Belt tensioning device

A process for the manufacture of a control element for a tensioning device for belts, chain or the like, in particular for the camshaft drive of an internal combustion engine with a tension pulley supported on a movable carrier, with a control element, by means of which in the case of heating, the carrier can be moved via an actuating element against the action of a pressure spring in the slackening direction of the belt characterized in that, the control element consists of a hollow cylindrical sleeve closed at the one end by a bottom and on the other end has a flange extending radially inwards, against which from the inside a washer abuts, which in its center receives a longitudinally movable and sealed pressure piston, in an annular hollow space between the bore of the sleeve and the pressure piston, arranging the pressure spring so that it is supported on one hand on the washer and on the other hand on the pressure piston, between the bottom and the pressure piston, whose end face is at a distance from the bottom, arranging a further pressure spring which with lower resilience opposes the action of the first mentioned pressure spring and sealing the whole inner area of the sleeve with a gas-free expansion fluid, inserting the pressure pistion assembled with a retaining ring, the diaphragm springs, the support ring and the U-bracket, with the helical spring and sealing ring into the sleeve, swagging over sleeve rim and inserting the thus assembled unit with protruding pressure piston into a vessel partially filled with hydraulic oil, immersing the sleeve with the support ring completely in the oil, the pressure piston presssing the support ring into an opening position of the sleeve and releasing after the flowing out of the air from the sleeve and the flowing in of oil.