Зображення сторінки
PDF
ePub

4. SAME.

The Stirling patents, No. 407,260 and No. 479,678, for improvements in water-tube boilers, construed, and held not infringed.

This was a suit in equity by the Stirling Company against the Pierpoint Boiler Company and others for alleged infringement of certain patents for improvements in steam boilers.

Banning & Banning, Kay & Totten, and Henry W. Blodgett, for complainant.

Bakewell & Bakewell, for defendants.

Before ACHESON, Circuit Judge, and BUFFINGTON, District Judge.

BUFFINGTON, District Judge. On July 10, 1889, letters patent No. 407,260, and on July 26, 1892, letters patent No. 479,678, issued to Allan Stirling, assignor to the International Boiler Company, for improvements in steam boilers. This bill is filed by the Stirling Company, to which the patents have been duly assigned, against the Pierpoint Boiler Company and the officers thereof, alleging infringement of all the claims of said patents. The answer denies novelty and patentability; avers anticipation in certain prior patents of the United States and France; that every substantial element of the second patent was disclosed in the first; and asserts that, in view of the prior state of the art, the claims cannot be so construed as to make respondents' structures infringements. The boilers of both parties are water-tube boilers; that is, water is confined in banks of tubes, the outer surfaces of which are exposed to the flame, as distinguished from locomotive or fire-tubes boilers, in which heating gases pass through tubes surrounded by water. Water-tube boilers include two classes,—those whose tubes are horizontal, or substantially so, and connected at the ends by headers, and those whose tubes are vertical, and connected at the ends to cylindrical drums. The boilers of the present case are of the latter type.

From the specification of the first patent it would seem Stirling conceived there were three objectionable features in prior boiler construction, which he proposed to improve or obviate, namely: First, lack of circulation through the mud drum; secondly, lack of compactness of construction; and, thirdly, difficulty in cleaning. He sets these forth in the specification of the first patent as follows:

"Heretofore, in the so-called 'water-tube' boilers, in which the water is in the tubes and the flame outside, the tubes have usually been inserted in headers made of cast metal, so arranged that a number of tubes have only one outlet to the steam and water space above and of the mud drum beneath. In these boilers there is no circulation through the mud drum, and the enormous velocity of the currents in the outlets to the steam and water space is detrimental to the boiler, and precludes a proper circulation. Watertube boilers, as heretofore constructed, have also been found objectionable because of the large space which they occupy, and the large number of handholes with covers and bolts necessary to get at the inside of the tubes for cleaning; and it has also been found impossible to get at the outside of the tubes to clean them from soot. These disadvantages have been obviated by my invention."

The alleged defects he overcomes by a new arrangement of parts in what is well termed a "fan-shaped" boiler. In the first patent, back of the grate a mud drum is shown, from which series of tubes extend upward, incline forward, and connect with two steam and water drums (the rear of which is a feed drum) adjacent to each other on the same plane. The steam and wa er spaces of these two are respectively connected by steam and water tubes. Each of the drums has a manhole for access to its interior. Over the grate is a fire-brick arch, intended to confine the flame and insure combustion of the gases at that point, and force them against the lower portions of the tubes leading from the mud drum to the front steam and water drum. A baftier, or fire-brick wall, at the back of these tubes, extending upward about two-thirds of their height, forces the gases to pass along the entire tube length. A shelf or apron projecting from the middle of the rear side of this baffler drives the gases against the upper portion of the tubes extending from the feed drum to the mud drum, and forces them along the entire tube surface to a flue back of the mud drum. Of the operation of the boiler the specification says:

"From this description it will be seen that in my boiler each of the water tubes, B, has an independent outlet to the steam and water space above, and also an independent outlet to the mud drum below, the boiler being constructed of wrought metal, and so arranged that the water is forced to pass through the mud drum, and deposits its sediment therein. Only three manholes are necessary for complete access to every part, and the outside of those water tubes on which the soot is formed can be readily cleaned by means of the steam nozzles, H. The two sets of tubes are connected into the upper drums, so as to allow for the expansion and contraction. For this purpose each of the water tubes, B, is curved at one or both ends. The brick arch, D, of the furnace aids materially in the proper combustion of the gases, and the peculiar arrangement of this arch and the fire-brick partition directs the gaseous products of combustion, so that they pass over every part of the heating surface, and so break up the currents as to extract the available heat therefrom."

While the course of the water circulation is not specified in the patent, and while the banks of tubes may at times be subjected to relatively different stages of heat than those assumed below, thereby causing different circulation, yet, as describing the usual main circulation of the boiler shown in the patent now under consideration, we quote the views of Prof. Cooley, complainant's expert, who says:

"It is sufficient for the present to state that the front bank absorbs sereral times as much heat as the rear bank, and, in consequence, the water is caused to ascend through the front bank with great velocity into the front steam and water drum, where the steam which has been formed in the front bank of the tubes is liberated, the water passing through the connecting water pipes to the rear steam and water drum or feed drum, thence downward again through the rear bank of the tubes to the mud drum. The steam which separated from the water in the front drum may pass through the upper connecting steam pipes to the rear drum, whence it may pass off into the main steam pipe leading from the boiler. This arrange ment of drums, tubes, and connecting pipes appears to be a convenient arrangement, and peculiarly adapted to secure this rapid and complete circu. lation of water with separation of steam, together with a corresponding complete and rapid circulation of gases with abstraction of heat."

Upon this device two claims were allowed, viz.:

"(1) A water-tube boiler consisting of the single mud drum, A, the two elevated steam and water drums, A1 A2, the water tubes, Bi, connecting the water spaces of the steam and water drums; the steam tubes, B2, connecting the steam spaces of said steam and water drums, and two sets of water tubes, BB, directly connected, respectively, at their upper ends, with the steam and water drums, and both sets connected at their lower ends with the single mud drum, substantially as described."

“(2) A water-tube boiler consisting of a furnace structure, a single mud drum, A, the two elevated steam and water drums, A1 A2, having their steam and water spaces respectively placed in communication; two sets of water tubes, BB, directly connected, respectively, at their upper ends, with the steam and water drums, and both sets connected at their lower ends with the single mud drum; the fire-brick arch, D, extending over the fire. place from the wall of the furnace structure to the front set of water tubes; and the fire-brick partition C, inclined between the two sets of water tubes, and located between the single mud drum and the two steam and water drums, substantially as described."

Bearing in mind what was well understood in boiler construction at the time Stirling's patents issued, namely, that in a boiler having several banks of rising tubes connected at the ends to drums or headers, there is a circulation upward of water through the tubes exposed to the greatest heat and downward through those exposed to the least, in our judgment the improvements disclosed in the patent and embodied in the claims are set forth and specified in language wholly void of uncertainty. Measured and limited by his own statement, what the patentee disclosed to the public, and what he claimed a limited monopoly for from the public, was to insure the circulation (then well understood) through the mud drum, and secure the deposit of sediment and scale, to compact a boiler into the narrow compass of a triangular structure, and to afford facility for cleaning and repairs. To accomplish these objects we find a structure specified and claimed in which are the elements of “a single mud drum” and “the water tubes, B', connecting the water spaces of the steam and water drums.” Concededly, the boiler devised by Stirling is a meritorious one, and embodies many desirable points not shown in combination in the previous art; and, assuming for present purposes the novelty and patentability of the combinations claimed, yet, in view of the prior art, the claims are not to be expanded beyond the specified combinations claimed or the substantial equivalents thereof. To an examination of this prior art we now turn. As early as 1871, Griffith and Emery secured patent No. 111,639 for a sectional steam boiler. In it fire-brick baffler walls divide the inclined tubes into thin banks or sections, and cause gases to circulate longitudinally along them, and pass through them back and forth three times. One of the stated objects of the patent is "the arrangement of one or more tubes in each section, wholly or partially out of direct contact with the flames or heated gases, and in such manner as to return the water from one tube head to the other, and thus complete the cir. culation.” The method of doing this and the process of circulation are set forth quite explicitly:

"As the water in the tubes receives heat its density is diminished, and it is forced by the heavier water in the rear tube heads, c, out of the tubes and up the front tube heads, B, into the steam drum, D, where the steam escapes, and the water flows over a cross partition or dam, E, and enters the upper

[ocr errors]

tubes, A1, which return it to the rear tube head, C, and thus maintain the circulation. The tubes, A1, in the upper row are wholly or partially screened from the flames and heated gases by the partition, F, made wholly of fire brick or tile. This is done for the reason that, if heat is admitted by the tubes, A1, the density of the water in the descending current will be diminished, and the rapidity of the circulation correspondingly lessened. By the construction shown, a heavy and light column are continually maintained, the water in the first continually displacing that in the other, and thus making a free circulation. It is not essential that the tubes, A1, should be entirely screened from the heated gases, but in no case should they receive sufficient heat to form steam bubbles."

This device shows a complete main rectangular circulation, theoretically understood and mechanically applied, and the same stimulated by the distribution and absorption of heat through the agency of baftlers. While the method employed is faulty as compared with Stirling's, in that the hottest gases come in contact with the pipes containing the coldest water, yet that principle was theoretically well understood at the time of the Stirling patent, as evidenced in Rankine's work on the Steam Engine, and was practically applied in the French patent of Grenier, hereafter referred to. Rankine says:

"When heat is to be transferred by convection from one fluid to another through an intervening layer of metal, the motions of the two fluid masses should, if possible, be in opposite directions, in order that the hottest particles of each fluid may be in communication with the hottest particles of the other, and that the minimum difference of temperature between the adjacent particles of the two fluids may be the greatest possible. In a steam boiler it is favorable to economy of fuel that the motion of the water and steam should on the whole be opposite to that of the flame and hot gas from the furnace. Thus, if there is a 'feed-water heater' consisting of a set of tubes through which the water passes to be heated before entering the boiler, that apparatus should be placed in or near the foot of the chimney, so as to be heated by gas that has left the boiler, and thus to employ heat that would otherwise be wasted. The coolest,that is, the lowest---portions of the water in the boiler should, if practicable and convenient, be contiguous to the coolest parts of the furnace and heating surface."

We next find—1875—the first patent to Firmenich, No. 165,222, for a steam generator, which was exhibited at the Centennial Exhibition of 1876, and whose workings were described in subsequent literature of the art. It is a sectional boiler, having upper connected steam and water drums and lower connected mud drums. Between these upper and lower drums are vertical connecting water tubes along which gases are made to travel in two passes by a mediately placed partition wall with a down-take flue. Of the tubes the patent says:

"The last one, or more vertical, heating tubes in each set are embedded in the rear or front wall of the masonry, and, being kept at a considerable lower temperature than the lower tubes, serve as circulating tubes."

The functional action of these circulating tubes is carried into one of the claims, viz.:

"The arrangement, with the steam and water receptacle, D, of the circu. lating end tubes, C, inclosed by the brick wall or walls, L, and a mud drum, A, situated below the fire line of the steam generator, substantially as described, and as for the uses and purposes set forth.”

In describing the prior art in his patent, Stirling, as we have seen in an extract quoted above, stated that in the header type of tubular

boilers there had been no circulation through the mud drum. If inferentially this statement was meant to apply to water-tube boilers with upper and lower drums, it was a mistake, for the Firme. nich device certainly shows a main rectangular circulation through a mud drum. In this type we also find an advance in compactness of structure and facility of cleaning over the “header" type. As showing also the vigorous circulation inherent to the general construction, it should be noted that in boilers subsequently built by Firmenich the imbedded rear circulating pipes were found need. less, and were omitted, the heat difference between the front and rear vertical tubes being sufficient to produce circulation.

Three years later—1878—we find in Firmenich's second patent, No. 210,312, a further advance in the line subsequently pursued by Stirling. In it we have the first development of the compact triangular or fan-shaped structure of the Stirling patents. In the latter the single mud drum is the center, from which the water tubes and two connected steam and water drums diverge upwardly, while in Firmenich's the conditions are reversed, and the single upper steam and water drum is the center from which the water tubes and two connected mud drums diverge downwardly. In Firmenich's the grate space is within the triangle, and by means of a mediately placed fire-brick partition wall the flames follow longitudinally and in two passes along and across the water tubes, first the front tubes on the upward pass, and next the rear tubes on the downward; while in the Stirling the fire chamber is outside the triangle, and the flame first impinges transversely on all the tubes on one side of the triangle, and next on all the tubes on the other. While no mention is made in the patent of the circulation, yet, as that principle was well understood in the art, and was set forth, as we have seen, in the prior Firmenich patent, and as the later patent states "the invention has special reference to improvements upon our recently patented steam generators,” the principle of circulation may be assumed as a constituent part of the device shown in the second patent. In it, therefore, we find a main circulation of such strength from the inherent character of construction that the down-flow pipes of prior constructions, imbedded in walls to subject them to less heat than that of the combustion chamber, were dispensed with, and the structure adapted in its several parts to absorb all the heat possible in the chamber. We find also the circulation through the mud drums, and, indeed, the two mud drums connected by a pipe which, from its relative scale size, as shown in the drawing, and from its being deemed worthy of mention in the specification, was obviously not a mere supply pipe for water which every boiler must have, but must have had a functional duty in the subsequent operations of the structure. The statement in Stirling's patent that "water-tube boilers, as heretofore constructed, have also been found objectionable because of the large space which they occupy, and the large number of handholes with covers and bolts necessary to get at the inside of the tubes for cleaning," if meant to apply to boilers other than the header type, is not a correct statement of the prior art, for in this

v.72F.no.6-50

« НазадПродовжити »