Constant force escapement for a watch movement

Abstract

The present invention relates to a constant force escapement mechanism (1) for a timepiece, the escapement mechanism (1) comprising: an escape wheel (3) having a plurality of teeth and configured to support a hairspring-balance oscillator (5, 7); a reset wheel (11) having a plurality of teeth and configured to be rotated by a drive source and connected to the escape wheel (3) via a return element (21); and a locking pallet fork (25) pivotally mounted to the escape wheel (3) and configured to move between first and second stable angular positions in response to the rotation of the escape wheel (3), and to lock and release the reset wheel (11) at the rate of one step of its rotation as it moves from one of the stable positions to the other. According to the present invention, the escapement mechanism (1) further comprises a control wheel (15) that rotates integrally with the escape wheel (3) and is attached so as to be angularly adjustable relative to the escape wheel (3), the control wheel (15) having a plurality of teeth and configured to engage with the locking pallet fork (25) and move the locking pallet fork (25) from one side to the other of its stable positions.

Description

[Technical Field]

[0001] The present invention relates to the field of watchmaking, and more particularly to constant force escapements. [Background technology]

[0002] The escapement mechanism that is the subject of the present invention is based on that first disclosed in Swiss Patent No. 353679 and then further developed in Swiss Patent No. 704275. Furthermore, this type of escapement was also used in a watch manufactured by Fabrication de Montres Normandes [Normandy Watchmaking Company] in 2009 (see https: / / forumamontres.forumactif.com / t68941-fabrication-de-montres-normandes).

[0003] In this type of escapement, the escape wheel is coaxial with the reset wheel, which at first glance appears to be an additional escape wheel. The reset wheel is fixed in rotation to the wheel or pinion that receives the torque transmitted from the barrel, while the escape wheel is mounted so that it can rotate freely around the same geometric axis. These two wheels are connected to each other via an elastic return element, which rotates the escape wheel.

[0004] The escape wheel cooperates with the pallet as usual, and also with a blocking lever having two stages of pallets: the first stage of pallets cooperates with the teeth of the escape wheel, and the second stage of pallets cooperates with the teeth of the reset wheel, alternately blocking and releasing the teeth of the reset wheel as the blocking lever moves from one of its stable positions to the other.

[0005] After the release of each pallet assembly and during the pivoting of the escape wheel, one of its teeth comes into contact with one of the pallets of the first stage, which induces the pivoting of the blocking lever from one of its stable positions to the other. During this, the reset wheel pivots under the influence of the drive spring housed in the barrel and, after winding up the elastic element, is reblocked by the blocking lever.

[0006] In this way, during operation of the escapement, the reset wheel advances stepwise in synchronism with the escape wheel, keeping the force supplied by the elastic element substantially constant and preventing torque fluctuations from affecting the escapement as the drive spring unwinds. The advancement of the reset wheel is offset in angle and time from the advancement of the escape wheel, so that the escape wheel advances when the pallet fork is not cooperating with the balance, thereby minimizing or eliminating any influence on the escape wheel.

[0007] The first drawback of this system is that the timing of the release of the blocking lever is predetermined by its shape (including its pallet) and the positioning of its pivot. Therefore, the release timing of the reset wheel (and therefore its phase difference with respect to the escape wheel) cannot be adjusted except by changing the shape of the blocking lever. Secondly, the angular movement of the blocking lever interferes with the operation of the escapement. Specifically, an impact occurs when the lever reaches a stop at the end of its travel, causing it to bounce back.

[0008] Swiss Patent No. 120028 discloses a constant force escapement in which the reset wheel is a three-pointed star and is blocked and released by a blocking lever controlled by a constant radius cam that is integral with and rotates around the escape wheel. The constant radius cam is integral with the axle, to which the escape wheel is riveted. Both this configuration and those disclosed in U.S. Patent No. 2,970,427 and French Patent No. 1,009,853 suffer from the same drawbacks as those mentioned above.

[0009] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a constant force escapement mechanism in which the above-mentioned drawbacks are at least partially overcome. Summary of the Invention

[0010] More specifically, the invention relates to a constant force escapement mechanism for a timepiece as defined in the first independent claim, said mechanism comprising:

[0011] - an escape wheel having a plurality of teeth and configured to support the balance spring oscillator in a known manner, typically via a pallet fork or the like;

[0012] - a reset wheel having a number of teeth and adapted to be driven in rotation by a drive source such as a mainspring housed in a barrel, or by any other known drive source, and connected to the escape wheel via a return element, which may be formed by a mainspring, another type of spring, a flexible guide system integrated into one of these wheels, or any other suitable element;

[0013] - a blocking lever pivotally mounted about a physical or virtual axis and adapted to move between first and second stable angular positions in response to the rotation of the escape wheel, and to block and release the reset wheel at the rate of one step of its rotation (i.e., typically at the rate of one half-pitch of its toothing) as it moves from one of its stable positions to the other.

[0014] According to a first aspect of the invention, the escapement mechanism further comprises a control wheel fixed in rotation relative to the escape wheel and mounted angularly adjustable relative to the escape wheel, the control wheel having a plurality of teeth and adapted to cooperate with the blocking lever to move the blocking lever from one of its stable positions to the other. Typically, the tooth profiles of all these wheels are identical, and the number of teeth on each wheel is also the same, although this does not necessarily have to be the case.

[0015] The adjustable angular position of the control wheel relative to the escape wheel allows the watchmaker to adjust the precise timing of the release of the blocking lever, optimizing the operation of the escapement mechanism for each individual escapement and improving performance and / or rate.

[0016] Advantageously, the control wheel is arranged between the escape wheel and the reset wheel, which is the easiest solution to implement, although other arrangements of the three wheels are possible.

[0017] Advantageously, the reset wheel is rotationally fixed to a pinion adapted to be driven in rotation by a drive source, the pinion being extended by an axle around which the assembly comprising the control wheel and escape wheel is mounted so as to be freely rotatable.

[0018] Advantageously, the escape wheel is rotationally fixed to the control wheel by means of at least one adjusting screw or in a frictional fit by means of a friction element.

[0019] Advantageously, the blocking lever has a number of pallets arranged to cooperate with the reset wheel on the one hand and the control wheel on the other hand, each pallet having a trapezoidal cross section, so that the same standard pallet can be used for each pallet.

[0020] Advantageously, the toothing of the escape wheel, reset wheel and control wheel may be substantially identical, or alternatively may simply have the same number of teeth but different profiles.

[0021] In another variant, the reset wheel has the same number of teeth as the control wheel, but fewer than the escape wheel. In this case, the teeth of the reset and control wheels are evenly distributed around each wheel and have the same theoretical tooth pitch as the escape wheel, but some teeth are omitted. This means that the blocking lever operates not at every escape wheel step, but at a set number of escape wheel steps.

[0022] According to another aspect, the invention also relates to a constant force escapement for a timepiece as defined in the second independent claim, said escapement comprising:

[0023] - an escape wheel having a plurality of teeth and configured to support the balance spring oscillator in a known manner, typically via a pallet fork or the like;

[0024] - a reset wheel having a number of teeth and adapted to be driven in rotation by a drive source such as a mainspring housed in a barrel, and connected to the escape wheel via a return element, which may be formed by a mainspring, another type of spring, a flexible guide system integrated into one of these wheels, or any other suitable element;

[0025] - a blocking lever pivotally mounted about a physical or virtual axis and adapted to move between first and second stable angular positions in response to the rotation of the escape wheel, and adapted to block and release the reset wheel at the rate of one step of its rotation (i.e., typically at the rate of one half-pitch of its toothing) as it moves from one of its stable positions to the other.

[0026] According to this aspect of the invention, the blocking lever cooperates with a flywheel that is separate from the balance spring-balance oscillator, i.e. the flywheel is a separate and independent part of this assembly and is therefore not the balance or its table roller. Typically, the flywheel is not coaxial with the balance spring-balance oscillator.

[0027] This flywheel increases the effective inertia of the blocking lever and makes it possible to smooth its movement, thereby improving the operation of the escapement compared to the prior art escapements mentioned above.

[0028] Advantageously, the flywheel is a rotatably mounted table roller, typically attached to a frame element, which allows the use of existing standard components, including in particular the balance table roller. Typically, the table roller comprises a pin which cooperates with a fork provided on the blocking lever.

[0029] Advantageously, the blocking lever has the shape of an anchor, again making it possible to use existing standard parts.

[0030] Of course, the two aspects of the invention can be combined within one and the same escapement mechanism. [Brief explanation of the drawings]

[0031] Other details of the invention will become clearer from the following description taken in conjunction with the accompanying drawings, in which: [Figure 1] 1 is an isometric view of a first embodiment of an escapement mechanism according to the present invention; FIG. [Figure 2] FIG. 2 is a cross-sectional isometric view of the car stack in the embodiment of FIG. 1. [Figure 3] FIG. 2 is a partial isometric view of a second embodiment of an escapement mechanism according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0032] FIG. 1 shows a first embodiment of an escapement mechanism 1 according to the invention, and FIG. 2 shows the specific arrangement of the wheels that the mechanism 1 comprises.

[0033] The mechanism 1 comprises an escape wheel 3 pivoted about an axis A1 and is arranged in a known manner to maintain the oscillations of a balance spring 7-balance 5 oscillator, in which the balance spring 7 is arranged to impart a return torque to the balance 5, causing the balance 5 to oscillate around a neutral point.

[0034] In the embodiment shown, the escape wheel 3 cooperates with a Swiss-type pallet 9 pivotally mounted about an axis A2. The escape wheel 3 is blocked and released by a pallet assembly 9 and is arranged to provide impulses to the balance 5 in a known manner, although a detent escapement system, an Omega-Daniels escapement, or any other escapement known to those skilled in the art could also be used. The assembly of the escapement 1, the balance 5, and the balance spring 7 therefore constitutes a regulating mechanism.

[0035] The escape wheel 3 is coaxial with a reset wheel 11, which has a plurality of teeth and is rotationally integrated with a pinion 13 that receives force from a drive source (not shown, typically a barrel housing the mainspring in a known manner). This pinion 13 functions as an escape pinion and is kinematically connected to the drive source via an appropriate gear train (typically called a "finishing gear").

[0036] The escape wheel 3 is rotationally integral with the control wheel 15, which can be mounted angularly offset relative to the escape wheel 3. In the embodiment shown, adjustment screws 17 serve to fix the two wheels 3, 15 together in terms of rotation, but by loosening these screws the watchmaker can angularly move one of the wheels 3, 15 relative to the other, for reasons that will become more clear later. Alternatively, the two wheels 3, 15 can be coupled by a friction fit, but must remain rotationally fixed relative to one another during normal operation of the escapement 1. The frictional coupling between the wheels 3, 15 can be of any known type, provided that the friction torque is appropriately set.

[0037] The assembly comprising the escape wheel 3 and the control wheel 15 is mounted so as to be freely rotatable relative to the assembly comprising the reset wheel 11 and the pinion 13. To this end, the pinion 13 is extended by an axis 13a which passes through the wheels 3, 15 and supports the assembly between a first bearing 18. The assembly comprising the wheels 3, 15 is mounted so as to be freely pivotable about this axis 13a by means of a second bearing 19 which surrounds the axis 13a.

[0038] The reset wheel 11 is connected to the escape wheel 3 via a return element 21, here a spiral spring, which is preloaded to provide a torque sufficient to pivot the escape wheel 3 and support the oscillators 5, 7. To this end, the inner end of the return element 21 is rotationally fixed to the shaft 13a (which rotates integrally with the reset wheel 11) and its outer end is fixed to a stud 3a fixed to the escape wheel 3. The assembly comprising the two wheels 3, 15 is therefore kinetically connected to the assembly comprising the reset wheel 11 and the pinion 13 via this return element 21, and the torque applied to the escape wheel 3 remains substantially constant as long as the return element 21 is recharged by the drive source.

[0039] In the illustrated configuration, the control wheel 15 is located between the escape wheel 3 and the reset wheel 11. Although this is the easiest configuration to implement, the stacking of the wheels 3, 11, and 15 along the axis A1 can also be defined differently. In fact, one of the wheels 3 and 11 can be located in the center, with the control wheel 15 located on one side or the other. Thus, provided that the assembly of the wheels 3 and 15 is connected to the assembly of the reset wheel 11 and pinion 13 via the reset element 21, the connection between these two assemblies can be appropriately configured according to the manufacturer's requirements. For example, one end of the reset element 21 can be fixed to one of the wheels 3 and 15, while the other end can be fixed directly to the wheel 3 or to the axle 13a, depending on the selected configuration. Additionally, the reset element 21 can alternatively be comprised of a suitably positioned flexible element (such as a flexible blade) and thereby integrated into one or more of the wheels 3, 11, and 15 (particularly the reset wheel 11 and / or the control wheel 15).

[0040] In order to maintain the preload of the return element 21 in the event that the drive source is unable to provide sufficient torque to the pinion 13 to fully wind it, a stud 23 on the assembly consisting of the escape wheel 3 and the control wheel 15 is placed in a slot 11a on the reset wheel, limiting the angular phase difference between the wheels 3 and 11 and maintaining the prewinding of the return element 21. Of course, other configurations are possible which achieve the same effect by limiting the angular deviation between the two assemblies 11, 13 and 3, 15 respectively, such as that used in Swiss Patent No. 704275.

[0041] The blocking lever 25 is arranged to block and release the reset wheel 11 under the control of the control wheel 15, which pivots in response to the movement of the escape wheel 3. To this end, the blocking lever 25 is pivotally mounted about a rotation axis A3 different from the axis A2 (which may be a conventional physical axis or a virtual axis when the blocking lever 25 is supported by a flexible guide) and is configured to pivot between first and second stable positions (extreme positions). The blocking lever 25 also comprises two pairs of pallets 25a, 25b arranged in two different stages and cooperating with the reset wheel 11 and the control wheel 15, respectively. The pallets 25a, 25b may have any suitable shape and may be formed integrally with the blocking lever 25 or attached to the lever as separate parts. In the non-limiting illustrated embodiment, the pallets each assume a conventional trapezoidal shape (i.e., a trapezoidal cross section perpendicular to the axis A3), similar to the pallets of a Swiss anchor escapement. In other words, each pallet has a straight side connected to an end face that forms an oblique impulse surface. The first-stage pallets 25a are long enough so that, when the blocking lever 25 is in its corresponding extreme angular position, the straight side of each pallet can block the teeth of the reset wheel 11, with one side of pallet 25a therefore being in the path of the teeth. On the other hand, pallet 25b is shorter than pallet 25a (i.e., it protrudes less from the blocking lever 25 than pallet 25a), so that, when the stop lever 25 is in its extreme angular position, only its oblique end can enter the path of the teeth of the control wheel 15. As with the anchor pallets, the upstream side of each pallet 25a, 25b (considered in relation to the direction of rotation of wheels 3, 11, 15) is shorter than the downstream side, and the end faces are configured so that the teeth of wheels 11, 15 cooperate with the end faces of pallets 25a, 25b to pivot the blocking lever 25.

[0042] The operation of the escapement is therefore as follows:

[0043] When at rest, the escape wheel 3 is blocked by the side of one pallet 9a of the pallet assembly 9, and the reset wheel 11 is also blocked by the side of one pallet 25a of the first stage.

[0044] When the pallet assembly 9 releases one of the teeth of the escape wheel 3 under the influence of the rotation of the balance, the escape wheel is free to pivot under the influence of the return element 21 until it is stopped, in a known manner, by the side of the other pallet 9a of the pallet assembly. The control wheel 15 is rotationally fixed to the escape wheel 3 and therefore pivots in the same way.

[0045] During this pivoting, one of the teeth of the control wheel 15 comes into contact with the end face of the pallet 25b adjacent to the pallet 25a which is engaged with one of the teeth of the reset wheel 11. The cooperation of the tooth of the control wheel 15 with the oblique end face of said pallet 25b causes the blocking lever 25 to lift, which disengages the pallet 25a from the tooth of the reset wheel 11, which then pivots under the influence of the mainspring.

[0046] At this time, the teeth of the released resetting wheel 11 cooperate with the oblique end face of the pallet 25a to accelerate the pivoting of the blocking lever 25, and the side face of the other pallet 25a of the first stage blocks the rotation of the resetting wheel 11.

[0047] By adjusting the angular position of control wheel 15 relative to escape wheel 3, the watchmaker can determine the pivoting timing of blocking lever 25 during the cycle, optimizing the time between the release of escape wheel 3 and the release of reset wheel 11 and thereby optimizing the performance of escapement 1. Because control wheel 15 is rotationally fixed relative to escape wheel 3, the release of reset wheel 11 always depends on the rotation of escape wheel 3, even though it is the teeth of control wheel 15 that control the pivoting of blocking lever 25.

[0048] To smooth the operation of the blocking lever 25, the latter has the shape of an anchor, whose fork lever 25c is provided with a fork 25d which cooperates with a pin (not shown) of a table roller 27 of the type well known in connection with balance wheels, pivoting between standard bearings 28. The table roller 27 acts as a flywheel, increasing the effective inertia of the blocking lever 25 and smoothing its movement, making it possible to improve the operation of the escapement 1 compared to the escapements of Swiss Patents No. 353679 and No. 704275. This flywheel counteracts in particular the dynamic effects of the impact when the blocking lever bounces back when it strikes the banking pin 29 or when the fork comes into contact with the impulse pin.

[0049] However, it is also possible to use a simple lever as the blocking lever 25, as in Swiss Patent Nos. 353679 and 704275, or a lever of other shapes, suitably adapted.

[0050] Figure 3 shows another embodiment of an escapement mechanism 1 according to the invention, using only the main reference numerals and omitting some elements (such as the return element 21). This embodiment differs from the embodiment of Figure 1 in the positioning of axis A2 relative to axis A1. In the embodiment of Figure 1, the angles between the lines joining axes A2-A1 and A3-A1 are obtuse, whereas in the embodiment of Figure 3 they are acute, and the two axes A2, A3 are on the same side in the plane of the mechanism.

[0051] In a variant not shown, it is also possible for the axes A2 and A3 to coincide, and for the pallet assembly 9 and the blocking lever 25 to be coaxial and overlapping.

[0052] In the illustrated embodiment, the three wheels 3, 11, and 15 may be substantially identical, at least in the shape of their toothings. Additionally, the pallet assembly 9 and the blocking lever 25 may also be identical, except for the mounting or thickened portion for supporting one pair of pallets 25a and 25b. Furthermore, the pallets 9a, 25a, and 25b may be conventional and identical in shape, except for the length of the pallet 25b. This minimizes the number of various parts that need to be manufactured. The shape of the toothings of the control wheel 15 and / or the reset wheel 11 can be selected arbitrarily and does not necessarily have to be conventional. Additionally, the reset wheel 11 and / or the control wheel 15 may be configured with any type of element suitable for achieving the desired operation, such as a wheel with edge teeth, a wheel with teeth configured with pins or fingers, etc. Therefore, the term "teeth" should be understood in a broad sense to encompass all less common variations known to those skilled in the art. The wheels 11 and 15 or the wheels 3 and 15 may be manufactured integrally with each other, with the two connected by a flexible element, such as a flexible blade. If the wheels 11, 15 are made in one piece, the flexible element connecting them can also function as the return element 21.

[0053] Furthermore, by reducing the number of teeth on the reset wheel 11 and removing one of two, two of three, three of four, four of five, etc. teeth on the control wheel 15 relative to the teeth on the escape wheel 3, it is possible to increase the number of balance changes per reset of the return element 21, just as in the case of a constant force device.

[0054] Regarding the material, all materials used in modern watchmaking can be considered (metals, non-metals such as silicon, silicon compounds, synthetic diamond, sapphire, structurable glasses, ceramics, glass-ceramics, metallic glasses, polymers, composite materials, additively sculptable materials, etc.) It should be noted that the pallets 9a, 25a, 25b may not only be separate parts attached to the pallet assembly 9 and lever 25, respectively, but may also be formed integrally with the pallet assembly / lever.

[0055] The escapement mechanism 1 according to the present invention can also be adapted to an inclined balance, and can be incorporated into any single-axis, double-axis, or triple-axis tourbillon mechanism, as well as into a carousel mechanism.

[0056] The present description is given as a non-limiting example of the invention, and those skilled in the art can make additions to the scope of the invention without departing from the scope of the invention as defined in the claims.

Claims

1. A constant force escapement mechanism (1) for a timepiece, an escape wheel (3) having a plurality of teeth and configured to support a balance spring oscillator (5, 7); a reset wheel (11) having a plurality of teeth, configured to be rotationally driven by a drive source, and connected to the escape wheel (3) via a return element (21); a blocking lever (25) pivotally mounted to the escape wheel (3) and adapted to move between first and second stable angular positions in response to the rotation of the escape wheel (3) and to block and release the reset wheel (11) at the rate of one step of its rotation when moving from one of its stable positions to the other; Equipped with The escapement mechanism (1) further comprises a control wheel (15) that is rotationally fixed to the escape wheel (3) and is attached so as to be angularly adjustable relative to the escape wheel (3), the control wheel (15) having a plurality of teeth and configured to cooperate with the blocking lever (25) to move the blocking lever (25) from one of its stable positions to the other.

2. 10. An escapement mechanism (1) according to the preceding claim, wherein said control wheel (15) is arranged between said escape wheel (3) and said reset wheel (11).

3. 10. An escapement mechanism (1) according to any one of the preceding claims, wherein the reset wheel (11) is rotationally fixed to a pinion (13) adapted to be driven in rotation by the drive source, the pinion being extended by an axle (13a) around which an assembly comprising the control wheel (15) and the escape wheel (3) is mounted so as to be freely rotatable.

4. 10. An escapement mechanism (1) according to any one of the preceding claims, wherein the escape wheel (3) is rotationally fixed to the control wheel by at least one adjusting screw (17) or by friction fit.

5. 10. An escapement mechanism (1) according to any one of the preceding claims, wherein the blocking lever (25) has a plurality of pallets (25a, 25b) adapted to cooperate with the reset wheel (11) and the release wheel (15), each pallet (25a, 25b) having a trapezoidal cross section.

6. 10. An escapement mechanism (1) according to any one of the preceding claims, wherein the toothings of the escape wheel (3), the reset wheel (11) and the control wheel (15) are substantially identical.

7. 6. An escapement mechanism (1) according to any one of claims 1 to 5, wherein the reset wheel (11) has the same number of teeth as the control wheel (15) but fewer than the escape wheel (3).

8. A constant force escapement mechanism (1) for a timepiece, an escape wheel (3) having a plurality of teeth and configured to support a balance spring oscillator (5, 7); a reset wheel (11) having a plurality of teeth, configured to be rotationally driven by a drive source, and connected to the escape wheel (3) via a return element (21); a blocking lever (25) pivotally mounted to the escape wheel (3) and adapted to move between first and second stable angular positions in response to the rotation of the escape wheel (3) and to block and release the reset wheel (11) at the rate of one step of its rotation when moving from one of its stable positions to the other; Equipped with Escapement mechanism (1), characterized in that said blocking lever (25) cooperates with a flywheel (27) different from said balance spring oscillator (5, 7).

9. 10. An escapement mechanism (1) according to the preceding claim, wherein said flywheel (27) is a rotatably mounted table roller (27).

10. 10. An escapement mechanism (1) according to the preceding claim, in which the table roller (27) comprises a pin cooperating with a fork (25d) provided on the blocking lever (25).

11. 10. An escapement mechanism (1) according to the preceding claim, in which the blocking lever (25) has the shape of an anchor.

12. An escapement mechanism (1) according to any one of claims 1 to 7 and any one of claims 8 to 11.

13. 10. A speed regulating mechanism comprising an escapement mechanism (1) according to any one of the preceding claims, a balance (5) adapted to cooperate with said anchor, and a hairspring (7) adapted to impart a return torque to said balance (5).

14. A timepiece movement comprising a regulating mechanism according to the preceding claims.

15. A timepiece comprising a timepiece movement according to the preceding claims.

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