Device for the automatic tensioning of a chain

摘要

The invention relates to a device for the automatic tensioning of a chain or the like, with a housing with a guiding part for an axially movable piston, with a spring which acts on the piston via a spiral feed drive and pushes the piston against the chain, and with a mechanical return-stroke lock for the piston. Known devices of this kind have a large number of parts and have the disadvantage of unilateral and essentially point-type support in the event of a reaction force of the spring. During the feed motion of the piston, support is also of the point type, and this increases wear. According to the provisions of the invention, a self-locking screw-thread engagement is provided between the piston and the guiding part, and the spring is at least one torsion spring prestressed between the housing and the piston. This leads to large-area and low-wear supporting surfaces for each direction of motion of the piston.