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Hirose Cherry Precision

Hirose Cherry Precision Co., Ltd. (株式会社ヒロセチェリープレシジョン; in short, ヒロセチェリー: “Hirose Cherry”, /çiɾosetɕeɾʲi/) was a joint venture between Hirose Electric Co., Ltd. (at that time the exclusive Cherry distributor in Japan) and Cherry Electrical Products.

Contents

Overview

The Company Profile (会社概要) page on the former Hirose Cherry website stated that the company was founded (“創業”) on the 15th of August 1968, and established (“設立”) on the 6th of March 1973. The あゆみ (chronology or milestones) page gave the joint venture as being concluded in March 1973, and the company as being established in May 1973.

Over their lifetime, Hirose Cherry appear to have both imported German switches and manufactured their own switches.

Hirose provided me with a number of old datasheets. These give fascinating insights into their product range, but only cover a portion of the products that we have discovered to date. It appears that there are no documents left at their office that offer a detailed view of each series, in particular all the variant type part numbers. Sadly I am not permitted to publish these datasheets here, even though there is nothing technical given in any of them that we do not already know from other Cherry literature, and despite repeated warnings from Hirose that they are no longer sold.

Switch characteristics

The different Cherry factories approached switch manufacturing in different ways. When two or more Cherry factories produced switches from the same series, they did not operate the same design of tooling, and the internal parts as well as external dimensions could differ. Hirose adopted some very specific differences from the US and German designs.

Keystem

Hirose MX and M8 switches are notable for sharing a keycap mount that is different to those of their Western counterparts. The following diagram shows the various 6 mm and 8 mm keystems; you can see that the Hirose switches share a common mount that is different from the 6 and 8 mm mounts used in the USA and Germany:

US and German keycaps will fit on Hirose switches, but Hirose keycaps will not fit on US and German switches.

No mention is made in the 1988 part number schema for the Hirose keystem. However, the Hirose MX datasheet uses stem type N, and switch type 0.

Contacts

Hirose developed their own switch contact point design. Their contact points are prisms formed from a solid copper or copper-alloy core that passes through the contact or terminal itself. These prisms appear to range from convex-top trapezoid to near semi-circular in section, but such details are difficult to discern. It appears that the top portion of the prism is solid silver alloy, above which there is gold alloy plating. The plating coverage varies, and often some or most of the core remains visible.

View full-size image Hirose M8 and MX stationary contacts (front and back views of each)
View full-size image Close-up of the Hirose M8 stationary contact design, showing the gold-plated copper core of the contact points

The designs of German and Hirose prisms are depicted in the following diagram that shows the cross sections of M8 stationary contacts:

Hirose’s datasheets depict standard US/German triangular prisms, but all production M8, MD and MX switches have been found with Hirose-style prisms. The following diagram shows a comparison of MX contacts:

Switch types

M5 and M6

According to correspondence with Hirose, they started manufacturing M5 switches from 1983 and M6 switches from 1985. There is very tenuous evidence at the moment to suggest that the M5 and M6 switches with trapezoidal holes in the base are Hirose-made switches. The following diagram—which is not drawn to accurate dimensions, being originally a quick sketch—illustrates the observed difference in switch design that could be attributed to Hirose:

The following photos are from eBay seller abc070506. He offers surplus Cherry M61-0100 as a replacement to Amada M61-0120. He retains a single Amada M61-0120 together with its packaging, which demostrates both the part number and that it is made in Japan. (Amada is a Japanese business.) He took an extra photograph upon request to allow us to see what design of base the switch has. This is the only documented example of a Japanese-made M5 or M6 switch, but an extended B70-4753 manufactured after the introduction of Japanese-made M6 switches is another strong clue.

View full-size image Amada M61-0120 switch
View full-size image Part number on packaging (“キースイッチ” simply denotes “keyswitch”)
View full-size image Base of switch showing the trapezoidal holes
View full-size image The Amadan-SS System II equipment to which the parts belong

This theory is not conclusive. Strange patterned marks on trapezoidal-hole M61-0100 sold in the US match those found on US-style M61-0120: thse could be from a manufacturing step common to both factories, but it could also indicate that the holes represent some optional feature of the switches rather than a sign of the factory of origin.

M5/M6 tactile

In 1979, Hirose filed Japanese utility model S56-090326 for a variant of M6 with a tactile leaf. Two leaf styles were shown: one similar to Alps, where the tactile leaf is folded and faces downwards, and one where the leaf is straight and faces upwards:

Curiously, this design pre-dates the point that Hirose claim to have started making M5 switches by several years. It also presents a tactile leaf design before Alps introduced them. (Although Fujitsu FES-8 also introduced tactile leaf springs before Alps, their design was an innovative take on Micro Switch’s sprung pin system, replacing the moving pin and rigid shell step with a fixed pin and moving step, very similar to the stepped contact shape in Datanetics DC-60). The Alps design is different.)

Such switches have yet to be discovered. Tactile types do exist (US-made M51-0229 and German-made M73-0176) but these are likely to rely on steps in the operating cam, not separate leaf springs.

M8, MD, MJ

Hirose manufactured their own variant of M8 series. They also introduced three more variants; two of these (MD and MJ series) were mentioned on the chronology/milestones page of the former Hirose Cherry website, which is why I returned to Hirose for answers:

Original text Translation
昭和58年4月 低背形キースイッチ(MDシリーズ)発売。 April 1983 Low-profile keyswitch (MD series) was released.
昭和58年4月 低背形キースイッチ(MJシリーズ)発売。 April 1983 Low-profile keyswitch (MJ series) was released.

The datasheet that covers M8, MD and MJ is not clear. All three types are shown with the Hirose M8 slider planform, but the M8 drawing appears to show a regular MX-style keystem. MD and MJ are shown with Hirose keystems. The keystem details are not clarified for any variant, but all types are shown with the shorter 3.5 mm keystem.

In summary, the types are as follows:

Series Travel Shell height
M83A 2.5 mm 6.7 mm
M83S 1.5 mm 6.7 mm
MD 3 mm 7.3 mm
MJ 4 mm 7.7 mm

Shell height includes the stand-off nubs, i.e. it is the distance from the top of the shell to the top of the PCB.

It turns out that Epson PX-8 used MD switches, with M83S used for the top row (Esc through PF5); I received some switches from this keyboard from UncleFan and I was able to match them with the types shown in the datasheet.

Switches with the Hirose planform but with German M81/M82–style contacts have been found in the German-made Basis 108 microcomputer keyboard, used for the unstabilised wider keycaps. The keystem however is German-style, suggesting that these special switches were moulded afresh in Germany. This type is not given in the M8 brochure.

The switch contacts in Hirose M8 are trapezoidal rather than the triangular and cylindrical designs of US and German switches. The small size of the parts makes determination of the exact design difficult, but the front faces of the contacts are slightly convex.

M85

M85 does not appear to be a computer keyboard switch. This appears to be a Hirose product, using again keystem type N (defined this time as “キートップ嵌合先端形状”: keytop mating tip shape). This type was also listed in the Hirose chronology:

Original text 昭和62年4月 センターLED式照光式押釦スイッチ(M85シリーズ)発売。
Translation April 1987 LED-type illuminated pushbutton switch (M85 series) released.

This type was at one stage appended to the German M8 brochure, but the relationship with M8 remains a mystery, as M8 and M85 bear no external resemblance to one another. Hirose filed Japanese utility model S63118123U in 1987 for M85, and from the patent it can be seen that internally it seems to use standard M8 contacts. As with other Hirose M8 types, it is single pole only.

MX

It was suggested somewhere that Japan got MX switches first; Hirose themselves told me that “Originally, German MX switch was based on Japan version.” This would account for the Hirose datasheet using switch type 0 (MX Black is type 1), but why would a Japanese type still use keystem N? MD and MJ series use keystem 1, but Hirose MX uses keystem N. The keystem is again shown as German-style but 3.5 mm tall.

The MX patent lists the inventors as Günter Murmann and Günter Bauer. Günter Murmann himself insists that MX is a German design. What we do know is that early Hirose MX switches were branded “HCP”, instead of “Cherry”. Hirose MX switches also use their existing contact system, rather than the gold-plated wire contacts adopted in Germany and then the US. Hirose MX switches also use a different design of movable contact, which is the same as that used by the US production line.

ML

Cherry ML was listed on the Hirose Cherry website. It is likely that these were imported from Germany. They only listed “MLシリーズキースイッチ” (ML series key switch) and “G84-4100シリーズ超薄形コンパクトキーボード” (G84-4100 Series Ultra Thin Compact Keyboard). The pictures were never archived and are now lost.

Capacitive

Hirose Cherry were granted patent JPS59828A in January 1984 for capacitive keyboards. Nothing is known about Hirose capacitive keyboards, although Cherry in the US had introduced foam-and-foil capacitive keyboards by 1979.