Could anyone give me any links to images/sites/existing products that show how a lid can pop/spring open about a pivot just using the plastic parts themselves and not an extra metal torsion spring?
Any help would be much appreciated.
Thanks.
Many of those things are hard to find.
The best examples I've seen are from the flip-top lids on shampoos and food container bottle caps. You just have to pick the style you like and model it yourself.
There have been some patented items, and you can see one type at:
Some designs just use two pieces molded with strong enough connecting hinges to open the item when a latch is "popped".
It takes some creativity and practical smarts and a good dose of prototyping with the Polypropylene like latest versions of the SLA epoxies that can somewhat mimick PP's flexible hinge capability.
Bo
Will, with respect to springs, I have use a wide array of pure leaf springs, torsion springs, and then over center type elements, some of which have also been hinges, made from partial spherical segments, like on the top of coffee cup lids that invert, conical segments that invert, and ones like Ed talked about as used on shampoo & condiment flip top bottle caps.
Some of the plastics companies like Dow and GE issue design guides and spec out general forms of springs and their sizing, and much of that is often associated with hinges.
There is a ton of stuff you can find with Google. Some good, some excerpts from expensive books, and some college lecture PPTs.
FlexureLecture.ppt by Brian Trease of Univ. of Michigan in 2004 is probably in the internet archive and has 109 slides and recommends 4 books on the 3rd slide for reference.
It is a 10 meg ppt, and if you get me your email, I can send you a copy, if you can't find it.
Bo
Start here:
And here:
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