GB2240820A - Conveyor for a pusher-type furnace - Google Patents

Abstract

A conveyor for a pusher-type furnace, eg for processing a metal slab, includes parallel rails (20) carrying sliding shoes (16) on which the slab or other load rests. To reduce the tractive effort needed to set or keep the slab in motion, pressurised fluid, typically air, is fed to the interfaces between the rails and shoes by providing ducts or chambers (26) within the rails feeding the fluid to apertures (40) and/or recesses (34) at or in said interfaces. <IMAGE>

Description

PUSHER-TYPE FURNACES This invention relates to pusher-type furnaces, typically for treatment of aluminium or aluminium alloy or other metal slabs or billets. The slab or other load of material to be processed may weigh several tonnes and is propelled through the furnace by pusher mechanism, commonly hydraulically powered though mechanically driven pushers may also be used.

The load rides on one or more shoe elements sliding along rail elements of a track through the furnace. Due to the hostile environment within the furnace it is not possible to employ most conventional lubricants, or lowfriction bearings such as rollers or wheels and the track and shoes are therefore subjected to substantial wear and tear and the power required to propel the load is high, particularly when first starting it from rest.

It has been proposed to reduce friction at the interface between the shoe elements and rail elements by including pads or slip plates of low friction material and one such proposal is described in US-A-4540364.

The object of the present invention is to provide a conveyor device incorporating shoe and rail elements for or in a pusher-type furnace which is effective and durable in use, which substantially reduces the frictional and other load forces at the interface or interfaces between the shoe and rail elements, particularly when starting the load from rest, and which therefore results in much less wear and tear on the elements of the conveyor device and a substantial reduction in the power needed for moving the slabs or other load through the furnace.

According to the invention there is provided a conveyor device for transporting a load of material to be processed through a pusher-type furnace, said device including a track comprising a rail element and defining a feed path through the furnace in use, and a shoe element in running engagement with said track for bearing at least part of said load for movement along said path; characterised in that said device further comprises means for feeding pressurised fluid to a load bearing interface between said elements in use to provide a force in opposition to that exerted by said load so as to reduce the tractive effort needed to propel the load along said path.

Preferably said pressurised fluid is compressed air.

Conveniently said feeding means includes a duct or chamber defined within the rail element and an aperture or apertures in a wall thereof leading from the chamber to said interface.

Said track may comprise a plurality of rail elements, and ducts or chambers in one or more adjoining said elements may be interconnected to form a continuous duct along all or part of the track.

The device may further include control means for selective application of the pressurised fluid to said interface or predetermined sections or zones thereof, e.g. as and when the shoe element is in or is passing along respective said sections or zones.

In one application of the invention the pressurised fluid is applied at the interface or interfaces of the shoe element or elements which bear the load at least when starting it in motion along the track from a position of rest so as to reduce the force needed to overcome its initial inertia.

Examples of the invention are now more particularly described with reference to the accompanying drawings wherein Figure 1 is a diagrammatic cross-section of a pusher-type furnace; Figure 2 is a diagrammatic perspective view of a shoe element and part of an associated rail element of a conveyor device of said furnace; Figure 3 is a plan view of the rail element of Figure 2; Figures 4a and b are lateral sections of two alternative forms of shoe and rail element, and Figure 5 is a part-sectional side elevation of the Figure 4b arrangement.

The furnace 10 itself (Fig.1) is of generally conventional construction comprising a tunnel-like body 12 provided with burners or other heating means and through which a load of material to be processed, typically a slab 14 of aluminium or aluminium alloy is propelled.

To avoid damage to or marking of the underface of slab 14, particularly as the material becomes softened by heat, it rests on a plurality of shoe elements 16 of a conveyor device of the furnace.

Said device further includes a track defining a feed path through the furnace comprising a pair of spaced parallel rail assemblies 18 along which the shoe elements slide.

A mechanical or hydraulically powered pusher of known design (not shown) propels the slab along the track.

Each rail assembly comprises a plurality of rail elements 20 supported in end to end relationship on short pillars 22 above the floor of furnace 10. While some of the rail elements 20 may be mounted in abutting end to end relationship so that they adjoin each other it is usually necessary to provide gaps between the ends at intervals along the assembly to allow for thermal expansion.

In the example shown in detail in Figures 2 and 3 each rail element 20 is an I section beam, its upper coplanar horizontal flanges 24 defining a pair of spaced parallel longitudinal ducts 26. Where ends of the elements abut each other as referred to above a fluid tight seal may be provided so that the ducts 26 thereof interconnect to form continuous longitudinal ducts.

Otherwise the ducts 26 of each element 20 will be closed at the ends thereof, and the ducts may be further subdivided along the length of the element by internal partition defining zones or sections of the track, the rail assemblies 18 being preferably so sub-divided to match each other laterally of the track.

Each shoe element 16 is a generally rectangular block having a lower face 30 which co-acts with top face 28 of the rail section to form a sliding interface.

Downwardly extending lip sections 32 on each side of element 16 extend towards each other below the flanges 24 of rail elements 20 to guide and locate the shoe element thereon. Said top face 28 has two rows of rectangular recesses 34 along it.

Ducts 26 are operatively connected to a source of compressed air e.g. a compressor, by way of control valves means (not shown).

If the ducts do not run the whole length of the rail assemblies the sections or zones thereof matching each other laterally of the track will be connected through common control valve means. The length of each said section or zone in one arrangement will not be substantially greater than the length of the lower faces 30 of the shoe elements, and may possibly be somewhat less than said length.

Apertures 40 within each recess 34 communicating with ducts 26 distribute the compressed air to top face 28 to act at the interface with the shoe elements 16.

In the examples illustrated in Figures 4a, 4b and 5 top faces 50 of the rail elements 20 are planar and the lower faces 30 of the shoe elements are provided with recesses 51.

In the arrangement shown in Figure 4a the construction of the rail elements 20 is also somewhat different. The side channels of the I section are enclosed by side walls 52 (only the left hand half of the element is shown in Fig.4a) to form larger volume chambers 54 along each element which may be continuous or sub-divided into sections or zones by lateral partition walls. Compressed air will be fed into chambers 54, or progressively into the sections or zones thereof as referred to above, to exit from a series of through apertures 40 in said top face so as to coact with the recessed lower faces 30 of the shoe elements.

In Figures 4b and 5 the rail elements 20 are similar to those shown in Figures 2 and 3, the compressed air being fed by longitudinal ducts 26 to apertures 40.

If the sectional or zoned arrangement is used the control valve means may be operated automatically in sequence during passage of the shoe elements 16 along rail element 20 so that the compressed air is applied progressively at said interfaces as the shoe elements are shifted along the track to reduce consumption of the compressed air.

While the upward force exerted by the air at said interface will not normally be sufficient to float the loaded shoe elements out of face to face contact with the rail elements 20 (though such floating is in contemplation of the invention), it will substantially reduce the face to face loading and frictional engagement therebetween by exerting an upward force in opposition to that exerted by the load.

The compressed air or other pressurised fluid may be applied throughout the full length of the track through the furnace either progressively as the shoe elements move therealong as referred to above or simultaneously, or said application may only take place in localised portions of the track, particularly the portion or portions in which the loaded shoe elements are started in motion from rest so as to reduce the power needed to overcome inertia and initial friction when first putting the slab 14 in motion. Thus useful results may be obtained by providing or applying the invention to portions of the track which are outside the main part of furnace 10 or in cooler regions thereof, e.g. in an area where the slabs 14 are first positioned on the shoe elements 16 ready for movement.

The use of the invention not only reduces stress and wear and tear on the components of the conveyor device and economises in power requirements but may also enable more efficient production by allowing larger slabs or other loads to be processed and/or longer furnaces to be employed.

It will be understood that the invention could be employed in combination with pads, slip elements, or facings of low friction material at said interfaces e.g.

located in or on the top faces 28 of the rail elements 20 and/or in or on the lower faces 30 of shoe elements 16.

The air or other pressurised fluid could be fed through apertures or into recesses in such pads, slip elements or the like.

The faces of either or both elements constituting said interface could also be provided with other arrangements of channels, grooves or recesses for distribution of the compressed air or other fluids at said interface. In some applications both faces might be flat, i.e. without recesses or the like.

Claims (11)

CLAICt,S

1 . A conveyor device for transporting a load of material to be processed through a pusher-type furnace, said device including a track comprising a rail element and defining a feed path through the furnace in use, and a shoe element in running engagement with said track for bearing at least part of said load for movement along said path; characterised in that said device further comprises means for feeding pressurised fluid to a load bearing interface between said elements in use to provide a force in opposition to that exerted by said load so as to reduce the tractive effort needed to propel the load along said path.

2. A device as in Claim 1 wherein said pressurised fluid is compressed air.

3. A device as in Claim 1 or 2 wherein the means for feeding said fluid includes a duct or chamber defined within the rail element and an aperture or apertures in a wall thereof leading from the duct or chamber to said interface.

4. A device as in Claim 3 wherein the track comprises a plurality of rail elements in end to end relationship to form a rail assembly.

5. A device as in Claim 4 wherein the track comprises two said rail assemblies in spaced parallel relationship with sections or zones thereof matching each other laterally of the track connected in common for feeding the pressurised fluid to load bearing interfaces with respective shoe elements running thereon simultaneously.

6. A device as in Claim 3, 4 or 5 including control means for selective application of the pressurised fluid to said interface or interfaces or predetermined sections or zones of the track.

7. A device as in Claim 6 wherein said control means operates to apply the pressurised fluid only to sections or zones as and when the shoe element or elements are therein or are passing therealong.

6. A device as in any preceding claim wherein the pressurised fluid is applied at the interface or interfaces at least when starting said load in motion along the track from a position of rest.

9. A device as in any preceding claim wherein the or each rail element or shoe element has recesses defined in a face which coacts with the other of the elements to provide said interface, the compressed fluid being fed to said recesses in use.

10. A conveyor device substantially as hereinbefore described with reference to and as shown in Figures 1.2, 3 and 4a; or in said Figures as modified by Figures 4b and 5 of the accompanying drawings.

11. A pusher-type furnace including a conveyor device as in any preceding claim.