US2848353A - Method and apparatus for spraying articles including separation and recirculation of coating material - Google Patents

Description

E. o. NORRIS Aug. 19, 1958 ICLES CULATION METHOD AND APPARATUS FOR SPRAYING ART INCLUDING SEPARATION AND RECIR OF COATINGMATERIAL 4 Sheets-Sheet 1 Filed Oct. 21, 1954 1 Q I mvsu'ro EOM/APO C2 9 45 I BY AiIJRNEY f Aug. 19, 1958 2,848,353

E. 0. NORRIS METHOD AND APPARATUS FOR SPRAYING ARTICLES INCLUDING SEPARATION AND RECIRCULATION 0F COATING MATERIAL Filed Oct. 21, 1954 4 Sheets-Sheet 2INVENTOR 5 izu/meo 0. A aIP/P/S ATTORN EY United States Patent METHOD AND APPARATUS FOR SPRAYING ARTICLES INCLUDING SEPARATION AND RECIRCULATION OF COATING MATERIAL Edward O. Norris, Westport, Conn. Application October 21, 1954, Serial No. 463,761

20 Claims. (Cl. 117-102) This invention relates to a method and apparatus for spraying articles which are capable of being fed into a Another object is to provide a spraying system using air gun sprayers for spraying liquids, such as paint in a solvent vehicle, having novel and improved means for maintaining uniform solvent viscosity conditions.

Another object is to provide a system of the above type in which the oversprayed material is recovered, separated and recirculated for respraying in a closed cycle.

Another object is to provide an apparatus of the above type including a closed cycle coating material circulating system, a substantially closed cycle atomizing gas system and a closed cycle solvent circulating system in which the volume of solvent gradually increases during the coating operation while all the oversprayed material is maintained at a constant viscosity, and collected for reuse.

Other objects and advantages will be apparent as the nature of the invention is more fully disclosed.

The invention will be better understood by referring to the following description, taken in connection with the accompanying drawings in which a specific embodiment thereof has been set forth for purposes of illustration.

In the drawings:

Fig. 1 is a diagrammatic view illustrating a system for carrying out the present invention;

Fig. 2 is a section through the spray chamber taken on theline 22 of Fig. but on a slightly larger scale;

Fig. 3 is a detail view of a further embodiment showing an air curtain at the exit end of the spray chamber;

Fig. 4 is a section taken on the line 4-4 of Fig. 3;

Fig. 5 is a section through a portion of the spray chamber on a slightly smaller scale taken on the line 5-5 of Fig. 2;

Fig. 6 is a vertical section through the entrance chamber, on a larger scale, illustrating another embodiment of air curtain and entrance tunnel;

Fig. 7 is a perspective view of the entrance end of the tunnel of Fig. 6 showing the air curtain; and

Fig. 8 is a horizontal section taken on theline 88 of Fig. 7.

Referring to the drawings more in detail, the apparatus is shown as comprising aspray chamber 10 havingend walls 11 and 12, and havingwalls 13 forming anentrance vestibule 14 andwalls 15 forming anexit vestibule 16. Thevestibules 14 and 16 are formed withend walls 17 and 18 respectively havingopenings 19 and 20 therein for the passage of articles to be sprayed. Aconveyor 21 extends through theopenings 19 and 20, through thevestibules 14 and 16, and through thespray chamber 10 to carryarticles 22 to be sprayed,

2,848,353 Patented Aug. 19, 1958 Thespray chamber 10 is provided with abottom sump 24 communicating with aduct 25 for the withdrawal of oversprayed liquid and gases therefrom.Ducts 26 and 27 communicate with thevestibules 14 and 16 respectively near the outer ends thereof for Withdrawing oversprayed liquid and gases from said vestibules.Dampers 28 serve to control the amount of material withdrawn through the respective ducts.

Theducts 25, 26 and 27 lead to an air cleaner 30, shown as of the rotary flow type having spiral air ducts 31 in which the spray particles are removed centrifugally from the gaseous phase and are reintroduced into the liquid phase. The cleaner 30 is connected to the top 32 of aseparator 33 in which the spray liquid containing the spray material in suspension or in solution is separated from the air and solvent vapor. The spray liquid is removed from theseparator 33 by means of apump 34 which may be a gear pump driven by a compressed air motor and which feeds through a feed pipe 35 into areceiver 36 containing atemperature control coil 37. This receiver contains the liquid for spraying, for example paint in a liquid solvent vehicle, solid particles in suspension or a solvent for cleaning purposes, and additional spray liquid may be added thereto from time to time as required.

From thereceiver 36 the liquid is withdrawn 'by apump 38 which may comprise a gear pump operated by a compressed air motor and is fed through a feed line 49 andpipes 41 and 42 to sprayingheads 43 and 44 to be described, which are of standard two fluid atomizing type and are adapted to atomize the liquid by use of air or gas under pressure.Pressure regulating valves 45 and 46 are shown as disposed in thelines 41 and 42 for controlling the pressure and therefore the quantity of the spray liquid fed to theheads 43 and 44.

Air and solvent vapor, which'may contain a small percent of fine spray dust, are withdrawn from theseparator 33 through a pipe 50 which projects through the top 32 and is provided with an intake slot 51 through which the gases are removed. The pipe 50 is connected to a float chamber 47 containing a ball float 48 seating against a seat 49 to prevent liquid from entering the subsequent stages. A release pin 39 is provided to unseat the ball 48 when required. The float chamber 47 is connected by a pipe 50a to acooling chamber 52 containing a refrigerating coil 53 which is operated at a temperature to freeze out any water vapor which may be contained in the air. The bottom of thecooling chamber 52 is divided into two compartments by apartition 54 capped with a flap valve 58 which during normal operation is in the position shown so that air, solvent vapor and liquid solvent flow into aliquid seal compressor 55 through duct 56. Thecompressor 55 is of the type using a seal liquid to compress the gas. A compressor of this type is shown in the Jennings Patent No. 1,718,294, dated June 25, 1929, which discloses an oval chamber in which a peripheral film of liquid is maintained by centrifugal force. The liquid forms an air chamber which expands and contracts due to the oval walls and thus compresses the trapped air. A compressor of this type hasthe advantage of passing without injury liquid or solid particles which may be present in the gas stream. The water vapor freezes on coil 53. Valve 58 moves into the position shown by the dotted lines when the coil 53 is defrosted at the end of the operation and the melting ice drains intocompartment 52 and is removed throughduct 57.

The high pressure side of thecompressor 55 leads by apipe 60 to a separator 61 which is adapted to separate from the compressed gas, the compressing liquid .and solvent vapor condensate produced by compression. The separated liquid solvent, under the pressure produced .by

the compressor which may be of the order of 5 to p. s. i., is fed from the separator 61 by apipe 62 into the top of areceiver 63 having a cooling coil 64 for controlling the temperature of the liquid therein. The liquid solvent in thereceiver 63 is fed by means of a pipe 65 andpipe 66 to the seal liquid intake side of thecompressor 55 to serve as the seal liquid.

The liquid separated in the separator 61, which constitutes liquid solvent under the pressure of the output of thecompressor 55, and which may be slightly contaminated by spray dust, is fed through pipe 68 andstrainer 69 intoheaders 70 within thechamber 10. These headers spray solvent onto the walls of the chamber to replace the solvent evaporated from the spray and to thus maintain the desired material viscosity. Solvent may also be sprayed by a pipe 71 into aheader 72 which is located at the top of thechamber 10 and is provided with side perforations for spraying the solvent onto the walls at the top of the chamber so that the solvent can flow downwardly along the inside of said walls.Valves 73 and 74 control the relative flow of solvent to theheaders 70 or 72 to maintain the correct viscosity. The solvent in the pipe 68, which is not supplied to the headers, returns to the compressor through pipe 75.

The compressed gas in the separator 61, consisting of air with some solvent vapor, is fed tooutlet pipes 78 and 79 connected in parallel. Pipe 78 is connected to a chamber 80 containing a cooling coil 81. The chamber 80 is connected by a pipe 82 andvalve 83 to thepipe 79. The relative flow of gases through thepipes 78 and 79 is controlled by valves .83 and 84. The cooling bypass is provided so that the gases may be cooled to further condense and strip solvent vapors from the compressed air. The pipe 82 is also connected to a header 85 which in turn is connected by apipe 86 through a valve 87 to apply air pressure to the top of thereservoir 63. The pressure supplied to thereservoir 63 is controlled by a manually adjustable pressure regulating valve 76 connected to a gauge 77. The header 85 is also connected through avariable orifice valve 93 to a pipe 91 discharging into the atmosphere and to apipe 94 which supplies compressed air for operating thecompressed air motors 34 and 38 above referred to. Theheader 88 is also connected through apressure relief valve 92 to a bleeder pipe to prevent the accidental build up of excessive i pressure in the system. The pipe 91, controlled byvalve 93, permits the controlled release of a predetermined volume of compressed air, stripped of its solvent vapor, to create a light negative pressure in thechamber 10.

Thepipe 79 connects above the header 85 with a heating chamber 95 containing aheating coil 96 which may be heated by steam or from the hot side of the refrigeration system, to control the temperature, and therefore the relative solvent saturation, of the compressed air to be accurately controlled. The compressed air is then fed through pipe 97 toheader 98. Leads 99 and 100 supply air fromheader 98 to theair guns 43 and 44 respectively within thespray chamber 10. Theheader 98 is also connected by apipe 101 to anair nozzle 102 within thespray chamber 10 which is adjustably mounted for redirecting some of the spray particles floating in the chamber against surfaces which would not otherwise be coated by the spray from the spray guns.

Theopenings 19 and 20 in thevestibules 14 and 16 may be lined withannular pipes 105 and 106 which are respectively connected toheader 98 bypipes 107 and 108. The annular pipe 105 (Fig. 2) is provided with a series ofslots 110 and a series of apertures 111 which are inclined in a direction to direct converging jets of air 112 (Fig. 1) into the vestibule 14 and around the opening 19. This virtually solid air barrier prevents the escape of spray material or solvent vapor from the opening 19 while permitting the passage of articles to be sprayed therethrough. Amember 113 forming the entrance tun- 4 nel is disposed in the vestibule 14 in registration with the opening 19.

The pipe 106 is provided with a similar series of slots and apertures to provide an air curtain 114. Amember 115 forming the exit tunnel is disposed in the vestibule 16 in registration with theopening 20.

in the embodiment of Figs. 3 and 4 only one slottedpipe 116 having a slot 116a is mounted below theopening 20a and directs the air current inwardly and upwardly. This simplified form may also be employed without a conveyor for painting pipes or the like.

Figs. 6, 7 and 8 show another embodiment wherein amember 117 forms anentrance tunnel 118 and is attached to an end plate 119 which forms the end wall of a vestibule 14a corresponding to thevestibule 14 of Fig. l. in thisembodiment pipes 120 are disposed at the top and bottom of the tunnel and are slotted todirect air jets 121 into the tunnel so as to create an air current which prevents the escape of vapor and spray particles. In this embodiment, it is assumed that the shape of thetunnel 118 corresponds to that of the material being sprayed so that theopening 19a may be made as small as possible. The tunnel and end plate 119 may be replaced according to the type of article being sprayed. Thesides 121 of the tunnel are shown as convex inwardly so as to assure that the air from thejets 121 seals against the side walls and completely fills thetunnel 118. The end of the tunnel is provided with alip 122 to prevent spray material from dripping therefrom onto the work which is passing through the tunnel.

In some cases air spray guns may be employed, in conjunction with special tunnel construction, to form air curtains in place of thepipes 120.

The spray nozzles 43 and 44, as shown more in detail in Figs. 2 and 5, are of the air gun type, havingdouble jets 123 which are adapted to form fan shapedspray 124. Theguns 43 and 44 are mounted incasings 125 and 126 to which air is supplied bypipes 127 and 128 from theheader 98 in order to prevent accumulation of spray particles on the outside and particularly the nozzles of the air guns. Air may also be passed over the surface of the air guns by Venturi action if thecasings 125 and 126 are open to the atmosphere.Shields 129 and 130 havinglips 136 are mounted to extend below thecasings 12S and 126 to catch any material which drips from the outside of the casing and to conduct the same away from the path of the articles being sprayed. These shields also assist in the spreading of the spray fan.

In the operation of this system the spray particles are separated from the air and reintroduced into the liquid phase in the air cleaner 31 and are removed wlth the liquid inseparator 33. The liquid removed from theseparator 33 and supplied to thereceiver 36 compnses spray liquid consisting of coating material in suspension or solution in the liquid solvent. In the case of paint the material comprises the liquid vehicle and pigment. Additional material is added to thereceiver 36 as required for feeding therefrom to the spray guns.

The gaseous phase taken from theseparator 33 consists of air and solvent vapor with minor portions of spray dust which has not been removed by the air cleaner 31 andseparator 33 together with such water vapor as may have been present in the air. The water vapor is frozen out on the cooling coils 53 so that the gases passing the coolingchamber 52 are stripped from water vapor and consist of air and solvent vapor with some spray dust and some liquid solvent which has been condensed in the coolingchamber 52. The water is removed from the coil 53 by a defrosting cycle during which the valve 58 is shifted to the left so that the water is drained through thepipe 57 and removed from the system.

The air, solvent vapor, condensate liquid solvent and such minor quantities of spray dust as may not have been removed are passed into theliquid seal compressor 55 wherein the gases are compressed. Any spray dust which is present passes through the liquid seal compressor without injury thereto due to the fact that the compressing medium is a liquid which usually takes up the spray dust.

The float valve 48 serves to seal off the coolingchamber 52 and the intake to the compressor in the event of an abnormal rise in liquid level in theseparator 33 due to the failure or loss of prime of thepump 34 so that liquid is prevented from entering the compressor.

Since liquid solvent is used as the liquid seal in the compressor a portion of the solvent vapor in the air is condensed by compression in the compressor and any solvent droplets and fine spray dust which are not removed in theseparator 33 mix with the seal liquid and do not interfere with the operation of the compressor. Compressed air, solvent vapor and liquid solvent which is condensed by the compressor flow into the separator 61 wherein the liquid solvent is separated from the gases.

The gaseous phase from the separator 61, which consists of compressed air with some solvent vapor passes through the cooling chamber 80 or through thebypass 79, depending upon the conditions required. In the cooling chamber 80 the temperature is maintained such as to condense substantially all of the remaining solvent vapor and strip the same from the air so that the air supplied by the pipe 82 consists essentially of compressed air stripped of solvent vapor. A portion of this compressed air is supplied bypipe 94 which is to be used for operating the air motors as above described. Another portion is discharged into the atmosphere through the pipe 91 so as to maintain the interior of the coating chamber under a slight negative pressure. A further portion of the compressed air is supplied through thepipe 86 to thereceiver 63 to maintain the pressure in said receiver suited for feeding the solvent therein through thepipes 65 and 66 back to the intake side of thecompressor 55. In the event of abnormal pressure rise in the system the pressure is released through the pressure relief valve in thepipe 90.

The quantity of solvent vapor in the air supplied to the pipe 97 is determined by controlling the ratio of gases supplied to the cooling chamber 80 and to thebypass 79. The heating chamber 95 heats this mixture to a temperature required to reduce the relative saturation to the desired value. This compressed air is then supplied by theheader 98 to thespray guns 43 and 44 andair curtain jets 113 and 114 as above described.

Referring to Fig. 5 thechamber 10 is shown as having acurved bottom wall 131 and slopingtop walls 132 hinged thereto and closing against anangle 133 at the top of the chamber. Thewalls 132 slope at an angle greater than 45 and are so selected that the solvent which is sprayed onto the walls will flow down the under surface of the walls without dripping onto the articles being sprayed.Deflectors 134 are disposed beneath theheader 72 to intercept any liquid which might spray downwardly and to direct the same intochannels 135 which feed the liquid along the under surfaces of thewalls 132 as above mentioned. Similar bafiles are not required under theheaders 70 since these headers are located beyond the path of the articles which are being sprayed. Hence any drip therefrom would not contact such articles.

The fine spray particles produced byspray guns 44 and 45 of the type above indicated have a very high aggregate surface area. Hence there is a substantial solvent evaporation from the spray particles, particularly if the compressed air has been dried as above, which tends to increase the vapor pressure within the spray zone and which would tend to cause escape of solvent vapor and spray particles from the chamber if it were not kept under light negative pressure. The system, however, condenses and thus recovers a substan tial portion of this vapor by compression and cooling so that it is available for reuse as a liquid. The solvent evaporated from the spray striking the articles being coated and from the surfaces of the freshly coated articles in the chamber is thus recovered and added to the solvent in the solvent system. The air curtains at the openings, in conjunction with the slightly reduced pressure maintained in the chamber, serve to substantially eliminate the escape of solvent vapor or spray particles particularly where a spray source has to be directed toward an opening. This system permits air pressure actuated spray nozzles to be used in a substantially closed chamber while maintaining the chamher at a reduced pressure. Dry compressor air is desirable for atomizing in many coating operations since it is generally considered advantageous to atomize material at the lowest practical viscosity and to have the spray particles strike the surfaces being coated at the highest viscosity comparable with flow-out and leveling. This tends to permit a coating of adequate thickness without sags and run-off while employing low atomizing energy.

The air guns may be mechanically oscillated if desired depending upon the nature of the articles being sprayed. If so, they should be oscillated in such a manner and in such an arc or plane as to throw any material droplets collecting on the nozzles, clear of the article being coated.

In some instances it has been found that the spray dust is not picked up by the seal liquid within thecompressor 55, but passes on through the compressor with the gases. In order to prevent this a detergent may be added to the seal liquid, particularly if it is aqueous, such for example as about 1% of Aerosol OT made by American Cyanamid Company together with about of an antifoaming agent (Antifoam 4007 of Cyanamid) which prevents frothing or foaming in the compressor. The seal liquid should be compatible with the liquid solvent or suspending agent and is preferably the same material.

Although solvent has been referred to specifically in connection with a system for spraying paint, it is to be understood of course that the system may be used for other purposes and that the liquid may constitute a suspending agent containing solid particles such as ceramic or abrasive or may constitute a solvent itself if the spray is to be used for washing or cleaning surfaces or may constitute a coating material, such as melted coconut oil. The cooling coil 64 is used in thereceiver 63 to remove the heat of compression from the seal liquid before recycling the same.

Since most organic solvents used in coating operations have a lower specific gravity than water the compressor capacity and efficiency is lowered when they are used as a sealing liquid. This loss is partially overcome by cooling the solvent and may be completely eliminated by the addition to these solvents ofsmall amounts of high specific gravity halogenated organic solvents.

What is claimed is:

1. Apparatus for spraying articles comprising a casing forming a substantially closed spray zone, means feeding articles for spraying into and out of said zone, an air gun type spray nozzle in said zone adapted to direct a spray onto said articles, means feeding compressed gas to said gun, means feeding a sprayable material to said gun, suction'means withdrawing oversprayed material and gases'from said zone, separating means separating the spray material from said gases, means recycling said separated spray material to said gun for respraying, a liquid seal compressor containing solvent liquid as the liquid seal, means feeding the gases from said separating means into said compressor, and means recycling the air compressed by said compressor to said spray gun for reuse.

2. Apparatus for spraying articles comprising a casing forming a substantially closed spray zone, means feeding articles for spraying into and out of said zone, an air gun type spray nozzle in said zone adapted to direct a spray onto said articles, means feeding compressed gas to said gun, means feeding a sprayable liquid in a vaporizable solvent to said gun, suction means withdrawing oversprayed material and gases from said zone, separating means separating the liquid spray material from said gases, means recycling said separated liquid spray material to said gun for respraying, a liquid seal compressor containing solvent liquid as the liquid seal, means feeding the gases from said separating means into said compressor for thereby compressing air and solvent vapor, means removing condensed solvent vapor from the compressed gases and returning the same to said compressor and means recycling the air compressed by said compressor to said spray gun for reuse.

3. Apparatus for spraying articles comprising a casing forming a substantially closed spray zone, means feeding articles for spraying into and out of said zone, an air gun type spray nozzle in said zone adapted to direct a spray onto said articles, means feeding compressed gas to said gun, means feeding a sprayable liquid in a vaporizable solvent to said gun, suction means withdrawing oversprayed material and gases from said zone, separating means separating the liquid spray material from said gases, means recycling said separated liquid spray material to said gun for respraying, a liquid seal compressor containing solvent liquid as the liquid seal, means feeding the gases from said separating means into said compressor for thereby compressing air and solvent vapor, means removing condensed solvent vapor from the compressed gases and returning the same to said compressor, means recycling the air compressed by said compressor to said spray gun for reuse, and means feeding solvent liquid onto the walls of said spray zone.

4. A spray coating system comprising a chamber having an opening through which articles to be coated may be introduced into said chamber, a spray source in said chamber for spraying liquid coating material in a vaporizable liquid carrier onto" said articles, means removing gases with liquid carrier vapor from said chamber, and means to condense liquid carrier vapor therefrom and reintroducing the condensed liquid carrier into said liquid coating material.

5. The method of spraying articles which comprises feeding said articles into a substantially closed spray zone, spraying said articles in said zone with a spray liquid in a liquid solvent atomized by compressed air, withdrawing from said zone oversprayed liquid and gases, stripping the gases of said liquid and recycling the same to said spray means for reuse, compressing the stripped gases in contact with liquid solvent, stripping a substantial portion of the liquid solvent from said compressed gases, and applying the stripped air to said spray means for atomization in a closed cycle.

6. The method of spraying articles which comprises feeding said articles into a substantially closed spray zone, spraying said articles in said zone with a spray liquid in a liquid solvent atomized by compressed air, withdrawing from said zone oversprayed liquid and gases, stripping the gases of said liquid and recycling the same to said spray means for reuse, compressing the stripped gases in contact with liquid solvent, stripping a substantial portion of the liquid solvent from said compressed gases, introducing controlled quantities of said solvent into said spray zone to compensate for solvent loss therein by evaporation and applying the stripped air to said spray means for atomization in a closed cycle.

7. Apparatus for spraying articles comprising a casing forming a substantially closed spray zone, means for feeding articles to be sprayed into and out of said zone, an air gun type spray nozzle in said zone adapted to direct an atomized spray of liquid sprayable material onto said articles, means for feeding said liquid sprayable material and a compressed gas to said gun for spraying, suction means withdrawing oversprayed material and gases from said zone, separating means for separating the liquid sprayable material from said gases, means for recycling said separated sprayable material to said gun, and means for further stripping sprayable material from said gases.

8. Apparatus for spraying articles comprising a casing forming a substantially closed spray zone, means for feeding articles to be sprayed into and out of said zone, an air gun type spray nozzle in said zone adapted to direct an atomized spray of liquid sprayable material onto said articles, means for feeding said liquid sprayable material and a compressed gas to said gun for spraying, suction means withdrawing oversprayed material and gases from said zone, separating means for separating the liquid sprayable material from said gases, means for recycling said separated sprayable material to said gun, means for compressing the separated gases and for further stripping sprayable material therefrom, and means for recycling said compressed gases to said gun.

9. Apparatus for spraying articles comprising a casing forming a substantially closed spray zone, means for feeding articles to be sprayed into and out of said zone, an air gun type spray nozzle in said zone adapted to direct an atomized spray of a sprayable material in a volatile liquid carrier onto said articles, means for feeding said liquid carrier and a compressed gas to said gun for spraying, suction means withdrawing oversprayed material and gases from said zone, separating means for separating the liquid carrier and sprayable material from said gases and vaporized carrier, means for recycling separated liquid carrier and sprayable material to said gun, means for stripping the vaporized carrier from said gases, and means for recycling the stripped gases to said gun.

10. Apparatus for spraying articles comprising a casing forming a substantially closed spray zone, means for feeding articles to be sprayed into and out of said zone, an air gun type spray nozzle in said zone adapted to direct an atomized spray of a sprayable material in a volatile liquid carrier onto said articles, means for feeding said liquid carrier and a compressed gas to said gun for spraying, suction means withdrawing oversprayed material and gases from said zone, separating means for separating the liquid carrier and sprayable material from said gases and vaporized carrier, means for recycling separated liquid carrier and sprayable material to said gun, means for compressing and cooling said gases to liquefy and collect the vaporized carrier therefrom.

11. Apparatus for spraying articles comprising a casing forming a substantially closed spray zone, means for feeding articles to be sprayed into and out of said zone, an air gun type spray nozzle in said zone adapted to direct an atomized spray of a sprayable material onto said articles, means for feeding said sprayable material and a compressed gas to said gun for spraying, suction means withdrawing oversprayed material and gases from said zone, separating means for separating the sprayable material from said gases, means for recycling separated sprayable material to said gun, and means for compressing and recycling the gases to said gun, and means for controlling the temperature of said recycled gases.

12. Apparatus for spraying articles comprising a casing forming a substantially closed spray zone, means for feeding articles to be sprayed into and out of said zone, an air gun type spray nozzle in said zone adapted to direct an atomized spray of a sprayable material in a volatile liquid carrier onto said articles, means for feeding said liquid carrier and a compressed gas to said gun for spraying, suction means Withdrawing oversprayed material and gases from said zone, separating means for separating the liquid carrier and sprayable material from said gases and vaporized carrier, means for recyling separated liquid carrier and sprayable material to said gun, means for stripping the vaporized carrier from said gases, means for recycling the stripped gases to said gun, and

means for controlling the temperature and carrier vapor content of said recycled gases.

13. Apparatus for spraying articles comprising a casing forming a substantially closed spray zone, means for feeding articles to be sprayed into and out of said zone, a spraying device in said zone adapted to direct an atomized spray of liquid sprayable material onto said articles, means for feeding said liquid sprayable material to said spraying device, means for withdrawing oversprayed material and gases from said zone, separating means for separating the liquid sprayable material from said gases, means for recycling said separated liquid sprayable material to said gun, means for separating and liquefying the vaporized component of the sprayable material from the gases, and means for reintroducing said liquefied component into the sprayable material to control the viscosity of said sprayable material.

14. Apparatus for coating articles, comprising a casing forming a substantially closed coating zone, means for feeding articles to be coated into and out of said zone,

means for applying coating material in a liquid carrier to said articles in said zone, suction means for withdrawing vaporized carrier and gases from said zone, means for passing said Withdrawn gases and vapor through a liquid seal type compressor containing carrier liquid as a sealing and compressing medium to compress and liquefy the carrier vapor component of said gases.

15. Apparatus for spraying articles comprising a casing forming a substantially closed spray zone, means for feeding articles to be sprayed into and out of said zone, and an air gun type spray nozzle in said zone adapted to direct an atomized spray of liquid sprayable material onto said articles, means for feeding said liquid sprayable material and a compressed gas to said nozzle for spraying, suction means Withdrawing said gas and said atomized sprayable material not deposited on the articles from said zone, means for flowing said liquid sprayable material through a separating zone in surface contact with said withdrawn mixture of gas and spray particles to collect in said liquid for reuse said spray particles suspended in said gases.

16. Apparatus for spraying articles comprising a casing forming a substantially closed spray zone, means for feeding articles to be sprayed into and out of said zone, an air gun type spray nozzle in said zone adapted to di rect an atomized spray of sprayable material in a liquid carrier onto said articles, means for feeding said sprayable material in said liquid carrier and a compressed gas to said air gun for spraying, suction means withdrawing oversprayed material and gases from said zone, means for flowing liquid carrier through a separating zone in surface contact with the withdrawn gases and suspended spray particles to collect these spray particles as a liquid for reuse.

17. Apparatus for spraying articles comprising a casing having walls forming a substantially closed spray zone, means for feeding articles to be sprayed into and out of said zone, a spraying device in said zone adapted to direct a spray of liquid sprayable material onto said articles, suction means withdrawingoversprayed material 10 and gases from said zone, separating means for separating the suspended sprayable material from said gases, means for recycling said separated sprayable material to said spraying device and means including a liquid seal compressor for further stripping sprayable liquid material from said gases.

18. The method of spraying articles which comprises feeding said articles into a substantially closed spray zone, spraying said articles in said zone with a sprayable material atomized by means of a compressed gas, withdrawing from said zone oversprayed sprayable material and gas, stripping the gas of said material and recompressing said gas in a liquid seal compressor.

19. Apparatus for spraying articles comprising a casing forming a substantially closed spray zone, means for feeding articles to be sprayed into and out of said zone, a spray gun in said zone adapted to. direct an atomized spray of sprayable material in a liquid carrier onto said articles, means for feeding said sprayable material in said liquid carrier to said spray gun for spraying, suction means withdrawing oversprayed liquid and gases from said zone, separating means for flowing the withdrawn liquid through a separating zone in surface contact with the withdrawn gases and spray particles suspended therein, to thereby strip said spray particles from said gases.

20. Apparatus for spraying articles comprising a casing forming a substantially closed spray zone, means for feeding articles to be sprayed into and out of said zone, a spray gun in said zone adapted to direct an atomized spray of sprayable material in a liquid carrier onto said articles, means for feeding said sprayable material in said liquid carrier to said spray gun for spraying, suction means withdrawing oversprayed liquid and gases from said zone, separating means for flowing the withdrawn liquid through a separating zone in surface contact with the withdrawn gases and spray particles suspended therein, to thereby strip said spray particles from said gases, suction means connected to remove said stripped gases from said separating means, and means including a member responsive to accumulated liquid between said separating means and said suction means to interrupt the fluid flow to said suction means.

References Cited in the file of this patent UNITED STATES PATENTS 1,659,179 Wilson Feb. 14, 1928 1,696,704 Zellner Dec. 25, 1928 1,794,764 Goethel Mar. 3, 1931 2,132,826 Ludwig Oct. 11, 1938 2,206,179 Frank July 2, 1940 2,227,465 Roche et al. Jan. 7, 1941 2,285,650 Faris et al. June 9, 1942 2,486,251 Braun Oct. 25, 1949 2,527,139 Loney Oct. 24, 1950 2,528,087 Schoppe Oct. 31, 1950 2,579,778 Allen Dec. 25, 1951 2,651,586 Cooper et a1. Sept. 8, 1953 2,658,796 Kopperschmidt Nov. 10, 1953 2,694,466 Bingman Nov. 16, 1954

Claims (1)

1. 6. THE METHOD OF SPRAYING ARTICLES WHICH COMPRISES FEEDING SAID ARTICLES INTO A SUBSTANTIALLY CLOSED SPRAY ZONE, SPRAYING SAID ARTICLES IN SAID ZONE WITH A SPRAY LIQUID IN A LIQUID SOLVENT ATOMIZED BY COMPRESSED AIR, WITHDRAWING FROM SAID ZONE OVERSPRAYED LIQUID AND GASES, STRIPPING THE GASES OF SAID LIQUID AND RECYCLING THE SAME TO SAID SPRAY MEANS FOR REUSE, COMPRESSING THE STRIPPED GASES IN CONTACT WITH LIQUID SOLVENT, STRIPPING A SUBSTANTIAL PORTION OF THE LIQUID SOLVENT FROM SAID COMPRESSED GASES, INTRODUCING CONTROLLED QUANTITIES OF SAID SOLVENT INTO SAID SPRAY ZONE TO COMPENSATE FOR SOLVENT LOSS THEREIN BY EVAPORATION AND APPLYING THE STRIPPED AIR TO SAID SPRAY MEANS FOR ATOMIZATION IN A CLOSED CYCLE.

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