Hitachi Koki Co., Ltd.

Takeshi Kamo

Yasuo Sasaki

Michio Wakabayashi

Haruhiko Oouchi

Akira Uno

A pneumatically operated screw driver ensuring a complete return of a piston to its top dead center. The screw driver has a compressed air return chamber for returning the piston to its top dead center by applying a compressed air in the return chamber to the piston. The piston includes a main piston and an auxiliary piston. The main piston is first reaches its bottom dead center, and then the auxiliary piston reaches its bottom dead center whereupon screw driving is terminated. Before the auxiliary piston reaches its bottom dead center, and after the main piston moves past a predetermined position, a compressed air is introduced into the return chamber. After the main piston reaches the bottom dead center, application of the compressed air pressure in the return chamber to the auxiliary piston is prevented.

Pneumatically operated screw driver

A pneumatically operated screw driver ensuring a complete return of a piston to its top dead center. The screw driver has a compressed air return chamber for returning the piston to its top dead center by applying a compressed air in the return chamber to the piston. The piston includes a main piston and an auxiliary piston. The auxiliary piston includes a piston section and a flange section those being disposed in the main piston. The piston section is slidably movable relative to the main piston, and the flange section is axially spaced away from the piston section and radially spaced away from the main piston. After the main piston reaches its bottom dead center, the auxiliary piston further moves toward its bottom dead center. An air space chamber is provided between the piston section and the flange section and within the main piston.

A compact and light-weight pneumatically operated screw driver providing high speed screw fastening with high operability. A rotary member rotationally driven by a pneumatic motor includes a main rotary member made from a plastic material and a sliding segment fixed to the main rotary member. A rotation slide member is axially slidably movable relative to the rotary member and is rotatable together with the rotation of the rotary member. A shut-off section is provided on which the rotation slide member is rotationally seated when the rotation slide member is moved toward the shut-off section. The rotation slide member is made from an elastic material. A sleeve like piston having a seal ring in sliding contact with a cylinder is provided. The seal ring shuts off a supply of compressed air to the pneumatic motor only by the seating of the rotation slide member onto the shut-off section.

Two guide members cooperatively constitute a chuck portion for holding a screw head. Opening and closing of the chuck portion is regulated depending on a mutual position between a machine body and a member into which a screw is driven. Guide pin portions of respective guide members engage with a stopper portion of a push lever until a screw is driven to a predetermined depth. The chuck potion tightly holds the screw head until a screw fastening operation is substantially finished, thereby suppressing the lifting of a machine body.

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Hitachinaka, Japan

Takeshi Kamo