US2867428A - Rotary hearth furnace provided with a removable sector for hearth maintainance - Google Patents

Description

Jan. 6, 1959 c. MONTAGNA 2,867,428

ROTARY HEARTH FURNACE PROVIDED wxm A REMOVABLE SECTOR FOR HEARTH MAINTAINANCE Filed Aug. 4, 1955 United States Patent ROTARY I-IEARTH FURNACE PROVIDED WITH A REMOVABLE SECTOR FOR HEARTH MAIN- TAINAN CE Carlo Montagna, Dalmine, Italy, assignor to Dalmine S. p. A., Milan, Italy, a corporation of Italy Application August 4, 1955, Serial No. 526,492 Claims priority, application Italy August 10, 1954 4 Claims. (Cl. 263-7) tact as much as possible restricted. For this purpose, the

hearth is provided with raised rails or. ribs on which the objects rest, whereby the contact area between hearth and material is greatly reduced thereby causing a good heating action even at the lower portion of the individual object.

The hearth has generally an annular shape and rotates at a moderate speed (for instance one complete revolution around its vertical axis) taking several hours.

The rails of the hearth are constituted of one or more continuous annular ribs, co-axial with the hearthand so spaced as to permit the objects to be heated to rest thereon only at two points (for instance, rolling mill ingots). The rails are made of refractory material and, on account of the continuous mechanical and thermic stresses to which they are subjected, they have usually a short life and it is frequently necessary to rapidly repair them in order to maintain a proper heating effect on the material.

In ordinary furnaces, however, it is not possible to do any repairing without entering the furnace, which, in turn, cannot be done without extinguishing the fire therein; in practice it follows from this, given the short life of the rails and in view of economical considerations which exclude frequently stopping the furnace, that the latter is usually operated without rails all the time.

These difliculties and drawbacks are obviated by the hearth according to the present invention, substantially characterized by the fact that the annular arch and walls of the furnace, along a sector-shaped portion of the zone located between the material charging and the discharging doors are interrupted, While two angularly spaced, radially extending vertical end walls having each an opening for the passage of the hearth including its rails, permit the latter to be fully accessible in its uncovered portion between said end walls, thus permitting operations of maintenance to be carried out on the hearth itself from the outside of the furnace in said uncovered area.

The invention will be described with reference to the accompanying drawing, description and drawing being given by way of example only, without limiting the scope of the invention.

Fig. 1 is a diagrammatic perspective view of the uncovered hearth zone of a furnace according to the invention.

Fig. 2 is a perspective view of the closing cover.

ice

The stationary arched part A of the furnace is annular in form and inside it rotates the annular hearth B in the direction of the arrow X. By C and D are respectively indicated the charging and discharging doors.

As stated, the hearth is provided with two or more continuous annular relief ridges or rails Bland B2 on which the material to be treated is placed.

The annular body of the arch of its furnace A and the walls down to the level of the hearth B, are interrupted within the area of the sector located between the access doors C and D of the furnace, i. e., in the portion in which the hearth is not carrying any material. Two vertical walls or ends A1 and A2 terminate the furnaces stationary part thus defining and bounding the open sector and keeping the heating chamber closed against the surrounding air. The walls A1 and A2 are provided in their lower part with an aperture having its edges somewhat spaced from the hearth B and thereby permitting the free movement of the latter.

When the rails B1 and B2 do not require any repair, the portion of the hearth located between the two walls A1 and A2 is conveniently covered with a bridge shaped cover E that fits between the walls A1 and A2 and prevents the hearth from coming in contact with the outside air and cooling off. The cover E, whose location, when put in place, is indicated by dash-dot lines in Fig. 1 may, for instance, be made of refractory material.

The cover E can, of course, instead of being one integral piece also be made up of several adjacent smaller sectors.

When the hearth is to undergo repairs, the cover E is removed so as to uncover the hearth B. Should the repair be one of short duration the furnace is not stopped since the time within which the portion to be repaired travels through the uncovered sector of the stationary part, of the furnace is generally sufficient for the repair work. Should more substantial repairs have to be made,

the hearth is stopped while leaving the fire burning and the rails B1 and B2 are repaired or wholly substituted as far as accessible in the uncovered part of the hearth. The hearth is then put in motion again until the repaired portion has disappeared through the opening in wall Al, so that a following or other portion to be repaired becomes accessible in the open sector during a new stop of the hearths rotation. The operation can be repeated until the entire repairs or substitution of the rails is completed, after which, the cover E having been replaced, the furnace can begin again to run under normal operational conditions.

It is therefore possible to carry-out repairs with the described furnace while it is in operation without discharging the material and even to entirely substitute the rails without stopping the hearth for any length of time that would be inconvenient or detrimental.

In practice the details of the furnace may be varied without departing from the gist and scope of the invention as claimed.

I claim:

1. A rotary hearth furnace comprising, in combination, housing means including an annular base portion and an arcuate hollow upper portion on said annular base portion, said upper portion having a pair of radially base portion and said upper portion and adapted to rotate along said base portion, said annular hearth means passing through said passage openings of said transverse end walls so that a portion of said annular hearth means is accessible from outside said housing means; and removable cover means fitting between saidtransverseend walls for covering said annular hearth means between said transverse end walls whereby said annular hearth means may be completely enclosed when access to said portion thereof is not desired.

2. A rotary hearth furnace comprising, in combination, housing means including an annular base portion and an arcuate hollow upper portion on said annular base portion, said upper portion having a pair of transverse end walls, each of said end walls being formed with a passage opening, said housing means being formed with a radially directed charging opening adjacent one of said end walls and with a radially directed discharging opening adjacent the other of said end walls; movable door means on said housing for covering and uncovering said charging and discharging openings thereof; annular 2 hearth means located intermediate said base portion and said upper portion and adapted to rotate along said base portion, said annular hearth means passing through said passage openings of said transverse end walls so that a portion of said annular hearth means is accessible from outside said housing means, said annular hearth means including rail means thereon adapted to hold an object to be treated by said furnace and passing through said passage openings of said transverse end walls so that a portion of said rail means is accessible from outside the housing means for-repair or replacement procedures; and removable cover means fitting between said transverse end walls for covering said annular hearth means between said transverse end walls whereby said annular hearth means maybe completely enclosed when access to said portion thereof and of said rail means is not desired.

3. A rotary hearth furnace as set forth in claim 1 wherein said passage openings in said end walls are of a predetermined height and width, and wherein said annular hearth means project from said base portion with a cross-section substantially equal to said height and-width of said passage openings, so that said hearth means can pass through said passage openings with a minimum of air gapbetween one and the other, and wherein the inside dimensions of said removable cover means are substantially the same as those of said passage openings.

4. A rotary hearth furnace as set forth in claim 2 wherein said passage Openings in said end walls are of a predetermined height and width, and wherein said annular hearth means project from said base portion with a cross-section substantially. equal to said height and width of said passage openings, so that said hearth means can pass through said passage openings witha minimum of air gap between one and the other, and wherein the inside dimensions of said removable cover means are substantially the same as those of said passage openings.

References Cited in the file of this patent UNITED STATES PATENTS 693,062 Potter Feb. 11, 1902 699,528 Hunt et a1 May 6, 1902 700,427 Keyes May 20, 1902 1,362,296 Hagan et al. Dec. 14, 1920 2,499,926 Lloyd Mar. 7, :1950 2,622,861 Talley Dec. 23, 1952

Images