Note: Descriptions are shown in the official language in which they were submitted.
115~Z
This invention pertains to cigarette manufacture and, in
particular, to control of cigarette manufacture at the cigarette
maker.
In cigarette manufacture, it is customary to provide con-
ditioning of the tobacco in the primary processing of same. As
part of this conditioning, the tobacco is subjected to procedures
wherein tobacco moisture content is measured, and measured mois-
ture content used to control drying or moistening apparatus to
achieve a predetermined moisture content. Procedures of this
type are disclosed in U.S. patents 3,840,025; 3,482,162; and
3,502,085.
After primary processing, the tobacco is usually stored for
a period of time, which may be up to three days, in storage areas
before being further processed into actual cigarettes at a
cigarette maker. In conventional practice, these storage areas
are subjected to a controlled climate in order to maintain the
tobacco moisture content at the predetermined level established
during the primary processing. This storage procedure is costly
and the tobacco may still undergo moisture changes during sub-
sequent transport of the tobacco to the cigarette maker. Thesemoisture changes adversely affect maker operation, particularly
in cases where the maker is provided with controls for estab-
lishing preselected values for various cigarette rod parameters
such as, for example, rod density and/or rod firmness~ This is
mentioned in British Specification 1,376,747 which discloses a
microwave system for controlling tobacco rod density. In this
system, since the microwave energy is affected by moisture as
well as tobacco content, the system is constructed to permit
obtaining values of each of these parameters from microwave
signals which depend on both.
~SS~ 2
It is an ob~ect of the present invention to provide more
effective moisture control in the manufacture of cigarettes.
It is a further object of the present invention to pro-
vide a method and apparatus for improved cigarette maker opera-
tion.
In accordance with the principles of the present invention,
the above and other objectives are realized in a practice for
cigarette manufacture wherein a cigarette maker is provided with
means for determining the moisture content of the rod of the
maker and wherein means responsive to the determined moisture
content is provided for controlling moisture content of the input
tobacco to the maker.
In the illustrative form of the invention disclosed
hereinafter, determined rod moisture content is utilized to
control the moisture content of the input tobacco as it is
being conveyed to the maker. Control is effected by determin-
ing the difference between the output rod moisture content and
a desired target moisture content and using this difference to
control the addition or substraction of moisture to the input
tobacco until output rod moisture content is at target
moisture.
The invention further contemplates utilization of a number
of techniques for determining rod moisture content. These
techniques require a number of sensors for generating sensor
signals related to output rod parameters such as moisture,
firmness, density and speed.
Also contemplated is utilization of the moisture control
system with a firmness control system to provide a rod of a
preselected or target firmness at a preselected or target
moisture.
~ss~
The above and other features and aspects of the present
invention will become more apparent upon reading the following
detailed description in conjunction with the accompanying draw-
ings, in which:
FIG. 1 shows a system for controlling cigarette rod
moisture content at a cigarette maker in accordance with the
principles of the present invention.
FIG. 1 shows a system in accordance with the principles
of the present invention for providing moisture control at a
cigarette maker 1. The latter maker can be of conventional
type such as that manufactured by Molins Ltd., of the United
Kingdom under model number MK8 or MK9.
In typical operation, the maker 1 provides from the
input tobacco stream 2 a continuous cigarette rod which is cut
into lengths to provide individual cigarettes. In accordance
with practice under the present invention, cigarette maker
operation is controlled such that the cigarette rod has a
moisture content which is substantially equal to a desired or
target moisture value Mt. In this manner, individual cigar-
ettes resulting from the rod have a substantially equal pre-
cisely determined moisture content, thereby providing enhanced
uniormity in cigarette production and improved quality control.
A moisture sensor 3 at the cigarette maker 1 monitors
the cigarette rod and generates an output electrical signal Ms
indicative of rod molsture content. The moisture sensor signal
Ms is fed to a signal processor 4 which develops an output con-
trol signal C for controlling the moisture content of the rod.
In accordance with the invention, such control is effected by
changing or varying the moisture content of the input tobacco 2
until the output rod moisture content is at the target moisture
~L~5~3Z
value. This may be accomplished by utilizing the signal C to
appropriately control conventional moistening means and/or dryer
means situated adjacent the conveyance path of the input tobacco.
In the illustrative case of FIG. 1, a moistening unit 5,
which might comprise, for example, a steam souxce followed by
a controllable valve, and a dryer 6 are responsive to the signal
C and add and subtract moisture, respectively, to and from the
input tobacco 2. With this form of control, the control signal
C brings the moistening unit 5 into operation during periods
when the output rod moisture content is below target moisture
and brings the dryer 6 into operation during periods when the
output rod moisture content is above target moisture.
In modified practices in accordance with the invention,
operation is carried out utilizing the moistening unit 5 or
the dryer 6 only. In the former modified practice, the tobacco
2 is processed during primary processing and storage such that
its moisture content is always below the target value Mt upon
entry to the moistening unit, thereby always requiring the
addition of moisture thereto to obtain a moisture content of
Mt for the output rod. In the latter modified practice, on the
other hand, the tobacco 2 is processed during primary processing
such that its moisture content is always above the target value
Mt upon entry to the dryer 6 thereby always requiring the sub-
traction of moisture to obtain a moisture content of Mt for the
output rod.
The processing operations of the signal processor 4 in-
volve the generating of a rod moisture content signal Mc from
the moisture sensor signal Ms and the formation of the control
signal C from comparison of the generated signal Mc with the
target moisture Mt. Generation of the signal Mc by the pro-
cessor 4 depends to a large degree on the particular moisture
1~i5~2
sensor being used and such generation is carried out by processing
the signal M to provide a signal which is representative of the
actual or true rod moisture content. Where the characteristics
of the moisture sensor are such that the sensor signal Ms is it~
self representative of true rod moisture content, then this
processing is carried out by equating Mc to Ms. On the other
hand, where the sensor characteristics result in an Ms signal
varying from the true rod moisture content, adjusting factors
are provided to account for the influence of the sensor charac-
teristics. In actual practice, these adjusting factors can beempirically determined for each particular moisture sensor.
As will be discussed hereinbelow, in further practice
in accordance with the present invention, further sensors 7 and
8 for measuring the mass or density and the firmness of the
cigarette rod are employed for enabling moisture sensor signal
àdjustment. In still further practice under the present inven-
tion, a speed or velocity sensor 9 may be provided for cigarette
rod speed determination and included for sensor signal adjustment.
A first sensor which might be employed for the sensor 3
is a resistance type moisture sensor. Such a sensor might be
formed on the above-mentioned conventional maker by inserting
probes through apertures spaced ~long the length of the so-called
tongue of the maker whereat the rod is being formed, the probes
being of sufficient length to enter into the tobacco rod. A
current or voltage could then be supplied to the probe and the
resultant voltage or current through the probe circuit measured
to determine the tobacco rod resistance and, therefore, the rod
moisture content. In particular, such probes could serve as
inputs to the internal circuitry of a model No. TM-80 sensor
manufactured by Testron to provide the moisture measurement.
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l~ssn.~2
Utilizing such a resistance moisture sensor provides a
moisture sensor signal Ms requiring adjustment for arriving at
the actual rod moisture content Mc. In particular it has been
found that the sensor moisture signal Ms requires adjustment
related to rod firmness and rod speed. Thus, for this sensor,
moisture content can be expressed as follows:
c Ao + AlMS + A2FS + A3S (1)
Where Ao-A3 are constants which can be empirically determined
for each particular tobacco blend and resistance sensor. With
the resistance type sensor, the signal processor 4 utilizes the
sensor signal Ms, the firmness sensor signal Fs and the speed
sensor signal S to derive the moisture content signal Mc based
on the expression (1).
Other techniques for monitoring rod moisture content
utilize microwave components. One microwave technique depends
upon the measurement of the power absorbed largely by the moisture
in the cigarette rod as it moves through a suitable microwave
cavity. With this type of moisture sensor, the moisture sensor
signal Ms is a function of reflected and transmitted microwave
power values in the absence and presence of the cigarette rod,
these values being suitably adjusted for temperature variations
in the cavity and/or the rod. Hence, Ms is as follows:
Ms = (Ra + Ta) - Rp + Tp) . 100 (2)
(Ra + Ta)
where Ra and Ta are temperature-adjusted values of the reflec-
tance and transmittance of microwave power in the absence of
the cigarette rod and Rp and Tp are temperature adjusted values
of the reflectance and transmittance in the presence of the
cigarette rod. In this case, the obtained sensor signal Ms
requires adjustment related to the mass of the cigarette rod.
llS5~;~2
Hence, the moisture content is given as:
Mc = Bo + Bl Ms/Ds
In this situation the constants Bo and B1 can also be empiriaal-
ly determined for the particular tobacco blend and microwave
sensor being used.
As above-noted, the signal processor 4 determines the
control signal C based upon the sensor signal Ms adjusted by
certain of the other sensor signal Fs, Ds and S as provided
in equations 1, 2 and 3. The processor 4 might typically take
the form of a general or special purpose digital computer prog-
rammed in accordance with such equations and having stored
therein the target values and appropriate constants. A typical
microcomputer might be an Intel System 80/204 provided with an
Intel System SBC 116 board. Interfacing such microcomputer
with the analog signals Ms, Fs, Ds, S and C might typically be
a model MP 8418-PGA-AO Burr-Brown A/D-D/A converter.
The firmness sensor 3 utilized with the present invention
can be of a strain gauge type and may, for example,be of a type
as shown and described in United States Patent No. 4,033,360.
Additionally, the density sensor 7 might be a beta gauge type
manufactured by Molins Ltd., and supplied with its model number
MK8 or MK9 cigarette maker. The speed sensor 9, on the other
hand, might be a tachometer of conventional design yielding a
value of voltage to represent revolutions per minute.
The practice of the present invention can be utilized
with other controls at the maker to enhance or promote maker
efficiency. Thus, for example, the signal processor may be
utilized to also generate a firmness control signal C' designed
to control the maker such that the output rod has a predeter-
mined or target firmness Ft at the target moisture Mt. Since
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.{, .
l~S5~32
the moisture control of the system maintains the output rodmoisture content substantially at target moisture Mt, the firm-
ness variations requiring correction will depend almost solely
on tobacco content variations.
A system for controlling firmness in this manner is dis-
closed in commonly assigned U.S. Patent Application Serial No:
111 607. In the system of the latter patent application, the
control signal C' is expressed as follows:
C' = (Fs ~ Fsm) Ft
where FSm is firmness content in the tobacco attributable to
moisture referenced to target moisture and is given as
FSm = Kl (Mc Mt)
The latter expression, in turn, is derivable from rod firmness
attributable to moisture which can be expressed as:
Fm = Ko + KlMc
where Kois a constant determined by the tobacco blend and the
rod weight per unit volume and Kl is a negative constant
determined by the tobacco blend only.
In a system of this type firmness control can be
achieved by utilizing the control signal C' to adjust the
height of the excreteur blade used to cut the tobacco stream at
a given depth during rod formation. Alternatively, the control
signal C' might be used to control the maker distributor to
obtain the desired control. Such practices are disclosed, for
example, in U.S. Patent No. 3,595,067.
