Coil Annealing Furnaces

Abstract

The invention provides a coil annealing furnace in which atmosphere is circulated out of a cover enclosing the coils and via an external circuit before returning to the cover, in which a heat exchanger is located in the external circuit but is physically movable so that when moved out of the circuit there is no impediment to free circulation through the circuit such as is inevitably provided when the heat exchanger is in the circuit, and with a seal between the cover and furnace structure comprising a compressed rubber ring which is watercooled, so as to prevent seal failure through pressure fluctations when the heat exchanger is moved into the circuit.

Description

BACKGROUND OF THE INVENTION

This invention relates to coil annealing furnaces of the kind comprising a base for supporting coils of sheet metal, usually stacked one on top of the other and possibly with convector plates or separators between each two adjacent superimposed coils, and at least one cover enclosing the coils and seating on the base via seals which prevent ingress of atmosphere, so that for example a reducing atmosphere or a neutral atmosphere may be confined within at least the inner of the covers. A fan or diffuser is provided for circulating the atmosphere within the inner cover to bring all of the furnace load to a uniform temperature and usually heating means are provided for example in the form of radiant tubes located within the outer cover for bringing the charge to the annealing temperature. Such furnaces will herein be referred to as "of the kind referred to."

Furnaces of the kind referred to have been in use on a widespread scale for many years, and it is usual to provide a series of such bases and a smaller number of covers so as to allow ones of the bases to be unloaded and others loaded whilst further bases in the series have both covers in place during the heating portion of the annealing cycle and further bases again have only the inner covers in place whilst the cooling portion of the cycle takes place. Many improvements have been suggested and incorporated successfully in the course of time in these furnaces generally with the aim of reducing the cycle time and hence enabling a smaller installation to cope with a given output. In particular, attention has been directed toward reducing the cooling time for example by the use of heat exchangers located in the atmosphere circulation path. In general however it has been difficult to provide adequate heat exchange surface area without providing impediment to the flow of atmosphere and hence causing power waste during the heating portion of the cycle, and other non-obvious problems occur when attempts along these lines are made.

SUMMARY OF THE INVENTION

The objects of the present invention are to provide improvements in furnaces of the kind referred to.

In accordance with the first aspect of the invention, an improved seal for a furnace of the kind referred to is characterised by the provision of a ring of resilient material located between said base and said cover or inner cover, and lying between a pair of surfaces which are respectively walls of fluid cooled chambers extending around the periphery of the cover and base respectively.

In accordance with the second aspect of the invention, a furnace of the kind referred to is provided with a heat exchanger which is movable between a position lying in the path of atmosphere circulation and a position removed from said path whereby the heat exchanger is ineffective to provide any impediment to atmosphere circulation when in the removed position, and said furnace also being provided with a seal as provided in the preceding paragraph.

The heat exchanger may be movable (from the effective position) into a chamber located laterally of an atmosphere circulation passage, and when moved from this chamber at the commencement of the cooling portion of a cycle, the atmosphere within the chamber becomes mixed with the circulating atmosphere and as these volumes of gas may be at substantially different temperatures, violent fluctuations of pressure may occur within the circulating atmosphere, which a conventional sand seal between the inner cover and the base could not tolerate, but the seal of the present invention can tolerate, and hence ingress of atmosphere and of sand particles via the seal is prevented.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic elevation showing a complete furnace and its work load;

FIG. 2 is a sectional elevation of the base portion of the same on a larger scale;

FIG. 3 is a sectional plan view taken generally on the line 3--3 of FIG. 2; and

FIG. 4 is a further enlarged fragmentary sectional elevation showing the seal areas.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings and particularly FIG. 1 thereof, the furnace comprises a base 10 located approximately at ground level and supporting a stack of coils 12 to be annealed, with an inner cover 14 seated on the base and enclosing the coils, and an outer cover 16 also seating on the base and enclosing the inner cover. The outer cover may be provided with heating means in the form of radiant tubes supplied with fuel gas via the pipes 18.

Atmosphere is circulated around and through the eye of the coils generally in the directions indicated by the arrows on FIG. 1, and the circulation path also extends through the base and via a series of passages defined by ducts in a pit below the base, a fan 20 being provided for inducing this circulation and a heat exchanger 22 being provided and being retractable into a chamber 24 located externally of the circuit.

Referring now more particularly to FIG. 2, it will be seen that the base includes a central throat 30 providing an annular passage for (in this case) up-flow of atmosphere from the fan, and the latter is driven via a motor 32 by way of a transmission system 34.

Within the throat 30 is a down flow passage defined by duct 36 and opening to the position occupied by the heat exchanger (when the latter is in circuit) and the heat exchanger and its supporting rails 40 can be retracted to the chain dot line position for example by motor 42 operating via worm and nut 44. The heat exchanger matrix is supplied with coolant via flexible pipes 48 so that coolant can be circulated through the heat exchanger for example by a pump from (and returning to) an external lagoon or pond. The heat exchanger assembly which is movable, includes wall portions 50, 52 which alternatively co-operate with the wall 54 defining part of the atmosphere circulation passage as an extension of duct 36.

The outer cover 16 is provided with a refractory lining 55 and with an annular web 56 (see particularly FIG. 4) or lip which rests in a trough 60 charged with sand 62 so as to provide a conventional sand seal between the outer cover and the base at this point. The trough 60 is carried by the inner cover 14 which is provided around its periphery and at its lower end with a chamber 64 which is fluid-cooled and preferably water-cooled. The chamber as seen in FIG. 4 is constructed from a series of metal sections particularly channel section 66 and two angle sections 68 with a strip section 70 which are welded together to provide the necessary structural strength and make the chamber water-tight.

A similar water-cooled chamber 72 is provided on the base 10 so as to provide a pair of parallel annular water-cooled surfaces 74, 76 extending around the periphery of the inner cover and between which a seal ring 80, made for example from a suitable rubber or like elastomeric material can be trapped. The ring may be attached to one or other of the parts, and conveniently is adhered to the surface 76 so as to be movable therewith. It will be noted that the structure defining chamber 64 extends below the ring, so that if the inner cover is placed on a horizontal surface other than a base, the chamber structure will rest on that surface and the ring will be spaced from that surface for protection.

As best seen in FIG. 4 also, a plurality of clamps may be provided for loading the seal ring to maintain the ring under compression, comprising lugs 90 secured effectively to the inner cover and bolts 92 pivoted to the base and including claws 94 for engaging the said lugs and hand wheels 96 screw engaged with the bolts to tighten and claws into engagement with the lugs.

In use, both inner and outer covers are located in place enclosing a work load, the heat exchanger is retracted to the chain dot line position FIG. 2, heat is applied via the outer cover and the gas or atmosphere is circulated in the direction indicated by the arrows and by means of the fan without any impediment from the heat exchanger which is out of circuit at this time.

When the work load has been raised to the required temperature and possibly after an additional soaking period, the heat exchanger is displaced into the full line position of FIG. 2 and becomes operative, and the possibly chilled atmosphere in the chamber 24 is at that time introduced into the circuit, but any fluctuation in pressure can be accommodated by the seal ring 80.

Rapid cooling then takes place until the work load is at a temperature which is safe and convenient for handling and exposure to ambient air, when the inner cover may be removed for unloading.

Claims

We claim:

1. A coil annealing furnace including a base member for supporting coils of sheet metal, a removable cover member having an open bottom and supported by the base member to form an enclosure for said sheet metal coils, a chamber located beneath the base member and in communication with said enclosure, means located in the chamber for circulating reducing or neutral atmosphere through said chamber and the enclosure, and a heat exchanger mounted beneath the base member and selectively movable into and out of the chamber, characterised in that the cover member is supported by the base member through a resiliently-deformable seal ring compressed between substantially parallel confronting annular webs of the cover member and the base member, each of said annular webs forming a wall of a coolant passageway.

2. A coil annealing furnace according to claim 1 wherein said seal ring is attached to said web of the cover member.

3. A coil annealing furnace including a base member for supporting coils of sheet metal, a removable cover member having an open bottom and supported on said base member to form an enclosure for said sheet metal coils, and a sealing assembly provided between the cover member and the base member, said assembly comprising:

a. first and second confronting annular surfaces presented by the cover member and the base member respectively;

b. an annular resiliently-deformable seal located between said confronting surfaces;

c. a first annular coolant passageway provided on the cover member, one of the walls which define said first passageway providing said first confronting surface; and

d. a second annular coolant passageway provided on the base member, one of the walls which define said second passageway providing said second confronting surface; the inner periphery of the gap between said first and second confronting surfaces being bounded by an annular portion of one of said coolant passageways.

4. A coil annealing furnace according to claim 3 wherein the inner periphery of the gap between said first and second confronting surface is bounded by an annular portion of the first coolant passageway.

5. A coil annealing furnace according to claim 4 wherein said confronting surfaces are both planar.

6. A coil annealing furnace according to claim 5 wherein said seal is attached to said first confronting surface.

7. A coil annealing furnace according to claim 4 wherein said first coolant passageway is T-shaped in radial section and is arranged with the stem portion thereof located horizontally in overlying relation with said second confronting surface, and with the cross limbs thereof extending vertically so that one cross limb depends downwardly to bound the gap between said confronting surfaces.

8. A coil annealing furnace according to claim 7 wherein the other cross limb of said first coolant passageway bounds the inner side of a channel extending around the outer periphery of the cover member, said channel containing a mass of sand, and wherein a second outer cover member having an open bottom is provided and is arranged with its bottom periphery embedded in the sand contained in said channel to sealingly enclose the first mentioned cover member.

9. A coil annealing furnace according to claim 3 further including a plurality of releasable clamping devices located at spaced positions around the periphery of the base and arranged to act between the cover member and the base member so as to draw said confronting surfaces towards one another to apply compression to said seal.

10. A coil annealing furnace according to claim 3 including a chamber located beneath said base member and in communication with said enclosure, means located in the chamber for circulating a reducing or neutral atmosphere through said chamber and the enclosure, and a heat exchanger mounted beneath the base member and selectively movable into and out of the chamber.