Nippon Light Metal Company, Ltd.

Honda Giken Kkk

Mitsuo Tsuge

Keiichi Sugiyama

Kunihiro Yasunaga

Shigeru Kohmura

Masayoshi Ohhashi

Shigenori Saitoh

Tadashi Hakamada

Hisao Saitoh

A method of bending extruded shapes of the present invention controls a bending radius and a bending angle in accordance with a moving distance of a movable bending die. In the bending process, hardness of an extruded shape to be processed is measured and converted into proof stress, and the bending condition for compensating the springback is determined. A correction coefficient C showing a ratio of a practical value of the moving distance and a theoretical value of the moving distance in a case of no spring-back occurring is defined by a function of Young's modulus E, geometrical coefficient Z, bending radius R and proof stress .sigma..sub.0.2 for the extruded shape to be processed. The correction coefficient C is obtained by measuring the hardness of the extruded shape to be processed, converting the measured hardness into the proof stress, and substituting the proof stress and a predetermined bending radius R into the function, and the practical value of the moving distance of the movable bending die is determined.

Method of bending extruded shapes

The can end is formed with a circular severing score for severing the area defined thereby from the can end by pulling a manipulating tab secured within the area defined by the score at a position adjacent thereto. In order to increase the pressure resisting strength against the internal pressure caused by the content in the can, the can end is made from a thin aluminum alloy sheet having the yield strength in the range of 24-29 kgf/mm.sup.2 as well as the elongation equal to or greater than 6%, while the aperture rate defined by the ratio of the area formed within the score with respect to the total area of the can end is made at least equal to or greater than 60% so that the pressure resisting strength is kept substantially at least 5 kgf/cm.sup.2. In order to more advantageously maintain the high pressure resisting strength of the can, score is located at a position spaced from the inner periphery of the bottom of the frustoconical portion at least a distance equal to or greater than 1 mm inwardly of the area of the can end, to make the inner radius of curvature of the corner formed around the inner periphery of the bottom of the frustoconical portion equal to or less than 0.5 mm, and to make the taper angle of the frustoconical portion of the can end equal to or less than 10.degree.. An auxiliary score having a score residual smaller than that of the score for severing the area defined thereby from the can end may be formed outwardly or inwardly of the score for severing. The score residual of the can end may be preferably increased from the thinnest portion adjacent to the position where the tab is provided while a plurality of elongated ridges or grooves may be formed within the area defined by the score substantially perpendicular to the line passing through the tab and the center of the can end in order to avoid rapid severing of the area defined by the score from the can end so as to prevent spilling of the content out of the can when the can end is being opened. All these measures are effective to most advantageously enhance the pressure resisting strength of the can end.

Aluminum can end

Growing community of inventors

Ihara-gun, Japan

Mitsuo Tsuge