Anders said > 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?
The idea behind the paper tape punch is that the solenoids themselves don't supply the force to do the actual punching, they instead set up the punch pins which are then driven by a cam by a motor with a lot of grunt. I suppose it's like the mechanical equivalent of a transistor switching on by applying a small base current. The once-popular Roytron punch mechanism is described in http://www.bitsavers.org/pdf/roytron/Roytron500_1966.pdf and may be what you are looking for. It's somewhat comparable to how the keyboard mechanism operates in a Selectric typewriter where interposers drop into place and the cam profile on the filter shaft drives them forward. Or a Creed teleprinter keyboard with toothed code bars that suspend lateral bars being moved with mechanical force. I've also thought about a home made punch that might be built using the Teletype punch blocks that have been on eBay, augmented with a bit of machining, motor and some 3D-printed parts such as the frame. But that's still just a bunch of ideas at present. As for making tape by means other than a punch, if you have a home vinyl/stencil cutting machine you can make working paper tapes using my ptaf2dxf utility https://github.com/1944GPW/ptap2dxf It's very slow compared to a real punch and on the standard 12" x 12" cutting mat these machines are supplied with, there will be a number of short tape segments cut that then need to be glued together. But, as a novelty, it works :) Steve.
