Metal working – Method of mechanical manufacture – Pulley making
Patent
1993-07-14
1995-09-12
Echols, P. W.
Metal working
Method of mechanical manufacture
Pulley making
298923, 72333, B21K 142, B21D 2800
Patent
active
054488320
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a method of forming a boss on a plate-like metallic blank, as in a poly-V pulley, a crank shaft pulley or the like, by which there is integrally formed, at the center of a plate-like metallic blank, a case-like boss projecting from one lateral side of the blank, the boss being adapted to be put on a rotary body such as a rotary shaft. The present invention also relates to a method of forming a pulley from a metallic plate such as a poly-V pulley, using the first-mentioned method.
BACKGROUND ART
As a method of forming, at the center of a plate-like metallic blank, a case-like boss projecting from one lateral side of the blank, there are conventionally available a cold forging method, a drawing method, a burring method and the like.
Of these conventional methods, the cold forging method is adapted to form a case-like boss with a plastic flow of material itself utilized. Accordingly, when there is formed, from a thick plate-like metallic blank, a pulley such as a crank shaft pulley requiring a boss having a small inner diameter and a relatively great projecting height, it is difficult to form such a boss having a predetermined projecting height, even though a large-size press machine of the class of 2,000 tons to 2,500 tons is used.
In the drawing method, material flows due to drawing, so that the resulting product and particularly the boss are excessively reduced in thickness, thus failing to provide a predetermined strength.
In the burring method, there is obtained a boss having a height substantially proportional to the diameter of a hole (which corresponds to the inner diameter of the boss) to be previously punched by a punch or the like. Accordingly, there cannot be formed a boss the inner diameter of which is small and the height of which is great. Thus, the range in which a boss can be formed, is automatically limited by the relationship between the inner diameter and height thereof.
In view of the foregoing, the present invention is proposed with the objects of providing (i) a method of forming a boss on a plate-like metallic blank, capable of forming, with high precision, a boss having a desired inner diameter, a desired thickness and a desired height with the use of a small press machine without the thickness of the initial material reduced so much in the course of the production steps, and (ii) a method of forming a pulley from a metallic plate, using the first-mentioned method.
SUMMARY OF THE INVENTION
To achieve the objects mentioned above, the present invention provides a method of forming a boss on a plate-like metallic blank by which there is formed, at the center of a plate-like metallic blank, a case-like boss projecting from one lateral side of the blank. This method is characterized by comprising the steps of: curving a plate-like metallic blank such that the blank is convex in a direction in which a boss is adapted to project; punching a hole in the top of the curved blank; and bending an arcuate portion of the blank between an outer peripheral edge portion and a hole peripheral portion of the blank in the direction opposite to the convex direction thereof with the outer peripheral edge portion of the blank restrained from extending radially outwardly, so that a case-like boss is formed.
According to the method of forming a boss on a plate-like metallic blank mentioned above, each of the steps of curving a plate-like metallic blank and bending the arcuate portion of the blank as punched, is a kind of bending operation. Such a bending operation restrains the blank from being reduced in thickness due to a plastic flow of the material as done in a drawing operation. Consequently, this restrains the strength from being lowered. Further, even though the plate-like metallic blank is considerably thick, a predetermined boss can be readily formed with the use of a relatively small press machine. At the bending step, the outer peripheral edge portion of the blank is restrained from extending radially outwardly. This prevents the material from
REFERENCES:
patent: 49649 (1865-08-01), Patterson
patent: 596770 (1898-01-01), Chillingworth
Kanemitsu Toshiaki
Oda Kazuyuki
Echols P. W.
Kabushiki Kaisha Kanemitsu
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