I got a circular membrane to look like it is flexing...whew!

Hey Everyone, I was working on my ventilator design. My valve actuations include that the valve parts will be moved because the pressure in a chamber changed and this pressure change caused a silicon rubber membrane to flex back and forth. I have been a little surprised that showing this type of flexion back and forth of a circular membrane is hard to do. I wanted the membrane to have a wavy form so it could flex repeatedly without cracking. I had to resort to Sketchup trickery…Ha! I uploaded the files to my Warehouse collection. One file shows how the flexing membrane looks, I put it in a picture showing one of the actuating valve designs. I uploaded another drawing file that shows how I made that wavy membrane and used the scale feature plus some “this and that” maneuvers to get the solid to look like that circular membrane of silicon rubber is flexing. What fun! I uploaded another file that shows how I did it. enjoy Dr. Gray
I guess I should add the file that has the actuating valves in it includes a flexing type membrane that I originally used, but it just didn’t look good, so that’s why I added some Sketchup scale maneuvers to get the look that I wanted.


Thanks everybody for your kind votes that you liked this. I am flexing the membrane by making it a solid and then selecting it and altering it along just one of its axes only by using the scale tool. It is a little weird because if you choose the axis that is perpendicular to the axis of rotation, I think (in this Sketchup Drawing file) it’s the green axis, then as one changes the scale, the membrane behaves in a visual manner like it it flexing. Just weird. But, alas, since you are adjusting the scale along the green axis, all the rectangular “pieces” of the solid will be elongated or shortened, so you need to go back into the solid, select the plane of the rectangular solid that got extended out too much and bring the rectangular solid back to its proper length along it’s green axis that it had before you did the scaling. This “re-adjusting” can be done with the push-pull tool. It is a bit of Sketchup Image Trickery, but oh well. I put the rectangular pieces in the membrane because I wanted the membrane to serve as an isolating boundary where pressure changes on one side of the membrane can be used to move physically real items located on the other side of the membrane. The need for this in human being related equipment is because the secretions, water vapor output, mucous, etc. that are exhaled by humans will act as gooey contaminants to a small precise delicate mechanical structure and will eventually “gum it up” so much that it will not be able to move. It’s a simple concept to me, but I feel it may be confusing to people trying to create mechanical items for use with humans because they may not be familiar with how much biological material flows away from humans. I wanted to show that membrane flexing because I felt people would say, “Well, hang on a second, why did that mechanical linkage move like that?” I would reply because the differential pressure across that thin flexible medical grade silicon rubber membrane, well, that differential pressure changed, and I was worried that a lot of people would say “So what.” Because people just don’t normally think that way, but a flexing membrane can definitely create linear motion, and a membrane can isolate one area of a machine from another area of a machine with a gas tight seal, it will all work, I just found it weirdly difficult to get Sketchup to show this type of mechanical linkage.
Ok, I read this post, and I left out an important point, so I will add that point here. One must “connect” the flexing membrane to the physical item that you want the flexing membrane to move. This requires that one must create the silicon rubber membrane so that it has a rectangular solid shaped area at it’s center point. Because a rectangular solid shaped area can easily be mechanically connected to a metal part. So you have to have the rectangular portions of the membrane, and those rectangular areas get way too much adjusted by the scale activity, so after you do enough scaling to get the membrane to move like you wanted it to, then you’ve got to go back into the silicon rubber membrane solid and bring your rectangular areas back to being their appropriate size. (this is the trickery part) So…There you go. Dr. Gray

I’ve tuned it up so it’s more precise, I’ll upload that soon. Of note, get this, one can show a cross section of the membrane with the section tool, then select the membrane as a solid, then adjust the scale just along the green axis, while showing the membrane in the section tool view. So you get to see the membrane in cross section in blue and flexing back and forth. Wow, that really surprised me!
Ok, I hope Sketchup will let me talk this much. The issue is that in a typical human ventilation setup, a tube goes to the patient and another goes from the patient. But it’s just a T joint at the place where the breathing tube goes into the patient. So if one pressurizes the bellows bag to “push” air into the patient, this air will just flow up the input tube and down the exhaust tube and out to the room. No air will go into the patient’s lungs. It is required that there be an “exhaust” valve, and the device must be configured so that when the input bellows is compressed, then at the same time, simultaneously, the exhaust tube valve is shut. Then the pressurized air in the bellows will go into the patient’s lungs and expand them. The very moment the pressure is taken off the bellows, the exhaust valve must be opened so the air one put into the patient’s lungs will then flow out into the exhaust tube, the air in the patient’s lungs flows out into just the output or exhause tube because there is a one-way valve at the start of the input tube so that, with respect to the input tube, gas can only go from the bellows out into the input tube. This structure that I am showing in these Sketchup drawings is the mechanical linkage where higher pressure in the bellows “pushes” out the silicon rubber membrane, and this movement closes the exhaust valve. When the pressure comes off the bellows, the silicon membrane flexes back the other way and opens the exhaust valve. Ha! magic. I apologize for using so many words, I don’t have the gift to explain anything in a simple manner. But I’m hoping this will help with those who say “Ummmm, so what is the point of all this anyway???” I think this on-off-on-off exhaust valve cycling is the major secret of creating a ventilator for humans that really would be helpful. enjoy, Dr. Gray. And here’s an image of that Section Plane stuff. My design is that the exhaust valve “plug” must move 1/4 inch to fully close the exhaust valve. At this point, I have the plug in its fully open state, and it has moved in 1/8th inch. So I need to make one more copy of the structure and advance the plug another 1/8th inch, then the valve will be closed. I am not quite done with that yet.