US3807415A

US3807415A - Method of comminuting and drying of tobacco leaves

Info

Publication number: US3807415A
Application number: US00342320A
Authority: US
Inventors: U Elsner; W Wochnowski
Original assignee: Hauni Werke Koerber and Co KG
Current assignee: Koerber AG
Priority date: 1970-05-11
Filing date: 1973-03-16
Publication date: 1974-04-30
Anticipated expiration: 1991-04-30
Also published as: DE2062343C2; NL7106275A; DE2062343A1; NL170590B; JPS5749190B1; US3736942A; NL170590C

Abstract

Several parallel tobacco comminuting machines deliver tobacco shreds onto a conveyor system which transports a stream of such shreds into a drying apparatus. The last comminuting machine is adjustable by a control system connected with a weighing device which is located upstream or downstream of the last machine and causes the control system to regulate the output of the last machine in such a way that the combined output of the machines forms a constant stream of tobacco shreds. The weighing device weighs successive increments of the tobacco stream which includes the output of all machines, the output of all but the last machine, or successive increments of a stream which is being withdrawn from a magazine serving to receive the output of all machines.

Description

United States Patent 191 Eisner et a l,

1451 Apr. 30, 1974 [54] METHOD OF COMMINUTING AND 1,704,216 3/1929 Rosener et a1 241/34 DRYING TOBACCO LEAVES 3,568,938 3/1971 Barrot et a1 241/34 [75] Inventors: Uwe Elsner, Hamburg-Bramfeld; FOREIGN PATENTS R P CATI Waldemar Wochnowski, Hamburg, 1,914,466 /1970 Germany 131 /22 R both of Germany 750,535 6/1956 Great Britain 241/34 [73] Assignee: Hauni-Werke Korber & Co. KG,

Hamburg Germany Primary ExammerRobert W. Michell Assistant Examinerlohn F. Pitrelli FlIedl 1973 Attorney, Agent, or FirmMichael S. Striker [21] Appl. No.: 342,320

Related us. Application Data [57] ABSTRACT [62] Division of ser. No. 141,164, May 7, 1971, Pat. No. Several Parallel tobacco commimlting machines 3,736,942. liver tobacco shreds onto a conveyor system which transports a stream of such shreds into a drying appa- Foreign Application Priority Dat ratus. The last comminuting machine is adjustable by May 11, 1970 Germany 2022816 a Control System Connected with a weighing device Dec. 17, 1970 Germany 2062343 which is located upstream downstream of the last machine and causes the control system to regulate the 52 US. Cl 131/22 R 131/145 241/34 Output Ofthe. last machine in Such a Way that the 51 Int. Cl A0l d 55/18 bined Output Of the machines frms a constant Stream [53] Field of Search H 131/22 R, 22 A 145, of tobacco shreds. The weighing device weighs succes- 241/34; 83/3563, 'sive increments of the tobacco stream which includes I the output of all machines, the output of all but the [56] Refrences Cited 7 last machine, or successive increments of a stream UNITED STATES PATENTS which is being withdrawn from a magazine serving to receive the output of all machines. 2,791,223 5/1957 Molins ct al. 131/145 2,827,058 3/1958 Bogaty 131/108 13 Claims, 5 Drawing Figures l :37 I 1 v 31 36 Ila PATENIEDAPR 30 $974 SHEEI 2 0F 5 PATENTEBAPR 30 m4 SHEEI t [If 5 PATENYEU KPH 30 I834 SHEET 5 OF 5 METHOD OF COMMINUTING AND DRYING OF TOBACCO LEAVES CROSS-REFERENCE TO RELATED CASE This is a division of our copending application Serial No. 141,164 filed May 7, 1971, now U.S. Pat. No. 3,736,942 granted June 5, 1973.

BACKGROUND OF THE INVENTION The present invention relates to a method of cutting or comminuting and drying tobacco leaves. More particularly, the invention relates to improvements in a method of shredding tobacco leaves and of subjecting the shredded material to a drying or moisture-expelling treatment.

If tobacco leaves are to be shredded in a modern high-speed cutting machine, it is necessary to raise the moisture content of such leaves well beyond the moisture content which is desirable for further processing of the resulting shreds. This applies in particular when the shreds are to be fed into a cigarette rod making machine for the production of a wrapped tobacco filler rod which is thereupon subdivided into sections of unit length or multiple unit length. In other words, the moisture content which is satisfactory for shredding of tobacco leaves is much too high for further processing of the tobacco shreds. It is, therefore, customary to convey shredded tobacco particles through a drying apparatus wherein the moisture content of the shreds is reduced to a desired value. Such treatment must be carried out with an extremely high degree of accuracy because a modern high-speed cigarette rod making or like machine must receive tobacco shreds whose moisture content cannot deviate from a desired optimum value by more than a small fraction of one percent.

The drying of tobacco shreds subsequent to shredding and prior to conversion into a continuous tobacco filler rod represents a rather lengthy stage in the conversion of tobacco leaves into smokers products. The duration of treatment in a heating or moistureexpelling apparatus depends not only on the desired extent to which the moisture content is to-be reduced but also on the regularity with which the tobacco shreds are fed into the heating apparatus. The primary purpose of the heating apparatus is to reduce the moisture content to a desired value which, as mentioned before, cannot deviate from a predetermined optimum value by more than a small fraction of one percent. The operation of drying or heating apparatus is further complicated if such apparatus must be constructed to be adjustable not only to account for fluctuations in the moisture content of admitted tobacco shreds but also for fluctuations in the rate at which the shreds are being admitted into the heating or moisture-expelling zone. Fluctuations in the quantity of tobacco shreds which are being fed into the drying apparatus are due to the fact that a modern drying apparatus can take up and process the output of two or more tobacco shredding machines. Such shredding machines are normally arranged in parallel and their outputs are combined into a stream which is fed into the inlet of the drying apparatus. It was found that the operation of the drying apparatus can be simplified to a considerable degree if such apparatus must be designed to account only for fluctuations in the moisture content but need not be adjustable in order to account for eventual fluctuations in the rate of admission of tobacco shreds. The presently known transporting systems which are used to deliver tobacco shreds from one or more tobacco shredding machines to a drying apparatus cannot meet such strict requirements as concerns the uniformity of the rate of tobacco shred admission into the drying or moisture-expelling zone.

SUMMARY OF THE INVENTION An object of the invention is to provide a novel and improved method of comminuting and transporting tobacco leaves into a drying or moisture-expelling zone in such a way that the drying zone receives a constant stream of tobacco shreds.

Another object of the invention is to provide a method of the just outlined character which can be carried out by resorting to presently available tobacco comminuting and drying apparatus and by necessitating only minor modifications or alterations in the construction and mode of operation of such apparatus.

A further object of the invention is to provide a method according to which the drying apparatus which is used to expel moisture from freshly formed tobacco shreds need not be provided with any means for adjusting its operation for the sole purpose of insuring that the drying operation will be carried out by full consideration of eventual fluctuations in the rate of admission of tobacco shreds.

One feature of the present invention resides in the provision of a method of forming and manipulating comminuted fibrous material, particularly shredded tobacco. The method comprises the steps of comminuting fibrous material at a plurality of discrete cutting or severing stations, for example, by employing known tobacco shredding machines, introducing the thus obtained comminuted material into successive regions of a predetermined path wherein the comminuted material is conveyed ina predetermined direction and builds up a growing stream which is to be introduced into a drying or moisture expelling zone, measuring the quantities of comminuted material in at least one predetermined portion of the path, comparing the quantities which are determined in the measuring step with a predetermined or optimum quantity, and varying the rate of introduction of comminuted material from at least one of the cutting stations as a function of differences between the measured quantity and the predetermined quantity so that the combined quantity of comminuted material which is furnished by all of the stations remains constant. This can be achieved by installing at each cutting station a discrete tobacco shredding machine or cutter at least one of which is adjustable, and by utilizing the results of measurements in the predetermined portion of the path for the tobacco stream to adjust the adjustable shredding machine so as to insure that the combined output of the shredding machines is constant. The total number of cutting stations preferably exceeds two. The region of admission of comminuted material from the station which accommodates an adjustable shredding machine is preferably located downstream of the other regions, as considered in the direction of transport of comminuted material toward the drying zone. The region of introduction of comminuted material from the one cutting station can be located upstream or downstream of the aforementioned predetermined portion of the path for comminuted material,

i.e., the point of admission of variable quantities of comminuted material into the path for comminuted material can be located upstream or downstream of that portion of the path wherein the quantities of material in successive increments of the growing stream are measured in order to insure appropriate adjustments in the rate of admission of comminuted material from the one station.

In accordance with a presently preferred embodiment of our method, the step of varying the rate of introduction of comminuted material from the one station includes changing the rate of comminution of fibrous material at the one station and introducing all of the thus comminuted material from the one station into the respective region of the path wherein the comminuted material advances toward the drying station. In other words, the step of varying the rate of introduction of comminuted material preferably includes changing the output of the shredding machine at the one station in accordance with deviations of the measured quantity of comminuted material from the desired or predetermined quantity.

The measuring step may comprise weighing the comminuted material in one or more predetermined portions of the path wherein the comminuted material is transported to the drying station. Such weighing step may include producing a first signal whose intensity increases proportionally with progressing transport of particles of comminuted material along the corresponding portion of the path and a second signal whose intensity is a function of the speed of transport of particles of comminuted material along such portion of the path. The rate-varying step then comprises utilizing at least one of these signals to adjust the introduction of comminuted material from the one station into the respective region of the path.

In accordance with a further modification, the method may further comprise the step of collecting comminuted material in the aforementioned predetermined portion of the path to accumulate and maintain in such portion a supply of comminuted material. The measuring step then comprises monitoring the quantity of comminuted material in such supply. The predetermined portion of the path wherein the supply is accumulated is located downstream of the regions where the comminuted material is admitted into the path for transport to the drying station. The rate-varying step then preferably comprises respectively reducing and increasing the rate of admission of comminuted material from the one station when the quantity of comminuted material in the supply respectively rises above and decreases below the predetermined quantity. The material which is to be admitted into the drying zone is withdrawn from the supply at a constant rate so that the thus withdrawn comminuted material forms a constant second stream which can be fed directly into the drying zone. The measuring step may comprise scanning the level of comminuted material in the supply.

In accordance with still another feature of the improved method, the fibrous material is admitted into a second predetermined path and the rate of admission of fibrous material into such second path is maintained at a constant value so that the fibrous material forms a constant stream from which the material is withdrawn for admission into the cutting stations where the thus introduced material is subjected to a comminuting treatment.

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

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a diagrammatic plan view of an apparatus which can be utilized for the practice of our method;

FIG. la is a sectional view as seen in the direction of arrows from the line IaIa of FIG. 1;

FIG. 2 is a plan view of a second apparatus;

FIG. 3 is an enlarged perspective view of a detail in the apparatus of FIG. 2; and

FIG. 4 is a similar perspective view of a detail in a third apparatus which constitutes a modification of the apparatus shown in FIGS. 2 and 3.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring first to FIGS. 1 and 1a, there is shown an apparatus for forming and manipulating comminuted fibrous material 20. The comminuted material 20 is shredded tobacco which is obtained in response to comminution or cuttingof tobacco leaves 7. The leaves 7 are supplied to four parallel cutting or severing stations A, B, C and D. These stations respectively accommodate tobacco cutting or severing machines la, 1b, 1c, 1d (hereinafter called cutters). Each of the cutters la-ld is of the type known as KTF-I produced by Hauni-Werke, Korber & Co. K.G., of Hamburg- Bergedorf, Western Germany.

The construction of each of the cutters la, 1b, 1c, 1d is identical. Therefore, the following part of this description will deal mainly with the cutter 1d. Similar parts of the four cutters are denoted by similar reference numerals followed by characters a, b, c, d. The cutter 1d comprises a duct or inlet 6d which receives tobacco leaves 7 and serves tocondense such leaves in order to form a cake which is thereupon fed to a rotary cutting device (see FIG. 1a). The means for supplying tobacco leaves 7 to the inlets 6a-6d comprises an endless conveyor 8 which is preferably a belt having an upper stretch serving to transport tobacco leaves toward and past the inlets 6a, 6b and 60. A deflector 9d is disposed above the upper stretch of the conveyor 8 and makes an acute angle with the direction of travel of tobacco leaves. This deflector serves to deflect a certain quantity of tobacco leaves 7 into the inlet 6d of the cutter 1d. The bottom wall of the inlet 6d is formed by the upper stretch of an endless conveying element here shown as a chain 11d which transports tobacco leaves downwardly, as viewed in FIG. 1, and upwardly as viewed in FIG. la. A portion of the upper stretch of the chain 11d is overlapped by the lower stretch of a second endless conveying element here shown as a chain 12d which cooperates with the chain lld to effect condensation of tobacco leaves 7 and to define a converging or tapering passage wherein the cake advances into the range of orbiting knives 15. The outlet of the passage which is defined by the chains lld, 12d is located in front of an adjustable mountpiece or spout 13d through which the cake advances into the range of the knives 15. The means for driving the

chains

11d, 12d comprises a variable-speed motor 14 d. The knives 15 are mounted on a rotary drum-shaped holder 10 which is driven by a motor 16d. The knives l5 shred the tobacco leaves 7 immediately adjacent to the outlet of the spout 13d and the resulting 'comminuted material is delivered by a pneumatic conveyor PC onto the upper stretch of an endless conveyor belt 22. The shreds 20 formed in the cutters 1a-1c are delivered onto the upper stretch of an endless conveyor belt 18 which accumulates a stepwise growing stream of tobacco shreds. The purpose of the illustrated apparatus is to form on the conveyor 22 a stream each increment of which contains a predetermined quantity of tobacco shreds. The stream is fed into a conventional drying apparatus (see the apparatus 144 in FIG. 2) which expels therefrom excess moisture so that the moisture content of tobacco leaving the drying apparatus is within a very narrow predetermined range. Such tobacco is then ready for introduction into a cigarette rod making machine.

. In accordance with a feature of the present invention,

the apparatus of FlG. 1 further comprises a measuring unit 19 here shown as constituting a weighing device which measures the quantities of tobacco shreds 20 furnished by the cutters Ila-1c and cooperates with a control system 17 to adjust the output of the last cutter-1d in such a way that the combined output of the cutters 1a-1d forms on the conveyor 22 a constant stream ready to be admitted into the drying apparatus. The illustratedweighing device 19 constitutes but one of several measuring units which can be used in theapparatus of FIG. 1 to measure the quantities of shreds that are furnished by the cutters la-lc. For example, the weighing device 19 can be replaced with a detector which employs beta rays and an ionization chamber or with a high-frequency measuring unit.

The weighing device 19 includes a potentiometer 21 having a wiper arm 21a whose position varies as a function of changes in the weight of tobacco shreds on the weighing device. Thus, the signal furnished by the wiper arm 21a is indicative of variations in the weight of successive increments of shreds 20 on the conveyor 18. The output signal of the potentiometer 21 is transmitted to one input of a signal comparing circuit 23 forming part of the aforementioned control system 17 for the last cutter 1d. The conveyor 18 delivers a normally constant stream of tobacco shreds 20 to the conveyor 22 which further receives the output of the cutter 1d and delivers the resulting final stream to the aforementioned drying apparatus. The control system 17 further comprises a detector 24 here shown as a tachometer generator which monitors the speed of the motor 14d in the cutter 1d and furnishes to a second input of the signal comparing circuit 23 a signal indicating the momentary speed of the motor Md. The motors 14a-14d are preferably d-c motors. The motor'l4d are monitored by the wiper arm 26 of a further potentiometer 27 which transmits signals to a third input of the signal comparing circuit 23 in the control system 17. It will be readily understood that the output of the cutter 1d can be changed by adjusting the cross-sectional area of the mouthpiece 13d and/or by changing the rotational speed of the motor 14d which drives the chains 1 1d, 12d. The output signal from the circuit 23 is transmitted to the input of an operational amplifier 28 for the motor 14d. The intensity of such signal depends on the intensity of signals transmitted by the potentiometers21, 27 and the tachometer generator 24. The signals transmitted to the circuit 23 by the potentiometer 27 and tachometer generator 24 are compared with the signal from the potentiometer 21 which latter signal is indicative of the quantity per unit length of the tobacco stream that is being delivered by the conveyor 18. The amplifier 28 regulates the speed of the motor 14d in such a way that the quantity of tobacco shreds 20 furnished by the cutter 1d complements the combined quantity of tobacco shreds furnished by the cutters la, 1b, 1c. Thus, the combined quantity of shreds 20 furnished by the four cutters 1a1d equals a predetermined quantity which is desirable to'insure that the drying apparatus which receives the constant stream from the conveyor 22 requires no adjustment for the purpose of taking into consideration varying quantities of tobacco but only such adjustments as are needed to insure that the drying apparatus will expel from the tobacco stream moisture in such a way that the moisture content of the treated tobacco stream will remain within a predetermined verynarrow range. The operational amplifier 28 is preferably of the type known as MINISEMI produced by the West-German firm AEG. The circuit 23 can compare the signal from the potentiometer 21 with a reference signal which is indicative of anticipated quantity of tobacco shreds furnished by the conveyor 18, and the signal which is transmitted to the amplifier 28 changes the speed of the motor 14d whenever the signal from the potentiometer 21 deviates from the reference signal. The adjustment is terminated when the signal from the tachometer generator 24 indicates that the speed of the motor 14d has been changed to the desired speed which is needed to insure that the combined output of the cutters 1a-ld is constant.

Referring again to FIG. 1a, the inlet 6d contains a rake 2 which is pivotable to feed tobacco leaves 7 into the passage between the

chains

11d, 12d. The chain 12d is trained over sprocket wheels 3 and 4 and the shaft of the sprocket wheel 4 is movable along an are having its center of curvature on the axis of the stationary shaft for the sprocket wheel 3. The means for moving the sprocket wheel 4 along this are comprises a fluid-operated cylinder 5 having a piston rod which supports the wiper 26 of the potentiometer 27.

The mouthpiece 13d comprises a stationary lower portion in front of the lower chain 11d and an upper portion which is movable by the cylinder 5 and is located in front of the sprocket wheel 4. The numeral 25 denotes a grinding or sharpening device for the cutting edges of the knives 15.

The density of the cake of tobacco leaves 7 between the

chains

11d and 12d determines the position of the sprocket wheel 4 and hence the position of the upper portion of the mouthpiece 13d with reference to the lower portion. When the mouthpiece 13d is wide open, the quantity of shreds 20 produced by the knives 15 increases provided that the speed of the motors 14d and 16d remains unchanged. The cylinder exerts pressure which is needed to effect satisfactory condensation of leaves 7 in the passage between the

chains

11d and 12d. The knives remove from the front end of the cake of condensed tobacco leaves 7 thin slices each of which consists of tobacco shreds which become separated from each other and enter the conveyor PC for transport onto the conveyor 22.

The position of the wiper 26 of the potentiometer 27 is indicative of the position of the upper portion of the mouthpiece 13d with reference to the lower portion. Thus, when the speed of the motors 14d and 16d is constant, the position of the wiper 16 is indicative of the quantity of shreds 20 which are formed in the cutter 1d. The lower portion of the mouthpiece 13d serves as a counterknife for the orbiting knives 15.

FIG. further shows a chute 29 which is disposed between the discharge end of the conveyor 18 and the receiving end of the conveyor 22 and serves to condense the shreds which are being furnished by the outlets of the cutters la-lc. The conveyors 18, 22 and the chute 29 together form a composite conveyor which serves to accumulate the shreds 20 furnished by the cutters la-ld and to convert such shreds into a continuous stream wherein each increment or unit length contains a predetermined quantity of tobacco shreds.

The left-hand end of the conveyor 8 receives tobacco leaves 7 from a magazine or hopper 41 which contains a supply of tobacco leaves and from which the leaves are withdrawn at a preferably constant rate by the upwardly moving stretch of an endless carded conveyor 42. The parts 41 and 42 constitute a source 39 of tobacco leaves 7. The conveyor 42 is driven by a variable-speed d-c motor 38 which is connected with an operational amplifier 37 preferably corresponding to the aforementioned amplifier 28 in the control system 17 and forming part of a second control system 31. The amplifier 37 receives signals from a signal comparing circuit 36 which has two inputs one of which is connected with the wiper arm of an adjustable porten tiometer 32 serving as a source of reference signals indicating the desired quantity of tobacco leaves 7 which are to be transported by the conveyor 8. The other input of the signal comparing circuit 36 is connected with the wiper arm of a second potentiometer 34 which forms part of a measuring or weighing device 33 preferably similar to the aforementioned weighing device 19. The weighing device 33 receives tobacco leaves from the conveyor 42 and its potentiometer 34 transmits to the corresponding input of the circuit 36 signals which are indicative of the measured quantities of tobacco leaves. The output signal from the circuit 36 to the amplifier 37 is indicative of the difference between the intensities of signals furnished by the potentiometers 32 and 34. The arrangement is such that the motor 38 drives the conveyor 42 at a higher speed when the weighing device 33 detects that the quantity of tobacco leaves which are being furnished to the conveyor 8 is less than desired and that the speed of the motor 38 increases when the weighing device 33 detects that the quantity of tobacco leaves 7 furnished to the conveyor 8 exceeds such desired quantity (as indicated by the signal from the potentiometer 32).

The hopper 41 receives tobacco leaves 7 from a balebreaking machine or the like, not shown. The discharge end of the conveyor 8 can deliver the surplus of tobacco leaves 7 to an endless recirculating conveyor 43 which cooperates with two additional recirculating conveyors 44, 46 to return the surplus into the hopper 41. Such surplus normally develops when the last cutter 1d is to operate at less than full capacity or is idle, for example, when the cutters la-lc operate at full capacity so that the cutter 1d must furnish only a relatively small quantity of tobacco shreds 20 (or no shreds at all) in order to form on the conveyor 22 a constant stream which is to be delivered into the drying apparatus.

The operation of the apparatus shown in FIG. 1 is as follows:

The deflectors 9a, 9b, 9c, 9d deliver tobacco leaves 7 from the upper stretch of the conveyor 8 into the respective inlets 6a, 6b, 6c, 6d. The control system 31 insures that the inlet of the conveyor 8 receives tobacco leaves at a constant rate. This is achieved by regulating the speed of the aforementioned motor 38 for the conveyor 42. The upwardly sloping stretch of the conveyor 42 draws tobacco leaves from the hopper 41 and showers tobacco leaves onto the weighing device 33.

The chains Ila-11c and 12a-l2c of the cutters 1a-1c form three continuous ckaes of condensed tobacco leaves which are fed through the respective mouthpieces into the range of rotating knives driven by the motors 16a, 16b, 160. The resulting shreds 20 are discharged onto the upper stretch of the conveyor 18 so that such shreds form a stepwise growing stream which advances in the direction indicated by the arrow, namely, toward the weighing device 19. The weighing device 19 weighs successive increments of the stream which is formed by the combined output of the cutters la-1c and the potentiometer 21 transmits to the corresponding input of the circuit 23 in the control system 17 a signal which is indicative of the measured quantity of tobacco shreds. At the same time, the other two inputs of the circuit 23 receive signals from the tachometer generator 24 which indicates the momentary speed of the motor 14d for the

chains

11d, 12d and from the potentiometer 27 which indicates the cross-sectional area of the mouthpiece 13d in the cutter 1d. The signal from the potentiometer 21 is compared with the signal from the tachometer generator 24 and the output signal from the circuit 23 determines the speed of the motor 14d in such a way that the quantity of tobacco shreds in the final stream, namely, in the stream which is conveyed by the conveyor 22 into the drying apparatus is constant. The circuit 23 adjusts the motor 14d of the cutter M by way of the amplifier 28 in such a way that the output of the cutter 1d at the station D supplements the combined output of the cutters la-lc. The exact construction of the signal-comparing circuit 23 forms no part of the present invention. The speed of the motor 14d is reduced when the weighing device 19 detects that the combined output of cutters la-lc exceeds a predetermined quantity, and the speed of the motor 14d is increased when the quantity measured by the weighing device 19 is less than the aforementioned predetermined quantity. As mentioned before, the delivery of a constant stream of tobacco shreds 20 to the drying apparatus is of considerable importance because this insures that the drying apparatus need not be adjusted in order to compensate for fluctuations in the rate of admission of tobacco shreds, but merely to account for eventual changes in the moisture content of incoming shreds.

In the apparatus of FIG. 1, the positioning of the weighing device 19 is such that itmeasures the quantities of tobacco shreds 20 in successive increments of the composite stream formed by the output of the cutters la-lc, i.e.', the weighing device 19 is located in a portion of the path for shreds 20 which is disposed upstreamof the region of the outlet of the last cutter 1d. Therefore, the cutter 1d can furnish such quantities of tobacco shreds that each increment of the stream containing the combined output of the cutters 1a 1d contains a predetermined quantity of tobacco shreds. However, it is equally within the scope of the present invention to place the weighing device 19 downstream of the last cutter 1d, for example, to the position indicated by phantom lines, as at 19. An advantage of mounting the weighing device 19 in the position 19' is that this weighing device measures quantities of ,tobacco shredsin that stream which is about to enter the drying apparatus.

It is further within the scope of the invention to employ in the apparatus of FIG. 1 two weighing devices one of which occupies the position shown at 19 and the other of which occupies the position shown at-19'. The

signal comparing circuit 23 of the control system 17 then comprises a further input which receives signals from the second weighing device located downstream of the cutter 1d .whereby the output signal from the circuit 23 accounts for eventual deviations of the quantity per unit length of the final stream from the desired quantity. The provision of two weighing devices prevents longrange fluctuations in the stream which leaves the conveyor 22 to enter the drying apparatus.

An advantage of the potentiometer 27 is, that it insures that the circuit 23 can compensate for eventual changes in the cross-sectional area of the spout or mouthpiece 13d in the cutter 1d.

Since the last cutter 1d merely serves to complement the output of the first three cutters la-lc, its output can be much smaller than the output of the other three cutters. However, it is normally desirable to employ a cutter 1d whose maximum output at least matches the maximum output of the cutter la, lb or 10. This is desirable in the event that one-of the cutters 1a 1c is out of commission. The control system 17 then operates the cutter 1d at or close to maximum speed so that the output of the cutter 1d replaces the output of that one of the cutters 1a, 1b, 1c which is temporarily out of commission. The control system 17 automatically causes the motor 14d to drive the

chains

11d, 12d at a maximum speed so that the output of the cutter 1d reaches or is close-to a maximum value when one of the cutters 1a, 1b, 1 c is arrested.

The aforementioned system of recirculating conveyors 43, 44,46 can be used in addition to or as a substitute'for the control system 31. Thus, if the control system 31 is omitted, the conveyor 8 simply transports a continuous stream of tobacco leaves 7 along the inlets 6a to 6d and each of these inlets receives a certain quantity of tobacco leaves. The surplus is recirculated by the conveyors 43, 44, 46 to reenter the hopper 41 and to be again withdrawn by the upwardly moving stretch of the carded conveyor 42. The motor 38 is then replaced by a constant-speed motor. The tachometer generator 24 can be of the type as disclosed in US Pat. No. Re 25,476 to Radley.

The apparatus of FIG. 2 again comprises four

cutters

101a, 101b, 1010, 101d. The cutter 10111 is adjustable in response to signals from a measuring or weighing device 151 the details of which are illustrated in FIG. 3. The weighing device 151 comprises a support 162 which is pivoted at 161 and is biased in a counterclockwise direction, as viewed in FIG. 3, by a helical spring 163. The support 162 carries two pulleys 162a, l62b for an endless conveyor belt 1620 which receives a stream of tobacco shreds from a conveyor 118 corresponding to the conveyor 18 of FIG. 1. The support 162 is connected to the wiper arm 164a of a potentiometer 164 which serves to transmit signals indicating the angular position of the support 162. Such angular position is indicative of the quantity of tobacco shreds 120 in successive increments of that portion of the tobacco stream which advances with the upper stretch of the belt 162c. The potentiometer 164 is mounted in a cabinet 152. This potentiometer constitutes a transducer which converts mechanical signals furnished by the support 162 into electrical signals.

The pulley 162a for the belt 1626 of the weighing device 151 is driven by a variable-speed d-c motor 166 by way of an endless chain or" belt 166a. The rotational speed of the output shaft of the motor 166 is monitored by a tachometergenerator .167 which is capable of producing electric signals indicating the forward speed of the upper stretch of the belt 162C. The potentiometer 164 and tachometer generator 167 are connected with a source 169 of constant potential which is in circuit with an adjustable resistor. 168.

The output signals from the potentiometer 164 and tachometer generator 167 are transmitted to the corre- 'sponding inputs of a signal multiplying circuit 171 of conventional design. Such circuits are disclosed, for example, in the German-language publication entitled Taschenbuch der Nachrichtenverarbeitung by K.- Steinbuch, pp. 1,179l,'l90, published in 1962 by Springer-Verlag. The'output signal from the circuit 171 is transmitted to one input of a signal comparing circuit 172 which is further connected with an adjustable potentiometerv 173 constituting a source of reference signals. The output signal from the circuit 172 is transmitted to an operational amplifier 174 which is preferably analogous to the amplifier 28of FIG. 1 and regulates the speed of the d-c motor 166 for the belt 1626 of the weighing device 151. The'adjustment of the motor 166 is such that the product of signals representing the speed of the upper stretch of the belt 162c and the angular position of the support 162 is constant.

The potentiometer 164 and/or the tachometer generator 167 transmits a signal to the corresponding input or inputs of the signal comparing circuit 123 in the control system 117 for the last cutter 101d. The control system 117 adjusts the speed of the motor 114d in the cutter 101d in the same way as described in connection with FIG. 1. The circuit 123 further receives a signal from the tachometer generator 124 and from the potentiometer 127. The

parts

124, 127 respectively correspond to the parts 24, 27 shown in FIG. 1. The construction of the output amplifier 128 which receives signals from the circuit 123 of the control system 117 is preferably identical with or analogous to that of the amplifier 28 shown in FIG. 1.

Referring again to FIG. 2, there is further shown a control system 131 which serves to regulate the rate of feed of tobacco leaves 107 to the upper stretch of the conveyor 108. The conveyor 108 delivers tobacco leaves to the inlets 106a-l06d. The control system 131 comprises and adjustable potentiometer 132 which serves as a source of reference signals indicating a desired quantity of tobacco leaves 107 to be furnished to the receiving end of the conveyor 108. The signals are transmitted to a signal comparing circuit 136 which further receives signals from a measuring or weighing device 133 corresponding to the weighing device 33 of FIG. 1. The output signal from the circuit 136 regulates the speed of a variablespeed d-c motor 138 by way of an operational amplifier 137. The amplifier 137 is preferably identical with the amplifier 28 of FIG. 1. The motor 138 drives a variable-speed withdrawing conveyor 142 which draws tobacco leaves 107 from a hopper 141 and delivers them onto the upper stretch of the conveyor 108.

It will be noted that the weighing device 133 is installed between two portions of a recirculating conveyor 154. The latter receives surplus tobacco leaves 107 from the conveyor 108 by way of a second recirculating conveyor 153 and delivers the surplus back into the hopper 141 by way of a third recirculating conveyor 156. The arrangement is such that when the weighing device 133 between the portions of the recirculating conveyor 154 does not transport any tobacco, the rotational speed of the motor 138 increases so as to create a surplus which is transported from the conveyor 108 to the conveyor 154 by way of the conveyor 153. When the quantity of tobacco leaves that pass over the weighing device 133 increases, the output signal from the weighing device 133 causes the amplifier 137 to reduce the speed of the motor 138 so that the conveyor 142 withdraws a smaller quantity of leaves 107 from the hopper 141.

FIG. 2 further shows an inlet 143 which is located downstream of the aforementioned weighing device 151 and serves to admit a constant stream of comminuted tobacco particles 120 into a rotary drum forming part of the aforementioned drying apparatus 144. Drying apparatus which can be used to treat tobacco shreds furnished by the apparatus of FIG. 1 or 2 are disclosed, for example, in U.S. Pat. No. 3,429,317 to Koch, et al., or in U.S. Pat. Nos. 3,386,447, 3,389,707, 3,409,025 and 3,419,015 to Wochnowski.

The operation of the apparatus shown in FIGS. 2 and 3 is as follows:

The deflectors 109a-109d deflect tobacco leaves 107 from the upper stretch of the conveyor 108 into the respective inlets 106a-106d. The left-hand end of the conveyor 108 receives tobacco leaves from the conveyor 142 at the rate which is determined by the control system 131. The chains 111a-111d cooperate with the respective chains 112a112d to condense the tobacco leaves which respectively enter the inlets 106a-l06d, and the leading ends of the resulting cakes are fed through the corresponding mouthpieces 113a-l13d into the range of rotating knives driven by the motors 116a-116d. The thus obtained tobacco shreds 120 are discharged by the outlets of the cutters 101a-101d and descend onto the upper stretch of the conveyor 118 for delivery to the conveyor belt 1620 of the weighing device 151 which is located downstream of the last cutter 101d. The discharge end of the conveyor 118 delivers successive increments of the combined stream of tobacco shreds onto that portion of the upper stretch of the belt 1620 which is close to the axis of the pulley 162a, namely, close to the pivot axis for the support 162. This insures that the dynamic forces which develop as the tobacco shreds descend onto the upper stretch of the belt 1620 cannot unduly influence the angular position of the support 162.

As a given increment of the tobacco stream delivered by the conveyor 118 advances with the upper stretch of the belt 1620 in a direction toward the pulley 162b, its influence on the angular position of the support 162 increases gradually, i.e., porportionally with increasing distance from the pivot 161 for the support 162. Consequently, the changes in angular position of the support 162 are indicative of changes in the weight of successive increments of the tobacco stream which is delivered by the conveyor 118. Such increments tend to pivot the support 162 against the opposition of the spring 163 and the changes in angular position of the support 162 are registered by the wiper arm 164a of the potentiometer 164 which transmits appropriate signals to the circuits 171 and 123. The output signal from the circuit 171 is transmitted to the signal comparing circuit 172 which compares such signal with the signal from the source 173 and adjusts the speed of the motor 166 for the belt 1620 by way of the amplifier 174. Such adjustments result in uniformization of the quantity of tobacco that is being transported by the belt 162 0 into the inlet 143 of the drying apparatus 144. For example, if the weight of successive increments that are being delivered onto the belt 1620 increases, the inclination of the support 162 also increases and the output signal from the potentiometer 164 causes the amplifier 174 to reduce the speed of the motor 166 so that the quantity of tobacco shreds 120 that are being furnished to the inlet 143 per unit of time decreases. lnversely, when the weighing device 151 detects that the quantity of tobacco shreds 120 in successive increments of the stream that passes over the conveyor belt 1620 is below the desired value as indicated by the potentiometer 173, the output signal from the potentiometer 164 causes the amplifier 174 to accelerate the motor 166 so that the upper stretch of the conveyor belt 1620 advances the tobacco shreds at a higher speed. This results in admission of larger quantities of tobacco shreds to the inlet 143 per unit of time.

In addition to regulating the speed of the motor 166 for the belt 1620 of the weighing device 151, the output signal from the potentiometer 164 preferably also regulates the operating speed of the last cutter 101d and hence the quantity of tobacco shreds 120 which are delivered by the cutter 101d to the conveyor 118. As mentioned before, the signal from the potentiometer 164 can be transmitted to the circuit 123 of the control system 117 in addition to or instead of the signal from the tachometer generator 167. An advantage of the operative connection between the weighing device 151 and the control system 1 17 is that the apparatus reacts more rapidly to eventual changes in the rate of tobacco feed to the drying apparatus 144 because the speed of the belt 1620 can change simultaneously with changes in the rate of delivery of tobacco shreds 120 by the last cutter 101d. The circuit 124 of the control system 117 causes the amplifier 128 to accelerate the motor 114d of the cutter 101d when the quantity of tobacco shreds which are delivered to inlet 143 per unit of time is less than desired and to decelerate the motor 114d when the quantity of tobacco shreds which are being fed to the rotary drum 144 exceeds the desired value.

It will be noted that the output of the cutter 101d complements the combined output of the cutters la-l01c and that changes in the output of the cutter 101d are effected in response to measurements of the tobacco stream in a portion of the path defined by the composite conveyor 118, 162c downstream of the last cutter. Thus, the weighing device 151 insures elimination of eventual minor deviations of the actually delivered quantity of tobacco shreds from a desired quantity.

The tobacco leaves 107 which bypass the last deflector 109d descend onto the recirculating conveyor 153 and are transported by the conveyor 154 over the belt of the weighing device 133 and back into the hopper 141 by way of the conveyor 156. The weighing device 133 measures the weight of successive increments of the stream of tobacco leaves 107 and determines the speed of the motor 138 for the conveyor 142. This con veyor forms with the hopper 141 a source 139 of fibrous material which is to be comminuted at thestations A, B, C and D.

The conveyor belt 1626 meters the contents of the stream of shreds 120 on the conveyor 118 to form a constant stream which is fed into the inlet 143. The rate varying step (by the control system 117) at the station D accommodating the cutter 101d includes varying the output of the cutter 101d in dependency on the metering step, i.e., in dependency on the speed of the belt 1620.

FIG. 4 illustrates a portion of a third apparatus which constitutes a modification of the apparatus shown in FIGS. 2 and 3. FIG. 4 merely shows a single cutter 301d which is adjacent to a conveyor 318 corresponding to the conveyor 118 of FIG. 3. The conveyor 318 receives tobacco shreds 320 from one or more additional cutters which may or may not be adjustable in the same way as the cutter 301d. The control system for the cutter 301d is shown at 317; the construction of this control system is preferably analogous to that of the system 117 shown in FIG. 3. v

The conveyor 318 discharges tobacco shreds 320 onto the upwardly moving stretch of an endless carded conveyor 387 which is driven by a constant-speed motor 387a. The upper end of the conveyor 387 discharges tobacco shreds 320 into a magazine 376 which accumulates and maintains a relatively small supply 379 of tobacco shreds. The magazine 376 contains or supports a detector including three photosensitive units 381a, 381b, 3810 which are located at different levels and are connected with a circuit 383 which is connected with the control system 317 by way of a preamplifier 384 and an operational amplifier 386. It will be noted that the parts of the apparatus shown in FIG. 4 are denoted by reference characters which are similar to those employed in FIG. 3 plus 200. Analogously, many parts which are shown in FIGS. 2-3 and 4 are similar to the parts which are denoted by similar reference characters employed in FIG. 1. Many of these parts are not specifically mentioned in connection with FIGS. 2-3 and .4.

One side wall of the magazine 376 is formed by a carded conveyor 377 which transports a continuous stream of tobacco shreds 320 from the supply 379 in the magazine and discharges the continuous stream onto the conveyor belt 3620 of the weighing device 351. The construction of this weighing device is analogous to the construction of the weighing device 151 shown in FIG. 3, and the discharge end of the belt 362C delivers a constant tobacco stream into the inlet 343 of the drying apparatus 344.

The purpose of the photosensitive detecting units 38la-38lc is to scan the upper level of the supply 379 of tobacco shreds 320 in the magazine 376 and to furnish to the control system 317 signals whose intensity is indicative of the detected level. The control system 317 then adjusts the output of the cutter 301d in dependency on such signals so as to insure that the combined output of the cutters including the cutter 301d and the cutters which are mounted upstream of this cutter is constant. Each of the units 381a-381c comprises a light source (not shown) and a photosensitive element which latter produces a signal in response to impingement on its photosensitive surface of the light beam issuing from the corresponding light source. The photosensitive elements are connected with the circuit 383. This circuit constitutes a time-delay device which transmits signals to the aforementioned amplifier 384. The parts 38lla-381c, 383, 384, 386 together constitute a regulating circuit 382 which transmits signals to the control system 317.

' The operation of the apparatus which includes the structure of FIG. 4 is as follows:

The conveyor 318 delivers shredded tobacco to the upwardly moving stretch of the carded conveyor 387. The conveyor 387 delivers the shreds into the magazine 376 to build up and to maintain the supply 379. This supply is relatively small because the conveyor 377 is capable of withdrawing from such small supply a con stant stream of tobacco shreds which are fed onto the belt 362s of the weighing device 351. The supply 379 contains loose tobacco shreds and the upper level of the supply is scanned by the units 381a-38lc which transmit appropriate signals to the time-delay device 383. The latter causes the amplifiers 384 and 386 to transmit signals to the control system 317 for the purpose of regulating or varying the output of the cutter 301d so that the rate of admission of shreds 320 from the cutter 301d to the conveyor 318 either increases or decreases, depending on the position of the upper level of the supply 379. In this manner, the regulating unit 382 insures that the supply 379 does not fluctuate beyond a permissible narrow range. As mentioned before, this enables the conveyor 37 7 to withdraw a continuous stream of tobacco shreds 320 for delivery into the inlet 343 of the drying apparatus 344.

The purpose of the weighing device 351 is to insure that the drying apparatus 344 receives a constant stream of tobacco shreds 320. Thus, the potentiometer 364 produces signals which are indicative of the inclination of the support 362 and the tachometer generator 367 produces signals which are indicative of the momentaryoperating speed of the motor 366 for the conveyor 377. When the weighing device 351 detects that the quantity of shreds 320 in successive increments of the tobacco stream on the belt 362c deviates from the desired quantity as indicated by the potentiometer 373 in the cabinet 352, the speed of the motor 366 is changed so that the weight of successive increments on the conveyor belt 362c either increases or decreases.

A modern high-speed cigarette making machine is normally installed in an air conditioned area in order to insure that the moisture content of tobacco which is fed into such machine does not deviate from the desired content as a result of eventual changes in the moisture content of the surrounding air. The drying apparatus 344 is capable of delivering to the cigarette rod making machine a continuous stream of dried tobacco shreds having an accurately determined moisture content if the apparatus 344 receives a constant stream of tobacco shreds. The apparatus of FIG. 4 has been found to be capable of forming a constant stream of shreds 320, and this is attributed to the provision of the magazine 376 which accumulates and maintains a relatively small supply of loose shreds 320. As mentioned before, the conveyor 377 is capable of withdrawing from the magazine 376 a constant stream of shreds 320 if the quantity of shreds in the supply 379 fluctuates within a narrow range.

The apparatus of FIG. 4 regulates the quantity of tobacco shreds 320 in the stream which enters the drying apparatus 344 in three successive stages. Thus, adjustments of the output of the machine 301d by means of the control system 317 result in an initial or coarse equalization of the stream. A second and more precise equalization is achieved with the conveyor 377 which draws a constant stream of tobacco shreds 320 from the magazine 376 wherein the supply 379 is maintained at a constant value. The third and final equalization is achieved with the belt 362s of the weighing device 351 which can be driven at a variable speed depending on the intensity of signals furnished by the potentiometer 364.

An important advantage of the improved method is that the drying apparatus 144 or 344 need not be provided with any adjusting means to compensate for eventual fluctuations in the rate of delivery of tobacco shreds. Thus, the drying apparatus merely embodies adjusting means which insures that the drying or moisture-expelling action can be regulated to account for eventual fluctuations in the moisture content of

shreds

20, 120 or 320. As mentioned before, this contributes to a substantial simplification of the controls for the drying apparatus.

It is further within the scope of our invention to utilize the

control system

17, 117 or 317 as a means for regulating the output of two or more cutters. For example, the control system 17 of FIG. 1 can be used to accelerate the chains llb-l 1d and 12b-12d of the cutters lb-ld if the cutter 1a must be arrested for the purposes of inspection and/or repair, or to accelerate the cutters la, lb, id or la, 1c, 1d if the cutter 1c or 1b is idle.

Without further analysis, the foregoing 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 our contribution to the art and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims:

1. A method of forming and manipulating comminuted fibrous material, particularly shredded tobacco, comprising the steps of comminuting fibrous material at a plurality of parallel cutting stations; introducing the thus obtained comminuted material into successive regions of a predetermined path wherein the comminuted material is conveyed in a predetermined direction and builds up a growing stream; measuring the quantities of comminuted material in at least one predetermined portion of said path; comparing the quantities determined in said measuring step with a predetermined quantity; and varying the rate of introduction of comminuted material from at least one of said stations as a function of differences between said measured quantities and said predetermined quantity so that the combined quantity of comminuted material furnished by all of said stationsremains constant.

2. A method as defined in claim 1, wherein the number of said stations exceeds two and the region of admission of comminuted'material from said one station is located downstream of the other regions, as considered in said predetermined direction.

3. A method as defined in claim 1, wherein the region of introduction of comminuted material from said one station is located downstream of said predetermined portion of said path and downstream of each other region, as considered in said predetermined direction.

4. A method as defined in claim 1, wherein the region of introduction of comminuted material from said one station is located upstream of said predetermined portion of said path, as considered in said predetermined direction.

5. A method as defined in claim 4, further comprising the step of metering the contents of the stream in said path to form said constant stream, said rate varying step including changing the output of comminuted material at said one station in dependency on said metering step.

6. A method as defined in claim 1, wherein said measuring step comprises weighing the comminuted material in said predetermined portion of said path.

7. A method as defined in claim 6, wherein said weighing step includes producing a first signal whose intensity increases proportionally with progressing transport of particles of comminuted material along said portion of said path and a second signal whose intensity is a function of the speed of transport of particles of comminuted material along said portion of said path, said rate varying step comprising utilizing at least one of said signals to adjust the introduction of comminuted material from said one station into the respective portion of said path.

8. A method as defined in claim 7, further comprising the step of utilizing said first and second signals to regulate the speed of transport of comminuted material along said portion of said path.

9. A method as defined in claim 1, further comprising the step of collecting comminuted material in said predetermined portion of said path to form a supply of comminuted material, said measuring step comprising measuring the quantity of comminuted material in said supply and said predetermined portion of said path being located downstream of said regions, as considered in said predetermined direction.

10. A method as defined in claim 9, wherein said rate varying step comprises respectively reducing and increasing the rate of admission of comminuted material from said one station when the quantity of comminuted material in said supply respectively rises and decreases.

path fibrous material for admission to said stations.

Claims

1. A method of forming and manipulating comminuted fibrous material, particularly shredded tobacco, comprising the steps of comminuting fibrous material at a plurality of parallel cutting stations; introducing the thus obtained comminuted material into successive regions of a predetermined path wherein the comminuted material is conveyed in a predetermined direction and builds up a growing stream; measuring the quantities of comminuted material in at least one predetermined portion of said path; comparing the quantities determined in said measuring step with a predetermined quantity; and varying the rate of introduction of comminuted material from at least one of said stations as a function of differences between said measured quantities and said predetermined quantity so that the combined quantity of comminuted material furnished by all of said stations remains constant.

2. A method as defined in claim 1, wherein the number of said stations exceeds two and the region of admission of comminuted material from said one station is located downstream of the other regions, as considered in said predetermined direction.

11. A method as defined in claim 10, further comprising the step of withdrawing from said supply a constant second stream of comminuted material.

12. A method as defined in claim 9, wherein said measuring step comprises scanning the level of comminuted material in said supply.

13. A method as defined in claim 1, further comprising the steps of admitting fibrous material into a second predetermined path, maintaining the rate of admission of fibrous material into said second path within a predetermined range, and withdrawing from said second path fibrous material for admission to said stations.