US3661159A

US3661159A - Apparatus for stemming tobacco leaves and separating the products obtained

Info

Publication number: US3661159A
Application number: US30427A
Authority: US
Inventors: Andre Pietrucci
Original assignee: Societe Nationale dExploitation Industrielle des Tabacs et Allumettes SAS
Current assignee: Societe Nationale dExploitation Industrielle des Tabacs et Allumettes SAS
Priority date: 1965-11-03
Filing date: 1970-04-21
Publication date: 1972-05-09
Anticipated expiration: 1989-05-09
Also published as: LU52279A1; BE689212A; NL160709C; NL160709B; SE367122B; NL6615512A; DE1532092B2; DE1532092A1; GB1160739A; SE333533B; SE368140B; US3513858A

Abstract

Apparatus for stemming tobacco leaves and for segregating the lighter and heavier parts of the resulting mixture comprises a stemming chamber for a rotary stemming unit serving to stem tobacco leaves which are admitted by way of a first inlet of the stemming chamber. The latter has at least one second inlet for admission of a current of separating air, at least one outlet for evacuation of heavier parts, and at least one outlet for evacuation of lighter parts with the air current. The distribution of outlets is such that the direction in which the lighter parts are evacuated with the air current is at least substantially counter to the direction of evacuation of heavier parts. This can be achieved by using the inlet or inlets for air as outlet or outlets for heavier parts.

Description

United States Patent [:51 3,661,159 Pietrucci 1 May 9, 1972 54] APPARATUS FOR STEMMING 2,460,938 2 1949 Koehne ..241 52 x TOBACCO LEAVES AND SEPARATING 2,474,314 6/1949 I Koehne ..131/ 146 UX 2,944,629 7/1960 Eissmann ..131/146 X THE PRODUCTS OBTAINED 3,229,698 1/ 1966 .lohansson et a1. 1 3 l/ 146 [72] Inventor: Andre Pietrucci, Loiret, France 3,362,414 1/1968 Wochnowski 131/146 [73] Assigneez Service dExploimfion lndustriene des 3,386,451 6/ 1968 Pietrucci et a1 1 3 l/ 146 Tabacs et des Allumettes, Paris, France Pnmary Examiner-Samuel Koren [22] Filed: Apr. 21, 1970 AssistantE.\'aminer.l. F. Pitrelli [62] Division of Ser. No. 591,606, Nov. 2, 1966, Pat. No.

[30] Foreign Application Priority Data Nov. 3, 1965 France ....37l53 Nov. 17, 1965 France..... ....38785 Aug. 26, 1966 France..... ....74210 Sept. 20, 1966 France ..769ll [52] U.S.Cl ..l3l/l46,241/53,241/58 [51] Int. Cl. ..A24b 05/10 [58] Field of Search ..l3 1/146, 145; 241/19, 53, 58

[56] References Cited UNITED STATES PATENTS 1,788,683 1/1931 Bramley-Moore ..24l/58 X Atmrne vMichael S. Striker [57] ABSTRACT Apparatus for stemming tobacco leaves and for segregating the lighter and heavier parts of the resulting mixture comprises a stemming chamber for a rotary stemming unit serving to stem tobacco leaves which are admitted by way of a first inlet of the stemming chamber. The latter has at least one second inlet for admission of a current of separating air, at least one outlet for evacuation of heavier parts, and at least one outlet for evacuation of lighter parts with the air current. The distribution of outlets is such that the direction in which the lighter parts are evacuated with the air current is at least substantially counter to the direction of evacuation of heavier parts. This can be achieved by using the inlet or inlets for air as outlet or outlets for heavier parts.

6 Claims, 18 Drawing Figures PATENTED 9 I saw 01 us 10 PATENTEUMAY 9 1912 sum 02 or 10 ruenrll Au: Plmutlb PATENTEDMAY 9 I972 sum 03 or 1o PATENTEUMAY 9|972 3 661 159 saw an or 10 I I Hg. I0

APPARATUS FOR STEMMING TOBACCO LEAVES AND SEPARATING THE PRODUCTS OBTAINED CROSS-REFERENCE TO RELATED APPLICATION The present application is a division of my copending application, Ser. No. 591,606, filed Nov. 2, 1966, now US. Pat. No. 3,513,858 granted May 26, 1970.

BACKGROUND OF THE INVENTION This invention relates to apparatus for stemming tobacco leaves and for separating the products obtained into fragments of parenchyma without leaf stems and stems from which parenchyma has been completely stripped.

It is known that stemming of tobacco leaves can be obtained by feeding the leaves into a unit which is known as a beater. This unit is essentially made up of a toothed drum which is adapted to rotate within a stationary coaxial casing comprising open portions. As soon as they have been admitted into the annular space between the drum and the casing, the tobacco leaves are subjected to shocks during which the parenchyma is more of less completely stripped from the stems. The products which are released are continuously discharged through the open portions of the casing and then undergo a pneumatic sorting process in an air stream which is usually an upward flow and the velocity of which is regulated so as to carry away the fragments of parenchyma without stems and to allow the well-stripped stems to fall together with the fragments of parenchyma which still remain attached to stems.

ln practice, the passing of tobacco through a single heater and a single separator is not sufficient to achieve complete separation of the tobacco into fragments of parenchyma without stems and perfectly stripped stems. In order to obtain such a result, it is necessary to employ a number of beaters and separators arranged in cascade, thereby resulting in bulky and costly installations.

It should also be noted that, in the case of certain types of tobacco and especially the Virginia type which is the most widely consumed throughout the world, the complete stripping of stems and midribs is a difficult operation by reason of the fact that the parenchyma adheres strongly to the midrib and cannot readily be detached. It has therefore been proved by experience that a single stripping stage is often insufficient and that sometimes two such operations are neces-.

sary in order to recover as a final result only a very small quantity of parenchyma corresponding to a percentage of a few units.

A further disadvantage of these installations is that the fragments of parenchyma which are obtained contain a notnegligible portion of small elements; it is frequently observed that the end product contains 20 to 25 percent of fragments having a surface area of less than two or three square centimeters. A brief analysis of the processes involved in the operation of an ordinary beater will give a clearer conception of the causes of this disadvantage, thereby affording a better understanding of the advantages which are provided by the present invention.

In an ordinary beater, the discharge of stemming products is mainly effected under the action of impulses which are imparted to the fragments of tobacco leaves by the teeth of the rotary drum, the force of gravity being added to this action in horizontal beaters of the type most commonly met with. In the case of the heaviest products, that is to say the leaf stems and the fragments of parenchyma or laminae which still remain attached to the stems, the two actions referred to above are practically the only factors which influence the discharge process. So far as concerns lightweight products which have a large surface area, that is to say fragments of parenchyma which have been detached from stems, additional influences are exhibited, namely, aerodynamic forces such as air resistance, turbulence and eddies generated by the rotation of the teeth and the rapid displacement of the material, and also interactions between the released fragments, said interactions being correspondingly greater as the internal space of the beater is filled to a greater extent. These additional influences slow down and hinder the discharge of lightweight products which are therefore caused to remain within the heater and to undergo shocks therein to no useful purpose. This state of affairs also compels the user to limit the rate at which the leaves are admitted into the beater so as to maintain the filling of'this latter within suitable limits as otherwise, if filling is excessive, the released fragments are not readily discharged and degradation of the parenchyma increases to a considerable extent.

A third disadvantage of conventional apparatus is that the leaf stems, the fragments of parenchyma which still remain attached to the stems and the fragments of parenchyma without stems are mixed together when delivered from the beater, thereby complicating their subsequent separation to a substantial extent. In fact, in-order that this separation can take place, the products must follow very different paths, so that those which are of lightest weight follow the motion of the air stream while those which have a higher density progress in countercurrent flow. Taking the initial mixture into account, these paths intersect frequently and result in interengagement of the different products, which in turn has the effect of reducing the separation efficiency to a substantial degree.

It can additionally be stated that, in the case of the vertical beater, the separation air stream receives during its upward motion the entire quantity of products which are discharged from the beater chamber and which are of very' different nature both in respect of density and surface area. In the case of a predetermined velocity of the air stream, some of these products such as fragments of stemless parenchyma move upwards rapidly, whereas other products such as stems which have been stripped to a more or less complete extent are permitted to fall without hindrance and, finally, other products. such as intermediate elements composed of parenchyma, which remains attached to the stems travel at a slower rate either in the direction of the air stream or in the opposite direction when they do not remain in suspension at a constant height. Inasmuch as products are circulated within the space formed between the beating chamber and the casing of the separating chamber at respective velocities which are very different and even in opposite directions in certain cases, interengagement of elements must inevitably occur, thereby giving rise to a danger of agglomeration followed by clogging of the separator if the rate of delivery of products from the beating chamber is of a high order.

The movement of rotation of the beaters and of the material contained in the beating chamber is comparable to the action of a centrifugal fan in that it imparts to the separation air a rotary motion which combines with the main upward motion and serves to concentrate discharged material against the wall of the separating chamber substantially in the manner as in a cyclone. The result thereby achieved is a further danger of agglomeration of material which may also be followed by clogging, especially if the annular separation space comprises stationary obstacles such as radial partitions, ridges, various projecting portions or the like.

SUMMARY OF THE INVENTION An object of the invention is to provide an apparatus comprising a stemming unit or beater which is rotatably mounted within a beating chamber, said chamber being provided with at least one inlet for the supply of tobacco leaves to be beaten, at least one air inlet, at least one air outlet and at least one outlet for the discharge of dense elements. The various inlets and outlets aforesaid are so designed that the air passes through the chamber and that the chamber outlets are separate from the outlets through which the dense elements are discharged; as a rule, the outlets are so designed that the air stream which passes through the chamber flows in a direction which is substantially opposite the direction of discharge of the dense elements.

The air inlets can be arranged in the periphery of the beating chamber, for example, in the lower portion of the chamber and the outlets for the discharge of dense elements can coincide with the air inlets.

The discharge of air and therefore the discharge of lightweight elements can be effected through a wide opening which is free of any obstacle, such as, for example, an annular opening which can be coaxial with the supply inlet and formed at the upper portion of the chamber which can be one of the bases of such chamber.

Provision can usefully be made for at least one means whereby the velocity of the separation air stream can be regulated such as, for example, a means for regulating the air intake openings.

The stemming chamber can comprise several superposed stemming levels, one of these levels being adapted to communicate, by way of its airstream outlet which is reduced to an annular surface, with the inlets of the level which is located next in succession thereto in the direction of flow of the air stream.

In accordance with a specific embodiment, the air outlets and the leaf supply inlets form two separate and distinct zones which may even be adapted to form part of different walls of the beating chamber.

Preferably, the fragments which are lightest in weight can be propelled to the outlet as soon as they are separated from the stems by insuring that the three separate openings are judiciously spaced around the beating chamber casing, while the whole leaves or insufficiently stripped leaves remain inside the beating chamber in order to undergo a further beating operation under the combined action of the rotating beating members and of the air stream which passes through the chamber and prevents such fragments as may still retain an appreciable quantity of parenchyma from being discharged through the airstream inlet.

In order that the air stream may be permitted to circulate countercurrentwise with full effectiveness for the purpose of preventing the discharge of the fragments aforesaid, provision can be made for an airtight opening through which tobacco leaves are supplied.

in order that fragments of parenchyma without stems may be separated from fragments with stems within the separating chamber, the invention further provides for the widening of the air stream as it passes out of the beating chamber into a volume of the separating chamber which has a larger crosssectional area than the cross-sectional area of the outlet, such volume being provided with an airtight unit for discharging insufficiently stripped elements from the device.

Provision is also made in accordance with the invention for processing dense fragments which are discharged from the beating chamber in countercurrent flow to the air stream and delivered into another beating chamber having a supply inlet which is connected to the air inlet of the preceding chamber. The outlet of the second chamber can also be connected to the air inlet of the preceding chamber and the complete assembly can be so arranged that the air which flows through the separating chamber passes entirely or almost entirely through the successive chambers.

Provision is advantageously made for a rotating unit which collects the mixed elements near the lateral opening provided at the base of the separating chamber so as to evacuate such elements through an airtight collecting unit.

The teeth which are rotatably mounted in the beating chamber can be angularly displaced in a manner and to an extent such that, taking into-account the velocity of the air stream and the speed of rotation, the force of impact of the teeth on the stripped leaf fragments is thereby reduced.

The apparatus of the present invention eliminates practically all of the disadvantages which have been mentioned earlier. Thus, fragments of parenchyma which have been detached from the stems are immediately discharged from the beater. Any unnecessary degradation is therefore suppressed. Furthermore, at each moment of operation, the beater virtually contains only those products which are to be stemmed, with the result that the rate of introduction of leaves can be of a high order without any attendant disadvantages.

The invention also makes it possible to collect the fragments of parenchyma without stems in order to permit reintroduction in the beater of fragments of parenchyma which still have stems attached and in order to direct practically stripped stems towards a second finishing beater.

All of the above-mentioned advantages are available regardless of whether the tobacco leaves are supplied to the apparatus in continuous operation or in non-continuous operation.

However, when the supply to the apparatus is noncontinuous or, more specifically, when the supply is effected in batches of tobacco leaves at uniformly spaced intervals, the means employed in accordance with the invention present a further advantage. In fact, there is delivered at the outlet of the beater a train of products corresponding to each feed batch, the leading end of such train being composed of fragments of parenchyma from which stems have been separated, the center being composed of fragments of parenchyma which still remain attached to the stems, and the trailing end being made up of stems which are almost completely stripped. The products are thus subjected inside the beater itself to a preseparation process which is conducive to considerably greater efficiency in the action of the separators which are placed downstream.

The invention additionally makes it possible to introduce the stream of tobacco in an air stream which is circulated at high velocity through the stemming chamber without any appreciable reduction in velocity. The stream of tobacco can in fact be made up of successive streams forming batches which are spaced in time in such a manner that one batch penetrates into the stemming unit only after discharge of the preceding batch. Preferably, the air stream and tobacco leaves or fragments to be stemmed pass through only one section of the stemming unit and, within such section,'the stream or successive streams are subjected to the action of different aerodynamic or mechanical forces which have the effect of 1 detaching the parenchyma from the stems. The aerodynamic forces initiate the transfer motion through the stemming unit while the mechanical forces which may be composed of mutually opposing forces also act in opposition to such transfer motion. The mechanical forces are so adapted that they are no longer applied as soon as the fragments which are obtained have a sufficiently small surface area.

Thus, those fragments which have a sufficiently small surface area are driven out of the stemming unit by the aerodynamic forces which are generated by the highwelocity air stream.

Tobacco leaves and fragments of leaves of insufficiently reduced surface area which have escaped from the action of the aerodynamic forces in that section of the stemming unit in which the aerodynamic forces are exerted are reintroduced into such section as a result of the application of some mechanical forces in that portion of the stemming unit through which the high-velocity air stream does not pass. On the other hand, fragments of tobacco leaves of sufficiently reduced surface area and of sufficient density which have escaped from the action of the aerodynamic forces also escape from the action of the mechanical forces and fall by gravity into the lower portion of the stemming unit for subsequent discharge.

However, the fragments last mentioned can first be taken again by a second stemming unit and the lightweight fragments released therefrom are carried along by an air stream at moderate velocity, such air stream being so directed as to come again into contact with the high-velocity air stream within the first unit.

In accordance with one embodiment of the invention, the stemming unit which receives the tobacco leaves includes a toothed drum rotatable about a stationary shaft which is oriented in any suitable manner. The drum is surrounded by a coaxial casing provided with counter-teeth and is connected to at least two separating chambers disposed in cascade, the first chamber being adapted to collect and discharge stems which are almost completely stripped, the following chamber or-chambers being adapted to collect and discharge fragments of parenchyma which still remain attached to stems, the last of such chambers being additionally adapted to transmit stemmed fragments of parenchyma to a unit for the recovery of parenchyma, a stream of transporting and separating air being circulated through all of the units.

The supply inlet and the air outlet can be located in oppositely facing relation in the two bases of the cylinder which constitutes the casing of the stemming unit.

The counter-teeth which are fixed to the internal wall of the stemming unit casing may occupy only that section of the chamber through which the high-velocity air stream circulates from one opening to the other.

In accordance with another embodiment, practically the entire air stream penetrates through open portions formed in the wall of revolution of the beating chamber and practically the entire air stream is discharged through open portions formed in the same wall.

Provision can be made for a series of separating chambers connected to each other. At least one of these chambers is adapted to communicate directly with the outlets of the beating chamber and at least one other separating chamber is adapted to communicate with the supply inlets of the beating chamber. Such communication is preferably effected by means of an airtight unit.

The aforesaid separating chamber which communicates with the outlets of the beating chamber is advantageously divided either wholly or in part by radial partition walls, the wall of revolution of the cylindrical bodies being provided before each partition wall with openings for the reintroduction of some fragments of tobacco which are discharged through the outlets formed in the wall of revolution.

Provision is advantageously made for deflectors which serve to join the internal wall of the one separating chamber to the wall of revolution of the beating chamber and which are directed toward the reintroduction openings.

The internal face of the separating chamber comprises helicoidal ribs which serve to deflect downwardly some of the products which are discharged from the beating chamber.

The entire air stream or nearly the entire air stream which issues from the beating chamber is preferably sucked through nozzles disposed between two successive partition walls and connected to the separating chamber, such nozzles being oriented in such a manner as to suck the air in a direction which is substantially opposite to the direction of rotation of the teeth of the beating chamber. The air stream is intended to remain at right angles to the axis of rotation of the beating unit.

The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved 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 fragmentary axial sectional view of an upright stemming and separating apparatus which embodies one form of the invention;

FIG. 2 is a fragmentary vertical sectional view of a horizontal stemming and separating apparatus which embodies a second form of the invention;

FIG. 3 is a fragmentary axial sectional view of a second upright apparatus which comprises two stemming and separatin g stages;

FIG. 4 is a fragmentary vertical sectional view of a second horizontal apparatus with two stemming and separating stages;

FIG. 5 is a horizontal sectional view as seen in the direction of arrows from the line V-V of FIG. 4;

FIG. 6 is a schematic partly elevational and partly sectional FIG. 8 isan enlarged sectional view as seen in thedirection;

of arrows from the line VIII-VIII of FIG. 7;

FIG. 9 is a vertical sectional view as seen'in the direction of arrows from the line IX-IX of FIG. 8; 7

FIG. 10 is a vertical sectional view as seen in the direction of arrows from the line X--X of FIG. 8;

FIG. 1 I is a schematic sectional view of another apparatus;

FIG. 12 is a vertical sectional view of a further apparatus;

FIG. 13 is a horizontal sectional view as seen in the direction of arrows from the line XIII--XIII of FIG. 12

FIG. 14 is a fragmentary vertical sectional view of still another apparatus;

FIG. 15 is a vertical sectional view of an additional apparatus;

FIG, 16 is a horizontal sectional view as seen in the direction of arrows from the line XVI-XVIof FIG. 15;

FIG. 17 is an enlarged perspective view of the lower part of the structure shown in FIG. 15, with certain parts broken away; and

FIG. 18 is a schematic axial sectional'view of a further apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring first to FIG. 1, a vertical stemming or threshing drum 5 is provided with teeth 6 and is rotatable in a casing which forms a cage or grid. The circumferential wall of the cage consists of bars 1 and its base 2 is a plate. The bars I are secured to the base 2 and to a peripheral retaining member 14 which defines the upper opening of the casing. The bars I define air inlet openings 7. The cage is surrounded by a conduit or duct 3 which is secured to the retaining member- I4 and is connected to a fan, not shown, serving to draw air through the openings 7. An adjustable flap or an analogous device (not shown) renders it possible to vary the flow rate and thus the velocity of air which is admitted into the apparatus. A feed pipe 4 for tobacco leaves is disposed in the duct 3.

FIG. 2 shows a second apparatus wherein the lower portion of the duct 3 constitutes in conjunction with the bar I a casing for a horizontal rotary stemming drum 5 having teeth 6. The bars 1 are parallel to the axis of the drum 5 and are mounted therewith on end walls which serve to close off the apparatus and form two sides of the suction duct 3. The end walls are located in planes which are parallel to the plane of FIG. 2 The pipe 4 is mounted centrally of the duct FIG. 3 illustrates a further apparatus having two stemming levels or stages of decreasing diameter from the bottom upwards. The top stage is installed in the duct 3 which has a frustoconical lower end surrounding the upper stage andresting on the retaining member 14. A second retaining member 15 is accommodated in the smaller-diameter upper end of the frustoconical portion of the duct 3. The base 16 of the upper stage has a diameter which is smaller than the diameter of the base 2 of the lower stage. The lower stage has a top opening which forms an annular space between the retaining member 14 and the base 16 of the upper stage.

The apparatus of FIGS. 4 and 5 constitutes a modification of the apparatus shown in FIG. 2. The horizontal shaft ofthe drum 5 is provided with teeth 6 and the stemming chamber has two stages. The smallerdiameter stage is installed in the duct 3 which terminates in a frustoconical hopper I3fixed to the retaining

members

14 and 15. The bases of the two stages are similar to those shown in FIG. 3.

As shown in FIG. 6, the envelopes or peripheral walls of the two stages are constituted by bars which together form two frustoconical bodies. The two superposed stages have the- 5 same mean diameter. The drum 5 is driven by a motor 8. A

circular conveyor 9 of the shaker type, for example, is placed beneath the stemming chambers. The air in the duct 3 is sucked upwardly by a fan 12. The suction system also comprises in serial arrangement a separator 17 and a dedusting cyclone l l. The separator 17 is a tangential separator having a cylindrical screen 18 which opens at the lower portion thereof onto a conveyor 19 by way ofa lock chamber 20. An adjustable flap 21 which is disposed in the suction system, for example, between the duct 3 and the separator 17, provides a secondary air intake the regulation of which permits to maintain the separation air velocity at a suitable value.

In each of FIGS. 1-6, the arrow F indicates the direction of flow of the suction air stream.

In accordance with the invention, the stemming operation is carried out in a stemming chamber the peripheral wall of which is constituted by the bars 1 which are mounted on the base 2 and a retaining member 14. The peripheral wall can be designed in a different manner without departing from the scope of the invention and can consist, for example, of a perforated plate. The tobacco leaves to be stemmed are admitted through the feed pipe 4 into the stemming chamber through the upper portion of the peripheral wall. The feed pipe 4 can be provided at the top portion thereof with a rotary lock chamber as shown in FIG. 6. The duct 3 which is connected to the suction fan 12 completely covers the peripheral wall ofthe stemming chamber. Thus, the aspirated air which is circulated in the direction of the arrow F and drawn either from the exterior or from a recycling duct connected on the downstream side to the suction fan flows first through the openings 7 between the bars 1, then through the stemming chamber and is discharged from this latter through the annular outlet between the retaining member 14 and the feed pipe 4. If the air velocity is correctly chosen, the air stream carries with it as it passes through the stemming chamber only those lightweight products which are separated as a result of the impact of the teeth 6 on the tobacco leaves which have been introduced therein. Such lightweight products pass between the teeth, out of the stemming chamber through the openings 7 and are carried away into the duct 3 as soon as they are formed. The higher-density products constituted by stems or midribs cannot be entrained by the upwardly flowing air stream and are accordingly discharged from the stemming chamber through the openings 7, that is to say countercurrentwise.

In accordance with a presently preferred embodiment of the invention which is shown in FIGS. 1, 3 and 6, the axis which is common to the drum and to the peripheral wall formed by the bars 1 is vertical. One advantage of this arrangement, among others, is that the apparatus is endowed with symmetry of revolution. A further advantage is that the driving motor can be placed directly beneath the stemming chamber, thereby achieving a saving in space.

In the apparatus of FIGS. 3, 4, 5 and 6, comprising a stemming chamber with two stemming stages, the operation takes place as follows: As in the previous examples, the products which are introduced are subjected to a first stemming action in that stemming stage which is located nearest the feed pipe.

The stems or midribs which are not carried along by the air streams are expelled in countercurrent flow between the bars 1 of the upper stage, while the lightest fragments consisting of parenchyma without stems are carried by the air stream through the suction duct 3. i

The stems which have been discharged countercurrent-wise fall into the second stage through the opening which is defined by the base 16 and the retaining member 14 and are then subjected therein to a second stemming action on completion of which any parenchyma which may have been attached to the stems is accordingly liberated, then carried by the up-flowing air stream away from the second stage into the first stage through the openings 7, then finally away from the first stage into the duct 3.

After this second stemming operation, the stems which are finally stripped are discharged from the second stage through the openings 7 between the bars 1.

The lightweight fragments are separated from the transporting air within the tangential separator 17. The fragments of parenchyma fall onto the conveyor 19 by way of the rotary lock chamber 20 while the dust-laden air passes through the cylindrical screen 18 to be subjected to dedusting in the cyclone 1 1 before passing through the fan 12.

It will be readily apparent that provision can be made for more than two superposed stages should this prove necessary for the purpose of obtaining perfectly stripped stems.

As shown in FIGS. 7-10, tobacco leaves to be stripped are fed from a conveyor 101 into a duct 102 which performs the function of a pneumatic conveyor. An air stream is circulated through the duct 102 at a high velocity which can exceed 10 m/s.

The tobacco leaves are then'admitted into the main beater which, in the example herein described, is essentially constituted by a shaft 103 which is rotatable about a vertical shaft fitted with radial teeth 104, and by counter-teeth 105 secured to the casing which surrounds the beater.

The air stream which passes through the beater in the direction of the arrow F carries with it the leaves which are subjected to a first stemming action in contact with successive obstacles which are both stationary and movable, as constituted by the counter-teeth and the teeth. The fragments of parenchyma which are liberated readily find a path between these obstructions and, by virtue of the high aerodynamic forces to which they are subjected, leave the beater almost immediately. On the other hand, insufficiently stemmed leaves as well as partially stripped stems which have both higher density and greater length than the fragments of parenchyma engage for short moments either with the counter-teeth or with the teeth, move upwards less rapidly and are therefore subjected to the stemming action for a longer period of time.

The stream which leaves the beater through the opening 106 is composed of fragments of parenchyma, of stems which still contain substantial quantities of parenchyma and stems which are almost completely stripped. This stream of material which is still conveyed by the air stream comes into a separating chamber 107 in which it slows down. The shape and section of the chamber 107 are so determined that the stems which have been almost completely stripped no longer move upwards and then fall into a zone which is'not swept by the air stream and from which the stems are-discharged by way of a rotary lock chamber 108.

The remainder of the material then enters a second separating chamber 109 in which the separation takes place between the fragments of parenchyma and the stems to which parenchyma still remains attached. Inasmuch as a single chamber may not prove sufficient to achieve the requisite degree of separation, provision can accordingly be made for two

chambers

109, 110 as shown in FIG. 7, or even a greater number.

The stream of stemless parenchyma which is still transported by the air stream then reaches a centrifugal-action separator 111, from which it is discharged by way of the rotary lock chamber 112.

So far as concerns the stems to which a large amount of parenchyma still remains attached, such stems are discharged from the separating

chambers

109 and 110 by means of

rotary lock chambers

113 and 114, then return again to the stream of leaves to be stemmed on the conveyor 101. Consequently, these products are again fed into the main beater in which they are subjected to a second stemming action.

In general outline, the beating process which is carried into effect in the apparatus herein described entails the introduction of leaves to be stemmed, the discharge of fragments of parenchyma without stems, and is partly characterized in that the fragments of parenchyma which still remainattached to stems circulate within the main beater and the separating chambers in a closed loop and for as long a period of time as the stemming of the fragments is not sufficient, that is to say until they have been transformed into stems which have been almost completely stripped and into fragments of parenchyma without stems.

In order to complete the description of the present invention, the subsequent progress of the stems which are discharged through the rotary lock chamber 108 deserves some mention.

The stems referred to can of course be simply directed towards a second separating beater of a standard type having characteristics which are adapted to the stripping operation to be performed.

In a form of construction to which preference is given on account of the fact that it is more compact and less costly, the aforesaid stems again penetrate into the main beater through an opening 115 which is placed substantially in such a manner as to be symmetrical with the opening 106. This arrangement exhibits the following advantage: Should the stream which leaves the rotary lock chamber l08-accidentally contain fragments of parenchyma which are attached to stems, these elements are taken again by the teeth of the main beater, brought back into the zone of the main beater, traversed by the air stream and are subjected therein to a further stemming action. So far as the stems proper are concerned, they pass downwardly through the main beater under the action of gravity and are admitted to the finishing beater through the opening 116.

The finishing beater comprises a rotary shaft 117 fitted with teeth 121 and adapted to rotate within a casing 122 provided with open portions 123 over part of its periphery. The outer air is drawn in through the open portions at a velocity which is sufficiently low not to prevent the discharge of stems which have been completely stripped and which is sufficiently high to draw towards the main air stream the fragments of parenchyma which have been released by the stripping process.

As will be understood, in addition to the components described which constitute one example of the invention, the apparatus also comprises a fan of sufficient capacity to maintain the transporting and separating air stream, as well as driving motors and a dedusting system such as filters or cyclones.

FIG. 11 is a diagram of another apparatus wherein the transporting and separating air is partially recycled. To this end, part of the air is discharged to the exteriorafter dedusting in the bank of cyclones 118 while an equal quantity of pure air is admitted through the opening 119 and through the open portions 123 of the finishing beater. In this case, the leaves to be stemmed and the products to be stemmed a second time are fed into the duct 102 by way ofa rotary lock chamber 120.

The utilization of the lock chamber is of advantage even when no recycling of air is performed. The lock chamber divides the stream of tobacco which is introduced in the form of successive batches. When one batch is admitted into the main heater and is transformed therein into fragments of parenchyma, into stems which are attached to the parenchyma and into stems which are almost completely stripped, the products of the stemming process undergo a first separation in space; the fragments of parenchyma issue first from the beater at a speed which is substantially higher than that of the products which still contain stems. As a result of this splitting-up process, the separation is carried out in a much more effective manner within the separating

chambers

107, 109 and 110 inasmuch as the danger of engagement between fragments of parenchyma without stems and stems to which parenchyma remains attached is considerably reduced. FIG. 11 shows the manner in which this process is achieved.

The apparatus which is illustrated in FIGS. 12 and 13 comprises a beating chamber, the axis of which is in this case vertical and which is coupled on the one hand to a device for supplying leaves to be stemmed and, on the other hand, to a separating chamber of cylindrical-conical shape which is coaxial with the beating chamber and located immediately above the beating chamber and which is connected to a pressure-reducing unit such as a fan (not shown).

The air which separates the dense fragments such as stems which have been almost entirely stemmed from the lightweight fragments such as fragments of parenchyma penetrates into the beating chamber through the openings 201 formed between the bars 202 which partly line the periphery of the beating chamber. The full portion 203 of such periphery is provided with an opening 204 which is connected to the rotary-blade lock chamber 205 having an axis 225 and permitting the introduction of products to be stemmed which are delivered from the conveyor 206.

The beating chamber also comprises a rotary shaft 207 having a vertical axis and fitted with teeth 208. In a presently preferred embodiment, these teeth are disposed ina helical arrangement and with an angular displacement such that they form only a single pitch of the helix along the axis. Under these conditions, it can be insured that, subject to a judicious choice of the velocity of the separation air and the speed of rotation of the shaft, any fragment of tobacco leaf which is liberated at the base of the beater is discharged from this latter through the opening 209 without any danger of being caught by one of the upper teeth.

The separating chamber 210 which is placed above the beating chamber operates according to the known method which consists in reducing the velocity of transporting airby enlarging the cross-sectional area available in such a manner as to separate the lightweight fragments proper or fragments of tobacco leaf without stems from the semi-lightweight fragments such as shredded leaves and, broadly speaking, the stems which still remain attached to fragments of tobacco which have a large surface area. The semi-lightweight fragments are deposited by gravity on the annular surface 211 as well as on the plate 212, the approximately triangular shape of which can be seen in FIG. 13. v

A rotary member 213 which is driven by the shaft 207 effects the sweeping of the annular surface 211 and of theplate 212 and propels the semi-lightweight products which are deposited thereon into a passageway 214 which is joined tangentially to the separation chamber and terminates in a lock chamber 215 of the rotary impeller type, the function of this lock chamber being to transfer the products towards the feed conveyor 206.

In order to adapt the flow velocity of the air stream within the chamber 210 to the requirements of the separation process, provision is made-for a device which consists of-a variable-volume container 216 such as, for example, a flexible envelope connected to a compressed-air source and suspended from the rod 217. Provision is also made over the entire periphery of the chamber '210 for openings 218 of variable effective area for admitting outside air.

The stems which are almost completely stripped and discharged from the beating chamber through the spacesi201 between the bars 202 are collected .by two

shaker conveyors

219 and 220 and conveyed thereon towards a stripping device 226Q The

conveyors

219, 220 are disposed beneath the volume which is defined by the open portions 201 and open portions 224 which are so dimensioned as to prevent escape of shredded fragments from the apparatus. This separating beater 226 can be coupled to a fan which is different fromthe fan which generates the air stream of the-main device. In the example of FIG. 12, the separating beater is connected to'the general suction system, the division of the air between the main device and stripping device being carried out bymeans of the regulating flap 221,

In the foregoing description, the expressions beating chamber" and separating chamber" were used for the purpose of designating respectively that portion of the apparatus in which the products to be stemmed are introduced-andthe container or chamber in which the separation of lightweight products from semi-lightweight products'takes place. The-socalled beating chamber also performs a separating function. This separation process which concerns solely the dense products or stems which are almost completely stripped is carried out at the envelope surface which is lined with-bars.,ln other words, the apparatus is characterized in'thatit comprises a beating and separating device which is completed by a separating chamber of conventional type which is more especially adapted to carry out the separation of light-weight products from semi-lightweight products.

FIG. 14 shows an apparatus wherein the beating and separating chamber 227 comprises in addition to a beater in accordance with the foregoing description asecond beater 222 which is coaxial with the preceding and which has a larger diameter. The second beater, which is located beneath the first, collects and strips the dense products which are discharged from the upper beater. In this apparatus, the separation air first penetrates into the secondary beater in which it separates the very small fragments of parenchyma which are stripped from the stems, then into the primary beater in which it separates the fragments of parenchyma which are stripped from the leaves and semi-lightweight products. The air stream path which is imposed by the presence of the conical casing 223 is shown by arrows. The path of the dense fragments is opposite to that of the air stream.

In the examples considered, the bars 202 which perform a double function of stationary obstacles for the purpose of stemming tobacco leaves and defining openings for the admission of air do not constitute an essential feature. Without departing from the scope of the invention, it would be possible to employ the bars 202 only for the purpose of performing the first function or even to replace them in this function by other types of obstacles such as counter-teeth, and the second function being carried out by means of an envelope surface or peripheral wall with open portions which is separate from the bar-grid.

As shown in FIG. 15, the beating or stemming chamber comprises a drum 301 which is rigidly fixed to a shaft 302 rotatable about a vertical axis and driven by a belt-transmission system from a motor, not shown. The beating chamber is bounded at the side by three bar-grids 303 which are mounted coaxially and in superposed relation and the respective diameters of which increase from the top downwards. The drum 301 is fitted with radial teeth 304 having lengths which are suitable for these diameters. The base of the beating chamber is formed by a circular plate 305 which can be provided with air inlets 306 and which also serves as a support table of the apparatus. The other bases of the cylinders which are defined by the grids are open except possibly the lower base of the uppermost cylinder which can advantageously be closed off by a plate 307 as shown in FIG. 15.

Inasmuch as the three grids are fitted with bars having a spacing which is smaller as the grid is lower, it can accordingly be considered that the beating chamber comprises three coaxial and superposed beaters having respective diameters which increase from the top downwards and which are intended respectively to carry out a first beating of leaves, a second beating operation and, finally, stripping of leaf stems. These three heaters are designated by the reference numerals 308, 309,310.

The delivery of tobacco leaves is effected through the vertical duct 311 which is coaxial with the beating chamber and located above this latter, the duct being rendered air-tight by means ofa rotary lock chamber 312.

The outer peripheral wall which is intended to collect, guide and separate products discharged from the beating chamber essentially comprises three stages:

A cylindrical first casing 313 which surroundsthe beater 310 for guiding the descent of stripped stems which are delivered from this beater. The lower base of the annular space between the casing 313 and the beater 310 can communicate directly with the surrounding air as shown in FIG. 15 or else be joined to a chamber through which air is circulated under pressure as supplied from the device for dedusting the transporting and separating air, this last-mentioned arrangement being provided in the event that it should be found desirable to recycle this air through the device.

A conical second casing 314 forms a screen for the dense products which are discharged from the beater 309 and assists their descent into the beater 310. The annular space between the casing 314 and the beater 309 is divided into three equal parts by the radial partition walls 315 which are shown in FIGS. 16 and 17. Close to such partition walls and immediate ly before these latter, the casing 314 assumes a substantially hyperbolic paraboloid configuration which facilitates the reintroduction of stems into the beater 309 as will be explained hereinafter.

A third casing surrounds the beater 308. The constructional design of this third casing will be more readily understood by referring to FIGS. 16 and 17. In the same manner as the casing 314, the third casing comprises three identical portions between the radial partition walls 315. By following the direction of rotation of the heaters, it will be noted that each of these portions in turn comprises three zones:

A first zone which may be referred to as a virtual zone constituted by the inlet of a suction nozzle 316 having substantially the shape of an oblique pyramid frustum and joined to a duct 317.

An arcuate second zone 318 having the same diameter as the beater 309 and joined to the feed hopper 319 which is mounted on the beater 308.

A third zone 320 which is also arcuate but of smaller radius and is joined to the second zone 318 and terminates in contact with the grid which limits the beater 308.

Each duct 317 communicates with an expansion chamber 321 which is mounted at the top of the apparatus. This expansion chamber is connected at its base to the hopper 319 and communicates through the opening 322 with a reduced-pressure source such as a fan which is not shown in the drawings. Provision is made between the fan and the opening 322 for a centrifugal-action lock chamber (not shown) or any similar device for collecting and discharging stemmed fragments of tobacco leaf.

The grids which are fitted on the

beaters

308 and 309 are arranged immediately before the partition walls 315 in such manner that some of the products which are discharged from the two

upper heaters

308, 309 can be fed back laterally into such beaters. The advantage of this reintroduction will become apparent hereinafter. It can already be stated that this arrangement consists in the example under consideration either in removing a portion of the annular retaining member 323 as shown in FIG. 17 in the case of the beater 309 or in giving the retaining member 324 a suitable shape as shown in the same Figure in the case of the beater 308. There are thus formed in both cases openings 325 and 326 which are free of any obstructions so as to permit the admission of some of the products which are expelled from the corresponding beater.

The tobacco leaves which are fed into the lock chamber 312 fall through the duct 311 onto a head-piece in the form ofa rotary impeller which covers the top of the drum 301. The rotating head-piece insures by centrifugal projection a uniform distribution of the leaves through an angle of 360 degrees.

Guided by the hopper 319, the leaves then penetrate into the beater 308 in which the stemming process begins. The shocks to which the tobacco leaves are subjected as they come into contact with the bars 303 result in the release of free parenchyma. A mixture of products composed of fragments of free parenchyma, fragments of parenchyma which still remains attached to stems and stems which are almost completely stripped is accordingly delivered from the beater 308 through the lateral wall of this latter which comprises open portions.

The expulsion of this mixture is followed by a first separation process, the mode of execution of which will be more readily understood with reference to FIGS. 16 and 17.

As a result of the high speed which is imparted to the ends of teeth on the beater 308 and which usually varies between 15 and 20 m/s, the products are discharged along paths which are located substantially in planes parallel to the planes described by the teeth, that is to say, in the present case, in

horizontal planes, and the shape of which is substantially tangential to the cylinder which is defined by the grid. In practice, the tangential discharge is achieved more effectively as the products have a higher density. Thus, as a result of their initial leaving force and their high inertia, the stems which are almost completely stripped are for the most part liberated by suction through the nozzles 316 and consequently strike the wall of the arcuate second zone 318; as the stems continue to travel, they slide along the wall of the zone 318, then along the Wall of the zone 320 and finally pass into the beater 308 through the opening 326. On the other hand, those fragments of free parenchyma which have lower inertia and higher responsiveness to the action of the aerodynamic forces of attraction are readily collected by the nozzles 316 and move up duct 317. Finally, the intermediate products, namely the fragments of parenchyma which still remain attached to stems, split up into two groups according to their densities and their surface areas, so that the lighter elements are collected by the nozzles 316 and the elements which have a higher density follow the same path as the stems. Naturally, both the stems and the dense intermediate products are subjected as soon as they reenter the beater 308 to a further stemmingaction for the purpose of freeing parenchyma and are then again discharged from the beater so as to be subsequently subjected to a further separating action according to the mode of operation hereinabove described.

Independently of their rotational path which is formed of successive expulsions and reintroductions, the stems and dense intermediate elements progress towards the base of the beater simply under the action of gravity. After a certain number of revolutions, such parts reach the beater 309 which is fitted with bars spaced at a smaller distance from each other and are subjected in this heater to a more extensive beating operation.

At this stage of treatment, the separation of liberated parenchyma is carried out according to a sequence of operation which is very different from that which has just been described. The principle of this separation process is based on the fact that practically the entire quantity of air which is admitted at the base of the apparatus through the bars of the beater 310 is admitted to the beater 309 through the bars of this latter. The velocity of this air flow is set at a sufficiently high value to insure that none of the fragments of parenchyma which are liberated in the beater 309 can pass through the grid which surrounds the beater 309. In other words, the parenchyma which is liberated against the grid is immediately drawn by the air stream which passes through this latter and conveyed into the upper casing in which it is collected by the nozzles 316. So far as concerns those stems which are discharged tangentially toward the casing 314, such stems are caused to slide over the casing 314 so as to be fed back into the beater 309 through the openings 32S and so on in sequence until the stems finally reach the stripping beater 310 on completion of their downward rotational motion.

Within the beater 310, the process of separation of small fragments which are freed in contact with the bars is identical with the process hereinabove described. When collected by the inflow of air, the small fragments of parenchyma pass through the grid of the beater 309 and from that point reach the nozzles 316.

So far as concerns the free parenchyma and lightweight intermediate products which are collected by the nozzles 316, these parts are conveyed pneumatically through the ducts 317 into the expansion chamber 321 in which the more dense elements fall down into the hopper 319 so as to be subsequently admitted again to the beating station while the lighter elements escape through the opening 322 towards a collecting device which has not been shown, thereby permitting of their separation from the transporting air and collection.

The description which has just been given in connection with the operation of the apparatus clearly shows the advantages over conventional apparatus in which the separation is carried out within a simple casing through which an upflowing air stream is circulated, The tobacco is not allowed to remain stationary or consequently to collect into a mass which might in turn result in clogging, either in the lower heaters in which the separation process is performed in the interior of the heaters and therefore in a space in which the movement of rotation of the teeth maintains a continuous agitation of the parts to be separated, or in the upper section in which-the expelled parts are sorted, as soon as they are expelled, into lightweight products and dense products which are immediately fed back into the beater.

The peripheral wall which surrounds the beating chamber can be divided by radial partitions 315 into more than three sections, each section comprising a nozzle 316 which is connected to the chamber 321. In addition, the chamber 321 can in turn be partitioned off into a number of sections in such a manner as to form a plurality of expansion chambers each provided with a discharge opening 322.

It is also possible to fix on the internal face ofthe wall of the zone 318 one or a number of helicoidal ribs 327 (as shown in FIG. 17) for the purpose of deflecting stripped stems, expelled from the beater 308, directly towards the beater 309.

Another apparatus which differs from the apparatus shown in FIGS. 15, 16 and 17 in the mode of recycling dense products which are separated in the chamber 321 is shown in FIG. 18. In this apparatus, the beating chamber is closed at the top by means of a lock chamber 328 comprising a rotary impeller while the expansion chamber 321 is closed off internally by means of a lock chamber 329. The conveyor 330 for supplying leaves is disposed between these two lock chambers. Such arrangement offers a number of advantages, namely:

The use of a feed conveyor which is smaller in height.

The elimination of a direct pneumatic connection between the beating chamber and the expansion chamber 321.

The possibility of collecting samples of dense recycled products in the beating chamber and consequently of objectively regulating the separation of products in the chamber 321.

The possibility of collecting dense products which are delivered from the lock chamber 329 and of admitting such. products prior to recycling into one or a plurality of pneumatic separators disposed in cascade as in an ordinary chain in such a manner as to free the products completely from the fragments of free parenchyma which they might contain.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features which fairly constitute essential characteristics of the generic and specific aspects of my contribution to the art and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended 1. Apparatus for stemming tobacco leaves to form lighter and heavier parts and for separating such lighter parts and heavier parts from each other, comprising a stemming chamber having at least one first inlet for admission of tobacco leaves, at least one air-admitting second inlet, at least one first outlet for evacuation of heavier parts in a predetermined direction, and at least one air-discharging second outlet; a stemming unit having beating elements rotatably mounted in said chamber and arranged to stem tobacco leaves which are admitted by way of said first inlet; and means for circulating through said chamber and between said beating elements at least one current of separating air which enters by way of said second inlet and entrains lighter parts by way of said second outlet, said second inlet being at least closely adjacent to saidfirst outlet so that the separation of lighter and heavier parts takes place in said stemming chamber and unit.

2. Apparatus as defined in claim 1, wherein said stemming chamber includes a peripheral wall and has a plurality of second inlets and first outlets, each of said second inlets constituting one of said first outlets.

5. Apparatus as defined in claim 1, further comprising an air lock for said first inlet.

6. Apparatus as defined in claim 1, wherein said stemming unit comprises tobacco engaging teeth angularly distributed about the axis of said unit.

Claims

1. Apparatus for stemming tobacco leaves to form lighter and heavier parts and for separating such lighter parts and heavier parts from each other, comprising a stemming chamber having at least one first inlet for admission of tobacco leaves, at least one air-admitting second inlet, at least one first outlet for evacuation of heavier parts in a predetermined direction, and at least one air-discharging second outlet; a stemming unit having beating elements rotatably mounted in said chamber and arranged to stem tobacco leaves which are admitted by way of said first inlet; and means for circulating through said chamber and between said beating elements at least one current of separating air which enters by way of said second inlet and entrains lighter parts by way of said second outlet, said second inlet being at least closely adjacent to said first outlet so that the separation of lighter and heavier parts takes place in said stemming chamber and unit.

3. Apparatus as defined in claim 1, wherein said stemming chamber includes an upper portion and a lower portion, said upper portion having an annular opening constituting said second outlet and surrounding said first inlet.

4. Apparatus as defined in claim 1, wherein said stemming chamber defines a plurality of communicating superposed stemming spaces.