IE59963B1 - 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.

Description

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 rear wall 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 of the fire space. A boiler with a hollow rear portion and hollow side 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 made to improve the thermal efficiency of this type 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 of the previous proposals is that the wrap-around boiler shown in the specification of United Kingdom patent number 2109537, which has a series of vertical hollow fins 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 of the hollow fins and closes the fronts of the vertical flues between the fins. This removable plate is hooked on to braces bridging some of the vertical flues.

The present invention has for its object the provision of a boiler for a domestic fireplace, which has very good thermal efficiency, but wherein cleaning of the flue passages of the 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 large area, it is quite heavy. Nothing appears simpler to the designer than to hook the plate on the boiler in some way, and in every instance prior to our invention this is what has been done. However, in practice, a boiler of this kind may be used by a quite frail person, who would find the removable plate very difficult to lift.for engagement and disengagement of the hooks. Moreover, during the removal or fitting 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 outlined 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 co che invention a boiler for use in a domestic fire space comprises a hollow plenum chamber which forms ac lease a rear portion of the boiler and a pair of hollow side members projecting forwardly from che rear portion and a series of hollow fins projecting forwardly from the rear portion but not to the same extent as the side members and communicating internally with the rear portion; the hollow fins, the side members and the rear portion defining at least one flue passage closed at the rear by the rear portion, but open at the front to permit access for cleaning the flue passage's) and a pair of doors which in a closed position together 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 side members, the hollow elements and the doors, but in the fully open position of the doors the flue passage(s) is or are substantially completely exposed, the hinging of the doors permitting movement of the doors between the closed and fully opening positions without the necessity to detach the doors.

Preferably the doors are hinged oxi their outside edges and meet in the closed position at a median position to cover the fronts of the hollow fins and the flue passage(s). in a preferred arrangement, the hollow fins define a plurality of flue passages, at least one of which follows a zig-zag path.

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

Two constructions of boilers for use with a solid fuel domestic fire, and in accordance with the invention will now be described by way of examples only, with reference to the accompanying drawings in which:Figure 1 is a front elevation partly ih section, taken on the line I~I of Figure 2 of a first boiler, i.

Figure 2 is a plan view of the boiler shown in Figure 1, looking at the direction of arrow n in Figure 1, Figure 3 is a section on the line III-III in Figure 1, Figure 4- is a scrap view to a larger scale showing part of the boiler and illustrating the closed position of a door, Figure 5 is a detail perspective view showing the of a boiler of Figure 6 is a part front view alternative construction.

The boiler shown in Figures 1 to 5 is made as a welded sheet steel or other metal fabrication, but it is to be understood that it could be made as a casting. Basically, the boiler has a hollow 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 unitary water jacket or plenum chamber is formed by the rear portion 10 and the side portions 12 and 14. The arrangement of the rear portion and the side portions 12 and 14 forms a channel as seen in plan, leaving a large space 16 bounded by the front wall 18 of the rear portion 10, and the inside walls 20 and 22 of the side portions 12 and 14. It will 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 a wrap-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 of the boiler, and this is the fundamental means whereby heat is transferred from the flue gases through 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 of all the hollow fins 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-ί section (see Figure 3) extends across the full width of the 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 tube 24. A centrally disposed vertical fin 26 extends forwardly from the rear portion 10„ This central vertical fin is of rectangular cross-section, and a pair of horizontal fins 28 and 32 extends on opposite sides of the vertical fin 26 at the top and bottom resectively of the vertical fin, as shown in Figure 1, thereby providing an I-shaped central fin arrangement comprising the three 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 of the 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, that the 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 of the side portion 12, and the fin 36 projects inwardly from the inner wall 22 of the 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 that they 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 I fin arrangement. It will be noticed that the fins 34 and 36 taper inwardly and 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 at their outer ends for a similar purpose. Each of the 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 of the boiler, a stationery throat plate 30 is welded to the inside walls 20, 18 and 22. This throat plate extends forwardly over only part of the depth, from front to rear, of the I-shaped fin arrangement and the side fins 34 and 35. 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 of the 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 for controlling the outlet flue 33. The damper rests on the top of the boiler and is able to slide forwardly and rearwardly, between a forward position where it fully closes the outlet 33 and a rear position where it fully opens the outlet 33. This kind of damper control for flues in domestic fire boilers is well known and further description is uneccessary.

Considering now the flue provided between the various fins, and taking the right hand side for example, the flue 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 180° onto the top side of the fin 32; then it passes around the end of the horizontal fin 35, again turning through 180° into a horizontal portion between the fins 36 and 28; then it turns around the end of the fin 28 into the space below the throat plate 30; finally it passes out through the outlet 33.

The two passages defined by the 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 the following features:i) The central vertical fin 25, 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 of the fins 28 and 36), but the total length of the horizontal limbs is considerably greater than the length of the vertical limbs. Improvements can be expected whenever the total length of the horizontal limbs is at least as great as the total length of the vertical limbs. iii) The interdigitation of the 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 doors 42 and 44 is provided for closing the front of the space bounded by the hollow side walls 12 and 14, the top bar 40 and the hollow bottom tube 24. In Figure 3, only the left hand door 42 is shown and it is illustrated in the closed position. A single boss 46 is welded on the inside face 20 of the wall 12, and a hinge pin 48 passes through this 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 hollow fins. Therefore, these passages are circumscribed by the front wall 18 of the rear part 10 of the 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 the flues and in intimate contact with 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 fits under the top bar 40 in the closed position and has a rearwardly angled lower part 60 which fits over the hollow bottom tube 24.

Whilst the flue 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 of the side portions 12 and 14, and then the entire flue arrangement is exposed, and there is ready access for cleaning. The hinging arrangement of the doors ensures that they can be manipulated very easily, without any necessity to completely remove them. This is significant, because in order to fulfil their function, 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 particular flue configuration. By way of example of an alternative arrangement, reference is made to Figure 6, wherein the hollow rear portion 10, the right hand side wall 14, the top bar 40 and the hollow bottom tube 24 are all constructed as described with reference to Figures 1 to 5. It is also to be understood that doors similar to the doors 42 and 44 are provided though these are not illustrated.

However, instead of the interdigitated fin arrangement, there is a single central vertical fin 62 and a series of short hollow cylinders 64 on each side of the central fin„ Each hollow cylinder is welded to the front wall of the 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 that the hollow cylinders 64 are arranged in horizontal rows, but that they are staggered with respect to the cylinders in the adjacent row(s). Consequently, flue passages are formed between the cylinders for the upward travel of the 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 (5)

1. X. A boiler for use in a domestic fire space comprising a hollow plenum chamber which forms at least a rear 5 portion of the boiler and a pair of hollow side members projecting forwardly from th® rear portion, and a series of hollow fins projecting forwardly from the rear portion but not to the seme extent as the side members, and communicating internally with the 10 rear portion; the hollow fins, the side members and the rear portion defining at least one flue passage closed at the rear by the rear portion, but open at the front to permit access for cleaning the flue passage(s) and a pair of doors which in a closed 15 position together 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 side members, the hollow elements and the doors, but in the fully open position of the 20 doors ths flue passage(s) is or are substantially completely exposed, the hinging of the doors permitting movement of the doors between the closed and fully open positions without the necessity to detach the doors.

2. A boiler for use in a domestic fire space as claimed in Claim I, in which the doors are hinged on the outside edges and meet in the closed position at a median position to cover the fronts of the hollow 30 fins and the flue passage(s).

3. A boiler for use in a domestic fire space as claimed in Claim l or Claim 2, in which the hollow fins « define a plurality of flue passages, at least one of 3S which follows a zig-zag path.

4. A boiler for use in a domestic fire space as claimed ixi Claim 3, in. which there is a central vertical hollow fin and the doors are hinged respectively to side members, each door extending across half the 5. Width between the side walls of the boiler, so that the doors meet each other and rest on the front of the central fin.

5. A boiler as claimed in Claim l s constructed and arranged substantially as herein described with reference to Figures 1 Co 5 or Figures 1 co 5 as modified by Figure 6 of che accompanying drawings.