Patent ID: 7293976

Claim:
A thermo-forming machine for forming three-dimensional work pieces with large surfaces and a relatively thin and uniform thickness from flat sheets of a thermoplastic material, the machine comprising: at least one mould ( 31 , 131 ) movable vertically between a passive lowered position and a raised forming position, a lower pressurizable chamber ( 14 ) delimited at the top by a horizontal reduction plate ( 12 ) with a first and a second aperture ( 12 a , 12 b ), spaced horizontally and of a size to allow the said mould ( 31 , 131 ) to pass through them, a first and a second counter-frame ( 29 , 30 ) for each holding a sheet to be formed around the said apertures ( 12 a , 12 b ) in the reduction plate ( 12 ), three heating panels ( 16 , 17 , 22 ) vertically aligned and spaced from one another and movable horizontally between a first position aligned vertically with the first aperture ( 12 a ) and a second position aligned vertically with the second aperture ( 12 b ), wherein an upper heating panel ( 16 ) and an intermediate heating panel ( 17 ) are disposed above the reduction plate ( 12 ) for preheating opposite surfaces of a flat sheet supported between these two panels ( 16 , 17 ), and a lower heating panel ( 22 ) is disposed beneath the reduction plate ( 12 ) for simultaneously heating from below another sheet held around one of the said apertures and heated from above by the intermediate panel ( 17 ).