Abstract: To make a thickness of a concavo-convex sheet as uniform as possible while ensuring the function of an air bubble sheet as a cushioning material. A synthetic resin air bubble sheet is provided in which a concavo-convex sheet (11) and a flat sheet (12) are joined and a plurality of air bubble portions (13) are formed that form sealed spaces between the concavo-convex sheet (11) and the flat sheet (12). Each of the air bubble portions (13) has a circular truncated cone shape whose diameter becomes smaller toward the top. Where A is the diameter of the part with the largest diameter, a height B from the flat sheet (12) is in the range of 35% to 40% of A, a diameter C of a flat top portion (11d), which is the part with the smallest diameter, is in the range of 50% to 80% of A, and a radius of curvature R of a top corner portion (11c) that is formed between the flat top portion (11d) and a side wall portion (11b) is in the range of 10% to 20% of A.

Abstract: An improved protective beam for automobile side door is disclosed, with a main body which includes a pair of elongate steel sheet members of corrugated cross-section. The steel sheet members are welded to each other along opposite groove portions such that a hollow space of box-like section is defined by each pair of opposite ridge portions of the steel sheet members. At least one steel sheet member has an end region as a mounting seat, where the beam is welded to the inner panel or pillar portion of the side door, and each ridge portion along the end region of the steel sheet member has a height which gradually decreases toward the end of the sheet member to form a generally flat mounting seat to be secured to a predetermined location of the side door.