STRUCTURE FOR IMPROVING STRENGTH OF TABULAR PORTION AND SUBSTANTIALLY RECTANGULAR PARALLELEPIPED MEMBER

摘要

A polygon in a tabular portion includes first and second axes of symmetry substantially orthogonal to each other. A top surface of the tabular portion has a swelling portion with an outline that is line-symmetric with respect to the first and second axes of symmetry. In a lateral half portion of the outline, a short-side side crest portion that is convex toward the polygonal outline in the direction of the first axis of symmetry, concave corner-side trough portions connected to each end of the short-side side crest portion and long-side side crest portions that are connected to each corner-side trough portion and convex toward the polygonal outline are formed. On one of a top surface and an undersurface of the swelling portion, a pair of lateral ribs or a pair of longitudinal ribs that spreads toward the polygonal outline and transversely crosses the swelling portion is formed.

主权项

1. A structure for improving strength of a resin-made substantially polygonal (four or more corners) tabular portion,
wherein the polygon comprises a first axis of symmetry and a second axis of symmetry which are substantially orthogonal to each other, a top surface of the tabular portion comprises a swelling portion formed so as to swell upward in a region inside the polygonal outline, the outline of the swelling portion is line-symmetric with respect to the first axis of symmetry and the second axis of symmetry, in a lateral half portion of the outline of the swelling portion: a short-side side crest portion that is convex toward the polygonal outline in a direction of the first axis of symmetry; a corner-side trough portion that is connected to each end of the short-side side crest portion and concave toward the polygonal outline in a region sandwiched between the first axis of symmetry and the second axis of symmetry; and a long-side side crest portion that is connected to an end opposite to the short-side side crest portion of the each corner-side trough portion and convex toward the polygonal outline, are formed, and on one of a top surface and an undersurface of the swelling portion, at least: a pair of lateral ribs that transversely crosses the swelling portion so as to spread toward the polygonal outline; or a pair of longitudinal ribs that longitudinally crosses the swelling portion so as to spread toward the polygonal outline, is formed.