[GreenKeys] GreenKeys Digest, Vol 102, Issue 29

[Randy and Sherry Guttery]

On 7/11/2012 11:40 PM, Ralph Irish wrote:
> George and others:
>
> Another device which was on some Model 28 equipment which did the same thing as the
> "Idle Line Monitor" described below was an all mechanical device somewhere on the
> keyboard of the 28.
The 28 uses an eccentric cam on the intermediate gear shaft 
between the motor and the the auto-typer to drive a cam 
follower arm that engages the "teeth" of two side-by-side 
"ratchet wheels" - one with 27 "teeth" and one with 28 
"teeth" around their circumference.  The effect is - The cam 
follower causes a front to back oscillation that advances 
the two wheels. Each wheel also has a cam surface - which 
faces it's "neighbor". Each cam surface has a single notch.  
Having a different number of "teeth" - they rotate at 
slightly different speeds - so that once in every so -many 
rotations (maximum of 756 - in a maximum of 172 seconds) the 
notch in the two gears lines up. When it does - a follower 
drops into it - and "arms" a two-step mechanism. The two 
gears continue to rotate. Every time the Auto-typer "cycles" 
(i.e. the main clutch is released) the main bail extension 
resets the "armed" mechanism - and the process continues. If 
there is no operation received by the Auto-typer - (i.e.the 
mechanism is still "armed") - the next time the "notch" 
lines up - the second step of the mechanism operates - which 
closes a microswitch.  The microswitch operates a latching 
relay on the LESU - that cuts off the motor.  The latching 
relay is held as long as there is line current.  If line 
current drops (character received, break switch operated, 
etc.) the bistable relay releases - and the motor is again 
powered.

Best regards...

-- 
randy guttery

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