| 摘要 |
PURPOSE:To prevent the sucking-in of a contaminant by a handpiece after the rotation of the handpiece is stopped, by respectively connecting an oxygen source to drive air, discharge air and chip air pipes through oxygen valves and providing a check valve to a water flow passage. CONSTITUTION:When the use of a handpiece 7 is stopped, a three-way valve 1v is changed over not only to close the communication of connection ports 1x, 1y but also to allow connection ports 1y, 1z to communicate with each other, and the valve 1w and three-way valve 5v constituting an oxygen valve are changed over to send oxygen gas in the handpiece 7 from an oxygen source 5a in a proper flow rate to prevent the part of the handpiece from becoming negative pressure. At this time, valves 2w, 3w, 4w are opened and three-way valves 2v, 3v, 4v are changed over if necessary to respectively supply oxygen gas into an exhaust pipe 2, a chip air pipe 3 and a water pipe 4. That is, operation for stopping the rotation of the handpiece to prevent the generation of internal negative pressure before the rotation is perfectly stopped and the sucking of a contaminant into the handpiece is prevented. |
