US2658617A - Tobacco cleaner and classifier - Google Patents

Description

Nov. 10, 1953 A. ROWELL TOBACCO CLEANER AND CLASSIFIER 5 Sheets-Sheet 1 Filed Feb. 4, 1950 Lia m W w Z Tim, 5 m N T efl my? Nov. 10, 1953 1.. A. RQWELL TOBACCO CLEANER AND CLASSIFIER 5 Sheets-Sheet 2 Filed Feb. 4, 1950 FIE.Z

INVENTOR LORNE A PO LL FIEJI wmanm Kw Nov. 10, 1953 L. A. ROWELL 2,658,617

TOBACCO CLEANER AND CLASSIFIER Filed Feb. 4, 1950 5 Sheets-Sheet 3 LOP/V5 A ROWE LL ATTOHNEYS Nov. 10, 1953 A. ROWELL 2,658,617

TOBACCO CLEANER AND CLASSIFIER Filed Feb. 4, 1950 5 Sheets-Sheet 4 ////////////////////fl/////1V% .ZivvewroR NOV- 10, 1953 ROWELL 2,658,617

TOBACCO CLEANER AND CLASSIFIER Filed Feb. 4, 1950 5 Sheets-Sheet 5 j/v VEN TOR rron /s Patented Nov. 10, 1953 TOBACCO CLEANER AND CLASSIFIER Lorne A. Rowell, Lachine, Quebec, Canada, assignor to Imperial Tobacco Company of Canada, Limited, Montreal, Quebec, Canada Application February 4, 1950, Serial No. 142,436

1 Claim.

This invention relates to a cleaning and classifying machine which, while capable of more general application, is particularly useful for cleaning and classifying tobacco products such, for example, as the product known as beater scrap.

In the present instance, the invention will be described as applied to the cleaning and classifying of beater scrap but the novel principles and procedures involved are applicable, in whole or in part, to the cleaning and classifying of various other materials.

The term beater scrap is herein used to designate a tobacco product consisting of detached laminae or strips, clean stems, dirty stems, and a small amount of sand and dust.

The term laminae is herein used to designate a fragment of tobacco leaf attached to a stem.

The term strip is herein used to designate the tobacco leaf, or a part thereof, which has been detached from the stem.

The term clean stems is herein used to designate tobacco leaf stems from which all laminae have been removed.

The term "dirty stems is herein used to designate tobacco leaf having laminae attached thereto.

A salient feature of the invention is the provision of a pneumatic cleaning and classifying machine in which the design and assembly of the component parts is such as to effect a substantial reduction in cost and floor space requirements as compared with previously available installations for doing the same work.

Another feature of the invention is the provision of a pneumatic cleaning and classifying machine in which all of the air used for classifying purposes is supplied by a single fan and, with the exception of a small amount which is preferably bled off to maintain a slight negative pressure in the machine, is rapidly recirculated and reused without being discharged to atmosphere.

Another feature of the invention is the provision of a pneumatic cleaning and classifying machine in which high Velocity jets of air are used in a novel manner in combination with pneumatic classifying chambers to effect an exceptionally efficient cleaning and classification of the material being treated.

A further feature of the invention is the provision of a pneumatic cleaning and classifying machine in which the material being classified is projected into a series of clasifying chambers by high velocity jets of air and in which the air jets are efficiently employed, in combination with the 2 classifying chambers, to free lighter particles of the material being classified from lumps in which such lighter particles are entangled with or entrapped by heavier particles.

A further feature of the invention is the provision of a pneumatic cleaning and classifying machine in which the material being classified is projected into each of a plurality of classifying chambers by high velocity jets of air delivered through suitable jet nozzles and in which the air thus delivered to the classifying chambers is collected therefrom and delivered to the suction side of a fan from which the air is conducted under pressure to the jet nozzles.

A further feature of the invention, as applied specifically to the cleaning and classifying of beater scrap, is the provision of a pneumatic cleaning and classifying machine in which high velocity jets of air cooperate in a novel manner with a series of classifying chambers to first separate the free strip from the clean and dirty stems and to then separate the clean stems from the dirty stems.

A further feature of the invention, as applied specifically to the cleaning of beater scrap, is the provision of a pneumatic cleaning and classifying machine in which the dirty stems and the longer clean stems from which the strip has been separated are subjected to a threshing operation which breaks down all the stems into shorter lengths of approximately one inch and removes the laminae from the dirty stems.

A further feature of the invention, as applied to the cleaning and classifying of beater scrap, is the provision of a pneumatic cleaning and classifying machine in which the mixture of short clean stems and detached laminae resulting from the aforesaid threshing operation is recirculated through the machine to separate the free strip from the stems of the threshed product.

Other characteristics features and advantages of the invention will appear from the following detailed description of the accompanying drawings, in which- Figure 1 is an end view of my improved pneumatic cleaning and classifying machine as it ap pears with one, of the end walls removed.

Figure 2 is a sectional view of said machine, the plane of the section being substantially along the section line 2-2 of Fig. 1.

Figure 3 is a partial front elevational view of said machine.

Figure l is a perspective view of one of a plurality of light fixtures incorporated in said machine; and

Figures 5 and 6 are detail views illustrating a slight modification in the design of certain of the classifying chambers forming part of said machine.

Fig. 7 is a fragmentary detail view showing a front elevational View of one of the screens forming part of the assembly shown in Figs. 1 and 2 and,

Fig. 8 is a cross sectional view of the apparatus shown in Fig. 2 with the plane of the screen passing through the three screens appearing in Fig. 2.

As shown in these drawings, my improved cleaning and classifying apparatus comprises a casing 5 provided with a top inlet opening 6 to which beater scrap is delivered by a supply chute 1. The beater scrap is transported to supply chute 1 by a conventional pneumatic conveying system (not shown).

The beater scrap falling downwardly through inlet 6 of easing 5 slides down an inclined deflector plate 8 onto an oppositely inclined wall memher 9 forming the top wall of an inclined pneumatic classifying chamber I0. The bottom wall II of chamber I9 is also inclined and forms the top wall of a second inclined classifying chamber I2 having an inclined bottom wall l3 forming the top wall of a third inclined receiving chamber I4. The bottom wall of chamber I4 is formed by an inclined plate I5. Tank 2I is provided with a clean-out pipe 2 Ir connected to the bottom of the tank.

The lower inlet ends of classifying chambers I9, I2 and I4 open into a vertical passage I1 bounded on one side by said classifying chambers and on the three remaining sides by the front casing wall I8, the rear casing wall I9 and the wall 20 of a plenum or pressure tank 2| arranged in said casing.

The upper ends of classifying chambers l9, I2 and 14 open into a collecting chamber 22 bounded on one side by said classifying chambers and on the three remaining sides by the casing walls I9, !9 and 23. The bottom of collecting chamber 22 is formed by an endless conveyor 24, which removes material delivered to said collecting chamber from the classifying chambers I0, I2 and I4. A power driven cylindrical air screen 25 is rotatably mounted in the upper portion of collecting chamber 22.

The beater scrap which is deflected onto the top wall 9 of classifying chamber It) by deflector 8 slides down said wall onto an inclined baffle 21 projecting into passage I1 from wall 20 of pressure tank 2 i. As it drops from baffle 21 the beater scrap is struck by a high velocity jet of air delivered from pressure tank 2I through a jet nozzle 28 located just below said baffle. This high velocity jet of air, which is indicated at 29, is so directed across passage I1 as to project all but the very heavy particles of beater scrap into classifying chamber I9. Some of the lighter strip thus projected into chamber I9 is carried therethrough by the air current and deposited in collecting chamber 22. A large proportion of the beater scrap projected into classifying chamber it by jet 29 drops onto bottom wall II of said chamber and slides down to the point P where it is struck by a second high velocity air jet 3!) delivered from pressure tank 2| through a jet nozzle 3|. The jet 39 is directed against a curved deflecting surface 3i at the lower end of bottom wall II of classifying chamber I0 and is deflected upwardly toward the jet 29. The jet 30 thus serves to throw the lighter material which slides down the wall I I to the point P back up into the air stream from jet 29 where this lighter material gets a second chance to be carried through classifying chamber II] to collecting chamber 22.

As roughly indicated by the arrows in Figures 2 and 5, the two air jets 29 and 30 conjointly serve to effect and maintain a circulating or tumbling movement of the beater scrap at the mouth of classifying chamber II! which enables more of the lighter scrap to clear itself from the heavier particles and to be carried upwardly through classifying chamber It to the collecting chamber 22. At this point it may be noted that the air velocity near the top of classifying chamber I9 is substantially uniform across a section of the chamber and is so adjusted that it will convey only the lighter material into the collecting chamber 22. The lighter material thus delivered to collecting chamber 22 is therein separated from the air stream by rotary screen 25 and drops into conveyor 24 by which it is removed from the collecting chamber and delivered, through a chute 33, to a rotatably mounted classifying screen 34 extending through the front and rear Walls of casing 5.

The finer material passing through the openings of screen 34 is delivered to any suitable point of discharge by means of an inclined trough 34a underlying said screen. The coarser material passing through the screen 34 is discharged onto the table 340 shown in Fig. 1.

The heavier material, consisting mainly of clean and dirty stems, continues downwardly past classifying chamber I0 against the resistance of air jet 30 and carries with it a certain proportion of light free strip which is separated from the stems in the classifying chambers l2 and I4 by repetition of the pneumatic separating procedure described in connection with separating chamber I0 and is delivered to the collecting chamber 22. In this connection it will be noted that the heavier material and the entrained strip which travels downwardly beyond classifying chamber I0 passes over a bafile 35 corresponding to the previously mentioned baffle 21 and is acted on by air jets 3'5 and 31 which are directed across passage I1 by jet nozzles 38 and 39 and correspond, respectively, to the previously mentioned air jets 29 and 30. The heavier material which continues downwardly past the second classifying chamber I2 usually carries with it some residual light strip which is separated in the third classifying chamber I4 and delivered to collecting chamber 22 by the action of air jets 40 and M which also correspond to the previously mentioned air jets 29 and 30, and are directed across passage I1 by jet nozzles 42 and 43.

The material passing downwardly beyond the third classifying chamber I4 consists of dirty and clean stems from which practically all of the light strip has been separated in the classifying chambers I0, l2 and I4 and delivered to collecting chamber 22. This residual stem material is subjected to further separation and to a threshing procedure whereby relatively short clean stems are separated from the dirty stems and from the longer clean stems in a fourth separating chamber 45 and removed from the lower portion of passage I1 by conveyor 46. The dirty stems and the longer clean stems from which the the shorter clean stems have been separated in classifying chamber 45 are carried through said chamber by air currents and mechanical action, as hereinafter described, and are delivered toa collecting chamber 41 and thence, through hopper 48, to a hammer mill 49 wherein the stems are subjected to a threshing operation which breaks down all the stems into lengths of approximately 1 inch and removes the laminae from the dirty stems. The mixture of short clean stems and detached laminae resulting from the threshing operation in hammer mill 49 is preferably discharged from the latter through discharge pipe 59 to the previously mentioned pneumatic conveying system by which the beater strap is delivered to inlet 6 of casing 5. In this way, the product from the hammer mill 49 may be re-circulated through the passage ll and subjected to further classification whereby the detached laminae is separated from the stems in the classifying chambers Ill, l2 and I l as previously described and delivered to collecting chanc ber22.

With reference to the separation of stems which takes place in the fourth separating chamber 45, it will be noted that said chamber is defined by inclined top and bottom walls 5! and 52;

The space between the lower entrance end of chamber 45 and the opposing wall 2c of pressure tank 2i is substantially closed by a curved plate 53 extending obliquely across passage H. A sec ond curved plate 55 extends downwardly from the lower wall 52 of separation chamber 45 and part way across passage ill in spaced relation to the lower surface of plate 53. The two plates 53 and 54 form, in effect, the top and bottom walls of a downwardly curved chute 55 open at the top and bottom, the top opening PN of the chute being defined by the upper edges of the plates.

The mixture of clean and dirty stems which drops below the classifying chamber it is intercepted by curved plate 53 and is immediately hurled into separating chamber 55 by a high velocity air jet 5'17 which is delivered against plate 53 through a jet nozzle 58. Some of the material, particularly dirty stems having considerable laminae attached thereto, will be carried through chamber it by the air current and delivered to collecting chamber ll and thence through hopper 4 8 to hammer mill 49 where the laminae is removed and the stems reduced to short lengths of approximately 1". Another part of the material projected into chamber 35 and consisting mainly of stems with little or no laminae attached will fall to the bottom wall 52 of chamber 45 and slide back down said wall to the point P. From this point, the longer stems, partly due to their greater mass and velocity, will slide across and bridge the opening Pl l of chute 55 and will be struck by the air stream from jet nozzle 56 and again projected into chamber 45. The longer stems which are thus repeatedly projected into chamber 55 are eventually carried through this chamber into collecting chamber 47, partly by the propelling action of the air stream and partly by mechanical action. The short clean stems which slide down the bottom wall 52 of chamber 45 to the point P do not have sufficient mass and velocity to slide across or bridge the opening P-N of chute 55. Consequently, these short stems, on reaching the point P, will continue downwardly through chute 55 and be deposited on conveyor 46 and removed from the machine. Another factor which ensures that only short clean stems will pass downwardly through the entrance opening P-N of chute 55 is the provision of a further jet nozzle 60 through which a jet of air is directed against the lower edge of plate 53. The current of air produced by this last mentioned jet nozzle is adjusted so that only clean stemsare permitted to pass through the opening P-N of chute 55. The same effect can also be accomplished by providing a. pair of jet nozzles similar to nozzle 58 through which two jets of air are directed into separating chamber 45 above plate 53 and providing a third nozzle through which a third jet of air is directed into chamber 55 entirely through chute 55.

The separating chamber 48 contains a rotatably mounted cylindrical air screen 25a by which the material delivered to collecting chamber ll is separated from the air stream.

At this point it may be noted that the pneumatic separation of the free strip from the stems in the classifying chambers Ill, l2 and it is more efficient and is based on different principles of pneumatic separation as compared with conventional separators in which the mixture of free strip and stems is simply dropped off the end of a conveyor into an uprising current of air. In the case of the conventional separator, the uprising current of air carries with it the light free strip which is sufficiently free of entanglements with the stems and other heavier particles to be supported and entrained by the air current. The particles which are too heavy to be supported by the ascending air stream include lumps in which a substantial percentage of attached light strip is entangled with and carried downwardly by the stems and other heavy particles. In the case of the present invention the lumps in which attached strip is entangled with heavier particles, such as stems, are subjected to a strip-freeing tumbling action at the entrance ends of classifying chambers It, It and M by the high velocity air jets delivered through the jet nozzles 2S, 3!, 38, 39, 42 and 43. This tumbling action disinterates the lumps sufficiently to free the entangled strip so that the latter may be carried through the classifying chambers l8, l2 and i l and by a comparatively low velocity current having, for example, an average conveying velocity of approximately 700 ft. per minute near the discharge ends of said classifying chambers. To obtain this average velocity at the discharge ends of the classifying chambers, the velocity of the air jets leaving the jet nozzles iii, 38. it and M should be of the order of 5000 ft. to 6000 ft. per minute, which is sufficient to effect the desired tumbling and disintegration the lumps in which attached strip is entangled.

While not shown in the present drawings, the various jet nozzles through which the high velocity jets of air are directed across passage H from pressure tank 2! are preferably made adjustable to provide for variation and control of the air jets to suit different operating conditions. Air delivered through these .let nozzles is supplied to a combination fan and dust collector t2 (usually called a rotoclone), having its discharge side connected by pipe 63 to an air intake Zia provided at the top of pressure tank H. The suction side of fan 62 is connected to the interior of the rotary air screens 25 and 25a by a pipe 64 having a branch 65 connected to screen 25 and a second branch 66 connected to screen The dust separated from the air drawn into fan E2 through pipe 56 is collected in a tank 5'! on which the fan is mounted. It will thus be seen that the air supplied to tank 25 and the various jet nozzles from the pressure side of fan 62 is returned to the suction side of said fan through the various classifying and collecting chambers and the screens 25 and 25a and thus travels in a closed circuit in which it is repeatedly re-circulated and re-used.

The machine described herein is totally enclosed except at the inlet opening 6 of easing and at the two points or openings where the clean strip and the clean stems are respectively removed from the machine by conveyors 24 and 46. In order to prevent or minimize escape of dust at these three points or openings, the entire machine is placed under a slight negative pressure. This is preferably accomplished by bleeding oif from pressure tank. 2! about of the air supplied thereto, thus leaving only 90% of the air to pass through the various jet nozzles. Since 108% of the air handled by fan 62 is collected through the screens 25 and 25a, the remaining 19% not supplied by the jet nozzles must be drawn into the casing at the inlet opening 6 and at the openings through which the conveyors 24 and 45 extend. In this way the escape of dust through the inlet opening and the conveyor openings of the casing is effectually prevented or reduced to a minimum. The relatively small amount of air which is bled from tank 2| may be drawn off through any suitable conventional bleed connection (not shown) and discharged to atmosphere through a suitable air cleaning filter. A1- ternately, air which is bled from pressure tank 2| may be piped to hammer mill M to assist in the discharge of the threshed product from the hammer mill through discharge pipe as to the pneumatic transporting system by means of which the threshed product is returned to inlet 6 of easing 5 along with fresh beater scrap.

Provision is made for adjusting the volume of air handled by the fan 62 to suit the effective openings of the various jet nozzles which, previously stated, are also capable of adjustment. In this connection, it will be noted that the flow through pipe 64 to the suction side of fan 32 is controlled by a valve I9 and that the flow of air through the branch pipes 65 and G6 to the pipe 64 is controlled by valves II and 12. After the effective openings of the jet nozzles have been properly adjusted, the valves II and T2 are used to regulate the amount of air drawn into the suction side of the fan through the branch pipes 65 and 66. The valve II should be set so that the amount of air drawn through screen 25 and branch pipe 65 is greater than the amount of air which is delivered from pressure tank 2! through nozzles 28, 3I, 38, 39, 42 and 43. The valve I2 should also be set so that the amount of air drawn through screen 25a and branch pipe 66 is greater than the amount of air which is delivered from pressure tank 2| through the two lowermost nozzles 58 and 69. In this way the two sections of the machines which are represented, respectively, by classifying chambers Iii, I2 and I4 and collecting chamber 22, on the one hand, and by separating chamber 45 and collecting chamber 41, on the other hand, are kept under a slight negative pressure. After they have been moved to their proper setting, the valves "II and I2 should not require re-adjustment and may, therefore, be locked in their set position by any suitable locking means. The valve I9 controls the amount of air handled by fan 52 and is used as a control valve which is set to regulate the amount of air handled by the fan in accordance with variations in the weight and type of the material being handled. When higher velocities are required in classifying chambers I0, I2 and I4, valve I0 is opened to permit the fan to handle a larger quantity of air.

In order to facilitate the inspection of the cleaning and classifying operation, suitable electric light fixtures I4 are fitted in openings provided in the rear casing wall I9 directly opposite inspection windows 15 provided in the front casing wall I8. This enables the operator to see at a glance exactly what is occurring in the various classifying chambers.

In order to increase the efficiency of the classifying chambers I0, I2 and I4, the top and bottom walls of each chamber may be designed, as shown in Figures 5 and 6, to provide a vertically directed flow passage 16 which ensures that the only product which escapes from the top of the classifying chamber into collecting chamber 22 will be those particles which are capable of being lifted vertically through passage I6 by a substantially uniform low velocity of air escaping through said passage.

The surface of each of the rotary screens 25 and 25a is brushed clean of tobacco products by means of a cleaning brush I8 which is carried by a pair of pivotally mounted arms I9 and is pressed against the surface of the screen by biasing spring 80.

Any suitable drive mechanism may be employed for driving the air cleaning screens 25 and 25a, classifying screen 34, hammer mill 49 and conveyors 24 and 46. In the present instance, I have shown a drive arrangement including an electric motor 82 driving one end of the shaft of hammer mill A9 through a belt drive generally indicated at 83. The other end of the shaft of the hammer mill is connected to a counter-shaft 84 by a belt drive generally indicated at 85. One end of countershaft 84 is connected by a chain and sprocket drive connection 86 to one of a pair of parallel shafts 81 on which classifying screen 34 is supported by means of suitable supporting rollers 89. The other end of counter-shaft 84 is geared to sprocket shafts 9! and 92 journalled in a gear box 93. Sprocket shaft 9| is connected by a chain and sprocket drive 95 to shaft 96 of conveyor 24. The remaining shaft 9'! of conveyor 94 is connected by a chain and sprocket drive connection 98 to shaft 99 of conveyor 46. Sprocket shaft 92 is connected by a chain and sprocket connection III! to the shaft I02 of rotary screen 25a. Shaft I02 is connected by a chain and sprocket drive connection I93 to the shaft I95 of screen 25.

For convenient operation thereof, the valve I0 arranged in the suction pipe 64 of fan 62 may be connected by a chain and sprocket connection I66 to a hand wheel operated shaft IU'I (see Figs. 1 and 3) Having thus described the nature of my invention and a preferred embodiment thereof, it will be understood that various modifications may be resorted to within the scope and spirit of the invention as defined by the appended claim. For example, conveyors 24 and 46 may be replaced by pneumatic conveyors designed to accomplish the same purpose. The rotoclone 62 may also be replaced by an ordinary fan for re-circulating the air through the machine but, in this event, some type of dust collecting apparatus preferably should be located in the air re-circulating system to remove the dust with which the air becomes quite heavily laden. The rotoclone unit shown in the drawings is preferred, however, since it draws in the dusty air, precipitates the dust into tank 6i and supplies dust-free air to pressure chamber 2 I.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined. as follows:

A pneumatic cleaning and classifying machine of the character described, comprising a plurality of superimposed inclined pneumatic classifying chambers having inlet opening at their lower ends and discharge openings at their upper ends, means for conducting a flowing stream of the material to be classified downwardly past the inlet openings of said classifying chambers, a plurality of pairs of jet nozzles through which high velocity jets of air are directed against the down flowing stream of material to project particles of said material into said classifying chambers where certain of the particles thus delivered to the separating chambers are separated from the other particles and pneumatically conveyed to and through the discharge openings of said chambers, each of said classifying chambers including a bottom wall having the upper surface of its lower end portion concavely curved and the nozzles of each pair being arranged one above the other opposite the inlet opening of one of said classifying chambers with the upper nozzle 10 arranged to direct an upper jet of air directly into the material-receiving space between the top and bottom Walls of the classifying chamber and the lower nozzle arranged to direct a jet of air against the concavely curved surface of the bottom wall of the classifying chamber.

LORNE A. ROWELL.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1365384 Vandervoort Aug. 21, 1923 1,588,511 Austin et a1 June 15, 19 6 1,945,771 Dahlstrom et a1. Feb. 6, 1934 1,987,640 Rothgarn Jan. 15, 1935 2,130,880 Durning Sept. 20, 1938 2,165,946 Smith July 11, 1939 2,173,087 Eissmann Sept. 19, 1939 2,477,935 Miller Aug. 2, 1949 FOREIGN PATENTS Number Country Date 3,481 Great Britain Oct. 7, 1875 382,776 Great Britain Nov. 3, 1932 661,963 Germany July 1, 1938 07,425 Sweden May 18, 1943

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