| 摘要 |
A power-driven bolt fastening tool or shearing wrench includes an outer socket adapted to fit over the head of a bolt to be fastened and an inner socket disposed coaxially in the outer socket and adapted to fit over the tip of the bolt. A planetary gear mechanism comprises an internal gear coupled to the outer socket through a lost-motion connection, planet gears supported on shafts coupled to the inner socket, and a sun gear in mesh with the planet gears. The lost-motion connection comprises a torsion spring acting between the internal gear and the outer socket for allowing the internal gear to angularly move for a limited angular interval before the outer and inner sockets fit fully over the bolt head and tip and before a fastening torque is transmitted from the sun gear to the outer socket.
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