Patent ID: 6341542
Filing Date: 2002-01-29
Classification: B23P,B25B

Abstract:
A motor-driven screwdriver comprising:a housing having an axial direction; a shaft within said housing; a reversible drive motor at said housing and adapted to drive said shaft; a screw driving tool connected to said shaft; a collet for holding a screw; a collet guide member disposed for axial movement with said collet relative to said housing and said screw driving tool; and a thread transmission disposed between said shaft and said collet guide member and adapted to produce relative axial movement of said collet guide member with said collet relative to said housing and said screw driving tool during rotation of said shaft and said screw driving tool, wherein said thread transmissions comprises a first threaded element formed on said shaft and at least one second threaded element which stands in working engagement with the first threaded element and acts on said collet guide member; and wherein first and second cooperating thread pairs are provided in said thread transmission, said first cooperating thread pair having a first thread pitch and said second cooperating thread pair having a second thread pitch different from said first thread pitch, whereby to produce two different speeds of axial movement of said collet relative to said screw driving tool for a constant speed of rotation of said first threaded element.