Part for attaching an outer last coil of a balance spring of a horological movement
An attachment part for attaching a free end of an outer last coil of a balance spring of a horological movement, this balance spring taking the form of a ribbon wound in coils and being delimited by first and second faces which extend parallel to and at a distance from one another, the attachment part including elastically deformable clamping means which are arranged to be brought into contact with the free end of the outer last coil of the balance spring in order to exert a resilient clamping force on this free end so as to guarantee the immobilisation thereof, this resilient clamping force being exerted along at least a first line of contact (A; B) on the first face of the balance spring and along a contact surface (S) on the second face.
1 . A part arranged to attach a balance spring of a horological movement, said balance spring, wound in coils in a plane, being delimited by first and second faces which extend at a distance from one another, said attachment part comprising:
elastically deformable clamping devices which are arranged to be brought into contact with the balance spring in order to exert a resilient clamping force on said balance spring so as to guarantee immobilisation thereof, said resilient clamping force being exerted along at least a first line of contact (A; B) on the first face of the balance spring and along a contact surface(S) on the second face, the first face and the second face being parallel to the plane of the coils,
wherein the clamping device takes the form of separate first and second clamping devices which face one another, and
wherein the first and second clamping devices take the form of two elastically deformable arms, the two arms being arranged such that free ends of the two arms face one another and are both brought into contact with the first face of the balance spring, the first face of the balance spring being located on a free end of an outermost coil of the coils of the balance spring in order to exert a resilient clamping force (F 1 ) on said free end in a direction (Z) perpendicular to a plane (X, Y) wherein the balance spring extends.
2 . The attachment part according to claim 1 , wherein the resilient clamping force is exerted on the first face of the balance spring along the first and second lines of contact (A, B).
3 . The attachment part according to claim 1 , wherein the attachment part takes the form of a tuning fork including a crosspiece with the two arms extending from the crosspiece and being bent such that the free ends of the two arms face a center of the crosspiece.
4 . The attachment part according to claim 1 , wherein the attachment part is provided with gripping devices which are arranged to allow the devices for clamping a free end of the outer last outermost coil of the balance spring to be moved apart in order to release said free end.
5 . The attachment part according to claim 1 , wherein the attachment part comprises a device for being mounted on a balance cock or around a pivot bearing of the balance.
6 . The attachment part according to claim 1 , wherein a free end of the outermost coil of the balance spring is removable from the attachment part.
7 . The attachment part according to claim 1 , wherein the attachment part is obtained by stamping and bending.
8 . The attachment part according to claim 1 , wherein the attachment part is made of a harder material than the material from which the balance spring is made.
9 . The attachment part according to claim 1 , wherein the balance spring takes the form of a ribbon, the first and second faces whereof extend parallel to one another.
10 . The attachment part according to claim 1 , wherein the balance spring is provided with a plate on which the clamping device exert the resilient clamping force to ensure the immobilisation thereof.
11 . The attachment part according to claim 1 , wherein the balance spring includes side faces that extend from the first face to the second face and, in a cross section of the balance spring, each of the side faces is longer than the first face and the second face.