the front body and rear body 2 3 and configured such that the writing point 10 is retracted into the front body 2 when the front and rear bodies 2 3 are in the intermediate position illustrated in fig1 and projecting beyond the front end of the front body 2 when the front and rear bodies 2 3 are in the positions illustrated in fig2 and 3 the angle of rotation a of the rear body 3 relative to the front body 2 between the intermediate position illustrated in fig1 and each of the positions illustrated in fig2 and 3 can be 120 u00b0 for example fig4 illustrates an exploded perspective of the instrument 1 showing its internal components in this way inside the instrument 1 illustrated the latter contains an elastic element 11 in the form of a helical spring a standard ballpoint refill 12 a slide 13 and a tubular piece 14 the refill 12 comprises the writing point 10 and an ink tank 15 and is received inside the slide 13 which is open to the front and at least partially closed to the rear the elastic element 11 supported against the internal face of the nozzle 5 at the front end of the front body 2 presses the refill 12 against the bottom of the slide 13 as is evident from fig5 which is a transversal section.