Pusher mechanism and system for tensioning a strap including such mechanisms

A pusher mechanism comprising a column (1, 7) capable of being subjected to a compression or pulling force in operation and having a height (H) defining a first direction, a width (l) and a thickness (E), the thickness (E) being constant, the height (H) being variable in operation between a value at rest (H0) and a maximum value (HM) and the width (l) being variable in operation between a value at rest (l0) and a minimum value (lm), said column comprising two uprights (2, 3;

• 27, 37) facing one another extending according to the height (H) and thickness (E), and reversible means (6, 67) supported by said uprights and designed to convert a compression force exerted on the uprights according to the width (l) of the column into a movement according to said first direction of the column whose width (l) then decreases (l<l0) and whose height (H) increases (H>H0), and vice versa, characterized in that the reversible means comprise:
• at least two corner-forming parts (50 to 59, 60) which extend according to the thickness (E) and have at least one surface defining a first inclined plane (510 to 590;
• 531 to 571), with respect to a plane at right angles to said first direction, said at least two first parts being each secured to one of the two facing uprights, by being situated on different uprights, and
• at least one complementary second part (40 to 43, 407 to 477) which extends according to the thickness (E) and has at least two surfaces each defining a second inclined plane (400 to 403;
• 410 to 413;
• 420 to 423;
• 430 to 433) with respect to said plane, this at least one second part being disposed between two first parts,
• the first inclined plane of a first part being designed to slip over one of the second inclined planes of the second part, such that a slippage of the corner-forming first parts over said at least one second part drives a movement according to said first direction of the at least one second part.