Voting resources, early voting, and poll worker information - VOTE. ... Adafruit is open and shipping.
0

Any Sort of Band Clamp Tighten/Loosen or Cinch Cord Actuator
Moderators: adafruit_support_bill, adafruit

Please be positive and constructive with your questions and comments.

Any Sort of Band Clamp Tighten/Loosen or Cinch Cord Actuator

by muttleytm on Wed May 27, 2020 9:59 am

I'm building something were a couple parts will move in and out radially to a center point. The travel will only be an inch or so and there is a third stationary part. The moving parts will be mounted on glides. I was originally thinking of using a couple electric linear actuators, but started wondering if there was something that would sort of like tighten or loosen a worm gear band ring sort of thing or wind and unwind a cable around the parts to close it and open it.

There could well be something off the shelf and cheap that would do this, but I don't really know what it might be called. I've tried a variety of terms and haven't found anything. Is there such a thing available?

TIA

muttleytm
 
Posts: 8
Joined: Tue Nov 24, 2015 8:12 pm

Re: Any Sort of Band Clamp Tighten/Loosen or Cinch Cord Actu

by adafruit_support_bill on Wed May 27, 2020 10:44 am

Do all the parts need to move in synchronization? A band-clamp type of mechanism would probably work unevenly. If you can tell us a little more about your application, we might be able to suggest something.

adafruit_support_bill
 
Posts: 78710
Joined: Sat Feb 07, 2009 10:11 am

Re: Any Sort of Band Clamp Tighten/Loosen or Cinch Cord Actu

by muttleytm on Wed May 27, 2020 12:23 pm

there are three parts one is larger and is stationary. They press down inward around a cylinder. The three pieces are made from one bigger piece that has a hole the diameter of the cylinder. The bigger piece is a semi circle and the two smaller ones is another semicircle cut in half.

I'm thinking of having the cylinder itself on a little sprung slide of its own. The two moving pieces, on linear glides should self center the cylinder, which will be on its own holder. The actuator or actuators will press together and then pull apart after a period of time. I imagine actuators can be had that are in a normally open position, overwise I suppose it can be done with a control or spring.

The diameter of the cylinder is a little over three inches and the outer diameter of the whole thing when it is closed is maybe eight to ten inches. The travel is probably only and inch or less and on glides. It seems like if there were some sort of band mechanism it would close pretty uniformly.

muttleytm
 
Posts: 8
Joined: Tue Nov 24, 2015 8:12 pm

Re: Any Sort of Band Clamp Tighten/Loosen or Cinch Cord Actu

by adafruit_support_bill on Wed May 27, 2020 12:56 pm

If you are cinching a band-clamp from one position, friction will tend to make the pieces closest to that point will tend to close first. If you can minimize the friction of the band over those pieces, the clamping motion will be more uniform.

How much clamping force is needed? Is this an occasional use mechanism, or something that will see hundreds of thousands of cycles?

adafruit_support_bill
 
Posts: 78710
Joined: Sat Feb 07, 2009 10:11 am

Re: Any Sort of Band Clamp Tighten/Loosen or Cinch Cord Actu

by muttleytm on Wed May 27, 2020 1:50 pm

the force would only be maybe five pounds or less. It just has to fit together snuggly. The movable parts are on linear glides that have bearings.

I guess I mainly want to know if there is something like this that is readily available off the shelf that is also inexpensive and what it might be called.

muttleytm
 
Posts: 8
Joined: Tue Nov 24, 2015 8:12 pm

Re: Any Sort of Band Clamp Tighten/Loosen or Cinch Cord Actu

by adafruit_support_bill on Wed May 27, 2020 2:04 pm

There are lots of clamping mechanisms and plenty of different types of motor/actuators you could use to drive them. But you need to understand the requirements of the application to choose an appropriate solution.

For a light-duty application such as you describe, an RC servo and some low-friction cord would probably suffice.

adafruit_support_bill
 
Posts: 78710
Joined: Sat Feb 07, 2009 10:11 am

Re: Any Sort of Band Clamp Tighten/Loosen or Cinch Cord Actu

by muttleytm on Wed May 27, 2020 10:21 pm

I'm going to make a little model and just play around by hand.

I'm thinking I could use some 1/8" or so wire roped looped about the pieces. At the cables would be arranged evenly around the pieces and come together into a crimped or swag cable end on the stationary object side. The cables and/or cable end would fit through a hole in a stationary block above the stationary full semicircle piece. Seems like the forces would be applied equally to each of the two moving pieces as it would be centered above the stationary semicircular piece. I think I could get a good feel for how evenly it closes, etc. Plus I need to make a little model first anyway to test it in general, work out some other details.

Well, that's my thinking at the moment. Looks like just one electric linear actuator might be all I need. I see you aren't supposed to run them to a hard stop. Would a spring or some elastomer in the chain keep the forces below the point I break anything?

muttleytm
 
Posts: 8
Joined: Tue Nov 24, 2015 8:12 pm

Re: Any Sort of Band Clamp Tighten/Loosen or Cinch Cord Actu

by adafruit_support_bill on Thu May 28, 2020 5:31 am

Looks like just one electric linear actuator might be all I need. I see you aren't supposed to run them to a hard stop.

The "R" series of the Firgelli/Actuonix linear actuators have an RC Servo style interface. Those are the easiest to interface and control with a microcontroller.

Would a spring or some elastomer in the chain keep the forces below the point I break anything?

Yes, some compliance built into the chain is a good idea.

adafruit_support_bill
 
Posts: 78710
Joined: Sat Feb 07, 2009 10:11 am

Please be positive and constructive with your questions and comments.