Cantilever Spring Clamp

[lostengineer2]

How would you design a clamp similar to this? I need a minimal clamping force to be generated from as little as .015" deflection, maximum deflection would be ~.09".

Plastics are new to me so I'm exploring the possibility of molding a clip/clamp rather than a hinge/spring combination.

 

[MikeHalloran]

I'm a little fuzzy on exactly what you're trying to do, which parts deflect, where the gaps are, how the clip is opened, etc.

Based on what I think I see:

Integral spring/hinge designs are difficult to get working.
It's more common these days to find separate springs, and sometimes hinge pins of sorts, possibly all molded at once on the same tree, possibly not.

You need to browse HomeGoods and/or Bed Bath and Beyond, and look at the all-plastic multi-piece clips sold to hold and dry towels and washcloths.



Mike Halloran
Pembroke Pines, FL, USA

 

[lostengineer2]

Thanks for the feedback, what I'm looking for is a cantilever beam based spring. Hopefully my MS paint scribbling makes more sense.

 

[MikeHalloran]

Just because you mark one part as static and one part as dynamic doesn't mean they're going to behave that way.

Because the stiffnesses of both leaves are similar, they're both going to deflect about the same when something like the edge of a car window is jammed into the throat.

... which may be the only way to open the clamp. There does not seem to be any other way to open it without a tool.

If you model the leaves as wide prismatical beams using ordinary beam theory, you will quickly realize why plastic cantilever beams are typically tapered in depth. You might as well rough out a spreadsheet to help you with this stuff and guide your design as it evolves.

There exist plastic extrusions with cross sections very similar to what you have shown, sold for edging holes and rough cut edges in metals and as document binders. Many of them have leaves that are strongly preloaded together; I have no idea how they do that. Don't get all lathered up about that; they are typically polyolefins and basically not bondable to anything else.









Mike Halloran
Pembroke Pines, FL, USA

 

[lostengineer2]

I'll mock a quick sketch up in CAD, appreciate the help. I understand in his particular example both would deflect because of the configuration . The application I'm interested in I would simply assume one side to be static as it is [permanently] fixed.

 

[Compositepro]

That clamp design will tend to rock on whatever it is clamping because there is only a single line of contact. For greater stability there should be two lines of contact on one side and a single line on the other side located between the other two.

 

[lostengineer2]

Realized I never uploaded a photo. Here is a similar concept to what I'm trying to design around; an integral cantilever spring in a flat plate.

 

[lostengineer2]

Any thoughts ? Can a plastic provide this type of cantilever spring force effectively and reliably ?

 

[MikeHalloran]

Until you stuff a Gypsy Bankroll in it, yes.

How's your plastic beam model coming along?


Mike Halloran
Pembroke Pines, FL, USA