avi,avi123 wrote:
Comment,
As a Mechanical and a Biomedical Engineer I know that when using seals in machines, the longer the linear length of a seal, the longer the probabilities of leaks if you're talking about the same composition of the seal all along its length.
Resmed's (and a few others) masks, use an advanced technology of the double flaps on their cushions, whereby the outer flap overlap the inner layer. Any leak inside the inner layer needs to travel between these flaps to reach the atmospheric pressure.
The more the flaps, the better the sealing b/c each flap reduces the pressures gradient, to a certain degree.
Here is a sketch showing the principal behind this technique in a Labyrinth seal used to seal rotating shafts:
From my experience, I know that the Fisher & Paykel full face masks #431 and #432 DON"T use such technique and thus I found them to be inferior leakage wise.
Thanks - that's a great explanation for a non-engineer like me.
Incidentally, if you are still considering trying the Wisp, I can attest to the fact that it has implemented the technique you describe, which contributes to the ease with which it seals. I am very much aware of the intricacy of the construction of its sealing "lip" every morning, when I try to take care to thoroughly wipe it with a fresh moist cpap wipe. It requires a thumb and opposing finger to carefully get into the curls which make up the lip.
Regards, Nate








