Plastics material mesh structure

A method of producing an integral plastics material mesh structure, comprising stretching in at least one stretching direction a plastics starting material having a regular pattern of holes or depressions therein, the pattern of holes or depressions comprising:

• at least two rows of first holes or depressions, said rows extending substantially at right angles to said stretching direction, said rows being adjacent with no intervening row of holes or depressions which are the same size or larger, the first holes or depressions having their centres on a notional, substantially square or rectangular grid with the side thereof substantially parallel to the stretching direction, and the first holes or depressions being of substantially the same size;
• and
• rows of second holes or depressions with the centre lines of the rows between and substantially parallel to the centre lines of the rows of first holes or depressions, said second holes or depressions being offset with respect to said first holes or depressions, as viewed in said stretching direction, and said second holes or depressions being substantially smaller than the first holes or depressions and not positioned substantially on the intersections of the notional diagonals joining two immediately adjacent first holes or depressions in one row with two immediately adjacent first holes or depressions in the immediately adjacent row of first holes or depressions and which form a square or rectangular configuration with the two first holes or depressions of said one row, whereby a structure is formed comprising generally-parallel, spaced, side-by-side, orientated strands extending generally in said stretching direction, an end of each of which side-by-side strands forks into only two further, generally parallel orientated strands.

An integral plastics material mesh structure which has been stretched in two stretching directions, comprising:

• aligned, highly orientated main strands running substantially parallel to one said stretching direction, the end of one main strand being connected to the adjacent end of the next main strand by way of a junction zone containing unorientated plastics material or plastics material which has been orientated only to a low degree;
• further such main strands extending substantially parallel to but spaced from the first-mentioned main strands, the end of one further main strand being connected to the adjacent end of the next further main strand by way of a junction zone containing unorientated plastics material or plastics material which has been orientated only to a low degree;
• and
• highly orientated interconnecting strands interconnecting the junction zones of adjacent, substantially parallel main strands, the interconnecting strands comprising substantially parallel, spaced, highly orientated first interconnecting strands extending substantially parallel to the other stretching direction, at least one end of each first interconnecting strand forking into two second interconnecting strands, the other ends of of which are connected indirectly or directly to a said junction zone;
• two said main strands and two said interconnecting strands meeting at any one said junction zone.

A method of producing an integral plastics material mesh structure, comprising stretching in at least one stretching direction a plastics starting material having a regular pattern of holes or depressions therein, the pattern of holes or depressions comprising:

• groups of rows of first holes or depressions, said rows extending substantially at right angles to said stretching direction, each said group comprising at least two said rows and said rows in each said group being adjacent with no intervening row of holes or depressions which are the same size or larger, the first holes or depressions having their centres on a notional, substantially square or rectangular grid with the side thereof substantially parallel to the stretching direction, and the first holes or depressions being of substantially the same size;
• and
• rows of second holes or depressions with the centre lines of the rows between and substantially parallel to the centre lines of the rows of first holes or depressions, said second holes or depressions being offset with respect to said first holes or depressions, as viewed in said stretching direction, and not being substantially smaller than said first holes or depressions, said stretching out into generally-parallel, spaced, side-by-side, first orientated strands extending generally in said stretching direction, zones between adjacent said first holes or depressions in any one said row, and also stretching out into further, generally-parallel, second, orientated strands forking from the ends of said first strands, zones between respective adjacent said first holes or depressions and said second holes or depressions.