Nakanishi Dental Mfg. Co., Ltd.

Norimasa Kaneko

Tadashi Baba

A rotational coupling device for a cordless dental instrument including a motor housing which has a pair of semi-annular projections integrally provided at a rear end thereof with a pair of arc-shaped recesses formed between the coupling projections and semi-annular slot provided around the inner peripheries of the semi-annular projections. A battery housing has a pair of semi-annular around an outer periphery adjacent its front end, a pair of arc-shaped projections coinciding with the arc-shaped recesses of the motor housing and a pair of semi-annular flanges coinciding with the pair of semi-annular projections of the motor housing so as to form a rotational coupling between the motor housing and the battery housing. An insulating disc having a pair of contacts connected to a motor fits into a rear opening of the motor housing. Another insulating disc having a pair of arc-shaped guide slots fits into a forward opening of the battery housing, each slot including a positive contact, a negative contact and a neutral non-contact point which are selectively connected to the pair of contacts of the motor housing. The motor housing has a standard marking, which is rotatably aligned with a normal marking, a reverse marking and a neutral, marking on the battery housing to drive the drive motor in a normal direction, in a reverse direction or to stop the motor, respectively.

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Utsunomiya, Japan

Norimasa Kaneko