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 relates to a disc-shaped material made from metal sheet, provided for the manufacture of a pulley or the like. According to the present invention, even if the metal sheet is thin and light weight, a peripheral wall of sufficient strength can be formed, by the following steps: rotating the material held between a pair of dies and pressing an outer periphery of the material by means of a forming roller, in a radially inward direction, thereby thickening axially the outer periphery of the material to be extended to both sides of a non-processed portion, thus forming the peripheral wall.

Abstract: A method of forming a cylindrical portion of a sheet metal member having a center hole, according to the present invention, comprises the steps of holding a sheet metal material having a boss portion between rotating dies, rotating the sheet metal material with the rotating dies, and pressing a cylindrical portion formed at an outer periphery of the base plate of the sheet metal material by means of a forming roller, thereby forming the cylindrical portion.

Abstract: In a sheet metal member having a boss which is obtained by the method of the present invention, a cylindrical portion is formed at an outer peripheral edge, thereby allowing the member to be used as a pulley for a flat belt, a V belt or a poly-V belt. According to the present invention, when the boss is to be formed, the positional accuracies of portions other than the boss with respect to the boss are improved. The present invention includes: a boring step of opening a circular hole in a circular blank; a curving step of shaping the circular blank into a projected shape; and a bending step of restricting a radially outward spread of an outer peripheral edge portion of the circular blank which has undergone the curving step, and bending an inclined portion between the outer peripheral edge portion of the circular blank and the circular hole into a recessed shape, thereby forming the case-like boss.

Abstract: A sheet metal pulley has a base part and a cylindrical peripheral wall for winding a belt formed integrally with the base part. An ear is disposed in an end part of the cylindrical peripheral wall. The base part is partitioned into an inner peripheral portion and an outer peripheral portion, with the inner peripheral portion being smoothly connected with the outer peripheral portion through a bent part. The outer peripheral portion is formed into a tapered shape which extends from the bent part and has a diameter which is increased toward the inner side of the cylindrical peripheral wall in the axial direction of the pulley. The outer peripheral portion connected with an end part of the peripheral wall on the side of the ear. Even when the pulley is used for a long term, the connecting portion between the peripheral wall and the base part, etc. is hardly cracked.

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: The present invention relates to a method of producing a sheet metal pulley for a V belt without cutting which may impair the environment of a factory. A sheet metal pulley for a V belt which is obtained by the production method of the present invention has plural valley portions around which V belts are to be wound. In the production method, an annular first valley portion which is opened in a V-like shape is formed by slitting a root portion of a cylindrical portion of a sheet metal cylindrical member and an outer periphery of a base plate portion continuous to the root portion.

Abstract: A method of forming a cylindrical portion of a cylindrical member made of a sheet metal according to the present invention relates to steps of rotating a cylindrical member fitted into rotating dies with the rotating dies while pressing the cylindrical portion against the rotating dies by the forming roller. In the present invention, a pressed portion of the cylindrical portion, pressed by a forming roller is moved from an opening end side of the cylindrical portion to a root portion side thereof according to each phase. For example, the pressed portion of the cylindrical portion pressed by the forming roller includes two sections, namely a first phase-pressed portion positioned on the opening end side of the cylindrical portion and a second phase-pressed portion positioned on the root portion side thereof.

Abstract: The present invention relates to a method of forming an inner flange on a sheet metal member having a cylindrical portion with an inner flange 3 required in coupling of a shaft such as a pulley used in an automobile. The axial length of a boss formed on the sheet metal member is reduced by pressing the boss in the axial direction of the boss, and an excess portion produced as a result of the reduction of the axial length of the boss is gathered in one place in the axial direction of the boss, for example, the end in the axial direction of the boss to project inwardly into the inside of the boss, so that the inner flange is formed by the projected excess portion. A step of gathering the excess portion produced as a result of the reduction of the axial length of the boss can be conducted by a pressing process in which a pressing die is moved in the axial direction of the boss.