The invention relates to a movement for a watch, which movement comprises an escape wheel having a plurality of teeth and an oscillator having anchor teeth, typically a so-called entry pallet or tooth and an exit pallet or tooth, which anchor teeth are controlled by the oscillator, e . g . are an integral part of or attached to the oscillator, to alternately block and release the teeth of the escape wheel , wherein at least the escape wheel and the anchor teeth, preferably the entire oscillator, share an imaginary plane , i . e . are planar .

NL 2024076 / CH 716 751 relates to a mechanical watch comprising an oscillator embodied with a vibratory mass or masses , wherein each vibratory mass connects to least one flexural member . The watch further comprises an escape wheel and anchor teeth that are connected to the vibratory mass or masses , which anchor teeth cooperate with the escape wheel , and wherein the anchor teeth are provided on at least one of the flexural members .

WO 2018 / 100122 relates to a device for a timepiece , comprising a base , an inertial regulating organ mounted to rotate relative to the base , by means of an elastic suspension means connecting the regulating organ to the base . The device comprises an anchor adapted to engage with an energy distribution member ( escape wheel ) provided with teeth and intended to be urged by an energy storage device , said anchor being controlled by said regulating member to regularly and alternately block and release the energy distribution member .

It is an obj ect of the present invention to improve consistency of energy trans fer between the oscillator and the escapement wheel and/or improve stability of the oscillator frequency, and thus provide more accurate time keeping . To this end, at least some, preferably most or each of the teeth of the escape wheel and/or at least one, preferably each of the anchor teeth of the oscillator comprises two surfaces defining a circumferential edge, i.e. an edge extending along and/or defining part of the circumference of the escape wheel or anchor teeth, seen in top view, that is aligned with the end surfaces of the teeth of the other .

In an embodiment, the end surfaces of the teeth of the escape wheel and/or of the anchor teeth define circumferential edges, preferably sharp edges, i.e. edges that, seen in cross-sectional side view, have an angle smaller than 90°, with the upper or lower surface of the escape wheel teeth and/or anchor teeth.

E.g. the escape wheel has a flat top surface, and typically a flat bottom surface parallel to the top surface, and the end surfaces of the teeth of the escape wheel are (slightly) oblique defining, seen in cross-section, a sharp edge with the top surface or the bottom surface of the escape wheel. Similarly, the oscillator including the anchor teeth has a flat top surface, and typically a flat bottom surface parallel to the top surface, and the end surfaces of the anchor teeth define a sharp edge with the top surface of the anchor teeth or oscillator. By aligning the edges of the escape wheel teeth with the end surfaces of the anchor teeth, or vice versa, impact between the two, in particular during impulse, i.e. during transfer of energy from the escape wheel to the oscillator, is more consistent and as a result the frequency of the oscillator is more stable, ultimately resulting in more accurate time keeping.

The edges may have an angle smaller than 89,5°, preferably smaller than 89°, preferably smaller than 88°. In principle, even sharper edges are preferred, although angles smaller than 80° are more time consuming to produce, i.e. angles in a range from 80° to 89,5° are preferred. Consistency can be further improved if the escape wheel and anchor teeth are configured such that during impulse and at the point of contact or line of contact the angle between the end surface (s) of the escape wheel tooth and the end surface (s) of the anchor tooth is larger 1°, preferably larger than 3°, preferably larger than 5°, preferably larger than 10°. It was found that at such angles electrostatic forces between the end surfaces of the teeth of the escape wheel and the anchor teeth are reduced significantly.

In an embodiment, the circumferential edges on the teeth of the escape wheel are, at least when the edge is in contact with an end surface, located between the upper and lower surfaces of the anchor teeth or vice versa, i.e., the circumferential edges on the anchor teeth are located between the upper and lower surfaces of the teeth of the escape wheel.

In a refinement, the circumferential edges on the teeth of the escape wheel are, at least when the edge is in contact with an end surface, located at least 50 pm, preferably at least 75 pm, preferably at least 100 pm removed from the upper and lower surfaces of the anchor teeth or vice versa .

The escape wheel, the oscillator and/or the anchor teeth may have a thickness smaller than 700 pm, preferably smaller than 550 pm, e.g. in a range from 250 pm to 500 pm.

It is preferred that the oscillator and the anchor teeth are monolithic, i.e. made from a single piece.

A very efficient way of providing oblique end surfaces is by shaping the escape wheel, the oscillator and/or the anchor teeth by means of reactive ion edging, such as RIE or DRIE and preferably from silicon.

The advantages of the present invention are particularly pronounced in so-called dead beat escapements, in escapements wherein the amplitude of the anchor teeth is at least substantially equal to the amplitude of the oscilla- tor, and/or in escapements with low torque escape wheels, such as escape wheels having a torque of less than 300 nanoNewtonmeter, less than 200 nNm or even less than 150 nNm. Torque is typically generated by a main spring and transmitted via a gear train.

The oscillator may have an amplitude smaller than 30°, preferably smaller than 20°, preferably smaller than 15°, e.g. in range from 3° to 10°. In this context, amplitude refers to the degrees of rotation of the oscillator from its neutral (or central) position to one of its extreme positions, in clockwise (CW) or counterclockwise (CCW) direction, with the main spring fully wound and the movement in a horizontal and stationary position.

The oscillator may have a natural frequency of 15 Hertz (Hz) or higher, preferably 25 Hz or higher, preferably 35 Hz or higher. In extreme instances, natural frequencies could be up to 100 Hz or even higher.

The invention further relates to a movement comprising a base, e.g. a base plate or platine, and the oscillator comprises a ground that is mounted to the base and an oscillatory mass that is suspended to the ground via one or more elastic links, typically a plurality of links, e.g. two or four links, and/or an escape wheel that is rotatably mounted to or in the base. In an embodiment, the ground, the one or more elastic links, and the mass form a compliant mechanism and/or are monolithic, i.e. made from one piece.

In an example, the escape wheel comprises a central shaft rotatably mounted in a bearing, such as rubies, on or in the base plate and on or in a bridge extending over the escape wheel. The movement may comprise an energy storage, typically a mainspring, in particular a spiral spring in a geared barrel, a gear train, e.g. comprising a center wheel, a third wheel (carrying or coupled to the minute and hour hands of the watch) , and a fourth wheel (carrying or coupled to the second hand) of the watch, to transmit torque and energy to the escape wheel . The invention also relates to a wrist watch comprising such a movement .

The invention also relates to a wristwatch comprising a movement as described above .

WO 2019/ 156552 relates to a mechanical watch oscillator comprising a platform and at least two vibratory masses that are individually suspended on the platform with at least one flexural member . When the masses are vibrating, extensions ( reference signs 51 , 52 in the drawings of WO 2019/ 156552 ) of these masses alternatively release and block an escape wheel , allowing the escape wheel to rotate in steps .

US 3 , 834 , 155 relates to an improved escapement mechanism for a horological device , especially a watch, with an improved pallet lever construction for coupling a conventional escape wheel and balance wheel . The pallet lever is constructed so that it can be pivotably mounted on an axis that lies within the outer diameter of the balance wheel by means of an of fset portion passing around the balance wheel . The pallet lever is preferably an integral plastic member .

EP 2 727 880 relates to a three-dimensional micromechanical component that is made of a base material provided with carbon ( C ) or silicon ( Si ) , glass-ceramics or alumi- num-containing glass-ceramics . A chamfer is placed at speci fic angle in the edges of the surface . The chamfer has speci fic surface roughness . The base material composed of silicon, Silicon dioxide ( SiO2 ) , quartz , Silicon carbide ( SiC ) , diamond, diamond-like carbon ( DLC ) , or crystalline diamond made of sapphire or ruby . An independent claim is included for a method for producing a micromechanical component .

EP 2 107 434 relates to a device that has a micromechanical component in contact with another micromechanical component such that a sliding relative movement occurs between contact surfaces of the components . The former compo- nent is formed from hard, dimensionally stable non-metallic material e . g . silicon, diamond, diamond-like carbon, synthetic ruby or sapphire , so that one of the contact surfaces includes longitudinal dimension of maximum 200 micrometers perpendicular to a relative movement direction and extends in the relative movement direction .

EP 2 840 059 relates to a method for manufacturing a micro-mechanical part , in particular a mechanical timepiece , by etching from a substrate , the method comprising at least a first step carried out by ion etching deep reactive ion etching ( DRIE ) with the parameters adj usted in order to perform an etching producing essentially vertical sides , as well as a second step carried out by deep reactive ion etching ( DRIE ) with the parameters adj usted in order to perform an etching producing the inclined sides under a predetermined angle with respect to the vertical , the first and the second step being carried out continuously, without stopping etching .

Below, the invention will be explained further, which reference to the appended figures in which an embodiment of the invention is shown .

Figures 1 and 2 are a perspective view and a top plan view of an oscillator and escape wheel according to the present invention .

Figure 3A to 3D are schematic cross-sections of a pallet and a tooth of an escape wheel illustrating the interaction according to the present invention .

Figure 4 and 5 show top-side etching and back-side etching using a Bosch DRIE process .

Elements in di f ferent embodiments that are similar or identical or that perform a similar or identical function are referred to by the same reference number .

Figures 1 and 2 show a monolithic oscillator 1 in a movement (not shown) comprising a substantially discshaped mass 2 that comprises two halves 2A, 2B that are com- pliantly interconnected by a set of flexures 3. Each of the halves is connected to a ground 4 by means of a plurality of further flexures, i.c. two radially extending flexures 5, four flexures in total, enabling the mass to oscillate. In the present example, the oscillator has a natural frequency in a range from 20 to 100 Hz, e.g. 40 Hz, and an amplitude in a range from 3° to 10° (in each direction, i.e. both in the CW direction and in the CCW direction) , e.g. 5°.

Each of the halves 2A, 2B is provided with an anchor tooth 8, traditionally known as pallet. Further, the halves define an aperture that accommodates an escapement wheel 9 comprising a plurality of teeth 10. During oscillation, the anchor teeth on the oscillator alternately block and release the teeth of the escape wheel.

Figure 3A shows one of the anchor tooth 8 and an escape wheel tooth 10 in cross-section just prior to impulse, i.e. just prior to contact between the escape wheel and the oscillator and energy being transferred from the escape wheel to the oscillator. The escape wheel 10 and the oscillator 1 including the anchor teeth 8 are made from a silicon disc having parallel upper and lower surfaces and were shaped by DRIE. The sides of the escape wheel and the oscillator extend at a slight inclination, e.g. at an angle fi> of 89, 6° with the top surfaces of the escape wheel and the oscillator. I.e. the teeth of the escape wheel and the anchor teeth have inclined end surfaces 8A, 10A that define a edge 8B, 10B with the respective top surfaces. Seen in top view, these edges 8B, 10B define the circumference of the teeth .

In Figure 3A, the circumferential edges of the escape wheel teeth and the anchor teeth are perfectly aligned (at exactly the same height, relative to the base plate of the movement) . In practice, a watch movement is subjected to i.a. changes in orientation and shock which may result in temporary misalignment of the edges which in turn introduces inconsistency in the transfer of energy from the escape wheel to the oscillator. Figures 3B to 3D show various way of reducing or preventing such misalignment.

In Figures 3B and 3C, the angle fi> is reduced e.g. to 88° and the circumferential edges on the teeth of the escape wheel are located at least 50 pm, e.g. 200 pm removed from the upper surfaces of the anchor teeth. In addition, in Figure 3C, the angle of the end surfaces 10A of the teeth of the escape wheel is much smaller, e.g. 82° (Figure 3C shows an even smaller angle for illustrative purposes) . This results in a larger angle, in this example 10°, between the end surface (s) of the escape wheel tooth and the end surface (s) of the anchor tooth, reducing electrostatic forces between the end surfaces of the teeth. In Figure 3D the circumferential edges on the teeth of the escape wheel are defined by a double taper.

The tapered angle described above can be achieved by, for instance: a. Top-side etching using Bosch or other DRIE process, shown in Figure 4, and creating negative slope larger than 0.5 deg by manipulating process parameters such as increasing the etch gas flow, time, etch pressure, power temperature, decreasing passivation gas flow, decreasing passivation time, or any other combination of these or other process parameters. b. Backside etching using Bosch or other DRIE process, shown in Figure 5, and creating a positive taper angle bigger than 0.5 deg by manipulating process parameters such as decreasing the etch gas flow, time, etch pressure, power temperature, increasing passivation gas flow, increasing passivation time, or any other combination of these or other process parameters. c. Backside etching using any isotropic etching method d. Backside etching using positively tapered masking layer with combination of (a) , (b) or (c) and transferring the taper into semiconductor material.

The tapered mask can be created by: i. Wet etching of the hard mask ii. Using grayscale lithography on the photoresist masking layer iii. Reflowing the photoresist masking layer iv. Combining (i) or (ii) with dry etching of hard mask layer v. Any combination above e. Creating a mold using any approach (a) - (d) and molding the escapement wheel from other material

Any other combination (a) - (e) which results in a tapered angle bigger than (alpha) .

The invention is not limited to the described embodiments and can be varied within the scope of the claims. For instance, the surfaces defining the circumferential edges could be e.g. curved, e.g. concave or convex. Also, the anchor teeth can be integrated in the flexures nearest the escape wheel, similar to what is described in NL 2024076.