Bicycle sprocket chain damper

A bicycle sprocket chain damper for the return run of a sprocket chain entrained about a drive sprocket and a rear sprocket and resiliently tensioned by entrainment about an idler sprocket mounted on a bicycle frame-supported transverse, horizontal axle having at least one protruding end, the return run extending along a chain running path which includes a segment extending from tangency with a gear pitch circle of the drive sprocket to tangency with a gear pitch circle of the idler sprocket, for restraining and thereby damping oscillatory excursions of the drive chain transversally of said path within said segment of said path, the drive chain having a given maximum dimension transversally of said path,

• said sprocket chain damper comprising:
• a tube having a longitudinal throughbore extending between a leading end thereof and a trailing end thereof, said longitudinal bore being between 25 percent and 75 percent as long as said segment and having internal dimensions just sufficient to permit easy passage of the chain;
• said tube being a longitudinally split tube having two circumferentially opposite longitudinal edges, there being insufficient spacing between said edges to permit said chain to enter transversally into or exit transversally from said longitudinal throughbore unless said split tube is temporarily flexed so as to temporarily open up a sufficient gap between said edges;
• said tube being made of synthetic plastic material;
• mounting means for mounting said trailing end of said tube to the bicycle frame with sufficient rigidity that when said chain, moving transversally of said path, impacts said tube from within, said tube restrains transverse oscillatory amplitude of said chain;
• said mounting means including a U-shaped bracket which has two opposed face plates having openings which are horizontally coaxially aligned transversally of said tube and arranged to receive respective ones of said protruding ends of said axle, with said idler sprocket sandwiched between said face plates;
• said face plates including corresponding generally semicylindrical leading portions which are concave towards one another;
• said leading portions sandwiching a trailing end portion of said tube between them;
• and
• said mounting means further including clamping means clamping said leading portions of said face plates radially inwardly against said trailing end portion of said tube.