U.S. patent application number 09/838808 was filed with the patent office on 2001-08-23 for heat treatment of metal castings and in-furnace sand reclamation.
This patent application is currently assigned to Consolidated Engineering Company. Invention is credited to Crafton, Scott P..
Application Number | 20010015515 09/838808 |
Document ID | / |
Family ID | 27411043 |
Filed Date | 2001-08-23 |
United States Patent
Application |
20010015515 |
Kind Code |
A1 |
Crafton, Scott P. |
August 23, 2001 |
Heat treatment of metal castings and in-furnace sand
reclamation
Abstract
The method and apparatus for reclaiming substantially pure sand
from a heat treating furnace; wherein a casting with sand core
and/or sand mold, comprising sand bound by a combustible binder,
attached thereto is introduced into the heat treating furnace; or,
wherein portions of sand core and/or sand mold that are not
attached to a casting are introduced into the heat treating
furnace. Wherein, the reclaiming within the furnace is carried out,
in part, by a fluidizer that promotes binder combustion by one or
more process of agitating, heating, and oxygenating. Wherein, the
characteristics of the reclaimed sand are selectively controlled by
controlling the dwell time of the sand is within the heat treating
furnace.
Inventors: |
Crafton, Scott P.;
(Marietta, GA) |
Correspondence
Address: |
WOMBLE CARLYLE SANDRIDGE & RICE
POST OFFICE BOX 725388
ATLANTA
GA
31139-9388
US
|
Assignee: |
Consolidated Engineering
Company
|
Family ID: |
27411043 |
Appl. No.: |
09/838808 |
Filed: |
April 20, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09838808 |
Apr 20, 2001 |
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09633406 |
Aug 7, 2000 |
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09633406 |
Aug 7, 2000 |
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09440021 |
Nov 12, 1999 |
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09440021 |
Nov 12, 1999 |
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09244007 |
Feb 4, 1999 |
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09244007 |
Feb 4, 1999 |
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09103795 |
Jun 24, 1998 |
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09103795 |
Jun 24, 1998 |
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08710376 |
Sep 16, 1996 |
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5850866 |
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08710376 |
Sep 16, 1996 |
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08419372 |
Apr 10, 1995 |
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5565046 |
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08419372 |
Apr 10, 1995 |
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08283958 |
Aug 1, 1994 |
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08283958 |
Aug 1, 1994 |
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08272153 |
Jul 8, 1994 |
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08272153 |
Jul 8, 1994 |
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08198879 |
Feb 18, 1994 |
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5354038 |
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08198879 |
Feb 18, 1994 |
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07930193 |
Aug 13, 1992 |
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07930193 |
Aug 13, 1992 |
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07705626 |
May 24, 1991 |
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07705626 |
May 24, 1991 |
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07415135 |
Sep 29, 1989 |
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Current U.S.
Class: |
266/172 ;
148/538; 266/44 |
Current CPC
Class: |
B22C 5/085 20130101;
B22D 29/003 20130101; B22D 31/002 20130101; C21D 1/53 20130101 |
Class at
Publication: |
266/172 ; 266/44;
148/538 |
International
Class: |
C21B 013/00; C22F
001/00; C22B 001/10 |
Claims
We claim:
1. An apparatus for heat treating a casting with sand core,
comprising sand bound by a combustible binder, attached thereto and
for reclaiming sand from the sand core, said apparatus comprising:
a furnace for receiving a casting therewithin; furnace heating
means for heating said furnace; and means for agitating portions of
sand core within said furnace.
2. An apparatus for heat treating a casting with sand core,
comprising sand bound by a combustible binder, attached thereto and
for reclaiming sand from the sand core, said apparatus comprising:
a furnace for receiving the casting therewithin; furnace heating
means for heating said furnace; means for loosening portions of
sand core from the casting; and means for reclaiming, within said
furnace, sand of loosened portions of sand core, wherein said means
for reclaiming comprises, at least, a means for agitating loosened
portions of sand core.
3. A method for heat treating a casting with sand core, comprising
sand bound by a combustible binder, attached thereto and for
reclaiming sand from the sand core, said method comprising the
following steps: introducing the casting into a furnace; heating
the furnace; and agitating, within the furnace, the sand core.
4. A method for heat treating a casting with sand core, comprising
sand bound by a combustible binder, attached thereto and for
reclaiming sand from the sand core, said method comprising the
following steps: introducing the casting into a furnace; heating
said furnace; loosening portions of sand mold from the casting
while the casting is in said furnace; and reclaiming, within said
furnace, sand of loosened portions of sand mold, wherein the step
of reclaiming includes, at least, agitating the loosened portions
of sand mold.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] This application is a continuation of application Ser. No.
08/1419,372, filed Apr. 10, 1995, which is a continuation of
application Ser. No. 08/283,958, filed Aug. 1, 1994, which is a
continuation of application Ser. No. 08/272,153, filed Jul. 8,
1994, which is a continuation of 08/198,879, filed Feb. 18, 1994,
U.S. Pat. No. 5,354,038, which is a continuation of application
Ser. No. 07/930,193, filed Aug. 13, 1992, which is a
continuation-in-part of application Ser. No. 07/705,626, filed May
24, 1991, which is a continuation-in-part of application Ser. No.
07/415,135, filed Sep. 29, 1989.
BACKGROUND OF THE INVENTION
[0002] The present invention relates generally to the field of heat
treating metal castings and the field of reclaiming sand from sand
cores and sand molds used to make metal castings.
[0003] Generally, prior art methods and apparatus require that two
or three distinctly separate steps be taken in order to heat treat
a metal casting formed by a permanent mold or sand mold with a sand
core, and reclaim sufficiently pure sand from the sand mold or sand
core. The present invention allows for heat treating and
reclamation of sufficiently pure sand in a single step.
[0004] Methods and apparatus for manufacturing metal castings are
well known. Molds and cores are used to displace molten material so
that when the molten material is solidified, a casting is formed
that reflects the features of the mold and core. Molds have the
exterior features of the casting formed on the interior walls of
the mold and cores have the interior features of the casting formed
on the exterior surface of the core. The cores are typically made
from sand whereas the molds are sometimes made from sand. Sand
molds and cores are typically pre-molded from a mixture of sand and
a combustible binder. For simplicity, sand molds and sand cores are
referred to hereafter as simply sand cores.
[0005] In accordance with some of the prior art, once the casting
is formed, three distinctly different steps are carried out in
order to heat treat the metal casting and reclaim sufficiently pure
sand from the sand core. The first step separates portions of sand
core from the casting. The sand core is typically separated from
the casting by one or a combination of means. For example, sand may
be chiseled away from the casting or the casting may be physically
shaken to break-up the sand core and remove the sand. Once the sand
is removed from the casting, the second and third steps are carried
out. In this typical, three-step prior art, the order in which the
second and third steps are taken is not important, since the sand
has already been separated from the casting. The second step
consists of heat treating the casting. The casting is typically
heat treated if it is desirable to strengthen or harden the
casting. The third step consists of purifying the sand that was
separated from the casting. The purification processes is typically
carried out by one or a combination of means. These may include
burning the binder that coats the sand, abrading the sand, and
passing portions of the sand through screens. It is important that
the reclaimed sand be sufficiently pure in order for it to be
properly reused in the construction of new sand cores. It is also
helpful if the reclaimed sand is rounded, at least to some degree,
so as to assist in the casting of smooth surfaces and to assist in
good bonding of the sand grains which causes strong cores.
Therefore, portions of sand may be re-subjected to reclaiming
processes until sufficiently pure sand is reclaimed.
[0006] The purity of the reclaimed sand can be measured in terms of
the quantity of unburned binder. The less unburned binder, the more
pure the sand. While seeking increased purity, some sand is reduced
to "fines". Fines is the term used for sand particles smaller than
a specified size. Fines are so small that they require excessive
amounts of binder. These two measures (purity and fines) generally
oppose each other in that the higher the measure of one, the lower
the measure of the other. It is important to balance these
measures; therefore, it is important that the sand reclaiming
processes be capable of controlling these measures.
[0007] In accordance with the present inventor's previous invention
disclosure of U.S. application Ser. No. 07/705,626, only one step
need be taken in order to heat treat metal castings formed by sand
cores and reclaim sand from the sand cores. This is carried out by
introducing the castings, with the sand cores attached thereto,
into a furnace with an oxygenated atmosphere that is heated to at
least the combustion temperature of the sand core binder material.
This causes combustion of some of the binder of the sand core
which, in combination with other means, causes the sand core to
separate from the casting. The system disclosed in application Ser.
No. 07/705,626 promotes more binder combustion than is required to
separate the sand core from the casting. The system disclosed in
application Ser. No. 07/705,626 ejects sand from the furnace in a
sufficiently pure state for some applications; but, that system is
not capable of combusting a sufficient amount of binder (or
otherwise processing the sand core) so as to render sand that is
sufficiently pure for certain other applications. Also, that system
does not make provisions for varying the characteristics of the
reclaimed sand; no selective control over sand roundness, amount of
fines, or amount of unburned binder in the reclaimed sand is
possible. Therefore, the sand reclaimed using the method and
apparatus disclosed in application Ser. No. 07/705,626 may require
further processing in order to obtain sand that is sufficiently
pure for certain applications or sand that has certain
characteristics. Therefore, previous sand reclaiming systems are
inherently inefficient in that they require at least a two step
process, carried out in two separate venues by separate,
specialized equipment, in order to heat treat a metal casting
formed by a sand core and reclaim sufficiently pure sand from the
sand core.
[0008] There is a need, therefore, for a more efficient method, and
associated apparatus, that allows for more efficient heat
treatment, sand core removal, and reclamation of sufficiently pure
sand from the sand core.
SUMMARY OF THE INVENTION
[0009] Briefly described, the present invention provides an
improved method and apparatus for heat treating metal castings that
are manufactured using sand cores and for reclaiming sand from the
sand cores. More specifically, the present invention provides an
improved method and apparatus for collecting sand within a heat
treating furnace, purifying the sand, and ejecting the sand from
the furnace. The present invention can reclaim sand that is more
pure than that typically extracted from heat treating furnaces. The
method and apparatus of the present invention also allows for
selective control over the amount of binder and fines in the sand
ejected from the furnace.
[0010] The preferred embodiment of the present invention includes,
associated with a furnace, apparatus for agitating sand which has
been collected within the furnace. In the preferred embodiment,
this agitation apparatus utilizes pressurized air to accomplish the
agitating function through a process of "fluidization", and shall
be referred to herein as a fluidizer. This fluidization process
passes air, from a pressurized source, through sand collected in
the furnace causing portions of the sand to be suspended and act
like a turbulent fluid. The fluidizer, in conjunction with other
components in the furnace, causes the binder portion of sand cores
to sufficiently combust within the furnace so that sufficiently
pure sand is reclaimed. In this embodiment, the sand cores, from
which binder is combusted, are attached to the castings that are
transported into the furnace. A preferred furnace embodiment, and
some of the elements within the furnace are disclosed in
application Ser. No. 07/705,626. The fluidizer and some of the
elements associated with it are disclosed for the first time in In
this application.
[0011] The fluidizer of the preferred embodiment of the present
invention causes the fluidization of sand that has collected within
the furnace hopper. The fluidizing causes portions of sand to
abrade against one another, and in at least one embodiment, to also
abrade against a metal target, in a manner that exposes the binder.
The exposed binder then combusts. The process is repeated until a
sufficient amount of binder has been combusted to satisfy the user
as to the purity of the sand.
[0012] In the preferred embodiment of the present invention, the
fluidizer adds oxygen to the furnace hopper so as to promote binder
combustion. In one preferred embodiment of the present invention,
the fluidizer is supplied with preheated air from a secondary heat
source so as to further promote binder combustion. In an alternate,
preferred embodiment, the air of the fluidizer is not pre-heated.
In accordance with one aspect of the present invention, multiple
fluidizers are employed, and, in such embodiment, appropriate
fluidizer embodiments are chosen and selectively placed along a
multiple zoned furnace.
[0013] The present invention further includes methods and apparatus
for discharging reclaimed sand from the furnace. In the preferred
embodiment of the present invention, this discharging is controlled
so as to control the volume of sand contained in the furnace. This
affects the amount of time that sand is subjected to the
fluidizing, thus effecting a control over the characteristics of
the reclaimed sand.
[0014] An alternate embodiment of the present invention includes a
supplemental sand reclamation unit (the "SSRU"). The supplemental
sand reclamation unit, which functions in conjunction with the
furnace heat source and in conjunction with the fluidizer and other
components in the furnace, provides supplemental reclamation of
sand previously reclaimed from casting cores. For example, sand
collected from prior art shakers and sand discharged from the
troughs of the furnace of Ser. No. 07/705,626 is reprocessed by the
supplemental sand reclamation unit. The supplemental sand
reclamation unit includes a bin that is outside of the furnace. A
tube is connected to a bin outlet and passes into the furnace. The
tube passes, within the furnace, in close proximity to furnace
heaters and terminates toward the furnace hopper. Collected sand is
deposited into the bin where it is heated to above the binder
combustion temperature and exposed to an oxygen-rich atmosphere;
this causes an initial binder combustion. The sand then enters the
tube. While passing through the tube, the sand is heated by the
furnace heaters and further binder combustion occurs. When the sand
exits the tube it falls into the furnace where it is, preferably,
further purified by the in-furnace sand reclamation unit of the
present invention.
[0015] It is, therefore, an object of the present invention to
provide an improved method and apparatus for heat treating
castings, with sand core material attached thereto, and reclaiming
sand from the sand core material.
[0016] Another object of the present invention is to provide an
improved method and apparatus for removing sand core material from
a casting and reclaiming sand from the sand core material.
[0017] Another object of the present invention is to provide a
method and apparatus for reclaiming, within a furnace, sand from
portions of sand core that are separated from castings within the
furnace.
[0018] Another object of the present invention is to provide a
method and apparatus for agitating, within a furnace, sand that is
collected within the furnace.
[0019] Another object of the present invention is to provide a
method and apparatus for fluidizing, within a furnace, sand that is
collected within the furnace.
[0020] Another object of the present invention is to provide a
method and apparatus for enhancing combustion, within a heat
treating furnace, of binder that coats sand that is collected in
the furnace.
[0021] Another object of the present invention is to provide a
method and apparatus for heating, from a secondary source, sand
that is collected within a furnace.
[0022] Another object of the present invention is to provide a
method and apparatus for providing oxygen to the area in which sand
is collected within a furnace.
[0023] Another object of the present invention is to provide a
method and apparatus for reclaiming sand outside of the furnace,
and purifying the reclaimed sand within a furnace.
[0024] Yet another object of the present invention is to provide a
method and apparatus for controlling the amount of time that sand
core material is exposed to sand reclamation processing within a
furnace so that the characteristics of the reclaimed sand can be
controlled.
[0025] Other objects, features and advantages of the present
invention will become apparent upon reading and understanding this
specification, taken in conjunction with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] FIG. 1 is a cut-away view of a combination heat treating
furnace and in-furnace sand reclamation unit, in accordance with
the preferred embodiment of the present invention.
[0027] FIG. 2 is a cut-away view-of selected elements of the sand
reclamation unit of FIG. 1.
[0028] FIG. 3 is a cut-away top view of selected elements of the
sand reclamation unit of FIG. 1, showing some of the elements that
are cut-away in FIG. 1.
[0029] FIG. 4 is a cut-away top view of selected elements of the
sand reclamation unit of FIG. 1, showing some of the elements that
are cut-away in FIG. 1.
[0030] FIG. 5 is a cut-away side view of the discharge valve
assembly of FIG. 1.
[0031] FIG. 6 is a cut-away top view of a portion of an in-furnace
sand reclamation unit, in accordance with an alternate, preferred
embodiment of the present invention.
[0032] FIG. 7 is a cut-away side view of a portion of the apparatus
of FIG. 6.
[0033] FIG. 8 is a cross-sectional view of the fluidizer conduit of
FIG. 6, taken along line 8-8 of FIG. 7.
[0034] FIG. 9 is a side view of a n in-furnace sand reclamation
unit, in accordance with an alternate, preferred embodiment of the
present invention.
[0035] FIG. 10 is a detailed perspective view of the fluidizing
ring of FIG. 9.
[0036] FIG. 11 is a cross-sectional view of the fluidizing ring of
FIG. 9, taken along line 11-11 of FIG. 10.
[0037] FIG. 12 is a cross-sectional view of the fluidizing ring of
FIG. 9, taken along line 12-12 of FIG. 11.
[0038] FIG. 13 is a cut-away view of a portion of an in-furnace
sand reclamation unit, in accordance with an alternate embodiment
of the present invention.
[0039] FIG. 14 is a cut-away view of a multi-zone embodiment of the
heat treating furnace and in-furnace sand reclamation system, in
accordance with the present invention.
[0040] FIG. 15 is an isolated side view of a supplemental sand
reclamation unit which is part of an alternate embodiment of the
present invention.
[0041] FIG. 16 is a cut-away, side view of the supplemental sand
reclamation unit of FIG. 15 mounted on top of the combination heat
treating furnace and in-furnace sand reclamation unit.
[0042] FIG. 17 is a cut-away view of the reclaimer hopper of FIG.
15.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0043] This section of the specification consists of two parts. The
first part introduces components and describes their orientation
and interconnections. The second part describes the operation of
the components and provides some examples of acceptable
components.
[0044] Referring now in greater detail to the drawings, in which
like numerals represent like components throughout the several
views, FIG. 1 shows a partially cut-away view of a combination heat
treating furnace 19 and in-furnace sand reclamation unit 20, in
accordance with the preferred embodiment of the present invention.
The in-furnace sand reclamation unit 20 includes a hopper 30 which
has a hopper wall 31 and defines a hopper inlet 33 and a hopper
outlet 35. A portion of the hopper wall 31 and other elements are
cut-away in FIG. 1 so that elements shown can be clearly seen. The
in-furnace sand reclamation unit 20 further includes a fluidizer
40, guidance tube 80, abrasion disk 90 and a discharge valve
assembly 100. The fluidizer 40 is shown passing through the hopper
wall 31. The guidance tube 80 is shown oriented above the fluidizer
within the hopper 30. The abrasion disk 90 is shown oriented above
the guidance tube 80 within the hopper 30. The discharge valve
assembly 100 is shown connected to the hopper outlet 35. In the
preferred embodiment of the present invention, the hopper 30 of the
in-furnace sand reclamation unit 20 doubles as the hopper 30 of the
heat treating furnace 19. An appropriate heat treating furnace 19
is disclosed in application Ser. No. 07/705,626. The specification
of U.S. patent application Ser. No. 07/705,626 is hereby
incorporated herein by reference. The discharge valve assembly 100
provides a path to the outside of the furnace.
[0045] FIG. 2, which is a cut-away side view of selected elements
of FIG. 1, shows the fluidizer 40 of the preferred embodiment of
the present invention, in greater detail. Sand 25 is also shown, in
representative form, collected at the hopper outlet 35. The
fluidizer 40 is seen as including a fluidizer conduit 41; the
fluidizer conduit 41 has a fluidizing end 42 that is within the
hopper 30 and a source end 43 that is outside of the hopper 30. A
portion of the fluidizer conduit 41 has been cut-away to expose a
conduit interior 44 which is defined by the fluidizing conduit 41.
The source end 43 of the fluidizer conduit 41 is sealed by an end
plate 47. The end plate 47 is attached to the source end 43 in a
manner that would be understood by those reasonably skilled in the
industry; for example, by welding. A portion of the end plate 47 is
cut away in FIG. 2, to fully expose a heater 60. The heater 60 is
secured through the end plate 47 in a manner that facilitates
removal for repair or replacement with a different type of heater.
The heater 60 has an exhaust end 61 located within the conduit
interior 44 and an intake end 62 outside of the fluidizer conduit
41. Pressurized air is supplied into the intake end 62 of the
heater 60 through an air intake 65. In the preferred embodiment of
the present invention, the heater 60 is a high pressure gas burner.
In an alternate embodiment of the present invention, the heater 60
consists of an electric heating element. Other heater types are
acceptable.
[0046] A signal generating pressure gauge 70 is connected to the
fluidizer conduit 41 by a gauge conduit 71. This connection is such
that the signal generating pressure gauge 70 is in communication
with the conduit interior 44 and can sense the pressure within the
fluidizer conduit 41. A signal adjuster 74 is associated with the
signal generating pressure gauge 70. The signal generating pressure
gauge 70 is connected to an electric power supply by a gauge power
cable 72. The signal generating pressure gauge 70 is connected by a
signal cable 73 to the discharge valve assembly 100, which is not
shown in FIG. 2.
[0047] The fluidizer end 42 of the fluidizer conduit 41 is turned
upward in FIG. 2 toward a the guidance tube 80 and the abrasion
disk 90. The guidance tube 80, part of which is cut away in FIG. 2,
has a tube wall 81 and defines a tube passage 82. The abrasion disk
90, part of which is cut away in FIG. 2, has disk back 92 and a
concave disk face 91.
[0048] FIG. 3 is a top view of the apparatus of FIG. 2 in greater
detail and with the abrasion disk 90 removed. As shown in FIG. 3,
the guidance tube 80 is connected to tube support rods 85a,b which
are connected to the hopper wall 31. These connections are made in
a manner as would be understood by those reasonably skilled in the
industry; for example, by welding or bolting. The guidance tube 80
is positioned such that the guidance tube 80 is oriented above the
fluidizer end 42 of the fluidizer conduit 41 and the tube passage
82 is in-line with the conduit interior 44 at the fluidizer end
42.
[0049] FIG. 4 is a top view of the apparatus of FIG. 2 in greater
detail. In FIG. 4 the disk face 91 of the abrasion disk 90 is
oriented toward the fluidizer end 42 and is therefore not seen. As
seen in FIGS. 2 and 4, the abrasion disk 90 is connected to disk
support cables 95 which are attached to the hopper wall 31. The
cables 95 have a disk end 96, a hook end 97, and a turnbuckle 98
disposed between the disk end 96 and the hook end 97. The disk ends
96 of the cables 95 are attached to the abrasion disk 90 in
a-manner that would be understood by those reasonably skilled in
the industry; for example, by welding or bolting. The hook end 97
of each cable 95 is attached to the inner hopper wall 31 by an
eyehook 99; the hook ends 97 are hooked to eyehooks 99. The
eyehooks 99 are connected to the hopper wall 31 in a manner that
would be understood by those reasonably skilled in the industry;
for example, by welding or bolting. There are a plurality of
eyehooks 99, each of which is oriented so that the height of the
abrasion disk 90 above the fluidizer end 42 is capable of being
adjusted, as will be explained below. The fluidizer end 42, conduit
interior 44, and guidance tube 80 are not seen in FIG. 4 because
they are concealed by the abrasion disk 90.
[0050] FIG. 5 is a cut-away side view of the discharge valve
assembly shown in FIG. 1. The discharge valve assembly 100 includes
a double dump valve 110 and a pneumatic valve operator 130. The
double dump valve 110 has a valve inlet 111 and a valve outlet 112.
The valve inlet 111 is connected to the hopper outlet 35 (see FIG.
1) in a manner that would be understood by those reasonably skilled
in the industry; for example, by welding or bolting. The valve
outlet 112 is located outside of the heat treating furnace 19 such
that the double dump valve 110 provides a path from within the
hopper 30 to the outside of the furnace 19. A portion of the double
dump valve 110 is cut away in FIG. 5 to expose a first disk 116, a
second disk 117, a first seat 118, and a second seat 119. The
pneumatic valve operator 130 is connected to the double dump valve
110, in a manner that is understood by those reasonably skilled in
the art, such that the pneumatic valve operator 130 controls the
operation of the double dump valve 110. The pneumatic valve
operator 130 is connected to a pneumatic supply line 131 and the
signal cable 73. In an alternate embodiment of the present
invention, the pneumatic valve operator 130 is replaced with an
electric, motorized valve operator; hydraulic valve operator; or
some other type of valve operator.
[0051] FIG. 6 and FIG. 7 show an alternate, preferred embodiment of
the present invention. FIG. 6 is a cut-away top view of portions of
the present invention in accordance with the alternate embodiment.
This alternate embodiment does not include the guidance tube 80 or
abrasion disk 90. This alternate embodiment does include a
fluidizer 40' which is somewhat similar to the fluidizer 40 of the
preferred embodiment. However, the fluidizer 40' has a fluidizer
conduit 41' that splits into three fluidizer conduits 41'a,b,c,
each of which pass through the hopper wall 31. The fluidizer
conduits 41'a,b,c originate from a conduit header 55. The conduit
header 55 originates from the source end 43 of the fluidizer
conduit 41'. Also, the fluidizer ends 43'a,b,c are sealed in a
manner that would be understood by those reasonably skilled in the
industry; for example, with a plug 50. Also, as is indicated by
FIG. 7, which is a side view of the fluidizer 40' showing a portion
of the hopper 30, each fluidizer conduit 41'a,b,c defines a
plurality of fluidizing holes 51 that are oriented toward the
hopper outlet 35. (In FIG. 7, two of the fluidizer conduits 41'b,c
are concealed by one of the fluidizer conduits 41'a.) FIG. 8 is a
cross-sectional view taken along line 8-8 in FIG. 7; only one
fluidizer conduit 41'a is shown for simplicity; the other conduits
41'b,c being similarly constructed. As seen in FIG. 8, the
fluidizing holes are in communication with the conduit interior
44'. Also, in the embodiment shown in FIGS. 7 and 8, the fluidizing
holes 51 are spaced linearly and radially along the portion of the
fluidizer conduit 41'a that faces the hopper outlet 35. Preferably,
the angle between the center-lines 52 defined by two fluidizing
holes 51 that are radially positioned with respect to one another
is ninety degrees. In alternate embodiments of the present
invention, the fluidizing holes 51 are spaced in a different
manner.
[0052] Another alternate embodiment of the present invention, which
is not shown, is similar to the previously disclosed alternate
embodiment of FIGS. 6-8, except that the fluidizer conduit 40
splits into six fluidizer conduits. Three of the six fluidizer
conduits penetrate one furnace hopper 30 and the other three of the
six fluidizer conduits penetrate a different furnace hopper 30.
Actually, there are a variety of alternate embodiments of the
present invention that are variations upon those just disclosed.
Although not shown in FIGS. 6 and 7, the signal generating pressure
gauge 70, with all of its associated elements, is included in these
alternate embodiments of the present invention.
[0053] FIG. 9 shows an alternate, preferred embodiment of the
present invention which does not include the guidance tube 80 or
the abrasion disk 90. In this alternate embodiment, a fluidizing
ring 140 is disposed between the hopper outlet 35 and the valve
inlet 111. The fluidizing ring 140 is connected to the hopper
outlet 35 and the valve inlet 111 in a manner that would be
understood by those reasonably skilled in the industry; for
example, by welding or bolting. Also shown in FIG. 9 is a fluidizer
conduit 41". The fluidizer conduit 41" defines a conduit interior
44" (not shown). The fluidizer conduit 41" has a fluidizing end
42", which is connected to the fluidizing ring 140, and a source
end 43", into which pressurized air is supplied.
[0054] FIG. 10 is a detailed perspective view of the fluidizing
ring 140 of FIG. 9. The fluidizing ring 140 includes a hollow ring
frame 141 which defines a ring interior 142 (see FIG. 11). The
fluidizing ring 140 bounds an open area 145 that is in
communication with the ring interior 142 by way of a plurality of
fluidizing holes 146 that are defined by the ring frame 141. Only
two of the fluidizing-holes are labeled in FIG. 10 for simplicity.
The ring frame 141 further defines a conduit connection hole 147.
The ring frame 141 is connected at the conduit connector hole 147
to the fluidizing end 42" of the fluidizer conduit 41" such that
the conduit interior 44" is in communication with the ring interior
142. This connection is made in a manner that would be understood
by those reasonably skilled in the industry; for example, by
welding.
[0055] FIG. 11 is a cross-sectional view taken along line 11-11 in
FIG. 10. FIG. 11 shows the ring interior 142. FIG. 12 is a cross
sectional view taken along line 12-12 in FIG. 11. FIG. 12 shows one
of the plurality of fluidizing holes 146 defined by the ring frame
141. The fluidizing holes 146 are angled steeply enough so that
portions of sand core which pass through the open area 145 defined
by the ring frame 141 cannot easily migrate up, through the
fluidizing holes 146, into the ring interior 142.
[0056] In an alternate embodiment of the present invention, no
signal generating pressure gauge 70 is included. As shown in FIG.
13, which is a cut-away view, this alternate embodiment of the
present invention includes signal generating sensors 170a,b,c that
are mounted within the hopper 30, to the hopper wall 31. The
sensors 170a,b,c are mounted such that they detect a predetermined
level of sand core in the hopper 30. Each signal generating sensor
170a,b,c is connected by signal cable 73' to the discharge valve
assembly 100 (not shown in FIG. 13). A selector 171 is associated
with the signal generating sensors 170a,b,c. In the preferred
embodiment of this alternate embodiment, the signal generating
sensors 170a,b,c are electric probes.
[0057] FIG. 14 shows a multi-zone embodiment of the present
invention, which includes a multi-zone furnace 211 employing
several embodiments of the in-furnace sand reclamation unit 20. An
example of furnace 211 is disclosed in application Ser. No.
07/705,626. As disclosed, in FIG. 14 hereof, the furnace 211
includes: a work chamber 215; zones 216A-H; furnace heaters 218; a
pre-heat chamber 224; a furnace input door 225; a furnace upper end
226; a furnace discharge door 227; a furnace lower end 228; a
roller hearth 234; rollers 236; baskets 240, for transporting
castings; axial fans 244; a furnace top 245; screens 252; baffles
253; a sand conveyor 259; and a central collection bin 260. For a
clear understanding of the furnace 211, please refer to application
Ser. No. 07/705,626, which has been incorporated into this
specification. The furnace 211 further includes hoppers 30 and
discharge valve assemblies 100. Zones 216A,B are equipped with the
fluidizer 40 (see FIGS. 1, 2, 3, and 4) guidance tube 80, and
abrasion disk 60. The pre-heat chamber and Zone 216E are equipped
with the fluidizer 40' (see FIGS. 6, 7, and 8), and Zones 216F,G,H
are equipped with the fluidizer 40" (see FIGS. 9, 10, 11, and 12).
Sand 25 is shown, in representative form, collected at the hopper
outlet 35.
[0058] FIG. 15 shows a supplemental sand reclamation unit 180 which
is part of an alternate embodiment of the present invention. The
supplemental sand reclaiming unit 180 includes a reclaimer hopper
181 which has a reclaimer inlet 182, a reclaimer outlet 183, and a
reclaimer wall 184. The supplemental sand reclamation unit 180
further includes a discharger 190 that has a discharger inlet 191
and a discharger outlet 192. In the preferred, alternate
embodiment, the discharger 190 is a screw auger. The discharger
inlet 191 is connected to the hopper outlet 183 in a manner that
would be understood by those reasonably skilled in the industry;
for example, by welding or bolting. The supplemental sand
reclamation unit 180 further includes a delivery tube 195 that
defines a tube interior 199. The delivery tube 195 also has a tube
inlet 196, a tube outlet 197, and an oxygen supply line 198 that is
in communication with the tube interior 199. The tube inlet 196 is
connected to the discharger outlet 192 in a manner that would be
understood by those reasonably skilled in the industry; for
example, by welding or bolting.
[0059] FIG. 16 is a cut-away view of the supplemental sand
reclamation unit 180 of FIG. 15 mounted on top of the combination
heat treating furnace 19 and in-furnace sand reclamation unit 20 in
accordance with an alternate embodiment of the present invention.
The reclaimer hopper 181 and discharger 190 are located outside of
the heat treating furnace 19. The delivery tube 195 penetrates the
heat treating furnace 19 and is in close proximity to u-tube
furnace heaters 218'. The tube outlet 197 is oriented toward the
hopper inlet 33.
[0060] FIG. 17 is a cut-away view of the reclaimer hopper 181 of
FIG. 15. A portion of the reclaimer wall 184 is cut-away to show a
reclaimer interior 185 that is defined by the reclaimer wall 184.
Included within the reclaimer interior 185 are heaters 186, oxygen
suppliers 187 and a level indicator 188. The reclaimer hopper 181
also includes a recycle exhaust duct 189 that exhausts into the
heat treating furnace 19 and a baghouse exhaust duct 198.
[0061] Operation
[0062] Referring back to FIGS. 1 and 14, as the casting, with sand
core attached thereto, is acted upon in accordance with the method
and apparatus disclosed in application Ser. No. 07/705,626,
portions of sand and sand core fall through the hopper inlet 33 and
sand collects within the hopper 30 toward the hopper outlet. Before
a defined level of sand accumulates in the hopper 30, the first
disk 116 and second disk 117 within the double dump valve 110 are
maintained in contact with the first seat 118 and second seat 119,
respectively. Therefore, as portions of sand and sand core continue
to fall through the hopper inlet 33, the level of sand core within
the hopper 30 increases.
[0063] FIGS. 1, 2, 3, and 4 disclose the first, preferred
embodiment of the present invention. The equipment and process that
are at the heart of the first, preferred embodiment are referred to
as "high temperature fluidization with a target". In this
embodiment, pressurized air is supplied through the air intake 65.
Oxygenated and heated exhaust from the heater 60 discharges from
the fluidizer end 42 of the fluidizer conduit 41. As the level of
sand rises above the level of the fluidizer end 42, fluidization
begins; the oxygenated and heated exhaust fluidizes portions of
sand core that are above the fluidizer end 42. That is, the exhaust
passes up through the sand, causing the sand to be suspended and
act like a turbulent fluid. The fluidization further propels
portions of sand through the guidance tube passage 82 where the
trajectory of the entrained portions of sand is oriented toward the
disk face 91 of the abrasion disk 90. Portions of sand contact the
abrasion disk 90 and fall back toward the fluidizer end 42 where
they are further fluidized. The portions of sand that are fluidized
abrade against each other and the disk face 91. The abrasion caused
by this process knocks away ash that is adhered to the sand. This
exposes unburned binder and thus promotes binder combustion. In
addition to promoting binder combustion by exposing unburned
binder, the fluidizer 40 promotes combustion by providing a hot and
oxygenated environment. Thus, the exposed binder combusts to
promote purification of the sand reclaimed from the sand core.
Since the "high temperature fluidization with a target"
incorporates a variety of techniques to reclaim sand (which
include, at least, fluidization, fluidization in combination with
an abrasion disk, heating to promote combustion, and oxygenating to
promote combustion) it has a relatively high capacity as compared
the processes referred to below.
[0064] Some alternate embodiments of the present invention, one of
which is shown in FIGS. 6, 7, and 8, are referred to as "hot
fluidization". "Hot fluidization" does not propel portions of sand
core toward a target. However, "hot fluidization" is otherwise
similar to "hot fluidization with a target". Pressurized air is
supplied through the air intake 65. Oxygenated and heated
exhaust-from the heater 60 discharges from the fluidizer holes 51.
As the level of sand approaches the level of the fluidizing holes
51, fluidization begins. Fluidization is promoted and enhanced by
the placement and orientation of the fluidizing holes 51. The
portions of sand that are fluidized abrade against each other. The
abrasion caused by this process knocks away ash that is adhered to
the sand. This exposes unburned binder and thus promotes binder
combustion. In addition to promoting binder combustion by exposing
unburned binder, the fluidizer 40' promotes combustion by providing
a hot and oxygenated environment. Thus, the exposed binder combusts
to promote purification of the sand reclaimed from the sand core.
Since "hot fluidization" does not utilize a target, it does not
typically cause as much abrasion as "hot fluidization with a
target". Thus, "hot fluidization" typically exposes less binder
than and therefore causes less combustion than "hot fluidization
with a target". Therefore, "hot fluidization" typically has less
capacity than "hot fluidization with a target". Thus, "hot
fluidization with a target" is used where relatively large portions
of sand and sand core fall through the hopper inlet 33 and "hot
fluidization" is used where relatively moderate portions of sand
and sand core fall through the hopper inlet 33.
[0065] Other alternate embodiments of the present invention, one of
which is shown in FIGS. 9, 10, 11, and 12, are referred to as "cool
fluidization". "Cool fluidization" is somewhat similar to "hot
fluidization" except that it does not incorporate heating.
Pressurized air is supplied to the source end 43" of the fluidizer
conduit 41". The pressurized air passes into the ring interior 142
by way of the fluidizer end 42" of the fluidizer conduit 41" and
the conduit connection hole 147. The pressurized air then escapes
from the fluidizing ring 140 through the fluidizing holes 146. As
the level of sand rises above the fluidizing holes 146,
fluidization begins. The portions of sand that are fluidized abrade
against each other. The abrasion caused by this process knocks away
ash that is adhered to the sand. This exposes unburned binder and
thus promotes binder combustion. In addition to promoting binder
combustion by exposing unburned binder, the fluidizer 40" promotes
combustion by providing added oxygen to the environment (the heat
necessary for combustion is provided by the heat treating furnace
19). Thus, the exposed binder combusts to promote purification of
the sand reclaimed from the sand core. Since "cool fluidization"
does not add heat to promote combustion, it does not typically
cause as much combustion as "hot fluidization". Therefore, "cool
fluidization" typically has less capacity than "hot fluidization".
Thus, "cool fluidization" is used where relatively small portions
of relatively clean sand fall through the hopper inlet 33. "Cool
fluidization", in addition to reclaiming sand, cools portions of
sand before they pass through the double dump valve 110. This
protects the double dump valve 110 from heat related stress and
strain and allows for the use of a less expensive double dump valve
110.
[0066] As specified above, the different embodiments of the present
invention have different capacities. As specified in application
Ser. No. 07/705,626, different zones 216 (see FIG. 14) within a
continuous-process furnace 211 have different capacities for
loosening sand core from castings. Therefore, it is necessary to
reclaim more sand in some zones 216 and less from others. In
accordance with one multi-zone embodiment of the present invention,
as shown in FIG. 14, higher capacity embodiments of the in-furnace
sand reclamation unit 20 (for example FIGS. 1-4) are employed in
high capacity zones 216A,B; moderate capacity embodiments of the
in-furnace sand reclamation unit 20 (for example FIGS. 6-8) are
employed in the pre-heat chamber 224 and moderate capacity zones
216E; and lower capacity embodiments of the in-furnace sand
reclamation unit 20 (for example FIGS. 9-12) are employed in lower
capacity zones 216F,G,H of the furnace 211. Likewise, it is
preferred to employ higher capacity embodiments of the present
invention in higher capacity batch-type furnaces and lower capacity
embodiments of the present invention in lower capacity batch-type
furnaces.
[0067] In several embodiments of the present invention, the signal
generating pressure gauge 70 and the equipment associated with it,
serves to provide positive control over the level, and therefore
the volume, of sand that accumulates within the hopper 30 (refer to
FIGS. 2 and 9). As portions of sand continue to fall through the
hopper inlet 33, the level of sand within the hopper 30 increases.
As the level increases there is more resistance to the flow of air
from the fluidizer end of the conduit 42 and the back-pressure in
the fluidizer conduit 41 increases. The signal adjuster 74
associated with the signal generating pressure gauge 70 is set such
that when a certain back-pressure is detected within the conduit
interior 44 by the signal generating pressure gauge 70, a "high
level" signal is generated. The pneumatic valve operator 140
receives the "high level" signal by way of the signal cable 73.
While the pneumatic valve operator 140 receives the signal it
operates the double dump valve 120. The double dump valve 120 is
operated such that the first disk 126 and second disk 127
alternately move away from and then return to the first seat 118
and second seat 119, respectively. This operation is such that
while the first disk 116 is not in contact with the first seat 118,
the second disk 117 is in contact with the second seat 119, and
visa-versa. Thus, while the double dump valve 110 is operating and
sand is flowing from within the hopper 30 to outside of the heat
treating furnace 19 by way of the double dump valve 110,
back-pressure is maintained at the hopper outlet 35 such that
fluidization is not disrupted. It is important that back-pressure
is maintained at the hopper outlet 35 because the pressurized air
that is being supplied through the fluidizer conduit 41 will take
the path of least resistance. If both-the first disk 116 and the
second disk 117 where off of their seats, and there was a level of
sand within the hopper, the path of least resistance would be
through the doubled dump valve 110 to the atmosphere outside of the
furnace. Therefore, the pressurized air would flow through the
double dump valve 110 rather than forcing its way up through the
sand accumulated in the hopper. In an alternate embodiment of the
present invention, the double dump valve 110 is replaced with a
star valve or screw auger, or another type of device that performs
a discharging and a sealing function.
[0068] In alternate embodiments of the present invention, signal
generating sensors 170, mounted to the hopper wall 31 (see FIG.
13), serve to provide positive control over the level, and
therefore the volume, of sand that accumulates within the hopper
30. In one embodiment the signal generating sensors 170 consist of
electric capacitance probes. An electric capacitance probe is
mounted to the hopper wall at each position that corresponds to a
level at which it is desired to operate the double dump valve 110.
The particular level at which the double dump valve will operate is
established by operating the selector 171 which establishes which
electric probe is controlling. As the level of sand increases and
comes into contact with the controlling electric probe, a "high
level" signal is generated. The pneumatic valve operator 140
receives the "high level" signal by way of the signal cable 73'.
When the pneumatic valve operator 140 receives the signal it
operates the double dump valve 110 as is disclosed above.
[0069] The characteristics of reclaimed sand are controlled by
controlling the dwell time of portions of sand within the hopper
30. The longer the dwell time, the longer the amount of time that
the portions of sand are fluidized. When portions of binder coated
sand are fluidized for a relatively longer period of time, less
binder is contained in the reclaimed sand but more fines are
contained in the reclaimed sand. When portions of binder coated
sand are fluidized for a relatively shorter period of time, more
binder is contained in the reclaimed sand but less fines are
contained in the reclaimed sand. The dwell time is controlled by
controlling the volume of sand that is allowed to accumulate in the
hopper 30. The greater the volume of sand allowed to accumulate in
the hopper 30, the greater the dwell time (assuming a constant
input of sand). The volume of sand that is allowed to accumulate in
the hopper 30 is selected by adjusting the signal adjuster 74 in
the one disclosed preferred embodiment of the present invention or
by adjusting the selector 171 in the second disclosed embodiment of
the present invention. In the embodiment which includes the signal
generating pressure gauge 70, a larger volume of sand accumulates
in the hopper 30 when the signal adjuster 74 is adjusted so that
the signal generating pressure gauge 70 emits a "high level" signal
at a higher pressure. A smaller volume of sand accumulates in the
hopper 30 when the signal adjuster 74 is adjusted so that the
signal generating pressure gauge 70 emits a "high level" signal at
a lower pressure. In the embodiment which includes signal
generating sensors 170 a larger or smaller volume of sand is
allowed to accumulate in the hopper 30 by adjusting the selector
171 to select the signal generating sensor 170 that is mounted at
the level that corresponds to the desired volume.
[0070] Referring back to FIGS. 2 and 4, the characteristics of the
reclaimed sand are also controlled, in the preferred embodiment of
the present invention, by adjusting the height of the abrasion disk
90 above the fluidizer end 42 of the fluidizer conduit 41. The
height is adjusted by loosening the turnbuckles 98, unhooking the
hook ends 97 from the eyehooks 99, hooking the hook ends 97 to the
appropriate eyehooks 99, and tightening the turnbuckles 98. These
components can be accessed by entering the hopper 30 through the
furnace 19 or through trap doors in the hopper wall 31. Generally,
when the height of the abrasion disk 90 is decreased more abrasion
occurs because propelled portions of sand impact the abrasion disk
90 with more force; therefore, less binder is contained in the
reclaimed sand and more fines are contained in the reclaimed sand.
Generally, when the height is increased less abrasion occurs
because propelled portions of sand impact the abrasion disk 90 with
less force; therefore, more binder is contained in the reclaimed
sand and less fines are contained in the reclaimed sand.
[0071] Referring back to FIGS. 15-17, the supplemental sand
reclamation unit 180 is used, in conjunction with the fluidizer 40
and other components in the heat treating furnace 19, to further
purify sand that has already been reclaimed by some other process,
and to reclaim sand from portions of sand core initially reclaimed
by another process. The portions of sand core and coated sand that
are introduced into the supplemental sand reclamation unit 180 are
not adhered to castings. For example only, if a core was accidently
molded into the wrong shape such that it could not be used for
casting, it could be crushed and the portions thereof could be
introduced into the supplemental sand reclamation unit 180.
Portions of sand core and coated sand are introduced into the
supplemental sand reclamation unit 180 through the reclaimer inlet
182. The heaters 186 and oxygen suppliers 187 maintain an
atmosphere within the reclaimer interior 185 that causes some of
the binder associated with the introduced sand and portions sand
core to combust such that sand is reclaimed within the reclaimer
hopper 181. The reclaimed sand is transferred from the reclaimer
hopper 181 to the delivery tube 195 by the discharger 190, The sand
within the delivery tube 195 is drawn by gravity from the tube
inlet 196 toward the tube outlet 197. The sand in the delivery tube
195 is heated due to the fact that the delivery tube 195 is in
close proximity to u-tube furnace heaters 218'. The sand in the
delivery tube 195 is also exposed to oxygen that is supplied
through the oxygen supply line 198. Therefore, at least some
exposed binder that passes through the delivery tube 195 is
combusted. As sand passes from the tube outlet 197 it falls into
the hopper 30 where it is further purified by fluidization, as is
discussed above.
[0072] The embodiments of the present invention can be constructed
from a variety of materials and include a variety of components.
The following is offered for example only. The hopper 30, guidance
tube 80, and abrasion disk could be made out of various abrasion
resistant alloys. More specifically, the hopper 30 and guidance
tube 80 could be made out of 4130, 4140 or 1020 steel, and the
abrasion disk 90 could be made out of a cast high manganese alloy.
The fluidizing ring 140 could be constructed of A36 structural
steel square tubing. The high pressure burner, which serves as the
heater 60 in one embodiment of the present invention, could be an
Eclipse brand. The signal generating pressure gauge 70 could be a
Dwyer brand photoelectric gauge. The electric capacitance probes,
that serve as the signal generating sensors 170 in one embodiment
of the present invention, and the level indicator 188 could be an
Endress Hauser brand, LSC 1110 Series capacitance probe. A low
voltage is applied to these probes, and when the probe comes into
contact with some material (for example sand) current flows into
the material and the probe senses the current flow. The double dump
valve 110 could be a Ni-Hard and nickel chrome alloy high
temperature double dump valve made by Plattco Corporation. The
Fluidizer conduit 41 can be constructed from stainless steel. The
heater 186 could be a National brand silicon carbide heating
element.
[0073] Whereas this invention has been described in detail with
particular reference to preferred embodiments and alternate
embodiments thereof, it will be understood that variations and
modifications can be effected within the spirit and scope of the
invention, as described herein before and as defined in the
appended claims.
* * * * *