| 摘要 |
PURPOSE:To obtain selective assembling among arms and pins and to enhance the quality in manufacturing crank shafts of various kinds and sizes, by fitting a crank pin into a hole, which is provided in advance in a crank arm, and welding the fitted part before assembling. CONSTITUTION:A crank arm 1 and a crank pin 3 are manufactured separately. To manufacture a crank shaft, the pin 3 is inserted into a hole, which is provided to the crank arm 1 in advance at the position for the pin 3 first, and then the joined part is welded into one body. An alternative method is not provide a circular arc part, which is concentric with the crank pin 3, to the position for the pin for installation of the crank pin 3 and the to weld the joined part. In addition, the shape of the crank pin 3 is formed in such a manner that different-diameter-parts are provided at both ends of the pin 3 and that the diameter 'a' of the welded part is larger than that 'b' of the working part. With this contrivance, since the welded part is situated at a position apart from the surface of the crank pin working part, the surface of the working part is not affected by the welding. In addition, the welded length is lengthened, thereby lowering the stress per unit length.
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