To provide a low-cost constitution having a wide application range without damaging the surface of a long-size object in a slack amount detection device for the long-size object.
A slack amount detection device for a long-size object includes: a first sensor pole 12 disposed on one of both sides with a festoon F therebetween and having a plurality of first light projectors S12 and first light receivers R12 alternately arranged in a vertical direction; and a second sensor pole 13 disposed on the other of both sides with the festoon F therebetween and having a plurality of second light projectors S13 paired with the plurality of first light projectors S12 and second light receivers R13 paired with the plurality of first light receivers R12 alternately arranged in the vertical direction. A plurality of optical sensors 15 consisting of the light projectors S12, S13 and the light receivers R12, R13 are sequentially and separately operated from a non-operation state in which all the light projectors and light receivers are deactivated, and in this case, a slack amount of the festoon F is detected from the height of the optical sensor 15 receiving no signal light.
Tadashi Takahashi
Hiroki Ninai
Makiko Otsuki
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