| 摘要 |
PURPOSE:To enable a fail-safe safety device, by arranging an emission means and a detection means for light, electromagnetic waves, ultrasonic waves and the like to face each other through the inside of a tube comprising a soft material. CONSTITUTION:While a man or an object is off a rubber tube 4, the tube 4 is stretched straight to allow the admission of light into a light-receiving element 8 from a light-emitting element 3 and an input is applied to a relay connected to the element 8 to close a relay contact, so that the contact detection signal will not be outputted. Then, when a man or an object 19 gets in contact with the tube 4 to bend or squeeze it 4 to more than a certain extent, light of the element 3 intercepted by a part of the wall surface of the tube 4and will not reach the element 8 at all or will do being reduced below a fixed level, so that the relay contact is opened to output the contact detection signal. Also when the elements 3 and 8 and the like fail to work owing to a trouble or interruption of the power source, the relay contact is opened to output the contact detection signal. Thus, the safety side output (contact detection signal) is sure to be produced when encountering an abnormality, thereby enabling a fail-safe safety device.
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