Fri Sep 4 21:15:02 PDT 2020
Ballpoint Pen Mechanisms
For some reason I became interested in the mechanisms of ballpoint pens recently. This is partly because the push button action of a ballpoint pen essentially divides by two. Two downward 'pulses' on a pens button result in one downward press of the ballpoint pen refill. If you were to connect ballpoint pens (with the appropriate levers) you could divide mechanical 'pulses' by any desired number of twos. This would enable you to count using mechanical counter.
I made an electronic divide by two device using bistable multivibrators - I will do a short article on that at some stage. It is interesting to observe that a mechanical version of this circuit could be constructed. The mechanical version would not be able to operate at a high frequency, of course.
I am also interested in ballpoint mechanisms because they can be diverse. The ratchet style mechanism seems to have one in the evolution of the ballpoint pen. Here (below) is a diagram of how the ratchet ballpoint mechanism works. The parts are actually cylindrical but they are easier to draw and understand in a 'flattened' view. So, the diagram is stylized and not to scale. The pen works by having a set of teeth at the top of the refill that can slip into either deep or shallow grooves. Then the teeth fit into shallow grooves the pen is extended, when the teeth fit into the deep grooves the pen is retracted. The push button pushes the teeth out of all grooves and moves the teeth around so that they will be pushed into the opposite type of groove that they were formerly in.
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The ratchet ballpoint mechanism only requires a refill, a spring, a set of teeth, a pusher, and the grooves; and no real assembly, except dropping the parts into the pen body in the correct order.
Another type of ballpoint mechanism was invented by Ballograf. The diagram below tries to show how this works. (And possibly it is better described in the patent GB851060). The Ballograf mechanism is rather different to the ratchet mechanism, it uses a little brass piece to 'record' the state of the pen. The position of the brass piece is moved with a flat blade to be in one of two positions in a slot. When the pusher is forced into the slot, the brass piece is moved into a particular side area (because the pusher has beveled edges). At one end of the slot, the brass piece catches its 'waist' on a lip. In this position the pen is extended. When the pen's button is pushed again, the brass piece is moved to the other end of the slot, where there is no lip, and the pen is retracted. The resulting clicking mechanism for the Ballograf is different to the ratchet mechanism but works very well in practice. (I really like my Ballograf Epoca!).
Billions of ballpoint pens have been manufactured and sold. The Bic crystal ballpen (which has no mechanism) has sold at least 100 billion units. So ballpoint pens have probably sold trillions overall. These huge numbers make intuitive sense. For example, if you imagine that for the last decade every person has used something like 10 ballpoint pens per year, and there are 7 billion people around, then in 10 years, it is easy to see that 700 billion ballpoint pens have been manufactured, sold, bought, and used. Of course some people do not write much, but others (like school children) use and lose many more than 10 pens per year.
Quite possibly the rate of production of ballpoint pens will slow now that many things are digital. Ballpoint pens made writing in ink cheap and accessible to everyone, they were an extraordinary invention in the twentieth century. Lots of innovation and mass production was involved, and the price of writing became more and more reasonable, which is the way that things should progress.
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There is a fantastic movie on YouTube showing how the Ballograf Epoca is manufactured (in Sweden, still, I believe). From the video you can see that the skill in making the pen is now encoded in clever robotic machines that automate the production process. Nevertheless, the mechanism behind the ballpoint pen is brilliant too!
(the second link features music from the band Television at the beginning - you cannot beat that!)
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