable to the patentee as well as to the party who has engaged innocently in the manufacture of the part unclaimed in the original patent previous to the filing of the application for the reissue.

105. Frequent Course of Infringing Manufacturers.

The words "engaged innocently" in the last preceding section have been used advisedly, because it rarely happens that such is the fact, as the following is a very common case: A patentee of a really valuable invention takes out his patent and, often with great difficulty, gets it into use, and proves it to be of great practical value so that it attracts the attention of manufacturers of articles of the same class. Some one of these, perceiving that a large profit can be had from the manufacture, lays the patent before his counsel and expert for the purpose of ascertaining whether he can possibly manufacture a rival article possessing the valuable qualities of the patented one without infringing the claims of the original patent, which frequently are inoperative to protect the full invention made by the patentee. If the report of the counsel and expert are favorable, the manufacturer at once engages in the manufacture, trusting to the later practice of the United States Supreme Court to declare a reissue of the patent with an enlarged claim invalid, although such claim covers as a matter of fact no more than exists and was new in the article described, or represented in the drawings or model or sample of the original patent when compared with the state of the art at the date of the application therfore. It can hardly be said that the manufacturer who persues