Patent ID: 7854156
Filing Date: 2010-12-21
Classification: B21D,B21K

Abstract:
1. A closing device which presses a die against a rotating pipe body such that an open end portion of the pipe body is plastically closed by the die, comprising: a cored bar inserted into the pipe body to close the open end portion of the pipe body on an opposite side to the die; and a reactive force applying mechanism which allows the cored bar to retreat and applies a reactive force to the retreating cored bar when the cored bar receives a predetermined load or more during processing of the pipe body by the die, the reactive force applying mechanism comprising: wherein the supply and discharge of the working fluid to and from the bottom side oil chamber of the hydraulic cylinder is shut off during processing of the pipe body, and when the cored bar receives a load during processing of the pipe body by the die, the air chamber of the second cylinder is compressed via the bottom side oil chamber and the oil chamber of the second cylinder, whereby the cored bar retreats and receives the reactive force.