GB2436866A

GB2436866A - Offset Fan Unit

Info

Publication number: GB2436866A
Application number: GB0606690A
Authority: GB
Inventors: Anthony Lawrence Croke; Paul Nicholas Kearsley
Original assignee: Greenwood Air Management Ltd
Current assignee: Greenwood Air Management Ltd
Priority date: 2006-04-03
Filing date: 2006-04-03
Publication date: 2007-10-10
Also published as: GB0606690D0; WO2007113552A1; EP2024687A1

Abstract

An in-duct fan unit comprising a housing 11 fitted in the duct, a spacing member 12 on the radially outer surface of the housing which offsets the housing within the duct (note different thickness of walls 8 and 9). The spacing member may be a single or a plurality of annuluses 3 around the housing or a series of extending ribs 12. The duct may contain a cylindrical housing, which is positioned to be non-coxial with the duct.

Description

2436866

Fan unit

The invention relates to a fan unit for mounting in a duct, either in a wall or in 5 a ceiling. The invention is particularly applicable to reduced noise or "silent" fans or to fans with the impeller mounted at the front.

In-duct axial extractor fans are commonly found around the home in kitchens and bathrooms. They are generally either fitted when the house is built or they can be installed later as part of D1Y projects or when replacing existing units. 10 In-duct fans are fitted into a duct which is fitted into a hole in the wall or ceiling. In wall mounted duct fans, the duct leads through the hole in the wall, usually to the outside for venting the extracted air. Ceiling mounted duct fans are mounted in a hole in the ceiling and a duct (usually flexible duct) carries the air to an outside vent.

When installing a fan, electrical power has to be supplied to the fan motor 15 from the building mains ring. In wall mounted fans, a power supply cable will be routed along the wall to the fan, so that the supply cable ends up in front of the fan unit, i.e. on the inside of the room which is being vented. Ceiling mounted fans will normally be supplied with power from behind as it is easier to route wiring through the ceiling or roof.

20 In some cases however it is not possible to make the electrical connection on the most convenient side of the fan. For example, the motor may be positioned at the back of a wall mounted fan, or the connection may have to be made to the front of a ceiling mounted fan.

One such case is in the use of silent fans. Silent fans have the impeller at the 25 front of the fan to provide sound proofing against noise from the motor which is positioned towards the back of the fan. If such a silent fan is to be mounted in a wall duct, the electrical connection will have to be passed from the front, past the impeller to the motor at the back.

There is usually not enough space for the cable between the inside of the duct 30 and the outside of the fan housing, so if the cable is routed along the outside of the housing, it will snag and tear against the duct. Instead the cable has previously been routed along the inside of the fan housing, but in this case it must be held in place with caps and it must be shielded from the moisture in the fan (although the electrical cables themselves are insulated, the cable as a whole serves to channel condensation

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straight to the motor). Another disadvantage of routing the cable inside the housing is that it blocks a small amount of air space which reduces the efficiency of the fan.

Also the cable must still be taken up outside the housing just before the impeller and so there is still a small section of cable which may snag on the duct.

5 According to the present invention, there is provided an in-duct type fan unit comprising a housing which in use is fitted into a duct, and a spacing member on the radially outer surface of the housing which in use radially offsets the housing within the duct.

Viewed from another aspect of the invention, there is provided an in-duct type 10 fan unit comprising a circular cylindrical housing which in use is fitted into a duct, and a spacing member formed on the radially outer surface of the housing, wherein in use the spacing member causes the housing to be non-coaxial with the duct.

By offsetting the fan housing within the duct, more space is created on one side of the housing, providing enough space for wires or cables to be routed from one 15 end of the fan to the other.

In its simplest form, the spacing member could be a single projection or a plurality of projections extending from a single or a plurality of points on the housing. However preferably the spacing member comprises an annulus around the housing. By forming the spacing member generally into the shape of an annulus, the housing 20 can be supported along more of its circumference, i.e. the fan unit fits more snugly into the duct. A single annulus could be used if it was sufficiently wide to support the fan with its axis parallel to that of the duct. However, preferably the spacing member comprises a plurality of annuluses around the housing. This allows the annuluses to be formed with a small width at a plurality of positions along the length of the 25 housing, thereby reducing the weight and the amount of material in the fan unit.

In a preferred embodiment, the or each annulus has a circumferentially varying radial thickness. Thus the radial thickness is large on the side of the housing where e.g. the wires are to be routed, but small on the opposite side where the housing is to be in close proximity to the duct.

30 The duct could be of any cross-sectional shape, however normally it is circular. Also the housing for the fan is normally circular as the fan impeller sweeps out a circle as it rotates and the housing closely matches this for better efficiency. Therefore preferably the or each annulus is in the form of a circle around the housing and the housing has a circular cross-section, the centre of which is offset relative to

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the centre of the or each annulus. With this arrangement, the circle formed by the outer edge of the annuluses can be formed to fit snugly within the duct, minimising movement of the fan unit within the duct.

Preferably the spacing member comprises an axially extending rib. More 5 preferably the spacing member comprises two axially extending ribs forming a channel therebetween. By providing axially extending ribs, the axis of the housing of the fan is kept substantially parallel with the axis of the duct which gives a better airflow. Two ribs are more stable than one rib and by providing a channel between them, they can form a protective conduit for wires and cables to be passed along. 10 Having ribs projecting out to the duct along the whole length of the wires and cables gives better protection for them, preventing them from snagging and tearing on the duct.

Whether or not ribs are used, the spacing member may define an axially extending channel in a radial space between the radially outer portion of the housing 15 and a radially outer portion of the spacing member. The radial space is created by the offsetting of the housing.

Preferably the axially extending ribs and/or the channel extend to one axial end of the housing. Thus in use the wires can lie flat along the length of the channel and out of the end where they can connect with the mains supply or external controls 20 without interfering at all with the duct. Also a hole is preferably formed through the housing at one end of the channel so that the wires can be directed into the main housing cavity and connected to the fan motor.

The spacing member could be a separate member, but preferably it is formed integrally with the housing. The spacing member can then be formed by the same 25 moulding process that forms the housing.

An axial fan may be housed in the housing of the fan unit and the fan may comprise a motor and an impeller mounted on the motor. The fan may be either an inner rotor motor with the impeller mounted on the axle of the inner rotor or it may be an outer rotor motor with the impeller being formed on the outer rotor. Preferably 30 the fan is mounted in vibation damping manner within the housing and preferably the impeller is arranged at the front end of the fan (facing into the room which is to be vented) with the motor mounted behind the fan. In the preferred embodiments a printed circuit board (PCB) is provided behind the motor which receives the external

power supply and transfers power to the motor. The PCB may comprise further logic circuitry for controlling the operation of the fan.

With the above arrangement, the wiring needs to be passed from the connection at the front (impeller) of the fan housing to the back (PCB) of the fan housing. Therefore, preferably the hole is formed in the end of the channel closest to the back of the fan and preferably the front end of the channel is open to provide access to the channel for the wiring from the front.

Preferably the fan unit is mounted in a substantially horizontal duct such that the housing is offset upwardly with respect to the duct.

A preferred embodiment of the invention will now be described by way of example only and with reference to the accompanying drawings in which:

Figure 1 shows a fan unit according to an embodiment of the invention; and Figure 2 shows an end view of the fan unit of Figure 1.

Figure 1 shows a fan unit 1 comprising an outer housing 10 which is generally cylindrical and which has an internal cavity formed through the centre which is generally circular in cross-section. The fan unit is made to fit into ducts of specific sizes. Common sizes which are in use for extractor fans in kitchens or bathrooms or as part of air conditioning systems are 100 mm, 125 mm or 150 mm in diameter.

Spacing members are provided on the outside of the outer housing 10 in the form of axially extending ribs 2 and annuluses 3. In this embodiment, the spacing members are integrally moulded with the housing 10. These spacing members serve to offset the central cavity of the housing 10 with respect to the duct when the fan unit 1 is inserted into the duct.

As can be seen more clearly in Figure 2, when viewed axially, the annuluses 3 form a circle around the housing 10 which has a larger diameter than the diameter of the housing 10. The diameter of the annuluses is chosen so as to fit snugly into the duct. The annuluses are also formed so that the housing 10 is radially offset relative to the duct when in use. In other words, the circle formed by the outside of the housing 10 is radially offset relative to the circle formed by the outside of the annuluses. The annuluses have a circumferentially varying radial thickness so that a thick part 8 is formed on one side of the housing 10 where a space is to be created and a thin part 9 is formed on the opposite side of the housing 10 where the housing is in close proximity to the duct.

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Two axially extending ribs 2 are also formed on the outer surface of the housing 10. These serve as separating members for offsetting the housing 10 relative to the duct when the housing is inserted into the duct. The ribs 2 also serve to form a channel 4 between them. The annuluses 3 are broken in the region of the channel, i.e.

5 between the ribs 2, so that no part of the channel is raised above the level of the outer surface of the housing 10.

The channel is open at one end 5. This end allows power supply wires from the mains ring to access the channel. Also wiring from controls which affect the operation of the fan can access the channel here. Such controls may include timing 10 switches or airflow sensors or humidity sensors.

At the other end of the channel, a hole 6 is formed through the outer housing 10 so that wires which have passed along the channel can access the motor and/or control circuits of the fan which are located inside the housing 10.

In use, the power supply cables are wrapped in a heat shrink wrapper to hold 15 them together. Then they are laid along the channel 4 and through the hole 6 where they can be connected to the motor and/or circuitry. Although not shown here, a protective conduit may be formed from the hole on the inside of the outer housing 10 to the motor/circuitry housing. This keeps the cables out of the path of moisture and prevents them from providing a route for water to ingress into the motor. 20 Figure 2 shows further structural details of the fan unit 1. The fan 7 is mounted inside an inner housing 11 which is separated from the outer housing 10 by radially extending air straighteners 12. The impeller of the fan 7 (not shown) has a diameter slightly smaller than the internal diameter of the outer housing for driving air through the space formed between the inner and outer housings, 11 and 10 25 respectively.

When the fan unit 1 is mounted in a horizontal duct, the channel 6 is preferably located at the bottom of the duct so that it does not form a basin for condensation to collect.

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Claims

1. An in-duct type fan unit comprising a housing which in use is fitted into a duct, and a spacing member on the radially outer surface of the housing which in use

5 radially offsets the housing within the duct.

2. A fan unit as claimed in claim 1, wherein the spacing member comprises an annulus around the housing.

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3. A fan unit as claimed in claim 2, wherein the spacing member comprises a plurality of annuluses around the housing.

4. A fan unit as claimed in claim 2 or 3, wherein the or each annulus has a circumferentially varying radial thickness.

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5. A fan unit as claimed in claim 2, 3 or 4, wherein the or each annulus is in the form of a circle around the housing and the housing has a circular cross-section, the centre of which is offset relative to the centre of the or each annulus.

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6. A fan unit as claimed in any preceding claim, wherein the spacing member comprises an axially extending rib.

7. A fan unit as claimed in claim 6, wherein the spacing member comprises two axially extending ribs forming a channel therebetween.

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8. A fan unit as claimed in claim 7, wherein the axially extending ribs and the channel extend to one axial end of the housing.

9. A fan unit as claimed in any of claims 1 to 5, wherein the spacing member 30 defines an axially extending channel in a radial space between the radially outer surface of the housing and a radially outer portion of the spacing member.

10. A fan unit as claimed in claim 7, 8 or 9, wherein a hole through the housing is formed at one end of the channel.

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11. A fan unit as claimed in any preceding claim, wherein the spacing member is integrally formed with the housing.

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12. A fan unit as claimed in any preceding claim, further comprising an axial fan housed in the housing.

13. A fan unit as claimed in claim 12, wherein the fan further comprises a motor and an impeller mounted on the motor.

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14. A fan unit as claimed in claim 13 and claim 10, wherein the impeller is provided at a front end of the housing and the hole is formed towards the rear of the housing.

15 15. A fan unit as claimed in any preceding claim mounted in a substantially horizontal duct, wherein the housing is offset upwardly with respect to the duct.

16. An in-duct type fan unit comprising a circular cylindrical housing which in use is fitted into a duct, and a spacing member formed on the radially outer surface of the

20 housing, wherein in use the spacing member causes the housing to be non-coaxial with the duct.

17. A fan unit substantially as hereinbefore described and with reference to the accompanying drawings.

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