Abstract: An off-road tire (1) comprises a tread portion (2) provided with blocks (10, 11) forming a sea area (8) therearound. The sea area (8) is provided in the bottom (14) thereof with recesses (13), wherein the recesses (13) are arranged circumferentially of the tire and each extend axially of the tire, and the depth (d) of each of the recesses (13) is gradually increased towards its center (13a), whereby the enveloping power is improved.

Abstract: A pneumatic tire having an improved off-road traveling performance, which has a block pattern that a plurality of blocks 7 are provided in a tread portion, in which each of the blocks 7 includes a tread surface 9 facing radially outward and a wall surface 10 extending radially inwardly from the edge “e” of the tread surface 9, and at least one of the blocks 7 is provided with at least one recess portion 11 which extends on the wall surface 10 in the radial direction, and whose radially outer end opens at the tread surface 9 and whose length L along the wall surface 10 is from 10 to 70% of the height BL of the blocks 7.

Abstract: A corrugation forming apparatus includes, as forming members, a rack tool assembled to a slide table and a pinion tool which rotates with rotation of a shaft. The apparatus also includes, as a displacement synchronization mechanism, a feed rack integrally assembled to the table and a feed pinion gear in meshing engagement with the feed rack. When a handle is rotated, its rotational force is transmitted to the feed rack via the feed pinion gear, so that the rack tool moves along the axial direction, and the pinion tool rotates in synchronism with the movement of the rack tool. This enables forming of successive recesses and projections on the thin metal plate, while reducing ductile cracks and warpage.

Abstract: A corrugation forming apparatus includes, as forming members, a rack tool assembled to a slide table and a pinion tool which rotates with rotation of a shaft. The apparatus also includes, as a displacement synchronization mechanism, a feed rack integrally assembled to the table and a feed pinion gear in meshing engagement with the feed rack. When a handle is rotated, its rotational force is transmitted to the feed rack via the feed pinion gear, so that the rack tool moves along the axial direction, and the pinion tool rotates in synchronism with the movement of the rack tool. This enables forming of successive recesses and projections on the thin metal plate, while reducing ductile cracks and warpage.