Writing instrument with a locking device

A writing instrument comprising:

• a first portion and a second portion, the second portion being at least partially fitted into the first portion and being moveable in an axial direction relative to the first portion;
• the first portion includes a first distal end while the second portion includes a second distal end opposite the first distal end and a locking device disposed in the second distal end;
• the first distal end includes a writing tip or a nib;
• the locking device includes a chamber and a lock mechanism accommodated in the chamber;
• the chamber, being provided only in the second portion, includes a wall which is moveable between a first position and a second position;
• when the first distal end is below the second distal end and positioned in a direction of gravity only, the lock mechanism under a force of gravity forces the moveable wall to move into the first position preventing the first portion from moving in the axial direction relative to the second portion;
• and
• when the first distal end is arranged above the second distal end, the lock mechanism moves towards the direction of gravity and locks the moveable wall in the second position.