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M. H. Detrick Co. v. Chicago Fire Brick Co.

June 7, 1935


Appeal from the District Court of the United States for the Northern District of Illinois, Eastern Division; John P. Barnes, Judge.

Author: Sparks

Before SPARKS, FITZHENRY, and ALSCHULER, Circuit Judges.

SPARKS, Circuit Judge.

This is an appeal from a decree dismissing appellant's bill of complaint which charged appellee with infringement of four patents. Only three of the patents are involved in the appeal. They are Hosbein, No. 1,544,580, issued July 7, 1925, on an application filed August 3, 1921; Stevens and Hosbein, No. 1,628,284, issued May 10, 1927, on an application filed November 9, 1920; and Hosbein and Foltz, No. 1,628,318, issued May 10, 1927, on an application filed April 14, 1921. They all relate to furnace arch construction. The answer was invalidity and non-infringement.

A general statement with respect to furnace arch construction will be helpful in grasping the underlying principles of all the patents in suit.

The main furnace arch is the top or roof portion of the combustion chamber. It is comprised of walls formed of refractories, otherwise known as fire brick or tile. This arch in cooperation with the side walls confines the hot gases and radiant heat, thus efficiently applying them to the work for which the furnace is intended, principally the heating of boilers for the generation of steam.

Refractories and the manner of supporting and assembling them are quite important in the construction and operation of high temperature furnances.

Formerly the main arch was a masonry structure reaching from one side wall to the other and arched over the combustion chamber. It was supported by the walls and was commonly called a sprung arch. The theory of it was that it would rise in the center to accommodate expansion caused by heat, and would lower with the contraction incidental to cooling, without displacing the ends. It was found, however, that the lower, weaker portions of the component refractories would break, due to the extra pressure of expansion, thus requiring repairs which involved the entire arch. For this reason the sprung arch was superseded by the suspended or flat arch, wherein the refractories are suspended by means of hangers carried upon a metallic framework. Refractories are made of high grade fire clay and expand as the furnace temperature increases. Upwards of 2,000 deg. F. they become incandescent. Expansion of individual refractories is not uniform throughout, due to the fact that different degrees of heat are applied to different portions of the refractory unit. This causes different degrees of expansion in the same unit and sometimes causes it to break. If a portion becomes vitrified or glassy by high temperature, a slight change in the temperature may cause it to crack and fall off. Also in arch structure, expansion of individual refractories causes them to exert pressure upon others, which may cause breakage. The breaking away of refactories is called "spalling." Again, portions of the ash of various fuels may become more or less molten in high temperatures. This molten ash is carried up in the burning gases and engages and adheres to the arch refractories, thus causing them to melt and slough off. This is known as "slagging."

The furnace arch must be a tight wall to prevent heat leakage.Steel structural elements rapidly lose strength at temperatures above 1,000 deg. F. Hence, the metallic hangers and framework supporting the arch require protection from the fire, and for that reason the refractories must fit closely together.

Temperature is a principal factor in furnace productivity. On the other hand, the higher the temperature, the more destructive is its action on the refractory arch. Appellant's disclosures, therefore, are alleged to be directed toward improvements in the shaping, arrangement and supporting of refractories to provide arches that will increase productivity and efficiency, and enable the refractories to best resist the destructive influences of high temperatures, and permit ready removal and replacement in making arch repairs.

We shall discuss first the patent of Stevens and Hosbein. In order to present more clearly the objects and claims of this patent, we here insert Fig. 1 of the patent in suit, and Fig. 2 of Duncan, No. 1,179,084, a patent of the prior art:


The patent in suit was asserted by the patentees to be adapted for use in furnaces equipped with either over-feed or traveling grate stokers. The drawings accompanying the application illustrate a travel-grate stoker, 12, as does Duncan, 10. In ach the coal is carried continuously into the fire box by the traveling grate, where it is supposed to be burned to an ash by the time it makes its exit at the opposite end of the fire box. In order to accomplish that result and thus benefit by the greatest possible combustion in the shortest time, it was quite necessary that the coal ignite as quickly as possible after entering the fire box. Duncan recognized that necessity, and for that purpose he provided an ignition arch, 21. He closed the forward end of the combustion chamber by a partition wall, 20, extending it down to a point somewhat above the opening gate, 12, thus forming the ignition arch over the forward end of the fuel bed. 15 represents the main arch, or roof, or the combusion chamber extending rearwardly to the convex combustion arch, 17, which gives passage for the gases into space 19 before they come into contact with the boiler. The roof, 15, is substantially parallel to the grate, so that the direct radiation of heat to and from the fuel bed is obtained at all points throughout the length of the fuel bed. However, the record fairly discloses that in Duncan the coal, upon entering the furnace, did not ignite until it had traveled some distance to the left of the entrance, and not to any appreciable extent until it had passed the left end of the ignition arch, 21. For that reason, it may fairly be said from the record, the travel-grate stoker was not successful with certain classes of coal. That was the problem which Stevens and Hosbein claim to have solved by the patent now under consideration. Its essential feature is the placing of an ignition arch of the character and for the purposes described in the contested claims 5, 7, 9, 22 and 24,*fn1 at and over the fuel inlet.

The court held that these claims were not infringed and were invalid in view of Duncan, Nos. 958,379 and 1,179,084, Detrick, No. 1,309,433, Lewis and Kerr, No. 1,686,976, and Crowe, No. 713,968, and also the Western Electric construction. With the exception of Lewis ...

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