Abstract: An automatic lead pencil device has a casing which is releasably mountable in a bracket of a drafting machine. Within the casing, there is a clamp sleeve in which a clamping member is axially movable for clamping and releasing a lead during use of the pencil device. An axial movable lead guide tube projects outwardly of the casing in the rest position, and there is a pencil brake within the lead guide tube. The contact zone between the clamping member and the clamp sleeve is constructed so as to be of the non-self-locking type. There is an operative connection between the clamping member and the lead guide tube such that the clamping member is closed when the lead guide tube moves axially inwardly to assume the working position and opens when the lead guide tube moves axially outwardly toward a rest position.

Abstract: An automatic lead advancing mechanism for a mechanical pencil has at its writing point a lead guide tube which is movable axially against a clamping member to cause radially movable components of the clamping member to clamp the lead therein during the writing position of the pencil. The lead guide tube moves axially inwardly against a force exerted by a compression spring interposed between the clamping member and a thrust member, a portion of which is engaged by the lead guide tube and another portion of which has a beveled surface engaging a correspondingly beveled surface on the clamping member. The co-acting beveled surfaces exert both axial and radial forces to the clamping member.