Linde Air Products Co. v. Graver Tank & Mfg. Co.

Decision Date14 May 1948
Docket Number9482.,No. 9481,9481
Citation167 F.2d 531
PartiesLINDE AIR PRODUCTS CO. v. GRAVER TANK & MANUFACTURING CO. (two cases).
CourtU.S. Court of Appeals — Seventh Circuit

Cahill, Gordon, Zachry & Reindel, of New York City, Carlson, Pitzner, Hubbard & Wolfe, of Chicago, Ill., and Crumpacker, May, Carlisle & Beamer, of South Bend Ind., (Richard Russell Wolfe, of Chicago, John T. Cahill, James A. Fowler, Jr., and Loftus E. Becker, all of New York City, George M. Beamer, of South Bend. Ind., of counsel), for Linde Air Products Co.

Charles L. Byron, of Chicago Ill., John F. Oberlin, Ashley M. Van Duzer and James R. Stewart, all of Cleveland Ohio, and L. L. Bomberger, of Hammond Ind., for Graver Tank & Mfg. Co.

Before SPARKS, MAJOR and MINTON, Circuit Judges.

SPARKS, Circuit Judge.

Plaintiff charged defendants with infringement of United States Patent No. 2,043,960 issued June 9, 1936, to Union Carbide and Carbon Corporation of New York, assignee of the inventors Lloyd Theodore Jones, Harry Edward Kennedy and Maynard Arthur Rotermund of California, who filed the patent application on October 9, 1935. The patent relates both to a process or method of electric welding, and to compositions for use therein. Of the process or method claims, numbered 1 to 17 inclusive, all were in issue except claim No. 10. Of the composition claims, those numbered 18, 20, 22, 23, 24, 26 and 27 were in issue.

The defenses were invalidity and non-infringement. The court held valid and infringed composition claims 18, 20, 22 and 23. and invalid, composition claims numbered 24, 26 and 27. It also held all of the process or method claims in issue invalid. From the decree plaintiff, in cause No.9481, has appealed from the rulings adverse to it, and the defendants, in cause No.9482, have appealed from the rulings adverse to them.

The specification states with considerable particularity the disclosures of the art at that time, as patentees then understood them. We refer in substance to the specification in order to get a fair disclosure of the problems which then confronted the applicants, and which they sought to solve. The fact that the patent was issued clothes plaintiff with the presumption of its validity.

Among the various ways in which electrical energy had been converted into heat for welding metals, the arc process was the one most generally practiced, a typical example of which is its use to join the abutting edges of steel plates. In the metal-arc variation of the arc process, molten metal, provided by the melting of a metal wire or rod of suitable composition, was introduced between the abutting edges of the plates, and the latter were fused sufficiently to permit the added metal to coalesce with the metal of the plates so that, on cooling, a structurally strong bond resulted. The requisite heat was developed by maintaining either a direct current or an alternating arc between the parts to be welded connected to one side of the power line, and the wire or rod used to supply the molten metal connected to the other side of the power line. The abutting plate edges were usually beveled to form a trough for receiving the molten metal, thereby facilitating coalescence of the added metal with the plates throughout the thickness of the latter.

The simplicity of bare wire-electrode welding recommended it above all other methods, but the metallurgical and physical properties of metal deposited in this manner were usually so poor that the method was unsuitable for many applications.

In order to avoid certain difficulties encountered in bare metal arc welding, it was customary to protect the freshly deposited molten metal with a blanket of molten metal compounds (usually compounds of the alkali or alkaline earth metals). The material used for forming this blanket is called the "flux." The usual method of providing a flux blanket on the weld was to encase the welding rod or wire, referred to as the electrode, in an adherent sheath of solid flux, and this gave rise to other difficulties. The sheath was usually fragile and, being nonmetallic in nature, was nonconductive when cold, so that electrical connection was required to be made with the electrode at points bared for that purpose at intervals and at variable distances from the weld, thereby imposing an additional burden on the automatic regulating devices widely used in welding. When the bared sections reached the melting zone, metal of inferior quality was deposited. The current passed through a variable length of rod, the length between the arc and the contact point, heating it sufficiently to crack off the flux covering and further to add an IR-drop to the arc voltage. This IR-drop was not constant in magnitude but varied according to the position of the contact point relative to the arc. The machine could not maintain the constant arc length so necessary to successful welding unless compensatory means were resorted to. These difficulties therefore limited the energy which might be expended in the arc. The inventors were not aware of current values in excess of about 500 amperes being used in this manner of welding.

For good welding a homogeneous deposit of metal is indispensable. In metal-arc welding the difficulties in securing such deposit are multiplied as the thickness of the deposit increases so that, in such case, it becomes necessary to make several traverses or passes, adding a layer of metal each time until the necessary thickness is attained. Such method is time and labor consuming.

Another known means of applying protective flux consisted in utilizing a thick coating of finely divided material, a flux, which covered the seam to be welded. The welding electrode which is a bare wire of suitable composition was fed down by conventional feeding means and the arc was struck under the powdered flux. The electrode was traversed at a constant rate along the path to be welded. Direct current was applied at a voltage of about 30 volts with a current up to about 900 amperes. The flux used in that system was a natural clay of approximately the composition used in making brick. Although this method retained the advantage of feeding current continuously to a bare wire at a point adjacent the weld, the weld metal thus deposited thereby was deficient in quality. A weld thus made had ample strength for some purposes, but it was quite porous, was not applicable to plates over one-half inch thick, and projected a cloud of material into the atmosphere, and often required the welders to use gas masks for protection from the dust.

The objects of the present invention are said to be to avoid the disadvantageous features above referred to; to provide a process by which thick plates can be strongly and rapidly electrically welded in a single pass or in a plurality of passes, with a weld of which the density and physical properties are at least equal to those of the parent metal; to provide a process in which heavier welding currents can be used and the rate of welding accelerated; to overcome the difficulties which, in prior processes, are caused by the inherent instability of an electric arc, and its liability to be extinguished by a variety of causes; and to avoid the necessity for a flux sheath on the electrode.

It is said that the patent discloses a novel process for electric welding wherein the necessary heat is generated by the passage of a heavy electric current between a metal electrode (usually bare) and the metal plates or similar objects to be welded, the electrode being out of mechanical contact with the objects, and the current being carried across the gap between the electrode and the object by and through a conductive melt or welding composition having appropriate electrical resistance properties. The heat thus generated melts successive portions of the electrode, and the molten material is deposited as weld filler material. The welding composition serves as an active instrumentality or welding medium, inasmuch as it provides heating means, controls the rate, penetration and quality of welding, and purifies and protects the molten metal.

The specification states that the properties of a successful welding composition for this method are: (1) The chemical reaction between the components of the welding composition must be completed before it is used in welding (failure in this regard produces porosity); (2) it must be capable of controlling the penetration and the width of the weld; (3) its fluidity at welding temperatures must be such that it will not become entrained with the molten metal; (4) it must consist of chemicals which are not detrimental to the properties of the steel; and (5) it must be readily removable from the finished weld.

The composition of the welding medium is of the utmost importance. The particular composition that is to be used is determined by the quality and thickness of the metal plates to be welded, by the current and voltage to be used, and by the properties it is desired to impart to the weld metal.

The inventors state in their specification that they have used calcium silicate and silicates of sodium, barium, iron, maganese, cobalt, magnesium, nickel and aluminum, both in binary and ternary combinations, in various proportions. They state also that they have used calcium titanate and various titano-silicates, particularly when they desired to introduce titanium into the weld metal. They further state that a number of these conductive welding compositions are more or less efficacious in this process, but it is preferred to use silicates of the alkaline earth metals, such as calcium silicate, and they also prefer to add to these silicates minor proportions of alumina and of a substance adapted to lower the melting point, such as a halide salt.

The preferred composition, however, comprises, as its principal ingredients, silica, at least one basic constituent consisting of an alkaline earth such as lime or...

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