Note: Descriptions are shown in the official language in which they were submitted.
I
The present invention relates to a spray booth and
sludge removal apparatus.
This is a division of cop ending Canadian patent
application serial No. 402,006 filed April 30, 1982.
Spraying of coatings such as paints, enamels,
lacquers, etc. is commonly conducted in booths in which a
flow of air carries over spray particles and volatile
organic solvents away from the worker. An efficient method
of removing over spray particles from the air within such
a booth is to provide water sprays including a sheet
or curtain of flowing water in the path of the coating
spray and/or air flow, the water curtain trapping the
over spray particles. A typical spray booth having a
water waste means with a water curtain and a spray behind
the water curtain is disclosed in my cop ending Canadian
patent application So 232,124, filed February 9, 1931.
While spray booths have been widely used in
the industry and have proven their worth in maintaining
a healthy interior environment for the workers in the
I plant, such booths require significant amounts of maintenance,
and problems remain pertaining to the disposal of coating
waste products into the general environment.
The trapped paint particles fall with the water
to the holding tank from which the water is recirculated.
Some of the paint particles float on the surface of the
water in the holding tank, and other paint particles
collect on the bottom of the holding tanks. lost of
these tanks have chemicals added to the water in the
holding tank to agglomerate the paint spray particles.
Many of the particles agglomerate to form a floating
piece of sludge. In heavy duty spray booths as much
as 100 to 150 gallons of paint may be sprayed in a spraying
booth on a daily basis resulting in a
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significant daily accumulation of particles within the
tank. In such heavy duty applications r the maintenance
procedure may involve skimming sludge from the tank
every night and to dispatch a crew at the end of every
week to drain and manually scrape sludge from the bottom
of the holding tank. For some very highly utilized
booths, the skimming may have to be done two to four
times a day and draining and scraping correspondingly
more frequently. Thus, the routine maintenance of a
spray booth requires substantial amounts of labor, and
booths are shut down for significant periods for
cleaning.
An additional problem with spray booths using
sol en hosed coatings is that the booths discharge
significant amounts of hydrocarbons into the air and
through the exhaust of the booth. For purposes of
maintaining the general environment, federal state and
local governments impose standards pertaining to the
maximum amount of hydrocarbon discharge, and it is
difficult for manufacturing plants to meet these
requirements when substantial amounts of spray coating
is carried out in the plant. Not only is solvent
released into the air during the initial spraying, but
the solvent continuously evaporates from the trapped
over spray particles floating in the water holding tank.
Discharge of the water utilized in the spraying
booth presents another substantial waste disposal
problem Because of the solvents, paint particles and
the paint agglomerating chemicals, regulations often
prevent discharge of the water directly into sewer
systems and the water must either be stored in large
holding tanks or disposed of under strict governmental
supervision. Hence, it is desirable to reuse the water
in the holding tank for as long as possible. however,
continued use of water entails further problems,
particularly the problem of preventing septic conditions
within the water. Althouc3h chemicals which would prevent
growth within the tank may be used, such chemicals further
add to the pollution problem en-tailed in -the eventual
discharge of the water.
While -the waste produced in spray coating is
generally hazardous to -the environment, at least a partial
solution to the waste disposed and maintenance problems
of spray coating is collection and recycling of the over spray
particles and other wastes. Chemicals such as solvents,
pigments and coagulents are recoverable from the over spray,
and, if collected, the ovexspray may be sold to chemical
companies.
It is a primary object of the present invention
to continuously remove waste products from spraying booths,
which utilize recirculating water, to ease maintenance
costs and reduce discharge of waste into the general
environment. It is another object of the invention to
treat the water in the booth to permit long term use
thereof. It is a further object of the invention to
collect waste products for recycling.
The present invention resides in a spray booth
which includes a housing having an air inlet for receiving
air flow and for housing articles while being sprayed
and for containing air-borne particles of the spray.
A water wash means is provided for washing air-borne
particles from the air, and a water holding tank is provided
at the bottom of the booth for holding water used in
-the water wash means. Water aeration means is used or
aerating the water to oxygenate the water being circulated,
and an auxiliary tank means is provided adjacent the
booth for receiving water and sludge from the holding
tank. Water inlet means is provided between the holding
tank and the auxiliary tank means for allowing surface
water of the holding tank to flow therefrom and into
the auxiliary tank. Sludge removal means removes sludge
from the water.
In a specific embodiment of the invention there
is provided in a spray booth and sludge removal apparatus
ma. MY;
which has a spry booth housing including upstanding
side walls and a rear wall to define a booth with water
_ curtain baffles in the booth having water flowing down the
baffles to trap air-borne over spry particles carried by the
air flowing through the baffles. A water holding tank
is located within the booth side walls and below the water
curtain baffles -to receive the water and trapped overstay
particles. An auxiliary tank is separated from the holding
tank for receiving water and floating sludge from the holding
tank, and the reciprocating skimmer means is provided at
the auxiliary tank for skimming floating sludge from the
top surface of the water in the auxiliary tank and for
pushing the floating sludge from the top surface of tile
auxiliary tank across a discharge end of the auxiliary
tank. Aeration means aerates the water to oxygenate the
water being recirculated through the water curtain buffs,
said holding tank and said auxiliary tank. Water sludge
in that means is provided for receiving water and sludge
from the holding the tank and for discharging the same
into the auxiliary tank, and water circulating jet nozzles
are provided in the holding tank for generating surface
currents to transport floating sludge on the water in the
holding tank to the inlet means of the auxiliary tank.
These and other features, objects and advantages
of the invention will become more apparent from the following
detailed description of the invention in reference to the
accompanying drawings in which
FIGURE 1 is an elevation view of a spraying booth
and an attached sludge removal -tank embodying various features
of the invention.
FIGURE 2 is a plan view of the spraying booth and
sludge removal tank of FIGURE 1.
FIGURE 3 is an enlarged front elevation view ox
the sludge removal tank.
FIGURE 4 is a side elevation view of the sludge
removal tank.
FIGURE 5 is a cross-sectional view of the sludge
removal tank showing its sludge skimmer in a rest position.
FIGURE 6 is a view similar to FIGURE showing the
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skimmer advancing to skim floating sludge to an edge of the
sludge removal tank.
FIGURE 7 is a view similar to FIGURES 5 and 6
showing the skimmer delivering sludge up an inclined beach
into a waste collector.
FAKER 8 is a perspective view of the skimmer.
In accordance with the present invention, prolonged
usage of water and less downtime for cleaning of spray
booths 10 is achieved by aerating the water and/or removing
of agglomerated spray particles from the surface of the water
in a holding tank 18. That is, the water is kept "fresh"
by deliberately injecting air into the water being recircu-
fated so as to oxygenate the water to prolong its usage
in the water holding tank 18. The floating sludges
directed by water currents into an automatic skimming
apparatus for removal. To
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this end, circulation means in the form of water jet 13
are preferably positioned to cause the surface water
carrying the sludge to flow toward and to carry the
sludge to a skimmer means 15 which, in this instance, is
in an auxiliary tank 30.
Also, in accordance with an important aspect of
the invention, a bottom surface 21 of the holding tank
18~ and a bottom surface 23 of the auxiliary tank are
swept by water circulating means to retard the
accumulation of settling particles from the bottom of
these respective tanks. herein, water jets 13 r 25 are
disposed to eject water under pressure across the bottom
surfaces 21, 23 of these respective tanks 18, 33 to
carry off particles dropping to the bottom of the tans.
In accordance with a further aspect of this
invention, a skimmer means 15 is provided particularly
suited for intermittent operation allowing the skimming
apparatus to shut off while sludge froth accumulates on
the surface of the water. Herein a carriage 27
reciprocates across the surface of the auxiliary tank 30
and a pusher plate 28 pivot ably mounted therefrom,
extends through the surface ox the water as the carriage
is driven in a sludge skimming direction and is tilted
out of the water as the carriage is driven in the return
direction.
Illustrated in Figure 1 is a spray booth
indicated generally at 10 of the type which utilizes a
water wash means including a water curtain 12 to remove
over spray particles from the air and preferably the
water wash means including a second spray wash at the
rear portion of booth, as disclosed in the aforesaid
patent application. The booth 10 has a nosing 11 for
housing articles while being sprayed and for containing
air-borne particles of the spray, the housing having an
front end opening 14 through which a worker directs a
spraying device or gun at objects (not shown) suspended
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within the booth. Air circulation apparatus (not shown)
draws air through the open front of the booth and
exhausts it exterior of the plant through an upper
exhaust pipe 16. The water curtain 12 is created by
water from a lower holding tank 18 which is circulated
through a conduit by a pump 19 to the upper end of the
booth into an upper reservoir 20 (FIG. 2) from which it
overflows back to the holding tank 18 to form the water
curtain 12.
The sludge removal tank 30, through which water
from the holding tank 18 is continuously circulated, is
designed to fit within a relatively small space along
side the spray coating tooth 10. on upper portion 31
(FIG. 3) of the auxiliary holding tank is rectangular.
A lower trough portion 33 of the tank on has a
trapezoidal transverse cross section having sides 34
(FIG. I which angle inward from the vertical sidewalls
35 of the tank and meet at a narrow bottom 37. As best
seen in FIGURE 5, the back 39 of the tank 30 is vertical
while a front panel 41 is inclined rearwardly from an
upper front Section 43 at an angle of about 45
In the embodiment of the invention illustrated,
the skimming apparatus is provided with a substantial
surface water inflow from the tanks to bring the
floating sludge to the skimmer means 15. To this end, a
large rectangular inlet opening 32 FOE&. 5) at the
surface of the water in the tanks 18, 30 communicates
the tanks along a substantial portion of the distance
from the front 45 of the holding tank 10 to the water
curtain 12. The elongated opening 32 provides for
substantial flow of surface water and floating sludge
from the portion of the holding tank I in front of the
water curtain 12 into the sludge removal tank 30. A
return opening 42 from the sludge removal tank on to the
holding tank 18 is disposed below the surface level of
the water in the tanks and behind the water curtain 12
allowing cleaned water, but not surface water and
floating sludge, to return from the sludge removal tank
to the holding tank assisted by the negative pressure
existing behind the water-curtain generated by the spray
booth exhaust. An intake manifold 46 of a sludge
conduit 29 is disposed along the bottom of the holding
tank 18 in front of the water current 12 where the major
portion of sludge accumulates,
As a means of producing the current in the
'0 holding tank 18 which causes the surface water to flow
through the inlet opening 32 and which sweeps the bottom
surface 21 of the holding tank, a water discharge
manifold 50 extends from the conduit 43 Ludwig from the
main circulation pump 19 of the spray booth 10 and
supplies pressurized water to the water jets 13. A
plurality of water jets 13 extend into the holding tank
18 in front of the water curtain 12 and just below the
surface and are directed at the rectangular opening 32
whereby the pressurized water from the main pump 19
creates a current in the holding tank lo which urges
floating particles toward the rectangular opening.
Typically, water jets 13 will be spaced about every 20
inches along the front 45 of the holding tank 18 to
shift the floating particles into the sludge removal
tank 30.
An additional water jet 13' disposed behind the
water curtain 12 helps to create a generally circular
flow of water throughout the holding tank 18 around the
water curtain 12 in the direction of the arrows 52
(FIGURE 2).
To remove sludge particles which sink to the
bottom 21 of the holding tank 18 and which are swept
along by the circulation therein, the water an sludge
intake manifold 46 of the sludge conduit 29 extends
across the bottom of the holding tank in front of the
water curtain 12. The sludge conduit 29 is connected to
the inlet and suction side of a motor driven pump 36
which is disposed below one of the sloping sides 34 of
the trough portion 33 for efficient use of space. A
plurality of inlets AYE are spaced along the intake
manifold 46, as best seen in FIGURE 2, to draw in water
and sludge. Water from the water jet sweeps the bottom
I ox the auxiliary tank 30. A diffusing cone I at the
outlet end 76 of the conduit 29 expands the stream from
the discharge water jet 25 providing a broad sweep of
lo the water-sludge-air mixture along the bottom 37 of the
tank 30.
The preferred apparatus for aerating the water
on the tanks 18, 30 comprises an air inject no means
including an air line 77 connected to the pipe I at a
venturi 78 (FIGURE 4) disposed in the pipe just upstream
of the pump 36. The high suction force of the pump
causes increased velocity of water flow through the
venturi which creates a negative pressure relative to
the ambient pressure to draw air down the upstanding air
pipe 77 and into the water flowing into the pump whereby
air is aspirated into the stream of sludge-laden water.
For a booth holding tank 18 approximately 20
ft. x 5 ft. and containing about 1400 gallons of water,
a 1~2 horsepower suction pump 36 is sufficient to keep
the bottom 21 of the holding tank 18 generally free of
sludge, and the air aspirated is sufficient to assist in
aerobic conditions within the water and to reduce
putrefaction thereof. In addition to preventing septic
conditions in the water, the entrained air bubbles
discharging through the water jet 25 in the lower
through portion 33 of the sludge removal tank 30 adhere
to the sludge particles and buoy the particles to the
surface where they, along with particles floated into
the sludge removal tank, form a sludge froth on the
surface. The narrow bottom 37 of the sludge removal
tank 30 is well swept by the discharge through jet t S
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diffuser cone 80, and sludge particles not immediately
floated, are eventually floated by continuously
discharged air bubbles.
As will be described in connection with FIGURE
I the major portion of the over spray particles
trapped by the water curtain and dumped in the holding
tank 18 and carried to the sludge removal tank 30 and
floated to the surface thereof are removed by the
skimming means 15 which shoves the sludge up over a
beach 84. Herein, an inclined panel 84 extending
outward from the back 39 of the sludge removal tank 30
and through the water surface level serves as a beach
over which sludge particle froth is pushed into a
collection bin a. The sludge particle froth is pushed
up over the beach 84 by the skimmer means 15 which
reciprocates over the surface of the water. The skimmer
means 15 includes a carriage 27 FIG. 8) having a
platform 94 which straddles the tank 30 and rolls on
four wheels 86 over parallel tracks 88 JIG. 3) running
along the sides of the tank and upwardly along side the
inclined beach 84. The sludge is skimmed from the
surface water by the pusher plate 28 which is pivot ably
mounted on the rear end 92 of a carriage platform 94.
The carriage 27 is driven by a double screw 95 which
cooperates with a threaded unit I carried on an
upstanding arm 98 which extends upward from the front
end of the carriage platform 94. The double screw
mechanism 96 operates to drive the carriage 27 in the
rearward or skimming direction a predetermined distance,
ire. until the carriage has driven up the tracks By
alongside the inclined beach 84, and then without a
change of screw rotational direction operates to drive
the carriage in the forward or return direction Such
reversing screws and nuts are commercially available.
The pusher plate 28, which has a transverse
dimension generally equal to the distance between the
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tanks side wills, is mounted to pivot between a vertical
skimming position (FIGURE 6), whereat it extends below
the surface of the water for skimming sludge froth as
the carriage 27 is driven rearward, to a tilted return
position, (FIGURE I in which it is entirely out of the
water when the carriage is driven in the return
direction. The pusher plate 28 is pivotal mounted on
vertical support bars 100 (FIGURE 8), which extend
upward from the carriage platform 94, by means of pivot
arms lo attached to one side 104 of the pusher plate
and pivot ably mounted on the upper end of the support
bars by pivot pins 103 which define a horizontal pivot
axis. With the pusher plate 28 in it's vertical skimming
position, the carriage support bars 100 and the pusher
pivoting arms 102 are normal to each other.
The pusher plate 28 is shifted automatically
between its skimming portion for travel to the right as
viewer in FIGURE 6, and to its raised return position
for travel to the left, as viewed in FIGURE 5, by a
calming means which excludes an upstanding contact arm
106 on one side of the pusher plate 28 and which serves
to pivot the pusher plate about the horizontal axis
through the pivot pins when the contact arm 106 hits a
lug aye or 107b mounted adjacent opposite ends of the
track 88 for contact with arm 106. Such lugs 107 are
mounted at each end of the carriages path of travel,
one such lug 107b contacting the outer surface of the
contact arm 106 generally at the rearward position of
the carriage 27 to pivot the pusher plate 28 from its
vertical position to its tilted position and one such
lug aye contacting the inner surface of the contact arm
generally at the forward position of the carriage to
pivot the pusher plate from its tilted position to its
vertical position.
To hold the pusher plate 28 in one position
during its forward or reverse travel, means have been
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provided in the form of an over center mechanism. The
latter preferably is the form of a weighting mechanism
110 (FIGURE 8) carried by the pusher plate 28 to
maintain the pusher plate in the position to which it
has been pivoted by the lug 107 at the front or rear end
of the track 88 before being contacted by the other lug
107. The weighting mechanism 110 has a slide or track
member 112 with a short arm 114 extending generally
vertically upward from the upper edge of the pusher
plate 28 and a longer arm 116 which angles upward (with
references to the pusher plate in its vertical position)
and inward over the carriage platform 94 therefrom. The
long arm 11~ extends cross thy pivotal axis ox the
pusher plate 28 at an angle whereby its inner end 118 is
uppermost in the vertical position of the plate but
lowermost when the pusher plate is in its tilted
position. The long arm 116 provides a track or slide
for a plurality of weighted washers 121 slid ably mounted
thereon which alternately slide from adjacent the pivot
axis defined by the pivot pins 103 at which time the
weight of plate 28 is sufficient to keep the pusher
plate horizontal against the turning torque in the
opposite direction by the weights. On the other hand,
when the weights slide to hit a stop 122 at the free end
of the longer arm, the weight of the pusher plate is
insufficient to overcome the turning moment exerted by
the weights. That is, the location and weight of the
washers 121 is sufficient to switch the center of
gravity of the pusher plate 28 from one side of the
pivotal axis to the other. When the arm 106 hits the
rear lug aye, and when the pusher plates pivoted to
its tilted position, the weighted washers 1~1 slide
against the stop 122 shifting the center of gravity to
maintain the plate 28 tilted until the contact arm 106
again hits the front lug aye.
Although sludge may be continually building up
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within the spray coating booth 10, it takes a period ox
time for sufficient froth to build up on the surface of
the sludge removal tank to require skimming.
Accordingly, the skimmer means 15 is operated
intermittently to skim sludge after a period of forth
build up. Typically, the carriage 27 will be actuated
by a control unit (not shown) and stop in the forward
(retraction direction just short of full retraction
(FIGURE I with the pusher plate 28 in its tilted
position. With the circulation system of the tans 18,
30 operating to provide circular flows in the tanks as
shown in Figures 2 and 5, the sludge particles are
gloated to the top and generally toward the inclined
beach 84 at the rear of the sludge removal tank. After
a predetermined time has elapsed with the carriage 27 at
rest, the drive motor 99 is actuated to turn the double
screw 96. The rotation of the screw 96 further drives
the carriage 27 forward until the contact arm 106 hits
the front lug aye and pivots the pusher plate 28 to its
vertical position extending into the water. Continued
rotation of the screw 96 results in automatic reversal
of the carriage direction driving the carriage 27 in the
rearward sludge skimming direction (FIG. 6). The
carriage 27 moves slowly across the surface of the
surface of the water with the pusher plate I pushing
sludge froth therein front.
At the rear of the tank 30, the rear wheels 86'
(FIG. I ride up the inclined portion of the track 88
along the inclined beach 84, and the pusher plate 28
travels up the inclined beach pushing sludge froth
Thorpe and over the edge into the collecting bin 83.
At the end of travel in the sludge-skimming direction,
the contact arm 106 hits the rear lug 107b pivoting the
pusher plate 28 to its tilted position, and immediately
thereafter, the screw 96 reverses the direction of
carriage travel. Just before the contact arm 1~6 hits
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the front lug aye, the drive motor 99 is deactuated for
a predetermined time, and the process repeats.
Jo Although the swimmer 15 is opera-ted intermittently,
the water circulatiorl apparatus will generally be operated
continuously even durincj brief periods when the booth 10
is not being used for spray coating This not only assures
continued aeration of the water in the tanks 18, 30, but
allows the circulation system to -thoroughly clean the water
between coating operations. If, however, the booth 10
is to be unutilized for extended periods of time, e.g.
over a weekend, the main pump 19 may be shut down and only
the suction pump 36 operated to aerate the water in the
tanks 18, 30.
The above described skimmer means is also disclosed
and is claimed in applicant's above-identified parent apply- ¦
cation serial No. ~02,006.
Several advantages of the invention may now be
more fully appreciated. The continual cleaning and aeration
of the water provides for longer use of a tank full of
water. Instead of remaining in the holding tank, releasing
hydrocarbons and sinking to the bottom, the greater portion it
of over spray particles are floated to the sludge tan where
they are skimmed off before releasing significant quantities
of hydrocarbons. After a collection bin 83 is filled it
is covered to prevent further release of hydrocarbons,
and the collected over spray may be sold back to a chemical
company for recovery of solvent, pigments, coagulents and
other recoverable chemicals. Maintenance costs are sub-
staunchly reduced, and generally, it is not necessary
to manually clean the booth nearly as often. The present
invention is usable both with new spray booths and could
be incorporated therein rather than be a separate stand
alone unit which is illustrated herein. The auxiliary
apparatus according to the present invention is easily
installed with only slight modifications in existing equipment
as the bulk of the water purification apparatus is associated
with the
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auxiliary sludge removal tank 30. Having the sludge
skimmer 15 entirely outside of the coating booth 10
prevents the accumulation of over spray particles thereon.
While the invention has been described in
reference to a preferred embodiment, modifications
obvious to one with Ordinary skill in the art may be
made without departing from the scope of the invention.
For example, known types of skimmers such as continuous
belt skimmers which carry one or more paddles may be
employed to skim the froth from the sludge removal
tank. The aeration may be achieved other than through
the sludge conduit, for example, by entrainment of air
through the circulating water jets in the holding tank.
The water jets 13, 13' are preferably ox a
commercially available nozzle kind which can be swiveled
and turned relative to their water supply pipe so that
the direction of outflow from each jet may be adjusted
when in an actual working state to accommodate
differences in liquid flow patterns which develop in the
field Likewise, these nozzles are of the Kind which
are adjustable to control the flow rate of water and the
velocity of water flow there through Preferably, the
nozzles are universally and infinitely adjustable.
Thus, by adjusting the water f1QW rate and the direction
of water flow from each nozzle 13 or 13', the
circulation of liquid and the sweeping of the Yank
bottom may be more readily attained my lessening the
likelihood of poor circulation or dead spots where
particles or sludge would accumulate.
various features of the invention are set forth
in the following claims.
