What pump is this and how does it work.

[x3qt0r]

Kindly check the attachment for the picture of the spray pump.
Please link me to the thread/post if this is already discussed elsewhere on the forum.
Is the working of this pump has anything to do with vapor pressure?
Thanks in advance for any help.

 

[rcgldr]

updated reply - You're picture resembles a "flit gun", although the pump looks more like a calking dispenser because the outlet hole appears to be too large. These were mostly used for insecticide, but I did find one hit where a modifie flit gun (air compressor versus hand pump) was used for painting, as a cheap alternative to an air brush.

http://pestworld.stjohn.hawaii.edu/studypackets/techniq.html

It appears to be a Venturi effect device, but note that the hole is much smaller than the one shown in your picture (photo in next link):

Here is a photo of the German equivalent, where you can see the outlet hole size:

http://forum.axishistory.com/viewtopic.php?f=20&t=136731

An ad photograph of "flit gun"

http://orpheus.ucsd.edu/speccoll/dsads/flit/flit29.shtml

These type of sprayers were replaced by pump sprayers or aerosol cans back in the 1970's.

http://science.howstuffworks.com/question673.htm

Venturi effect pumps are still used to drain aquariums.

http://andysworld.org.uk/aquablog/?postid=247

Follow the links to the patents, then images, and you can see the image of the internals (quicktime is needed to see the USA patent).

 

[x3qt0r]

Thanks,that was one fine search.
The thing in my picture looks like that of the flit gun (including the internals)so i presume that it should be based on flit gun's mode of operation which in itself a bit puzzling.

The wikipedia and also pestworld's explanation talks about the following which I am not able to understand : "The stream of air passes over the tube, syphons the liquid from the tank and atomizing it as it reaches the sir supply"
I am not able to understand the "atomizing" part, I am getting the working till the "pulling" of the plunger action but not after that.How does the blow of air causes a fine spray?

 

[rcgldr]

My guess is that it's a crude venturi device (I'm assuming that there's no tapered cone exiting at that small hole inside the pump that would improve the venturi effect). Until the air exits the pump the mass flow across any point is constant. This means the air travels much faster through the tiny hole than it does through the larger part of the tube, and the only source for this acceleration of air is a pressure differential, from higher in the large part of the tube to lower in the small part of the tube. Note that friction and viscosity intefere with this transition, slowing flow near the perimeter of the hole, with faster still flow in the middle of the small hole.

In order to draw fluid out from the container, the pressure of the air stream above the nozzle has to be lower than the pressure inside the container, so the hole at the end of the pump has to be pretty small for a hand powered device to work, and close to the fluid dispensing nozzle, because the air is declerating and it's pressure transitioning back to ambient as soon as it leaves the hole. This is why your picture seems suspicious, because the pump's exhaust cone appears to be too far away from the dispensinig nozzle, although it's possible that the device was bent to end up like that.

The container needs to be vented (the hole in the cap), in order for it's pressure not to be reduced as the fluid exits.

Anyway, the end result is a high speed, lower pressure air flow over the fluid nozzle. The low pressure draws the fluid into the air stream, and the high speed air flow spreads out the fluid into small droplets, atomizing the fluid.

This brought back memories as I recall using these back in the early 1960's in Houston (mosquitos with potential sleeping sickness were an issue, and fire stations were distributing insectiside, probably DDT, and the sprayers for free).

It took a while to find out about flit gun, and many of the hits I found where to stories that mentioned flit guns without any real description. A bit of trivia popped up as the guy that did the cartoon ads for the early flit guns is Dr Seuss. Although I actually use the phython venturi based aquarium pump, I also recall these being used as general water draining devices back in the 1960's and couldn't find a link to of those. If you look at the patent for the Python, then look at prior art, you can see that it's essentially the same as a basin draining and filling device patented in 1933.

Besides carberators, air brushes that feed paint from below also use venturi effect with effeciently designed nozzles.

Most modern day sprayers are true pumps, using one way valves, and slightly increase pressure inside the container to force fluid up to the dispensing nozzle. I checked out an old perfume sprayer my wife had, and the fluid rose in the tube while the bulb was relaxing. I'm not sure what was preventing fluid from getting into the bulb (perhaps a very tiny hole allowed air flow, but not fluid).

 

[x3qt0r]

OK now that confused me more.
And about the suspicion ,I can get it cleared by posting more photos/videos of that pump cause I own it and its pretty common in India.
Plus its in working condition.

 

[rcgldr]

I assume that when used, the cannister is below the nozzle as shown in the picture? How narrow is the opening in the tube at the end of the pump part? The air velocity would need to be fairly fast in order to reduce pressure enough to draw the fluid out. However if the cannister is held upside down, so the fluid just flows out, then the air speed out the nozzle isn't critical. What is this sprayer used for?

 

[LURCH]

Is it the Ventury Effect itself that you do not understand? When air (or any fluid) moves "sideways" across a surface, it generates less pressure against that surface than air that is sitting still. You can test this yourself by holding up two sheets of paper parrallel to one another with a small gap in between them. If you blow between the two sheets, you might expect them to be pushed apart, but instead they are drawn together. This is because the air in betweem them is moving, but the air pushing on their outside surfaces is still, so the air between them generates less pressure and the outside air (which remains at normal pressure) pushes them inward.

There are some good explanations http://en.wikipedia.org/wiki/Venturi_effect" . It is basically an application of Bernoulli's Principle, which states that as the velocity of flow in a fluid increases, the pressure in that fluid decreases.

So, the inside of the cylinder on your sprayer suddenly gets much narrower right where the tube from the cannister comes in. This narrowing of the tube causes air to flow faster. The higher speed causes lower pressure, or suction (all suction is just lower pressure in one place than another). It is this suction that draws the liquid up from the cannister into the cylinder. When the liquid reaches the cylinder, it comes in at a place where air pressure is very low, and this helps it to atomize into a fine spray.

Does that help?

 

[rcgldr]

When air (or any fluid) moves "sideways" across a surface, it generates less pressure against that surface than air that is sitting still. It is basically an application of Bernoulli's Principle, which states that as the velocity of flow in a fluid increases, the pressure in that fluid decreases.

Bernoulli's principle only applies when no work is done. Bernoulli principle is approximated if a small amount of work is performed. The cause or the acceleration of air needs to be known before a relationship between velocity and pressure can be established. In the case of the pump, the hole performs a small amount of work on the air, resisting the flow and requiring a higher pressure inside the tube to compensate, but the pressure still drops below ambient as the air accelerates into the hole.

Since the pump is peforming work on the air (assuming more energy added by the pump than lost through the hole), the velocity of the affected air will be non-zero after it's pressure returns to ambient, but this doesn't matter as long the cannister nozzle is located close enough to the hole where the air stream pressure is still below ambient.

 

[x3qt0r]

I assume that when used, the cannister is below the nozzle as shown in the picture?

Yes.

How narrow is the opening in the tube at the end of the pump part?

Very small, same as that on the cannister.

What is this sprayer used for?

To kill bugs.

I understood the Ventury Effect.
But am still not getting the "atomizing part".
Just not fitting in my intuition.

 

[rcgldr]

But am still not getting the "atomizing part".

The high speed air breaks up the fluid into small droplets, and this is called atomizing. Because the air flow is decelerating (moving from lower to higher pressure area) it should be turbulent which should help. Also the air flow of these is designed to spread out as opposed to staying in a narrow stream. All of these factors will help spread out the fluid droplets into a larger area.

Newer hand sprayers rely on one way valves (balls kept close to a hole via a small cage) and are more efficient. You get about the same spray by just squeezing a trigger type handle with your fingers that you get with the old type by moving the pump handle with your entire arm.

I'm not sure which is cheaper to make, but my guess is that the flit gun type sprayers simply last a long time, and there's no point in replacing something that works. In the USA, flit guns were first made back in 1928, and they quit being made around 1970. How old is that sprayer in the picture?

Documentation of some forms of older technology, such as a flit gun, was difficult to find on the internet. If it hadn't been for the childrens book writer, Dr Seuss, doing the cartoon ads, the "flit gun" would have been even more difficult to find.

 

[x3qt0r]

The high speed air breaks up the fluid into small droplets, and this is called atomizing.

Why does that happen.Because even when i blow the plunger slowly there is still amount of spary.


The spray is like 5 to 6 months old.

 

[rcgldr]

The high speed air breaks up the fluid into small droplets, and this is called atomizing.

Why does that happen.Because even when i blow the plunger slowly there is still amount of spray.

The fluid itself has the quality of easily being dispersed into spray. What happens if you pump very slowly? If you block the flow from the nozzle out of the pump, how fast does the air stream feel?

Is the pump part made of metal? How is the pump part attached to the can part?