CRAWLER VEHICLE

PURPOSE:To improve traversability in going up and down a stairway, by installing movable auxiliary wheels and then altering the form of a crawler tread. CONSTITUTION:Driving wheels 2, sub-wheels 3 and supporting wheels 4 are all attached to a car body 1 and crawler treads 6 are wound round these wheels at both sides. First arms 7 being pivotally supported by the car body support second arms 8 in a fulcrum manner, and auxiliary wheels 5 attached to these second arms 8. Crawler treads 6 stretched over these auxiliary wheels 5. With both first and second arms actuated, the auxiliary wheels 5 are moved subsequently and thereby the form of each crawler tread can be fittably altered. Accordingly, when the auxiliary wheels 5 are lifted upward, a ground contact area is well reduced so that the steering shift comes easy. Likewise, when the crawler treads get adjusted with the shape of each step by moving them somewhat forward, this crawler vehicle can easily run onto a stairway. And, when the clawler treads are moved backward so as to make contact with the floor surface, the vehicle can prevent a violent fall backward.