Patent ID: 7284774

Claim:
In a plug-in coupling for connecting a fluid line with a pipe, wherein the pipe includes a holding rib extending in a circumferential direction, the plug-in coupling comprising a pipe piece having a first end portion connectable to the fluid line and a second end portion adapted to be plugged together with the pipe, further comprising a coupling ring having a first coupling ring part and a second non-circular elastically expandable coupling ring part, wherein the second end portion is connectable to the first coupling ring part which is connected through elastic holding arms to the second coupling ring part, wherein the second coupling ring part has locking sections which are distributed over a predetermined circumferential angle range of a circumference of the pipe piece, wherein, when the pipe and the pipe piece are being plugged together, the locking sections slide over the holding rib and expand the second coupling ring part and engage behind the holding rib, wherein components located between the locking sections of the second coupling ring part are arched outwardly, wherein the improvement comprises that the second coupling ring part has at least three locking sections and the circumferential angle range is greater than 180°, wherein the outwardly arched parts protrude beyond a circumscribed circle of the locking sections.