GB2533960A - An escapement comprising a magnetically braked escape wheel and a tuned mechanical resonator for time keeping in clocks, watches, chronometers and other - Google Patents

Abstract

An escapement for a timepiece comprising a tuning fork shaped resonator 2 with tines 3 having permanent magnets 5, and an escape wheel 1 with non-magnetic, conductive areas 6 regularly spaced around its circumference. The escape wheel rotates so that the conductive areas sequentially interact with the tines of the resonator. The movement of the conductive areas adjacent to the magnets 5 on the tines creates eddy currents that cause the magnetic tines to vibrate, creating a braking force as the conductive areas pass closest to the tines. The acceleration of the escape wheel and the braking force will come to equilibrium when the resonator is oscillating at its resonant frequency. The physical dimensions of the resonator can be adjusted so that the resultant rotational velocity is appropriate to the gearing of the timepiece.

Description

DESCRIPTION

BACKGROUND OF THE INVENTION Field of the invention

The present invention relates to the field of horology and time keeping. It relates, more particularly, to a mechanical mechanism known by the name of an escapement.

Description of the prior art

In mechanical clocks and watches and other time keeping devices an escapement is used to convert the stored mechanical energy (in a spring or potential of a mass) into a rotation at a fixed frequency. The fixed frequency is maintained by a regulating member such as a penduhun,balance wheel or mechanical resonator acting as an oscillator. The present invention concerns in particular the escapement and the regulating member.

The oscillator formed by a pendulum offers remarkable properties for measuring time. However it is unsuitable for any mobile application as the pendulum must be maintained in a fixed position.

Mobile timepieces such as conventional mechanical watches most often use a balance wheel as a regulating member. The balance wheel is mounted on a rotational axis has also proved to be very effective at acting as a frequency regulator. The balance wheel typically uses a return member in the form of hairspring,which transmits a restoring torque to the balance to bring it back towards a resting position following excitation via the escapement which supplies the energy to maintain continuous oscillations.

Both the balance wheel and escapement have timing errors associated with design and the prior art is focussed on improving designs to reduce such errors. The balance wheel has disadvantages in that is subject to positional errors due to gravity. Mechanisms have been successfully used to correct for errors introduced into the balance via motion. In such devices the balance wheel itself is rotated over a fixed period to average out positional errors the use of such devices is discusses. However, these add a considerable complexity to the design of the time piece. Numerous works have focused on describing the different escapement mechanisms. Reference can be made to "Theorie de l'horlogerie" by Reymondin et al, Federation des Ecoles Techniques, 1998, ISBN 2-940025-10-X, pages 99 to 128.

Continued improvements are being sought to improve mechanical time pieces. Examples of balance wheel improvement are given in patent applications W02006045824 and US8534910 B2 which proposes replacement of the spiral hairspring of the prior art by at least one permanent magnet that pushes the balance back towards its resting position against the force of the escapement's pulses. Disturbances of the isochronicity that characterize spiral hairsprings when they deform under the action of gravity can be avoided as the magnet's magnetic force is independent of its orientation in space. However, these patents use traditional escapements utilising a mechanically coupled escape wheel that drives the magnetic balance. This has disadvantages that the system has errors associated with the transfer of energy from the escape wheel to the balance via the mechanical coupling. Improvements in mechanical escapement design are also being sought. For example, patent EP0018796B1 proposed a co-axial design that has been developed to improve timing accuracy and reducing service intervals and has been widely implemented and formed the bases of further prior art.

Tuned mechanical resonators in the general form of a tuning fork with tines have are used to keep time in both mechanical and electrically driven clocks and watches. Unlike a balance wheel that pivots to and throe around a central point these resonators have tines, as in a tuning fork, that vibrate at a frequency depending on the physical properties and dimensions of the resonator. These tines can be driven by a mechanical escapement for example patent W02013045573A1. US patent US2888582A describes an example of the prior art where an electrically powered circuit includes a coil to energise fixed magnets that may be mounted to one or both tines. The tuning fork based clocks and watches based on these movements have proved remarkably accurate. US3616636A patent proposed a design that included a balanced tuned mechanical resonator optimised to reduce the positional errors that occurred in the prior art; this balanced tuned resonator further improved accuracy of electro mechanical tuning fork watches. Electro mechanical tuning fork based watches and clocks reached accuracies achieved by the best timepieces using balance wheel regulators and traditional escapements. Unlike balance wheel watches electro mechanical tuned resonator based watches have the advantage that they do not need the setting up to accommodate the positional crrors due to gravity as frequently required by balance wheel based watches.

In addition, electrically powered clocks and watches using a tuning fork regulator have the advantage that they do not have a mechanical contact based escapement requiring oiling and maintenance.

The prior art, for example US3616636A, shows the system of transferring lateral movement of a tuning fork type resonator to rotational movement uses a system of ratchets and jewels that turn a very delicate index wheel. Although not needing oiling this is a complex system and later prior art, for example patent US3813871, describes the use of magnet system to transfer the lateral movement of the tines into rotational movement in escapement for an electromechanical tuning fork based clock. In addition, patent US3727396A describes magnetic system for translating the lateral movement of the resonator into rotational movement to drive in a watch movement. However, electromechanical watch, clocks and other timepieces have that the disadvantage that a battery or other source of electrical energy needs to be provided and maintained.

British patent GB660584 describes a magnetic escapement for a tuning fork type mechanical resonator; an escape wheel and tuning fork resonator are magnetically locked together via a wavy magnetic path on the escape wheel which rotates in a plane between the tines forcing the tines to move. Although eliminating the need for a lever type escapement, challenges in production exist due to the difficulty in the complexity of the design and manufacture of materials to create the wavy path and keeping the two synchronously locked via the magnetic torques created by this arrangement. A conducting disk, rotating in a magnetic field as described in the patent produces an electrical breaking force as a result of induced Eddy currents within the rotating body due to Lorenz's law. There is no discussion of these factors within the patent of these factors and this may account for why this approach has not been implemented.

The approach taken in patent GB660584 was developed further in patent US3208287A for a motor driven escapement in which an undulating magnetic track is described to move in the plane between tines which have a forked end. The undulating track in patent US3208287A replaces the wavey path as described in patent GB660584. As in patent GB660584 in operation the escape wheel forms a magnetic flux conducting or modifying material that interacts with the magnets mounted on the tines to drive the tuning fork type tuned mechanical resonator. This latter approach also has not been implemented possibly due to the manufacture of the undulating track and possibly as a result of magnetic braking forces created by Eddy currents in the rotating disk in a magnetic field.

In an effort to incorporate the advantages of a tuned mechanical resonator into mechanical timepieces and to over come these problems free running escape wheels with regularly spaced magnets permanent have also been described which transmit energy to the tines of a tuned mechanical resonator. Patent US3877215A describes a member comprising a tuning fork type resonator whose high frequency vibrations are transmitted to a lower frequency member comprising a balance wheel, through magnetic coupling. However, this has the disadvantage that it increases the complexity of two frequency regulators and a mechanical escapement is still required for the balance wheel and has not been implemented.

In another effort to incorporate a tuned mechanical resonator into a mechanical timepiece Patent US2013/0279302 Al describes a tuned mechanical resonator that is powered by permanent magnets fixed to an escape wheel that transmits power to permanent magnets mounted on the tines of the tuned mechanical resonator.

In both US3877215A and US2013/0279302 Al the rotating magnets on the periphery of the escape wheel create fields that can cause magnetic braking effects in conductive materials effecting the design. In addition, as the escape wheels rotate and the magnets of the escape wheel pass those on the tines of the tuned mechanical resonator, a vector force to the spindle or bearing is generated that create additional energy requirements and impact on performance. Both have a complexity of design that may also impact upon difficulties in production.

A conductive surface moving past a stationary magnet will have circular electric currents called eddy currents induced in it by the magnetic field. This is described by Faraday's law of induction. The circulating currents create a magnetic field which opposes the field of the magnet as described by Lenz's law. Thereby, a moving conductor will experience a force from a nearby permanent magnet that opposes its motion, proportional to its velocity. This effect sometimes known as a magnetic brake, Eddy current brake or electromagnetic brake is widely used in a wide range of devices and has considerable prior art. As the braking effect is proportional to rate of change of the magnetic field, it can be used to regulate device velocity.

BRIEF SUMMARY OF THE INVENTION

One aim of the present invention is to make a tuning fork type tuned mechanical resonator based mechanical escapement that is dimensioned and can be used in watches and clocks.

A particular aim is to use a tuning fork type tuned mechanical resonator rather than a balance as used in mechanical watches in the prior art.

A particular aim is to design a mechanism that optimally transfers energy from a kinetically driven escape wheel to a tuned mechanical resonator using the magnetic braking effect, whereby a moving magnet induces an opposing magnetic force in a non-magnetic conductive material.

Another particular aim is to use an escape wheel that uses as series of non-magnetic conductive brake surfaces to transfer kinetic energy to a tuned mechanical resonator and thereby convert the lateral movement of the mechanical resonators arms into rotational motion of fixed frequency.

Another aim of the present invention is to use an escapement that transfers energy to the tuning fork type tuned mechanical resonator that avoids mechanical contacts as traditionally used in the prior art.

Another aim of the present invention is to reduce the complexity and number of parts of the mechanical escapement as used in the prior art.

In the prior art a traditional mechanical escapement is typically achieved by an escape wheel and a system of locking and unlocking the wheel to give pulses of energy to a regulating member. One aim of the present invention is to use the regulating member, a tuning fork type tuned mechanical resonator with tines and a non-magnetic escape wheel, to form an escapement.

The prior art describes a magnetic escapement using a tuning fork type timed mechanical resonator and an escape wheel with a complex magnetic wavey path where the plane of the escape wheel rotates between the tines to lock the movement of the two component together. The prior art also describes an escapement using a free running escape wheel with regularly spaced peripherally mounted magnets that are used to transfer energy to a permanent magnets mounted on the tine of a tuned mechanical resonator.

One aim is to replace this arrangement with a simpler system of regularly spaced conductive nonmagnetic brake surfaces on an escape wheel.

Another aim of the invention is to produce an escape that can be more easily manufactured and does not permanently lock the movement escape wheel to the movement of the tines but optimally transfer kinetic energy as the escape wheel braking surfaces interact with magnets on the tines of the tuned mechanical tuned resonator.

Another aim of the invention is to propose the tuned mechanical resonator can be dimensioned to vibrate at a high frequency and thus it can be used to measure time periods to a high level of precision.

It represents a considerable challenge to propose technical innovations in the field of horology, and particularly watch making. One aim of the present invention is to propose a new and different mechanical watch escapement that is different from the prior art.

An aim is to take advantage of the properties of a tuning fork type tuned mechanical resonator with tines and by the invention regulate an, all mechanical, watch, clock, chronograph or other timepiece.

According to the invention these aims are achieved by an escapement comprising an escape wheel with a series of regularly spaced of non-magnetic conductive brake surfaces and a tuning fork type tuned mechanical resonator with tines having the characteristics of the main claim, with preferred embodiments described in the dependent claims.

These aims are achieved by means of a mechanical escapement for a wristwatch, clock or timepiece including: * using an escape wheel and mechanical tuning fork type tuned mechanical resonator comprising; * a mechanical tuning fork type tuned mechanical resonator with at least one permanent magnet attached to one of the tines; * an escape wheel comprising a series of non-magnetic conductive brake surfaces to directly transfer by the kinetic energy to the mechanical resonator; * a bridge which enables the the relative position between the escape wheel and the tuned resonator fines of the tuned resonator to be fixed.

The frequency of the escapement is achieved by the following methods: * the physical dimensions of the tuning fork type tuned mechanical resonator and fixed permanent magnets; * the material of the tuned mechanical resonator, these together with the physical dimensions define the resonant frequency of the resonator; * the number of non-magnetic conductive brake surfaces on the escape wheel; * The shape and form of the non-magnetic conductive brake surfaces on the escape wheel.

Particular choice of the materials. For example, materials used in the tuned mechanical resonator and permanent magnets will be selected for minimum temperature coefficient, ensuring that the frequency of the resonator is stable and does not change with temperature. In addition components will be selected to minimise the effect of stray magnetism, where possible, and made from a nonmagnetic and minimally conducting material to avoid adverse effects of currents and magnetism induced by a moving magnetic field.

Particular choice of the shape of the resonator and permanent magnets attached to the resonator. It will be possible, for example, to use different shapes to maximise the transfer of energy from the escape wheel to the resonator. Shapes include both elliptical and rectangular magnets.

Particular choice of the shape of the conductive non-magnetic brake surfaces. It will be possible, for example, to use different shapes to maximise the transfer of energy from the escape wheel to the resonator. Shapes include both solid surfaces and surfaces with spaces and voids.

For example care in the design of the watch, clock or time piece to minimise any effects of stray magnetic fields is possible. This, in one example, would use magnetic shielding, designed and shaped, to encapsulate the escapement components. In addition this encapsulation and bridge design can include components to constrain and optimise the magnetic fields between the escape wheel and tuned mechanical resonator.

The transfer of the stored mechanical energy into kinetic energy is achieved by the following methods: * For example, it will be possible to use by selection of the number, shape, and form of the non-magnetic conductive brake surfaces located on the escape wheel to modify the rate of transfer of stored energy to the tuned mechanical resonator.

* In addition, the position the permanent magnets are set in the tines can be modified to alter the braking force between the escape wheel and the tuned mechanical resonator converting the rotational movement of the escape wheel into lateral movement of the tines.

* In addition, it will be possible to alter the gap between the escape wheel braking surfaces and the tuned resonator to optimise the energy transferred to maintain the resonance of the resonator.

* Regarding the tuned mechanical resonator, the shape of the resonator and position, shape and angle of the permanent magnets can be modified to optimise the transfer of energy from the escape wheel to the resonator.

In the embodiment of the invention the regulation of the frequency of the escapement is achieved as a result of the stored kinetic energy being transferred from the escape wheel to the tine or tines of the tuned mechanical resonator and the escape wheel and resonator being set at a fixed distance apart: * In one advantageous embodiment of the invention the escape wheel, interacts with a fixed permanent magnet on a single tine of the tuned mechanical resonator.

* In another advantageous embodiment of the invention the escape wheel is mounted between the tines of the tuned mechanical resonator to interact with fixed permanent magnets mounted on one or both tines of the tuned mechanical resonator.

* In another advantageous embodiment of the invention the escape wheel has brake surfaces that alternatively pass on either side of a fixed permanent magnets mounted on one or both tines of the tuned mechanical resonator.

DESCRIPTION OF THE DRAWINGS

FIG. 1 a A schematic diagram of the escapement according to a first embodiment.

FIG. lb A schematic diagram of the escapement according to a first embodiment.

FIG. lc A schematic diagram of the escapement according to a first embodiment.

FIG. 2 A schematic diagram of the escapement according to a second embodiment.

FIG. 3 A schematic diagram of the escapement escape wheel according to a third embodiment.

FIG. 4 A schematic diagram of the escapement according to a fourth embodiment.

DETAILED DESCRIPTION OF THE INVENTION

FIG.I a illustrates a schematic view from the side of an escapement according to a first embodiment of the invention. The escapement includes a tuning fork type tuned mechanical resonator 2 with tines 3 and a fixed permanent magnet 5 attached to one of tines. The escapement includes an escape wheel 1 with a series of regularly spaced non-magnetic conductive brake surfaces 6 have been represented in the plane; the complete wheel preferable includes a non conducting feloe, not shown, to the non-magnetic conductive brake surfaces.

The escape wheel turns around an axis 7 connected to a bridge (not shown) and the escapement plate 4 by means of bearings, not represented, for example incabloc bearings or magnetic bearings. In this embodiment the escapement plate may preferably be part of the timepiece incorporating the escapement.

FIG. la schematically illustrates a view from the side of the the first embodiment of the invention where the escape wheel 1 is positioned so that the brake surface faces 6 rotate across an outer magnetic face of the permanent magnet 5 mounted on a tine 3 of the resonator; in this example the axis of rotation 7 is between the two tines 3 of the resonator.

FIG. lb schematically illustrates a view from the side of a second example the first embodiment of the invention where the escape wheel 1 is positioned so that the brake surface faces 6 rotate across a magnetic face of the permanent magnet 5 mounted on the tine 3 of the resonator. In this example the escape wheel 1 is positioned with the axis of rotation 7 is in line with the tines of the resonator 2, so that the brake surface faces 6 rotates across a face of the permanent magnet 5 mounted at the end of the tine 3 of the resonator 2.

FIG. lc schematically illustrates a view from above of a third example of the the first embodiment of the invention where the escape wheel 1 is positioned so that the brake surface faces 6 rotate across a magnetic face of the permanent magnet 5 mounted on the fine 3 of the resonator. In this example the escape wheel 1 is mounted orthogonally to resonator 2 so that the brake surface 6 rotate across a magnetic face of the permanent magnet 5 mounted at the top 3 a tine on the resonator.

An adjustment mechanism, not shown, may be used to vary the gap between the escape wheel I and the tuned mechanical resonator 2 and to adjust the position and angle of the magnet attached to the tine to facilitate optimal functioning of the escapement.

The escape wheel I includes a drive pinion, not shown, to transfer the kinetic driving force the escapement is regulating. During operation a kinetic mechanical force is applied to escape wheel pinion from a gear train driven from a spring or gravity. As the escape wheel 1 moves energy is transferred to the tuned mechanical resonator. The interaction between the non-magnetic conductive brake surfaces 6 and the permanent magnet 5 on the tine induce a repelling force on the tine of the tuned mechanical resonator that has to be overcome. After each brake surface 6 passes the permanent 5 magnet mounted on the tine it is then free to naturally follow the natural resonance of the resonator. The shape and form of the conductive non-magnetic brake surfaces 6 and the permanent magnet 5 on the tine are selected so the escapement can overcome the braking forces.

When continuously working, energy is kinetically transferred via the brake surfaces 6 on the escape wheel 1 to the tuned mechanical resonator 2 as each brake surface 6 passes the permanent magnet 5 mounted on the tine of the tuned mechanical resonator 2. At the resonance frequency of the resonator, the interaction between the brake surfaces 6 on the escape wheel 1 and the magnet 5 on the tine of the tuned mechanical resonator 2 locks and regulates the rotational frequency of the escape wheel 1. The rotational frequency of the escape wheel 1 is directly proportional to the frequency of the tuned mechanical resonator. The frequency of rotation of the escape wheel 1 is calculated by dividing the frequency of the tuned mechanical resonator 2 by the number of brake surfaces 6 on the escape wheel that pass the permanent magnet face 5. For example, if the tuned mechanical resonator 2 vibrates at 300 cycles per second and there are 10 regularly spaced brake surfaces 6 the frequency of the escape wheel would be, 300 divided by 10, ie 30 rotations per second.

The kinetic force applied to the pinion of the escape wheel has to be sufficient to transfer enough energy energy from the non-magnetic brake surfaces 6 on the escape wheel to the permanent magnets 5 on the tine of the tuned mechanical resonator to maintain resonance. However, the tuned mechanical resonator 2 has the property that it will maintain the frequency for a range of stored energy. Once vibrating at the tuned mechanical resonators 2 frequency the resonator stores energy in its vibrational mode and release that energy in an exponential decay. Therefore as long as there is sufficient energy source to continuously drive the escapement, the tuned mechanical resonator 2 will maintain its resonant frequency despite any small variations in the driving energy. Sufficient kinetic energy is applied to the escapement to top up energy losses from the escapement.

The kinetic energy regulated by the escapement is controlled by mechanical and magnetic properties of the escapement including both the magnetic braking and the physical properties of the tuned mechanical resonator which determine its resonant frequency.

The magnetic braking can be single sided as in the first embodiment of the invention where the escape wheel 1 interacts with a single permanent magnet 5 on one of the tines 3 of the tuned mechanical resonator 2 as in the first embodiment of the invention and schematically illustrated in FIG. 1A, FIG. lb and FIG1c. Alternatively, the coupling between the escape wheel 1 and the tuned Mechanical resonator can take advantage of permanent magnets 5 mounted on both tines 3 of the tuned mechanical resonator 2 as in the second embodiment of the invention. FIG. 2 illustrates a view from the side of an escapement according to a second embodiment of the invention. In this variant the escape wheel 1 is mounted between and in the plane of the tines 3 of the resonator 2, one or both of the tines 3 may have one or more fixed permanent magnets 5. The axis 7 of the escape wheel 1 is positioned on the main plate 4 relative to the tuned mechanical resonator 2 so that the faces of the conductive non-magnetic brake surfaces 6 on the escape wheel move across the face of the permanent magnets 5 on the tines 3. Operation in the second embodiment is similar to that of the first embodiment with energy transferred by magnetic braking induced by the nonmagnetic conductive brake surfaces 6 from the escape wheel to 1 one or more permanent magnets 5 mounted on one or both tines 3 of the tuned mechanical resonator 2.

FIG. 4 schematically illustrates a view from the side of the the fourth embodiment of the invention where the escape wheel 1 is positioned so that the alternate brake surfaces 6 of the escape wheel pass opposite faces of a permanent magnet 5 mounted on a fine 3 of the resonator; in this example the axis of rotation 7 is between the two tines 3 of the resonator. In this embodiment of the invention energy is transferred to the resonator 2 as alternate brake surface 6 interact with the permanent magnet on the tine 5. The movement of the escape wheel 1 creates an opposing repulsive magnetic field that has to be overcome after which the tine 3 is released. In this embodiment the alternating brake surfaces 6 transfer energy in both directions of the natural to and fro movement of the tine 3.

The mechanical tuned resonator 2 can manufactured to a balanced design to account for gravity and materials selected for temperature stability; in addition, micrometric adjustments can be incorporated to make fine adjustments to its resonant frequency. The shape and three dimensional form of the tuned mechanical resonator 2, including the shape and position of mounting of the permanent magnets on and tines, can be produced in a calculated manner to provide a stable and precise resonant frequency; for example, by the means of finite element analysis so as to ensure suitable optimal locking and energy transfer between the escape wheel 1 and the tuned mechanical resonator 2 and to minimise sensitivity from external perturbations and temperature.

The three dimensional form of the escape wheel 1 including the shape and position of the conductive non-magnetic brake surfaces 6 can be produced in a calculated manner to optimise the transfer of energy from the escape wheel 1 to the tuned mechanical resonator 2. The driving forces and energies can be calculated, for example, by the means of finite element analysis so as to ensure suitable locking and energy transfer between the escape wheel 1 and the tuned mechanical resonator 2 and minimise sensitivity from external perturbations and temperature.

FIG. 3 schematically illustrates an escape wheel 1 according to a third embodiment of the invention where the conductive non-magnetic brakes surfaces 6 are extensions that radiate from the centre of the escape wheel 1.

The claimed solution has the advantage of combining the escape wheel 1 directly with the regulating member, a tuned mechanical resonator 2, and reducing the number of bearings to only one pair for the escape wheel 1 thereby minimising the complexity of the escapement and need for servicing. The escapement, advantageously, has no, physical contact point between the escape 1 wheel and tuned mechanical resonator 2 that need oiling or servicing. The claimed solution uses an escape wheel 1 with no rotating permanent magnets reducing both complexity and minimising unwanted magnetic effects.

The escapement of the invention can operate at very high frequencies and be used to regulate time in watch, clock or other timepieces to indicate time. Advantageously the mechanism can be used to measure time to high resolution and high precision in chronometers and chronograph.

In the applying the escapement to a watch, clock or other timepiece it is preferable that the bridges, plates, gear trains and other component positioned in close proximity to the escapement are made from a non-magnetic material to limit disturbances caused by any stray magnetic fluxes that may emanate from the escapement. In addition, any nearby components to the permanent magnetic components should be made of non conducting materials to reduce any possible effects of magnet induced eddy current or where not possible advantageous use of electrically grounding the plate and bridge and other nearby components should be made to minimise the effects of any stray eddy currents.

In practice an escapement can be implemented by one skilled in the art, using a mechanical resonator differing from that according to the embodiment described here, but comprising an escape wheel described above, without departing from the scope of the present invention.

Other variant embodiments can be conceived of in the frame of the example. For example, a modular escapement that is encapsulated to limit the effects of magnetic fields.

PATENT CITATIONS

Cited Patent Filing Date Publication Applicant Title Date W02006045824 26/10/05 04/05/06 Tag Heuer SA Wristwatch regulating member and mechanical movement comprising one such regulating member US8534910 B2 01/05/12 17/09/13 Lvmh Swiss Manufacturers SA Regulating member for a wristwatch,and timepiece comprising such a regulating member EP0018796B1 25/04/80 07/11/84 George Daniels Watches,clocks and chronometers and escapements therefor W02013045573A1 29/09/11 04/04/13 Asgalium Unitec SA Resonator having a tuning fork for a mechanical clock movement US2888582A 14/02/56 26/05/59 Bulova Watch Co Inc. Tunng fork oscillator US3616636A 27/02/70 ' 02/11/71 1 Ebauches SA Electric Timepiece US3727396A 12/04/72 17/04/73 Omega Brandt &Freres SA Louis Oscillating Motor US381387I 27/10/72 13/03/73 Jekko Kabushiki Kaisha Clock utilizing a magnetic escapement mechanism US3877215A 10/12/73 15/04/75 Ebauches SA Resonator for a timepiece GB 660584 30/06/49 7/11/1951 Horstmann Clifford Magnetics Ltd Improvements in or relating to Escapement,Counting and like mechanisms comprising a rotor coupled by magnetic forces to an oscillatory or reciprocatory device for synchronous movement therewith.

US3208287A 12/10/62 28/09/65 Mc° Mr Magnetic escapement US2013/0279302 Al 15/12/11 24/10/13 Asgalium Unitec SA Magnetic resonator for a mechanical timepiece