BigPatents India

The synthetic resin cap comprises a cap body (4) having a top plate part (2) and a tube part (3) extending downward from the peripheral edge part (2b) thereof and an inside seal projection (12) fitted to the inside of a container mouth part (21). A connection part (15) is formed between the top plate part (2) and the inner seal projection (12), and an outside thin-walled part (16) is formed at the top plate part (2). When a container inside pressure rises, the top plate part (2) is deformably swelled upward, and an inward tension is applied to the inside seal projection (12) by the connection part (15). Since the outside thin-walled part (16) is deformably bent, the portion of the cap positioned on the inner side of the outer thin-walled part is deformably swelled largely upward, and the inclination of the top plate part (2) is increased at the formed part of the inside seal projection (12). Thus, the inside seal projection (12) is displaced inward, and gas in the container can be easily discharged to the outside. (FIG. 1)