The invention has been developed primarily for use as a roof-top rotor ventilator and will be described hereinafter with reference to this application. However, it will be appreciated that the invention is not limited to this particular field of use.

DESCRIPTION OF THE PRIOR ART Roof-top rotor exhaust ventilators are utilised to aid in the removal of exhaust air from the building upon which they are employed. Such buildings may include factories, farm sheds or domestic houses.

The principle behind the roof-top rotor ventilator is that air movement passing the ventilator will cause the ventilator to rotate about its vertical axis. This movement causes the vanes of the ventilator to force air out from within the ventilator, causing the air pressure within the ventilator to be lower than the air pressure within the building in fluid communication with the ventilator. Air within the building is then be moved through the ventilator to be exhausted to the outside of the building.

The efficiency of a roof top rotor ventilator relies on several factors, though importantly: the initial torque required to rotate the ventilator ; the amount of friction resisting the ventilator's rotation; and the vane configuration.

SUMMARY OF THE INVENTION In the description and the claims, when the terms "upper""above"and"lower"are used with respect to the rotor ventilator they refer to a typical in-use orientation of the rotor ventilator, but if the rotor

ventilator was used in a sideways, angled or upside down configuration, their orientations may be changed or reversed. Hence,"upper","above"and"lower"are to be interpreted broadly in this context, and as relative terms.

According to one aspect of the present invention there is provided a rotor ventilator including: a base to which a shaft is connected to extend upwardly therefrom; a rotor including a plate and a plurality of vanes extending downwardly therefrom, the rotor being rotatable about the shaft; bearing means for rotatably supporting the rotor on the shaft ; and a deflector located with respect to the shaft and between the base and the plate to deflect gas passing through the rotor ventilator away from the bearing means.

Advantageously, the deflector aids in increasing the working life of the bearing means, by reducing the amount of gas passing through the rotor ventilator from coming into contact with the bearing means. This is particularly advantageous where the gas is either high temperature (eg.

>100°C) or corrosive.

Preferably, the deflector is located on the shaft adjacent the plate. Preferably, the deflector is coupled about the shaft and includes a flared portion being flared outwardly from a longitudinal axis of the shaft and toward the plate. The flared portion may be concave on a side of the deflector which faces the base. Preferably, the deflector is symmetrical about the longitudinal axis.

The bearing means may be located on an opposite side of the plate to the deflector.

Preferably, a heat sink is located about the bearing means. Advantageously, the heat sink aids in increasing the working life of the bearing means by reducing the heat in the bearing means. The heat sink may include at least one heat diffusing fin extending radially with respect to

the axis of the shaft.

According to another aspect of the present invention there is provided a rotor ventilator including : a base to which a shaft is connected to extend upwardly therefrom ; a rotor including a plate and a plurality of vanes extending downwardly therefrom, the rotor being rotatable about the shaft ; and a double race rotatable bearing assembly for supporting the rotor on the shaft and located at the plate.

Preferably, the rotatable bearing assembly includes : a bearing including a central bore and two internal axially spaced bearing races; a central shaft extending longitudinally through the bore, with a space being defined between the bearing and the shaft, the shaft including two external axially spaced bearing races, with the shaft races being aligned with the races on the bearing ; a plurality of ball bearings captively engaged between respective aligned races; and a low friction seal located at one end of the bearing and projecting radially inwards towards the shaft.

Preferably, the bearing assembly is located above the plate.

Preferably, a second radially inwardly projecting seal is located at another end of the bearing.

Preferably, a support means is rotatably mounted at one end to the shaft and mounted at another end to the rotor. The one end of the support means may include a bearing unit for rotatable mounting on the shaft, and may be intermediate the plate and base.

Preferably, an end of each vane is mounted to the plate by tab fastening means including at least one tab projection for receipt in a corresponding slot in the plate.

BRIEF DESCRIPTION OF THE DRAWINGS Preferred embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a side elevation of a first preferred embodiment of a rotor ventilator according to the present invention; Figure 2 is a plan view of the rotor ventilator of Figure 1 with the dome removed; Figure 3 is a cross-sectional side elevation of the rotor ventilator of Figure 1, taken on line 3-3; Figure 4 is a plan view of an alternate embodiment of a rotor ventilator with the dome removed ; Figure 5 is a sectional side elevation of the rotor ventilator of Figure 4, taken on line 5-5 ; Figure 6 is a part sectional side elevation of a bearing for use with the present invention ; Figure 7 is the cross-sectional side elevation of the rotor ventilator of Figure 3, including a deflector; Figure 8 is a cross-sectional side elevation of the deflector illustrated in Figure 7; Figure 9 is a plan view of the rotor ventilator of Figure 1 with the dome removed, and including a heat sink; and Figure 10 is a cross-sectional side elevation of the rotor ventilator illustrated in Figure 9, taken on line 10-10.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings, where like reference numerals are used to denote similar or like parts, Figures 1 to 3 and 6 show a preferred embodiment of a rotor ventilator according to the invention including a base in the form of a hollow cylindrical base element 10 for mounting on a roof, wall, ceiling, floor, etc. The base element 10 allows gas to pass through its opening 11 and into the interior 12 of the rotor ventilator. The type of

gas to pass through the ventilator is typically hot air, but may also be corrosive exhaust gases. A shaft 13 is connected to extend upwardly therefrom. A bracket 14 is typically employed for added transverse stability of the shaft and to mount the shaft to the base element 10. The bracket 14 includes lower frame brace 15 and upper frame brace 16. Each frame brace 15 and 16 is configured to ensure air flow through the base element 10 into the rotor ventilator interior 12 is not substantially impeded.

Also included is a rotor 17 which is rotatable about the shaft 13. The rotor 17 which has a plate 18 and a plurality of vanes 19 extending downwardly therefrom. An end 20 of each vane 19 is mounted to the plate 18. For added stability of the vanes when the rotor 17 is rotating, the rotor ventilator can also include a second plate in the form of an annulus 21 mounted to the other ends 22 of the vanes.

For mounting the vanes 19 between the plate 18 and annulus 21, each end 20 and 22 of each vane 19 has four projecting tabs 23, though in alternative embodiments each end 20 and 22 may have different numbers of tabs 23. When the vanes 19 are manufactured, the tabs 23 are in planar alignment with their respective vanes 19. These projecting tabs 23 are then employed to mount an end 20 and 20 of each vane to the plate 18 and annulus 21 respectively. To achieve the mounting, the plate 18 and annulus 21 have slots which correspond to the projecting tabs 23. To mount the ends 20 of the vanes 19 to the plate 18, the tabs 23 are passed through their corresponding slots on the plate 18 and then folded laterally onto the plate to be in the mounted position seen in Figures 2 and 4. This secures the end 20 of the vane 19 to the plate 18. Similarly, to secure the ends 22 of the vanes 19 to the annulus 21, projecting tabs 23 on the end 22 are passed through corresponding perforations on the annulus 21 and are then folded over on the annulus in a similar fashion to the folding of tabs 23 on the end

20. This secures the end 22 of the vanes 19 to the annulus 21.

This method of mounting the vanes to the plate 18 and annulus 21 requires no additional fastening means, such as rivets or screws, to mount the vanes 19 to the plate 18 and annulus 21. This has the advantages of reducing the overall weight of the rotor and reducing manufacturing time and cost for manufacturing rotor ventilators.

As external air moves past the vanes 19 of the rotor, the leading edge 24 of each of the vanes 19 will catch the passing air, causing the rotor to rotate. In the case of the embodiments of the invention shown in Figures 1 to 5, the rotor would be caused to rotate in a clockwise direction, when viewed from above, by air movement past the rotor ventilator. The movement of the vanes 19 through the surrounding air causes the gas within the rotor ventilator to be exhausted therefrom. This is achieved by trailing edge 25 cutting through the gas present in the interior 12 of the rotor ventilator, and forcing this gas out from the rotor ventilator between the vanes 19. This reduces the gas pressure in the interior 12 of the rotor ventilator. Thus higher pressure gas is drawn up into the ventilator through the opening 11 of the base element 10 and subsequently exhausted from the rotor ventilator.

The rotor ventilator also includes bearing means in the form of a support structure 26 for supporting the rotation of the rotor 17 on the shaft 13. The support structure 26 is typically mounted on top of the plate 18, to place the bearing point of the rotor 17 on the shaft 13 well above the centre of gravity of the rotor 17, while still keeping the support structure 26 in the rotor ventilator.

There are several advantages of having the support structure 26 on top of the plate 18. The position of the support structure 26 above the plate 18 means that the centre of gravity of the rotor 17 is well below the

bearing point of the support structure 26 on the shaft 13.

Therefore, the rotor basically hangs from the support structure. This allows for greater stability of the rotor ventilator in use because the rotor will have reduced transverse movement which would otherwise occur if the bearing point was below the centre of gravity. If the bearing point was below the centre of gravity, the rotor would overbalance, causing lateral stress on the bearing point. It then follows that in turn there is less working stress upon the support structure.

Another advantage of having the support structure 26 on top of the plate 18 is when the rotor ventilator is used to exhaust corrosive and/or high temperature (ie over 100°C) gases. Since the support structure 26 is above the plate 18, the support structure will not come into contact with the exhaust gases, since they are exhausted below the plate 18, via the vanes 19.

In alternate embodiments, the support structure is located in such a position to ensure the centre of gravity of the rotor 17 is below the support structure 26.

The support structure includes a fixture 27 for secure mounting to the plate 18. In the embodiment shown in Figures 2 and 3, the fixture 27 has three relatively long radially spaced support arms 28 and three relatively short radially spaced support arms 29. These arms 28 and 29 are used to stably secure the support structure to the plate 18. The arms are typically riveted to the plate 18, but may be welded or screw fastened, for example.

The support structure 26 also includes a bearing assembly in the form of a double race ball bearing unit 30. As seen in Figure 6, the double race ball bearing unit 30 includes a central shaft 32, and an outer casing 34 which rotates on the central shaft 32. The central shaft 32 and outer casing 34 have corresponding ball bearing races 36 and 38 between which are tracked a plurality of ball bearings 40 to support the configuration.

The double race ball bearing unit 30 is securely centrally located within the fixture 27, such that the central shaft 32 is in axial alignment with the central axis of the plate 18. When the double race ball bearing unit is secured within the fixture 27, the outer casing is fixed relative to the fixture 27, while the central shaft 32 is free to rotate with respect to the outer casing 34.

To allow the rotational mounting of the rotor 17 about the shaft 13, an end 42 of the central shaft 32 is mounted to an end 44 of the shaft 13 such that shafts 13 and 32 are coaxially aligned and fixed together.

The rotor ventilator typically includes a dome 45 placed on top of the rotor ventilator to both cover the support structure 26 and reduce resistance to air movement about and around the rotor ventilator. Also typically, a skirt 46 is mounted to the lower side 47 of the annulus 21 to also aid in reducing resistance of air movement around the rotor ventilator.

The above embodiment of the rotor ventilator was described with respect to rotor ventilators having a diameter of approximately 700mm and a height of approximately 460mm. For ventilators of this size and smaller, the double race ball bearing unit 30 is generally all that is required to maintain transverse stability of the rotor 17 in use. Only having to provide a rotor ventilator with one bearing unit provides significant advantages for ease of manufacture and reduced costs of manufacture of rotor ventilators of this size, given that only a single bearing unit is required to allow the rotor to efficiently and stably rotate.

Furthermore, the double race ball bearing unit 30 for use in the invention is unknown for the provision of reduced friction rotational bearing for rotor ventilators.

Double race ball bearing units of the type employed in the invention were developed for use in wet environments in motors and the like and therefore employ the use of high friction seals to ensure no water, etc has access to the

ball bearings and bearing races. A non-inventive person skilled in the relevant art would therefore not consider the use of such a double race ball bearing unit in a rotor ventilator application such as the rotor ventilator of the present invention.

The inventors have surprisingly found that by replacing the high friction seals with low friction, non/low contact seals, the double race bearing unit 30 becomes suitable for use as the ball bearing unit in rotor ventilators and provides several advantages in comparison with single race ball bearing units.

One example of an advantage in using a double race ball bearing unit is that double race ball bearing units are more laterally stable and stronger than single race ball bearing units. Therefore, in the case of the embodiment of the smaller rotor ventilator illustrated in Figure 3, one double race ball bearing unit is all that is required to maintain sufficient lateral stability of the rotor 17. This would not be sufficiently achieved with one single race ball bearing unit. Another example is that the increased stability and strength of the double race ball bearing unit 30 means it is possible to position the ball bearing unit 30 above the plate 18 and still maintain sufficient lateral stability in certain conditions.

Referring now to Figures 4 and 5, where like reference numerals are used to denote similar or like parts, another embodiment of the rotor ventilator is shown that is relatively larger than the rotor ventilator described above. An additional support means in the form of an intermediate bearing 48 is employed to improve transverse stability of the larger rotor in use. The intermediate bearing 48 includes a structural member 49, which has ends 50 and 52. End 50 is mounted to the plate 18, while end 52 is mounted to the annulus 21. A structural arm 54 extends laterally from the structural member 49 toward the shaft 13. The end 55 of arm 54 is

connected to a spider bearing 56 which is rotationally mounted to the shaft 13.

Figure 7 illustrates a deflector 58 in use in a rotor ventilator. The deflector 58 is located on the shaft, between the plate 18 and the base 10. The deflector is immediately adjacent the plate 18, being as close as possible to the plate 18, with enough clearance such that its upper edge 60 does not come into contact with the plate 18 when in use. The deflector includes a narrow portion 62 coupled to the shaft 13, and a flared portion 64 being flared outwardly from a longitudinal axis of the shaft 13 and toward the plate 18. As is evident in Figure 8, the flared portion 64 is symmetrical about its axis 66, and concave on its side 68 which faces the base 10.

As will be apparent to the skilled addressee, the deflector 58 advantageously deflects gas entering the interior 12 of the ventilator toward the vanes 19 and away from the bearing unit 30. This is particularly useful when the exhaust gas is of the kind that can affect the bearing unit 30, and the bearing unit greases. For example, high humidity exhaust gases can detrimentally affect clay based bearing greases by solidifying them, while high temperature exhaust gases of 100°C or more may reduce viscosity of the bearing grease, such that it flows out of the bearing unit 30.

Also, conventional rotor ventilators are typically configured to withstand normal exhaust gas temperatures of 60-70°Ce High temperature exhaust gases of 100°C or greater can detrimentally affect known rotor ventilators severely affecting their working life. However, with the configuration of the rotor ventilator of the present invention including the deflector 58, the resultant ventilator can withstand such higher temperatures for even greater working times when compared with conventional rotor ventilators.

Different materials may also be used in construction of various components of the rotor ventilator for

different exhaust environments. For example, in high temperature environments, the deflector and other components, such as the shaft 13, are typically constructed from aluminium, since aluminium has been found to reflect radiation and also acts as a heat sink, thereby minimising the effects of radiation. The aluminium components may also be powder coated to reduce the formation of an oxide layer on the components. For corrosive exhaust environments, the deflector 58 and other components are typically constructed from stainless steel.

However, stainless steel can also be used for the shaft in high temperature environments because it minimises heat conduction to the plate 18 and thus to the bearing assembly. In lower heat, but high corrosion environments, the bearing housing and some other components may also be formed from a polymer (ie. that has no tendency to corrode). Ceramic and glass may also be used for some components.

In high temperature environments, the rotor ventilator may also employ the use of a heat sink in the form of a bearing jacket 70, as illustrated in Figures 9 and 10. The bearing jacket 70 is coupled to the plate 18 by screws 72, and located about the bearing unit 30. As will be apparent to the skilled addressee, in this configuration of the invention, the dome 45 is removed in use to expose the bearing jacket 72 to its surrounding environment. Therefore, when for example the ventilator is attached externally to a roof, the bearing jacket 72 is exposed to air which moves past the ventilator.

The bearing jacket 72 usually substantially consists of aluminium, due to its aforementioned heat radiative properties. The bearing jacket 72 includes six pairs of minor fins 74 and three major fins 76. The fins 74 and 76 aid in the release of heat from the bearing jacket 72 by increasing the surface area of the bearing jacket 72 in contact with the surrounding atmosphere. The bearing jacket 72 therefore aids in drawing heat away from the

bearing unit 30, which is useful when the rotor ventilator is employed in high heat environments.

In use, a hole is made in, for example, the roof of a building where improved ventilation is required. The base element 10 is typically fixedly attached to the roof in such a way that positions the shaft 13 in a substantially vertical position and allows free rotation of the rotor 17 about the shaft 13. Therefore, when air passes the rotor ventilator and causes rotation of the rotor 17 as described above, air exhausted from the interior 12 of the rotor ventilator is replaced by air from below the roof.

This air is then subsequently exhausted, and improved ventilation is achieved.

Although the invention has been described with reference to particular examples, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms.