Electric heating – Metal heating – Cutting or disintegrating
Reexamination Certificate
2003-08-14
2004-08-24
Evans, Geoffrey S. (Department: 1725)
Electric heating
Metal heating
Cutting or disintegrating
C219S069170
Reexamination Certificate
active
06781082
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates in general to machine tools and finishing operations for vehicle wheels and in particular to machine tools and finishing operations for vehicle wheels that reduce radial runout.
One conventional process for manufacturing vehicle wheels involves pouring molten metal into a wheel mold to form a one piece wheel casting. Typically, one piece wheels are cast with an alloy of a light metal, such as aluminum. After the molten metal solidifies, the wheel casting is removed from the mold. The wheel casting is oversized and is machined to final shape.
Another process involves, a full face wheel disc, which includes the outboard tire bead retaining flange, that is cast or forged from a lightweight alloy and-machined to final shape. A partial wheel rim, which can be rolled from a strip of metal, for example steel, is then welded to an inboard surface of the wheel disc to form a two piece wheel. Such a wheel can combine the low cost and strength of a steel rim with a pleasing aesthetic appearance of a wheel disc cast from a lightweight metal and is usually referred to as a bimetal wheel.
A third process utilizes a wheel disc stamped from steel that is welded to a rolled full wheel rim to form a wheel.
Machining a wheel or wheel disc, regardless of how formed, typically includes multiple operations. First, sawing machines cut casting gates and risers from wheel castings. Then, a drilling machine is used to drill wheel mounting holes through the wheel hub. Next, the wheel is mounted upon a wheel lathe for machining to its final shape. During the lathe operations, the wheel is rotated and a cutting tool is applied against the wheel surfaces. The inside surface of the wheel hub is usually faced to provide a flat mounting surface. Similarly, the outboard wheel disc surface is finished to its final contour. Then, the outside of the wheel rim is turned to its final shape. Optionally, the inside surface of the wheel rim may also be turned to a final shape. The inboard and outboard tire beadseats are turned. The central pilot hole is usually drilled while the casting is clamped in the lathe for turning the inboard tire beadseat.
Referring to the drawings,
FIG. 1
illustrates a typical one piece vehicle wheel
10
. The vehicle wheel
10
can be cast or forged from an aluminum alloy to produce a wheel casting or forging having physical dimensions that are close to the desired final wheel dimensions. The casting is then machined to the desired final dimensions. Vehicle wheels also may be formed from any other suitable material, such as steel, and may be formed by any other suitable process, such as welding a partial wheel rim rolled from a strip of steel to a cast full face wheel disc.
The vehicle wheel
10
includes an annular wheel rim
20
, which carries a tire. The annular wheel rim
20
of the vehicle wheel
10
has an inner annular surface
22
and an outer annular surface
24
. An inboard tire beadseat
26
and an outboard tire beadseat
28
, which support the tire beads formed upon the ends of the walls of a pneumatic tire (not shown), are formed on the outer annular surface
24
at the inboard and outboard ends
27
and
29
of the wheel rim
20
. The inboard and outboard tire beadseats
27
and
29
cooperate with the tire beads of the pneumatic tire (not shown) to form a seal. In addition, wheel flanges
30
and
31
and safety humps
32
and
33
are formed at the inboard and outboard ends
27
and
29
of the rim
20
for retaining the pneumatic tire (not shown) on the vehicle wheel
10
.
The vehicle wheel
10
also includes a circular inner wheel disc
12
formed across the outboard end
29
of the annular wheel rim
20
. The inner wheel disc
12
has a central hub portion
14
supported within the annular wheel rim
20
by a plurality of wheel spokes
19
. The inner wheel disc
12
mounts the vehicle wheel
10
on an associated drive member (not shown), such as a vehicle axle. The central hub portion
14
has a central pilot hole
16
cast and machined therein, in which the associated drive member end is closely received. A plurality of wheel bolt holes
18
are cast into the central hub portion
14
for receiving wheel studs, which cooperate with wheel nuts, to secure the vehicle wheel to the associated drive member. Alternatively, the central pilot hole
16
and the plurality of wheel bolt holes
18
may be machined into the central hub portion
14
using conventional machining techniques.
When the vehicle wheel
10
is machined, the inboard and outboard tire beadseats
26
and
28
are turned. To minimize vibration, it is desirable that the inboard and outboard tire beadseats
26
and
28
have uniform radii, meaning that every point on the beadseats
26
and
28
be equidistant from a central axis Z of the vehicle wheel
10
. Ideally, the beadseats
26
and
28
are perfect circles with centers that are coincident with the central axis Z of the vehicle wheel
10
. A measure of the tire beadseat radial uniformity is radial runout. Radial runout is the radial distance between the “highest point” and the “lowest point” on the annular wheel rim
20
as measured from the axis Z of the vehicle wheel
10
. As shown in
FIG. 1
, the radial runout of the outboard tire bead seat
28
can be described as the difference between two radii X and Y, where X is the shortest radial distance from the axis Z to the outboard tire beadseat
28
and Y is the longest radial distance from the axis Z to the outboard tire beadseat
28
.
SUMMARY OF THE INVENTION
This invention relates in general to machine tools and finishing operations for vehicle wheels and in particular to machine tools and finishing operations for vehicle wheels that reduce radial runout.
When the outside surface of the wheel rim is machined, the tire beadseats are turned. Even when machined under optimal conditions a vehicle wheel rim will have some radial runout. Machining upon a conventional wheel lathe, the current processes for finishing the beadseats, is, at best, typically capable of producing a radial runout within a range of 0.005 inches (0.127 Millimeters) to 0.010 inches (0.258 Millimeters). Radial runout will tend to increase when machining conditions are less than optimal, for example, when the wheel is not mounted upon the lathe with the wheel axis coincident with the lathe axis. Excessive radial runout in the tire beadseats may cause undesirable vibrations in a vehicle even when the tires and wheels have been balanced. Accordingly, it would be desirable to reduce radial runout.
The present invention contemplates using an Electric Discharge Machining (EDM) apparatus for machining tire beadseats to reduce radial runout. EDM is a thermal erosion process in which material is removed by a series of recurring electrical discharges between an electrode and a workpiece, in the presence of a dielectric fluid. The EDM apparatus includes a support structure that is adapted to support a vehicle wheel. The apparatus further includes an electrode for machining at least one beadseat of the vehicle wheel.
The invention also contemplates a method for using the apparatus that includes the step of providing an EDM apparatus having at least one electrode. A vehicle wheel is mounted upon the EDM apparatus. The vehicle wheel is immersed in a dielectric fluidic bath and then rotated. The vehicle wheel is then moved toward the electrode and voltage is applied to the electrode. As the vehicle wheel continues to move toward the electrode, at least one spark is generated between the electrode and the vehicle wheel. The resulting spark removes material from the tire beadseats of the vehicle wheel to reduce radial runout.
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.
REFERENCES:
patent: 2938104 (1960-05-01), Paillarse
patent: 3878353 (1975-04-01), Anderson
patent: 4134807 (1979-01-01), Briffod
patent: 4471200 (1984-09-01), Takahash
Evans Geoffrey S.
Hayes Lemmerz International Inc.
MacMillan, Sobanski & Todd, LLCC
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