GB2340888A

GB2340888A - Twin fan with induced airflow

Info

Publication number: GB2340888A
Application number: GB9814685A
Authority: GB
Inventors: Wayne Glover
Original assignee: Nuaire Ltd
Current assignee: Nuaire Ltd
Priority date: 1998-07-07
Filing date: 1998-07-07
Publication date: 2000-03-01
Also published as: GB9814685D0

Abstract

A fan assembly comprises two fan units 10,12 having respective outlets 15,17 coupled to a common outlet duct 18. One fan is intended to lie dormant until a fault develops in the other unit. The interior volumes of the two fan units are in communication via their outlets such that when either fan unit is running, it induces a flow of air in the other fan unit towards the common duct. Dispenses with return prevention shutter on dormant fan.

Description

2340888 EXTRACTION FAV ASSEMBLY The present invention relates to

ventilation or extraction fans and more particularly to a twin fan assembly.

It is known to provide air extraction fans in the form of a twin fan assembly, which includes two fan units having respective impellers and electric drive motors and independent air inlets, but respective outlets which are coupled to a common outlet duct. Normally one of the units is driven and the other unit remains dormant, but if any fault develops in the first unit, then the second unit is switched on. The assembly includes a pivoted flap which swings over from a position in which it closes the air outlet of the second unit, to a position in which it closes the air outlet of the first unit.

We have now devised a twin fan assembly of simplified construction.

In accordance with the present invention, there is provided a fan assembly which comprises two fan units having respective air outlets coupled to a common outlet duct, the interior volumes of the two fan units being in communication via their outlets such that when either fan unit is running, it induces a forward flow of air through the other fan unit.

Thus, we have found, surprisingly and contrary to expectations, that if the interior volumes of the two fan units are arranged to communicate via their outlets, none of the air expelled by the active fan unit will pass back through the dormant fan unit, but instead a forward flow of air is induced through the dormant fan. This enables the outlet closure flap of the prior art to be dispensed with, so simplifying the construction and avoiding the noise which is usually emitted when the flap is moved abruptly from one closure position to the other.

The forward flow of air which is induced through the dormant fan unit will cause the impeller unit of that fan unit to turn in the forward direction. However, if the dormant fan unit is damaged such that its impeller is jammed against rotation, the induced forward flow of air will be maintained.

2 An embodiment of the present invention will now be described by way of example only and with reference to the accompanying drawings, in which:

FIGURE 1 is a schematic sectional view through a prior 5 art twin fan assembly; and FIGURE 2 is a similar sectional view through a twin fan assembly in accordance with the present invention.

Referring to Figure 1 of the drawings, there is shown a prior art twin fan assembly which comprises two fan units comprising respective impellers 10, 12 mounted within respective casings 14, 16. Each impeller 10, 12 has its own electric drive motor (not shown) at one end and air inlets are provided into each casing 14 or 16 at both its opposite ends. Each casing 14,16 has a tangential outlet 15,17, the two outlets being coupled into a common outlet duct 18. Adjacent wall portions of the outlets 15,17 of the two fan casings form a barrier between the interior volumes of the two fan units. A closure flap 20 is pivotally mounted and movable between one position in which it closes the outlet 15 of one fan unit and a second position in which is closes the outlet 17 of the other fan unit.

In use of the assembly shown in Figure 1, normally one of the impellers, say unit 12, is driven whilst the other remains dormant. The impeller 12 draws in air through its inlets, at the opposite ends of its casing 14, and expels the air through its outlet 15 and the common outlet duct 18. The closure flap 20 closes the outlet of the other or dormant fan unit, to prevent air passing out through the outlet of the active fan unit then back into the building through the dormant fan unit.

A fan assembly in accordance with the present invention is shown in Figure 2, like parts being given like reference numerals. In this assembly, the outlets 15,17 of the two fan units merge together, the common portions of their casing walls being shortened so that there is no significant barrier between the interior volumes of the two fan casings. Further, the closure flap of the prior art assembly of Figure 1 is dispensed with.

In the fan assembly of Figure 2, normally one of the 3 fan units is driven and the other is dormant. Thus, air is drawn into the active fan unit and expelled through its outlet and through the common outlet duct 18. Surprisingly, and contrary to expectations, none of the expelled air passes back through the dormant fan unit: instead, a f low of air is inducted in the forward direction through the dormant fan unit; normally this induced flow will turn the impeller itself, but if the fan unit is damaged and its impeller or motor is jammed, the induced flow of air will continue through that fan unit.

It will be appreciated that either fan unit can be energised, an induced flow of air being promoted through the other fan unit. The construction is simplified relative to the prior art fan assembly of Figure 1 particularly because the closure flap is dispensed with.

1 4 claims 1) A fan assembly which comprises two fan units having respective air outlets coupled to a common outlet duct, the interior volumes of the two fan units being in communication via their outlets such that when either fan unit is running, it induces a forward flow of air through the other fan unit.

2) A fan assembly as claimed in claim 1, in which the fan units have respective tangential outlets coupled to said common outlet duct.

3) A fan assembly as claimed in claim I- or 2, there being no movable closure flap for the outlet of either fan unit.

4) A fan assembly substantially as herein described with reference to the accompanying drawing.