U.S. patent application number 09/319255 was filed with the patent office on 2001-05-31 for method for dynamic separation into two zones with a screen of clean air.
This patent application is currently assigned to Gregory J. Maier. Invention is credited to LABORDE, JEAN-CLAUDE, MOCHO, VICTOR MANUEL.
Application Number | 20010002363 09/319255 |
Document ID | / |
Family ID | 9498506 |
Filed Date | 2001-05-31 |
United States Patent
Application |
20010002363 |
Kind Code |
A1 |
LABORDE, JEAN-CLAUDE ; et
al. |
May 31, 2001 |
METHOD FOR DYNAMIC SEPARATION INTO TWO ZONES WITH A SCREEN OF CLEAN
AIR
Abstract
An air curtain (14) is used to dynamically separate a zone (10)
to be protected and a contaminating zone (12) communicating with
each other through at least one separation zone (11), the air
curtain being formed by simultaneously injecting at least two
adjacent clean air jets into the same direction in the separation
zone (11). More precisely, the air curtain (14) comprises a slow
jet, in which the tongue (16) covers the entire separation zone
(11) and a fast jet inserted between the slow jet and the zone (10)
to be protected and for which the injection flow is such that it
induces an air flow equal to approximately half the injection flow
of the slow jet, on its surface in contact with the slow jet.
Preferably, clean ventilation air is also injected into the zone
(10) to be protected at a flow equal to at least the air flow
induced by the surface of the air curtain in contact with the
ventilation air, and in any case at a speed not less than 0.1
m/s.
Inventors: |
LABORDE, JEAN-CLAUDE; (LES
ULIS, FR) ; MOCHO, VICTOR MANUEL; (MONTREUIL,
FR) |
Correspondence
Address: |
OBLON SPIVAK MCCLELLAND MAIER & NEUSTADT
1755 JEFFERSON DAVIS HIGHWAY
FOURTH FLOOR
ARLINGTON
VA
22202
|
Assignee: |
Gregory J. Maier
|
Family ID: |
9498506 |
Appl. No.: |
09/319255 |
Filed: |
July 16, 1999 |
PCT Filed: |
December 9, 1997 |
PCT NO: |
PCT/FR97/02238 |
Current U.S.
Class: |
454/190 |
Current CPC
Class: |
F24F 9/00 20130101; F24F
2009/007 20130101 |
Class at
Publication: |
454/190 |
International
Class: |
F24F 009/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 10, 1996 |
FR |
96/15151 |
Claims
1. Process for dynamic separation of a contaminating zone (12) and
a zone to be protected (10), communicating with each other through
at least one separation zone (11), this process comprising the
following steps: a first relatively slow clean air jet is injected
into the said separation zone (11) at a first injection flow,
comprising a tongue (16) capable of covering the entire separation
zone; a second relatively fast clean air jet is injected at the
same time into the separation zone (11) at a second injection flow,
adjacent to and in the same direction as the first jet, between the
zone to be protected (10) and the first jet; the said process being
characterized by the fact that the second injection flow is
adjusted so that the air flow induced by the surface of the second
jet in contact with the first jet is not greater than about half of
the first injection flow.
2. Process according to claim 1, in which the second injection flow
is adjusted so that the air flow induced by the surface of the
second jet in contact with the first jet is equal to approximately
half of the first injection flow.
3. Process according to either of claims 1 and 2, in which clean
ventilation air is injected simultaneously inside the zone to be
protected (10) at an injection flow equal to at least the air flow
induced by the second jet, the surface of which is in contact with
clean ventilation air.
4. Process according to either of claims 1 and 2, in which a third
relatively slow jet is injected into the separation zone (11) at a
third injection rate, adjacent to the second jet and in the same
direction as the first and second jets, between the zone to be
protected (10) and the second jet, the third jet comprising a
tongue (32) capable of covering the entire separation zone (11),
and the third injection flow is adjusted so that it is
approximately equal to the first injection flow, such that the air
flows induced by the surfaces of the second jet in contact with the
first and the third jets respectively, are not more than
approximately half the first and third injection flows.
5. Process according to claim 4, in which the third injection flow
is adjusted such that the air flows induced by the surfaces of the
second jet in contact with the first and third jets respectively
are equal to approximately half of the first and third injection
flows.
6. Process according to either of claims 4 and 5, characterized in
that clean ventilation air is injected simultaneously inside the
zone to be protected (10), at an injection flow equal to at least
the air flow induced by the third jet on the surface of the air
flow in contact with the clean ventilation air.
7. Process according to any one of claims 3 and 6, characterized in
that clean ventilation air is injected at a speed such that the
speed of this clean ventilation air divided by the area of the
plane of the separation zone (11) is equal to at least 0.1 m/s.
8. Process according to any one of claims 3, 6 and 7, characterized
in that clean ventilation air is injected over the entire surface
of a wall of the zone to be protected (10), in the direction of the
separation zone (11).
9. Process according to claim 8, characterized in that the wall on
which the clean ventilation air is injected is the rear wall of the
zone to be protected (10), which is parallel to the plane of the
separation zone (11).
10. Process according to claim 8, characterized in that the wall on
which the clean ventilation air is injected is the top of the zone
to be protected (10), laid out approximately perpendicular to the
plane of the separation zone (11).
11. Process according to any one of claims 3 and 6 to 10,
characterized in that the temperature of the clean ventilation air
is regulated.
12. Process according to any one of the previous claims,
characterized in that all clean air jets are injected in directions
approximately parallel to the plane of the separation zone
(11).
13. Process according to any one of the previous claims,
characterized in that all clean air jets are recovered through an
intake grille (24, 24') installed facing the injection nozzles (20,
22, 30) through which the said jets are injected and located in a
plane approximately perpendicular to the direction of the clean air
jets.
14. Process according to any one of the previous claims,
characterized in that the separation zone (11) is bounded by side
walls (26) located on each side of the clean air jets extending
towards the contaminating zone (12) over a distance equal to at
least the maximum thickness of the jets.
Description
TECHNICAL DOMAIN
[0001] This invention relates to a process for dynamically
separating a contaminating zone and a zone to be protected,
communicating between each other through at least one separation
zone, by means of a clean air curtain obtained by injecting at
least two adjacent clean air jets into the separation zone in the
same direction.
[0002] The process according to the invention may be used in many
industrial sectors.
[0003] A first family of industries concerned by this process
includes all industries (food processing, medical, biotechnologies,
high technologies, etc.), in which it is necessary to prevent the
atmosphere in a given working zone from being contaminated by the
ambient air carrying thermal, microbial, particular and/or gaseous
contamination.
[0004] Another family of industries concerned by the process
according to the invention includes industries (nuclear, chemical,
medical, etc.) in which man and his environment must be protected
from toxic or dangerous products placed inside a confinement
containment.
STATE OF THE ART
[0005] At the present time, there are two types of solutions for
dynamically separating two zones communicating with each other
through one or more separation zones, 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.
[0006] Protection by ventilation consists of artificially creating
a pressure difference between the two zones so that the pressure in
the zone to be protected is greater than the pressure inside the
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 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 separation zone through which the two zones communicate in
order to prevent contamination from being transferred into the zone
to be protected.
[0007] 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 through the
separation zone inserted between the two zones. Furthermore, this
type of protection makes it necessary to process and control the
entire zone to be protected from 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 only useful when contamination
transfers are only possible in one direction.
[0008] 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.
[0009] 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.
[0010] The transition zone corresponds to the central part of the
jet adjacent to the nozzle in which the speed vector is constant.
This zone corresponds to the part of the jet in which there is no
mix between the injected air and the air on each side of the jet.
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.
[0011] 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 flow. This results in
variations in the speed vector and mixing of air. Air entrainment
on both sides of the jet within this development zone is called
"induction". Thus an air jet induces an air flow on each of its
faces which depends particularly on the injection flow of the jet
considered.
[0012] Document JP-B-36 7228 proposes producing an air curtain by
simultaneously injecting three adjacent air jets in the separation
zone and in the same direction. More precisely, a relatively fast
air jet is injected between two relatively slow air jets. This
arrangement is supposed to provide more efficient confinement than
a single air jet, because the entrained air mixed by the central
jet is only slightly contaminated, and originates from relatively
slow jets injected on each side of this central air jet.
[0013] However, this document does not consider the length of the
tongues of each jet, nor their injection flows, such that the
confinement efficiency is very uncertain.
[0014] Document FR-A-2 530 163 proposes to control confinement in a
polluted room with an opening by injecting an air curtain into it
consisting of two clean adjacent air jets blowing in the same
direction. More 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 to be protected. Its function is to
stabilize the slow jet by a suction effect which brings this slow
jet into contact with the fast jet.
[0015] Document FR-A-2 530 163 describes that the slow jet tongue
is sufficiently long to cover the entire opening when the width of
the injection nozzle for this slow jet is equal to at least one
sixth of the height of the opening to be protected. It also states
that injection flows of the two air jets must be such that the air
flow induced by the surface of the fast jet which is in contact
with the slow jet is approximately equal to the injection flow
through the slow jet.
[0016] Document FR-A-2 652 520 suggests using an air curtain to
protect a clean working zone provided with an opening, from the
contaminating external environment. The main characteristics of the
air curtain are similar to the characteristics described in
document FR-A-2 530 163. It is also specified that the injection
speed of the slow jet must be of the order of 0.4 m/s or 0.5 m/s.
It is also specified that jets should be emitted such that the
external surface of the fast jet reaches the limit of the opening
plane. Due to the jet expansion angles, this results in an angle of
about 12.degree.between the median plane of the jets and the plane
of the opening.
[0017] Document FR-A-2 652 520 also proposes simultaneously
injecting clean ventilation air at a temperature adapted to
requirements, inside the working zone to be protected. This
document states that this clean ventilation air must be injected at
a flow approximately equal to the flow induced by the surface of
the fast jet that is in contact with clean ventilation air.
[0018] Furthermore, document FR-A-2 652 520 also indicates that the
intake grille through which the two jets are recovered is located
outside the opening and below the work station, so that the
ventilation in the contaminated zone can be controlled.
Furthermore, the two side walls which delimit the opening are
extended towards the outside over a distance equal to at least the
thickness of the air curtain.
[0019] Document FR-A-2 659 782 proposes adding a third relatively
slow clean air jet to the two clean air jets described in document
FR-A-2 530 163, so that the fast air jet is located between the two
adjacent slow jets and in the same direction.
[0020] With this arrangement, which uses the main characteristics
described in documents FR-A-2 530 163 and FR-A-2 652 520, the clean
ventilation air injection flow inside the zone to be protected is
considerably reduced. Furthermore, dynamic confinement is provided
in both directions, which was not the case in the previous
documents.
[0021] The reduction in the injection flow of clean ventilation air
inside the zone to be protected is a result of the fact that
induction in this zone is obtained as a result of the development
zone of one of the slow jets, and no longer the development zone of
the fast jet as was the case of an air curtain with two jets.
[0022] Despite the improvements made to the air curtain technique
in these various documents, experiments and simulations made by the
applicants have shown that the confinement efficiency obtained with
air curtain devices described in documents FR-A-2 530 163, FR-A-2
652 520 and FR-A-2 659 782 could be considerably improved,
particularly in infraction situations.
DESCRIPTION OF THE INVENTION
[0023] The purpose of the invention is a process for dynamic
separation of two zones communicating with each other through at
least one separation zone using an air curtain, the principle of
which is similar to the principle described in documents FR-A-2 530
163, FR-A-2 652 520 and FR-A-2 659 782, but for which the
confinement efficiency is significantly improved, particularly in
infraction situations.
[0024] According to the invention, this result is achieved by means
of a process for dynamic separation of a contaminating zone and a
zone to be protected, communicating with each other through at
least one separation zone, this process comprising the following
steps:
[0025] a first relatively slow clean air jet is injected into the
said separation zone at a first injection flow, comprising a tongue
capable of covering the entire separation zone;
[0026] a second relatively fast clean air jet is injected at the
same time into the separation zone, at a second injection flow,
adjacent to and in the same direction as the first jet, between the
zone to be protected and the first jet;
[0027] this process being characterized by the fact that the second
injection flow is adjusted so that the air flow induced by the
surface of the second jet in contact with the first jet is not
greater than about half of the first injection flow.
[0028] The applicants have discovered and verified by experiments
and by calculation, that all these characteristics are essential in
order to obtain a "barrier effect" between the two zones, in other
words so that the tongue effectively covers the entire separation
zone.
[0029] If the induction at the surface of the fast jet created by
the jet blower flow is too high, it may be considered that the slow
jet tongue is over-consumed with the consequence of reducing the
length of the slow jet; consequently, the coverage of the opening
to be protected is imperfect (which is the case of all documents
according to prior art). On the other hand, if the fast jet flow is
too low, stabilization of the slow jet by induction of the surface
of the fast jet in contact with the slow jet is not maximized. This
is why the applicants have determined that it is essential that the
air flow induced by the surface of the second (fast) jet in contact
with the first (slow) jet is less than, or preferably approximately
equal to half of the injection flow of this first jet, and not
equal to the entire injection flow as described in documents FR-A-2
530 163, FR-A- 89 12861 and FR-A-2 659 782.
[0030] The air curtain may provide dynamic confinement in either
direction if a third relatively slow jet is added to the first two
jets. In this case, a third relatively slow clean air jet is
injected into the separation zone at a third injection flow
adjacent to the second jet and in the same direction as the first
and second jets, between the zone to be protected and the second
jet. The third jet comprises a tongue capable of covering the
entire separation zone. The third injection flow is then adjusted
so that it is approximately equal to the first injection flow, so
that the air flows induced by the surfaces of the second jet in
contact with the first and third jets respectively are not more
than approximately half of the first and third injection flows. Due
to these characteristics, the third jet effectively covers the
entire separation zone.
[0031] Preferably, clean ventilation air is injected simultaneously
inside the zone to be protected at an injection flow equal to at
least the air flow induced by the second or third jet (depending on
whether the air curtain has two or three jets), on the surface of
the jet in contact with clean ventilation air. The applicants have
discovered that this characteristic can give a "purifying effect"
in the zone to be protected, particularly in infraction situations
through the air curtain.
[0032] In order to optimize the purifying effect, and regardless of
the number of jets used to form the air curtain, it is advantageous
to inject clean ventilation air at a speed such that the speed of
this clean ventilation air divided by the plane area of the
separation zone is equal to at least 0.1 m/s.
[0033] If internal ventilation is used, clean ventilation air is
injected over the entire rear wall or top of the zone to be
protected, towards the separation zone. Therefore, the wall through
which the clean ventilation air is injected is parallel to or
approximately perpendicular to the plane of the separation
zone.
[0034] If it is also required to control the temperature inside the
protected zone, clean ventilation air is injected at a regulated
temperature.
[0035] In order to further optimize the barrier effect provided by
the air curtain, all clean air jets are preferably injected in
directions approximately parallel to the plane of the separation
zone. Furthermore, all clean air jets are advantageously recovered
by an intake located facing the injection nozzles of these jets in
a plane approximately perpendicular to the direction of the clean
air jets.
[0036] The barrier effect provided by the air curtain may also be
optimized by extending the side walls of the openings, located on
each side of the clean air jets, so that they extend towards the
contaminating zone over a distance equal to at least the maximum
thickness of the jets.
BRIEF DESCRIPTION OF THE DRAWINGS
[0037] We will now describe two embodiments of the invention as
non-limitative examples, with reference to the attached drawings,
in which:
[0038] FIG. 1 is a perspective view that diagrammatically
illustrates the protection of a clean working zone by means of an
air curtain composed of two adjacent air jets according to a first
embodiment of the process according to the invention; and
[0039] FIG. 2 is a perspective view similar to FIG. 1 which
diagrammatically illustrates the protection of a clean working zone
by means of an air curtain composed of three adjacent air jets
according to a second embodiment of the process according to the
invention.
DETAILED DESCRIPTION OF TWO EMBODIMENTS
[0040] A zone to be protected and a contaminating zone are marked
by references 10 and 12 respectively in FIG. 1.
[0041] In the embodiment shown, the zone 10 to be protected is
composed of the clean space specific to a work station, and the
contaminating zone 12 includes everything outside this work
station. This external space forms a source of thermal, particular,
gaseous and/or microbial contamination of the space specific to the
work station.
[0042] The work station that forms the zone 10 to be protected is
delimited by airtight walls in all directions, except towards the
right as shown in FIG. 1. More precisely, the surface of the work
station facing towards the right in FIG. 1 forms a separation zone
consisting of an opening 11 through which the zone 10 to be
protected communicates with the external contaminating zone 12.
This opening 11 may be used for example to enable objects to be
taken into and out of zone 10 to be protected, and for handling
when necessary inside this zone, from the outside contaminating
zone 12. Note that this illustration is simply an example
embodiment and is in no way restrictive, since zones 10 and 12
could communicate with each other through one or more separation
zones with arbitrary orientations which are not necessarily
materialized by openings, without going outside the framework of
the invention.
[0043] In particular, in one embodiment not shown in which the zone
to be protected is a conveyor moving along a linear, circular or
winding path, the separation zone between the contaminating zone
and the zone to be protected extends longitudinally along the path
of the said conveyor.
[0044] In order to preserve dynamic separation between zones 10 and
12 despite the presence of opening 11, a permanent air curtain 14
is formed in this opening when the installation is being used. In
the embodiment shown diagrammatically in FIG. 1, this air curtain
14 is formed by injecting two clean adjacent air jets
simultaneously in the same direction.
[0045] More precisely, a first clean, relatively slow air jet is
injected into opening 11 (of which only tongue 16 is shown) and a
second clean air jet is also injected into opening 11, relatively
fast compared with the first jet (of which only the tongue 18 is
shown) The second jet is injected between the first jet and the
zone 10 to be protected. For simplification purposes, the first jet
and the second jet are called the "slow jet" and the "fast jet"
respectively in the rest of this text.
[0046] The slow jet and the fast jet are injected into the opening
11 by adjacent nozzles 20 and 22 respectively.
[0047] In the embodiment shown in which the opening is rectangular
and comprises two horizontal edges and two vertical edges (and in a
non-restrictive manner), the injection nozzles 20 and 22 extend
over the entire length of the upper edge of opening 11 such that
the air curtain 14 is formed over the entire width of the opening
11. The two jets forming the air curtain 14 are then completely
recovered through a single intake 24 that extends along the lower
edge of the opening and over the entire length of this edge. The
vertical edges of the opening 11 are materialized by two side walls
26 located on each side of the two jets forming the air curtain 14.
These two side walls 26 extend in the contaminating zone 12 over a
distance equal to at least the maximum thickness of the jets.
[0048] As shown diagrammatically in FIG. 1, the slow jet injected
through nozzle 20 is sized such that its tongue 16 covers the
entire plane of the opening 11 to be protected. This result is
obtained by taking steps to ensure that the range, or length, of
the tongue 16 is equal to at least the height of the opening 11.
Consequently, the width of the nozzle 20 parallel to the plane of
FIG. 1 is equal to at least 1/6.sup.th, and preferably 1/5.sup.th,
of the height of the opening 11 to be protected. Thus, and solely
as an example, the width of the nozzle 20 will be at least 0.20 m
for a 1 m high opening.
[0049] Furthermore, in order to minimize turbulence and for
economic reasons, the speed of the slow jet output from nozzle 20
is beneficially fixed at 0.5 m/s. Since the length of the tongue 16
of the slow jet is equal to at least the height of the opening to
be protected and this jet is relatively slow, air streams follow
the contour of objects that pass through the air curtain 14 without
breaking the confinement.
[0050] However, the low speed of the slow jet injected by nozzle 20
has the consequence that this jet, if it were used alone, could be
destabilized by aeraulic or mechanical disturbances that could
occur close to the air curtain, thus breaking the confinement of
the work station. This is why the fast jet injected by nozzle 22 is
injected adjacent to the slow jet, at a higher speed in order to
stabilize the first jet and consequently to improve the confinement
efficiency in infraction situations through the dynamic barrier
formed by the air curtain 14. As an example which is in no way
restrictive, the width of the nozzle 22 through which the fast jet
is injected may be equal to about {fraction (1/40)}.sup.th of the
width of nozzle 20, which is equal to 0.005 m in the example
described.
[0051] In order to optimize the barrier effect provided by
combining the two jets, the applicants have determined that the
injection flow of the fast jet injected through nozzle 22 must be
adjusted such that the air flow induced by the surface of this fast
jet which is in contact with the slow jet injected through nozzle
20, is less than or preferably approximately equal to half the
injection flow of this slow jet. Experiments and simulations have
shown that this characteristic significantly improves the barrier
effect compared with prior art, in which the flow of the fast jet
is adjusted such that the air flow induced by the surface of this
fast jet in contact with the slow jet is approximately equal to the
injection flow of the slow jet.
[0052] As an example which is in no way restrictive, if the blowing
flow of the slow jet injected through nozzle 22 is 360 m.sup.3/h,
the blowing flow of the fast jet injected through nozzle 22 should
be about 42 m.sup.3/h. This value should be compared with the value
of about 84 m.sup.3/h recommended in prior art.
[0053] In order to recover all air blown through nozzles 20 and 22
and air entrained by the air curtain 14, the intake 24 communicates
with suction means (not shown) sized for this purpose. In practice,
air recovered from intake 24 is advantageously cleaned by special
cleaning means (not shown) before being recycled to injection
nozzles 20 and 22. Excess air is then released towards the outside
after a second special cleaning.
[0054] In the numeric example given above, the air suction flow
through the intake 24 is 825 m.sup.3/h.
[0055] The applicants have also determined that the barrier effect
is further optimized when each of the two jets is injected along a
direction approximately parallel to the vertical plane of opening
11, and when the intake 24 is perpendicular to this direction. In
other words, it is desirable that output orifices from nozzles 20
and 22 are located in the same horizontal plane and that the intake
24 should be located below nozzles 20 and 22 in another horizontal
plane.
[0056] Furthermore, a purifying effect of zone 10 to be protected
is obtained by providing internal ventilation inside this zone and
respecting a defined injection flow for this internal ventilation.
This purifying effect added to the barrier effect provided by the
air curtain 14 significantly improves the confinement efficiency,
particularly in infraction situations.
[0057] More specifically, in the embodiment shown in FIG. 1 which
relates to an air curtain 14 composed of two adjacent jets in the
same direction, the clean ventilation air injection flow inside
zone 10 to be protected is equal to at least the air flow induced
by the fast jet injected through nozzle 22, on the surface of this
fast jet which is in contact with clean ventilation air, in other
words on the surface of the fast jet facing zone 10 to be
protected. Furthermore, clean ventilation air is injected at a
speed such that the speed of this air divided by the area of the
plane of the opening 11 is equal to at least 0.1 m/s.
[0058] In the embodiment illustrated diagrammatically in FIG. 1,
clean ventilation air is injected into zone 10 to be protected
through a blower intake grille 28 that extends over the entire back
wall of the zone to be protected, in other words over the entire
wall of the working zone facing the opening 11 and laid out
parallel to the vertical plane of this opening. The blower intake
grille 28 through which clean ventilation air is injected is
located at the left in FIG. 1. In one embodiment already mentioned
(not shown) according to which the zone to be protected is a
conveyor moving along a given path, the wall on which the clean
ventilation air forming the purifying flow is injected is the top
surface of the zone to be protected. This surface is laid out
facing the conveyor and then approximately perpendicular to the
plane of the separation zone.
[0059] When the temperature inside the zone 10 to be protected has
to be kept at a given uniform value, the clean ventilation air is
injected through the blower intake grille 28 at a regulated
temperature. Consequently, temperature regulation means such as a
heat exchanger (not shown) are placed in the ventilation circuit on
the upstream side of blower intake grille 28.
[0060] In the non-restrictive example described above, the internal
ventilation blower flow is 360 m.sup.3/h.
[0061] Experiments and simulations have shown that if the
characteristics described above are respected, confinement
efficiencies 10 to 100 times better than efficiencies possible with
prior art can be obtained. Thus with the characteristics described
above, the confinement efficiency of a dynamic barrier defined as
the ratio of the concentration of particular or gaseous pollutants
in the contaminating zone to the concentration of the same
pollutants in the zone to be protected, can reach values of between
10.sup.4 and 10.sup.6.
[0062] FIG. 2 shows a second embodiment of the process according to
the invention. This second embodiment uses the same main
characteristics described above with reference to FIG. 1, plus a
third relatively slow jet between the fast jet and the zone to be
protected. This is why elements of the installation illustrated in
FIG. 2 that are identical to the elements in the installation
described above with reference to FIG. 1, are referenced with the
same reference numbers, and will not be described in detail.
[0063] Thus, FIG. 2 shows the zone 10 to be protected, the
contaminating zone 12, the opening 11, nozzles 20 and 22 through
which the slow jet and the fast jet respectively are injected, the
respective tongues being illustrated as 16 and 18, the side walls
26 of the opening 11 and the blower intake grille 28 providing
internal ventilation of the zone 10 to be protected.
[0064] The air curtain, in this case, denoted by reference 14',
also comprises a third clean air jet, relatively slow with respect
to the fast jet, output through a nozzle 30 adjacent to nozzle 22
between the fast jet and zone 10 to be protected, such that it is
adjacent to the fast jet and in the same direction as the other
jets. The tongue from this third jet is illustrated as 32 in FIG.
2.
[0065] The dimensions of the nozzle 30 are chosen such that the
tongue 32 of the third jet covers the entire opening. Consequently
nozzle 30 extends over the entire length of the upper edge of
opening 11, like nozzles 20 and 22, and the width of this nozzle 30
is equal to at least 1/6.sup.th and preferably 1/5.sup.th of the
height of opening 11. In practice, the widths of nozzles 20 and 30
are the same, for example 0.20 m in the case of the numeric
illustration given non-restrictively above with reference to FIG.
1.
[0066] In the second embodiment of the process according to the
invention, the slow jet injection flow output through nozzle 30 is
adjusted such that this flow is approximately equal to the slow jet
injection flow output through nozzle 20. Thus, air flows induced by
the surfaces of the fast jet output through nozzle 22 in contact
with each of the slow jets, are less than or preferably
approximately equal to half of the injection flows from these slow
jets.
[0067] As illustrated in FIG. 2, note that the width of the intake
grille, in this case denoted by reference 24', is adapted to the
width of the air curtain so that all jets can be recovered through
this intake grille 24'. More precisely, the intake grille 24' for
air curtain 14' formed by three jets, is wider than the intake
grille 24 of the air curtain 14 formed by two jets.
[0068] The use of an air curtain 14' formed by three adjacent jets
in the same direction gives efficient dynamic separation of the two
zones in both directions.
[0069] Furthermore, in the second embodiment illustrated in FIG. 2,
the presence of another slow jet between the fast jet and zone 10
to be protected, can reduce the injection flow of the internal
ventilation compared with the first embodiment. The injection flow
of clean ventilation air through the blower intake grille 28 is
then equal to at least half the air flow induced by the slow jet
emitted through nozzle 30 on the surface of this third jet which is
in contact with the clean ventilation air.
[0070] In the numeric example given above, the injection flow from
each of the slow jets is 360 m.sup.3/h, the blower flow of the
internal ventilation is 360 m.sup.3/h and the suction flow in the
intake grille 24' is 1185 m.sup.3/h.
[0071] As in the first embodiment of the invention, the three jets
are preferably injected in directions parallel to the plane of the
opening 11 and the intake grille is located below the injection
nozzles 20, 22 and 30 and is perpendicular to this plane.
Furthermore, the speed at which ventilation air is injected in the
zone 10 to be protected is advantageously equal to at least 0.1
m/s.
[0072] The confinement efficiencies obtained in the second
embodiment of the invention illustrated in FIG. 2, are similar to
the confinement efficiencies given in the case of the first
embodiment described above with reference to FIG. 1.
[0073] Note that many modifications may be made to the described
installations, without going outside the framework of the
invention.
[0074] These modifications firstly relate to applications, which
are many and relate to all cases in which it is necessary to make a
thermal and dynamic separation between two environments with
different gaseous, particular and/or bacteriological concentrations
(one clean environment and the other contaminated environment, and
possibly at different temperatures), while allowing objects to pass
repeatedly from one zone to the other without the clean zone
becoming contaminated. Examples of these applications are to
protect food processing, medical, biotechnological or high
technology work stations, display counters for the distribution of
sensitive products, etc.
[0075] Possible modifications also relate to the shape, orientation
and the number of separation zones through which the two zones
communicate, and the choice of edges of the separation zone on
which injection nozzles and the intake grille may be located, which
may be different from the layout described above.
* * * * *