Hollow rack manufacturing method and manufacturing apparatus

Abstract

A steel pipe (1A) (hollow material) both ends of which are open and having a processing wall portion (5) in which a rack is formed with the tooth die (14c) is held in a die assembly (13) having a tooth die (14c). With a first metal core push rod (31) which is to be inserted / removed into / from the steel pipe (1A) through an opening (2) at one end and a second metal core push rod (35) which is to beinserted / removed into / from the steel pipe (1A) through an opening at the other end, a metal core (25) disposed on a side on which the first metal core push rod (31) is inserted / removed into / from the die assembly (13) is sandwiched and this metal core (25) is stopped from rotating with the first metal core push rod (31).; With the state of stopping the rotation of the first metal core push rod, the metal core (25) is introduced into the steel.pipe (1A) through the opening (2) at the one end by both the metal core push rods (31, 35). After the metal core (25) is pressed into the steel pipe (1A)while stopped from rotating with the first metal core push rod (31), this metal core (25) is pushed back by the second metal core push rod (35). Consequently, the flesh of the processing wall portion(5) adjoining the tooth die (14c) is fluidized plastically outward from inside of the steel pipe (1A) so as to form a rack corresponding to the tooth die (14c).

Description

technical field [0001] The present invention relates to a method and apparatus for manufacturing a hollow rack used as a steering rack or the like for a moving body having wheels, such as a steering device of an automobile. [0002] This application claims priority based on Japanese Patent Application Nos. 2007-73622, 2007-73623, and 2007-73624 filed on March 20, 2007, and cites these patent applications in the specification. all content. Background technique [0003] Conventionally, there are known methods and apparatuses in which a long rod-shaped mandrel having a plurality of enlarged diameter portions is alternately inserted and withdrawn from the openings at both ends thereof into a pipe held by a mold composed of an upper mold and a lower mold. In this way, there is a method and apparatus for forming teeth corresponding to the tooth die of a die in a flat tooth profile processing portion of a pipe material (eg, paragraphs [0023] to [0027] in Patent Document 1: Japanes...

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Problems solved by technology

[0020] However, installing the demoulding device into the mold will inevitably lead to a complicated mold structure, and at the same time, the cost of the mold will increase, and the maintenance of the mold will also become difficult.

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