COUNTER CONTACT, IN PARTICULAR FOR A KNIFE CONTACT OF A KNIFE FUSE AND METHOD FOR MAKING SAME

Abstract: Counter contact in particular for a knife contact of an electrical fuse, consisting of punched electrically conducting sheet metal bent to the necessary shape and having two nearby parallel contact jaws (6) and a connection strip (5), connected to a U-shaped connecting portion (3).

Description: Counter contact, in particular for a knife contact of a knife fuse and method for making same. The invention relates to a counter contact, in particular for a knife contact of a knife fuse for electrical systems, consisting of electrically conducting sheet metal bent to the necessary shape and comprising two nearly parallel contact jaws, connected with one another by a connecting portion, whilst a connection strip is connected with the connecting portion. Such counter contact is known from the Dutch Patent 98,321. These contacts are used mainly for knife fuse holders, but also for instance for safety fuse load switches. These known counter contacts are made for instance of sheet metal, for instance by punching a T-shaped primary part from copper tape or copper strip. The horizontal upper parts of the T-shaped primary part is folded then to obtain two opposite contact jaws, whereas the vertical leg forms the connection strip. In order to obtain the necessary spring tension these counter contacts may comprise separate pressure springs. Although these contacts satisfy in practice yet there are a number of drawbacks. For instance because of the T-shaped primary part, punched from sheet metal, the ratio between the net and gross quantity of used sheet material is rather unsatisfactory, which means a relatively high cost price. Moreover, the application of separate springs for the necessary contact pressure is complicated because of the closed lower side of the contact. In order to mount the counter contact on a base plate, housing or the like mounting material is necessary moreover, such as bolts and nuts. This also influences the cost price unsatisfactory. Above drawbacks are avoided now by the counter contact of the present invention, which is characterized in that it is made from a rectangular plate having two parallel slits, which extend from one side of the plate to the opposite side and thus forming three separate parallel strips, connected with one another by a cross strip extending along the said opposite side, which cross strip is bent to a U-shape along lines which mainly are aligned with the two slits, in which both outer strips of the the three parallel strips are bent to one another in order to form the two contact jaws while the center strip is bent perpendicular to the cross strip, in order to form the connection strip, said cross strip forming the con necting portion. Punching the primary part such that a rectangular plate is obtained having two parallel narrow slits, results in a substantial saving in material. The counter contact can be mounted with ease on a base body of for instance the fuse holder by means of the U-shaped connecting portion, so that further mounting material can be dispensed with, which lowers the price of the fuse holder. Also the mounting operation by itself is easy because no additional mounting material is necessary. A device having counter contacts according to the present in vention is characterized in that the U-shaped bent cross strip of each counter contact is received in a matching Shaped recess in the belonging support part of the insulating support body of the device. The counter contacts can be fixed in the said recess by deformation of the inserted cross strip, for instance by upsetting the lower edge of this strip. It is remarked, that counter contacts are known per se, also fabricated in a material saving method. However, these known coun ter contacts are suitable only for lower nominal current values, for instance lower than 250 amperes. In case of current values above 250 amperes it is necessary to use several such contacts in parallel so that the advantage of the material saving process is eliminated. On the contrary a counter contact of the present invention can be used for a plurality of current values, using the same contact shape. The invention will now be elucidated on the basis of the draw ings, showing an embodiment. Figure 1 shows a known contact in folded out configuration as described in Dutch Patent 98,321; Figure 2 shows a counter contact in folded out configuration of the present invention; Figure 3 shows a front view of a counter contact of the present invention mounted on a body; Figure 4 shows a side view of the counter contact of the present invention mounted on a support body; Figure 5 shows in perspective view a counter contact of the present invention, shown above a support part of the insulating supports of a fuse holder. Figure 1 shows in which way the primary part of the known counter contact is punched from a copper tape or copper strip. The continuous lines shows the folded out configuration of the said known contact 1. The interrupted lines show in which way further counter contacts can be punched from this tape material in the most economical way. The shaded portions clearly show that relatively much material is lost doing so. Because predetermined lengths are necessary for the contact jaws (6) and connection strip 5 to be formed, the material saving of the shaded portions is limited. Figure 2 shows a folded out configuration of a counter contact of the present invention, for a fuse holder for nearly the same nominal current value as the counter contact of Figure 1. Here also the shaded portions show the not used material and it appears clearly that this is substantially less than in the known contact. This results from the parallel position of the strips 6 and 5 in this primary part, forming after bending the respective contact jaws and the connection strip. In Figures 1 and 2 it is shown by interrupoted lines where the folded out configurations have to be bent in order to obtain the ultimate counter contacts. Figure 3 shows the counter contact 1 mounted on a support body, which means received in a U-shaped recess 8 of the belonging support part 2 of the insulated support body of a fuse holder for instance. 7 is a knife fuse, separation knife or the like. The contact jaws and connection strip are shown using the same reference numbers as in Figures 1 and 2. Figure 4 shows a side view of such a counter contact 1 received in a support part 2. In Figures 3, 4 and 5 it is shown, that as distinct from the known counter contact, the counter contact of the present invention need not be mounted on top of the support part 2 of the fuse holder by means of bolts or screws, but matches with its lower portion, which means the U-shaped cross strip 3 partly or wholly in the recess. Hereby the counter contact is supported largely in the support part, whereas for a firmer mounting within this support part it is necessary only to deform by upsetting or bending and the like. Also the support part 2, in case this is made of thermoplastic material, can be plastically deformed therefore. An additional spring for additional contact pressure of the contact jaws, as used in the counter contact of above-said Dutch Patent 98,321, also can be used in this counter contact of the present invention in a simple way and placed in position from the open lower side, before the counter contact is received in the U-shaped recess 8 of support part 2. In Figures 3, 4 and 5 the U-shaped recess 8 extends over the whole height of support part 2. This is not necessary, however. At the lower side this recess can be enlarged by leaving out the center portion, vide reference number 9 in Figures 3 and 4. This facilitates the deformation of the lower edge of the U-shaped cross strip 3. The counter contact of the present invention is fabricated in the following way. First the folded out configuration, shown in Figure 2, is punched from sheet material. Upon this punching operation at the same time a connection opening 4 in the connection strip 5 can be made, and openings for a spring to increase the contact pressure of the contact jaws 6, in case this is considered necessary. For clearness' sake these springs and belonging openings are not shown in the drawings. When punching also the necessary curvatures and camber can be made in the contact jaws 6. The connection strip 5 is bent perpen dicular to the plane of the folded out configuration, which means perpendicular to the cross strip 3. Hereafter the contact can be silver-plated where necessary, whereafter in the last fabrication step both contact jaws 6 are bent to one another by bending the cross strip 3 such that a U-shape is obtained. In this way it is guaranteed that at all locations of the contact the necessary thickness of the silverplating is obtained. In case the distance between the contact jaws 6 is large with respect to the width of the contact jaws, which means in particular in case of counter contacts for low current values, the silverplating can be applied also in a last fabrication step. The counter contact thus obtained can be placed with the perpendicularly bent parts a, b and c in the recess 8 of the support part 2 and fastened therein. This offers a satisfying initial fastening of the contacts and it need be guaranteed only that the contact is not drawn from the support part 2 upon removing a knife fuse or knife contact. By deformation of the lower side of the contact to be received in in the support part 2, this relatively small force upon removing the knife contact or knife fuse can be taken care of. Also the support part 2 can be deformed plastically, for instance by ultrasonic vibrations such, that the cross strip 3 with parts a, b and c are firmly held in place. A light curvature of parts a, b and c is of advantage here for accepting draw forces. The cross strip 3 also can have a short transversely bent edge at its lower side, which after pushing in the U-shaped recess 8 will snap below the upper wall of recess 9. This also will take care of forces upon removing a knife contact of a knife fuse, so that the counter contact is not drawn out then. As a matter of course other snap connections are possible with adapted modifications of the support part 2 or the recess 8. By means of other modifications, for instance broadening or narrowing the contact jaws 6 as well as the connection strip 5, the contact can be made appropriate for different current values. As a matter of course the invention is not limited by the embodiment shown on the drawings.

Claims: Claims 1. Counter contact, in particular for a knife contact of a knife fuse for electrical systems, consisting of electrically conducting sheet metal bent to the necessary shape and comprising two nearly parallel contact jaws, connected with one another by a connecting portion, whilst a connection strip is connected with the connecting portion, c h a r a c t e r i z e d i n that this counter contact is made from a rectangular plate having two parallel slits, which extend from one side of the plate to the opposite side and thus forming three separate parallel strips, connected with one another by a cross strip extending along the said opposite side, which cross strip is bent to a U-shape along lines which mainly are aligned with the two slits, in which both outer strips of the the three parallel strips are bent to one another in order to form the two contact jaws while the center strip is bent perpendicular to the cross strip, in order to form the connection strip, said cross strip forming said connecting portion. 2. Counter contact as claimed in claim 1, c h a r a c t e ri z e d in that the line of bending between the connection strip and the cross strip is located more closely to the said opposite side of the plate than the lines of bending between the outer contact jaws strips and the cross strip. 3. Counter contact as claimed in claim 1 or 2, c h a r a ct e r i z e d in that the center strip forming the connection strip is shorter than the outer contact jaw strips. 4. Device comprising counter contacts as claimed in one of the preceding claims, c h a r a c t e r i z e d in that the U-shaped bent cross strip of each counter contact is received in a matching U-shaped recess in the belonging support part of the insulating support body of the device. 5. Device as claimed in claim 4, c h a r a c t e r i z e d in that the counter contacts are secured by mechanical plasti deformation of the U-shaped cross strip received in the U-shaped recess. 6. Device as claimed in claim 5, c h a r a c t e r i z e d in that the deformation is obtained by upsetting the lower edge of the cross strip. 7. Device as claimed in claim 4, c h a r a c t e r i z e d in that the lower edge of the cross strip is bent, so that after pushing in the recess this bent portion can snap behind a surface of the support part. 8. Device as claimed in claim 4, c h a r a c t e r i z e d in that the counter contacts are secured by ultrasonic plastic deformation of the support part. 9. Method for making a counter contact as claimed in claims 1 through 3, c h a r a c t e r i z e d by: punching the rectangular plate with the said parallel slits; bending the two outer strips until each have the necessary form of a contact jaw and take the necessary position of the contact jaw with respect to the adjacent parts of the cross strip; bending the center strip at a right angle with respect to the cross strip to form the connection strip; bending the cross strip to a U-shape along the lines which mainly form the elongations of the said slits; 10. Method as claimed in claim 9, c h a r a c t e r i z e d in that at least said surfaces of the outer strips forming the contact jaws are silver-plated, which will come into contact with the knife contact (of the knife fuse).

Inventors: KUIPERS, KAREL
Applicants: HAZEMEIJER B.V.
Application year: 1983
Main classification: H01H1
IPC codes: H01H1