Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~3369~
FIELD OF T~IE INVENTIO~ .
This invention relates generally to the powder
coating art, and more particularly relates to a booth in
which to carry out the spray application of the powder.
B CXGROUND OF THE INVENTION
The powder coating art is fairly well known to
the coatin~ industry. In general, a powdered resin is
applied to a substrate, and then the substrate and powder
are heated so that the powder melts and forms a coating on
the substrate when it cools. The powder is almost invariably
deposited on the substrate with the aid of electrostatic
application techniques. These electrostatic application
techniques generally lnclude some process of imparting an
electrical charge to the powder, the substrate, or both in
order to aid deposition and retention of the powder on the
substrate. These electrostatic techniques are well known,
and therefore need not be discussed in detail here.
By and large, the powder deposition is performed
in a booth, some co~trolled area which functions to contain
any oversprayed powder which is not deposited on the
articles to be coated. In many systems, the containment of
the powder in the booth is aided by an exhaust system which
creates a negative pressure within the booth and causes the
oversprayed powder to be drawn out of the booth to recovery
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and filtering devices in a controlled manner. In some
systems, the oversprayed powder which is collected i5 .
merely saved for future use, while in others it is
recycled to the application device automatically.
In a powder coating installation, there are
several critical or desirable aspects which must be
considered, some of which include: safety; efficiency;
the size of the equipment; the complexity of the opesation
and construction; color change; cleaning; maintenance; and
the containment and/or recovery of powder not deposited on
the substrate, as-well as others. The spray booth used in
these systems, being an integral part of the installation,
must also be considered from these ætandpoints. Therefore,
it is a general object of this invention to provide a spray
booth which provides a substantial overall improvement in
spray booths in view of these criteria.
In many regards, it is desirable to use static,
cartridge type filters or the typical "bag house~ type as
part of the filter and recovery aspects of the system.
These types of filters have no moving parts, and therefore
offer simplicity, combed with reliability and efficiency.
However, if these filter/recovery units are located remotely,
the powder laden air is drawn out of the spray booth to the
filter/recovery unit through ductwor~ os some other restriction,
or through a confined area. In many systems, if not all, the
filter/recovery unit itself represents a confined area. ~his
gives rise to a deficiency in these prior art systems, in that
they present a possibility of explosionO
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~133691
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~ he resins used in powder coating are, as a class,
generally flammable. In their powdered form, and within
certain air-to-powder ratios, they can burn rapidly. Thus,
it can be appreciated that if an air/powder mixture were
somehow to become ignited in an enclosed or restricted space,
the result could be an explosion. Although burning of the
powder even in an open space, can be inconvenient and present
safety hazards to both life and limb, an explosion generally
gives rise to more dreaded consequences. Thus, because these
confined areas in the prior art systems give rise to the
possibility of an explosion, it is an object of this invention
to provide a booth/recovery system without confined areas
which could create a potentially explosive condition. The
recovery/filter portion of the system is located integrally
with the booth 50 that there is no necessity of having ductwork
which could create a confined area.
Although some prior art booths did incorporate an
integral recovery system with the booth, and although some of
them did substantially reduce the ~confined areas~, these prior
art systems were complex and costly to build, operate and/or to
maintain. Therefore, it is another object of certain aspects
of this invention to provide a powder spray booth/recovery
system which is simple in its design, manufacture, maintenance
and operation, but yet which eliminat~ confined areas having
25 ¦¦explosiv ir/powdes mix~uros.
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~ 1133691
Another important consideration with respect to
¦powder coating booths is the ability to quickly change the
¦powders, or color of the powder being sprayed. In this
¦regard, it is important that the previous composition be
¦effectively removed from the system, lest it contaminate the
¦subsequent coating operation with a different powder.
¦Therefore, it is an object of certain aspects of this
¦invention to provide a spray booth/recovery system which
¦is safe, simple and yet which will provide the ability to
¦quickly and efficiently be capable of being changed from
¦one color or powder to another, and which further will
¦facilitate maintenance of the system without disabling the
¦spray coating operationO
In general then, this invention provides a spray
booth/recovery system which utilizes static filters and
which provides improved safety and color change capabilities
in a very compact system.
The booth/recovery system compr~ses a booth in which
to powder coat substrates, having a ceiling area, walls, and
a floor, and having a recovery system underneath the floor of
the booth. The recovery system comprises a powder collector
area below the booth, and a clean air chamber sealed from the
booth and from the powder collection area, but being provided
with an opening from the collection area into the chamber
through static filters. The collection area is open to the
interior of the spray booth through a hole of substantial
cross sectional area in the floor of the booth and leading
directly to the collection area.
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~33691
A blower is provided to create a negative pressure in the
chamber so that powder laden air is drawn down through the
opening in tha floor of the booth into the collection area
immediately below the booth, and thence upward through
filters to the clean air chamber. This filtered air having
only traces of fine powder in a non-explosive ratio, is
withdrawn from the clean air chamber through the blower, and
passed to an absolute filter for final filtering.
Because of the location of the complete recovery
system underneath the spray booth, the space required for
the booth/recovery system is reduced to the floor space
required for the booth itself, whereas prior systems required
floor space for both the booth and the recovery system.
Because of the substantial cross sectional area
of the opening in the floor of the booth to the collecting
area, there are no "confined areas" to present explosive
conditions. The only confined area in the air flow path is
downstream of the filters, where the air/powder ratio is
non-hazardous.
The integral collector below the booth can be
detachably attached to the booth, mounted on wheels and be
provided with detachable fastenings to the ductwork for the
blower, so that when color change is desired, or when filter
change is desired, or when maintenance must be done on the
collector, another recovery system can quickly and efficiantly
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b~ placed under the booth, attached, and started up so that
spray coating can continue even during these operations.
Therefore, in accordance with the present inven-
tion there is provided a powder spray booth and powder
recovery/static filter unit configuration comprising;
booth means providing a controlled area in which to powder
coat substrates, defined generally by a ceiling, side and 3
end walls and a floor; a powder collection chamber in com-
munication with the interior of the booth means; a clean
air chamber sealed from t~e booth and from the powder col-
lection chamber, the clean air chamber being provided with
an opening from the powder collection chamber into the clean
air chamber; static filter means located within the powder
collection chamber and operative to effectively prevent
powder from entering the clean air chamber; blower means
operative to create a negative pressure in the clean air
chamber; and means for preventing a fire within the powder
collection chamber from cauSIng an explosion~ the explosion
prevention means including a substantially unrestricted flow
path from the powder collection chamber into the booth oper-
ative to effectively vent any fire created pressure build-
up within the powder collection chamber into the booth
without the occurrence of an explosion.
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1~3369~
B~IEF DESCRIPTION OF THE DRAWINGS
¦ The above noted and other benefits will be readily .
¦ appreciated by those skilled in the art by reference to the
¦ drawing figures, and the following specification wherein:
5 ¦ FIGURE 1 is a perspective view of a spray
¦ coating booth having a recover~collection
¦ system in its base; and
¦ FIG~RE 2 is a fragmentary view of the interior
¦ construction of the recovery/collection system
10 ¦ in the base of the booth of Figure 1.
1~ ,
113;3691
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring first to Figure 1, the system comprises
generally a spray booth 1, having a base 2 which comprises
the filter/recovery system for the powder, and an absolute
filter 5 connected to the base 2 through ductwork 3. The
ductwork 3 connects on either side of one end of the base 2
by means of quick-disconnect connections 30 to holes 22
(see Figure 2) in the base. This ductwork 3 communicates
the interior of the base 2 to a blower 4 which creates a
negative pressure in the base 2 as will be more fully dis-
cussed later. The blower 4 exhausts into a plenum 29 having
filters 28 which clean any air discharged therethrough. The
blower 4 can be mounted on a base l0 for convenience.
The spray booth 1 defines a controlled area for
spraying and comprises generally a ceiling portion 6,
opposed side wall portions 7, opposed end walls 32 and a
floor area 8. The floor area 8, in this embodiment, actually
comprises the top of the recovery/collector unit 2 and hence
the two elements are designated by a common reference
numeral herein. The booth 1 is supported by legs over the
base 2. An opening is provided in one of the side walls 7
of the booth l and both end walls 32. The opening in the side
wall 7 provides access into the interior of the booth 1 for
spraying equipment, or for access for a man to enter the
booth himself. Openings are provided in each end wall 32
for product to be transported through the booth 1 for spraying.
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A slot 9 in the ceiling portion 6 of the booth allows the
passage of conveyor hooks or the like from an overhead
conveyor to carry the articles to be coated through the
booth 1.
S Referring now to Figure 2, the details of the
recovery/filter unit in the base 2 of the booth 1 can be
seen. Figure 2 is a fragmentary view of the collector/
recovery unit 2 showing the interior details of the unit.
The base 2 is generally comprised of opposed
exterior side walls 21, end walls 33, an upper wall 8, and
a bottom portion 13. As noted above, the upper wall 8
also forms the floor of the booth. Along each of the
opposed side walls 21 of the base 2 is a clean air chamber 19
below the floor 8 of the booth 1, defined between part of an
exterior side wall 21 of the base, the upper wall 8 of the
base, part of an inner side wall 11 and a bottom chamber-
wall 20.
There are holes 22 in one end wall 33 for each
clean air chamber 19 to connect the ductwork 3 (See Figure 1),
in order to create a negative pre~sure in the clean air
chamber 19 and to draw air thereinto.
The interior side wall 11 extends downward from
the floor 8 and forms a centrally located air flow passage 12
directly from the booth to a powder collection area 14 below
the clean air cha~bers 19. The centrally located air flow
passage 12 is elongated in the direction of travel of the
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articles to be coated and extends across the whole ~ength
of the booth 1. It is of substantial cross sectional area
so as not to present a restriction which would result in a
"confined area" subject to explosion.
S Each chamber 19 is provided with multiple holes 17
on the underside through the bottom walls 20. Each of these
hoies 1~ is capped by a static cartridge type filter 16.
~he filters 16 can be removeably attached to the chamber 19
by any suitable means. In this embodiment the holes in the
bottom wall 20 of the clean air chamber 19, and associated
filter elements 16, are arranged in three banks of ~ix
filters on each side of the unit making a total of six
filter banks. Each bank consists of two rows, three deepO
In the plane of Figure 2, four filters 16 can be seen, two
on each side.
~ elow each of the six banks of filters, the
bottom 13 of the base 2 tapers downward in the shape of a
pyramid, each pyramid defining one of six powder collection
areas 14 where powder filtered out of the air by the filters 16
is collected. At the apex of each "pyramid" is a venturi
pump 15 or other suitable means to transport the collected
powder to a recycling bin, or storage for future use or
discarding. There is an opening (not shown) at the apex of
ach pyra~id communi ating with a respective ~e~tori pgmp 15.
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~3369~
- - Interiorly of the clean air chamber 19, venturi
throats 18 are situated above and around each of the holes 17
through which filtered air passes. A series of pipes 25
extend across the base 2, one each in alignment with all four
of the venturi throats 18, and hence the filters 16, across
in a row. Each of the pipes 25 has four holes 26 in its
underside which are aligned one each with a respective
venturi throat 18. An air solenoid 24 associated with each
pipe 25 and mounted exteriorly of the outside wall 21 is
effective to discharge a burst of air into a respective
pipe 25, and thus out of the holes 26 in the underside of
the pipe 25 into each venturi throat 18. The burst causes
momentary reverse air flow through the filters 16, and dis-
lodges collected powder from the filter material. The
dislodged powder falls into a respective "pyramid" collection
area 14. The solenoids 24 are sequentially operated through
any suitable control mechanism well known in the art, so that
only one bank or row is cleaned at a time. Therefore, there
is no net interruption of the air flow through the filter/
collector unit 2. Access doors 27 are mounted on the exterior
side walls 21 for servicing or replacing the filters 16.
The whole base 2 is mounted on wheels 23 to allow the base 2
to be easily removed from underneath the spray booth 1, so
¦that a new base 2 can be substituted therefor in order to
25 ¦facilitate the spraying of a new powder or color, or to
~service the unit.
If necessary, a rubber gasket can be used to seal
the periphery of the base unit to the booth.
Having described my invention, I claim:
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