U.S. patent application number 09/760074 was filed with the patent office on 2001-08-23 for method and apparatus for vibration casting of vehicle wheels.
Invention is credited to Chen, Bor-Liang, Mason, Douglas P., Rao, Srinivas S..
Application Number | 20010015270 09/760074 |
Document ID | / |
Family ID | 22234546 |
Filed Date | 2001-08-23 |
United States Patent
Application |
20010015270 |
Kind Code |
A1 |
Rao, Srinivas S. ; et
al. |
August 23, 2001 |
Method and apparatus for vibration casting of vehicle wheels
Abstract
A vehicle wheel mold is vibrated during a casting process. The
vibration reduces the solidification time needed to form a wheel
casting while improving tensile strength of the wheel.
Inventors: |
Rao, Srinivas S.; (Novi,
MI) ; Chen, Bor-Liang; (Ann Arbor, MI) ;
Mason, Douglas P.; (Livonia, MI) |
Correspondence
Address: |
MACMILLAN SOBANSKI & TODD, LLC
ONE MARITIME PLAZA FOURTH FLOOR
720 WATER STREET
TOLEDO
OH
43604-1619
US
|
Family ID: |
22234546 |
Appl. No.: |
09/760074 |
Filed: |
January 12, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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09760074 |
Jan 12, 2001 |
|
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PCT/US99/15719 |
Jul 13, 1998 |
|
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60092684 |
Jul 13, 1998 |
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Current U.S.
Class: |
164/98 |
Current CPC
Class: |
B22D 15/005 20130101;
B22D 27/08 20130101 |
Class at
Publication: |
164/98 |
International
Class: |
B22D 019/00 |
Claims
What is claimed is:
1. An apparatus for casting a vehicle wheel component comprising: a
multi-segment mold for the vehicle wheel component; and a device
for vibrating a portion of said mold while said mold contains a
charge of molten metal and continuing to vibrate said portion of
said mold while said charge of molten metal solidifies.
2. An apparatus according to claim 1 wherein said device for
vibrating includes a ball vibrator.
3. An apparatus according to claim 2 wherein said mold includes a
top core and further wherein said ball vibrator is mounted adjacent
to said mold and is operable to vibrate said top core.
4. An apparatus according to claim 3 wherein said ball vibrator is
pneumatically powered.
5. An apparatus according to claim 4 wherein said mold forms a one
piece vehicle wheel.
6. An apparatus according to claim 4 wherein said mold forms a full
face wheel disc.
7. An apparatus according to claim 1 wherein said device for
vibrating includes a reciprocating hammer.
8. An apparatus according to claim 7 wherein said mold includes a
top core and further wherein said reciprocating hammer is mounted
adjacent to said mold and is operable to vibrate said top core.
9. An apparatus according to claim 8 wherein said reciprocating
hammer is pneumatically powered.
10. A method for forming a vehicle wheel component comprising the
steps of: (a) providing a multi-segment mold for casting the wheel
component and a device for vibrating a portion of the wheel mold;
(b) filling the cavity of the wheel component mold with a charge of
molten metal; (c) vibrating a portion of the wheel component mold
while the molten metal solidifies; and (d) removing the wheel
component from the mold.
11. The method according to claim 10 wherein during step (c) the
portion of the mold is vibrated while the mold cavity is filled
with the molten metal.
12. The method according to claim 10 wherein the portion of the
mold is vibrated in step (c) after the mold cavity is completely
filled.
13. The method according to claim 10 wherein the portion of the
mold is vibrated in step (c) after a predetermined time period has
elapsed following the filling of the mold cavity.
14. The method according to claim 10 wherein during step (b) the
molten metal is poured into the mold cavity with gravity causing
the molten metal to flow throughout the mold cavity.
15. The method according to claim 10 wherein during step (b) the
molten metal is forced under pressure into the mold cavity with the
pressure causing the molten metal to flow throughout the mold
cavity.
16. The method according to claim 14 wherein the mold forms a one
piece vehicle wheel.
17. The method according to claim 14 wherein the mold forms a full
face wheel disc.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 60/092,684, filed on Jul. 13, 1998 and
International Patent Application No. PCT/US99/15719, filed on Jul.
12, 1999.
BACKGROUND OF THE INVENTION
[0002] This invention relates in general to casting of vehicle
wheels and in particular to a method and apparatus for vibration
casting of vehicle wheels.
[0003] 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.
[0004] 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.
[0005] 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.
[0006] 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.
[0007] 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.
SUMMARY OF THE INVENTION
[0008] 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.
[0009] 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.
[0010] Alternately, the device for vibrating can be a pneumatically
powered reciprocating hammer.
[0011] 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 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.
[0012] 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
[0013] FIG. 1 is a sectional view of a multi-segment vehicle wheel
mold according to the prior art.
[0014] FIG. 2 is a sectional view of a multi-segment vehicle wheel
mold in accordance with the invention.
[0015] FIG. 3 is a sectional view of a multi-segment vehicle wheel
mold equipped with an alternate embodiment of the invention.
[0016] FIG. 4 is a flow chart for a method for casting a vehicle
wheel in accordance with the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0017] 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.
[0018] 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.
[0019] 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.
[0020] 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.
[0021] The inventor has found that vibration of the mold 20 while
the molten metal contained therein solidifies has significantly
reduced the solidification time for a wheel casting. 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 spacing of the dendrite arms within the
casting is reduced when the mold is vibrated while the metal
solidifies. Accordingly, the tensile strength of the wheel is
improved by the application of vibration.
[0022] 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.
[0023] 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. Furthermore, 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.
[0024] 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 40, 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 in functional block 41. The mold is then vibrated in
functional block 42 for a predetermined time period, T.sub.1, which
is a function of the volume of metal being cast. 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. At the end of T.sub.1,
the vibratory device is turned off, as shown in block 43. The mold
and casting are allowed to continue to cool for a additional time
period, T.sub.2, in functional block 44; however, this step is
optional. In functional block 45, the mold is opened and the wheel
casting removed therefrom.
[0025] Additionally, the method can be practiced with vibration
being applied to the mold while the mold cavity is being charged
with the molten metal (not shown). Similarly, the method can
include 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. 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.
[0026] 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). Additionally,
vibration can be applied simultaneously to a plurality of mold
segments (not shown).
[0027] 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.
* * * * *