US2543549A - Refractory support for ware in a tunnel kiln - Google Patents

Description

Feb. 27, 1951 s. N. JEPPSON REFRACTORY SUPPORT FOR WARE IN A TUNNEL KILN 2 Sheets-Sheet 1 Filed 001;. 30, 1948 l/vvs/v TOP Gnoims N. JEPPsoN ATToRA/Ey Fig.

Feb. 27, 1951 G. N. JEPPSON 2,543,549

REFRACTORY SUPPORT FOR WARE IN A TUNNEL KILN Filed Oct. 50, 1948 2 SheetsSheet 2 /NVENTOR GE ORGE N. JEPPS o N A TTOFIZNEY Patented Feb. 27, 1951 REFRACTORY SUPPORT FOR WARE IN A TUNNEL KILN George N. Jeppson, Worcester, Mass, assignor to Norton Company, Worcester, Mass, a corporation of Massachusetts Application October 30, 1948, Serial N 0. 57,511

The invention relates to refractory supports for wars in a tunnel kiln.

One object of the invention is to provide a refractory support for ware in a tunnel kiln which has a fast heating and cooling .cycle. An-

other object of the invention is to provide a system of batts to support a .grinding wheel being vitrified in a tunnel kiln of such construction and arrangement that the batts may be mechanically propelled through the kiln without the use of cars or movable elements other than the batts themselves and whereby a rapid vitrifying and annealing cycle may be achieved without excessive breakage of the batts due to thermal shock or otherwise. to provide a sliding batt construction especially adapted for the vitrification of large grinding wheels in a fast heating cycle. Another object of the invention is to provide a support for large articles to be vitrified in a tunnel kiln having planes of radiant energy above and below the support.

Other objects will be in part obvious or in part pointed out hereinafter.

The invention accordingly consists in the features of construction, combinations of elements and arrangements of parts, all as will be illustratively described herein and the scope of the application of which will be indicated in the following claims.

In the accompany ng drawings illustrating one of many possible embodiments of the mechanical features of thi invention, I

Figure l is a plan view showing a plurality of batt elements supporting a single large grinding r wheel to be vitrified and illustrating the rods upon wh ch the batts slide.

igure 2 is a cross sectional View taken on the line 2-2 Figure 1.

Figure 3 a cross sectional view taken on the line 33 of Figure 1.

Figure is a longitudinal sectional view through a portion of the heating or firing zone of a tunnel kiln in wh ch the refractory support of the invention may be used showing such refractory support in section.

Figure 5 is a cross sectional View of the kiln and sup ort, the section being taken on the line Ei-5 of Figure l.

Referring first to Figures 1, 2 and 3, in this illustrative embodiment of the invention, a unit which is moved through the kiln comprises four batts as which straddle the tunnel and slide on rods 3!, six batts 32 which rest upon the batts 3D and extend parallel to the rods 3!, four end J Another object of the invention is r 7 Claims. (01. 153) bafiles 33, two center baffles 34 and a grinding wheel to be vitrified 35. Preferably a layer of quartz sand or the like 35a is placed on top of the longitudinally extending batts and the grinding wheel 35 rests upon this layer. The baffles 33 and and grooves as shown .in Figure 3.

34 may rest upon the longitudinally extending batts 3-2. The purpose of the baffles 33 and 34 is to form with the roof and sidewalls of the tunnel and the batts 3E] and 32 a compartment for each grinding wheel as it is being preheated, as it is being fired, and as it is being annealed. These baflles accordingly have curved edges as shown. A pair of bafiles 33 with a center baffle 36 form a segmental wail following the contour of part of the periphery of the grinding wheel 35. By using three pieces to form each baflle means ahead of and'behind the grinding wheel, fracturing of such bafile means due to heat shock or thermal differential is substantially eliminated.

L kewise the lower support for the grinding wheel 35 consists of four narrow batts 38 instead of a single batt in order that thermal differentials will be less liable to cause fracture. The upper support for the grinding wheel 35 consists of six batts 32 for the same reason. Each batt therefore is long in one dimension and relatively narrow. I have found that narrow batts will with.- stand a great many cycles of heat ng and cooling whereas more or less souare batts have a greater tendency to break when subjected to repeated cycles of heating and cooling.

Also by forming the batt sup ort for the wheels in two layers of batts, that is to say a lower layer of batts 3B and an upper layer of batts 32, I provide a support which will withstand many more cycles of heatin and cooling than if the att or batts were in a single layer. Thus it may be said that the batts are not only narrow, they are also thin. There is another reason for supporting each wheel 35 by means of a nluralitv of batts. A batt in the form of a sin le thick plate or even in the form of a pair of thin plates superimposed unon each other will warp after a number ofcyc'les of heating and cool ng. In order to produce grinding wheels with plane sides these grinding wheels should have flat, that is to say planesurfaces to rest upon during vitrification. Another feature of the support for the wheels is the laying of the upper layer of batts 32 across insteadof along the lower layer of b it: 39. This helps to produce a level fiat surface for supporting the wheel 35.

Referring to Figure 2, it will be seen that the fbatts 3!! have a groove 36 at one end and a tongue 31 at the other end. These batts extend the ent re length of the kiln in a lon line of batts. They arepushed through the kiln by a force applied against the end batt at the entrance end of the kiln. Consequently each batt 3D is firmly pressed against adjacent batts and the "tongue and groove junction will hold a broken .batt in place if the adjacent batts are still whole.

Preferably also the upper batts 32 have tongues As will be noted by reference to Figures 2 and 3, the batts so are thicker than the batts 32. Since the batts- 30 are the ones which span the tunnel they are the primary conveyors of the load.

Figures 4 and 5 illustrate respectively a longitudinal section and a cross section of a tunnel kiln in which the refractory supports of the invention can be used. This tunnel kiln has a rectangular parallelepipedal box structure comprising steel side plates 40, steel bottom plates 4i, and steel top plates 42. To the side plates 40 are secured steel legs 43 and to the bottom plates 4| are secured a number of centerline legs 46. The bottom plates 4| are braced with angle irons 45 and the top of the kiln is strengthened by cross beams 46.

Resting on the bottom plate 4| in the firing zone of the kiln is a mass 5!! of refractory bricks forming a generally rectangular parallele inedal structure the top face 5| of which is the bottom of the tunnel 52. This mass 50 stops .iust s ort of the side plates 40 leaving spaces which are filled with refractory insulating powder such as porous silica 53.

Bricks 54 continue the structure upwardly on either side of the tunnel 52 and large bricks 55 continue the structure still further upwardly, the bricks 54 and 55 forming vertical side walls 56 of the tunnel 52 and also inclined walls 5'! of the tunnel 52.

Secured to the side plates 4!! are lon an le irons 6B which support channel irons 6! (Figure 4) arranged in pairs. Each pair of channel irons 6| hel s to support two courses of roof bricks 62. Stating this in another way, two channel irons 'Sl whose open sides are opposite each ot er support between them a course of roof bricks 62 extending clear across the kiln. These roof bricks 62 in the firing zone are short to give room for the combustion tubes and the burners: roof bri ks 62a are cut away a shown while roof bricks 62b are long to bring down the roof of the tunnel close to t e ware and the baffles 33 and 34. In the reheating zone and in the annealin zone roof bricks 621) are used.

As will clearly be seen. porous silica 53 is locat d in s ces adjacent t e side lates u to t e to of the kiln and there is more DOIOlls silica '53 on to oi the roof bricks R2. 620. and 8'").

S p orted bv the bricks 55 are bricks 85 having bor s to receive refractory tubes 66 on one side of the kiln in which are burners 61. On the other side of t e k ln o os te. a b rner 6' the bores in the bricks 65 receive refr ctory fine tubes 68 and short refractory tubes 69 in which are plu s 1n. I

Simi arl in the m ss of ricks are bri ks 55 havin bores receivin refra torv tu s 5 in w ich ar burners 1. t e bores in the br ck also alte at lv hav n re ractorv flue tubes 68 and s ort r fractorv tub s 69 plugged w th plu s 10. The t' bes 6 and 68 are conn cted b combustion tub s 15. The arran em nt o urn rs and. time tubes 62 i alt rnate both or zontally and verticall That is to a on eit er side of a burn r 61 t ere is a flue tube 63 and below a burner 6.1 is a flue tube '68. etc.

Connec ions 16 connect the burners R1 to niping. not shown. which pi n is connected u to sources of gas and air und r pres ure in order to supnlv t e burn rs 61 with combust n gases. The eases burn mo tlv in the co bustion tubes which. for exam l c n be D1950 o bon ed sili on carbide and \nhlt'th become ery ot. The combustion ea es from t e re ract y flue tubes 68 go into fiues 18 in the bricks 50, 54 and 55 whence they lead to fiues, not shown, to preheat the preheating zone of the kiln. Since this invention relates to the refractory supports for the ware, I do not deem it necessary to describe the entire kiln, and enough of the structure of the kiln has been described so that the utility of the invention may be readily apparent.

The rods 3! may be located in grooved elongated refractory members 30 which form part of the bottom of the tunnel 52 of the kiln in the firing zone; elsewhere the batts 30 may ride upon rollers, not shown. The batts 30 have wide grooves 8| at either end so that they will not slip off the rods 3! nor off the rollers, not shown. In the operation 'of this kiln the operator from time to time places an additional load in front of the entrance end and then causes a ram to push t e new load against the last previous load to be introduced and this pushes all the loads ahead of it moving every load the distance of one section in the kiln and causing one load to move out of the exit end of the tunnel. The assembly of batts 30 and with the baffles 33 and 34 and a grinding wheel 35 constitutes a unit load. A unit load has a length just equal to one section of the kiln and one section of the kiln is the distance between successive legs 43.

For annealing pur oses the batts 39 and 32 may have cut-outs to form a hole 82 in each unit load to allow air to move upwardly through the refractory support in the annealing zone of the kiln.

A solid batt of the overall dimensions of the composite support of the invention would quickly go to pieces in a tunnel kiln of the type described operating at a top temperature of 1200 C. But the composite structure of refractory support for wheels to be vitrified enables a tunnel kiln of the type illustrated to be successfully operated. It will readily be seen that this type of tunnel kiln is efficient because the entire supporting means for the ware to be vitrified has a mass not greatly in excess of the were to be vitrified in contra distinction to the usual tunnel kiln where the cars and refractory supports have a mass many times that of the ware to be vitrified. Furthermore, the baflies 33 and 34 substantially seal off each section of the kiln from every other section of the kiln and thus optimum preheating, firing and annealing conditions can be achieved. That is to say, at a given time the entire area of the wheel 35 is subject to the same temperature conditions. There is one exce tion to the foregoing statement, namely that deliberately during the annealin the wheels are cool d from the inside to the outside thus to take advantage of the reverse strain annealing des ribed and claimed in U. S. L tters Patent No. 2.034.721. to my colleague W. L. Howe dated March 24, 1936. However. so far as the broad features of this invention are concerned, the holes 82 can be omitted and very satisfactory vitrified whees neverthel ss can be produced. The bafiles 33 and 34 not only protect the wheels 35 from temperature gradients during all the stages of vitrification, viz. preheating, firing and annealing, but they also protect the batts 30 and 32 from such temperature gradients and. even protect themselves. By providing these baflles 33 and 34 there is very little difference of temperature from one part to another of any given section of the kiln tunnel 52 although there are predetermined differences of temperature be tween any two sections.

Batts are customarily made of materials that are matured to a strong condition at temperakiln furniturehave long been made of refractory fire clays. These give products of satisfactory expansivity characteristics but of relatively low strength and low heat conductivity. Silicon carbide as the main ingredient of batt mixtures gives improved products because in addition to low expansivity they have high strength and high heat conductivity. Likewise, batts composed of mullite which mullite may have been essentially originally of the electric furnace fused variety, or may have been developed by the maturing operation to which the batt was subjected in manufacture, have advantages over fire clay batts. Furthermore, refractory batts for very high temperature use may now be made as sintered or recrystallized products, often substantially bondless, many of which may be classed as pure oxide refractories. The refractory supports for ware according to this invention are preferably made of bonded silicon carbide but so far as the broader features of my invention are concerned they may be made of other refractory materials.

As an example of a bonded silicon carbide composition for batts according to the present invention, I may make a mixture according to the following formula:

Example Material: Parts by Weight No. 14 to No. 24 grit size silicon carbide 45 No. 30 to No. 90 grit size silicon carbide No. 100 grit size and finer silicon carbide-" 18 Ball clay 12 Dextrine powder 2 Rye flour 1 Water -i 4 Total 107 The silicon carbide is the ordinary black grade and is put into a mixing machine of conventional type and the dextrine is added. After mixing for a minute or two the water is added and mixing is continued for a minute or two more. Then the ball clay and rye flour are screened into the mix together and the mixing is continued for five minutes more. This procedure produces a damp granular mixture that is suitable for tamping or pressing. This mixture is then molded in molds shaped to produce the batts and baffles of the shapes shown, and then the green batts and bafiles are fired in a suitable kiln at a temperature substantially higher than the highest temperature which will be found in the kiln in which they will be used. For example, if the firing zone of the tunnel kiln herein described is heated to a temperature of 1250 0., the batts and bafiies should be fired to a top temperature of at least about 140 0 C.

It will thus be seen that there has been provided by this invention refractory supports for ware in a tunnel kiln in which the various objects hereinabove set forth together with many thoroughly practical advantages are successfully achieved. As many possible embodiments may 'be made of the above invention and as many changes might be made in the embodiment above set forth, it is to be understood that all matter hereinbefore set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

I claim:

1. A batt assembly comprising a pair of parallel rods, a plurality of rectangular batts with grooves on the undersides and having dovetailed edges in contiguous relation with the dovetails in engagement and with the grooves on the rods,

and a second plurality of rectangular batts positioned in contiguous relation transverse to and resting upon the first plurality of rectangular batts.

2. In a batt assembly as claimed in claim 1, the combination with the parts and features therein specified of a pair of baffles on said second plurality of batts.

3. An assembly of batts comprising a plurality of rectangular batts with dovetailed edges said batts being located in a plane with the dovetails in engagement, a second plurality of rectangular batts resting cross-ways upon said. first plurality of rectangular batts, and a pair of bafdes with concavely curved edges resting upon said second plurality of batts, the planes of the curves of the concavely curved edges of the baffles being parallel to the planes of both pluralities of batts and the baffles being located on the second plurality of batts so that the curved edges face each othzr.

4. In a batt assembly as claimed in claim 3, the combination with the parts and features therein specified of the further feature that each of said baffles consists of a plurality of separate parts.

5. A refractory support for ware in a tunnel kiln comprising two lines of rods said lines being parallel, a plurality of unit loads resting on said rods, each load consisting of a plurality of rectangular batts having grooves on the underside resting upon said rods with the rods being located in the grooves, dovetailed means in each edge of each batt which runs perpendicular to the lines of rods, all of the batts being in dovetailed engagement in a load and from load to load, and in each load an additional plurality of rectangular batts resting upon the first described batts said additional batts extending generally in the same direction as the rods.

6. In a refractory support for ware in a tunnel kiln as claimed in claim 5, the combination with the parts and features therein specified of a pair of baffles having concavely curved edges in each unit load the concavely curved edges of the baffles facing each other thus to provide an insulated space for a grinding wheel to be vitrified.

7. In a refractory support for ware in a tunnel kiln as claimed in claim 6, the combination with the parts and features therein specified of the additional feature that each baffle is in three parts.

GEORGE N. JEPPSON.

' REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 971,160 Vance -i Sept. 27, 1910 979,425 Butler Dec. 27, 1910 1,262,010 Brownlee Apr. 9, 1918 FOREIGN PATENTS Number Country Date 6,139 Great Britain 1914

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