Click leaf

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Click leaf

A click leaf is a folded metal spring used to provide a click sound and tactility in many keyswitches. It is referred to as the tactile leaf in tactile keyboards.

Description

The oldest keyboard known to use a clicky leaf is the Fujitsu N860-8282, produced in 1979. It is subsequently used in Alps SKCL/SKCM series switches and switches derived from that design. The switch utilizes a folded sheet of metal, placed down one side of the switch. One half rests vertically against the inside of the switch, and the other half protrudes diagonally forward under the slider. Small downward hooks snag the slider as it is depressed, impeding its progress; when the slider is pressed far enough, the slider clears the hooks and drops rapidly.

This rapid drop provides the tactility in all click and tactile leaves. In click leaves, the whole spring is pulled forward, and snaps back once the slider clears the hooks. The impact of the spring returning to its vertical position against the inside of the switch provides the click. A small raised area along the rear half of the spring provides a controlled impact point for the click.

Tactile leaves, typically only found in Alps SKCL/SKCM and SKBL/SKBM series switches, have two additional side folds at the top, that stop the spring from being pulled forward. This modification allows the spring to provide a similar tactile feel, without noise.

Variations

Metal

More click leaves are made of steel than other materials. A number of switches, in particular Alps clones and copies, use a copper-coloured metal; Hua-Jie and Xiang Min cite this as being "PBS", seemingly a region-specific abbreviation for phosphor bronze (Hua-Jie give the English name as "phosphor copper", but phosphor bronze is specifically used for springs amongst other things).

Design

Most switches with tactility springs are clicky switches. Alps produced a variant of the leaf that would offer tactility without a click. A few other manufacturers produced tactile switches with tactile leaves that did not follow the Alps design. Tactile SMK second generation switches have a rounded base to the slider on one side, to allow the slider to pass the hooks on the leaf without pulling it forwards; this achieves considerable tactility without needing to change the leaf shape significantly. Tai-Hao make APC switches with leaves almost identical to those in their clicky switches, but with longer, straighter hooks; again, this allows the slider to pass more easily, although without anywhere near as much tactility as SMK switches (it's easy to become confused as to which are their linear and which are their tactile switches).

Width

Wide leaf

Alps SKCM switches introduced a steel click leaf the width of the inside of the switch. Tactile leaves have parallel sides, while click leaves have cutout areas at the top, forming a broad, inverted "T". Some Alps clone switches including early APC switches and Simplified Alps Type IV switches had wide click leaves, before moving to narrow leaves.

Narrow leaf

Many Alps clones, including most produced today, use narrow click leaves. These are sometimes referred to as a "mantis foot" leaves. In most cases, these are made from phosphor bronze. Narrow leaves were never found in any Alps switch. The SMK Alps mount switch also used narrow leaves, but they were made of steel.

Gallery