Pellet dispensing device for a stove and stove with such a device

Abstract

A device (13) for dispensing pellets (12) for a stove (10), which comprises, considering its vertical axis of extension downward from above, in the following order: - a reservoir (18) for the pellets (12), the reservoir (18) being open upwardly and having a spiral path (19) for the pellets (12), - a base, - vibration means (20) of the reservoir (18), which are interposed between the reservoir (18) and the base (21).

Description

[0001] The present invention relates to a device for dispensing pellets for a stove.

[0002] The invention also relates to a stove with such a device.

[0003] A stove fired by pellets is a heating apparatus, nowadays increasingly widespread especially in domestic settings.

[0004] Such an apparatus burns wood pellets to generate heat.

[0005] A stove fired by pellets comprises: a hopper for loading and stowing the pellets, a motorized screw feeder to convey the pellets from the hopper to a brazier, the brazier, where combustion of the pellets occurs, a heat exchanger, adjacent to the brazier, which enables the exchange of heat between the hot fumes of combustion and the air in the space to be heated, or optionally the water in a heating system, an extractor of the combustion fumes, a fan, for moving the air in the space to be heated.

[0006] With respect to traditional wood stoves, stoves fired by pellets make it possible to burn biomass that is traditionally less amenable to combustion than gas, so obtaining two advantages: a more homogeneous fuel / combustion agent mix, they are dosed with relative continuity and accuracy.

[0007] Such mixing makes it possible to provide a reactive system that is more evenly distributed in space, one that is much less affected by the unevenness typical of a wood log, which burns with a combustion front that proceeds inward from outside.

[0008] The dosing makes it possible to control the flow of pellets and the flow of air by acting on the rotation speeds of the screw feeder and of the fume extractor, in so doing modulating the power dispensed by the appliance, according to requirements.

[0009] Therefore, the overall effect of the combustion of ligneous biomass reduced to pellets is to render the combustion more stationary, and, with a suitable pellet / air dosage ratio, more efficient and less polluting than that of a wood log.

[0010] The pollutant substances with which to quantify the environmental impact of a stove fired by pellets are made up of emissions of: carbon monoxide (CO), nitrogen oxides (NOx), partially-oxidized carbon compounds (COT), particulates (PM).

[0011] Nowadays, the importance of environmental impact is increasingly felt, both by public opinion and by national legislatures.

[0012] To promote the reduction of environmental impact, for example the national legislature in Italy has set upper limits for each one of the emissions listed above and has enacted tax incentives for appliances that pollute less.

[0013] As a consequence, the sector of manufacturing stoves fired by pellets, which, especially in Italy's northeast, is one of the most prominent industrial districts in Europe, needs to reduce the emission levels of pollutant substances in the new products brought to market.

[0014] As it is not possible to alter the pellets, achieving this target relies in particular on achieving a combustion that is as stationary as possible, i.e. a regular and continuous dosing of the combustion air and of the pellets.

[0015] The known art has a number of drawbacks, however.

[0016] In fact, the screw feeder for conveying the pellets from the hopper to a brazier, although it rotates continuously as it draws the pellets from the hopper, is not capable of providing a constant pellet flow rate owing to the variable length of the pellets, even in the case of pellets from the same bag emptied into the hopper, and owing to the unpredictable orientation of the pellets with respect to the base of the screw feeder.

[0017] In particular, shorter pellets fill the troughs of the screw feeder more, so determining a higher flow rate than longer pellets, and vice versa.

[0018] Furthermore, the release of the pellet from the screw feeder to the brazier is impulsive, and instantaneous discharges of pellets alternate with periods of complete absence of flow, with consequent development of flames of different heights.

[0019] From the point of view of combustion, this behavior results in a rapid alternating of oxidation reactions with a far-from-optimal stoichiometric ratio, because they are either too fuel-rich or too fuel-poor, with consequent increase in emissions of pollutant substances.

[0020] Furthermore, during actuation, the screw feeder, by virtue of its rotation, can cause the pellets to crumble, with consequent increase of particulates in the fumes and at the same time emissions of pollutant substances.

[0021] The need is therefore felt to provide a stove fired by pellets that enables a lower emission of pollutant substances and therefore a lower environmental impact with respect to conventional pellet stoves.

[0022] The aim of the present invention is to provide a device for dispensing pellets for a stove and a stove with such a device, that are capable of improving the known art in one or more of the abovementioned aspects.

[0023] Within this aim, an object of the invention is to provide a device for dispensing pellets for a stove that makes it possible to dispense the fuel in a substantially constant manner.

[0024] Another object of the invention is to provide a device for dispensing pellets for a stove that enables the stove to reduce emissions of pollutant substances with respect to similar, conventional devices.

[0025] A further object of the invention is to provide a device for dispensing pellets for a stove that, when the device is actuated, makes it possible to prevent / reduce crumbling and the consequent emission of particulates in the fumes, with respect to similar, conventional devices.

[0026] Another object of the invention is to provide a stove with a device for dispensing pellets that makes it possible to achieve the objects listed above.

[0027] Another object of the present invention is to overcome the drawbacks of the known art in a manner different from any existing solutions.

[0028] Not least an object of the invention is to provide a device for dispensing pellets for a stove and a stove with such a device that are highly reliable, easy to implement, and at low cost.

[0029] This aim and these and other objects which will become more apparent hereinafter are achieved by a device for dispensing pellets for a stove, as defined in claim 1.

[0030] This aim and these and other objects which will become more apparent hereinafter are also achieved by a stove with such a device for dispensing pellets.

[0031] Further characteristics and advantages of the invention will become more apparent from the detailed description that follows of a preferred, but not exclusive, embodiment of a device for dispensing pellets for a stove and a stove with such a device, according to the invention, which is illustrated for the purposes of non-limiting example in the accompanying drawings wherein: Figure 1 is a schematic cross-sectional side view of a stove fired by pellets according to the invention; Figure 2 is an overall perspective view of a device for dispensing pellets for a stove, according to the invention.

[0032] With reference to the figures, a stove fired by pellets according to the invention is generally designated by the reference numeral 10.

[0033] The stove 10 comprises: a hopper 11 for loading and stowing the pellets 12, a device 13 for dispensing pellets 12, which is interposed between the hopper 11 and a brazier 14, the brazier 14 where the combustion of the pellets 12 occurs, which is connected to the device 13 via a chute 15, a heat exchanger 16 adjacent to the brazier 14, an extractor 17 of the combustion fumes, a fan, not shown in the figures.

[0034] The device 13 for dispensing pellets 12 comprises, considering its vertical axis of extension downward from above, in the following order: a reservoir 18 for the pellets 12, such reservoir 18 being open upwardly and having internally a spiral path 19 for the pellets 12, vibration means 20 of the reservoir 18, which are interposed between the reservoir 18 and a base 21, the base 21.

[0035] In the present description, the expressions "below", "in a lower region", "upwardly", etc. refer to the configuration for use of the stove 10 and of the device 13.

[0036] With particular reference to the figures, the spiral path 19 extends, for example, ideally along the outer surface of a truncated cone 22 with the smaller end face of such truncated cone 22 arranged below the larger end face of such truncated cone 22 and coinciding with the bottom 26 of the reservoir 18.

[0037] In such case, the base 21 is arranged parallel to the smaller end face of the truncated cone 22, below the latter.

[0038] In variations of embodiment, not shown in the figures, the spiral path extends ideally along the outer surface of a vertically extending cylinder.

[0039] In such case, the base 21 is arranged parallel to the lower end face of the cylinder, below the latter.

[0040] Advantageously, the hopper 11 has a lower portion 27 with a frustum-like or pyramid-like profile for conveying the pellets 12 into the reservoir 18, adjacent to the upper end of the latter, but mechanically separated from it.

[0041] In particular, the spiral path 19 leads out, in an upper region, onto the chute 15.

[0042] Advantageously, the vibration means 20 comprise: a magnet 23 associated in a lower region with the reservoir 18, an electromagnet 24, arranged below the magnet 23 and associated with the base 21, a plurality of elastic elements 25, extending between the reservoir 18 and the base 21, mutually coupling the reservoir 18 and the base 21.

[0043] These elastic elements 25 are, for example, leaf springs, arranged transversely between the plane of arrangement of the bottom 26 of the reservoir 18 and the plane of arrangement of the base 21.

[0044] The operation of the device 13 is the following.

[0045] The electromagnet 24 is electrically powered with a single-phase AC voltage.

[0046] When the electromagnet 24 is powered, a magnetic field develops, which causes a vertical movement of the magnet 23 and, therefore, of the reservoir 18.

[0047] Simultaneously, by virtue of the presence and arrangement of the elastic elements 25, the reservoir 18 is also subjected to a twisting movement.

[0048] In this manner, the pellets 12 are forced to shift and orient themselves, moving one step at a time, along the spiral path 19, so forming a continuous train of pellets 12.

[0049] In this way the pellets 12 are transferred from the bottom 26 of the reservoir 18 to the chute 15 (arrow F in Figure 2) and from there to the brazier 14 (arrow Q of Figure 2).

[0050] It should be noted that the effective value of the input voltage to the electromagnet 24 controls the frequency of the mechanical vibration and, therefore, the flow rate of pellets 12 to the brazier 14.

[0051] The device 13 can comprise, by way of non-limiting example, an electronic and / or electromechanical device for modulating the amplitude and frequency of the electromagnet 24, such as for example a potentiometer and / or a variable turns-ratio transformer and / or an autotransformer (Variac), not shown in the figures, for modulating the effective value of the input voltage to the electromagnet 24 and in this manner also vary the flow rate of pellets 12 to the brazier 14, according to requirements.

[0052] It should be noted that, since the pellets 12 move along in a stepped manner, one step at a time, substantially like a continuous train, the dispensing of the pellets 12 into the brazier 14 is uniform and constant.

[0053] It should also be noted that the absence of a mechanical connection between the hopper 11 and the reservoir 18 prevents / limits the propagation of vibrations to the rest of the structure of the stove.

[0054] Furthermore, with such a device the crumbling of pellets is limited / prevented, so limiting an increase in the particulates drawn into the fumes.

[0055] In practice it has been found that the invention fully achieves the intended aim and objects by providing a device for dispensing pellets for a stove that makes it possible to dispense the fuel in a substantially constant manner.

[0056] With the invention a device for dispensing pellets for a stove has been provided that enables the stove to reduce emissions of pollutant substances with respect to similar, conventional devices.

[0057] Furthermore, with the invention a device for dispensing pellets for a stove has been provided that, when the device is actuated, makes it possible to prevent / reduce crumbling, so limiting an increase in the particulates drawn into the fumes, with respect to similar, conventional devices.

[0058] Also, with the invention a stove with a device for dispensing pellets has been devised that makes it possible to achieve the objects listed above.

[0059] The invention thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the appended claims. Moreover, all the details may be substituted by other, technically equivalent elements.

[0060] In practice the materials employed, provided they are compatible with the specific use, and the contingent dimensions and shapes, may be any according to requirements and to the state of the art.

[0061] The disclosures in Italian Patent Application No. 102024000006382 from which this application claims priority are incorporated herein by reference.

[0062] Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly, such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.

Claims

1. A device (13) for dispensing pellets (12) for a stove (10), characterized in that it comprises, considering its vertical axis of extension downward from above, in the following order: - a reservoir (18) for said pellets (12), said reservoir (18) being open upwardly and having a spiral path (19) for said pellets (12), - a base (21), and - vibration means (20) of said reservoir (18), which are interposed between said reservoir (18) and said base (21).

2. The device (13) according to claim 1, characterized in that said vibration means (20) comprise: - a magnet (23) associated in a lower region with said reservoir (18), - an electromagnet (24), arranged below said magnet (23) and associated with said base (21), - a plurality of elastic elements (25), extending between said reservoir (18) and said base (21), said plurality of elastic elements (25) mutually coupling said reservoir (18) and said base (21).

3. The device (13) according to claim 2, characterized in that said elastic elements (25) are leaf springs, arranged transversely between the plane of arrangement of a bottom (26) of said reservoir (18) and the plane of arrangement of said base (21).

4. The device (13) according to claim 1, characterized in that it comprises an electronic and / or electromechanical device for modulating the amplitude and frequency of said electromagnet (24).

5. The device (13) according to claim 3, characterized in that said spiral path (19) ideally extends: along an outer surface of a truncated cone (22) with a smaller end face of said truncated cone (22) arranged below a larger end face of said truncated cone (22) and coinciding with the bottom (26) of said reservoir (18), said base (21) being arranged parallel to said smaller end face of said truncated cone (22), below the latter, - and / or along an outer surface of a vertically extending cylinder, said base (21) being arranged parallel to a lower end face of said cylinder, below the latter.

6. A stove (10) fired by pellets (12), comprising: - a hopper (11) for loading and stowing said pellets (12), - a device (13) for dispensing said pellets (12), which is interposed between said hopper (11) and a brazier (14), - said brazier (14), connected to said device (13) by means of a chute (15), - a heat exchanger (16) adjacent to said brazier (14), - an extractor (17) of the combustion fumes, - a fan, characterized in that said device (13) for dispensing said pellets (12) comprises, considering its vertical axis of extension downward from above, in the following order: - a reservoir (18) for said pellets (12), said reservoir (18) being open upwardly and having a spiral path (19) for said pellets (12), - a base (21), - vibration means (20) of said reservoir (18), which are interposed between said reservoir (18) and said base (21).

7. The stove (10) according to claim 6, characterized in that said hopper (11) has a lower portion (27) with a frustum-like / pyramid-like profile for conveying said pellets (12) into said reservoir (18), adjacent to the upper end of said reservoir, said lower portion (27) of said hopper (11) being mechanically separated from said reservoir (18).

8. The stove (10) according to claim 6 or 7, characterized in that said spiral path (19) leads out, in an upper region, onto said chute (15).

9. The stove (10) according to any one of claims 6 to 8, characterized in that said vibration means (20) comprise: - a magnet (23), associated in a lower region with said reservoir (18), - an electromagnet (24), arranged below said magnet (23) and associated with said base (21), - a plurality of elastic elements (25), extending between said reservoir (18) and said base (21), said plurality of elastic elements (25) mutually coupling said reservoir (18) and said base (21).

10. The stove (10) according to any one of claims 6 to 9, characterized in that said elastic elements (25) are leaf springs, arranged transversely between the plane of arrangement of said bottom (26) of said reservoir (18) and the plane of arrangement of said base (21).

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