Open Source Eccentric Bowtie Ventilator (WIP Just Starting)

Note: Obviously, this project is not anywhere near presenting to a doctor for consideration, and further development. Do not make this. Do not try this under any circumstances.

You only have to pump about a half-litre of air to save a human life. I realize that a lot of people are working on designs, but for every one of use messing with this, it puts more pressure on the corporate world to compete.

I messed around with this idea yesterday, and some, tonight. There are only concepts here. I am just moving stuff around, so go easy on me. I just need to step away from it and think more.

The device would be 3D printed in the 1st world, but perhaps it could be made of plywood in the 3rd world, so, I am going to try to keep it K.I.S.S. . Because I mean for it to be 3d printed, the largest part must be smaller than 200mm x 200mm x 180mm.

I want it designed so it can be 3D printed in sections, so a trashed print will only set you back no more than 25%, so it cannot be monolithic, BUT the parts need alignment surfaces and edges, so it cannot be assembled out of alignment. Perhaps there will be bolts and 3D printed pins, so there is no misalignment.

The idea is to make something rugged that would use as many ordinary materials as possible. Instead of using linear rails, I thought to use skateboard bearings because they are good, cheap, and plentiful.

Oddly, fasteners will be a problem. In the U.S. metric fasteners are rare. Elsewhere USCU/SAE are likely unobtainium.

Yes, I know I have the NEMA 23 motor interfering with the top. It needs a motor mount, too. The whole thing is going to have to be redrawn with gussets and holes to save filament. It will have to be triangulated and filleted.

The motor would likely be a stepper, but perhaps in poorer regions, the could use some other geared controllable motor.

I am not happy that there are sliding parts, but squashing some kind of bag with a rotating part tended to want to pinch it.

Perhaps the displacement could be adjusted by offsetting the eccentric or changing it out, but that is where a lever and bellows design was better. Perhaps the bottom plate could be movable. Doctors check the progress by reducing the volume, and see how people respond.

Perhaps a column of water could be used to eliminate overpressure, just the opposite that a vacuum lock works for pnumothorax chest tubes, which I spent a few weeks with : O

Hi Brenda,

Don’t know if you’ve seen this one, with links to a project that is close to presenting:

Interesting to see they include their discarded mechanisms on github.


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This is the beginning of the presser bottom, without the X brace.

Standard skateboard shafts are 5/16" NF; the bearings are metric 8mm ID : O

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The presser part isn’t joined yet for fillets.

I was not happy with the previous mechanism. I still fancy something that rotates, rather than something that slides.

Those resuscitation bulbs shown in other ventilators might be difficult to find because they are related to the very shortage they aim to fix.

I had hoped to figure out something capable of squeezing two layers of thick plastic bags–just the thing in developing countries. They are throwing them away, and I am sure that there are bi-axially stretched plastic bags capable of holding the pressure, so two layers should do.

Then perhaps a sealing connector could be made, where you put 2 bags through an nozzle, fold them around, and place another ring over to seal them, and then fix them with some screws or bolts. It’s like being a kid, and blowing up a paper bag before you pop it.

But how to squeeze them easily?

After several different designs, this appeared.

Yes, I know, it looks like a big variable capacitor, or a hard drive voice coil, but I think it can squeeze 600cc or air from heavy plastic bag. It uses the same eccentric and roller from the other design.

There will be some sliding happening at the bag or air bladder, but perhaps after a few days the bags can be changed. The parts would be filleted for smoothness. There needs to be a small gap between the layers.

There is an extra little curve in there to minimize the pinching of the bags. I imagine this will make noise, but that’s not the biggest issue.

It needs a bearing mount, motor mounds, something to hold a spring, a cage to mount everything in…
I am too tired to do any more.

As long as there are no toxic materials used and very questionable fans for generating the air flow you have my :+1:

@brenda have you found any data regarding the output airflow rate and pressure requirements?

Unfortunately I don’t have 3d printer to test but you may also try it might be more efficient that the hand-respirator they are suggesting in the design.

NOTE: Do not use 3d printed parts touching the air that would go inside people’s lungs it is toxic and has small particles that may worsen the person’s health. They must be created with other means and materials. This suggestion was only for testing purposes.

Also if I understand correctly you’re using the eccentric rotated part to “squeeze” the hand-respirator. Have you thought about the damage this rotating part will cause on the hand respirator?

PLA, polylactic-acid is food-safe, but probably not good inside the body. The idea of the thing is to squeeze the air from a bag.

Apparently, we breathe about a .5 liter per breath.

I am sure that the screw compressor would be more efficient, but there will be infections material, so I as in the other designs, want a device that can be used for a few people before it is scrapped, with disposable parts for anything the the patient’s breath may touch.

I worry about the availability of the hand-respirators. Yes, the air bladder needs to be protected, perhaps by cloth overbag. Presently, I am trying to figure out a system that can use ordinary plastic bags. There are several materials, perhaps one will endure. There would be a bag-within bag, for strength.

I would like to figure out something that will not pinch the bag, like this later design, but also would have no sliding on the bag, but also no sliding on the mechanism, which are hard all to do.

Imagination, where are you when I need you…

A while ago I was reading about hypoalergenic, odor-stopping bags, and found about Mylar Apparently it’s relatively wide spread. Also this is material they use in space to protect the space-walkers from high-speed debri impact.

If properly designed you can pull from outside to fill it with air and push it with your mechanism to re-direct the collected air towards the patient. I haven’t seen such bags in Germany, but I’ve seen them on amazon so I guess they are accessible. Also not very expensive.

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AFAIK, ordinary shopping bags are polyester, too.