Production of plastic mesh

Claim 1

A method of making a plastics material mesh structure, comprising: providing a plastics starting material which has a regular pattern of holes or depressions, the holes or depressions being in parallel lines, the distance between the holes or depressions of one line and those of the adjacent line being substantially greater than the distance between the holes or depressions in each line, the holes or depressions defining elongate, side-by-side main zones between the lines of holes or depressions and intermediate zones between the holes or depressions in each line, each of which intermediate zones is generally symmetrical about a line at right angles to the line of holes or depressions, the major part of the thickness of each intermediate zone being between planes defined by the outer faces of the main zones; and drawing the starting material at a temperature above the glass transition temperature but low enough so that melt flow orientation is prevented, said drawing being only in a direction substantially parallel to the main zones while preventing substantial reduction of the pitch of the main zones though permitting reduction in width of each individual main zone, thereby stretching the main zones out into continuous, uniaxially-orientated main strands with the orientation therein extending substantially uniformly from end to end and generally parallel to the drawing direction, substantially decreasing the width of the main zones when forming the main strands, the distance between the holes or depressions of one line and those of the adjacent line being sufficiently greater than the distance between the holes or depressions in each line so that the force of contraction of each main strand as the main strand reduces in width causes said intermediate zones to stretch in a direction generally at right angles to the drawing direction to form discontinuous, uniaxially-orientated initerconnecting strands which interconnect the main strands, whereby a biaxially-orientated mesh structure is produced comprising said orientated main strands and said orientated interconnecting strands with the orientation in the interconnecting strands extending generally at right angles to the main strands and the cross-sectional area of the mid-points of the interconnecting strands being less than the minimum cross-sectional area of the main strands, and in which mesh structure there is adjacent each end of each interconnection strand a zone of plastics material which is thicker than the material of the remainder of the interconnecting strand.

Claim 2

A method of making a plastics material mesh structure, comprising: providing a plastics starting material which has a regular pattern of holes or depressions, the holes or depressions being in parallel lines, the distance between the holes or depressions of one line and those of the adjacent line being substantially greater than the distance between the holes or depressions in each line, the holes or depressions defining elongate, side-by-side main zones between the lines of holes or depressions and intermediate zones between the holes or depressions in each line, each of which intermediate zones is generally symmetrical about a line at right angles to the line of holes or depressions, the major part of the thickness of each intermediate zone being between planes defined by the outer faces of the main zones; and drawing the starting material at a temperature above the glass transition temperature but low enough so that melt flow orientation is prevented, said drawing being only in a direction substantially parallel to the main zones while preventing substantial reduction of the pitch of the main zones though permitting reduction in width of each individual main zone, thereby stretching the main zones out into continuous, uniaxially-orientated main strands with the orientation therein extending substantially uniformly from end to end and generally parallel to the drawing direction, substantially decreasing the width of the main zones when forming the main strands, the distance between the holes or depressions of one line and those of the adjacent line being sufficiently greater than the distance between the holes or depressions in each line so that the force of contraction of each main strand as the main strand reduces in width causes said intermediate zones to stretch in a direction generally at right angles to the drawing direction to form discontinuous, uniaxially-orientated initerconnecting strands which interconnect the main strands, whereby a biaxially-orientated mesh structure is produced comprising said orientated main strands and said orientated interconnecting strands with the orientation in the interconnecting strands extending generally at right angles to the main strands and the cross-sectional area of the mid-points of the interconnecting strands being less than the minimum cross-sectional area of the main strands, and in which mesh structure there is adjacent each end of each interconnection strand a zone of plastics material which is thicker than the material of the remainder of the interconnecting strand.

Claim 22

A method of making a mesh structure, comprising: providing a plastics starting material which has a regular pattern of holes or depressions, the holes or depressions being in parallel lines, the distance between the holes or depressions of one line and those of the adjacent line being at least four times the distance between the holes or depressions in each line, the holes or depressions defining elongate, side-by-side main zones between the lines of holes or depressions and intermediate zones between the holes or depressions in each line; and each of which intermediate zones is generally symmetrical about a line at right angles to the line of holes or depressions, the major part of the thickness of each intermediate zone being between planes defined by the outer faces of the main zones; and drawing the starting material at a temperature above the glass transition temperature but low enough so that melt flow orientation is prevented, said drawing being only in a direction substantially parallel to the main zones while preventing substantial reduction of the pitch of the main zones though, permitting reduction in width of each individual main zone, thereby stretching the main zones out into continuous, uniaxially-orientated main strands with the orientation therein extending substantially uniformly from end to end and generally parallel to the drawing direction, substantially decreasing the width of the main zones when forming the mains strands, the distance between the holes or depressions of one line and those of the adjacent line being sufficiently greater than the distance between the holes or depressions in each line so that the force of contraction of each main strand as the main strand reduces in width causes said intermediate zones to stretch in a direction generally at right angles to the drawing direction to form discontinuous, uniaxially-orientated interconnecting strands which interconnect the main strands, whereby a biaxially-orientated mesh structure is produced comprising said orientated main strands and said orientated interconnecting strands with the orientation in the interconnecting strands extending generally at right angles to the main strands and the cross-sectional area of the mid-points of the interconnecting strands being less than the minimum cross-sectional area of the main strands, and in which mesh structure there is adjacent each end of each interconnection strand a zone of plastics material which is thicker than the material of the remainder of the interconnecting strand.

Claim 23

A method of making a mesh structure, comprising: providing a plastics starting material which has a regular pattern of holes or depressions, the holes or depressions being in parallel lines, the distance between the holes or depressions of one line and those of the adjacent line being at least four times the distance between the holes or depressions in each line, the holes or depressions defining elongate, side-by-side main zones between the lines of holes or depressions and intermediate zones between the holes or depressions in each line; and each of which intermediate zones is generally symmetrical about a line at right angles to the line of holes or depressions, the major part of the thickness of each intermediate zone being between planes defined by the outer faces of the main zones; and drawing the starting material at a temperature above the glass transition temperature but low enough so that melt flow orientation is prevented, said drawing being only in a direction substantially parallel to the main zones while preventing substantial reduction of the pitch of the main zones though, permitting reduction in width of each individual main zone, thereby stretching the main zones out into continuous, uniaxially-orientated main strands with the orientation therein extending substantially uniformly from end to end and generally parallel to the drawing direction, substantially decreasing the width of the main zones when forming the mains strands, the distance between the holes or depressions of one line and those of the adjacent line being sufficiently greater than the distance between the holes or depressions in each line so that the force of contraction of each main strand as the main strand reduces in width causes said intermediate zones to stretch in a direction generally at right angles to the drawing direction to form discontinuous, uniaxially-orientated interconnecting strands which interconnect the main strands, whereby a biaxially-orientated mesh structure is produced comprising said orientated main strands and said orientated interconnecting strands with the orientation in the interconnecting strands extending generally at right angles to the main strands and the cross-sectional area of the mid-points of the interconnecting strands being less than the minimum cross-sectional area of the main strands, and in which mesh structure there is adjacent each end of each interconnection strand a zone of plastics material which is thicker than the material of the remainder of the interconnecting strand.

Claim 27

A method of making a plastics material mesh structure, comprising: providing a substantially unorientated, plastics starting material which has a regular pattern of holes or depressions, the holes or depressions being in parallel lines, the distance between the holes or depressions of one line and those of the adjacent line being substantially greater than the distance between the holes or depressions in each line, the holes or depressions defining elongate, side-by-side main zones between the lines of holes or depressions and intermediate zones between the holes or depressions in each line, each of which intermediate zones is generally symmetrical about a line at right angles to the line of holes or depressions, the major part of the thickness of each intermediate zone being between planes defined by the outer faces of the main zones; and drawing the starting material at a temperature above the glass transition temperature but low enough so that melt flow orientation is prevented, said drawing being only in a direction substantially parallel to the main zones while preventing substantial reduction of the pitch of the main zones though permitting reduction in width of each individual main zone, thereby stretching the main zones out into continuous, uniaxially-orientated main strands with the orientation therein extending substantially uniformly from end to end and generally parallel to the drawing direction, substantially decreasing the width of the main zones when forming the main strands, the distance between the holes or depressions of one line and those of the adjacent line being sufficiently greater than the distance between the holes or depressions in each line so that the force of contraction of each main strand as the main strand reduces in width causes said intermediate zones to stretch in a direction generally at right angles to the drawing direction to form discontinuous, uniaxially-orientated interconnecting strands which interconnect the main strands, whereby a biaxially-orientated mesh structure is produced comprising said orientated main strands and said orientated interconnecting strands with the orientation in the interconnecting strands extending generally at right angles to the main strands and the cross-sectional area of the mid-points of the interconnecting strands being less than minimum cross-sectional area of the main strands, and in which mesh structure there is adjacent each end of each interconnecting strand a zone of plastics material which is thicker than the material of the remainder of the interconnecting strand.

Claim 28

A method of making a plastics material mesh structure, comprising: providing a substantially unorientated, plastics starting material which has a regular pattern of holes or depressions, the holes or depressions being in parallel lines, the distance between the holes or depressions of one line and those of the adjacent line being substantially greater than the distance between the holes or depressions in each line, the holes or depressions defining elongate, side-by-side main zones between the lines of holes or depressions and intermediate zones between the holes or depressions in each line, each of which intermediate zones is generally symmetrical about a line at right angles to the line of holes or depressions, the major part of the thickness of each intermediate zone being between planes defined by the outer faces of the main zones; and drawing the starting material at a temperature above the glass transition temperature but low enough so that melt flow orientation is prevented, said drawing being only in a direction substantially parallel to the main zones while preventing substantial reduction of the pitch of the main zones though permitting reduction in width of each individual main zone, thereby stretching the main zones out into continuous, uniaxially-orientated main strands with the orientation therein extending substantially uniformly from end to end and generally parallel to the drawing direction, substantially decreasing the width of the main zones when forming the main strands, the distance between the holes or depressions of one line and those of the adjacent line being sufficiently greater than the distance between the holes or depressions in each line so that the force of contraction of each main strand as the main strand reduces in width causes said intermediate zones to stretch in a direction generally at right angles to the drawing direction to form discontinuous, uniaxially-orientated interconnecting strands which interconnect the main strands, whereby a biaxially-orientated mesh structure is produced comprising said orientated main strands and said orientated interconnecting strands with the orientation in the interconnecting strands extending generally at right angles to the main strands and the cross-sectional area of the mid-points of the interconnecting strands being less than minimum cross-sectional area of the main strands, and in which mesh structure there is adjacent each end of each interconnecting strand a zone of plastics material which is thicker than the material of the remainder of the interconnecting strand.

Claim 29

A method of making a plastics material mesh structure on a machine, comprising: providing a substantially unorientated, plastic starting material which has a regular pattern of holes or depressions, the holes or depressions being in parallel lines, the distance between the holes or depressions of one line and those of the adjacent line being substantially greater than the distance between the holes or depressions in each line, the holes or depressions defining elongate, side-by-side main zones between the lines of holes or depressions and intermediate zones between the holes or depressions in each line, each of which intermediate zones is generally symmetrical about a line at right angles to the line of holes or depressions, the major part of the thickness of each intermediate zone being between planes defined by the outer faces of the main zones, said lines extending in the machine direction; subjecting the starting material to a small stretch in a direction substantially at right angles to said machine direction; and drawing the starting material at a temperature above the glass transition temperature but low enough to that melt flow orientation is prevented, said drawing being in said machine direction while preventing substantial reduction of the pitch of the main zones though permitting reduction in width of each individual main zone, thereby stretching the main zones out into continuous, uniaxially-orientated main strands with the orientation therein extending substantially uniformly from end to end and generally parallel to the machine direction, substantially decreasing the width of the main zones when forming the main strands, the distance between the holes or depressions of one line and those of the adjacent line being sufficiently greater than the distance between the holes or depressions in each line so that the force of contraction of each main strand as the main strand reduces in width causes said intermediate zones to stretch in a direction generally at right angles to the machine direction to form discontinuous, uniaxially-orientated interconnecting strands which interconnect the main strands, whereby a biaxially-orientated mesh structure is produced comprising said orientated main strands and said orientated interconnecting strands with the orientation in the interconnecting strands extending generally at right angles to the main strands and the cross-sectional area of the mid-points of the interconnecting strands being less than the minimum cross-sectional area of the main strands, and in which mesh structure there is adjacent each end of each interconnecting strand a zone of plastics material which is thicker than the material of the remainder of the interconnecting strand.

Claim 30

A method of making a plastics material mesh structure on a machine, comprising: providing a substantially unorientated, plastic starting material which has a regular pattern of holes or depressions, the holes or depressions being in parallel lines, the distance between the holes or depressions of one line and those of the adjacent line being substantially greater than the distance between the holes or depressions in each line, the holes or depressions defining elongate, side-by-side main zones between the lines of holes or depressions and intermediate zones between the holes or depressions in each line, each of which intermediate zones is generally symmetrical about a line at right angles to the line of holes or depressions, the major part of the thickness of each intermediate zone being between planes defined by the outer faces of the main zones, said lines extending in the machine direction; subjecting the starting material to a small stretch in a direction substantially at right angles to said machine direction; and drawing the starting material at a temperature above the glass transition temperature but low enough to that melt flow orientation is prevented, said drawing being in said machine direction while preventing substantial reduction of the pitch of the main zones though permitting reduction in width of each individual main zone, thereby stretching the main zones out into continuous, uniaxially-orientated main strands with the orientation therein extending substantially uniformly from end to end and generally parallel to the machine direction, substantially decreasing the width of the main zones when forming the main strands, the distance between the holes or depressions of one line and those of the adjacent line being sufficiently greater than the distance between the holes or depressions in each line so that the force of contraction of each main strand as the main strand reduces in width causes said intermediate zones to stretch in a direction generally at right angles to the machine direction to form discontinuous, uniaxially-orientated interconnecting strands which interconnect the main strands, whereby a biaxially-orientated mesh structure is produced comprising said orientated main strands and said orientated interconnecting strands with the orientation in the interconnecting strands extending generally at right angles to the main strands and the cross-sectional area of the mid-points of the interconnecting strands being less than the minimum cross-sectional area of the main strands, and in which mesh structure there is adjacent each end of each interconnecting strand a zone of plastics material which is thicker than the material of the remainder of the interconnecting strand.

Claim 31

A method of making a plastics material mesh structure, comprising: providing a plastics starting material which has a regular pattern of holes or depressions, the holes or depressions being in parallel lines, the distance between the holes or depressions of one line and those of the adjacent line being substantially greater than the distance between the holes or depressions in each line, the holes or depressions defining elongate, side-by-side main zones between the lines of holes or depressions and intermediate zones between the holes or depressions in each line, each of which intermediate zones is generally symmetrical about a line at right angles to the line of holes or depressions, the major part of the thickness of each intermediate zone being between planes defined by the outer faces of the main zones; and drawing the starting material at a temperature above the glass transition temperature but low enough so that melt flow orientation is prevented, said drawing being only in a direction substantially parallel to the main zones while preventing substantial reduction of the pitch of the main zones though permitting reduction in width of each individual main zone, thereby stretching the main zones out into continuous, uniaxially-orientated main strands with the orientation therein extending substantially uniformly from end to end and generally parallel to the drawing direction, substantially decreasing the width of the main zones when forming the main strands, the distance between the holes or depressions of one line and those of the adjacent line being sufficiently greater than the distance between the holes or depressions in each line so that the force of contraction of each main strand as the main strand reduces in width causes said intermediate zones to stretch in a direction generally at right angles to the drawing direction to form discontinuous, uniaxially-orientated interconnecting strands which interconnect the main strands, whereby a biaxially-orientated mesh structure is produced comprising said orientated main strands and said orientated interconnecting strands with the orientation in the interconnecting strands extending generally at right angles to the main strands and the cross-sectional area of the mid-points of the interconnecting strands being less than the minimum cross-sectional area of the main strands.

Claim 32

A method of making a plastics material mesh structure, comprising: providing a plastics starting material which has a regular pattern of holes or depressions, the holes or depressions being in parallel lines, the distance between the holes or depressions of one line and those of the adjacent line being substantially greater than the distance between the holes or depressions in each line, the holes or depressions defining elongate, side-by-side main zones between the lines of holes or depressions and intermediate zones between the holes or depressions in each line, each of which intermediate zones is generally symmetrical about a line at right angles to the line of holes or depressions, the major part of the thickness of each intermediate zone being between planes defined by the outer faces of the main zones; and drawing the starting material at a temperature above the glass transition temperature but low enough so that melt flow orientation is prevented, said drawing being only in a direction substantially parallel to the main zones while preventing substantial reduction of the pitch of the main zones though permitting reduction in width of each individual main zone, thereby stretching the main zones out into continuous, uniaxially-orientated main strands with the orientation therein extending substantially uniformly from end to end and generally parallel to the drawing direction, substantially decreasing the width of the main zones when forming the main strands, the distance between the holes or depressions of one line and those of the adjacent line being sufficiently greater than the distance between the holes or depressions in each line so that the force of contraction of each main strand as the main strand reduces in width causes said intermediate zones to stretch in a direction generally at right angles to the drawing direction to form discontinuous, uniaxially-orientated interconnecting strands which interconnect the main strands, whereby a biaxially-orientated mesh structure is produced comprising said orientated main strands and said orientated interconnecting strands with the orientation in the interconnecting strands extending generally at right angles to the main strands and the cross-sectional area of the mid-points of the interconnecting strands being less than the minimum cross-sectional area of the main strands.