Writing implement with tip having attaching projections

In a writing implement having an elongated hollow barrel with an inner wall surface, a spiral groove on the inner wall surface, a cap rotatably mounted at one end of the barrel, a part-annular elongated supporting member extending from the cap into the hollow barrel to be rotated within the barrel by rotation of the cap, a tip attachable to the other end of the barrel, a bore through the tip coaxial with the central axis of the barrel to slidingly receive a writing element therein, a carrier within the barrel adapted to engage with the writing element, and a guide element projecting from the outer surface of the carrier engaging in the spiral groove, the carrier engaging with the supporting member so that rotation of the cap and supporting member with respect to the barrel drives said carrier rotatably and axially in said barrel to move the writing element axially through the tip, the improvement comprising:

• multiple spiral grooves on the inner wall surface of the barrel so that the guide element of the carrier within the barrel is selectively engageable with one of said multiple spiral grooves;
• an insert portion on the tip rotatably attachable in the other end of the barrel;
• and
• multiple spiral protrusions projecting from the outer surface of said insert portion corresponding to and engageable with said multiple spiral grooves.