PURPOSE: To enable, by means of roll forming, the manufacture of the special shaped tube with steps which is provided with a reduced diameter part functioning as a connector.
CONSTITUTION: A plural number of round tubes P1, P20, P30...of which a reduced diameter part P.. is formed on one end of the tube are prepared, and the round tubes P10, P20, P30 are mutually connected through the reduced diameter part P.. to forum a base tube Pno. When the base tube Pno is worked by a forming roll R from the outside, the reduced diameter part Pco corresponding to the cross sectional shape of a angular tube is formed at the end of the angular tube P11, P21, P21.... After the roll forming, a special shaped tube Pn1 in the connected state are divided into plural angular tubes P11, P21, P31.... Thus, without the use of a special die, a special shaped tube with the reduced diameter part Pe0 functioning as the connector is easily manufactured. The special shaped tube, being easily connected through the reduced diameter part Pe0, an on-site work is made easy at the time of installing rain gutters, hand rails, etc.
JPS62220214 | THICKNESS DEVIATED STEEL TUBE |
AZUMA TSUTOMU
NAKAKO TAKEFUMI