Wiping device for windows of power vehicles

A wiping device for windows of a power vehicle, comprising a wiper shaft;

• a wiper arm including one part of said wiper arm mounted on said wiper shaft and another part of said wiper arm hingedly connected with said one part of said wiper arm on an axle of said wiper arm;
• a wiping element arranged on a free end of the other part of said wiper arm;
• and a unit for changing an abutment force of said wiper arm and including a pulling spring loading said wiping element toward a window of a power vehicle, and means for changing a pretensioning of said pulling spring, said means consisting of an actuating unit, a first hinge rod having one end directly hingedly connected with said actuating unit and another end, a second hinge rod having one end and another end, a first axle on which said hinge rods are hingedly connected with one another by said another ends, a second fixed axle about which said one end of said second hinge rod is turnable, said actuating unit displacing said first hinge rod in direction toward said second fixed axle of said second hinge rod so that said hinge rods are freely movable together and said first axle is movable over an arc, wherein said arc defines a concave surface facing the spring and convex surface facing the wiper shaft said second fixed axle being located substantially under said axle of said wiper arm, said another part of said wiper arm extending in one direction from said axle of said wiper arm, while said hinge rods extend in an opposite direction with respect to said one direction of said another part of said wiper arm, said pulling spring having an end which is spaced from said wiping element and suspended on said first axle.