Hitachi Koki Co., Ltd.

Shigeru Ishikawa

Shinki Ohtsu

Kenji Kataoka

Hideki Watanabe

Takuma Saito

Kazuhide Ohzeki

Jyunichi Toukairin

Yukio Terunuma

Junichi Tokairin

A vibration drill unit capable of obtaining an intensive drilling force. The vibration drill unit includes a first ratchet, anon-rotatable second ratchet having a claw engageable with the claw of the first ratchet, and a main body frame for accommodating a motor, a spindle, the first ratchet and the second ratchet. The respective claws of the first ratchet and the second ratchet include the first inclined surfaces formed so as to be engaged in the rotation direction by rotations of the first ratchet and so as to be separated from each other, the second inclined surfaces having greater inclination in the reversed direction than the first inclined surfaces, top parts that link the upper parts of both inclined surfaces to each other, and flat parts that link the bottom parts of both inclined surfaces to each other.

Vibration drill unit

An impact drill for boring a workpiece includes a main frame, a motor housed in the main frame, a spindle movably supported by the main frame and rotatable by the motor and movable in its axial direction, a first ratchet positioned fixedly with respect to the spindle, a second ratchet positioned with respect to the first ratchet, a spring biasing the second ratchet toward the first ratchet. The spring has at least one of a spring constant and a biasing force which prevents the second ratchet and the spindle from abutting against the main frame at least one of when a force ranging from 15 to 25 kg is applied to the main frame for boring the workpiece and when the spindle is moved to a retracted position.

Impact drill

An impact drill minimizing transmission of vibration to a handle gripped by a user's hand. A spindle extends through a main frame and is movable in its axial direction and rotatable about its axis. A first ratchet is rotatable and axially movable together with the spindle. A second ratchet is axially movable but unrotatable. In an impact drilling mode, the first ratchet is brought into abutment with the second ratchet so that the spindle is reciprocally moved in the axial direction.

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Hitachinaka, Japan

Shigeru Ishikawa