Electric heating – Metal heating – Cutting or disintegrating
Patent
1989-06-21
1991-05-07
Evans, Geoffrey S.
Electric heating
Metal heating
Cutting or disintegrating
B23H 710
Patent
active
050138812
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a wire-extension end detector for a wire-cut electric discharge machine, which is highly reliable in detecting action.
An apparatus provided in a wire-cut electric discharge machine for carrying out an automatic extension of a wire, disconnected intentionally to allow a workpiece to be shifted to change a discharge machining portion thereof or disconnected accidentally during the discharge machining, is disclosed in Japanese Patent Disclosure No. 62-44319, for example. In this type of automatic wire extension apparatus, a wire, supplied through a wire passage of an upper wire guide arranged above a workpiece, is fed into a groove or hole of the workpiece while being restricted by a machining liquid jetted from a nozzle formed in the upper wire guide. The wire is then passed through a wire passage of a lower wire guide. Subsequently, the wire is fed to a conveyor device arranged under the lower wire guide. The conveyor device includes a pair of belts pressed against each other, so that the wire is conveyed, while held between the belts, in between a wire drive roller and a pinch roller arranged downstream of the coveyor device. The wire extension is completed when the wire is held bewteen the wire drive roller and the pinch roller. When the wire extension comes to an end, an electric power supplying section which is electrically connected to the wire becomes connected through the wire, the electrically conductive outer peripheral wall of the wire drive roller, and an electrically conductive brush pressed against the outer wall of the wire drive roller, to an electric power supplied section which is connected to the brush. The resulting supply of electric power from the power supplying section to the power supplied section is detected by a suitable means as an end of wire extension.
As described above, the prior art wire-extension end detector uses the brush pressed against the wire drive roller, and therefore is liable to suffer disconnection between the brush and the roller as the brush is worn away with repeated use, thus failing to detect the end of a wire extension.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an automatic wire-extension end detector for a wire-cut electric discharge machine, which does not use electrical components that mechanically contact one another, and thus is capable of highly reliable detection of the end of a wire extension.
To achieve the above object, a wire-extension end detector of the present invention is provided in a wire-cut electric discharge machine which has a wire conveyor device including wire drive means for running a wire delivered by automatic wire extension means. The wire-extension end detector comprises a rotary member arranged to face a wire travel path and rotatively driven by the wire which is driven to travel by the wire drive means, detection means arranged in a non-contact relation to the rotary member, for generating an output indicating that the rotary member is rotating, when the rotary member is rotated, and discrimination means responsive to an operation of the wire drive means, an operation of the automatic wire extension means, and to the output of the detection means. The discrimination means is operable to detect the end of a wire extension when an output of the detection means is generated before a predetermined time passes after the automatic wire extension means starts operation, during the operation of the wire drive means.
As described above, the wire-extension end detector of the present invention is so arranged as to detect the end of a wire extension in a non-contact fashion in which the wire is driven to by the wire drive means, without using any electrical components that mechanically contact one another, and accordingly can reliably detect the end of the wire extension.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic side view of a wire-cut electric discharge machine equipped with a wire-extension end detector according to one emb
REFERENCES:
patent: 4581514 (1986-04-01), Inoue
patent: 4608475 (1986-08-01), Inoue
patent: 4698476 (1987-10-01), Yamamoto et al.
patent: 4719449 (1988-01-01), Cousseau
Arakawa Yasuo
Aso Toshiyuki
Evans Geoffrey S.
Fancu Ltd.
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