US3184224A - Tunnel kiln and method of operation - Google Patents

Description

May 18, 1965 D. P. SHELLEY TUNNEL KILN AND METHOD OF OPERATION 5 Sheets-Sheet 1 Filed Oct. 4, 1963 g j @Q Ch n-"file OM, i MN i OM, In wwwnnluflr NW NW TLT NM 07/ ,u M 5Q livv lm DONALD P; BSHELLEY x Allorneij May 18, 1965 D. P. SHELLEY TUNNEL KILN AND METHOD OF OPERATION 5 Sheets-Sheet 2 Filed Oct. 4, 1965 A a a M \w F o 3 i m L .A U 1i 2 fil. v n 0 L \W O 2 w ,r o \3 I l a 3 2 M I nuenlor A ltomey s May 18, 1965 D. P. SHELLEY 3,184,224

TUNNEL KILN AND METHOD OF OPERATION Filed Oct. 4, 1963 5 Sheets-Sheet 3 I ;nvenlor DONALD P. SHELLEY Attorney 5 May 18, 1965 D. P. SHELLEY TUNNEL KILN AND METHOD OF OPERATION 5 Sheets-Sheet 4 Filed Oct. 4, 1963 Inventor DONALD P. SHELLEY By 1 I z Aiforney;

y 13, 1955 D. P. SHELLEY 3,184,224

TUNNEL KILN AND METHOD OF OPERATION Filed 001;. 4, 1963 I 5 Sheets-S heet s M 7 w 7 I Q g'g g r\, l 0 Q N L O \l g E L E Q I 4 P, m Q s 6 1 x Q) Q K! Q Q R?- -g Q 3 D Inventor DONALD P. SHELLEY By/f r mad Attorney United States Patent 3,184,224 TUNNEL KILN AND METHOD OF OPERATIGN Donald P. Shelley, Ravenswood, Airdale Road, Stone, England Filed Oct. 4, 1963, Ser. No. 313,861 Claims priority, application Great Britain, Oct. 9, 1962,

13 Claims. (Cl. 26328) This invention relates to kilns, furnaces and other heat treatment chambers or tunnels, which for the sake of convenience in description will be broadly referred to as kilns. The invention is particularly applicable to the firing of ceramic ware such as tiles, table ware and so forth.

Present trends towards high-speed firing create difiiculties in effecting the travel of the goods through the kiln. Typical arrangements now available include the provision of run-ways along the kiln floor over which batts carrying the goods are pushed. The batts usually take the form of flat slabs of refractory material.

The object of this invention is to provide a more smooth and easy way of carrying the goods through the kiln.

The invention includes both a method of doing this and an apparatus for carrying the method into effect.

The invention consists in creating a film or cushion of air over the surface of the kiln hearth or floor, and sup porting the goods on the film or cushion while at the same time effecting their propulsion through the kiln.

The invention also consists in a kiln having a hearth which is provided with perforations, means being provided for blowing air under pressure upwards through the perforations, and means for feeding goods into the kiln on the hearth, whereby the air blown upwards through the perforations will impinge on the underside of the goods, and so support the goods while they travel through the kiln.

Constructional forms of the invention will now be described with reference to the accompanying drawings in which:

FIGURE 1 is a longitudinal section, partly broken away, through a tunnel kiln comprising a number of separate units.

FIGURE 2 is a sectional part plan on line CC of FIGURE 1.

FIGULRES 1 and 2 are drawn to a smaller scale than the other views.

FIGURE 3 is a longitudinal section through one of the units which make up the complete kiln.

FIGURE 4 is a diagram showing two streams of goods moving in opposite directions through the kiln.

FIGURE 5 is a transverse section on lines AA of FIGURES 1 and 2.

FIGURE 6 is a transverse section on lines BB of FIGURES l and 2.

FIGURE 7 is a cross-section through the kiln hearth illustrating a modified arrangement and FIGURE 8 is a perspective view showing an air deflector member used in the arrangement of FIGURE 7.

FIGURE 9 is a similar view to FIGURE 7 illustrating another modified arrangement.

The kiln comprises a refractory structure It defining an internal cavity 11 extending lengthwise of the kiln. The refractory structure is enclosed in insulating walls 12. The kiln is of considerable length and is built up from a number of separate units, one of which is shown separately in FIGURE 3. Each unit is supported on four pillars -13 each provided with a runner Wheel or roller 14 at its base riding upon a rail track 15.

If any one unit should become faulty for any reason it can therefore be lifted out of the kiln as soon as its neighbouring units have been slightly opened out, and a reserve unit, which can easily be maintained heated up in readiness, can he quickly inserted.

Heating elements 16, for example gas or oil burners or electric radiants, are mounted underneath the hearth I? of the kiln in a heating chamber 11, and the hearth has perforations :18 which allow the heat to rise up among the goods. Perforated baflles 19 at each side of the hearth allow heat to circulate among the goods from above. The hearth is supported on pillars 20 which are spaced apart from each other so as to allow free air circulation from the elements 16. As shown the hearth is formed in two parts, indicated as 17' and I7 and these each extend lengthwise through the kiln and are sloped to opposite gradients, see especially FIGURE 4; in this figure, however, the gradients are exaggerated; in practice they are probably not steeper than 1 in 500. Thus in the kiln illustrated the goods move in two streams, side by side, the direction of flow being down the gradient in each case.

In some cases the goods are supported on batts 22 the goods in this case being indicated as cups or similar articles 23. FIGURE 7 shows a modification in which the batts are omitted and the goods themselves are in the form of ilat articles such as til-es 24, which can move along without the need for supporting b-atts. Where batts are used, see especially FIGURE 2, upstanding guide members 2 5 of refractory material are cemented in pockets in the hearth to prevent sideways movement of the advancing batts. Where batts are not used, the tiles 24 or other articles .are centered by means of air deflector members 26 fitted at both sides of each stream of tiles and designed to direct jets of air inwards against the sides of the tiles, the deflector members 26 being formed with gaps 27, FIGURE 8, by Way of which air can escape from underneath the tiles. These jets of air are derived from a closed circuit of air which is blown through .a duct '30 in each unit of the kiln by means of a fan 31, the duct being an expander, widening downwardly to its lower end where it delivers the air underneath the hearth 17. This air rises up through the perforations 18 in the hearth and supports the batts 22 (or tiles 24 as the case may he) on a film or cushion of .air over the hearth. The travel of the goods through the kiln on this film or cushion is initiated by means of an endless conveyor 32 which may consist of wire bands, the conveyor being driven at a suitable speed so that it feeds the batts or tiles successively into the kiln. Each batt or tile pushes against the preceding one and this action, in conjunction with the slight gradient to assist the flow, is sufficient to effect propulsion. There is a similar endless conveyor 32 at the other end of the kiln operating at the same speed to remove the goods. Each stream of goods has two conveyors, one feeding into the higher end of the stream, and one removing at the lower end. The fans 31 are each carried by a frame structure .35 on the top of each unit of the kiln, the frame structure carrying a driving motor 36, which is connected through pulleys 37, 38 and a belt 39 with a hollow driving shaft 46 carried in bearings 41, 42. The frame 35 also carries a refractory plug 43 inserted into the top of the kiln unit to enable the fan assembly to be withdrawn when necessary for inspect-ion or service purposes. It is desirable to provide for cooling the bearings of the fan and its driving gear, for which purpose cooling water is allowed to circulate through a tube 44 passing centrally through the driving shaft 40, the water entering by way of one of a pair of connections 45, 46 and leaving by the other. flowing down the tube 44 and back upwards again between the tube 44 and the hollow shaft 40. Further cooling water is introduced into a jacket 47 for cooling the bottom bearing. In addition the shaft 40 carries a spinner 48 above the top of the plug 43 which assists in the dissipation of heat arising.

Each unit of the kiln is amount of heat transfer from one zone or unit to its neighbours; To assistin this, each unit includes a b-afile member 50 depending downwards'into the main'internal cavity 11, at right angles to the direction of flow, and the bottom of the bafile is arranged at such .a level that'the goods the kiln hearth 17. r

-It will be seen that each unit or zone of the kiln has its own fan unit which delivers hot air to the hot air chamher under the hearth where the heating elements '16 are situated, so that a continuous circulation of hot air is thus promoted by drawing the hot air from the top of the kiln and introducing it at the bottom, and the recirculating air thus promotes forced convection for both heating and cooling. Each z-one forms in eflect a heat exchanger, removing heat from fired goods moving in one direction and heating up goods moving in the opposite direction. a g

In the arrangements illustrated therheating means is separate from the circulating air blown through the kiln by the fans, but it would be possible to pre-heat the circulating air, for example by means external to the kiln,

so that the circulating air itself constituted the heating medium. Provision may be made in any case for introducing fresh air or allowing some of the circulating air to be drawn 01f, in each separate unit.

FIGURE 9 shows a modification in which a centralising effect is obtained :on batts travelling through the kiln by shaping the undersides of the battsZZ, as shown at 22, and the upper surface of the hearth 17, with a shallow V-shaped, concavo-convex or trough-like relationship in their contours. v

Although only two streams of goods have been shown in the drawings, it will be evident that a kiln can be de-' signed to accommodate a larger number of streams, and these may be in one or more layers.

1 claim: v

1. A method of heating workpieces of ceramic, jorjlike material, in a kiln having a hearth, comprisingthe steps of creating a film of heated 'air under pressure over, the

surface of the hearth to support the workpieces slightly above'thehearth, continuously feeding the wo r kpieces on to the hearth from both ends of the kiln in plural streams that, are oifset from each other, pushing the pieces through the furnace by placing each piece in contact with the pre ceding piece, so that while supported by the pressurized air the work-pieces are propelled in opposite directions 1 arranged to form a self-contained heating zone, asvfa-r as possible, with the minimum batts, and continuously feeding the batts on to, the hearth firom both ends of the kiln in plural streams that are offset from each other, pushing the batts through the furnace by placing each batt in contact with the preceding batt,

so that while supportedby the pressurized air the batts are propelled by the" incoming batts pushing forward those already in the kiln.

4.A method ofv heating workpieces of ceramic, or like material, in a kiln having a hearth, comprising the steps of creating a film of heated air under pressure over the surface of the hearth to support the workpieces slightly above the hearth, placing the workpieces on supporting propelled in opposite directions from each end of the length and through said chamber, means for creating supporting cushions of hot gas under said workpieces, means longitudinally dividing the chamber into a series of zones, and means for dilferentially heating said cushions of hot gas in the series of zones so astto progressively heat the workpieces in each stream to peak temperature and then progressively cool the workpieces as they move through the chamber.

6. Apparatus for heat treating workpieces of ceramic,

or like material, comprising a kiln, a chamber in the kiln,

a plurality of batts each for supporting at least one Workpiece, means for propelling at least two continuous streams of contacting batts in'opposite directions along the length and through said chamber, means for creating supporting cushions of hot gas under'said batts, means longitudinally dividing the chamber into a series of zones, and means for difierentially heating said cushions of hot gas in the series of zones so as to progressively heatthe batts and supported workpieces in each stream to peak temperature and then progressively cool them as they move through;

thetchamber, V

7. Apparatus for heat treating workpieces of ceramic, or like material, comprising a kiln,a tunnel-like chamber extending through the kiln, bafiles dividing the. chamber longitudinally'into separate zones to minimize heat, trans- V for between adjacent zones, a pair of hearths in each of said zones dividing each zone transversely to the length of said chamber, apertures in said hearths, means for propelling at leasttwo continuous streams of contacting workpieces through the kiln in opposite ends of the chamber, and means for projecting hot gas through said hearth apertures to create supporting cushions 'of hot gas below the streams ofworkpieces, said meansforiprojecting the that are offset from each other, pushing the pieces-through;

the furnace by placing each piece in contact with the preceding piece, so that while. supported'by the pressurized air the workpieces are propelled in oppos te directions from each end ofthe hearth'by'the incoming workpieces pushing forward those already in the kiln, circulating said heated air upwardlyglaterahy and downwardly to again contact both streams of workpieces, and utilizing gravity 2 to assistin propelling the workpieces by providingthe hearth with a downward gradient.

- 3. method of heating workpieces of ceramic, orlike material, in a kiln having a hearth, comprising the steps ofv creating a film of heatedair under pressure over the surface of the hearth to support the workpieces slightly above the hearth, placing the workpieees on supporting hot gas including means for progressively increasing temperature up to a peak and then progressively decreasing temperature from said peak in both the oppositely moving streams as said workpieces move through the kiln.

'8. Apparatus according to claim 5, wherein means for circulating the hot gas is provided in each of said zonesso 9. A kiln as claimed in'claim 8, wherein [said means for-circulating the hot gas in each :zone includes a fan disposed in the upper part of said chamber and adapted to be above said workpieces, a passageway in thelwall' of the kiln communicating the spacejoccupie'd by said fan with the space in the chamber adapted to be under said work- 'pieces said fans being so arranged as to direct hot gas in each zone through said passageway on to workpieces in both said streams so that incoming pieces to the zone are adapted to be heated and workpieces outgoing from a zone are adapted to be cooled by the same gas.

1 10. Apparatus as claimed in claim 9, wherein each said fan is arranged to receive both gas which has passed over incoming workpieces to heat them and gas which has passed over outgoing workpieces to cool them.

11. Apparatus as claimed in claim 5, wherein means are provided to enable workpieces being cooled in a zone to exchange heat directly to workpieces being heated in the same zone.

12. Apparatus according to claim 7, wherein said pair of hearths in each zone is provided with oppositely disposed gradients facilitating propulsion of both streams of workpieces.

13. Apparatus according to claim 10, wherein said means longitudinally dividing the chamber includes a separate furnace unit forming each of said zones of the kiln,

and means for removably fitting together the separate units to form said tunnel-like chamber.

References Cited by the Examiner UNITED STATES PATENTS 756,600 4/04 Dodge 2633 X 1,829,710 10/31 Dauch et al. 263-28 1,867,772 7/32 Smalley 263-28 1,948,173 2/34 Hagan 2633 X 2,215,581 9/40 Fackt 263-28 2,311,908 2/44 Vranken 263-26 X 2,538,972 1/51 Magnani 30229 2,749,109 6/56 Maud 263-6 3,071,356 1/63 Duffy 2636 CHARLES SUKALO, Primary Examiner. JOHN J. CAMBY, Examiner.

Claims (1)

1. 3. A METHOD OF HEATING WORKPIECES OF CERAMIC, OR LIKE MATERIAL, IN A KILN HAVING A HEARTH, COMPRISING THE STEPS OF CREATING A FILM OF HEATED AIR UNDER PRESSURE OVER THE SURFACE OF THE HEARTH TO SUPPORT THE WORKPIECES SLIGHTLY ABOVE THE HEARTH, PLACING THE WORKPIECES ON SUPPORTING BATTS, AND CONTINUOUSLY FEEDING THE BATTS ON TO THE HEARTH FROM BOTH ENDS TO THE KILN IN PLURAL STREAMS, THAT ARE OFFSET FROM EACH OTHER, PUSHING THE BATTS THROUGH THE FURNACE BY PLACING EACH BATT IN CONTACT WITH THE PRECEDING BATT, SO THAT WHILE SUPPORTED BY THE PRESSURIZED AIR THE BATTS ARE PROPELLED BY THE INCOMING BATTS PUSHING FORWARD THOSE ALREADY IN THE KILN.

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