Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~058396
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This invention xelate to a method &nd apparatu~
for c~ecting exces~ paint spray particles in a paint
spraying operation.
The term nspray booth" is a term of art generally
denoting a large 3heet metal structure or hou~i~g having so-
called working area or ~pace within which ~pray painting
operations are carried out, an exhaust chamber ~ith an
a~ociated stack communicating with the working area, a
fan in the stack for dra~in~ fresh air into and through the
working area to maintain it well ventllated, and means be-
; . ...
t~een the working area and the exhau~t chamber for removingpaint particles from the air before the air is exhausted up
the ~tack. In es~ence then, the booth structure defines an
~, air rlow pas~a~e through which air i~ moved at high veloc-
ity to eliminate mists created by a spray paint operation.
Remo~al of alr laden with spray mist and overspray is
necessary, among other reason~, to prevent excessive or
explosively high concentration of Yolatile solvents and
;~ other rlammable materials, to protect per~onnel in the
vicinity from exposure to toxic ~aterials, and to maintain
a clean environment ~or proper finishing Or the ware.
~ Current standards require a minimum air Mow rate at the ; ~;
; faee of the booth of 60 cubic reet per minute per square
foot, or at least 60 linear ~eet per mlnute at each point
at the face o~ the booth for unattended booths, and 100 c~m
1 per square foot or 100 linear feet per mi~ute for attended
¦ booths. In order to collect the paint particles and
~i minimize pollution of the at~osphere, especially at the high
rates of air flow, the exhaust air laden with spray residue
i8 circulated throu~h an eliminating de~ice or medium, which
serves to remove the paint particles be~ore the air is
exhausted into the atmosphere.
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- Eliminating media in current use include the dry
-~; baf~le system, the dry filter syste~, and the water wAsh
-; system. In the dry bafrle syste~, the air i8 circulated in
a tortuous path over solid baf~le sur~aces disposed bet~een
;' the working area and the exhaust cha~ber, ~hich causes the
'd~ paint resldue to be depo~ited thereon~ The dry filter
~ystem employs rilters Or a varlety of types through whlch
the alr 18 clrculated. Both Or these dry systems involve
requent cleaning and maintenance problems due to paint
accu~ulatlon, and also the problem Or ~lsposal of waste
matter and spent rilters as well as presènting a fire hazard.
In the water wash booth, such as that descrlbed in
Pearson ~nlted States patent No. 2,545,672, wate~ i8 caU8ed
to ~low do~nward over an imperforate wall at the back oi the
working area and acro~s an open gap between the bottom or
$ said ~all and the liquid level in an underlying water
.~ . . .
reservolr in the form ~ore or less Or a water~ ~ll, thereby
to ror~ a curtaln Or descending water against and through
which paint laden air is drawn at high velocity, and whereby
~; 20 the!paint mist is entrained in the water and collected in
the reser~oir. Principal drawbacks Or the water system are
that the water ~ust be treated wlth chemlcals to prevent
.
growth of`algae and to control the paint collected ln the
reser~oir, and that the waste water is a pollutant. A180,
since thè area ior passage Or air into the exhaust chamber
~8 relatlvely ~mall in co~parison with the booth size, and
located solely at the bottom regions o~ the booth, the air
~lo~ rate i~ not uniform within the booth, and a high
horsepower fan must be used to maintain the mini~um pre-
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;~ 30 scribed air flow rate in all areas at the face Or the boothO
Moreover, the accumulated paint solids cannot be reclaimed
and reused and tend to clog the system. Rusting of the
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booth interior is al80 a problem, and a severe loss ofefriciency in paint remo~al is experienced if the water
curtain is interrupted. ~-
In a development entirely separate from the paint
spray booth art, proposals were made during the 1930's to
remove dust particles from air by drawing the air a~ low
velocity in a tortuous path through an oil coated baffle
syætem, Representative United States patents relating to
this development include Hines patent No. 1,751,999;
Adams et al, patent No. 1,807,950, Ga4en patent No.
1,895,61~3 Dauphinee patent No. 1,899~017; and
WeiQgerber patent No. 1,083,764. Hines patent No.
1,751,999, for example, discloses a low velocity air filter
having a plurality of closely spaced, angularly disposed
baffles, together wlth means to circulate oil over the baf-
fles and through a filter.
Notwithstanding general similarities between the
arts of dust air filters and spray booths, a~d a high degree
of further development in the art of spray boothæ since the
above devel~pment, the use of oll or other viscous liquid
as an eliminating medium in a spray booth of the structure
hereinafter described has not been de~eloped in the prior
art, and the arb o~ alr filters has developed separately and
independently from the art of spray booths. Qne fair sup-
position for this divergence is that the use of oil in a
conventional water wash booth would cause conta~ination of
the external atmosphere with oil, due to the high velocity
air flow. Conversely, the requirement of a high velocity
air flow in ~ spray booth would be incompatible with the
a~oresaid air filter devices becauæe large amounts of oil
would be stripped off the baffle surfaces, causing such
devices to become inoperable.
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In accordance with the present invention, a sup-
ported moving film Or oil is ~ ed as the paint collecting
medium in a speeially designed paint spray booth. The
booth comprises an enclosure having an i~let opening there-
in through which air is drawn at a high velocity, or in
excess of 60 cfm per square foot of opening. Spaced in~ard
from said opening are a plurality of rows o~ baffles ar-
; ranged substantially perpendicular to the air flow. The
rront row of baffles are substantially planar with wide
frontal faces, and are closely spaced to define naxrowvertical spaces therebetween through which air may pass.
A film of oil iB continuously flowed over the front sur-
faces of the baffles in order to entrain therein paint mist
càrried by the air stream, and the oil is circulated through
a reser~oir wherein the paint settles and may be removed and
reclaimed. Means downstream of the baffles are al90 pro-
vided to remove oil droplets from the high velocity air
before it is exha~sted into the atmosphere.
The use of mineral oil as a permanent paint eol-
lecting or eliminating medium provides unexpected and uniquebenefit~ not attainable by prior art methods. The paint is
;~ not chemically modified by the oil and may be easily separ-
ated and reclaimed. The oil is continuously rec$rculated
through the system, which allows for self-cleaning of the
booth interior and prevents adherence of paint on any ex-
posed surface, and the ~el~-contained oil circulation
system eliminates pollution problems. The baffle arrange-
~en~ provides for a uniform high ~elocity flow of air
through the working area of the booth without stripping the
oil from the ba~les.
The benefits herein recited are unexpected because
both oil and paint mist are combustible materials, and it
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~ould be expected that the combination of the two would be
unacceptable becau~e of the possible fire hazard.
Unexpectedly, for reasons explained in detail
herein, the combination of mineral oil and paint mist in a
spray booth does not result in a flammable mixture at normal
or above normal operating temperatures. The high rate of air
flow through the booth prevents absorption of the volatile and
highly flammable paint components into the thin film of oil,
whereas the paint solids are entrained in the oil in a highly ~;
efficient manner. The entrained paint solids are thus coated
with non-flammable mineral oil and tend to collect in a harmless
manner at the bottom of the oil reservoir.
In one particular aspect the present invention
provides a paint spray booth comprising, in combination, an
enclosure having side and top walls defining therein a spray
painting chamber, an air inlet in one side of said chamber and
an air outlet in the other side of said chamber, means for
trawing air through said inlet and said chamber and discharging
lt through said outlet, substantially vertical wall means in
said enclosure between said chamber and said outlet extending
~from side wall to side wall and from top to bottom thereof,
said vertical wall means including a plurality of longitudinally
spaced sets of vertically extending laterally spaced baffle
plates, the baffle plates of the first set having broad front
faces exposed to said chamber and forming a rear wall for
said chamber against which spray painting operations may be
performed, the baffles of said first set being mounted closely
ad~acent to define narrow vertical slits between said plates
for escape of air from said chamber, the baffle plates of each
-30 succeeding set being staggered relative to the plates of the
preceding set with each plate of each succeeding set being aligned
wlth and laterally broader than a respective one of the spaces
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between the plate~ of the preceding set and spnced sligh~ly rearwaldl.y there-
from as to ca~lse alr passing through said sets of plates to bc divertcd into
tortuous paths around the plateæ of each set, the sets of baffle plates
succeeding said first set belng shorter than the first set and suspended :
therebehind by an imperforate web coextensive with the upper portions of the
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baffle plates of the first set, said web equalizing the greater air flow over ~ -
! and through said first eet of baffle plates and thus throughout said chamber,
an oil reservoir in said enclosure beneath said baffle plates, oil in said
reservoir the level of which is spaced below the l.ower ends of said baffle :.
plates, means between the lower ends of said baffle plates and the oil in said
i. -~; .reservoir for preve~ting passage of air below said baffle plates and for con-
straining the air to pass through said sets of baffle plates, means for con-
tinuously pumping oil from said reservoir to the upper ends of the baffle plates
of at least the first and second sets and for gravitationally flowing a film ~
of oil uniformly over the front faces of the baffle plates of the first and : :
second sets, whereby particles of paint sprayed against the baffle plates of
the first set and carried in the air passing through the slits between the
baffle plates of the first set are entrained in the oil and flushed thereby
into the reservoir, the oil flowing over said baffle plates belng returned to
said reservoir and having a free fall from the lower edges of said baffle : .
plates to the level of the oil in the reservoir whereby to cause the entrained.
paint particles to penetrate the surface of the oil and become immersed therein
and to sink to the bottom on the reservoir, the baffle plates of the first set .
having the side edges thereof bent rearwardly toward the baffle plates of said
; second set and the baffle plates of said second set having a central concave
., ':
portion for catching and retaining oil and paint particles passing thereto from
the preceding set of plates, the baffle plates of the last set each having the
slde edges thereof bent forwardly into spaced generally parallel relation with
the side edges of the respective plates of the preceding set for catching and
retaining oil and paint particles passing thereto from the preceding set,
whereby the paint particles are entrained in the oil and
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~058396
deposited in the reservoir and air substantial].y free of paint
and oil particles ls delivered to said outlet, and a second
baffle system in said enclosure between the last set o~ said
baffle plates and said outlet, said second baffle system
comprising a vertical chamber rearwardly of said last set of
baffle plates extending from sidewall to sidewall of said .
enclosure and including a vertical wall spaced rearwardly from
said last set of baffle plates and terminating at its lower edge
in upwardly spaced relation to the lower ends of said baffle
plates to define an entrance into the lower end of said vertical
chamber, a pair of laterally spaced baffles converging upwardly
from the walls of said vertical chamber above said entrance, and
a horizontal deflecting baffle mounted centrally in said
vertical chamber above the upper ends of said converging
baffles, said horizontal baffle being wider than the space
between the upper ends of said converging baffles and having
edges bent downwardly into spaced generally parallel overlying
relation with an adjacent one of said converging baffles, said
baffles in said vertical chamber causing the air passing there-
through.to strike several baffle surfaces and to travel in atortuous path having several sharp turns therein for removing
substantially all traces of paint and oil from the air, said
vertical chamber having a bottom wall sloping toward said
reservoir for returning to the reservoir all oil removed from
the air.
In another particular aspect the present invention
provides a paint spray booth comprising, in combination, an
-anclosure having side and top walls defining therein a spray
~ainting chamber, an air inlet in one side of said chamber and :~
an air outlet in the other side of said chamber, means for
=drawing air -through sald inlet and said chamber and discharging
-lt through said outlet, substantially vertical wall means in
-.said enclosure between sald chamber and said outlet extending
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1058396
: from side wall to side wall and from top to bottom thereof,
sald vertical wall means including a plurality of longitudinally
spaced sets of vertically extending laterally spaced baffle
plates, the baffle p].ates of the first set having broad front
faces exposed to said chamber and forming a rear wall for said
chamber against which spray painting operations may be performed,
the baffle plates of said first set being mounted closely
adjacent to define narrow vertical slits between said plates
for escape of air from said chamber, the baffle plates of each
succeeding set being staggered relative to the plates of the
preceding set with each plate of each succeeding set being
aligned with and laterally broader than the respective one of
the spaces between the plates of the preceding set and spaced
slightly rearwardly therefrom so as to cause air passing through
said sets of plates to be diverted into tortuous paths around
the plates of each set, an oil reservoir in said enclosure
beneath said baffle plates, oil in said reservoir the level of
which is spaced below the lower ends of said baffle plates,
means between the lower ends of said baffle plates and the oil -
in said reservoir for preventing passage of air below said
~ baffle plates- and for constraining the air to pass through said
i` sets of baffle plates, means for pumping oil from said reservoir
to the upper ends of the baffle plates of at least the first
and second sets for gravitationally flowing a film of oil
uniformly over the front faces of the baffle plates of the first
and second sets, whereby particles of paint sprayed against the
baffle plates of the first set and carried in the air passing -
. through the slits between the baffle plates of the first set
'~ are-entrained in the oll and flushed thereby into the reservoir,
the baffle plates on the first set having the broad front faces
-thereof in substantially a common plane and having the side
-etges thereof bent rea-rwardly toward the baffle plates of said
~second set, the baffle plates of said second set havlng a central
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concave portlon aligned with the s].lts between the baffl.e plates
of the first set for receiving the flowing film of oll and catching
; and retainlng oil and paint particles passing thereto from said
first set of plates, and a third set of baffle plates rearwardly
of said second set to which oil is not supplied, the baffle
plates of said third set having ~he side edges thereof bent
. forwardly into spaced generally parallel relation with the side
edges of the respective plates of the second set for catching
and retaining oil and paint particles passing theret~ from said
second set, the longitudinal spacing between the successive sets
. of baffle plates being progressively smaller so as t-o cause a
progressive increase in the volocity of the air passing through
the successive rows of the baffle plates to increase the air
scouring action thereof, the spacing of said baffle plates above
the oil level causing the oil flowing over said baffle plates to
be returned to said reservoir with a free fall from the lower
edges of said baffle plates to the level of the oil in the
reservoir whereby to cause the entrained paint particles to
penetrate the surface of the oil and become immersed therein to
sink to the bottom of the reservoir.
s In yet another particular aspect the present invention .
provides a paint spray booth comprising, in combination, an
. enclosure having side and top walls defining therein a spray -:.
painting chamber, an air inlet in one side of said chamber and
an air outlet in the other side of said chamber, means for
drawing air through said inlet and said chamber and discharging
it through said outlet, substantially vertical wall means in
: said enclosure between said chamber and said outlet extending
, .
from sidewall to sidewall and from top to bottom thereof, said
; 30 ~ertical wall means including a plurality of longitudinally
.. 8paced sets of vertically extending laterally spaced baffle .~
plates, the baffle plates of the.first set having broad front
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faces exposed to said chamber and forming a rear wall for 8a:Ld
chamber against whlch spray pa~nting operations may be performed, ~.
the baffle plates of Eaid first set being mounted closely -
ad~acent to define narrow vertical slits between said plates for :
escape of air from said chamber, the baffle plates of each ~.
succeeding set being staggered relatlve to the plates of the ::
preceding set with each plate of each succeeding set being aligned
~: with and alterally broader than a respective one of the spaces
between the plates of the preceding set and spaced slightly
rearwardly therefrom so as to cause air passing through said sets
of plates to be diverted into tortuous paths around the plates
of each set, the sets of baffle plates succeeding said first set
being shorter than the first set and suspended therebehind by
an imperforate web coextensive with the upper portions of the
baffle plates of the first set, an oil reservoir in said enclosure
beneath said baffle plates, oil in said reservoir, means for
pumping oil from said reservoir to the upper ends of the baffle
. plates of at least the first and second sets for gravitationally
flowing a film of oil uniformly over the front faces of the
baffle plates of the first and second sets, whereby particles
of paint sprayed against the baffle plates of the first set and
carried in the air passing through the slits between the baffle
; plates of the first set are entrained in the oil and flushed -:-
thereby into ehe reservoir, the oil flowing over said baffle
. plates being returned to said reservoir for recirculation over
-~aid plates.
In a further aspect the present invention provides
a paint spray booth comprising, in combination, an enclosure
baving side and top walls defining therein a spray painting
~0 -chamber, an air inlet in one side of said chamber and an air
outlet in the other side of said chamber, means for drawing air
-through said inlet and said chamber and discharging it through
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1058396
~aid outlet, means i.n said enclosure between ~aid chRmber and
said outlet for removing from the air passing through sald
chamber the majority of the paint partlcles resultlng from the
spray palnting operations, and a baffle system between said
particle removing means and said outlet for further cleaning
- the air and removing therefrom substantially all traces of paint,
said baffle system comprising a vertical chamber rearwardly of
said particle removing means having an entrance into the lower
end thereof, means immediately above said entrance for converging
10 the flow of air into the central portion of said vertical chamber
at the lower portion thereof, and horizontal deflector means
spaced from the sides of said vertical chamber and positioned
. in said converging air flow immediately above said converging
means.
In the drawings: i
Figure 1 is a perspective view of a simplified form
Z of spray booth, which incorporates features of the present
invention;
Figure 2 is a vertical sectional view taken sub-
`l 20 stantially on line 2-2 of Figure l;
Figure 3 is a sectional view taken along line 3-3 of
Figure 2; and
Figure 4 is a sectional view taken along line 4-4
~ of Figu~e 2.
; Figures 1 and 2 illustrate a spray booth 10 having a
forwardly extending sheet metal enclosure defining a spray '
paintlng or working area 11 and an air intake opening 12 at one :
side thereof, and a rearwardly disposed exhaust outlet 14 at the
' top. Ob~ects to be spray painted, such as indicated at 16, are ::
supported in the working area 11 inwardly of the opening 12, and ~ :~
~, a spray of paint or coating material is directed toward the
ob~ects by use of a spray device, such as shown schematically at
18. The paint may ~ ~.
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compr~Be any number of the known coating materials, includ-
i~g but not limited tt~ water and solvent based materials,
such as alkyd~, nitrocell~lose laquers~ watei ba~e
enamels, polyurethanes and epoxy resin
Means are provided for forcibly drawing air
horizontally throug~h the inlet openin~ 12 and verticallg~ up
and out through the exhaust outlet 14 in æubstantially an
L-pattern, such as a pt~wer driven ~an 20 located in the
exha~st outlet. Excess paint mist and paint overspray~ at
10 the inlet is thus drawn into the interior of the spray bocth
by a hlgh velocity air flt~w.
The working area leads rearwardly to the solids
.
eli~inator portion of the spray booth or baf~le section
and is surrounded by a top wall 22 and side walls 24.
Spaced rearward from the working area are a plurality of
row~ of baffle plates 26, 28 and 30, the fir~t rt~w o~
plates 26 ln effect constituting the rear wall o~ the work-
ing area. In general, the rt~w~ oi baffle plates are
j arranged in a parallel relationship, and each row comprises
t 20 a plurality of spaced, generally vertica~ members rigidly
~A supported by their ends $n a ~ixed position. ~
The ba~le plates 26 comprising the outermost row, ,
as shown in Figure~ 2 and 3 are substantially flat and are
arranged substantially in a common plane which is substantial-
ly pterpendicular to the direction of alr flow at the inlet,
as indicated shhe~atically by the arrows. Ad~acent plates
- are spaced from one a~other to derine ~arrow open vertical
slots 32 therebetween. The baffles are ~rom about four to
seven times ~ider than the ~idth of the slots, and the side
30 edges thereo~ are bent rearward on an obtuse angle ~or
reason~ here~nafter m~re fully described.
; The second set of ba~fle plates 28 are similar to
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the first set in terms o~ width and spacing rrom each o~her,
except said plates are slightly V shaped or concave rela~i~e
to the direction of air flow, with the side edge~ being
bent rearward on an obtuse a~gle. The longitudinal
centerline of the second set of plates 28 coincides with
the transverse vertical centerlines of the slots 32 whereby
the first and second rows of baffles are arranged in a
staggered relationship.
The third row ~f pl~tes 30 are relatively narrower
th~n the plates of the first two rows and are located behind
and are coextensive with the vertical slots 34 between the
plates of the second row. The side edges of the plate~ are
bent forwardly, and the ~pace between the third and second
rows is less than the space between the ~irst and ~econd
rows. The described spacing causes a progre~sive increase
In velocity of air passing through successive rows of
barrles .
It will be noted that the re~pective second and
i third rows of baf~les 28 and 30 are not entlrely ~erticallg ~;~
coextensive with the first row 26; instead, the former ~re
6horter than the f~rst row and are suspended in a spaced
relationship from a solid or non-per~eable web 36 extending
downward and supported from the top of the enclosure in
parallel with the first row Or baffles. Preferably, the
length of the web 36 is abo~t one-third of the length of
the first row of baffle plates 26. me web 36 serves to alter
the normal rate of air flow from the top to bottom of the
first two rows of baffle plates, such that the flow is
equalized or uniform from top to bottom Or the plates and RO
area of the plates will be s~b~ected to a~ excessively high
flow that would strip the oil~therefrom.
~he rows of baffle plates are arranged in a spaced
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.' '' st~ggered relationship tQ provide for s~ccessive positive
and at least right angle de~lection of any paint and oil
particles which emerge through the first group of ~ertical
sl~ts 32, ~nd the final row of b¢a~fle plates 30 serve
as collectors ~f oil ~nd solids p¢articles which m¢~y be car-
ried through the downstre¢amipas~ges by the hlgh velocity
air flow. The air velocity is alBO rapidly increased up
to the final row of b¢affles in order to increase the
strai~ht line momentumi of ¢~ny oil particles, which would
otherwi~e tend to move in a tortuous path with the air flow
around the b~ffles instead Or collecting on the fin¢al r¢~w
i of b~ffles as desired. ~;
Me¢ans are provided for establishing a continuous
and unirorm ilow of oll down the front surf¢aces of the first
~j; .
and second rows of baffle plates, 26 and 28 respectively.
A reservoir 38 of mineral oil is provided in the bottom of
the enclosure, ¢and i$ connected, via a suitable pump 40 ¢and
line ~2, to the top of the enclosure. The line 42 is con-
nected to a bifurcated branch 44 leading into respective
.~ .
2~ troughs 46 ¢and 48 located respectively over and coextensiYe ~ -
with the first and second ro~ o~ b¢a~fle plates 26 and 28.
The troughs 46 ¢and 48 have lowered forward edges which ¢~llow
!, the oil to 5pill over an~ do~n the front surfaces of the
¢ fir~t row of baffle plates 26 and web 36.
As shown ~n Figure 4, the lower edge portion of
the web 36 is provided with a spaced ~eries of V-shaped
channels 50 located above respective individual baffle
~` plates of the second row 28. The channels 50 serve to
funnel or concentrate the oil moving downward on the web in-
3Q to the central portio~ of the front surf~ce6 of baffles 28,
which ha~ been found to minimize stripping and 105s 0~ oil
by the air ~low as the oil moves down the ba~les. The ~ ;
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~05~3g6
third row of baffle plate~ 28 are not directly supplied
with oil and are ~upported by a bracket 51 secured to the
rear æide of the web 36.
The lower ends of the front bafrles 26 are cQn-
nected to a substantially horizontal drain board 52 spaced
slightly above the oil level in the reservoir 38~ such
that the paint laden oil falls a short distance into the
reservoir3 which has been found to minimize ~plashing and
build-up of paint scum on the sur~ace of the oil reservoir.
1~ ~he ~ere draining of oil onto the surface of the reser~oir
may allo~ the paint solids to float and cling together,
whereas a ~light drop allows for penetration of the surface.
The lower edges o~ the rear baffles 28 and 30 are spaced
above the reservoir oil level to provide the same ef~ect.
It will be noted that the baffles 26, 28 and 30
are preferably inclined dcwn~ard and outward on a slight
vertical angle, preferably in the order of 3 to 4 degrees
and no greater than 5 degrees, in order to enhance the .
co~tlnuity of oil ~low thereon. An angle greater than
5 d~grees ~rom vertical i~ not desirable due to the
tendency of the barfle edges to 108e their o~l coating.
Important features of the baffle system l~clude ~.
the substantial width or front~l sur~ace area of the
baffles in com~ari~oa to the width of the air pas~age
810ts therebetween3 and the arrangement of the baf~leæ in
a plane which i8 substantially perpendicular to the path
of air flow through the booth. These features allow for
a maximum exposure of the mcving films of oil to the
contaminated air. Also, the planar or slightly conc~ve
3~ quality of the baf~les~ together wlth the uniform spacing
of the air ælot~ therebetween~ permits a very high air
flow thereo~er without the oil being wiped from the surface,
~058396
which would allow the undesirable accumulation of palnt on
the bare surfaces. The ba~fles are free fr~m sharp corners,
or corners which are less than 90 degreeæS because 8harp
corners would be wiped clean of oil by the high velocity
air, especially in the vicinity o~ the slots. Hence, the
baffle deslgn described herein i8 particularly adapte~ to
present large and eificlent oil coated surfaces which re-
tain their oil coating under conditions of high velocity
air flow, which, at the first set Or baffles may be 125
10 linear feet per minute and at the second set Or baffles, ~-
in the order of 2300 linear feet per minute.
Another important feature in the design of the
bafrle system is the existence Or a substantially uniform
air flo~ from top to bottom and from side to æide in the
inlet opening, Inoontrast wlth a water wash booth having
a relatively æmall waterfall area and high resistance to
air flo~, the present baffle system ofrers relativelg low
resistanoe to air flow due to the length of the slit open-
ings and spa~ing of the baffle rows, thus allo~ing use c~
2~ a relatively low horsepower motor.
As shown in Figure 2, located rearwardly or
do~nstream of the first baffle system i~ a second baffle
system, the primary purpose Or which is to collect and
remove oil particles which escape from the flrst baffle
system. Whereas the first baffle æystem is arranged in
substantially a vertical plane, the second system is
arranged horizontally in a verti~al exhauæt chamber 54 up- -
stream from the exhaust outlet 14. The chamber 54 co~-
prises a forward vertical wall 56 spaced rearward from the
rirst bafrle system, which extends downward ~rom the top
of the enclosure and terminates at a location above a
forwardly sloping base 58 and below the tops of the rear
.
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. . . ~ . .
.. ;~......
~05839~;
baf`fle~ 28 and 30, preferably at a point approximately at
the horizontal center line of said bai~fles. As shown by the
arrows indicating air flo~, a1r entering at the top of
the first set of ba~les is swept d~wnward around the wall
56 and then upward into the vertical chamber 54~
~ s shown, the second baffle ~ystem comprises, at
the louer entrance of the chamber 54, a first pair of up-
wardly converging baffles 60 connected to opposite chamber
walls by respecti~e horizontal portions 62 having covered
openings 64 therein to collect and drain away accumulated
oil. The respective end edges Q~ the baffles 60 are sup-
ported upon rods 66, said edges having a relatively wide
space therebetween to channel and concentrate air flowing
therethrough.
A deflecting baffle 68 supported on rode is pro-
vided upstream from and in the outlet path of the converging
baf~les 60. The baffle 68 comprises a horizontal portion
which i8 wider than the outlet of baffles 60 and i5 connec-
ted to opposite legs 70, whlch are dispose~ in a downward
obtuse angle ~rom the horizontal portion, the endæ of said
leg~ being spaced outward ~rom and about on the same level
as the ends o~ the baffles 60. The legs 70 are spaced from
the sides of the chamber 54, and air is cau~ed to flow in a
tortuous path around the legs, causing oil to accumulate
thereon and fall downward onto horizontal portions 62.
A pair of downwardly angle~ baffl~s 72 are connec-
ted from the chamber w~118 above the legæ 70 of the deflect-
ing baf~le 68. ~he ba~fleæ 72 are substantially planar and
have terminal edges which extend over the juncture between
the legs 70 and the horizontal portion of baffle 68. Thus,
the baffles 72 are disposed in the path of the air which
emerges around the baffle 68 and serve to further de~lect
~58396
the alr rlow toward the top of the underlying baffle 68.
Di~posed above baf~les 72 are a pair of permeable
air filters 74 arranged in an inverted V-configuration.
The filters 74 may be composed of a mesh material composed
~f metal, glass fibers~ or the like, supported in a frame.
The filteræ 74 ser~e to remove the ~inal finite traces of
oil before the air reaches the exhaust outlet 14.
~ he type of oil employed is preferably a mineral
oil without detergents or other additives, and ha~ing a
viscosity to easily ~low down the baffles at room tempera
ture without undue vaporization. A mineral oil having a
~igcosity of 660 Standard Saybolt Units at 100F have been
found to be suitable~ although other viscosi*ies ~ay be
employed. A suitable oil ~low rate is approximately
8 gallons per minute for each foot of width of baffles, and
the reservoir pre~erably conta~ns at least about 25 gallons
per foot of bafrle width, to provide sufricient ~olume for
settling of the paint solids.
Mineral oil o~fers se~eral advantages, including
a hlgh fla~h point ~na burning point, and is incompa~ible
and chemically unreactive with paint solids in current use. :- ;
Because the oil has a lower density than the paint solids,
the solids tend to settle to the bottom of the reservoir
where they may be removed~ M~reover, the flammable
volatile solvent components of the paint are not absorbed
by the oil and do not lower the flash point or burning
point thereof~ me presence of paint solids which may re-
main entra~ned in the circulating oil do not su~stantially
a~fect the efficiency of the elimlnator baffles.
In operation, the fan 20 and oil pump 40 are
activate~, such that oil is pumped from the reservoir 38
upward through the line 42 into the troughs 46 and 48. A
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continuous supply of oil flows down over the ~irst and
æecond rows of baffles, 26 and 28, and air is drawn through
the inlet opening 12 at a rate of at least 60 linear feet
per minute and preferably in excess o~ 100 linear ~eet per
minute.
Wlth the booth in readiness, objects, such as
indicated at 16, are diæpo~ed in or near the opening 12,
and a paint æpray device 18 i~ located upstream of the
ob~ect and i8 aimed at the ob~ect.
Atomized paint which does not adhere to the object -~
16 i$ carried by the high air flow into contact with the
first ba~fle~ 26, which are entirely covered with a continu-
ously moving film of oil. As a result~ the solid paint
particles are entrained in the oil and flow downward into
the reservoir 38, where the paint solids are allowed to
settl~. Paint particles which avoid the first baffle3 26
an~ p~s8 through the air slots 32 increase in momentum and
are depo~ited on the second set of baffles 28, and any
particles passing the baffles 28 through the slots 34 are
collected by the baffles 30, which are normally wetted by
oil removed from ~he first two rows of baffles.
After the air has passed through the eliminator
baffles, it passes un~er the barrier wall 56 and moves
upwardly in the chamber 543 thereby encouraging elimination
of oil mist by gravity forces. Also, the chamber 54
presents a relatively larger volume than the volume near the
eliminator baffles, which causes a reduction in air
velocit~ and ~ecreases the ability of the air to carry any
residual oil.
me air is deflected off the successive ba~fle~
60, 68 and 72 such that virtually all residual oil is re-
moved from the air and is returned to the reservoir. The
, . . .
1058396
filters 74 serve aæ a final precaution to the e~cape of
minute particles into the air.
After the booth has been used over a period of
~ime, the paint solids which have collected in the bottom
of the reservoir may be removed and reclaimed.
In comparison to other known spray boothæ, the
~pray booth offers the following advantages: very low
emission of particulates into the atmosphere since the
booth will normally operate at 99 or 100% efficicncy; easy
collection and recla~mation o~ coating material solids and
ability to accommodate a greater variety of coatings;
easier cleaning of booth and no corrosiQn of booth
material~; quieter operation and uni~orm air velocity at
~ace, les8 electrical power required; and various other
advantages mentioned hereinbefore.
3o
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