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Omron B3G series

Omron B3G series is the switch series that preceded its well-known successor, B3G-S series. Discontinued in December 1987, it is possible that it has yet to be sighted by the keyboard community. The design of the switch is similar in some ways to first-generation SMK switches, with a vertical contact that rests against a crossbar when the switch is closed.

Having put in a request to David Luna at Quest Components in the US, he was (very promptly!) able to obtain an Omron catalogue page documenting the B3G series, with a cutaway diagram of the switch (from “1984/7”):

The catalogue page provided me for the first time with a clear illustration of the switch, which I recognised — it turned out to be the switch that I had encountered a year or two ago while trawling through switch patents. There are three patents that correspond to the latching switch from B3G series:

Patent Title Filed Published
US 4495391 A Alternate on-off switch mechanism 1982-12-29 1985-01-22
EP 0083508 B1 Contact structure for an alternate switch mechanism 1982-12-30 1987-05-06
US 4647742 A Alternate on-off switch mechanism 1984-07-16 1987-03-03

All three patents were given a priority date of 1982-12-29, giving a rough indication of the age of the switch. Between the specification and the patents, it is possible to get a fairly good idea of what the switch looks like.

What is not know is how far into the lifetime of B3G series this switch was introduced.

B3G series was discontinued in favour of B3G-S on 1987-12-01 (PDF document).

Many thanks of course to David for the catalogue page, and to Sandy with help with translation (all Omron PDFs are in Japanese).