I'm trying to make a adaptor to fit a nozzle about 5mm wide which only applies pressure radially during insertion. Pushing in a standard O Ring would apply some force axially up or down the inlet due to friction.

The adaptor should seal in the inlet, before injecting gas to the object, see sketch. I can't change the object in any way, only the adaptor. Considering the size, can anyone suggest something off the shelf I can use for this? Or how I might make it at all? radial seal sketch

  • $\begingroup$ Why don't you glue the nozzle into the inlet? Any other hints on the applications? Are solvents present, do you need it food safe etc $\endgroup$ – mart Sep 30 '20 at 10:53
  • $\begingroup$ @mart that would be changing the object though - it needs to be able to go into a number of the object and apply the same seal, inject and release the seal $\endgroup$ – Oliver Walters Sep 30 '20 at 11:28
  • $\begingroup$ wait... why can't you use an O ring? :s $\endgroup$ – Jonathan R Swift Sep 30 '20 at 11:28
  • $\begingroup$ @JonathanRSwift because the oring will apply downwards force axially on the object when the nozzle is inserted $\endgroup$ – Oliver Walters Sep 30 '20 at 11:29
  • $\begingroup$ riiiight - I was only considering after install, when the only force would be radial - your wording was a bit confusing! $\endgroup$ – Jonathan R Swift Sep 30 '20 at 11:34

The idea that I was describing in the comments earlier is pretty similar to that described by Mart - I imagined the tube (red) flaring out underneath the O ring, and the opposing taper being either pushed down by hand or driven by a standard nut (black) depending on the sealing forces required.

The key difference is that instead of relying on the squashing of the seal to make it oval so it reaches the walls, you are stretching the seal onto a larger diameter.

seal idea


You could have a barely undersized O-ring around the nozzle, then use a thread around the nozzle to press on the O-ring with a nut. This would require to machining a custom nozzle and nut:

enter image description here

The part of the nozzle where the O-ring rests and the machined part of the nut should probably be larger than in the drawing, 4.5mm or so. I would also consider a seperate piece of metal or plastic between the nut and the O-ring, so that the nut doesnt turn on the o-ring.

  • 1
    $\begingroup$ Thanks for your version - I've gone with Jonathan's as, for my application and with my resources, it will be easier to make, since it allows me to make the nozzle, nut and squasher (as the nut won't fit in the hole also) wider and stronger $\endgroup$ – Oliver Walters Sep 30 '20 at 15:42

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