| 摘要 |
The actual step 1 has, at its ends, supports or brackets (heel plates) 3 extended beyond its lower rear edge, on which there are a pair of articulation pins 4 and 5 by means of which a pair of connecting rods 6 and 7 are joined to each one of the supports 3, said connecting rods in turn being joined in an articulated manner via their other end to respective pins 8 and 9 mounted on the fixed structure 10 of the element with which the step is associated, the lower connecting rods 6 being actuated by pistons 11 and in such a manner that the said connecting rods 6 and 7, the fixed structure 10 and the support 3 determine a deformable quadrilateral for which two limit positions are defined, that of retraction and that of operation of the step, in which the centre of gravity of said step is located at minimum levels between which there is an intermediate dead point at which the height position of said centre of gravity is at its maximum. <IMAGE>
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