US2888901A

US2888901A - Coating control apparatus

Info

Publication number: US2888901A
Application number: US690834A
Authority: US
Inventors: Henry W Nieman; George O Maish
Original assignee: Bethlehem Steel Corp
Current assignee: Bethlehem Steel Corp
Priority date: 1957-10-17
Filing date: 1957-10-17
Publication date: 1959-06-02
Anticipated expiration: 1976-06-02

Description

June 2, 1959 H. w. NIEMAN ETAL 90 COATING CONTROL APPARATUS v Filed Oct. 17, 1957 2 Sheets-Sheet 1 1N VENTORS Henry 14/. M'eman George 0. MG'I'S/I BY W? ATTORNEY June 1959 H. w. NIEMAN ETAL 2,888,901

comma CONTROL APPARATUS W 9 lb W l INVENTORS Henry M/. A/ieman George 0. Maish ATTORNEY are usually provided with circumferential grooves.

COATING IONTROL APPARATUS Henry W. Nieman and George 0. Maish, Bethlehem, Pa., assignors to Bethlehem Steel Company, a corporation of Pennsylvania Application October 17, 1957, Serial No. 6%,834

Claims. (til. 118:-103) Our invention relates to apparatus for controlling the coating thickness on the edges of sheet material and particularly to apparatus for controlling metallic coating thickness on the edges of hot dipped sheet or strip material.

In hot dipped coating practice, such as galvanizing it is common practice to have the sheets or strip leave the molten bath between a pair of rolls which are partly submerged. These rolls act to regulate the thickness of metal coating on the surface. If they are smooth and held together with normal pressure the coating will be thinner than is usually desired, so that in practice rolls Coating thickness is then controlled by varying the spacing and depth of the grooves; the closer and deeper they are the thicker the coating.

Following this practice it is found that the coating metal is thicker at or near the edges. This is a very undesirable condition. Not only does the waste of coating metal represent a large expense, but when the strip is to be coiled after coating the thicker edges makes it diflicult or impossible to wind a flat coil. Since the advent of con tinuous galvanizing the trouble has become more serious both because of the higher speeds and because of the market that has been built up for coiled material of thinner gauges.

Various schemes have been and are being used in an endeavor to remedy this condition, such as wipers made of asbestos or other material, blasts of air or gas, or gas flames directed adjacent the edges. However, none of these remedies are entirely satisfactory, since it is very difficult to secure an adjustment which will remove some of the liquid coating metal without stripping all of it 01f, thereby leaving little more than the alloy layer.

Observations of the flow of zinc in the bite of the rolls has led to a clear picture of the mechanism which causes the heavy edge coating with zinc. In the case of smooth rolls it appears that since there is no space between the rolls and the sheet, or strip, almost no zinc can pass through in this region. Beyond the edges of the sheet, however, there is a space equal to the thickness of the sheet, which space may have parallel or tapering sides,

defined by the rolls, depending on the degree to which the rolls are urged towards each other in their housings, and it is here that pumping action of the coating metal occurs. The metal adhering to the rolls by surface tension is drawn up through the bite of the rolls at each side of the sheet and forms a pool in the trough above. This metal then flows over the edges of the sheet, spreading as far from the edges toward the middle of the sheet as it can between the time of emergence from the rolls and the point of solidification. The depth of the pool formed and therefore the edge build-up of the coating on the sheet will depend on the roll spacing and on their surface speed. The presence of grooves in the roll increases the amount have shown that of the to al zinc used in the case of 30 .gauge strip 36" wide run at a speed of 160 feet per 1 atent the two inches of the strip along each edge.

One object of our invention is to provide a device to engage the edges of strips of sheet material to prevent excess coating being applied to the material adjacent the edges of the said material.

A more specific object of our invention is to provide a device having a member approximately the thickness of the material being coated to engage the edges of the's'trip or sheet material as it passes through the bite of the rolls at the exit of the coating bath to prevent excess coating being applied to or adjacent the edges of the material being coated.

The apparatus of the present invention will be understood from the accompanying drawings of which:

Fig. 1 is a front elevation of a continuous galvanizing pot in diagrammatic form showing the exit rolls through which the strip of sheet material passes from the coating bath with the application of the device of the present invention.

Fig. 2 is a section on the line 2-2 of Fig. 1.

Fig. 3 is a front elevation of the device of the invention.

Fig. 4 is an end view of the device represented in Fig. 3.

Referring to the drawings, 11 represents a framework supporting the exit rolls 12 which are shown partly submerged in a zinc bathcontained in a pot or receptacle 10. The level of the zinc bath is indicated by the dotted line 12a. 13 designates a strip of sheet material movingupwardly out of the bath through the rolls 12 as shown by the arrow, and 14 designates the device of our invention which is shown with its upper end mounted on said framework 11 and with its lower end engaging the edges of the strip of sheet material 13 and extending into the bite of the rolls 12. The device 14 comprises a bracket 15 which is shown mounted on one of the beams 16 of the framework 11 and clamped thereto by means of the cap screws 17. This bracket member 15 is capable of movement along the beam 16 to provide adjustment thereof for different widths of strip material. Rotatably mounted upon the bracket 15 is a bar 18 which has its bearings in the notched projections 19. A hole 20 is provided at one end of the bar 18 through which a rod, or a pipe 22 as shown in the drawings, passes, the pipe 22 having a free fit in the hole 20 to allow for free rotation and endwise sliding movement of the pipe. Attached to the lower end of the pipe 22 preferably by a weld 21 is member 23, and shown attached to this member 23 by cap screws 24 is the movable clamp member 25 for the plate 26 which is adapted to be inserted between the

members

23 and 25 and clamped in operative position by the cap screws 24.

In service, as shown in Figs. 1 and 2, the plate 26 extends down into the bite of the rolls, the weight of the plate and the pipe 22 being supported by its contact with the rolls. The pipe 22 is suspended from the bracket 15 at an angle to the vertical, as shown in the drawings, so that the plate 26 tends to float sideways to press against the edge of the strip and is assisted in doing so by spring 29. As a safeguard against the plate 26 accidentally climbing over the edge of the strip, guard member 27 is fastened to this plate 26 by suitable means such as the rivets 28 as shown in the drawings.

Preferably the plate 26 is selected to have a thickness only slightly greater than that of the strip being coated so that initially the plate 26 fits well down into the bite of the rolls. Preferably the lower end of the plate is out off at an angle as shown in the drawings so that, when in position, the edge next to the strip will be slightly further into the bite than the opposite edge. However the plate may be provided initially with a square edge, in view of the fact that after a short period of operation it wears down to conform to the space defined by the rolls of an inch excess thickness.

inches of the strip along each edge.

' 3 so, that its forward edge may actually pass through the said bite.

The action of this plate 26 is twofold. First it acts .as a stopperor closure to prevent the pumping of the coating metal through the bite of the rolls in the immediate vicinity of the edge of the strip. Inasmuch as the area of the roll wiped by the plate 26 is prevented from receiving the normal amount of liquid such as occurs on the roll surface beyond the wiped area, it can be considered to be a relatively dry area. Excess liquid will overflow onto this dry area from the unwiped portion of the roll beyond. However, it does not reach the edge of the strip since it is conducted away over the top of the roll within the dry zone. Any liquid pumped by the grooves in the wiped area is effectively conducted away in this same manner. The plate 26 may be considered as a dummy piece of strip which by engaging the edge of the strip being coated prevents the build-up on said strip, as it receives the edge build-up of coating material which would without it reach the edge of the actual strip being coated and form a build-up of excess coating on the edges of said strip.

Tests conducted over a considerable period of time have proven that the use of this device effectively eliminates the difliculty of this edge build-up. Where normally the edges of thin galvanized strip run from one to five thousandths of an inch thicker than the middle of the strip and interfere with winding of the coated strip into commercial coils, with the use of the devices of our invention they seldom show more than one thousandth This small amount of excess thickness does not interfere with the winding of the coated strip into commercial coils, as it is within the tolerance to permit winding commercially acceptable coils. As previously stated coating stripping tests have shown that of the total zinc used in the case of 30 gauge strip, 36 inches wide, run at a speed of 160 feet per minute as much as 7% is in the form of excess zinc on the two More than three quarters of this is saved by the use of the devices of our invention.

From the foregoing, it is evident that we have devised an apparatus which is especially adaptable for controlling the coating thickness adjacent the edges of strips of hot dipped sheet material.

While we have shown our invention in one form, it

will be obvious to those skilled in the art that it is not so limited but is susceptible to various changes and modifications without departing from the spirit thereof.

We claim:

1. In an apparatus for applying a liquid coat to strip material comprising a receptacle containing a coating bath through which said material passes, a pair of spaced rolls at the exit of said bath partly submerged in said bath through the bite of which the material emerges from the coating bath, a device comprising a closure member in engagement with the edge of the material and the rolls to close the space between the rolls adjacent the edge of the strip material and thereby prevent excessive coating material from passing through said rolls adjacent the strip material and build-up on said material adjacent the edges of said material.

2. In an apparatus for applying a liquid coat to strip -material, comprising a receptacle containing a coating bath through which said material passes, a pair of spaced rolls at the exit of said bath partly submerged in said bath through the bite of which the material emerges from the coating bath, a device comprising a closure member positioned between said rolls and projecting downward adjacent the bite of said rolls and bearing against an edge of said material to close the space between the rolls adjacent the edge of the strip material and thereby prevvent excessive coating material from passing through said rolls adjacent the strip material and build-up on said material adjacent the edges of said material.

3. In an apparatus for applying a liquid coat to strip material, comprising a receptacle containing a coating bath through which said material passes, a pair of spaced rolls at the exit of said bath partly submerged in said bath through the bite of which the material emerges from the coating bath, a device comprising a closure member positioned between said rolls and projecting downward adjacent the bite of said rolls and bearing against an edge of said material to close the space between the rolls adjacent the edge of the strip material and thereby prevent excessive coating material from passing through said rolls adjacent the strip material and build-up on said material adjacent the edges of said material, said closure member being of an elongated form contacting each of said rolls along a considerable dimension in an axial direction.

4. In an apparatus for applying a liquid coat to strip material, comprising a receptacle containing a coating bath through which said material passes, a pair of spaced rolls at the exit of said bath partly submerged in said bath through the bite of which the material emerges from the coating bath, a device comprising a closure member positioned between said rolls and projecting downward adjacent the bite of said rolls and bearing against an edge of said material to close the space between the rolls adjacent the edge of the strip material and thereby prevent excessive coating material from passing through said rolls adjacent the strip material and build-up on said material adjacent the edges of said material, said closure member comprising an element of plate like form having a thickness not greatly exceeding that of the material being coated and having an edge of the plate in contact with the edge of said material.

5. In an apparatus for applying a liquid coat to strip material, comprising a receptacle containing a coating bath through which said material passes, a pair of spaced rolls at the exit of said bath partly submerged in said bath through the bite of which the material emerges from the coating bath, a device comprising a closure member positioned between said rolls and projecting downward adjacent the bite of said rolls and bearing against an edge of said material to close the space between the rolls adjacent the edge of the strip material and thereby prevent excessive coating material from passing through said rolls adjacent the strip material and build-up on said material adjacent the edges of said material, said closure member comprising an element of plate like form having a thickness not greatly exceeding that of the material being coated and having its lower edge out diagonally so that the edge of said closure member engaging said material projects further downward between the rolls than the opposite edge of the closure member.

6. In an apparatus for applying a liquid coat to strip material, comprising a receptacle containing a coating bath through which said material passes, a pair of spaced rolls at the exit of said bath partly submerged in said bath through the bite of which the material emerges from the coating bath, a device comprising a closure member positioned between said rolls and projecting downward adjacent the bite of said rolls and bearing against an edge of said material to close the space between the rolls adjacent the edge of the strip material and thereby prevent excessive coating material from passing through said rolls adjacent the strip material and build-up on said material adjacent the edges of said material and a member attached to said closure member and extending upwardly therefrom, said closure member being of an elongated form contacting each of said rolls along a considerable dimension in an axial direction, and means mounting said upwardly extending member so as to allow free rotation and vertical sliding movement thereof while preventing horizontal movement of said upwardly projecting member.

7. In combination with a continuous galvanizing pot containing a zinc bath, a pair of exit rolls partly sub merged in the zinc bath and means cooperating with said rolls and strip material being coated to prevent an excessive thickness of zinc coating on or near the edges of said strip material passing from said bath through said rolls, said means comprising a closure member positioned between said rolls and projecting downward towards or into the bite of said rolls and said members comprising an edge portion bearing against an edge of said strip material.

8. In an apparatus for coating strip material, coating means comprising a coating bath, a pair of rolls partially submerged in the coating bath through which said coated material travels for controlling the thickness of the coating applied to said material, and a member having face portions in contact with said rolls adjacent the bite of the rolls and an edge portion in bearing engagement with the edge of said material being coated to control the coating adjacent the edge of the said material.

9. In an apparatus for coating strip material, coating means comprising a coating bath, a pair of rolls partly submerged in the coating Ibath between the bite of which the strip material being coated passes, said means abundantly supplying said rolls with coating material on the entering side of the bite of said rolls, a closure member cooperating with said rolls to prevent the passage of an excessive amount of coating material through said rolls contiguous to the edges of said strip material, said closure member comprising a portion projecting downward into the bite of the rolls and an edge portion bearing against an edge of said strip material.

10. In combination with a coating mechanism, comprising a coating tank and a pair of rolls at the exit of the said coating tank through which material coated in the tank passes, said pair of rolls comprising end portions and an intermediate portion, said intermediate portion contacting said material being coated and said end portions extending beyond the edges of said material, and spaced from each other adjacent said edges thereby constituting a passageway between the rolls adjacent each of the edges of said material passing through said rolls, a closure for each of said passageways disposed in contact with the rolls adjacent the bite thereof and each edge of said material, said closures comprising a member at least the thickness of the material passing through said rolls.

No references cited.