| US 7,357,195 B2 | ||
| Power tool and gear unit assembled therein | ||
| Junichi Kamimura, Hitachinaka (Japan); Hiroto Inagawa, Hitachinaka (Japan); Kenichirou Yoshida, Hitachinaka (Japan); and Takashi Kawamata, Hitachinaka (Japan) | ||
| Assigned to Hitachi Koki Co., Ltd., Tokyo (Japan) | ||
| Filed on Apr. 07, 2005, as Appl. No. 11/100,441. | ||
| Claims priority of application No. P2004-116451 (JP), filed on Apr. 12, 2004. | ||
| Prior Publication US 2005/0224245 A1, Oct. 13, 2005 | ||
| Int. Cl. E21B 4/04 (2006.01) | ||
| U.S. Cl. 173—216 [173/210; 173/211; 74/411] | 9 Claims |
| 1. A power tool comprising:
a housing;
a motor disposed in the housing and having a drive shaft;
a gear unit supported in the housing and driven by the drive shaft; and
a rotary shaft rotatably supported to the housing and driven through the gear unit, the gear unit comprising:
an intermediate member force-fitted with the rotary shaft at a predetermined force-fitting pressure, the predetermined force-fitting
pressure allowing the rotary shaft and the intermediate member to rotate relative to each other when a load exceeding a predetermined
load is applied between the rotary shaft and the intermediate member, the intermediate member having an abutment projection;
and
a gear driven by the drive shaft and disposed concentrically with the rotary shaft so as to rotate in at least one direction
about the drive shaft and having a surround portion surrounding the intermediate member and provided with a convex portion,
the surround portion being drivingly connected to the intermediate member to rotate the rotary shaft, the abutment projection
being abuttable against the convex portion when the rotary shaft and the gear are rotated relative to each other.
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