| 摘要 |
<p>Impulse drive traction and device comprising at least a pair of support elements (1, 1', 1 '', 2, 2,', 2 '') reciprocally movable between a proximal position and a distal position along a direction. Each of said elements has a variable coefficient of friction with respect to a support surface (S,W). During a reciprocal approaching step, a first of said element develops a friction force (Ff1) which makes it integral with said support surface; a second of said elements develops a lower friction force (Ff2) with respect to that developed by said first element, sliding towards said first support element of said support surface. During a reciprocal departing step of said support elements, the friction force (Ff2) developed by said second element is higher than that (Ff1) developed by the first of said elements, therefore the traction device moves forward along said direction.</p> |
