US3419015A

US3419015A - Method and apparatus for mixing additives with tobacco

Info

Publication number: US3419015A
Application number: US605899A
Authority: US
Inventors: Wochnowski Waldemar
Original assignee: Hauni Werke Koerber and Co KG
Current assignee: Koerber AG
Priority date: 1966-01-14
Filing date: 1966-12-29
Publication date: 1968-12-31
Anticipated expiration: 1985-12-31
Also published as: DE1532058A1; SE326394B; GB1166296A; DE1532058B2; DE1532058C3; NL6700387A

Description

w. WOCHNOWSKI 3,419,015 METHOD ANDYAPPARA'VIUS FOR MIXING ADDITIVES WITH TOBACCO Dec. -31. 1968 Sheet Filed Dec. 29, 1966 v mvsmon. 4m em 01 mam! w w. WOCHNOWSKI 3,419,015

METHOD AND APPARATUS FOR MIXING ADDITIVES WITH TOBACCO Filed Dec. 29, 1966 Sheet Z of 2 INVENTOR. I 4/0, ldum'v 4/061 W4.

United States Patent Ofifice 3,41%,015 Patented Dec. 31, 1968 3,419,015 METHOD AND APEARAT US FOR MiXlNG ADDITIVES WlTH TOBACCO Waldemar Wochnowski, Hamburg, Germany, assignor to Hauni-Werke Korber & (30., K.G., Hamburg-Bergedorf, Germany Filed Dec. 29, 1966, Ser. No. 605,899

Claims priority, application Germany, Jan. 14, 1966,

H 58,240 20 Claims. (Cl. 131138) ABSTRACT OF THE DISCLOSURE Method and apparatus for mixing tobacco particles with liquid additives, particularly with casing or flavoring solutions. A tobacco stream is withdrawn from a fluctuating supply of tobacco particles at a lower first speed when the supply is depleted to the lower limit and at a higher second speed when the supply is replenished to the upper limit of a predetermined range. The quantity of tobacco in the supply is measured, and the result of such measurement is utilized to change the speed at Which the stream is withdrawn as well as to regulate the admission of additives into successive increments of the travelling stream.

Background of the invention The present invention relates to a method and apparatus for mixing particulate material with additives which are preferably supplied thereto in liquid state. More particularly, the invention relates to a method and apparatus which may be utilized to mix tobacco particles with causing and/or flavoring substances.

It is well known to mix tobacco with liquid additives which improve the aroma and otherwise enhance the quality of cigarettes, cigars or other tobacco-containing commodities. The mixing should be carried out in such a way that each unit quantity of tobacco is permeated or impregnated with the same amount of additives. Otherwise, the quality of tobacco-containing commodities would vary from pack to pack or from batch to batch. A smoker or a chewer expects a certain aroma or taste when he or she purchases a certain brand of tobacco-containing commodities.

The simplest mode of insuring uniform mixing is, of course, to convey tobacco and additives at a constant rate into a mixing zone. Uniform feed of a liquid additive can be readily achieved by resorting to known flow regulating devices. However, it is much more diflicult to convey tobacco at a uniform rate, for example, when the system which receives tobacco from the main source is supplied with tobacco in batches rather than in the form of a continuous stream.

Accordingly, it is an important object of the present invention to provide a novel method of mixing tobacco particles and like foliate material with liquid additives in such a way that each unit quantity of tobacco is mixed with the same amount of additives, regardless of fluctuations in the delivery of tobacco.

Another object of the invention is to provide a method which can be used to mix tobacco particles with liquid additives on a large scale and with desired uniformity so that each unit quantity of tobacco is invariably permeated with the same amount of additives.

A further object of the invention is to provide an automatic mixing apparatus which may be utilized in practicing of the above outlined method.

An additional object of the invention is to provide an apparatus which can convert a fluctuating supply of tobacco into a continuous stream and is capable of mixing each unit quantity of tobacco in such a stream with a predetermined amount of liquid flavoring solution or casing, irrespective of changes in speed at which the tobacco stream is advanced during mixing.

Summary of the invention One feature of the present invention resides in the provision of a method of mixing additives wit-h particulate material, particularly for mixing casing or flavoring solutions with tobacco particles. The method comprises the steps of accumulating a fluctuating supply of particulate material, measuring the quantity of particulate material in such supply, withdrawing from the supply a stream of particulate material at first and second rates of speed which are respectively high and low enough to effect gradual depletion and replenishing of the supply, switching from withdrawal at the first rate of speed to withdrawal at the second rate of speed and vice versa when the supply of particulate material is respectively depleted to a predetermined minimum value and replenished to a predetermined maximum value, and introducing into the stream of particulate material additives in such amounts that each unit quantity of particulate material is mixed with the same amount of additives. For example, the weight ratio of tobacco to additives may be 10:1 if the additives constitute a casing.

The stream of particulate material is preferably advanced in a predetermined path defined by a conveyor system and extending through a mixing zone which accommodates one or more spray nozzles for sprinkling the additives in liquid state onto successive increments of the stream which are being advanced through the mixing zone. Such mixing zone is preferably remote from the supply of particulate material and the introducing step then comprises regulating the amounts of additives with a delay which is a function of the speed of travel of successive unit quantities of the stream from the supply to the mixing zone.

The conveyor system for the stream of particulate material is preferably arranged to shower the material into or to agitate the material in the mixing zone in order to effect more uniform mixing of such particulate material with the additives. Each unit length of the stream preferably contains an unchanging first and second quantity of particulate material when the stream is respectively withdrawn at the first and second rates of speed. This can be achieved by brushing back surplus material during withdrawal from the supply.

The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved mixing 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 drawing.

Brief description of the drawing FIG. 1 is a diagrammatic side elevational view of a mixing apparatus which embodies my invention;

FIG. 2 is a similar view of the mixing apparatus, further showing the electric circuit which controls the delivery of tobacco and additives to a mixing zone as a function of the quantity of tobacco which constitutes the supply; and

FIG. 3 is a diagram showing the construction of a time delay unit in the electric circuit of FIG. 2.

Description of the preferred embodiments FIG. 1 illustrates a mixing apparatus comprising a variable-speed conveyor system 3 which includes a first endless conveyor belt 21, a second endless conveyor belt 22 arranged to receive successive increments of a tobacco stream TS from the belt 21, a revolving mixing drum 23 which receives tobacco from the belt 22, a third endless conveyor belt 26 which receives tobacco from the mixing drum 23, and a fourth endless conveyor belt 24, here shown as an upwardly inclined apron or elevator which supplies tobacco onto the upper stringer of the belt 21. The upper stringer of the belt 21 is located at a level above a suitable weighing device 10 which measures the weight of successive unit lengths of the tobacco stream TS travelling toward the upper stringer of the belt 22. The drive means 7 for the

belts

21, 22, 26 and mixing drum 23 comprises a variable-speed electric motor 7a driving a transmission 7b having three output members 107a, 107b, 1070 which are respectively arranged to drive the belts 21, 22, a ring gear 23a of the mixing drum 23, and the belt 26. A manually operated speed changer 28 is provided to select the speed of the motor 7a. As a rule, the drive 7 will operate the parts 2123 and 26 of the conveyor system 3 at a constant speed. The apron 24- is operated at two speeds.

The magazine of the mixing apparatus comprises an endless belt 2 whose discharge end is adjacent to the apron 24. The upper stringer of this apron is adjacent to a pair of equalizing wheels 27 serving to insure that the apron invariably withdraws from the supply S on the belt 2 a tobacco stream TS of constant height. The belt 2 is driven at two speeds to assist the apron 24 in withdrawing the stream TS from the magazine. The supply S of tobacco on the belt 2 can be built up by hand or by resorting to a suitable endless belt or other feeding mechanism which is not shown. It sufiices to say that the quantity of tobacco particles forming the supply S fluctuates between a maximum value and a minimum value, and that such quantity is measured continuously by a detector 1 whose exact construction and operation will be described in connection with FIG. 2. The detector 1 comprises two level indicators one of which spots the minimum permissible level of tobacco in the supply S and the other of which spots the maximum permissible level of such tobacco. When the quantity of tobacco in the supply S is reduced to the aforementioned minimum value, the detector 1 sends a signal to a time delay unit and to a junction 18. When the supply S has been replenished so that the level of tobacco on the belt 2 rises to a maximum value, the detector 1 ceases to send a signal to the time delay unit 5 and sends a different signal to a second time delay unit 6 as well as to the junction 18. The junction 18 is further connected with a signal generator 9 which transmits signals as a function of measurements carried by the weighing device 10, with a rated value setting device 8, and with a variable-speed drive 11 for the belt 2 and apron 24. The speed of the drive 11 is adjusted as a function of measurements carried out by the weighing; device and as a function of signals transmitted to junction 18 by the rated value setting device 8.

The numeral 25 denotes a spray nozzle forming part of an applicator 4 for mixing successive increments of the tobacco stream TS with requisite amounts of a liquid casing or flavoring solution which is stored in a tank 12 and is fed through a conduit 20 and a flow meter 16 by a variable-delivery pump 14 having a variable-speed motor 14a which is regulated by a control circuit 13. The spray nozzle 25 is installed in a mixing zone 100 in the interior and close to the downstream end of the mixing drum 23. The internal surface of the drum 23 is provided with axially parallel vanes or blades 23b which shower successive increments of the stream TS into the mixing zone 100 to promote uniform mixing of tobacco with flavoring solution discharged through the orifices of the nozzle 25. The blades or vanes 23b may be constituted by heating or cooling coils which condition the tobacco stream TS during travel through the mixing drum 23.

The flow meter 16 is connected with a signal generator 17 which transmits signals to a second junction 19. The

latter sends signals to the control circuit 13 for the pump motor 14a and receives signals from the signal generator 17 (such signals are indicative of the throughput of the applicator 4), from a second rated value setting device 15, from the time delay unit 5, or from the time delay unit 6.

The drive means 7 for the conveyor system 3 is operatively connected (see the line 29) with the time delay units 5 and 6 so that the delay selected by these units is a function of the speed at which the conveyor system 3 advances the tobacco stream TS through the mixing zone 100. The direction of tobacco travel is indicated by arrows. The arrows applied to the lines indicating operative connections between the components of the arrangement which regulates the speed of the apron 24 and the throughput of the applicator 4 are intended to indicate the directions in which the components transmit control signals but have no other meaning.

When the apron 24 is driven at a lesser speed, each unit length of the tobacco stream TS on the belt 21 contains less tobacco even though the speed of the belt 21 (and of belt 22, drum 23 and belt 26) remains unchanged. The axis of the drum 23 is slightly inclined with refer ence to a horizontal plane so that its blades or vanes 23]) compel successive increments of the stream TS to advance toward and onto the upper stringer of the belt 26. This belt feeds the tobacco stream to a further processing station.

The operation is as follows:

The magazine including the belt 2 receives a certain amount of tobacco particles to build up a supply S. The rate at which the belt 2 receives tobacco from a further endless belt (not shown) or by hand is preferably such that the average quantity supplied to belt 2 per unit of time remains within a range (upper and lower limits) determined by the rated value setting device 8.

FIG. 1 shows that the supply S of tobacco particles on the belt 2 has been reduced to a predetermined minimum value. This is sensed by the lower level indicator of the detector 1 which transmits a suitable signal to the junction 18. The latter comprises an evaluating unit (to be described in connection with FIG. 2) which resets the device 8 so that the latter sends a signal indicative of a reduced rate at which the apron 24 should withdraw tobacco particles from the supply S. The junction 18 then transmits an appropriate signal to the drive means 11 to reduce the speed at which the belt 2 and apron 24 are operated. The belt 21 of the conveyor system 3 receives less tobacco per unit of time and this is detected by the weighing device 10 which cooperates with the upper stringer of the belt 21. Once the drive means 11 is adjusted, the rate of tobacco withdrawal from the supply S per unit of time remains constant, and such rate is determined by the setting device 8. Of course, and since the supply S is assumed to be replenished at a constant average rate, the level of tobacco on the belt 2 rises and ultimately reaches the maximum level which causes the detector 1 to send to the junction 18 a different signal. During such replenishing of the supply S, the time delay unit 5 causes the control circuit 13 to operate the motor 14a at such a speed that the nozzle 25 discharges flavoring solution at the rate which corresponds to the rate of tobacco feed through the mixing zone 100. The delay with which the unit .5 causes the control circuit 13 to reduce the speed of the motor 14a when the supply of tobacco on the belt 2 is depleted to the lowermost permissible level corresponds to the interval necessary to advance an increment of the tobacco stream TS from the supply S to the mixing zone 100. The delay unit 5 may be further calibrated to account for certain other factors, such as the inertia of components which transmit the signals for effecting a change in the speed of the drive means 11. The interval necessary to move successive increments of the stream TS from the supply S to the [mixing zone also depends on the selected speed of the drive means 7, and a corresponding signal is transmitted to the delay unit 5 through the connection 29. The output signal of the delay unit 5 is transmitted to the junction 19 and thence to the device which is reset so that its output signal then causes a reduction in the throughput of the applicator 4. The flow meter 16 measures the throughput of the applicator 4 and causes the signal generator 17 to transmit appropriate signals to the junction 19. Such signals are utilized to adjust the control circuit 13 if the actual rate of solution flow to the nozzle 25 is above or below the optimum flow rate for the lower operating speed of the drive means 11.

When the level of tobacco in the supply S on the belt 2 rises to the maximum permissible level, the upper level indicator of the detector 1 responds and sends an appropriate signal to the junction 18 and time delay unit 6. Such signal simultaneously erases the output signal of the lower level indicator and hence the output signal of the time delay unit 5. The signal from the upper level indicator causes the junction 18 to reset the device 8 which then transmits a modified signal in order to bring about a higher rate of tobacco withdrawal from the supply S. The drive 11 then operates the belt 2 and apron 24 at a higher speed so that the level of tobacco on the belt 2 begins to descend. The conveyor system 3 advances more tobacco per unit of time and the delay unit 6 causes the control circuit 13 to adjust the motor 14a of the pump 14 so that the applicator 4 discharges larger amounts of flavoring solution per unit of time, again at such a rate that the ratio of flavoring solution to unit quantities of tobacco remains unchanged. The delay effected by the time delay unit 6 in adjustment of speed of the motor 14a corresponds to the interval required to move an increment of tobacco from the belt 2 to the mixing zone 100 at the second or higher speed. Of course, and as explained hereinabove, the delay selected by the unit 6 is also a function of the speed of the drive means 7 for the parts 2123 and 26 of the conveyor system 3.

The lower level indicator of the detector 1 responds automatically when the level of tobacco particles forming the supply S decreases to that shown in FIG. 1, and the changeover from higher speed to lower speed of the apron 24 is then carried out in the above described manner.

The rates at which the conveyor system 3 delivers successive unit quantities of tobacco through the mixing zone 100 and at which the applicator 4 discharges flavoring solution into the mixing zone are selected by the setting devices 8 and 15 in such a way that the amount of solution admixed to a given unit quantity of tobacco particles remains unchanged, irrespective of the speed at which such unit quantities of tobacco particles are being conveyed through the mixing zone 100.

FIG. 2 illustrates the electric circuit of the apparatus. The detector 1 comprises a simple minimum level indicator 31 and a simple maximum level indicator 32. These indicators respectively comprise light sources 33, 34 and

photoelectric receivers

35, 36. The

receivers

35, 36 are connected with signal storing units 37 38 each having two inputs a and b. A signal received via input a will cause the respective storing unit to transmit an output signal, and a signal received via input b will erase the output signal. Such storing units are well known in the art and the details of their construction form no part of the present invention. The outputs of the storing

units

37, 38 are connected with an evaluating unit 39 which forms part of the junction 18. The signal indicating the rated value is supplied to evaluating unit 39 by a slider 40 forming part of a potentiometer 41 which, in turn, forms part of the rated value setting device 8. The evaluating unit 39 determines the quantity of tobacco to be fed into the mixing zone 100 of the drum 23 per unit of time.

The lower level indicator 31 will produce a signal when its receiver 35 is exposed to light issuing from the source 33, and the upper level indicator 32 produces a signal when its receiver 36 ceases to receive light from the corresponding source 34. If the quantity of tobacco in the supply S accumulated on the upper stringer of the belt 2 is depleted down to a preselected minimum value (determined by the mounting of receiver and light source 33), so that the receiver 35 receives light from the source 33, the storing unit 37 sends an output signal to the evaluating unit 39 and such output signal is added to the signal received from the slider of the potentiometer 41. The signal received via input a of the storing unit 37 remains stored therein even though the quantity of tobacco on the belt 2 increases gradually and such tobacco interrupts the light beam between the source 33 and receiver 35 of the lower level indicator 31. At the time the receiver 35 receives light from the source 33, it sends a signal via input b of the storing unit 38 whereby such signal erases the output signal of the unit 38.

The apron 24 is driven at reduced speed as long as the storing unit 37 continuesto send an output signal to the evaluating unit 39 whereby the quantity of tobacco on the belt 2 increases gradually because the tobacco stream TS is advanced at a reduced speed. When the quantity of tobacco on the belt 2 increases sufliciently to interrupt the light beam between the source 34 and receiver 36 of the upper level indicator 32, the receiver 36 sends a signal to the inputs 1) and a of storing

units

37, 38 whereby such signal erases the output signal of the unit 37 and causes the unit 38 to send an output signal on to the evaluating unit 39. The output signal of the storing unit 38 is weaker than that of the storing unit 37, and such signal is added to the signal received from the slider 40 of the potentiometer 41 to effect an increase in the speed of the apron 24.

The evaluating unit 39 further receives a signal from the slider 42 of a potentiometer 43 which forms part of the signal generator 9. The slider 43 is biased by a torsion spring 46 and can be turned by a motion transmitting linkage 44 which is coupled to the weighing device 10. The linkage 44 is turnable on a pivot 45. The shaft of the slider 42 is shown at 47. The slider 42 simultaneously constitutes an index and is placed in front of a suitably graduated scale (not shown) to permit visual observation of measurements carried out by the weighing device 10. Signals transmitted to the evaluating unit 39 by the slider 42 of the signal generator 9 are opposites of the signals transmitted by the slider 40 of the potentiometer 41.

The drive means 11 for the belt 2 and apron 24 receives signals from the evaluating unit 39 and includes a signal amplifier 48 whose output is connected with a transducer circuit 49. The control currents flowing through the control coils 49a, 49b of the circuit 49 will vary, dependmg upon whether the evaluating unit 39 receives an output signal from the storing

unit

37 or 38. The working coils 49c, 49d then furnish requisite voltage for a D-C motor 50 which drives the belt 2 and apron 24 and whose r.p.m. varies as a function of the quantity of tobacco forming the supply S on the belt 2.

The outputs of the

signal storing units

37, 38 are further connected with the time delay units 5, 6 and through such delay units with a second evaluating unit 52 forming part of the junction 19. The construction of the delay unit 5 will be described in connection with FIG. 3.

The evaluating unit 52 adds the signal received from the slider 53 of a potentiometer 54 to the output signal received from the storing

unit

37 or 38 through the delay unit 5 or 6. The potentiometer 54 forms part of the rated value setting device 15. The unit 52 further receives signals from the signal generator 17 which is connected with the flow meter 16.

The flow meter 16 comprises an upright conical cylinder 58 which accommodates an axially reciprocable conical float 59. The flavoring solution is stored in the tank 12 and is conveyed by the variable-delivery pump 14 whose outlet is connected with the lower end of the cylinder 58 by conduit 20. The float 59 is immersed in the solution which flows through the cylinder 58 and its axial position is a function of the rate at which the solution flows (per unit of time) upwardly and on to the spray nozzle 25.

The float 59 is connected with an upwardly extending core 60 which is surrounded 'by an induction coil 61. The

inductance of this coil varies as a function of axial movement of the fioat 59 and core 66. The coil 61 is connected in one branch of a Wheatstone bridge 62 whose output is connected to a rectifier 6.3 and an amplifier 64. The output signal of the amplifier 64 is transmitted to the evaluating unit 52 and is indicative of the actual throughput of flavoring solution. This signal is deducted from the signal transmitted by the slider 53 of the potentiometer 54. The just described combination of flow meter 16 and signal generator 17 is known in the art and its details form no part of the present invention.

The output signal of the evaluating unit 52 is transmitted to the control circuit 13 for the pump motor 14a. This control circuit comprises a preamplifier circuit 164 and a second amplifier circuit 65. The control coils 66, 67 of the circuit 65 are connected with the output of the circuit 164, and the working coils 68, 69 are connected with the motor 14a of the pump 14. The motor 14a is a D-C motor.

FIG. 3 illustrates the time delay unit 5 which is identical with or analogous to the time delay unit 6. The unit 5 comprises an endless magnetic tape 70 which is trained around an idler roller 71 and a second roller 72 driven at a constant speed by a synchromotor 73. A recording head 74 receives signals from the storing unit 37 of FIG. 2. An erasing head 75 is adjacent to and is located ahead of the recording head 74, as viewed in the direction of tape travel.

A guide rail 76 carries a signal reproducing head 77 which can transmit signals to the evaluating

units

39 and 52, see FIG. 2. The reproducing head 77 is shifted along the rail 76 in dependency on the speed of drive means 7 for the mixing drum 23 and

belts

21, 22, 26 so that signals recorded on the tape 70 by recording head 74 reach the reproducing head 77 with a shorter or longer delay. Such delay is indicative of the interval required by an increment of the tobacco stream TS to advance from the supply S on the belt 2 into the mixing zone 100.

The recording head of the second time delay unit 6 is connected with the signal storing unit 38.

The connection 29 between the drive means 7 for the parts 21-23 and 26 of the conveyor system 3 and the time delay units 5, 6 will be provided only if the drive means 7 is of the variable speed type. Such drive means is desirable in order to insure that the speed at which the tobacco stream TS travels through the mixing zone 100 can be adjusted, for example, when switching from treatment of one brand to treatment of another brand of tobacco. If the drive means 7 is not adjustable, the delays selected by the units 5 and 6 remain unchanged.

It will be seen that the electric circuit of FIG. 2 comprises three groups. The first group includes the control unit 13, rated value setting device 15, and signal generator 17. The purpose of this first group is to insure that the pump 14 supplies the applicator 4 with liquid additives at a constant higher or lower rate, depending on the setting of the device 15.

The second group includes'the signal generator 9, rated value setting device 8, junction 18 and variable-speed drive 11. Its function is to insure that the apron 24 will withdraw the tobacco stream TS at a constant higher or lower rate of speed, depending on the measurement carried out by weighing device 10 and device 8.

The third group includes the detector 1, the time delay units 5, 6, the connections from detector 1 to junction 18 and units 5, 6, and the connections from units 5, 6 to the junction 19. The function of this third group is to effect switching from high-speed operation to low-speed operation, i.e., from high-speed travel of successive increments of the stream TS and from higher rate at which the nozzle 25 sprays liquid additives per unit of time to low-speed travel and lower rate, or vice versa. The third group is controlled by the level of tobacco in the magazine including the belt 2. The feed of tobacco to the magazine may be continuous or intermittent, regular or irreg- Gil (j ular, as long as the magazine receives a predetermined amount of tobacco per unit of time. The apron 24 and wheels 27 take care of forming a continuous tobacco stream TS each unit length of which contains the same quantity of tobacco at the discharge end of the apron. The quantity of tobacco per unit length of the stream on the belts 21, 22 will remain constant when the drive 11 operates the apron 24 at the one or the other speed. However, such quantity per unit length will change in response to acceleration or deceleration of the apron 24, i.e., only during the short stage of transition when the rpm. of the motor 59 in the drive 11 increases or decreases.

The present invention solves the problem of conveying tobacco from the actual source to the mixing zone at an accurately controlled rate. This problem has been solved by utilizing a magazine (belt 2) which accumulates a supply S of tobacco particles (leaves or shredded tobacco, depending upon whether the material in the tank 12 is a casing or a flavoring solution), and by withdrawing from such magazine a continuous tobacco stream at a plurality of speeds. In this way, the rate at which the magazine receives tobacco cannot affect the mixing of tobacco particles with additives, as long as the magazine receives a certain amount of tobacco per minute, per five minutes or per another selected unit of time. Each of the plural speeds at which the apron 24 withdraws tobacco from the magazine corresponds to a dilierent rate at which the pump 14 delivers liquid additives to the applicator 4, and the rate of pump delivery is changed with a delay which corresponds to the length of intervals required by successive increments of the tobacco stream to cover the distance between the magazine (detector 1) and the mix ing zone 100.

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

1. A method of mixing additives with particulate material, particularly for mixing casing or flavoring solutions with tobacco particles, comprising the steps of accumulating a fluctuating supply of particulate material; measuring the quantity of particulate material in said supply; withdrawing from said supply a stream of particulate material at first and second rates of speed which are respectively high and low enough to effect gradual depletion and replenishing of said supply; switching from withdrawal at said first rate of speed to withdrawal at said second rate of speed and vice versa when the supply is respectively depleted to a predetermined minimum value and replenished to a predetermined maximum value; and introducing into said stream additives in such amounts that each unit quantity of particulate material is mixed with the same amount of additives.

2. A method as defined in claim 1, further comprising the step of advancing said stream in a predetermined path extending through a mixing zone, said introducing step being carried out in said mixing zone.

3. A method as defined in claim 2, wherein said mixing zone is remote from said supply and wherein said introducing step comprises regulating the amount of additives with a delay which is a function of the speed of travel of successive unit quantities of said stream from said supply to said mixing zone.

4. A method as defined in claim 3, wherein said additives are in liquid state and are sprayed Onto successive increments of said stream.

5. A method as defined in claim 4, wherein successive increments of said stream are showered into said mixing zone.

6. A method as defined in claim 1, wherein said measuring step comprises scanning the level of particulate material in said supply.

7. A method as defined in claim 1, wherein each unit length of said stream contains an unchanging first and second quantity of particulate material when said stream is respectively withdrawn at said first and second speeds.

8. A method as defined in claim 1, further comprising the step of feeding to said supply particulate material at such a rate that the supply receives equal quantities of particulate material per unit of time.

9. A method as defined in claim 1, further comprising the step of weighing successive unit lengths of said stream.

10. Apparatus for mixing additives with particulate material, particularly for mixing casing or flavoring solutions with tobacco particles, comprising a magazine arranged to accommodate a fluctuating supply of particulate material; conveyor means for Withdrawing from said supply a stream of material and for advancing successive unit quantities of the stream at different speeds through a mixing zone; detector means for measuring the quantity of material in said supply; variable-speed drive means for changing the rate of which said conveyor means withdraws successive unit quantities as a function of such measurement to respectively accelerate and decelerate said rate of withdrawal when the quantity of material in said supply respectively increases to a predetermined maximum value and decreases to a predetermined minimum value; adjustable applicator means for admitting additives into the stream in said mixing zone; and control means operative to adjust said applicator means as a function of changes in the rate of withdrawal of said unit quantities so that each successive unit quantity of the stream is mixed with the same amount of additives.

11. Apparatus as defined in claim 10, wherein said applicator means comprises nozzle means and said additives are sprayed in liquid state through the orifices of such nozzle means.

12. Apparatus, as defined in claim 10, wherein said detector means comprises level indicator means arranged to spot the minimum and maximum level of particulate material in said magazine.

13. Apparatus as defined in claim 10, wherein said mixing zone is remote from said magazine and further comprising time delay means for effecting operation of said control means with a delay corresponding to the time interval required to advance a unit quantity of said stream from said magazine to said mixing zone.

14. Apparatus as defined in claim 13, wherein said conveyor means comprises a conveying member and said variable-speed drive means is arranged to drive said conveying member at two speeds, said time delay means being responsive to measurements carried out by said detector means.

15. Apparatus as defined in claim 13, wherein said conveyor means comprises a first conveying member arranged to withdraw the stream from said supply and said variable-speed drive means is arranged to operate said first conveying member at two speeds, said conveyor means further comprising at least one additional conveying member which receives the stream from said first conveying member and second variable-speed drive means for said additional conveying member, said time delay means being further responsive to changes in the speed of said second drive means.

16. Apparatus as defined in claim 10, further comprising an operative connection between said detector means and said drive means including rated value setting means adjustable by said detector means, and signal generating means responsive to changes in the weight of successive unit lengths of said stream.

17. Apparatus as defined in claim 16, further comprising weighing means arran-ged to weigh successive unit lengths of said stream and to operate said signal generating means.

18. Apparatus as defined in claim 10, wherein said applicator means comprises means for discharging liquid additives into said mixing zone, a source of additives, and variable delivery means operative to supply additives from said source to said discharging means, said control means being arranged to regulate the operation of said variable delivery means.

19. Apparatus as defined in claim 18, further comprising signal generating means responsive to changes in throughput of said variable delivery means, rated value setting means, time delay means for producing signals indicative of the length of intervals required by successive increments of said stream to advance from said supply to said mixing zone, and evaluating means for adjusting said control means in response to signals received from said signal generating, rated value setting and time delay means.

20. Apparatus as defined in claim 19, wherein said rated value setting means is adjustable by said detector means through said time delay means.

References Cited UNITED STATES PATENTS 477,909 6/ 1892 Meier & Fritsche. 2,382,648 8/1945 Martin 13457 X 3,059,566 10/1962 Grau. 3,138,482 6/1964 Gehl 11824 X 3,372,488 3/1968 Koch et al 131-137 X SAMUEL KOREN, Primary Examiner.

J. H. CZERWONKY, Assistant Examiner.

US. Cl. X.R.