US1983018A - Method of and apparatus for rolling sheets - Google Patents

Description

19344 c. A. DAVIS METHOD OF AND APPARATUS FOR ROLLING SHEETS Filed June 4, 1932 EZWZ ZEEZZEZZ WITNESS .FITTOHNE) Patented Dec. 4, 1934 UNITED STATES 14 Claims.

My invention relates to the manufacture of ferroussheets and more particularly to the production of such sheets on what are known as l automatic mills as distinguished from the hand 5 mills formerlyemployed for the purpose. These automatic mills are of relatively recent development in the iron and steel industry andare replacing the hand mills insheet production quite rapidly despite certain drawbacks which it is the purpose of the present invention to remedy; As at present constructed, automatic mills are capable of producing sheets morerapidly land with less labor than hand mills but priorto my invention it has been impossible to obtain sheets of as high quality through the medium of the former as those which are normally produced on the latter, principally because at a certain stage of the process of manufacture in an automatic mill, the sheets,

then in the form of packs, are necessarily sub- 26 jected to a large loss of heat. This cooling of the sheets results in oxidation and also in some change in the-character of the metal so that after finish rolling, they have undesirable rolling char- 5 acteristics which tend to reduce the average yield of prime finished product. Moreover, the cost of reheating the sheets increases the cost of production through the expenditure of the relatively large amount of fuel required to raise them 0 from their relatively cold condition to a proper working temperature. These disadvantages are not inherent in the production of sheets on hand of operation thereof since any material cooling of the sheet packs is avoided at any stageo-f the process.

improve the present practice of sheet production on automatic mills through the provision of a method of operation which avoids material loss stage of the process as well as toprovide improved apparatus adapted for carrying out the said method whereby through the practise of my invention the production on an automatic mill of sheets of as high quality as those normally produced on hand mills is made possible while the cost of production of such sheets is reduced through economization of fuel.

Other objects, advantages and novel features of design, construction and arrangement of apparatus comprehended by or incident to my invention are hereinafter more particularly pointed out 101' will be apparent to those skilled in the-art from the following description of the invention,

they are reheated to a temperature proper for mills in accordance with the customary method It is therefore an object of my invention to of heat from the sheets or sheet packs at any PATENT OFFICE METHOD, OF AND APPARATUS FOR ROLLING SHEETS during which reference will be had to the accompanying diagrammatic drawing.

i A brief reference at this point to the present method of rolling sheets on an automatic mill of usual design will facilitate a proper understanding of my invention. Such a mill comprises, generally speaking, a heating furnace through which extends a pair of sheet conveyors arranged in parallel relation, the furnace being of relatively great length in comparison to its width. At the charging end of the furnace is a charging platform to which the breakdowns, namely,- slabs of metal which have been given a preliminary rolling in a suitable mill, are delivered in stacks by a suitable conveyor or in any other 7 convenient way preparatory totheir being superposed in matched relation to form packs andthen chargedinto one side of the furnace by an operative standing on the charging platform. Beyond the opposite end of the heating furnace is dis- ,75 posed a stand of rolls upon which the rolling operations are performed, the center of these rolls being in approximate alignment with the center of the furnace; on each side of the rolls is a table by suitable actuation of which the sheets are passed back and forth between and over the rolls, and between the end of the furnace and this table is an apron comprising a suitable conveyor by means-of which the sheets can be transferred from either furnace conveyor to the table when and as required. At one side of the furnace, generally that opposite to the one on which the breakdown conveyor is disposed, is arranged a return conveyor upon which the breakdown sheets after having been heated in the furnace,

rolled for a suitable number of times in the mill stand, separated, matched and doubled (and now termed runovers) are returned to the charging end of the furnace preparatory to a second passage therethrough designed to raise them to a 9 proper temperature for finish rolling. With an apparatus of this general character, the normal sequence of operations when onceestablished is as follows: The charger at the charging end of v the furnace-consecutively feeds the breakdown packs onto the conveyor at one side of the furnace and alsoconsecutively feeds the doubled packs onto the conveyor at theother side of the furnace sothat a series of breakdown packs and a series of doubled packs are continuously moving therethrough from the charging end towards the discharge or rolling end. The operatives at the latter first withdraw a'breakdown pack and subject it to a suitable number of passes through the I roll "stand, thus reducing the thickness of the 0 sheets in the pack and effecting substantial elongation thereof, the pack, of course, when withdrawn from the furnace being at proper working temperature. As soon as this pack is rolled it is moved to one side, the sheet are separated to prevent permanent adherence to each other and rematched, and the pack is then doubled by hand, the fold pressed down in a doubling press, and the doubled pack placed on the return conveyor by which it is slowly moved toward the charging end of the furnace and from which in due course it is recharged onto the furnace conveyor by the charger and again moved through the furnace. As soon as one breakdown pack has been rolled in this manner, and while it is being doubled, the leading doubled or finish pack is withdrawn from the furnace and subjected to the requisite number of passes through the rolls to reduce the sheets in it to the desired finished thickness after which it is removed from the table on the far side of the rolls and subjected to the usual finishing operations which form no part of the present invention. It is thus appar-- ent that the breakdown packs and doubled or finish packs are alternately withdrawn and rolled and that until the leading pack on either furnace conveyor is so withdrawn it is impossible for the charger to introduce a fresh pack onto that conveyor at the charging end of the furnace irrespective of the length of the latter. It is consequently the usual practice to operate the return conveyor at a comparatively low speed so that the doubled packs will consecutively reach the charging end of the furnace in properly timed relation to the withdrawal of the corresponding packs at the rolling end, thus preventing accumulation of the doubled packs on the charging platform. The time interval between the doubling of the pack and its return to the furnace at its charging end-is thus necessarily considerable and results in a material loss of heat by the pack irrespective of the particular speed at which the conveyor is operating, for any given pack, whatever be the time required to return it to the charging platform, cannot be recharged into the furnace until the leading pack on the furnace conveyor is removed. Consequently, if the conveyor be speeded up, it merely results in an accumulation of a large number of doubled packs on the charging platform where they lose heat just as rapidly as they do while on the conveyor. In short, the rate at which the doubled packs can be returned and charged into the furnace for reheating preparatory to finish rolling is definitely determined by the rate at which the doubled and reheated packs are withdrawn and finish rolled, and as this rolling operation on each pack requires a considerable amount of time and can be performed only alternately with the rolling of the breakdown packs, the doubled packs from the time they are doubled until they are returned to the furnace lose large quantities of heat which results in oxidation of the metal, renders it less desirable for subsequent rolling, and finally requires that the pack be reheated from a comparatively cold condition to proper working temperature before it can be finish rolled. It is an ob ject of my invention, as hitherto stated, to largely prevent this loss of heat and the disadvantages incident thereto.

In carrying out my invention I utilize an automatic .sheet'mill of the general character of that to which I have just referred with suitable modifications in accordance with the invention as shown on the accompanying diagrammatic draw arranged for the practice of the invention in a ing in which Fig. 1 is a top plan view, partially in horizontal section, of such a mill and its auxiliary apparatus arranged for the practice of the invention; Fig. 2 is a similar but fragmentary view of the charging end of another such mill somewhat different way, while Figs. 3 and 4 are respectively enlarged transverse sections on the lines 33 of Figs. 1 and 2 and the line 44 of Fig. 1, the same characters of reference being used to designate corresponding parts throughout the drawing.

As automatic sheet niills are in common use and well understood, specific illustration or description of the details thereof and/or of the auxiliary apparatus employed in the operation of 'such mills would be superfluous, and I therefore shall refer thereto only sufficiently to enable those skilled in the art to readily comprehend and practise the present invention.

Referring now to the drawing, the mill therein shown in Fig. 1 comprises the usual furnace 1 adjacent the charging end of which is a charging platform 2. Extending longitudinally through the furnacein parallel relation are conveyors 3, 4 desirably of chain type which, when the mill is in operation, move in the direction of the arrows, each conveyor being preferably independently driven by driving mechanisms 6, which are under the control of the rolling crew. Extending outwardly from the discharge end of the furnace is an apron 7 provided with a roller conveyor 8 by means of which the sheet packs can be directed from either of the conveyors 3 or 4 to the table 9 disposed between the apron and the roll stand 10, another table 11 being arranged on the opposite side of the roll stand in the usual way. These tables are operated automatically or otherwise so as to pass a sheet pack coming from the furnace first between the rolls of the roll stand and thence in the opposite direction over the upper roll to thereby reduce the thickness of the sheets in the pack by successive application of rollingv pressure thereto. Extending alongside the furnace from a point adjacent 1 the roll stand is a return conveyor 12 desirably of the chaintype and conveniently driven by suitable mechanism 13, while the usual doubler 14 is disposed at a convenient point for pressing the doubled packs prior to their being placed on 1 the return conveyor. In an automatic mill of usual construction, the return conveyor terry;- nates adjacent the charging platform 2 so that the charging operator can readily remove the returned packs consecutively therefrom and place 1 them on the conveyor 4; this arrangement I preferably modify somewhat as hereinafter more fully explained. On the opposite side of the furnace from that on which the return conveyor 12 extends, a breakdown conveyor 15 of any 1 suitable type may be provided for facilitating delivery of the breakdown sheets to the opposite side of the platform from which point they are charged onto the conveyor 3 bythe charging operative when and as required.

In accordance with the present invention, I place in alignment with the return conveyor 12 a furnace 20 which I term a, holding furnace. This furnace may be of any construction suitable for the performance of its intended function and may be provided with heating means such as the gas burners 21 if desired. It is so arranged that the doubled packs are discharged into it automatically from the conveyor 12, the end of which: remote from the roll stand 10 de- .sirably terminates adjacent the proximate end of the holding furnace, while from the opposite endofltheyholding furnace a conveyor 22 ofany suitable type is extended to a point adjacent the chargingend of the conveyor 4 so that as the sheet packs are withdrawn from the holding furnace on the conveyor 22 when and as required, they can be readily charged onto the conveyor 4 preparatory tobeing conveyed for a second time through the main furnace 1. The conveyor 22 may be extended substantially through the holding. furnace so as to furnish a support for the sheet packs when and as discharged thereinto but is ofsuch character and the furnace is so arranged that the rate of discharge of the packs from the holding furnace in the direction of the charging end of the main furnace is under the control of. the charging operator to thereby enable him to maintain the packs in the holding furnace until one of them is required for charging into the main furnace.

For the purpose of conserving the heat in the packs from the time theyare placed on the return conveyor 12 until they are discharged into the holding furnace, the upper run of the conveyor, as best shown in Fig. 3, is preferably disposed within a substantially closed casing 25, either of refractory material as shown or, in some cases, of sheet iron, with the result that the packs enter the holding furnace at a relatively higher temperature than would be the case in the absence of the casing 25. Additionally, with a view to getting the packs into the holding furnace in a minimum amount of time, I prefer to materially increase the speed of the return conveyor 12 above that usually employed, as in accordancewith my invention, the speed of this conveyor need not be timed with relation to the speed of the conveyor 4 for it is of little or no moment if the packs accumulate in the holding furnace faster than they can be withdrawn therefrom, whereas in the absence of the holding furnace it isundesirable that an accumulation of packs take place on the charging platform. 1

In accordance with the preferred practice of the invention, I furthermore provide the furnace 1 with a longitudinally extending partition wall which serves to divide it into two chambers respectively containing the conveyors 3 and 4, and to arrangeheating means, exemplified by the burners 31, 32, fo-rindependently controlling the temperature of these chambers, whereas in the usual type of heating furnace employed in automatic sheet mills, both conveyors are disposed in a single chamber, and the sheet packs respectively disposed on the conveyors are thus subjected to the same temperature in their passage throughthe furnace. Desirably, as shown, the casing 25 is extended overthe conveyor 22 so as to prevent material loss of heat by the packs during their passage from the holding furnace to themain furnace.

In the production of sheets in accordance with the method of my invention on an automatic sheet mill embodying the several improvements shown in Fig. 1, the breakdowns are delivered in stacks by the conveyor 15 to the charging platform 2. The charging operator then matches them into packsof two or more and consecutively charges these packs onto the conveyor 3 by which they are carried through the furnace 1 while being raised to a suitable working temperature. At the same time, after normal conditions of operation re established, doubled packs consecutively withrawnfrom the holdingfurnace 20 are passing through the main furnace upon the conveyor 4. The rolling crew at the discharge end of the furnace first withdraw a pack of breakdowns from the furnace and give it one or two passes through the mill. This pack is then placed on the floor and, after the sheets have been separated and re-matched, is doubled, pressed in the doublet l4, and placed on the return conveyor 12 as quickly as possible, and bythis conveyor carried into the holdingfurnace. While the. separating, rematching and. doubling of this pack are under way, the leading doubled pack is withdrawn from the conveyor 4, given a finish-rolling in the mill 10, and finally removed from the table 11 for the usual subsequent finishing operations. The holding furnace is generally kept at a, temperature such that the packs therein are maintained at approximately-the same temperature as that at which they entered it, or, if preferred, the holding furnace may be so operated as to increase the temperature of the packs somewhat. In either case, itis apparent that when each pack is withdrawn from the holding furnace and re-charged into the main furnace, it enters the latter at amaterially higher temperature than would be the'case in the'absence of the holding furnace, and thus not, only requires less heating in the main furnace to bring it to suitable temperature for further rolling, but is prevented from attaining a condition unsuitable for the production of a high quality product as is the case when theqpacks are allowed to cool materially between the doubling and the re-charging operations. Normally, therefore, it is unnecessary to maintain the furnace chamber containing the conveyor 4 in as highlyheated condition as that containing theconveyor 3, and since these chambers are preferably made separate and provided with independent heat controlling means as above described, they may be respectively kept at proper temperatures for insuring the delivery of the breakdowns and doubled packs at the discharge end of the furnace in the best condition for the rolling operations. i

In Fig. 2 I have shown a slightly different arrangement of apparatus adapted for the performance of my improved method and which under some conditions may be preferred to the arrangement hitherto described. Thus, instead of providing a separate holding furnace 20, the main furnace 1 may be extended laterally to provide a chamber 40 adjacent its charging end and on the side of the furnace on which the re-. turn conveyor 12 is located. Adjacent this conveyor the wall of the chamber is provided with a door 41 for the passage of the packs, while within the chamber is positioned a suitable conveyor' 42-, conveniently of the roller type, in prolongation of the conveyor 12 and adapted to receive the packs therefrom. Extending transversely of this conveyor are one or more conveyors 43 of the chain or walking beam type controlled from the exterior of the chamber and adapted to pick up a pack from the conveyor 42 andmove it transversely onto the conveyor 4. In this form of apparatus the doubled packs are carried into the chamber 40 by the return conveyor 12 and held in this chamber until a vacancy occurs on the conveyor 4 when by suitable manipulation of the transverse conveyors 43 one of the packsis shifted thereto preparatory to its final movement through the main furnace. Desirably, as in. the. case of the form'of apparatus shown in Fig. 1, the main furnace is provided with a'longitudinal partition wall 30 whilethe return conveyor 12 is enclosed in a suitable casing 25 to minimize heat losses from doubled packs during their passage to the chamber 40.

It will be understood that it is within the scope of my invention to also provide a holding furnace adjacent the breakdown conveyor 15 for receiving the breakdown sheets and conserving their heat while they are waiting to be charged onto the conveyor 3 and I have indicated such furnace 50 in broken lines in Fig. l; as its function will be readily appreciated from the foregoing and its particular form and construction are a matter of choice, further reference thereto would be superfluous.

It will, of course, be appreciated that in the normal operation of an automatic sheet mill the movement of the conveyors 3 and 4 is under the control of the rolling crew so that the said conveyors can be operated to deliver the sheet packs at properly timed intervals for the rolling operations and, consequently,"if the rolling of any particular pack takes a littlelonger than usual, one or both conveyors are stopped or slowed down suifioiently to compensate for the delay. In short,

the rate at which the packs are alternately withdrawn and rolled is the controlling factor in the sequence of operations and, as hitherto pointed out, necessarily control the rate at which the breakdown packs and the doubled or finish packs can be charged into the furnace at the charging end. In order to avoid complication of the drawing no attempt has been made therein to indicate the sheet packs or their relative position with respect to the different parts of the apparatus at any stage of the method.

It will thus be apparent that in accordance with my invention I prevent material cooling of the doubled packs during their return movement from the point at which they are doubled to the holding furnace by operating the return conveyor at a speed relatively high in comparison with the average movement of the conveyors 3 and 4; that the doubled packs are then retained in the holding furnace or equivalent chamber 40 for so long as may be necessary without further loss of heat and, in some instances, are actually raised in temperature therein, and that they are finally recharged into the main furnace for their final movement therethrough in a relatively highly heated condition, thus avoiding excessive oxidation and inherent changes in the character of the sheets with corresponding alteration in their rolling characteristics, and by conservation of the heat imparted to the packs in their initial movement through the furnace effecting a material economy in the amount of fuel required for the production of each finished sheet. Moreover, the use of my invention in no way interferes with but on the contrary tends to facilitate the operations incident to the manufacture of finished sheets on an automatic mill and enables the production on such a mill of sheets of as high average quality as can be produced on the customary hand mills.

While I have herein described a preferred manner of performing the method of my inventionand desire to protect by Letters Patent of the United States:

1. That method of rolling sheets which comprises the steps of moving sheets in parallel lines from the charging end of a heating furnace toward its delivery end, rolling a sheet taken from one of said lines, doubling the rolled sheet, moving the doubled sheet in reverse direction to a point adjacent the charging end of the furnace and positively subjecting said sheet to a relatively high temperature during'said reverse movement, recharging it into the furnace and again moving it therethrough in a path other than that of its initial movement, and rolling a doubled sheet taken from said last-mentioned path while the first sheet is being doubled and reversely moved preparatory to recharging.

2. A cyclic process of producing rolled sheets which comprises the steps of consecutively charging packs of sheets into one end of a heating furnace and moving them therethrough in parallel paths, withdrawing one of said packs from the opposite end of said furnace, rolling said pack, doubling said rolled pack, returning the doubled pack to a point adjacent the charging end of the furnace, positively subjecting the pack during said return to a relatively high temperature, and, while said return is taking place, Withdrawing another doubled pack from the furnace, finish-rolling said pack, and finally recharging said first-mentioned pack into the furnace as soon as said last-mentioned pack is withdrawn therefrom.

3. In sheet production, the steps of moving sheet packs through a heating furnace in parallel lines, removing a pack from one of said lines atthe delivery end of the furnace and subjecting it to rolling pressure, doubling said rolled pack, moving the doubled pack in reverse direction toward the charging end of the furnace, removing another pack from the other line and subjecting it to rolling pressure during said reverse movement of the doubled pack, subjecting the doubled pack to a predetermined and relatively high degree of heat during said reverse movement, and finally recharging said doubled pack into the furnace in a line other than that at which it was first moved therethrough preparatory to reheating and finish-rolling said pack.

4. In sheet production, the steps of consecutively charging sheet packs into a furnace in separate lines, moving said packs through the furnace, alternately withdrawing the heated packs from said lines at the delivery end of the furnace and subjecting the Withdrawn packs to rolling pressure, doubling every alternate rolled pack, consecutively returning said doubled packs to a point adjacent the charging end of the furnace and during said return movement subjecting said packs to a predetermined temperature to thereby prevent excessive heat loss from the packs, and finally recharging said packs'into the furnace in a line other than that in which they were first moved therethrough.

5. In sheet production, the steps of consecutively charging packs of sheets into a heating furnace, moving said packs therethrough in two parallel paths to raise them to working temperature, alternately removing the packs from said paths at the delivery end of the furnace and subjecting them to rolling pressure, doubling each rolled pack withdrawn from one of said paths, consecutively returning each doubled pack to a point adjacent the charging end of the'furnace and during said return movement temporarily holding each pack in a zone of predetermined relatively high temperature, and finally recharging the doubled packs consecutively to the furnace after removal from said zone.

6. In sheet production, the steps of consecutively charging sheet packs into a heating fur nace, moving said packs therethrough in parallel paths, alternately withdrawing said packs from said paths at the delivery end of the furnace and subjecting them to rolling pressure, doubling each rolled pack withdrawn from one of said lines, moving each doubled pack toward the charging end of the furnace at a speed greater than that at which it was initially moved therethrough, passing said pack through a zone of elevated temperature to conserve its heat content prior to moving it to position for recharging, and recharging it into the furnace in a path other than that at which it was initially moved therethrough preparatory to re-raising it to working temperature and finish-rolling it.

'7. In sheet production, the steps of moving sheet packs consecutively through a heating furnace, withdrawing said packs therefrom consecutively and subjecting them to rolling pressure,

doubling each rolled pack, moving the rolled pack toward the charging end of the furnace at a speed greater than that at which it was initially moved therethrough, passing the pack through a zone of relatively high temperature to thereby conserve its contained heat, and finally recharging the pack into the furnace and reheating it therein preparatory to finish-rolling while moving it in a path other than that in which it was initially moved therethrough.

8. In sheet production, the steps of consecutively charging sheet packs into a heating furnace, raising the packs therein to a temperature suitable for rolling, withdrawing the packs therefrom, rolling and then doubling the packs, and then temporarily maintaining the packs in a zone of relatively high temperature to prevent substantial heat loss therefrom prior to their being recharged into the same heating furnace, and finally recharging them thereinto for reheating to a temperature suitable for further rolling.

9. Sheet rolling apparatus comprising a heating furnace having a pair of conveyors extending therethrough respectively adapted to move sheet packs consecutively from the charging to the delivery end of the furnace, rolling means disposed adjacent said delivery end, a return conveyor extending from the vicinity of said rolling means toward said charging end adapted to move the packs, after rolling in a direction opposite that in which they were initially moved through the furnace, a holding furnace adapted to receive the packs from the conveyor and inhibit material dissipation of their heat content while they are maintained therein, and means for discharging the packs from the holding furnace to a point convenient for recharging into the heating furnace.

10. Sheet rolling apparatus comprising a heating furnace having a pair of conveyors extending therethrough respectively adapted to move sheet packs consecutively from the charging to the delivery end of the furnace, rolling means disposed adjacent said delivery end, a return conveyor extending from the vicinity of said rolling means toward said charging end adapted to move the packs after rolling in a direction opposite that in which they were initially moved through nace at a predetermined temperature, and means for discharging the packs from the holding furnace to a point convenient for recharging into the heating furnace.

11. Sheet rolling apparatus comprising a heating furnace having a longitudinally extending partition wall dividing it into two separate chambers, a conveyor extending in each chamber adapted to move sheet packs therethrough, rolling means disposed adjacent one end of the furnace, a return conveyor, extending from a point adjacent said rolling means toward the opposite end of the furnace, adapted to move the packs after rolling in a direction opposite their initial movement through the furnace, means providing a heating chamber for receiving the packs from said return conveyor, and means for discharging said packs from the chamber preparatory to recharging them into the heating furnace.

12. Sheet rolling apparatus comprising a heating furnace having separate chambers, means for independently controlling the temperature of each chamber, a conveyor extending through each chamber adapted to move sheet packs therethrough from the charging to the delivery end of the furnace, rolling means disposed adjacent said delivery end, a return conveyor, extending from the vicinity of said rolling means toward the charging end of the furnace adapted to move the packs after rolling in a direction opposite to that of their initial movement through the furnace, a holding furnace aligned with said return conveyor for receiving the packs therefrom, and means for discharging said packs from said furnace preparatory to recharging them into the heating furnace.

13. Sheet rolling apparatus comprising a heating furnace having separate chambers, means for independently controlling the temperature of each chamber, a conveyor extending through each chamber adapted to move sheet packs therethrough from the charging to the delivery end of the furnace, rolling means disposed adjacent said delivery end, a return conveyor extending from the vicinity of said rolling means toward the charging end of the furnace adapted to move the packs after rolling in a direction opposite that of their initial movement through the furnace, means enclosing said conveyor to minimize heat loss from the packs while disposed thereon, a holding furnace aligned with said return conveyor for receiving the packs therefrom, and means for discharging said packs from said furnace preparatory to recharging them into the heating furnace.

14. In sheet rolling apparatus, a heating furnace having separate chambers, means for individually controlling the temperature of each chamber, a holding furnace, means for controlling the temperature thereof, a sheet pack conveyor in each heating furnace chamber, rolling means disposed adjacent the delivery end of said furnace, a return conveyor extending from adjacent said rolling means to the holding furnace, and conveying means extending from the holding furnace to a point adjacent the charging end of the heating furnace.

CHARLES A. DAVIS.

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