US3129934A - Cast sand seal skirt rings - Google Patents

Description

A ril 21, 1964 J. A. WILSON CAST SAND SEAL SKIRT RINGS Filed Aug. 8, 1960 INVENTOR John A. \Vi l son.

0 m w 0 a v ATTORNEY United States Patent 3,129,934 CAST SAND SEAL SKIRT RINGS John A. Wilson, Griiiia, Qntario, Canada, assignor to Fahrailoy Canada Limited, ()riiiia, Ontario, Canada Filed Aug. 8, 196%, Ser. No. 48,138 1 Claim. (Cl. 263-49) This invention relates to cast sand seal skirt rings for incorporation in inner covers used in the heat treatment of coiled steel strip in cover type annealing furnaces.

Skirt rings of this type are usually formed of wrought materials. Such conventional skirt rings not only have limited strength and rigidity but they frequently become distorted or damaged in use due to the temperature stresses to which they are subjected. Moreover, inner covers using the standard skirt rings tend to go out of round and require regular servicing to press the skirt ring end of the cover back into true circle.

It is an object of this invention to provide a skirt ring which is simple in structure, easy to manufacture, and inexpensive to produce, which possesses higher strength characteristics and greater rigidity, which absorbs heating and cooling stresses without distortion, and in which cracking tendencies are substantially eliminated, whereby the inner cover associated therewith maintains its shape during operation, and whereby the service life of the inner cover is significantly prolonged.

The invention resides in a cast skirt ring comprising a flat circular ring portion having a flat unobstructed upper surface for reception of an inner cover, and an inte gral leg depending from the outer edge of said ring.

The invention will be described with reference to the accompanying drawing, in which FIGURE 1 is a sectional elevation of a cover type annealing furnace having incorporated therein a skirt ring of the present invention,

FIGURE 2 is a partial plan vieW of the skirt ring of the invention, and

FIGURE 3 is a sectional elevation of the skirt ring.

In the drawing, 1 is a cover type annealing furnace such as is used in the heat treatment of coiled steel strip in basic steel mills. The furnace comprises a base 2, fan 3, an outer cylindrical refractory lined cover 4 carrying heating elements 5, and a cylindrical inner cover 6, all in accordance with conventional structure. The coils of steel strip under treatment are indicated at 7. In usual practice, the outer cover is lifted off the base by means of a crane, and the pile of steel strip is built up on the base. The inner cover is then lowered over the pile of strip and the outer cover finally dropped over the whole assembly.

The heating elements provide the source of heat which is transferred through the inner cover to the coils of strip, which are heated to the desired annealing temperature. The fan 3 provides for the recirculation of atmosphere gas within the inner cover, thus accelerating the heating of the charge through convection heat transfer.

The inner cover is normally fabricated out of carbon low alloy steel or stainless steel.

A skirt ring 8 is Welded to the lower open end of the inner cover and is arranged to seat in the sand 9 of an annular sand trough 10 in the base. It will be evident that the inner cover provides a confined protective atmosphere to reduce the seating of the strip and exclude external air.

In accordance with the invention, the skirt ring 8 comprises a flat circular ring portion 8a having a flat unobstructed upper surface 8b for reception of the edge of the inner cover 6. A circular leg 11 depends from the outer edge of the ring portion 8a, such leg being con tinuously corrugated with corrugations 12 which extend laterally from the ring portion 8a to the free edge of the leg. Preferably, a plurality of stiffening gussets 13 connect the outer surface of the leg with the under surface of the ring portion.

The skirt ring 8 comprises a plurality of uniform arcuate or segmental sections 14 welded together at their abutting end edges.

Each section 14 is composed of cast steel, such as plain carbon or stainless steel.

The use of castings, rather than Wrought metal, in the formation of the skirt ring has many advantages. It permits greater economy of construction and provides higher strength characteristics and greater rigidity, thus greatly contributing to the maintenance of the shape of the inner cover in operation. Moreover, the use of castings permits the use of the stiffening gussets 13 at very small extra cost as compared with a fabricated structure.

Since stress cracks tend to develop and work radially inwardly from the outer diameter of the angle flange or leg of skirt rings, the location of such flange or leg on the outer edge rather than the inner edge of the cover receiving ring portion substantially eliminates cracking tendencies and thus adds significantly to the service life of the inner cover. I

An important feature resides in the corrugation of the vertical leg 11. These corrugations add markedly to the strength of the skirt ring and assist in absorbing heating and cooling stresses without distortion of the ring.

I claim:

A unitary inner cover for an annealing furnace, comprising, a circumferentially-continuous cylindrical wall having a vertical axis of symmetry and a top secured to and closing the upper end of said wall, and a circular skirt ring reinforcing the open circular lower end of said wall, said ring comprising first and second portions integral with each other, said first portion being a horizontally planar annulus coaxial of said axis and having an outer diameter slightly greater than the corresponding diameter of said wall, the lower edge of said wall being fixed to and supported on said first portion, said second portion being a cylindrical skirt depending vertically from the outer periphery of said first portion normally thereto, said ring forming the sole support for said cylindrical Wall, the wall of said second portion being continuously vertically corrugated throughout its peripheral extent, said skirt ring being formed from a plurality of cast metal segments integrally united in end-to-end relation to form a continuous circular ring, and a plurality of vertical, reinforcing plates disposed generally radially of said axis and in equiangularly-spaced relation thereabout, each said plate being integrally connected with the inner surfaces of said first and second portions, respectively.

References Cited in the file of this patent UNITED STATES PATENTS 1,961,221 Hunter June 5, 1934 2,144,374 Hoffman Jan. 17, 1939 2,145,074 Dreifein Jan. 24, 1939 2,233,580 Breedon et a1. Mar. 4, 1941 2,260,214 Deahl Oct. 21, 1941 2,414,530 Jacob Jan. 21, 1947 2,854,226 Cone Sept. 30, 1948

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