Floating Draw Plug and Method of Drawing Tube

Abstract

A floating draw plug for shaping tube comprises a necking body and a rib forming member. The necking body has an axis and a trailing end portion. The trailing portion has a cross-section that is symmetric about the axis and that converges toward the axis as it extends downstream. The rib forming member comprises helical protrusions and helical grooves. The helical protrusions and the helical grooves are aligned with the axis. The rib forming member is connected to the necking body in a manner such that at least a portion of the helical protrusions and at least a portion of the helical grooves extend downstream of the trailing portion of the necking body and such that the rib forming member is free to rotate about the axis relative to the necking body.

What is claimed is: 
     
         1 . A floating draw plug for shaping tube, the draw plug comprising:
 a necking body, the necking body having an axis and a trailing end portion, the trailing end portion having a cross-section that is symmetric about the axis and that converges toward the axis as it extends downstream; and,   a rib forming member, the rib forming member comprising helical protrusions and helical grooves, the helical protrusions and the helical grooves being aligned with the axis, the rib forming member being connected to the necking body in a manner such that at least a portion of the helical protrusions and at least a portion of the helical grooves extend downstream of the trailing portion of the necking body and such that the rib forming member is free to rotate about the axis relative to the necking body.   
     
     
         2 . A floating draw plug in accordance with  claim 1  wherein the helical protrusions have a constant radius from the axis as they extend downstream. 
     
     
         3 . A floating draw plug in accordance with  claim 1  wherein the necking body has an axial downstream recess and a portion of rib forming member extends therein. 
     
     
         4 . A floating draw plug in accordance with  claim 1  wherein the rib forming member is attached to the necking body via a threaded fastener. 
     
     
         5 . A floating draw plug in accordance with  claim 4  wherein the necking body has an axial through-hole and a shaft member extends through the axial through-hole in a manner connecting the rib forming member to the necking body, and the shaft member is configured and adapted to rotate relative to at least one of the necking body and the rib forming member. 
     
     
         6 . A floating draw plug in accordance with  claim 1  wherein the necking body has a leading end portion that diverges from the axis as it extends downstream. 
     
     
         7 . A floating draw plug in accordance with  claim 6  wherein the necking body has an intermediate cylindrical portion that extends axially between the leading portion and the trailing portion of the necking body. 
     
     
         8 . A method of drawing tube in a manner forming internal helical protrusions in the tube, the method comprising:
 floating a draw plug inside the tube, the draw plug comprising a necking body and a rib forming member, the necking body having an axis and a trailing end portion, the trailing end portion having a cross-section that is symmetric about the axis and that converges toward the axis as it extends downstream, the rib forming member comprising helical protrusions and helical grooves, the helical protrusions and the helical grooves being aligned with the axis, the rib forming member being connected to the necking body in a manner such that at least a portion of the helical protrusions and at least a portion of the helical grooves extend downstream of the trailing portion of the necking body and such that the rib forming member is free to rotate about the axis relative to the necking body; and   pulling the tube through a die and radially between the draw plug and the die in a manner forming the internal helical protrusions into the tube.   
     
     
         9 . A method of drawing tube in accordance with  claim 8  wherein the rib forming member rotates about the axis relative to the necking body as the tube is drawn. 
     
     
         10 . A method of drawing tube in accordance with  claim 9  wherein the die forces the tube radially inward toward the axis against the helical protrusions and into the helical grooves as the tube is drawn. 
     
     
         11 . A method of drawing tube in accordance with  claim 8  wherein the helical protrusions have a constant radius from the axis as they extend downstream. 
     
     
         12 . A method of drawing tube in accordance with  claim 8  wherein the necking body has an axial downstream recess and a portion of rib forming member extends therein. 
     
     
         13 . A method of drawing tube in accordance with  claim 12  wherein the rib forming member is attached to the necking body via a threaded fastener. 
     
     
         14 . A method of drawing tube in accordance with  claim 8  wherein the necking body has an axial through-hole and a shaft member extends through the axial through-hole in a manner connecting the rib forming member to the necking body, and the shaft member is configured and adapted to rotate relative to at least one of the necking body and the rib forming member. 
     
     
         15 . A floating draw plug in accordance with  claim 8  wherein the necking body has a leading end portion and an intermediate cylindrical portion, the leading end portion diverges from the axis as it extends downstream, and the intermediate cylindrical portion that extends axially between the leading portion and the trailing portion of the necking body.