The opinion of the court was delivered by: MCVICAR
The court makes the following findings of fact and conclusions of law:
(1) Plaintiff, the Cold Metal Process Company, is a corporation of Ohio, having a place of business at Youngstown, Ohio. Defendant, United Engineering & Foundry Company, is a Pennsylvania corporation having a place of business at Pittsburgh, in the Western District of Pennsylvania.
(2) The patent in suit, No. 1,779,195, issued October 21, 1930, covers a method and apparatus for rolling thin, sheetlike material. Abram P. Steckel is the inventor. Plaintiff is the owner by assignment from Steckel.
(3) Sheets are used for a variety of purposes, as, for example, roofing, the making of utensils and various formed parts. Such material must have a good surface, and is usually under 10 gauge (.1379") in thinkness. There was and is a great demand for thin material having a high ratio of width to thickness. Typical products made from such material are radiators and radiator shells; hub caps, stainless steel veneer for steel spokes, light shells, covering for airplane wings, cans, metal ceilings, stampings, toys, weather stripping, razor blades, textile machine parts, etc. A very large tonnage of highratio steel is coated with tin to make so-called "tin plate" for use in tin cans. There is a large demand for tin plate.
(4) The difficulties of rolling thin metal increase as the ratio of width to thickness increases, and the difficulties become so marked at a ratio of about 400 to 1 that this figure constitutes a dividing line between high and low ratio material. It is necessary to use extraordinary precautions in rolling high-ratio material, and it has been much more costly than low-ratio material. There has always been a constant demand from the steel manufacturers for mills which would produce more product and better product than existing mills.
(5) Prior to 1923 thin steel was rolled by three processes as follows: (1) Pack rolling; (2) hot strip rolling; (3) cold strip rolling.
(6) Pack rolling is performed by first heating so-called sheet bars which are manually fed through the rolls of a sheet mill by a workman standing on the entering side of the mill. As they issue from between the rolls they are caught by a man standing on the delivery side, lifted up and handed back over the top of the mill to the first workman. This process is continued until the bar has been reduced to a thickness where it is impracticable to go any further. Then two such pieces are laid on top of one another and th rolling is continued. After reheating, the metal is further rolled and then doubled upon itself so as to make it four plies thick, the rolling continuing in this fashion until the desired thinness is reached. The finished packs may contain 4, 8, or 16 plies. It is necessary to pile up the sheets and roll them in packs because, in this hand process, it is impossible to roll single sheets with sufficient accuracy.
(7) Pack rolling is carried out on 2-high mills having ordinary brass bearings. The rolls employed are 28 to 32 inches in diameter. As the sheets are passed through the mill, the rolls become hot and expand. Heat is also produced by the friction of the roll neck on the brasses. The heat of the steel and the heat of friction in the necks both have an effect on the expansion of the roll body. It is necessary for the workman to control these influences in order to get a merchantable sheet. He uses steam and flame jets on the rolls for this purpose.
(8) In starting the run of a mill for the week it requires about eight hours of rolling in order to bring the rolls up to the right temperature and shape for rolling tin plate accurately. If the middle portion of the roll expands too much, it produces a buckled pack, while if the end portions of the roll expand too much it makes a riffled pack. To be commercially flat, the material must be free of buckles or wrinkles.
(10) There are limitations on the size of the sheets which can be produced by pack rolling, because of the limited ability of the workmen to handle the material.There are limitations on thickness due to the difficulties in controlling the roll pass contour. The pack rolling process is essentially slow, and cannot be speeded up because of the limitations on the workmen.
(11) There are further limitations on the process due to scrap loss. Buckled and riffled packs are difficult or impossible to separate. The edges of the packs have to be sheared off to make the sheets square, thus increasing the scrap loss. It is necessary to use expensive materials such as phosphorous and silicon in the steel and to make the steel of special analysis in order to prevent sticking of the sheets together.
(12) It is impossible to get extreme accuracy of product in pack rolling, and about the best workmen are able to do is to get within 10 per cent. of the thickness on tin plate and 8 per cent. of the thickness on sheets.
(13) Pack rolling is hot, hard work because of the heat of the mill, the furnace, and other equipment. It is generally known as a man-killing job.
(14) Hot strip rolling, prior to 1923, was carried out on 2-high mills with brasses. The process consists in passing a hot slab between the rolls and rolling it out into a long, thin ribbonlike strip. This is usually done in a continuous mill.By a continuous mill is meant a multiplicity of stands set in a row one after the other so that the piece being rolled is in one or more stands at one time.
(15) Despite a great demand for high-ratio material, a ratio of 200 to 1 was as high as could be gotten with the limitations of the art prior to 1923. This is far below the dividing ratio (400 to 1) between high and low ratio material.
(16) The essential difference between cold strip rolling and hot strip rolling is that in cold strip rolling the material fed to the rolls is cold or at room temperature. Hot rolled strip, pickled to get the scale off the surface, is the material which is fed to the cold mills.
(17) In the old cold rolling process it was necessary to stop at intervals to anneal the steel and thereby soften it so as to permit of further cold rolling.
(18) Cold rolling is advantageous, in that it makes it possible to reduce the steel to thinner gauges than can be done by hot rolling; a highly finished surface is obtainable; and it is possible to get pieces which are of lengths impossible of production by pack rolling.
(19) The difficulties of pass distortion in cold mills provided with brass bearings are the same, due to roll neck heating, as in the pack rolling process, but are emphasized by the high pressures. The pressures in cold rolling are enormously high, and may be in the neighborhood of 40,000 pounds per inch of length of the roll, so that, for example, in rolling a piece 10 inches wide, the total pressure required may be in the neighborhood of 400,000 pounds. The high pressure breaks the oil film in the bearing, thus increasing the frictional resistance. The frictional resistance in brasses is high and variable, in consequence of which the amount of heat generated is variable.
(20) The amount of heat generated in the bearings is proportional to the speed. If the speed is doubled, the amount of heat generated is doubled. If it were attempted to increase the speed of the old 2-high cold rolling mills with brasses, the result would have been to distort the pass and destroy the bearing. Because of these limitations, the speed was necessarily slow, and this was particularly true as the ratio increased. When a ratio of 250 to 1 was reached, it became necessary to reduce the speed, and, when the dividing ratio of 400 to 1 was reached, it became necessary to roll at the lowest speeds of the mill. If this was not done, the brasses heated up, causing riffled edges or causing the piece to run into the guides. For rolling high-ratio steel the maximum speed was 100 to 135 feet per ...