PATENT DOCUMENT

Publication Number: US-12164344-B2
Application Number: US-202217859668-A
Country: US
Kind Code: B2

Title: Hinges for folding display devices

Abstract:
A foldable display device may have housing portions coupled by a hinge. The hinge may have a series of interconnected links. The links may be formed from interdigitated fingers in a friction clutch. The fingers or other portions of the links may be provided with crescent-shaped slots that receive pins. During folding of the device, the pins may slide along the crescent-shaped slots, thereby ensuring that adjacent links rotate relative to each other about a rotation axis that lies outside of the hinge and within a flexible display panel. Links may also be formed from link members with curved mating bearing surfaces that slide relative to each other as adjacent links are rotated relative to each other. A housing rotation synchronization mechanism may be formed using a set of gears that extends between the first and second housing portions.

Claims:
What is claimed is: 
     
       1. An electronic device, comprising:
 a foldable housing that is configured to bend about a bend axis; 
 a flexible display panel that overlaps the bend axis; and 
 a hinge having multiple links, wherein the links include pairs of links that rotate relative to each other about a rotation axis that lies outside of the links, wherein the links have friction clutch structures, wherein the hinge comprises pins, wherein the links have curved slots that receive the pins, and wherein the friction clutch structures of the links comprise interdigitated fingers. 
 
     
     
       2. The electronic device defined in  claim 1  wherein the curved slots are crescent-shaped. 
     
     
       3. The electronic device defined in  claim 1  wherein the curved slots are formed in the interdigitated fingers. 
     
     
       4. The electronic device defined in  claim 1  wherein the pins slide within the curved slots as the links rotate relative to each other. 
     
     
       5. The electronic device defined in  claim 1 , wherein the interdigitated fingers comprise a first set of fingers and a second set of fingers that are interdigitated with each other. 
     
     
       6. The electronic device defined in  claim 5 , wherein the pins are configured to press the interdigitated fingers towards each other. 
     
     
       7. The electronic device defined in  claim 5 , wherein the foldable housing comprises a hinge mounting member to which the first set of fingers is attached. 
     
     
       8. The electronic device defined in  claim 7 , wherein the first set of fingers is mounted in a recess of the hinge mounting member under a mounting plate. 
     
     
       9. An electronic device, comprising:
 a housing having a first housing half and a second housing half that are configured to rotate relative to each other about a bend axis; 
 a foldable display configured to bend about the bend axis, wherein a first portion of the foldable display is mounted to the first housing half and a second portion of the foldable display is mounted to the second housing half; 
 a hinge with multiple links, wherein a first of the links is attached to the first housing half and a second of the links is attached to the second housing half, wherein adjacent pairs of the links each rotate about a respective rotation axis that is outside of the hinge, and wherein the links are formed from interdigitated fingers that form friction clutch structures; and 
 a rotation synchronization mechanism coupled between the first and second housing halves. 
 
     
     
       10. The electronic device defined in  claim 9  further comprising crescent-shaped slots in the interdigitated fingers that receive pins. 
     
     
       11. The electronic device defined in  claim 10  wherein the crescent-shaped slots have ends that prevent excessive rotation of the links with respect to each other. 
     
     
       12. The electronic device defined in  claim 9  wherein the rotation synchronization mechanism comprises rotation synchronization gears. 
     
     
       13. The electronic device defined in  claim 12  wherein a first of the rotation synchronization gears is attached to the first housing half and wherein a second of the rotation synchronization gears is attached to the second housing half. 
     
     
       14. The electronic device defined in  claim 13  wherein the rotation synchronization gears are configured so that clockwise rotation of the first rotation synchronization gear due to clockwise rotation of the first portion produces counterclockwise rotation of the second rotation synchronization gear and counterclockwise rotation of the second portion. 
     
     
       15. An electronic device, comprising:
 a first housing portion; 
 a second housing portion configured to rotate about a bend axis relative to the first housing portion; 
 a flexible display having a first display portion coupled to the first housing portion and a second display portion coupled to the second housing portion, wherein when the first and second housing portions are folded against each other, the flexible display is bent about the bend axis and exhibits an unfolding torque to unfold the first and second housing portions; and 
 a hinge having interconnected links, wherein the interconnected links include pairs of adjacent links, wherein the adjacent links in each of the pairs rotate with respect to each other about a rotation axis that lies within the flexible display, wherein each of the rotation axes is parallel to the bend axis, wherein the interconnected links are configured to form a friction clutch for the hinge, and wherein the hinge comprises a counterbalance mechanism configured to provide a folding torque that tends to fold the first and second housing portions about the bend axis to counterbalance the unfolding torque. 
 
     
     
       16. The electronic device defined in  claim 15  wherein the links each have fingers with crescent-shaped slots, wherein the fingers of the adjacent links of each of the pairs are interdigitated, and wherein the hinge comprises pins that slide along the crescent-shaped slots. 
     
     
       17. The electronic device defined in  claim 15  wherein the links comprise curved bearing surfaces that bear against each other to allow rotation of the adjacent links in each of the pairs with respect to each other. 
     
     
       18. The electronic device defined in  claim 15  further comprising a camera at an edge of the second housing portion, wherein the flexible display is configured to cover the camera when the first and second housing portions are folded against each other and is configured to retract and expose the camera when the first and second housing portions are unfolded. 
     
     
       19. The electronic device defined in  claim 15  further comprising speakers at corners of the first and second housing portions. 
     
     
       20. The electronic device defined in  claim 15  further comprising a two-dimensional array of haptic output devices overlapped by the flexible display. 
     
     
       21. The electronic device defined in  claim 15  wherein the counterbalance mechanism comprises a pad, a spring coupled to the pad, and a roller that is mounted on a portion of the interconnected links and that bears against the pad. 
     
     
       22. The electronic device defined in  claim 21  wherein the first and second housing portions are configured to rotate relative to each other about the bend axis between an open position and a closed position, wherein in the closed position the roller positions the pad to allow the spring to uncompress relative to the open position. 
     
     
       23. The electronic device defined in  claim 15  wherein the links each have fingers with crescent-shaped slots, wherein the fingers of the adjacent links of each of the pairs are interdigitated, wherein the hinge comprises pins that slide along the crescent-shaped slots, and wherein the hinge has parallel first and second elongated strips of links and comprises synchronization gears located between the first and second elongated strips. 
     
     
       24. An electronic device, comprising:
 a foldable housing that is configured to bend about a bend axis; 
 a flexible display panel that overlaps the bend axis; and 
 a hinge having multiple links, wherein the hinge extends across the bend axis and couples first and second portions of the foldable housing together, wherein the links include a first set of rotational synchronization gears that synchronize rotation of odd links in the multiple links and include a staggered parallel second set of rotational synchronization gears that synchronize rotation of even links in the multiple links. 
 
     
     
       25. The electronic device defined in  claim 24  wherein the multiple links include at least a first pair of links and second pair of links, wherein the first and second sets of rotational synchronization gears are configured so that the links in the first pair of links rotate relative to each other by a first angular value when the foldable housing is placed in a folded state and so that the links in the second pair of links rotate relative to each other by a second angular value when the foldable housing is placed in the folded state, and wherein the first and second angular values are different. 
     
     
       26. An electronic device, comprising:
 a foldable housing that is configured to bend about a bend axis; 
 a flexible display panel that overlaps the bend axis; and 
 a hinge having a first link with an outwardly facing curved surface and an inwardly facing curved surface, having a second link with an inwardly facing curved surface, and having a retention member with an outwardly facing curved surface configured to slide along the inwardly facing curved surface of the first link, wherein the retention member holds the inwardly facing curved surface of the second link against the outwardly facing curved surface of the first link and wherein the hinge includes an attachment member with a first portion attached to the second link and a second portion attached to the retention member.

Description:
This application claims the benefit of provisional patent application No. 63/232,021, filed Aug. 11, 2021, which is hereby incorporated by reference herein in its entirety. 
    
    
     FIELD 
     This relates generally to electronic devices, and, more particularly, to electronic devices with displays. 
     BACKGROUND 
     Electronic devices often have displays. Portability may be a concern for some devices, which tends to limit available real estate for displays. 
     SUMMARY 
     A foldable electronic device may have a display formed from a flexible display panel that overlaps a bend axis. The device may have first and second housing portions coupled by a hinge. The device may be opened and closed by rotating first and second housing portions about the bend axis. 
     The hinge may have a series of interconnected links. The links may be formed from thin sheets of material that form interdigitated fingers in a friction clutch. The fingers or other portions of the links may be provided with crescent-shaped slots that receive pins. During folding of the device, the pins may slide along the crescent-shaped slots, thereby ensuring that adjacent links rotate relative to each other about a rotation axis that lies outside of the hinge and within the flexible display panel supported over the links. 
     If desired, links may be formed from link members with curved mating bearing surfaces that slide relative to each other as adjacent links are rotated relative to each other. A housing rotation synchronization mechanism may be formed using a set of gears that extends between the first and second housing portions. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic diagram of an illustrative electronic device in accordance with an embodiment. 
         FIG.  2    is a perspective view of an illustrative electronic device with a display in accordance with an embodiment. 
         FIG.  3    is a cross-sectional side view of an illustrative electronic device in accordance with an embodiment. 
         FIG.  4    is a side view of a portion of an illustrative electronic device having a hinge with links in accordance with an embodiment. 
         FIG.  5    is a side view of a portion of an illustrative hinge in accordance with an embodiment. 
         FIG.  6    is a top view of an illustrative friction hinge having interleaved hinge fingers in accordance with an embodiment. 
         FIG.  7    is a top view of a portion of an illustrative electronic device having structures coupled to friction hinge fingers in accordance with an embodiment. 
         FIGS.  8  and  9    are cross-sectional side views of illustrative electronic device portion of  FIG.  7    in accordance with embodiments. 
         FIG.  10    is a side view of a portion of hinge with a rotation synchronization mechanism formed from interlocked gears in accordance with an embodiment. 
         FIG.  11    is a side view of a portion of an illustrative hinge in accordance with an embodiment. 
         FIG.  12    is a top view of a portion of an illustrative hinge in accordance with an embodiment. 
         FIG.  13    is a top view of an illustrative electronic device in accordance with an embodiment. 
         FIG.  14    is a side view of an illustrative electronic device in accordance with an embodiment. 
         FIG.  15    is a cross-sectional end view of the illustrative electronic device of  FIG.  14    in accordance with an embodiment. 
         FIG.  16    is a top view of an illustrative hinge with a counterbalance mechanism in accordance with an embodiment. 
         FIG.  17    is a side view of an illustrative hinge with a counterbalance mechanism in accordance with an embodiment. 
         FIG.  18    is an exploded perspective view of an illustrative hinge in accordance with an embodiment. 
         FIG.  19    is a perspective view of an illustrative hinge in accordance with an embodiment. 
         FIG.  20    is a front perspective view of an illustrative bent hinge in accordance with an embodiment. 
         FIG.  21    is a rear perspective view of an illustrative bent hinge in accordance with an embodiment. 
         FIG.  22    is a cross-sectional side view of an illustrative hinge in accordance with an embodiment. 
         FIG.  23    is a cross-sectional side view of a portion of the illustrative hinge of  FIG.  22    in a bent state in accordance with an embodiment. 
         FIG.  24    is a cross-sectional side view of the illustrative hinge of  FIG.  22    taken through a parallel plane in accordance with an embodiment. 
         FIG.  25    is a cross-sectional side view of the illustrative hinge of  FIG.  24    in a bent state in accordance with an embodiment. 
         FIG.  26    is an exploded perspective view of another illustrative hinge in accordance with an embodiment. 
         FIG.  27    is a front perspective view of the illustrative hinge of  FIG.  26    in accordance with an embodiment. 
         FIGS.  28  and  29    are cross-sectional side views of the illustrative hinge of  FIG.  26    in accordance with embodiments. 
         FIG.  30    is a side view of the illustrative hinge of  FIG.  26    in a bent state in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Electronic devices may be provided with displays. Displays may be used for displaying images for users. Displays may be formed from arrays of light-emitting diode pixels or other pixels. For example, a device may have an organic light-emitting diode display or a display formed from an array of micro-light-emitting diodes (e.g., light-emitting diodes formed from crystalline semiconductor dies). 
     A schematic diagram of an illustrative electronic device having a display is shown in  FIG.  1   . Device  10  may be a cellular telephone, tablet computer, laptop computer, wristwatch device or other wearable device, a television, a stand-alone computer display or other monitor, a computer display with an embedded computer (e.g., a desktop computer), a system embedded in a vehicle, kiosk, or other embedded electronic device, a media player, or other electronic equipment. Configurations in which device  10  is a cellular telephone, tablet computer, or other portable electronic device may sometimes be described herein as an example. This is illustrative. Device  10  may, in general, be any suitable electronic device with a display. 
     Device  10  may include control circuitry  20 . Control circuitry  20  may include storage and processing circuitry for supporting the operation of device  10 . The storage and processing circuitry may include storage such as nonvolatile memory (e.g., flash memory or other electrically-programmable-read-only memory configured to form a solid state drive), volatile memory (e.g., static or dynamic random-access-memory), etc. Processing circuitry in control circuitry  20  may be used to gather input from sensors and other input devices and may be used to control output devices. The processing circuitry may be based on one or more microprocessors, microcontrollers, digital signal processors, baseband processors and other wireless communications circuits, power management units, audio chips, application specific integrated circuits, etc. During operation, control circuitry  20  may use a display and other output devices in providing a user with visual output and other output. 
     To support communications between device  10  and external equipment, control circuitry  20  may communicate using communications circuitry  22 . Circuitry  22  may include antennas, radio-frequency transceiver circuitry (wireless transceiver circuitry), and other wireless communications circuitry and/or wired communications circuitry. Circuitry  22 , which may sometimes be referred to as control circuitry and/or control and communications circuitry, may support bidirectional wireless communications between device  10  and external equipment over a wireless link (e.g., circuitry  22  may include radio-frequency transceiver circuitry such as wireless local area network transceiver circuitry configured to support communications over a wireless local area network link, near-field communications transceiver circuitry configured to support communications over a near-field communications link, cellular telephone transceiver circuitry configured to support communications over a cellular telephone link, or transceiver circuitry configured to support communications over any other suitable wired or wireless communications link). Wireless communications may, for example, be supported over a Bluetooth® link, a WiFi® link, a wireless link operating at a frequency between 6 GHz and 300 GHz, a 60 GHz link, or other millimeter wave link, cellular telephone link, wireless local area network link, personal area network communications link, or other wireless communications link. Device  10  may, if desired, include power circuits for transmitting and/or receiving wired and/or wireless power and may include batteries or other energy storage devices. For example, device  10  may include a coil and rectifier to receive wireless power that is provided to circuitry in device  10 . 
     Device  10  may include input-output devices such as devices  24 . Input-output devices  24  may be used in gathering user input, in gathering information on the environment surrounding the user, and/or in providing a user with output. Devices  24  may include one or more displays such as display  14 . Display  14  may be an organic light-emitting diode display, a liquid crystal display, an electrophoretic display, an electrowetting display, a plasma display, a microelectromechanical systems display, a display having a pixel array formed from crystalline semiconductor light-emitting diode dies (sometimes referred to as microLEDs), and/or other display. Configurations in which display  14  is an organic light-emitting diode display or microLED display are sometimes described herein as an example. 
     Display  14  may have an array of pixels configured to display images for a user. The pixels may be formed as part of a display panel that is bendable. This allows device  10  to be folded and unfolded about a bend axis. For example, a flexible (bendable) display in device  10  may be folded so that device  10  may be placed in a compact shape for storage and may be unfolded when it is desired to view images on the display. 
     Sensors  16  in input-output devices  24  may include force sensors (e.g., strain gauges, capacitive force sensors, resistive force sensors, etc.), audio sensors such as microphones, touch and/or proximity sensors such as capacitive sensors (e.g., a two-dimensional capacitive touch sensor integrated into display  14 , a two-dimensional capacitive touch sensor overlapping display  14 , and/or a touch sensor that forms a button, trackpad, or other input device not associated with a display), and other sensors. If desired, sensors  16  may include optical sensors such as optical sensors that emit and detect light, ultrasonic sensors, optical touch sensors, optical proximity sensors, and/or other touch sensors and/or proximity sensors, monochromatic and color ambient light sensors, image sensors, fingerprint sensors, temperature sensors, sensors for measuring three-dimensional non-contact gestures (“air gestures”), pressure sensors, sensors for detecting position, orientation, and/or motion (e.g., accelerometers, magnetic sensors such as compass sensors, gyroscopes, and/or inertial measurement units that contain some or all of these sensors), health sensors, radio-frequency sensors, depth sensors (e.g., structured light sensors and/or depth sensors based on stereo imaging devices that capture three-dimensional images), optical sensors such as self-mixing sensors and light detection and ranging (lidar) sensors that gather time-of-flight measurements, humidity sensors, moisture sensors, gaze tracking sensors, and/or other sensors. In some arrangements, device  10  may use sensors  16  and/or other input-output devices to gather user input. For example, buttons may be used to gather button press input, touch sensors overlapping displays can be used for gathering user touch screen input, touch pads may be used in gathering touch input, microphones may be used for gathering audio input, accelerometers may be used in monitoring when a finger contacts an input surface and may therefore be used to gather finger press input, etc. 
     If desired, electronic device  10  may include additional components (see, e.g., other devices  18  in input-output devices  24 ). The additional components may include haptic output devices, audio output devices such as speakers, light-emitting diodes for status indicators, light sources such as light-emitting diodes that illuminate portions of a housing and/or display structure, other optical output devices, and/or other circuitry for gathering input and/or providing output. Device  10  may also include a battery or other energy storage device, connector ports for supporting wired communication with ancillary equipment and for receiving wired power, and other circuitry. 
       FIG.  2    is a perspective view of electronic device  10  in an illustrative configuration in which device  10  is a portable electronic device such as a cellular telephone or tablet computer. As shown in  FIG.  2   , device  10  may have a display such as display  14 . Display  14  may cover some or all of the front face of device  10 . Touch sensor circuitry such as two-dimensional capacitive touch sensor circuitry may be incorporated into display  14 . 
     Display  14  may be mounted in housing  12 . Housing  12  may form front and rear housing walls, sidewall structures, and/or internal supporting structures (e.g., a frame, an optional midplate member, etc.) for device  10 . Glass structures, transparent polymer structures, and/or other transparent structures that cover display  14  and other portions of device  10  may provide structural support for device  10  and may sometimes be referred to as housing structures. For example, a transparent housing portion such as a glass or polymer housing structure that covers and protects a pixel array in display  14  may serve as a display cover layer for the pixel array while also serving as a housing wall on the front face of device  10 . In configurations in which a display cover layer is formed from glass, the display cover layer may sometime be referred to as a display cover glass or display cover glass layer. The portions of housing  12  on the sidewalls and rear wall of device  10  may be formed from glass or other transparent structures and/or opaque structures. Sidewalls and rear wall structures may be formed as extensions to the front portion of housing  12  (e.g., as integral portions of the display cover layer) and/or may include separate housing wall structures. 
     Housing  12  may have flexible structures (e.g., bendable housing wall structures) and/or hinge structures such as hinge  30 . Hinge  30  may have a hinge axis aligned with device bend axis  28 . Hinge  30  and/or flexible housing structures that overlap bend axis  28  may allow housing  12  to bend about bend axis  28 . For example, housing  12  may have a first portion on one side of bend axis  28  and a second portion on an opposing side of bend axis  28  and these two housing portions may be coupled by hinge  30  for rotational motion about axis  28 . 
     As housing  12  is bent about bend axis  28 , the flexibility of display  14  allows display  14  to bend about axis  28 . In an illustrative configuration, housing  12  and display  14  may bend by 180°. This allows display  14  to be folded back on itself (with first and second outwardly-facing portions of display  14  facing each other). The ability to place device  10  in a folded configuration in this way may help make device  10  compact so that device  10  can be stored efficiently. When it is desired to view images on display  14 , device  10  may be unfolded about axis  28  to place device  10  in the unfolded configuration of  FIG.  2   . This allows display  14  to lie flat and allows a user to view flat images on display  14 . The ability to fold display  14  onto itself allows device  10  to exhibit an inwardly folding behavior. Display  14  may be sufficiently flexible to allow device  10  to be folded outwardly and/or inwardly. 
     Device  10  of  FIG.  2    has a rectangular outline (rectangular periphery) with four corners. As shown in  FIG.  2   , a first pair of parallel edges (e.g., the left and right edges of device  10  in the example of  FIG.  2   ) may be longer than a second pair of parallel edges (e.g., the upper and lower edges of device  10  of  FIG.  2   ) that are oriented at right angles to the first pair of parallel edges. In this type of configuration, housing  12  is elongated along a longitudinal axis that is perpendicular to bend axis  28 . Housing  12  may have other shapes, if desired (e.g., shapes in which housing  12  has a longitudinal axis that extends parallel to bend axis  28 ). With an arrangement of the type shown in  FIG.  2   , the length of device  10  along its longitudinal axis may be reduced by folding device  10  about axis  28 . 
       FIG.  3    is a cross-sectional side view of an illustrative foldable electronic device. Device  10  of  FIG.  3    may bend about bend axis  28 . Bend axis  28  may be aligned with display cover layer  14 CG or other structures in device  10 . For example, bend axis  28  may pass through a portion of display cover layer  14 CG or may be located above or below layer  14 CG. 
     As shown in  FIG.  3   , display  14  includes an array of pixels P forming display panel  14 P under an inwardly facing surface of display cover layer  14 CG. Display panel  14 P may be, for example, a flexible organic light-emitting diode display or a microLED display in which light-emitting pixels are formed on a flexible substrate layer (e.g., a flexible layer of polyimide or a sheet of other flexible polymer). Flexible support layer(s) for display  14  may also be formed from flexible glass, flexible metal, and/or other flexible structures. 
     Display cover layer  14 CG may be formed from polymer, glass, crystalline materials such as sapphire, other materials, and/or combinations of these materials. To locally increase flexibility, a portion of layer  14 CG that overlaps and extends along bend axis  28  (e.g., a strip-shaped region running along axis  28  and hinge  30 ) may be locally thinned (e.g., this portion may be thinned relative to portions of layer  14 CG that do not overlap bend axis  28 ). The thickness of layer  14 CG (e.g., the non-thinned portions of layer  14 CG) may be 400 microns, 50-600 microns, 70-150 microns, 100-500 microns, 200-600 microns, at least 100 microns, at least 300 microns, less than 600 microns, less than 500 microns, less than 250 microns, less than 150 microns, less than 100 microns, at least 50 microns, or other suitable thickness. In an illustrative configuration, the unthinned portion of layer  14 CG has a thickness of 400 microns and the locally thinned portion of layer  14 CG has a thickness of 100-200 microns (as an example). Other arrangements for layer  14 CG may be used, if desired. 
     In the example of  FIG.  3   , housing  12  has a portion on rear face R that forms a rear housing wall and has side portions forming sidewalls 12 W. The rear housing wall of housing  12  may form a support layer for components in device  10 . Housing  12  may also have one or more interior supporting layers (e.g., frame structures such as an optional midplate, etc.). These interior supporting layers and the rear housing wall may have first and second portions that are coupled to opposing sides of a hinge that is aligned with bend axis  28  (see, e.g., hinge  30  of  FIG.  2   ) or may be sufficiently flexible to bend around bend axis  28 . 
     Electrical components  32  may be mounted in the interior of device  10  (e.g., between display  14  and the rear of housing  12 . Components  32  may include circuitry of the type shown in  FIG.  1    (e.g., control circuitry  20 , communications circuitry  22 , input-output devices  24 , batteries, etc.). Display  14  may be mounted on front face F of device  10 . When device  10  is folded about axis  28 , display cover layer  14 CG, display panel  14 P, and the other structures of device  10  that overlap bend axis  28  may flex and bend to accommodate folding. 
     Hinge  30  may have a multilink design. As shown in  FIG.  4   , for example, hinge  30  may have multiple interconnected portions such as hinge links  40 . Links  40  may be coupled to each other for rotational motion and may extend in a linked series between first and second portions of housing  12  (e.g., the portions of housing  12  of  FIG.  2    that rotate with respect to each other). Each pair of adjacent hinge links may be restricted in its amount of overall rotation. For example, links  40  may be configured so that no two adjacent links  40  are allowed to rotate more than a maximum rotation angle RA with respect to each other where RA has a value of less than 180°, less than 90°, less than 45°, less than 25°, 5-50°, or other suitable amount. With this arrangement, links  40  collectively allow hinge  30  to rotate by a desired amount (e.g., 180°) without creating an excessively small bend radius for display  14  about bend axis  28 . The value of RA may be the same for all pairs of adjacent links  40  or different pairs of adjacent links may have different values of RA. As an example, the angle RA may be 30° for the link pairs that are adjacent to housing  12 , whereas the angle RA may be 60° for the link pairs in the middle of hinge  30 . Arrangements where each link rotates by the same maximum angle RA with respect to its neighboring links and/or in which the middle links  40  in hinge  30  have higher RA values than the links immediately adjacent to housing  12  may also be used, if desired. 
     With an illustrative arrangement, links  40  may have crescent shaped slots with mating pins and/or other structures (e.g., links with mating crescent-shaped bearing surfaces) that place the axes of rotations of the links outside of the layer of links themselves. As shown in  FIG.  4   , for example, each link in a pair of adjacent links may rotate with respect to the other about a rotational axis  42  that is located outside of the links towards hinge bend axis  28 . Although each adjacent set of links can only rotate by a limited amount in this type of arrangement, the overall amount of bending of display  14  may be 180° or more by using multiple links  40  in hinge  30 , thereby allowing display  14  to fold back on itself. To help minimize bending stress on display  14 , display  14  may be placed in alignment with axes  42 . The bend radius R of display  14  when device  10  is folded shut may be sufficient to prevent excess stress to display  14 . For example, R may have a value of 5 mm, at least 1 mm, at least 3 mm, less than 10 mm, less than 6 mm, 2-7 mm, or other suitable value). 
       FIG.  5    is a side view of a set of multiple hinge links  40  in a portion of hinge  30 . There may be any suitable number of hinge links  40  in hinge  30 . There may be, for example, at least 2 links  40 , at least 3 links  40 , at least four links  40 , 5-10 links  40 , at least 10 links  40 , fewer than 15 links  40 , fewer than 7 links  40 , fewer than 5 links  40 , or other suitable number of links  40  in hinge  30 . In the example of  FIG.  5   , link  40 - 1  has crescent-shaped slot  44 - 1  and link  40 - 2  has crescent-shaped slot  44 - 2 . Pins  46  and link  40 - 3  may be used to couple links  40 - 1  and  40 - 2 . During operation, pins  46  and the slots of hinge  30  allow adjacent links  40 - 1  and  40 - 3  to rotate with respect to each other about rotational axis  42 - 1  and allow adjacent links  40 - 3  and  40 - 2  to rotate with respect to each other about rotational axis  42 - 2 . As shown in  FIG.  5   , rotational axes  42 - 1  and  42 - 2  are located out of the plane of links  40  (e.g., above links  40 ), which allows display  14  (e.g., a flexible thin-film display such as a flexible thin-film organic light-emitting diode display, a microLED display, or other flexible display) to be mounted so that potentially sensitive thin-film layers of the display, a display cover layer in the display, and/or other sensitive portions of the display are aligned with axes  42 - 1  and  42 - 2 . In this way, the locations of axes  42 - 1  and  42 - 2  may establish a neutral stress plane for display  14  that coincides with the thin-film layers, display cover layer, and/or other sensitive portions of display  14 . 
     The lengths of the crescent-shaped slots and the amount of curvature of each slot may be selected to adjust the locations of axes  42 - 1  and  42 - 2  (e.g., the distance of these axes above links  40 ) and to adjust the amount of permitted rotation of each link with respect to the next. If, as an example, slots  44 - 1  and  44 - 2  are nearly straight, axes  42 - 1  and  42 - 2  will be relatively far from links  44 , whereas if slots  44 - 1  and  44 - 2  exhibit strong curvature, then axes  42 - 1  and  42 - 2  will be close to links  44 . For a given curvature, slot length affects the amount of permitted motion. If the slots are long, more rotational motion of the links will be permitted (because pins  46  will have farther to slide along the length of the slots), whereas if the slots are short, less rotational motion of the links will be permitted before the pins reach the ends of the slots and are prevented from sliding further. 
     To maintain satisfactory friction between rotating parts of device  10 , hinge  30  may be provided with friction clutch structures. As an example, adjacent links  40  and/or other portions of hinge  30  may be provided with interdigitated sets of fingers that are pressed together to create rotational friction when rotating with respect to each other. These friction-producing structures, which may sometimes be referred to as friction clutch structures, a friction clutch, a hinge friction structure, rotational friction structures, etc., may be integrated into links  40 , may be attached to links  40  so that the friction-producing structures produce rotational friction for the attached links  40 , and/or may otherwise be coupled between portions of housing  12  that rotate with respect to each other. The friction produced by the friction clutch structures allows a first portion of housing  12  to be maintained in a desired rotational orientation with respect to a second portion of housing  12  (e.g., housing halves may be placed perpendicular or nearly perpendicular to each other, may be closed onto each other, may be placed in an open planar configuration, and/or may otherwise be positioned as desired by rotating these portions with respect to each other about bend axis  28  of hinge  30 ). 
       FIG.  6    is a top view of a friction clutch formed from interdigitated friction clutch members. In the example of  FIG.  6   , clutch  48  has a first set of fingers  50  (e.g., first fingers  50 - 1 ) and a second set of fingers  50  (e.g., second fingers  50 - 2 ). Fingers  50  in the first and second sets are interdigitated. Pin  46  may be configured to press fingers  50  towards each other along the axis passing through pin  46 . Fingers  50  may be relatively thin (e.g., fingers  50  may have a relatively small dimension along the axis of pin  46 ) and may have relatively larger surface areas where fingers  50  contact each other (e.g., fingers  50  may form blade-shaped members). This allows satisfactory friction to be created without requiring an overly bulky clutch. Pins  46  may be configured to squeeze fingers  50 - 1  and  50 - 2  together to impart a desired amount of friction (e.g., sufficient friction to hold first and second portions of housing  12  at a desired angle relative to each other when the first portion is resting on a surface). 
     In an illustrative configuration, a pair of pins  46  are used to couple each adjacent set of fingers  50  and each adjacent set of fingers  50  forms a corresponding link  40 . The pair of pins  46  may travel within a crescent shaped slot in the set of fingers  50  that form the link, as described in connection with slots  44 - 1  an  44 - 2  of  FIG.  5   . 
     Fingers  50  may be coupled to housing  12  using any suitable arrangement (e.g., using welds, adhesive, fasteners, press-fit connections, interlocking engagement structures such as interlocking clips, and/or other mounting structures). In the example of  FIG.  7   , fingers  50  (e.g., fingers  50  in one of hinge links  40 ) are being attached to hinge mounting member  52 . Hinge mounting member  52 , which may sometimes be referred to as a housing structure or housing portion, may be formed as an integral portion of a housing wall or other structure(s) of housing  12  (e.g., member  52  may form part of one of the halves of housing  12  that rotate relative to each other) or may be formed from a separate structure that is attached to a portion of housing  12 . There may be, as an example, a pair of members  52  attached to one half of housing  12  (e.g., at opposing ends of axis  28 ) and another pair of members  52  attached to corresponding portion of another half of housing  12  (and optionally additional pairs of members  52  at one or more additional locations along the length of axis  28 ). Hinge  30  may have a first set of links that form a first hinge portion spanning between two of members  52  (e.g., at one end of axis  28 ) and may have a second set of links that form a second hinge portion spanning between two more of members  52  (e.g., at an opposing end of axis  28 ). Arrangements with a different number of hinge structures coupled to members  52  and/or different numbers of members  52  may also be used. 
     As shown in  FIG.  7   , each member  52  may have openings such as through-hole openings  54  that allow screws or other fasteners to be used to attach member  52  to housing  12 . If desired, fingers  50  may be received within one or more recesses in member  52  such as recess  56 . Fingers  50  may be mounted in recess  56  under a mounting plate such as plate  58  that helps hold fingers  50  within recess  56 . Plate  58  may be attached to member  52  using welds, adhesive, fasteners, press-fit connections, interlocking engagement structures, and/or other mounting structures. 
     A cross-sectional side view of fingers  50  of  FIG.  7    taken along line  60  and viewed in direction  62  is shown in  FIG.  8   . A cross-sectional side view of fingers  50  of  FIG.  7    taken along line  64  and viewed in direction  66  is shown in  FIG.  9   . Other configurations for coupling fingers  50  (and links  40  formed from fingers  50  and/or other structures) may be used, if desired. The configuration of  FIGS.  6 ,  7 , and  8    is illustrative. 
     To help ensure that links  40  rotate evenly throughout hinge  30 , device  10  may have intermeshed gears that extend between rotating portions of housing  12  (e.g., in parallel with hinge  30 ). The gears and/or other rotation synchronization structures may help ensure that movement of a first half of housing  12  will produce equal and opposite movement of an opposing second half of housing  12 . An illustrative rotation synchronization mechanism (mechanism  98  of  FIG.  10   ) with gears  68  of the type that may be used for rotational (angular movement) synchronization in hinge  30  are shown in  FIG.  10   . In the example of  FIG.  10   , a first half of housing  12  (housing portion  12 A) and a second half of housing  12 B are coupled using hinge  30  (see, e.g.,  FIG.  4   ). During operation, housing portions  12 A and  12 B can rotate with respect to each other about axis  28 . Angular movement synchronization gears  68 , which are mounted to gear support structure  90  and rotate with respect to structure  90 , are coupled in series between housing portion  12 A (which is connected to gear  68 - 1  and does not rotate relative to gear  68 - 1 ) and housing portion  12 B (which is connected to gear  68 - 2  and does not rotate relative to gear  68 - 1 ). This arrangement causes rotation of one side of device  10  to cause equal and opposite rotation of the other side of device  10 . 
     Consider, as an example, a scenario in which device  10  is lying flat on a table in its open state. A user who desires to close device  10 , rotates portion  12 A from flat position  80  to upright position  82  (e.g., portion  12 A is rotated in direction  84  by 90°). The movement of housing portion  12 A in direction  84  causes gear  68 - 1  to rotate clockwise, which causes adjacent gear  68 - 3  to rotate counterclockwise and thereby causes gear  68 - 4  to rotate clockwise. Clockwise rotation of gear  68 - 4  causes gear  68 - 2  to rotate counterclockwise. Housing portion  12 B is attached to gear  68 - 2 , so counterclockwise rotation of gear  68 - 4  causes housing portion  12 B to rotate in counterclockwise direction  92  from initial position  94  to final position  96  (e.g., the rotational movement of housing portion  12 B is synchronized to that of housing portion  12 A). 
     The use of a set of four gears in rotation synchronization mechanism  98  of  FIG.  10    is presented as an example. Mechanism  98  may have a different number of gears, if desired, (e.g., 4-12 gears  68 , at least 4 gears  68 , at least 8 gears  68 , fewer than 20 gears  68 , fewer than 10 gears  68 , fewer than 5 gears  68 , and/or other suitable number of angular movement synchronization gears). 
     If desired, the curved inwardly facing surfaces of the crescent-shaped slots may be replaced by curved (crescent-shaped) outwardly facing surfaces in links  40 . Consider, as an example, illustrative hinge  30  of  FIG.  11   . As shown in  FIG.  11   , portions of links  40  in hinge  30  may, if desired, have curved crescent-shaped surfaces such as outwardly facing curved surfaces  104  and mating inwardly facing curved surfaces  102 . Links  40  may be held together using attachment members  100  (e.g., threaded screws or other fasteners that travel within slots in portions  40 P of links  40 ). Each of members  100  may have a first portion attached to a link  40  and a second portion that is attached to corresponding retention member  106 . Retention members  106  may help hold surfaces  102  against surfaces  104  as links  40  slide along their mating curved surfaces relative to each other (and thereby rotate about rotation axes  42  that lie outside of the plane of the links). The amount of tightening exerted by each member  10  may be used to adjust the amount of friction exhibited by hinge  30 , so that links  40  can serve as a friction clutch that imparts a desired amount of friction to hinge  30  (e.g., sufficient friction to hold first and second portions of housing  12  at a desired angle relative to each other when the first portion is resting on a surface). Members  106  each have an outwardly curved (crescent-shaped) surface  110  that slides along a corresponding inwardly curved (crescent-shaped) link surface  112 . Any number of links  40  having external surfaces with curved cross-sectional surfaces such as surfaces  104  and  102  of  FIG.  11    may be used in forming hinge  30 . For example, hinge  30  may have at least 3, at least 5, at least 10, fewer than 15, fewer than 7, fewer than 4, or other suitable number of links  40  of  FIG.  11   . The configuration of  FIG.  11    is presented as an example. 
     Links  40  may have rectangular outlines (footprints when viewed from above) or may have other suitable shapes. The example of  FIG.  12   , which shows an illustrative top view of links  40  of the type shown in  FIG.  11   , illustrates how links  40  may, if desired, have a staircase-shaped edge where these links abut. Other link shapes may be used, if desired. 
       FIG.  13    is a top view of device  10  showing how components may be arranged within device  10  (in an illustrative embodiment). As shown in  FIG.  13   , speakers  120  may be mounted at the four corners of device  10 . Camera  122  and/or other sensors (e.g., an ambient light sensor, three-dimensional image sensor, etc.) may be located at one of the ends of device  10  (so that the camera can be used to capture the face of a user when device  10  is partly folded into a laptop configuration). An array of haptic output devices  126  may be arranged in an array (e.g., a two-dimensional array having multiple rows and multiple columns) to provide display  14  (which overlaps devices  126 ) with haptic feedback functionality. Display timing controller integrated circuits (TCONs)  124  may be located at opposing ends of display  14  (e.g., so that each TCON can handle display driving operations for a respective half of display  14 ). If desired, the outer periphery of housing  12  may have a metal band that is divided into multiple segment using gaps such as gaps  128 . With this type of arrangement, each segment may, if desired, form an antenna resonating element for an inverted-F antenna or other antenna (e.g., for cellular telephone transmissions, wireless local area network transmissions, and/or other wireless communications). 
       FIG.  14    is a side view of an illustrative electronic device in accordance with an embodiment. As shown in  FIG.  14   , display  14  may be attached to one end of housing  12  (e.g., in attachment region  144  and may have an opposing end that floats with respect to housing  12 . Springs or other tensioning mechanisms may be used to tension the floating end of display  14  in direction  146  to help hold display flat. When device  10  is folded, display  14  may cover region  142 . When device  10  is unfolded, display  14  may be retracted from region  142 . Components  140  (e.g., a camera and/or other optical components) may be mounted in region  142 , so that these components are uncovered as the end of display  14  is pulled away from region  142  during device opening. 
       FIG.  15    is a cross-sectional end view of device  10  of  FIG.  14    showing how the edges of display  14  may be confined within channels formed by overlapping portions  12 P of housing  12 . Other arrangements for aligning and guiding display  14  as device is opened and closed may be used, if desired. 
     Display  14  may be formed from a flexible organic light-emitting diode panel or other flexible pixel array overlapped by a protective layer. The protective layer may be, for example, a display cover layer formed from a thin layer of transparent material such as glass. When the cover layer is folded, the cover layer will tend to exhibit a restoring force (sometimes referred to as an unfolding force). This resorting force attempts to unfold housing  12 . Left unopposed, this unfolding (opening) torque from the folded display may not be appealing to users of device  10  and may make it challenging to stabilize device  10  in a desired partly-opened state. 
     To help even out the amount of torque required to open and close housing  12  over its allowed range of rotation and thereby improve the user experience when interacting with device  10 , hinges  30  may be provided with a counterbalance mechanism. The counterbalance mechanism may provide a torque (sometimes referred to as a closing torque or folding torque) that opposes the unfolding torque of the display. With this counterbalance in place, the folding and unfolding torques will balance each other, so the amount of friction supplied by hinge  30  may potentially be reduced.  FIG.  16    is a top view of an illustrative hinge having a counterbalance mechanism (mechanism  150 ). 
     As shown in  FIG.  16   , hinge  30  has friction hinge links  40 . Links  40  may have interdigitated fingers and crescent-shaped slots as described in connection with  FIGS.  4  and  5   . There may be two sets (e.g., two parallel elongated strips) of links  40 . A set of linked synchronization gears  68  may be located between these sets of links. Gears  68  span the left and right portions of housing  12  of  FIG.  16    and engage with teeth in these housing portions, thereby synchronizing rotational motion between the left and right portions of housing  12  about rotational axis (hinge axis)  28 . The presence of sets of links  40  running parallel to gears  68  on opposing sides of gears  68  may help support and stabilize gears  68  during operation. 
     Counterbalance mechanism  150  may use springs  152  to help counterbalance the unfolding torque applied to device  10  by display  14  as one or more hinges such as hinge  30  are opened and closed. In the example of  FIG.  16   , each of the four corners of hinge  30  has a pair of springs  152  that press inwardly on a corresponding pad  154  (toward axis  28  and links  40  and away from the adjacent portion of housing  12 ). This causes each pad  154  to bear against a corresponding roller  156 , which is mounted within a respective link portion  40 P with a respective roller axle  158 . 
       FIG.  17    illustrates how the folding torque imposed by counterbalance mechanism  150  counteracts the corresponding unfolding torque generated by the folding of display  14  to help even out the amount of torque that a user needs to apply when rotating the left and right portions of housing  12  of device  10  and thereby help reduce the holding force requirements for the friction mechanism of hinge  30 . 
     In the example of  FIG.  17   , hinge  30  is illustrated in two positions: a fully opened position OP and a fully closed position CL. 
     In open (unfolded) position OP, links  40  lie flat and roller  156  pushes pad  154  outwardly (away from links  40  toward housing  12 ). This compresses spring  152  and positions roller  156  so that contact point A between roller  156  and pad  154  is located a first distance D 1  from the link rotational axis  42  associated with the link  40  that is attached to roller  156 . 
     In closed (folded) position CL, links  40  are folded back on themselves and bend about axis  28 . As shown in  FIG.  17   , in position CL, roller  156  contacts pad  154  at a contact point B, which is different than contact point A. The distance D 2  between link rotational axis  42  and contact point B is less than the distance D 1 , so that pad  154  is located farther from housing  12  than in open position OP. As a result, spring  152  is allowed to expand and the expansion force generated by spring  152  is reduced. The amount of folding torque produced by the counterbalance mechanism is related to the values of distance D 1  and D 2  and the expansion force from spring  152 , so that the folding torque produced by counterbalance mechanism  150  need not be constant as a function of rotational angle. As an example, there may be more folding torque T tending to close device  10  about axis  28  when device  10  is being opened from position CL and less folding torque when device  10  is in position OP. 
       FIGS.  18 - 25    illustrate embodiments for hinge  30  in which links  40  are synchronized using laterally staggered sets of synchronization gear teeth. A first set of gears is located in a first plane and a second set of gears is located in a parallel second plane that is offset from the first plane. During bending, the first and second sets of gears work together to synchronize motion of the first and second portions of housing  12 . 
     An exploded perspective view of this type of hinge is shown in  FIG.  18   . As shown in  FIG.  18   , hinge  20  has links  40 A and  40 F that may be formed as integral parts of the first and second housing portions  12  and has a series of coupled intervening links  40 E,  40 D,  40 C, and  40 B. During folding of device  10 , the rotational motion of the first and second housing portions is synchronized by links  40 , so that stress on display  14  is maintained at a desired low amount (e.g., so that the length of display  14  is not changed by the bending of display  14  because the length of display  14  is the same in both its flattened and bent states). 
     As shown in  FIG.  18   , links  40  have integral gears—see, e.g., the gear in link  40 D formed from gear teeth  200 D. Additional gears  202  are mounted in links  40  using shafts  204  that are received in corresponding openings  206  in the frame members that make up the links. 
       FIG.  19    is a perspective view of hinge  30  of  FIG.  18    when assembled and lying in its flat (unbent) state.  FIG.  20    is a front perspective view of hinge  30  when hinge  30  is in its bent configuration.  FIG.  21    is a rear perspective view of hinge  30  when hinge  30  is in its bent configuration. 
     As shown in  FIGS.  18   , hinge  30  may have two sets of laterally offset synchronization gears that run in parallel between the first and second housing portions. A first of the two sets of gears lies in a plane running along line  210  of  FIG.  18   . A second of the two sets of gears lies in a parallel plane running along line  214  of  FIG.  18    (e.g., a plane that is laterally offset parallel from the plane of the first gear set along a direction parallel to the bend axis). 
       FIG.  22    is a cross-sectional side view of an illustrative portion of hinge  30  taken along line  210  of  FIG.  18    and viewed in direction  212 . As shown in  FIG.  22   , hinge  30  has first gears  202 - 1  that lie in a first plane that includes line  210 . Hinge  30  also has second gears  202 - 2  that lie in a second plane that includes line  214 . Hinge  30  is unbent in the configuration of  FIG.  22   . Links  40  include alternating odd and even links (e.g., odd links  40 F,  40 D, and  40 B and even links  40 E,  40 C, and  40 A). 
       FIG.  23    shows a portion of hinge  30  of  FIG.  22    in a bent hinge configuration. As shown in  FIG.  23   , gears  202 - 1  in the first plane that includes line  210  are used to synchronize rotational movement of the even links (e.g., links  40 E and  40 C in the example of  FIG.  23   ) as these links rotate about axes  230 . 
       FIG.  24    is a cross-sectional side view of an illustrative portion of hinge  30  taken along line  214  of  FIG.  18    and viewed in direction  216 .  FIG.  24    shows how second gears  202 - 2 , which lie in the second plane that includes line  214  of  FIG.  18   , are coupled between the odd links of hinge  30  (e.g., odd links  40 F,  40 D, and  40 B). 
       FIG.  25    shows a portion of hinge  30  of  FIG.  24    in a bent hinge configuration. As shown in  FIG.  25   , gears  202 - 2  in the second plane are used to synchronize rotational movement of the odd links (e.g., links  40 D and  40 B in the example of  FIG.  25   , which rotate about axes  232 ). 
     As the example of  FIGS.  18 - 25    demonstrates, hinge structures in device  10  may include a rotational synchronization mechanism with two sets of gear couplings lying in parallel planes. Each pair of gears synchronizes rotation between a left-hand adjacent link and a corresponding right-hand adjacent link. As an example, gears  202 - 1  of  FIG.  23    synchronize rotation between link  40 E on the left of link  40 D (which holds gears  202 - 1 ) and link  30 C on the right. The first gears are used in synchronizing motion of the odd links (e.g., gears  202 - 1  mounted on link  40 D are used to synchronize motion of links  40 E and  40 C). By using two staggered parallel gear sets, all links  40  in hinge  30  can be synchronized, even when those links are far from each other (e.g., rotation of link  40 F rotates link  30 D, which in turn rotates ink  40 B and rotation of link  40 E rotates link  30 C, which in turn rotates link  40 A). The gear structures of hinge  30  thereby synchronize rotation of the first portion of housing  12  (which may be attached to link  40 F or formed as part of link  40 F) with rotation of the second portion of housing  12  (which may be attached to link  40 A or formed as part of link  40 A). 
     The gears of the hinge of  FIGS.  18 - 25    may be used as a synchronization mechanism that is located between a pair of parallel strips of friction hinges with interdigitated fingers as described in connection with  FIG.  16   , may be used as a hinge in device  10  in place of friction hinges with interdigitated fingers, may be used in the same device that includes one or more friction hinges with interdigitated fingers elsewhere in the device, and/or may otherwise be used in folding device structures to form a hinge that synchronizes rotational motion between folded housing portions. 
       FIG.  26    is an exploded perspective view of another illustrative hinge in accordance with an embodiment. As shown in  FIG.  26   , some of synchronization gears  220  of hinge  30  may have gear portions of different diameters mounted on a common axle (see, e.g., smaller gear  220 L and larger gear  220 B on common axle  222  of  FIG.  26   ). The gear ratio established by the ratio of the number of teeth in gear  220 B to the number of teeth in gear  220 L is not 1:1, which causes different pairs of adjacent links  40  to rotate by different amounts relative to each other as device  10  is folded to transition from its flat opened state to its folded closed state).  FIG.  27    is a front perspective view of illustrative hinge  30  of  FIG.  26    in the open (flat) state.  FIG.  28    is a cross-sectional view of hinge  30  of  FIG.  27    taken along line  226  of  FIG.  27    and viewed in direction  228 , which shows the presence of larger gear portion  220 B on axle  222 .  FIG.  29    is a cross-sectional side view of hinge  30  of  FIG.  27    taken along line  230  of  FIG.  27    and viewed in direction  232 , which shows the presence of smaller gear portion  220 L on shared axle  222 . 
     The uneven gear ratio presented by the different sizes of gears  220 B and  220 L allows different portions of hinge  30  to rotate by different amounts as hinge  30  is folded. As shown in  FIG.  30   , for example, which shows hinge  30  in its folded configuration, the outermost pairs of links  40  in hinge  30  may, when folded, rotate with respect to each other by a value of 180°-AB, whereas the innermost pairs of links  40  in hinge  30  (the links closes to the center of hinge  30 ) may rotate by a value of 180°-AL. The value of rotation angle 180°-AB may be, as an example, 40° or other suitable value, whereas the value of rotation angle 180°-AL may be, as an example, 50° or other suitable value that is different (e.g., greater than) the value of rotation angle 180°-AB. The use of different rotation angle values at different locations across hinge  30  may help allow hinge  30  to be compact while accommodating the curved shape of panel  14 P when folded. 
     As with the gears of the hinge of  FIGS.  18 - 25   , the gears of the hinge of  FIGS.  26 - 30    may be used as a synchronization mechanism that is located between a pair of parallel strips of friction hinges with interdigitated fingers as described in connection with  FIG.  16   , may be used as a hinge in device  10  in place of friction hinges with interdigitated fingers, may be used in the same device that includes one or more friction hinges with interdigitated fingers elsewhere in the device, and/or may otherwise be used in folding device structures to form a hinge that synchronizes rotational motion between folded housing portions. 
     As described above, one aspect of the present technology is the gathering and use of information such as information from input-output devices. The present disclosure contemplates that in some instances, data may be gathered that includes personal information data that uniquely identifies or can be used to contact or locate a specific person. Such personal information data can include demographic data, location-based data, telephone numbers, email addresses, twitter ID&#39;s, home addresses, data or records relating to a user&#39;s health or level of fitness (e.g., vital signs measurements, medication information, exercise information), date of birth, username, password, biometric information, or any other identifying or personal information. 
     The present disclosure recognizes that the use of such personal information, in the present technology, can be used to the benefit of users. For example, the personal information data can be used to deliver targeted content that is of greater interest to the user. Accordingly, use of such personal information data enables users to calculated control of the delivered content. Further, other uses for personal information data that benefit the user are also contemplated by the present disclosure. For instance, health and fitness data may be used to provide insights into a user&#39;s general wellness, or may be used as positive feedback to individuals using technology to pursue wellness goals. 
     The present disclosure contemplates that the entities responsible for the collection, analysis, disclosure, transfer, storage, or other use of such personal information data will comply with well-established privacy policies and/or privacy practices. In particular, such entities should implement and consistently use privacy policies and practices that are generally recognized as meeting or exceeding industry or governmental requirements for maintaining personal information data private and secure. Such policies should be easily accessible by users, and should be updated as the collection and/or use of data changes. Personal information from users should be collected for legitimate and reasonable uses of the entity and not shared or sold outside of those legitimate uses. Further, such collection/sharing should occur after receiving the informed consent of the users. Additionally, such entities should consider taking any needed steps for safeguarding and securing access to such personal information data and ensuring that others with access to the personal information data adhere to their privacy policies and procedures. Further, such entities can subject themselves to evaluation by third parties to certify their adherence to widely accepted privacy policies and practices. In addition, policies and practices should be adapted for the particular types of personal information data being collected and/or accessed and adapted to applicable laws and standards, including jurisdiction-specific considerations. For instance, in the United States, collection of or access to certain health data may be governed by federal and/or state laws, such as the Health Insurance Portability and Accountability Act (HIPAA), whereas health data in other countries may be subject to other regulations and policies and should be handled accordingly. Hence different privacy practices should be maintained for different personal data types in each country. 
     Despite the foregoing, the present disclosure also contemplates embodiments in which users selectively block the use of, or access to, personal information data. That is, the present disclosure contemplates that hardware and/or software elements can be provided to prevent or block access to such personal information data. For example, the present technology can be configured to allow users to select to “opt in” or “opt out” of participation in the collection of personal information data during registration for services or anytime thereafter. In another example, users can select not to provide certain types of user data. In yet another example, users can select to limit the length of time user-specific data is maintained. In addition to providing “opt in” and “opt out” options, the present disclosure contemplates providing notifications relating to the access or use of personal information. For instance, a user may be notified upon downloading an application (“app”) that their personal information data will be accessed and then reminded again just before personal information data is accessed by the app. 
     Moreover, it is the intent of the present disclosure that personal information data should be managed and handled in a way to minimize risks of unintentional or unauthorized access or use. Risk can be minimized by limiting the collection of data and deleting data once it is no longer needed. In addition, and when applicable, including in certain health related applications, data de-identification can be used to protect a user&#39;s privacy. De-identification may be facilitated, when appropriate, by removing specific identifiers (e.g., date of birth, etc.), controlling the amount or specificity of data stored (e.g., collecting location data at a city level rather than at an address level), controlling how data is stored (e.g., aggregating data across users), and/or other methods. 
     Therefore, although the present disclosure broadly covers use of information that may include personal information data to implement one or more various disclosed embodiments, the present disclosure also contemplates that the various embodiments can also be implemented without the need for accessing personal information data. That is, the various embodiments of the present technology are not rendered inoperable due to the lack of all or a portion of such personal information data. 
     The foregoing is merely illustrative and various modifications can be made to the described embodiments. The foregoing embodiments may be implemented individually or in any combination.

Metadata:
Filing Date: 20220707
Publication Date: 20241210
Grant Date: 20241210
Priority Date: 20210811
Inventors: KRAHN, Scott J
Garelli, Adam T
HAMEL, Bradley J
MATHEW, Dinesh C
KIM, HOON SIK
HENDREN, KEITH J
CAO, ROBERT Y
LAM, TERRY C
ROBINSON, Kevin M
FARAHANI, HOUTAN R
SANO, TATSUYA
Assignee: APPLE INC
CPC Classifications: [{"code": "G06F1/1652", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/1616", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10K2102/311", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F1/1641", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04M1/0235", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10K77/111", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10K50/84", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/1652", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/1681", "inventive": true, "first": true, "tree": "[]"}, {"code": "G09F9/301", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F1/1681", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F1/1652", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/1616", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/1681", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 82898984