US2155418A - Furnace construction - Google Patents

Description

April 25, 1939. J. o. GRIGGS El AL 7 2,155,418

.- FURNACE CONSTRUCTION Filed Sept. 22, 1936 3 Sheets-Sheet l Ar z jelv zs s April 25, 1939. O. GRIGGS ET AL 2,155,418

FURNACE CONSTRUCTION Filed Sept 22, 1956 5 Sheets-Sheet 2 w a T Q 2 a Q;

a 3 A 2 Q g 2" i N INVENTORS Q JOHN C. GRIGGS 8.

N e BERT H. LEEKS A TTOR E Y6 April 25, 1939. J. o. GRIGGS ET AL 2,155,418

FURNACE CONSTRUCTION Filed Sept. 22, 1936 3 Sheets-Sheet 3 INVENTORJ JOHN o. GRIGGS &

A TTORNEYS Patented Apr. 25, 1939 UNITED STATES FURNACE CONSTRUCTION John 0. Griggs, Lakewood, and Bert H. Leeks,

. Bcdf 11, Ohio Application September 22, 1936, Serial No. 101,970

4 Claims.

This invention relates to improvements in furnace construction and more particularly to an arrangement of a furnace roof to permit top charging.

Our invention is particularly applicable to open hearthfurnace roofs. At the present time, open hearth furnaces are charged through doors arranged along one of the longitudinally extending side walls of the furnace. Because it is desirable to keep the furnace roof low for the control of combustion and'for the better heating of the charge, the side walls are of limited height which limits the size of the doors. It is therefore necessary to cut the scrap steel to be charged into the furnace to a small enough size to be accommodated in rectangular charging boxes which. will pass through the furnace doors. Much time and expense, and risk of injury, is involved in thus preparing steel scrap and arranging it in charging boxes. Furthermore, there is heavy expenditure in the provision and maintenance of equipment for transporting the charging boxes to the charging floor and for special charging machines for handling the boxes into and out of the furnace. through the doors during a charging operation.

Necessarily, the handling of a large number of relatively small boxes-during a charging operation involves considerable time,--approximately three hours in the charging of a 150-ton furnace. During this charging period the doors are open, the fuel is off, and the furnace cools down considerably. Therefore time is lost and the number of heats which may be produced from a given furnace in a given periodof time is greatly reduced. There is also an undesirable effect upon steel quality due to the alternate cooling down and heating up of the charge during the melting down period. It is one of the objects of our inventionto minimize or avoid all of the above costs and delays and disadvantages by providing a furnace which may be charged from the top.

One of the objects of the present invention is to provide, in a full size open hearth furnace, a roof which may be opened over substantially the entire area of the hearth in a manner to permit top charging at any point thereof.

Another object of the invention is to provide in such a furnace a roof .openable in sec tions to permit top charging at a selected point in said furnace without the necessity for opening the entire roof area.

Another object of the present invention is to provide a roof having one edge pivotally mounter at the top of one of the longitudinally extending side walls. Preferably the pivotal mounting is so arranged that the roof or a portion thereof may be lifted off vertically without disconnecting any fastenings, but at the same time the pivot functions as intended by a pull upon the roof, or a section thereof, which has a horizontal component directed toward the pivoted edge of the roof;

Other objects and advantages of the present invention reside in the novel construction of an arched roof permitting the same to be moved, novel arrangement of a pivotal mounting therefor, improvements in pivot construction for a furnace. roof of this type including a watercooled construction, and the arrangement of an open hearth roof in reversible sections with advantages which will be pointed out later.

The present invention includes various novel structures pointed out in the accompanying specification and illustrated in the drawings and the essential features will be set forth in the claims.

In the drawings, Fig. 1 is a front elevation of a portion of an open hearth furnace above the charging floor level, the same being broken away to show parts of the furnace construction. One of the roof sections is shown in raised position. Fig. 2 is a fragmental enlarged transverse section through a furnace embodying our invention, certain parts being broken away to more clearly show the construction, while Fig. 3 is a transverse section through the furnace taken at another point to show additional features of the construction and to show the general position of the furnace in a shop.

Our .invention is illustrated as applied to an open hearth furnace of usual construction, comprising a bottom. III, a front wall H, a back wall l2, a roof l3 and suitable ends II. The left end portion in- Fig. 1 has been shown broken away to indicate the usual port l5 for directing the flame against the bath and the up-takes l6 lead to the usual checker chambers for preheating airor gas, or both. It will be understood by those skilled in this art that if liquid fuel is used. it is introduced by burners suitably arranged to direct the fuel through the ports IS. The front wall is provided with door openings I'I 'covered by the usual water-cooled doors l8, which are hung from above for opening and closing. In the application of our invention we are able to reduce these door openings from the usual size because large material is all charged through the roof and the doors are used only for the addition the taining the door openings.

The side walls of the furnace are supported by buckstays I9 which are of sufficient rigidity to support the side walls and to take the side thrust arising from the arched roofconstruction; There is practically no side thrust using our improved roof structure, as the metal frame 22 withstands such stresses. Through the rear of the furnace is provided a tap hole 20 and it will be understood without further description that the furnace is provided with all of those appurtenances necessary to the usual operation of open hearth furnaces.

Our invention provides a roof which is removable or adapted to be swung so as to open the furnace at the top for the introduction of bulky material to be charged. In the preferred form the roof is pivotally mounted at one edge at the top of one of the longitudinally extending side walls and means is provided for opening the roof about the pivot. Preferably the pivot mounting is arranged with interfitting parts which permit ready separation of the parts by a mere vertical lifting of the roof. This is for the purpose of permitting a portion of the roof to be removed for repairs or replacement without the necessity of disconnecting fastenings which might become corroded in the atmosphere surrounding the furnace and in any case are hot and not readily accessible. The pivot construction, however, is so arranged that the parts do not become separated in the opening and closing of the roof by a pull exerted on the roof with a horizontal component in the directionof the pivoted edge.

In carrying out our invention we prefer to provide roof sections A, B, C and D so that only a portion of the roof need be opened at one time when desired and so that the entire roof need not be handled at one time, as it will be understood the contruction is very heavy. As best seen in Fig. 2, each section comprises refractory material 2!, supported substantially rigidly in a frame 22. The material 2| is usually silica brick whose expansion characteristics are well known and may be accurately calculated. The frame is provided with transversely extending flanges 23 and longitudinally extending flange portions 24. The frame 22 is lined with the brick work 2| .so calculated that when the roof is heated the brick work expands and the bricks are wedged tightly between the flanges 23 in one direction and the flange portions 24 in the other direction, so that a sprung arch is provided with insuflicient strain against the embracing flanges to cause spalling of the brick. Such a method of constructing a spring arch is old and well known.

When the various sections of the roof are closed and the furnace is in operation we prevent any fusion of the brick work at the joints 25 by sealing the joints on the outside of the roof.

The frame 22 is of any suitable metallic construction. It may be a casting, but preferably is built up of heavy steel plates welded together. Upstanding transversely extending ribs 22a are provided tostiffen the frame. Lifting bars 26 and 26a are provided on each frame for the attachment of a lifting device for opening the roof. Preferably a cable 21 is secured to the bar 26 and passes over a pulley 23 and thence to any suitable type of hoist. It will be understood without illustration that a suitable counterweight may be provided to balance a portion of the weight of each roof section.

The roof may be provided with a pivotal mounting along one of its longitudinally extending edges only, but we find an advantage in providing pivotal mountings along both edges. We

have therefore illustrated this construction wherein the pivot parts 29 and 29a are interchangeable, that is to say, the roof section may be reversed so that the pivot portion of the roof shown at 29a engages and coacts with the pivot portion of the side wall shown at 29. One advantage in thus reversing a roof section is the prolongation of the life of the roof. It often happens that holes are burned in the roof near the rear skew-back and in such case by reversing the roof the hole is placed near the front wall where it is less subject to erosion. In any case, where the roof section wears unevenly, by reversing the front and back portions of the roof section its life is prolonged.

Our preferred form of pivot mounting comprises a rib-like formation 30 formed along one of the longitudinally extending edges of a roof section and having an outer surface substantially semicircular in form. Preferably the frame 22 is provided with flange portions 24 and 24a which act as abutments for the roof arch and the curve of the rib 30 begins substantially at the point 3|. To the top of the side wall I2 is se cured a metallic member 32 which may be a casting or may be built up of welded plates. The top wall of the member 32 is provided with a trough-like surface 33 extending longitudinally of the furnace and substantially semicircular and open at the top. The semicylindrical surface 33 ends in substantially a horizontal plane. The coacting surfaces 30 and 33 are complementary cylindrical surfaces arranged to permit relative rotation between them when the roof is raised and lowered. By this construction the parts 30, 32 seal the junction between the roof section and side wall. Means is provided to protect the interfltting parts 30, 32 from the heat of the furnace. The part 30 is protected partly by the refractory material 2| and partly by the part 32. Preferably cooling means is provided for the member 32 and we have illustrated inlet and outlet pipes for water-cooling at 34 and 35. Iftthe member 32 is a casting, water circulation channels are provided extending the entire length of the member 32 and closely adjacent thesurface 33 so as to properly cool the same. It will be apparent from the construction above described that a vertical lift on the roof section will separate the coacting pivot members but that a pull upon the bar 26 in the direction shown by cable 21 in Fig. 3 will provide a force having a horizontal component acting toward pivot 29 suflicient together with the weight of the roof to hold the pivotal mounting together during its operation.

Preferably the opposite edge of the roof section is provided with a pivot structure 29a in all respects similar to that just described. The parts having similar functions have been given similar reference numbers with the sufflx a.

It will be understood that when, by reversal of a roof section, the surface 300 is placed in position to coact with the surface 33, then the cable 21 will be secured to the lifting bar 26a.

During-furnace operation one or more roof 7:;

sections are raised as indicated in brokenlines, Fig. 3, and material may be deposited on the furnace bottom by an overhead crane indicated generally at 36. If long material is to be charged, all or nearly all of the roof sections will be simultaneously raised. If material is to be charged at one spot as for instance by a drop-bottom bucket, only one section need be raised, as shown at D in Fig. l, with the advantages previously described.

When repairs are necessary to a roof, one or all of the roof sections may be removed to be repaired by a hot patch and replaced at once; or spare sections may be kept on hand so that no time is lost for roof repairs.

In a 150-ton furnace the length of roof opened up by sections A to D as shown in Fig. 1 will be approximately forty feet, so that if divided into four parts as shown, each section will be approximately ten feet wide and the span transversely across the furnace will be between fifteen and twenty feet.

By providing a roof which may be opened up as above described, large material such as skulls or ingots may be charged at any time, whereas heretofore they could be placed in the furnace only when the furnace was rebuilt. Furthermore,

by using large drop-bottom boxes handled by the: crane 36, as much as 75,000 pounds may be charged at one time as against. approximately 2,000 poundshandled in the usual chargingbox in the prior practice. This greatly reduces the time necessary to charge a furnace. There is a gi'eat saving in the amount of crane service necessary and the labor of charging machine operators during the charging period. Damage is avoided to the furnace lining and the cost of cutting up scrap by a skull cracker or burning is avoided.

Great savings are thus provided both in time and money and in quality of product produced.

We claim:

1. In an open hearth furnace having a bottom, front and back walls, ends, and a roof, a semicylindrical trough at the top of one of said walls, a roof section engaging the top of said wall and including a metallic frame having flanged edges,

a refractory lining held by said frame, and one of said edges located at the wall-engaging portion of said roof section being bent to form a cylindrical portion complementary to said trough, interfltting therewith andadapted to rotate therein to form a pivotal mounting for said roof section.

2. In a furnace having opposed longitudinally extending side walls, roof construction comprising a roof section adapted to extend from one of said walls to the other, said section including a substantially rigid 'metallic frame and a refractory lining held by said frame, pivotal mountings between the longitudinally extending edges of said roof section and the top edges of said walls respectively, each ofsaid mountings comprising disconnected interfltting parts separable by substantially vertical movement of said roof, said pivotal mountings being alike and interchangeable, and

each mounting comprising interfltting members one of which is a downwardly-facing semi-cylindrical rib extending substantially entirely along the longitudinally extending edge 'of said roof portions engaging top portions of said walls, said roof end portions and said wall portions having interfltting parts, said parts along at least one of said walls consisting of a semi-cylindrical trough extending continuously along one of said engaging portions and a semi-cylindrical member extending continuously along the other of said engaging portions; said trough and member having complementary surfaces closely engaging when said roof is in place on said walls, whereby said interfltting parts form a pivotal mounting and sealing means between said wall and roof section.

4. Furnace construction as in claim 3 in which said interfltting parts are provided along both of said'walls and the two sets of interfltting-parts are constructed alike.

JOHN O. GRIGGB. BERT H. LEEKB.

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