Abstract: In an apparatus and a method for welding of workpiece layers, a feed device is activated with a predefined adjustment force without ultrasound activation and the sonotrode is advanced in the direction of an anvil. The adjustment force is subsequently reduced and the sonotrode is activated. The sonotrode can subsequently be deactivated and the adjustment force can be increased on the basis of a deactivation signal.

Abstract: An apparatus for the connection of articles via at least one connection element plasticizable by heat includes a cap, in particular a heatable cap, which is movable toward and away from the connection element and which has a shaft, for the forming of a rivet head at the connection element and having means for the cooling of the cap by means of a cooling fluid, in particular air. A first variant is characterized in that the shaft of the cap has a central cooling fluid supply passage preferably reaching up to and into the cap body and a plurality of respective at least generally radially outwardly directed cooling fluid passages starting from the central cooling fluid supply passage are provided within the cap body. Provision can alternatively be made that the cap is manufactured at least partly from porous, air-permeable material, in particular ceramic material, and the shaft of the cap is provided with a cooling fluid supply bore preferably reaching up to and into the cap body.