The bidirectional button made of a cylinder you can push in both directions had become lose, so I opened the switch.
When I opened it, I found a copper spring standing vertically in a hole like on the first 2 pictures.
I don't understand how to place this spring before closing the switch and make it work again.
Has anyone seen such a model before?
Thanks

 

I think the spring lays over/around the central barrel.

The spring resting in the lower (smaller diameter) section of the barrel works to hold the switch in either position. Between positions the high spot in the middle wants to slide out from underneath the spring spring tension.

 

I agree.

 

I think the spring is also the conductor. In the off position the barrel bump holds the spring away from the contacts. It pops into the groove toward the black end. In the on position the spring jumps the bump and falls into the groove toward the red end and hits the contacts.

 

I was thinking that too 2john but it looks like the switch may be under the slide part.

We've been trying to not use "upvote" as that's what is putting the posts out of order.

 

In either case the spring goes over the shaft.

 

Thanks for your answers.
I agree with the idea that the spring was probably resting on the narrow part of the barrel.
I doubt it was creating the contact, because the two metal parts are actually just one connected below.
I tried various ways of putting the spring back, like an arch above the groove, flat between the screws, wrapped around the barrel, but nothing stays in place till I close the case.
I'll get a new one.

 

Almost looks like the spring should attach to itself, end to end, around the shaft. Did the loop(s) on each end of the spring break, maybe?

 

"" The spring should attache to itself end to end """

That looks like the answer.

When the red button is pressed, the spring shaped into a miniature wreath is pushed away from the contacts and against a gray barrier. When the bulge in the middle of the shaft between the buttons passes through the spring , the spring suddenly rolls back against the metal contacts to complete the circuit. (The spring doe not jump far; it remains more or less centered in the switch body.)

When the black button is pushed, the spring is pusned against the contacts. When the bulge in the shaft passes, the spring suddenly rolls away from the contacts (and back against the gray barrier).

Th aim is for the bridging of the contacts (by the spring) to occur and to break quickly to minimize arcing.