US1807147A - Furnace - Google Patents

Description

May 26, 1931.

F. w. BROOKE FURNACE 2 Sheets-Sheet 1 Filed June 9. 1928 INVENTOR May 26, 1931. F. w. BROOKE FURNACE Filed June 9, 1928 2 Sheets-Sheet 2 Patented May 26, 1931 UNITED STATES PATENT- oFF cE FRANK W. BROOKE, OI PITTSBURGH, PENNSYLVANIA, ASSIGNOB TO WILLIAM SWIN- IDELL & BROTHERS, OI- PITTSBURGH, PENNSYLVANIA, A CORPORATION OF PENN- SYL'V'ANIA.

returner:

Application fled June s, 1928. Serial No. 284,065.

The present invention relates broadly to are especially adaptable for use in the ceramic industry. It will be understood, however, a

that the utility of the present invention is not limited with respect to the particular adaptation to which it is placed.

. In the art to which the present invention relates, it has heretofore been proposed to provide elongated tunnel kilns through which suitable carriers or conveyors for the Inaterial to be heated are adapted to travel in side by side relationship in opposite directions. With such a construct on, heating means are provided at desired points along the length of travel for the purpose of raising the temperature of'the material carried by the conveyors to the required point. With such an operation, the material which has previously been heated on each conveyor during its travel in opposite directions, imparts heat to the incoming material on the other conveyor, thereby preheating it. In order to obtain the most efficient operation, in view of the nature of the material being handled, and the preheating and heat transfer conditions involved, it is essential to maintain continuous operation of the kiln.

In actual practice, several difficulties with respect not only to continuous operation, but also with respect to uniform heating, have been encountered. The heating is customarily acomplished by means of a suitable resistance material placed within a refractory trough of high heat conducting material, such as silicon carbide. Under conditions of constant use, at the high temperatures involved, these heating units break down. Heretofore, so far as I am aware, it has been necessary to permit the entire furnace to drop to a workable temperature before the units could be repaired or removed. In many cases this results in t-ne loss of at least a large portion of the material within the furnace, as well as the loss of several days time.

The present invention provides an improved kiln furnace structure adapted to effeet more uniform heating of the material therein, and to permit the rapid renewal, repair, or substitution of heating elements without discontinuing the operation of the furnace.

. In accordance with one embodiment of my inventlon, there may be provided heating un1ts arranged in adjacent substantially parallel relationship, and so connected as to permlt simultaneous use of both of the units, or the independent use of either of the units in case'of break down of one of them. In this manner, it is possible to maintain the kiln at a working temperature even in case of fail- 'ure of one or more of the heating units. Pro- 6i vision also may be made for adjusting the units either vertically or horizontally so as to obtain exactly the heat distribution and heat location desired for the most eflicient results.

In the operation of kilns of the general nature herein contemplated, difiiculties are alsoencountered due to the tendency of the coatlng or coloring glazes to sublime or vaporize, the vapor frequently traveling to a relatively cooler part of the kiln where it condenses and drops onto the ware, thereby spoiling certain arts of it. In accordance with the present invention, provision is preferably made for effecting condensation of any such vapors at predetermined definite points, so located with respect to the ware as to insure dropping of any condensed vapor at a point intermediate successive charges.

In the accompanying drawings, I have shown for purposes of illustration only, a preferred embodiment of the present invention, it being understood that the drawings are largely diagrammatic for purposes of 11- lustrating the present invention, and not limiting the same. It will be understood that changes in the construction and arrangement of the parts and in the operation herein disclosed may be made without departing either from the spirit of my invention or the scope of my broader claims.

In the drawings Figure 1 is a vertical transverse sectional view through a furnace or kilnstructure, in accordance with the present invention;

t, Figure 2 is a horizontal longitudinal sectional view, partly broken away, illustrating the furnace orrkiln construction and the manner of operating the same lustrating another form of heating unit; and Figure 7 is a partial transverse sectional ture of Figure 1, illustrating the relationship between the center heating unit and the seal;

Figure 5 is a longitudinal sectional view through a modified form of heating unit;

Figure 5 is a transverse sectional view, on

an enlarged scale, through a heating unit as shown in Figure ,5, modifie'd by the addition of heat radiating means thereon;

Figure 6 is aview similar to Figure 5, il-

I view, similar to Figure 1, illustrating another embodiment of the invention.

In carrying out the present invention, there may be provided a kiln 2, of thetunnel type, of suitable length and construction, for the purposes intended, the invention not being limited with respect to the construction or manner of'use thereof.

Extending lengthwise of the furnace in substantially parallel relationship, are tracks 3 and 4, upon which are adapted to travel earriers or conveyors 5 and 6 respectively. As illustrated inFigure 2 of the drawings, the carriers 5 may move in the direction indicated by the arrow A, while the carriers 6 maytravel in the direction indicated by the arrow B. Eachof the carriers may be loaded at any desired point exteriorly of the furnace so as to permit them to travel fully charged throughout the entire length of the kiln.

At a point, or points, intermediate the ends of the kiln, there is provided a heating zone or. zones, in which the material M on the carriers is brought to the desired temperature.

In Figure ,2 of the drawings there is illustrated one heating zone only, this'heating zone comprising laterall offset heating chambers 7, on opposite si esof the kiln, each heating chamber being provided with a heating unit8. The dimensions of each of the heating chambers are preferably such as to constitute a relatively confined heating s ace for each unit, the width W of each 0 amber being such, with respect to the width w of each heating unit, as to make it possible to effect bodily endwise movement of either of the heating units 8, as indicated in dotted linesin Figure 2, it being understood that theend walls 9 of the heating chambers may be provided with openings temporarily luted or closed, of suchdiameter as to mit endwise movement of the character reper-- ment, the contacts 10 for the'heating units extend substantially in longitudinal, axial .alignment with the units so that they do not afford any obstruction to free endwise movement. V e As illustrated more particularly-in Figure 1, each of the heating units 8 may comprise a trough of suitable material, such as silicon [carbide having a high heattransfer coefii- 'cient, the troughs being filled with a suitable resistance materialzR, protected by a cover 11. The improved furnace or kiln structure herein illustrated also provides means for effecting a more uniform heating of the lmaterial on the carriers.

This is obtained by an intermediate heat ing unit 12, of a construction generally similar to that of the units 8." The unit 12, however, i 'preferably carried'on the upper end of a ram 13, adapted to be raised or lowered by the'admission of fluid under pressure to 7 one end or the other of a cylinder 14.

For efi'ecting the desired sealing of the carriers, they may be provided on opposite sides thereof with downwardly projecting knife edges 15, with the two outside knife edges cooperating with troughs 16, in which are placed a pulverant sealing material. The

innermost knife edges cooperate with troughs 17, formed on opposite sides of the ram 13,

thereby permitting the ram to be 'bodily' raised or lowered regardless of the presence or absence of carriers within the furnace,

and regardless of whether-such carriers are moving or stationary, the movement ofthe center unit into position effecting the desired sealing automatically.

The 12 may be provided with flexible electricleads 18, as indicated in Figure 3 of the drawin s, thereby permitting the center unit to be odily raised or lowered at any time during the operation of the furnace.

Considerable difficultyhas. heretofore been experienced in efiectingan eflicient connection for heating units of the general character referred to, and for preventing oxidation of the parts thereof under the temperature'conditions to which they are subjected. In accordance with the present invention, I may provide terminal blocks 19 for each of the heating units, which blocks may beof gra hite or other suitable material, and provided with angularly arranged, threaded openings 20'and 21 for the reception of the conductors 22 and terminals 23 respectively. In order to prevent the free access of air to these parts, the trough and the cover may be extended to embrace and substantially and thereby shield the same.

At one, or both sides, of the ram, there may be provided a suitable arrangement of fans 24, adapted to direct blasts of cooling air onto the center unit when lowered, not only for the purpose of cooling the same, but for enclose these parts,

the purpose of enabling workmen to perform the necessary re air operations thereon, or

bodily removal 0 the same to substitute a new unit. "By the substitution, or rapid repair, of such a unit, it will be apparent that it is ossible to quickly elevate the same into p ace without interrupting the continuity of the furnace operation, and without permitting moval of the center unit, or the making of the necessary repairs thereon.

All of the material within the zone defined by the. heating units is raised to a substantially uniform temperature and thereafter travels onwardly in opposite directions from this heating zone in such manner that the previously heated material on the carriers 5 serves to preheat the incoming material on the carriers 6, while the previously heated material on the carriers. 6 likewise serves to preheat the incoming material on the carriers 5. I

I have found that by the provision of a center heating unit of the character herein illustrated, it is possible to maintain the two lines of carriers in such closely adjacent relationship as not to interfere with the desired heat interchange between previously heated material and the incoming raw material. Such a center heating unit also enables the width of the carriers to be materially increased without interfering with the proper heat treatment of thematerial carried thereby. This, as will be apparent, materially increases the capacity and economy of operation of the total installation. The economy is further increased by the use of removable heating units permitting the same to be almost immediately repaired or renewed, as may be required.

Under the temperature conditions to which the ceramic material is raised, the glaze or coating, particularly where it comprises a lead compound, is caused to sublime, the resulting vapors traveling to cooler portions of the kiln wherein they condense, the condensate dropping indiscriminately at diiferent points throughout the length of the kiln. In accordance with the present invention, there may be provided on opposite sides of each heating zone, regardless of the number of zones, a definite condensation zone. In Figure 2 of the drawings these condensation zones are designated C and C, respectively. In.

Figure 2 there is illustrated one form of kiln construction effective for providing definitely located zones of this nature. Such a construction embodies a battle 25, formed on the roof of the kiln, as indicated in Figure 1, and preferabl provided with downwardly converging si( e walls terminating in a. relatively sharp condensate collecting edge 26.

This edge is so located with respect to the length of the individual carriers and/or the disposition of ware thereon, as to cause any condensate to drip downwardly between succcssive charges, as illustrated diagrammatically in Figure 2'. In this manner, the possibility of damage to the material is correspondlngly reduced. IVhile such a construction does not preclude the possibility of droppingsome of the condensate on the ware while the carriers are moving, the moving period under ordinary operation comprises only about two (2%) per cent. of the total time, it thus being obvious that the chances of damage of the character herein contemplated are materially reduced.

If desired, artificial cooling means 27 may be provided for cooperation with each of the condensation baffles in order to produce such a marked change in temperature as to insure the condensation of vapors at the desired points and preclude the passage of any sub stantial quantity of uncondensed vapors to other arts of the kiln.

In igure 5 there is illustrated a slightly modified form of heating unit adapted to replace the heating units heretofore described. Such a unit may comprise an outer shell or shield 28, preferably of substantially cylindrical shape, of silicon carbide or other hi h heat conducting material. Mounted in t e opposite ends of this shield are terminal blocks 29, of graphite or similar material, threaded at one end for the reception of terminals 30 and at the opposite end for cooperation with current carrying conductors 31. These conductors are preferably formed in relatively short lengths and are connected at their inner ends by supplemental blocks 32 threaded to provide the desired support and electrical connection therewith.

By making the blocks 29 and 32 of relatively larger cross-sectional area than that of' the conductors 31, they are kept at a relatively lower temperature, and thereby the tendency toward oxidation and deterioration is minimized. In order to operatively support the blocks 29 and 32, and also electrically insulate them from the shield 28, there may be provided spacing rings 33 for each of these blocks, such rings preferably comprising a material of refractory nature such as fire clay, or the like.

As illustrated in Figure 5, the shield 28', corresponding to the shield 28, may be provided with any desired number or arrangementlof radiatin fins 34 forincreasing the dispersion rate heat therefrom.

In Fi e 6'there is illustrated another embodi ent of the invention in .which con duct s 31f project into opposite ends of a shield through fire clay or other non-conducting refractory rings 33. The conductors are normally urged inwardly into conducting relationship with the center block 32', by means of springs or. the like 35, Working against suitable abutments 36. This constructlon has the advantage of permitting ,a quicker replacement of'any of the units should occasion require. \s; I

The heating units illustrated in Figures 5- and 6 constitute avery decided advance,;ob-

it viating difiiculties heretofore encountered commercially. Heretofore, the high resistances neoessltated have required constant reduction inthe cross-sectional areas of the resistanceunits, thereby weakening the same to such an extent that they have frequently.

. mediate joint or joints constituting a comare utilized, they will preferably be of the bined tie and support, give the desired re: sults with respect to current carrying ability so that the unit has substantially perfect heat uniformity throughout the. entire length.

It will be apparent that the number of intermediate joints or supports may be increased at will. p

The structure also takes care of excessive oxidation due to the fact that the initial oxygen contained'in the shield isimmediately changed to carbon monoxide and further oxidation thereby eliminated. In any particular case if excessive infiltration of air should develop, it may be counteracted by trickling into the tube or shield 28 a stream of inert or reducing. atmosphere.

In the form of the invention illustrated in Figures land 2, there is shown a combined shield and distributing means in the form of a baflle wall S, located between the side heating units and the tunnel portion of the kiln. Such baflies are rendered unnecessary by the use of heating means of the character il-.

lustrated in Figures 5 and 6, in which the shields effectively operate in substantially the same manner. Where the baflie walls S serrated or corrugated construction generally illustrated in Figure 2 in order to obtain, by virtue of the larger surface, greater heat absorption and heat emission properties.

In somecases I have found itadvantageous to provide duplicate heating units at both sides of thekiln and in the center thereof, as indicated in Figure 7 wherein there are shown units 37 in su erimposed relationship. Theseunits are pre erably connected in parallel with respect to the by either unit may be with the-operation of the furnace. The necessary changes in connections to permit the removal of one unit could be made, as well understood in the art, by means of a suitable'series-parallel switch, or its equiva lent. A construction of this character inpower supply, whereremoved at Wlll inde- P nfly f the other without interfering sures the provision of at least one heating unit at all times effective for supplying heat to the material and enables the kiln operation to be carried on regardlessof the failure of one unit. a y

A series-parallel arrangementof the general character referred to has also been found to be of advantage in obtaining a slower initial heating with aconsequent minimizing of the possibility of cracking and breaking. For example, if a furnace orkiln is started up cold, the units may be placed in series and later'switched over to parallel. With two unitsin series, they will obviously develop onlyone-fourth as much heat as will be de-:

veloped when in parallel, whilewith three units in series, the heat developed will only be one-ninth of what it will be with three in" parallel. Asmall rate of heat input during the starting will slowly" cure the tubes and units, and decrease the possibility of damage thereto. y

I The construction of the heating chambers 7 will also referably be such as to pennitthe heating units, particularly when of the construction illustrated in Figures 5 and 6, to be adjusted vertically or laterally with re-. spect to the material in the kiln whereby the y Y desired heating and heat distribution may be obtained in order to tory results.

I claim a 1. In a continuous, direct, electric resistance heating furnace, a plurality of material conveying means arranged in substantially parallel horizontally extending paths, a sup-" port mounted between the pathsand extending through the bottom of the furnace, an electric resistance heating unit mounted on the support, and means for lowering the support with the heating unit thereon clear of said material conveying means to a point without the furnace.

2. In a continuous,'direct, electric resist-y ance heating furnace, a plurality of material conveying means arranged in substantially parallel horizontally extending paths and extending through the bottom of the furnace, a' support between the paths, means for preventing loss of heat from the furnace between the conveying means and the aforesaid support, an electric resistance heating unit give the most satisfao.

removably mounted on the support, and means for lowering the support and the heating means thereon clear of said material conveying means to a point without the furnace.

3. In a continuous, direct, electric resistance heating furnace, a plurality of material conveying means arranged in substantially parallel horizontally extending paths, said conveying means being provided with means.

for moving them in opposite directions through the furnace, angles attached to the material conveying means, a support mount ed between the paths, means attached to the support cooperating with the aforesaid angles for effecting sealing of the heating chamber, an electric resistance heating unit removably mounted on the support, and means for lowering the support with the heating unit thereon clear of the material conveying means and the an le attached thereto to a point without the urnace.

4. In a continuous, direct, electric resistance heatingfurnace, a plurality of material conveying means arranged in substantially parallel horizontally extendin paths, a support mounted between the pat s and extending through the bottom of the furnace, a substantial rigid intermediate electric resistance heating unit mounted on the support, means for lowering the support and the heating unit thereon clear of said material conveying means to a point without the furnace, and

' electric resistance heating units located along the outside edges of the aforesaid paths, said last mentioned heating units being mounted for easy removal from the furnace, whereb the furnace may be continued in'operation during the period of removal of the intermediate heating unit.

5. In a continuous, direct, electric resistance heating furnace, a plurality of material conveying means arranged in substantially parallel horizontally extendin paths, a su port mounted between the pat 1s and exten ing through the bottom of the furnace, an electric resistance heating unit mounted on the support, means for lowering the support and the heating unit thereon clear of the material conveying means to a point without the furnace, and heating units and bafile plates located along the outside edges of the aforesaid paths whereby the furnace may be continued in operation during the period of rem-oval of the first mentioned heating unit.

6. In a continuous, direct, electric resist ance heating furnace, a plurality of material conveying means arranged'in substantially parallel horizontally extending paths, a heating unit mounted between the paths and extending through the bottom of the furnace, heating units located in laterally offset portions of the furnace and adjacent the outside edges of said paths and individual means for removing each heating unit from my hand.

FRANK W. BROOKE.

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