US2257552A - Apparatus and method for cleaning and separating leaf tobacco - Google Patents

Description

Sept.'3( 1941. w. HAMMAQK 1 ,257,5

APPARATUS AND METHOD FOR CLEANING 'AND SEPARATING LEAF TOBACCO Filed March 29, 1939 INVENTOR 6:01 m. lam lax.

BYWA I MW ATTORNEY Patented Sept. 30, 1941 APPARATUS AND METHOD FOR CLEANING AND SEPARATING LEAF TOBACCO George W. Hammack, Richmond,Va. Application March 29, 1939, Serial No. 264,890 10 Claims. (Cl. 209-139) My invention relates to methods and machines for cleaning, grading, and separating leaf tobacco; and particularly Bright tobaccos and .Burley tobaccos after it leaves the stemmery.

All'machines will not handle light and heavy tobacco equally well; and in pneumatic machines, adjustment is necessary for handling the heavier Bright tobaccos" and the lighter Burleys. In many factories the cleaning, grading, and separating is done by a series of dif+ ferent operations; involving several handlings, much floor space, and much time. My object is to .dowhat is necessary for the best results in one continuous operation; to use as little space as possible; to take less time per unitof product; to obtain better results; and to provide a machine in which difierent tobaccos can be handledwith the least amount of adjustment.

From the stemmery comes the tobacco,--leaf and stems, scraps, stems, with small pieces of leaf adhering, and No. 4 scrap-that is scrap small enough to pass through a No. 4 screen, which has a quarter-inch mesh. This agglomeration is to be cleaned and separated; the leaf from the stems and the small scrap from the larger leaf. The first operation is to remove from the tobacco as much dust and dirt as possible. This I do in a rotary pneumatic separator, such as that which is fully described in the Patent No. 2,117,845, granted to me on May 17th, 1938. From this rotary pneumatic separator the tobacco is dropped upon a shaker or shaking screen, on which the No. 4 scrap is separated. The larger scrap and stem pass from the shaking screen into a stationary pneumatic separator in which a considerable part of the leaf is separated and carried upward by the exhaust from a fan. Heavy bunches of leaf and stem fall from the bottom of this separator on to a belt conveyor. It is not always practicable to separate all leaf from the stem material' in one stationary separator. Some of the leaf, when it/passes from the shaking screen, may be so bulked, that is, stuck or twisted together, that if the draught in the first separator is strong enough to lift it, the stem material would also be lifted. After separating as much leaf as possible in the first separator I drop the heavier material from this first stationary separator onto a, belt conveyor. In passing throughthe separator the tobacco is subjected to more than the lifting force of the current of air. First, the heavier parts are thrown, as they leave "the shaker, against the opposite wall of the separator; they drop towards the lower part of the separator, where they are tossed up again by a stronger current of air; and by this tossing and buffeting the outer leaves are loosened, and they are lifted by the upward current of air, and are carried out at the top of the separator. The heavier parts drop into the lower part of the separator. In this part the tossing and buffeting is continued; and more leaf is separated and lifted. The remainder is dropped onto the conveyor. It is now necessary to open up or thin out the tobacco on the belt conveyor so that when it is delivered into a second stationary separator as much surface as possible may be presented to the air current. This thinning out of the tobacco I effect by running the belt conveyor at such a speed that the tobacco falling upon it is carried onward more rapidly than it falls from the separator. In practice I usually run the belt conveyor at a speed of three hundred feet a minute; but the speed may be varied to suit the condition of the tobacco.

My belt conveyor now delivers the heavier leaf and the heavier stem material into a second stationary separator, also connected with the exhaust system; and in this separator more leaf is separated from the stem material; the latter being dropped from the bottom of the separator. In this separator too the tobacco is subjected to a tossing in the air current and a buifeting against the walls.

The art of stemming tobacco differs in the factories. Different equipment is used, with different results. In one type of factory, and where stemming machines are used, the tobacco leaves are fed by hand into the beater-box end of the stemming machine (sometimes called the butter-box) in which the end or butt of the leaf stem is: stripped or combed of leaf for a length of about two inches, to present a free stem to the gripping fingers of the stemming machine proper. In this beater-box sometimes the end of a stem is broken oil; and sometimes a whole leaf is pulled through. In the stemming machine the stem is gripped by fingers while the leaf is stripped off. The stem is delivered in one direction, the leaf in another. But here too stems break, and stem material is passed on with the leaf. Consequently the proportion of stem material passed on with the leaf willvary, both in quantity and size; from small pieces to whole stems. I am speaking of separate leaf and stem; not of fins of leaf still attached to stem material. Whatever the proportion of stem, it is to be :removed, as far as maybe possible and eco- 55 nomical.

In order that diiferent tobaccos may be handled by my method, it is important that the "air currents through the separators and through the main air line between the separators and the exhaust fan shall be under control. Even if only one class of tobacco is to be handled the control of the air currents is a factor in the success of the system. Tobaccos vary in weight; the heavier tobaccos need heavier air currents;

and the lighter tobaccos, such as Burley, need l lighter air currents. Thesecurrents must not be stronger than is necessary to lift and to carry the tobacco, lest a whipping action be set up, and

much of the leaf be broken. It is partly for this reason that the process of separating the leaf from the stem may not be carried out by using currents of air strong enough to lift both light and-heavy leaf. The process must be carried out in steps, .lest the lighter leaf be broken. 1 adjust the air velocity in' the main airline and through the separators for the reasons and, in the manner described hereinafter.

In the drawing: the figure shows in part elevation and in part section the devices I use in my method of cleaning and grading leaf tobacco,

having particular reference to my double separator. used in connection with my rotary. pneumatic separator, andjwith other devices;

The stemmed tobacco-is delivered tothe rotary 1 separator I. through thepipe .or conveyor 2'. This rotary separator is fully described in my separator 46. This separator comprises the inlet chamber 48, the front rising duct 48, the front falling duct 48, the back rising duct 58, the top outlet II, and the bottom outlet 62. The crosssectional area of the inlet chamber '45 is made i appreciably greater than the cross-sectional area of each of the ducts 48 and 49, so that the air current passing upward through the inlet a chamber shall have an appreciably less velocity go than the velocity of the air currents in the ducts 48 and 49 above and below it, for the. reasons 1 statedhereinafter'. This separator is'connected.

by exhaust piping 6t and 5 4 to the rotary pneumatic separator, the air outlet 66 of which is v connected with the exhaust system. In this Patent No. $117,845, hereinbefore 'mentionled'.v Air is drawn through and out of the separator" by exhaust means attached to the opening 3; through which can be'seen a part of the rotary screen 4. Dust and dirt are drawn through the screen, while the vanes I carry the-tobacco around to the discharge outlet 6. From the outlet 6 the cleaned tobacco drops through pipe I, onto the vibrating and shaking tray 8,hereinafter referred tests the "shaker. This shaker is mountedon the limbe'r jacksq. These limberjacks have substantial feet l0, which are fixed to the floor or to a frameby brackets ll. Their heads l2 embrace pins l3 or other fastenings by which they are attached to the :shaker 8. The stem 8 of the limber-jack is'slight and has considerable spring in'it; 'so.;that when the shaker is pulled lengthwise in either direction," and is released, it will return to the position shown. 50

The limber-jacks are simply vertically 'arranged springs by which the shaker is supported.

Spaced from the bottom of the shaker tray'8 is a wire screen l5, which has a mesh of one quarter inch, large enough to pass small particles of tobacco leaf. Under the bottom of the shaker tray, and under the end of the screen 15,. is a hopper l6, into which the small pieces which have passed through the screen may fall. From the hopper l6 the small particles of tobacco pass to the pipe II, from which they are usually collected in other receptacles. All tobacco which. is too large to pass through the screen l5 travels along to the shaker mouth l8. 1

A frame-work consisting of uprights l9 and 20, braces 2| and 22, top rails 23, and foot rails 24, is arranged on each side. of the shaker tray 8. On the uprights l9 are mountedbearings 25', supporting a shaft 26. Mounted on the shaft 2615 an eccentric 2'I, therod of which is pinned to a bracket 28 which is well bracedto the. bottom of the shaker tray 8. Also on shaft 26 is a pulley 2s, driven by belt at from the motor. 3|. As shaft 26 turns, the eccentric 21 will impart to the shaker a rapid lengthwise reciprocating 65. It is shown at the back separator 55 the tobacco leaf is separated from V the exhaust air currents, and'from which itis usually dropped upon a conveyor; "The; tobacco iscarried through the separator by the-vanes 61 30 tothe material outlet 58.. This separator Ills I similar in design to the separator].

, Returning'to thesep'arator; a swinging and adjustable plate 59 is placed over the material inlet #44 and over the mouth l8 or the shaker to control the volume of air passing into the separator atthis inlet and-over.

fed in by the shaker.

The strengthof the air-pull on the leaf up the first duct- 48 is controlled by the air door and the strength of the air-pull up the second duct 60. is controlled by the airgdoor .8l, The purpose of the adjustableair. vane 62 is to passing up flrstduct 48 and second duct 58, by partially closing the 'outlet from either duct.- The purpose of thelip 63 is to projectldownsliding tobacco into the air stream, and to prethe outIet 62. In the upper wall of theupper part of the separator I set-an inspection glass of the separator, but it may be placed on the side in such a manner that the upward flow in both first duct 48 3h: second duct 60 may be seen atthe same e. l When the tobacco is introduced at the inlet 44 it is caught by the air-entering at 52 and carried up duct 48. The heavier leaf and stem material will drop into duct'49 whereit will be tossed on the rising current of air, and leaf material will be separated from stem material. The heavier portions will 49, and slide off lip 63, there to be thrown against the opposite wall of the'separator, and to be tossed on the air current entering at the foot 62,

up either ofv the ducts 49 rent entering at 52 again catches. up. leafinatev rial and carries it up the second .duct- 50. Heavier material drops through the outlet 52, and onto the conveyor; in' a traveling belt 61, mounted and ,60. The air cura shaft to is mounted in bearings A the tobacco being I so; and the strength of the air-pull .upthe s'ec- Y. 2 ond duct 60 is controlled by the air door 68;

balance or adjust to oneanother the draughts vent it from just sliding over the corner 64 intorising in duct 49. The lighter free leaf will be then 'fall through duct which current is stronger than the currents '2 I this-case shown 2 v on rollers 68, and

. ass-1,052 omen through belting u. by motor 10. The

free air at the door n, that the draft below the door BI is sufllcient, to lift the separated leaf, and yet be not so strong as to iniure the leaf or to cause it to hang on the lower edge of the. baiiie 43. To avoid such hanging, the air inlet 52 .is preferably in line with duct ll.

Now we want to spread out or thin out our material, before subjecting it to the action of the air streams in a second separator. so that the air may have a lighter burden. This I do onthe belt 61, by adjusting the speed of the belt so that it moves the tobacco away from the outlet 52 faster than the belt receives it from the said outlet. This hasthe effect of thinningout, the leaf on the belt 01. It is my usual practice to run this belt at a speed of 300 feet per minute, or somewhat less. The belt "I carries leaf and stem material to a second separator 15, which may be constructed on the same lines as the separator 44. The traveling belt 61 throws the tobacco leaf and stem into the entrance chamber TI. The movement of the belt 61 together with the air-flow into the chamber 11 will throw the heavy bulked material against the opposite wall ofthe baille I4, loosening the outside leaves of leaf material. Part of the loosened material is drawn up the duct II, and through the top outlet ll, into the exhaust pipe ",and into the exhaust main 54. The remaining separated leaf will be carried up the back duct 1" to the top outlet"; while the heavier stem will drop through the bottom outlet '2. On this stem material there may be still a small proportion of the leaf. This is removed by threshing" in another machine.

The control and the adjustment of the air currents through my separators 46, I5, and i8, and through the air line 54, are very important, and are a factor in the success of my system.

, Tobaccos vary in weight. The heavier tobaccos need heavier air currents; and the lighter tobaccos, such as Burley, need lighter air currents. The air currents must not be stronger than is necessary to lift and to carry the tobacco, lest a whipping action be set up, which will break the leaf.

I adjust the air velocity in the main line '4 to 3500 feet per minute. This air line l4 and its branches I3 and II must be free of any obstruction, to eliminate the possibility of tobacco collecting at the obstruction and blocking the pipe. I therefore place the air regulatingvalve between the exhaust fan and the outlet I of the separator 55, through which separator the leaf is passed in order to separate it from the draught. n

The separators 48 II are approximately forty-two inches wide, cross wise. They differ in width, fore and aft, according to the size of the separator. In this case assume that this width is ten inches across the top outlet, and that the width of each of the ducts 48, ll, 18, and ll, is five inches, fore and aft. Then the combined areas of these four ducts will be eight an air velocity through them of about one thousand feet per minute when the diameterof thepipe i4 is eighteen inches. Note that the pipe '4 is found to be a suitable speed for keepin: the tobacco moving in the pipe on its way to the separator I.

The drawing shows that the width (fore and aft) of the outlet I2 is substantially the same as that of the ducts 48 and II; and it also shows that the outlet 82 is practically the air inlet for the duct II; or that 52' is the bottom inlet to duct ll. Again we may regard the separator as a structure comprising an outer casing with openings at top and bottom, the lower one having an area less than the area of the upper one, and an inner baflle dividing the easing into two ducts of substantially equal cross-sectional area, bothducts communicating, without obstruction,

with the upper opening, and the ducts uniting near their lower ends and communicating, without obstruction, with the casings lower opening. Obviously, the air current flowing in at 52 is stronger than is the air current above at the in the said ducts.

junction of the two ducts 49 and Ill; for the air which supplies them must enter at 52; and if the air inlet 52 were so large that the velocity at l! were no greater than the velocity up the duct 5| or at the junction of 49 and 50, material falling down duct 49 would simply fall out at I2. That is, it would not be held at the junction of the ducts until more leaf was separated, and leaf separated there would not be carried up duct ill. This applies also to the separator 15 and its ducts and openings.

The drawing also shows that the fore and aft dimension of the material inlet chamber 45, and also of the inlet chamber 11, is appreciably greater than the fore and aft dimensions of the ducts 4! and 49, and of ducts l8 and 19. The greater fore and aft dimension of these inlet chambers 45 and TI multiplied by the uniform width of the separator, mentioned above as substantially 42 inches, will give a greater volume per unit of height, than the volume of the ducts 48, 4|, and I8, 19, for the same unit height or length. Consequently the air velocity in the enlarged chambers will beless than the air velocity The purpose of enlarging these inlet chambers is to give very light leaf mixed with light pieces of stem a better opportunity to drop onto the current rising in duct 4!, lest it be whipped up by the current entering the inlet at inlet 44 with the leaf and passed air under the damper 59 in the inlet 44 and under the damper 89 in the inlet to the separator 75.

The air speed of one thousand feet per minute through the ducts 48 and ll of the separators go 4' and II respectively is suitable for separating hundred and forty square inches, which will giveleaf of average weight. For heavier leaf I use a little higher speed; and for lighter leaf I may use a lower speed. Taking one thousand feet per minute as the air speed through these two ducts 44 and I8: I adjust the opening of the air doors I and ll so that the air speed below these doors is less than the air speed above them an amount sumcient so that the movement of tobacco leaf is slower below the doors than it is above them. The object is to hold the tobacco in the lower part of the ducts and in the inlet chamber 45 and 11 while the leaf is being separated from the stems, and then to move the leaf away quickly by way of the upper parts of the speed of 3500 feet perrminute of the air in the ducts 48 and It. For the same reason the air 9-11. Apneumatic separator comprising a casingdefining a-substantially vertical duct open at.

drawing they are shown adjusted ior a greater volume oi draft up the ducts "and II than up the ducts 50 and 80. The air dampers 59 and 89 are used to close the openings oi the material inlets to the separators irom the shaker andthe conveyor respectively as much as possible without interiering with the passing oi the leai tobacco, and to limit the amount of air entering at these points They also serve to increase the velocity oi the air which does enter, ior the air speed at these points aids in throwing the tobacco irom the shaker and theconveyor intothe separators, The eii'ective height oi the material inlet being only enough to allow the leaf tobacco to pass freely, it iollows that the eflective area oi the inlet is less than the crosssectionalarea oi the duct 48 above it. Hence the air inflow at inlet 44 does notsatisfy the exhaust pull up duct 48; and the air necessary to supply the deficiency must come up duct '49. Thereiore the direction oi the air current in duct 49 is upward.

I do not confine myself to the exact shape oi the separator shown in the drawing. For

instance: ducts l8 and 50' are not necessarily duct beingoi substantially uniiorm cross-sectional area throughout its length, except that the area in the region oi the said inlet is larger than the area above and below it; a second duct vertically disposed and'at its'upper end contiguous to the upper end oi the first duct, and near its lower end communicating with the first duct at its ioot; exhaust means without and beyond the separator adapted to induce upward currents oi air through the ducts; and an ad- Justable plate valve hinged on the common edge oi the first and second ducts at their upper ends and adapted to adjust the relative air-flows between the two ducts.

3. A pneumatic separator comprising a first duct vertically disposed and bent intermediateits ends, and having in its wall at the bend an inlet ior material and air less in area than the cross-sectional area oi the duct above it; a vertically disposed second duct open at its lower end ior the free passage of air and material, and at its upper end joining with the upper end of the first duct to form an exhaust passage, and near contiguous at their upper ends; and' duct 48 first air current of suitable F. P. M., above which is a current oi greater F. P. M. to liit only the separated leai; below which first current is a current through which the rest. oi the material will fall, and be tossed, while more leaiis separated, until it meets the strong current rising.

from the air inlet at the bottom of the separator, uponthe crest of which it will be tossed, and "the remaining iree leai will be separated, and caught up in a current whichis stronger than the said first current. 9

both ends,- the, said duct having an inlet for its'lower and communicating openly with the first duct at the foot of. the latter; the said ducts aiTording free passage ior material and air throughout their lengths; exhaust means connected with the exhaust passage ior inducing upward currents oi air through the separator; and means for ieeding the material to be separated into the separator at'the material inlet.

4. A pneumatic separator comprising a first duct vertically disposed, and having in its wall intermediate its ends an inlet for material and air, the said duct being enlarged in the region of the inlet to reduce the velocity of the air current flowing up the duct and past the inlet; a vertically disposed second duct open throughout for the passage of material and air, at its upper end material and air iormedin its iront wall: a

baiile 'set' within and across. from side to side of the casing and extending from nearthe upper end of thecasing to near the lower end oi the casing, and forming within the casing a first joining with the upper end of the first duct to form an exhaust passage, and near its lower end communicating openly with the first duct at the foot oi the latter; exhaust means connected with the said exhaust passage ior inducing upward currents oi air through the separator; and means ior ieeding'the material to be separated into the separator at the material inlet.

- L5. A pneumatic separator comprising a vertically disposed bifurcated duct branching up- .wardly,the said duct being open throughoutior the free passage of material and air, the combined area of the two branches being greater, than the "air in the wall '01 one of the branches, the area duct and a second duct, the said first and second ducts communicating openly at their lower ends to iorm the lowerv opening in the casing, the said lower opening in the casing communicating directly and openly with the first duct and the second duct, and having a cross-sectional areamaterially less than the cross-sectional area oi the portion oi the casing above it at the junction or the first and second ducts so that the velocity of the air currentinduced upwardly in the lower, opening will be greater than the velocity of the air currents above it at the Junetionoi the first and second ducts; and exhaust means withoutan'dfbeyond the separator ior-inducing upward currents oi, airthrough the separater.

2. A pneumatic separator comprising a first Y I the inlet and above and below the said inlet to reduct vertically disposed and bent intermediate its ends and having in the outer'iace oi .the

oi they said inlet being less than the cross-sectional area of the duct above it so that the current of air in the said branch below the said inlet shall flow upwardly; exhaust means connected with the free ends of the branches for inducing upward currents of air through the duct and through its branches; and means for feeding the material to be separated into the separator at the material inlet.

6. A pneumatic separator comprising a vertically disposed bifurcated duct branching upwardly, the said duct and branches being open for the free passage of material and air, and the combinedcross-sectional areas of the two branches being greater then the cross-sectional area oi the said duct; 8. inlet-for material and air in the wall of one oithe branches, the cross-sectionalarea of the said branch being enlarged in the region of duce the velocity of the air currents rising through the said region; and the area oi the inlet being a into the separator at the material inlet.

7. A pneumatic separatorcomprising a first duct and a second duct vertically disposed, the

lower end of the first duct being inclined and velocity thanthe air current in the first duct above the inletj and means for feeding the material to be separated into the inlet.

8. A pneumatic separator comprising a first and a second duct vertically disposed, the lower end of the first duct being inclined and connected into the side of the second duct, the said second duct being open throughout its length; exhaust means connected with the upper ends of the ducts and adapted to draw currents of air upward through the ducts; an open inlet for material and air formed in the wall of the first duct intermediate its ends, the said inlet having an area less than the cross-sectional area of the said first duct above it, so that the air current in the first duct below the inlet shall be upward and of less velocity than the air current in the first duct above the inlet; and means for feeding the material to be separated into the inlet.

9. A pneumatic separator comprising a first duct and a second duct vertically disposed, the

lower end of the first duct being inclined and connected into the second duct, the said ducts being open throughout their lengths for the free passage of material and air exhaust means connected with the upper ends of the ducts for inducing upward currents of air through the ducts;

means located in the walls of the ducts for adlusting the relative velocities of the air currents up the two ducts; an open inlet for material and air formed in the wall of the first duct intermediate its ends; and means for feeding the material to be separated into the separator at the material inlet.

10. The method of separating leaf tobacco from stem which consists of producing at less than atmospheric pressure a confined main upward current of air strong enough to support leaf tobacco but not strong enough to support stem, then taking off from the said main current branch currents also at less than atmospheric pressure, allowing a relatively small volume of free air to enter and mingle with one of the branch currents so that the branch current below the point at which the free air enters shall have an upward flow and a lower velocity than the velocity of the branch current above the said point, and projecting the loose tobacco material into the said branch current at the said point, whereupon light leaf will be lifted on the branch current above the said point while heavier leaf and stem is dropped into the slower current rising below the said point where it is tossed on the said rising slower current until more leaf is sepa rated, the lighter of'which leaf is carried upward, and the heavier of which leaf is dropped with the stem material to the stronger upwardly flowing main current of air on which the material is again tossed and leaf is separated and carried up on a second branch current while the heavier stem material is dropped through the main current.

GEORGE W. HAMMACK.

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