Patent Publication Number: US-11647819-B2

Title: Tension spring assisted protective cover

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of U.S. Non-Provisional patent application Ser. No. 16/743,562 filed Jan. 15, 2020, which claims the benefit of U.S. Provisional Patent Application Ser. No. 62/794,443 filed Jan. 18, 2019, the entireties of which are hereby incorporated herein by reference for all purposes. 
    
    
     TECHNICAL FIELD 
     The present invention relates generally to the field of protective covers for electronic devices, and more particularly to a tension spring assisted foldable protective cover for a portable foldable electronic device. 
     BACKGROUND 
     Protective and/or decorative cases are used in connection with portable electronic devices such as cell phones, smart phones, electronic readers, handheld game devices and the like. It is to the provision of a tension spring assisted folding protective cover for a foldable portable electronic device that the present invention is primarily directed. 
     SUMMARY 
     In example embodiments, the present invention provides a tension spring assisted protective cover for a portable foldable electronic device having a first housing and a second housing. The case comprises two jackets or shells coupled by a plurality of tension coupling mechanisms or spring coupling elements to a hinge cover shell, wherein a first shell is configured to receive the first housing of the electronic device and a second shell is configured to receive the second housing of the electronic device. The first and second shells generally comprise a back or base panel and a sidewall or frame extending substantially about the periphery of the base panel. The first and second shells further comprise one or more holding posts or members located on the exterior surface of the top and bottom sidewalls and extending externally therefrom. The hinge cover shell further comprises a plurality of holding posts or members located on the exterior surface of the top and bottom ends and extending externally therefrom. The holding posts are configured to receive the tension coupling mechanisms wherein one end of a first tension coupling mechanism is connected to one holding post of the front shell by means of a first engagement feature and the other end of the first tension coupling mechanism is connected to a first holding post of the hinge cover shell. Similarly, one end of a second tension coupling mechanism is connected to one holding post of the back shell by means of a second engagement feature and the other end of the second tension coupling mechanism is connected to a second holding post of the hinge cover shell. 
     In one aspect, the present invention relates to a cover for a foldable electronic device including a plurality of tension coupling mechanisms to assist the user keep the device in fully open or fully closed positions when intended, and to prevent unintended opening or closing of the device. 
     In another aspect, the invention relates to a case for a foldable electronic device, the case including a front or first shell having a rigid back panel and a peripheral frame. One or more holding posts preferably protrude externally from the exterior surface of the peripheral frame. The case further includes a back or second shell having a rigid back panel and a peripheral frame of the first shell. One or more holding posts preferably protrude externally from the exterior surface of the peripheral frame of the second shell. The case further includes a hinge cover or third shell having a rigid, elongate, semi-tubular body. One or more pairs of holding posts preferably protrude externally from at least one end of the of hinge cover shell. The case preferably further includes a plurality of coupling mechanisms, wherein one end of a first tension mechanism is connected to the holding post of the front shell by means of a first engagement feature and the other end of the first tension mechanism is connected to at least one of the pair of holding posts on the hinge cover shell by means of a second engagement feature of the first tension mechanism, and wherein one end of a second tension mechanism is connected to the holding post of the back shell by means of a first engagement feature and the other end of the second tension mechanism is connected to at least one other holding posts on the hinge cover shell 
     In still another aspect, the invention relates to a case for a foldable electronic device, the case including a front shell, a back shell, and a protective shell for the device&#39;s hinge. The hinge protection shell includes semi-tubular body with a closed top end and a closed bottom end. In example embodiments, a plurality of coupling mechanisms retain the first and second shells operatively engaged with the hinge protection shell to allow a pivotal folding movement of the front and back shells upon opening and closing of the device housed in the case. 
     In another aspect, the invention relates to a foldable case for at least partially housing a foldable electronic device. The foldable electronic device preferably has a first device portion, a second device portion, and a hinged device coupling between the first and second device portions allowing a pivotal range of motion between the first and second device portions. The foldable case preferably includes a first case portion configured to at least partially house the first device portion when the case is installed on the device, a second case portion configured to at least partially house the second device portion when the case is installed on the device, a third case portion configured to at least partially house the hinged device coupling, and engagement means between the first and second case portions and the third case portion. The engagement means preferably maintains a biasing force between the first and third case portions and between the second and third case portions, and further retains the first and second case portions in operative engagement with the third case portion through the pivotal range of motion when the case is installed on the device. 
     These and other aspects, features and advantages of the invention will be understood with reference to the drawing figures and detailed description herein, and will be realized by means of the various elements and combinations particularly pointed out in the appended claims. It is to be understood that both the foregoing general description and the following brief description of the drawings and detailed description of example embodiments are explanatory of example embodiments of the invention, and are not restrictive of the invention, as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a perspective view of a tension spring assisted protective cover or case for a foldable portable electronic device in an open position, according to an example embodiment of the present invention. 
         FIG.  2    is a perspective view of the cover of  FIG.  1    in a closed position. 
         FIG.  3    is a perspective assembly view of the front and back cover shells of the cover of  FIG.  1   . 
         FIG.  4    is a back view of the cover of  FIG.  1    and shows detail views of holding posts on the exterior of the cover. 
         FIGS.  5 A- 5 D  show a sequence of operation of a cover according to an example embodiment, moving from a closed configuration to an open configuration. 
         FIGS.  6 A- 6 D  show additional detail of the tension spring and forces applied on the cover shells, according to an example embodiment, as the cover moves from a closed configuration to an open configuration. 
         FIG.  7    shows the relative positions of the front and back shells of  FIG.  3    in a fully open, semi-open, semi-closed, and fully closed position. 
         FIG.  8    is a perspective view of a tension spring according to an example embodiment. 
         FIG.  9    shows the relative positions of holding posts and the associated fulcrum points in a fully open, semi-open, semi-closed, and fully closed position. 
         FIG.  10    is a perspective view of an optional hinge cover plate. 
         FIG.  11 A  shows the hinge cover plate of  FIG.  10    attached to the cover of  FIG.  1    in a fully closed position. 
         FIG.  11 B  shows the hinge cover plate of  FIG.  10    attached to the cover of  FIG.  1    in a fully open position. 
         FIG.  12    is a perspective view of the tension spring assisted protective cover or case for a foldable portable electronic device in an open configuration with a top hinged endcap removed, according to another example embodiment of the present invention. 
         FIG.  13    is a perspective view of the cover of  FIG.  12    in a closed position. 
         FIG.  14    shows an exploded view of one set of tension spring and hinge link element and an assembled view of another set of tension spring and hinge link element of the tension spring assisted protective cover of  FIG.  12   . 
         FIGS.  15 A- 15 D  show a sequence of operation of the cover of  FIG.  12    according to another example embodiment, moving from a closed configuration to an open configuration. 
     
    
    
     DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS 
     The present invention may be understood more readily by reference to the following detailed description of example embodiments taken in connection with the accompanying drawing figures, which form a part of this disclosure. It is to be understood that this invention is not limited to the specific devices, methods, conditions or parameters described and/or shown herein, and that the terminology used herein is for the purpose of describing particular embodiments by way of example only and is not intended to be limiting of the claimed invention. Any and all patents and other publications identified in this specification are incorporated by reference as though fully set forth herein. 
     Also, as used in the specification including the appended claims, the singular forms “a,” “an,” and “the” include the plural, and reference to a particular numerical value includes at least that particular value, unless the context clearly dictates otherwise. Ranges may be expressed herein as from “about” or “approximately” one particular value and/or to “about” or “approximately” another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another embodiment. 
     With reference now to the drawing figures, wherein like reference numbers represent corresponding parts throughout the several views,  FIGS.  1 - 4    show a foldable protective case or cover  10  for a foldable portable electronic device D, according to an example embodiment of the present invention. In the depicted embodiment, the case or cover  10  includes a housing for receiving and at least partially covering the foldable electronic device. In example embodiments, the case or cover  10  is configured to fit a foldable smart-phone, tablet computer, cell phone, MP3 player, music and/or video player, electronic reader, handheld game device, or other foldable portable electronic device. Case  10  generally comprises a first or front jacket or shell  20 , a second or back jacket or shell  30 , and one or more tension or spring mechanisms  40  operatively engaged between the front and back shells. In example forms, the front and back jackets  20 ,  30  are at least partially formed of polycarbonate or other hard plastic, metal, composite, polymeric, ceramic, and/or other material(s) of construction. 
     As shown in  FIG.  1   , the front shell  20  generally comprises a front plate or base panel  22  and a raised sidewall  24 . In the depicted embodiment, the sidewall  24  projects transversely outward along the top edge, the bottom edge, and a first or outer side edge of the base  22 , forming a continuous sidewall  24  with two radiused corners partially bounding an interior chamber for receiving an electronic device. The sidewall  24  preferably comprises a ridge or flange along its perimeter at its distal rim that extends inwards towards the center of the shell  20  to help retain the case on an electronic device. In the depicted embodiment, the front base panel  22  is generally flat and generally rectangular with rounded corners, but in alternate embodiments may comprise different configurations to match the shape of a particular electronic device for which the case is configured. In yet other embodiments, the sidewall  24  comprises two or more separate sidewalls extending from discrete sections of the base periphery resulting in a plurality of discrete sidewalls. 
     The front shell  20  further comprises one or more biasing element retainers or retention elements, for example in the form of holding posts or support members  28 , as shown in  FIGS.  1  and  4   . In alternate embodiments, the biasing element retainers may be in the form of a recess, projection or other surface feature, and/or a coupling, connector or other attachment means, for coupling a spring or other biasing element to the front shell  20 . In the depicted embodiment, one holding post  28  is located on the top sidewall of jacket  20  and extends externally therefrom. A second holding post  28  is located on the bottom sidewall of jacket  20  and extends externally therefrom. The two posts  28  are preferably located near the side of base  22  opposite the first side edge. The posts  28  further comprise a groove or channel  29  along the perimetric surface, as shown in the detail view of  FIG.  4   . In the depicted embodiment, the posts  29  comprise a cylindrical shape or a circular cross-section; however, the cross-sectional shape of posts  28  can comprise of various geometric shapes, such as for example, rectangle, triangle, star, and the like. 
     The back shell  30  generally comprises a back plate or base panel  32  and a raised sidewall  34 . In the depicted embodiment, the sidewall  34  projects transversely outward along the top edge, the bottom edge, and a first side edge of the base  32 , forming a continuous sidewall  34  with two radiused corners partially bounding an interior chamber for receiving the electronic device. The sidewall  34  preferably comprises a ridge or flange along its perimeter at its distal rim that extends inwards towards the center of the shell  30  to retain the case in place on an electronic device. Back base  32  is generally flat and rectangular with rounded corners, but it may comprise different configurations to match the shape of a particular electronic device in alternate embodiments. In yet other embodiments, the sidewall  34  comprises two or more separate sidewalls extending from discrete sections of the base periphery resulting in a plurality of discrete sidewalls. 
     The back shell  30  further comprises one or more biasing element retainers or retention elements, for example in the form of holding posts or support members  38 , as shown in  FIGS.  1  and  4   . In alternate embodiments, the biasing element retainers may be in the form of a recess, projection or other surface feature, and/or a coupling, connector or other attachment means, for coupling a spring or other biasing element to the front shell  30 . In the depicted embodiment, one holding post  38  is located on the top sidewall of jacket  30  and extends externally therefrom. A second holding post  38  is located on the bottom sidewall of jacket  30  and extends externally therefrom. The two posts  38  are preferably located near the side of base  32  opposite the first side edge. The posts  38  further comprise a groove or channel  39  along the perimetric surface, as shown in the detail view of  FIG.  4   . In the depicted embodiment, posts  38  comprise a cylindrical shape or a circular cross-section; however, the cross-sectional shape of posts  38  can comprise various geometric shapes, such as for example, rectangle, triangle, star, and the like. 
     The front and back bases  22 ,  32  and sidewalls  24 ,  34  optionally include one or more cutouts or apertures  26  and  36  extending therethrough, as shown in  FIG.  3   . Apertures  26  and  36  are positioned such that buttons, switches, ports, touch-screen(s), camera lenses, microphones, and/or other user interfaces or mechanisms on an electronic device installed into the case  10  can be accessed and operated therethrough. 
     The front and/or back shells  20 ,  30  can additionally include one or more buttons  50  positioned in the cutouts of the shells, as shown in  FIG.  1   , wherein the buttons  50  are configured to engage buttons on the device such as the volume controls and power button. The buttons  50  can include a T-shaped retaining feature configured to engage a flange on the front and back shells to keep the buttons  50  engaged with the shells. In the example embodiments, buttons  50  are formed of polycarbonate or other injection molded material. 
     In example embodiments, one or more biasing elements or engagement means such as tension or spring mechanisms  40  are installed on the case  10  by securing a first distal end of the tension mechanism to one support post  28  on the front shell  20  and securing a second distal end of the tension mechanism to a support post  38  on the back shell  30 . In the depicted embodiments, the biasing elements or tension mechanisms  40  are tension springs, as shown in  FIG.  8   . The first and second distal ends of the tension springs comprise engagement features  42  in the form of a loop or ring. In alternate embodiments, the biasing elements or engagement means may comprise an elastic cord, band, strip, living hinge and/or other elastically resilient member, a helical, coil, torsion, leaf or other form of extension or compression spring, one or more magnetic and/or magnetically-attracted elements, a gravity-assisted or manual closure mechanism, and/or other form of biasing or engagement means. In yet other embodiments, engagement features  42  are in the form of hooks and/or clips. In further alternate embodiments, the ends of the spring or other tension member engage within recesses or other retention elements or engagement features on the front and back shells, or are secured by adhesive, fasteners or other attachment means. 
     The springs or other tension mechanisms  40  are installed onto case  10 , connecting together the front and back shells  20 ,  30  via support posts  28 ,  38 . Engagement feature  42  of the first distal end of spring mechanism  40  is fitted over groove  29  of support post  28 . Engagement feature  42  of the second distal end of spring mechanism  40  is fitted over groove  39  of the support post  38 . According to example embodiments, loop  42  at the first distal end of tension spring  40  is contoured over support post  28  and nestled into groove  29 . Similarly, loop  42  at second distal end of tension spring  40  is contoured over support post  38  and adjusted to fit securely in groove  39 . In the depicted embodiments, one tension spring  40  with loop features  42  is connected to holding posts  28  and  38  located on top sidewalls  24  and  34  of front and back shells  20 ,  30 , and a second tension spring  40  is connected to holding posts  28  and  38  located on the bottom sidewalls  24  and  34  of the front and back shells  20 ,  30 . In alternate embodiments, a single biasing spring  40  may be provided at either the top or the bottom of the case  10 , and a pivotal hinge mechanism at the other of the top or bottom of the case. 
     In use, the user installs the case  10  onto a foldable electronic device having a first housing and a second housing, where the first housing and the second housing are connected by a hinge element H. The user installs the front shell  20  onto the device&#39;s first housing and the back shell  30  onto the second housing of the device. In an example method of use, the first housing of a foldable electronic device is inserted into front shell  20  such that the exterior of the first housing fits snugly within the sidewall  24  and front panel  22 . The flange of sidewall  24  helps retain the device within shell  20 . Similarly, the second housing of the device is inserted into the back shell  30  such that the exterior of the second housing fits snugly between sidewall  34  and back panel  32 , and the second housing is further retained by the flange of sidewall  34 . The hinge or fulcrum geometry of the case  10  generally corresponds to the hinge or fulcrum geometry of the folding electronic device intended to be housed in the case, whereby the relative pivotal or folding movement of the case shells  20 ,  30  substantially matches the relative pivotal or folding movement of the corresponding folding elements of the device for smooth operation and closely conforming fit. 
     In example embodiments, a foldable electronic device is generally capable of pivotal movement through a range of motion including the depicted four relative positions—fully closed, semi-closed, semi-open, and fully open—as shown in  FIGS.  5 A-D  and  FIG.  7   .  FIGS.  6 A-D  show detail views of tension mechanism  40  in the four positions collectively shown in  FIG.  7   , and depict a sequence of opening ( FIGS.  5 A to  5 D  and  FIGS.  6 A to  6 D ) and closing ( FIGS.  5 D to  5 A  and  FIGS.  6 D to  6 A ) the device within the case or cover  10  according to example methods of use. 
     In an example method of use, spring  40  is under tension when the case and electronic device are in a fully closed position ( FIGS.  5 A,  6 A ). The tensional load on spring  40  biases the case  10  toward the fully closed position, and resists external forces to spread apart the top and bottom shells  20 ,  30  rotationally about a fulcrum point fixed by the device&#39;s hinge. As the user applies greater force and overcomes the resistance, the front and back shells  20 ,  30  spread apart about the device&#39;s hinge. As the angle between the front and back shells  20 ,  30  increase ( FIGS.  5 B,  5 C  and  FIGS.  6 B,  6 C ), the location of the tensional force between holding posts  28  and  29  moves relative to the fulcrum points  25 ,  35  and determines the direction of the resulting rotation, as shown in  FIG.  9   . 
     A semi-closed position, as shown in  FIG.  9   , refers to any configuration of case  10  where the tensional force vector or line is above or forward of a line extending through the fulcrum points  25 ,  35  of the shells  20 ,  30  as the shells rotate or pivot relative to one another along an opening and/or closing range of motion constrained by the device&#39;s fixed hinge. In a semi-closed position, the tension in the spring will cause rotation of the top and bottom shells to return the case to a fully closed position. A semi-open position refers to any configuration of case  10  where the spring mechanism is below or behind the fulcrum points  25 ,  35 , as depicted in  FIG.  9   . In a semi-open position, the tension in the spring will apply a force to both top and bottom shells causing rotation about their respective fulcrum points  25 ,  35  to bias the device toward the fully open position ( FIGS.  5 D,  6 D ). 
     In further example embodiments of the present invention, the case  10  optionally comprises an hinge protection plate or panel  60 , as shown in  FIGS.  10  and  11   . According to example embodiments, the hinge protection panel  60 , when provided, comprises a generally flat base  62  with a top end and a bottom end. A top wall or frame  64  extends transversely from the top end of the base and includes a top bore or channel  65  for containing or covering the upper spring  40  or biasing element. Similarly, a bottom wall or frame  66  extends transversely from the bottom end of the base and includes a bottom bore or channel  67  for containing or covering the lower spring  40  or biasing element. In example embodiments, as shown in  FIGS.  11 A-B , the hinge protection panel  60  is configured such that the top bore  65  aligns concentrically with spring  40  between the holding posts  28  and  38  on the top ends of front and back shells  20 ,  30  and the bottom bore  67  aligns concentrically with spring  40  between holding posts  28  and  38  on the bottom ends of the front and back shells  20 ,  30 . In this manner, spring(s)  40  engaged between engagement posts at the top and/or bottom of the first and second shells  20 ,  30  extend through the respective top and/or bottom channels  65 ,  67  to retain and bias the first and second shells, while shielding against user contact with the spring(s) and at potential pinch points between the shells. 
     In example embodiments, the first and second shells, and the hinge protection plate can be formed from polycarbonate or other hard plastics, thermoplastic polyurethane or other soft plastics, metal, composite, ceramic, and/or other material(s) of construction. In particular embodiments, the components of the case  10  optionally comprises a hard and durable outer shell for impact resistance, for example comprising polycarbonate (PC) or other hard plastic; and a softer cushioning inner layer or lining, for example comprising thermoplastic polyurethane (TPU) for shock absorption, to provide improved protection to the electronic device housed in the case. In further example embodiments, the case optionally also comprises an inner frame or wall that conforms to the inner surfaces of sidewalls  24  and  34 . The inner frame preferably comprises a resilient or compressible material such as silicon, rubber, elastomer or the like, to cushion the electronic device from impacts and assist in retaining the case or cover in place on an electronic device contained therein. 
       FIGS.  12 - 13    show a foldable protective case or cover  110  for a foldable portable electronic device, according to another example embodiment of the present invention. In the depicted embodiment, the case or cover  110  includes a housing for receiving and at least partially covering the foldable electronic device. In example embodiments, the case or cover  110  is configured to fit a foldable smart-phone, tablet computer, cell phone, MP3 player, music and/or video player, electronic reader, handheld game device, or other foldable portable electronic device. Case  110  generally comprises a first or front jacket or shell  120 , a second or back jacket or shell  130 , a hinge cover  160 , top and bottom hinge cover endcaps  170 , and one or more spring-and-link coupling mechanisms or systems  140  operatively engaged between the front and back shells  120 ,  130  and the hinge cover  160 . In example forms, the front and back shells  120 ,  130  are at least partially formed of polycarbonate or other hard plastic, metal, composite, polymeric, ceramic, and/or other material(s) of construction. 
     As shown in  FIG.  12   , the front shell  120  generally comprises a front plate or base panel  122  and a raised sidewall  124 . In the depicted embodiment, the sidewall  124  projects transversely outward along the top edge, the bottom edge, and a first or outer side edge of the base  122 , forming a continuous sidewall  124  with a top sidewall portion, a first radiused corner, a first side sidewall portion, a second radiused corner, and a bottom sidewall portion partially bounding an interior chamber for receiving an electronic device. The sidewall  124  preferably comprises a ridge or flange along its perimeter at its distal rim that extends inwards towards the center of the shell  120  to help retain the case on an electronic device. In the depicted embodiment, the front base panel  122  is generally flat and generally rectangular with rounded corners. In example embodiments, the front base panel  122  and sidewall  124  may comprise one or more cutouts or openings adapted to show or allow access to at least a portion of the electronic device, for example, a display screen, controls, ports and/or other user interfaces. In the depicted embodiment, for example, the front shell  120  comprises an opening  126  adapted to show an exterior display screen or surface of the electronic device. The front shell  120  may further comprise additional openings along the top, side and/or bottom edges of sidewall  124  configured to allow access to or operation of various user interfaces or mechanisms and input/output ports (e.g., charging ports, audio cable ports, speakers, microphones, etc.) In alternate embodiments, the front base panel and openings may comprise different configurations or profiles to match the shape or configuration of a particular electronic device for which the case is configured. In yet other embodiments, the sidewall  124  comprises two or more separate sidewalls extending from discrete sections of the base periphery resulting in a plurality of discrete sidewalls. 
     The front shell  120  further comprises one or more coupling element retainers or retention elements, for example in the form of holding posts or support members  128 , as best shown in  FIG.  14   . In alternate embodiments, the coupling element retainers may be in the form of a recess, projection or other surface feature, and/or a coupling, connector or other attachment means, for coupling a spring and/or other coupling elements to the front shell  120 . In the depicted embodiment, one holding post  128  is located on the top sidewall of front shell  120  and extends transversely outward therefrom away from the center of the front shell. A second holding post  128  is located on the bottom sidewall of front shell  120  and extends transversely outward therefrom away from the center of the front shell. The two posts  128  are preferably located near the side of base panel  122  opposite the first side edge (or near the ends of the top and bottom portions of sidewall  124  opposite from the radiused corners). The posts  128  further comprise enlarged heads for retaining or preventing accidental disengagement of spring and/or coupling elements. In other example embodiments, the posts comprise a groove or channel along the perimetric surface (see for example posts  28  in  FIG.  4   ). In the depicted embodiment, posts  128  comprise a cylindrical shape or a circular cross-section; however, the cross-sectional shape of posts  128  can comprise of various geometric shapes, such as for example, rectangle, triangle, star, and the like. 
     The back shell  130  generally comprises a back plate or base panel  132  and a raised sidewall  134 . In the depicted embodiment, the sidewall  134  projects transversely outward along the top edge, the bottom edge, and a first side edge of the base  132 , forming a continuous sidewall  134  with a top sidewall portion, a first radiused corner, a first side sidewall portion, a second radiused corner, and a bottom sidewall portion partially bounding an interior chamber for receiving the electronic device. The sidewall  134  preferably comprises a ridge or flange along its perimeter at its distal rim that extends inwards towards the center of the shell  130  to retain the case in place on an electronic device. In the depicted embodiment, back base  132  is generally flat and rectangular with rounded corners. In example embodiments, the back base panel  132  and sidewall  134  may comprise one or more cutouts or openings adapted to show or allow access to at least a portion of the electronic device, for example, a display screen, controls, and/or other user interfaces or ports. In the depicted embodiment, for example, the back shell  130  comprises an opening  136  configured to be aligned with one or more camera lenses on the exterior of the electronic device. The back shell  130  further comprises additional openings along the top, side and/or bottom edges of sidewall  134  configured to allow access to or operation of various user interfaces or mechanisms and input/output ports (e.g., charging ports, audio cable ports, speakers, microphones, etc.) In alternate embodiments, the back base panel and openings may comprise different configurations or profiles to match the shape or configuration of a particular electronic device. In yet other embodiments, the sidewall  134  comprises two or more separate sidewalls extending from discrete sections of the base periphery resulting in a plurality of discrete sidewalls. 
     The front shell  130  further comprises one or more coupling element retainers or retention elements, for example in the form of holding posts or support members  138 , as best shown in  FIG.  14   . In alternate embodiments, the coupling element retainers may be in the form of a recess, projection or other surface feature, and/or a coupling, connector or other attachment means, for coupling a spring and/or other coupling elements to the front shell  130 . In the depicted embodiment, one holding post  138  is located on the top sidewall of back shell  130  and extends transversely outward therefrom away from the center of the back shell. A second holding post  138  is located on the bottom sidewall of jacket  130  and extends transversely outward therefrom away from the center of the back shell. The two posts  138  are preferably located near the side of base panel  132  opposite the first side edge (or near the ends of the top and bottom portions of sidewall  134  opposite from the radiused corners). The posts  138  further comprise enlarged heads for retaining or preventing accidental disengagement of spring and/or coupling elements. In other example embodiments, the posts comprise a groove or channel along the perimetric surface (see for example posts  28  in  FIG.  4   ). In the depicted embodiment, the posts  138  comprise a cylindrical shape or a circular cross-section; however, the cross-sectional shape of posts  138  can comprise of various geometric shapes, such as for example, rectangle, triangle, star, and the like. 
     The front and/or back shells  120 ,  130  can additionally include one or more buttons  150  positioned in the cutouts of the shells, as shown in  FIG.  12   , wherein the buttons  150  are configured to engage buttons on the device such as the volume controls and power button. The buttons  150  can include a T-shaped retaining feature configured to engage a flange on the front and back shells to keep the buttons  150  engaged with the shells. In the example embodiments, buttons  150  are formed of polycarbonate or other injection molded material. 
     In example embodiments, the case  110  further comprises a hinge cover or shell  160 , as shown in  FIG.  13   . According to example embodiments, the hinge cover  160  generally comprises an elongate channel-like or semi-tubular structure extending from a top end to a bottom end. In example embodiments, the top and bottom ends of the hinge cover  160  are closed comprising a short transverse wall generally perpendicular to the axis of elongation of the hinge cover. In the depicted embodiment, the hinge cover  160  comprises a generally arcuate cross-section, but other cross-sectional profiles and shapes may be used. The hinge cover  160  further comprises a plurality of coupling element retainers or retention elements, for example in the form of holding posts or support members  162  and  163 , as shown in  FIG.  14   . In alternate embodiments, the coupling element retainers may be in the form of a recess, projection or other surface feature, and/or a coupling, connector or other attachment means, for coupling a spring and/or other coupling elements to hinge cover  160 . In the depicted embodiment, a first pair of holding posts  162 ,  163  is located on the top end of hinge cover  160  and extends in a direction opposite the bottom end. A second pair of holding posts  162 ,  163  is located on the bottom end of hinge cover  160  and extends in a direction opposite the top end. In some example embodiments, holding posts  162 ,  163  are provided on only one end of the hinge cover and a hinge component is secured to the other end. 
     In example embodiments, holding posts  162  and  163  on the top end of the hinge cover  160  are generally co-planarly aligned to the top holding post  128  of front shell  120  and top holding post  138  of the back shell  130 , respectively. Similarly, holding posts  162  and  163  on the bottom end of the hinge cover  160  are generally co-planarly aligned to the bottom holding post  128  of front shell  120  and bottom holding post  138  of the back shell  130 , respectively. In example embodiments, hinge cover tops or endcaps  170  are provided and configured to be secured to the top and bottom ends of the hinge cover  160 . When secured to the hinge cover, the hinge cover endcaps  170  help prevent the coupling elements from becoming accidentally detached from the holding posts, and also shields against user contact with the coupling elements and at potential pinch points between the shells and hinge cover. In example embodiments, hinge cover  160  further comprises a threaded bore on each end of the hinge cover which are adapted for receiving reciprocally threaded bolts or screws S used to secure the hinge cover endcaps  170  to the hinge cover  160 . In the depicted embodiment, threaded bores are provided by means of threaded rivet nuts N. In alternate embodiments, the hinge cover end caps  170  may be configured for removable engagement with hinge cover  160  by means of push-fit, friction fit, snap fit, adhesives, hook-and-loop fasteners or other suitable fastening or securing means. 
     As shown in  FIGS.  12 - 14   , a plurality of coupling elements or engagement means  140  are installed on the case  110  to pivotally secure the front and back shells  120 ,  130  to the hinge cover  160 . Particularly,  FIG.  14    shows a detail view of a first set of coupling mechanisms secured to the holding post  138  of the back shell  130  and holding post  163  on the top end of the hinge cover  160 .  FIG.  14    also shows an exploded view of a second set of coupling mechanisms aligned to the holding post  128  of the front shell  120  and holding post  162  on the top end of the hinge cover  160 . In example embodiments, each of the sets of coupling elements  140  comprises a link or linkage element  142  and a biasing element or springs  144 . 
     In example embodiments, link  142  is generally a flat, elongate crosspiece or strip comprising an oblong or elongate aperture  142   a  at its first, proximal end and a round aperture  142   b  at its second, distal end. Generally, the oblong aperture  142   a  is configured for a pin-in-slot joint or engagement with holding post  128  or  138  which provides an additional degree-of-freedom to the movement of the front and back shells  120 ,  130  in comparison to a pin joint configuration. For example, if the link  142  comprised round apertures at both ends, movement of the holding post  128 , and thus front shell  120 , relative to holding post  162  of hinge cover  160  would be fixed to a substantially constant radius from holding post  162 . However, the oblong or elongate aperture  142   a  provides an additional degree of freedom in the radial direction between the holding posts  128 ,  138  and holding post  162 ,  163  to accommodate the rotation or pivot of the front and back shells  120 ,  130  around their corners. In example embodiments, link  142  also comprises a pair of raised ridges or fingers  142   c  adapted for receiving and supporting the tension spring  144 . In the depicted embodiment, the raised ridges  142   c  include curved or arcuate inner surfaces configured to generally conform to the exterior surface of the biasing element or spring  144 . The curved inner surfaces of the ridges  142   c  provide support and help retain the spring  144  directly over the link  142  to further ensure the two coupling element components move or operate in tandem. In alternate embodiments, the link  142  and spring  144  may incorporate alternate arrangements and configurations. For example, in an alternate embodiment, the link  142  may comprise a tubular structure configured to receive and retain a spring therein. In yet another example embodiment, the spring may be positioned below the link. In still another example embodiment, the coupling element may comprise either only a link made at least in part from elastic material(s) or only a spring. 
     In example embodiments, the front shell  120  is connected to the hinge cover  160  by securing the first distal ends of first link and spring elements  142 ,  144  to one support post  128  on the front shell  120  and securing the second distal ends of the link and spring elements  142 ,  144  to the support post  162  on the hinge cover  160 . The back shell  130  is connected to the hinge cover  160  by securing the first distal ends of second link and spring elements  142 ,  144  to one support post  138  on the back shell  130  and securing the second distal ends of the second link and spring elements  142 ,  144  to the support post  163  on the hinge cover  160 . In a similar manner, third and fourth link and spring elements are secured to holding posts  128 ,  138 ,  162  and  163  connecting the bottom sidewalls of the front and back shells  120 ,  130  to the bottom end of the hinge cover  160 . In the depicted embodiments, the biasing elements or springs  144  are tension springs, as shown in  FIG.  14   . The first and second distal ends of the tension springs comprise engagement features in the form of a loop or ring. In alternate embodiments, the biasing elements or engagement means may comprise an elastic cord, band, strip, living hinge and/or other elastically resilient member, a helical, coil, torsion, leaf or other form of extension or compression spring, one or more magnetic and/or magnetically-attracted elements, a gravity-assisted or manual closure mechanism, and/or other form of biasing or engagement means. In yet other embodiments, engagement features are in the form of hooks and/or clips. In further alternate embodiments, the ends of the spring or other tension member engage within recesses or other retention elements or engagement features on the front and back shells, or are secured by adhesive, fasteners or other attachment means. In alternate embodiments, a single pair of coupling mechanisms  140  may be provided at either the top or the bottom of the case  110  while a pivotal hinge mechanism is provided at the other, opposite end of the case. 
     In use, the user installs the case  110  onto a foldable electronic device having a first housing and a second housing, where the first housing and the second housing are connected by a hinge element. The user installs the front shell  120  onto the device&#39;s first housing and the back shell  130  onto the second housing of the device. In an example method of use, the first housing of a foldable electronic device is inserted into front shell  120  such that the exterior of the first housing fits snugly within the sidewall  124  and front panel  122 . The flange of sidewall  124  helps retain the device within shell  120 . Similarly, the second housing of the device is inserted into the back shell  130  such that the exterior of the second housing fits snugly between sidewall  134  and back panel  132 , and the second housing is further retained by the flange of sidewall  134 . The hinge or fulcrum geometry of the case  110  generally corresponds to the hinge or fulcrum geometry of the folding electronic device intended to be housed in the case, whereby the relative pivotal or folding movement of the case shells  120 ,  130  substantially matches the relative pivotal or folding movement of the corresponding folding elements of the device for smooth operation and closely conforming fit. 
     In example embodiments, a foldable electronic device is generally capable of pivotal movement through a range of motion including the depicted four relative positions—fully closed, semi-closed, semi-open, and fully open—as shown in  FIGS.  15 A-D .  FIGS.  15 A-D  further show detail views of link and spring mechanism  142 ,  144  in the four positions, and depict a sequence of opening ( FIGS.  15 A to  15 D ) and closing ( FIGS.  15 D to  15 A ) the device within the case or cover  110  according to example methods of use. 
     In an example method of use, springs  144  are under tension when the case and electronic device are in a fully closed position ( FIG.  15 A ). The tensional load on springs  144  bias the case  110  toward the fully closed position and resists external forces to spread apart the front and back shells  120 ,  130  rotationally about a fulcrum point fixed by the device&#39;s hinge. As the user applies greater force and overcomes the resistance, the front and back shells  120 ,  130  spread apart about the device&#39;s hinge. As the angle between the front and back shells  120 ,  130  increase ( FIGS.  15 B and  15 C ), the distances between the holding posts  128 ,  138  and holding posts  162 ,  163  increase as corners of the front and back shells interact with the hinge cover and one another to pivot about fulcrum points  125 ,  135 . In turn, the tension in the springs  144  increase during the pivoting motion and the springs bias the shells to either the fully open or fully closed positions where the springs are closest to their neutral state. The tension in the springs also pull the front and back shells  120 ,  130  towards the hinge cover  160  such that the hinge cover is in contact with at least portions of both the front and back shells during operation. For example, as shown in  FIGS.  15 A- 15 D , as the front and back shells  120 ,  130  are rotated or pivoted between the closed and open positions, at least portions of the sides of the front and back shells adjacent the hinge cover  160  slide or move along an interior surface of the hinge cover  9  (e.g., the flat surface of hinge cover shown in  FIGS.  15 A- 15 D ). 
     In a fully open position, as shown in  FIG.  14   , the fulcrum points  125  and  135  of the shells  120  and  130 , respectively, are at their farthest position from the hinge cover  160 . Conversely, in a fully closed position, the fulcrum points  125  and  135  are at their closest position to the hinge cover. As the shells rotate or pivot relative to one another along an opening and/or closing range of motion constrained by the device&#39;s coupling elements  140 , the fulcrum points move along a line of motion between the position of the fulcrum points at the fully open and fully closed states. A semi-closed position refers to any configuration of case  110  where the fulcrum points  125  and  135  are between the fulcrum points&#39; positions at the fully closed state and the middle point along the line of motion between the fully open and closed states. In a semi-closed position, the tension in the spring will cause rotation of the top and bottom shells to return the case to a fully closed position ( FIG.  15 B  to  FIG.  15 A ). A semi-open position refers to any configuration of case  110  where the fulcrum points  125  and  135  are between the middle point along the line of motion between the fully open and closed states and the fulcrum points&#39; positions at the fully open state. In a semi-open position, the tension in the spring will apply a force to both top and bottom shells causing rotation about their respective fulcrum points  25 ,  35  to bias the device toward the fully open position ( FIG.  15 C  to  FIG.  15 D ). 
     In example embodiments, the front and back shells  120 ,  130 , hinge cover  160 , hinge cover endcaps  170  and links  142  can be formed from polycarbonate or other hard plastics, thermoplastic polyurethane or other soft plastics, metal, composite, ceramic, and/or other material(s) of construction. In particular embodiments, the front and back shells, hinge cover and hinge cover endcaps optionally comprise hard and durable outer shells for impact resistance, for example comprising polycarbonate (PC) or other hard plastic, and softer cushioning inner layers or linings, for example comprising thermoplastic polyurethane (TPU) for shock absorption, to provide improved protection to the electronic device housed in the case. In further example embodiments, the case optionally also comprises an inner frame or wall that conforms to the inner surfaces of sidewalls  124  and  134 . The inner frame preferably comprises a resilient or compressible material such as foam, silicon, rubber, elastomer or the like, to cushion the electronic device from impacts and assist in retaining the case or cover in place on an electronic device contained therein. 
     While the invention has been described with reference to example embodiments, it will be understood by those skilled in the art that a variety of modifications, additions and deletions are within the scope of the invention, as defined by the following claims.