Can lid shell, manufacturing method for same, and forming device

Abstract

A can lid shell 10 includes a panel section 11 having a circular peripheral edge, a countersink section 12 formed and recessed along the peripheral edge of the panel section 11, a chuck wall section 13 rising from an edge of the countersink section 12, and a flange section 14 protruding from an upper end of the chuck wall section 13. The countersink section 12 includes a first curved surface portion 123C that is convex toward an internal space SP1. The chuck wall section 13 includes a second curved surface portion 131 that is connected to the first curved surface portion 123C and that is concave toward the internal space SP1. Furthermore, the second curved surface portion 131 and the first curved surface portion 123C are formed to be thicker as both are directed from an edge p8 on the flange section 14 side to an edge p6 on the panel section 11 side.

1 . A can lid shell comprising:
 a panel section having a circular peripheral edge;   a countersink section formed and recessed along the peripheral edge of the panel section;   a chuck wall section rising from an edge of the countersink section; and   a flange section protruding from an upper end of the chuck wall section,   wherein an internal space set inside the panel section, the countersink section, and the chuck wall section is provided,   the countersink section includes a first curved surface portion that is convex toward the internal space,   the chuck wall section includes a second curved surface portion that is connected to the first curved surface portion and that is concave from the internal space, and   thicknesses of the second curved surface portion and the first curved surface portion increase from an edge on the flange section side toward an edge on the panel section side.   
     
     
         2 . The can lid shell according to  claim 1 ,
 wherein the countersink section includes a third curved surface portion formed in such a manner that the first curved surface portion is disposed between the second curved surface portion and the third curved surface portion, the third curved surface portion is connected to the first curved surface portion, and is convex toward the internal space, and furthermore, a thickness of the third curved surface portion increases as the third curved surface portion is directed from the edge on the panel section side to an edge connected to the first curved surface portion.   
     
     
         3 . The can lid shell according to  claim 2 , further comprising:
 a plurality of thin portions recessed and formed from the second curved surface portion to the third curved surface portion, and provided to be separated in a circumferential direction of the can lid shell on a front surface or a back surface of the can lid shell; and   a thick portion that is provided between the can lid shell and the thin portion and that is thicker than the thin portion,   wherein in the plurality of thin portions and a plurality of the thick portions, dimensions along a radius of the can lid shell in a plan view or in a bottom view of the can lid shell are longer than dimensions along a direction orthogonal to a direction of the radius.   
     
     
         4 . A forming device comprising:
 a lower die; and   an upper die,   wherein the forming device forms a can lid shell by pinching a circular blank between the lower die and the upper die,   the lower die includes a die core ring, and a panel punch disposed inside the die core ring,   the upper die includes a tubular upper piston, a tubular inner sleeve disposed inside the upper piston, and a die center disposed inside the inner sleeve,   an outer portion of a tip portion of the die core ring and a tip portion of the upper piston are disposed to face each other,   an inner portion of the tip portion of the die core ring and a tip portion of the inner sleeve are disposed to face each other,   the panel punch and the die center are disposed to face each other,   the inner portion of the tip portion of the die core ring includes a first lower die curved surface portion that is concave toward the inner sleeve, and a second lower die curved surface portion that is connected to the first lower die curved surface portion, that is disposed to be further shifted to a central axis side, and that is convex toward the inner sleeve,   the tip portion of the inner sleeve includes a first upper die curved surface portion that is convex toward the first lower die curved surface portion, a second upper die curved surface portion that is connected to the first upper die curved surface portion, that is disposed to be further shifted to the central axis side, and that is convex toward the first lower die curved surface portion in an arc shape whose curvature radius is different from a curvature radius of the first upper die curved surface portion, and a third upper die curved surface portion that is connected to the second upper die curved surface portion, that is disposed to be further shifted to the central axis side, and that is concave toward the second lower die curved surface portion, and   a mold clearance formed between the first lower die curved surface portion and the second lower die curved surface portion of the die core ring and the second upper die curved surface portion and the third upper die curved surface portion of the inner sleeve is an interval equal to or larger than a plate thickness of the circular blank, and is further widened as the mold clearance is directed to the central axis.   
     
     
         5 . A forming device comprising:
 a lower die; and   an upper die,   wherein the forming device forms a can lid shell by pinching a circular blank between the lower die and the upper die,   the lower die includes a die core ring, and a panel punch disposed inside the die core ring,   the upper die includes a tubular upper piston, a tubular inner sleeve disposed inside the upper piston, and a die center disposed inside the inner sleeve,   the die core ring includes a tubular fixing portion provided to be fixed to the lower die, a movable portion provided inside the fixing portion, and a biasing member configured to be expandable and contractible along a central axis, supporting the movable portion from below, and biasing the movable portion,   a tip portion of the fixing portion of the die core ring and a tip portion of the upper piston are disposed to face each other,   a tip portion of the movable portion of the die core ring and a tip portion of the inner sleeve are disposed to face each other,   the panel punch and the die center are disposed to face each other,   the tip portion of the movable portion includes a lower die curved surface portion that is convex toward the inner sleeve,   the tip portion of the inner sleeve includes an upper die curved surface portion that is concave toward the lower die curved surface portion,   a mold clearance formed between the lower die curved surface portion of the movable portion and the upper die curved surface portion of the inner sleeve is an interval equal to or larger than a plate thickness of the circular blank, and is further widened as the mold clearance is closer to the central axis, and   the movable portion retreats toward the biasing member by being pushed against an intermediate formed body when deep drawing is performed on the circular blank.   
     
     
         6 . The forming device according to  claim 5 ,
 wherein the lower die further includes a tubular lower piston surrounding a portion of an outer peripheral surface of the die core ring,   the fixing portion includes a through-hole penetrating from the inside of the fixing portion to an outside of the fixing portion, and a block disposed in the through-hole,   the block has an outer inclined surface protruding to the outside of the fixing portion and an inner inclined surface protruding to the inside of the fixing portion,   the lower piston has an inner inclined surface that abuts on the outer inclined surface of the block,   the movable portion has an outer inclined surface that abuts on the inner inclined surface of the block, and   when the lower piston is lowered by being pushed against the upper die, the inner inclined surface of the lower piston abuts on the outer inclined surface of the block, and in a state where the outer inclined surface of the retreated movable portion abuts on the inner inclined surface of the block, the lower piston is further lowered to move the movable portion toward the inner sleeve.   
     
     
         7 . A manufacturing method for a can lid shell in which a can lid shell is formed by pinching a circular blank between a lower die and an upper die, the method comprising:
 a deep drawing step of forming the circular blank in a first formed body having a tray shape; and   a reverse step of moving a flat portion at a bottom of the first formed body pinched between a panel punch and a die center, upward to form a countersink section recessed around the flat portion,   wherein in the deep drawing step, a first inflection portion including a concave surface and a convex surface is formed between the flat portion of the first formed body and a flange section by deforming a portion of the circular blank with a tip portion of a die core ring and a tip portion of an inner sleeve, and   in the reverse step, in a state where a space between the tip portion of the die core ring and the tip portion of the inner sleeve is formed as a mold clearance widened as the mold clearance is closer to a central axis, a portion of the first formed body protruding from between the panel punch and the die center is pushed into a gap which is not filled with the first inflection portion in the mold clearance, and a second inflection portion in which the first inflection portion is thickened is formed.   
     
     
         8 . The manufacturing method for a can lid shell according to  claim 7 ,
 wherein the die core ring includes a movable portion forming a portion facing the tip portion of the inner sleeve in the tip portion of the die core ring, and a biasing member configured to be expandable and contractible along the central axis and supporting the movable portion from below to hold the movable portion at a position where the mold clearance is formed, and   in the deep drawing step, an intermediate formed body pushes the movable portion, and the movable portion retreats toward the biasing member.