Apparatus and process for forming vehicle wheel rims

Details Apparatus and process for forming vehicle wheel rims Apparatus and process for forming vehicle wheel rims

1997-10-29

2001-02-20

Larson, Lowell A. (Department: 3725)

Metal deforming

By use of tool acting during relative rotation between tool...

With cutting of work or product

Reexamination Certificate

active

06189357

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates in general to vehicle wheels and in particular to an apparatus and a process for simultaneously spin forming a pair of partial wheel rims.
It is known in the art to fabricate a two piece vehicle wheel by attaching a wheel disc to a separately formed wheel rim. Typically, the wheel disc is cast or forged while the wheel rim is rolled or spun from strip stock. Such two piece wheels are less expensive to manufacture than a cast one piece wheel while permitting use of stylistic designs for the wheel disc. Both the wheel disc and wheel rim can be formed from alloys of the same light weight metal, such as aluminum, magnesium or titanium, or, as a further cost reduction, a wheel disc formed from an alloy of a light weight metal can be attached to a rim rolled from steel. When different metals are used to form the wheel disc and wheel rim, the assembled wheel is commonly called a bimetal wheel.
To further improve the appearance of the wheel, the wheel disc can be formed to include the outboard tire retaining bead. The resulting wheel disc, which is usually called a full face wheel disc, is attached to the outboard end of a partial wheel rim. The attachment can occur at the outboard tire bead seat, the dropwell, or another location. The assembled wheel is often referred to as a full face wheel. When a tire is mounted upon a full face wheel, the joint between the wheel disc and wheel rim is completely hidden and only the wheel disc is visible. A decorative finish is often applied to the face of the wheel disc to further enhance the appearance of the wheel. Examples of typical decorative finishes include metal plating, such as chromium plating, clear coatings and paint.
As described above, the partial wheel rims used to form full face wheels can be spun from a hoop of metal. The spinning process begins by placing the hoop upon a mandrel having the desired shape of the wheel rim. The mandrel is mounted upon a conventional spin forming machine which rotates the mandrel and hoop while rollers are pressed against and traversed axially across the outer surface of the hoop to form a wheel rim. The rollers axially stretch and radially thin the hoop while forcing the hoop to conform to the shape of the mandrel. Usually several axial passes of the roller are required to form the wheel rim. Additionally, a plurality of rollers may be sequentially applied to the hoop to form specific portions of the wheel rim.
Increasingly, vehicle manufactures are requiring wheels designed for specific vehicles. Such wheels can require different wheel rim shapes to accommodate tires designed for the vehicle. Accordingly, in order to efficiently utilize the spin forming machinery, it is often necessary to change the mandrel on a spin forming machine to spin a differently shaped wheel rim.
Referring now to the drawings, there is shown in
FIG. 1
a time line for a typical operations sequence for a spin forming machine being utilized to spin two differently shaped wheel rims which is in accordance with the prior art. For illustrative purposes, the wheel rims are designated rim “A”, which is spun upon a mandrel A, and rim “B”, which is spun upon a mandrel B. Before t
1
, mandrel A is mounted upon the spinning machine.
At t
1
, a first production run begins with wheel rim A being spun on mandrel A. The first production run continues until t
2
, at which time the spin forming machine is stopped. Mandrel A is removed from the spin forming machine and mandrel B is mounted thereon. The time period from t
2
to t
3
is referred to “changeover”, or “down”, time and, because the spin forming machine is not operating, represents a period of non-production of wheel rims. At t
3
, a second production run begins with wheel Rim B being formed upon the spin forming machine. The second production run continues until t
4
, when the spin forming machine is again stopped for another changeover period to reinstall mandrel A. The process described above is repeated, beginning at t
5
. Accordingly, one complete cycle for the spin forming machine, which extends from t
1
through t
5
, includes two production runs and two changeover periods.
SUMMARY OF THE INVENTION
This invention relates to an apparatus and a process for simultaneously spin forming a pair of partial wheel rims.
As described above, a typical process for spin forming different wheel rims on a single spin forming machine requires periodic changeover time periods during which production is halted while the mandrel is changed. These changeover time periods can represent a significant loss of production for the spin forming machine. For example, assume that the production run time periods shown in
FIG. 1
, which are from t
1
to t
2
and from t
3
to t
4
, last 20 hours each. Also, assume that each of the change over periods lasts ten hours. Accordingly, for the example, during a 60 hour period, wheel rims are being produced for only 40 hours while the spin forming machine is down for 20 hours to change mandrels. Thus, 33 percent of potential production is lost for the spin forming machine because of changeovers. Additionally, the wheel rims formed immediately following a changeover are often defective. Accordingly, additional production time can be lost, Furthermore, the physical act of changing the mandrel can result in damage to the spin forming machine and/or mandrel.
The wheel rim inventory resulting from the above described production process is illustrated in
FIG. 2
, where the shaded areas represent changeover periods. As shown in
FIG. 2
, during the first production run, from t
1
to t
2
, wheel rim A is produced at a greater rate than the rims are being attached to wheel discs to form assembled two piece wheels. Accordingly, the inventory of wheel rim A, which is shown by a solid line in
FIG. 2
, increases to a maximum at t
2
. Then during the two changeover time periods and the wheel rim B production run, the inventory of wheel rim A is reduced as completed wheels with wheel rim A continue to be produced. While
FIG. 2
shows the inventory of wheel rim A reaching zero at t
5
when production of wheel rim A resumes, it will be appreciated that some minimum inventory would be maintained. Similarly, the inventory of wheel rim B, which is shown by a dashed line in
FIG. 2
, also fluctuates. Because of the changes in wheel rim inventory, additional warehouse space is required to store the inventory for each of wheel rims during the production runs of the other wheel rim.
Accordingly, a more efficient spinning apparatus and manufacturing process which would increase spin forming machine productivity while levelizing wheel rim inventory would be desirable.
The present invention is directed toward a mandrel for a spin forming vehicle wheels. The mandrel includes a first portion having a first shape, the first portion being adapted for spin forming a first vehicle wheel rim. The mandrel also includes a second portion having a second shape, the second portion being adapted for spin forming a second vehicle wheel rim. In the preferred embodiment, the second shape is different from the first shape, whereby the second vehicle wheel rim formed on the second mandrel portion has a different shape from the first vehicle wheel rim formed on the first mandrel portion. However, the invention also contemplates that the second portion of the mandrel can be symmetrical to the first portion of the mandrel. In such a case, two identical wheel rims can be spun upon the mandrel. Additionally, the first and second portions of the mandrel can have different widths and/or different diameters such that wheel rims spun upon the mandrel are formed having different widths and/or diameters, respectively.
The present invention also is directed toward an apparatus which includes a spin forming machine having the mandrel mounted thereon. The apparatus also includes at least one forming roller adapted to spin form a hoop of metal over the mandrel to form a double wheel rim having a first portion shaped to conform to the first portion of the mandrel an

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