Sealing machine for glue-coated material in sheets

A machine for sealing material in sheets, which have been coated with toner beads of heat-activated glue, the beads coming into engagement with each other after folding a sheet to an envelope format, the sheets then being taken into the machine for adhering the beads to each other, the machine comprising a first sealing zone and a second sealing zone positioned at 90.degree. to each other, advancing means for conveying the sheet through the sealing zones, each sealing zone having at least one pair of rotationally driven sealing discs, said at least one pair including a first sealing disc and a second sealing disc, heating means for heating said first sealing disc, said second disc being a freely rotating sealing disc engaging against the first disc with a pre-adjustable pressure, wherein heat transfer takes place from the first disc to the second disc so that, when the sheet folded to the envelope format is taken through the machine with the aid of said advancing means, the toner beads of the sheet in an advancing direction are first caused to pass through the first sealing zone and the envelope-foled sheet is then given a new advancing direction extending at 90.degree. to said advancing direction, the toner beads in the new advancing direction being caused to pass through the second sealing zone, each sealing zone including a heating zone which includes pre-heating means and final heating means, said pre-heating means being arranged in a pre-heating zone, the pre-heating zone including a first, fixed glide plate and a vertically movable second guide plate, the fixed glide plate being mounted with heat contact on a heated bracket, and surfaces of the glide plates facing towards each other being mounted substantially parallel to a tangent to a contact surface between the sealing discs.