US2954613A - Apparatus and method for drying materials - Google Patents

Description

Oct. 4, 1960 Filed April 13, 1955 D. S. BAKER APPARATUS AND METHOD FOR DRYING MATERIALS 11 Sheets-Sheet 1 I INVENTOR. fia/yul mr ATTORNEYS Oct. 4, 1960 D. s. BAKER 2,954,613

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United States Patent APPARATUS AND METHOD FOR DRYING MATERIALS David S. Baker, 475' th Ave., New York 17, NY.

Filed Apr. 13, 1955, Ser. No. 501,087

28 Claims. (Cl. 34-102) This invention relates to apparatus for drying various materials by the removal of volatile fluid therefrom. Generally the fluid which is removed by the drying is water and its removal is accelerated by heat. However, this in- ,vention is applicable to the removal of other volatile foodstuffs.

The main object of this invention is to provide improvement in apparatus and method for drying, driving off or otherwise removing fluid from materials of the kinds exemplified hereinabove. It is a further object of this invention to overcome difficulties and drawbacks which have been incident to the provision of economical and efiicient apparatus and methods for drying wet materials,

the term drying being applied generally to the driving off or other removal of a volatile fluid with the recovery of a non-volatile residue in either a dry or partially dry condition. When reference is made herein to a material being wet, the volatile liquid or fluid may either be water, which is commonly the case, or some other substance or substances which may be removed in the form of a vapor.

Certain objects and features of this invention relate to the provision of improved apparatus for drying materials of the kinds referred to and exemplified hereinabove in which there is a rotary drum having a heated outside surface surrounded in part by an endless conveyor belt means adapted to retain, compress or sandwich material being dried between it and the outside surface of the drum, the apparatus including improved and simplified means for repeatedly removing materialbeing dried from the outside surface of the drum and refeeding it between the drum surface and the endless conveyor belt means.

In connection with the foregoing objects and features of this invention, other objects and features relate more particularly to apparatus wherein the inside surface of the endless conveyor belt means and the outside materialreceiving surface of the drum cooperate to form a feed throat through which material being dried must enter in being compressed or sandwiched between the inside surface of the belt and the outside surface of the drum, means being employed which provides improved control and better feeding action as the material enters and The improved feeding means which constitutes a feature of this invention is applicable to the formation into a layer of unformed workable material such as a mass of wet material to be dried, as by feeding the material between traveling surfaces ice posed adjacent relation at which the workable material becomes formed into a layer. Furthermore, specific objects and features of this invention relate to the provision in contiguous relation to one of the traveling surfaces providing the feed throat of what is referred to here'- in and in the claims as curtain means that provides a restriction plate for contacting unformed workable material during its ingress into the feed throat and providing diminished but effective tractive contact. with the material entering the feed throat. Still further objects and features of this invention relate .to the provision of such curtain means in the form of fingers such as spaced flexible strips which extend into the feed throat and preferably are contiguous with or drag against the outside surface of the drum when the feed throat is provided by and between the outside surface of a drum and an endless conveyor belt means which approaches the outside surface of the drum generally tangentially so as to provide a material-feeding portion in addition to a portion concentrically surrounding a portion of the outside surface of the drum.

Other objects and features of this invention relate to the provision of improved apparatus for drying materials whereby more effective and simplified means may be utilized for causing the material to become sandwiched between the outside heated surface of a rotatable drum and endless conveyor belt means concentrically surrounding a portion of said drum and Worked axially along the drum while being repeatedly removed. from the drum for contact with an atmosphere into which vapor may escape and being refed through feed throat means constituted by the outside surface of said drum and the inside surface of the endless conveyor belt means. Further objects and features of this invention relate to the improvements that are afforded by the combination of the means for providing such axial movement of the material during the aforesaid operations of being repeatedly removed from the drum and refed so as to be carried thereby with the improved means hereinabove referred to for controlling and making more effective for attaining the desired drying the tractive action of the converging traveling surfaces at the feed throat where the inside surface of the endless conveyor belt means approaches the outside surface of the drum.

Other objects and features of this invention relate to the improvement of drying apparatus of the type comprising a rotary drying drum surrounded in part by an endless conveyor belt means by the provision of means whereby material may be first cam'ed on the surface of the drum and then removed therefrom in a space where the material may become exposed to an atmosphere for receiving vapor separated from the material being dried. More particularly, such objects and features of this invention include the disposition and actuation of the endless conveyor means so as to form a loop at one side of the drum, thereby providing an aeration space adjacent that portion of the drum surface within the loop of the endless conveyor belt means. Within the loop so formed means may be provided for removing material from the drum surface and causing it to fall in the aeration space and become redeposited on the inside surface of the endless conveyor belt means for being refed between the outside surface of the drum and the inside surface of the endless conveyor belt means. Preferably the curved ex- *tremity of the loop is so supported as to provide upper in the form of a feed throat that brings them into opand lower reaches of the endless conveyor belt means and thereby provide an aeration space of substantial size. Both the drum surface and the endless conveyor belt means are normally imperforate and by thus providing a loop of the character aforesaid an aeration chamber is provided which utilizes the upper and lower reaches of the endless conveyor belt means and part of the outside surface of the heated drum. Moreover, in such case a material after removal from the outside surface of the drum for aeration in the space within the loop may fall directly on the inside surface of the lower portion of the loop and any material which may adhere to the upper portion of the loop and fall therefrom becomes refed without loss for repeated compression so as to be sandwiched between the outside surface of the drum and the inside surface of the endless conveyor belt means so as to be carried on one side of the drum over the top of the drum for entry into the top of the space within the loop.

Further objects and features of certain embodiments of this invention relate to the provision of wall means within the space provided by disposing the endless conveyor belt 'means' in the form of a loop at one side of the .-;rotatably mounted drying drum. Preferably the wall .means includes both a dividing partition wh1ch 1s normal to the drum axis and a confining partition spaced from the outside surface of the drying drum whereby .improved removal of vapor-laden atmosphere from the .space within the loop is provided. However, either or both of such wall or partition means may be omitted.

Other features of this invention relate more generally to means for providing a zone wherein material to be dried is exposed to atmosphere for escape of vapor and for removal of vapor-laden atmosphere therefrom.

Other features ofthis invention relate to improved means for inducing axial travel of material to be dried ;while it is being repeatedly removed from the surface of ;a drying drum and refed so as to become sandwiched be- -tween the outside surface of the drying drum and the inside surface of endless conveyor belt means that concenjtrically surrounds a portion of the outside surface of the drum.

In connection with such means, improved seal means is provided according to this invention between the inside surface of the endless conveyor belt .means and the outside surface of the rotatably mounted -dru.m adjacent one or both ends of the drum.

Improved seal means is also provided according to this in- Such seal adjacent the other end of the drum for receiving and directing the wholly or partially dried material so that it .will not be refed onto the surface of the drum while .maintaining uniformity of the compacted layer at all times notwithstanding shrinkage due to loss of fluid from the mass being dried. Preferred seal means which conzstitute a further feature of certain embodiments of this invention utilizes a succession of pieces of flexible resilient material attached to one member so that the ex- .tremities thereof remain in resiliently maintained con- .tacting relationship with another member. means may be provided between the endless conveyor belt means and either a confining side wall or the circum- Such seal ferential periphery of the drum at one or both ends. For providing a seal for a drum or other circular member I and another concentric member the seal means preferably is so made that the resilient flexible pieces are overlapping in side-by-side relationship as, for example, by using a plurality of overlapping leaf springs of stainless steel or the like which extend laterally so as to provide a resiliently deformable ring adapted to be maintained in resil- .1ent contacting relation with an opposed arcuate surfac for maintaining a seal.

Another object and feature of this invention resides in the provision of apparatus of the type and for the purpose set forth which includes a rotary drum having a .peripheral surface surrounded in part by an endless con- :veyor belt means in which there is improved means for sealing one end of the drum and the endless Conveyor '15- 4 belt means and means for cleaning impacted material from the seal means.

Other objects and features of this invention relate to improved utilization of a drying drum so that an effective drying surface is provided both by the outside surface and by the inside surface of the drum. More particularly, such objects and features of this invention preferably provide means whereby material being dried is repeatedly cascaded in an aerating atmosphere while being dried on the outside of the drum but is maintained in sliding contact with the inside surface of the drum with minimum of agitation or tumbling, such apparatus being especially suitable for carrying out the final drying of a product with minimum of difficulty resulting from excessive dusting. Other objects and features of certain embodiments of this invention relate to improvements in temperature control as between the outside and inside surfaces of the drying drum.

Other objects and features of certain embodiments of this invention relate to the provision of drying apparatus comprising a drum having a material-receiving outside surface and improved means for heating the drum. More particular objects and features of such embodiments of this invention relate to the locating of zones of combustion with reference to the drum and to the provision of a combustion Zone or chamber provided at least in part by the inside surface of the drum and to improved means for directing and utilizing the products of combustion.

vOther objects and features of this invention relate to improved methods for drying materials of the kinds referred to and exemplified hereinabove and to the provision of improved apparatus for carrying out the im proved methods of the invention.

Preferably the features and improvementsof this invention are employed in combination so as to obtain the most effective and efiicient manner of practicing this invention. However, the features and improvements of this invention may be employed in apparatus wherein they may be employed separately or in coacting relation not involving all of the features of the preferred combinations that are shown and described herein. Moreover, other objects, features and advantages of this invention will appear from the following description in connection with the accompanying drawings which, for purposes of exemplification, show typical embodiments of this invention and illustrate the practice thereof.

In theaccompanying drawings:

Fig. 1 is a view in elevation of one side of a drier apparatus including features of the invention, the drive mechanism for the-primary feeder of the apparatus being omitted;

Fig. 2 is a view in elevation, with parts broken away, of the right hand side of the apparatus seen in Fig. 1;

Fig. 3 is a diagrammatic view in section of the upper portion of the apparatus seen in Figs. 1 and 2,-the view being taken generally on line 3-3 of Fig. 2, and, for the sake of clarity, omitting certain frame members and the primary feeder mechanism of the apparatus;

Fig. 4 is a partial plan view, partly in section, taken on the line 4-4 of Fig. 3;

Fig. 5 is a view in plan showing portions of the endlessbelt conveyor, the rotary drum and a seal means on one end of the drum for sealing or closing a materialreceiving space between the belt and the drum;

Fig; 6 is a view taken on the line 66 of Fig. 5

i and looking at the left side of the structure seen in Fig. 5;

Fig. 7 is a view in section, the section being taken on the line 7-7 of Fig. 5;

Fig. 8 is a fragmentary. perspective sectional showing .of certain of the parts appearing in Figs. 5, 6 and 7;

Fig. 9 is a view in section through certain elements of the seal structure seen in Fig. 7;

Fig. 10 is a more or less diagrammatic side view in elevation on a larger scale of a portion of the apparatus seen in Fig. 1, the view showing particularly one end of the rotary drum of the apparatus and mechanism associated with it;

Fig. 11 is a more or less diagrammatic view in elevation taken on line 11-411 of Fig. with parts broken away or in section;

Fig. 12 is a view on a larger scale of some of the elements seen in Fig. 11;

Fig. 13 is an elevational view on line 13-13 of Fig. 12 with some parts in section;

Fig. 14 is a view somewhat similar to Fig. 1 2 but showing a modified form of material feeder structure for feeding material between the drum and endless conveyor belt;

Fig. 15 is a view somewhat similar to Fig. 13 but showing the modified form of material feeder structure seen in Fig. 14;

Fig. 16 is a diagrammatic view in section of a modified form of the apparatus seen in Figs. 1 and 2;

Fig. 17 is a diagrammatic view in plan of a portion of the apparatus seen in Fig. 16;

Fig. 18 is a diagrammatic view in section, the section being taken on line 1818 of Fig. 16;

Fig. 19 is a diagrammatic sectional, elevational view of a modified form of drying cylinder or drum and asso ciated apparatus which may be substituted for the drying cylinder or drum in the drier shown in Figs. 1, 2 and 3, or the drying cylinder and drum shown in Figs. 16, 17 and 18;

Fig. 20 is an end view in elevation, with parts broken away, of the apparatus seen in Fig. 19;

Fig. 21 is a detail section taken on the line 21-41 of Fig. 20;

Fig. 22 is a diagrammatic view, partly in section and partly in elevation, of another modified form of cylinder or drum and heating means therefor, which may be substituted for the drier or cylinder or drum in the drier seen in Figs. 1, 2 and 3 or the drier cylinder and drum shown in Fig. 16 of the drawings;

'Fig. 23 is a view in section, the section being taken on line 23-23 of Fig. 22;

Fig. 24 is a view in section, the section being taken on line 24-24 of Fig. 22;

Fig. 25 is a view, partly in section and partly in elevation, showing means for preventing axial movement of the cylinder or drum seen in Figs. 22 through 24;

Fig. 26 is a diagrammatic view illustrating the mechanism for rotating the cylinder or drum seen in Figs. 22 through 25 and also the cylinder or drum seen in Figs. 27 through 29;

Fig. 27 is a diagrammatic view, partly in section and partly in elevation, of another modified form of cylinder and heating means therefor, which may be substituted in the drier seen in Figs. 1, 2 and 3;

Fig. 28 is a diagrammatic view in section, the section being taken on line 2823 of Fig. 27; and

Fig. 29 is a diagrammatic side view in section, the section being on the line 29-29 of Fig. 27.

The drier apparatus shown in Figs. 1 through 4 of the drawings includes an open generally rectangular main frame 30 formed of suitable upright and cross angle members welded together. Within the frame 3%) there is a hollow material-heating cylinder or drum 31 adapted to be heated by steam or hot water. Drum 31 includes two axially aligned stub shafts 32, one at each of its opposite ends, by which it is mounted for rotation about a generally horizontally disposed laterally extending axis through bearings 33 on horizontal members of the frame 30 and adjacent one of its upright ends.

Steam or hot water is introduced into the cylinder or drum 31 through a conduit formed by one of the stub shafts 32 which is hollow and through which water or condensate may be exhausted from the drum through a conduit or pipe that extends to adjacent the bottom of the inside surface of the cylinder or drum.

6 Adjacent the opposite upright end of main frame 30 there is a generally horizontally extending shaft 34 carried for rotation in suitable bearings 35 mounted on the frame 30. The axis of shaft 34 is parallel with and spaced forwardly of the axis of rotation of cylinder or drum 31 and the two lie on substantially the same horizontal plane. This shaft 34 carries a pair of spaced sprocket wheels 36 that carry and drive an endless conveyor belt 37 looped around and extending between the spaced cylindrical drum 31 and the sprocket wheels 36. Endless conveyor belt 37 is fully described hereinafter, but it is pointed out here that it includes two endless chains 38, one at each side, that cooperate with the sprocket wheels 36 and rims on the ends of the drum 31.

Shaft 34, and consequently the sprocket wheels 36, conveyor belt 37 and cylinder or drum 31 are driven in a counter-clockwise direction, as viewed in Figs. 1 and 3 of the drawings, by an electric motor 39 through a speed reducer 30, a sprocket 41, chain 42 and a sprocket 43 on shaft 34.

A portion of the endless conveyor belt 37 is concentrically disposed about one side of the cylinder or drum 31 and another portion is looped outwardly from the opposite side to form an aeration chamber, pocket or space 44 in which material being dried is subjected to aeration. In the embodiment shown the curved extremity of the loop portion of the endless conveyor belt means is supported by the sprocket wheels 36 and the aeration chamber, pocket or space 44 is defined at its bottom by the bottom run or reach 45 of the conveyor belt 37, at one end by the exposed or uncovered side of the cylinder or drum 31, on the top by the top run or reach 46 of conveyor belt 37, and at the end opposite the drum 31 by that portion of the conveyor belt 37 which curves around the drive sprocket wheels 36.

In order to better control the removal of vapor-laden atmosphere from the chamber 44 and prevent accidental losses of material undergoing drying from the chamber 44, it is preferable to employ the side walls 92 and 92' which are shown best in Figs. 1, 4, 11 and 13 and which will be described more in detail hereinbelow. However, it may be mentioned at this point that the marginal edges thereof are disposed in contiguous relation with the inner surface of the loop portion of the endless conveyor belt means and the outside surface of the drum 31 that is within the chamber 44. For promoting the removal of vapor-laden atmosphere at suitable exhausting fan (not shown) may be connected to an opening such as the port 65 (Figs. 1 and 11) in the wall 92. The exhausting fan or other suitable exhausting means may be similar to exhausting fan-means 66 shown in Fig. 16 but has been omitted from Figs. 1, 2 and 11 in order to simplify the drawings of the embodiment shown in these figures. While such side wall means preferably are employed, they may be largely or wholly omitted and in such case convection currents and atmosphere movements resulting from the operation of apparatus may be relied upon to remove the vapor-laden atmosphere from the chamber 44 without the employment of an exhausting fan and in such case the wholly or partially open sides which permit such currents and movements of the atmosphere are to be regarded herein and in the claims as means for removing vapor-laden atmosphere from the chamber 44 wherein the wet material to be dried is exposed to drying atmosphere.

The endless conveyor belt is maintained under proper tension at all times by a pair of sprocket wheels 47 adjacent the drum 31 that carry or engage the conveyor belt 37 through its endless chain side elements 38. Sprocket wheels 47 are mounted on a shaft 48 (see Fig. 3) carried at its opposite ends on a frame 49 pivoted to the main frame 30 by a shaft 50 and weighted by weights 51 to urge the sprocket wheels 47 upwardly.

The inside surface of that portion of the endless conveyor belt 37 which surrounds the heated outside cylindrical peripheral surface 52 of cylinder or drum 31 is spaced therefrom by structure fully described hereinafter to provide a wide, thin heating chamber or space 53 in which material being dried is heated. It is a feature of this invention that by employing the resiliently acting tensioning means, the thic'kness of the layer of material that becomes sandwiched in the space 53 between the outside surface of the drum 31 and the inside surface of the endless conveyor belt means may be permitted to become increased. Ordinarily the apparatus is intended to operate so as to maintain a predetermined desired thickness for this layer. However, under certain conditions such as increase in the amount of feed either accidentally or deliberately the thickness of the that because the endless conveyor belt 37 approaches generally tangentially the bottom of the heated outside peripheral surface 52 of drum 31 and because the outside drum surface 52 and the inside surface of the conveyor belt 37 travel in the same direction they cooperate to provide a gradually narrowing or tapering feed throat '54 (Fig. 3) formed by approaching travelling surfaces throughout the axial length of the heated surface 52 and through which material being dried is fed, as hereinafter described, into the wide, thin heating chamber 53.

Damp, wet or pasty material to be dried is fed into the apparatus through a primary feeder 55 located on top and at one side of the main frame 30. Feeder 55 includes a material-receiving hopper 56, the bottom of which is formed by a pair of side by side rolls 57 mounted on spaced parallel shaft means 58 carried in bearings 59 on main frame 30. The cylindrical peripheral surfaces of the rolls 57 abut each other and one of the rolls 57 is formed throughout its length to include a smooth cylindrical surface while the peripheral surface of the other roll 57 includes throughout its length a plurality of side by side circumferential grooves, not shown, whereby material fed or extruded from the hopper 56 between the rolls 57 will be in the form of a plurality of strips or ribbons. ,connected by similar gears 60 (see Fig. 1) so that when The shafts 58 of rolls 57 are interrthe rolls are driven they will rotate together in opposite directions. The rate of speed at which the rolls 57 are rotated, of course, determines the rate at which material 7 is fed into the drier apparatus, and these rolls 57 are driven by conventional apparatus by which their rate of a rotation may be controlled.

The mechanism for driving the rolls 57 as aforesaid may comprise the motor 61 (see Fig. 2), the belts 62 and 63 and some conventional means 64 for reducing the motor speed and regulating the speed at which the rolls 57 are driven.

Material fed from the hopper 56 by the rolls 57 falls by gravity upon a steeply inclined feed chute or trough 71 and from it directly onto the upper surface of the bottom run 45 of conveyor belt 37 and at the right side thereof as seen in Fig. 2. Trough 71 is hung loosely at its top end from the main frame 3 and because the materials being fed therethrough may have sticky characteristics, an electrically operated vibrator 72 of any wellknown construction is mounted upon the bottom of the feed chute 71 for vibrating it, thereby to cause the material to feed down the chute 71.

As mentioned previously, the bottom run 45 of conveyor belt 37 travels toward the drum 31 and approaches the bottom of the latter tangentially to form the gradually narrowing or tapering feed throat 54 and thus material dropped upon the insideor top surface of the bottom run 45 of endless conveyor belt 37 by the feed chute 71 will be conveyed toward the bottom of the drum 31, through the feed throat 54 and will become compressed and confined or sandwiched in the heating chamber 53 between the inside surface of the conveyor belt 37 and the outside heated peripheral surface 52 of the drum 31. Because the drum 31 and conveyor belt 37 rotate together as a unit, material confined or sandwiched in the heating chamber 53 will be carried from the bottom of drum 31 up one side and over the top thereof and into the top of the aeration chamber 44.

As the material enters the top of the aeration chamber 44 it will, for the most part, be in a compressed sheetlike condition forming a blanket or coating adhering to the outside surface 52 of drum 31, though some of it may adhere to and travel with the inside surface of the top run 46 of the conveyor belt and some small particles of it may fall in the aeration chamber directly onto the bottom run 45 of the conveyor belt 37.

A scraper assembly, indicated generally by the reference character 73, for scraping material that adheres to top run 46 of conveyor belt 37 extends transversely through the aeration chamber and side walls 92 and 92',

and includes a support formed of an inverted angle bar 74 attached at its opposite ends to the center portion of upright lever arms 75. The upper ends of arms 75 are pivotally attached to the main frame 30 by pivot pins 76. A scraper blade 77 made from a sheet of flexible resilient material, such as stainless steel, is secured along its bottom edge to one flange of the angle bar 74 and its top edge is urged against the inside surface of the top run 46 of the conveyor belt 37 by a pair of springs 78 extending between the lowermost or free ends of the lever arms 75 and the main frame 30. Any material scraped from the inside surface of the top run 46 of the conveyor belt 37 by the scraper blade '77 will fall by gravity in the aeration chamber 44 directly onto the bottom run 45 of the conveyor belt.

A scraper or doctor blade assembly, indicated generally by the reference character 79, is provided in the aeration chamber 44 for scraping, breaking or digging material from the outside heated cylindrical surface 52 of drum 31 and causing it to fall in the aeration chamber 44 directly onto the bottom run 45 of the conveyor belt 37.

The details of construction of the scraper or doctor blade assembly 79 may best be understood by reference to Figs. 3, ll, 12 and 13 of the drawings. It includes an angle member 86 that extends horizontally through the aeration chamber 44 parallel to the axis of rotation of the drum 31. Angle member 8i includes an integral downwardly extending leg 81 at each of its opposite ends which are pivotally attached through a pair of axially aligned bolts 82 to brackets 83 bolted to the main frame 30. Angle member 80, and consequently the entire doctor blade assembly 79, may be adjusted about the axes of bolts 82 by threaded adjusting rods 84that interconnect the top of the angle member and the main frame 30. As best seen in Figs. 3 and 10 of the drawings, the angle member 80 lies in a horizontal plane below a generally horizontally extending plane passing through the axis of rotation of shaft 34 and the axis of rotation of the drum 31, and its flanges extend toward the drum 31, one sloping upwardly toward it, and the other sloping downwardly.

The upwardly sloping flange of angle member 80 carries an upwardly extending scraper blade 85 formed of a thin resilient sheet of stainless steel. Blade 85 extends throughout the axial length of the heated outside cylindrical surface 52 of drum 31 and its upper or scraping edge engages said surface 52 under pressure to scrape, break or dig material from the surface 52 of the drum as the latter rotates against the blade 85. Blade 85 is rigidly attached along its bottom edge to the upwardly sloping flange of angle member 80 and the scraping pressure exerted by the upper scraping edge of said blade 85. on

the surface 52 of the drum 31 is, of course, adjusted or determined by adjusting the position of the scraper or doctor blade assembly 79 about the axis of bolts 82 by the rods 84. The scraping edge of said blade 85 is just above the said plane that passes through the axis of rotation of shaft 34 and the axis of rotation of the cylinder or drum 31 in order that the sloping upper surface of blade 85 will deflect, direct, or otherwise cause material which has been scraped from the drum surface 52' and is falling toward the bottom run 45 of endless conveyor belt 37 to follow a trajectory beginning at the surface 52 and terminating at the inside or upper surface of the bottom run 45 of said conveyor belt 37 in order that the falling material will land upon the latter at a point more remote from the drum 31 and the mouth of the feed throat 54.

It will, of course, be seen that the material will be broken into pieces upon being cracked, broken or dug from the surface 52 and that this cracking or breaking of the material will expose more surfaces of it toaeration as it falls in the aeration chamber 44. It will also be seen that when the material impacts upon the inside surface of the bottom run 45 it may be further broken to prepare it better to be refed to the heating chamber 53 and that there may occur a splashing action when the material strikes the bottom run 45 of conveyor 37. This splashing action has a tendency to distribute the material more evenly upon the bottom run 45, thereby aiding in the refeeding of the material through the feed throat 54 and into the heating chamber 53.

The bottom flange of angle member 80 carries a plurality of hooks 8t; spaced along its length and from which there is hung for swinging motion an angle member 87 (see Figs. 3, 12 and 13). Angle member 87 extends across the aeration chamber 44 and has a restriction plate or curtain means 88 depending therefrom into the feed throat 54. In the embodiment shown the curtain-88 is formed from a thin resilient or springlike sheet of stainless steel disposed particularly in the region of its lower end contiguously with respect to the outside material-receiving surface 52 of the drum 31 so that when the apparatus is in operation material being fed through the throat 54 will contact the curtain and in the zone of the throat 54 where the curtain is located it will be prevented from coming into tractive contact with the outside surface of the drum, as is apparent especially in connection with Figs. 3 and 12.

The bottom of the restriction plate or curtain 88 is notched at 89 (see Figs. 11 and 13) to provide a succession of restricting elements in the form of side-by-side tongues, fingers or ribbonlike strips 90 between which the spaces provided by the notches 89 are disposed.

The length of the restriction plate or curtain means 88 is such that when material to be dried is being fed through the feed throat 54 a portion of the material will rest against the curtain rather than the travelling surface of the drum. As indicated in Figs. 3 and 12 of the drawings, the length of the curtain preferably is such that the bottom ends of the striplike fingers extend into the feed throat 54 so that when the apparatus is not in use they may rest upon the inside surface of the bottom run 45 of the conveyor belt 37 in the feed throat 54 adjacent the heating chamber 53. However, when the apparatus is in use and material is being conveyed upon the conveyor belt 37 through the feed throat 54, the material in being compressed within the feed throat will press against the striplike tongues 9i) and press them into rubbing contact with the outside travelling surface 52 of the drum 31. However, in the regions of the notches 89 between the striplike fingers 9n the material being fed through the feed throat is exposed to tractive contact with respect to the travelling outside surface 52 of the drum 31.

The exact action of the restriction plate or curtain means 88 on the feed of material to be dried through the feed throat 54 and into the heating chamber 53 has not been fully ascertained, but experience has shown that the presence of the restriction plate or curtain means very greatly improves the overa'il action of the drier of this invention. While the action of the restriction plate or curtain means has not as yet been fully ascertained, it is believed, however, that the curtain means serves to control and improve the feed of the material through the feed throat 54 by diminishing the tractive contact of the material to be dried with the travelling converging surfaces at the feed throat while at the same time permitting such tractive contact with the approaching travelling surfaces as to effectively draw the material to be dried into and through the feed throat. This is especially the case in the region of the striplike fingers for to the extent that portions of the material to be dried come in contact with these fingers the tractive contact with the travelling drum surface is diminished. On the other hand, in those zones or areas between the fingers the material to be dried is exposed to tractive contact with the drum surface so as to effectively draw the material into the feed throat without bridging or other damming up of the material so as to fail to enter and pass through the feed throat into the heating chamber 53. While normally not essential, a vibrator (not shown) may be employed so as to minimize any bridging or other damming up of material entering the feed throat if there should be any such tendency. The fingers 39 may to a certain extent result in the material to be dried being somewhat less compressed in the regions of the fingers as compared with the compression in the regions of the notches 89. However, in the final stages of compression any such inequalities are largely or substantially completely equalized in the final formation of the substantially continuous layer as it enters the heating chamber 53. In a typical operation such as the drying of finely divided coal or sewage the material to be dried may pile up at the feed throat to a depth of about 5" to 6 and during passage through the feed throat the layer ultimatelyproduced may be in the neighborhood of to A in thickness. Under such conditions, which have been mentioned merely for purposes of illustration, it has been found desirable to employ a curtain which is about 12" from top to bottom and wherein the fingerlike strips are at least about 6" or preferably at least about 8 long. When the fingerlike strips are made of stainless steel which, for example, may be 0.007" in thickness, it has been found that very satisfactory feeding can be obtained when the strips are about 1 in width and are spaced apart by a distance of about 1. Under such conditions there is an overall effect of the curtain means on the material passing through the throat so that a substantially continuous layer is produced. Preferably, the bottom edge of the curtain means does not extend completely to the base of the throat 54 where the approaching travelling surfaces come into closest proximity to each other. For example, it is usually desirable to accomplish the last to of reduction in thickness under conditions which expose the material to be dried to the full tractive effect of the approaching travelling surfaces.

While an illustrative example has been given of the use of curtain means for controlling and improving the feeding of material to be dried, it is to be understood that this has been for illustrative purposes and that the restriction plate or curtain means may have different applications and different structural embodiments. For example, it may be mentioned that while the curtain means has been shown as in contiguous relation with respect to the outside surface of the drum, an analogous effect in reducing the amount of tractive contact of the material passing through the feed throat with the converging travelling surfaces may be accomplished by disposing the curtain means in contiguous relation with the endless conveyor belt means. Moreover, in certain cases the curtain means may be used in contiguous relation with both the outside surface of the drum and the inside surface of the endless conveyor belt means where these surfaces converge to provide the feed throat. It also is to be understood that the curtain means that has been hereinabove described is merely illustrative of apparatus and utilization-of such curtain means for the purpose of controlling and improving the feeding of materials between two surfaces whenever such surfaces travel in the same direction on approaching orbits so as to form a feed throat within which a workable material is exposed to tractive contact with the approaching travelling surfaces.

While an example has been given as regards the construction and proportioning of one type of curtain means, it is to be understood that both the construction and the dimensions may be changed substantially, depending on such factors as the action to be achieved, the type of material being handled by the apparatus and the size of the apparatus as a whole. For use in connection with commercial scale drying operations wherein the material to be dried is a material such as finely divided coal, pigment or sewage, it is preferable to employ curtain means having finger elements which are at least is possible to utilize other types of construction such as a succession of wires, cords or chains which are disposed adjacent at least one of the approaching travelling surfaces in contiguous relation therewith. While it is preferable to use a succession of spaced flexible members which in use drag on the surface of at least one of the approaching travelling surfaces, the curtain means could be rigidly supported so as to be maintained out of contact with an approaching travelling surface so long as the curtain means is in closely contiguous relation therewith so that the regions where material being fed into the feed throat is in contact with the curtain means are in immediately adjacent relation with regions where the material is in tractive contact with the travelling surface. The striplike fingers which are used should be such that the material being dried may readily occupy a the spaces between them for tractive contact with the travelling surface that is contiguous with the fingers.

In its use it has been found that the curtain means which is .a feature of this invention serves to minimize the occurrence of uneven compacting or wadding of material being formed into a layer at the base of the feed throat, which uneven compacting or wadding may be very serious in the handling of certain materials. Moreover, the control on the compaction that occurs in the feed throat aids very materially in enabling the material to travel from one end of the drum to the other under the conditions hereinbelow to be described while the material is being repeatedly removed from the drum and being refed through the feed throat so as to again become sandwiched between the outside surface of the.

drum and the inside surface of an endless conveyor belt means.

At the discharge side of the drier apparatus there is a chute or trough 91 through which dried material is discharged from the drier (see Figs. 1, ll, 12 and 13).

Discharge chute 91 is mounted at its upper end on an upstanding wall 92 that extends longitudinally of the conveyor belt 37 and at the side thereof. A seal means 93 is attached to the bottom edge of the wall 92 and is preferably composed of either a single strip of thin resilient sheet material or a plurality of abutting shorter lengths of such sheet material, e.g., a thin flexible sheet of stainless steel, the lowermost edge of which is resiliently maintained in pressure contact with the upper surface of the bottom run 45 of the endless conveyor belt means 37. A similar wall 92 (see particularly Fig.

11) and seal means 93 are provided at the opposite or feed side of the bottom run 45 of the endless conveyor belt means 37. It is desirable that the walls 92 and 92' and the seals 92' and 93, particularly the latter, be extended as far as possible into the feed throat 54 so as to cooperate with the seal means hereinafter described that is provided between the periphery of the drum 31 and inner surfaces of the conveyor belt means 37 for preventing any loss of material that has been fed into the chamber over the edges of the endless belt conveyor means and so that when the material is compressed and compacted in passing through the feed throat 54 and in becoming sandwiched between the drum surface 52 and the inside surface the endless conveyor belt means will spread in one direction and be caused to travel in movements from the feed side to the discharge side of the chamber 44 as the material is repeatedly removed from the drum and refed therein during the drying operation.

As more clearly shown in Fig. 11 seal means 67 is provided at the top of the 'wall 92 and is resiliently maintained in pressure contact with the under surface of the upper rim 46 of the endless conveyor means 37. The seal means 67 is similarly provided along the upper edge of the side wall 92. Preferably the side walls 92 and 92' have the inwardly sloping portions 68 and 68' respectively.

The ends of the walls 92 and 92' that are adjacent the drum 31 are shaped so as to be contiguous therewith and the opposite ends of the walls are shaped so as to be contiguous with the inner surface of the curved extremity of the'loop portion of the endless conveyor belt means as it passes around the sprocket wheels in supported relation therewith. The side walls 92 and 92' may be supported from frame 30 in any suitable way, e.g., by the employment of brackets 69 and 69 as illustrated in Fig. 11.

It is apparent from the foregoing that an enclosed drying chamber is provided which, except for the side walls 92 and 92', is formed by the moving functional parts of the apparatus. Where portions of the apparatus pass through the side walls, as, for example, the feed chute 71, the discharge chute 91 and the angle 80, appropriate I openings are provided and incoming dryingatmosphere may enter through these openings to compensate for vapor-laden atmosphere exhausted through the opening in the side wall 92. Moreover, as mentioned above it is not essential to operability that the side walls 92 and 92 extend to the top of the chamber 44 but it is important that suitable side wall means he provided along the upper surface of the lower run of the endless con-,

- veyor belt means particularly in the region of the feed throat 54.

Discharge chute 91 slopes downwardly from its upper edge, which is located within aeration chamber 44, to the outside of the main frame and chamber 44 and it rests adjacent its bottom against main frame 30 as indicated in Fig. 13 of the drawings. At its top or material-receiving end discharge chute 91 carries a control element in the form of a short trough 94 pivoted on a horizontal axis at its bottom by a hinge to the top edge of the bottom of chute 91 so that dried material received or caught by it will flow into the chute 91 to be discharged from the drier. Trough 94 is positioned below the bottoms of the angle members and 87 and in the trajectory of material falling from the heated outside cylindrical surface 52 of drum 31 whereby it will catch some of said falling material. Trough 94 may be adjusted about the axis of its mounting hinge by an adjusting rod 95 thereby to adjust the depth to which the top edge of its bottom drawings.

extends laterally into said falling material and consequently to adjust the amount of material removed from the drier apparatus upon each revolution of the drum 31.

The endless conveyor belt 37 includes two spaced endless chains 38 disposed along and forming the marginal edges thereof. One of these chains 38 is shown in detail in Figs. 5, 6 and 7 of the drawings. Each chain 38 is built up of a plurality of yoke shaped links 96 including a knuckle barrel 97 and two side arms 93 that extend therefrom and overlap the ends of the knuckle barrel 97 of the next adjacent link 96. The links are pivotally interconnected by knuckle pins 99 that extend through the ends of the arms 98 of one link and pivot in the knuckle barrel 97 of another. One arm 98 of each link 96 includes an ear or lug 100 to which a flange 101 of an angle member 102 that extends transversely of the conveyor belt 37 and between the spaced chains 38 is bolted. The other flange 103 of the angle member 102 extends at a right angle to flange 101 and is notched adjacent each of its ends as at 104 to clear the ends of the adjacent knuckle pins 99.

As indicated in Fig 6 of the drawings, the flanges 1 of the adjacent angle members 102 all lie at the inside of the endless conveyor belt 37 and adjacent the heated surface 52 of drum 31 and they provide a backing surface for a plurality of overlapping imperforate sheets or liner plates 105 which is flexible only at right angles to the direction of travel of the conveyor belt to permit it to pass concentrically around the drum 3'1 and the sprocket wheels or pulleys 36 and 47.

upright side edges of the notches 104 in the flanges 103 of angle members 102, as clearly shown in Fig. 7 of the The leading end 106 of each of the liner sheets or plates is bent at a right angle and extends between two adjacent angle members 102 and is attached as by rivets 107 to the flange 103. The trailing end or edge 108 of each liner sheet or plate overlaps the leading edge of the next or following liner sheet or plate 105, as indicated in Fig. 6 of the drawings, and the marginal portion of this trailing end may be bent toward the inside surface of the next or following liner sheet or plate in order that when the sheet or plate 105 is forced toward the flanges 1.01 the trailing edge of the liner sheet or plate 105 will be held resiliently in sealing relation with the next liner sheet or plate.

The chains 38 of conveyor belt 37 engage and rotate with peripheral rims 109 one of which is adjacent each I end of the drum 31, and the ends of the drum 31 at the sides of the heating chamber 53 adjacent said rims 109 are sealed to the inside surface of the endless conveyor 37 formed by the liner sheets or plates 105 to prevent material from working or being worked from said chamber 53 at the ends of the drum 31.

The rims 109 are each formed of a plurality of segments (see Fig. 10) bolted onto the end of drum 31 to provide the complete circular rim 109. As best seen in Figs. 7 and 9 of the drawings, each segment of the rim 109 includes a band or tire element 110 and an end element 1 11 that forms a radially inwardly extending flange through which the segment may be bolted to one side of a cylindrical band 112 that surrounds the outside or heated cylindrical peripheral surface 52 of the drum 31 and is welded to the latter. It will be seen from Fig. 7 of the drawings that the thickness of the band 112 and/ or tire 110 may be changed to adjust the distance between the heated surface 52 of drum 31 and the inside surface of conveyor belt 37 and, consequently, the thickness of the heating chamber 53.

Each rim 109 carries a plurality of overlapping rec tangular leaf springs 113 that cooperate to form a resilient compressible ring that surrounds the end of the drum and is compressed by the inside surface of the liner sheets or plates of the endless conveyor 37 as the latter travels concentrically around the drum 31. Each leaf spring 113 is made of a thin rectangular sheet of stainless steel and they are arranged in side-by-side overlapping or shingle-like relation, as indicated in Figs. 5, 6 and 10 of the drawings. These springs 113 extend between the band or tire and the band 112 and are riveted to the inside surface of the band or tire 110, as clearly seen in Fig. 9 of the drawings. The free ends of leaf springs 113, as indicated in Fig. 7 of the drawings, are bent or curved radially outwardly of the drum 31 and bear against the inside surface of the liner sheets or plates 105 of conveyor belt 3 7 as said conveyor belt is carried around the drum. The leaf springs 113 instead of being made of stainless steel may be made of pieces of some other flexible resilient sheet material, and it has been found that such pieces when attached to one arcuate member in side-by-side overlapping relation so that their extremities are maintained in resilient contact with an adjoining arcuate member an effective sealing means is provided between such members. Preferably such resilient contact is provided by causing the pieces to be normally curved and causing pressure contact with the extremities of the pieces to deform them from their normal curvature, as by causing them to be straightened out in the case of the embodiment shown.

In order to remove material which might become packed between the leaf springs 113 and the peripheral surface of the cylindrical band 112 there is provided within the aeration chamber 44 a pair of scraper fingers 114, one for the seal at each end of the drum. These scraper fingers 114 (see Figs. 11, 12 and 13) extend upwardly from and are carried by the angle member 80 of the doctor blade assembly 79. The upper end of each finger 11 4- includes two scraping edges 115 and 116. Scraping edge 115 scrapes material from the heated surface 52 of the drum adjacent the band 112 and scraping edge 116' projects under the leaf springs 11.3 and scrapes material from the peripheral surface of said band 112. Each finger 114 also includes a cam surface 117 over which the leaf springs 113 pass. This cam surface 117 functions to scrape material from. the inside surfaces of the springs 113 and it also tends to maintain said springs properly shaped since the springs 113 are deflected radially outwardly as they pass over the cams 117. It will be seen that material removed from the drum assembly 31 by the scraper fingers 114 will fall directly onto the bottom run 45 of conveyor belt 37.

It may be pointed out here that when the drier apparatus is to be used to dry certain chemicals and foodstuffs it is desirable that the surfaces of the parts of the drier that come in direct contact with the material, such, for example, as the feed chute 71, the inside of the conveyor belt 37, the cylindrical member of the drum assembly 31 that forms the heated surface 52, the scraper blades 77 and 85, the discharge chute 91, etc., be made of a material which will not react with or contaminate the material being dried, or itself be detrimentally acted upon by the material. It has been found that stainless steel is one such material, and although other materials may be used for the purpose, or the parts may be plated with other materials, all of said elements in the machines herein described are made of stainless steel.

It-may also be pointed out here that since the liner sheets or plates 105 of the endlms conveyor belt 37 are attached to the transverse angle members 102 thereof only at their leading edges it is desirable to support them as they travel along the top run 46 of the chain loop between the drum 31 and the sprockets 36 and to shape them as they travel around the sprockets 36. For this purpose a plurality of curved bars 118 having straight upper leg portions 119 are mounted to the main frame 30 with their top leg portion 119 extending from between the sprockets 36 toward the drum 31 (see Fig. 3).

Suitable hold-down arms 120 are provided for hold- 15 ing and shaping the liner sheets or'plates 105 to*cause them to follow the curvature of the conveyor belt 37 where it passes over the tensioning sprockets 47; These arms 120 are each mounted for vertical swinging or pivotal motion about a horizontal axis extending transversely in the aeration chamber 44 by a plurality of axially aligned pivot pins 121 in brackets on an angle member 122 which is supported by members 196 in vertically adjustable relation thereto as by nuts 197 carried by bolts that pass through vertical slots 198 in the member 1% (Figs. 1 and Each arm 120 is urged by a spring 123 to rotate in a clockwise direction, as seen in Fig. 3 of the drawings, and the free end of each am 120 extends into the feed throat 54 and is properly curved to hold and guide the liner sheets or plates 105 as they pass thereunder. These arms 120 are provided for the sole purpose of causing the liner sheets or plates 105 to flex and follow the path of the chains 38. They in no way aid in feeding material either through the feed throat 54 or axially of the drum 31 and may even be omitted in certain embodiments of the invention (see Fig. 16) wherein the tensioning sprockets 47 engage the bottom run 45 of the conveyor belt 37 where the latter becomes'tangent V to the bottom of the drum 31.

. upon the travelling bottom run 45 of the endless conveyor belt 37 adjacent one edge thereof and is conveyed by the conveyor belt 37 through the feed throat 54 and under the restriction plate or curtain means 88. After a being compressed in said feed throat 54 the material is fed or sandwiched into the heating chamber 53 and carried therein, while being heated by the heated surface 52 of the drum 31, from the bottom of the drum up or around one side-of the latter and into the top of the aeration chamber 44. The material will, of course, be quite hot when it enters the top of the aeration chamber 44 and immediately upon passing from the heating chamber 53 it will be exposed to air in the aeration chamber and will begin to give up to it some of its fluid content. It will be apparent that, as previously described, most of the material after leaving the heating chamber will adhere in the form of a blanket to the heated surface 52 of the drum and will travel with it substantially through .a quadrant or 90 arc of travel until said material is scraped therefrom by the doctor blade 85. While said :material is adhering to and travelling with said heated :surface 52 throughout said quadrant it is, of course, still Ibeing heated, with the result that some of its fluid constituent, generally water, may be driven by said further Fheating from the material and into the air in the aeration chamber 44.

The doctor blade 85, as previously described, scrapes, :breaks or digs the material from the outside heated surface 52 and in so doing disintegrates the material, thereby exposing more surface or surfaces thereof through which the material may give up its moisture to the air in the aeration chamber 44. The material may be further disintegrated in the aeration chamber 44 when it strikes the bottom run 45 of the conveyor belt 37. It will be seen that the effect, which may be compared to a splashing effect, on the material upon striking or impacting upon the bottom run 45 of conveyor belt 37 will tend to cause the material to become more evenly distributed upon the conveyor. Likewise when the material is forced through the feed throat a very substantial crushing action takes place so as to disintegrate lumps that may be present in the material to be dried either when it is fed into the apparatus orastheresult of caking on drum surfac e during those intervals when it is in the drying chamber 53 between the drum surface and the endless conveyor belt means. Some materials, such, for example, as certain pigments, tend to become caked into lumps that, if not broken up, are relatively difiicult to dry because of the extent of the travel of liquid to be removed from the interior to the exterior of the lumps. However, by intially breaking up such lumps and likewise breaking up and crushing any lumps formed during the drying operation, the rate and uniformity of the drying is greatly improved. 7

The above described travel of material by the conveyor belt 37 from the aeration chamber 44, around the drum 31 in the heating chamber 53 and replacement of the material upon the conveyor belt 37 is repeated numerous times by the same material as it works or is worked axially along the drum in the heating chamber53 from the feed side to the discharge side thereof; The number of times any given quantity of material rotates around said drum 31 and hence also the rate of lateral travel may be controlled by controlling the amount of .material removed from the apparatus at the discharge end of the drum 31. This may be determined by adjusting the receiving portion 94 of the discharge trough to catch more or less of the material scraped from the drum 31 as it falls in the aeration chamber 44. be seen that the rate of feed of material through the apparatus may be controlled merely by balancing the rates of feed of material into and out of the machine by adjusting the speed of operation of the primary feeder 55 and the position of the discharge trough 94, and thus the material being fed through the machine may beretained therein and subjected to drying action for various periods of time, as may be necessary, to dehydrate or dry it to any desired percent of fluid content.

It has been found that the lateral travel of the material to be dried may be effected and controlled in a very desirable manner as has been referred to hereinabove. During drying the removal of fluid such as water results in change in the physical characteristics of the material. One of these changes that frequently occurs is overall shrinkage of the material and this presents certain prob lems in keeping the content of the space between the drum and the endless conveyor belt means full and under desired conditions of compactness throughout the lateral extent of the drum. By feeding the material to be dried adjacent one end of the drum at which a seal is maintained between it and the inner surface of the endless conveyor means as the material is sandwiched therebetween a gradual movementof the material occurs from adjacent the feed end of the drum to adjacentthe discharge end as the'material is repeatedly fed so as to. be carried on the surface of the drum, removed and refed thereon. Moreover, notwithstanding changes in the physical characteristics of the material while being dried, the drying chamber 53 remains full and in like condition of compaction along the lateral extent of the drum for it is the material itself which in being compacted under lateral pressure differential conditions that pushes other portions of the material ahead of it, thus preventing the possible formation of zones of low pressure or even voids. Moreover, the presence of the curtain means greatly assists in maintaining the desired conditions by' reducing somewhat the extent to which the material is' compacted in being reduced to the thickness of the chamber 53 and thereby retaining greater workability so that the lateral migration is more effectively obtained However, movement laterally of the drum also will occur but in a less desirable manner even if the curtain means isomitted.

In Figs. 14 and 15 there is shown a modified form of feeder mechanism which may be employed in thelembodiment of the apparatus shown in Figs. 1, 2,. 3 and.4 or that of Figs. 16, 17 and 18 of the drawings. ,In this mechanism a restriction plate. or curtain means 188 similar to It will thus cin'tainirneansfi sis hungor suspended from its upper end on a plurality of chains 124 attached to a rod- 125 that extends transversely through the aeration chamber 44 and which is mounted for rotation at its opposite ends in bearing blocks 126 attached .to the legs 81 of the doctor blade assembly 79. Rod 125 may be rotated by a crank 127 to raise and lower the curtain means 188 and the rod is provided with a ratchet wheel 128 that is engaged by a dog 129 on one of the brackets "83. It will be seen that by rotating the rod 125 the depth to which the bottom ends of the fingersior strips 190 extend into the feed throat 54 may be adjusted and that such adjustment of the curtain means 188 will also adjust. the action thereof in the feed throat 54 as well as the feed rate.

Figs. 16, 17 and 18 showa modification of the machine shown in preceding figures of the drawings, in which the aeration space corresponding to the aeration chamber or space 44 is enclosed by an upright wall or confining partition 129 extending transversely ofthe main frame 30 and betweenzthe upper and Flower runs 46 and 45, respectively, of the endless conveyor belt 37 and with the upper and lower edges thereof, respectively, contiguous therewith. The aeration space between. the wall 129 and the heated surface .52 of drum 31 is divided by an upright dividing partition 130 into two sideby- side aeration chambers 132 and 133 and the outermost ends of these chambers 132 and 133 are closed by identical upright walls 134 provided with wiper or seal strips 135 that engage the inner surface of the' bottom run 45 of the endless conveyor belt 37. Dry air may be introduced into each of the aeration chambers 132 and 133' through ducts or conduits 136 and air containing fluid removed from material being aerated in the chambers may be removed from the latter through ducts or conduits 137, each of which may be connected with an exhausting device 66 which may, for example, comprise an exhausting fan. Embodiments of this in vention comprising a dividing partition such as the partition 130 are preferred due to the fact that by causing the material to be disposed in a different separated zone during the final stages of drying when dusting tends to occur, the dust-laden drying atmosphere from which it 'may be desirable to remove dust by means of a dust collector may be cut down, e.g., to only about 2% or 3% of the total drying atmosphere used to carry away vapor being separated from the material during drying.

In the embodiment shown in Figs. l6, l7 and 18 the lower end of the primary feed chute 71., which may be in the form of a duct, not shown, is extended through an opening 138 in the wall 134 at the feed side of the machine .and the discharge chute '91, .94 may extend from the aeration chamber 133 through a similar opening in the other end wall 134. It will be noted that in this embodiment of the apparatus the sprockets 147 corresponding generally to sprockets 47 do not function to adjust the tension of the endless belt conveyor but are located directly under the drum 31 and support the endless conveyor 37 immediately below the point where it feeds onto and is tangent with the drum 31. The sprockets 147 are placed in this location to assist in holding the conveyor belt 37 tangent to the drum 31 at the discharge end of the feed throat to and it in compressing material both in the feed throat and where it enters the heating chamber 53. To resiliently :maintain the endless conveyor belt means under tension the bearing 35 for the axle 36 is spring loaded by resilient "means such as the spring means 199. ld hen sprockets 147 are in the position shown in Fig. 14 it is not necessary to employ holddown arms adjacent the feed throat such as the arms 12] shown in Fig. 3.

In Figs. '19, 20 and 21 there is shown a modified form of heating 131 and mechanisms associated with it that may be substituted for the drum 31 in the embodiment of the machine shown in Figs. 1, 2 and 3 or in Figs.- 14, 15 and 16 of the drawings. In this modified structure the drum 131 is formed of two cylindrical tubes 139 and 140, one within the other and mounted to rotate concen' trically about the axis of a central shaft 141. The inner tube 1391is of greater length than the outer tube and projects axially at its ends beyond the end of the outer tube 140. The cylindrical space, steam or hot water chamber 142, provided between the inside surface of the outer cylinder or tube 140 and the outside surface of the inner cylinder or tube 139 is closed at the ends of the outside cylinder 140 by a pair of identical rings 143 welded to both cylinders 139 and 14%. The outside cylinder 141i is provided at each of its ends with structure identical to that shown in Figs. 5, 6, 7 and 8 of the drawings for re ceiving the chains 38 of the endless conveyor 37 and for sealing the ends of the heating chamber 53 provided between the circumferential surface of the outer heated peripheral surface 52 of the outer cylinder or tube 141) and the inside surface of the endless conveyor belt 37.

The cylinders or tubes 139 and 140 are carried as an assembly upon a central shaft 141 by a plurality of tubular conduits in theform of spokes 144 which connect the steam chamber 142 with the hollow ends of the shaft 141. It will be seen that steam, or hot water, introduced into one end of shaft 141 will flow through the spokes 144 connected therewith into and through the steam or hot water chamber 142 to the spokes at the opposite endof the inner cylinder 132 and through these latter spokes to be exhausted from the drum 131 at the opposite end of the shaft 141.

Within the cylinder 139 there is another cylinder 172 that is carried by the spokes 144 which is separated from the cylinder 139 so as to leave an air space which provides a certain amount of insulation whereby the inner surface of the cylinder 172 will be maintained at a lower temperature than would be the case if the inner surface of the drum were to be provided by the inner surface of the cylinder 139. If a greater temperature differential is desired a heat insulation material could be placed between the cylinders 139 and 172. It also would be possible to effect other control as by connecting the space between the cylinders 139 and 172 so as to pass therethrough some fluid for controlling the temperature of the inner surface of the cylinder 172. Alternatively, the cylinder 172 may be omitted. In any case, it is apparent that the structure of the apparatus may be such that the inner surface of the drum may be maintained at whatever temperature may be desired.

In the embodiment shown in Figs. 19, 20 and 21, the doctor blade 85 which is located as shown in the preced ing figures is terminated so that for discharge of material from the apparatus a second doctor blade section 173 is used which causes material that is scraped off thereby to be discharged onto the inclined screen 174 which is such that any lumps of substantial size do not fall therethrough but are returned to the endless conveyor belt means to be refed into and through. the throat 54 wherein the lumps are crushed and disintegrated. The liner material, on the other hand, passes through the screen 174 and is caught by the chute or slide which conveys the partially dried material to the .inside of cylinder 172 which is preferably provided with a smooth or even polished inner surface so that the partially dried material will tend to slide on the surface without subs'tautial tumbling or agitation. In order to minimize any tumbling of the partially dried material the spokes 144 are preferably streamlined so as to present the narrow edges as shown in Fig. 21. During operation and continued rotation of the drum the material fed into the inside of cylinder 172 while sliding on the inner surface will gradually work itself to the other end of the cylinder where it may be discharged as onto the discharge chute 146. To assist in the travel to the discharge end of the inner cylinder 172, the vertical disposition of the surface over which the material flows in being discharged is somewhat lower than the level of the upper edge of the annular wall 205 or other confining means at the feed end of cylinder 172. Such differential in level may be accom-

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