Stove fan

Abstract

A stove fan 501 comprises a bladed rotor 502 driven by an electric motor 503 powered by a thermoelectric generator 504. A housing 505 forms a duct with an internal diameter (506, Fig. 5) that is great

Description

Field of the Invention The present invention relates to a fan for a stove, such as a wood-burning or multi-fuel stove. Background of the Invention A stove fan is a device for improving the output of heat from a stove, such as a wood burner or a multi-fuel burner. A known type of stove fan comprises a bladed rotor, which is supported by a base that allows the stove fan to be placed on the top of a stove, and a thermoelectric module that is designed to utilise heat generated by the stove to drive the bladed rotor, which circulates warm air in the vicinity of the stove. The stove fan operates using only the heat from the stove and the rotating blades function to distribute heat from the stove more effectively. It is an object of the present invention to provide an improved stove fan. Summary of the Invention According to a first aspect there is provided a stove fan, comprising: a bladed rotor, an electric motor for driving the bladed rotor, a thermoelectric generator arrangement operative to power the electric motor, and a housing forming ducting having an internal diameter that is greater than the diameter of the tip path of the bladed rotor, the thermoelectric generator arrangement comprising: a thermoelectric module to generate electricity from a temperature differential between a first surface and a second surface, a heat transfer element in contact with the first surface of the thermoelectric module, a heatsink in contact with the second surface of the thermoelectric module, and a resilient biasing arrangement to radially bias the heat transfer element towards an outermost position, for contacting a surface of a stove in use; the thermoelectric module and the heatsink movable with the heat transfer element, and the heat transfer element physically isolated from the housing. In an example, the bladed rotor is enclosed by the housing. This provides efficiency and safety benefits. In an example, the housing forms a base for resting on a stove. In an example, a front end of the housing is inclined downwards with respect to a rear end of the housing when the base is oriented on a horizontal plane. This serves to improve effectiveness by directing warm air downwards, the hotter air then rising naturally to distribute heat from the stove into a room. In an example, the heat transfer element extends through an aperture defined in the housing. Thus, the heat transfer element is partially enclosed within partially enclosed by the housing, for practical and aesthetic purposes, but is physically isolate from the housing to inhibit the undesirable transfer of heat from the heat transfer element to the housing, and encourage the transfer of heat from the heat transfer element to the thermoelectric module. In an example, the resilient biasing arrangement comprises a pair of compression springs. In an example, the blades of the bladed rotor are provided with an edging element over the free edge thereof. In a specific example, the bladed rotor comprises metal and the edging element is a silicone overmolding. In an example, the stove fan comprises a control module, the control module comprising a controller, a power device, and a wireless communication device for communicating with a wireless communication network. In a specific example, the controller is configured to control the speed of rotation of the bladed rotor with reference to a detected room temperature. In an example, the power device comprises a rechargeable battery. In a specific example, the controller is configured to control charging of the rechargeable battery by energy generated by the thermoelectric module and the discharging of the rechargeable battery to power the electric motor. In an example, the bladed rotor is selectively operable in a stationary mode and in an oscillating mode. In an example, the stove fan is provided with a mounting arrangement for securing the stove fan to a flue of a stove. The mounting arrangement may comprise any suitable element or elements, and may at least one mechanical element, for example a bracket, and may comprise at least one magnetic element. According to a second aspect there is provided, in combination, a stove and a stove fan according to the first aspect. In an example, the stove is a wood-burning stove. In an example, the stove is a multi-fuel stove. Further particular and preferred aspects of the invention are set out in the accompanying dependent claims. Brief Description of the Drawings The present invention will now be more particularly described, with reference to the accompanying drawings, in which: Figure I shows a stove fan according to the prior art, placed on a stove; Figure 2 shows a perspective, bottom view of a prior art stove fan; Figure 3 shows a front view of the prior art stove fan of Figure I ; Figure 4 shows a cross-sectional view of the prior art stove fan of Figure 2, along the line A-A of Figure 3; Figure 5 shows a perspective, front view of a stove fan according to a first example; Figure 6 shows a front view of the stove fan of Figure 5; Figure 7 shows a cross-sectional view of the stove fan of Figure 5, along the line A-A of Figure 6; Figure 8 shows a perspective, rear view of the stove fan of Figure 5; Figure 9 shows a rear view of the stove fan of Figure 5; Figures 10, II &12 show top, side and bottom views respectively of the stove fan of Figure 5; Figure I 3 shows a perspective, front view of a stove fan according to a second example; Figure 14 shows a front view of the stove fan of Figure 13; Figure 15 shows a cross-sectional view of the stove fan of Figure 13, along the line A-A of Figure 14; Figure 16 shows a perspective, rear view of the stove fan of Figure 13; Figure 17 shows a rear view of the stove fan of Figure 13; Figures 18, 19 &20 show top, side and bottom views respectively of the stove fan of Figure 13; Figure 21 shows a pair of stove fans according to the present invention, positioned for use on a stove, according to a first example scenario; and Figure 22 shows a stove fan according to the present invention, positioned for use on a stove, according to a second example scenario. Description Illustrative embodiments and examples are described below in sufficient detail to enable those of ordinary skill in the art to embody and implement the apparatus described herein. It is to be understood that embodiments and examples can be provided in many alternate forms and the invention should not be construed as limited to the embodiments and examples set forth herein but by the scope of the appended claims. Unless otherwise defined, all terms (including technical and scientific terms) used herein are to be interpreted as is customary in the art. In addition, features referred to herein in the singular can number one or more, unless the context clearly indicates otherwise. Similarly, the terms “comprises”, “comprising”, “includes”, “including”, “has” and / or “having” when used herein, specify the presence of the stated feature or features and do not preclude the presence or addition of one or more other features, unless the context clearly indicates otherwise. In the following description, all orientational terms, such as upper, lower, radially and axially, are used in relation to the drawings and should not be interpreted as limiting on the invention, unless the context clearly indicates otherwise. The drawings are not necessarily drawn to scale, and in some instances the drawings may have been exaggerated or simplified for illustrative purposes only. A prior art stove fan 100 is shown in Figures I to 4. Figure I shows the prior art stove fan 100 located for use on a stove 200. Figures 2, 3 &4 show details of the prior art stove fan 100. The prior art stove fan 100 comprises a carrier handle I (at the top of the main body), a bladed rotor 2 (with the rotor blades forward of the main body), an extruded aluminium heat sink (cold) 3 (upper side of main body), a DC electric motor 4, a thermoelectric module 5, an extruded aluminium heat sink (hot) 6 (lower side of main body), and a bimetallic strip 7 (at the bottom of the main body). In use, heat from the stove 200 is transferred to the thermoelectric module 5 through the aluminium heat sink (hot) 6 and from the thermoelectric module 5 through the extruded aluminium heat sink (cold) 3. The thermoelectric module 5 utilises a temperature differential between hotter and colder sides of the thermoelectric module 5 to generate electricity (using the Seebeck effect), which is provided to the DC electric motor 4, which drives the bladed rotor 2. The greater the temperature differential between hot and cold sides of the thermoelectric module 5, the greater the power generated. The rotating blades function to move radiant heat into the room, in turn making the stove 200 more efficient, with the objective of saving fuel. Various design limitations have been identified in relation to the prior art stove fans such as prior art stove fan 100. The optimum working temperature of a stove is around 300 °c. The thermoelectric module has a relatively low melting point, around 200 °c, and is at risk of malfunction through overheating. The bimetallic strip is provided to address this issue. When the bimetallic strip is heated above a particular temperature, it bends to lift the stove fan to reduce the amount of heat being transferred from the stove to the thermoelectric module. This results in the energy output by the thermoelectric module being throttled, reducing efficiency. The bending of the bimetallic strip also causes the airflow through the stove fan to be angled upwards and, as heat rises, this reduces efficiency further. Further, the stove fan being lifted by the bimetallic strip bending reduces its stability on the stove, leading to the stove fan vibrating and causing undesirable noise and sound annoyance. The achievable airflow is related to the size of the blades and the speed they are rotated. Increasing the blade size and / or RPM to improve airflow can exacerbate problems mentioned above. For example, increasing the size of the heat sink (cold) of the thermoelectric module to achieve a greater power output makes the stove fan more top heavy, which increases instability when the bimetallic strip bends to lift the stove fan to prevent overheating. The fan blades can easily be bent out of shape and become unbalanced, which can lead to excessive noise being created at higher RPM. Increasing the blade size and render the blades more susceptible to warping. In addition, the heat sink (cold) is exposed to high radiant temperature, reducing efficiency. The present invention provides improvements in relation to stove fan design. A stove fan 501 according to a first example is shown in Figures 5 to 12. The stove fan 501 comprises a bladed rotor 502, an electric motor 503, the electric motor 503 for driving the bladed rotor 502, and a thermoelectric generator arrangement, indicated generally at 504, the thermoelectric generator arrangement 504 operative to power the electric motor 503. The stove fan 501 further comprises a housing 505, the housing forming ducting having an internal diameter 506 that is greater than the diameter 506 of the tip path of the bladed rotor 502. The thermoelectric generator arrangement 504 comprises a thermoelectric module 507 to generate electricity from a temperature differential between a first surface 508 and a second surface 509, a heat transfer element 510 in contact with the first surface 508 of the thermoelectric module 507, and a heatsink 51 I in contact with the second surface 509 of the thermoelectric module 507. The thermoelectric generator arrangement 504 further comprises a resilient biasing arrangement, indicated generally at 512, to radially bias the heat transfer element 510 towards an outermost position (shown in Figures 6, 7, 9 &II) for contacting a surface of a stove in use. The heat transfer element 510 has a stove-facing surface 513. The thermoelectric module 507 and the heatsink 51 I are movable with the heat transfer element 510. Thus, if the heat transfer element 510 is pushed radially inwardly, the thermoelectric module 507 and the heatsink 51 I will move radially inwardly in a corresponding manner so that the contact between the heat transfer element 5 10 and the thermoelectric module 507 and between the thermoelectric module 507 and the heatsink 51 I is maintained. This feature will be discussed further below. The heat transfer element 5 10 is physically isolated from the housing 505. This feature will be discussed further below. According to the shown example, the housing 505 forms a base, indicated generally at 514. According to the specific example illustrated, the base 514 of the housing 505 comprises feet, such as foot 515. The base 514 is profiled to create a hollow 516, into which the heat transfer element 510 projects. According to the shown example, the heat transfer element 510 extends through an aperture 517 defined in the housing 505. According to the specific example illustrated, the resilient biasing arrangement 512 comprises a pair of compression springs located around mounting elements, such as spring 518 located around respective mounting element 519. The spring mounting of the heat transfer element 510 and the profile of the base 514 serves to concentrate heat transfer from the stove to the heat transfer element 5 10 (and, in turn, to the thermoelectric module 507) and reduce the transfer of heat from the stove to the housing 505 via surface contact between the base 5 14 and the stove. In use, air flows through the housing in the direction indicated by arrow 520 (Figure 5) as the bladed rotors spins in the direction of rotation indicated by arrow 521 (Figure 5). The thermoelectric generator arrangement 504, including the resilient biasing arrangement 512, is designed to optimise contact with a stove and maintain a heat transfer path from the stove through the thermoelectric module 507 without compromising the stability of the stove fan 501 on the stove. The spring-loaded heat transfer element 510 is held against the stove, utilising the mass of the housing 505, to provide a consistent surface-to-surface contact between the stove-facing surface 5 13 of the heat transfer element 5 10 and the heated top plate of the stove. The physical isolation of the heat transfer element 510 from the housing 505 is designed to concentrate heat transfer from the stove to the thermoelectric module 507. The separation of the heat transfer element 510 from the housing 505 prevents the undesired transfer of heat to the housing 505 and other key components of the stove fan 501. According to the shown example, the housing 505 surrounds the bladed rotor 502. This feature serves to improve user safety and reduce the risk of accidental damage to the bladed rotor, by providing shielding for the blades as they rotate. The ducting formed by the housing 505 is designed to increase airflow (m3 / hr) across the heatsink 51 I and through the blades. It also reduces noise from vortices that form at the tips of the blades as they rotate. As shown, the electric motor 503 is enclosed by the housing 505. The electric motor 503 is protected from radiant heat emitted by the stove. As shown, the thermoelectric module 507 and the heatsink 51 I are enclosed by the housing 505 (the heat transfer element 5 10 is only partially enclosed by the housing 505). The heatsink 5 I I is protected from radiant heat emitted by the stove. By virtue of the airflow through the housing 505 when the stove fan 501 is in use, radiant heat is drawn from the heatsink 511 and transferred into the room. The airflow is channelled through the heatsink 511 which improves the transfer of heat from the second surface 509 (cool side) of the thermoelectric module 507. This serves to improve the temperature differential between the first surface 508 (hot side) and the second surface 509 (cool side) of the thermoelectric module 507, which results in more energy being generated by the thermoelectric module 507. In effect, a feedback loop is implemented within the design of the stove fan 501, in which rotation of the bladed rotor 502 drives airflow through the housing 505, which draws more heat from the heatsink 511, which causes more cooling of the second surface 509 (cool side) of the thermoelectric module 507, which causes more power to be generated by the thermoelectric module 507 and provided to the electronic motor 503 that drives the bladed rotor 502. In this way, the design of the stove fan 501 promotes efficiency. In the shown example, the bladed rotor 502 comprises six blades, such as blade 522. It is to be appreciated however that any suitable number of blades may be used. In the present example, the heatsink 511 is made from copper and incorporates aluminium nickel-plated sheets, which has been found to provide enhanced cooling, in turn improving the temperature difference between the first and second surfaces 508, 509 of the thermoelectric module 507, In the present example, the thermoelectric module 507 is operational within a range of temperatures that accommodates the typical optimum working temperature of a stove of around 300 °c. The housing 505 has a front end 523 and a rear end 524. According to the present example, the front end 523 of the housing 505 is inclined downwards with respect to the rear end 524 when the base 514 of the housing 505 is oriented on a horizontal plane. This serves to direct airflow issuing from the front end 523 of the housing 505 downwards, so that air is driven towards the ground. This serves to improve the effectiveness of the stove fan 501. The inclination may be provided by the arrangement of the housing 505 and / or the resilient biasing arrangement 504 acting to urge the heat transfer block 5 10 into contact with the stove. In a specific example, the housing 505 comprises an extruded aluminium body. In a specific example, the heat transfer element 5 10 is aluminium. According to the present example, the springs 5 18 of the resilient biasing arrangement 5 12 are arranged relative to the housing 505 to reduce the impact of vibration from the bladed rotor 502 and quieten operation. A stove fan 1501 according to a second example is shown in Figures 13 to 20. The stove fan 1501 is like the stove fan 501 of Figures 5 to 10 but includes some optional features as will now be described. According to the shown example, each of the blades 1522 of the bladed rotor 1502 is provided with an edging element, such as a silicone overmolding 1525, over the free edge thereof. Optimising the performance of the stove fan 1501 increases the maximum RPM of the bladed rotor 1502. Providing the blades 1522 with the edging element 1525 serves to enhance the profile of the blade 1522 and generate greater airflow. In addition, the edging elements 1525 add weight to the blades 1522 that will slow down and steady the spinning bladed rotor 1502, increasing safety and reducing noise. According to the shown example, the bladed rotor 1502 is stationary. In an example, the bladed rotor is configured to oscillate to vary the direction of airflow into the room. In an example, the bladed rotor is selectively operable in a stationary mode or in an oscillating mode. In an example, the heatsink 1511 is designed with a round shape. According to the shown example, a funnel 1526 within the housing 1505 is design to force the airflow through the heatsink 1511 (utilising the Venturi effect) and improve the transfer of heat from the heatsink 1511 into the room. This enhanced cooling increases the effectiveness of the stove fan 1501, transferring more heat into the room and increasing the temperature differential across the thermoelectric module 1507. The heat transfer block 1510 may be made from copper with a graphite layer to increase the heat throughput to the thermoelectric module 1507. It may then be possible to reduce the depth (in the direction indicated by arrow 1527) of the heat transfer block 1510 without reducing performance. According to the shown example, the stove fan 1501 is provided with a control module, indicated generally at 1528. According to a specific example, the control module 1528 comprises a controller, indicated at 1529, which may be any suitable device, for example a programmable logic controller (PLC). The controller 1529 may comprise, or otherwise have access to, a non-transitory computer-readable medium, with program instructions being stored on the non-transitory computer-readable medium that are executable by the controller to cause the controller to perform each of a plurality of functions. According to the present example, the control module 1528 comprises a power device 1530 for providing power to at least the controller 1529. In a specific example, the power device 1530 comprises a rechargeable battery 1531. In a specific example, the controller 1529 is configured to control charging and discharging of the rechargeable so that excess energy generated by the thermoelectric module 1507 is stored in the rechargeable battery 1531 and used to drive the electric motor 1503 when the amount of heat being transferred to the thermoelectric generator 1507 is lower. According to a specific example, the control module 1528 comprises a wireless communication device 1532 that is suitably arranged for communicating with a wireless communication network. In a preferred embodiment, the wireless communication device 1532 provides the capability of two-way data communication between the controller 1529 and a wireless network. The stove fan 1501 may be an “Internet of Things” device. According to a specific example, the controller 1529 is configured to receive an indication of the temperature of the room, for example via an external temperature sensor 1533 and determine whether to initiate an adjustment to the speed at which the bladed rotor 1502 is spinning; a determination may be made to initiate a reduction in the R.PM of the bladed rotor 1502 when the room temperature is detected to be above a predetermined threshold temperature. Thus, the controller 1529 may be configured to control the speed of rotation of the bladed rotor 1502 with reference to a detected room temperature. According to a specific example, the control module 1528 comprises an input device 1533 allowing a user to control one or more functions of the stove fan 1501. According to a specific example, the controller 1529 is configured to record data relating to operation of the stove fan 1501, allowing analysis for use in optimising performance. In an envisaged example, the stove fan 1501 may be provided with at least one additional bladed rotor (not shown in the Figures) arranged to improve airflow through the heatsink 1511. Stove fans 500, 500’, 500” according to the present invention are shown in Figures 21 &22 positioned for use on a stove 200. According to a first example scenario, shown in Figure 21, each of a pair of stove fans 500, 500’ according to the present invention is sited upon a top surface 201 of the stove 200, with one placed on each side of the flue 202 of the stove 200. According to a second example scenario, shown in Figure 22, stove fan 500” according to the present invention is shown sited on the flue 202. According to another example scenario, at least one stove fan according to the present invention is sited on a surface of the stove and at least one stove fan according to the present invention is sited on the flue. It is to be appreciated that any suitable mounting arrangement may be used to secure a stove fan according to the present invention in a suitable position on a stove, for use, for example, comprising one or more of at least one mechanical element, such as a bracket, and at least one magnetic element. The present invention provides an improved design of stove fan that offers various technical advantages and benefits when compared to the prior art. Although illustrative embodiments and examples of the invention have been disclosed in detail herein, with reference to the accompanying drawings, it is to be understood that the invention is not limited to the precise embodiment and examples shown and / or described and that various changes and modifications can be effected therein by one skilled in the art without departing from the scope of the invention as defined by the appended claims.

Claims

I. A stove fan, comprising:a bladed rotor,an electric motor for driving the bladed rotor,a thermoelectric generator arrangement operative to power the electric motor, anda housing forming ducting having an internal diameter that is greater than the diameter of the tip path of the bladed rotor,the thermoelectric generator arrangement comprising:a thermoelectric module to generate electricity from a temperature differential between a first surface and a second surface,a heat transfer element in contact with the first surface of the thermoelectric module,a heatsink in contact with the second surface of the thermoelectric module, anda resilient biasing arrangement to radially bias the heat transfer element towards an outermost position, for contacting a surface of a stove in use;the thermoelectric module and the heatsink movable with the heat transfer element, andthe heat transfer element physically isolated from the housing.

2. The stove fan of claim I, wherein the bladed rotor is enclosed by the housing.

3. The stove fan of claim I or claim 2, wherein the housing forms a base for resting on astove.

4. The stove fan of claim 3, wherein a front end of the housing is inclined downwards with respect to a rear end of the housing when the base is oriented on a horizontal plane.

5. The stove fan of any one of claims I to 4, wherein the heat transfer element extends through an aperture defined in the housing.

6. The stove fan of any one of claims I to 5, wherein the resilient biasing arrangement comprises a pair of compression springs.

7. The stove fan of any one of claims I to 6, wherein the blades of the bladed rotor are provided with an edging element over the free edge thereof.

8. The stove fan of claim 7, wherein the bladed rotor comprises metal and the edging element is a silicone overmolding.

9. The stove fan of any one of claims I to 8, comprising a control module, the control module comprising a controller, a power device, and a wireless communication device for communicating with a wireless communication network.

10. The stove fan of claim 9, wherein the controller is configured to control the speed of rotation of the bladed rotor with reference to a detected room temperature.I I. The stove fan of claim 9 or claim 10, wherein the power device comprises a rechargeable battery.

12. The stove fan of claim I I, wherein the controller is configured to control charging of the rechargeable battery by energy generated by the thermoelectric module and the discharging of the rechargeable battery to power the electric motor.

13. The stove fan of any one of claims I to 12, wherein the bladed rotor is selectively operable in a stationary mode and in an oscillating mode.

14. The stove fan of any one of claims I to 13, provided with a mounting arrangement for securing the stove fan to a flue of a stove.

15. In combination, a stove and a stove fan according to any one of claims I to 14.

16. The combination of claim 15, wherein the stove is a wood-burning stove.

17. The combination of claim 15, wherein the stove is a multi-fuel stove.