The Harris Patent and The Coleman Patent

[dw_junon]

I don't think I've seen this come up before here, so here goes...

Thanks I suppose to Mr Ermita, it seems that US Patent #4118611 Aug 30, 1977 by Richard Hunter Harris for the "Buckling spring torsional snap actuator" is pretty familiar around here.

It's immediately obvious (at least to us lot) that it refers to keyboard switches, though there is an earlier Harris patent from '71, referenced in the '77 patent, which appears to be the initiation of using a spring like this, developing the idea from snap action switches.  He also refers to a '71 Holzer patent with a very interesting system, but I digress.

However, The Harris Patent of '77 refers to "Individual electrical contacts... shown mounted on a circuit board or other similar non-conductive substrate" and furthermore states that the contacts "constitute plates in a capacitive switching system".

This sounds distinctly like Model F technology.

There is a later patent by Edwin T. Coleman, III which references The Harris Patent, for a "Rocking switch actuator for a low force membrane contact switch", filed in October '83, issued July '85, which describes "a pivoting rocking actuator"  with a "membrane contact switch assembly".  The membrane assembly "includes an upper layer... of an electrically insulating material, an intermediate layer... of an electrically insulating material, and a lower layer... of an electrically insulating material."

Coleman makes clear that the new "invention is an improvement of the aforesaid Harris patent in that the cost of the present invention is substantially less, approximately half, than the apparatus of the aforesaid Harris patent.".  This corresponds to the view presented by DeFosse et al. in "Development of a membrane switch-type full-travel tactile keyboard" in the IBM Research Journal in September '85, which opens with opens with the words "To reduce cost in the area of keyboards...".

In other words, I'm pretty sure that this Coleman patent is a better reference for the Model M than The Harris Patent.

Note that while Coleman refers to a "low force" switch, the key travel/key force plots are remarkably similar (click for the entries at Google Patents):

[Chloe]

Good find. The Harris patent 4118611 does sound like Model F.

In U.S. Pat. No. 4,118,611 to Harris, there is shown a pivoting switch actuator using a buckling compression spring to move the actuator in response to depression of a key whereby the actuator causes closing and opening of a switch through changing the capacitance between contacts with which the actuator cooperates. The actuator of the aforesaid Harris patent pivots about a single pivot point when a key is depressed.

The rocker actuator in Coleman patent 4528431 (Fig. looks just like the one in the 5576-A01. I assume this is the same as Model M:
http://park16.wakwak.com/~ex4/kb/tech_bucklingspring_e.htm

[wellington1869]

I'd like to put that graph on a t-shirt

[dw_junon]

Good find. The Harris patent 4118611 does sound like Model F.

In U.S. Pat. No. 4,118,611 to Harris, there is shown a pivoting switch actuator using a buckling compression spring to move the actuator in response to depression of a key whereby the actuator causes closing and opening of a switch through changing the capacitance between contacts with which the actuator cooperates. The actuator of the aforesaid Harris patent pivots about a single pivot point when a key is depressed.

The rocker actuator in Coleman patent 4528431 (Fig. looks just like the one in the 5576-A01. I assume this is the same as Model M:
http://park16.wakwak.com/~ex4/kb/tech_bucklingspring_e.htm

Ah, interesting; thanks.  Not an exact replica perhaps, but surely very much the same idea.  There's not really any reason why those should be identical to the original drawing anyway, particularly given that this was redesigned in Japan(?).

I'd like to put that graph on a t-shirt

heh, yeah.  In my case, I imagine I'd just scare people, but that could be fun in itself, perhaps.

[wellington1869]

so thats the actual rocker switch, huh? Interesting. Its much bigger than I expected.

[dw_junon]

so thats the actual rocker switch, huh? Interesting. Its much bigger than I expected.

Well, they're from the Japanese Type 5576 keyboards, submodels 003 and A01, which use individual detachable modules for each key (click the photos).

Ah, there is a photo on 3m3718.com's mpr0n page of some from a '401:

http://www.3m3718.com/imx/keyboard/modelm/rockers.jpg

I'm not even going to dare to try to display it in-line; I suspect shenanigans.  So paste into something unlikely, like Links maybe, and see if you can manage to get it to display.  If that doesn't even work, just go to http://www.3m3718.com/ on the right day of the week and click Model M, and then the deconstructive bullet point.

Perhaps there is an image elsewhere on this forum?...

[bhtooefr]

Transloaded to my photobucket:

[wellington1869]

thanks bht.  they look about the same size to me though. the rocker switch almost looks wider than the actual key!

[dw_junon]

Transloaded to my photobucket:

Show Image

Ah, super.  Thanks for that.

While it is harder to see the detail in that picture, I reckon they do resemble that figure 8 from the Coleman patent pretty near.  More so than the 5576 rockers, anyway.

[sandy55]

some pictures of rocking hammer

comparison; bottom image of A01 and M


comparison; upper image of A01 and M


upper image of M's rocker


bottom image of M's rocker


upstanding post

[dw_junon]

some pictures of rocking hammer

Fantastic pictures, Sandy!  Thank you!

I must say, I did not realise the M rocker was so much wider than the A01's from the earlier pictures.

[wellington1869]

great pics

[Chloe]

Here are some pictures of the capacitive rocker actuator:
http://sandy55.fc2web.com/keyboard/model_m_trivia.html#5640991