US2142762A - Furnace - Google Patents

Description

Jan. 3, 1939.

c. REYNDERS FURNACE Filed March 29, 1957 Patented Jan. 3, 1939 UNITED STATES PATENT OFFICE FURNACE Charlton Reynclers, New York, N. Y., assignor to International Chromium Process Corporation, New York, N. Y., a corporation of Delaware Application March 29, 1937, Serial No. 133,719

5 Claims.

:naces and more particularly those of the open hearth type.

In the conventional metallurgical furnaces of the open hearth type, the arched roof subjected to excessively high temperatures rests at each side in a skewback channel. In one design, fixed binding is used and the skewback channel is rigidly supported by a buckstay.

When tie-rods are employed instead of fixed binding, as in another design of furnace, some horizontal movement of the skewback is permitted, but angular movement is prevented.

Tie-rods are rarely adjusted, with the result that in each instance the skewback channel, or brick, is immovable, and when the roof arch is heated enormous stresses are placed on the lower surface of the adjacent bricks constituting the arch, while the upper surfaces tend to separate. The result is that after short usage the roof bricks will disintegrate, necessitating repair or replacement of the arch.

It is an object of the present invention to so support one or both sides of a conventional arched roof to compensate for a part of the expansion and contraction of the roof and thereby prevent destruction of adjacent roof bricks due to internal stresses and strains.

It is a further object of the invention to equalize strains and pressures in the brick arch throughout the area of contact of the adjacent bricks by mounting one or both sides of the arch on a movable skewback channel extending longitudinally of the buckstays and capable of a free or rocking movement relative to the buckstays. In this construction the skewback channel has that limited freedom of movement sufficient to relieve excessive pressure between adjacent arch bricks at a lower point in the arch and to equalize the pressure between the surfaces of the adjacent bricks throughout such contacting surfaces. This results in a structure whereby each brick has a full surface contact with neighboring bricks, materially increasing the life of the arch.

In the accompanying drawing I have disclosed an embodiment of the invention for the purpose of illustrating the principles thereof. It will be understood that the invention is not to be limited to the embodiment herein illustrated.

In the drawing, Figure 1 represents a sec tional view through a portion of a furnace of the open hearth type illustrating one embodiment of the invention; and

Figure 2 is a perspective view of a fragment of one of the skewback channels.

Referring now more particularly to the drawing, wherein likereference characters indicate corresponding parts, the numeral I designates the roof arch of the furnace, comprising a series of adjacent bricks or other refractory material, the surfaces of which contact and are united in any suitable way. The roof arch is of the flat type ordinarily subjected to violent internal compression stresses during the operation of the furnace. The arched roof, of course, overlies the hearth and in operation is subjected to the highly heated gases constantly passing through the furnace.

The furnace, of course, has the usual hearth at the lower portion thereof surrounded by suitable refractory walls 2 composed of any wellknown refractory material.

The furnace is also provided at each side with conventional buckstays 3 extending longitudinally of the furnace throughout its length. These buckstays are composed of metal or other nonresilient material. At suitable points the buckstays may, at their upper ends, be connected by tie-rods or fixed elements 4.

The roof arch at each side is supported by longitudinally extended metallic U-shaped skewback channels 5. channel of the embodiment shown there is a rafractory skewback which may be an end brick 6 of the roof arch. The outer faces of the two end bricks 6 therefore bear throughout their surface area on the complemental surfaces of the skewback channels and the surfaces of the intermediate bricks constituting the arch have a similar full surface contact throughout the arch.

Each skewback channel 5 at the outer surface Disposed within each skewback thereof and at a point near the designed line of thrust is provided with a continuous rounded bar or rocking member 1 contacting with a bearing plate attached to the buckstay. The preferred designed line of thrust is approximately onethird the distance from the outside to the inside of the arch and the rocking members 1 respectively are disposed in this line of thrust.

The skewback channels 5 may be in one piece, although these channels may, if desired, be in sections. The rounded protuberance or extension 7 contacting with the bearing plate on the buckstay provides a rocking or movable support for the skewback channel, the skewback and the arch. This permits each skewback channel to shift or move in response to stresses and strains imposed thereon by the roof arch. Consequently, the adjacent bricks forming the arch form both a toe and heel contact, or, otherwise stated, a surface contact throughout the area constituting the side wall of each adjacent brick.

As indicated in Fig. 3, a bearing plate ll] may project inwardly of the buckstay and present toward the rocking member 'i of skewback channel 5 a flat outwardly inclined surface. A substantially flat bearing surface for the rounded rocking member to permit free pivotal movement is desirable for the reason that the enormous horizontal forces encountered would develop friction in a substantially complemental seat to the extent that pivotal movement would be virtually impossible. The horizontal forces exerted by the arch are so great that the arch needs no support other than that provided by the rocking members 1 and their bearing surfaces, but as a matter of precaution to prevent a possible but unlikely vertical drop of the skewback channel, an inwardly extending ridge or projection of any suitable character may, if desired, be provided on the bearing surface if care is taken to position such ridge or projection sufficiently below the rocking member so as not to interfere with its free pivotal movement.

In the conventional type of open hearth furnace the horizontal distance between the two sides of an arch remains constant, either because of a rigid binding or the disuse of tie-rods. Consequently, when the arch is subjected to heat with the inevitable expansion, it can only move upwardly and this movement is the maximum at the point of the highest furnace temperature. In the conventional type of furnace, when this expansion occurs, there is a decided tendency on the partof the adjacent bricks to open up or separate along their upper surfaces as indicated by the reference character 8, Fig. 1, whereas the lower or highly heated contacting surfaces are subjected to an enormous compression stress or strain, which is most severe at the point 9 of Fig. 1. Thus, when the arch is retained against any lateral movement, the effect of the heat to which it is subjected is to provide a localized or limited point of contact between the adjacent bricks where the entire compression strain is carried and this point of contact is in a zone where the bricks are at a maximum temperature and incapable of resisting the enormous stresses or strains without rapidly disintegrating or spalling, necessitating either repairs to the roof or the installation of a new arch.

These difficulties are avoided by the present invention wherein the sides of the arch rest on movable skewback channels which shift during the operation of the furnace as the arch expands to permit the limited expansion of the arch to an extent that is necessary to maintain a toe and heel contact between the adjacent bricks of the arch or a relation of the bricks forming the arch whereby the adjacent surfaces contact throughout their area, thus distributing the pressure over the entire surfaces of the adjacent arch bricks.

In operation, when a new roof is built for a furnace, it should preferably be laid on a shorter radius than exists when the roof is subjected to normal heat. The skewback channels should be tilted out at the top so as to give a greater: included angle when the furnace is cold than the angle ultimately assiuned in the operation of the furnace. As the furnace is brought to temperature, the inner ends of the bricks expand more than the outer ends, because the inner ends are subjected to the maximum temperature. This creates a somewhat greater pressure on the lower siuface of each skewback brick, effecting a tilting or movement of each skewback channel inwardly until the pressure on the heel and toe of each skewback brick is substantially equalized, at which time the roof assumes a longer radius with a smaller included angle.

During the entire operation of the furnace, the skewback channels are free to shift or rotate to an extent sufficient to provide contact between the adjacent surfaces of the arch bricks throughout their areas. When the bricks have this full surface contact, the stresses and strains generated in the arch are distributed throughout the contacting surfaces and are not localized or focussed at a restricted point where the arch bricks are at their maximumv temperatures and incapable of carrying these localized stresses and strains.

While I have disclosed the invention for use in connection with open hearth furnaces of the metallurgical type, it will, of course, be appreciated that it is applicable for use in other and related fields.

Having described the invention, what I claim is:

1. In a furnace having buckstays and a refractory roof arch of uniform curvature movable as a unit upon expansion and contraction, the combination of a skewback channel at each side of the arch and means for pivotally supporting the arch disposed between each skewback channel and the adjacent buckstay, said pivotal supporting means comprising a rounded rocking memher and a fiat bearing surface for the rocking member.

2. In a furnace having buckstays and a refractory brick roof arch of uniform curvature movable as a unit upon expansion and contraction,

- the combination of a skewback channel at a side of the arch, and means for pivotally supporting said side of the arch disposed between the skewback channel and the adjacent buckstay, said pivotal supporting means comprising a rounded rocking member and a flat bearing surface for the rocking member.

3. In a furnace having buckstays and a refractory brick roof arch of uniform curvature movable as a unit upon expansion and contraction, the combination of a skewback channel at a side of the arch, and means for pivotally supporting said side of the arch comprising a rounded rocking member carried by the skewback channel and a flat bearing surface for the rocking member provided on the adjacent buckstay.

4. In a furnace having buckstays and a refractory brick roof arch movable upon expansion and contraction, the combination of a skewback channel at a side of the arch, and means for pivotally supporting said side of the arch disposed between the skewback channel and. the adjacent buckstay, said pivotal supporting means comprising a rounded rocking member and a flat inclined bearing surface for the rocking member.

5. In a furnace having buckstays and a refractory brick roof arch movable upon expansion and contraction, the combination of a skewback channel at a side of the arch, and means for pivotally supporting said side of the arch disposed between the skewback channel and the adjacent buckstay, said pivotal supporting means comprising a rounded rocking member carried by the skewback channel and a bearing plate having a flat inclined bearing surface provided on the adjacent buckstay.

CHARLTON REYNDERS.

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