US3196555A - Drying apparatus - Google Patents

Description

July 27, 1965 w. FRIEDEL ETAL 3,

DRYING APPARATUS Filed Oct. 3, 1961 3 Sheets-Sheet 1 -CAPACITY MEANS (WEAK BLOWER) HIGH- CAPACITY SUCTION MEANS (STRONG FIG.|

TmvEmoRs: I 21 2Q WolfgangFriedel BY Heinz Fleissner AGENT.

5 Sheets-Sheet 2 Wolfgang Friedel Heinz Fleissner INVENTORS.

flw WAGENT w. FRIEDEL ETAL DRYING APPARATUS ll @@@@ZQO@Q@ lIr/II/I/ IIYIIIIII/I/ Ill/J July 27, 1965 Filed Oct. 3, 1961 Q Q 5 O O O G O O Q 0 0 0 0 0 6 FIG.5

July 27, 1965 w. FRIEDEL ETAL 3,196,555

DRYING APPARATUS Filed Oct. 3, 1961 3 Sheets-Sheet 3 AGENT of its periphery to define the suction area. particularly advantageous in the case of overshot drums United States Patent F 32,263; Get. 27, 1960, F 32,423 8 Qlaiins. (Cl. 34--115) Our present invention relates to a drum-type dryer for pervious or impervious materials such as veneer, textile sheets, fibrous or granular material, etc.

It is the general object of our invention to provide an improved drying mechanism of the type wherein the goods to be processed are carried by suction on alternate ly the upper. and the lower surface of a plurality of drunn rotating about substantially horizontal axes. v A more particular object of this invention is to utilize the action of gravity in alternate drums for minimizing the power requirements of the air blowers used as suction creating means.

An important feature of our invention resides in the provision of circulation means adapted to deliver the treatment fluid (usually air) at a relative high pressure to a lower plenum chamber, communicating with the interior of one or more drums through a perforated lower portion of their respective peripheries, and at a relatively "low pressure to an upper plenum chamber, communicating with the interior of the remaining drum or drums througha perforated upper portion of their peripheries.

The difference in delivery pressures may be realized most conveniently with the aid of two blowers of different power. These blowers may respectively discharge into the two plenum chambers while aspirating the treatment fluid in a closed circuit from the interior of the drums communicating with these chambers; with an alternate mode of operation, however, we provide the stronger blower with two outlet ports of substantially equal crosssectional area respectively serving the two plenum chambers while the weaker blower has but a single outlet which opens into the lower chamber to supplement the pressure created therein. In a system enabling a switchover from onemode of operation to the other, the ratio of the pressure differentials effective at the lower and upper drum surfaces may then be selectively established at (p-l-q) p such contact is necessary or desired. To this end we prefer to provide some or all of the drums, especially the undershot ones or those which receive and/or transmit thetreated material at locations substantially below their horizontal median plane, with special internal nozzles forming extensions of the suction ports of the associated circulation means and terminating close to the inner p..- ripheries of the drums. These nozzles are preferably adjustable as to their edective cross-sectional area which may extend over the entire width of the drum or be confined to specific zones, e.g. at the center and near the ends. Since the most critical locations in need of augmented aspiration are the generatrices where the material to be dried meets and leaves the periphery of the drum, it will be advantageous to mount such nozzles directly on the edges of the shield plates internally obstructing a portion This will be embraced by the load layer over an arc greater than the nozzles then serving to supplement, at locations below the median horizontal plane of the drum, the relatively weal: pressure differential prevailing along the greater part of the working surface.

The above and other objects, features and advantages of the present invention will become more fully apparent from the following detailed description, reference being made to the accompanying drawing in which:

FIG. 1 is a side elevation of a dryer embodying the in vention, with the front wall of its housing omitted;

FIG. 2 is a cross-sectional view taken on line III1 of FIG. 1;

FIG. 3 is a cross-sectional view taken on line IIIIIl of FIG. 1;

PEG. 4 is a View similar to FIG. 1 (parts broken away) illustrating an alternate embodiment of the invention with more than two drums;

FIG. 5 is an axial sectional view of one of the drums of the system of FIG. 4; and

FIG. 6 is a sectional detail View, drawn to a lar er scale, on the line vr vr of FIG. 4. D

The embodiment shown in FEGS. l and 3 comprises two peripherally perforated drums i and 2. that rotate on horizontal shafts 3, 3 in bearings 4+, 5 and 4', 5 and are driven in synchronism by a suitable power source 26 The end of each drum facing power source 20 is solid and sealed to the shafts 3, 3'. The other ends of the drums are open and peripherally embraced by flanges 6 and 7 surrounding the intake ports of blowers 8 and 9 driven through beit-and-pulley transmissions 1t) and is by motors 11 and 11. The blowers 8, 9 suck the air from the interior of the perforated drums and blow it out through exhaust ports i2, 12. and i3, 13. These exhaust ports, the surrounding machine housing 14 and partitions is, 15 therein constitute guidance means to direct the air flow to the plenum chambers 16 and 17 of drums 1 and 2 its ports 12, 13 and ports 32, 13' serving the lower chamber 16 and the upper chamber 17, respectively. The suction area of the undershot drum 1 is confined to its lower portion by a shield plate L; while the suction area of the overshot drum 12. is confined to its upper portion by a shield plate 19. The shield plates 1-3 and 39 are mounted by bolts 33, 34 on the flange portions 6, 7 of the associated blowers along with the inner bearings 5, 5' of the drum shafts 3, 3, those bearings being supported on spiders 35', 36.

Air is drawn into drum 1 from chamber 16 around a coherent layer 25 of material to be treated and/or through the interstices thereof. it is then driven by blower 3 into outlet ducts 12 an 12 which split the air stream delivered by this blower into two flows respectively issuing above and below the common axial plane of the drums. Outlet duct 12 and partition 15 guide the airflow thereof over lower heating elements 21 and back into chamber 16 for recirculation through and/or around the layer 25. Air leaving outlet duct 12 passes around partition 35' over upper heating elements 21 into drum 2 whence it is extracted by blower 9 and returned via outlet 13 (outlet 13 being considered closed) into chamber 16 for recirculation. Thus, the upper air flow passes through both drums in cascade whereas the lower air iiow circulates only through the drum 1 which carries the layer 25 along tis underside and which in this manner is given the extra air-pressure differential needed to overcome the opposing force of gravity.

The drying system provided by this invention is essentially a closed-circuit system; in order to remove the moisture extracted from layer 25, conventional dehumidifiers 5t and 50'v are provided ahead of heaters 21, 21' in the path of the air streams directed into plenum chambers 16 and 17, respectively. Dehumidifiers 50 and 50 are equipped with integral catch pans 51, 51, drains 2, 52, coolant inlets 53, 53' and coolant outlets 54, 54', respectively.

r The material to bedried is delivered by a conveyor belt 26 tothe underside of drum 1. The conveyor rides on rollers 27 and 27, one or both of which are driven by conventional means not further illustrated. The material is forced against the bottom of drum 1 by the difference in pressure existing between the plenum chamber 16 and the interiorv of drum'l. By the rotation of the drum the material 25 is carried' to drum 2 across, the intervening gap,'the;pressure difference between the interior of dr1un,2and its plenumlchamber 17 causing the material'to adhere to'the upper surface of drum 2 which conveys it to a d'ischargechute 28.

In the embodiment of the invention thus far described, wherein two drums 1 and. 2' are served by two blowers with th'reeactive exhaust ports 12, 12' and 13, if blower 8 has a speed of n revolutions per minute, blower 9 (having the same characteristics) will preferably have a speed of n/ 2 revolutions per minute. The pressure delivered by blower 9, which discharges through only one port, will then be one fourth of that delivered by blower 8,:the power requirement of blower 9Lbeing thus only one eighth of that of blower 8 since the former circulates only half the air volume of the latter. I

In order to enable different modes of operation ofthe system of FIGS. 1-3, the exhaust outlets 1 2-, 13 and 13' of blowers 8 and 9 are each provided with a set of louvers 29, 31, and 31. Each setrof louvers can be opened or closed independently by conventionalmanual controls 30, 32 and 32, illustrated schematically; v By closing louvers 29 and 31 while opening louvers 31' it is possible to isolate each drum into a separate operating. unit This louver'setting applies the full force of the more'powerful blower 8 to the underside of drum 1 while directing the entire output of the otherblower-9 onto the top surface of drum 2, thereby. again establishing at the undershot V drum a pressure differential greatly exceeding that prevailing at the .overshot drum.

This invention is not restricted to the 'use'of blowers with identical characteristics; the blowers may beof different diameters and operate at the same or different rotative speeds; Thus, '1ow-, middle-, and high-pressure blowers can be used in various combinations; Changes in 7 speed and/or adjustable baflies similar to louvers 12,13,

13 may, of course, be usedto control the output pressure of each blower withinspecified limits.

In FIG. 4 a plurality of "drums are illustrated with their axes of rotation vertically offset from one another, thus .providingan arc of contact greater than 180 and affording an extension of the. drying regime, optimum space utilization, and maximum drying area on each drum. This embodiment of my invention comprises four. drums 1a, 2a, 1b, 2b which alternately transport the load layer 25 on their lower-and upper surfaces. Shield plates 18a, 19a, 18b and 1911 block OK the inoperative portions of their respective drum surfaces.

Drums 1a, 2a have been shown in section whereas drums 1b and 2b, respectively identical therewith in their internal construction except for the extent and location of their shield plates, are seen in view; The respective drum shafts have been designated 3a, 3a, 3b 'and 3b; the'rear bearings 5, 5a of the two first-mentioned shafts are visible, as are their spider supports a, 35a in the intake ports of blower flanges 6a and 7a, respectively. ,Flanges 6a and 6b, supporting by means take-forming flanges 7a and 7b of another blower 109 whose sole outlet port 113 delivers the dried and reheated air to the top surfaces of overshot drums 2a, 2b overlain by layer 125. This layer is introduced into the housing 114 by a conveyor 126 and discharged from it via a chute 128.

In the system of FIGS; 46 it is necessary toprovide in creased aspiration not only on the lower peripheral surfaces of drums 1a, 112 but also along part of the surfaces of drums 2a, 2b, i.e. atthe locations where the layer 125 contacts these overshot drums below their median horizontal plane. For this purpose we prefer to provide, in accordance with a feature of'our inventio n, special means designed to concentrate or reinforce the suction of blower 109 along these lower contact areas of drums 2a,'2b while correspondingly weakening the pressure differential at the upper peripheral halves of the drum. An effective arrangement for accomplishing thisresult comprises a nozzle for each of these contact areas, drum 2a being accordingly equipped with a pair of such nozzles 40', 40, respectively facing the areas T, T nearest the gaps bridged by the layer 125 in its transfer from drum 1a to drum 2a and from the latter to drum 1b. Similarnozzles, notshown, are present at the corresponding areas. of drum 2b; they could,-if desired, also be included in either or bothof the remaining drums if increased suction were desired at certainperipheral locations thereof. I I V a The nozzles 40, 40' 'are 'carried alongopposite axially extending edges of shieldplate 19a and, as particularly illustrated for nozzle 40 inFIGS. 4 and 5 consist each of two relatively adjustable halves 41,1 42 defining a nozzle of bolts 133 the shield plates lfia and 18b of undershot j drums 1a andllb, form the two intake ports of a single" blower 108 whose sole outlet port 112 returns the stream of drying air via dehumidifiers and heaters, .not illustrated mouth of variable intake area. Lower nozzle half 41 is integral with shield plate 19a and therefore fixedly positionechupper nozzle half 42 is hinged at 43, 44 to a pair of pivot pins on opposite ends of-a slot 45 formed in an exhaust duct .46 which extends axially within drum 2a from the intake port of' blower. flange 7a and partially registers with this port to communicate its suction to the two nozzlesj40, 40'- served by it. Adjustment of the nozzle width is carriedout with the aid of a pair of wires 47,47 which are anchored to the .outer extremities of movable 'nozzlehalves42, 42 and passoutwardly of housing 14 via a narrow tube48 traversing the partition their other ends are shown attached to a ring- 49 adapted to v be selectively slipped over'hooks'61, 62 on'the outside of housing114, this arrangement being of course representative of any conventional mechanism for elevating the nozzle sections 42, 42' (e.g.'against the force of gravity) 1 to a greater or less extent. It will also be apparent that lower nozzle halves 41, 41' could, if desired, be divorced from shield plate 19a and hinged to the duct 46 in the same manner 'as nozzle halves 42, 42 for controlled positioning jointly with the latter or independently therefrom. 'Packing strips 63, 64 are carried on the triangular end walls of nozzle halves 41, 41 to contact the end'walls of nozzle halves 42, 42':so as to minimize the escape of air therebetween without interfering with the'relative motion of these parts. I

The effective length ofeach nozzle mouth, as will be apparent from FIG. 5, equals substantially the axial 'width'of'the perforated portion of the drum periphery and, accordingly, the corresponding dimension of layer although the width of the latter may be somewhat 1 reduced, particularly in the case of impervious material,

to enable the suction air to flow around it. In some instances, especially with layers of good transverse co- "herency, a 'further'selective increase in pressuredifferential may be realized by concentrating the effect of the blower oncertain axially limited zones of the perforated 7 '0' geously, along'thelongitudinal edges in the median region of the layer. 'For'this purpose we have shown in FIGS.

drum surface. ,Such zones may be located, advanta- 46 a set of arcuate cover plates 71, 71' disposed in the clearance between shield plate 19a and the peripheral. wall 'ofdrunr 2a,:these coversbeing mounted p the shield plate with freedom of angular displacement into or beyond the positions illustrated in dot-dash lines in FIGS. 4 and 5. The covers 71, 71' are provided in axially spaced pairs so as to register with two annular drum zones Z located between the extremities and the center of the perforated surface. As best seen in FIG. 6, sleeve 19a carries on its outer periphery an arcuate rail 72 slidably engaging a pair of mating brackets 73, 74 on the inner surface of each cover 71. Between these brackets the cover is formed with a rack 75 meshing with a pinion 76 whose shaft 77, common to both plates 71, is journaled in the rails 72 thereof and extends outwardly through partition 115 and housing 114, its projecting end carrying a knob '78 whose manipulation enables angular displacement of the respective cover pair. Again, such cover plates may also be provided on the remaining drums, if desired, in order to control the advance of layer 125 as it meanders along an undulating path around the successive drums.

The selective intensification of suction at critical loca tions, by means of nozzles 4d, 40' and/ or cover plates 71, '71, enables the use of a relatively weak blower 109 in comparison with blower 168. Such intensification requires, in the case of nozzles, that the ratio of the intake area of duct 46 to the combined area of the nozzle mouths, i.e. the sum of the areas T, T registering therewith, be greater than the ratio of the remaining area of the blower port (unobstructed by duct 36) to the free perforated area of the drum, i.e. the surface area thereof not registering with either the shield 19a or the nozzles 46, 40. It will be seen that, under these conditions, the pressure differential at the last-mentioned surface area of rums 2a, 2b will be weaker than that at the free areas of drums 1a, 1b even if the two blowers 168, 109 are of equal power or are, in fact, parts of the same circulation system.

The present improvement is, of course, not limited to the specific mechanical details described and illustrated as modifications and adaptations thereof, which will be readily apparent to persons skilled in the art, are intended to be embraced within the spirit and scope of our invention as defined in the appended claims.

We claim:

1. A system for drying a coherent layer of material, comprising a plurality of closely spaced drums including at least one undershot drum and at least one overshot drum rotatable about parallel horizontal axes, said drums being provided with perforated peripheral wall-s, first fluid-circulating means having an intake port communicating with the interior of said undershot drum for subjecting same to a relatively strong suction, second fluid circulating means having an intake port communicating with the interior of said overshot drum for subjecting same to a relatively weak suction, each of said circulating means having at least one outlet port, drive means for rotating said drums in unison and adapted for carrying a layer of a material to be dried on the underside of said undershot drum and on the topside of said overshot drum, shield means within said drums registering with portions of said walls not adapted to be covered by said layer, thereby rendering the respective circulating means ineffective .at said portions, guide means for directing the outflow of said outlet ports onto the outer surfaces of said drums at locations adapted to be covered by said layer, said first circulating means comprising a relatively strong blower and said second circulating means comprising a relatively weak blower, said strong blower having two outlet ports and said weak blower having one outlet port, said guide means directing the outflow from said two outlet ports of said strong blower onto the surfaces of both of said drums adapted to be covered, respectively, and the outflow of said one outlet port of said weak blower onto the surface adapted to be covered of said undershot drum only, said strong blower having an out-put pressure substantially douole that of said weak blower.

2. A system for drying a coherent layer of material, comprising a plurality of closely spaced drums including at least one undershot drum and at least one overshot drum rotatable about parallel horizontal axes, said drums being provided with perforated peripheral walls, first fluidcirculating means having an intake port communicating with the interior of said undershot drum for subjecting same to :a relatively strong suction, second fluid circulating means having an intake port communicating with the interior of said overshot drum for subjecting same to a relatively weak suction, each of said circulating means having at least one outlet port, drive means for rotating said drums in unison and adapted for carrying a layer of a material to be dried on the underside of said undershot drum and on the topside of said overshot drum, shield means within said drums registering with portions of said walls not adapted to be covered by said layer, thereby rendering the respective circulating means ineffective at said portions, and guide means for directing the outflow of said outlet ports onto the outer surfaces of said drums at locations adapted to be covered by said layer, said overshot drum having a peripheral region below its median horizontal plane exposed to the suction of said second circulating means and adapted to be covered by said layer, further com-prising suction-reinforcing means within said overshot drum registering with said peripheral region.

3. A system according to claim 2 wherein said suctionreinforcing means comprises a nozzle mounted on the shield means of said overshot drum and communicating with the intake port of said second circulating means.

4. A system according to claim 3 wherein said nozzle has a mouth of adjustable cross-sectional area positioned adjacent said peripheral region, further comprising mechanism positioned externally of said overshot drum and coupled with said mouth for adjusting same.

5. A system according to claim 4 wherein said mouth includes a pair of relatively movable sections, at least one of said sections being connected with said mechanism.

6. A system for drying a coherent layer of material, comprising a plurality of closely spaced drums including at least one undershot drum and at least one overshot drum rotatable about parallel horizontal axes, said drums being provided with perforated peripheral walls, first fluidcirculating means having an intake port communicating with the interior of said undershot drum for subjecting same to a relatively strong suction, second fluid circulating means having an intake port communicating with the interior of said overshot drum for subjecting same to a relatively weak suction, each of said circulating means having at least one outlet port, drive means for rotating said drums in unison and adapted for carrying a layer of a material to be dried on the underside of said undershot drum and on the topside of said overshot drum, shield means within said drums registering with portions of said walls not adapted to be covered by said layer, thereby rendering the respective circulating means ineffective at said portions, guide means for directing the outflow of said outlet ports onto the outer surfaces of said drums at locations adapted to be covered by said layer, and coverplate means within at least one of said drums for obstructing an axially limited peripheral zone thereof at a location beyond said shield means, said overshot drum having a peripheral region below its median horizontal plane exposed to the suction of said second circulating means and adapted to be covered by said layer, further comprising suc-tion-reinforcin g means within said overshot drum regis tering with said peripheral region.

7. A system according to claim 6 wherein said cover means comprises an angularly displaceabl-e member adjacent the inner peripheral drum surface and mechanism for selectively displacing said member.

8. :In a system for drying a coherent layer of material,

provided with perforated peripheral walls; first and second fluid-circulating means each having an intake port communicating with the interior of said under-shot and said' overshot drum, respectively, for subjecting same to suction, each of said 'fluid-circul-atingrmeans having at least one outlet port; drive means for rotating said drums in unison and adapted for carrying a layer of a material to be dried on the underside ofsaid under-shot drum and on t the topside of said overshot drum; shield means within each of saiddrums registering with portions of s-aid walls not adapted to be covered by said layer,- thereby rendering the-respective circulating means ineffective at said portions; and guide means for directing the outflow of said outlet ports onto the outer surfiaces of said drums at locations adapted to be covered by said layer, the suction force created by said first fluid-circulating means in said undershot drum being greater than the suction in said over-shot drum, said guide means being positioned to direct the outflow of the outlet port'oft'he second circulating means through both of said drums and to direct the outflow of the outlet port of said first circulating means through said undershot drum only.

References Cited by the Examiner UNITED STATES PATENTS 2/40 Mellor L. 34-77 FOREIGN PATENTS 1,038,517 9/58 Germany.

828,008 2/60 Great Britain.'

PERCY L. PATRICK, Primary Examiner. NORMAN YUDKO'EF, 'Exar niner.

Claims (1)

1. 8. IN A SYSTEM FOR DRYING A COHERENT LAYER OF MATERIAL, THE COMBINATION COMPRISING A PLURALITY OF CLOSED SPACED DRUMS ADAPTED TO BE TRAVERSED BY SAID LAYER INCLUDING AT LEAST ONE UNDERSHOT DRUM AND AT LEAST ONE OVERSHOT DRUM ROTATABLE ABOUT PARALLEL HORIZONTAL AXES, SAID DRUMS BEING PROVIDED WITH PERFORATED PERIPHERAL WALLS; FIRST AND SECOND FLUID-CIRCULATING MEANS EACH HAVING AN INTAKE PORT COMMUNICATING WITH THE INTERIOR OF SAID UNDERSHOT AND SAID OVERSHOT DRUM, RESPECTIVELY, FOR SUBJECTING SAME TO SUCTION, EACH OF SAID FLUID-CIRCULATING MEANS HAVING AT LEAST ONE OUTLET PORT; DRIVE MEANS FOR ROTATING SAID DRUMS IN UNISION AND ADAPTED FOR CARRYING A LAYER OF MATERIAL TO BE DRIED ON THE UNDERSIDE OF SAID UNDERSHOT DRUM AND ON THE TOPSIDE OF SAID OVERSHOT DRUM; SHIELD MEANS WITHIN EACH OF SAID DRUMS REGISTERING WITH PORTIONS OF SAID WALLS NOT ADAPTED TO BE COVERED BY SAID LAYER, THEREBY RENDERING THE RESPECTIVE CIRCULATION MEANS INEFFECTIVE AT SAID PORTIONS; AND GUIDE MEANS FOR DIRECTING THE OUTFLOW OF SAID OUTLET PORTS ONTO THE OUTER SURFACES OF SAID DRUMS AT LOCATIONS ADAPTED TO BE COVERED BY SAID LAYER, THE SUCTION FORCE CREATED BY SAID FIRST FLUID-CIRCULATING MEANS IN SAID UNDERSHOT DRUM BEING GREATER THAN THE SUCTION IN SAID OVERSHOT DRUM, SAID GUIDE MEANS BEING POSITIONED TO DIRECT THE OVERFLOW OF THE OUTLET PORT OF THE SECOND CIRCULATING MEANS THROUGH BOTH OF SAID DRUMS AND TO DIRECT THE OUTFLOW OF THE OUTLET PORT OF SAID FIRST CIRCULATING MEANS THROUGH SAID UNDERSHOT DRUM ONLY.

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