US757442A - Furnace. - Google Patents

Description

' No. 757,442. 7 PATENTED APR. 19, 1904'.

S. G. DAVIDSON.

FURNACE,

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PATENT OFFICE.

FURNACE.

SPECIFICATION forming part of Letters Patent No. 757,442, dated April 19, 1904.

Application filed July 2, 1903. Serial No. 164,048. (No model.)

- To all whom, it may concern.-

Be it known that I, SAMUEL OLELAND DAVID- SON, a subject of the King of Great Britain and Ireland, residing in Belfast, Ireland, have invented certain new and useful Improvements in Furnaces, of which the following is a specification.

In my Patent No. 682,674, dated September 17, 1901, I have described a furnace-front with a double wall forming an airchamber from which air is supplied to the furnace and to the ash-pit.

My present invention aims to provide a furnace-front showing certain points of improvement especially applicable to the type shown in said patent and also showing improvements applicable to other types of furnaces.

The principal objects of the present invention are to lengthen the life of the furnacefront, to facilitate the throwing of coal far into the back and the wings of the furnace, and to facilitate the passage of the air from one to another furnace when they are arranged as, for example, in the ordinary marine boilers. The improved furnace-front is also simplified in construction and presents other advantages in detail referred to hereinafter.

The accompanying drawings illustrate the invention as embodied in a furnace for marine boilers.

Figure 1 is a front elevation. Fig. 2 is a horizontal cross-section approximately on the line 2 2 of Fig. 1. Fig. 3 is a vertical approximately central section. Fig. 4: is a horizontal section just above the passages into the ash-pit. Fig. 5 is a vertical section approximately on the line 5 5 of Fig. 3, illustratinga modification of the invention. Fig. 6 is a front elevation of the tube-box or shell surrounding the doorway omitting the connected parts. Fig. 7 is a front elevation of an ordinary marine boiler having three fur- According to my aforesaid patent the doorway comprising a short arched passage extending longitudinally of' the furnace was joined to the inner transverse wall at a sharp angle, approximately a right angle. The corner formed by the meeting of these lonprior patent.

gitudinal and transverse walls has been found in practice to obtain a considerably higher temperature than either of the walls, owing to the exposure of this corner to the heat of the fire on its two faces and to the comparatively slow dissipation of the heat received by the very restricted surface of the interior of the angle inside the airchamber. The intense heat has frqeuently caused the metal at this point to burn away. Furthermore, it has been found that the straight axial walls of the doorway render it diflicult for the stokers to throw the coal into the wings or sides of the furnace.

According to the present improvement the walls of the doorway and the transverse wall at the inner end of the doorway meet in a curve, preferably of as large a radius as the space will permit and preferably connecting the transverse Wall and the doorway-wall in one integral casting. The doorway flares upwardly inward, so that, the stoker can give a certain amount of elevation to the shovel full of coal as he throws it in, and so facilitate throwing it. to the extreme back of the furnace. Preferably the opening is flared laterally also, which facilitates the throwing of the coal into the extreme front corners of the wings of the furnace. Where the inner wall of the air-chamber and the wall of the doorway are in one casting, the front plate of the air-chamber is preferably separate and attached by bolts to the inner or top plate. Airtubes leading into the furnace are preferably provided similar to those described in my said Preferably the air from the chamber to the ash-pit leads through a valved passage or passages, so that the relative quantities of air admitted to the furnace and the ash-pit are under control. It has been found that the admission of air to the top of the furnace in the manner described sometimes causes a back sweep of the flame under the baflie plate of the door, where it rises between the door proper and the baflie-plate, heating the door to a too high temperature. In my present furnace provision is made to avoid this action by the admission of air behind the baffle-plate.

Referring now to the drawings, A is the longitudinal wall of the doorway, B the inner transverse wall, and C the outer or front wall. These three walls A, B, and 0 include the air-chamber D. The walls A and B meet in a curve E of such radius as to include nearly all of the walls A and B themselves, at least at the top and sides of the opening. The heat from the fire on the grate-bars F strikes the curved wall E and is equally distributed over it, so that there is no concentration at any particular point, while the inner face of the curve within the air-chamber is of sufficient length to dissipate the heat rapidly. As indicated by the arrows G in Fig. 2, the lateral flare of the doorway enables the stoker to throw the coal much more into the front part of the wings than with the prior straight-walled doorway. Likewise, as indicated by the arrow H in Fig. 3, the stoker can give a degree of elevation to a shovel full of coal not possible with the prior construction, and so throw it much farther back into the furnace. The air which in a marine boiler furnace may come down through funnels or through forced draft is admitted at one side of the chamber, as at J, Fig. 5, and where three or more furnaces are employed for a single boiler the air after passing around the doorway passes out through the opposite opening J to the air-chamber of the adjacent furnace. Tubes or blowpipes K are mounted in the casting composing the plates A B and extend back into the air-chamber, so as to heat the air and direct it to a desired point in the furnace. The space D surrounds the doorway A on all sides and is made quite large, so as to present as little resistance as possible to the passage of air therethrough from one of the openings J to the opposite opening. The openings J, as shown, run down nearly to the top of the ash-pit door-opening, so as to give a straight passage for the air between the bottom of the furnace door-opening and the top of the ash-pit door-opening. The portion of the chamber below the doorway connects by passages L through a horizontal partition M with the ash-pit. The passages are preferably valved, as by means of a slide N, with solid portions 0 a little wider than the passages L. The slide N is connected by a link, as shown, to an arm on a shaft P, projecting through to the front and there provided with an operating-arm Q, carrying at its end on its under face a pin or rivet adapted to engage any one of the depressions or holes in the plate B, so as to hold the grid-valve N in any position to which it may be moved.

Any suitable valve may be used for admitting the air from the chamber D to the ashpit. For example, in Fig. 5 I show the horizontal partition M provided with two passages L, closed by gates or valves 0, pivoted at their outer edges and swinging downward,

. so as not to interfere with the clear passage for the air above, and connected to move together by suitable levers and links operated from a shaft P,which may extend through to the outside, like the shaft P, previously described.

The door may be provided with the usual or any suitable baflie plate S, spaced some distance within the door. In order to admit air within the space between the door proper, T, and the baflie plate S, I preferably provide passages U, formed by grooves in the front face of the tube-plate A B and disposed around the top and sides of said plate, as indicated in Fig. 6. For the access of a greater quantity of air I may substitute or add additional tubes or blowpipes K, Fig. 2, or openings V, Fig. 5, extending through the body of the plate A and preferably valved to regulate the quantity of air admitted according to requirements. For example, a pair of valves W might be applied, as shown, arranged to open and close together and under the control of an operatinglever on the outside, similar to the lever for operating the grid-valve described.

The front plate C and the surrounding ring X, as well as the horizontal partition M, are preferably formed in one casting, which is bolted, as indicated, to the tube-plate at suitable intervals and to the inner ash-pit plate Y, which engages the lower horizontal part of the door-opening A and which also carries the dead-plate Z, which supports the ends of the grate-bars F. The making of the plates Y and Z in one casting simplifies the construction and the assembling or separation of the parts. The usual hand-holes are provided in the front plate C.

The furnace-door Tis hinged, as usual, upon lugs a, cast on the front plate. Notched lugs 5 and '0 are provided at opposite sides of the door, the former being notched on its upper edge and the latter on its lower edge to engage an operating-bar (Z, pivoted on the outside of the door. The bar d is of the special shape shown in Fig. 2. At the end adjacent to the free edge of the door it is curved to provide a sort of handle 6, while at its opposite end it is bent around, as indicated at f.

A strap g is provided near each edge of the door, which overlies the end of the bar (Z and holds it close up to the door. The bar (Z is pivoted, as by a rivet h, the arm on the pivoted side of the door being a little shorter than the other arm, so that the outer portion is always weighted downward and the inner portion upward. Consequently when the door is slammed shut the outer arm of the bar (Z rides up over the inclined upper edge of the lug b and drops into the notch, locking the door shut. When the outer end 6 is lifted and the door opened, the arm being then dropped the door swings back until the portion f, moving in the are indicated in dotted lines in Fig. 2, strikes the inclined under face of the lug c and engages in the notch, holding the door open at about the position shown in dotted lines. The whole construction is very simple and strong, so as to minimize the possibility of its getting out or order.

The fire-pit door j is supported from lugs k on the front plate. The straps Z are hooked over the shaft m, running through the lugs 70, and the door j is provided with handles n, by which it can be swung open or lifted off the shaft m. A bolt 0 at the lower edge serves for looking it closed.

Fig. 7 shows the application of my invention to an ordinary marine boiler having three furnaces arranged in an ordinary manner. The air from a centrifugal fan or other suitable source enters by a tube A, leading into the air-chamber B of either furnace-front, as may be most convenient. The air circulates from the chamber of this furnace-front into the corresponding chambers of the other furnace-fronts through the passages J J of Fig. 5. Any suitable communicating chamber or passage between the furnace-fronts may be provided. A suitable construction is to provide a single chamber inclosed between a front plate D and the boiler-front; but any construction by which the air admitted to the chamber D of one furnace-front may circulate into the corresponding chambers of the other furnace-fronts may be used.

Though I have described with great particularity of detail certain embodiments of the invention, yet it is to be understood that the invention is not limited to the particular embodiments disclosed. Applications thereof to other types of boilers than that shown and various modifications 'in the details and in the arrangement and combination of the parts may be made by those skilled in the art without departure from the invention.

What I claim is 1. A furnacefront having a detachable doorway and being formed with an air-chamber entirely surrounding the lateral and top and bottom sides of said doorway, and leading to the furnace-fire, said doorway on the surface facing the fire being flared laterally and upwardly inward, and having tubular airpassages through said flared surfaces, to heat and admit air to the top surface of the fire from said air-chamber.

2. A furnace-front having a detachable doorway and being formed with an air-chamber entirely surrounding the lateral and top and bottom sides of said doorway, and leading to the furnace-fire, in combination with a substantially horizontal and straight partitionplate extending from side to side of said furnace-front, and separating the air-space which is below said detachable doorway from the ash-pit, and valved air-admission ports in said partition-plate for passage of air from said air-chamber into the ash-pit.

3. A furnace-front having a detachable doorway and being formed with an air-chamber entirely surrounding the lateral and top and bottom sides of said doorway, and leading to the furnace-fire, said doorway on the surface facing the fire being flared laterally and upwardly inward, and having tubular airpassages through said flared surfaces, to heat and admit air to the top surface of the fire from the said air-chamber, and a substantially horizontal and straight partition-plate extending from side to side of said furnacefront and separating the air-space which is below said detachable doorway from the ashpit, and valved air-admission ports in said partition-plate for passage of air from said air-chamber into the ash-pit.

4:. A furnace-front having a doorway, and being formed with an air-chamber surrounding said doorway on top, sides and bottom thereof, combined with a horizontal plate arranged below the bottom of said doorway, so as to leave a space between the two, an airadmission passage in said front arranged with a part of its effective opening below the bottom of said doorway, whereby air may be admitted directly to said space, and ports in said plate leading to the ash-pit.

5. A furnace-front having a doorway and an inner plate formed integrally with each other, and an outer plate and surrounding ring formed integrally with each other, said two parts being bolted together.

6. A furnace-front comprising a doorway and an inner plate formed integrally with each other, an outer plate and surrounding ring formed integrally with each other, and an inner ash-pit plate and dead-plate formed integrally with each other, said several parts being bolted together.

In witness whereof I have hereunto signed my name in the presence 'of two subscribing witnesses.

SAMUEL CLELAND DAVIDSON.

Witnesses;

THOMAS F. WALLACE, FRED WHITE.

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