What's the story behind the GE Chronotel (flip-tile) mechanism?

[dpwellis]

I recently got drawn into flip clock hobbyism...

My first clock was a GE 7-4300 from eBay, which incorporated a Copal motor/flip mechanism. Browsing around, I saw a whole sequence of similar clock-radios from GE: The 7-4305 moves the alarm selection slider to the top of the unit, the 7-4310 which includes a sleep timer (and puts the AM/FM switch on the top), and the 7-4320 which puts all the switches and clock controls on the front. These seem like mainly cosmetic changes, although I think the radio circuitry also improves (as I recall, the 7-4320 includes an actual transformer rather than having the radio run directly off the mains current as in the 7-4300 and 4305).

But one thing sticks out to me: All these clocks use Copal mechanisms *except* the 7-4305A through C, which use the GE Chronotel 12 hour flipping tile mechanism. The 7-4305F goes back to the Copal split-flap mechanism.

Does anyone know more about how and why the Chronotel flipping-tile mechanism was developed, and why it was tried then abandoned for the 7-43xx series clock radios? I can see the 12 hour cycle is a major functionality regression, but I'm wondering why they tried it at all?

[RetroFlip]

I shared a 1978 GE sales binder a while back here
The various types co-existed and were sold along side each other, I'm not sure why they made that change.
Perhaps it was related to production cost or excess inventory of the Chronotel, which caused it to be placed into a clock radio format to sell through. The 7-4305A is marked Singapore, which is the same as many of the smaller alarm clocks.

[dpwellis]

Thanks! I hadn't thought about inventory factors possibly driving the design of a product to use up extra mechanisms. The recent availability of new-in-box 8142-4 Chronotel clocks does hint that they were overproduced at some point.

BTW, I took a quick search through the US Patent records. I found US3780524A (inventor Robert L. Boyles, obituary here) which describes the Chronotel mechanism; the patent focuses on the "Geneva gearing" which allows the minutes to change quickly despite a continuously-rotating drive. However, the part that I find most surprising about the mechanism - the double-sided minutes tiles, allowing a relatively small drum relative to the digit height - is only casually mentioned as a dependent claim, making me wonder if that idea was from some prior art.