GB2561776A

GB2561776A - Weatherproof fan grill

Info

Publication number: GB2561776A
Application number: GB1811622.8A
Authority: GB
Inventors: Chabin Philippe; De La Ville Montbazon Guillaume
Original assignee: Electricite de France SA
Current assignee: Electricite de France SA
Priority date: 2015-12-15
Filing date: 2016-12-07
Publication date: 2018-10-24
Anticipated expiration: 2036-12-07
Also published as: WO2017102480A1; FR3045138A1; GB201811622D0; JP6936227B2; CN108700331B; CN108700331A; GB2561776B; FR3045138B1; JP2018537648A

Abstract

The present invention relates to a weatherproof fan grill comprising a series of rigid bars (100) generally parallel to one another and not vertical, having a first generally vertical leading edge (110) intended to be directed towards the outside, and two auxiliary faces which converge at a distance from the main face (110), defining, between two adjacent bars (100), a channel diverging from the outside to the inside and a series of deflecting fins (200) connected respectively to the base of the main face (110) of each bar (100), the fins (200) being inclined towards the outside with respect to the main face (110) with an inclination and a height such that the free edge (210) of one fin (200) is at least on the same horizontal line as the upper edge (112) of the main face (110) of the underlying bar (100), or even overlaps said main face (110), in such a way that the fins (200) form a deflector and have a specific height that is greater than the distance separating the lower edge of the main face (110) from a bar (100) and the upper edge of the main face (110) from the underlying bar (100).

Description

(56) Documents Cited:

GB 2482129 A DE 007534836 U (58) Field of Search:

E06B7/08 (2006.01)

GB 2411716 A US 20030050006 A1 (86) International Application Data:

PCT/EP2016/079997 Fr 07.12.2016

INT CL E06B, F24F

Other: EPO - Internal, WPI Data (87) International Publication Data:

WO2017/102480 Fr 22.06.2017 (71) Applicant(s):

Electricite De France (Incorporated in France)

22-30 avenue de Wagram, 75008 Paris,

France (including Overseas Departments and Territori es) (72) Inventor(s):

Philippe Chabin

Guillaume De La Ville Montbazon (74) Agent and/or Address for Service:

Carpmaels & Ransford LLP

One Southampton Row, London, WC1B 5HA,

United Kingdom (54) Title ofthe Invention: Weatherproof fan grill Abstract Title: Weatherproof fan grill (57) The present invention relates to a weatherproof fan grill comprising a series of rigid bars (100) generally parallel to one another and not vertical, having a first generally vertical leading edge (110) intended to be directed towards the outside, and two auxiliary faces which converge at a distance from the main face (110), defining, between two adjacent bars (100), a channel diverging from the outside to the inside and a series of deflecting fins (200) connected respectively to the base ofthe main face (110) of each bar (100), the fins (200) being inclined towards the outside with respect to the main face (110) with an inclination and a height such that the free edge (210) of one fin (200) is at least on the same horizontal line as the upper edge (112) of the main face (110) of the underlying bar (100), or even overlaps said main face (110), in such a way that the fins (200) form a deflector and have a specific height that is greater than the distance separating the lower edge ofthe main face (110) from a bar (100) and the upper edge ofthe main face (110) from the underlying bar (100).

FIG. 16

1/8

FIG. 1 Prior art

2/8

FIG. 2

3/8

FIG. 3 FIG. 4 FIG. 5

4/8

Loss of load of the grill in normal operation

FIG. 10

Residual pressure after the grill subject to explosion according to angle of incidence Ot

Residual pressure (Pa)

1100

1080

1060

1040

1020

1000

980

960

940

920

900

Ί-1-1-1-Γ

20 30 40 50

T

Angle a (°) “I

5/8

Load loss of grill in normal operation according to angle of incidence (X (grill used in air extraction)

Behavior of grill relative to explosion as a function of spacing between bars

FIG. 12

Residual pressure after grill (p_a)

100

7/8

FIG. 16

8/8

FIG. 17 FIG. 18

o

CM o

o

Weatherproof fan grill

TECHNICAL FIELD

The present invention relates to the field of ventilation grills.

Ventilation grills are designed to allow ventilation of equipment, by extraction or blowing of air, and protect equipment from bad weather, risk of entry by animals and/or projectiles, as well as overpressure or depression waves.

PRIOR. ART AND TECHNICAL PROBLEM POSED

In particular, but non-limiting, buildings of installations subjected to high safety demands, such as for example production sites in the chemical or petrochemical industry, or nuclear production sites must be protected from multiple potential external attacks, and especially the following risks:

meteorological (rain, ice, frost, wind, hail, high winds...), entry by projectiles or animals (birds, especially) into ventilation ducts, pressure waves, for example sudden overpressure due to the blast of an external explosion or even depression caused by tornados/hurricanes or similar.

If the external walls of buildings constitute effective fortification against current attacks subject to adequate sizing, the openings made in these walls such as windows, but more specially openings taking up the end of ventilation ducts, are directly exposed to said attacks and need specific sizing.

In fact and non-limiting:

- ingress by fluids, typically rain in the liquid state or hail in the solid state, can cause a range of damage such as for example corrosion of circuits,

- by partially or fully obstructing openings, ice can substantially lower the efficiency of a ventilation system due to load losses especially,

- a overpressure wave can cause damage to internal circuits and to ventilation units, as well as to all equipment housed in a building,

- the depression wave of a tornado can cause effects similar to an overpressure wave.

In both latter cases, the movements of relevant fluids, air or other gases, can transport projectiles likely to cause severe damage.

The first function of ventilation systems is to ensure heat conditioning of premises, as a normal operation. Secondly, these systems must carry out renewal of air in the premises by circulation of this air in a set of distribution circuits. These two functions are in particular sureties of proper operation of equipment and accordingly contribute to safety, in particular for a nuclear production site, then to a lesser extent the comfort of personnel, or even its integrity.

Devices designed to contribute a parry to external attacks described hereinabove must not degrade the main functions of the system.

Many types of ventilation grills have already been proposed, but none is completely satisfactory.

To treat problems of rain, entry by animals and ice, vent systems can be put in place, arranged uniformly and sized and oriented so that rain does not penetrate the inner space of the building to be protected. If possible, moving vents away is configured so that birds do not enter the inner space. The outer dimensions of the device are generally defined such that even in the presence of partial blockage of the device by ice, the required air flow is ensured.

However vent systems do not offer effective protection against high-speed projectiles and therefore considerable kinetic energy.

It has therefore been proposed to sometimes replace the vents by more rigid bars.

This solution gives effective protection against projectiles having strong kinetic energy. Adopting an appropriate arrangement of bars even makes it possible to protect against the intrusion by animals, and the risk of ice gel.

It is also possible to orient the profile of the bars so as to limit the ingress of rain.

Yet, due to their shape, bars proposed to date disrupt flow and create considerable load loss, degrading airflow as normal operation.

The following attempts at a solution can also be cited:

. adding buffer fortification in front of the air input grills of ventilation systems to protect from tornados in this respect, though this solution has a high cost and fails to resolve the problem of external explosion.

. implanting motorized dampers for fast blocking of ventilation networks, controlled by differential pressure transmitters. This solution is very expensive and is based on active equipment. Also, resistance of this equipment to PGEW (Projectiles Generated by Extreme Wind) projectiles and tornados is not possible.

In conclusion, to date no solution has effectively resolved all problems posed and in particular offers mechanical effective protection relative to all projectiles and ensures reliable protection with respect to rapid variations in external pressure.

In fact, devices proposed to date only slightly mitigate fluctuations in pressure likely to originate for example from explosions or hurricanes.

To date, designers of ventilation systems therefore have had no other choice than to multiply the amount of equipment and installation configurations in the region of interfaces to be protected.

As a consequence, in practice protection devices of the type illustrated in the attached figure 1 are often used these days, comprising a complex stack of stages for ward off all external attacks: an external stage formed by rain-guard grills 10, also preventing the ingress of birds, a stage formed by steel bars 12 intended to prevent the ingress of projectiles, an antifrost stage 14, a stage 16 formed by anti-explosion flaps constituted by fast-close flaps, then an anti-tornado isolation damper 18 stage connected to a ventilation duct.

However such devices are complex to manufacture and have many disadvantages:

. They are expensive, . They generate considerable load losses generally requiring oversizing of some elements of the ventilation circuit, and . Their efficacy is not always demonstrated, in particular for antiexplosion flaps.

Document DE 7534836 describes an example of weatherproof ventilation grill comprising rigid bars and deflecting fins.

In short, today there is no simple device for effectively countering all possible attacks.

BASIS OF THE INVENTION

In this context, the aim of the present invention especially is to propose a novel ventilation grill which:

- eases airflow in normal operating conditions,

- disperses an incidental pressure front,

- limits the rise in pressure in the inner space.

The above aim is attained according to the invention by way of a weatherproof ventilation grill comprising:

- a series of rigid bars overall parallel to each other and non-vertical, having a first leading edge directed towards a first side of the grill intended to be directed to the outside, overall parallel to the mean plane of the grill and intended to be overall vertical to use, and two auxiliary faces which converge in moving away from the main face, defining between two adjacent bars a channel diverging from the first side intended to be directed to the outside in the direction of the second side of the grill intended to be directed towards the inside, and

- a series of deflecting fins attached respectively to the base of the main face of each bar, the fins being inclined towards the first side intended to be directed to the outside, relative to the main face, according to inclination and height such that the free edge of a fin is at least on the same line as a projection orthogonal to the mean plane of the grill on the upper edge of the main face of the underlying bar, or even straddles this main face, such that the fins form a deflector and have a specific height greater than the distance separating the lower edge of the main face from a bar and the upper edge of the main face from the underlying bar.

The operation and the advantages of the invention will emerge from the following of the following detailed description.

The invention offers in particular synergy of the following technical effects:

- on the one hand, the section of the bars defining diverging channels from the outside to the inside, and therefore the edge presented by the bars towards the inside, limits the load losses for what is extraction of air from the inside to the outside, while presenting diverging factors with respect to the fraction of an incidental pressure wave from the outside to the inside, suitable for attenuating the effects of this wave,

- on the other hand, the overall vertical main face of the bars forms a deflector/reflector for another fraction of incidental waves or object,

- and also, the inclined fins form not only an anti-rain barrage but also serve as a potential deflector for some of the waves and incidental objects, moreover cooperating with the main face for sending back in different directions suitable for breaking the incidental wave front (the fraction of a horizontal wave which impacts the main face is sent back horizontally, while the horizontal wave fraction impacting a fin is sent back perpendicularly to the fin, partly to the outside and overall upwards, and partly towards the main face if the angle of inclination between the fins and the horizontal is adapted, typically less than 45°, before being sent back by the main face), potentially while forming « gates » suitable for closing the channels between the bars, by deformation, the height of the fins being greater than the interval between two adjacent bars, in case of excessive pressure (the lower edge of a fin in this case able to rest on the underlying bar).

The invention also relates to buildings comprising at least one grill such as previously defined according to the invention.

BRIEF PRESENTATION OF FIGURES

Other characteristics, aims and advantages of the present invention will emerge from the following detailed description and with respect to the appended drawings given by way of non-limiting example and wherein:

- figure 1 previously described illustrates a schematic view of a system according to the prior art,

- figure 2 illustrates a partial view according to a view in vertical section of a weatherproof grill according to the present invention,

- figures 3, 4, 5, 6, 7 and 8 illustrate views in vertical section of the section of bars as per variants of the invention,

- figure 9 illustrates the load loss caused by a grill according to the invention as a function of air speed,

- figure 10 illustrates the residual pressure after a grill according to the invention as a function of the angle of the auxiliary faces of the bars relative to the horizontal,

- figure 11 illustrates the load loss caused by a grill according to the invention as a function of the angle of the auxiliary faces of the bars relative to the horizontal,

- figure 12 illustrates the residual pressure after a grill according to the invention as a function of the spacing between the bars,

- figure 13 illustrates the load loss caused by a grill according to the invention as a function of the spacing between the bars,

- figures 14, 15 and 16 illustrate respectively two opposite perspective views and a partial sectional view of a grill according to the present invention, and

- figures 17 and 18 illustrate two implantation variants of the grill in an arrangement not strictly vertical.

DETAILED DESCRIPTION OF THE INVENTION

The weatherproof ventilation grill according to the present invention is formed by the combination of a series of bars 100 and deflecting fins 200.

A fin 200 is fixed to the base of each bar 200.

The bars 100 are preferably fixed on the stanchions 310 of a frame 300. However as a variant the bars 100 can feasibly be fixed directly to the structural work of a building at the level of the framework of a ventilation opening to be protected.

The same applies for the fins 200 which can be fixed to the stanchions 310 of a frame 300. However as a variant provision can be made to fix the fins 200 directly to the structural work of a building at the level of the framework of a ventilation opening to be protected.

Preferably the ventilation grill according to the present invention is installed in a vertical position. However the grill according to the invention can also be installed with a certain inclination relative to the vertical (the mean plane M defined by the frame not being vertical), for example in a range of +/- 20° relative to the vertical.

The weatherproof grill according to the invention will be described hereinbelow in reference to the vertical or semi-vertical position it occupies in position of use and in reference to a horizontal plane H and a vertical plane V shown in figure 2.

The bars 100 are rigid and are formed preferably from metal and highly preferably made of steel.

The bars 100 are parallel to each other and are non-vertical. More precisely the bars 100 are preferably horizontal to around +/- 10°. In other terms each bar 100 is centred on a longitudinal axis which is horizontal to use, at around more or less 10°.

The straight section of the bars 100 is constant over their entire length. All bars 100 preferably have an identical straight section.

As is evident in figure 2, the bars 100 preferably have an overall triangular straight section.

The bars 100 can be formed by a solid body or can be formed by assembling three sheets or strips of steel welded in pairs in the region of their adjacent edges.

The bars 100 have a first leading edge 110 and two auxiliary faces 120, 130.

The first leading edge 110 is attached to the upper auxiliary face 120 in the region of a horizontal edge 112 and on the lower auxiliary face 130 in the region of an also horizontal edge 114.

The two auxiliary faces 120 and 130 are joined together in the region of a common internal and also horizontal edge 116.

The distance separating the edges 116 of two adjacent bars 100 is referenced d in the attached figure 2.

The distance separating the upper edge 112 from a bar 100 and the lower edge 114 of the adjacent bar 100 is referenced hl in the attached figure 2.

To limit load losses relative to a directed extraction flow from the inside to the outside, the link between the two auxiliary faces 120, 130, opposite the main face 110 defines an inner edge of bar 116 pointed or rounded and presenting a maximum radius of curvature of 5mm, advantageously less than 3mm.

The first leading edge 110 is intended to be directed to the outside. It is overall vertical and its height (or width) vertical is referenced h2 in the attached figure 2.

The leading edge 110 reflects those incidental pressure waves it receives to the outside.

Preferably all the first leading faces 110 of the bars 100 of the same grill, are coplanar and vertical.

The two auxiliary faces 120 and 130 converge in moving away from the main face 110. In this way the straight section of the bars 100 diminishes, from the outside to the inside. Between each pair of two adjacent bars 100 the two auxiliary faces 120 and 130 define a channel 140 diverging from the outside to the inside, and therefore converge for airflow which moves from the inside to the outside, by comparison. The evolution of section of the channel 140 is progressive, that is, without sudden change, so as not to disrupt flows and to optimise load losses.

The first leading edge 110 is preferably flat, as illustrated in figures 2, 3 and 6 to 8.

But it can be convexly curved as illustrated in figure 4 or concavely curved as illustrated in figure 5.

Preferably the straight section of the bars 100 is isosceles, its two auxiliary faces 120 and 130 having identical widths, as is evident in figure 3. Even more precisely the straight section of the bars 100 is preferably equilateral, its two auxiliary faces 120 and 130, as well as the first leading edge 110, having identical widths as is evident in figure 2.

However by way of variant the two auxiliary faces 120 and 130 can have different widths, as is evident in figure 6 (the straight section of each bar remaining constant over its entire length and all the bars being of section identical).

The two auxiliary faces 120 and 130 are preferably flat, as illustrated in figures 2 to 6.

But they can be concavely curved as illustrated in figure 7 or convexly curved as illustrated in figure 8.

The deflecting fins 200 are attached respectively, for example by welding, the base 114 of the main face 110 of each bar 100.

The fins 200 are relatively rigid and are preferably formed from metal and highly preferably made of steel.

The fins 200 are parallel to each other. The straight section of the fins 200 is constant over their entire length. All the fins 200 preferably have an identical straight section.

As is evident in figure 2, the fins 200 are preferably formed from a flat metallic blade of width L constant and therefore have a straight rectilinear section at rest.

The fins 200 are inclined to the outside relative to the main face 110. In other terms each fin 200 moves away from the vertical plane of the leading edge 110 to which it and attached, by moving away from its edge of link 114 on the abovementioned associated leading edge 110, or by moving towards its free edge 210. The inclination and the height of the fins 200 are such that the free edge 210 of a fin 200 is at least on the same horizontal line as the upper edge 112 of the main face 110 of the underlying bar 100. If needed, each fin 200 can straddle the main face 110 of the underlying bar 100, according to a horizontal projection.

So the fins 200 form a deflector and have an intrinsic height (or width) L greater than the distance hl = (d-h2) separating the lower edge 114 of the main face 110 from a bar 100 and the upper edge 112 of the main face 110 from the underlying bar 200.

The ratio between the vertical height h2 of each main face 110 and the vertical height hl = (d-h2) of the interval defined between two adjacent bars 100 is preferably between 0.5 and 2, preferably of the order of around 1 to ± 10%. Due to this arrangement the section of the bars 100 offers a maximal reflection surface to an overpressure wave, without as such generating crippling load losses.

As pointed out earlier and as is evident in figures 14 to 16, the bars 100 can be fixed to the stanchions 310 of a frame 300 whereof the dimensions are adapted to the size of the ventilation system. In figures 14 to 16, the upper crossbeam of the frame 300 is referenced 320 and the lower crossbeam is referenced 330.

The inclination a of the auxiliary faces 120 and 130 relative to the horizontal is preferably less than 40°, preferably less than 30° and highly advantageously less than 25°.

This inclination has been calculated to facilitate the flow of fluid as normal operation during extraction of air from the inside to the outside for a flow rate of conventional dimensioning of 2.5 m/s, so as to limit load losses.

The distance hl between the bars 100 is also calculated such that it prevents ingress of projectiles and limits the risk of blockage by frost.

The distance hl separating two adjacent bars 100 is preferably less than or equal to 90mm.

Highly advantageously, the distance hl separating two adjacent bars 100 is between 50 and 85mm, highly advantageously between 60 and 80mm.

Also the height h2 of the main face 110 of each bar 100 is preferably greater than or equal to 70mm.

Highly advantageously, the height h2 of the main face 110 of each bar 100 is between 70 and 85mm, highly advantageously between 60 and 80mm.

Due to their orientation (angle β) and their width (L), the fins or vents 200 fixed to the base of each bar 100 and preferably by their ends to the frame support 300 oppose ingress by rain and limit additional load loss caused as a normal operation.

The inclination β between each fin 200 and the horizontal H is less than 50°, preferably less than 45° and highly advantageously less than 30°.

According to the invention, the width L of each fin 200 considered between its link edge on a bar 100 and its free edge 210, the inclination β between each fin 200 and the horizontal, the distance d separating the inside convergence points 116 between the two auxiliary faces 120, 130 of two adjacent bars 100 and the vertical height h2 of each main face 110 of the bars 100, respect the relation: (L x sin β) > = (d - h2).

The thickness of the fins 200 made of steel is dimensioned so as to be resistant to variations in explosion and tornado wave, typically at least equal to 0.8mm.

According to a first embodiment of the invention, some at least of the fins 200, preferably all the fins 200, are connected by a link fixed to the base 114 of the associated bar 100.

However according to a second embodiment of the invention, some at least of the fins 200, preferably all the fins 200, can be connected to the base 114 of the associated bar 100 by an articulated link.

In this latter case, in the region of their link with the base 114 of the bars 100, the vents or fins 200 can be fitted with return devices forming a spring, adapted to allow permissible freedom in rotation, between the fins 200 and the associated bars 100 respectively, in case of substantial overpressure, while allowing the vents or fins 200 to be folded up on the openings of the channels 140 and block the latter, further reinforcing protection against said overpressure. The above springs ensure the return of the vents or fins 200 to the initial position, once overpressure is finished.

When the free edge 210 of a fin 200 is located at the same horizontal level as the free edge 112 of the underlying bar 100 or beyond this free edge 112, the height L of the fins 200 is greater than the interval hl between two adjacent bars 100. So in case of excessive pressure, by deformation or articulation, the fins 200 can close the channels 140 between the bars 100, the lower edge 210 of a fin 200 resting on the underlying bar 200.

Because of the combination of the above characteristics, the weatherproof grill according to the present invention is adapted to cover and optimise parries to many (PGEW or « Projectiles Generated by Extreme Wind » attacks, tornado, explosion external, icing). It also protects ventilation systems and equipment the inside premises.

In particular, the weatherproof grill according to the invention:

- Effectively stopping projectiles projected in case of tornado and the Projectiles Generated by Extreme Wind (PGEW).

- Effectively attenuating sudden variations in pressure engendered by tornados and external explosions so as not to damage the ventilation network (duct, ventilator, flaps) inside buildings.

- Not engendering substantial load losses on the ventilation networks on which they are installed (so as not to have to install load recovery fans or modify the characteristics of installed fans).

- Fulfilling the functions of a conventional ventilation grill (rain-guard and anti-bird) to be able to carry out installation of the grill according to the invention to replace a former grill.

- Considering the problem of icing.

To optimise the weatherproof grill according to the invention, the inventors have conducted a series of parametric studies on each of the major characteristics of the grill, on the basis of the reference parameters below:

- Air speed as a normal operation: 2.5 m/s,

- inclination a of the auxiliary faces 120 and 130 relative to the horizontal: 25 °,

- geometry of the leading edge 110 of the triangular cross-section of the bars: straight,

- spacing hl between two adjacent bars 100: 80 mm.

The parameter « air speed » as normal operation a been studied on the base of the above reference grill.

The results obtained in terms of load loss (Pa) as a function of the air speed (m/s) are shown in figure 9.

Examination of this figure 9 reveals a sharp rise in load losses when air speed is increased. However load losses of the grill according to the invention (around 50Pa to 2.5m/s for a grill of dimensions 1000 x 1000mm) are relatively low. By way of comparison, a classic rain-guard grill exhibits load loss of the order of 30 Pa to 2.5m/s, and an anti-blast flap exhibits load loss of the order of 200Pa and up to 350Pa, so that the classic combination exhibits load losses at least four times higher than the grill according to the invention.

The results obtained in terms of residual pressure measured after the grill, that is, on the inside of the latter, during simulation of an external explosion, as a function of the angle of incidence a, to optimise the angle of incidence of the triangular section, are shown in figure 10.

These results show that a reference grill responding to the parameters defined previously is effective against explosions and therefore tornados, since it divides the wave of an explosion by 10.

The value of residual pressure of lOOOPa, downstream of the grill, is much lower than conventional values of HVAC equipment behaviour (2000Pa), even if the pressure generated by the fan of HVAC networks is added (generally 500Pa).

The impact of the value of the angle a is negligible (less than 1%) as to its capacity to « break » an explosion wave.

On the contrary, as shown in figure 11, the value of the angle a plays an important role on load losses ofthe grill in normal conditions from 25°. The smaller the angle, the less the flow lines are perturbed.

The spacing hl between the bars 100 of the grill has been studied on the basis of figure 12 which illustrates the residual pressure downstream ofthe grill as a function ofthe spacing during simulation of application of an explosion.

Figure 12 reveals that in selected simulation conditions, the aeraulic behaviour of the grill facing an explosion is uniform from 60mm spacing hl.

The figure 13 illustrates the load losses of the grill according to the reference as normal operation as a function of the spacing hl between the bars 100.

Figure 13 shows that the more the bars 100 are tightened, the more effective the grill is against explosions (and therefore tornados), but also the greater the specific the load loss of the grill is. Moreover, the bars 100 must be spaced by fewer than 80mm to retain PGEW projectiles and projectiles « Tornado of steel tube type of 170mm in diameter ».

However, the distance hl between bars must be the greatest possible to improve protection ofthe grill relative to the phenomenon of clogging by icing.

Figures 9 to 13 illustrate in solid lines, for each figure, the curve corresponding to the average of the values of simulation obtained and in interrupted lines of the upper and lower terminals of these values corresponding to ranges of possible values.

In light of the above the inventors consider that spacing hl of around 80 mm between the bars ofthe grill:

- conserve considerable efficacy of the grill facing an explosion,

- retains the projectiles of tornado and PGVE

- limits exposure of the grill to the phenomenon of frost.

The efficacy of the geometry of the leading edge 110 of the triangle section of the bars has been studied with respect to the profiles shown in figures 3, 4 and 5.

Relevant simulations performed have revealed:

- For a leading edge 110 flat as illustrated in figure 3: residual pressure downstream of the grill of 990 Pa under the effect of an explosion, for a load loss as normal operation of 49 Pa,

- For a leading edge 110 convex of 44mm of radius of curvature as illustrated in figure 4: a residual pressure downstream of the grill of 984 Pa sous the effect of an explosion, for a load loss as normal operation of 88 Pa, and

- For a concave leading edge 110 of 44mm of radius of curvature as illustrated in figure 5: residual pressure downstream of the grill of 998 Pa under the effect of an explosion, for a load loss as normal operation of 42 Pa.

The results hereinabove show that the impact of the attack profile 110 of the bars 100, that is, that this profile is flat, convex or concave, is negligible (the impact is less than 1%) relative to an explosion (and therefore a tornado).

Grills according to the invention could therefore comprise bars 100 whereof the leading edge 110 responds to any one of these geometries, flat, convex or concave.

But the flat geometry of the leading edge 110 which gives a highly satisfactory result in terms of barrage and reflection relative to an explosion and of the wave generated by a tornado can be considered as preferred for a section of triangular profile of the bars to the extent where such a flat leading edge 110 has the advantage of manufacturing simplicity. Also, implanting fins or vents 200 is made easy by such a bar profile.

The geometry of the fins 200 has also been studied.

The rain-guard function is one of the basic functions of a ventilation grill. Optimised design of the rain-guard fins 200 prevents both rain from entering the inside of the building (even horizontal rain) and also having sufficient horizontal spacing to avoid substantial load losses, typically of the order of 80 mm, between the two bars.

The structure proposed by the present invention benefits from the vertical face 110 of the bars 100 serving to counter explosions and tornados to redirect rain downwards and decrease by two the number of rain-guard fins for a gain in terms of load loss as a normal operation.

The simulations also give the following results.

Conditions	Residual pressure applied to the input of the duct	Residual pressure obtained at output of the duct	Loss of load of the grill
Grill sized 500x500 mm
Normal	P atmospheric	P atmospheric	57
Tornado of type EF3	2600 Pa	532 Pa	2068
Tornado of type EF4	4400 Pa	905 Pa	3495
Explosion	10,000 Pa	1200 Pa	8800
Grill sized 1000x1000 mm
Normal	P atmospheric	P atmospheric	53
Tornado of type EF3	2600 Pa	580 Pa	2021
Tornado of type EF4	4400 Pa	968 Pa	3432
Explosion	10,000 Pa	1487 Pa	8513
Grill sized 1500x1500 mm
Normal	P atmospheric	P atmospheric	53
Tornado of type EF3	2600 Pa	517 Pa	2083
Tornado of type EF4	4400 Pa	883 Pa	3517
Explosion	10,000 Pa	1638 Pa	8362

Of course, the present invention is not limited to the embodiments previously described, but refers to any variant according to its sense.

The weatherproof grill according to the invention can be installed on new installations, but it can also be installed in place of existing ventilation grills for replacing the latter.

The weatherproof grill according to the invention can be installed on many installations, for example but non-limiting on electrical energy production installations from a nuclear energy source.

The weatherproof grill according to the invention has been described previously in reference to the vertical or semi-vertical position it occupies in position of use and in reference to a horizontal plane H and a vertical plane V shown in figure 2.

The side called « outer » of the grill, in reference to the position of use, the outside being the outside of the building, corresponds to a « first side ». The side called « inside » of the grill, in reference to the position of use, the inside being the inside of the building, corresponds to a « second side ».

And as pointed out earlier, in some implantation conditions, the mean plane M of the grill cannot be strictly vertical during implantation, according to the architecture of the building.

In this case it can be provided either that the main faces 110 of 10 the bars 100 remain coplanar to each other and parallel to the mean plane M of the frame 300 of the grill, as illustrated in figure 17, or that the main faces of the bars 110 are inclined relative to the mean plane of the frame 300, remaining parallel to each other but offset such that these faces 110 remain vertical to use, as illustrated in figure 18. In all cases the width of the fins 200 is preferably adapted so that the free edge 210 of the fins is at least located on the same horizontal line as the upper edge 114 of the main face 110 of the underlying bar 100, or even is located below this line.

Claims

1. A weatherproof ventilation grill comprising:

- a series of rigid bars (100) overall parallel to each other and nonvertical, having a first leading edge (110) directed towards a first side of the grill intended to be directed to the outside, overall parallel to the mean plane of the grill and intended to be overall vertical to use, and two auxiliary faces (120, 130) which converge in moving away from the main face (110), defining between two adjacent bars (100) a channel (140) diverging from the first side intended to be directed to the outside in the direction of the second side of the grill intended to be directed towards the inside, and

- a series of deflecting fins (200) attached respectively to the base (114) of the main face (110) of each bar (100), the fins (200) being inclined towards the first side intended to be directed to the outside relative to the main face (110) according to an inclination and a height such that the free edge (210) of a fin (200) is at least on the same line as a projection orthogonal to the mean plane of the grill on the upper edge (112) of the main face (110) of the underlying bar (100), or even straddles this main face (110), such that the fins (200) form a deflector and have a specific height greater than the distance (hl) separating the lower edge (114) of the main face (110) from a bar (100) and the upper edge (112) of the main face (110) from the underlying bar (100).

2. The grill according to Claim 1, characterized in that the bars (100) extend according to a longitudinal central axis horizontal to around more or less 10°.

3. The grill according to any one of Claims 1 or 2, characterized in that the bars (100) are of triangular cross-section.

4. The grill according to any one of Claims 1 to 3, characterized in that the main face (110) of each bar (100) is flat.

5. The grill according to any one of Claims 1 to 4, characterized in that the auxiliary faces (120, 130) of the bars (100) are flat.

6. The grill according to any one of Claims 1 to 5, characterized in that the bars (100) have a section in form of an isosceles triangle, preferably in the form of an equilateral triangle.

7. The grill according to any one of Claims 1 to 6, characterized in that the ratio between the vertical height (h2) of each main face (110) and the vertical height (hl) of the interval defined between two adjacent bars (100) is between 0.5 and 2, preferably of the order of around 1 to ± 10%.

8. The grill according to any one of Claims 1 to 7, characterized in that the height (h2) of the main face (110) of each bar (100) is greater than or equal to 70mm.

9. The grill according to any one of Claims 1 to 8, characterized in that the height (h2) of the main face (110) of each bar (100) is between 70 and 85mm, highly advantageously between 60 and 80mm.

10. The grill according to any one of Claims 1 to 9, characterized in that the inclination (a) between the auxiliary faces (120, 130) of the bars (100) and the horizontal is less than 40°, preferably less than 30° and highly advantageously less than 25°.

11. The grill according to any one of Claims 1 to 10, characterized in that the distance (hl) separating two adjacent bars (100) is less than or equal to 90mm.

12. The grill according to any one of Claims 1 to 11, characterized in that the distance (hl) separating two adjacent bars (100) is between 50 and 85mm, highly advantageously between 60 and 80mm.

13. The grill according to any one of Claims 1 to 12, characterized in that the width L of each fin (200) considered between its link edge (114) on a bar (100) and its free edge (210), the inclination β between each fin (200) and the horizontal, the distance d separating the inner points of convergence (116) between the two auxiliary faces (120, 130) of two adjacent bars (100) and the vertical height h2 of each main face (110) of the bars (100), respect the relation: (L x sin β) > = (d - h2).

14. The grill according to any one of Claims 1 to 13, characterized in that some at least of the fins (200) are connected by a fixed link to the associated bar (100).

15. The grill according to any one of Claims 1 to 13, characterized in that some at least of the fins (200) are connected to the associated bar (100) by an articulated link.

16. The grill according to any one of Claims 1 to 15, characterized in that the link (116) between the two auxiliary faces (120, 130) opposite the main face (110) defines a pointed or rounded inner edge of a bar (100) presenting a maximum radius of curvature of 5mm, advantageously less than 3mm.

17. The grill according to any one of Claims 1 to 16, characterized in that the inclination (β) between each fin (200) and the horizontal is less than 50°, preferably less than 45° and highly advantageously less than 30°.

18. The grill according to any one of Claims 1 to 17, characterized in that the bars (100) and the fins (200) are formed from metal, preferably made of steel.

19. The grill according to any one of Claims 1 to 18, characterized in that the thickness (θ) of the fins (200) made of steel is at least equal to 0.8mm.

20. The grill according to any one of Claims 1 to 19,

characterized in that the bars (100) are borne by a frame support (300).

21. A building comprising at least one grill according to any one of Claims 1 to 20, which comprises:

- a series of rigid bars (100) overall parallel to each other and nonvertical, having a first leading edge (110) directed to the outside, and two auxiliary faces (120, 130) which converge in moving away from the main face (110), defining between two adjacent bars (100) a channel (140) diverging from the outside to the inside and

- a series of deflecting fins (200) attached respectively to the base (114) of the main face (110) of each bar (100), the fins (200) being inclined to the outside relative to the main face (110) according to an inclination and a height such that the free edge (210) of a fin (200) is at least on the same horizontal line as the upper edge (112) of the main face (110) of the underlying bar (100), or even straddles this main face (110), such that the fins (200) form a deflector and have a specific height greater

5 than the distance (hl) separating the lower edge (114) of the main face (110) from a bar (100) and the upper edge (112) of the main face (110) from the underlying bar (100).