PATENT DOCUMENT

Publication Number: US-7638717-B1
Application Number: US-18699508-A
Country: US
Kind Code: B1

Title: Can spring housing contact

Abstract:
An electromagnetic interference (EMI) shield is provided. The EMI shield may include a frame and a cover operative to be placed over the frame. The cover may include snaps or tabs extending from the surface of the cover and operative to engage side walls of the frame. At least one edge of the cover, for example an edge operative to be placed near an electronic device housing, may not include snaps or tabs to reduce the size of the EMI shield near the housing. Instead, the frame may include one or more stepped returns, the top-most of which may be operative to be placed in contact with the cover. The cover may include a spring, an emboss and one or more grounding points to ensure that the cover remains in contact with the frame despite the absence of snaps or tabs securing the cover to the frame.

Claims:
1. An electromagnetic interference shield, comprising:
 a frame comprising:
 a side wall; 
 a return extending substantially perpendicular to the side wall, the return extending from the top edge of a first portion of the wall; and 
 a stepped return extending vertically from the top edge of a second portion of the wall, the stepped return comprising at least two returns extending substantially perpendicular from the wall, the at least two returns at different heights relative to the bottom of the wall; and 
 
 a cover operative to be placed over the frame, the cover comprising:
 a planar surface extending over a portion of the return and a portion of the stepped return; and 
 at least one snap extending vertically from the planar surface and operative to engage the first portion of the wall, wherein no snap engages the second portion of the wall. 
 
 
   
   
     2. The electromagnetic interference shield of  claim 1 , wherein:
 the frame defines an enclosure; and 
 the return and the stepped return extend vertically substantially perpendicular from of the wall into the defined enclosure. 
 
   
   
     3. The electromagnetic interference shield of  claim 1 , wherein the stepped return further comprises a plurality of offset returns, each of the plurality of offset returns positioned at different heights relative to the bottom of the side wall. 
   
   
     4. The electromagnetic interference shield of  claim 3 , wherein the distance of the edge nearest the side wall of each of the plurality of offset returns from the wall is different. 
   
   
     5. The electromagnetic interference shield of  claim 1 , wherein the cover further comprises at least one cantilever spring extending from the planar surface and operative to contact an electronic device component. 
   
   
     6. The electromagnetic interference shield of  claim 5 , wherein the cantilever spring is operative to provide a force pressing the cover against the frame in response to contacting the electronic device component. 
   
   
     7. The electromagnetic interference shield of  claim 5 , wherein the electronic device component is a housing. 
   
   
     8. The electromagnetic interference shield of  claim 1 , wherein the cover further comprises at least one embossed grounding point operative to be placed in contact with a portion of the stepped return. 
   
   
     9. The electromagnetic interference shield of  claim 8 , wherein the cover further comprises at least one cantilever spring extending from the planar surface and operative to provide a force pressing the cover against the frame by contacting an electronic device component. 
   
   
     10. The electromagnetic interference shield of  claim 9 , wherein the cover further comprises an emboss feature operative to distribute the force to the at least one grounding point. 
   
   
     11. The electromagnetic interference shield of  claim 8 , wherein the portion of the stepped return comprises at least one indentation operative to receive the at least one embossed grounding point. 
   
   
     12. An electronic device, comprising:
 a housing operative to receive electronic device components; 
 a circuit board comprising at least one component; and 
 an EMI shield for protecting the at least one component, comprising:
 a frame coupled to the circuit board and enclosing the at least one component, the frame comprising a wall and at least one stepped return, wherein the stepped return comprises a plurality of returns extending over the portion of the circuit board enclosed by the frame and at different heights from the circuit board; and 
 a cover operative to be coupled to the frame, the cover comprising at least one snap operative to engage the wall, wherein no snap extends from the portion of the cover placed adjacent to the at least one stepped return. 
 
 
   
   
     13. The electronic device of  claim 12 , wherein the height from the circuit board of one of the plurality of returns is less than the height from the circuit board of the plurality of returns positioned at a larger distance from the frame wall. 
   
   
     14. The electronic device of  claim 12 , wherein the cover further comprises at least one spring extending from the surface of the cover, the spring operative to contact the housing when the electronic device is assembled. 
   
   
     15. The electronic device of  claim 14 , wherein the cover comprises an emboss operative to distribute the force generated by the contact between the spring and the cover to the portion of the cover placed adjacent to the at least one stepped return. 
   
   
     16. The electronic device of  claim 15 , wherein the cover further comprises at least one grounding point operative to contact the at least one stepped return. 
   
   
     17. The electronic device of  claim 16 , wherein the emboss is operative to distribute the force to the at least one grounding point. 
   
   
     18. A method for assembling an EMI shield, comprising:
 coupling a frame defining an enclosure having a plurality of sides to a circuit board, the frame comprising a wall and a stepped return extending from the top surface of the wall into the enclosure, the stepped return comprising a plurality of returns extending over the portion of the circuit board enclosed by the frame and at different heights from the circuit board; 
 engaging a cover with the frame, the cover comprising a planar surface and at least one snap operative to engage the wall, wherein the wall of the at least one side of the enclosure is not engaged by any snaps; and 
 placing a housing over the cover, wherein the housing is operative to contact a spring extending from the cover and operative to press the cover against the return adjacent to the wall of the at least one side of the enclosure that is not engaged by any snaps. 
 
   
   
     19. The method of  claim 18 , wherein the return adjacent to the wall of the at least one side of the enclosure that is not engaged by any snaps comprises a stepped return.

Description:
BACKGROUND OF THE INVENTION 
   This invention is directed to an electromagnetic interference (EMI) shield for use in an electronic device. 
   Many electronic devices include various electronic components that emit electromagnetic radiation. To prevent disturbances of the electronic components, EMI shields may be provided in the electronic device. For example, the electronic device components may be placed in a conductive enclosure (e.g., a metallic box) that prevents radiation from escaping the box. As another example, the enclosure in which the electronic components are placed may be coated with a metallic or conductive paint. The enclosure may be formed by providing a frame over which a cover having vertically extending tabs is placed. The tabs may engage side walls of the frame around the periphery of the frame to ensure that the enclosure is secure. 
   When used in devices with curved housings, or when placed against curved surfaces, these shields may cause significant space to be lost. For example, when a corner of an enclosure (e.g., where a cover has a snap extending away from the cover to engage a frame wall) is placed against a curved housing, space may be lost around the corner to accommodate the entire housing. In particular, the housing may need to be enlarged to wrap around the enclosure, thus increasing the electronic device size. Furthermore, the size of components to be protected by the EMI shield may prevent the size of the enclosure from being reduced to accommodate the curved housing. There is a need, therefore, to provide an EMI shield that can substantially follow or accommodate a curved housing while retaining suitable EMI protection. 
   SUMMARY OF THE INVENTION 
   An EMI shield for protecting components of an electronic device from electromagnetic interferences is provided. 
   The EMI shield may include a frame operative to be coupled to a circuit board and a cover operative to be placed over the frame. The electronic device components in need of EMI protection may be placed within the boundary defined by the frame. The frame may include a side wall extending from the surface of the circuit board, and a return extending substantially parallel to the circuit board and over the surface enclosed by the frame. 
   In portions of the frame operative to be placed against or adjacent to a curved housing or other curved electronic device component that restricts the size of the EMI shield, the single return may be replaced by several returns offset at different heights and the side wall height may in addition be reduced. For example, the return may be stepped such that several returns, having the same or different dimensions, may be staggered in distance from the circuit board (e.g., along a z-axis) to form steps substantially following the shape of the curved housing or other component. 
   The cover may include a substantially planar surface and several tabs or snaps extending substantially perpendicular to the planar surface. The cover may be placed over the frame such that the planar surface is substantially bound by the periphery of the frame and the snaps overlap and engage the side walls of the frame (e.g., using one or more snapping mechanisms or any other suitable engagement mechanism). To reduce the space taken by the EMI shield, and in particular to limit the amount of the cover placed along the portions of the EMI shield that are adjacent to the housing (e.g., where the frame includes a stepped return), the cover may not include any snaps along the edge of the cover aligned with the stepped return. 
   Instead, the cover may include a spring (e.g., a cantilever spring) extending from the surface of the planar surface in a direction opposite the snaps and operative to be placed in contact with the curved housing when the electronic device is assembled. The contact between the spring and the housing may provide a force operative to hold the cover against the frame despite the absence of snaps engaging the side walls of the frame. To distribute the force from the spring along the edge of the cover, the cover may include an emboss or other feature operative to distribute the force. The emboss may be designed to distribute the spring force in any suitable manner, for example to one or more specific points of the cover. 
   The cover may include, along the portion of the planar surface in contact with the top-most stepped return, one or more grounding points (e.g., embossed features) operative to engage or contact one or more corresponding indentations or other features of the stepped return. The emboss may distribute the spring force to the grounding points to ensure that the grounding points always remain in contact with the frame, thus ensuring that the EMI shield remains grounded and operational. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other features of the present invention, its nature and various advantages will be more apparent upon consideration of the following detailed description, taken in conjunction with the accompanying drawings in which: 
       FIG. 1  is a cross-section of an illustrative EMI shield used in an electronic device in accordance with one embodiment of the invention; 
       FIG. 2  is a cross-section of another illustrative EMI shield used in an electronic device in accordance with one embodiment of the invention; 
       FIG. 3  is an exploded view of an electronic device having a modified EMI shield in accordance with one embodiment of the invention; 
       FIG. 4  is a schematic view of the assembled electronic device of  FIG. 3  in accordance with one embodiment of the invention; and 
       FIG. 5  is a cross-sectional view of the assembled electronic device of  FIG. 3  in accordance with one embodiment of the invention. 
   

   DETAILED DESCRIPTION 
     FIG. 1  is a cross-section of an illustrative EMI shield used in an electronic device in accordance with one embodiment of the invention. Electronic device  100  may include housing  102  forming an outer surface of the device. To protect electronic device components (e.g., coupled to circuit board  104 ) stored within housing  102  from electromagnetic interference, electronic device  100  may include EMI shield  110 , which may be formed from frame  112  over which cover  120  may be placed. Frame  112  may include side walls  114  and upper lip or return  116 . Side wall  114  may be coupled to circuit board  104  to form the side walls of a box (e.g., enclosing electronic device components). Side wall  114  may be coupled to circuit board  104  using any suitable approach, including for example soldering, snapping or clipping into a structural element of circuit board  104  (e.g., snaps extending in apertures in the circuit board, or snaps coupling to a receiving element incorporated in the circuit board), an adhesive or tape, or any other suitable approach. 
   Cover  120  may include planar surface  122  operative to extend over the area defined by side wall  114 . Cover  120  may include walls or snap  124  extending vertically from at least a portion of the periphery of surface  120  to engage side wall  114  of frame  110 . The combination of circuit board  104 , frame  110  and cover  120  may form a box in which electronic components may be isolated and shielded from electromagnetic radiation. 
     FIG. 2  is a cross-section of another illustrative EMI shield used in an electronic device in accordance with one embodiment of the invention. Electronic device  200  may include housing  202  forming an outer surface of the device. To protect electronic device components (e.g., coupled to circuit board  204 ) stored within housing  202  from electromagnetic interference, electronic device  200  may include EMI shield  210 , which may be formed from frame  212  over which cover  220  may be placed. Frame  212  may include side walls  214  and upper lip or return  216 . Side wall  214  may be coupled to circuit board  204  to form the side walls of a box (e.g., enclosing electronic device components). Side wall  214  may be coupled to circuit board  204  using any suitable approach, including for example soldering, snapping or clipping into a structural element of circuit board  204  (e.g., snaps extending in apertures in the circuit board, or snaps coupling to a receiving element incorporated in the circuit board), an adhesive or tape, or any other suitable approach. 
   Cover  220  may include planar surface  222  operative to extend over the area defined by side wall  214 . Cover  220  may include walls or snap  224  extending vertically from at least a portion of the periphery of surface  220  to engage side wall  214  of frame  210 . The combination of circuit board  204 , frame  210  and cover  220  may form a box in which electronic components may be isolated and shielded from electromagnetic radiation. 
   When EMI shields  110  and  210  are located near housing  102  and  202 , respectively, the shape of the housing may provide constraints to the size and shape of the frame and cover of the EMI shields. This may be particularly true when housing  102  includes a curved surface. For example, if EMI shield  110  maintains a high height (e.g., to accommodate tall or large components coupled to board  104 ), cover  120 , and in particular portions of cover  120  adjacent to the periphery of surface  122  from which snap  124  extends may abut housing  102  and prevent electronic device  100  from being assembled properly. 
   Alternatively, if the height of EMI shield  210  is reduced to allow housing  202  to be properly assembled to other electronic device components, components coupled to circuit board  204  may not fit beneath cover  220 . In particular, as can be seen by comparing  FIGS. 1 and 2 , the height Y in  FIG. 2  is less than the height Y in  FIG. 1  by a value at least equal to the height of secondary return  118  of frame  112 . 
   To accommodate curved housings while maintaining sufficient height between the circuit board (e.g., circuit board  104 ) and the housing (e.g., housing  102 ), the design of the EMI shield (e.g., EMI shield  110 ) must be modified.  FIG. 3  is an exploded view of an electronic device having a modified EMI shield in accordance with one embodiment of the invention. 
   Electronic device  300  may include housing  302  and circuit board  304 . Electronic device component  306  may be coupled to circuit board  304 . Housing  302  may include a curved surface such that a standard EMI shield design having a cover overlapping the sides of a frame is not suitable. 
   Electronic device  300  may include EMI shield  310 , which may be constructed by combining can or frame  320  with cover  330 . EMI shield  310  may have any suitable shape (e.g., any suitable footprint on circuit board  304 ), including for example a shape driven or determined by the electronic device components to be placed within EMI shield  310 . Frame  320  may include side walls  322  and upper lip or return  324 . Side walls  322  may extend partially or entirely around the periphery of frame  320  and may be coupled to circuit board  304  to form the side walls of a box (e.g., enclosing electronic device components such as component  306 ). Side walls  324  may be coupled to circuit board  304  using any suitable approach, including for example soldering, snapping or clipping into a structural element of circuit board  304  (e.g., snaps extending in apertures in the circuit board, or snaps coupling to a receiving element incorporated in the circuit board), an adhesive or tape, or any other suitable approach. 
   In some embodiments, portions of frame  320  near a curved surface of housing  302  (e.g., portions of frame  320  that would otherwise come into contact with housing  302 ) may include a stepped return  326 . For example, stepped return  326  may include first and second returns  326 A and  326 B having different heights from circuit board  304  and offset to roughly follow the curved shape of housing  302  (e.g., the distance of the leading/inner or trailing/outer edge of each of returns  326 A and  326 B to wall  322  is different). The width of each return  326 A and  326 B, as well as the height  328  between each return, may be selected based on any suitable criteria, including for example the component underneath the return, the shape or curvature of housing  302 , structural limitations of frame  302 , or any other suitable criteria. Stepped return  326  may include any suitable number of consecutive returns having any suitable width and offset by any suitable height. 
   One or more of stepped returns  326  may include one or more indentations  329  for grounding cover  330 . For example, cover  330  may include an element (described below) operative to engage indentations  329  to ensure that cover  330  and EMI shield  310  remains grounded (e.g., because no snap of cover  330  engages frame  320  in locations adjacent to stepped return  326 ). In the example of  FIG. 3 , only top-most stepped return  326 B includes indentations  329 . It will be understood, however, that any other stepped return  326  or ordinary return  324  may include indentations  329 . 
   Cover  330  may include planar surface  332  operative to extend over the area defined by frame  320 . Cover  330  may include walls or snap  334  extending vertically from at least a portion of the periphery of surface  332  to engage side walls  322  of frame  320 . For example, cover  330  may include snaps  334  operative to engage side walls  322  that are not adjacent to stepped return  326 . 
   Cover  330  may be coupled to frame  320  using any suitable approach. In some embodiments, snaps  334  may be substantially aligned with side walls  322  such that the snaps may engage a portion of the side walls. Snaps  334  may include one or more mechanisms for engaging side walls  322 . For example, snaps  334  may be elastically biased towards side walls  322  such that snaps  334  may deflect when they are placed over frame  320 , thus creating an interference or frictional fit. As another example, snaps  334  may include a tab or protrusion  335  operative to engage a corresponding indentation, aperture or tab  323  in the side wall. As still another example, a tape, adhesive or mechanical fastener (e.g., a screw passing through snaps  334  and engaging side wall  322 ) may be used to secure snaps  334  to frame  320 . 
   Cover  330  may include any suitable number of snaps  324 . For example, cover  330  may include snaps  334  offset at distances larger than the width of a snap. In some embodiments, different snaps  334  may have different sizes, for example based on the component  306  lying adjacent to the snap on circuit board  304 , or based on the position of snap relative frame  320  (e.g., a snap adjacent to a corner may be wider than a snap in the middle of a wall). The snaps may also be distributed along the periphery of the cover using any suitable approach, including for example evenly, or based on the EMI shielding or structural requirements of the shield. 
   In some embodiments, portions of cover  330  may not include snaps  334 . For example, portions of cover  330  operative to be placed over or adjacent to stepped return  326  may not include snaps  334 , but may instead simply end at the boundary of the top-most stepped return (e.g., stepped return  326 B). By not including additional material to be placed over side walls  322  near the stepped return, the thickness of EMI shield  310  along the portion of EMI shield  310  that is in closest contact with housing  302  (e.g., due to the curvature of housing  302 ) may be reduced. This in turn may provide more space for components within EMI shield  310  and allow for a reduction in the overall shape of electronic device  300 . 
   Cover  330  may include several features to ensure that cover  330  remains in contact with stepped return  326  despite not having snaps  334  engaging frame  320  along the associated edge of cover  330 . For example, cover  330  may include cantilever springs  336  extending from surface  332 . To provide sufficient force to the edges of cover  330  that do not include snaps  334 , spring  336  may be positioned near or adjacent to the portion of surface  330  in contact with stepped return  326 . Spring  336  may include a cantilever extending from opening  337  in surface  332  (e.g., material from surface  332  remaining after opening  337  was formed), or may instead include a cantilever coupled to a complete surface  332  (e.g., additional material coupled to surface  332 ). Spring  336  may be biased away from circuit board  304  so that when housing  302  is assembled over circuit board  304  and EMI shield  310 , spring  336  may be in contact with and resist housing  302 , thus forcing cover  330  against frame  320 . Spring  336  may include an emboss or other feature  336 A at the free end of the spring to increase the contact surface between spring  336  and housing  302 . If spring  336  is constructed from the same material as cover  330 , or is otherwise conductive, spring  336  may serve as a ground for EMI shield  310 . 
   Cover  330  may include emboss  338  constituting a canyon parallel or substantially parallel to the edge of cover  330  that does not include snaps  334  (e.g., the edge configured to be placed in contact with stepped return  326 ). Because emboss  338  may change the amount of material along the edge of surface  332 , emboss  338  may be operative to distribute the force provided by the contact between spring  336  and housing  302  along the entire edge of cover  330 . In some embodiments, emboss  338  may be designed or shaped to distribute the force evenly or to maximize the force in one or more desired locations (e.g., at grounding points  339 , described below) using any suitable mechanical feature (e.g., a flange, chamfer, detent, bevel, or a fillet). 
   To further ensure that cover  330  remains in contact with frame  320  along stepped return  326 , and to further ensure that proper electrical contact is maintained to sufficiently ground each portion of EMI shield  310 , cover  330  may include one or more grounding points  339  along the portion of surface  332  that is placed in contact with stepped return  326 . In some embodiments, grounding points  339  may include one or more embossed features operative to contact return  326 . Grounding points  326  may be positioned and sized using any suitable approach, including for example to align with indentations  329  (e.g., such that grounding points  339  extend at least partially into indentations  329 ). Spring  336 , emboss  338  and grounding points  339  may be positioned and sized such that a maximum amount of force generated by the contact between spring  336  and housing  302  is transferred to grounding points  339 , thus ensuring that grounding points  339  and indentations  329  remain in contact, thus grounding the associated edge of EMI shield  300 . 
   Frame  320  and cover  330  may be manufactured from any suitable material operative to shield the components of contained within EMI shield  310  from electromagnetic interference (e.g., from other components of the electronic device). In some embodiments, shield  310  may be constructed from an electrically conductive material such as, for example, metal (e.g., copper, silver, aluminum, steel), graphite, plasma, or any other conductive material. Frame  320  and cover  330  may include unbroken surfaces, or materials with a mesh or holes (e.g., so long as the holes are smaller than the wavelength of the radiation being kept out). 
     FIG. 4  is a schematic view of the assembled electronic device of  FIG. 3  in accordance with one embodiment of the invention. Electronic device  400  may include housing  402 , circuit board  404  and EMI shield  410 , which may include some or all of the features of housing  302 , circuit board  304  and EMI shield  310  of electronic device  300  ( FIG. 3 ). EMI shield  410  may further include frame  420  and cover  430 , which may further include spring  436 , emboss  438  and grounding points  439 , which may include some or all of the features of frame  320 , cover  330 , spring  336 , emboss  338  and grounding points  339  of EMI shield  310  ( FIG. 3 ). The transparent display of housing  402  indicates the contact between spring  436  and housing  402 . 
     FIG. 5  is a cross-sectional view of the assembled electronic device of  FIG. 3  in accordance with one embodiment of the invention. Electronic device  500  may include housing  502  and EMI shield  510 , which may include some or all of the features of housing  302  and EMI shield  310  of electronic device  300  ( FIG. 3 ). EMI shield  510  may further include frame  520  and cover  530 , which may further include stepped return  526 , indentation  529 , spring  536 , emboss  538  and grounding points  539 , which may include some or all of the features of frame  320 , cover  330 , stepped return  326 , indentation  329 , spring  336 , emboss  338  and grounding points  339  of EMI shield  310  ( FIG. 3 ). As clearly shown in  FIG. 5 , spring  536  may be in contact with housing  502  while grounding point  539  is in contact with indentation  529  of stepped return  526 . 
   The above described embodiments of the present invention are presented for purposes of illustration and not of limitation, and the present invention is limited only by the claims which follow.

Metadata:
Filing Date: 20080806
Publication Date: 20091229
Grant Date: 20091229
Priority Date: 20080806
Inventors: YEATES KYLE
MYERS SCOTT
DABOV TEODOR
Assignee: APPLE INC
CPC Classifications: [{"code": "H05K9/0032", "inventive": true, "first": true, "tree": "[]"}, {"code": "H05K9/0032", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 41432988