The touchscreen keyboards on Apple's iOS devices are great space savers, as they're never around when you don't need them. For all the great leaps forward Apple has made with Multi-Touch technology over the past five years in both its iOS devices and Mac touchpads, its physical keyboards still use some well-established and comparatively old technology. Apple has apparently turned its eye on the traditional mechanical keyboard and tried to figure out ways to shrink that down, too.
AppleInsider discovered a patent filed in August of 2010 that shows Apple is brewing up ideas to shrink its physical keyboards even farther than it has already. Current keyboards rely on a somewhat elaborate system consisting of a "scissor" mechanism that keeps keys suspended over a rubber dome switch, which when pressed, completes a path on the underlying keyboard circuitry, sending that key's signal to the computer's logic board. Apple has been thinking of ways to improve that system.
All keyboard design is fundamentally about a spring-loaded pressure switch completing an electrical circuit. When pressure is applied -- usually via an intentional keypress, sometimes by a wandering cat -- the switch completes a circuit and sends an input signal. When pressure lets off, the circuit breaks. Older keyboards relied on actual spring mechanisms, which is why those older keyboards were quite large, heavy, and loud (clackety clackety CLACK).
Some companies briefly experimented with membrane-style keyboards, but in a way those are almost worse than touchscreen keyboards; they have the same suboptimal level of tactile feedback to the user, but they also generally require more pressure to operate than a capacitive touch-style keyboard.
Apple's proposed new keyboard design replaces the currently prevalent "scissor" style mechanical lever with a setup that reminds me of a device that pre-dates even the original typewriter: a telegraph machine. Like one of the old-style telegraph generators, the assembly consists of a key at the end of a long lever which, when pressed, completes a circuit and sends a signal. The support lever in Apple's proposed design would be made of a flexible material with good tensile feedback to the user.
Design for an electric Morse key, patented in 1837
The upshot of this design? Traditional spring-loaded keyboards required a key travel of between 4 and 5 millimeters, with the "scissor" style setup in current notebook and portable keyboards requiring a smaller travel length of 1.5 to 2 millimeters. Apple's patent allows for a keyboard that needs only 0.2 millimeters of key travel.
This obviously has implications for the design of Apple's notebooks. So far the keyboard itself hasn't been an especially important constraint on the overall thickness of Apple's notebooks -- battery design and the need to keep motherboards from spontaneously combusting has been more of a factor -- but it's not hard to envision a point where that 1.3 to 1.8 millimeters of potential space savings does indeed come in handy for an even thinner version of the MacBook Air.