| 主权项 |
1. A lattice piece for a crane, comprising:
four corner posts comprising a first pair of corner posts comprised of a first corner post and a second corner post parallel to each other and a second pair of corner posts comprised of a third corner post and a fourth corner post parallel to each other, wherein the first pair of corner posts and the second pair of corner posts are parallel to each other; and null bars foldably hinged about swivel axes, the null bars comprising:
a first null bar connecting one end of the first corner post and one end of the second corner post;a second null bar connecting the other end of the first corner post and the other end of the second corner post;a third null bar connecting a center of the first corner post and a center of the second corner post;a fourth null bar connecting one end of the third corner post and one end of the fourth corner post;a fifth null bar connecting the other end of the third corner post and the other end of the fourth corner post; anda sixth null bar connecting a center of the third corner post and a center of the fourth corner post; diagonal bars, a length of which is adjustable, the diagonal bars foldably hinged about swivel axes, comprising:
a first diagonal bar connecting the first corner post and the second corner post in a way that the first diagonal bar is diagonally positioned in a space formed from the first null bar and the third null bar connecting the first and second corner posts;a second diagonal bar connecting the first corner post and the second corner post in a way that the second diagonal bar is diagonally positioned in a space formed from the second null bar and the third null bar connecting the first and second corner posts;a third diagonal bar facing the first diagonal bar and connecting the third corner post and the fourth corner post in a way that the third diagonal bar is diagonally positioned in a space formed from the fourth null bar and the sixth null bar connecting the third and fourth corner posts; anda fourth diagonal bar facing the second diagonal bar and connecting the third corner post and the fourth corner post in a way that the fourth diagonal bar is diagonally positioned in a space formed from the fifth null bar and the sixth null bar connecting the third and fourth corner posts;wherein the lengths of the first and third diagonal bars are extended and the second and fourth diagonal bars are retracted when the lattice piece is folded;the lengths of the second and fourth diagonal bars are extended and the first and third diagonal bars are retracted when the lattice piece is erectedthe extended lengths of the first and third diagonal bars are longer than the extended lengths of the second and fourth diagonal bars. |
