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Any idea what this spring is called?

Any idea what this spring is called?

Any idea what this spring is called?

Hi All!
Please see the image. It shows the workings of an eyeglasses case that has bi-stable lid. The spring straddles the hinges. This spring is what drives the glasses case to have the open-or-closed-no-in-between functionality that I crave.

I am looking for ways to create a compact linear bi-stable mechanism, and I like this spring.

Please let me know.

RE: Any idea what this spring is called?

It's a leaf spring. I've designed a couple of hinges like this. Fun project.

It's simple to lay out in a 2D parametric sketch in SolidWorks (or Creo, etc.). When the line between the spring ends is through the hinge axis, the spring should be at max tension and the system is static. Any movement in either direction and the spring induces torque and forces motion to continue in that direction.

I use simple FEA to determine spring factor (k). Once determined, k is linear proportional to spring width. Stresses are high; you must use tempered spring steel.

RE: Any idea what this spring is called?

I would have called it a clip spring myself. Leaf spring is normally used for virtually flat vehicle axle springs, at least for me if someone talked about a leaf spring.

A clip spring is just trying to stay the shape it's put in and won't have much movement.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Any idea what this spring is called?

I believe the mechanism shown is called a "holdback hinge". The leaf spring and the way its ends are connected to the hinge plates provides an over-center action. This forces the hinge to rotate in whichever direction it is released relative to center. There are many ways to achieve this holdback hinge function, with varying levels of complexity and performance. Obviously the one shown has the advantage of being very simple.

If you want to see some examples of holdback hinge concepts, take a look at the patents in US patent class 16/291:


RE: Any idea what this spring is called?

One could just as well name it for its function rather than its shape, and call it a toggle spring.

RE: Any idea what this spring is called?

It is not a leaf spring. My 1940 Ford had leaf springs for suspension.

RE: Any idea what this spring is called?


I checked a couple US patents that describe the specific hinge arrangement you show in the OP. Some of them agree with LittleInch and describe the component using some variation of clip & spring (spring clip, C-clip spring, clip spring), others used different terms (resilient brace, curved spring member), but the one I liked best was "arcuate resilient spring". Below are links to the specific patents. Worth taking a look at if you have some time.


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