Patent ID: 7213894

Claim:
A shaft for rotatably supporting a roller wheel used in a crawler type traveling apparatus, the shaft comprising: end portions having the roller fitted therebetween; a middle portion having the roller fitted thereon; a bushing interposed between an inner peripheral surface of the roller and an outer peripheral surface of the middle portion; and a center portion provided in a site of the middle portion which does not correspond to the bushing, wherein said shaft receives a load from the roller along a diametrical direction of the shaft, and a cross-section of the middle portion of the shaft excluding the center portion is constituted by an upper portion and a lower portion, each of which receive the load from the roller, and a connection portion connecting the upper and lower portions; wherein the shaft further includes a first pair of recess portions extending in a horizontal direction from the connection portion and a second pair of recess portions provided at an outer peripheral surface of the center portion in a vertical direction.