delivered the opinion of the Court.
This is a suit by thé Anchor Company brought under the Act of June 25, 1910, c. 423, 36 Stat. 851, as amended July 1, 1918, c. *114, 40 Stat. 704,-705, to recover-for the infringement of Letters Patent No. 1,228,120 for a cargo beam, granted May 29,1917, to Melchior Lenke, 'and assigned by^ Lenke to Thomas E. Chappell, and by Chap-pell to the Anchor Company.
The Court of Claims first decided that the plaintiff-was entitled to recover from the United States. Thereafter the court made a second decision, on December 7, 1925, in which it found as an additional fact that through the contractors who manufactured for the United States, the United States had installed, on or before January 1, 1919, 810 cargo beams covered by the Lenke patent, and that it did not thereafter install any more; that the use of the Lenke cargo beams by the United States resulted in a saving in the expense of installation of cargo beams used by it amounting in the case of each beam to 2,000 pounds of metal, with a value of -6% cents per pound; that the single advantage which the United States gained by the use of the beams was the saving in cost of the same and the convenience resulting from their novelty.
Upon the additional findings of fact, the Government contended that the former judgment should be set aside, *338 and a. new one entered dismissing the plaintiff’s petition, for the reason that the-assignment of the claims for infringement to the plaintiff whs void and of no effect under section 3477 of the Revised Statutes. The Court of Claims on the second hearing yielded to this contention and dismissed-the petition.
A cargo beam is abeam employed in combination with .other elements to-carry th*e weight of cargo to be removed from the holds of vessels alongside a pier or wharf ahd deposited on the pier or in the warehouses fronting on the same. Such beams are old and have been used for y?1ars. The method existing prior to.this invention was the use of two channel beams, spaced several inches apart, firmly riveted together at the top and bottom by means of angle irons or plates, and rigidly affixed at either end to two uprights extending upward through the roof of the warehouse in brackets designed for the purpose. The record showed that a beam adaptable for the purpose weighed 3,300 pounds and must possess the full strength of withstanding the pull of cargo weights from’ both a vertical and diagonal angle.
Lenke conceived the -idea of substituting for the fixed beam a single I beam of about 1,300 pounds in weight. At each end of the I beam he attached laterally a strong bar by means of rivets- and'angle irons'providing holes near its upper end, through which holes he introduced pivots, thereby enabling the cargo beam to swing into any angle from which the load was applied. Lenke fastened U bolts into the .center or neutral zone of the beam to receive the hoisting tackle. The real worth of the, invention lay in the lightness of the cargo beam he used because the operator could present it so as to make the strain on the beam to be vertical even when force-was applied from an angle.
The patent was a combination patent, and in view of the prior art was-,limited to the exact terms of the *339 claims, which made it quite narrow, as its course through the Patent Office clearly demonstrated.
It is argued, on behalf of the United States, that Lenke’s invention was unpatentable because it embodied nothing more than a natural and normal modification of existing ideas. Such modifications and their advantage were all very clear after the fact; but the old beams had been in use for a number of years and a heavy weight of metal had been used when, by Lenke’s device, it was cut down two-thirds. Lenke’s cargo beam almost universally superseded the old one. • The United States used it and it was installed in nearly every pier in the country. No one else had foreseen its advantage. Lenke offered it as a solution of the problem at a minimum cost with a maximum effir ciency. The United States conceded in the Court of Claims that Lenke’s patent was novel in the sense that there was nothing in the prior art exactly like it, and that it* was useful. While thus, in a way, he improved aft existing idea, he'developed a new idea. The question of its patentability was worked out in‘the Court of Claims and all the judges concurred in upholding its validity and did not change their conclusion in the second judgment. We see no reason for differing from that conclusion. .
The Court of Claims based its second judgment against the plaintiff on the strength of section 3477 of the United States Revised Statutes, as construed by this Court in
Brothers
v.
United States,
“All transfers and assignments made of any claim upon the United States, or of any part or share thereof, or interest therein, whether absolute or conditional, and whatever may be the consideration therefor, and all powers of attorney, orders, or other authorities for receiving payment of any such claim, or of any part or share thereof, shall be absolutely-null and void, unless they are freely made and executed in the presence of at least two attest *340 ing witnesses, after the allowance of such a claim, the ascertainment of the amount due, and the issuing of a warrant for the payment thereof. • Such transfers, assignments, and powers of attorney, must recite the warrant for payment, and must be acknowledged by the person making them, before an officer having authority to take ácknowledgments of deeds, and shall be certified by the officer; and it must appear by the certificate that the officer, at the time of the acknowledgment, read and fully explained the transfer, assignment, or warrant of attorney to' the person acknowledging the same.”
In the Brothers case, Mr. Justice Pitney said the claim of Brothers for compensation for a patent he had secured by assignment could not apply to an “ unliquidated claim against the Government arising prior to the time he became the owner of the patent. Rev. Stats., § 3477.”
Counsel for the petitioner here insist that- this statement was not necessary to the decision because the conclusion in that case was clearly made to depend on the non-infringement of the patent and that the reference to section 3477 could only be regarded as obiter dictum. It does not make a reason given for a conclusion in a case obiter dictum that it is only one of two reasons for the same conclusion. It is true that in this case the other reason was more dwelt upon and perhaps it was more fully argued and considered than section 3477, but we can not hold that the use of the section in the opinion is not to be regarded as authority except by directly reversing the decision in that case on that point, which we do not wish to do.
An elaborate argument has been made to show that the section should not apply to the assignment of claims for infringements of a patent, for the reason that a claim for infringements is not a common law chose in action but grows out of rights created by the statutes covering patents, the provisions for their assignment and for suits by
*341
the assignee to be. found in sections 4898, 4919, 4921 and other related sections.
Crown Die & Tool Co.
v.
Nye Tool & Machine Works,
We come then to the question whether section 3477 and the
Brothers
case apply jo the case before us, and that requires an interpretation of the- amending Act of 1918 and its operation upon the rights of the assignee and owner of the patent and its claims for infringement. Exceptions to the general language of section 3477 have been recognized by this Court because not within the evil at which the statute aimed.
Seaboard Air Line Ry.
v.
United States, supra; Western Pacific R. R. Co.
v.
United States, supra; Goodman
v.
Niblack, supra; Price
v.
Forrest,
This Court held, March 4,1918, in
Cramp & Sons
v.
International Curtis Marine Turbine Company,
On April 20, 1918, the Acting Secretary of the Navy wrote a letter to the Chairman of the Committee on Naval' Affairs of the Senate, in which he said, referring to the Cramp case, that the Department was “ confronted with a difficult situation as the result of a recent decision by the Supreme Court affecting the government’s rights as to the manufacture and use of patented inventions, and it seems necessary that amendment be made of the Act of June 25, 1910 .... the decision is, in effect, so far as it is of importance here, that a contractor for the manufacture of a patented article for the government is not exempt, unless he is only a contributory infringer, from injunction and other interference through litigation by the patentee.
“A prior decision of the Supreme Court, that in the case of Crozier v. Krupp, had been interpreted as having the opposite meaning, and the department ¡was able up to the time of the later decision, on March 4th last, to proceed satisfactorily with the procuring of such patented articles as it needed, leaving the matter of compensation to pat-entees for adjustment by direct agreement, or, if necessary, by resort to the Court of Claims under the above mentioned act of 1910. . Now, however, manufacturers are exposed to expensive litigation, involving the possibilities of prohibitive injunction, payment of royalties, rendering of accounts, arid payment of punitive damages, and they *343 are reluctant to take contracts that may bring such severe consequences. The situation promises serious disadvantage to ‘the public interests, and in order that vital activities of this department may not be restricted unduly at this time, and also with a view of enabling dissatisfied patentees to obtain just and adequate (Compensation in all cases conformably to the declared.purpose of said act, I have the honor to request that the act be amended by the insertion of a proper provision therefor in the pending naval appropriation bill.”
In response to this communication, the Act of July
1,
1918, amending the Act of 1910, was adopted. (See
Wood
v.
Atlantic Gulf & Pacific Co.,
“ That whenever an invention described in and covered by a patent of the United States shall hereafter be. used or. manufactured by or for the United States without license of the owner thereof or lawful right to use of manufacture the same; such owner’s remedy shall be by suit against the United States in the Court of Claims for the recovery of his reasonable and entire compensation for such úse and manufacture.”
This is followed by the same provisos as in the Act of 1910, which need not be- repeated here.
The purpose of the amendment was to relieve the contractor entirely from liability of every -kind for the infringement of patents in manufacturing anything for the Government and to limit the owner of the patent and his assigns and all claiming through or under him to' suit against the United States in the Court of Claims for the recovery of his reasonable and entire compensation for such use and manufacture. The word “ entire ” emphasizes the exclusive and comprehensive character of the remedy provided. As the Solicitor General says in his *344 brief with, respect to the Act, it is more than a waiver of immunity and effects an assumption of liability by the Government, ' ■. . , .
Under the Act of 1910, the remedy of the owner of a patent where the United States had used the invention without his license or lawful right to use it, was to 'sue_ for reasonable compensation in the Court of Claims, and that remedy was open.to Lenke for the cargo beams covered by his patent installed and used by the United States' before July-1, 1918,
The evidence does not show nt what time during the year 1918 the beams were installed. _ Thé first finding is that Lenke wrote to an officer in the Quartermaster’s Department on duty at the Army supply base at Brooklyn, on December 31, 1918, complaining that the Lenke cargo beam was being used by the Government at that supply base 'without permission from the patentee, but nothing happened but a fruitless correspondence.
The findings of the Court of Claims show that, on January 1, 1919, 810 of the beams had been installed at the instance of the Government, but how many were installed after July 1, 1918, when the law in question was passed, has not been found by the Court of Claims. ■
. On September 29, 1920, the Lenke patent was assigned by Lenke to- one Thomas É. Chappell, who in turn on March 7, 1921, assigned it' to the plaintiff company, in accordance with the statute, and the assignment in each case covered all rights of action for past infringements of the patent and all rights to recoveries* by suit for damages, profits and royalties for infringements of every 'kind whatsoever.
It is settled that, b.ut for the Act of 1918, the two assignments vesting title in the Anchor Company would enable it to recover from the contractor for all his infringements
(Crown Die & Tool Co.
v.
Nye Tool & Machine Works, supra; Gordon
v.
Anthony,
*346
It is our duty in the interpretation of federal statutes •to reach a conclusion which will .avoid serious doubt of their constitutionality.
Phelps
v.
United States,
Such a conclusion requires us to reverse the case and remand it to the Court of Claims for additional findings to show how many of the patented beams were made by contractors and furnished to the United States after the passage of the Act of July 1,1918, and what would have been á reasonable royalty therefor. .
The question of the amount of or the rule for measuring the recovery we do not decide, but. leave that for further argument .and consideration by the Court of Claims, because of the novel and only, partial application of § 3477 Rev. Stat. •
Reversed and remanded.
