Creating a clamping device

[dogboy74]

Hi-

I hope this is OK to post here. I board certified prosthetist and orthotist that makes custom braces and artificial limbs for kids.

A lot of the stuff we use in the lab is homegrown and I am trying to make a clamp to hold a brace so that we can vacuum form tread on the bottom of it.

I am in the process of making a little vacuum press to speed up the process of putting tread on the bottom of ankle foot braces. Right now we take a 6mm piece of tread out of the oven and place in on the bottom of the brace (brace turned upside down). Then we use a ton of electrical tape to wrap the hot piece of rubber tread around the bottom and top the side of the brace a bit until it cools. Once this is all done with trim it up and glue it on.

I would like to speed this up by using a vacuum press I am in the process of putting together. I am currently using a 5 gallon bucket with the vacuum coming in from the bottom. Then I am going to use a 2mm silicone sheet to pull over the top of the bucket so that is wraps around the brace and pulls the tread down and around the edges of the brace. The braces we fabricate all sizes, and this is the problem. Imagine that you have someones leg cut off below the knee and turned upside down, that is the general shape of the brace but with an open front so that you slide your leg and foot back into it before the straps are secured.

I need to come up with some type of universal clamp or holder that can sit in the bucket and allow us to:

1) clamp on a brace that fits a 1 year old kid or 18 year old kid.
2) move the clamp up and down so that the footplate or bottom of the brace is a few inches above the top of the bucket so that when we pull the silicone sheet down and secure it pressure is applied to the bottom of the brace and tread so that it vacuum molds.

I can have some stuff milled from metal if need be but we are also open to just using something pre-made or parts from the local hardware store. Any ideas on how to create a clamp would be really appreciated. We are used to going through iterations of improving tools and devices we make. I have attached a pic that shows what an average ankle foot orthosis (AFO) looks like.

Thanks.

 

[MintJulep]

Search for "strap clamp".

 

[EdStainless]

Perhaps a series of inflatable pads.
Three upper and three lower so that you adjust for the size of part.

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P.E. Metallurgy, consulting work welcomed

 

[3DDave]

A photograph of the way it's done now would help, along with a "before" picture of that example from several directions.

 

[dogboy74]

Thanks everyone. I’ll get some photos and post them to make things more clear when I get a chance.

 

[dogboy74]

The upper left pic the bottom half of an articulated brace upside down with orange electric tape wrapped around the warmed up tread.
Bottom left is how it comes out after it’s cooled. Then it gets trimmed and glued on the brace.

The pic on the upper right is the brace now I think it will be positioned in the vacuum bucket just above the lip so we can pull the vacuum bladder over it instead of the tape. And the bottom right is the amount of room we have in the bucket on the sides where we will have some type of bracket to keep it centered.

The only hole will be in the bottom wheee the vacuum tube comes in and the top will have an air right seal with the silicone vacuum bladder. So the grasping device will have to sit inside and not pierce the sidewalls so we don’t have to deal with vacuum leaks. Thx

 

[dhengr]

Dogboy74:
Why not a 1" thk. steel plate, the diameter of the bot. of the inside of the bucket, this for weight and stability of the whole system. Maybe 4" of concrete in the bot. of the pail. This pl. has a hole for the vac. pipe, fits in the bot. of the bucket and has a 2" std. pipe coupling welded on its top surface, offset a bit from the center, because the toe of the boot is longer than the heel distance from the tibia. The tibia is a 2" piece of threaded stl. pipe, screwed into the bot. coupling, and of various length, in 1" or 2" increments, to get your brace a couple inches above the top of the pail. On a ball joint atop another coupling, you could have a rough cobblers last covered with dense foam rubber which kinda fits (fills out) your boot. Now, the length of pipe and the upper coupling and last screw into the coupling in the bot. of the pail to get the right height and some fairly firm support for your boot. The brace is packed with dense foam, around the 2" pipe, and then just strapped around it. Good Luck.

 

[dogboy74]

Good ideas, thx!