WO2016100639A1

WO2016100639A1 - Protection mechanisms for cover glass of handheld device during drop event

Info

Publication number: WO2016100639A1
Application number: PCT/US2015/066327
Authority: WO
Inventors: Petr GORELCHENKO; Jason Thomas HARRIS; Guangli Hu; Po-Jen Shih; Irene Marjorie Slater; Vijay Subramanian; Yu XIAO; Bin Zhang; Chunfeng ZHOU
Original assignee: Corning Incorporated
Priority date: 2014-12-19
Filing date: 2015-12-17
Publication date: 2016-06-23
Also published as: TWI670581B; TW201633046A

Abstract

A protection mechanism (100) for a cover glass (102) of a handheld device (101) during a drop event includes preventing direct contact between the cover glass (102) and a hard surface (25) or minimizing the impact force on the cover glass (102) when the handheld device (101) lands on the hard surface (25). The protection mechanism (100) may include a bezel (104) that is deployed or deformed to a position where the bezel (104) is proud of the cover glass (102) when a free-fall motion of the handheld device (101) is detected. Or the protection mechanism may involve folding the handheld device to hide the cover glass during the drop event. An airbag or deceleration device may be used to soften impact on the cover glass. The protection mechanism may include a mass whose motion adjusts an angular momentum of the handheld device such that the handheld device lands at an angle where impact force on the cover glass will be minimized.

Description

PROTECTION MECHANISMS FOR COVER GLASS OF HANDHELD DEVICE DURING DROP EVENT

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority under 35 U.S.C. § 119 of U.S. Provisional Application Serial No. 62/094496 filed on December 19, 2014 the content of which is relied upon and incorporated herein by reference in its entirety.

BACKGROUND

[0002] The mobile nature of handheld devices, such as smartphones, tablets, portable media players, personal computers, and cameras, makes these devices particularly vulnerable to accidental dropping on hard surfaces, such as the ground, or in some pool of liquid. These devices typically incorporate cover glasses, which may become damaged upon impact with hard surfaces. In many devices, these cover glasses function as display covers, and may incorporate touch functionality, such that use of the devices is negatively impacted when the cover glasses are damaged.

[0003] There are two major failure modes for a handheld device cover glass when the device is dropped on a hard surface. One of the modes is flexure failure, which is caused by bending of the glass when the device is subjected to dynamic load due to impact. The other mode is sharp contact failure, which is caused by introduction of damage to the glass surface. Impact of the glass with rough hard surfaces, such as asphalt, granite, etc., can result in sharp indentations in the glass surface. For example, a rough granite surface might have indentations with in-plane feature size (width) as large as 10 mm and out-of-plane feature size (height) on the order of several hundred micrometers. Such a rough surface can result in indentations in the glass surface upon contact. These indentations can become failure sites in the glass surface from which cracks may develop and propagate.

[0004] Glass can be made more resistant to flexure failure by ion-exchange technique, which involves inducing compressive stress in the glass surface. However, the ion- exchanged glass will still be vulnerable to dynamic sharp contact, owing to the high stress concentration caused by local indentations in the glass from the sharp contact. Thus it has been a continuous effort for the glass makers and handheld device manufacturers to improve the resistance of handheld devices to sharp contact failure.

SUMMARY

[0005] The present disclosure describes mechanisms for protecting a cover glass from damage, such as damage due to sharp contact failure, during a handheld drop event.

[0006] In one aspect, a protection mechanism for a cover glass involves preventing direct contact of the cover glass with a surface by raising the bezel of the handheld device, allowing the bezel to make direct contact with the surface instead of the cover glass. For example, the protection mechanism can include a bezel shaped for mounting about a periphery of the handheld device in a position to circumscribe a periphery of the cover glass, the bezel being arranged for movement along a select direction

perpendicular to a plane of the cover glass, the bezel having a normal position and a landing position spaced apart along the select direction, wherein in the landing position a front end of the bezel is raised by a select height relative to a front surface of the cover glass, the select height being sufficient to prevent direct contact of the front surface of the cover glass with a surface when the handheld device lands on the surface during the drop event; a sensing device comprising at least one motion sensor for sensing a parameter related to a free-fall motion of the handheld device; and a mechanism for adjusting the position of the bezel along the select direction, the mechanism being configured to adjust the position of the bezel from the normal position to the landing position in response to an output of the sensing device. In another example the protection mechanism can include a bezel shaped for mounting about a periphery of the handheld device in a position to circumscribe a periphery of the cover glass, the bezel having a normal position and a landing position along a select direction perpendicular to a plane of the cover glass, the bezel being composed of a shape changing structure having a first length in the normal position and a second length in the landing position, the second length being greater than the first length;

a sensing device comprising at least one motion sensor for sensing a parameter related to a free-fall motion of the handheld device; and a mechanism for inducing a change in shape of the bezel in response to an output of the sensing device. [0007] In another aspect, a protection mechanism for a cover glass involves cushioning the landing of the handheld device on a surface using an airbag. For example, the protection mechanism can include an airbag shaped for mounting about a periphery of the handheld device in a position to circumscribe a periphery of the cover glass; a sensing device comprising at least one motion sensor for sensing a parameter related to a free-fall motion of the handheld device; and a mechanism for deploying the airbag in response to an output of the sensing device.

[0008] In another aspect, a protection mechanism for a cover glass involves decelerating the handheld device during a drop event. For example, the protection mechanism can include a bezel shaped for mounting about a periphery of the handheld device in a position to circumscribe a periphery of the cover glass; a deceleration device coupled to the bezel; a sensing device comprising at least one motion sensor for sensing a parameter related to a free-fall motion of the handheld device; and a mechanism for deploying the deceleration device in response to an output of the sensing device.

[0009] In another aspect, a protection mechanism for a cover glass involves changing the angular momentum of the handheld device using fluid in a fluid chamber or channel or balls in a track within the handheld device. The change in angular momentum may be passive or involve active control. For example, the protection mechanism can include a fluid chamber located with the handheld device, the fluid chamber containing a fluid, wherein motion of the fluid within the fluid chamber during the drop event adjusts an angular momentum of the handheld device. As another example, the protection mechanism can include a sensing device including at least on motion sensor for sensing a parameter related to a free-fall motion of the handheld device; and a fluid channel located within the handheld device, the fluid channel containing a fluid and at least one valve to control motion of the fluid within the fluid channel, wherein the at least one valve is responsible to an output of the sensing device and motion of the fluid within the fluid channel adjusts an angular momentum of the handheld device. As yet another example, the protection mechanism can include a track located within the handheld device, the track containing a set of balls, wherein motion of the balls within the track during the drop event causes a select change in angular momentum of the handheld device. [0010] In another aspect, a protection mechanism for a cover glass involves preventing rebound of the handheld device using a bezel having a sticky surface, suction cups, or sticky pads. For example, the protection mechanism can include a bezel shaped for mounting about a periphery of the handheld device in a position to circumscribe a periphery of the cover glass, wherein a front end of the bezel for positioning nearest to a front surface of the cover glass can include a releasable adhesive.

[0011] In another aspect, a protection mechanism for a cover glass involves folding the handheld device to hide the cover glass within the handheld device during a drop event. For example, the protection mechanism can include a sensing device comprising at least one motion sensor for sensing a parameter related to a free-fall motion of the handheld device; and a hinge mechanism for folding the handheld device such that the cover glass is hidden within the handheld device during the drop event, wherein the hinge mechanism is responsive to an output of the sensing device.

[0012] In another aspect, a protection mechanism for a cover glass includes an active material having a variable stiffness. For example, the protection mechanism can include a sensing device having at least one motion sensor for sensing a parameter related to a free-fall motion of the handheld device; and an active material having a variable stiffness located underneath the cover glass, wherein the stiffness of the active material is responsive to an output of the sensing device.

[0013] In another aspect, a handheld device includes a cover glass and any of the protection mechanisms described herein.

[0014] It is to be understood that both the foregoing general description and the following detailed description are exemplary and intended to provide an overview or framework for understanding the nature and character of the invention as it is claimed. The accompanying drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification. The drawings illustrate various embodiments of the invention and together with the description serve to explain the principles and operation of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The following is a description of the figures in the accompanying drawings. The figures are not necessarily to scale, and certain features and certain views of the figures may be shown exaggerated in scale or in schematic in the interest of clarity and conciseness.

[0016] FIG. 1A shows a device dropped onto a rough surface.

[0017] FIG. IB shows high failure and low failure regions of a dropped device.

[0018] FIG. 2A shows maximum principal stress of glass stress as a function of drop height for different levels of glass recession in a device drop analysis.

[0019] FIG. 2B shows contact forces corresponding to the device drop analysis of FIG.

2A.

[0020] FIGS. 3A and 3B show a cover glass protection mechanism including an adjustable bezel according to one embodiment.

[0021] FIGS. 4A and 4B show a cover glass protection mechanism including a change shaping bezel according to one embodiment.

[0022] FIGS. 5A and 5B show a cover glass protection mechanism including an air bag according to one embodiment.

[0023] FIGS. 6A and 6B show a cover glass protection mechanism including a deceleration device incorporated into a handheld device according to one embodiment.

[0024] FIGS. 7A-7D show a cover glass protection mechanism including a fluid chamber according to one embodiment.

[0025] FIG. 8 shows a cover glass protection mechanism including a fluid channel according to one embodiment.

[0026] FIGS. 9A and 9B show a cover glass protection mechanism including a track with balls according to one embodiment.

[0027] FIGS. 10A and 10B show two types of contacts in drop events.

[0028] FIGS. IOC and 10D show contact forces as a function of drop angles for the contact types shown in FIGS. 10A and 10B, respectively.

[0029] FIG. 11A shows a cover glass protection mechanism including a sticky bezel incorporated into a handheld device according to one embodiment. [0030] FIG. 11B shows a cover glass protection mechanism including suction cups incorporated into a handheld device according to one embodiment.

[0031] FIG. llC shows a cover glass protection mechanism including pads with sticky surfaces incorporated into a handheld device according to one embodiment.

[0032] FIGS. 12A-12C show a cover glass protection mechanism for a handheld device having a flexible display according to one embodiment.

[0033] FIGS. 13A-13C show a cover glass protection mechanism for a handheld device having a split display according to another embodiment.

[0034] FIG. 14A shows a cover glass protection mechanism including an active material with variable stiffness.

[0035] FIG. 14B is a graph of maximum principal stress as a function of cover glass underlying layer modulus.

DETAILED DESCRIPTION

[0036] In a tilted/angled face down drop, such as illustrated in FIG. 1A, an

edge/corner area 27 of the handheld device 20 makes contact with a hard surface 25. The first contact occurs when the handheld device 20 is first dropped from a height above the rough surface 25. Subsequent contacts may occur during rebounds of the handheld device 20. For this type of drop, damage may be introduced on the top of the cover glass when the handheld device 20 makes contact with the hard surface 25. The glass may fail by fracture(s) propagating from the top of the glass and induced by the bending stress on the top of the glass. FIG. IB illustrates typical failure regions of the handheld device 20 due to the first contact with the hard surface 25. The non-shaded region 30 represents a high probability of failure region due to sharp contact, and the shaded region 32 represents a low probability of failure region due to sharp contact. FIG. IB shows that the cover glass is most vulnerable to damage around the corners and edges from tilted/angled face down drop. Some mechanisms are described herein for protecting the cover glass against damage from tilted/angled face down drops. Some mechanisms described herein may also protect the cover glass against damage from full face down drops. [0037] In one aspect, a protection mechanism for a cover glass involves preventing direct contact of the cover glass with a hard surface during a drop event. Herein and subsequently, the term "hard surface" will generally refer to any solid surface that may result in damage to the cover glass upon impact. A "drop event" may include dropping a handheld device from a height above the hard surface and any subsequent rebounds of the handheld device. To achieve this, a bezel circumscribing a periphery of the handheld device is raised during a drop event such that the bezel, rather than the cover glass, makes direct contact with the hard surface when the handheld device lands on the hard surface. In the event that there is not enough time to raise the bezel during the first contact of the handheld device with the rough surface, the bezel may still function to protect the cover glass if it is raised before a second contact of the handheld device with the rough surface. Such a second contact may occur due to rebounding of the handheld device. FIG. 2B shows the maximum principal stress of glass stress during a second corner contact of the handheld device with a hard surface for different levels of glass recession within the handheld device in a device drop analysis. In FIG. 2B, line Dl represents a glass recession of 50 microns, and line D2 represents a glass recession of 250 microns, where glass recession is equivalent to raising of the bezel. FIG. 2B shows the maximum contact force during the second corner contact of FIG. 2B. FIGS. 2A and 2B show that larger glass recession (higher bezel) leads to lower contact forces on the cover glass, thus lower failure probability during drop events.

[0038] Referring to FIGS. 3A and 3B, in one embodiment, a handheld device 101 has a cover glass 102. The handheld device 101 may be any handheld device having a cover glass, such as a smartphone, tablet, portable media player, personal computer, and camera. The cover glass 102 may or may not be a display cover and may be made of glass or glass-ceramic material. A protection mechanism for the cover glass, generally identified at 100, is incorporated into the handheld device 101. In the embodiment shown in FIGS. 3A and 3B, and in subsequent embodiments, only the details of the handheld device relevant to the description of the cover protection mechanism will be illustrated. This also means that any disclosed protection mechanism embodiments can be used with any handheld device regardless of the particular configuration or intended use of the handheld device. It should also be noted that some features of protection mechanism embodiments may be exaggerated in scale relative to the overall dimensions of the handheld device in the interest of clarity.

[0039] The protection mechanism 100 has a bezel 104, which may be in the form of a ring shaped to circumscribe the periphery of the handheld device 101 as well as the periphery of the cover glass 102. The bezel 104 is not fixed to the cover glass 102 and is movable relative to the cover glass 102 in a direction perpendicular to the plane of the cover glass 102 (i.e., in a vertical direction relative to the drawings of FIGS. 3A and 3B). The bezel 104 has a normal position, which is shown in FIG. 3A, and a landing position, which is shown in FIG. 3B, relative to the cover glass 102 (and along the displacement direction 107). In the normal position (FIG. 3A), the front end 104A of the bezel 104 is flush with the front surface 102A of the cover glass 102. (Here and in other

descriptions, the "front surface" of the cover glass is the surface of the cover glass that is exposed, and the "front end" of the bezel is the end of the bezel nearest to the front surface of the cover glass.) In other embodiments, in the normal position, the bezel front end 104A may stand proud of the cover glass front surface 102A (i.e., the bezel front end 104A may be raised relative to the cover glass surface 102A) or the cover glass front surface 102A may stand proud of the bezel end 104A (i.e., the cover glass surface 102A may be raised relative to the bezel end 104A). If the bezel front end 104A is proud of the cover glass front surface 102A in the normal position, the difference in height between the bezel front end 104A and cover glass front surface 102A should be slight so as not to interfere with the normal use of the handheld device 101. In the landing position (FIG. 3B), the front end 104A of the bezel 104 is raised relative to the front surface 102A of the cover glass 102 by a height H ( or the bezel end 104A is proud of the cover glass surface 102A by a height H). This may also be thought of as the front surface 102A of the cover glass 102 being recessed by the height H relative to the front end 104A of the bezel 104. This height H is selected such that the bezel 104 forms a protective raised lip 105 around the periphery of the cover glass 102. The appropriate height H can be determined from drop tests or modeling.

[0040] The handheld device 101 may be used normally with the bezel 104 in the normal position. During a drop event, before the handheld device 101 lands on a hard surface, the bezel 104 is deployed to the landing position. In this way, if the handheld device 101 lands on the front side including the cover glass 102, the protective raised lip 105 of the raised bezel 104 rather than the cover glass 102 will make direct contact with the hard surface. After the drop event, the bezel 104 may be returned to the normal position.

[0041] The protection mechanism 100 includes features to move the bezel 104 from the normal position to the landing position. In one embodiment, such features may include a bezel spring 106 situated between a back end 104B of the bezel 104 and a body 108 of the handheld device 101. In the normal position of the bezel 104, as shown in FIG. 3A, the bezel spring 106 is compressed in between the bezel 104 and the body 108 of the handheld device 101. In the landing position of the bezel 104, as shown in FIG. 3B, the bezel spring 106 extends to a length sufficient to place the bezel 104 at the landing position. Other devices besides a spring may be used to move the bezel 104 from the normal position to the landing position.

[0042] The protection mechanism 100 may include features to retain the bezel 104 in the normal position until the handheld device 101 is in a drop event. In one

embodiment, such features may include a lower retainer element 110, arranged adjacent to the bezel 104 to engage the bezel 104, and an actuator 112 coupled to the lower retainer element 110. A flexible link, such as a spring 116, may be provided between the lower retainer element 110 and the actuator 112, which would make it possible to displace the lower retainer element 110 laterally (i.e., in a direction generally perpendicular to the displacement direction 107 of the bezel 104). The actuator 112 is operable to extend or retract the lower retainer element 110 such that the lower retainer element 110 may engage or disengage from the bezel 104. The actuator 112 may be selected from two-way shape memory alloys, pneumatic actuators, piezoelectric actuators, miniature electric motors with a mechanical system to convert rotation to linear translation, and other actuators.

[0043] In one example, the lower end of the bezel 104 includes a ledge 114, which is arranged to abut against a bottom surface 110A of the lower retainer element 110 when the lower retainer element 110 is in the extended position and the bezel 104 is in the normal position. For example, FIG. 3A shows the lower retainer element 110 sitting on the ledge 114 in the normal position of the bezel 104. Retraction of the lower retainer element 110, by the actuator 112, in a direction away from the bezel 104 will disengage the lower retainer element 110 from the bezel 104 such that the bezel 104 becomes free to move to the landing position.

[0044] In FIGS. 3A and 3B, the lower retainer element 110 is shown as a body having a flat bottom surface llOA and a sloped top surface HOB. One possible use of the sloping of the top surface HOB will be explained later. However, in general, the lower retainer 110 may take on a variety of forms other than the one shown in FIGS. 3 A and 3B as long as the selected form allows selective engagement and disengagement of the lower retainer element 110 from the bezel 104. For example, the lower retainer element 110 may be in the form of a key or peg that fits into a lock or hole, respectively, in the bezel 104.

[0045] The protection mechanism 100 may include features to retain the bezel 104 in the landing position until a decision is made to return the bezel 104 to the normal position. In one embodiment, such features may include an upper retainer element 120, arranged adjacent to the bezel 104 to engage the bezel 104, and an actuator 122 coupled to the upper retainer element 120. A flexible link, such as a spring 124, may be provided between the upper retainer element 120 and the actuator 122, which would make it possible to displace the upper retainer element 120 laterally (i.e., in a direction generally perpendicular to the displacement direction 107 of the bezel 104). The actuator 122 is operable to extend or retract the upper retainer element 120 and may receive commands from the handheld device 101. Such commands may come, for example, from an application running on the handheld device 101 or a switch activated by a user. The actuator 122 may be selected from two-way shape memory alloys, pneumatic actuators, piezoelectric actuators, miniature electric motors with a mechanical system to convert rotation to linear translation, and other micro-machines.

[0046] In FIGS. 3A and 3B, the upper retainer element 120 is shown as a body having a flat top surface 120A and a sloped bottom surface 120B. One possible use of the sloping of the bottom surface 120B will be explained later. However, in general, the upper retainer element 120 may take on a variety of forms other than the one shown in FIGS. 3A and 3B as long as the selected form allows selective engagement and disengagement of the upper retainer element 120 from the bezel 104. For example, the upper retainer element 110 may be in the form of a key or peg that fits into a lock or hole, respectively, in the bezel 104.

[0047] In one embodiment, the actuator 112 coupled to the lower retainer element 110 responds to the output of a sensing device 118. The sensing device 118 may include one or more motion sensors 118A (e.g., accelerometer, gyroscope, etc.) for measuring one or more parameters useful in determining if the handheld device 101 is experiencing a drop event. The motion sensor(s) may measure parameters related to free-fall motion of the handheld device 101. Further, the sensing device 118 may include a microprocessor (or processor) 118B for processing the sensor data before using the sensor data to drive operation of the actuator 112. For example, the sensor data may be processed to determine if the handheld device 101 is experiencing a drop event or free-fall motion. For example, if the sensor data shows that the handheld device 101 is moving at a velocity that exceeds a predetermined threshold or that the handheld device has experienced a sudden acceleration, the microprocessor 118B may determine that the handheld device 101 is experiencing a drop event and issue an appropriate signal to the actuator 112.

[0048] If the actuator 112 receives a drop event signal, the actuator 112 will disengage the lower retainer element 110 from the bezel 104 in response to the signal, allowing the bezel spring 106 to extend and push the bezel 104 to the landing position. As the bezel 104 moves to the landing position, it will contact the upper retainer element 120. The sloped surface 120B of the upper retainer 120, along with the flexibility of the spring 124, will allow the bezel 104 to push the upper retainer element 120 laterally until the bottom of the bezel 104 is pushed above the upper retainer element 120. Once the bottom of the bezel 104 is above the upper retainer element 120, the upper retainer element 120 will spring back into its extended position and support the bezel 104 from the bottom, as shown in FIG. 3B.

[0049] After a drop event, the bezel 104 may be returned to the normal position. In one embodiment, to move the bezel 104 to the normal position, a command is sent to the actuator 122 to move the lower retainer element 110 to its extended position, if not already at the extended position, and move the upper retainer element 120 to its retracted position. In one example, the command may be issued by a user action, such as by pushing a button on the handheld device 101. In another example, the command may be issued by an application running on the handheld device 101. The application itself may be started by the user or a preprogrammed event, such as expiration of a predetermined time following the drop event.

[0050] Once the upper retainer element 120 is in the retracted position, the user can push the bezel 104 until the ledge 114 meets the sloped surface HOB of the lower retainer 110. Further pushing of the bezel 104 will cause the ledge 114 to slide down the sloped surface 110B, moving the lower retainer element 110 laterally and compressing the spring 116 (the flexibility of the spring 116 will allow the lower retainer element 110 to move laterally). Additional pushing of the bezel 104 will place the ledge 114 under the lower retainer element 110, allowing the lower retainer element 110 to spring back to the extended position and retain the bezel 104 in the normal position.

[0051] In one embodiment, the bezel spring 106, retainer elements 110, 120, springs 116, 124, and actuators 112, 122 may be regarded as an embodiment of a mechanism 126 for adjusting the bezel 104 between the normal and landing positions. A similar mechanism 126A may be arranged at another location in the handheld device 101, e.g., in opposed relation to the mechanism 126, and operated contemporaneously with the mechanism 126 to give the bezel 104 a balanced motion between the normal and landing positions. Also, the mechanism for adjusting the bezel 104 need not be limited to the particular one described above. Any mechanism for moving the bezel 104 between two spaced-apart positions, subject to space constraints in the handheld device 101, may be used. For example, a smart deformable material may be used in place of the bezel spring 106 to extend the bezel 104 to the landing position or retract the bezel 104 to the normal position.

[0052] Referring to FIGS. 4A and 4B, in another embodiment, a handheld device 201 has a cover glass 202. A protection mechanism for the cover glass, generally identified at 200, is incorporated into the handheld device 201. The protection mechanism 200 includes a bezel 204, which may be in the form of a ring shaped to circumscribe the periphery of handheld device 201 as well as the periphery of the cover glass 202. The bezel 204 is not fixed to the cover glass 202. The front end 204A of the bezel 204 is unrestrained. The back end 204B of the bezel 204 may be retained on a body 203 of the handheld device 201. As in the embodiment described with reference to FIGS. 3A and 3B, only the details of the handheld device 201 relevant to the description of the protection mechanism 200 are illustrated in FIGS. 4A and 4B.

[0053] The bezel 204 is made of a shape changing material. In one embodiment, the protection mechanism 200 is configured such that the change in shape of the bezel 204 occurs when the handheld device 201 is experiencing a drop event. During a drop event, before the handheld device 201 lands on a hard surface, the shape of the bezel 204 may change such that the bezel 204 becomes elongated in a direction perpendicular to the plane of the cover glass 202, as shown in FIG. 4B. This elongation will allow the bezel 204 to form a protective raised lip 205 of height HI around the periphery of the cover glass 202. In this way, if the handheld device 201 lands on the side including the cover glass 202, the protective raised lip 205, rather than the cover glass 202, will make direct contact with the hard surface. After the drop event, the bezel 204 may be returned to its normal length and shape.

[0054] One example of a material that may be used for construction of the shape changing bezel 204 is a class of polymers called dielectric elastomers. Some types of silicones and acrylics have the properties to be a dielectric elastomer. For example, VHB 4910 Acrylic from 3M Company is a good example of a dielectric elastomer that can reach 300% elongation. These materials are soft like rubber, which is advantageous in damping out the impact from the drop on the cover glass. When dielectric elastomers are sandwiched between compliant electrodes, for example, graphite powder or gold, they form an actuator. When a voltage is applied to the electrodes, the electrodes will apply a pressure on the elastomer in the middle due to Coulomb forces, which would squeeze the elastomer and produce an elongation of the elastomer.

[0055] In the example shown in FIGS. 4A and 4B, the bezel 204 is made of a dielectric elastomer 213 sandwiched between electrodes 212, 214 made of a compliant material. In the normal position of the bezel 204 shown in FIG. 4A, the front end 204A of the bezel 204 is flush with the front surface 202 A of the cover glass 202. In other

embodiments, the front end 204A of the bezel 204 may stand proud of the front surface 202A of the cover glass 202 or the cover glass surface 202A may stand proud of the bezel end 204A. In this normal position, the circuit 210 is open and does not apply voltage to the electrodes 212, 214. When a drop of the handheld device 201 is detected by a sensing device 218, the circuit 210 is closed, applying voltage to the electrodes 212, 214 to produce the desired elongation in the bezel 204, as shown in FIG. 4B. Once the drop event ends, and the sensing device 218 detects that there is no acceleration or velocity or free-fall motion, the circuit 210 may be automatically opened, allowing the bezel 204 to return to its normal length and shape. The command to open the circuit 210 may come from the sensing device 218.

[0056] Another example of a material that may be used for construction of the shape changing bezel 204 is two-way shape memory alloy (SMA), such as those made of Nitinol (nickel and titanium alloy). SMAs are specially-trained materials that remember their shape at two temperatures. At room temperature, the bezel 204 made of SMA would maintain its normal length. When the SMA bezel is heated to a threshold temperature (typically greater than 60 deg. C), it remembers its high temperature length, which is longer than the original length. When the SMA bezel cools down to room temperature, it would automatically go back to its shorter length. With SMA, reversible strains of up to 10% can be obtained, which will be sufficient for protecting the cover glass 202. A heating device may be needed to apply heat to the bezel 204 to achieve the desired increase in length during a drop event.

[0057] In another aspect, a protection mechanism for a cover glass involves cushioning the landing of the handheld device in a drop event.

[0058] Referring to FIGS. 5A and 5B, in one embodiment, a handheld device 301 has a cover glass 302. A cover glass protection mechanism, generally identified at 300, is incorporated into the handheld device 301. The protection mechanism 300 includes a bezel 304, which may be in the form of a ring shaped to circumscribe the periphery of handheld device 301 as well as the periphery of the cover glass 302. The protection mechanism 300 further includes an airbag 306 arranged along the periphery of the handheld device 301 and the periphery of the cover glass 302. In one embodiment, the airbag 306 is folded into a cavity 308 in the bezel 304, where the cavity 308

circumscribes the periphery of the cover glass 302. The front end 304A of the bezel 304 may include a frangible portion or removable cover 309 that can be broken or removed by inflation of the airbag 306. The airbag 306 will be deployed along the rim of the handheld device during a drop event, as shown in FIG. 5B, thereby providing protection for the cover glass 302 when the handheld device 302 lands on a hard surface.

[0059] The protection mechanism 300 may include an inflator 310 for inflating the airbag 306. The protection mechanism 300 may include one or more motion sensors 312, such as sensors that measure acceleration or velocity, for sensing when the handheld device 301 is in a drop event. The protection mechanism 300 may include a microprocessor 314 for making a decision on whether to deploy the airbag based on the data received from the motion sensor(s) 312. The motion sensor(s) 312 and

microprocessor 314 may be collectively referred to as a sensing device 315. In one embodiment, the inflator 310 includes powders that can be chemically reacted together to generate hot blasts for inflating the airbag. The inflator 310 may generate hot blasts of nitrogen from sodium azide, potassium nitrate, and silica powders, for example. Also, the inflator 310 may include a device for heating the powders to trigger the necessary chemical reaction. The airbag 306 would need to be replaced with a new unit once deployed. In this case, it may be beneficial to install the airbag 306 in the handheld device 301 by arranging the airbag 306 in a removable insert that can be arranged in, for example, the cavity 308 in the bezel 304.

[0060] In another aspect, a protection mechanism for a cover glass involves reducing the acceleration of the handheld device during a drop event.

[0061] Referring to FIGS. 6A and 6B, in one embodiment, a handheld device 351 includes a cover glass 352. A cover glass protection mechanism, generally identified at 352, is incorporated into the handheld device 351. The protection mechanism 350 includes a bezel 354, which may be in the form of a ring shaped to circumscribe the periphery of the handheld device 351 as well as the periphery of the cover glass 352. The protection mechanism 350 includes a deceleration device 356, such as a parachute device, arranged in a cavity 358 in the bezel 354. The deceleration device 356 responds to output from a sensing device 360, which monitors when the handheld device 351 is experiencing a drop event as described above for the other embodiments. The deceleration device 356 is deployed at the onset of a drop event. The deceleration device 356 will reduce the acceleration of the handheld device 351 during a drop event such that the impact force experienced by the cover glass 352 when the handheld device 351 lands on the hard surface is minimized.

[0062] In the example shown in FIG. 6B, the deceleration device 356 is deployed from the backside of the handheld device 351. Other measures can be used to protect the cover glass 302 from the front side of the handheld device 351, such as making at least the front end 354A of the bezel 354 out of a shock absorbing material, which will absorb shock when the handheld device 351 lands on the hard surface. Also, the protection mechanism 350 may incorporate multiple deceleration devices. For example, a second deceleration device is shown at 362 in FIGS. 6A and 6B. The second deceleration device 362 may also be deployed in response to output of the sensing device 360.

[0063] In another aspect, a protection mechanism for the cover glass involves changing the angular momentum of the handheld device using fluid.

[0064] Referring to FIG. 7 A, in one embodiment, a handheld device 401 includes a cover glass 402. A bezel 401 may be fitted around the handheld device 401 and may circumscribe the cover glass 402. A cover glass protection mechanism, generally identified at 400, is incorporated into the handheld device 401. The protection mechanism 400 includes a fluid chamber 404 containing a fluid 406.

[0065] At any angle of the handheld device 401 with respect to the direction of gravity, the fluid 406 will occupy a position in the fluid chamber 404 such that the fluid 406 is in hydrostatic equilibrium, as shown by the fluid level 406A. Any deviations of the handheld device 401 from a horizontal line 408, such as when the handheld device 401 is experiencing a drop event, will cause the fluid 406 to flow to one side of the fluid chamber 404, which in turn would shift the center of gravity 403 of the fluid chamber 404 to one side, as illustrated in FIG. 7B. This shift would produce rotational acceleration that would cause further rotation of the handheld device 401, which would cause more of the fluid 406 to shift to the other side of the fluid chamber 404, as illustrated in FIG. 7C. This system would result in the fluid 406 moving to one side of the handheld device 401, and given enough time, the handheld device 401 would end up landing on the bezel 410, as illustrated in FIG. 7D. The bezel 410 could be made of a shock absorbing material, such as rubber. [0066] The weight of the fluid 406 as a fraction of the total weight of the handheld device 401 would be a design parameter. In some embodiments, the weight of the fluid 406 is selected such that the handheld device 401 tends to land at a predetermined angle with respect to the horizontal line 408 for typical drop heights. In some embodiments, this predetermined angle is about 15 degrees. In general, the

predetermined angle can be selected to minimize contact forces on the cover glass 402 when the handheld device 401 lands on a hard surface.

[0067] In another embodiment, active control of the flow path, viscosity, and stiffness of the fluid inside the fluid chamber may be used to achieve better drop orientation of the handheld device, by changing the center of the mass and the angular momentum of the handheld device, and to reduce the bending stress on the front surface of the cover glass by changing the flexural stiffness.

[0068] During a free fall, liquid has a tendency to remain in the original place (or "shoot up") due to its inertia. To change the center of mass and angular momentum, conduits (with shutters) can be designed to determine the path through which the fluid will "shoot up." FIG. 8 shows a fluid channel 420 formed in a handheld device 421 (with a cover glass not identified separately). The fluid channel 420 is filled with a smart fluid, such as an electro- rheological (ER) or magneto-rheological (MR) fluid. The pattern of the fluid channel 420 determines the path in which the fluid will flow. The channel pattern is for illustration purposes only and can be changed to achieve the desired outcome. Valves 424 are arranged along the fluid channel 420. The valves 424 may be individually controllable valves and may be used to control the viscosity of the fluid in the fluid channel 420. Control of the valves 424 may involve determining whether the valves 424 are opened or closed and to what extent the valves are opened, if opened. The valves 424 may be controlled in response to output from a sensing device 426, which may include one or more sensors (gyroscope, accelerometer, inclinometer, etc.) that detect orientation and speed of the device. The sensing device 426 may also include a microprocessor to calculate the best drop orientation for the device based on the sensor data and use this information to control the valves 424 in the fluid channel 420 to achieve a safe landing of the handheld device 421 on a hard surface. One or more fluid channels can be arranged in the handheld device and used to achieve the desired safe landing of the handheld device on a hard surface.

[0069] In another embodiment, as shown in FIGS. 9A and 9B, a track 450 may be formed in a handheld device 451 having a cover glass 452. The track 450 may be in a ring or loop form, generally running alongside the periphery of the handheld device 452. In one embodiment, the track 450 is partially filled with balls. When the handheld device 451 is falling in a drop event, the balls (454 in FIG. 9B) will move along the track 450 to change the location of the center of gravity of the handheld device 452 and thereby the landing angle of the handheld device 451, as shown in FIG. 9B. The weight of the balls 454 as a fraction of the total weight of the handheld device 452 may be selected such that the handheld device 451 lands at a predetermined angle with respect to the horizontal for typical drop heights.

[0070] FIG. 10A shows a first type of contact 500 that may occur between a handheld device 501 and a hard surface 503 when the handheld device 501 lands on the hard surface 503 during a drop event. FIG. 10B shows a second type of contact 505 that may occur between the handheld device 501 and the hard surface 503. The second type of contact 505 involves more surface area contact between the handheld device 501 and the hard surface 503 compared to the first type of contact 500. The second type of contact 505 generally occurs after a rebound of the handheld device. FIG. IOC shows contact forces associated with the first type of contact 500 as a function of drop angle, where the drop angle is measured relative to the horizontal (drop angle 507 is illustrated in FIG. 10A). FIG. 10D shows contact forces associated with the second type of contact 505 as a function of drop angle. In FIGS. IOC and 10D, to the left of the lines 508A, 508B, only the glass contacts the target surface. To the right of the line 508A, 508B, the bezel also contacts the target surface. FIGS. IOC and 10D show drop angles, for example, 15 degrees, where the first contact and second contact forces are similar without spiky contact forces. Such favorable drop angles can be achieved through manipulation of the location of the center of gravity of the handheld device using, for example, fluid in a chamber or channel or balls in a track within the handheld device.

[0071] In one aspect, a protection mechanism for a cover glass involves preventing rebound of the handheld device during a drop event. [0072] Referring to FIG. 11A, a handheld device 510 has a cover glass 512. A bezel 514 is fitted around the periphery of the handheld device 510 and cover glass 512. The front surface 514A of the bezel 514 may be flush with the front surface 512A of the cover glass 512 or slightly raised above the front surface 512 of the cover glass 512. The bezel front surface 514A is provided with a "sticky" material 516 that will provide a releasable adhesion between the bezel 514 and a hard surface when the handheld device 510 lands on the hard surface with the side including the cover glass 512. The adhesion between the "sticky" material and the hard surface can prevent or minimize a rebound of the handheld device during the drop event. For example, releasable adhesives mimicking the spatula structure on gecko's footpads are being developed, and such adhesives could be used on the bezel 514. (See, for example, Haimin Yao and Huajian Gao, "Mechanics of robust and releasable adhesion in biology: Bottom-up designed hierarchical structures of gecko," Journal of the Mechanics and Physics of Solids, 54 (2006) 1120-1146.) It should be noted that a bezel with a sticky landing surface may also be used in any of the other cover glass protection mechanisms described above.

[0073] Suction cups may alternatively be used to provide releasable adhesion between a handheld device and a hard surface to prevent rebound of the handheld device during a drop event. For illustration purposes, FIG. 11B shows suction cups 526 deployed from a bezel 524 of a handheld device 520 having a cover glass 522 during a drop event. The suction cups 526 may be stored in a cavity 528 in the bezel 524 and deployed to a landing position in response to a drop event signal from a sensing device 530, which may be as described above for the other embodiments. The deployment may include using an actuator 531 to push the suction cups 526 out of the cavity 528 in response to the drop event signal. In the "landing position," the curved surfaces 526A will be in a position to land on the hard surface. The suction cups 526 may be deployed prior to the handheld device 520 landing on the hard surface or upon the handheld device 520 landing on the hard surface. The suction cups 526 will releasably adhere to the hard surface upon contacting the hard surface.

[0074] Referring to FIG. 11C, in another embodiment, the suction cups (526 in FIG. 11B) may be replaced with pads 532 having sticky surfaces 534. The pads 532 may be initially stored in the cavity 528 in the bezel 524 and then deployed to a landing position, for example, by the actuator 531, in response to a drop event signal. In the "landing position," the sticky surfaces 534 will be in a position to land on the hard surface. The pads 532 may be made of deformable material to allow them to be folded into the cavity 528.

[0075] In another aspect, a protection mechanism for a cover glass involves folding the cover glass within the handheld device during a drop event.

[0076] Referring to FIGS. 12A and 12B, in one embodiment, a handheld device 600 has a split device body 606A, 606B. A split bezel 608A, 608B is fitted around the split device body 606A, 606B. A flexible display 610, with a corresponding cover glass 610A, is mounted across the device body halves 606A, 606B. A hinge mechanism 612 is provided for folding the flexible display 610 into two, as shown in FIG. 12C. The hinge mechanism 612 can be controlled by a microprocessor (not shown separately in view of previous discussions) inside the handheld device 600, which uses an actuator (not shown separately in view of previous discussions) to release the hinge 612 when a drop event is detected by one or more motion sensors (not shown separately in view of previous discussions) inside the handheld device 600. The hinge mechanism 612 may have a damping mechanism for slowing down the rate of closure of the handheld device 600. The front ends of the bezel halves 608A, 608B may be slightly raised such that when the handheld device 600 is fully closed, the raised portions of the bezels 608A, 608B will meet at the fold line 620 (FIG. 12C) and provide a separation between the folded halves of the flexible display 610.

[0077] Referring to FIGS. 12A and 12B, a handheld device 650 has a split device body 650A, 650B. The device body haves 650A, 650B are coupled together by a hinge mechanism 652. A split bezel 658A, 658B is fitted around the device bodies 650A, 650B. A first half 660A of a split display (with a corresponding cover glass 662A) is mounted on the first device body 650A, and a second half 660B (with a corresponding cover glass 662B) of a split display is mounted on the second device body 650B. The hinge mechanism 652 will allow the handheld device 650 to be folded into two during a drop event, with the cover glasses 662A, 662B hidden within the fold, as shown in FIG. 13C. The bezel halves 658A, 658B may be slightly raised such that when the handheld device 650 is fully closed, the raised portions of the bezel halves 658A, 658B will meet at the fold line 664 (FIG. 13C) and provide a separation between the cover glasses 662A, 662B. The hinge mechanism 652 may respond to signals from a sensing device (not shown separately in view of previous discussions) that is located in the handheld device 650 and sensitive to motion of the handheld device 650, as described above for the other embodiments.

[0078] In another aspect, a protection mechanism for a cover glass involves placing an active material whose stiffness can be varied beneath the cover glass, particularly along the periphery of the cover glass where most of the impact is expected to occur during a drop event.

[0079] Referring to FIG. 14A, in one embodiment, a handheld device 701 has a cover glass 702. A bezel 704 may circumscribe the periphery of the handheld device 701 and cover glass 702. A cover glass protection mechanism, generally identified at 700, is incorporated into the handheld device 701. In one embodiment, the protection mechanism 700 includes an active material 706 positioned underneath the cover glass 702. The active material 706 may have a loop shape for positioning underneath and generally along the periphery of the cover glass 702 and may be made of one or more layers. The active material 706 preferably has a stiffness that can be controlled. In one embodiment, the active material 706 may be an electro-rheological or magneto- rheological material. When a drop event is detected by a sensing device in the handheld device (not shown separately), the active material 706 can be made softer by

appropriate means, e.g., an electrical field or magnetic field. The softer underlying material will reduce the stress experienced by the glass when the glass makes contact with a hard surface.

[0080] FIG. 14B shows stress analysis results for a material underlying a cover glass subject to indentation by a spherical indenter at the corner when the stiffness of the material is reduced. Results are shown for material thickness ranging from 0.1 to 1.0 mm. Line 710 represents the reference case where there is no active material underneath the cover glass.

[0081] In one embodiment, the active material 706 is an electro-rheological material. Electro-rheological materials are materials that can change from behaving like solid under the application of an electric fluid to behaving like fluid when no electric field is applied. Under normal operations, it is desirable to keep the active material 706 stiff for a good user experience and handling of the device. In the case of an electro- rheological material, this is done by maintaining an electric field in the active material 706, thereby keeping the material solid. For example, the active material could be arranged between two electrodes, and voltage can be applied to the electrodes to maintain an electric field in the active material. When a drop event is detected, the electric field can be lowered or turned off to make the active material 706 behave like fluid, thereby greatly reducing the stiffness of the active material 706, which in turn would reduce the stresses generated in the cover glass 702 during the drop event, thereby reducing failure probability of the cover glass 702. It is desirable to have the underlying active material 706 not be bonded to the cover glass 702 and to have enough space around the ends of the active material 706 such that the active material 706 can flow freely into the extra space when compressed and freely allow the cover glass to deform during the drop event. Once the drop event has ended, an actuator system (not shown separately) can then push the active material 706 back to its original configuration, after which the electric field may be reapplied to convert the fluid-like active material into solid active material. A similar behavior can be obtained with a magneto-rheological material, where a magnetic field is used to change the state of the material from solid to fluid, and vice versa.

[0082] While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as disclosed herein. Accordingly, the scope of the invention should be limited only by the attached claims.

Claims

1. A protection mechanism for a cover glass of a handheld device during a drop event, comprising:

a bezel shaped for mounting about a periphery of the handheld device in a

position to circumscribe a periphery of the cover glass, the bezel being arranged for movement along a select direction perpendicular to a plane of the cover glass, the bezel having a normal position and a landing position spaced apart along the select direction, wherein in the landing position a front end of the bezel is raised by a select height relative to a front surface of the cover glass, the select height being sufficient to prevent direct contact of the front surface of the cover glass with a surface when the handheld device lands on the surface during the drop event; a sensing device comprising at least one motion sensor for sensing a parameter related to a free-fall motion of the handheld device; and

a mechanism for adjusting the position of the bezel along the select direction, the mechanism being configured to adjust the position of the bezel from the normal position to the landing position in response to an output of the sensing device.

2. The protection mechanism of claim 1, wherein the mechanism for adjusting the position of the bezel comprises a spring member arranged relative to the bezel such that an extension of the spring member from a compressed state moves the bezel from the normal position to the landing position.

3. The protection mechanism of claim 2, wherein the mechanism for adjusting the position of the bezel further comprises a first retainer mechanism for retaining the bezel at the normal position and a second retainer mechanism for retaining the bezel at the landing position.

4. A protection mechanism for a cover glass of a handheld device during a drop event, comprising: a bezel shaped for mounting about a periphery of the handheld device in a position to circumscribe a periphery of the cover glass, the bezel having a normal position and a landing position along a select direction perpendicular to a plane of the cover glass, the bezel being composed of a shape changing structure having a first length in the normal position and a second length in the landing position, the second length being greater than the first length;

a sensing device comprising at least one motion sensor for sensing a parameter related to a free-fall motion of the handheld device; and

a mechanism for inducing a change in shape of the bezel in response to an output of the sensing device.

5. The protection mechanism of claim 4, wherein the mechanism for inducing a change in shape of the bezel comprises a dielectric elastomer sandwiched between compliant electrodes and a circuit for applying a voltage to the compliant electrodes.

6. The protection mechanism of claim 4, wherein the mechanism for inducing a change in shape of the bezel comprises a two-way shape memory alloy.

7. A protection mechanism for a cover glass of a handheld device during a drop event, comprising:

an airbag shaped for mounting about a periphery of the handheld device in a position to circumscribe a periphery of the cover glass;

a mechanism for deploying the airbag in response to an output of the sensing device.

8. The protection mechanism of claim 7, further comprising a bezel shaped for

mounting about a periphery of the handheld device in a position to circumscribe a periphery of the cover glass, the bezel having a cavity in which the airbag is arranged.

A protection mechanism for a cover glass of a handheld device during a drop event, comprising:

a bezel shaped for mounting about a periphery of the handheld device in a

position to circumscribe a periphery of the cover glass;

a deceleration device coupled to the bezel;

a mechanism for deploying the deceleration device in response to an output of the sensing device.

a fluid chamber located within the handheld device, the fluid chamber

containing a fluid, wherein motion of the fluid within the fluid chamber during the drop event adjusts an angular momentum of the handheld device.

a fluid channel located within the handheld device, the fluid channel containing a fluid and at least one valve to control motion of the fluid within the fluid channel, wherein the at least one valve is responsive to an output of the sensing device and motion of the fluid within the fluid channel adjusts an angular momentum of the handheld device.

a track located within the handheld device, the track containing a set of balls, wherein motion of the balls within the track during the drop event causes a select change in angular momentum of the handheld device.

13. A protection mechanism for a cover glass of a handheld device during a drop event, comprising:

a bezel shaped for mounting about a periphery of the handheld device in a

position to circumscribe a periphery of the cover glass, wherein a front end of the bezel for positioning nearest to a front surface of the cover glass comprises a releasable adhesive.

14. A protection mechanism for a cover glass of a handheld device during a drop event, comprising:

a bezel shaped for mounting about a periphery of the handheld device in a

position to circumscribe a periphery of the cover glass;

a sensing device comprising at least one motion sensor for sensing a parameter related to a free-fall motion of the handheld device;

at least one surface mounting member coupled to the bezel; and

a mechanism for deploying the surface mounting member to a landing position in response to an output of the sensing device.

15. The protection mechanism of claim 14, wherein the at least one surface

mounting member comprises a suction cup.

16. The protection mechanism of claim 14, wherein the at least one surface

mounting member comprises a pad having a sticky surface.

17. A protection mechanism for a cover glass of a handheld device during a drop event, comprising:

a hinge mechanism for folding the handheld device such that the cover glass is hidden within the handheld device during the drop event, wherein the hinge mechanism is responsive to an output of the sensing device.

18. A protection mechanism for a cover glass of a handheld device during a drop event, comprising: a sensing device comprising at least one motion sensor for sensing a parameter related to a free-fall motion of the handheld device; and

an active material having a variable stiffness located underneath the cover glass, wherein the stiffness of the active material is responsive to an output of the sensing device.

19. The protective mechanism of claim 18, wherein the active material has a loop shape for positioning underneath the cover glass along a periphery of the cover glass.

20. The protective mechanism of claim 18, wherein the active material comprises a magneto-rheological material or an electro-rheological material.

21. A handheld device comprising: a cover glass; and a protection mechanism according to any one of claims 1-20.