The invention relates to a device for moulding a plastic article in which the article is obtained by the compression of a quantity of plastic material (3) in the molten state between the two parts of a mould, comprising at least one supply of plastic material (1), a rod (11), sliding in a sleeve (8) suitable for temporarily supporting said quantity of plastic material (3), a mould for the head of the article (6, 7) and a mandrel (18) cooperating with said mould (6, 7), characterized in that it comprises non-elastic retaining means (12-14, 23, 24) which are suitable for limiting the bidirectional displacement of the rod (11) in the sleeve (8). The invention also relates to a method using the aforementioned device.