US1746228A - Process and apparatus for spray coating - Google Patents

Description

Feb. 4, 1930. RDARUNG 1,746,228

PROCESS AND APPARATUS FOR SPRAY COATING Filed Jan. 24, 1927 2 Sheets-Sheet 1 i L h: 5 ml w 50 ii 1 I 14. H

Illi

INVENPOR,

ATTORNEYS.

Feb.,4, 1930. H. R. DARLING PROCESS AND APPARATUS FOR SPRAY COATING Filed Jan. 24, 1927 2 Sheets-Sheet 2 INVENT y Rpm .0 1 1 M Q I ATTORNEYS.

72 174 75 HcLTT Patented Feb. '4, 1930 4 HARRY R. DARLING, OF BOGHESTER, NEW YORK PROCESS AND APPARATUS FOR SPRAY GOATING Application filed January 24, 1927. Serial No. 162,985.

This invention relates to coating machines,.

particularly to spray-coating machines and to a process by which such coating can be economically and safely carried out. One object of my invention is to provide an apparatus for. spraying articles in which the unused spray is recovered. Anotherobject is to provide an apparatus for keeping the coating composition properly mixed in condition for use. Another object is to provide for conditioning the coating material by constant circulation. Another object is to provide a process of coating in which unused spray coating is entrapped in a body of the coating 1 composition, and other objects will appear from the following specification, the novel features being particularly pointed out in the claims at the end thereof.

It is common practice to coat articles by spraying with a. suitable coating material which usually contains an organic liquid, and the waste spray, that is the spray which does not adhere to the article being coated usually passes into a hood from which the spray laden air is evacuated. This is necessary to protect the workman. A large loss results, however, from such practice, since frequently only a small percentage of the total spray coating adheres to the article he ing coated and consequently a large part of the spray is lost. 1 This invention not only recovers the waste I spray in -a flow of coating compositionbut also leaves less impurities in the form of sprayed particles and volatile solvents in the hood to be removed by the ventilating sys form of plate for supporting a curtain of coating composition,

Fig. 5 is a perspective view of a work holding tray adapted for use with the coating machine, and i Fig. 6 is a diagrammatic view, partly front elevation and partly section of a battery of coating machines showing another embodiment of my invention.

As an example of my invention, I have shown a typical spraying hood 1 comprising a body portion 2, spraying opening 3 and a tapering top 4 from which the vent pipe 5 leads to a suitable air evacuating mechanism of any standard type. The apparatus may rest on a table 6 supported on legs 7.

Coming now to my invention, I provide a supply. tank 10 for a coating composition containing an organic liquid, which coating composition may be of any well known type. Tank 10 is preferably raised above the work opening 3 in hood 1 and may be supported on a bracket 11.

From tank 10 I provide a supply system divided into-two parts. One part includes a pipe 12 having a valve 13 and a distributing head. 14, this latter part here consisting of a pipe 15 having spaced apertures 16. The other part consists of a pipe 17 which is preferably flexible, supporting a spraying head, preferably a well known type of spray gun 18. A valve 19 controls the flow of coating composition. I

An angularly disposed plate 20 is mounted in the hood and this plate may have sides 21 and a top 22, the distributing head 14 lying near the top 22. When valve 13 is opened the coating composition will flow through apertures 16 down plate 20 thus forming a curtain C towards which the spray from gun 18 is directed. The flow may be controlled by valve 13 so that an even film or curtain of composition covers plate 20.

A recovery system is employed. A tray 25 receives the flow of coating composition from plate 20 and the bottom 26 is slanting towards a drain pipe 27 so that the composition may be again used. I prefer to have drain pipe 27 lead-to a pump 28 so that the recovered material will be returned to the supply tank -through pipe 29, filter 30 and pipe 31, since this not only replenishes tank 10 but keeps the coating composition continuously a itated by circulating through the systems a ove described and thus keeps the composition in ideal condition for use.

Referring to Fig. 3, it will be noted that the work W received only a comparatively small amount of the spray S directed towards it, and that the spray which does not adhere to the work, the waste spray, passes on and is entrapped in the curtain C of coating composition flowing down plate 20. By thus converting the spray back into the stream of coating composition, much less volatile solvent is released than is usually the case and practically none of the waste spray is carried from the hood through -vent 5, because the spray is projected with considerable force from gun 18 and quickly travels the short distance from the gun to the curtain. Thus much less evacuating power is required and the workman is correspondingly more fully protected from inhaling coating composition laden air.

Additional material may be added to tank 10 to replenish the supply of coating composition, and when necessary a volatile solvent may be added to reduce the viscosity of the composition. The short travel of the spra before it again is converted from finely divi ed droplets into the stream of coating composition, greatl lessens the surface exposed to the air an consequently the loss of volatile solvents is small. One skilled in the art can easily regulate the supply of coating composition to produce the best results for the wor at hand. e

In the first three fi ures the plate is mounted at a considera le angle to. the top 6 of the bench so that the curtain C which flows over plate 20 forms a target against which the spray S is directed when work W is held in front of the curtain. In Fig. 4 I have" illustrated another type of angularly disposed plate 40 which is particularly suitable for some ty es of work. Here the plate ma be provided with sides 31 and ends 32. distributing head 33 may consist of a pipe 34 having a series of apertures 35 through which the coating composition may pass so that it may flow in a curtain .0 across the plate 30. An inlet pipe 36 supplies pipe 34 at one end, at the opposite end of plate 30 there is an exit pipe 37. The plate 30 is mounted at an angle to the table top 6 resting on the block 38 atone end and a wedge 39 at the other, the inclination of the wedge being just suflicient to direct the coating composit1on in a smooth even flow across plate 30 to theexit pipe 37.

Ipre'ferably provide a basket mount such as a post 40 which may be supported by the plate 30 in position to receive a coupling 41 i on the bottom of a wire basket 42 which may be of any well known construction and which may support small pieces of work Wa. When spraying small pieces of work the spray is generally directed downwardly so that the unused spray passes through the wire mesh 43 of the basket and becomes entrapped in the curtain C.

So far I have described a typical spraying machine as consisting of a single unit. I

generally find, however, that it is preferable to provide a series of spraying units, as shown in Fig. 6, for this leads to certain economies; particularly facilitating cleaning, as will be hereinafter described.

In Fig. 6 there is shown a series of spraying cabinets 1 having the usual air exhaust pipes 5 leading to a main exhausting line 55. These cabinets are substantially alike, althrough I have here shown two of the cabinets as being provided with a circular opening 56 and two with a square front opening 57; the former type is useful when the curtain C is made to flow over an angularly disposed plate 20 which is mounted to receive spray directed substantially horizontally, while the latter type of opening 57 is chiefly used where the angularly disposed plate 30 is mounted to receive spray directed more nearly in a vertical direction. For the first two hoods the distributing heads 14 are similar to those described above in detail referring to Figs. 1 to 3 inclusive, and in the second two illustrated hoods the sprinkling heads 33 are similar to those described with special reference to Fig. 4.

The piping of the multiple system will now be described. A supply tank 60 is provided, and from this tank a pipe line 61 leads downwardly, being broken by a valve 62. From pipe line 61 lines 63 extend to each side to supply through pipes 64 the air brush lines 65. Valves 66 control the entrance of coating composition to pipe lines 64, and faucets 19 control the entrance of coating composition to the flexible connections 17 which lead to the air brushes 18.

- A second coating composition supply line 67 leads from pipes 61 to pipes 68, thus farnishing coating composition to the spraying heads 14 and 33, the individual spraying heads being controlled by valves 69. After the curtain C flows over the angularly disposed plates, the exhaust pipes 27 and 37 collect the coatin composition which then flows through pipes 0 to a pipe 71. which leads into a tank 72 divided into two parts, the upper part 73 carrying a screen 74 which filters the collected coating composition which flowsthrough into section 75 from which a pipe 76 leads to a power pump 7 7.- Pump 77 directs the coating material through pipe 78 past valve 7 9 into the top 80 of tank 60. v

It will be noted that pipe 78 is connected to pipe 61 b means of a pipe 81 in which there is a va ve 82 which is normally closed.

With the parts as a ove described, there is to time byreplenishing the supply intank 60 or filter tank 72.

Usually it is necessary to add .to tank 72 small quantities of a volatile solvent from time to time, and to occasionally replenish the supply of coating composition therein. I find, however, that with sprayingcabinets,

.as above described, there is a much less loss of volatile solvents than is usually the case, because, on account of the short travel of the spray'before it becomes entrapped in the curtain, the finely divided droplets are not carried off through the vent pipes 5 in large quantities. I have found it possible to reduce the flow of air through the vent pipes approximately 90%, (although it is to be understood that this and the following figures are given by way of illustration only) over the usual hood wherein the unused spray is carried out by the exhaust.

By thus reducing the quantity of exhausted air, the quality of the Work has been increased, so that for certain classes of Work the rejects have been around 3% where with the old type of machines about 15% of the Work was rejected. This improvement may be due to the fact that where a much greater air evacuation was necessary for the old type hoods, the dirt and dust from the floor and in the spraying room were drawn into the hoods through the openings in which the Work being sprayed was held, so that foreign matter. was thus accumulated while spraying process was going on.

I have found that with the curtain equipped spraying hoods that the air pipes 15 do not require to be cleaned every six or eight weeks as was prev ously required where the hoods were not equipped with such curtains. Since the quantityof coating which passes up into pipes 5 is practically negligible with the curtain equipped machines, the pipes 5 need to be cleaned only at very infrequent intervals.

With the pipe arranged as above described with reference to Fig. 6, the cleaning operation may be easily performed as follows:

After the days work is over the supply of coating composition from the air guns 18 is cut off by turning the faucets 19, and if desired, the valve 66 may also be turned to prevent further flow of coating composition into pipe 64, valve 62 is also turned off preventing further flow of coating composition into pipes 67 and 68, the valve 69 being left open so that the remaining coating composition may passfrom pipes 68 and will become exhausted, flowing over the angularly disposed plates-20 and 30. After the coating composition has passed from these plates through pipes 70 and 71 through basket 72, the pump 77 continues to operate until the coating composition in compartment 75 is exhausted bepump 77 is again set in motion and the cleaning fluid is circulated through pipes 78,

81, 67 and 68, distributing heads 14 and 33,

draining pipes 37 and 27 and thence to tank 72 through pipe 71. When the parts have thus been cleaned, valve 83 may be opened and valve 84 may be closed so that the cleaning fluid may be drawn off through pipe-85. During the cleaning operation the pipes 64 and 65 remain vfull of the coating composition, since no air can come in contact with the coating composition it will remain in workable condition for considerable time. At the infrequent occasions when it is necessary to clean these pipes, the supplv tank may be filled with cleaning fluid which may be circulatedthrough the various lines.

While I have described preferred embodiments of my invention, obviously numerous difierent arrangements of parts can be made without departing from the scope of my invention, and I claim as within the scope thereof all such embodiments as may come within the terms of the following claims.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

1. In a coating apparatus, a supply tank for coating composition, an angularly disposed plate, a pipe for supplying coating composition to the plate over which it may flow in a curtain, a pipe leading to a spraying head adapted to be directed towards the curtain whereby waste spray not adhering to an article being sprayed may be entrapped by the composition flowing over the angularly disposed plate.

2. In a coating apparatus, the combination with an angularly disposed member, ofa distributing member mounted to deliver a curtain of coating composition along the top thereof, a source of supply of coating composition, connections between the supply and distributing member, a spraying'head, connections between the supply and the spraying head, said spraying head being adapted to direct a spray against an article held between said head and said curtain whereby wva'ste spray may become entrapped by said curtain, means for collecting the coating com-- lot positions, connections between the supply and distributing member, a spraying head, connections between the supply and the spraying head, said spraying head being ada ted to direct a spra against an article hel between said hea and said curtain whereby waste spray may become entrapped 5 by said curtain, and means for returning the coating composition flowing from the curtain and containing said waste spray to the source of supply.

4. n a coatin a paratus, the combination with an angular y isposed member, of a distributing member mounted to deliver a curtain of coating composition along the top thereof, a source of supply of coating composition, connections between the supply and distributing member, a spraying head, connections between the supply and the spraying head, said spraying head being adapted to direct a s ray against an article held between said head and said curtain whereby waste spray may become entrapped by said curtain,

and means for collecting the coating composition flowing from said curtain containing wastespray, means for agitating the coating composition including a pump, and connections between said pump, coating composition collecting means and source of supply through which said pump may deliver the collected coating composition to the source of pp y 5. n a coating a paratus, the combination with a hood, 0 an angularly disposed plate therein, a source of coating composition, a pipe leading from said source to said plate adapted to furnish coating composition to flow over said plate in a curtain, a spraying head adapted to face said plate, a pipe connecting said source of supply and said spraying head, whereby an article held in front of said curtain may be sprayed, the waste s ray being entrapped by said curtain, and a rain alon an edge of said angularly disposed plate a apted to collect said coating composition.

6. In a coating a paratus, the combina tion with a hood, 0 an angularly disposed plate therein, a source of coating composition, a pipe leadin from said source to said plate adapted to urnish coating composition to flow over said plate in a curtain, a spraying' head adapted to face said plate, a pipe connecting said source of supply and said spraying head, whereby an article held in front of said curtain may be sprayed, the waste spray being entrapped by said curtain, a drain, a return system for carrying said coating composition collected by the drain into the source of supply.

7. In a spray coating, machine, the combination of a spraying chamber, a source of coating materlal, an angularly disposed plate adapted to support a curtain of coating comsystem adapted to deliver the coating composition from the spray and curtain to the source of materials and a by-pass and valve system connected to the supply and return pipes adapted to cut off the supply tank, permitting cleaning fluid to 'be circulated through parts of the return and supply system.

8. In a spray coating machine, the combination of a spraying chamber, a source of coating material, an angularly disposed plate adapted to support a curtain of coating composition, a spraying head, separate supply lines leading to the spraying head and plate, valves for controllin the flow of coating composition to these lines, a return piping system adapted to deliver the coating com- "position from the spray and curtain to the source of materials and a by-pass and valve system connected to the supply between the spraying head and the curtain and to the return pipe whereby the tank and spraying head may be cut off and the remainder of the system may be flushed out for cleaning.

9. In a spraying machine, the combination witha plurality of spraying chambers, of a tank adapted to contain a su ply of coating'composition, an angularly isposed plate in each chamber, a pipe line connected to the tank adapted to supply coating com position to the angularly disposed plates, a spraying head for each chamber, a pipe line adapted to supply each spraying head, said pipe line being connected to said tank, valves for independently permitting a flow of coating composition in the two pipe lines, a return pipe line adapted to deliver coating composition from the spraying head and the angularly disposed plate to the supply tank, a filterbeing located in the return line, and a by-pass located between the two supply ipe lines and the return pipe whereby cleaning composition may be flowed through one of the supply systems.

Signed at Rochester, New York, this 20th .day of January, 1927.

HARRY R. DARLING.

position, a spraying head, separate supply lines leading to the spraying head and plate, valves for controlling the flow of coating composition to these 1 nes, a return piping

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