Method and device for establishing a shield connection of a shielded cable

Abstract

Method for forming a shield connection of a shielded cable with the steps of pushing a sleeve onto a shield of a cable, inserting the cable with the sleeve into a magnetic pulse welding coil, and energizing the magnetic pulse welding coil with a current pulse in such a way that the sleeve is joined to the shield with a material bond.

Claims

1. Method for establishing a shield connection of a shielded cable comprising: pushing a sleeve onto a shield of a cable; inserting the cable with the sleeve into a magnetic pulse welding coil; and energizing the magnetic pulse welding coil with a current pulse in such a way that the inner wall of the sleeve is joined with the shield with a material bond.

2. Method of claim 1, wherein an outer insulation of the cable is removed in one area and the sleeve is pushed onto the one area.

3. Method of claim 1, wherein the pulse has a duration of less than one second.

4. Method of claim 1, wherein the pulse has a current of at least 100 kA.

5. Method of claim 1, wherein the magnetic pulse welding coil is a toroidal coil and the cable with the sleeve is inserted into the magnetic pulse welding coil concentrically with the coil axis of the toroidal coil.

6. Method of claim 1, wherein the sleeve is cold-formed by the pulse.

7. Method of claim 1, wherein an outer insulation of the cable is removed at one end of the cable.

8. A cable comprising: an inner conductor; an inner insulation surrounding the inner conductor; a shield surrounding the inner insulation; an outer insulation surrounding the shield; a sleeve surrounding the shield pushed onto an area freed from the outer insulation, an inner wall of the sleeve being adjacent the shield wherein the shield is welded as a material bond to the inner wall of the sleeve using magnetic pulse welding.

9. The cable of claim 8, wherein the sleeve and the shield are made of the same metal, in particular from aluminium or alloys thereof or from copper or alloys thereof.

10. The cable of claim 8, wherein at least the inner conductor has a round or a rectangular cross-section.

11. The cable of claim 8, wherein the shield is formed from a metal braid and/or a metal foil.

12. The cable of claim 8, wherein the sleeve has an opening cross-section and an outer cross-section, wherein the opening cross-section is different from the outer cross-section.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the following, the object is explained in more detail by means of a drawing showing embodiments. In the drawing show:

(2) FIG. 1 a cable with sleeve,

(3) FIG. 2 a cable inserted into a magnetic pulse coil;

(4) FIG. 3 a sleeve welded to a shield by a magnetic pulse.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

(5) FIG. 1 shows a cable with an inner conductor 1. The inner conductor 1 can be stranded or solid. The inner conductor 1 is preferably made of copper or an alloy thereof, but can also be made of aluminium or an alloy thereof. The cross-section of the inner conductor 1 is preferably round or rectangular.

(6) A primary insulation 2 is provided around the inner conductor 1. The primary insulation 2 is made of an electrically insulating material.

(7) A shield 4 is wound around the primary insulation 2. The shield 4 can be formed as metal foil or metal braiding or a combination of both.

(8) The shield 4 surrounds a secondary insulation 5. The secondary insulation 5 can be made of the same material as the primary insulation 2.

(9) It can be seen that at the front end of the cable the secondary insulation 5 has been removed from the shield 4. The shield 4 is exposed in an area of the end face. The sleeve 3 can be pushed onto this area. The sleeve 3 preferably has an inner diameter which corresponds to the outer diameter of the primary insulation 2 together with shield 4.

(10) The sleeve 3 is preferably made of the same material as the shield 4. Especially copper or aluminium and their alloys are suitable.

(11) After the sleeve 3 has been pushed onto the shield 4, the cable is positioned by a feeding device in a magnetic pulse coil 6, as shown in FIG. 2. The magnetic pulse coil 6 has a plurality of windings and is in particular formed as a toroidal coil. The windings run around the cable. The cable is preferably collinear with its longitudinal axis to the longitudinal axis of the magnetic pulse coil 6.

(12) It can be seen that the cable with the sleeve 3 is positioned at the inside of the magnetic pulse coil 6.

(13) A short current pulse can be transmitted to the magnetic pulse coil 6 by a pulse generator, which in particular has at least one capacitor and an ohmic resistor as well as a switch. For this purpose the magnetic pulse coil 6 is short-circuited via the capacitor and the resistor. This causes the capacitor to discharge and the stored charge flows very quickly through the magnetic pulse coil 6, resulting in currents of up to several 100 kA.

(14) The currents flowing in the coil 6 cause an eddy current in the sleeve 3. This creates a Lorentz force on the sleeve 3, which acts towards of the inside of the cable.

(15) By this Lorentz force, a cold forming of the sleeve 3 occurs, as shown in FIG. 3. The Lorentz force acts in direction 7 onto the sleeve 3 and the sleeve 3 is plastically deformed in fractions of a second and pressed onto the shield 4. The high acceleration creates an intermetallic connection between the inner wall of the sleeve 3 and the shield 4. Thereby the sleeve 3 is not only positively form fit and force fit to the shield 4, but also joined together with a material bond.

(16) The cable is subsequently removed from the magnetic pulse coil 6 and the next cable can be inserted.

(17) The cycle time is very short, as the welding is carried out in a very short period of time, especially in less than 1 second. The pulse generator can be charged while the cable is removed from the magnetic pulse coil 6 and a new cable is inserted. This duration may be sufficient to charge the pulse generator or its capacitors with a sufficient charge, so that in the next step a sufficient Lorentz force acts on the sleeve 3 again.

(18) With the aid of the method and the device shown, long-term stable connections between sleeves and shield can be established in a process-safe manner.