Apparatus for producing internally grooved tube

Abstract

An apparatus for producing an internally grooved seamless tube by rolling. The apparatus has pressing rolls 3 and back-up rolls 20, which work with a constant load under control by the load detector 21 to form uniform grooves without breaking the mother tube.

What is claimed is:  
     
         1 . An apparatus for producing an internally grooved tube comprising a rolling-grooving unit, said rolling-grooving unit comprising: 
 a plug shaft placed in a mother tube;    a grooved plug placed in the mother tube, said grooved plug being rotatably supported by said plug shaft;    a pair of pressing rolls, with inwardly rounded periphery, rolling on said mother tube, said pressing rolls being placed outside said mother tube at a position corresponding to said grooved plug, with their axes being parallel to each other and perpendicular to the axial direction of said mother tube;    a drive mechanism to rotate said pressing rolls in the drawing direction of the mother tube;    a pair of back-up rolls to press said pressing rolls in the direction in which said pressing rolls press the mother tube;    a load detector to detect the load applied to at least either of said pressing rolls and said back-up rolls; and a control unit to keep constant the pressing load applied to at least either of said pressing rolls and said back-up rolls according to the values measured by said load detector.    
     
     
         2 . The apparatus for producing an internally grooved tube as defined in  claim 1 , wherein the number of said rolling-grooving unit is more than one.  
     
     
         3 . The apparatus for producing an internally grooved tube as defined in  claim 2 , wherein the number of said rolling-grooving unit is two.  
     
     
         4 . The apparatus for producing an internally grooved tube as defined in  claim 3 , further comprising a correcting die between said two rolling-grooving units.  
     
     
         5 . The apparatus for producing an internally grooved tube as defined in  claim 3 , wherein at least one of said two rolling-grooving units which is mounted downstream in the drawing direction is rotatable through an angle (θ) which is made between the vertical direction and the axis of the pressing rolls in the plane perpendicular to the axial direction of the mother tube.  
     
     
         6 . The apparatus for producing an internally grooved tube as defined in  claim 3 , wherein said angle (θ) ranges from 0° to 90°.