PATENT DOCUMENT

Publication Number: US-10932382-B2
Application Number: US-202016820484-A
Country: US
Kind Code: B2

Title: Cold worked metal housing for a portable electronic device

Abstract:
A cold worked stainless steel bezel for a portable electronic device is provided. The bezel is secured flush to a housing to form part of the case of the portable electronic device. A brace that includes a slot for receiving a wall extending from the bezel is fixed to the housing. When the bezel engages the housing, the wall of the bezel is inserted in the slot of the brace and releasably held by a spring that engages both the brace and the wall. The bezel can be released by disengaging the spring, (e.g., using a special tool or a magnetic field). Because the bezel is manufactured from cold worked stainless steel, it is hard and resistant to impacts. Cold worked steel also facilitates manufacturing within design constraints and tolerances, and requires very little machining after manufacturing to comply with those constraints.

Claims:
What is claimed is: 
     
       1. A mobile phone comprising:
 a screen that defines a front surface of the mobile phone; and 
 a case at least partially enclosing the screen and comprising:
 an upper housing structure surrounding the screen and attaching the screen to the case, the upper housing structure defining a first curved portion of a sidewall of the case; and 
 a bottom housing structure attached to the upper housing structure and defining a second curved portion of the sidewall of the case and a back surface of the case, the first and second curved portions forming a continuous curved surface that extends around a substantial entirety of a periphery of the case. 
 
 
     
     
       2. The mobile phone of  claim 1 , wherein:
 the first and second curved portions meet at a seam; and 
 the seam is located along a middle portion of the sidewall. 
 
     
     
       3. The mobile phone of  claim 1 , wherein:
 the upper housing structure is formed from a metal material; and 
 the bottom housing structure is formed from the metal material. 
 
     
     
       4. The mobile phone of  claim 1 , wherein:
 the upper housing structure comprises a lip extending around at least a portion of the screen; and 
 the lip couples the screen to the case. 
 
     
     
       5. The mobile phone of  claim 1 , wherein:
 the front and back surfaces are flat; and 
 the continuous curved surface defined by the upper and bottom housing structures extends from the front surface to the back surface. 
 
     
     
       6. The mobile phone of  claim 1 , further comprising a retaining feature that attaches the upper housing structure to the bottom housing structure. 
     
     
       7. The mobile phone of  claim 6 , wherein the retaining feature comprises a snap feature that engages an engagement feature of the bottom housing structure. 
     
     
       8. The mobile phone of  claim 1 , wherein the upper housing structure is positioned at least partially below the screen. 
     
     
       9. A portable electronic device comprising:
 a screen defining a front surface of the portable electronic device; and 
 a case comprising:
 a bottom housing structure defining a bottom surface and a lower portion of an external sidewall of the portable electronic device; 
 and 
 an upper housing structure attached to the screen and the bottom housing structure, the upper housing structure defining an upper portion of the external sidewall, the upper portion of the external sidewall and the lower portion of the external sidewall defining a curved exterior surface extending from the bottom surface to the front surface, the curved exterior surface extending along at least three sides of the case. 
 
 
     
     
       10. The portable electronic device of  claim 9 , wherein:
 the bottom surface is substantially planar; 
 the front surface is substantially planar; and 
 the screen defines substantially all of a front exterior surface of the portable electronic device. 
 
     
     
       11. The portable electronic device of  claim 9 , wherein the curved exterior surface defines a substantially continuous curvature from the bottom surface to the screen of the portable electronic device. 
     
     
       12. The portable electronic device of  claim 9 , wherein the upper housing structure extends around an outer edge of the screen. 
     
     
       13. The portable electronic device of  claim 9 , wherein:
 at least a portion of the upper housing structure is positioned below the screen; and 
 the upper housing structure couples the screen to the bottom housing structure. 
 
     
     
       14. The portable electronic device of  claim 9 , wherein at least one of the upper housing structure or the bottom housing structure is formed from a metal material. 
     
     
       15. The portable electronic device of  claim 9 , wherein the upper portion of the external sidewall abuts the lower portion of the external sidewall to form a seam between the front surface and the bottom surface. 
     
     
       16. The portable electronic device of  claim 15 , wherein the seam extends around a perimeter of the external sidewall. 
     
     
       17. A mobile phone comprising:
 a bottom housing structure defining a back surface and a first curved portion of an external surface that extends along a first, a second and a third side of the mobile phone; 
 an upper housing structure coupled to the bottom housing structure and defining a second curved portion of the external surface that extends around the first, the second and the third side of the mobile phone; and 
 a screen defining a front surface of the mobile phone and positioned in an opening defined in the upper housing structure. 
 
     
     
       18. The mobile phone of  claim 17 , wherein:
 the first curved portion of the external surface defined by the bottom housing structure is a first portion of a curved sidewall; and 
 the second curved portion of the external surface defined by the upper housing structure is a second portion of the curved sidewall. 
 
     
     
       19. The mobile phone of  claim 18 , wherein:
 the bottom housing structure defines a flat bottom surface of the mobile phone: 
 the screen defines a flat front surface of the mobile phone; and 
 the first curved portion and the second curved portion define a continuously curved profile that extends from the flat front surface to the flat bottom surface. 
 
     
     
       20. The mobile phone of  claim 19 , wherein:
 the upper housing structure defines a ledge that extends over at least a portion of the screen; and 
 the screen is retained within the mobile phone by the ledge.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application is a continuation patent application of U.S. patent application Ser. No. 16/440,896, filed Jun. 13, 2019 and titled “Cold Worked Metal Housing for a Portable Electronic Device,” which is a continuation patent application of U.S. patent application Ser. No. 15/817,063, filed Nov. 17, 2017 and titled “Cold Worked Metal Housing for a Portable Electronic Device,” now U.S. Pat. No. 10,420,231, which is a continuation patent application of U.S. patent application Ser. No. 14/313,505, filed Jun. 24, 2014 and titled “Cold Worked Metal Housing for a Portable Electronic Device,” now U.S. Pat. No. 9,955,599, which is a continuation patent application of U.S. patent application Ser. No. 13/561,853, filed Jul. 30, 2012 and titled “Cold Worked Metal Housing for a Portable Electronic Device,” now U.S. Pat. No. 8,760,866, which is a continuation patent application of U.S. patent application Ser. No. 12/706,444, filed Feb. 16, 2010 and titled “Cold Worked Metal Housing for a Portable Electronic Device,” now U.S. Pat. No. 8,243,429, which is a divisional patent application of U.S. patent application Ser. No. 11/650,068, filed Jan. 5, 2007 and titled “Cold Worked Metal Housing for a Portable Electronic Device,” now U.S. Pat. No. 7,688,574, the disclosures of which are hereby incorporated herein by reference in their entireties. 
    
    
     BACKGROUND 
     This invention is directed to a cold worked stainless steel bezel for a portable electronic device. 
     By their very nature, portable electronic devices (e.g., MP3 players, cellular telephones) are carried around and subject to impacts and inadvertent blows to which static electronic devices (e.g., desk-top computers, televisions) are not subject. To protect the electronic systems of these portable devices, manufacturers have constructed impact resistant cases. 
     Existing cases, however, are not always easily manufactured, aesthetically pleasing, or sufficiently resistant to impacts. Accordingly, there is a need for a hard, easily manufactured and aesthetically pleasing case for portable electronic devices. 
     SUMMARY 
     A bezel for a portable electronic device case is provided. 
     The bezel is configured to be releasably engaged with a housing to form the case. The bezel includes an attachment portion that extends from the outer surface of the bezel such that the attachment portion is received in a brace fastened to the housing. The brace includes a slot configured to simultaneously receive the attachment portion and a spring. The spring is configured to engage both a lip of the brace and an engagement member of the attachment portion. The brace is secured to the housing when both the brace and the attachment portion engage the spring. When the case is assembled, the bezel and the housing are flush. 
     The bezel may be constructed from cold worked stainless steel. By cold working the steel during or prior to manufacturing of the bezel, the steel undergoes a martensitic transformation that increases the hardness of the bezel, which may provide the bezel with desired impact and scratch resistant properties. A cold working manufacturing process also allows the bezel to be manufactured with greater precision than other manufacturing processes. This limits the post-manufacturing machining required to ensure that the bezel satisfies design tolerances (e.g., the attachment portion fits snugly in the slot of the brace, and the outer surface of the bezel is flush with the housing) and reduces costs. The bezel may also be polished to provide an aesthetically pleasing finish. 
    
    
     
       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 an exploded view of a portable electronic device in accordance with an embodiment of the present invention; 
         FIG. 2  is a perspective view of the assembled portable electronic device case of  FIG. 1  in accordance with an embodiment of the present invention; 
         FIG. 3  is a wire frame perspective view of the bottom of the assembled portable electronic device case of  FIG. 2  in accordance with an embodiment of the present invention. 
         FIG. 4  is an end view of a brace and spring of the portable electronic device case of  FIG. 1  in accordance with an embodiment of the present invention; 
         FIG. 5  is a perspective view of a spring of the portable electronic device case of  FIG. 1  in accordance with an embodiment of the present invention; 
         FIG. 6  is a cross-sectional view of the assembled portable electronic device case of  FIG. 2  in accordance with an embodiment of the present invention; and 
         FIG. 7  is a flow chart of an illustrative process for assembling a bezel with a housing to form the case of a portable electronic device in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     In accordance with the present invention, a cold worked steel bezel for a portable electronic device is provided. 
       FIG. 1  is an exploded view of the elements of an illustrative portable electronic device case in accordance with an embodiment of the invention.  FIG. 2  is a perspective view of the assembled portable electronic device case of  FIG. 1  in accordance with an embodiment of the present invention. Case  100  includes bottom housing  110 , brace  210 , bezel  310 , and spring  410 . Bottom housing  110  includes substantially level plate  112  that curves away from level plate  112  to form side walls  114 . Inner surface  113  of plate  112  (i.e., the surface of plate  112  that faces the electronics of the portable electronic device) can include topographical features for receiving or supporting particular electronics elements (e.g., indentations, perforations, ridges and slots). 
     Bottom housing  110  can be in any suitable shape. For example, bottom housing  110  can be substantially rectangular, square, elliptical, circular, irregular, or any other suitable shape. In the example of  FIG. 1 , bottom housing  110  is substantially rectangular. Bottom housing  110  can include left side  120 , right side  122 , bottom  124  (not shown) and top  126 . The corners of bottom housing  110  where adjacent sides meet (e.g., right side  122  and top  126 ) may be rounded to provide a housing having a comfortable feel (e.g., no hard angles). 
       FIG. 3  is a wire frame perspective view from the bottom of the assembled portable electronic device case of  FIG. 2  in accordance with an embodiment of the invention. As shown in  FIGS. 2 and 3 , brace  210  can be fastened to bottom housing  110  to provide a support for coupling bottom housing  110  and bezel  310 . Brace  210  can be fastened to bottom housing  110  in any suitable manner including, for example, an adhesive. In this example, inner surface  115  of side walls  114  may be substantially smooth to provide a suitable surface for gluing brace  210  to side walls  114 . As another example, brace  210  and side walls  114  of bottom housing  110  may include complimenting structures (e.g., a tab extending from brace  210  and corresponding notch in bottom housing  110 ) for fastening brace  210  to bottom housing  110 . As still another example, brace  210  may be fastened to bottom housing  110  using a fastener (e.g., a screw, bolt and nut, or a clip). In other embodiments, any other suitable manner or combinations of manners for fastening brace  210  to bottom housing  110  may be used. 
     Brace  210  may be fastened to any portion of bottom housing  110 . For example, case  100  may include two braces  210  that are fastened to left side  120  and right side  122  of bottom housing  110 . As another example, braces  210  may be fastened instead or in addition to bottom  124  (not shown), top  126 , or one or more corners of bottom housing  110 . Case  100  may include several designs for brace  210 , each design configured to be fastened to a different portion of bottom housing  110  (e.g., left side  120  or right side  122 ). In some embodiments, brace  210  may be designed to be fastened to two or more sides of bottom housing  110  (e.g., brace  210  configured to be fastened to top  126 , the top portion of left side  120 , and the top portion of right side  122 ). 
     Brace  210  can include any suitable structure for fastening to bottom housing  110  or for engaging bezel  310 .  FIG. 4  is an end view of a brace and spring of the portable electronic device case of  FIG. 1  in accordance with an embodiment of the invention. As shown in  FIG. 4 , brace  210  includes smooth lower portion  212  and irregular upper portion  220 . Lower portion  212  may be a curved surface whose curvature matches that of side walls  114 . The matching curvature may allow lower portion  212  to be fixed tightly to the inner surface of side walls  114  (e.g., using an adhesive). Brace  210  also includes upper lip  238  that extends from the periphery of brace  210  and is configured to be received by notches  116  in side wall  114 . 
     Upper portion  220  may include several elements for engaging bottom housing  110  and bezel  310 . In the example of  FIG. 1 , upper portion  220  includes interior wall  221  and exterior wall  230  (with respect to the center of the portable electronic device) that define U-shaped slot  225 . Interior wall  221  may be a continuous or discontinuous wall that includes apertures  222  and cutouts  224  (shown in  FIG. 3 ). Cutouts  224  may be aligned with apertures  334  of bezel  310  (and with apertures  414  of spring  410 ) such that case  100  to align brace  210  and bezel  310  when case  100  is assembled. In some embodiments, cutouts  224  and apertures  334  (and apertures  414  of spring  410 ) may be configured to receive fasteners (e.g., screws) to secure case  100 . The surfaces of walls  221  and  230  that define slot  225  may be substantially smooth so as to receive bezel  310  tightly in slot  225 . 
     Exterior wall  230  may be a discontinuous wall that is slightly recessed from outermost edge  214  of lower portion  212  (shown in  FIG. 1 ). Exterior wall  230  may include several wall elements  232  that are separated by free space  234 . Each wall element  232  includes lower lip  236  and upper lip  238  (with respect to lower portion  212 ) that extend out from each wall element  232  towards bottom housing  110  and away from the electronics contained within case  100 . Lower and upper lips  236  and  238  may be configured to extend into notch  116  of side wall  114 . Lower and upper lips  236  and  238  define recessed portion  240  of wall elements  232 . 
     As shown in  FIGS. 3 and 4 , brace  210  may include ribs  242  extending parallel to wall elements  232  from edge  214  in free space  234 . Ribs  242  may define a U-shaped enclosure for receiving and/or capturing spring  410 . 
     Spring  410  may be used to releasably couple brace  210  to bezel  310 .  FIG. 5  is a perspective view of a spring of the portable electronic device case of  FIG. 1  in accordance with an embodiment of the invention. As shown in  FIGS. 1 and 5 , spring  410  may include elongated strip  412  that features apertures  414  at intervals calculated to coincide with features of bezel  310  (described below in more detail in connection with  FIG. 6 ). Spring  410  includes several U-shaped cantilevers  420  that are distributed along strip  412 . 
     Spring  410  may be configured to be received in brace  210 . In particular, elongated strip  412  may be received in recessed portion  240  such that a portion of strip  412  is captured in ribs  242 . The distance between lower and upper lips  236  and  238  (i.e., the height of recessed portion  240 ) and the width of strip  412  may be selected such that strip  412  may fit securely between lips  236  and  238  (e.g., in a press fit relation), and ribs  242  may further be designed secure and maintain strip  412  in recessed portion  240  (e.g., with a notch for securing strip  412 ). Spring  410  may further be secured in brace  210  by the proximity of side wall  114  of bottom housing  110 , which borders spring  410  on the side that is not adjacent to brace  210 . 
     Cantilevers  420  may be distributed along spring  410  such that cantilevers  420  fit within free space  234  of brace  210 . As shown in  FIG. 4 , which is an end view of brace  210  and spring  410 , cantilevers  420  are attached to lower edge  422  of strip  412 , and bent toward upper edge  423  of strip  412  such that a front or rear view of spring  410  shows a U-shape. Tip  424  of cantilever  420  is a free tip that may be configured to bend elastically in response to an external force on cantilever  420  (e.g., as a cantilever spring). For example, cantilever  420  may bend when bezel  310  is pressed into bottom housing  110  and brace  210 . Each cantilever  420  may include an aperture  426 . 
     When spring  410  is placed in brace  210 , cantilevers  420  extend from exterior wall  230  towards interior wall  221  such that cantilever  420  takes the place of wall elements  232  in free space  234  ( FIG. 1 ). Apertures  426  may be configured to receive tabs or protrusions of bezel  310  (e.g., engaging member  336 ) such that bezel  310  engages spring  410 . 
     Bezel  310  may be configured to be placed over bottom housing  110  to assemble case  100 . As shown in  FIGS. 1 and 6  (described in more detail below), bezel  310  may include base structure  312  that provides the outer upper surface of case  100 . Inner surface  320  of structure  312 , shown in  FIG. 6 , includes steps  322  and  324  for supporting electronic or other components of the portable electronic device. For example, step  322  may be configured to support screen  350  and step  324  may be configured to support reflective layer  352 . Inner surface  320  may include any other suitable feature for supporting one or more components of the portable electronic device (e.g., an input component such as a scroll wheel). 
     Lower surface  326  of base structure  312  is substantially level and configured to be placed against the top surface  115  of wall  114  when bezel  310  is engaged with bottom housing  110 . Both lower surface  326  and top surface  115  may be designed to remain in close contact when case  100  is assembled. For example, lower surface  326  and top surface  115  may include complimentary features configured to unite and provide a tight fit. Bezel  310  may be constructed using methods and materials that allow for very tight tolerances in all directions (e.g., x, y and z directions), which may ensure that bezel  310  is flush with bottom housing  110  when case  100  is assembled. 
     Outer surface  314  of base structure  312  may be a curved structure configured to be flush with side walls  114  when bezel  310  engages bottom housing  110 . Outer surface  314  may be polished to provide an aesthetically pleasing finish to bezel  310 . Outer surface  314  may be polished in any suitable manner including, for example, with an abrasive disk having 120 or 240 grit silicone carbide, a grinding disk or cloth having 3 or 9 μm diamond suspension, or a cloth having 0.05 μm colloidal silica or alumina suspensions. 
     Attachment portion  330  extends from base structure  312  towards bottom housing  110  and brace  210 . Attachment portion  330  includes wall  332  that extends beyond lower surface  326 . In some embodiments, wall  332  is not continuous, but includes discrete segments distributed around the periphery of bezel  310 . To provide a strong connection between bezel  310  and brace  210 , wall  332  may be continuous in the sections of attachment portion  330  that are configured to be placed in slot  225  of brace  210 . Attachment portion  330  may include a plurality of apertures  334  that are aligned with apertures  414  of spring  410  and cutouts  224  when case  100  is assembled to assist in aligning brace  210 , bezel  310  and spring  410 . In some embodiments, apertures  334 ,  414  and cutouts  224  may be configured to receive a fastener (e.g. a screw) for securing bezel  310  to bottom housing  110 . 
     The sections of wall  332  that are configured to be placed in slot  225  may include one or more engaging members  336 . Engaging members  336  may be tabs or other such elements that extend from wall  332  toward the exterior of the portable electronic device. Each engaging members  336  may include angled tip  338  and level tab  340  for engaging at least one of apertures  426  and  414  of cantilever  420 . 
       FIG. 6  is a cross-sectional view of the assembled portable electronic device case of  FIG. 2  in accordance with an embodiment of the present invention. To engage bezel  310  with brace  210 , spring  410  is first placed and captured in brace  210 . Bezel  310  may then be pressed into brace  210  such that wall  332  extends into slot  225 . When bezel  310  is pressed into bottom housing  110 , wall  332  is inserted in slot  225  and engaging members  336  press cantilevers  420  into free space  234  to create enough room to fully occupy slot  225 . Angled tip  338  may be configured to progressively apply a force on cantilever  420  to progressively deflect cantilever  420  as bezel  310  is pushed into housing  110 . Once wall  332  has been fully inserted in slot  225 , aperture  426  is aligned with tab  340  (e.g., by designing the placement of aperture  426  appropriately). Tab  340  then extends into aperture  426  and ceases to apply a force on cantilever  420 , which springs back to its equilibrium position in free space  224 . Tab  340  then engages aperture  426  and prevents wall  332 , and thus bezel  310 , from disengaging brace  210  unless tab  340  is released from spring  410 . 
     To disengage bezel  310  from brace  210  and bottom housing  110 , an external force may be applied to spring  410  that forces cantilevers  420  to bend away from wall  332  such that engaging members  336  are released from apertures  426 . Once engaging members  336  are released, bezel  310  may be removed from slot  225 . The external force may be applied to spring  410  in any suitable manner. For example, a tool may be configured to be inserted in case  100  to engage cantilever  420 . As another example, if cantilever  420  is made from a material that is subject to a magnetic force in the presence of a magnetic field, a magnetic field (e.g., provided by a magnet) may provide an external force for disengaging engaging members  336 . Suitable materials that are operative to move in the presence of a magnetic field include ferrite materials such as, for example, cold worked 304 stainless steel or 404 stainless steel. 
     The elements of case  100  may be manufactured using any suitable manufacturing process and using any suitable material. For example, bottom housing  110  may be formed using one or more of casting, molding (e.g., power metallurgy molding), forging, machining, rolling, extrusion, milling, or any other suitable manufacturing process. Bottom housing  110  may also be finished using any suitable manufacturing process including, for example, polishing, buffing, burnishing, grit, shot or sand blasting, tumbling, wire brushing, flame blasting, electropolishing, or any other suitable process for finishing bottom housing  110  (e.g., to provide an aesthetically pleasing appearance). Bottom housing  110  may be constructed from any suitable material such as, for example, aluminum, steel, iron alloys, titanium, magnesium, copper alloys, other metallic alloys, plastics, polymers, ceramics or composites. In one embodiment, bottom housing  110  may be constructed from aluminum. 
     Brace  210  and spring  410  may be constructed using one or more of the manufacturing processes listed above in connection with forming bottom housing  110 . In addition, brace  210  and spring  410  may be constructed using one or more of the materials listed above in connection with bottom housing  110 . In one embodiment, brace  210  may be made from a magnesium and spring  410  may be made from stainless steel (e.g.,  404  series stainless steel). 
     Bezel  310  may also be constructed using one or more of the manufacturing processes and one or more of the materials listed above in connection with forming bottom housing  110 . In one embodiment, bezel  310  may be constructed using stainless steel such as, for example, 304 stainless steel. 304 stainless steel may be hardened by cold work, and enable bezel  310  to withstand heavy loads and impacts (e.g., caused by dropping the portable electronic device). 
     304 stainless steel is an austenitic steel, which is a non-magnetic solid solution of iron and carbon. The iron and carbon molecules are arranged in a face-centered cubic (FCC) lattice structure that contains a high proportion of carbon as compared to ferrite, which has a body-centered cubic lattice structure. The higher density of carbon atoms in austenitic steel exhibits a more durable and harder material than ferrite. Austenitic steels may contain a maximum of 0.15% carbon, a minimum of 16% chromium and sufficient nickel and/or manganese to retain an austenitic structure (i.e., FCC lattice structure) at all temperatures from the cryogenic region to the melting point of the alloy. Without the addition of sufficient nickel and/or manganese, the FCC lattice structure is unstable and may revert to a BCC lattice structure (i.e., revert from austenitic steel to ferrite). 304 stainless steel has a composition of 18% chromium and 8% nickel, commonly known as 18/8 stainless steel, and is one of the most common grades of stainless steel. 
     Some metals may be strengthened by heat treatment, which is typically used to manipulate the properties of a metal by controlling the rate of diffusion of particles in the metal, and the rate of cooling within the microstructure. Austenitic steels such as 304 stainless, however, cannot be strengthened by heat treatment alone. Instead, two other methods may be used: plastic deformation of the steel, and refining the grain size of the steel. 
     Plastic deformation of a material is an irreversible deformation of the material. In the particular case of austenitic steel, a plastic deformation causes an irreversible modification of the crystal structure of the steel. The modification creates irregularities in the lattice structure of the crystals, which are called dislocations (e.g., edge and screw dislocations). As more dislocations are introduced in the material by further plastic deformation (e.g., by the formation of new dislocations and dislocation multiplication), the strain fields of adjacent dislocations overlap and gradually increase the material&#39;s resistance to additional dislocation. This causes the material to become harder. This effect is known as strain hardening or work hardening. 
     One process for hardening the material by plastic deformation is cold work, which is the process by which material is hardened as a result of plastic deformation of the material at low to moderate temperatures. Cold work may be provided by any suitable process that is performed at low temperatures such as, for example, extrusion, drawing or coining. 
     Plastic deformation of an austenitic steel, such as 304 stainless steel, may induce martensitic transformation. The martensitic transformation is the transformation of austenite in the austenitic steel to martensite. Austenite and martensite have an identical chemical composition, and very similar crystal structures, where the cubic structure of austenite is distorted by interstitial atoms of carbon that do not have time to diffuse out during the process causing transformation (e.g., plastic deformation or quenching) form martensite. Martensite is thus supersaturated with carbon. The carbon atoms cause the martensite crystal structure to stretch, which stretches the crystal lattice of the metal and creates additional strain, therefore creating additional strain fields that combine with those of the dislocations caused by the plastic deformation to harden the material. 
     For plastic deformation to be effective to form martensite, it must occur below the martensitic deformation temperature of the material. Because the martensitic deformation temperature (M d ) is dependent on chemistry and initial grain size, it is difficult to determine, and an approximation is used instead. One suitable approximation is M d30 , which varies similarly to M d . M d30  is the temperature at which 50% of the microstructure would transform to martensite given a 30% true strain. 
     The grains in an austenitic steel may be refined by annealing the steel after cold work. Annealing the metal causes the crystals in the material to recrystallize and nucleate and grow larger grains. Dislocations in the crystal lattice caused by cold work disappear as new grains are formed. There is a point, however, where a material may be cold worked at a level where there are too many dislocations for recrystallization using annealing to be practical. 
     The annealed material may be cooled in any suitable manner including, for example, cooled in the furnace (i.e., full anneal heat treatment), in air (i.e., normalizing heat treatment), or quenched (e.g., quickly cooled). The metal may be quenched, for example, with forced air or gas (e.g., nitrogen), in oil, polymer dissolved in water, water, or brine. Quenching may cause the introduction of martensite in the austenitic steel, which is harder than austenite. The steel must be rapidly cooled through its eutectoid point, the temperature at which austenite becomes unstable, for martensite to be introduced. 
     The resulting grain size and distribution in the material may depend on the amount of cold work prior to annealing (e.g., the number of dislocations in the steel prior to heat treatment), the annealing temperature, the duration the metal is left in the furnace, and the cooling temperature. For example, the longer the steel is left in the furnace, and the higher the furnace temperature, the more new grains are nucleated and the more dislocations are eliminated (e.g., leading to a more ductile steel). As another example, if the steel is rapidly cooled through its eutectoid point, martensite may be introduced (e.g., hardening the steel). 
     304 stainless steel may be polished to provide an aesthetically pleasing surface (e.g., aesthetically pleasing outer surface  314  of base structure  312 ). The steel may be polished using a sequence of polishing steps at different grits (e.g., higher grits as the sequence progresses). 
     Bezel  310  (and spring  410 ) may be manufactured from 304 stainless steel using a cold worked process which, as discussed above, provides high strength. But cold working also provides for very precise constraints in all directions (e.g., x, y and z directions) without additional manufacturing processes. This combination of properties may make cold working a preferable process for manufacturing bezel  310 . For example, cold working may be substantially cheaper than machining, which includes a cost for the skilled machining labor. As another example, a cold worked metal component may be stronger than a die cast metal component, as it is difficult to cast stainless steel (e.g., alloys tend to pull away from the steel, leaving a weaker structure). In addition, die casting may be imprecise, and require post-casting machining to resize components within the design tolerances. 
     For bezel  310  to be perfectly flush with bottom housing  110 , bezel  310 , spring  410  and housing  110  may be manufactured with tight tolerances. In particular, wall  332  and tab  340  may be manufactured precisely so that wall  332  fits flush in slot  225  and tab  340  engages at least one of apertures  426  and  414 . Also, lower surface  326  of base structure  312  of bezel  310  and surface  115  of wall  114  of bottom housing  110  may be manufactured precisely so that lower surface  226  and surface  115  are flush, and outer surface  314  of bezel  310  is flush with the outer surface of wall  114 . Manufacturing at least bezel  310  (and bottom housing  110 , brace  210  and spring  410 ) using a cold work process provides a near perfect net component that only requires minimal machining or touching up to satisfy the tight tolerance requirements of the component. 
     The following flow chart will serve to illustrate a process involved in some embodiments of this invention.  FIG. 7  is a flow chart of an illustrative process for assembling a bezel with a housing to form the case of a portable electronic device in accordance with an embodiment of the present invention. Process  700  begins at step  702 . At step  704 , a brace is affixed to the inner surface of the housing of the case. The brace may be affixed using any suitable approach including, for example, an adhesive or a fastener. The brace may include a rib for securing a spring, and a slot for receiving the bezel. At step  706 , a spring is inserted and secured in the brace. The spring may be configured to fit in a rib of the brace such that the spring remains positioned within the rib. In some embodiments, the order of steps  704  and  706  may be reversed. 
     At step  708 , the bezel is placed over the brace, and the walls of the attachment portion of the bezel are aligned over the slot of the brace. At step  710 , the bezel is pressed into the brace such that the wall is inserted in the slot of the brace, and such that at least one engaging member of the bezel engages an aperture in the spring. The case is assembled once the spring simultaneously engages the brace and the bezel. Process  700  then ends at step  712 . 
     In another embodiment, the assembly process may be performed as follows. The spring may be assembled to the brace. The spring/brace combination is assembled to bezel, which may cause the spring to be captured between the bezel and the brace. 
     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: 20200316
Publication Date: 20210223
Grant Date: 20210223
Priority Date: 20070105
Inventors: ZADESKY, STEPHEN P.
HOBSON, PHILLIP M.
TAN, TANG YEW
Assignee: APPLE INC
CPC Classifications: [{"code": "H05K5/15", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05K5/15", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04M1/0252", "inventive": true, "first": true, "tree": "[]"}, {"code": "Y10T29/477", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y10T29/18", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y10T29/49826", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K5/0217", "inventive": true, "first": true, "tree": "[]"}, {"code": "Y10T29/49826", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y10T29/18", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04M1/0252", "inventive": true, "first": false, "tree": "[]"}, {"code": "Y10T29/477", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04M1/0252", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05K5/0217", "inventive": true, "first": true, "tree": "[]"}, {"code": "Y10T29/49826", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K5/0013", "inventive": true, "first": false, "tree": "[]"}, {"code": "Y10T29/477", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y10T29/18", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K5/0213", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04M1/0252", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05K5/0243", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05K5/0018", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 39594045