Turning – Lathe – Headstock
Reexamination Certificate
1999-11-19
2001-08-14
Tsai, Henry (Department: 3722)
Turning
Lathe
Headstock
C082S147000, C082S155000, C082S165000
Reexamination Certificate
active
06272956
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a device for holding a workpiece or a bar of a material to be machined on a rotating spindle of a machine tool, especially an automatic lathe or a profiling lathe provided with a spindle equipped with such a holding device.
2. Description of the Related Art
As modern high-productivity machine tools operate at high spindle speed and with tools having a large turning-removal capacity, the problem of keeping the workpiece or the bar in the spindle, or of holding the chuck mounted in the spindle, respectively, becomes most important.
The known purely mechanical holding devices, generally actuated by a bell-shaped cam, can no longer be used on machines such as mentioned above, seeing that the holding force must be transmitted by mechanical means, for example ball bearings.
The known purely pneumatic holding devices do not offer a sufficient holding capacity unless they are very voluminous. On the other hand, disappearance of the pressure generally causes a loosening of the chuck, which may be dangerous, as much for the machine as for the user.
To avoid the loosening of the chuck in case of disappearance of the pressure, it is known to effect the holding by means of the force of the spring means and, for the loosening, to use pneumatic means. In order to attain a sufficient holding capacity, it is necessary to use very strong spring means, which necessitates corresponding pneumatic means for the loosening.
Patent EP 0 213 075 describes such a holding device with a spring for attaining the holding force and pneumatic means for attaining the loosening force. For attaining a sufficient loosening force, the device is equipped with a hydraulic force amplifier. Seeing that the diameter of the primary pneumatic piston is relatively wide, the moment of inertia of the device is rather great, which is undesirable in a machine where the spindle is often stopped and accelerated. Moreover, one of the drawbacks of this device is that bubbles of air in the hydraulic liquid may make it impossible to remove the workpiece or the bar to be machined.
SUMMARY OF THE INVENTION
A first object of the invention is to provide a holding device which overcomes the drawbacks of the known devices of the prior art, i.e., offering a great holding force, not comprising any hydraulic circuit, and being capable of keeping the workpiece to be machined held in the chuck in case of disappearance of the pressure.
A second object of the invention is to provide a holding device of minimum bulk having low inertia and permitting large-diameter bars to be accepted for machining.
A third object of the invention is to provide a holding device of which the holding force is adjustable, for example in order to be able to adapt it to the material of the workpiece or the bar to be machined.
A fourth object of the invention is to provide a holding device of which the force necessary for the loosening is less than in the devices according to the state of the art, where the whole holding force is effected only by a spring.
These different are details of execution, modifications, or other embodiments the characteristics mentioned according to the invention.
One object of an embodiment of the device according to the invention is to provide a holding device, the construction of which can be adapted to the desired holding force, as well as to the air pressure available for the machine.
Another object of the invention is to provide a machine-tool spindle equipped with a holding device as above.
Still another object is to propose a machine tool, especially an automatic lathe or a profiling lathe, equipped with at least one spindle provided with a device as above.
REFERENCES:
patent: 2782044 (1957-02-01), Gabriel et al.
patent: 2886007 (1959-05-01), Manchester
patent: 3361433 (1968-01-01), Holdridge
patent: 3385607 (1968-05-01), Hughes
patent: 3678790 (1972-07-01), Riley
patent: 4791841 (1988-12-01), Pruvot et al.
patent: 44 42 395 A1 (1996-06-01), None
patent: 0 213 075 A1 (1987-03-01), None
patent: 2 236 590 (1975-02-01), None
patent: 1401275 A1 (1975-07-01), None
Oliff & Berridg,e PLC
Tornos-Bechler SA
Tsai Henry
LandOfFree
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