This invention relates to an arrangement for firing solid fuels, comprising a substantially vertical fuel space with an upwardly located, preferably sealable opening for fuel filling-up, and with a bottom consisting of a grate or the like for passing ash to an ash-space located beneath the fuel space, at least one feed means for controlled supply of combustion air at least to the fire box located above said grate, and a duct connected to a chimney and communic¬ ating with the fire box for carrying away flue gases to the chimney.

At the combustion of solid fuels in conventional fire-places with manually or automatically controlled damper or draught valve, irrespective of whether the combustion air is taken from outside or from within, the damper or valve normally must be fully open for rendering complete combustion poss¬ ible. As soon as the damper or valve is closed fully or partially, in order to throttle the air supply and thereby to reduce the heat emission from the fire-place, for example when a predetermined temperature has been achieved in one or several rooms, in a water heater, heat magazine, in one or several ovens and/or hotplates to be heated and maint¬ ained heated, the combustion normally is incomplete due to insufficient air supply. It has been tried since long to manage this problem, but without ^" full success . Incomplete combustion as known results a.o. in unecor-c ic surplus of ur.ccmbusted gases as well as in the formation of tar and soot, which constitute a great risk of chimney fire and precipitate _. on the surfaces of the fire-box and flue gas ducts where they develop an insulating coat and thereby effectively reduce the heat emission from the fire-place

and deteriorate its efficiency degree. This in its turn gives rise a.o. to a fuel consumption higher than necess¬ ary.

The object of the present invention, therefore, is to pro uce an arrangement for the firing of solid fuels which does not show the aforesaid disadvantages, but renders ^' possible a combustion as complete as possible even when the air supply is cut off at maximum or partially, and which also is capable to include a greater fuel amount without giving rise to a combustion thereof which is fast than necessary for maintaining a certain predetermined temperature in one or several rooms, in a water heater, heat magazine, in a stove and/or one or several hotplates

This object is achieved in that the arrangement according to the present invention has been given the characterizin features defined in the attached claims . According to the principles, on which the present invention is based, a separate fire-place for combusting combustible gases from the hearth is provided after the hearth in the draught direction.

The invention is explained in greater detail in the follo ing, with reference to the accompanying drawing, in which Fig. 1 is a schematic section through a firing arrange¬ ment according to the present invention, Fig. 2 is a partial section substantially along the line II-II in Fig. 1, Fig. 3 is a partial section substantially along the lin III-III in Fig. 1 through a pair of air supply ducts , and Fig. -. shows a mechanism for closing and opening two doors comprised in the arrangement.

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In the drawing, 1 designates a fuel space, which at its upper portion is provided with an opening 3 for filling- in fuel. Said opening preferably can be sealed by means of a door 2 and has a bottom in the form of a grate 4 for supporting the fuel in the fuel space 1 and for passing ash formed at the combustion to an ash-space 5, which is located beneath said grate 4 and said fuel space 1 and includes a preferably sealable door 6 for removing ash from the ash space.

To the lower portion of the fuel space which can be said to constitute a part of the fire-place of the present invention, a relatively wide duct 8 is connected which extends to a chimney 7 for conducting away flue gases from the combustion. Said duct 8 is in other respects separated entirely from the fuel space 1 by means of a partition wall 9 , which should be provided with incombust¬ ible insulation 10 for restricting the heat transfer from the duct 8 to the fuel space 1.

In said duct 8, in close connection to the fire-place of the fuel space, a throttling 11 is provided, for example in the form of a perforated plate 12, which has at least one through hole 13, the cross-sectional area of which is smaller than the duct 8 in general on both sides of the throttling. The said throttling acts as a combustion nozzle and is intended to bring about an effective combustion ^■ of combustible gases, hich come from the fire-place of the fuel space and must pass through the throttling 11, because this is located, seen in the draught direction, after the fire-place of the fuel space which generally is designated by 11.

At the embodiment shown in the drawing, the primary comb¬ ustion air required for the combustion is supplied both to the fire-place It of the fuel space and to the combustion

nozzle 11 through a common piping system 15, which by an adjustable damper or draught valve 17 is connected to an intake 16 with adjustable damper or draught valve 17. Δl- though not shown in the draining, it is possible, within the scope of the principles on which the present inventio is based, to arrange separate piping systems for the supp of the primary combustion air to the fire-place of the fuel space and to the combustion nozzle 11.

The piping system shown in the drawing comprises a plur¬ ality of pipes 18, which extend from an air distribution chamber 19 provided in connection to said intake 16 inwar beneath the fuel space 1, and which at least in their por ion facing toward the fuel space 1 are provided with air holes 20, which are arranged in at least two rows and are directed obliquely upward-outward at a relative angle of e.g. 80 to 90 . Through these air holes 20 in the pipes 18 necessary combustion air is supplied to the fire-place i*+ of the fuel space in a way distributed over the surfac of the fire-place, in order to maintain the combustion in said fire-place, which combustion per se need not be complete, but may take place with a certain air deficit. The combustion, however, shall be such that in the fire- -place 14- of the fuel space a more or less glowing or burning fuel-hearth, depending on the amount of supplied air, is maintained, to which hearth new fuel is fed cont- inuoulsy from above as long as fuel is available in the fuel space.

In order to prevent this continuous feed of fuel to the fuel-hearth from being stopped, particularly when the fue is in the form of wood, the fuel space -1 widens downward to the grate **• as shown in the drawing.

At the embodiment shown in the drawing, the pipe of said pipes 18 which is located beneath the throttling 11 is

OMPI

provided with an upward pipe neck 21, the end of which located at some distance from the nozzle opening 13 is closed but provided with a number of air holes 22 both at the end and in adjacent wall portions for the supply of necessary primary combustion air to the nozzle open¬ ing formed by the throttling 11, which opening thus con¬ stitutes the remaining portion -of the fire-place of the present arrangement, in which fire-place the combustible gases coming from the fuel-hearth are mixed with the combustion air, which flows out of the air holes 22 of said pipe neck and is preheated by the heat ^' from the fuel-hearth, and thereby are combusted at a high comb¬ ustion temperature, not the least due to the increase in speed caused by the throttling and the short distance to the fuel-hearth.

For adjusting the primary combustion air, the intake to the air distribution chamber 19, in which the combustion air is distributed to the different pipes 18, is formed as an exchangeable high-efficiency nozzle 16 and controlled in known manner by means of the draught-valve 17, which is located in front of the intake or nozzle 16 and can be controlled automatically in response to the temperature in or outside the fire-place for obtaining continuous or intermittent draught control, though it is shown in the drawing to be manually adjustable in different draught positions between fully open and fully closed position. The high-efficiency nozzle is shown in the drawing in the form of an exchangeable plate 23 with one or several holes 24 having a total flow area ensuring the supply of an air amount required for high-e iciency combustion at fully open draught valve.

In order to be able to maintain the fuel-hearth even at fully closed draught valve 17 so as to prevent the hearth from going out, an exchangeable idling nozzle in the form

of an exchangeable plate 25 is provided in the draught valve, which plate has a small flow hole 26, which per¬ mits the passage only, of the air amount required for keeping the fuel-heart -alive and in the nozzle opening 13 to effect the combustion of gases coming from the fuel-hearth. When the combustion air flowing out through the pipe neck 21 is not sufficient for effecting a com¬ plete combustion of said gases, preferably pre-heated secondary air can be supplied through an adjustable secondary air damper, which in the drawing is shown to consist of a slide 38 movable in the holder and provided with a plurality of. holes 35 located to the side of each other at a predetermined distance. In open position of the damper shown in Fig. 1, said holes are located dir¬ ectly in front of corresponding holes 37 in the wall ;to the duct 8, and by moving the slide 38 in its longitud¬ inal direction the damper, thus, can be adjusted by cover ing the holes 37 entirely or partially, whereby a control of the secondary air is obtained. The secondary air dampe can be used for supplying extra combustion air whenever required and also at fully open draught valve 17.

The combustion air flowing in through the intake or nozzl 16, thus, is distributed,independently of the position of the draught valve -in the distribution chamber IS, to the different pipes 18 and then, in proportions defined by the air holes 20 and, respectively, 22, to the two fire-places, Owing to the increase in speed and the resul ing higher turbulence brought about by the throttling 11 in the duct 8, the combustion air supplied to the nozzle opening 13 is mixed intimately with the gases coming from the fuel hearth whereby an efficient and substantially complete combustion is obtained which substantially is independent of 'whether the combustion speed is high or low. The flue gases leaving the arrangement according to the present invention are thereby clean and protective to the environment.

In order to prevent smoke from flowing out when the door 3 is opened for filling-in fuel, -the fuel space 1 can be connected to the chimney 7 through a door 29 which, thus, must be opened about simultaneously with the door 2. For this reason, the filling-in door 3 is locked in closed position by a locking arm 32, which is attached on an axle 31 connected to the door 29. For being able to open the door 3, the locking arm 32 must be pivoted upward, whereafter by said locking arm the door 29 can be displac¬ ed and the fuel space 1 be connected to the chimney 7. Before the filling-in door 3 again can be locked, the door 29 first must be moved back to the position shown in Fig.

I by means of the locking arm 32, which first thereafter can be pivoted downward for locking the filling-in door 3. Said arm is arranged to co-operate by a clamp nose 33 with a guide groove 34 in order to be drawn in to the door 3 and by a pressure nose 35 to press on the door 3 and hold it closed in locked position.

The partition wall 9 between the fuel space 1 and the duct 3 is at its lower portion and beneath the throttling

II in the duct 8 formed as fingers 27, along which the fuel can slide and which partly prevent the fuel from gushing in and clogging the space beneath the throttling 11. For this reason, the grate 4 also is bent upward and by its upward bent portion rests against the pipe neck 21 and against support brackets on the other pipes 18, which brackets however are not shown in the drawing.

As shown in Fig. 3, also a grate 23 can be provided beneath -the pipes IS, which grate should have a finer mesh than the grate 4. In certain cases it may be suff¬ icient with a grate located beneath the pipe 13.

The present invention is not restricted to what is described above and shown in the drawing, but may be altered and.modified in many different ways within the scope of the invention idea defined in the claims