Turning – Process of turning
Reexamination Certificate
2000-03-17
2001-10-16
Briggs, William (Department: 3722)
Turning
Process of turning
C082S124000, C082S125000, C082S126000, C082S127000
Reexamination Certificate
active
06302003
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a bar stock loader for feeding shaped bar stock to an automatic spindle machine.
BACKGROUND ART
Bar stock loaders are used with automatic spindle machines having one or more spindles. Bar stock, generally from 8-12 feet in length, is fed from a magazine or hopper into a bar stock loader having bar stock retention members spaced along the length of the bar stock. In most instances, bar stock is cylindrical and requires no alignment between a bar being fed from the bar stock feeder to the automatic screw machine spindle as one segment of bar stock is depleted and a fresh length of bar stock is supplied to the spindle. The bar stock loader is typically arranged to automatically provide a new segment of cylindrical bar stock to the automatic screw machine without the need for direct operator control. Thus, when processing cylindrical bar stock, a single operator can generally supervise operation of several automatic spindle machines at the same time.
Shaped bar stock having a triangular, square, hex, or other cross-section offer important advantages over cylindrical bar stock in some applications. By using shaped bar stock, machining operations necessary to form flats, or flat surfaces, on a workpiece can be eliminated. By eliminating machining steps to form flats, labor requirements, cycle times and tooling costs can be reduced or additional processing steps may be added. However, conventional bar stock loaders required manual alignment of the flats of shaped bar stock with the flats of the bar stock in the automatic screw machine collet. Manual alignment increases labor requirements and reduces machine productivity. Other known arrangements have failed to overcome this deficiency.
For example, U.S. Pat. No. 3,664,215 discloses a machine tool having a spindle assembly operable to rotate non-circular bar stock about its longitudinal axis and a gripper assembly that engages a leading portion of the bar stock. The gripper is aligned with the chuck as the spindle is slowly rotated. This approach is slow and does not suggest synchronizing a fresh length of bar stock with a bar stock remnant at spindle operating speeds.
Similarly, U.S. Pat. No. 4,068,545 discloses an apparatus for feeding non-round cross-section bars to spindle machines. A feed apparatus detects the rotational speed of the chuck and generates a speed output when the rotational speed lies in a low speed range. When the spindle rotates within a desired range, the controller actuates an electromagnet to withdraw an abutment, thereby allowing movement of the bar stock.
U.S. Pat. No. 5,456,146 discloses a bar stock pre-alignment collar prior to chucking in a collet. A plurality of spring-loaded veliers are used to urge flats of the bar stock into a pre-alignment position.
Thus, while the above patents have addressed, in part, the problem of aligning flats on bar stock, none of the patents provides an acceptable system for automatically synchronizing the rotation of a fresh section of bar stock with a bar stock remnant in the spindle or collet of an automatic machine tool. The prior art approaches impede machine productivity and require substantial operator intervention and supervision.
The solution to the above problems and other objects and advantages achieved by the invention are summarized below.
SUMMARY OF THE INVENTION
According to the present invention, a bar stock loader for feeding shaped bar stock having one or more flats to an automatic spindle machine tool having one or more spindles includes a drive motor that is attached to a drive member which is selectively brought into engagement with a driven member. The driven member is attached to a bushing that grips a fresh section of bar stock fed by the bar stock loader. A bar stock engaging member is rotated by the spindle of the automatic screw machine. A clutch selectively connects the bar stock engaging member to the driven member. A signal generator associated with the spindle of the automatic screw machine produces a timing signal corresponding to the speed of rotation of the spindle. The drive motor is selectively driven in accordance with a timing signal to cause the drive member and driven member to rotate the bushing at a rotational speed approximating the speed of rotation of the spindle. An alignment locking mechanism is disposed between the driven member and the bar stock engaging member to align the flats of the fresh section of bar stock in the bushing with the flats of a remnant section of bar stock in the spindle. The flats of the fresh and remnant sections of bar stock are aligned prior to feeding the fresh section of bar stock through the bushing to the bar stock engaging member.
According to further features of the present invention as described above, the alignment locking element has two relatively rotatable members that have an interlock associated with both of the relatively rotatable members for locking the two members together in a radially aligned orientation. More particularly, the interlock may be at least one ball retained by one of the relatively rotatable members and a race defined by the other of the two relatively rotatable members. The race defines at least one ball seat for selectively receiving at least one ball when the flats of the fresh section of bar stock and the remnant section of bar stock are aligned.
According to another aspect of the present invention, the clutch may be a single position torque limiter having a pneumatically actuated clutch that disengages the bushing relative to the spindle when the remnant section of bar stock in the spindle is to be replaced by the fresh section of bar stock.
According to a preferred embodiment of the present invention, the bar stock feeding machine generates the timing signal with a digital tachometer indicating the speed of rotation of the machine tool spindle. The timing signal from the digital tachometer is provided to the drive motor, which is preferably a servomotor operated at a speed controlled by the digital tachometer signal.
According to another aspect of the present invention, a spindle interfacing assembly is provided between the automatic machine tool and the bar stock loader. The spindle interfacing assembly allows the bar stock loader to be retrofit to an existing automatic machine tool.
According to the method of the present invention, shaped bar stock is fed to an automatic spindle machine by first providing a length of bar stock to a bar stock loader. The bar stock in the bar stock loader is advanced to a bushing retained by a driven member. The driven member may be interlocked with a bar stock engaging member that is rotated with the spindle of the automatic screw machine. The driven member is selectively disengaged from the bar stock engaging member and rotated at a relatively slow rotational speed while the bar stock is advanced until a flat on the bar stock is matched to a flat on the bushing. This may be done while the bar stock engaging member is rotated at its machining speed. The bar stock is advanced through the bushing until a switch is actuated indicating that the bar stock is in the bushing and advanced to a predetermined preload position. The rotational speed of the driven member is then increased to rotate the bushing at a speed approximating the speed of rotation of the bar stock engaging member. The driven member and bar stock engaging member are then rotated relative to one another until a positioning element disposed between the driven member and the bar stock engaging member lock them together. When locked together, the flats on the bar stock in the bushing are aligned with the flats on a remnant section of bar stock in the bar stock engaging member. The fresh bar stock is then advanced with the bar stock remnant through the bar stock engaging member to the collet of the automatic screw machine.
According to another aspect of the method of the present invention, the step of disengaging the driven member from the bar stock engaging member further comprises supplying compressed air to a single positio
Haller Dennis A.
Saputo John J.
Winkler Mark W.
Briggs William
Brooks & Kushman P.C.
Ski Industries, Inc.
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