Spreading and lap-forming machine

A spreading and lap-forming machine for converting a web (4) to a lap (6) by folding in pleats, comprising:

• at least two conveyor-belts (2, 5) which follow a closed path (20 to 31, 50 to 59) and are associated with rollers (32 to 43, 60 to 69) for respective guiding and displacing of said conveyor-belts, the closed paths (20 to 31, 50 to 59) being external to each other and adjacent to each other in a pinching zone (23, 53) delimited by guide rollers (35, 61;
• 38, 64) carried by two main carriages (10, 14) which are displaced in translational motion in a horizontal direction at right angles to longitudinal axes of the rollers (32 to 43, 60 to 69);
• compensating means including at least one auxiliary carriage (16, 18) which is displaced in translational motion at right angles to the longitudinal axes of the rollers (32 to 43, 60 to 69) so as to maintain the length of each closed path (20 to 31, 50 to 59) at a substantially constant value, each closed path (20 to 31, 50 to 59) making a 180-degree turn around at least one guide roller (41, 67) carried by at least one auxiliary carriage (16, 18);
• belt section means (20, 21,k 22) for conveying the web (4) to the entrance of the pinching zone (23, 53);
• an apron (8) which moves in a direction parallel to the longitudinal axes of the rollers (32 to 43, 60 to 69) and receives the web (4) passing out of the pinching zone (23, 53);
• and
• driving means (84, 85, 88, 89) for applying reciprocating movements of translation to the two main carriages (10, 14) and to the compensating means (16, 18);
• wherein the driving means (84, 85, 88, 89) include at least one motion-transmission element (84, 88) which engages with a driving pinion (85, 89), said motion-transmission element (84, 88) being attached at one end to one of the two main carriages (10, 14) and at an opposite end to at least one auxiliary carriage (16, 18);
• whereby rotation of the driving pinion (85, 89) in one direction pulls the main carriage (10, 14) in a first stage of the reciprocating movements and whereby rotation of the driving pinion (85, 89) in an opposite direction pulls the auxiliary carriage (16, 18) in a second stage of the reciprocating movements;
• wherein each main carriage (10, 14) is connected to at least one auxiliary carriage (16, 18) by coupling means (92, 96) which are less extensible than the conveyor-belts (2, 5), said coupling means (92, 96) being put under tension under the action of the driving means (84, 85, 88, 89).