Belt tensioner and method for making a belt-tensioner arm and a spring case

A belt tensioner comprising:

• a) a coil spring that is coiled about a longitudinal axis, the coil spring having first and second end portions projecting radially inward from a coil in a direction toward the longitudinal axis;
• b) a belt-tensioner arm rotatable about the longitudinal axis, the belt-tensioner arm being adapted to support an idler pulley and having a first hook, wherein the first end portion of the helical spring is retained by the first hook;
• and
• c) a belt-tensioner spring case having a second hook, wherein the second end portion of the helical spring is retained by the second hook;
• d) a pivot bushing disposed between, and in contact with, the arm and the spring case and circumferentially surrounding the coil spring;
• e) an idler pulley supported by the arm, wherein the pivot bushing has a centroid, wherein the idler pulley has a plane of belt loading, and wherein the centroid is disposed proximate the plane of belt loading;
• wherein the retention of the first end portion of the helical spring by the first hook of the arm and the retention of the second end portion of the helical spring by the second hook of the spring case allows the helical spring to be axially stretched into tension.