Had taken out a cheap measuring tape from my tool kit for some measurements earlier this week. These are the ones which spring back when you release them. Turns out my darn tape won’t coil back. It was stuck with the entire section hanging out. Then I thought why not, let’s open it up and see what’s happening.
Measuring tape consists of a metallic yellow/white unit with black markings(Usually high contrast colours are used for easy reading). It’s coiled all along a central hub. The magic happens in the central hub which consists of a tightly coiled spring(Guessing it’s made of some form of spring steel) which rotates in the other direction (Creating more tension) when the tape is pulled out. The length of the coil of the spring is almost the same as the measurement tape itself. When released, the spring coils back pulling the entire tape back in a snap. An elegant design which looks simple enough. Seems that in my unit, the spring steel part is broken. It’s not really worth repairing these by cutting the spring steel and reattaching, as a new one will cost you only around INR 100($1.2), but sure you can repair it if you want to, be ready to deal with unwinding a mangled tape though.
When I searched the patent databases, I found the potentially first design of this tape which was filed more than 150+ years ago in 1864. Patent No. US45372A. Nice to see that a design engineered that far back is still relevant and fully functional today.