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US-12625468-B2 - Horological assembly comprising a balance spring and a stud

US12625468B2US 12625468 B2US12625468 B2US 12625468B2US-12625468-B2

Abstract

An assembly ( 1 ) for attaching a free end ( 8 ) of an outer last coil ( 10 ) of a balance spring ( 12 ) for a horological movement, this attachment assembly ( 1 ) including a stud ( 2 ) and a blocking element ( 14 ), the stud ( 2 ) being provided with a groove ( 6 ) in which the free end ( 8 ) of the outer last coil ( 10 ) of the balance spring ( 12 ) is engaged, the blocking element ( 14 ) also being engaged in the groove ( 6 ), in contact with the outer last coil ( 10 ) of the balance spring ( 12 ), the attachment assembly ( 1 ) further including a clamping member ( 16 ) which presses the blocking element ( 14 ) against the free end ( 8 ) of the outer last coil ( 10 ) of the balance spring ( 12 ), such that the free end ( 8 ) of the outer last coil ( 10 ) of the balance spring ( 12 ) is immobilised in the groove ( 6 ) of the stud ( 2 ).

Inventors

  • Julien Christan

Assignees

  • Eta Sa Manufacture Horlogère Suisse

Dates

Publication Date
20260512
Application Date
20231005
Priority Date
20221121

Claims (16)

  1. 1 . An assembly ( 1 ) for attaching a free end ( 8 ) of an outer last coil ( 10 ) of a balance spring ( 12 ) for a horological movement, the attachment assembly ( 1 ) comprising a stud ( 2 ) and a blocking element ( 14 ), the stud ( 2 ) being provided with a groove ( 6 ) in which the balance spring ( 12 ) is engaged at a point along its length, and a bottom ( 46 ) that is separated by the groove ( 6 ) in a first direction (Z) that is perpendicular to a plane in which a winding of the coils lies, the blocking element ( 14 ) being elastically engaged with the stud ( 2 ) in the groove ( 6 ), and being in contact with the balance spring ( 12 ), the attachment assembly ( 1 ) further comprising a clamping member ( 16 ) which presses the blocking element ( 14 ) in the first direction (Z) against the balance spring ( 12 ) and the bottom ( 46 ), such that the balance spring ( 12 ) is immobilised in the groove ( 6 ) of the stud ( 2 ) in the first direction (Z).
  2. 2 . The attachment assembly ( 1 ) according to claim 1 , wherein the balance spring ( 12 ) is engaged within the groove ( 6 ) of the stud ( 2 ) via the free end ( 8 ) of its outer last coil ( 10 ).
  3. 3 . The attachment assembly according to claim 2 , wherein the free end ( 8 ) of the outer last coil ( 10 ) of the balance spring ( 12 ) is immobilised by mechanical clamping and blocking in a direction perpendicular to the plane in which this free end ( 8 ) of the balance spring ( 12 ) extends.
  4. 4 . The attachment assembly ( 1 ) according to claim 1 , wherein the groove ( 6 ) extends from an outer wall ( 4 ) of the stud ( 2 ) towards the inside thereof.
  5. 5 . The attachment assembly ( 1 ) according to claim 4 , wherein the groove ( 6 ) has a height and the blocking element ( 14 ) a thickness such that, once the blocking element ( 14 ) is engaged in this groove ( 6 ), enough space remains to be able to engage the free end ( 8 ) of the outer last coil ( 10 ) of the balance spring ( 12 ) within the groove ( 6 ).
  6. 6 . The attachment assembly ( 1 ) according to claim 5 , wherein the space in which the free end ( 8 ) of the outer last coil ( 10 ) of the balance spring ( 12 ) is engaged extends between the blocking element ( 14 ) and the bottom ( 46 ) of the groove ( 6 ).
  7. 7 . The attachment assembly ( 1 ) according to claim 6 , wherein the free end ( 8 ) of the outer last coil ( 10 ) of the balance spring ( 12 ) terminates in a plate ( 50 ) which is attached to this free end ( 8 ) or which is made in one piece with this free end ( 8 ).
  8. 8 . The attachment assembly ( 1 ) according to claim 1 , wherein a hole ( 22 ) in which the clamping member ( 16 ) is engaged is formed in the stud ( 2 ) such that the clamping member ( 16 ) extends into the groove ( 6 ) and presses against the blocking element ( 14 ), pressing the latter against the free end ( 8 ) of the outer last coil ( 10 ) of the balance spring ( 12 ).
  9. 9 . The attachment assembly ( 1 ) according to claim 8 , wherein the clamping member ( 16 ) is a threaded rod ( 18 ) and wherein the hole ( 22 ) is tapped.
  10. 10 . The attachment assembly ( 1 ) according to claim 8 , wherein the blocking element ( 14 ) is a clamp ( 28 ) provided with two jaws ( 30 a , 30 b ) connected to one another at a distal end ( 32 a , 32 b ), these two jaws ( 30 a , 30 b ) defining therebetween a space ( 34 ) that is open on their proximal end ( 36 a , 36 b ) side.
  11. 11 . The attachment assembly ( 1 ) according to claim 10 , wherein the stud ( 2 ) comprises a wall ( 38 ) which delimits the groove ( 6 ).
  12. 12 . The attachment assembly ( 1 ) according to claim 11 , wherein the inner face of one of the jaws ( 30 a , 30 b ) of the clamp ( 28 ) has a surface ( 40 ) which extends away from the wall ( 38 ) of the stud ( 2 ) in the direction of engagement of the clamp ( 28 ) on the stud ( 2 ).
  13. 13 . The attachment assembly ( 1 ) according to claim 11 , wherein the inner faces of the jaws ( 30 a , 30 b ) of the clamp ( 28 ) are provided with recesses ( 42 a , 42 b ), the shapes of the recesses are complementary and match a shape of the wall ( 38 ), allowing the clamp ( 28 ) to grip the wall ( 38 ) and hold it.
  14. 14 . The attachment assembly ( 1 ) according to claim 1 , wherein the balance spring ( 12 ) is configured to be immobilised in the groove ( 6 ) of the stud ( 2 ) in the first direction (Z) without any adhesive.
  15. 15 . The attachment assembly ( 1 ) according to claim 1 , wherein the blocking element ( 14 ) is a clamp ( 28 ) provided with two jaws ( 30 a , 30 b ) and formed with elasticity, these two jaws ( 30 a , 30 b ) defining therebetween a space ( 34 ) that is open on their proximal end ( 36 a , 36 b ) side, and wherein the two jaws ( 30 a , 30 b ) elastically are engaged with the stud ( 2 ) in the groove ( 6 ).
  16. 16 . The attachment assembly ( 1 ) according to claim 15 , wherein the stud ( 2 ) comprises a wall ( 38 ) which delimits the groove ( 6 ) along the first direction (Z) between the stud ( 2 ) and the bottom ( 46 ), and wherein the two jaws ( 30 a , 30 b ) are engaged with the wall ( 38 ) of the stud ( 2 ).

Description

CROSS REFERENCE TO RELATED APPLICATIONS This application claims priority to European Patent Application No. 22208644.9 filed Nov. 21, 2022. TECHNICAL FIELD OF THE INVENTION The present invention relates to a balance spring for a balance of a horological movement. The present invention further relates to a stud for attaching an outer last coil of such a balance spring. The invention further relates to a method for manufacturing such a balance spring. TECHNOLOGICAL BACKGROUND In the horological field, a balance spring, associated with a balance, forms a regulating member commonly referred to as a sprung balance for mechanical timepieces. The balance spring is initially viewed as a very thin spring that is wound about itself in concentric coils when no stress is exerted thereon. In the mounted state, a first end of the balance spring, referred to as the inner first coil, is attached to a collet fitted on a staff of the balance, and a second end of the balance spring, referred to as the outer last coil, is attached to a stud which is a part typically attached by means of a stud holder in a bridge for the balance, also referred to as a balance cock. More specifically, the time base for mechanical timepieces, also referred to as the oscillating system, comprises a sprung balance pair and an escapement. The balance consists of a balance staff pivoted between a first and a second bearing and connected to a balance rim by means of radial arms. The balance spring is attached, by its inner first coil, to the staff of the balance, for example by means of a collet, and is attached, by its outer last coil, to a fixed attachment point such as a stud carried by a stud holder. The escapement, in a very widespread embodiment thereof, comprises a double roller system consisting of a table-roller carrying an impulse pin and a safety-roller in which a notch is made. The escapement further comprises a pallet-lever with a pallet-staff pivoted between a first and a second bearing. The pallet-lever consists of a lever that connects a fork to an entry arm and to an exit arm. The fork consists of an entry horn and of an exit horn, and carries a dart. The travel of the fork is limited by an entry banking pin and an exit banking pin, which can be made in one piece with a pallet-bridge. The entry arm and the exit arm carry an entry pallet and an exit pallet respectively. Finally, the pallet-lever cooperates with an escape wheel set comprising an escape wheel and an escape pinion, this assembly formed by the escape wheel and pinion being pivoted between a first and a second bearing. A balance spring is a spring which adopts the shape of a spiral when at rest. Wound in a horizontal plane, parallel to the plane of the horological movement, the balance spring serves only one purpose: to make the balance oscillate about its position of equilibrium, also referred to as the dead centre, at as constant a frequency as possible. When the balance leaves its position of equilibrium by pivoting in a given direction, the balance spring contracts. This creates a restoring torque in the balance spring that causes the balance to return to its position of equilibrium. During this beat, the balance spring expands. However, as the balance has acquired a certain speed, and thus kinetic energy, it exceeds its position of equilibrium in the opposite direction to the previous until the restoring torque exerted by the balance spring on the balance stops it again and forces it to turn in the other direction. The balance spring thus alternately expands and contracts: it is said to breathe. However, many factors can play a part in preventing a balance spring from developing isochronously during the expansion and contraction phases. In particular, the balance spring must withstand oxidation and magnetism, which cause the coils to stick together and work to disrupt the precision of the watch, or even stop it entirely. The influence of atmospheric pressure, on the other hand, is low. For a long time, temperature has been the main problem, because heat expands the metal, while cold shrinks it. The balance spring must thus be resilient so that it can deform and yet always return to its original shape. The material used to produce balance springs is usually steel. Being ductile, the steel used must resist corrosion. Developments over the past two decades have also proposed producing balance springs from silicon. Silicon balance springs allow a greater precision of the rate than their steel predecessors, in particular because they are insensitive to magnetism. However, they have a higher cost price and, because they are fragile, they are more difficult to assemble. A balance spring must be isochronous. Regardless of how far the balance turns, it must always take the same amount of time to oscillate. If the balance spring contracts by just a few degrees, it accumulates little energy and returns slowly to its position of equilibrium. If the balance spring has moved far fro