US2281184A - Apparatus for partially drying moist clay bodies - Google Patents

Description

p 2 1942- I 1.. J. DYKSTRA AL 2,281,184

APPARATUS FOR PARTIALLY DRYING MOIST CLAY BODIES Filed Nov. 5, 1940 2 Sheets-Sheet l INVENTORS. Jaarence JZykEZTw 270M Me e7" @4927- Aieavrn P 1942- L. J. DYKSTRA ETAL. I 2,281,184

APPARATUS FOR PARTIALLY DRYING MOIST CLAY BODIES Filed Nov. 5. 1940 2 Sheets-Sheet 2 laurenc JZyksZ a B Mger Patented Apr. 28, 1942 UNITED. STATES [PATENT OFFICE a APPARATUS FOR PARTIALLY DRYING MOIST CLAY BODIES Laurence J. Dykstra and Edwin M. Meyer, Rochester, N. assignors to Victor Insulators, Inc., Victor, N..Y., a corporation of New York Application November 5, 1940, Serial No. 364,438

' f j 1 Claim. (Cl- 3 4 zss) This invention relates to an apparatus for parmove the surface moisture always at a rate ometially drying moist clay bodies, with more par ticular reference to the treatment of thick clay pugs after they come from a pugmill during the ,manufacture of porcelain insulators or the green 5 clay insulator bodies after they have been'turned or otherwise shaped, previously to firing in a kiln, and it has for its purpose to afford an apparatus by which the necessary moisture-removing operation can be carried on successfully and eflicientlyln a much shorter period of 'time than is possible with the apparatus now in use and without the losses attendant upon conventional practices, due to cracking of the insulator surfaces or complete breakage when subjected to heat of the i6 kiln.

The common method of drying clay bodies in' the insulator industry is to place the clay pieces I in a room where they-are subjected to currents clay body by meansof radiant energy, preferably of hot air that are first passed over steam coils, infra-red heat; and to remove such surface moisa procedure that requires a week or more to reture continually by meansprefe'rably in theform move the amount of moisture that must be taken of a relatively cold current of air acting in oppoout before the clay is ready for'the kiln treatsition to the radiant energy,-andcorrelated with ment. According to this old method, it is neces- I the heat applying means in such fashion as to insary to apply heat very slowly and to control humidity accurately in orderto prevent forming a crust at the surface of theclay and-consequent excessive shrinking and cracking, or complete breakage when subjected to the heat of a-kiln, and it is a particular purpose ofthis invention ac to remove moisture from a clay bodyin-such a manner that there is no likelihood of cracking the surface, or bursting the claybody upon application of the intense heat of the kiln, and to' bring about the required drying in'from six to as seven hours, or little more than one-fourth of a day as compared with a week or more under the general practices heretofore followed.

The difliculty with drying a moist clay body by means of hot air or heat convection currents is 4 that when applied in this manner, the heat is driven from the outside or surface of the clay body inwardly to its interior by the air currents ranged at the top and on opposite sides of the air and consequently the surface of the clay is likely 'duct and also at opposite sides of the housing, to reach a higher temperature than the interior 45 preferably open at both ends to permit moveand removal of moisture takes place at a faster -ment of air outwardly from the housing, andconrate than it migrates from the interior to the sur- 'taining radiant face. As a result, crusting of the surface takes form of infra-red electric heaters, or otherwise, place, causing excessive shrinking of the outer which act to direct radiant energy into the housstrata and cracking, or explosion of 'the'clay ing and upon the clay bodies which are thereby body when it is subjected to kiln treatment, and uniformly heated throughout, causing the moisthe present invention overcomes this difficulty by ture within each clay mass to migrate to its surusi y r nt ene y, preferably in the form face, the cool air passing to the clay bodies before o infrad heal? rays, to Cause migration of the coming into contact with the heat units and being moisture from the interior of the clay body to its exhausted from the housing around the heat surface, and simultaneously vremoving u c units through the chambers in which they are moisture y a current ofair at a temper t r contained and thus acting in opposition to the that is somewhat lower than the temperature heat units. I

of theclay body produced by the radiant energy, To these and other ends, the invention conthe air current acting merelyto evaporate or re-' 6 sists in the apparatus that will appear clearly the interior of the clay body to the surface and without raising the temperature of the clay, thus effectively preventing the'formation of a surface crust and insuring the maintenance of a uniform ing the drying operation. I

By applying radiant energy, it possible to heat a clay mass of considerable thickness to a uniform temperature throughout both the interior and surface portions, but unless facilities surface, such a system of drying is limited in time bythe natural process of evaporation which is much too slow for practical purposes, and it is an object of the invention to cause migration of maximum speed but always at a rate somewhat slower than that at which the-moisture'migrates to the surface of the clay, so that a uniform moisture contentis retained throughout the clay body both at the surface as well as at the interior, and there is no danger of the surface reaching a higher temperature than the interior, or otherwise causing a crusting, or excessive shrinking, or hardening at the surface.

The invention has for another object to afford a structure which in general includes a housing in a suitable conveyor, coupled with an air duct arranged to direct a current of relatively cool air downwardly into the housing and around the clay bodies, in conjunction with chambers arwhat slower than that at which it migrates from moisture content throughout the clay mass dur are provided'for removing the moisturefrom the moisture from the interior to the surface 01' a sure removal of moisture from the surface at a in which clay bodies are positionable, or movable preferably located at the top of the housing, and

energy units preferably in the from the following description, when read in conjunction with the accompanying drawings, the

. novel featuresibeing pointed out 'in the claims at the end of the specification. g

trated inFig. 5.

Referring more particularly to the drawings sectional view; v

ber ofair ductsan'd presently, the 'lez ji'gthof *apparatus'of given length with a certain'nuniheating units to be; described the'machine may be increased to anydesi'ed extentby the used additional air ducts 'andheating units arranged similarly'to thosenowfto: be described.

The. general practice heretofore :in drying clay bodies of this character has-been to place them .in a room where theyare subjected to currents of airheated'by'isteam coils or similar units and '-='contr'olled' humidity, it being essential not to evaporate moisture from the surface faster than glthe moisture travels from :the interior of the clay .;body to the surface, because otherwise the sur- I 15. Fig. 6 is a bottom plan view of the partsillusface becomesdryand'formsa crust, which results u1timately incracking the surface, or bursting the insulator when it issubjected to heat -=treatment=in thekiln, To prevent this underithe in which like reference numerals refer :to .the

same parts throughout the several views, and in which there is illus'tratedan example of-one practical embodiment of'the invention; the apparatus'includes a housingmounted upon a framework including uprights I and cross barsl carried by the uprights, bottom wall 3, side walls 4, and atop wallS, and being fopen at both ends, The housing just describedafiords a tunnel to receive-the 'clay bodies and through which travel the endless "conveyors 6 in the formof chains or the like to permit :'con-- venient positioning of the clay bodies within 1 the housing, gMountedupon the endless conveyors are plates 1 that" are preferably perforatedto permit free-passage of air therethroughywhile t designates net-like supports preferably in the form of inatsof wire net that are positioned. upon the plates. 1 by the operator feeding the machine, and which are adapted' to receive and-support. a

the housing including 1 a conventional adryingxprocess just referred to, 'it ,isnecessary to proceed quite slowly, and the drying operation requires approximately one hundred 'andwsixtyfeight hoursor longer to remove the necesary-iamountrof *moisturedna manner "that will leavefthejclay in proper condition for "firing.

A'primary objective of the/present invention is toreduce the jtiinerequired for removing moisture from suchlclaybodies and to reduce the percentage-of ids resulting fromimproper drying operationsgand 1 this is accomplished by employing radiant energy, preferably in the form --of .energy*fromj a radiant heater, resulting in :uiiiformly raisingQthetemperature of each clay body throughoutdts entire ,mass,-without the .instrumentality'fof, convection or air currents,

thus causing a. continuous migration of moisture from the interior 'of each :clay body to its surclay pug 9 after it comes from thepugniill, or

a clay'insulator or other object after -it'has beenturned or shaped, when it is desirable" to extract v .7 mg over.andzentirely-around the clay-bodies and -thence towardjand around the heating units in moisture from the :clay, "preparatory -to heat treatment .in akiln. 1'

In the manufacture of porcelaininsulators and similar products, the pugs when they come from a pugmill containabout 22%;moisture, and itis necessaryto remove about 18% moisture-before glazing and firing the article, approximately 4% of the moisture being left in the clay when it'is placedin the kiln. For finishing or shapingtheclay while green, as by turning or cutting grooves, skirts, or other curved or irregular surfacespit is necessary to remove only about 4% of the original moisture. leaving approximately 18% to permit handling and shaping the green clay, while after the turning, cutting or other shaping operations are completed, the clay article is" again subjected to treatment in the drier for removing an additional 14% moisture, permitting approximately 4% 'to-remain asstated above when the clay is placed in the kiln.

The endless conveyors are operated by any suitable mechanism, not shown, andmovedintermittently by automatic mechanism, or at the control of the operator. mats 8 are placed upon the conveyor plates"! and the pugs 9 or other clay bodies positioned upon the mats 8 at the feeding end of them'achine by an operator and similarly removed-at-the discharge end of the machine after completion of the moisture removal operationjthetiming 'of the movement of the conveyors being preferably such as to retain a given clay body within the housing for a desired length "of time. It'will be understood that while this applicationshows an" The-wire net supporting,

face. "l'he'surfac'e moisture is =continuously re-- :moved by means of a current of air that is relatively cool," or; atja somewhat lower temperature than'that' of the clay body, the cool air travela "direction generally opposed to the heat rays.

, "The cool-air currents 1 thus act in opposition to the beam of radiantrenergy; or the heat-rays and ,lfunction\only tofremove the surface moisture from the clay'i'without raising the temperature of the surface'of the clay and without any tendency .to cause a'crusting of thesurface by remov- 1ng moisture faster than it migrates from the interior to the surface.

This is attained by a series of radiant heating units located in chambers ll disposed at the top 'of'the housington opposite sides of the airduct to'be described-presently; The chambers H are preferably inclined in opposite directions as shown, and communicate with the housing at their w inner ends while preferably though not necessarily open at theirouter ends, while 12 designates similar chambers located at opposite sides ofthe housing, communicating attheir inner ends'with the housing and preferably though not necessarily open at their'outer ends.

These chambers may be arranged at suitable intervalsalong the housing, the chambers II at the top being' staggered with reference to the chambers II, as showndnFig. 1, and suitably spaced'from each other endwise oi the housin -each chamber beingprovided with a heatin unit II preferablyconsisting of an infra-red electric heater employing a carborundum resistor or Globar element; to which current is supplied inany suitableifashion. *It has been ascertained that the energy from the infra-red region of the surfaces, the necessary qualification being that the energy is transmitted in such a manner as a to elevate the temperature of the clay and to maintain a substantially uniform degree of moisture throughout'each clay body to insure maintaining a temperature at the interior of the clay body as high as the temperature at its surface. By this means, it is possible to insure continuous and uninterrupted migration of moisture to the surface and to prevent efifectually any crusting or excessive drying at the surface.

Each heating unit l3, consisting of'an infrared carborundum resistor heater, as described above, is suitably supported upon an adjustable standard H, see Fig. 6, which is mounted in the opposite walls l5 and I6 of the chamber and slidably adjustable in slots I! so that each heat-' ing unit, which is preferably provided with a suitable reflector, can be adjusted endwise of its chamber closer to or further away from the housing, and also tilted to vary the general direction of travel of its rays with relation to the clay bodies within the housing.

With this arrangement, radiant-heat, is directed on to the clay bodies from both sides and from thetop, and in order to remove the moisture from the surface of the clay bodies, air ducts I8 are provided arranged centrally of the top of the housing and extending endwise thereof with tapering reduced ends [9, as shown, while 20 designates fans or blowers operated by any convenient means, one located at the top of each a A perature of the clay bodies 'of 30 0., it has been possible to remove 1% moisture during each twenty-two minute period, or a total of 18% moisture in approximately si and three-quarter hours without cracking the s rfacelof the clay, or destroying the-insulator when fired. The

partial drying of the green clay for turning, cutting or otherwise shaping the article has been completed in one and one-half hours, and the complete drying operation in an additional five and one-quarter hours, as compared with a total of one hundred and sixty-eight hours for complete drying with hot air currents passing over steam coils and with controlled humidity. The drying time has been reduced from one hundred and sixty-eight to eight hours, with an attendant reduction of insulator losses, due to cracking the surface of or bursting the clay bodies upon firing, from 3.9% under the hot air drying system to .9% with the present system of radiant energy and relatively cool air currents acting in opposition to the radiant energy and functioning only to remove the moisture'from the surfaces.

of the clay.

'Iihe results described are due to the combining he manner set forth of the two factors of fradiant energy and relatively cool air, or air at "room temperature, which contacts the clay bodmoisture, there is no gain in the drying time over duct and acting to force air downwardly through the duct into the housing. The air that is thus forced into the housing may be taken into the air duct I8 at the top thereoffrom the room in which the apparatus is located at normal room temperature of from 65 F. 'to' 70F. and without any control of humidity, although the temperature ofthe air may be somewhat higher or lower than that stated, so long-as the air enters the housing at a temperature considerably less than the temperature induced in the clay bodies by the radiant-heat units. .Thus no heat is carried to the clayby convection and the air currents cannot remove moisture from the surface of the clay at a faster rate than it collects uponthe surface or migrates from the interior.

The air traveling downwardly through the ducts l8 spreads out within the-housing, contacting substantially the entire surfaces of the clay bodies uniformly, and travels thence out wardly from the housing through the respective chambers II and I2 and through the open ends of the housing. The air which makes an exit through the chambers H and I2 thus contacts the clay bodies before coming in contact with the heating units, thus acting in opposition to the latter, and the air as it enters the housing may be at any desired temperature below that of the clay bodies, provided it is not sufficiently low as to reduce materially the temperature of the carborundum elements of the heating units and lessen the heating eifect of the latter.

With an apparatus operating as indicated above, maintaining an ambient temperature within the housing or tunnel of 51 C. and a temreference to the existing methods and such procedure is too slow for practical purposes, while on the other hand, if the air currents are used without radiant energy to raise the temperature of the clay uniformly throughout, moisture is removed from the surface so much faster-than it migrates from the interior of the clay that the surface portion forms into a relatively hard dry crust, leaving an excess of moisture in the interior to cause bursting of the body upon 'firing, or cracking, and rendering the insulator unfit for practical purposes.

While the invention has been described with particular construction shown, it is not confined to the details or exact procedure set forth, and this .application is intended to cover any modifications or departures in the structure that may come within the purposes of the invention and the scope of the following claim.

We claim: I

Apparatus for partially drying moist clay bodies comprising a housing, a conveyor movable through said housing, a net-like support for the clay bodies whereby air has access around substantially the entire surfaces thereof, an air duct located centrally above the housing and in communication therewith, a blower acting to force air through said duct into the housing, chambers located above the housing on opposite sides of said duct, chambers located on opposite sides of the housing, said chambers having their-inner open at their outer ends, and radiant-heat units located in the chambers, the air being movable around the clay bodies and thence outwardly through said chambers in a direction opposite to the rays from the heat units.

LAURENCE J. DYKSTRA. EDWIN M. MEYER.

Images