If it is an article he may

nal term of the patent has expired. use it until it is worn out, and repair it as long as its identity can be retained. His license, however, is not transferable like that of a purchaser of a patented article. Arising out of the relations between himself and his employee it is personal in its character, and cannot be applied to the benefit or protection of any other users of the patented invention. A corporation, whether municipal or private, has the same right to the enjoyment of the inventions of its employees as is possessed by individual employers.8

§ 833. Implied License: License to Use Inventions of Co-partner sometimes Implied in favor of the Firm.

From the relations between a partnership and its members a similar license is implied. If one co-partner makes an invention at the cost of the firm, and applies it to their common benefit, the right to use it becomes vested in the partnership, and is not affected by the retirement of the inventor from the firm. Upon the dissolution of the partnership this license

of the design until the patent expires, whether or not the employment continues, see Herman v. Herman (1886), 29 Fed. Rep. 92; 37 O. G. 892.

That if a workman uses his invention in his masters' employment without claiming it against them, they may have an implied license to use it, see Hall v. Johnson (1883), 23 O. G. 2411. 5 See Wade v. Metcalf, cited in note 4, ante.

until the devices used are used up, is implied, see Brickill v. Mayor of New York (1880), 18 Blatch. 273; 5 Bann. & A. 544; 18 O. G. 463; 7 Fed. Rep. 479.

§ 833. In Wade v. Metcalf (1883), 16 Fed. Rep. 130, Lowell, J.: (132) "The plaintiff contends that this law only applies to employers and employed. But there is no such limitation in the statute. When the plaintiff, as a mem6 See Wade v. Metcalf, cited in note ber of the firm, and at the joint expense,

4, ante.

7 That the implied license of an employer is personal, not assignable, see Hapgood v. Hewitt (1886), 119 U. S. 226; 37 O. G. 1247; Hapgood v. Hewitt (1882), 11 Fed. Rep. 422; 21 O. G. 1786; 11 Bissell, 184.

8 That where the employee of a city invents a device, and uses it on machines belonging to the city before his application for a patent, a license to the city to continue its use on such machines,

made and altered these machines, and permitted their use by the firm, how does he escape the statute by being himself one of the firm? The law was applied without hesitation to a case of this kind in Slemmer's Appeal, 58 Pa. St. 155. Again, the plaintiff contends that if the statute has any application, it only grants a limited and personal license to a certain legal individual called a firm, which ends when the firm ends. But the section in question describes in

terminates; though where the patented invention is an article, and several having been constructed at the firm's expense are at its dissolution distributed among its members, each has the right to use the article conveyed to him, as if the partnership were still in being. A license of the same character arises in favor of a corporation, one of whose members is the owner of a patented invention, if he knowingly permits its employment in their business, and receives his proportion of the benefit to be derived therefrom.8

§ 834. Implied License: Licenses Arising by Estoppel: Implied

Licenses, how Construed.

Besides these special cases, which are of definite character and frequent occurrence, an implied license may arise out of any circumstances which operate as an estoppel on the owner of the patent to prevent him from denying the rights claimed by the apparent licensee.1 Such circumstances must, however,

unmistakable language a complete and perpetual release of the specific articles from the monopoly."

That under circumstances like the above a license is implied in favor of each member of the firm, see Wade v. Metcalf (1883), 16 Fed. Rep. 130.

2 That where one partner invents a device and permits the firm to use it, this is no implied license to a member of the firm to increase the number used after the firm is dissolved, although the firm paid the expense of procuring the patent, if the firm received from it a benefit greater than the expense, see Keller v. Stolzenbach (1884), 20 Fed. Rep. 47; 27 O. G. 209.

That where one member of a firm patented a design and used it in the firm's business, an implied license arose to use the design till the firm dissolved, and after dissolution to sell, by receiver or otherwise, all existing devices embodying such design, see Montross v. Mabie (1887), 30 Fed. Rep. 234; 41 O. G. 931.

members as if it were a licensee, is licensee until the firm can close up its business, and if a receiver is necessary for that purpose, he will be a licensee, see Montross v. Mabie (1887), 41 O. G. 931; 30 Fed. Rep. 234.

That articles made under an implied license to a firm may be sold by any one of the partners after dissolution for the benefit of the firm, see Montross v. Mabie (1887), 41 O. G. 931; 30 Fed. Rep. 234.

That articles used by a firm under an implied license from one of its members, and afterwards distributed among the partners at the dissolution of the firm, may be used by them in like manner, see Wade v. Metcalf (1883), 16 Fed. Rep. 130.

8 That where the members of a corporation own patents, and permit the corporation to use the patented devices without objection, a license will be implied, see Detweiler v. Voege (1881), 19 Blatch. 482; 8 Fed. Rep. 600.

§ 834. 1 That a license may arise by That a firm, dealing with one of its estoppel, see Gear v. Grosvenor (1873),

be unequivocal and fulfil the ordinary requisites of an estoppel in pais. An acquiescence in known infringements does not authorize their continuance, nor does a judgment for past infringements license the infringer to practise the invention in the future. An unmolested use during a defective patent affords no presumption of a license under the re-issue. But any conduct by which the owner of the patent induces the person who employs the invention to place himself in a situation where he must suffer injury unless his right to practise the invention is conceded will be regarded as implying such a right, and as estopping the owner of the patent from asserting his prohibitory powers in its defeat. An implied license is construed primarily according to the legal rules under which it arises out of the circumstances or relations of the parties; and subject to these rules, by the evident intention of the licensor and licensee.

6 Fisher, 314; Holmes, 215; 3 O. G. 380; Reutgen v. Kanowrs (1804), 1 Wash. 168; 1 Robb, 1.

2 That a license is not implied from the mere failure of the patentee to sue for infringements, see City of Concord v. Norton (1883), 16 Fed. Rep. 477; McWilliams Mfg. Co. v. Blundell (1882), 11 Fed. Rep. 419; 22 O. G. 177.

That no license is implied from a judgment for damages for past infringe ment, see Hayden v. Suffolk Mfg. Co.

(1862), 4 Fisher, 86; Earle v. Sawyer (1825), 4 Mason, 1; 1 Robb, 490.

3 That a use under a defective patent does not imply a license to use under a renewed patent, see McWilliams Mfg. Co. v. Blundell (1882), 11 Fed. Rep. 419; 22 O. G. 177.

4 That an implied license is construed according to the circumstances of the case and the evident intention of the parties, see Montross v. Mabie (1887), 41 O. G. 931; 30 Fed. Rep. 234.

VOL. II.-41

CHAPTER VI.

OF THE EXTENSION OF LETTERS-PATENT.

§ 835. Extension of Letters-Patent: Origin and History of Ex

tensions.

FROM the earliest history of Patent Law the fact has been recognized that through various causes an inventor may fail to obtain an adequate recompense for his inventive skill during the original term of his patent, and that justice to him and a due regard to the public interest may thus sometimes require an extension of his monopoly in the invention. The ancient crown grants were on this account frequently renewed after the expiration of their original terms, and though for a long period after the statute of James I. no such increase of the patent privilege was permitted by the laws of England, yet with the development of industrial enterprise in the first quarter of this century the importance of additional protection to the inventor became so apparent that Parliament in 1835 expressly provided means for extending letters-patent, at first for seven and then for fourteen years. In this country the propriety of such extensions in special cases has always been conceded, the principal variations in our law relating to the tribunal in which the authority to grant extensions should reside. Prior to the act of 1836 this power was lodged in Congress, by whom alone the original term of the monopoly could be prolonged. In 1836 jurisdiction over the renewal as well as the first issue of letters-patent was conferred upon the Patent Office, subject to numerous restrictions as to the grounds of renewal and the duration of the extended term. In 1861 this jurisdiction over extensions was withdrawn as to all patents granted after the passage of that act, and Congress thus became the only source from which an increase of the monopoly created by future patents could

be obtained. This is the present state of the law, the Patent Office having authority to renew a patent issued before March 2, 1861, and acting as an examining and advisory tribunal concerning the extension of later patents when the existence of the conditions precedent to such extension is submitted to its judgment by a special act of Congress. Occasions for the exercise of its former power cannot now arise; and an exposition of the current law upon this subject might therefore leave unnoticed those peculiar doctrines which apply only to extensions granted by the Office when having general jurisdiction under provisions similar to those of 1836. Inasmuch, however, as Congress may at any time restore this jurisdiction, and when restoring it will probably preserve unchanged the leading characteristics which it previously possessed, this aspect of the law will also be considered in connection with the rules now practically in force.

§ 836. Extension: to Whom Granted.

As the sole object of an extension is to furnish to an inventor an additional opportunity to secure the recompense which he has hitherto failed to obtain, so no extension will be granted unless the inventor is to enjoy at least a substantial portion of its benefits. It is not necessary that the legal title to the extended patent should vest permanently in him, for he may already have contracted to convey this to another; but even here the consideration for the transfer must be reasonable in amount or the purpose of the extension will fail, and the extension itself will consequently be refused.2 extension it will be refused, see Ex purte Peberdy (1872), 2 O. G. 644.

§ 835. 1 That under Sec. 16, act of 1861, no future patents can be extended, see De Florez v. Raynolds (1880), 17 O. G. 503; Fed. Rep. 434; 5 Bann. & A. 140; 17 Blatch. 436.

§ 836. 1 That an extension is for the benefit of the inventor, see Case v. Redfield (1849), 4 McLean, 526; 2 Robb, 741.

That no extension will be granted unless the inventor is to profit by it, see Ex parte Baker (1872), 1 O. G. 632. That when the patentee is to receive but five per cent of the benefits of the

2 That an extension may be granted. to an inventor who owns an interest in the patent, see Ex parte Woodman (1872), 10. G. 550.

That the patentee's interest in the extension may be equitable only, see Gear v. Grosvenor (1873), 3 0. G. 380; 6 Fisher, 314; Holmes, 215.

That a patent will not be extended where the assignees are to reap the entire benefit, see Ex parte Munger (1873), 3 O. G. 323.