Cherry reed switches
Cherry filed a patent for a tactile reed switch in July 1970. US patent 3644855 was granted in February 1972. It seems that this switch was only marketed for a brief time: it was included in Cherry marketing literature in 1971, and no longer mentioned by 1973.
The design given in the patent achieves the tactile feel by way of magnetic separation. A metal disc embedded into the switch attracts the magnet and stops it moving. After a spring above the magnet is sufficiently compressed by the operator via the plunger, the force within that spring becomes great enough to force the magnet off the disc. There is a separate main return spring placed under the magnet. The illustrations in Cherry’s literature do not depict this arrangement, and there is no mention of tactile feedback.
The reed switches are tall, with a distance of 1.12″ (28.4 mm) from the top of the PCB to the top of the plate, and 0.06″ (1.5 mm) of the shell above the plate.
Cherry reed switches used the old model numbering system; only the following models are known:
|Operating force||2.5±0.5 oz|
|Pretravel||3⁄32±1⁄32″ (also given as 0.093±0.031″; approx. 2.4±0.8 mm)|
|Total travel||3⁄16″ maximum (approx. 0.188″, or 4.8 mm)|
|DC resistive load||7 W maximum|
|AC resistive load||12 VA maximum|
|Current||0.25 A maximum|
|Voltage||28 V maximum|
|Bounce time||1 ms maximum|
|Initial contact resistance||250 mΩ maximum|
|Rated lifetime||10 million cycles minimum|
- Cherry electronic data entry keyboards: Key Module and Keyboard Specifications (December 1971)
- New Cherry electronic data entry keyboards (December 1971)