97 the piston rod 99 of each pneumatic cylinder 100 acts on the outer ends of the holding rail 97 via a fork head 98 the pneumatic cylinders 100 are arranged on the angles 82 and 83 respectively as is apparent from fig1 a plate 101 provided with a hole for passing through the hinge pin 92 is fastened on the strip 86 and a bent pate 102 which also has a hole for passing through the hinge pin 92 is fastened to the strip 87 the strip 88 is fastened to the flat iron 84 and to the sliding block 80 by a plurality of screws 103 fig1 in the vicinity of one end and to the flat iron 85 and the sliding block 81 by screws 103 a horizontal guide web 104 fig9 for a groove 105 is provided in the strips 88 and 89 for support on the vertical leg of the angle brackets 82 and 83 the strips 90 and 91 of the third pair of strips have a groove 106 as shown in fig9 on the lower side a guide web 107 is provided on the strips engages the groove 106 on the side adjacent to the conveyor belts 2 3 and 5 a plurality of horizontal holes 108 and an equal number of vertical grooves 109 corresponding to the diameter of the holes are provided in the strips 86 and 87 of the first pair of strips and in the strips 90 and 91 of the third pair of strips approximately z shaped folding tools 110 and 112 as well as two straight folding bars 111 are provided for folding folds by twofold angular bending the desired number of the folding tools 110 is inserted with one horizontal leg into a.