PENCIL HAVING AN ERASER-HOLDING FERRULE SECURED BY ULTRASONIC WELDING, AND A FERRULE ADAPTED FOR THAT PURPOSE

摘要

In a pencil having a central lead, provided at its top end with an eraser mounted in a ferrule fixed on the body of said pencil, both the ferrule and the peripheral body surrounding the lead are made of thermoplastic materials that are compatible, the bottom of the ferrule is fixed to the top end of the pencil by localized interpenetration of said 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 said body includes a setback in which said 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.