Impulse heat joining of wrapping tapes for wire cables

A method of joining end abutting metal tapes in order to continuously supply the tapes for the production of sheathed cables formed by longitudinally wrapping cable cores with the tapes, the tapes being laminated on the side remote from the cable core with a plastic film having a relatively low melting temperature, said method cmprising:

• placing end abutting metal tape portions on a first, relatively fixed pressing block with the film layer of said metal tapes in contact with said block,
• overlying the abutting ends of said metal tape on the side opposite the plastic film with an adhesive plastic film strip having a melting temperature above that of the plastic film laminated to said metal tape,
• pressing said adhesive plastic film strip against said abutting ends of said metal tape by applying under pressure a second metal block of high thermal conductivity forming a heat dissipating sink and having an electric heating element of high electrical resistance mounted to the face of the second block which immediately faces said adhesive plastic film strip with said electric heating element being electrically insulated from said second block, and
• applying an electrical current pulse to said electric heating element having an amplitude and duration sufficient to establish an acute temperature gradient across the metal tape assembly sufficient to melt the adhesive plastic film strip insufficient to melt the low melting temperature plastic film on said metal tape;
• whereby, said abutting ends of said metal tape portion are quickly joined and the resulting joint has high mechanical strength and electrical continuity.