Editing Tactility (section)

==Mechanisms==
There are many different approaches to providing a tactile feel. Major implementations of tactile feel are detailed below. Some of these types also generate audible feedback, which is noted as applicable.

===Obstructing metal leaf===
{{Main|Click leaf}}

An obstructing metal leaf is a [[leaf spring]] bearing kinks that obstruct the passage of the [[slider]]. In order for the slider to pass the leaf spring, the leaf spring must be deflected out of the way; the kinks in the metal cause the slider to catch on the leaf spring, requiring a sharp increase in force to clear the obstruction.

This leaf spring can be a dedicated part, one of the switch contacts, or the actuator leaf. [[Alps SKCM Brown]] and [[Omron B3G-S White Tactile]] in particular use a modified actuator leaf placed on the opposite side of the slider. Some [[Mitsumi standard mechanical]] switches have a kinked actuator leaf instead, while [[Siemens STB]] switches use the switch contacts as the tactile leaf.

<gallery widths=250 heights=187>
File:Omron B3G-S white tactile -- actuator and tactile leaves, top.jpg    | Omron B3G-S White Tactile actuator and tactile leaves
File:Omron B3G-S white tactile -- actuator and tactile leaves, bottom.jpg | Omron B3G-S White Tactile actuator and tactile leaves
File:Mitsumi std -- leaf comparison.jpg                                   | Mitsumi standard mechanical standard and tactile switchplates
</gallery>

This approach may optionally provide audible feedback. If the leaf is folded back against itself, and allowed to be pulled forwards and released by the slider, a sound is generated as the spring snaps back into its rest position. A leaf spring in this configuration is called a '''click leaf'''.

The effectiveness of tactile leaves is debatable. The most successful non-audible implementations appear to be [[Alps SKCM Orange]], [[Alps SKCM Brown]], [[Alps SKCM Green]] and [[SMK second generation]]. When a click sound is permitted, the tactile feel is always sharpened and strengthened. A compromise implementation is [[Alps SKFS White]], which uses a click leaf but has an empty space behind it to prevent impact occurring when the leaf is released; this gives a stronger tactile response without the accompanying sound.

The official force curves for 1994 Alps switches depict the difference between Alps SKCM Green and all other types of SKCM (tactile) switches, showing how the force curve of green differs:

[[File:Force graph--Alps tactile 1994.svg|centre]]

The force curve of Alps SKCM Brown is confirmed to be the same as what Alps depicted for Alps SKCM Green.<ref name="plotly_brown" />

===Non-linear slider surface===
[[Cherry MX]] switches in particular are notable for a non-linear engaging surface on the slider. A protrusion from this surface provides a non-linear feel without any accompanying sound. Generation of sound has not been achieved with this design. Older Cherry switches are also known to be tactile, but only [[Cherry M9]] has a confirmed tactility implementation, which is a related approach.

===Inverting metal leaf===
{{Main|Stacked spring}}

A number of switch designs use a "plate spring", a leaf spring that is bowed upwards in its resting state. As pressure applied to the top of this leaf, it eventually inverts such that it is now bowed downwards. This inversion is an instantaneous event, and can generate a loud sound. The total motion of this inverting action is comparatively low, so a [[motion reducer]] is required, typically a helical spring placed between the slider and the plate spring. This "stacked spring" arrangement provides the desired full travel as well as [[hysteresis]].

===Rubber dome===
{{Main|Rubber dome|Buckling rubber sleeve}}

A rubber dome provides a number of functions, including actuation (when conductive), tactile feel, and sealing (when implemented as a rubber sheet). In terms of tactile feel, a rubber dome functions similarly to an inverting metal leaf, but the dome collapses instead of inverts.

When buckling rubber is added to an existing switch mechanism to provide tactility (as with [[ITW magnetic valve]], [[BTC foam and foil]], [[Key Tronic foam and foil]] and [[SMK spring over membrane]]) the dome has a hole in the centre; this design is referred to as "buckling rubber sleeve" as the rubber part does not form a complete dome.

===Bowed helical spring===
There are multiple ways to use a [[helical spring]] to generate tactility.

[[Buckling spring]] switches involve a laterally bowed, vertically orientated helical spring being pressed downwards. When a certain threshold is reached, the spring buckles, or snaps outwards suddenly. The containing chamber ("barrel") that guides the slider obstructs the path of the spring, causing a collision and a corresponding sound.

[[File:Force graph--clicky--capacitive buckling spring.svg|centre]]

[[ITT ETL18]] switches place the helical spring horizontally across the switch, which is assumed to be bowed upwards within its slot. The spring runs through the slider, and pressing down on the slider causes the spring to be first compressed before the slider can pass, after which the spring is now exerting force downwards on the slider. In effect this is a similar principle to stacked spring, but with greater travel and using only a single spring.

[[Mitsumi standard mechanical]] switches and most tactile [[Mitsumi miniature mechanical]] switches achieve tactility using a similar principle. Here, instead of the spring passing through the slider, the spring is held by the slider and a raised nub within the switch presses on the slider instead. This approach results in a much rougher feel, while ETL18 is very smooth.