U.S. patent application number 10/787535 was filed with the patent office on 2004-09-16 for method and apparatus for vibration casting of vehicle wheels.
Invention is credited to Chen, Bor-Liang, Mason, Douglas P..
Application Number | 20040177942 10/787535 |
Document ID | / |
Family ID | 32962857 |
Filed Date | 2004-09-16 |
United States Patent
Application |
20040177942 |
Kind Code |
A1 |
Mason, Douglas P. ; et
al. |
September 16, 2004 |
Method and apparatus for vibration casting of vehicle wheels
Abstract
A vehicle wheel mold is vibrated at a frequency within a range
of 0.1 to 10,000 Hz during a casting process. The vibration reduces
the solidification time needed to form a wheel casting while
improving the tensile strength of the wheel.
Inventors: |
Mason, Douglas P.; (Livonia,
MI) ; Chen, Bor-Liang; (Ann Arbor, MI) |
Correspondence
Address: |
MACMILLAN SOBANSKI & TODD, LLC
ONE MARITIME PLAZA FOURTH FLOOR
720 WATER STREET
TOLEDO
OH
43604-1619
US
|
Family ID: |
32962857 |
Appl. No.: |
10/787535 |
Filed: |
February 26, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10787535 |
Feb 26, 2004 |
|
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|
09760074 |
Jan 12, 2001 |
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Current U.S.
Class: |
164/71.1 ;
164/260; 164/340 |
Current CPC
Class: |
B22D 27/08 20130101;
B22D 15/005 20130101 |
Class at
Publication: |
164/071.1 ;
164/260; 164/340 |
International
Class: |
B22D 027/08; B22D
033/04 |
Claims
What is claimed is:
1. An apparatus for casting a one piece vehicle wheel comprising: a
mold base segment; a plurality of movable mold side segments; a
movable top core segment, said top core segment co-operating with
said base and side segments to define a gravity fed mold cavity for
gravity casting a vehicle wheel; and a vibration device mounted
upon one of said mold segments, said vibration device being
operative to selectively vibrate said mold segment at a frequency
within a range of 0.1 to 10,000 Hz whereby the cooling of molten
metal contained within said mold cavity is accelerated and the
mechanical strength the resulting cast vehicle wheel is
enhanced.
2. The apparatus according to claim 1 wherein said vibration device
is operative to selectively vibrate said mold segment at a
frequency within a range of 1 Hz to 1,000 Hz.
3. The apparatus according to claim 2 further including a timer
device connected to said vibration device, said timer device
operative for controlling the duration of the mold vibration.
4. The apparatus according to claim 3 wherein said vibration device
is pneumatically powered and adapted to be connected to a supply of
compressed air and further wherein the apparatus includes a
solenoid valve for controlling the flow of compressed air into said
vibration device and an adjustable pressure regulator for
controlling the frequency and force of said vibration device.
5. The apparatus according to claim 3 wherein said vibration device
is electrically actuated.
6. The apparatus according to claim 5 further including a frequency
controlling device connected to said vibration device, said
frequency controlling device operative to vary the frequency of
vibration as a function of time.
7. The apparatus according to claim 5 further including a manifold
mounted upon said mold and communicating with said mold cavity,
said manifold operative to inject an inert gas into said mold
cavity.
8. The apparatus according to claim 7 wherein said inert gas is
helium.
9. A method for forming a one piece vehicle wheel casting
comprising the steps of: (a) providing a multi-segment gravity fed
mold for gravity casting the vehicle wheel, the mold having a
vibration device mounted upon a segment thereof, the vibration
device being selectively operable to vibrate the mold; (b) filling
the cavity of the wheel mold by gravity with a charge of molten
metal; (c) activating the vibration device to vibrate mold at a
frequency within the range of 0.1 Hz to 10,000 Hz upon completion
of the filling of the mold cavity with molten metal; (d)
deactivating the vibration device; (e) opening the mold; and (f)
removing the wheel casting from the mold.
10. The method according to claim 9 further including, subsequent
to step (d), allowing the metal in the mold cavity to continue to
cool before the mold is opened.
11. The method according to claim 10 wherein the top core is
vibrated in step (c) after a predetermined time period has elapsed
following the filling of the mold cavity.
12. The method according to claim 10 wherein the vibration device
provided in step (a) is pneumatically powered.
13. The method according to claim 10 wherein the vibration device
provided in step (a) is electrically powered.
14. The method according to claim 10 further including a manifold
mounted upon the wheel mold, the manifold in communication with the
mold cavity, and further wherein step (d) includes using the
manifold to inject an inert gas into the mold cavity.
15. The method according to claim 14 wherein the inert gas is
helium.
16. A method for forming a one piece vehicle wheel casting
comprising the steps of: (a) providing a multi-segment gravity fed
wheel mold for gravity casting the vehicle wheel, the mold having a
vibration device mounted upon a segment thereof, the vibration
device being selectively operable to vibrate the mold; (b)
activating the vibration device to vibrate the wheel mold at a
frequency within a range of 0.1 Hz to 10,000 Hz; (c) filling the
cavity of the wheel mold by gravity with a charge of molten metal;
(d) continuing to vibrate the top core while the molten metal
cools; (d) deactivating the vibration device; (e) opening the mold;
and (f) removing the wheel casting from the mold.
17. The method according to claim 16 further including, subsequent
to step (d), allowing the metal in the mold cavity to continue to
cool before the mold is opened.
18. The method according to claim 17 wherein the vibration device
provided in step (a) is pneumatically powered.
19. The method according to claim 17 wherein the vibration device
provided in step (a) is electrically powered.
20. The method according to claim 17 further including a manifold
mounted upon the wheel component mold, the manifold in
communication with the mold cavity, and further wherein step (d)
includes using the manifold to inject an inert gas into the mold
cavity.
21. The method according to claim 20 wherein the inert gas is
helium.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a Continuation-in Part of U.S. patent
application Ser. No. 09/760,074, filed on Jan. 12, 2001, which
claims priority from International Application No. PCT/US99/15,719
filed on Jul. 12, 1999, which claims the benefit of U.S.
Provisional Application No. 60/092,684, filed on Jul. 13, 1998. The
disclosures of all three of the above applications are incorporated
herein by reference.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not Applicable
REFERENCE TO A SEQUENCE LISTING, A TABLE, OR A COMPUTER PROGRAM
LISTING COMPACT DISC APPENDIX
[0003] Not Applicable
BACKGROUND OF THE INVENTION
[0004] This invention relates in general to casting of vehicle
wheels and in particular to a method and apparatus for vibration
casting of vehicle wheels.
[0005] Vehicle wheels include a circular wheel disc attached to an
annular wheel rim. The wheel disc includes a central wheel hub
having a pilot hole and plurality of wheel mounting holes formed
therethrough. A plurality of equally circumferentially spaced
radially extending spokes support the wheel hub within the wheel
rim. The wheel rim is adapted to support a pneumatic tire.
[0006] In the past, vehicle wheels typically have been formed
entirely from steel. However, one piece wheels formed entirely from
light weight metals, such as aluminum, magnesium and titanium or
alloys thereof, are becoming increasingly popular. In addition to
weighing less than conventional all-steel wheels, such light weight
wheels can be manufactured having a pleasing esthetic shape. Weight
savings also can be achieved with two piece wheels formed by
attaching a light weight metal alloy wheel disc to a steel wheel
rim.
[0007] Light weight wheels are typically formed by forging or
casting operations. During a forging operation, a heated billet of
the light weight metal alloy is squeezed by very high pressure
between successive sets of dies until the final shape of the wheel
is formed. During a casting operation, molten metal is poured or
forced under pressure into a cavity formed in a multi-piece wheel
mold. After the metal cools sufficiently to solidify, the mold is
opened and a rough wheel casting is removed. The wheel casting is
then machined to a final shape. Machining can include turning the
outside and inside surfaces of the wheel rim, facing the inboard
and outboard wheel disc surfaces and drilling the center pilot hole
and the mounting holes through the wheel hub.
[0008] Conventional casting operations include numerous processes,
such as die casting, low pressure injection casting and gravity
casting. Conventional casting operations typically utilize a wheel
mold formed from a number of movable segments which are opened to
allow removable of the wheel casting from the mold. Referring now
to the drawings, there is illustrated in FIG. 1, generally at 10, a
typical multi-segment wheel mold used for gravity casting. The mold
10 includes a base segment 11 which supports a plurality of movable
side segments 12, two of which are shown in FIG. 1. The side
segments 12 can be retracted and extended in a horizontal direction
by a conventional mechanism 13. A movable top core 14 extends
between the side segments 12. The top core 14 can be raised and
lowered in a vertical direction by the mechanism 13. When the mold
10 is closed, the top core 14 cooperates with the side and base
segments 12 and 11 to define a wheel mold cavity 15. The outline of
a finished vehicle wheel cast in the mold 10 is illustrated in FIG.
1 by the dashed line labeled 16.
[0009] For high volume production of castings, such as vehicle
wheels, a highly automated gravity casting process is frequently
used. Such automated gravity casting processes typically use a
casting machine having a plurality of multi-segment molds mounted
upon a moving structure, such as a rotatable carousel. Each mold is
indexed past a refractory furnace containing a pool of molten
metal. A charge of molten metal is poured into a gate formed in the
mold which communicates with the mold cavity. Gravity causes the
metal to flow from the gate into the mold cavity. The mold and the
molten metal cool as the casting machine indexes the other molds to
the refractory furnace for charging with molten metal. After a
sufficient cooling time has elapsed for the molten metal to
solidify, the mold is opened and the wheel casting removed. The
mold is then closed and again indexed to the refractory furnace to
be refilled with another charge of molten metal.
BRIEF SUMMARY OF THE INVENTION
[0010] This invention relates to a method and apparatus for
vibration casting of vehicle wheels. As explained above, casting of
vehicle wheels is a highly automated process. However, the
production of a casting machine is constrained by the length of
time required for the molten metal to solidify within the
individual wheel molds. A reduction in the length of time needed
for the molten metal to solidify would allow an increase in the
speed of operation of the casting machine, thereby increasing the
number of wheels produced in a given time period. Accordingly, it
would be desirable to reduce the length of time needed for the
molten metal to solidify.
[0011] The present invention contemplates an apparatus for casting
a vehicle wheel component which includes a multi-segment mold for
the vehicle wheel component and a device for vibrating a portion of
the mold. In the preferred embodiment, the device for vibrating
includes a pneumatically powered ball vibrator. The ball vibrator
is mounted adjacent to the mold and is operable to vibrate a top
core of the mold. The wheel component can be either a one piece
vehicle wheel or a full face wheel disc.
[0012] Alternately, the device for vibrating can be a pneumatically
powered reciprocating hammer or an electrically powered device. The
invention contemplates vibrating the mold at a frequency within the
range of 0.1 Hz to 10,000 Hz. Additionally, the vibration frequency
may be varied as a function of time. The invention also
contemplates mounting an manifold upon the mold for injection of an
inert gas into the mold cavity after the cavity is charged with
molten metal. In the preferred embodiment, helium is used as the
inert gas.
[0013] The invention also contemplates a method for forming a
vehicle wheel component which includes providing a multi-segment
mold for casting the wheel component and a device for vibrating a
portion of the wheel mold. The cavity of the wheel component mold
is filled with a charge of molten metal. A portion of the wheel
component mold is vibrated at a frequency within the range of 0.1
Hz to 10,000 Hz while the molten metal solidifies. The wheel
component casting is then removed from the mold. The molten metal
can be poured into the mold cavity with gravity causing the molten
metal to flow throughout the mold cavity or forced under pressure
into the mold cavity with the pressure causing the molten metal to
flow throughout the mold cavity. The invention also contemplates
injecting an inert gas into the mold cavity as the molten metal
cools. Additionally, the vibration can be started either before or
after the mold cavity is charged with the molten metal.
[0014] Various objects and advantages of this invention will become
apparent to those skilled in the art from the following detailed
description of the preferred embodiment, when read in light of the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a sectional view of a multi-segment vehicle wheel
mold according to the prior art.
[0016] FIG. 2 is a sectional view of a multi-segment vehicle wheel
mold in accordance with the invention.
[0017] FIG. 3 is a sectional view of the multi-segment vehicle
wheel mold shown in FIG. 2 equipped with an alternate embodiment of
the invention.
[0018] FIG. 4 is a sectional view of the multi-segment vehicle
wheel mold shown in FIG. 2 equipped with another alternate
embodiment of the invention.
[0019] FIG. 5 is a flow chart for a method for casting a vehicle
wheel in accordance with the invention.
[0020] FIG. 6 is a flow chart for an alternate embodiment of the
method for casting a vehicle wheel shown in FIG. 4.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0021] The inventor has determined that vibrating a wheel mold can
significantly reduce the amount of time needed for the molten metal
contained within the mold cavity to solidify. Referring again to
the drawings, there is illustrated in FIG. 2 a multi-segment wheel
mold 20 used for gravity casting of wheels which is in accordance
with the present invention. Components of the mold 20 which are
similar to components shown in FIG. 1 have the same numerical
designators. As shown in FIG. 2, a conventional commercially
available ball vibrator 21 is mounted upon the mold top core 14.
The vibrator 21 is secured to the top core 14 by a plurality of
threaded fasteners 22. In the preferred embodiment, the vibrator 21
selected has a base which fits upon the top core 14 to minimize
installation effort and time.
[0022] In the preferred embodiment, the vibrator 21 is operated by
compressed air supplied though an air line 23; however, the
invention also can be practiced with ball vibrators operated by
other mediums, such as a hydraulically powered vibrator, or the
vibrator can be powered by an electric motor. For the vibrator 21
shown, compressed air forces a chrome steel ball around bearing
grade races to impart vibratory energy through the top core 14 to
the molten metal contained in the mold cavity 15.
[0023] The compressed air, which is not affected by the high
temperatures encountered in a foundry, can be supplied from a
readily available source, such as tapping into the foundry air
supply. The compressed air flows though a regulator (not shown) for
controlling the pressure to adjust the speed and force of the
vibrator. In the preferred embodiment, the air pressure is
adjustable over range of from 60 pounds per square inch (psi) to
100 psi.
[0024] The compressed air also flows through either a manual valve
or a solenoid valve (not shown) which is connected between the
regulator and the vibrator 21. The valve controls the operation of
the vibrator 21. In the preferred embodiment, a solenoid valve is
utilized with the valve coil connected to a microprocessor which
controls the casting machine. This assures that the vibrator 21 is
actuated during the appropriate periods in the cycle. A filter (not
shown) also is included in the air supply to remove an contaminants
from the supplied air which may damage the vibrator 21. The
compressed air is vented from the vibrator 21 through an exhaust
port 24. An optional muffler (not shown) can be attached to the
exhaust port 24 to reduce the noise generated by the discharge of
the compressed air.
[0025] The inventors have found that vibration of the mold 20 while
the molten metal contained therein solidifies has significantly
reduced the solidification time for a wheel casting. The cooling of
the molten metal is accelerated as the vibration of the mold
increases contact between the molten metal and the steel mold
segments. During tests, the solidification time has been reduced
from six minutes without vibration to 4 to 5 minutes. Thus,
vibration can reduce solidification time by 20 to 33 percent.
Additionally, the inventor has observed that, with vibration, the
microstructure grain size of a wheel casting is reduced from the
size resulting without vibration. Also, the dendrite arms within
the casting are broken off while the spacing of the dendrite arms
within the casting is reduced when the mold is vibrated while the
metal solidifies. Accordingly, the tensile and other mechanical
strength of the wheel is improved by the application of
vibration.
[0026] An alternate embodiment of the invention is illustrated by
the mold 30 shown in FIG. 3. As before, components of the mold 30
which are similar to components shown in FIG. 1 have the same
numerical designators. As shown in FIG. 3, a conventional pneumatic
knock out hammer 31 is mounted adjacent to the mold top core 14.
The hammer 31 is held in position by a mounting bracket (not shown)
which is attached to the mold support mechanism 13. The hammer is
31 actuated by compressed air supplied through an air line 32.
Similar to the ball vibrator 21 described above, the compressed air
is vented through an exhaust port (not shown). The hammer 31 has a
reciprocating head 33 which is located adjacent to a top plate 34
of the mold top core 14. When actuated, the hammer head 33 taps the
top plate 34 to impart vibrations through the top core 14 to the
molten metal contained within the mold cavity 15. Operation of the
hammer 31 produces results similar to those described above for the
ball vibrator 21.
[0027] While the preferred embodiments of the invention have been
illustrated and described above for a ball vibrator 21 and a knock
out hammer 31, it will be appreciated that the invention also can
be practiced with other conventional devices for imparting
vibrations to the wheel mold 10. For example, electrically operated
vibrator 35, as illustrated in FIG. 4, may be mounted upon the mold
top plate 34. As shown in FIG. 4, the electric vibrator 35 receives
power from an oscillator 36. The oscillator 36 is connected through
a switch 37 to a power supply 38. In the preferred embodiment, the
timer and oscillator frequency are controlled by a control unit 39,
that also receives energy from the power supply 38. In the
preferred embodiment, the control 39 activates the electric
vibrator 35 at a predetermined time in the casting operation and,
as will be described below, times a vibration cycle with the
vibrator 35 being deactivated after a predetermined time period
T.sub.1 passes. The oscillator frequency is adjusted for the
particular mold and metal being cast. While an oscillator with an
adjustable frequency is shown in FIG. 4, it will be appreciated
that the invention also may be practiced with a fixed frequency
oscillator (not shown). The invention also contemplates that
similar control equipment (not shown) is utilized with the ball
vibrator 21 and knock out hammer 31 described above.
[0028] Additionally, while gravity casting has been shown and
described above, it will be appreciated that the invention also can
be practiced with other conventional casting processes, such as,
for example, low pressure and die casting.
[0029] The invention contemplates that the mold is vibrated at a
frequency within the range of 0.1 Hz to 10,000 Hz. Preferably, the
mold is vibrated at a frequency within the range of 10 Hz to 1,000
Hz, or within the range of 10 Hz to 500 Hz. Additionally, the
invention contemplates varying the vibration frequency as a
function of time. For example, the vibration may commence at 1,000
Hz and be reduced to 10 Hz as the molten metal solidifies. The
frequency reduction may be either a linear or non-linear function
of time.
[0030] The present invention also contemplates enhancing the
casting process by injecting an inert gas into the mold cavity
after the cavity has been charged with molten metal. In the
preferred embodiment, helium is used; however, other inert gases
also may be utilized. The gas displaces any air that may remain
between the metal and the mold segments to increase conduction of
heat from the molten metal to the mold segments, thereby further
decreasing the cooling time for the casting. As the mold cavity is
charged, the molten metal displaces air contained within the cavity
through vents provided in the mold. The vents are sized
sufficiently small to prevent molten metal from entering the vents
and thereby plugging them upon solidification. Therefore, the
invention also contemplates mounting a manifold 40 upon the mold
that is in communication with the air vents, as illustrated in FIG.
4. Inert gas is supplied to the manifold 40 via external piping or
hoses 41. Once the air has vented from the mold cavity, and an
initial skin formed on the casting, the inert gas would be admitted
via the manifold and air vents into the mold cavity. The manifold
would have valves (not shown) mounted thereupon to allow the air
within the mold cavity to vent to the atmosphere as the molten
metal is added. The valves would then be switched to close the
vents to the atmosphere and to receive the pressurized inert gas.
Alternately, the manifold could be mounted to communicate with the
bores holding the ejector pins with the inert gas being injected
through the injector pin holes. Again, valves would be provided on
the vents to seal the mold from the atmosphere as the inert gas is
injected. Additionally, the manifold could cover both the vents and
injector pin bores and inject the inert gas through both types of
openings. Thus, while the manifold 40 has been shown mounted upon
the upper portion of the mold 30 in FIG. 4, it will be appreciated
that the manifold also may be mounted upon other portions of the
mold. Additionally, the invention also contemplates mounting a
similar manifold upon molds 20 and 30 shown in FIGS. 2 and 3,
respectively.
[0031] The present invention also contemplates a method for
vibratory casting of a vehicle wheel. The method is illustrated by
the flow chart shown in FIG. 4. In functional block 42, a wheel
mold, which is equipped with a vibratory device, is charged with
molten metal. The metal may be poured under gravity or injected
into the mold cavity by a low pressure. The vibratory device is
activated and the mold vibrated in functional block 43. The
vibration continues at a constant frequency for a predetermined
time period, T.sub.1, which is a function of the volume of metal
being cast. Alternately, as described above, the vibration
frequency may be varied as a function of time. In the preferred
embodiment, the vibration time is between 200 and 250 seconds;
however, it will be appreciated that the invention also can be
practiced with other vibration time periods. For example, the
vibration may continue until the casting is completely cooled and
ready to be removed from the mold (not shown). In decision block
44, it is determined whether the time T.sub.1 has passed. If, in
decision block 44, the total vibration time is less than T.sub.1,
the method returns to functional bock 43 and vibration continues.
If, in decision block 44, the total vibration time is greater than
or equal to T.sub.1, the method advances to functional bock 46 and
the vibratory device is turned off. If the total cooling time
needed for the casting has not elapsed, the mold and casting are
allowed to continue to cool for a additional time period, T.sub.2,
in functional block 48; however, as indicated, this step is
optional. In functional block 50, the mold is opened and the wheel
casting removed therefrom.
[0032] In the preferred embodiment, the method is be practiced with
vibration being applied to the mold while the mold cavity is being
charged with the molten metal. This enhances release of gases
entrapped within the molten metal. A flow chart for the preferred
method is shown in FIG. 5, where functional blocks that are similar
to those shown in FIG. 4 have the same numerical identifiers. The
method begins with activation of the vibratory device in functional
block 52. The vibration continues for a predetermined time period,
T.sub.1', which is a function of the volume of metal being cast and
includes the time needed to charge the mold. In the preferred
embodiment, the vibration time is between 200 and 250 seconds;
however, as before, it will be appreciated that the invention also
can be practiced with other vibration time periods. In functional
block 54, the wheel cavity is charged with molten metal as the mold
continues to be vibrated. The metal may be poured under gravity or
injected into the mold cavity by a low pressure. Once the mold
cavity is charged with molten metal, an inert gas, such as helium,
is injected into the mold, as shown in functional block 56. As
indicated in FIG. 5, such use of inert gas is optional and may be
omitted from the method. Once the inert gas is added, the method
advances to functional block 58 where vibration of the mold
continues for the remainder of the predetermined time period
T.sub.1'. The remainder of the method is the same as described
above. Accordingly, the method advances to decision block 44, where
it is determined whether the time T.sub.1' has passed. If, in
decision block 44, the total vibration time is less than T.sub.1',
the method returns to functional bock 58 and vibration continues.
As described above, the vibration applied to the mold may be at a
constant frequency or the vibration frequency may vary as a
function of time. For example, one frequency may be used while the
mold cavity is being charge, and another frequency may be used as
the molten metal solidifies. If, in decision block 44, the total
vibration time is greater than or equal to T.sub.1', the method
advances to functional bock 46 and the vibratory device is turned
off. If the total cooling time needed for the casting has not
elapsed, the mold and casting are allowed to continue to cool for a
additional time period, T.sub.2, in functional block 48; however,
as indicated, this step is optional. In functional block 50, the
mold is opened and the wheel casting removed therefrom.
[0033] Another alternate embodiment of the method contemplates a
delay before actuating the vibrator to allow the mold to be charged
with molten metal and for the molten metal to be begin to solidify
(not shown). In the preferred embodiment, the delay is in the range
of from zero to 30 seconds; however, it will be appreciated that
the invention also can be practiced with delays which exceed 30
seconds.
[0034] While the preferred embodiment of the invention has been
illustrated and described with vibration applied to the top core of
a wheel mold, it will be appreciated that the invention also can be
practiced with the vibration applied to other portions of the mold,
such as, for example, to a side segment (not shown) or to the base
segment (not shown). Additionally, vibration can be applied
simultaneously to a plurality of mold segments (not shown).
[0035] In accordance with the provisions of the patent statutes,
the principle and mode of operation of this invention have been
explained and illustrated in its preferred embodiment. However, it
must be understood that this invention may be practiced otherwise
than as specifically explained and illustrated without departing
from its spirit or scope. For example, while the preferred
embodiment of the invention has been illustrated and described for
casting a one piece wheel, it will be appreciated that the
invention also can be practiced for casting a component of a
vehicle wheel, such as a full face wheel disc or a wheel rim.
* * * * *