EP2407830A1 - Timepiece - Google Patents

Abstract

The timepiece has a locking lever (2) for locking an escapement wheel (1), and provided with two locking pallets (2a, 2b), a fork (2c) and a guard pin (2d). The guard pin is pivoted on the fork around an axis parallel to a pivoting axis (3) of the locking lever. The guard pin includes a displacement unit e.g. tail (2d1), shaped to engage with a drive unit secured to a frame, so as to amplify angular displacement of the guard pin caused by passage of the locking lever from one locking position to another locking position.

Description

The present invention relates to a timepiece provided with a direct-impulse escapement, comprising a frame on which are pivotally mounted an escape wheel, an immobilizer of the escape wheel provided with two locking pallets , a fork and a stinger, a balance-balance oscillator with a double plate carrying a pulse pallet, a release pin and a notch to allow the passage of the stinger; the pulse pallet being arranged to cut the trajectory of the teeth of the escape wheel and the release pin being arranged to engage with the fork at each half-period of oscillation of the balance, to move the blocking lever between two locking positions of the teeth of the escape wheel and allow the force transmission of a tooth of the escape wheel to the pulse pallet at each oscillation period of the balance. The present invention also relates to a timepiece equipped with an indirect impulse escapement based on the same inventive concept.

The fixed dart commonly used in the case of all Swiss anchor escapements effectively fulfills the function of preventing the anchor from overturning in the event of a shock for which it was designed. It is also thanks to the sting that the Swiss lever escapement owes much of its success and its wide distribution is, because of its safety, the exhaust used in almost all wristwatches.

Unfortunately, while favoring the Swiss anchor, the dart has greatly penalized most other exhaust systems, mainly because of geometric construction constraints and / or operation (sizing) which characterize these systems. The only way to use the dart with other types of exhaust and in particular the direct impulse exhausts (such as the Robin exhaust) is to increase the tilting angle of the blocking lever, which leads to yield reduction as it virtually negates the benefits of these exhausts.

The Robin exhaust is an exhaust that combines the advantages of the escapement escapement (high efficiencies and direct transmission of energy between the escape wheel and the balance) to those of the anchor escapement (better operating safety) . It is therefore a direct impulse exhaust which uses a blocking rocker equipped with two stop pallets and which switches between two extreme stop positions. Unlike the Swiss lever escapement, the impulse is transmitted directly by the escapement wheel to the balance and the rocker is only used to stop the escape wheel outside the pulse phases.

The integration of a Robin escapement into a wristwatch is made difficult by the impossibility of effectively using a fixed dart. The dart, which is usually a fixed piece driven close to the fork of the blocking rocker prevents, in combination with the small notch tray of the double plate secured to the balance, the overturning of the blocking rocker during an impact. Indeed, there is no spring that keeps the latch in its stopping position as is the case for a detent escapement. Such a reversal has catastrophic consequences on the operation of the watch, because the release of the blocking lever inadvertently will place it in its second extreme position which it can no longer be released by the peg secured to the balance, with the consequence the stop of the watch. The sizing and the use of a dart imposes a tilting angle of the locking lever comparable to that of the Swiss anchor (typically 15 °), while it is typically 3-4 ° for a current Robin exhaust.

However, it has already been mentioned that a tilting angle of 15 ° greatly limits the efficiency of the escapement and makes it lose its essential interest. One solution is obviously to find another way to secure the exhaust against shocks, but no system as simple and effective as a dart has been proposed to our knowledge.

The object of the present invention is to provide a solution to prevent the reversal of a locking lever or an anchor when their tilting angle is very low, typically less than 5 °, as is the case with the blocking of a direct impulse escapement, such as the Robin escapement in particular, but this could also be the case for indirect impulse escapements, such as the Swiss lever escapement in a particular configuration, in which the anchor would have a tilt angle very significantly lower than that of the usual anchor.

For this purpose, the subject of the invention is a timepiece provided with a direct-impulse escapement according to claim 1, as well as a timepiece equipped with an indirect impulse escapement according to claim 2, based on the same inventive concept.

The pivotally mounted dart according to the invention makes it possible to amplify its angular displacement without modifying the angular displacement of the blocking lever or the anchor, which increases the safety against overturning even if the tilting angle of the rocker blocking or anchor itself is very small, typically less than 5 °. The solution that solves the problem is also very simple design, which is a guarantee of reliability.

• La figure 1 est une vue en plan illustrant le principe de fonctionnement d'un dard fixe selon l'état de la technique;
• la figure 2 est une vue en plan illustrant le principe de fonctionnement d'un dard pivotant selon l'invention;
• la figure 3 est une vue en plan d'une première forme d'exécution appliquée à un échappement à impulsion directe;
• les figures 4 et 5 sont des vues en plan de deux variantes de la figure 3;
• la figure 6 est une vue en plan d'une seconde forme d'exécution appliquée à un échappement à impulsion indirecte.

The accompanying drawings illustrate, schematically and by way of example, two embodiments and various variants of the escapement of the timepiece object of the present invention.

• The figure 1 is a plan view illustrating the principle of operation of a fixed dart according to the state of the art;
• the figure 2 is a plan view illustrating the principle of operation of a pivoting dart according to the invention;
• the figure 3 is a plan view of a first embodiment applied to a direct impulse exhaust;
• the Figures 4 and 5 are plan views of two variants of the figure 3 ;
• the figure 6 is a plan view of a second embodiment applied to an indirect impulse escapement.

The figure 1 is taken from the book "Escapes", (C. Huguenin, S. Guye, M. Gauchat, Technicum Neuchâtelois, Le Locle, 1965 ) and illustrates the effectiveness of the stinger depending on the diameter of the small plate secured to the balance shaft.

As can be deduced from the figure 1 , the security provided by the dart increases inversely to the radius of the small plate of the balance. It can indeed be seen that the arrow f of the rope, the ends of which correspond to the points of contact of the stinger with the plate, increases as the diameter of the plate decreases for a given tilt angle α. The H position is therefore the least favorable, because the more the dart comes into contact with the small plateau near the center line, the more the risk of jamming increases.

When dimensioning the stinger, one of the first parameters to be set is the value of the arrow f which must be correctly determined according to the dimensions of the parts, the manufacturing technique, and / or tolerances. For a given sting length and corresponding to point D on the figure 1 and the standard dimensions for the anchor and the small balance plate, the only way to avoid the friction between the dart and the same plate is to have a total angle of tilt of the anchor (α) important, typically of 16 °. This value is perfectly compatible with the functioning / dimensioning of the Swiss lever escapement.

However, it is no longer the case with the Robin exhaust. The Robin escapement is characterized by the fact that its blocking lever has a tilt angle which is between 4 and 5 times smaller than that of a Swiss anchor. In fact, since the force is transmitted directly from the teeth of the escape wheel to the pallet of the balance (more compact system) and that the pallets of the locking lever do not transmit any force but only serve to block alternately the teeth of the escape wheel, the distances (angles) to be covered for the clearance of the wheel are substantially reduced. This low tilt angle therefore represents a certain advantage from the point of view of the efficiency of the escapement and the isochronism of the balance-balance oscillator but, at the same time, renders practically unusable a fixed dart. Indeed, because of the small tilt angle (≈α / 4), a dart length D would come into contact with the small plate, which forces to reduce its length, so the arrow f and finally the safety of the exhaust in case of shocks. Consequently, the use of a fixed dart to secure a Robin exhaust is made very difficult because of manufacturing tolerances of the components of the exhaust and their pivoting games.

To solve this problem, the present invention proposes to separate the tilting of the tilting rocker of the stinger by rotating the latter around a axis integral with the locking lever and parallel to the pivot axis of the locking lever.

The idea behind the swivel stinger comes from the need to have a large tilt angle to achieve proper operation of the stinger while keeping the low tilt angle of the rocker Robin exhaust. The only way to achieve this goal is to mount the pivoting dart by creating a kinematic connection between the pivoting of the stinger and the tilting of the locking lever. For this purpose, the stinger comprises displacement means, preferably located at a distance s from its pivot axis less than the distance r between these displacement means and the pivot axis of the blocking lever, these distances being measured in FIG. one of the extreme positions of the rocker, and shaped to engage with integral drive means of the frame of the timepiece. This arrangement makes it possible to amplify the angular displacement of the stinger, generated by the passage of the locking lever from one to the other of its two positions.

With such a solution, we will have a blocking rocker with a tilt angle of about 2 ° -4 ° amplitude while the dart will tilt at an angle of 12 ° -19 °, large enough to ensure good safety against overturning of the blocking scale.

The solution realized and tested is illustrated by the figure 3 on which there is shown a Robin exhaust mounted on the frame (not shown) of a timepiece. This exhaust comprises an escape wheel 1, a locking rocker 2 of the escape wheel 1, pivotally mounted about a pivot axis 3 on the frame of the timepiece and a double plate 4 secured to a pivot shaft 5 of a balance-balance oscillator (not shown).

The locking lever 2 comprises two locking vanes 2a, 2b, intended to penetrate alternately into the path of the teeth of the escape wheel 1, a fork 2c intended to work with a pin 4c integral with the largest plate 4a of the double plate 4. A stinger 2d is pivotally mounted on the fork 2c of the locking lever 2, around a pivoting pivot pin 2e parallel to the pivot axis 3 of this latch 2. The stinger comprises a tail 2d ₁ , constituting the means for moving the stinger and mounted between two limit stops 6a, 6b constituting the drive means of the stinger 2d.

The double plate 4, integral with the pivot shaft 5 of the balance, still carries a pulse pallet 4d which directly receives a pulse of a tooth of the escape wheel once per oscillation period of the balance. The small plate 4b of the double plate 4 has as usual a notch 4e radially aligned with the pin 4c, to allow the passage of the pin during the driving of the latch 2 by the pin 4c engaging between the arms of the fork 2c.

Sizing of the pivoting dart 2d is particularly simple and a single trigonometric relationship is sufficient to determine all the parameters that are needed. To understand the formula, we will refer to the figure 2 which represents the main geometrical parameters of the mobile stinger exhaust in one of the extreme positions of the blocking lever.

P corresponds to the tilting angle of the pivoting dart 2d relative to the center line which connects the pivot center 3 of the locking lever 2 to the pivot center 5 of the balance. α corresponds to the tilting angle of the locking lever (and to the tilt angle of the stinger when it is fixed) relative to this same line of centers. The cosine theorem allows us to write the following relation: $${\mathrm{<figure-callout\; id="2"\; label="l"\; filenames="imgf0002.png"\; state="\{\{state\}\}">l</figure-callout>}}^2={\mathrm{<figure-callout\; id="2"\; label="s"\; filenames="imgf0002.png"\; state="\{\{state\}\}">s</figure-callout>}}^2+{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="imgf0002.png"\; state="\{\{state\}\}">r</figure-callout>}}^2+2\cdot \mathit{sr}\cdot \cos \left(\beta \right)$$

That we can solve for the distance (r): $$r=\frac{-2\cdot s\cdot \cos \left(\beta \right)\pm \sqrt{{\left(2\cdot s\cdot \cos \left(\beta \right)\right)}^2-4\cdot \left(s^2-{\mathrm{<figure-callout\; id="2"\; label="l"\; filenames="imgf0002.png"\; state="\{\{state\}\}">l</figure-callout>}}^2\right)}}{2}$$

As a function of the angle β necessary for the correct operation of the pivoting dart 2d and the length 1 between the pivot point of the second dart and the pivot point of the lever 3, the position r of the limit stops 6a can be determined, 6b on the center line. In particular, s represents the distance between the pivot point of the stinger and the point of intersection between the line of wheel-balance centers and the tail of the stinger measured in one of the extreme positions of the rocker. The distances l and s are further linked by the relation l / sin (β) = s / sin (α). It should also be noted that for a given tilt angle β, the distance d of the abutments 6a, 6b only depends on the width p of the tail 2d ₁ of the stinger 2d.

To test the mobile sting, an achievement similar to that illustrated in figure 3 was mounted on a test pose comprising a balance-balance oscillator, a Robin exhaust, a gear train and a barrel to simulate conditions close to use in a watch movement. The stinger 2d and the limit stops 6a, 6b have been made of Ni by the LIGA technology. The pivot pin of the dart was made of 20AP steel.

For a first evaluation of the effect of the mobile stinger, we compared the pendulum amplitudes in different positions before and after mounting the mobile stinger. The first results are presented below according to the number of winding turns of the barrel. The amplitudes are the averages of the two horizontal positions and the four vertical positions, respectively. Amplitude at 3 turns of armoring [°] Amplitude at 6 turns of armoring [°] Amplitude at 12 turns of armoring [°] Without mobile stinger Horizontal position 232 270 282 Vertical position 201 233 252 With mobile dart Horizontal position 232 264 275 Vertical position 201 229 243

The losses due to the presence of the mobile stinger are low, of the order of 10 ° with complete arming (12 turns), and decrease with the degree of winding of the barrel. The effect of the mobile stinger therefore decreases with amplitude, which is ideal because it is at low amplitudes of oscillation that a loss of amplitude is critical for the movement of the movement. We also noticed a small difference in the amplitudes between the different vertical positions. No stopping occurred, and the test positions turn smoothly with a range of about 3 days, as is the case with a Swiss lever escapement movement with the same barrel and the same oscillator.

At this stage, the surface states of the prototype parts are not optimal, the material torques are not optimized, no lubrication was used and some dimensions were slightly out of tolerance. Despite this, no reversal of the blocking lever was found even after several severe shocks. The results thus show that the swiveling stinger exhaust works satisfactorily.

Some modifications can still be made to improve the behavior of the pivoting dart. Among them we can mention the improvement of the pivoting of the sting, in order to reduce the friction. It is conceivable to use a liquid lubrication, a tribological coating with a low coefficient of friction, or to use a ruby bearing driven or glued to the mobile stinger pivotally mounted on the integral pivot pin of the fork.

Another conceivable possibility would be to make the dart by growing Ni through a Liga process around a ruby bearing. This method of manufacture would avoid problems gluing or hunting of the bearing.

The figure 4 illustrates a variant of the figure 3 in which the tail of the stinger is formed in the form of a fork 2d ₂ , the abutments 6a, 6b being replaced by a fixed pin 6 engaged between the arms of the fork 2d ₂ . The position of this pin 6 can be adjustable, for example by associating the pin 6 to an eccentric, to allow to change the tilt angle of the stinger. Such a solution would reduce the size compared to the stops 6a, 6b.

In order to reduce the friction and to keep the possibility of a fine adjustment of the angle of tilt of the stinger 2d, it is possible to use stoppers 6a, 6b made of ruby in the form of an exhaust pallet. These pallets could be mounted in slides allowing a simple and distinct adjustment of the two stops 6a, 6b, as shown by the double arrows on the figure 2 , to facilitate the settings of the exhaust and correct any manufacturing defects.

The figure 5 illustrates a second variant of the figure 3 wherein the tail 2d ₃ of the stinger 2d has a toothing engaged with a rack 7 secured to the frame of the timepiece. The effect is the same as the stops.

The form of execution illustrated by the figure 6 refers to an indirect impulse escapement, of the Swiss anchor escapement type. The tilting of the dart 2d is provided by two pins 6'a, 6'b integral with the frame. In the example illustrated, the angle of tilting of the anchor is 6 °, substantially lower than in a traditional Swiss anchor escapement. Thanks to the 2d swivel system, the tipping angle of the stinger is 15 °. The angles are calculated relative to the line of the wheel-balance centers.

Claims (8)

Timepiece provided with a direct-impulse escapement, comprising a frame on which are mounted pivoting an escape wheel (1), a latch (2) for locking the escape wheel provided with two locking pallets ( 2a, 2b), a fork (2c) and a stinger (2d), a balance-balance oscillator provided with a double plate (4) carrying a pulse pallet (4d), a release pin ( 4c) and a notch (4e) to allow the passage of the dart (2d); the impulse pallet (4d) being arranged to cut the path of the teeth of the escape wheel (1), the release pin (4c) being arranged to engage with the fork (2c) at each half-period oscillation of the balance to release the latch (2) to allow it to tilt between two locking positions of the teeth of the escape wheel (1) and allow the transmission of force of a tooth of the wheel of escapement at the pulse pallet at each oscillation period of the balance, characterized in that the dart is pivotally mounted on the fork about an axis parallel to the pivot axis of the locking lever (2) and that it comprises displacement means (2d ₁ , 2d ₂ , 2d ₃ ), shaped to engage drive means secured to said frame, so as to amplify the angular displacement of the stinger (2d) generated by the passage of the latch (2) from one to the other of its two positions. Timepiece provided with an indirect impulse escapement, comprising a frame on which are mounted pivoting an escape wheel, an anchor provided with two pallets, a fork and a stinger, a balance-balance oscillator provided with a double plate carrying a release pin and a notch to allow the passage sting; the release pin being arranged to engage with the fork at each half-oscillation period of the balance, to move the anchor between two locking positions of the teeth of the escape wheel, characterized in that the dart is pivotally mounted on the fork about an axis parallel to the axis of pivoting of the anchor and that it comprises displacement means, shaped to engage with driving means integral with said frame, so as to amplify the angular displacement of the stinger generated by the passage of the anchor from one to the other of its two positions. Timepiece according to one of claims 1 and 2, wherein said displacement means are located at a distance from the pivot axis of said dart below the distance between these displacement means and the pivot axis of said blocking rocker, respectively said anchor, measured in one of their extreme positions. Timepiece according to one of the preceding claims, wherein the stinger (2d) is pivotally mounted via a ruby bearing. Timepiece according to one of the preceding claims, wherein the drive means integral with the frame comprise two stops (6a, 6b), each mounted in an adjustable manner. Timepiece according to one of claims 1 to 4, wherein the stinger (2d) is integral with a toothed sector meshing with a rack (7) integral with the frame. Timepiece according to one of claims 1, 2, 3 and 4, wherein said means for moving the stinger comprises a fork (2d ₂ ) between the arms of which is engaged a pin (6) integral with the frame. Timepiece according to claim 7, wherein said pin (6) is associated with means for adjusting its position.

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