GB2280225A

GB2280225A - Fan impeller

Info

Publication number: GB2280225A
Application number: GB9314117A
Authority: GB
Inventors: Gerald Rodney Godden
Original assignee: Truflo Air Movement Ltd
Current assignee: Truflo Air Movement Ltd
Priority date: 1993-07-08
Filing date: 1993-07-08
Publication date: 1995-01-25
Anticipated expiration: 2013-07-08
Also published as: GB9314117D0; GB2280225B

Abstract

An impeller for a power driven axial flow fan comprises a hub spider 10 with radial blade mounting arms 16. Blades 20 of the impeller are preferably aluminium alloy extrusions of common cross section throughout their length and have an aerofoil profile with a hollow interior defining a mounting socket 22 fitting onto respective spider arms 16. One or more additional spiders may be provided for added strength secured to outer faces of the blades to form a sandwich construction. <IMAGE>

Description

FAN IMPELLER This invention relates to impellers for power driven fan assemblies of the axial flow type.

The object of tlie invention is to provide a fan impeller of simple and economical construction and which is aerodynamically efficient and strong and durable in use.

According to the invention there is provided a fan impeller comprising a hub spider having a plurality of radially extending blade mounting arms and a corresponding number of hollow aerofoil section blades each defining a longitudinally extending socket open to at least one end in which the respective spider arm is received and secured.

Conveniently the blades are extrusions, e.g. of aluminium alloy, of constant cross-section throughout their length, thus a number of blades can be cut to length from a common longer extrusion.

For added strength e.g. in heavier duty applications and/or larger sizes and capacities of fan assembly the hub of the fan may be built up from a pair of said spiders, the arms of one spider being secured within the blade sockets and the arms of the other spider abutting faces of the blades to form a sandwich construction.

An example of the invention is now more particularly described with reference to the accompanying drawing being an exploded perspective view of a fan impeller.

The impeller comprises a pair of identical hub spiders 10, typically pressed from metal plate. Each spider 10 has a central aperture 12 in which is secured a hub adaptor 14 in the form of a flanged bush including a keyway for securing the assembled impeller on a drive shaft in known manner.

In this example each spider has eight radially extending and equi-angularly spaced blade mounting arms 16. Each arm has parallel side edges and they are each twisted so that they are angled with respect to the centre portion to present the leading edges of the blades carried thereon upstream of the direction of axial flow in known manner.

It will be appreciated that the number of arms and hence blades included in the impeller may be varied according to requirements e.g. from two blades at 1800 to each other upwards.

The impeller further comprises eight identical blades 20 (three only shown in the drawing). The blades are aluminium extrusions of common cross-section throughout their length, i.e. they may be cut from a greater common extruded section, having an aerofoil external profile and a cellular hollow interior divided into longitudinal through openings by longitudinally extending interior webs or walls. A main through opening along a central region of each blade constitutes a mounting socket 22 open to each end and which is a press or close fit on the spider arm 16.

The impeller is assembled by engaging socket 22 of a respective blade 20 onto each of the arms 16 of one of the spiders 10 with the leading edge of each blade aerofoil section facing the same way so that they act in common in generating axial flow.

The second spider 10 (to the left as viewed in the drawing) has its arms 16 brought into abutment with the rear faces of the set of blades, a stiffening collar 24 being positioned between the central portions of the two spiders locating on adaptor 14, acting as an axial spacer and also being finally secured to the two spiders e,g, by spot welding.

The sandwich assembly so formed is finally secured by rivets 26 or other fastening elements extending through the two spaced walls of each blade and through the associated arms 16 of the two spiders 10. This forms a particularly strong and rigid assembly providing longitudinal stiffening and support to the individual blades.

The hollow extruded form of blades 20 is light in weight yet strong and the extruded formation can be formed to high tolerances and consistent dimensions, thus little or no balancing may be needed to provide low vibration and quiet operation even at high speeds and loading.

For light duty applications and/or smaller sizes of impeller a single spider 10 may be sufficient with its arms received and secured in the blade sockets. On the other hand further stiffening and added strength could be provided by using a third spider whose arms overlie the front faces of the blades 20 and secured by fastenings passing through all three arms of the sandwich assembly.

Claims

1. A fan impeller comprising a hub spider having a plurality of radially extending blade mounting arms and a corresponding number of hollow aerofoil section blades each defining a longitudinally extending socket open to at least one end in which the respective spider arm is received and secured.

2. An impeller as in Claim 1 wherein the blades are hollow extrusions of constant cross section throughout their length.

3. An impeller as in Claim 1 or 2 wherein the blades are formed from alluminium alloy.

4. An impeller as in Claim 1,2 or 3 including an additional hub spider abutting outer faces of the blades to form a sandwich construction for added strength.

5. An impeller as in Claim 4 comprising three hub spiders, one having mounting arms received in the blade sockets and each of the other two abutting respective opposite side faces of the blades.

6. A fan impeller substantially as hereinbefore described with reference to and as shown in the accompanying drawing.