GB2172936A - Fan having individually mounted blades - Google Patents

Abstract

A fan has an electric motor (1) with a central stator (2) and an external rotor (3). A radial flange (5) projects from the rotor and has tapped holes (7) disposed around it. Each impeller blade (10) is mounted separately on top of the flange by means of a locating ring (20) having apertures (23, 24 Figure 2 not shown) which receive studs projecting from the upper surface of each blade root mount (11). Screws (30) extend through the locating ring (20) and blade root mounts (11), and are screwed into the tapped holes (7) in the flange (5). The blades (10) may be made by extruding and subsequent twisting, and may be of fibreglass-reinforced plastics or aluminium. <IMAGE>

Description

SPECIFICATION Fans This invention relates to fans.

The invention is more particularly concerned with fans having external rotor motors.

Fans can use two different forms of motor. In one form, the motor casing is fixed and energisation of the motor causes rotation of the central motor shaft. In the other form, employing a motor with an external rotor, the stator is located centrally and energisation causes rotation of a surrounding rotor. With the first form of motor, the impeller hub is secured to the motor shaft, whereas, when an external rotor is used, the impeller is secured to the external motor.

There are many different applications for fans, which require impellers having different characteristics, although a small number of different motors will generally be sufficient to drive these impellers.

With external rotor motors, the impeller takes the form of a ring, that is bolted or cast onto the rotor, and that is formed integrally with the required number of radially-extending blades. The impeller may be formed by moulding as a single piece or by welding the blades to the ring prior to assembly on the rotor. Because the impeller is preformed in this way for each application, it makes the manufacture of small numbers of fans relatively expensive.

It is an object of the present invention to provide a fan that can be used to overcome this disadvantage.

According to one aspect of the present invention there is provided a fan including an electric motor having a central stator and an external rotor surrounding the stator that is rotated on energisation of the stator, the fan including a plurality of impeller blades, each said blade being separately mounted on the rotor.

The rotor may include a radially extending flange provided with a plurality of mounting locations, each said mounting location being adapted to mount an individualone of said blades. Preferably the fan includes a locating ring, said blades being mounted between the said flange and the locating ring. Each blade may be provided with an aperture that aligns with respective apertures in the flange and the locating ring, a fastener extending through each aperture in the blade to secure the blades with the rotor. Each blade may include a surface formation that engages a respective surface formation on the flange or location ring so as thereby to locate the blades in position. The fastener may be a screw.

The inner end of each blade is preferably terminated by a respective blade root mount, each said blade root mount being formed separately of the remainder of the blade. The remainder of each blade may be formed by extrusion and subsequent twisting. Each blade may be of a plastics material, which may be fibreglass-reinforced plastics, or of aluminium.

According to another aspect of the present invention there is provided a blade for a fan according to the above mentioned one aspect of the invention.

A fan in accordance with the present invention, will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a partly cut away side elevation of the fan; and Figure 2 is a partly cut away plan view of the fan.

The fan incorporates an external rotor electric motor 1 with stationary axial stator spigot 2 by which the motor is mounted, such as, in a housing (not shown). The motor 1 has a central stator (not shown) and an external rotor 3 which is rotated about the motor axis 4 when the stator is energised. The rotor 3 includes an integral, coaxial mounting flange 5. The flange 5 extends radially and is provided with tapped holes 7 disposed about the flange and grouped together in pairs of diametrically opposite holes.

Secured directly to the mounting flange 5 of the rotor 3 are six impeller blades 10, of which only two are shown in the drawings. The blades 10 are of fibreglass- reinforced polypropylene and are made by extruding and twisting to give the desired characteristics. Alternatively, the blades 10 may be extruded of aluminium. Each blade 10 is terminated at its inner end by a respective blade root mounting segment 11 which is of the same material as the main part of the blade and is joined with it, such as, in the case of plastic blades by ultrasonic welding. Centrally, at the inner end of each mounting segment 11 there is provided a hole 12 which aligns with a respective one of the holes 7 in the rotor mounting flange 5. Two locating studs 13 and 14 project a short distance above the upper surface of the mounting segment 11, one on each side of the hole 12.

The locating studs 13 and 14 on each mounting segment 11 engage in apertures 23 and 24 respectively formed around a locating ring 20 which encompasses the rotor 3. The locating ring 20 is also formed with six apertures 27 which align with the holes 7 in the rotor flange 5 and with the holes 12 in the mounting segment 11. The blades 10 are secured in position on the motor 1 by means of screws 30, or other fasteners, which pass through the apertures 27 and 12 in the locating ring and the mounting segments 11 respectively and are screwed into the tapped holes 7 in the flange 5.

The screws 30 hold the locating ring 20 against the top surface of the blade mounting segments 11 with the locating studs 13 and 14 in location in the apertures 23 and 24. This maintains the blades 10 in position on the flange 5, extending radially outward from the motor 1.

When the stator of the motor 1 is energised, the rotor 3 and mounting flange 5 are rotated about the axis 4, thereby causing rotation of the blades 10 so as to move air substantially parallel to the axis, in the usual way.

Since each blade 10 is separately mounted with the rotor, it is possible to use any number and disposition of blades, according to the number of mounting holes 7 provided in the flange 5, to suit the particular application to which the fan is to be put. Instead of mounting a blade 10 at each of the six locations labeiled A to F around the flange 5, it would, for example, be possible to use four blades, one blade being secured at each of the locations A,B,D and E, or to use three blades, one blade being secured at each of the locations A, C and E.

The blades can therefore be made individually in large numbers, and the same blade can be used with different external rotor motors. This thereby leads to economy, by avoiding specialised low-volume manufacture. By making the mounting segment 11 separately of the main part of the blade 10, it is possible to use the same mounting segment in blades of different length, twist and other characteristics, although the blade and mounting segment could be made as an integral one-piece moulding if desired.

Claims (14)

1. A fan including an electric motor having a central stator and an external rotor surrounding the stator that is rotated on energisation of the stator, wherein the fan includes a plurality of impeller blades, each said blade being separately mounted on the rotor.

2. A fan according to Claim 1, wherein the rotor includes a radially extending flange provided with a plurality of mounting locations, each said mounting location being adapted to mount an individual one of said blades.

3. A fan according to Claim 2, including a locating ring, and wherein said blades are mounted between the said flange and the locating ring.

4. A fan according to Claim 3, wherein each said blade is provided with an aperture that aligns with respective apertures in the flange and the locating ring, and wherein a fastener extends through each aperture in the blade to secure the blades with the rotor.

5. A fan according to Claim 4, wherein each blade includes a surface formation that engages a respective surface formation in the flange or locating ring so as thereby to locate the blades in position.

6. A fan according to Claim 4 or 5, wherein the said fastener is a screw.

7. A fan according to any one of the precedings claims, wherein the inner end of each blade is terminated by a respective blade root mount, and wherein each said blade root mount is formed separately of the remainder of the blade.

8. A fan according to Claim 7, wherein the said remainder of each blade is formed by extrusion and subsequent twisting.

9. A fan according to any one of the preceding claims, wherein each said blade is of a plastics material.

10. A fan according to Claim 9, wherein each said blade is of fibreglass-reinforced plastics.

11. A fan according to any one of Claims 1 to 8, wherein each said blade is of aluminium.

12. A fan substantially as hereinbefore described with reference to the accompanying drawings.

13. A blade for a fan according to any one of the preceding claims.

14. A blade substantially as hereinbefore described with reference to the accompanying drawings.