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Statement of the Case.
patent number 272,660, issued February 20, 1883, to Alfred A. Cowles for an "insulated electric conductor."
In his specification, the patentee stated that “ before my invention copper wires had been covered with one or two braidings of cord, and paraffine, tar, asphalt and various substances had been employed for rendering the covering waterproof and furnishing a proper insulation. With conductors of this character several accidents occurred in consequence of the conductor becoming heated and setting fire to the insulation. For this reason objections were made to insuring buildings against loss by fire where electric lamp wires were introduced. To render the conductor fire-proof without interfering with the insulation led me to invent and manufacture the insulated electric conductors to which the present invention relates, which conductors have gone extensively into use during about a year and a half before the date of this specification."
His method of preparing the wire was stated substantially as follows: The wire was first passed through a braiding machine, and a layer of cotton or other threads braided about it; the covered wire was then passed through a vessel containing paint, preferably white lead or white zinc ground in oil and mixed with a suitable drier. A second braiding was then applied directly upon the fresh paint; the threads thus braided upon the paint force the paint into the first braided covering and at the same time the paint oozes through between the threads. In this way the paint was incorporated throughout the braided covering and filled up the pores; and the wire was thus perfectly insulated, and there was no possibility of inflaming the covering. “With intense heat the threads may char, but they will not burn."
“If desired,” said he, “a coat of paint may be applied outside of the outer layer of fibrous material, and this may be colored, so as to be used in distinguishing the wires. It is always preferable to braid the second or subsequent coats upon the paint when fresh ; but I do not limit myself in this particular, as the paint may be dried, or partially so, before the next layer of braiding is applied. Paint might be applied to the wire before the first braiding."
Opinion of the Court.
“I am aware that wire has been covered with braided threads; also that india-rubber, asphaltum and similar materials have been applied upon the covering, either hot or cold; but one coating of such material was allowed to setor harden before the next layer of braided material was applied. Hence the asphaltum or similar material was not forced into the interstices, and besides this all these substances ignite by the wire becoming heated, or fire will follow along upon such covering
“I have discovered that ordinary paint composed of lead or zinc with linseed oil is practically non-combustible, and it prevents the covering being ignited by the wire becoming hot if there is a resistance to the electric current; besides this, fire will not burn along the conductor, as is the case where the fibrous covering is saturated with asphaltum, india-rubber, or similar material.
“I claim as my invention
“1. The method herein specified of insulating electric conductors and rendering the coating substantially non-combustible, consisting in applying a layer of fibrous material, a layer of paint, and a second layer of fibrous material upon the paint before it dries or sets, substantially as set forth.
“2. An insulated and non-combustible covering for electric conductors, composed of two or more layers of cotton or similar threads, with paint that intervenes between the layers and fills the interstices of the covering, substantially as set forth.”
Upon a hearing upon pleadings and proofs in the Circuit Court plaintiff's bill was dismissed, (32 Fed. Rep. 81, and 35 Fed. Rep. 68,) and an appeal taken to this court.
Mr. Charles E. Mitchell and Mr. Joshua Pusey for appellant.
Mr. Charles R. Ingersoll and Mr. Morris W. Seymour for appellee.
MR. JUSTICE Brown delivered the opinion of the court.
The stress of this case is upon the question of patentable
Opinion of the Court.
novelty. The art of insulating electric wires has been known almost as long as that of conducting electricity for practical purposes by means of wires. Prior to the use of electricity for lighting, however, the feeble character of the currents conveyed upon these wires did not require that the insulating material should be non-combustible, and the skill of the inventor was directed toward a method of insulation which should protect the wire from moisture and other external injury. For this purpose the wires were covered with braid which had been saturated or covered with tar, paraffine, india-rubber, gutta-percha, asphaltum and various substances of like nature, to exclude the action of the water and afford a proper insulation.
Upon the introduction of electric lighting it was found that this method of insulation, while efficient to protect the wire from external influences, was unable to withstand the intense heat frequently generated in the wire itself by the powerful currents of electricity necessary for illuminating purposes. At first these wires were covered with cotton which had been saturated in paraffine and other similar substances; the result was that the insulating material was melted or set on fire, and dropped off the wire while still burning, and became so frequently the cause of conflagrations that the insurance como panies declined to issue policies upon buildings in which this method of insulating wires was employed. A new substance was needed which would not only operate as a non-conductor of electricity, and as a protection against moisture, but which should also be non-combustible.
This material was discovered in ordinary paint. Mr. Cowles was not the first, however, to discover that paint was useful for the purpose of insulating electric wires. In several English patents put in evidence, paint is suggested as a proper covering for protective as well as for insulating purposes, in lieu of gutta-percha, india-rubber, resin, pitch or other similar substances, but as a non-combustible insulator was never required for telegraphing purposes, there is no intimation in any of them that it possessed this quality. It had, however, been a matter of common knowledge for many years that paint was
Opinion of the Court.
practically non-combustible. While the linseed oil in paint is to a certain extent combustible, the carbonate of lead is a material both non-combustible and a non-conductor.
It is clear that none of these English patents can be claimed as anticipations, since they all relate to the protection of land or submarine telegraph cables, and the use of paint, so far as it was used at all, was simply as a water-proof covering for a braided wire. There is nothing to indicate that the paint, as used by them, was applied in the manner indicated by the patent, or that it made the covering non-combustible, or was intended at all for that purpose.
The most satisfactory evidence of the use of a non-combustible covering for electric wires is found in the testimony of Edwin Holmes, manufacturer of an electric burglar alarm, who states that when he first commenced using electric conductors “the wire was insulated by winding a thread, larger or smaller as the case might be, around the wire, and that thread was covered with paint,” and that all his wires were “insulated in that way until paraffine was substituted for the paint.” The paint was applied by drawing the wire through a vessel containing the paint, and then through a piece of thick rubber or gutta-percha, which removed the surplus paint and left a smooth surface on the thread which covered the wire. He began to cover his wires in this way as early as 1860, and says that he accomplished his insulation “sometimes by covering the wire with a thicker thread and two coats or more of paint; sometimes by a thread covering and a coat of paint, then another thread covering and a coat of paint on that.” And upon being asked to describe the condition of the first coating of paint when the second coating of fibrous material and paint was put on, he said: “The first coat was partially dried, so as to keep its place, but would admit of an impression from the next covering of thread.” On being called upon
subsequently for an affidavit to be used on an application for a rehearing, he stated that his object was not to produce a noninflammable wire, and that the wire used by him was not noncombustible or non-inflammable, and was no better adapted for electric light conduction than the paraffine-coated wire. He
Opinion of the Court.
further stated that when the second layer of braid was laid on, the condition of the first layer was not such as to cause the threads of the second layer to force the paint into the interstices, and so load the wire with an abnormal quantity of paint, as is done in the process described in the Cowles patent. The substance of his testimony in this particular was, that the coating of paint upon his first layer was allowed to harden before the second layer was applied, so that the application of the second layer would not cause the paint upon the first layer to be forced into the interstices of that layer or to ooze through the braiding of the second layer.
Thomas L. Reed, another witness, gave a somewhat similar experiment of the method of insulating wires by passing the naked wire through a tub containing paint, then braiding it, and then immersing it in a second tub containing paint, and finally passing it through jaws to scrape off the surplus paint and compress it. As this method of insulation, however, does not resemble so closely the Cowles patent as that employed by Mr. Holmes, it is unnecessary to notice it further.
Practically the only difference between the Holmes and Cowles insulators is in the fact that the coat of paint applied to the first braid in the Holmes process was allowed to dry before the second coat of braid was applied, and thereby the braid was not so thoroughly permeated with the paint as is the case in the Cowles patent. That the idea of applying the second coat of braiding upon the interposed insulating material, while such material was wet or unset, is not in itself a novel one is evident from the English patents to Brown and Wil: liams, to Duncan and to Henley, all of which describe a method for insulating conductors by applying a layer of fibrous material, a layer of insulating material, and a second layer of fibrous material upon the former, before the insulating material is set or hardened. Indeed, it is doubtful whether Cowles considered this feature of his process as of any great importance at the time he made his application, since he speaks of it only as a preferable method, and says that he does not limit himself in this particular, “ as the paint may be dried, or partially so, before the next laver of braiding is applied." But howerer