US2515416A - Batt - Google Patents

Description

July 18, 1950 1.. H. MlLLlGA-N BATT 3 Sheets-Sheet 1 Filed May 22, 1948 0 WW W U w J l I i w 2 r 10 M ur nlUU IIKIIQ I- a b ii .-----\Hm---:::- w 2 u T My Lb 3 T 3 twp lmilhwmit w -m lvyiiltiki: x j v4, a f w w m U m w LOWELL H. MILLIGAN G 8 0 w 2 M WW 3 J V K a 0 0 m M 3 w 2 3 0g, TQ W July 18, 1950 H. MILLIGAN BATT 3 Sheets-Sheet 2 Filed May 22. 1948 58-4 amend/Co LOWELL. H. MILL/SAN Patented July 18, 1 950 STATES PATENT OFFICE BATT -LowellH. 'Milligan, Worcester, Mass, assignor to N ortozwOnmnany, 'Worcester, -Mass, at corporzw tion=-of .Massachusetts 'A'p'plicationlvlay 22, 1948, Serial'No."2 8',689

The invention relatestdbatts *for "use in kilns,

furnacesand the like.

one object 'of'the .inventionis to "providea refractory 'batt capable oi*"withstanding intense thermal'shock; Another object ofthe invention is to provide la'batt'lofi.thebharacterindicated which can be pushedthroughaliiln.havingzones of sharp rise and .drop 'in' temperature without fracturing. Another object of the invention .is to provide .a refractory .batt ...for use in a kiln provided with. sources otheatabove and. below the batt, the ware..being carriedon thebatt and the batt beingsupported solely at theends thereof. Another objectof the. invention is to provide a b'ttt .of the characterindicated oflong, life. Another object-.is to .provide a long lifebattof large size. .Another object is to provide longlife batts for building stands of ware-thatare to be heatedandcooled from the directions-of the edges of thebatts.

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

.The invention :accordinglyconsists; in the features of construction, combinations of elements and arrangements of partslalhaswill be .ill-ustratively describedherein and thescope of the application of which will beindicated -.in the following claims.

I In the accompanyingdrawingsillustrating one of "manypossible .embodiments of th ;'mechanical. features of .this invention,

l-Figure lzis a: top1'plamviewIof. a hatti constructed in accordance -"with the invention,

li'igure 2 is a bottom plan-lview of: thebatt,

FigureB is-an end view of-the batt,

Figure 4 is a sectional view through a=-tunnel kiln showing the batt -'with *ware= on it-therein, illustrating a use of "the "batt whieh markedlyimproves the operation of such1a*kiln,

Figure 5 is an end=view of 'a "bait illustrating another embodimentof "the invention.

-As-- conducive to a-ciearer-understanding of "the present invention; 'a" batt is a "plate -or other shape-toholtl'ceramic-"or nther ware during a :heat-ingoperaition: "Thus, for example, green ceramic-articles;such as-unfired molded spark plugs, dishes -or grinding "wheels "are placed on 'batts' whicharethemputintonrpassedthrough a kiln, and 'thespark plugs, grinding Wheei's'or 'dishes' are "fired, that is' to say, "vitrified. The batt is therefore necessarily a refractory article.

Many ceramicmanufacturers"have estimated the-cost "of hatts"'onthetotal cost of their product and inpracticallyall'casesithas'b'een foundth'at the cost".of"batts" isa large percentage of the cost'of manufacturing the ceramic" product which is'soid; ThiSlSISO because there is'not" merely a first cost "of thebatts butthe'costof continually replacing 'batts. A:batt"'is'icold when it is placed in 'a'kiln butibecornesheatedto 'the'firin'g temper ature or temperatures; usually "high; inithe Kiln, then it is allowed Lto" cool or may be rapidly cooled" by special'means such as blowing .air'ion it, andlate'r on, after becoming cold, .it is used again to support more green'jware and is'again heated, allowedtocool, and'soon. .Batt's do-iiot indefinitely surviveitliisalternateheatinglto high temperatures and coolingleven if the temperature gradients .are gentle. Eventually the batts break or crack and While a crackebllbattmaylbe used, it eventually. becomes a'broken batt and thereafter is 'useiulf if .at all only for smaller pieces of .warepand eventually, .at-t'er .furthei' cracking or'breaking, not.at'.all'.' The .for-egoing being true even when the slope of the tempera.- ture-time curve is very slight, it is all the more true and th'epercentage of the cost ofbatts-to the total costp'f 'manufacture of the product is much greater when theslope of the temperaturetime'cu-rve is steep.

For sometime past; tunnel-kilns have been replacing periodic-kilns -and in the tunnel kilns the slope orthe'temperature-time curve-isnteeper than in the periodic' kilnsrand''efiortsiiiavetcon- 1 tinual'ly"'been" made to'steepen'the'sl'opes of these curves" in orderto nbtaingreater production and in order "that the manufacturer may fill orders more promptly. A particular type .of ..tunnel kiln having a very steeptem'p'erature ti'me curve is illustrated in i cross-section in l igi'ire #4; in-' this kiln, :as willbe :more -'--eiear1y explained' hereinafter, the "batts -themsel ve's constitute'the slowly movable conve'yers for the ware; Thus a=batt atthe entranee-endera kiln" receivesthrus-t from a ram "or the -like "and 'pushes'the'batt ahead of it, whichpush'esthe battnextahead,

which pushes the batt next ahead and so on until we reach the batt emerging from the tunnel. To the disruptive forces of thermal shock is added mechanical strain tending to break such batts. Kilns of the type shown in Figure 4 have successfully made small articles such as small grinding wheels utilizing narrow batts but it is desired to vitrify larger l grindi'ng'wheels ,insuch kilns to do which calls for the use of wider batts. The use of such wider batts in kilns of the type indicated in Figure 4 has been found to result in such large increase of batt breakage as greatly to increase the proportion of cost of batts to the total cost of manufacturing the grinding wheels. Furthermore, utilizing plain batts in such kilns many batts have broken in the kiln thus clogging or jamming the kiln and necessitating a shut-down, which is expensive.

is continued for five minutes more. This pro cedure produces a damp granular mixture that is suitable for tamping or pressing.

Referring now to Figure 3, a batt according to this invention has a plane side Ill comprising as better shown in Figure l a plurality of plane rectangular portion ll separated by straight slots 12. As shown, the rectangles of the portions II are identical and thi is a preferred construction, but the rectangles of the end portions Ila are shown as narrower although here again they might be identical with the other rectangles.

The other side 13 of the batt is parallel to side Batts are customarily made of materials that I are matured to astrong condition at temperatures higher than those experienced by the batt in use. This gives a product having maximum stability in use against change in dimensions, etc. It is advantageous to employ materials of as low expansivity as feasible so as to reduce the amount of dimensional change and resulting stress as a function of temperature change. Batts and other kiln furniture have 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're'crystallized' products, often substantially bondless, many of which may be classed as pure oxide refractories. This invention, although described particularly for silicon carbide products, is also advantageous when embodied in batts composed 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 gritsize silicon car bide 45 No. to No. 90 grit sizesilicon car- I hide v n 2 5 No. 100 grit size and finer silicon carbide 18 Ball clay 12 Dextrine powder 2 Rye flour 1 Water 4 Total 107 The-silicon carbide is the ordinary black grade Then the ball clay, and rye flour are I I l which are straight and parallel to the slots 12 but are in staggered relation with them as clearly shown in Figure 3. The grooves l4 have nearly parallel side walls I5 and rounded bottoms lt; they merge by Way of rounded shoulders It with plane rectangular portions l3 which are like unto the portions II and of equal length therewith but not so wide. The grooves M are of a depth to extend beyond the level of the slots l2 or may be so, except that as shown the grooves Ma Which are outside or beyond the slots ii are of lesser depth. Between the grooves i4 and between the grooves Md. and merging with the slots 52 under them are bores 20, which may be cylindrical but might be of other shapes such as polygonal in cross section. These bores 20 are parallel to each other and to the grooves 14 and they extend through the entire width of the batts. This term width to save confusion is used in this specification to indicate the dimension along which the batts are propagated, and in Figures 1 and 2 this dimension is indicated as les than the dimension at right angles thereto which for convenience will be termed the length of the batts, but so far as the invention is concerned, the dimension in the direction of the bores 29 might be greater than the dimension of the batts parallel to the faces perpendicular to the bores 20.

The foregoing construction makes an accordion construction with the pleats in the direction of the thickness of the batts to permit expansion and contraction without breakage in the direction of the length of the batts. Furthermore, it will be seen thatthe face It has a total plane area very large in proportion to its total area by reason of the width of the portions 5 l as compared to the narrowness of the slots l2. Thi face 'or'side I0 is thus readily adapted to receive ware. On the other hand, the face or side I3 has a total plane area which is somewhat less than half of the total area of the face or side; this will ordinarily be the underside of the batt.

.So far as the use of the batt for the vitrifying of many kinds of ware is concerned and so far as the use of the batt in many types of kilns is concerned, in the direction of length the batt might terminate at the dotted lines '2! in Figure 3, these dotted lines representing plane rectangular edges of the batt. However, for the pre-.

ferred construction-of the batt for use in atunne1 kiln of the type indicated in Figure 4, I, preferably provide the following additional .portions and features,.it.beingv understood that all portions of thebatt are, preferably portions of ;one integral piece. v r l Thus I provide extension 25, 25 on the ends of the batt which are generally rectangular in plan view although they, may have truncated corners 26 and which are of a length in the. direction of the width of thebatts the same as the ermis "liflnis 2 extfior thereof shaii be relatively thin.

tl'ie l'lfiders'ide of the extensions 2 are Shal- Wide grooves 3 0. Furt ermore, l 'pief'el' ably provide sew-ove s; on one thicke'dgeof'fthe batt and a tongue 32 on the other thick edge of the Watt:

it errin ow to Figure 4. a tan as above as ribe'd is shown having' its egten'sieiis 25 ---eston refractory rods I00 laid in rooves of set-rectory supporting ns-em ers- I o'l' located the Blittbr'r'i or akilr'i tunnel I02. The" kiln- IM may be'for rned by a large rerracto y'bbttom in rely perpendicular" tome plane or the section" 4a At a certain locus in the tunnel I02 Between the entrance endand the exit end thereof are a: plurality of electrical resistor bars I II'IText'c'hdin'g' horizontally through the bricks I05 and f thereof of the tunnel, that is to say near "the refractory tunnel top I04. Likewise extendi iig'through the bricks I01 and through holes I I I in the members IOI' and close'to the bottom I03 aireelectrical resistor bars- II Z. The bars III) and II 2 preferably are recrystallized silicon carbide resistor rods; round in cross section and having cold ends H5. Sucl'rr'esistor bars or rods are now wellknownin the art, so I shall not further describe them.

. The rods I00 as well as the supporting members I 0I extend from end to end of the tunnel I02"; There are many of therods I00 and they are all parallel to each other andflsp'acedthe same distance apart-.- Their ends are preferably tapered so that the batts will ride from one to another without jolting. The batts maintain their position on the rods in the direction of the length of the batts which is the same as the Width of the tunnel because the extensions 25 are in contact with the rods I00 at the grooves 30. I

provide a long. line of batts touching each other for propagation through the tunnel I02 in the direction of the width of the batts as heretofore explained. When starting the kiln, the first batt is pushed in the tunnel I02 a ram or the like.

Thereafter at predetermined intervals of time additional batts, one by one, are pushed into the tunnel, each new batt engaging the last one of the series. 'Thus the batts constitute the sole conveying means in the tunnel I02 and it can be be seen that no metal parts are required in the tunnel.

Resting on a layer of silica sand II! or like comminuted refractory material on each batt is a grinding Wheel W or other article to be vitrifled. As this grinding wheel W proceeds through the tunnel I02, it is first gradually heated to the vitrifying temperature, maintained there for a certain period of time, and then gradually cooled. Each batt may carry an article to be vitrified or there may be a plurality of articles on some or all of the batts, depending upon the size of the articles and the requirements of production.

In a tunnel kiln such as herein briefly described, preheating was at the rate of about 17.5 C. per minute from a temperature of 200 C. to 900 C., then in the heating zone the temperature rise continued at the same rate to a temperature of about 1260 C. and was there maintained for about twenty-five minutes. Then, in the anneal- IUB and alarge refractory-top I00 sepa' ted on iii) mg zo'ne, the temperature dropped from 1260110 is C. inl'54 minutes. This-annealingfthen was at the rate of about 7.53 C'. pr"minute. Such temperature changes cause" thermal shock which an ordinary batt could not withstand. Initially only narrow batts supporting small wheels were used in such-a tunnel-kiln. Itwas desired, however, to verify larger Wheels such as the wheel W shown in Figure! the size of which will apparent when itis pointed out that the disti c'e between the centers ofthe' rods I00 was e and one-half m'ches. Batts' Wide enough-to such wneeisahd-o'r ordinary construeuen soon fractured. Batts accordin to the present invention as above described being 'ele've'nand one-quarter inches long and eight and one-half inches wide werefput in operation inthis kiln and'in over 100 heating cycles showed no signal cracking and ofcourse thereforeno fracture. These batts were introduced into the -kilnso that the tongue 32 onone'batt would enter the groove 3| on the adjacent batt. This was a matter of precaution so that two batts wouldh'ol'd a broken batt between them and although this precaution was found to be unnecessary during the testing, the feature is nevertheless advantageous because over a long. period of time extending perhaps into years a batt may break.

The reason why these batts are able to withstand thermal shock; which would break ordinary batts is because the thin walls between'the'grooves I4 and the bores 20 can flex somewhat when the batt is heated, thus relieving the strain'due to the fact that oneedge of the batt ishotter than the other edge. The actuallength-of the pro-heating zone was about 3 feet 10 inches and in this zone the temperature gradient totalled 700 0. So therefore in the pre-heating zone oneedge of the batt-was subjected toa temperature of about C. above the other edge of the batt. Thisis severe usage for any refractory article; In the annealing zone,- the total distance was about l5 feetand the temperature drop was 1160 C. and sothereforethe same batt 8-.5" wide'would be almost 55 hotter on the trailing edge than on the leading edge. When it is considered that these 'temperature differentials are maintained at a-wi cle; range of temperatures, the severity of the conditions will'be still further appreciated.

One advantage of the batt construction of the invention is that for a given thickness of batt the weight thereof ismuch less than it would be if the batt were solid. The batts must be handled when they are outside of a kiln and accordingly lightness is a desirable quality. Furthermore the greater the mass of the batts the more heat units will be taken out of the kiln thus wasting heat. This is another reason why a light weight batt is desired.

A modified form of batt is illustrated in Figure 5. This batt has a plane top face I20 and a plane bottom face I2I. The surface of the face I20 is interrupted by straight slots I22 which extend the full distance of the width of the batt. The surface I2I is interrupted by straight slots I23 which likewise extend the full distance of the width of the batt. Rounded rectangular bores I24 likewise extending the full distance of the length of the batt are located at the bottoms of the slots I22 and at the tops of the slots I23.

Slots I23 alternate with slots I22 as shown. This 4 edge view of Figure 5 is suiiiciently illustrative; the batt is rectangular in plan view except for truncated corners I25. This batt may have grooves I26 at the edges of the plane surface The batt of Figure is, resistant to thermal shock because the thin portions l2! and also the walls I28 can flex somewhat when heated and subjected to differential heating. The molding of a batt such as shown in Figure 5 may be done by apparatus and methods similar to those already described. Many other variations in shape may be made within the scope of thisinvention. In each embodiment of the invention herein illustrated the batt is in the form of a plate having surfaces, each surface being broken by par,- allel depressions (slots and bores or grooves) arranged alternately so that a depression from one surface is followed by a depression from the other surface which is followed by a depression from the first surface so arranged as to leave walls between the depressions whichare less in thickness than the overall thickness of the batt, so that when the batt is differentially heatedsaid.

, walls by flexure prevent fracture of the batt.

It will thus be seen that there has been provided by this invention batt constructions in which the various objects hereinabove set forth together with many thoroughly practical advantages are successfully achieved; As many .pos-

sible embodiments may be made of the. above invention and as many changes might be madein the embodiments above set forth, it is to be understood that all matter hereinbefore set forth are shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

I claim: 1

1. A batt for kilns, furnaces and the like comprising a piece of refractory material in the shape .of a plate having one side face with parallel grooves each groove having substantiallyparallel .side walls and a rounded bottom and, on-the other side slots in staggered relationto' said grooves but parallel to them and to each other, said slots extending into bores between the grooves, said bores being substantially cylindrical except for the slots, thus forming an accordion structure in the direction of thickness. v

2. A batt for kilns, furnaces and the like comprising a piece of refractory material in the shape of a plate having parallel slots'on each side and slots of the other side that ,is the slots on one side being betweenthaslots onthe other side and eachof the; slotsbeing parallel to alliofthe other slots.

3. A batt for kilns, furnaces and'tne like ingthe form of a plate having surfaces, each surface being-broken by parallel depressions arranged alternately so that a depression from one surface is followed by adepression from the other surface which-is followed by a depression from the first surface so arranged as to leavewalls between the depressions which are less in thickness, than the overall thickness of the batt, so that when the batt is difierentially heated said walls by flexure prevent fracture of the batt, I

4. A batt for kilns, furnaces and the like comprising a piece of refractory material in the shape of a plate havingone side face with parallel grooves and, on theother side slots in staggered relation to said grooves but parallel to them and to each other, said slots extending into bores be- 5. A batt for kilns, furnaces and the ,like in the form of a plate having opposite parallel surfaces, each surface being broken by parallel 'depressions arranged alternately so that a depression from one surface is followedby a depression from the other surface which is followed "by a depression from the first surface so arranged as to leave walls between the depressions which are less in thickness than the overall thickness of the batt, so that when the batt is differentially heated said Walls by fiexure prevent fracture of the batt, said depressions between the end depressions extending fromone surface of the batt at least half way to the opposite surface of the batt.

LOWELL H. MILLIGAN;

REFERENCES crrsn T he following'jreferenc'es are of record 'in the file of this patent: v PATENTS; v,

' UNITED STATES Number Name -Date 1,893,123 Beth Jan. 3,- 1933 v 2,246,443 T Mahan, Jr. June17, 1941 tween the grooves, said bores being substantially

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