ITT discrete snap-action
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| Manufacturer | ITT |
|---|---|
| Inventor | Michael Muller, Reed A. Palmer, Harry R. Marker |
| Sense method | Metal contact |
| Actuation force | 75 gf |
| Pretravel | 0.100 in (2.54 mm) |
| Total travel | 0.160 in (4 mm) |
| Patents | US 4316066 (1980) |
ITT snap-action is a discrete modular switch from ITT that is not presently known to have been observed. The patent covers both discrete switch modules, and a non-discrete array, ITT snap-action array, used in the Apple II. The design provides hysteresis and tactility; it is also likely to generate audible feedback, but this is not mentioned in the patent. The actuator leaf is also similar to that used in Fujitsu Leaf Spring.
Description
The design is reminiscent of Fujitsu Leaf Spring. The slider bears down on a leaf spring that serves as both the actuator leaf and the return spring, The patent notes that the "[use] of coil springs (which are awkward to handle and tend to tangle during assembly operations) is avoided, and the need for a separate keystem return spring is eliminated." (The term keystem in the patent refers to the slider.)
The switch terminals are twist-locked in place using a 45° turn. The snap action spring is held in place by one terminal, and makes contact with the top of the other terminal.
The patent gives total travel of 0.160 in (4 mm) and 0.06 (1.5 mm) of overtravel. Actuation force is 75 grams, and preload is 30 grams. The snap-action spring containing the switch contacts is closed at 125 grams, but mechanical advantage is used to reduce the force required from the operator.
The tactile peak provides—according to the patent—a 5 to 10 gram reduction in force.
Datanetics DC-70
ITT snap-action is a candidate switch for Datanetics DC-70 series. ITT snap-action array was used by The Keyboard Company for Apple II keyboards; Mike Muller is one of the inventors, and also the founder of The Keyboard Company, and Datanetics's takeover by ITT may explain why the patent for DC-70 went to ITT, while it was also used by Mike Muller's company.
Keyboards
None known to date.
