Patent ID: 6038902
Filing Date: 2000-03-21
Classification: B21D

Abstract:
A method of making a tight radius bend in a tube, the tube having a wall thickness and a diameter, the wall thickness being a function of the radius of the bend, and the tube having a wall thickness which is less than about 10% of the diameter of the tube, the method comprising the step of:providing the tube;applying longitudinal compression to the tube;heating only an intrados of the tube with an inductor coil to create a temperature gradient around a circumference of the tube to untreated sides and an extrados of the tube;bending the tube in a tight radius bend while applying the longitudinal compression and immediately following heating the intrados, whereby the tube may be bent in a tight radius bend with the extrados of the tube experiencing wall thinning of almost 10% of the original tube wall thickness or less.