EP0906546B1 - Method and device for protecting a work surface - Google Patents

Abstract

PCT No. PCT/FR97/01106 Sec. 371 Date Mar. 2, 1999 Sec. 102(e) Date Mar. 2, 1999 PCT Filed Jun. 20, 1997 PCT Pub. No. WO97/49955 PCT Pub. Date Dec. 31, 1997A method and apparatus for closely protecting a workstation. The method includes the steps of (a) providing a horizontal work surface having a top face, an upstream side and a free side opposite the upstream side, the free side having an edge, the work surface being unobstructed and accessible from above the top face and from at least the free side; (b) continuously blowing clean air over the work surface from the upstream side toward the free side so as to form a substantially horizontal flow of the clean air across the work surface and so that the flow of air has a velocity gradient with an upper layer or stream of air having a substantially higher velocity of flow than a lower layer or stream of the air flowing proximal to the top face; and (c) continuously sucking air from the flow of air into a suction intake disposed near the edge of the free side. The apparatus includes (a) an air blower for blowing clean air continuously over the work surface from the upstream side to the free side so as to form a substantially horizontal flow of the clean air across the work surface and so that the flow of air has a velocity gradient with an upper layer or stream of the air having a substantially higher velocity of flow than a lower layer or stream of the air flowing proximal to the top face; and (b) a suction intake disposed near the edge of the free side for collecting air from the flow of air blown to the free side.

Description

The present invention relates to close protection of a plane of horizontal work by means of a clean air flow.

The invention relates to both a method and a device implementing such a protection.

The invention relates more specifically to the protection of a work that is clear, and therefore accessible, both on top and on at least one side, called the free side, of this work plan.

The problem of protecting workstations from contamination due to ambient air arises in different branches of industry, especially in the food industry, with artisans and manufacturers in the food industry (butchers, pork butchers for example), in the pharmaceutical, chemical industries, microbiological, aeronautical, hospital and surgical, in laboratories, in military and even domestic applications.

In fact, all the fields of application in which the quality of the product (s) processed at a work station must be preserved or maintained whatever the pollution of the surrounding atmosphere.

In general, to protect the worktop, it is installed inside a sterile room - called a clean room - in which the air is filtered and treated to present a given level of cleanliness.

The main disadvantage of this solution is the difficulty of maintaining a air quality in a large volume at acceptable economic conditions. A another disadvantage is related to the fact that the personnel must be dressed in a special dress, itself sterile, whose cleanliness is difficult to maintain impeccable and to control, and whose wearing is tedious. In addition, despite this special outfit, the staff and equipment present in the work room can be sources of air pollution.

The close protection technique provides a solution to this problem.

It consists of bathing the work surface, as well as the objects carried by this one, in an atmosphere of clean moving air, which is constantly renewed.

The work surface is thus protected by a clean air shield which puts the protected from external contamination, although the rest of the room in which finds the work plan contains air likely to be polluted, the personnel assigned to tasks relating to said objects which may therefore be subject to constraints less strict hygienic.

This work plan can be a fixed tray, on which are placed items to be processed or subjected to any operation, either manual or automated.

It can also consist of a carrier, for example a carpet mobile, which successively brings articles to be treated to the work station, and then evacuated when the operation is complete.

For example, the articles are for example containers which are transported to the tail leu leu by the moving belt, and which is filled by a dispensing head arranged in the protected area, so that the filling product is free from contamination.

The state of the art in this area can be illustrated by the documents FR-A-1 257 562 and EP-A-0 375 343.

The document FR-A-1 257 562 relates to a device for maintaining an atmosphere with specific characteristics in an open room of a side.

This room has a floor constituting a work surface horizontal above which flows a clean air flow.

The room is open on only one of its sides, accessible to a operator, and this side is traversed by a second stream of clean air, which affects the shape an approximately vertical curtain, directed from top to bottom.

Air is drawn in at the front edge (open side of the chamber) of the working surface and is recycled via an atmosphere regeneration device, so that his journey is on a closed circuit.

The horizontal air flow, which crosses the interior of the chamber, presents almost constant speed distribution over the entire height of the chamber; the value of the speed is independent of the height of the point considered in relation to the work surface.

A major drawback of the device described in FR-A-1 257 562 results from the fact that the room is delimited upwards by a ceiling, which limits considerably accessibility to the work plan.

This poses difficulties in particular when the operation for processing items carried or transported by said work plan requires the implementation of machines, or other materials, overhanging the work plan.

This is the case for example for dispensing and / or dosing machines used to fill containers transported by a moving belt, for filling in the close protection zone.

The device which is the subject of document EP-A-0 375 343 comprises a horizontal work surface which is clear both on the top and on one of its sides.

A fan placed under the worktop, at the outlet of which is a filter, generates pressurized air in a box opening into a room dispenser located on the unopened side of the worktop.

This chamber produces a double flow, namely a horizontal flow passing above the worktop, and a multi-directional flow formed of a plurality of small jets produced by holes formed in the various partitions of the chamber.

Cylinder arc shaped guides lining the interior of this chamber ensure the deflection of air from the box to produce the flow horizontal above.

If this known device has the advantage of its accessibility both by one side of the worktop and from the top, it has the disadvantage that the distribution of the horizontal flow velocities, above the work plane, is constant.

However, it appears that a distribution of this kind does not provide protection perfect of the items placed on the worktop. It results from tests carried out by applicants, on the contrary, it is desirable to provide a speed gradient, the value must be increasing as a function of the distance from the work surface. A particularly effective protection is obtained when clean air moves at low speed, even almost stationary, near the work surface, while on the contrary the upper layer of the flux has a relatively high speed.

The present invention aims to overcome these drawbacks by proposing a method and a device of close protection which, while allowing a good accessibility to the work surface, ensures perfect protection of the items placed on this work plan.

• on insuffle en continu de l'air propre au-dessus du plan de travail à partir du côté opposé audit côté libre, et appelé côté amont, sous la forme d'un flux sensiblement horizontal qui balaie le plan de travail transversalement, en direction du côté libre, et qui présente un gradient de vitesses tel que la couche supérieure - ou veine haute - ait une vitesse sensiblement plus grande que celle de l'air circulant au voisinage de la face supérieure du plan de travail ;
• on aspire en continu la totalité ou la majeure partie du flux par le côté libre, au moyen d'une bouche d'aspiration s'étendant le long et à proximité immédiate du bord du plan de travail.

The close protection method which is the subject of the invention, which aims to protect, by means of a clean air flow, a horizontal work surface which is clear and accessible both on the top and on at least one side, called the side free, is remarkable by the fact that:

• clean air is continuously blown over the worktop from the side opposite to said free side, and called upstream side, in the form of a substantially horizontal flow which sweeps the worktop transversely, towards the free side, and which has a speed gradient such that the upper layer - or upper vein - has a speed substantially greater than that of the air circulating in the vicinity of the upper face of the work surface;
• the whole or most of the flow is continuously sucked in from the free side, by means of a suction mouth extending along and in the immediate vicinity of the edge of the work surface.

• on recycle l'air recueilli par ladite bouche d'aspiration, cet air étant réinsufflé du côté amont après filtration ou autre épuration ;
• le plan de travail est un plateau fixe ;
• le plan de travail est un transporteur.

In addition, according to a certain number of possible additional characteristics:

• the air collected by said suction mouth is recycled, this air being reinsuffed on the upstream side after filtration or other purification;
• the work plan is a fixed tray;
• the work plan is a transporter.

The invention also relates to a close protection device a horizontal worktop by means of a clean air flow, in which the worktop work is clear and accessible both on top and on at least one side, called side free.

• des moyens pour insuffler de l'air propre en continu au-dessus du plan de travail à partir du côté opposé audit côté libre, et appelé côté amont, sous la forme d'un flux sensiblement horizontal qui balaie le plan de travail transversalement, en direction du côté libre, et qui présente un gradient de vitesses tel que la couche supérieure - ou veine haute - ait une vitesse sensiblement plus grande que celle de l'air circulant au voisinage de la face supérieure du plan de travail ;
• une bouche d'aspiration s'étendant le long et à proximité immédiate du bord du plan de travail ;
• des moyens d'aspiration branchés à ladite bouche.

This device is remarkable in that it includes:

• means for continuously blowing clean air above the work surface from the side opposite to said free side, and called the upstream side, in the form of a substantially horizontal flow which sweeps the work plane transversely, in direction of the free side, and which has a speed gradient such that the upper layer - or upper vein - has a speed substantially greater than that of the air circulating in the vicinity of the upper face of the work surface;
• a suction mouth extending along and in the immediate vicinity of the edge of the worktop;
• suction means connected to said mouth.

• un générateur unique de flux tel qu'un ventilateur (ou un groupe de ventilateurs juxtaposés), assure l'insufflation de l'air propre côté amont et son aspiration côté libre, une partie au moins du flux étant recyclée par un trajet en circuit fermé ;
• l'insufflation d'air est réalisée au moyen d'un générateur de flux, tel qu'un ventilateur en aval duquel est disposé au moins un filtre, ou autre moyen d'épuration.
• l'insufflation d'air est réalisée au moyen d'un générateur de flux, tel qu'un ventilateur, qui est situé en-dessous du plan de travail, et produit un flux sensiblement horizontal qui est dévié à 180° au niveau du côté amont par un guide tubulaire de forme semi-cylindrique, ou approximativement semi-cylindrique ;
• lesdits moyens d'insufflation d'air comprennent un conduit vertical, ou approximativement vertical, disposé du côté amont, dont l'extrémité basse est branchée à un générateur de flux d'air tel qu'un ventilateur, tandis que son extrémité haute débouche, sensiblement au niveau du plan de travail, dans un guide tubulaire en forme de quart de cylindre, ou approximativement en forme de quart de cylindre, apte à dévier le flux pour lui donner une direction sensiblement horizontale ;
• ledit conduit vertical, ou approximativement vertical, est muni intérieurement d'au moins un déflecteur formant un angle aigu par rapport à la verticale, et apte à dévier une partie du flux vers l'extérieur (par rapport audit plan de travail) afin de constituer ladite veine haute ;
• le conduit est pourvu de plusieurs déflecteurs, qui sont constituées par des plaques planes juxtaposées disposées en éventail, de manière à diverger du bas vers le haut ;
• la plaque déflectrice la plus intérieure (par rapport audit plan de travail est sensiblement verticale ;
• ledit guide tubulaire est garni intérieurement d'au moins un déflecteur en forme d'arc de cylindre, coaxial au guide ;
• lesdits moyens d'insufflation d'air sont munis d'une partie en débord, formant visière, qui surplombe la zone amont du plan de travail et est adaptée pour rabattre légèrement vers le bas la veine haute ;
• ladite bouche d'aspiration est subdivisée en deux bouches d'aspiration secondaires : l'une supérieure, apte à capter le flux d'air correspondant à la veine haute et à le laisser passer sans - ou pratiquement sans - perte de charge, l'autre inférieure, apte à freiner le flux situé sous la veine haute, par exemple au moyen d'un étranglement ;
• le plan de travail est un plateau fixe ;
• le plan de travail est un transporteur.

Furthermore, according to a certain number of additional, non-limiting characteristics:

• a single flow generator such as a fan (or a group of juxtaposed fans), ensures the blowing of clean air upstream side and its suction on the free side, at least part of the flow being recycled by a closed circuit path ;
• the air blowing is carried out by means of a flow generator, such as a fan downstream of which is arranged at least one filter, or other purification means.
• blowing air is achieved by means of a flow generator, such as a fan, which is located below the worktop, and produces a substantially horizontal flow which is deflected 180 ° at the side upstream by a tubular guide of semi-cylindrical shape, or approximately semi-cylindrical;
• said air blowing means comprise a vertical, or approximately vertical, duct arranged on the upstream side, the lower end of which is connected to an air flow generator such as a fan, while its upper end opens out, substantially at the work surface, in a tubular guide in the form of a quarter cylinder, or approximately in the form of a quarter cylinder, capable of deflecting the flow to give it a substantially horizontal direction;
• said vertical, or approximately vertical, duct is internally provided with at least one deflector forming an acute angle with respect to the vertical, and capable of deflecting part of the flow towards the outside (relative to said work plane) in order to constitute said upper vein;
• the duct is provided with several deflectors, which are constituted by juxtaposed flat plates arranged in a fan, so as to diverge from the bottom to the top;
• the innermost deflector plate (relative to said work surface is substantially vertical;
• said tubular guide is internally lined with at least one deflector in the form of an arc of a cylinder, coaxial with the guide;
• said air blowing means are provided with an overhanging part, forming a visor, which overhangs the upstream area of the work surface and is adapted to fold down the upper vein slightly;
• said suction mouth is subdivided into two secondary suction mouths: the upper one, able to capture the air flow corresponding to the upper vein and to let it pass without - or practically without - pressure drop, the another lower, able to brake the flow located under the upper vein, for example by means of a constriction;
• the work plan is a fixed tray;
• the work plan is a transporter.

By the term "carrier" is meant both a single carrier than a group of two or more than two carriers arranged side by side, for example several adjoining carpets.

• la figure 1 est une vue schématique, coupée par un plan vertical transversal, d'un premier mode de réalisation d'un dispositif conforme à l'invention, le plan de coupe étant référencé I-I sur la figure 2.
• la figure 2 est une vue de dessus du dispositif de la figure 1 ;
• la figure 3 est une vue schématique, analogue à la figure 1, d'un second mode de réalisation du dispositif ;
• la figure 4 est un schéma montrant un troisième mode de réalisation, également coupé par un plan vertical transversal ;
• les figures 5 et 6 sont des schémas, respectivement en perspective et en coupe, par un plan vertical transversal, d'une partie du système d'insufflation et de déviation d'air susceptible d'équiper les dispositifs;
• les figures 7 et 8 sont des schémas, respectivement en perspective et en coupe transversale, d'un quatrième mode de réalisation possible du dispositif ;
• la figure 9 est une courbe représentative d'une possibilité de variation de la vitesse au sein du flux d'air propre au-dessus du plan de travail, en fonction de la distance du point de mesure par rapport à ce plan ;
• les figures 10 et 11 sont des schémas en perspective montrant deux transporteurs susceptibles d'être associés à un dispositif conforme à l'invention ;
• les figures 12, 13 et 14 sont des illustrations montrant la configuration des flux d'air dans trois dispositifs de géométrie différente, les représentations résultant de simulations faites par ordinateur, l'appréciation des vitesses se faisant en référence à une échelle de gris, qui va du plus clair au plus foncé, dans le sens des vitesses croissantes.

Other characteristics and advantages of the invention will appear from the description which follows, as well as from the appended drawings, which represent, by way of non-limiting examples, preferred embodiments.

• FIG. 1 is a schematic view, cut by a transverse vertical plane, of a first embodiment of a device according to the invention, the cutting plane being referenced II in FIG. 2.
• Figure 2 is a top view of the device of Figure 1;
• Figure 3 is a schematic view, similar to Figure 1, of a second embodiment of the device;
• Figure 4 is a diagram showing a third embodiment, also cut by a transverse vertical plane;
• Figures 5 and 6 are diagrams, respectively in perspective and in section, through a vertical transverse plane, of a part of the insufflation and air deflection system capable of equipping the devices;
• Figures 7 and 8 are diagrams, respectively in perspective and in cross section, of a fourth possible embodiment of the device;
• FIG. 9 is a curve representative of a possibility of variation of the speed within the clean air flow above the work plane, as a function of the distance from the measurement point relative to this plane;
• Figures 10 and 11 are perspective diagrams showing two carriers capable of being associated with a device according to the invention;
• FIGS. 12, 13 and 14 are illustrations showing the configuration of the air flows in three devices of different geometry, the representations resulting from computer simulations, the appreciation of the speeds being made with reference to a gray scale, which goes from lightest to darkest, in the direction of increasing speeds.

In FIGS. 1 and 2 which represent a first possible embodiment of the device, the reference 1 has designated a work surface which, in this case, is a fixed horizontal tray, of rectangular shape, supported by a base 11 placed or fixed to the ground S.

The upper face 10 of the work surface is intended to receive articles to be subjected to any manipulation and / or treatment which must operate in a clean atmosphere.

An article, in this case a bottle, has been represented and referenced A in the figures.

We have designated by the references 10a and 10b the longitudinal edges of the tray 10. These preferably have a rounded profile (without sharp edges).

Its transverse edges 10c are in abutment against a pair of transverse partitions 12 which extend upwards at a certain height relative to at work plan level 1.

Under the tray 1 is installed a box 2.

It is a tubular conduit extending under the entire plate 1, and ensuring transverse communication from one side to the other of the device.

The box 2 is fixed to the plate 1 and / or to the base 11 by members appropriate, not shown.

In this box is installed a system 4 for generating an air flow, consisting of one or more electric fan (s) able to draw air from the inlet 20 of the box, edge side 10b, to inject it on the other side, on the edge side 10a.

The air inlet portion 20 of the box has a smaller section than the main portion 22 which receives the generator 4.

This portion 20 constitutes a suction mouth located under the plate 1, just near ledge 10b. The transition between the narrowed portion 20 and the portion main 22 is done via a divergent portion 21.

On the opposite side, the main portion 22 opens into a semi-cylindrical guide 3, whose radius corresponds to the height of the portion 22, and whose axis of revolution is located at the edge 10a location.

Guide 3, the inner wall of which is referenced 30, opens out above of the tray 1, directly above the edge 10a.

Of course, the box 2 and the guide 3 are closed on their sides transverse, by appropriate transverse walls.

Inside the box portion 22, downstream of the generator 4, is mounted an air purification or filtration device 5, composed for example of one or several filter pads.

The filter elements are of known type, adapted to retain the impurities or particles in the air supplied by the generator 4.

The composition and porosity of these elements are chosen according to the application, and in particular according to the degree of cleanliness required.

The operation of the device is illustrated in FIG. 1, arrows symbolizing the path of the air intended to protect the bottle A located on the work surface.

The length of the different arrows was chosen so that it is approximately proportional to the speed of the air flow at the location considered.

The device represented in FIGS. 1 and 2 constitutes a work station for a person (not shown) assigned to a certain task on article A , this person standing on the free side of the device, referenced 100, side which corresponds to the edge 10b.

This side 100 will conventionally be called "free side".

The other side, referenced 101, where the guide 3 is located will be called "side upstream ", by reference to the direction of movement of the clean air flow above the plane of job.

Finally, the space above the worktop, which is also clear, is referenced 102.

The spaces 100 and 102 being clear and accessible, the operator can move place without difficulty near the work surface, handle the articles to be treated, and can involve different instruments or materials, for example mobile fillers located in the upper space 102.

The generator 4 having been started, it will continuously suck a flow of air through the mouth 20, as symbolized by the arrow a .

After filtration, the air flow leaves the box 2, as symbolized by the arrows b , and is deflected 180 ° inside the semi-cylindrical guide 3.

Inside the guide 3, one observes, as a result of the effect of inertia, a variation of speeds in radial direction.

At the end of the reversal of the flow, at the outlet of the guide 3, the external vein, which becomes the upper vein - or high vein - V ₁ , has a speed significantly greater than the rest of the flow.

This vein has been materialized by cross-hatching in FIG. 1, while the rest of the flow, or lower vein, is referenced V ₀ .

Within the vein V ₀ there is a gradient of velocities, the latter being very low, or even zero, in the vicinity of the face 10, to gradually increase upward, up to the vein V ₁ .

The radius of the guide 3, which determines the height of the air flow supplied by the guide above the work surface, is preferably chosen according to the height of the articles A considered, so that these articles are immersed in the lower flow V ₀ .

In the embodiment of FIGS. 1 and 2, the axis of revolution of the semi-cylindrical guide 3 coincides substantially with the edge 10a. Of course, this provision is not mandatory. The position of the axis could be shifted, up or down, and the radius modified to adjust the intensity of the speeds of V ₀ and V ₁ .

The high vein V ₁ plays the role of a vault-shaped shield which protects all the space above the surface 10, which it shelters from pollution of the ambient air, being in the open upper space 102 and on the open side 100.

Any contamination particles which arrive near the vein V ₁ are immediately carried away by this flow, and transferred at high speed to the free side 100.

Protection on the transverse sides is provided by the fixed partitions 12.

The air flows from the lower vein V ₀ and from the upper vein V ₁ are respectively symbolized by the arrows d and e .

These two flows meet on the downstream side, beyond the free edge 10b, and at least part of the overall flow goes down around the edge 10b - as symbolized by the arrows f - to enter the mouth 20. This bypass is favored by the rounded shape of the edge 10b.

The air is thus recycled, at least for the most part; like him it is practically clean air, or for the most part clean, the clogging of the elements filtering is done slowly.

This air circulation is continuous, as long as there are items to protect on the work surface.

Thanks to the transverse partitions 12, the flow of the clean air flow above of the work plan is not disturbed, or is practically not disturbed, when neighborhood of the transverse sides 10c of the work plan.

Of course, it is desirable that the operator has his hands protected by sterile gloves and that any instrument or apparatus introduced into the protected space be perfectly clean.

However, the nature of the flow generated favors the immediate evacuation of pollutants that could be introduced by such a break-in.

In the second embodiment shown in Figure 3, the elements identical or similar to those of the first embodiment have been assigned the same reference signs.

It is a variant without side walls and therefore suitable for a work plan extending beyond the sides referenced 10c in the first mode of realization, in particular in the form of a conveyor (mobile work plan).

The device illustrated in FIG. 3 comprises a work plan 1 which is constituted not by a fixed plate, but by a transporter, and more precisely by the upper strand - or "go" strand 13 - of a moving endless belt.

Usually, the return strand, designated 13 ′, extends under the outward strand 13.

These two strands 13, 13 'are supported in a well known manner by suitable guide means such as rotary support rollers 14, 14 '.

Appropriate drive means make it possible to move the mat, either continuously, step by step.

The upper strand 13 transports objects, for example bottles A.

These objects must be subjected, at a stage of their journey, to a any treatment - for example a filling - in a space which must be protected from contamination of ambient air.

The device according to the invention is therefore installed on the trajectory of the carrier, to ensure the protection of a portion of it.

As can be easily understood from a simple observation of FIG. 3, the presence of the two strands 14 and 14 'one above the other occupies under the worktop 1 a relatively large space, which prevents the installation of the air flow generator immediately below the work plan.

An arrangement identical to that of the first embodiment (Figures 1 and 2) is therefore not transposable in this configuration.

In this second embodiment, the suction mouth 20, at the inlet of the box 2, with its opening directed horizontally, opposite the space located just above the worktop 1.

This suction mouth 20 is bent downwards, according to a quarter of cylinder, for connection to a vertical tubular portion 200 extending along the side free 100.

The tubing 200 is itself connected to box parts 21 and 22 which are similar to those of the first embodiment, and which are installed below the return belt strand 13 'and its support rollers 14' , near the ground S.

It is in this portion 22 that the generator 4 is mounted, composed of a or multiple fans.

Via a right angle bend 23, the box 22 itself opens into a vertical pipe, or chimney 6 arranged on the upstream side 101.

Finally, the tubing 6 is connected, in its upper part, to a guide 7 in shape of quarter cylinder which opens near the work surface 1, upstream side.

One or more filter (s) 5 is (are) mounted at the outlet of the fans 4, for example at the base of the chimney 6.

Unlike the first embodiment previously described, the guide 7 which channels the clean air flow at its inlet above the deflected worktop air only on a quarter of circumference (90 °).

The tests carried out by the applicants have shown that this angle value was insufficient, on its own, to ensure proper speed distribution at within the clean air flow generated above the worktop.

Indeed, the velocity gradient is such that there is not a significant difference between the velocities measured in the high vein V ₁ and in the rest of the flow V ₀ .

This is why, in order to obtain a frank increase in distributions speed in the upper part of the flow, it is provided in this embodiment de.garnir la vertical chimney 6 of a series of deflectors 60.

These are flat blades whose large faces are parallel to the edges longitudinal of the work surface 1, that is to say on the lateral edges of the mat 13.

In the embodiment illustrated in FIGS. 3, 5 and 6, provision is made a series of three deflectors 60. The internal deflector - that is to say facing towards the plane working -, referenced 60a, in Figures 5 and 6 is a vertical flat plate.

The external plate referenced 60c in this same figure, is composed a vertical lower zone, of limited height, its main part forming an angle acute with respect to the vertical, direction directed upwards and outwards.

The intermediate deflector 60b is a plate also inclined by vertical, in the same direction as the deflector 60c, but with a more angle low.

The series of deflectors 60 therefore presents, side view (FIG. 6) the appearance general of the members of a fan which diverges upwards, i.e. downstream if the displacement of the air in the chimney 6 is considered.

The observation of Figures 5 and 6 allows us to understand the role of these deflectors.

The air flow at the base of the chimney 6 has been designated by the arrows F.

After having passed through a filter which, in this case, is composed of two superposed filter elements 5a and 5b, a large part of the air will be intercepted and directed outwards by the deflector 60c, as symbolized by the arrows I.

On the contrary, the innermost air flow, to the right of the internal deflector 60a in Figure 6, is not deviated at all, and its path is purely vertical.

In the zones between the deflectors 60a and 60b on the one hand, and 60b and 60c on the other hand, the air flow is deflected more and more towards the outside, as symbolized by the arrows G and H.

At the entrance to the guide 7 in the form of a quarter cylinder, at the base thereof, there is therefore a progressively increasing air flow from the inside to the outside of the quarter cylinder.

As illustrated in the figures, the guide 7 is also internally lined of a set of three deflectors 70.

In FIGS. 5 and 6, the internal deflector is assigned the index a , the intermediate deflector of the index b and the external deflector of the index c .

These deflectors are curved plates, in the shape of a cylinder arc coaxial with guide 7.

The deflector 70a is positioned so as to channel the innermost vertical flow F , to give it a horizontal orientation (arrow F ' ).

Between the deflectors 70a and 70b is channeled most of the air flow from the space between the deflectors 60a and 60b (arrow G ' ), while the deflectors 70b and 70c channel most of the current d between them. 'air from between deflectors 60b and 60c (arrows H' ).

Finally, the stream of air I , of higher speed, which circulates near the internal wall 60 of the chimney 6, after having been channeled by the deflector 60c is guided in the channel formed by the internal wall of the guide 7 and the outermost deflector 70c.

It is in this space that the air current has the greatest speed, symbolized by the arrow I ' , it is this air current which will constitute the high vein V ₁ , visualized by hatching in the figure 3.

The presence of curved deflectors inside the guide 7 is essential when, as is the case in the second embodiment, the device does not has no transverse partitions delimiting the protected space in the direction longitudinal - as was the case with the partitions 12 of the first embodiment -.

Indeed these deflectors, by giving the air flow a direction substantially horizontal, prevent the formation of a low pressure area at the entrance and proximity to the work surface, which would draw in ambient air from the sides transverse work plan open.

It is certain that such partitions cannot be provided when the plan work consists of a conveyor, because the partitions would prevent the passage of transported items.

It goes without saying that similar arched deflectors can be provided. also inside the semi-cylindrical guide 3 of the device of FIGS. 1 and 2, that the device may or may not have transverse partitions 12.

The operation of the device which is the subject of the second mode of embodiment of FIG. 3 is entirely similar to that of the first embodiment, the air being mainly recycled after sweeping the worktop, by suction to through the mouth 20, passage in the fan 4 and in the filter 5, deflection and pipe in chimney 6 and guide 7.

In the variant of Figure 4, the air is not recycled.

The generator - for example fan - 41 draws ambient air for the propel after filtration or purification, via a box 8, above work surface 1.

On the other side, the suction mouth 20 is connected, via a conduit 2, to a vacuum cleaner 40 separate from the fan 41.

In the illustrated embodiment, the box 8 is arranged on the upstream side of work plan 1 - which can be either a fixed platform or a conveyor -.

The fan 41 is located at the base of the box.

In the lower part, the box has a flared portion 81 which opens out upwards in a substantially vertical duct 8a extending by a guide approximately quarter-cylinder 8b.

An internal deflector, composed of a flat part 800a extending obliquely upward and outward and extending in guide 8b with a arc-shaped portion of cylinder 800b, coaxial with the wall of guide 8b, ensures the correct distribution of speeds above the work surface.

As in the previous embodiments, the air flow is composed of a high vein V ₁ , of high speed, which protects a lower vein of reduced speeds V. The dimensions of the device according to the invention will of course be adapted to the application concerned, and in particular to the dimension of the articles to be treated.

• largeur du plan de travail (c'est-à-dire distance entre les bords 10a et lOb) entre 0,3 mètre et 2 mètres ;
• longueur de la zone protégée (c'est-à-dire distance en direction longitudinale) entre 0,3 mètre et 3 mètres ;
• hauteur du flux d'air propre en sortie du guide 3, 7 ou 8b : entre 0,25 mètre et 0,7 mètre.

For purely indicative purposes, the following values can be given as examples of dimensions:

• width of the work surface (that is to say distance between the edges 10a and 10b) between 0.3 meters and 2 meters;
• length of the protected area (i.e. distance in longitudinal direction) between 0.3 meters and 3 meters;
• height of the clean air flow at the outlet of the guide 3, 7 or 8b: between 0.25 meters and 0.7 meters.

The air flow generated by the fan (s) will of course be directly dependent on these dimensions, as well as the speed of circulation of the flow.

The fourth embodiment illustrated in Figures 7 and 8 includes a air blowing system 6, 7 similar to that of FIGS. 5 and 6, and the same references have been used to designate identical or similar elements.

Note however that the guide 7 which channels the air above the plane of work 1 is extended at the outlet by an overhanging part - or visor 71 - which overhangs the upstream border zone of plane 1 and is slightly inclined downwards with respect to the horizontal.

The function of this visor 71 is to slightly fold down the high vein V ₁ to orient it towards the top of the suction mouth 20 and to reduce air leaks above this mouth.

Inside the suction pipe 200 are mounted a partition 24 and a flow retarder element 25.

The partition 24 is disposed in the upper part of the tube 200, near of its outer wall. The shape of the partition 24 is similar to that of the portion of the wall external facing which it is located, these two elements forming a channel whose upper part forms a quarter-circle and whose lower part is rectilinear and vertical.

The element 25 is fixed against the internal wall of the tube 200. It comprises, from top to bottom, an upper face 250 forming a converging dihedron with the lower portion of the partition 24, a vertical face 251 substantially in the extension of this portion, and a divergent face 252.

Elements 24 and 25 divide the suction mouth 20 into two secondary outlets, one upper and outer 20b of constant section and the other lower and inner 20a of decreasing section up to a throttle located at the level from the mouth exit area 20b.

This arrangement has the advantage of creating in the suction tube 200 a vertical distribution of speed homologous to that which was created on the blowing side. Mouth suction 20 is done with a higher air speed in its part high.

The vein V ₁ of high speed is stabilized and its tendency to rise under the effect of external disturbances (drafts), or to fall back towards the work plan, is reduced. Indeed, the upper secondary mouth 20b, in which the air flow is direct (without pressure drop) captures almost all of the upper vein V ₁ . On the contrary, the slowing of the flow in the mouth 20a forms an air mattress which prevents the high vein V ₁ from falling back down.

This embodiment is particularly recommended when there is no transverse partitions (referenced 12 in Figures 1 and 2) bordering the sides (referenced 10c) of the work plan.

It significantly reduces the penetration of outside air which can produce on these sides. Particle count tests have shown, in effect, that polluted air can penetrate by one side 10c, but that it is quickly channeled towards the suction mouth 20. It can therefore alter the clean area only on a small depth.

The presence of the visor 71 and the elements 24, 25 has the effect of limiting and to stabilize this depth.

These provisions are of course applicable as well with a plan of work 1 in the form of a fixed platform only in the form of a conveyor, and that the air flow either produced in a closed circuit (Figures 1 and 3) or open (Figure 4).

Figure 9 shows, by way of example, a possible distribution of speeds above the work plane in the central zone of the latter, within a flow clean air having a height of 0.30 m. The outside air is assumed to be stationary.

The curve in FIG. 9 represents the distance (height) X , in meters, from the measurement point in relation to the upper face of the work plane.

On the ordinate is represented the speed v in meters per second.

It can be seen that between the height 0 and the height approximately 0.17 m, the speed gradually increases to a value of around 0.6 m / s.

This range corresponds to the low speed vein V ₀ .

The increase in speed is then smaller; we reach a level and the air speed is almost constant, of a value close to 0.8 m / s, in the area of height between 0.18 and 0.25 m.

It is this range which corresponds approximately to the vein V ₁ .

The speed then drops sharply, becoming close to zero to one 0.30 m high, where the polluted ambient air is found.

The diagram in Figure 10 shows an installation for depositing topping products on a base which is moved continuously by means of a mat carrier 13.

The advance of the conveyor is referenced D ₁ , while the covering removal tool is referenced 90.

As an indication, the conveyor 13 has a width of 1.5 m and a speed 5 to 10 m / min in advance.

The transporter passes inside a protected area by means of a device according to the invention, the outline of which is shown diagrammatically by a broken line, and which is designated D.

The installation illustrated in FIG. 11 comprises a conveyor belt 13, the advance of which is done step by step, as symbolized by the arrow D ₂ .

The mat 13 transports thermoformed trays B intended to receive a product, for example a food product, which is supplied by dosing or manual filling tools 91.

Each tool 91 is assigned to a tray, the latter being transported in adjacent rows by the mat 13.

The close protection device D is installed at the level of tools 91.

The illustrations illustrated in FIGS. 12 to 14 relate to modeled flows, calculated by computer.

The air enters the guide according to a uniform distribution of the speeds, the value of the speed being E.

At certain points in the flow, white arrows are represented, whose length is proportional to the speed intensity.

In addition, apart from the arrows, the speed distribution is represented by a gradation of gray, going from lighter to darker in the direction of increasing speed. The speed value is given by the scale shown in the drawing.

The diagram of Figure 12 corresponds to a similar configuration to that of the first embodiment, using a semi-cylindrical guide.

The height of the flow leaving the guide is 0.30 m; the width of the plane work 1 is 0.60 m; the thickness of the worktop is 6 cm; mouth height suction is 9 cm.

The drawing shows the existence of an almost static space (light gray) above the work plan and visualize the high vein, high speed (very dark gray) which forms a shield overhanging the worktop and surrounding the edge free up to the suction mouth.

The representations of Figures 13 and 14 relate to devices similar to the second embodiment (Figure 3).

These two views make it possible to distinguish the high and low veins, dark tone (high speed) and light tone (low speed) respectively.

The drawings of Figures 13 and 14 are on different scales, the height of the flux produced by the guide, upstream side of the work surface, being the same in both case, namely equal to 0.30 m.

In the modeling of figure 13, the width of the work plan is 0.60 m whereas in that of Figure 14 it is 1.20 m.

The device according to the invention is not necessarily associated with a processing operation for articles supported or transported by the work surface.

Thus, the invention can also be implemented to equip a simple transfer facility, from one place to another, of sensitive products, so that the products transported are protected from the external environment, possibly polluted.

When dealing with article processing, possible applications are very large.

As an example of application, we can cite the transfer of bottles between a bar turning station and a filling station using a liquid susceptible to contamination.

• les cabinets dentaires, le dispositif pouvant servir à maintenir stériles des instruments orthodontiques posés sur un support ;
• les blocs opératoires, pour la protection du champ opératoire du patient ;
• les métiers de bouche, pour la protection de la table où l'artisan prépare et conditionne ses plats ;
• les laboratoires des industries agro-alimentaires, de micro-biologie, de micro-électronique, de traitement ou de montage de composants opto- et/ou acousto-électroniques, dans lesquels il faut protéger des produits de la contamination particulaire ;
• des applications domestiques variées, par exemple pour protéger une personne contre le pollen et les poussières, ou pour protéger des zones de préparation de lentilles de contact.

As an application using a fixed work plan, in which a clean room would be oversized equipment, we can cite:

• dental offices, the device being able to be used to maintain sterile orthodontic instruments placed on a support;
• operating theaters, for the protection of the patient's operating field;
• the trades of mouth, for the protection of the table where the craftsman prepares and conditions his dishes;
• laboratories in the food industry, micro-biology, micro-electronics, processing or assembly of opto- and / or acousto-electronic components, in which products must be protected from particulate contamination;
• various household applications, for example to protect a person against pollen and dust, or to protect areas for preparing contact lenses.

Claims (17)

1. A method of closely protecting a horizontal work surface (1) by means of a flow of clean air, the work surface (1) being unobstructed and accessible both from above (102) and from at least one side, referred to as the "free side" (100), in which method:

   clean air is blown continuously over the work surface (1) from the "upstream" side (101), which is the side opposite from said free side (100), in the form of a substantially horizontal flow which sweeps the work surface (1) transversely towards the free side (100), and which has a speed gradient such that its upper layer - or "high stream" - (V₁) has a speed significantly higher than the speed of the air flowing in the vicinity of the top face (10) of the work surface (1); and

   all or most of the flow is sucked in continuously via the free side (100) by means of a suction intake (20) extending along and in the immediate vicinity of the edge (10b) of the work surface (1).
2. A method according to claim 1, characterized by the fact that the air collected by said suction intake (20) is recycled and blown out via the upstream side (101) after it has been filtered or purified.
3. A method according to claim 1 or 2, characterized by the fact that the work surface (1) is a stationary table top.
4. A method according to claim 1 or 2, characterized by the fact that the work surface (1) is a conveyor (12).
5. Apparatus for closely protecting a horizontal work surface (1) by means of a flow of clean air, the work surface (1) being unobstructed and accessible both from above (102) and from at least one side, referred to as the "free side" (100), said apparatus being characterized by the fact that it comprises:

   air blowing means (2, 4; 41, 3) for blowing clean air continuously over the work surface (1) from the "upstream" side (101), which is the side opposite from said free side (100), in the form of a substantially horizontal flow which sweeps the work surface (1) transversely towards the free side (100), and which has a speed gradient such that its upper layer - or "high stream" - (V₁) has a speed significantly higher than the speed of the air flowing in the vicinity of the top face (10) of the work surface (1);

   a suction intake (20) extending along and in the immediate vicinity of the edge (10b) of the work surface; and

   suction means (4; 100) connected to said intake (20).
6. Apparatus according to claim 5, characterized by the fact that a single flow generator (4) such as a fan (or a group of juxtaposed fans) blows out the clean air on the upstream side (101) and sucks it in on the free side (100), at least of portion of the flow being recycled via a closed circuit path.
7. Apparatus according to claim 5 or 6, characterized by the fact that the air is blown by means of a flow generator (4), such as a fan, downstream from which at least one filter (5) or some other air purification means, is disposed.
8. Apparatus according to any one of claims 5 to 7, characterized by the fact that the air is blown by means of a flow generator (4), such as a fan, which is situated below the work surface (1) and which produces a substantially horizontal flow which is deflected through 180° at the upstream side (101) by a tubular guide (3) that is semi-cylindrical or approximately semi-cylindrical in shape.
9. Apparatus according to any one of claims 5 to 7, characterized by the fact that said air blowing means comprise a duct that is vertical or approximately vertical (6; 8a) disposed on the upstream side (101), the duct having its low end connected to an air flow generator (4; 41) such as a fan, while its high end opens out substantially level with the work surface (1), into a tubular guide (70; 8b) that is quarter cylinder shaped, or approximately quarter cylinder shaped, and that is suitable for deflecting the flow so as to impart a substantially horizontal direction to it.
10. Apparatus according to claim 9, characterized by the fact that the inside of said vertical or approximately vertical duct (6; 8a) is provided with at least one deflector (60; 800) forming an acute angle relative to the vertical, and suitable for deflecting a portion of the flow outwards (relative to said work surface (1)) so as to constitute said high stream (V₁).
11. Apparatus according to claim 10, characterized by the fact that the duct (6; 8a) is provided with a plurality of deflectors (60) which are constituted by juxtaposed plane plates disposed in a fanned-out configuration so as to diverge going from the bottom upwards.
12. Apparatus according to claim 11, characterized by the fact that the deflector plate (60) that is innermost (relative to said work surface (1)) is substantially vertical.
13. Apparatus according to any one of claims 8 to 12, characterized by the fact that the inside of said tubular guide (3; 7; 8b) is provided with at least one deflector (70; 800b).
14. Apparatus according to any one of claims 5 to 13, characterized by the fact that said air blowing means are provided with an overhanging portion (71) forming a visor which overlies the upstream zone of the work surface (1), and is suitable for directing the high stream (V₁) slightly downwards.
15. Apparatus according to any one of claims 5 to 14, characterized by the fact that said suction intake (20) is subdivided into two secondary suction intakes: namely a top intake (20b) suitable for collecting the air flow corresponding to the high stream (V₁) and for allowing it to pass through without headloss, or almost without headloss, and a bottom intake (20a) suitable for braking the flow (V₀) situated under the high stream;
16. Apparatus according to any one of claims 5 to 15, characterized by the fact that the work surface (1) is a stationary table top (1).
17. Apparatus according to any one of claims 5 to 15, characterized by the fact that the work surface (1) is a conveyor (12).

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