Patent ID: 6905273

Claim:
A pen comprising a first casing and a writing unit which is inserted into the first casing in the form of a refill or a writing fluid storage means characterised by a first stop which is coupled to the writing unit and which is operative in the peripheral direction about the longitudinal axis L of the writing unit, a second stop which is coupled to the first casing and which is operative in the peripheral direction about the longitudinal axis L and which co-operates with the first stop in a predetermined first rotational position of the writing unit with respect to the first casing, wherein the first and second stops butt against each other in the predetermined first rotational position, a third stop which is coupled to the writing unit and which is operative in the direction of the longitudinal axis L, and a fourth stop which is coupled to the first casing and which is operative in the direction of the longitudinal axis L and co-operates with the third stop, wherein the third stop is in the form of a guide device for the fourth stop, along which the fourth stop is displaceable upon rotation of the writing unit with respect to the first casing until the predetermined first rotational position is attained.