Tensioning device without counterweights, for applying a tension on a cable of a railway line

A tensioning device for applying a tension on a cable, comprising:

• at least one circular spring;
• and
• a pulley rotatably connected to the circular spring so that a torque generated by the circular spring acts on the pulley,
• wherein:
• the pulley has a constant radius,
• the pulley comprises a circumferential groove, the circumferential groove having a V-shaped cross-section defined by two lateral converging walls,
• the pulley comprises a flexible rope, expending between a first end connected to the pulley and a second end intended to be connected to the cable, the flexible rope having a cross section that decrease from the first end towards the second end,
• the pulley is rotatably movable around a pulley axis, between a first position in which the flexible rope is arranged in the circumferential groove around the pulley axis, and a second position in which the flexible rope is unwound, and
• the circumferential groove and the cross section of the flexible rope are dimensioned in such a way that the two together define a radial position of the flexible rope in the groove as a function of the position of the pulley between the first position and the second position.