Joining element equipped with a plurality of recesses and energy concentrating elements

摘要

A joining element to be anchored in an object with the aid of a thermoplastic material and mechanical vibration comprises a sealing portion and a wall anchoring portion. The sealing portion is substantially cylindrical and has a smooth circumferential surface. The wall anchoring portion has a circumferential surface which comprises the thermoplastic material and energy directors. A cross section of the sealing portion envelops the cross section (including energy directors) of the wall anchoring portion and is arranged adjoining to the latter on its proximal side. The joining element is anchored in an opening provided in the object wherein a cross section of the opening corresponds to the cross section of the sealing portion of the joining element such that the latter can be forced into a mouth of the opening resulting in a press fit. For anchoring the joining element in the opening, mechanical vibrations e.g. ultrasonic vibrations are coupled into the joining element and the latter is forced into the opening until at least a distal part of the sealing portion is positioned within the opening. Thereby, the thermoplastic material of the circumferential surface of the wall anchoring portion is liquefied and pressed into the opening wall, wherein the sealing portion prevents the liquefied material to penetrate through the mouth and therefore the mouth remains clear cut, i.e. does not get blurred by the liquefied material.