| 摘要 |
Differential pressure thermoforming apparatus for forming large articles such as trailer bodies and boats in relatively thin sheets of thermoplastic material comprising a sheet supporting box frame for clamping the edge portions of a sheet of thermoplastic material and defining a cavity spanned by the clamped sheet. Load assist bars are disposed in the cavity to initially support the mid-portion of the thermoplastic sheet while it is being clamped on the frame and then fluid under pressure is admitted to the cavity to lift the midportion of the sheet upwardly off the bars. A sheet heating oven is mounted laterally adjacent one side of the mold box frame and is movable into superposed relation with the box frame where it is then tilted so that the sheet carried thereby is heated to a substantially uniform temperature. The clamped sheet, having its mid-portion supported by fluid pressure, is then moved upwardly toward a differential pressure mold to form a shape in the sheet of material. Doors are provided on the sides of the mold box frame and are opened to exhaust cooling air which is introduced to the cavity. After the shape is formed and the mold box frame is moved away from the mold, the load assist bars function to eject the molded part from the frame.
|
