Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates to a novel and
improved apparatus for controlling or obtaining the actual
weight of materials which are charged to a receptacle or other
receiving means, such as a shipping container. The present
invention is particularly applicable to determining the actual
weight of lightweight materials such as tobacco, cereals, wood
pulp, dehydrated vegetables, fiberboard and chemicals, which
have a certain moisture content. The present invention also
resides in a novel apparatus for simultaneously determining
the weight and moisture content of such materials.
The present invention will be described particularly
with reference to controlling or determining the weight and
moisture content of tobacco charged to a shipping container or
other receptacle, although it will be apparent from the
following description that the invention is equally applicable
to materials other than tobacco, and has other applications;
for instance, determining the weight and moisture content of
materials which have been stored, or materials which are
further processed.
It is desirable in the processing of tobacco to
; produce a product having a moisture content within certain
limits. The limits become particularly critical in the case
of tobacco shipped abroad and subject to import taxation. The
tobacco is contained in shipping containers and is presumed
by the taxing authorities to have a specified moisture content.
Should the moisture content be higher than that stated, the
excess water is taxed as tobacco resulting in an unnecessary
tax expense. The extra water also incurs undue shipping costs.
Thus, the tobacco industry traditionally, at least
in the case of tobacco for export to certain countries, has
resorted to considerable expense to produce the tobacco within
closely controlled moisture content limits. This is
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accomplished by drying the tobacco to a high degree of
dryness, cooling it and then remoistening it with steam. By `-
way of example, for tobacco to be shipped abroad, the tobacco
may be dried to as little as 6-7% moisture in order to obtain
a final moisture content of about 11%.
Following the drying and remoistening steps, the
tobacco i5 moved on a series of conveyors, one being a
climbing conveyor, to the top of a packing tower where the
tobacco is introduced onto a cross-conveyor which is capable
of being reversed in direction to feed the tobacco into one
of a pair of charging tubes. From each tube the tobacco
flows into a shipping container. A hydraulic plunger is
associated with each charging tube to press the tobacco into
the shipping container, after which the container is capped.
After filling of one of the shipping containers is completed,
the cross-conveyor is reversed in direction to fill the other
container.
Traditionally, the moisture content of the tobacco
; charged to a shipping container is measured by a moisture
determining means positioned at the outlet end of the drying
and remoistening apparatus. This permits the operator of the
drying and remoistening apparatus to determine the moisture
content of the tobacco as it comes out of the apparatus and to
- immediately make any corrections or adjustments in the
apparatus that are necessary in order to obtain, as close as
possible, the desired moisture content. While this does
permit ~uick adjustment of the drying and remoistening
apparatus, it is apparent that the moisture conte~t in any
particular shipping container can vary from that desired
3~ primarily due to drying of the tobacco between the moisture
determining apparatus and the charging tubes. Thus, in order
to obtain a moisture content of 11% in a particular shipping
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container, the tobacco may have to be remoistened to as much
as 11-1/2%. The problem is that the rate of drying will vary
dependent upon ambient temperature and humidity conditions,
and an operator may unwittingly introduce into a shipping
container tobacco having a moisture content above the desired
11%. In addition to resulting in excess taxes and shipping
costs, too high a moisture content can cause spontaneous
combustion of the tobacco and destruction of at least part of
a shipment.
As a further problem, the tobacco industry
traditionally has employed moisture readers which take a
moisture reading only of samples of the tobacco being
processed. The assumption then has to be made that the
readings obtained are average readings representative of the
entire product flow. Clearly, substantial variations can
occur in the moisture content of the product limiting the
usefulness of the sampling technique.
These and other disadvantages are overcome by the
present invention wherein there is provided a novel and
improved apparatus in which the weight and moisture content
readings of the material being processed are taken at the end
point of disposition of the material. In the case of tobacco
for shipment abroad, the readings are taken at the point of
loading of the tobacco into shipping containers, rather than
at the outlet end of the drying and remoistening apparatus.
If a shipping container is filled with tobacco having too high
a moisture content, that tobacco can be removed from the
container and can be reprocessed. The point is that the exact
weight and moisture content of the tobacco in a particular
container become known, and excess taxes are thus avoided, as
well as the danger of spontaneous combustion of the tobacco.
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More particularly, the present invention relates
to a novel apparatus for continuously processing materials
having a desired moisture content, comprising a drying and
remoistening means for obtaining a desired moisture content
in said materials, a receiving means remote from said drying -
and remoistening means, means for conveying said materials
from said drying and remoistening means to said receiving
means, and weight and moisture determining means for
determining the weight and moisture content of said materials,
said weight and moisture determining means being adjacent said
receiving means to continuously determine the weight and
moisture content of the materials fed thereto.
As a preferred embodiment, the present invention is
directed to a tobacco processing and packing apparatus
comprising a drying and remoistening chamber, a packing tower
including loading means for loading tobacco into shipping
containers, conveyor means for transmitting tobacco from said
chamber to the packing tower, said conveyor means including
a weigh conveyor positioned adjacent the packing tower,
loading means whereby tobacco flowing from the weigh conveyor
is transmitted to the shipping containers with minimum time
delay, and a moisture reading means associated with the weigh
conveyor for determining the moisture content of the tobacco
on said weigh conveyor. Preferably, said moisture reading
means comprises a probe which extends the full width of the
tobacco layer on the weigh conveyor. In a preferred
embodiment, the probe comprises at least one driving element
~ and at least one driven element producing a stable radio
-- frequency electrical field which passes into the layer of
tobacco, the energy transferred from the driving element to
the driven element varying with the product's moisture content.
The driving and driven elements are parallel members which
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extend across the entire width of the weigh conveyor.
Also in an embodiment of the present invention, the
weight determining means comprises a pivotal balance
positionable in response to the weight of the material on
the weigh conveyor including a weigh cell capable of
producing a pneumatic signal proportional to the weight. A
converter converts the pneumatic signal to an electrical
signal, and a pulser produces a series of electrical pulses
proportional to the electrical signal. Means are provided
for counting said pulses, the total number of pulses
indicating the weight of tobacco which has been moved on the
weigh conveyor in a unit length of time.
It will become evident in view of the following
description that the concepts of the present invention are
also applicable to controlling the weight of tobacco fed to
a shipping container, or to controlling the weight of materials
fed to another receiving means, in addition to determining the
weight and moisture content of such tobacco or materials.
In one aspect of the invention there is provided
an apparatus for continuously processing materials having
a critical moisture content and disposition of such materials,
werein said apparatus comprises a drying means for obtaining
a desired moisture content in said materials, a point of
disposition remote from said drying means, means for conveying
said materials from said drying means to said point of dis-
position, and weight and moisture determining means for de-
termining the weight and moisture content of said materials;
the improvement comprising employing as said weight determining
means a gravimetric weight determining means, positioning said
weight and moisture determining means adjacent said point of
disposition whereby weight and moisture responsive readings
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of the same sample are simultaneously taken, thereby continuously
determining the weight and moisture content of the materials
fed to said point of disposition.
The invention and advantages thereof will become
more apparent upon consideration of the followin~ specification
with reference to the accompanying drawings, in which:
Fig. 1 is a schematic illustration of a tobacco `
processing apparatus and packing tower embodying the concepts ` -
of the present invention;
Fig. 2 is an enlarged, elevation and partial
schematic view of the weight and moisture determining means
of the present invention employed in the tobacco processing --
apparatus of Fig. l;
Fig. 3 is an enlarged, perspective view of the -
moisture sensing means employed in the tobacco processing
apparatus of Fig. l;
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Fig. 3A is an elevation and partial section view of
an embodiment of the present invention; and
Fig. 4 is an embodiment of the moisture sensing
means of Fig. 3.
Referring to the drawings, and in particular Fig. 1,
there is illustrated a tobacco processing apparatus 12
comprising a drying and remoistening apparatus 14 and a
packing tower 16. conventionally~ the apparatus 14 is
comprised of a drying section, a remoistening section, and a
cooling section which is disposed between the drying and
remoistening sections. For purposes of the present applica-
tion, the entire apparatus 14 shall be referred to as the
dryer, since its end object is to achieve a predetermined
dryness or moisture content in the tobacco being processed.
In the dryer 14, the tobacco is subjected to drying and then
remoistening to a particular moisture content. By way of
example, the tobacco may be dried to a moisture content of
about 6-7% and then remoistened to a moisture content of
about 11.5%. The tobacco, identified by the numeral 18, is
; 20 conveyed through the dryer on a conveyor which is not shown,
from which the tobacco flows onto a horizontal cross-conveyor
22, and from there to a climbing conveyor 24 by which it is
brought up to the elevation of the top of the packing tower
16. The packing tower is provided with a reversible delivery
conveyor 26 which conveys the tobacco alternatively to one or
` the other of laterally disposed upright shipping containers
28. Each shipping container is beneath a charging tube 30,
the tobacco flowing through the tubes into the containers.
; Above each tube is positioned an hydraulic plunger 32 adapted
to compress the tobacco through the tube into each shipping
container. By using a reversible delivery conveyor 26, it is
; apparent that while one of the containers is being loaded,
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the other one, as shown, can be subjected to packing and
sealing.
In accordance with the concepts of the present
invention, the tobacco from the climbing conveyor is
transmitted to the reversible delivery conveyor past a weigh
conveyor 34 which is at right angles to the delivery conveyor
and is positioned at about the middle of the delivery
conveyor. The weigh conveyor 34 is relatively short in length
so that the tobacco which is weighed on it flows substantially
immediately onto the delivery conveyor and from there into a
tube for a container being packed. Thus, when a predeter-
mined amount of tobacco has been weighed on the weigh
conveyor, the delivery conveyor is reversed in direction with
a controlled time delay. In this way, an accurate determina-
tion of the weight of the tobacco packed in a particular
container is obtained.
Details of the weigh conveyor are shown in Fig. 2.
Essentially, the conveyor is a continuous belt 36 which
travels in a clockwise direction around a pair of spaced-apart
end rolls 38. The upper carrying run 40 is divided into a
dump area 42 on the left side of the weigh conveyor, referring
to the drawing of Fig. 2, and a weigh area 44 on the right
side. A pair of weigh arms 46 on opposite sides of the weigh
conveyor, in about the middle of the conveyor, pivotally
support a weigh roll 48 which is linked via upright posts 50
to a weigh cell 52 disposed beneath the weigh conveyor. The
- weigh roll support posts 50 and other linkage provide a
balanced beam which has a short stro~e in linear response to
the weight of material conveyed on the conveyor belt carrying
run.
A suitable weigh conveyor which may be employed is
one manufactured by Proctor & Schwartz, Inc., identified as
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Model 736 Weigh Belt. It employs a weigh cell manufactured
by CompuDyne Controls, Inc. This cell has two internal air
- chambers (not shown), one being a net weight chamber, while
- the other is what is called a tare chamber. Each is closed
on one side by a flexible diaphragm. Compressed air is fed
to the net weight chamber and bleeds to atmosphere through a
nozzle. When weight or force is applied, a flapper regulates
the flow of air through the nozzle. As more weight is
applied, the flapper reduces the nozzle opening and air
pressure in the chamber increases until a state of equilibrium
is established. When the weight is reduced, the nozzle opens
to reduce pressure, until equilibrium is established. By the
tare chamber, the unit is calibrated to zero weight without
any load.
The chamber pressure, which is proportional to
weight, is transmitted to a converter 54 which converts the
pressure signal to an electrical signal. A suitable
converter is one manufactured by Bell and Howell, Series
; 18-118 Pneumatic-to-Electric Transmitter. This electrical
signal which has a varying current output (voltage may be
used) dependent upon the magnitude of the air signal is
transmitted to a pulser 56. A suitable pulser is one sold by
Acromag, Inc., identified as their Series 1320 Integrator-
Totalizer. This pulser accepts a varying current input and
produces a pulse output which is linearly proportional to the
input. This pulse output is then sensed by a counter 58, the
number of pulses being proportional to the tobacco weight on
the conveyor during a unit period of time. A suitable counter
is one identified as Durant Series 2000.
In a particular example in accordance with the
concepts of the present invention, the weigh conveyor may be
about 2-1/2 feet in width carrying a bed of moisture-containing
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tobacco which is about 4 inches deep. The weigh cell produces
a pressure output which varies between 3 psig and 15 psig,
measuring from zero load to maximum load. The output from
the converter may vary from 4 to 20 milliamps producing zero
pulses at 4 milliamps and maximum pulses at 20 milliamps. At
20,000 pounds per hour of tobacco, which can be maximum flow,
the pressure from the weigh cell is 15 psig producing a 20
milliamp current from the converter. This then provides
200,000 pulses per hour, equivalent to about 10 pulses per
pound.
Operation of the weigh conveyor is automatic. In
the case of packing of 1,000-pound containers, the flow is
maintained up to 10,000 pulses or 1,000 pounds. The reversible
delivery conveyor 26 is then reversed in direction to divert
the flow to the second container. The time delay before
reversing of the delivery conveyor 26 is such that all of the
tobacco on the conveyor weighed for the first container flows
to the first container.
; Above the weigh conveyor 34, there is positioned a
moisture meter 62, details of which are shown in Fig. 2. One
suitable moisture meter that may be employed is that manu-
- factured by Diversified Engineering, Inc., Model JS,~2
Continuous Moisture Meter. As shown in Figs. 2 and 3, the `
moisture meter is provided with a probe 64 which seats on top
of the tobacco layer 18. The probe extends the entire width
of the conveyor belt. It is provided with a pivot bar 66
which is adjustable to slightly raise the leading edge of the
probe. The probe rests right on the layer of tobacco in
contact with it, but if no material is on the conveyor, a
supp~rt wire 68 holds the probe away from the conveyor carrying
surface. As shown iIl Fig. 3, the probe is provided with a
driving element 70 and a driven element 72 which are in
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parallel with each other and extend substantially the entire
length of the probe. The elements establish an electrical
field between them which extends into the tobacco layer at -
least three-quarters of an inch. The energy transferred from
the driving element to the driven element varies with the
product's moisture content. Changes in moisture content
cause changes in the amounts of energy transferred from one
element to the other. The coupled energy is demodulated and `
amplified in apparatus 74 to provide a moisture reading. This
moisture reading is transmitted to a meter 76, which provides
a continuous reading of the total moisture content of the
tobacco introduced into a shipping container. If desired, -
the moisture reading can be fed in to a control instrument
for automatically controlling the remoistening of the tobacco
following drying. Alternatively, it can be used by the
operator to control manually the remoistening step in the
event of a trend or change away from that desired. ~ddition-
ally, the moisture content signal can be continuously recorded
on any suitable recording instrument.
Referring to Fig. 4, an alternative probe is
illustrated. This probe has multiple driving and driven
elements in parallel which are suitably interspersed to
provide multiple electrical fields and a moisture reading of
improved accuracy.
An embodiment of the present invention is
illustrated in Fig. 3A. In this embodiment, the moisture
probe comprises members 84 and 86 above and below the layer of
tobacco 82 on conveyor 80. The conveyor 80 is the same as
conveyor 40 in Fig. 2. The members 84 and 86 are provided
with driving and driven elements 88 and 90 which establish an
electrical field which penetrates the layer of tobacco. The
members 84 and 86 and the elements 88 and 90 extend the entire
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width of the layer of tobacco. The energy transferred from
the driving element to the driven element varies with the
tobacco moisture content, and as with the embodiment of Fig.
- 3, changes in the moisture content are appropriately amplified
and read in a moisture reading device.
Although the present invention has been described
- with reference to simply determining the moisture content and
weight of tobacco fed to a shipping container, it is obvious
that the principles of the present invention are equally
applicable to controlling the flow of tobacco to a shipping
container. That is, the weight signals can be employed to
manually or automatically reverse the direction of movement
of the delivery conveyor 26, thus interrupting the flow of
tobacco to a shipping container being filled at a predeter-
mined or desired point of loading.
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