PURPOSE: To simplify manufacture of a coupler element and to certainly connect it by integrally forming a plastic clip with a ring disc having an inside diameter equal to an outside diameter of a peripheral groove and having thickness in a groove engagement range equal to width in the axial direction of the peripheral groove respectively and an elastic web having an engagement projection to be engaged with a rear part of an engagement collar.

CONSTITUTION: An inside diameter of a C type ring disc 16 is made equal to an outside diameter of a peripheral groove 15 of an injection nozzle 11, and thickness of a groove engagement range is made equal to width in the axial direction of the peripheral groove 15. Additionally, an elastic web 17 on inner surfaces facing each other of which engagement projections 18 to be engaged with rear parts of an engagement collar 14 of an injection conduit 13 are formed is projected in the axial direction of the ring disc 16, and they are formed as a plastic clip 10 by one member. Consequently, it is possible to manufacture it at low cost and easily and to certainly connect it.