Note: Descriptions are shown in the official language in which they were submitted.
108145~
The present invention relates to a method applicable
during spray painting to improve the enconomy of the spray painting
booth particularly as regards the use of the ventilation air.
When it is desired to paint objects by means of a spray
gun in a painting booth, the following arrangement is usually
followed in the construction of the booth. It comprises a chamber
in which the object to be painted is placed. The person doing
the painting remains outside the chamber and paints through the
front end of the chamber, which front end is open. A water
curtain or the like filter is provide~on the rear wall upon which
paint, driven with high velocity against the object, is projected.
The booth is fitted with a blower drawing air through the open
front end of the booth thereby to prevent escape of paint mist
from the booth through its open front end. The ventilating air
is drawn from the booth through a suction slit, along the surface
of water tray below the water curtain. Air-paint mixture passes
over the water surface with a speed such that water is drawn along
with the air. The mixture rises with high velocity into a water
- washing section behind the painting chamber, where separator baffle
plates force the mixture to change direction several times. In
this connection, the heavier paint particles are driven by cen-
; . .
trifugal force into the water stream. The water ascending along
with the ventilation air is separated on the separation plates
foundin the washing section. The water flows down into the tray,
and the ventilation air exists through the blower into the
atmosphere. The ventilation air still contains gases which have
come from the paint substances. In spray painting booths, of the
type described, the air drawn from the painting chamber passes
through the blower into the atmosphere.
When, in the course of painting, the air to be used
is drawn from the room in which the booth and the painter stands,
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10~3~L451
a considerable quantity of air is used during the work, which air
is heated if the work takes place during the prolonged cold period ~;
in certain countries as in Finland. It follows that much heating
energy is~wasted because the painting method itself does not
necessarily require heated air, although it is indispensable that
the room in which the worker stand~s has to be heated.
The object of the present invention is to eliminate
this drawback. This is accomplished, according to the invention,
by taking only part of the ventilation air from inside. The
major part of the ventilation air is either returned and reused
or taken straight from outdoor.
No such method has been applied in the prior art. Thus
large amounts of warm air have been wasted. Only in a spraying
method, of the type wherein the paint substance is blown with the
aid of compressed air in a closed chamber, is it known to return
the air, purified of paint substances, to the pressure tank and
to reuse a great proportion thereof in the spray gun. sut this
last-described spraying method is completely different from what
the spraying according to the present invention implies. The spray
painting method of the invention is intended for use in such spray
painting wherein the spraying booth is open on the side facing the
operator and wherein, with the aid of the exhaust air, the spreading
of paint fog frqm the spraying side to interior spaces, out from the
spraying chamber, is prevented.
Accordingly, the invention as herein broadly claimed is
a method of ventilating a spray painting booth standing in a
heated room, this booth having a painting chamber, painting being
carried out by spreading paint through an open front end of the
- chamber. The method lies in introducing ventilation air through
the front end of the painting chamber from around this front end
and controlling pressure conditions in the booth so that about 20%
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108~45
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of the ventilation air is drawn from the heated room.
The invention, also as herein broadly claimed, is a
spraying paint booth comprising a painting chamber adapted to
stan~ in a heated room and having an open front end through which
paint is sprayed by a painter standing in the heated room. Means
are provided around the open front end of the chambee for intro-
; ducing ventilation air into the chamber and other means are
provided for controlling pressure conditions in the booth so
that about 20% of the air introduced into the chamber is drawn
from the heated room.
A preferred embodiment of the invention will now be
^ described in conjunction with the appended drawings wherein:
Fig. 1 shows a spray painting booth wherein one intendsto apply the procedure of the invention. Fig. 2 is an axonometric
drawing of a spray painting booth in which the procedure of the
invention has been applied.
Fig. 1 shows schematically a spray booth which stands
in a heated room. A painter 12 sprays an object 10 that has been
;- placed in a chamber 1 of the booth. A water curtain 4 flows
. . .
downwardly alor.g the rear wall of the painting booth, from a
pipe 5, to the bottom of the chamber. Paint drawn along with the
, . .
;~ water is collected in a box 2 on the bottom of the chamber. Ven-
.
tilation air is drawn from the booth through a suction slit 9
provided along and above the tray, suction being obtained by a
centrifugal blower 6 placed on top of the booth, this blower
being driven by a motr 7. The air-paint mixture, in which water
. is also present, rises with high velocity into a water cleaning
~,'r flue 3, where separator baflle plates 8 force the mixture to
change direction several times. The heavier paint particles are
.: . .
captured by the water stream which is separated from the air by
means of the said baffle plates 8. Clean air exhauts, through the
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~08145~
blower, into the atmosphere. In order that no warm air be ~ -
wasted, the invention provides two ways in which this can be
achieved. Both serve the purpose of saving heated room air and
substituting, largely, air from other sources.
The first way implies that the air which is carried
through the water curtain or through another filter and which is
free of paint particles is recycled, that is returned to the booth,
as shown by the arrows in Fig. 2. However, the arrangement is
such that in each cycle a given part, e.g. about 20~, of the used air is al-
lowed to escape to atmosphere. This quantity is replaced byheated air taken from the room in which the booth stands.
The recycled or recirculated air will carry residual
gases from the paint substances. If the paint substances contain
gases in such quantity that the circulation according to the first
mode is not allowed by fire authorities, then about 80% of the
ventilation air is taken directly from outdoors and the rest, about
20~, consists of heated indoor air, drawn from the room,similarly
; as in the foregoing. The ventilation air is introduced into the
chamber in such manner that it does not come into contact with the
object to be painted nor with the operator. As a consequence,
the cleanness and temperature of this air have no significance.
During the cold season the use of outdoor air may cause
freezing of the~water. This may be prevented by using salt and,
for prevention of rust, an inhibitor agent, or other expedients
known in prior art. When the entry of recirculated air into the
painting chamber has been properly arranged and the suction and
pressure conditions have been correctly chosen, the appropriate
~ quantity of room air will flow towards the ob~ect that is being
`~` painted.
By the process and spray painting booth of the invention,
which is employed in association with painting booths with open -
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1081~51
front end in which booths at present the ventilation air is
taken from that room in which the operator stands, major economic
savings are achieved, especially now that the fuel prices have gone
up consid~rably.
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