The opinion of the court was delivered by: ABRUZZO
This is a suit for infringement of the Pacz patent No. 1,410,499, filed February 20, 1917, and issued March 21, 1922.
The patent contains claims covering a process and a product. However, only product claims 25, 26, and 27 are here in suit.
These three claims cover an incandescent lamp filament and read as follows:
"25. A filament for electric incandescent lamps or other devices, composed substantially of tungsten and made up mainly of a number of comparatively large grains of such size and contour as to prevent substantial sagging and offsetting during a normal or commercially useful life for such a lamp or other device.
"26. A drawn filament for electric incandescent lamps or other devices, composed substantially of tungsten and made up mainly of a number of comparatively large grains of such size and contour as to prevent substantial sagging and off-setting during a normal or commercially useful life for such a lamp or other device.
"27. A filament for electric incandescent lamps or other devices, composed of tungsten containing less than three-fourths of one per cent of non-metallic material and made up mainly of comparatively large grains of such size and contour as to prevent substantial sagging or offsetting during a normal or commercially useful life for such a lamp or other device."
The plaintiff contends that the filament covered by these claims represents an important advance in the art. The plaintiff and its licensees have undoubtedly sold billions of incandescent lamps embodying that filament. The defendants, Wabash Appliance Corporation, Abe Adler, and Abe Parker, the latter two being the sole stockholders and officers of the corporate defendant, are not licensed under the Pacz patent.
The plaintiff charges the defendants with infringement, in that the claim is made that the defendants make and sell electric incandescent lamps containing filaments which are in fact Pacz filaments of the claims in suit.
The history of the incandescent lamp began about fifty years ago, when Edison brought out the first commercial lamp that was successful. The Edison lamp contained a carbon filament and remained the standard of the industry until the advent of tungsten as a filamentary material.
Tungsten was disclosed in 1906 by the invention of Just and Hanaman. These tungsten filaments were of the squirted or pressed type, tungsten powder being mixed with a binding material in a plastic mass and then squirted under pressure through a die to a fine thread. It was then dried and sintered to form a filament of pure tungsten. Loops of this filament were then assembled on supports inside a glass bulb to form an incandescent filament. Plaintiff's Exhibit 8. This squirted tungsten filament was an improvement over the carbon filament but, because this filament was a little brittle and weak, it could not be made into long lengths or of accurate gauge.
While this tungsten filament was an improvement over the carbon lamp of Edison it, nevertheless, presented a problem known as "offsetting," which is the bodily shifting of a portion of the filament from an adjacent portion during the burning of the filament. These early tungsten filaments consisted of comparatively large crystals, many of which were large enough to extend clear across the filament, but they shifted. Because of the bodily shifting of portions of the filament (Plaintiff's Exhibit 12), the available cross sectional area of the filament for carrying electric current was reduced at the point of the "offsetting." The filament then became overheated and burned out.
The next step in the history of the filament was the Coolidge patent 1,082,933. His method of making the drawn tungsten filament included means for preventing "offsetting." Since "offsetting" was known to occur when, as Coolidge put it Plaintiff's Exhibit 2), the crystals became "so large as to extend across the entire section of the filament," Coolidge made provision (by the addition of certain chemical materials at an early stage of his process) for arresting crystal growth in the final filament. His theory was the maintenance of a small crystal structure. He did not have large crystals so as to extend the entire section of the filament. As a result of his method his filament was a non-offsetting filament.
The Coolidge method was, of course, a great improvement over the weak squirted filament. Its grains were so small and numerous that none extended all the way across the filament, which prevented slipping and in turn this made a non-offsetting filament. However, there was another serious defect characteristice of a tungsten filament. This was the defect of "sagging."
The Coolidge patent did not take care of the problem of "sagging." The filament in a lamp is not stiff enough to support itself and consequently must be strung between supports. The Coolidge filament ...