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(11) | EP 2 236 249 A3 |
(12) | EUROPEAN PATENT APPLICATION |
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(54) | Hammer drill |
(57) In a hammer drill (1), a torque limiter includes: a cam ring (14) adjacent to a gear
(13), and configured to be provided onto a tool holder (6) so as to be unitarily rotatable
with the tool holder (6) and to have cam projections (18) on a surface facing to the
gear (13); rollers (21) received in corresponding through-holes (20) formed in the
gear (13) and engageable with the cam projections (18) in their rotational directions;
and urging means (washer (16) and coil spring (17)) configured to urge the rollers
(21) toward the cam ring (14) so that the rollers (21) are brought into engagement
with the cam projections (18), and when a torque applied to the tool holder (6) exceeds
a setting torque, the rollers (21) pass the cam projections (18) within the through-holes
(20) against the urging means and roll on the cam ring (14), so that the gear (13)
slips on the cam ring (14) to thereby uncouple the torque transmission to the cam
ring (14).
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