Electric heating – Metal heating – Cutting or disintegrating
Patent
1992-08-24
1993-10-12
Evans, Geoffrey S.
Electric heating
Metal heating
Cutting or disintegrating
226190, 242157R, B23H 710
Patent
active
052527999
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
Technical Field
The present invention relates to a wire cut electric discharge machine having an improved support structure for supporting a wire which functions as an electrode.
Background Art
As shown in FIG. 5, in the conventional wire electric discharge machine 1, an unused wire 2 is usually wound around a supply reel 4 which is rotatably attached to a machine body 3, in order to be ready for a machine operation. The wire 2 is fed along a path starting at the wire supply reel 4, as a start point, and ending at a wire recovery box 12, as an end point, through a brake roller 5, upper wire guide roller 6, upper guide 7, lower guide 8, lower guide roller 9, guide roller 10 and feed roller 11, which are disposed in the order named. Used wire 2 is recovered in the wire recovery box 12.
The brake roller 5 is one of wire braking means displaying a braking ability in cooperation with a pinch roller 13, while a feed roller 11 is one of wire traction means displaying a tractive ability in cooperation with a pinch roller 14. Reference numeral 15 denotes a workpiece which is arranged at a machining position in FIG. 5. Furthermore, the wire 2 serves as electrodes and functions as one of the electrodes in an electric discharge machining.
During the machining of the workpiece 15, the wire 2 is drawn out of the wire supply reel 4 by means of a tractive force generated by the feed roller 11, to be moved along the wire path. On the half way of the path, resistance is given to the movement of the wire 2 by means of the brake roller 5, or the wire 2 is braked. Whereby a tensile force (wire tension) is applied to the wire 2 on the downstream side (the feed roller 11 side) with respect to the brake roller 5. The tension is required to maintain a normal discharge state during the electric discharge machining.
Therefore, during the wire cut discharge machining, when the wire 2 is suddenly broken anywhere in its downstream side portion by any reasons (e.g. damage on the surface of the wire, contact with the workpiece, fusion caused by irregular supply of machining fluid, or the like), the wire portion on the upstream side of the broken point (on the side of brake roller 5) bounces upwardly due to reaction of the tension applied so far. On the other hand, the portion of wire on the downstream side of the broken point is drawn out by means of the feed roller 11 to be received by the wire recovery box 12.
In this case, when the portion of wire on the upstream side of the broken point bounces hard, the wire 2 waves as shown by one dotted chain line in FIG. 6, hangs down as shown by a dotted line and will come off the wire guide roller 6 which is situated right above the upper guide 7. As a result, it will become difficult for an operator to make a wire feeding work for restoring normal state for the wire after its break, or it will be impossible to make an automatic wire feeding by actuating an automatic wire feeding device (AWF) even if the wire cut electric discharge machine 1 is provided with such a device.
Thus, in order to prevent the problem mentioned above, conventionally, as shown in a side view of FIG. 7, the wire guide means 17, which is a combination of a wire deviation preventive member 16 and the wire guide roller 6, is used. The wire deviation preventive member 16 comprises a spring plate 18 fixed on the side of a body 3 of the wire cut electric discharge machine 1 and a pad 19 attached to a free end of the spring plate. The pad 19 is arranged to face the wire guide roller 6 with a slight clearance therebetween. The position of the pad is in a range where the wire 2 is applied around a wire groove 20. Thus, when the wire break occurs, the wire 2 bounces to come into contact with the pad 19, whereby the wire 2 will be prevented from bouncing further and also from deviating from the wire guide roller 6. Incidentally, the wire groove 20 of the wire guide roller 6 is formed into a V-shape in cross section and is usually about 5 mm deep.
However, according to the conventional wire guide means 17, a dista
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patent: 4383161 (1983-05-01), Corcelle
patent: 4414458 (1983-11-01), Nomura
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patent: 4733038 (1988-03-01), Girardin
patent: 4842251 (1989-06-01), Porter
patent: 5178313 (1993-01-01), LeCompte et al.
Evans Geoffrey S.
Fanuc Ltd
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