Apparatus for Reducing the Cross Sectional Area of a Wire

This invention relates to apparatus for reducing the cross sectional area of a wire at spaced intervals along its length so as to form a fusible element for use particularly in high voltage current limiting fuses.

According to one known practice, the fusible element for a current limiting high voltage fuse is of ribbon or tape form and its cross sectional area is reduced at spaced intervals along its length by punching or notching procedures. There are advantages in using fusible elements formed of wire rather than of ribbon form but known procedures for varying the cross sectional area of wire involve expensive and time consuming electroplating or machining techniques for enlarging or reducing the wire diameter at spaced intervals along its length.

According to this invention in one form apparatus for reducing the cross sectional area of a length of wire is provided and comprises stabilizing means arranged to receive the wire and to limit transverse extrusion thereof and means including moveable projecting means for engaging and deforming the wire while restrained by the stabilizing means so as to reduce its cross-sectional area.

In the drawing

FIG. 1 is an isometric view of one form of the apparatus for reducing the cross sectional area of a wire;

FIG. 2 is an enlarged fragmentary view showing deformation of a wire by the apparatus shown in FIG. 1;

FIG. 3 is an isometric view of alternate apparatus for reducing the cross sectional area of a wire; and

FIG. 4 is an enlarged view showing deformation of the wire by the apparatus shown in FIG. 3.

In FIGS. 1 and 2, the numeral 1 designates the wire, the cross sectional area of which is reduced according to this invention. Wire 1 is wound on spool 2 which in turn is mounted on shaft 3. Wire 1 is wound from spool 2 onto spool 4 which in turn is mounted on shaft 5. Spool 4 is rotated by conventional means such as motor 6 and clutch arrangement 7 both of which cooperate with shaft 5 to wind wire 1 onto spool 4.

In order to deform the wire according to this invention and as shown in FIG. 1 in one form initially wire 1 proceeds through slot 8 formed in the upper portion of the wire stabilizing means in the form of stabilizing block 9. For the purpose of deforming the wire, reciprocable element 10 is mounted above stabilizing block 9 by an appropriate conventional reciprocable mechanism which is partially shown in the drawing and is indicated by the letter M. Reciprocable element 10 is provided with plate 11 formed on one side thereof and projection 12 formed on the lower edge of plate 11. Plate 11 is disposed in longitudinal alignment with slot 8.

In operation wire 1 is wound onto spool 4 by means of motor 6 in an intermittent fashion. As wire 1 proceeds through slot 8 reciprocable element 10 is intermittently lowered whereby plate 11 and projection 12 are lowered into slot 8 a distance sufficient to allow for the accurate deformation indicated by the letter "a", of wire 1 by means of projection 12. Plate 11 and projection 12 are shown in their lowermost positions in FIG. 2.

The width of slot 8 determines the width of deformation "a" while the height of deformation "a" is determined by the lowermost reach of projection 12 of reciprocable element 10 and the lower surface 8a of slot 8. Of course the size of deformation "a" can be changed by simply varying these dimensions.

An alternate form of this invention is shown in FIGS. 3 and 4. More specifically the apparatus as shown in FIG. 3 comprises wheels 13 and 14 which are mounted on shafts 15 and 16 respectively. Wheels 13 and 14 are each provided with spaced projections p.

Stabilizing means for this apparatus is provided in the form of supporting discs 17 and 18 which are mounted on shaft 15 and disposed on either side of wheel 13 and supporting discs 19 and 20 which are mounted on shaft 16 and are disposed on either side of wheel 14. As is best viewed in FIG. 3, supporting discs 17 and 18 are of a smaller diameter than supporting discs 19 and 20. Rotation of wheel 14 and supporting discs 19 and 20 is provided by appropriate motor means 21. In addition motor 21 rotates gear 22 fixedly mounted on shaft 16 which in turn rotates gear 23 and the other elements mounted on shaft 15. The entire assembly of FIG. 3 is mounted on base plate 24 and wheel 14 is rotated in synchronism with wheel 13. According to this invention, wire 1a is advanced between wheels 13 and 14 by any suitable means such as the spool arrangement shown in FIG. 1. As wire 1a proceeds between wheels 13 and 14, corresponding projections P on each wheel are synchronized in such a manner that deformations b and c are intermittently formed in wire 1a as it passes between the wheels and as shown in detail in FIG. 4.

Since supporting discs 19 and 20 are larger in diameter than corresponding supporting discs 17 and 18 wire 1a is positioned between supporting discs 19 and 20 as it proceeds between wheels 13 and 14. Discs 19 and 20 thus constitute stabilizing means for receiving the wire 1a and for limiting transverse extrusion thereof. This arrangement not only provides stabilization for wire 1a but also limits the lateral extrusion of the wire material when the deformations b and c are formed. Of course the spacing of wheels 13 and 14 can be adjusted to provide varying degrees of vertical deformation in the wire. In addition supporting discs 19 and 20 are positioned such that minimum interference with wire 1a occurs so as to facilitate movement of the wire through the apparatus.

Extrusion of the wire in a transverse direction is thus limited by the width of slot 8 and by the lateral distance between adjacent faces of supporting discs 19 and 20. Extrusion of the wire in a longitudinal direction is not limited by the apparatus but occurs as the projection 12 and the bottom 8a of slot 8 effect a squeezing action on wire 1. Similarly projections P squeeze and extrude wire 1a in a longitudinal direction while disposed between supporting discs 19 and 20. The length along the wire 1 of deformation a and of deformations b and c along wire 1a is not critical. It is important however that the reduced cross sectional area be substantially rectangular. Thus the aspect ratio determined by dividing the cross sectional area of the wire by the cross sectional area of deformations such as a, b and c should be in the range of 1.25 to 5. The rectangular cross sectional configuration of the deformations a, b and c assures that the aspect ratio is constant along the length of the wire. These relationships may, of course, be varied depending on the wire diameter and on the rating of the fuse.

By this invention means are provided to reduce the cross sectional area of the wire element for use as the fusible element in a high voltage current limiting fuse. The deformations are accomplished economically at room temperature by means which also controls the physical and electrical properties of the wire with a high degree of accuracy.