CA1041756A - Method and apparatus for conditioning tobacco - Google Patents
Method and apparatus for conditioning tobaccoInfo
- Publication number
- CA1041756A CA1041756A CA204,572A CA204572A CA1041756A CA 1041756 A CA1041756 A CA 1041756A CA 204572 A CA204572 A CA 204572A CA 1041756 A CA1041756 A CA 1041756A
- Authority
- CA
- Canada
- Prior art keywords
- tobacco
- particles
- path
- moisture content
- current
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
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- A—HUMAN NECESSITIES
- A24—TOBACCO; CIGARS; CIGARETTES; SIMULATED SMOKING DEVICES; SMOKERS' REQUISITES
- A24B—MANUFACTURE OR PREPARATION OF TOBACCO FOR SMOKING OR CHEWING; TOBACCO; SNUFF
- A24B3/00—Preparing tobacco in the factory
- A24B3/04—Humidifying or drying tobacco bunches or cut tobacco
Landscapes
- Manufacture Of Tobacco Products (AREA)
- Storage Of Fruits Or Vegetables (AREA)
- Drying Of Solid Materials (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
The moisture content of tobacco, particularly greenleaf tobacco, is reduced to an accurately determined value by conveying a continuous tobacco stream through three successive sections of a transporting system wherein the tobacco is contacted by air currents.
The particles of tobacco are subjected to the homogenizing action of moist air currents in the third and/or first section of the trans-porting system whereby the homogenizing of tobacco in the first sec-tion insures that tobacco entering the second section has a uniform moisture content and the homogenizing in the third section compen-sates for eventual lack of uniform drying action in the second sec-tion.
The moisture content of tobacco, particularly greenleaf tobacco, is reduced to an accurately determined value by conveying a continuous tobacco stream through three successive sections of a transporting system wherein the tobacco is contacted by air currents.
The particles of tobacco are subjected to the homogenizing action of moist air currents in the third and/or first section of the trans-porting system whereby the homogenizing of tobacco in the first sec-tion insures that tobacco entering the second section has a uniform moisture content and the homogenizing in the third section compen-sates for eventual lack of uniform drying action in the second sec-tion.
Description
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~ The present invention relates to a method and apparatus . , .
for conditioning tobacco particles, and more particularly to a method and apparatus for conditioning tobacco particles in the form of whole leaves, laminae, ribs and stem and/or shreds which preferably form a continuous stream~and are transported through a series of con-ditioning zones. ~till more particularly~ the invention relates to improvements in a method and apparatus for conditioning tobacco par-ticles by means of a gaseous fluid, preferably air.
Many treatments of tobacco must be preceded by increasing '! ', its mois~ure content so as to enhance the flexibility of tobacco particles (e.g.~ prior ~o shredding) and to thus reduce the likeli- -hood of undesirable breakage or comminution and the formation of dust. It is also known to treat tobacco with a variety of substan-ces ~known as casing) in order to improve its aroma; such treatment also involves increasing the moisture content of tobacco. At least some moisture must be expelled from tobacco prior to final process-ing into cigarettes, cigarillos, cigars, pipe tobacco, chewing to-bacco and/or other types o~ smokers~ products. For example, prior to feeding tobacco shreds into a modern mass-producing cigarette
~L~3 ,. . .
~ The present invention relates to a method and apparatus . , .
for conditioning tobacco particles, and more particularly to a method and apparatus for conditioning tobacco particles in the form of whole leaves, laminae, ribs and stem and/or shreds which preferably form a continuous stream~and are transported through a series of con-ditioning zones. ~till more particularly~ the invention relates to improvements in a method and apparatus for conditioning tobacco par-ticles by means of a gaseous fluid, preferably air.
Many treatments of tobacco must be preceded by increasing '! ', its mois~ure content so as to enhance the flexibility of tobacco particles (e.g.~ prior ~o shredding) and to thus reduce the likeli- -hood of undesirable breakage or comminution and the formation of dust. It is also known to treat tobacco with a variety of substan-ces ~known as casing) in order to improve its aroma; such treatment also involves increasing the moisture content of tobacco. At least some moisture must be expelled from tobacco prior to final process-ing into cigarettes, cigarillos, cigars, pipe tobacco, chewing to-bacco and/or other types o~ smokers~ products. For example, prior to feeding tobacco shreds into a modern mass-producing cigarette
2~ making machine~ it is necessary to insure that the moisture content of tobacco shreds is invariably within an extremely narrow range `
which cannot deviate from an optimum moisture content by more than a small fraction of one percent~ Heretofore known procedures whlch ~;
-, are employed in connection with conditioning of tobacco particles normally involve contacting tobacco with a gaseous fluid which is conveyed countercurrent to or concurrently with the direction of ~ ;
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` tobacco transport through the conditioning apparatus, or a combined concurrent-countercurrent treatment.
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i The countercurrent treatment involves conveying a cur- -- rent of hot air counter to direction of transport of tobacco parti ,~ ~
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''. ~' : ' cles and across the tobacco stream. Such treatment is desirable in many in~tances because the~obacco is ~rea~ed gently. This is due to the fact that the particles of tobacco are contacted fir~t by a current of hot air at less than maxi~um ~e~perature, i.e., the hot-test portion of the air stream comes into contact with that portion of the tobacco s~re~m which ~a8 aLready ~reated by cooler air. In other wordæ, the moi~ture content of tobacco particle~ is inversely proportional to the temperature ~ air which contacts successive in-crements of the stream As the temperature of air decreases in re-~ponse to continued contact and energy exchange with tobacco, themoi~ture content of air rises 80 that each increment of the tobacco stream is contacted first by an air current having a relatively high -- moisture con~ent and a relatively low tempera~ure; the moisture con-~ent of air decrea~es and the temperature of air increases in the direc~ion of ~obacco ~ransport. Thu5~ the very hot air con~acts those particles of tobacco whose moi~ture content is already reduced and the re~tlvély cool air cnntacts ~obacco particleæ whose moisture content is high. Otherwise stated, the maximum exchange of energy takes place at the down~tream end of the conditioning zone where ~he partialLy conditioned tobacco is contacted by freshly admitted air .
whose temperature if high. An advantage oi such countercurrent con-di~ioning i5 ~hat the final moi5ture content of tobacco can be se-lected and maintained ~ith a high degree of accuracy becau6e, if ; the moi~ture content in a region slightl~ ahead of the down~tream ~ end of ~he conditioning zone deviate~ from the deæired optimum moi~-.
ture content, the temperature of freshly admitted hot air can be readily changed to compens~effor ~ch differences without any delay or with negligible delay. However7 the ju~t described countercur-rent conditioning cannot insure that the moiæture content o~ each portion of each ~obacco particle is within the deæired range, i.e ,
which cannot deviate from an optimum moisture content by more than a small fraction of one percent~ Heretofore known procedures whlch ~;
-, are employed in connection with conditioning of tobacco particles normally involve contacting tobacco with a gaseous fluid which is conveyed countercurrent to or concurrently with the direction of ~ ;
, . :
` tobacco transport through the conditioning apparatus, or a combined concurrent-countercurrent treatment.
. . :
i The countercurrent treatment involves conveying a cur- -- rent of hot air counter to direction of transport of tobacco parti ,~ ~
~ 2 .; ~ ''-' .
''. ~' : ' cles and across the tobacco stream. Such treatment is desirable in many in~tances because the~obacco is ~rea~ed gently. This is due to the fact that the particles of tobacco are contacted fir~t by a current of hot air at less than maxi~um ~e~perature, i.e., the hot-test portion of the air stream comes into contact with that portion of the tobacco s~re~m which ~a8 aLready ~reated by cooler air. In other wordæ, the moi~ture content of tobacco particle~ is inversely proportional to the temperature ~ air which contacts successive in-crements of the stream As the temperature of air decreases in re-~ponse to continued contact and energy exchange with tobacco, themoi~ture content of air rises 80 that each increment of the tobacco stream is contacted first by an air current having a relatively high -- moisture con~ent and a relatively low tempera~ure; the moisture con-~ent of air decrea~es and the temperature of air increases in the direc~ion of ~obacco ~ransport. Thu5~ the very hot air con~acts those particles of tobacco whose moi~ture content is already reduced and the re~tlvély cool air cnntacts ~obacco particleæ whose moisture content is high. Otherwise stated, the maximum exchange of energy takes place at the down~tream end of the conditioning zone where ~he partialLy conditioned tobacco is contacted by freshly admitted air .
whose temperature if high. An advantage oi such countercurrent con-di~ioning i5 ~hat the final moi5ture content of tobacco can be se-lected and maintained ~ith a high degree of accuracy becau6e, if ; the moi~ture content in a region slightl~ ahead of the down~tream ~ end of ~he conditioning zone deviate~ from the deæired optimum moi~-.
ture content, the temperature of freshly admitted hot air can be readily changed to compens~effor ~ch differences without any delay or with negligible delay. However7 the ju~t described countercur-rent conditioning cannot insure that the moiæture content o~ each portion of each ~obacco particle is within the deæired range, i.e ,
- 3 -the overall moisture content of a batch of tobacco particles is sat--: isfactory but the ~oisture content is likely to vary from portion to portion of a discrete tobacco particle.
The conditio~ing of tobacco with a current of hot air which is conveyed concuræent with the direction of tobacco transport in- :
volves conveying the tobacco in and often by a current of air. Such .. treatment render~ it possible to achieve a hygroscopic equilibrium between tobacco and air at the downstream end of ~he conditioning zone,i.e., all portions of each to~cco particLe will have a desired moisture ~ontent. However, the concurrent treatment exhibits a ser-ious drawback, namely that the tobacco particLes are c~tacted firs~
by very hot air which effect~ an abrupt drying ~ strata adjacent to the external ~urfaces of tobacco particles. As a re~ult of such treatment, certain types of tobacco are likeLy to develop hard crusts. `
Moreover, the intervals between the me~surement of moi~ture content -:
and an efective adjustment in the event that the flnal moisture con~
~` tent of tobacco is unsatisfac~ory are very long. m us, if the mois~
ture content o tobacco i~ m~aqured dow~stream o~ the conditioning zone and if such mois~e co~tent i~ unsatisfactory, it takes a rela~
tively long intervaL of tl~ ~o change the mol~ture content by chang-. ing the characteristics of the alr current~ This mean~ that a sub~
: stantial amount of tobacco i~ allowed to Leave the conditioning zone with a final moi~ture content which is unsatisfactory for further processing. Also, the regulating system whichiis used to change the ch~racteri5tic~ of the air current flowing concurrent with the di-rection of tobacco tran~port i~ likeLy to begin to oscillate. Since the main drying action t~kes place in the relatively short 0remo6t portion of the conditi~ning zone, it is difficult to influence the moisture con~ent of tobacco in the remaining portion of the condi-tioning zone if such moisture content i9 unsatisfactory.
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The combinQd concurrent-countercurrent conditioning of to-bacco exhibits the advantage ~hat ~he adverse effects of ~he preced-ing (concurrent) treatment can be compensated for during the next- -following ~coun~ercurrent) treatmen1:. However, this takes place at the expense of uniformity of moisture content in all portions o~ to-bacco particles which leave the conditioning zone. Thus, the count-e~curren~ treatment which follows the concurrent ~rea~ment is likely to reduce the unl~ormity of~!moisture content in each portion of a to-bacco particle which leaves the ~reating appara~us. Furthermore, even though the concurrent treatment aLlows for ~onvenient elimina-tion or substantial devlation~ of measu~ed moisture content from a desired moi9~ure content by proper regulation of ~he tempera ure of air currents which axe transported concurrent with tobacco particles, auch concurrent treatment is likely to bring about undesirable in-crustation of tobacco particles in that portion of the condi~ioning zone where a current of very hot air comes into contact with tobacco.
; Therefore~ conditioning apparatus whose operation is based on the just discussed principle have failed t~ find wide~pread acceptance in the tobacco indu~try.
Freshly gathered tobacco leaves are normalLy dried at the farm, Prior to compac~ing of leaves in barrels, hogsheads or in the form of bales (this i8 the customary form of compacting tobacco for ,~
shipment to manuf~cturing plants), the moisture cnntent of tobacco leaves must be reduced to an accurately determined relatively low value. Such accurate drying cannot be achieved by m~re exposure of toba~co leaves to atmospheric air because various portions of tob~aco leaves lose moisture at a different rate. Thus, the laminae wi~L
dry much faster than ribs and ~tem. Therefore, fre~hly gathered to-bacco leaves are often stemmed or destalked to separate Laminae from stem so that the thus separated stem and laminae can be dried inde-pendently of each o~her. Tobacco which is subjected to a drying ac-kion after gathering is oft~n called greenleaf tobacco. Accurate drying of greenleaf tobacco (~o that the mois~ure content of each tobacco particle and of each portion of each tobaccco particle remains within a narrow range) is desirable and necessary because~ af~er ~he tobacco is compacted in barrel~ or in the form of bales, batches with a high moisture content tend to mildew and the molding spreads very rapidly throughout an ent~e barrel or bale to cause substantial dam- ;
age. A contemporary drying apparatus for greenleaf tobacco norm~lly comprises a rotary open-ended ve~sel or barrel through which a stream of tobacco is conveyed with a current of air and attendant agitation of tobacco to in9ure more ~atiæfactory exchange of energy ., .
- between air and tobacco particles. It is also known to employ dry-ing apparatus in the form of pneumatic conveyors wherein greenleaf tobacco is conveyed in a current of hot air passing through a pipe or the like.
Since a b~le or barrel of dried greenleaf tobacco ls like-Ly to remain in storage for extended periods of timeS the manufacture;
ers require that the moisture con~ent of such ~obacco be main$ained within an extremely narrow range because a very ~all nest of mildewy tobacco is likely to contaminate the contents of an entire barreL
or an ent~e bale before the barrel or bale ls removed from storage.
A~ mentioned before, the molsture content must be ~educed to a very low value, and the transport through a drying or conditioning appa-ratus wherein the moisture content is reduced to ~uch l~w value i5 Likely to result in undesirable breakage or comminution of tobacco and/or ~ ~he formation of excess~ve quantities of tobacco dust. ~he like~ihood of breakage or dust forma~ion iæ particularly pronounced in the aforementioned drying apparatus wherein a stream of tobacco ic conveyed through a revolving open-ended vessel in the presence of hot air, This is due to the fact ~hat the revolving vesseL sub-jects the particles of tobacco to a pronounced agitating ac~ion dur-ing which the particles are repeatedly lifted well above the bottom : zvne of the vessel by orbiting rakes or blades and are allowed to drop by gravity back into the bottom zone. NevertheLess, many to-bacco growers s~ill employ such types of dryi~g apparatus because their conditioning action is more uniform than that of pneumatic dry-ing apparatus~
Additional problems in connection with conditioning of to-baccc arise due to the fac~ ~hat the ~pace in a modern tobacco pro~
cessing plant is at a premium, Thu~, the manufac~rers strive to accommodate the conditioning apparatus in a small area while simuL-taneously desiring a high output and an accurate conditioning of each and every t~bacco particle, i.e., the temperature and/or mois-ture content of conditioned tobacco should equal or should be very close to an optlmum temperature and moisture content. This can be achieved if the dimensions of condi~ioning appara~us can be increased - at will, i.e., if the drying of moist tobacco can be carried out while the particles of tobacco are advanced a~ a rela~ively low speed - 20 a~d through a re~atively long conditioning zone so that the reduction :: of molsture content can be achieved gradually. In other words, a ~a~isfactory reduction of moisture content and a ~atisfactory heat~
- ing or cooling of tobacco presunts no probLems if the changes in such characteristics are efected at a slow rate, namely if the ex-tent of drying per unlt length of the conditloning apparatus and per unit of time i~ relatl~eLy smaLl~ Such treatment insures a reLiable homogenization of the final product so that the temperature as weLl as the moisture content of ea~h particle issuing from the condition-ing zone is best suited ~or further processing. Thi8 is due to the 30 fact that a conditioning for a long period of time and in a relative;
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ly long conditioning zone can readily compensate for ~luctuations in initial --temperature and/or moisture content as well as for eventual fluctuations in the intensity of treatment during one or more drying stages.
In certain recent types of conditioning apparatus J a relatively short heating zone is followed by a homogenizing zone whose function is to eliminate eventual variations in moisture content of tobacco which issues from the drying zone ~see German DAS No. 2,103,671~. Such procedure is satisfactory only if the initial moisture content of tobacco ~i,e., of . ~
tobacco which enters the drying zone) is constant or deviates only slightly ln from a fixed value. It has been found that the just described conditioning ; apparatus fail to ensure a satisfactory homogenization and cannot achieve a ` reduction of moisture content to a fixed value unless the initial moisture -- content is constant or deviates only negligibly from a fixed value. Thus, fluctuations of ini~ial moisture content are likely to adversely influence the drying action or to prevent a satisfactory drying to such an extent that the homogenizing or uniformizing treatment cannot cure the defective drying ~ -action.
According to one aspect of the present invention there is provided ; . .
a method of drying tobacco which comprises feeding a continuous stream of tobacco particles into an elongated path, transporting the particles along ~;
the path, subjecting the particles to the homogenizing action of a heated first gas current (preferably air) in a first portion (first homogenizing zone) of the path including establishing a state of exact or substantial hygroscopic equilibrium between the first current and tobacco particles in a first portion of the path, reducing the moisture content of tobacco particles in a second portion of the path (for example and preferably by ;
contacting the particles with hot air or another suitable gas which flows .~ .
transversely of the tobacco stream in the second portion of the path), .' '~
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subjecting the particles to the ac~ion of a hea~ed second gas cur-rent (preferably air) in a third portion (second homogenizing zone) of the pa~h including est~blishing a state of hygro~copic equilibrium .between the second current and the par~icles of tobacco in the ~hird po~tion of the path, and removing the thus dried and homogenized ,~. .
stream of tobacco particles from ~he path.
ThP method may further comprise the ~teps of measuring the moisture content of tobacco particles upstream of the first portion of the path and changing the moisture content of the first current in response to changes in ~easured moisture content of tobacco part-icles; this insures a desirable homogenizing action in the first por-tion of the path, i,e., prior to e~pulsion of moistur~ in the second porti~n of the path. In other words, the first gas current need not change the characteristics of the main portion of tobacco but merely the characteristics o~ those minor portions (if any) whose :~characteri~tics deviate from the characteristics Df the main portion.
The method may further cooprise the steps ~ measuring the moisture content of tobacco particles downstream of the third por-tion of the path9 comparing the measured moisture content with a 20 predetermined optimum or desirabLe moisture content, and changing the extent of reduction of moisture content in the second portion of the path when the measured moisture content devLates from ~he predetermined moisture con~nt.
The step o~ estabLi3hing a state of hygroscopic equilibr-ium betwecn the 5econd current and the particles of tobacco in the third portion of the path may include maintaining the moisture con-`.tent of the second current in a predetermined reLationship with a predetermined desired or optlm~m moisture content of ~obacco parti-cles which leave the third portion of the path. This insures that the second current need not change the characteristics of the main . -~J
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portion of dried tobacco but only the characteristics of that or those minor portions (if any) whose characteristics deviate from the desirable characteristics of the main portion. The homogenizing action of the second :~ gas current is automatic and takes up a short interval of time.
The method may further comprise the steps of measuring the tem-perature of at least one gas current, comparing the measured temperature with a given temperaturel and changing the temperature o~ the one current when the measured temperature deviates from the given temperature. This also contributes to a rapid and pronounced homogenizing action of the respective gas current.
- At least a portion of at least one of the two currents can be cir-culated along an endless second path which intersects the respective portion -:
- of the elongated path for tobacco particles.
The transporting step may comprise agitating the particles of tobacco in at least one of the irst and third portions of the path for ~
tobacco particles so that the respective current contacts and passes through ~ -a layer of agitated floating particles.
The step of reducing the moisture content of tobacco particles in the second portion of the path may comprise subjecting the particles in the second portion of the path to the action of a heated third gas current which is preferably conveyed in a direction to intersect the second portion of the path for tobacco particles. The particles in the second portion of the elongated path are preferably vibrated or otherwise agitated during contact -~ with the third gas current.
, The speed of at least one of the currents is preferably reducedduring contact with tobacco particles in the respective ~first, second and/or - third) portion of the elongated path.
3 According to another aspect of the present invention there is pro-vided in an apparatus for drying tobacco a combination compri5ing means for ! 3Q transporting tobacco particles along an elongated path, said transporting ; ;~ : ' ::
L7~
means comprising a plurality of successive sections defining successive portions of said path; means for feeding a continuous stream of moist tobacco particles to said transporting means; means for homogenizing the particles of tobacco with a first heated gas current in a first section of ~ said transporting means, including means for maintaining said first current - in a state of at least substantial hygroscopic equilibrium with tobacco particles in the respective portion of said path; means for reducing the .' moisture content of homogenized tobacco particles in a second section of said transporting means; means for homogenizing the thus dried tobacco particles with a second heated gas current in a third section of said trans-. porting means, including means for maintaining said second current in a state of at least substantial hygroscopic equilibrium with dried tobacco particles in the respective portion of said path; and means for receiving the thus , . .
dried and homogenized tobacco particles in a continuous stream.
;- In the accompanying drawings which illustrate an exemplary embodi . ment of the present invention:
Figure 1 is a schematic partly elevational and partly sectional view of a conditioning apparatus which embodies the invention; and .:'' .
Figure 2 iS an enlarged transverse vertical sectional view of a 2~ vibratory conveyor in the apparatus of Figure 1.
The conditioning apparatus of Figure 1 comprises a tobacco feeding unit la and a transporting system 1 including a first homogenizing section 2 ~ located immediately downstream of the feeding unit la, a drying section 3 . located immediately downstream of the section 2, and a second homogenizing section 4 located immediately downstream of the drying section 3. The -. second homogenizing section 4 is followed by a removing unit 6 which accepts ~ "
conditioned tobacco from the transporting system 1. .;
The feeding unit la comprises a set of three conveyors for a contin~
- uous stream of tobacco particles 7. These conveyors include a first belt . 30 conveyor 8 whose discharge end showers successive increments of the tobacco . ' . . .
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stream onto the upper stretch of a second belt conveyor 9, and a vibratory ; conveyor 11 having a trough which receives successive increments of the tobacco stream from the discharge end of the belt conveyor 9. The trough of the conveyor 11 is vibrated by the eccentric lOa of an electric motor lOb through the medium of a connecting rod 10. The conveyor 9 forms part of a weighing device 12 which serves to ensu:re that the trough of the vibratory . ~
conveyor 11 receives tobacco particles 7 at a uniform and - -.
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unchanging rate per unit of time.
me conveyor Ll dischargeæ tobacco particles 7 onto a down-wardly inc~ined chute 20 which i~ installed in an opening provided - in the left-hand side wall of a chamber 2a forming part of the first homogenizing section 2.
The rhamber 2a of the fLrst homogenizing section 2 of the transporting system 1 receives the leftm~st part of a~ elongated vibratory conveyor 13 a portion of which is ilLu~trated in FIG. 2, Th2 trough of the conveyor 13 comprises a f~raminous bottom wa11 or lO platform 15 having perforations or holes 16 and ~eing supported by leaf springs 14 mounted on a carrier l4a in ~he frame F. The trough of the conveyor 13 further comprises two side wall5 17, l8 which di-. verge upwardly and outwardly in order to reduce the speed o air '. currents which flow up~ardly through the holes L6 of the bottom wall 15 and to prevent such currents from entraining lighter tobacco part-icles. The vibra~ory conveyor 13 is sub~tantially horizontal and : extends through alL ~hree sections 2~ 3~ 4 of the tran~porting sys-tem l as well as beyo~d the second homogenizing section 4 to deLiver condi~ioned tobacco to the removing unit 6. The means for vibrating the trough of the conveyor 13 comprises a variabLe-speed elect~ic motor l9 having an eccentric l~a which tran~mits motion to the trough , by way of a connecting rod l9b.
- The one-piece vibratory conveyor 13 o~ FIGS. l and 2 can ;
be replaced by a series of di~crete co~veyor~ fox example~ by three ~ :
conveyors, one for each of the sectio~ 2, 3 and 4. At least ~ne of the three conveyor~ need not be a vibratory cc~eyor.
; The means for contacting tobacco in the sec~ion 2 wi~h a gaseous homogenizin~ medium comp~ise5 a pipe 21 which comm~nicates with the chamber 2a at a level below the bottom wall lS of the vib- :
ratory conveyor 13. Spent gaseous fLuid (preferably air) is with- .
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drawn from the chamber 24 at a level above the layer of tobaco par- ~
ticles 7 in the trough of the conveyor 13 bya pipe or conduit 22. ~-A sieve or filter 5 is provided in the chamber 2a to prevent the ho- -- mogenizing fluid from entraining lighter tobacco particles into the inlet of the conduit 22.
The discharge end of the conduit 22 is connected with the inlet of the pipe 21 by an air conditioning unit having an atomiz-- ing nozzle 23 for discharging controlled quantities of water into the air current supplied by the conduit 22~ and an adjustable elec-lQ tric resistance heater 24. The means for circulating air through - the chamber 2a comprises a blower 25 which draws air from the con-~, duit 22 and forces the thus withdrawn air into the pipe 21. The :
nozzle 23 and the heater 24 are installed in a suction pipe 61 which receives air from the conduit 22 and supplies air to the inlet of the blower 25. Air which enters the suction pipe 61 is heated by the heater 24 and thereupon receives moisture from the nozzle 23.
The second section 3 of the transporting system 1 compris-es three chambers 26, 27, 28 which are separated from each other by ~;~
c transverse partitions having openings 2p for the adjacent portions : ~ .
-~ 20 of the vibratory conveyor 13 and for the layer of tobacco particles 7 on the bottom wall 15. The upper portion of the chamber 26 (above , the conveyor 13~ communicates with the lower portion of the chamber 27 (below the conveyor 13) by way of a suitably con~igurated conduit or pipe 29. The upper portion of the chamber 27 communicates with l the lower portion of the chamber 28 by a similar conduit or pipe 30.
,I The upper portion of the chamber 28 has an outlet opening 32 which discharges air into the atmosphere. A first sieve 35 in the upper ~;
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portion of the chamber 26 prevents lighter particles of tobacco from entering the inlet of the conduit 29. Similar sieves or filters 35 are provided in the upper portions of the chambers 27 and 28 to re-~'f "' .
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spectively prevent lighter tobacco particles from en~ering the con-dui~ 30 and outlet opening 32.
The lower portion of the chamber 26 receives heated air by way of a pipe 31 which is connected ~o the outlet of a blower 34.
The intake end of the blower 34 is connected with a suction pipe 74 having an open end for admissiion o atmospheric air and an adjust-able regulating valve or flap 77 which can be piuoted by a ~ervomot-or 76. Atmospheric ~ir which enter~ the inLe~ of the suction pipe 74 is heated by a preferably adjustable electric resistance heater . 10 33, and the ~emperature of hea~ed air entering the blower 34 can be - regulated by changing the angular po~iition of the flap 77 which thereby admit~ a controlled quantity of unheated atmospheric air into the current of air which has passed the heater 33.
.: me third section 4 of the ~ransporting sys~em 1 comprise~
a chamber 4a having side walls which are provided with openings 4p for the vibratory conveyor 13. The lower portion of the chamber 4a (below the conveyor 13) receives a hom~genizing fluid (preferably :~
air) by ~ay of a pipe 36 which receives air fxom a blower 41. The .. intake of the blower 41 i5 connected with a ~uction plpe 89 which . ;
receive~ air from an elongated conduit or pipe 37 communica~ing with the upper portion of the chamber 4a, A sieve or filter 42 in the , - upper portion of the chamber 4a prevents lighter tobacco par~iclPs ~r~m e~tering the inlet of the conduit 37. The ~uction pipe 89 contains an adju~table electric resistance heater 39 and the air curren flowing therein can recei~e controlled quantities of water thr~ugh the orifice5 of an atomizing nozzle 38.
The rernoving unit 6 co~priqes a take-off conveyor 43 here sh~wn as an endless belt the upper stretch of which receives condi-tioned tobacco particLes 44 from the di~charge end of the vibratory conveyor 13. The belt 43 transports cond~tioned tobacco to a ~ur- :
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ther processing station, e,g,, to a baling machine or to ~he maga-zine of a cigarette rod making machine, depending up~n the na~ure : of tobacco particle~ which are being supplied by the feeding unit la.
:. The moi~ture content of ~uccessive increments of tobacco : in the trough of the vibratory conveyor 11 is determin~d by a detect~
: or 46, e.g,, a detector known as H~1K produced by Hauni~Werke of Ham-.~ burg-Bergedorf, Western Germany. The signals which are generated ~, by the detector 46 are trans~itted toca signal c~mparing jun¢tion 52 ~arming part of a control unit 51 which c~nstitutes a m~ans for .~ 10 regulating the moisture content of the curre~t of air flowi~g into ,. the lower portion of the chamber 2a. The junction 52 ls further con-nected with a potentiometer 53 or another suitable rated value ~et-ting device whihh is ad~ustable to fuxnish signals indicating the desired or op~imum initial moisture con~ent of tobacco particles 7 - in ~he conveyor 11. The output of the junction ~2 tranbmit~ a posi~
tive or a nggative signal when the intensity of signals furnished by the detector 46 de~iates from the intensity of signals ~upp~ied by the potenti~meter 53.
The signal from the output of the junction 52 i~ transmit- :
~ed to a ~econd ~ignal comparing junction 54 of the con~rol u~it 5L
as well as to orle input o a signal comparing junction 66 forming part of a ~econd control unit 65 which regulates the heater 24 in , . -~: the suction pipe ~1 of the blower 25. The junction 54 o the con-~rol unit 51 further receives ~ignals from a detector 56 whlch ls . i -- mounted in the pipe 21 and monitors the moisture content of the air current fLowing into the lower portion of the chamber 2a, The de-tector 56 may constltute a conventional hyg~ometer. The ~ignal - from the output of the junction 54 is indicative of the difference between the intensities of signals furnished by the junction 52 a~d 30 de~ector 56, and is amplified by an amplifier 57 which is in circui~
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1~4.L~7~
with a variable~peed electric motor 58 for a variable-delivery pump 59 which supplie~ water to the atomi~ing nozzle 23 in the suc~ic~n pipe 61. The pump 59 draws water from a reservoir (no~ shown) via conduit 59a, The ~uction pipe 61 is further provided wi~ch an adjustable regulating v~lve or flap 62 which i~3 located downstream of the heat-er 24 and up~tream of the nozzle 23 (as considered in the direction of air flow from the cvnduit 22 into the blower 2i~) and who5e posi-tion i~ adjuætable by a servomotor 63. The ~ignals for adjustment of the flap 62 via servomotor 63 are supplied by the output of a threshold circuit 64 which receives signals from the junction 54 of the control unit 51.
The potentiometer 53 of the control unit 51 is preferably ad~lsted in ~uch a way that the current of air flowing into the low-er portion of the chamber 2a is in a s~ate of hygro~copic equilibrium with tobacco particles 7 which are being supplied by the chute 20 onto ~he Leftmost part of the vibra~ory conveyor 13. Thu~, 2~ lea~t ::
.f ,.
~he major part of tobacco which i8 caused to ~ravel through the cham~ ~ :
ber 2a does n~t accept moisture from and is not relieved of moisture . . .
by the current of air which i8 being supplied by the pipe 21, The definit~on ~Ihygroscopic equilibrium" need not nece~saril~ i~dicate that the moisture content of tobacco in the cha~ber 2a is identical with or even close to the moi~ture content of air issuing from the ~:
pipe 21. In fact, in most instances, the moi~ture content of air which is in a state of hygroscopic equilibrium with tobacco deviates considerably from (it i8 much higher than) the moi~ture content of tobacco. The difference between the moi~ture content of tobacco and .
the moisture content of air which i8 in a state of h~Tgroscopic equil-ibrium with tobacco depends on a number of factors, especially the 30 condi.tion of tobacco (e, g,, the nature and percentage o:E fluid and/or .
other matter which is confined in tobacco particles and the chemical composition of such matter or fluid), the structure oF tobacco (e,g,, the formation of capillaries in the ti~ue o F tobacco particles), and the brand of tobacco. For exampLe, the composition of casing and/or the nature and percentage of salts in tobacco will infLuence that moisture content of air or another gas at which the gas is in a state `~ of hygroscopic equilibrium with tobacco, The signal whi~ch is transmitted f~om the junction 52 of the control unit 51 to the junction 66 of the control unit 65 is ` 10 amplified by an ampliier 68 which controls the heater 24 in the - suction pipe 61 of the blower 25. The junctinn 66 further receLves signals from a detec~or 67 which is installed in the pipe 21 and monitors the temperature of air flowing into the Lower porti~n of the chamber ~a. The detector ~7 may constitute a commercially avail-able heat-isensitive PTC or NTC i~emiconductor.
A further detector 71 (which may be identicaL with or sim-ilar to the detector 46) is adjacent to the path of conditioned to-bacco particles 44 in the vibratory conveyor 13 immediately upstream of the take-off conveyor 43. The detector 71 monitor~ the final mois~ure content of ~obacco and transmits appropriate signals to a first input of a ~ignal comparing junction 72 forming par~ o a third control unit 73 for regulating the temperature of air entering the blower 34. A second input of the junction 72 i8 connected with the output of a~ adjustabLe rated value setting device 75 (e.g~, a po-tentiometer) which transmits a slgnal indicating the desired ~empera-ture of air which flows intu the lower portion of the chamber 26.
The output of the junction 72 is connected with an amplifier 74 which tran~mits amplified signals to the servomotor 76 for the adJustable flap 77 in the sucti~n pipe 74.
; 30 The characteristics o F air whihh is admitted in~o the low-'A, . _ ~
~! '` /~
~ h 7~ ~
.. er portion of the chamber 4a are determined by two eontroL unlts 81 and 96, The control unit 81 determines the exact moisture content of inflowing air, and the control unit 96 de~ermines the exact te~p~
- erature of such airc The difference between the control units 81 and 96 on the one hand and the control units 51 and 65 on the other hand i8 i:that the control units 81 Imd 96 are adjusted to insure that the final moiRture content of tobacco particLes (44~ doe~ not devi_ ~. ;
- ate from a desired or optimum value.
The control unit 81 co~pri~es an ad~us~able rated value setting device 8~ (e.g., a potentiometer) which transmits signaLs .: .
- to one input of a ~ignal comparing junctio~ 84. Another input of the junctivn 84 receives signals from a detector 83 which monitors ' the moia~re con~en~ of air flowing in the pipe 36. The signal at .~ the output of the junction 84 is amplified by an amplifier 86 which : :
i5 in circuit with a varlable-speed electric motor 87 for a vaxiable-delivery pump 88. The Latter supplies controlled quantities of wat-: er to the nozzle 38 in the suction pipe 89 of the blower 41 and is ~. connected with a source of water by a condu~t 88a. The suction pipe , :. ~9 is provided with an adjustable regulating valve or flap gl which is mounted between the heater 39 and nozzle 38 and iæ pivotable by a servomotor 93 receiving signals from a threshoLd circuit 92 which : is connected to the output of the junction 84.
The control unit 96 compri~es an adjustable rated value .. .
setting device 97 (e~gr~ a poten~iometer) w~ich transmi~s signals :
of selected inten~i~y ~o one;.input of a ~ignal comparing junc~ion 99. Another input of the junction 99 is connected with a detector 98 whi h monitor~ the temperature of air in the pipe 36. The 8ig- :
nal from ~he output of ~he junc~ion 99 is amplified by an amplifier 100 and regulates the heater 39 in the suction pipe 89.
The ope~ation:
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:
The moisture content of tobacco particleæ 7 on the convey-or 8 exceeds the desired mois~ure content of tobacco on the ~ake-off conveyor 43. The conveyor 8 delivers the particle 7 in the form ` of a continuous stream which is equalized by the weighing device L2 and i~ fed into the trough of the vibratory conveyor 11. ThU8, ~he `. conveyor 11 receives and discharges identicaL or nearly identical s quantitites of moist tobacco per unit nf time. The detec~Dr 46 mon-itors ~he moistuxe content of tobacco particles 7 and ~ransmits ~ig-nals bo~he junction 52 of hhe con~rol unit 51. The detector 46 is a t~arl~ducer which furnishes to the juncl:lon electric signals of varying in~Qns ity.
The co~aveyor 11 discharges tobacco particles 7 into or on-to the chute 20 which supplies such particles into the leftmost part of the trough forming part of the vibratory conveyor 13, i. e~, ~nto .
the chamber 2a of the first homogenizing ~ection 2. The holes 16 in .the bottom wall 15 of the conveyor L3 permit the passage of small currents of conditioned air whieh is 9upplied by the pipe 21. Such currents cause the par~icles 7 of the tobacco stream on the bottom wall 15 to rLse and to float within the confines of divergent side wall~ 17, 18 which in~ures a highLy satisfactory conditioning of all sides of e~ch tobacco par~icleO
An important function of the first homogenizing section ~ .
2 is to insure a pronounced and reliable homogenization of tobacco .~ which is being supplied by the feeding unit La. Thus, the section 2 eliminates eve~tual differences in the moi9ture con~ent of tobacco entering the chamber 2a, and such elimination of differences ~akes place in response to signals furnished by the detector 46. This in-sures ~hat the drying sction of air in the chambers 26, 27 and 28 of the section 3 is highly satisfactory since the moisture content 30 and temperature o~ tobacco particle~ 7 entering the chamber 26 are , '7~
con~tant due to homogenizing action of the air currents passing through ~he holes 16 of the bottom wall L5 in ~he chamber 2a.
The control unit 51 insures that the moisture content o~
air entering ~he pipe 21 change~ as soon as the intensity of signaL~
furnished by the detector 56 in the pipe 21 devia~es from the intens-ity of signals furnished by the junction 52. The control unit 65 in-sures that the heater 24 is adjuste~d (to effect a more or less pro-nounced heating of air which is belng supplied by the conduit 22) when the intensity of signals furnished by the detector 67 deviates from the int~nsity o that signal which is supplied by the junction 52 (to junction 66). Thus, no~ only the moi~ture content bl1t also the temperature of air which flows in the pipe 21 is regulated by the in~lal moi~Ee content of tobacco par~icles 7. As mentioned ~;
above, the moisture content o~ air in the pipe 21 is selected with a view to insure that the air is in a state o hygroscopic equilibr-ium with tobacco in the cha~ber 2a, i.e., air which enters and pass-es through the chamber 2a should n~ remove moisture from 0r add mois- :
ture to tobacco which passes through the section 2 toward the cham-ber 26. Changes in the mois~ure content of ~obacco passing through the section 2 are not necessary since the main (and preferably the sole) purpose of air supplied by the blowe~ 25 is to homogenize the tobacco before the particles 7 ~ch the drying section 3. The hom~
ogenizing ~ction of air in the chamber 2a is regualted ~or the pur-pose of insuring that the moisture cQntent of all particles 7 leav~ :
lng the section 2 is ~ ticaL with the m~i~ture content of the bulk of tobacco particles supplied by the feeding unit la. Such homogen-izing action of ~he current of air which is circulated along the .,: . . ..
endless pa~h deiined by ~he pipe 21, chamber 2a, con~ui~ 22, suction p~pe 61 and blower 25 is very r~ bl~ whereby the characteristic5 30 of this current change very littLe since the air is not 3upposed to . - -~
,~ o;7, .
:
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.L~7~
supply moisture ~o or remove moisture from ~he tobacco particles 7, EventuaL fluc~uations in moisture content of the just described air curre~t are eliminated by the co~trol unlt 51 which regulates ~he admission of moisture via no~zle 2:3. If the air flowing in the pipe 21 is so moist that ~ts moisture content e~ceeds the desired value, even if the admission o~ a water spray through thP nozzle 23 is term-inated, the signal from the output of the junction 54 causes the threshold circuit 64 to actuate the servomotor 63 which opens the flap 62 to admit atmospheric air into the suction pipe 61 and to .~ . .
thereby reduce the mois~ure content of air which flows into the low~
er portion of the chamber ?a. Such reduc~io~ in the moi8~ure con-tent of air in the pipe 21 takes place practically withou~ delay.
The particles 7 o~ tobacco in the trough of the vibratory conveyor 13 form a floating stream which advances through the first opening 3p and ent~r~ the first chamber 26 of the drying section 3.
Such particles are contacted from aLl sides by hot air which is be-ing admitted by the pipe 3L to thus insure a pronounced exchange of energy and rapid drying of~tobacco. The temperature of hot air en-tering the lower portion of the chamber 26 i8 regulated by the con-trol unit 73 in response to signals furni~hed by the detector 7L.
The drying i8 contin~t in the chamber~ 27 and 28 ~o that the mois-ture content of tobacco lea~ing the chamber 28 via first opening 4p is normally reduced to a desired optim~m value for further process-ing. The dimension5 o~ the drying section 3 are relatively 5mall which is desirable in a modern to~acco processing plant.
,,:, 9 In order to i~ure a still more satlsfactory homogeniza-tion or uni~ormizing of all characteristics o~ tobacco par~icles which Leave the drying section 3, the conditi~ning apparatus incLudes the second homogenizing section 4 which is especially de~îrable when the drying section 3 is very short and compact, i.e., when the in-~ ,;7~
.
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`~ .L~
tensive drying of tobacco particles takes place within a very short ` ~ interval of time. The current of air which is circulated by the ,' blower 41 has a constant temperature and moisture c~ntent (see the: control units 96 and 81) and is in a state of hygroscopic equilibr-ium with tobacco in the chamber 4a. Thus, the function o~ air in the chamber 4a iB analogous to that of air in the chamber 2a.
The signal from the output of the junc~ion 84 causes the threshold circuit 92 to actuate the servomotor 93 and to open the flap 91 in order to admit atmospheric air into the suction pipe 89 when the moisture content of air in the pipe 36 is exce~sive whlle the admission of water via nozæLe 38 i~ interrupted. This results ~; in practically instantaneous reduction of mo~sture content of air~~ which enters the lower portion of the chamber 4a.
:: The improved ~onditioning apparatus exhibits the advantage ~hat ~he interval w~ich i~ required for the drying of tobacco ~in ~ .
the section 3~ can be reduced to a minimum without adversely af~ect- :
ing the de~irable characteristics of tobacco particles 44 which is-sue from the section 4. This is attributed to homogenlzation in the sections 2 and 4, i.e., prior to and fifter drying in the cham~
bers 26, ~7 and 28. Relatively short and compact drying means are desirable for a number of reason$.
Another ad~antage of ~he improved conditioning apparatu5 is that at lea~t a portion of at least one of th~ homogenizing gas - currents which contact ~obacco particles in the chambers 2a and 4a is circulated along an endle~ path which interæects the path of toba co particles in the respectlve portion of the vibratory convey-or 13, This insures that the characteris~ics o the circulating gas .
current or currents must be altered very little or not at ~all with :~ attendant ~gs in space and energy requirements of the apparatus, Thus, the control units 51, 65 and 81, 96 are used to change the re-~3 i spective characteristics of the gas currents in the plpes 21 and 36 only when ~uch characteristics deviate from an optimum or given . value. The deviations could be much more pronounced if each of the - pipes 31, 36 would have to draw atmospheric air which would have to be conditioned prior to entry into the lower portion of the respec-tive chamber 2a, 4a. These controL units are called upon to regu-late the respective characteristic5 of gas currents in the pipes 21 .
and 36 only when the moi~ture con~en~ of incom~ng tobacco (cnnve~or 11 and chute 20) is not uniform and/or when the moisture cnntent of tobacco leaving the chamber 28 is not uniform. Therefore~ the con-trol unit 51, 65, 81 and/or 96 normally effects only minor changes ; .
in the respective characteri~tic of the corresponding ga~ cureent 50 that, and referring to the reguLation of temperature ~y the flap 62 br 91, a minor change in the position of such flap suf~ices to rapidly change the temperature of the gas current in the pipe 21 or 36 ~o a desired value.
.j : The convey~r 13 al~o contributes to a more intensive and - reliable homvgenizing and drying of tobacco particles by causing -: the particles to vibrate dltring transport through ~uccessive cham-.,, bers so that the currents of air which are admitted via pipes 21~ 3 and 36 can contact all side of each particle in the respectlve sec-:.
~!, tion of the tran~porting system. Thi8 insures an inten~ive exchange of heat energy a~d/or moi~ture between tobacco particLes and gas currents The g~s current which enters the L~wer portion o the cham-ber 4a homogenizes the particles of tobacco in the respective portion .
of the conveyor 13 (when necessary) so that the tempèrature of part-icles leaving the section 4 equals the temperature of gas in the chamber 4a, either by heating or by cooling the conveyed fibrous ma-terial. At least the major portion of tobacco ln the chamber 4a : ; , , , .. , ~ .
does not receive additlonaL moisture and is not relieved of moisture so that the gas in ehe chamber 4a supplies moisture to or withdraws .
moisture from a small portion of tobacco but does not change the moisture content of the ma~or portion of material ~n the conveyor 13.
The treatment of tobacco in the chamber 2a does not affect ~:
the flexibility sf particLes 7 so that such particles are not com-minuted during transport toward the take-off conveyor 43. In fact, such treatment (by the current of gas enering the chamber 4a via pipe 21) enhances the elasticity of tobacco particles while the part-icles are being homogenized prior to entering the first chamber 2S
of the drying section 3.
Still another advantage of the conditioning apparatu~ i5 ~hat it can dispense with several vibratory conveyor~ in the chamber .i 2a. This allows for a reduction of the dim~n~ions of the chamber 2a with attendant ~avings ~ s~ace and lesser and fewer problems in connection with sealing of the chamber. As regards the homogenizing action prior to actual drying, such homogenizing action is perform~
ed by the entire gas current which enters the chamber 2a via pipe 21. ~:
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,~ "'''"' ~' ~: ,'^.: .
', ' ~'' .
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The conditio~ing of tobacco with a current of hot air which is conveyed concuræent with the direction of tobacco transport in- :
volves conveying the tobacco in and often by a current of air. Such .. treatment render~ it possible to achieve a hygroscopic equilibrium between tobacco and air at the downstream end of ~he conditioning zone,i.e., all portions of each to~cco particLe will have a desired moisture ~ontent. However, the concurrent treatment exhibits a ser-ious drawback, namely that the tobacco particLes are c~tacted firs~
by very hot air which effect~ an abrupt drying ~ strata adjacent to the external ~urfaces of tobacco particles. As a re~ult of such treatment, certain types of tobacco are likeLy to develop hard crusts. `
Moreover, the intervals between the me~surement of moi~ture content -:
and an efective adjustment in the event that the flnal moisture con~
~` tent of tobacco is unsatisfac~ory are very long. m us, if the mois~
ture content o tobacco i~ m~aqured dow~stream o~ the conditioning zone and if such mois~e co~tent i~ unsatisfactory, it takes a rela~
tively long intervaL of tl~ ~o change the mol~ture content by chang-. ing the characteristics of the alr current~ This mean~ that a sub~
: stantial amount of tobacco i~ allowed to Leave the conditioning zone with a final moi~ture content which is unsatisfactory for further processing. Also, the regulating system whichiis used to change the ch~racteri5tic~ of the air current flowing concurrent with the di-rection of tobacco tran~port i~ likeLy to begin to oscillate. Since the main drying action t~kes place in the relatively short 0remo6t portion of the conditi~ning zone, it is difficult to influence the moisture con~ent of tobacco in the remaining portion of the condi-tioning zone if such moisture content i9 unsatisfactory.
~ 4 ~
~ 7 ~ ~
The combinQd concurrent-countercurrent conditioning of to-bacco exhibits the advantage ~hat ~he adverse effects of ~he preced-ing (concurrent) treatment can be compensated for during the next- -following ~coun~ercurrent) treatmen1:. However, this takes place at the expense of uniformity of moisture content in all portions o~ to-bacco particles which leave the conditioning zone. Thus, the count-e~curren~ treatment which follows the concurrent ~rea~ment is likely to reduce the unl~ormity of~!moisture content in each portion of a to-bacco particle which leaves the ~reating appara~us. Furthermore, even though the concurrent treatment aLlows for ~onvenient elimina-tion or substantial devlation~ of measu~ed moisture content from a desired moi9~ure content by proper regulation of ~he tempera ure of air currents which axe transported concurrent with tobacco particles, auch concurrent treatment is likely to bring about undesirable in-crustation of tobacco particles in that portion of the condi~ioning zone where a current of very hot air comes into contact with tobacco.
; Therefore~ conditioning apparatus whose operation is based on the just discussed principle have failed t~ find wide~pread acceptance in the tobacco indu~try.
Freshly gathered tobacco leaves are normalLy dried at the farm, Prior to compac~ing of leaves in barrels, hogsheads or in the form of bales (this i8 the customary form of compacting tobacco for ,~
shipment to manuf~cturing plants), the moisture cnntent of tobacco leaves must be reduced to an accurately determined relatively low value. Such accurate drying cannot be achieved by m~re exposure of toba~co leaves to atmospheric air because various portions of tob~aco leaves lose moisture at a different rate. Thus, the laminae wi~L
dry much faster than ribs and ~tem. Therefore, fre~hly gathered to-bacco leaves are often stemmed or destalked to separate Laminae from stem so that the thus separated stem and laminae can be dried inde-pendently of each o~her. Tobacco which is subjected to a drying ac-kion after gathering is oft~n called greenleaf tobacco. Accurate drying of greenleaf tobacco (~o that the mois~ure content of each tobacco particle and of each portion of each tobaccco particle remains within a narrow range) is desirable and necessary because~ af~er ~he tobacco is compacted in barrel~ or in the form of bales, batches with a high moisture content tend to mildew and the molding spreads very rapidly throughout an ent~e barrel or bale to cause substantial dam- ;
age. A contemporary drying apparatus for greenleaf tobacco norm~lly comprises a rotary open-ended ve~sel or barrel through which a stream of tobacco is conveyed with a current of air and attendant agitation of tobacco to in9ure more ~atiæfactory exchange of energy ., .
- between air and tobacco particles. It is also known to employ dry-ing apparatus in the form of pneumatic conveyors wherein greenleaf tobacco is conveyed in a current of hot air passing through a pipe or the like.
Since a b~le or barrel of dried greenleaf tobacco ls like-Ly to remain in storage for extended periods of timeS the manufacture;
ers require that the moisture con~ent of such ~obacco be main$ained within an extremely narrow range because a very ~all nest of mildewy tobacco is likely to contaminate the contents of an entire barreL
or an ent~e bale before the barrel or bale ls removed from storage.
A~ mentioned before, the molsture content must be ~educed to a very low value, and the transport through a drying or conditioning appa-ratus wherein the moisture content is reduced to ~uch l~w value i5 Likely to result in undesirable breakage or comminution of tobacco and/or ~ ~he formation of excess~ve quantities of tobacco dust. ~he like~ihood of breakage or dust forma~ion iæ particularly pronounced in the aforementioned drying apparatus wherein a stream of tobacco ic conveyed through a revolving open-ended vessel in the presence of hot air, This is due to the fact ~hat the revolving vesseL sub-jects the particles of tobacco to a pronounced agitating ac~ion dur-ing which the particles are repeatedly lifted well above the bottom : zvne of the vessel by orbiting rakes or blades and are allowed to drop by gravity back into the bottom zone. NevertheLess, many to-bacco growers s~ill employ such types of dryi~g apparatus because their conditioning action is more uniform than that of pneumatic dry-ing apparatus~
Additional problems in connection with conditioning of to-baccc arise due to the fac~ ~hat the ~pace in a modern tobacco pro~
cessing plant is at a premium, Thu~, the manufac~rers strive to accommodate the conditioning apparatus in a small area while simuL-taneously desiring a high output and an accurate conditioning of each and every t~bacco particle, i.e., the temperature and/or mois-ture content of conditioned tobacco should equal or should be very close to an optlmum temperature and moisture content. This can be achieved if the dimensions of condi~ioning appara~us can be increased - at will, i.e., if the drying of moist tobacco can be carried out while the particles of tobacco are advanced a~ a rela~ively low speed - 20 a~d through a re~atively long conditioning zone so that the reduction :: of molsture content can be achieved gradually. In other words, a ~a~isfactory reduction of moisture content and a ~atisfactory heat~
- ing or cooling of tobacco presunts no probLems if the changes in such characteristics are efected at a slow rate, namely if the ex-tent of drying per unlt length of the conditloning apparatus and per unit of time i~ relatl~eLy smaLl~ Such treatment insures a reLiable homogenization of the final product so that the temperature as weLl as the moisture content of ea~h particle issuing from the condition-ing zone is best suited ~or further processing. Thi8 is due to the 30 fact that a conditioning for a long period of time and in a relative;
~ 7 -`
7~ :
, . ~
ly long conditioning zone can readily compensate for ~luctuations in initial --temperature and/or moisture content as well as for eventual fluctuations in the intensity of treatment during one or more drying stages.
In certain recent types of conditioning apparatus J a relatively short heating zone is followed by a homogenizing zone whose function is to eliminate eventual variations in moisture content of tobacco which issues from the drying zone ~see German DAS No. 2,103,671~. Such procedure is satisfactory only if the initial moisture content of tobacco ~i,e., of . ~
tobacco which enters the drying zone) is constant or deviates only slightly ln from a fixed value. It has been found that the just described conditioning ; apparatus fail to ensure a satisfactory homogenization and cannot achieve a ` reduction of moisture content to a fixed value unless the initial moisture -- content is constant or deviates only negligibly from a fixed value. Thus, fluctuations of ini~ial moisture content are likely to adversely influence the drying action or to prevent a satisfactory drying to such an extent that the homogenizing or uniformizing treatment cannot cure the defective drying ~ -action.
According to one aspect of the present invention there is provided ; . .
a method of drying tobacco which comprises feeding a continuous stream of tobacco particles into an elongated path, transporting the particles along ~;
the path, subjecting the particles to the homogenizing action of a heated first gas current (preferably air) in a first portion (first homogenizing zone) of the path including establishing a state of exact or substantial hygroscopic equilibrium between the first current and tobacco particles in a first portion of the path, reducing the moisture content of tobacco particles in a second portion of the path (for example and preferably by ;
contacting the particles with hot air or another suitable gas which flows .~ .
transversely of the tobacco stream in the second portion of the path), .' '~
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.; .
. ,~,,,~
. .
subjecting the particles to the ac~ion of a hea~ed second gas cur-rent (preferably air) in a third portion (second homogenizing zone) of the pa~h including est~blishing a state of hygro~copic equilibrium .between the second current and the par~icles of tobacco in the ~hird po~tion of the path, and removing the thus dried and homogenized ,~. .
stream of tobacco particles from ~he path.
ThP method may further comprise the ~teps of measuring the moisture content of tobacco particles upstream of the first portion of the path and changing the moisture content of the first current in response to changes in ~easured moisture content of tobacco part-icles; this insures a desirable homogenizing action in the first por-tion of the path, i,e., prior to e~pulsion of moistur~ in the second porti~n of the path. In other words, the first gas current need not change the characteristics of the main portion of tobacco but merely the characteristics o~ those minor portions (if any) whose :~characteri~tics deviate from the characteristics Df the main portion.
The method may further cooprise the steps ~ measuring the moisture content of tobacco particles downstream of the third por-tion of the path9 comparing the measured moisture content with a 20 predetermined optimum or desirabLe moisture content, and changing the extent of reduction of moisture content in the second portion of the path when the measured moisture content devLates from ~he predetermined moisture con~nt.
The step o~ estabLi3hing a state of hygroscopic equilibr-ium betwecn the 5econd current and the particles of tobacco in the third portion of the path may include maintaining the moisture con-`.tent of the second current in a predetermined reLationship with a predetermined desired or optlm~m moisture content of ~obacco parti-cles which leave the third portion of the path. This insures that the second current need not change the characteristics of the main . -~J
.' .,~
portion of dried tobacco but only the characteristics of that or those minor portions (if any) whose characteristics deviate from the desirable characteristics of the main portion. The homogenizing action of the second :~ gas current is automatic and takes up a short interval of time.
The method may further comprise the steps of measuring the tem-perature of at least one gas current, comparing the measured temperature with a given temperaturel and changing the temperature o~ the one current when the measured temperature deviates from the given temperature. This also contributes to a rapid and pronounced homogenizing action of the respective gas current.
- At least a portion of at least one of the two currents can be cir-culated along an endless second path which intersects the respective portion -:
- of the elongated path for tobacco particles.
The transporting step may comprise agitating the particles of tobacco in at least one of the irst and third portions of the path for ~
tobacco particles so that the respective current contacts and passes through ~ -a layer of agitated floating particles.
The step of reducing the moisture content of tobacco particles in the second portion of the path may comprise subjecting the particles in the second portion of the path to the action of a heated third gas current which is preferably conveyed in a direction to intersect the second portion of the path for tobacco particles. The particles in the second portion of the elongated path are preferably vibrated or otherwise agitated during contact -~ with the third gas current.
, The speed of at least one of the currents is preferably reducedduring contact with tobacco particles in the respective ~first, second and/or - third) portion of the elongated path.
3 According to another aspect of the present invention there is pro-vided in an apparatus for drying tobacco a combination compri5ing means for ! 3Q transporting tobacco particles along an elongated path, said transporting ; ;~ : ' ::
L7~
means comprising a plurality of successive sections defining successive portions of said path; means for feeding a continuous stream of moist tobacco particles to said transporting means; means for homogenizing the particles of tobacco with a first heated gas current in a first section of ~ said transporting means, including means for maintaining said first current - in a state of at least substantial hygroscopic equilibrium with tobacco particles in the respective portion of said path; means for reducing the .' moisture content of homogenized tobacco particles in a second section of said transporting means; means for homogenizing the thus dried tobacco particles with a second heated gas current in a third section of said trans-. porting means, including means for maintaining said second current in a state of at least substantial hygroscopic equilibrium with dried tobacco particles in the respective portion of said path; and means for receiving the thus , . .
dried and homogenized tobacco particles in a continuous stream.
;- In the accompanying drawings which illustrate an exemplary embodi . ment of the present invention:
Figure 1 is a schematic partly elevational and partly sectional view of a conditioning apparatus which embodies the invention; and .:'' .
Figure 2 iS an enlarged transverse vertical sectional view of a 2~ vibratory conveyor in the apparatus of Figure 1.
The conditioning apparatus of Figure 1 comprises a tobacco feeding unit la and a transporting system 1 including a first homogenizing section 2 ~ located immediately downstream of the feeding unit la, a drying section 3 . located immediately downstream of the section 2, and a second homogenizing section 4 located immediately downstream of the drying section 3. The -. second homogenizing section 4 is followed by a removing unit 6 which accepts ~ "
conditioned tobacco from the transporting system 1. .;
The feeding unit la comprises a set of three conveyors for a contin~
- uous stream of tobacco particles 7. These conveyors include a first belt . 30 conveyor 8 whose discharge end showers successive increments of the tobacco . ' . . .
,. ..
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stream onto the upper stretch of a second belt conveyor 9, and a vibratory ; conveyor 11 having a trough which receives successive increments of the tobacco stream from the discharge end of the belt conveyor 9. The trough of the conveyor 11 is vibrated by the eccentric lOa of an electric motor lOb through the medium of a connecting rod 10. The conveyor 9 forms part of a weighing device 12 which serves to ensu:re that the trough of the vibratory . ~
conveyor 11 receives tobacco particles 7 at a uniform and - -.
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unchanging rate per unit of time.
me conveyor Ll dischargeæ tobacco particles 7 onto a down-wardly inc~ined chute 20 which i~ installed in an opening provided - in the left-hand side wall of a chamber 2a forming part of the first homogenizing section 2.
The rhamber 2a of the fLrst homogenizing section 2 of the transporting system 1 receives the leftm~st part of a~ elongated vibratory conveyor 13 a portion of which is ilLu~trated in FIG. 2, Th2 trough of the conveyor 13 comprises a f~raminous bottom wa11 or lO platform 15 having perforations or holes 16 and ~eing supported by leaf springs 14 mounted on a carrier l4a in ~he frame F. The trough of the conveyor 13 further comprises two side wall5 17, l8 which di-. verge upwardly and outwardly in order to reduce the speed o air '. currents which flow up~ardly through the holes L6 of the bottom wall 15 and to prevent such currents from entraining lighter tobacco part-icles. The vibra~ory conveyor 13 is sub~tantially horizontal and : extends through alL ~hree sections 2~ 3~ 4 of the tran~porting sys-tem l as well as beyo~d the second homogenizing section 4 to deLiver condi~ioned tobacco to the removing unit 6. The means for vibrating the trough of the conveyor 13 comprises a variabLe-speed elect~ic motor l9 having an eccentric l~a which tran~mits motion to the trough , by way of a connecting rod l9b.
- The one-piece vibratory conveyor 13 o~ FIGS. l and 2 can ;
be replaced by a series of di~crete co~veyor~ fox example~ by three ~ :
conveyors, one for each of the sectio~ 2, 3 and 4. At least ~ne of the three conveyor~ need not be a vibratory cc~eyor.
; The means for contacting tobacco in the sec~ion 2 wi~h a gaseous homogenizin~ medium comp~ise5 a pipe 21 which comm~nicates with the chamber 2a at a level below the bottom wall lS of the vib- :
ratory conveyor 13. Spent gaseous fLuid (preferably air) is with- .
. ~ ~ 5 . . ~.,~ .
. .. . . . . .. . . ....
~: ;
drawn from the chamber 24 at a level above the layer of tobaco par- ~
ticles 7 in the trough of the conveyor 13 bya pipe or conduit 22. ~-A sieve or filter 5 is provided in the chamber 2a to prevent the ho- -- mogenizing fluid from entraining lighter tobacco particles into the inlet of the conduit 22.
The discharge end of the conduit 22 is connected with the inlet of the pipe 21 by an air conditioning unit having an atomiz-- ing nozzle 23 for discharging controlled quantities of water into the air current supplied by the conduit 22~ and an adjustable elec-lQ tric resistance heater 24. The means for circulating air through - the chamber 2a comprises a blower 25 which draws air from the con-~, duit 22 and forces the thus withdrawn air into the pipe 21. The :
nozzle 23 and the heater 24 are installed in a suction pipe 61 which receives air from the conduit 22 and supplies air to the inlet of the blower 25. Air which enters the suction pipe 61 is heated by the heater 24 and thereupon receives moisture from the nozzle 23.
The second section 3 of the transporting system 1 compris-es three chambers 26, 27, 28 which are separated from each other by ~;~
c transverse partitions having openings 2p for the adjacent portions : ~ .
-~ 20 of the vibratory conveyor 13 and for the layer of tobacco particles 7 on the bottom wall 15. The upper portion of the chamber 26 (above , the conveyor 13~ communicates with the lower portion of the chamber 27 (below the conveyor 13) by way of a suitably con~igurated conduit or pipe 29. The upper portion of the chamber 27 communicates with l the lower portion of the chamber 28 by a similar conduit or pipe 30.
,I The upper portion of the chamber 28 has an outlet opening 32 which discharges air into the atmosphere. A first sieve 35 in the upper ~;
.. . .
portion of the chamber 26 prevents lighter particles of tobacco from entering the inlet of the conduit 29. Similar sieves or filters 35 are provided in the upper portions of the chambers 27 and 28 to re-~'f "' .
'' .
''~ ' .
spectively prevent lighter tobacco particles from en~ering the con-dui~ 30 and outlet opening 32.
The lower portion of the chamber 26 receives heated air by way of a pipe 31 which is connected ~o the outlet of a blower 34.
The intake end of the blower 34 is connected with a suction pipe 74 having an open end for admissiion o atmospheric air and an adjust-able regulating valve or flap 77 which can be piuoted by a ~ervomot-or 76. Atmospheric ~ir which enter~ the inLe~ of the suction pipe 74 is heated by a preferably adjustable electric resistance heater . 10 33, and the ~emperature of hea~ed air entering the blower 34 can be - regulated by changing the angular po~iition of the flap 77 which thereby admit~ a controlled quantity of unheated atmospheric air into the current of air which has passed the heater 33.
.: me third section 4 of the ~ransporting sys~em 1 comprise~
a chamber 4a having side walls which are provided with openings 4p for the vibratory conveyor 13. The lower portion of the chamber 4a (below the conveyor 13) receives a hom~genizing fluid (preferably :~
air) by ~ay of a pipe 36 which receives air fxom a blower 41. The .. intake of the blower 41 i5 connected with a ~uction plpe 89 which . ;
receive~ air from an elongated conduit or pipe 37 communica~ing with the upper portion of the chamber 4a, A sieve or filter 42 in the , - upper portion of the chamber 4a prevents lighter tobacco par~iclPs ~r~m e~tering the inlet of the conduit 37. The ~uction pipe 89 contains an adju~table electric resistance heater 39 and the air curren flowing therein can recei~e controlled quantities of water thr~ugh the orifice5 of an atomizing nozzle 38.
The rernoving unit 6 co~priqes a take-off conveyor 43 here sh~wn as an endless belt the upper stretch of which receives condi-tioned tobacco particLes 44 from the di~charge end of the vibratory conveyor 13. The belt 43 transports cond~tioned tobacco to a ~ur- :
. . .
ther processing station, e,g,, to a baling machine or to ~he maga-zine of a cigarette rod making machine, depending up~n the na~ure : of tobacco particle~ which are being supplied by the feeding unit la.
:. The moi~ture content of ~uccessive increments of tobacco : in the trough of the vibratory conveyor 11 is determin~d by a detect~
: or 46, e.g,, a detector known as H~1K produced by Hauni~Werke of Ham-.~ burg-Bergedorf, Western Germany. The signals which are generated ~, by the detector 46 are trans~itted toca signal c~mparing jun¢tion 52 ~arming part of a control unit 51 which c~nstitutes a m~ans for .~ 10 regulating the moisture content of the curre~t of air flowi~g into ,. the lower portion of the chamber 2a. The junction 52 ls further con-nected with a potentiometer 53 or another suitable rated value ~et-ting device whihh is ad~ustable to fuxnish signals indicating the desired or op~imum initial moisture con~ent of tobacco particles 7 - in ~he conveyor 11. The output of the junction ~2 tranbmit~ a posi~
tive or a nggative signal when the intensity of signals furnished by the detector 46 de~iates from the intensity of signals ~upp~ied by the potenti~meter 53.
The signal from the output of the junction 52 i~ transmit- :
~ed to a ~econd ~ignal comparing junction 54 of the con~rol u~it 5L
as well as to orle input o a signal comparing junction 66 forming part of a ~econd control unit 65 which regulates the heater 24 in , . -~: the suction pipe ~1 of the blower 25. The junction 54 o the con-~rol unit 51 further receives ~ignals from a detector 56 whlch ls . i -- mounted in the pipe 21 and monitors the moisture content of the air current fLowing into the lower portion of the chamber 2a, The de-tector 56 may constltute a conventional hyg~ometer. The ~ignal - from the output of the junction 54 is indicative of the difference between the intensities of signals furnished by the junction 52 a~d 30 de~ector 56, and is amplified by an amplifier 57 which is in circui~
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with a variable~peed electric motor 58 for a variable-delivery pump 59 which supplie~ water to the atomi~ing nozzle 23 in the suc~ic~n pipe 61. The pump 59 draws water from a reservoir (no~ shown) via conduit 59a, The ~uction pipe 61 is further provided wi~ch an adjustable regulating v~lve or flap 62 which i~3 located downstream of the heat-er 24 and up~tream of the nozzle 23 (as considered in the direction of air flow from the cvnduit 22 into the blower 2i~) and who5e posi-tion i~ adjuætable by a servomotor 63. The ~ignals for adjustment of the flap 62 via servomotor 63 are supplied by the output of a threshold circuit 64 which receives signals from the junction 54 of the control unit 51.
The potentiometer 53 of the control unit 51 is preferably ad~lsted in ~uch a way that the current of air flowing into the low-er portion of the chamber 2a is in a s~ate of hygro~copic equilibrium with tobacco particles 7 which are being supplied by the chute 20 onto ~he Leftmost part of the vibra~ory conveyor 13. Thu~, 2~ lea~t ::
.f ,.
~he major part of tobacco which i8 caused to ~ravel through the cham~ ~ :
ber 2a does n~t accept moisture from and is not relieved of moisture . . .
by the current of air which i8 being supplied by the pipe 21, The definit~on ~Ihygroscopic equilibrium" need not nece~saril~ i~dicate that the moisture content of tobacco in the cha~ber 2a is identical with or even close to the moi~ture content of air issuing from the ~:
pipe 21. In fact, in most instances, the moi~ture content of air which is in a state of hygroscopic equilibrium with tobacco deviates considerably from (it i8 much higher than) the moi~ture content of tobacco. The difference between the moi~ture content of tobacco and .
the moisture content of air which i8 in a state of h~Tgroscopic equil-ibrium with tobacco depends on a number of factors, especially the 30 condi.tion of tobacco (e, g,, the nature and percentage o:E fluid and/or .
other matter which is confined in tobacco particles and the chemical composition of such matter or fluid), the structure oF tobacco (e,g,, the formation of capillaries in the ti~ue o F tobacco particles), and the brand of tobacco. For exampLe, the composition of casing and/or the nature and percentage of salts in tobacco will infLuence that moisture content of air or another gas at which the gas is in a state `~ of hygroscopic equilibrium with tobacco, The signal whi~ch is transmitted f~om the junction 52 of the control unit 51 to the junction 66 of the control unit 65 is ` 10 amplified by an ampliier 68 which controls the heater 24 in the - suction pipe 61 of the blower 25. The junctinn 66 further receLves signals from a detec~or 67 which is installed in the pipe 21 and monitors the temperature of air flowing into the Lower porti~n of the chamber ~a. The detector ~7 may constitute a commercially avail-able heat-isensitive PTC or NTC i~emiconductor.
A further detector 71 (which may be identicaL with or sim-ilar to the detector 46) is adjacent to the path of conditioned to-bacco particles 44 in the vibratory conveyor 13 immediately upstream of the take-off conveyor 43. The detector 71 monitor~ the final mois~ure content of ~obacco and transmits appropriate signals to a first input of a ~ignal comparing junction 72 forming par~ o a third control unit 73 for regulating the temperature of air entering the blower 34. A second input of the junction 72 i8 connected with the output of a~ adjustabLe rated value setting device 75 (e.g~, a po-tentiometer) which transmits a slgnal indicating the desired ~empera-ture of air which flows intu the lower portion of the chamber 26.
The output of the junction 72 is connected with an amplifier 74 which tran~mits amplified signals to the servomotor 76 for the adJustable flap 77 in the sucti~n pipe 74.
; 30 The characteristics o F air whihh is admitted in~o the low-'A, . _ ~
~! '` /~
~ h 7~ ~
.. er portion of the chamber 4a are determined by two eontroL unlts 81 and 96, The control unit 81 determines the exact moisture content of inflowing air, and the control unit 96 de~ermines the exact te~p~
- erature of such airc The difference between the control units 81 and 96 on the one hand and the control units 51 and 65 on the other hand i8 i:that the control units 81 Imd 96 are adjusted to insure that the final moiRture content of tobacco particLes (44~ doe~ not devi_ ~. ;
- ate from a desired or optimum value.
The control unit 81 co~pri~es an ad~us~able rated value setting device 8~ (e.g., a potentiometer) which transmits signaLs .: .
- to one input of a ~ignal comparing junctio~ 84. Another input of the junctivn 84 receives signals from a detector 83 which monitors ' the moia~re con~en~ of air flowing in the pipe 36. The signal at .~ the output of the junction 84 is amplified by an amplifier 86 which : :
i5 in circuit with a varlable-speed electric motor 87 for a vaxiable-delivery pump 88. The Latter supplies controlled quantities of wat-: er to the nozzle 38 in the suction pipe 89 of the blower 41 and is ~. connected with a source of water by a condu~t 88a. The suction pipe , :. ~9 is provided with an adjustable regulating valve or flap gl which is mounted between the heater 39 and nozzle 38 and iæ pivotable by a servomotor 93 receiving signals from a threshoLd circuit 92 which : is connected to the output of the junction 84.
The control unit 96 compri~es an adjustable rated value .. .
setting device 97 (e~gr~ a poten~iometer) w~ich transmi~s signals :
of selected inten~i~y ~o one;.input of a ~ignal comparing junc~ion 99. Another input of the junction 99 is connected with a detector 98 whi h monitor~ the temperature of air in the pipe 36. The 8ig- :
nal from ~he output of ~he junc~ion 99 is amplified by an amplifier 100 and regulates the heater 39 in the suction pipe 89.
The ope~ation:
." , .
..... . .
:
The moisture content of tobacco particleæ 7 on the convey-or 8 exceeds the desired mois~ure content of tobacco on the ~ake-off conveyor 43. The conveyor 8 delivers the particle 7 in the form ` of a continuous stream which is equalized by the weighing device L2 and i~ fed into the trough of the vibratory conveyor 11. ThU8, ~he `. conveyor 11 receives and discharges identicaL or nearly identical s quantitites of moist tobacco per unit nf time. The detec~Dr 46 mon-itors ~he moistuxe content of tobacco particles 7 and ~ransmits ~ig-nals bo~he junction 52 of hhe con~rol unit 51. The detector 46 is a t~arl~ducer which furnishes to the juncl:lon electric signals of varying in~Qns ity.
The co~aveyor 11 discharges tobacco particles 7 into or on-to the chute 20 which supplies such particles into the leftmost part of the trough forming part of the vibratory conveyor 13, i. e~, ~nto .
the chamber 2a of the first homogenizing ~ection 2. The holes 16 in .the bottom wall 15 of the conveyor L3 permit the passage of small currents of conditioned air whieh is 9upplied by the pipe 21. Such currents cause the par~icles 7 of the tobacco stream on the bottom wall 15 to rLse and to float within the confines of divergent side wall~ 17, 18 which in~ures a highLy satisfactory conditioning of all sides of e~ch tobacco par~icleO
An important function of the first homogenizing section ~ .
2 is to insure a pronounced and reliable homogenization of tobacco .~ which is being supplied by the feeding unit La. Thus, the section 2 eliminates eve~tual differences in the moi9ture con~ent of tobacco entering the chamber 2a, and such elimination of differences ~akes place in response to signals furnished by the detector 46. This in-sures ~hat the drying sction of air in the chambers 26, 27 and 28 of the section 3 is highly satisfactory since the moisture content 30 and temperature o~ tobacco particle~ 7 entering the chamber 26 are , '7~
con~tant due to homogenizing action of the air currents passing through ~he holes 16 of the bottom wall L5 in ~he chamber 2a.
The control unit 51 insures that the moisture content o~
air entering ~he pipe 21 change~ as soon as the intensity of signaL~
furnished by the detector 56 in the pipe 21 devia~es from the intens-ity of signals furnished by the junction 52. The control unit 65 in-sures that the heater 24 is adjuste~d (to effect a more or less pro-nounced heating of air which is belng supplied by the conduit 22) when the intensity of signals furnished by the detector 67 deviates from the int~nsity o that signal which is supplied by the junction 52 (to junction 66). Thus, no~ only the moi~ture content bl1t also the temperature of air which flows in the pipe 21 is regulated by the in~lal moi~Ee content of tobacco par~icles 7. As mentioned ~;
above, the moisture content o~ air in the pipe 21 is selected with a view to insure that the air is in a state o hygroscopic equilibr-ium with tobacco in the cha~ber 2a, i.e., air which enters and pass-es through the chamber 2a should n~ remove moisture from 0r add mois- :
ture to tobacco which passes through the section 2 toward the cham-ber 26. Changes in the mois~ure content of ~obacco passing through the section 2 are not necessary since the main (and preferably the sole) purpose of air supplied by the blowe~ 25 is to homogenize the tobacco before the particles 7 ~ch the drying section 3. The hom~
ogenizing ~ction of air in the chamber 2a is regualted ~or the pur-pose of insuring that the moisture cQntent of all particles 7 leav~ :
lng the section 2 is ~ ticaL with the m~i~ture content of the bulk of tobacco particles supplied by the feeding unit la. Such homogen-izing action of ~he current of air which is circulated along the .,: . . ..
endless pa~h deiined by ~he pipe 21, chamber 2a, con~ui~ 22, suction p~pe 61 and blower 25 is very r~ bl~ whereby the characteristic5 30 of this current change very littLe since the air is not 3upposed to . - -~
,~ o;7, .
:
.. . . ~ . . .. .
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supply moisture ~o or remove moisture from ~he tobacco particles 7, EventuaL fluc~uations in moisture content of the just described air curre~t are eliminated by the co~trol unlt 51 which regulates ~he admission of moisture via no~zle 2:3. If the air flowing in the pipe 21 is so moist that ~ts moisture content e~ceeds the desired value, even if the admission o~ a water spray through thP nozzle 23 is term-inated, the signal from the output of the junction 54 causes the threshold circuit 64 to actuate the servomotor 63 which opens the flap 62 to admit atmospheric air into the suction pipe 61 and to .~ . .
thereby reduce the mois~ure content of air which flows into the low~
er portion of the chamber ?a. Such reduc~io~ in the moi8~ure con-tent of air in the pipe 21 takes place practically withou~ delay.
The particles 7 o~ tobacco in the trough of the vibratory conveyor 13 form a floating stream which advances through the first opening 3p and ent~r~ the first chamber 26 of the drying section 3.
Such particles are contacted from aLl sides by hot air which is be-ing admitted by the pipe 3L to thus insure a pronounced exchange of energy and rapid drying of~tobacco. The temperature of hot air en-tering the lower portion of the chamber 26 i8 regulated by the con-trol unit 73 in response to signals furni~hed by the detector 7L.
The drying i8 contin~t in the chamber~ 27 and 28 ~o that the mois-ture content of tobacco lea~ing the chamber 28 via first opening 4p is normally reduced to a desired optim~m value for further process-ing. The dimension5 o~ the drying section 3 are relatively 5mall which is desirable in a modern to~acco processing plant.
,,:, 9 In order to i~ure a still more satlsfactory homogeniza-tion or uni~ormizing of all characteristics o~ tobacco par~icles which Leave the drying section 3, the conditi~ning apparatus incLudes the second homogenizing section 4 which is especially de~îrable when the drying section 3 is very short and compact, i.e., when the in-~ ,;7~
.
. .. . : .. - . : . ~ .
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tensive drying of tobacco particles takes place within a very short ` ~ interval of time. The current of air which is circulated by the ,' blower 41 has a constant temperature and moisture c~ntent (see the: control units 96 and 81) and is in a state of hygroscopic equilibr-ium with tobacco in the chamber 4a. Thus, the function o~ air in the chamber 4a iB analogous to that of air in the chamber 2a.
The signal from the output of the junc~ion 84 causes the threshold circuit 92 to actuate the servomotor 93 and to open the flap 91 in order to admit atmospheric air into the suction pipe 89 when the moisture content of air in the pipe 36 is exce~sive whlle the admission of water via nozæLe 38 i~ interrupted. This results ~; in practically instantaneous reduction of mo~sture content of air~~ which enters the lower portion of the chamber 4a.
:: The improved ~onditioning apparatus exhibits the advantage ~hat ~he interval w~ich i~ required for the drying of tobacco ~in ~ .
the section 3~ can be reduced to a minimum without adversely af~ect- :
ing the de~irable characteristics of tobacco particles 44 which is-sue from the section 4. This is attributed to homogenlzation in the sections 2 and 4, i.e., prior to and fifter drying in the cham~
bers 26, ~7 and 28. Relatively short and compact drying means are desirable for a number of reason$.
Another ad~antage of ~he improved conditioning apparatu5 is that at lea~t a portion of at least one of th~ homogenizing gas - currents which contact ~obacco particles in the chambers 2a and 4a is circulated along an endle~ path which interæects the path of toba co particles in the respectlve portion of the vibratory convey-or 13, This insures that the characteris~ics o the circulating gas .
current or currents must be altered very little or not at ~all with :~ attendant ~gs in space and energy requirements of the apparatus, Thus, the control units 51, 65 and 81, 96 are used to change the re-~3 i spective characteristics of the gas currents in the plpes 21 and 36 only when ~uch characteristics deviate from an optimum or given . value. The deviations could be much more pronounced if each of the - pipes 31, 36 would have to draw atmospheric air which would have to be conditioned prior to entry into the lower portion of the respec-tive chamber 2a, 4a. These controL units are called upon to regu-late the respective characteristic5 of gas currents in the pipes 21 .
and 36 only when the moi~ture con~en~ of incom~ng tobacco (cnnve~or 11 and chute 20) is not uniform and/or when the moisture cnntent of tobacco leaving the chamber 28 is not uniform. Therefore~ the con-trol unit 51, 65, 81 and/or 96 normally effects only minor changes ; .
in the respective characteri~tic of the corresponding ga~ cureent 50 that, and referring to the reguLation of temperature ~y the flap 62 br 91, a minor change in the position of such flap suf~ices to rapidly change the temperature of the gas current in the pipe 21 or 36 ~o a desired value.
.j : The convey~r 13 al~o contributes to a more intensive and - reliable homvgenizing and drying of tobacco particles by causing -: the particles to vibrate dltring transport through ~uccessive cham-.,, bers so that the currents of air which are admitted via pipes 21~ 3 and 36 can contact all side of each particle in the respectlve sec-:.
~!, tion of the tran~porting system. Thi8 insures an inten~ive exchange of heat energy a~d/or moi~ture between tobacco particLes and gas currents The g~s current which enters the L~wer portion o the cham-ber 4a homogenizes the particles of tobacco in the respective portion .
of the conveyor 13 (when necessary) so that the tempèrature of part-icles leaving the section 4 equals the temperature of gas in the chamber 4a, either by heating or by cooling the conveyed fibrous ma-terial. At least the major portion of tobacco ln the chamber 4a : ; , , , .. , ~ .
does not receive additlonaL moisture and is not relieved of moisture so that the gas in ehe chamber 4a supplies moisture to or withdraws .
moisture from a small portion of tobacco but does not change the moisture content of the ma~or portion of material ~n the conveyor 13.
The treatment of tobacco in the chamber 2a does not affect ~:
the flexibility sf particLes 7 so that such particles are not com-minuted during transport toward the take-off conveyor 43. In fact, such treatment (by the current of gas enering the chamber 4a via pipe 21) enhances the elasticity of tobacco particles while the part-icles are being homogenized prior to entering the first chamber 2S
of the drying section 3.
Still another advantage of the conditioning apparatu~ i5 ~hat it can dispense with several vibratory conveyor~ in the chamber .i 2a. This allows for a reduction of the dim~n~ions of the chamber 2a with attendant ~avings ~ s~ace and lesser and fewer problems in connection with sealing of the chamber. As regards the homogenizing action prior to actual drying, such homogenizing action is perform~
ed by the entire gas current which enters the chamber 2a via pipe 21. ~:
.... . .. ..
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Claims (22)
1. A method of drying tobacco, comprising the steps of feeding a continuous stream of moist tobacco particles into an elon-gated path; transporting the particles of said stream along said path; subjecting the particles to the homogenizing action of a heat-ed first gas current in a first portion of said path, including main-taining said current in a state of hygroscopic equilibrium with the particles; reducing the moisture content of tobacco particles in a second portion of said path; subjecting the particles to the action of a heated second gas current in a third portion of said path, in-cluding establishing a state of hygroscopic equilibrium between said second current and the particles; and removing the particles from said path in a continuous stream.
2. A method as defined in claim 1, further comprising the steps of measuring the moisture content of tobacco particles upstream of said first portion of said path and changing the moisture content of said first current in response to changes of measured moisture content of tobacco particles.
3. A method as defined in claim 1, further comprising the steps of measuring the moisture content of tobacco particles down-stream of said third portion of said path, comparing the measured moisture content with a predetermined moisture content, and changing the extent of reduction of the moisture content in said second por-tion of said path when the measured moisture content deviates from said predetermined moisture content.
4. A method as defined in claim 1, wherein said step of establishing a state of hygroscopic equilibrium between said second current and the particles in said third portion of said path includes maintaining the moisture content of said second current in a prede-termined relationship with a predetermined desired moisture content of tobacco particles leaving said third portion of said path.
5. A method as defined in claim 1, further comprising the steps of measuring the temperature of at least one of said currents, comparing the measured temperature with a given temperature, and changing the temperature of said one current when the measured temp-erature deviates from said given temperature.
6. A method as defined in claim 1, further comprising cir-culating at least a portion of at least one of said currents along an endless second path which intersects the respective portion of said first mentioned path.
7. A method as defined in claim 1, wherein said trans-porting step comprises agitating the particles of tobacco in at least one of said first and third portions of said path so that the re-spective current contacts and passes through a layer of floating particles.
8. A method as defined in claim 1, wherein said step of reducing the moisture content of tobacco particles comprises subject-ing the particles in said second portion of said path to the action of a heated third gas current.
9. A method as defined in claim 8, wherein said trans-porting step comprises agitating the particles in said second por-tion of said path.
10. A method as defined in claim 8, further comprising the step of reducing the speed of at least one of said currents dur-ing contact with tobacco particles in the respective portion of said path.
11. In an apparatus for drying tobacco a combination com-prising means for transporting tobacco particles along an elongated path, said transporting means comprising a plurality of successive sections defining successive portions of said path; means for feed-ing a continuous stream of moist tobacco particles to said transport-ing means, means for homogenizing the particles of tobacco with a first heated gas current in a first section of said transporting means, including means for maintaining said first current in a state of at least substantial hygroscopic equilibrium with tobacco parti-cles in the respective portion of said path; means for reducing the moisture content of homogenized tobacco particles in a second section of said transporting means; means for homogenizing the thus dried to-bacco particles with a second heated gas current in a third section of said transporting means, including means for maintaining said sec-ond current in a state of at least substantial hygroscopic equilibr-ium with dried tobacco particles in the respective portion of said path; and means for receiving the thus dried and homogenized tobacco particles in a continuous stream.
12. A combination as defined in claim 11, further compris-ing means for measuring the moisture content of tobacco particles up-stream of said first section of said transporting means, said means for maintaining said first current in a state of hygroscopic equili-brium with tobacco particles including control means for changing the moisture content of said first current in response to changes in measured moisture content of tobacco particles.
13. A combination as defined in claim 11, further compris-ing means for measuring the moisture content of tobacco particles downstream of said third section and means for adjusting said means for reducing the moisture content of tobacco particles in said sec-ond section in response to changes in measured moisture content.
14. A combination a defined in claim 11, wherein said means for maintaining said second current in a state of hygroscopic equilibrium with dried tobacco particles comprises control means for regulating the moisture content of said second current.
15. A combination as defined in claim 11, wherein at least one of said means for maintaining the respective current in a state of hygroscopic equilibrium with tobacco particles comprises means for measuring the temperature of the respective current prior to con-tact with tobacco particles and control means for adjusting the temp-erature of the respective current when the measured temperature devi-ates from a given temperature.
16. A combination as defined in claim 11, wherein at least one of said homogenizing means comprises means for circulating at least a portion of the respective current along an endless second path which crosses the respective portion of said first mentioned path.
17. A combination as defined in claim 11, wherein at least one of said first and third sections of said transporting means com-prises means for agitating the particles of tobacco in the respec-tive portion of said path.
18. A combination as defined in claim 17, wherein said agitating means comprises a vibratory conveyor having a trough in-cluding a foraminous bottom wall below the particles of tobacco in said one section and the respective current passes upwardly through said bottom wall and form a plurality of smaller currents which pass between the particles of tobacco above said bottom wall.
19. A combination as defined in claim 11, wherein said transporting means comprises a vibratory conveyor for particles of tobacco in said second section and said means for reducing the mois-ture content of tobacco particles comprises means for contacting the particles in said conveyor with a heated third gas current.
20. A combination as defined in claim 19, wherein said conveyor comprises a foraminous bottom wall below the particles of tobacco in said second section and said third current passes through said bottom wall to form a plurality of smaller currents which pass between the particles of tobacco above said bottom wall.
21. A combination as defined in claim 11, wherein said means for reducing the moisture content of tobacco particles in said second section comprises means for contacting the particles with a heated third gas current and further comprising means for reducing the speed of at least one of said currents during contact with to-bacco particles in the respective portion of said path.
22. A combination as defined in claim 21, wherein said speed reducing means forms part of said transporting means.
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DE19732335970 DE2335970C2 (en) | 1973-07-14 | 1973-07-14 | Method and device for drying tobacco |
Publications (1)
Publication Number | Publication Date |
---|---|
CA1041756A true CA1041756A (en) | 1978-11-07 |
Family
ID=5886972
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
CA204,572A Expired CA1041756A (en) | 1973-07-14 | 1974-07-11 | Method and apparatus for conditioning tobacco |
Country Status (6)
Country | Link |
---|---|
JP (2) | JPS5644706B2 (en) |
CA (1) | CA1041756A (en) |
DE (1) | DE2335970C2 (en) |
FR (1) | FR2236428B1 (en) |
GB (1) | GB1476364A (en) |
IT (1) | IT1017119B (en) |
Families Citing this family (17)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE2904308C2 (en) * | 1979-02-05 | 1986-10-23 | Hauni-Werke Körber & Co KG, 2050 Hamburg | Method and arrangement for drying tobacco |
DE2647438C2 (en) * | 1976-10-21 | 1986-11-13 | Hauni-Werke Körber & Co KG, 2050 Hamburg | Method and device for drying burley or green leaf tobacco |
JPS579609Y2 (en) * | 1977-01-27 | 1982-02-24 | ||
JPS5423198A (en) * | 1977-07-25 | 1979-02-21 | Kaneko Agricult Machinery | Metod and apparatus for controlling tobacco leaf drying |
GB2062203B (en) * | 1979-10-25 | 1984-08-30 | Tobacco Res & Dev | Drying of tobacco products |
US4543736A (en) * | 1983-05-27 | 1985-10-01 | Brooks Derrick W | Conditioning apparatus |
JPS6054028B2 (en) * | 1983-12-23 | 1985-11-28 | 日本たばこ産業株式会社 | Tobacco drying and conditioning equipment |
JPS6184463U (en) * | 1984-11-09 | 1986-06-03 | ||
JPS63258553A (en) * | 1987-04-15 | 1988-10-26 | Hokuto Koki Kk | Stevia drying system |
IT1291059B1 (en) | 1997-02-12 | 1998-12-14 | Comas Spa | DRYING MACHINE FOR CHOPPED TOBACCO, IN PARTICULAR FOR CHOPPED AND EXPANDED TOBACCO RIBS |
CN101254022B (en) * | 2008-04-21 | 2010-06-02 | 中国烟草总公司郑州烟草研究院 | Smoked sheet multiple roasting method and special-purpose equipment thereof |
CN103404957B (en) * | 2013-07-10 | 2015-03-25 | 四川金叶生物防治有限公司 | Gas composition and environmental factor controllable tobacco sealing, storage and maintenance method |
CN104068460B (en) * | 2014-07-21 | 2015-11-25 | 江西中烟工业有限责任公司井冈山卷烟厂 | A kind of control method regulating tobacco leaf moisture content, temperature |
CN104305515B (en) * | 2014-08-13 | 2015-12-02 | 上海烟草集团有限责任公司 | The diagnostic system of moisture content of cut tobacco stability and diagnostic method in cut tobacco drying process |
CN109875089A (en) * | 2018-12-29 | 2019-06-14 | 德宏州高达化工实业有限责任公司 | It is a kind of based on natural gas combustion engine be energy resource supply environmentally friendly tobacco flue-curing house |
CN111528510B (en) * | 2020-05-11 | 2022-03-18 | 厦门烟草工业有限责任公司 | Method for drying tobacco shreds, tobacco products and application |
CN113383980B (en) * | 2021-06-25 | 2022-11-22 | 湖南美瑞科技有限公司 | Material baking temperature control method based on combustor, combustor and readable storage medium |
Family Cites Families (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB957532A (en) * | 1961-11-23 | 1964-05-06 | British American Tobacco Co | Improvements relating to the drying of tobacco |
DE2103671C2 (en) * | 1971-01-27 | 1982-12-23 | Hauni-Werke Körber & Co KG, 2050 Hamburg | Process and system for conditioning tobacco |
-
1973
- 1973-07-14 DE DE19732335970 patent/DE2335970C2/en not_active Expired
-
1974
- 1974-06-13 JP JP6761574A patent/JPS5644706B2/ja not_active Expired
- 1974-07-11 FR FR7424107A patent/FR2236428B1/fr not_active Expired
- 1974-07-11 CA CA204,572A patent/CA1041756A/en not_active Expired
- 1974-07-12 IT IT2511174A patent/IT1017119B/en active
- 1974-07-15 GB GB3117474A patent/GB1476364A/en not_active Expired
-
1979
- 1979-02-21 JP JP54019595A patent/JPS589669B2/en not_active Expired
Also Published As
Publication number | Publication date |
---|---|
FR2236428A1 (en) | 1975-02-07 |
FR2236428B1 (en) | 1980-05-16 |
JPS5048199A (en) | 1975-04-30 |
IT1017119B (en) | 1977-07-20 |
GB1476364A (en) | 1977-06-10 |
JPS559794A (en) | 1980-01-23 |
JPS5644706B2 (en) | 1981-10-21 |
JPS589669B2 (en) | 1983-02-22 |
DE2335970C2 (en) | 1982-02-18 |
DE2335970A1 (en) | 1975-02-06 |
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