EP1892589B1 - Swiss anchor escapement - Google Patents

Description

The present invention relates to a Swiss lever escapement for a timepiece, in particular for a wristwatch. A Swiss lever escapement is a well-known type of escapement, in which an anchor having entry and exit pallets and cooperating with an escape wheel gives a pulse to the pendulum of the timepiece at each alternation of the latter, the pulse comprising two parts, namely a first part where a pulse tip of a pallet slides on a plane or impulse face of a tooth of the escape wheel, and a second part where an impulse beak of the tooth slides on a plane or impulse face of the pallet.

The present invention relates more particularly to a high performance Swiss lever escapement. The output of an escapement means the ratio between the energy received by the balance and the energy supplied by the escape wheel.

We know from the document CH 570 644 a Swiss lever escapement whose performance is increased by increasing the number of teeth embraced by the anchor and by moving the entry pallet away and bringing the pallet closer to the center of the anchor, the yield obtained is at first sight high at the entrance and low at the exit. However, the removal of the entry pallet has the consequence that, after the release of the anchor, the tooth of the escape wheel comes into contact with the impulse face of the entry pallet at a point relatively far from the resting spout of the pallet. A good part of the impulse face of the input pallet therefore does not participate in the impulse, so that the input efficiency is certainly not as high as hoped. Moreover, as it embraces a large number of teeth, the anchor must be large so heavy, which increases its inertia and reduces performance.

The document US 3,628,327 describes a Swiss lever escapement in which the length of the impulse face of the teeth of the escape wheel is increased with respect to the length of the impeller face of the pallets of the anchor, in order to increase the efficiency of the escapement. This approach does not take into account, however, that during the part of the impulse where the impulse tip of a pallet slides on the impulse face of a tooth, the yield is generally not very good.

The book L. Defossez entitled "General Theory of Horology", 1952, Swiss Watchmaking Schools, Le Locle, CH, shows in Figure 314 (page 217 ) a Swiss lever escapement in which the impeller face of the anchor output pallet has an angular length of 7 ° and the impeller face of the escape wheel teeth has an angular length of 4 ° , these quantities being measured from the center of the escape wheel and, for the first angular length, in a position where the mouthpiece of a tooth of the escape wheel is in contact with the mouthpiece of the output pallet. The book G. Daniels entitled "The watch: Principle and Methods of Manufacture" 1993, Editions Scriptar, Lausanne, CH , shows in Figure 468 (page 223) a Swiss lever escapement in which the impeller face of the pallet outlet pallet has an angular length of 7 ° and the impulse face of the teeth of the wheel of the exhaust has an angular length of 4 °, these quantities being measured from the center of the escape wheel and, for the first angular length, in a position where a tooth of the escape wheel is at rest on the pallet of anchor entrance.

The present invention aims to provide a Swiss lever escapement whose construction allows to obtain a higher yield.

For this purpose, there is provided a Swiss lever escapement comprising an escape wheel provided with teeth and an anchor provided with an entry pallet and an output pallet, the angular length of the impulse face of the outlet pallet being greater than 6.5 degrees, said angular length being measured from the center of the escape wheel and in a position where the rest of a tooth is in contact with the rest mouth of the pallet Release, characterized in that the ratio between the angular length of the impeller face of the output pallet and the angular length, measured from the center of the escape wheel, of the impeller face of the impeller teeth. exhaust is greater than 2.5. The angular length of the impulse face of the output pallet is preferably greater than 7 degrees and even 7.5 degrees.

The present invention thus proposes another approach to increase the efficiency of a Swiss lever escapement, namely to increase the angular length of the impulse face of the output pallet. In conventional constructions, the outlet of an exhaust contributes more to the output than the inlet, because the cooperation between the tooth of the escape wheel and the pallet is easier because the tooth and the pallet move in the same way. The present invention therefore seeks to increase the yield in priority where it is already the highest.

This new approach does not require unbalancing entry and exit. In the present invention, the angular length of the impulse face of the inlet pallet is preferably greater than 7.5 degrees, more preferably greater than 8 degrees.

The present invention also does not require to move one of the pallets from the center of the anchor. After the release of the anchor, the tooth of the escape wheel can thus come into contact with the impulse face of the pallet at a point relatively close to the mouthpiece of the pallet, which allows a large part said pulse face to participate in the pulse and thus the efficiency of the exhaust, this being valid for the input and output.

The present invention also allows obtaining a higher efficiency than those which can be obtained by increasing the length of the impeller face of the teeth of the escape wheel, because in the usual constructions the yield is better during the first part of the impulse where the impulse beak of the tooth slides on the impulse face of the pallet only during the second part where the impulse spout of the pallet slides on the impulse face of the tooth.

Particular embodiments of the invention are defined in the appended claims 6 to 11.

• la figure 1 est une vue en perspective de dessus d'un échappement selon l'invention en position de repos au niveau de la palette d'entrée,
• la figure 2 est une vue en perspective de dessus de l'échappement selon l'invention en position de fin de dégagement au niveau de la palette d'entrée, et
• la figure 3 est une vue en perspective de dessus de l'échappement selon l'invention en position de fin de dégagement au niveau de la palette de sortie.

Other features and advantages of the present invention will appear on reading the following detailed description given with reference to the accompanying drawings in which:

• the figure 1 is a perspective view from above of an escapement according to the invention in the rest position at the level of the entry pallet,
• the figure 2 is a perspective view from above of the escapement according to the invention in the end of release position at the level of the entry pallet, and
• the figure 3 is a perspective view from above of the exhaust according to the invention in the end of release position at the level of the output pallet.

With reference to the appended figures, in particular to the figure 1 , a Swiss lever escapement according to the invention comprises, in known manner, an escape wheel 1 provided with teeth 2 and which is secured to a pinion 1a, an anchor 3 provided with an entry pallet 4, 'an exit pallet 5, a fork 6a and a dart 6b, and large and small trays 7a, 7b mounted on the axis 9 of a pendulum, the large plate 7a carrying an ankle or ellipse 8.

Each pallet 4, 5 comprises a pulse face 10, a rest face 11, a reverser 12, a rest nozzle 13 and an impulse nose 14. The teeth 2 of the escape wheel 1 comprise a face 15, a rest face 16, a rest spout 17 and a heel 18.

The efficiency of the escapement according to the invention is increased compared with conventional exhausts by increasing the angular length Ls of the impeller face 10 of the output pallet 5 (cf. figure 3 ), more precisely by giving this pulse face 10 an angular length Ls greater than 6.5 °, preferably greater than 7 °, more preferably greater than 7.5 °.

Preferably, the angular length of the pulse face 10 of the input pallet 4 (cf. figure 2 ) is also increased. More precisely, this pulse face is given an angular length greater than 7.5 °, preferably greater than 8 °.

In particular embodiments of the invention, the angular length Ls is between 7.5 ° and 8 ° and the angular length Le is between 8 ° and 8.5 °.

The angular lengths Ic and Ls are measured from the center C1 of the escape wheel 1 and, for each of the pallets 4, 5, in an end-of-release position where the rest mouth 13 of the pallet is in contact with the spout 17 of a tooth 2 of the wheel 1.

$$\mathrm{Le}/\mathrm{d}>2.5$$

$$\mathrm{Le}/\mathrm{d}>2.5$$

où d est la longueur angulaire de la face d'impulsion 15 des dents 2 de la roue d'échappement 1 (cf. figure 1), mesurée depuis le centre C1 de la roue 1.It has been found by the present inventors that the efficiency of the exhaust can be substantially increased by adding to the conditions mentioned above relating to the angular lengths Ls and Le the following conditions: $$\mathrm{d}>2°$$

$$\mathrm{The}/\mathrm{d}>2.5$$

$$\mathrm{The}/\mathrm{d}>2.5$$

where d is the angular length of the impulse face 15 of the teeth 2 of the escape wheel 1 (cf. figure 1 ), measured from the center C1 of the wheel 1.

In particular, the choice Ls / d> 2.5 defines the present invention.

In the present invention, the number of teeth 2 (or pitch) of the escape wheel 1 embraced by the anchor 3 may be conventional, or be equal to 2.5 for an escape wheel of about 15 teeth or 3.5 for an escape wheel of about 20 teeth.

The number of teeth 2 of the escape wheel 1 is preferably equal to 16 as shown in the drawings. This number has the advantage of allowing the wheel 1 to have a limited size and a sufficiently large space between its teeth 2 to receive the large pallets 4, 5. It also allows the pinion 1a associated with the escape wheel 1 to have a sufficient number of teeth to be able to be manufactured under standard conditions.

The aforementioned conditions relating to the angular lengths Ls, Le and d increase the angle of lift of the anchor 3 which is advantageously greater than 15 °, preferably greater than 16.5 °. To prevent this from causing an increase in the angle of lift of the balance, which would be detrimental to isochronism, the plate pin 8 is further away from the axis 9 of the balance wheel than in conventional exhausts. Thus, the path traveled by the pin 8 will be greater for the same angle of displacement of the pendulum. This allows the balance to maintain a conventional lifting angle, of the order of 48 to 54 °.

It has been observed that with the present invention, an increase in efficiency of the order of 20% can be obtained compared to conventional exhausts.

Claims (11)

1. Swiss lever escapement comprising an escapement wheel (1) provided with teeth (2) and an anchor (3) provided with an entry pallet (4) and an exit pallet (5), the angular length (Ls) of the impulse face (10) of the exit pallet (5) being greater than 6.5 degrees, the said angular length (Ls) being measured from the centre (C1) of the escapement wheel (1) and in a position where the locking beak (17) of a tooth (2) is in contact with the locking beak (13) of the exit pallet (5), characterised in that the ratio between the angular length (Ls) of the impulse face (10) of the exit pallet (5) and the angular length (d), measured from the centre (C1) of the escapement wheel (1), of the impulse face (15) of the teeth (2) of the escapement wheel (1) is greater than 2.5.
2. Escapement as claimed in claim 1, characterised in that the angular length (Ls) of the impulse face (10) of the exit pallet (5) is greater than 7 degrees.
3. Escapement as claimed in claim 2, characterised in that the angular length (Ls) of the impulse face (10) of the exit pallet (5) is greater than 7.5 degrees.
4. Escapement as claimed in any one of claims 1 to 3, characterised in that the angular length (Le) of the impulse face (10) of the entry pallet (4) is greater than 7.5 degrees, the said angular length (Le) being measured from the centre (C1) of the escapement wheel (1) and in a position where the locking beak (17) of a tooth (2) is in contact with the locking beak (13) of the entry pallet (4).
5. Escapement as claimed in claim 4, characterised in that the angular length (Le) of the impulse face (10) of the entry pallet (4) is greater than 8 degrees.
6. Escapement as claimed in claim 5, characterised in that the angular length (Ls) of the impulse face (10) of the exit pallet (5) is between 7.5 and 8 degrees and the angular length (Le) of the impulse face (10) of the entry pallet (4) is between 8 and 8.5 degrees.
7. Escapement as claimed in any one of claims 1 to 6, characterised in that the angular length (d) of the impulse face (15) of the teeth (2) of the escapement wheel (1) is greater than 2 degrees.
8. Escapement as claimed in any one of claims 1 to 7, characterised in that the ratio between the angular length (Le) of the impulse face (10) of the entry pallet (4) and the angular length (d) of the impulse face (15) of the teeth (2) of the escapement wheel (1) is greater than 2.5.
9. Escapement as claimed in any one of claims 1 to 8, characterised in that the lift angle of the anchor (3) is greater than 15 degrees.
10. Escapement as claimed in claim 9, characterised in that the lift angle of the anchor (3) is greater than 16.5 degrees.
11. Escapement as claimed in any one of claims 1 to 10, characterised in that the number of teeth (2) of the escapement wheel (1) is 16.

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