US3567196A

US3567196A - High temperature furnace and conveyor therefor

Info

Publication number: US3567196A
Application number: US799552A
Authority: US
Inventors: Frederick James Edwards; Norman Hughes
Original assignee: Thermal Syndicate Ltd
Current assignee: Thermal Syndicate Ltd
Priority date: 1968-02-06
Filing date: 1969-02-06
Publication date: 1971-03-02
Anticipated expiration: 1988-03-02
Also published as: GB1227994A; NO125063B; DE1905690A1; CA931353A; FR2001416A1

Abstract

D R A W I N G
THE INVENTION RELATES TO A HIGH TEMPERATURE FURNACE IN PARTICULAR FOR APPLICATION IN EXCESS OF 1000*C. COMPRISING A HEATING CHAMBER, GUIDE MEANS EXTENDING THROUGH THE HEATING CHAMBER FROM A CHAMBER INLET TO A CHAMBER OUTLET, A PLURALITY OF SEPARATE SLATS OF GRAPHITE OR OTHER REFRACTORY MATERIAL ADAPTED TO REST IN EDGE-TO-EDGE ABUTTING RELATIONSHIP ON THE GUIDE MEANS TO DEFINE A SUPPORT SURFACE FOR AN ARTICLE OR ARTICLES TO BE CONVEYED THROUGH THE HEATING CHAMBER, ADVANCING MEANS UPSTREAM OF THE CHAMBER INLET FOR INTERMITTENTLY ADVANCING AN ABUTTING ARRAY OF SUCH SEPARATE SLATS OVER THE GUIDE MEANS AND THROUGH THE HEATING CHAMBER, AND MEANS DOWNSTREAM OF THE CHAMBER OUTLET FOR REMOVING SLATS AND RETURNING THEM TO A POSITION INTERMEDIATE THE ADVANCING MEANS AND THE CHAMBER INLET.

Description

March 2; 1 971 W RD m1. 3,567,196

HIGH TEMPERATURE FURNACE AND CONVEYOR THEREFOR Filed Feb. 6, 1969 Attorney United States Patent 3,567,196 HIGH TEMPERATURE FURNACE AND CONVEYOR THEREFOR Frederick James Edwards, Hebron, Morpeth, Northumberland, and Norman Hughes, Ponteland, New Castle upon Tyne, England, assignors to Thermal Syndicate Limited, Wallsend, Northumberland, England Filed Feb. 6, 1969, Ser. No. 799,552

Claims priority, application Great Britain, Feb. 6, 1968,

Int. Cl. F27b 9/.14

US. Cl. 263-6 12 Claims ABSTRACT OF THE DISCLOSURE The invention relates to a high temperature furnace in particular for application in excess of 1000 C. comprising a heating chamber, guide means extending through the heating chamber from a chamber inlet to a chamber outlet, a plurality of separate slats of graphite or other refractory material adapted to rest in edge-to-edge abutting relationship on the guide means to define a supporting surface for an article or articles to be conveyed through the heating chamber, advancing means upstream of the chamber inlet for intermittently advancing an abutting array of such separate slats over the guide means and through the heating chamber, and means downstream of the chamber outlet for removing slats and returning them to a position intermediate the advancing means and the chamber inlet.

This invention relates to a high temperature furnace and to an improved slat-type conveyor therefor. The invention has particular utility in relation to furnaces with operating temperatures in excess of 1000 C. where conventional slat-type conveyors could not be used or could be used only with difliculty.

In a preferred embodiment of furnace in accordance with the invention, a conveyor is provided which can satisfactorily be employed at temperatures up to 2000 C.

There are occasions when it is desirable to subject one or more articles to high temperature in a furnace for a particular period of time and in these circumstances it is known to provide a heating chamber having an inlet opening and an outlet opening therein, to mount the article on a conveyor which passes through the inlet opening, along the heating chamber, and through the outlet opening, and to advance the conveyor so that the time of the article within the heating chamber gives the required heating time to the article. Many conveyors have already been proposed for a wide variety of applications but difl'iculties arise as the operating temperature of the furnace is increased, since the choice of materials which can be used for the conveyor becomes more restricted and the actual design of the conveyor becomes more diflicult.

This invention relates to a high temperature furnace, and in particular to a slat-type conveyor for use in such a furnace, where the limiting operating temperature is set purely by the maximum temperature which a supported block of material, from which the slats of the conveyor are constructed, can withstand. It is a particular advantage of a conveyor in accordance with the invention that it is of extremely simple constnlction and in consequence is highly reliable in operation.

According to one aspect of the present invention a furnace comprises a heating chamber. guide means extending through the heating chamber from a chamber inlet to a chamber outlet, a plurality of separate slats adapted to rest in edge-to-edge abutting relationship on the guide means to define a supporting surface for an article or articles to be conveyed through the heating chamber, advancing means upstreamof the chamber inlet for intermittently advancing an abutting array of such separate slats over the guide means and through the heating chamber, and means downstream of the chamber outlet for removing slats and returning them to a position intermediate the advancing means and the chamber inlet.

Preferably, the individual slats are arranged so that the edges which abut the adjacent slats are contoured to provide an interlocking relationship. Such contouring of the edges of the slats may be by providing them with serrations extending lengthwise of the slats or by providing a tongue along one edge of the slat and a groove, in which the tongue of an identical slat could be received, along the opposite edge of the slat.

The means for advancing the slats through the heating chamber can be a simple pusher mechanism having a slow forward stroke to advance an assembled array of slats and a rapid return stroke to leave a clearance between the last slat in the array which has just been advanced, into which gap one or more slats recovered from the chamber outlet can quickly be placed to extend the array prior to a subsequent new advance stroke of the pusher mechanism.

The means for returning slats from the chamber outlet to the chamber inlet can be a simple chute along which the slats fall under the influence of gravity as they separate after leaving the chamber.

Conveniently, the guide means comprises two spaced apart rails one having a flat upper surface and the other having an inverted V-form in cross-section. With such guide means, the individual slats would be provided with a V-shaped groove into which the V-shaped rail would engage. By providing two rails of this form (i.e. one rail of which positively engages with the individual slat and the other rail of Which merely serves to support the slats) it is possible to guide the slats through the heating chamber whilst allowing freedom for expansion and contraction of the slats as their temperature changes during passage through the heating chamber.

It will be appreciated that the dimensions of the slats and the material from which they are made can be widely varied to suit the purpose required.

For a continuously operating furnace, the conveyor should be long enough to allow for a filling section upstream of the chamber inlet and this can be provided merely by spacing the pusher mechanism sufiiciently far from the said inlet. Conveniently, the chamber outlet is disposed adjacent to a cooling section, the downstream end of the cooling section serving as an unloading station from which heat-treated articles can be removed from the conveyor before the slats are allowed to separate and be returned to the chamber inlet.

According to a further aspect of the present invention a slat-type conveyor comprises guide means for the conveying flight, a plurality of separate slats for sliding over the guide means, reciprocating means for pushing a slat at the upstream end of the conveying flight in the conveying direction to cause all the slats in the conveying flight to move along the guide means, means for removing slats one by one from the downstream end of the conveying flight and returning them separately to the upstream end of the conveying flight, and means for pacing slats recovered from the downstream end of the guide means between the reciprocating means and the slat last contacted thereby.

The invention will now be described, by way of example, with reference to the accompanying drawing, in which:

FIG. 1 is a schematic side elevation showing a furnace and its associated conveyor,

FIG. 2 is an isometric view on an enlarged scale of one form of conveyor slat which may be employed in the conveyor of FIG. 1,

FIG. 3 is a view corresponding to FIG. 2 showing an alternative form of slat, and

FIG. 4 is a further enlarged section of one slat of the kind shown in FIG. 2.

Referring to FIG. 1, a furnace 1 embodies an openended heating chamber having an inlet end 2 and an outlet end 3. Passing through the heating chamber is a slat-type conveyor (generally designated 4) which is formed from a plurality of separate slats 5 arranged in edge-to-edge abutting relationship so that together they define an article-supporting surface 6. Adjacent to the outlet end 3 of the heating chamber is a cooling station 7. A pusher mechanism 8 having a reciprocating ram 9 is arranged at the upstream end of the conveyor to periodically advance the slats 5 through the heating chamber. The arrow 10 indicates some means for returning disassembled slats from the downstream end of the conveyor to the upstream end for repassing through the furnace 1.

FIG. 2 shows three slats 5 resting on

guide rails

11 and 12. Guide rail 11 has a smooth flat upper surface in contact with a smooth fiat lower surface of the slats 5 whereas rail 12 has a ridged upper surface which locates in an inverted V-shaped groove 13 formed in the undersurface of each slat. The abutting edges 14, of the slats 5 are serrated so that when the slats are placed in edge-to-edge abutting relationship, the

serrated edges

14 and 15 of adjacent slats 5 interlock. The location of the rail 12 in the grooves 13 guides the slats in their passage through the heating chamber while the smooth coaction between the rail 11 and the underside of the slats 5 allows freedom for thermal expansion.

FIG. 3 shows a modified form of slats 5 in which the leading edge 14 is provided with a longitudinal groove 16 and the trailing edge 15 is provided with a co-operating tongue 17. In other respects, the conveyor of FIG. 3 is similar to the conveyor of FIG. 2.

It will be appreciated that each time a slat is passed through the furnace, it must be raised to the temperature of the heating chamber and then cooled down again. In order to reduce the thermal capacity of the slats, each slat may be recessed on the undersurface with an aperture 18 in the manner shown in FIG. 4. The aperture 18 can be as large as possible provided it does not undesirably weaken the slat.

The slats can easily be separated one from the other at the downstream end of the conveyor by terminating the rails and allowing the slats to drop downwardly under the influence of gravity. The interlocking features shown on the

edges

14 and 15 in FIGS. 2 and 3 are shaped with a curved upper surface 21 to allow the leading slat to follow a downward curve relative to the following slat without binding and thus facilitate such a separation of slats under the influence of gravity. From the outlet end of the conveyor the individual slats may drop into a chute which returns them to the inlet end, where they can be reassembled during each return stroke of the ram 9.

The interengagement between the

edges

14 and 15 of the individual slats provides a seal between adjacent slats and prevents small articles (e.g. granular material) resting on the conveying surface 6, from falling between slats during their passage through the furnace. Further, the interlocking between the adjacent edges of the slats reinforces the transverse strength of the conveyor so that should any slat break during its pasage through the furnace it will be supported by the two adjacent slats and safely carried through to the downstream end.

As can be seen in FIGS. 2 and 4 and also FIG. 3, this transverse strength is derived from a positive support where the transversely extending teeth (such as projection 17) interlock with corresponding teeth (such as form the groove 16) on the other edge 14. This positive support is given by the horizontally flat lower surface 19 of one tooth resting on the similarly fiat upper surface 21 of the corresponding tooth on an adjacent slat 5. Note also that if the upper surface 21 of these teeth slants downwardly, then such positive support is lost, but if it slants upwardly from its base, then the positive support is maintained.

As already indicated, the particular forms of interengagement shown in FIGS. 2 and 3 have the advantage that they do allow easy separation of the slats at the downstream end of the conveyor merely by leading the slats over support rails which are downwardly curved so opening up the interlocking features between adjacent slats and allowing the individual slats to fall away.

The top surface of the slats can be profiled with grooves or depressions to assist in positively locating articles on the conveyor. In the case of the fusing or sintering of a continuous layer of particulate material, the depression (which may be on individual slats or may extend across the joint between two slats) will have the effect of forming appropriately shaped thickened regions on the under surface of the fused or sintered layer. In place of depressions, projections can be employed and these can be used (again in the case of a layer of particulate material) to selectively reduce the thickness of the fused or sintered layer. If the projections extend above the layer of material, the fused or sintered layer will have apertures formed therein or will be divided into separate parts.

A further possibility when using the invention for the fusing or sintering of a layer of particulate material is to perforate the slats with channels running from top to bottom through the slats so that the particulate material poured onto the conveyor in the vicinity of any channel will flow through that channel, so that after fusing or sintering the layer, a perforated plate or grid is formed.

A preferred material from which the slats manufactured is graphite which is particularly suitable because of its high mechanical strength at the highest temperatures likely to be met in an industrial furnace. However, when graphite is used, the furnace atmosphere should be either neutral or reducing in order to limit the oxidation of the slats and enhance their working life. It will be appreciated that graphite is not the only material which can be used and any suitable refractory material can be employed. It will further be appreciated that since the slats are purely passive members which are pushed through a heating chamber the only requirement on the material employed for the slats is that it should have adequate strength at the maximum temperature to which it is likely to be subjected.

Where a ceramic refractory material is chosen as the material for the slats, it will be appreciated that the contouring on the

edges

14 and 15 can readily be produced by an extrusion process, the slats being extruded as a continuous profiled rod which is subsequently cut to appropriate lengths.

What is claimed is:

1. A high temperature furnace comprising a heating chamber, a chamber inlet, a chamber outlet, guide means extending through the heating chamber from the chamber inlet to the chamber outlet, a plurality of separate slats resting in edge-to-edge abutting relationship on the guide means to define a supporting surface for articles to be conveyed through the heating chamber, teeth transversely formed in the leading and trailing edges of each of said slats such that the abutting edges of adjacently positioned slats interlock in a sealing and supportive relationship by one of said teeth in each of said slats being shaped to support postively an appropriately shaped tooth in an abutting edge of the adjacent slat, each of said slats having a longitudinally extending groove at a given position on its under side, and said guide means comprising a pair of longitudinally extending rails with one shaped to ride in said groove of said slats without significant transverse play and with the other shaped to support said slats while accommodating transverse expansion, ad-

vancing an abutting array of such separate slats over the guide means and through the heating chamber, and means downstream of the chamber outlet for removing slats and returning them to a position intermediate the advancing means and the chamber inlet.

2. A furnace as claimed in claim 1, in which a tooth on one edge of each slat has a horizontally flat upper surface and a tooth on the other edge has a horizontally flat under surface, both such teeth being positioned on each slat such that the upper surface of the one supports and forms a seal with the under surface of the other in abutting slats.

3. A furnace as claimed in claim 2, in which said longitudinal groove in said slats is an inverted V-shape and with said corresponding rail of the guide means having a similar V-shaped cross-section, said other rail of said guide means having a flat upper surface.

4. A furnace as claimed in claim 3, in which the tooth in one edge of each of the slats is shaped as a tongue and the teeth of the other edge are shaped to form a groove, in which the tongue of an identical slat is received.

5. A furnace as claimed in claim 2, in which the slats are functional in the temperature range of 1000 C. to

6. A furnace as claimed in claim 2, in which each of the leading and trailing edges of said slats have a plurality of teeth forming a multiply serrated surface.

7. A furnace as claimed in claim 2, in which the means for advancing the slats through the heating chamber is a pusher mechanism having a forward stroke to advance an assembled array of slats and more rapid return stroke.

8. A furnace as claimed in claim 7, in which the means for returning slats from the chamber outlet to the chamber inlet includes a chute along which the slats fall under the influence of gravity as they separate after leaving the chamber.

9. A furnace as claimed in claim 7, in which a filling section is provided upstream of the heating chamber and a cooling section is provided at the downstream end of the heating chamber.

10. A furnace as claimed in claim 2, in which each slat is provided with at least one depression on that surface which defines the supporting surface in the heating chamber.

11. A furnace as claimed in claim 2, in which each slat 6 is provided with at least one projection on that surface which defines the supporting surface in the heating chamber.

12. A high temperature slat-type conveyor extending through a heating chamber, comprising a pair of spacedapart guide means, a plurality of separate slats adapted to rest in edge-to-edge abutting relationship on the guide means to define a supporting surface for articles to be conveyed through the heating chamber, advancing means upstream of the chamber inlet for intermittently advancing an abutting array of such separate slats over the guide means and through the heating chamber, and means downstream of the chamber outlet for removing slats and returning them to a position intermediate the advancing means and the chamber inlet, one of the pair of guide means having a ridged upper surface, the other of the pair of guide means having a flat upper surface, each slat having an inverted V-shaped groove formed on its under surface to locate each slat transversely on the ridged guide means, one edge of each slat having at least one projection formed thereon with a flat lower surface and a downwardly sloping or curved upper surface, the opposite edge of each slat having a cooperating groove for each such aforesaid projection, the lower surface of each groove also being flat to provide area contact with the flat lower surface of a projection received therein.

References Cited UNITED STATES PATENTS 2,366,088 12/1944 Coody 2636 2,982,530 5/1961 Drakengren 26328 3,168,2 99 2/1965 Miller 26328 FOREIGN PATENTS 561,006 4/ 1951 Italy 263-6 OTHER REFERENCES Pages 246, 247, and 248 of Industrial Furnaces Vol. 11, Third Edition by W. Trinks, published 1955 by John Wiley & Sons, Inc., New York, NY.

JOHN J. CAMBY, Primary Examiner U.S. C1. X.R. 2632-8 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,567,196 Dated March 2, 1971 Inventor(s) Frederick James Edwards & Norman Hughes It is certified that error appears in the above-identified patem and that said Letters Patent are hereby corrected as shown below:

Column 5, line 1, after the word "advancing" insert -means upstream of the chamber inlet for intermittently advancing-.

Signed and sealed this 15th day of June 1 971 (SEAL) Attest:

EDWARD mmnmcnmmm. WILLIAM E. SCHUYLER, Attesting Officer Commissioner of Patel FORM PO-IOSO (10-69 USCOMM'DC 603 i u s covununn "nu-nu: nrnn- "n. n