FR2484296A1 - METHOD AND DEVICE FOR DISCHARGING AND FORMING A WIRE THREAD - Google Patents

Abstract

A USED WIRE, CONTINUOUSLY COMING OUT OF A MACHINE FOR CUTTING A METAL PART BY EROSIVE ELECTRICAL DISCHARGES, IS SUBJECTED IN A DEVICE 10 TO PERMANENT DEFORMATIONS WHICH GIVE IT FOR EXAMPLE A SINUSOIDAL SHAPE AND AT THE SAME TIME A SOME STEADY; THE DEVICE 10 FURTHER GIVES THE WIRE A GENERAL RECTILINE SHAPE. THANKS TO THESE PERMANENT DEFORMATIONS, THE WIRE WALLS SPONTANEOUSLY IN A CONTAINER 13 IN THE FORM OF A TORIC WINDING, OR CROWN, COMPACT, 12, WITHOUT EVER CHANGING DIRECTION DURING ITS RUNNING.

Description

-1- Method and device for removing and shaping a used wire

The invention relates to a method and a device for evacuating and compacting a worn wire after it has passed through the machining zone of a machine for cutting a metal part by

erosive electrical discharges.

Such a machine comprises an electric pulse generator for bursting the erosive discharges between the wire and the part; it further comprises guiding and wire entrainment members which allow, on the one hand, a slow displacement so as to cut the part according to a desired shape and, on the other hand, rapid longitudinal scrolling! The latter allows to constantly renew the portion of wire

  subject to the action of erosive discharges, otherwise the wear of the provo-

would be almost immediate rupture. Specifically because of this wear, and also because of structural changes, the wire cannot be used for machining; if we still wanted to do it, we would have to considerably reduce the power supplied by the generator.

why used wire is usually sold as scrap metal

ration and means must be provided to store it in the form

compact. To fix the ideas, it should be noted that the speed of

  ment is typically 5 meters per minute, so that 200 mi = processing time gives 1 km of scrap wire; such a flow requires

  obviously compact means of evacuation and storage.

  The simple solution is to wind the wire on a take-up spool driven by a motor. However, there is an increasing demand for wire machines to be able to work for hours without manual intervention, and automatic threading devices have been developed for this purpose which intervene in the event of wire breakage or change of part; therefore, the thread is no longer in one piece and the take-up reel requires a complicated device to cause the winding to start at each threading operation. The solution of letting the wire get loose in a container is unacceptable, because of the exaggerated volume that - 2 would take the kilometers of wire produced for example during one night of machining. We used a system to cut the wire into small pieces using a knife driven by a reciprocating movement (patent

  American No. 3,822,374) or using a rotary tool fitted with more

sharpshooters (German Patent No. 2,755,740). The material is stored in compact form only if the cut pieces are short, which causes rapid wear of the cutting parts and therefore requires maintenance; for transport, closed containers must be provided. In the first cited patent, a guide tube has also been proposed which forces the wire to wind regularly in a container mounted on a turntable, which requires a motor and an adjustment to adapt the speed.

of rotation at the scrolling speed.

The object of the invention is a process for compacting used thread which is simple, does not require any human intervention and which avoids having to use cutting parts requiring maintenance. It is characterized in that said wire is subjected, as and when it leaves the machine, alternating bending causing permanent deformations, so as to erase the uncontrolled deformations produced on the wire during its passage through the machine and in that we direct this wire in a container so that it winds up by itself

in this last.

  In this way, a winding of toroidal shape, or crown, is obtained in a container situated in the axis of exit of the wire. Without this

process, the wire would come out of the machine with unconformed deformations

  trôlées with large radius of curvature which result from the passage through

  the machine, so that from time to time the thread would change spontaneously--

  winding direction; we would thus obtain a winding

cluttered and excessively bulky. Thanks to the permanent deformations according to the process, the wire hardens and acquires a certain stiffness; moreover, it is preferably given a straight general direction. Once the movement has started in one direction, the winding continues

in the container perfectly evenly.

The fundamental advantage of the invention is that the alternating permanent deformations are obtained by a particularly simple and inexpensive device and nevertheless lead to a fully automatic solution to the problem of winding in compact form the waste wire produced by a machine. thread, despite the complication -3- caused by breaks in continuity in the unwinding of the thread which

  appear during automatic threading operations.

  The attached drawing represents, schematically and by way of ex-

  example, an embodiment of a device for implementing the method according to the invention. FIG. 1 is a general view of a wire machine equipped with a device for discharging the used wire allowing it to be wound up under

compact shape.

  Figure 2 is an enlarged view of said device.

  We recognize in Figure 1 the usual organs of a machine

  using a wire 1 for cutting a metal part 2 by cutting

erosive electrical charges. The wire is delivered by a coil 3 fixed on a plate 4; two guides 5 and 6, integral with a rigid double arm 7 in the shape of a U, ensure precise guidance of the wire 1 which passes through the part 2 from top to bottom. An electric generator, not shown, is connected to the wire by current supply contacts, not shown, to burst erosive discharges between the wire and the part. After the last guide 6, the wire is taken between two flat belts 8 and 9 which provide and

  its friction traction and its transport to an evacuation device 10

  cuation allowing its winding in the form of a compact toroidal winding 12 stored in a container 13. This device 10 which will be described below, gives the wire the deformation 11 visible in the figure, 2. The flat belts 8 and 9, the layout is best seen in the figure

  2, are driven at the same linear speed by a motor, not re-

present.

Regarding the kinematics of the movements of the wire relative to the workpiece, it should be noted that all of the entrainment and guide members of the wire are secured either to the plate 4 or to the double arm 7 in the shape of a U. This set forms a whole animated by an X movement

perpendicular to the plane of the drawing, driven by a motor, not

presented, and sliding using a slide 14 on a gantry 15 secured to a fixed base 16 of the machine. On the other hand, the part 2, mounted on a support 17, itself mounted on a table 18, forms with a tray 19 a whole driven by a movement Y perpendicular to the first, thanks to a part 20 sliding on the base 16 under the effect of a motor

  21. A digital control, not shown, coordinates the movements

X and Y elements for cutting the part into a desired shape.

- 4 - Figure 2 shows, on a large scale, a possible embodiment of the used wire discharge device allowing its winding in the form of a toroidal winding, or crown, compact. There are the flat belts 8 and 9 already mentioned and it should be remembered that they are driven by a motor, not shown. The trajectory of the wire has been indicated by its entry axis 22 and its exit axis 23. By friction, the flat belt 8 interarne a toothed belt 24 and the latter in turn drives another toothed belt 25 by meshing on a path common located on the axis 23. The medallion 26 shows the design of the teeth, which corresponds to a succession of trapezoids whose angles may be somewhat rounded; as an example, the periodicity can be 5 mm and the height 2 mm. The wire, trapped between these teeth, undergoes permanent deformation, or

work hardening, of great amplitude, which is much higher than any de-

  training that was previously experienced during the passage through the ma-

China. It then has a sinusoidal shape, as indicated by 11. The main stresses are those which result from the alternating flexions imposed by the shape of the teeth of the toothed belts. To a lesser extent, the wire is also stressed in pure elongation, because the path between the toothed belts is longer than between the flat belts. The main point is that the large permanent deformations which result from bending have the effect of erasing the small deformations undergone previously during the passage through the machine. This erasure phenomenon is basically the same as that which occurs when the wire is stretched so as to give it a great elongation. However, the implementation of pure elongation with sufficient deformation leads to strong traction on the wire, traction which generates high pressures and heavy wear on the drive system constituted by flat belts. The engagement on toothed belts makes it possible to greatly reduce the traction force, and of course the wear of the toothed belts. The most remarkable point of the invention is that it requires only a minimum of additional parts without any motor or automatic adjustment, provided that the traction and transport system constituted by the flat belts 8 and 9

Already exists.

  -5 - Ultimately, as shown in Figure 1, the wire is spontaneously wound in the container 13 in the shape of a crown, without ever changing winding direction during the passage of a wire in one piece. Other embodiments can be implemented. For example, belts having a different tooth shape than that shown in FIG. 2 can be successfully used. As a more significant modification, it is possible to dispense with direct drive of the toothed belts 24 and 25 by friction on one of the flat belts. 9; in this case, the interlocking of the set of toothed belts is carried out by an auxiliary mechanism, for example another belt reserved for this purpose with a set of pulleys of different diameters. This way of doing things has the advantage of being able to adjust the tensile force on the wire to a predetermined value, thanks to a judicious choice of the diameters of the 1 pulleys of this auxiliary mechanism. Going further in this way, we can even replace the toothed belts by two toothed wheels with mesh; by playing on the alternating flexions imposed by the teeth and on a sufficient tensile force, we can achieve the same

result, but at the cost of a more delicate mechanism to realize.

-6-

Claims (3)

Claims   1. Method for evacuating and compacting a worn wire after it has passed through the machining zone of a machine for cutting a metal part by electrical erosive discharges, characterized in that one subjects said wire, as it leaves the machine, to alternate bending causing permanent deformation, so as to erase the uncontrolled deformation produced on the wire during its passage through the machine, and in that 'we run this thread in a container so that it wraps itself in the latter.   2. Method according to claim 1, c a r a c t é r i s in that said flexions are alternated so as to give the wire a form general rectilinear.   3. Device for implementing the method according to the resale   dication 1 or claim 2, c a r a c t e r i s in that it comprises   carries a set of two toothed belts meshed with each other and displaced on a common path, so as to force the wire to take said path and to undergo the bends imposed by the shape of the teeth said notched belts.