BUTTERFLY-TYPE CHECK VALVE

摘要

A butterfly-type check valve (30) employs a secondary check valve (38) that is carried on the valve plate (36). The valve plate (36) is revolvable and translatable relative to the pivot shaft (34). In operation, the check valve (30) opens in response to a change in aerodynamic forces which act on the valve plate (36), the change being effected as a response to the opening of the secondary check valve (38). As the valve plate (36) rotates to an open position, its revolutionary movement relative to the shaft (34) changes the location of pivot points (40) relative to the surface (62) of the plate. This changes the areas (42, 44) of the surface (62) on both sides of the pivot points (40) so that the aerodynamic forces cause the valve (30) to open still further.