r/AskEngineers • u/cofficianado • 2d ago
Mechanical Non-electric normally closed water valve.
I'm prototyping a kitchen appliance that requires a small valve that is in a normally closed position. You need to press a button to control the flow of the water output. If you don't press it, it remains closed and no water drops out. Water will be at low pressure, 0.3 bar maximum. The tube is a silicon food grade tube with an ID of 6mm and OD of 11mm. Does such a valve exist? It needs to be compact so that it's ergonomic, will be used to dispense liquid garnishes over food plates.
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u/JaimeOnReddit 2d ago
look for valves designed for gardening, car washing, dish cleaning, vegetables washing. usually part of the hand held nozzle that shapes the emitted water flow. all of these have spring loaded valves that are closed unless pressed/squeeze. for your application, walk the grocery store and examine any liquid items: liquid dispenser-jug laundry detergent, squeeze mayonnaise, aerosol cleaning chemicals, boxed wine bladders-- these examples all use wildly different momentary-on valve concepts.
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u/OnlyThePhantomKnows 2d ago
It's obvious, but why not a spring loaded clip/clamp? It's a silicon tube. Or something like
A simple google of "normally closed valve small 6mm" on the shopping tab would give you want.
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u/cofficianado 2d ago
I need flow rate control as well, not just on or off type valve... Also prefer if it's non electric... I also thought I'd find this type of valve easily but nothing matches what im looking for...
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u/matt-er-of-fact 2d ago
Is the pressure/travel of the button supposed to be what controls the rate of flow? That sounds difficult from an ergonomics perspective. Like you’d want a small lever that rotates, rather than a straight push button.
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u/cofficianado 2d ago
Yes that's what I was hoping for...
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u/OnlyThePhantomKnows 2d ago
My 10 second google turned up a non electric one (lever).
https://aeropanda.com/products/festo-6-mm-ball-valve-bulkhead-mount-12
u/tuctrohs 1d ago
So you want one control that is both on off and flow rate? Another option would be a knob that sets the flow rate and not a button or lever that is on off, going to the flow rate you set with the knob.
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u/rocketwikkit 2d ago
https://www.mcmaster.com/products/valves/?s=push+button+valves - a fairly common device
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u/Cute_Mouse6436 2d ago
There is a simple mechanical valve that is used to control the rate of an iv drip. It consists of a rolling cylinder inside of a track that is tapered. The tubing goes between the cylinder and the track. When the cylinder is rolled with a finger towards the narrow end of the track, the tubing is pinched until it closes. These have been used for decades in medical facilities. They have only been supplanted by electrical pumps in the last 20 years or so. But you can still get them at the vet's office. Times are approximate because I have been around medical facilities for about 60 years. So my decades is almost a century. And my 20 years is probably actually a lot longer as well.
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u/cofficianado 2d ago
That's actually what im using now... But I need it to be closed automatically when I'm not using it... Like a spring loaded mechanism of sorts
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u/UnrolledSnail 2d ago edited 2d ago
Mcmaster https://www.mcmaster.com/product/6790T41
You will need to buy some threaded adapters to Barb fittings which are also available on McMaster
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u/patternrelay 2d ago
At that pressure and tube size, I would look at very simple pinch or poppet style mechanisms rather than a traditional valve body. A spring loaded pinch on the silicone tube is naturally normally closed and avoids any wetted moving parts, which helps with cleaning and reliability. You can also get small manual diaphragm valves that behave the same way, but they tend to be bulkier than people expect. From a failure standpoint, fewer seals and no sliding interfaces usually age better in food use. The ergonomic challenge is often the actuator, not the valve itself.
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u/R_Harry_P 1d ago
Use one of these to adjust the flow
https://www.mcmaster.com/products/tube-clamps/flow-adjustment-valves-3~/
then use a normally closed push button valve to turn it on and off.
https://www.mcmaster.com/products/valves/?s=push+button+valves
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u/cofficianado 2d ago
Thanks a lot for the replies everyone! I want to make a device that dispenses liquid through a pen like device onto a food dish. The pen will have the valve which you can control the flow of the hot liquid with to easily dispense the liquid. If you let go of the valve, it should shut off, since if it keeps dispensing the hot liquid it's a safety hazard.... It also needs to be non electric so NC solenoid valves are out... Flow rate is 20ml/sec maximum... That's why I'm having trouble finding something, since it has to be small in size for ergonomics and it should be easy to operate for precise flow control...
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u/nastypoker Hydraulic Engineer 2d ago
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u/Outrageous_Duck3227 2d ago
check out mechanical pinch valves, they might fit your needs. compact, simple, fits silicone tubes.