EP2663776A1

EP2663776A1 - An axial fan assembly

Info

Publication number: EP2663776A1
Application number: EP12701364.7A
Authority: EP
Inventors: Russell Wheeler
Original assignee: Individual
Current assignee: Individual
Priority date: 2011-01-13
Filing date: 2012-01-13
Publication date: 2013-11-20
Also published as: GB201100523D0; WO2012095674A1

Abstract

An axial fan assembly is provided for a ventilation assembly such as a commercial/industrial extractor fan assembly, or an underground car park exhaust system, the fan assembly (23) comprising a fan duct (25) and two casing halves (27) which encase the fan duct in use. The fan duct comprises a circular cross section metal tube formed from a metal spinning process whereby the wall of the tube is formed from continuous material having no seam or joint. The fan duct is adapted to house a fan (35) comprising a fan impeller (37) and a fan motor (39), the two casing halves (27) each comprising a first diameter portion (29) of the same diameter as the metal tube of the fan duct and a wider diameter portion (33). Each casing half is also formed from a metal spinning process whereby the wall of each casing half is formed from continuous material having no seam or joint.

Description

AN AXIAL FAN ASSEMBLY

The present invention relates to an axial fan assembly for a ventilation assembly. Examples of such ventilation assemblies include a commercial/industrial extractor fan assembly, or an exhaust system for an underground car-park or tunnel or the like.

It has previously been proposed to provide an axial fan assembly for connection between the ends of two ducts, in order that the fan of the fan assembly pumps air through the connected ducts in use. Such a prior art fan assembly, typically known as a 'cased axial fan assembly' or a 'flanged axial fan assembly', takes the form shown in Figure 1 and comprises a tubular inner fan duct housing a fan impeller and fan motor. The ends of the fan duct are bent through 90° to form radially outwardly directed mounting flanges. Separate components comprising a pair of so called 'matching flanges' are then bolted to each mounting flange on the fan duct. Each matching flange comprises a boss onto which one end of a flexible duct connector can be clamped. The other end of the flexible duct connector can be clamped to the end of one of the ducts of the ventilation assembly. Furthermore, a sound/thermally insulating sleeve can be mounted around the fan duct. Finally, the above assembled fan assembly is then bolted to a pair of mounting feet which are used to either support the fan assembly on the floor, or to mount the fan assembly on a wall or ceiling as required.

Such flanged axial fan assemblies have been used historically for decades and as the name suggests, require the ends of the fan duct to be bent to form the flanges. This bending process requires very high forces to be applied to the duct material and is therefore very machine and energy expensive. It also necessarily requires the material of the duct wall to be relatively thick to enable the flanges to be bent without the material breaking or tearing. This leads to the fan duct being relatively heavy. For example a 500mm diameter fan might lead to a fan duct of around 75kg. This weight has to be manhandled by the operatives fitting the fan assembly and may have to be lifted if the fan assembly is to be mounted to a wall or ceiling or the like. The same considerations apply to the separate mounting flanges which are also comprise bent flanges necessitating use of relatively thick material, for example 2.5mm mild steel. Additionally, all of the above components, ie the fan duct, the mounting flanges, the flexible ducts, the sound insulating sleeve, and the mounting feet all have to b e assembled together on site, by the operative. The flanges on the fan duct have to be bolted in multiple locations to the mounting flanges, the mounting feet to the fan duct etc. Thus the assembly time and complexity, on site, of the prior art flanged axial fan assemblies is relatively high, and thus the labour cost is also high.

There is a need to reduce the cost of manufacture, the assembly and fitting time, and the ease of assembly and fitting of such fan assemblies. The present invention stems from some work in trying to solve this problem.

According to a first aspect of the invention there is provided an axial fan assembly adapted to be mounted between two adjacent ducts of a ventilation system, the fan assembly comprising a fan duct and two casing halves which encase the fan duct in use, the fan duct comprising a circular cross section metal tube formed from a metal spinning process whereby the wall of the tube is formed from continuous material having no seam or joint, the fan duct being adapted to house a fan comprising a fan impeller and a fan motor, the two casing halves each comprising a first diameter portion of the same diameter as the metal tube of the fan duct, and a wider diameter portion, each casing half being formed from a metal spinning process whereby the wall of each casing half is formed from continuous material having no seam or joint, the fan assembly being adapted to be received inside the wider diameter portions of the casing halves such that each opposed end of the fan duct abuts the narrower diameter portion of a respective casing half to form a contiguous duct through the fan assembly, the exterior of the narrower diameter portion of each casing half comprising a boss onto which the end of a duct of the ventilation system can be slidingly mounted.

Thus neither the fan duct nor the casing halves require any form of fixing on their respective walls in order to retain their shape and structure. Amongst other things this provides the internal surface of the contiguous duct with a relatively smooth and unimpeded surface, facilitating flow of the fluid through the duct.

Preferably the casing halves are adapted to be secured together using at least one of adhesive and rivets.

Preferably each casing half comprises an intermediate wall portion leading from the narrower diameter portion to the wider diameter portion. Preferably the intermediate wall portion is inclined radially outwardly from the narrower diameter portion to the wider diameter portion.

Preferably the intersection of the intermediate wall portion with the narrower diameter wall portion functions as an end stop against which a duct of the ventilation system abuts when mounted on the fan assembly.

Preferably a cavity is defined between the wider diameter portion of the casing half and the fan duct, when the fan duct and casing halves are assembled together, the cavity being provided with insulating material operative to attenuate at least one of the sound and heat generated by the fan assembly in use.

Thus preferably, the cavity for the insulating material is pre-formed as an integral part of the outer casing, and serves to encase and locate the insulating material on the fan assembly without any further components or additional fixings.

Preferably the insulating material comprises a sleeve of material adapted to be slid around the exterior of the fan duct.

A mounting bracket may be provided adapted to mount at least one casing half to a support structure such as a building or the like.

The mounting bracket may be integral with at least one casing half.

The fan assembly may further comprise a ducted silencer comprising radially inner and outer silencer ducts, sound absorbing material being sandwiched therebetween, one end of the inner duct being dimensioned to be slidingly mounted on a boss of one of the casing halves of the fan assembly.

Preferably the one end of the inner silencer duct has an end profile adapted to mate with the profile of the intermediate wall portion of the casing half.

According to a second aspect of the invention there is provided a ventilation system comprising the axial fan assembly of the first aspect of the invention. According to a third aspect of the invention there is provided the axial fan assembly of the first aspect of the invention, and a fan comprising a fan impeller and a fan motor, the fan being housed within and mounted on the fan duct of the axial fan assembly.

Other aspects of the present invention may include any combination of the features or limitations referred to herein.

The present invention may be carried into practice in various ways, but embodiments will now be described by way of example only with reference to the accompanying drawings in which:

Figure 1 is an exploded, part sectional side view of a prior art flanged axial fan assembly;

Figure 2 is a sectional side view of an axial fan assembly in accordance with the present invention;

Figure 3 is an end view of the axial fan assembly of Figure 2;

Figure 4 is an exploded side view of the axial fan assembly of Figures 2 and 3 ;

Figure 5 is an exploded end view of the axial fan assembly of Figures 2 to 4;

Figures 6a to 6c are sectional side views of the axial fan assembly of Figures 2 to 5, in various states of assembly with connecting ducts of a ventilation system; and Figure 7 is a part sectional side view of the axial fan assembly of Figures 2 to 6 in use with a silencer duct.

Referring initially to Figure 1 , a prior art 'cased' or 'flanged' axial fan assembly' 1 comprises a tubular inner fan duct 3 inside which a fan 5 comprising a fan impeller and fan motor are mounted. The prior art fan duct 3 is formed from a sheet of metal typically mild steel, that is rolled or bent and then seam welded or riveted to form the circular cross section duct. The ends of the fan duct 3 are then bent to form radially outwardly directed flanges 9. The formed duct is then weather treated by hot dip galvanising and/or painting for example.

A pair of so called 'matching flanges' 1 1 are provided each of which comprise a short length of duct, manufactured as above, one end of which is bent to form a mounting flange 13. The mounting flanges 13 are bolted at multiple locations to the flanges 9 of the fan duct 3 and may need to be pre- drilled.

The matching flanges 1 1 each comprise a short boss 15 onto which one end of a flexible duct connector 17 can be clamped. The other end of each flexible duct connector 17 can be clamped to a respective end of a duct 19 of a ventilation assembly (not shown).

Furthermore, a sound insulating sleeve (not shown) can be mounted around the fan duct 3. Finally, the assembled fan assembly 1 is then secured to a pair of mounting feet 21 which are used to either support the fan assembly 1 on the floor, or to mount the fan assembly 1 on a wall or ceiling as required.

The disadvantages of such a prior art fan assembly are significant and are discussed above. Referring now to Figures 2 to 6, an axial fan assembly 23 in accordance with the present invention comprises an inner fan duct 25 in the form of a circular cross section metal tube formed from a metal spinning process that results in the wall of the tube being continuous about the tube's circumference such that there are no seams, joints, welds or other fixings holding the tube in shape. Thus the duct 25 is formed from a blank of sheet metal material that is spun about an axis adjacent a form tool, the blank being forced onto the form tool. The interior of the fan duct 25 is thus entirely smooth and devoid of any protuberances that might disrupt fluid flow.

The fan assembly 23 further comprises an outer casing formed from two metal casing halves 27 arranged to encase the fan duct 25 when the front margins 27A of the casing halves 27 are mounted together.

Each casing half 27 comprises a narrower diameter tubular portion 29 leading to a wider diameter tubular portion 33 via an intermediate inclined walled, increasing radius portion 31. The narrower diameter portion 29 is of the same internal diameter as the tube of the fan duct 25. The exterior of the narrower diameter portion 29 of each casing half comprises a boss 32 onto which a duct 19 of the ventilation assembly is slidingly mounted as described below. Each casing half 27 is formed from a metal spinning process as described above in connection with fan duct 25. Thus the wall of each casing half 27 is also continuous about its circumference, with no seams, welds or joints.

The fan assembly 23 further comprises a fan 35 provided with a fan impeller 37, a fan motor 39 and a fan mount 41 , the mount 41 comprising a plurality of arms 43 that extend from the hub 42 of the fan 35 radially outwardly to the inner wall of the fan duct 25. The mount 41 may be secured to the inner wall of the fan duct 25 using any suitable fixing which may be adhesive or rivets for example. The fan assembly 23 further comprises a sleeve of acoustic/thermal insulation 43 that is mounted around the fan duct 25 as described further below.

Finally, the fan assembly 23 comprises a mounting bracket 45. This can be of any desired form, including the advantageous form described in our international patent application PCT/GB2009/001741. The bracket 45 may be substantially channel shaped, the outer casing being at least partially received in the channel. The bracket 45 may be integral with one or other casing half 27. Referring in particular to Figures 4 and 5, the above components are assembled by first mounting the fan 35 inside the metal spun fan duct 25. The sleeve of insulation 43 is slid over the outside of the fan duct 25. The two casing halves 27 are then brought together around the fan duct 25 and the sleeve of insulation 44 such that both of these components are entirely contained within the casing halves 27. The inside surface of the wall of the fan duct 25 is contiguous with the inside surface of the narrower diameter portions 29 of the casing halves 27 so as to form a continuous, smooth surfaced duct through the fan assembly 23. The sleeve of insulation 44 is contained in the circumferential cavity defined between the outside surface of the fan duct 25, and the inside surface of the wider diameter tubular portion 33 and inclined walled, increasing radius portion 31 of each casing half 27.

The abutting margins 27A of the casing halves 27 are sealed together by any suitable sealing means which could be for example adhesive or a riveted joint as required.

The so assembled components are then mounted on the mounting bracket 45.

It will be appreciated that the fan duct 25 and casing halves 27 entirely avoid the previous need to have relatively thick mounting flanges on each component. The requirement for separate matching flanges is also entirely removed. By avoiding the need for mounting flanges, this removes the need to perform four energy and financially expensive metal bending steps in the manufacturing process, and this means that the wall thickness of the sheet material used to form the components can be significantly reduced from, for example, about 2.5mm to less than 1mm.

Furthermore, the removal of the need for a sheet bending manufacturing step means that materials other than mild steel can be used. So for example, the fan duct 25 and casing halves 27 can be formed from a pre-weather treated material such as galvanised or stainless steel for example. Thus the requirement for a separate metal treatment step is also removed. Finally, the need for any kind of seaming process to join the seams of the duct components is avoided as there are no margins to join together. So a further manufacturing step inherent in the prior art assembly is avoided.

The overall number of components in the fan assembly 23 is also significantly reduced over the prior art assembly 1. These improvements lead to improvements in the speed, complexity and cost of manufacture and also the speed, complexity and cost of assembly on site. In fact the fan assembly 23 may be supplied as a pre-manufactured assembly, only requiring connection to the two ducts 19 of the ventilation assembly. This much simplified onsite process can be seen with reference to Figure 6 where each duct 19 of the ventilation assembly is simply slid over the boss 32 on each narrower diameter portion 29 of the casing halves 27. The inclined portion 31 of each casing half 27 where it intersects the narrower diameter portion 29 forms a duct end stop 47 against which the ducts 19 abut.

It will also be appreciated that the casing for the thermal/ acoustic insulating sleeve 44 is pre-formed as an integral part of the outer casing, and serves to encase and locate the sleeve 43 on the fan assembly 23 without any further components or additional fixings.

As non-limiting examples only, it is envisaged that the internal diameter of the fan duct 25 might be in the range of 200mm to 600mm although this can of course be adjusted as required to suit the desired performance characteristics of the ventilation assembly.

Referring additionally to Figure 7, an optional ducted silencer 49 is slidingly mounted on boss 32 on one end of the fan assembly 23.

The silencer 49 comprises inner and outer ducts 51 , 53 sandwiching thermally and/or acoustically insulating material 55.

The end of silencer 49 is profiled 57 to match the profile of inclined casing wall portion 31 against which it abuts in use.

Claims

1. An axial fan assembly adapted to be mounted between two adjacent ducts of a ventilation system, the fan assembly comprising a fan duct and two casing halves which encase the fan duct in use, the fan duct comprising a circular cross section metal tube formed from a metal spinning process whereby the wall of the tube is formed from continuous material having no seam or joint, the fan duct being adapted to house a fan comprising a fan impeller and a fan motor, the two casing halves each comprising a first diameter portion of the same diameter as the metal tube of the fan duct, and a wider diameter portion, each casing half being formed from a metal spinning process whereby the wall of each casing half is formed from continuous material having no seam or joint, the fan assembly being adapted to be received inside the wider diameter portions of the casing halves such that each opposed end of the fan duct abuts the narrower diameter portion of a respective casing half to form a contiguous duct through the fan assembly, the exterior of the narrower diameter portion of each casing half comprising a boss onto which the end of a duct of the ventilation system can be slidingly mounted.

2. The fan assembly of claim 1 wherein the casing halves are adapted to be secured together using at least one of adhesive and rivets.

3. The fan assembly of claim 1 or claim 2 wherein each casing half comprises an intermediate wall portion leading from the narrower diameter portion to the wider diameter portion.

4. The fan assembly of claim 3 wherein the intermediate wall portion is inclined radially outwardly from the narrower diameter portion to the wider diameter portion.

5. The fan assembly of claim 3 or claim 4 wherein the intersection of the intermediate wall portion with the narrower diameter wall portion functions as an end stop against which a duct of the ventilation system abuts when mounted on the fan assembly.

6. The fan assembly of any one of the preceding claims wherein a cavity is defined between the wider diameter portion of the casing half and the fan duct, when the fan duct and casing halves are assembled together, the cavity being provided with insulating material operative to attenuate at least one of the sound and heat generated by the fan assembly in use.

7. The fan assembly of claim 6 wherein the cavity for the insulating material is pre-formed as an integral part of the outer casing, and serves to encase and locate the insulating material on the fan assembly without any further components or additional fixings.

8. The fan assembly of claim 6 or claim 7 wherein the insulating material comprises a sleeve of material adapted to be slid around the exterior of the fan duct. 9. The fan assembly of anyone of the preceding claims wherein a mounting bracket is provided adapted to mount at least one casing half to a support structure such as a building or the like.

10. The fan assembly of claim 9 wherein the mounting bracket is integral with at least one casing half.

1 1. The fan assembly of any one of the preceding claims further comprising a ducted silencer comprising radially inner and outer silencer ducts, sound absorbing material being sandwiched therebetween, one end of the inner duct being dimensioned to be slidingly mounted on a boss of one of the casing halves of the fan assembly.

12. The fan assembly of claim 1 1 wherein the one end of the inner silencer duct has an end profile adapted to mate with the profile of the intermediate wall portion of the casing half.

13. A ventilation system comprising the axial fan assembly of any one of claims 1

14. An axial fan assembly according to any one of claims 1 to 12 and a fan comprising a fan impeller and a fan motor, the fan being housed within and mounted on the fan duct of the axial fan assembly.