AU719625B2 - Bonding of open mesh sheet material - Google Patents

Description

WO 98/21020 PCT/AU97/00774 1 BONDING OF OPEN MESH SHEET MATERIAL FIELD OF THE INVENTION This invention relates to the bonding of open mesh materials and in a specific aspect to shade cloth which is edged, for example to contain wires, ropes or cords in folded edges.

BACKGROUND OF THE INVENTION Welding of continuous thermoplastic sheet material is well known and used and has application such as in the joining of two sheets and might be used, for example, in the sealing of a thermoplastics bag. In the instance of bonding continuous sheeting, two opposing sheets will contact each other on being pressed together, with a continuous join being easily formed. The weld is typically formed by heating and also commonly by reason of the application of ultrasonic energy.

With open mesh material such as shade cloth it can be that only a minor proportion of the sheet material comprises fibre material, the chances of contact being made by a fibre or sets of fibres being urged together and being directly aligned with a corresponding set of fibres on the opposing sheet is quite small. Additionally there is the problem that melting of the fibres may lead to an inherent weakness of the overall open mesh sheet. There is therefore a greater criticality of achieving a more controlled welding process where the joining of two sheets of open mesh material is concerned.

Thus it can readily be seen that there are quite different consideration for welding of open mesh material compared to welding of continuous sheet material.

One specific application of the present invention is in relation to shade cloth. Shade cloth as commonly used is an open mesh polymer, for example high density polyethylene or a polypropylene/polyethylene mixture, is sometimes produced with increased density along its edges. However, there is perceived by the inventors need for a folded edge, preferably defining an elongate aperture which can contain a wire, cord or other like flexible tension member, and the folded edge needs to be secured back onto the main body of the shade cloth sheet.

OBJECT OF THE INVENTION One object of the present invention to provide for a means of bonding portions of an open mesh material that obviates or minimises any one of the above problems or at least provides the public with a useful choice.

WO 98/21020 PCT/AU9/00774 2 The main object of a specific aspect of this invention is to provide a better method of securing a shade cloth edge onto the body of the sheet after folding the edge over the body.

SUMMARY OF THE INVENTION In a first aspect the invention relates to a method of forming an elongate bond between a base portion and an overlying portion of open mesh thermoplastic sheet material which method in a broad form, could be said to comprise the steps of, a) overlapping the base portion with the overlying portion at a bonding zone to form an elongate overlap, b) holding the sheet material in longitudinal tension at least at the overlap c) pressing the overlying portion and the base portion together at the overlap to thereby impress plasticised thermoplastics into at least some of interstices between strands of the base portion whilst maintaining the base portion substantially intact, to thereby bond the two portions together.

It is preferred that heat is applied only to the overlying portion during the pressing to assist with impressing the plasticised thermoplastics and the overlying portion and the base portion are pressed together over a set longitudinal length respectively by an overlying bar and a base bar. The use of tension and the use of cooperating bars over a set longitudinal length provide a process amenable to good control over the quality of the join.

The application of heat may plasticise the overlying portion which plasticised overlying portion may be pressed at least in part into the base portion. Alternatively and preferably further thermoplastic material, separate from the open mesh material, is added and is plasticised and impressed into the base portion, and alternatively or additionally into the overlying portion. The further material preferably has a lower melting point and a higher melt index than the base portion or the overlying portion, this provides perhaps the capacity to operate at lower temperatures, but certainly to maintain greater integrity of both the overlying portion and the base portion of the sheet material after heating.

In one form of this aspect of the invention an edge of a single sheet of the open mesh sheet material is folded, the folded edge forming the overlying portion, and the remainder of the sheet material being the base portion, and the bond is positioned so that an elongate pocket is formed along the edge. A tension member can then be introduced between the base portion and the overlying portion, adjacent the edge so as to be located in the elongate pocket in the finished product. This folded edged open WO 98/21020 PCT/AU97100774 3 mesh sheeting provides a convenient product that has a number of applications, in amongst others, fencing, land management, provision of shade, depending upon the nature of the open mesh material.

It is preferred that the method is extended to form repeated bonds in a roll, or other suitable collection of material, and it will be understood that the bonding process of such a roll of material is preferably intermittent whereby the sheet is maintained stationary whilst the bond is being formed.

The invention encompasses bonds being formed transverse of the roll of open mesh material or alternatively longitudinal with respect to the roll of open mesh material. In the case of longitudinal repeated bonds these might overlap or abut to form a continuous bond, or alternatively may be spaced apart to form a non-continuous bond.

The extent to which the material is fed compared to the length of the heating bars will determine how much or little overlap is formed.

In a second aspect of the invention there is provided means for achieving a bond between the folded edge and the sheet which will minimise loss of strength and that means comprises pressing the folded edge over the body of the sheet with a hot bonding bar, the body of the sheet being supported with a relatively cold bonding bar, so that most deformation takes place in the folded edge without damaging the body of the sheet, and the folded edge is impressed in its ductile condition into the interstices and around the mesh material of the folded sheet.

If the product is to be produced under production conditions, it is desirable that the equipment used should be elongate, and in one embodiment of the invention the equipment has an aspect ratio of between 2 and 4, but this results in a long piece of equipment. If use were to be made of a flying bonding mechanism which moved with continuously moving work pieces, the equipment design would be most complex and the aspect ratio would need to be considerably increased. To overcome this problem in an embodiment of the invention the material is moved through the equipment intermittently by means of a shuttle clamp or clamps, so that it is stationary while the bonding is effected.

Edge folding of material with the characteristics of shade cloth is very difficult to achieve and in an embodiment of the invention, edge folding is achieved by firstly passing the edge material through a slot defined by a primary flattening guide the edge then passing a flat, conical or other sloping surface which is preferably one that rotates WO 98/21020 PCT/AU97iOO77 4 in the direction of feed of the material and the fold finally passing through a secondary flattening guide before entering the bonding zone of the equipment.

Even when folded over wire, for example, the edge is likely to be slack and imperfections in the folded edge could occur. Therefore there are provided two clamps, one at the upstream end of the bonding zone and the other at the downstream end, the clamp at the downstream end being movable along a guide, and being coupled to extendable power means so that the sheet and wire may be tensioned before bonding occurs and retained in its tensioned state for a short period of time after bonding has been effected, and before the bonded sheet is carried through to the downstream (discharge) end of the equipment.

Most conveniently, the material after having been folded, together with a wire or other stiffener if used, will be discharged onto a roll in accordance with known art, and if the material edge contains a wire, rope or other stiffener, the edges will clearly be much stiffer than the intermediate part of the sheet. In one form of this aspect of the invention advantage is taken of this feature, and the roller is provided with removable flange or flanges enabling a roll of edge folded sheet to be moved across the shaft of the roller, and to be thereby ejected in a lateral transverse direction (with respect to the direction of travel of the sheet), and having been so ejected, to be concertinaed between the stiff edges so as to make a very small package which is convenient for merchandising purposes.

Sometimes the required width of the product of this invention needs to be different from the width of the material that is supplied, and in a still further embodiment of the invention, a feature is that the processing portion of the equipment should be in two sub-assemblies, so that by mounting on a frame to which one sub-assembly can be moved transversely, the width of the product can be readily varied without any major change to the equipment.

The invention will also be understood to encompass a joined open mesh sheet as formed by any one or more of the methods defined or described herein.

In a third aspect the invention might be said to reside in a bonding apparatus for bonding two portions of open mesh thermoplastics material together, said two portions comprising an overlying portion and a base portion, and said apparatus including, a bonding zone within the apparatus including a pressing means comprising a base bar and an overlying bar, supported for radial movement between a spaced apart position WO 98/21020 PCT/AU97/00774 and an abutting position; bar drive means to exert a pressure so as to press the two bars together; a feeding means to feed said two portions of open mesh material into the bonding zone so as to overlap between the two bars an overlying portion and a base portion of the open mesh material, a tension means to provide tension to the open mesh material at least at the overlap in the bonding zone, and control means to control operation of the apparatus.

Preferably the apparatus includes a heating means to heat only the overlying bar to a temperature so as to melt a thermoplastics and the heating means preferably includes heat distribution means to provide even heat along the overlying bar. Preferably cooling means is also provided to cool the base bar.

A filler feed means is also preferably provided to feed a low melting point thermoplastics material on or between the overlap.

Preferably the tension means includes a pair of stationary clamps upstream of a first end of the bonding zone and a pair of moving clamps slidable in tandem between a first position at an upstream part of the bonding zone through to a second position downstream of the bonding zone whereby such movement effects traverse of the material across the bonding zone and the tensioning of the material.

In the case where it is desired to form a fold the apparatus includes a fold means to fold an edge of open mesh material over, during feeding through the feed means the folded edge being the overlying portion and a base of the sheet being the base portion, and preferably a guide means to guide the fold to a position whereby the bond is formed spaced apart from the folded edge to form an elongate pocket, the apparatus including tension member feed means to feed a tension member into said elongate pocket.

BRIEF DESCRIPTION OF THE DRAWINGS While the invention need not necessarily include the abovementioned details an embodiment is described hereunder in some further detail with reference to the accompanying diagrammatic sketches in which: Figure 1 is a partial perspective view of an upstream end of an apparatus for producing a folded edge sheet material; WO 98/21020 PCT/AU97/00774 6 Figure 2 is a partial perspective view of the downstream end of the apparatus shown in Figure 1 Figure 3 is a plan view from above showing the manner in which the open mesh material is folded over before bonding, Figure 4 is a rear plan view of the open mesh material initially being folded over passing around the conical guide of the wire; Figure 5 is a rear plan view of the open mesh material further folded, and bearing against the flat conical surface; Figure 6 is a rear plan view showing the fully folded material passing beneath an adjustable spacer bar; Figure 7 is a perspective view of means for feeding the further thermoplastic material onto the overlap before the bonding zone; Figure 8 is a cross sectional view through the overlying heating bar with the arrangement of heating elements, and heat distribution arrangement; Figure 9 is a plan view of the folded and bonded open mesh having a flexible tension member inserted into the elongate pocket; Figure 10 is a plan view of two sheets of mesh joined according to this method; Figure 11 is a magnified cross sectional representation of a bond formed by the invention without the aid of further thermoplastics material; and Figure 12 is a magnified cross sectional representation of a bond formed by the invention with the aid of further thermoplastics material.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS Similar reference characters indicate corresponding parts throughout the several views of the drawings.

WO 98/21020 PMTAU97077 7 Dimensions of certain of the parts as shown in the drawings may have been modified and/or exaggerated for the purposes of clarity of illustration.

Referring first to Figures 1 and 2, it will be clear that for explanation purposes it is inconvenient to draw full assembly drawings because of the high aspect ratio of the equipment and the need for interacting portions of the equipment to move in different planes, for example the cold bonding bar to be retracted to allow traverse of the movable clamp.

In interpreting Figures 1 and 2, the zone marked in Figure 1 with the letter would receive the movable clamp marked with the letter in Figure 2.

Briefly describing the workings of the illustrated embodiment then.

Working from the left hand (upstream) end of the apparatus, a sheet of shade cloth which is of open mesh polymeric material initially passes through an elongate slot (11) of a primary flattening guide which might be adjustable, on each of its sides (one side only being shown), and this has the effect of flattening and tensioning, by back tension or drag, the edge which might otherwise tend to pucker. A tension member (15) in the form of a wire is fed through a sharp conical tubular guide (16) which is supported from a main frame (not shown) of the apparatus by a conical tube support member (12) which is downwardly open (13) having an aperture (14) to permit passage therethrough of partially folded edge (14) of the material. The edge of the material is further folded over a sloping surface, in this embodiment being the conical surface of a roller (18) which has a flat conical shape. The conical surface of conical guide(16) defines an included angle which is less than 450, whereas the conical surface of the roller (18) defines an angle which exceeds 1200. Those angles, however, are not necessarily critical.

The folded edge (17) then extends between an adjustable spacer bar (20) which is spaced above a fixred platen (21) and has the function of finalising the folding of edge (17) until it is substantially parallel with the base of the sheet material The material then passes through the fixed clamp (24) and the projecting plate (25) also overlies fixed platen (21) to clamp both the wire and the edge (17) with respect to fixed platen (21) when tensioning is required before bonding is effected.

The traverse of the material is effected by means of flying clamps one on each side of the apparatus, both of which are traversed by means of a central rodless cylinder WO 98/21020 PCT/AU97100774 8 the clamp (26) containing a lineal bearing of the recirculating ball type designated (28) which freely slides over a guide (29) as best seen in Figure 2. The rodless cylinder utilised, together with the control equipment which is computerised, was purchased from Festo Pty Ltd at 179 Browns Road, Noble Park, Victoria, Australia, and is a computer controlled pneumatic actuator. The computer which controls the actuator is interacted with a proportional control, which allows control of velocity, distance travelled and tensioning pressure.

The distance travelled can be varied to allow the instance of unwelded pockets at predetermined distances. For the advantage of access to or the withdrawing of the tension member.

After traversing the fixed clamp the material moves between an overlying hot bonding bar (31) and a base cold bonding bar At the end of one traverse, the flying clamp (26) is reduced in its speed and stops while the fixed clamp (24) clamps the upstream end of the material. Further movement of the flying clamp (26) tensions the material and the wire or cord to a preset tension or position whereupon the end clamp (40) closes and holds the material and tension member in tension, whereupon the base bonding bar (32) elevates and then the overlying bonding bar (31) lowers, abutting opposite surfaces of the shade cloth, and heat is applied at carefully controlled temperatures and pressures for a carefully controlled period of time to press some of the plasticised the material of the overlying fold (17) into the interstices of the base material of the sheet After bonding, the bars (31) and (32) are retracted and the material which is now edged is wound around a spool severed from the upstream material if necessary, and the flange (34) is removed transversely and the roll of material is removed transversely, concertinaed into a smaller transverse width, and tied and packaged.

The sequence is as follows: The material is moved by the clamps (26) actuated by their pneumatic cylinders (36) to clamp the edge and move longitudinally by a rodless cylinder. At the end of the traverse, the fixed clamp cylinder (37) of clamp (24) clamps the material and wire as described above, and then the computer controls air valves to actuate firstly the tensioning of cloth and wire or cord by the action of the rodless cylinder. Then the clamping of the cloth and wire or cord by end cylinder (41) followed by actuation of firstly the lower cylinder (38) and secondly the upper cylinder (39) and to effect WO 98/21020 PCT/AU97/00774 9 bonding. Although times, temperatures and pressures must be carefully adjusted, the bonding can be effected in a period of about 2-5 seconds before the clamp cylinders (38) and (39) are retracted. During retraction cylinder (37) and end cylinder (41) however retains clamp (24) and clamp (40) closed while clamp (26) is opened by cylinder (36) and the clamp (26) is traversed back until it is adjacent the clamp that is in the space marked in Figure 1. The cylinders (36) and (37) are then reversed so that further actuation of the rodless cylinder will effect longitudinal movement of clamp indexing the material for a further bonding of the folded edge.

Turning now to more detail of some aspects of the invention.

Firstly the manner of folding is shown in more detail in figures 3 to 6. The folding of the edge is effected by first passing an edge of the material through the slot (11) of the primary flattening guides These flattening guides are preferably adjustable whereby the height of the slot can be varied to accommodate thicker material, or to provide for a greater or lesser degree of drag. The distance between the two opposing primary flattening guides can also be varied by adjusting their position relative to the base frame (not shown). The tension member does not pass through the primary flattening guides which guides are primarily for presenting the open mesh material properly aligned for the folding process.

In setting up the apparatus the open mesh material is then hand fed through aperture (14) of the conical tube support member with which there is minimal if any contact. The material is then fed past the conical roller (18) and finally fully folded when positioned under the adjustable spacer bar The folding is thus primarily by the location of the mesh in an unfolded position through the primary flattening guides and location of the mesh material in the folded position through the adjustable spacer bar The conical roller (18) assists the folding process by bearing against the partially folded edge The conical roller (18) isjournalled for rotation about a conical roller shaft (47) supported by a conical roller support member The conical roller is free to rotate but is not driven, so that any rotation imparted on it is due to contact with the partially formed edge. The conical roller has an inner face which is substantially conical apart from a lowermost vertical face The material is supported over the conical roller shaft (47) and an apex (46) of the fold is located against the vertical face of the conical roller. The position of the partially folded edge as it passes through the conical guide support member can be seen in Figure 4. The conical face minimises any adverse effects on the folding material. Alternatively in place of the conical roller it might be desired to provide a plate appropriately shaped to WO 98/21020 PCT/AU9100774 guide the partially folded edge, however the provision of a roller facilitates the passage of the uneven apex (46) of open mesh material. A detailed view of the arrangement of the conical roller can be seen in Figure 5. It can be seen that the apex (46) of the folded edge (17) is beginning to form and is urged inwardly with respect to the apparatus by the conical roller Final location is between the vertical face of the conical roller and the downstream end of the conical guide. A close up view of the adjustable spacer bar can be seen in Figure 6. It can be seen that the spacer bar fits quite closely with its fixed platen and a lower edge of the spacer bar is recessed to accommodate wire In terms of the tension member (15) this can take the form of a metal wire of a gauge suitable for the purpose required, or alternatively may take other forms such as cord or other platted synthetic or natural material. In use in the finished product this will generally be used to support the open mesh material between two supports, and the present method and apparatus is able to introduce any one of a range of such tension members into the elongate slot (50) formed by the folding process without great difficulty. The tension member is taken from a tension member spool (not shown) and fed through the conical wire guide (16) to a relatively precise position adjacent to the conical roller where it is fed into the forming folded edge. This positive placement of the tension member in the forming fold is found desirable to give reliable positioning within the elongate slot.

The above method can be enhanced in many applications of the invention by locating a strip of further plastics material over the top of the overlap in the bonding zone and incorporating the strip between the surfaces the overlap. The further plastics material is a thermoplastic material. The strip could be heated to allow the filler strip to melt and pass through the interstices of the mesh. Still further, the further material may be extruded in molten form either on top or between the material at the bonding area, and in some cases, the bonding bars need not be heated, or, if heated, to a lesser degree than required for welding shade cloth directly to shade cloth. This modification permits a wider range of open mesh materials to be used, and in particular materials that have a more fragile construction whereby deformation of the overlying portion of the mesh may unduly weaken the integrity of the material for certain purposes. This modification has been trialled with a filler strip of thermoplastics material with a lower melting point and a higher melt index than the plastics material of the open mesh material. This has so far given a satisfactory result, and minimised the damage caused by the bonding process above.

WO 98/21020 PCT/AU97/00774 11 Figure 7 illustrates one manner of introducing a filler strip onto the folded edge. It can be seen that the filler strip (52) is stored on a filler spool (51) from which the filler strip is guided by filler strip guide (53) onto the folded edge. The filler strip is guided onto the folded edge between the fixed clamp (25) and the flying clamp The filler strip adds further thermoplastics that can be molten into the interstices of both the overlying fold portion of the material and the base portion of the material. It is evident from Figure 7 that the filler strip is drawn out by the action of the flying clamp, in much the same way as the tension member (15) and the open mesh material itself is taken off.

The filler strip may be a strip of material that is about 15 mm wide and approximately 0.2 to 1 mm in thickness. The filler strip is configured so as to insulate the fibres of the open mesh material from the action of the heated overlying bar. Thus the filler strip could be configured so as to be a little wider than the width of the foot (70) of the heated overlying bar (31) so that there is no direct contact between the two, or alternatively the strip might have raised edges, which raised edges are formed to extend upwardly on either side of the foot (70) of the heated overlying bar. The raised edges, particularly if they are taper outwardly, have the added advantage of having some degree of a locating effect, whereby to correct any slight misalignment with the heating bar.

The mechanism in which the material traverses the apparatus has already been described in some details and this will not be discussed any further. Turning now to the manner in which the overlying heater bar (31) is constructed. It is highly desirable, especially where no filler strip is used, to provide for a very even heat over the entire length of the heater bar, which defines the bonding zone Variation of only a few degrees Celsius is desirable. As discussed already the overlying bar (31) and the base bar (32) press the overlying portion of the mesh at the folded edge (17) and the base portion of the mesh together, heating only the overlying portion at a region of overlap between the two portions. The construction of the illustrated overlying bar is best seen in the transverse cross sectional view seen in Figure 8. An heating portion (60) of the heating bar is housed within an outer housing The outer housing provides insulation resulting in very much improved performance by reducing considerably heat losses.

Additionally whereas the inner portion changes shape considerably due the expansionary influences of heat, thereby rendering mechanical coupling such as to cylinders complex, the outer housing does not suffer a similar defect. The outer housing is constructed of RHS steel with is preferably teflon lined as an insulative material. The heat generation is provided by to heating elements (62, 63) drawing electrical power provided by leads (64, 65). The heating elements heat up an appropriate oil (66) which partially fills a trough (69) in an elongate aluminium block WO 98/21020 PCT/AU970077 12 A cover (68) seals the trough apart from a breather tube (not shown) which leads to an overflow reservoir, to accommodate the expansion and contraction of air. The aluminium block includes an elongate depending foot (70) which protrudes out of the outer housing, and which has at its lowermost surface a teflon coating and which lowermost surface contacts the overlying portion of the mesh at the region of overlap.

The heating elements each have a capacity in the order of 500 to 750 watts, and extend for the majority of the 1 metre or so length of the heated bar. The temperature is controlled temporally and in use has been found to vary only by approximately one degree Celsius from one end of the bar to the other.

The base bar may be cooled however conventional means of cooling can be employed.

It would be clear, of course, that in order to illustrate the functions it has been convenient to show only one side of the equipment, and the base frame has not been illustrated herein at all. However, the other side of the equipment is the same as the side which is illustrated and described, except for being of opposite hand, and there is no invention claimed in the base. It merely provides a foundation for the equipment and a means by which the equipment can handle materials of different width.

Figures 9 though to 12 provide an illustration of two different joins that can be made.

Thus Figure 9 shows an example of a product made according to the earlier illustrated embodiments. The sheet material has a folded edge (17) with an elongate slot (50) in which is position a tension member (15) in the form of a metal wire. The bond can be see at 77 whereby a slight depression has formed as a result of the melting of the overlying portion. A schematic cross sectional view of this type of join can be seen in figure 11, whereby the strands of the base portion can be seen to be intact, whereas the strands of the overlying portion can be seen to have plasticised and pressed into the interstices and around the strands of the base portion.

Figure 10 shows a product made by a slightly modified method, whereby instead of folding over an edge, two sheets of open mesh material are drawn into an apparatus with a similar bonding zone to that shown in the above illustrated embodiment, which apparatus is adapted to join the two sheets together. In the present instance a filler strip has been used to augment the amount of plasticised material. The residuum of a filler strip can be seen by a slightly raised portion on the bond that has formed at the region of overlap The bond has thus no raised portion and the plasticised material is all derived from the overlying portion of the sheet material. A schematic cross section of that type of join using further material from a filler strip can be seen in figure 12. Itcan WO 98/21020 PCT/AU97/00774 13 be seen that strands (71) of the open mesh material remain substantially intact, and the filler material is pressed into many of the interstices (72) and around the strands to form a bond between the overlying portion or folded edge (74) and the base portion A residuum (76) of the filler strip also remains. The filler strip in experiments to date has been shown to exert a protective or insulative effect on the strands of the overlying portion in addition to providing further plasticised material. The use of the filler strip also enable the use of this method on open mesh materials that are not themselves thermoplastics materials, additionally open mesh materials that have relatively thin or fragile strand can also be joined by this embodiment.

Claims (21)

1. A method of forming an elongate bond between a base portion and an overlying portion of open mesh sheet material comprising the steps of, a) overlapping the base portion with the overlying portion at a bonding zone to form an elongate overlap, b) holding the sheet material in longitudinal tension at least at the overlap c) pressing the overlying portion and the base portion together at the overlap with a heated overlying bar and a base bar to thereby impress plasticised thermoplastics into at least some of interstices between strands of the base portion whilst maintaining the base portion substantially intact, to thereby bond the two portions together.

2. The method of forming an elongate bond as in claim I wherein the method includes pressing the overlying portion and the base portion together over a set longitudinal length and melting the overlying portion but not the base portion.

3. The method of forming an elongate bond as in claim 2 wherein the sheet material is a thermoplastics material and the overlying portion is plasticised by the step of applying heat, to assist with impression of the plasticised thermoplastics into said interstices. The method of forming an elongate bond as in claim 1 wherein further thermoplastic material, separate from the open mesh material, is added and is plasticised by the step of applying heat to assist with impression of the plasticised thermoplastics into said interstices. S* 5. The method of forming an elongate bond as in claim 4 wherein the further material has a lower melting point and a high melt index than the base portion or said overlying portion.

6. The method of forming an elongate bond as in either claim 4 or 5 wherein the further thermoplastics material is powdered or granulated.

7. The method of forming an elongate bond as in either claim 4 or 5 wherein the further material is a filler strip and the method includes the additional step of introducing the filler strip over the overlying portion, during or before step a).

8. The method of forming an elongate bond as in any one of claims 1 to 7 wherein an edge of a single sheet of the open mesh sheet material is folded, the folded edge 21/03 '00 TUE 16:46 [TX/RX NO 7978] 21/03/2000 16:13 +61-8-84105042 APT PAGE 05/13 forming the overlying portion, and the remainder of the sheet material being the base portion, said bond formed so as to form an elongate pocket along the edge.

9. The method of forming an elongate bond as in claim 8 wherein a flexible tension member is introduced between the base portion and the overlying portion, adjacent the edge so as to be present in the elongate pocket in the finished product. The method of forming an elongate bond as in any one of claims 1 to 9 in a roll or rolls of open mesh sheet material of dimensions longer than the bonding zone, and the method includes the further step of feeding a length of material into the bonding zone, before step a) of claim 1 and then the step d) of carrying the bonded material from the bonding zone after step c) and repeating the steps to d) so that there are repeated joins in the roll or rolls of open mesh material. n' 15 11. The method of forming an elongate bond as in claim 10 wherein the roll or rolls S* are stationary whilst steps b) and c) are performed.

12. The method of forming an elongate bond as in claim 10 wherein the repeated bonds are transverse of the roll open mesh material.

13. The method of forming an elongate bond as in claim 10 wherein the repeated o bonds are longitudinal with respect to the rolled open mesh material.

14. The method of forming an elongate bond as in claim 13 wherein the repeated 25 bonds overlap or abut to form a continuous bond.

15. The method of forming an elongate bond as in claim 13 wherein the repeated bonds are spaced apart to form a non-continuous bond.

16. A method of forming an edged open mesh plastic sheet including forming a bond between a folded edge of the sheet and the sheet, the method comprising the steps of pressing the folded edge over the body of the sheet with a hot bonding bar, the body of the sheet being supported with a relatively cold bonding bar, so that most deformation takes place in the folded edge without damaging the body of the sheet, and the folded edge is impressed in its ductile condition into the interstices and around the mesh material of the folded sheet. 21/03 '00 TUE 16:46 [TX/RX NO 7978] 21/03/2000 16:13 +61-8-84105042 APT PAGE 0E6/13 16 17, A method of forming an edged open mesh plastic sheet as in claim 16 wherein the material is moved intermittently so that as. to be stationary while the bonding is effected.

18. A method of forming an edged open mesh plastic sheet as in either claim 16 or 18 wherein the sheet and wire is tensioned before bonding occurs and retained in its tensioned state for a short period of time after bonding has been effected, and before the bonded sheet is carrier through to a downstream end of the equipment.

19. A method of forming an edged open mesh plastic sheet as in any one of claims 16 to 18 wherein the bond is formed spaced apart from the folded edge to form. an elongate pocket and a flexible tension miember is introduced between the folded edge and the body of the sheet so as to be present in the elongate pocket. .20. A method of forming an edged open mesh plastic sheet as in any one of claims 16 to 19 wherein a filler strip of thermoplastic material is located over or between the folded edge and the sheet to provide for a greater mass of molten thermoplastics to form said bond.

21. A method of form~ing an edged open mesh plastic sheet as in one of claims 16 to 20 wherein the edged sheet is discharged onto a roller and the method including the step ofcompressing the roll. A joined open mesh sheet as formed by the method of any one of claims I to 21.

23. A bonding apparatus for bonding two portions of open mesh material together, said two portions comprising an overlying portion and a base portion, anid said apparatus including, a bonding zone within the apparatus including a pressing means comprising a base bar and an overlying bar, supported for radial movement between a spaced apart position and an abutting position; bar drive means to exert a pressure so as to press the two bars together; a heating means to beat said overlying bar to a temperature so as to melt a thermoplastics -material to thereby impress plasticised thermoplastics into at least some of interstices between strands of the base portion whilst maintaining the base portion substantially intact, a feeding means to feed said two portions of open mesh material into the bonding zone so as to overlap between the two bars an overlying portion and a base portion of the open mesh material, 21/03 '00 TUE 16:46 [TX/RX NO 7978] 21/03/2000 16:13 +61-8-84105042 APT PAGE 07/13 17 a tension means to provide tension to the open mesh material at least at the overlap over the bonding zone, and control means to control operation of the apparatus.

24. A bonding apparatus as in claim 23 adapted to feed one sheet of the open mesh material said apparatus including a fold means to fold an edge of open mesh material over, during feeding through the feed means the folded edge being the overlying portion and a base of the sheet being the base portion. A bonding apparatus as in claim 24 wherein the apparatus includes guide means to guide the fold to a position whereby the bond is formed spaced apart from the folded edge to form an elongate pocket, said apparatus including tension member feed means to :.feed a tension member into said elongate pocket.

26. A bonding apparatus as in claim 23 including a heating means to heat the said overlying bar to a temperature so as to melt a thermoplastics material.

27. A bonding apparatus as in claim 26 wherein the heating means includes heat distribution means to provide even heat along the overlying bar. a S28. A bonding apparatus as in claim 27 including cooling means to cool said base bar.

29. A bonding apparatus as in claim 23 including a filler feed means, to feed a low melt point filler onto the overlap.

30. A bonding apparatus as in claim 26 wherein the tension means includes a pair of stationary clamps up stream of a first end of the bonding zone and a pair of moving clamps slidable in tandem between a first position at an upstream part of the bonding zone through to a second position downstream of the bonding zone whereby such movement effects traverse of the material across the bonding zone and a tensioning of the material. Dated this 21st day of March 2000 LILA MARGARET MARZEC and ROBERT DOUGLAS SHEEHAN By their Patent Attorneys A.P.T. Patent and Trade Mark Attorneys 21/03 '00 TUE 16:46 [TX/RX NO 7978]