Ansonia Brass Copper Co v. Electrical Supply Co

• Decision Date: 14 March 1892
• Citation: 12 S.Ct. 601,36 L.Ed. 327,144 U.S. 11
• Parties: ANSONIA BRASS & COPPER CO. v. ELECTRICAL SUPPLY CO
• Court: U.S. Supreme Court

144 U.S. 11

12 S.Ct. 601

36 L.Ed. 327

ANSONIA BRASS & COPPER CO. v. ELECTRICAL SUPPLY CO.

March 14, 1892.

STATEMENT BY MR. JUSTICE BROWN.

This was a bill in equity for the infringement of letters patent No. 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 water-proof 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 fireproof 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 through out 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.

'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 set or 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. Justice FIELD, dissenting. 35 Fed. Rep. 68, and 32 Fed. Rep. 81, affirmed.

Joshua Pusey and Chas. E. Mitchell, for appellant.

C. R. Ingersoll and M. W. Seymour, for appellee.

Mr. Justice BROWN, after stating the facts in the foregoing language, delivered the opinion of the court.

The stress of this case in upon the question of patentable 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 towards 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 companies 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 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...