Device for joining ends of material strips

In a device for joining ends of material strips of rubber or plastic materials with rubber properties, wherein the ends to be joined have areas of reduced wall thickness and wherein the end cut first is stretched shortly before joining the two ends;

• the improvement comprising:
• a plurality of force-transmitting elements positioned adjacent to one another transverse to a longitudinal direction of the material strip at a forward end thereof and acting on one face of the material strip, wherein at least said force-transmitting elements positioned at the areas of reduced wall thickness of the forward end are moveable in the longitudinal direction of the material strip for stretching the forward end of the material strip at least within the areas of reduced wall thickness;
• wherein said force-transmitting elements comprise a first set acting on the areas of reduced wall thickness cut first in a transverse direction of the material strip and a second set acting on portions of the material strip cut subsequently in a transverse direction of the material strip, wherein said force-transmitting elements of said first set move together in the longitudinal direction and wherein said force-transmitting elements of said second set pivot together about at least one common pivot axis extending perpendicular to the face of the material strip such that said second set stretches the portions of the material strip in the longitudinal and transverse directions.