Note: Descriptions are shown in the official language in which they were submitted.
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APPARATUS AND METHOD FOR MONITORING
AND REGULATING CRYOGENIC COOLING
[0001] This application claims the benefit of Provisional Application No.
60/968,479, filed on
August 28, 2007, which is incorporated herein by reference in its entirety as
if fully set forth.
BACKGROUND
[0002] The present invention relates to cryogenic spray cooling, which is
commonly used in
metalworking and other industrial applications that demand cooling to maintain
optimal process
parameters.
[0003] Direct sensing of workpiece and tool surface temperature in
metalworking applications
is challenging. Due to the fact that both the work and tool are in motion,
contact-based temperature
measurement is not desirable. Conventional non-contact temperature measurement
devices, such
as infra-red (IR) sensors and thermometers, are often inaccurate due to
measurement errors
induced by the reflectivity of the work and tool materials, as well as low
radiation levels in the low-
temperature range. In applications where cryogenic cooling is used, accurate
temperature
measurement is of increased importance. Accordingly, a more accurate method of
non-contact
temperature measurement is needed.
[0004] Related art includes U.S. Patent No. 5,517,842 and PCT Publication No.
W02006/074875A1.
SUMMARY OF THE INVENTION
[0005] The present invention comprises an apparatus for a system having a
cryogenic cooling
component that generates a vapor cloud when operated. The apparatus senses the
cooling and
sends a signal to a controller that is programmed to set and/or adjust at
least one operating
parameter of the system.
[0006] In one respect, the invention comprises an apparatus for use with a
system having a
cryogenic cooling component that generates a vapor cloud when operating. The
apparatus
including a first emitter that is adapted to emit a first light beam at a
first intensity. The apparatus
further includes a first receiver having a first sensor that is adapted to
detect a first sensed intensity.
The first sensed intensity being the intensity of the first light beam at the
first sensor when the first
light beam is directed at the first sensor. The first receiver being adapted
to generate a first sensor
signal that is a function of the first sensed intensity, and the first emitter
and first sensor having a
first operating position, where the first emitter and first sensor are
positioned and oriented so that
the first light beam is directed onto the first sensor and the first light
beam passes through the vapor
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cloud at least once before being received by the first sensor. A controller is
also provided and is
programmed to set and/or adjust at least one operating parameter of the system
based on
controller data. When the first emitter and second sensor are in the first
operating position, the
controller data comprises the first sensor signal.
[0007] In another respect, the invention comprises an apparatus for use with a
system having a
cryogenic cooling component that generates a vapor cloud when operated. The
apparatus includes
means for determining relative opacity of the vapor cloud and generating data
relating to the relative
opacity of the vapor cloud and a controller in communication with the means
for determining, the
controller being adapted to set and/or adjust at least one operating parameter
of the system based
on the data.
[0008] In yet another respect, the invention comprises a method used with a
system having a
cryogenic cooling component, the method including measuring the relative
opacity of a cryogenic
vapor cloud, and setting and/or adjusting at least one operating parameter of
the system based on
the measured relative opacity of the cryogenic vapor cloud.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The following detailed description of the preferred embodiments of the
invention will be
better understood when read in conjunction with the appended drawings. For the
purposes of
illustrating the invention, there is shown in the drawings embodiments which
are presently
preferred. It is understood, however, that the invention is not limited to the
precise arrangements
and instrumentality shown in the drawings:
[0010] Fig. 1 is a first embodiment of a basic cryogenic vapor cloud opacity
measurement
apparatus, in accordance with the present invention;
[0011] Fig. 2 is a second embodiment of a basic cryogenic vapor cloud opacity
measurement
apparatus, in which the light beam is reflected;
[0012] Fig. 3 is a schematic representation of a preferred embodiment of an
apparatus for
monitoring and regulating cryogenic cooling of a workpiece and roller
according to the present
invention; and
[0013] Fig. 4 is a schematic representation of a second embodiment of an
apparatus for
monitoring and regulating cryogenic cooling of a workpiece and roller.
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DETAILED DESCRIPTION OF THE INVENTION
[0014] The present invention is an apparatus for use with a system having a
cryogenic cooling
component that generates a vapor cloud when operating. Systems that have a
cryogenic cooling
component may include, but are not limited to, metal rolling and machining
operations such as lathe
turning, boring, milling, thermal spray coating applications, and food
freezing applications.
[0015] "Cryogenic vapor" is a suspension of microscopic water ice crystals
which forms when
water contained in ambient air comes in contact with a cryogenic spray, such
as liquid nitrogen
(hereinafter "LIN"), gaseous nitrogen, argon and carbon dioxide or a mixture
of two or more of these
liquids and/or gases. Cryogenic vapor is typically white and opaque or semi-
opaque.
[0016] During experiments relating to the development of the present
invention, it was
observed that the amount of "cryogenic vapor" evolving from an area in which a
cryogenic spray is
being directed onto a substrate, e.g. workpiece and/or tool area and/or part
surface and/or other
surface of an object to be cooled, was inversely proportional to the surface
temperature of the
surface onto which the spray was being applied. In all cases observed, a large
amount of cryogenic
vapor was observed when the substrate (e.g. workpiece, part and/or tool)
surfaces were below the
desired temperature range (i.e., overcooling) and almost no cryogenic vapor
was visible when the
workpiece and tool surfaces were above the desired temperature range (i.e.,
insufficient cooling). It
was observed that the "cloud" generated by a large amount of cryogenic vapor
was more opaque
than a smaller amount of cryogenic vapor. Applicants discovered that the
opacity of the vapor
cloud could be measured with reasonable accuracy by measuring the drop in
intensity of a light
beam that is directed through the vapor cloud. The intensity drop is due to
dispersion and
absorption of the light beam on the solid surfaces of microscopic ice
crystals, which form part of a
cryogenic vapor cloud. These concepts form the basis for the present
invention.
[0017] Fig. 1 illustrates a basic apparatus used to measure cryogenic vapor
opacity. As can be
seen in Fig. 1, a cryogenic cooling device 12 is generating a vapor cloud 13.
A light source 23 is
positioned to direct a light beam 25 through the vapor cloud 13. In this
embodiment, the light
source 23 is a laser emitter. A receiver 29 is positioned in the path of the
light beam 25 after the
light beam 25 has passed through the vapor cloud 13. The receiver 29 has a
light sensor 31 that is
adapted to detect the intensity 33 of light within the wavelength range of the
light beam 25. The
light beam 25 has a known initial intensity 27 at the light source 23 and a
lower intensity 33 when it
reaches the sensor 31 ("sensed intensity"), after passing through the vapor
cloud 13. Preferably,
the sensor 31 generates an electrical signal that is proportional to the
sensed intensity. In this
embodiment, the sensor 31 is an optical sensor that generates a signal in the
range of 4-2OmA,
based on the sensed intensity.
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[0018] As noted above, the light source 23 is a laser emitter in this
embodiment. It should be
understood that other emitters could be used. For the purposes of the
specification and claims, the
terms "emitter" means any device capable of emitting light and is used
interchangeably with the
term "light source." Red or green lasers are examples of preferred light
sources for the present
invention because the vapor cloud opacity results from the dispersion and
absorption of the light
beam on the solid surfaces of microscopic ice crystals. Such lasers are
particularly suitable forthe
present invention because they are inexpensive, produce a very focused, easy
to measure beam of
light, and produce a visible light beam, which facilitates proper positioning
of the sensor 31. Light
sources that emit light at ultraviolet (UV) or infrared (IR) wavelengths could
also be used, but are
less preferred because they do not produce visible light beams.
[0019] Fig. 2 shows an alternate arrangement for the apparatus shown in Fig.
1. In Fig. 2, a
reflector 59 is used to re-direct the light beam 25 before being received by
the sensor 31. This
allows the receiver 29 and sensor 31 to be located in close proximity to the
light source 23. As
shown, in this configuration, the light beam 25 passes through the vapor cloud
13 twice.
Alternatively, the light beam and the reflector could be positioned so that
the light beam passed
through the vapor cloud once before being received by the sensor (not shown).
[0020] The signal generated by the sensor 31 can be advantageously used in a
wide variety of
applications. For example, the signal could be used (in combination with other
process data) to
calculate the temperature of a substrate (workpiece or tool or other object)
surface, to generate a
notification or alarm if the signal indicates a vapor opacity level that is
outside of a preferred
operating range, or to control one or more process parameters.
[0021] Fig. 3 shows an embodiment of one such application, which includes a
mill stand in
which a workpiece 119 is being drawn through upper and lower rollers 121, 122.
The workpiece
119 and rollers 121, 122 are cooled by a cryogenic spray device 112 that
generates a vapor cloud
113. In this embodiment, the cryogenic spray device 112 is being directed onto
the upper roller
121. Many other configurations are possible, depending upon the metalworking
application. For
example, the cryogenic spray device 112 could be directed at the surface of
the workpiece 119 or
could be directed at the intersection of the workpiece and one of the rollers
121, 122.
[0022] In this embodiment, the light source 123 and the receiver 129 are
located on opposing
sides of the workpiece 119 and rollers 121, 122 (similar to the configuration
shown in Fig. 1). The
light source 123 generates a light beam 125 having an initial intensity 127
(i.e., before it passes
through the vapor cloud 113). As in Fig. 1, the light source 123 and a sensor
131 (part of the
receiver 129) are positioned so that the light beam 125 from the light source
123 is directed onto
the sensor 131 (i.e., an operating position). The sensor 131 generates an
electrical signal 135,
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which is proportional to the intensity 133 of the light beam 125 as it is
received by the sensor 131.
[0023] In this embodiment, the light beam 125 is a laser and the signal 135
generated by the
sensor 131 is a 4-2OmA analog signal.
[0024] A controller 137 is programmed to set and/or adjust one or more
operating parameters
of the system based controller data received from the system. In accordance
with the present
invention, the controller data preferably includes data concerning the opacity
of the vapor cloud
113, which is provided by the signal 135 from the sensor 131. For example, the
controller 137
could be programmed to increase the cooling rate of the cryogenic spray device
112 if the signal
135 indicates that there is too little cryogenic vapor. The controller 137
could also be configured to
activate an alarm if the signal 135 indicates that opacity of the vapor cloud
113 is outside of a
predetermined range. Examples of other operating parameters that the
controller could be used to
adjust include, depending upon the application of the system, mill/drive load,
speeds, and rolling
speed.
[0025] In order to enable the controller 137 to more accurately set and/or
adjust operating
parameters, the controller data preferably includes data concerning variables
(other than the
temperature of the workpiece 119) that may affect the opacity of the vapor
cloud 113. For example,
the opacity of the vapor cloud 113 is directly proportional to the relative
humidity of the air in the
vicinity of the cryogenic spray device 112. Therefore, this embodiment
includes a relative humidity
sensor 145, which generates a signal 147 to the controller 137 that is
proportional to the relative
humidity of the air in the vicinity of the sensor 145. The controller 137 is
programmed to adjust the
cooling rate of the cryogenic spray device 112 based on signals 135 and 147.
[0026] Airflow in the vicinity of the vapor cloud 113 may also affect the
measured opacity of the
vapor cloud 113. Assuming all other pertinent variables are kept constant, the
measured opacity of
the vapor cloud 113 will decrease if airflow in the vicinity of the vapor
cloud 113 increases. Airflow
can be approximated by measuring the velocity of the workpiece 119 or rollers
121, 122.
Accordingly, this embodiment includes a velocity sensor 149, which is
configured to measure the
velocity of the workpiece 119 and to generate a velocity signal 151. In an
alternate embodiment in
which the velocity of the workpiece 119 is an operating parameter that is set
and/or adjusted by the
controller 137, the velocity of the workpiece 119 would serve a dual role -
being both an operating
parameter and controller data.
[0027] In order to provide maximum operational flexibility, the cryogenic
spray device 112
preferably allows for precise and simple adjustment of its cooling rate.
Examples of cryogenic
spray devices having this capability are disclosed in U.S. Patent Application
No. 11/846,116, filed
August 28, 2007, which is hereby incorporated by reference as if fully set
forth. It should be
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understood, however, that the concepts of the present invention could be
applied to any type of
cryogenic cooling device that generates a vapor cloud.
[0028] In this embodiment, the cryogenic spray device 112 includes a liquid
nitrogen ("LIN")
feed line L1, two throttling gas lines G1, G2 (located at opposing ends of the
cryogenic spray device
112) and a gas purge line Gp. The LIN feed line L1 is preferably connected to
a pressurized source
of LIN (not shown). Similarly, the throttling gas lines G1, G2 and purge gas
line Gp are preferably
connected to a pressurized source of gaseous nitrogen. As described in greater
detail in U.S.
Patent Application No. 11/846,116, filed August 28, 2007, which is hereby
incorporated by
reference in its entirety as if fully set forth, the cooling rate and cooling
profile of the cryogenic spray
device 112 (i.e. the flow rate of LIN through the cryogenic spray device 112)
can be precisely
controlled by adjusting the gas pressure on the throttling gas lines G1, G2.
In addition, the purge
line Gp can be used to purge and clean the cryogenic spray device 112 and/or
the surface at which
the cryogenic spray device 112 is directed (in this embodiment, roller 121).
[0029] As noted above, the opacity of the vapor cloud 113 can be correlated
with the
temperature of the workpiece 119. Therefore, the controller 137 can use the
signal 135 to set
and/or adjust operating parameters of the system in which the controller 137
is used which are
normally set and/or adjusted based on the temperature of the workpiece 119.
[0030] Fig. 4 shows an alternate configuration for a vapor cloud opacity
measuring apparatus,
which comprises a light source 223 that generates a light beam 225 having an
initial intensity 227
(i.e., before it passes through the vapor cloud 213) and a sensor 231, which
is part of a receiver
229. As in the embodiment shown in Fig. 2, the light source 223 and sensor 231
are positioned so
that the light beam 225 passes through the vapor cloud 213, is reflected on
the surface of a roller
221, passes through the vapor cloud 213 a second time, and is then received by
the sensor 231.
This configuration enables the light source 223 to be positioned adjacent the
sensor 231 and, if
desired, to be provided as a unitary assembly. The reflection of the light
beam 225 against the
surface of a roller 221 is particularly useful in the industrial cold and
temper rolling operations where
a near mirror roller finish is required.
[0031] This configuration also enables the vapor cloud opacity measurement
apparatus to be
located at any desirable position along the length of the cryogenic spray
device 212. In addition,
multiple vapor cloud opacity measurement apparatuses (not shown) could be
positioned along the
length of the cryogenic spray device 212. Such a configuration would enable
more precise
measurement and control of the temperature of the workpiece 219, to the extent
that it varies along
its width. For example, if higher vapor opacity was detected at the edges of
the workpiece 219 than
at its center, the cryogenic spray device 212 could be adjusted to provide
more cooling to the center
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of the workpiece 219 and less cooling to the edges of the workpiece 219. This
functionality is highly
desirable in the majority of metal rolling operations, where workpiece and
roller edges tend to be
overcooled resulting in numerous production and product quality problems.
[0032] If multiple vapor cloud opacity measurement apparatuses are to be used
along the
length of a cryogenic spray device 212, it is preferable that the cryogenic
spray device 212 be
adapted to provide a non-linear cooling profile (i.e., the ability to provide
different cooling rates
along the length of the cryogenic spray device 212). Examples of this type of
cryogenic spray
device are disclosed above in connection with the embodiment shown in Fig. 3,
as well as in U.S.
Patent Application No. 11/846,116. It should be understood, however, that the
concepts of the
present invention could be applied to any type of cryogenic cooling device
that generates a vapor
cloud.
[0033] Other than the configuration of the vapor cloud opacity measurement
apparatus, the
embodiment shown in Fig. 4 includes all of the components (including a
controller) of the
embodiment shown in Fig. 3. In the interest of simplicity, many of these
components are not shown
in Fig. 4.
[0034] In this embodiment, a second light source 261 and a second receiver 263
are provided
to supply the controller (not shown) with controller data concerning the
reflectivity of the roller 222.
The second light source 261 and sensor 269 are positioned so that the light
beam 265 is reflected
on the surface of a roller 222 and is received by the sensor 269, but does not
pass through any
portion of a vapor cloud. The receiver 263 generates a signal 273, which is
proportional to the
intensity of the light beam 265 when it is received by the sensor 269.
[0035] The signal 273 enables the controller to "normalize" the signal 235 to
compensate for
changes in reflectivity of the rollers 221, 222. In addition, the signal 273
could be used to determine
if the reflectivity of the roller 222 is outside a predetermined operating
range, which may be an
indication of excess water condensation, surface oxidation, deposit, and/or
dust buildup on the
roller 222.
[0036] It is recognized by those skilled in the art that changes may be made
to the above-
described embodiments of the invention without departing from the broad
inventive concepts
thereof. It is understood, therefore, that this invention is not limited to
the particular embodiments
disclosed but is intended to cover all modifications which are in the spirit
and scope of the invention.
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