Petitioner, General Electric Company, brought this patent infringement suit based on Pacz patent, No. 1,410,499, relating to a tungsten filament for incandescent lamps. The patent, issued March 21, 1922, on an application filed February 20, 1917, contains process and product claims; only the latter are here involved. The District Court for Eastern New York held claims 25, 26, and 27 valid and infringed, and gave petitioner a decree for an injunction and accounting. 17 F.Supp. 901. The Court of Appeals for the Second Circuit held that petitioner's product was anticipated by filament produced under the teachings of the Coolidge patent, No. 1,082,933, and reversed with directions to dismiss the bill of complaint. 91 F.2d 904. This decision conflicted with that handed down by the Circuit Court of Appeals for the Ninth Circuit, Anraku v. General Electric Co., 80 F.2d 958, which held the same claims valid and infringed. To resolve the conflict, this Court granted certiorari. 302 U.S. 676, 58 S.Ct. 143, 82 L.Ed. --.
In incandescent lamps, the tungsten filament, through which the electric current passes, grows more luminous than the carbon filament of the early days of the art. There were faults of 'offsetting' and 'sagging,' however, affecting the efficiency of the first tungsten filaments. 'Offsetting' occurs when, during heating in the use of the lamp, the filament forms crystals which extend their boundaries across the entire diameter of the filament, substantially perpendicular to its axis. The crystals in the filament thus come to have an appearance, somewhat analogous to the joints in a bamboo rod. Lateral slipping of the crystals reduces the cross-sectional area at the point of contact of the crystals with the result that the temperature at that point is increased, thus hastening the burnout, and the filament is weakened. 'Sagging' is a change of position by the filament during incandescence. It elongates and thus is forced out of the plane it occupied between fixed supports. Sagging has many objections. The sagging filament may touch the glass and end the life of the lamp. In gas-filled lamps, when sagging causes the coils to spread apart, the gas flows in between the coils and unduly cools the filament. Combatting sagging by additional supports is also said to cool the filament, and reduce electrical efficiency.
Pacz undertook to remedy these faults. He carried out many experiments, and his 218th effort, made while he was in the employ of petitioner company, yielded the discovery disclosed by the patent in suit. The specification asserts that by means of his invention 'the sagging is substantially eliminated and 'offsetting' of the filament is substantially prevented, during a normal or commercially useful life of the lamp.' He brings 'into intimate association with tungsten a material (an alkaline silicate) which will have the desired influence upon the grain growth of the metal.' The specification continues as follows:
'When the meta r eaches the temperature at which extensive grain growth would ordinarily take place, the presence of this material intimately associated with the tungsten particles has a marked effect on the shape and size of the tungsten grains. The ingot of tungsten thus produced, whether it be due to the fact that the grains have not reached the equilibrium grain size or to other causes, is particularly susceptible to grain growth during subsequent heat treatments.
'The probable reason why filaments made according to my invention do not sag, is that the structure is comparatively coarse grained. The coarse grained filament produced by means of my invention does not 'offset' so as to cut short the life of the lamp appreciably.'
The District Court found that Pacz's patent exhibited novelty and invention; that Pacz produced large crystals early in the life of the lamp; that although coarsegrained, and thus non-sagging, filaments meant 'offsetting' to the art, where it was 'common knowledge' that grains large enough to extend across the filament induced slippage, Pacz procured a particular kind of coarse-grained filament which did not 'offset' because of the nature of the boundaries of the grains, their contour being 'a very important element.'
The Circuit Court of Appeals held that the Pacz product was anticipated by patent No. 1,082,933, issued December 30, 1913, to William D. Coolidge for a process of producing ductile tungsten for incandescent electric lamp filaments and for the product itself.