(dissenting in part).
*644Defendant mounts on a disc affixed to the crankshaft six bifilar pendulum bal-ancers, the multiple number being so provided and designed as to eliminate vibrations of different frequencies. Each one of these pendulum rolls around with the disc and the crankshaft and, at the same time, oscillates to and fro according to the laws of centrifugal force. For each balancer two holes about 2 inches apart are drilled in the disc and two corresponding holes of oversize and larger than those in the disc are drilled through the balancer. In each of the two holes on each disc is placed a steel roller and on these two rollers the balancer’s two over-size holes are hung, thus affording opportunity for oscillation of the balancer on the two suspension points of the pendulum. Thus I think it is undisputed that each unit constitutes a bifilar pendulum balancer, which rolls and oscillates freely without substantial friction. I think it perfectly obvious from examination of this device that it works according to the same physical law, in the same mechanical manner and produces the same result as the pendulum rolling weight disclosed in the Salomon patent. The result is a substantially frictionless centrifugal pendulum balancer. It includes pendulum masses which roll on rollers along arcuate guideways eccentric to the axis of rotation of the main shaft, relatively free of friction. This damper, as Salomon’s, balances its vibratory thrusts against those of the disturbing impulses. Each is capable of being tuned to an order and automatically remains tuned to that order at all speeds of rotation of the crankshaft. Each is substantially frictionless. Defendant, I think, employs Salomon’s means for damping oscillation in a rotatable shaft, “comprising a part fixed to and rotatable with such shaft; said part being provided with at least one arcuate guideway the center of curvature of which is eccentric to the axis of rotation of said shaft and a structurally integral damping mass freely movable substantially frictionlessly along said gu'ideway, in the direction of and in response to shaft vibrations and in response to centrifugal force” in the words of Claim 8. The device seems to me equally applicable to the language of the other claims in suit.
The District Court reached its conclusion of no infringement upon the sole ground, apparently, that Salomon is limited to a unifilar construction and that, inasmuch as defendant employs a bifilar construction, it does not infringe. It was the difference between bifilar and unifilar construction which the court believed to be decisive. But I can not agree that the language of the claims justifies a conclusion that Salomon’s invention was limited to unifilar construction and that, therefore, any device which did not employ unifilar construction could not infringe. It is clear that the use of both unifilar and bifilar pendulums was old and that any engine designer, in deciding what balancer he would build, had the option of choosing either bifilar or unifilar pendulums. This was the skilled workman’s choice, well known to the art. Salomon’s invention lay essentially, not in the choice of one of the two kinds of suspensions, but an entirely different thought, the free rocking substantially frictionless movement, whichever type was used. He was not inventing a bifilar or a unifilar balancer. He was prescribing the essential elements an efficient and successful pendulum balancer should have. Invention could not lie in the choice of the one of the two old forms of suspension, and Salomon did not pretend that his invention lay in any such prescription. It lay entirely in his inventive idea applied to either form of pendulum. This is clear from the contents of the file-wrapper. True it is that Salomon, through his agent Robissow, expressed disbelief in the efficiency of the bifilar construction, but he complained at all times that devices which employ a bifilar construction infringe. “It is,” he said in effect, “an infringement, whatever method of suspension or whatever principle of suspension is involved.”
The trial court found also that Chenard in his French patent of 1927 discloses “a substantially frictionless bifilar pendulum.” I think the Chenard patent omits any teaching of the necessity of the reduction of friction to a minimum and, indeed, *645Judge Bright, in the Sarazin case, in D.C., 54 F.Supp. 244, 247, expressly so found, and the Circuit Court of Appeals, on appeal in Clark v. Wright Aeronautical Corp., supra, approved. In view of those decisions, I shall not elaborate upon their reasoning in this respect except to observe that Judge Bright said, in Sarazin v. Wright, “it depends upon friction for its reactional effect.”
The District Court found that Carter’s British patent of 1930 discloses a construction “substantially like that of the Pratt & Whitney engine put out prior to 1935.” But Carter’s idea was to obtain friction. Indeed, he said the desired effect could be obtained by “solid or fluid friction” or by internal friction. Frictional restraint is a part of every form of embodiment suggested by Carter without any hint of tuning the balancer to suppress any particular kind or order of vibration. The complete specifications clearly show that he was working solely in the art of friction-impeded pendulums, none of which achieved the results of Salomon. Judge Bright said that his patent clearly taught friction as the solution, and this interpretation, I think, was correct. The prior art disclosed both unifilar and bifilar devices, but none of it revealed a substantially frictionless damper, such as Salomon’s or defendant’s.
The trial court found that Salomon’s invention is “characterized” by the presence of a stubshaft which so limits the mass of the roller as to be incapable of accomplishing the results accomplished by defendant’s bifilar damper. I think this is a gratuitous finding beyond the scope of what is essential to the achievments of Salomon’s patent. The so-called stubshaft appears in the figures accompanying the patent, which show a round piece of material in the center of the track around which the roller travels in its free movement. The roller is not in contact with the stubshaft in normal operation and the latter serves only to prevent the roller from falling against the walls of the container whenever the motor stops. There is a small clearance between the central part, the so-called stubshaft, and the periphery of the container and the roller is smaller than that clearance so that there is sufficient leeway. The stubshaft may serve a useful purpose, but it is unnecessary to a complete realization of Salomon’s invention and detracts in no wise from rolling or rocking freely and unrestrictedly on a curved guideway. Defendant’s expert witness testified that it would not require invention to remove the stubshaft, saying that it would depend upon engineering judgment or mechanical skill. The stubshaft is described in Qaim 12 but is omitted from other claims. I think it is not an essential element in Salomon’s set-up. Furthermore, “where a patent contains both a broad and a narrow claim and suit is brought on the broad claim, we cannot construe into it a limitation not therein expressed, but which is expressed in the narrower claim and by which alone one is distinguished from the other. To do so would be making over the contract between the public and the patentee.” National Tube Co. v. Mark, 6 Cir., 216 F. 507, 521.
I reach the question of estoppel. Whatever Rubissow said, I agree, the patentee became responsible for. Though Rubissow testified that he was reprimanded for acting beyond the scope of his authority, he was permitted to appear and act for Salo-mon. Secret limitations upon his authority in representing his principal may not be invoked against third persons with whom he dealt in pursuance of his apparent authority. Indeed, plaintiffs, as I understand their position, do not contend otherwise. So Salomon is bound by whatever Rubissow said in his transactions in behalf of his principal.
Fortunately all of Rubissow’s statements upon which defendant relies were in writing, and this court’s duty in this respect becomes one of determining from the four corners of the documents just what he conveyed by express statement and inevitable implication.
In effect defendant contends that Rubis-sow effectually limited Salomon’s invention, in the proceeding before the patent office and in communications to defendant, to devices of unifilar character and, for all practical purposes, disclaimed bifilar devices. In doing so, defendant relies upon such express statements as: “Mr. *646Salomon is in no way interested in the principle of twofold suspension, which, in his opinion is uselessly complicated * * * is not interested in bifilar suspension, * * * has a more simple solution * * * for the reduction of high frequency oscillations, * * * leaves the bifilar suspension to others,” as “a useless and injurious complication.” Standing alone these quotations from voluminous documents might well sustain defendant’s contention. But the precise intent of Ru-bissow and its effect in patent law must be deduced from an examination of all he said. In all his writings Rubissow was insisting that Salomon was the first to teach and put into practice the thought “that the use of free or quasi-free suspended masses” successfully reduces to a minimum “oscillation vibration and torsion irregularities in rotary shafts axial or torsional * * * by means * * * of the centrifugal forces acting with” or “applied to said masses” during the motion of the shaft. This, said he repeatedly, was without restraint by springs or connecting rods so that the masses moved freely with a minimum of friction. “Each rolling body,” said he, “rolls * * * on a guiding surface which is solidary with the shaft” and “constitutes a rolling surface for a second body.” This teaching of Salo-mon, Rubissow expressly claimed, was infringed by Sarazin, Reed, Wright, His-pano, Taylor and Chilton, all of whom, the record discloses, employed bifilar suspension devices. Directly following his statement that Salomon preferred a unifilar construction, he added “But Salomon attacks Wright and Hispano because they obtain their suspension by using the fundamental characteristics of the Salomon patents.” It seems perfectly clear that Rubis-sow was continually and constantly insisting that the bifilar devices mentioned infringed Salomon not because they were bifilar in character, but in spite of that fact, and because, in each of the bifilar devices, the designer availed himself of Salomon’s elemental discovery. He pointed out that use of bifilar devices was old in the art. In effect, he said that Salomon did; not object because the builder employed bifilar construction, for he (Salomon) believed that the choice between unifilar suspension and bifilar suspension was one within the option of the skilled designer; that both methods were old, but that if the designer of either a unifilar or bifilar construction employed Salomon’s essential principles, he infringed. He attributed some such language as this to Salomon. “I don’t care which kind of suspension you employ, uni-filar or bifilar, but if you employ my inventive idea, you infringe.” This seems perfectly obvious from the documents in evidence. And I agree that bifilar suspension was old in the art, that anyone was free to employ it and that if the skilled designer saw fit to employ bifilar suspension instead of Salomon’s preferred unifilar idea, he could not escape infringement, if he made use of Salomon’s essential inventive idea as expressed in his claims.
This, I think, is a far cry from estoppel; it possesses none of the essential elements. Nor can it be interpreted as a limitation of the claims so as to include only unifilar devices and to exclude those which employ bifilar suspension. It is merely a statement that Salomon does not consider the choice between the two methods of construction an essential element of his invention.
The District Court found that all claims in suit were inserted in Salomon’s application after the accused Allison damper was being manufactured and sold. However, the court did not find that the substance of these claims was then asserted for the first time. Upon examination of the file it appears that the essence of each claim in suit appears in the claims as they were originally filed; that there was continuity of the same inventive idea from the time of the filing of the original application until the patent finally issued and that there was no material deviation from or expansion in the subject matter. Consequently, interpretation, as well as validity, is to be tested as of the time of the original application. Crown Cork & Seal Co. v. Ferdinand Gutmann Co., 304 U.S. 159, 58 S.Ct. 842, 82 L.Ed. 1265; Ceramic Process Co. v. General Porcelain Enameling & Manufacturing Co., 7 Cir., 129 F.2d 803.
I would reverse the judgment with directions to find the claims valid and infringed and to order an accounting as prayed.