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Development of the suction channel
Development of the suction channel
In order for the seal of the mask to be effective, it needs to closely match the contour of facial features.
The suction channel of our mask was designed in reference to a NIOSH medium head form, by defining a 3D reference curve through distinct mask profile contact points.
First Method
First Method
Our first prototype used an extrusion-based model for the channel. It was modeled by extruding a solid until it intersected with the STL of the NIOSH head form. Thus, the suction channel for Prototype 1 matched the medium symmetry face form exactly.
This was an excellent method for deriving facial geometry, however through testing, we realized we needed a more complex suction channel cross-section.
Revised method
Revised method
In order to create a suction channel shape that was constant across the profile of the face, we swept our new cross-section for our best channel geometry and defined its central axis to be normal to the face reference curves. This allowed us not only to design a more flexible silicone channel that could hold a seal better but also let us keep that channel consistent in shape at all parts along the face.
Final Channel Design
Final Channel Design
A key remaining issue from the initial prototypes was the inadequate seal around the nose. This was due primarily to the harsh angles in the nose region. The seal for our final design was improved by lengthening both the inner and outer channel flap by a few millimeters, and then specifically adjusting the geometry of the seal around the nose.
Nose Region of Final Prototype
Nose Region of Final Design
Final Prototype / Final Design Comparison Overlap
These relatively subtle changes to the silicone channel ultimately made the difference between the suction assisted respiratory mask exhibiting no suction, to being able to hold a complete vacuum seal against positive pressure ventilation.
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