To provide a safety device for a pole trailer capable of preventing the breakage of a draw bar connecting a tow car and the pole trailer mutually in advance.
This safety device S1 has a length detector 11 detecting a length of expansion and shrinkage of the draw bar, an alarm signal generation part 21, and an alarm device 31. The alarm signal generation part 21 includes a threshold value storage part 23 and an alarm region advance judging part 25. The alarm region advance judging part 25 reads a value of expansion limit length of the draw bar 3 stored in the threshold value storage part 23, compares a value smaller than the expansion limit length of the draw bar 3 by a predetermined length with a value of expansion and shrinkage length of the draw bar 3 detected by the length detector 11, and outputs an alarm signal to the alarm device 31 judging that a condition of the expansion and shrinkage length of the draw bar 3 approaches the expansion limit length of the draw bar 3 by exceeding a predetermined value if the value of the expansion and shrinkage length of the draw bar 3 detected by the length detector 11 is larger than the value smaller than the expansion limit length of the draw bar 3 by the predetermined length.
YOSHIBA MASATSUGU
KITASHIRO ICHIRO
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