Apple has won a patent (number 7,688,574) from the US Patent & Trademark Office for a cold worked metal housing for a portable electronic device. Said device seems to be the iPad.

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. The portable electronic device may include a personal media device, a mobile telephone, or any other suitable device or combination thereof. The inventors are Stephen P. Zadesky, Philip M. Hobson and Tan Tang Yew.

Here's Apple's background and summary of the invention: "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.

"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."

-- Dennis Sellers