delivered the opinion of the court.
The defences set up to the complainant’s bill for an infringement are, that the patent is void for want of novelty in the invention, and for want of utility, and also that it has not been infringed by the defendant.
To determine how far these defences are sustained it is important to have a clear apprehension of the state of the art when the patent was granted, and of the invention which it was intended to secure to the patentee. Prior to the 2d of August, 1847, cast-iron railroad wheels had been cast, and cast in chills, that is, they had been cast in sand moulds with an outer circumference of iron. The effect of this outer circumference was to produce a more rapid chill on the periphery of the wheel, thereby crystallizing and hardening it, so that the. wheel was made stronger, and more capable of .resisting the friction of the rails. But the parts of the wheel were of different thicknesses. The hub and the rim were much thicker than the plate which connected them,, and of course they cooled after casting more slowly than the plate. The consequence of this puequal cooling was to produce a strain between the thick and thin parts that greatly impaired the strength of the wheel. Yarious devices had
If now we proceed to inquire what Whitney’s alleged invention was, as described in his specification and claim, it will be seen chat it was a process, not to make, a car-wheel or to destroy any of the advantages which had already been secured, but to add another. Its avowed object was to obtain a new value, or rather exemption from imperfection. It was to remedy the evil of strain resulting froto the more, rapid cooling of out? part of the wheel than the cooling oí the other parts. And this was sought to be accomplished by a process that insured the cooling of all parts, both the thick and the thin, with equal slowness. The process consists of several parts. The first is taking the wheels from the moulds after the melted iron has been run into the moulds, before they become so much cooled as to produce strain on any part sufficient to impair their ultimate strength. The second is placing the wheels immediately after their removal in a furnace or chamber previously heated to about the temperature of the wheels when taken from the moulds, the heat in the furnace being subject to control. The third is applying heat until the temperature of all parts of the wheels shall again be raised to the same point (indefinitely said to be a little below that at which fusion commences). The fourth and last stage in the process is allowing the wheels after they have been thus reheated, to cool so fast as, and no faster than, is necessary for every part of each wheel to cool and shrink simultaneously together, and no one part before another. It is therefore a patent for a process, not for a combination. Neither as a whole nor in parts can it be considered without reference to the ultimate object in view, which was to retard cooling by a second application of heat supplied until all parts of the wheel are raised to the same temperature, and then permit the heat to subside so gradually that the cooling of the parts shall not only commence at the same point of temperature, higher than that where hurtful strain begins, but shall continue
The validity of the invention is next assailed for the reason that the process described in it, and claimed, is denied to be useful, because it would destroy the hardness of the rim, or tread of the car-wheel known as the chill, and thus greatly detract from the durability and usefulness of the wheels.
It is undoubtedly true that a chilled periphery or tread is essential to the usefulness of a car-wheel. Indeed, the evidence is, that whenever car-wheels are spoken of, wheels with chilled tread are meant, and any process which destroys the chill must render them valueless for the purposes for which thcy are needed.
It is also true that the fusing-point of cast iron is in the neighborhood of 2786 degrees of Fahrenheit, twelve or fifteen hqndred degrees above the point at which, according to the evidence, the chill of the tread óf a car-wheel would be destroyed. If, therefore,- the process patented to Whitney, requires, after the removal of the wheel to the heated furnace or chamber, the application of a degree of heat closely approximating the point of fusion, it must be conceded that instead of being beneficial it is positively hurtful. And this is what is contended by the appellant. The objection seems to be aimed at the sufficiency' of the description of the
Now, any one skilled in making cast-iron railroad car-wheels in view of this specification must see that the object of the process is to relieve from and guard against hurtful strain, without destroying the chill, and that heat is applied ouly for that purpose. It requires no particular science of skill to enable an operator to perceive that the moment all parts of the wheel are raised from a point above where serious strain begins, and where yet the thick and .thin parts are n different stages of cooling', to a stage where the degree ot temperature of all parts is the same, and above the degree where serious strain commenced, the thing sought has been attained. Then the avowed purpose of the inventor has been accomplished. It would be most unreasonable to read the directions' of the specification without reference to the object which they profess to have in view. The evidence is that the chill is formed while the casting is in the mould, and that the hurtful strains commence after the formation of the chill. Indeed, it is manifest there can be no strain until the chill is complete. It must be, therefore, that all the heat which is needed to relieve from the strain is that which suffices to raise the temperature of the thin part, or plate, to the degree at which the strain commenced — a lower
And we do not think it a fair construction of the patentee’s language to hold that it requires the heat to be raised in all cases to a degree only a little below the point of fusion. He does not attempt to give any more definite direction than that all parts of the wheel must be raised to the same temperature, suggesting in a parenthesis (“say, a little below that at which fusion commences”). He fixes a maximum. The heat must not reach the point of fusion, and the prescribed minimum, is that degree where the heat of the different parts of the wheel is equal. Within those limits the degree is left to the judgment of the operator, and withiu those limits it is clear from the evidence that the process may be applied without injury to the chill. The proof is that it has been successfully applied in the manufacture of a vast number of wheels, and that failure has been very rare.
There are some witnesses who have testified that the Whitney process, as they understand it, would destroy the chill of the wheel. But they explain their understanding to h- chat the wheels are to be reheated to a degree far beyond what is required to relieve from strain, and thus heated for no purpose. They keep in sight the maximum limit., and approach near to that, overlooking entirely the minimum, and disregarding the single object of the process, namely, relief of the plate, or thin part of the wheel, from the strain caused by unequal contraction.
We are, therefore, of opinion that the patent is not void for want of utility, and that the specification sufficiently describes the process invented and claimed.
The remaining defence is a denial that the process conducted by the defendant is an infringement of Whitney’s patent.
What the process'of the defendant was is clearly set out
It hardly seems necessary to resort to the opinions of experts in order to reach the conclusion that the process of the defendant is only formally different from that of Whitney, while the essential element of the two processes is the same. But the testimony of the experts examined, taken as a whole, clearly supports such a conclusion. It is true some-of the ■witnesses testify that in their opinion the processes are different, but when they’ attempt to describe the difference they point out only matters which are merely .formal,' only variances in the mode of using the same process. On the other hand, several witnesses, entirely competent to apprehend the principle of the invention, and the devices for practically using it, have testified that the processes of the defendant and of the complainant are substantially the same in principle, mode of operation, aud in the effect produced. We must, therefore, conclude that the charge of infringement made in the bill has been sustained, and that the complainant was entitled to a decree for an injunction and an account.
We come next to the consideration of the account stated by the master and confirmed by the Circuit Court.
The master reported that Mowry, the defendant, used Whitney’s process in the manufacture of 19,819 wheels, and the account has been stated on that basis. For the.use of the process in making these wheels the defendant has been charged with $91,501.86 as profits made by him (more than four dollars and sixty cents on each wheel), besides $19,984.21 interest upon such profits to the first day of August, 1868, and the further sum of $10,980.22, being interest from August 1, 1868, to August 1, 1870.
It is very obvious, in view of what the patentee himself stated, under oath, in 1862, when applying for an extension of his patent,
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that the account has been erroneously stated. If
Exception was taken to the charge of the profit made by the entire manufacture of the wheel, including not only the. selection and mixing of the iron, but its' melting, pouring into moulds, forming the chill, removing from the moulds, and cleaning, as well as annealing and slow cooling; aud the case was again sent to the master with instructions to inquire:
Second. If they had, or could have been made to’ have such value by any annealing or slow-cooling process, outside of the Whitney patent; how much additional value, if any, they derived from being subjected to that patented process.
Upon the findings (stated supra, 632—Rep.) made by the master on this order, the court decreed against the defendant the entire profits made by him in the manufacture and sale of the wheels from beginning to end, not only the profits resulting from the reheating and regulated slow cooling in connection, but also those which may have resulted from mixing and melting the iron, casting in moulds, making the chill, and from the possible advance on the iron above its cost, with interest on the whole.
This we think was an error. The’-findings of the master justified no such decree. It must be conceded that the findings áre incomplete, obscure, and in some particulars incongruous, but-it is not a legitimate construction of them taken together, that the benefit which the defendant derived from the use of the complainant’s 'invention was equal to the aggregate of profits-, he obtained from the manufacture and sale of the wheels as entireties, after- they had been completed. It is. as true of a process invented as -an improvement in a manufacture, as it is of an improvement in a machine, that an infringer is not liable to the extent of his entire profits in the manufacture.
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If the wheels made by the defendant would-have had no market value above that of cast iron if they had not been annealed and slow cooled, the same may.be said if they had beeh cast without a chill. The same principle, therefore, which gives to the complainants the- aggregate profits of the entire manufacture would give the same profits to a patentee of the process of chilling,
The record shows that the court overruled the alternative finding of the master, that if there is no infringement of the. complainant’s patent unless the wheels are subjected to the process of reheating — that is to say, if the process of slow cooling used in connection with reheating is old, and not a part of the complainant’s invention, no part of the profit derived by the defendant from the manufacture and sale of the wheels was due to the use by him of that invention
We add only that in our opinion the defendant should not have been charged with interest before the final decree. The profits which are recoverable against an infringer of a patent are in fact a compensation for the injury the patentee has sustained from the invasion of his right. They are the measure of his damages. Though called profits, they are really damages, and unliquidated until the decree is made. Interest is not generally allowable upon unliquidated damages. We will not say that in no possible case can interest be allowed. It is enough that the case in hand does not justify such an allowance. The defendant manufactured the wheels of which the complaint is made under a patent granted to him in 1861. His infringement of the complainant’s patent was not wanton. ' He had before him the judgment of the Patent Office that his process was not an invasion of the patent granted to the complainant, and though this does not protect him against responsibility for damages, it ought to relieve him from liability to interest on profits.
Decree reversed, and the cause remanded with instructions to proceed in accordance with the rules laid down' in this OPINION.
