RELATED APPLICATIONS

[0001] This application claims priority from U.S. Provisional Application No.

61/296,982 filed January 21 , 2010 and U.S. Provisional Application No. 61/379,767 filed September 3, 2010, both of which are hereby incorporated by reference.

FIELD

[0002] The present application relates generally to a fan and more particularly to a thermoelectric fan, sometimes referred to as a heat powered fan.

BACKGROUND

[0003] Conventional heat powered fans are known in the art. One example of a conventional heat powered fan is described in US Patent No. 5,544,488, issued on August 13, 1996 to Randall H. Reid, the contents of which are hereby incorporated herein by reference. Another example of a conventional heat powered fan is described in US Patent No. 7,812,245 issued on October 12, 2010 to Randall H. Reid.

[0004] Conventional heat powered fans have proved useful in dispersing warm air created by a heat source such as wood stoves and similar devices. These fans allow a greater area to be warmed more quickly than just letting the heat radiate from the heat source directly. These fans are convenient in that they generate the energy needed to power the fan from the heat source itself.

[0005] Conventional heat powered fans can sometimes have problems with overheating. As such, there is a need in the marketplace for an improved heat powered or thermoelectric fan.

SUMMARY

[0006] In one aspect, there is provided a thermoelectric fan having: a base; a cooling top; a thermoelectric module located between the base and the cooling top; a motor powered by the thermoelectric module; a fan blade operatively connected to the motor; and a mounting system for attaching the motor to the fan, wherein the mounting system substantially isolates the motor from the base.

[0007] In some cases, the mounting system of the thermoelectric fan has a conductive bracket that is attached between the cooling top and the motor. [0008] In some further cases, the motor of the thermoelectric fan is attached to the conductive bracket in a manner that prevents the motor from making contact with the base.

[0009] In a particular case, the conductive bracket of the thermoelectric fan has a plurality of cooling fins.

[0010] In another case, the conductive bracket of the thermoelectric fan includes a motor sleeve configured to receive the motor. In this case, the motor sleeve may have a plurality of cooling fins.

[0011] In another particular case, the motor sleeve of the thermoelectric fan includes an air gap between the motor and the motor sleeve. The motor sleeve may also include apertures configured to allow air to be drawn over the motor. In another case, the motor sleeve may have a layer of insulating material.

[0012] In some cases, the mounting system of the thermoelectric fan is further configured to cool the motor.

[0013] In another aspect, there is provided a thermoelectric fan having: a base; a cooling top; a thermoelectric module located between the base and the cooling top; a motor powered by the thermoelectric module; a fan blade operatively connected to the motor; and a mounting system for attaching the motor to the fan, wherein the mounting system is configured to cool the motor.

[0014] In some cases, the mounting system of the thermoelectric fan is further configured to substantially isolate the motor from the base.

[0015] In yet another aspect, a thermoelectric fan is provided, having: a base; a cooling top; a thermoelectric module located between the base and the cooling top; a motor powered by the thermoelectric module; a fan blade operatively connected to the motor; and a mounting system for attaching the motor to the fan, wherein the mounting system comprises a conductive bracket that is attached between the cooling top and the motor.

[0016] In some cases, the mounting system of the thermoelectric fan is further configured to substantially isolate the motor from the base.

BRIEF DESCRIPTION OF DRAWINGS

[0017] Embodiments of an improved heat powered fan will now be described, by way of example only, with reference to the attached figures, wherein: Fig. 1 shows an exploded view of a fan according to an embodiment herein;

Fig. 2 shows the fan of FIG. 1 when in use;

Fig. 3 shows the fan of FIG. 2 at another location;

Fig. 4 shows a side-view of the fan of Fig. 1 ;

Fig. 5 shows an alternative bracket for a fan;

Figs. 6A and 6B show a bracket having a motor sleeve;

Figs. 7A and 7B show a bracket having an alternative motor sleeve;

Figs. 8A and 8B show a bracket having a motor shield with vent holes; Figs. 9A - 9D are views of a fan according to another embodiment;

Fig. 10 shows an exploded view of the fan of Figs. 9A-9D;

Figs. 11 A - 11 D illustrate various views of a base of a fan;

Figs. 12A - 12D show a perspective, front, side and top view of a cooling top;

Fig. 13 illustrates a cooling top according to another embodiment;

Fig. 14 shows a cooling top according to yet another embodiment;

Fig. 15 shows a cooling top according to still yet another embodiment;

Figs. 6A to 16H illustrate a fan blade according to one embodiment;

Fig. 17A illustrates a fan according to one embodiment used for testing and Figs. 17B and 17C illustrate a previous model of a fan used for testing;

Fig. 18 is a graph illustrating a comparison of airflow and power at the motor shaft; and

Fig. 19 is a graph illustrating a comparison of the airflow at various temperatures.

DETAILED DESCRIPTION

[0018] Figure 1 shows an exploded perspective view of a heat powered or thermoelectric fan (10) according to an embodiment herein. The fan (10) includes a heat collecting base (100), a cooling top (102), a fan blade (104), a thermoelectric module (106), the motor (108), and a conductive bracket (112).

[0019] Figure 2 shows the fan when in use on a heat source (12 such as a wood stove). Figure 3 shows the fan (10) placed on a heat source (12) in a different location than Figure 1. The fan is placed on the top (14) of the heat source (12) and the heat collecting base (100) becomes hot transferring heat to the bottom face of the

thermoelectric module (106). The cooling top (102) dissipates heat into the surroundings and cools the top face of the thermoelectric module (106). The cooling top ( 02) can be further cooled with the help of airflow generated by the blade (104) as shown by arrows (13). With this arrangement the thermoelectric module (106) sees a temperature differential (delta T) between its top and bottom faces, which causes the thermoelectric module (106) to produce electrical power. The electrical power is used to power the motor (108), which then spins the fan blade (104). The fan (10) may be placed in many positions with respect to a chimney (16). It will be understood that the fan (10) may also be attached to rather than placed on the stove.

[0020] The base (100) and cooling top (102) are made from a heat-conductive material, such as aluminum. Aluminum is chosen for good heat conductivity properties although other materials are contemplated such as ferrous and non-ferrous metals as well as other heat conducting materials as are known or become known.

[0021] In embodiments herein, the fan blade (104) may be generally positioned below the cooling top (102) so that the fan blade draws air through the cooling top (102). This can assist with creating a thermal difference between the base (100) and the cooling top (102) so that an appropriate gradient is created across the thermoelectric element (106). The arrangement of the fan blade (104) below the cooling top (102) also allows for the use of a variety of cooling tops on a common base/motor arrangement. However, positioning the fan blade (104) and correspondingly, the motor (108) in this way brings the motor closer to the heat collecting base (100), which can cause the motor to run hotter.

[0022] As noted above, some conventional arrangements of heat-powered fans can have problems with the motor heating to inappropriate levels, which in turn can cause premature motor failure and/or reduce motor efficiency. At greater motor efficiencies, fan airflow will be increased as more power is delivered to the fan's blade. For example, in some arrangements, the motor (108) can see operating temperatures which exceed manufacturer's recommendations and which may cause the motor to fail or limit the overall life of the motor. In particular, when a conventional fan is placed in front of a wood stove's chimney (similar to the location shown in Figure 2) and the wood stove is run at high temperatures the fan's motor (108) can overheat. When placed in front of the stove's chimney hot air is drawn off the chimney and over the fan assembly heating the motor (108) higher than intended. Although the fan (10) should be placed away from the stove's chimney (similar to the location shown in Figure 3) so that cooler air from the

surroundings is drawn over the fan assembly, this is not always the chosen location by the operator and can be impacted by other factors such as how close the stove is to surrounding surfaces and the like. It will be understood that the motor (108) can be heated by convection where warm air is drawn over the motor's surface and also heated by conduction and radiation from hot adjacent fan components.

[0023] Further, in some conventional designs, the mounting arrangement may also place the blade at a distance from the cooling top, which can reduce airflow and thus reduce performance.

[0024] In the arrangement shown in FIG. 1 , the base is provided with an aperture in which the motor (108) is mounted. The use of an aperture assists with keeping the motor (108) away from the base (100). As shown in Figure 1 , the motor (108) is further isolated from the base (100) and cooled by attaching the motor (108) to the cooling top (102) via a mounting system (110) involving the conductive bracket (112) (sometimes called a cooling bracket). It will be understood that the conductive bracket (112) is intended to move heat away from the motor (108) and conduct this heat to the cooling top (102). Heat generated by or otherwise impacting the motor (108) can be conducted away through the conductive bracket (112) into the cooling top (102). The motor (108) preferably has no contact with the base (100) at all, through brackets or otherwise.

[0025] The conductive bracket (112) or the combination of the conductive bracket

(112) with the aperture in the base (100) can be referred to as the mounting system (110) for the motor (108). The mounting system (110) is intended to substantially isolate the motor (108) from the base (100) and provide a cooling function. It will be understood that various other mounting systems may be apparent that can achieve this functionality. For example, the motor (108) does not necessarily need to be in an aperture in the base but could be supported to the side of the base or in other locations by one or more cooling brackets or the like.

[0026] The embodiments of a fan described herein are intended to overcome at least some of the problems with conventional fans. For example, embodiments are intended to reduce the motor's operating temperature by substantially isolating the motor from the effects of hot fan components, in particular, the base. Other embodiments provide a mounting system configured to assist with cooling the motor. There are also embodiments including a combination of these two features.

[0027] An added benefit of using this conductive bracket (112) is that the cooling top (102) may be further cooled depending on the size and orientation of the bracket (112). This added cooling can also improve performance of the fan by increasing the temperature gradient across the thermoelectric module (106). [0028] In testing, there has been a reduction of temperature at the motor showing an unexpected level of in the order of 20% or more. Physical tests have shown that when placed on a hot (400° Celsius) woodstove and situated in front of the woodstove's chimney the motor of a conventional fan could see temperatures of over 125° Celsius. In the embodiment described above, temperatures recorded have been reduced to below 100° Celsius.

[0029] It will be understood that the shape of the conductive bracket does not need to be restricted to the shape shown in Figure 1. Other shapes may be possible for isolating the motor (108) from the base (100) and/or cooling the motor (108) to a reduced temperature by, for example, joining the motor (108) to the cooling top (102).

[0030] Figure 4 shows a side view of the assembled fan of Figure 1. As shown in

Figure 4, the bracket (112) is secured to the cooling top (102) via an indented portion (114) so that a front face (116) of the bracket (112) aligns with a front face (118) of the cooling top (102) permitting the fan blade (104) to align closely to the cooling top (102). Aligning the cooling top (102) so that its front face (118) is close to the fan blade (104) is intended to improve the overall performance since the cooling top (102) is kept cooler by more air movement. As well, a front face (120) of the heat collecting base (100) may be angled or otherwise formed to be more removed from the fan blade (104) and thus heat may not be as readily stripped from the base (100) by the airflow generated by the blade (104). In this way, the thermoelectric module (106) will generally have a greater temperature gradient or temperature differential intended to result in improved fan performance. It will be understood that the bracket (112) may also be connected to the cooling top (102) in various ways, for example, with the use of a fastener such as a screw, a nut and bolt, adhesive, or the like.

[0031] Figure 5 shows a conductive bracket of a type that does not engage with the cooling top (102) in the same manner as the conductive bracket (112) of Figure 4 but instead includes a plurality of cooling fins (130), which are intended to help keep the bracket/motor cooler by thermal convection without relying as much on the cooling top (102). In some cases, the bracket (112) and/or the fins (130) may be in contact with the cooling top (102). Similarly, cooling fins (130) may be applied to the motor (108) or other parts of the bracket (112) as well.

[0032] Figures 6A and 6B show an addition to the fan (10) or conductive bracket

(112) by providing a motor sleeve or shield (140), which surrounds the motor (108). The motor sleeve (140) may help conduct heat away from the motor through the bracket (112) and/or block thermal radiation from other fan components. [0033] Figures 7A and 7B show cooling fins (142) added to the bracket and sleeve (140) of Figure 6, which surround the motor and aid in cooling the motor.

[0034] Figures 8A and 8B show an alternate embodiment of a motor sleeve or a shield (150) such as that of Figure 6A and 6B. As above, the shield (150) is intended to block radiation from the surrounding environment and/or from the heat collecting base (100) which is intended to reduce the motor's temperature. In this embodiment, a large air gap may surround the motor (108) and a plurality of air holes or apertures (152) may be provided in front of the motor (108) intended to allow cooling air to be drawn over the motor. It will be understood that the air holes (152) should not be so large as to compromise the integrity or structure of the shield (150). The shield (150) may be directly coupled to the bracket (154) in order to assist in keeping the shield (150) cool. Adding a layer of insulating material to the inner or outer faces of the shield may improve the cooling performance by reducing heat transfer through radiation. A plurality of fins, similar to those shown in Figures 7A and 7B, may also be beneficial if added to the inner or outer faces.

[0035] In another embodiment, as shown in a perspective view in Figure 9A and in front, side and top views in Figures 9B, 9C, 9D and an exploded view in Figure 10, a fan (200) includes a heat collecting base (201), a cooling top (202), a fan blade (204), a thermoelectric module (206) and a motor (208). The motor (208) is mounted to the fan (200) via a mounting bracket (210), which in some cases may be similar to the brackets described above. In this embodiment the fan blade (204) is intended to provide increased airflow (for example, increased CFM (cubic feet per minute). Other features, described in further detail herein are intended to reduce noise and provide a greater power generation capability over conventional thermoelectric fans.

[0036] In Figures 9A - 9D and 10, a connector (205) and wire (207) is shown extending from the rear of the fan (200). This connector (205) and wire (207) provides a connection between the thermoelectric module (206) and the motor (208).

[0037] As shown in Figures 9A - 9D and 10, the fan (200) includes a motor shield

(240), similar to that described with reference to figures 6A and 6B. The cooling top (202) is attached to the heat collecting base (201) via fasteners (222), which may include, for example nuts and bolts, screws, adhesives, or the like. In this case, the thermoelectric module (206) is also held in place by the fasteners (222), in particular, frictionally by the force exerted by the fasteners (222) attaching the cooling top (202) to the base (201). In other cases, the thermoelectric module (206) may be adhesively attached to the cooling top (202), the base (201) or both. A handle (212) may be included and is intended to make the fan (200) more portable. A label (211) may also be provided, and may be attached to the handle. The label may provide instructions or warnings to the user.

[0038] Further, the motor (208) may be attached to the mounting bracket (210) via screws (224) of through other fasteners. The mounting bracket (210) may be fastened to an indented portion (214) of the cooling top (202), as shown or to the base (201). As discussed above, it may be preferable to mount the mounting bracket (210) to the cooling top (202), as this attachment may reduce the amount of heat at the motor (208). The fan blade (204) is operatively connected to the motor (208), either by way of a rotatable protrusion (228) from the motor (208) that may connect to the fan blade (204), via a blade set screw (226), or by other ways known in the art.

[0039] Figure 11 A illustrates a perspective view and Figures 11 B, C and D illustrate front, side and top views of the heat collecting base (201). The base design is intended to transport heat energy to the thermoelectric module (206) to allow for the generation of power based on a heat differential between the base (201) side of the thermoelectric module (206) and the cooling top (202) side of the thermoelectric fan (200). It will be understood that the thicker the stem (230) the more heat may be transferred to the thermoelectric module (206) for power generation. It will be further understood that if too much heat is carried by the base (201), the motor (208) may be prone to overheating. In one embodiment, the stem (230) of the base may be between 5 mm and 10 mm thick. In a particular case, the stem (230) may be 8 mm thick. Through testing, it was noted that with an 8 mm base and the cooling top (202) illustrated in Figure 10, the fan (200) was able to deliver approximately 54 watts when the heat source attained a temperature of about 400 degrees Celsius.

[0040] The cooling top (202) is shown in perspective view in Figure 12A, in front view in FIG. 12B, side view in FIG. 12C and top view in 12D. The design of the cooling top (202) is intended to provide heat flow through the thermoelectric module (206). The cooling top (202) may include a plurality of fins (250) that operate as a heat sink. It will be understood that the greater the surface area of the cooling top (202) the greater amount of heat may be dissipated. The plurality of fins (250) are positioned generally inline with the air flow but are intended to be adequately spaced apart in order that forced convection can contribute to removal of heat from the cooling top. It will be understood that if the plurality of fins (250) are too close, the airflow may be restricted and the arrangement may limit forced convection. The thickness of the fins (250) may also be adjusted to create larger or smaller gaps between each fin. It will be understood that the manufacturing process as well as levels of heat conduction through material of the cooling top (202) may limit how thin each fin can be. The plurality of fins (250) may also include ridges on the surfaces thereof to further expand the surface area of the cooling top. In one embodiment, each fin may have a thickness of between 7 mm and 13 mm. In one particular case each fin may be 11 mm thick.

[0041] The cooling top may also include a plurality of intermediate fins (252).

Testing has shown that with these intermediate fins (252), performance was improved while overall temperature was lowered. In one case, the plurality of intermediate fins (252) increased the surface area by approximately 14 percent.

[0042] The cooling top (202) may be sloped, as shown in the side view in figure 12C, in order for the cooling top (202) to be closer to the fan blade (204) near the center yet slope away from the fan blade (204) nearer to the top of the cooling top (202). It will be understood that the highest velocity air is typically at the edge of the cooling top (202) closest to the fan blade (204). It is preferable to have the fan blade (204) closer to the cooling top (202) to dissipate a greater amount of heat without the need for more electrical power generation. In testing, it was found that this design decreased the thermal resistance of the cooling top significantly.

[0043] Various designs were contemplated with respect to the cooling top (202) as shown in figures 14, 15, and 16. The number of fins (250) and intermediate fins (252) may be altered, as may be the shape of each fin, as shown in Fig 13. In any of the cooling tops (202) shown in figures 12 to 15, apertures (254) may be included for attaching the handle (212).

[0044] Figures 16A, 16B, 16C and 16H further illustrate the fan blade (204) according to one embodiment. The fan blade (204) is intended to reduce turbulent airflow, which can lead to excess power consumption. In many fan applications, power is readily available from an outlet so little consideration has been made regarding efficiency of conventional fan blades. Further, although additional airflow can sometimes be obtained by increasing the revolutions per minute (RPMs) of the fan blade, there can be aesthetic reasons to provide a fan without a cover or grate that prevents the entry of fingers or the like. As such, it may be preferred to have the maximum speed of the blades to be in the range of 1000 revolutions per minute for safety reasons. In a heat powered fan, the limitations of limited power availability and lower speed complicate the design of an appropriate blade.

[0045] For the fan shown in figures 9 and 10, the fan blade (204) was designed consisting of two vanes (260), sometimes referred to as arms, slightly offset from the centre. The vanes (260) are configured in this way to attempt to reduce the mass of the blade, which is intended to lower the motor load and lower the power requirement.

[0046] As seen in figure 16B, the airfoil shape of the fan blade (204) is intended to increase efficiency and to give higher lift while lowering drag. This airfoil is configured to have a variable pitch throughout the length of the fan blade (204).

[0047] Each vane (260) consists of a leading edge adapted to spin in close proximity to the cooling top. The leading edge may have a predetermined curvature of the blade and a rounded edge or tip. The trailing edge of the vane (260) may also be curved at an equal or greater angle than that of the leading edge. This allows the load of the work to be moved towards the inner or center of the blade as oppose to the outer edge.

[0048] Figures 16D to 16G illustrate cross sections of the fan blade (204). Figure

16D shows a cross section close to the centre of the fan blade (204), followed by figure 16E which illustrates further along the fan blade (204). Figure 16F also shows the cross section of one arm (260) of the fan blade (204) nearer to the tip of the blade, away from the centre and figure 16G shows a cross section of one vane (260) near the tip. From these figures the variation of the predetermined curvature can be seen. Also from these figures, the tapering of each vane (260) of the fan blade (204) can be seen. In some cases, the predetermined curvature near the center may be between 15° and 20°, while near the tip the angle may be between 20° and 25°. In a particular case, the

predetermined curvature near the center may be approximately 18°, while near the tip of the vane (260) the predetermined curvature may be closer to approximately 23°.

[0049] The thermoelectric fan (200) shown in Figure 17A was tested against a previous model fan (shown in Figure 17B) that contained a 3 mm thick base stem, a cooling top (shown in FIG 17C) and a fan blade with a constant pitch. The graphs shown in Figures 18 and 19 illustrate the comparison of the airflow and the power at the motor shaft and at various wood stove (heat source) temperatures. From these test results, improvements can be seen at each of the various temperatures of the heat source and at the various power levels.

[0050] In the preceding description, for purposes of explanation, numerous details are set forth in order to provide a thorough understanding of the embodiments. However, it will be apparent to one skilled in the art that these specific details are not required in order to practice the embodiments. In other instances, well-known structures are not described in detail as one of skill in the art may select a suitable structure.

[0051] Further, the above-described embodiments are intended to be examples only. Alterations, modifications and variations can be effected to the particular embodiments by those of skill in the art without departing from the scope of the invention, which is defined solely by the claims appended hereto.