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I am trying to model a machine that uses eyelets to support a piece of fabric, and this design uses a chain to hold the eyelets in a loop; the links are pictured below.

Eyelet Chain Link

As this machine runs more and less of these links will be needed, and so I'm trying to design a support to keep the chain under tension. The ideas i have are segments of a circle to act as a hand to pull outward from outside, or a loop that is made to push outwards.

The circle segments could be good but there would need to be more of these segments when you increase the number of links. This means either the operator or machine would have to know when to add these supports and be able to.

The loop could be good as well, but it would need to able to range in size from ~1cm to 20cm in circumference. This would be difficult to make durably.

Is there any other way that machines have supported adjusting chains?

Destiny Rose
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Consider having a "loop" of chain on an idler pulley that can move to add / remove slack and sprung or weighted (gravity is free) as necessary : this could be on the return side.

Edit: This image gives an idea : just assume the lhs is vertical, those, or only one, wheels can be pulled by a spring or even simpler just have weights hanging on them. The total can be adjusted for the amoun t of chain or the effect of different fabrics...

The rhs shows a little slack - that before adjustment gets longer; where you add extra chain to provide the loop - need an extra gear for the return though...

enter image description here

Edit for idea 2 : sorry for poor image - just a hack with copy/paste... enter image description here

Solar Mike
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  • this is actually where the first idea came from, but I had to remove the "inside" of the pulley for the fabric to be able to fit through the inside of the chain loop. – Destiny Rose Oct 22 '17 at 05:50
  • When I put "return side" I meant the chain below the working surface : I will see if I can find a pic of what I mean... – Solar Mike Oct 22 '17 at 06:37
  • re the "inside of the pulley" could you "open" that loop to make room for the fabric feed? so the lhs becomes like a pyramid with two pulleys at the bottom and the fabric feed inside that triangle? needs much more chain though... – Solar Mike Oct 22 '17 at 06:51
  • each chain link would have a eyelet with a bit of fabric on it so the whole chain is actually the work surface so the fabric would have to come through the the inside or outside of the chain. so I need that straight work surface you're depicting to be a circle. – Destiny Rose Oct 22 '17 at 07:41
  • the loop of chain would be much like this knitting machine but it would need to be able to handle different sizes of circle. http://www.tikp.co.uk/knowledge/technology/knitting/priciples/ – Destiny Rose Oct 22 '17 at 07:47
  • Could you use a semi-circular guide but is all the surface of the circle working or just a sector? – Solar Mike Oct 22 '17 at 07:52
  • the entire surface is working, my first idea is semi circular guides (or smaller segments of a circle) with their spacing used to evenly hold pressure, but with the scales this guides would need to cover they would also need to be added and subtracted, so that's complex but doable. – Destiny Rose Oct 22 '17 at 07:57