Gas cleaning apparatus containing a centrifugal type paint mist separator

A centrifugal separator type paint mist containing gas cleaning apparatus having a concave guide face extending downwardly from a downstream side end of a cleaning liquid flow-down face in a flowing down direction of cleaning liquid, the concave guide face being formed as a curved arc, a discharge guide face disposed at a downstream side end of the concave guide face for laterally discharging the cleaning liquid, a gas orienting face for orienting a paint mist containing gas fed from the upperside towards the concave guide face, whereby the paint mist containing gas is discharge through a discharge opening formed between a downstream side end of the gas orienting face and a portion of the concave guide face most adjacent the downstream side end of the gas orienting face, the discharge opening having a width smaller than an average radius of the concave guide face, the paint mist containing gas being discharge in a direction substantially along a tangential line of the concave guide face, the discharge opening is disposed with a slope in such a way that the tangential line of the concave guide face forms an angle relative to the horizontal line with the angle being larger than 45 degress and smaller than 90 degrees.

BACKGROUND OF THE INVENTION 
(1) Field of the Invention 
The present invention relates to a centrifugal separator type paint mist 
containing gas cleaning apparatus to be installed in e.g. a painting 
booth, and more particularly to a cleaning apparatus of the above-noted 
type comprising a concave guide face extending downwardly from a 
downstream side end of a cleaning liquid flow-down face in a flowing down 
direction of cleaning liquid, the concave guide face being formed as a 
curved arcate face, a discharge guide face disposed at a downstream side 
end of the concave guide face for laterally discharging the cleaning 
liquid, a gas orienting face for orienting a paint mist containing gas fed 
from the upperside towards the concave guide face, whereby the paint mist 
containing gas is discharged through a discharge opening formed between a 
downstream side end of the gas orienting face and a portion of the concave 
guide face most adjacent the downstream side end of the gas orienting 
face, the discharge opening having a width smaller than an average radius 
of the concave guide face, the paint mist containing gas being discharged 
in a direction substantially along a tangential line of the concave guide 
face. 
(2) Description of the Prior Art 
As for the conventional paint mist containing gas cleaning apparatus, in 
addition to the above-described centrifugal separator type (see FIG. 7), 
there are also known other types as shown in FIGS. 8 through 10. 
FIG. 8 shows a so-called target type, in which paint mist containing gas A 
and flowing-down cleaning liquid W are caused to strike at a high speed 
against a target plate 01 trapping the paint mist contained in the gas 
trapped into the cleaning liquid W (BP 2,110,952 Official Gazette). FIG. 9 
shows an angularly curved flow passage type. In the case of this type, the 
paint mist containing gas A is caused to flow through an angularly curved 
flow passage 02 in which the paint mist is separated by inertia from the 
gas and trapped into the flowing down cleaning liquid W (BP 2,110,952 
Official Gazette). FIG. 10 shows a vortex flow type. In the case of this 
type, the paint mist containing gas A and the flowing down cleaning liquid 
W are caused to flow at a high speed through a flow passage having a pair 
of curved flow passages 03 and 04 laterally symmetrical to each other and 
a constricted discharge opening 05 having a small diameter, during which 
one portion of the gas-liquid mixture guided by the left side curved flow 
passage 03 and the other portion of the gas-liquid mixture guided by the 
right side curved flow passage 04 are caused to collide with each other at 
a vortex flow chamber 06 while flowing in the form of vortex streams 
because of the effect of the respective curved flow passages, whereby the 
paint mist is trapped into the cleaning liquid W. 
Aside from the above apparatus, there are also known other types of 
mist-containing gas cleaning apparatuses (e.g. U.S. Pat. No. 4,350,506, 
U.S. Pat. No. 4,257,784, USSR 628,379, Japanese published patent 55-6427). 
In comparison with the above-described target type or the vortex flow type, 
the centrifugal type, to which the present invention relates, has the 
following advantages. First, there occurs less pressure loss. Second, 
there occurs less adhesive accumulation of the paint. Third, there is 
wasted less energy because of the less pressure loss. Fourth, there occurs 
less operating noise. Last, because of the less adhesive accumulation of 
the paint, even with less frequent maintenance operations, the apparatus 
may maintain a high paint mist collecting efficiency for a long period of 
time. 
Further in comparison with the angularly curved flow passage type having 
only the angularly curved flow passage, the centrifugal separator type is 
advantageous in its much higher paint mist collecting efficiency. 
Conventionally, the centrifugal separator type paint mist containing gas 
cleaning apparatus having the above-noted advantages is constructed as 
shown in FIG. 7 (BP 2,110,962). In this conventional apparatus, a 
discharge opening 1E formed between a downstream side end P of a gas 
orienting face 1D and a portion Q of a concave guide face 1B most adjecent 
the downstream side end P of the gas orienting face 1D is disposed in such 
a way that a tangential line l of a concave guide face 1B is formed 
substantially along the horizontal line or formed with an extremely small 
slope relative to the horizontal line. 
Incidentally, in this FIG. 7, a reference mark 1A denotes a cleaning liquid 
flowing-down face extending continuously from an upstream side end of the 
concave guide face 1B, a mark 1C denotes a discharge guide face for 
laterally discharging the cleaning liquid W, a mark d denotes a width of 
the discharge opening 1E and a reference mark R denotes a radius of the 
arcuate concave guide face 1B, and denotes a discharge direction of 
paint-mist containing air A. 
With all the above-described advantages over the other conventional 
apparatuses, the above conventional centrifugal separator type paint mist 
containing gas cleaning apparatus still need be improved in that there is 
still a tendency of the adhesive accumulation of the excess paint, though 
less conspicuous than the other types, at a portion of the concave guide 
face adjacent the discharge opening. 
SUMMARY OF THE INVENTION 
With view to the above-noted state of the art, it is the primary object of 
the present invention to provide a centrifugal separator type paint mist 
containing gas cleaning apparatus retaining the advantages of the cleaning 
apparatus of this type and further capable of more effectively avoiding 
the adhesive accumulation of the excess paint at the concave guide face 
portion in the vicinity of the discharge opening through an improvement on 
the structure of the discharge opening. 
In order to accomplish the above object, a centrifugal separator type paint 
mist containing gas cleaning apparatus according to the present invention 
is characterized in that the discharge opening is disposed with a slope in 
such a way that a tangential line l of the concave guide face forms an 
angle .theta. larger than 45 degrees and smaller than 90 degrees relative 
to the horizontal line. 
Functions and effects of the above construction will be particularly 
described next. 
The inventor conducted various experiments on the causes of the adhesive 
accumulation of excess paint on the concave guide face 1B adjacent the 
discharge opening 1E in the conventional apparatus shown in FIG. 7. As the 
results, the following facts were discovered. That is, in the case of this 
conventional apparatus in which the discharge opening 1E is disposed in 
such a way that the tangential line l of the concave guide face 1B is 
formed substantially along the horizontal line or formed with an extremely 
small slope-relative to the horizontal line, when the paint mist 
containing gas A is discharged through and departed from the discharge 
opening 1E, there occurs, due to the effect of the gravity, a temporary 
departure of the cleaning fluid W from the downwardly directed portion of 
the concave guide face 1B in the vicinity of the discharge opening, which 
liquid W need flow in the form of film along the concave guide face 1B for 
a proper operation. Because of this, there occurs the adhesive 
accumulation of the excess paint contained in the gas at the downwardly 
directed portion, which is not sufficiently covered with the liquid film, 
of the concave guide face 1B in the vicinity of the discharge opening 1E. 
Taking the above facts into consideration, the inventor found through 
intensive research that the above-noted problem may be avoided if the 
discharge opening is disposed, as shown in FIG. 3, with a slope in such a 
way that the tangential line l of the concave guide face forms an angle 
.theta. larger than 45 degrees and smaller than 90 degrees relative to the 
horizontal line or more preferrably larger than 60 degrees and smaller 
than 75 degrees. With this arrangement, the disadvantageous effect of the 
gravity acting on the cleaning liquid to cause the latter to depart from 
the downwardly portion of the concave guide face may be reduced. Thus, the 
temporary departure due to the effect of the gravity of the cleaning 
liquid W from the downwardly directed portion of the concave guide face 1B 
in the vicinity of the discharge opening, may be effectively avoided. 
Consequently, the cleaning liquid may properly flow along the entire 
length of the concave guide face 1B, i.e. from the discharge opening 1E to 
the discharge guide face 1C. 
Incidentally, the slope angle O and the width d of the discharge opening 1E 
should be determined within the above-described range in consideration of 
the flow amount of the paint mist containing gas A passing through the 
discharge opening 1E, the downflow amount of the cleaning liquid W, the 
ratio of the paint mist contained in the paint mist containing gas A and 
of the type of paint (i.g. viscosity or the like). 
With the apparatus of the present invention having the above feature, the 
original advantages of the centrifugal separator type apparatus over the 
other types such as less adhesive accumulation of excess paint and less 
pressure loss are retained. And; moreover, the problem of the conventional 
centrifugal separator type apparatus of the partial adhesive accumulation 
of the paint at the portion of the concave guide face in the vicinity of 
the discharge opening is effectively solved. Consequently, the present 
invention has achieved a centrifugal separator type paint mist containing 
gas cleaning apparatus capable of not only achieving even less adhesive 
accumulation of the paint, but also of maintaining a high paint mist 
collecting efficiency for a long period of time even with less frequent 
maintenance operations. 
Other and further features and advantages of the present invention will 
become more apparent from the following description with reference to the 
accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIGS. 1 and 2 are a construction view and a perspective view showing a 
sample installation of a paint mist containing gas cleaning apparatus 1 
related to the present invention, respectively. In these drawings, a 
reference numeral 2 denotes a painting booth forming a spraying work area 
3, a reference numeral 4 denotes a suction fan for feeding into the 
painting booth 2 ventilation air of which temperature is controlled by an 
air-conditioner 5. After passing through a box filter, the ventilation air 
is supplied through a ceiling blowout opening 8 having a filter 7 into the 
work area 3 in the form of a downwardly directed laminar air flow, with a 
portion of the ventilation air being laterally supplied through a right 
and left pair of side blowout openings 9 into a lower region of the work 
area 3. A reference numeral 10 denotes an outlet fan for downwardly 
exhausting the air along with excess paint mist inside the work area 3 
through a grating floor 11. 
Under this grating floor 11, there are disposed a pan 13 for flowing down a 
cleaning water W overflowed from a trough 12 and a centrifugal separator 
type paint mist containing gas cleaning apparatus 1 positioned at a 
lateral center of the pan 13. 
The cleaned exhaust air having its paint mist component separated and 
removed therefrom by its passage through the cleaning apparatus 1 goes 
through a draining section 14 and then is exhausted externally of the 
installation. 
On the other hand, the cleaning water W into which the paint mist has been 
trapped by its passage through the cleaning apparatus 1 is received by a 
receiver tank 16. Then, the water W is sent through a pipe 17 into a 
separator tank 18, where paint residue S is separated and removed from the 
cleaning water W. 
This cleaning water W having its paint redidue S separated and removed 
therefrom at the separator tank 18, is recycled by a recycling pump 19 
through a pipe 20 into the trough 12. 
Next, the construction of the centrifugal separator tye paint mist 
containing air cleaning apparatus 1 will be particularly described with 
referece to FIGS. 3 and 4. 
First, the apparatus 1 continuously forms an arcuate concave guide face 1B 
for the cleaning water W flowing down from the pan 13. This arcuate 
concave guide face 1B extends downwardly with a curve from a downstream 
side end of a cleaning water flow lower face 1A connected to and in fluid 
communication with the cleaning water pan 13 and in the flowing down 
direction of the cleaning water. At one downstream side end of this 
concave guide face 1B, there is provided an upwardly directed and 
horizontally positioned discharge guide face 1C for laterally discharging 
the guided cleaning water W. Further, there is also provided a gas 
orienting face 1D connected to and in fluid communication with the 
cleaning water pan 13 for orienting the paint mist containing air A from 
the upperside towards to the concave guide face 1B. Moreover, there is 
provided a discharge opening 1E formed between a downstream side end P of 
the gas orienting face 1D and a portion Q of the concave guide face 1B 
most adjacent the downstream side end P of the gas orienting face 1D. The 
gas orienting face 1D is disposed so as to discharge the paint mist 
containing air A through the discharge opening 1E in a direction l' 
substantially along a tangential line l of the concave guide face 1B. 
The concave guide face 1B is formed as a large-radius arcuate face having 
an average radius at least more than two times larger than a width d of 
the discharge opening 1E. On the other hand, the gas orienting face 1D is 
formed as a convex curved inclined face having its slope angle relative to 
the horizon gradually increasing in the downstream direction. 
Incidentally, a portion of the cleaning water W flowing at the left side of 
the drawing of the cleaning water W flowing down from the pan 13 flows 
down in the form of a liquid film along the gas orienting face 1D, whereby 
adhesive accumulation of the paint mist component to this gas orienting 
face 1D may be effectively and reliably prevented. The discharge opening 
1E is disposed with a slope in such a way that the tangential line of the 
concave guide face 1B forms an angle .theta. relative to the horizontal 
line with the angle .theta. being larger than 45 degrees and smaller than 
90 degrees, or more preferrably, the angle .theta. being larger than 60 
degrees and smaller than 75 degrees. 
According to the above-described construction, in the process where the 
paint mist containing gas A is caused to flow at a high speed along the 
arcuate concave guide face 1B having the average radius R which is 
sufficiently larger than the width d of the discharge opening 1E, the 
cleaning water W is caused by the effect of the centrifugal force to flow 
down in the form of liquid film along the concave guide face 1B and at the 
same time the centrifugal effect also serves to separate by inertia the 
paint mist from the air. Then, the separated paint mist is trapped into 
the cleaning water W flowing down in the form of liquid film along the 
concave guide face 1B. 
The above-described inclined positional arrangement of the discharge 
opening 1E serves to prevent the phenomenon of temporary departure due to 
the gravity of the cleaning water W from the concave guide face 1B in the 
vicinity of the discharge opening 1E. As the result, the adhesive 
accumulation of the excess paint to the concave guide face 1B in the 
vicinity of the discharge opening 1E due to such temporary departure of 
the cleaning liquid may be effectively and reliably avoided. 
Next, alternative embodiments of the present invention will be described. 
As shown in FIG. 5, the paint mist containing gas cleaning apparatus 1 may 
be attached to the pan 13 via a bell-mouth type opening frame 28. This is 
advantageous in that the cleaning water film may be formed more uniformly 
and stably on the respective guide faces. 
As shown in FIG. 6, it is possible to provide an overflow weir 29 for the 
cleaning water W flowing from the pan 13. This arrangement is advantageous 
in that the cleaing water W may be supplied constantly and stably even if 
there occurs a slight variation in the amount of water from the trough 12. 
The cross sectional shape of the arcuate concave guide face 1B is not 
limited to the partial circle, but may be a partial oval or the like. 
The specific configuration of the gas orienting face 1D may be modified in 
various ways. 
The discharge guide face 1C may be directed upwardly with a horizontal 
posture or may be positioned with a slight downward slope relative to the 
horizon. 
Also, needless to say, in place of the water used in the above embodiments, 
the cleaning liquid may include other chemicals by a suitable amount such 
as an adhesion-preventing agent or a defoaming agent for the paint mist. 
It is to be understood that reference marks and numerals are provided in 
the following claims for the purpose of facilitating reference to the 
accompanying drawings but that the present invention is not limited to the 
construction shown in these drawings.