U.S. patent application number 11/688611 was filed with the patent office on 2007-10-25 for apparatus for verifying the treatment of ductile cast iron and method thereof.
This patent application is currently assigned to THYSSENKRUPP--WAUPACA DIVISION. Invention is credited to Robert Jezwinski, Gene A. Johnson, Timothy Owens, Ronald Thurston.
Application Number | 20070246184 11/688611 |
Document ID | / |
Family ID | 38618360 |
Filed Date | 2007-10-25 |
United States Patent
Application |
20070246184 |
Kind Code |
A1 |
Thurston; Ronald ; et
al. |
October 25, 2007 |
APPARATUS FOR VERIFYING THE TREATMENT OF DUCTILE CAST IRON AND
METHOD THEREOF
Abstract
Disclosed is an apparatus and method for verifying the treatment
of molten metal wherein a sensing device detects an in situ
response resulting from the treatment of the molten metal. The in
situ response is compared to a pre-set limit or condition in order
to determine whether or not proper treatment of the molten metal
has occurred. In particular, the sensing device detects an in situ
response resulting from the mixture of a molten metal addition to a
molten metal. An electronic transformation device can be used to
transform the in situ response into a response data set. The
response data set can be transmitted to and received by a
microprocessor. The microprocessor can manipulate the response data
set. The in situ response to the treatment of the molten metal can
be in the form of heat, light intensity, light wavelength, density
of smoke particles, composition of smoke particles, mechanical
vibration and combinations thereof.
Inventors: |
Thurston; Ronald; (Iola,
WI) ; Jezwinski; Robert; (Waupaca, WI) ;
Johnson; Gene A.; (Stephenson, MI) ; Owens;
Timothy; (Wallace, MI) |
Correspondence
Address: |
GIFFORD, KRASS, SPRINKLE,ANDERSON & CITKOWSKI, P.C
PO BOX 7021
TROY
MI
48007-7021
US
|
Assignee: |
THYSSENKRUPP--WAUPACA
DIVISION
Waupaca
WI
|
Family ID: |
38618360 |
Appl. No.: |
11/688611 |
Filed: |
March 20, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60793207 |
Apr 19, 2006 |
|
|
|
60802934 |
May 24, 2006 |
|
|
|
Current U.S.
Class: |
164/57.1 ;
164/457 |
Current CPC
Class: |
B22D 1/00 20130101; B22D
2/00 20130101; B22D 46/00 20130101 |
Class at
Publication: |
164/57.1 ;
164/457 |
International
Class: |
B22D 27/00 20060101
B22D027/00; B22D 46/00 20060101 B22D046/00 |
Claims
1. An apparatus for the automated and quantitative verification of
a molten metal treatment comprising: a sensing device, said sensing
device monitoring an in situ response resulting from the mixture of
a molten metal addition with a molten metal; an electronic
transformation device, said transformation device transforming said
in situ response into a response data set; and a microprocessor,
said microprocessor receiving said response data set, for the
purpose of automatically and quantitatively verifying the treatment
of molten metal.
2. The invention of claim 1, wherein said in situ response is
selected from the group consisting of heat, light intensity, light
wavelength, density of smoke particles, composition of smoke
particles, mechanical vibration and combinations thereof resulting
from the mixture of said addition with said molten metal.
3. The invention of claim 2, wherein said sensing device is a
photodetector, said photodetector monitoring the light intensity
resulting from the mixture of said addition with said molten
metal.
4. The invention of claim 2, further comprising a ladle with a
ladle hydraulic line, wherein said sensing device is a hydraulic
pressure sensor, said hydraulic pressure sensor monitoring the
change in hydraulic pressure in said ladle hydraulic line resulting
from mechanical vibration caused by the mixture of said addition
with said molten metal in said ladle.
5. The invention of claim 1, wherein said addition to said molten
metal is an alloying addition.
6. The invention of claim 1, wherein said electronic transformation
device is an analog-to-digital converter, said converter
transforming an analog signal from said sensing device into said
response data set in digital form.
7. The invention of claim 6, wherein said microprocessor compares
said digital response data set to a threshold data set.
8. The invention of claim 7, wherein said threshold data set is
light intensity data.
9. The invention of claim 7, wherein said threshold data set is
hydraulic pressure data.
10. The invention of claim 1 wherein said molten metal is molten
iron.
11. The invention of claim 10 wherein said addition to said molten
metal is magnesium.
12. The invention of claim 7, wherein said microprocessor
manipulates said digital response data set.
13. The invention of claim 12 wherein said manipulation is selected
from the group consisting of storing, graphically displaying,
mathematically transforming, comparing to said threshold data and
combinations thereof, for the purpose of automatically and
quantitatively verifying the treatment of molten metal.
14. An apparatus for the automated and quantitative verification of
molten metal treatment comprising: a photodetector, said
photodetector monitoring an in situ light intensity response
resulting from the mixture of an addition to a molten metal with
said molten metal; an analog-to-digital converter, said converter
transforming said in situ light intensity response into a response
data set in digital form; and a microprocessor, said microprocessor
receiving said digital response data set and comparing said
response data set to a threshold data set stored therein, for the
purpose of automatically and quantitatively verifying the treatment
of molten metal.
15. The invention of claim 14, wherein said photodetector is in the
form of a light intensity meter.
16. The invention of claim 14, wherein said addition to said molten
metal is an alloying addition.
17. The invention of claim 14, wherein said molten metal is molten
iron.
18. The invention of claim 14, wherein said addition to said molten
metal is magnesium.
19. An apparatus for the automated and quantitative verification of
molten metal treatment comprising: a ladle, said ladle having a
hydraulic line and containing a molten metal therein; a hydraulic
pressure sensor, said hydraulic pressure sensor monitoring the
hydraulic pressure response in said hydraulic line resulting from
the mechanical vibration caused from the mixture of an addition
with said molten metal; an analog-to-digital converter, said
converter transforming said hydraulic pressure response into a
response data set in digital form; and a microprocessor, said
microprocessor receiving said digital response data set and
comparing said response data set to a threshold data set stored
therein, for the purpose of automatically and quantitatively
verifying the treatment of molten metal.
20. The invention of claim 19, wherein said addition is a magnesium
addition into molten iron.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority of U.S. Provisional Patent
Application Ser. No. 60/793,207, filed Apr. 19, 2006, and U.S.
Provisional Patent Application Ser. No. 60/802,934, filed May 24,
2006, both of which are incorporated herein by reference.
FIELD OF THE INVENTION
[0002] This invention relates generally to an apparatus and method
for verifying the treatment of a molten metal. More specifically,
the invention relates to the verification of the treatment of
ductile cast iron.
BACKGROUND OF THE INVENTION
[0003] Cast metals are used to produce a vast number of useful
products and have significant industrial importance throughout the
world. One of the most used and developed cast metals is cast iron.
Cast irons are a family of ferrous metals with a wide range of
properties. Objects, components and articles are made from cast
iron by being cast into shape as opposed to being formed. Cast
irons typically contain 2 to 4 weight percent (wt %) carbon and 1
to 3 wt % silicon, with other elements used to control specific
properties for particular applications. Cast irons have a wide
range of mechanical properties which make them suitable for use in
a multitude of engineering components.
[0004] Cast iron production is typically initiated with the
remelting of charges which consist of pig iron, steel scrap,
foundry scrap and other ferro-alloys in order to give a desired
composition. A small blast furnace, also known as a cupola, is a
typical melting unit wherein cold pig iron and scrap are charged
from the top of said furnace onto a bed of hot coke through which
air is blown. In the alternative, a metallic charge is melted in a
coreless induction furnace or in a small electric-arc furnace.
[0005] Various types of cast iron can be produced depending on
alloying additions and/or the thermal processing of the material.
For example, gray cast iron is comprised of ferrite and graphite or
pearlite and graphite structures resulting from iron with 2.5 to 4
wt % carbon and greater than 2 wt % silicon. White cast iron has a
structure of pearlite in a cementite matrix and is hard, brittle
and very difficult to machine. Malleable cast iron is typically a
heat treated form of white cast iron which improves the ductility
while maintaining the high tensile strength of white cast iron.
Ductile cast iron is obtained by adding magnesium to the molten
iron just before casting. The magnesium results in the graphite
within a melt forming spheres or nodules. The spheres or nodules of
the graphite afford for much of the improved mechanical properties
of the cast iron when compared to graphite in the form of flakes in
gray cast iron. As such, ductile cast iron competes favorably with
steels since it possesses improved strength, ductility, toughness
and hot workability.
[0006] Although the melting and casting of molten metals can be
relatively unsophisticated, determining whether or not a particular
batch or heat of a molten metal has been sufficiently treated prior
to pouring can be a time-consuming process. For example, the
correct composition of the molten metal just prior to pouring is
critical to obtaining the desired properties of a subsequently cast
component. Typically, the composition of the molten metal just
prior to pouring is obtained by taking a sample of the molten metal
and performing a chemical analysis thereon. The chemical analysis
of the sample can be obtained using wet chemistry or methods such
as optical emission spectrometry (OES) using arc and spark
excitation of a solidified metal sample.
[0007] Wet chemistry analysis can take hours and sometimes days to
perform. Optical emission analysis can be performed in minutes once
the sample has been taken, solidified and properly prepared for the
OES analysis equipment. However, while a metal sample is being
evaluated with respect to its chemical composition using OES, the
molten metal from which it was obtained must be held at elevated
temperatures until confirmation of an appropriate composition is
determined and pouring can ensue. In the event that the chemical
composition of the molten metal is determined to be outside an
acceptable range, additional alloying conditions must be input into
the charge, the molten bath allowed to equilibrate, and samples
taken again for chemical composition analysis. During this time,
molds waiting to be poured remain idle and productivity of the
given casting process is reduced. Therefore, a method and apparatus
to verify the sufficient treatment of a molten metal which provides
feedback in a more timely fashion is desired.
SUMMARY OF THE INVENTION
[0008] Disclosed is a method and an apparatus for verifying the
treatment of molten iron wherein a sensing device detects and
monitors an in situ response resulting from the treatment of the
molten iron. The in situ response is compared to a pre-set limit or
condition in order to determine whether or not proper treatment of
the molten iron has occurred. In particular, the sensing device
detects and monitors an in situ response resulting from the mixture
of a molten iron with magnesium. An electronic transformation
device transforms the in situ response into a response data set.
The response data set is then transmitted to and received by a
microprocessor, said microprocessor comparing the response data set
to a pre-set limit and/or condition.
[0009] The in situ response to the treatment of the molten iron can
be in the form of heat, light intensity, light wavelength, density
of smoke particles, composition of smoke particles, mechanical
vibration and combinations thereof. In one embodiment of the
present invention, the sensing device is a photodetector that
detects and monitors the light intensity resulting from the mixture
of a molten iron with magnesium. In a second embodiment, the
sensing device is a hydraulic pressure sensor within a hydraulic
line that is attached to a ladle. The hydraulic pressure sensor
detects and monitors the change in hydraulic pressure in the
hydraulic line caused by ladle mechanical vibrations resulting from
the mixture of the molten iron with the magnesium.
[0010] The electronic transformation device can be an
analog-to-digital converter that converts an analog in situ
response signal to a response data set in digital form. The
response data set is transmitted to and received by the
microprocessor. The microprocessor can manipulate the received
response data set by storing the data set, graphically displaying
the data set, mathematically transforming the data set, comparing
the response data set to a pre-set limit and/or condition and
combinations thereof. The microprocessor can also determine whether
or not the response data set has met a pre-set limit and/or
condition that may or may not be a function of a threshold data set
stored within the microprocessor.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a schematic diagram illustrating steps of the
present invention;
[0012] FIG. 2 is a schematic diagram showing steps within the
microprocessor of the present invention;
[0013] FIG. 3 is a perspective view of molten metal being poured
into a ladle;
[0014] FIG. 4 is a side view of an alloying addition being added to
the ladle;
[0015] FIG. 5 is a side view of the alloying addition being mixed
with the molten metal;
[0016] FIG. 6 is a side view of an in situ response to the
treatment of the molten metal;
[0017] FIG. 7 is a graph of the lack of an in situ response by the
molten metal;
[0018] FIG. 8 is a graph of the presence of an in situ response by
the molten metal;
[0019] FIG. 9 is a top view of a ladle with hydraulic lines;
[0020] FIG. 10 is a graph showing the lack of an in situ response
by the molten metal; and
[0021] FIG. 11 is a graph showing the presence of an in situ
response by the molten metal.
DETAILED DESCRIPTION OF THE INVENTION
[0022] The present invention comprises an apparatus and method for
the automated and quantitative verification of molten metal
treatment. As such, the present invention has utility for
increasing the efficiency and productivity of casting operations
such as the casting of metal parts, components, articles and the
like. The apparatus of the present invention is comprised of a
sensing device that detects and monitors an in situ response
resulting from the treatment of a molten metal. In addition, an
electronic transformation device receives the captured in situ
response from the sensing device and transforms said response into
a response data set. The response data set is transmitted to and
received by a microprocessor for the purpose of automatically and
quantitatively verifying the treatment of the molten metal.
[0023] In some instances, the in situ response resulting from the
treatment of the molten metal is in the form of heat, light
intensity, light wavelength, density of smoke particles,
composition of smoke particles, mechanical vibration and
combinations thereof. The sensing device can include a
photodetector and/or a hydraulic pressure sensor within a hydraulic
line attached to a ladle wherein molten metal is treated.
[0024] Referring now to FIG. 1, a schematic diagram with components
and steps for one embodiment of the present invention is shown. In
this figure, an iii situ response results from the mixture of a
molten iron with magnesium. Additions to the molten iron can
include but are not limited to alloying additions, impurity removal
additions and combinations thereof. The in situ response resulting
from the addition to the molten iron can include the increase, or
decrease, of heat, light intensity, light wavelength, density of
smoke particles, composition of smoke particles, mechanical
vibration and combinations thereof.
[0025] The in situ response resulting from the mixture of the
magnesium with the molten iron is detected and monitored by a
response sensing device 100. The response sensing device 100 can be
any sensing device that detects and monitors an in situ response by
a molten metal undergoing a treatment, illustratively including a
photodetector, a photoconductor, a photoresistor, a light meter, a
camera, a hydraulic pressure sensor, a thermocouple, a smoke
detector, a smoke particle density detector and combinations
thereof. The response sensing device 100 typically captures the in
situ response in the form of an analog signal. In the alternative,
the response sensing device 100 captures the in situ response in
the form of a digital signal.
[0026] If an analog signal 110 is captured by the response sensing
device 100, the analog signal 110 is transmitted to and received by
an electronic transforming device 200. The electronic transforming
device 200 preferably transforms the analog signal 110 into a
response data set 210 in digital form. For the purposes of the
present invention, the term response data set is synonymous with
the term response data and is defined as at least one piece of
datum that is related to the in situ response described above and
is transmitted, received and/or stored by an electronic device. Any
electronic transforming device 200 known to those skilled in the
art can be used to transform the analog signal 110 into data
acceptable by a microprocessor 300, illustratively including an
analog-to-digital converter. In one embodiment of the present
invention, the electronic transforming device 200 transmits the
response data set to the microprocessor 300, as shown in FIG.
1.
[0027] Turning to FIG. 2, possible steps or functions performed by
the microprocessor 300 are shown. Upon receiving the digital
response data 210, the microprocessor 300 can compare said data 210
at step 330 with a threshold data set 310 and/or a threshold
criteria 320 stored within said microprocessor 300 or any other
electronic storage device. For the purposes of the present
invention, the term threshold data set is synonymous with the term
threshold data and is defined as at least one piece of datum that
can be used as a limit(s) and/or condition(s).
[0028] After comparing the digital response data 210 with the
threshold hold data 310 and/or threshold criterion 320, the
microprocessor determines whether said data 210 meets a pre-set
limit or condition 340. In the alternative, the present invention
affords for the determination of whether or not the response data
210 meets the pre-set limit 340 before comparing said data 210 with
the threshold data 310 and/or threshold criterion 320. In fact, the
comparison of the response data 210 with the threshold data 210
and/or threshold criterion 320 is not required. Furthermore, the
pre-set limit or condition 340 may or may not be based or derived
from the threshold data 310 or threshold criterion 320. For
example, and in no way limiting the scope of the present invention,
the operator may dictate that the digital response data 210 must
exceed or be less than the threshold data 310 by a specified
amount. Exceeding or being less than the threshold data 310 by the
specific amount could be the threshold criterion 320. In the
alternative, a criterion at step 340 can be established which is
not dictated or based upon the threshold data 310 or threshold
criterion 320.
[0029] If comparison of the response data 210 does meet the pre-set
limit 340, the microprocessor 300 can afford for an alert
communication 350 to an operator that the molten metal treatment
was sufficient. In the alternative, if the comparison of response
data 210 does not meet the pre-set limit 340, the microprocessor
300 can afford an alert communication 360 to the operator that the
molten metal treatment was not sufficient. In this manner, an
apparatus and method automatically and quantitatively verifies a
molten metal treatment is provided.
[0030] In order to aid in the understanding of the present
invention and yet not limit the invention in any way, two examples
are described and provided below.
EXAMPLE 1
[0031] Turning to FIG. 3, a first ladle 10 pours molten metal 15,
for example molten iron, into a treatment ladle 20. In addition,
alloying addition 30, for example magnesium, is prepared to be
added to the ladle 20. Also shown is a response sensing device 102.
The sensing device 102 is a photodetector that detects and monitors
the intensity of light.
[0032] After the pouring iron 15 into the treatment ladle 20 has
been completed, the magnesium addition 30 is placed within the
ladle 20 as shown in FIG. 4. Upon causing the treatment ladle 20 to
incline at an angle relative to horizontal using hydraulic lifting
arm 22, as shown in FIG. 5, the magnesium addition 30 and molten
iron 15 come into contact and begin mixing. FIGS. 5 and 6
illustrate a violent or combustion chemical reaction between the
magnesium addition 30 and the molten iron 15 wherein a high density
of smoke particles 50 and light 60 result from the chemical
reaction.
[0033] When magnesium is the addition to molten iron, the reaction
of magnesium with oxygen and molten iron results in an exothermic
combustion reaction that produces light. The magnesium reacts with
oxygen to form magnesium oxide that exits the treatment ladle 20 in
the form of smoke particles 50. Some of the magnesium alloys with
the molten iron and affords for the casting of ductile cast iron.
The heat of formation for the manganese oxide is approximately -600
kilojoules per mole which produces heat. In addition, approximately
10% of the energy of combustion when manganese reacts with oxygen
occurs as light 60. The response sensing device 102 detects and
monitors the intensity of light 60 escaping from the treatment
ladle 20 as illustrated in FIG. 6. If magnesium is not added to the
molten iron and/or an insufficient reaction of the magnesium with
the iron occurs, a relatively low intensity and/or duration of
light 60 is detected and monitored.
[0034] Turning to FIG. 7, a graph is shown wherein the light
intensity as a function of time was detected and monitored for a
heat of molten iron wherein magnesium was not added thereto. This
heat of molten iron subsequently would not produce ductile cast
iron. In contrast, FIG. 8 shows a graph of the intensity of light
for light escaping the treatment ladle 20 as a function of time for
a molten iron heat wherein magnesium was added thereto and an in
situ response was detected by the sensing device 102. The sensing
device 102 was a photodetector that detected and monitored the
intensity of light 60 as a function of time. This heat of molten
iron subsequently would and did produce ductile cast iron. It is
appreciated that these graphs are comprised of the response data
sets of the respective heats.
[0035] As shown in FIGS. 7 and 8, the intensity of light as a
function of time is much greater for a heat of molten iron that
undergoes a sufficient treatment to produce ductile cast iron when
compared to a heat of molten iron without a sufficient treatment to
produce ductile cast iron. Referring back to FIGS. 1 and 2, the
response data set 210 for each heat was derived from an analog
signal 110 detected and monitored by the response sensing device
102, wherein a microprocessor 300 afforded for the graphical
display of the response data set 210. In the alternative, for
example, the microprocessor could average the values of light
intensity and compare said average value with a pre-set limit.
Also, the microprocessor could be directed to determine the area
under the intensity of light versus time plot and compare said area
value with a pre-set limit. In this manner, the detection and
monitoring of an in situ light response can be used to
automatically and quantitatively verify the treatment of molten
metal.
EXAMPLE 2
[0036] Turning to FIG. 9, a different embodiment of the present
invention is illustrated. As shown in this figure, the treatment
ladle 20 includes hydraulic lifting arms 22, hydraulic lines 24 and
load sensing pins 26. The load sensing pins 26 afford for the
monitoring of the weight of the treatment ladle 20 before, during
and after molten iron 15 is poured into said ladle 20. A hydraulic
pressure sensor 106 is in communication with the hydraulic lines
24. Any load sensing pin 26 and hydraulic pressure sensor 106 known
to those skilled in the art can be used, illustratively including a
load pin such as Part # LMP sold by Delphi Force Measurement
located at 64 Township Drive, Gold Coast, Australia and a hydraulic
pressure sensor such as Part # PN3320 sold by IFM Effector located
at 805 Springdale Drive, Exton, Pa.
[0037] As illustrated in FIGS. 5 and 6, when a magnesium addition
30 is added to molten iron 15, it is not uncommon for a violent
and/or combustion reaction to occur. The forces exerted by such a
reaction can be transmitted to the treatment ladle 20 in the form
of mechanical vibration, In an effort to maintain the stability of
the treatment ladle 20, the hydraulic pressure in the ladle
hydraulic arms 22 and hydraulic lines 24 will vary. As mechanical
vibration is experienced by the treatment ladle 20 the hydraulic
system responsible for supporting, tilting and moving the treatment
ladle 20 seeks to stabilize said ladle. In so doing, the hydraulic
pressure within the hydraulic ladle arms 22 and hydraulic lines 24
will vary and/or fluctuate. The change in the hydraulic pressure
within the hydraulic lines 24 is detected and monitored using the
hydraulic pressure sensing device 106.
[0038] Turning to FIG. 10, a graph is shown wherein the weight of
the treatment ladle 20 and the hydraulic pressure within the
hydraulic lines 24 was monitored as a function of time for a ladle
20 wherein molten iron was poured into and magnesium was not mixed
therewith. This heat of molten iron would not produce ductile cast
iron. As shown in this figure, there is a smooth monotonic increase
in the hydraulic pressure, shown as "Hydraulic Pressure Feedback"
in the graph, as the molten iron is poured into the ladle. The
hydraulic pressure within the hydraulic lines 24, and changes
therein, is detected and monitored by hydraulic pressure sensor
106. The weight of the ladle as measured by the load sensing pins
26 is also shown on the graph.
[0039] In contrast, FIG. 11 illustrates a discontinuous increase
and decrease in the hydraulic pressure detected and monitored by
the sensor 106 when magnesium was mixed with molten iron. This heat
of molten iron would and did produce ductile cast iron. The sharp
decrease in hydraulic pressure feedback shown in FIG. 10 at a scan
time value of approximately 5, represents an anomaly in the data
collection and is not used for data analysis. Thus the vertical
dashed lines in FIGS. 10 and 11 represent an area of preferred data
analysis. Also, as illustrated by the increase in weight with time
of the ladle 20, this embodiment demonstrates that the present
invention is operable when the magnesium addition 30 is added to
ladle 20 while molten iron 15 is being poured into said ladle.
[0040] Referring back to FIGS. 1, 2 and 9, it is appreciated that
the graphs shown in FIGS. 10 and 11 are comprised from the response
data sets derived from the respective molten iron treatment, said
data sets being transmitted to and received by the microprocessor
300, wherein said microprocessor 300 afforded for the graphical
display of the response data sets 210.
[0041] Comparison of FIG. 10 with FIG. 11 demonstrates a method and
apparatus that affords for me detection and monitoring of an in
situ mechanical vibration response resulting from mixing magnesium
with molten iron. In this manner, a method and apparatus for the
automated and quantitative verification of molten metal treatment
is provided.
[0042] It is understood that a sensing device 100 can be in the
form of any sensing device that will detect an in situ response
resulting from a molten metal treatment. In addition, if the
sensing device is capable of providing data to the microprocessor
300 in a form usable by said microprocessor 300, the electronic
transformation device 200 is not required. The microprocessor can
be in the form of, or within, a computer, electronic meter, sensing
device, and the like. It is also within the scope of the present
invention for the apparatus to include not only a sensing device,
an electronic transforming device, and a microprocessor, but also a
communication system wherein the results of a comparison of the
response data set to a threshold data set or a threshold criterion
are communicated to additional electronic equipment and/or
personnel.
[0043] The foregoing drawings, discussion and description are
illustrative of specific embodiments and examples of the present
invention, but they are not meant to be limitations upon the
practice thereof. Numerous modifications and variations of the
invention will be readily apparent to those of skill in the art in
view of the teaching presented herein. It is the following claims,
including all equivalents, which define the scope of the
invention.
* * * * *