US449381A - Downdraft tubular boiler - Google Patents

Description

D v OBRIEN DOWN DRAFT TUBULAR BOILER.

Patented Mar. 31,1891.

UNITED STATES PATENT OFFICE.

DENNIS V. OBRIEN, OF BOSTON, MASSACHUSETTS.

DOWNDRAFT TUBULAR BOILER.

SPECIFICATION forming part of Letters Patent No. 449,381, dated March 31, 1891.

Application filed January 3, 1891. Serial No. 376,593. (No model.)

.To aZZ whom it may cancer/u:

Be it known that I, DENNIS V. OBRIEN, of Boston, in the county of Sufiolk and State of Massachusetts, have invented certain new and useful Improvements in Downdraft Tubular Boilers, of which the following is a specification.

This invention relates to downdraft tubular boilers; and it has for its object to provide a large area of heating-surface exposed to the heated products of combustion from the furnace at a point where the heat is the mostintense.

The invention consists in the interposition of a short tubular boiler-section between the rear end of the grate and the usual tube-sheet which supports the front ends of the boilertubes, said section comprising two tube-sheets located near each "other at the'rear end of the grate, and inclosing a water-space which communicates with the usual water-spaces of the boiler and a number of tubes connected with said sheets below the grate, said tubes conducting the products of combustion through the said water-space, so that the water therein is subjected to the action of a high degree of heat, the products of combustion passing directly from the grate through the said sec tion, and from thence to the usual longitudinal tubes of the boiler through a chamber between said section and the usual tube-sheet, all of which I will now proceed to describe and claim.

The accompanying drawing represents a sectional perspective View of a boiler embodying my invention.

In the drawing,- (t represents the outer shell of the boiler, and a represents the section or portion of the inner shell, which, with the crown-sheet c, surrounds the fire-box 7; and ash-pit 712'.

g represents the grate, and f a tube-sheet, which supports the rear end of the grate and extends across the space inclosed by the crown-sheet c and shell a, said tube-sheet extending vertically from the crown-sheet to the bottom of the shell a, and entirely across said shell. f represents another tube-sheet of the same form and size as the sheet f Said sheet f with the shorter crown-sheet c, shell a and tube-sheet f constitute a combustionchamber 1', separated from thegrate by the water-space between the tube-sheets f f The sheetsf f support a large number of short tubes f which are located below the grate and conduct the heated products of combustion from the space below the grate through the water-space between the sheets f f to the combustion-chamber t'.

It will be observed that the tube-sheets f and f and the tubes f therein constitute a short section of tubular boiler, the water-space of which communicates on all sides with the usual water-spaces of the boiler, so that there is a free circulation of water through said section. The tubes f being located below the grate and constituting the only outlet for the products of combustion, cause a downward draft through the grate and afford large areas of surface on which the highly-heated products of combustion, fresh from the bed of burning fuel, act. The location of said tubes below the grate also causes the products of combustion to enter the lower portion of the chamber 1 so that the natural tendency of heat to rise will insure a thorough distribution of heat in said chamber, so that each of the usual elongated tubes 21, extending from the tube-sheet f through the main body of the boiler, will be heated to practically the same degree as all the others, the heat being equalized throughout the chamber 2'.

It will be seen that the tube-sheet f and the tubes If have the same form and arrangement as in ordinary boilers, the distinguislr ing feature of my invention being the two additional tube-sheets ff and the tubesf connected therewith, the whole forming a shorttubular boiler-section located close to the grate and having its tubes located below the grate.

I am aware that downdraft boilers have been made in which a depending water-leg supports the rear end of the grate, said waterleg terminating just below the grate, so that the products of combustion pass through a large opening between the lower end of the water-leg and the bottom of theinner shell of the boiler, there being no direct connection between the interior of the water-leg and the water-space at the bottom of the boiler below the ash-pit. Boilers so constructeddo not have that large area of heating-surface exposed to thehighly-heated products of combustion fresh from the fire that is presented by the short tubular boiler-section of my invention. Hence the action of the water-leg boiler in generating steam is not so rapid nor so economical of fuel as that of my improved boiler. Moreover, the said water-leg does not constitute a vertical passage or conduit communicating at its bottom or lower end with the waterspace at the bottom of the boiler, but terminates in a closed bottom just below the grate, said bottom affording a resting-place for sediment which, owing to the intense heat at this point, is very liable .to cause the burning of the metal. My improved tubular section, on the other hand, opening into the water-space at the bottom of the boiler, affords no surface for the accumulation of sediment or scale, there being a continuous circulation through the said section from bottom to top.

In addition to the advantages of my improvement above specified, another i m portan t advantage is the increased strength imparted to the boiler by the two fiue-sheetsff the same extending entirely across the inner shells of the boiler, vertically as well as hori zontally, and being connected all around their edges by rivets r with the said inner shell.

I claim- The improved downdraft tubular boiler having the inclined grate, the tube-sheet located at a distance from the rear end of the grate and supporting the forward ends of the ordinary tubes, the short tubular boilersection interposed between the grate and the flue-sheet at the rear end of the grate and composed of the tube-sheets extending entirely across the inner shell of the boiler, vertically as Well. as horizontally, and the short tubes in said sheets located below the grate, said short tubular section being separated from the tube-sheet by a chamber, into the lower portion of which the products of combustion pass through the tubes of the tubular section, the tubes and tube-sheets composing said section presenting large areas of heating-surface to the highly-heated products of combustion close to and below the grate, as set forth.

In testimony whereof I have signed my name to this specification, in the presence of two subscribing Witnesses, this 17th day of December, A. D. 1890.

DENNIS V. OBRIEN. iVitnesses:

O. F. BROWN, EWING W. HAMLEN.

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