GB2175349A - A cross flow fan - Google Patents

Abstract

A cross flow fan (2) comprising a housing (4), a cylindrical bladed rotor (6) supported for rotation in the housing (4), an air inlet (24) in the housing, an air outlet (26) in the housing, and ducting (52,54) for controlling the path of air through the fan, the ducting being flat and straight sided. <IMAGE>

Description

SPECIFICATION A cross flow fan This invention relates to a cross flow fan.

Cross flow fans are well known and they are also called tangential or vortex fans. The cross flow fans have been known for many years although they have not been widely used until relatively recent times. The cross flow fans comprise a housing, a cylindrical bladed rotor supported for rotation in the housing, an air inlet in the housing, and an air outlet in the housing. Ducting inside the housing controls the path of air through the fan.

The cross flow fans are used in many instances where heating, ventilation or other types of air movements are required over a long area which is occupied by the housing.

The cross flow fans provide good air flow and they avoid the need for employing a plurality of axial fans or centrifugal fans disposed side by side.

The known cross flow fans are such that the ducting is curved. This curved ducting has always been used and the curves on the ducting are widely thought to be the best manner of formulating the ducting. Depending upon the shape of the ducting, air can be introduced into and exhausted from the housing in an L-shaped manner, a U-shaped manner or an S-shaped manner. The known cross flow fans are thus often referred to as L-flow fans, U-flow fans and S-flow fans.

I have now surprisingly discovered that the cross flowfans can provide an increased performance if the ducting is straight sided instead of being curved.

Accordingly, this invention provides a cross flow fan comprising a housing, a cylindrical bladed rotor supported for rotation in the housing, an air inlet in the housing, an air outlet in the housing, and ducting for controling the path of air through the fan, the ducting being flat and straight sided.

The ducting may be made from flat folded sheet metal. The folding of the sheet metal is preferred to welding together flat pieces of sheet metal because the welds joining separate pieces of flat sheet metal together may tend to give rise to noise generation.

Preferably, the ducting is constituted by two separate spaced apart pieces of folded sheet metal.

One piece of the folded sheet metal may have one fold in it, and the other piece of folded sheet metal may have two folds in it.

The piece of the folded sheet metal that has one fold in it preferably extends down a wall of the housing remote from the air inlet to approximately one half of the width from the said wall.

Usually, the cross flow fan will include a filter. A filter is especially desirable where the fans are working in a dirty air atmosphere, for example as often occurs in factories.

Advantageously, the filter is such that it extends over three walls of the housing. The filter will then be approximately twice the size of existing filters in known cross flow fans of a similar size.

With the filter extending over three walls of the housing, the cross flow fan may be such that there is no ducting over approximately that half of the housing that receives inlet air so that the ducting is only present in that half of the housing in which the air is being directed out of the housing.

The combination of the ducting having the flat and straight sides and the larger than usual filter gives a cross flow fan that has a good improved performance, for example of the order of 5% or more, over existing known fans of similar size.

An embodiment of the invention will now be described solely by way of example and with reference to the accompanying drawings in which: Figure 1 is a perspective view of a known cross flow fan in giving an L-shaped flow; Figure 2 is a perspective view of another known cross flow fan giving a U-shaped flow; Figure 3 shows somewhat schematically a cross section through the fan shown in Figure 1 and illustrates the L-shaped flow; Figure 4 is a somewhat schematic cross section through the fan shown in Figure 2 and illustrates the U-shaped flow; Figure 5 is a somewhat schematic cross section through a further known cross flow fan and illustrates a S-shaped flow; and Figure 6 is a cross section through a cross flow fan in accordance with the present invention.

Referring to Figure 1, there is shown a known cross flow fan 2 comprising a housing 4 and a cylindrical bladed rotor 6. The rotor 6 has forward curved blades 8 and the blades 8 are separated by strengthening discs 10. The end discs 10 can be provided with stub axles which run in appropriate recesses in end walls 12 of the housing 4. Alternatively, the rotor 6 may rotate about a long shaft (not shown) which passes through the centre of the rotor 6 and is supported by the end walls 12. The fan is rotated by an electric motor 14 and the motor 14 usually has a capacitor 16. The fan 2 can be mounted by means of a pair of Lshaped brackets 18,20. The brackets 18,20 are provided with mounting holes 22 as shown for the bracket 18 in Figure 1.The fan 2 shown in Figure 1 has an air inlet 24 at its top in the position shown in Figure 1, although of course the fan 2 can be mounted at any desired angle. The fan 2 also has an air outlet 26 as shown so that the air flow through the fan 2 is L-shaped as indicated by the arrows 28,30.

Referring now to Figure 2, similar parts as in Figure 1 have been given the same refer ence numerals and their precise construction and operation will not again be given. In Figure 2, it will be seen that the flow of air through the fan 2 is U-shaped.

Referring to Figure 3, the passage of air through the fan 2 is clearly shown as Lshaped.

Referring to Figure 4, the passage of air through the fan 2 is clearly shown as Ushaped. In Figure 4, it will be seen that the housing 4 includes a separator member 32 which separates the air inlet 24 from the air outlet 26.

Figure 5 shows a similar fan 2 in which the flow of air through the fan 2 is S-shaped as illustrated.

It will be noted from Figures 3,4 and 5 that the path of the air through the fan 2 is in each case controlled by ducting. More specifically, the ducting shown in Figure 3 is in two separate ducting parte 34,36. The ducting shown in Figure 5 is also in two separate ducting parts 38,40. In Figure 4, in order to get the U-shaped flow, the ducting is essentially in one ducting part 50. In each case, the ducting parts 34, 36; 38,40; 50 are all curved as illustrated and this curved type of ducting has always been used. It is assumed that the curved ducting was thought to facilitate the passage of air through the fan 2.

Referring now to Figure 6, similar parts as in the previous Figures have been given similar reference numerals for ease of illustration and understanding. Figure 6 shows a cross flow fan that essentially gives an L-shaped flow of air between the air inlet 24 and the air outlet 26. The ducting is in two ducting parts 52,54 and it will be noticed that the ducting part 52,54 are flat and straight sided. Each ducting part has been made from a separate piece of folded sheet metal. Thus, the ducting part 52 has two folds 56,58, and the ducting part 54 has one fold 60. I have surprisingly discovered that the performance of the fan 2 is increased with the flat straight sided ducting parts 52,54.

I have also surprisingly found that if the ducting part 54 does not extend around and under the rotor 6 as occurs with the ducting parts 36,50,40 as shown in Figures 3,4 and 5 respectively, then the performance of the fan 2 is again further increased. More specifically, stopping the ducting part 54 short affords the opportunity of installing a filter 62 over three sides 64,66,68 as shown of the housing 4. In other words, the air inlet 24 which in the known fans 2 illustrated in Figures 3,4 and 5 only extends over one housing wall comparable to the side 64 shown in Figure 6, now extends over a much larger area and over the three walls 64,66,68. This means that the air inlet 24 in Figure 6 is greatly enlarged and this facilitates the movement of air by the rotor 6.The action of the air in the fan 2 illustrated in Figure 6 can be as in any of theknown fans so that the air will pass through the blades 8 and into the centre of the rotor 6 and a vortex may in some cases be formed.

It will be seen that the filter 62, which may be a mesh filter, extends over approximately that half of the housing 4 that receives the inlet air so that ducting is only present in that half of the housing in which the air is being directed out of the housing 4 via the air outlet 26.

It is to be appreciated that the embodiment of the invention described above with reference to Figure 6 of the accompanying drawings has been-given by way of example only and that modifications may be effected. Thus, for example, the shape of the fan ducting may be altered to give a U-shaped flow of air through the fan 2 or to give an S-shaped flow of air through the fan 2. Generally, the ducting can be altered as desired providing that it is kept flat and straight sided. If desired, the flat sided straight sided ducting can be formed by welding but it is preferred just to bend sheet metal, e.g. aluminium or other appropriate desired material. The cross flow fans of the invention are preferably for use with convector heaters but they may also be used in other applications such for example as simple extractor fans, air extractors, cooker hoods, ventilators, and generally anywhere where a relatively long circulation of air is required.

Claims (9)

1. A cross flow fan comprising a housing, a cylindrical bladed rotor supported for rotation in the housing, an air inlet in the housing, an air outlet in the housing, and ducting for controlling the path of air through the fan, the ducting being flat and straight sided.

2. A cross flow fan according to claim 1 in which the ducting is made from flat folded sheet metal.

3. A cross flow fan according to claim 1 or claim 2 in which the ducting is constituted by two separate spaced apart pieces of folded sheet metal.

4. A cross flow fan according to claim 3 in which one piece of the folded sheet metal has one fold in it, and in which the other piece of folded sheet metal has two folds in it.

5. A cross flow fan according to claim 4 in which the piece of folded sheet metal that has one fold in it extends down a wail of the housing remote from the air inlet to approximately one half of the width of the said wall.

6. A cross flow fan according to any one of the preceding claims and including a filter.

7. A cross flow fan according to claim 6 in which the filter is such that it extends over three walls of the housing.

8. A cross flow fan according to claim 7 which is such that there is no ducting over approximately that half of the housing that receives inlet air so that the ducting is only present in that half of the housing in which the air is being directed out of the housing.

9. A cross flow fan according to claim 1 and substantially as herein described with reference to the accompanying drawings.