Device for tightening an endless element trained over driving members

Claim 1

A tightening device for a drive transmission comprising, in combination: a housing having a pair of substantially flat side walls disposed in spaced-apart, parallel relationship to define an interior, a pair of sprockets journaled for rotation in said housing interior in a common plane, one of said sprockets comprising a primary driving member and the other sprocket a driven member, an endless sprocket chain including a plurality of chain rollers trained over said sprockets and disposed within said common plane, said sprocket chain having a width slightly less than the distance between said housing side walls and disposed in close spaced-apart relationship therewith, a freely pivotal bow-shaped member pivotally mounted at one end on said housing side walls within said housing interior in underlying relationship with the lower reach of said chain for pivotal movement within said common plane, said bow-shaped member extending from one end in the direction of movement of said chain and having a convex upper surface and a concave lower surface, said bow-shaped member having a width for sliding engagement between said convex upper surface and said chain rollers, a rotatable shaft mounted on one of said housing side walls and extending transversely into said housing interior in parallel relationship to the axis of rotation of said sprockets below said bow-shaped member, said shaft having an end portion extending outwardly from one of said housing side walls, a radially extending arm member on said shaft end portion disposed exteriorly of said housing in spaced-apart relationship with said housing one side wall, and urging means supported on the outer surface of said one housing side wall connected to the outer end of said arm member for rotating said shaft in one direction to yieldingly urge said rocker arm other end into said engagement with said bow-shaped member for tensioning engagement of said bow-shaped member with said chain.