US2171574A - Method and apparatus for cleaning air - Google Patents

Description

.Sept 5, 1939- H. c. LAMBERT ET AL 2,171,574

METHOD AND APARATUS FOR CLEANING AIR Filed April 21, 1936 2 Sheets-Sheet l ?4 @43 @0% 5V @ma Sept 5, '1939. H. c. LAMBERT ET AL. 2,171,574

METHODv AND APPARATUS FOR CLEANING AIR Hoc/mun,

Patented. Sept. 5, 1939 UNITED STATES' PATENT OFFICE Henry C. Lambert and Squire E. Garnsey, Toledo,

Ohio, assignors to The De Vilbiss Company," Toledo, Ohio, a corporation of Ohio Application April 21, 1936, serai No. '15,563

s claims. (ci. iss- 27) This invention relates to air cleaning means, and particularly to such a means for use in con.- nection with paint spraying booths, or the like, to remove from the air waste paint particles or 5 mist entrained therein as the result'l of paint spraying operations.

It has heretofore been the practice to clean the air of booths used in connection with paint spraying operations by creating a draft from the booth through an outgoing conduit and causing the air extracted therefrom to pass through a water spray so that the paint particles resulting from the spraying operation were mixed with and taken up by the water spray. Such spray is from a plurality of spray nozzles set within the booth and the wateris discharged to a tank at the bottom of the booth from which it is pumped back to the spray nozzles bya system of plumbing. Under the proper conditions, the paint particles 0 remain on the surface of the water tank and can only be skimmed therefrom by shutting down operation o f the booth and removing a number of plates to make the tank accessible. An objection. f

to the use of such apparatus is that in pumping 5 the water from the tank `for re-use as a spray, the pump and spray nozzles are apt to become clogged with paint in the event that the Water in the tank becomes disturbed, so that the paint globules no longer remain on the top of the surface of the water. Further, in such apparatus the receptacle for the waste water is not readily accessible for cleaning, so that it is necessary to stop operations while the skimming of the collected paint particles takes place.

5 An object of the present invention is the provision of an improved, economical and highly efiicient means for removing from air any paint or other impurities of a. liqid nature entrained therein by washing the air with a Water spray so i that the particles of water mix with and surroun the entrained paint particles.

Another object of the invention is the provision of an apparatus of this class, wherein the impurity laden air is efciently cleaned by appli- 5 cation of a water spray thereto, the impurity laden waste water resulting therefrom being d irected to a point convenient of access for skimming or cleaning and then returned for re-use in the apparatus without the use of a water pump,

l thus obviating the clogging and cleaning of the pump system heretofore used.

Other objects and advantages of the invention will be apparent from the following detailed description thereof, andl from the accompanying Figure 1 is a. side elevation of an apparatus embodying the invention, with parts broken'away; Fig. 2 is a section on the line 2-2 in Fig. 1, with parts broken away and parts in full; Fig. 3 is a top perspective view of the waste waterreceiv- 6 ing tank of the apparatus, wherein the Water is separated from its impurities; Fig. 4 is a top plan view of the apparatus, and Fig. 5 is a fragmentary view similar to Fig. 2, showing a slightly modified form of the inventio l0 Referring to the drawings, l designates a room or compartment containing the air to be cleaned. and which, in the present instance, comprises part of a booth commonly used in paint spraying work. '15

At one side of the compartment l is a housing 2 in which the cleaning of the air received from the compartment I takes place. Interiorly of this housing, in its lowerv portion, is a tank 3 for containing a quantity of water 4, and having an opening 5 through which water may be admitted .from a source of supply as hereinafter described.

Above the normal water level in the tank 3 is an air conduit 6 of circuitous form leading from thecompartment l and forming what may be termed a mixing chamber. This conduit has an` enlarged horizontally elongated mouth 6 opening into the compartment I and has its body portion correspondingly elongated in crosssection, so that the air `column passing through 80 the conduit is of relatively shallow, broad form and its velocity is relatively high due to the restricted cross-section of the passage as shown in Fig. 2.

The conduit 6, in its present embodiment, after entering the interior of the housing from the compartment I, dips down slightly so that its bottom is in contact, or substantially so, with the surface of the water 5 and then continues rearward on an incline for a distance and then turns back upon itself, so that the conduit is of substantially U-form,lwith its discharge end opening into a chamber 1, which may be termed an expansion chamber.

The chamber' 1 is above the tank 4 and the 45 mixing chamber 6 and is closed to the former, except as'hereinafter described. Ihis chamber has an inclined trough 8 in its bottom extending transversely of the chamber 6 and havinig a discharge outlets at its lower end. In-the upper 50 portion of the chamber 1 are a series of eliminator or baille plates I0 forming a plurality of zig-zag passages Il from the chamber 'I for the paint and cleaning liquid laden air discharged therein. This portion of the air passage may be termed a separating chamber.". The air in the expansion chamber 1 is not only filled with the paint glob-E ules or'mist created by the spraying operation in the compartment I, but is also heavily charged with water, due to its mixing therewith in the chamber 6. As this charged air passes through the passages II in bailled contact with the plates I0, the water and paintI globules are removed from the air by impingement onthe plates and flow down the plates, dripping from their lower ends into the chamber 1 and thence passing to :he trough 8. It will also be appreciated that the velocity of the air stream is suddenly reduced by passing from the restricted mixing chamber 6 to the expansion chamber 1, so that the ability of the stream to carry entrained moisture is correspondingly reduced and some of the paint laden liquid drops to the trough 8.

The draft or current Ithrough the mixing chamberv 6, expansion chamber 1 and plates It is induced by a blower I2 mounted on top of the housing 2 and having a conduit I3 leading thereto from the top of the housing 2 above the plates Ill. The cleaned air has its outlet from the blower through a conduit I4 leading to any suitable point of exhaust. The blower is driven by a motor I5.

A relatively small branch return conduit I6 carrying about 15% to 25% of the exhaust air leads from the exhaust conduit I4 to the upper interior portion 3' of the water tank 3, and the air thereby directed into the tank is caused to pass under the inclined rear end portion of the conduit or mixing chamber 6 in contact with the surface of the water, and to have entrance to the interior of the mixing chamber through transverse slots I1 and I8 in its bottom. The rearmost the compartment I. In practice, it is found that very good results are obtained by discharging two to five gallons of water per foot length of slot per minute into the chamber 6. f

It is apparent that the paint laden air rush-I ing through the chamber 6 must pass through the water stream or curtain directed therein through the slot I8 and that the restricted form of the chamber 6as well as its circuitous course, causes a thorough mixing of the water with the air and the paint globules carried thereby, andv that this'mixing action is further augmented by the-admission of an atomizng air jet or stream under pressure to the chamber 6 through the slot I1.-

The paint and water laden air passes through the chamber 6 at considerable velocity and as it discharges into the chamber 1 expands and passes with much less velocity through the zigzag passages between the bailie plates ID, due to the combined area of such passages being considerably greater than the'cross-sectional area of the mixing chamber 6. This permits the paint y laden water globules to impinge on the baiiie f The trough-8 hasits discharge end 9 opening the compartment .23, in the present instance,

into the compartment 2|, and each compartment has communication with the next lin order through respective openings 26, 21 and 28 provided in the partitions, and the compartment 24 opens into the tank 3 through the opening 5. The openings 5 5, 26, 21 and 28 are below the normal level of the water in the tank 20 to prevent any scum or impurities collecting on the surface of the water in any compartment passing to the next compartment. Likewise, the bottoms of these openings are above the bottoms ofthe compartments to prevent sediment collecting in the bottoms of the compartments from passing from one to another.

Fresh water is supplied to the tank 2B into l5 through a pipe 3i), which has a valve controlled by a iloat 3l, whereby the water level in the two tanks 3 and 2B is maintained substantially constant.l i In the modication shown in Fig. 5, the air,

2i! which is delivered to the upper portion 3 of the water tank 3, does not comprise a part of the air discharging from the blower I2, but constitutes an independent source of supply which is created by a blower 40 having its-outlet conduit 4I opening into the upper portion of thev tank` chamber. This modification also shows a positive means in the form of a water wheel 42 for discharging water from the tank 3 into the mixing chamber 6 to mix with the air drawn therein yfrom the compartment I. Thewheel 42 is disposed in a slot 43 in the bottom ofthe chamber 6 and is driven by a motor 44. The air current in the top of the tank 3 may also be utilized to assist the wheel 42 in throwing the water into the chamber 6l in addition to passing through the A slot I1 in the bottom of the chamber 6 to mix with and atomize the paint and water laden air passing through such chamber.

It is apparent from the foregoing that an air current of considerable velocity is created through the mixing chamber 6, which chamber is of restricted form relative to the expansion chamber 1 and the remainder of the passage to the blower or exhaust i'an I2, and that this, combined 4g with the circuitous form of the mixing chamber 6, effects a thorough mixing of the paint laden air and liquid in the mixing chamber, such liquid being received in curtain form from thel tank 3. It is also apparent that the velocityv of 51 the air and liquid and the mixing thereof in their passage through the chamber 6 is augmented and facilitated by the admission of additional air under pressure to the chamber through either or both slots I 1 and I8. It is found in prac- 5l tice that this method of treating the paint laden air eliminates practically all of the liquid globules i of paint therefrom before the air passes to and is discharged by the blower I2, so that an undetectable quantity of paint or impurities carried by 61 the air received from the compartment I is dscharged to the atmosphere, and ythat there is very little, if any, collecting of paint particles and impurities on the fan and conduit walls after passing between the 'eliminator plates III. In 6 practice, it .has been found that the cleaning is so thorough that the interior of the expansion chamber 1 as well as the plates I0 remain free from any discoloration.

It is also found that the impurities removed 7 from the air are practically all eliminated from the water within the tank 20, where they can easily be skimmed from the surface of the water in the various compartments in such tank, and also removed as sediment therefrom without im- 7` pairing the continued operation of the booth. In practice, it is found desirable to use a softening agent in the water 4, as this facilitates the freeing of the paint globules from the Water.

We wish it understood that our invention is not limited to any specific construction, arrangement or form of the parts, as it is capable of numerous modifications and changes without departing from the spirit of the claims.

Having-thus described our invention, what we claim as new, and desire to secure by United States Letters Patent, is:

1. In an apparatus for cleaning air, a draft creating means, means forming a passage between.

said first means and a source of air to be cleaned, said passage having diierent portions forming, in successive order away from the air source, a re-. stricted mixing chamber, an expansion chamber and a baiile chamber, the mixing chamber having a. plurality of openings in a side wall thereof spaced lengthwise of the chamber, liquid means closing at least one of said openings, and pneumatic means for forcing air through said openings into the mixing chamber and acting on the liquid means to force it in spray form into the mixing chamber.

2. The method of cleaning air by removing entrained liquid particles therefrom which consists in' passing the air at high velocity through and its ability to carry entrained moisture, and

iinally removing entrained liquid particles by baiiling the iiow of the air stream.

3. 'I'he method of cleaning air by removing entrained liquid particles therefrom which consists in passing the air at high velocity through' a spray of cleaning liquid, then in introducing a jet of atomizing air into the rapidly moving air stream to mix the entrained liquid particles with the cleaningliquid, then in reversing the direction of flow to cause turbulence in the air stream, then in expanding the air stream to reduce its velocity and its ability to carry entrained moisture, and nally removing the entrained liquid Lparticles by baiiiing the flow of the stream.

'4. In an apparatus for removing waste paint particles from air, means forming an air passage in communication at one end with a source of air to be cleaned, means for creating a draft through said passage, said Apassage having diiferent portions forming, in successive order away from the air source,la lengthwise elongated transversely restricted mixing chamber, an expansion cham-` ber, and a baille portion, the latter collecting liquid globules from the air passing there-- through, said mixing chamber having two successively arranged openings in a side wall thereof intermediate its ends, means for containing a liquidV in closing relation to said first opening,

and means for directing air under pressure through the liquid closing said iirst opening, whereby a spray of liquid is .discharged into the mixing chamber to mix with the air to be cleaned, and also for directing air underpressure into the mixing chamber through said second opening.

5. In an apparatus for removing waste paint particles from air, means forming an air passage in communication at one end with a source of air to be cleaned, means for creating a draft through said passage, said passage having different portions forming, in successive order away from the air source, a lengthwise elongated transversely restricted mixing chamber, an expansion chamber, and a baille portion, the latter collecting liquid globules from the air passing therethrough, said mixing chamber having an opening in a side 'wall thereof intermediate its ends, means for containing a liquid in closing relation to said opening, and means for directing air under pressure through the liquid closing said opening, whereby a spray of liquid is discharged linto the mixing chamber to mix withthe air to be cleaned, and means for discharging air laterally into said mixing chamber at a poin in advance of said opening.

6. In an apparatus for removing waste paint particles from air, a draft creating means, means forming a passage between said first means and a source of air to be cleaned, said passage having different portions forming, in successive order away from the air source, an elongated/transversely restricted mixing chamber, and a baille chamber, the latter collecting liquid globules from the air passing therethrough, said mixing chamber having an opening in its bottom, means for containing a liquid in submerging relation to said opening, means forming communication between said baiile chamber and liquid containing means to return the liquid to one from the other, means interposed in said communication to clean the liquid before being returned to the liquid containing means, and means for spraying liquid into the mixing chamber throu'gh said opening.

7. In an apparatus for removing waste paint particles from air, a draft creating means, means forming a passage between said first means and a source of air to be cleaned, Qsaiol passage having diierent portions forming, l,in successive order away from the air source, an elongated transversely restricted mixing chamber, and a baille chamber, the latter collecting liquid globules fromv the air passing therethrough, said mixing chamber having an opening in its bottom, means for containing a liquid in submerging relation to said opening, and means connecting said draft creating means and said liquid containing means to force air from the former into the mixing chamber through its said side opening and to carry therewith a spray of liquid from the liquid in said liquid containing means. g

8. In an apparatus for cleaning air, a draft creating means, means forming a liquid chamber, means forming a passage between said first means and a source of air to be cleaned, said passage having diierent portions forming, in successive order away from the air source, a restricted mixing chamber oi shallow transversely broadened form having a slot in a side thereof adapted to be

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