Patent ID: 7657986

Claim:
A method for fabricating a condenser tube having a pre-determined tube length and multiple channels extending the length of the tube comprising the steps of; moving a flat strip of metal having a center line and outer edges extending the length of the strip through a plurality of forming operations, forming a downwardly facing first V shaped groove extending the length of the strip and positioned inwardly of each outer edge of the strip leaving a flat portion of the strip between each first V shaped groove and each adjacent outer edge, forming an upwardly facing second V shaped groove in the flat portion and a flange extending to the adjacent outer edge, forming the first and second V shaped grooves into first and second U shaped grooves having first and second groove bottoms and sides, forming an upward bow having a shallow height in the middle portion of the strip between the grooves along the respective edges and moving the two outer edges upwardly to an inclined angle to form a first bend spaced inwardly from the first U-shaped groove the width of a bottom of a third groove, increasing the height of the upward bow to define a deep height and moving the two outer edges upwardly from the inclined angle to a position just short of vertical to form a second bend spaced inwardly from the width of the bottom to define a third groove side extending along the strip, straightening the upwardly bowed middle portion to rotate the two outer edges inwardly past vertical, forming a downward bow in the middle portion and moving the two outer edges inwardly and downwardly toward one another and toward the middle portion, straightening the downwardly bowed middle portion of the strip and moving the flanges and the bottoms of the first U shaped grooves downwardly and into engagement with the middle portion to close the second and third U shaped grooves to define respective channels and leaving the first U shaped groove opening upwardly between the second and third U shaped grooves, forming a third bend inwardly of each of the flanges and moving the bottoms of the second and third U shaped grooves into engagement with the middle portion to close the first U shaped grooves to define a channel and to abut the sides of the third grooves to define a channel positioned outwardly of each of the second U shaped grooves and inwardly of each third bend to produce an enclosed tube having eight channels extending the length of the enclosed tube, and severing the enclosed tube for separating the enclosed tube into successive condenser tubes each of the pre-determined length.