| 摘要 |
PURPOSE:To prevent a void part from being contaminated by providing a check valve between the arranging part of an ultrasonic transmitter/receiver and a duct in the void part, filling the void part and the duct with liquid for ultrasonic wave propagation, and shutting off the void part and duct. CONSTITUTION:In order to prevent a foreign matter in a duct 27 from going into a void part 22, a check valve 33 is provided at a position close to a joint part 21 rather than the arranging position of an ultrasonic transmitter/receiver 11 in the void part 22. The check valve 33 allows the flowing of liquid from the void part 22 side to the duct 27 and presents the function to prevent the liquid from reversely flowing from the duct 27 side to the void part 22. Thus, the inside of the void part 22 is kept clean and the propagation of ultrasonic waves is not obstructed. Further, bubbles are easily generated on the side of a flexible shaft 13 and it is necessary to keep the bubbles from entering into the void part 22. However, the check valve 33 surely prevents the bubbles from going from the duct 27 side to the void part 22. |
