On Thursday the US Patent & Trademark Office published a patent application from Apple that relates to the basics behind the Apple Watch Charger and charging the Apple Watch and other devices in general using Solenoids. Even though Apple launched Apple Watch in 2015, this is the first Apple Watch specific patent for charging with solenoids to surface.

Apple's invention covers a wireless power transmitting device such as a device with a wireless charging surface or a device with a cradle or other support structure can transmit power wirelessly to a wireless power receiving device. The wireless power receiving device may have a housing such as a metal housing. A display may be mounted in the metal housing on a front face of the device. A rear housing wall on a rear face of the device may be provided with a wireless power receiving solenoid.

The wireless power receiving solenoid may have a core formed from a magnetic material such as a ferrite strip that is wrapped with a wire. The wire may be formed from a solid metal wire with a dielectric coating, a solid metal wire with a magnetic coating layer, a metal wire having a rectangular cross-sectional shape, or a wire formed form intertwined metal filaments.

The solenoid may have a linear strip shape that extends along a longitudinal axis. The wireless power receiving device may have a strap coupled to sidewalls of the metal housing. The longitudinal axis may extend in a direction that is perpendicular to the strap and parallel to the sidewalls to which the strap is coupled.

The wireless power receiving solenoid may have opposing first and second ends. In some arrangements, the wireless power transmitting device may have a wireless power transmitting solenoid with opposing first and second ends that are configured to transmit wireless power signals respectively to the first and second ends of the wireless power receiving solenoid when the wireless power receiving solenoid has been received within a cradle. The wireless power receiving device may also use the wireless power receiving solenoid to receive power from a wireless charging mat or other wireless power transmitting device that emits wireless power signals from a wireless charging surface.

As note in the graphic below, wireless transmitting device #12 is a wireless charging mat or other wireless power transmitting equipment that has an array of coils that supply wireless power over a wireless charging surface. This type of arrangement is shown in FIG. 2 below. As shown in FIG. 2, wireless power receiving device #10 may be located over one or more of coils #36 during charging.

In respect to patent FIG. 4 above, the opposing rear face of the housing may be formed from a metal rear housing wall structure or other suitable housing wall structure and may be provided with windows to accommodate light emission and/or light detection and/or may be provided with a solenoid (coil) to receive wireless power. Device #10 may be an Apple Watch, iPhone, iPad or other equipment.

Apple's patent FIG. 11 noted in the graphic above is a perspective view of an Apple Watch in an illustrative configuration in which solenoid #14 is oriented perpendicular to the surface (X-Y plane) of charging device #12. As shown in FIG. 11, the solenoid may have an elongated shape (e.g., an elongated strip shape) that extends across some or all of rear wall 62R of Apple Watch housing. Configurations in which the solenoid is mounted elsewhere in the watch housing may also be used.

Apple further noted that it may be desirable to place the solenoid within a charging cradle in device #12 during charging. A cradle in the device may, for example, have a single wireless power transmitting coil such as illustrative C-shaped solenoid #36 of FIG. 12 illustrated above.

As shown in FIG. 12, solenoid #36 may, in this illustrative configuration, have multiple turns of wire 36W (e.g., wire such as wire 14W of solenoid #14) wrapped around magnetic core 36C (see, e.g., the materials and structures used in forming core 14C of solenoid #14). This type of arrangement for wireless power transmitting solenoid #36 may be used in a wireless charging puck, in a stand, in a puck or other device that is tethered to the end of a cable, or other wireless power transmitting device #12.  

Interestingly the patent figures below suggest that Apple considered a design where the solenoids formed in the bottom portion of the Apple watch would stand out as it does today but would recoil back into the watch once the user placed it on their wrist. This could have been thought to provide better comfort or fit while allowing specialized sensors for heart rated to better touch the users skin. Whether Apple has abandoned this idea or plans to introduce it in the future is unknown at this time.

Apple's Solenoid #14 may be incorporated into Apple Watch in a position in which the solenoid is proud (stands out) of the outermost surface of rear housing the wall 62R. For example, dielectric material 62D (polymer, ceramic, glass, etc.) may be used to hold the solenoid in a position of the type shown in FIG. 15 in which the solenoid is spaced apart from planar rear surface 62R of the housing 62 an Apple Watch.

In patent FIG. 16 we're able to see a cross-sectional side view of the Apple Watch in a configuration in which the solenoid has been mounted flush with the outer surface of housing 62. As shown in FIG. 16, the inner surface 14' of solenoid 14, which faces housing #62, may be flush with the outwardly facing (external) surface 62R of the planar rear housing wall of housing 62.

Apple's patent FIG. 17 shows how a portion such as region 62R' of rear housing surface 62R may be recessed below the rest of rear surface 62R.

As shown in FIG. 18, Apple considered a different form factor for an Apple Watch charger in the form of a cradle box. Apple states that solenoid #36 may be mounted in cradle #90.

Apple's patent application 20180123392 was filed back in Q2 2017, with working dating back to at least 2016. The information about this patent doesn't allow me to go back further than 2016.

The listed inventors include: Zaki Moussaoui Ph.D., Director of Power Technology / Systems Architecture. Moussaoui came to Apple via Exar Corporation – a Maxlinear Company; and Chris Pinciuc, System Integrator.

On April 18 Patently Apple posted a report titled "Apple's First PowerbyProxi Patent Application Surfaces about a Charging Mat with an Object Detection System." A Second charging patent application from Apple inherited by PowerbyProxi surfaced on Thursday relating to an improved Inductive Power Transfer system. To learn more, review patent application 20180123399 in full here.

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