To keep the tensile force of a crawler constant by providing a rack pinion mechanism linearly reciprocating a tension ring in response to the relative rotary change of a link against a truck frame.
A truck frame 26 provided with multiple idler rollers 21 and a tension roller 22 is lowered against a fixed frame 25 supporting a drive wheel 20. Multiple rollers 21 and the tension roller 22 are separated from the drive wheel 20 to increase the tensile force of a crawler. When the truck frame 26 is lowered, the attitude of a rear link 28 is changed against the truck frame 26. A pinion 35 is rotated, and the rotation is transferred to a rack 34 provided on the side of the tension roller 22. The rack 34 is moved linearly forward, and the tensile force of the crawler is kept constant. When the truck frame 26 is lifted, the pinion 35 is reversely rotated, the rack 34 is moved linearly backward, and the tensile force of the crawler is kept constant.
FUJITA SHIGEO
TAKENAKA MITSURU
SOYA TAMOTSU
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