Note: Descriptions are shown in the official language in which they were submitted.
103913~;
BACKGROUND O~ THE INVENTION
.
Historically, the harvesting and curing of tobacco
has presented the greatest bottleneck to efficient, economi-
cal production. Tobacco leav~s were hand harvested over
a five to eight week period and the leaves strung on sticks
which were placed on tiers in curing barns 16 to 24 feet high.
Labor requirements for harvest through curing were in the
range of 180 to 220 man-hours per acre. Mechanical harvest-
ing and bulk curing systems introduced during the 1960's
reduced these requirements to about 50 man-hours per acre.
The advent of mechanical harvesting introduced a
new problem, however, from a material handling viewpoint.
A machine is capable of harvesting up to 12 to 15 tons of
material per day. This meant that hand rac~ing of tobacco
! at the barn now became the bottleneck to further gains in
- efficiency.
My research has indicated certain limitations to
the current approaches, particularly in regard to achieving
maximum economy in the handling and curing system. With
large containers, tobacco is inherently packed to a higher
~'' ~
rw/S~ 2 -
1039136
density than in the normal racks and barn capacity is
increased, llith the small racks, the avera~e density of
tobacco in the curjn~ space is six to eight pounds/ft3;
~rhereas, with the large conta~ners, the average density
may be 14 to 18 pounds/ft3, For tinnely curing and to
achieve hi~h quality, it is necessary that static pressures
in the inlet plenum be increased to move air at the required
rate through the more dense tobacco. Furthermore, since
the drying front moves progressively from the ~nlet to
outlet, increasing this djstance through ~!hich the air must
be forced has the effect of increasing power re~uirements
for the fan and increasing the length of the drying period,
factors which are contrary to the goal of improving curing
efficiency. Another very important factor is that the
tobacco within the container near the exit side is subjected
to near saturated air conditions throughout the vellowing
phase and for some time into the drying phase until a con-
siderable portion of water in the tobacco has been removed
from leaves near the inlet side. Ilhile this may be
satisfactory for many leaf conditions, a number of con-
ditions have been noted in ~rhich leaf deterioration can
rapidly occur. Under certain field conditions, depending
upon weather ? 50i 1 moisture and temperature, soil pathogens,
(particularly Erwinia) can develop rapidly and be splashed
onto lower leaves of the plant. During curin~, at high
humidities, infected leaves can develop soft rot and rapidly
deteriorate both midrib and laminar portions of the leaf.
- During the past two years, several cases of soft rot have
1039~36
been observed to occur jn large curing containers ~Ihere
tobacco was infected by leaf rotting pathogens 7 wjth
losses up to 50~. It appears evident, that there are
strict limitations to the practical distances throu~h
~lhich the air passes through tobacco in lar~e containers.
SUMMARY OF THE PRESENT INVENTION
The present invention relates to a new curing
module design and curin~ system which greatly increases
the efficiency of handljng and curing tobacco, improves
cured leaf quality, facilitates mechanized load-out in
preparing cured leaf for market, and substantially reduces
curing equipment cost per pound of cured lc-af. These
advantages are accomplished by prov;ding a curing module
design which provides for horizontal, cross-flow air move-
ment through the modules with practical levels of tobaccoresistance to airflow, fork lift handling and stackin~
of curing modules to increase capacity within a curing
structure, and side-unloading capability. The cross-flow
curing modules are moved easily into the curing facili~y
by fork-lift equipment and, by the arrangement of stack-
in~, forms a high pressure plenurn on one side of the
modules ~Ihich permits effective air movement through the
ti~htly packed tobacco ~Ihile providinq ~reatly increased
curing capacity per square foot of floor area. Further-
more, the module desi~n ~ith side unloading featurepermits rapid, mechanized unloading for market prepara-
tion. Unlike existin~ bulk curing systems "~hich
1039136
necessitate incr~ased statia pressures for the inlet
plenum as heighk of curing container is increased, this
system permits the establishment of a fixed static pressure
as height of the column of material to be cured is increased.
Broadly speaking, therefore, the present invention
may be defined as a method of curing or drying tobacco com-
prising; a) placing tobacco to be cured in a container of
rectangular solid configuration having gas impervious top
and bottom walls, a pair of opposed generally impervious
side walls and a pair of gas pervious opposed side walls;
b) supporting the tobacco in the containers by passing a
plurality of rods therethrough with the axes of the rods
parallel to the place of the top and bott~m walls; c) stack-
ing a plurality of the containers in a curing barn in at least
one row with the row being spaced from a pair of opposed
side walls of the barn to define a pair of isolated ohambers
between the opposed side.walls of the barn and the air per-
vious side walls of the containers, and the chambers being
generally coextensive with the row of containers; d3 direct-
ing a curing or drying gas stream into one of the isolated
chambers; and.e) withdrawing gas from the other of the isol-
ated chambers whereby the curing gas stream flows generally
horizontally and uniformly through the tobacco maintained in
the containers of the row.
. The above method may be carried out through a tobacco
curing or drying system comprising: a) a barn having a floor,
roof and side walls; b) a transverse partition extending
between a pair of opposed side walls and separating the
interior of the barn into a curing or drying chamber and a
gas conditioning chamber; c) gas heating and gas moving means
in the gas conditioning chamber; d) a plurality of containers
103'~1;~6
of rectangular solid con~iguration each having gas imper-
vious top and bottom walls, a pair of generally gas imper-
vious opposed side walls and a pair of gas pervious opposed
side walls; e~ a plurality of rods extending between the
pair of gas impervious side walls parallel to the top and
bottom walls; f) said pluralit~ of containers b~ing stacked
in at least a pair of spaced rows in the curing or drying
chamber with each row being spaced from a wall of the curing
and drying chamber to define with the walls of the chamber
gas outlet zones and said space between the pair of rows
comprising a gas inlet zone; and g) means connecting the
gas inlet zone and the pair of gas outlet zones with the
gas outlet and inlet respectively of the gas moving means
in the gas conditioning chamber.
OB~ECTS OF THE PRESENT INVENTION
To provide a-mechanized handling, curing and
unloading system which enables direct placement of tobacco
into curing modules holding 1000 pounds or more of tobacco.
To provide a curing module of simplified design
and construction which reduces equipment cost per pound
of cured material and which permits cross-flow circulation
of the curing air with dimensions such that air flow resis-
tance is maintained wi-thin nominal levels and fan efficiency
is highO
To provide a curing module which enables establishing
26 of yellowing and drying conditions which
rw/'i~
iO39136
minilnize the development of leaf deterioration by
soft-rot pathogens and which permits timely remova1 of
moisture and reduced curing time over existing bulk
systems
To provide a curing module which supports the
tobacco by horizontal tines or rods which penetrate the
tobacco perpendicular to the general plane of tobacco
leaves and which permits horizontal passage of forced
- conditioned air through the tobacco such that yellowing
drying and conditioning phases of curing are performed
with high reliabllity and uniformity of cured leaf Droduct.
To provide a mndular curing system ~hich receives
the above cross-flow modules and which provides conditioned
airflo:~ for complete curing and post-curing conditioning
of the leaf.
To provide a modular curing system llhich enables
by insertion of the above cross-flow modules the for-
mation of a vertical high-pressure inlet plenum for
effective air movement through the tobacco during curing
and reduces heat losses from the curing system.
To provide a modular curing system which reduces
the overall equipment investment per pound of cured output
in comparison ~ith existing or modified bulk curing units.
These and other objects and advantages ~lill
become a~parent to those skilled in the art from the
follo~ing discussion of the invention in detail.
103'~13~i
eRlEF DE~CRIPTI~rl nF THE DR~
Fig. 1 is a perspective view of a preferred
form of the cross-flo~l curing module of the invention.
Fig. 2 is a sectional vjew on the line 2-2 of
Fig. 1 and illustrating the interior ledge supports of
the rear wall of the curing module.
Fig. 3 is a sectional view on the line 3-3 of
Fig. 1 and illustrating leaf support by tines ~Jhich pene-
trate the leaves generally perpendicular to their plane
of orientation.
. . .
Fig. 4 is a top plan view of a conveyor with
- tilting mechanism for rotating a filled module by 90
degrees.
Fig. 5 is a side elevational view of the
conveyor with the tilting mechanism.
Fig. 6 is a perspective view of a cross-flo~
modular curing barn ~lith the doors open.
Fig. 7 is a longitudinal sectional vlew of the
barn shown in Fig. 6.
Fig. 8 is a sectional vie~l~ on the line 8-8 of
Fig. 7.
Fig. 9 is a sectional view on the line 9-9 of
Fig. 7-
Fig. 10 is a side elevational view partially
schematic illustrating fork lift handlin~ ~nd stacking
of the cross-flo~-~ modules.
--7--
iO3913~
DESCRIPTI~N OF THE PREFERR~D EllBODIMENTS
Referring to Figs. 1-3, specific details of
construction of the improved module are illustrated.
While numerous types of materials could be utilized for
construction of the module, such as sheet steel, angle
iron, etc., preferable ~aterials are lumber, plywood,
and expanded metal for economy, light ~eight and ease
of constructjon. Module djmensions may vary considerably
in terms of width, length and hei~ht; however, greatest
economy is realized in the use of 4' X 8~ plywood sheets
~hen the module is approximately 4' cube. Furth~ermore, a
container of this size is almost ideal from the stand-
point of fork-lift handlin~ and stackin~. The module 10
includes an imperforate bottom 12 mounted to runners 11,
an i~perforate top wall 13; generally imperforate rear
wall 14, and essentially imperforate front door 15, and
t~!o perforate side ~lalls 16 and 17. In the illustrated
form of the invention the module 10 is essentially cubical
in configuration, and a module of 4' X 4' X 4' outside
dimensions is designed to hold from about 900 to about
1300 pounds of uncured tobacco, with an empty container
weight of about 175 to 200 pounds.
The runners 11 and imperforate bottnm 12 provide
a durable base ~hich facilitates fork-lift handling.
The runners 11 are pre-ferably of 2" X 4" or 4" X 4" oak
or pine members for durability and stren~th. The imperfor-
ate bottom 12 is preferably of exterior grade plywood of
such thiclriess as to withstand heavy loads of stacked
~035~136
modules up to 12 to 20 feet high, ~ 5/8" ~lywood
(group 1) sheet on three runners will support stacked
modules to 20 feet high, The bottom plywood sheet 12
may be secured to the runners 11 with coated nails,
~rood screws, etc, to form a base upon which the remainder
of the module is constructed.
The structural framework to which the plywood
sides are attached consists of ~nterior framing of
2" X 4" or 2" X 2" wood members. While exterior framing
and braces could conceivably be used, interior framing
provides greater interior volume for specified external
dimensions and better exterior surfaces for obtaining an
effective air seal between modules. Four corner posts
18 are preferably of 2" X 4" size, ~hich rest directly
on the bottom 12. Top structural side members 19 are
preferably of 2" X 4" size and are turned edgewise to
rest on the top ends of the corner posts 18. Front and
rear top structural members 20 are also of 2" X 4" size
but laid flat, and connected with an end lap joint to
the side memhers 19. Froni and rear bottom structural
members 21 are of 2" X 2" size and are simple butt
jointed to the corner posts 18.
The perforate side walls 16 and 17 permit a hori-
zontal, cross-flow of conditioned air through the tobacco
during curing. The peripheral portion of plywood, being
imperforate, serves to reduce excessive leakage of air
along the front, top and rear ~alls. For the front
portion 22 and rear portion 23 of the side wall 16,
1039136
widthS of 3" to 5" for the imperforate par~ of the
wall has been found advantageous. For the top portion
24, an 8 to 10 - inch i~perforate baffle is more suit-
able, since tobacco tends to settle away from the top
wall 13 by gravity as dryin~ proceeds. Construction
of the two perforate walls 16 and 17 is almost
identical, except the perforate screen 25 of side wall
17 is shown fixed, whereas the perforate screen 26 of
wall 16 is shown hinged at the top 27 with a latch 28
to secure the screen. The hinged side screen door 29
permits mechanical dumping of the cured leaf with a
fork-lift equipped with a load inverter designed to
clamp the module at the top and bottom.
The imperforate portion of side walls 16 and
- 15 17 is secured to the structural framework of the module
by wood screws, nails or the like. The perforate
screen portions 25, 26 may be easily fabricated from
expanded metal welded into an angle iron frame 30. For
the fixed perforate screen 25, wood screws should be
used to attach the frame 30 to the plywood. Butt hinges
- 27 are preferably welded to the angle frame 30, then
the hinge connected with screws to the ply~ood panel
24.
The imperforate rear wall 14 is constructed
also of plywood of 1t2" or 5/~" exterior grade. The
wall panel is cut to fit inside the side and top wall
plywood panels, as shown, and to rest directly on the
bottom 1?. This panel ~ay bc secured by nails, etc.
-10-
1039136
to the interior framework members 18, 19, 20 and 21.
Provided also on the inner surface of the rear wall 14
are several horizontal ledges 31, Fig. 3 which may be
spaced from 6" to 8" apart. These ledges, as will be
described later, serve to support the ends of rods or
tines which in turn provide vertical support for the
tobacco during curing. The led~es 31 may consist of
1" X 2" furring strips, 1 1/2" X 1 1/2" angle iron, etc.
secured ~irmly to the rear wall 14.
The front generally imperforate door 15, as
shown in Fig. 1 is recessed within the opening 32, is
removable and is attached by means of wood bolts 33.
While this door may be hinged, it appears preferable to
simply remove the door as needed, since hin~e mounts
1~ would receive considerable strain immediately after
filling the module and sealing could pose a problem.
The door 15 is constructed preferably of 1/2" or 5/8"
exterior ply~Yood and is reinforced by wood furring strips
34 along tlle periphery and center. A number of holes 35
of about 1/2" diameter are provided in the plywood sheet
to enable insertion of sharpened rods 38, Fig. 3, ~Jhich
penetrate the tobacco after the module is filled. The
holes are spaced preferably in ro~qs at about 6 to 10-inch
intervals "Yith holes sta~ered relative to holes in
2S adjacent rows. The sharpened rods 38 should be sliqhtly
smaller in diameter than the hole diameter, to permit
insertion but to m;nimize air leakage through the holes
3S.
-1 1_
103913~i
During ~illing, the module lO is oriented such that
the opening for the door 15 is at the top. Tobacco leaves,
cut-strip tobacco, or chopped material may be conveyed
directly into the module Also hand harvested leaves (or
complete tobacco plants) may be packed by hand directly into
the module. At this point, the door is installed, and con-
nected by means of wood bolts 33 which pass through the holes
36, and appropriate nuts installed. A gasket may be provided
on the face 37 of the construction members of the module to
assure minimal air lea~age from inside to outside the `
container.
Insextion of the rods or tines 38 and rotation of
the container are accomplished after the door 15 is secured
to the module lO. The module lO may either have the door
lS at the top or be rotated 90 degrees to the orientation
of Fig. l for insertion of-the rods. Insertion of rods
after rotation is permissible only if the tobacco is suf-
ficiently firm within the container such that it does not
tend to settle away from top wall 13 during rotation. The
rods penetrate the do~r~ pass through the tobacco within
the container and are supported on the rear wall ledges
31 as previously described.
Referring now t~ Fig. 3 showing a sectional view of
the curing module and illustrating the tine support of to-
bacco, rods 38 pass through the door 15, through the
tobacco 39 and rest on the ledges 31 on the rear wall 14.
27 As noted in this Figure, the tobacco is now oriented
rw/~ 12 -
1039136
generally vertic~ ith the ~eneral plane of the leaves
perpendicular to the perforate side walls. Hence ajr
can be forced ~yith relatlve ease through the perforate
side walls and the tobacco. As pointed out earlier, as
dryin~ proceeds there is always the tendency for air leak-
age along side wal1s as the tobacco shrinks. This can be
overcome to a great extent by the described design of
the imperforate portion of the side walls 16 and 17. Since
shrinkage and gravity both tend to cause separation of
tobacco from the top wall 13 inner surface 40, longitudinal
top strips 41, are used advantageously to help block leak-
age along the top wall. Other means for reducing this
leakage include gravity baffle strips mounted similar to
- strips 41 or flexible strips of canvas, plastic, rubber,
-1~ etc. which are attached to the perforate side walls such
that the air pressure mainta~ns the strips in contact with
the tobacco.
The above discussion pertains essentially to the
improved features and fabrication of the curinQ module,
20- and to cross-flow characteristics which can be achieved
with this module. It will be readily apparent to one
skilled in the art of harvest and curing of tobacco that
the cross-flow curing module lends itself to various
mechanjzed or hand harvest schemes. For example, with
mechanical harvesting two modules can be positioned side
by side ~ith the open front door side oriented upwardly
on the rear of the machine to receive the defoliated
tobacco. Current mechanical harvesters have two forks
which lift a trailer on the rear of the machine. A
- -13-
1039136
preferred arrangement with the cross-flo~ modules of 4'
cube sjze is to provide ~our forks which si~ply lift two
empty modules from the bed of a transport truck or trailer.
The bed on the truck should be provided ~rith cross members
5 on which the modules are carried to permit insertion of
the harYester forks beneath the rear wall 14 of the module.
An additional man on the rear deck of the harvester can
assist in distributing tobacco into the modules and assure
proper filling of corners, or a mechanical distributor can
be provided. After filling, the modules are lowered to
the transport truck or trailer, taken to the barn and there
lifted by fork l~ft from the transport unit. Operations
of installing the door, insertions of rods and rotating
90 remain to be completed before the module is positioned
into the curing barn.
Figures 4 and 5 illustrate a simple mechanism for
aiding the above-mentioned operations. The fork-lift, as
discussed, lifts the fitled module from tne transport unit
and places the module 10 on a roller conveyor 60. The
door 15 is installed and rods inserted. The module 10 is
next rolled to the mechanical tilt device, shown generally
at 61. This device rotates the closed module 90 de~rees
to permit lifting from the module bottom 21 with a fork lift.
The tilt mechanism 61 includes a platform 62 connected
rigidly to a main shaft 63 which has two forks 64 welded
at right anyles to platform 62, The main shaft 63 is
mounted on bearin~s 65 with one end sprocket driven by a
suitable gear motor 66 A hydraulic cylinder could
similarly provide the necessary force for rotatin~ the tilt
mechanism.
-14-
1039~36
l~ith hand harvesting, the module 10 may be filled
and packed by hand in the field, as on a trailer puiled
behjnd a tractor in the skip row, or the leaves from
various harvestin~ aid leaf conveyor belts may carry and
drop the leaves directly into the containers. ~nother
possible scheme is to hand pack the modules at the curing
site,.i.e, ~here the tobacco is brought to the curing
facility in bulk or in small containers, sheets, sleds and
the like. In any event, the module must be turned by 90
after filling and closure, and this preferably by tilt
device 61, or other suitable means such as chain hoist.
Regardless of the method of loading the modules
and regardless of the form of the tobacco loaded there into,
it is desirable to obtain an optimum loading density. It
1~ will be reco~nized that the loading density of tobacco for
modules ~lill vary with the size and form of the tobacco
material loaded therein. Ilhile a density of 14-20 lbs/ft3
is considered to be optimum, a ran~e of from 10-25 lbs/ft
would be functional
Design and construction of the cross-flo~ modular
curing system 70, ~hich receives the modules 10 and provides
conditioned air for complete curing and post-curing con-
ditioning, are illustrated in reference to Figs. 6-10. ~he
curing system 70 includes preferably a concrete floor 71
upon ~hich the remainder of the curing facility is constructed.
Above the concrete floor 71, the curing system 70 includes
side ~alls 72, a rear wall 73, a roof 74, an interior parti-
tion ~lall 75, a front gable ~all 76, hinged front doors 77,
an interior ceilin~ 87, and a heating-conditioning unit 78
-15-
103gl36
along with certain dampers and duct openin~s to be
described later. The side wa11s 72 may be constructed of
readily available building materials, for example, framed
with 2" X 4" studs and plates, covered with plywood on the
interior surface, and covered with plywood or sheathing
insulating board and metal siding on the exterior surface.
The side walls 72 support only the structural frame of the
building, hence economy of construction may be satis~ac-
torily obtained by eliminating the interior surface of ply-
wood; however, some suitable insulating board should beprovided between the wall studs to conserve heat.
- The re~r wall 73 is provided to protect the heating-
conditioning unit 78 from ~Jeather and to form along with the
interior wall 75 a suction plenum for inducin~ outside air
~5 79 to move within the roof plcnum 80 for pre-heating prior
to entering the heating-ccnditioning unit 78. The rear wall
73 may be constructed the same as the side walls 72, and
should include a door (not sho~ln) for access to the heating-
conditioning unit room 90. The roof 74 is of conventional
- 20 construction including rafters, bracing and the like pre-
- ferably covered ~/lith galvanized metal roofing, painted black
or dark color to absorb solor energy. Preferably the gab~e
wall is uninsulated, since heat transmission throu~h the
wall from outside to inside the roof plenum ~0 ~lill aid in
improvin~ the efficiency o-f the system. The interior parti-
tion wall 75 and the interior ceiling 87 serve to form a
curing chamber sho~n generally at 100 for receivin~ the
modules 10. ~lall 75 is preferably constructed Wi th
2" X 4" studs covered on bnth sides with plywood and
should be insulatecl to prevent condensation on the ~lall
_16-
1~')39136
surface during the high humi~ity phase of curing and
to minimize heat loss, The ceiling 87 may be of plywood
nailed to the ceiling joists ~2. Insulation between the
` ceiling joists will aid in preventing condensation on
the ceiling. Note should be given that the walls and
ceiling of the curing chamber 100 should be tight to
minimize air leakage. ~inged front doors 77 provide
complete freedom of moving the curing modules 10 into
and from the curing system 70. The top door is provided
as shown in Fig. 6, since the curing system 70 as
illustrated accommodates modules 10 stacked four high,
which, with 4-ft. cubicals, would require an interior
chamber height of at least 16 feet. A triple-door
arrangement provides greater ease of closure and sealing
than two extremely high doors. A center support post 83
provides a means for securing the doors 76 with tight
seals. A suitable gasket material should be used to
weatherstrip the doors to minimize air leakage.
A fork lift 75' for handling of the modules 10
permits ease of loading and stacking filled containers
in the curing chamber 100, as illustrated in Fig. 10.
In the curing facility 70 illustrated in Figs. 7 and 8,
modules are stacked four high and in two rows. The
first column of modules in each row is placed directly
against the partition wall 75 to effect a ti~ht seal.
If necessary, a gasket material may be glued to the
- wall 75 to assure a tight fit. Similarly, the second
and additional columns of modules are positioned,
- sealing against the previously formed column. As
-17-
1039~3~i
depicted in Fig. 7, the curing chamber 100 is designed
to receive two rows of curing modules, 4 high, and 5 front
to back, giving a total of 40 modules. When the two rows
are completed, the front doors 77 are closed to seal with
the last two columns of modules. Th;s can easily be
accomplished by compressible gasket material attached to
the front doors 77. Complete sealing and formation of a
central, high pressure inlet plenum is accomplished by
means of the flexible strips 84 attached to the ceiling
87. Note should be made that by the manner of stacking
and sealing, the space between the two rows of stacked
modules becomes a high pressure plenum when air is intro-
duced through air inlet 110. Similarly the two spaces
formed between each row of stacked modules 10 and the
side walls 72 of the curing facility 70 become the return
or low pressure plenums. These high and low pressure
plenums provide an exceptional degree of access for inspec-
ting the progress of curing in any curing module 10. Pre-
ferably the high pressure plenum should be about 3-ft. wide
and the low pressure plenum about 2-ft. wide. Air return
outlets 111 to the heating-conditioning unit 78 are provided
- near the upper corners of the partition wall 75. Air is
therefore forced horizontally through the perforate side
walls 16, 17 of the curing modules 10, as illustrated by
the arrows 112 of Fig. 12.
- It is to be noted that this unique arrangement
of stacking and formation of high and low pressure (inlet
and return) plenums is accomplished without the necessity
of special construction, thereby introducing further
economy to the design. Furthermore, ~he cross-flow
-18-
103~136
distance through the curing modules is maintained to a
nominal level of 4 feet or less which has the effect
of reducing air flow resistance and accelerating the
cure. Stacking permits high capacit~v loading within
the curing space and does not necessitate high cross-
flow distances to achieve high capacity. By retaining
nominal cross-flow distances of 4 feet or less, curing
conditions are more uniform throughout the tobacco than
in current bulk curing systems where air is forced
upwardly or do~nwardly through depths of up to six or
seven feet. The hazard of rotting pathogens is also
greatly reduced since drying throughout the modules I0
can take place earlier.
It is also of particular interest to note that
heat loss from the central high pressure plenum is
reduce~ in comparison with conventional bulk barn designs.
This is due to the fact that heat dissipating surface area
is reduced. ~ssuming a 3-ft ~lide central high pressure
plenum, a cross-f10w modular system 70 as described has
216 ft2 of heat dissipating surface area in the high
pressure plenum compared with 977 ft2 ~or typical bulk
barns to cure an equivalent amount of tobacco. Further-
more, with the cross-flow design, air exitin~ from the
modules 10 has been evaporatively cooled, thereby placing
the "cooler" air next to the exterior walls 72 of the curing
facility This aids further in minimizing heat transfer
through the walls of the curing facility.
Referring again to Figs. 7-9, the specific modes
of operation of the curing facility 70 ~lill be described.
- 19-
~ 039136
After the fac~lity is filled, the doors are closed and
the heating~conditjon~ng un~t 78 energized. Air ~nlet
damper 113 is normally closed to permit essentially
complete recycling of the curing air, and the desired
curing temperature is established by thermostatic
control. The heating-conditioning unit 78 ;ncludes a
fan 114, a suitable gas or oil-fired burner 115, and a
water atomizer 116 (optional). Typically for curing of
Virginia-type tobacco (flue-cured type), tobacco is
yellowed for 36-72 hrs. at about 90-100F and 85 to 90%
r.h. These conditions may be easily maintained thermo-
statically with either automatic or manual damper control.
In this case, air at regulated temperature is
forced into the central plenum through air inlet 110 to
develop a static pressure which produces cross-flow circu-
lation through the tobacco in the curing modules 10 and the
air is essentially recycled back to the heating-conditioning
unit 78 by means of the air return outlets 111. A small
quantity of fresh air, from roof plenum 80, may be intro-
duced by opening the air inlet damper slightly if desired,or if automatically controlled the damper will adjust to
maintain the preset conditions.
- For leaf and stem drying, the air temperature
introduced to the curing chamber 100 is normally gradually
increased about 2-4 F/hr until reaching 170F. nuring
this tlme, increasing amounts of fresh outside air are
introduced to the heating-conditioning unit as shown by the
arrow 117 in Fig. 7 ~Yhen the air inlet damper 113 is o?ened.
-20-
1039136
It is to be noted that by the design of th~ roof plenum
80 and gravlty louver damper 118, fresh alr is drawn
through the roof plenum ~here it is preheated by solar
ener~y tduring the day period) and by conduction
through the chamber ceiling 87 prior to reaching the
inlet to the heating-conditioning unit 78. This further
contributes to high efficiency of energy utilization by
minimizing heat loss from the structure and the advantage
of heat gain through the roof 74.
Under these conditions of curing, as the inlet
damper 113 opens, it simultaneously blocks the return
air from the curing chamber. This causes the static
pressure in the return 1O~ pressure plenums near the
- walls 72 to increase above atmospheric pressure, forcing
air to the outside through gravity louver dampers 119,
~hich are located on both side walls 72 of the curing
- faci1ity 70. As leaf and stem drying near completion,
the inlet damper 113 is gradually closed to conserve
energy. The total curin~ time is normally about 4 to 5
days.
Following drying, leaf conditioning to moisture
contents of 16 to 18% is accomp1ished by adding known
amounts of atomized ~ater into the air stream (or by
introducing humid outside air, if available).
2~ Unl~ading of the cured tobacco is accompl~shed
mechanically. The fork lift 120 removes the curing
modules from the curing chamber 100 and places them out-
side where the rods or tines 38 are removed. The fork lift
10391;~6
120, equipped llith a load inverter, then raises the
module 10 and dumps the cured tobacco from the module 10
by tilting the container to the side havin~ the hinged
side screen door 29, The latch 28 is released and the
contents of the module 10 transfer readily to a sheet or
other suitable container used for packaging tobacco for
market. Removal of the front door 15 of the module 10
is not required until the module is again ready for re- -
filling with freshly harvested leaf.
The above description of the invention presents
in detail the specific embodiments which lead to noted
advances in technology of handling and curing tobacco.
It is apparent that certain modifications in curing
module construction or curing system layout may be made
without altering the spec~fic embodiments. For example,
the curing module could include either none, one or two
hin~ed perForate doors on the module sides. In regards
- to curing system layout, considerable latitude exists for
size and capacity of the structure. One could provide
also a layout with one row of modules stacked one or more
high with the high pressure plenu~ on one side and the
low on the other. Or, a system layout could be provided
with more than two ro\~s of stacked modules with alternate
high and low pressure vertical plenums.
~lhile the above description and operating pro-
cedures have been descrjbed for tobacco of the flue-cured
type, it is apparent that the cross-flo~1 modular tobacco
curin~ system ma~ be used for curing other tobaccos such as
-22 -
103~13f~
Burley, Maryland, cigar filler tobacco, Oriental, etc.
by simple modification of curing schedules for tempera-
ture, humidity and air flow.
From the foregoing general and detailed descrip-
tion of the various embodiments of the invention, it will
be seen that the aims and objects hereinbefore set forth
and others are fully accomplished.
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