U.S. patent application number 09/734616 was filed with the patent office on 2001-05-10 for method of and apparatus for ascertaining at least one characteristic of a substance.
Invention is credited to Moeller, Henning, Noack, Andreas, Tobias, Joerg.
Application Number | 20010000946 09/734616 |
Document ID | / |
Family ID | 27215922 |
Filed Date | 2001-05-10 |
United States Patent
Application |
20010000946 |
Kind Code |
A1 |
Moeller, Henning ; et
al. |
May 10, 2001 |
Method of and apparatus for ascertaining at least one
characteristic of a substance
Abstract
At least one characteristic, such as the mass/density and/or
moisture content and/or dielectric constant, of a substance (such
as the rod-like tobacco filler of a continuously advancing
cigarette rod or a continuously advancing rod-like filler of filter
material for tobacco smoke) is ascertained by an evaluating circuit
receiving high-frequency signals from a resonator arrangement which
receives microwave signals at least at two different frequencies
from one or more microwave generators. The substance is caused to
advance through a dielectric resonator of the resonator
arrangement, and the high-frequency signals are influenced by the
substance. For example, the circuit can compare first and second
curves of high-frequency signals which respectively are and are n
ot influenced by a selected substance; the curves can have sloping
flanks and each of the two frequencies can be allocated to a
sloping flank of a curve. The circuit compares the amplitudes of
the curves to ascertain the extent of damping of the output signals
due to the presence of a substance at the resonator.
Inventors: |
Moeller, Henning; (Hamburg,
DE) ; Tobias, Joerg; (Drage/Elbe, DE) ; Noack,
Andreas; (Hamburg, DE) |
Correspondence
Address: |
VENABLE, BAETJER, HOWARD & CIVILETTI, LLP
Suite 1000
1201 NEW YORK AVENUE
Washington
DC
20005-3917
US
|
Family ID: |
27215922 |
Appl. No.: |
09/734616 |
Filed: |
December 13, 2000 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09734616 |
Dec 13, 2000 |
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09047481 |
Mar 25, 1998 |
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6163158 |
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09047481 |
Mar 25, 1998 |
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08799129 |
Feb 13, 1997 |
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Current U.S.
Class: |
324/640 |
Current CPC
Class: |
G01N 22/00 20130101;
A24C 5/3412 20130101 |
Class at
Publication: |
324/640 |
International
Class: |
G01R 027/32 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 20, 1996 |
DE |
196 06 183.0 |
Aug 20, 1997 |
DE |
197 34 978.1 |
Claims
What is claimed is:
1. A method of ascertaining at least one characteristic of a
substance by means of a high-frequency resonator arrangement which
is detuned in the presence of the substance, comprising the steps
of supplying to an input of the resonator arrangement microwaves
having at least two different frequencies whereby an output of the
resonator arrangement respectively furnishes first and second
curves of high-frequency output signals in the presence and absence
of a substance, said curves having different amplitudes; and
evaluating said output signals including comparing said curves to
ascertain shifts of resonance frequencies of said output signals
due to the presence of a substance, and comparing the amplitudes of
said curves to ascertain damping of output signals due to the
presence of a substance.
2. The method of claim 1, wherein said supplying step includes
continuously transmitting to the input microwaves having at least
two different frequencies.
3. The method of claim 1, further comprising the step of
periodically varying the frequencies of microwaves supplied to the
input of the resonator arrangement.
4. The method of claim 3, wherein said varying step includes
repeatedly shifting between higher and lower frequency values.
5. The method of claim 3, wherein said varying step includes
repeatedly and continuously wobbling between higher-frequency and
lower-frequency values.
6. The method of claim 5, wherein said microwaves have frequencies
each allocated to a sloping flank of a curve.
7. The method of claim 6, further comprising the step of
substantially sinusoidally wobbling the frequencies of said
microwaves between threshold values with relatively small frequency
changes.
8. The method of claim 7, wherein said output signals have d-c
fractions and substantially sinusoidally varying a-c fractions.
9. The method of claim 8, wherein said evaluating step comprises
transmitting said d-c fractions and said a-c fractions to discrete
calculating stages, polynomially computing said fractions in the
respective stages with constants to thus generate partial signals,
and adding said partial signals.
10. The method of claim 9, wherein said evaluating step further
comprises ascertaining said constants by parameterization on the
basis of reference values of the substance, said reference values
including--as a function of the at least one characteristic to be
ascertained--at least one of the density/mass, moisture content and
dielectric constant of the substance.
11. The method of claim 7, wherein said threshold values are at
least substantially symmetrical to an inversion point of a
downwardly sloping flank of a curve.
12. The method of claim 1, wherein said at least two different
frequencies are symmetrical with reference to a resonance frequency
which is not influenced by the substance, said at least two
different frequencies being allocated to downwardly sloping flanks
of the resonance curve.
13. The method of claim 1, further comprising the step of
generating said microwaves including substantially sinusoidally
modulating the amplitude of a microwave oscillation at a relatively
low frequency.
14. The method of claim 13, wherein said modulating step includes
maintaining the basic frequencies of the developing frequency bands
at a downwardly sloping flank of the curve, particularly at an
inversion point of said flank.
15. The method of claim 1, wherein said supplying step includes
transmitting to the input of the resonator arrangement microwaves
at two modulation-established frequencies, said evaluating step
including scaling down the microwave frequencies and selectively
filtering those frequency ranges which influence said shifts of
resonance frequencies and said damping of output signals.
16. The method of claim 1, wherein the substance is tobacco and
said at least one characteristic is the mass/density of
tobacco.
17. The method of claim 1, wherein the substance is tobacco in a
tobacco particle flow and said at least one characteristic is the
moisture content/mass of tobacco.
18. The method of claim 1, wherein the substance is tobacco in a
flow of shredded tobacco particles and said at least one
characteristic is the dielectric constant of shredded tobacco.
19. Apparatus for ascertaining at least one characteristic of a
substance, comprising a resonator arrangement; means for supplying
to an input of said arrangement microwave signals at least at two
different frequencies, said arrangement having output means for the
transmission of first and second high-frequency signals
respectively generated in the presence and in the absence of a
substance at said arrangement; and means for evaluating said first
high-frequency signals, including means for comparing first and
second resonance curves having different amplitudes and
respectively denoting said first and said second high-frequency
signals to thus ascertain shifts of resonance frequency
attributable to the presence of a substance at said arrangement,
and means for comparing the amplitudes of said first and second
resonance curves to thus ascertain the damping of such amplitudes
by a substance.
20. The apparatus of claim 19, wherein said supplying means
includes at least one microwave generator arranged to
uninterruptedly transmit to said input microwave signals at said at
least two different frequencies.
21. The apparatus of claim 20, wherein said generator includes
means for periodically altering the frequency of said microwave
signals.
22. The apparatus of claim 19, wherein said supplying means
comprises a microwave generator connected to said input and a
frequency regulator connected with said generator to periodically
vary the frequency of signals from said generator between higher
and lower values.
23. The apparatus of claim 19, wherein said supplying means
comprises a microwave generator connected to said input and a
frequency regulator connected with said generator to continuously
and regularly vary the frequency of signals from said generator
between higher and lower values.
24. The apparatus of claim 19, wherein said at least two different
frequencies are symmetrical with reference to a resonance frequency
of said second curve and are located at downwardly sloping flanks
of said second curve.
25. The apparatus of claim 19, wherein said supplying means
comprises a microwave generator connected to said input and a
frequency regulator connected with said generator to continuously
and regularly vary the frequency of signals from said generator
between higher and lower values, said microwave signals being
allocated to downwardly sloping flanks of at least one of said
curves.
26. The apparatus of claim 25, wherein said frequency regulator is
arranged to substantially sinusoidally vary the frequency of
signals from said microwave generator.
27. The apparatus of claim 26, wherein said comparing means
comprises means for ascertaining d-c and a-c fractions of said
first high-frequency signals.
28. The apparatus of claim 19, wherein said supplying means
includes means for transmitting to said input microwaves at
frequencies having upper and lower threshold values and
continuously wobbling between said values, said values being at
least substantially symmetrical with reference to an inversion
point of a downwardly sloping flank of a resonance curve.
29. The apparatus of claim 19, wherein said evaluating means
includes calculating stages which respectively receive d-c
fractions and a-c fractions of said high-frequency signals and
include means for polynomially computing said fractions with
constants to thus generate partial signals, and means for adding
said partial signals.
30. The apparatus of claim 29, wherein said evaluating means
further comprises means for ascertaining said constants by
parameterization on the basis of reference values of a substance,
said reference values including--as a function of the at least one
characteristic to be ascertained--at least one of the density/mass,
moisture content and dielectric constant of the substance.
31. The apparatus of claim 19, wherein said supplying means
includes means for substantially sinusoidally modulating the
frequencies of said microwave signals with a relatively low
frequency.
32. The apparatus of claim 31, wherein bands of said modulated
frequencies include a basic frequency at a downwardly sloping flank
of the resonance curve, particularly at an inversion point of such
curve.
33. The apparatus of claim 19, wherein said supplying means
includes means for continuously transmitting to said input
microwave signals at two different frequencies, and further
comprising means for scaling down the high-frequency signals
between said output means and said evaluating means and means for
selectively filtering, between said scaling down means and said
evaluating means, those frequency ranges which influence said
shifts of resonance frequencies and said damping of the resonance
curves by a substance.
34. The apparatus of claim 19, wherein said arrangement comprises a
metallic housing having an inlet and an outlet for a flow of a
substance to be tested, such as a tobacco stream.
35. The apparatus of claim 34, wherein said housing is dynamically
balanced.
36. The apparatus of claim 35, wherein said housing includes a
cylinder.
37. The apparatus of claim 34, wherein said arrangement further
comprises at least one dielectric resonator in said housing.
38. The apparatus of claim 37, wherein said at least one dielectric
resonator provides a path for the advancement of a substance
between said inlet and said outlet.
39. The apparatus of claim 38, wherein said arrangement further
comprises a tubular guide for the substance, said guide including
portions at said inlet and said outlet.
40. The apparatus of claim 39, wherein said guide extends through
said at least one dielectric resonator.
41. The apparatus of claim 39, further comprising conductive
sleeves surrounding said guide in the regions of said inlet and
said outlet.
42. The apparatus of claim 41, wherein said sleeves contain a
metallic material.
43. The apparatus of claim 19, wherein said arrangement comprises
two resonators each receiving microwave signals from said supplying
means, one of which transmits said high-frequency signals, and the
other of which transmits to said evaluating means additional
signals influenced by a reference substance to compensate for
disturbances.
44. The apparatus of claim 43, wherein said arrangement further
comprises at least substantially identical housings for said
resonators.
45. The apparatus of claim 19, wherein said at least one
characteristic is density/mass of tobacco.
46. The apparatus of claim 19, wherein said at least one
characteristic is the moisture content of cut tobacco in a
cigarette rod.
47. The apparatus of claim 19, wherein said at least one
characteristic is the dielectric constant of cut tobacco,
particularly in a cigarette rod.
48. A method of ascertaining at least one characteristic of a
substance by means of a high-frequency resonator arrangement which
is detuned in the presence of the substance, comprising the steps
of supplying to an input of the resonator arrangement microwaves
having two frequencies whereby an output of the resonator
arrangement respectively furnishes first and second curves of
high-frequency output signals in the presence and absence of a
substance, said curves having amplitudes and sloping flanks and
each of said frequencies being allocated to a sloping flank of a
curve; and evaluating said output signals including comparing said
curves to ascertain shifts of resonance frequencies of said output
signals due to the presence of a substance, and comparing the
amplitudes of said curves to ascertain damping of output signals
due to the presence of a substance.
49. The method of claim 48, further comprising the step of
periodically varying the frequencies of microwaves supplied to the
input of the resonator arrangement, said varying step including
repeatedly switching between higher and lower frequency values.
50. The method of claim 48, further comprising the step of
modulating the frequencies of said microwaves with a
lower-frequency rectangular a-c voltage.
51. The method of claim 50, wherein said output signals are d-c
signals and said modulated frequencies have maximum and minimum
values, and further comprising the steps of ascertaining the d-c
signals which are transmitted by the output of the resonator
arrangement at said minimum and maximum values of said modulated
frequencies, and processing the thus ascertained maximal and
minimal signals into evaluation signals.
52. The method of claim 51, wherein said processing step includes
providing a further signal denoting the sum of said maximal and
minimal signals and processing said further signal into a signal
denoting an average value of said maximal and minimal signals, said
processing step further including providing an additional signal
denoting the difference between said maximal and minimal signals,
transmitting said further and additional signals to discrete
calculating stages, polynomially computing said maximal and minimal
signals in the respective stages with constants to thus generate
partial signals, and adding said partial signals.
53. The method of claim 52, further comprising the step of
ascertaining said constants by parameterization on the basis of
to-be-ascertained reference values of the substance.
54. The method of claim 53, wherein said reference values include
the density/mass, moisture content and dielectric constant.
55. The method of claim 48, wherein said substance is tobacco and
said at least one characteristic is the mass/density of
tobacco.
56. The method of claim 55, wherein said substance is a rod-like
filler of cut tobacco.
57. The method of claim 48, wherein said substance is tobacco and
said at least one characteristic is the moisture content of
tobacco.
58. The method of claim 57, wherein said substance is a rod-like
filler of cut tobacco.
59. Apparatus for ascertaining at least one characteristic of a
substance, comprising a resonator arrangement; means for supplying
to an input of said arrangement microwave signals at two
frequencies, said arrangement having output means for the
transmission of first and second high-frequency signals
respectively generated in the presence and in the absence of a
substance at said arrangement; and means for evaluating said first
high-frequency signals, including means for comparing first and
second resonance curves having amplitudes and sloping flanks, each
of said frequencies being allocated to a sloping flank of a curve
and said first and second curves respectively denoting said first
and second high-frequency signals to thus ascertain shifts of
resonance frequencies attributable to the presence of a substance
at said arrangement, and means for comparing the amplitudes of said
first and second resonance curves to thus ascertain the damping of
such amplitudes by a substance.
60. The apparatus of claim 59, wherein said supplying means
comprises a microwave generator connected to said input and a
frequency regulator connected with said generator to periodically
vary the frequency of signals from said generator between higher
and lower values.
61. The apparatus of claim 59, further comprising means for
modulating the frequencies of microwaves with a lower-frequency
rectangular a-c voltage.
62. The apparatus of claim 61, wherein the first and second
high-frequency signals are d-c signals and the modulated
frequencies have maximum and minimum values, and further comprising
means for ascertaining the d-c signals which are transmitted by the
output means of the resonator arrangement at said minimum and
maximum values of said modulated frequencies, and means for
evaluating the ascertained d-c signals into evaluation signals.
63. The apparatus of claim 62, wherein said evaluating means
comprises summing and subtracting circuits having outputs for
signals which are transmitted to discrete calculating stages having
means for polynomially computing signals from the respective
circuits with constants to thus generate partial signals, and means
for adding said partial signals.
64. The apparatus of claim 63, wherein said evaluating means
further comprises means for ascertaining said constants by
parameterization on the basis of reference values of a substance,
said reference values including--as a function of the at least one
characteristic to be ascertained--at least one of the density/mass,
moisture content and dielectric constant of the substance.
65. The apparatus of claim 59, wherein said resonator arrangement
comprises a metallic housing having an inlet and an outlet for the
flow of a substance to be tested, such as a tobacco stream.
66. The apparatus of claim 65, wherein said housing is dynamically
balanced.
67. The apparatus of claim 66, wherein said housing includes a
cylinder.
68. The apparatus of claim 65, wherein said arrangement further
comprises a least one dielectric resonator in said housing.
69. The apparatus of claim 59, wherein said at least one
characteristic is density/mass of tobacco.
70. The apparatus of claim 59, wherein said at least one
characteristic is the moisture content of cut tobacco in a
cigarette rod.
Description
BACKGROUND OF THE INVENTION
1. The invention relates to improvements in methods of and in
apparatus for ascertaining one or more characteristics of certain
substances, such as tobacco. More particularly, the invention
relates to improvements in methods of and in apparatus for
ascertaining one or more characteristics (such as the mass per unit
length and/or the moisture content) of mass flows of particulate
materials, such as fragments of tobacco leaf laminae and/or other
smokable substances.
2. It is already known to ascertain certain characteristics of mass
flows of tobacco particles by evaluating the extent of detuning,
due to the presence of such substances, of a high-frequency
resonator which receives microwaves from a suitable generator and
transmits high-frequency signals to a suitable evaluating circuit.
The extent of shift of the resonance frequency and damping of such
high-frequency signals (in comparison with output signals which are
transmitted in the absence of mass flows within the range of the
high-frequency resonator) is indicative of the characteristic(s) of
the material of the mass flow.
3. The making of smokers' products, such as plain or filter
cigarettes, normally involves a testing of the mass flow of tobacco
particles which are to form the rod-like fillers of such products.
As a rule, the testing involves a determination of the mass of
tobacco per unit length of the mass flow and/or the moisture
content of the particles in the mass flow and/or the dielectric
constant of tobacco (as used herein, the term "tobacco" is intended
to embrace natural, reconstituted and artificial (substitute)
tobacco). An accurate determination of the mass per unit length and
of the moisture content is particularly important in connection
with the making of cigarettes or other rod-shaped smokers' products
(hereinafter referred to as cigarettes for short). For example,
once the percentages of dry ingredients and moisture in a mass flow
of tobacco particles are known, one can accurately determine the
overall mass of the tested substance by simple addition of the
signals denoting the dry mass and the moisture content. The
situation is similar in connection with the processing of certain
other substances such as foodstuffs, chemicals, textile materials,
paper and many others.
4. German patent No. 40 04 119 discloses the determination of the
moisture content of substances in a cavity resonator which is
connected to a microwave generator. The patented apparatus resorts
to a calibration curve to ascertain the resonance frequency and the
half intensity width of the resonance line.
OBJECTS OF THE INVENTION
5. An object of the invention is to provide a novel and improved
method of rapidly and accurately ascertaining one or more
characteristics of various substances, such as fragments of tobacco
in a mass flow of tobacco particles in a production line for the
making of rod-shaped smokers' products.
6. Another object of the invention is to provide a method which can
be resorted to for rapid and accurate determination of various
ingredients (such as dry mass and/or wet mass) in mass flows of
particulate materials of the type being utilized in the tobacco
processing, textile, paper making, chemical, food processing and
other industries.
7. A further object of the invention is to provide method of
ascertaining one or more characteristics of mass flow of filter
material for tobacco smoke.
8. An additional object of the invention is to provide method of
rapidly and accurately ascertaining one or more characteristics
(such as the percentages of solid and liquid ingredients, the total
mass and/or the dielectric constant) of a rapidly advancing stream
or flow of tobacco or filter material in a cigarette making
machine.
9. Still another object of the invention is to provide a method of
in line determination of one or more characteristics of smokable
materials, filter materials for tobacco smoke and/or other
materials which are being conveyed in the form of mass flows or
streams or rods or fillers in various plants of the tobacco
processing industry.
10. A further object of the invention is to provide a novel and
improved apparatus for the practice of the above outlined
method.
11. Another object of the invention is to provide a machine or
production line which embodies one or more apparatus for the
practice of the above outlined method.
12. An additional object of the invention is to provide the
apparatus with novel and improved means for transmitting signals to
a resonator arrangement of the above outlined apparatus.
13. Still another object of the invention is to provide the
apparatus with novel and improved means for processing signals
being transmitted by the resonator arrangement of the above
outlined apparatus.
14. A further object of the invention is to provide an apparatus
which can be utilized with advantage in modern high-speed
production lines for the mass-manufacture of plain or filter
cigarettes, cigars, cigarillos, cheroots and/or other rod-shaped
products of the tobacco processing industry.
15. Another object of the invention is to provide an apparatus
which can be designed to accurately and rapidly ascertain one or
more characteristics various substances, such as the dry mass, the
moisture content, the total mass and/or the dielectric constant of
tobacco particles or filter material for tobacco smoke, in
cigarette makers, filter rod makers or other types of production
lines.
SUMMARY OF THE INVENTION
16. One feature of the present invention resides in the provision
of a method of ascertaining at least one characteristic of a
substance by resorting to a high-frequency resonator arrangement
which is detuned in the presence of the substance. The method
comprises the steps of supplying or transmitting to an input of the
resonator arrangement microwaves having at least two different
frequencies whereby an output of the resonator arrangement
respectively furnishes or transmits first and second curves of
high-frequency output signals in the presence and absence of a
substance at the resonator arrangement. Such curves have different
amplitudes, and the method further comprises the step of evaluating
the output signals including comparing the curves to ascertain
shifts of resonance frequencies of the output signals due to the
presence of a substance at the resonator arrangement and comparing
the amplitudes of the curves to ascertain damping of output signals
due to the presence of a substance at the resonator
arrangement.
17. The supplying step can include continuously transmitting to the
input of the resonator arrangement microwaves having at least two
different frequencies.
18. The method can further comprise the step of periodically
varying the frequencies of microwaves which are being transmitted
to the input of the resonator arrangement. This varying step can
include repeatedly shifting between higher and lower frequency
values. Such varying step can also include repeatedly and
continuously wobbling between higher-frequency and lower-frequency
values. The frequencies of the microwaves can be allocated to a
sloping flank of a curve of high-frequency output signals. The
wobbling step can involve substantially sinusoidally wobbling the
frequencies of the microwaves between threshold values with
relatively small frequency changes or differences. The output
signals can have d-c fractions and substantially sinusoidally
varying a-c fractions. The evaluating step of such method can
comprise transmitting the d-c fractions and the a-c fractions to
discrete calculating or computing stages, polynomially computing
the fractions in the respective stages with constants to thus
generate partial signals, and adding or summing the partial
signals. Such evaluating step can further comprise ascertaining the
constants by parameterization on the basis of reference values of
the substance; such reference values can include--as a function of
the at least one characteristic to be ascertained in accordance
with the novel method--at least one of the density/mass, moisture
content and dielectric constant of the substance being tested.
19. The aforementioned threshold values can be at least
substantially symmetrical with reference to an inversion point of a
downwardly sloping flank of a curve.
20. The at least two different frequencies of microwave signals can
be symmetrical with reference to a resonance frequency which is not
influenced by the substance being tested, and the at least two
different frequencies can be allocated to downwardly sloping flanks
of a resonance curve.
21. The method can further comprise the step of generating the
microwaves, and such step can include substantially sinusoidally
modulating the amplitude of a microwave oscillation at a relatively
low frequency. The modulating step can include maintaining the
basic frequencies of the developing frequency bands at a downwardly
sloping flank of the curve, preferably or particularly at an
inversion point of such flank.
22. The supplying step can also include transmitting to the input
of the resonator arrangement microwaves at two
modulation-established frequencies, and the evaluating step of such
method can comprise scaling down the microwave frequencies and
selectively filtering those frequency ranges which influence the
shifts of resonance frequencies and the damping of the output
signals.
23. The substance can consist of or it can contain tobacco, and the
at least one characteristic to be ascertained is or can be the
mass/density of tobacco.
24. The substance to be tested can be tobacco in a tobacco particle
flow, and the at least one characteristic to be tested can be the
moisture content/mass of tobacco. The substance to be tested can
contain or can constitute tobacco in a flow of shredded and/or
otherwise comminuted (cut) tobacco particles, and the at least one
characteristic to be ascertained can be the dielectric constant of
cut or comminuted or shredded tobacco.
25. Another feature of the invention resides in the provision of an
apparatus for ascertaining at least one characteristic of a
substance (e.g., tobacco). The apparatus comprises a resonator
arrangement, and means for supplying to an input of the resonator
arrangement microwave signals at least at two different
frequencies. The resonator arrangement has output means for the
transmission of first and second high-frequency signals which are
respectively generated in the presence and in the absence of a
substance to be tested at the resonator arrangement, and the
apparatus further comprises means for evaluating the first
high-frequency signals. The evaluating means comprises means for
comparing first and second resonance curves having different
amplitudes and respectively denoting the first and second
high-frequency signals to thus ascertain shifts of resonance
frequency attributable to the presence of a substance to be tested
at the resonator arrangement, and means for comparing the
amplitudes of the first and second resonance curves to thus
ascertain the damping of such amplitudes by a substance to be
tested.
26. The means for supplying microwave signals can include at least
one microwave generator which is designed to uninterruptedly
transmit to the input of the resonator arrangement microwave
signals at the at least two different frequencies. The generator
can include means for periodically altering the frequency of the
microwave signals.
27. The means for supplying microwave signals can be designed in
such a way that it comprises a microwave generator which is
connected to the input of the resonator arrangement and a frequency
regulator which is connected with the microwave generator to
periodically vary the frequency of signals from the microwave
generator between higher and lower values.
28. Alternatively, the means for supplying microwave signals can
comprise a microwave generator which is connected to the input of
the resonator arrangement and a frequency regulator which is
connected with the generator to continuously and regularly vary the
frequency of signals from the generator between higher and lower
values.
29. The at least two different frequencies can be symmetrical to
each other with reference to a resonance frequency of the second
curve and are located at downwardly sloping flanks of the second
curve.
30. It is also possible to design the means for supplying microwave
signals in such a way that it comprises a microwave generator
connected to the input of the resonator arrangement and a frequency
regulator connected with the generator to continuously and
regularly vary the frequency of signals from the generator between
higher and lower values. The microwave signals are allocated to
downwardly sloping flanks of at least one of the curves. The
frequency regulator can be arranged to substantially sinusoidally
vary the frequency of signals from the microwave generator. The
comparing means of the evaluating means can comprise means for
ascertaining d-c and a-c fractions of the first high-frequency
signals.
31. The means for supplying microwave signals can include means for
transmitting to the input of the resonator arrangement microwaves
at frequencies having upper and lower threshold values and
continuously wobbling between such values. The threshold values are
at least substantially symmetrical to each other with reference to
an inversion point of a downwardly sloping flank of a resonance
curve.
32. The evaluating means can comprise calculating or computing
circuits or stages which respectively receive d-c fractions and a-c
fractions of the high-frequency signals and include means for
polynomially computing or calculating the fractions with constants
to thus generate partial signals, and means for summing or adding
such partial signals. Such evaluating means can further comprise
means for ascertaining the constants by parameterization on the
basis of reference values of a substance. The reference values can
include--as a function of the at least one characteristic to be
ascertained by the improved apparatus--at least one of the
density/mass, moisture content and dielectric constant of the
substance to be tested.
33. The means for supplying microwave signals can also comprise
means for substantially sinusoidally modulating the frequencies of
the microwave signals with a relatively low frequency. Bands of
modulated frequencies can include a basic frequency at a downwardly
sloping flank of the resonance curve, particularly or preferably at
an inversion point of such curve.
34. The resonator arrangement can comprise a preferably metallic
housing having an inlet and an outlet for a flow of a substance to
be tested (e.g., a tobacco stream). The housing can be dynamically
balanced; for example, such dynamically balanced housing can
include or constitute a cylinder. The resonator arrangement can
further comprise at least one dielectric resonator in the housing,
and such resonator can provide a path for the advancement of a
substance (e.g., a cigarette rod) between the inlet and the outlet
of the housing. The resonator arrangement can further comprise a
tubular guide for the substance, and such guide can include
portions at the inlet and at the outlet of the housing. A presently
preferred guide extends through the at least one dielectric
resonator. The just described resonator arrangement can further
comprise conductive sleeves which surround the guide in the regions
of the inlet and the outlet of the housing; such sleeves can
contain or they can consist of a metallic material.
35. Alternatively, the resonator arrangement of the improved
apparatus can comprise two resonators each of which receives
microwave signals from the supplying means, one of which transmits
the aforementioned high-frequency signals, and the other of which
transmits to the evaluating means additional signals which are
influenced by a reference substance to compensate for disturbances.
Such resonator arrangement can further comprise at least
substantially identical housings for the two resonators.
36. The at least one characteristic which is to be ascertained by
the improved apparatus can be the density/mass of tobacco or the
moisture content of cut tobacco in a cigarette rod or the
dielectric constant of cut tobacco, particularly in a cigarette
rod.
37. A further feature of the invention resides in the provision of
a method of ascertaining at least one characteristic of a substance
by means of a high-frequency resonator arrangement which is detuned
in the presence of the substance to be tested. This method
comprises the steps of supplying to an input of the resonator
arrangement microwaves having two frequencies whereby an output of
the resonator arrangement respectively furnishes first and second
curves of high-frequency output signals in the presence and absence
of a substance (the curves have amplitudes and sloping flanks and
each of the two frequencies is allocated to a sloping flank of a
curve), and evaluating the output signals including comparing the
curves to ascertain shifts of resonance frequencies of the output
signals due to the presence of a substance, and comparing the
amplitudes of the curves to ascertain damping of output signals due
to the presence of a substance. The just outlined method can
further comprise the step of periodically varying the frequencies
of the microwaves which are supplied to the input of the resonator
arrangement, and the varying step of such method can include
repeatedly switching between higher and lower frequency values.
38. Still further, the just outlined method can comprise the step
of modulating the frequencies of the microwaves with a
lower-frequency rectangular a-c voltage. The output signals can
constitute d-c signals and the method can further comprise the
steps of ascertaining those d-c signals which are transmitted by
the output of the resonator arrangement at the minimum and maximum
values of the modulated frequencies, and processing the thus
ascertained maximal and minimal signals into evaluation signals.
The processing step can include providing a further signal which
denotes the sum of the maximal and minimal signals and processing
the further signal into a signal denoting an average value of the
maximal and minimal signals. Such processing step can further
include providing an additional signal which denotes the difference
between the maximal and minimal signals, transmitting the further
and additional signals to discrete calculating stages, polynomially
computing the maximal and minimal signals in the respective stages
with constants to thus generate partial signals, and adding
(summing up) the partial signals. Such method can further comprise
the step of ascertaining the aforementioned constants by
parameterization on the basis of those reference values of the
substance which are to be ascertained. Such reference values can
include the density/mass, the moisture content and the dielectric
constant of the substance to be tested.
39. The substance to be tested can be tobacco, and the at least one
characteristic can be the mass/density of tobacco. For example, the
substance can constitute a rod-like filler of cut tobacco.
Alternatively, the at least one characteristic can be the moisture
content of tobacco, for example, the moisture content of successive
increments of a rod-like filler of cut tobacco.
40. Still another feature of the invention resides in the provision
of an apparatus for ascertaining at least one characteristic of a
substance. The apparatus comprises a resonator arrangement, means
for supplying to an input of the resonator arrangement microwave
signals at two frequencies (the resonator arrangement has output
means for the transmission of first and second high frequency
signals which are respectively generated in the presence and in the
absence of a substance at the resonator arrangement), and means for
evaluating the first high-frequency signals. The evaluating means
comprises means for comparing first and second resonance curves
having amplitudes and sloping flanks. Each of the frequencies is
allocated to a sloping flank of a curve and the first and second
curves respectively denote the first and second high-frequency
curves to thus ascertain shifts of resonance frequencies
attributable to the presence of a substance at the resonator
arrangement. The evaluating means further comprises means for
comparing the amplitudes of the first and second resonance curves
to thus ascertain the damping of such amplitudes by a
substance.
41. The supplying means of the just discussed apparatus can
comprise a microwave generator which is connected to the input, and
a frequency regulator which is connected with the generator to
periodically vary the frequency of signals from the generator
between higher and lower values.
42. The apparatus can further comprise means for modulating the
frequencies of the microwaves with a lower-frequency rectangular
a-c voltage. The first and second high-frequency signals can
constitute d-c signals, and the modulated frequencies have maximum
and minimum values. The apparatus can further comprise means for
ascertaining the d-c signals which are transmitted by the output
means of the resonator arrangement at the minimum and maximum
values of the modulated frequencies, and means for evaluating the
ascertained signals into evaluation signals. The evaluating means
can comprise summing and subtracting circuits having outputs for
signals which are transmitted to discrete calculating stages having
means for polynomially computing signals from the respective
(summing, subtracting) circuits with constants to thus generate
partial signals. Such evaluating means can further comprise means
for adding (totalizing) the partial signals as well as means for
ascertaining the aforementioned constants by parameterization on
the basis of reference values of a substance. The reference values
can include (as a function of the at least one characteristic to be
ascertained) at least one of density/mass, moisture content and
dielectric constant of the substance.
43. The resonator arrangement can comprise a metallic housing
having an inlet and an outlet for the flow of a substance to be
tested, such as a tobacco stream. The housing is or can be
dynamically balanced and can include a cylinder. The resonator
arrangement can comprise at least one dielectric resonator in the
housing.
44. In accordance with one presently preferred embodiment, the at
least one characteristic is the density/mass of tobacco and/or the
moisture content of cut tobacco in a cigarette rod.
45. The novel features which are considered as characteristic of
the invention are set forth in particular in the appended claims.
The improved apparatus itself, however, both as to its construction
and the mode of assembling, installing and utilizing the same,
together with numerous additional important features and advantages
thereof, will be best understood upon perusal of the following
detailed description of certain presently preferred specific
embodiments with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
46. FIG. 1 is a diagrammatic partly elevational and partly
sectional view of an apparatus which is designed to ascertain one
or more characteristics of a continuous cigarette rod and is
constructed and assembled in accordance with a first embodiment of
the invention;
47. FIG. 2 is a coordinate system showing the resonance curves of a
resonator arrangement in the apparatus of FIG. 1, one curve being
indicative of the output signals when the dielectric resonator of
the resonator arrangement is not influenced and the other curve
being indicative of the output signals when the resonator is
influenced by a substance to be tested;
48. FIG. 3 is a view similar to that of FIG. 1 but showing certain
details of a modified apparatus wherein the resonator arrangement
receives wobbled microwave signals;
49. FIGS. 4a, 4b and 4c illustrate coordinate systems wherein the
curves denote the high-frequency signals transmitted by the
resonator arrangement in the apparatus of FIG. 3;
50. FIG. 5 is a diagrammatic view of an evaluating circuit which
can be utilized to ascertain the dry mass and/or the wet mass of
successive increments of a rod-like tobacco filler which is
confined in the tubular envelope of a continuous cigarette rod;
51. FIG. 6 is a diagrammatic view of an evaluating circuit which is
utilized to furnish signals denoting the dielectric constants of
successive increments of a flow of tobacco particles;
52. FIG. 7 is a diagrammatic view of a third apparatus wherein the
evaluating circuit receives three signals having frequencies
obtained as a result of modulation of a microwave signal;
53. FIG. 8 is a coordinate system showing a modulated microwave
signal;
54. FIG. 9 is coordinate system similar to that of FIG. 2 but
showing curves denoting the signals transmitted by the output means
of the resonator arrangement in the apparatus of FIG. 7;
55. FIG. 10 is a diagrammatic view similar to that of FIG. 1 but
showing the details of still another apparatus with different means
for transmitting microwave signals to the resonator arrangement and
with different means for transmitting high-frequency signals to the
evaluating circuit.
56. FIG. 11 is a diagrammatic view similar to that of FIG. 1 but
showing the details of a further presently preferred apparatus;
57. FIGS. 12a, 12b and 12c illustrate coordinate systems wherein
the curves denote the high-frequency signals transmitted by the
resonator arrangement in the apparatus of FIG. 11; and
58. FIG. 13 is a diagrammatic view of an evaluating circuit which
can be utilized in the apparatus of FIG. 11.
DESCRIPTION OF PREFERRED EMBODIMENTS
59. Referring first to FIG. 1, there is shown an apparatus which is
designed to ascertain at least one characteristic of a substance
(tobacco) forming a rod-shaped filler 12b in a tubular envelope 12a
of a continuous rod 12, e.g., a rod containing fragments of tobacco
leaf laminae in a cigarette paper wrapper and being ready to be
subdivided into plain cigarettes of unit length or multiple unit
length. For example, the making of the rod 12 can take place in a
machine known as PROTOS 100 which is distributed by the assignee of
the present application. PROTOS 100 is a high-performance
production line with an output of 11000 cigarettes per minute or
more.
60. The apparatus of FIG. 1 comprises a high-frequency resonator
arrangement 1 including a dielectric resonator 21 in a housing 2
which is dynamically balanced and can constitute a cylinder. The
illustrated housing 2 is made of a conductive metallic material,
such as copper. It is equally possible to employ other types of
rotationally symmetrical housings or housings having a polygonal
cross-sectional outline and made of a material other than copper or
other than a metallic material.
61. The resonator arrangement 1 receives high-frequency signals
(preferably microwave signals) from a source 3 (such as a
generator) by way of a first conventional coaxial cable 4, and a
second conventional coaxial cable 6 is employed to connect the
output of the resonator arrangement 1 with an evaluating
arrangement 11. The cables 4 and 6 are provided with customary
coupling loops, not shown in FIG. 1.
62. The resonator 21 is made of a dielectric material, such as a
ceramic or a synthetic plastic substance having a high dielectric
constant (for example, the resonator can be made of
BaO--PbO--Nd.sub.2 O.sub.3--TiO.sub.2). This resonator is a hollow
cylinder which is fixed in the housing 2 by resorting to suitable
distancing or spacer means, not shown. A portion 21a of the
resonator 21 is movable axially of the other portion or portions,
e.g., for the purpose of ascertaining and/or adjusting (selecting)
the resonance frequency. An advantage of a dielectric resonator is
that it contributes to higher sensitivity and greater accuracy of
measurements.
63. The housing 2 is provided with an inlet 7 and an outlet 9. This
renders it possible to insert a tubular guide 13 which defines a
path for the advancement of the cigarette rod 12 in the direction
which is indicated by an arrow 15. The apparatus of FIG. 1 is
designed to ascertain the dry mass and/or the wet mass and/or the
overall mass or the dielectric constant of the filler 12b. The
guide 13 is made of a non-conductive material, such as quartz. One
of the functions of the guide 13 is to prevent undesirable foreign
matter (such as dust and small particles of tobacco) from
penetrating into the housing 2; foreign matter in the housing could
interfere with proper operation of the resonator arrangement 1.
Tubular sleeves 14a and 14b surround the guide 13 in the region of
the inlet 7 and outlet 9 to prevent the radiation of excessive
quantities of the high-frequency field from the housing 2 by way of
the inlet and/or outlet. The sleeves 14a and 14b are preferably
made of a conductive material, e.g., a suitable metallic
material.
64. The axis 17 of the resonator 21 preferably coincides with the
axes of the guide 13 and housing 2; such symmetrical arrangement of
these parts also contributes to the accuracy and reliability of the
measurements. The sensitivity of the measurements is further
enhanced due to the fact that the guide 13 extends through the
central opening 20 of the resonator 21; such positioning of the
parts 13 and 21 relative to each other has been found to greatly
enhance the sensitivity as well as the accuracy of the
determination of one or more parameters of the filler 12b in the
cigarette rod 12.
65. The cable 4 supplies to the dielectric resonator 21 two
microwave signals having different frequencies in the GHz range,
e.g., approximately 6 GHz. A conventional circulator 18 is employed
to prevent a feedback from the resonator arrangement 1 to the
microwave generator 3. FIG. 2 shows that the cable 4 supplies
microwave signals having frequencies f1 and f2 which are
symmetrical to each other with reference to the resonance frequency
fo (note the curve uo of FIG. 2 denoting the resonance frequency of
the housing 2 when the guide 13 is empty). The microwave generator
3 is controlled by a frequency regulator 24 which causes the
generator 3 to periodically shift from the transmission of signals
having the lower frequency f1 to the transmission of signals having
the higher frequency f2, back to the transmission of
lower-frequency signals, and so forth.
66. It is also possible to employ two microwave generators in lieu
of the single generator 3; the two generators are then designed to
transmit signals having slightly or somewhat different frequencies,
and a modified frequency regulator then causes the two generators
to alternately supply different-frequency signals via cable 4 and
on to the high-frequency resonator arrangement 1. For example, the
regulator which is used in conjunction with two generators can be
set up to turn off one of the generators when the other generator
is on, to thereupon shut off the other generator while turning on
the one generator, and so forth.
67. It is equally possible to supply (wobble) microwave signals
which are frequency modulated symmetrically relative to the
resonance frequency fo and to employ for the measurement only those
signals which exhibit the frequencies f1 and f2.
68. The cable 6 transmits output signals from the resonator
arrangement 1, by way of a (feedback preventing) circulator 19 and
on to a microwave diode 22. For example, the diode 22 can be that
known as Type HP 8472B which is distributed by Hewlett-Packard,
Herrenberger Strasse 130, D-71034 Boblingen, Federal Republic
Germany. The purpose of the diode 22 is to convert the microwave
signals into d-c signals. The signals U at the output of the diode
22 are represented by the curve uo of FIG. 2 when the guide 13 is
empty, and by the curve u when the guide 13 contains an advancing
cigarette rod 12.
69. Since the frequencies f1 and f2 are symmetrical with reference
to the resonance frequency fo, the signals U10 and U20 which are
transmitted by the diode 22 are identical, i.e., the difference
between the signals U10 and U20 (as measured along the ordinate in
the coordinate system of FIG. 2) is zero. Such situation prevails
when the guide 13 is empty. When the apparatus of FIG. 1 is in use
(i.e., when a cigarette rod 12 or any other body to be tested in
caused to advance through the guide 13), the values of the
resonance frequency f are reduced and, furthermore, the amplitude
is also reduced (reference should be had to the curve u of FIG. 2).
At the frequencies f1 and f2, the diode 22 then transmits signals
U1 and U2 having different values (as measured along the ordinate).
The difference between the signals U1 and U2 is dependent on the
extent of shift of resonance frequency, i.e., it increases in
response to an increase of such shift. An evaluation of the signals
at the frequencies f1 and f2 renders it possible to ascertain the
extent of damping and the extent of shift of resonance frequency.
Thus, and the same as in connection with other types of
high-frequency measurements, the evaluating arrangement 11 can
ascertain the mass/density ratio (independently of the moisture),
the moisture (independently of the density) as well as the
dielectric constant. If the corresponding signals are added up
(summed), one can ascertain the total mass including the dry mass
and the wet mass.
70. The connection between the output of the diode 22 and the input
of the evaluating arrangement 11 comprises an analog-to-digital
(A/D) converter 23 (e.g., a circuit known as Type MX 7672-03
distributed by Maxim Integrated Products, 120 San Gabriel Drive,
Sunnyvale, Calif. 94086). The circuit 23 digitalizes the signals
from the diode 22 and further serves as a gate circuit which
permits the signals from the diode 22 to reach the input of the
evaluating arrangement 11 when it receives a corresponding signal
from the frequency regulator 24 via conductor means 25. The
regulator 24 applies to the microwave generator 3 voltage impulses
of different intensities, and such signals influence the
frequencies of signals which are being transmitted via coaxial
cable 4. As already explained above, the arrangement can be such
that the generator 3 is caused to shift from the transmission of
signals having a lower frequency f1 to the transmission of signals
having a higher frequency f2, thereupon back to the transmission of
signals having the frequency f1, and so on.
71. In order to exclude transitional phenomena, the A/D converter
23 receives signals to connect the output of the diode 22 with the
input of the evaluating arrangement 11 only when the resonator
arrangement 1 actually receives (via cable 4) a signal having the
frequency f1 or a signal having the frequency f2.
72. FIG. 3 illustrates a modified apparatus. Those component parts
of the modified apparatus which are identical with or clearly
analogous to the corresponding component parts of the apparatus of
FIG. 1 are denoted by similar reference characters. The microwave
generator 3 is again designed to transmit microwave signals having
a frequency in the GHz region (e.g., about 6 GHz). A frequency
regulator 24 is operatively connected with and causes the generator
3 to periodically vary the frequency of output signals in a
sinusoidal fashion. This can be readily seen in FIG. 4a wherein the
curve s denotes the changes of frequency f as a function of time t.
The average frequency fm (for example, several hundred KHz) is
continuously varied sinusoidally (as indicated by the curve s)
within a frequency range .DELTA.f. As shown in FIG. 4b, the average
frequency fm is preferably at the inversion point Uow of the
resonance curve uo which has been determined while the housing 2 of
the resonator arrangement 1 was empty. The output signal U of the
diode 22, which receives signals from the generator 3 via
circulator 18, resonator arrangement 1 and circulator 19 fluctuates
between the values Uomin and Uomax when no tobacco is caused to
pass through the housing 2 of the resonator arrangement 1. In
actual use, i.e., when a filler 12b or another flow of fibrous
material of the tobacco processing industry is caused to advance
through the dielectric resonator in the housing of the resonator
arrangement 1 of FIG. 3, the progress of the damping curve is that
shown in FIG. 4b, as at u, which exhibits the values Umin and Umax.
The reference characters Uomit and Umit denote average values which
are available at the average frequency fm. In FIG. 4b, the
reference character fo again denotes the resonance frequency when
the housing of the resonator arrangement of FIG. 3 is empty, and
the character f denotes the resonance frequency when the apparatus
of FIG. 3 is in actual use.
73. The coordinate system of FIG. 4c shows the variations of the
signals U at the output of the diode 22 of FIG. 3 as a function of
time. When the apparatus of FIG. 3 is not in actual use, the
corresponding curve includes a d-c fraction Uog and an a-c fraction
Uoa; however, the curve has a d-c fraction Ug and an a-c fraction
Ua when the apparatus is in actual use.
74. FIG. 3 shows that the signals at the output of the diode 22 are
transmitted to a d-c fraction filter 26 and to an a-c fraction
filter 27. The two filters 26 and 27 respectively transmit signals
to A/D converters 28 and 29 wherein the corresponding signals are
digitalized prior to being transmitted to the corresponding inputs
of the evaluating arrangement 11. The latter can transmit (via
conductor means 31) to the frequency regulator 24 suitable
correction signals as soon as the average frequency fm migrates
beyond the inversion point of the resonance curve uo shown in FIG.
4b. Such correction via conductor means 31 causes the frequency fm
of the output signal from the generator 3 to reassume the value Uow
which corresponds to the inversion point of the resonance curve
Uo.
75. Based on a comparison between the d-c fractions Uog and Ug, as
well as between the a-c fractions Uoa and Ua (when the housing 2
respectively does not contain a filler 12b and contains such a
filler), the evaluating arrangement 11 can draw conclusions
regarding the characteristics of tobacco (such as its wet mass, its
dry mass and/or is dielectric constant). This will be explained in
detail with reference to FIGS. 5 and 6.
76. FIG. 5 shows schematically the processing of the signals Ua, Ug
(see FIG. 4c) in the evaluating arrangement 11 of the apparatus
which is shown in FIG. 3 for the purpose of ascertaining the
mass/density values. In the following description, the signal Ua is
intended to denote the d-c value of the a-c fraction shown in FIG.
4c. The first step involves the storage of digitalized signals in
the memories SUg and SUa which are shown in FIG. 5. Such signals
are addressed by a scanner in a sequence corresponding to
predetermined increments of the cigarette rod 12, e.g., increments
each having a length of 1 mm. This means that, if the cigarette rod
12 is advanced at a rate required to turn out 10000 plain
cigarettes of unit length (60 mm) per minute, the addressing or
scanning frequency is 100 microseconds. In other words, the
memories SUg and SUa are addressed at intervals of 100
microseconds. The duration of the pulses Ig and Ia of transmission
of signals (values) from the memories Sug and SUa to the
calculating stages Rg and Ra, respectively, of the evaluating
arrangement 11 is even less. In the stages Rg and Ra, the
transmitted signals are processed with constants to furnish output
values Ag and Aa, respectively. In a simple case, the processing of
signals in the stages Rg and Ra can be carried out with polynomials
of the type a+b Ug=Ag and c+d Ua=Aa, respectively. The constants a,
b, c and d are ascertained by resorting to parameterizing, namely
by measuring the values Ug and Ua of cigarettes which were weighed
to accurately ascertain their masses/densities. The relationships
between different masses/densities and the corresponding values of
Ug and Ua render it possible to ascertain the aforementioned
constants.
77. In principle, it is equally possible to resort to polynomials
of a higher order or to other types of functions.
78. The signals Ag and Aa at the outputs of the respective
calculating stages Rg and Ra are transmitted to the corresponding
inputs of a first adding or summing circuit or stage Ad, and the
signal Ae at the output of the circuit Ad is indicative of the
density/mass. If the intensity and/or other characteristic(s) of
the signal Ae departs or depart from the desired or required
characteristic or characteristics, a correction stage Kg can be
utilized to transmit an empirically determined correction signal Ak
to the corresponding input of a second adding or summing circuit or
stage Add which processes the signals Ae and Ak to furnish an
output signal Aed which is even more accurately representative of
the density/mass value of the filler 12b in the tested cigarette
rod 12.
79. The evaluation of signals in the arrangement 11 of the
apparatus which is shown in FIG. 1 can be carried out in a manner
analogous to the just described mode of operation of the
arrangement 11 in the apparatus of FIG. 3. The signals furnished by
the A/D converter 23 of FIG. 1 are stored in memories corresponding
to the memories SUg, SUa of FIG. 5.
80. The evaluation with the evaluating circuit arrangement of FIG.
5 can also be realized by employing a third memory SU3. The
memories SUg=SU1 and SUa=SU2 receive the signals U1, U2 (FIG. 7).
The calculating stages are denoted by the characters R1, R2, R3 and
the signals at the outputs of these stages are respectively shown
at r1, r2 and r3. The transmission or transfer pulses are
respectively shown at I1, I2 and I3.
81. Basically, an evaluation of high-frequency measurement signals
for the purpose of ascertaining the moisture content of tobacco in
a cigarette rod can be carried out in the same way as already
described hereinabove. The difference is that, in lieu of utilizing
cigarettes having a known weight/mass, the parameterization
involves the utilization of cigarettes having certain known
moisture quantities or percentages, i.e., various values of
relative moisture.
82. FIG. 6 shows schematically the processing (evaluation) of
signals Ua, Ug (reference should be had again to FIGS. 4a, 4b and
4c) in an evaluating circuit 11 of the type utilized in the
apparatus of FIG. 3 for the purpose of ascertaining the dielectric
constant .epsilon. of the tobacco filler 12b in the cigarette rod
12. The first step involves temporary storage of the signals Ug and
Ua in the memories SUg and SUa. As already described with reference
to FIG. 3, memories SUg and SUa are addressed periodically and at
relatively short time intervals, i.e., the contents of these
memories are transmitted by transmission or transfer impulses Ig
and Ia to selected calculation or computing stages. As shown, the
real portion of the information stored in the memory SUg is
transmitted to the stage R'g and the imaginary portion of such
information is transmitted to the stage R"g. Analogously, the real
portion of the information obtained in the memory SUa is
transmitted to the stage R'a, and the imaginary portion of such
information is transmitted to the stage R"a. The stages R'g and R'a
process the real portions with constants into output signals E'g
E'a, and stages R"g, R"a process the imaginary portions with
constants into imaginary signals E"g, E"a. Computing in the
respective stages takes place with polynomials the constants of
which are determined by resorting to actual measurements of the
real and imaginary parts of the dielectric constants of sample
cigarettes. Output signals E'g and E'a which correspond to the real
parts are transmitted to an adding or summing circuit or stage A'd,
and the imaginary parts E"g and E"a are transmitted to a second
adding or summing circuit A"d. The added signals .epsilon.' provide
the real part of the dielectric constant (at the output of the
circuit or stage A'd) and the added signals .epsilon." provide the
imaginary part of the dielectric constant (at the output of the
circuit or stage A"d). The reference character V denotes in FIG. 6
a conventional circuit which furnishes a complex value .epsilon. on
the basis of the values 6'.epsilon. and .epsilon.".
83. A correction stage or circuit (corresponding to the stage Kg
shown in FIG. 5) can be utilized to furnish, when necessary,
empirically determined correction signals. The value of the complex
dielectric constant .epsilon. can be ascertained (in V) by
vectorial addition of the values .epsilon.' and .epsilon.".
84. FIGS. 7, 8 and 9 illustrate certain features of a further
apparatus employing a microwave generator 3 for the transmission of
microwaves, preferably in the GHz range (for example, approximately
6 GHz). The signal from the generator 3 is transmitted as carrier
frequency to a modulating circuit 36 wherein the microwave signal
is amplitude modulated with at least one substantially sinusoidal
signal having a considerably lower frequency and being transmitted
by a sender 37. A modulator which can be utilized at 36 in the
apparatus of FIG. 7 to generate a secondary frequency signal by
resorting to amplitude modulation is known as Module MDC-177 and is
distributed by the Firm Adams Russel, Anzac Division, 80 Cambridge
Street, Burlington, Md.
85. A specific example of an acceptable modulating circuit 36 is as
follows: 5.8 GHz modulated with 10 MHz provides 5.790 GHz and 5.810
GHz. A similar or identical component part can be utilized in the
apparatus of FIG. 10 as a mixer 47 to effect a downward mixing of
the GHz frequency. Example: The characteristic frequencies of 5.790
GHz and 5.810 GHz mixed with 5.7850 GHz provide 25 MHz and 45
MHz.
86. The progress of an amplitude modulated microwave signal Umod is
shown in the coordinate system of FIG. 8 as a function of time t.
It comprises high-frequency microwave oscillations u of the
generator 3 and the superimposed modulating oscillation which forms
a substantially sinusoidal envelope curve h. The amplitude
modulated microwave signal is transmitted, by way of the circulator
18 shown in FIG. 7, to a resonator arrangement 1 and the
high-frequency signals furnished by the output means of the
arrangement 1 are caused to pass through a further circulator 19 to
the input e of a signal splitting or dividing circuit 38, e.g., a
circuit of the type known as Type HP Power Splitter 116678
distributed by the Firm Hewlett-Packard, Herrenberger Strasse 130,
D-71034 Boblingen, Federal Republic Germany. As shown in FIG. 9,
the amplitude modulated signal furnishes (in the embodiment of FIG.
7) three frequency bands, namely a basic frequency band f2 and two
auxiliary or secondary frequency bands f1 and f3. As concerns the
resonance curve, the basic frequency band f2 for an empty resonator
arrangement 1 is preferably selected in such a manner that it is
located at the inversion point Uw of the resonance curve uo. The
corresponding signals U1, U2 and U3 on the resonance curve u of
signals which are damped by a substance in the resonator
arrangement 1 (the resonance frequency of the curve u has been
shifted due to the presence of the filler 12b in the arrangement 1)
are ascertained in that an input signal furnished to the input e of
the signal dividing circuit 38 is split into three signals which
are transmitted by the outputs a, b, c of the circuit 38 to three
filters 39a, 39b, 39c, respectively. These filters are set up in
such a manner that each thereof permits the passage of a signal of
a frequency band f1, f2, f3. For example, the filters 39a, 39b, 39b
can be of the type known as MAX 274 distributed by Maxim Integrated
Products, 120 San Gabriel Drive, Sunnyvale, Calif. 94086. The
outputs of the filters 39a, 39b, 39c are respectively connected to
the inputs of diodes 22a, 22b, 22c which transmit d-c signals, and
such signals are digitalized by the respective ones of three A/D
converters 41a, 41b, 41c. The outputs of the converters 41a, 41b,
41c are connected to the respective inputs of the evaluating or
processing circuit 11 of FIG. 7.
87. In principle, it suffices to process two of the three
ascertained signals (such as the signals U1, U2 or U1, U3 or U2,
U3) of the damped resonance curve u for the ascertainment of the
wet mass or dry mass. However, it is also possible to carry out
such determination by resorting to three signals. Furthermore, it
is possible to form by modulation more than two auxiliary or
secondary bands and to thereupon evaluate the corresponding
signals.
88. The apparatus of FIG. 7 can be modified in such a way that the
average frequency f2 is not located at a flank of the resonance
curve u (see FIG. 9) but rather at its apex, i.e., at fo. In such
apparatus, the auxiliary or secondary frequencies f1 and f2 are
symmetrical thereto so that the corresponding signals U1, U3 can be
evaluated in a manner to be described with reference to FIG.
10.
89. The apparatus of FIG. 10 also employs a generator 3 which
transmits microwave signals in the GHz frequency range. A modulator
36 is provided to modulate the signals from the generator 3 in a
manner as already described with reference to FIGS. 5 and 6; the
input a of the circuit 36 receives a modulating signal from a
suitable source. The circuit 36 transmits several microwave signals
having frequencies which are closely adjacent each other. Such
signals are amplified at 46 and are transmitted to the input of the
resonator arrangement 1. As already described with reference to
FIGS. 1 and 2, the microwave signals which are being transmitted to
the input of the resonator arrangement 1 are symmetrical to the
resonance frequency for the idle (empty) resonator arrangement 1.
Basically, it is equally possible to employ two microwave
generators in lieu of the single generator 3 of FIG. 10, and each
discrete generator transmits microwave signals at a selected
frequency other than the frequency of the signals transmitted by,
the other generator. The decoupling can take place in the same
manner as described, for example, with reference to FIG. 1, i.e.,
by resorting to circulators 18 and 19 (not shown in FIG. 10).
90. The microwave signals are influenced by the presence of tobacco
(such as shredded and/or otherwise cut tobacco particles in the
filler 12b of a cigarette rod 12) in the resonator arrangement 1 of
FIG. 10, and the high frequencies of the thus influenced microwave
signals are considerably reduced in the aforementioned mixer 47
having an input a for the reception of a suitable signal. Two
selected characteristic signals having considerably lower
frequencies are transmitted to the diodes 22a, 22b by way of the
respective filters 39a, 39b. The d-c signals at the outputs of the
diodes 22a, 22b are digitalized in the corresponding A/D converters
41a, 41b, and the thus obtained signals are transmitted to the
corresponding inputs of the evaluating circuit 11. The lowering of
frequencies renders it possible to employ simpler and sharper
filters for the selected frequency bands.
91. Signals which are transmitted by the microwave diodes (such as
the diodes 22a-22c of FIG. 7 or the diodes 22a, 22b of FIG. 10) are
influenced by the temperature of the tested material (such as
tobacco). In accordance with the invention, such influence of the
temperature can be compensated for by ascertaining the temperature
of the tested substance in any well known manner (for example, by
employing a temperature sensor in the resonator arrangement 1). It
is also possible to utilize a temperature sensor upstream of the
resonator arrangement 1, for example, in that part of a cigarette
making machine or production line where the cigarette rod 12 or the
rod-like filler 12b is formed (an example of such part of a
production line is the so-called distributor or hopper of a
cigarette maker). It is also possible to employ an infrared
radiation thermometer which is trained upon the ends of cigarettes
obtained as a result of severing of the cigarette rod 12 at regular
intervals to turn out plain cigarettes of unit length or multiple
unit length. The thus obtained signals are utilized to compensate
for the influence of the temperature of the tested substance upon
the diode or diodes.
92. The resonator arrangement 1 can be heated to an appropriate
temperature to avoid the condensation of water.
93. In accordance with still another feature of the invention, a
drift of the measuring or monitoring system can be compensated for
by resorting to reference diodes or, if necessary, by utilizing an
additional resonator arrangement. For example, the apparatus can
employ two resonator arrangements having identical or substantially
identical housings and a discrete dielectric resonator in each
housing. The inputs of such discrete resonator arrangements are
connected to suitable means (such as one or more microwave
generators 3) for supplying microwave signals.
94. Still further, it is within the purview of the invention to
employ a resonator arrangement wherein the closed or substantially
closed metallic housing (such as the housing 2 of the arrangement 1
shown in FIG. 1) is replaced with an open housing having at least
one part (e.g., of a ceramic material) which is permeable to
microwaves. Microwaves can penetrate through such permeable part to
enter into a flow or another body of a substance to be tested,
e.g., a flow of shredded and/or otherwise comminuted tobacco
leaves. An advantage of such resonator arrangements is that they
can be utilized for the ascertainment of one or more
characteristics of a substance which need not be confined in an
envelope (such as the tubular wrapper 12a of the cigarette rod 12
shown in FIG. 1). The non-confined substance can be tested to
ascertain one or more characteristics, such as the mass/density
and/or the moisture content and/or the dielectric constant of
tobacco or other flowable substances.
95. An advantage of the improved method and apparatus is that they
permit rapid and accurate determination of various characteristics
of numerous semiconducting substances, such as tobacco,
particularly the wet mass and/or dry mass and/or dielectric
constant.
96. FIG. 11 shows a further apparatus wherein the frequency of an
output signal furnished in the gigahertz range (e.g., about 6 GHz)
by a microwave generator 3 is periodically shifted between two
values by a frequency regulator circuit 24. For example, one can
employ a rectangular a-c voltage of approximately 100 KHz. This can
be seen in FIG. 12a which illustrates changes of the frequency f as
a function of time t. The median or average frequency fm is
periodically varied within a frequency range .DELTA.f in accordance
with a rectangular curve s, namely between a higher value f2 and a
lower value f1.
97. The output signals which are transmitted by the microwave
generator 3 are supplied to a circulator 18 which prevents a
feedback of the output signals and transmits such signals to a
high-frequency (HF) resonator arrangement 1, e.g., an arrangement
of the type shown in and already describe with reference to FIG. 1.
It is assumed that the resonator arrangement 1 of FIG. 11 confines
a length of a continuous cigarette rod, e.g., a rod of the type
shown in FIG. 1 (as at 12). Such rod comprises a tubular envelope
surrounding a compacted rod-like filler of smokable material.
However, it is equally possible to employ the high-frequency
resonator arrangement 1 of FIG. 11 as a means for monitoring one or
more characteristics of another substance, e.g., of filter material
for tobacco smoke such as a rod-like filler of synthetic fibrous
material within a tubular wrapper of paper, artificial cork or the
like. The details of the resonator arrangement 1 of FIG. 1 can
match those of the similarly referenced resonator arrangement of
FIG. 1.
98. As shown in FIGS. 12a and 12b, the average or median frequency
fm of the signals denoted by the rectangular curve s of FIG. 12a is
preferably located at the inversion point of the resonance curve uo
which was ascertained in the resonator arrangement 1, in the
absence of tobacco or filter material, for different frequencies of
the supplied microwaves (from the source 3 via circulator 18) . The
progress of the resonance curve s (when the resonator arrangement 1
confines a portion of an advancing tobacco stream 12 shown in FIG.
1) is shown in FIG. 12b. The resonance frequency when the resonator
arrangement 1 is not being traversed by a continuous rod of
confined tobacco or tobacco smoke filtering material is denoted by
the curve uo of FIG. 12b, and the curve u denotes how the resonance
frequency f1 develops when the resonator arrangement 1 is actually
traversed by a continuous wrapped filler of tobacco, filter
material for tobacco smoke or the like. The resonance frequency fo
develops when the resonator arrangement 1 is empty, and the
resonance frequency f develops when a wrapped rod-like filler (such
as 12 in FIG. 1) is caused to pass through the resonator
arrangement 1.
99. The lower frequency value f1 on the rectangular curve s in the
coordinate system of FIG. 12a corresponds to the value denoted by
the point Uof1 on the resonance curve uo (resonator arrangement 1
empty) of FIG. 12b, and to the value denoted by the point Uf1 on
the resonance curve u (resonator arrangement 1 confining a length
of an axially advancing cigarette rod 12) of FIG. 12b. The upper
frequency value f2 of the rectangular curve s shown in FIG. 12a
corresponds to the values respectively denoted by the points Uof2
and Uf2 on the curves uo and u of FIG. 12b. The values Uf1, Uf2,
Uof1 and Uof2 are also shown in the coordinate system of FIG.
12c.
100. The output signals of the resonator arrangement, namely the
resonance signals at the lower modulation value (f1) and the higher
modulation value (f2), are transmitted to a resonance diode 22 by
way of a second circulator 19 which prevents a feedback to the
resonator arrangement 1. The diode 22 can be of the character known
as Type HP/8472 B available at Hewlett-Packard. The purpose of the
diode 22 is to convert the incoming microwave signal into a d-c
signal. The d-c signal is transmitted to a sensor 51 in response to
signals from a synchronizer 52 whose operation is a function of the
rectangular a-c voltage supplied by the frequency regulator 24. The
regulation is carried out in such a way that the voltage values of
the resonator arrangement 1 are addressed at the exact instants
when the microwave generator 3 furnishes to the resonator
arrangement 1 microwaves with the higher (f2) or lower (f1)
frequency values of the rectangular curve s.
101. The above outlined mode of operation ensures that one can
obtain the values Uf2 and Uf1 (FIGS. 12b and 12c) which are
respectively stored in short-term memories 53 and 54. The output
signals of the memories 53 and 54 are transmitted to a summing
circuit 56 and to a subtracting circuit 57. The circuit 56
establishes the value 1/2(Uf2+Uf1)=Ug, and the circuit 57
establishes the value (Uf2-Uf1)=Ua (see also FIG. 12c). The signals
or values Ug and Ua are transmitted to the corresponding inputs of
the evaluating arrangement 11 the details of which are illustrated
in FIG. 13 and which serves to ascertain, for example, the
density/mass or the moisture content of a continuously moving body
of a substance, e.g., a rapidly advancing cigarette rod containing
a rod-like tobacco filler within a tubular wrapper of cigarette
paper or the like.
102. A specially designed circuitry can be provided to ensure that
the microwave generator 3 receives a correction signal from the
evaluating arrangement 11 via conductor means 31 as soon as the
average frequency fm (FIG. 12a) migrates beyond the inversion point
of the resonance curve uo. The correction signal which is
transmitted via conductor means 31 ensures that the frequency fm at
the output of the microwave generator 3 is caused to reassume the
value corresponding to the inversion point of the resonance curve
uo.
103. The manner in which the signals Ua and Ug are processed in the
evaluating arrangement 11 of FIG. 1 in order to ascertain the
mass/density value of the rod-like tobacco filler is shown in FIG.
13. The first step involves storing the signals Ua and Ug in
digitalized form in memories SUa and SUg. A readout device is
provided to address the memories SUg and SUa in a sequence
corresponding to selected movements of the cigarette rod passing
through the resonator arrangement 1 of FIG. 11. For example, each
such movement can have a length of 1 mm. Thus, if the cigarette rod
is transported through the resonator arrangement at a speed which
is required to produce 10000 cigarettes (each having a length of 60
mm) per minute, the scanning frequency is in the range of 100
microseconds. In other words, the information which is stored in
the memories SUg and SUa is addressed at a frequency of 100
microseconds. The pulses Ig and Ia for the transmission of such
information to calculating stages Rg and Ra are even shorter than
100 microseconds, and the stages Rg and Ra process the incoming
signals together with constants to furnish output signals Ag and Aa
entering the corresponding inputs of a first summing or adding
stage Ad. In a simple case, the calculation in the stages Rg and Ra
can be carried out with polynomials of the type a+b Ug=AG and c+d
Ua=Aa. The constants a, b, c and d are ascertained by resorting
to
104. Without further analysis, the foregoing will so fully reveal
the gist of the present invention that others can, by applying
current knowledge, readily adapt it for various applications
without omitting features that, from the standpoint of prior art,
fairly constitute essential characteristics of the generic and
specific aspects of the above outlined contribution to the art of
ascertaining the characteristics of tobacco or other substances
and, therefore, such adaptations should and are intended to be
comprehended within the meaning and range of equivalence of the
appended claims.
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