EP2224292B1 - Detent escapement for timepiece movement - Google Patents

Description

The present invention relates to a direct impulse escapement, in particular a detent, for a watch movement, comprising a pendulum secured to a momentum element, an escapement wheel whose teeth intersect the trajectory of the element pulse, a trigger rocker having a stop member and a release member, means for engaging the stop member in the path of the toothing of the escape wheel, a release finger integral in rotation with the balance, and means for engaging said release finger with the latch release member once per swing period of the balance to disengage the stop member from the toothing of the escape wheel, in wherein said means for engaging the stop member in the path of the toothing of the escape wheel comprises a sliding surface integral with the trigger rocker, arranged to enter the trailing jectoire of the toothing of the escape wheel when the stop element comes out, this sliding surface being shaped so that the force exerted on it by a tooth of the escape wheel causes the return of the element of stopping of the trigger rocker in the path of the toothing of the escape wheel.

One of the most famous exhausts for its general performance (efficiency and isochronism) is the so-called trigger which releases the gear train when the balance rotates in one direction, while the same system allows the passage of the balance without any other action than the deflection of the elastic release member during its return. This advantageous function can be obtained thanks to a flexible element (generally a blade) which is blocked in a direction to allow to release the escape wheel following the flexion of a second flexible element. When the pendulum turns in the opposite direction, the first blade can bend freely without releasing the escape wheel, thus avoiding unnecessary energy loss.

The second flexible element is necessary to return the blocker to its initial position. However, at the time of release of the escape wheel, the system must overcome the draft of the escape wheel and the second flexible element, which causes a considerable loss of energy because the energy supplied to the second flexible element to deform it (about 50% of the total energy needed to release the wheel) is lost.

The sizing of the trigger (and in particular the flexible parts) is clearly one of the critical points in the development of the trigger escapement. It requires sufficient rigidity to keep the escapement wheel locked but, at the same time, it does not take too much energy to release the escape wheel during the impulse to be provided to the balance, the risk being a disturbance no - Negligible spiral balance system and a significant drop in the associated performance. The unlocking torque required for the release of the escape wheel also represents a shock-proofing which imposes a lower limit on the rigidity of the second flexible element.

A trigger escapement of the aforementioned type is described in US 40,508 .

This mechanism has been especially employed in marine chronometry; it is expensive and delicate, requires perfect execution and is not suitable for mass production. It is also an excellent exhaust that allows a very precise adjustment and consequently the highest chronometric performances.

However, in such an exhaust, the pull of the escape wheel is the only security which is insufficient in the case of a wristwatch likely to be subjected to shocks that would seriously disrupt its proper operation.

The object of the present invention is to overcome, at least in part, the aforementioned drawbacks.

For this purpose, the subject of the present invention is a direct-impulse escapement, in particular an expansion escapement for a watch movement according to claim 1.

The main advantage of such an exhaust is to increase the safety with respect to shocks. In addition, the trigger rocker with a stop element and a sliding surface which penetrate alternately in the path of the toothing of the escape wheel constitutes additional security.

• La figure 1 est une vue en plan de l'échappement à détente objet de l'invention associé à un oscillateur balancier-spiral;
• les figures 2 à 11 illustrent l'échappement de la figure 1 à plus grande échelle, sans le balancier, dans différentes positions au cours d'un cycle d'oscillation;
• la figure 12 est une vue en perspective éclatée d'une variante de la forme d'exécution des figures précédentes.

The stop element of the trigger rocker comprises a safety surface situated outside the path of the teeth of the escape wheel and adjacent to this trajectory when the trigger rocker is in the unlocking position. Advantageously, the length of this safety surface corresponds to the angle traveled by the escape wheel to communicate the driving pulse to the balance, to prevent the premature return of the stop element in the trajectory of the teeth of the wheel. exhaust. It is therefore a second security. The accompanying drawings illustrate, schematically and by way of example, an embodiment and a variant of an escapement trigger object of the invention.

• The figure 1 is a plan view of the detent escapement object of the invention associated with a balance-balance oscillator;
• the Figures 2 to 11 illustrate the escape of the figure 1 on a larger scale, without the balance, in different positions during an oscillation cycle;
• the figure 12 is an exploded perspective view of a variant of the embodiment of the preceding figures.

The exhaust illustrated by the figure 1 comprises an escape wheel 1 whose circular trajectory of the teeth intersects the trajectory of a pulse pallet 2 integral with the balance 3 associated with a spiral (not shown).

A trigger rocker 4 can move freely between two stops 5, 6. It comprises on the one hand a stop element whose stop face 4a serves to stop a tooth of the escape wheel 1 and secondly a sliding surface 4b to allow a tooth of the escape wheel to slide on this surface 4b and to tilt the rocker in the opposite direction of that of the clockwise to bring the abutment face in the trajectory of the teeth of the escape wheel 1. This trigger rocker 4 further comprises an elastic release member 4c bearing against a stop 4d and whose free end enters the path of a release finger 7 integral with the rocker 3.

The stop element of the trigger rocker 4 still has a safety surface 4e which is situated outside the path of the teeth of the escape wheel 1 and adjacent to this trajectory when the trigger rocker 4 bears against the stop 5 ( Figures 3 to 6 ). This surface extends over an angle of the escape wheel 1 corresponding to the angle during which a tooth of the escape wheel communicates its impulse to the pulse pallet 2 of the balance 3.

An oscillation cycle of the spring balance 3 is decomposed according to the different phases illustrated by the Figures 1 to 11 .

In the phase illustrated by the figure 1 , the balance 3 rotates in the opposite direction of that of the clockwise. The abutment face 4a of the stop element of the latch 4 retains the escape wheel 1 which holds the latch 4 against the abutment 6.

The phase illustrated by the figure 2 corresponds to the moment when the release finger 7 integral with the rocker 3 meets the elastic release member 4c bearing against the abutment 4d. Due to the stop 4d and the direction of rotation opposite that of clockwise balance 3, the elastic release element 4c behaves as a rigid element.

The trigger rocker 4 then passes under the action of the release finger 7 of the abutment against the abutment 6 against the abutment 5 ( figure 3 ), thus releasing the escape wheel 1, one tooth of which was stopped by the abutment face 4a of the stop element of the trigger rocker 4.

The escape wheel 1 is subjected to the torque of the mainspring (not shown) transmitted by the finishing train (not shown), is then driven in the direction of clockwise. One of his teeth then meets the impulse pallet 2 of the pendulum 3 ( figure 4 ). This is the beginning of the impulse phase during which the energy of the mainspring is transmitted to the balance 3 to transmit the energy necessary to maintain its oscillating movement.

This impulse phase ends when the tooth of the escape wheel leaves the impulse pallet, that is, practically in the position illustrated by the figure 5 . As can be seen, throughout this pulse phase, the safety surface 4e of the stop element of the trigger rocker 4 prevents the stop member from entering the path of the teeth of the wheel exhaust 1, following an impact for example.

After the impulse phase, the escape wheel 1 continues its rotation and one of its teeth meets the sliding surface 4b ( figure 6 ). By sliding against this surface 4b, the tooth of the escape wheel rotates the lever 4 in the opposite direction of that of the clockwise and returns it against the stop 6 ( figure 7 ). This tilting also brings the stop element of the rocker 4 into the path of the teeth of the escape wheel 1, so that a tooth of the escape wheel abuts against the abutment face 4a of the stopping element and exerts on the rocker 4 a couple which holds it against the abutment 6 ( figure 8 ).

Meanwhile, the balance 3 has continued to turn counterclockwise until the hairspring stops and rotates it clockwise.

When the release finger 7 encounters the elastic disengagement element 4c of the trigger rocker 4 ( figure 9 ), it moves it away from the stop 4d ( figure 10 ) without moving the trigger rocker 4. The pulse pallet 2 of the balance 3 passes between two adjacent teeth of the escapement wheel 1 without coming into contact with them.

The rocker 3 continues its rotation until it is stopped by the hairspring and is driven in a counter-clockwise rotation ( figure 11 ), thus starting a new oscillation cycle.

The figure 12 represents a variant of the pulse and release device associated with the pivoting shaft of the balance in replacement of the pulse pallet and the release finger of the previous embodiment. This variant comprises a circular plate 12 provided with a tubular element 12a designed to be driven on the balance shaft. This tubular element 12a has a partially circular outer section cut by two parallel outer plane faces 12b on which is engaged a pulse ring 13, provided with an opening 13a of complementary section to that of the outer section of the tubular element 12a . The impulse ring 13 is retained axially between two retaining rings 8a, 8b driven. The impulse ring 13 has a finger or pulse face 13b projecting from the outer lateral face of the impulse ring 13. The finger of the impulse ring may be an insert such as a pallet.

Two pegs 9 and 10, of semicircular sections in this example, are driven into two diametrically opposed openings 12c, 12d respectively and of corresponding sections, formed in the plate 12.

An inertial member 11 is provided with three openings 11a, 11b, 11c, two openings 11a, 11b are off-center and preferably symmetrical and diametrically opposed. One of these openings 11b is semicircular limited by two radii forming an angle greater than 180 ° to receive a pivot pin 10 of the inertial member 11 allowing it an angular displacement. The other opening is elongate 11a to receive the pin 9. The third opening is a central opening 11c for the clearance passage of the tubular portion 12a of the plate 12 and can be used, in the absence of the opening 11a and the pin 9, to limit the angular displacement of the inertial member 11. A release finger 11d protrudes from the outer lateral face of the inertial member 11. This release finger 11d is of triangular shape in the example in question, with a drive face oriented radially relative to the center of the inertial member 11 and the other inclined face. The release finger 11d could also be formed by a reported palette, ruby for example. The inclined face of the release finger 11d is used to push the inertial element 12 in the event that a shock would have moved it into a projecting position when it should be in the retracted position.

The inertial member 11 is disposed at the base of the tubular portion 12a. As we see on the figure 12 , the openings 11a, 11b, 11c are arranged, dimensioned and shaped to allow the inertial member 11 to perform a limited angular displacement around the axis of the pin 10, which is parallel to the axis of the tray 12 driven on the pivot shaft of the balance, and which constitutes the pivoting member of the inertial member 11. The elongate opening 11a extends symmetrically to a diameter of the inertial element 11 passing through the respective axes of the openings 11b , 11c, so that the two limit positions of the inertial member 11 are respectively symmetrically on either side of the axis of pivoting of the balance.

In an angular position of the inertial member 11, the release finger 11d protrudes outside the periphery of the circular plate 12. By rotating in the direction of clockwise, the radial face of the triangular finger meets the clearance element 4c which no longer needs to be elastic, so that the release finger 11d raises the trigger rocker 4.

The inertial member 11 has two stable positions, each dependent on the direction of rotation of the balance. The tests carried out show that the inertial member 11 moves before the balance has completed each of the two alternations making up its oscillation period, but its rotation around the ankle 10 begins around the neutral point of the balance (angle 0 of its position).

In neutral, the pendulum has the maximum speed and thus passes from a positive acceleration to a negative acceleration (it starts to decelerate) and that is when the inertial effects begin to be felt.

When the inertial member 11 is moved clockwise about the axis of the pin 10, the release finger 11d is retracted inside the peripheral edge of the circular plate 12.

Therefore, the release finger 11d does not cooperate with the trigger rocker 4 as it passes vis-à-vis the release member 4c. Unlike all the known forward impulse transmission exhausts, the clearance finger 11d has no element to overcome to pass the obstacle of the element 4c of the disengagement lever 4 during the alternation of the balance wheel or the it does not receive a maintenance pulse of its oscillating movement, since the finger disappears inside the circular periphery of the plate 12. There is therefore no energy loss or disturbance of the oscillation period of the pendulum.

When the balance 3 reaches the end of its rotation in the opposite direction to that of the hands of the watch ( figure 7 ), its deceleration again causes a displacement of the inertial member 12 which returns to the position in which the release finger 11d protrudes out of the circular periphery of the plate 12.

The angular displacement of the inertial member 11 between its two limit positions is only a few degrees, typically of the order of 5 ° to 10 °, these two limit positions being located symmetrically on either side of the axis of pivoting of the balance. This inertial member 11 may be made of a material of low specific mass, the inertial effect being always sufficient to guarantee the function. The freedom of choice of the outer geometrical shape makes it possible to produce an inertial element of symmetrical shape, which guarantees a weak added imbalance. Experience shows that with a sparse material such as silicon, the influence on the equilibrium of the balance is negligible.

Claims (4)

1. Direct-impulse escapement, especially of detent type, for a horological movement, comprising a balance wheel (3) attached to an impulse element (2), an escape wheel (1) whose teeth intersect the path of the impulse element (2), a detent rocker (4) having an arresting element (4a) and a clearance element (4c), means for inserting the arresting element into the path of the teeth of the escape wheel (1), a clearance pin (7, 11d) rotating integrally with the balance wheel (3), and means for engaging said clearance pin (7, 11d) with the clearance element (4c) of the rocker (4) once per period of oscillation of the rocker to clear the arresting element (4a) from the escape wheel tooth; in which said means for inserting the arresting element (4a) into the path of the teeth of the escape wheel (1) comprise a sliding surface (4b) integral with the detent rocker (4) and arranged so as to move into the path of the teeth of the escape wheel (1) when the arresting element (4a) leaves it, this sliding surface being shaped so that the force applied to it by a tooth of the escape wheel (1) causes the arresting element (4a) of the detent rocker (4) to move back into the path of the teeth of the escape wheel (1); which escapement is characterized in that the arresting element (4a) of the detent rocker comprises a safety surface (4e) situated outside of the path of the teeth of the escape wheel (1) and adjacent to this path when the detent rocker (4) is in the unlocking position, in order to prevent the arresting element (4) from moving into the path of the teeth of the escape wheel (1) while the latter is communicating a movement impulse to the balance wheel (3).
2. Escapement according to Claim 1, in which the length of the safety surface (4e) corresponds to the angle travelled by the escape wheel (1) to communicate the movement impulse to the balance wheel (3), in order to prevent the premature return of the arresting element (4a) into the path of the teeth of the escape wheel (1).
3. Escapement according to one of the preceding claims, in which said clearance element (4c) is pressed elastically against a stop (4d), so that it behaves like a rigid element when said clearance pin (7) meets it while rotating in one direction and moves away elastically when the disengagement pin (7) meets it while rotating in the other direction.
4. Escapement according to one of Claims 1 and 2, in which said clearance pin (11d) is integral with an inertial member (11) mounted freely between two extreme positions, in one of which the path of the clearance pin (11d) passes by said clearance element (4c) of the rocker (4), and in the other of which this path does not pass by this clearance element (4c), the passage of the inertial member (11) from one position to the other resulting from the inertial force acting on the inertial member due to the variations of speed of the balance wheel during each half-cycle of oscillation of the balance wheel.

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