Abstract:
A device for dynamically separating two zones by a bufer zone and two clean air curtains. When transferring objects at high speed between two zones, a buffer zone which is connected to the two zones, forms a dynamic lock in order to separate them. a dynamic confinement system placed between each pair of adjacent communication zones forms an air curtain including two or three clean air jets. The buffer zone includes a blower ceiling and an intake grill facing it.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a device used to dynamically separate at least two zones in which there are different environments, to enable objects or products to be transferred from one zone to the other at high speed without breaking the confinement. 
     The process according to the invention may be used in many industrial sectors. 
     Thus, this process is applicable to all industries (food processing, medical, biotechnologies, high technologies, nuclear, chemical, etc.) in which different environments have to be maintained in zones communicating with each other to enable frequent passage of objects or products. The term “environment” refers particularly to aeraulic conditions, gaseous and particular concentrations, temperature, relative humidity, etc. 
     2. Discussion of the Background 
     At the present time, there are two types of solutions for dynamically separating two zones communicating with each other, for example in order to allow objects to be brought in and out; these two types are protection by ventilation and protection by air curtain. 
     Protection by ventilation consists of artificially creating a pressure difference between the two zones so that the pressure in a zone to be protected is greater than the pressure inside a contaminating zone. Thus, if the zone to be protected contains a product that could be contaminated by ambient air, a laminar flow is injected into the zone to be protected that blows outwards through the access opening to this separation zone. In the opposite case in which personnel and the environment outside a contaminated space need to be protected, dynamic confinement is achieved by using extraction ventilation in this contaminated space. In each case, an empirical rule imposes a minimum ventilated air speed of 0.5 m/s in the plane of the opening through which the two zones communicate in order to prevent contamination from being transferred into the zone to be protected. 
     However, the efficiency of this ventilation protection technique is not perfect, particularly in a so-called “infractions” situation, in other words when objects are transferred between the two zones. Furthnermore, this type of protection makes it necessary to process and control the entire zone to be protected ron the contaminating external atmosphere or the entire contaminated zone. When the zone to be processed and controlled is large, this introduces a particularly high investment and operating cost. Finally, this technique of protection by ventilation only provides protection in one direction, in other words it is onlv useful when contamination transfers are only possible in one direction. 
     The air curtain protection technique consists of simultaneously injecting one or several adjacent clean air jets in the same direction into the separation zone between the two zones, which form an immaterial door between the zone to be protected and the contaminating zone. 
     Note that according to the theory of turbulent plane jets, a plane air jet is composed of two separate zones; a transition zone (or core zone) and a development zone. 
     The transition zone corresponds to the central part of the jet adjacent to the nozzle in which clean air is injected. Within this zone in which there is no mix between the injected air and the air on each side of the jet, the speed vector is constant. Considering a cross-section through a plane perpendicular to the plane of the separation zone, the width of the transition zone gradually decreases as the distance from the nozzle increases. This is why this transition zone is called a “tongue” throughout the rest of the text. 
     The-development zone of the jet is the part of this jet located outside the transition zone. In this jet development zone, outside air is entrained by the jet low. This results in variations in the speed vector and mixing of air. Air entrainment on both surfaces of the jet within this development zone is called “induction”. Thus an air jet induces an air flow on each of its surfaces which depends particularly on the injection flow of the jet considered. 
     Documents FR-A-2 530 163 and FR-A-2 652 520 propose an air curtain to separate a polluted zone from a clean zone. in both cases, the air curtain consists of twio adjacent clean air jets blowing in the same direction. Nllore precisely, dynamic separation is provided by a first relatively slow jet (called the “slow jet”), for which the tongue entirely covers the opening. The second jet (called the “fast jet”) is faster than the slow jet, and is installed between the slow jet and the zone. Its function is to stabilize the slow jet by a suction effect which brings this slow jet into contact with the fast jet. 
     In these documents, it is specified that the tongue of the slow jet is sufficiently long to cover any opening when the width of the slow jet injection nozzle is equal to at least ⅙ th  of the height of the opening to be protected. 
     Document FR-A-2 652 520 also proposes to simultaneously inject clean ventilation air at a temperature adapted to the requirements, inside the clean zone to be protected. Note that this clean ventilation air must be injected at a rate approximately equal to the rate induced by the surface of the fast jet which is in contact with clean ventilation air. 
     Furthermore, document FR-A-2 659 782 proposes to add a third relatively slow clean air jet to the two clean air jets used in documents FR-A-2 530 163 and FR-A-2 652 520 so that the fast jet is located between two adjacent slow jets in the same direction. The flow of clean ventilation air injected inside the zone to be protected is then considerably reduced due to the fact that induction in this zone is produced by the development zone of one of the slow jets, rather than by the development zone of the fast jet as in the case of an air curtain with two jets. Furthermore, dynamic confinement is provided in both directions, which was not the case in the previous documents. 
     Document WO-A-96 241011 also describes an installation in which a chamber containing a confined atmosphere, communicates with the same outside atmosphere through one or two openings, with which gas curtains are associated. Each gas curtain is formed of a slow jet sustained by a fast jet as described in documents FR-A-2 530 163 and FR-A-2 652 520. The chamber can be used for continuous processing of products due to the injection of a reagent inside it. Products pass from the outside atmosphere into the confined atmosphere in this chamber to be processed in it before being taken out again to the external atmosphere. 
     Despite the improvements made to the air curtain technique described in these various documents, the problem of transferring objects or products at a high rate between two zones in which there are different environments without breaking the confinement has not been satisfactorily solved by any known device, particularly if there is a risk of cross-contamination between the two zones. 
     SUMMARY OF THE INVENTION 
     More particularly, the purpose of the invention is a device for dynamic separation of at least two zones in which there are different environments authorizing high speed transfer of objects or products between these zones, without breaking the confinement, even in the case in which there is a risk of cross-contamination between the two zones. 
     According to the invention, this result is obtained by means of a dynamic separation device separating at least two zones in which there are different environments, characterized by the fact that it comprises: 
     at least one buffer zone with controlled atmosphere used for communication between the zones to be separated; 
     dynamic confinement means placed between each pair of adjacent communicating zones to create an air curtain between these zones comprising a first relatively slow clean air jet which comprises a tongue which completely closes off communication between the zones, and a second relatively fast clean air jet in the same direction as the first jet and adjacent to it, on the side of the buffer zone. 
     The expression “with controlled atmosphere” means that all characteristics of the air present in the buffer zone such as temperature, relative humidity, aeraulic conditions, gaseous and particular concentrations, etc., are controlled. 
     The expression “adjacent communicating zones” means each group of two zones in the assembly formed by the zones to be separated and by the buffer zones, that communicate directly with each other. Thus in the case in which the device comprises a single buffer zone located between two zones to be separated, there are two pairs of adjacent communicating zones each formed by the single buffer zone and one of the zones to be separated. When there are several buffer zones, there is at least one other pair of adjacent communicating zones formed of two buffer zones. 
     The arrangement consisting of one of several buffer zones between the zones to be separated, and air curtains formed from at least two jets of clean air between adjacent communicating zones, enable objects or products to be transferred at high speed while preventing contaminants present in either of the controlled environment zones from reaching the other controlled environment zone, and vice versa. Each buffer zone thus acts as a dynamic lock between the zones to be separated. 
     Preferably, the dynamic confinement means that are inserted between each pair of adjacent communicating zones are such that the second (fast) jet in each air curtain is injected at a flow such that the air flow induced by the surface of the second jet in contact with the first (slow) jet is less and preferably approximately equal to half the first jet injection rate. 
     In one special embodiment, these dynamic confinement means are such that each air curtain comprises a relatively slow third jet in the same direction as the first and second jets and adjacent to the second (fast) jet on the same side as the buffer zone. This third jet then comprises a tongue that completely closes off communication between the zones and it is injected at a flow significantly equal to the injection flow in the first jet, so that the air flows induced by the surfaces of the second jet in contact with the first and third jets respectively are less than, or preferably approximately equal to half of the injection flows of the jets. 
     In practice, each of the dynamic confinement means comorises at least two adjacent air supply nozzles and an intake grille facing the supply nozzles and located in a plane parallel to them. The supply nozzles and the intake grilles are advantageously located in line with the upper and lower surfaces of the buffer zone. 
     In order to further improve the behavior of the device particularly in infraction situations through air curtains, the buffer zone preferably comprises ventilation, such as a blower ceiling, associated with the injection means that inject clean air into this zone. The flow from these injection means is then equal to at least the sum of the air flows induced by each of the surfaces of the jets in the air curtains in contact with the buffer zone. Furthermore, the flow from the injection means is such that it provides a minimum speed of 0.1 m/s across the areas of the planes at the ends of the buffer zone. 
     In this case, the buffer zone may also comprise an intake grille distributed over its entire lower surface. The flow from the injection means is then equal to at least the sum of the air flow drawn in by the intake grille and the air flow induced by each of the surfaces of the air curtain jets in contact with the buffer zone. Furthermore, the flow from the injection means must always be sufficient to provide a minimum speed of 0.1 m/s across the areas of the planes at the ends of the buffer zone. This arrangement corresponds particularly to the case in which the buffer zone is used to carry out an elementary operation (proportioning, packaging, etc.) on objects or products transferred between the zones to be separated. 
     In the latter case, several buffer zones may be placed in series between the zones to be separated. The air curtains inserted between the two buffer zones are then delimited by side walls with a width equal to the width of the adjacent air supply nozzles. 
     Furthermore, regardless of the number of buffer zones used on the device, the air curtains inserted between a buffer zone and one of the zones to be separated are delimited by side walls with a width equal to at least the maximum thickness of these air curtains. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     We will now describe some non-limitative examples of different embodiments of the invention with reference to the attached drawings in which: 
     FIG. 1 is a perspective view that diagrammatically illustrates the use of a single buffer zone to provide communication between two zones with controlled environments through two air curtains each formed of two adjacent clean air jets according to a first embodiment of the invention; 
     FIG. 2 is a perspective view comparable to FIG. 1 which illustrates the case in which each air curtain is formed of three adjacent clean air jets according to a second embodiment of the invention; and 
     FIG. 3 is a perspective view that diagrammatically illustrates the use of several buffer zones in series between two zones with controlled environments, with the insertion of an air curtain between each pair of adjacent communicating zones. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 shows two zones denoted by reference  10   a  and  10   b , in which there are different environments and in which it is required to be able to transfer objects or products at high speed in at least one direction. These zones  10   a  and  10   b  are called the “zones to be separated” or “zones with controlled environments” throughout the rest of this text. For example, it is assumed non-restrictively that objects or products must be transferred at high speed from zone  10   a  to zone  10   b.    
     Zones  10   a  and  10   b  are delimited by air tight surfaces (not shown) and the environment in each zone is different, in other words at least one of the characteristics, specifically such as gaseous and particular concentrations, aeraulic conditions, temperature, relative humidity, etc. is different in the two zones. 
     According to the invention, zones  10   a  and  10   b  are linked to each other through at least one dynamic separation system which, in the embodiment shown in FIG. 1, includes a buffer zone  12  through which zones  10   a  and  10   b  communicate. More precisely, the buffer zone  12  is a zone with a controlled atmosphere, in other words a zone in which various parameters such as gaseous and particular concentrations, aeraulic conditions, temperature, relative humidity, etc., are controlled. 
     The dynamic separation device according to the invention also comprises dynamic confinement means denoted in general by references  14   a  and  14   b  on FIG. 1, which are inserted between zone  10   a  and buffer zone  12 , and between buffer zone  12  and zone  10   b  respectively, in other words eacn pair of adjacent communicating zones in the installation. 
     Dynamic confinement means  14   a  create a first air curtain  16   a  between zone  10   a  and buffer zone  12 . imilarly, dynamic confinement means  14   b  create a second air curtain  16   b  between buffer zone  12  and the zone  12   b  with controlled environment. 
     As illustrated diagrammatically in FIG. 1, the buffer zone  12  is delimited by air tight surfaces in order to form a horizontal corridor with a rectangular cross-section, the ends of which lead into zone  10   a  and into zone  10   b  through air curtains  16   a  and  16   b  created by dynamic confinement means  14   a  and  14   b.    
     The upper horizontal surface of the buffer zone  12  forms a blower ceiling  18 . This blower ceiling  18  is associated with injection or ventilation means (not shown) that output clean air to the buffer zone  12  at a determined flow. As will be seen later, this flow depends on the characteristics of the air curtains  16   a  and  16   b  and whether or not there is an intake grille in buffer zone  12 . 
     In the embodiment shown in FIG. 1, the horizontal lower surface  20  of the buffer zone  12  forms a working plane. As a variant, an intake grille may be distributed over this entire lower surface  20 , to recover part of the ventilation air flow injected into buffer zone  12  through the blower ceiling  18 . 
     In addition to its upper horizontal surface that forms the blower ceiling  18  and its lower horizontal surface  20 , the buffer zone  12  is delimited by two side walls  22 , also oriented vertically parallel to the plane of FIG.  1 . 
     The dynamic confinement means  14   a  and  14   b  are placed in line with the air tight walls that delimit the buffer zone  12  so as to form the air curtains  16   a  and  16   b  when these confinement means are used. 
     More precisely, in the embodiment shown in FIG. 1, dynamic confinement means  14   a  and  14   b  are designed to create air curtains  16   a  and  16   b  each of which are formed of two clean air jets adjacent to each other and in the same direction. Consequently, dynamic confinement means  14   a  comprise two air supply nozzles  24   a  and  26   a  that extend across the entire width of buffer zone  12  in line with the blower ceiling  18  on the zone  10   a  side. Similarly, dynamic confinement means  14   b  comprise two air supply nozzles  24   b  and  26   b  that extend across the entire width of buffer zone  12  in line with the blower ceiling  18  on the zone  10   b  side. All air supply nozzles  24   a ,  26   a ,  24   b  and  26   b  output into the same horizontal plane located in line with the lower surface of the blower ceiling  18 . 
     The dynamic confinement means  14   a  also comprise a horizontal intake grille  28   a  located on the surface of the air supply nozzles  24   a  and  26   a  and extend over the entire width of buffer zone  12 , in line with its lower surface  20 . Similarly, dynamic confinement means  14   b  comprise a horizontal intake grille  28   b  placed below the air supply nozzles  24   b  and  26   b  and extending over the entire width of buffer zone  12 , in line with its lower surface  20 . 
     Each of the dynamic confinement means  14   a  and  14   b  also comprises means (not shown) of injecting air at a controlled speed and flow through the air supply nozzles  24   a  and  26   a , and through the air supply nozzles  24   b  and  26   b  respectively, and means (not shown) of drawing in all air flows injected through the nozzles and induced air flows, through intake grilles  28   a  and  28   b  respectively. 
     As shown diagrammatically in FIG. 1, the air tight side walls  22  that delimit the buffer zone  12  extend beyond the ends of this zone over a length equal to at least the maximum thickness of the air curtains  16   a  and  16   b , in order to avoid any break in the confinement at the sides of air curtains. 
     As already mentioned, the embodiment in FIG. 1 corresponds to the case in which each air curtain  16   a  and  16   b  is formed of two adjacent clean air jets in the same direction. The two air curtains  16   a  and  16   b  have exactly the same characteristics which will now be described in more detail. 
     When the dynamic confinement means  14   a  and  14   b  are used, each of the air supply nozzles  24   a  and  24   b  outputs a relatively slow clean air jet, for which only tongues  30   a  and  30   b  are shown. Furthermore, each of the air supply nozzles  26   a  and  26   b  located on the same side of the blower ceiling as the nozzles  24   a  and  24   b  outputs a relatively fast clean air jet compared with the jets output by nozzles  24   a  and  24   b . FIG. 1 only shows the tongues  32   a  and  32   b  of these relatively fast jets. To simplify the description, the relatively slow and relatively fast jets are called “slow jets” and “Last jets” in the rest of the text. 
     Since the air supply nozzles  24   a ,  26   a ,  24   b  and  26   b  extend over the entire width of the buffer zone  12 , the air curtains  16   a  and  16   b  also extend over the entire width of the burrer zone between the buffer zone side walls  22 . 
     As shown diagrammatically in Iigure  1 , each of the slow jets injected by nozzles  24   a  and  24   b  is sized such that its tongue  30   a ,  30   b  covers tne entire cross-section of the buffer zone at the ends of the buffer zone adjacent to zones  10   a  and  10   b  respectively. This result is obtained by making sure that the range, or length, of the tongues  30   a  and  30   b  is at least as long as the height of the buffer zone  12 . This is achieved by making the width of the injection slit for each nozzle  24   a  and  24   b  parallel to the plane of the figure equal to at least ⅙ th  and preferably ⅕ th  of the height of the buffer zone  12 . 
     Furthermore, the speed of each of the slow jets emitted by nozzles  24   a  and  24   b  is advantageously equal to 0.5 m/s, in order to minimize turbulence and for economic reasons. Since the length of the tongues  30   a  and  30   b  of the slow jets is equal to at least half of the height of the buffer zone  12  and since these jets are relatively slow, the air streams go around the contours of the objects or products that pass through the air curtains  16   a  and  16   b  without breaking the confinement. 
     However, the low speed of the slow jets injected by nozzles  24   a  and  24   b  mean that these jets, if they were alone, could be destabilized by aeraulic or mechanical disturbances that could occur close Lo the air curtains, thus breaking the confinement of zones  10   a  and  10   b . This is why fast jets injected by nozzles  26   a  and  26   b  are added to each of the slow jets. The highest speed of these fast jets stabilizes the slow jets and consequently improves the confinement efficiency of zones  10   a  and  10   b  in infraction situations through the dynamic barriers forred by each of the air curtains  16   a  and  16   b . As a nonrestrictive example, the width of each fast jet air supply nozzle  26   a  and  26   b  may be equal to about {fraction (1/40)} th  of the width of the slow jet air suoplv nozzles  24   a  and  24   b.    
     Preferably, in order to optimize the barrier effect provided by air curtains  16   a  and  16   b , the injection flow of each fast jet through nozzles  26   a  and  26   b  is adjusted such that the air flow induced by the surfaces of these fast jets that are in contact with the slow jets injected through nozzle  24   a  and  24   b  is less than, or preferably approximately equal to half of the injection flow through these slow jets. 
     As already noted, the intake grilles  28   a  and  28   b  recover the entire air blown through the supply nozzles under which they are placed, and all entrained air by each air curtain  16   a  and  16   b . In practice, air recovered through intake grilles  28   a  and  28   b  may be purified by specific purification means (not shown) before being recycled to air supply nozzles  24   a ,  26   a ;  24   b ,  26   b . Excess air is then released outside after a second specific purification. 
     Note that the horizontal orientation of the air supply nozzles that determines a vertical orientation of the air curtains, and the horizontal arrangement of the intake grilles facing the air curtains, optimize the barrier effect obtained using each of the dynamic confinement means  14   a  and  14   b.    
     Furthermore, internal ventilation of the buffer zone  12  provided by the blower ceiling  18  produces a purifying effect in this zone. This purifying effect contributes to the efficiency of the dynamic separation of zones  10   a  and  10   b , particularly in the case of a high transfer rate of objects or products between these two zones. 
     More precisely, in the embodiment shown in FIG. 1 in which each of the air curtains  16   a  and  16   b  is formed of two adjacent jets in the same direction, the clean ventilation air flow injected in the buffer zone  12  through the blower ceiling  18  is equal to at least the air flow induced by the fast jets output from nozzles  26   a  and  26   b , on the surfaces of these fast jets that are in contact with the buffer zone  12 . Furthermore, the clean ventilation air is injected into the buffer zone  12  through the blower ceiling  18  at a speed such that the air speed across the areas of the planes at the ends of the buffer zone  12  that lead into zones  10   a  and  10   b , is equal to at least 0.1 m/s. 
     Furthermore, note that the physical characteristics (temperature, relative humidity, gaseous and particular concentrations, etc.) are controlled by appropriate means (not shown), so as to establish and maintain a determined atmosphere in Lhe buffer zone  12 . This atmosphere may be identical to the atmosphere in one of the two zones  10   a  and  10   b , or it may be different from this atmosphere, depending on the application being considered. 
     Each of the intake grilles  28   a  and  28   b  has a width approximately equal to the total width of the air supply nozzles  24   a  and  26   a , and  24   b  and  26   b  respectively. However this width may be varied, particularly to take account of some aeraulic conditions in zones  10   a  and  10   b , tending to deviate the jets forming the air curtains  16   a  and  16   b  from the vertical. Thus, it is desirable to reduce the width of the corresponding intake grille towards the inside of buffer zone  12 , When the jets forming the air curtain Lend to be deviated towards the outside of this zone. Conversely, the width of the intake grille must be increased towards the inside of the buffer zone  12  when the jets forming the air curtain tend to be deviated towards the inside of this zone. 
     FIG. 2 illustrates a second embodiment of the invention which is essentially different from the embodiment in FIG. 1 due to the fact that each air curtain denoted by references  16 ′ a  and  16 ′ b  comprises three jets of adjacent clean air in the same direction. 
     This is achieved by providing each of the dynamic confinement means denoted by references  14 ′ a  and  14 ′ b , in addition to the air supply nozzles  24   a ,  26   a  and  24   b  and  26   b  respectively, with a third supply nozzle  34   a  and  34   b  adjacent to nozzles  26   a  and  26   b  respectively on the side of the blower ceiling  18 . More precisely, nozzles  34   a  and  34   b  extend over the entire width of the buffer zone  12  and their output is arranged in the same horizontal plane as the other nozzles  24   a ,  26   a ;  24   b ,  26   b , in other words in a horizontal plane which is coincident with the plane of the lower surface of the blower ceiling  18 . 
     When dynamic confinement means  14 ′ a  and  14 ′ b  are implemented, each of the air supply nozzles  34   a  and  34   b  outputs a third clean air jet which is relatively slow with respect to fast jets emitted by nozzles  26   a  and  26   b , between this fast jet and the buffer zone  12 . The tongues of these third jets are illustrated as  36   a  and  36   b  in FIG.  2 . 
     The dimensions of nozzles  34   a  and  34   b  are chosen such that the tongues  36   a  and  36   b  of the third jets in each of the air curtains  16 ′ a  and  16 ′ b  cover the entire section of the buffer zone  12 . Consequently, the lower slit in each of the nozzles  34   a  and  34   b  has a width equal to at least ⅙ th , and preferably ⅕ th  of the height of the buffer zone  12 , in the cross section parallel to the plane of FIG.  2 . In practice, the widths of nozzles  24   a ,  34   a  and  24   b , and  34   b  are identical. 
     In the second embodiment of the invention illustrated in FIG. 2, the injection flow from the slow jets output by nozzles  34   a  and  34   b  is adjusted to be approximately equal to the injection flow from the slow jets output by nozzles  24   a  and  24   b . Thus, the air flows induced by the surfaces of the fast jets output through nozzles  26   a  and  26   b  in contact with each of slow jets in the corresponding air curtain, are less than or preferably approximately equal to half of the injection flows in these slow jets. 
     As is also shown in FIG. 2, the width of each of the intake grilles  28 ′ a  and  28 ′ b  is adapted to the width of the air curtains  16 ′ a  and  16 ′ b , so that it is approximately equal to the total width of the nozzles forming these air curtains. Obviously, this width may be varied as described previously with reference Lo FIG. 1, when the aeraulic conditions in at least one of the zones  10   a  and  10   b  tend to deviate the air curtains from the vertical. 
     The second embodiment that has just been described briefly with reference to FIG. 2 provides dynamic confinement in both directions between buffer zone  12  and each of zones  10   a  and  10   b . Furthermore, the clean ventilation air flow injected through the blower ceiling  18  may be considerably reduced. The air injection flow through the blower ceiling  18  is then equal to at least the air, flows induced by the slow jets emitted through the injection nozzles  24   a  and  24   b , on the surfaces of these jets in contact with the buffer zone  12 , and it is such that it provides a minimum speed of 0.1 m/s across the areas of the planes at the ends of the buffer zone. 
     In the embodiments described above with reference to FIGS. 1 and 2, the buffer zone  12  is a passive zone in which no operations are carried out on objects or products that are transferred between zones  10   a  and  10   b.    
     In other embodiments of the invention, the buffer zone  12  is an active zone, in other words it is used to carry out an elementary operation (proportioning, packaging, etc.) on objects or products transferred between zones  10   a  and  10   b.    
     The architecture of the dynamic separation device is then identical to the architecture described above with reference to FIGS. 1 and 2. However, an intake grille is distributed over the entire lower surface  20  of buffer zone  12 . The intake speed through this intake grille varies for example between about 0.1 m/s and 0.2 m/s. The internal ventilation supply flows through the blower ceiling  18  is then larger, and is equal to at least the sum of the air flows induced by each of the surfaces of the air curtains in contact with the buffer zone  12  and the intake flow through the intake grille. 
     Furthermore, this internal ventilation supply rate should correspond to a minimum speed of 0.1 m/s across the areas of the planes at the ends of the buffer zone. 
     Note that the ventilation flows through the blower ceiling  18  and the intake flows through the intake grille may be higher. However, the operating cost of the installation will then be higher. 
     As shown diagrammatically in FIG. 3, several successive individual operations (proportioning, packaging, etc.) may be carried out between zones  10   a  and  10   b  during the transfer of objects or products. In this case, the dynamic separation device according to the invention will comprise several buffer zones  12  laid out in series, through which zones  10   a  and  10   b  can communicate. Each buffer zone  12  then has characteristics similar to the characteristics described above, and particularly a blower ceiling  18  and an intake grille  20 ′ facing it. 
     In this case, dynamic confinement means denoted by references  14   a ,  14   b  and  14   c  are inserted between each pair of adjacent communicating zones. More precisely, dynamic confinement means  14   a  are inserted between zone  10   a  and buffer zone  12  which leads into zone  10   a , the dynamic confinement means  14   c  are inserted between each pair of adjacent buffer zones  12  and dynamic confinement means  14   b  are inserted between zone  10   b  and buffer zone  12  that leads into this buffer zone. 
     Dynamic confinement means  14   a ,  14   b  and  14   c  are identical with each other and they may be made as described above with reference to FIG. 1, or as described above with reference to FIG. 2, depending on the case. 
     As described above, the air curtains formed by the dynamic confinement means  14   a  and  14   b  separating zones  10   a  and  10   b  are delimited at the sides by side walls  22  of the buffer zones considered which extend into zones  10   a  and  10   b , so as to have a width equal to at least the maximum thickness of the air curtains considered. 
     On the other hand, the air curtains formed by dynamic confinement means  14   c  that separate two consecutive buffer zones  12  are delimited at the sides by extensions of the side walls  22  of these buffer zones over a width equal to the width of the supply nozzles forming these air curtains. 
     As illustrated as an example in the case of the central buffer zone  12  in FIG. 3, note that a single buffer zone can provide dynamic separation of more than two zones  10   a ,  10   b  and  10   c . In this case, one or several openings are formed in at least one of the side walls  22  of the buffer zone considered and each of the openings is controlled by dynamic confinement means  14   d , the characteristics of which are similar to the characteristics of the dynamic confinement means  14   a  and  14   b  in FIG. 1, or dynamic confinement means  14 ′ a  and  14 ′ b  in FIG.  2 .