Membrane Keyboard History?

Henro88

25 Sep 2019, 23:15

Hi guys. I work in the membrane switch industry, and I'm trying to find information online about the first membrane keyboards. It's surprisingly hard to find! My own company's products go back over 30 years, so no one in R&D has been around long enough to really know what was going on back then.

The information I'm looking for is:

- Who can claim to have made the first membrane keyboards in the world? In the US? In Japan?

- What were the conductive inks these keyboards used? Who was making conductive ink back then?

- Were there other membrane switch products that preceded the keyboards and led to their development?

Looking over the detailed information people are sharing here, I feel like one of you must know some or all of this information. Any help, leads, or suggestions you can offer are also appreciated!

Thanks!

Findecanor

26 Sep 2019, 00:00

I'm not sure that the first membrane keyboards even used conductive ink.
Many calculators from the 1970s have switches made of domes of sheet metal in-between plastic layers.
If I would speculate, I would guess that those sheets of metal could have been "cut" through photo-etching (I know that method is used to construct precision saws for plastic model making, anyway). The top layer of plastic has adhesive, and is similar to packing tape.

As for the membranes printed with ink, I would also try to find leads to the inventor of the "flexible circuit board".

Henro88

26 Sep 2019, 13:02

Hey, thanks for the response.

The news report from the 80's that I found online indicated that at least by the 1980's they were using conductive ink, but there was no indication of when that started or whose ink it was. The conductive material we use wasn't even invented until the 1950's, so it would stand to reason that the flexible version wasn't around in the 1960's - you're probably right that they used etched metal sheets. I know for a fact that the ink we work with goes back to at least 1981.

I forgot that this site has a wiki of its own - maybe there is an entry for inks. I'll check it out.

Thanks!

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ZedTheMan

26 Sep 2019, 16:04

If I had to guess the first membrane designs
using conductive ink were more likely to be spring over membrane, and more likely than not on a calculator than a full computer or terminal due to the price involved in those at the time. I'll do a quick scan over some of the wiki and get back to you with what I find.

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ZedTheMan

26 Sep 2019, 18:40

wiki/Datanetics_elastic_diaphragm_array
This is the earliest mention I could find of a membrane on the wiki, though, it isn't exactly the same as a modern membrane. No conductive pads or whatnot. See the version without actuation module.

Henro88

28 Sep 2019, 17:31

Hey, thanks for digging through the wiki for me. I did look a bit myself, but none of the entries I found had the exact info I was looking for. I'll try some of the other searches people have suggested here.

User avatar
SneakyRobb

28 Sep 2019, 18:33

Hi, one thing I would do is head over to google patents. You can often find a lot of information there.

To start:
Basically try to find something you think might have a patent like an IBM model M membrane. This is your starting point. Patents are organized into family and citation sort of branches.

So maybe start with this one? It looks right! An ibm patent about membrane keyboards! Not exactly about the membrane, but close enough.

https://patents.google.com/patent/US460 ... %2c+switch

Then we go down to patent citations, this is where this patent references previous works. So maybe some random person previously invented some aspect which references some aspect etc.

You can find loads of information this way.

You can sometimes find stuff under slightly different names. Try "mat" or "sheet" "diaphragm" etc as search terms.

A ha! This one seems closer.
https://patents.google.com/patent/US330 ... m&sort=old



Edit: you can do the same with the zedtheman linked switches as well. The deskthority wiki references many patents.

So just for fun what else can we find.
Well from that diaphragm patent we can look at what patents cite this one.
Ah one is an IBM, for "Pushbutton actuator for elastomeric switch"

That sounds... like what we want.
https://patents.google.com/patent/US338 ... m&sort=old

What other weird stuff can we find?
Patent citation... Alps plate spring membrane keyboard... wat.. 1973... by the inventor of skcm blue... but why.
https://patents.google.com/patent/US391 ... m&sort=old


Anyway this is just a random example of how this is a great way to track this sort of stuff and get into the history.

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