Expander for expanding metal pipes

Abstract

An improved expander for expanding metal pipes comprises a plurality of flexible rods (3), which are fed in parallel manner towards a corresponding plurality of parallel pipes (5) to axially insert respective expander mandrels (4) placed at the front end of the flexible rods (3) therein. The aforesaid flexible rods (3) are made in form of a harmonic steel stem with round section and smooth outer surface.

1 . An expander for expanding metal pipes, comprising a plurality of flexible rods, which are fed in parallel towards a corresponding plurality of parallel pipes to axially insert respective expander mandrels placed at the front end of the flexible rods therein, wherein said flexible rods are made in form of a harmonic steel stem with round section and smooth outer surface and wherein a moving assembly for said flexible rods is provided, which assembly comprises a plurality of driving elements arranged side-by-side, one for each flexible rod, each of which is formed by a set of pairs of superimposed slotted gears which define grooves for the passage and driving of a flexible rod. 
     
     
         2 . The expander according to  claim 1 , wherein each driving element comprises means for controlling the mutual movement of the coupled slotted gears towards mutual engagement and disengagement positions with the rods interposed. 
     
     
         3 . The expander according to  claim 2 , wherein said means present in each driving element for controlling the mutual movement of the coupled slotted gears towards mutual engagement and disengagement positions comprise a cylinder-piston assembly which controls the rotation of a lever which acts on movable supporting plates of said upper and lower slotted gears. 
     
     
         4 . The expander according to  claim 1 , wherein said moving assembly takes lengths of flexible rods from a rod winding drum during a step of executing of a pipe expansion operation and reinserts said lengths into the drum at the end of the expansion operation. 
     
     
         5 . The expander according to  claim 4 , wherein said drum comprises circular-shaped perforated metal sheets which form two sides and at least one intermediate separating wall of the drum itself, spiral-shaped successions of idle rolls being placed between said metal sheets, each of which is provided with parallel radial fins which form grooves for housing respective flexible rods, which grooves extend longitudinally along all or a part of the total extension of the successions of rolls.