Method and apparatus for separation of objectionable particles from tobacco material

A method of separating objectionable particles from host tobacco material which includes fluidizing the tobacco material with a fluidizing air stream to allow heavy unwanted particles to fall, to cause light unwanted particles to rise and be air transported away and to leave a carpet of acceptable material.

This invention relates to a method and apparatus for separation of 
objectionable particles from tobacco material, for example from cut or 
un-cut tobacco. 
The objectionable particles may be "heavies", for example coarse cut stem 
pieces and/or "lights", for example particles or dust. 
In processing, different tobacco components are treated in different ways 
before being combined to form the final blend. For example, lamina 
undergoes a different conditioning treatment to stem and is cut more 
finely. If there is some cross-contamination of tobacco type such as stem 
or lamina or lamina on atom, problems will occur after cutting. After 
cutting, some of the stem in lamina will be so coarsely cut it will be 
deemed to be objectionable and some of the lamina will be so finely cut it 
will, in the latter stages of processing, be rendered to dust. For the 
maintenance of quality, both the overtly large and small particles must be 
removed from the tobacco prior to being manufacturered into the cigarette 
rod. 
One way of removing objectionable particles has been provided for in 
cigarette making machines, in that prior to forming the unwrapped 
cigarette rod, the tobacco in the machines is passed through a winnower 
and air lifted. In passing through the winnower, some heavy objectionable 
particles are removed. In air lifting, some of the dust passes through the 
machine to be removed by filtration before the air is exhausted to the 
atmosphere. Both of these processes are inefficient and remove only a 
portion of the objectionable material present. Their efficiency is also 
load dependent, that is, the more objectionable material present, the 
lower their efficiency. Their discrimination of the winnower is also poor, 
resulting in acceptable material being rejected with the objectionable. 
Another method of removing objectionable material for example is to 
classify it out by air lifting. There are several styles of classification 
in existence. These work on the principle that the heavy particles can be 
separated from the light particles by passing them through a moving stream 
of air which carries the light particles off with it for separation later, 
while the heavy particles due to their mass/aerodynamic qualities are left 
behind. 
As the light particles are usually the acceptable and less robust portion 
of the tobacco and the air velocities used are in the order of 3,000 
ft/min or higher, this form of separation usually results in some 
degradation of the good tobacco components. Again discrimination between 
heavy and light particles is poor due to the aerodynamic shadowing and the 
very short time in which separation occurs. 
U.S. Pat. Specification No. 4,646,759 shows apparatus for the separation of 
tobacco into two fractions, for example"heavies" and "lights". The tobacco 
is supplied to a separator unit including a vibrating conveyor and streams 
of air rising through the conveyer plate lift the lighter particles away. 
The particles most desirable for use as cigarette filler are pulled away 
and into an upper collector chamber and there deposited into a collector 
tray leaving the heavy particles to be discharged separately. 
The general objective of the present invention is to effectively separate 
the objectionable particles from the acceptable tobacco product by a means 
which does not cause the acceptable tobacco components to degrade. 
Specifically the objectives are: 
To remove heavy objectionable particles such as coarse or uncut stem or 
heavy foreign objects from tobacco. 
To remove light objectionable particles such as dust from tobacco. 
To cool, condition or maintain the physical status of the host tobacco 
during the separation of the above. 
To effect the above without degrading the host tobacco. 
According to the present invention a method of separating objectionable 
particles from host tobacco material includes fluidising the tobacco 
material with a fluidising air stream to allow heavy unwanted particles to 
fall, to cause light unwanted particles to rise and be air transported 
away and to leave a carpet of acceptable material. 
Preferably the method includes agitating the tobacco material whilst it is 
fluidised. 
The vertical air velocity across the working zone of the bed can be low and 
can change from as little as 300 ft/min to 1000 ft/min, and the 
combination of agitation and air flow causes the tobacco to stratify and 
be teased open so that the dust if lifted away and the heavy particles 
sink to the lower strata. The average fluidised air velocity is set such 
that the heavy particles cannot be supported by the air flow and 
consequently sink. 
The advantage of the invention is that tobacco components are fluidised in 
the fluidising air stream rather than air-lifted and transported, and as 
such have more time to discretely separate and do not suffer the 
degradation found in other separation systems. 
If desired however the acceptable material may be gently air transported 
from the carpet. Thus sufficient time is allowed for the particles to 
become aerodynamically supported and separated with the acceptable 
material then finally being carried on a gentle air stream and lifted from 
the carpet and transported and as such do not suffer the same degradation 
found in other separation systems. 
The invention also includes apparatus for the separation of objectionable 
particles from tobacco material comprising means for fluidising the 
material to form a carpet in a fluidising air stream, means for 
simultaneously agitating the material to release the dust and heavy 
particles, arranging the air flow velocity to cause the dust to rise and 
heavy particles to sink from said carpet, and means for removing said dust 
and said heavy particles. 
If desired means can be incorporated for lifting the acceptable material 
from the carpet on a gentle removal air stream and transporting it. 
Preferably the said fluidising air stream forms a stratified fluidised bed 
on a deck which is vibrated to cause agitation of the tobacco. 
In a preferred embodiment, the said fluidised bed deck has a convoluted and 
at least partly perforated surface which provides peaks and troughs, the 
air velocity of said fluidising air stream being arranged to cause a 
portion of the tobacco carpet to be below the peaks but spaced above the 
bottoms of the troughs. As the deck is convoluted, the air volume to deck 
area within the bed is higher than that at the troughs of the 
convolutions, the resultant air velocity being such that the bottom of the 
fluidised carpet of the tobacco is supported below the peaks of the 
convolutions, teasing via the vibratory bed is effected throughout the 
whole tobacco carpet. 
The heavy particles can be removed through openings in the deck and thus 
the openings can be in the form of slots in the troughs. 
The heavy particles can be arranged to pass through the slots to a 
collector which moves them to at least one side or end of the vibratory 
deck. 
The tobacco carpet can be transported by the fluidising deck to a position 
where the acceptable tobacco can be transferred by gravity onto a take off 
conveyer. 
Alternatively the tobacco carpet can be transported by the fluidising deck 
to a position where the acceptable particles are gently air lifted via one 
or more suctions tubes at such a low velocity as to leave any remaining 
heavy particles behind and to be further transported to the end of the 
deck. 
The dust can be removed through a tapered extraction hood in which the air 
velocity at its higher level is less than the air velocity at its lower 
level thus ensuring that only dust can be entrained. 
If desired, the heavy particles can be delivered to a classifier for 
segregation and re-cycling. 
The invention also includes apparatus for the separation of objectionable 
particles from tobacco material which comprises a deck adapted to receive 
thereon tobacco material at a reception end and discharge it at a 
discharge end, means for vibrating the said deck, means for providing as 
air flow through openings in the deck to fluidise the tobacco material, 
said deck having a convoluted surface comprising a number of 
longitudinally extending troughs separated by peaks, each of said troughs 
having a bottom, opposed side walls, and a mouth extending between 
adjacent said peaks, air guiding means which in combination with the shape 
of the troughs and peaks causes the velocity of the fluidising air passing 
upwardly in each of said troughs to initially increase to a located spaced 
away from said bottom and then decrease as it exits the mouth of said 
trough, to provide stratified air velocities over the deck to cause the 
tobacco material to form a carpet at least a portion of which is below the 
peaks but spaced above the bottom of the troughs and which together with 
the vibration of the deck agitates the carpet and causes the dust to be 
released and rise and heavy particles to sink, said carpet moving 
lengthwise along said troughs during operation toward said discharge 
location, means for removing the dust. 
The bottom and side walls of each trough can be perforated and said air 
guiding means is provided by longitudinally extending baffle means which 
direct air to said perforations. 
Preferably the baffle means are shaped to provide an air control chamber 
around each trough, each chamber having spaced apart baffle walls which 
extend downwardly from points on the trough side walls beneath the peaks 
to points below the bottom of the trough and a lower wall joining said 
baffle walls and through which air is supplied to the air control chamber. 
Preferably means are provided for smoothing the flow of and pre opening the 
incoming tobacco. This can take the form of spreading on a vibrating deck 
using deflectors followed by passing the material across an air stream or 
by using a spiked belt or spiked roller; again this may be followed by 
passing the material across an air stream 
The invention can be performed in various ways and various embodiments will 
now be described by way of example and with reference to the accompanying 
drawings in which: 
FIG. 1 is a diagrammatic view of a first embodiment of the apparatus 
according to the invention; 
FIG. 2 is a diagrammatic cross-section through part of the apparatus shown 
in FIG. 1; 
FIG. 3 is an enlarged isometric view of part of the fluidised bed deck; 
FIG. 4 is a diagrammatic view showing the relative position of a tobacco 
carpet on the fluidised bed deck; 
FIG. 5 is a side elevation of a part of the apparatus; 
FIG. 6 is an end elevation of the apparatus shown in FIG. 5; 
FIG. 7 is a plan view of part of the fluidised bed deck; 
FIG. 8 is a cross-sectional view on the line VIII--VIII of FIG. 7: 
FIG. 9 is a diagrammatic cross-section through a second embodiment; 
FIG. 10 is a diagrammatic cross-section of an alternative deck 
configuration; 
FIG. 11 is a diagrammatic cross-section of another deck configuration; 
FIGS. 12(a)-12(d), 12(a-12(c) and 14(a)-14(d) are diagrammatic 
representations showing the principle of progressive separation of 
acceptable tobacco material from the heavier material; 
FIG. 15 is a diagrammatic cross-sectional view of part of a separation deck 
showing a construction applying the principles set out in FIGS. 12, 13 and 
14; 
FIG. 16 is a diagrammatic cross-sectional view of a deck provided with four 
troughs; 
FIG. 17 is a diagrammatic cross-sectional view showing an alternative 
construction; 
FIG. 18 is a diagrammatic perspective view of the construction shown in 
FIG. 17; 
FIG. 19 is a part cross-sectional diagrammatic view of an alternative 
construction; 
FIG. 20 is a graph showing the air velocities at different levels in the 
trough of the construction shown in FIG. 19; 
FIG. 21 is a cross-sectional diagrammatic view of the construction shown in 
FIGS. 19; 
FIG. 22 is a diagrammatic cross-section through another construction 
according to the invention; 
FIG. 23 shows a typical air velocity profile required for the apparatus to 
work; 
FIGS. 24 and 25 are diagrammatic cross-sectional views of trough shapes; 
FIGS. 26 and 27 are diagrammatic cross-sectional views of further trough 
shapes according to the invention; 
FIG. 28(a)-28(c) show a series of cross-sections through a trough peak of 
the type shown in FIG. 15: 
FIG. 29 is a plan view of the trough peaks shown in FIG. 28; and, 
FIG. 30 shows a method of cleaning heavy materials or winnows delivered by 
the discharge openings in the trough.

As shown in FIG. 1 of the drawings, the apparatus comprises a feed conveyer 
1, which transports tobacco material to be treated onto a vibrating fluid 
bed deck 2. If desired, the tobacco having left conveyer 1 can be teased 
by a stream of air which acts to spread, separate and untangle the 
material As the material reaches the deck 2, means can be provided to 
further spread it evenly over the full deck width, for example by means of 
a baffle (not shown). The deck 2 is inclined and its vibratory action 
causes the tobacco to be transported along it. A flared hood 3 is provided 
and beneath the hood a combination of perforated and/or perforated and 
plain, and perforated sheets with slots is used to cause the tobacco to 
become fluidised with the combination of the deck's vibrating action and 
air velocity introduced from a plenum 4 beneath the deck 2. Air is 
introduced into the plenum through suitable ducting 5 from a fan 6. 
The deck 2 beneath the hood 3 is corrugated to provide higher air velocity 
at its peaks than in its troughs. Heavy particles fall through the 
fluidised carpet of tobacco thus produced which is teased open by the 
action of the air and vibration and fall into the troughs between the 
peaks of the corrugated bed. Slots (to be described in more detail) are 
provided through which the heavy particles fall, and the air-flow through 
the slots is set so that it cannot support the heavy objectionable 
material. 
Collectors (not shown in FIG. 1) are arranged beneath the slots which 
transport the heavy material to a gallery 7 at one side of the bed 2 and 
the material progresses down the gallery to a window 8 through which it 
falls onto a conveyer 9. Conveyer 9 lifts the particles to a classifier 10 
where any acceptable tobacco in the heavy particles is segregated and 
re-cycled by being passed through a ducting 11 to a separator 12 through 
which it is returned to the loading conveyer 1. Heavy objectionable 
particles are dropped out of the bottom of the classifier 10 and are 
passed through ducting 13 to a separator 14 from which they are ejected at 
17. An extraction fan filter is indicated by reference numeral 15. Ducting 
16 returns air from the separator 12 via the separator 14 to the fan 
filter 15. 
Light objectionable particles such as dust are lifted above the top of the 
fluidised carpet of tobacco by the air-stream and taken to a fan-filter 18 
via extraction ducting 19 leading from the top of the hood 3. As the hood 
3 is flared from bottom to top, the air velocity within it is reduced from 
bottom to top. This prevents the fluidised carpet of tobacco from being 
lifted beyond fluidisation and ensures that any acceptable particles of 
tobacco entrained in the fluidised air drop out as its velocity reduces 
before it is extracted from the hood 3. 
The air used to fluidise the tobacco can be of a specific temperature and 
RH to influence the final temperature and moisture of the tobacco at the 
discharge end of the vibrating bed 2. 
Throughout the whole process, the bulk of the acceptable tobacco is 
supported on a cushion of air which produces the fluidisation required and 
this gentle form of support prevents the host tobacco from degrading. 
FIG. 2 is a diagrammatic cross-sectional view of part of the apparatus and 
the same numerals are used to indicated similar parts as in FIG. 1. As 
will be seen from FIG. 2, the vibrating deck 2 is carried on a 
spring-mounted frame to which it is connected by fiberglass springs 21. 
The deck is vibrated by a drive-arm 22 as shown in FIG. 1 and the 
collectors of the "heavies" are shown as channels 23. The cleaned, cut 
lamina emerging from the deck is delivered to a removal conveyer 24. 
Reference numeral 25 indicated a baffle in the plenum which acts to 
distribute air and reference numeral 26 indicates a further baffle in the 
base of the deck. The convoluted deck is preferably made with a 10% open 
area from perforated sheet and is indicated by reference numeral 27, but 
larger or smaller cores of perforation could be used. 
An air deflector 28 is provided in the upper part of the hood 3 and baffles 
are indicated by reference numeral 29. 
The construction of the vibrating deck is shown more clearly in FIGS. 3, 7 
and 8. FIG. 3 shows the corrugated deck surface with the peaks of the 
corrugations indicated by reference numeral 30 and the troughs by 
reference numeral 31. The bottom 32 of each trough is flat and the whole 
construction is made from perforated material so that an air flow can be 
passed through it. As will be seen from FIG. 8, the corrugated surface is 
carried on the perforated channels 23, which are connected on each side to 
lengthwise extending box section galleries 35 and 36. Reference to FIG. 7 
will show that a row of slots 37 is provided which extends angularly 
across the deck, each slot being located at the bottom of one of the 
troughs 31. A collector channel 23 is located beneath each row of slots 
and additional support is provided by supports 41. It will be seen that 
this collector channel is angled downwardly towards the gallery 35 and is 
also angled across the deck. Where the channel meets the gallery 35, a 
window opening 42 is provided to provide communication between the gallery 
and the channel. The channel 23 is made from a perforated material to 
allow an appropriate air flow through it for the fluidised bed. 
FIG. 4 shows how the carpet of tobacco material indicated by reference 
numeral 45 is located by the fluid bed in relation to the corrugated 
surface provided by the deck of the bed. Approximately one third of the 
carpet impinges into the channels below the peaks 30 although it will be 
appreciated that there will be large fragments falling from the lower 
surface, indicated by reference numeral 47 and dust and other smaller 
fragments indicated by reference numeral 48 rising above it. As the peaks 
of the deck extend into the carpet of material, vibration of the deck is 
transmitted to the material, thus teasing it while it is in a fluid state. 
Moreover, because the vibration is transmitted to the carpet of material, 
it helps to move it down the conveyer thus ensuring a rapid throughput of 
material. It has been found that a relatively thin layer of material 
transported rapidly through the conveyer is more effective than moving a 
much thicker layer at slower speed. 
Due to the angled construction of the collector channels 23, heavy material 
which has fallen through the openings 37 is transported across the deck 
and into the gallery 35 through the appropriate window 42. Because the 
whole deck is vibrating, the gallery 35 now acts as a conveyer to move the 
heavy material to the position indicated by reference numeral 8 in FIG. 1 
so that it can be removed. 
FIG. 5 shows the external construction of the deck together with its hood, 
the same reference numerals being used to indicate similar parts as the 
other FIGS. 
FIG. 6 shows the entry end of the apparatus with a part section through the 
deck once again employing the same reference numerals as the previous FIGS 
to indicate similar parts. As will be seen from FIG. 6 a nylon skirt 50 is 
employed at the entrance and exit, and transparent windows can be provided 
in the hood 3 in order to observe the process. Similarly transparent 
windows 52 can also be provided in the sides of the gallery 35 opposite 
the collector troughs 23 for observation purposes. Flexible plastics 
material rubbing seals 54 are provided between the hood 3 and the 
vibrating deck 2 and flexible seals (not shown) are also provided between 
the plenum 4 and the underside of the deck 2. 
In an alternative construction shown in FIG. 9 similar reference numerals 
are used to indicate similar parts as shown in FIGS. 1 and 2. Thus, the 
deck 2 is surmounted by a hood 3 and air is supplied through a plenum 
chamber 4. The deck 2 is carried on a spring mounted frame to which it is 
connected by fiber glass springs 21 in a similar manner to the arrangement 
shown in FIG. 5 and the deck is vibrated by any suitable means, for 
example by a drive arm similar to that also shown in FIG. 5. 
In this construction tobacco is conveyed via a feed conveyer 60 and it is 
metered into the apparatus by spiked wheels indicated by reference numeral 
61 which will also act to open up the tobacco. If desired the apparatus 
might also be fitted with an air stream provided through a baffled duct 62 
which further opens the tobacco up before it falls onto the fluidised bed 
2. 
Fluidised air is blown from a fan to the underside of the deck in a similar 
manner to that described with regard to the other Figures and the deck is 
perforated in the manner described above or in the manner shown in FIGS. 
10 and 11 to be described hereafter. The combination of the perforations 
and the deck shape cause the fluidised air velocity to increase from the 
trough to the peaks of the convolutions or as described with regard to 
FIGS. 10 and 11. Tobacco particles with different aerodynamic qualities 
will be support at different air velocities and stratify vertically within 
the convolutions such that the heavy objectionable particles will be at or 
near the bottom of the trough and acceptable material at a higher level. 
Dust is carried off in the air stream through the hood 3 and a hood 
extraction duct 62 to a fan filter combination, again as described. The 
hood 3 is flared out to cause the fluidising air velocity to drop with its 
increase in cross-section thus ensuring that good tobacco is not carried 
away with the dust. 
The objectionable particles again drop through slots in the deck and the 
vibratory action of the bed ensures that the tobacco is teased open and 
all particles are transported away from the infeed end. 
The carpet of acceptable tobacco particles can again be discharged as 
described above but in the arrangement shown in FIG. 9 this acceptable 
material may be gently air lifted in a gentle removal air stream via 
suction tubes 64. In this arrangement the level of suction is kept to a 
minimum to limit degradation and also to ensure that any heavy 
objectionable particles which did not pass through the slots in the bed 
are left behind on the vibrating deck where they can be channelled off by 
the vibration and eventually pass off the apparatus with the material 
which falls through the slots. 
The velocity of said gentle air stream will depend upon the cross section 
of the tube 64 and other factors, for example it can be as low as 200 feet 
per minute, but in a typical example is about 1,000 feet per minute which 
is added to the fluidising air stream. 
It will be appreciated that the air lift arrangement is very soft and is 
merely strong enough to gently lift the tobacco away. It is not used in 
the normal sense or as in known constructions as a separator. 
The rate of objectionable material leaving the apparatus may be measured 
and compared to a desired level in order to provide control by altering 
the velocity of air fluidising air. 
In the trough construction shown in FIG. 10 the material of the deck 
surface is again perforated, a typical perforation being indicated by 
reference numeral 66. The peaks of the corrugations are indicated by 
reference numeral 67 and the trough by reference numeral 68. The bottom of 
each trough may be flat or curved and, as mentioned above, the whole 
construction is made from perforated material so that air flow can pass 
through it. Slots 69 are again provided at the bottom of each trough. As 
will be seen from the drawing the shape of the peaks and troughs is not 
triangular, for example as shown in FIG. 4, but each side wall of each 
trough is multi-angled. Thus at the bottom of each trough there is a first 
side wall portion 70 which leads into a more upright portion 71 which in 
turn leads into a more angled portion 72. The included angles between the 
portions 72 and 71 and 71 and 70 are different. The upper end of the 
trough 62 is rounded to lead into the next side wall. In cross-section the 
trough therefore has a wider angle at the area indicated by reference 
numeral 73 than in the middle portion 74 and it is even more restricted in 
the lower portion 75. The gap between the upper ends of opposed portions 
71 provide what is in effect a neck. The net result of this shaping is 
that the velocity of the general air flow upwardly through the trough 
rises from the space between the lower side wall portions 70, gradually 
increasing until it reaches the neck between the upper ends of the opposed 
side walls 71, as it passes upwardly into the upper part of the trough 
between the opposed side walls 72 which form the peaks the velocity 
decreases. This effect is pronounced and provides better separation 
between the bottom of the trough through which unwanted particles, 
indicated by reference numeral 76, can fall through the openings 69 and 
the upper part of the trough where the carpet of tobacco, indicated by 
reference numeral 77, can float and be vibrated. 
A similar construction is shown in FIG. 11 and the same reference numerals 
are used to indicate similar parts but in this construction the upper ends 
of the peaks carry no air perforations and are shown in solid lines. This 
portion of each peak incorporating the more angled parts of the side walls 
indicated by reference numeral 72. This construction offers the advantage 
that less air flow is required and a better separation is obtained between 
the bottom of the trough 69 and the carpet of tobacco 77. Moreover, the 
carpet of tobacco tends to lie more evenly in the upper part of the 
troughs so that it is contained. 
Investigations have shown that the progressive separation of acceptable 
tobacco material from the heavier material can be achieved progressively 
and FIGS. 12, 13 and 14 show such progressive separation principles. 
In these three FIGS. the perforated trough is indicated by reference 
numeral 100, the peaks at each upper side of the trough are indicated by 
reference numeral 101 and air is supplied to the underside of the trough 
through a duct 102 having baffle side walls 103 and 104. 
FIGS. 12(a)-12(d) show four stages of progressively altering the shape of 
the trough 100. Thus at the top of the Figure the trough is a flat curved 
shape and is progressively curved bringing the curve in steeper as shown 
at the lower end of the FIG.. With a constant air flow indicated by arrow 
105 the lighter acceptable tobacco indicated by reference numeral 106 
progressively separates from the heavier material 107 and at the bottom of 
the FIG. it will be seen that the light acceptable material 106 has 
remained at the top of the trough between the peaks 101 and the heavy 
material 107 is now clearly spaced away from it at the bottom of the 
trough. 
FIGS. 13(a)-13(c) a similar schematic progressive diagram showing how with 
a trough shaped substantially as shown at the bottom of FIG. 12 separation 
can be achieved by progressively increasing the volume of air available to 
the underside of the perforated shape. Thus at the top of the FIG. the air 
inlet for air flow 105 is relatively small but at the bottom of the FIG. 
the air inlet extends across the whole width of the duct. 
FIGS. 14(a)-14(d) illustrate the use of combined control of air volume by 
entry size and distribution control by shape of the duct can provide 
separation. The same reference numerals are again used to indicate similar 
features. It should be noted that the bottom diagram in FIG. 14 is not to 
scale, the width of the mouth of the trough should be the same as that in 
the diagrams above it. From this it will be understood that with this last 
arrangement the base of the duct is wider than the width across the throat 
of the trough between the peaks 101. Alternatively the width of the mouth 
of the trough can be smaller than those shown above it, illustrating that 
progressive separation can be achieved individually, or by a combination 
of a progressive increase in the curve of the perforated material, an 
increase of the volume of air (and hence its pressure) below it or by an 
increase of the velocity of the air at the peaks of the curve by reducing 
the width of the curve in this area. 
From FIGS. 12, 13 and 14 it will be appreciated that the use of baffle 
walls 103 and 104 enables careful control of the the air flow through the 
bottom and opposed side walls of the trough to give accurate control of 
the separation. 
The principles illustrated in FIGS. 12, 13 and 14 are applied to a deck as 
shown in FIG. 15. In this diagrammatic cross-section of one trough in a 
deck, the trough is indicated by reference numeral 100. The trough has 
opposed side walls 110, a bottom portion 111 which is of a narrower 
V-shape than the side walls 110, and an upper portion formed by angled 
walls 112 which form peaks between the troughs. In FIG. 15 two peaks are 
shown each side of the trough. 
The bottom and side walls of each trough are perforated and air guide means 
are provided by longitudinally extending baffle means in the form of 
spaced apart baffle walls 113, 114 which extend downwardly from the points 
where the side walls 110 merge into the upper walls 112 that is 
immediately beneath the peaks. To beneath the bottom 101 of the trough 
where they are joined by a lower wall 115. This wall is perforated to 
allow air to be supplied to an air control chamber 116 formed by the 
baffle walls around the trough 100. 
Air is supplied to the air control chamber 116 from plenum chamber 117 
below the deck, air entry being indicated by arrows 118. 
With the appropriate air pressure the air control chamber around the trough 
together with the shape of the trough and the peaks causes the carpet of 
good tobacco 119 to be lifted to the throat of the trough between the 
peaks whilst the heavy unwanted material 120 drops downwardly. 
In order to gather the unwanted heavies 120 an opening 121 is provided in 
the troughs 100 towards the discharge end of the deck. This discharge 
opening 121 leads downwardly through a passage 122 to a heavy particle 
discharge location 123 beneath the peak adjacent the trough concerned. The 
discharge location 123 is formed between the baffle walls 113 and the 
baffle wall of an adjacent trough (not shown in FIG. 15). 
Openings 124 are provided in a lower wall 125 of the passage 122 to allow 
an air flow into the discharge opening to maintain separation above the 
opening. 
FIG. 16 is a diagrammatic cross-sectional view of a deck provided with four 
troughs constructed as shown in FIG. 15. For ease of calibration/trimming 
of air flow through the passages 122 additional air flow can be provided 
through control opening 126 from the plenum chamber 117. 
For some materials, for example CRS,-expanded tobacco and most British 
blends, one discharge opening per channel is sufficient to remove the 
majority of the winnows. Burly and Cased blends however are more difficult 
to open and require longer decks and may require more than one discharge 
opening per channel. Using several discharge openings in series together 
with progressively reducing the air flow through the openings will give a 
very discriminating and positive separation of good from bad. 
FIGS. 17 and 18 show how individual/paired discharge opening control can be 
achieved by gating bleed in areas between the discharge openings and 
venting the air flow through the peaks 112. 
In FIGS. 17 and 18 the same reference numerals are used to indicated 
similar parts as in FIGS. 15 and 16. As shown in FIG. 17 air flow through 
the openings 126 is bled off through control openings 127 at the upper end 
of each peak. The openings 127 are provided above the openings 126. With 
this arrangement the bleed openings 127 are more accessible than the 
openings 126 being above the deck and can be reduced or enlarged as 
required to achieve the necessary flow through the discharge openings 121. 
The flow out of the openings 127 is indicated by arrows 128. 
FIG. 18 is a diagrammatic perspective view showing the trough 100, the 
peaks and the baffle walls 113 and 114. It will be appreciated that there 
will be further troughs on each side of the baffle walls shown. With this 
arrangement there are two longitudinally spaced apart discharge openings 
121 in the slot but only one of which is shown in broken lines in the 
drawing. The entrances into the passages 122 through the baffle wall 113 
are indicated by reference numeral 130. In this construction the discharge 
openings 121 in the trough 100 to the left of that shown also exit the 
drawing. These discharge openings 121 leading to openings 131 in the wall 
114. Thus two troughs empty into the same discharge location 123. 
For some tobaccos it may be desirable to provide means to allow good 
material which has inadvertently passed through the discharge openings to 
come out again and FIGS. 19, 20 and 21 show a construction which provides 
for this. Again, the same reference numerals are used to indicate similar 
parts as in FIG. 15. In this construction however baffle walls 135 and 136 
are provided which may be vertical or as shown inclined to each other so 
that the cross-sectional width at their upper ends is less than the 
cross-sectional width across their lower ends. The discharge opening 137 
is however shaped as a venturi by the side plates 138 and the gap between 
the side plate 135 and 138 is closed by a perforated lower wall 139, the 
gap between the side plate 138 and wall 136 being closed by a similar 
perforated lower wall 140. Extending between the plates 138 is a 
perforated screen 141 to catch any heavy material which has passed through 
the discharge opening 137. 
As in the previous constructions air enters the control chamber 116 through 
the perforated walls 139 and 140. The volume of air passing to the shaped 
trough 100 on each side of the discharge opening is controlled as before 
by the baffle plate angle/perforated pattern/open area of the bottom walls 
139, 140 and as before the distribution of air in the trough is controlled 
by the shape/perforation pattern of the trough and the shape of its peak. 
Instead of passing out through a discharge opening and location area 
combination the heavy material passes through the discharge opening 137 
into a shaped section 142 where, the side walls 138 control the velocity 
of air coming up through the perforated screen 141 which is below a point 
A indicated on the drawing. This perforated screen is preferably curved, 
as shown, to encourage stems to orientate lengthwise on it and settle 
below the point A. 
Any good piece of lamina which may have fallen through the discharge 
opening 137 will, by turbulence in the region A, lift to the area 
indicated by reference letter B, and subsequently if they are light 
enough, pass back through the discharge openings 137 to the point C and be 
ejected back into the shaped trough thus leaving only heavy objectionable 
material behind. 
For trimming purposes both the perforated screen 141 and/or the perforated 
lower walls 139 and 140 can be masked. 
FIG. 20 is a graph showing the relative air flow velocities at the various 
points through the trough and the discharge opening along the center line 
142 in FIG. 19. It will be seen that the discharge opening now, in effect, 
contains a venturi which lifts the light material back out through it and 
ejects it back into the trough where the air velocity is controlled by the 
various factors referred to above. Using this configuration material is in 
effect classified twice as this arrangement provides two vertical tiers of 
classification in series thus enhancing the level of discrimination. 
FIG. 21 is a diagrammatic cross-sectional view which shows that the heavy 
material can be carried to the end of the deck by the screen 141 and 
discharged at point 143. The good material 119 is taken off the deck at a 
higher level and discharged at point 144. 
This arrangement can be used where the discharge opening is continuous 
throughout the length of the trough or it can be used for a long final 
discharge opening. If this arrangement is used as a final discharge 
opening in combination with previous openings their take off arrangements 
would be set with an air flow commensurate to only letting big heavies 
through. The final slot according to the construction shown in FIG. 19 
will allow more material through for cleaning up. The air flow through the 
discharge opening at the discharge end of the deck can be arranged to be 
higher than its in feed end by simple masking or making the appropriate 
design to the geometry of the shapes below the opening. 
FIG. 22 is a diagrammatic cross-section through another construction which 
can be used to provide the desired air flow through the trough 100. With 
this arrangement the upper surface of the deck is made up from perforated 
sheet 150 which is carried on baffle elements 151. Each baffle element has 
baffle walls 152, 153 and an upper wall 154. As will be seen the baffle 
walls are shaped to provide the air flow into the trough and the top walls 
154 prevent air flow through the peaks indicated in this embodiment by 
reference numeral 155. Any of the discharge constructions described above 
can be used with this arrangement. 
FIG. 23 shows a typical air velocity profile required for the bed to work. 
It will be seen that at the bottom of the trough the air velocity is 450 
feet per minute, at a mid-point 500 feet per minute plus, as the air slows 
down towards the peak it reaches 450 feet and above the peak 150 feet per 
minute, this being the profile to provide the desired stratification 
effect. This profile can be achieved not only by using a variety of shapes 
of trough but also a variety of perforation patterns in the trough and two 
such arrangement are shown in FIGS. 24 and 25. 
In FIG. 24 a nominal triangular shape is used with a flat bottom to the 
trough 100. The density of holes at the flat bottom 160 of the trough 100 
is ten holes per centimeter. The lower part of the side walls 110 as 
indicated at 161 has eight holes per centimeter which reduces to four 
holes per centimeter at the top 162. Thus in this embodiment the air 
profile is achieved not only by the shape of the trough but also by the 
air guiding means provided by the particular hole pattern. 
FIG. 25 shows another arrangement in which the trough 100 is substantially 
straight sided but the upper part of its walls 112 which form the peaks 
are of triangular construction. With this arrangement the perforation 
pattern has four holes per centimeter in the bottom 163 of the trough 100, 
four holes per centimeter reducing to two holes per centimeter at the 
upper end in the side walls 110 and two holes per centimeter in the upper 
side walls 112 which form the peaks. 
FIGS. 26 and 27 are diagrammatic cross-sectional views of further 
constructions according to the invention and show how the air velocity 
profile required for the bed to work can also be achieved by what is, in 
effect, selected baffling over a flat perforated sheet. In the 
construction shown in FIG. 26 the bed has a number of longitudinally 
extending rail members 170, 171, 172. These rail members are shaped to 
provide together the trough side walls and peaks. Each trough 100 has 
diverging side walls 173, 174 which provide a throat 175 at their upper 
ends. The walls then diverge to provide upper walls 176, 177 which provide 
a mouth to the trough 100- Air is supplied to the troughs 100 from a 
plenum chamber 117 and due to the shape of the trough the throat 175 acts 
as a venturi. The air therefore accelerates upwardly through the trough 
175 and then slows down again as it exits through the throat which in the 
construction shown in FIG. 26 is of a shallow bell shape. This type of 
unit, even when multi-sided shapes are used, is relatively cheap to 
produce and in applications where cost is critical would be a convenient 
design. The heavies could be taken off at any convenient point either by 
openings in the perforated base wall 178 or by allowing the heavies to 
move to the end of the deck in a manner described and shown in FIG. 21. 
FIG. 27 shows another construction of somewhat similar type but in this 
case the rail members 180, 181, 182, 183 are shaped to provide a deeper 
bell shaped portion between upper walls 184,185 above the throat 186. The 
lower walls 187, 188 open out as shown above the support plate 178. 
Although the rail sections are shown as having solid walls air bleeds into 
the troughs could be provided if desired to further enhance the air flow. 
FIGS. 28(a-28(c) show a series of cross-sections through a peak of the type 
of construction shown, for example, in FIG. 15 taken at various points in 
the length of the deck and illustrate how just the shape of the peak can 
be used to increase the opening and separation of the tobacco. FIG. 29 
shows a plan view of the deck incorporating this arrangement and shows two 
troughs 100. The sections A, B and C are indicated in FIG. 28 
appropriately. The peak 190 between the troughs 100 and taken at 
cross-section line A--A is relatively wide and the good tobacco 119 is 
carried at the level of the peak and partly into the troughs 100. The 
section B--B which is at a mid-point in the length of the deck is 
approximately half the width of the peak at A--A but the width of the 
troughs 100 remains constant. As will be seen from FIG. 29 the troughs 
converge towards each other at the discharge end of the deck. The 
alteration in shape of the peak 190 has caused the air flow velocity to 
increase and the good tobacco is now raised somewhat and is only just 
below the peak. Finally, at section C--C at the end of the deck the peak 
has merely become the joint between the two side walls of the trough 100, 
there is air flow through the side walls as indicated by the perforated 
construction and the air flow is now about 800 feet per minute. This 
causes the good tobacco to become totally airborne and completely split 
from the heavy/winnows 120 which remain in the bottom of the trough. With 
these arrangements the final mechanical splitting/air lifting is much more 
positive and easier to achieve. 
This type of construction can be employed with any of the other 
constructions described above to enable easy discharge of the good 
materials. 
FIG. 30 shows a method of cleaning heavy materials or winnows which come 
out of the discharge openings and off the end of the deck. These materials 
may contain a small amount of good tobacco and they can be cleaned as 
shown in FIG. 30, which is a diagrammatic cross-sectional view of the end 
of the apparatus by allowing them to pass through an opening 200 in a 
horizontal deck 201. One side of the opening is perforated at 201 and is 
in communication with the plenum chamber 117. Thus as the heavies 120 pass 
through the opening 200 a blast of plenum air passes through them and 
carries any light materials away into a discharge chamber 203 . The air 
direction through this chamber is indicated by arrow 204 and any good 
materials are carried out into the flow of goods material 119 issuing from 
the deck and passing over a support tray 205. 
This arrangement is most suitable when a mode is employed in which the good 
product is not air lifted off the deck.