Over the years, Apple has been issued various patents for the design of foldable devices, but it is yet to actually produce one (and its first foldable keeps getting delayed). The latest patent (issued today) is US 12,164,344 or “Hinges for folding display devices”.
The patent describes a series of interconnected links that are formed from interlinked “fingers” and a friction clutch. A key part of the patent is using crescent-shaped slots, which allow each link to rotate relative to others – crucially, this moves the axis of rotation outside of the link itself.
Schematics from Apple’s patent on hinges for folding display devices
The patent is written pretty broadly, saying that this hinge can be applied to phones, tablets, laptops or even watches and other wearable devices. This is likely just Apple covering all its bases. Still, it’s not clear whether this is a new and improved version of the previous hinges that Apple patented or whether they will coexist and will be used in different devices.
Anyway, the patent describes how the fingers, pins and gears interact to create a small but capable clutch that will offer the desired amount of friction, allowing the hinge to keep the device folded at a required angle. The gears are needed to ensure that both sides of the hinge rotate equal amounts.
The hinge in an unfolded state and a folded state
Apple has variously been reported to be working on a flip-style iPhone and larger iPad/MacBook foldables as its first foldable device. Either way, the company is facing “technical challenges”, as reported by analyst Ming-Chi Kuo, in designing the display and mechanical components (such as the hinge).
Source (PDF)