GB2167169A - A wrap-around back boiler - Google Patents

Abstract

A wrap-around back boiler comprises a main rear tank 2 and a pair of outwardly directed main side tanks 3,4 connected thereto to define therewith a channel-shaped firebed and flue enclosure. Additional tanks 15,16,20,202,203,204,205 extend into the enclosure and a removable front bridging plate (not shown) extends between at least two of the additional tanks to allow cleaning and to define therewith a tortuous passageway 11 for combustion gases which extends from an inlet adjacent a firebed to an exhaust flue outlet and are arranged to constrain the flue gases to move laterally between the side tanks. In one case additional tanks 15,16,20 are arranged to define two combustion gas passageways having a common inlet rising leg 17, intermediate falling legs 24,25 and outlet rising legs 26,27. In another case additional tanks 202,203,204,205 are arranged to direct the gases successively across the enclosure from one main side tank 3 towards the other main side tank 4 <IMAGE>

Description

SPECIFICATION A wrap-around back boiler The present invention relates to wrap-around back boilers for domestic fireplaces, such boilers being used for a hot water supply system, a central heating system or for a combination of both.

These domestic boilers am generally referred to as wrap-around back boilers because they usually are arranged in domestic fireplaces and can be said to surround three sides of the fire, hence the term "wraparound back boiler" or simply "back boiler".

Fuel conservation and the relatively high cost of fuel has led to a considerable increase in concentration by designers on the construction of such back boilers. The major area of improvement has been directed towards providing an increased heat exchange surface and thus a more efficient heat transfer from the boiler to the use required. Unfortunately, while some extremely useful and efficient designs of back boilers have been designed one of the major problems is that if they are not efficiently cleaned the thermal efficiency of the boiler reduces dramatically in use. Thus, it is essential that such boilers be cleaned regularly and efficiently so that all the heat transfer surfaces are clean and are not allowed build up a deposit of soot. After soot has built up on the surface of a boiler it is extremely difficulty to remove except by chemical means.One of the major reasons why boilers are often difficult to clean is due to restricted access.

It has been proposed to provide wraparound back boilers in which a plurality of hollow fins project forwardly of the hollow back portion and communicate therewith. A removable plate conforming to the shape of the fins covers the front of the fins. The fins and plate together define a plurality of flues above the combustion zone. Such removable plates are generally in close contact with all the fins or slightly spaced therefrom. Again, there have been problems with such boilers in that while the basic idea of providing a removable plate is attractive as the flues are accessible for cleaning such boilers are not particularly efficient.

The present invention is directed towards providing an improved construction of wraparound back boiler which will have not only access for cleaning the heat transfer surfaces of the boiler but which will also be thermally efficient.

According to the invention there is provided a wrap around boiler comprising a main rear tank; a pair of outwardly directed main side tanks connected to the rear tank and defining therewith a channel-shaped firebed and flue enclosure; a plurality of additional tanks connected to at least one of the main tanks and extending into the enclosure; and a front bridging member extending between at least two of the additional tanks; the main tanks, additional tanks and front bridging member together defining a tortuous flue gas passageway which extends from an inlet adjacent a firebed to a discharge outlet to an exhaust flue, the front bridging member being removable to leave a front opening allowing access to the passageway for cleaning, the additional tanks being so arranged that in use, the flue gases travelling along the passageway are constrained to move laterally between the main side tanks.

In one embodiment of the invention the front bridging member comprises a removable front plate for the combustion gas passageway.

Preferably the passageway includes at least three interconnected successively rising and falling legs. Usually the boiler includes two combustion gas passageways, each having at least three interconnected successively rising and falling legs.

In one embodiment of the invention the passageways extend from a common inlet. In this case preferably the inlet is substantially centrally disposed between the main side tanks. Typically the passageways include a common central rising leg and successively rising and falling legs on each side of the central rising leg. Usually each passageway includes two successively rising and falling legs on each side of the common central rising leg.

In a particularly preferred embodiment of the invention the boiler comprises a pair of inlet auxiliary side tanks connected to the rear tank and respective side tanks and spaced-apart to define therebetween the substantially central inlet rising leg, and an upper auxiliary central tank connected to the rear tank and extending downwardly between the inlet side auxiliary tanks and each main side tank to form, on each side of the inlet rising leg, a successive intermediate falling leg and an outlet rising leg for combustion gases. Usually each inlet auxiliary side tank initially extends inwardly from a main side tank and is then directed upwardly.

Typically each inlet auxiliary side tank is initially inclined upwardly from a main side tank.

Usually each inlet auxiliary side tank initially extends inwardly substantially at right angles to the main side tank to which it is connected. Preferably each inlet auxiliary side tank is then directed upwardly substantially parallel to a main side tank.

Preferably the upper auxiliary central tank includes a top roof portion extending over the first rising leg of the combustion gas passageway. The top roof may either include a substantially flat portion extending forwardly substantially at right angles to the main rear tank or a substantially inverted V-shaped portion having a substantially centrally disposed apex.

Typically the upper auxiliary central tank includes a pair of depending side portions ex tending downwardly between the inlet side auxiliary tanks and each main side tank to form, on each side of the inlet rising leg, a successive intermediate falling leg and an outlet rising leg for combustion gases in each passageway.

In a particularly preferred embodiment of the invention the boiler includes an inlet additional tank, bridging the main side tanks adjacent the front plate. Typically the inlet additional tank includes a rearwardly and downwardly extending top wall. Preferably the inlet additional tank includes a rearwardly extending bottom wall.

In a further embodiment of the invention the boiler comprises a pair of upper auxiliary bridging members extending from a respective side tank and the rear tank and being spacedapart to define therebetween the discharge outlet to an exhaust gas flue. Preferably the boiler also includes a rear auxiliary bridging member extending from the main rear tank to define, together with the side auxiliary bridging members the discharge outlet to an exhaust gas flue. Each bridging member may comprise a bridging plate extending from a respective main tank or an upper bridging side tank connected to the main rear tank and a respective side tank. Each bridging tank may be substantially wedge-shaped in transverse cross section.

In a further embodiment of theinvention the combustion gas flue passageway includes at least three interconnected legs which extend successively sidewardly, at least partially across the enclosure, towards and away from the main side tanks. In this case the boiler may include a lower additional tank connected to the main rear tank and spaced-apart from at least one main side tank to define an inlet opening for combustion gases, at least one intermediate additional tank above the lower tank and connected to the rear tank to define, together with the lower additional tank a sidewardly extending leg of the combustion gas passageway, and an upper additional tank connected to the rear tank and above the intermediate tank to define therewith another sidewardly extending leg of the combustion gas passageway.

The additional tanks may be parallel with each other. Alternatively at least some of the additional tanks are inclined inwardly upwardly with respect to the main side tanks. At least some of the additional tanks may also be inclined inwardly downwardly with respect to the main side tanks.

In a particularly preferred embodiment of the invention the boiler comprises a lower central auxiliary tank connected to the rear tank and spaced-apart from each main side tank to define an opening through which combustion gases pass, a pair of intermediate side auxiliary tanks above the lower central auxiliary tank and connected respectively to the main side tanks and spaced-apart to define therebetween a central opening for flue gases and an upper central auxiliary tank above the side auxiliary tanks connected to the rear tank and spaced-apart from the main side tanks to define an opening through which gases rising from the central opening between the side auxiliary tanks pass.

In a further embodiment of the invention the boiler includes an inlet additional tank, bridging the side tanks adjacent the front plate. The inlet tank may be rearwardly and upwardly inclined.

Preferably the boiler includes retaining means for the front plate. Typically the retaining means comprises a retaining bracket bridging the side tanks adjacent the discharge outlet. Usually the retaining bracket comprises an angle bracket having a downwardly extending first arm and an interconnected inwardly extending second arm, a top edge of the front plate being retained, in use behind the first arm. Typically the removable front plate is supported, in use, on the inlet additional tank.

In a particularly preferred embodiment of the invention the additional tanks abut, in use against the front plate.

Preferably the boiler includes a damper for the discharge outlet from the combustion gas passageway.

The invention also provides a tool for cleaning a back boiler having a handle and a cleaning head wherein the handle or head includes means for operating a damper and/or a removable front plate for the boiler. Preferably a cut-out slot is provided in the cleaning head for engaging with a complementary lug on a damper and/or a removable front plate.

The invention will be more clearly understood from the following description thereof given by way of example only with reference to the accompanying drawings in which: Fig. 1 is a perspective view of a wraparound back boiler according to the invention, Fig. 2 is a perspective, partially cut-away, view of the boiler of Fig. 1 with a front plate and damper plate removed, Fig. 3 is a front, partially cross sectional view of the boiler of Fig. 2, Fig. 4 is a side, partially cross sectional view of the boiler of Fig. 1, Fig. 5 is a diagrammatic perspective view of portion of the boiler of Figs. 1 to 4 illustrating the use of a hand tool for removing the front plate, Fig. 6 is a diagrammatic perspective view illustrating the use of a hand tool in cleaning the boiler of Figs. 1 to 4, Figs. 7 to 9 are perspective views of three different constructions of back boiler similar to the boiler of Figs. 1 to 4, with a front plate and damper plate removed, Figs. 10 and 11 are perspective partially exploded views of two different constructions of back boiler similar to the boiler of Figs. 1 to 4, Figs. 12 and 13 are perspective views of two different constructions of back boiler similar to the boiler of Figs. 1 to 4, with a front plate and damper plate removed, Figs. 14 and 15 are perspective, partially exploded views of two different constructions of back boiler similar to the boiler of Figs. 1 to 4, Figs. 16 and 17 are perspective views of two further constructions of back boiler similar to the boiler of Figs. 1 to 4 with a front plate and damper plate removed, Fig. 18 is a perspective view of another construction of boiler with a front plate and damper plate removed, and Figs. 19 to 21 are perspective views of three different construction of boiler, similar to the boiler of Fig. 18, with a front plate and damper plate removed.

Referring to the drawings and initially to Figs. 1 to 6 thereof there is illustrated a wraparound back boiler according to the invention indicated generally by the reference numeral 1.

The wrap-around back boiler 1 comnprises a main rear tank 2 and a pair of outwardly directed main side tanks 3 and 4 respectively which form extensions of the rear tank 2. The rear tank 2, side tanks 3 and 4 and a removable front bridging member, in this case a removable front plate 5, define a combustion gas flue enclosure and a lower portion of the rear tank 2 and side tanks 3 and 4 form a firebed enclosure indicated generally by the reference numeral 6 where a standard grate 7 supported on mounting lugs 8 on the mnain tanks 2, 3, 4 may be sited. A suitable water inlet connection 9 and outlet connection 10 are provided.

A plurality of additional tanks connected to one or mnore of the main tanks project into the combustion gas flue enclosure and abut against the front plate 5 to define in this case two combustion gas passageways 11 through which combustion gases are led from a common inlet 12 adjacent a firebed to a common discharge outlet 13 to an exhaust flue (not shown). In this case the inlet 12 is centrally disposed and each of the passageways 11 includes successively rising and falling legs through which the gases are led. Gases in each passageway 11 are directed at least partially across the flue enclosure between the main side tanks 3,4 to follow a substantially tortuous path for heat transfer to the main and additional tanks. It will be noted that in this case the side tanks 3,4 project forwardly of all of the additional tanks.

The additional tanks comprises a pair of inlet auxiliary side tanks 15,16 each connected to the main rear tank 2 and respective side tanks 3,4 and being spaced-apart to define therebetween a common substantially centrally disposed inlet rising leg 17 of the passageways 11. Each auxiliary inlet side tank 15,16 is substantially L-shaped and includes a lower portion 18 which extends inwardly from a main side tank 3,4 and an upper portion 19 which is directed upwardly substantially parallel to the main side tanks 3,4. It will be noted that the lower portion 18 of the auxiliary side tanks 15,16 are inclined upwardly from adjacent respective side tanks 3,4 for ease of cleaning and for directing combustion gases rising from a firebed into the inlet rising leg 17 of the flue gas passageway 11.

An upper auxiliary central tank 20 is connected to and extends forwardly of the main rear tank 2 and includes a central top roof portion 21 and a pair of depending side portions 22,23 which extend downwardly substantially parallel to the main side tanks 3,4 into the space defined between the auxiliary side tanks 15,16 and the respective main side tanks 3,4. The roof portion 21 extends over the first rising leg 17 of the combustion gas passageway so that combustion gases rising through the central inlet leg 17 between the auxiliary side tanks 15,16 are turned into intermediate falling legs 24,25 defined between the side portions 22,23 of the upper auxiliary central tank 20 and the respective upper portions 19 of the auxiliary side tanks 15,16.The gases are then turned again through 1800 by the lower portion 18 of the auxiliary side tanks 15,16 into second rising legs 26,27 defined between the side portions 22,23 of the upper auxiliary central tank 20 and the respective main side tanks 3,4. The gases then pass over the roof portion 21 of the upper auxiliary central tank 20 for discharge through the flue gas exit 13 defined between apair of spacedapart side bridging plates 28,29 welded to the rear tank 2 and respective main side tanks 3,4 and a rear bridging plate 30 welded to the rear tank 2 and the side bridging plates 28,29.

It will be noted that the roof portion 21 of the upper auxiliary central tank 20 is in this case of inverted V-shape and extends downwardly from a central apex 31.The advantage of having an apex roof portion is to direct combustion gases rising from the second vertical rising legs into the flue gas exit 13 and also to facilitate cleaning.

An inlet additional tank 35 extends between and bridges the main side tanks 3,4 below the front plate 5 and is spaced-apart from the main rear tank 2 to define therewith an inlet combustion gas opening 31 through which gases and flames pass into the combustion gas inlet 9 to the flue gas passageways. In this case the inlet additional tank 35 is substantially wedge-shaped in transverse cross section and comprises a rearwardly and downwardly extending top wall 36, a pair of depending side walls 37 which extend substantially parallel to the main rear tank 3 and a rearwardly and upwardly extending bottom wall 38. The bottom wall 38 is inclined rear wardly upwardly for directing combustion gases and flames into the flue gas passageway.

Retaining means for the front plate 5 is in this case provided by a front mounting bracket 40 bridging the side tanks 3,4 adjacent the bridging plates 28,29. The mounting bracket 40 is angle-shaped and includes a downwardly extending arm 41 and an inwardly extending arm 42. In use, an upper edge 43 of the front plate 5 is inserted behind the arm 41 and, the lower edge of the front plate 5 resting on the top wall 36 of the inlet additional tank 30, as will be particularly apparent from Fig. 4. The front plate 5 is formed with a centrally disposed handle 44.

A damper 45 is used to adjust the width of the discharge outlet 13 and hence the rate of combustion and flow of combustion gases through the flue gas passageway 11. The damper 45 is supported on the bridging plates 28,29,30 and the bracket 40 and includes a downwardly extending handle 46.

In use, when a fire is lit on the grate 7 the combustion gases pass through the combustion gas passageways 11 as indicated by the arrows in Figs. 3 and 4. The combustion gases first rise up from the firebed enclosure and impinge against the bottom wall 38 of the inlet auxiliary tank 30 and are directed upwardly and against the rear tank 2. The gases then impinge against the lower portions 18 of the auxiliary side tanks 15,16 and are directed into the central inlet rising leg 17 of the flue gas passageway 11 where they impinge against the upper portions 19 of the auxiliary side tanks 15,16.At the upper end of the inlet leg 17 of the passageway the gases are directed against the roof portion 21 of the upper auxiliary central tank 20 and are turned through substantially 1800 and pass down the intermediate falling legs 24,25 of the passageways in which they impinge against the side portions 22,23 of the upper auxiliary central tank 20 and the upper portions 19 of the auxiliary side tanks 15,16.At the lower end of the intermediate falling legs 24,25 the gases are directed against the lower portions 18 of the auxiliary side tanks 15,16 and are again turned through substantially 1800 to rise through the second vertical rising legs 26, 27 in which the gases impinge against the side portions 22, 23 of the upper auxiliary central tank 20 and the main side tanks 3,4 of the boiler At the upper end of the second vertical rising legs 26,27 the gases are again turned through substantially 90" by the bridging plates 28,29 and impinge against the roof portion 21 of the upper auxiliary central tank 20 before discharge through the exhaust flue exit 13.

It will be noted that both the upper portions 19 of the auxiliary side tanks 15,16 andthe side portions 22;23 of the upper auxiliary central tank 20 are spaced-apart from the respective main side tanks 3,4 to provide, within each passageway 11, two gaps which are offset between the main side tanks. The lateral offset of the gaps results in the gases being directed across the flue enclosure in each passageway 11 to follow a substantially tortuous path.

It will be appreciated that the tortuous combustion gas passageway just described allows for especially good heat transfer while still allowing the heat transfer surfaces to be easily cleaned, on removal of the front plate 5.

It has been found that the inlet additional tank 35 allows particularly good heat transfer to be achieved as it is located adjacent the firebed and is licked by both flame and gases rising from a firebed.

Referring to Figs. 5 and 6 there is illustrated a dual purpose tool 47 for use with the boiler described above with reference to Figs. 1 to 4. The tool 47 comprises a substantially rectilinear plate 48 at one end of a handle 49. A cut-out slot 50 is formed in the plate 48 and is sized to accommodate both the handle 46 of the damper 45 and the handle 44 of the removable front plate 5 of the boiler so that the tool can be used for adjusting the damper or for removal of the front plate 5. As will be particularly apparent from Fig. 6 the tool 47 may also be used for cleaning the heat exchange surfaces of the boiler, the plate 48 being sized to allow it to be easily inserted and withdrawn from the various legs of the flue gas passageways.

Referring to Fig. 7 there is illustrated a further construction of wrap-around back boiler indicated generally by the reference numeral 55. This wrap-around back boiler 55 is of similar construction to the wraparound back boiler illustrated in Figs. 1 to 6 and parts similar to those described with reference to these drawings are identified by the same reference numerals. In this case the roof portion 21 of the upper central auxiliary tank 20 is flat. This provides a boiler of slightly simpler and cheaper construction. Instead of bridging plates a flue gas exit 56 is defined by a further pair of upper auxiliary side tanks 57,58 connected respectively to the side tanks 3 and 4 and the rear tank 2. The use of the upper auxiliary side tanks 57, 58 leads to a slightly more complex construction of boiler however improved heat transfer may be achieved.

Referring to Fig. 8 there is illustrated a construction of boiler 60 according to the invention which is very similar to the wrap-around back boiler described above with reference to Figs. 1 to 6 andlike parts are identified by the same reference numerals. In this embodiment two wedge-shaped upper side auxiliary tanks 61 and 62 are connected to the side tanks 3 and 4 respectively and form a flue exit indicated generally by the reference numeral 63.

These additional tanks 61, 62 provide for im proved heat transfer however this is at the expense of a slightly more complex construction. It will also be noted that the roof portion 21 of the upper central auxiliary tank and the lower side auxiliary tanks 18 are inclined upwardly at a larger angle than in the case of the boiler of Figs. 1 to 6. This assists in cleaning and in directing gases into the flue gas passageways 11.

Referring to Fig. 9 there is illustrated another boiler according to the invention indicated generally by the reference numeral 65.The boiler 65 is again of similar construction to the boiler described above with reference to Figs. 1 to 6 and like parts are assigned the same reference numerals. In this case the roof portion 21 of the upper central auxiliary tank 20 is flat and the lower portions 18 of the inlet auxiliary side tanks 15,16 extend at a 90" angle from the respective main side tanks 3,4. This boiler is of particularly simple construction however there is some sacrifice in both heat transfer, ease of cleaning and draught over the boiler of Figs. 1 to 6.

At the lower end of the first falling legs 106,107 the combustion gases impinge against the horizontal additional tanks 101,102 and are directed upwardly into a second rising legs 108,109 defined between respective side additional tanks 94,95 and 98,99. At the upper end of the second rising legs 108,109 the combustion gases again impinge against the upper horizontal additional tank 103 and are directed downwardly into second falling legs 110,111 defined between the side additional tanks 93,94 and 99,100 respectively. At the lower end of the second falling leg 110,111 the combustion gases impinge against the lower horizontal additional tanks 102,103 and are directed upwardly into final third rising legs 112,113 at the upper end of which they impinge against the respective bridging plates 28,29 before discharge through the flue gas exit 13.

Because of space limitations it will be noted that the side additional tanks 93 to 100 and the legs of the combustion gas passageway are substantially narrower than the corresponding tanks and legs of the boiler described above with reference to Figs. 1 to 6.

The boiler of Fig. 10 however provides particularly good heat transfer efficiency. 8ecause of space limitation such an arrangement of tanks may be suitable only for larger size boilers.

Many modifications on the particular embodiment of the boiler shown in Fig. 12 will be readily appreciated. For example additional rising and falling legs may be incorporated by providing additional tanks and bridging members. It will also be appreciated that while the bridging members have been described as formed from horizontally disposed additional tanks such tanks may be inclined upwardly or downwardly with respect to the side tanks. It is particularly envisaged that the upper horizontal additional tank 83 may be of inverted V-shape. In addition, instead of tanks one or more of the bridging members may be provided by removable plates, firebricks, or the like. Similar comments apply to the various other constructions of boilers described above.

Referring to Fig. 10 there is illustrated a further construction of wrap-around back boiler indicated generally by the reference numeral 70.The boiler 70 is of similar construction to the boiler described above with reference to Figs. 1 to 4 and like parts are assigned the same reference numerals. In this case there are again two combustion gas passageways 71,72 through which the gases are led from separate offset centrally disposed inlets 73,74 to separate offset discharge outlets 75,76. In this case the upper auxiliary central tank 21 includes an additional centrally disposed depending portion 77 which extends into the space defined between the auxiliary side tanks 15,16 to define first rising legs of each of the passageway 71,72.It will be noted that the lowermost end of the central portion 77 of the auxiliary tank is cut-away to a substantially V-shape to direct combustion gases rising from a firebed into the first inlet rising legs of the passageway 71,72. The flow of gases through the passageways 71,72 is controlled by a damper plate 80 which is slidably movablein the direction of the arrow R between the main side tanks 3,4 in a track defined by a pair of spaced-apart guide rails 79,80. The damper 78 is formed with two rectilinear slots 81,82 which are moved, on operation of the damper, into and out of alignment with the outlet openings 75,76 of the passageway 71,72 to control the flow of gases.

It will be noted that in this case the front plate 5 is formed with two mounting holes 83 for engagement with mounting bolts 84 projecting forwardly from the depending side portion 22,23 of the upper auxiliary tank.

Referring to Fig. 11 there is illustrated another boiler indicated generally by the reference numeral 85. This wrap-around back boiler 85 is of similar construction to the boiler of Fig. 10 and parts similar to those described with reference to Fig. 10 are identified by the same reference numerals. In this case the two combustion gas passageways 71,72 have a common inlet 86 leading to a common first rising leg at the upper end of which the gases are separated into two first falling legs by a deflector plate 87 which projects downwardly from the roof portion 21 of the upper central auxiliary tank 20.

Referring to Fig. 12 there is illustrated another boiler according to the invention indicated generally by the reference numeral 90.

The boiler 90 is of similar construction to the boiler described above with reference to Figs.

1 to 6 and again like parts are assigned the same reference numerals. The main difference between this boiler and the boiler described above with reference to Figs. 1 to 6 is that there are two additional successive falling and rising legs adjacent each main side tank 3,4 through which the combustion gases are led before discharge through the flue gas exit 13.

One way of arranging such passageways is illustrated in Fig. 12. In this case eight additional tanks 93 to 100 are provided, each extending substantially parallel with the main side tanks 3,4. Bridging means between alternate tanks is in this case provided by three horizontally disposed additional tanks 101,102,103, the tanks 101 and 102 being interconnected with the additional tanks 94 to 96,97 and 99 respectively and to the respective sidetanks- 3,4 while the horizontal additional tank 103 is interconnected with the side additional tanks 93,95,98 and 100 and with the rear tank 2. Combustion gases from a firebed are led into the combustion gas passageway through a centrally disposed inlet opening 104 to a first central rising leg 105 of the passageway.At the upper end of the first rising leg 105 the combustion gases impinge against the horizontal additional tank 103 and are directed downwardly into respective first falling legs 106,107 defined respectively between the side additional tanks 95,96 and 97,98 respectively.

Referring to Fig. 13 there is illustrated another boiler according to the invention indicated generally by the reference numeral 120.

This boiler 120 is again of similar construction to the boiler described above with reference to Figs. 1 to 6 and like parts are assigned the same reference numerals. In this case the auxiliary side tanks and upper central auxiliary tank of the boiler of Figs. 1 to 6 are, as it were, turned upside-down so that in this case there is provided a lower central auxiliary tank 121 and two upper side auxiliary tanks 122,123 which are spaced-apart to define therebetween a centrally disposed final rising leg 124 through which combustion gases are led before discharge through the discharge outlet 13 to an exhaust gas flue.

The lower central auxiliary tank 121 is connected to the back tank 2 and includes a lower bridging portion 125 and a pair of upwardly extending side portions 126 which define, together with a respective main side tank 3,4, first rising legs 127,128 of the combustion gas passageways. Each upper auxiliary side tank 122,123 is of substantially inverted L-shape and includes an upper sidewardly extending portion 129 extending over the rising leg 127,128 and a downwardly depending portion 130 which extends downwardly towards the bridging portion 125 of the lower central auxiliary tank 121 to define, together with the side portion 126 of the lower auxiliary tank 121, respective first falling legs 131 and 132 for combustion gases.

In use, combustion gases and flames from the firebed are drawn towards the side inlet openings and pass up the first rising legs 127,128 of the combustion gas passageway and then down the first falling legs 131,132 and up the final common rising leg 124 before discharge to an exhaust gas flue as indicated by the arrows in Fig. 13.

Referring to Fig. 14 there is illustrated another boiler according to the invention indicated generally by the reference numeral 140.

The boiler 140 is of similar construction to the boiler described above with reference to Fig. 13 and like parts are assigned the same reference numerals. In this case the lower central auxiliary tank 121 includes a central portion 141 which extends upwardly into the space defined between the downwardly depending portions 130 of the auxiliary side tanks 122,123 so that instead of a common final rising leg, two separate rising legs 142,143 are formed having discharge outlets 144. A damper plate 145 is slidably movable in the direction of the arrows S in tracks defined between a pair of facing channel guide members 146 to adjust the flow of gases through the passageways. It will be noted that to assist in directing combustion gases into the passageways the lower bridging portion 125 of the lower central auxiliary tank 121 is substantially V-shaped in transverse cross section.In this case, the removable front plate 5 is formed with two mounting holes 147 which engage with complementary mounting bolts 148 carried by the side portions 126 of the lower auxiliary tank 121.

Referring to Fig. 15 there is illustrated another boiler according to the invention indicated generally by the reference numeral 150.

The boiler 150 is of similar construction to the boiler described above with reference to Fig. 13 and like parts are again assigned the same reference numerals. In this case a deflector plate 151 projects upwardly from the bridging portion 125 of the lower auxiliary tank 121 into the final rising leg 124 defined between the downwardly depending side portions 130 of the upper side auxiliary tanks 121,123 to direct gases upwardly into the final rising leg. The bridging portion 125 is again of V-shape to direct combustion gases from the firebed into the combustion gas passageways. The common outlet 13 from the combustion gas passageways is in this case closable by a damper plate 152 which is slidably movable in the direction of the arrow R between the main side tanks 3,4 in a guide track defined by a pair of facing rails 153,154. The damper plate 152 includes a central aperture 155 which is of the same size and shape as the discharge outlet 13 from the combustion gas passageways to control the flow of gases through the outlet.

Referring to Fig. 16 there is illustrated a wrap-around back boiler indicated generally by the reference numeral 160 in which parts similar to those described with reference to the previous drawings are identified by the same reference numerals. In this embodiment there is provided a lower offset inclined auxiliary tank 161 connected to and extending from a main side tank 4 and spaced-apart from a main side tank 3. Mounted above the lower offset inclined auxiliary tank 161 is an intermediate vertical auxiliary tank 162 connected to the main rear tank 2 and the lower offset inclined auxiliary tank 161. Above and spacedapart from the intermediate vertical auxiliary tank 162 is an upper offset auxiliary tank 163 connected to the main side tank 3 and portions of the main rear tank 2.The upper offset auxiliary tank 163 communicates with the further intermediate vertical auxiliary tank 164.

There is thus formed by the two intermediate vertical auxiliary tanks 162 and 164 the lower offset inclined auxiliary tank 161, the upper offset auxiliary tank 163, and the main two main side tanks 3 and 4, a rising leg 165, a falling leg 126 and a further rising leg 167 for exhaust flue gases, the passage of the flue gases being illustrated by the arrows. One particular advantage of this embodiment is that there will be relatively good heat transfer in a small compact boiler.

Referring to Fig. 17 there is illustrated a further construction of wrap-around back boiler indicated generally by the reference numeral 180 in which parts similar to those described with reference to Fig. 16 are identified by the same reference numerals. Again, there is a single combustion gas passageway.

In this embodiment there is a lower offset horizontal auxiliary tank 181 and four intermediate vertical auxiliary tanks 182,183,184 and 185 alternatively connected to the lower offset horizontal auxiliary tank 181 and an upper offset auxiliary tank 186, thus forming a rising leg 187, a falling leg 188, a rising leg 189, a falling leg 190 and a final rising leg 191.

Essentially this the same construction as the boiler of Fig. 16 except that instead of three legs or passes of the flues gases in a vertical direction through the boiler there are now five legs, thus, more efficient heat transfer will be achieved.

Referring to Fig. 18 there is illustrated a boiler according to another embodiment of the invention indicated generally by the reference numeral 200. The boiler 200 is of similar construction to the boiler described above with reference to Figs. 1 to 6 and like parts are assigned the same reference numerals. In this embodiment the gases are led sidewardly across the flue enclosure respectively towards and away from the respectiveside tanks 3,4.

A lower central auxiliary tank 202 is mounted above the inlet auxiliary tank 35 and is connected to the rear tank 2. The lower central auxiliary tank 202 is spaced-apart from the side tanks 3 and 4 and in this case is substantially horizontal.

A pair of side auxiliary tanks 203 and 204 are connected respectively to the side tanks 3 and 4 andthe rear tank 2. The side auxiliary tanks 203 and 204 are mounted above the lower central auxiliary tank 202 to allow the passage of the flue gases therebetween. A further upper central auxiliary tank 205 is mounted above the side auxiliary tanks 203 and 204. A pair of upper side auxiliary tanks 206 and 207 are mounted above the upper central auxiliary tank 206 to define a flue exit 208. The upper side auxiliary tanks 206 and 207 are each respectively connected to the side tanks 3 and 4 and the rear tank 2 and against the front plate 5.

In use, when a fire is lit in the firebed enclosure, the combustion gases rise as shown by the arrows in Fig. 18. The combustion gases first rise up from the firebed enclosure 7 and impinge against the bottom of the inlet auxiliary tank 35 and are directed upwardly and against the rear tank 2. The flue gases then impinge against the lower central auxiliary tank 202 and are forced outwards between the lower auxiliary tank 202 and the side tanks 3 and 4. The rising gases then impinge against the side auxiliary tanks 203 and 204 and are forced to pass between them when on rising, they encounter the upper central auxiliary tank 205 and are again diverted side-ways between the said upper central auxiliary tank 155 and the side tanks 3 and 4. The gases then are directed by the upper sideauxiliary tanks 206 and 207 through the flue exit 208.

Referring to Fig. 19 there is illustrated another boiler according to the invention similar to the boiler described above with reference to Fig. 18 and like parts are assigned the same reference numerals. In this case the combustion gas passageway includes five interconnected legs which extend successively sidewardly towards and away from the main side tanks 3,4. The interconnected legs of the passageway are in this case defined by six auxiliary side tanks 211 to 216, three 211,213,215 of which are connected to the main side tank 4 and project inwardly upwardly therefrom towards but spaced-apart from the other main side tank 3. The other three of the auxiliary side tanks 212,214,216 project inwardly downwardly from the main side tank 3 towards but spaced-apart from the other main side tank 4.It will be noted that alternate tanks are spaced-apart along a vertical axis to facilitate flow of gases between the tanks. The advantage of this construction ofboilerisin providing a boiler with a relatively high heat transfer efficiency and which can be easily cleaned. The particular arrangement of the tanks facilitates cleaning.

Referring to Fig. 20 there is illustrated another boiler according to the invention indicated generally by the reference numeral 220.

The boiler 220 is of similar construction to the boiler described above with reference to Fig. 19 and like parts are assigned the same reference numerals. In this case there are five additional tanks, three of which 211,213,215 are connected to the main side tank 4, and two of which 212,214 are connected to the main side tank 3. The additional side tanks 212, 214 in this case project inwardly upwardly from the main side tank 3 towards the main side tank 4. The advantage of this construction of boiler is in possibly improved heat transfer over the boiler of Fig. 19 as the arrangement of the tanks causes the gases to impinge against substantially all of the heat transfer surface leading to a high heat transfer efficiency.

Referring to Fig. 21 there is illustrated another boiler according to the invention indicated generally by the reference numeral 230 which is of similar construction to the boiler described above with reference to Fig. 20 and like parts are assigned the same reference numerals. In this case the auxiliary side tanks 213,215 are inclined inwardly downwardly towards the main side tank 3 and the auxiliary side tanks 212,214,216 are inclined inwardly upwardly towards the other main side tank 4.

The advantage of this construction of boiler is in that it is of a relatively simple construction and can be easily cleaned while still providing relatively good heat transfer efficiency.

It will be appreciated that in the case where a lower auxiliary tank such as a tank 35 is used this may extend forwardly into the enclosure from, and be connected with, the rear tank. The particular advantage however, of having a spacing between the rear tank and such an additional tank is in providing a relatively large heat transfer surface as close as possible to the hottest point of the firebed, all the surfaces of which can be licked by the flames and combustion gases. It also has the advantage of providing a support for the removable front plate, in use.

It will be appreciated that instead of tanks in certain instances fins or deflector means, such as plates, may be used. It will also be appreciated that the removal of the front plate will facilitate the cleaning of the boiler as is well known. Additionally, instead of a front plate a conventional hinged door may be used. Such a door may incorporate a viewing window if desired.

It will also be appreciated that any or all of the additional tanks need not necessarily be connected to one of the main tanks. For example, while such constructions of boiler may not be as easily cleaned and may have reduced heat transfer efficiency any or all of the additional tanks could be connected to the main tanks through auxiliary tanks such as a header tank extending between the main side tanks.

The boilers according to the present invention are of mild steel plate welded construction but other constructions may be used.

Claims (46)

1. A wrap-around back boiler comprising: a main rear tank; a pair of outwardly directed main side tanks connected to the rear tank and defining therewith a channel-shaped firebed and flue enclosure; a plurality of additional tanks connected to at least one of the main tanks and extending into the enclosure; and a front bridging member extending between at least two of the additional tanks; the main tanks, additional tanks and front bridging member together defining a tortuous flue gas passageway which extends from an inlet adjacent a firebed to a discharge outlet to an exhaust flue, the front bridging member being removable to leave a front opening allowing access to the passageway for cleaning, the additional tanks being so arranged that in use, the flue gases travelling along the passageway are constrained to move laterally between the main side tanks.

2. A boiler as claimed in Claim 1 in which the front bridging member comprises a removable front plate for the combustion gas passageway.

3. A boiler as claimed in Claim 1 or Claim 2 which combustion gas passageway includes at least three interconnected successively rising and falling legs.

4. A boiler as claimed in any of Claims 1 to 3 in which the boiler includes two combustion gas passageways, each having at least three interconnected successively rising and falling legs.

5. A boiler as claimed in claim 4 in which the combustion gas passageways extend from a common inlet.

6. A boiler as claimed in claim 5 in which the inlet is substantially centrally disposed between the main side tanks.

7. A boiler as claimed in claim 5 or 6 in which the passageways include a common central rising leg and successively rising and falling legs on each side of the central rising leg.

8. A boiler as claimed in claim 7 in which each passageway includes two successively rising and falling legs on each side of the common central rising leg.

9. A boiler as claimed in any of claims 5 to 8 comprising a pair of inlet auxiliary side tanks connected to the rear tank and respective side tanks and spaced-apart to define therebetween the substantially central inlet rising leg, and an upper auxiliary central tank connected to the rear tank and extending downwardly between the inlet side auxiliary tanks and each main side tank to form, on each side of the inlet rising leg, a successive inter mediate falling leg and an outlet rising leg for combustion gases.

10. A boiler as claimed in claim 9 in which each inlet auxiliary side tank initially extends inwardly from a main side tank and is then directed upwardly.

11. A boiler as claimed in claim 10 in which each inlet auxiliary side tank is initially inclined upwardly from a main side tank.

12. A boiler as claimed in claim 10 in which each inlet auxiliary side tank initially extends inwardly substantially at right angles to the main side tank to which it is connected.

13. A boiler as claimed in claim 11 or 12 in which each inlet auxiliary tank is then directed upwardly substantially parallel to a main side tank.

14. A boiler as claimed in any of claims 9 to 13 in which the upper auxiliary central tank includes a top roof portion extending over the first rising leg of the combustion gas passageway.

15. A boiler as claimed in claim 14 in which the top roof portion includes a substantially flat portion extending forwardly substantially at right angles to the main rear tank.

16. A boiler as claimed in claim 14 in which the top roof portion includes a substantially inverted V-shaped portion having a substantially centrally disposed apex.

17. A boiler as claimed in any of claims 9 to 16 in which the upper auxiliary central tank includes a pair of depending side portions extending downwardly between the inlet side auxiliary tanks and each main side tank to form, on each side of the inlet rising leg, a successive intermediate falling leg and an outlet rising leg for combustion gases in each passageway.

18. A boiler as claimed in any of claims 2 to 17 including an inlet additional tank, bridging the main side tanks adjacent the front plate.

19. A boiler as claimed in claim 18 in which the inlet additional tank includes a rearwardly and downwardly extending top wall.

20. A boiler as claimed in claim 18 or 19 in which the inlet additional tank includes a rearwardly extending bottom wall.

21. A boiler as claimed in any preceding claim comprising a pair of upper side auxiliary bridging members extending from a respective side tank and the rear tank and being spacedapart to define therebetween the discharge outlet to an exhaust gas flue.

22. A boiler as claimed in claim 21 comprising a rear auxiliary bridging member extending from the main rear tank to define, together with the side auxiliary bridging members the discharge outlet to an exhaust gas flue.

23. A boiler as claimed in claim 21 or 22 in which each bridging member comprises a bridging plate extending from a respective main tank.

24. A boiler as claimed in claim 21 or 22 in which each bridging member comprises an upper bridging tank connected to the main rear tank and a respective side tank.

25. A boiler as claimed in claim 24 in which each bridging tank is substantially wedgeshaped in transverse cross section.

26. A boiler as claimed in any of claims 23 to 25 in which the combustion gas passageway includes four successively rising and falling legs on each side ofa central rising leg.

27. A boiler as claimed in any of claims 1 to 4 in which the inlet to the or each combustion gas passageway is provided by an inlet opening adjacent a main side tank.

28. A boiler as claimed in claim 1 or 2 in which the combustion gas flue passageway includes at least three interconnected legs which extend successively sidewardly, at least partially across the enclosure, towards and away from the main side tanks.

29. A boiler as claimed in claim 28 including a lower additional tank connected to the main rear tank and spaced-apart from at least one main side tank to define an inlet opening for combustion gases, at least one intermediate additional tank above the lower tank and connected to the rear tank to define, together with the lower additional tank a sidewardly extending leg of the combustion gas passageway, and an upper additional tank connected to the rear tank and above the intermediate tank to define therewith another sidewardly extending leg of the combustion gas passageway.

30. A boiler as claimed in claim 29 in which the additional tanks are substantially parallel with each other.

31. A boiler as claimed in claim 29 or 30 in which at least some of the additional tanks are inclined inwardly upwardly with respect to the main side tanks.

32. A boiler as claimed in any of claims 29 to 31 in which at least some of the additional tanks are inclined inwardly downwardly with respect to the main side tanks.

33. A boiler as claimed in claim 28 comprising a lower central auxiliary tank connected to the rear tank and spaced-apart from each main side tank to define an opening through which combustion gases pass, a pair of intermediate side auxiliary tanks above the lower central auxiliary tank and connected respectively to the main side tanks and spaced-apart to define therebetween a central opening for flue gases and an upper central auxiliary tank above the side auxiliary tanks connected to the rear tank and spaced-apart from the main side tanks to define an opening through which gases rising from the central opening between the side auxiliary tanks pass.

34. A boiler as claimed in any of claims 28 to 33 including an inlet additional tank, bridging the side tanks adjacent the front plate.

35. A boiler as claimed in claim 34 in which the inlet additional tank is rearwardly and upwardly inclined.

36. A boiler as claimed in any of claims 2 to 35 including retaining means for the front plate.

37. A boiler as claimed in claim 36 in which the retaining means comprises a retaining bracket bridging the side tanks adjacent the discharge outlet.

38. A boiler as claimed in claim 37 in which the retaining bracket comprises an angle bracket having a downwardly extending first arm and an interconnected inwardly extending second arm, a top edge of the front plate being retained, in use behind the first arm.

39. A boiler as claimed in any of claims 18 to 27 or 35 in which the removable front plate is supported, in use, on the inlet additional tank.

40. A boiler as claimed in any of claims 2 to 39 in which the additional tanks abut, in use against the front plate.

41. A boiler as claimed in any preceding claim including a damper for the discharge outlet from the combustion gas passageway.

42. A boiler substantially as hereinbefore described with reference to Figs. 1 to 17.

43. A boiler substantially as hereinbefore described with reference to Figs. 18 to 21.

44. A tool for cleaning a back boiler having a handle and a cleaning head wherein the handle or head includes means for operating a damper and/or a removable front plate for the boiler.

45. A tool as claimed in claim 44 in which a cut-out slot is provided in the cleaning head for engaging with a complementary lug on a damper and/or a removable front plate.

46. A hand tool substantially as hereinbefore described with reference to Figs. 5 and 6.