Patent ID: 8066302

Claim:
A center frame in a crawler tractor, the center frame comprising: a center member made of a metal sheet and supporting an upper rotating body; a pair of front legs and a pair of rear legs made of a metal sheet and disposed on each of left and right sides of the center member such that there are spaces between the pair of front legs and the pair of corresponding rear legs; a lower plate to which the center member and the pair of front legs and the pair of rear legs are welded and fixed; a center front plate welded and fixed to a front face side of the center member and the lower plate; a center rear plate welded and fixed to a rear face side of the center member and the lower plate; a pair of blade support brackets disposed on the center front plate; and a cylinder support bracket for a blade actuating cylinder; wherein the center member comprises a circular base for supporting the upper rotating body in a central area of the metal sheet and is formed to have a substantially reverse square U-shaped cross-section having straight folding portions that are axisymmetrical relative to a center line extending in a front and rear direction of the center member; wherein each of the legs formed separately from the center members has a substantially reverse U-shaped cross-section by bending; wherein the lower plate has an approximate X shape which is pronged in two in the front and rear direction on both right and left sides and the right and left sides are bent to be formed in an isosceles trapezoidal shape in a lateral cross-section, and are bent in the same angle along the straight bending line which is parallel and line-symmetric with the center line in the front and rear direction of the lower plate; and wherein one end of each of the legs is welded and fixed to a corresponding bent side face of the center member.