US2450836A - Heakth tile - Google Patents

Description

l atented Oct. 5, 1948 HEARTH TILE Sylvan N; Levy and William B. Levy,

' Wilmington, Del.

Application November 20, 1945, Serial No; 629.786

3 Claims.

. 1 I This invention relates to hearth tiles for use in metal treating furnaces, such as the one disclosed in our prior United States Letters Patent N0. 2,277,595, dated March 24, 1942.

Hearth tiles for furnaces of the muffle type,

like that disclosed in the aforesaid patent, are usually of a solid one-piece construction consisting of a flat slab of refractory material and provided with supporting feet at or near each of the four corners or along the opposite ends of the rectangular slab.

The slab is usually so dimensioned, with respect to the plan of the, mufile, as to provide a clearance around the marginal edges of the tile and between such edges and the side walls of the muffle, whereby the metal-treating atmosphere, which is introduced into the mufile under the hearth tile, may rise around the work specimens situated on the hearth tile.

Under the extremely high temperatures at which these furnaces frequently operate, the hearth tiles are subject to warping, cracking, and actual breakage under internal strains and stresses set up within the hearth tile.

One object of the present invention is to relieve the hearth tile of the destructive strains and stre ses, or at least to minimize said strains and stresses and thereby increase the normal useful life of the hearth tile.

As a, result of considerable experimentation directed toward the attainment of the above object, it has been found that,- by distributing a multiplicity of perforations over substantially the entire area of the tile, in a substantially uniform manner, and by extending the perforations completely through the slab of refractory material constituting the body of the hearth tile, the tile will expand and contract without undue warping, cracking, or breaking of the tile.

Normally, the increased thickness of the tile at the corners or ends of the slab where the supporting feet are located, has a tendency to cause the tiles to break in the areas adjacent such supporting feet, where the thicker portion of the tile blends into the thinner portion thereof. It has been found that this condition can be remedied by providing the under side of the tile with a pair of parallel ribs running substantially the full length of the tile, in inwardly spaced parallel relation to the opposite side edges of the tile, and by distributing the perforations uniformly between these longitudinally extending ribs.

The aforesaid longitudinally extending ribs serve another useful purpose, in that they support the tile completely from end to end thereof as the lower edges of the ribs bear on the bottom inside surface of the muflle and prevent sagging of the tile intermediate its opposite ends under the weight of the work specimens supported thereby, when working temperature of the furnace is attained.

The perforations also serve a dual purpose, in that they also permit the treating atmosphere in the lower part of the muffle, beneath the hearth tile, to rise through the tileand more readily envelop the work specimens thereon.

In the accompanying drawing:

Fig. l is a perspective view of a hearth tile constructed in accordance with the present invention;

Fig. 2 is an inverted plan view of the tile shown in Fig, 1; and

Fig. 3 is a transverse sectional elevation taken on the line 3-3, Fig. l. H

As shown in Fig. l, the hearth tile A comprises a substantially rectangular slab of high refractory material of predetermined thickness, as illustrated at l. Preferably the upper surface 2 of the slab l is substantially smooth while the under surface 3 of the slab is provided with a pair of laterally spaced longitudinally extending ribs 4, 4, which are parallel to each other and to the side edges 5, 5 of the slab I from which the ribs 4, 4 are spaced inwardly.

As shown in Fig. 2, the ribs 4, 4 extend substantially the full length of the slab l, between the end surfaces 6, 6 thereof. As shown in Figs. 1 and 3, the ribs 4, 4 are of downwardly converging or V-shaped construction in transverse crosssection. The narrow lower edges 1, I of said ribs are adapted to rest on the inner bottom surface of the muffle, as diagrammatically indicated at :c in Fig. 3, whereby the tile is supported adjacent its opposite longitudinal edges for the full length of the tile, and whereby sagging of the slab I under the weight of the specimens supported thereby will be effectively prevented.

As shown in Figs. 2 and 3 particularly, the central longitudinal area y of the slab l lying intermediate the ribs 4, 4 is provided with a multiplicity of perforations H], H] which are distributed in a uniform pattern over substantially the entire area y of the slab I. If desired, the marginal portions 2, z, of the slab I disposed intermediate the side edges 5, 5 and the adjacent ribs 4,4 of the tile may be provided with one or more rows of perforations l I, ll.

As previously noted, the uniform distribution of the perforations l0, l0 and II, II relieve the 3 slab l of internal strains resulting from the high temperature of the furnace and the load supported by the slab I, which latter strains are relieved to at least some extent by the provision of the full length ribs 4, 4.

If desired, the lower corners of the side edges 5, 5 of ,the slab I may be rounded, as indicated at 8, 8 to provide clearance for the passage of the treating atmosphere between the lower corners of the slab l and the fillets between the bottom surface and side walls of the mufiie in which the hearth tile is mounted.

It will be noted that the lower edges 1, I of the legs or ribs 4, 4 are relatively narrow, transversely, due to the downwardly converging sidewalls of the cross sectionally triangular construction of the ribs or legs 4, 4. This construction provides for lapping of these narrow surfaces of the legs 4, 4 into the surface a: of the muffle, whereby the edges 1, 1 will bear solidly at all points along the length of the legs 4,4 on the muffle-surface 11:, to support the hearth tile A evenly over. its entire top "surface .2 and. thereby prevent cracking or warping of. the hearth tile A under load when heated: to working temperature of the furnace.

- We claim:

1. A hearth tile for metal treating furnaces, comprising a substantially rectangular slab of refractory material provided with a multiplicity of perforations extending completely through saidslab and distributed substantially uniformly over apredetermined major portion of the area of the slab, and a pair of longitudinalribs of 'V- shaped cross-section projecting downwardly from the bottom. surface of the slab in substantially parallel inwardly spaced relation to the opposite longitudinal edges respectively of the slab.

2. A hearth tile for metaltreating furnaces, comprising a substantially rectangular slab of refractory material provided with a multiplicity of 4 perforations extending completely through said slab and distributed substantially uniformly over a predetermined major portion of the area of the slab, a pair of longitudinal ribs of substantially V- shape cross-section projecting downwardly from the bottom surface of the slab and extending substantially the full length of the slab in substantially parallel inwardly spaced relation to the opposite longitudinal edges respectively of the of parallel transversely extending rows of rela-: tlvely' staggered perforations extending 'com-.

pletely througlr said slab and distributed sub-' stantially uniformly over the portion of the area of the slablying between said ribs, and a row:

of perforations extending completely through the slab in; the areas thereof lying between said ribs and said longitudinal edges of the slab.

SYLVAN N. LEVY. WILLIAM B. LEVY.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,148,463 Harris Feb-28, 1939 40 2,189,624 Bramble Feb. 6, 1940

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