Patent ID: 7665392
Filing Date: 2010-02-23
Classification: B25B,F16D

Abstract:
1. A tightening tool adapted to tighten a fastener, comprising: a motor; a spindle that transmits torque from the motor to a tool bit that can engage with the fastener; a pair of clutch members disposed between the motor and the spindle and comprising a first clutch member and a second clutch member that face each other, the first clutch member is connected to the motor, to be rotated by the motor and the second clutch member is connected to the spindle to rotate with the spindle; and a spring member that pushes at least one of the pair of clutch members towards the other, wherein: one of the pair of clutch members comprises a first engaging portion and a second engaging portion for engaging the pair of clutch members, the first engaging portion and the second engaging portion being formed on a surface that faces the other of the pair of clutch members and being separately arranged along a rotational direction of the pair of clutch members; the other of the pair of clutch members comprises a contacting portion for engaging the pair of clutch members formed on a surface that faces the one of the pair of clutch members, the contacting portion alternatively makes contact with the first engaging portion and the second engaging portion in accordance with rotation of the first clutch member with respect to the second clutch member; the first engaging portion comprises a gradient face with which the contacting portion makes contact to engage the pair of clutch members, the gradient face is angled such that the contacting portion passes over the gradient face to disengage the pair of clutch members when the torque applied to the tool bit is equal to or above a first predetermined value; the second engaging portion is located posterior to the first engaging portion in a direction toward which the contacting portion passes over the first engaging portion such that the contacting portion makes contact with the second engaging portion to engage the pair of clutch members after the first engaging portion has disengaged the pair of clutch members; the second engaging portion comprises a gradient face with which the contacting portion makes contact to engage the pair of clutch members, the gradient face is angled such that the contacting portion passes over the gradient face to disengage the pair of clutch members when the torque applied to the tool bit is equal to or above a second predetermined value; and the gradient face of the second engaging portion is angled at a different angle from the gradient face of the first engaging portion, and the second predetermined value is different from the first predetermined value.