WO2008109938A1

WO2008109938A1 - Mesh and its use for screening guttering

Info

Publication number: WO2008109938A1
Application number: PCT/AU2008/000329
Authority: WO
Inventors: Theofani Tsioris
Original assignee: Polymesh Australasia Group Pty Ltd
Priority date: 2007-03-11
Filing date: 2008-03-11
Publication date: 2008-09-18
Also published as: CA2680539A1; GB0917402D0; AU2008226322A1; GB2460373A

Abstract

A screen applied to overlay a guttering (14) on an outside edge of a roof (10) of a building. The screen is a panel (15) of generally planar mesh moulded from a plurality of plastics materials. It is affixed along one edge (16) to the roof (10) and along the opposite edge (17) to the top outside edge of the guttering (14). At least part of the plastics material on the bottom face (40) of the mesh has a higher content of carbon black, or a higher resistance to degradation by UV light, than does the plastics material forming the top face (38) of the mesh. The degradation resistant parts of the mesh may comprise stripes (49) of plastics material containing carbon black. The black stripes (49) are not visible from above when the mesh is installed.

Description

MESH AiND ITS USE FOR SCREENING GUTTERING

Background and Summary of the Invention

This invention concerns the use of mesh materials as screens over guttering along the edge of the roof of a house, for the purpose of preventing the entry of unwanted materials such as sticks, leaves, and other tree debris, large insects, litter and the like into the guttering. In some places such guttering is called a gutter or spouting, but the general shape remains the same being a gently sloped open topped channel, usually made of metal or plastics material, positioned to collect rainwater as it runs off a roof.

It is well known that the collection of unwanted materials in guttering causes overflowing of the guttering, blockage of the outflow pipes, constitutes a fire hazard and contributes to corrosion of the guttering. It also contaminates any water collected from the roof for drinking or other domestic purposes.

Many systems are in use, and more have been proposed, which provide a screen of mesh to cover the top of the guttering. Some of these systems require the mesh to be tensioned between rigid fastenings on the roof and the top outer edge of the guttering. The mesh in such systems must be kept somewhat tensioned in order for the leaves and sticks to slide over the edge of the gutter. These are the systems to which the present invention is particularly adapted.

Many attempts have been made to produce a mesh system which successfully excludes foreign matter from guttering. Types of mesh that have been tried include punched metal, expanded (slit) metal, woven wire meshes and fibreglass flyscreen fabric. However in recent years moulded plastic meshes have been the most widely used. These are usually formed from plastic which has been coloured, so a building owner can choose a desired colour to match or blend in with the adj oining roof or the guttering colour. US patent no. 6,938,379 to Groom describes a mesh screen for overlaying the guttering where a first array of strands aligned in a first direction of the mesh are made from a stiffer material than a second array of strands aligned at right angles. The strands in the two arrays are co-extruded from HDPE-rich and LDPE-rich plastics materials respectively. The strands in both orientations are visible from both sides of the mesh, so both the HDPE-rich and LDPE-rich materials are coloured identically in order to maintain a uniform colour across the upper face when in use. Uniform colour across that upper face is necessary for market acceptance as this is the face visible when the mesh is installed.

A problem with plastic meshes is the tendency for plastic to degrade when exposed to ultraviolet (UV) light which is present in sunlight. To alleviate this, existing meshes use a variety of UV stabilizers in the plastic formulations. It is known to add carbon black to plastics formulations in order to improve UV resistance. Carbon black additions can also significantly increase the strength of plastic materials. But such meshes are necessarily black (they cannot be coloured conventionally) and this is unacceptable to customers who want the mesh to be coloured otherwise. If one or both of the arrays of strands in the above mentioned US patent no. 6,938,379, the black strands so produced would be visible from both sides of the mesh (on one side more than the other) and this would be unacceptable to users wanting to colour match the mesh to their roof or guttering.

The present invention aims to provide the UV resistance and strength advantages of carbon black addition, together with the advantages of a mesh that can be selectively coloured on its entire top face.

Accordingly, in one aspect the present invention provides a screen applied to overlay a guttering on an outside edge of a roof of a building said screen comprising a panel of generally planar mesh moulded from a plurality of plastics materials and affixed along one edge of the panel to the roof and along the opposite edge of the panel to the top outside edge of the guttering, the mesh having a top face and a bottom face on respective opposite sides of the mesh, wherein at least part of the plastics material on said bottom face has a higher content of carbon black than does the plastics material forming the top face of the mesh. Preferably there is no carbon black in the material forming the top face of the mesh.

In another aspect the invention provides a screen applied to overlay a guttering on an outside edge of a roof of a building said screen comprising a panel of generally planar mesh moulded from a plurality of plastics materials and affixed along one edge of the panel to the roof and along the opposite edge of the panel to the top outside edge of the guttering, the mesh having a top face and a bottom face on respective opposite sides of the mesh, wherein at least part of the plastics material on said bottom face has a higher resistance to degradation by ultra-violet light than does the plastics material forming the top face of the mesh.

Preferably at least part of the plastics material on said bottom face has a higher content of carbon black than does the plastics material forming the top face of the mesh, but there is no significant amount of carbon black in the material forming the top face of the mesh.

- The strands of one of said arrays may be made of said material forming the top face of the mesh, and at said bottom face the strands of the other of said arrays may be made of said material having a higher carbon black content.

The strands of the other of said arrays may have their upper portion made of said material forming the top face of the mesh and their lower portion made of said material having a higher carbon black content.

The strands of said one of the arrays are preferably the lateral strands, and said strands of said other of said arrays are preferably the longitudinal strands.

Preferably the lateral strands together with that portion of the longitudinal strands having no carbon black form a generally laminar structure, and those portions of the longitudinal strands which have a higher carbon black content protrude below said laminar structure and cross the lateral strands beneath the lateral strands. The at least part of the plasties material on said bottom face is preferably polyethylene containing carbon black in the range 1 to 5 parts carbon black to 100 parts polyethylene, and more preferably carbon black in the range 2 to 3 parts carbon black to 100 parts polyethylene.

The mesh preferably comprises:

- a first array of parallel strands, hereinafter called longitudinal strands, aligned in the direction of said one edge of the panel; and - a second array of parallel strands, hereinafter called lateral strands, integrally moulded with and aligned at right angles to the first array, said first and second arrays of strands defining mesh apertures therebetween extending from said top face to said bottom face; such that on the bottom face: — the strands of one of said arrays are made of said material having a higher resistance to degradation by ultra-violet light, and

— the strands of the other of said arrays are made of the same material as on said top face.

The lateral strands are preferably formed at least substantially of high density polyethylene, and preferably the longitudinal strands have an upper portion having substantially the same composition as the lateral strands and a lower portion formed at least substantially of a blend of high density polyethylene with low density polyethylene and carbon black.

Preferably said blend is in the range of 10% to 20% high density polyethylene in low density polyethylene and 2 to 3 parts carbon black to 100 parts polyethylene.

A flat strip portion may lie along said opposite edge of the panel and parallel to the longitudinal strands, said strip portion being free of said lateral strands and comprising an upper layer having substantially the same composition as the lateral strands and a lower layer formed of said blend of high density polyethylene with low density polyethylene and carbon black. The mesh may be affixed to the guttering by means of screws through the flat strip portion.

In a further aspect the invention provides a method of preventing the entry of unwanted materials into a guttering on an outside edge of a roof of a building including affixing a screen over the edge of the roof and the guttering, said screen having a panel of mesh in a generally planar form affixed along one edge of the panel to the roof and along the opposite edge of the panel to the top outside edge of the guttering, the mesh having a top face and a bottom face each formed of moulded plastics material on respective opposite sides of the mesh, wherein the composition of plastics material on the bottom face has a higher content of carbon black than does the plastics material forming the top face of the mesh-

Brief Description of the Drawings

hi order that the invention may be more fully understood there will now be described, by way of example only, preferred embodiments and other elements of the invention with reference to the accompanying drawings where:

Figure 1 shows diagrammatically an installation of a mesh to a tiled roof of a building in accordance with one embodiment of the invention; Figure 2 shows diagrammatically an installation of a mesh to a corrugated steel roof hi accordance with a second embodiment of the invention;

Figure 3 is a perspective view part way through the process of installing the mesh to the guttering of the roof shown in Figure 1, although showing a different guttering profile; Figure 4 is a top view of a portion of a mesh in accordance with a third embodiment of the invention;

Figure 5 is a bottom view of the portion of mesh shown in Figure 3;

Figure 6 is a section view of part of the mesh along A-A indicated in Figure 3; and

Figure 7 is a section view of part of the mesh along B-B indicated hi Figure 3. Detailed Description of the Invention

Referring to the installations shown in Figures 1 and 3, the edge of a roof 10 has roofing tiles 11, fascia 12, soffit 13 and guttering 14. A panel 15 of mesh is fixed over the guttering to prevent the entry of unwanted materials. The panel 15 is formed by unrolling a roll of mesh along the length of the guttering 14 and attaching one edge 16 of the mesh to the roof and the other edge 17 to the guttering. The panel 15 is attached to the roof by the weight of the second bottom row of tiles 11 and to the guttering 14 by screwsl9 through the outside edge 17 of the mesh and into the lip 18 of the guttering. The lip 18 forms the top outside edge of the guttering and lies at the top of the guttering's outer face 20. The mesh must be flexible enough to easily bend to the profile of the roofing tiles 11 so that the tiles continue to be located by correct engagement with neighbouring tiles.

The roof shown in Figure 2 is clad with corrugated steel sheets 21. The inside edge of the mesh panel 25 is cut and tailored and attached to the roof with appropriate cleats or clips 23 screwed through the mesh onto every alternate corrugation of the roof metal. The opposite outside edge of the mesh is attached to the outer lip 28 of the guttering by angle trim 26 which is screwed down at intervals through the mesh to the outer lip 28 of the guttering.

hi the case (not shown in the Figures) of a roof with a metal tray or deck cladding, the mesh panel would be cut at each high point of the cladding profile, fixed by cleats screwed to the pan of the profile, and the edges sealed to the roof cladding by means of silicone sealant.

The mesh 15 as shown in more detail in Figures 4 to 7 comprises a particularly preferred embodiment of the present invention. The mesh has the form of a semi-rigid sheet formed from plastics materials and is provided in a roll of constant width which would preferably be within the range of 25 cm to 100 cm wide depending on the particular application. The mesh as installed has a top face 38 and bottom face 40. Parallel strands 42 in a first array 34 run longitudinally of the mesh so when it is installed, the strands 42 run in the direction of the length of the guttering 14. Parallel strands 44 in a second array 35 run laterally of the mesh so, when installed, they run in the direction of the width of the guttering. Figure 6 is cross-section A-A indicated in Figure 4 and this cross- section runs along the centre line of one of the lateral strands 44. Figure 7 is cross-section B-B indicated in Figure 4 and this runs along a line halfway between two lateral strands 44.

The longitudinal strands 42 extend for the full thickness of the mesh, that is for their full length they occupy the full depth between the top face 38 and bottom face 40. The lateral strands 44 extend from the top face 38 down about halfway towards the bottom face. In other embodiments of the invention the depth of the lateral strands 44 may be the same as the thickness of the mesh or down to as little as 20% of the thickness. Preferably the depth of the lateral strands is between 30% and 70% of the depth of the longitudinal strands.

Running along the edge of the mesh is aflat strip portion 46. This is approximately 20mm wide and its thickness is approximately equal to the depth of the lateral strands 44. The strip 46 is free of longitudinal and lateral strands. The strip 46 provides excellent physical reinforcement to the outer edge of the mesh and also provides an excellent location site for the means by which the mesh is affixed to the lip 18 of the guttering. Preferably the flat strip portion 46 is not perforated except by the screws 19 which affix it to the guttering.

The top face 38 of the mesh is flat apart from minor irregularities due to non-uniform shrinkage of the plastics material as it solidifies during manufacture. Such shrinkage is somewhat greater at the longitudinal strands due to their greater depth.

The lateral strands 44 are formed of a high density polyethylene (HDPE) to which is added a colorant for colouring the plastic any desired colour plus a UV stabilizer added in the conventional manner. The longitudinal strands 42 are formed as 2-phase items, each strand having an upper half 41 and a lower half 43 firmly bonded to each other, these halves having different compositions. The upper half 41 has the same formulation as that of the lateral strands, namely HDPE to which is added a colorant for colouring the plastic as desired plus a UV stabilizer added in the conventional manner in order to produce a plastic of the same colour as the lateral strands.

The lower half 43 of the longitudinal strands 42 is formed of a blend of low density polyethylene (LDPE) and HDPE to which is added carbon black. A blend of 15 parts by weight HDPE with 85 parts by weight LDPE plus 2.5 parts by weight carbon black has been found to be suitable. This can be referred to as a 2.5% addition of carbon black in a 15% blend of HDPE in LDPE.

By this means the mesh may be made stiffer in the lateral direction than in the longitudinal direction, despite the strands in the longitudinal direction having a deeper profile. The mesh thus has an improved resistance to sagging into the guttering.

The small proportion of HDPE is blended with the LDPE in the lower half 43 in order to improve its bonding with the upper half 41 which is of a different type of polyethylene.

The strip portion 46 is also formed with the top half 45 of its thickness formed of the coloured HDPE but with the bottom half 47 of its thickness formed of the 15% HDPE with 85% LDPE blend with the 2.5% addition of carbon black. The upper layer 45 and lower layer 47 are firmly bonded together.

As seen in Figures 3 and 5, the underside 30 of the main body of the mesh has the appearance of a series of parallel black stripes 49 running longitudinally along the underside of the mesh. But, as seen in Figures 3 and 4, no black portions of the mesh are visible from the topside 32 of the mesh and thus when the mesh is fastened in position above the guttering.

As seen in Figure 7, the lateral strands 48 together with the upper portion 41 of the longitudinal strands 42 together form a laminar structure having a thickness equal to the depth of the lateral strands. The lower portions 43 of the longitudinal strands protrude downwards below the laminar structure. As readily seen in Figure 5, the lower portions 43 of the longitudinal strands cross the lateral strands 48 beneath the lateral strands, so obscuring the lateral strands at that crossing point

It has been found mat inadequate UV resistance is conferred if the carbon black addition rate is less than 1% by weight, and the desired flexibility of the plastic deteriorates at greater than 5% carbon additions. A carbon black addition rate of between 2% and 3% has been found to be optimal.

Although it is counter-intuitive to place the more UV-resistant material on the underside of the mesh where it sees no direct sunlight when installed, the UV resistance does become important when the top surface has eventually lost much of its strength due to UV degradation, even though the top layer has maintained its colour, so the user gains the benefits of both longer life, with sufficient maintained strength and complete colour coverage on the upper surface.

The lateral and longitudinal strands may be formed by extruding plastic melt through separate nozzles and then pressing the still molten strands together. Alternatively, in a co- extrusion process, the lateral strands and the upper portion of the longitudinal strands may be first formed together as a unitary extrusion which is then brought into contact with the lower portion of the longitudinal strands.

Where the longitudinal strands 42 and the lateral strands 44 intersect, that intersection is heavily gusseted in the plane of the mesh thus rounding off the comers of the holes.

Typical dimensions for the mesh are: centre to centre spacing of longitudinal strands 42: 7.0 to 8.5mm and preferably

7.5mm centre to centre spacing of lateral strands 44: 4.5 to 5.5mm and preferably

5.0mm depth of longitudinal strands 42: 2mm depth of lateral strands and flat strip portion: lmm major axis of apertures 48: 4.0 to 5.5mm minor axis of apertures 48: 2.5 to 3.0mm'

The smooth top face 38 on the mesh is particularly advantageous. It should be appreciated that the whole of the surface that can be seen in Figure 3 is substantially flat The smoothness of the top face provides outstanding "slip-off' of debris. Experiments have indicated that a 60% improvement in "slip-off' of pine needles is achieved by this mesh compared with a corresponding mesh where the strands form a rippled top surface. Any deviation from flatness (for example that caused by differential shrinkage during manufacture) is preferably kept to less than 0.25mm.

The ridged bottom face 40 on the mesh provides a substantial advantage in that the water flow down the underside of the mesh is substantially disturbed from a smooth flow and each longitudinal strand 42 provides a break-off point for the water flow.

HDPE has a greater elastic resilience than LDPE. HDPE thus tends more to spring back to its originally moulded position whereas LDPE tends to more readily retain the shape to which it is bent during tailoring of the mesh to suit the profile of the roof to which it is installed, hi localities with a high fire danger, the mesh material preferably has a self- extinguishing fire retardant characteristic which desirably conforms to a fire rating of 3 under Australian Standard AS1530 Part 2.

Those skilled in the art will appreciate that the invention described herein is susceptible to variations and modifications other than those specifically described. It is to be understood that the invention includes all such variations and modifications which fall within its spirit and scope.

It will be understood that the present invention does not encompass the use of a mesh with a woven structure, namely one with the strands alternately passing from one side of the mesh to the other.

It will be also understood that where the word "comprise", and variations such as "comprises" and "comprising", are used in this specification, unless the context requires otherwise such use is intended to imply the inclusion of a stated feature or features but is not to be taken as excluding the presence of other feature or features.

The reference to any prior art in this specification is not, and should not be taken as, an acknowledgment or any form of suggestion that such prior art forms part of the common general knowledge in Australia.

Claims

1. A screen applied to overlay a guttering on an outside edge of a roof of a building said screen comprising a panel of generally planar mesh moulded from a plurality of plastics materials and affixed along one edge of the panel to the roof and along the opposite edge of the panel to the top outside edge of the guttering, the mesh having a top face and a bottom face on respective opposite sides of the mesh, wherein at least part of the plastics material on said bottom face has a higher content of carbon black than does the plastics material forming the top face of the mesh.

2. A screen applied to overlay a guttering on an outside edge of a roof of a building said screen comprising a panel of generally planar mesh moulded from a plurality of plastics materials and affixed along one edge of the panel to the roof and along the opposite edge of the panel to the top outside edge of the guttering, the mesh having a top face and a bottom face on respective opposite sides of the mesh, wherein at least part of the plastics material on said bottom face has a higher resistance to degradation by ultra-violet light than does the plastics material forming the top face of the mesh.

3. A screen according to claim 1 or 2 wherein said at least part of the plastics material on said bottom face has a higher content of carbon black than does the plastics material forming the top face of the mesh, but there is no significant amount of carbon black in the material forming the top face of the mesh.

4. A screen according to claim 3 wherein said mesh comprises:

- a first array of parallel strands, hereinafter called longitudinal strands, aligned in me direction of said one edge of the panel; and

- a second array of parallel strands, hereinafter called lateral strands, integrally moulded with and aligned at right angles to the first array, said first and second arrays of strands defining mesh apertures therebetween extending from said top face to said bottom face; wherein the strands of one of said arrays are made of said material forming the top face of the mesh, and at said bottom face the strands of the other of said arrays are made of said material having a higher carbon black content.

5. A screen according to claim.4 wherein said strands of the other of said arrays have their upper portion made of said material forming the top face of the mesh and their lower portion made of said material having a higher carbon black content.

6. A screen according to claim 4 or 5 wherein said strands of said one of the arrays are the lateral strands, and said strands of said other of said arrays are the longitudinal strands.

7. A screen according to claim 5 or 6 wherein:

- the lateral strands together with that portion of the longitudinal strands having no carbon black form a generally laminar structure, and — those portions of the longitudinal strands which have a higher carbon black content protrude below said laminar structure and cross the lateral strands beneath the lateral strands.

8. A screen according to any one of claims 3 to 7 wherein said at least part of the plastics material on said bottom face is polyethylene containing carbon black in the range 1 to 5 parts carbon black to 100 parts polyethylene.

9. A screen according to claim 8 wherein said at least part of the plastics material on said bottom face is polyethylene containing carbon black in the range 2 to 3 parts carbon black to 100 parts polyethylene.

10. A screen according to claim 1 wherein said mesh comprises:

- a first array of parallel strands, hereinafter called longitudinal strands, aligned in the direction of said one edge of the panel; and - a second array of parallel strands, hereinafter called lateral strands, integrally moulded with and aligned at right angles to the first array, said first and second arrays of strands defining mesh apertures therebetween extending from said top face to said bottom face; and wherein on the bottom face:

— the strands of one of said arrays are made of said material having a higher resistance to degradation by ultra-violet light, and

- the strands of the other of said arrays are made of the same material as on said top face.

11. A screen according to any one of claims 4 to 10 wherein: - the lateral strands are formed at least substantially of high density polyethylene, and

— the longitudinal strands have an tipper portion having substantially the same composition as the lateral strands and a lower portion formed at least substantially of a blend of high density polyethylene with low density polyethylene and carbon black.

12. A screen according to claim 11 wherein said blend is in the range of 10% to 20% high density polyethylene in low density polyethylene and 2 to 3 parts carbon black to 100 parts polyethylene.

13. A screen according to any one of claims 4 to 12 wherein a flat strip portion lies along said opposite edge of the panel and parallel to the longitudinal strands, said strip portion being free of said lateral strands and comprising an upper layer having substantially the same composition as the lateral strands and a lower layer formed of said blend of high density polyethylene with low density polyethylene and carbon black.

14. A screen according to claim 13 wherein the mesh is affixed to the guttering by means of screws through the flat strip portion.

15. A method of preventing the entry of unwanted materials into a guttering on an outside edge of a roof of a building including affixing a screen over the edge of the roof and the guttering, said screen having a panel of mesh in a generally planar form affixed along one edge of the panel to the roof and along the opposite edge of the panel to the top outside edge of the guttering, the mesh having a top face and a bottom face each formed of moulded plastics material on respective opposite sides of the mesh, wherein the composition of plastics material on the bottom face has a higher content of carbon black than does the plastics material forming the top face of the mesh.