US 8,025,832 B2 · Method for shaping sheet thermoplastic and the like

Abstract

Processes and apparati for shaping sheet glass or thermoplastic materials use force from a layer of a flowing fluid, such as air, between the sheet and a mandrel at close to the softening temperature of the thermoplastic. The shape is preserved by cooling. The shape of the air bearing mandrel and the pressure distribution of the fluid contribute to the final shape. A process can be conducted on one or two surfaces such that the force from the air layer is on one or two surfaces of the sheet. The gap size between the sheet and mandrel determines the pressure profile in the gap, which also determines the final sheet shape. In general, smaller gaps lead to larger viscous forces. The pressure profile depends on the shape of the mandrel, the size of the fluid gap and the sheet and the fluid supply pressure.

Claims16

Dependent claims

A method for shaping a thermoplastic material workpiece to a specified shape, having a softening point and at least one surface, the method comprising:

supporting a workpiece of the thermoplastic material so that the at least one surface is spaced away from a mandrel having a shaped surface, the shape of which surface bears a relationship to the specified shape, thereby establishing a gap between the workpiece and the surface;
flowing a fluid across the workpiece surface, establishing a predominantly viscous flow in the gap, which flow establishes a pressure profile across the workpiece surface such that force from the pressure inversely depends on the size of the gap;
heating the workpiece to a temperature close to the softening point;
while maintaining the fluid flowing across the workpiece surface such that the workpiece remains spaced away from the shaped surface, waiting until the workpiece conforms to the specified shape, due to the mandrel shaped surface and the fluid pressure profile;
cooling the workpiece below the softening point so that it retains the specified shape.

2 more elements

Dependencies are inferred from the claim text.

Method for shaping sheet thermoplastic and the like

Life of this patent

Method for shaping sheet thermoplastic and the like

Life of this patent

Abstract

Claims16