MAINSPRING FOR A MAIN BARREL MINIMIZING WEAR ON THE DRUM

摘要

The invention relates to a mainspring (1) mounted in a main barrel (30) of an self-winding clock, comprising: a first spiral-shaped spring portion (2) having a first curvature and having an inner end (3) secured to a shaft of a barrel (32); a second spring portion (4) extending from the first spring portion (2) and arranged to interact with a drum of a barrel, the second spring portion (4) having a second curvature a direction opposite that of the first curvature and a curvature radius that decreases from an end that is near the first spring portion (2) towards an outer end (7) of the second spring portion (4); the second spring portion (4) furthermore includes a tangency area (5) having a smaller curvature radius than the curvature radius of the drum (31), such that, when the mainspring (1) is mounted in the barrel (30), the tangency area (5) engages the inner surface of the drum (31) along at least one line of intersection between the tangency area (5) and the inner surface of the drum (31).