US3601416A

US3601416A - Self-adjusting wraparound seal

Info

Publication number: US3601416A
Application number: US833016A
Authority: US
Inventors: Aubert Y Coran
Original assignee: Monsanto Co
Current assignee: Monsanto Co
Priority date: 1969-06-13
Filing date: 1969-06-13
Publication date: 1971-08-24
Anticipated expiration: 1988-08-24

Abstract

A self-adjustable seal for an axially movable furnace electrode has a sealing strip adapted to wrap completely around the electrode and extend therefrom. One end on the strip is anchored and the end is tensioned to maintain the central portion of the strip in tight engagement with the electrode.

Description

United States Patent Inventor Appl. No.

Filed Patented Assignee SELF-ADJUSTING WRAPAROUND SEAL Aubert Y. Coran St. Louis, Mo. 833,016

June 13, 1969 Aug. 24, 1971 Monsanto Company St. Louis, Mo.

6 Claims, 5 Drawing Figs.

US. Cl. 277/151, 277/168, 277/203 1nt.C1. Fl6j15/24 [50] Field of Search 277/151, 138, 168, 203,204; 118/125, 106, D16. 18

[ 5 6 References Cited UNITED STATES PATENTS 664,925 1/1901 Born et a1. 277/151 2,429,867 10/1947 Bryant 277/151 X Primary Examiner- Robert 1. Smith Attorneys-J. E. Maurer, F. A. Brusok and William H. Duffey ABSTRACT: A self-adjustable seal for an axially movable furnace electrode has a sealing strip adapted to wrap completely around the electrode and extend therefrom. One end on the strip is anchored and the end is tensioned to maintain the central portion of the strip in tight engagement with the electrode,

' PAT ENTED A0824 am FIG.|

FIG. 4

INVEN'TOR AUBERT Y. CORAN ATTORNEY SELF-ADJUSTING WRAPAROUND SEAL This invention relates to a wraparound-type seal particularly adapted for use with cylindrical and other geometrical shapes under high thermal stress.

The seal of the present invention finds particular utility in electric arc furnaces for sealing electrodes. Electrodes employed in arc furnaces are generally of four types, viz, prefabricated graphite, prefabricated carbon, self-backing and composite electrodes. In certain installations, the electrodes are made from a refractory alloy metal. Cylindrical carbon electrodes are made in sizes up to 40inches in diameter while graphite electrodes may be up to 18 20inches in diameter. Self-backing electrodes consist of a steel casing filled with a pasty mass similar to that used in the production of prefabricated carbon electrodes. As the casing with the mass is fed into the furnace, both burn off. Self-backing electrodes have been built up to 8 feet in diameter.

The temperature of the electric arc in an arc furnace can approximate 6600 F. The ambient furnace temperature may be in the order of 2500-3000 F., depending on the use.

Because of the high temperatures encountered in electric arc furnaces and because of the temperature differential between the furnace interior and exterior, the thermal growth and thermal contraction of parts is significant. Some type of sealing member must be employed to seal the furnace electrode and prevent the escape of heat and furnace gases to the surrounding atmosphere. Although the rate of advancement of the electrode into an arc furnace is low because of therelatively slow manner in which the electrode is consumed, the sealing problem is nevertheless difficult. The difficulty arises from the high thermal expansion and contraction of the electrode parts and those parts adjacent thereto. v

A longstanding need has prevailed for a self-adjusting seal capable of accommodating the thermal stress encountered in high temperature devices such as electric arc furnaces. Many conventional self-adjusting seals lack the capacity to constantly conform to the dimensional changes which occur in a high temperature chamber. Eventhough furnace electrodes are generally cylindrical in shape, the large dimensional changes impose severe requirements on a self-adjusting seal.

The present invention provides a self-adjusting wraparoundtype seal which is particularly adaptable for sealing electrodes in arc furnaces. The seal of the present invention is equally effective whether the electrode is stationary or movable. This seal, because of its geometrical construction, can accommodate substantial amounts of thermal expansion and contraction while still maintaining high sealing efficiency.

The wraparound-type seal of the present invention, it is to be understood, is not confined to use in arc furnaces. It can find utility in many applications where a cylindrical member, elliptical member, or the like, is to be sealed. For example, the seal of the present invention can be employed to seal the outer race of an antifriction bearing. It may also be employed to seal cylindrical members such as pistons wherein the linear velocity of the member with respect to the seal is not excessive.

It is an object of the present invention, therefore, to provide a wraparound-type seal adapted for use with cylindrical or other geometrical shapes under high thermal stress.

Another object of the present invention is to provide a wraparound-type seal particularly adaptable for sealing electrodes in arcfurnaces.

Other objects, aspects and advantages of the present invention will become apparent from a consideration of the accompanyingdisclosure, drawing and claims.

In the drawing:

FIG. I is a partially sectioned elevation view showing the wraparound seal olthe present invention adapted to seal a fur nace electrode.

FIG. 2 is a partially sectioned top view showing the wraparound seal in circumferential contact with the furnace electrode of FIG. I.

FIG. 3 is a perspective view of one embodiment of the wraparound seal of the present invention.

FIG. 4 is a perspective view of a slotted embodiment of the wraparound seal of the present invention.

FIG. 5 is an elevation view of the slotted seal embodiment of FIG. 4.

Referring now to FIG. 1 of the drawing, cylindrical elec trode 10 is typical of a consumable electrode found in an electric arc furnace. As electrode 10 is consumed, it advances in the direction of the arrow through furnace wall 11, a structural member of refractory material. Affixed to furnace wall 11 is border plate 11' which is contoured to receive and retain the lower loop section of wraparound seal 14. Outer seal retaining plate 12 is contoured to receive and retain the upper loop section of seal 14. Plate 12 is retained to border plate 11 by a series of cap screws indicated typically by reference numeral l3. Tension in screws 13 is light enough to permit expansion and contraction of seal 14.

With further reference to FIG. 1, one end of wraparound seal 14 is retained by anchor pin 15. The other end of seal 14 has a slotted hole to afford engagement of tension spring 16, the latter being retained by anchor pin 17. Spring 16 performs the important function of maintaining tension in seal 14 during dimensional changes caused by thermal factors. This tension, in turn, assures adequate clamping of the circular portion of seal 14 about electrode 10. Considerable latitude is permitted in selecting the spring rate of tension spring 16. Optimum tension is achieved when the clamping action of seal 14 is great enough to obtain efficient sealing without impeding the advancement of electrode 10. Instead of the coil spring illustrated in the drawing, a leaf spring or other tension-producing member can be employed.

When the seal of the present invention is installed in a furnace environment such as illustrated in FIG. 1 of the drawing, a viscous lubricant capable of withstanding high temperatures can be advantageously employed on the rubbing surfaces of the seal and in the surrounding cavity. Besides assisting the flexing action of the seal, the lubricant improves the sealing efficiency by inhibiting leakage of furnace gases around the seal.

In the perspective view of FIG. 3, one embodiment of the wraparound seal of the present invention is illustrated. Seal 14 has a rectangular cross section and is preferably made of ductile metal. Prior to being shaped, it is simply a straight section of rectangular stock. Through either hot or cold working, the stock is drawn or rolled about a cylindrical mandrel and the ends are urged outwardly with an overlap, resulting in the configuration shown in FIG. 3. Hole 18 is drilled through the seal near one end to receive anchor pin 15 of FIG. 1. Slotted hole 19 is provided near the opposite end to receive tension spring 16. For use in high temperature environments such as are furnaces, seal 14 should be made of a refractory metal alloy.

In certain mechanical installations, the overlapping portion of seal 14 may be desirable. A slotted embodiment shown in FIGS. 4 and 5 and identified by reference numeral 20, eliminates the overlap. Seal 20 affords uniform seal thickness while maintaining free adjustability. Offset 21 is provided for this purpose and is machined into the seal stock before shaping takes place.

As hereinbefore indicated, the wraparound seal of the present invention is not confined to cylindrical shapes. It can be employed to seal elliptical cross sections, for example. In shaping such a seal, an elliptical mandrel is employed.

Although the wraparound seals illustrated in the drawing have a rectangular cross section, this is merely a preferred embodiment. Equivalent seals may be formed from square, circular, elliptical or other stock. Furthermore, it is sometimes desirable to chamfer the edges where square or rectangular stock is employed.

The flexible member which comprises the main component of the wraparound seal assembly of the present invention can have cooperating with it, in addition to the tension-producing means, a liner which improves sealing efficiency. The liner can be in the form of asbestos rope packing disposed between the inside diameter of the flexible member and the object to be sealed. The liner can also be a wiper of suitable material attached to the face of the flexible member along its length, positioned so as to wipe the surface of the object to be sealed.

Instead of anchoring one end of the seal of this invention while attaching the tension-producing member to the opposite end, tension-producing members can be applied to both ends with desirable results.

While this invention has been described with respect to certain specific embodiments, it is not so limited. It is to be understood that variations and modifications thereof may be made without departing from the spirit or scope of the following claims.

The embodiments of this invention of which an exclusive property or privilege I claim are defined as follows:

1. A self-adjusting seal assembly comprising a flexible member have a main section defining the shape of the object to be sealed, the ends of said member being axially overlapped, extending tangentially away from said main section and in a different rotational direction, and adapted to expand and contract said main section, and tension-producing means cooperating with said ends to maintain said main section in contiguity with said object.

2. A self-adjusting seal assembly of claim 1 wherein said main section defines a circle.

3. A self-adjusting seal assembly of claim 1 wherein the cross section of said flexible member is substantially rectangular.

4. A self-adjusting seal assembly of claim 1 wherein the overall thickness of said flexible member is uniform.

5. A self-adjusting seal assembly of claim 1 wherein said tension-producing means is a coil spring.

6. A self-adjustable seal assembly of claim 1 wherein plates are disposed on opposite sides of said member to restrain the same against axial movement.