Patent ID: 7740422

Claim:
A geogrid manufactured by a continuous production process comprising the steps (a) furnishing a number of single-layer, homogeneous, molecular-oriented thermoplastic bars with a high tensile strength positioned parallel to one another in a direction of the machine, and designated as longitudinal bars, in such a way that a continuous stress in the individual longitudinal bars is ensured during a subsequent friction welding operation; (b) laying a number of single-layer, homogeneous, molecular-oriented thermoplastic bars with a high tensile strength onto the longitudinal bars transversely to the direction of the machine, and designated as transverse bars, in such a way that a constant stress remains in the individual transverse bars, forming a multiplicity of crossing areas arranged next to and behind one another; (c) conveying intermittently said longitudinal bars together with the transverse bars laying on the longitudinal bars, into a friction welding apparatus having at least one vibration-welding device equipped with a vibration plate, which vibration plate has a large surface area and which vibration plate is used to friction weld at least 100 crossing areas simultaneously; and (d) friction welding all crossing areas of the thermoplastic bars under pressure simultaneously by vibration, whereby the plastic bars at their crossing areas are made to vibrate with frequencies and amplitudes which are such that the surfaces soften, and, in this way, are welded together under pressure.