| 摘要 |
PURPOSE:To prevent a moving material from going within a certain distance from an object to be examined, by detecting the distance to the object to be examined without contacting and clamping the advance of the moving material when the moving material approaches the object to be examined and releasing the clamping when the moving material goes away. CONSTITUTION:A person S to be examined undergoes the test of eyes with his lower jaw put on a jaw receiving part 4. The light, the ultrasonic wave, or the like emitted from a transmitting and receiving part 5 of a device part 2a is received to measure the distance to the part to be examined. When a moving part 2 is moved forward in the direction of an arrow A, the reflected light is increased by approach if light is used in the transmitting and receiving part 5. Consequently, a clamp-on signal is sent to a solenoid by the quantity of light larger than a certain value. Thus, a damping lever 9 is clamped, and the moving part 2 is stopped by the friction to the lever 9 and cannot be moved forward in the direction of the arrow A furthermore. When the person to be examined pulls back slightly the moving part 2 in the direction of an arrow B against the force of the torque of the lever 9, the quantity of reflected light is smaller than said certain value because the distance to the person S to be examined is longer, and clamping of the moving part 2 is released.
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