Tube forming on an end fitting

A process of making a torque tube, comprising:

• cutting a metal tube to a desired length for said torque tube;
• inserting a tubular body of an end fitting axially into one end of said metal tube, said end fitting having a torque coupling at one end of said tubular body for coupling to a driven or driving device;
• forming said metal tube onto said tubular main body of end fitting to establish a rigid, torque transmitting coupling between said end fitting and said metal tube, said forming step including the steps of:
• a) creating a first powerful transient magnetic field within a coil around said one end of said metal tube and inducing rapidly increasing eddy currents in said one end of said metal tube;
• b) generating a second rapidly rising transient magnetic field with said eddy currents in said one end of said tube, said second transient magnetic field being opposite in direction from said first transient magnetic field;
• c) generating equal and opposite radial forces on said coil and said one end of said metal tube by reaction of said first and second magnetic fields;
• and
• d) restraining and radially supporting said coil to prevent radial translation thereof under influence of said radial forces;
• whereby said one end of said metal tube is formed around and against said tubular main body of said end fitting, conforming said metal tube around said tubular main body to form a torque transmitting rigid joint between tube and said end fitting.

A process of transmitting torque from a driver at one end of a torque tube to a driven device at the other end of said torque tube, comprising:

• engaging a torque coupling on an end fitting with said driver for receiving torque from said driver and driving said end fitting;
• conveying said torque from said torque coupling to a tubular body of said end fitting, said tubular body having a longitudinal axis and a center section having a cross section perpendicular to said axis that is polygonal in shape, said center section having a plurality of flat faces lying parallel to said axis, said flat faces each having a longitudinal groove therein;
• transmitting said torque from said tubular body to a tube formed at one end thereof around said tubular body by electromagnetic pulse forming, said tube tightly conforming around corners at intersections of said flat faces of said tubular body and projecting at least partially into said grooves;
• transferring said torque through said tube to an opposite end thereof and to a similar end fitting attached to said opposite end by electromagnetic pulse forming;
• and
• engaging a torque coupling on said similar end fitting with said driven device for delivering torque from said torque tube and thereby driving said driven device.

A process of forming a metal tube onto an end fitting to establish a rigid, torque transmitting coupling therebetween, comprising:

• inserting an end fitting axially into one end of said tube, said end fitting having a tubular body for torque transmitting connection to said metal tube, and a torque coupling at one end of said tubular body for coupling to a driven or driving device, said tubular body having a center section with a cross-sectional shape, on a plane normal to said axis, that is a regular polygon having flat faces between circumferentially spaced corners, and having an elongated groove in said flat faces extending parallel to said axis;
• creating a first powerful transient magnetic field axially along said one end of said metal tube by current in a field concentrator around said metal tube, and thereby inducing rapidly increasing circumferential eddy currents in said one end of said metal tube;
• generating a second rapidly rising transient magnetic field with said eddy currents in said one end of said tube, said second transient magnetic field being opposite in direction from said first transient magnetic field;
• generating equal and opposite radial forces on said field concentrator and said one end of said metal tube;
• restraining and radially supporting said field concentrator against radial deformation thereof under influence of said radial forces;
• and
• forming said one end of said metal tube around and against said end fitting with said radial forces on said tube, conforming said metal tube around said corners of said polygonal shape and partially forming said metal into said grooves to accommodate spring-back of said metal tube and prevent said metal from rebounding away from said faces of said polygonal shape.