The Wave Washer
Quantized Fasteners Revisited

T   
his is another form of fastener with similar workings as given on
THIS PAGE though it is quite a bit simpler and should be easier to manufacture than the Gak Fastener. It is a form of "quantized" fastener ... meaning that unlike a standard nut & bolt, it cannot assume a continuous array of possible settings, i.e. the force holding the workpiece is in increments in the manner of a rachet wrench.

All such quantized fasteners require a semi-loose fit. They must have a compression spring effect and when the spring is fully compressed no further force settings are possible.

The Wave

Here is what I am getting at. These are the parts. Rollover the image to see the "action" when assembled.

If the bolt cannot rotate relative to the workpiece (it is prevented from doing so by the rubber washer so long as it seals out moisture) ... and ... the wave washer also cannot rotate relative to the workpiece ... then ... the wave nut will slide over the wave washer and "click" into place at each successive wave, gradually tightening the fastener to the workpiece. At each click, the nut cannot, in principle, come undone by long term vibrations because ...

the pitch of the bolt thread
is much less than
the pitch of the wave form
at its maximum.

There is a force during vibration that wants to loosen the nut ... but ... if the nut loosens it must further compress the rubber washer. This produces a greater force tending to tighten the nut back to where it was. Hence, the nut can never vibrate loose. [This is exactly analogous to a sailboat tacking into the wind.]

Manufacturing ...

It should be possible to manufacture a simple variation on a standard flat washer that will do the trick. By changing the die to punch the steel into a wave form instead of leaving it flat, two such washers should perform the desired function. However, there is the problem of keeping the washer stationary relative to the nut. This could be accomplished by further altering a die so as to "nest" a common hex nut into the washer. Then, all one would need in the way of specialized pieces is the washer itself.

wavwash3.gif By turning up three "flaps", the nut can be held in place while its mate can be flipped over so that its flaps don't interfere with the waves lining up. Such flaps are nothing new.

In fact, though this is an excellent way to fasten things together that do not require a weld-like solidity (like a toilet seat), I cannot say why it is not used. Certainly, it has been thought of before ... probably as soon as rubber washers were available, i.e. some hundred years ago. Perhaps the design is in limbo. Those who should know about it ... don't. And those who do ... never give it any thought figuring its been considered since it's

SO SIMPLE.


Addendum 01/11/04 :
It occurred to me that this could be even simpler yet if we just let a common hex nut ride up on the waves on a six waved washer. The hex shape nests in a fitted depression then ... when turned ... the corners ride up onto the wave and back down into the fitted depression. Here's a pic.

simplest wave washer

This would require no special manufacturing step ... just a single punch and there it is. Put on two rubber washers, the washer and the nut and it stays in place in perpetuity. Come to think of it, the more I look at it the more familiar it looks. Maybe it's available at ACE hardware. I'll check it out.




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