| 摘要 |
A two-speed power transmission for a power tool comprises a housing (10), an input shaft (20), an output shaft (15), a planetary gear (18) and a torque responsive gear shift mechanism (19) for directing torque through the planetary gear (18) in a high torque/low speed drive mode or past the planetary gear (18) in a low torque/high speed drive mode. The gear shift mechanism (19) comprises a driving member (26) connected to the sun wheel (21) of the planetary gear (18), a driven member (27) connected to the output shaft (15), and a number of axially movable coupling elements (30) arranged to intercouple in a first position the driving member (26) and the driven member (27) and intercouple in a second position the planet wheel carrier (24) of the planetary gear (18) and the driven member (27). The coupling elements (30) are continuously supported in the radial direction by an axially extending coupling sleeve (28) formed in one piece with the planet wheel carrier (24). A first cam (35) on the driving member (26) exerts an axial force on the coupling elements (30) against the action of a biassing spring (31) to move the coupling elements (30) from the first to the second positions, and a second cam (36b) on the driven member (27) for exerting an axial shifting force upon the coupling elements (30) toward the second positions of the coupling element (30) as they have left their first positions. |
