Micro check valve/air relief valve hybrid?

[Thomas Boland]

Hello! Just joined the forum.

I'd like to pick the brain of some of us that knows a lot about valves that currently exist.

I'm looking for a valve that will both act as a 1 way flow check valve, and a air release valve. Basically the application is a small fluid tank, that needs to be filled with liquid, via syringe (the Ø4mm end plastic type), such that the liquid can enter into said tank, and expel/displace the air previously in the tank, with zero leakage after the filling process is complete.

The target is to have these two functions within a small cylindrical form factor, ideally Ø7mm x 12mm or so long.

So could anyone enlighten to me as to if something similar to this description already exists, or of something that would perform the same way?

Thanks in advance!
- Thomas

 

[LittleInch]

Which way is the check valve? i.e. air allowed out of the tank and not in or vice versa?

If vice versa it is not possible to easily mix flow out (air displacement) with flow in only check valve. You would need two separate valves.

But if the former then a simple air release valve will do this for you. Getting one that small isn't easy - you're into laborotory sized equipment. Try someone like this

http://pages.norgren.com/uk-new/val...e1zUHWLDrpbxhxvWA1CGr3DWgXet7HiAaAu9uEALw_wcB

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Compositepro]

Use a needle on the syringe, which penetrates a rubber septum, like what is used on intravenous medicine vials. Inject liquid until it starts to come out of the septum around the needle.

 

[Thomas Boland]

Which way is the check valve? i.e. air allowed out of the tank and not in or vice versa?

If vice versa it is not possible to easily mix flow out (air displacement) with flow in only check valve. You would need two separate valves.

But if the former then a simple air release valve will do this for you. Getting one that small isn't easy - you're into laborotory sized equipment. Try someone like this

http://pages.norgren.com/uk-new/valves.html?keywor...

The valve most allow water to enter the tank (ofcourse not allow it back out), and allow air out of the tank, but does not need to, and should not let air back in (vacuum would not occur, due to other unmentioned elements in this tank assembly).

Thanks for the reply. I'll look into it!

 

[Thomas Boland]

Use a needle on the syringe, which penetrates a rubber septum, like what is used on intravenous medicine vials. Inject liquid until it starts to come out of the septum around the needle.

Thanks for the suggestion, this is quite a effective solution, except the fact that the indication that it is full would be water overflow through the septum, which isn't desirable. What would be ideal, would be a valve that would let air out, and then close as soon as coming into contact with a liquid. The first idea that comes to mind is a float ball, that pushes against a seal. But this tank needs to be able to be able to be handled, and rotated in all directions, in which case, a simple float would leak when turned 180.

 

[Compositepro]

Is one droplet of water leakage less desirable than a bubble of air left in the container? Because, in reality, that is the choice that has to be made.

 

[LittleInch]

I think you need something spring loaded that when you insert the syringe pushes a flap down to allow liquid in and air out. Then when you remove the syringe it closes up again.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Thomas Boland]

Is one droplet of water leakage less desirable than a bubble of air left in the container? Because, in reality, that is the choice that has to be made.

Yes, you are right. In this instance though, a little hair left in the tank is more desirable.

 

[Thomas Boland]

I think you need something spring loaded that when you insert the syringe pushes a flap down to allow liquid in and air out. Then when you remove the syringe it closes up again.

Yeah, thats right. I think i have designed a solution now, the only issue is easily manufacturing and getting it small enough to work for the application.

I appreciate your help LittleInch and Compositepro! I think i have it worked out now.

Thanks,
- Thomas

 

[moltenmetal]

The traditional way you fill something with a syringe while providing means for venting is to use TWO needles, both fitted with syringes if necessary for containment. For instance, to transfer a pyrophoric chemical in the laboratory, we would insert two syringe needles through the septum- one connected to a dry, empty syringe, the other connected to a syringe full of argon. As you withdraw the liquid into the empty syringe, the argon-filled one will be pushed by atmospheric pressure to recharge the headspace.

When filling, you simply insert another needle to an empty syringe. As you inject liquid, the air will be displaced and will fill the empty syringe. If contamination, venting or discharge of any un-necessary excess liquid is not an issue, you simply have the 2nd needle discharge to the air.

Want a tiny micro-check valve to act as an air vent/relief valve? You might find such check valves available for use in services like high pressure liquid chromatography- at very high prices- from somebody like Chromatographic Specialties.

https://chromspec.com/Products/c/Valves-and-Accessories

 

[Thomas Boland]

The traditional way you fill something with a syringe while providing means for venting is to use TWO...

The more you know, the better! Thanks for the info, i appreciate it. The main requirement in this project though is ease of use, and pleasant results, because this is for a consumer application, so multiple needles etc. isn't ideal. And thanks! I will check the link out that you sent.

 

[hydtools]

See Vernay:

http://www.vernay.com/Markets/Medic...vE1wy51qo3NcFI93UWcl-Erd4X6qhA9BoCKgYQAvD_BwE

Ted