GB813873A - Improvements in or relating to the production from paper or cardboard of tubes having a polygonal cross-section - Google Patents

Abstract

813,873. Moulding resin-impregnated cardboard &c. tubes. ETABLISSEMENTS J. J. CARNAUD & FORGES DE BASSEINDRE. Feb. 19, 1957 [Dec. 21, 1956], No. 5658/57. Class 87(2). A paper or cardboard tube of polygonal crosssection is produced by axially moving a rotating helically wound tube from a mandrel of circular cross-section, on which it is formed in known manner, over a freely rotatable mandrel of polygonal cross-section so that the cross-section of the tube is changed from circular to polygonal. A tube of square cross-section is produced by the apparatus illustrated in which the tube is initially formed by winding gummed paper on a round mandrel 1 and is rotatably and axially moved onto a mandrel of generally square crosssection having three parts ; a chamfered first part 12; a second part 18 of cross-section greater than part 12 and perimeter equivalent to that of mandrel 1, and a third part formed of four rods 22 rigidly coupled to part 18 ; the parts 18, 22 being rotatable independently of part 12. As the tube passes onto the part 18 it rotates it and the faces of the tube are flattened by the transverse tension between the chamfered edges 20. These faces are then engaged by the axially extending steel strips 29 which are carried on a ring 25 rotated by the rotating mandrel. This ring when at rest is supported by two peripherally grooved rollers 26 carried by a stationary annular plate 2. The steel strips 29 force the tube walls into the concave faces 19 of part 18 to form concave tube walls ; the purpose being to compensate for the elasticity of the walls, which are almost flat when they reach said rods 22 which are adapted to serve as supports for the tube when engaged by a saw.