GB2189312A - A boiler for a domestic fireplace - Google Patents

Abstract

A boiler, particularly a wrap-around type, has a series of hollow elements 28, 32, 34, 36 projecting forwardly from the hollow rear portion 10 of the boiler and so arranged as to define a flue passage(s) closed at the rear by the rear portion but open at the front to permit access for cleaning. There is also a door or doors 42, 44 which in a closed position substantially cover the front of the flue passage, and the hingeing of the doors permits movement between the fully open and fully closed conditions without the necessity to detach the doors. Fin arrangements are described, which include a substantially vertical fin 26 dividing the flue passage into two substantially separated passages and interdigitated fins 32, 36, 28 and 32, 34, 28 creating tortuous passages. The total length of the horizontal limbs of the flue passages is considerably greater than the total length of the vertical limbs of the flue passages. Alternatively, a series of short hollow cylinders project forwardly either side of a central vertical fin to provide zig-zag paths for the hot gases. <IMAGE>

Description

SPECIFICATION A boiler for a domestic fireplace This invention relates to boilers for use in domestic fireplaces, particularly those which are intended to burn solid fuel, though they can also be used with gas fires, particularly coal or log-effect gas fires.

Boilers of the kind to which the invention relates usually form part of a central, or partially central heating system, for a house, but it is to be understood that they can be used for other purposes, e.g. for domestic hot water supply.

Such a boiler usually comprises a water jacket shaped to provide the rearwall of the fire space of the fire grate and sometimes the water jacket also has forwardly extending hollow side cheeks which form the side walls ofthe fire space. A boiler with a hollowrearportion and hollowside cheeks, which as seen in plan, is of channel shape, with the fire space located within the channel, is usually referred to as a wrap-around boiler.

Many attempts have been madeto improvethe thermal efficiency ofthistype of boiler, generally by providing flues which increase the surface area of the boiler exposed to the hot flue gases when the boiler is in use. Typical ofthe previous proposals is thatthewrap-around boiler shown in the specification of United Kingdom patent number 2109537, which has a series of vertical hollowfins extending forwardly from the rear portion of the boiler, the interior of each of the fins communicating with the interior of the rear portion, the vertical spaces between the fins providing flues. A large removable steel plate extends across the front ofthe hollowfinsandclosesthefrontsoftheverticalflues between the fins. This removable plate is hooked on to braces bridging some of the vertical flues.

The present invention has for its objectthe provision of a boilerfor a domestic fireplace, which has very good thermal efficiency, but wherein cleaning ofthe flue passages ofthe boiler is facilitated. It will be appreciated, that any attempt to improve the thermal efficiency of this type of boiler by providing enclosed flues will be thwarted, if the flues are not cleaned at frequent intervals. Hence, ready access to the flues is very important. In many instances, it appears that the flues are not cleaned frequently enough, if at all. A probable reason for this which has not occurred to others attempting to improve the efficiency of this type of domestic boiler, is the difficulty of removing the plate which is used (as in specification 2109537 for instance) to close the fronts of the flues.The plate has to be of considerable thickness to withstand the heat of the fire and since it also has to cover a comparatively iarge area, it is quite heavy. Nothing appears simpler to the designerthan to hook the plate on the boiler in some way, and in every instance priorto our invention this is what has been done. However, in practice, a boilerofthis kind may be used byaquite frail person, who would find the removable plate very difficult to lift for engagement and disengagement of the hooks. Moreover, during the removal or flitting of the plate, it may easily slip from the grasp of the person holding it and in falling, it may inflict injury on that person. Having regard to these difficulties, it is apparent why many people particularly frail and elderly people living alone simply leave the flues uncleaned.

For some years now, various manufacturers have been fitting the removable front plate but a solution to the above outiined problem has avoided them, either because they could not devise an economic alternative to the removable plate, or because they simply failed to appreciate the nature of the problem.

According to a first aspect of the invention a boiler for use in a domestic fire space comprises a hollow plenum chamberwhichforms at leasta rear portion ofthe boilerand a series of hollow elements projecting forwardlyfrom the hollow plenum chamber and communicating internally therewith, the hollow elements defining at least oneflue passage closed at the rear by the plenum chamber, but open at the front to permit access for cleaning the flue passage(s) and a door or doors which in a closed position substantially cover the front(s) oftheflue passage(s), so thatthe flue passage(s) is or are completely circumscribed by the plenum chamber, the hollow elements and the door or doors, but in the fully open position of the door(s) the flue passage(s) is or are substantially completely exposed, the hinging of the door(s) permitting movement of the door(s) between the closed and fully opened positionswithoutthe necessity to detach the door(s).

Preferably, there are two doors hinged on their outside edges and meeting in the closed position art a median position to cover the fronts of the hollow element(s) andtheflue passage(s). In a preferred arrangement there is a series of hollow fins projecting from and contiguous with the hollow plenum chamber, the hollow fins defining a plurality offlue passages, at least one of which follows a zig-zag path.

According to a further preferred feature ofthis aspect of the invention there is a central vertical hollow fin and two hinged doors hinged respectively to side walls of the boiler, each door extending across halfthewidth between the side walls of the boiler, so that the doors meet each other and rest on the front of the central vertical fin.

According to a second aspect of the invention a boiler for use in a domestic fire space comprises a hollow plenum chamberwhich forms at least the rear portion of the boiler and a series of hollow elements projecting forwardly from the hollow plenum chamber and communicating internally therewith, the hollow elements defining two flue passages and including a substantially vertical fin so arranged that it divides the two flue passages from each other through the greater part oftheir lengths, and the flue passages being completely open at the frontthroughout substantiallythe whole oftheir lengths.

According to a third aspect of the invention, a boilerforuse in a domesticfirespace comprisesa hollow plenum chamberwhich forms at least the rear portion ofthe boiler and a series of hollow elements projecting forwardly from the hollow plenum chamber and communicating internally therewith, the hollow elements defining at least one tortuous flue passage comprising horizontal limbs and vertical limbs, the horizontal limbs having a total length at least equal to the total length ofthe vertical limbs and the flue passage being completely open at the front throughout substantially the whole of its length.

Preferably, the boiler comprises a hollow side wall; a substantially vertical hollow fin spaced inwardly of the hollow side wall; a substantially horizontal hollowfin projecting laterally inwards from the hollow side wall and communicating internally therewith and a substantially hollowfin projecting laterally outwards from the vertical fin and communicating internally therewith, at least parts of the two laterally projecting fins overlapping each otherto define partofthe tortuous flue passage.In the preferred construction of the third aspect of the invention, there are two hollow side walls and a vertical hollow fin is located approximately centrally between the side walls, there being two substantially horizontal hollowfins projecting laterally from each side ofthe vertical fin and a substantially horizontal hollow fin projecting laterally inwards from each side wall between the two hollow fins on that side ofthe vertical fin and overlapping both those hollowfins, so that the flue passage on each side of the central vertical fin has alternating horizontal limbs between the horizontal fins and vertical limbs around the ends ofthe horizontal fins.

According to a fourth aspect ofthe invention, a boiler for use in a domestisfire space comprises a hollow plenum chamberwhich forms at leastthe rear portion ofthe boiler and a plurality of interdigitated hollow fins each communicating with the interiorofthe plenum chamber, the interdigitation ofthe hollowfinsforming aflue passageway with at least five changes of direction, the said flue passageway being completely open at the front throughout su bstantiallythe whole of its length.

According to a fifth aspect of the invention a boiler for use in a domestic fire space comprises: a hollow plenum chamber forming at least the rear portion of the boiler and a plurality of discrete hollow protuberances projecting forwardly from the plenum chamber and communicating internally with the interior ofthe plenum chamber, each of the protruberances being closed at its front end, and the arrangement ofthe protruberances being such that flue gases flowing upwardly past them are forced to follow a zig-zag path.

Two constructions of boilers for use with a solid fuel domestic fire, and in accordance with the invention will now be described byway of examples only, with reference to the accompanying drawings, in which: Figure lisa front elevation partly in section,taken on the line I-I of Figure 2 of a first boiler, Figure2 is a plan viewofthe boiler shown in Figure 1, looking in the direction farrow II in Figure 1, Figure3isa section on the line Ill-Ill in Figure 1, Figure 4 is a scrap view to a larger scale showing part ofthe boiler and illustrating the closed position of a door, Figure is a detail perspective view showing the overlapping of a pair of doors and the means four securing those doors, and Figure 6 is a part front view, of a boiler of alternative construction.

The boiler shown in Figures 1 to 5 is made as a welded sheet steei or other metal fabrication, but it is to be understood that it could be made as a casting.

Basically,the boiler has a hoilow rear portion 10 and two hollow side portions 12 and 14,which project forwardly from the rear portion 10, and are in communication with the rear portion, so that a completely unitarywaterjacket or plenum chamber is formed by the rear portion 10 and the side portions 12 and 14. The arrangement ofthe rear portion and the side portions 12 and 14forms a channel as seen in plan, leaving a large space 16 bounded bythefront wall 18 ofthe rear portion 10, and the inside walls 20 and 22 ofthe side portions 12 and 14. Itwill be appreciated that the conventional fire grate shown in chain dotted lines at 23 in Figure 3, is received within the space 16, though the fire grate will probably project forwardly of the space 16.The boiler is therefore awrap-around domestic fire boiler.

The hot flue gases from a fire (shown at 25 in Figure 3) on the fire grate 23, are in contact with the walls 18,20 and 22 ofthe boiler, and this isthe fundamental means whereby heat is transferred from the flue gases thrugh the boiler to water contained within the boiler. The boiler is provided with an inlet connection 27 and an outlet connection 29, whereby water can be fed into the boiler and withdrawn from it, for supply to, for example, a central heating system and a domestic hot water supply system.

A series of hollow fins, which will be described in detail, extends forwardly from the front wall 18 of the rear portion 10, the interiors ofall the hollowfins being in communication with the unitary interior provided within the rear portion 10 and the side portions 12 and 14.

A bottom horizontal water tube 24 of rectangular cross-section (see Figure 3) extends across the full width ofthe fire space 16, and constitutes a complete bridge between the side portions 12 and 14. This water tube 24 is located at the rear of the actual fire position and at its rear it is spaced from the front wall 18, so that a flue passage 31 extends upwardly behind the bottom water tu be 24. Acentrally disposed vertical fin 26 extendsforwardlyfromthe rear portion 10. This central vertical fin is of rectangularcross-section, and a pair of horizontal fins 28 and 32 extends on opposite sides of the vertical fin 26 at the top and bottom respectively of the vertical fin, as shown in Figure 1,thereby providing an I-shaped central fin arrangement comprising the th rae fins 26,28 and 32. It will be observed, that the interior of this I fin arrangement is unitary, and is in communication with the interior of the rear portion 10 ofthe boiler (see Figure 3).

Indeed, the interior of the I arrangement can be regarded as a forward projection of the rear portion of the boiler. It will be appreciated however,thatthe provision of this I fin arrangement provides a considerable increase in the surface area of the rear portion 10.

Two hollow horizontal fins 34 and 36 are also provided. The fin 34 projects inwardly from the inner wall 20 ofthe side portion 12, andthefin 36 projects inwardlyfrom the innerwall 22 ofthe side portion 14.

The fins 34 and 36 are located between the horizontal fins 28 and 32 projecting from the central vertical fin 26, and it is to be observed, that the horizontal extension of the fins 34 and 36 is such thatthey overlap their respective parts of the fins 28 and 32.

Thus the fins 28,34 and 32 at one side and 28,36 and 32 at the other side are interdigitated, with spaces between them, so that a tortuous flue passage is provided on each side of the If fin arrangement. It will be noticed thatthefins 34and 36taper inwardlyand that they are rounded at their inner ends. The taper assists convection within the boiler and reduces the tendency of the boiler to hiss. If desired, the fins 28 and 32 could taper outwardly and be rounded attheir outer ends fora similar purpose. Each ofthe hollow fins 34 and 36 is in communication internally with the side portion from which it projects, and also with the interior of the rear portion. Thus, the horizontal fins 34 and 36 also extend the surface area of the boiler exposed to hot flue gases.

At the top ofthe boiler, a stationery throat plate 30 is welded to the inside walls 20, 18 and 22. Thisthroat plate extends forwardly over only part ofthe depth, from front to rear, of the I-shaped fin arrangement and the side fins 34 and 36. A top bar 40 bridges the side parts 12 and 14 of the boiler and is welded to the side parts. The top bar is level at the front with the front edges ofthe hollow fins 26,28,32,34 and 36, but it is spaced forwardly of the throat plate 30, so that an outlet flue 33 is provided between the throat plate and the top bar.

A damper (not shown) is provided forcontrolling theoutletflue33. The damper rests on the top ofthe boilerand isabletoslideforwardlyand rearwardly, between a forward position where it fully closes the outlet 33 and a rear position where itfullyopensthe outlet33. This kind of dampercontrol forflues in domestic fire boilers is well known and further description is uneccessary.

Considering now the flue provided between the variousfins, andtaking the right hand sidefor example,theflue passage in question commences in the passage 31 behind the bottom tube 24 and below the fin 32; it then passes upwardly around the end of the fin 32 and the side wall 22 and turns through 1800 onto the top side ofthefin 32; then it passes around the end ofthe horizontal fin 36, again turning through 180 into a horizontal portion between the fins 36 and 28; then itturns around the end ofthefin 28 into the space below the throat plate 30; finally it passes outthrough the outlet 33.

The two passages defined bythe hollow fins just described have been found to give a much greater efficiency than previous hollow fin arrangements.

The precise theory is not yet understood, but it appears that considerable advantages accrue from thefollowingfeatures:- i) The central vertical fin 26, which effectively divides the flue gases, so that after entering through the flue inlet 31, the gases follow two quite separate paths, one at each side of the boiler before reuniting above the top hollow fin 28.

ii) The fact that the flue passages have both horizontal limbs (e.g. between the fins 32 and 36) and vertical limbs (e.g. around the ends ofthefins 28and 36), butthetotal length ofthe horizontal limbs is considerably greaterthan the length ofthe vertical limbs. Improvements can be expected whenever the total length ofthe horizontal limbs is at least as great asthetotal length ofthevertical limbs.

iii) The interdigitation ofthe hollow fins 32,36 and 28 or 32,34 and 28 which produces the characteristic C-shaped flue passage, with relatively long horizontal limbs.

A pair of hinged doors42 and 44 is providedfor closing the front of the space bounded by the hollow side walls 12 and 14,thetop bar40 and the hollow bottom tube 24. In Figure 3, only the left hand door42 is shown and it is illustrated in the closed position. A single boss 46 is welded on the inside face 20 ofthe wall 12, and a hinge pin 48 passesthroughthis boss and through a boss 50 welded to the front of the door 42. It will be appreciated that a similar hinge arrangement is provided for the door 44. The only difference between the two doors is that, as shown in Figure 5, the door 44 has a joggled lip 52 which in the closed position overlaps the door 42 and holds the latter closed so long as the door 44 is closed.

It has been found that a single hinge pin per door is adequate, though it will be appreciated that any other hinge arrangement could be used. For securing the doors in the closed position, a catch 54 is provided, pivoted on the top bar 40. The catch 54 has an arm 56 which in the closed position engages with the front face of the door 44 and the rear edge 58 of this arm is inclined so that there is a cam action on the door 44 as the catch is turned into the locked position.

In the closed condition, the doors 42 and 44 effectively close the fronts of the flue passages between the hol low fins. Therefore, these passages are circumscribed bythefrontwall 18 ofthe rear part 10 ofthe boiler; the walls of the fins and the doors. In this condition of the doors, if the damper is moved to an open position, the natural draft through the flue passages will cause hot flue gases to pass upwardly through theflues and in intimate contactwith the walls of the hollow fins. Indeed it has been noted that the horizontal travel of the flue gases is greater than their vertical travel and this makes for a high thermal efficiency. If the damper is moved to the closed position there is virtually no flow of hot gases through the flues.

Each door fists underthe top bar 40 in the closed position and has a rearwardly angled lower part 60 which fits over the hollow bottom tube 24.

Whilsttheflue arrangement is particularly efficient, it will only remain so, if it is kept clean. If the doors 42 and 44 are moved into the fully open condition, they rest against the inside walls 20 and 22 ofthe side portions 12 and 14, and then the entire flue arrangement is exposed, and there is ready accessforcleaning.Thehinging arrangementofthe doors ensures that they can be manipulated very easily, without any necessity to completely remove them. This is significant, because in ordertofulfil theirfunction,the doors have to be of substantial thickness and weight, and could not be easily removed, particularly by a frail person.

It is to be understood that in its first aspect, the invention is not restricted to any particularflue configuration. Byway of example of an alternative arrangement, reference is made to Figure 6, wherein the hollow rear portion 10,the right hand sidewall 14,thetop bar40 and the hollow bottom tube24are all constructed as described with reference to Figures 1 to 5. It is also to be understood that doors similartothe doors42 and 44are providedthough these are not illustrated.

However, instead ofthe interdigitated fin arrangement, there is a single central vertical fin 62 and a series of short hollow cylinders 64on each side ofthe central fin. Each hollow cylinder is welded to the front wall ofthe rear portion 10, and opens into that portion in the same manner as the fins 28,32,34 and 36. The front end of each cylinder 64 is closed by a cap.

It will be observed thatthe hollow cylinders 64 are arranged in horizontal rows, butthatthey are staggered with respect to the cylinders in the adjacent row(s). Consequently, flue passages are formed between the cylinders for the upward travel ofthe hot gases, but the gases have to travel in a zig-zag path as indicated by the arrows shown in Figure 6. This extended flue path provides an efficient heat exchange system.

As with the construction illustrated in Figures 1 to 5, once the doors are fully opened, there is ready access to the flue passages for cleaning purposes.

Claims (14)

1. A boilerfor use in a domesticfire space comprising a hollow plenum chamber which forms at least a rear portion ofthe boiler and a series of hollow elements projecting forwardly from the hollow plenum chamber and communicating internally therewith, the hollow elements defining at least one flue passage closed at the rear by the plenum chamber, but open at the front to permit accessforcleaning the flue passage(s) and a door or doors which in a closed position substantially cover the front(s) of the flue passage(s), so that the flue passage(s) is or are completely circumscribed by the plenum chamber, the hollow elements and the door or doors, but in the fully open position ofthe door(s) the flue passage(s) is or are substantially completely exposed, the hinging ofthe door(s) permitting movement ofthe door(s) between the closed and fully open positionswithoutthe necessityto detach the door(s).

2. A boiler for use in a domestic fire space as claimed in claim 1 r in which there are two doors hinged on their outside edges and meeting in the closed position art a median position to coverthe fronts ofthe hollow element(s) and the flue passage(s).

3. A boiler for use in a domestic fire space as claimed in claim 1 claim 2, in which there is a series of hollow fins projecting from and contiguous with the hollow plenum chamber, the hollow fins defining a plurality of flue passages, at least one of which follows a zig-zag path.

4. Aboilerforuse in domesticfirespaceas claimed in claim 3, in which there is a central vertical hollow fin and two hinged doors hinged respectively to side walls of the boiler, each door extending across half the width between the side walls ofthe boiler, so that the doors meet each other and rest on the front ofthe central vertical fin.

5. A boiler as claimed in claim 1, constructed and arranged substantially as herein described with reference to Figures 1 to 5 or Figures 1 to 5 as modified by Figure 6 of the accompanying drawings.

6. A boiler for use in a domesticfire space comprising a hollow plenum chamber which forms at least the rear portion of the boiler and a series of hollow elements projecting forwardly from the hollow plenum chamber and communicating internallytherewith, the hollow elements defining two flue passages and including a substantially vertical fin so arranged that itdividesthetwoflue passages from each other through the greater part of their lengths, and the flue passages being completely open atthe front throughout substantiallythe whole of their lengths.

7. A boilerfor use in a domestic fire space comprising a hollow plenum chamberwhich forms at least the rear portion ofthe boiler and a series of hollow elements projecting forwardly from the hollow plenum chamber and communicating internally therewith, the hollow elements defining at leastonetortuousfluepassagecomprising horizontal limbs and vertical limbs, the horizontal limbs having a total length at least equal tothetotal length ofthevertical limbs.

8. A boiler for use in a domestic fire space as claimed in claim 7, and comprising a hollow side wall; a substantially vertical holiowfin spaced inwardly of the hollow side wall; a substantially horizontal hollow fin projecting laterally inwards from the hollow side wall and communicating internally therewith and a substantially hollow fin projecting laterally inwards from the hollow side wall and communicating internally therewith and a substantially hollow fin projecting laterally outwards from the vertical fin and communicating internally therewith, at least parts ofthetwo laterally projecting fins overlapping each other to define part ofthetortuousflue passage.

9. A boiler for use in a domestic fire space as claimed in claim 8, wherein there are two hollow side walls and a vertical hollow fin is located approximately centrally between the sidewalls, there being two substantially horizontal hollow fins projecting laterally from each side of the vertical fin and a substantially horizontal hollow fin projecting laterally inwards from each side wall between the two hollow fins on that side of the vertical fin and overlapping both those hollow fins, so that the flue passage on each side of the central vertical fin has alternating horizontal limbs between the horizontal fins and vertical limbs around the ends ofthe horizontal fins.

10. Aboilerforuse in a domestisfirespace comprising a hollow plenum chamberwhichforms at least the rear portion ofthe boiler and a plurality of interdigitated hollow fins each communicating with the interior of the plenum chamber, the interdigitation of the hollow fins forming a flue passageway with at least five changes of direction, the said flue passageway being completely open at the front throughout substantially the whole of its length.

11. A boilerfor use in a domesticfire space as claimed in anyone of claims 6to 10, fitted with a door or doors which in a closed position substantially coverthe front(s) ofthe flue passage(s), so that the flue passage(s) is or are completely circumscribed by the plenum chamber, the hollow fins and the dooror doors, but in the fully open position ofthe door(s) the flue passage(s) is or are substantially completely exposed,the hinging ofthe door(s) permitting movement of the door(s) between the closed and fully open positions without the necessity to detach the door(s).

12. A boilerfor use in a domesticfire space having a plenum chamber and hollowfins constructed and arranged substantially as herein described with reference to Figures 1 to 5 ofthe accompanying drawings.

13. Aboilerfor use in adomesticfirespace comprising a hollow plenum chamberforming at least the rear portion of the boiler and plurality of discrete hollow protruberances projecting forwardly from the plenum chamber and communicating internally with the interior of the plenum chamber, each ofthe protruberances being closed at its front end, and the arrangement ofthe protruberances beingsuchthatfluegasesflowing upwardly past them are forced to follow a zig-zag path.

14. Aboilerasclaimed inclaim 13,constructed and arranged substantially as herein described with reference to Figure 6 ofthe accompanying drawings.