Yes, it's such an obvious question that's not addressed in the article. I was thinking about why they don't pinch the plastic tube closed at the point where the

Yes, it's such an obvious question that's not addressed in the article. I was thinking about why they don't pinch the plastic tube closed at the point where the ink stops being filled. The following statement in one of the patents[1] seems to confirm your explanation: The aims of the arts are to make the ink follower follow the ink smoothly. [1] https://patents.google.com/patent/EP1002663A1/en https://patents.google.com/patent/EP1002663A1/en