BIOMASS STOVE, IN PARTICULAR FOR PELLET, EXHIBITING AN AUTOMATIC OPERATION

Abstract

 An innovative biomass stove (10), in particular pellet, comprising:
- a heat generator (11) apt to be loaded with a biomass (BM);
- a feeding system (13) apt to feed a primary flow (f) of combustion air to the heat generator (11), so as to produce a combustion flame (12) and generate heat;
- a ventilation system (14) including a fan (14a) apt to blow a secondary flow (14b) of forced air in the gaps of the biomass (BM), loaded in the heat generator (11), so as to increase the size of the flame combustion (12);
- a temperature sensor (16) apt to detect the temperature (Tf) of the combustion flame (12); and
- an electronic control unit (18) apt to govern and control the operation of the biomass stove (10);
wherein the electronic control unit (18, SW) is configured to automatically control the speed of the fan (14a) and consequently the secondary flow of forced air aimed at supplying the combustion of the biomass, as a function of the temperature (Tf) of the combustion flame (12), in particular during the final phase of the biomass combustion cycle and therefore its carbonisation, so as to determine the complete combustion of the biomass (BM) at the end of its combustion cycle.

Description

Field of the invention

[0001] The present invention relates in general to the technical field of biomass heating systems, or of systems of heating and for the production of heat that use energy sources and fuels of vegetable origin such as wood chips and the like, and more particularly its object is a new biomass stove, typically employing pellets as fuel, which has innovative features and superior performance, such as automatic operation, with respect to similar biomass stoves currently in use and offered on the market.

Background of the invention and state of the prior art

[0002] Biomass stoves have been known for some time and are widely available on the market, i.e. apt to be fed and to burn material, such as pellets, of vegetable origin and therefore of biological type.

[0003] A typical biomass stove, of known features, is essentially constituted by a heat generator in which a flame is produced by the combustion of a biomass, so as to generate heat to be diffused in the environment in which the stove is located.

[0004] The type of biomass stove to which the present invention applies comprises in particular a double-walled cylinder, the dimensions of which are variable as a function of the heat generator and therefore of its power, that is the capacity of the stove for generating heat, which extends along a vertical axis and is fully closed in the lower part and partially closed in the upper part so as to form between the outer cylinder and the inner cylinder, of the double-walled cylinder, a cavity or air chamber.

[0005] The outer cylinder of the double-walled cylinder also has in the lower part a series of holes, in order to allow the entrance, from the external environment, of a primary flow of combustion air that flows and rises in the air chamber in a natural way, substantially by convection, until exiting through a series of combustion holes that are formed in the upper part of the inner cylinder.

[0006] A mobile grate with adjustable height is positioned inside the double-walled cylinder, above the level of the holes for the primary air inflow, and has the function of receiving the biomass that is loaded in the stove to be burnt and to support it during its entire combustion cycle.

[0007] In order to obtain a good combustion, the double-walled cylinder must be filled with the biomass up to a level slightly lower than the upper combustion holes.

[0008] In addition, the biomass stove comprises a pipe, with function of conveyor, which is placed in the lower part of the heat generator and traverses the two walls of the double-walled cylinder in a substantially orthogonal direction so as to convey a secondary flow of air, aspirated from the external environment by means of a fan, in the interior of the heat generator in an area under the mobile grate on which the biomass has been loaded, and therefore feed the various stages of combustion of the biomass.

[0009] In use, the stove is filled with the biomass, usually consisting of wood pellets, up to a level slightly below the upper combustion holes, as already stated, after which the lighting of the flame is performed with an igniter of the solid or liquid type.

[0010] During the combustion of the biomass the combustion air, cold, of the primary flow, enters through the lower holes and generates a natural flow, in vertical direction, along the cavity defined by the double-walled cylinder, so as to heat gradually, and then exits from the upper holes so as to feed the combustion flame and therefore generate heat which is transmitted to the external environment heated by the stove.

[0011] A diffuser, placed in the area of the flame and therefore in the upper part of the stove, has the function of spreading the flame directly into the environment and therefore the heat produced by it, making sure that the flame follows a certain path depending on the type of heat generator.

[0012] In addition, the air blown by the fan and conveyed by the pipe passes between the interstices of the biomass, loaded over the grate, and allows an increase in the size of the flame with a consequent increase in the heat produced.

[0013] In particular, in the first stage of ignition, the flame ignited by the solid or liquid igniter propagates uniformly inside the double-walled cylinder of the heat generator, until igniting a uniform combustion in the upper layer of the biomass.

[0014] Then, in a subsequent second phase which represents the longest and most extended operating phase of the overall cycle of use of the stove, the combustion gradually depletes the biomass until obtaining a carbonification of the fuel, or of the biomass.

[0015] Then, during a subsequent third stage, it is possible, by increasing the forced ventilation or the air flow induced by the fan, to deplete and burn almost totally the carbonised fuel, passing at the same time from a characteristic yellow flame to a flame colour tending towards blue.

[0016] Finally, once the biomass carbon has been exhausted, the flame gradually goes out until the stove is totally cooled.

[0017] This known biomass stove is not however exempt from the limits and disadvantages linked in particular to the fact that the operation of the fan that aspirates air from the outside environment and blows it and feeds it towards the combustion area, inside the heat generator in the area below the grate on which the biomass to be burnt has been loaded, is controlled in a substantially manual manner.

[0018] In the practical use of this known biomass stove it happens that, during the first and the second phase, corresponding as previously mentioned respectively to the lighting and main operation under normal conditions of the stove, the fan is usually set in manual mode to operate at a certain fixed speed, regardless of the size of the flame.

[0019] However, always during the first and the second phase of operation, manual intervention may occur in order to vary the power and the fan speed in order to obtain a net improvement in the combustion as a function of the flame.

[0020] Therefore, when the third phase arises, in which the burnt material or biomass has a carbonified form, the fan speed is manually increased in order to increase the intensity of the flame and therefore the heat produced, so as to determine a complete combustion and a consequent virtually total depletion of the carbon mass, as illustrated previously.

[0021] It is clear, however, that, in the case of no manual intervention to increase the speed and power of the fan, and therefore the air flow supplied to the stove, or to the respective heat generator, in order to burn and deplete the residual carbon, in this third phase there will be a progressive and unwanted extinguishing of the flame with the consequent formation of an excessive carbon deposits inside the stove.

[0022] Now such an unwanted extinguishing may cause the generation, for even a long time, of fumes and latent heat developed by the carbon mass, thus making the stove and the respective heat generator de facto unusable until their manual emptying or the disposal and natural exhaustion of this latent heat.

[0023] The need is therefore clear to find a solution that improves the operation and the safety of these known stoves, and also frees the user from performing troublesome and inconvenient operations in the management of the stove, and in particular is such as to avoid having to manually intervene to vary the forced air flow fed by the fan in order to improve the operation of the stove and completely burn the fuel, that is the biomass, with the risk, in the case of lack of intervention by the user, of encountering serious problems.

[0024] For clarity and completeness of information, Figs. 4A and 4B show, with reference to the following list, a typical biomass stove, denoted by A, in accordance with the prior art, such as that described previously, on which the present invention is applied, substantially improving it, and the respective mode of operation.

A

known biomass stove;

B

combustion flame;

C1

outer cylinder of the double-walled cylinder;

C2

inner cylinder of the double-walled cylinder;

D

biomass fuel;

D1

biomass level;

E

biomass support grate;

F

diffuser of the combustion flame;

G

air chamber or cavity;

H

lower holes for entry of the combustion air;

I

upper holes of combustion;

J

entry of air blown by the fan;

K

cold combustion air flow;

L

hot combustion air flow.

Summary of the invention

[0025] Therefore the primary object of the present invention is to propose a new biomass stove which remedies the limitations and disadvantages, illustrated previously, of biomass stoves currently known and in use, by optimising combustion in the various operating phases of the stove and in particular realising a complete and total combustion of the biomass safely and automatically, i.e. without the burnt biomass leaving at the end of its combustion cycle and therefore the extinguishing of the flame any carbonaceous residue.

[0026] Another object of the present invention, moreover connected to the primary one formulated previously, is also to realise a new stove that can be fed with biomasses which, besides having excellent yield, totally exempts its user from any manual intervention, in particular to adjust by means of the fan the forced air ventilation which feeds the combustion of the biomass.

[0027] The above objects can be considered fully achieved by the biomass stove, in particular pellet stove, having the features defined by the independent main claim 1.

[0028] Particular embodiments of the present invention are also defined by the dependent claims.

[0029] As will be disclosed by the description here below, the invention has as a starting point, in order to achieve safe and automatic operation of the stove and in particular such as to obtain a total exhaustion and burning of the biomass at the end of its combustion cycle, the observation, by the inventor, based on tests and measurements performed on a prototype of the stove of the invention built by the same inventor, that the temperature in the zone of formation of the flame, as detected in a given zone or fixed point, is subject to vary as a result of the variation of the fan speed, that is of the intensity of the forced ventilation produced by the fan, as well as the observation, also verified by practical tests, that during the carbonification process of the biomass and the consequent change in colouring of the combustion flame the temperature of the latter is subject to a drastic reduction and drop until an intervention is performed to increase the fan speed, or the forced ventilation, so as to prevent and counteract this drop and maintain the temperature of the flame high.

[0030] Likewise, it has been observed during the tests performed by the inventor that it is possible, even during operation under normal conditions of the stove, that is before the third phase starts and the carbonisation of the biomass, to effectively counteract the increase or the decrease of the flame by acting and intervening in the opposite direction on the power and speed of the fan, so as to maintain a practically constant flame.

[0031] The biomass stove of the invention has a series of numerous and significant advantages, in part already implicitly disclosed previously and further illustrated here below, among which the following are cited purely by way of an example:

• great safety;
• an excellent yield;
• a substantially automatic operation, that is such as not to require manual interventions and specific adjustments by the user, during the entire combustion cycle of the biomass that is loaded into the stove to be burned;
• total and complete exhaustion of the carbonaceous material at the end of biomass combustion cycle;
• therefore simple and inexpensive maintenance of the stove, without the necessity of having to clean it periodically and frequently, as in the case of biomass stoves currently available on the market;
• an automatic turning off of the stove after all the biomass load loaded in the stove has been burned and has therefore released all its caloric potential.

Brief description of the drawings

[0032] These and other objects, features and advantages of the present invention will be made clear and evident by the following description of one of its preferred embodiments, given by way of a non-limiting example, with reference to the accompanying drawings, in which:

Fig. 1 is a schematic view which illustrates in perspective form a biomass stove according to the present invention;

Figs. 2A and 2B are two diagrams illustrating the electronic part of the biomass stove of Fig. 1;

Fig. 3 is an operational block diagram that illustrates the operation of the biomass stove of the invention of Fig. 1 and the respective phases;

Figs. 4A and 4B are graphic views illustrating in a schematic way a typical biomass stove in accordance with the prior art and the respective operation; and

Figs. 5A, 5B, 5C and 5D show an advantageous variant of the biomass stove of the invention further comprising a heat exchanger having the function of increasing the efficiency and performances of the biomass stove.

Description of a preferred embodiment of the biomass stove of the invention and of the respective operation

[0033] Referring to the drawings, a biomass stove or heater, that is, apt to be fed by a biomass, denoted by BM, such as for example pellets, to burn it and thus generate heat, made in accordance with the present invention, is denoted as a whole by 10.

[0034] Fig. 1 shows schematically the structure of the biomass stove 10 of the invention which, as can be seen, is apparently very similar to that of a usual stove, known and available commercially, such as that previously described and shown in Figs. 4A and 4B.

[0035] Therefore, it is possible to refer to these Figs. 4A and 4B for every detail and part of the biomass stove 10 of the invention that may not be mentioned in this description.

[0036] In particular, the biomass stove 10 of the invention comprises:

• a heat generator, denoted as a whole by 11, substantially cylindrical and extended along a vertical axis X, apt to be loaded with the biomass BM and to produce a combustion flame, schematically shown in Fig. 1 with an arrow 12, and therefore generate heat, due to the combustion of the biomass BM;
• a feeding system, denoted in general by 13, apt to feed in a natural way, i.e. not forced, a primary flow of combustion air to the heat generator 11, so as to produce the combustion flame 12 and generate heat;
• a forced ventilation system, denoted in general by 14, comprising in turn a fan 14a suitable for aspirating from the external environment and blowing, along a conveying pipe 14c, a secondary flow, denoted by 14b, of forced air inside the heat generator 11, to ensure that this secondary flow 14b of forced air passes through the interstices of the biomass BM, loaded in the heat generator 11, so as to increase the dimension of the combustion flame 12 with a consequent increase in the heat generated by the biomass stove 10; and
• an electronic control unit, shown with a block 18 in Fig. 1, apt to govern and control the general operation of the biomass stove 10.

[0037] In addition, the biomass stove 10 comprises a flame temperature sensor, denoted by 16, of known features, also simply called a temperature sensor, which is positioned in the upper part of the heat generator 11, that is adjacent to the combustion flame 12, in a given point or area denoted by 12' and shown in Fig. 1, wherein this temperature sensor 16 has the function of continuously measuring the temperature Tf of the flame 12 during operation of the biomass stove 10 to generate heat.

[0038] The positioning of the temperature sensor 16 in this given point or area 12', adjacent to the combustion flame 12, is not random, but is essential for allowing the optimal operation of the biomass stove 10 of the invention and therefore obtain from it the maximum of its performances, as will be described here below by the description, in particular the operation of the stove 10.

[0039] In fact, as verified experimentally by the inventor through numerous tests on a prototype of the biomass stove 10, and illustrated in detail here below, this given point or zone 12', in which the temperature sensor 16 is located, must be such that the temperature developed by the flame (Tf), as detected by the same temperature sensor 16, is subject to vary due to the variation of the speed of the fan 14a of the ventilation system 14, that is it tends to increase in response to an increase in the speed of the fan 14a and vice versa tends to decrease in response to a decrease in the speed of the fan 14a.

[0040] The biomass stove 10 further comprises a flame diffuser, denoted by 17, which has the function of diffusing in the space the flame 12 produced by the heat generator 11.

[0041] The heat generator 11 has a substantially cylindrical shape wholly similar to that of known stoves, like the one shown in Figs. 4A and 4B, and in particular comprises a double-walled casing having an outer cylindrical wall 11a and an inner cylindrical wall, not shown in Fig. 1, which define one with the other a cavity for the primary flow of combustion air that feeds the combustion flame 12.

[0042] The feeding system 13, apt to feed in a natural way, essentially by convection, the primary flow of combustion air comprises, like the known stove shown in Figs. 4A and 4B, a series of holes 13a, formed on the outer surface of the heat generator 11, for the entry from the external environment of the primary combustion air, as denoted by arrows f in Fig. 1, in the cavity formed by the cylindrical outer and inner walls of the casing of the heat generator 11.

[0043] The biomass stove 10 further comprises a grate, adjustable in height along the axis X of the heat generator 11, not shown in the drawings but substantially corresponding to that, denoted by E, included in the known biomass stove shown in Fig. 4A, which has the function of receiving and supporting, during combustion, the biomass BM that is loaded in the stove 10 to be burned.

[0044] With respect to known biomass stoves and in use, such as that shown schematically in Figs. 4A-4B, the biomass stove 10 of the invention has some changes and improvements, illustrated here below, in particular aimed at improving the biomass combustion process and the diffusion of the heat generated by such combustion.

[0045] In particular, a first modification, not shown for reasons of brevity in the drawings, consists of a mechanical system that ensures a virtually airtight coupling between the flame diffuser 17 and the structure of the heat generator 11, wherein this mechanical system is substantially constituted by a telescopic ring which is inserted in a corresponding housing formed in the cylindrical body of the heat generator 11, and firmly coupled to the flame diffuser 17 by means of a lever device or of a system of guides.

[0046] Therefore, thanks to this airtight coupling, any entry of cold air from the outside is avoided, between the flame diffuser 17 and the structure of the heat generator 11, which could disturb the regularity of combustion.

[0047] In addition, this airtight coupling between the flame diffuser 17 and the structure of the heat generator 11 with the consequent impossibility of any passage of air between these parts, creates a better flow, in the stove 10, of the heated air that passes almost exclusively in the air chamber defined by the double-walled cylinder of the heat generator 11, as well as a more extensive flow of preheated air.

[0048] A second modification, also not shown in the drawings for reasons of brevity, consists in positioning inside the upper part of the cylindrical body of the heat generator 11, that is in proximity of the upper combustion holes, a system of tilted fins that encourage the ascent and the development in the vertical direction of the combustion flame 12 and influence its form, given that, through the effect of these fins, the combustion flame 12 assumes a dynamic form that tends to rotate.

[0049] Therefore, this change, in the embodiments of the biomass stove 10 of the invention which provide that the combustion flame 12 is to be visible, greatly improves the overall aesthetic effect of the biomass stove 10.

[0050] According to an essential feature of the present invention, which differentiates it substantially from the prior art, the electronic control unit 18, which governs and controls the operation of the biomass stove 10, is configured to control in an automatic way, by means of a program or software SW, indicated schematically by a block in Fig. 1, stored in the same electronic control unit 18, the speed of the fan 14a, and therefore the secondary flow of forced air intended to feed inside the heat generator 11 the combustion flame 12, depending on the temperature Tf of the combustion flame Tf, as detected by the temperature sensor 16, in particular during the final stage of the cycle of combustion of the biomass and therefore its phase of carbonification or carbonisation, in order to determine the complete and total combustion of the biomass load, i.e. without leaving at the end of its combustion any carbonaceous residue in the heat generator, as described in detail here below.

[0051] The diagrams of Figs. 2A and 2B relate specifically to the electrical and electronic part, denoted as a whole by 20, which is included in the biomass stove 10 of the invention, respectively in the case of power supply from the mains at 220 volts and by means of a battery.

[0052] In particular the diagrams of Figs. 2A and 2B show, in addition to the electronic control unit 18, the fan 14a and the temperature sensor 16, already mentioned and described previously, some further components and salient functions of this electrical and electronic part 20, such as a safety thermostat 21, a safety solenoid 22, a display or visualiser 23 apt to provide the operator with useful data concerning the operation of the biomass stove 10, and a potentiometer 24 in order to be able to make any manual adjustments during the use of the stove.

[0053] It is clear, however, that the program or software SW implemented of the control unit 18 of the biomass stove 10 of the invention can replace the functions of the potentiometer 24, so as to avoid manual adjustments, or to ensure that adjustments which become necessary in the operation of the stove are carried out in automatic mode, in particular as regards the regulation of the power and of the speed of the fan 14a.

[0054] For example, the software SW can be configured to adjust automatically, therefore without having to use the potentiometer 24, the power of the fan 14a during operation of the stove 10, by setting certain levels for this power as a function of the established operating temperature for the stove 10, or by setting a minimum threshold of revolutions of the fan 14a.

[0055] A description will now be given, with reference to the operation diagram of Fig. 3, of the use and the operation of the biomass stove 10 of the invention.

[0056] Initially, the operator turns on the stove 10, as indicated by a label 20, in a known manner and by means of the electronic control unit 18.

[0057] Immediately after igniting a first phase of ignition and start-up begins, shown schematically with a block 21 in Fig. 3, during which the fan 14a, included in the forced ventilation system 14, operates under the control of the software SW, at a determined constant speed, as indicated by a block 22, so as to feed at a constant flow rate the secondary flow 14b, of forced air, which feeds the combustion flame 12 by blowing air, in the heat generator 11, from the area below the grate on which the biomass BM is loaded.

[0058] As indicated by blocks 23, 24 and 25, this first phase 21 of igniting and start-up, with the fan 14a operating at a given constant speed, continues and lasts until the temperature sensor 16 detects that the temperature of the flame Tf has reached the normal operation temperature Tr, corresponding to the stabilisation of the combustion of the biomass BM, or to the achievement of a normal condition and regularity of the combustion of the biomass BM.

[0059] Then, always under the control of the software SW, a second phase starts, as indicated by a block 26, corresponding to the phase of the main operation and temporally longest of the entire combustion cycle of the biomass BM, during which the biomass BM loaded in the stove 10 is progressively burnt.

[0060] In this phase 26 of the main operation, the temperature sensor 16 detects, by performing samplings at intervals of defined time, as indicated by a block 27, the temperature Tf of the flame 12 and sends a corresponding signal to the electronic control unit 18, which in turn regulates the ventilation on the basis of the received signals.

[0061] Therefore, the electronic control unit 18, when from this sampling of the signals received from the temperature sensor 16 it determines, as indicated by a block 28a, that the temperature Tf of the flame 12 is lower than the normal temperature Tr of the flame 12, namely, as mentioned, than the temperature of the flame 12 corresponding to a regular pattern and operation of the combustion of the biomass BM, commands an increase in the speed of the fan 14a so as to increase the temperature Tf of the flame 12 thanks to a greater supply of forced air in the area of combustion, so as to make sure that the temperature Tf of the flame 12 returns to being once again in accordance with the normal operation temperature Tr.

[0062] Instead, the electronic control unit 18, when it detects, as indicated by a block 28b, that the temperature Tf of the flame 12 is greater than the normal operation temperature Tr of the flame 12, commands a decrease in the speed of the fan 14a so as to reduce correspondingly the temperature Tf of the flame 12 due to a lower supply of forced air in the combustion zone, and thus makes sure that also in this case the temperature Tf of the flame returns again to being once again in accordance with the normal operation temperature Tr.

[0063] The phase 26 of regular and normal operation continues and lasts, under the control of the software SW, until the electronic control unit 18 detects, as indicated by a block 29, a progressive and drastic reduction in the temperature Tf of the flame 12, indicating that the combustion cycle of the biomass BM loaded in the stove 10 is coming to an end, i.e. that the biomass BM is carbonising and therefore is about to deplete its caloric potential.

[0064] At this point, therefore, a third phase begins, indicated by a block 30, which precedes precisely the end of the combustion cycle of the biomass and in which the biomass BM has a carbonified shape.

[0065] Also in this third phase 30, during which the temperature Tf of the flame 12 tends inexorably to drop, the biomass BM, as mentioned, having practically exhausted its caloric potential and therefore approaching the end of its combustion cycle, the temperature sensor 16 detects in continuation, as indicated by a block 31, the temperature Tf of the flame 12 and sends a corresponding signal to the electronic control unit 18.

[0066] Therefore, as indicated by blocks 32 and 33, the electronic control unit 18 until it determines, on the basis of the signals received from the temperature sensor 16, that the temperature Tf of the flame 12 is greater than the temperature Ts, corresponding to the extinguishing of the flame 12 and consequently to the end of the entire combustion cycle of the biomass BM, controls a gradual increase in the speed of the fan 14a.

[0067] This gradual increase in the speed of the fan 14a in turn has the effect, thanks to the greater supply of forced air in the area of the biomass BM, of counteracting the decrease in the temperature Tf of the flame 12, consequent to the carbonification of the biomass BM, and of maintaining this temperature Tf high, so as to cause, advantageously, the total combustion and exhaustion of the biomass BM initially loaded in the stove 10, i.e. without leaving in the same stove 10 any carbonaceous residue at the end of the combustion cycle of the biomass BM, as indicated by a block 34.

[0068] Finally the electronic control unit 18, when it determines by means of the signals received from the temperature sensor 16 that the temperature Tf of flame 12 has dropped until it is equal to or less than the extinguishing temperature Ts, as indicated by a block 35, commands in automatic mode the turning off of the stove 10, in turn indicated by a block 36, that is the stop of the fan 14a and the interruption of any forced ventilation in the heat generator 11.

[0069] As already underlined previously and clearly deducible from the previous description of the operation of the biomass stove 10, the position of the temperature sensor 16 that detects continuously the temperature of the flame 12 has its own specific importance in the context of the invention and therefore should not be overlooked.

[0070] In fact, as also confirmed by numerous tests carried out by the inventor on a prototype of the stove of the invention, this position of the temperature sensor 16, in the area of the combustion flame 12, must be such, in order to obtain a correct and optimal operation of the biomass stove 10, as to allow the temperature sensor 16 to detect with sufficient precision the temperature response of the combustion flame 12 to the variations of the speed of the fan 14a, i.e. to the varyingly intense flow 14b of forced air which feeds the combustion of the biomass BM.

[0071] In particular, from the tests carried out on the prototype of the biomass stove 10 it was found how it is particularly advantageous and effective, in order to generate by means of the temperature sensor 16 a good signal indicative of the temperature of the combustion flame 12 and therefore obtain an optimal operation of the stove 10, to place the temperature sensor 16 downstream of the combustion flame 12, namely in the area where the heat escapes from the stove 10 in order to be transmitted to the surrounding environment.

[0072] In particular, this arrangement of the temperature sensor 16, after the combustion flame 12, has the advantage compared to other arrangements, while still in the zone of the flame 12, of allowing operation in a range of relatively lower temperatures.

[0073] It is clear, however, that the temperature sensor 16 can be placed in various positions and modes, in the zone of the combustion flame 12, therefore more or less distant from it, or also within the same flame 12, provided the condition is met of being able to detect with sufficient precision the response in temperature of the flame 12 to the variations in the speed and the power of the fan 14a.

[0074] Naturally the program or software SW, that governs the operation of the biomass stove 10, may take into account the specific and exact position of the temperature sensor location 16 in order to determine, as a function of the temperature signal received from the same temperature sensor 16, the response for the fan 14, that is to command an increase and decrease in the speed thereof or maintain its speed unchanged.

[0075] It is therefore clear, from the description given, that the present invention fully achieves the intended objects, and in particular proposes a new stove, apt to burn biomasses and in particular pellets in order to generate heat, having the capacity to govern and control in a totally automatic way the entire combustion cycle of a biomass load loaded into the stove, without leaving, at the end of its combustion and once the flame has gone out, any residual carbonaceous material inside the stove.

Variations and improvements

[0076] Without prejudice to the basic concept of the present invention, it is also clear that changes and improvements may be made to the biomass stove, as described heretofore, for reasons of brevity not shown in the drawings, without thereby departing from the scope of the same invention.

[0077] For example, the biomass stove of the invention may include an electromechanical device apt to lock directly or indirectly, during the operation of the stove, the cylindrical body of the respective heat generator, so as to prevent the extraction thereof from the stove, until a minimum temperature limit deemed safe has been reached.

[0078] Furthermore, in the case of operation of the fan by means of buffer battery, the program that manages the operation of the stove can be configured so as to determine a minimum level of load of the biomass such as to allow the execution of the complete cycle of combustion, and to emit a light or sound report should faults occur concerning the load level of the biomass or in general malfunctions of the stove.

[0079] Again in the case of operation of the fan by means of a buffer battery, the software or program that manages the operation of the biomass stove can be appropriately configured so as to control and command the fan which determines the ventilation of forced air in the biomass combustion zone, at a constant speed, or in general conforms to the value required by the program, regardless of the level of charge of the battery that powers the fan.

[0080] In addition, the biomass stove or the respective program or software can be configured to vary and control the operating power of the stove, or the heat generated by it, as a function of a certain temperature range detected, so that, once minimum and maximum limits of temperature have been established, it is possible to regulate and control in various ways the minimum and maximum power delivered by the stove.

[0081] It is also possible to provide for the detection of the temperature at various points of the stove deemed critical and use the data detected to optimally manage its operation.

[0082] Further it is possible to detect by means of a probe the temperature in the environment surrounding the stove, to display the value of this environment temperature on a display for the benefit and information of the user of the same stove and to process this value in order to control, that is increase or decrease , the heat generated by the stove.

[0083] Finally it is noted that, though having described the biomass stove of the invention, in its preferred but not exclusive embodiment, for use to produce heat intended to heat the room in which the stove is located, other applications and uses are possible in which the biomass stove of the invention can be advantageously applied and its innovative features appropriately exploited.

[0084] For example the stove i.e., in general, the heater of the invention can be realised and configured, as well as in the form of a typical heating stove for indoors or outdoors, also for use as a barbecue, or as a module which can be integrated in a fireplace, or as part of a wider heating system or equipment, or still for other uses, for reasons of conciseness not described here.

[0085] According to a further variant, denoted by 110 and represented in Figs. 5A-5D, the biomass stove of the invention advantageously includes a heat exchanger, denoted as a whole by 21, which is arranged between the cylindrical heat generator 11, that produces the flame 12, and the diffuser 17, which has the function of diffusing in the space the flame 12 produced by the heat generator 11.

[0086] In detail, this heat exchanger 21 is constructed by inserting and soldering in a sealed and tight way in a box 21a, which serves as outer casing, a plurality of through pipes 21b, which are designed to convey the flame 12, produced by combustion of biomass and coming from the cylindrical body of the heat generator 11, and define an extended and good exposure surface that is exposed to the same flame 12 so as to receive its heat.

[0087] Furthermore the heat exchanger 21 comprises two openings, in particular contiguous each other, respectively, 21c and 21d, faced on the outside of the heat exchanger 21 and formed on one side of the box 21a, and a separation wall or separator 21e that separates the two openings 21c and 21 d, wherein this separator 21e extends and is configured, inside the same box 21 a, such that the air that enters in the heat exchanger 21 through one of the respective two openings 21 c, 21d is conveyed by the separator 21e so as to lap the tubes 21b before exiting from the heat exchanger 21 through the other opening.

[0088] Therefore these two openings 21c and 21d have the function of receiving, by one of these two openings, the air that passes through the heat exchanger 21, so as to lap the surface of the pipes 21b and therefore receive heat from them, and that then, once heated, exits from the other opening to spread in the external environment.

[0089] More specifically, these two contiguous or adjacent openings 21c and 21d, formed on one side of the heat exchanger 21, are dimensioned in such a way as to exert the least possible resistance on the flow of forced air which enters in the same heat exchanger 21.

[0090] The separator 21 e, arranged within the heat exchanger 21, in turn is configured so as to convey the flow of air and force it, while passing and flowing through the heat exchanger 21, to lap all the surfaces and in any case most of the surfaces of the tubes 21b heated by the flame 12, so as to obtain an optimal heat exchange.

[0091] A Venturi tube indicated with 22 can be advantageously placed on top of the biomass stove 110, above the diffuser 17, to facilitate the flow of fumes to the outside and the development of the flame 12 inside the tubes 21b of the heat exchanger 21.

[0092] Therefore, in the operation of the biomass stove 110, the air that enters in a forced manner in the heat exchanger 21 through one of the respective openings 21c and 21d comes out, once suitably heated, from the same heat exchanger 21, through the other of these two openings 21c and 21d.

[0093] For clarity, the diagram of Fig. 5D illustrates the operation of the heat exchanger 21, wherein the cold forced air which enters, to be heated, in the heat exchanger 21 through one of its two contiguous openings 21c and 21d, is indicated with an arrow F1, and the hot forced air exiting, once heated, from the heat exchanger 21 through the other of its two openings 21c and 21d, is indicated with an arrow F2.

[0094] This variant 110 of the biomass stove of the invention, thanks to the heat exchanger 21, makes it possible to propagate and spread in a forced way the hot air in the external environment, so as to obtain a heating effect at a greater distance with respect to the embodiment of the biomass stove 10.

[0095] It follows that the biomass stove, according to this variant 110, is suitable to be advantageously used for heating outdoor spaces and that it has also the further advantage of allowing an optimal perception of heat in the immediate vicinity of the biomass stove itself

[0096] Moreover, always in the use of this biomass stove 110 in external environments or open spaces, it will be possible to achieve better performances and an improved exploitation of the heat of the flame produced by the heat generator 11, by conveying in the heat exchanger 21 the hot air that is generated in the lower zone of the biomass stove.

Claims

1. Biomass stove (10; 110), in particular of the pellet type, comprising:

- a heat generator (11), substantially cylindrical, apt to be loaded with a biomass (BM) and therefore to produce a combustion flame (12), so as to generate heat, as effect of the combustion of the biomass (BM);

- a feeding system (13) apt to feed in a natural way a primary flow (f) of combustion air to the heat generator (11), so as to produce said combustion flame (12) and generate heat;

- a forced ventilation system (14) including a fan (14a) apt to blow a secondary flow (14b) of forced air in the interstices of the biomass (BM), loaded in the heat generator (11), so as to increase the size of the combustion flame (12) with consequent increase in the heat generated by the biomass stove (10); and

- an electronic control unit (18) apt to govern and control the operation of the biomass stove (10),

characterised in that it further comprises a temperature sensor (16) apt to detect the temperature (Tf) of the combustion flame (12), and
in that said electronic control unit (18) is configured to control in an automatic way, by means of a program or software (SW), the speed of said fan (14a), and consequently said secondary flow (14b), of forced air, aimed at feeding the combustion of the biomass (BM), as a function of the temperature (Tf) of the combustion flame (12), as detected by said temperature sensor (16), during the final stage of the combustion cycle of the biomass (BM) and therefore its carbonisation, so as to cause the complete combustion of the biomass load (BM), that is without leaving at the end of its combustion cycle any carbonaceous residue in the heat generator (11) of the biomass stove (10).

2. Biomass stove (10; 110) according to claim 1, wherein said temperature sensor (16) is arranged in a certain position or area (12'), adjacent to said combustion flame (12), such that the temperature (Tf) of the combustion flame (12), as detected by the same temperature sensor (16), is subject to vary due to a variation of the speed of the fan (14a) of the ventilation system (14), that is tends to increase in response to an increase of the speed of the fan (14a) and vice versa tends to decrease in response to a decrease of the speed of the fan (14a).

3. Biomass stove (10; 110) according to claim 1 or 2, wherein said temperature sensor (16) is arranged downstream of the combustion flame (12), that is in the area where the heat generated by the biomass stove (10) comes out into the external environment.

4. Biomass stove (10; 110) according to any one of the preceding claims, wherein said heat generator (11) comprises a double-walled cylinder in turn including a cylindrical outer wall (11a) and an inner cylindrical wall which define one with the other an interspace for the primary flow (f) of the combustion air,
wherein said outer cylindrical wall (11a) has at the bottom part a series of inlet holes (13a) for the entry of the combustion air (f) in said interspace, and wherein said inner cylindrical wall has on the upper part a series of combustion holes for the supply of the combustion air, which is heated by flowing vertically along said interspace, in the zone of the flame (12) produced by the combustion of biomass (BM).

5. Biomass stove (10; 110) according to any one of the preceding claims, comprising a conveying pipe (14c) which passes through the outer casing (11a) of said heat generator (11) and has the function of conveying the secondary flow (14b) of forced air blown by said fan (14a) in an area, inside of the heat generator, arranged below a grid on which the biomass (BM) has been loaded to be burned.

6. Biomass stove (10; 110) according to any one of the preceding claims, wherein said heat generator (11) comprises a grid adjustable in height and apt to receive the biomass (BM) to be burned.

7. Biomass stove (10; 110) according to any one of the preceding claims, further comprising a flame diffuser (17) having the function of diffusing in the space the combustion flame (12) produced by the heat generator (11).

8. Biomass stove (10; 110) according to claim 7, characterised by a hermetic mechanical coupling, including a telescopic ring, between the flame diffuser (17) and the structure of the heat generator (11), so as to prevent any entry of cold air from the outside, between these two parts, in the heat generator (11).

9. Biomass stove (10; 110) according to any one of the preceding claims, further comprising, in the upper zone of the cylindrical body of the heat generator (11), a system of inclined fins that favour the ascent and the development in the vertical direction of the combustion flame (12) and condition its form, whereby, as a result of these fins, the combustion flame (12) assumes a dynamic form that tends to rotate.

10. Biomass stove (10; 110) according to any one of the preceding claims configured for a plurality of uses, for example as a heating stove for indoors and outdoors, barbecue, a module integrated in a fireplace, as a part of a wider heating system.

11. Biomass stove (110) according to any one of the preceding claims as dependent on claim 7, further comprising a heat exchanger (21) arranged between said heat generator (11), cylindrical, and said flame diffuser (17).

12. Biomass stove (110) according to claim 11, wherein said heat exchanger (21) comprises:

- a box or outer casing (21a);

- one or more through tubes (21b) extending inside said outer box (21a) and adapted to receive the flame (12) produced by the heat generator (11);

- at least two openings (21c, 21d), in particular adjacent each other, faced on the exterior of said outer box (21a); and

- at least one separator (21e), arranged in said outer box (21a), which separates said at least two openings (21 c, 21d) one from other;

wherein said separator (21 e) is configured such that the air which enters the heat exchanger (21), through one of its two openings (21 c, 21 d), is conveyed by said separator (21e) in such a way to lap said one or more through tubes (21b) before exiting, once heated, from the heat exchanger (21) through the other of its two opening (21c, 21d).

Drawing