DIY Paper Tape Punch - Mechanism diagram?

[Tony Duell]

On Fri, May 1, 2020 at 5:02 AM Anders Nelson via cctalk
<cctalk at classiccmp.org> wrote:
>
> Hi all,
>
> I've had a paper tape reader for a while but never had a punch to make new
> tapes, and the ones i've found are not only very large but also very
> expensive. So I'm toying with the idea of making an open-source punch, but
> I can't find any detailed diagrams of how the mechanism works.
>
> I'm assuming (without any data to back it up) that there is a cam, an array
> of spring-levered pins, and horizontal spacers controlled by solenoids that
> bridge the gap between the cam and each punch pin when called for.
>
> Does anyone have insight into how reliable/fast paper tape punches work?

There are 2 basic designs....

The mechanically simpler one has a solenoid that directly operates
each punch pin. The well-known Facit 4070 is of this design, using
rotary solenoids and drive levers (I am sure the service manual and
parts list (which contains the exploded diagrams) are on-line. Another
example of this type is the Heathkit H10 which uses normal linear
solenoids.

More common is to have a motor driven crankshaft moving a little frame
up and down. This goes over the ends of the punch pins and has a
bracket to pull them down at the end of the punch cycle. Solenodis
(quite small solenoids, almost like relay coils) move spring metal
strips (normally called 'interposers' in the manual) into said frame
under the punch pin so that the pin is then forced up and through the
tape as the frame rises. The Teletype BRPE, GNT34, many Data Dynamics
punchs, etc are of this design (to name the ones I can see without
getting up).

Be warned that making any paper tape punch is going to be non-trivial.
Grinding and hardening the punch pins and making the die block for
them to run in is quite a difficult machining task. And that's needed
what ever drives them.

-tony