US2388131A - Method of coating sheets - Google Patents

Description

2 Sheets-Sheet l Oct. 30, 1945. F. E. FAIRLEY ETAL METHOD OF COATING SHEETS Filed Fel?. 2, 1943 /ZD/VA/ CZ Patented Oct. 3 0, 1945 2,888,131 METHOD OF/COATING SHEETS Frank E. Fairley, Birgiilghdambhois 'l'. lindquist, Bessemer, an y e cliaels and Boilers, Birming Howard C.

ham, Ala., aneignors to Tennessee Coal, Iron and Company, Birmingham, Ala.. a corporation of Ala- Application February 2, 1943, Serial No. 474,460

ZCiaims.

The present invention relates to improvements in methods of coating sheets, and in its broadest aspects aims to provide for effectively transferring heat from the molten coating metal to the body of oil floating on top of the metal so as to maintain the oil body in the optimum operating condition.

. metal sheet through a molten bath of the coating metal, then upwardly out of the bath through a body of palm oil. In the normal operation of such methods, difficulties are frequently caused directly or indirectly by non-,uniformity of the oil temperature. The present invention aims to overcome the shortcomings of theI prior practice by the provision of a method of transferring small quantities of the molten metal upwardly into the region of the .upper zone of the oil body and to permit such hot molten metal to descend through the oil body and thereby give up heat thereto. In this way the oil body is maintained at the optimum operating temperature and condition, due in part to the rapid heat exchange and in part to the gentle turbulence set up by the descending cascade of molten metal through the oil body.

By way of example, apparatus suitable for the practice of the method is shown in the accompanying drawings, inwhich: l

Figure 1 is a vertical longitudinal section through the apparatus.

Figure 2 is a transverse section on line lI-lI thereof.

Referring in detail to the drawings, I represents the wall structure of a suitable heating chamber supporting the melting pot I2 the con- -tents of which are adapted to be heated chiey by a burner I4 supplied with gases or other suitable fuel under control of the valve I 6. There is an intermediate wall is approximately in line with the transverse division wall 2li of the melting pot. As distinguished from prior practice, the portion of the melting pot to the exit side of the division wall is not directly heated by fire, since the chamber 22 below the exit half of the pot is blanked oil' by the wall I8.

Located on the exit side of the division wall .2l there are a plurality of conventional pairs of exit rolls 24, 2l, and 2l driven by the gears 30, I2 and 14. The apparatus is also equipped with a pair of conventional feed-in rolls 38 which feed the plate P to be coated with molten metal through flux contained vin a box 3l, thence downwardly through the metal bath 4l which may be regarded either as terne metal 0r molten tin. A pair of feed rolls 42 driven in any suitable'manner force the plate through a conventional guide or apron 44 which directs the plate to the lower set of exit rolls 24.

'Ihe top level of the bath of .molten metal at the inlet side of the division plate 2l is indicated at 46. The metal level at the right exit side of l 1e division plate 2li is slightly lower, as indicated at 48. Superposed on the metal bath above the metal level 48 on the exit side of the melting pot is a body of palm oil indicated at 50. through which the outgoing sheets are compelled to pass as they leave the pot. 1

The chief feature of novelty of the present invention resides in elevating the molten metal to a point above the normal top metal level 48 into the upper region of the body of oil 50, and permitting it to fall by gravity or cascade through the oil body to thus raise its temperature and create a mild degree of turbulence or agitation. This maintains the optimum temperature and condition of the oil body. In the embodiment of the invention illustrated, we provide upper and lower shafts 52 and 54, the upper shaft can'ying a plurality of sprockets 56 immersed in the intermediate or upper region of the oil body, and the 1" lower shaft 54 carrying a plurality of sprockets 58 whose lower portions extend into the molten metal bath. Conveyor chains 60, each carrying a plurality of buckets 62 are trained around the sprockets 56 and 58, and suitable means are provided for driving the conveyor. In the machine illustrated,.the upper shaft 52 carries a gear 64 which meshes with the gear l2 carried by .one of the exit rolls 26. ever, that the conveyor may be driven independently of the exit rolls, if desired, by a separate motor drive, so that the bucket conveyor for lifting the molten metal and dropping it through the oil body can be driven at times when it is not possible to run the exit rolls. Thus the condition of the oil bath can be maintained, even though temporary shut-downs are necessary to make repairs or adjustments in the coating apparatus.

In the normal operation of the method, it will be readily understood that the sheet to be coated is fed downwardly by the feed rolls 36 through It is to be understood, how? 2 l assaisi the nux in the box il and into the molten bath 40. then via feed rolls l2 and exit rolls 24, 20 and 28 the sheet is fed upwardly and out to a suitable discharge point, and while being discharged is passed through the body oi' palm oil l0, which oil is e'ectively maintained at a proper temperature without the application of direct heat to the metal pot in the zone of the oil body, the heat y transfer being effected by the cascading eitect oi l t the molten metal through the oil body. which is a very eillcient manner oi' effecting a rapid transfer of heat uniformly through all regions of the oil body. The improved method disclosed will improve over prior practice because it will lessen the tendency o! the oil to break down,and the useful life of a given batch of oil will be longer. Thus there will be a marked economy in oil consmnption. Coupled with this economic advantage, the lack o! oil troubles will increase production, and the absence of direct iiring under the oil body will lessen the danger from nres and will also cut down the fuel cost. Practice indicates that the invention contributes longer life to the melting pot. This makes for lower maintenance costs. Because of the maintenance olf the oil body at optimum temperature and condition,V a better coated metal product of more uniform quality is produced, and experience teaches that theproduction of seconds known to those skilledin the art as menders and waste waste, is materially reduced. t

The apparatus herein illustrated is claimed in a division of this application, Serial No. 591,508, tiled May 2, 1945. While the invention is peculiarly well suited for the coating of ferrous metal sheets or plates with terne metal, it is to be understood that the improved method is also applicable to the coating of sheets or plates with tin. Various modifications may be made by those skilled in the art without departure from the invention as defined in the appended claims'.

We claim:

1. In the production of metal coated sheets involving passing each sheet through a bath of molten coating metal and then through a body of oil superposed on said bath, the improved method comprising elevating some of the molten metal above the top level of the bath in a path in spaced relation to the path o! movement of the sheet, and emptying the thus elevated metal into the upper portion of the oil body and allowing it to cascade by gravity therethrough so as to maintain the oil at the optimum operating temperature.

2. In the production of metal coated sheets involving passing each sheet through a bath of molten coating metal and then through a body of oil superposed on said bath. the improved method comprising sequentially elevating separate quantities oi the molten metal above the top level of the bath in a path in spaced relation to the path of 'movement of the sheet, and dumping the thus elevated metal and allowing it to cascade by gravity through the oil body so as to maintain the oil at the optimum operating temperature.

FRANK E. FAIRLEY. LOUIS '1'. LnIDQUIGT. CLYDE .D. MICHAELB. HOWARD C. RODGERB.

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