Note: Descriptions are shown in the official language in which they were submitted.
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WO 00/16017 PCT/EP99/06418
1
Description
Method and device for protecting persons and/or products from airborne
particles
The invention relates to a method for separating at least two spatial areas
and for reducing the transmission of airborne particles between the spatial
areas in order to protect persons and/or products from the airborne
particles, the person being located at least in part in the first spatial area
and the products in the second spatial area, and at least one planar air jet
of purified air being used for the separation.
The invention further relates to devices for carrying out the method.
Products within the meaning of this application are all articles, starting
products, intermediate products and end products which are in any way
handled, filled, tested or modified.
In many industries, for example in the manufacture of pharmaceuticals and
electronics components, either the product has to be protected from
airborne foreign particles or the persons involved in the operating process
have to be protected from airborne product particles. It is also common for
both protective functions, for product and persons, to have to be provided.
Such devices (also called safety workbenches depending on their size and
design) operating according to the laminar flow principle are known from
the prior art, which devices, in order to protect personnel or products,
permit only limited access to the product space. This principle is employed,
for example, in the HERAsafe cytostatic safety workbenches according to
DIN 12980 and in the LaminAir workbencties from the company Heraeus
Instruments GmbH, Hanau. Filtered air is delivered in the form of a vertical,
low-turbulence displacement stream onto the top surface of the workbench
and is suctioned off at the base in front of the rear wall of the workbench
and at the front behind the front boundary of the workbench. The front has
a vertically displaceable protective screen. When the protective screen is
fully or partly raised, outside air flows into the workbench through the
access port of the workbench, and this air is likewise suctioned off via the
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suction arrangements on the base. A disadvantage of these devices is that
the narrow access into the product space greatly restricts the operator's
freedom of movement. Maneuvers requiring greater freedom of movement
than these devices permit in the operating state cannot be performed in
such devices unless the protective screen is raised above the correct
operating position or is completely removed, as a consequence of which
the protection of persons and products is no longer ensured to the full
extent.
Devices operating according to the laminar flow principle are also known,
which devices do not spatially separate the product from the personnel.
This principle is employed, for example, in the Dispensing Booths from the
company Extract Technology Limited, Huddersfield, England. Purified air is
delivered, for example in the form of a vertical, low-turbulence
displacement stream, to the top of the booth and is suctioned off at the
base area. A disadvantage of these devices is that the product can only be
handled well below the head level of the personnel if protection of the
personnel from the product is to be guaranteed. A further disadvantage is
that the product in these devices is not adequately protected from foreign
particles caused by the personnel.
Moreover, devices operating according to the laminar flow principle are
known in which only the product is protected, not the operating personnel.
This principle is employed, for example, in the horizontal laminar flow
workbenches from the company Babcock-BSH, Bad Hersfeld, Germany.
Purified air is delivered horizontally behind the product space in the
direction of the personnel. A disadvantage of these devices is the total lack
of protection of the personnel.
Devices operating according to the support jet principle are also known
which protect only the personnel. This principle is employed, for example,
in the WIBOjekt work tables from the company GWE, Hude. The
operating personnel pass their hands through a support jet which is
delivered via an ejector rail in the front area of the work table and
generates a curtain of air between the head level of the operator and the
product space. Further support jets can also be directed from the ceiling to
the rear area of the work table. In this principle, the suctioning
arrangements are located in the rear area of the work table. The air
capacity of the support jet is typically 1 to 10 liters per second per meter
of
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booth width. A disadvantage of these devices is the lack of product
protection.
Against the background of this prior art, the object of the invention was to
develop alternative methods and devices for protecting persons and
products from airbome particles, and which methods and devices will not
have the disadvantage of significantly restricting the freedom of movement
of the operating personnel.
According to the invention, this object is achieved by a method of the type
specified in the introduction, in which at ieast one low-turbulence
displacement stream is generated with purrfied air near the at least one air
jet in at least the second spatial area, said at least one displacement
stream being directed in essentially the same direction as the at least one
air jet.
The subject of the invention is therefore a method for separating at least
two spatial areas and for reducing the transmission of airbome particles
between the spatial areas in order to protect persons and/or products from
the airbome particles, the person being located at least in part in the first
spatial area and the products in the second spatial area, and at least one
planar air jet of purified air being used for the separation, wherein at least
one low-turbulence displacement stream is generated with purified air near
the at least one air jet in at least the second spatial area, said at least
one
displacement stream being directed in essentially the same direction as the
at least one air jet.
A"iow-turbulence displacement stream" within the meaning of the invention
is a stream in which a unidirectional air stream flows over the whole cross
section of a defined area with as far as possible a uniform velocity and
almost parallel flow lines (laminar flow). This definition is taken from the
guidelines of the Verein deutscher Ingenieure (VDI) No. 2083 of December
1976.
A further subject of the invention is a device for carrying out this method,
having one or more first means for generating one or more planar air jets,
with which, in its intended use, at least one space is divided into at least a
first spatial area and a second spatial area by means of the planar air jet or
by means of each planar air jet, and products being able to be arranged in
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the second spatial area, the device in the second spatial area having
second means for generating a low-turbulence displacement stream.
In a first preferred embodiment of the method according to the invention,
the displacement stream is guided at least partially at a distance of at most
0 to 50 cm from the at least one air jet. A displacement stream with an air
velocity of 0.1 to 1.5 m/s, preferably 0.2 to 0.6 m/s, especialiy preferably
0.3 to 0.45 m/s, is advantageously generated, likewise at least one air jet
with an air outlet velocity of 2 to 30 m/s, preferably 3 to 10 m/s, especially
preferably 5 to 8 m/s. In a further preferred embodiment, an air jet or a
displacement stream is generated with an air outlet capacity of at least
101i.N. (liters in norm) per second per meter breadth of the air jet
transverse
to the direction of flow, preferably 10 to 300 Ii.N., especially preferably 20
to
100 li.-v., very especially preferably 40 to 80 ILN. At least the second
spatial
area can have zones which are not traversed by the air stream. In a further
particular embodiment, at least the total air quantity of the at least one air
jet and of the at least one displacement stream is suctioned off in at least
one of the spatial areas. It is also advantageous for the air jet or each air
jet
to be oriented at a predetermined or selectable or adjustable angle, from
the range of -45 to +45 , preferably -30 to +30 , especially preferably -
15 to +15 , very especially preferably -5 to +50, toward a lateral face of
the displacement stream, relative to the direction of flow.
Preferred configurations of the device according to the invention for
carrying out the method can also be constructed accordingly.
In one preferred configuration of the device according to the invention, said
device has one or more suction arrangements which are dimensioned such
that altogether they can suction off at least the total air quantity of the
air
jets and of the displacement streams. The suction arrangement or each
suction arrangement is preferably arranged opposite the first means for
generating the air jets or the displacement flow.
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The subject of the invention also includes a device for protecting persons
and/or products from airborne particles, having a partially open front with a
height of H [m] for access to the device, two side walls, a rear wail, one or
more means for blowing in filtered air, which means are arranged on a side
5 wall, and one or more suction devices, wherein the blowing-in means are
designed and arranged, on the one hand (4, 5), such that a planar air
jet (13) with an air outlet capacity of in all more than 10 ILN. per second
and
height H[m] can be guided from the area of one side wall near the front to
the other side wall in order to separate the internal space (2) of the device
from the surrounding area (1), and, on the other hand (3), such that, on that
side of the air jet (13) facing away from the front, a purified, low-
turbulence
displacement stream (14) can be guided from one side wall to the other,
and wherein the suction devices (6) are arranged at least partially in the
area of the device near the front and are dimensioned such that altogether
they can take up at least the total air quantity of the air jet (13) and of
the
displacement stream (14).
It is advantageous if the lateral suctioning extends over the entire height H
[unit meters] of the access cross section of the device.
It is advantageous for the air jet to be guided at a predetermined or
selectable or adjustable angle, from the range of --45 to +45 , preferably
-30 to +30 , especially preferably -15 to +15 , very especially preferably
-5 to +5 , toward the front face of the displacement stream, relative to the
direction of flow.
In a further configuration, the high air capacity of the support jet is
achieved
by combining a plurality of ejector rails one behind the other, preferably by
2 parallel ejector rails. The ejectors used can include all ejector systems
known to the skilled person, for example orifice or slit nozzles.
In a further particular configuration, the suctioning is obtained using two
parallel rows of orifices (suction rail) in a side wall at the front boundary
(front face) of the device.
In a further particular configuration, the air jet is inclined, at a defined,
predetermined or selectable or adjustable angle, from the range of -30 to
+30 , preferably -20 to +20 , especially preferably -10 to +10 , very
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especially preferably -5 to +5 , to the connection plane between ejector
rail and suction rail or to the horizontal.
In a further particular configuration, an air jet or a low-turbulence
displacement stream with an air velocity of 0.1 to 1.5 m/s, preferably 0.2 to
0.6 m/s, especially preferably 0.3 to 0.45 m/s, can be generated.
In a further particular configuration, the ejectors are suitable for an air
outlet
velocity of 2 to 30 m/s, preferably 3 to 10 m/s, especially preferably 5 to 8
m/s.
In a further particular configuration, the ejector rails are designed such
that
they can together generate an air outlet capacity of 10 to 300 liters per
second per meter height of that part of the front provided for access,
preferably 20 to 100 liters per second per meter height, especially
preferably 40 to 80 liters per second per meter height.
This device according to the invention can in particular also be combined
with one or more features from the other configurations.
The subject of the invention also includes a device for protecting persons
and/or products from airborne particles, having a partially open front with a
breadth of B [m] for access to the device, a top, a base, a rear wall, one or
more means for blowing in filtered air, which means are arranged on the
top, and one or more suction devices, wherein the blowing-in means are
designed and arranged, on the one hand, such that a planar air jet with an
air outlet capacity of in all more than 10 ILN. per second and breadth B[m]
can be guided downward from the area of the top near the front in order to
separate the internal space of the device from the surrounding area, and,
on the other hand, such that, on that side of the air jet facing away from the
front, a purified, low-turbulence displacement stream can be guided
downward, and wherein the suction devices are arranged at least partially
in the area of the device near the front and are dimensioned such that
altogether they can take up at least the total air quantity of the air jet and
of
the displacement stream.
It is advantageous if the suctioning at the base extends over the entire
breadth B [unit meters] of the access cross section of the device.
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The air jet and the displacement stream can likewise be guided from the
bottom upward counter to the force of gravity. A corresponding device
according to claim 23 is also the subject of the invention.
It is advantageous if the low-turbulence displacement stream can be guided
at an angle which is inclined -20 to +20 , preferably -10 to +100,
especially preferably -5 to +5 , to the vertical.
In a further configuration, the high air capacity of the support jet is
achieved
by combining a plurality of ejector rails one behind the other, preferably by
2 parallel ejector rails. The ejectors used can include all ejector systems
known to the skilled person, for example orifice or slit nozzles.
In a further particular configuration, the suctioning is obtained using two
parallel rows of orifices (suction rail) in the base area at the front
boundary
(front face) of the device.
It is advantageous if the air jet is inclined, at a defined, predetermined
angle, from the range of -30 to +30 , preferably -20 to +20 , especially
preferably -10 to +100, very especially preferably -5 to +5 , to the
connection plane between ejector rail and suction rail or to the vertical.
In a further particular configuration, a low-turbulence displacement stream
with an air velocity of 0.1 to 1.5 m/s, preferably 0.2 to 0.6 m/s, especially
preferably 0.3 to 0.45 m/s, can be generated.
In a further particular configuration, the ejectors are suitable for an air
outlet
velocity of 2 to 30 m/s, preferably 3 to 10 m/s, especially preferably 5 to 8
m/s.
In a further particular configuration, the ejector rails are designed such
that
they can together generate an air outlet capacity of 10 to 300 liters per
second per meter breadth of that part of the front provided for access,
preferably 20 to 100 liters per second per meter breadth, especially
preferably 40 to 80 liters per second per meter breadth, with which ranges
from other combinations of said limits are also intended to be disclosed.
The device according to the invention can also be combined in any desired
way with one or more features from the other configurations.
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The invention is based on the surprising effect
that the displacement stream stabilizes the planar air jet,
so that the protective action of the combination of both is
considerably better than expected.
It is especially surprising that, for example, the
front boundary screen of a horizontal laminar flow work
zone, which allows only limited access to the product space,
can be replaced by a broad support jet with high air
capacity if the suctioning is largely limited to the area of
the device near the front, and that then, despite the
boundary screen being removed, both a high level of product
protection and a high level of personnel protection are
guaranteed.
The advantages of the devices according to the
invention are to be seen in the fact that while the
operating personnel are allowed the greatest possible
freedom of movement, the protection of persons and products
from airborne particles is guaranteed.
In accordance with this invention, there is
provided a method for separating at least two spatial areas
and for reducing the transmission of airborne particles
between the spatial areas in order to protect persons and/or
products from the airborne particles, the person being
located at least in part in the first spatial area and the
products in the second spatial area, and at least one planar
air jet of purified air being used for the separation, in
which at least one low-turbulence displacement stream is
generated with purified air near the at least one air jet in
at least the second spatial area, said at least one
displacement stream being directed in the same direction as
the at least one air jet, wherein said at least one planar
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air jet comprises at least two planar air jets with an air
outlet velocity of 2 to 30 m/s.
The device according to the invention is explained
in more detail on the basis of a number of examples and with
reference to Figures 1 to 5. This is not intended in any
way to limit the scope of the invention.
Fig. 1 shows a diagrammatic representation of the
method according to the invention, using a device according
to the invention represented diagrammatically in cross
section;
Fig. 2 shows a diagrammatic representation of a
device and of a method in accordance with Example 2;
Fig. 3 shows a diagrammatic representation of a
device and of a method in accordance with Counter Example 1;
Fig. 4a shows a diagrammatic representation of a
first particular embodiment of the method and of the device
in a plan view;
Fig. 4b shows a cross section through the device
from Fig. 4a along the line A-B;
Fig. 4c shows a cross section of the device from
Fig. 4a along the line C-D;
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Fig. 5 shows a diagrammatic representation of a second particular
embodiment of the method and of the device in a lateral cross section.
Example 1
A LaminAir workbench, type HL 2472, with a protected product area
(corresponds to the second spatial area) 2 and surrounding personnel area
1 (corresponds to the first spatial area) is equipped at the top with second
means for generating a low-turbulence displacement stream 14, namely
with two-layer laminar flow generators 3 which are sealed off against the
workbench walls except for a gap, the breadth of the workbench and 8 mm
deep, at a front screen 25. The diagramatically illustrated screen 25 of the
workbench is raised as far as the lower edge of the laminar flow
generators. Arranged at the height of the lower edge of the laminar flow
generators, directly from outside on the raised workbench screen, there are
first means 4, 5 for generating a planar air jet 13, namely an ejector rail 4
the breadth of the workbench, and a gap 5 with downward air outlet. The
ejector 4 is equipped with a combination of orifice and slit nozzles with an
effective cross section of 0.9 mm. The resulting gap 5 between laminar flow
generators 3 and raised screen serves as an 8-mm wide ejector 5 with
downwardly directed air outlet.
The base of the workbench is sealed off except for the suction openings 6
on the open screen. The laminar flow generators 3 are in this example
operated at an air outlet velocity of about 0.45 m/s.
Ejector 4 in this example is operated at an air outlet velocity of 5 m/s.
Ejector 5 in this example is operated at an air outlet velocity of 7 m/s. The
planar air jet 13, which is generated by the two ejectors 4, 5, consequently
has an air outlet capacity of 46 li.rv. per second and meter breadth of the
air
jet 13. The air distribution in the workbench is shown diagrammatically in
Fig. 1 in cross section. The arrows 14 below the laminar flow generators 3
indicate the low-turbulence displacement stream of uniform velocity and
with parallel flow lines.
Protection factors are determined below by measurements. The protection
factor is defined as the ratio of the dust content between "unclean side" and
"clean side" when a dust source is provided on the unclean side. The
device therefore gives better protection, the higher the protection factor.
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For personnel protection, the workbench center 5 cm in front of the
workbench opening (personnel area 1) is regarded as the clean side, and
the workbench interior behind the suction arrangement (product area 2) is
regarded as the unclean side. For assessing product protection, the
5 unclean and clean sides are correspondingly reversed.
The protection factor for personnel protection is 400,000 when the
workbench is in the rest state, i.e. without intervention by the operator.
With
simulated work movements, i.e. moving the hands in and out, and other
10 movements of both arms in the booth, a value of 750 is obtained for
personnel protection.
The protection factor for product protection is 160 million when the
workbench is in the rest state, i.e. without intervention by the operator.
With
simulated work movements, i.e. moving the hands in and out, and other
movements of both arms in the booth, a value of 6,000 is obtained for
product protection.
Example 2
A workbench is constructed and operated as in Example 1. In contrast to
Example 1, however, the gap between laminar flow generators 3 and
raised screen is sealed off, so that no air escapes from ejector 5. Ejector 4
is operated, as in Example 1, at an air outlet velocity of 5 m/s. The planar
air jet consequently has an air outlet capacity of 6.3 I-.N. per second and
meter breadth of the air jet. The air distribution in the work bench is shown
diagrammatically in cross section in Fig. 2 below.
The protection factor for personnel protection is now 300 when the
workbench is in the rest state, i.e. without intervention by the operator.
With
simulated work movements, i.e. moving the hands in and out, and other
movements of both arms in the booth, a value of 30 is obtained for
personnel protection.
The protection factor for product protection is now 50 million when the
workbench is in the rest state, i.e. without intervention by the operator.
With
simulated work movements, i.e. moving the hands in and out, and other
movements of both arms in the booth, a value of 40 is obtained for product
protection.
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Counter Example 1
A workbench is constructed and operated as in Example 1. In contrast to
Example 1, however, the gap between laminar flow generators 3 and
raised screen is sealed off, so that no air escapes from ejector 5. Ejector 4
is also not operated, so that no air escapes from it either. The air
distribution in the work bench is shown diagrammatically in cross section in
Fig. 3.
The protection factor for personnel protection is now 20 when the
workbench is in the rest state, i.e. without intervention by the operator.
With
simulated work movements, i.e. moving the hands in and out, and other
movements of both arms in the booth, a value of 10 is obtained for
personnel protection.
The protection factor for product protection is now 6000 when the
workbench is in the rest state, i.e. without intervention by the operator.
With
simulated work movements, i.e. moving the hands in and out, and other
movements of both arms in the booth, a value of 30 is obtained for product
protection.
Example 3
A device for combined product protection and personnel protection is made
up of an air delivery element 19 and an air suction element 20, as shown
diagramatically in Figures 4a and 4b. Both elements stand in a room (not
shown) with separate clean air supply system and exhaust system with
integrated air cleaning (not shown). The open and at the same time
protected product area 2 in which dust-producing products can be handled
openly is situated in this device between the air delivery element 19 and
the air suction element 20, as shown in Fig. 4c. The protected personnel
area 1 is located in the entire spatial area surrounding the protected
product area.
The air delivery element 19 consists essentially of an air admission pipe 7,
into which purified air is fed from the delivery system, a distributor 8, a
downwardly angled air delivery segment 22, and an upright segment 9. The
air delivery segment 22 conveys the air delivered via the distributor on the
one hand via a rectangular laminar flow generator 10 and on the other
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hand via four ejector rails 11, which enclose the laminar flow generator 10,
in the direction of the suction element 20. The air velocity of the air
delivered by the laminar flow generator 10 is 0.45 m/s in this example. The
air outlet velocity from the ejector rails is 5 m/s in this example. The
resulting air distribution at the air delivery element 19 is likewise shown
diagrammatically in Figures 4a and 4b.
The air suction element 20 has two suction rails 12 via which 1.4 times the
air quantity delivered by the air delivery element can be suctioned off and
conveyed to the extraction system.
Example 4
A mobile device for the combined protection of personnel and products
protection is shown diagramatically in cross section in Fig. 5. The device
has a protected product area 2 which is open both to the sides and also in
the upper front area. The protected personnel area 1 comprises the area
surrounding the device. Side openings can be used to supply the product
area with product containers, whereas the front opening gives the person
shown free access for protected handling of products 26.
Situated in the front ceiling area of the device there are two parallel
ejector
rails via which a planar air jet 13 can be delivered downward at an angle of
about 100 to the vertical front face of the device. Behind these in the
ceiling
area there are laminar flow generators which can form a downward low-
turbulence displacement stream 14. The delivered air is taken up, on the
one hand, in the front area of the device, via an exhaust air channel 18
which is provided at the top with suction openings, and, on the other hand,
in the lower rear area of the product area, at the base of the device and fed
to a filter 16 via a fan 15. Some of the purified air flowing from the filter
serves as intake air 21 for the laminar flow generator and the ejector rails
and some of it is discharged as exhaust air 17.
