Abstract: A writing instrument is provided, including a writing tip, a reservoir containing a liquid ink, and a capillary transfer rod extending from a first end to a second end of the reservoir. The capillary transfer rod transfers the liquid ink from the reservoir to the writing tip. A capillary element having an orifice is slidably mounted around the capillary transfer rod so as to move freely in the reservoir. An outside edge of the capillary element comes into the immediate vicinity of an inside wall of the reservoir in such a manner that the capillary element comes substantially flush with an inside wall of the reservoir as it slides along the transfer rod.

Abstract: In a pencil having a central lead, provided at its top end with an eraser mounted in a ferrule fixed on the body of the pencil, both the ferrule and the peripheral body surrounding the lead are made of thermoplastic materials that are compatible, and the bottom of the ferrule is fixed to the top end of the pencil by localized interpenetration of the thermoplastic materials in at least one ultrasonic weld zone. The material of the peripheral body of the pencil is preferably expanded so as to have a relative density of about 0.5 to 0.6, and the top end of the body includes a setback in which the density has been increased, locally. The ferrule includes a shoulder on the outside face of its bottom, the shoulder being annular in shape and forming an energy director for ultrasonic welding.