Self-adjusting mechanism for a friction clutch

A self-adjusting mechanism for a friction clutch having a cover, a pressure plate movable relative to the cover to cause friction members of the clutch to move into engagement, a clutch release mechanism movable toward and away from the pressure plate, and an adjustment ring rotatable to compensate for wear of the friction members, the self-adjusting mechanism comprising:

• a mounting bracket adapted to be secured to the cover;
• first and second rotatable hub members supported for rotation by the bracket;
• mating ratchet teeth on the first and second hub members configured such that the first hub member can rotate in a first rotational direction relative to the second hub member but can engage and drive the second hub member in a second rotational direction opposite the first rotational direction when the first hub member rotates in the second rotational direction, said mating ratchet teeth being contained inside one of the hub members;
• an adjustment arm on the first hub member for affecting rotation of the first hub member in first and second rotational directions;
• a worm gear supported for rotation by the bracket;
• an anti-slip device configured to hold the worm gear against rotation in the first rotational direction but to allow rotation of the worm gear in the second rotational direction;
• the second hub member and the worm gear having a lost-motion connection permitting a limited range of rotational free play of the second hub member relative to the worm gear;
• and
• a connection between the adjustment arm and the clutch release mechanism such that movement of the clutch release mechanism in a first axial direction causes movement of the adjustment arm in the first rotational direction, and movement of the clutch release mechanism in a second axial direction opposite the first axial direction causes movement of the adjustment arm in the second rotational direction;
• wherein said clutch release mechanism is movable through a non-adjustment cycle wherein the release mechanism moves in said first axial direction and drives the adjustment arm to rotate the first and second hub members in said first rotational direction through a non-adjustment angle of rotation without rotating the worm gear, and wherein the release mechanism then moves in said second axial direction and drives the adjustment arm to rotate the first and second hub members in said second rotational direction back through the non-adjustment angle of rotation without rotating the worm gear;
• and
• wherein said clutch release mechanism is movable through an adjustment cycle wherein the release mechanism moves in said first axial direction and drives the adjustment arm to rotate the first hub member in said first rotational direction through an adjustment angle of rotation greater than the non-adjustment angle of rotation by a delta angle of rotation, said mating teeth separating during said delta angle of rotation to permit movement of the first hub member relative to the second hub member, and wherein the release mechanism then moves in said second axial direction and drives the adjustment arm to rotate the first and second hub members in said second rotational direction back through said adjustment angle of rotation, said lost-motion connection being configured such that rotation of the second hub member back through said adjustment angle of rotation causes rotation of the worm gear to affect rotation of the adjustment ring to compensate for wear of the friction members.