Abstract: The outer side of a pair of curved parts 3d of a longitudinal annular blank is pressed and energized towards the curved part 3d of the opponent side with a molding outer die 14 of a shaping device 13 to press and widen each curved part 3d to a large curved part of large curvature radius, and a half-finished article 17 is molded, and thereafter, the half-finished article 17 is pressed and widened by cooperative operation of a finishing inner die of the shaping device and a window part of a perfect circle functioning as an outer die to manufacture a ring-shaped member. Therefore, a yield rate or a percentage of the weight of the ring-shaped member with respect to the weight of the raw material and the yield rate or the percentage of the ring-shaped member with respect to the blank can be improved, and the cost can be reduced.

Abstract: The outer side of a pair of curved parts 3d of a longitudinal annular blank is pressed and energized towards the curved part 3d of the opponent side with a molding outer die 14 of a shaping device 13 to press and widen each curved part 3d to a large curved part of large curvature radius, and a half-finished article 17 is molded, and thereafter, the half-finished article 17 is pressed and widened by cooperative operation of a finishing inner die of the shaping device and a window part of a perfect circle functioning as an outer die to manufacture a ring-shaped member. Therefore, a yield rate or a percentage of the weight of the ring-shaped member with respect to the weight of the raw material and the yield rate or the percentage of the ring-shaped member with respect to the blank can be improved, and the cost can be reduced.

Abstract: The yield rate or the percentage of the weight of the ring-shaped member with respect to the weight of the raw material and the yield rate or the percentage of the ring-shaped member with respect to the blank are improved to achieve the cost reduction. A half-finished article 18 having large curved parts 3D obtained by widening the curved parts 3d so as to have a curvature radius larger than the initial curvature radius, and bulge-out parts 3E curved to a circular arc shape at a curvature radius larger than the curvature radius of the curved parts 3d at the linear parts 3b, 3c is molded, and thereafter, the half-finished article 18 is molded into an annular shape to obtain the ring-shaped member 1.

Abstract: The yield rate or the percentage of the weight of the ring-shaped member with respect to the weight of the raw material is improved to achieve the cost reduction of the ring-shaped member. A plurality of longitudinal annular blanks 3 is punched out from a raw material 2 of a predetermined width, and the longitudinal annular blank 3 is molded into an annular ring-shaped member 1.

Abstract: The invention relates to a sheet metal member having an annular peripheral wall and a method of thickening an annular peripheral wall of the member. In the invention, the thickness of the annular peripheral wall is increased to be 2 or more times or 3 or more times that of a base plate. Teeth for a timing toothed belt, a gear, or the like are cut in the annular peripheral wall which is thickened in this way. In the method of thickening an annular peripheral wall of the invention, a base plate integrally having a flange-shaped portion is held between a circular bottom pattern tool and a circular top pattern tool, the flange-shaped portion which is projected outside and the circular top pattern tool is sequentially pressed in a radially inward direction by annular forming faces of circular rollers of plural kinds, thereby thickening the flange-shaped portion, and the flange-shaped portion is then formed into a cylindrical shape which is concentric with the base plate.

Abstract: The present invention relates to a sheet metal member having an annular peripheral wall and a method of thickening an annular peripheral wall of the sheet metal member. The thickness of the annular peripheral wall is increased to be 2 or more times or 3 or more times that of a base plate. Teeth for a timing toothed belt, a gear, or the like are cut in the annular peripheral wall which is thickened in this way. In the method of thickening an annular peripheral wall of the present invention, a base plate integrally having a flange-shaped portion is held between a circular bottom pattern tool and a circular top pattern tool, the flange-shaped portion which projects outwardly and the circular top pattern tool is sequentially pressed in a radially inward direction by annular forming faces of circular rollers of plural kinds, thereby thickening the flange-shaped portion. The flange-shaped portion is then formed into a cylindrical shape which is concentric with the base plate.

Abstract: The present invention provides a rim rolling method in which slotting can be correctly performed at an arbitrary position in the thickness direction of an outer peripheral face of a blank. A preforming roller die 7 is prepared in which a groove 8 is formed in an outer peripheral face 7a in the circumferential direction, and a groove forming blade portion 9 is protruded in the circumferential direction on an inner bottom portion of the groove 8. A preforming process is performed in which the groove 8 and the groove forming blade portion 9 of the preforming roller die 7 are pressed against an outer peripheral portion 10 of a disk-like metal blank 1, to form an outer peripheral groove 11 in the whole outer peripheral portion of the blank 1 by the groove forming blade portion 9.

Abstract: The present invention provides a slotting method in which, during production of a metal sheet V-pulley or the like, slitting can be correctly easily performed at an arbitrary position in the thickness direction of an outer peripheral face of a blank. A blank housing recess (5) a depth of which is smaller than the thickness of a disk-like metal blank (1) is formed in an upper face of a lower rotary die (4) on which the blank (1) is to be placed, and a roller die guiding face (6) which is lower in level than an upper face of the blank (1) in the blank housing recess (5) is horizontally formed in an outer periphery of the blank housing recess (5).

Abstract: The present invention relates to a method of producing a sheet metal gear in which a metal sheet (2) is used as a starting material and a gear is formed in the outer peripheral edge of the metal sheet. The object of the production method is to finish easily and accurately pitches of valleys and peaks of the gear which is formed in a simple production facility. The time period required for completing the formation of the gear in the outer peripheral edge of the metal sheet is shortened, thereby enhancing productivity. According to the production method, in the initial preparation step, a number of places of the outer peripheral edge of the circular metal sheet (2) which are arranged with a regular pitch are punched out in the axial direction, thereby forming preliminary valleys and preliminary peaks. Then, the method transfers to a gear forming step.

Abstract: A sheet metal member thickening method according to the present invention comprises the steps of rotating a disc-shaped sheet metal member held between rotating dies, and pressing a first forming roller and a second forming roller subsequently against a periphery thereof while rotating it, thereby forming a base plate and a thickened peripheral wall thereof. A first forming step comprises plural small steps, including a previous small step in the first forming step and a post small step following the previous one.