US8742A - Improvement sn steam-boilers - Google Patents

Description

J. 'MILLHOLLAND.

Steam Boiler Fire Tube.

No. 8,742. I Patented Feb. I7, 1852.

NITED STATES ATENT rrrcE,

JAMES MILLHOLLAND, OF READING, PENNSYLVANIA.

IMPROVEMENT EN STEAM-BOILERS.

Specification forming part of Letters Patent No. @,74%, dated February 17, 1852-.

To all whom it may concern: Be it known that I, JAMES l\IILLHOLLAND, 0 Reading, in the county of Berks and State of Pennsylvania, have invented certain new and useful Improvements in Steam-Boilers and Furnaces therefor, with a view to adapt them the better to the use of coal as fuel, which improvements are particularly applicable to locomotive-engines for railroads; and I do hereby declare that the following is a full, clear, and exact description of my said improvement, reference being had to the accompanying drawings, which form part of this specification, and in which- Figure 1 represents a vertical longitudinal section through the middle of a locomotiveboiler. Fig. 2 is a plan of the fire-box, and

-Figr3-is'a transverse section through the supplementary combustion-chamber.

It has long been a desideratum to obtain a locomotive-engine with its furnace and boiler constructed in such manner that anthracite coal could be employed successfully as the fuel for generating steam, because of its cheapness and great heating-power; but the intensity of the heat generated by this fuel when supplied with a sufficient quantity of air to insure its thorough combustion has generally acted with such energetic and destructive effect upon the sides of the fire-box as to render its use exceedingly difficult and its economy doubtful.

The object of my invention is to protect the fire-box from overheating and at the same time to insure the most thorough and complete combustion of the coal burned therein. The means I have adopted to attain this end is to place a contracted grate in the fire-box, which by excluding the air from direct access to the outer margin. of the coal keeps down the heat sufficiently to protect the sides of the box; but in doing this a large volume of inflammable gas is allowed to pass off unburned, and therefore without producing the proper heating effect or generating the quantity of steam due to the consumption of fuel, which defect, if not remedied, would preclude the use of the contracted grate, as it would diminish the efficiency of the engine, to maintain which is the first consideration in point of importance; but I have provided for the completion of the combustion of the gases thus evolved from the coal by combining with thecontracted grate a supplementary chamber of combustion which is duly supplied with air and arranged in a well-known manner between the fire-box and the smokebox and connected with both by flues. Those which communicate with the fire-box, for more efficiency, should be of large area to conduct the gases freely into the chamber where they are to be burned, and those which communicate with the smoke-box of small area, that they may not allow the burning gases and flame to escape too freely, and also that they maypresent a large evaporatingsurface to absorb the heat more readily from the escaping gases.

In the accompanying drawings, A is the firebox; B, the steam-dome; C, the smoke-box; D, the cylindrical shell which connects the firebox and smoke-box and contains the supplementary chamber of combustion, E, the small tubular flues F, which connect the chamber with the smoke-box, and the larger tubular fines, G, which connect the chamber with the firebox. The lines G are considerably larger than those ordinarily used in locomotiveboilers to give an enlarged area for the passage of the unburned gases from the fire-box into the combustion-chamber.

The fiues F are of the size ordinarily used in locomotives and are more numerous than the fines G, so that with a large evaporatingsurface their aggregate areais sufficiently contracted to prevent the escape of the burning gases and flame without giving time to absorb their heat.

To complete the combustion of the inflammable gases in the intermediate chamber, E, atmospheric air is injected into the chamber from an air-box, II, which is introduced into the lower part of the chamber. The top of this box is perforated with numerous small holes, through which the air passes into the chamber in a corresponding number of small jets. A pipe, j, supplies the chamber with air, which in this instance is caused to pass through the ash-pit and there get warmed by the waste heat on its way to the pipe.

The grate occupies the usual position in the fire-box A; but its area is contracted by mar= ginal plates K, or otherwise, to a sufficient extent to afford a lodgment for a stratum of ashes all around the lower part of the sides of the fire-box to protect them from the intense heat of the burning coals. These plates also prevent the air from passing up immediately at the sides of the boX and thussuffer the coals around the margin of the fire adjagent to the sides of the box to burn with less heat and evolve a large volume of inflammable gas, which passes off through the flues G into the chamber E to be mixed with air and burned.

The draft in this boiler may be generated in the usual manner by a steam-blast in the chimney, as well to draw air through the grate into the fire-box as to draw it through the pipe j and wind-chest H into the supplementary chamber of combustion.

The slackening of the current of gas and flame while passing through the supplementary combustion-chamber causes a precipitation into the bottom of the chamber of the greater portion of the ashes carried by the draft from the fire-box. The ashes thus precipitated must from time to time be withdrawn bya door arranged for the purpose in the bottom of the chamber. The enlarged flues G, by giving free vent to the hot gases, lower the temperature of the fire-box and thereby prolong its duration, which is further increased by the contraction of the grate, which prevents the direct contact of the draft with the sides of the box and permits the accumulation of a lining of ashes around the lower edge of the side plates. -With these advantages is also combined a considerable saving of fuel; but the chief merit and advantage of this arrangement is its distribution of the burning of the fuel and of the heat evolved thereby through two chambers of combustion, which prevents the excessive and destructive concentration of heat which occurs when the combustion of anthracite coal is completed in a single chamber of the neoessarily-contracted dimensions of the fire-box of a locomotive.

Having thus described myimprovements in locomoti ve-boilers,what I claim'therein asnew, and desire to secure by Letters Patent, is-

The contracted grate in the fire-box, in combination with a supplementary chamber of combustion supplied with air and situated at a point intermediate between the fire-box and smoke-box which is connected with the former and the latter by fines, in the manner substantially as herein described.

In testimony whereof I have hereunto subscribed my name.

JAMES MILLHOLLAND.

Witnesses:

D. A. GRIFFITH, J. O. ALLEN.

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