Abstract: Apparatus for screwing a writing instrument tip into a writing fluid reservoir in a writing instrument in which the connection from the reservoir to the tip, in order to supply the writing fluid to the tip, is made by the screwing action just prior to using the writing instrument, in which the writing instrument tip has at least a first working surface upon which at least a second working surface of a wrench acts, the working surfaces being formed as a ratchet and pawl which only engage in a screwing direction and permitting a relative rotation of the working surfaces in an unscrewing direction. As a result the tip cannot be unscrewed from the writing fluid reservoir, avoiding contamination, air entry or blockages.

Abstract: An axially removable cylindrical holding shaft or cap for placement over and for unscrewing or removing the tip of a writing or drawing instrument, the holding shaft or a cap having a receiving bore for the instrument tip, and being comprised of at least one approximately axially extending lever which can be tilted about an axis extending approximately tangentially to the cylinder wall. The lever has an arm on each side of the axis. One of the arms forms part off the wall and has a detent at its end, the detent projecting into the receiving bore for engaging a groove or an undercut of the tip when the tip is inserted into the receiving bore, fixing the tip in the axial direction. The structure makes it possible to clean the adjustment system of the tip, avoiding the danger of getting it dirty, and without touching the tip while reinserting it into the housing.