Patent ID: 8764923

Claim:
A method of pre-shaping a ply of interlayer material for use in a laminated glazing, wherein at least a portion of the ply of interlayer material has a wedged cross-section before the pre-shaping, by stretching at least a portion of the ply of interlayer material, the method comprising: in a first step, providing heat and moisture to a first surface of the ply of interlayer material to perform a first heating stage; in a second step, providing heat and moisture to a second surface of the ply of interlayer material, opposite the first surface, to perform a second heating stage; and in a third step, stretching the ply of interlayer material into a desired shape; wherein in the first and second steps, the rate at which the heat and moisture are supplied is controlled such that the shaping of the ply of interlayer material is uniform, and the standard deviation in the magnitude of the wedge angle of the wedged portion of the interlayer material after the pre-shaping is less than 0.05 mrad, wherein the first step is carried out by passing the ply of interlayer material over the surface of a first rotating drum, and the heat and moisture is provided by water, and wherein the second step is carried out by passing the ply of interlayer material over the surface of a second rotating drum, and the heat and moisture is provided by water.