Vacuum Seal with linear movement

[Gerard Agudo]

Hello everyone,

I've had this porblem for a while and after thinking for quite a while I haven't found any solution.
It's quite a complex problem but i've tried to simplify it as much as possible down to only the key elements that dictate te limits of the possible solutions.
I've made a simple representation to help visualize what exacty I'm referring to.
So i have a big volume drawn in black in the first attatched image (number 1), which is divided into 2 different areas by a blue drawn solid surface. We can call the bottom area as A and the top as B as image number 2 shows.
The A zone is at 250mbar of vacuum pressure, while zone B is at atmospheric pressure. There is a rod, drawn in red, that comes through the slotted hole that the blue surface has, which it can freely move on the radial X axis.

This is where the problem starts. This rod has an O-ring around it so that no air can pass through between the O-ring and the rod. Now, this O-ring has an elastic material which is , on one side thermosealed to the O-ring and on the other side, to the blue surface that makes the division of the two A and B zones. This elastic material is drawn in orange in the attatched images.
The objective of this is to keep the vacuum pressure of 250mbar on the A zone, while the rod can move through the X axis of the slotted hole linearly and not have any leaks of vacuum. Not necesairly freely, it's okay if it has some resistance due to the elastic force of the material.
I've tried to solve this for months and haven't found any solution. I've tried with latex and multiple elastic materials and different geometries and tey all lose vacuum and end up tearing a part after some movements.

Thanks!
Gerard.

 

[3DDave]

Not going to open any "rar". Can images be added using the "Image" button?

 

[MechyMarco]

Yeah a better image would help. Sounds like you just need a gas tight rod seal? A plain o-ring won't work very well. Try out a T-seal. They make them in standard sizes to retrofit standard o-ring grooves. Assuming you designed the rod to a standard size. You should be able to get a perfect seal with that.

 

[Gerard Agudo]

Sorry 3DDave, i wanted to attatch multiple images but i am new to this forum and didn't find an option to do that.
As I wanted to attatch the second picture it overwrote it from the previous one.

Sorry for the bad image but my 3D CAD software wasn't workking at the time and had to draw it by hand.

I'll have a look at these seals you've said MechyMacro.

I'll try to update you guys today with a better image explaining the issue i have.

Thanks for your quick answers

 

[3DDave]

Seem like this button works OK.

as I was able to post 3 separate pictures.