Anyone here know about metering pumps?

Stepper driven syringe pump perhaps? For example:

Zt sounds as if you are going to need at the very least a timer. Perhaps so me intelligence.

Consider using an Arduino. they aer dirt cheap microcontrolers. The cheap est one can work as a timer and can be set to 1/1000 of a second to any rea sonable length of time. I do not remember the exact number but the max ti me is measured in days. They are easy to program, And I will help you.

Dan

How about a simple tube roller type pump. A savvy machinist can make his own.

With a tube/roller pump you just need to control the speed of whatever motor you are using. About the simplest low pressure low volume pump you can get - and it can be a steady flow, as compared to pulsed outpot with either a double loop or double roller setup

AKA Peristaltic pump. As low as about 6 bucks on EBay - up ton several thousand - - - -

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s some intelligence.

heapest one can work as a timer and can be set to 1/1000 of a second to any reasonable length of time. I do not remember the exact number but the ma x time is measured in days. They are easy to program, And I will help you .

Peristaltic pumps usually aren't very good for long-term or continuous use. The tube materials suitable for handling many active liquids, like cutting fluids, are short on fatigue life, or vice versa.

However, I saw one used many years ago for pumping machine oil, and it held up for at least a year, said the guy who made it. He used silicone tubing made for carrying fuel in model aircraft.

I made one for my son's school science project on filtering water, when he was in fourth grade. I used latex tubing I got from a drug store. But it on ly pumped water and it only had to last through one science fair. d8-)

I've used a lot, 1/2 liter syringe, triplex diaphragm, gear. The syringe was expensive, the triplex diaphragms with vfd drive very expensive. Even the gear pumps were expensive. Gear and syringe pumps were $5-10,000, triplex diaphragms $25,000 and up. All of mine were even more expensive because of the need for mass flow meters for my accuracy requirements, 0.1% or better.

Peristaltic pumps are much less expensive. I even saw a 3d printed one as a feature article in the digital machining mag. Delivery can be controlled pretty well by tube size and motor speed. Pressure capability is somewhat limited and tubes fail.

I think you're going to have to get creative. The solenoid idea is good if the service life is adequate. Most piston and diaphragm pumps I used had double sapphire ball checks at inlet and outlet. I imagine you could get by with something a little cheaper, maybe plastic. Usually they were seated by gravity, no springs. But you'd need a spring for a valve near the nozzle. Try disassembling some pump spray bottles for springs and checks.

Good luck. An interesting challenge.

Pete Keillor

Your description, request sounds a lot like a diesel injector pump. They aren't cheap either but there are lots of old ones around. Maybe find one for a four cylinder.

Not sure but I would try hooking all four output lines into a manifold and then plumb it into an old injector nozzle. That should keep it from dripping.

You could vary the speed of the pump and throttle control to vary the output. I think it would hold up okay as long as you were running some sort of thin oil through.

The real diesel mechanics can speak-up now and tell how stupid this is ;-)

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some intelligence.

eapest one can work as a timer and can be set to 1/1000 of a second to any reasonable length of time. I do not remember the exact number but the max time is measured in days. They are easy to program, And I will help you.

I've got a Stenner peristaltic pump that doses chlorine into my well water. Something smaller, with thin tygon fuel line tubing?? (maybe) might work. What do you mean by a double loop, or double roller? (The Stenner goes around in a circle with three rollers.)

George H.

Last yime I saw one of those, it was hooked to my wife's arm, trying to induce the birth of Junior two weeks early since it was thought he was trying to live "in" and not gaining any weight - after three days he weighed in at 7lb.12. As to the peristaltic (?) pump, I paid $2for the example down in the shop.

I tought about some sort of stepper driven piston but I need a larger reservoir than a syringe. Maybe some sort valve that fills the syringe when the stepper motor retracts the plunger when it has reached the end of travel. Eric

I thought about peristaltic pumps but the tubing doesn't seem to last. And I think a pulsing pump might be better since I'm only needing a drop or two at a time. Eric

I thought about peristaltic pumps but the tubing doesn't seem to last. And I think a pulsing pump might be better since I'm only needing a drop or two at a time. Eric =======================================================================

First estimate a flow rate. I think you said something about a drop every second or two. Using an old fashioned eye dropper the rule of thumb was 20 drops to the mL, or 50 microliters per drop, but I always thought those were pretty big drops :-). As a swag, lets say 10 uL per drop, and a drop every two seconds or 30 drops per minute, so 10 uL/drop * 30 drops/min = 300 uL/min as a typical flow rate, with max and min maybe a factor of 10 up and down. Next, decide if you want pulsed flow, a squirt at a time, or continuous flow. If you want squirts, you need 10 uL per squirt and maybe some kind of variable stroke piston pump driven by a solenoid, but that's going to be a pretty tiny bore and a very short stroke, plus check valves that barely crack and then reliably re-seal. If you want continuous flow, maybe you could adapt the smallest gear type automotive oil pump - connect up a dc motor with a big reduction gear ratio and vary the voltage to vary flow. You will have internal leakage but that won't hurt anything, you just spin it a tad faster to get your desired output flow. Might not be able to get the flow down enough. 0.3 mL/min is in the range used for conventional HPLC (high pressure liquid chromatography, say 0.1 to 10 mL/min and up to

5000 psi which you don't need), so you could buy a used HPLC pump off of ebay. I saw some Altex 110's for under $100, and Eldex has some cheap models, too. Course the risk there is you may have to rebuild the pump head which could be $$. Another possibility is to use the nebulizer air flow as an aspirator. Turn the air on all the time and use a needle valve to control the continuous flow, or use a solenoid valve to pulse the air flow with the same needle valve for control. Or, door number 3, buy this little oil rated gear pump off aliexpress for $10 and see if you can turn the flow down enough:

----- Regards, Carl Ijames

Eric, maybe you could set up a tiny fuel injector for that use. A pulse from the requisite Arduino circuit board would time it. That would be tons cheaper than even a used medical pump.

They weren't pervasive back when I quit wrenching, so I never worked on them.

Any porting of the syringe body to refill would end up in lots of leakage as you reinserted the plunger beyond it. :-/

Valve would be on a tee off the output. or rather, valves, plural - one to stop suck-back form the output, one to allow suck-in but prevent outward flow on the reservoir. Not a novel problem.

I think combining two of the other answers gets a better result - use a pump such as as a vehicle oil pump to develop pressure into a manifold, and provide an over-pressure bleed back to the reservoir rather than trying to throttle it down. Then plug a fuel injector into the manifold.

No suggestion as to tubing life, but as to pulsing: you could drive it with a stepper motor & control the size of drop and frequency.

The beauty of most of the (at least cheaper) peristalic pumps is the tubing is easily replaced and VERY cheap - and you CAN use differnt tubing for different chemical makeup. A PWM controller can control the speed of the little DCPM motors quite well, so if sized appropriately you can control the coolant delivery very well - and they ARE available with stepper drives or geared drives - but significantly more money.