0284353-A2 is referenced by 10 patents and cites 8 patents.

The exhalation valve (14) of a respiratory face mask (10), while taking up only a small area, can afford extraordinarily low pressure drop for easy breathing if constructed with a valve seat (16) having a seal edge (18) that defines an orifice (21) and also forms a parabola in the plane bisecting the mask (10). Preferably the seal edge (18) forms a rectangle as viewed against the direction of composite fluid flow (34) through the valve (14), and a flexible flap (24) is attached to a bridge (19) across the center of the orifice at the apex of said parabola, each end of the flap (24) being free to be lifted to allow fluid to flow through the valve (14).

Title
Unidirectional fluid valve.
Application Number
EP19880302510 19880322
Publication Number
0284353 (A2)
Application Date
March 22, 1988
Publication Date
September 28, 1988
Inventor
Braun David L C O Minnesota Mi
Assignee
Minnesota Mining & Mfg
US
IPC
A62B 18/10
F16K 15/14
A62B 18/00
A62B 09/00
F16K 15/16
A62B 18/10
A62B 09/02
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