US3783823A

US3783823A - Film thickness control apparatus

Info

Publication number: US3783823A
Application number: US00142927A
Authority: US
Inventors: W Sievert; W Carter; J Munson
Original assignee: Inland Steel Co
Current assignee: Inland Steel Co
Priority date: 1971-05-13
Filing date: 1971-05-13
Publication date: 1974-01-08
Anticipated expiration: 1991-01-08
Also published as: CA991928A

Abstract

A coating system for a continuous strip comprising a roller means station and an air knife station spaced from and vertically above the roller means station with a fluid depositing means located between the roller means station and air knife station.

Description

United States Patent 1 Sievert et a1.

[ Jan. 8, 1974 FILM THICKNESS CONTROL APPARATUS [75] Inventors: William C. Sievert, Chesterton;

William A. Carter, Gary; James L. Munson, Highland, all of Ind.

[73] Assignee: Inland Steel Company, Chicago, 111. 22 Filed: May 13, 1971 21 App1.No.: 142,927

[52] US. Cl 118/63, 118/325, 118/415 [51] Int. Cl. B05c ll/06, B05c 5/00 [58] Field of Search 118/63, 415, 21,

[56] References Cited UNITED STATES PATENTS 1,604,941 Hofmann 1 18/63 X 1/1946 Groncy 118/415 2,393,502 2,583,220 1/1952 Lanigan 117/64 R FOREIGN PATENTS OR APPLICATIONS 807,805 1/1959 Great Britain 118/63 Primary ExaminerJohn P. McIntosh Attorney-Merriam, Marshall, Shapiro & Klose [5 7] ABSTRACT A coating system for a continuous strip comprising a roller means station and an air knife stationspaced from and vertically above the roller means station with a fluid depositing means located between the roller means station and air knife station. I

10 Claims, 1 Drawing Figure msmwm 8M4 3.783.823

IIIIIIIII'I'III INVENTORS.

' WILLIAM C. SIEVERT WILLIAM A.CARTER JAMES L. MUNSON 771W WW ATTORNEYS.

1 FILM THICKNESS CONTROL APPARATUS In the coating of strips of material such as metal, it is often desired to coat one side of the material without coating the other side. For example, in the process of galvanizing metal, a continuous metal strip is coated on one side with a material which will prohibit any galvanizing-occurring on that side of the material. Subsequently, the strip is subjected to a hot dip galvanizing step which will coat one side of the strip with zinc but will not coat the previously coated side of ths strip.

Often the coating fluid or materials will have low viscosities (essentially water) such that the problem of preventing the fluid from wrapping around the side of a strip opposite to the side which is to be coated is quite significant.

Moreover, it is important to regulate the thickness of the coating material that is deposited on a metal strip so that a uniform fluid coating is deposited on the strip.

In our pending U.S. Pat. application S.N. 91,914 filed Nov. 23, 1970 now U.S. Pat. No. 3,716,019, we have disclosed a method and apparatus for providing a coating system which permits uniform coating of a strip with a fluid, including those having low viscosities, with no fluid wrap around. While this system, which includes the roller coating of fluid, has a number of advantages over the prior art, it is limited in certain respects to line speeds that are tolerable with a roller coating system.

What is desired is to increase the line speed of a strip which is to be coated, In some instances, depending upon the viscosity of the coating material, it is possible to operate at line speeds of approximately 500 to 600 feet per minute. If this line speed is increased to 1,000 feet per minute and higher, a drawback exists in that, when coating with a system which includes rollers which regulate provide a uniform coating of fluid, an increase in line speed causes a corresponding increase in the speed of the rollers to such an extent that coating fluid is thrown off the coating rollers before it is deposited on the strip. The result of this increased centrifugal force is that a non-uniform coating is deposited on the metal strip.

Further, in some instances, it is necessary to deposit the coating material on the top side of the strip only without wrap around to the bottom side of the strip because as the strip passes beyond the coating station, it often will pass over rollers would remove or affect the uniformity of a fluid coating that had been deposited on the bottom side of the strip. Accordingly, in these instances, it is important that the metal be coated on the top side of the strip.

In order to obviate deficiencies with conventional systems presently used and to increase the line speed of a continuous metal strip, it is desired to employ an air knife coating system. However, in order to use an air knife system such as exemplified in U.S. Pat. Nos. 3,117,847 and 2,583,220, it is necessary to have the coating material spread entirely across the width of the metal strip without any wrap around of the coating material to the opposite side of the strip prior to the strip passing under the air knife. Additionally, the coating system must be able to prevent wrap around when a fluid, including those that have low viscosities (essentially water), are used in coating the strip.

SUMMARY OF THE INVENTION It has been found that if a fluid depositing station is suitably placed between an air knife means and a roller whereby a coating material can be deposited on a strip prior to the strip passing to the air knife station such that there is a gravity flow-back of the material to the roller in a direction opposite the movement of the strip, the strip can be properly treated without any wrap around prior to reaching the air knife station. At the air knife station, an air knife can be employed to regulate the coating to provide a uniform fluid coating on the strip.

As a result, a strip can be coated on one side only with fluids, including those of low viscosities, at a line speed significantly increased over those presently available.

Accordingly, the invention disclosed and claimed herein relates to the uniform coating of a continuous strip of material without wrap around in which high line speeds can be utilized in association with a new, novel .and unobvious association of an air knife and a fluid coating station located on the upstream side of the air knife station.

The system involves initially passing a continuous strip under a first roller located upstream of an air knife station. The roller is positioned vertically below the air knife station so that a strip will be angled upwardly toward the air knife station after it passes the roller.'Be-

tween the first roller and air knife station there is located a fluid dispensing or depositing means which releases fluid onto the surface of the strip. The fluid as it contacts the strip, flows by gravity back toward the first roller where a damming action occurs at the nip or interface of the entry roller and strip. The fluid is spread out across the entire width of the strip and the roller which applies sufficient tension to thestrip so that the fluid, as it reaches the side of the strip, will be squeezed off the strip and fall into a collecting pan positioned below the strip without wrapping around the strip.

As the coated strip passes downstream to the air knife station, the air knife provides for a uniform fluid thickness with any excess fluid being squeezed or forced out and away from the strip so'that fluid wrap around does not occur.

The system also includes a second downstream, backup roller which serves to assist in providing the necessary tension in the strip between the two rollers.

Other features and advantages are inherent in the structure claimed or disclosed and will become apparent to those skilled in the art from the foregoing detailed description in conjunction with the accompanying diagrammatic drawing.

DESCRIPTION OF THE DRAWING The drawing discloses a fragmentary side view of a portion of a continuous strip situated relative to the strip coating system of the present invention.

DESCRIPTION OF THE EMBODIMENT Referring to the drawing, there is shown acontinuous strip 10 which is to be coated with a fluidon one side of the strip only. As strip 10 progresses towards air knife station 12, it initially passes under entry roller 14 and under fluid depositing station 16. I I

As strip 10 travels through the line, fluid depositing means 15 is actuated to deposit fluid on the strip. The

fluid is deposited on inclined strip in such a manner that the fluid will flow back, by gravity, toward entry roll 14 where it will dam up at the strip roller interface 19. The damming action causes the fluid to spread out over the entire width of the strip. At the edge of the strip, the fluid, because of the pressure at the interface of roll 14 and strip 10, will not wrap around the strip but will be squeezed away or forced outward from the edges of the strip sufficiently to prevent the fluid from being drawn onto the bottom side of strip 10 where no coating is desired. The excess fluid is permitted to drip into one or more fluid collecting pans 8 located below each edge of the strip. The fluid drippage occurs approximately one-half inch away from the respective edges of the strip.

Roller 14 must be level and not tilted transversely for a slight tilt of roll 14 will cause a fluid coating to wrap around to the bottom surface of strip 10.

As the strip leaves the area of roller 14, it passes under fluid dispensing station 16 where additional fluid is deposited on the strip such that as strip 10 passes downstream of station 16, an uneven coating of fluid is dispensed on the top side 21 of strip 10. However, as strip 10 continues further downstream, it passes under air knife which comprises a slotted member 32 which extends transverse to, at least, the entire width of strip 10. The slot is preferably about 0.03 inches in width.

Air knife 30, which dispenses a suitable gas, such as air, is employed to regulate and provide for a uniform coating thickness across the entire width of strip 10. The air knife is preferably located immediately above and in axial alignment with roller 18, however the air knife may be positioned at a location between the fluid depositing means and the roll 18. This assures that at the location of film regulation by knife 30, the strip is flat across its entire width. The distance between the nozzle and the strip in addition to the strip speed, air knife slot opening,'pressure of the gas exiting from slot 21 all affect the regulation of the thickness of the film to be deposited on the strip. By adjusting one or more of these variables, the desired coating thickness can be procured. Any excess coating is forced away from the edges of the strip so that no wrap around of the coating fluid occurs at the air knife station. The excess fluid forced away from the edges of strip 10 will be deposited in pan 8. Because the initial coating of the strip has already occurred at roller station 14, the final regulation of the fluid thickness so as to procure a uniform coating thickness is readily accomplished at air knife station 16.

in carrying out the fluid coating operation of the present invention, it is necessary that the strip, at least between interfaces l9 and 31, be under tension to make certain that strip 10 is wrapped on roller 14 along the entire width of the strip. This will assure that coating fluid is deposited across the entire width and additionally will permit the use of strips, which have a wavelike configuration, because at the point where the strip contacts roller l4, the strip will be flat across its entire width.

Rollers l4 and 18 are adjustable vertically and h0rizontally. The rollers need not be independently driven but rather can turn at the same speed as the strip passing through the system. The rollers are adjusted relative to each other so that a downward angle a exists between the strip in a substantially horizontal position and the inclined position of the strip between the interfaces 19 and 31. Angle a must be sufflcient to permit gravity feed back of the fluid whereby fluid deposited on strip 10 at station 16 feeds back to roller 14. While it hasbeeiifixundflfat fiafigi'fifapp'roxifnately 10 has been satisfactory in one application, the angle will depend upon the viscosity of the fluid being deposited on strip 10. Further the flow rate of the fluid from dis pensing means 16 should also be controlled to avoid excessive damming at the roll-strip interface.

The foregoing detailed description has been given for simplicity and cleamess of understanding only and no unnecessary limitations should be understood therefrom as modifications will be obvious to those skilled in the art.

What is claimed is:

1. Apparatus for depositing fluid on a strip, said apparatus comprising:

a first entry damming roll means adapted to be positioned above and contiguous to a strip to be coated, for providing a dam at the interface of a strip to be coated and said roll;

a second exit roll means located downstream of and adapted to be positioned below and contiguous to a strip to be coated;

the uppermost surface of said second roll means being higher than the lowermost surface of said first roll means whereby a strip to be coated is inclined upwardly from said first roll means to said second roll means;

a fluid depositing means positioned downstream of said first roll means and between said first roll means and second roll means;

an air knife means for providing a uniform fluid coating on a strip to be coated, said air knife station being positioned at a location from a point adjacent said fluid depositing means to a point above said second roll means; and,

said fluid depositing means and air knife means being positioned on the same side of a strip to be coated as said first roll means;

whereby fluid which is adapted to be deposited on said strip is dammed at the interface of said first damming roll means and a strip to be coated.

2. The apparatus of claim 1 wherein said first roll means is adjustable both vertically and horizontally.

3. The apparatus of claim 1 wherein said second roll means is adjustable both vertically and horizontally.

4. The apparatus of claim 1 wherein said air knife means is positioned above and in axial alignment with said second roll means.

5. The apparatus of claim 1 wherein said first roll is substantially level and free of tilting transversely.

6. Apparatus for depositing fluid on a strip, said apparatus comprising:

a first entry damming roll adapted to be positioned above and contiguous to a strip to be coated for providing a darn at the interface of a strip to be coated and said roll whereby a coating fluid can be deposited across the entire width of a strip to be coated;

said first roll being adapted to exert sufflcient pressure at said interface whereby a fluid will be spread across the width of a strip and at the side of the strip will be squeezed away'from the edges of a strip to be coated;

a second exit roll located downstream of and adapted to be positioned below and contiguous to a strip to be coated;

the uppermost surface of said second roll means being higher than the lowermost surface of said first roll whereby a strip to be coated is inclined upwardly from said first roll to said second roll;

fluid depositing means positioned downstream of said first roll and between said first roll and said second roll;

an air knife means for providing a uniform fluid coating on a strip to be coated, said air knife station being positioned at a location from a point adjacent said fluid depositing means to a point above said second roll; and,

said fluid depositing means and knife means being positioned on the same side of a strip to be coated as said first roll whereby fluid which is adapted to be deposited on said strip is dammed at the interface of said first damming roll and a strip to be substantially level and free of tilting transversely.

P0405) UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,783,323 Dated JanuaryB, 1974 Inventor) William C. Sievert et al. 7

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Col. .1, line 38, insert -and-- between "regulate" and "provide".

Col 1, line 50, insert --which-- between "rollers" I "would" Col. 3, line 35, after "18" insert ,however the 'air knife may be positioned at a location between the :fluid depositing means and the roll l8-.

Signed and sealed this 18th day of June 1974;

(SEAL) Attest:

EDWARD M.FLETCHER,JR. v C. MARSHALL DANN Attestlng Officer Commissioner of Patents 7

Claims

1. Apparatus for depositing fluid on a strip, said apparatus comprising: a first entry damming roll means adApted to be positioned above and contiguous to a strip to be coated, for providing a dam at the interface of a strip to be coated and said roll; a second exit roll means located downstream of and adapted to be positioned below and contiguous to a strip to be coated; the uppermost surface of said second roll means being higher than the lowermost surface of said first roll means whereby a strip to be coated is inclined upwardly from said first roll means to said second roll means; a fluid depositing means positioned downstream of said first roll means and between said first roll means and second roll means; an air knife means for providing a uniform fluid coating on a strip to be coated, said air knife station being positioned at a location from a point adjacent said fluid depositing means to a point above said second roll means; and, said fluid depositing means and air knife means being positioned on the same side of a strip to be coated as said first roll means; whereby fluid which is adapted to be deposited on said strip is dammed at the interface of said first damming roll means and a strip to be coated.

6. Apparatus for depositing fluid on a strip, said apparatus comprising: a first entry damming roll adapted to be positioned above and contiguous to a strip to be coated for providing a dam at the interface of a strip to be coated and said roll whereby a coating fluid can be deposited across the entire width of a strip to be coated; said first roll being adapted to exert sufficient pressure at said interface whereby a fluid will be spread across the width of a strip and at the side of the strip will be squeezed away from the edges of a strip to be coated; a second exit roll located downstream of and adapted to be positioned below and contiguous to a strip to be coated; the uppermost surface of said second roll means being higher than the lowermost surface of said first roll whereby a strip to be coated is inclined upwardly from said first roll to said second roll; fluid depositing means positioned downstream of said first roll and between said first roll and said second roll; an air knife means for providing a uniform fluid coating on a strip to be coated, said air knife station being positioned at a location from a point adjacent said fluid depositing means to a point above said second roll; and, said fluid depositing means and knife means being positioned on the same side of a strip to be coated as said first roll whereby fluid which is adapted to be deposited on said strip is dammed at the interface of said first damming roll and a strip to be coated.

7. The apparatus of claim 6 wherein said first roll is adjustable both vertically and horizontally.

8. The apparatus of claim 6 wherein said second roll is adjustable both vertically and horizontally.

9. The apparatus of claim 6 wherein said air knife is positioned above and in axial alignment with said second roll means.

10. The apparatus of claim 6 wherein said first roll is substantially level and free of tilting transversely.