US3389707A

US3389707A - Method and apparatus for expelling moisture from tobacco

Info

Publication number: US3389707A
Application number: US565426A
Authority: US
Inventors: Wochnowski Waldemar
Original assignee: Hauni Werke Koerber and Co KG
Current assignee: Koerber AG
Priority date: 1965-07-22
Filing date: 1966-07-15
Publication date: 1968-06-25
Anticipated expiration: 1985-06-25
Also published as: DE1532070B2; GB1149524A; DE1532070A1

Description

June 25, 1968 w. WOCHNOWSKI 3,389,707

METHOD AND APPARATUS FOR EXPELLING MOISTURE FROM TOBACCO Filed July 15, 1966 INVENTOR. (/4 #dauzNl/MML BY I MMJ- Min r United States Patent 3,389,707 METHOD AND APPARATUS FOR EXPELLING MQISTURE FROM TOBACCO Waldemar Wochnowski, Hamburg, Germany, assignor to Hauni-Werke Koerber & (10., KG, Hamburg-Bergedorf, Germany Filed July 15, 1966, Ser. No. 565,426 Claims priority, application Great Britain, July 22, 1%5, 31,264/ 65 31 Claims. (Cl. 131-135) The present invention relates to a method and apparatus for conditioning tobacco by expulsion of surplus moisture. More particularly, the invention relates to improvements in a method and apparatus for controlled expulsion of moisture from a continuous stream of tobacco particles.

It is already known to expel moisture from a tobacco stream by conveying such stream through a series of separate driers in each of which the stream is heated to expel therefrom moisture in a series of successive stages. A serious drawback of such methods and apparatus is that the operation is too expensive and that the expulsion of moisture requires too much heat energy. This is due, at least to a certain extent, to the fact that, while travelling between successive driers, the particles of the tobacco stream are exposed to atmospheric air.

Accordingly, it is an important object of the present invention to provide a method of expelling moisture from a continuous stream of tobacco particles in such a way that the operation consumes little heat energy.

Another object of the invention is to provide a highly versatile and compact apparatus which may be utilized in carrying out the improved method.

A further object of the invention is to provide an apparatus of the just outlined characteristics which can be readily converted for treatment of tobacco particles containing relatively small or relatively high percentages of moisture.

An additional object of the invention is to provide a novel heating system which can be utilized in the above outlined apparatus.

A concomitant object of the invention is to provide an apparatus for expelling moisture from tobacco which, though provided with a single drier, is capable of treating each successive increment of the stream in a plurality of stages and in such a way that the amount of heat energy consumed in each such stage is selected as a function of certain important characteristics of tobacco particles.

Briefly stated, one feature of my invention resides in the rpovision of a condition ng apparatus which may be utilized for expelling moisture from freshly destalked tobacco leaf laminae or from cured lea-f laminae subsequent to shredding. In its simplest form, the apparatus comprises a feed arranged to advance a stream of moist tobacco lengthwise toward, through and beyond a conditioning zone, a drier preferably assuming the form of a rotary drum which is accommodated in the conditioning zone and defines a continuous conditioning chamber having an intake end which receives successive increments of the stream and a discharge end from which such increments issue, heating means comprising a pair of supply means the first of which admits into the intake end of the conditioning chamber at least one first current of hot air or other suitable fluid which flows concurrent with the stream and expels moisture from tobacco and the second of which admits at least one second current of hot fluid into the discharge end of the conditioning chamber whereby such second current or currents flow countercurrent to the stream and expel additional moistrue from tobacco, and evacuating means communicating 3,339,7b7 Patented June 25, 1968 with the conditioning chamber intermediate the intake and discharge ends of this chamber to receive the first and second currents from the drier.

The heating means preferably comprises two adjustable heating units each of which includes one of the aforementioned supply means and each of which can be adjusted by a separate control unit. One of these control units is arranged to adjust the respective heating unit in accordance with changes in one or more characteristics of the stream which enters the intake end of the conditioning chamber and the other control unit adjusts the corresponding heating unit in accordance with changes in one or more characteristics of the stream after such stream leaves the conditioning chamber. For example, each of the control units may comprise a weighing device and/ or a moisture detector.

The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved tobacco conditioning apparatus itself, however, both as to its construction and its mode of operation, together with additional features and advantages thereof, will be best understood upon perusal of the following detailed description of certain specific embodiments with reference to the accompanying drawings, in which:

FIG. 1 is a diagrammatic side elevational view of a tobacco conditioning apparatus which embodies one form of my invention, a portion of the drier being broken away;

FIG. 2 is a transverse vertical section through the drier and evacuating means substantially as seen in the direction of arrows from the line IIII of FIG. 1; and

FIG. 3 is a fragmentary axial section through the drier and evacuating means.

Referring first to FIG. 1, there is shown a conditioning apparatus which comprises a feed 10, 12, 16, 8, 18, 2G, a drier 2, heating means including two

adjustable heating units

28, 48 and a third or auxiliary heating unit 148, two control units 135, 136 and an evacuating device 76 serving as a means for selecting the areas in which the

heating units

28, 48 are effective. The feed is arranged to advance a stream T of tobacco leaves lengthwise and through the conditioning chamber 2a (see FIG. 2) of the drier 2. This drier resembles a hollow cylinder or drum whose axis is inclined downwardly, as seen in the direction of feed, so that successive increments of the stream T which are admitted at the intake end of the conditioning chamber 2:: tend to advance automatically through and to leave the conditioning chamber in response to rotation of the drier. Therefore, the variable speed motor 8 which rotates the drier 2 can be said to form part of the feed for the tobacco stream T. The drier is rotatable on supporting rolls 1 which are mounted in bearing brackets 4 and 6, and the output shaft of the motor 8 carries a pinion 3 which meshes with a ring gear 5 at the intake end of the conditioning chamber 2a. Instead of utilizing a variable speed motor 8, the feed of my conditioning apparatus may comprise a constant-speed motor and a variable speed transmission whose output shaft is then connected with the pinion 3 in a manner as disclosed, for example, in US. Patent No. 3,039,201 to Esenwein.

In addition to the motor 8, the feed includes a conveyor belt 10 which advances the stream T lengthwise in the direction indicated by an arrow 7 so that successive increments of the stream descend onto a second conveyor belt 12 which cooperates with a first detector 12a forming part of the control unit 135. The detector 21a constitutes a weighing device which weighs successive increments of tobacco in the stream T and produces impulses which are indicative of the measured results. The conveyor belt 12 delivers the tobacco stream T into a vibrating trough 14 forming part of a dielectric moisture detector of the type disclosed, for example, in the copending application Ser. No. 192,834 to Esenwein which is assigned to the same assignee. The dielectric moisture detector determines the moisture content of successive increments of tobacco in the stream T (in percent) and produces impulses which are indicative of the results of such measurements. This detector also forms part of the control unit 135.

The trough 14 discharges tobacco into an inclined chute 16 which delivers such tobacco into the intake end of the conditioning chamber 2a in the rotary drier 2. Successive increments of conditioned tobacco are discharged into a second inclined chute 18 which delivers such tobacco onto a conveyor belt 20, and this belt in turn discharges tobacco into a vibrating trough 22 forming part of a second dielectric moisture detector and constituting a component of the second control unit 136.

The auxiliary heating unit 148 comprises a series of heating elements here shown as coils 24 which extend along the full length of the conditioning chamber 2a and are supported by the drier 2 so that each such coil rotates about the axis of the drier when the motor 8 is on. As shown in FIG. 2, the coils 24 are distributed in such a way that they form vanes or blades which perform an agitating and mixing action to make sure that the particles of the stream T are loosened and intermixed and that each such particle is fully exposed to undergo a highly satisfactory drying or moisture expelling treatment. The coils 24 of the heating unit 148 are connected to a header 24a which is accommodated in the discharge end of the conditioning chamber 2a and rotates with the drier 2. This header 24:: receives hot water, steam or another suitable heating fluid from a supply pipe 26. A discharge pipe 27 serves to evacuate spent heating fluid from the coils 24. The coils 24 heat the tubular wall 62 of the drier 2 so that the particles of the stream T are heated by contact with the coils 24 as Well as by contact with the internal surface of the wall 62. The coils 24 of the auxiliary heating unit 148 can be replaced by electrically heated heating elements and the wall 62 of the drier 2 can be heated independently of such heating elements without in any way departing from the spirit of my invention. The wall 62 resembles a hollow cylinder.

The first adjustable heating unit 28 operates with hot air and comprises a blower 34 whose pressure side is connected with a supply pipe 36 discharging into the intake end of the conditioning chamber 2a. The inlet of the blower 34 is connected with a suction pipe 32 whose intake end accommodates an electric resistance heater 30 so that the current of air drawn into the pipe 32 is heated prior to flowing past an adjustable valve 38 constituting the adjusting means of the control unit 135. This valve 38 controls the admission of relatively cool atmospheric air through a nipple 37 which is connected with the suction pipe 32. Thus, the momentary position of the valve 38 will determine the temperature of the current of hot air which flows into the supply pipe 36 and thence into the intake end of the conditioning chamber 2a. The position of the valve 38 can be adjusted by a servomotor 40 which forms part of the control unit 135. The current of hot air issuing from the supply pipe 36 flows concurrent with the tobacco stream T and traverses successive incerements of the stream even before such increments descend into actual contact with the coils 24 and/or with the wall 62. This air current also performs a combined agitating, loosening and mixing action and this contributes to more uniform drying of the stream T.

The second adjustable heating unit 48 also operates with hot air and comprises a blower 134, a supply pipe 56 which discharges into the discharge end of the conditioning chamber 2a a suction pipe 132 whose intake end accommodates an electric resistance heater 130, a valve 50 which is installed in the suction pipe 132 and constitues the adjusting means of the second control unit 136, and a nipple 51 which can admit relatively cool atmospheric air into the suction pipe 132 at the rate determined by the position of the valve 50. This valve is adjustable by a servoinotor 52 of the control unit 136. It will be noted that the current of air issuing from the supply pipe 56 flows countercurrent to the tobacco stream T, i.e., in a direction toward the intake end of the conditioning chamber 2a and counter to the direction of flow of the current which issues from the supply pipe 36 of the first adjustable heating unit 28.

A substantially centrally located median portion 83 of the wall 62 of the drier 2 is formed with apertures or perforations 34 which are closely adjacent to each other. Thus, the perforated median portion 83 forms a foraminous annulus or sieve intermediate the axial ends of the wall 62. The dimensions of the apertures 84 are selected in such a way that they permit escape of fluid but that the particles of tobacco forming the stream T remain in the conditioning chamber 20.

The sieve 83 is surrounded by an annular fluid collector or hood 64 which forms part of the evacuating device 76 and is movable axially of the wall 62 as indicated by a double-headed arrow 76a. This hood 64 comprises two annular end portions or

flanges

65, 67 which are in scaling engagement with the external surface of the wall 62 and are disposed substantially at the opposite axial ends of the sieve 83. The hood 64 defines with the wall 62 an annular compartment 113 which communicates with the central region of the conditioning chamber 2a through the perforations 84. As shown in FIG. 3, the axial length of the compartment 113 is somewhat less than the axial length of the sieve 83. The difference between the two axial lengths can approximate the thickness of the

flange

65 or 67.

The numeral 68 denotes a pipe also forming part of the evacuating device 76 and serving to receive or to withdraw fluid from the compartment 113. This evacuating device 76 further comprises a substantially conical or funnel-shaped portion 66 which is connected with the hood 64 and pipe 68 in such a way that its cross-sectional area diminishes in a direction away from the compartment 113. The discharge end of the pipe 68 is connected to a fan 68a or another suitable suction generating device through the intermediary of a flexible hose 112.

The hood 6-4 is reciprocable axially of the drier 2 (arrow 76a) to the extent determined by two annular external stops or

collars

80, 82 provided on the wall 62. The lefthand end position of the hood 64 is shown in FIG. 1 by solid lines. the phantom lines indicate the right-hand end position of the hood 64 when the latters flange 67 abuts against the collar 80. When the hood 64 assumes the solid-line position of FIG. 1, its flange 67 overlies and seals a group of perforations 84 at the righthand axial end of the sieve 83. In other words, the compartment 113 then communicates with the conditioning chamber 2a only through such perforations 84 which are located at a relatively great distance from the supply pipe 56 of the second adjustable heating unit 48 so that the current of hot air issuing from the pipe 56 will cover a greater distance prior to being drawn into the compartment 113 and thence into the pipe 68. If the hood 64 is thereupon shifted to its phantom-line position, the distance which the current of hot air issuing from the supply pipe 56 must cover on its way into the compartment 113 is reduced. The reverse holds true for the current of hot air which issues from the supply pipe 36 of the first adjustable heating unit 28. In the phantom-line position of the hood 64, the left-hand flange 65 seals a group of perforations 84 at the left-hand axial end of the sieve -83. Of course, the hood 64 can be moved to any desired number of intermediate positions each of which corresponds to a different distance which the currents of hot air issuing from the

supply pipes

36, 56 must cover on their Way into the compartment 113. The combined crosssectional area of all such perforations 84 which remain exposed in any desired axial position of the hood 64 is always the same and the perforations which are surrounded by the flange 65 and/or 67 are airtightly sealed from the compartment i113.

The means for shifting the hood 64 axially of the drier 2 comprises a threaded spindle 70 One end of which is rotatably afiixed to the funnel 66 and which meshes with a fixed spindle nut 72. The other end of the spindle 70 carries a hand wheel 74 or an analogous actuating device which can be rotated by hand or by remote control to select the exact axial position of the hood 64. If desired, the spindle 70 may be provided with an index which is movable with reference to a fixed scale whose graduations indicate various axial positions of the hood 64.

The pipe 68 withdraws or receives the air currents which are admitted by the

supply pipes

36 and 56 as well as all such vapors which develop in response to drying of tobacco in the conditioning chamber 2a. If desired, the pipe 68 can be arranged to discharge such air currents and vapors directly into the atmosphere, i.e., the fan 68a can be dispensed with.

It will be seen that the currents of air admitted by the

supply pipes

36, 56 respectively flow concurrent and countercurrent with reference to the direction of tobacco feed and are withdrawn from the conditioning chamber 2a via perforations 84, compartment 113, and pipe 68. The two air currents meet in a region somewhere between the axial ends of the dried 2 (depending on the momentary axial position of the hood 64). The hood 6-4 cannot rotate with the dried 2 because the funnel 66 is connected with the spindle 70. In other words, save for relatively small axial movement in response to rotation of the spindle 79, the entire evacuating device 76 remains stationary. If this evacuating device is provided with a fan, such as the fan 68a, it also comprises the flexible hose 112 (shown in FIG. 2) so that the fan 6811 need not move with the hood 64. Alternatively, the entire pipe 68 may consist of flexible material.

It was found that the heating action of air currents which are discharged by the

supply conduits

36, 56 is more intensive in that region of the conditioning chamber 2a which is located diametrically opposite the funnel 6 6 of the evacuating device 76. Such localized intensification of heating atcion is particularly strong when the fan 68 is on. In order to eliminate -(or at least to reduce) localized intensification of heating action, the evacuating device 76 may comprise a series of pipes 68 and an equal number of hoses 112 which are distributed circumferentially of the hood 64 and are connected to a common suction fan or to a series of separate fans. A second flexible hose 112' is indicated in FIG. 2 by phantom lines.

The control unit 135 comprises the aforementioned dielectric detectors 12a, 14, the valve 38 and the servomotor 40. This control unit 135 is preferably identical with or analogous to that described and claimed in the copending application Ser. No. 411,788 of Koch et al. which is assigned to the same assignee. Therefore, the exact construction of the control unit 135 (and/or 136) forms no part of the present invention.

The detector or weighing device 12a. of the control unit 135 sends impulses to a transducer '85 which converts such impulses into appropriate electrical signals and transmits the signals to a junction 88. The junction 88 is further connected with the output of a second transducer 86 which receives impulses from the dielectric moisture detector including the trough 14. A third transducer 46 transmits to the junction 88 signals which are generated in response to impulses transmitted by a third detector 44 located in the supply pipe 36 and serving to measure the temperature of the air current which is admitted into the intake end of the conditioning chamber 2a.

The control unit 135 also comprises a suitable rated value selecting device 108 whose output is connected with the junction 88 and which can be adjusted manually by means of a handle 109 or the like. The junction 88 will transmit signals through two amplifiers 90, 92 and on to the servomotor 40 for the valve 38 when the signal emitted by the device 108 is not cancelled by signals transmitted to the junction 88 from the outputs of the transducers 46, 85 and 86.

The second control unit 136 includes the aforementioned valve 56, its servomotor 52, the dielectric moisture detector which includes the trough 22, and a junction 96 which receives signals from the output of a transducer 94 connected to the dielectric detector. The junction 96 is further connected with the output of a rated value selecting device which is adjustable by a handle 111. The connection between the junction 96 and the servomotor 52 for the valve 50 comprises three

amplifiers

100, 102 and 104. The amplifier 164 has two Outputs one of which is connected to the servomotor 52 and the other of which is connected with the input of a timer 106. This timer can send signals to the junction 96 through a conductor 116. The control unit 136 also comprises a second detector 58 which is installed in the supply pipe 56 to measure the temperature of the hot air current flowing toward the discharge end of the conditioning chamber 2a. The detector 58 is connected with the input of the amplifier 102 through a transducer 60.

The operation of my conditioning apparatus is as follows:

The tobacco stream T can consist of shredded tobacco or of tobacco leaf laminae coming directly from a separator which receives a mixture of leaf laminae and ribs or veins from a stripping or destalking machine. In other words, the particles of the stream T can consist of cured or uncured tobacco. The operation of the distributor or another suitable unit which feeds tobacco to the conveyor belt 10 is preferably as uniform as possible so that each succesive increment of the stream T preferably contains the same or approximately the same amount of tobacco. The moisture content of the particles in the stream T is to be reduced in the conditioning chamber 2a under the action of the three

heating units

28, 48 and 148.

The detector 12:: weighs successive increments of the stream T and produces impulses which are indicative of such measurements. The impulses are transmitted to the transducer 85 which transmits appropriate signals to the junction 88 of the control unit for the first adjustable heating unit 28. During travel through the vibrating trough 14, the dielectric moisture detector of the control unit 135 determines the moisture content of each successive increment and produces impulses which are transmitted to the transducer 86. The latter transmit electric signals to the junction 88. The drier 2 is rotated by the motor 8 so that the particles admitted by the inclined chute 16 are entrained by the vanes formed by the coils 24 of the auxiliary heating unit 148 and are repeatedly lifted from a lower level to a higher level whence the particles descend back to the lower level to be separated from each other and to be fully exposed to the heating action of coils 24, of the heating wall 62 and of the air current admitted by the supply pipe 36 of the first adjustable heating unit 28. Since the axis of the drier 2 is inclined downwardly toward the chute 18, the orbiting coils 24 cause successively admitted increments of the stream T to travel through, toward and beyond the discharge end of the conditioning chamber 2a. The increments of the tobacco stream T are heated by the current of air admitted by the supply pipe 56 and pass through the chute 18, along the upper stringer of the belt 20 and into the vibrating trough 22 of the dielectric moisture detector in the second control unit 136. This detector sends impulses to the transducer 94 which transmits electric signals to the junction 96 of the control unit 136. The trough 22 discharges the particles of the stream T onto a further conveyor (not shown) which serves to adavnce the stream to a further processing station.

The purpose of the auxiliary heating unit 148 is to subject the tobacco stream T to a constant heating action, i.e., to supply a certain minimum amount of heat energy which is invariably required for proper conditioning of tobacco. The heating action of the unit 148 can be selected by adjustment of a steam valve 26a in the supply pipe 26, and such heating action then remains unchanged. The header 24a seals or almost seals the discharge end of the conditioning chamber 2a so that this discharge end receives air only or mainly from the supply pipe 56. The intake end of the chamber 2a is also closed against entry of atmospheric air so that this intake end receives tobacco from the chute 16 and a current of hot air from the supply pipe 36. The air current issuing from the supply pipe 36 passes through successive increments of the stream T before such increments descend onto the orbiting coils 24 and/or onto the internal surface of the revolving wall 62 in the lower zone of the conditioning chamber 2a so that the particles are subjected to a further heating, loosening and agitating action. The heating action of the unit 28 is felt mainly in the upstream section of the conditioning chamber 2a which extends between the left-hand axial end of the drier 2 and the unsealed perforations 84 of the sieve 83. Since the coils 24 of the auxiliary heating unit 148 repeatedly lift the particles of the stream T from a lower level to a higher level and allow the thus lifted particles to descend back to the lower level, each individual particle is allowed to come into intimate contact with the current of hot air issuing from the supply pipe 36 of the first adjustable heating unit 28. The temperature of the air current issuing from the supply pipe 36 depends on the position of the valve 38 in the suction pipe 32, and the position of this valve depends on the magnitude of signals transmitted to the servomotor 40. If the valve 38 admits more air from the nipple 37, the temperature of the air current which enters the supply pipe 36 is reduced. The magnitude of signals which are transmitted to the servomotor 4t) depends on the measurements carried out by the two upstream detectors (weighing device 12a and the dielectric moisture detector which includes the trough 14). The signals transmitted to the junction 88 of the control unit 135 for the first adjustable heating unit 28 are compared with signals emitted by the rated value selecting device 108 and the resulting positive 01' negative signal is transmitted to the servomotor 40 via amplifiers 90, 92 to bring about appropriate adjustments in the position of the valve 38. In other words, if the dielectric moisture detector of the control unit 135 detects that the moisture content of successive increment of the stream T is higher than warranted by the setting of the device 108, the servomotor 40 will cause the valve 38 to reduce the inflow of cold air through the nipple 37 so that the temperature of the air current entering the supply pipe 36 rises. Also, and if the moisture content of the stream T upstream of the drier 2 is satisfactory but the weighing device 12a detects an increase in the rate at which the stream T flows toward the drier, the servomotor 40 will adjust the valve 38 in such a way that the latter reduces the inflow of cold air via nipple 37, i.e., the heating action of the unit 28 is intensified because the conditioning chamber 2a receives more tobacco per unit of time.

The detector 44 in the supply pipe 36 senses all variations in the temperature of the air current which enters the intake end of the conditioning chamber 2a and transmits impuses to the transducer 46 which transmits appropriate signals to the junction 88. This purpose of the detector 44 is fully disclosed in the aforementioned copending aplication Ser. No. 411,788 of Koch et al. An important function of this detector is to prevent sudden and substantial changes in the temperature of air which is discharged by the supply pipe 36.

When the successive increments of the stream '1 leave the upstream section of the conditioning chamber 2a, they are subjected to the heating action of the air current which is discharged by the supply pipe 56 of the second adjustable heating unit 48. This air current flows counter to the direction of travel of the tobacco stream T. The heating action of the unit 48 is regulated by the control unit 136 as a function of the moisture content of successive increments which have left the drier 2 and pass through the trough 22 of the second dielectric moisture detector. Signals transmitted by the transducer 94 in response to impulses received from this moisture detector are utilized to operate the servomotor 52 which adjusts the valve 50 in a sense to admit more cool air via nipple 51 if the moisture content of increments travelling in the trough 22 is below a value selected by the device 110. If the moisture content is too high, the valve 58 reduces the inflow of cold air via nipple 51 so that a greater percentage of the air current issuing from the supply pipe 56 is heated by the heater in the suction pipe 132.

The detector 58 and the associated transducer 60 of the control unit 136 constitute a damper which performs an equalizing or smoothing action to prevent sudden variations in the temperature of the air current entering the discharge end of the conditioning chamber 2a.

The operation of the second adjustable heating unit 48 and the respective control unit 136 is based on the premise that any changes in the moisture content of successive increments of the tobacco stream T issuing from the conditioning chamber 2a are gradual, i.e., that an increment having a relatively high moisture content does not follow immediately an increment whose moisture content is much lower, or vice versa. Also, it takes a certain amount of time before a change in the heating action of the unit 48 is sensed by the dielectric moisture detector which includes the trough 22. The purpose of the timer 106 is to compensate for eventual fluctuations in the regulatin action which are due to such time lag between changes in heating action of the unit 48 and detection of the effect of such changes upon the moisture content of increments which travel in the trough 22. As stated before, the timer 106 is connected with one of two outputs of the amplifier 104 and sends delayed signals whose magnitude is inversely proportional to the magnitude of output signais received from the amplifier 194. This delays the operation of the servomotor 52 by an interval which corresponds to the time constant of the timer 106. Such time constant is selected in dependency on that interval of time which elapses between a change in the temperature of hot air issuing from the supply pipe 56 and the detection of the effect of such change in response to measurement of moisture content in the trough 22.

The resistance which the blowers 34, 134 of the

adjustable heating units

28, 48 encounter in drawing air through the

suction pipes

32, 132 depends on the momentary setting of the

valves

38, 50. If these valves admit relatively large quantities of cool air (nipples 37 and 51), the resistance which the

blowers

32, 132 must overcome is reduced, and vice versa. The output of these blowers depends from the resistance which they must overcome in forcing air into the

supply pipes

36, 56, Le, the throughput of the

heating units

28, 48 is higher if the temperature of the respective air currents is lower. For example, and if the valve 33 of the control unit 135 is adjusted in a sense to reduce the inflow of cold air via nipple 37, and if the valve 5% of the control unit 136 is adjusted in the opposite sense so that the temperature of the air current issuing from the supply pipe 56 is lower, the rate of air admission into the upstream section of the conditioning chamber 20 is lower than in the downstream section. This means that the region where the two air currents meet is shifted toward the intake end of the chamber 2a and the effect of hot air admitted by the pipe 56 is felt along a greater part of the conditioning zone which accommodates the drier 2.

The purpose of the aforementioned evacuating device 76 which includes the axially movable hood 64 is to withdraw or receive the air currents admitted by the

supply pipes

36, 56 exactly in the region where the two air currents meet. All that is necessary is to rotate the spindle 70 through the intermediary of the hand wheel "/4 so that the hood 64 moves toward or away from the collar 82. The solid lines show in FIG. 1 the hood 64 in its left-hand end position. When the hood 64 is caused to move to such position, the air current issuing from the supply pipe 56 is effectve along a greater part of the conditioning chamber because the air current admitted by the supply pipe 36 is assumed to be relatively cool. It goes without saying that the operators can influence the exact position of the region where the two air currents meet by changing the axial position of the hood 64 independently of the exact setting of the valve 38 and/or 50. As a rule, the region where the two air currents meet will be shifted in the same direction in which the hood 64 is shifted by the spindle 70. This is invariably true if the setting of the valves 38 and 59 remains unchanged. Such axial adjustability of the hood 64 enables the operators to intensify the preliminary heating action (unit 28) at the expense of the secondary or final heating action (unit 48) or vice versa.

It will be seen that the control units 135, 136 regulate the heating action of the

heating units

28 and 48, i.e., that the heating action of the third or auxiliary heating unit 148 is not dependent on measurements of one or more characteristics of hte tobacco stream T upstream and/ or downstream of the conditioning zone. As stated before, the heating action of this auxiliary unit is selected in advance and thereupon preferably remains constant so that any changes in the moisture content and/or in the rate of admission of the tobacco stream T are compensated for by regulation of the heating action of the unit 28 and/or 48. The auxiliary heating unit 148 supplies a predetermined minimum amount of heat energy which is invariably necessary and which enables the

adjustable heating units

28, 48 to operate with lesser quantities of hot air so that they can react more rapidly to changes in the moisture content and/or to changes in the weight of successive increments of the stream T. Stated otherwise, the auxiliary unit 148 supplies such heat energy which would have to be furnished by the

heating units

28, 48 regardless of changes in the weight and/or the moisture content of the stream T. The provision of this auxiliary heating unit 148 constitutes an advantageous feature of our conditioning apparatus because its heating action need not be too intensive so that the particles of the stream T which come in direct contact with the heated coils 24 and wall 62 are not subjected to excessive heating action. In other words, the heating action of the auxiliary unit 14-8 is invariably selected in such a way that tobacco particles passing through the chamber 2a are not subjected to excessive heating by direct contact with steam-heated parts of the apparatus.

In conceiving my present invention, I was guided by the following considerations: It a tobacco stream which passes through the conditioning chamber of a drier is heated only by a current of hot fluid which flows concurrent with the stream, i.e., from the intake end toward and through the discharge end of the conditioning chamber, the drop in temperature of the air current is not linear because the progressing air current comes in contact with increments whose temperature increases in the direction of air flow. In other words, the main conditioning action of such an air current is concentrated at the intake end of the conditioning chamber.

If the tobacco stream passing through the conditioning chamber is heated solely by a current of hot air which fiows from the discharge end toward and through the intake end of the drier, the drop in temperature of air is almost linear but the air current is effective solely or mainly in the downstream section of the conditioning chamber.

If the current of hot air were admitted into the median region of the conditioning chamber and were caused to flow upstream toward the intake end as well as downiii stream toward the discharge end of the chamber, the conditioning action of such air would be concentrated mainly in the median region. By admitting the air in the just outlined way, the tobacco particles advancing through the upstream portion of the drier would flow countercurrent to the flow of air and the particles advancing through the downstream part of the drier would advance concurrent with the flow of air. Also, the air would be admitted in a region which is located at a maximum distance from the detectors which measure the moisture content upstream and downstream of the conditioning chamber. Due to such maximum distance between the zone of air admission and the detectors, the detectors would be too late in detecting eventual variations in moisture content (and/or other characteristics of the stream) and it could happen that long portions of the stream would be treated improperly.

In accordance with an important feature of my invention, the two currents of air are controlled independently of each other, i.e., by control units 135, 136 whose detectors are respectively located upstream and downstream of the conditioning chamber 2a. Since the upstream detector 1211, 14 control the temperature of air which is admitted at the upstream end of the conditioning chamber 2a, they are located at a minimum distance from the first adjustable heating unit 28. The same holds true for the detector 22 or detectors which determine the characteristics of the tobacco stream T downstream of the conditioning chamber 2a and control the second adjustable heating unit 48.

It was further found that the major percentage of surplus moisture should be withdrawn in the upstream section of the conditioning chamber 2a, i.e., by heat energy transmitted to tobacco by the left-hand portions of the coils 24, by the left-hand portion of the wall 62, and by the air current issuing from the supply pipe 36 of the first adjustable heating unit 28. In most instances, the effect of the heating unit 28 will be felt exclusively in the upstream section of the chamber 2a. The second adjustable heating unit 4-8 carries of a corrective heating action which is not as intensive as the heating action in the upstream part of the drier 2 but is sufiiciently effective to insure that the stream T leaving the chamber 2a will have a desired moisture content, i.e., that the moisture content of each successive increment of the stream will remain Within a relatively narrow range. The detector 12a constitutes an advantageous optional feature of the control unit 135, and its provision is particularly desirable when the tobacco stream T is not formed at a constant rate so that each successive unit length of this stream does not contain the same amount of tobacco particles.

The exact percentage of moisture which should remain in tobacco that leaves the conditioning chamber 2a depends on many factors. For example, such percentage will depend on the type of tobacco, on the dimensions of tobacco particles, and on the desired characteristics of the ultimate product. Such percentage can be selected by appropriate adjustments of the rated value selecting device 108 and/or 1G9.

It is clear that the control unit and/or 136 could also operate with detectors which measure the characteristics of the tobacco stream T at shorter or longer regular or even irregular intervals. However, it was found that the conditioning operation is much more reliable if the detectors are arranged to scan each successive increment of the tobacco stream.

Adjustments of the evacuating device 75 in the axial direction of the drier 2 are desirable for the reasons which were discussed hereinabove and also in view of the following considerations. If the tobacco stream T contains a relatively high percentage of moisture and should be relieved of a substantial amount of surplus moisture, the current of hot air admitted by the supply pipe $5 will be cooled more rapidly and will take up a large amount of moisture. In

order to insure that the increments of the stream T flowing in the median region of the condensing chamber 2a are not subjected to the action of an overlying moist current of air, the operator will shift the evacuating device 76 (i.e., the hood 6 in a direction toward the supply pipe 36 so that the first current of air is evacuated after a relatively short-lasting contact with the tobacco particles. The effect of the relatively dry second air current which issues from the second supply pipe 56 is then felt along a greater portion of the drier 2. By the same token, the operator might wish to adjust the evacuating device 76 in the opposite direction to thereby prevent long-lasting contact of tobacco with a relatively moist current of air which is adiitted by the pipe 56.

Under certain circumstances, the operators might wish to condition a given brand of tobacco particles by heat which is supplied by only one or two heating units. This can be achieved by hutting off the auxiliary heating unit 148, by partially shutting of the unit 148, or by shutting d the unit 143 (either partially or completely) and by simultaneously shutting off or by at least reducing the conditioning action of one of the adjustable heating units 23, 48. Such operation will be warranted when the moisture content of the tobacco stream is only slightly higher than the desired moisture content. Also, the auxiliary heating unit 148 can be omitted altogether, especially if the

adjustable heating units

28, 48 are capable of supplying the basic amount of heat energy plus such heat energy which fluctuates in response to impulses transmitted by the various detectors of the two control units. The wall 62 is then heated solely by air currents which are discharged by such adjustable heating units.

The improved conditioning apparatus is susceptible of many additional modifications without departing from the spirit of my invention. For example, the

components

66, 68 of the evacuating device 76 can be mounted in such a way that they can rotate with or with reference to the hood 64 about the axis of the drier 2. This can be achieved by changing the angular position of the spindle nut 72 with reference to the drier 2 so that the hose 112 can be moved to a plurality of angular positions including the one occupied by the hose 112' shown in FIG. 2. Such angular displacement of the hose 112 can be carried out without necessitating rotation of the fan 68a which is connected to the pipe 68, i.e., the hose 112 can be long enough to allow for rotation of the funnel 66 and pipe 68 through up to 180 degrees in either direction.

The construction of the apparatus shown in FIGS. 1 to 3 can be simplified if the hood 64 remains in a selected axial position so that the spindle 7i nut '72 and hand wheel 74 can be dispensed with. The collars 8t 82 are then placed into abutment with the

flanges

65, 67. These collars are preferably adjustable in the axial direction of the drier 2. In such modified construction, the hood 64 can be held against rotation with the cylindrical wall 62 by means of a suitable arresting device, for example, a brake shoe or the like.

It is also possible to provide a common source of hot fluid for the

adjustable heating units

28 and 48, i.e., the

supply pipes

36, 56 can receive hot air from a common lower. The

valves

38, 50 are then installed directlly in the

supply pipes

36, 56 and are adjustable by the servomotors 4t), 52 to respectively regulate the admission of hot air in dependency on changes in the characteristics of the tobacco stream T upstream and downstream of the drier 2. Instead of resortin to a common source of hot fluid for the

supply pipes

36, 56, at least one of these pipes can receive hot air from two or more blowers. Also, at least one of the

heating units

28, 48 can comprise two or more supply pipes, at least one blower for each such supply pipe, and a separate valve for regulating the temperature of hot air passing through each supply pipe. For example, and if the heating unit 28 were to be replaced by a heating unit having two blowers 28, two supply pipes 36, two suction pipes 32, two nipples 37 and two heaters 30, the control unit 135 would be provided with two valves 38 one of which would regulate the temperature of hot air in one of the supply pipes as a function of measurements carried out by the weighing device 12a and the other of which would regulate the temperature of hot air in the other supply pipe as a function of measurements carried out by the dielectric moisture detector including the trough 14.

Furthermore, the axial ends of the wall 62 can remain open if the pipe 68 is connected with the fan 68a or with another suitable suction generating device. The suction in the funnel as and compartment 113 should be strong enough to prevent escape of hot air at the axial ends of the drier 2. However, and assuming that the axial ends of the drier 2 are open, suction in the compartment 113 should not be overly strong because, otherwise, the fan or fans connected with the pipe 68 would draw cold atmospheric air at the upstream and downstream ends of the conditioning chamber 2a. In order to avoid such uncontrolled admission of cool atmospheric air, the axial ends of the drier 2 are preferably sealed in a manner as pointed out hereinabove. For example, the right-hand axial end of the drier can be sealed by the header 24a which provides just enough room for escape of conditioned tobacco into the chute 18. Each of the chutes 1-6, 18 may include a conventional air lock one of which permits entry of tobacco particles but prevents entry of air and the other of which permits escape of tobacco particles but holds back air. If such air locks are used, the blowers 34, 134 and the fan 68a willl be preferably adjusted in such a way that the conditioning chamber 2a is maintained at a pressure which is slightly higher than atmospheric pressure. This will insure that the air locks will not admit cold air if the rate at which the tobacco stream T is being fed is reduced below an average value, i.e., when the rate of tobacco feed decreases, the air locks will permit escape of hot air from the chamber 2a but will not permit entry of cool atmospheric air.

Finally, it is equally possible to construct the hood 64 in such a way that it defines with the wall 62 two or more separate compartments 113 each of which can be connected with the pipe 68 independently of the other compartment or compartments. In this way, the operators can control the rate at which the evacuating device withdraws hot air and vapors from the chamber 2a.

The method of my invention can be shortly described as comprising the basic steps of conveying a continuous stream T of moist tobacco lengthwise along a predetermined path defined by the feed 10, 12, 16. 8, 18, 20 toward and beyond an elongated conditioning zone (chamber 211) which includes a first section (between the chute 16 and the central portion of the hood 64) which is first to receive successive increments of tobacco and a second section (between the central portion of the hood 64 and the chute 18) which receives successive increments from the first section, admitting into the first section of the conditioning zone a first current of hot fluid (supply pipe 36) and conveying such hot fluid concurrent with the stream T so that the fluid expels moisture from tobacco, admitting into the second section of the conditioning zone a second current of hot fluid (supply pipe 56) and conveying the second current countercurrent to the stream T so that the second current expels additional moisture from tobacco, and evacuating the two currents from the conditioning zone in the region (compartment 113) between the two sections. By moving the region of evacuation lengthwise of the conditioning zone, the operators can lengthen one of the aforementioned sections at the expense of the other section, or vice versa.

Without further analysis, the foregoining will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features which fairly constitute essential characteristics of the generic and specific aspects of my contribution to the art and, therefore, such adaptations should and are intended to be 13 comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be protected by Letters Patent is:

1. A tobacco conditioning apparatus, comprising a feed arranged to advance a stream of moist tobacco lengthwise toward, through and beyond a conditioning zone; a drier accommodated in said zone and defining a continuous conditioning chamber having an intake end which receives successive increments of the stream and a discharge end from which such increments issue; heaitng means comprising first supply means for admitting into said intake end at least one first current of hot fluid which flows concurrent with the stream and expels moisture from tobacco, and second supply means for admitting into said discharge end at least one second current of hot fluid which flows countercurrent to the stream and expels additional moisture from tobacco; and evacuating means communicating with said conditioning chamber intermediate said intake and discharge ends for receiving the currents from said drier and exhausting them from the chamber.

2. An apparatus as set forth in claim 1, wherein said heating means further comprises blower means for delivering hot air to said supply means.

3. An apparatus as set forth in claim 1, wherein said heating means comprises two heating units each including one of said supply means and at least one hot air blower for delivering hot air to the respective supply means.

4. An apparatus as set forth in claim 1, wherein said heating means further comprises an adjustable heating unit including one of said supply means, and further comprising control means for said heating unit, said control means comprising detector means for measuring the moisture content of succesive incremnets of the stream outside of said conditioning chamber and adjusting means for regulating the temperature of heating fluid which is admitted into said chamber by said one supply means in accordance with the results of measurements carried out by said detector means.

5. An apparatus as set forth in claim 4, wherein said one supply means is said first supply means and wherein said detector means is arranged to measure the moisture content of successive increments prior to entry of such increments into said conditioning chamber.

6. An apparatus as set forth in claim 5, wherein said control means further comprises servomotor means for operating said adjusting means only when the results of measurements carried out by said detector means deviate from a predetermined value.

7. An apparatus as set forth in claim 5, wherein said control means further comprises second detector means for measuring the weight of successive incremnets on their way to said intake end and wherein said adjusting means is arranged to regulate the temperature of hot fluid admitted by said first supply means in accordance with the results of measurements carried out by said second detector means so that the temperature of fluid in said first current is higher if the stream is fed at a higher rate and that the temperature of fluid is lower if the stream is fed at a reduced rate.

8. An apparatus as set forth in claim 7, wherein said control means further comprises servomotor means for operating said adjusting means only when the combined results of measurements carried out by both said detector means deviate from a predetermined value.

9. An apparatus as set forth in claim 4, wherein said one supply means is said second supply means and wherein said detector means is arranged to determine the moisture content of successive increments after such in- .crements issue from said conditioning chamber.

10. An apparatus as set forth in claim 9, wherein said control means further comprises servomotor means for operating said adjusting means only when the results of i i measurements carried out by said detector means deviate from a predetermined value.

11. An apparatus as set forth in claim 9, wherein said control means further comprises damper means for preventing sudden changes in the temperature of hot fluid admitted by said second supply means.

12. An apparatus as set forth in claim 1, wherein said heating means comprises first and second adjustable heating units which respectively include said first and second supply means, and further comprising first control means including first detector means for measuring the moisture content of tobacco prior to entry of such tobacco into said chamber and adjusting means for regulating the temperature of hot fluid admitted by said first supply means in accordance with the results of such measurements, and second control means including second detector means for measuring the moisture content of tobacco downstream of said chamber and adjusting means for regulating the temperature of hot fluid admitted by said second supply means in accordance with the results of measurements carried out by said second detector means.

13. An apparatus as set forth in claim 12, wherein each of said detector means is arranged to determine the moisture content of tobacco in successive increments of said stream.

14. An apparatus as set forth in claim 1, wherein said conditioning chamber is elongated and wherein said evacuating means comprises a member movable in the longitudinal direction of said chamber to increase the moisture expelling effect of one of said currents at the expense of the other current, or vice versa.

15. An apparatus as set forth in claim 1, wherein said drier comprises a tubular wall surrounding said conditioning chamber and having a median portion provided with perforations through which said evacuating means can communicate With said chamber.

16. An apparatus as set forth in claim 15, wherein said tubular wall is rotatable about its own axis and wherein said evacuating means comprises a hood sur-; rounding said wall and defining with said median portion at least one compartment which communicates with said chamber through at least some of said perforations.

17. An apparatus :as set forth in claim 16, further comprising means for holding said hood against rotation with said wall.

18. An apparatus as set forth in claim 16, wherein said compartment extends circumferentially around the entire median portion of said wall.

19. An apparatus as set forth in claim 16, where-in the length of said compartment is less than the length of said median portion, as seen in the axial direction of said wall.

20. An apparatus as set forth in claim 19, further comprising means for moving said hood axially of said wall.

21. An apparatus as set forth in claim 20, wherein said evacuating means further comprises :a substantially funnel-shaped portion whose cross-sectional area diminishes in a direction away from said compartment, said funnel-shaped portion being connected with said hood and communicating with said compartment.-

22. An apparatus as set forth in claim 16, further comprising means for moving said hood axially of said wall and stop means for limiting such movements of said hood.

23. An apparatus as set forth in claim 22, wherein said hood comprises portions which seal at least some of said perforations, at least when said hood abuts against said stop means.

24. An apparatus :as set forth in claim 22, wherein the means for moving said hood comprises manually operable actuating means.

25. An apparatus as set forth in claim 1, wherein said heating means comprises :an auxiliary heating unit provided in said chamber and arranged to expel moisture 15 from tobacco in addition to such moisture which is expelled by said currents of hot fiuid.

26. An apparatus as set forth in claim 25, wherein said drier comprises a rotary cylindrical wall which surrounds said conditioning chamber and said auxiliary heating unit comprises heating elements extending substantially all the way between said intake and discharge ends and being supported by and rotatable with said wall so that such heating elements transmit heat energy to said wall and simultaneously agitate the tobacco in said chamber.

27. An apparatus as set forth in claim 1, wherein said evacuating means comprises suction generating means for drawing said currents from said conditioning chamber.

28. An apparatus as set forth in claim 1, wherein said hot fluid is air and further comprising control means for regulating the temperature of hot air admitted by said first and second supply means as a function of the moisture content of tobacco in successive increments of the stream respectively measured prior to and subsequent to passage of such increments through said conditioning chamber, said control means further comprising means for comparing the measured moisture content with a predetermined value and means for adjusting the temperature of hot air in the respective supply means when the result of measurement upstream or downstream of said chamber deviates from the respective predetermined value.

29. A method of conditioning tobacco, comprising the steps of conveying a continuous stream of moist tobacco lengthwise along a predetermined path toward, through and beyond an elongated continuous conditioning zone having a first section which is first to receive successive increments of tobacco and a second section which receives successive increments from said first section; admitting into said first section a first current of hot fluid and conveying such fluid concurrent with the stream so that the fluid expels moisture from tobacco; admitting into said second section a second current of hot fluid and conveying the second current counter-current to the 16 stream toward said first section so that the second current expels additional moisture from tobacco; and evacuating and expelling said currents from said conditioning zone in the region between said sections.

30. A method as set forth in claim 29, further comprising the step of moving said region lengthwise of said conditioning zone to lengthen one of said sections at the expense of the other section, or vice versa.

31. A method as set forth in claim 29, further comprising the steps of measuring the moisture content of tobacco in successive increments of the stream upstream and downstream of said conditioning zone, regulating the temperature of said first current in accordance with the results of measurements upstream of said zone, and regulating the temperature of said second current in accordance with the results of measurements downstream of said zone.

References Cited UNITED STATES PATENTS 1,393,086 10/1921 Carrier 131-135 1,551,676 9/1925 McConnell 131-136 X 1,823,554 9/1931 Mewborne 131-133 X 1,976,487 10/1934 El'berty 68-9 2,322,272 6/1943 Bailey et al 34-46 X 2,596,183 5/1952 Sowa 131-140 2,679,115 5/1954 Bogaty et al 131-136 X 2,768,629 10/1956 Maul 131-135 2,882,910 4/1959 Jones et al. 131-135 2,933,090 4/1960 Hamilton et al 131-140 3,102,794 9/1963 Arnold 34-46 X FOREIGN PATENTS 1,416,676 9/1965 France.

1,499 4/ 1881 Great Britain. 953,893 4/1964 Great Britain.

ALDRICH F. MEDBERY, Primary Examiner.

Claims

29. A METHOD OF CONDITIONING TOBACCO, COMPRISING THE STEPS OF CONVEYING A CONTINUOUS STREAM OF MOIST TOBACCO LENGTHWISE ALONG A PREDETERMINED PATH TOWARD, THROUGH AND BEYOND AN ELONGATED CONTINUOUS CONDITIONING ZONE HAVING A FIRST SECTIN WHICH IS FIRST TO RECEIVE SUCCESSIVE INCREMENTS OF TOBACCO AND A SECOND SECTION WHICH RECEIVES SUCCESSIVE INCREMENTS FROM SAID FIRST SECTION; ADMITTING INTO SAID FIRST SECTION A FIRST CURRENT OF HOT FLUID AND CONVEYING SUCH FLUID CONCURRENT WITH THE STREAM SO THAT THE FLUID EXPELS MOISTURE FROM TOBACCO; ADMITTING INTO SAID SECOND SECTION A SECOND CURRENT OF HOT FLUID AND STREAM TOWARD SAID FIRST SECTION SO THAT THE SECOND CURRENT EXPELS ADDITIONAL MOISTURE FROM TOBACCO; AND EVACUATING