On April 2, 2015, The European Patent & Trademark Office published Apple's patent application WO2015047612 that reveals their new butterfly hinge mechanism that debuted with the new MacBook earlier in March. This is another patent fulfilled.

Butterfly Mechanism

Apple introduced the new MacBook keyboard butterfly mechanism this way:

Traditional keyboards use a scissor mechanism, which tends to wobble around the edges. This creates a lack of precision when you strike anywhere except the center of the key. We needed to reduce key wobbling for a keyboard this thin; otherwise, striking a key off-center could result in the keycap hitting bottom before a keystroke registers. So we designed an entirely new butterfly mechanism, which is wider than the scissor mechanism and has a single assembly made from a stiffer material — allowing for a more stable, responsive key that takes up less vertical space. This innovative design improves stability, uniformity, and control — no matter where you press on the key.

Apple's Patent Background

It is often desirable to reduce the size of electronic devices and minimize machining costs and manufacturing time of such devices. For example, laptops may be designed to be as small and light as possible, but input devices such as a keyboard may occupy relatively large portions of the available interior space. One way to alleviate design constrains of a keyboard is to minimize the z-stackup of key mechanisms. Accordingly, what is needed is an improved key mechanism design.

Apple Invention: Low-Travel Key Mechanisms using Butterfly Hinges

In one aspect, a key mechanism includes a butterfly hinge. The butterfly hinged key mechanism according to various embodiments enable substantially low travel distances with desired tactile response. The key mechanism uses a double wing design operative to move between a depressed position and non-depressed position. In one embodiment, a low travel key mechanism includes a keycap assembly, a support structure, and a butterfly hinge having two independently articulating wings, each wing coupled to the keycap assembly and the support structure, wherein each wing is operative to pivot about its own pivot axis during a keystroke of the key mechanism.

In another aspect, a low travel key mechanism includes a keycap assembly includes a support structure, and a butterfly hinge including two separate wings positioned adjacent to each other such that a cavity is formed between the two wings, each wing comprising a pair of pivot pins and a pair of keycap pins, wherein the pivot pins are coupled to the support structure and the keycap pins are coupled to the keycap assembly. In addition, a dome switch is secured within the cavity between the keycap assembly and the support structure, the dome switch operative to bias the keycap assembly in a first position.

In yet another aspect, a low-travel key mechanism includes a keycap assembly having a keycap and a substructure having a pair of locking pivot receiving members and a pair of sliding pivot receiving members. The key mechanism further includes a butterfly hinge having four pairs of pins, wherein a first pair of the pins is securely coupled to the pair of locking pivot receiving members and a second pair of pins is moveably coupled to the pair of sliding pivot receiving members. It includes a support structure that secures third and fourth pairs of the pins in place so that they rotate freely when the key mechanism is subjected to a keystroke, and wherein when the keycap assembly moves vertically up and down with respect to the support structure during the keystroke event, the second pair of pins moves horizontally within the pair of sliding pivot receiving members.

In another aspect, a low-travel key mechanism includes a keycap assembly, a carrier structure comprising a plate and arms fixed to opposite ends of the plate, wherein each arm includes a plurality of pivot pin retaining members, and a butterfly hinge comprising two separate wings positioned adjacent to each other, each wing comprising a pair of pivot pins and a pair of keycap pins, wherein the pivot pins are coupled to the carrier structure and the keycap pins are coupled to the keycap assembly. The carrier structure can house an electronics package that includes circuitry such as a switch, light source, or a display.

In yet another aspect, a key mechanism can include a keycap assembly, a support structure, and a half-butterfly hinge. The half-butterfly hinge includes two separate wings positioned adjacent to each other such that a cavity is formed between the two wings. Each wing includes a full or major arm and a minor arm that is shorter than the major arm.

Each wing includes a pair of pivot pins that couple to the support structure and a pair of keycap pins that couple to the keycap assembly. A coupling mechanism couples the major arms of the half-butterfly hinge together. The coupling mechanism can be, for example, a flexible or living hinge or a gear hinge.

Apple's patent FIGS. 5A-5C noted below show illustrative views of a new key butterfly hinge structure that is now found in Apple's new MacBook.

Apple's patent FIG. 20 shows us an illustrative exploded view of a key mechanism.

Apple's patent FIG. 33A shows an illustrative view of the butterfly hinge 3300 in accordance with an embodiment.  The hinge includes wings 331O and 3320 that each include pins and upstops, as shown.  Wing 331O has gear members 3315 and wing 3320 has gear members 3325.  Gear members 3315, 3325 interface with each other to form a gear hinge.

For the record, two older scissor styled keyboard key patents were also published today by the U.S. Patent and Trademark Office under numbers 20150090570 and 20150090571. 

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