AU656093B2 - Smoke spill ventilator - Google Patents

Description

AUSTRALIA

AUSTRALIA

Patents Act 1990 Name of Applicant AIR DESIGN (QLD) PTY LTD (ACN 010 185 958) Actual Inventor(s) Address for Service NEIL KENRIC BONE and FREDERICK CHARLES

GATTEGNO

ALBERT

GRANT ADAMS COMPANY Patent Trade Mark Attorneys Level 9 National Mutual Centre 144 Edward Street BRISBANE QLD 4000

AUSTRALIA

Invention Title 'SMOKE SPILL VENTILATOR' Details of Associated Provisional Applications Numbers PL5912 The following statement is a full description of the invention including the best method of performing it known to me.

THIS INVENTION relates to ventilators such as but not exclusively of the type which is used to exhaust smoke from a building.

Smoke spill, axial, roof mounted ventilators are well establi:shed products which are commonly produced to Australian Standards. These units can consist of a fabricated stieel base intended to mount on a roof kerbing; a fan tube with motor and axial impeller mounted therein; an outer wind band or shield thereover; and air operated damper flaps mounted over the impeller to close the fan tube. When the fan is not running, the flaps are normally closed so that there is no return path for air flow and so that water ingress is prevented. When the fan runs, the air flow which it 15 generates causes the flap to open and internal air can be driven from the building. Continuing development or evolution of building codes has required that greater volumes of air be able to be evacuated from buildings by the ventilators for smoke spill purposes. In a fire, 20 air temperatures at and passed through the ventilator can be high at around 200 0 C and the fans are preferably run by high temperature motors which, in being required to move large volumes of air, are relatively expensive.

With the above in mind, building designers are 25 faced with a significant capital cost to install high volume handling, roof ventilators that will only be run in the event of a fire. The fact that these units must exist prompts designers to seek to make some real use of them and the more general building ventilation requirements have been considered as an additional useful role for the smoke spill ventilators.

A particular characteristic of the fire relief fans of the above type is that they usually run at high speed so as to be able to pass significant volumes of smoke filled air. They are therefore inherently too t 3 noisy for normal ventilation purposes. The most cost efficient method by which to have these fans operate to effect general ventilation is to fit them with two speed motors with general ventilation effected at the lower speed. The cheapest and most common motor choice is one able to operate at half synchronous speed, for example, 4/8 pole or 6/12 pole motors.

The air operated flaps of the above described ventilators have thus far been constructed from appropriately strong galvabond material. They have been cheap, robust, and relatively heavy. They open with ease when faced with the higher air velocities used to spill smoke from a building. However, when the same unit is worked with the fan running at half speed, the flaps will tend to open and close, flap or chatter continuously, or not open at all. The units therefore need to be modified if use for general ventilation is to "be realised. Reducing weight leads to flaps which can S""open at the wrong time under wind loading on the oo: 20 building.

It is an object of the present invention to improve the operation of smoke spill ventilators and other like ventilators so as to suit them to general building ventilation purposes and other like purposes.

25 Other objects, and particular advantages, of the ventilators of the present invention will hereinafter become apparent.

The invention achieves its object in one S"particular aspect thereof in the provision of an axial roof ventilator comprising: an axial roof ventilator for use in the ventilation of a building or the like said axial roof ventilator comprising: a motor driven impeller for driving air through the ventilator; one or more flaps or baffles pivotally mounted across the impeller which flaps or baffles drop across an outlet from the ventilator, said flaps or baffles being structured to be held open by the air flow induced by the impeller; and flap or baffle control means for holding the flaps or baffles in their dropped position against wind pressure over the roof and operable to release said flaps or baffles at a predetermined air pressure so as to open the ventilator to flow of air under action of the impeller.

A relatively lightweight flap can be produced by attention to the construction parameters such as by utilising a material such as aluminium. By themselves, such lightweight flaps suffer the disadvantage that should the building become pressurised internally, such as under a wind load, the flaps might lift to open the ventilator at an inappropriate time. The introduction of the locking or hold down means provides for 20 positively holding a relatively lightweight flap closed *e under all the usual conditions which might cause it to otherwise open inappropriately whilst still permitting the flaps to open when the fan runs. There are a number ,00 of ways in which the locking or hold down means can be realised.

Preferably the locking, or hold down, means is c a positive closure device such as a fully encapsulated permanent magnet with selected temperature co-efficient, S"anisotropic alignment and controlled field direction, combined with a matched striker plate mounted on the flap or baffle. These characteristics enable the device to withstand the high temperatures experienced on metal roofs; ensure that the shock loads as flaps shut do not cause damage; and generally ensure that the device has a working life span commensurate with the ventilator. The 4A variations that are possible within these design parameters are known to those skilled in the relevant art and the design of a particular hold down to suit a set of operational parameters is readily achievable. To enable setting of a desired hold down force, where parameters might vary from unit to unit, the closure device might be adjustable, as by mounting the magnet in an adjustable saddle or by mounting the magnetic hold **0

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o S I down device to an adjustable bracket.

A further preferred development of the magnetic hold down means involves use of a magnetic hold down means whose hold down force is greater than what is desired, provided in conjunction with a reverse polarity, switchable, repulsive magnetic means, set to reduce the hold down force to release the flaps when desired. This can be achieved with an electromagnet, wired into the ventilator motor circuit, to be activated when the ventilator is switched on. By this means the lightweight flap is readily able to be released when desired.

The invention will now be described with reference to a preferred embodiment set out in the accompanying drawings, in which: FIG. 1 is a schematic section through a ventilator in accordance with the present invention; and FIG. 2 illustrates a form of locking or hold down device which might be used in the ventilator of FIG. 1.

The drawings are purely schematic to illustrate the operation of the invention and the }character of a hold down device. In practice the hold down device will be applicable to a wide range of V660 25 ventilators with differing geometries and appearances.

In FIG. i, the ventilator 10 has an electric motor 11 driving a fan or impeller 12 inside shroud or housing 13. Flaps or baffles 14 and 15 are mounted over the fan to close off the passage through shroud 13 when the flaps are in the position shown in dotted outline.

A shield 16 may be provided to screen the flaps 14 and from wind. The flaps 14 and 15 may be held down by respective locking or hold down means 17 and 18. These may be as in FIG% 2. As is usual with these ventilators, the motor may be supported on mounting brackets attached to the shroud or housing. The means of supporting the flaps or baffles for pivotal movement can be in any of the forms which are now common. The invention is not limited to any particular feature of the flaps, motor, fan, etc.

In FIG. 2, a hold down means 19 can comprise a permanent magnet in a housing 20 and it can be mounted to the shroud 13 for example on an adjustable saddle (described in greater detail below) by means of suitable connectors such as bolts through holes 23, or other like type connectors passed through a suitable flange thereto such as 22. The connector can attach to either the shroud 13 directly or an adjustable bracket thereon (not shown). Matched to the magnet 20 is a pole piece 21 15 mounted by suitable connectors such as nut and bolt sees to flap 24, said flap 24 being a flap or baffle such as 14 or 15 in FIG. 1. As the magnetic force between the magnet 20 and pole piece 21 reduces as their separation increases, the force being experienced by the flap 24 20 can be adjusted by adjusting the distance between the pole piece and the magnet when the flap is closed. This is readily effected by mounting the magnet to an intermediary which is vertically locatable up the side of shroud 13 of FIG. 1. Alternately the connectors 25 through holes 23 can be passed through vertical slots in **jthe mounting surface so that the height can be selected at will. The permanent magnet in housing 20 of FIG. 2 can be provided in a weatherproof body and its material is best selected for longevity and consistent performance. A suitable magnet might be fully encapsulated in a compatible material so as to achieve a long lasting construction. Thus a permanent magnet can be mounted in a stainless steel or aluminium housing.

This can be sealed to be waterproof. Mounting of the magnet inside such a housing might be designed to cushion the magnet against shock. Shock p2.jofing can be achieved by floating the magnet in its housing in a resilient filler such as silicone. The magnet can be provided on an adjustable saddle internally of its own housing and adjusted by a set screw or other like means.

An adjustable saddle can be a screw operated threaded plate supporting the magnet thereon internally of its housing. The set screws can be located beneath the unit so that its waterproofing is not compromised by the existence of its set screws. Alternate"y, the magnet housing might be attached to an adjustable mounting bracket. The temperatures which the magnet can be exposed to in practice can be considerable and the *.00 design of the hold down may have to take this into 15 consideration by appropriate choice of materials.

h"e In a typical installation, in accordance with the above invention, a 1400 mm diameter unit can be provided with a two speed 10/16 pole motor to pass 20,000 litres/second of air at high speed and 12,000 20 litres/second at low speed. Such a unit, built to standard, with galvabond flaps, will operate correctly at 20,000 1/s when the pressure on the flaps is adequate. However, when switched to the low speed, the flaps will commence to 'chatter'. Tests on such an V. 25 installation show that sufficient force can be generated at the slow speed to properly open a flap which is about 3.4 kg or less than the weight of the galvabond flap.

Construction of a lightweight flap in a material such as aluminium, for example, achieves this weight saving and such flaps work as required when the fan is operated at its low speed. With an installation of this latter type, a wind speed exceeding 20 km/hr can pressurise the building (when the fans were not running) sufficient to cause the flaps to open and close randomly and continuously.

In the above circumstance, a closure or hold down device need only produce a force equivalent to an extra three kg of weight in the panel or flap, at the full flap radius to produce acceptable operation and usefully duplicate the weight of the galvabond flap. In operation, the lightweight flaps will lift, when the fan runs, as do galvabond flaps, but once lifted, not having the galvabond weight, they remain open at the slow speed. The extra force of the magnet serves to resist pressure within the building when the fans do not run.

In some circumstances, the above described hold down device has limitations in that roof ventilators fitted with the magnetic lock or hold down may have to be operated first on high to cause release 15 and then on low such that a start up sequence 'Hi', pause 'Lo' may be necessary. It is possible to provide a means whereby the lightweight flaps can be activated reliably with a 'Lo' speed only start up.

A permanent magnet can be used as above to 20 hold the flaps closed. This can be coupled with a reverse polarity electromagnet, possibly of greater strength, that activates on start up of the fan to .,.reduce, negate, or reverse the magnetic force on the flap. Construction of such an electromagnet and its 25 controlling circuitry is well within the competence of a man skilled in the art, there being many different ways to achieve the general object. This electromagnet might be powered with a 240 V supply coming from the three phase tails to the motor. The complete assembly could be pre-wired, ex-factory, to a three phase isolator/terminal box. Alternately, for example, if a permanent magnet/electromagnet combination does not have appropriate parameters for a particular application, then a mechanical or electro-mechanical latching device might be developed with release being effected by a solenoid activated on powering on (start up).

It will be clear from the above that what the invention proposes to be done can be applied to any of the existing types of smoke spill ventilators and their construction is not critical to realising the present invention. The invention is achieved in provision of a locking or hold down means to the flap or baffle of a smoke spill vertilator, or the like, said means releasing when a particular condition exists. The characteristics of a flap and their performance will depend on customer needs, points of pivot, wind loadings in the area of operation, flap design which sets the centre of gravity and other related factors which interrelate with design spill requirements to determine what 15 the flap does in any particular circumstance. Whatever the design, parameters can be optimised with application of a hold down of the type set out herein and set forth in the appended claims.

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Claims (7)

1. An axial roof ventilator for use in the ventilation of a building or the like said axial roof ventilator comprising: a motor driven impeller for driving air through the ventilator; one or more flaps or baffles pivotally mounted across the impeller which flaps or baffles drop across an outlet from the ventilator, said flaps or baffles being structured to be held open by the air flow induced by the impeller; and flap or baffle control means for holding the flaps or baffles in their dropped position against wind pressure over the roof and operable to release said flaps or baffles at a predetermined air pressure so as to open the ventilator to flow of air under action of .the impeller. o2. An axial roof ventilator as claimed in claim 1 20 wherein the flap control means is a magnetic latch using 20 a magnetic field applied to a flap or baffle to effect .latching, the strength of the magnetic field setting the predetermined air pressure at which the flaps or baffles are released.

3. An axial roof ventilator as claimed in claim 2 25 wherein the magnetic latch comprises a permanent magnet *mounted to the ventilator and a pole piece or striker o: plate mounted to the flap or baffle.

4. An axial roof ventilator as claimed in claim 3 wherein the permanent magnet is adjustably mounted relative to the pole piece or striker plate whereby the distance to the striker plate is adjustable. An axial roof ventilator as claimed in any one of claims 1 to 4 wherein the one or more flaps or baffles are each a lightweight construction in a material such as aluminium tailored to lift at a 11 predetermined air pressure.

6. An axial roof ventilator as claimed in claim wherein the impeller is mounted coaxially with a vertically oriented shroud and designed to overcome the flap control means at a certain speed.

7. An axial roof ventilator as claimed in any one of claims 1 to 6 wherein an electromagnetic field is switched on to overcome the action of a magnetic latch as the flap control means and release the flaps or baffles at the predetermined air pressure.

8. An axial roof ventilator as claimed in claim 7 wherein the electromagnetic field is generatec. by a solenoid wired into the power supply leads to the motor driven impeller.

9. An axial roof ventilator as claimed in any one of the preceding claims wherein the motor to the I impeller is a two speed motor, the high speed being sufficient to open the flaps and the low speed sufficient to maintain them open. 20 10. An axial roof ventilator substantially as hereinbefore described with reference to the accompanying drawings. DATED this Fifteenth day of September 1994. S" AIR DESIGN (QLD) PTY LTD S" 25 (ACN 010 185 958) By its Patent Attorneys GRANT ADAMS COMPANY 4 I I 12 ABSTRACT 'SMOKE SPILL VENTILATOR' A smoke spill ventilator is operable to effect general building ventilation with flaps (14, designed to remain open at low motor (11) speeds fitted with flap closures (17, 18) to hold the flaps down when the impeller (12) is not operated. The flap closure (17, 18) can be adjustably mounted magnetic devices with a magnet (20) opposed to a striker plate (21) on a flap (24). fee. S S S I•