| 摘要 |
A hammer drill may be set for operation in a hammer mode or a drill mode through a mode selector 41. In the drill mode, output shaft 25 is locked in a forwardly biased position and is rotatably driven through spur gears 29, 31. In the hammer drill mode, output spindle 25 is rotatably driven by spur gears 29, 31 and is axially reciprocated by hammer clutch 55. An output clutch plate 57 of clutch 55 is axially and rotatably fixed to spindle 25 and has a first annular tooth array 63 on rear face 61. An input clutch plate 59 of clutch 55 is axially and nonrotatably fixed in tool housing 15 and has a second annular tooth array 67 on a forwardly inclined front face 65. Tooth arrays 63, 67 are engageable in the hammer mode. Output clutch plate 57 is shiftable in use in the hammer mode to position the rear face 61 generally parallel to the front face 65. The forward inclination of input clutch front face 65 compensates for the movement of output clutch rear face 61 from a no-load to a load position so that the faces 65, 61 are generally parallel in use. By ensuring parallelism of the clutch faces 65, 61 in use, clutch 55 has a significantly improved life.
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