1. Field of the Invention
This invention relates to apparatus and method for folding-in end closure portions at an end of a packaging sleeve.
2. Description of Prior Art
Various apparatus and methods of folding-in end closure portions of packaging sleeves are known from, for example, U.S. Pat. Nos. 3,820,303; 4,337,059 and 4,524,460; British Patent 1292822; German Patent 687399; Federal German Patent 1952266 and French Patent 7024151.
French Patent 7024151 discloses a system for folding inwards a smaller pair and a larger pair of end closure flaps of a carton. The system includes a compressed-air piston-and-cylinder device which advances, along a supporting rod, an encircling yoke having a smaller pair and a larger pair of arms, the four arms of the yoke being angularly distributed at 90.degree. spacings around the yoke. Mounted diametrically opposite each other upon a ring axially movable along the rod against a spring bias is a first pair of spring-biassed, bell-crank levers, outer free ends of which form a first pair of jaws oscillatable transversely of the axis of the rod. The larger pair of arms acts upon inner free ends of the bell-crank levers to swing the pair of jaws inwards against the spring bias on the levers to fold inwards the smaller end closure flaps. Mounted diametrically opposite each other upon a ring fixed onto the rod is a second pair of spring-biassed, bell-crank levers, outer free ends of which form a second pair of jaws oscillatable transversely of the rod axis. After the larger pair of arms has began to act upon the first pair of bell-crank levers, the smaller pair of arms begins to act upon inner free ends of the second pair of bell-crank levers to swing the second pair of jaws inwards against the spring bias on their levers to fold inwards the larger flaps. Thus, the smaller flaps are folded inwards before the larger flaps. The spring bias on the ring mounting the first pair of levers allows the yoke to advance that ring and the first pair of jaws to remain in their innermost positions while the jaws of the second pair of jaws continue to move towards each other. This system has the disadvantage that the first pair of levers remains in the closure throughout the folding-in of the larger flaps and is thus unsuitable for use in a packaging method in which tucking-tacking of outer sub-panels is required.
U.S. Pat. No. 3,820,303 discloses a system in which a mandrel wheel transports carton sleeves anti-clockwise through various treatment stations. In a folding station, score lines of bottom end closure panels of the sleeves are "broken" by turning inwards a pair of jaws in the form of pivotally mounted, triangular wings, to cause them to bear upon respective inner panels of the end closure. The sleeve is then indexed to a heating station in which selected zones of thermoplastics coating of the bottom end closure are heated to soften the thermoplastics. The heated sleeve is then indexed to a sealing station on the path to which is a tucking device by which the pre-broken panels of the bottom end closure are folded inwards, with a smaller rectangular outer panel thereof becoming tucked under a larger rectangular outer panel thereof. The tucking device includes two folders articulatedly interconnected by a link and turnable, relative to a fixed support plate, about respective axes parallel to the mandrel wheel axis. A first of the two folders is in the form of a U-shaped arm whereof the base of the U is arranged to bear against the smaller outer panel. The second folder is in the form of a bell-crank lever whereof each arm is in the form of a U, the base of the U of one arm being arranged to bear against the larger outer panel and the base of the U of the other arm being attached to a helical tension spring urging this second folder to turn anti-clockwise towards the first folder and thus urging both folders to move oppositely to the advancing bottom end closures. In operation, the second folder is struck by the larger outer panel and thus swung clockwise against the spring bias, thereby, through the link, turning the first folder clockwise to cause it to come to bear on the smaller panel. The design and setting of the tucking device are such that the smaller outer panel is to be folded-in just before the larger panel, so that the smaller panel is tucked under the larger panel. However, during their displacement from the folding station to the tucking device by way of the heating station, the panels can move into relative positions which do not lend themselves to accurate folding and tucking by folders bearing upon only the two outer panels, especially since the carton sleeve is actually moving past the tucking device during the folding and tucking. Moreover, correct initial positioning and return of the folders is dependent upon the tension spring, with the consequence that accuracy of positioning and movement of the folders reduces with increased speed of the mandrel wheel and thus increased production rate.
U.S. Pat. No. 4,337,059 discloses a tucker-tacker station for folding-in, tucking and tacking the bottom end closures of pairs of carton sleeves when they have been indexed to the station by a rotary turret including pairs of vertical mandrels. The station includes a pair of vertical, cam-operated, reciprocatory, drive rods each of which drives, via a toggle arrangement, a pair of folding jaws arranged to oscillate transversely of the rod axis. The jaws of this pair swing inwards towards each other, transversely of the path of the mandrel pairs, to bear upon and thereby fold inwards the inner pair of panels of the bottom end closure and thus begin the inward folding of the two outer panels of the end closure. Each rod also drives, via a horizontal end plate fixed thereto, a pair of tucker-tacker jaws pivotally mounted upon brackets fixed to the end plate so as to oscillate transversely of the rod axis. The jaws of this pair swing inwards, along a tangent to the mandrel path, to bear on and thus fold inwards the respective panels of the outer pair and thereby to continue the inward folding of the inner pair of panels, one of the latter pair of jaws causing one of the outer pair of panels to lead the other of the outer pair in its inward turning, so that the one becomes tucked beneath the other. At the ends of their inward swings, the tucker-tacker jaws press the panels against the end face of a water-cooled cap of the mandrel to tack them together prior to pressure-sealing at a subsequent bottom sealing station. Because the toggle arrangement passes through dead centre during the lowering of the vertical drive rods and again during the raising of the rods, the pair of folding jaws is moved inwardly and outwardly twice during one bottom end closing operation, with the first inward movement of the folding jaws producing the folding of the inner pair of panels and the second inward movement being superfluous. During the upward movement of the end plate, the tucker-tacker jaws come to bear on the outer pair of panels to fold them inwards, tuck one beneath the other and tack them together. The vertical rods are moved downwards to lower the end plates and then the carton sleeves with tacked bottom end closures are stepped to the pressure-sealing station. This known assembly is relatively complex, with four pivotally mounted jaws.