Writing instruments

A writing instrument comprising a body extending along an axis, the body having a first end and a second end opposed to the first end along the axis, the first end being provided with a writing tip and with an eraser, the writing instrument further comprising a first helical cam propelling mechanism configured to move the writing tip along the axis between a retracted position and a protruded position and a second helical cam propelling mechanism configured to move the eraser along the axis between a retracted position and a protruded position, the first helical cam propelling mechanism comprising a first cam follower and a first helical cam, the second helical cam propelling mechanism comprising a second cam follower and a second helical cam, each of the first cam follower, the first helical cam, the second cam follower and the second helical cam being provided on distinct elements, wherein the first helical cam propelling mechanism and the second helical cam propelling mechanism are configured to be actuated and, when actuated together, the first helical cam propelling mechanism and the second cam propelling mechanism are configured to move the writing tip from the retracted position to the protruded position first, move the eraser from the retracted position to the protruded position after moving the writing tip from the retracted position to the protruded position, and then move both the writing tip and the eraser back to the retracted position.