Contact module
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This article requires additional photographic illustration — full Alps switchplate disassembly for example |
A switchplate or switch plate is the keyboard community term for a fully self-contained contact assembly in metal leaf contact switches.
Contents
Description
The switchplate is a plastic assembly that contains and supports the electrical contact plates and the actuator leaf. After removing the top of the switch, the contact assembly is still fully supported.
The Alps switchplate design appears to have originated in the Alps vintage tee mount switch, and was adopted wholesale into the Alps SKCL/SKCM series switches with no discernable alteration. The Alps design comprises a complex sandwich of metal and plastic layers, hence the term "complicated" when referring to Alps switches. Alps SKBL/SKBM series (simplified Alps) and Alps clones replaced this whole assembly with bare switch terminals, using various slots and grooves in the upper shell for support. Simplified Alps switches are fairly easy to reassemble, but with many clones switches, forcing the thick contact plates down the fine grooves in the upper shell is fiddly and taxing.
Switchplate
Grey full-height switchplate from an early Alps CM switch
Simplified clone switch
Simplified contact mechanism in an early APC switch; the front contact plate is still the full width of the switch
Usage
Switches that use switchplates include:
- Alps vintage tee mount
- Alps SKCL/SKCM series
- Mitsumi Alps clone
- Omron keyswitch
- Omron Alps-style switch
Gallery
Alps vintage tee mount
Alps vintage tee mount switches appear to have exclusively used long black switchplates, as these were adopted into the SKCL/SKCM switches.
Alps vintage tee mount switchplate, together with the slider and return spring
Rear view of the long Alps switchplate
Alps SKCL/SKCM series
Long switchplates
Complicated Alps switches initially used long black switchplates. The colour changed twice, first to grey, and then to translucent white. These three variants appear to have maintained the same internal construction.
Full disassembly: top view of parts (rear to front)
Full disassembly: bottom view of parts (front to rear)
Short switchplates
Around 1988, the switchplate height was reduced, and the internal construction was altered. The large foil membrane was reduced to a smaller strip, and instead of being a loose fit, it was crimped into two holes in the front terminal. The switch shell gained two small posts on the inside to support the switchplate which now sat a short distance above the bottom of the switch.
Full disassembly of a short switchplate is extremely difficult, as the foil membrane is fragile and likely to tear if an attempt is made to remove it from the terminal.
Short and long switchplates
Long and short switchplate front mounting blocks
Front view
Rear view
Rear contact/terminal removed to reveal the separator and foil membrane
Foil membrane comparison from short (left) and long (right) switchplates
Foil membrane is fragile
Omron B3G-S series
Omron B3G-S series switchplates have an actuator leaf almost identical to Alps Electric's design, but the internals are completely different, with simple metal leaf contacts. Additionally, the switchplate is sealed and cannot be safely disassembled.
Switchplate opened up
Switchplate opened up
