| 摘要 |
<p>An electrically powered hammer comprising a hammer housing (10) with a hollow cylindrical spindle (4) mounted within it. The hammer has a tool holder arrangement (36) located at a forward end of the spindle for releasably holding a tool or bit (34) within the spindle so as to enable limited reciprocation of the tool or bit within the spindle. An air cushion hammering mechanism is mounted within the spindle for generating repeated impacts on the tool or bit which hammering mechanism includes a piston (24). A motor is mounted within the housing for rotatingly driving an intermediate shaft (6) rotatably mounted in the housing. A wobble drive arrangement (12, 16, 18, 20) reciprocatingly drives the piston (24) and includes a wobble sleeve (12) rotatably mounted on the intermediate shaft (6). A mode change element (72) is selectively engageable, by movement along the intermediate shaft, with a set of drive teeth (74) provided on the intermediate shaft and a set of driven teeth provided on the wobble sleeve, such that when the mode change element (72) is engaged with both sets of teeth it transmits rotary drive from the intermediate shaft (6) to the wobble sleeve (12) so that the wobble sleeve arrangement reciprocatingly drives the piston (24). The mode change ring (72) is formed integrally with at least one axial stop surface (86) and the or each axial stop surface (86) is engageable with a cooperating end stop surface formed integrally with one of the intermediate shaft and the wobble sleeve to limit the movement of the mode change element along the intermediate shaft. <IMAGE></p> |
