ES361338A1 - Bookbinding - Google Patents

Abstract

A method of bending prongs 14 of a strip of zig-zagged wire 10 to form a slotted tubular form, Fig. 2, comprises feeding the strip over an anvil 36, clamping the strip so that the tips and roots of the prongs 14 overhang the anvil and striking the overhanging portion of each prong with two or more rotary hammers 38 to cause the strip to progressively conform to a shape determined by the anvil. The strip 10 is longitudinally fed by a feed table 26 to a pair of stepped rollers 28, 30 rotating in opposite directions and having helical grooves 32 and 34 which engage the strip. A sector 5 of the grooves, Fig. 5, lies at right angles to the axis of the cylinder which stops the movement of the strip along the table 26 while the strip is engaged in that part of the grooves. As the strip passes from the table 26 to the anvil 36 its ends project beyond the side edges of the anvil 36. A hammer 38, located in the portion 5 of the first convolution of each roller, strikes the projecting ends and bends them to the shape of the anvil. In a further convolution there is another hammer at a greater radial distance from the axis of the cylinder which, on further rotation of the latter, causes the partially bent strip to be bent further. The final tubular form is achieved by a third hammer. A platform 52 is provided on each roller so as to engage the strip to position it centrally on the anvil 36, whereupon the strip is held by clamp 44. In other embodiments the hammer may be a hardened steel insert in a slot, a cam extending radially across the groove of the roller or a spring pressed roller.