GB2272049A

GB2272049A - Back-draught shutter

Info

Publication number: GB2272049A
Application number: GB9222978A
Authority: GB
Inventors: John Francis Watson
Original assignee: Individual
Current assignee: Individual
Priority date: 1992-11-03
Filing date: 1992-11-03
Publication date: 1994-05-04
Anticipated expiration: 2012-11-03
Also published as: GB2272049B; GB9222978D0

Abstract

For use with, or forming part of, a ventilation system for transfer of heat between outgoing stale air and incoming fresh air, a back-draught shutter comprises two dampers 12, 13 operatively linked with one another, damper 12 having at least one blade with an off centre pivot axis and damper 13 having at least one blade with a central pivot axis, the arrangement being such that in use and under normal external atmospheric pressure the damper 12 opens causing the damper 13 to open, and under abnormal external atmospheric pressure, the damper 12 closes causing damper 13 to close preventing an increased airflow through the supply duct into the building. The shutter may be positioned upstream or downstream of the fans of the ventilation system. The dampers 12, 13 may be linked by a rod 17 or gearing, or damper-driving motors may be electrically linked. The damper blades are provided with gaskets 19, and are made of an alloy or plastics. <IMAGE>

Description

BACK-DRAUGHT SHUTZTER Field of the Invention The invention relates to a back-draught shutter for balanced ventilation systems.

Background to the Invention Balanced ventilation systems are used widely in a variety of environments, for example, offices, kitchens and living rooms. They are frequently installed in high rise buildings where opening a window to ventilate a room can be impractical because of the air turbulence which causes disarray in the room.

A balanced ventilation system is an environmentally favoured method of recirculating and cleaning air. The stale air from the room is passed through a filter and over a heat-exchanger where absorption of heat from the stale air occurs. The stale air then passes into the atmosphere. Fresh air is drawn into the ventilation system and passes over the heat exchanger and filter. Warm fresh air is then pumped into the room.

The advantages of this system include a saving of energy, prevention of excessive condensation build up within the building and the separate treatment of the stale and fresh air to prevent cross-contamination. Such a balanced ventilation system is exemplified in the units supplied by Advanced Design and Manufacture Limited, Aylsham Industrial Estate, Brighouse Road, Low Moor, Bradford BD12 ONQ.

The first sheet of the accompanying drawings shows a series of diagrammatic sketches, labelled collectively "technological background", which illustrate various forms of balanced ventilation system in practical embodiments. The two units shown in "exploded" detail are in fact the units from the range just referred to and manufactured by Advanced Design and Manufacture Limited under the trade mark INDUX They are not to be taken as necessarily limiting the scope of the invention which now follows, nor as being in every way typical of or summarising across-the-board the state of the art. But they do represent valid illustrative examples of the background to the invention.

When a balanced ventilation system is installed a back-draught shutter is fitted when necessary. The function of this shutter is to prevent the ingress of, for example, wind, rain and debris from the atmosphere through the ventilation system. Although the shutter functions adequately, the problem of it being forced open by a strong wind remalns present. This is especially true in, for instance, a high-rise building.

The applicant has sought to overcome this problem by providing an improved shutter system for use in, or forming part of, a balanced ventilation system where respective air supply and exhaust ducts are sufficiently adjacently situated that corresponding first and second dampers for the ducts can have their opening and closing movements operatively linked.

Summary of the Invention According to the invention in its broadest aspect there is provided a backdraught shutter for use in, or forming part of, a balanced ventilation system and comprising at least two dampers operatively linked; a first damper having a pivot point off centre and a second damper having a central pivot point; the two pivot points being so spaced that in use, and under normal atmospheric pressure, the first damper opens causing the second damper to open and characterised in that under conditions of abnormal atmospheric pressure the first damper closes substantially and the second damper is held substantially rigid.

Preferably the dampers are operatively linked by a mechanical arrangement.

An electrically linked arrangement (e.g separate damper-driving motors suitably programme-linked) could be used but in the kind of conditions envisaged for this shutter system the inherent strength and relatively maintenance-free reliability of a straightforward mechanical system is preferably preferred.

The back-draught shutter may have at least one damper of a single blade configuration; alternatively at least one damper is of a multi-blade configuration.

Brief Description of the Drawings The 'Technological Background" sheet is as described above; Figure 1 is a perspective view of the rear of the back-draught shutter assembly; and Figure 2 is a side cut away view of the embodiment of Figure 1.

Description of the Preferred Embodiment As shown in Figure 1, the back-draught shutter comprises a basic support plate 11, a first damper 12 and a second damper 13. Mounted on each damper are respective clamps 14 each pair of which secures an associated square drive shaft 15 having round ends. Mounted on the rounded end of each drive shaft 15 is a nylon push-in bearing 16. As shown most clearly in Figure 1, one drive shaft 15 is mounted off centre of the first damper 12. The other drive shaft 15 on the second damper 13 is mounted centrally.

The drive shafts 15 are connected by a mechanical linkage most clearly shown in Figure 2, a rod 17 being connected to each drive shaft by arms 18. The actual shape and sizing of the dampers 12 and 13, and the mechanical linkage 17, 18, can be selected readily by the intended skilled addressee of this specification. Some examples of materials are given later on in this text but, again, these are not to be take as unduly restrictive of the scope of the invention.

In use, the back-draught shutter is mounted on an external wall with the linkage mechanism facing internally and aligning with the balanced ventilation system. The first damper 12 is sited opposite the exhaust fan and the second damper 13 is aligned opposite the fan bringing in fresh air from the atmosphere.

The mode of operation of the back-draught shutter 10 is as follows. When the exhaust and supply fans are switched off, both dampers 12 and 13 are in a closed position. The atmospheric pressure in the building will maintain the dampers in a closed position thus prevent the ingress of air into the building.

When the ventilation system is running, the pressure exerted by the exhaust fan will open the first damper 12. The damper 12 pivoting at a point off centre, will cause rod 17 to rise and open the second damper 13. Under conditions of wind pressure on the building, the first damper 12 will partially or fully close and simultaneously the position of the second damper 13 will close preventing an increase of air through the supply duct into the building.

Gaskets 19 are fitted to each damper to prevent air leakage when shut and eliminate excessive noise under wind pressure. The linkage mechanism shown could with advantage have an alloy rod 17 but the rod 17 can be of any suitable material, for example wire, and the damper blade made from alloy sheet. The back-draught shutter can have any of its components made from an appropriate plastics material or from a plastics/non-plastics combination.

A geared common centre drive mechanism could be fitted, instead of the linkage shown, to effectively direct-couple the shutter.

Amongst the advantages of this system are firstly that it requires no electrical components being a mechanical device. The back-draught shutter acts as a shut-off damper for both exhaust and supply ducts when the fans are not running. Thirdly, the unit permits operation of the fans during high winds when the routine practice is to turn off the fans to prevent the ingress of air into the building. The cost of the unit is relatively low when compared with electrically driven damper systems and it follows from this that the maintenance costs will also be reduced.

This unit will obviate the need for e.g. tenants in high rise buildings to have access to turn off the fans which is often currently the case. The disadvantage of tenants having such access is the build up of condensation within the building which causes mould growth and damage to the building itself when the fans are voluntarily shut rather than incur the results of the strong winds in conventional systems The siting of the unit can be either upstream or downstream of the fans and so provides flexibility in installation. The unit can of course be used in any situation of an air movement system where the exhaust and supply ducts are sufficiently adjacent each other.

Claims

1. A back-draught shutter for use in, or forming part of, a balanced ventilation system and comprising a at least two dampers operatively linked; a first damper having a pivot point off centre and a second damper having a central pivot point; the two pivot points being so spaced that in use, and under normal atmospheric pressure, the first damper opens causing the second damper to open and characterized in that under conditions of abnormal atmospheric pressure the first damper closes substantially and the second damper is held substantially rigid.

2. A back-draught shutter according to Claim 1 wherein said first and second dampers are operatively linked by a mechanical arrangement.

3. A back-draught shutter according to Claim 2 wherein the mechanical arrangement comprises a rigid control rod of pre-determined length linked as a first end to said first off-centre pivot point and at a second end to said second central pivot point.

4. A back-draught shutter according to Claim 2 wherein the mechanical arrangement comprises a conventional gearing system.

5. A back-draught shutter according to Claim 2 wherein the mechanical arrangement comprises a conventional cam system.

6. A back-draught shutter according to any preceding Claim wherein at least one of said dampers comprises a single blade configuration.

7. A back-draught shutter according to Claims 1 to 6 wherein at least one of said dampers comprises a multi-blade configuration.

8. A back-draught shutter according to Claim 1 wherein said dampers are provided with electrical means for controlling the operation of same.

9. A back-draught shutter according to Claim 8 wherein said electrical means comprises separate damper driving motors.

10. A back-draught shutter according to Claim 9 wherein said motors are suitably programme-linked so as to operate in accordance with Claim 1.

11. A back-draught shutter according to any preceding Claim wherein at least one of said dampers is provided with gasket means to ensure secure closing of the relevant damper.