US2547833A - Drying method and machine - Google Patents

Description

April 3, 1951 R. c. PARKE's ETAL L 2,547,833

DRYING METHOD AND MACHINE Filed Jan. 28, 194? 4 Sheets-Sheet 1 m g F:

INVENTOR.

RAL H C. PAEKEfi DAVlD H. Gomez 4 Sheecs-Sheet 2 R. c. PARKES ETAL DRYING METHOD AND MACHINE April 3; 1951 Filed Jan. 28, 1947 INVENTOR. RALPH C. FARKES BY :DAIYD H-.COL\ EE 6 A-rToBA/EY.

April 3, 1951* R. c. PARKES ETAL 2,547,833

DRYING METHOD AND MACHINE Filed Jan. 28, 1947 I 4 Sheets-Sheet 3 fl h il INVENTOR. Q, EAL A FHI KE BY IDAWD H. CoLKEE ATToEA/EY April 3,1951 R. c. PARKEs ETAL DRYING METHOD AND MACHINE 4 Sheets-$heet 4 Filed Jan. 28, 1947 lllll l'll'lillll 5 E v 2% M VP T g ww m h v a mm mm Patented Apr. 3, 1951 UNITED STATES, ATENT GFF-ITCE" Ralph G.Parkes,- Glen side; and DavidHQ- Colken, Philadelphia, Pa

A'pp'licationfianuary 28,1947, Serial No. 724,903

This inventioni'relatesto machine insw hich, and .to a' m'ethod offdryinghy which, the drying potential of the drying medium and the contact of the. drying medium With the 4 i-Claims. (Cl.- 34 -33) a: drying rnethodzand materials orobjects: to be: dried may beaccuratelyii" 5 enumerated.

It tispof course, appreciated that each class 0E1 objects presentsminor problems peculiar to: it, but -it is I believed that v the accurate: control and adjustment of the drying; potential, as Well as its distribution according: to the nature, .size, I shape and drying characteristicsiofthe objects 'toai'zw 'be dried, are fundamental to, andunderlie, the "drying of most, if not all, kinds of objects or materials.- Therefore,-whi1e the invention is applicable to the drying. of all kincisioftimaterials and objects, it is especially valuable for therdrying of. ceramics 'and other.- synthetic'zonnatural obj ects and materials Where? the rate; at which theobje'cts or materialsrare driedza'nd where the uniform drying; ofv variousparts of such objects and materialsiarercritical. 1

Taking ceramics-s as a representative example,

it is. noted that the'rdrying-t of this class of ob-' jects, prior to:firing,i.presentsi exceptional difiiculties. This isdue tathesfact that a wetceramic or other: objectcontains :shrinkage water (which is in the: nature of afilm of waterdisposed .be-

' tween the grains of'whichthe object is formed,

and the removal of which causes the ,objectto shrink), and pore water (which-is in the nature of'moisturel carried in the pores of the grains; .-:and which remains in thei'body ofthefceramic object Lafter perceptible shrinkage has ceased but before the drying operation'has been completed).

Asa ceramic or other object is dried, evaporation first takes place at the surface thereof, and, the'removalof shrinkage water-causes the grains "in the, exterior layer to-come1 closer together, thus: shrinking, the exterior. of the obj ect.- Obviously, if thedryin'g, and consequent shrinking of the exterior-of theobject israpid enough, rela-.--- tive to theld-rying and, corresponding shrinking v of ttheinteriorflthereof; visible "ori'invisible cracks may result, .or deleterious:strainszmam be setwup -.withintthebody"ofrtherobjectl Also, wherrimdrying iia ceramic:;obj'ect,a.therexv 2LT. terior of the object is driedtrapidly relative to the drying of \thercenter thereof and the grains of the. exterior: layer rnovev close together, the capillary network'within the interior of the object' v is interrupted. I This makes-the center-tosurface diffusion; of; the: residuarywater (be it shrinkagewater; orrporeiwater) .very slow and difiicult and thus greatly retards the drying'process: if cracking and. other defects are to be avoided. ,7

This invention, .therefore,,still further relates to improved-i apparatus for, and method of drying ceramic obj ects: at a relatively rapid .rate, while eliminating or greatly reducing development of crackscand otherdefects;

Ceramics shave heretofore been dried-by, means ofldifierent kindszofdriers andnaccordingto different processesone of which is a continuous process idryinggcarried out. in a tunnel-type -machinezzl In thiswtype orrdrying the objects to be driedareplaced in-orv propelled; .through an enclosureof the: desiredlength, and. are subjected to the continuous action-10f a,fluid drying medium,n.,such asgair, having therdesired heat and moisture content. An. example. of. this type. of

. drying isi-oneginwh-ich the drying, medium is discharged, under more or less. pressures from one or morenozzlesllocated in ornear the plane- 0f one :of thevertical side Wallsof the: enclosure. By? this arrangement, the proximal side of the 0bject,thatis, the sidethereof iacingthelnozzles,

- will besubjected to'the predetermined drying potential ofthe-dryingimedium as it emanates I fromlthe nozzles, ,whilethe-distal side oflthe ob- ,jectwill besubjectedtothe drying medium after its dryingpotential. has been reduced by-contact of, the drying, medium with the proximal side. of

, theobject. Obviously; theroppositezsides ofthe object cannottbewsimultaneously uniformlydried,

and if cracking andother damage is to-be avoided,

anobject so-driedmustbedried at avery slow rate and,- hence, inefiiciently and at-an increased a cost.

Thisvinvention, therefore; still further relates to an improved continuous or non-continuous chamber, or tunnel-type, drier in'which the drying-medium can always be applied directly to at least two or three sidesof'an object tobe-dried. such, forjexample; totthe-zsides and top, or: to the z-bcttom" and/or: sides of an object whereby; all

7 .parts tof saidzobject mayy be dried with 'suflicient uniformity; so asl' toceliminate or: greatly reduce I thedevelopmentcof cracks. and other defectst The' diificulties rabove' suggestedl are especially acute: innthe casersofrobjects having..- non -sym metrical contours, because, if such objects were dried according to conventional practice, and at a rate consistent with eflicient operation, considerable losses would be incurred due to cracking or other defects resulting from non-uniform drying of such objects. If the drying operation is slowed down enough to prevent or reduce losses due to cracking, strains, etc., there will be considerable increase in costs duev to inefficient operation of the drying apparatus.

This invention, therefore, still further relates to an improved, tunnel-type, drying apparatus, whereby non-symmetrical ceramic and other objects can be uniformly dried at a rate consistent with efficient operation of the apparatus while eliminating or reducing cracking and other defectives.

These and other objects are attained by this invention as set forth in the following specification and as illustrated in the accompanying drawings, in which:

Fig. l is a fragmentary and diagrammatic top plan view of a drying machine embodying the invention.

Fig. 2 is a side elevational view of the machine looking in the direction of line 22 on Fig. 1.

Fig. 3 is a vertical sectional view taken on line 33 of Fig. 1.

Fig. 4 is an enlarged fragmentary view looking in the direction of line 4-4 on Fig. 3.

Fig. 5 is an enlarged fragmentary view looking in the direction of line 55 on Fig. 3.

Fig. 6 is an enlarged, fragmentary view looking in the direction of line 6-6 on Fig. 2.

Fig. '7 is a diagrammatic view looking in the direction of line 1-1 on Fig. 3, illustrating the manner in which the flow of air is reversed relative to the objects being dried according to the improved method forming part of the invention. Fig. 8 is a fragmentary enlargement showing details of construction of the air nozzles.

Fig. 9 is an enlarged fragmentary view, showing details of construction.

Fig. 10 is a top plan view of Fig. 9 looking in the direction of line Ill-I0 on Fig. 9.

In the drawings, and as shown in Fig. 1, there Each of the units includes a While it is dependently, it is the practice, in order to take advantage of continuous process operation, to

' use a plurality of sections A, B, C, etc., placed in alignment so as to form a tunnel of the desired length. The sections A, B, C, etc., may each comprise a single drying chamber I0, so as to -'forma single-lane tunnel, or, preferably, each section will have a plurality of drying chambers l0 and l0a, etc., disposed side by side to form a multi-lane tunnel, as best shown in Figs. 1 and 3.

' Extending through each lane of the tunnel is a monorail I6 on which travels pendant racks l8. Each rack [8 preferably carries a plurality of superimposed perforated trays or the like 2:: and 2i for carrying ceramic or other objects 22 and T 23 to be dried. At the opposite ends of the tunnel, there are provided vacant chambers 24 and 26 which are closed by hinged doors 21, and

through which racks may be fed into, or withdrawn from the adjacent tunnel chambers with 4 minimum loss of heat. For example, if it is assumed that the racks [8 move from left to right as viewed in Fig. 1, the chamber 24 at the feed end of the tunnel and the chamber 26 will be at the discharge or delivery end of the tunnel.

The pendant racks 18 may be driven through the tunnel by any suitable means, but in the preferred form disclosed, each of the lanes I0 and Illa of the tunnel is-provided with a worm 30 which is driven by a source of power, such as a motor M, and each of the racks is provided with a pair of shoes 32 which are threaded and shaped to engage the upper portion of the worm so as to propel the racks along the monorail when the worm is turned. Since the rate of movement depends on the pitch of the worm thread and/or on the speed or rotation of the worm, the rate of movement of the racks I8 may be regulated as desired.

When the tunnel is relatively short, the worm may be made in one piece, but, when the tunnel is long, the worm preferably is made in sections joined together, or if it is in one piece, the thread is interrupted at intervals and the Worm is supported at these intervals by means of journal bearings 33 carried by pedestals 34, as shown in Fig. 2. It will be noted that the journal bearings are slightly below the axis of the worm and that the gearing 35, intermediate the worm and the shaft of the motor M, is likewise below the worm. Since the shoes 32 engage only the upper portion of the worm and since the journal bearings engage only the lower portions of the worm, the provision of the bearings does not interfere with the progress of the racks l8 along the monorail. It will be noted that the shoes 32 are spaced so that each rack has one shoe near its leading edge and the other shoe near the trailing edge thereof. By this-arrangement, added stability is attained and the racks are continuously propelled because, as the leading end of a rack is passing over one of the journal bearings, the rack will continue to be, propelled by the shoe at the trailing end thereof, and vice versa. 7

'In order to expedite loading and unloading,

' means has been provided for readily engaging the shoes 32 with, and disengaging them from, the

" Worm so as to permit quick feeding of the racks action of the worm, there will be considerable carry the shoes.

to the dotted-line position of Fig. 6, the shoes are loss of heat and time. But, by providing means for disengaging the shoes 32 from the worm, the racks can be rapidly placed in the loading chamber 24 and can equally rapidly be removed from the unloading chamber 26. This means, as best shown in Fig. '6, includes a lever 40, which is fulcrumed at 42 and pivoted at 44 to arms 46, which When the lever 40 is depressed raised out of engagement with the worm. Therefore, when loading the tunnel, the accessible lever 40 on any given rack is depressed to raise the shoes 32, the rack is placed on the monorail and pushed into the feed chamber 24 as far as there is room, and the lever 40 is then raised to lower the shoes 32 into engagement with the worm to cause the rack to be propelled by the worm. Similarly, when the racks reach the delivery chamber 26, theshoes 32 are disengaged, andthe :racks arei qui'cldy"pulled ofithefmo'ndrail. In other "words; the levers for? engaging and disengaging the 'sh oeslon' any: rack are; connected" in tandem sothat? by operatinglthe lever 46 at the leading, or at thejtrailing; endflofa rack, both of the'shoes carried by said: rack are actuated. This permitsdisengagement'of the shoe at the trailing Thecompartment 50 5 is'providediwithair-air inlet 56 controlledby adjustable louvers 58, and-jacontrolled air exhaust 60.

. The=chamber fifi -communicates'at its top with a: plenum, chamber-fi l'which' overlies the lanes l0 and l'flhof the adjacent tunnelunit. The chamher-'50 also communicates at its-bottom with a compartment 65 Which-underlies, and communi cates;with the interior-ofthe lanes H} and [0a.

The air delivery by the blowerjis selectively directed;='byfmeans of turnihgvanes 66 and 51, into the upper-ends ofjuXtaposed-- pairs of vertical ducts-jfil'l and 10, as shown by'the arrows B9 and H, respectively. The-ductsBB and llliarepr ovided withoppositely-facing; vertically-spaced nozzles H} which; extend substantially the entire length of the drying chamberand whjich'directthe drying air against the opposite sides of'the objects carried by the racks I8; or'across the-path of movement of 'said objects; asshown by-the ar- It will be noted that each of thalanesl0 and rectly from the main source so that the drying potential in these lanes'can be maintainedat substantially the same value; This; makes it possible; simultaneously; to dry as many objects, or

as many series of'ob'jects "(having substantially: the? same; drying characteristics) as theregare 'l'anes. velocity of thedrying medium from onelaneflto Also, by varying the-volume; and/or another, it is possible; simultaneously, to dry objects having difierent dryingcharacteristics.

' In order to subject various portions of the'objects 22, 23, etc., to the predetermined drying alct ion-ofthe heatedfair 'as-it 'em'anates from the nozzles, the" nozzles are slanted in the direction of 'movement of the objeets; as diagrammatically fia shown'-inFig. 4"so that; as an object progresses pasttlietier of nozzles, di ifrent portions thereof drill be successively exposed to the-direct blasts oi 'air issuing from the nozzles. For'example, as th'e' ob j ect 22 moves from-left-to right; successively higher'portions thereotwillregister with; and

will receive air ficmgsucce'ssiye, corresponding portions of the juxtaposednozzles, until, when the obj'ect z 2 has reached its extreme right-hand-posh tion the t'op of tlia objectgwhich was'well-aldove the highest nozzle portion as it entered' the drymg chamber, will" be belowthe' corresponding veloped' by air, the drying potential 'of whichhas been-reduced byits 1 initial contact with various {parts of the --object.

This arrangementplays an important partin preventing, or minimizing, cracking and other defects which may result from conventional drying and, at the same time, by making for more uniform drying, permitsspeedingup of the'rate of drying. For example, if portions 3: and z of object 22 are subjected to the' action of air 'as it flows'from the nozzles during the'entire travel of the object through the tunnel, while other portions of the object areonly subjected to the'dry' ing' action of air which hasalready come in contact with the portions a? and z' of theobject,-the portions :1: and 2 will (a) dry more rapidlythan the remaining portions; thus'setting up strains andpossible warping, (b) dry'more rapidly than corresponding interior portions, thus causing cracking, and"(c) lose their surfaceshrinkage overcome.

The nozzles" 74 may be'spaced-and slantedin the successive tunnel units; as shown in Fig. 4, or the spacing and slanting'may bealmost infinitely varied, as shown in Fig. 5', .forexample, so as to adapt the distribution of the, drying medium to the various shapes'of any num-ber'of different objects having non-symmetrical contours. For example if the object bulges out laterally, so that r r h 7, portions thereof arevery close to one or both of 4 llmis'providedwitlritsown drying airsupply dithe corresponding nozzles, while other portions of the'object recede and arerelatively remote from the corresponding nozzle, the flow of airwill be regulated accordingly, either by omitting or partially'or wholly closingyanozzle or more at one point, and by opening Wide, or by increasing the sizei'or number of'the nozzles at another point. This can be donejby providing the nozzles With adjustable shutters82; as'shown in Fig. 8, or the nozzles can be built in banks having diiierent arrangements (as to slanting and non-slanting, andas to size andnumber and'direction of nozzles), and the banks of nozzles can be made bodily removable so that, when dryinga job lot of one type of object, one set of nozzles'will be used, and, when drying a job lotof another type of object, a

different set of nozzles will be substituted.

In the dryin of certain types of ceramic and other objects, it may be necessary, ,or desirable,

to humidify the drying air'so as to retard surface drying While the temperature of the interior of the object is being raised to a value which will insure substantially uniform drying of the exterior and'interior of the object. In such cases,

. the relative humidity maybe controlled by varying the proportion of outside air admitted through the louvered inlet 56, or'the humidifier-5t may be 1 usedas'and to' the extent indicated, itbeing noted that; as the drying progresses, the relative humidity-of the drying air'is progressively lowered;

While satisfactory drying may be achieved by themean-s thus far described, the invention-also contemplates provision of one or more pendant nozzles i8 whichmay be used for directing he'at- =ed1aindirectlytoward theaupp'er surface of tlrieaobject 22 on the upper tray 28, as best shown in Fig. 3. The nozzles 18 may converge, vertically speaking, so as to direct the air delivered therethrough directly onto the top of the object, thus minimizing the interference of the downward blast of the nozzles I3 with the horizontal blasts of the nozzles 14. The nozzles 18 are also preferably provided with adjustable louvers 82, like those shown in Fig. 8, for regulating the flow of air as may be desired.

Since, as shown in Fig. 3, the air is delivered to the ducts'68 and through the upper plenum 64 and since all of the air delivered to a tunnel unit is withdrawn through the lower compart ment 65, it follows that the lower portion of a single, vertically-extending object 22 and the low- ;er object 23 of a plurality of superposed objects,

will be subjected to the drying action of the air directed laterally thereagainst through the adjacent nozzles, as well as to the drying action of such air as was initially directed against the upper portion of a single vertically-extending object 22, or against the uppermost object 22 of a plurality of superposed objects. In other words, an object near the lower portion of a tunnel unit will be subjected to the drying action of all of the air delivered to such unit, while an object near the upper portion of a tunnel unit is subjected only to the action of the air blown directly thereagainst. When it is remembered that the air in the upper portion of the tunnel is that which is delivered by the upper nozzles while the air is in I the lower portion is a mixture of the air delivered through the lower nozzles and the air which has already come in contact with the object 22 in the upper portion of the tunnel unit, it will be seen that the drying potential in the lower portion of the tunnel unit will be difierent from the drying potential in the upper portion of the tunnel unit.

This condition is somewhat undesirable when two.-

' the differential between the drying conditions prevailing in the uppermost and lowermost portions of the tunnel unit will be correspondingly increased.

In order to overcome this difficulty, the present invention contemplates intermittently reversing the relation or direction of movement of the drying medium relative to the superimposed objects in the various tunnel units. This is done by delivering air to one tunnel unit, horizontally, from nozzles in the vertical side walls thereof, and/or downwardly through nozzles in the top of said unit, and then withdrawing all of the air delivered to said unit through the bottom of such unit, as shown in Fig. 3, and by delivering air to another tunnel unit, horizontally, through nozzles in the vertical side walls and/or upwardly through nozzles in the bottom of such unit and then withdrawing all of the air delivered to said said other unit through the top thereof.

For example, and designating the various tunnel units shown in Fig. 7 by the letters D, E, F, and H, it will be seen that, in the unit D, the blower it, turning vanes 66 and '61, the nozzles 18, when used, and the heaters l2 are arranged, vertically, in the order shown in Fig. 3. In the next unit E, the blades of the blower are reversed so as to blow air downwardly, and at least the turning vanes 66 and 61, and the nozzles I4 are associated with the lower compartment so that it now becomes the plenum, and the upper jects 22 and 23 in one drying chamber, or tunnel unit, and upwardly past said objects in another tunnel unit, thus insuring more uniform drying of the upper and lower portions of a single, vertically-extending object and more uniform drying of a plurality of vertically-spaced or superimposed objects.

In the drying of objects having complementary, complicated and highly non-symmetrical contours, it may be desirable to rotate the objects being dried as they move through the drying chamber so as more efiectively to expose the various portions of the objects to the drying medium. For example, and as diagrammatically shown in Fig. 9, the racks [8 which support the objects to be dried, are pivoted as at 86, so as to be freely rotatable, and are provided with gears 88 which, as the racks l8 move through the drying chamber, engage a toothed rack'89. By this, or any other suitable means, the trays 20 and 2| and the objects 22 and 23 thereon are rotated about vertical axes as they move horizontally through the drying chamber or chambers. Obviously, with a slight change of the parts, the objects can be made to rotate about horizontal axes, if so desired.

Having described the invention, what we claim is: '1. The method of drying a ceramic object or the like which method consists in moving said object through a plurality of longitudinally aligned enclosures, discharging individual streams of a fluid drying medium from opposite sides of said enclosures onto opposite sides of said object, exhausting said drying medium through the upper portion of one of said enclosures, and exhausting said drying medium through the lower portion of another of said enclosures.

2. A drying machine for drying a ceramic object or the like said machine including an elongated drying chamber, means for propelling an object to be dried through said chamber, and means for delivering individual streams of a fluid drying medium horizontally from opposite sides of said chamber, there being an exhaust outlet near the top of one portion of said drying chamher, and an exhaust outlet near the bottom of another portion of said chamber.

3. A drying machine for drying a ceramic object or the like, said machine including an elongated chamber, means for propelling a plurality of superimposed objects through said chamber, means for delivering individual streams of a fluid drying medium from opposite sides of said chamber onto opposite sides of said objects, as they move through said chamber sections, there being a first outlet opening near the bottom of one of section, through which said drying medium is exhausted, whereby, as said objects move through said one section, the lower of'said obiects, and the lower portions of the upper 01 the top of another section of said chamber through which said drying medium is exhausted from said other section of said chamber, whereby, as said objects move through said other section, the upper of said objects, and the lower portions of the lower of said objects, will be subjectedto the action of the drying medium directed thereagainst as well as to the action of the drying medium directed against the lower portions of said lower objects.

4. The structure recited in claim 3 together with means for supplying drying medium downwardly through the first mentioned section and means for supplying drying medium upwardly through the second mentioned section.

RALPH C. PARKES. DAVID H. COLKER.

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

UNITED STATES PATENTS Number Name Date 520,869 Titus June 5, 1894 1,279,086 Davoran Sept. 17, 1918 1,298,285 Bogaty Mar. 25, 1919 1,360,705 Allsop Nov. 30, 1920 1,541,889 Baetz June 16, 1925 1,547,891 Ayres July 28, 1925 1,570,659 Wilson et a1. Jan. 26, 1926 1,700,994 Buck Feb. 5, 1929 2,073,669 Zademach Mar. 16, 1937 2,168,478 Hyde et a1. Aug. 8, 1939 2,295,475 Hurxthal Sept. 8, 1942

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