U.S. patent number RE33,791 [Application Number 07/455,289] was granted by the patent office on 1992-01-07 for non-invasive temperature monitor.
This patent grant is currently assigned to M/A-COM, Inc.. Invention is credited to Kenneth L. Carr.
United States Patent |
RE33,791 |
Carr |
January 7, 1992 |
Non-invasive temperature monitor
Abstract
A non-invasive temperature monitoring apparatus used in
association with a guided wave member that may be for the purpose
of sterilization and that is adapted for microwave heating of a
substance that is absorptive at microwave frequencies and that is
held in some type of container or connector that is transparent at
microwave frequencies. The apparatus comprises a length of
waveguide. A coupling aperture is defined in the guided wave
member. The length of waveguide is supported with one end thereof
about the coupling aperture. A microwave radiometer detection
circuit is also coupled from the length of waveguide for detecting
on a continuing basis the temperature of the substance which is
usually liquid being heated by the microwave energy.
Inventors: |
Carr; Kenneth L. (Harvard,
MA) |
Assignee: |
M/A-COM, Inc. (Burlington,
MA)
|
Family
ID: |
27037808 |
Appl.
No.: |
07/455,289 |
Filed: |
December 22, 1989 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
627761 |
Jul 5, 1984 |
04715727 |
Dec 29, 1987 |
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Current U.S.
Class: |
374/122; 219/710;
324/636; 600/549; 607/102 |
Current CPC
Class: |
A23L
3/01 (20130101); H05B 6/80 (20130101); A61L
2/24 (20130101); A61L 2/12 (20130101) |
Current International
Class: |
A23L
3/005 (20060101); A23L 3/01 (20060101); A61L
2/00 (20060101); A61L 2/08 (20060101); A61L
2/24 (20060101); A61L 2/12 (20060101); H05B
6/80 (20060101); A61N 005/02 (); G01J 005/00 () |
Field of
Search: |
;374/121,122,130
;219/1.55A ;128/804,736 ;604/113,114 ;324/636 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Yasich; Daniel M.
Attorney, Agent or Firm: Wolf, Greenfield & Sacks
Claims
What is claimed is:
1. A temperature .[.appparatus.]. .Iadd.apparatus .Iaddend.used in
association with a guided wave means that is adapted for microwave
heating, from a microwave heating source, of a substance that is
absorptive at microwave frequencies and that is held in retaining
means that is transparent at microwave frequencies, both said
substance and said retaining means therefor being enclosed by said
guided wave means, said apparatus comprising; a length of
waveguide, means defining a coupling aperture in said guided wave
means, means supporting said length of waveguide with one end
thereof about said coupling aperture, a microwave radiometer
detection circuit, means coupling from the length of waveguide to
the detection circuit, wherein said microwave heating is at one
frequency and the detection is at another frequency, and wherein
said microwave heating and said microwave detection are at
different frequencies, said coupling aperture having a
cross-sectional area less than the waveguide cross-sectional area,
the coupling aperture being sufficiently small in comparison to the
waveguide cross-section so as to leave the heating characteristics
of the .[.guides.]. .Iadd.guided .Iaddend.wave means substantially
undisturbed.
2. A non-invasive temperature monitoring apparatus as set forth in
claim 1 wherein said length of the waveguide is sufficiently long
so as to provide a cut-off at the heating frequency.
3. A non-invasive temperature monitoring apparatus as set forth in
claim 1 wherein the length of the waveguide functions as a high
pass filter preventing any heating energy from being detected at
the radiometer detection circuits whereby the circuit detects only
energy associated with the temperature of the liquid being
heated.
4. A temperature monitoring .Iadd.apparatus .Iaddend.used in
association with a guided wave means that is adapted for microwave
heating, from a microwave heating source, of a substance that is
absorptive at microwave frequencies and that is held in retaining
means that is transparent at microwave frequencies, both said
substance and said retaining means therefor being enclosed by said
guided wave means, said apparatus comprising; a length of
waveguide, means .[.to.]. defining a coupling aperture in said
guided wave means, means supporting said length of waveguide with
one end thereof about said coupling aperture, a microwave
radiometer detection circuit, means coupling from the length of
waveguide to the detection circuit, and wherein said guided wave
means comprises a pair of curved conductors, one having said
coupling aperture therein and the other forming a reflector
directing energy back to the coupling aperture to .[.provie.].
provide an enhanced signal thereat.
5. A temperature monitoring apparatus used in association with a
guided wave means that is adapted for microwave heating, from a
microwave heating source, of a substance that is absorptive at
microwave frequencies and that is held in retaining means that is
transparent at microwave frequencies, both said substance and said
retaining means therefor being enclosed by said guided wave means,
said apparatus comprising; a length of waveguide, means defining a
coupling aperture in said guided wave means, means supporting said
length of waveguide with one end thereof about said coupling
aperture, a microwave radiometer detection circuit, means coupling
from the length of waveguide to the detection circuit, wherein said
microwave heating is at one frequency and the detection is at
another frequency, and wherein the coupling aperture is dimensioned
in comparison to the guided wave means so as to leave the heating
characteristics of the guided wave means substantially
undisturbed.
6. A temperature monitoring apparatus used in association with a
guided wave means that is adapted for microwave heating, from a
microwave heating source, of a substance that is absorptive at
microwave frequencies and that is held in retaining means that is
transparent at microwave frequencies, both said substance and said
retaining means therefor being enclosed by said guided wave means,
said apparatus comprising; a length of waveguide, means .[.to.].
defining a coupling aperture in said guided wave means, means
supporting said length of waveguide with one end thereof about said
coupling aperture, a microwave radiometer detection circuit, means
coupling from the length of waveguide to the detection circuit,
wherein said microwave heating is at one frequency and the
detection is at another frequency, and wherein the length of
waveguide is selected so that the waveguide operates as a filter
passing said detection frequency and rejecting said heating
frequency.
7. A temperature monitoring apparatus in combination with a guided
wave means used for sterilization and/or heating of a substance,
comprising means for operating the guided wave means to provide
microwave heating of the substance in a container, said substance
being absorptive at microwave frequencies and wherein said
container is transparent in microwave frequencies, both said
substance and said container being enclosed by said guided wave
means, a length of waveguide, means defining a coupling aperture in
said guided wave means, means supporting said length of waveguide
with one end thereof about said coupling aperture, a microwave
radiometer detection circuit and signal coupling means coupling
from the length of waveguide, at a location remote from said
coupling aperture, to the detection circuit.
8. A non-invasive temperature monitoring apparatus as set forth in
claim 7 wherein said waveguide is dielectric filled.
9. A non-invasive temperature monitoring apparatus as set forth in
claim 7 wherein said microwave heating is at one frequency and the
detection is at a higher frequency, said coupling aperture having a
cross-sectional area less than the waveguide cross-sectional area,
the coupling aperture being smaller in comparison with the guided
wave means so as to leave the heating characteristics of the guided
wave means substantially undisturbed, said waveguide being
dimensioned to operate as a high pass filter passing said higher
frequency and rejecting said heating frequency.
10. A non-invasive temperature monitoring apparatus as set forth in
claim 7 wherein said substance that is absorptive at microwave
frequencies comprises a liquid and said container comprises a
coupling means.
11. A non-invasive temperature monitoring apparatus as set forth in
claim 7 wherein said substance that is absorptive at microwave
frequencies comprises a liquid and said container comprises a
connector means.
12. A non-invasive temperature monitoring apparatus as set forth in
claim 7 wherein said substance that is absorptive at microwave
frequencies comprises a liquid. .Iadd.
13. A temperature monitoring apparatus used in association with a
guided wave means that is adapted for microwave heating, from a
microwave heating source, of a substance that is absorptive at
microwave frequencies and that is located during temperature
monitoring in means transparent at microwave frequencies, both said
substance and said transparent means being surrounded by said
guided wave means, said apparatus comprising; electromagnetic
transmission means adapted for the transmission of microwave energy
at selected frequencies, means defining a coupling aperture in said
guided wave means, means supporting said electromagnetic
transmission means with one end thereof about said coupling
aperture, a microwave radiometer detection circuit, and, means
coupling said electromagnetic transmission means to the detection
circuit, wherein microwave heating is at one frequency and
detection is at another frequency, and wherein said microwave
heating and said microwave detection are at different frequencies,
said coupling aperture having a cross-sectional area less than
electromagnetic transmission means cross-sectional area, the
coupling aperture being sufficiently small in comparison to said
electromagnetic transmission means cross-section so as to leave the
heating characteristics of the guided wave means substantially
undisturbed. .Iaddend. .Iadd.
14. A non-invasive temperature monitoring apparatus as set forth in
claim 13 wherein said electromagnetic transmission means comprises
a length of waveguide that is sufficiently long so as to provide a
cut-off at the heating frequency. .Iaddend. .Iadd.
15. A non-invasive temperature monitoring apparatus as set forth in
claim 13 wherein said electromagnetic transmission means functions
as a high pass filter preventing any heating energy from being
detected at the radiometer detection circuits whereby the circuit
detects only energy associated with the temperature of the liquid
being heated. .Iaddend. .Iadd.16. A temperature monitoring
apparatus used in association with a guided wave means that is
adapted for microwave heating, from a microwave heating source, of
a substance that is absorptive at microwave frequencies and that is
located during temperature monitoring in means transparent at
microwave frequencies, both said substance and said transparent
means being surrounded by said guided wave means, said apparatus
comprising; electromagnetic transmission means adapted for the
transmission of microwave energy at selected frequencies, means
defining a coupling aperture in said guided wave means, means
supporting said electromagnetic transmission means with one end
thereof about said coupling aperture, a microwave radiometer
detection circuit, and, means coupling said electromagnetic
transmission means to the detection circuit, wherein said guided
wave means comprises a pair of curved conductors, one having said
coupling aperture therein and the other forming a reflector
directing energy back to the coupling aperture to provide an
enhanced signal
thereat. .Iaddend. .Iadd.17. A temperature monitoring apparatus
used in association with a guided wave means that is adapted for
microwave heating, from a microwave heating source, of a substance
that is absorptive at microwave frequencies and that is located
during temperature monitoring in means transparent at microwave
frequencies, both said substance and said transparent means being
surrounded by said guided wave means, said apparatus comprising;
electromagnetic transmission means adapted for the transmission of
microwave energy at selected frequencies, means defining a coupling
aperture in said guided wave means, means supporting said
electromagnetic transmission means with one end thereof about said
coupling aperture, a microwave radiometer detection circuit for
microwave detection, and, means coupling said electromagnetic
transmission means to the detection circuit, wherein microwave
heating from the microwave heating source is at one frequency and
the microwave detection by said microwave radiometer detection
circuit is at another frequency, and wherein the coupling aperture
is dimensioned in comparison to the guided wave means so as to
leave the heating characteristics of the guided
wave means substantially undisturbed. .Iaddend. .Iadd.18. A
temperature monitoring apparatus used in association with a guided
wave means that is adapted for microwave heating, from a microwave
heating source, of a substance that is absorptive at microwave
frequencies and that is located during temperature monitoring in
means transparent at microwave frequencies, both said substance and
said transparent means being surrounded by said guided wave means,
said apparatus comprising; electromagnetic transmission means
adapted for the transmission of microwave energy at selected
frequencies, means defining a coupling aperture in said guided wave
means, means supporting said electromagnetic transmission means
with one end thereof about said coupling aperture, a microwave
radiometer detection circuit for microwave detection, and, means
coupling said electromagnetic transmission means to the detection
circuit, wherein microwave heating from the microwave heating
source is at one frequency and the microwave detection by said
microwave radiometer detection circuit is at another frequency, and
wherein the electromagnetic transmission means is selected so that
it operates as a filter passing a detection frequency and rejecting
a heating frequency. .Iaddend. .Iadd.19. A temperature monitoring
apparatus in combination with a guided wave means used for
sterilization and/or heating of a substance, comprising means for
operating the guided wave means to provide microwave heating of the
substance in a container, said substance being absorptive at
microwave frequencies and wherein said container is transparent in
microwave frequencies, both said substance and said container being
surrounded by said guided wave means, an electromagnetic
transmission means, means defining a coupling aperture in said
guided wave means, means supporting said electromagnetic
transmission means with one end thereof disposed about said
coupling aperture, a microwave radiometer detection circuit and
signal coupling means coupling from said electromagnetic
transmission means, at a location remote from said coupling
aperture, to the detection
circuit. .Iaddend. .Iadd.20. A non-invasive temperature monitoring
apparatus as set forth in claim 19 wherein said electromagnetic
transmission means is dielectric filled. .Iaddend. .Iadd.21. A
non-invasive temperature monitoring apparatus as set forth in claim
19 wherein said microwave heating is at one frequency and the
detection is at a higher frequency said coupling aperture having a
cross-sectional area less than the electromagnetic transmission
means cross-sectional area, the coupling aperture being smaller in
comparison with the guided wave means so as to leave the heating
characteristics of the guided wave means substantially undisturbed,
said electromagnetic transmission means being dimensioned to
operate as a high pass filter passing said higher frequency and
rejecting said heating frequency. .Iaddend. .Iadd.22. A
non-invasive temperature monitoring apparatus as set forth in claim
19 wherein said substance that is absorptive at microwave
frequencies comprises a liquid and said container comprises a
coupling means. .Iaddend. .Iadd.23. A non-invasive temperature
monitoring apparatus as set forth in claim 19 wherein said
substance that is absorptive at microwave frequencies comprises a
liquid and said container comprises a connector means. .Iaddend.
.Iadd.24. A non-invasive temperature monitoring apparatus as set
forth in claim 19 wherein said substance that is absorptive at
microwave
frequencies comprises a liquid. .Iaddend. .Iadd.25. A temperature
monitoring apparatus used in association with a guided wave means
that is adapted for microwave heating, from a microwave heating
source, of a substance that is absorptive at microwave frequencies
and is located during temperature monitoring in means transparent
at microwave frequencies, both said substance and said transparent
means being surrounded by said guided wave means, said apparatus
comprising; electromagnetic transmission means adapted for the
transmission of microwave energy at selected frequencies, means
defining a coupling port in said guided wave means, means
supporting said electromagnetic transmission means with one end
thereof about said coupling port, a microwave radiometer detection
circuit for microwave detection, and, means coupling said
electromagnetic transmission means to the detection circuit,
wherein microwave heating from the microwave heating source is at
one frequency and the microwave detection by said microwave
radiometer detection circuit is at another frequency, and wherein
the coupling part is dimensioned in comparison to the guided wave
means so as to leave the heating characteristics of the guided wave
means substantially
undisturbed. .Iaddend. .Iadd.26. A non-invasive temperature
monitoring apparatus as set forth in claim 24, wherein said liquid
is stationary
during said microwave heating. .Iaddend. .Iadd.27. A non-invasive
temperature monitoring apparatus used in association with a guided
wave means that is adapted for microwave heating of a substance
that is absorptive at microwave frequencies and that is held in
means that is transparent at microwave frequencies, said apparatus
comprising; a length of waveguide, means defining a coupling
aperture in said guided wave means, means supporting said length of
waveguide with one end thereof about said coupling aperture, a
microwave radiometer detection circuit, and means coupling from the
length of waveguide to the detection circuit, wherein said
microwave heating is at one frequency and the detection is at a
higher frequency, and wherein said coupling aperture has a
cross-sectional area less than the waveguide cross-sectional area.
.Iaddend. .Iadd.28. A non-invasive temperature monitoring apparatus
as set forth in claim 27 wherein the coupling aperture is
dimensioned in comparison with the guide wave means so as to leave
the heating characteristics of the guided wave means substantially
undisturbed. .Iaddend. .Iadd.29. A non-invasive temperature
monitoring apparatus as set forth in claim 28 wherein the waveguide
is dimensioned to operate as a high pass filter passing said higher
frequency and rejecting said one frequency. .Iaddend. .Iadd.30. A
non-invasive temperature monitoring apparatus in combination with a
guided wave means used for sterilization and including means for
operating the guided wave means to provide microwave heating of a
substance that is absorptive at microwave frequencies and that
includes a container or the like for the substance which container
is transparent at microwave frequencies, a length of waveguide,
means defining a coupling aperture in said guided wave means, means
supporting said length of waveguide with one end thereof about said
coupling aperture, a microwave radiometer detection circuit and
means coupling from the length of waveguide to the detection
circuit, wherein said microwave heating is at one frequency and the
detection is at a higher frequency, said coupling aperture having a
cross-sectional area less than the waveguide cross-sectional area,
the coupling aperture being dimensioned in comparison with the
guided wave means so as to leave the heating characteristics of the
guided wave means substantially undisturbed, said waveguide being
dimensioned to operate as a high pass filter passing said higher
frequency and rejecting said heating frequency. .Iaddend.
Description
BACKGROUND OF THE INVENTION
The present invention relates in general to a non-invasive
technique for monitoring the temperature of a material or substance
that is absorptive at microwave frequencies while being held in a
container, connector, bar, or the like that is transparent at
microwave frequencies. More particularly, the non-invasive
temperature monitor of the invention may be used in association
with a microwave sterilizer for providing an accurate reading of
the temperature of the material or substance being heated which in
the case of microwave sterilization is typically a liquid, such as
might be used in continuous ambulatory peritoneal dialysis (CAPD)
microwave sterilization. Even more particularly, and in accordance
with at least one embodiment of the present invention, there is
provided a non-invasive technique for temperature measurement in a
microwave sterilization apparatus and in which the liquid being
sterilized is held within a connector means to be heated therein by
microwave energy for the purpose of sterilization.
Reference is now made herein to copending application Ser. No.
466,894 filed Feb. 17, 1983, now U.S. Pat. No. 4,614,514, on a
microwave sterilizer and assigned to the present assignee herein.
This sterilizer is described therein as being used for the purpose
of sterilizing a coupling or connector that intercouples a conduit
from a source of liquid such as a saline solution to a conduit
implanted in the body. The apparatus of this sterilizer comprises a
guided wave member adapted to enclose the coupling or connector and
means for heating by excitation of the guided wave member to heat
an initial charge of the liquid to an elevated temperature for a
time long enough to destroy bacteria. In this apparatus, it has
been assumed that the proper sterilization occurs by virtue of the
microwave power having been applied for a specified period of time.
The basic problem that has come about is that, because the actual
temperature of the liquid or solution is not being measured, one
cannot be assured that sufficient sterilization has taken place.
For example, if the microwave source is not functioning properly
and is say, not putting out the require power, then even though the
sterilization occurs for what appears to be a sufficient period of
time, in fact, sufficient sterilization may not have occurred.
The common technique for measuring temperature is to monitor the
surface of the container. However, if the container, connector, bar
or the like is of insulating or semi-insulating material, it will
not be possible to obtain exact temperature measurements. Also,
there will tend to be a thermal lag.
Accordingly, it is an object of the present invention to provide a
technique for monitoring the temperature, on a non-invasive basis,
of a material or substance, usually a liquid, that is absorptive at
microwave frequencies (also being heated by microwave energy) while
being held in a container, bag, connector, or the like that is
transparent at microwave frequencies.
Another object of the present invention is to provide a
non-invasive technique for the measurement of temperature of a
sterilizing substance which is usually a liquid in association with
microwave heating of the liquid for sterilization purposes. In
accordance with the invention, this combination of sterilization
and temperature detection occurs without any interference whereby
the heating applied is at a different frequency than the detection
frequency.
Another object of the present invention is to provide a
non-invasive temperature monitor that is of relatively simple
construction, adapts itself readily to the microwave sterilizer and
which can be made in miniature size and in which monitoring can
occur quite easily so that the required temperature for
sterilization can be readily achieved.
Still another object of the present invention is to provide an
improved means for in particular, the warming of the solutions
which are absorptive to microwave energy and which are typically
contained in plastic bags or the like that are transparent to
microwave energy.
A further object of the present invention is to provide a means as
set forth in the preceding claim and which is in the form of a
conformal array of elements particularly adapted for heating of
relatively large solution bags or containers.
SUMMARY OF THE INVENTION
To accomplish the foregoing and other objects, features and
advantages of the invention, there is provided a non-invasive
temperature monitoring apparatus which is used in association with
a guided wave means that may comprise part of a microwave
sterilizer. This guided wave means is adapted for microwave heating
of a substance of material, usually a liquid, that is absorptive at
microwave frequencies and that is held in means, such as a
container, bag, connector or the like, that is transparent to
microwave energy. The apparatus of the present invention comprises
a length of waveguide and means defining a coupling aperture in the
guided wave means. The length of waveguide is supported with one
end thereof about the coupling aperture for coupling energy from
inside of the guided wave means to an opposite end of the length of
waveguide. There is also provided a microwave radiometer detection
circuit and means are provided for coupling from the length of
waveguide to this detection circuit. The output of the detection
circuit provides an accurate, high resolution temperature display
output indicating on a continuous basis the temperature that is
being detected of the material or substance (usually a liquid) that
is being heated. The microwave heating is at one frequency and the
detection is at a higher frequency. For example, the heating may be
at 915 MHz while the detection may be designed at a frequency of
4.7 GHz. The coupling aperture preferably has a cross-sectional
area less than the waveguide cross-sectional area. Also, the
coupling aperture is dimensioned in comparison with the guided wave
means so as to leave the heating characteristics of the guided wave
means substantially undisturbed. Also, the waveguide is dimensioned
to operate as a high pass filter passing the higher frequency and
rejecting the lower heating frequency. The waveguide is simply
designed so as to provide rejection by cut off of the lower
frequency heating energy.
In accordance with another embodiment of the present invention,
there is provided a non-invasive temperature monitoring apparatus
used in association with a guided wave means in which this guided
wave means is of generally larger size so as to accommodate a bag
or container. In this embodiment of the invention, the microwave
energy is used for the purpose of the warming of solutions
absorptive to microwave energy contained in the plastic bag or
container. The bag or container is transparent to microwave energy.
In still another embodiment in accordance with the present
invention there is provided an array of elements that are used in
association with relatively large volume bags or containers. The
array of elements may be disposed directly on the bag or container
outer surface and the array enables heating and warming of
materials or solutions contained in the bag. The array of elements
provides good heat uniformity and the arrangement is particularly
advantageous in connection with materials or solutions that are not
good conductors of heat or that are not homogeneous.
BRIEF DESCRIPTION OF THE DRAWINGS
Numerous other objects, features and advantages of the invention
should now become apparent upon a reading of the following detailed
description taken in conjunction with the accompanying drawing, in
which:
FIG. 1 is a perspective view illustrating the non-invasive
temperature monitoring apparatus of the present invention as used
in conjunction with a microwave sterilizer;
FIG. 2 is a cross-sectional view taken through the microwave
sterilizer apparatus and the temperature monitoring apparatus;
FIG. 3 is a longitudinal cross-sectional view additionally showing
the connector means with a liquid being heated therein;
FIG. 4 is a circuit diagram of a microwave radiometer used for
providing an indication of temperature being sensed;
FIG. 5 is an alternate perspective view showing the non-invasive
temperature monitoring apparatus of the present invention as used
in association with a bag-type container for a liquid being
heated;
FIG. 6 is a perspective view showing a conformal array of elements
that is used in connection with a bag or container for the purpose
of heating or warming solutions contained in the bag or container;
and
FIG. 7 is a cross-sectional view taken along the line 7--7 of FIG.
6 showing the matching array elements.
DETAILED DESCRIPTION
In FIGS. 1-3 herein, there is shown a technique for non-invasively
monitoring the temperature of a liquid that is being heated by
microwave energy for the purpose of sterilization. Thus, there is
described herein at least part of a CAPD microwave sterilizer such
as referred to in copending application Ser. No. 466,894 filed Feb.
16, 1983, now U.S. Pat. No. 4,614,514. Although the concepts of the
invention are described primarily in connection with a CAPD
microwave sterilizer, it is to be noted that the principles may
also be applied to any device in which a material or substance that
is absorptive at microwave frequencies is heated while being held
in a container, bag, connector or the like that is transparent at
microwave frequencies.
Reference may now be made to FIGS. 1-3 which shows a microwave
sterilizer which is operated from a microwave source 10 which
couples to a short coaxial cable 12. As noted in FIG. 2, there is
also provided a balun 11 for converting from an unbalanced to a
balanced configuration. Also depicted in FIG. 2, are the end tuning
variable capacitors 14 and 15 for providing proper tuning of the
guided wave structure. The electrical coupling is from capacitors
14 and 15 to conductors 17 and 18, respectively. The conductors 17
and 18 form a balanced transmission line which may be terminated in
either a short circuit or open circuit. In this way the transmitter
power not absorbed by the liquid initially is reflected, or
directed back, into the lossy liquid. The loss of the structure is
adequate to present a proper match to the microwave
transmitter.
The microwave source 10 is preferably at a frequency of 950 MHz and
operates from a typical voltage supply of say 12 volts, allowing
safe operation from either battery or a low voltage power supply.
The output of the 915 MHz solid state source is approximately 15
watts. With this low power operation, the device is thus compact,
efficient, and safe in operation.
FIGS. 2 and 3 show the pivotal heater block 20 and the stationary
heater block 22. The mechanical motions that are involved provide
for the closing of the pivotal heater block 20 against the
stationary heater block 22 enclosing the connector 24 which is
comprised of the male member 26 and the female member 28. FIG. 2
shows the spike 27 of the male member 26 engaged with the female
member 28. FIG. 3 also shows the liquid 30 that is being heated
within the connector 24 for the purpose of sterilizing the
connector 24.
As noted in FIG. 2, the two wire transmission line is comprised of
the curved conductors 17 and 18. Each of these may be made of
stainless steel to minimize heat transfer from the liquid. A rotary
hinge joint 33 is provided to permit the pivotal movement of the
heater block 20. Each of the heater blocks preferably also includes
respective housing members 34 and 35 and internal insulation 37 and
38. The outer members 34 and 35 may be of plastic material and the
insulation is adapted to maintain the heat concentrated within the
connector 24.
FIGS. 2 and 3 also show the spring 39. This is disposed at the
bottom of the heater blocks. This is instrumental in providing for
an opening mechanism to the rotatable heater block 20. In FIG. 2
the end of the male spike 27 is shown inside of the female
connector with the liquid thereabout in readiness for heating.
Now, in accordance with the present invention and in order to carry
out the temperature monitoring on a non-invasive basis, there is
provided a length of waveguide 40 that couples to one of the curved
conductors comprising the guided wave member used for sterilization
purposes. One of the curved conductors 17 is mechanically fixed in
position and the fixed conductor preferably contains or
incorporates the temperature sensor. In the illustration of FIGS. 1
and 2, the waveguide 40 couples from the curve member 17. This
coupling of microwave energy to the waveguide 40 for temperature
sensing is carried out by means of a coupling aperture 42 through
the wall of the conductor 17. The waveguide 40 has its end 44
suitably secured to the curved conductor 17. This securing may be
provided by means of a small weld or by some other suitable means
of attachment. The coupling aperture is preferably uniformly
centered relative to the waveguide 40. The coupling aperture is
sufficiently small so as not to disturb the heating characteristics
of the curved conductors 17 and 18. With regard to the length of
the waveguide 40, this should be sufficiently long so as to provide
a cut off at the lower frequency of 915 KHz. In this way the
waveguide 40 functions as a high pass filter preventing any heating
energy from being detected at the radiometer so that the radiometer
detects only energy associated with the temperature of the liquid
being sterilized.
The waveguide 40 is a dielectric filled waveguide. The waveguide
thus includes a core of a ceramic material such as aluminum oxide
with the outer boundaries of the waveguide being formed by means of
a metallic conductive plating on the ceramic. This arrangement is
depicted in FIG. 1 by a small cut out portion showing the plating
and the ceramic material. In this regard, also note in FIG. 2, the
plating 46 and the aluminum oxide core 48.
FIG. 2 also illustrates the coupling from the end 50 of the
waveguide 40. This includes a connector 52 which is of conventional
design coupling by way of line 53 to radiometer 54.
As indicated previously, in the preferred embodiment of the present
invention, the waveguide 40 is dielectrically filled. The waveguide
is constructed so as to provide adequate attenuation at the 915 MHz
to prevent direct coupling of the heating frequency to the
sensitive receiver.
In the example given in conjunction with a microwave sterilizer, it
is noted that the plastic used in the connector 24 is low loss and
therefore the radiometer reads primarily only the emission from the
liquid contained therein. Also, the other curved conductor 18 such
as depicted in FIGS. 1 and 2 functions as a reflector to direct
energy back toward the coupling aperture which is also desired.
This arrangement provides for good signal strength allowing the use
of a relatively simple radiometer scheme.
FIG. 4 depicts the microwave radiometer circuit illustrating the
waveguide coupling device at 60. This is representative of the
waveguide 40 depicted in FIG. 2. The coupling device connects to
the Dicke switch 62. The radiometer is preferably of the Dicke
switch type utilizing a diode switch rather than a ferrite switch.
This allows the use of a low cost microwave integrated circuit
technique for fabrication of the circuit. In one version, the diode
associated with the Dicke switch 62 may be supported across the
waveguide 40. As indicated previously, the waveguide itself is
sufficiently long enough to provide a cut off at the lower
frequency of 915 MHz.
The output of the Dicke switch 62 couples to the RF amplifier 64.
The output of the RF amplifier 64 couples to a mixer circuit 66
which also receives an output from the local oscillator 68. The
output of the mixer 66 couples by way of the video amplifier 70 to
the lock-in amplifier 72. There is also provided a low frequency
100 cycle per second switch driver 74 which is connected in a
feedback arrangement for providing control to both the lock-in
amplifier 72 and the Dicke switch 62. The output of the microwave
radiometer circuit is taken at the output line 75 from the lock-in
amplifier 72. For the most part the microwave radiometer circuit
depicted in FIG. 4 is of conventional design and thus is not
discussed in detail herein. The operation of this circuit is in
substance the same as the operation of the circuit depicted in U.S.
Pat. No. 4,346,716 also owned by the present assignee herein.
FIG. 5 is a schematic diagram illustrating guided wave conductors
80 and 81 which may be of larger diameter than the conductors 17
and 18 illustrated in FIG. 1. The purpose of the embodiment to FIG.
5 is to illustrate the concepts of the invention in association
with a bag 83 or the like container for containing a material which
is usually a substance which is absorptive at microwave frequencies
and which is being heated within the conductors 80 and 81 while
being held in the container or bag with the container or bag being
transparent at microwave frequencies. In the embodiment of FIG. 5,
it is noted that there is also shown the waveguide 84 similar to
the waveguide 40 of FIG. 2 and the coupling to a radiometer 86. The
construction of the waveguide section 84 and the use of a coupling
aperture in the conductor 81 may be substantially identical to that
previously shown and described in connection with FIGS. 1-3.
The array of elements may be disposed directly on the bag or
container outer surface and the array enables heating and warming
of materials or solutions contained in the bag. The array of
elements provides good heat uniformity and the arrangement is
particularly advantageous in connection with materials or solutions
that are not good conductors of heat or that are not
homogeneous.
FIGS. 6 and 7 show the principles of the present invention as
applied in connection with the heating or warming of a solution
contained in a bag or container. Typically, this may be a two liter
bag such as the bag 88 illustrated in FIG. 6. The bag 88 may
contain a dialysate solution.
A conformal array of antenna elements 90 are disposed preferably
one array on each side of the bag. In this connection, FIG. 7 shows
element 90A on one side and element 90B on the opposite side. FIG.
7 also shows the corresponding terminals 91A and 91B. Each of the
elements 90 is connected in common to one of the terminals as also
illustrated in FIG. 6. The elements 90 may be deposited on the
outer surface of the bag. The elements may be refracted onto the
bag surface. The array of elements 90 is preferably disposed in a
manner so as to cover the majority of the surface of the container.
The elements 90 are also preferably disposed in some type of an
orderly array so as to provide proper coverage and thus proper
uniform heating.
Unlike microwave ovens used for heating, the array shown in FIGS. 6
and 7 provides for a much more uniform heating pattern. For
example, in connection with a commercial microwave oven, because of
the standing wave patterns established therein, there is a need for
physically spinning or moving the material that is to be heated.
The conventional microwave oven is far less efficient than the
arrangement depicted in FIGS. 6 and 7 herein because in the
microwave oven it is designed to heat a wide variety of materials
of various sizes and shapes. On the other hand, in accordance with
the present invention, the array is meant to heat only the solution
contained within the bag.
Also, in accordance with the conformal array aspect of the
invention depicted in FIGS. 6 and 7, much more flexibility is
provided. For example, the array can be arranged so as to provide a
non-uniform heating pattern if there would be some reason to heat
one portion of the bag more than another portion. This might be the
case where the bag is divided and contains two different types of
liquids therein. One may desire to heat one of the liquids more
than the other and in this connection the conformal array adapts
itself very well to providing different heating patterns or even
non-uniform heating patterns if desired.
It is also noted that all of the elements 90 of each group on each
side of the bag is coupled out to a single terminal. This is
illustrated in FIG. 7 as terminal 91A for elements on one side of
the bag and terminal 91B coupling to elements on the opposite side
of the bag. FIG. 6 also illustrates the electrical interconnections
that essentially tie all of the elements 90 in common to terminal
91A in FIG. 6. Appropriate microwave energy is coupled to terminals
91A and 91B in the same manner as microwave energy is applied in
connection with the embodiments described earlier.
Having now described a limited number of embodiments of the present
invention, it should be apparent to those skilled in the art that
numerous other embodiments may be contemplated as falling within
the scope of this invention.
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