Loader for signatures, sheets and similar products, for the feeders of packaging machines, bookbinding machines and the like

A loader for signatures, sheets and similar products, for those feeders of packaging machine, bookbinding machines and the like which comprise a box-type magazine, characterised by comprising a product feed channel with a descending inclined base formed from at least one conveyor belt guided about a deviation roller at the lower end of the channel, and with lateral containing walls, the products being disposed in said channel transversely in a standing position and in mutual contact, a mechanism for controlling the stepwise advancement of said conveyor belt, a transverse counteracting plate spaced apart from the lower end of the feed channel and having its lower edge raised from the inclined surface of said conveyor belt so as to create a withdrawal zone for the products fed through said channel, a group of arms provided at their free ends with suckers arranged to be put into communication with a suction source, said arms being carried by a rockable transverse shaft, control means for imparting rocking movements to said shaft and for moving the suckers of said arms alternately into the withdrawal zone and into a position removed from said zone, a second transverse shaft parallel to said arm-carrying shaft, said second shaft carrying wheels offset with respect to said arms, gripper members mounted on said wheels and arranged to grip the products transferred by the sucker arms when these are in the position removed from the withdrawal zone, for each of said wheels a first endless belt guided about deviation and tensioning rollers and wrapped about said wheel through an arc of greater than 180.degree., and a second endless belt guided about deviation and tensioning rollers and wrapped about said wheel over said first belt through an arc of less than 180.degree., said two belts travelling together in mutual contact from the point in which the second belt wraps over the first on said wheel to a discharge point determined by respective deviation rollers which withdraw them from each other, and cooperating in order to convey the product inserted between them as far as said discharge point, motor means for rotating said second wheel-carrying shaft and for driving the pairs of belts wrapped about said wheels, a mechanism controlled by fixed cams for operating said gripper members during the rotation of the gripper-carrying wheels, feeler elements acting in the product withdrawal zone and mounted to swivel between a position in which they are in contact with the product abutting against said counteracting plate and a position removed from the withdrawal zone, means linked to the control means for said sucker arms in order to remove said feeler elements from the withdrawal zone when the sucker arms are moved into this zone, and to enable the feeler elements to be moved under the action of elastic means into contact with the product abutting against the counteracting plate when the sucker arms are removed from the withdrawal zone, and a switch operationally associated with said feeler elements and acting on said mechanism for controlling the stepwise advancement of the conveyor belt in the feed channel in order, at any given time, to halt the advancement through one step when the feeler elements in the product withdrawal zone detect a thrust determined by the products in the feed channel which exceeds a predetermined value.