On the IDSA Materials and Processes blog, a fascinating look at a one-piece plastic latch designed to close large cardboard boxes, like the ones giant TVs come in.
It’s passed though a hole that goes through two walls of corrugated (the top and the bottom) and then the two locking surfaces are pushed inward, hooking onto the backside of the inside of the carton. The latch is locked in place with a snap, which can be opened by squeezing…
Okay, now for a few points of interest: This part takes advantage of polypropylene’s flexibility – particularly for snaps and living hinges. The image below shows the part in the position it’s molded in. Part of the mold comes from underneath and part from the top, but they meet in the middle at a “bypass” to create a break between the two moving parts. Except they leave a little bit of flash to connect they (and probably to improve the flow of the material in the mold). That flash is broken with the latch is used for the first time…
What’s That?: Plastic Cardboard Box Latch