| 摘要 |
A high speed air-driven powerhead in a dental handpiece includes an automatic chuck with outside surfaces protection from overheating. An autochuck release push button on the back of the powerhead is constructed of low thermal conductivity and heat reflective materials to reduce heat due to friction from inadvertent contact with the chuck while rotating. In addition, a sudden stop mechanism is provided which arrests chuck rotation if the force of contact exceeds a level which would raise the temperature of the push button beyond a predetermined threshold. A vortex air barrier is also provided to seal the front end bearing of the powerhead. The barrier also permits spacing which prevents static axial overload of the bearing and eliminates possible damage to the bearing.
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