US Patent 9205386 Gas injection device having check valve

A gas injection device is provided. A separation plate is disposed between inlet and outlet ends of a main body. At least one flow hole is disposed around a through hole of the separation plate. Top, middle and bottom sections of a valve body are disposed respectively at the inlet end, through the through hole and at the outlet end. Respective outer diameters of the top and bottom sections are larger than an inner diameter of the through hole, and the largest outer diameter of the bottom section is larger than a smallest inner diameter of the outlet end. A length of the middle section is longer than an axial length of the through hole. An elastic member through the middle section abuts against the separation plate and the bottom section to bias the valve body toward the outlet end and normally unclose the bottom section.