GB557330A - Improvements in or relating to roller tube expanders - Google Patents

Abstract

557,330. Tube expanders. BABCOCK & WILCOX, Ltd. May 12, 1942, No. 6426. Convention date, May 15, 1941. [Class 83 (iv)] A tube expander of the kind comprising a cage containing axially adjustable rollers co-operating with a longitudinally movable positively rotated tapered mandrel particularly for expanding tubes of substantial thickness into long seats in the drums of steam generators, has a cage 10 movable longitudinally during the expanding operation and idlers whose expanding surfaces are arranged to complete the tube metal flow progressively from the innermost to the outermost part of the tube. The rollers have portions 112, 110, 114, the portion 112 extending outwardly of the mandrel axis further than the portion 110. The portion 110 and the curved end 114 do the initial part of the expanding which is finished by the portion 112. The portion 112 has a taper slightly greater than half the mandrel taper the surface part being substantially parallel to the mandrel axis and the portion 110 has a taper slightly less than one half the mandrel taper. The rollers are guided in recesses in the cage having curved outer ends to prevent the rollers falling out, the recesses being closed by a ring 62. They are inclined to the mandrel axis in a horizontal plane at 2 degrees so that the cage moves longitudinally of the tube during operation. They are also inclined in the vertical plane at an angle of 3¢ degrees to the mandrel axes. In expanding the tubes into the tube seat in the drum the tube is first expanded against a zero of the tube seat remote from the adjacent end of the tube and the expander moves outwardly of the tube during operation to effect progressive expansion of the tube towards the end thereof so that the flow of metal is outwards thus avoiding compres- 'sive stresses in the portion of the tubes between the drums 4. The expander is provided with a removable stop collar 40 and after placing the expander in the tube so that the inner end of each roller is inch to ¢ inch beyond the wall 14 the mandrel is longitudinally adjusted by an air motor engaging the squared end 28 thereof, while a rotatably mounted screwed sleeve 30 inserted in the cage between a thrust bearing 36 and a locking ring 38 is held by a spanner engaging an extension 32 thereof. When the rollers have been moved radially sufficient to expand the tube the sleeve 30 is released and rotation of the mandrel by the air motor maintains the pressure and automatically advances the expander outwardly of the tube. When frictional resistance resulting from contact of the rollers with the tube reaches a sufficient value the rollers rotate planetarily and so rotate the cage and the inclination of the rollers feeds the expander progressively to the end of the tube.