US2229942A

US2229942A - Method for conditioning tobacco

Info

Publication number: US2229942A
Application number: US75352A
Authority: US
Inventors: Rush D Touton
Original assignee: Wurton Machine Co
Current assignee: Wurton Machine Co
Priority date: 1936-04-20
Filing date: 1936-04-20
Publication date: 1941-01-28
Anticipated expiration: 1958-01-28

Description

2 Sheets-Sheet 1 R. D. TOUTON F'led April 20, 1936 METHD FOR CONDITIONING TOBACCO Jan. 28, 1941.

WWA/Ess.- @44% Jan.\28, 1941. l R. D. Tou'roN 2,229,942

METHOD FOR CONDITIONING TOBACCO Filed April 20, 1936 2 Sheets-Sheet 2 Patented Jan. 28, 1941 UNITED STATES PATENT oi-"rlcEii METHOD FOR CONDITIONING TOBACCO Rush Tonton, Cynwyd, Pa., assigner to Wurton Machine Company, Philadelphia, Pa., a, cor-, poration of Pennsylvania Application April 2o, 1936, `serial No. 75,352

3"Claims.

This invention relates to a method for condi-F tioning tobacco. i i

More particularly, this invention relates to a method for the treatment of tobacco, more parl ticularly by the` addition or extraction of moiswith this invention will be adaptable for usein the preparatiommore particularly by regulation of the moisture content, of uncured tobacco for curing as, for example, by fermentation, in the preparation, by regulation of the moisture content, of tobacco for packing, in the preparation,

by regulation of the moisture content, of tobacco 5 for fabrication as, for example, the production of cigars, and in the `treatment or preparation of tobacco iorsuch other purposes where regula-.-

tion of the moisture content, by mositening or drying, is desirable. A

Heretofore it haspof course, been `well known to condition tobacco by moistening or drying and, to accomplishthe conditioning, it has been well known to subject the tobacco to an atmosphere conditioned with respect `to l temperature and moisture content of humidity.v

In the conditioning of tobacco' by procedures i heretofore known, results have not beenentirely satisfactory, in that desired uniform conditioning has notbeen obtained, the color of the tobacco hasbeen deleteriously affected and variously tobacco in a lot subjected to conditioning has been damaged by spotting, or the tobacco `has been made tender or deprived ofelasticty.

Now in c accordance with this invention a method` is provided by which tobacco will be readily uniformly conditioned and brought to a desired moisturecontent by the addition or subtraction of moisture without injury to the tobacco and, indeed, in many cases and in connection with certain subsequent treatments, as fermentation,` with positive improvement in the tobacco, more especially from the standpoint of color, aroma, tensile strength and general quality.

Generally speaking, the method in accordance with this invention involves subjecting tobacco, desirably in hands comprising leavesin laminated relation, to a large volume of a circulating gas, as air, conditioned as to `temperature and moisture contentv and maintained with respect to its condition during the, conditioning operation within a narrow range of difference between the dry bulb temperature and the Wet bulb temperature. From a more detailed standpoint, the temperature of the conditioned gas when moisture is bewith this invention involves circulating a con# ditioned gas within and through a chamber in which the tobaccowill be contained, preferably secured to a conveyor, or carried on trucks, by which it will be` `moved within and about the chamber. A conditioned gas, its precise condition from the standpoint of wet and dry bulb temperatures depending upon whethertmoisture is to be added to or taken from the tobacco, will be prepared in a suitable conditioning apparatus and caused to circulate in large volume about the tobacco therein, as through a suitably directed system of ducts. The conditioned gas will be recirculated or withdrawn or discharged from the chamber before the change in the spread .or difference between its wet bulb temperature and its dry bulb temperature, or change in depression of the wet bulb temperature, exceeds about 1.5 F., or more particularly with changein spread or difference within` about the range 0.1-2.0" F. The gas withdrawn from the chamm ber `is then, for economy, in whole or in part brought back to its original condition, bythe addition or extraction of moisture and/or heat,

by passage through` a suitable conditioning apparatus and/or the addition of fresh gas, as air,

from the atmosphere, and recirculated about the In carryingout the method in accordance with` this invention the maintenance of a substantially uniform condition of the gas to which the tobacco is subjected, or maintenance ofthe narrow change in spread between the wet and dry bulb temperatures of the gas introduced into the chain--` ber containing the tobacco and that withdrawn from the chamber will be accomplished by the circulation through the chamber of asufciently large volume of air, or air at a sufficient` rate so that the total heat released `or absorbed by thetobacco in the absorption or release of mois` ture taken `with the heat input or loss` tothe conditioned gas from various sources, such as lights, a circulating fan, the conveyor, persons in the chamber, input or loss through the Walls of the chamber, or otherwise, will' be absorbed and carried out of the chamber, and, at the same time, the moisture loss to the tobacco or gain therefrom lwill be such that the air leaving the chamber will retain wet and dry bulb tempera tures such-that their change in spread will be within the range indicated.

The conditioning, when moisture is addedto the tobacco, will desirably be carried out with the conditioning gas at a slightly lower temperature than that 'of the tobacco and the tobacco may be subjected yto forceful jets of gas at slightly higher temperature and/ or moisture content than 'lli that in general circulation about the tobacco. Generally, the condition of the gas will always be such with respect to the temperature of the tobacco that condensation oi' moisture on the tobacco will not occur.

Having now indicated in a general way thek nature and purpose of my invention, I will proceed to a detailed description of a form of apparatus adapted for use in carrying out the method, preferred procedure in accordance therewith being described in detail in connection with description of .the apparatus, all with reference to the accompanying drawings in which:

Figure i is a plan view, partly in section and partly diagrammatic, of a preferred form of apparatus for carrying out this invention.

Figure 2 isa side view, partly in section and partly diagrammatic, of the apparatus shown in Figure 1.

Figure 3 is a detailed view, partly diagrammatic, showing control means for controlling and maintaining the temperature and relative humidity of the conditioning gases used.

Figure 4 is a similar detailed view of a modied control means.

Figure 5 is a detailed view, partly in section, of means for controlling wet or dry bulb temperature.

The conditioning chambe? Referring to the Figures 1 and 2, a indicates a chamber, which may be of any suitable dimensions, depending upon the amount of tobacco to be treated, and which is desirably insulated. 'I'he chamber is provided with suitably placed doors for the introduction and removal of tobacco. The chamber is also provided with openings i and i', controlled by dampers :i and i', for the admission and dischargarespectively, of air from the chamber.

Within the chamber a is positioned an endless conveyor b of any desired type and which may comprise a pair of endless chains c from which are supported at spaced intervals cross members or bars to which the hands of tobacco may be attached.

The chains c pass over a series of relatively large sprockets e, e secured to shafts f, f journaled in a suitable frame and arranged in line in the upper portion of the chamber; and also over a series of relatively small sprockets h, h secured to shafts f', f' journaled in the frame and arranged in line in the lower portion of the chamber and in staggered relation with the sprockets e, e; and iinally over sprockets Ic, k secured to shafts journaled in the frame and positioned above and beyond the ends of the series of sprockets e, e.

The conveyor will be driven through a sprocket on one of the shaft f' by any suitable connection with any suitable prime mover, as through a chain or belt froman electric motor, the prime mover being desirably positioned without the chamber.

By virtue of the arrangement of the several sprockets e, h and k, the conveyor will have a number of pairs of substantially vertical reaches I in its travel from one end to the other of the series of sprockets e and h, which in pairs will be relatively close together, the pairs being relatively widely separated; and a horizontal overhead return reach o. The conveyor may be reversed over the arrangement shown in the drawings, i. e. the horizontal reach may run below the vertical reaches instead of above, with reversal of the relative positions of the large and small sprockets, the tobacco passing over the small sprockets instead of beneath them.

Within the chamber a adjacent one end thereof is positioned a gas, as, for example, air, conditioning apparatus comprising a casing n pr:- vided with inlet openings and containing a fan positioned adjacent the inlet openings and driven by a motor M positioned outside of the chamber. 'I'he fan willv be arranged to deliver gas or air, drawn from the chamber, through a humidifier, which may comprise a water spray or sprays l0 supplied by a pump p positioned outside the chamber, and over a heating element q, which may be an electrical unit or a steam coil supplied with steam from a boiler r positioned outside of the chamber. 'I'he conditioned gas or air is discharged from the conditioning apparatus under the influence of the fan, into a main duct s, which extends longitudinally in the upper part of the chamber along one side thereof.

The humidifier may, for various uses of the apparatus, as in the moistening of tobacco, operate in effect as a cooler, dehumidifier and humidier and for such operation will be supplied with cold water at a temperature such as to effect desired cooling, dehumidiiication and humidiflcation for the provision of gas or air having desired wet and dry bulb temperatures for delivery to the duct s. Cooling may also be effected by admission of cold air to the humidifier,

or by the provision of a cooling surface suitablyk positioned within the chamber a.

From the duct s, a series of vertical ducts t, t lead downwardly at one side of the chamber to the bottom thereof on lines between the pairs of vertical reaches l of the conveyor and terminate in lateral outlet openings u, u from which conditioned gas is discharged transversely of the chamber between the pairs of vertical reaches l of the conveyor for the provision of general circulation of air in the chamber. The air issuing from outlet openings u, u will travel toward the opposite wall of the chamber and deflected thereby will assume a rotary motion in the chamber or travel in a circulatory path so that tobacco carried by the conveyor will be surrounded by a sheath of conditioned gas in rotary circulation.

From the series of ducts t, t a series of horizontal ducts v, v extend transversely of the chamber beneath the sprockets e, e on lines between the pairs of vertical reaches l. Upwardly extending nozzles y, y are adapted to direct forceful jets of conditioned gas into hands of tobacco carried by the conveyor as the conveyor passes over the sprockets e, e.

A second series of horizontal ducts z, z leading from the main ducts extend transversely of the chamber between pairs of the sprockets e, e, and adjacent the top thereof. The ducts z, z' are provided with lateral nozzles '2, 2 adapted to direct conditioned gas at an angle with respect to the butts of hands of tobacco carried by the carrier and to promote local circulation in the upper portion of the chamber. Suitably valved

pipes

3, 3, terminating in spray nozzles and connected to a suitable source of water are let into the ducts z, z for the supply of additional moisture or a changed temperature to air passing therethrough.

A series of horizontal ducts I, 4 arranged in vertical alignment and leading from they main duct s, extend transversely of the chamber and adjacent to the sprockets lc at the rear' of the chamber over which the conveyor passes into the horizontal return reach o. The ducts4, 4 are provided with nozzles 5, 5 spaced at angles to the vertical such as to direct forceful jets of air into hands of tobacco carried by the conveyor as it passes over the sprocketslc.

A horizontal duct 6 leading from the main duct s extends transversely over the return reach o of the conveyor. The duct 6 is provided with downwardly extending nozzles adapted for the 4direction of forceful jets of air into hands of tobacco carried on the horizontal reach c of the conveyor. A suitably valved pipe 6 provided with a spray nozzle at its end and connected with a supply of water may be let into the duct s and similar Valved pipes 3 provided with spray nozzles connected with l'. supply of water may be let into ducts a for the supply of moistune to the conditioned gas passing therethrough.

The various ducts may be provided with dampers, as dampers whereby the amount of air passing from thf various ducts may be controlled or entirely shut off. e

Those portions of the apparatus described above and the method of conditioning tobacco therein are substantially those described `and claimed in my copending application Serial No.`

perature in the chamber a. The opposite end of the tube or rod 35 is rigidly connected by a crossbar 38 to a second metal tube or rod 36, substantially identical in form with 35. The crossbar 38 and the outer ends of the

rods

35 and 36 are supported by means of roller bearings 39 on the frame 31 and hence are free to move longitudinally with respect to the frame. The end of the rod or tube 36 opposite the cross-bar 36 is supported and guided by the hanger 46 depending from the rod 35, and is formed into a valve member 4|. This valve member 4I cooperates with a valve seat 42 in the adjustable block 51 to close a restricted passage 43 in this block. The block 51 is adjustable with reference to the frame 31 `by means of the screw 44. A cloth or wick 45 covers substantially all of the metal tube or rod 36 and extends into a pan 46 formed in the frame 31. The wick 45 is kept wet by water in pan 46 and hence the metal tube or rod 36 is responsive to the wet bulb temperature chamber a.

The pan 46 is kept constantly full of water fromV is well known and is no part of the present invention. Each comprises a casing within which is positioned a diaphragm 28 to which is connected a plunger 29 extending outside the casing. The space on one side of the diaphragm is provided with an opening for the admission `of air under pressure, and forms a pressure chamber,

All the pressure responsiveY while the space on the other side of the diaphragm is open to the atmosphere. A spring 36 urges the diaphragm against air pressure in the pressure chamber. The diaphragm of one of the pressure responsive control elements 21 is connected by a plungerl29 with a valve 6| in the Water line supplying the sprays I6 and by means of the branch air line 23 with thefmain-air supply line 22.` The diaphragm of another element 21 is similarly connected with a valve 62 in the steam line leading to the heating element q, by a branch air line 24 to the air line 22M Similarly, the diaphragme of the other control elements are connected by means `of the linkages. 3| and 3|' with the

louvres

9 and 7", respectively, in the openings i and i', and by means of the

branch air lines

25 and 26, respectively, with the main air line 22. l,

The main air pressure line 22 is supplied from any suitable source of air pressure (notshown) and this pressure, after passing through restricted orice 56,- is registered on the air pressure gauge 56 and passes by means of the

branch connections

23, 24, 25 and 26 to the pressure chambers ofthe several pressure responsive con trol elements 21. `A branch air line 2| connects the main air pressure line 22 with the temperature and humidity control device 26 at the restricted passage 43.

The operation of the conditioning control apparatus described above will, it is believed, be obvious, it being noted that the tubes or

rods

35 and 36 will respond respectively to variation in the dry and wet bulb temperatures in the chamber a and the result of this response, by expansion or contraction, will effect -a variation in the position of valve member 4| with respect to valve seat 42and more or less air from the line 22 will be led through passage 2|, resulting in variation of the pressure on the diaphragm of the control elements 21 and consequently variation in the setting of the steam andwater valves 62 and 6| and Aof the louvres 1 and j'. The springs 36 of the several elements 2 will be of a strength with re- I spect to the limits of variation of4 pressure in the line 22 under control of the element 26 so that with variation of wet and dry bulb temperatures in the air entering the conditioning apparatus the valves controlling the admission of water and steam to the conditioning apparatus and the louvres j and 9" will be automatically adjusted to recondition the air for return to chamber a to the precise amount required to maintain in the chamber a the conditions required for the particular treatment.

Referring to `Figure 5, 16 indicates a dry bulb temperature control device, comprising a metal tube or rod 1|, having a high coefficient of expansion, xedly mounted at one end in a support 'I2 and slidably mounted adjacent its other end in a support 13. Thefree end of rod 1| is forced into a valved member 14, adapted to cooperate with a valve seat 15 in an adjustablev block 16. The device 16 actuates the water and steam valves 86 and 3| by control of `the pressure in air line 96 in the same manner as does the control device 26 more fully described above. As will be obvious, if it is desired that the control device 16 control wet bulb temperature, it is only necessary to surround the rod 1| with a wick extending into a supply of water, as in the case of device 26.

Referring to Figure 4, a modified form of conditioning control means 26 is shown. This control m :ins is responsive only to changes in relative humidity and comprises strands of humidityresponsive material 53, such as, for example, human hair, adjustably connected at one end by means of a screw 54 to the frame 31 of the control means. The opposite end of the strands of hair is connected to the link 5I pivotally connected to the frame 31. The link 5I is formed at one end into a valve member 4i' cooperating with a valve seat 42' to close the passageway 43' in the frame 31'. A spring 55 urges the valve 4| against its seat. 'Ihe control device may be connected with the air pressure line 22' by means of a branch line 2|' in the same manner as the control device shown in Figure 3.

A decrease in the moisture i intent of the conditioning gases as they pass over the control element will cause the strands of hair 53 to contract, thus moving the valvezelement 4|' away from its seat l2' against the action of the spring 55 and thereby opening the passageway 43'. This will cause a reduction in the air pressure obtaining in the line 22 which will be transmitted in the manner described above to the various pressure responsive control elements used to actuate the water and steam valves and shutters.

It will be appreciated that the entire humidifying apparatus shown largely within the chamber a may be placed without the chamber, a suitable duct being proviccd to lead air from the chamber to the inlet side of the fan and the duct system within the chamber being connected by a suitable conduit with the discharge from the humidifier.

In the operation of the apparatus embodying my invention as above described for the carrying out of the method in accordance with this invention, for example, for the addition of moisture to tobacco, tobacco in the form of hands comprising bunches of leaves bound at their butts are secured to the cross bars extending between the conveyor chains c. The tobacco, for the addition of moisture, may be in an extremely dry condition, such as is received by, for example, manufacturers of cigars, or it may be in such a state of dryness as to require the addition of but a small amount of moisture to condition it, for example, for fermentation. y

The tobacco inhands may be secured to the cross bars of the conveyor by any suitable form` of clip or fastening means, which will desirably engage the butts of the hands only, leaving Vthe leaves free. The tobacco can be readily secured to the conveyor at one end, as, for example, the front end, the conveyor being gradually advanced until completely iilled with the tobacco. Before or immediately after the conveyor is charged with tobacco the humidifying apparatus is placed in operation and circulation of humidied air through the chamber a is set up. The condition of the air will depend upon the tobacco subjected to treatment and upon the ultimate condition desired for the tobacco. Hence, it will be appreciated that when adding moisture to the tobacco, the exact condition of the air from the standpoint of temperature and humidity, or, in other words, the wet bulb and dry bulb temperature, are not of the essence of this invention, since they may be varied, depending upon the type or kind of tobacco subjected to treatment and the ultimate condition of the tobacco. It will be obvious that the time of treatment may be varied.

By way of illustration, Where, for example, very dry tobacco, as, for example, wrapper tobacco, is to be conditioned for use, for example. in the fabrication of cigars, the air introduced will desirably have a temperature of '70 F., and

The volume or rate of circulation of conditionedv air through the chamber a and the conditioning apparatus will be such that the loss of moisture to the tobacco and absorption of heat released by the tobacco and heat absorbed by the air from other sources of heat within the chamber will not produce a change in the difference between the dry bulb and wet bulb temperatures of the air in excess of 2.0 F. and preferably not in excess of about 1.0 F.

The air leaving the chamber, as has been indicated, is reconditioned by passage through the humidifying apparatus and is returned for recirculation in and through the chamber a. The temperature and humidity control device 20, responsive to the dry bulb and wet bulb temperatures of the air leaving the chamber a, is so adjusted as to cause variation in the conditioning elements included in the hurnidifying apparatus, with variation in the difference -between the dry and wet bulb temperature of the air leaving the chamber. Thus, the device 20 controls, as has been described in detail, the Water and heat supplied to the humidifying apparatus and hence varies the conditioning from the standpoint of temperature or moisture content of the conditioned air, to insure maintenance of the Wet and dry bulb temperature difference for which the control is set. Likewise, the control device operates to maintain the condition of the air in chamber a through control of the louvres y' and y", through which air from outside the chamber a may be taken into the chamber and air from the chamber a may be discharged from the chamber, respectively.

AIt will now be noted that by virtue of the control devices 20 and 10 affected by the condition of air leaving the chamber and passing into the humidifying apparatus, the conditioning apparatus functions, with respect to the condition of the air drawn -from the chamber to recondition the air for discharge into the chamber, from the standpoint of temperature and moisture content, to an extent such as to maintain the difference between wet and dry bulb temperatures Within the limits prescribed for the air leaving the chamber, and to maintain the desired temperature. It will be observed that in proceeding in accordance with the method embodying this invention theair circulating about the tobacco in the chamber a is constantly at a substantially uniform condition throughout the period required to effect desired moistening of the tobacco, due to large volume of air used. As a result, all the tobacco within the chamber is subjected to a uniformly conditioned air. In other words, portions of the tobacco are not subjected to air having diierent conditions from the standpoint of humidity, such as has heretofore been customary. Consequently, all the tobacco in the chamber a receives moisture at a uniform rate and without the possibility of local heating or of local condensation, with the result that all the tobacco is moistened to a uniform degree and the possibility of discoloration or spotting is eliminated.

Recirculation of `the air will avoid excessive loss from the tobacco of valuable components in that the recirculated air will be as it were saturated with components of the tobacco capable of being lost to the air. l

In the carrying out of the method in accordance with this invention for the molstening of tobacco, it will be desirable that the temperature n of the air circulated about the tobacco in chamberfa be lower than the temperature of the tobacco. The tobacco in absorbing moisture tends to heat. The conditioned air will desirably be cool relative to the temperature of the tobacco to the end that the tobacco as it absorbs moisture will be constantly and uniformly subjected to a cooling action by the air. Under certain conditions, the air discharged from the nozzles 2 and y leading from the conduits v and z will be cooler, or at a lower temperature than the air in general circulation `in the` chamber in order to insure against any local heating of the tobacco, more Particularly, within the hands into which the nozzles discharge. The discharge of air through nozzles u and 2 at a lower temperature than that oi the air in general circulation may be readily accomplished by the provision of cooling devices within the conduits v and z. The provision of brine coils within the conduits v and z will adequately provldefor air at a lower temperature than that in general circulation. Again, it will be desirable in manycases that the air discharged angularly against the butts lof the hands of tobacco through nozzles 2 have a higher moisture content than that of the air in general circulation in the chamber, or, in some cases. that it actually carry Iree moisture. The moisture content of air discharged through nozzles 2 may be increased over that in lgeneral circulation. as supplied by the humidifying apparatus, or free moisture added to the air by the introduction ci a spray of water into the conduit z through the valved pipes 3.

In carrying out the method in accordance with this invention for the extraction of moisture from tobacco, for example, for the extraction of moislture from green tobacco to prepare it for Iermentation or packing. the procedure described above in connection with the molstening of tobacco will be followed, with control of the humidifying apparatus, which will in such .case act as a dehumidiiying apparatus, so that. thelimitation on the diirerence between the wet and dry bulb temperatures oi the air leaving the chamber,.as

` indicated, will be maintained.

In the extraction or moisture from tobacco or drying, the conditioned air will beat a higher temperature or warmer than the tobacco and ordinarily heat generated by air movement of a big volume or air by the fans will supply all evaporation requirements. Usually because o! working at low change in depression. heat must be extracted from the air leaving the chamber. Variousiy. it may be desirable that air at a temperature higher than that in general circulation in the chamber a be discharged through the several jets described above. 'I'he discharge from the lets o: air at a higher temperature than that in general circulation in the chamber will be readily accomplished by the provision of any suitable Storm of heating device in the conduits v and/or e, from which the nozzles 1; and 2 discharge. 'I'he provision or an` electric heating elementg or of a steam coil in the conduits will adequately serve the purpose.

Generally speaking, in practice, the wet bulb depression of the air introduced into chamber a will not exceed about 10 F. For drying the wet bulb depression preferably will be within about the range 4.5-10" F., while for moistening the wet bulb depression will preferably be within about the range 0.1-4.0" F. and the air discharged from the chamber will not have a change in depression in excess of about 2.0 F., and preferably the change will bevwithin the range 0.5-1.5 F. `In. either case the temperature'change will desirably not exceed 2.5 F. and preferably the temperature change will not exceed 0.5-1.0 F.

The air discharged from the various iets de scribed will desirably be under some pressure, as for example, a pressure of 0.2-1.5 inch water gauge.

It will be appreciated `that various modiilcations may be made in the preferred embodiment of apparatus as illustrated and described and that various modlcations in procedure according to the method of this invention as described may be made without departing from .the scope of the inaddition of moisture thereto, which includes circulating a gas conditioned with respect to temperature and moisture content about tobacco in a chamber, withdrawing the gas from the chamber in a condition such that the change in depression o! its wet bulb temperature does not exceed about 2.0 F., the conditioned gas being characterized by the fact that its temperature is lower than that of the tobacco as it absorbs moisture from the gas and periodically subiecting the tobacco to forceful jets of conditioned gas characterized by the iact that its temperature is lower than that oi the conditioned gas in general circulation about the tobacco. v

2. The method of conditioning tobacco which includes circulatinga gas conditioned with re` spect to temperature and moisture content about the tobacco in a chamber, withdrawing the gas from the chamber in a condition such that the change in depression of its wet bulb temperature does not exceed about 2 F. and periodically subiecting the tobacco to forceful jets of conditioned gas characterized by the fact that its temperature is lower than that of the conditioned gas in general circulation about the tobacco.

3. The method of conditioning tobacco by the addition of moisture thereto which includes circulating a gas conditioned with respect to temperature and moisture content about the tobacco in a chamber, withdrawing the gas from the chamber in-a condition such that the change in depression of its wet bulb temperature does not exceed about 2 F., .the conditioned gas being characterized by the fact that the conditioned gas enters the chamber with a wet bulb depression not exceeding about 10 F., and periodically subjecting the tobacco to forceful jets of conditioned gas characterized by the fact that its temperature is lower than that of the conditioned gas in general circulation about the tobacco.

RUSH D. TOUTON.