The present invention relates to an auxiliary device for a conven¬ tional boiler. Most buildings are normally equipped with a boiler having a hearth. The boiler may run on solid fuels, such as coke, wood and so, on as well as on oil. Electric immersion heating is also be¬ coming popular. If a conventional boiler is to be utilized at regular intervals, fuel of a different type is added, generally consisting of coke or wood. A stoker device can be connected to the boiler in order to avoid having to fill the conventional boiler with solid fuel. Such an arrangement is unusually bulky and cannot be fitted to conventional boilers due to lack of space.

The object of the present invention is to enable the use of solid fuels without the need to refill them at short intervals. According to the invention this is achieved by the use of a cylindrical or pillarlike auxiliary device comprising a lower part and an upper part. The lower part is in the form of a hearth for solid fuels and the upper part is a store for solid fuels. The solid fuels are preferably supplied to the upper part from above. The lower part has a connecting part or channel for connection of the lower part to an opening in the hearth of a conventional 'boiler. The lower part or connecting channel includes an opening, preferably adjustable, for the supply of secondary air to the lower part.

The lower part is suitably lined to thermally insulate it. Insulation may be effected with refractory brick, mineral wool or some other insulating material. The combustion gases formed in the auxiliary device can be influenced by one or more throttle means, these being arranged inside or outside the auxiliary device.

According to an advantageous embodiment of the invention it is suit¬ able to arrange a fan supplying combustion air to the auxiliary device The quantity of air supplied can be regulated and regulation is per¬ formed by means of a thermostat or some other means sensing the tem¬ perature in the boiler itself. Inside the auxiliary device the air

supplied is spread in a manner ensuring satisfactory and uniform com¬ bustion without expended ash being blown about. The air can be spread in two different ways; either by nozzles arranged at the exhaust end of the fan or by using fuel already in the auxiliary device to spread the air. Nozzles are used when the air is supplied to the auxiliary device grate from below. On the other hand, if air is supplied from above, the fuel already in the auxiliary device can be used to spread the air.

The grate in the auxiliary device is preferably arranged below the outlet opening of the connecting channel. The size of the grate can be varied depending on the desired combustion. Together with a plate, the grate forms a transverse wall in the auxiliary device. The plate is not generally horizontal but inclines gently up from its junction with the grate. This is to enable solid fuel to fall more easily down towards the grate.

The outlet end of the fan supplying combustion air may be located either above or below said grate and plate. In the latter case, the fan nozzle is arranged so that the air flows along both side surfaces of the auxiliary device and rebounds against the surface of the side walls before passing the grate.

Additional characteristics of the present invention are revealed in the following claims.

The present invention will be described more fully with reference to the accompanying drawings, in which

Fig.1 is a perspective view of a conventional boiler provided with an auxiliary device according to the present invention,

Fig.2 shows a vertical cross-section through the conventional boiler and auxiliary device,

Fig.3 shows a variation of an auxiliary device having a fan arranged with its outlet below the auxiliary device grate,

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Fig.3A shows a vertical section through the connecting part of the auxiliary device, Fig.3B shows the attachment flange of the connecting part Fig.4 shows a cross section of the auxiliary device taken below the grate, and Fig.5 shows a vertical section through an auxiliary device in which the combustion air is supplied to .the device above its grate.

In the drawings, 1 is a conventional boiler with a flue 14. The boiler 1 has a hearth which may have been designed for a conventional oil- burner and been attached to the opening 3. However, if the boiler 1 had been used for solid fuels such as coke or wood, the opening 4 would have been used as supply opening for the solid fuel and the opening 3 might have been used for the removal of ash. The hearth 2 contains a baffle plate 5 providing a throttling means for combustion gases from the hearth 2 in order to utilize .the heat content of the combustion gases to the full. In front of the conventional boiler 1 is a cylin¬ drical unit consisting of a lower part 6 and an upper part 12. The lower part 6 has a bottom.7, a peripheral wall 8 and a connecting channel 10. Both peripheral wall and connecting channel are made of heat-insulating material and preferably covered inside and outside with metal, preferably stainless steel. The mouth of the connecting channel 10 is designed for connection to the opening 3 of a hearth 2 in a conventional boiler 1. The heat-insulating material in the lower part 6 may be mineral wool or refractory brick. The connecting channel 10 is provided with a valve 11 for the supply of secondary air to the lower part 6. The lower part 6 is provided with an inspection hatch 9, also used for the removal of ash and the supply of primary air. The lower part 6 also includes a grate 15. The lower part 6 has an upper section constituting a direction continuation of the lower part. This upper part is designated 12 and is made of any suitable material, preferably metal. The upper part 12 is provided at the top with a lid 13 and is designed for the supply of solid fuel such as wood, peat, wood-chips, paper, pellets and other solid fuels having too short a combustion time to be used in conventional boilers. The conventional

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boiler 1 is provided with an opening 4 for the supply of solid fuels and in this case the opening 3 is used for the removal of ash. To make use of the heat content in the combustion gas, the conventional boiler includes a baffle plate 5 which has a throttling effect since the gas can only pass outside the edges of the baffel plate 5. Obviously such a baffle plate can be placed in the lower part 6.

The present invention functions as follows: In a conventional boiler 1 previously used for oil-firing, for instance, the oil-burner is dis¬ mantled from the opening 3. The cylindrical auxiliary device 6 and 12 is then placed in front of the conventional boiler 1 so that the mouth of the connecting channel 10 fits the opening 3 of the conventional boiler 1. The lid 13 is then removed and solid combustible material poured in. This is ignited through the inspection hatch 9 upon reach¬ ing the grate 15 and when it is burning properly the supply of secon¬ dary air is adjusted by means of the valve 11. The upper part 12 is then filled with fuel right up to the lid 13. The auxiliary device now contains enough fuel to give a reasonable interval before the operat¬ ing personnel must refill it. Combustion gases from the auxiliary device are throttled by the baffle plate 5 so that the heat content from the combustion gases is utilized to the full.

Figure 3 shows an auxiliary device 16 corresponding to the-device 6 and 12 in Figure 2. The connecting part 17 is equivalent to the connecting part 10 in Figure 2. A grate 19 is located below the opening to the auxiliary part and provided with an inclined section 20. The parts 19 and 20 together form a transverse wall dividing the space into two separate parts, an upper and a lower part. The upper part is provided with a supply section 21 for fuel and the lower part with a fan 22 with exhaust nozzle 25 blowing out air so that it flows along the side walls of the auxiliary device. The quantity of air blown out from the fan may vary and is adjusted in accordance with the combustion desired. The fan can also be controlled by members sensing the temperature of the water in the boiler itself and regulating the fan in accordance there¬ with. The size of the grate 19 may vary depending on the desired combustion. The connecting part 17 may also be adjusted to give the

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desired throttling effect. The combustion can thus be controlled by three factors; variation of the combustion air, variation of the grate size and variation of the throttling capacity of the connecting part. The auxiliary device shown in Figure 3 functions as follows: The device is filled with fuel through opening 21. The solid fuel is then ignited and the desired quantity of combustion air supplied by means of fan 22. Figure 4 shows clearly how the combustion air leaves the fan 22 through the nozzle 25. The air will flow along the two side walls of the auxiliary device and rebound against the wall opposite the fan and below the grate 19. The reflected air passes through the grate and maintains the combustion process. Combustion gases then leave the grate 19 through the connecting part and enter the hearth of the boiler 1.

Figure 5 shows the auxiliary device 16 with its grate 19 and inclined plate 20. The fan in this device is however arranged in the roof and is designated 22a. Air from the fan 22a passes through the solid fuel above the transverse wall 18 and will be spread upon its passage through the solid fuel so that good combustion is obtained.

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