U.S. patent application number 10/530933 was filed with the patent office on 2006-06-29 for spinner preparation machine and cavity resonator.
Invention is credited to Chokri Cherif, Otmar Kovacs.
Application Number | 20060137145 10/530933 |
Document ID | / |
Family ID | 32102791 |
Filed Date | 2006-06-29 |
United States Patent
Application |
20060137145 |
Kind Code |
A1 |
Kovacs; Otmar ; et
al. |
June 29, 2006 |
Spinner preparation machine and cavity resonator
Abstract
A spinning preparation machine includes a drafting device for
drafting at least one fiber sliver. The machine includes a
microwave sliver thickness sensor through which the fiber sliver is
guided, the sensor disposed at the inlet or outlet, or both, of the
drafting device and includes at least one cavity resonator defined
by a resonator wall. A device or system is incorporated with the
sensor for minimizing temperature-conditioned deformations of the
resonator during measurement of sliver thickness.
Inventors: |
Kovacs; Otmar; (Berching,
DE) ; Cherif; Chokri; (Ingolstadt, DE) |
Correspondence
Address: |
DORITY & MANNING, P.A.
POST OFFICE BOX 1449
GREENVILLE
SC
29602-1449
US
|
Family ID: |
32102791 |
Appl. No.: |
10/530933 |
Filed: |
October 15, 2003 |
PCT Filed: |
October 15, 2003 |
PCT NO: |
PCT/EP03/11411 |
371 Date: |
December 9, 2005 |
Current U.S.
Class: |
19/236 |
Current CPC
Class: |
D01H 13/32 20130101;
D01H 5/38 20130101; D01G 31/006 20130101 |
Class at
Publication: |
019/236 |
International
Class: |
D01H 5/00 20060101
D01H005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 16, 2002 |
DE |
102 48 322.1 |
Claims
1-24. (canceled)
25. A spinning preparation machine with a drafting device for
drafting at least one fiber sliver, comprising: a microwave sliver
thickness sensor through which the fiber sliver is guided, said
sensor disposed at at least one of an inlet or an outlet of said
drafting device, said microwave sensor comprising at least one
cavity resonator defined by a resonator wall; and means for
minimizing temperature-conditioned deformations of said resonator
during measurement of sliver thickness.
26. The spinning preparation machine as in claim 25, wherein said
means comprises at least one wall of said resonator being made of a
material having a low coefficient of thermal expansion at operating
temperatures of said spinning preparation machine.
27. The spinning preparation machine as in claim 26, wherein said
material is steel having a coefficient of thermal expansion of
about 0 at 20.degree. C.
28. The spinning preparation machine as in claim 27, wherein said
steel is a Ni36 steel having a nickel component of between about
35% to about 37%.
29. The spinning preparation machine as in claim 25, wherein said
means comprises thermal insulation means for insulating said
microwave sensor from surrounding components of said spinning
preparation machine.
30. The spinning preparation machine as in claim 29, wherein said
thermal insulation means comprises thermally insulating connecting
elements between said microwave sensor and said machine
components.
31. The spinning preparation machine as in claim 29, wherein said
thermal insulation means comprises a thermally insulating housing
disposed at least partially around said microwave sensor.
32. The spinning preparation machine as in claim 25, wherein said
means comprises means for actively adjusting temperature at said
microwave sensor to obtain a substantially constant temperature at
resonator walls of said microwave sensor.
33. The spinning preparation machine as in claim 32, further
comprising a temperature measuring element disposed with respect to
said microwave sensor to detect temperature of said resonator
chamber or wall.
34. The spinning preparation machine as in claim 33, further
comprising a temperature regulating unit operably interfaced with
said temperature measuring element and said active temperature
adjusting means.
35. The spinning preparation machine as in claim 32, wherein said
active temperature adjusting means comprises means for heating said
microwave sensor.
36. The spinning preparation machine as in claim 35, wherein said
heating means comprises a heating foil disposed in contact with and
at least partially around said resonator.
37. The spinning preparation machine as in claim 35, wherein said
heating means is incorporated into said resonator wall.
38. The spinning preparation machine as in claim 32, wherein said
active temperature adjusting means comprises means for cooling said
microwave sensor.
39. The spinning preparation machine as in claim 38, wherein said
cooling means comprises cooling agents that reduce resonator wall
temperature.
40. The spinning preparation machine as in claim 32, wherein said
active temperature adjusting means comprises means for generating
and controlling a directed airflow in or around said resonator.
41. The spinning preparation machine as in claim 40, wherein said
airflow is a suction flow or a blowing flow.
42. The spinning preparation machine as in claim 40, wherein said
airflow is directed so as to clean said resonator chamber as it
actively cools said resonator chamber.
43. The spinning preparation machine as in claim 32, wherein said
active temperature adjusting means comprises at least one Peltier
element.
44. A cavity resonator for use in a microwave sensor of a textile
spinning preparation machine, said resonator comprising resonator
walls wherein at least one of said walls is formed of a material
having a low coefficient of thermal expansion at operating
temperatures of the spinning preparation machine.
45. The cavity resonator as in claim 44, wherein said material is
steel having a coefficient of thermal expansion of about 0 at
20.degree. C.
46. The cavity resonator as in claim 45, wherein said steel is a
Ni36 steel having a nickel component of between about 35% to about
37%.
Description
FIELD OF THE INVENTION
[0001] The invention relates to a spinning preparation machine with
a drafting device for drafting at least one fiber sliver band, in
particular a carding, drafting or combing machine, with at least
one microwave sensor at the inlet and/or at the outlet of the
drafting device for measuring the sliver thickness of the at least
one sliver, which microwave sensor comprises at least one cavity
resonator through which the at least one sliver is to be guided
during the measurements. The invention also comprises such a cavity
resonator.
BACKGROUND
[0002] In the spinning industry at first an evened-out fiber
structure is produced from, e.g., cotton, in several process steps
and finally a twisted yarn is produced as the end product. The
spinning preparation machines such as carding, drafting and combing
machines arranged upstream from the manufacture of yarn have the
particular task of leveling out fluctuations of sliver mass of one
or several slivers. To this end, sliver sensors are arranged, e.g.,
on drafting frames that measure the sliver thickness, also called
sliver mass, and their fluctuations and transmit this information
to a regulating unit that appropriately regulates at least one of
the drafting members of the drafting device. Even in non-regulated
drafting frames, information about the fluctuations of sliver
thicknesses is desired in many instances. An appropriate sensor at
the output of a drafting device emits, e.g., a corresponding
cut-out signal for the machine and/or a warning signal if a
threshold value of the sliver thickness is exceeded or dropped
below.
[0003] The known measuring methods for determining fluctuations of
sliver thickness are primarily based on mechanical scans. However,
the dynamics of these mechanical sensors are no longer sufficient
in the case of delivery speeds at the output of the drafting device
of in particular more than 1000 m/min. In addition, the necessary
strong mechanical compression in front of a mechanical sensor makes
itself noticeable in a negative manner on the drafting
capacity.
[0004] WO 00/12974 teaches a microwave resonator for the continuous
detection of fluctuations of sliver thicknesses of moved textile
strands at the inlet of the drafting device. Alternatively or
additionally, a microwave sensor is arranged at the outlet of the
drafting device that can be used in particular for monitoring the
quality of the evened-out fiber material.
[0005] The device according to WO 00/12974 comprises a temperature
sensor in order to compensate temperature influences by means of a
processor. However, the cited design has the disadvantage that this
temperature compensation for taking into account influences of
temperature on the measured results is not an optimal solution
since it is cost-intensive on the one hand and on the other hand is
based on necessarily empirical calculating algorithms.
SUMMARY
[0006] The present invention has the problem of improving the
precision of measurements of sliver thicknesses relative to the
conditions prevailing in spinning mills. Additional objects and
advantages of the invention will be set forth in part in the
following description, or may be apparent from the description, or
may be learned through practice of the invention.
[0007] This problem is solved in the spinning preparation machine
of the initially cited type by means for preventing
temperature-conditioned deformations of the resonator walls of the
microwave sensor during the measurements. The problem is likewise
solved by a cavity resonator with resonator walls that are
manufactured at least in sections from a material with a low
coefficient of thermal expansion.
[0008] The advantages of the invention reside in particular in the
fact that temperature variations that have an influence on the
measuring precision when microwaves are used can be eliminated to a
great extent. Expensive calculating compensation solutions can
possibly be completely eliminated.
[0009] During the production start, the temperatures in and on the
machine are relatively low but rise with the time. In particular
the development of heat due to the machine motors and other moved
components, as well as the sliver friction on the input and output
of the cavity resonator, cause a rise in temperature that results
in deformations of the cavity resonator walls. Such changes of the
resonator geometry cause a shifting of the resonator frequency
(given an unchanged cross section of the sliver) and therewith a
falsification of the measured values and/or result in inaccuracies
of measurement. The measuring accuracy can be significantly raised
by the means in accordance with the invention for preventing these
temperature-conditioned deformations of the resonator walls. Thus,
it is in particular immaterial whether the machine has just started
or has been in operation for some time. If, on the other hand, a
single calculating compensation regarding temperature influences
were to be performed, at first the temperature would have to be
measured and the appropriate point in the correction curve found
that represents the correction value for a certain temperature.
[0010] In the cavity resonator in accordance with the invention
that is used in an advantageous embodiment of the machine, the
resonator walls are manufactured at least in sections from a
material with a low coefficient of thermal expansion. Such a
selection creates the advantage that temperature variations and
therewith expansions and shrinkings of the resonator walls can
occur only to a very slight extent. A preferred material in this
connection is steel with a low thermal expansion, which steel has a
thermal expansion at customary operating temperatures of
approximately 1/5 and preferably approximately 1/10 of the thermal
expansion of steel customarily used in textile machines. Such a
steel is, e.g., an Ni36 steel, that is, a steel with a nickel
component of approximately 35-37% as well as lesser amounts of
other metals as well as carbon or a steel comparable to it. Ni36
steel has an almost negligible thermal expansion, that is, the
coefficient of thermal expansion at 20.degree. C. is approximately
zero for such a steel. Such a steel is known, and referred to as
"Invar" steel. Other comparable steels have other trade names.
Furthermore, Ni36 steels are distinguished in addition to an almost
negligible thermal expansion in that they are relatively elastic in
comparison to ceramic material, that is, they do not have its
brittleness and therewith its susceptibility.
[0011] If materials are used for the resonator walls that oppose
the formation of a resonance and/or the ability to measure the
resonance frequency and the damping at this frequency in the cavity
of the sensor, its inner walls can be provided with a conductive
layer. Such a layer can be, e.g., 5 .mu.m thick.
[0012] It is alternatively or additionally advantageous to largely
decouple the sensor from the rest of the machine in a thermal sense
with thermal insulating material. Such a thermally screened island
prevents waste heat from motors or other moving machine elements
from reaching the sensor and causing changes of volume there and
therewith a shifting of the resonance frequency of the
resonator.
[0013] In the case of such a thermal decoupling, e.g., insulating
foils can be arranged around rather large sections of the
resonator. Alternatively or additionally, the sensor can be at
least partially surrounded by a thermally screening housing. In
another alternative or in an additional design the connecting
elements with which the sensor is attached to a machine part are
fastened with a material with low thermal conductivity so that the
thermal conduction at this location is substantially
interrupted.
[0014] Alternatively or additionally to the previously cited
passive means for preventing temperature-conditioned deformations
of the resonator walls, active temperature adjustment means are
preferred. This achieves great flexibility in the adjusting of the
temperature of these walls. An undesired heating or cooling off of
the resonator walls can be counteracted in this instance in that
the temperature is adjusted to the desired extent. To this end it
is especially preferable if the temperature adjustment means can be
regulated.
[0015] In order to realize such a regulation it is advantageous to
provide one or several temperature measuring elements for measuring
the temperature of the inner chamber of the resonator and/or the
temperature of the resonator walls. To this end a conclusion can be
made about the temperature of the resonator walls and/or of the
ambient, e.g., by a resistance measurement. Such a known
temperature measuring device, that is economical in addition, is,
e.g., a so-called PT100, that is fastened, e.g., to an outer wall
of the resonator. Alternatively, an inductive coil or some other
suitable measuring method can be used.
[0016] The at least one temperature element is advantageously
attached to a location that is representative for the temperature
behavior of the entire resonator. Alternatively, several
temperature sensors arranged at different locations can be used
whose signal is preferably preprocessed. It is advantageous in this
connection, e.g., to use an average value or some other evaluation
for estimating a representative temperature value that is used for
regulating the temperature.
[0017] An inhomogeneous temperature distribution in the resonator
chamber with a undesired consequence of imprecise temperature
measurements can be largely prevented if air with a constant
temperature is conducted through the resonator and/or past the
resonator. Such an airflow can also be used to clean the resonator
chamber, especially to eliminate fibers that became loose from the
fiber structure.
[0018] The regulation of the active temperature adjustment means
can take place in various ways. For example, a separate control
unit is provided in one embodiment. Alternatively or additionally,
an evaluation unit associated with the at least one microwave
sensor can be used to regulate the temperature. However, even the
central machine control can assume the regulation of the
temperature adjustment means.
[0019] It is especially advantageous that the temperature
adjustment means comprises a heating means and that the end
temperature of the resonator walls is advantageously above the
temperature produced by the influences of the machines, the ambient
and friction. A heating means that can be used with advantage is,
e.g., a heating foil that can be attached in particular around
rather large-area sections on the outside of the resonator.
[0020] Alternatively or additionally, at least one resonator wall
is directly heated in that a heating voltage is preferably applied
to it.
[0021] Instead of heating the resonator walls, cooling agents can
be provided that adjust the resonator walls below the temperature
produced by the influences of the machines, the ambient and
friction.
[0022] Alternatively or additionally, cooling agents are designed
to produce a cooling airflow. Such an airflow can also be used to
clean the resonator chamber and/or bordering machine sections. The
above-mentioned homogeneous temperature distribution, that is
desired in a few instances, can likewise be achieved in the inner
chamber of the resonator by such an airflow if this airflow is
conducted at least partially through the inner chamber of the
resonator.
[0023] Independently of whether the active temperature adjustment
means bring about a heating or a cooling of at least one resonator
wall, the corresponding electrical circuit of the heating or
cooling agent can be interrupted, e.g., upon reaching the desired
temperature or shortly before it. If the desired temperature is
exceeded or drop below, the current is closed again in order to
heat or cool. It is likewise advantageous to regulate the heating
or cooling agents when the machine is engaged in order to rapidly
achieve the desired temperature.
[0024] The temperature adjustment means are advantageously designed
as a Peltier element in order to heat or cool at least one
resonator wall. The at least one Peltier element removes, e.g., the
heat from the resonator wall to be cooled when used as cooling
agent and the temperature of the at least one resonator wall can be
maintained distinctly below the temperature that would be achieved
using conventional cooling.
[0025] It is also possible to regulate different elements of the
resonator differently. E.g, the resonator side facing the inner
chamber of the resonator can be cooled and the side facing away
from it can be heated and the corresponding resonator sections do
not necessarily have to have the same end temperature, but rather
the goal is to maintain the resonator geometry constant during the
measurements.
[0026] The various means for preventing deformations of the
resonator walls during the measurements can be combined in various
ways.
[0027] An independent aspect of the invention provides keeping the
resonator chamber clean or cleaning it by an airflow. The strength
and/or the flow path of the airflow can be advantageously adjusted
by an airflow control means, e.g., by at least one throttle flap on
an air baffle element of these means. The opening width of the at
least one throttle flap can be adjusted in particular manually or
electrically. In particular, an automatic actuation of the at least
one throttle flap can be realized. The degree of contamination of
the resonator can be taken as a control value, that can be
determined with at least one appropriate sensor in an advantageous
exemplary embodiment. Such a sensor can be, e.g., an optical sensor
whose received signals become weaker with increasing contamination
and finally fall below a threshold value. Other embodiments can be
based, e.g., on the measuring of contamination-dependent resistance
values that are a function, e.g., of a thickness of a contaminant
film or grease film on the resonator walls. A conclusion about a
contamination of the inner chamber can optionally also be made from
the resonance signal itself, advantageously when a boundary value
of the resonator characteristics (resonator quality) is exceeded
when the resonator is empty. In this case the evaluation unit of
the sensor advantageously emits an appropriate signal for
controlling the at least one throttle flap of another airflow
control means.
[0028] The airflow can be used as a suction flow or as a blowing
flow. In addition, a continuous or an interrupted airflow can be
used. The time intervals can be, e.g., periodic or made dependent
on an exceeding of threshold or boundary values, e.g., on the
degree of contamination or on the quality of the resonator.
[0029] The sequence of the successive suction or blowing impulses
can advantageously be adjusted in their duration and/or their
interval in time, e.g., on an operator desk (so-called panel)
and/or from a central control device in the spinning mill. In
correspondence with the above, the duration, interval, strength,
flow path, etc. of the airflow can be adjusted manually and/or
automatically.
[0030] In an advantageous variant the airflow is actuated during a
can change since, if no so-called flying can change is being
realized during continuous sliver production, no measurements are
being carried out on the stationary sliver or slivers at this
time.
[0031] It proved to be advantageous if the airflow is directed
along the fiber material and it is especially preferred if the air
is conducted on sides opposite the fiber material so that an
effective removal of individual fibers and other contaminating
particles is assured.
[0032] The airflows for cleaning and/or temperature adjustment can
be directed differently. E.g., suction can be applied to the sensor
from below. Likewise, a vacuum can be generated by airflow in a
housing surrounding the sensor and insulating it thermally.
[0033] Advantageous further developments are characterized by the
features of the subclaims.
[0034] The invention is explained in detail in the following with
reference made to the figures.
BRIEF DESCRIPTION OF THE FIGURES
[0035] FIG. 1 shows a drafting frame with a regulation
schematically shown as a block diagram.
[0036] FIGS. 2a, 2b, 2c schematically show a microwave sensor with
funnel in front and downstream calendar rollers in a top view,
lateral view and rear view.
[0037] FIG. 3 schematically shows a microwave sensor in a
housing.
DESCRIPTION
[0038] Reference is now made to one or more embodiments of the
invention, examples of which are illustrated in the drawings. The
embodiments are provided by way of explanation of the invention,
and are not meant as a limitation of the invention. For example,
features illustrated or described as part of one embodiment may be
used with a different embodiment to yield still a further
embodiment.
[0039] A regulating principle for drafting frame 1 is explained by
way of example in the following using FIG. 1. The sliver thickness
of entering slivers 2, in this instance six slivers 2, is detected
at the inlet of drafting frame 1 by microwave sensor 3, that works
in accordance with the resonator principle (microwave generator not
shown). Funnel 18 designed as a compression means for compressing
slivers 2 is connected in front of the sensor 3. After passing
microwave sensor 3, slivers 2 are spread out to a fleece (shows as
a triangle widening out toward drafting device 1a) that runs into
drafting device 1a. Drafting device 1a is formed in this instance
by an entrance roller pair, middle roller pair and a supply roller
pair (only the lower roller 20, 21 and 22 of the roller pairs is
shown). A draft of slivers 2 is realized by clamping the slivers or
fleece 2 between the rollers of the various roller pairs, that
rotate with increasing circumferential speeds, viewed in the
direction of sliver travel.
[0040] The measured values of sensor 3 are converted by evaluation
unit 4 into electric voltage values that represent the fluctuations
of sliver thickness and are supplied to memory 5. This memory 5 is
designed as a FIFO memory (first-in-first-out) and forwards the
voltage with a defined delay in time to theoretical value stage 7.
To this end memory 5 receives a number of impulses from impulse
generator 6 that is a measure for the speed of slivers 2 running
through sensor 3. The slivers are transported here from the pair of
entrance rollers so that it is appropriate to couple impulse
generator 6 to this roller pair. Using the impulses from impulse
generator 6, the voltage values of sensor 3 are retained in memory
5 in accordance with the path traversed by slivers 2 between sensor
3 and drafting device la. When the slivers or fleece 2 with the
sliver piece to be regulated reach the fictitious draft location in
the draft field of drafting device 1a, the corresponding measured
value is released by memory 5 and an appropriate placing handling
is performed, which will be discussed in detail in the following.
The interval between the measuring location a sensor 1 and the
drafting location is called the regulation start point.
[0041] Alternatively, impulse generator 6 can be coupled to another
roller pair, e.g., to a transport roller pair directly behind
sensor 3 (viewed in the direction of sliver travel). In this
instance the entrance roller pair does not transport the slivers
through sensor 3 but rather the transport roller pair does.
[0042] Moreover, theoretical value stage 7 receives a pilot voltage
from pilot tachometer 9 that is a measure for the speed of lower
roller 22 of the supply roller pair, which roller 22 is driven by
main motor 8. Subsequently, a theoretical voltage is calculated in
theoretical value stage 7 and forwarded to control unit 10. A
theoretical-average value comparison takes place in control unit 10
and the actual values of regulating motor 11 are transmitted to
actual value tachometer 12 that then forwards the corresponding
actual value to control unit 10. The theoretical-actual value
comparison in control unit 10 is used to impart a quite determined
speed corresponding to the desired draft change to regulating motor
11. Regulating motor 1 1 drives planetary transmission 13 so that
the speeds of lower roller 20 of the entrance roller pair and of
lower roller 21 of the middle roller pair is changed in accordance
with the desired evening-out of the slivers. The sliver thickness
in drafting device la is regulated at the so-called regulating
start point, that is, at the draft location by the proportional
superpositioning of the speeds of main motor 8 and of regulating
motor 11 taking account of the cited dead [idle] time.
[0043] Other drive concepts, e.g., individual drives can be
realized in other variants (not shown).
[0044] Microwave sensor 30 is arranged at the discharge of drafting
device la and is connected in downstream from fleece nozzle 19
designed as a compression device in the exemplary embodiment shown.
The sliver or sliver fleece 2' leaving the drafting device is drawn
off by calender roller pair 35 connected in downstream from sensor
30. The signals of sensor 30 are supplied to evaluation unit 31
that supplies the electrical voltage signals in accordance with the
sliver thickness of drafted sliver 2' and forwards them to control
unit 10. For example, long-wave periodic fluctuations of slivers 2
presented to drafting device 1a can be regulated by the signals
from sensor 30. Alternatively or additionally, the signals of
sensor 30 are used for quality control during which the machine is
advantageously turned off if a threshold value is exceeded or
dropped below.
[0045] FIG. 1 schematically shows that a temperature element 40, 41
is arranged on sensors 3, 30 for measuring the temperature in the
inner chamber of the resonator or on a resonator wall. Several
temperature measuring elements can also be used in order to order
to obtain, e.g., an average temperature value. Since it was found
that the measuring accuracy of sensors 3, 30 suffers on account of
temperature fluctuations due to turning the machine on and off as
well as on account of the machine environment and associated
heating and cooling of the resonator walls, an appropriate
temperature control is desirable.
[0046] Temperature elements 40, 41 forward the measured temperature
values to evaluation units 4, 31. In the exemplary embodiment shown
evaluation units 4, 31 likewise serve for temperature control in
order to control correspondingly designed temperature adjustment
means 14, 15. In the case of sensor 3 arranged in front of drafting
device la evaluation unit 4 regulates heating circuit 14 that
assumes the heating of at least one resonator wall of sensor 3.
Alternatively, at least one heating foil can be tied into heating
circuit 14 that is arranged at least sectionally around the
resonator, advantageously making contact, (not shown). Care is to
be taken that these heating means do not cause any disturbance of
the microwave resonance signals.
[0047] Heating circuit 14 can be actuated immediately after the
machine has been turned on after it has been standing still for a
rather long time in order to rapidly achieve the desired heating
temperature. The goal is to bring the resonator walls to a largely
constant temperature that is independent from the temperature in
the interior of the machine but also from the ambient temperature
of the machine and, if applicable, from temperature effects
produced by sliver friction on resonator elements. Then, no
temperature-conditioned deformations can occur at such a constant
temperature, so that the accuracy of the measured values is
increased.
[0048] During normal operation temperature measuring element 40
determines the current temperature, whereupon evaluation unit 4
regulates heating circuit 14 if a given threshold value is dropped
below. If a given temperature registered by measuring element 40 is
exceeded, evaluation unit 40 furnishes a corresponding command to
heating circuit 14 for interrupting the heating process.
[0049] A corresponding design with an analogous heating method is
provided at the discharge of drafting device 1a for sensor 30.
Evaluation unit 31 likewise assumes the control of heating circuit
15, that is designed to adjust the temperature of at least one
resonator wall of resonator 30.
[0050] The control of heating circuits 14, 15 can also be realized
by control unit 10 in an embodiment that is not shown. Even
specific [individual] control units can be provided in another
alternative.
[0051] Instead of a heating of the resonator walls and/or of the
resonator chamber a cooling can be realized. It is important that
the resonator walls are adjusted to a substantially constant
temperature in order to suppress volumetric fluctuations of the
resonator chamber as well as distortions of the resonance
field.
[0052] In alternative or additional designs, the resonator walls
are manufactured at least partially from a material with a low
thermal expansion, e.g., Ni36 steel (e.g., Invar steel). Other
possibilities that can be used alternatively or additionally
include the thermal insulation of the sensor with the aid of
fastening elements that suppress the conduction of heat that are
attached to the machine and/or include thermal insulation housings
and the like.
[0053] FIGS. 2a (top view), 2b (side view) and 2c (rear view) show
microwave sensor 300, shown without a microwave generator, with
funnel 118 in front and calender roller pair 135 that draws the at
least one sliver 2 through funnel 118 and sensor 300. In FIGS. 2a,
2b the at least one sliver 2 is indicated solely by a dotted arrow;
in FIG. 2c sliver 2 is shown in cross section as a composite of
many individual fibers. Furthermore, funnel 118 and calender
rollers 135 are not shown in FIG. 2c.
[0054] Instead of funnel 118 other sliver guide elements can also
be used, e.g., horizontally and/or vertically arranged deflection
rods that can, e.g., also have concave guide surfaces in order to
allow the at least one sliver 2 to run into sensor 300 in a
centered manner. Furthermore, calender rollers 135 can be arranged
rotated through 90.degree. or any other angle.
[0055] Sensor 300 comprises resonator 300a with two semicylinders
301, 305 separated by slot 310. Outer walls 302, 306 of
semicylinders 301, 305 are manufactured from metal and inner walls
303, 307 oriented toward sliver 2 are manufactured from ceramic
material. The resonance develops in the inner resonator chamber
between walls 302, 306.
[0056] An airflow is conducted through slot 310 in the direction of
sliver travel on both sides of sliver 2. This airflow is shown in
FIGS. 2a, 2b in dotted lines and in FIG. 2c as a circle with
crossed lines sketched in it (direction of airflow is directed away
from the observer). The air flow or airflows 50 can assume several
functions. On the one hand they assure a largely homogeneous
distribution of temperature in slot 310 and on the other hand they
prevent a depositing of, in particular, fibers on inner walls 303,
307 of semicylinders 301, 305 as well as on the discharge of
resonator 300a and at the transition to calender rollers 135. Such
deposits of contaminants would detune resonator 300a and result in
inaccurate measurements.
[0057] Furthermore, airflow 50 can be used for a purposeful
adjustment of temperature, in particular of resonator walls 302,
306. In particular, it is possible to use cooling air in order to
cool off resonator walls 302, 306 to the most constant temperature
possible, that is lower in comparison to that of normal
operation.
[0058] FIG. 3 shows another embodiment of a microwave sensor 3000
in which, in contrast to the embodiment of FIG. 2, a housing 45 is
additionally provided around cavity resonator 3000a. Housing 45,
whose front wall facing the observer is shown removed, is thermally
insulated in order to keep heat coming from the machine room and
the environment from resonator 3000a. In addition, two slots 312,
314 are provided between the outer walls of resonator 3000a and the
inner walls of the housing through which slots airflow 51 is
conducted. Even these airflows 51 can be used to clean slots 312,
314 and/or to adjust the temperature of the resonator walls.
[0059] In FIG. 3, the airflows guided to sensor 3000 branch off
into two partial flows, on the one hand into airflow 51 already
described and on the other hand into airflow 50 running through
slot 310. As an alternative, no airflow 50 through slot 311 or an
airflow 50 provided specifically for slot 310 is provided.
[0060] Airflow 50, 51 in FIGS. 2, 3 can be blowing or suction
flows, which latter produce a vacuum in slots 310, 312, 314.
[0061] It should be appreciated by those skilled in the art that
modifications and variations can be made to the embodiments
described above without departing from the scope and spirit of the
invention as set forth in the appended claims and their
equivalents.
* * * * *