EP2687916B1 - Anchor for an escapement in a mechanical clock - Google Patents

Description

Technical field of the invention

The present invention relates to an anchor for a watch escapement in a mechanical movement with escape wheel, comprising two anchor arms, in each of which a pallet is held, and a fork, which acts on the balance.

State of the art

The basic features of the function of a mechanical watch are today well known and well documented. The movements of mechanical watches generally draw their energy from a spring, usually a spiral spring, the elevator spring or the so-called Barillet. This energy is delivered to a gear transmission, which in turn, for example, via pointer elements, the information for the display of the hour reproduces, to the last element, the so-called inhibition. The latter has three functions, namely to count the number of oscillations of the balance, that is, to measure the time, to block the energy of the gear during the additional turn of the balance, and to give the balance an impulse to maintain its oscillating motion. The so-called Swiss lever escapement, where each of the pallets held in the anchor alternatively receives an impulse from the escapement wheel to pass it on to the balance, is the most widely used in the watch industry.

Like any mechanical system, the flow of force in a movement is subject to friction. The energy that has been collected in the elevator spring experiences losses in the transmission from the elevator spring through the transmission to the last element, the balance. This has several disadvantages. To compensate for the energy losses, the elevator spring must be increased in order to maintain a sufficient service life of the clock and the drain reserve. In order to reduce the influence of the friction losses relatively, the Increase vibration frequency or the inertia of the balance. The improvement in accuracy achieved in this way would have to be bought in turn with the enlargement of the balance or the mainspring, which is undesirable.

Part of the energy stored in the elevator spring is lost due to friction in the tooth meshing process and when turning the gear train into its bearing. Typically, each stage of the gear train has an efficiency of about 90% to 95%. The tooth engagement and profile of the teeth have been optimized as a result.

• Übertragung der Energie des Hemmungsrades an die Paletten des Ankers;
• Führung des Ankers durch seine Achse in den Lagersteinen;
• Übertragung der Energie des Ankers an die Unruh und Reibungsverluste der Lagerung der Spindel der Unruh in einem entsprechenden Lagerstein.

Another part of the energy is lost at the inhibition, especially by sliding friction. Typically, the latter is about 40%. The losses at the inhibition can be separated in several parts:

• Transmission of the energy of the escapement wheel to the pallets of the anchor;
• Guide the anchor through its axis in the jewels;
• Transferring the energy of the armature to the balance and friction losses of the bearing of the spindle of the balance in a corresponding bearing stone.

In order to improve the efficiency of the inhibition, many solutions have been proposed in which adjustments have been made to achieve the most energy efficient way of transferring the escape wheel to the pallets of the anchor. This is how the documents reveal CH-A-570644 and CH-342897-A , the document CH-342 897 , the document EP1770452-A1 or even the WO-2007/003539 Solutions that refer to the optimized geometry of the pallet.

Other documents, like the DE-2050013-A and the CH-A-510 285 are aimed at improving the transfer of energy from the anchor to the balance.

The storage and leadership of the anchor or its axis in jewels (usually rubies) has been substantially improved since the first watches with anchor inhibitors. Natural rubies and later synthetic rubies have been used as a material to reduce the friction and wear of the trunnions of the axles. It has also reduced the diameter of the journals of the axis of the anchor and adapted. Also, lubricants were used on the journal and the lubricants were continually improved.

The lubricants, however, have the disadvantage of deteriorating over time, namely aging, oxidizing, cracking and rancidity. In addition, lubricants are susceptible to the absorption of dust and tend to harden. Lubricants are therefore hardly used for bearing journals of the anchor.

Disclosure of the invention

Despite all precautions, friction and play between the journals of the anchor axle and their jewels with the well-known disadvantages are still present today. It is therefore the object of the present invention to provide an armature which oscillates virtually free of play and without friction, whereby the efficiency of the inhibition is to be improved.

This object is achieved by an anchor of the aforementioned type with the features of claim 1.

Further advantageous embodiments of the subject invention will become apparent from the dependent claims and their meaning and effect are explained in the following description with reference to the accompanying drawings.

• Figur 1: eine Aufsicht auf eine erste Ausführungsform des erfindungsgemässen Ankers;
• Figur 2: den Anker aus Figur 1 in einer perspektivischen Ansicht;
• Figur 3: eine zweite Ausführungsform des erfindungsgemässen Ankers in der Aufsicht, wobei die Schwenkbewegung des Ankers beziehungsweise dessen Gabel beschränkt ist;
• Figur 4: die zweite Ausführungsform des erfindungsgemässen Ankers in einer perspektivischen Darstellung;
• Figur 5: eine dritte Ausführungsform des erfindungsgemässen Ankers, der so gestaltet ist, dass er gewisse parasitäre Bewegungen zu kompensieren vermag;
• Figur 6: den Anker aus Figur 5 in perspektivischer Lage;
• Figur 7: eine vierte Ausführungsform des erfindungsgemässen Ankers in der Aufsicht;
• Figur 8: den Anker aus Figur 7 in perspektivischer Darstellung; und
• Figuren 9 bis 11: einen herkömmlichen Anker in der Seitenansicht in der Aufsicht und in perspektivischer Darstellung.

It shows:

• FIG. 1 : a plan view of a first embodiment of the inventive anchor;
• FIG. 2 : the anchor off FIG. 1 in a perspective view;
• FIG. 3 a second embodiment of the inventive anchor in the plan view, wherein the pivoting movement of the armature or its fork is limited;
• FIG. 4 : the second embodiment of the inventive anchor in a perspective view;
• FIG. 5 a third embodiment of the inventive anchor, which is designed so that it can compensate for certain parasitic movements;
• FIG. 6 : the anchor off FIG. 5 in perspective position;
• FIG. 7 a fourth embodiment of the inventive anchor in the plan view;
• FIG. 8 : the anchor off FIG. 7 in perspective view; and
• FIGS. 9 to 11 a conventional anchor in the side view in the plan view and in perspective.

Detailed description of the invention

For now, with respect to the FIGS. 9 to 11 a conventional anchor described.

The anchor as a whole is denoted by A. The anchor has two anchor arms B, in each of whose ends a pallet C is held. In the middle between the two anchor arms in their connection area engages a Fork D on, which is practically perpendicular or at least on an angle bisector of the two armature arms. The fork D ends in tines E and the pivotal movement of the armature or the fork D is limited by two lateral anchor boundary pins F in the pivoting movement. This pivoting movement takes place about a bearing axis G with bilateral bearing journals H, which rest in bearing stones, not shown here. It goes without saying that these journals H store with a certain friction and thus with loss of energy in the jewels and it is also clear that these journals can not be stored without clearance in the jewels. As mentioned above, this leads to the corresponding energy losses and a gear inaccuracy.

In all of the following embodiments of the inventive armature is immediately apparent that this has in any of the embodiments shown here a concrete bearing axis. This also applies correspondingly in the first embodiment according to the Figures 1 and 2 to. Overall, the anchor according to the invention is always designated 1. Also, this anchor has like two anchor arms 2 like a conventional anchor. The pallets 3 are held at the end in the two anchor arms 2. These two armature arms 2 are integrally connected to each other and in the connection area, the fork 4 engages the armature. The fork 4 is practically perpendicular to the two armature arms 2, when they are stretched aligned with each other. If the two anchor arms 2 enclose an angle deviating from the angle 180 °, the fork 4 lies on the bisector of said angle. Terminally, the fork 4 forks 5 and the fork horn on. This part again corresponds to the conventional style. The region in which the fork 4 is connected to the two armature arms 2 is defined here as the connection region 6. In this connection region 6, two fastening arms 7 engage. These attachment arms 7 extend exactly straight in the simplest embodiment shown here. With respect to the central axis through the fork 4, the two attachment arms 7 extend mirror-symmetrically. Consequently, so forms the fork 4 and the center axis bisecting the angle with respect to the two mounting arms 7 include each other.

Terminal at the two mounting arms 7 are fasteners 8, which are configured in the preferred embodiment here as an annular eyelets. Accordingly, the following is also spoken of eyelets 8, the expert will understand, of course, other fastener forms underneath.

The choice of fasteners as eyelets is therefore preferred because they are both suitable to be connected by means of screws with a corresponding fixed part of the movement, for example, the movement board. But the eyelets 8 are also suitable for a soldered or welded connection as well as for an adhesive connection. For the latter types of connection but simple disc-shaped embodiments of the fasteners would be just as suitable.

In the case of the anchor according to the invention, the introduction of force also takes place from the escape wheel via the pallets 3, as in the case of a conventional anchor. The entire anchor 1 is usually made in one piece, with the exception of the two pallets 3, of a plate-shaped material. It is preferable to choose a high modulus material.

The force exerted by the escape wheel on the pallets 3 force leads to a bending deformation of the mounting arms 7. The width b of the mounting arms 7 is kept as small as possible. The height h of the attachment arms 7 is a multiple of the width b of these arms. With regard to the flexural strength of the attachment arms, the following formula results: $$\mathrm{K}=\mathrm{3}\mathrm{EGG}/{\mathrm{I}}^{\mathrm{3}}$$

It is true that $$\mathrm{I}=\mathrm{b}\times {\mathrm{<figure-callout\; id="3"\; label="H"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">H</figure-callout>}}^{\mathrm{3}}/\mathrm{12}$$

• b = Breite des Befestigungsarmes
• h = Höhe des Befestigungsarmes
• I = Länge des Befestigungsarmes
• I = Flächenträgheitsmoment des Balkens
• K = Die Gesteifigkeit des Balkens.

In this formula: $$\mathrm{e}=\mathrm{e}-\mathrm{Module\; of\; the\; material}$$

• b = width of the attachment arm
• h = height of the attachment arm
• I = length of the attachment arm
• I = area moment of inertia of the beam
• K = the stiffness of the beam.

It can be seen from this formula that as smooth as possible an embodiment of the inventive armature is achieved by making each mounting arm 7 as long as possible and as thin as possible in width. With regard to the height of each attachment arm 7 is of course not free, since this must be sufficiently large so as not to obtain rotational degrees of freedom that are not in the plane of the anchor. Would you choose the height of the mounting arm 7 also very small, so each arm 7 would behave like threads and would be stiff only on train and pressure but otherwise very flexible in all Biegerungen. However, this is not desirable, but the freedom of movement should be limited to a bending movement of each mounting arm 7 within the extension plane in which the anchor is located.

However, the simplest embodiment of the inventive armature with flexible attachment arms 7 described so far still has a relative disadvantage. This anchor has a so-called parasitic motion. This is the unwanted, albeit small, erroneous movement of the rotation center, so called the virtual axis. The third embodiment of the subject invention, as shown in the FIGS. 5 and 6 is shown, also solves this problem.

Ideally, the armature 1 should rotate about a predetermined virtual axis without offset movement of the center. This problem can be largely reduced, for example, by allowing the mounting arms 7, as in the FIGS. 5 and 6 represented, designed. Here are the attachment arms 7 designed with two parallel elastic sections 70 and 71. These two sections 70 and 71 are hairpin-like. The two sections are parallel and arranged in opposite directions. The two elastic partial sections 70, 71 are connected to one another via a thickened connection point 72. The first elastic section 70 thus extends between the thickened connection point 72 and the connection region 6 of the armature 1 or to a thickened part of the attachment arms 7 which is referred to here as the connection part 73. The second elastic section 71 extends from the thickened connection point 72 to a thickened fastening arm part 74, on which the fastening element or fastening eye 8 is formed at the end.

The in the first described embodiment according to the Figures 1 and 2 As mentioned, the solution results in a slight shift of the center of the virtual axis of rotation. This shift is triggered by the deformation movement of the attachment arms 7. The attachment arms shorten their length somewhat when they are bent. The strength of this displacement depends both on the length of the attachment arms 7 and on the angular position, the deflection, of the armature. This parasitic movement is now largely compensated by the third embodiment of the subject invention according to FIGS FIGS. 5 and 6 , A further advantage of this embodiment is that twice the length of the movable part of the fastening arms 7 is achieved by the two elastic partial sections 70 and 71 practically with the same space requirement. Consequently, this solution not only compensates for the parasitic movements, but also reduces the stiffness of the attachment arms, so that the energy required for deformation is less.

There are also other embodiments for the reduction of parasitic movements known, which would also be suitable. For this purpose, for example, the solution according to the EP-1013949 Figure 4 directed. Other suggestions also go from the publication of WH Wittrick "The properties of crosslecture pivots and the influence of the cross-section" (The aeronautique, born 1951 ).

Normally, and in particular with conventional anchors, their movement is limited by means of anchor-limiting pins. In one embodiment, as in the FIGS. 3 and 4 is shown, the fastening elements 8 are designed such that they themselves form stops which limit the oszilierende rotational movement of the fork 4. For this purpose, the attachment lugs 8 movement limiting stops 9, which are designed in the form of bulges in the direction of the fork 4 out. Again, these attachment limit stops 9 are monolithically designed as part of the fasteners or eyelets 8 in turn. Thus, it is unnecessary in the clockwork itself provide anchor limit pins.

Finally, there is also a fourth in the FIGS. 7 and 8 shown embodiment. The embodiments described so far also have a small residual rigidity in the direction of movement. Although part of the momentum given by the armature 1 to the balance is also reimbursed by it, a part of the work is spent on the movement of the armature 1 itself and on the elastic deformation work of its attachment arms. This work is significantly lower than the energy delivered by the escapement wheel. In order to reduce the spring stiffness of the armature 1, it is proposed in this embodiment, again monolithically integrally form a zugelastisches spring element 10 on the armature 1 again. At the free end of the elastic spring element 10, a mounting plate 11 is attached. Through this slot 12, the mounting plate 11 can be adjustably screwed by means of a screw on the board of the clockwork. As a result, the bias of the zugelastischen spring element 10 can be adjusted. The zugelastische spring element 10 is located in the same plane as the mounting arms 7 and the other parts of the inventive anchor 1. Of course, the attachment arms 7 must be fastened with their fastener 8 either on the same board of the movement or at least on another fixed part of the movement, the lies in the same plane. Also, the zugelastische spring element 10 has a much smaller width b in relation to height h. The zugelastische spring element 10 may in principle any Own form, which deviates from a straight line. Thus, the zugelastische spring element 10 could be designed as a simple arcuately curved arm or as shown here, as in the plane meandering extending route.

While in the embodiments described above, the two fastening arms 7 are arranged mirror-symmetrically with respect to the central longitudinal axis of the fork 4, a different solution is shown here. The elastic attachment arms 7 are in turn as elongated elements between the connecting portion 6 and the terminal fasteners 8, which in turn are configured here as eyelets, extending. These two fastening arms 7 are now both arranged on the same side of the fork 4 between these and an armature arm 2. The zugelastische spring element 10 is now placed so that the connecting line between the center of the slot 12 and the connection point of the zugelastischen spring element 10 at the connecting portion 6, the bisector between the two mounting arms 7 represents. The virtual axis of rotation is always at the intersection of the extensions of the two mounting arms 7. While in the examples described above, where the mounting arms 7 are arranged mirror-symmetrically with respect to the fork 4, this virtual axis of rotation can also lie outside the connection area 6, it is in the Embodiment according to the FIGS. 7 and 8 preferably such that the virtual axis of rotation lies in the center of the connecting region 6. In other words, the location of the virtual axis of rotation can thus be determined virtually freely by the choice of the arrangement of the fastening arms 7.

Thanks to the use of an elastic spring element 10, as described above, a preload force is now exerted on the attachment arms 7. Thanks to this biasing force, the angular stiffness of the armature 1 can be changed or set thanks to the slot 12. This bias can be increased so far that in principle the anchor gets into an unstable position. The armature is then operated in the so-called bistable buckling mode. In other words, with little force acting the armature 1 jumps about the virtual axis of rotation pivoting from one end position to the other end position.

In the FIG. 7 is contrary to FIG. 8 also shown the possibility that the pallets 3 also monolithic one piece and thus made of the same material as the anchor 1 in one operation. Since one chooses according to the invention and preferably a manufacturing process for the manufacture of the inventive armature 1, in which the boundary edges of the armature are extremely regularly finished with a very low roughness, friction losses are also reduced. In particular, two methods are suitable for the production. One method is called a DRIE method. DRIE stands for Deep Reactive Ion Etching. This procedure was developed by the company Bosch and in this regard, for example, to the documents DE-3927163 or DE-4420962-A directed.

By means of this method, fastening arms 7 can be produced with a very small width. Typically, the attachment arms 7 are made with a width of 15-50 microns. The geometry of an inventive armature 1 produced in this way has an extreme accuracy, with deviations which are usually less than one micrometer.

Among other things, silicon in the form of wafers may be considered as the material of manufacture for this process. This material is particularly suitable for the production of the inventive anchor. In fact, this material has ideal properties for this application. It has a high mechanical strength and a very low plastic deformability, so that the areas with large thickness in the loading direction have virtually no deformation. This leads to extremely low losses. Material fatigue practically does not occur as long as the applied stresses at the alternating stresses are kept below the elastic breaking point. Finally, silicon has a very low coefficient of friction. The only problem is that the parts etched by the DRIE method have very sharp edges. For the watchmaker who works with the tweezers, it is thus possible for the watchmaker to produce very high pressures locally on the sharp edges. This can lead to the destruction of the anchor. To remedy this disadvantage, one can change the surface of the workpiece by either oxidizing or nitriding the surface. This is superimposed around the edges Material on or material is removed, so that the edges undergo certain curves. The silicon oxide and the silicon nitride also have tribological advantages in which in turn the coefficient of friction is positively influenced.

It is also possible to apply a hard layer to the silicon surface by growing a synthetic diamond or sapphire thereon. These are also known coating methods.

Although silicon is the preferred material for the anchor, it can also be made of quartz, pyrex glass, sapphire or diamond. All these materials can be produced synthetically, are accordingly hard and abrasion resistant. In addition, these materials can be at least partially processed by the DRIE method. Another preferred manufacturing method is known from the so-called LIGA technology. With regard to the LIGA process, reference is made, for example, to the European patents EP-0183910A or the EP-1431844-A as well as on the U.S. Patent 6458263-B directed. In particular, nickel or nickel phosphorus compounds are used for the LIGA process. Also by means of this method, an anchor according to the invention can be produced with the required dimensions and accuracy, which has the desired physical properties. The LIGA process is a lithographic-galvanic etching process.

In addition to the two preferred production methods described here, of course, other suitable methods come into question with the respectively suitable materials. Merely for the sake of completeness, the possibility of wire-electric erosion may be mentioned here as an example, in which case the armature is formed from a corresponding steel or the production of metallic glasses by the so-called micro-structuring method (micro-molding) is mentioned.

Claims (13)

1. Anchor (1) for a timepiece escapement in a mechanical clockwork with escape wheel, comprising two anchor arms (2) in each of which is held a pallet (3) and with a fork (4) which is disposed in order to act on the balance wheel, whereby the anchor (1) comprises at least two fastening arms (7), which are integrally manufactured with the anchor arms (2) and the fork (4), and by means of which the anchor (1) is connectible to an immobile part of the clockwork, whereby the at least two fastening arms (7) are designed at least in part in such an elastically flexible way that the anchor (1) is able to swing under the effect of the energy transmitted to it by the escape wheel.
2. Anchor according to claim 1, characterized in that the at least two fastening arms (7) are elastically designed on the entire length.
3. Anchor according to claim 1, characterized in that the at least two fastening arms (7) have two elastic sections (70, 71) which are disposed in a way running opposite and parallel.
4. Anchor according to claim 3, characterized in that the two sections (70, 71) are designed hairpin-like, and in that the two sections (70, 71) are connected to one another via a thickened place of attachment (72).
5. Anchor according to one of the claims 1 to 4, characterized in that integrally shaped in one piece on the anchor (1) is a tenso-elastic spring element (10), which is provided with a mounting plate (11) for fastening, in order to reduce the torsional rigidity of the anchor (1).
6. Anchor according to claim 5, characterized in that the mounting plate (11) has a long slot (12) for fastening of the spring element (10) with adjustable pretension in order to adjust the torsional rigidity of the anchor (1).
7. Anchor according to one of the claims 1 to 6, characterized in that the at least two fastening arms (7) are fixed to the immobile part of the clockwork by means of screws.
8. Anchor according to one of the claims 1 to 6, characterized in that the at least two fastening arms (7) are non-detachably fixed to the immobile part of the clockwork by means of welding, soldering, or adhesive bonding.
9. Anchor according to one of the claims 1 to 8, characterized in that the anchor (1) comprises two fastening arms (7), whereby the two fastening arms (7) are disposed symmetrically with respect to the fork (4), so that the fork lies on the bisecting lines of the angle enclosed by the two fastening arms (7) or respectively their two elastic sections.
10. Anchor according to one of the claims 1 to 8, characterized in that the anchor (1) comprises two fastening arms (7), whereby the two fastening arms (7) lie on the same side between the fork (4) and an anchor arm (2).
11. Anchor according to claim 9 or 10, characterized in that the two fastening arms (7) are connected by a common connecting region (6).
12. Anchor according to one of the claims 1 to 11, characterized in that it is made of one of the following materials: of

    - synthetic jewel, in particular diamond;

    - synthetic semi-precious stone;

    - silicon or silicon compound.
13. Anchor according to one of the claims 1 to 12, characterized in that its surface is nitrided or oxidised.

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