TRACK FRAME OF SWIVELING OPERATION CAR

PROBLEM TO BE SOLVED: To prevent a harmful influence on the movement of the center of gravity occurring in case construction applied to a compact swiveling operation car with high swiveling efficiency is applied to a large-sized swiveling operation car in a state to remain unchanged as well as a large-sized machine-tool for machining parts. SOLUTION: For a member mounted to a track frame 1, a swivel joint mounting member 3 is formed of a cutting square bar SS, and a bearing mounting seat 4 is welded to the track frame 1 after the machining. An upper plate 1U of the track frame 1 is constituted of left and right upper plates 1UL and 1UR divided into left and right parts, a bent section P1 of a rear rib plate 1R between upper plate 1U and lower plat 1D is closed to the center between both left and right, and distance L between the front ends P2a of the rear rib plates 1R of welding sections in the upper surface of a crawler frame 2 and the front ends P3a of front and middle rib plates 1MR is lengthened.