Cord tightening device

A cord tightening device molded from synthetic resin comprising:

• a body having a pair of spaced face and back plates and a pair of spaced side walls interconnecting said face and back plates defining first and second openings permitting cord to pass therethrough, said face plate having a guide groove defined therein said guide groove defining a straight groove line down a center of the groove;
• and
• a slider movably disposed in said body and slidable in a slide direction along said guide groove, said slider having a retainer for pressing cord portions against said side walls, and a knob integral with said retainer and projecting through said guide groove above said face plate, said retainer having step-like teeth on opposite peripheral surfaces thereof for biting engagement with the cord portions, each of said step-like teeth being defined by a surface substantially parallel to said slide direction and another surface substantially perpendicular to said slide direction said step-like teeth serving as means for monotonically increasing the distance from each side wall to the groove line from adjacent the first opening toward the second opening, said side walls having respective series of teeth on inner surfaces thereof defined by a surface substantially Parallel to said direction and another surface substantially perpendicular to said direction for biting engagement with the cord portions, said retainer teeth being located on opposite sides of a central line of said retainer extending substantially perpendicularly to the direction in which said slider is slidable along said guide groove said retainer teeth serving as means for monotonically decreasing the distance from each of the peripheral surfaces to the groove line from the central line to nearly the end of the slider adjacent either the first or second opening.