EP2199875B1 - Detent escapement - Google Patents

Description

The present invention relates to a detent escapement for a timepiece comprising a pendulum secured to a pulse element, an escape wheel whose toothing intersects the trajectory of the pulse element, 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, and a release finger or pallet integral with the rocker for rotation engaged with the rocker release member once per swing period of the rocker arm to disengage the stop member from the toothing of the escape wheel.

Since the detent escapement does not use an anchor between the escapement wheel and the balance wheel, the impulse of the escape wheel on the pendulum pulse finger can only occur in a direction of rotation of the pendulum, either once per oscillation period or alternately in half, the alternation corresponding to half a oscillation period.

This type of exhaust requires a release rocker which comprises firstly a stop element which cuts the path of the teeth of the escape wheel, and which further comprises a release element with which comes into engagement a release finger integral with the balance. However, this release finger must come into engagement with the release element only during the alternation during which the rocker receives a pulse from the escape wheel, the stop element having to remain in engagement with the impeller. exhaust during the other alternation.

In conventional expansion exhausts, the release rocker comprises an elastic blade whose end free press against a stop of the rocker so that the blade causes the rocker in a direction of rotation of the rocker release finger, while in the opposite direction of rotation, the blade bends and lets the release finger without causing the release latch. This makes it possible to prevent the escape wheel from rotating without transmitting a pulse to the balance during one of the two alternations, as in the case of the Robin exhaust, which causes a loss of energy and therefore a decrease performance.

The sizing of the flexible parts of the trigger is clearly one of the critical points in the development of this exhaust. It requires sufficient rigidity to keep the stop in its natural position but, at the same time, it is not necessary that the energy to release the escape wheel or to perform the relaxation function is too high, the risk being a disturbance non-negligible balance-balance oscillator, associated with a significant drop in yield, or even the system shutdown. In addition, the unlocking torque required for the release of the escape wheel also represents an operating safety (impact safety) which imposes a lower limit on the rigidity of the blade.

This mechanism has been especially employed in marine chronometry; it is delicate, requires perfect execution and does not lend itself to mass production. This solution is fragile and does not support the stresses that wear wristwatches suffer. It is also an excellent exhaust which allows a very precise adjustment and consequently the highest chronometric performances.

It has been proposed in EP 1 538 490 to solve the problem of the flexible blade by making it no longer secured to the release lever but secured to the balance. This spring then takes the form of a spiral spring whose end free ends with a finger having a radial driving face and an inclined release face, intended to bend the spiral spring, so that the finger causes the trigger rocker in a direction of rotation of the balance.

This solution, although interesting, however still requires to overcome the force of the spiral spring to spread the finger when the trigger rocker must not release the escape wheel, causing interference on the period of the sprung balance as well as a loss of energy.

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

For this purpose, this invention relates to a detent escapement for a timepiece according to claim 1.

With this arrangement, it becomes possible to use the inertia of an organ subjected to the oscillatory movement of the balance to actuate the release finger of the balance according to its direction of rotation, so that in a direction of rotation, the path of the release finger passes through the release member of the rocker, while in the opposite direction of rotation, this path passes outside this release element.

It is therefore a detent escapement in which the release finger must no longer overcome elastic force. Therefore, it does not use any energy to remove an elastic member and does not create any disturbance of the pendulum swing period, since the release finger is removed from the release element of the trigger rocker when alternation where the escape wheel is not released by the rocker and therefore does not transmit impulse to the pendulum.

The operation of this exhaust does not present certain risks of conventional expansion exhausts. If a shock moves the inertial organ to its other extreme position, the consequences will not be of an unfortunate nature. In one case, the release finger will meet the release member instead of fading and move the inertial member to its correct position with negligible effort. In the other case, instead of coming into contact with the release element, the finger will not meet it, which will lose an impulse to the pendulum and an increment to the gear, this having no impact on the good watchmaking as it is only an occasional event.

In addition, the operation of this exhaust reduces certain risks associated with the use of conventional expansion exhausts. Indeed, a shock applied to the timepiece may cause its balance to rotate beyond a normal operating angle, which leads, during the alternation where the pulse occurs, to a new release of the train of gear. There is a gallop, because two clearances and two pulses take place during the same alternation. The system object of the invention does not present this kind of problem because the release finger is at that moment already erased from the path of the unlocking element and does not cause the displacement of the blocker and therefore no second pulse .

• Les figures 1 à 7 montrent cet échappement à détente dans différentes positions, au cours d'une période d'oscillation du balancier;
• la figure 8 est une vue de dessous partielle de la figure 1;
• la figure 9 est une vue en coupe selon la ligne IX-IX de la figure 8;
• la figure 10 est une vue éclatée de la partie illustrée par la figure 9;
• la figure 11 est un diagramme de déplacement angulaire de l'élément inertiel pendant la période d'oscillation du balancier, avec le temps en seconde sur l'abscisse et l'angle en degré sur l'ordonnée;
• la figure 12 est un diagramme du déplacement angulaire du balancier sur une période d'oscillation, avec le temps en seconde sur l'abscisse et l'angle en degré sur l'ordonnée.
• Les figures 2 à 7 illustrant l'échappement à détente ne représentent pas le balancier, mais uniquement le dispositif d'impulsion et de dégagement solidaire en rotation de l'arbre de pivotement du balancier. Pour des raisons de clarté, le balancier B n'est illustré que dans la figure 1.

Other features and advantages of the invention will become apparent from the following description made with the aid of the accompanying drawings which illustrate, schematically and by way of example, an embodiment of the detent escapement object of the invention.

• The Figures 1 to 7 show this detent escapement in different positions, during a pendulum swing period;
• the figure 8 is a partial bottom view of the figure 1 ;
• the figure 9 is a sectional view along the line IX-IX of the figure 8 ;
• the figure 10 is an exploded view of the part illustrated by the figure 9 ;
• the figure 11 is an angular displacement diagram of the inertial element during the oscillation period of the pendulum, with the time in seconds on the abscissa and the angle in degree on the ordinate;
• the figure 12 is a diagram of the angular displacement of the pendulum on a period of oscillation, with the time in second on the abscissa and the angle in degree on the ordinate.
• The Figures 2 to 7 illustrating the detent escapement do not represent the pendulum, but only the pulse and release device integral in rotation with the pivot shaft of the pendulum. For the sake of clarity, the pendulum B is illustrated only in the figure 1 .

The detent escapement comprises an escape wheel 1 connected to a mainspring (not shown) by a finishing train (not shown) which tends to rotate the escapement wheel 1 ( Figures 1 to 7 ) in the opposite direction to clockwise.

In the position illustrated by the figure 1 , a tooth of the escape wheel 1 bears against a stop element 2a, advantageously formed by a ruby paddle, of a release rocker 2. This release rocker 2 is biased by a spring 3 which tends to to hold it against a stop 4, position in which the stop pallet 2a is engaged in the path of the teeth of the escape wheel, so that a tooth of this wheel bears against the stop pallet 2a as illustrated by the figure 1 .

The pulse and disengagement device associated with the pendulum pivot shaft is represented in detail by the Figures 8-10 . It comprises a circular plate 6 provided with a tubular element 6a designed to be driven on the balance shaft. This tubular element 6a has a partially circular outer section cut by two parallel outer flat faces 6b ( figure 8 ) on which is engaged a pulse ring 7, provided with an opening 7a ( figure 10 ) of complementary section to that of the outer section of the tubular element 6a. The impulse ring 7 is retained axially between two retaining rings 8a, 8b driven. The impulse ring 7 has a finger or impulse face 7b projecting from the outer lateral face of the impulse ring 7. The finger of the impulse ring may be an insert such as a pallet.

Two pins 9 and 10, of semicircular sections in this example, are driven into two diametrically opposed openings 6c, 6d respectively and of corresponding sections, formed in the plate 6.

An inertial member 11, elliptical in this example, 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 the pivot pin 10 of the inertial member 11 allowing it an angular displacement. The other opening is elongated 11a to receive the pin 9. The third opening is a central opening 11c for the clearance passage of the tubular portion 6a of the plate 6 and can be used, in the absence of the opening 11a and the ankle 9, to limit the displacement angular 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 under consideration, with a radially oriented drive face. relative to the center of the inertial member 11 and an inclined face, as illustrated by the figure 8 . The release finger could also be formed by a palette reported ruby, as the finger 7b. The inclined face of the release finger 11d is used to push the inertial element 6 in the event that a shock would have moved to the projecting position when it should be in the retracted position.

As illustrated on the figure 9 , the inertial member 11 is disposed at the base of the tubular portion 6a. As we see on the figure 10 , 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 6 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 order to minimize the impact on the balance of the balance, the axes of the two openings 11a, 11b occupy diametrically opposite and symmetrical positions relative to the center of the inertial member 11. The pins 9, 10 also occupy diametrically opposite positions and symmetrical relative to the center of the circular plate 6 to cooperate with the respective openings 11a, 11b.

On the figure 1 , the angular position occupied by the inertial member 11 corresponds to that in which the release finger 11d protrudes outside the periphery of the circular plate 6. By rotating in the direction of clockwise, the radial face the triangular finger meets a clearance member 2b located at the free end of the release rocker 2, so that the release finger 11d raises the release rocker 2 against the pressure of the return spring 3, as illustrated by the figure 2 .

As soon as the escape wheel 1, kept in tension by the mainspring through the finishing gear, is released, it is driven in the opposite direction to that of the clockwise so that a tooth of the escape wheel 1 meets the pulse finger 7b, directly transmitting the force of the mainspring to the balance, as illustrated by the figure 3 .

The figure 4 illustrates the return of the release lever 2 under the pressure of the spring 3 against the stop 4 after the release of the rocker by the release finger 11d, so that when the tooth of the escape wheel is released by the finger d 7b impulse, another tooth of the escape wheel is stopped by the pallet 2a of the release lever 2, as illustrated by the figure 5 .

This figure 5 also illustrates the reversal of the direction of rotation of the balance which passes from the rotation in the direction of clockwise to a rotation of opposite direction. The balance shaft is integral in rotation with the pulse finger 7b and the release finger 11d. The balance is braked by the spiral spring, and passes through a zero speed before being driven in the opposite direction of rotation.

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 pendulum 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 pendulum (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.

This behavior depends on the inertia of the inertial member 11, (material, geometry, in particular), of the friction between the inertial member 11 and the surfaces with which it is in contact, but it is also influenced by the effect of the centrifugal force acting on the center of mass of the inertial member 11 (offset relative to the axis of rotation of the balance) and which is added to the initial acceleration due to the balance.

In the phase illustrated by the figure 5 , the inertial member 11 is moved clockwise about the axis of the pin 10. In this position, the release finger 11d is retracted inside the peripheral edge of the circular plate 6.

Therefore, the release finger 11d does not cooperate with the disengagement latch 2 as it passes opposite the disengagement member 2b, as illustrated by FIG. figure 6 . Unlike all known forward impulse transmission exhausts, the clearance finger 11d has no elastic element to overcome to pass the obstacle of the element 2b of the trigger rocker 2 during the alternation of the balance where this one does not receive a maintenance pulse of its oscillating movement, since the finger disappears inside the circular periphery of the plate 6. There is therefore no loss of energy or disturbance of the pendulum swing period.

When the pendulum B 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 6 which returns to the position in which the release finger 11d protrudes out of the circular periphery of the plate 6.

The figure 11 is a diagram of the angular displacement of the balance during a period of oscillation. It is to be compared with the diagram of the figure 12 which shows the angular displacement of the inertial member 11 between its two limit positions determined by the two radial edges of the opening 11a alternately abutting against the pin 9 secured to the plate 6.

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 pivoting axis of the balance. This inertial member 11 may be made of a low specific mass material, 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.

It is also possible to produce the inertial member 11 made of nickel by the LIGA technique with a small thickness, typically of the order of 0.10 to 0.15 mm, so that the influence on the equilibrium of the balance can be considered. as negligible.

Claims (4)

1. A detent escapement for a timepiece comprising a balance wheel fastened to an impulse element (7a), an escape wheel (1) the teeth whereof intersect the trajectory of the impulse element (7a), a detent swing-arm (2) having a stop element (2a) and a disengagement element (2b), elastic means (3) for engaging the stop element (2a) in the trajectory of the teeth of the escape wheel (1), and a disengagement finger (11d) suitable for becoming constrained to rotate with the balance wheel, to come into engagement with the disengagement element (2b) of the detent swing-arm (2) once per oscillation period of the balance wheel to release the stop element (2a) from the teeth of the escape wheel (1), the disengagement finger (11d) being fastened to an inertial member (11) mounted to move freely between two extreme positions in one of which the trajectory of the disengagement finger (11d) passes through the disengagement element (2b) of the swing-arm (2) and in the other of which this trajectory does not pass through this disengagement element (2b), the passage of the inertial member (11) from one position to the other resulting from the inertia force acting on the inertial member caused by the variations of speed of the balance wheel in each half-cycle of oscillation of the balance wheel.
2. The detent escapement as claimed in claim 1, wherein the inertial member (11) is an element mounted on a plate (6) fastened to the pivot shaft of the balance wheel via a pivot member (10) about an axis parallel to the pivot axis of the balance wheel and eccentric relative to the center of said element that is provided with an opening (11c) for the pivot shaft of the balance wheel to pass through with clearance, the two limit positions of the inertial member (11) being situated symmetrically on either side of the pivot axis of the balance wheel.
3. The escapement as claimed in claim 2 wherein one member of the pair of members comprising the plate (6) and the element of the inertial member (11) carries two pins (10, 9), respectively a pivot pin and a pin for limiting the angular movement, occupying diametrically opposed and symmetrical positions, while the other member of said pair has two openings (11b, 11a) the axes of which occupy homologous diametrally opposite and symmetrical positions intended to receive the respective pins (10, 9), the element of the inertial member (11) including a central opening allowing the passage with clearance of a tubular element (6a) adapted to be chased onto the shaft of the balance wheel, fastened to the plate (6).
4. The escapement as claimed in claim 3 wherein said tubular element (6a) adapted to be chased onto the balance wheel shaft has a part-circular external section on which a ring (7) provided with said impulse element (7a) is engaged, the section of the opening of this ring (7) being complementary to the external section of the tubular element (6a), this ring (7) being retained axially on the tubular element by a retaining ring (8).

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