US3029778A

US3029778A - Coater

Info

Publication number: US3029778A
Application number: US750922A
Authority: US
Inventors: Kaplan Robert; Edward N Sienko
Original assignee: M S KAPLAN Co
Current assignee: M S KAPLAN Co
Priority date: 1958-07-25
Filing date: 1958-07-25
Publication date: 1962-04-17
Anticipated expiration: 1979-04-17

Description

April 17, 1962 R. KAPLAN ET AL COATER Filed July 25, 1958 Eoberf [fa Dian Edward M fi/ienlw Q ,4 HZZHE 7&

United States Patent Ofilice 3,029,778 COATER Robert Kapian, Chicago, and Edward N. Sienlro, Clarendon Hills, 11L, assignors to M. S. Kaplan Company, a corporation of Illinois Filed .luly 25, 1958, Ser. No. 750,922 4 filaims. (til. 113-67) The instant invention relates to a coater, and more particularly, to a device for continuously coating a travelling sheet.

Although the instant invention may have application in a number of arts, it is particularly useful in connection with the coating of a travelling sheet of metal by the application of a plurality of coatings or films thereto. The instant invention employs a plurality of superimposed ovens which are used to evaporate volatile material from the coating and fuse the same. Means are provided for exhausting hot gases from a lower oven and discharging the gases into the next uppermost oven, so that heat economy is obtained. In addition, guide means are provided for suitably reversing the sheet in direction so that it will make a plurality of passes through the superimposed ovens. At the entrance of each oven coating means are provided for applying a coating and at the exit of each lower oven there is provided cooling means which reverse the direction of sheet travel and feed the sheet back between the ovens to a second coating means mounted at the entrance of the next uppermost oven.

The instant coating means are unique in that they afford a high speed coating device for continuous coating of a sheet. The instant coating means also permits the application of a plurality of successive coatings, with removal of volatile material from each prior to the application of the next coating. The instant coating device also provides for a superior handling arrangement for guiding the sheet through successive ovens.

It is, therefore, an important object of the instant invention to provide an improved coating device.

It is another object of the instant invention to provide an improved device for coating a travelling sheet, which comprises superimposed upper and lower ovens, means ex hausting hot gases from the lower oven and discharging the gases into the upper oven, first coating means applying a coating to the sheet and feeding the coated sheet into the lower o-ven, second coating means applying a coating to the sheet and feeding the coated sheet into the upper oven, and a cooled turning roll receiving the coated sheet from the lower oven and feeding the coated sheet back between the ovens to said second coating means.

Other and further objects, features and advantages of the present invention will become apparent to those skilled in the art from the following detailed disclosure thereof and the drawings attached hereto and made a part thereof.

In the drawing, the device of the instant invention, indicated generally by the reference numeral 10, is shown in side elevational view, with parts shown in section, parts broken away and parts shown diagrammatically.

The device 1!} coats a travelling sheet S of carbon steel, aluminum or the like metal which is a relatively thin flexible sheet of such metal that may be unwound from suitable unwind means (not shown) and fed into the device 10. The device comprises superimposed upper 12 and lower 13 ovens. As is indicated, the upper oven 12 has a lower heating section 14 which may be in the form of a plurality of sections of gas burners 14a, 14b and 140, that are separated from the interior of the oven by a floor plate 15. The floor plate 15 mounts baffies 16a, 16b, 16c, 15d, etc. and the front side wall 17 and the rear side wall 18 are provided with air inlets such as at 17a and at 18a, 18b, etc. for permitting air to how into the interior of the oven 12 above the floor plate 15. The inward flow of air is circulated by virtue of the baflles 16a, 16b, etc., so that the air is heated by 21 in which

exhaust ducts

22 and 23 are mounted for drawing exhaust air and hot gases out of the oven 12, via

blowers

24 and 25, to a stack (not shown). It will thus be seen that fresh inlet air is swept up from the bottom of the oven 12 past the travelling sheet S and out the

exhaust ducts

22, 23 so as to remove volatile matter in the coating on the sheet S. The fresh incoming air is heated by heating means such as the burners 14a, 14b, 140, which may be gas or oil burners.

The lower oven 13 has a similar structure. The lower oven 13 is also provided with burner sections 31a, 31b, 31c separated from the furnace interior by a floor plate 32 mounting baflles 33. The sheet S enters the furnace 13 through an entrance wall 34 and exits through an exit wall 35 that is slotted at 35a. The front side wall 36 and the back side wall 37 are provided with inlet air apertures as at 36a, 3619, so that air may enter and be circulated past the bafiles 33 and heated, via the floor plate 32, by the heater 31a, 31b, 310. This air then passes upwardly past the sheet S removing volatiles therefrom and, if desired, fusing the coating onto the sheet S. The top wall 38 of the oven 13 is provided with an exhaust duct 39 feeding into a blower 40, which exhausts hot gases from the lower oven 13. The blower 40 feeds into

parallel headers

41, 42 along opposite sides of the upper oven 12 and from there feeds into the interior of the upper oven 12 through discharge ducts 41a, 41b, 410, etc. connected to the header 41 and discharge ducts such as the duct 42a connected to the header 42 on the .back side of the oven 12. The hot gases leaving the oven 13 are very much unsaturated with volatile matter, so that they are capable of removing additional volatile matter and they also possess a high B.t.u. content. The addition of this B.t.u. content to the system of the oven 12 materially reduces the B.t.u. input for the oven 12 required by the burners 14a, 14b, 140. In actual practice a saving of 40% of the B.t.u. requirement for the oven 12 is obtained by this arrangement.

The instant invention also contemplates a unique guide system for sheet S so that it may be fed through the ovens 12 and 13 in the desired manner; it may be cooled at the desired point in its travel to below the fusion temperature of a coating thereon; and so that the sheet may properly be wrapped around backup means for the coating means, which will be described. Following the travel of the sheet S through the device 10, it will be noted that at the lower right hand corner of the drawing the sheet is taken from unwind means (not shown) and passed through a nip between a bridle roll 50 and a rubber covered snubber roll 51. The bridle roll 50 is a rubber covered roll also and the travelling sheet is reversed in direction as it wraps around the bridle roll 50. The travelling sheet 3 is again reversed in direction as it wraps around the following backup roll 52, which is also a rubber covered roll. The bridle roll 50 and the backup roll 52 are preferably coordinated so as to drive the sheet S at this point. A rubber covered coating roll 53 also defines a nip N-1 with the backup roll 52, so that it may function as a snubber roll and also to apply coating material which is furnished to the coating roll 53 by a furnish- Patented Apr. 17, 1962.

ing roll 54 rotating in a dip pan 55 carrying a level of coating material therein. The coating material here applied is preferably a thin subcoat indicated by the reference letter c. As applied to 18 gauge SAE 1010 carbon steel sheeting, the subcoating c is applied in the form of concentrated (75%) mineral spirits solution of polyvinyl chloride in an amount sufiicient to deposit a dried resin film on the sheet S at the exit of the oven 13 of 0.0005 inch thickness. The lower oven 13 is approximately 60 feet long and the sheet S travels therethrough at a rate of approximately 100 feet per minute. The blower 4d circulates 11,500 cubic feet per minute of air which is heated to 650 F. in the oven 13. The polyvinyl chloride resin film thus formed is heated at least briefly to about 350 F. so that it may fuse. It is converted only momentarily to a viscous liquid and does not have an opportunity to flow freely off the sheet S, but rather it consolidates the film into a coherent uniformly thick resinous film.

At the exit of the furnace 13 the sheet S is air cooled to some extent and the coated side or top side thereof is brought into contact with a water cooled turning roll 56 provided also with a water cooled snubber roll 57. The turning roll 56 is supplied with cooling water in a conventional manner, as will be appreciated by those skilled in the art, and as shown somewhat schematically by the cooling water supply line 56a. The water cooled turning roll 56 immediately reduces the hot subcoating c to less than its fusion temperature and this subcoating c is thus carried on the underside of the she S as it passes back between the ovens 12 and 13 and .rp to a second backup roll 58 which is wrapped by the uncoated side of sheet S. The backup roll 58, of course, again reverses the direction of the sheet S again turning the coated side to the top side. A second coating roll 59 defining a nip N-2 with the backup roll 58 applies additional coating material C to the subcoated surface of the sheet S. A furnish roll 60 rotating in a dip pan 61 picks up coating material from the dip pan 61 and applies it to the coating roll 59. The coating roll 59 is also a rubber covered roll which acts as a snubber for the reversal of the sheet direction and the sheet again travels in a generally horizontal plane through the upper oven 12.

Preferably, the coating C at the second coating station 58, 59 is applied so as to obtain a dried coating thickness of 0.005 inch. The coating material is the same material as that used in the application of the subcoating c. The oven temperatures 12 are preferably maintained at about 650 F. throughout the main portion of the oven 12., and the

blowers

24 and 25 circulate 11,500 cubic feet per minute of gases.

At the exit of the oven 12 cooling means indicated dlagrammatically at 62 (such as a water spray) are preferably employed to return the coating C to temperatures below the fusion temperature thereof. The fusion temperature is about 350 F. and this temperature is reached within the oven 12 so as to obtain uniform coherent flowing of the upper layer C over the subcoat c and so as to obtain mutual fusion therebetween. The resulting coating is distinctly superior in adherence.

In controlling the temperature of the coatings c and C, it will be noted that the instant device has a distinctly superior arrangement. For example, the initial coating is applied at the first nip N1 at substantially room temerature so as to avoid any premature volatilization of the carrier or mineral spirits. Within the oven 13 complete volatilization of the carrier is obtained and fusion of the coating 0 takes place. The fused coating 0 is quickly cooled at the exit of the lower oven 13, particularly by the water cooled turning roll 56, so that a temperature below the fusion temperature of the subcoat c is obtained and this coating is not disturbed during its travel back between the ovens 12 and 13. The subcoating c is, however, cooled to approximately room temperature by normal air circulation during its travel between the turning roll 56 and the second backup roll 58. In this way uniform application of coating at the second nip N-Z is accomplished without premature volatilization of the carrier or mineral spirits. Once the coating C has been uniformly applied (again to the top side of the travelling sheet S) the sheet passes into the oven 12 and the desired volatilization of the carrier takes place. It is important to note that it is necessary to cool the subcoat c before applying the final coating C and this would ordinarily require a substantial loss in B.t.u.s. This loss in B.t.u.s is, however, minimized by the removal of hot gases from the oven 13 and discharging of such gases into the oven 12. This is made possible through a minimum of duct work 39, 4t}, 41, and 4-2, so that heat losses are reduced at this point also and the maximum amount of B.t.u.s withdrawn from the oven 13 is recovered or retained for use in the oven 12. In addition, moving the sheet S through open air between the ovens 12 and 13 affords inexpensive cooling of the sheet S as it approaches the second coating nip N-Z.

It will be understood that modifications and variations may be effected without departing from the spirit and scope of the novel concepts of the present invention.

We claim as our invention:

1. A device for coating a travelling sheet which comprises superimposed upper and lower ovens with a vertical space between them each having a head end and a discharge end with the respective ends adjacent so that the sheet travels in the same direction in each oven, means exhausting hot gases from the lower oven and discharging the gases into the upper oven, a first coating teans at the head end of the lower oven applying a coating to the upper surface of the sheet and feeding the coated sheet into the head end of the lower oven, second coating means at the head end of the upper oven applying ,a coating to the upper surface of the sheet and feeding the coated sheet into the head end of the upper oven, a cooled turning roll positioned at the discharge end of the lower oven receiving the coated sheet from the discharge end of the lower oven and engaging said upper surface to directly cool the coating on the surface, said sheet extending in said vertical space between said turning roll and said second coating means so that the coated surface of the sheet will face upwardly in passing through each of the ovens, and means for cooling said turning roll.

2. A device for coating a travelling sheet which comprises superimposed upper and lower ovens with a vertical space between them each having a head end and a discharge end with the respective ends adjacent so that the sheet will travel in the same direction through each of the ovens, means exhausting hot gases from the lower oven and discharging the gases into the upper oven, first coating means at a first coating station at the head end of the lower oven applying a coating to one side of the sheet and feeding the coated sheet into the head end of the lower oven, a back-up roll at a second coating station positioned at the head end of the upper oven and feeding the coated sheet into the head end of the upper oven, a coating roll in nip-defining relation with the back-up roll at the second station engaging said one side of the sheet and applying a coating to one side of the sheet, and a cooled turning roll positioned at a discharge end of the first oven with the sheet carried on the surface thereof, said sheet extending from the turning roll to the back-up roll in said vertical space between the ovcns so that the coated side of the sheet will face the same direction while moving through each of said ovens.

3. A device for coating a travelling sheet which comprises superimposed upper and lower ovens with a vertical space between them each having a head end and a discharge end with the respective ends adjacent so that the sheet will travel in the same direction through said ovens, conduit means extending directly from the lower oven to the upper oven and exhausting hot gases from the lower oven and discharging the gases into the upper oven, first and second coating nips respectively positioned at the head end of the lower and upper ovens and applying a coating to one side of the sheet, cooling means positioned at the discharge end of the lower oven and cooling the coated side of the sheet, said sheet extending from the discharge end of the first oven through said vertical space between said ovens to said second coating nip so that the coated side of the sheet will face in the same direction passing through each of said ovens.

4. A device for coating a travelling sheet which comprises superimposed upper and lower ovens each having a head end and a discharge end with the respective ends adjacent each other and with a vertical space between said ovens, means exhausting hot gases from the top of the lower oven discharging the gases into the bottom of the upper oven, first heating means in the bottom of the lower oven, second heating means in the bottom of the upper oven, means feeding air into each of said ovens to remove volatile material from a coating on the sheet travelling through the ovens, a bridle roll at the head end of the lower oven reversing the direction of sheet travel, a first back-up roll receiving the sheet from the bridle roll and again reversing its direction of travel and positioned at the head end of the lower oven and feeding the sheet generally horizontally into the lower oven above said first heating means, a first coating roll in nipdefining relation with the first hack-up roll applying coating material in a volatile carrier to the top side of said sheet, a cooled turning roll at the discharge end of the lower oven engaging the top coated surface of the sheet at the exit of the lower oven and reversing the direction of sheet travel, said sheet extending in said vertical space between said ovens to the head end of the upper oven, a second back-up roll engaging the uncoated side of the sheet and positioned at the head end of the upper oven reversing the direction of travel of the sheet and feeding the sheet generally horizontally into the head end of the upper oven above said second heating means, and a second coating roll in nip-defining relation with the second back-up roll applying a coated material in a volatile carrier to the top side of the sheet superimposed on the coating applied by said first coating roll, said sheet having its coated top side facing upwardly in both of said ovens.

References (Jited in the file or" this patent UNITED STATES PATENTS 1,837,682 Searight Dec. 22, 1931 1,989,455 Loomis Jan. 29, 1935 2,450,681 Muench Oct. 5, 1948 2,629,940 Runton et al. Mar. 3, 1953 2,647,842, Griesheirner et al Aug. 4, 1953 2,679,086 Andrews May 25, 1954 2,813,041 Mitchell et a1 Nov. 12, 1957 2,851,372 Kaplan et al. Sept. 9, 1958