Electric heating – Metal heating – Cutting or disintegrating
Patent
1997-07-28
1999-01-19
Evans, Geoffrey S.
Electric heating
Metal heating
Cutting or disintegrating
B23H 710
Patent
active
058615989
DESCRIPTION:
BRIEF SUMMARY
The instant invention relates to a wire supply device on a machine for spark erosion of workpieces, comprising an electrode wire which is withdrawn from a pay-off spool and passed around guide rolls to a machining span, the pay-off spool being rotatably supported on a pivot pin, the pivot pin being fastened to a carrier member which is displaceable in axial direction of the pay-off spool, a measuring means being provided between the pay-off spool and the first guide roll to detect deviations of the position of the electrode wire from a predetermined position, and the carrier member being connected to a slide drive means which corrects any deviation detected of the position of the electrode wire being unwound from the pay-off spool by axially shifting the carrier member.
BACKGROUND OF THE INVENTION
In the case of a known wire supply device of this kind (DE 89 12 810 U1) the axial slidability of the pay-off spool containing a wire supply is based on the finding that oscillations may be induced at the guide roll which immediately follows the pay-off spool, and these oscillations may be transmitted to the machining span where they may affect the accuracy to size and the surface quality of the workpieces being processed. When the pay-off spool is supported so as not to be movable axially, such oscillations are caused by the fact that the electrode wire, arranged in layers on the spool, is payed off at a different angle at the beginning of each layer than at the end of the layer. From a certain angle on, the electrode wire tends to move up periodically on flanks of a groove formed in the guide roll which receives the wire next down the line from the pay-off spool and then to slide down again into the bottom of the groove. With the known device of the generic kind in question this is prevented by controlled shifting of the pay-off spool so that the electrode wire constantly maintains a certain position at which it runs perpendicularly to the axis of the pay-off spool.
It is also known (JP 07 001 247 A) to wind up spent electrode wire on a take-up spool for disposal, causing the spool to carry out controlled axial reciprocating movements during the winding process in order to make full use of the winding space available.
SUMMARY OF THE INVENTION
The invention starts from the finding that oscillations may be generated also during the winding up of the used electrode wire and that these oscillations may propagate as far as the machining span where they may affect the accuracy to size and surface quality of the workpiece being processed.
It is the object of the invention to prevent such oscillations as well.
This object is met, in accordance with the invention, in a wire supply device of the kind specified initially by the fact that second pivot pin, first pivot pin, same plane normal to the axes when being wound up on the take-up spool and also when being unwound from the pay-off spool.
As a result, the electrode wire is wound up on the take-up spool in the same layered fashion as it was wound originally on the pay-off spool. The original wound configuration of the electrode wire on the pay-off spool thus is reproduced on the take-up spool by the mere fact that the measuring means which monitors only the unwinding electrode wire effects control of the common carrier member of both spools. In this manner the electrode wire is prevented from slipping off a previously laid wire winding on the take-up spool and thereby starting to oscillate.
The device according to the invention preferably is developed further by providing that parallel with the axis of the pay-off spool for free axial movement and has an annular groove to guide the electrode wire, and that correction to the slide drive means when the measuring roll deviates from a normal axial position.
The sensors preferably are inductive proximity switches.
It is of advantage if the slide drive means comprises a servo motor and a spindle drive.
Finally, it is convenient if the two spools are connected to a motor each, mounted on the carrier member, and acting s
REFERENCES:
patent: 4242556 (1980-12-01), Ullmann et al.
patent: 4386248 (1983-05-01), Inoue
patent: 5281787 (1994-01-01), Arakawa
Bailer Norbert
Bailer Peter
Browning Clifford W.
Evans Geoffrey S.
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