GB2131672A

GB2131672A - Winnowing shredded tobacco

Info

Publication number: GB2131672A
Application number: GB08333630A
Authority: GB
Inventors: Warren Arthur Brackmann; Stanislav Miroslav Snaidr
Original assignee: ROTHMANS OF PALL MALL; Rothmans of Pall Mall Canada Ltd
Current assignee: ROTHMANS OF PALL MALL; Rothmans Benson and Hedges Inc
Priority date: 1982-12-16
Filing date: 1983-12-16
Publication date: 1984-06-27
Also published as: GB2131672B; GB8333630D0

Abstract

Winnowing of shredded tobacco stem material, or other particulate tobacco material, is effected by metering the shredded stem material from a reservoir and then picking the metered flow to open and separate the particles one from another. The resulting stream of separated individual particles of shredded tobacco stem material is projected into an upwardly-flowing air stream to entrain a desired lighter fraction of the particles and carry it out of the separator device. The undesired heavy fraction falls in the separator device and is collected. The collected heavy fraction preferably is reprocessed to separate agglomerates of shredded stem material present in the heavy fraction into individual particles, which are then entrained in a second upwardly-flowing air stream which subsequently joins up with the first gas stream. <IMAGE>

Description

SPECIFICATION Tobacco winnowing device The present invention relates to the winnowing of tobacco.

In the processing of tobacco, there often occurs at various stages a mixture of lighter tobacco fragments and heavier tobacco fragments which require separation to permit further processing of the lighter and/or heavier fragments. Winnowing techniques of various types have been used for this purpose.

Such winnowing may be effected, for example, on threshed tobacco leaves to separate the desirable tobacco lamina from the undesirable tobacco stem material. Such winnowing also may be effected on the final blend of shredded tobacco intended for cigarette manufacture to remove unwanted stem material. Another example of winnowing is in the processing of material resulting from the cutting of whole tobacco leaves, such as described in U.S. Patent No. 4,233,996 issued November 18, 1980 to Warren A.

Brackmann et al. and assigned to the assignee herein, the disclosure of which is incorporated herein by reference, to separate heavier shreds of tobacco having stem portions associated therewith from lighter shreds which do not have stem portions associated therewith. Further, winnowing also is effected following threshing of the heavier shreds to separate the lamina shreds from the stem fragments.

In U.S. Patent No. 4,386,617 issued June 7, 1 983 to Warren A. Brackmann et al. and assigned to the assignee herein, the disclosure of which is incorporated herein by reference, there is described a procedure for forming shredded tobacco stem material wherein tobacco stem material is fiberized between counter-rotating disc plates. The material which results usually contains heavy fragments and clusters of fibres which are unwanted in the end use of the shredded stem material and need to be removed. There is a need, therefore, for some form of separation or winnowing procedure to remove the unwanted heavy fragments and fibre clusters from the shredded stem material.

One problem which arises with existing tobacco winnowing procedures, which generally rely on gravity-induced separation of heavier particles from lighter particles in air, is that a satisfactory separation of desired material from undesired material often is not achieved, and desirable material may be lost or further processing necessary at a later stage of processing. In addition, when the undesired material is the heavy fraction, which often is the case, some heavier material which comprises agglomerations of desired lighter material forms part of the heavy fraction and hence desirable material may be lost.

One example of such material is the clusters of shredded stem material mentioned above, which are removed from the desired individual shredded stem particles along with the heavy stem fragments upon winnowing. Another example is pods of Oriental tobacco leaves which often result when opening and winnowing Oriental tobacco.

A need, therefore, exists for a tobacco winnowing procedure which will achieve substantially complete separation of lighter particles from heavier particles and will further process heavier particles which are multiple components of desired lighter particles to recover the lighter particles therein.

In accordance with one aspect of the present invention, there is provided a winnowing method for separating a mass of particulate tobacco material into a first fraction containing lighter tobacco particles and a second fraction containing heavier tobacco particles, wherein the mass of particulate tobacco material is introduced to a generally upwardly-flowing air stream substantially in the form of individual separated particles and the flowing air stream has a velocity sufficient to convey the lighter particles therewith but insufficient to convey the heavier particles therewith. Since the tobacco particles are presented in the flowing air stream in separated condition, each particle of tobacco is influenced by the flowing air stream in its intended manner, so that substantially-complete separation of the lighter particles from heavier particles occurs, contrary to the prior art.

As mentioned above, the heavier fraction resulting from this winnowing may contain agglomerates of lighter fraction material, as a result of the resistance of some particles to separation by the particle separation procedure prior to presentation of particles to the upwardlyflowing air stream. In accordance with another aspect of this invention, these agglomerates are collected and are subjected to further mechanical actipn to alter the aerodynamic characteristics of the agglomerates. After mechanical action, the agglomerate particles are exposed to an upwardlyflowing air stream, which conveys the particles upwardly, entraining separated individual particles but permitting agglomerates to be re-collected and reprocessed until all the individual particles have been separated one from another and carried upwardly away in the air stream.

In another aspect of this invention, there is provided apparatus for carrying out the method aspects of the invention. A novel winnowing device comprises opening metered tobacco and projecting the tobacco into a housing through which flows an upwardly-moving air stream.

Further, a novel winnowing device comprises reseparator means within a housing to effect repeated treatment of openable tobacco material to form individual particles therefrom.

The invention is described further mainly with reference to shredded tobacco material from which the lighter fraction is the desired product, preferably shredded tobacco stem material, but also including shredded lamina material and any other tobacco material provided in the form of shreds. However, it will be understood that the invention has general application to any processed tobacco material which contains differently weighted fractions which require separation one from another for further processing, including any of the materials discussed above.

A method in accordance with the present invention for the treatment of shredded tobacco smoking material, comprising metering shredded tobacco smoking material from a reservoir containing a mass of the shredded tobacco material; opening the shredded tobacco material particles in the metered flow to substantially separate the particles one from another, projecting the substantially separated particles into a generally upwardly flowing gas stream having a velocity sufficient to convey the desired lighter particles therewith but insufficient to convey the undesired heavier particles, and conveying tobacco material particles of the lighter fraction in their substantially separated condition in the flowing gas stream while permitting the tobacco material particles of the heavier fraction to fall in the gas stream.

By first forming a metered flow of shredded tobacco material and then picking the particles from that metered flow, substantially complete separation of the particles one from another is effected, so that the particles enter the upwardlyflowing conveying gas stream, usually an air stream, in separated form, so that winnowing into lighter and heavier fractions is readily achieved.

As noted earlier, some of the shredded tobacco material resists opening by this operation and the resulting agglomerates, or clumps of the desired material separate out of the air stream with the heavier fraction.

Since these agglomerates contain potentially useful shredded tobacco material, it is desirable that their shredded tobacco material content pass with the remainder of the desired shredded tobacco material in the conveying air stream. In accordance with a preferred embodiment of the invention, the heavier fraction collected in the above-described winnowing operation is subjected to further opening and winnowing, to open and separate the agglomerates into individual particles and to convey them in a generally upwardly-conveying gas stream, usually an air stream, to join with the conveying gas stream from the main winnowing operation.Some of the agglomerates may be so resistant to ready separation of the individual agglomerate particles one from another, as often is the case when agglomerates or clusters of shredded stem material are encountered, that several exposures to the reopening operation are required before full opening and separation of all the particles in the agglomerate one from another is achieved.

The latter reopening procedure may be effected on a mass of tobacco material containing agglomerates of tobacco particles with or without undesired heavy tobacco fragments, arising in any manner, not just as a result of the specific winnowing operation on the original mass of tobacco material. The reopening procedure may be effected on any agglomerated form of tobacco particles, including, for example, clusters of shredded stem material and pads of Oriental tobacco leaves.

The method of treating masses of tobacco material containing heavy stem fragments and shredded stem agglomerates comprises subjecting the mass to an opening operation so as to effect separation of some of the individual particles of shredded stem material in the agglomerates one from another while leaving substantially unaffected the heavy stem material fragments; entraining the separated individual particles of shredded stem material in an upwardly-flowing gas stream without entraining the heavy stem material fragments, recycling the unopened portions of the agglomerates to the separation operation; and repeating the entraining, recycling and separation operations until the agglomerates are completely separated into individual particles.

As described in our earlier U.S. Patent No.

4,386,617, the shredded stem material is discharged from the air stream into which it is first dumped from the shredder and may be partially dried from its shredder discharge moisture level to a moisture level of about 1 9 to about 35 wt %, using any conventional tobacco drying equipment, such as, a rotary tumbler drier. The winnowing operation of the present invention conveniently is effected on this partially dried form of the shredded stem material, with the heavier fraction or winnowings, preferably after reseparation, being recycled to the shredder for further processing, if desired.

The sole Figure of the drawing is a schematic representation of winnowing apparatus in accordance with a preferred embodiment of the invention.

Referring to the drawing, there is illustrated therein a winnowing apparatus 10 for the winnowing of shredded stem material. The principles illustrated therein are applicable to a wide variety of tobacco materials, as described earlier. Shredded stem material for winnowing is fed to a reservoir tube 12 to form a mass 14 of shredded stem material therein containing both desired lighter particles and undesired heavier particles. Located at the lower end of the reservoir tube 12 in communication with the mass 14 are a pair of rotating metering rollers 1 6. Each roller has a plurality of pins 1 8 which project radially outwardly from the surface. The pins 1 8 of the rollers 1 6 are arranged, so that in the gap 1 9 between the rollers 16, the pins 1 8 are aligned.

The rollers 1 6 rotate in opposite directions, so that the pins 1 8 cooperate in the gap 1 9 between the rollers 1 6 to control and meter the desired quantity of shredded stem material between the rollers 1 6 from the mass of shredded stem material 14. The quantity of shredded stem material metered by the rollers 1 6 may be varied by varying the speed of rotation of the rollers.

A third roller 20 is located below and substantially equidistantly from the rollers 1 6 and includes radially-directed pins 22. A curved wall 24 usually having approximately the same centre of curvature as the roller 20 is provided as a guide surface for the flow of shredded stem particles in a curved path round the roller 20 while pins 25 project upwardly from the curved surface 25 towards the roller 20. The pins 22 on the roller 20 and the upstanding pins 25 interact to effect separation of individual shredded stem particles one from another as the metered flow is conveyed over the curved surface 24. As the separated stem particles reach the length of the curved surface 24, they are projected as a generally horizontallymoving stream 26 of separated tobacco stem particles into an enclosed housing 28.A set of rollers suitable for use as the rollers 1 6 and 20 is described and illustrated in detail in our U.K.

Patent No. 1,556,370.

An upwardly-flowing air stream 30 enters the housing 28 through an inlet pipe 32 under the influence of vacuum applied to the interior of the housing 28 and engages the horizontally moving stream 26 of separated tobacco shredded stem particles entering the housing 28. The speed of flow of the air stream 30 is adjusted to a value, so that the desired lighter particles 34, constituting a lighter fraction of the shredded stem material 14, are entrained by and carried upwardly in the air stream 30 towards a flow conduit 36 through which the vacuum is applied to the interior of the housing while remaining in their substantially separated condition, and the heavier particles 38, constituting a heavier fraction of the shredded lamina material 14, are not entrained and fall in an arcuate path 39 onto a collection surface 40.

In this way, there is produced a flowing air stream containing suspended shredded stem particles in separated condition free from unwanted improperly processed heavy stem material fragments and clusters of shredded stem particles. The winnowed tobacco particles 34 conveyed in the air stream 30 away from the winnowing device 10 in substantially separated condition in conduit 36 may be cqllected and used as desired, for example, for blending with shredded lamina material in accordance with the procedure of our U.K. Patent Publication No.

2,115,681 to form a blend useful in cigarette making.

A high speed picker roll 44 having radial pins 45, in cooperation with a curved surface 46 and pins 47 upstanding therefrom, serves to treat the heavy fraction collected on the surface 40 in an attempt to open and separate the aggregates of desirable stem material contained therein.

The processing of the heavy fraction 42 by the cooperating pins 45 of the roller 44 and pins 47 upstanding from the curved surface 46 forms a stream of tobacco stem particles 48 which projects from the end of the curved surface 46.

This stream 48 is engaged by an upwardly flowing air stream 50, entering the housing 28 through a lower inlet opening 52 under the influence of the internal vacuum of the housing 28. The processing of the heavy fraction achieves some separation of individual particles of shredded stem material but often complete separation of the individual particles of the agglomerates is not achieved. The speed of flow of the air stream 50 is adjusted to a value so that the individual reseparated shredded stem material particles 54 are entrained by and are carried upwardly in the air stream 50, while the unwanted heavy stem fragments are substantially unaffected and the partially-treated agglomerates are carried upwardly towards the heavier stream 39. The air stream 50 with entrained tobacco stem material 54 joins the stream 34 and thence exits the housing 28 through conduit 36.

The heavy stem fragment stream 56 ultimately falls in a curved path and is collected on an inclined surface 58 on the opposite side of the housing 28 from the reseparator wheel 44, off which they are able to slide to a collection device (not shown). The heavy stem fragments so collected may be further processed in any desired manner.

The partially opened agglomerates in stream 60 become entrained under within the heavy fraction stream 39 and, in this way, are recycled to the collection surface 40, whence they are further processed. The procedure of partial opening and recycle of agglomerates is effected repetitively until all the individual tobacco stem particles of the initial agglomerate have been separated one from another.

The shredded stem material 14 which is winnowed by the above-described procedure may have any convenient moisture content. It is convenient to effect the winnowing on shredded stem material which has an intermediate moisture level requiring further drying to its final moisture level for inclusion in cigarettes, since the shredded stem material tends not to be degraded by the opening operations at such moisture level. Further, the final drying of the shredded stem material to its desired final moisture level is more efficiently conducted on particles which have been opened and separated, especially when the selective drying procedure described in our U.K. Patent Publication No. 2,117,881 is used.

In summary of this disclosure, the present invention provides a method of opening and winnowing tobacco material to remove unwanted heavier particles, which is beneficial in providing the winnowed tobacco in an improved form for further processing and the ultimate formation of tobacco filler rod. Modifications are possible within the scope of this invention.

Claims

1. A method of processing a mass of tobacco fragments, which comprises opening the mass of tobacco fragments to form a light fraction of individual separate particles and a heavy fraction, entraining the individual particles of the light fraction in a flowing gas stream having a velocity which does not entrain the heavy fraction, and collecting the heavy fraction.

2. A method as claimed in claim 1, in which the opening step provides a substantial proportion of the tobacco fragments in substantially separated condition, and the entraining step is effected by exposing the opened tobacco mass to the gas stream flowing generally upwardly with a velocity sufficient to entrain the lighter tobacco fragments but insufficient to entrain the heavier tobacco fragments.

3. A method as claimed in claim 2, in which the mass of tobacco fragments is contained in a reservoir, tobacco fragments are metered from the reservoir prior to the opening step, and the exposing of the opened tobacco to the upwardlyflowing air stream is effected by projecting the substantially separated tobacco fragments generally horizontally into the upwardly-flowing air stream.

4. A method as claimed in claim 2 or 3, in which the collected heavy fraction contains agglomerates of lighter tobacco fragments and undesired heavy tobacco fragments, and the agglomerates are further processed to open the same and to entrain the lighter fragments contained therein in the upwardly-flowing air stream.

5. A method as claimed in claim 4, in which the agglomerates are further processed by removing some lighter fragments from the agglomerates, entraining those fragments in the upwardlyflowing air stream, collecting the residual agglomerates, and repeating the opening, entraining and collecting steps until all the lighter fragments are separated from the agglomerates.

6. A method as claimed in claim 1, in which the mass of tobacco fragments comprises agglomerates of desired tobacco particles, the heavy fraction contains agglomerates of the desired tobacco particles from which some desired particles have been removed by the opening step, and the steps of opening and collecting a heavy fraction containing agglomerates are continued until all the desired tobacco particles have been released from the agglomerates.

7. A method as claimed in any one of claims 1 to 6, in which the mass of tobacco fragments is that which results from the threshing of tobacco to effect separation of lamina material from stem material; is that which results from blending shredded tobacco lamina material and processed tobacco stem material to form a cigarette making feed; is that which results from the cutting of whole tobacco leaves to form narrow strands of tobacco; is that which results from threshing strands of tobacco having lamina material joined to stem material to separate the lamina material from the stem material; is that which results from shredding tobacco lamina material; or it is that which results from shredding tobacco stem material.

8. A method of processing a mass of tobacco fragments substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawing.

9. An apparatus for processing a mass of tobacco fragments, which comprises a housing having an entraining gas stream inlet to form a generally upwardly-flowing gas stream, and opening and projecting means for opening the tobacco fragments and separating the fragments one from another and for subsequently projecting the separated fragments onto the upwardlyflowing gas stream.

10. An apparatus as claimed in claim 9, including a reservoir vessel for holding the mass of tobacco fragments and a metering device for metering tobacco fragments from the lower end of the reservoir vessel to the opening and projecting means.

11. An apparatus as claimed in claim 10, in which the metering device is comprised of a pair of rollers and the opening and projecting means comprises a third roller in communication with the pair of rollers.

12. An apparatus as claimed in claim 11, in which the opening and projecting means further comprises a curved guide surface of centre of curvature corresponding to that of the third roller and stationary pins upstanding from the guide surface and cooperate with radially-projecting pins extending from the third roller to effect separation of tobacco fragments one from another.

13. An apparatus as claimed in claim 12, in which the curved surface terminates at a location which enables the separated fragments to be projected generally horizontally into the upwardlyflowing air stream.

14. An apparatus as claimed in any one of claims 10 to 13 including a collector surface located in the housing and positioned to receive thereon projected tobacco fragments which are not entrained by the upwardly-flowing gas stream, and a second opening and projecting means is provided in communication with the collector surface.

1 5. An apparatus as claimed in claim 8 or 14, in which the opening and projecting means comprises a picker roll and a curved stationary surface having a centre of curvature corresponding to that of the picker roll and terminating at a location to permit the separated particles to project in an arc into an upwardlyflowing gas stream.

1 6. An apparatus as claimed in claim 15, in which a plurality of pins extend upwardly from the stationary surface and cooperate with the radiallyprojecting pins extending from the picker roller to effect separation of tobacco fragments one from another.

1 7. An apparatus for processing a mass of tobacco substantially as hereinbefore described with reference to, and as illustrated in the accompanying drawing.