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Chomerics

History

Chomerics, Inc. was an American keyboard manufacturer from Woburn, Massachusetts, now seemingly part of Parker. Along with Oak and Micro Switch, Chomerics was one of the early adopters of membrane keyboards in what could possibly be called “second generation”, using only membrane sheets and no PCB.

Chomerics, Inc. was incorporated in Delaware on the 24th of July 1961, and in Massachusetts on the 14th of September 1961. A Boston Globe article RFI-pollution you can hear from the 10th of January 1971 describes Chomerics’ RFI shielding material: this was a variety of conductive plastics and rubbers, formed by impregnating the material with metal particles. One application of their conductive materials was keyboards. US patent 3780237 “Keyboard switch assembly with multi-sectional key actuator” filed in October 1972 depicts such a device. The arrangement is similar to a membrane keyboard, but the sandwich here is formed of a “conductive plastic” layer, a spacer layer (such as Mylar) and a printed circuit board. The conductive plastic connects tracks on the PCB. The PCB layout is not depicted, but is indicated to follow the principles of patents US 3705276 and US 3721778. Those earlier patents describe a self-encoding arrangement where a conductive plastic material connects a common pad to multiple additional pads, each one being for one bit of the output word. These patents are not for full-size (alphanumeric or “QWERTY”) keyboards, but for keypads, such as those found on calculators. Calculators were big business at the time, and this was the focus for many such designs.

Few details are known about Chomerics’ full-size keyboards. Chomerics appear to have adapted their keypad designs to full-size keyboards, but such keyboards are only known from advertisements. A New York Times article “The Membrane Keyboard” from March 1981 describes Oak’s and Chomerics’ membrane keyboards; the article notes that “Oak has so far made only one volume sale and Chomerics none”. This gives an indication of the age of Chomerics’ design. Chomerics advertised full-size keyboards prior to this (Series EA, mentioned below) but no details are known about the implementation.

In Information Display, March 1981 on page 11, Len Halio, the general manager of Chomerics’ alphanumeric products is quoted as saying, “Furthermore, Chomerics is in the unique position of being the world leader in membrane switch technology. The company invented this technology in the late ’60s and holds more than 100 patents covering the spectrum of material and component developments critical to its reliability and economy.” The article also notes that Chomerics has “delivered more than 15 million membrane keyboards for over 1,000 applications since 1970.” Their market at the time included “a computerized PABX system, an industrial robot, applicances, telephones, electronic toys, instruments, and terminals.” The term “keyboard” in this instance is most likely the older meaning that included keypads, such as those found on desktop calculators.

Keyboards

Series EA

Series EA was Computer, Volume 10, Issue 12, December 1977 within the Recent Microsystems Announcements section (archived by IEEE under Recent IC Announcements). The new product is described as follows:

Typically packaged models provide 60 keys and a space bar with as few as 24 output lines on a flexible tail to decode all of the contact closures. Bounce is less than 3 msec, resistance less than 50 ohms. Key travel is 0.125 inches.

Series EA was also seen advertised in December 1977 in Computer Design magazine. Here, the specifications were given exactly as in the previous instance. The illustration in the magazine appears to be only the key assembly, without any electronics, which would have been a separate module.

Screened Mylar

Chomerics placed an advertisement into Electronic Design magazine in March 1978 for screen-printed Mylar contact keyboards. This date is curious, because these products were suggested to be new in the New York Times article of March 1981, when Chomerics had yet to receive any volume orders. No further technical details were given. Conceivably this was also Series EA.

A photograph of a Chomerics membrane sheet is included within the article FOCUS on keyboards in Electronic Design in October 1976 [ED1976-FOK]. This implementation uses two membrane sheets: the circuit sheet that is folded back on itself to form the outer layers, and a Mylar spacer with holes in. The design is said to use “screened bubbles” which “provide both the contacts and spring mechanism”, making it the same general implementation as that of the 1981 newspaper article. Nothing more is said about the implementation in the article, and thus one cannot know whether this is simply a flat panel implementation (as per Datanetics Series 700 that is illustrated in the same article) or a full-travel system. It may be that Chomerics looked for a way to use this flat panel assembly for full-travel keyboards, while Datanetics did the reverse and adapted their full-travel arrangement for flat panels.

Fastype

Fastype™ (also FASTYPE) was seen advertised in April 1980 in Computer Design magazine. This is a full travel membrane design, with a bounce time of under 2 ms and a rated lifetime of 50 million operations. Operating force is given as 3 to 5 oz (0.8 to 1.4 N) for most keys, and 5 to 7 oz (1.4 to 1.9 N) for space bar. Key travel is given as 0.150″ (3.81 mm). Three quite different designs are pictured in the advertisement, but the photograph is too small for any clear details to be observed. Additional depictions are given in the aforementioned Information Display advertisement.

The Membrane Keyboard article from the New York Times says of the Chomerics membrane design, “It uses a plunger and only one spring and has also inflated the membrane switch by putting a tiny air bubble between the top and bottom polyester slices. The air bubble allows the key to have greater movement.”

Documentation

The following documents were scanned in by Bitsavers unless otherwise noted.