US3419015A - Method and apparatus for mixing additives with tobacco - Google Patents

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 A tobacco stream is withdrawn from a fluctuating supply of tobacco particles at a lower first speed when the supply is depleted to the lower limit and at a higher second speed when the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in the supply is measured, and the result of such measurement is utilized to change the speed at Which the stream is withdrawn as well as to regulate the admission of additives into successive increments of the travelling stream.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 secondendless conveyor belt 22 arranged to receive successive increments of a tobacco stream TS from the belt 21, a revolvingmixing drum 23 which receives tobacco from thebelt 22, a thirdendless conveyor belt 26 which receives tobacco from themixing 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 asuitable weighing device 10 which measures the weight of successive unit lengths of the tobacco stream TS travelling toward the upper stringer of thebelt 22. The drive means 7 for thebelts 21, 22, 26 and mixingdrum 23 comprises a variable-speedelectric motor 7a driving a transmission 7b having threeoutput members 107a, 107b, 1070 which are respectively arranged to drive thebelts 21, 22, aring gear 23a of themixing drum 23, and thebelt 26. A manually operatedspeed changer 28 is provided to select the speed of themotor 7a. As a rule, the drive 7 will operate theparts 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 anendless belt 2 whose discharge end is adjacent to the apron 24. The upper stringer of this apron is adjacent to a pair of equalizingwheels 27 serving to insure that the apron invariably withdraws from the supply S on the belt 2 a tobacco stream TS of constant height. Thebelt 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 thebelt 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 ajunction 18. When the supply S has been replenished so that the level of tobacco on thebelt 2 rises to a maximum value, the detector 1 ceases to send a signal to thetime delay unit 5 and sends a different signal to a second time delay unit 6 as well as to thejunction 18. Thejunction 18 is further connected with asignal generator 9 which transmits signals as a function of measurements carried by theweighing device 10, with a rated value setting device 8, and with a variable-speed drive 11 for thebelt 2 and apron 24. The speed of thedrive 11 is adjusted as a function of measurements carried out by the weighing; device and as a function of signals transmitted tojunction 18 by the rated value setting device 8.

Thenumeral 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 atank 12 and is fed through a conduit 20 and aflow meter 16 by a variable-delivery pump 14 having a variable-speed motor 14a which is regulated by acontrol circuit 13. Thespray nozzle 25 is installed in amixing zone 100 in the interior and close to the downstream end of themixing drum 23. The internal surface of thedrum 23 is provided with axially parallel vanes orblades 23b which shower successive increments of the stream TS into themixing zone 100 to promote uniform mixing of tobacco with flavoring solution discharged through the orifices of thenozzle 25. The blades orvanes 23b may be constituted by heating or cooling coils which condition the tobacco stream TS during travel through themixing drum 23.

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

latter sends signals to thecontrol circuit 13 for thepump 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 thetime 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 thetime 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 mixingzone 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 ofbelt 22,drum 23 and belt 26) remains unchanged. The axis of thedrum 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 thebelt 26. This belt feeds the tobacco stream to a further processing station.

The operation is as follows:

The magazine including thebelt 2 receives a certain amount of tobacco particles to build up a supply S. The rate at which thebelt 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 thebelt 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 thejunction 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. Thejunction 18 then transmits an appropriate signal to the drive means 11 to reduce the speed at which thebelt 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 weighingdevice 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 thebelt 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, thetime delay unit 5 causes thecontrol circuit 13 to operate themotor 14a at such a speed that thenozzle 25 discharges flavoring solution at the rate which corresponds to the rate of tobacco feed through the mixingzone 100. The delay with which the unit .5 causes thecontrol circuit 13 to reduce the speed of themotor 14a when the supply of tobacco on thebelt 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 themixing zone 100. Thedelay 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 thedelay unit 5 through theconnection 29. The output signal of thedelay unit 5 is transmitted to thejunction 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. Theflow meter 16 measures the throughput of the applicator 4 and causes the signal generator 17 to transmit appropriate signals to thejunction 19. Such signals are utilized to adjust thecontrol circuit 13 if the actual rate of solution flow to thenozzle 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 thebelt 2 rises to the maximum permissible level, the upper level indicator of the detector 1 responds and sends an appropriate signal to thejunction 18 and time delay unit 6. Such signal simultaneously erases the output signal of the lower level indicator and hence the output signal of thetime delay unit 5. The signal from the upper level indicator causes thejunction 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. Thedrive 11 then operates thebelt 2 and apron 24 at a higher speed so that the level of tobacco on thebelt 2 begins to descend. The conveyor system 3 advances more tobacco per unit of time and the delay unit 6 causes thecontrol circuit 13 to adjust themotor 14a of thepump 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 themotor 14a corresponds to the interval required to move an increment of tobacco from thebelt 2 to themixing 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 theparts 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 mixingzone 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 mixingzone 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 compriselight sources 33, 34 andphotoelectric receivers 35, 36. Thereceivers 35, 36 are connected withsignal 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 storingunits 37, 38 are connected with an evaluatingunit 39 which forms part of thejunction 18. The signal indicating the rated value is supplied to evaluatingunit 39 by aslider 40 forming part of apotentiometer 41 which, in turn, forms part of the rated value setting device 8. The evaluatingunit 39 determines the quantity of tobacco to be fed into the mixingzone 100 of thedrum 23 per unit of time.

The lower level indicator 31 will produce a signal when itsreceiver 35 is exposed to light issuing from thesource 33, and the upper level indicator 32 produces a signal when itsreceiver 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 thebelt 2 is depleted down to a preselected minimum value (determined by the mounting of receiver and light source 33), so that thereceiver 35 receives light from thesource 33, the storingunit 37 sends an output signal to the evaluatingunit 39 and such output signal is added to the signal received from the slider of thepotentiometer 41. The signal received via input a of the storingunit 37 remains stored therein even though the quantity of tobacco on thebelt 2 increases gradually and such tobacco interrupts the light beam between thesource 33 andreceiver 35 of the lower level indicator 31. At the time thereceiver 35 receives light from thesource 33, it sends a signal via input b of the storingunit 38 whereby such signal erases the output signal of theunit 38.

The apron 24 is driven at reduced speed as long as the storingunit 37 continuesto send an output signal to the evaluatingunit 39 whereby the quantity of tobacco on thebelt 2 increases gradually because the tobacco stream TS is advanced at a reduced speed. When the quantity of tobacco on thebelt 2 increases sufliciently to interrupt the light beam between the source 34 andreceiver 36 of the upper level indicator 32, thereceiver 36 sends a signal to the inputs 1) and a of storingunits 37, 38 whereby such signal erases the output signal of theunit 37 and causes theunit 38 to send an output signal on to the evaluatingunit 39. The output signal of the storingunit 38 is weaker than that of the storingunit 37, and such signal is added to the signal received from theslider 40 of thepotentiometer 41 to effect an increase in the speed of the apron 24.

The evaluatingunit 39 further receives a signal from theslider 42 of apotentiometer 43 which forms part of thesignal generator 9. Theslider 43 is biased by atorsion spring 46 and can be turned by amotion transmitting linkage 44 which is coupled to the weighingdevice 10. Thelinkage 44 is turnable on apivot 45. The shaft of theslider 42 is shown at 47. Theslider 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 weighingdevice 10. Signals transmitted to the evaluatingunit 39 by theslider 42 of thesignal generator 9 are opposites of the signals transmitted by theslider 40 of thepotentiometer 41.

The drive means 11 for thebelt 2 and apron 24 receives signals from the evaluatingunit 39 and includes asignal 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 evaluatingunit 39 receives an output signal from the storingunit 37 or 38. The working coils 49c, 49d then furnish requisite voltage for aD-C motor 50 which drives thebelt 2 and apron 24 and whose r.p.m. varies as a function of the quantity of tobacco forming the supply S on thebelt 2.

The outputs of thesignal storing units 37, 38 are further connected with thetime delay units 5, 6 and through such delay units with a second evaluatingunit 52 forming part of thejunction 19. The construction of thedelay unit 5 will be described in connection with FIG. 3.

The evaluatingunit 52 adds the signal received from theslider 53 of a potentiometer 54 to the output signal received from the storingunit 37 or 38 through thedelay unit 5 or 6. The potentiometer 54 forms part of the rated value setting device 15. Theunit 52 further receives signals from the signal generator 17 which is connected with theflow meter 16.

Theflow meter 16 comprises an upright conical cylinder 58 which accommodates an axially reciprocableconical float 59. The flavoring solution is stored in thetank 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. Thefloat 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 thespray nozzle 25.

Thefloat 59 is connected with an upwardly extendingcore 60 which is surrounded 'by an induction coil 61. The

inductance of this coil varies as a function of axial movement of thefioat 59 andcore 66. The coil 61 is connected in one branch of aWheatstone bridge 62 whose output is connected to a rectifier 6.3 and anamplifier 64. The output signal of theamplifier 64 is transmitted to the evaluatingunit 52 and is indicative of the actual throughput of flavoring solution. This signal is deducted from the signal transmitted by theslider 53 of the potentiometer 54. The just described combination offlow 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 evaluatingunit 52 is transmitted to thecontrol circuit 13 for thepump motor 14a. This control circuit comprises apreamplifier circuit 164 and asecond amplifier circuit 65. The control coils 66, 67 of thecircuit 65 are connected with the output of thecircuit 164, and the working coils 68, 69 are connected with themotor 14a of thepump 14. Themotor 14a is a D-C motor.

FIG. 3 illustrates thetime delay unit 5 which is identical with or analogous to the time delay unit 6. Theunit 5 comprises an endlessmagnetic tape 70 which is trained around anidler roller 71 and asecond roller 72 driven at a constant speed by asynchromotor 73. Arecording head 74 receives signals from the storingunit 37 of FIG. 2. An erasinghead 75 is adjacent to and is located ahead of therecording head 74, as viewed in the direction of tape travel.

Aguide rail 76 carries asignal reproducing head 77 which can transmit signals to the evaluatingunits 39 and 52, see FIG. 2. The reproducinghead 77 is shifted along therail 76 in dependency on the speed of drive means 7 for the mixingdrum 23 andbelts 21, 22, 26 so that signals recorded on thetape 70 by recordinghead 74 reach the reproducinghead 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 thebelt 2 into the mixingzone 100.

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

Theconnection 29 between the drive means 7 for the parts 21-23 and 26 of the conveyor system 3 and thetime 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 mixingzone 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 theunits 5 and 6 remain unchanged.

It will be seen that the electric circuit of FIG. 2 comprises three groups. The first group includes thecontrol unit 13, rated value setting device 15, and signal generator 17. The purpose of this first group is to insure that thepump 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 groupincludes'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 weighingdevice 10 and device 8.

The third group includes the detector 1, thetime delay units 5, 6, the connections from detector 1 tojunction 18 andunits 5, 6, and the connections fromunits 5, 6 to thejunction 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 thenozzle 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 thebelt 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 andwheels 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 thebelts 21, 22 will remain constant when thedrive 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 themotor 59 in thedrive 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 thetank 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 thepump 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 themix 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 inclaim 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 inclaim 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 inclaim 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 inclaim 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 inclaim 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 inclaim 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 inclaim 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 inclaim 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 inclaim 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 inclaim 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 inclaim 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.

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