Note: Descriptions are shown in the official language in which they were submitted.
2180318
PROCESS AND APPARATUS FOR
TOBACCO BATCH PREPARATION AND EXPANSION
Field Of The Invention
The invention relates to processes and
apparatus for the preparation, treatment and infeed of
tobacco batches particularly in association with
tobacco batch expansion processes. The invention also
provides processes and apparatus for enhancing tobacco
expansion.
Background Of The Invention
In the past two decades, tobacco expansion
processes have become an important part of the
cigarette manufacturing process. Tobacco expansion
processes are used to restore tobacco bulk and volume
which are lost during curing and storing tobacco leaf.
Tobacco expansion processes are also used to increase
the bulk of cured tobacco above that of the tobacco
leaf in order to lower the "tar" and nicotine content
of many cigarette products including low tar and ultra-
low tar cigarettes.
Tobacco expansion processes involving
contacting of tobacco with an impregnant followed by
rapid heating to volatilize the impregnant and thereby
expand the tobacco, are described in U.S. Patent No.
3,524,451 to Fredrickson et al. and U.S. Patent No.
3,524,452 to Moser et al. A process employing a vapor
state impregnation of tobacco followed either by
heating or rapid pressure reduction for tobacco
DD-135-R&D:l
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expansion is disclosed by U.S. Patent No. 3,683,937 to
Fredrickson et al.
Carbon dioxide has been used in tobacco
expansion processes as disclosed in U.S. Patent No.
4,235,250 to Utsch; U.S. Patent No. 4,258,729 to Burde
et al.; and U.S. Patent No. 4,336,814 to Sykes et al.,
among others. In these and related processes, tobacco
is impregnated with carbon dioxide, either in gas or
liquid form, and the impregnated tobacco is subjected
to rapid heating conditions for expansion. These known
carbon dioxide expansion processes, however, require
excessive heating of the impregnated tobacco in order
to achieve substantial and stable expansion. This
excessive heating can harm the tobacco flavor and/or
generate an excessive amount of tobacco fines. In
addition, those processes which use liquid carbon
dioxide for impregnating tobacco often result in
impregnated tobacco in the form of solid tobacco blocks
containing dry ice which must then be broken up prior
to heat treatment. This can harm the tobacco and also
increases the complexity and cost of the expansion
process.
U.S. Patent No. 4,531,529 to White and Conrad
describes a process for increasing the filling capacity
of tobacco, in which tobacco is impregnated with a low
boiling, highly volatile expansion agent, such as a
normally gaseous halocarbon or hydrocarbon, at process
conditions above or near the critical pressure and
temperature of the expansion agent. The pressure is
quickly reduced resulting in expansion of the tobacco
DD-135-R&D:2
_ 21a~.~18
-3-
without the necessity of a heating step to either
expand the tobacco or fix the tobacco in the expanded
condition. The pressure conditions of this process
range from 36 Kg/cmz (512 psi) and higher with no known
upper limit. Pressures below 142 Kg/cm2 (2000 psi) were
used to produce satisfactory tobacco expansion without
excessive fracturing. Normally gaseous hydrocarbons
such as methane, ethane, and propane, are among the
preferred impregnants used in this process.
U.S. Patent No. 4,554,932 to Conrad and White
describes a fluid pressure treating apparatus including
a tubular shell housing a spool assembly. The spool
includes a cylindrical body portion of relatively small
diameter that extends between the two spool ends, which
have a diameter greater than the spool body, but less
than the diameter of the shell. The spool is mounted
within the shell for reciprocating movement between a
loading position outside the shell, a treating position
within the shell, and an unloading position outside of
the shell. When.the spool is within the shell,
deformable sealing rings carried in annular grooves on
the cylindrical ends of the spool are forced radially
outwardly for engagement with the interior of the
shell. This provides a sealed, annular-shaped pressure
chamber inside the shell, in the space between the
spool ends surrounding the smaller spool body. One or
more ports through the shell cooperate with conduit
shaped cavities extending radially into the spool ends
and axially along the spool body to allow input and
removal of processing fluids into and from the annular
DD-135-R&D:3
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2180318
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space around the spool body within the shell. The use
of this apparatus for high pressure impregnation of
tobacco with an expansion agent permits rapid loading
and unloading of tobacco and avoids the closure and
opening problems associated with conventional pressure
sealing and locking mechanisms, such as the pivoting
autoclave lids of conventional pressure vessels. The
spool and shell pressure vessel can thus produce time
savings and improve economics in tobacco expansion.
Tobacco expansion processes, including those
described above and others, must be conducted in batch
processes when impregnation pressures substantially
exceed atmospheric pressure. In order to achieve
efficient and repeatable tobacco expansion in such
batch processes, it is necessary to repeatedly form
tobacco batches of a precise size based on the interior
volume of the pressure treating vessel and/or density
and expansion characteristics associated with the type
of tobacco being expanded. Typically, design of the
batch forming process is constrained by other
manufacturing considerations associated with tobacco
expansion processes including the desire to minimize
leakage of volatile tobacco expansion agent as the
tobacco is formed into batches and then fed and loaded
into a pressure vessel for impregnation.
Summary of the Invention
In one aspect of the invention there is provided a tobacco expansion
apparatus for batch processing which includes a tobacco batch forming
chamber and a horizontally extending conduit defined by side walls and an
2180318
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upper and a lower wall, the conduit having a first portion in operative
communication with the batch forming chamber to periodically receive
individual batches of tobacco from the chamber. A permeable barrier is
operatively associated with the conduit and is mounted for movement
between a retracted position outside of the conduit and a barrier position
within and extending transversely across the conduit at a location between
the first portion of the conduit and a second end of the conduit. A loading
member is arranged to move the individual tobacco batches along axially
adjacent first and second paths within the horizontal conduit toward the
second end thereof. The first path extends between the first portion of the
conduit and a predetermined precompaction position longitudinally spaced
from the barrier position, the space between the precompaction position and
the barrier position defining a precompaction zone. The second path extends
from the precompaction position to a position adjacent the second end of the
conduit and at least one aperture through a wall of the conduit in the
precompaction zone communicates with a source of steam for heating tobacco
in the precompaction zone.
A process for expanding tobacco is also provided and comprises the
steps of:
a) forming a batch of tobacco comprising a predetermined amount of
tobacco;
b) partially compacting said batch of tobacco by providing a loading
member to compress said batch against a permeable barrier;
c) steaming said batch of tobacco while said batch is in said partially
compacted condition;
d) removing said permeable barrier; further compacting said batch of
tobacco by moving said loading member to compress said batch into an
impregnating chamber;
218A31~
e) impregnating said batch of tobacco with an expansion agent; and
f) subjecting the impregnated batch of tobacco to conditions sufficient to
expand the tobacco.
i
v
_ 280318
The tobacco expansion apparatus and processes of the
invention can be employed for expanding tobacco at rapid
throughput rates employing high pressure tobacco impregnation
conditions, and flammable, gaseous expansion agents.
The apparatus and processes of this invention
are particularly useful in conjunction with the
processes and apparatus of U.S. Patent No. 5,483,977 to
Conrad et al., which provides for dramatically
improving tobacco throughput in high pressure tobacco
impregnation systems; and U.S. Patent No. 5,469,872 to
Beard et al., which provides various tobacco batch
forming and feeding processes and apparatus, and other
improvements in high throughput tobacco expansion
processes. The processes and apparatus of these
applications typically involve tobacco impregnation and
expansion cycle times less than 20 to 30 seconds; the
use of pre-heated, high pressure expansion agents such
' 20 as propane; the use of an increased moisture content,
pre-heated tobacco feed; and/or the compression of
tobacco within a high pressure impregnation vessel for
greatly improving use of available space in the
impregnation vessel.
It has been found that tobacco batch forming and feeding
has been found that tobacco batch forming and feeding
steps, particularly in preferred embodiments of the
above-identified Conrad et al., and Beard et al.
patents, present unforeseen difficulties which can be
parti.cular7_y severe because of the rapid rate at which
lily ! ~'~ Rf,l): ';
2180318
-6-
consistent sized tobacco batches must be formed and fed
to an impregnation zone. In practice, it has been
found that tobacco pre-heating and moisturization
unexpectedly complicate high speed tobacco batch
forming and feeding steps because the tobacco forms
clumps under these conditions resulting in a tobacco
feed stream of non-uniform density. Additionally, it
has been found that heating of the moistened tobacco
releases and/or softens various natural tobacco gums
and resins which further complicates the clumping
problem and interferes with transfer of the tobacco
from one location to another since the tobacco tends to
adhere to processing equipment. These difficulties not
only interfere with the batch forming steps, but can
also result in blockage of the tobacco infeed apparatus
in some cases. In those expansion processes which use
flammable, gaseous expansion agents like propane,
overcoming of the clumping problem is further
aggravated by the need for process and apparatus
controls that ensure safe operation of the process.
Disclosed herein are tobacco batch forming and feeding systems
for reliably and economically forming and feeding tobacco batches of
predetermined size to a downstream operation,
preferably a tobacco impregnation operation. This
apparatus includes a tobacco batch forming chamber
defined in part by a substantially vertical inlet wall
and a substantially vertical, abutment wall, which is
horizontally spaced from the inlet wall. An inlet port
through the inlet wall is positioned to admit tobacco
1)1) - 1i'~--lZf,1): ~~
:~
._ 218031 ~
_7_
into the chamber in a direction transverse to the
abutment wall. A pneumatic conveyor is connected to
the inlet for supplying tobacco to the inlet at a flow
rate sufficient to cause the tobacco to accumulate
against the abutment wall. A screen is positioned in
an upper portion of the chamber to allow escape of
pneumatic transport gas associated with the incoming
tobacco while providing an upper barrier to prevent
escape of tobacco from the chamber. A sensor is
operatively associated with the chamber for determining
when a predetermined amount of tobacco has accumulated
horizontally against the abutment wall. The screen is
moveable between at least two vertical positions to
vary the volume of the tobacco batch forming chamber.
Preferably the bottom wall of the chamber is formed at
least in part by a closure member arranged to pivot
downwardly for controlled release of the tobacco
batches through the bottom of the chamber.
This apparatus avoids use of moving parts for
conveying the tobacco, and for-separating the tobacco
into discrete batches, and thus minimizes problems
associated with tobacco clumping including lack of
uniformity in the density of tobacco feed, difficulties
associated with detangling of individual tobacco
clumps, etc. The apparatus can rapidly and
economically provide tobacco batches of consistent,
predetermined size, but can readily be adjusted to
change the size of the tobacco batches in response to
process variations or variations in the nature or
density of the tobacco feed.
DD-135-R&D:7
2180318
_8_
Also disclosed herein is an apparatus and process for transferring a
provides an apparatus and process for transferring a
tobacco batch to an impregnation zone while minimizing
escape of the tobacco expansion agent from the
S impregnation zone into the tobacco feed. The apparatus
includes a tobacco batch forming chamber, preferably of
the type described above. The batch forming chamber is
defined in part by a chamber closure member arranged
for movement between a closed position in which the
closure member forms at least a portion of a bottom
wall of the chamber and an open position in which the
closure member defines a port in a lower portion of the
chamber to release tobacco batches from the chamber. A
vertically oriented tobacco delivery conduit is located
below the batch forming chamber and includes a
separable zone between the chamber closure member and a
conduit closure member positioned below the chamber
closure member. The conduit closure member is arranged
for movement between a closed position defining a
' 20 .substantial seal in the conduit and an open position
defining an opening in the conduit. An inert gas
supply communicates with the separable zone in the
vertical conduit to supply inert gas into the zone.
The separable zone in the vertical tobacco
2S delivery conduit provides a gas barrier that prevents
any substantial amount of impregnation gas from
traveling upwardly through the tobacco delivery conduit
and into the batch forming chamber thereby
cont=aminating the pneumatic supply system. In
30 operation, the conduit closure member is maintained in
1->I~ -n ,'~ lZaii: ~S
;Rs.~
5
2
280318
_g_
the closed position when the chamber closure member is
opened for delivery of a tobacco batch into the
conduit. The conduit closure member receives and
supports the tobacco batch delivered from the batch
forming chamber. When the chamber closure member is
returned to its closed position, the conduit closure
member is opened to release the tobacco batch into a
lower portion of the conduit. The conduit closure
member is then returned to its closed position while
the chamber closure member is maintained in its closed
position to thereby substantially isolate the separable
zone pneumatically from the tobacco batch forming
chamber and from the lower portion of the tobacco
delivery conduit. The inert gas supply in the
separable zone admits inert gas into the pneumatically
isolated zone so that when the chamber closure member
is subsequently opened for delivery of another tobacco
batch into the vertical conduit, any gasses which might
escape into the batch forming chamber are primarily
purge gasses.
Simplification and improvement of the process for
expansion of uniform batches of heated, moistened tobacco
involves forming a batch having a predetermined size from
tobacco having a moisture content above about 12a by
weight. The preformed batch of moistened tobacco is
then contacted with steam to substantially increase the
temperature and moisture of the tobacco batch. The
heated and moistened tobacco batch is then loaded into
IOI) 1 ,'> 11.,1>: ~3
P
t
2180318
o-
an impregnation zone and impregnated with expansion
agent. Preferably the impregnation zone is defined by
a spool and shell apparatus, and steaming of the
preformed tobacco'batch is carried out at a location
closely adjacent the impregnation zone. In accordance
with this aspect of the invention, it has been found
that by separately forming batches of moistened tobacco
and thereafter heating the individual batches, the
problems associated with release and softening of
natural tobacco gums can be substantially avoided.
Moreover, it has been found that direct steam contact
can uniformly heat individual tobacco batches extremely
rapidly, e.g., in a matter of seconds or less, while
also increasing the tobacco moisture level. In
addition, temperature variations between individual
tobacco batches can be minimized by the rapid heating
of the individual tobacco batches at a location close
to the impregnation zone, in turn providing more
uniform tobacco expansion.
A precompaction zone may be provided for heating and steaming the
tobacco batch. A tobacco batch is delivered into a first portion of a
horizontally
extending conduit. A permeable barrier is operatively
connected with the conduit for movement between a
retracted position outside of the conduit and a barrier
position within and extending across the conduit at a
location between the first end and a second end of the
conduit. A loading member is arranged to move
individual tobacco batches along adjacent first and
1)1)- 1 3 '~ -1?Ftl) : ~ U
A
2180318
-~1-
second paths within the horizontal conduit. The first
path extends between the first end portion of the
conduit and a precompaction position spaced
longitudinally from the barrier position; the second
path extends from the precompaction position to a
position adjacent the second end of the conduit. A
tobacco precompaction zone is defined in the conduit
between the precompaction position and the barrier
position, and at least one aperture is provided through
a wall of the conduit in the precompaction zone and
communicates with a source of steam for heating tobacco
in the precompaction zone. Preferably, the tobacco
precompaction zone is positioned closely adjacent a
loading position at which the tobacco batch is
subsequently loaded into an impregnation apparatus.
The use of a tobacco batch precompaction zone in accord
with this aspect of the invention allows the rapid
preparation and feeding of tobacco batches having
optimum moisture content and temperature thus enhancing
throughput and process economies.
The various embodiments disclosed herein can be
used independently or in combination. In preferred
e~odiments that include a tobacco batch impregnating and
expansion system, a profoundly effective system apparatus
can be provided for sizing, heating, feeding and expanding
tobacco to thereby provide significant advances in
tobacco throughput and tobacco expansion economies.
1)I> ;~~ 12r,1): 1 7
2180318
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Brief Description Of The Drawings
In the drawings which form a portion of the
original disclosure of the invention:
Figure 1 is a schematic view, in perspective,
of a preferred tobacco batch sizing, feeding and
heating apparatus of the present invention in which two
separate tobacco batch forming, feeding and heating
systems are provided for simultaneously preparing and
loading two preheated and premoistened tobacco batches
onto a reciprocating spool body;
Figure 2 is a front elevation view of the
apparatus of Figure 1;
Figure 3 is a side elevation view taken along
lines 3-3 of Figure 2 and illustrates a preferred
tobacco batch forming chamber of the invention;
Figure 4 is an enlarged, partially broken
away side elevation view of vertical and horizontal
tobacco delivery conduits located below the batch
forming chamber shown in Figure 3 and illustrates the
20~ pneumatically separable zone within the vertical
conduit for preventing escape of the gaseous expansion
agent from the impregnation zone into the batch forming
chamber, and also illustrates the loading member within
the horizontal conduit, shown at a precompaction
position;
Figure 5 is a partially broken away plan view
taken along lines 5-5 of Figure 4 illustrating a
preferred arrangement of apertures within a steam
manifold for evenly injecting steam into a precompacted
tobacco batch and also illustrates a plurality of
DD-135-R&D:12
a ' 2180318
-13-
closely spaced tines shown in cross-section which move
into and out of the horizontal conduit for providing a
permeable tobacco barrier; and
Figure 6 is a partially broken away cross-
sectional view of Figure 5 taken along lines 6-6
illustrating a precompacted tobacco batch positioned
between the loading member and the permeable tobacco
barrier which is adjacent a loading position at which
the tobacco batch is subsequently loaded onto a
reciprocating spool body forming a portion of a tobacco
impregnation apparatus, and also illustrates preferred
condensation blocking plugs positioned over apertures
within a steam manifold located above the tobacco
precompaction zone.
Detailed Description Of The Preferred Embodiments
Preferred process and apparatus embodiments
of the invention are set forth below. While the
invention is described with reference to specific
processes and apparatus, including those illustrated in
the drawings, it will be understood that the invention
is not intended to be so limited. To the contrary, the
invention includes numerous alternatives,
modifications, and equivalents as will become apparent
from a consideration of the foregoing discussion and
following detailed description.
Figure 1 schematically illustrates preferred
impregnation processes and apparatus of the invention,
including a spool and shell apparatus generally
DD-135-R&D:13
218~3~g
-14-
constructed in accordance with U.S. Patent No.
4,554,932, issued November 26, 1985 to Conrad et al.;
U.S. Patent No. 5,483,977 issued January 16, 1996 to
Conrad et al.; and U.S. Patent No. 5,469,872 issued
No~~ember 28, 1995 to Beard et al. Various details disclosed in the '932,
'977, and '872 patents, are not repeated here for the
sake of brevity. However, reference may be had to the
'932, '977, and '872 patents for such details.
The spool and shell assembly detailed in the
above '932, '977, and '872 patents includes a tubular
shell housing a spool assembly. The spool includes a
cylindrical body portion of relatively small diameter
that extends between the two spool ends, which have a
diameter greater than the spool body, but less than the
diameter of the shell. The spool is mounted within the
shell for reciprocating movement between a loading
position outside the shell, a treating position within
the shell, and an unloading position, also outside of
the shell. While in the loading position, the spool is
preferably loaded with tobacco on both of its opposing
sides.
Figures 1 and 2 illustrate a preferred
apparatus of the present invention, including two
tobacco batch forming and processing systems, each
including a batch forming chamber, and vertical and
horizontal conduits which cooperate to simultaneously
form, process, and load two tobacco batches onto a
spool for subsequent impregnation with an expansion
DD-135-R&D:14
X180.318
-15-
agent. In the following, one of the tobacco batch
forming and processing systems is described in detail
although it will be understood that two substantially
identical systems are provided as seen in Figures 1 and
2.
Figure 3 illustrates a preferred tobacco
batch forming apparatus. Tobacco in any of various
forms including the form of leaf (including stem and
veins), strips (leaf with the stem removed), cigar
filler, cigarette cut filler (strips cut or shredded
for cigarette making), mixtures of the above, scrap
tobacco and tobacco shorts, etc., and preferably cut
filler tobacco, is delivered to the tobacco batch
forming chamber 10 through a tobacco inlet or conveyor
11. Prior to delivery into the batch forming chamber
10, the tobacco is preferably first treated by any of
various means known to those skilled in the art (not
shown) to increase its moisture content to a value of
at least about 13o by weight, preferably at least about
16 percent by weight, and more preferably above about
20 percent by weight. When cut filler is treated in
accord with the invention, the cut tobacco which is
normally moistened to enhance cutting can be directly
used in the invention or treated to further increase
moisture. The moistened tobacco is then delivered to
the tobacco batch forming chamber 10 by any
conventional means, but in the most preferred
embodiment is pneumatically delivered through the
tobacco inlet 11 under pressure generated by a vacuum
source 12.
DD-13S-R&D:15
?180318
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The tobacco batch forming chamber 10 includes
a substantially vertical inlet wall 13, through which
the tobacco inlet 11 communicates with tobacco batch
forming chamber 10, and a substantially vertical
abutment wall 15, which is spaced horizontally from the
vertical inlet wall 13. The tobacco is delivered to
the batch forming chamber 10, preferably by a pneumatic
conveyor, and enters the chamber 10 through tobacco
inlet 11 under the pressure of the vacuum source 12,
which provides sufficient force to propel the tobacco
across the chamber, causing the tobacco to accumulate
against abutment wall 15.
The tobacco batch forming chamber 10 further
includes a chamber closure member 16 which forms the
bottom wall of the tobacco batch forming chamber, and
an adjustable screen 17 which forms the top wall of the
chamber. Although gas permeable to allow the ready
passage of air therethrough, the screen 17 is of
sufficiently fine mesh to prevent the passage of
tobacco and thus provides an upper barrier preventing
exit of the tobacco from the batch forming chamber 10.
Thus, the tobacco being delivered through inlet 11 will
contact the abutment wall 15 and accumulate adjacent
the wall 15 below the screen 17. In the most preferred
embodiment, the screen 17 is provided as an upper
barrier to the tobacco batch because the screen-like
configuration permits the air pressure created by the
vacuum source 12 to exit the batch forming chamber
through the vacuum source 12 while the tobacco is
maintained below the screen 17. However, other
DD-135-R&D:16
2180318
-17-
aperatured or foraminous members which permit air to
exit while maintaining the tobacco within the chamber
can alternatively be used to provide an upper
barrier as will be apparent.
5 The screen 17 is adjustable in its vertical
position, and thus can be moved to different vertical
positions and thereby define a different volume for the
tobacco batch forming chamber 10 and thus for tobacco
batches formed therein. This is particularly
10 advantageous in light of the fact that different
tobaccos, e.g., cut filler, leaf, cigar tobacco etc.,
can have different densities and packing
characteristics. The adjustable barrier 17 for the
chamber 10 thus allows variations in tobacco types as
well as variations in processing needs to be readily
accommodated in the formation of different sized
tobacco batches.
The position of the screen 17 is
advantageously adjusted by means of a vertical position
adjustor 18 which, in the most preferred embodiment,
comprises a vertical drive associated with a control
for actuating the drive according to a predetermined
set of instructions. The predetermined set of
instructions can be based on the density of the tobacco
being processed, processing variables and the like.
While an automated position adjustor 18 is depicted in
the drawings, the present invention is not limited to
this precise configuration and other means of adjusting
the vertical height of the adjustable screen 17, such
as, for example, a mechanically adjustable gear or the
DD-135-R&D:17
_ ?180~~8
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like can readily be used in the invention as will be
apparent.
To ensure a consistent and substantial flow
of moistened tobacco through the pneumatic conveying
tube supplying tobacco inlet 11, the tobacco inlet tube
or conveyor 11 is advantageously provided with separate
portions of differing diameter, including a first
portion 20 and a second portion 21. The first portion
is associated with the tobacco inlet 11 at tobacco
inlet wall 13 and the second portion 21 of inlet tube
11 is located at or near the tobacco supply from which
the tobacco is retrieved. The diameter of the second
portion 21 is larger than the diameter of the first
portion 20 to provide a somewhat increased vacuum
therein which ensures that tobacco feed is consistently
picked up and supplied to the tobacco inlet 11 by the
second portion 21 of the conveyor 11. In a preferred
embodiment, the smaller conveyor tube portion 20 can
have a 4 inch diameter while the larger conveyor tube
portion 21 can have a 5 inch diameter to provide a
tobacco flow rate of 3 lbs of tobacco every 5 seconds.
In general, this inlet tube arrangement reduces the
amount of force used to convey the tobacco while
achieving a relatively high conveying rate and also
minimizes the pressure drop, i.e., pressure
differential, used to convey the tobacco. In turn,
this reduces compression of the tobacco while it is
being conveyed which improves the consistency of the
tobacco batches. On the other hand, if the tobacco is
conveyed at a relatively slow rate with a relatively
DD-135-R&D:18
21 X0318
-19-
high pressure drop, the force of the conveying air can
cause the tobacco to be compressed which produces a
higher density in the tobacco batches, thus interfering
with the formation of consistent sized tobacco batches.
Operation of the tobacco batch system of
Figures 1 and 3 is initiated by the delivery, under the
pressure provided by the vacuum source 12, of tobacco
to the batch forming chamber 10 via tobacco inlet 11
through inlet wall 13. The tobacco entering chamber 10
is constrained vertically by the adjustable screen 17
and is horizontally constrained by the abutment wall
15. Under the pressure of the vacuum source 12, the
tobacco is delivered in a flow direction transverse to
the abutment wall 15 such that it accumulates
horizontally in the tobacco batch forming chamber 10.
A position sensor 22 detects when a predetermined
amount of tobacco has been received within tobacco
batch forming chamber 10.
In one embodiment of the invention, the
sensor 22 is positioned to detect when the horizontal
accumulation of tobacco against the abutment wall 15
has reached a predetermined distance from the abutment
wall 15. Since the side, upper, and lower walls of the
chamber 10 are fixed, the predetermined distance
defines the volume of the tobacco batch. While any
conventional position sensor 22 can be utilized, in one
preferred embodiment one or more optical sensors, e.g.,
a light source and photocell detector, are provided in
optical alignment on opposed sides of, or above and
below, the chamber 10, at the predetermined distance.
DD-135-R&D:19
2180310
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In another advantageous embodiment, a proximity
detector in the form, e.g., of a capacitance sensor,
can be provided at the predetermined location along a
wall, and/or the top or bottom of the chamber 10 to.
detect the predetermined horizontal accumulation of
tobacco against the abutment wall 15.
Alternatively, or in addition to the position
sensor 22, a pressure sensor 23 can be used to detect
accumulation of the predetermined amount of tobacco in
the batch forming chamber 10. Sensor 23 is preferably
a pressure detector which detects a predetermined
pressure differential between a location above the
adjustable screen 17 and a location below the screen
17. As tobacco accumulates against abutment wall 15 an
increasing portion of the screen 17 becomes covered.
The pressure differential across the screen 17 thus
increases as more tobacco accumulates in the chamber
10. Accordingly, the pressure differential reaches the
predetermined setting when a predetermined amount of
tobacco has accumulated in the chamber 10.
When either or both sensors 22 and/or 23 have
detected the formation of the predetermined tobacco
batch size within the batch forming chamber 10, a
pneumatic valve 24 located in vacuum line 12A is closed
which causes termination of tobacco delivery to the
chamber 10. The chamber closure member 16, which is
maintained in its closed position during the chamber
filling operation is then moved to an open position
thereby forming a port in the bottom wall of the
chamber 10 which releases the tobacco batch from
DD-135-R&D:20
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-21-
chamber 10. The chamber closure member 16 is
preferably a planar wall member 25 which pivots about a
pivot point 26 although differing constructions can be
used as will be apparent.
Advantageously, the chamber closure member 16
is operated by an actuator 27 (Figure 2), which is
connected to a control 28, which in turn is connected
to one or both of sensors 22 and/or 23 and to an
actuator for pneumatic valve 24. Alternatively, the
chamber closure member 16 and valve 24 can be operated
manually in response to signals from one or both of
sensors 22 and/or 23. Actuator 27, best seen in Figure
3, moves the chamber closure member 16 from a closed
position forming the bottom of the batch forming
chamber 10, as is shown in cross-section in Figure 4,
to an open position which is best illustrated in Figure
1. In the preferred embodiment in which the actuator
27 communicates with the sensor 22, and/or 23 via
control 28, the control 28 can be a series of pneumatic
or electrical switches, or can be a microprocessor
provided with a predetermined set of.instructions for
initiating operation of the closure member actuator 27
and valve 24.
Located below the batch forming chamber is a
vertically oriented conduit 30 which comprises a
separable zone 31 defined between the closure member 16
and a conduit sealing member 32 (Figure 2). The
conduit 30 also includes a closure member associated
with its bottom end, in the form of a conduit closure
member 33. The conduit sealing member 32 can be
DD-13S-R&D:21
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substantially similar in configuration to the chamber
closure member 16 and is preferably a substantially
planar member which pivots about a pivot point 36
between a closed position in which the conduit is
generally sealed, although typically not pneumatically
sealed, and an open position in which the conduit is
open. The conduit closure member 33 pivots upwardly to
provide a port or exit for the tobacco batch from the
lower end of the vertical conduit 30, and pivots
downwardly to close the lower end of the conduit.
Preferably the conduit closure member 33 also functions
to compact tobacco exiting the vertical conduit 30, as
discussed later. As best seen in Figures 1 and 4, the
conduit closure member 33 comprises a flat planar
surface 38 which pivots about pivot point 39. The
conduit sealing member 32 and the conduit closure
member 33 are preferably operated by actuators 40 and
41, respectively.
The conduit sealing member 32 and the conduit
' closure member 33 are advantageously operated in
cooperation with one another. The conduit sealing
member 32, when in its closed position, receives a
tobacco batch released from the batch forming chamber
10, and temporarily supports the tobacco batch within
vertical conduit 30. While the tobacco batch is being
released from the batch forming chamber 10 via the
chamber closure member 16, and for a short time
thereafter, both the conduit sealing member 32 and the
conduit closure member 33 are maintained in their
closed positions, thereby forming dual physical
DD-135-R&D:22
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barriers to the passage of any expansion agent upwardly
into the batch forming chamber 10. Subsequently, when
the chamber closure member 16 has returned to its
closed position, the conduit closure member 33 is moved
to an open position and then the conduit sealing member
32 is moved to its open position which releases the
tobacco batch supported thereon into the vertically
oriented conduit 30. The tobacco batch then falls past
the now open conduit closure member 33, and out of the
vertically oriented conduit 30.
An inert gas, such as nitrogen is emitted
through ports 42 to blanket the generally sealed
portion of the vertical conduit 30 between the batch
forming chamber closure member 16 and the conduit
sealing member 32 when both are closed. The nitrogen
gas blankets the separable zone and because it is
admitted under positive pressure and is a lighter gas
than propane, it forms a gaseous barrier within the
separable portion of the vertical conduit 30 against
any tobacco expansion agent, such as propane, which may
enter into the bottom of the vertically oriented
conduit 30, and thus minimizes the likelihood of the
expansion agent escaping upwardly through the vertical
conduit and into the batch forming chamber 10.
The control 28 coordinates operation of the
chamber closure member 16, the conduit sealing member
32, and the conduit closure member 33 to provide for
the delivery of tobacco through the conduit 30, and the
simultaneous closure of the separable zone, which in
turn ensures that the propane or other expansion agent
DD-135-R&D:23
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will not escape through the vertically oriented conduit
30 into the batch forming chamber 10, (at least without
substantial dilution and blanketing by the inert gas)
and/or into the vacuum source 12 while the tobacco
batch is delivered through conduit 30. This is
achieved by the coordinated operation of the three
members 16, 32, 33.
With reference to Figure 4, when a tobacco
batch 43 of predetermined amount, i.e., volume or
weight, has accumulated against the abutment wall 15 of
the tobacco batch forming chamber 10, the sensors) 22
and/or 23 provide an appropriate signal to the control
28 (Figure 2), which then stops the delivery of tobacco
into the chamber 10 by initiating closure of valve 24.
Advantageously the control 28 also verifies that the
conduit sealing member 32 is in a closed position and
then initiates the opening cycle operation of the
chamber closure member actuator 27 causing the chamber
closure member 16 to pivot in the downward direction
about pivot point 26 thereby permitting the tobacco
batch 43 to fall into the vertically oriented conduit
30.
The tobacco batch 43 then falls onto the
closed conduit sealing member 32. Control 28 then
initiates the closure cycle operation of the chamber
closure member actuator 27 causing the chamber closure
member 16 to return to its closed position thereby
sealing the separable zone between the batch forming
chamber closure member 16 and the conduit sealing
member 32. Once chamber closure member 16 has returned
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to its closed position, the control 28 initiates
opening of pneumatic valve 24 to thereby begin the
pneumatic delivery of tobacco into the chamber 10.
While a new tobacco batch is being formed in
the chamber 10 and the chamber closure member 16 is
maintained in the closed position, the control 28 sends
an opening signal to the actuator 40 (Figure 3) of the
conduit closure member 32 causing it to pivot
downwardly about pivot point 36 and thereby permit the
tobacco batch to fall downwardly and out of the
separable zone 31. Prior to the opening of the conduit
sealing member 32, the control 28 sends an opening
signal to the actuator 41 for the conduit closure
member 33 causing the conduit closure member 33 to
pivot upwardly about pivot point 39 to provide an exit
port 45 at the bottom of the conduit 30. The tobacco
batch 43 falling from the conduit sealing member 32
exits the vertically oriented conduit 30 through port
45. The conduit sealing member 32 and the conduit
closure member 33 are then returned to their closed
positions whereupon a new cycle is initiated by release
of a new tobacco batch from the batch forming chamber
10.
A particularly advantageous feature of this
tobacco batch forming and feeding sequence is that this
particular combination not only maintains the tobacco
expansion agent below the vertically oriented conduit,
but it also improves the distribution of the tobacco
and the density uniformity within the tobacco batch.
When the tobacco batch falls through the vertically
DD-135-R&D:25
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oriented conduit 30 and impacts the planar surface of
the conduit sealing member 32 under the force of
gravity, the resultant forces within the tobacco batch
cause it to spread more or less evenly on the surface
of the conduit sealing member 32. The distribution of
tobacco within tobacco batch is further normalized as
it subsequently falls out of the separable zone 31,
through the port 45 of the vertical conduit, and then
impacts on the lower wall 46 of a horizontal conduit
47.
In the above-described embodiment, the
coordinated operation of the various steps and
apparatus for forming and transporting tobacco batches,
including operation of the pneumatic conveyor, the
chamber closure member, the conduit closure member, and
the conduit closure member have been described in the
context of a single integrated control. However, it
will be apparent that different and widely varying
controls can be used in the invention. For example,
the coordination of the process steps and apparatus
control can involve individual controls, can be
coordinated with upstream or downstream operations or
conditions, and/or mechanical controls can be
implemented if desired.
Located below the vertically oriented conduit
is the tobacco batch receiving zone 44 of horizontal
conduit 47. The conduit 47 is substantially defined by
sidewalls 48, a lower wall 46, and an upper wall 49. A
loading member 50 having a concave, semi-cylindrical
30 face, (best illustrated in Figure 4), is positioned
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within the horizontal conduit 47 for axial movement
within the horizontal conduit 47 to move the tobacco
batch in the receiving zone 44 along the lower wall 46
of the horizontal conduit. The loading member 50 is
operatively connected by a rod 51 to a reciprocating
force means such as a hydraulic piston 52 or the like
for cyclic movement along a path between fully
retracted and fully extended positions. In its fully
retracted position, the loading member 50 is positioned
upstream of the tobacco batch receiving zone 44. In
its fully extended position, the loading member 50 is
positioned adjacent a spool 53 of a tobacco
impregnation apparatus for loading of the tobacco batch
onto the spool 53.
Port 45, which communicates between the
vertical conduit 30 and the horizontal conduit 47,
advantageously extends transversely across the full
width of the horizontal conduit 47 so that the tobacco
batch fed to the receiving zone 44 is distributed
substantially uniformly across the width thereof.
After the tobacco batch is delivered to the receiving
zone 44, the conduit closure member 33 pivots closed.
If the height of the tobacco batch exceeds that of the
horizontal conduit 47, the conduit closure member 33
will compress the tobacco batch into the space within
the horizontal conduit 47 as it moves into its closed
position.
A gas permeable barrier 54 in the form of a
plurality of parallel, closely spaced tines 55 is
retractably positioned within the horizontal conduit 47
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between the receiving zone 44 and the spool 53. The
tines 55 are received in a plurality of apertures 56
(best seen in Figure 6), extending through the upper
wall 49 of the horizontal conduit 47, and are mounted
for reciprocal movement between a retracted position
outside of the conduit and a barrier position 57 within
and extending transversely across the conduit 47. When
in its barrier position, the permeable barrier 54
prevents forward movement of the tobacco batch along
the horizontal conduit 47. In addition the permeable
barrier 54 also preferably forms a compressing surface
which cooperates with the loading member 50 to provide
precompression of the tobacco batches moved along the
horizontal conduit 47 by the loading member 50. The
closely spaced tines 55 which form the permeable
barrier 54 in preferred embodiments of the invention
provide a barrier for the tobacco batch, yet permit air
pressure created by the moving loading member 50 to
exit the horizontal conduit 47.
As best illustrated in Figure 6, a tobacco
heating zone 63 is provided in the horizontal conduit
47 upstream of and adjacent the permeable barrier 54.
A plurality of steam injecting ports 68 are provided
through the upper wall 49 of the horizontal conduit 47
within the heating zone 63. These ports permit steam
shown generally by arrow 70 to be injected into the
heating zone to rapidly heat and moisten a tobacco
batch 43 while it is positioned in the heating zone 63,
and preferably maintained in a compressed state between
the loading member 50 and the tines 55. Each of the
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steam ports 68 advantageously communicates with a steam
manifold 69, located above the tobacco heating zone,
via a condensate blocking plug 71 comprising a
longitudinally passage 72. As seen in Figure 6, the
condensate blocking plug 71 and its longitudinally
passage 72 extend upwardly above the lower surface 73
of the steam manifold 69 to permit steam to pass
through the condensate blocking plug 71 while
preventing any liquid condensation on the lower surface
73 of the steam manifold 69 from entering into the
heating zone 63. The walls of the steam manifold 69
are also advantageously configured to prevent
condensation from passing through the steam ports. As
seen in Figure 6, the manifold extends in a dome-like
fashion above the heating zone so that any condensation
forming on the manifold wall, will be carried
downwardly along the dome-like wall and will thus not
drip onto the open passages in the condensate blocking
plugs 71.
The use-of steam for heating of the
tobacco batch in the heating zone 63 is particularly
advantageous because heat can be effectively
transferred to a tobacco batch during a time of only a
few seconds or even less. This is particularly the
case when the tobacco batch is maintained in a
relatively small zone in a compressed state. At the
same time the moisture level of the tobacco can also
can be increased by the steam in an added moisture
amount up to about 2 to about 4 percent by weight. The
temperature of the steam injected is sufficient to heat
DD-135-R&D:29
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the tobacco to a temperature above ambient temperature,
preferably above about 150°F, more preferably a
temperature of above 175°F, e.g., to a temperature of
150° to about 200°F.
Because preferred expansion processes used in
the present invention can readily expand tobacco of
different and various densities, and different batch
sizes, it can be advantageous to vary the size of the
heating zone, and/or the rate at which heat is added to
the heating zone on a unit volume (based on the heating
zone volume) basis. This can be accomplished in one
embodiment of the invention by employing a plurality of
steam injecting ports 68 which are distributed in a
grid-like fashion and which are constructed so that
they can be selectively covered by a barrier such as an
obstructing plug 74 shown in Figure 5. The obstructing
plugs 74 are provided to prevent steam from entering
preselected ones of the ports. This allows less steam
and or heat to be applied to a less dense or smaller
volume tobacco batch. Figure 5 depicts a top plan view
of one advantageous steaming port configuration within
upper wall of the heating zone 63. As shown in Figure
5, several steaming ports contain obstructing plugs 74,
while others contain condensate blocking plugs 71.
While a grid-like port configuration is depicted in
Figure 5, and-individual obstructing plugs 74 are
illustrated, it will be apparent that numerous
different configuration of ports, and various
arrangements for selectively blocking or separately
DD-135-R&D:30
21~0.3i8
-31-
feeding steam to selected single ports or groups of
ports can be used.
The steaming ports 68 can have various
diameters but preferably are a predetermined size to
control the velocity and quantity of the impregnating
steam. In the preferred embodiment, wet steam, at low
pressure, e.g. 15 psi, is used and the ports are
configured to emit the wet steam under sufficient
velocity to rapidly increase the tobacco temperature to
between about 125°F about 200°F as discussed above. In
certain situations when maximum tobacco expansion is
not required, the tobacco batches may not need
additional moisture and/or heating. In such instances,
the steaming step can be eliminated.
Preferably, the walls of the horizontal
conduit are heated by heating elements 82, best
depicted in Figure 1, in order to prevent condensation
formation in or around the tobacco batch. In order to
achieve consistent tobacco expansion at a desirably
20high level, the moisture added to the tobacco is
advantageously distributed through the tobacco in a
relatively uniform manner. However liquid condensate
is believed to be absorbed and concentrated in small
areas of the tobacco, and thus the exposure of the
tobacco to liquid condensate is preferably avoided.
Preferably, the horizontal conduit 47 has a
substantially rectangular cross-section and is formed
of a material, such as hardened aluminum, which can
withstand wear associated with the repeating horizontal
movement of the loading member 50. The side walls 48
DD-135-R&D:31
-- 2180318
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of the horizontal conduit 47 are provided with a force-
bearing surface 84 of a material which produces a
surface upon which the loading member 50 may readily
move without wearing the more costly and friction-
causing surface of the horizontal conduit. Surface 84,
in a preferred embodiment, is formed of a hardened
plastic to provide lubrication between the interior
walls of the horizontal conduit and the exterior
surface of the loading member and to prevent buckling
or jamming of the loading member. Exemplary materials
used to form the force bearing surface 84 include
polyetheretherketone (PEEK), available from ICI
Americas, Inc., and RTP Co.
In operation, the loading member 50 is moved
in the direction towards the spool 53 upon closure of
the compacting member 33, to move the tobacco batch
axially along the horizontal conduit 47. Prior to or
during initial movement of the loading member 50, the
tines 55 are moved into the barrier position .57 within
the conduit 47. The movement of the loading member 50
is paused when the loading member 50 reaches a
predetermined precompaction position, in or adjacent
the heating zone, spaced longitudinally upstream from
the tines 55. The precompaction position can be varied
for varying tobacco batches and is determined based on
the volume, density, and make-up of the tobacco batch.
Preferably the precompaction position sufficiently
close to the tines 55 that the tobacco batch will
occupy the entire volume between the loading member and
the tines. Advantageously the tobacco can be
DD-135-R&D:32
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compressed at least a small amount, e.g., 10-50% by
volume against the tines 55. While the tobacco batch
is maintained against the tines 55, steam 70 is
injected into the tobacco batch 43 for a time
sufficient to heat the tobacco.
The tines 55 are then withdrawn from the
horizontal conduit 47, and the loading member 50 is
once more moved axially along the conduit until it
reaches its fully extended position adjacent spool
assembly 53. The semi-cylindrically shaped loading
member 50 cooperates in its fully extended position to
form a portion of a shell around the connecting rod of
the spool 53 so that the compressed tobacco is
maintained on the connecting rod of the spool during
its movement to an impregnating position. The spool is
thus loaded with heated, moistened tobacco at the
loading position as depicted in Figure 6.
Preferably, the movement of the loading
member, the insertion and retraction of the tines, and
the delivery of steam into the manifold, are
coordinated and controlled by a control means
comprising a predetermined set of instructions to
achieve the process as previously set forth. It will
be apparent that different and widely varying controls
can be used in the invention, as discussed previously.
The invention has been described in
considerable detail with reference to preferred
embodiments. However, many changes, variations, and
modifications can be made without departing from the
spirit and scope of the invention as described in the
DD-135-R&D:33
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foregoing specification and defined in the appended
claims.
DD-135-R~D:34
