| 摘要 |
Air driven dental handpiece motors include a tubular housing and a rotor rotatably supported within the housing. One motor is geared down by the provision of a plurality of idler gears rotatably supported on a hub which rotates between a sun gear on the output end of the rotor and a ring gear fixed within the housing. A drive shaft connects an exposed drive gear with the hub. A bearing is provided between the drive shaft and the inner bore of skirt extending from the ring gear to reduce a number of tolerances built up between the drive shaft and the bearing. The motor further includes a valve member rotatable through about 140.degree. of arc to vary maximum motor speed and motor rotation direction. The valve member abuts a valve plate having a circular air inlet opening and a semicircular air outlet or exhaust opening. The valve member has an air supply opening which is an elongated arcuate slot having radiused circumferential ends. Shallow, curvilinear recesses are provided in line with circumferential outer and inner walls of the central slot at each circumferential end of the slot and provide fine, low speed adjustment capability to the valve. Deeper recesses at the center of the slot provide an effective air supply orifice diameter at least as great as the effective orifice diameter of the valve plate inlet air opening to maximize top motor speed.
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