Metal working – Method of mechanical manufacture – Wheel making
Reexamination Certificate
1999-11-08
2001-04-24
Echols, P. W. (Department: 3726)
Metal working
Method of mechanical manufacture
Wheel making
C029S02700R, C082S122000, C409S165000, C409S166000, C409S216000, C451S061000
Reexamination Certificate
active
06219918
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the manufacture of a spoked wheel rim. More particularly this invention concerns the finish machining of such a rim.
BACKGROUND OF THE INVENTION
A standard one-piece spoked wheel rim comprises a center hub formed with lug holes for attachment to the vehicle, a plurality of spokes extending radially from the hub, and an outer ring on which the tire is mounted. Such a wheel hub is typically cast of an aluminum alloy and then machined to shine and smooth the spokes, to form accurate circular outer edges for holding the tire, and to provide accurately positioned and sized lug and valve holes.
While it has been suggested to use some automatic machining tools to do parts of the finish machining of such a workpiece, it is standard to do the final smoothing, the removal of parting lines from the mold, and all the boring in manual steps. Furthermore since the outer edges of the rim must be cut to very high tolerances, it is standard to mount the rim in a separate lathe that serves solely to perform this machining operation.
OBJECTS OF THE INVENTION
It is therefore an object of the present invention to provide an improved method of finish machining a spoked wheel rim.
Another object is the provision of such an improved method of finish machining a spoked wheel rim which overcomes the above-given disadvantages, that is which simplifies the finish machining and that largely eliminates the need for manual operations.
SUMMARY OF THE INVENTION
A spoked wheel rim having a hub defining an axis, a plurality of spokes projecting radially from the hub, and a rim ring attached to outer ends of the spokes is machined by first mounting it in a loading/unloading station into a holder rotatable about a holder axis with the rim axis generally coaxial with the holder axis. Then the holder is orbited by a turntable carrying the holder from the loading/unloading station into a working station angularly offset relative to the loading/unloading station about a turntable axis between the stations. A rotating tool is then displaced by means of a head carried on a hexapod positioner at least over surfaces of the spokes while holding the rim stationary in the working station to machine the surfaces. The rim is then continuously rotated about the holder axis in the working station while engaging a rotating tool carried on the hexapod positioner with an edge of the rim ring to machine the edge.
Thus with this system all the machining operations are carried out while the rim workpiece is held in the rotatable holder, without having to dechuck it. The spoke and other surfaces can be machined and then the rim edge all in succeeding operations, with one done before or after the other, by means of rotary tools carried on a hexapod positioner such as described in German patent document 196 36 100. Such a hexapod positioner can accurately position a machine tool and its rotary drive so as to By finish even very complex shaped surfaces.
According to the invention the tool is changed after machining the surfaces of the spokes. This can be done by using a turret-type system holding a plurality of different tools that are rotated through the drive, or by an automatic chucking/dechucking device.
In accordance with the invention a plurality of holes are drilled through the rim while it is stationary in the working station with a rotary tool. Thus the lug and valve-stem holes can also be formed or fully shaped with the system of this invention.
The turntable according to the invention has a pair of such holders. A fresh unfinished rim is loaded into the holder in the loading/unloading station while machining the rim in the other holder in the working station. Similarly a finished rim can be taken out of the holder in the loading/unloading station by means of an automatic unloading device.
Normally in accordance with the invention the surfaces of the spokes are machined in a plurality of separate operations during each of which the rim is stationary. To this end the rim is displaced angularly about the holder axis in the working station through a partial revolution between succeeding operations. If there are six spokes, the rim is indexed angularly through 60° after each surface-machining operation, so that the hexapod positioner need only be effective over a small sector of the working station.
The position of the rim on the holder is sensed automatically and the holder is then angularly displaced to place the rim in the holder into a predetermined angular position. Thus the detected position is used as an actual value that is compared to a set point to ensure that at the workpiece is angularly properly positioned.
REFERENCES:
patent: 5664308 (1997-09-01), Deitert
patent: 6155758 (2000-12-01), Wieland et al.
patent: 196 36 100 (1998-03-01), None
Dubno Herbert
Echols P. W.
Variomatic GmbH & Co. KG
Wilford Andrew
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