US2894856A

US2894856A - Apparatus for and method of controlling the coating thickness in continuous galvanizing

Info

Publication number: US2894856A
Application number: US607480A
Authority: US
Inventors: Edward T Schwendemann; Jr Maurice J Sadowsky; Murway Edward
Original assignee: Inland Steel Co
Current assignee: Inland Steel Co
Priority date: 1956-08-31
Filing date: 1956-08-31
Publication date: 1959-07-14
Anticipated expiration: 1976-07-14

Description

E. T. SCHWENDEMANN ET AL July 14, 1959 v 2,894,856

. APPARATUS FOR AND METHOD OF CONTROLLING THE COATING THICKNESS IN CONTINUOUS GALVANIZING Flled Aug 31 1956 2 Sheets-Sheet l fnuehib r6:- fiduardfvzwendemnn Maurice $361,510

is iami?? y 1959 E. -r. SCHWENDEMANN ET AL 4,

APPARATUS FOR AND METHOD OF CONTROLLING THE COATING THICKNESS IN CONTINUOUS GALVANIZING Flled Aug 31, 1956 2 Sheets-Sheet 2 [Ya/87225715. Z'dzuardTSc/zzoevzfimanm JSQdou/s I 7;: I Haunce Edward United States Patent APPARATUS FOR AND METHOD OF CONTROL- LING THE COATING THICKNESS 1N CONTINU- OUS GALVANIZING Edward T. Schwendemann and Maurice J. Sadowsky, Jr.,

Highland, and Edward Murway, Hammond, Ind., assignors to Inland Steel Company, Chicago, 111., a corporation of Delaware Application August 31, 1956, Serial No. 607,480

23 Claims. (Cl. 117-114) The invention relates generally to improvements in continuous coating of metal strip with molten metal and more particularly to novel and improved means for controlling the coating thickness adjacent the edges of the strip. The invention, while particularly useful in connection with continuous galvanizing, is adapted for use in any continuous hot dip process for applying a metallic coating such as aluminum, tin, etc.

In continuous galvanizing lines of the type now commercially employed, the strip is led from an annealing furnace directly into a pot of molten zinc maintained at a temperature on the order of 800 F. to 875 F. In the pot, the direction of travel is changed by a sinker roll to feed the strip vertically between a pair of coating rolls. The latter are mounted with their axes horizontal and are partially submerged in the molten zinc. The strip thus acquires a coating of zinc, the thickness of which is controlled by the coating rolls.

The coating rolls are provided with annular grooves which draw molten metal upwardly to form an elongated pool in the nip above the rolls. Throughout the major portion of the width of the strip, the metal pool is of substantially uniform height or depth so that the resultant coating for a major portion of the width of the strip is of uniform thickness. However, the pool of molten metal at the portions of the coating rolls beyond the side edges of the strip will attain a higher level because more metal will be drawn upwardly by those portions of the rolls where the strip is absent and because none of the metal at those portions is carried away on the strip. The change in level occurs inside the marginal edge portions of the strip and, unless it is controlled in some manner, will result in a thickened coating on such marginal portions. Such build-up along the edges of the strip prevents satisfactory coiling of the strip after the galvanizing operation since it will tend to cause a stretching of the edge portions and is generally undesirable in fabrication of the strip.

The build-up on the edge portions may be kept within commercial tolerances by reducing the speed of travel of the strip, eg to about 70 feet per minute. At such reduced speed, the difference in level of the pool between that portion adjacent the strip and the portions beyond the edges of the strip is not excessive, but such reduced speed is much below the speed at which the rest of the line may be economically operated. Consequently, reduction of speed of the line is not a satisfactory solution to the problem when it is otherwise possible to operate the line at much higher speeds, e.g. 140 to 200 feet per minute.

The general object of the present invention is to provide a novel apparatus for and method of preventing edge build-up of the coating during continuous coating with a molten metal.

Another object of the invention is to prevent such edge build-up while at the same time operating the line at the ice maximum speed available as determined by factors other than the coating thickness.

A further object of the invention is to provide a novel apparatus and method for preventing edge build-up on the strip in a continuous galvanizing line with a uniform spangle on the strip throughout the width thereof.

Other objects and advantages will become apparent from the following description taken in connection with the accompanying drawings in which:

Fig. 1 is a fragmentary front elevation view of an apparatus embodying the features of the invention;

Fig. 2 is a side elevational view of the apparatus as seen from the right hand side in Fig. 1 but on a somewhat larger scale than Fig. 1; s

Fig. 3 is a horizontal sectional view taken on the line 3-3 of Fig. 1;

Fig. 4 is an enlarged fragmentary front elevational view of a portion of the apparatus; and

Fig. 5 is a side elevational view of in Fig. 4.

For illustrative purposes, the invention as hereinafter described in detail is concerned with a continuous galvanizing operation. However, it is to be understood that the principles of the invention are broadly applicable to other metal coating operations as previously indicated.

While excessive edge build-up can be prevented by reducing the speed of the line, such measure is not satisfactory, as heretofore stated. Other proposals have been the portion shown suggested to prevent excessive thickness of the coatingat the edge portions of the strip by mechanically forcing off the excess coating metal after an excessive thickness thereof has deposited but before it has solidified. Such method may result in removal of too much or too little of the coating so that the edge portions are not uniform in thickness with the major portion of the width of the strip.

The present invention contemplates apparatus for and a method of attaining a coating of substantially uniform thickness throughout the entire width of the strip by preventing initially the formation of excessive thickness at the edge portions. Broadly, such result is attained by maintaining a substantially constant level in the pool of molten metal in the nip of the coating rolls throughout the entire width of the strip so that no thickening of the coating will occur at the edge portions of the strip. Thus, rather than letting the thickening occur and then attempting to reduce it, the coating is held with substantially uniform thickness as it is formed, and the diificulty in removing the excess thickness is avoided. Furthermore, the present invention permits operation of the line at a speed determined only by other factors without need for a reduction in speed to avoid edge build-up. In addition, the technique of the present invention offers the advantage of readily providing a uniformly spangled surface condition on the galvanized metal which is a desirable commercial quality.

Referring first to Figs. 1 to 3 of the drawing, an apparatus comprising one specific embodiment of the present invention is shown as it would be mounted above a galvanizing pot having a pair of the usual grooved coating rolls 11 mounted on a horizontal axis with a continuous steel strip 12 moving upwardly between the rolls in the usual manner. The pot contains molten zinc at a temperature in the neighborhood of 800 F. to 875 F. with the level of the zinc bath (not shown) being approximately at the axes of the coating rolls. As the strip 12 passes upwardly betwen the rolls 11, the surface of the strip picks up a zinc coating, the thickness of which is controlled by the coating rolls. After leaving the coating rolls the strip passes upwardly to a cooling tower and thence to other parts of the apparatus which are not] pertinent to the present invention and accordingly need not be described.

In accordance with the present invention, a plurality of nozzles 13 are mounted at an angle adjacent each of the longitudinal edges of the strip 12 and also at the opposite flat sides of the strip. In other words, four sets of nozzles are employed, and in this particular instance there are three nozzles in each set. Although the number of nozzles in each set may be varied to meet the requirements of a particular installation, we have found that the use of three nozzles in each set in the manner hereinafter described in detail produces highly effective results. In order to retain the individual nozzles within each set in predetermined fixed relation, a bar or plate 14- is rigidly affixed to the nozzles in each set. The nozzles 13 are supported at opposite edges of the strip12'by means of a pair of U-shaped nozzle supports 16 each having a pair of arms 17 (Fig. 3) extending parallel to and closely adjacent the opposite flat sides of the sheet 12. Each U-shaped support 16 is rigidly affixed at its outermost end to the lower end of an upright tubular housing 18. The nozzles 13 are individually connected to a supply of gaseous material by means of a plurality of tubular conduits 19 communicating with the nozzles through cored passages 20 in the supports 16 and extending upwardly through a slot 21 in the side of the housing 18 and thence projecting from the top of the latter. A bracket 22 is rigidly affixed to the upper end of the housing 18 and carries a generally rectangular frame 23' for supporting the conduits 19 in spaced relation. Flexible hoses 24 extending from a source (not shown) are secured to the inlet ends of the tubes 19, and individual control valves 24' are provided so that the fluid pressure and exit velocity may be controlled independently for each nozzle.

As will hereinafter be understood, the gaseous material supplied to the nozzles 13 may comprise any available g'as, e.g. air, steam, an inert gas such as nitrogen or the like, combustion gases, etc., or any combination thereof. Preferably, the gaseous material supplied to at least one of the nozzles in each set is a combustible gas such as coke oven gas or the like, in which event the nozzle comprises a burner for burning the gas. In the latter case the effluent combustion gases accompanying the gas flame are obviously at an elevated temperature, but even when a non-combustible gas is employed it may be desirable insome cases to preheat the gas so that the stream emerging from the nozzle is at an elevated temperature. However, it is not essential in the present invention that the gas streams supplied by the nozzles 13 be hot. In fact, gaseous material at room temperature will sufiice as long as the water content of the gas is below the saturation level so that no water is present in liquid form. Heating the gas to an elevated temperature assists in maintaining the water in the vapor state.

From the foregoing it will be understood that the two parallel sets of nozzles at each edge of the strip 12 are suspended as a unit from the support means comprising the tabular housing 18 and its interconected nozzle support 16. However, in accordance with the principles of our invention, the nozzles 13 must be positioned rather accurately with respect to the edges of the strip 12 and also with respect to the surface of the pool of molten metal in the nip between the coating rolls 11. Accordingly, in order to provide for both vertical and lateral adjustment of the nozzles, we employ a pair of movable carriages designated generally at 25 and disposed at opposite edges of the sheet 12 for adjustably carrying the support means 1618. Each carriage 25 comprises a pair of elongated side frames 26 provided with longitudinally extending slots 27 and rigidly interconnected at one end by means of a block portion 28 (Figs. 2 and 3) so as to provide a generally U-shaped carriage structure adapted to fit around the edges of the strip 12 in the same general manner as the U-shaped nozzle supports 16. The carriages 25 are rollably supported above the coating rolls 11 by means of a plurality of wheels 29 and 30 mounted at the ends of the side frames 26. The wheels 29 at one side of each carriage are grooved, as at 31, for coaction with the upright leg portion 32 of an elongated supporting angle iron 33 which extends across the galvanizing bath. The opposite wheels30 of the carriages 25 have fiat surfaces for rolling engagement along a flat support member 34 extending across the galvanizing pot in parallel relation with the angle iron 33 and forming with the latter a track for the carriages 25. It will be understood that by reason of. the coaction between the grooved wheels 29 and the angle iron 33 of the track, movement of the carriages is accurately guided.

At the outermost end of each carriage 25 one of the elongated housings 18 extend throughan opening or slot 35 in the side of the block portion 28 and is retained therein by means of a pair of vertically spaced bars 36 extending transversely between the side frames 26 of the carriages. A retainer plate '37 (Fig. 2) is adjustably mounted in a slot at the underside of the block 28 and has an inner V-shaped opening 37' (Fig. 3) for engaging the housing 13 and retaining the same in the block 28. For adjustably supporting each nozzle mounting structure 16-18 on its cariage 25, the housing 18 is provided with an adjusting block 38 having a bore 39 (Fig. 2) through which the housing 18 extends, and a set screw 41 with a lock nut 42 are provided for rigidly securing the adjusting block 38 to the housing 18 in any desired adjusted position thereon. The adjusting block 38 also has a laterally extending portion having another vertical bore through which extends an elongated vertical adjusting screw 43 rigidly secured at its lower end in the block portion 28 of the carriage. An elongated internally threaded adjusting nut 44 is mounted on the screw 43 and has a shoulder with a knurled head portion 46 disposed below the adjusting block 38 for coaction with the latter. As will readily be understood, by manipulating the head portion 46 of the adjusting screw 44, the entire assembly 331816 may be raised or lowered as a unit relative to the carriage 25 thereby providing rapid vertical adjustment means. To prevent undesired rotary movement of the tube housing 18, a collar 47 is rigidly afiixed to the housing 18 by a screw 48 above the adjusting block 38 and is provided with a pair of integral lugs 4% (Fig. 1) which extend into complementary grooves 50 located at opposite sides of the adjusting block 38 thereby retaining the housing 18 against rotation.

For controlling the lateral position of the nozzles, each carriage 25 also has a transversely extending guide roller 51 which is adjustably mounted at its ends in the slots 27 at the sides of the carriage. As best seen in Figs. 1 and 3, the guide rollers 51 engage the opposite edges of the strip 12 and by adjustment of the guide rollers 51 along the slots 27, it will be seen that the position of the nozzles 13 relative to the edges of the strip 12 may be regulated. In order to prevent any possibility of the edge portions of the strip 12 becoming jammed between the ends of the guide rollers 51 and the corresponding side frames 26 of the carriages, a pair of shields or guard plates 52 are adjustably fitted to the side frames 26 by means of screws 53 and wing nuts 54, and each shield 52 has a wedge-shaped end portion 56 extending laterally inwardly and overlying the corresponding end of the guide roller 51 so as to bridge the gap between the end of the guide roller and the framework of the carriage.

For retaining the guide rollers 51 in engagement with the edges of the strip 12, the carriages 25' are resiliently interconnected and urged inwardly toward each other by' means of a spring mechanism including an elongated bar or rod 57 which extends through a pair of tubular elements 58 rigidly aflixed to the upper edges of the carriage side frames 26. Although only one red 57 is em- 5.. ployed, the carriages 25 are provided with the tubular elements 58 along both side frames 26 so that the carriages may. be used interchangeably. The ends of the rod 57 extend beyond the respective carriages 25 and are fitted with adjustable thrust collars 59 secured to the rod 57 by set screws. A coil spring 61 is interposed between each collar 59 and a similar collar 62 located at the outermost end of each of the tubular elements 58, it being understood, of course, that the rod 57 extends loosely through the tubular elements 58 and the collars 62 to permit relative movement therebetween. Thus, the springs 61 by coaction with the interconnecting rod 57 serve to urge the carriages 25 inwardly toward the edges of the strip 12 thereby resiliently maintaining the guide rollers 51 in rolling engagement with the edges of the strip 12. By means of this arrangement, it will be seen that any slight lateral movement or displacement of the strip 12 relative to the rolls 11 or any variation in the width of the strip 12 will be reflected by a corresponding change in the lateral position of the carriages 25 so that the tips of the nozzles 13 are maintained at all times at a predetermined distance from the edges of the strip 12.

As heretofore mentioned, the control over coating thickness at the edges of the strip is maintained in the present invention by preventing, from the very outset, excessive deposition of zinc at the marginal edge portions of the strip 12. In order to accomplish this result, the nozzles 13 are carefully positioned between the strip 12 and the coating rolls 11 so that the exit gas streams are directed substantially entirely against the pool of molten metal between the rolls rather than against the strip 12. Referring now to Figs. 4 and 5, it will be seen that the nozzles 13 in each set extend at their tips into the nip area between the rolls 11 and are positioned at an angle extending downwardly and outwardly toward the edges of the strip 12. In this manner, the gases emerging from the tips of the nozzles 13 impinge against the surface of the elongated pool of molten metal designated at 63. In Fig. 4 the normal tendency of the pool of molten metal to rise at the ends of the pool adjacent the longitudinal side edges of the strip 12 is illustrated somewhat diagrammatically by the broken line 64, and it will be understood that this line 64 represents the usual profile of the metal pool in the absence of the present invention. However, by reason of the location and angular relation of the nozzles 13 with respect to the metal pool 63, the mechanical effect of the gases impinging upon the metal surface causes longitudinal or axial displacement of the surface portion of the metal pool so that the surface profile of the pool is substantially as shown in full lines in Fig. 4. In other words, the undesirable tendency for the level of the metal pool to rise adjacent the longitudinal side edges of the strip 12 is completely prevented and the level of the pool is maintained substantially uniform at least across the entire width of the strip. In marked contrast to previously proposed techniques, the present invention does not attempt to blow away excess metal from the strip 12 after it has been deposited thereon, but on the contrary the gases are directed substantially solely against the surface of the metal pool 63 and not against the strip 12.

In order to realize the full benefits of the invention as discussed above, it will be apparent that the angular position of the nozzles 13 as well as the vertical and lateral location thereof with respect to the surface of the metal pool and the side edges of the strip 12 and also the pressure or velocity of the gases emerging from the nozzles 13 must be carefully adjusted. Obviously, for any given installation the foregoing factors must be correlated and adjusted to give the desired result. Once the proper location for each set of nozzles has been obtained by manipulation of the vertical and lateral adjustment mechanism heretofore described, the nozzles will thereafter be maintained in the desired locations. ally, it may be necessary to adjust the elevation of the Occasionnozzles by means of the screws 44- in order to compensate for slight changes in the depth of the metal pool 63. However, any variation in the width of the strip 12 or the lateral location of the strip 12 with respect to the coating rolls 11 is automatically compensated for through coaction of the strip edges with the guide rollers 51 as heretofore described. As previously mentioned also, the pressure in the individual nozzles and the velocity of the efliuent gases are controlled separately for each nozzle by the valves 24' so as to obtain relatively smooth nonturbulent displacement or blowing aside of the pool of molten metal without causing any substantial penetration of the surface of the pool or otherwise causing turbulence or agitation of the molten metal. In this connection, the nozzles 13 are preferably provided with flared tips 65 (Figs. 4 and 5) to assist in preventing penetration of the gas streams into the pool and otherwise facilitating the desired non-turbulent outward displacement of the molten metal.

As was previously mentioned, we have found that best results are obtained by utilizing a plurality of nozzles arranged in side-by-side substantially coplanar relation as herein illustrated. By this arrangement the metal at the surface of the pool 63 is displaced outwardly beyond the edges of the strip 12 in a generally stepwise manner way of example, the use of three nozzles in each set has proven to be highly effective, e.g. when using a gas flame in one of the nozzles and air at about 200 F. in the other two nozzles of each set. However, good results have also been obtained using steam or air in all the nozzles of each set.

To further facilitate effective operation of the plurality of nozzles in each set in the manner described it is also preferred that the gas presure and exit velocity increase from the innermost to the outermost nozzle in each set. More specifically, referring to Fig. 4, the pressure and exit velocity in nozzle 13b should be greater than in 13a and the pressure and exit velocity for nozzle 13c should be greater than for 13b. Moreover, it will also been seen, particularly in Fig. 4, that the relative angle between each individual nozzle and the longitudinal axis of the metal pool and coating rolls increases slightly from the innermost nozzle 13a to the outermost nozzle 130. This increase in the angle of blowing causes a somewhat greater vertical pressure component with respect to the gases issuing from the outermost nozzle as compared with the inner nozzles 13a and 13b and we have found that this arrangement also further facilitates the desired smooth metal displacing effect.

By means of the apparatus and technique described above, highly effective control over the thickness of the metal coating is obtained along the marginal edge portions of the strip and the invention possesses the advantage of eliminating the very source of the commonly experienced difficulty with thickened edge coatings during continuous hot dip metal coating. In other words, the tendency of the metal pool to assume a non-uniform profile between the coating rolls is eliminated so that a uniform coating is obtained across the width of the strip at all times and it is unnecessary to attempt to cure edge build-up after it has already occurred on the strip. Furthermore, the invention eliminates edge build-up without imposing any outside limitations on the speed of the line. Also by avoiding direct impingement of flames or hot gases against the strip there is no tendency to overheat the strip so that it is possible, in the case of galvanizing, to obtain a uniformly spangled product.

Although the invention has been described with particular reference to a certain specific structural embodi ment thereof, it is to be understood that various modifications and equivalent structures may be resorted to .fined in the appended claims.

We claim:

1-. In a continuous metal coating apparatus having a receptacle adapted to contain a bath of molten metal through which a strip is passed and a pair of horizontal coating rolls partially submerged in the bath and adapted to engage opposite sides of the strip with an elongated pool of molten metal being formed in the nip between the rolls, the improvement comprising means for directing gaseous material at an angle downwardly and outwardly toward the longitudinal edges of the strip and substantially solely against the surface of the pool at the ends thereof with suflicient velocity to prevent the pool from rising to a higher level adjacent the edges of the strip whereby to maintain the level of the pool substantially uniform at least for the entire width of the strip.

2. In a continuous metal coating apparatus having a receptacle adapted to contain a bath of molten metal through which a strip is passed and a pair of horizontal coating rolls partially submerged in the bath and adapted to engage opposite sides of the strip with an elongated pool of molten metal being formed in the nip between the rolls, the improvement comprising means including a plurality of nozzles for directing gaseous material at an angledownwardly and outwardly toward the longitudinal edges of the strip and substantially solely against the surface of the pool, and adjustable nozzle mounting means for positioning said nozzles at a predetermined angle and location at the ends of the pool adjacent the longitudinal edges of the strip so that the gaseous material impinges downwardly and outwardly against the surface of the pool whereby to prevent the pool from rising to a higher level adjacent the edges of the strip and thereby maintaining the level of the pool substantially uniform at least for the entire width of the strip.

3. The apparatus of claim 2 further characterized in that said nozzles are arranged side-by-side for directing gaseous material against the pool surface in successive streams spaced lengthwise of the pool.

4. In a continuous metal coating apparatus having a receptacle adapted to contain a bath of molten metal through which a strip is passed and a pair of horizontal coating rolls partially submerged in the bath and adapted to engage opposite sides of the strip with an elongated pool of molten metal being formed in the nip between the rolls, the improvement comprising a plurality of nozzles at each side of the strip adjacent each longitudinaledge'thereof, said nozzles being directed substantially-solely against the surface of the pool at an angle downwardly and outwardly toward the longitudinal edges of the strip, and means for supplying gaseous material under varying pressure to the respective nozzles whereby gas streams are directed against said surface of the pool with sufiicient velocity and dispersion to maintain the level of the pool'substantially uniform without turbulence for at least the entire width of the strip.

5. The apparatus of claim 4 further characterized in that said nozzles are provided with flared tips to effect dispersion of the gases over the pool surface for preventing penetration and turbulence of the molten metal.

6. In a continuous metal coating apparatus having a receptacle adapted to contain a bath of molten metal through which a strip is passed and a pair of horizontal coating rolls partially submerged in the bath and adapted to engage opposite sides of the strip with an elongated pool of molten metal being formed in the nip between the rolls, the improvement comprising a plurality of nozzles disposed at each side of the strip adjacent the longitudinal edges thereof, said nozzles being directed toward the surface of the pool at an angle downwardly and outwardly toward the longitudinal edges of the strip for impinging streams of gaseous material substantially solely against the surface of the pool and thereby preventing the pool fromrising' to a Mgher level adjacent the edges of the strip whereby to maintain the level of the pool substantially uniform at leastfor the entire width of the strip, and shiftable means for supporting said nozzles and movable in response to variations in the- Width and lateral position of the strip for maintaining the coating rolls partially submerged in the bath and adapted to engage opposite sides of the strip with an elongated pool of molten metal being formed in the nip between the rolls, the improvement comprising a plurality of nozzles disposed at each side of the strip adjacent the longitudinal edges thereof, said nozzles being directed toward the surface of the pool at an angle downwardly and outwardly toward the longitudinal edges of thestrip for impinging streams of gaseous material substantially solely against the surface of the pool and thereby preventing the pool from rising to a higher level adjacent the edges of the strip whereby to maintain the level of the pool substantially uniform at least for the entire Width of the strip, a pair of wheeled carriages rollably supported adjacent the opposite edges of the strip for movement laterally of the strip, said nozzles being supported from said carriages, roller means on said carriages engageable with the edges of the strip, and resilient means coacting with said carriages for urging the latter inwardly toward the respective edges of the strip whereby to maintain said roller means in contact with the edges of the strip at all times, said carriages being movable laterally of the strip in response to variations in width and lateral position of the strip whereby to maintain said nozzles at a predetermined distance from the edges of the strip.

9. The apparatus of claim 8 further characterized in that said resilient means comprises an elongated connecting element extending across the strip between said carriages, and spring means operatively coacting between said element and at least one of said carriages for resiliently urging the carriages toward each other.

10. In a continuous metal coating apparatus having a receptacle adapted to contain a bath of molten metal through which a strip is passed and a pair of horizontal coating rolls partially submerged in the bath and adapted to engage opposite sides of the strip with an elongated pool of molten metal being formed in the nip between the rolls, the improvement comprising a plurality of nozzles disposed at each side of the strip adjacent thelongitudinal edges thereof, said nozzles being directed toward the surface of the pool at an angle downwardly and outwardly toward the longitudinal edges of the strip for impinging streams of gaseous material substantially solely against the surface of the pool and therebypreventing the pool from rising to a higher level adjacent the edges of the strip whereby to maintain the level of the pool substantially uniform at least for the entire width of the strip, a pair of carriages each having a frame structure with wheels mounted thereon for rollably supporting the carriages adjacent the opposite edges of the strip for movement laterally thereof, said nozzles being supported from said frame structure, edge-contacting rollers journaled in the frame structure of said carriages and extending transversely across the edges of the strip in engagement therewith, and resilient means coacting with said carriages for urging the latter inwardly toward the respective edges of the strip whereby to maintain said rollers in contact with the edges of the strip at all times, said carriages being movable laterally of thestrip in response'to variations in width and lateral positionof the strip whereby to maintain said nozzles at a predetermined distance from the edges of the strip.

11. The apparatus of claim further characterized in that each of said rollers is adjustably mounted for bodily movement relative to the frame structure of its respective carriage for determining the lateral position of said nozzles relative to the edges of the strip.

12. The apparatus of claim 10 further characterized in that the frame structures of said carriages are provided with guard means for preventing the edges of the strip from becoming jammed between the ends of said rollers and the frame structures.

13. The apparatus of claim 10 further characterized in that said frame structure is generally U-shaped having a pair of spaced elongated side frames extending parallel to the strip at the opposite sides thereof and interconnected at their outer ends beyond the edge of the strip, and the edge-contacting roller being journaled between said side frames intermediate the ends of the latter.

14. In a continuous metal coating apparatus having a receptacle adapted to contain a bath of molten metal through which a strip is passed and a pair of horizontal coating rolls partially submerged in the bath and adapted to engage opposite sides of the strip with an elongated pool of molten metal being formed in the nip between the rolls, the improvement comprising a plurality of nozzles disposed at each side of the strip adjacent the longitudinal edges thereof, said nozzles being directed toward the surface of the pool at an angle downwardly and outwardly toward the longitudinal edges of the strip for impinging streams of gaseous material substantialy solely against the surface of the pool and thereby preventing the pool from rising to a higher level adjacent the edges of the strip whereby to maintain the level of the pool substantially uniform at least for the entire width of the strip, nozzle supporting structure disposed at the opposite edges of the strip for holding said nozzles in predetermined position relative to the edges of the strip and to the surface of the metal pool and shiftable carriage means mounted at the opposite edges of the strip and carrying said nozzle supporting structure, said carriage means being adjustable laterally of the strip for determining the lateral position of said nozzles relative to the edges of the strip and said nozzle supporting structure being adjustable vertically on said carriage means for determining the elevation of the nozzles above the pool surface.

15. The apparatus of claim 14 further characterized in that said nozzle supporting structure comprises an elongated upright housing supported on said carriage means for vertical movement relative thereto, means extending rigidly from the lower end of said housing and carrying said nozzles, conduit means extending through said housing and connected to said nozzles for supplying gas thereto, and adjustable means between said carriage means and said housing for regulating the elevation of said nozzles relative to the pool surface.

16. The apparatus of claim 15 further characterized in that said housing is provided with means for preventing rotary movement thereof whereby to retain said nozzles in position above the pool surface.

17. The apparatus of claim 15 further characterized in that said means extending rigidly from the lower end of said housing and carrying said nozzles comprises a generally U-shaped member having parallel arm portions extending along the opposite sides of the strip with said nozzles depending from said arms at both sides of the strip.

18. In the continuous metal coating of a strip wherein the strip is passed through a bath of molten metal and thence upwardly between a pair of coating rolls partially submerged in the bath with an elongated pool of molten metal being formed in the nip between the rolls, the improvement comprising directing gaseous material at an angle downwardly and outwardly toward the longitudinal edges of the strip against the surface of the pool at the opposite ends thereof with sufficient velocity to prevent the pool from rising to a higher level adjacent the edges of the strip whereby to maintain the level of the pool substantially uniform at least for the entire width of the strip, and confining contact of said gaseous material substantially entirely to the surface of the pool without substantial contact with the strip.

19. The method of claim 18 further characterized in that said gaseous material comprises a gas flame.

20. In the continuous metal coating of a strip wherein the strip is passed through a bath of molten metal and thence upwardly between a pair of coating rolls partially submerged in the bath with an elongated pool of molten metal being formed in the nip between the rolls, the improvement comprising directing a plurality of streams of gaseous material at an angle downwardly and outwardly toward the longitudal edges of the strip against the pool surface at the opposite ends of the pool, said streams being arranged in spaced relation lengthwise of the pool at each end thereof and said streams having sufficient velocity to displace the surface portion of the pool outwardly by successively applied increments of fluid pressure whereby to prevent the pool from rising to a higher level adjacent the edges of the strip so that the level of the pool is maintained substantially uniform at least for the entire width of the strip, and confining contact of said gaseous material substantially entirely to the surface of the pool without substantial contact with the strip.

21. The method of claim 20 further characterized in that the fluid pressure of said streams is controlled to provide increasing pressure and fluid velocity from the innermost to the outermost stream relative to the edges of the strip.

22. The method of claim 20 further characterized in that the angle of application of the respective streams increases from a less vertical to a more vertical direction from the innermost to the outermost stream relative to the edges of the strip.

23. In a continuous metal coating apparatus having a receptacle adapted to contain a bath of molten metal through which a strip is passed and a pair of horizontal coating rolls partially submerged in the bath and adapted to engage opposite sides of the strip with an elongated pool of molten metal being formed in the nip between the rolls, the improvement comprising a plurality of nozzles disposed at each side of the strip adjacent the longi tudinal edges thereof, said nozzles being directed toward the surface of the pool at an angle downwardly and outwardly toward the longitudinal edges of the strip for impinging streams of gaseous material substantially solely against the surface of the pool and thereby preventing the pool from rising to a higher level adjacent the edges of the strip whereby to maintain the level of the pool substantially uniform at least for the entire width of the strip, a pair of supports carrying said nozzles and movably disposed adjacent the opposite edges of the strip, said supports having means engaging the respective strip edges, and means resiliently urging the supports inwardly toward the strip edges.

References Cited in the file of this patent UNITED STATES PATENTS 2,034,348 Lytle Mar. 17, 1936 2,155,083 Drewsen Apr. 18, 1939 2,438,787 Nicholas Mar. 30, 1948 2,653,566 Worden Sept. 29, 1953 2.708.171 Inglefield May 10, 1955

Claims

18. IN THE CONTINOUS METAL COATING OF A STRIP WHEREIN THE STRIP IS PASSED THROUGH A BATH OF MOLTEN METAL AND THENCE UPWARDLY BETWEEN A PAIR OF COATING ROLLS PARTIALLY SUBMERGED IN THE BATH WITH AN ELONGATED POOL OF MOLTEN METAL BEING FORMED IN THE NIP BETWEN THE ROLLS, THE IMPROVEMENT COMPRISING DIRECTING GASEOUS MATERIAL AT AN ANGLE DOWNWARDLY AND OUTWARDLY TOWARD THE LONGITUDINAL EDGES OF THE STRIP AGAINST THE SURFACE OF THE POOL AT THE OPPOSITE ENDS THEREOF WITH SUFFICIENT VELOCITY TO PREVENT THE POOL FROM RISING TO A HIGHER LEVEL ADJACENT THE EDGES OF THE STRIP WHEREBY TO MAINTAIN THE LEVEL OF THE POOL SUBSTANTIALLY UNIFORM AT LEAST FOR THE ENTIRE WIDTH OF THE STRIP, AND CONFINING CONTACT OF SAID GASEOUS MATERIAL SUBSTANTIALLY ENTIRELY TO THE SURFACE OF THE POOL WITHOUT SUBSTANTIALLY CONTACT WITH THE STRIP.