Mechanical pencil with automatic lead feed

Claim 1

In a mechanical pencil with automatic lead feed, a combination comprising tubular housing means having opposite ends; a tubular lead magazine coaxially guided in said housing means moveable between a retracted and an extended position in which one end of the tubular lead magazine projects further beyond one end of said housing means than in said retracted position; a lead guide tube coaxially guided in said housing means in the region of the other end of the latter movable between a first and a second position in which one end of said tubular guide projects through a smaller distance beyond said other end of said housing means than in said first position; first spring means cooperating with said lead guide tube for biasing the latter to said first position; means for feeding a lead from said lead magazine into said lead guide tube and comprising tubular means coaxially guided in said housing means between two end positions and having at one end adjacent said other end of said housing means an inner conical guide face having a large diameter at said one end of said tubular means and tapering from said large diameter toward the axis of said tubular means, clamping means extending longitudinally through said tubular means and comprising a pair of resilient clamping arms having front ends adjacent said conical guide face and biased to move toward the latter and rolling elements carried by said front ends and engaging said conical guide face, said clamping means being movable relative to said tubular means between a rear clamping position in which said rolling elements are spaced from said one end of said tubular means to clampingly engage with clamping faces thereof a lead located therebetween and a forward releasing position, and second spring means between said tubular means and said clamping means and biasing the latter to said clamping position; third spring means between said housing means and said tubular lead magazine for biasing the latter to said extended position and to yieldably couple said tubular lead magazine to said tubular means, whereby during movement of said tubular lead magazine from said extended toward said retracted position, said tubular means is moved from one to its other end position; cooperating means on said tubular magazine and said clamping means for moving the latter together with said tubular means during movement of said tubular means to said other end position while said clamping means remain in said clamping position so as to feed a lead clamped therebetween toward said lead guide tube until said tubular means reaches its other end position, whereby during further movement of said tubular lead magazine to said retracted position said clamping means is moved relative to said tubular means so that said rolling elements move toward said large diameter of said conical guide face causing thereby disengagement of said clamping faces from a lead therebetween; and entrainment means on said lead guide tube constructed to exert on a lead extending through said lead guide tube during movement relative to the tube into said housing means a greater friction force than during movement of the lead relative to the tube in the opposite direction.