Abstract: The invention relates to a method and an apparatus for welding thermoplastic molded articles wherein additional simultaneous irradiation, in the welding area (18), of one of the join partners (1) will lead to a temperature increase of this join partner, occasioning process-reliable welding.

Abstract: In a method and an apparatus for irradiation welding of two thermoplastic components, a local temperature maximum, which circulates together with the laser beam and increases from cycle to cycle, and a correspondingly circulating, locally increased clamping pressure are generated in the area of joining.

Abstract: An extractable mast structure for a fork-lift truck, including an outer mast fixed to the carriage, the spaced columns being interconnected via upper and lower traverses, an extractable inner mast guided by said outer mast on which a load-carrying means is guided to be movable up and down and the columns of which are interconnected via upper or lower traverses or a cross-beam, one mast lift cylinder for each column of said inner mast supported on said outer mast, piston rods of which are adapted to be connected to said cross-beam, and setting means between said piston rods and cross-beam for an equalization of the lift, wherein a male-threaded setting component is attached to the upper end of said piston rod of one of said two mast lift cylinders and a female-threaded bushing is screwed onto the male thread of said setting component and has supporting surfaces for said cross-beam.