GB2160924A

GB2160924A - Axial flow fan

Info

Publication number: GB2160924A
Application number: GB08515824A
Authority: GB
Inventors: Anthony David Colliver
Original assignee: FF Seeley Nominees Pty Ltd
Current assignee: FF Seeley Nominees Pty Ltd
Priority date: 1984-06-26
Filing date: 1985-06-21
Publication date: 1986-01-02
Also published as: GB2160924B; JPS6116300A; GB8515824D0; ZA854778B; NZ212467A; AU4396385A; KR860000484A; AU573349B2

Abstract

The fan comprises a motor 11 having a shaft 13 on which the curved hub 15 of an impeller is mounted, the hub partly surrounding the motor and forming a gap 22 through which air is drawn to cool the motor. The cooling air flours through apertures 17 in the hub to the low pressure side of the fan. <IMAGE>

Description

SPECIFICATION Axial flow fan This invention relates to an axial flow fan mounting arrangement which incorporates motor protection and motor cooling means.

Although the invention is not limited to evaporative coolers, it is particularly suitable for use with such coolers, wherein air flow may contain droplets of entrained water.

BACKGROUND OF THE INVENTION There are many applications, including applications in evaporative coolers, wherein it is desirable to provide optimum protection for a fan motor which might otherwise have its insulation damaged by moisture. However to fully enclose a motor requires the use of a frame much larger than is needed for a vented motor, and it is desirable that the motor should be vented to allow the passage of cooling air therethrough. A limiting factor is temperature rise in the motor windings, which must not be allowed to exceed limits imposed by the characteristics of the insulation used.

The main object of this invention is to provide an improved mounting arrangement whereby a motor is protected against excessive ingress of moisture which may otherwise be entrained in an airstream, but nevertheless is cooled by an airflow created by that airstream.

BRIEF SUMMARY OF THE INVENTION This invention makes use of the phenomenon that all except very small particles of moisture will tend to continue in a direction of travel when entrained in an airstream notwithstanding that the direction of travel of the airstream itself is varied, and the invention may be summarised in that a motor carries a fan hub comprising a hollow dish-like member with a curved leading end, apertures extending through the leading end at a high velocity low pressure zone from the inside to the outside of the hub upstream of fan blades carried by the hub, the motor being mounted on a motor mounting frame and at least partly contained within the hub, such that an air entry gap exists between the downstream end of the hub and the motor.

With this arrangement there is a "back flow" of air from the high pressure zone at the locality of the air entry gap, past the motor and into the high velocity low pressure zone on the hub.

More specifically, this invention consists of an axial flow fan mounting arrangement wherein a motor is mounted on a motor mounting frame, and the motor shaft carries a fan hub thereon, with fan blades radiating from the hub, wherein said fan hub comprises a hollow dish-like member with a forwardly converging leading end, airflow apertures extending through the leading end at a high velocity low pressure zone from the inside to the outside of the hollow hub upstream of the fan blades, the motor being at least partly contained within the hollow space of the fan hub, and there being an air entry gap between the downstream end of the hub and the motor, and sufficient space between the hub and the motor to form an airflow passage from the air entry gap to the airflow apertures.

BRIEF DESCRIPTION OF THE DRAWINGS An embodiment of the invention is described hereunder with reference to, and is illustrated in, the accompanying drawings, in which Figure 1 is a perspective "exploded" view showing a motor mounting frame (which is portion of an evaporative cooler), a motor and an axial flow fan, Figure 2 is a front elevation view of the fan, and Figure 3 is a partly sectioned side elevation view showing the fan, motor and motor mounting frame.

In this embodiment, in an evaporative air cooler 10 a relatively small fan motor 11 is arranged for air cooling by the passage of air not merely over the outer surface but also through the windings of the motor. The motor has a projecting shaft 1 2 having a non-circular forward end 13, and this shaft is retained within a central boss 1 4 of a hollow hub 1 5.

The hollow hub 1 5 is the hub of a dish-like member having a dome, or otherwise curved, end 1 6 at its upstream end, and a plurality of air flow apertures 1 7 extend from within the dish-like member to the outer surface of the dome at spaced localities surrounding the central part of the dome and near the transition from the dome to a cylindrical portion, and, in being away from the centre of the dome, the apertures open out into a high velocity and therefore low pressure zone Z1 on the outer surface of the hollow dome.

The dome walls extend in a downstream direction and are substantially cylindrical, and support a plurality of spaced radially outwardly extending fan blades 20 which are generally in accordance with known art.

The motor and fan assembly are portion of an evaporative cooler, and draw air through an absorptive pad over which water runs, so that the air, when it passes the motor and fan assembly, not only is cooled, but may entrain small droplets of water.

The motor 11 is mounted on a motor mount 21 which is part of the frame of cooler 10, and is spaced downstream from the downstream end of the hub 15, so that there exists an air entry gap 22 (Fig. 3) between the downstream end of the hub 1 5 and the motor mount 21 through which air passes from the high pressure Zone Z2 downstream of the fan blades 20, over the motor 11 and past its windings, and issues through the airflow apertures 17 at the upstream end of the hub 15, and near the outer periphery of the dome surface thereof.

A consideration of the above embodiment will indicate that the invention has many advantages over prior art.

Firstly, the motor is well air-cooled by air which has itself been pre-cooled due to entraining evaporated water, but most of the unevaporated moisture droplets which are entrained in the flow of air continue in an axial direction and are not carried over the motor by the small inflow of air from the high pressure zone Z2 downstream of the fan blades, into the hollow of the hub. Secondly, since the motor is efficiently cooled its frame can be of relatively small size for a given power. Thirdly, the total space occupied by the motor fan assembly is much less than in prior art arrangements, so that for example an appliance containing a fan, is much thinner front to back, and occupies less space than if the motor is in tandem with the fan (that is the usual arrangement). It will of course be seen that many variations can be introduced into this invention and for example the smooth contour of the dome and cylindrical surface of the hub can be interrupted by a ramp surface which applies even less pressure to the locality of the apertures through which the air flows from the motor and back into the main airstream. Use can also be made of an annular scoop arrangement for scooping the air from the downstream side back into the hollow of the hub. However, the efficiency of the arrangement shown in the preferred embodiment is so high that these additional features are not usually required. Although the machine as described above requires no metal fastenings for the fan to motor shaft, these can be used if required, however these and similar variations will be seen to lie within the invention.

Claims

1. An axial flow fan mounting arrangement wherein a motor is mounted on a motor mounting frame, and the motor shaft carries a fan hub thereon, with fan blades radiating from the hub, wherein said fan hub comprises a hollow dish-like member with a forwardly converging leading end, air flow apertures extending through the leading end at a high velocity low pressure zone from the inside to the outside of the hollow hub upstream of the fan blades, the motor being at least partly contained within the hollow space of the fan hub, and there being an air entry gap between the downstream end of the hub and the motor, and sufficient space between the hub and the motor to form an airflow passage from the air entry gap to the airflow apertures.

2. An axial flow fan mounting arrangement according to claim 1 wherein said motor mounting frame is part of an evaporative cooler and located downstream of a wet evaporative pad, so that the air which passes the motor and fan is both cooled and may entrain moisture particles from said pad.

3. An axial flow fan mounting arrangement according to claim 1 or claim 2 wherein said hub leading end is dome shaped and the hub includes a trailing cylindrical portion, and said high velocity low pressure zone is near the transition between the dome shaped leading end of the hub and the trailing cylindrical portion.

4. An axial flow fan mounting arrangement according to any preceding claim wherein said motor comprises a motor shaft which projects both forwardly and rearwardly, said hub being carried on the fowardly projecting end of the shaft.

5. An axial flow fan mounting arrangement substantially as herein described with reference to and as illustrated in the accompanying drawings.