US Patent 7334646 Electric power tool with improved speed change gearing

A battery-operated driver-drill (1) includes an epicycle reduction gear unit (8) which encases a switchover sleeve (26) having inner teeth (27) and outer teeth (28). The gear unit (8) is rotatably mounted on second and third internal gears (19, 20) and integrally slidably connected with a slide pate (37). By operating the slide plate (37), the switchover sleeve (26) may be slid between a first position, in which the slide plate (37) engages one of the second and third internal gears (19, 20) while engaging axial ridges (29) of a first gear case (5), and a second position, in which the slide plate (37) simultaneously engages both the second internal gear (19) and a first carrier (10) adjacent to the second internal gear (19) while disengaged from the axial ridges (2).