Abstract: A web of molten thermoplastics material (4) from extruder die (3) is fed through a pair of temperature controlled rolls (5) having a gap (13) of width less than that of the web thickness leaving the extruder die (3) and is fed from the rolls (5) directly and continuously under uniform tension to a thermoforming machine (9) (10) as a formable web (6) of substantially uniform temperature through its thickness.

Abstract: Subsoil drain strip or sheet elements comprising a core surrounded by a polymer or glass fibre filter cloth. The core has a generally planar configuration with hollow formed-in flat topped projections on one or both sides which create internal volume for flow of water as well as supporting the filter cloth against imposed soil loads. The depth of the supporting projections on each side of the core and their relative spacing is to be such that the surrounding filter cloth is restrained against being forced into the hollow interiors of the projections so that adequate longitudinal flow of water can take place in the strip without the need for additional drainage tubes to be provided. The depth of the projections may be greater than one quarter of their closest spacing. Additionally, the average diameter of the projections may be between 0.2 and 0.35 of their closest spacing.

Abstract: A substantially planar reticulated material is formed by the conjunction of a plurality of strips of non-planar material so that the strips lie substantially perpendicular to the plane of the reticulated material with their edges lying coplanar with the reticulated material and forming opposite surfaces thereof. Each strip of nonplanar sheet material is formed on each opposite surface with a pattern of crests and valleys of repetitive wavelength such that each pattern repeat contains at least two crests and at least two valleys; in each pattern repeat the height of at least one crest or valley on at least one surface of the strip is different from that of at least one of the other respective crests and valleys on said surface; the recurring height difference produces a corrugation along the strip having a wavelength greater than the wavelength of the crests and valleys; and adjacent strips are abutted with the corrugation opposed to interfit at least one crest in a valley of each opposed corrugation.

Abstract: Apparatus for stretch-forming a heat softened sheet of thermoplastics material. The apparatus includes a stretching tool and means to move the stretching tool relative to means holding the sheet so as to stretch the sheet in a preselected direction with the tool. The stretching tool includes a plurality of blades having edges for pressing against the sheet to stretch the sheet and a cam to move the blades transversely away from each other to stretch the sheet transversely of the preselected direction as the tool is moved to stretch the sheet in the preselected directions.