Cap for an ampoule of an injection unit

A closure for an ampoule for an injection unit, said ampoule having a hollow, cylindrical barrel (11) with a distal end and a proximal end, said distal end terminating in a neck (12), an outwardly directed annular projection (30) on the neck, and a piston closing the proximal end of the barrel, said closure comprising:

• a disc shaped part (31);
• a holding cap comprising a proximal section in the form of a skirt (35;62) having one or more interior projections (38) at its proximal end for engagement behind the annular projection (30) of the barrel neck, and a distal section having means for attaching a needle thereto, the holding cap engaging the disc-shaped part (31) pressing it sealingly against the annular projection;
• and a locking ring (20;64) provided on the outside of the skirt (35;62) locking the projections (38) in their engagement position behind the annular projection (30), wherein the locking ring (20;64) and the skirt (35;62) are a pair of elements provided with mutually engaging means in the form of resilient fingers (37;65) on one of the elements, recesses (36;66) are provided behind the fingers in the element carrying the fingers to accommodate said fingers when the locking ring (20;64) is passed over the skirt (35;62), and an edge is provided on the other element not carrying the fingers (37;65) over which edge the fingers (37;65) grip irreversibly when the locking ring is mounted in a locking position on the skirt.