Assembly for securing the outer end of the balance-spring of a sprung balance device for a timepiece

Watch including an assembly for securing the peripheral end of the balance-spring of a sprung balance device for a timepiece, including:

• a balance-spring stud holder, secured to a balance-cock and positioned to enable the outer end of the balance-spring to be fixed in a channel in the stud holder, and devised to house a stud against which the balance-spring can be locked;
• a screw for locking the balance-spring stud, which comprises a threaded body for assembly inside an inner thread of the stud holder that opens onto the channel and which pushes the stud towards a back face of the channel and allows the balance-spring to be secured by insertion between the stud and said back face of the channel,
• wherein:
• the locking screw has a tip in the extension of the threaded body, at the opposite end to the screw head;
• and
• the stud has a housing into which the tip can be inserted.

Sprung balance device for a timepiece including:

• a balance-spring capable of generating an oscillating movement in a balance that is pivotably mounted on a balance staff;
• a balance-cock used as a support for one of the ends of the balance staff;
• a collet fixed the balance staff for securing the inner end of the balance-spring;
• a balance-spring stud holder, secured to the balance-cock, positioned to enable the outer end of the balance-spring to be fixed in a channel on the balance-cock, said stud holder being devised to house a balance-spring stud against which the balance-spring can be locked;
• a screw for locking the stud, which comprises a threaded body for assembly in the inner thread of the stud holder that opens onto the channel and which pushes the stud towards a back face of the channel and allows the balance-spring to be secured by insertion between the stud and said back face of the channel,
• wherein
• the locking screw has a tip in the extension of the threaded body, at the opposite end to the screw head;
• the stud includes a housing into which the tip can be inserted.

Method of securing the peripheral end of a balance-spring in a sprung balance device for a timepiece including a balance-spring stud holder secured to a balance-cock and said balance-cock being provided, on the one hand, with a channel devised for housing a balance-spring stud and, on the other hand, with an inner thread that opens onto the channel, said method including the steps of:

• arranging the balance-spring stud in the channel, a housing having previously been made in the stud,
• aligning the housing of the balance-spring stud with the inner thread of the stud holder;
• inserting a locking screw that has a tip in the extension of the threaded body at the opposite end to the screw head, in said inner thread;
• arranging the peripheral end of the balance-spring in said channel, radially inside the balance-spring stud;
• partially tightening the screw so as to allow insertion of the tip in the housing and so as to allow the outer end of the balance-spring to slide laterally in the channel;
• adjusting the lateral position of the end of the balance-spring in its fixed place so as to regulate the active length of the balance-spring;
• completely tightening the screw so as to prevent any lateral sliding of the outer end of the balance-spring in the channel.