US2475568A - Method of curing bright-leaf tobacco - Google Patents

Description

July 5, 1949. J. B. MOORE, JR 2,475,563

I METHOD OF CURING BRIGHTLEAF,TOBACCO I Filed Jan. 23, 1945 2 Sheets-Sheet 1 v V #vvz-NI'OR v JA/VAS 49. moo/95 24 J.. B. MOORE, JR METHOD OF CURING BRIGHT-LEAF TOBACCO July 5, 1949. 0

Filed Jan. 23, 1945 2 Sheets-Sheet 2 M H H hm hb. llw i A/ TOR/VE Y Patented July 5, 1949 METHOD OF CURING BRIGHT-LEAF TOBACCO James B. Moore, Jr., Lexington, Ky.

Application January 23, 1945, Serial No. 574,078

12 Claims. 1

The present invention relates to the curing of tobacco leaves and more particularly, to tobacco leaves having the physical and chemical characteristics of tobacco leaves grown in Florida, Georgia, South Carolina, the eastern North Carolina belt, the middle belt of North Carolina and Virginia, and the old belt of North Carolina and Virginia, said tobacco being known as brightleaf flue-cured tobacco, identified by the United States Department of Agriculture as types 11 to 14, inclusive, type 11 being divided into sub-types 11A and 11B.

In accordance with the present invention there is provided a method of curing tobacco leaves which produces thecured tobacco in a relatively short period, said method being characterized by simplicity and economy in operation.

One object of the present invention is to yellow the tobacco in a short period of time while maintaining the relative humidity of the heated air above about 90% or 95% and below but adjacent the dew point without over-ripening the tobacco leaves, that is, spotting said leaves, said humidity preferably varying from about 95% to 98%.

Another object is to accomplish the yellowing process in a relatively short period of time, preferably varying from 36 to 48 hours, and in some cases in 30, 36 or 60 hours. 7

Another object is to accomplish the yellowing step under the conditions above set forth, while utilizing a composite circulating air-treatment medium comprising a predominating quantity of recirculated air and a small quantity of fresh air, just about sufiicient to keep the composite circulating medium below the dew point, that is, to prevent the composite air from being saturated. If the relative humidity approaches 100%, water drops out and therefore it is best to operate at 95% to 98%.

Another object is to carry out the yellowing step under the conditions set forth while circulating the air through the tobacco curing chamber about every 21/ minutes to about 3 minutes. Another object is to effect the yellowing step at a temperature inhibiting any substantial drying of the tobacco leaves, said temperature being preferably below 100 F. and desirably 90 F. to

Another object is to dry the yellowed tobacco .in a relatively short period, preferably 24 to 48 2 structure so that the moisture on the inside of the leaves cannot be removed. Preferably, the tobacco during the drying period is brought up to a temperature varying between F. and F. although it may be brought up to F. or even F. and in some cases even up to a temperature of F. But, at the higher temperatures there is a deteriorating change in the tobacco, sealing or facing beginning to appear at about 135 F. or 140 F.

A further object is to effect drying of the yellowed tobacco while using substantially fresh air, that is, no circulating air is used.

Another object is to effect killing out of the tobacco stems in a relatively short period of time, usually varying from about 24 to 48 hours, using a composite air medium comprising a predominating quantity of recirculated air and a small quantity of fresh air to prevent the composite air medium from building up a high humidity.

A further object is to recirculate air during the drying period every minute to 2 minutes, and preferably 1 minute, that is, the air that enters the chamber at the beginning of the minute period is completely removed from the chamber at the end of 2 minutes and a new cycle starts.

Another object is to effect killing out below For F., and preferably, below 150 F. under the conditions set forth.

In order that the present invention may be more clearly understood, reference is made to the accompanying drawing wherein Fig. 1 is a transverse section more or less diagrammatic of an apparatus for carrying out the present invention, Fig, 2 is a section taken on the line 22 of Figure 1 and Fig. 3 is a cross section takenon line 3-3 of Fig. 1.

Referring to the drawing, in represents a tobacco barn in which tobacco leaves II are hung, the latterbeing tied on sticks, the sticks of tobacco being supported on tier rails l2. The barn l0 is provided with an exit duct I3 and a return air duct M, the former being provided with a pressure damper [5. The return air duct M is also equipped with a regulating damper l6 and the return air duct has an opening H with a slide cover l8 by which means fresh air can be admitted to the duct and to the system. A pressure blower I9 is operatively connected to the duct l4, said blower being equipped with an electrical or gasoline motor 2|]. The blower is operatively connected to the base of the jacket 22 of the furnace 23, the latter being equipped with a vaporizing oil burner means 24 which is connected 3 to the heat exchanger '25 provided with a flue pipe 26 passing through the roof of the shed 21. Operatively connected to the bonnet of the furnace is a supply duct 28 provided with a limit control 29, said control functioning to cut off and on the oil burner at a predetermined temperature, usually within a range of 100 to 200 F. The duct 28 passes into the barn l0, preferably centrally thereof, at the point 281) and is connected by means of a duct 28a to an auxiliary supplying duct 30 provided with a splitter damper 3|. The aux; iliary supply duct is operatively connected to dis tributing ducts 32 and 33 respectively, said ducts,

being of any appropriate shape but preferably:- triangular, and the sides thereof are provided with staggered apertures 34 whereby air is introduced into the barn and distributedevenly over. g

the tobacco leaves therein. Suitably disposed outside of the tight barn I0 is the remote bulb-ther mostatic temperature control 35, preferably having a range from about 80 to 180.?;F.1

The .oil burner is .provided. with an automatic fiow metering valve 36 which is connected by meansof a pipe 31to the oil tank38. The thermostat 35 controls theoif and on magnetic valve of the flow control valve. 36.

The following is a specific example illustrating the present invention:

The barn II] which .is gas tight is filled with about 6,000 pounds of tobacco, the amount which can be introduced into a barn which is 16, x16 x 16.. The tobacco leaves are leaves which have been primed from the tobacco stalks and tied onto sticks, said sticks. being hun ,over. tier rails until thebarn is filled. ,The field ripened tobacco Q.

is introducedinto the .barn ID. as quickly as pos, sible after the priming. The object of introducing the tobacco leaves into the.barn ID as soon as. possible after the priming is toprevent deterioration. of the tobacco. Itmay. be stated that tobacco of thecharacter being ,treated. by the present invention is rather. perishable, it being Well-known that if the tobacco is leftin the fields and subjected .to sunlight for a period of a days time, .itwill. materially depreciate-in value. It is therefore desirable, in order .to preserve the high quality of the tobacco, that the tobacco be introduced into. the barn as .soonas practicable.

Itgislquite desirablethat the process of yellowing, drying and killing the tobacco be started as soon as practicable. after the ,tobacco leaves have beenintroduced into the barn J0; However.

if thetobacco in the barn is kept dark and away.

from-sunlight no appreciable harm ,will result in 24; to 36 hours. However, as.v stated, itis the preferred procedure. that after. the barnis filled with about 6,000 pounds of field ripened tobacco leaves, to initiate the treatment of the tobacco leaves in accordance with the present invention. It may. be stated that the field. ripened tobacco contains between 80% to 88% of moisture. and

one of the objects of .thepresent invention is to. complete the ripening of the tobacco and then'to;

duct 14. Damper I6: isz-placedin its fullopenposition to allow free access .of return air from, the barn ID to the return air-.duct Ill. .The belt connecting blower l9 and the motor 20 is then adapted. on operation to deliver about 1,500 C. F. M. of air composed of 100 cubic feet of fresh air and 1,400 cubic feet of return air to the furnace 23. The small amount of outside fresh air functions to keep the relative humidity of the circulated air from reaching the dew point where, as is well-known, condensation occurs. If condensation forms on the tobacco leaves, the latter become oxidized and assume what is known in the art as a spongy state. As stated, the function of the fresh air is to keep the recirculated air from-reaching the dew point and therefore,

functionally stated, enough outside fresh air' is started, the blower l9 having been placed in.

operation. The mixture of airproduced as above set forth thenbegins to circulate through the barn l0.

It is desiredto point out that the relative humidity of therecirculated air is maintained within a range which will allow the tobacco-leaves to yellow\ without any substantial. drying-.. In

accordance with the present invention it is found.

thatthe most satisfactory results are obtained during the yellowing period when the recirculated air is maintained ,with-a relative humidity. of 95' to 98%. Less. satisfactory results: are. obtained when the humidity is maintained between to Itis therefore desired not to limit the invention to.-,a rangeiof. humidity during yellowing of 95 -to 9,8%.

When-processing a batch of 6,000 pounds of tobacco it has been foundthat operating with the above uantity of air and under. the above conditions of humidity, the tobacco is yellowed in a period ranging from about 36 to 60 hours.

Naturally, this period will vary.- somewhat tiependingon thephysical and chemical characteristics of the tobacco,.the size .of the tobacco leaves, and theirstate of field ripeness. If the tobacco leaves are thick and the stems are large and,

only partially ripened, the time of yellowing under the, conditions 'setforth will approximate the period of 60 hours; thinnerand the stems arev smallen-the time of yellowing under the conditions above set forth may decrease to about 50;.hours; Tobacco leaves have been satisfactorily yellowed using thepresent inventionywhemtreated under the conditions .set forth for a periodof. 36.and .40hours respectively. Depending on the above circum-- stances the time of.- yellowingunder the-conditions,-.set -for.th nayvary froml36- toes hours, 36:

l to 55 hoursor 36 to 60 hours;

It is desiredto-point outthat, for. a burner of thesize set forthyandoperating under'the con-- ditions set forth that there is a substantially completgrecirculation .of air in; the barn every 2% to .3 minutes.- This rateotair movement. through crea ed. sothattheai is recirculated atthe rate;

If .the tobacco leaves are above set forth, that is, a complete recirculation of all the air in the. barn occurs every 2 to 3 minutes. Using a barn x 20' x 16', and having a. Volume of 6,400 cubic feet, the amount of cubic feet of air circulated through the barn would be increased to 2,100. During a threeminute cycle air would be recirculated at the rate of 6,025 cubic feet of recirculated air and 375 cubic feet fresh air, making a total of 6,400 cubic feet for the three-minute cycle. Using the 16' x 16 x 16 barn for a three-minutes period the total amount of air circulated would be 4,500 cubic feet of which 300 cubic feet would be fresh air and 4,200 cubic feet recirculated air.

When the tobacco leaves reach their desired yellow color as indicated. by visual inspection, the yellowin step is terminated and the drying step is initiated by first setting the thermostat to about F. to F. or F. Thereafter the damper I 5 in the exhaust duct is is placed in its full open position, the return air damper I6 is placed in its full closed position, and the belt connecting the motor and fan is placed in its maximum position for the full operation of the blower. Air is drawn in through the opening I! into the return air duct l4 and is forced by the blower l9 through the duct 28, preferably at the rate of 4,000 C. F. M. From the duct 28 the air traveling at the rate set forth is introduced into the barn 10, preferably for a period varying between 24 to 48 hours. The air functions to dry the tobacco leaves and the temperature of the tobacco will gradually increase during the time period set forth from 95 F. to about 120 F. or 130 F. It is desired to point out that by maintaining this lower temperature and increasing the air flow across the tobacco the rate of drying is increased without damaging the cell structure of the tobacco and, the volatile oils of the tobacco are retained. Therefore, while 120 F. or 130 F. has been set forth as the maximum or preferred temperature durin the drying period, it is recognized that even using the exeedingly high rate of 4,000 cubic feet of fresh air per minute that the temperature of drying may be increased to 130 F., F., or even F. Experiments have been carried out using a drying temperature as high as F. or F. but the best and most satisfactory results .are obtained when using a drying temperature of 120 F. to 130 F. If the temperature is increased over about 120 F. or 130 F., with each increase there is usually a deteriorating change in the quality of the tobacco until complete facing occurs which seals the cell structure so that moisture on the inside of the leaf cannot be removed. This is highly undesirable.

During the drying period the humidity of the air leaving the exit duct l3 will change from approximately 98% relative humidity at the initiation of the drying period to approximately 25% to 30% and substantially all of the moisture has been taken out of the tobacco leaves, but a considerable amount of moisture still is left in the tobacco stems. The amount of moisture present in the leaves will depend upon the particular kind of tobacco being treated and its growing history. During the drying period the air in the barn is changed approximately every minute, this having given the most satisfactory results. The general statement as to the frequency of change is that the air may be changed in the barn l 0 during a period ranging in length from 45 seconds to about 1, 1 or 2 minutes. The rate of drying may be increased to approximately one-half minute air change but care would have to be exercised to inhibit facing of the tobacco. It should be borne in mind that the rate of evaporation of the moisture fromthe tobacco leaves should be governed by the total amount of heat being introduced into them and if this rate is accelerated beyond a certain point the cell structure would be damaged and facing would occur.

After the tobacco leaves have been properly dried it is necessary to dry the tobacco stems and this stage is technically known as the killing out stage. At the end of the leaf-drying period, the damper l 5 and exit duct l3 are practically closed, that is, only a small opening remains suflicient to bleed off the excess air from the barn. The damper It in the return air duct I4 is then placed in its full open position and the slide damper I8 is practically closed to within one or two inches of its full shut position. This will allow a small quantity of fresh air to enter the return air duct l4 and be mixed with the recirculated air from the barn l0. At approximately the same time the thermostat 35 is set to about 150 F. to 190 F. The limit control 29 is then set in its full open position and preferably at 250 F. During the killing out period the object is to gradually increase the temperature of the tobacco and of the air circulating in the barn to that point which is suflicient to remove the remaining moisture in the tobacco stems, preferably the tobacco temperature and that of the circulating air being allowed to reach about 150 F., but may be as high as F. of F. After the moisture has been removed from the tobacco leaves during the drying period, the increase in temperature will not have any deleterious effect upon the properties or the quality of the dried tobacco leaves. During the killing out period, the air is circulated at approximately the same rate as used during the drying period, it being pointed out, however, that during the drying period all fresh air is used and that during the killing out period only about 10% fresh air is introduced into the barn. In other words, at any given period of time the circulating air in the barn comprises 90% of old recirculated air and 0% of fresh air. During the killing out period a small portion of the total contents circulated through the barn I0 is exhausted through the exhaust duct l3 and to com pensate for this loss of air, a small amount of fresh air is let into the barn to keep the circulated air from building up to a high humidity. Usually it is best to maintain the relative humidity of the air circulating in the barn l0 during the killing out period as low as possible and generally within a range of 10% to 15%. At the initiation of the killing out period the humidity of the circulating air will probably be in the neighborhood of 20%, 25% or 30%.

The killing out period will usually range from 24 to 48 hours depending upon the physical and chemical characteristics of the tobacco and depending on the thickness of the stems. It is preferred that during the killing out" period that there be a complete air recirculation every minute although here again this may be reduced to onehalf minute or may be increased to 1%, 1 1%, or 2 minutes. The total amount of air circulated per minute through a barn 16' x 16 x 16' is 4,000 cubic feet, of which approximately 7 to 15%, but preferably 10% is fresh air.

It is desired to point out that the tobacco stems should be substantially completely dried so that when the tobacco is exposed to the unconditioned air it will not readily absorb moisture and in ture of the tobacco below a maximum of about 170 F. by passing over the tobacco a current of heated air, the relative humidity of which decreases during the killing out to a relatively dry state.

2. The method of curing tobacco consistingof stems and leaves, said tobacco having the characteristics of tobacco grown in Florida, Georgia, South Carolina, the eastern North Carolina belt, the middle belt of North Carolina and Virginia, and the old belt of North Carolina and Virginia, said tobacco being known as bright-leaf fluecured tobacco, comprising confining the tobacco in a Substantially airtight curing chamber having inlet and outlet ducts, yellowing the tobacco by subjecting it for a period varying from about 36 hours to about 60 hours to a current of heated air which inhibits any substantial drying of the tobacco and has a relative humidity above about 95% and below but adjacent the dew point, said current of air comprising a predominating quantity of recirculated air and a small quantity of fresh air which keeps the composite circulating air-medium below the dew point, drying the yellowed tobaccofor a period of time varying from about 24 to about 48 hours while gradually increasing the temperature of the tobacco to about 130 F. while simultaneously subjecting the tobacco to a current of circulating fresh air, the relative humidity of which at the outlet of the curing chamber is gradually reduced from adjacent the dew point to a relatively dry state, and subjecting the so-treated tobacco to a circulating current of heated air for a killing out period of time varying between from about 24 to about 48 hours while gradually increasing the temperature of the tobacco below a maximum of about 150 F. by passing over the tobacco a current of heated air, the relative humidity of which decreases during the killing out to a relatively dry state.

3. The method of curing tobacco consisting of stems and leaves, said tobacco having the characteristics of tobacco grown in Florida, Georgia, South Carolina, the eastern North Carolina belt, the middle belt of North Carolina and Virginia, and the old belt of North Carolina and Virginia, said tobacco being known as bright-leaf fluecured tobacco, comprising confining the tobacco in a substantially airtight curing chamber having inlet and outlet ducts, yellowing the tobacco by subjecting it for a period. varying from about 36 hours to about 60 hours to a current of heated airwhich inhibits any substantial drying of the tobacco and has a relative humidity varying between from about 95% to about 98%, said current of air comprising a predominating quantity of recirculated air and a small quantity of fresh air which keeps the composite circulating airmedium below the dew point, drying the yellowed tobacco for a period. of time varying from about 24 to about 48 hours while gradually increasingthe temperature of the tobacco to about 130 F, while simultaneously subjecting the tobacco to a current of circulating fresh air, the relative humidity of which at the outlet of the curing chamber is gradually reduced from adjacent the dew point to a relatively dry state, and subjecting the so-treated tobacco to a circulating current of heated air for a killing out period. of time varying between from about 24 to about 48 hours while gradually increasing the temperature of the tobacco below a maximum of about 170 F. by passing over the tobacco a current of heated air, the relative humidity of which decreases during the killing out to a relatively dry state.

4. The method of curing tobacco consisting of stems and leaves, said tobacco having the char acteristics of tobacco grown in Florida, Georgia, South Carolina, the eastern North Carolina belt, the middle belt of North Carolina and Virginia, and the old belt of North Carolina and Virginia, said tobacco being known as bright-leaf fluecured tobacco, comprising confining the tobacco in a substantially airtight curing chamber having inlet and outlet ducts, yellowing the tobacco by subjecting it for a period varying from about 36 hours to about 60 hours to a current of air having a temperature varying from about F. to about F. and a relative humidity above 90% and belowbut adjacent the dew point, said current of air comprising a predominating quantity oi recirculated air and a small quantity of fresh air which keeps the composite circulating air-medium below the dew point, drying the yellowed tobacco for a period of time varying from about 24 to about 48 hours while gradually increasing the temperature of the tobacco to about 130 F. while simultaneously subjecting the tobacco to a current of circulating fresh air, the relative humidity of which at the outlet of the curing chamberis gradually reduced from adjacent the dew point to a relatively dry state, and subjecting the so-treated tobacco to a circulating current of heated air for a killing on period of time varying between from about 24 to about 48 hours while gradually increasing the temperature of the tobacco below a maximum of about 170 F. by passing over the tobacco a current of heated air, the relative humidity of which decreases during the killing out to a relatively dry state.

5. The methodof claim 1 wherein the circulating air is completely circulated through the curing chamber during the yellowing period every 2% minutes to 3 minutes; during the drying period every of a minute to 2 minutes; and during the killing out period every 1 minute to 2 minutes.

The method of claim 1 wherein the circulating air is completely circulated through the curing chamber during the yellowing period every 2 minutes to 3 minutes; during the drying period every 1 minute; and during the killing ou period every 1 minute.

'7. The method of curing tobacco consisting of stems and leaves, said tobacco having the characteristics of tobacco grown in Florida, Georgia, South Carolina, the eastern North Carolina belt, the middle belt of North Carolina and Virginia, and the old belt of North Carolina and Virginia,

said tobacco being known as bright-leaf fluecured tobacco, comprising confining the tobacco in a substantially airtight curing chamber having inlet and outlet ducts, yellowing the tobacco by subjecting it fora period varying from about 36 hours to about 60 hours to a current of heated air which inhibits any substantial drying of the tobacco and has a relative humidity above about 90% and below but adjacent the dew point, said current of air comprising a predominating quantity of recirculated air and a small quantity of fresh air which keeps the composite circulating air-medium below the dew point, drying the yellowed tobacco for a period of time varying from about 24 to' about 48 hours while gradually increasing the temperature of the tobacco to between about -and F. while simultaneously subjecting the tobacco to a current of cir- QA-ZMQQ acteristi s o a co rown F ori a G o ia.

South Carolina, the eastern'North Carolina belt the middle belt of Northgarolina and Virginia and the old belt ofaNorth Gar-olina, and Virginia, said tobacco being; known as bright-leaf fluecured tobacco, comprising confining the tobacco a I in a substantially, airtight curing chamber havn inlet and outletduc s, yell win -the oba co y subiectin it for. ap ri d va ying from abou 36 hours to. about fiflihours to a. current. or heat d.

air which inhibits, anysubstanti-al dryin of the tobacco and has. a relative humidity above about 90% andbelow but adjacent thedewpoint, said current of air comprising a predominating quantity of recirculated air and-a small quantity'ofifresh air which keeps. rthecompositecirculatingair-j medium below the; dew point-,drying-the yellowed tobacco for a period 015 time varying. from about 24 to about 48 hourswhi-le. gradually increasing the temperature. of-the tobacco ,tobetween about 120? and 130..F..while simultaneously subjecting" the tobacco to a currentof: circulating fresh air, the relative humidity of which at the, outlet; of' the curing chamber is graduallyreduced from ad. jacent the. dew point tola relatively dry state, and subjecting the. so-treated ,tobaccoito; a circulatin current at heated. air .for. a .flrillinghout -period. of time varying between from. about? 24 to about 48 hours while graduallyincreasingthei temperature, of the tobacco belowama'ximum. of. about 170-911 by passing over the tobacco a current otheated air, the relative humidity. of which. decreases during. the killing. out to aerelativelye. dry state.

9'. The method oficuringztobaccol consistingofi stems and leaves, said .tobaccohavingthel characteristics of. tobacco grownin Florida,- Georgia, South Carolina, the eastern North-Carolina, belt, theemiddle belt. t North 'Garolina. and Virginia, and. the old belt ofiNorth Carolina and Virginia, said: tobacco. being known as: bright-leaffluecured. tobacco,.coniprising. confining the tobacco.

in a substantially. airtight curing; chamber. having. inlet and outlet.ducts yellowing the tobacco by subjectingit for. aperiod varying. trom about 36 hours to aboutffiodhour's to a. current. or. heated air which inhibits. any substantialidrying: of the tobacco. and lhasa relative. humidity above. about 90% and below but. adjacent the'.;dW;pDint-, .S&ld' current of airicomprising a predominatingquan: tity of recirculated. air iandifa small. quantity of: fresh air keeps the composite. circulating airemedium below tlieadewipoint; dryin'githe yel-l lowed tobacco/tore a period? of: time varying from. aboutles to about id-hours; while. gradually in: creasing the. temperature ofi-the tobacco; tobee tweenv about Iftand. 140% E. whilesim ultaneously subjecting,the-tobacco to a currentloflcirculatingi-fi esh air, the relative humidity of which at the. outlet? of the curing, chamber is gradually reduced from. adjacent thedewpointtoa rela.. tively dry state, andcsubjectinggthe. so'etreated tity ofrecirculated airanda ater-zeta a circulat n curr n f heated ai 117 a b ll n u relie Qf' ime var in b t een om about 4 tqabuu abo rs whi gr dual y 'e r e i-a th emeera e o he heat b owa maximum of about 170 F. by passing overrt he o a o. curren o a ed 1 3, he re a iv humidity of which decreases during-the ,killing out to a relatively dry state.

10. The method of curing tobacco consisting of-stems and leaves said tobaccohavingthee "f acteristics of tobacco grown in Florida; Georgia, South Carolina, the. eastern-North Carolina; belt the middle belt of North Carolina and Virgin and the old belt of. North Carolina andvirginia said tobacco being. known as brightrleaf fluee cured tobacco, comprisingconfining the tobacco; in. a substantially airtight curing-chamber have inginlet and outlet ducts, yellowing the tobacco; by subjecting it for a period varying from. about; 3 ur to a t 6.0 h s a c rren heated: air which inhibits any substantial drying ogthe;

0% nd l w- -t; e ia entth 11 at current of aireompri sing. a predominat quali:

that fresh air which keeps; the comp osit i airFmediu-m below; the dew point;- lowed tobacco, for a period; ofti I M I about 24= to about 4-8 hours wlg ilegra creasing the temperature ct thetebac tween about and 1403 1. while s is y ubi t n eto a e to a curr n v cul-ating .tresh air, the relative humidity at e u t o eu ee Qbam eree allr reduced from adjacent the dew nt-toar tivelydrystate, and :killing outiGthe-tob stems o f the so-treated tobacco by subjectingqthe; at r to. a c cula i r e e -hea ed air h t: radua cr as n he t mhe e en b o a m x mum o 7- ing of saidl eated current of air ere a yehu i o t e hea. ts du th in o tpee i l -errs a h a siheated air e -reela e i nd; b t en /2=%. a d cash ..1:- T metho of wi n tobac onsi ting: efi t ms anc a es a d qhaceoh e r ti s o ac erow E1. afieore a; Sou h e r l a; he s rn No h; Ca ina belt, the. middle beltot North Carolinaan dtirginia; and the oldbelt of North Carolina and; Virginia said tobacco being k -nown as bright' leaf; flue-N cured tobaeco, comprising confining the. tobacco in a substantially airtight curing chamber have ing inlet and: outlet ducts, yellowing the tobacco by. subjecting it for a period varyi ,-f;rornabout. 36 hours to about 60 hours-to a-cur nt of ,l eated; a r which inhibits substantial-dryingOfgtht tobacco and has. a relative humidity alcoye about 0 andbemw t d acen ;theoewrqin curr nt ia r compri n a redem netina ty etres rqelated a rand a sma h ua ti r i re a wis kee s the compo ite q sr ahe e eme ium l w th de wi te time ravel lowed tobacco for a p riod of time varying iijbm about 24 to about 48 hours while gradually in creasing the temperature of the tobaccoto 'b' e-. tween about 120 and F. while simultaneously subjecting the tobacco to a cur-rntof circulating fresh air, therelativehumidity-ofi.which at the outlet of the curing chamber is gradually reduced from adjacent the-dew, point, to a. rela-' tively dry state, and killing; out" the tobacco stems. ot the. sol-treated: tobacco! by subj ectingi thelatter to a circulating current of heated air comprising recirculated air and between 7 and 15% of fresh air for a "killing out period of time varying between about 24 and 48 hours while gradually increasing the temperature of the tobacco below a maximum of 170 F. by the passing of said heated current of air over the tobacco, the relative humidity of the heated air decreasing during the killing out period to a relatively dry state.

12. The method of claim 11 wherein the circulating air is completely circulated through the curing chamber during the yellowing period every 2 minutes to 3 minutes; during the drying period every of a minute to 2 minutes; and during the killing out period every minute to 2 minutes.

JAMES B. MOORE, JR.

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

UNITED STATES PATENTS Number Name Date Re. 22,221 Mayo Nov. 10, 1942 211,210 Barnett Jan. 7, 1879 1,194,351 Benjamin Aug. 15, 1916 1,327,692 Beinhart Jan. 13, 1920 1,339,374 Buensod May 4, 1920 1,811,980 Smith June 30, 1931 2,273,284 Plott et a1. Feb. 17, 1942

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