US3717121A

US3717121A - Curtain coating head

Info

Publication number: US3717121A
Application number: US00045690A
Authority: US
Inventors: G Bruckbauer; M Corty
Original assignee: PPG Industries Inc
Current assignee: PPG Industries Inc
Priority date: 1970-06-12
Filing date: 1970-06-12
Publication date: 1973-02-20
Anticipated expiration: 1990-02-20

Abstract

A high speed uniform coating method may be carried out with the use of a curtain coating head comprising a means for dispersing coating material in a first of a laterally disposed succession of open reservoirs each reservoir disposed at a lower elevation than the next and the last reservoir terminating in a vertically disposed smooth continuous face plate containing two vertically disposed rods along the face and width of the face plate.

Description

United States Patent 1 Bruckbauer et al.

[ Feb. 20, 1973 [54] CURTAIN COATING HEAD [75] Inventors: Gerald J. Bruckbauer, Plainfield; Michael E. Corty, Matteson, both of 111.

[73] Assignee: PPG Industries, Inc., Pittsburgh, Pa.

[22] Filed: June 12, 1970 [21] Appl. No.: 45,690

[52] US. Cl ..1l8/324, l18/DIG. 4, 222/572 [51] Int. Cl ..B05c 5/00 [58] Field of Search ..1 18/324, 325, DIG. 4, 24;

[56] References Cited UNITED STATES PATENTS 3,271,184 9/1966 Poletika et al ..l18/D1G. 4

2,815,595 1/1958 Rosewall 15/306 2,884,898 5/1959 Peterson ....118/D1G. 4 3,293,063 12/1966 Pohl et a1 ..118/324 X 3,205,089 9/ 1 965 Kinzelman ..1 18/D1G. 4

Primary Examiner.lohn P. Mclntosh Att0rney-Chisholm and Spencer [57] ABSTRACT A high speed uniform coating method may be carried out with the use of a curtain coating head comprising a means for dispersing coating material in a first of a laterally disposed succession of open reservoirs each reservoir disposed at a lower elevation than the next and the last reservoir terminating in a vertically disposed smooth continuous face plate containing two vertically disposed rods along the face and width of the face plate.

7 Claims, 3 Drawing Figures PATENTEI] FEB20|973 L INVENTORS GERALD J. bfiucmuat MICHAEL E. with" OALLA M.

TT EYS CURTAIN COATING HEAD This application is related to a curtain coating head which may be used to provide high speed uniform curtain coating applications. The curtain coating head may be used to coat any type of flowable coating material so that it forms a continuous uniform film on the substrate at very high speeds.

As we now have processes for curing coatings which may be carried out at greatly increased speeds than we have had previously, a coating operation which may be carried out at the same high speeds as the curing operations is extremely desirable. Prior to the use of these high speed curing processes, the coating process was necessarily slow as for automated coating and curing lines as the coating and curing operations must be carried out at the same speed. Now with the use of radiation cure and other high speed curing processes, the coating industry has been searching for high speed coating operations.

Curtain coaters have been frequently used in high speed coating applications but involve many problems. In a curtain coating operation, the coating picks up air as the coating material is coated on to the substrate and during the recycling process air bubbles form in the coating and as the coating hits the substrate, the areas where air bubbles have formed will produce bare or uncoated spots on the substrate and, hence, a very nonuniform film will be produced. Although the coating process may be slowed down to prevent some of the air bubbles from forming, the coatings produced still tend to be somewhat non-uniform due to the air bubbles in the coating.

According to this invention, a new curtain coating head has been designed which deairates the coating such that high speed curtain coating operations may be carried out to produce uniform coatings. As the air in the coating is forced out, no air bubbles appear in the coating material and smooth coatings may be produced on high speed lines such as conveyor belts used to convey panel and sheet substrates to the coating zone and then on to the curing zone. In this manner, the coating operation can be carried out at the same speed as the curing operation which will optimize the process as well as reduce the space ordinarily required for the process.

The curtain coating head may be readily and clearly understood by reference to the drawing which is a perspective view of the curtain coating head. In FIG. 1 of the drawing numeral 1 refers to the curtain coating head in general. The head comprises a means 2 for dispersing coating material in a first reservoir 6 which is disposed above a succession of lower reservoirs such as 9. The last of said reservoirs terminating in a vertically disposed smooth continuous face plate 16 which supports two vertically disposed

rods

17 and 18.

The means for dispersing coating material may be any apparatus designed to flow the coating material into the first reservoir 6. The preferred means is a foraminous enclosed conduit containing an inlet. The conduit 2 is preferred to be cylindrical, although any shaped conduit will be operable. The conduit has an inlet 3 through which the coating material is directed to the conduit. The inlet 3 is preferably centered along the length of the conduit. In order to maintain an even flow of coating material from conduit 2, the openings 4 are spaced along a straight line and the spacing between opening to opening is greater toward the center of the conduit as shown in FIG. 2 of the drawing. Alternatively, the openings may be spaced equidistant from one another but with the openings at a greater distance from the center of the conduit being larger than those toward the center of the conduit as shown in FIG. 3 of the drawing.

In the preferred embodiment of this invention, the conduit 2 is centrally mounted within the first reservoir 6.

First reservoir 6 has two opposite sides 7 and 8 of which side 7 is higher than side 8. The other two sides of reservoir 6 are approximately equal in height to side There then follows a succession of reservoirs disposed at successively lower elevation than that of reservoir 6 wherein each successive reservoir has two opposite sides of which one side is of lesser height than the other and the side of lesser height forms a common wall with the side of the next reservoir which is of greater height than its opposite side.

Hence, reservoir 9 is the next lower reservoir from reservoir 6 and side 11 of reservoir 9 forms a common wall with side 8 of reservoir 6. The opposite side of side 1 l of reservoir 9 is side 12 which is of lesser height than side 11. The other walls of reservoir 9 are of approximately equal height with wall 1 1.

There may be as many successive reservoirs as desired each being disposed with the same relation as those of reservoirs 6 and 9. Although the drawing illustrates apparatus wherein there are at least three succeeding reservoirs after reservoir 6, it is possible to use only one reservoir under reservoir 6. In such case, reservoir 13 would be disposed as reservoir 9 is depicted in the drawing and would be the last reservoir.

The last reservoir 13 has

opposite sides

15 and 14 of which side 15 is of greater height than side 14 and wherein the other sides are approximately equal in height to side 15. Side 14 of the last reservoir 13 terminates in a vertically disposed smooth continuous face plate 16. The face plate must be perfectly smooth. For this reason, it is preferred that the plate be polished metal such as steel, however any smooth continuous material may be used as the face plate. The face plate must be at least as wide as side 14 of the last reservoir and is preferably wider. The top of the face plate should be the same height as that of side 14 of reservoir 13 and the face plate should extend below the height of the bottom of reservoir 13. The face plate must be at an approximately degree angle with the'ground level.

The thickness of face plate 16 may vary widely but the preferred plate is very thin. The top of the face plate 19 is also smooth and continuous.

Face plate 16 supports two

rods

17 and 18 which are vertically disposed along the face of plate 16. The rods hang vertically from the face plate and parallel to one another. The distance between the rods should be the same as the length of side 14 of reservoir 13 and should be positioned so that each rod will follow the two corners of side 14.

Rods l7 and 18 should extend at least as low as and preferably lower than face plate 16. There is no preferred length for the rods as long as they extend beyond the bottom of face plate 16.

The rods may be any thin material such as wire, chain, etc. Although they may be composed of any material, it is preferred to use thin metal rods. The

rods

17 and 18 should also be positioned across the top 19 of the face plate at a 90 angle from the position at the face of the plate. In this way the coating material is directed over the top of the face along the face plate and on to the substrate.

The excess coating material is caught in trough 24 and may be pumped back to paint vat 20 and recycled through the coating head.

In the operation of this device, a coating composition 5 stored in vat 20 is pumped through tube 21 to the inlet 3 of the means for dispersing 2. The vat 20 may be any shape as long as it is capable of storing the coating composition 5. Any method of pumping or transporting the coating composition from vat 20 to inlet 3 may be used.

The coating material 5 may be any flowable composition which may be used as a coating on various surfaces. The best results are naturally obtained when the coating composition is a liquid which is not viscous, although high viscosity materials may also be used.

The coating composition flows through the openings 4 of the conduit 2 into first reservoir 6. The coating composition fills reservoir 6 to the height of side 8 of the reservoir and overflows straight down side 8 of reservoir 6 to side 11 of reservoir 9. The coating is then flowed over side 12 of reservoir 9 into the next reservoir. The coating is thus transported down from reservoir to reservoir until it reaches side 15 of last reservoir 13. This flowing action has the effect of deairating the coating so that the coating composition will contain few air bubbles.

Coating material 5 then tumbles over side 14 of last reservoir 13 and on to the top 19 of face plate 16. The coating composition is guided over the top down to the face of face plate 16 by

rods

17 and 18 and flows straight down the face of plate 16 between the

rods

17 and 18. In this manner, the coating material 5 is substantially deairated and hence will form a smooth continuous coating on substrate 23.

Under the face plate 16, a conveyor 22 moving at high speed carries substrates 23 to be coated with coating material 5. The substrate to be coated may be any material such as wood, paper, metal, plastic, etc. It may also be in any form such as coil or sheet form or in the form of panels as depicted in the drawing.

Generally the distance between

rods

17 and 18 is wider than the substrate 23 to be coated. The coating material is guided through

rods

17 and 18 on to the substrate 23. Thus, generally, the

rods

17 and 18 will terminate directly above the substrate by only a few inches or if the distance between the rods is greater than the width of the substrate the rods may terminate high rate of speed through a curing zone. In this manner substrate 23 is coated quickly and uniformly.

While the invention has been described with respect to certain embodiments and details thereof, it is not intended to be limited to such details except insofar as they appear in the appended claims.

We claim:

1. A curtain coating head comprising a means for dispersing coating material in a first of a laterally disposed succession of elongated upwardly open channel-shaped reservoirs each successive reservoir disposed at a successively lower elevation than said first reservoir and wherein each successive reservoir has two opposite sides of which one side is of lesser height than the other and the side of lesser height forms a common wall with the side of the next reservoir which is of greater height than its other side and wherein the last of said reservoirs tenninates in a vertically disposed smooth continuous face plate which extends lower than the last of the said reservoirs and which supports two vertically disposed rods along the face of said smooth continuous face plate, said rods extending lower than said face plate.

2. The curtain coating head of claim 1 wherein the means for dispersing coating material is a foraminous enclosed conduit containing an inlet.

3. The curtain coating head of claim 2 wherein the foraminous enclosed conduit is centrally mounted in the first reservoir.

4. The curtain coating head of claim 2 wherein the inlet on the conduit is in the center of the length of the conduit and the openings in the conduit are spaced along a straight line and wherein the spacing from opening to opening is greater toward the center of the conduit.

5. The curtain coating head of claim 2 wherein the inlet of the conduit is in the center of the length of the conduit and the openings in the conduit are spaced equidistant from one another with the openings located at a greater distance from the center of the conduit being larger than the openings closer toward the center of the conduit.

6. The curtain coating head of claim 1 wherein the two vertically disposed rods along the face of the face plate also extend perpendicularly across the thickness of the upper edge of the face plate.

7. The curtain coating head of claim 1 wherein the face plate is a polished metal material.

Claims

1. A curtain coating head comprising a means for dispersing coating material in a first of a laterally disposed succession of elongated upwardly open channel-shaped reservoirs each successive reservoir disposed at a successively lower elevation than said first reservoir and wherein each successive reservoir has two opposite sides of which one side is of lesser height than the other and the side of lesser height forms a common wall with the side of the next reservoir which is of greater height than its other side and wherein the last of said reservoirs terminates in a vertically disposed smooth continuous face plate which extends lower than the last of the said reservoirs and which supports two vertically disposed rods along the face of said smooth continuous face plate, said rods extending lower than said face plate.