US1270017A - Steam-boiler and appliances. - Google Patents

Description

C. W. CROWELL.

STEAM BOILER AND APPLIANCES.

APPLICATION FILED OCT. 31, 1914.

Patented June 18, 1918.

2 SHEETSSHEET I.

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STEAM BOILER AND APPLIANCES.

APPLICATION FILED OCT. 31. 1914.

1,270,017. Patented June 18, 1918.

2 SHEETS-SHEET 2.

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STEAM-BOILER AND APPLIANCES.

Application filed October 31, 1914. Serial No. 869,647.

To all whom it may concern:

Be it known that I, CHARLES W. GRownLL, of Salisbury, in the county of Rowan, and in the State of North Carolina, have invented a certain new and useful Improvement in Steam-Boilers and Appliances, and do hereby declare that the following is a full, clear, and exact description thereof.

My invention relates to steam boilers, and while I have had in view particularly the application thereof to horizontal, or approximately horizontal boilers for use on railway locomotives, ships and big stationary plants, it is to be understood I do not restrict my invention in such of its characteristics as do not require a particular type of boiler, to application of boilers of the kind named. Inasmuch as this application discloses subject matter. common with that of an applicationfiled by me April 5, 1911, Serial No. 619,051, the present application is a continuation of that application in respect of the subject matter common to both.

The object sought to be achieved by my present invention is the provision, in the best and most complete embodiment of the invention, of a boiler, suited for high pres sure and 'quick steaming, of small initial buildin cost and repair, which will be of long lifle, equalize expansion and contraction, economical in the consumption of fuel and utilize to the utmostthe unconsumed gases, or products of combustion which leave the fire box by utilizing them before they can escape into the atmosphere; and in which any desired kind of fuel may be burned.

In the accompanying drawings which are for the purpose of illustration only Figure 1 is a longitudinal section of one embodiment of my invention, as embodied in a locomotive boiler;

Fig. 2 is a vertical transverse section on two planes, one passing through the fire box and the other through the fire chamber;

Fig. 3 is a rear elevation of the boiler;

Fig. 4 is a detail view in side elevation showing one method of constructing the adjoining portions of the fire box and the fire chamber;

Fig. 5 is a longitudinal section of a. different construction embodying my invention showing another manner of its use;

Fig. 6 is a transverse vertical section there of on the line 66 of Fig. 5;

Fig. 7 is a detail view on a larger scale Specification of Letters Patent. Pate nee June 18, 1918.

showing the location of the man hole construction I prefer.

In the embodiment of my invention illustrated in the drawings,the boiler shell 10, is, generally described, of cylindrical form, but of larger diameter at its rear end-Wherein is situated in the, form of my invention shown in Fig. 1, a fire box and a fire cham her one in advance of the other, the rear one being the fire box, and which is designated 11 and contains the grate 12 and the front one, which for convenience and designation, I

shall term the fire chamber, and which is.

designated 13, these being also preferably cylindrical in form, and the shell 14 there- The front end of the fire box 11 is closed of being preferably a single sheet, although the two may be constructed of separate by a vertical flue sheet 16 and the front and the rear ends of the fire chamber 13 are closed by vertical flue sheets 17 at the rear end and 17 at the front end. A full set of fire tubes, or fines 18 connect the flue sheet of the fire box and rear flue sheet of the fire chamber, said fire chamber and said sheets I are also connected by stay bolts 19, and the space between said front and rear flue sheets is in communication with the interior of the boiler by holes 20 in the shell 14:, so that the fire tubes 18 are covered with the water in the boiler. The fire box flue sheet 16 and the fire chamber rear flue sheet 17 at the bottom portion are inwardly turned about alining openings in the two flue sheets for the reception of a collar 21 that is riveted to said flanges and said flue sheets have outturned flanges riveted to the shell- 14, the flange or flue sheet 16 being also riveted to a portion of the mud frame, all as best shown in'Fig. 7 By the flange and collar construction, a horizontal man-hole 22 is @provided. that gives access to the interior of the fire chamthat constructed as just described is very with the fire chamber and fire box and with all the fines, if so desired, through the opening provided through the back head 24 in the rear end of the boiler shell without removing the mud frame 23 or the back head 24: or interfere with the staying of either, or their connections to the boiler shell 10 and it possesses the very important advantage that it expands and contracts together with the fire box forward and backward and thus avoids danger of leaks which might be expected if'it' entered through the shell of boiler and the fire chamber. The bottom of the inner shell 14 that is coextensive with the fire box 11 is cut away to provide for the grate so that that'portion of the shell 14. is are, or crescent shape in cross section. A mud frame 23 is provided between. the bottom portion of the boiler shell 10 and the bottom portion of the firebox shell'14 and the boiler shell 10 to the rear of the mud frame is cut away in. correspondence with the cut away of the bottom portion of the shell'le' of the fire box.

The back end of the boiler extending be tween the outer shell 10, and the inner shell '14 is closed by a back head 2d, the opening in which is preferably slightly larger indiameter than the shell 14 of the firebox and fire chamber having a filling rim 25 secured removed, this being possible by separating it from the fire chamber, either by cutting the shell between them in two, if a single shellis employed, or by disconnecting them if the shell portion of each is separately made from the other. A filling ring 25, as of metal, is placed between the outside o'fthe fire box shell at the rear end and the interior of the h ole through the back head 24 so as toclosely fill up the slight space provided for the passage of the fire box shell M'through the opening in the back head.

The portion of the fire box shell contignous to the man hole is cut away, or a large opening 26 is provided in order to prevent mud accumulations, or deposit around the man hole and also to render the structure convenient for building and repair or removing without interfering with the other construction.

\Vithin the fire chamber 13 there is a partition 27 that rises from the bottom thereof between the front line sheet 17 and back flue sheet 17 we desirable point. thence forward to the front fiuesh'eet 17. constituting a supplementary combustion chamber 28 in the forward lower portion of the fire chamber 13. From the fire chamber 13 above said partition, a group of fire tubes 29 pass forward'to a flue sheet 30 at the rear end of the smoke box 31 and from the bottom of said smoke box a group of fines 32 extends rearward and communicates with the interior of the combustion chamber 28 at the bottom thereofand from the upper part of said combustion chamber a group of fiues extend forward to aninner or supplemental smoke chamber 34 in the smoke box 31 from which smoke chamber 34 a pipe 35 leads to the stack, while into the bottom of said smoke chamber 34 reaches a pipe, or conduit 36 for exhaust steam. The group of tubes 29 is larger in number than the group of tubes 32 and the latter'is larger in number than the group of tubes 33, so that as it will be seen fromthe arrangement shown and described, the gas and products of combustion will pass from the fire box 11 through fines 18. thencethrough the fire chamber 13 forward through the fines 29 to the smoke box 31, thence back through the lines 32 to the combustion chamber 28and finally forwardfrom the latter throughthe fines 33 to the outlet through chambers 34 and stack 35. The gradual, diminishing capacity of the tubes produces a condition equivalent to a long tapered smoke chimney. Inasmuch as air, steam, oil, or other combustible, or means for promoting combustion, is introduced into the combustion chamber 28, as I hereinafter more fully point out, with which the furnace gases, or unconsumed products of combustion that reach such chamber are thoroughly mixed in the'lower part ofthe combustion chamber 28, and as the contents of said combustion chamber 28 are subjected to fierce heat from the partition 27 (which is exposed to the heat from the fire box 11' and preferably is made of fire brick. or the like) they are ignited and it will be seen that the extraction of heat in a high degree is secured from the fuel used and'it is applied to the water in theboiler by the passage of the high temperature derived from the combustion of gaseous products in chamber 28. through the third group of fire tubes 33 before the stack is finally reached. By the grouping of the fines, and extending them to the top of the flue sheet 30, and arranging parts mentioned therewith, as shown and described, I provide a return tube boiler and get a large area of heating surface.

For the supply of air, steam, oil, or other combustible to the lower part of the combustion chamber 28, I pass a pipe 37 (or more than one should it be desired) horizontally through the partition 27 from the fire chamber 13, which in the latter is formed into a coil 38 and extends through a hole, or flue in the fire box fine sheet 16 andthe rear fire chamber flue sheet 17 between the grate and the mud ring and leads to some convenient point outside the boiler where any desirable means may be provided for regulating the air or other a ent passing therethrough. The air, or other agent is heated to a very high temperature in the coil 37 preliminary to its entering the com-' bustion chamber 28. The partition wall 27 and the pipes 37 are exposed to the heat from the fire box 11, and give additional heat to the gases as they arrive in the combustion chamber 28, and thus the air, or other fluid agent before its delivery to the combustion chamber 28 is highly heated so that it most efliciently promotes the combustion of gases enterin the combustion.

' tube can be located, as I have shown, where it. gives ready access to the fire chamber and expands and contracts equally with its con nections. 1 I

As shown in Fig. 4, the rear fire box 11, and the fire chamber 13 have independent shells and they are abutted together, or placed endwise and joined by numerous plates 39 riveted to adjacent portions of the respective shells.

In the form of my invention illustrated in Figs. 5 and 6, the fire chamber 40 is located farther forward than in the construction shown in Fig. 1 so that the fire tubes corresponding to the fire tubes 18, shown in Fig. 1. are, of course, of greater length and a par tition 41 is provided which may be of sheet metal, or fire brick corresponding with the partition 27. when the structure shown in Fig. 1 is employed to provide the supplemen tary combustion chamber in the lower for ward side of the fire chamber. A baflle '42 consisting of two horizontally projecting plates, one of which is adjustable, is extended from the front flue sheet 17 rearward in the case of both the structures illustrated in Figs. 1 and 2 in order to direct thecurrents issuing from the lowermost group, or tubes 32 in the combustion chamber 28. The structure shown in Figs. 5 and 6 is similar to what appears in my aforesaid Patent No. 1,115,787, and may be used in connection with any kind of fire box.

My fire chamber and combustion chamber and return flue arrangement is not dependent upon the particular type of fire box shown in Fig. 1, as will be noticed in the drawings Fig. 5, as well as the drawings in Fig. 1 of Patent No. 1,115,787.

1n designing and building the described con struction, the flue sheet 30 may be made as large as desired to carry the number of flues wanted. The outer shell 10 extending about the inner shell 14 may be made as large as possible for locomotives, and tapered from near the front portion of the inner shell forward to a point near the flue sheet 30. The inner shell l4'may be made the sainesize'as the flue sheet 30, but in order to get more. grate and heating area, it can be made" larger than the flue sheet 30. by placing the top the same height as the top of fine sheet 30, and reducing the width of the mud frame 23. By so doing it enables me to get more than the required grate area per heating flue, the grate area 12 is figured against the number of fines in series 29 only. 'The back head ofthe boiler shell is placed in the edges, of said inner and outer shells at the rear end, said back head and the mud frame 23 being stayed to shell 10, as shown in Figs. 1 and 2, and are permanently located being finished up before the inner shell 14 is inserted, said inner shell maybe built on the outside with or without all parts secured therein, and inserted through the opening in the back head 24 and secured to the mud frame with filling rim 25 inserted between the opening in the back head and said inner shell and secured therein, after which stays 15 can be secured between said inner and outer shells. It is preferred though in Fig. 1 that the front head 43 and rear head 44' forming the rear water wall 45' in the rear 1 end of the inner shell-14 and the flue sheets 16 and 17 with flues 20 and man hole 22,v and the flue sheet 17 all be installed in said inner shell. before it is inserted into the boiler shell. i

In repairing my described construction either head 43 or 44 may be renewed or both and all rivets held from the outside by re-..

moving the filling rim 25.

To renew the fire box 11 if shell 14 is in one sheet, cut shell, in two between flue sheets 16 and 17. remove tlues 18. remove rivets from man hole 22 which are secured toflue sheet. 16, remove stay bolts 19, and the rivets from the mud frame 23, remove stays 1-5 and the filling rim 25, and the fire box 11 will pass out rearward without removing the mud frame 23 or the back head 24 or the staying of either.

The fire box may also be removed in the same manner, and leave the fiue sheet 16 and the flues 18 intact; I

The flue sheet 16 may be renewed alone, or include the flue sheet 17, flues'18, stay bolts 19, and'man hole 22. 1

The man hole tube may be removed rearward alone by cutting rivets loose from flue sheets 16 and 17. box 11 and fire chamber 13 may be made'in one piece, but for convenience in repairing it, may be made in two sections, and buttedtogether between the flue sheets 16 and 17,

The shell'14 around fire and secured together with butt straps 39 shown in Fig, l.

By cutting the fines 29, 32, and 33 loose from the flue sheet 30 and removing stays 15 and cutting rivets loose from the mud frame 23 and removing filling rim 25, all of the fines, the combustion chamber 28, the fire chamber 13, the fire box 11 and the man hole tube 22 may be removed in a body through the opening in the hack head 24.

The man hole tube 22, has a cover 46 to be removed for entering fire chamber 13.

Having thus described my invention what I claim is i 1. A steam boiler having a fire box, a fire chamber and a smoke box arranged in advance of each other, all being substantially circular in cross section, a group of fines extending from said fire box to said fire chamber, and a second group of fines extending from said fire chamber to said smoke box forming a forward passage, a third group of fines forming a rearward passage from said smoke box to a combustion chamber within said fire chamber, and a fourth group of fines forming a forward passage to an inclosed member in said smoke box, having an outlet thence through a stack.

2. A steam boiler having inner and outer shells spaced apart, both being substantially cylindrical with portions removed at their bottoms forming an opening for grates, a grate situated therein, said shells having a mud frame extending around the edges of said opening and between said shells and secured thereto; a portion of said inner shell extending forward from its connection at the front portion of the mud frame a distance from said grate opening, a flue sheet in its forward end and heating fines extending forward therefrom in three groups, upper, lower, and intermediate, a combustion chamber being formed between said shells and said flue sheet in advance of said grate opening, and means for directing the flames and gases forward through said upper series of fines; thence through said lower series into said combustion chamber, and thence forward through the intermediate series to the outlet.

3. A steam boiler having inner and outer shells spaced apart, both being substantially cylindrical with portions removed at their bottoms forming an opening for grates, a grate situated therein, said shells having a mud frame extending around the edges of said opening and between said shells and secured thereto, said inner shell being extended forward beyond the mud frame a distance and having a flue sheet in the front portion thereof, a flue sheet in the front portion of said outer shell, heating fines con necting said flue sheets, said inner and outer shells being formed and arranged in position so as to allow the tops of said flue sheets to be placed substantially on a horizontal line with each other and said heating fines extending to the tops thereof.

4. A steam boiler having inner and outer shells spaced apart, both being substantially cylindrical with portions removed at their bottoms forming an opening for grates, a grate situated therein, said shells having a mud frame extending around the edges of said openings and between said shells and secured thereto, a per ion of said inner shell extending forward from its connection at the front portion of the mud frame a distance from said grate opening, a flue sheet in its forward end, and heating fines extending forward therefrom, said inner shell be ing removable through the opening in the back head 2% of the boiler, by cutting rivets from its connection and from said mud frame connection.

5. A steam boiler having inner and outer shells spaced apart, both being substantially cylindrical with portions removed at their bot-toms forming an opening for grates, av grate situated therein, said shells having a mud frame extending around the edges of i said opening and between said shells and secured thereto, a fire chamber in said inner shell extending forward from said mud frame, a fire box being above said grates and two flue sheets forming a water wall between said fire chamber and fire box having heating fiues secured therein, a man hole formed in said flue sheets through said water space below said grates and above said mud frame for gaining admission into the fire chamber.

6. A steam boiler comprising inner and outer shells spaced apart, a back head secured between the rear ends thereof, having an opening therein for the reception of an open bottom fire box, the opening in said back head being greater in size than said fire box, a member being fitted between the edges of said back head opening and said fire box, said member being removable so that the fire box may be easily inserted, or withdrawn through said opening.

7. A steam boiler having a fire box and a fire chamber consisting of a substantially cylindrical shell, three flue sheets, front, rear, and intermediate spaced apart and secured therein, two heads secured in the rear end'of said shell forming a rear water wall, a water wall being formed between said rear and intermediate fine sheets which separates said fire box and fire chamber, heating flues extending therethrough, said front flue sheet being secured in the front end of said shell and heating flues extending therefrom, holes being provided in said shell for the circulation of water between the rear and intermediate flue sheets, a grate opening being provided in the bottom of shell extending between said rear flue sheet and rear water wall, said fire box and chamber being removable through the boiler head rearward.

8. A steam boiler having a fire box and a fire chamber consisting. of a substantially cylindrical shell having three flue sheets front, rear, and intermediate, spaced apart therein, the fire chamber being in front of the fire box, heating flues extending forward from said front flue sheet, other heating flues extending from said rear flue sheet to said intermediate fine sheet, a water wall consisting of two heads spaced apart and secured in the rear end of said shell, a grate opcningbeing provided between said water wall and said rear flue sheet, a grate secured therein, said fire box and fire chamber being removable through the rear end of the boiler.

9. The combination i na steam boiler having a fire box and a fire chamber consisting of a substantially cylindrical shell having three flue sheets, front, rear, and intermediate spaced apart therein, the fire chamber being in front of the fire box, heating flues extending forward from said front flue sheet, other heating flues extending from said rear flue sheet to said intermediate flue sheet, a water Wall consisting of two heads spaced apart andsecured in the rear end of said shell, a grate opening being provided between said water wall and said rear flue sheet, a grate secured therein, a man hole tube extending from rear flue sheet to said intermediate flue sheet for entrance to said fire chamber, a ortion of said shell extending between sai rear and intermediate flue sheets being removed suflicient to prevent mud from settling around said man hole tube, and to make it easy in building and repairing same, other openings being made in said shell between said rear and intermediate flue sheets to allow water to circulate through the top thereof, and openings being formed'in said shell between said rear heads for the circulation of water there between said construction being removable through the rear end of boiler.

1.0. A steam boiler comprising an inner and an outer shell, said inner shell having an opening in a portion of its bottom, three flue sheets spaced apart therein forming a fire chai'nberin advance of the fire box, a combastion chamber formed within said fire chamber, flues extending between said fire chamber and fire box, a pipe leading from the outside of boiler through the fire chamber into said combustion chamber for heating andvconveying air or other fluid agent into said combustion chamber.

11. A steam boiler comprising an inner and an outer shell, the inner shell having a grate opening in a ortion of its bottom, a fire box and a fire c amber formed therein, flues extending between said firebox and tire chamber, other flues leading from said 12. A steam boiler comprising an inner and an'outer shell both being substantially circular in cross sect1on,-sa1d inner shell having three flue sheets spaced apart therei in, front, rear, and intermediate forming a fire chamber and a fire box therein, said inner and outer shells having a grate opening in their bottoms extending rearward from said rear flue sheet, the fire chamber being formed between said intermediate and front flue sheets, and having a combustion chamber formed therein for igniting and returning the flames, means for admitting air or other fluid agent into said combustion chamber from a feeding point through said fire chamber.

13. A boiler having a fire chamber, a combustion chamber and means for discharging flames, gases, or other combustible matter from the fire chamber through another portion of the boiler, and then into the combustion chamber to beconsumed, and discharge through another portion of the boiler to the outlet, said fire chamber and combustion chamber being separated by a partition wall, said partition wall being exposed to the fierce heat of the fire chamber for increasing the temperature, and igniting gases in said combustion chamber. o 14. A boiler having inner and outer cylindrical shells, an open bottomfire box formed in the rear portion of said shells, flue sheets spaced apart in the forward end of said inner shell and forming a fire chamber, heat ing flues extending forward from the front sheet of said fire chamber, heating flues connected to the flue sheets between said fire box and said fire chamber, a partition 'dividing the fire chamber in two parts, the lower front part forming a combustion chamber, said partition being arranged for directing the flames from the fire box through the upper part of said fire chamber, and for receiving them inthe lower part of said combustion'chamber where combustion takes place and directing the heat upward and forward through said combustion chamber. v

15. In a boiler, a firebox and a fire chamher being separated by two flue sheets, said fire box having an opening with grates in said openmg, a man hole for entering said fire chamber being provided through said flue sheets below said grates.

16. A boiler having a fire box with a flue sheet in its forward end, a fire chamber forward of said flue sheet, heatingflues communicating with said fire box and the rear end of, said fire chamber, other heating flues extending forward from said fire chamber,

a partition arranged in said fire chamber forming a combustion chamber, means for passing the flames and gases from the fire box over said partition into the flues, and returning them into the lower part of said combustion chamber, and one or more pipes leading into said combustion chamber for the purpose of discharging hot air or other combustible matter into said combustion chamber to ignite the unconsumed combustible matter received in said chamber from the flues.

17. A boiler having a smoke box and a fire box, a chamber circular in cross sections having front and rear flue sheets, heating flues communicating with said rear flue sheet and the fire box, other heating flues communicating with said front fiue sheet and the smoke box, and which are divided into upper, lower, and intermediate series, a partition dividing said circular chamber into two parts and forming a combustion chamber of the lower front part, said partition separating the lower and intermediate series of flues from the upper series, also separating the lower and intermediate seriesof flues from the flues in the rear flue sheet, the fines from said rear flue sheet all discharging in one portion of said circular chamber and passing out through the upper series into said smoke box and returning through the lower series into said combustion chamber where the unconsumed gases are mixed with hot air or other combustible matter admitted into said chamber, and a pipe, or pipes from the outside of boiler, entering the combustion chamber to ignite the gases and pass the heat forward again through the intermediate series of flues to the outlet.

18.-A steam boiler having a fire box, a fire chamber forward of said fire box, a combustion chamber within said fire chamber, a smoke box forward of said fire chamber, a group of heating flues extending between said fire box and the rear end of said fire chamber, three groups of heating flues, upper, lower and intermediate, extending between the front head of said fire chamber and said combustion chamber to the flue sheet of said smoke box, and means for returning the flames and gases from said fire chamber through said upper series 'of fines into said smoke box, thence through said lower series of flues into said combustion chamber, thence through the intermediate series of flues to an inclosed member in said smoke box, thence through a conduit to the outlet, the capacity of the groups of flues in the successive series being graduated.

19. The combination in a steam boiler having a fire box, a smoke box, a fire chamber and heating flues, said fire box having a fine sheet in its forward end, said fire chamber having a flue sheet in each end, a partition in said fire chamber dividing it in two parts, the lower part forming a combustion chamber, and said heating flues extend ing from the flue sheet of the fire box to the rear flue sheet of said fire chamber into which they discharge over and against the rear side of said combustion chamber, other of said heating flues extending from the front fiue sheet of said fire chamber to the flue sheet of the smoke box and divided into three series, upper, lower, and intermediate, and means for returning the flames and gases from said fire chamber and upper series of flues, through said smoke box and lower series of flues into said combustion chamber, thence through the intermediate series to the outlet.

20. A steam boiler having an inner and an outer shell, said inner shell comprising three distinct chambers therein, a fire box, a fire chamber, and a combustion chamber and heating flues communicating with each chamber.

21. A steam boiler having an inner and an outer cylindrical shell spaced apart, said inner shell containing three chambers, the rear one of which has an opening in the bottom for-the reception of a grate, said outer shell being cut away under the grate, axfire chamber forward of said rear chamber having another chamber formed therein, and heating flues communicating with all three chambers.

22. A boiler having a fire box, a fire chamber forward of said fire box, means'for the discharge of products of combustion from said fire box to said fire chamber, a combustion chamber, and one or more pipes for delivering air or other combustible matter into the combustion chamber that loads from outside the boiler into the fire chamber where it is subjected to heat therein, and thence passes into said combustion chamber.

23. A boiler having a fire box, a. fire chamber forward of said fire b'ox means for the discharge of products of combustion from said fire box to said fire chamber, a combustion chamber, and one or more pipes for delivering air or other combustible matter into the combustion chamber that leads from outside the boiler into the fire chamber where it is subjected to heat therein, and thence passes to said combustion chamber, said fire chamber being composed of a shell and two 'flue sheets, and the combustion chamber being formed therein by a partition that divides off a portion of the interior of said shell.

2st. A steam boiler having a smoke box, a fire chamber, a combustion chamber within said fire chamber, a group of flues extending from said fire chamber to said smoke box forming a forward passage, a second group of flues extending from said smoke box to said combustion chamber forming a rearward passage, a third group of flues extending from said combustion chamber forming a forward passage to the outlet through said smoke box;

25. The combination in a steam boiler having a fire box, a flue sheet in its forward end, a fire chamber in advance of said fire box, a fiue sheet in its rear end, both being substantially circular in cross section, the fire box having an opening for the reception of a grate, the shells of said fire box and said fire chamber extendin beyond said flue sheets, and being abuttec together about midway the distance between said flue sheets, and butt straps securing the abutted ends together so that said fire box may be re moved rearward through the rear end of the boiler without moving said fire chamber by cutting butt straps loose from the extension of the shell of said fire box, openings being provided in the abutted ends of said shell for the circulation of water between said flue sheets, heating flues, a man hole tube and stay bolts being secured in said flue sheets, and a portion of the abutted ends of said shells being removed from the bottom to prevent mud from settling around said man hole tube, also to make it convenient for building and repairing said man hole connection.

26. A steam boiler comprising inner and outer shells spaced apart, aback head secured in the rear ends thereof, having an opening for the reception of an open bottom fire box, the opening in said back head being greater in size than said fire box, a member being fitted between the edges of said back head opening and said fire box, and being removable so that the fire box may be easily inserted, or withdrawn through said open-- ing.

27. The combination in a steam boiler comprising an inner and an outer shell both being substantially cylindrical and having an opening in a portion of their bottoms, a mud frame fitted between said shell bounding the edges of said opening, a flue sheet, heating flues, and a combustion chamber, said inner shell extending forward from said mud frame and said opening, said fiue sheet secured in its front end, heating flues extending forward therefrom being divided into upper, lower, and intermediate series, a partition wall resting against said flue sheet and against said inner shell forming said combustion chamber and dividing the upper series of flues from the lower and intermediate series, and means for directing the flames and gases forward through the upper series of flues and returning them into said combustion chamber through the lower series of flues thence forward through the intermediate series to a point of discharge.

28. A steam boiler comprising an inner and an outer shell, the inner shell having an opening in its bottom, a fire chamber in its forward end, a combustion chamber formed within said fire chamber, flues connecting said fire chamber from its rear end andflues communicating with the fire chamber and the combustion chamber, and means including flues connecting the combustion chamber with the stack.

29. A steam boiler having a fire box, a combustion chamber and heating flues, said heating flues being divided into upper, lower and intermediate series, said combustion.

chamber being separated from said fire box by a partition wall, and arranged in posi tion' so as to allow the flames and ases from said fire box to pass forward a ove said combustion chamber, through said upper series of fiues, thence through said lower series of flues into said combustion chamber, thence forward through said intermediate series of flues to a point of discharge.

30. A boiler having a fire box, a fire chamber forward of said fire box having a partition dividing it into two compartments, one of wh ch is a combustion chamber, flues bustion chamber formed therein by a -partition at its forward end made of refractory material, said partition being exposed to flames and gases from ltsrear side for increasing the temperature in said com-- bustionchamber, and means for directing the flames and gases over said combustion chamber through a portion of the boiler, and returning them through another portion of the boiler into said combustion chamber-for the gases to be ignited and discharged through another portion of the boiler to the outlet.

In testimony that'I claim the foregoing I'have hereunto set my hand.

i CHARLES W. CROWELL.

Witnesses:

M. L. GANTT, WILLIE LEE.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents,

Washington, D. C.

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