| 摘要 |
A handpiece for dental use has primary and secondary housings arranged concentrically and slidably with respect to each other. A primary drive shaft mounted to rotate within the primary housing is connected slidably, preferably by splines, with a secondary drive shaft mounted to rotate within the secondary housing so that the handpiece can be extended and retracted for work. The primary housing may also have a planetary transmission, the planets in which drive a quill concentric with a motor shaft mounted to rotate in the primary housing and connected to the transmission. The primary shaft is slidable to engage the motor shaft directly and alternatively to engage the quill. Controls accessible from the exterior of the housings are effective to slide the housings relative to each other and to engage and disengage the planetary transmission and the motor shaft.
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