Note: Descriptions are shown in the official language in which they were submitted.
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METHOD AND APPARATUS FOR ASSISTING REMOVAL OF SAND
MOLDINGS FROM CASTINGS
FIELD OF TI-IE INVENTION
The present invention relates generally to the manufacturing of metal castings
and more particularly to manufacturing castings within sand mold packs and
enhancing
the removal of the sand mold packs and cores from the castings.
BACKGROUND
A traditional casting process for fonning metal castings generally employs a
mold or die, such as a permanent, metal die or a sand mold, having the
exterior
features of a desired casting, such as a cylinder head, formed on its interior
surfaces.
A sand core comprised of sand and a suitable binder material and defining the
interior
features of the casting is typically placed within the die to fiirther define
the features
of the casting. Sand cores generally are used to produce contours and interior
features
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within the metal castings, and the removal and reclaiming of the sand
materials of the
cores from the castings after the casting process is completed is a necessity.
Depending upon the application, the binder for the sand core and/or sand mold
may coinprise a phenolic resin binder, a phenolic uretllane "cold box" binder,
or other
suitable organic binder nlaterial. The die or mold is then filled with a
molten metallic
alloy, which is allowed to cool to a certain, desired degree to cause the
alloy to
solidify. After the alloy has solidified into a casting, the casting is then
moved to a
treatment furnace or fiirnaces for fiirther processing, including heat-
treating,
reclamation of the sand from the sand cores, and aging. Heat treating and
aging are
processes that condition metallic alloys so that they will be provided with
different
physical characteristics suited for different applications. Heat treating may
include
processing and/or thennal processing.
Sand molds and/or cores generally are removed from the casting prior to
completion of heat treathnent. The sand molds and/or cores are typically
separated
from their castings by one or a combination of means. For example, sand may be
chiseled away from the casting or the casting may be physically shaken or
vibrated to
break-up the sand molds and intenlal sand cores within the castings and remove
the
sand. In addition, as the sand moldsand castings are passed tluough a heat
treatment
and/or theimal sand removal furnace, the organic or thermally degradable
binder for the
sand molds and cores, generally is brolcen down or comUusted by exposure to
the higll
fiemperattues for heat treating the castings to a desired metal properties so
that the sand
from the molds and cores can be removed from the castings and reclaimed,
leaving the
finished, heat-treated castings. Such fi.iniace systems and methods of heat
treating
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CA 02491937 2008-10-22
castings are found in U.S. Patent Nos. 5,957,188, 5,829,509, and 5,439,045.
Once the sand is removed from the casting, heat treating and aging of the
casting generally are completed in subsequent steps.
Technology such as that disclosed in the above mentioned patents is
driven, for example, by competition, increasing costs of raw material, energy,
labor, waste disposal, and environmental regulations. These factors continue
to mandate improvements in the field of heat-treating and reclamation of sand
from such metal castings.
SUMMARY
The present invention comprises a method and system for enhancing
the removal of sand molds and cores from castings formed within sand
molds. According to one embodiment of the present invention, the sand
molds may be removed from the castings by scoring the molds at
predetermined locations or points about the molds and applying a force
sufficient to cause the mold to fracture and break into pieces. For example,
the molds may be fractured by thermal expansion of the castings being
heated therein by the application of radiant energy or inductive energy to
the molds, or by other applications of force and/or energy. Additionally,
high-pressure fluids, pulses or shockwaves also may be directed at the
exterior walls of the mold to further aid in breaking down the mold. Once
the molds are fractured and broken into various pieces they generally are
then dislodged from the casting. After the molds have been removed, the
castings may be heat treated while the pieces of the sand molds are heated
to a temperature sufficient to cause the binder materials thereof to combust
for breakdown and reclamation of sand from the molds and cores.
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The present invention generally is directed to use with precision sand molds,
green sancl molds, semi-permanent molds and the like, whieh molds generally
are
designed to be broken down and removed from their castings, such as during
heat
treatment. Other types of molds having sections that are mated together such
as along
joint lines also can be used in the present in.vention. For example, the
present
invention can be utilized with core locking type molds in which the molds are
formed
in sections that are held together by a central loclcing core piece which will
be
fractured and/or brolcen by the application of pulse waves or force thereto,
resulting in
the sections of the sand mold being released and falling away from the
casting.
In a fiirther embodiinent, the method of dislodging a mold from a casting can
include placing one or more explosive charges or organic or thermally
degradable
materials at one or niore selected locations within exterior walls of the
mold. The
explosive charges are detonated at specific times in the process so as to
cause the
mold to fracture and break into pieces. The broken pieces may then be
dislodged
from the casting.
Additionally, score lines may be added to the inold containing the explosive
charges or organic or tliemzally degradable or reactive materials. The score
lines are
operatively placed in coinUination with the explosive charge(s) and/or organic
or
thennally degradable materials in predeternnined locations to enhance the
breaking
down and dislodging of portions of the mold from the casting upon initiation
of the
explosive charge(s). After the mold has been dislodged, heat treatment of the
casting
may begin or continue.
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An additional embodiment includes a method of dislodging a mold from a
casting formed within the casting by stimulating the mold with a high energy
pulsation. The mold typically fractures after being stimulated by the high
energy
pulse and the fractured pieces may then be dislodged from the casting. The
high
energy pulsation typically includes a shockwave, pressure wave, acoustical
wave,
electroniagnetic waves or conibination thereof produced from mechanical means,
such as cannons or pressurized gas delivery systems, electromechanical means,
microwaves and/or electromagnetic or other pulse wave generators.
Additionally,
score lines may also be applied to the mold to aid in brealcing down and
dislodging
the mold from the casting.
The method and system of dislodging the molds and/or cores from castings
can be utilized as part of an overall casting process in which the castings
are poured
and, after the castings have cooled to a sufficient amount to enable
solidification of at
least a portion of the outer surfaces of the casting, the molds can be
dislodged prior to
or as an initial step of a solution heat treatiilent process for the castings,
with the
dislodged sections of the molds and cores being collected and subject to a
reclamation
process while the castings are heat treated. As a ftlrther alternative, the
molds and
cores can be broken up and dislodged from the castings after which the
castings can
be transferred to a quench tanlc in which the water soluble cores of the
castings can be
broken down and removed, and/or can then be subjected to an aging process as
needed. Typically, the pulse waves or force applied to dislodge and/or break
up the
portions of the molds and to eiAlance breakdown of the sand cores within the
castings
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will be applied in a chamber or along a transfer path from a casting station
to a heat
treatment, quenching, or aging line.
Applicator mechanisms, such as pressure nozzles, acoustical or
electromechanical shockwave generators or similar pulse generating mechanisms
are
positioned at spaced locations or stations and oriented or aligned with
desired points
about the molds, such as faeing or aligned witll score lines or joints in the
molds. The
molds generally are transported in known, indexed positions for directing
pulse
waves, such as blasts of high pressure fluids, shoclcwaves, microwaves or
other
mechanical, electromechanical or electrical applications of force at desired
points or
locations such as along score luies found in the molds or at the connecting
joints
between sections of the molds to separate and break apart the molds into
several
larger chunlcs or pieces for more efficient and rapid removal of the molds
therefrom.
As the molds are broken down by the application of the pulse waves, the
sections or
pieces of the molds are free to fall away from the castings for collection and
reclamation. Accordingly, various handling or conveying niethods or systems
can be
used with the present invention, including rotaiy conveyors such as tin-
ntables, in-line
conveyors, including both horizontal and vertically oriented conveying
systems,
flighted conveyors, indexing saddles, or similar mechanisms.
In fiirther embodiments, the castings can be moved between indexed positions
for the application of pulse waves or forces at desired locations by robot
conveying
mechanisms which can also be used to aid in the breaking apart and removal of
the
sections of the sand molds such as by physically engaging and removing
portions of
the molds. Altematively, the castings and molds can be maintained in a
sttbstantially
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fixed position and pulse wave generators or other force applicators can be
moved to
desired orientations thereaUout.
Various objects, features and advantages of the present invention will become
apparent to those skilled in the art upon reading the following specification,
when
taken in conjtunction with the accoinpanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
Figs. lA-1B are cross sectional views of a sand mold, illustrating the
formation of score lines at desired locations thereon and the resultant
fracture of the
mold along the score lines;
Figs. 2A-2B are cross sectional views of a sand mold and casting, illustrating
the use of score lines and explosive charges placed within the sand mold and
fracture
and dislodging of the mold upon initiation of the explosive charges;
Fig. 3 depicts a cross sectional view of a mold passing though an energy pulse
chamUer within or adjacent a treatment furnace, illustrating the mold pack and
casting
being treated with high energy pulses;
Figs. 4A-4B illustrate movement of the molds through an oxygen enriched
chainber for applying a flow of oxygen to promote combustion of the organic or
thennally degradable binder of the molds.
Figs. 5A-5C illustrate the application of pulse waves to a mold for breakdown
of the mold;
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Figs. 6A-6B illustrate an example embodiment of a chamber or unit for
application of pulse waves to the molds;
Fig. 7 is a schematic illustration of the application of the present invention
as
part of an overall casting process; and
DETAILED DESCRIPTION
The present invention generally coinprises a inethod for eilllancing the
breakdown and removal of a mold and sand core from a casting formed within the
mold to speed up the exposure of the casting to heat treatment temperatures
and
enhance the breakdown and reclamation of sand from the sand molds and sand
cores.
The mold may be removed from around its casting either prior to the
introduction of
the sand mold and casting into a heat treatment fiu7lace or unit, or within
the heat
treatment fiuzlace or unit itself for heat treatment and sand reclamation
within the unit.
Further, the system and method of the present invention for the enhanced
breakdown
and removal of a mold from a casting can be part of an overall or continuous
metal
casting and/or heat treatment process. The present invention also can be used
as a
separate or stand-alone process for removing the mold from "hot" (freshly
poured and
sufficiently solidified) and/or "cold" castings depending on the application.
In use,
the method of the present invention generally will be carried out when the
molten
metal of the castings has at least partially solidified along the outer
surfaces of the
castings to avoid defonnation of the castings.
An example heat treatment fiirnace system for heat treatment of castings and
at least partial breakdown and removal of sand molds and sand cores and
reclanlation
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of sand is shown in U.S. Patent Nos. 5,294,994, 5,565,046, 5,738,162, and
5,957,188, 6,217,317 and 6,672,367. By enhancing the breakdown and
removal of the molds from their castings, the castings are more rapidly
exposed to the ambient heating environment of the heat treatment furnace or
chamber. Less energy and time thus are required to increase the
temperature of the casting to achieve the desired treatment and resulting
metal properties of the casting when the mold is removed from the casting.
Metal casting processes are generally known to those skilled in the
art and a traditional casting process will be described only briefly for
reference purposes. It will also be understood by those skilled in the art
that
the present invention can be used in any type of casting process, including
metal casting processes for forming aluminum, iron, steel and/or other types
of metal and metal alloy castings. The present invention thus is not and
should not be limited solely for iuse with a particular casting process or a
particular type or types of metals or metal alloys.
As illustrated in Figs. 1A-1B, typically, a molten metal or metallic
alloy is poured into a die or mold 10 at a pouring or casting station to form
a
casting 11, such as a cylinder head or engine block or similar cast part.
Typically, casting cores 12 formed from sand and an organic binder, such as
a phenolic resin, are received or placed within the molds 10, so as to create
hollow cavities and/or casting details or core prints within the castings
being formed within each mold. The molds typically can include "precision
sand mold" type molds and/or "green sand molds," which molds generally
are formed from a sand material such as silica sand or zircon sand,
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mixed with a binder such as a phenolic resin or other binder as is known in
the art,
similar to the sand casting cores 12. The molds further can include no-bake,
cold box
and hot box type sand molds as well as semi-perinanent sand molds, which
typically
have an outer mold wall foi7ned from sand and a binder material, a metal such
as
steel, or a combination of both types of materials. Still fiirther, loclcing
core type
molds can be used, in which the molds are formed as interloclcing pieces or
sections
that are locked together by a sand core. It will be understood that the teilii
"mold"
will hereafter generally be used to refer to all types of molds as discussed
above.
The method of dislodging a mold from a casting can include "scoring" the
sand mold and thus forming fault lines, indentations or weakened areas in the
sand
molds. The mold typically fractures and breaks along the score lines set into
the mold
as the binder material combusts to facilitate the dislodging and removal of
the mod
from the casting contained therein. The score lines generally are placed at -
predetermined locations along or about the sides and/or top and bottom of each
mold,
with these locations generally selected to be optimal for brealcing down the
mold.
The placing of the score lines in such predetennined locations is dependent
upon the
shape of the mold and the casting fonned within the mold.
The term "scoring" can include any type of cut, line, scratch, indentation,
groove or other such marlcings made into the top, bottom and/or side walls of
the
mold by any mechanism including cutting blades, milling devices and other,
similar
automatically and/or manually operated cutting or grooving devices. The
scoring
generally may take place on the exterior of the mold, but is not limited only
to the
exterior surfaces of the mold, and it will be tuiderstood that the interior
surfaces of the
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mold also can be scored or grooved, in addition to or alternatively of the
scoring of
the exterior surfaces. Each mold may be scored by any conventional means such
as
by molded or scratched lines placed or fonned on the exterior and/or interior
surfaces
of the mold during forniation of the mold, or at some point thereafter, up to
the
introduction of the mold, with a casting therein, into a heat treatment
fiirnace..
A force may fiirther be applied to the mold to enhance the fracture and
breaking of the mold into various pieces, which can then be easily dislodged
or
dropped away from the casting. Such a force may be applied to the inner walls
of the
mold, to the outer walls of the mold or a coinbination of the two. The force
applied to
the inner walls of the mold typically results from the thernnal expansion of
the casting
within the mold, with the expansion of the casting fiirther beingenhanced or
accelerated by heating the casting using radiant energy, inductive energy or a
conibination thereof. The energy sources used to heat the casting may include
electromagnetic energy, lasers, radio waves, microwaves and combinations
thereof.
The energy sources used to heat the mold and/or casting may also include
lasers, radio waves, microwaves, or other forms of electromagnetic energy
andlor
combinations thereof. In general, these and other energy sources are radiated
toward
the exterior or directed to specific areas of the mold or casting for the
purpose of
heating the mold and casting to cause themial expansion leading to mold and/or
core
sand fracture or breakdown. Altemately, inductive energy generally involves
enveloping the casting and mold in a field of electromagnetic energy which
induces a
euirent within the casting leading to the heating of the metal, and to a
lesser degree,
the mold. Typically, with the molds being insulative rather than conductive,
inductive
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energy generally offers some limited heating effect directly within the mold,
but not
to the degree of the heat generated witliin the casting. Of course there may
be other
niethods of heating and expanding the casting for fractLUing the molding.
Additionally, score lines can be added to the mold or by the mold itself to
aid in the
dislodging of the mold from the casting or mold.
Pulsations of energy also may be applied within specially designed process
chambers such as for example a fiiniace. Design features may include the
capability
of withstanding pulsations and resultant effects, provide for the
transportation of
mold/casting into and out of the chamber to provide precise control of the
pulsation.
The energy pulsations generally enliance to some degree heat transfer to the
moYi
cores and castings. The pulsations also promote mass transport of deconiposed
binder
gases out of the mold and cores, oxygen bearing process gas to the mold and
cores,
and loosens sand out of the casting. The pulsations may occur at both low or
high
frequencies, where low frequency pulsations would generally be utilized to
generate a
force for frachiring the mold or cores and the higher frequencies would be
employed
to enhance the transfer, mass transport and some fracturing on a smaller
scale. Higher
frequency pulsations induce vibration effects to some degree witllin the
casting to
promote the mechanical effects of the above process.
Furtherniore, the mold and/or cores may be broken down by the application of
any or all of these energy sources to the mold and/or cores to promote the
decomposition of the organic or thermally chemical binder of the sand mold
and/or
core, whicll binder breaks down in the presence of heat thus facilitating the
degradation of the mold. Additionally, the mold may be broken downby the
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application of a high pressure fluid(s) such as air, products of coinbustion,
oxygen
enriched gases or other fluid materials to the exterior walls of the mold.
Furthermore, a direct application of force in the form of pulses or
shockwaves,
application of pressurized fluids, acoustical waves, or other mechanical,
electroinechanical or electromagnetic pulses, or a combination thereof can be
applied
to the mold, cores, or casting to aid in fracturing and brealcing the mold
into pieces.
In one embodiment, the mold and/or core is stimtilated with a high energy
pulsation
for direct application of a force, which may also penetrate the walls of the
mold and
cause heating of the mold to fiirtlier aid in the combustion of the mold
binder and the
resultant breaking down of the mold. The pulsation energy may be a constantly
recurring or intermittent force or pulses and can be in the form of
shoclcwaves,
pressure waves, icoustical waves, or any combination thereof produced by
mechanical, electromechanical, electrical and/or other lcnown means such as
compression cannons or pressurized gasses. Such energy pulsations or force
applications are collectively referred to hereinafter as "pulse waves," which
teim will
be understood to cover the above-described energy pulsations and other laiown
mechanical, electrical and electromechanical force applications.
Alternatively, low
power explosive charges or organic or tllennally degradable materials can be
placed
in the mold and set off or initiated by the heating of the mold to assist in
break up and
dislodging of the mold fronl about its casting.
In greater detail, the present invention envisions several altenlative
embodiments and/or methods for perfonning this fiulction of dislodging or
brealcing
up the sand molds prior to or during heat treatment of the castings. It will
also be
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understood that any of the described methods can be used in conjunction with
or
separately from one another. These various methods are illustrated in Figs. lA
through 6B.
In a first einbodiment of the invention illustrated in Figs. lA and 1B, a sand
mold 10 with a casting 11 therein is shown with at least one, and typically
inultiple,
score lines 13 or relief lines fonned in the exterior side walls 14A of the
mold 10.
The score/relief lines 13 typically will be cut or otherwise fonned as grooves
or
notches in the exterior side walls of the mold and act as brealc lines for the
exterior
walls of the mold pack. It is also possible to cut or form the score/relief
lines 13A in
the interior walls 14B of the mold 10 as shown in Fig. 1 A and/or in the top
and
bottom walls 16 and 17 of the mold 10.
As filrther illustrated in Fig. 1B, these score/relief lines weaken the mold
walls
so as to predetermine the locations and positions of the fracture or breaking
apart of
the mold 10, such that as a force F is applied to the walls of the mold, walls
of the
mold are caused to crack and break apart along these score/relief lines as
illustrated at
18 in Fig. 1B. Typically, this force F includes the exertion of pressure
against the
interior walls 14 of the mold 10 by the castings themselves due to the thermal
expansion of the metal of the castings as they are subjected to heating or
elevated
teinperatures for heat treating the castings. As the metal of the castings
expands in
response to heat in the heat treatment fiirnace, it presses against and urges
the walls of
the mold outwardly, causing the mold to crack and break apart at the points of
weakctiess therein created by the score/relief lines. As a result, sections or
portions of
the mold will be readily and easily dislodged from the mold and its casting
generally
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prior to or during an initial phase of the heat treatinent process for the
castings, rather
than the mold simply breaking down and slowly degrading as its binder
materialis
conlUusted over time in the heat treatinent fiinlace.
Figs. 2A-2B illustrate an alternative einbodiment of the present invention for
brealcing down and dislodging a mold 20 from a casting 21 foimed therein. In
this
alternative method, low impact explosive charges 22 are mounted at one or more
points within the side walls 23 of the mold pack 20. The explosive charges
generally
are strategically located witliin the mold pack structure, generally near
critical joints
24 within walls, such as between the side walls 23 and the top and bottom
walls 26
and 27, so as to dislodge the mold from the casting, while still retaining the
casting
intact. As additionally shown in Fig. 2B, after explosion of the low intensity
explosive charges, gaps or chaiuiels 28 are formed in the mold pack 20,
extending
deeply through the side walls and upper and lower portions of the mold. As a
result,
the mold is substantially wealcened at or along these channels or gaps such
that the
mold tends to readily break apart in sections or pieces along these channels
28 in
response to presence from the therinal expansion of the castings and/or as the
binder
materials of the mold is coinbusted for ease of removal of the mold from its
casting.
Still a fitrther embodiment of the present invention for Urealcing apart and
ei-Aiancing the removal of mold 30 and from the castings is illustrated in
Fig. 3. In this
einUodiment of the present invention, vibratory forces to promote fracture of
mold/core
sand are applied to the molds by the higlrenergy pulses or waves 32 which are
directed
at the molds 30 as they are passed through a process-chainber 33, which
typically is
positioned in fiont of or at the input end of a heat treatment fiuzlace so
that the molds and
CA 02491937 2005-01-07
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castings generally pass therethrough prior to heat treatment of the castings.
The higl}
energy pulses of variable frequency or wavelength are typically directed at
the side walls
34 and/or upper poi-tions or top walls 36 of the molds from one or more
pulsation or
wave generators 37 mounted within the chamber. Such high energy pulsations or
waves
would typically be generated in the form of shock waves, pressure waves, or
acoustical
waves propagated through the atniospliere of the process chamber.
Alternatively,
electromagnetic energy could be pulsed or radiated onto the walls of the molds
as
described to promote fracture, heat absorption, binder degradation, or other
process
effect for the purpose of dislodging mold and core sand from the casting. Such
electromagnetic radiation would be in the fonn of lasers, radio waves,
microwaves, or
other form that would result in the process effects described above.
The high energy pulses directed towards the molds stimulate the molds and
cause
them to vibrate without requiring physical contact with the mold packs. Asthe
pulsations pass through the molds, the stimulation and vibration of the molds
tends to
cause fiacturing and brealcing apart of the molds. The pulsation may be either
a
sustained pulse or directed as discrete pulses. The discrete pulses may be
adminisbred
at regular intervals. Pulsations adniinistered in sustained or discrete
fashion would be
carefiilly controlled in teinls of frequency, interval of application, and
intensity, so as to
accomplish the process effects without haniiing the casting. In addition, the
molds can
also be scored or pre-stressed/wealcened, at selected points as discussed
above and as
indicated at 38 in Fig. 3, so as to facilitate or promote the breaking apart
of the molds as
they are vibrated or otheiNvise impacted by the high energy pulses.
16
CA 02491937 2008-10-22
The molds accordingly are caused to be broken down and dislodged
from their castings as the castings are moved into a heating chamber of the
heat treatment furnace or other processing of the castings. In addition, as
discussed in U.S. Patent No. 6,672,367, the energy pulses further typically
cause the castings within the molds to be heated, which further results in
thermal expansion of the castings so as to apply a force against the interior
side walls of the molds to further facilitate and enhance the breaking apart
of the molds.
Figs. 4A-4B illustrate an alternative embodiment of the present
invention for heating and enhancing the breakdown and removal of molds
40 and potentially the sand cores 41 from castings 42 contained within the
molds. In this embodiment, prior to or as the molds 40 and their castings 42
are moved into a heat treatment furnace or chamber 43, they are passed
through a low velocity oxygen chamber 44. The oxygen chamber generally
is an elongated autoclave or similar pressurized heating chamber capable of
operating under higher than ambient pressures. The oxygen chamber 44 is
provided with an enriched oxygenated environment and includes a high
pressure upstream side 46 and a low pressure downstream side 47 that are
positioned opposite each other to assist in drawing an oxygen flow
therebetween.
As the molds are passed through the low velocity oxygen chambers
of the heating chamber 44, heated oxygen gas is directed at and is forced
through the molds, as indicated by arrows 48 (Fig. 4A) and 49 (Fig. 4B).
The oxygen gas is drawn or flows under pressure from the high atmospheric
pressure side to the low atmospheric pressure side of the oxygen chamber,
17
CA 02491937 2008-10-22
so that the oxygen gas is urged or forced into and possibly through the
molds and/or cores. As a result, a percentage of the oxygen gas is
combusted with the binder materials of the sand molds/cores/so as to
enhance the combustion of the binder material within the heating chamber.
This enhanced combustion of the binder materials of the molds and cores
are further supplied with energy from the enhanced combustion of the
binder material thereof and the oxygen, which helps enhance and/or speed
up the breakdown and removal of the molds from their castings. This
breakdown of the molds can be further assisted by scoring or forming relief
lines in the molds, as discussed in greater detail above, so as to pre-
stress/weaken the molds so that as the binder materials are combusted, the
mold walls will tend to crack or fracture so that the molds will break and
fall away from their castings in sections or pieces.
In addition, the enhanced combustion of the binder materials further
serves as an additional, generally conductive heat source to thus increase the
temperature of the castings in the molds and facilitate combustion of the
binder materials of the sand cores for ease of removal and reclamation. As
a result, the castings are raised to their heat treatment temperatures more
rapidly, which helps reduce the residence time of the castings in the heat
treatment furnace that is required to properly and completely heat treat the
castings, as discussed in copending U.S. Patent No. 6,672,367.
Still a further embodiment of the present invention for
enhancing the breakdown and removal of a sand mold 50 and potentially
for breakdown and removal of a sand core located within the
casting from a casting 51 formed or contained within the mold is
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illustrated in Figs. 5A-5B. In this einbodiment, a series of pulse wave
generators or
force applicators 52, such as air cannons, fluid nozzles, acoustic wave
generators or
other mechanical and/or electro-mechanical mechanisms generally are positioned
at
specific locations or positions along the path of travel (arrows 53 inFigs. 6A-
6B) of the
mold/core laden casting into or within a heat treatinent fiu7lace, eitlier as
a pai-t of the
heat treatinent furnace, such as in an initial, prechamber of the fiirnace, or
within a mold
breal:down or process chamber 54 generally positioned infiont of or upstream
from the
heat treatment fiirnace, to aid in the removal of the sand core fiom the
castings. Such
force or pulse wave applications will be applied at a point after the outer
surfaces of the
castings contained within the molds have had a chance to solidify to an extent
sufficient
to prevent or avoid deforination or damage to the outer surfaces of the
castings by the
applieation of such forces or pulse waves.
The number of pulse generators or force applicators 52 (hereinafter
"applicators") can vary as needed, depending upon the core print or design of
the casting
being fonned in the mold such that different types of castings having
differing core
prints can utilize an optionally different arrangement or number of
applicators within the
charnber. As indicated in Fig. 5A, each of the applicators 52 generally is
mounted
within the interior 56 (Fig. 6A) of the process chamber 54, oriented at known
or
registered positions with respect to the side walls 57 (Figs. 5A-5B), top or
upper walls 58
and/or lower or bottom walls 59 of the molds 50 corresponding to laiown,
indexed
positions of the cores and castings. For example, the applicators 52 can be
mounted at
spaced locations along the length of chamber 54 (Fig. 6A) or along path of
travel of the
molds and castings, so that the molds will be engaged at varying points along
their patli
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of travel, within different applicators directed toward the same or different
ores of the
core openings, joints or score lines fonned in the molds. As the molds are
movei along
the cliamber 54, the applicators apply force against the joints or score lines
of the molds
to physically cause fracturing and/or brealcing apart of the molds.
The applicators also may be automatically controlled through a control system
for the heat treatment station or ftu7lace that can be operated remotely to
catise the
nozzles to move to various desired positions about the side walls 56 and top
and bottom
walls 58 and 59 of the mold as indicated by arrows 61 and 61' and 62 and 62'
in Fig. 5B.
As a fi.trther alternative, as illustrated in Fig. 5C, the molds 50 can be
physically
manipulated or conveyed through the process chan7ber by a transfer mechanism
65 (Fig.
5C) such as a robotic ann 66, or an overhead hoist or conveyor or other
similar type of
transport mechanism in which the castings are physically engaged by the
transport
mechanism wliich can be used to rotate the molds witli their castings therein
as indicated
by arrows 67 and 67' and 68 and 68'. As a result, the molds can be reoriented
with
respect to one or more applicators 52, so as to be rotated or otherwise
realigned into
lazown, indexed positions such that score lines fonned in the molds or joints
formed
between sections or pieces of the molds are aligned with applicators 52 for
the directed
application of force or pulse waves thereto to facilitate breaking apart and
dislodging of
pieces of the molds from their castings. Still filrther, the robot ann or
other transfer
mechanism fiirther could be used to apply a mechanical force directly to the
molds,
including picking tip or pulling sections or portions of the molds away from
the castings.
Such mechanized application of force to the molds can also be applied in
conjunction
with other applications of force or heating of the sand molds to cause the
more rapid
fracture and dislodging of pieces of the sand molds fiom their castings.
CA 02491937 2005-01-07
WO 2004/007120 PCT/US2002/021795
Figs. 6A and 6B illustrate an example enihodiment of a mold brealcdown or
process chamber 54 of the present invention for the rapid breakdown and
dislodging of
the sand molds in significantly larger pieces or sections to facilitate the
more rapid
removal of the molds from their castings. In this embodiment, the applicators
52 are
illustrated as caiuions 70 or fluid applicators that direct flows or pulses of
a higl}pressure
fluid media through a series of directional nozzles or applicators 71. Each of
the nozzles
71 generally is supplied with a high-pressure heated fluid media such as air,
thermal oils,
water or other lcnown fluid materials from a storage such as pressurizedtanlcs
72, pumps
or compressors connected to the nozzles or applicators 71. As indicated in
Fig. 6B, the
nozzles 71 direct pressurized fluid flows, indicated by arrows 73 at the side
walls, top
wall and/or Uotl:om wall of each mold/core.
These pressurized fluid flows are converted to high fluid velocities at the
exit
openings of the nozzles which enhances the energy of the fluid flow applied to
the
mold/core so as to apply forces sufficient to at least partially fiacture
and/or otherwise
degrade the mold and/or cores. Such high fluid velocities fiirther typically
cause or
promote higher heat transfer to the casting, mold, and cores which has added
benefit in
brealcing down mold and sand core. The pressurized fluid flows, which are
administered
by the nozzles, can be applied in continuous flows or as inteimittent blasts
or pulse
waves that iinpact or contact the mold walls to cause the mold walls to
fracture or crack
and can promote more rapid decomposition and/or comhustion of the binder
materials of
the molds, and potentially the sand cores, to help at least partially degrade
or break down
the molds. These fluid flows are applied under high pressure, in the range of
about 5 psi
to about 200 psi for compressed air pulses, about .5 psi to about 5000 psi
forfiiel fired
gas and air mix pulses, and aUout.1 to about 100 psi for mechanically
generated
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gaseous pulses, although greater or lesser pressures also can be used as
required for the
particular casting application. For intermittent pulses, such pulses typcally
will be
applied at a rate of about 1-2 pulses per second up to one pulse eveiy several
minutes. In
addition, the pressurized fluid flows can be directed at score lines or joints
formed in the
molds to facilitate Urealcup of the molds.
For example, utilizing a process chamher such as depicted in Figs.6A and 6B,
a series of molds generally will be indexed through the chanlber 54 at
approximately
1 to 2 minute inteivals, through approximately 5 inline positions or stations,
with the
molds being treated at each position over approximately 1 to 2 minute
intervals,
although greater or lesser residence times also can be used. Such inline
stations or
positions generally would include loading, top removal, side removal, end
removal
(and possibly bottom removal) and an unloading station with the top side and
end
(and possibly bottom) removal stations generally being located within the
interior of
the process chainber sealed within blast doors at each end. Fewer or a greater
number
of stations or positions having varying applicators also can be provided as
desired.
As indicted in Fig. 6A, the chamber generally will include up to 6 pulse
generators, although fewer or greater numbers of pulse generators also can be
used.
The pulse generators will deliver a high piessure blast or flow or air
directed at
desired mold joints and/or, if so provided, score lines formed in the molds.
Typically,
each of the pulse generators will deliver approximately 30 to 40 cuUic feet of
air/gas
at approximately 70 to 100 psig per charge or pulse for compressed air, which
pulses
generally will be delivered at approximately 1 minute firing intervals,
although
greater or lesser firing intervals also can be used, so as to deliver
approxiniately 200
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to 250 cfin of air up to about 300 cfin or niore of a gas-air mixture to the
mold joints
and/or score lines.
Typically, a screw-type or scroll compressor can be used to supply the air
directly to the pressurized tanks of the pulse generators on a substantially
continuous
basis. For example, a 50 to 100 hp. compressor can be used to supply a
sufficient
amount of compressed air to process approximately 50-100 molds per hotlr. For
gas-
air fired pulses/fluid flows, power requirements generally range from about 2-
75 hp.
In addition, the nozzles of the pulse generators can be externally adjustable
by moving
the generator mounts in at least two dimensions, with the nozzles or
applicators of the
pulse generators generally being pre-configured to accommodate desired or
specified
mold packages. In addition, althougli the pulse generators are indicated in
Fig. 6A as
being mounted on top of the process chainber, it will be also envisioned that
there is
other types of pulse generators, other than compressed air generators or
applicators,
also can be tised and that the pulse generators can be positioned along the
sides and/or
adjacent the bottoms or ends of the process chamber.
The molds generally will be indexed tlirough the inline positions, such as at
a
nominal index speed of approximately 30 to 40 feet per minute, although
varying
indexing speeds will be envisioned depending upon the size and configuration
of the
sand molds. T'he indexing motion and pulse firing of the pulse generators
generally will
be controlled according to safety interlocks by a computer cont7al system,
such as a PLC
control or a relay logic type control system. As the molds break apart, the
fragments or
sections of the nlolds generally will fall into collection shoots located
below the
chainber, which will direct the collected fraginents toward feed conveyors for
removal of
the fragrnents. Thereafter, the recovered fragments of the molds can be
pulverized for
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reclamation or passed through magnetic separation means to first remove
chills and the like therefrom after which the sand molds would then be
passed to reclamation for later reuse. Additionally, excess gases or fumes
can be collected and exhausted from the process chamber and sand
conveyors.
As further indicated in Figs. 6A and 6B, the present invention can
utilize a variety of different types of conveying mechanisms for moving the
sand molds with their castings therein into known, indexed positions as
desired or needed for application of pulse waves or other direct force
applications thereto, such as along score lines or joint lines between the
sections of the molds. Such conveying mechanisms include indexing
conveyors or chain conveyors 80, as indicated in Fig. 6A, and which can
include locator pins or other similar devices for fixing the position of the
molds on the conveyors, indexing saddles such as disclosed in U.S. Patent
No. 6,672,367, overhead crane or boom type conveyors, robotic transfer
arms or similar mechanisms, as well as flighted conveyors 90, in which the
molds are contained within flights or sections 91 of the conveyor such as
indicated in Fig. 6B. It is also possible for the chamber to be oriented
horizontally or vertically as desired.
Still further, in all the embodiments of the present invention, the
applicators and conveying mechanisms are generally positioned or mounted
within the chamber in such a fashion so that they will not interfere with the
dislodging of the pieces of the molds from their castings so as to enable the
mold pieces to fall away under force of gravity away from their castings
without interference. Alternatively, the transport or other mechanized
systems or mechanisms, such as a robot arm, can physically remove and
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WO 2004/007120 PCT/US2002/021795
transport pieces or sections of the molds away from the castings and deposit
them at a
collection point such as a bin or transport conveyor.
The method of the present invention typically will be used to brealc down and
enhance the removal of sand molds, and possibly the sand cores, from metal
castings
as a part or step in an overall or continuous casting process in which the
metal
castings are formed from molten and metal and are heat treated, quenched
and/or aged
or otherwise treated or processed, as indicated in Fig. 7. As Fig. 7
illustrates, the
castings 100 will be foi7iied from a molten metal M poured into a mold 101 at
a
casting or pouring station 102. Typically, the mold 101 will be formed in
sections
along joint lines 103, and fiirther can include score lines or indentations
forined in
portions of the outer walls of the molds, as indicated at 104.
After pouring, the molds, with their castings contained therein, generally
will
be conveyed or transferred to a mold breal:down or process chamber, indicated
at 106.
Within the mold breakdown or process chamber 106, the molds generally are
subjected to applications of forces or pulse waves, as discussed with respect
to
Figs. 5A - 6B, high or low energy pulsations (Fig. 3), and/or application or
oxygenated air flows (Figs. 4A-4B) so as to eillzance and promote the rapid
break
down or fracturing and removal of the sand molds in fragments or sections 108
from
the castings. Typically, the fraginents 108 of the sand molds that are broken
down are
dislodged in the mold break down or process chamber 106 are allowed to fall
through
a collection chute downwardly to a transport conveyor 109 or into a collection
bin for
transferring or conveying away of the pieces for reclamation and/or chill
removal.
Thereafter, as indicated in Fig. 7, the castings, with the molds having been
substantially removed therefrom, generally are introduced directly into a heat
CA 02491937 2008-10-22
treatment unit, indicated at 110 for heat treatment, and which further can
complete any additional mold and sand core break down andlor sand
reclamation in addition to solution heat treatment such as disclosed in U.S.
Patent Nos. 5,294,994, 5,565,046, 5,738,162, 5,957,188, and 6,217,317, and
6,672,367. After heat treatment, the castings generally are passed into a
quench station 111 for quenching and can thereafter be passed or transferred
to an aging station indicated at 112 for aging or further treatment of the
castings as needed or desired.
Alternatively, as indicated by dashed lines 113 in Fig. 7, following
breakdown and removal of the molds from their castings, the castings can
be transferred directly to the quench station 111 without requiring heat
treatment. The disintegration and removal of the cores can be completed
within the quench station, i.e., the water soluble cores of the castings are
immersed in or sprayed with water or other fluids so as to cause the water
soluble cores to be further broken down and dislodged from the castings.
As still a further alternative, as indicated by dashed lines 114, if so
desired,
the castings can be taken from the mold breakdown of chamber 106 directly
to the aging station 112 for aging or other treatment of the castings if so
desired.
In addition, as further indicated in Fig. 7, following the breakdown
and removal of the molds from their castings, the castings can be
transferred, as indicated by dashed lines 116, to a chill removal/cutting
station 117 prior to heat treatment, quenching andlor aging of the castings.
At the chill removal/cutting station 117, any chills or other relief forming
materials generally will be removed from the castings for cleaning and
reuse of the chills. The castings also can be further subjected to a
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sawing or cutting operation in which risers or other unneeded pieces that are
fonned
on the castings will be cut away fionl the castings and/or the castings
subjected to a
degating operation. The removal of the risers or other unneeded metal or
pieces of the
castings helps promote quenching and reduces the aniount of metal of the
castings
that must be treated or quenched so as to reduce in furriace and/or quench
time. After
removal of chills and/or cutting away of the risers or other unneeded pieces
of the
castings, the castings generally are rettumed to the process/treatment line
such as
being introduced into the heat treatment unit 110, as indicated by dash lines
118,
although it will also be understood by the skilled in the art that the
castings can
thereafter be taken directly to the quench station 111 or to the aging station
112 as
needed for further processing.
It will also be understood by the skilled in the art that the present
invention,
while enhancing the breakdown and removal of molds from their castings,
fiirther
enables the enhanced breakdown and removal of the sand cores from castings.
For
example, as the castings are heated tluough being subjected to higli energy
pulsations,
as discussed with respect to Fig. 3, or as the coinbustion of the binder
materials for the
molds of the castings is enhanced or promoted through the application of
oxygenated
air flows thereto, the sand cores likewise will be heated and their binder
materials
caused to combust to more rapidly brealcdown the sand cores for ease of
removal as
the molds or mold pieces are dislodged fiom the castings.
Still fiirther, pulse waves or force applications can be directed at core
openings
foi7ned in the molds so as to be directed at the sand cores theniselves to
enhance the
breakdown of the sand cores for ease of removal from the castings.
Accordingly, the
present invention can be used with conventional locking core type molds in
which the
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cores fonn a key lock that locks the sections or pieces of the molds together
about the
casting. Utilizing the principles of the present invention, energy pulsations
or
applications of pulse waves or force can be directed at such loclcing cores to
facilitate
the breakdown and/or disintegration of the locking cores. As a result, with
the
desttlictioil of the loclcing cores, the mold sections can be more easily
urged or
dislodged from the castings in larger sections or pieces to facilitate the
rapid removal
of the molds from the castings.
It will be understood by those slcilled in the art that while the present
invention
has been disclosed above with reference to prefen-ed embodiments, various
modifications, changes and additions can be made to the foregoing invention,
without
departing fiom the spirit and scope tllereof.
28
