Protective gas mouthpiece for a joining device, the protective gas mouthpiece for supplying a protective gas during a connection process between a connecting element and a workpiece, the protective gas mouthpiece comprising: - a base member partially defining an axial opening extending along a longitudinal axis and a mouth arranged around the opening and which can be placed onto a workpiece, wherein the opening adjacent to the mouth defines a cleaning space in which the protective gas can be introduced and which, when the joining process is carried out, is axially delimited by the workpiece which covers the opening, - at least two protective gas supply channels (38a, 38b, 38c, 38d) are arranged within the base member and directed into the cleaning space, each protective gas supply channel comprising an inlet and an outlet which opens into the cleaning space, the distribution of the protective gas supply over the periphery of the cleaning space being non-uniform so that no outlet is arranged in a peripheral portion which extends over more than 120°, and preferably over more 160°, and - a gas distributor member comprising a distribution chamber, the inlets of all the protective gas supply channels opening into the distribution chamber, the gas distributor member extending from an end of the base member opposite the mouth, wherein the base member comprises a flattened portion and a frustroconical shape, characterized in that the base member further comprises a notch provided opposite the flattened portion, wherein the inlets are arranged on the flattened portion and the gas distributor member is fixed to the flattened portion, and wherein each protective gas supply channel (38a, 38b, 38c, 38d) comprises at least one straight portion and one bent portion such that an interfering contour for the gas flow is significantly reduced. - a base member partially defining an axial opening extending along a longitudinal axis and a mouth arranged around the opening and which can be placed onto a workpiece, wherein the opening adjacent to the mouth defines a cleaning space in which the protective gas can be introduced and which, when the joining process is carried out, is axially delimited by the workpiece which covers the opening, - at least two protective gas supply channels (38a, 38b, 38c, 38d) are arranged within the base member and directed into the cleaning space, each protective gas supply channel comprising an inlet and an outlet which opens into the cleaning space, the distribution of the protective gas supply over the periphery of the cleaning space being non-uniform so that no outlet is arranged in a peripheral portion which extends over more than 120°, and preferably over more 160°, and - a gas distributor member comprising a distribution chamber, the inlets of all the protective gas supply channels opening into the distribution chamber, the gas distributor member extending from an end of the base member opposite the mouth, wherein the base member comprises a flattened portion and a frustroconical shape, characterized in that the base member further comprises a notch provided opposite the flattened portion, wherein the inlets are arranged on the flattened portion and the gas distributor member is fixed to the flattened portion, and wherein each protective gas supply channel (38a, 38b, 38c, 38d) comprises at least one straight portion and one bent portion such that an interfering contour for the gas flow is significantly reduced.