Machine for sealing parallelepiped boxes

A machine for sealing parallelepiped boxes composed of two vertical side walls, two vertical end walls, a group of upper closing flaps and a group of lower closing flaps, comprising a support surface for the boxes to be sealed, a pair of entraining elements including conveyor belts disposed in a transversely displaceable manner at the two sides of said support surface to engage with respective side walls of the boxes in order to feed them along said support surface, and at least one taping head disposed above said support surface to apply an adhesive sealing tape to the top of the boxes as they advance along said support surface, each conveyor belt extending as an endless loop about a respective succession of rollers with their axes parallel and spaced apart along the feed direction of the boxes, of which the most downstream roller is rotated by motor means, wherein said most downstream roller associated with each conveyor belt has a drive shaft rotatably supported by a slide which can be controllably spaced along a guide transverse to the feed direction of the boxes, on said shaft there being mounted a sprocket which cooperates with the analogous sprocket associated with the other conveyor belt, with a drive sprocket disposed in proximity to one side of said support surface and rotated by a motor, and with a chain tightening sprocket disposed in proximity to the other side of said support surface, by way of a chain which engages at its opposite ends with said sprockets associated with the conveyor belts.