Hairspring for timepiece

摘要

The spring has an inner end (10) linked to a collet (2) driven on an arbor (3) of a balance system. An outer end (11) has a rigid part and a flexible part to define an oblong opening (14) which deforms elastically to receive and to lock a balance spring stud (4). The opening has a recess (17) near its open end (15) for positioning the stud and is oriented in a direction of winding of the spring. An independent claim is also included for clockwork having a balance system with a balance spring.