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Title:
WEARABLE CHARGING DEVICE
Document Type and Number:
WIPO Patent Application WO/2019/228929
Kind Code:
A1
Abstract:
A wearable charging device (2) for charging a wearable device (4), such as a smartwatch, fitness bracelet or an alerting device, comprises a flat charging section (6) and a bulkier battery section (8) containing a battery (18). The charging section (6) can be inserted between the wearable device (4) and the user's body. It comprises a first opening (14) for allowing access of the wearable device's sensors to the user's skin. The charging device (2) can be used to charge the wearable device (4) while it is being worn by the user.

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Inventors:
TSCHABOLD BRENDAN (CH)
Application Number:
PCT/EP2019/063498
Publication Date:
December 05, 2019
Filing Date:
May 24, 2019
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
TSCHABOLD BRENDAN (CH)
International Classes:
H02J7/00; G04G19/10; H02J7/02; H02J50/10
Domestic Patent References:
WO2016179030A12016-11-10
Foreign References:
US20160291550A12016-10-06
US20170338449A12017-11-23
US20170040825A12017-02-09
US20160091922A12016-03-31
US20170033567A12017-02-02
Attorney, Agent or Firm:
E. BLUM & CO. AG (CH)
Download PDF:
Claims:
Claims

1. A wearable charging device comprising

a housing (9),

a battery (18) arranged in said housing (9),

a charging interface (19),

a driver (36) arranged between said battery (18) and said charging interface (19),

wherein said housing (9) forms a charging section (6) having a first and a second surface (10, 12) and having a height (Hl), along a first direction (XI) extending between said first and said second surface (10, 12), of less than 5 mm, in particular of less than 2 mm.

2. The charging device of claim 1 wherein said housing (9) is rigid.

3. The charging device of any of the preceding claims wherein said charging section (6) comprises a first opening (14) extending between said first and said second surface (10, 12) through said charging section (6).

4. The charging device of claim 3 wherein said first opening (14) has a diameter (D) of at least 10 mm, in particular of at least 20 mm. 5. The charging device of any of the preceding claims wherein said charging interface (19) comprises a coil (20) arranged in said charging section (6).

6. The charging device of claim 5 and of any of the claims 3 or 4, wherein said coil (20) extends around said first opening (14).

7. The charging device of any of claim 6 further comprising a second opening (62) arranged radially outside said coil (20).

8. The charging device of claim 7, wherein said second opening (62) is annular and extends around said coil (20), and in particular with at least one strut (64), in particular at least three struts (64), extending through said second open- ing (62).

9. The charging device of any of the preceding claims, wherein said housing (9) forms at least one battery section (8) arranged at an edge (16) of the charging section (6), wherein said battery (18) is arranged in said battery section (8) and wherein a height (Bl) of said battery section (8) along said first direction (XI) is at least two times larger than the height (Hl) of said charging section (6).

10. The charging device of claim 9 wherein the height (Bl) of said battery section (8) is at least 8 mm.

11. The charging device of any of the claims 9 or 10 wherein, in said first direction (XI), said battery section (8) extends further beyond said first surface (10) than above said second surface (12). 12. The charging device of claim 11 wherein

said battery section (8) is flush with said second surface (12) or said battery section (8) extends further beyond said first surface (10) than said second surface (12). 13. The charging device of any of the claims 9 to 12 comprising only one battery section (8) arranged at a single side of said charging section (6).

14. The charging device of any of the claims 9 to 12 comprising at least two battery sections (6), in particular exactly two battery sections (6), on oppo- site sides of said charging section (6).

15. The charging device of any of the claims 9 to 14 wherein said charging section (6) extends away from said battery section (8) by at least 10 mm, in particular by at least 20 mm, along a second direction (X2), wherein said second di- rection (X2) extends perpendicular to said first direction (XI).

16. The charging device of claim 15 wherein, in a third direction (X3) perpendicular to said first direction (XI) and said second direction (X2), said charging section (6) has an extension (H3) of at least 10 mm, in particular of at least 20 mm, and/or of no more than 40 mm.

17. The charging device of any of the claims 9 to 16 wherein an ex- tension (W) of said battery section (8) along a second direction (X2) is no more than 5 cm, in particular no more than 3 cm, wherein said second direction (X2) extends perpendicular to said first direction (X2).

18. The charging device of any of the preceding claims wherein said charging section (6) is fixedly mounted to said battery section (6).

19. The charging device of any of the preceding claims further com- prising at least centering element (30) located at a periphery of said charging section

(6) and extending, along said first direction (XI), above said first surface (10).

20. The charging device of any of the preceding claims wherein a minimum diameter of said charging section (6) in at least one direction (X2, X3) perpendicular to said first direction (XI), in particular in any direction perpendicular to said first direction (XI), is at least 1 cm, in particular at least 2 cm.

21. The charging device of any of the preceding claims wherein the driver (36) is adapted and structured to feed power from said battery (18) to said charging interface (19).

22. The charging device of claim 21 wherein said driver (36) is further adapted and structured to also feed power from said charging interface (19) to said battery (18).

23. The charging device of any of the preceding claims, wherein said first and/or second surface (10, 12) is/are concave in at least one direction (X2, X3) perpendicular to said first direction (XI).

24. The charging device of any of the preceding claims comprising a temperature sensor (52), wherein said driver (36) is adapted and structured to limit a temperature of said charging device, while charging and/or discharging said battery (18), to a threshold temperature (Ts), wherein said threshold temperature (Ts) is lower than 50°C, in particular lower than 40°C.

25. The charging device of any of the preceding claims wherein said charging interface (19) comprises electrical contacts (22) arranged on said charging section (6). 26. The charging device of any of the preceding claims further com- prising a control unit (50) adapted and structured to enable and disable said driver (36).

27. The charging device of claim 26 further comprising a user-op- eratable control (54), in particular a button, for enabling and disabling said driver

(36), and in particular wherein

- said user-operatable control (54) is not arranged at the first side of said charging device and/or

- wherein said user-operatable control (54) is arranged on a battery section (8) of said charging device.

28. The charging device of any of the preceding claims 26 or 27 comprising a timer (56) adapted to automatically and repetitively enabling and disabling said driver (36).

29. The charging device of any of the preceding claims comprising an interface (58) for communication with an external device, and in particular wherein said interface (58) is adapted to communicate with said wearable device, and wherein said charging device is adapted to

- enabling and disabling said driver in response to commands through said interface (58), and/or

- changing an operation setting of said charging device in response to commands through said interface (58) and/or

- exchanging data through said interface, and in particular to pro- vide read and write access to a mass storage device (60) of said charging device through said interface.

30. A system comprising the charging device (2) of any of the pre- ceding claims and a wearable device (70), wherein said charging device (2) is adapted and structured to charge said wearable device (70), and wherein said system is adapted and structured to issue alerts for both following events: - a charging state of said battery (18) of said charging device (2) is below a given first threshold; and

- a charging state of a battery (76) of said wearable device (70) is below a given second threshold,

5 and in particular wherein the system is structured to issue both said alerts on said wearable device (70), in particular on a display (78) of said wearable device (70).

io 31. Use of the charging device of any of the preceding claims for charging a wearable device while it is being worn by a user.

32. The use of claim 31 comprising the step of inserting said charg- ing section (6) between said wearable device and a body section of said user.

15

Description:
Wearable Charging device

Technical Field

The invention relates to a charging device and to a use of such a charging device for charging a wearable device.

Background Art

Wearable devices, such as smart watches, fitness bracelets, and/or communication devices, can integrate rich functionality, but they are known to re- quire substantial power, especially if the device has a screen that is not turned off/dimmed or if it uses WiFi or Bluetooth or general communication (e.g. a cellular network) a lot. Thus, a user has to recharge them regularly, often at least once a day. To do so, the device has to be removed from the body and to be connected to a charging station. While the device is being charged, it cannot be used or only be used with limited functionality. This can be a problem, in particular for users who need vital monitoring functions like heart rate, blood pressure, or an SOS function.

This is a particularly severe limitation for alerting devices that have SOS functionality.

Disclosure of the Invention

The problem to be solved by the present invention is to provide a system that alleviates such charging issues.

This problem is solved by the independent claims.

Hence, in a first aspect, the invention relates to a wearable charging device comprising the following elements:

- A housing: This is a single-piece or multi-piece housing e.g. form- ing the exterior structure of the device.

- A battery: The battery provides power for charging the wearable device. It is arranged in the housing.

- A charging interface: The charging interface can be connected to the wearable device for charging it. The details of its structure depend on the charging standard used by the wearable device. - A driver: The driver is functionally arranged between the battery and the charging interface. It provides the circuitry for feeding power from the battery to the charging interface. It e.g. comprises power limiters, voltage converters, temperature controller, oscillators, etc. The nature of the circuitry depends on the charging standard used by the wearable device.

Further, the housing forms a charging section having a first and a second surface and having a height, measured along a first direction extending between said first and said second surface. This height is less than 5 mm.

A device of this type is suited for insertion under a wearable device, i.e. the charging section can be inserted below the wearable device, i.e. between the wearable device and the user’s body, thus allowing to charge the wearable device while it is being worn. Once the wearable device has been charged (usually after one or two hours), the charging device can be removed.

The charging section can be even thinner, in particular less than 2 mm, in order to fit even more easily under the wearable device.

Advantageously, the charging section is flat.

In an advantageous embodiment, the charging section comprises an first opening/hole extending therethrough, between its first and its second surface. Such an first opening allows sensors on the wearable device to still have access (and monitor) to the user’s body surface.

Advantageously, the charging device comprises a coil arranged in the charging section. Such a coil can be used for wirelessly charging the wearable device, e.g. using the Qi-standard.

In particular, the coil can be arranged to extend around the first opening in the charging section.

In one embodiment, the housing forms at least one battery section arranged at an edge of the charging section, in particular at an edge of said first and second surface. The battery is arranged in the battery section. The height of the bat- tery section along said first direction is at least twice of the height of the charging sec- tion.

In one embodiment, there is only one battery section arranged at a single side of the charging section. In this case, the charging section forms a tongue that can easily be slid below the wearable device until the battery section comes to rest laterally against the wearable device.

In another embodiment, the charging device can have two or more battery sections on opposite sides of the charging section. In this case, the wearable device can be nested between the two battery sections. Advantageously, the first and/or the second surface of the charging section is/are concave in at least one second direction perpendicular to the first direc- tion. This is to be understood such that the given surface appears to be concave in a sectional view along a plane containing the first and second directions. This allows the first or second direction to better adapted to the convex shape of the user’s body and/or the wearable device.

The housing of the device is advantageously rigid. A rigid housing has the advantage that it can be handled easily and e.g. be brought into place, e.g. in- serted with its charging section under the wearable device, using a single hand only.

Advantageously, the charging section extends away from the battery section of the housing by at least 10 mm, in particular by at least 20 mm, along a second direction, wherein said second direction extends perpendicular to said first di- rection. This allows to slide the charging section under the wearable device while keeping the battery section at the side of the wearable device.

The invention also relates to the use of such a charging device for charging a wearable device while it is being worn by the user. In other words, the user does not take off the wearable device for charging.

For this use, the charging section of the charging device can be inserted between the wearable device and the body of the user.

The wearable device can e.g. be a watch, in particular a smartwatch, a medical monitoring device, a smart- or fitness bracelet, and/or an alerting device adapted to alert the user or a third party of an emergency situation (SOS-device). The invention is particularly advantageous in combination with wearable devices for permanent/continuous fitness or health monitoring.

The invention also relates to a system comprising the charging de- vice and the wearable device.

In such a system, the wearable device advantageously comprises an app communicating with the charging device.

Brief Description of the Drawings

The invention will be better understood and objects other than those set forth above will become apparent when consideration is given to the following de- tailed description thereof. This description makes reference to the annexed drawings, wherein: Fig. 1 is a view of a first embodiment of a wearable charging de- vice,

Fig. 2 is a top view of the charging device of Fig. 1, Fig. 3 is a lateral view of the charging device of Fig. 1,

Fig. 4 is a top view of the charging device of Fig. 1 under a smart- watch,

Fig. 5 is a lateral view of the arrangement of Fig. 4 as seen from a direction tangential to the wristband,

Fig. 6 is a lateral view of the arrangement of Fig. 4 as seen from a direction perpendicular to the wristband,

Fig. 7 is a top view of a second embodiment of a charging device charging a smartwatch,

Fig. 8 is a sectional view of the charging device along line VIII-VIII of Fig. 7,

Fig. 9 is a sectional view of the charging device along line IX-IX of

Fig. 7,

Fig. 10 is a view of a third embodiment of the charging device, e.g. with two battery sections,

Fig. 11 is a top view of the charging device of Fig. 11,

Fig. 12 is a first lateral view of the charging device of Fig. 11,

Fig. 13 is a second lateral view of the charging device of Fig. 11, Fig. 14 is a block circuit diagram of a possible embodiment of the components of the charging device,

Fig. 15 shows a top view of a fourth embodiment of the charging device,

Fig. 16 shows a sectional view of the fourth embodiment along line XVI-XVI of Fig. 15, and

Fig. 17 shows a system comprising the charging device and the wearable device.

Modes for Carrying Out the Invention

First embodiment:

Figs. 1 - 3 show a first embodiment of a charging device 2 and Figs. 4 - 6 show it while charging a wearable device 4. The shown charging device comprises a charging section 6 and a battery section 8.

Charging section 6 has a first surface 10 and a second surface 12

(Fig. 3).

In a first direction XI extending between first surface 10 and second surface 12, and in particular perpendicular thereto, charging section 6 is thin enough to be inserted between a wearable device and the user’s body.

Hence, along first direction XI, the height Hl of charging section 6 is, in particular at all its points, less than 5 mm, in particular less than 2 mm.

Charging section 6 extends away from battery section 8 along a sec- ond direction X2, with X2 being perpendicular to XI .

A third direction X3 is defined as being perpendicular to the first and second directions XI, X2.

In the second and third directions X2, X3, charging section 6 has extensions H2, H3 that are much larger in order to give the device a firm hold while in its charging position. Both these extensions are advantageously at least 1 cm. In particular, at least one or both of H2, H3 are at least 2 cm.

Advantageously, the extension of charging section H3 in the third direction X3 is no more than 4 cm in order to fit snugly against the wearer’s wrist.

Charging section 6 advantageously comprises an first opening 14 extending therethrough from first surface 10 to second surface 12. First opening 12 allows sensors at the inner surface of the wearable device to access the user’s skin.

Advantageously, first opening 14 has, in any direction perpendicu- lar to first direction XI, a diameter D of at least 10 mm, and in particular along at least one such direction a diameter of at least 20 mm.

Charging device 2 further comprises a battery section 8, which is ar- ranged at an edge 16 of charging section 6. Battery section 8 contains a battery 18 holding the energy for charging the wearable device.

The height B1 (see Fig. 3) of battery section 8 along first direction XI can be considerably larger than the height Hl of charging section 6 because, during charging the wearable device, battery section 8 is arranged laterally to the wearable device.

In particular, height Bl of the battery section can be at least two times larger than height Hl of the charging section. For example, it can be at least 8 mm.

Advantageously, though, height Bl is smaller than 15 mm in order to be not higher (or not much higher) than typical smartwatches. Along first direction XI, battery section 8 extends beyond first surface 10. It may also extend, typically to a lesser degree, beyond second surface 12. It advantageously extends further beyond first surface 10 than second surface 12 because, while charging the wearable device, there is room on the side of first surface 10 while the user’s body is located at the side of second surface 12.

In a particularly advantageous embodiment, battery section 8 is flush with second surface 12, as shown in Fig. 3.

Advantageously, charging section 6 is fixedly mounted to battery section 8.

Charging device 2 has a housing 9, which can be a single-part of a multi-part housing, and which is e.g. formed at least in part by the outer surface of charging section 6 and battery section 8.

Advantageously, housing 9 is rigid, in particular in the sense that a maximum non-destructive deformation of one part of the housing in respect to another part of the housing is less than 5 mm.

In particular, charging section 6 is rigidly mounted to battery section 8.

The extension W (see Fig. 3) of battery section 8 along second direction X2 is advantageously no more than 5 cm, in particular no more than 3 cm, so it can be worn comfortably along the side of the wearable device. Advantageously, extension W is measured from the edge of charging section 6 along direction X2 to the outmost part of the housing of battery section 8.

In the embodiment of Figs. 1 - 3, charging device 2 has only one battery section 8 located at one side of charging section 6. Charging section 6 extends away from battery section 8 along second direction X2, for the distance H2 (i.e. at least by 10 mm, in particular at least by 20 mm). Thus, charging section 6 can be easily slid under a wearable device for charging the same.

Charging section 6 comprises a charging interface 19 for charging the wearable device. As mentioned above, its nature depends on the charging standard used by the wearable device.

If, for example, charging device 2 is intended to charge wearable devices using the Qi standard, the PMA (Power Matters Alliance) standard, or the AirFuel standard, the charging interface 19 will comprise a coil 20, as it is schematically shown in Fig. 2.

If charging device 2 is intended to charge wearable devices using direct electrode contact pads, charging interface 19 will comprise suitable contacts 22 (Fig. 2) on either side of first surface 10. If charging device 2 is intended to charge wearable devices using capacitive coupling, charging interface 19 will comprise suitable capacitive electrodes (not shown).

Charging interface 19 may also embody a combination of different charging techniques.

If a coil 20 is provided, is advantageously extends around first opening 14 as shown in Fig. 2.

Figs. 4 - 6 show the charging device of Figs. 1 - 3 while charging a wearable device 4. In the shown embodiment, the wearable device 4 comprises a housing 24 and a wristband 26.

In the shown embodiment, wearable device 4 comprises a user-op- eratable interface element 28, such as a knob or button, at an edge thereof.

When using a charging device 2 has its battery section 8 at one side only, such as the one shown in Figs. 1 - 6, the charging device will not obstruct inter- face element 28 during charging.

Second embodiment:

Figs. 7 - 9 show a second embodiment of charging device 2.

This embodiment differs from the first one in that it comprises a centering element 30, which is located along the periphery of charging section 6. It extends, in first direction XI, beyond first surface 10 by a height M (Fig. 8), and it forms (optionally together with charging section 8) a cradle or recess 32 for receiving the wearable device and centering the same on charging section 6 in the second and/or third directions X2, X3.

Centering element 30 can comprise a single, continuous projection or bulge, as shown, or it can comprise a plurality of individual projections.

At least, centering element 30 should form at least one first projection 30a on the side of the charging device opposite to battery section 8 in order to center wearable device 4 along second direction X2. It may also form projections 30b, 30c at edges of charging section 6 opposed along third direction X3 in order to center wearable device 4 along third direction X3.

Height M should be at least 1 mm for providing good guidance to wearable device 4.

Advantageously, height M should be no more than 5 mm, in partic- ular no more than 3 mm, in order not to obstruct wristband 26 and/or interface ele- ment 28. Third embodiment:

Figs. 10 - 13 show a third embodiment of charging device 2.

This embodiment comprises two battery sections 8 at opposite sides of charging section 6. The two battery sections 8 together with charging section 6 for a cradle for receiving wearable device 4, as shown in Fig. 11.

Charging section 6 can again comprise an first opening 14 for the sensors of wearable device 4.

Just like all embodiments, the charging interface of this charging device may comprise a coil, electrodes, and/or contacts 22 for feeding power to the wearable device.

This design is particularly suited for wearable devices 4 without in- terface elements at their edges.

Circuitry:

As mentioned, the circuitry of charging device 2 strongly depends on the type of charging interface.

Fig. 14 show a block circuit diagram for a charging device adapted to use the Qi standard for charging the wearable device.

In particular, charging device 2 comprises a driver 36 functionally arranged between battery 18 and charging interface 19. It is adapted and structured to feed power from battery 18 to charging interfaced.

In the shown embodiment, driver 36 comprises, by way of example, an AC generator 38 and a current amplifier 40.

Depending on the interface used, driver 36 may also comprise e.g. a voltage upconverter and/or current limiters, etc., in order to match the output of batter 18 to charging interface 19.

Charging device 2 also comprises components to charge battery 18 using an external charger. These may e.g. comprise a USB interface or any other wire-bound interface 42 for charging battery 18 directly. This is particularly advanta- geous if charging device 2 is also to be used as a stationary charging device.

The external charger may e.g. be any of the following:

- a dedicated charger device that can e.g. be directly connected to a wall outlet; for example, it may be the charger used for charging the wearable device.

- a smartphone, tablet, or computer.

In addition to this, or alternatively thereto, driver 36 may also be adapted and structured to feed power from charging interface 19 to said battery 18. In this case, charging interface 19 can not only be used to charge wearable device 4 but also to receive power in order to charge battery 18.

In must be noted that the charging device can also be used to charge devices other than wearable devices, such as e.g. a smartphone, a tablet computer, etc.

In the embodiment shown in Fig. 14, driver 36 comprises a filter 44, a rectifier 46, and a charging controller 48 for receiving power through charging in terface 19 and feeding it to battery 18.

The operations of driver 36 are controlled by a control unit 50, such as a microprocessor.

Driver 36 further comprises a temperature sensor 52, which is used to limit the temperature of charging device 2.

In particular, driver 36 is structured to limit the temperature of charging device 2 while charging and/or discharging battery 18 to a threshold temper- ature Ts. Advantageously, the threshold temperature Ts is lower than 50°C, in partic- ular lower than 40°C. Since charging device 2 can be worn against the user’s skin, such a low threshold temperature is advisable.

Limiting the temperature can e.g. be carried out by control unit 50 limiting the average current through battery 18.

In an advantageous embodiment, the device comprises a user-op- eratable control 54, such as a button, which allows the user to enable and disable driver 36. When driver 36 is enabled, it tries to charge the wearable device if it is within range. When disabled, driver 36 does not charge the wearable device even if it is within range. This is particularly advantageous if the wearable device suspends part or all of its operation while it is charged. For example, if the wearable device is adapted to measure physiological parameters of its wearer but does not do so while being charged, the user can operate control 54 to disable charging temporarily and therefore to cause the wearable device to measure the physiological parameters be- tween charging intervals.

Advantageously, and as shown by way of example in Fig. 7, user- operatable control 54 is not arranged at the second side 12 of the device such that it is accessible even when the device is worn by the user. Advantageously, user-operatable control 54 is arranged on the battery section 8 of the device because that part of the charging device remains accessible when in use.

In addition to or alternatively to this, the charging device may comprise a timer 56 for automatically and repetitively enabling and disabling driver 36, in particular at regular intervals. In this case, when driver 36 is disabled and therefore stops charging the wearable device, the wearable device can resume its full operation until charging restarts. For example, when enabling timer 56, timer 56 enables driver 36 for a first time period Tl, disables it for a second time period T2, and then repeats this cycle. Tl and T2 may each e.g. be in the order of 1 - 60 minutes, even though, depending on the wearable device, other intervals may make sense. Advantageously, Tl > T2, in particular Tl > 2-T2, in order to keep charging times low.

Timer 56 may e.g. be enabled/disabled by pressing control 54 for at least a given minimum duration, such as for at least one second.

The device may further comprise an interface 58 for communicating with an external device and for exchanging data therewith. Interface 58 is advanta- geously a wireless interface, such a Bluetooth interface or an NFC interface. It may, however, also be a wire-bound interface, such as a USB interface.

In particular, interface 58 may be used for communication with at least one of the following external devices:

- The wearable device.

- A smartphone or tablet computer.

- A computer.

- A cellular network.

Interface 58 may be used e.g. for any of the following purposes: a) The device can be adapted to receive operating instructions if om the remote device:

- For example, an app on the remote device may be used to enable or disable driver 36, in the same way as described for user-operatable control 54 and timer 56 above.

- In another example, an app on the remote device may be used to change an operation setting of the device. For example, it can be used to enable and disable timer 56 or to change its settings (e.g. the intervals Tl, T2 mentioned above), or it can enable or disable access to the mass storage device mentioned below.

b) The device can be adapted to send information to the remote device, such as information regarding the charging status of battery 18.

c) The device may be adapted to exchange data through interface 38 with the remote device. In particular, the device may comprise a mass storage device 60 and it may be adapted to provide read and write access to mass storage device 60 via interface 58. Advantageously, mass storage device 60 is a mass storage in the sense that it comprises at least 1 MB of data storage, in particular at least 100 MB of data storage, that can be accessed through interface 58.

Mass storage device 60 may e.g. be used to backup data from the wearable device. Alternatively or in addition thereto, mass storage device 60 may be used to exchange data between the wearable device and another external device via the present device.

Fourth embodiment:

Figs. 15 and 16 show a fourth embodiment of the charging device.

In this embodiment, charging section 6 comprises a second opening 62 in addition to first opening 14. First opening 14 is arranged (in the plane X2, X3) radially within coil 20, i.e. coil 20 surrounds first opening 14 same as in the previous embodiments. Second opening 62 is, however, arranged (in the plane X2, X3) radially outside coil 20. Such a second opening is advantageous for charging wearable devices that have sensors located radially outside their charging coil.

Advantageously, second opening 62 is annular and extends around coil 20, with at least one radial strut 64 extending through it in order to mechanically connect the housing section of coil 20 to the rest of the housing and to provide a pas- sage for wires for feeding coil 20.

Advantageously, there are at least three such struts 64 for better me- chanical stability. Fig. 15 shows an embodiment with four struts.

Charging management:

Fig. 17 illustrates a system (device combination) comprising the charging device 2 and a wearable device 70.

As described, charging device 2 comprises control unit 50, battery 18, and charging coil 20.

Similarly, wearable device 70 comprises its own charging coil 72, control unit 74, and battery 76.

The two control units 50, 70 can exchange data as described above. Charging coil 20 is adapted to transfer power to charging coil 72.

The system of Fig. 17 is adapted and structured to smartly manage the charging process by suitable programming of the control units 50 and 74.

In particular, the system can be adapted and structured, in particular by suitable programming, to issue alerts for both of the following events:

- the charging state of battery 18 of charging device 2 is below a given first threshold; and

- the charging state of battery 76 of wearable device 70 is below a given second threshold.

Advantageously, the system is structured to issue these alerts on wearable device 70, in particular on a display 78 of wearable device 70. In this way, the system may assure that both batteries 18, 76 are sufficiently charged at all times in order to maintain a continuous operation of wearable device 70.

In particular, wearable device 70 can alert the user that the charging device 2 needs charging, which obviates the need to provide charging device 2 is its own alert means.

As mentioned, the system can charge battery 72 of wearable device 70 in charging intervals while preventing battery 72 to become discharged completely.

The system may be adapted to switch between continuous charging and charging in intervals depending on the state of wearable device 70, in particular e.g. depending on applications currently activated on wearable device 70.

Wearable device 70 may run an app communicating with charging device 2 for controlling and/or querying charging device 2.

Notes:

The charging device can be used as a stationary and/or a portable charger, i.e. it can be worn by the user while it charges the wearable device, or it can be arranged away from the user, e.g. on a table, and the user places the wearable device on the charging device for charging the wearable device. Hence, in order to securely place the charging device on a table or another surface, second surface 12 of charging device 2 is advantageously flat and/or provided with anti-friction members.

The charging device can be used for charging different types of wearable devices. And may e.g. be used for charging both a watch as well as a phone.

At least the first and/or the second surface 10, 12 of the charging section can be provided with an area or a full coating of a rubber-like material in order to increase friction. This is of particular advantage on the first surface 10 because it helps to retain charging device 2 in its proper position in respect to wearable device 6.

Not only first surface 10 but also (or alternatively) second surface 12 can be concave in at least one direction perpendicular to first direction XI in order to better fit against a user’s curved body part, such as an arm.

The charging device can comprise a magnet, in particular in charging section 6, for positioning it against wearable device 4.

The charging device can be equipped to emit a sound once charging is complete. The charging device and/or its charging section 6 may have a thickness between 2 and 3 mm.

To keep the non-transparent parts of charging section 6 small and therefore to provide room for large openings therein, the charging device advanta- geously does not comprise a ferrite core for coil 20.

Where present, first opening 14 and second opening 62 are advantageously true through-holes extending through charging section 6. Alternatively, though, they may be filled with a transparent window material.

Housing 9 is advantageously water-proof, advantageously at an In- temational Protection Rating of at least 4 (splashing water), in particular at least 7 (immersion up to 1 meter).

The present charging device allows operating a wearable device, such as a smartwatch, continuously, i.e. without the need to pull off the wearable device for charging.

While there are shown and described presently preferred embodiments of the invention, it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied and practiced within the scope of the following claims.