Abstract:
Active cushioning mechanisms that detect imminent impact and activate a damper by driving power from an onboard power supply into an electromagnetic actuator. The electromagnetic actuator transforms the stored electric power into an electromechanical damping force. The actuators may be arranged about the exterior surface of the device, and may be selectively activated to provide protection at different points on the surface depending on the location of expected impact.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This claims the benefit of copending, commonly-assigned U.S. Provisional Patent Application No. 61/008,711, filed Dec. 21, 2007, which is hereby incorporated by reference herein in its entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    This invention relates to methods and systems for protecting a device from the destructive force of an impact. 
         [0003]    Portable electronic devices, such as handheld and laptop computers, mobile telephones, and portable media players, are easily carried about, and therefore are at risk of being dropped often from several feet above the ground or another surface. The result of a hard fall can be damaging. 
         [0004]    To address these problems, systems have been developed to at least partially protect portable devices from the impact caused by a free fall. Some of these systems may protect only working parts while others are designed to protect the housing of the entire device. However, the latter type of device may increase the size and/or weight of a portable device, while the market trend is for portable devices to become ever smaller. 
       SUMMARY OF THE INVENTION 
       [0005]    The systems and methods described herein provide active cushioning mechanisms that detect imminent impact and activate a damper by driving power from an onboard power supply, which typically is a battery, into an electro-magnetic actuator. The electromagnetic actuator transforms the stored electric power into a mechanical damping force that can be applied to the area of expected impact. 
         [0006]    According to one embodiment of the invention, apparatus for cushioning an object against impact includes a sensor for detecting an unrestrained change in position of the object, and an electromagnetic actuator. The apparatus also includes a controller electrically coupled to the actuator and responsive to the sensor for driving a current through the electromagnetic actuator to create an electromagnetic force to protect the object. The actuator may have two magnets, wherein at least one of the magnets is an electromagnet. The magnets may be opposed to each other with at least one magnet being movable between a first position relative to the other magnet and a second position that is further from the other magnet than the first position. The aforementioned force is exerted between the magnets to dampen an impact on the object. 
         [0007]    According to another embodiment of the invention, the housing of a portable electronic device includes an exterior sidewall defining an interior cavity and having an electromagnetic actuator disposed on the exterior sidewall. The housing also encloses a sensor for detecting an unrestrained change in position of the portable electronic device, and a controller electrically coupled to the actuator and responsive to the sensor for driving a current through the electromagnetic actuator to create an electromagnetic force to protect the object. The actuator may include two magnets, wherein at least one of the magnets is an electromagnet. The magnets may be opposed to each other, with at least one magnet being movable between a first position relative to the other magnet and a second position that is further from the other magnet, and from the exterior sidewall, than the first position. 
         [0008]    According to another embodiment of the invention, a method for cushioning an object against impact includes mounting an electromagnetic actuator to a surface of the object, wherein the actuator has two opposing members, one of which is adjacent the surface, and the second of which is movable between a first position relative to the first magnet and a second position that is further from the first magnet than the first position. The method also includes detecting an unrestrained change in position of the object, and, responsive to detection of an unrestrained change in position, driving a current through the electromagnetic actuator to move the second member from the first position to the second position to dampen the force of an impact. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    Further features of the invention, its nature and various advantages will be apparent upon consideration of the following detailed description, taken in conjunction with the accompanying drawings, in which like reference characters refer to like parts throughout, and in which: 
           [0010]      FIG. 1  depicts schematically the structure of a system according to the invention; 
           [0011]      FIG. 2  depicts pictorially the generation of an electromagnetic damping force; 
           [0012]      FIG. 3  depicts the relationship between applied current and mechanical separation; 
           [0013]      FIGS. 4A and 4B  depict an embodiment of an actuator for use with the systems described herein; 
           [0014]      FIGS. 5A and 5B  present an interior view of the actuator depicted in  FIGS. 4A and 4B ; 
           [0015]      FIGS. 6A and 6B  depict an embodiment of a system according to the invention that uses an electromechanical actuator disposed at an exterior sidewall of a device to create an electromechanical damper; 
           [0016]      FIG. 7  depicts one embodiment of a housing for a handheld device having impact protection mechanisms according to the invention located at corners of the housing; and 
           [0017]      FIG. 8  is a flow diagram illustrating an embodiment of a method according to the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    As stated above, systems have been developed to at least partially protect portable devices from the impact caused by a free fall. 
         [0019]    For example, laptop computers or other portable devices that incorporate disk drives have been equipped with devices that sense a free fall event and park the disk drive heads as quickly as possible to prevent the heads from colliding with the platters of the hard drive and ruining the drive. Examples of free fall sensors for use in such devices are described in commonly-assigned U.S. Pat. Nos. 6,520,013, 6,786,066, 7,307,228 and 7,351,925, each of which is hereby incorporated by reference herein in its respective entirety. Although these systems can help the drive survive the shock of impact, such systems do not prevent damage to other internal elements of the device, or to external elements such as the display or the housing. 
         [0020]    To address these problems, manufacturers may try to provide as rugged an exterior housing as possible given the application, and use resilient shock absorbing materials, such as rubber and silicone, as gaskets and supports for more sensitive components of the device such as glass display screens. 
         [0021]    As a more extreme measure, some manufacturers have gone even further and have provided airbag systems that deploy a plastic airbag from underneath a falling portable device, thereby providing a cushion that can absorb the impact of the fall and minimize or prevent damage to the portable device. A system that reacts to the output of an accelerometer in a portable device is described in commonly-assigned United States Patent Publication 2006/0017692, which is hereby incorporated by reference herein in its entirety. 
         [0022]    Although airbag devices and rugged housings can prevent damage to the fragile elements of a portable device, these protective mechanisms are bulky and add to the size and weight of portable devices. Consequently, these technologies interfere with designers&#39; ability to create smaller and lighter portable devices. 
         [0023]    To provide an overall understanding of the present invention, certain illustrative embodiments will now be described, including an active impact protection device that provides actuators on the exterior surface of a portable device to protect the device against damage from impact. However, it will be understood by one of ordinary skill in the art that the systems and methods described herein can be adapted and modified for other suitable applications and that such other additions and modifications will not depart from the scope hereof. For example, the systems and methods described herein include active impact protection devices that may be incorporated into a sleeve or tube that can fit over a portable device and protect the devices from damage due to impact. These and other embodiments will be made apparent by the following illustrative examples of the systems and methods. 
         [0024]    The systems and methods described herein include, among other things, systems for using onboard power to provide impact protection. In particular, the systems and methods described herein use the onboard electrical power supply to power an electromechanical transducer that creates a damping force that can oppose the force from an impact resulting from a collision or free fall. Where the protective device or system is incorporated in a sleeve or tube that fits over the device to be protected, the protective device may includes its own power supply, or a connection may be provided to the power supply of the device being protected. 
         [0025]      FIG. 1  depicts a functional block diagram that shows a system  10  that provides active impact protection for a handheld device. The system  10  includes a controller  12 , a sensor  14 , a power supply  16 , an actuator  18  and a movable sidewall  20 . 
         [0026]    In one embodiment, the system  10  is included in a portable device such as a personal media player of the type that includes a microprocessor, a program memory, a data memory, and a video screen. In such an embodiment, the depicted controller  12  may comprise the onboard microprocessor of the portable media player. However, a separate microprocessor may be provided for portable devices that have no onboard programmable logic, or when other factors demand a separate processor. In either case, the microprocessor will be programmed to operate the actuator  18  so that the actuator  18  creates a mechanical damping force in response to an expected impact. 
         [0027]    To that end, the system  10  includes the sensor element  14 . The sensor element  14  may also be an onboard element already built into the portable device. For example, certain computers including the portable computer sold by Apple Inc., of Cupertino, Calif., under the trademark POWERBOOK®, may include an onboard acceleration sensor that detects whether the device is going through a free fall, as well as the general orientation of the device. 
         [0028]    Accordingly, the sensor  14  may be a free fall sensor of the kind used in portable electronic devices. These free fall sensors have been provided within electronic devices for, among other things, protecting a hard disk drive so that head-disk interference does not occur as the result of an impact from a collision or free fall. These sensors typically include a plurality of accelerometers. Examples of such sensors are the tri-axis multiplexed analog and digital sensors commercially available from the Kionix Corporation, of Ithaca, N.Y. Those sensors are silicon micromachined linear accelerometers and inclinometers in an ASIC package ready for use in a circuit board. 
         [0029]    Typically, the three-axis sensor is set up as a low-power linear accelerometer that measures the magnitude of acceleration applied to the portable device. Normally the magnitude of acceleration is approximately 1 G. However, when the device is falling during a free fall event the acceleration magnitude will change to approximately 0 G. The sensor  14  detects this transition phase from 1 G to 0 G and provides a warning signal to the control  12  as shown in  FIG. 1 . Other events of unrestrained movement, such as a rapid sliding of the portable device, or a tumbling event, may also be detected and addressed. 
         [0030]    Optionally and additionally, the sensor  14  may include a proximity sensor and an orientation sensor, as well as a free fall sensor. The proximity sensor can predict when the portable device may experience the moment of impact. Proximity sensors are commercially available, such as the HSDL-9100 optical proximity sensor manufactured by Agilent Corporation, of Palo Alto, Calif., and any suitable proximity sensor may be employed with the systems and methods described herein. The orientation sensor may predict the orientation the portable device at the moment of impact. One example of a commercially available onboard orientation sensor is the aforementioned orientation sensor provided within the portable computer available from Apple Inc. under the trademark POWERBOOK® However, any suitable sensor or group of sensors may be employed for determining the orientation of the portable device, and its proximity to the impact surface, as it goes through an unrestrained movement toward impact. 
         [0031]    The sensor  14  may provide to the controller  12 , in addition to the warning signal, an indication as to the orientation of portable device and its proximity to the impact surface. For example, the sensor  14  may indicate to the controller  12  that the device is falling on its face versus its rear side, and indicate when the impact is imminent. 
         [0032]    The controller is electrically coupled to the actuator  18  and drives the operation of the actuator  18  to create an electromechanical damping force that may be applied to the movable sidewall  20  to enable the sidewall  20  to absorb the expected impact. To this end, the controller  12  can direct the actuator  18  to draw power from the power supply  16 . Typically the power supply  16  will be a lithium-ion battery that is the main onboard power supply for the portable device. However, where the protection system is a separate device that fits over the portable device to be protected, the power supply may be a separate onboard power supply of the protective device. 
         [0033]    As impact approaches, the controller  12  can cause the electrical power stored within power supply  16  to be delivered to the actuator  18 . To this end, the power supply  16  can have a low impedance coupling to the actuator to allow for rapid delivery of power. The controller  12  can optionally connect to the power supply to switch the low impedance path on and drive current from the electrical supply  16  to the actuator. Alternatively, the power supply can connect to the sensor to allow the sensor to switch the supply to the low impedance coupling. The actuator  18  transforms the electrical power into a magnetic field that mechanically drives the movable sidewall  20  away from the interior elements of the handheld device and toward the expected point of impact. 
         [0034]      FIG. 2  depicts the action of the actuator  18  in an embodiment where an exterior surface of the portable device includes a resilient or expandable exterior material that is pushed away from the actuator  18  as the magnetic force drives the movable wall  20  against the resilient exterior material  24 . Thus, the actuator  18  transforms the electrical power from the power supply  16  into a force that creates a physical separation between the interior elements of the portable device and its outer most exterior surface  24 . As further shown in  FIGS. 1 and 2 , the actuator  18  creates a magnetic field B that drives the movable wall  20  away from the actuator  18  and against the resilient exterior surface  24 . The magnetic field B generates a magnetic damping force that absorbs at least a portion of the impact delivered to the portable device upon contact with the floor or another surface. The magnetic force generated by magnetic field B, as will be described in more detail below, acts as a spring force to protect the portable device from damage. 
         [0035]      FIG. 3  depicts an illustrative relationship between the current driven from power supply  16  into the actuator  18  and the distance D that the movable wall  20  is driven away from the interior of the portable device. In particular,  FIG. 3  is a graph on which the current, I, is presented on the vertical axis and the distance, D, is presented on the horizontal axis. As depicted in  FIG. 3 , as the current increases, the distance D also increases, showing that the physical separation that is achieved between the exterior surface  24  of the portable device and the interior elements being protected by the actuator  18  is proportional to the amount of current provided to the actuator  18 . 
         [0036]      FIGS. 4A and 4B , and  5 A and  5 B, show, in more detail, one embodiment of an actuator such as actuator  18  depicted in  FIG. 1 .  FIGS. 4A and 4B  depict an actuator  30  having two plates  32  and  34 . In one embodiment, the two plates  32  and  34  may be square plastic plates, which may be made, e.g., of polystyrene and may measure approximately one-half centimeter on each side. As shown by  FIGS. 4A and 4B , the plates  32  and  34  can move relative to each other. In one embodiment, the plate  32  may be a fixed plate that attaches to an interior structure of the portable device, while the plate  34  may be a movable plate that can move away from the interior of the portable device and can push against the optional resilient exterior material  24  shown in  FIG. 2 . As discussed above, the movable plate  34  can move away from the lower plate  32  by action of an electrically-generated force. 
         [0037]      FIGS. 5A and 5B  depict an embodiment of the interior structure of the actuator  30 , illustrating the electromagnetic elements that generate the aforementioned force. In particular, as shown in  FIG. 5A , movable plate  34  can include a permanent magnet  38  located (e.g., centrally) on the plate  34  and connected to the plate  34 . The other plate  32  may includes a plurality of wire windings  40  that are electrically conductive and that can couple to the power supply  16  of the portable device. As shown in  FIG. 4A , the magnet  38  is disposed over the coils  40  when the plates  32  and  34  are aligned. The magnet  38  can optionally fit inside of the interior of the coils  40 , or may overlap the coils  40  and sit on top of them. The actual geometry of the magnet  38  and the coils  40  can vary according to the configuration of the portable device, and any suitable geometric configuration including squares, rectangles, and three-dimensional elements may be employed without departing from the scope of the invention. In any case, upon application of a current into the coils  40 , the coils  40  behave as an electromagnet or short solenoid carrying a steady current I, thereby generating a magnetic flux that drives the permanent magnet  38  away from the coil  40 . This results in the movable plate  34  moving from a first position close to plate  32  and coils  40 , to a second position further from plate  32  and coils  40 . To keep the plate  32  and  34  aligned, some flexible mechanical structure may be applied that connects the plates  32  and  34  but allows them to move relative to each other. These connecting elements are not shown in order to allow clear illustration of the components of the actuator  18  depicted in  FIGS. 4 and 5 . 
         [0038]      FIGS. 6A and 6B  illustrate in more detail the actuator  30  as it may be used to protect a portable device. In particular,  FIG. 6A  depicts the actuator  30  positioned against an exterior wall  42  of a portable device. Above the exterior wall  42  is an interior cavity  48  into which the components of the portable device such as the microprocessor, the glass display and other elements can be contained. The exterior wall  42  forms part of the outer casing of the portable device. A flexible membrane  44  extends over the exterior wall  42 . The actuator  30  sits between the flexible membrane  44  and exterior wall  42 . 
         [0039]    When sensor  14  detects a free fall, the sensor delivers a warning signal to the controller  12 . The controller  12  can activate the actuator  30 . The actuator  30  will draw power from the onboard power supply  16  filling the coils  40  with current and generating a magnetic field that drives the plate  34  away from the exterior wall  42 . The movable plate  34  pushes against the flexible membrane  44  and deforms that membrane as shown in  FIG. 6B . A physical separation is formed between the plate  32  and the plate  34  and a magnetic force exerted in that space acts as a damping force to can absorb at least some of the impact caused by the free fall. 
         [0040]    The exterior casing of the handheld device may include a plurality of actuators  30  to provide cushioning across a large area of the device. Alternatively, as shown in  FIG. 7 , actuators  30  may be placed at select locations of the portable device, such as the corners of portable device  1 . Optionally, the controller  12 , upon receiving a warning signal from the sensor  14 , can activate all of the actuators  30  positioned on the surface of the portable device. Optionally and alternatively, an orientation sensor located within sensor  14  may provide the controller with an indication as to which portion of the portable device is likely to strike upon impact. In such an embodiment, the controller  12  can selectively activate only certain selected ones of the actuators fixed to the exterior surface of the portable device. 
         [0041]      FIG. 8  depicts an exemplary flow diagram of a process according to the invention. In particular,  FIG. 8  depicts a process  60  that begins in step  62  wherein the device begins to go through an unrestrained movement, which in this example is a free fall drop to the floor, ground or other surface. 
         [0042]    In step  64  the sensor detects the free fall and estimates a time to impact (e.g., 0.5 seconds). Preferably, the sensor filters out any acceleration profile that is not representative of a sustained free fall. For example, an unrestrained movement can be ignored for a few milliseconds, because any movement that does not last longer than that is unlikely to cause damage to the portable device. If the movement is not filtered out, the sensor may deliver a warning signal that will begin preparation of the device for impact. Alternatively, preparation for impact may be begin only after both the warning signal and a signal from a proximity detector that the device is approaching a surface. 
         [0043]    As part of the preparation for impact, in step  66 , the onboard power supply electronically switches to a lower impedance circuit. This switching is done to avoid overheating from the rapid discharge experienced as the battery powers the actuator. In step  68 , the battery powers the cushioning mechanism to arm it in preparation for impact. The discharge from the battery can occur at a rate that would lead to 100% discharge in 3-6 minutes. As an example of the discharge, for a battery that normally lasts for one hour, the discharge rate may be 20 C. At such a rate, the battery will be able to deliver 20 times its nominal rated current (or power) for one-twentieth its normal discharge time. Therefore, a 55 W-hr battery discharging at 20 C could deliver 1100 W for up to three minutes. The total energy delivered to the impact protection system during the 0.5-second interval that occurs in the fall before impact would be 550W-sec. 
         [0044]    An optional step  70  relies on the aforementioned proximity sensor and orientation sensor to detect the approximate point on the exterior of the device that will impact the surface. This allows the controller to selectively focus power to those actuators that will need to cushion the device. In step  72  the selected cushioning elements telescope out before impact as predicted. In step  74  contact with the surface occurs, and in step  76  the cushioning element absorb some impact energy before the device itself impacts the surface. In step  78  the battery is switched back to normal circuit as before, and the process  60  ends. 
         [0045]    Although the systems and methods described above have discussed active impact protection for a portable device that cushioning the entire device from impact, such active impact protection devices may be used to support and protect specific elements within a device. For example, a portable device having a breakable display may use active impact protection as described herein to protect the display. During a free fall, the actuators may deploy so that the display is held in place by the deployed actuators, providing shock absorption for the display. Further, in a device that has the display relatively flush with the exterior surface of the device, the actuators may be used to move the display inwardly into the interior of the device, helping to prevent the display from making first contact with the surface and absorbing the majority of the impact. 
         [0046]    Similarly, while the active protection mechanisms described herein have been illustrated by embodiments that are integrated into the portable device to be protected, an active impact protection device may be realized as a separate sleeve or covering that is independently powered and can fit over a portable device to protect that device. 
         [0047]    Accordingly, it will be understood that the invention is not to be limited by the embodiments disclosed herein, which are presented for purposes of illustration and not of limitation, and the present invention is limited only by the claims which follow.