GB2358661A

GB2358661A - Protective mesh for a polymeric glazing panel

Info

Publication number: GB2358661A
Application number: GB0029091A
Authority: GB
Inventors: George Murray; Kevin Mclernon
Original assignee: Individual
Current assignee: Individual
Priority date: 1999-11-29
Filing date: 2000-11-29
Publication date: 2001-08-01
Anticipated expiration: 2020-11-29
Also published as: GB9928061D0; GB2358661B; GB0029091D0

Abstract

A polymeric glazing panel 2 has affixed to at least one surface a metal mesh or grid 3 which stands proud of that surface. The mesh may be partially embedded in the panel or may be adhered thereto. A thin additional layer of material such as polyethylene may be applied between the mesh and the panel to improve bonding, the layer preferably being between 25 and 100 microns thick. Preferably, the mesh comprises steel strands of diameter 0.4-0.45mm and spaced 1-1.75mm apart. Fixing of the mesh may be performed by heating it beyond the melting point of the polymeric panel and then pressing it into the panel. The mesh prevents breakage and vandalism of the panel, which may be either transparent or opaque.

Description

2358661 Glazing Panels and a Method of Manufacturing Glazing Panels This

invention relates to glazing panels that have been adapted to resist deliberate damage and a method of manufacturing such glazing panels, in particular, to damage resistant glazing for use in buses, trains, shelters and phone boxes.

Recently throughout the UK and Europe, there has been a move towards unmanned railway stations and a reduction in the number of major stops on bus routes. This has led to an increase in the number shelters both in rural and city centre locations. Modem shelters have been designed to give maximum visibility all around so that the user has better sense of security. Consequently, modem shelters have a predominant amount glazing.

Unfortunately, the glazing in these shelters has become the object of attack for some of the more destructive minded members of society, as well as the young. The attacks can lead to damage to the shelter that can vary between simple defacing to breakage. Whilst defacing of the shelter may be upsetting it is unlikely to present the type of hazard that breakage etc. can do. To reduce this danger and the damage, and in particular from the broken glazing, glass has been replaced with polymeric windows, for example, polyethylene terephtalate (PET) or polycarbonate (PC) sheets. This type of glazing is a little more difficult to break than standard glass but it can be damaged in other ways, for example scored or burnt. An indication of how expensive and difficult a problem this can be is indicated by the fact that the average life of a sheet of glazing is 14 days and in some locations can be measured in hours not days.

The aim of the present invention is to provide glazing in which the above problem is further overcome and alleviated.

In accordance with a first aspect of the present invention there is provided a glazing panel which comprises a sheet of polymeric material which has fixed to one or both surfaces thereof a grid or mesh of metal strands that stand proud of the surface of the sheet to which they are fixed.

This grid or mesh provides a barrier more resilient to damage than the polymeric material. Consequently, any attempt to damage the panel is resisted by the barrier acting as a 2 shield to take the force of the intended damage. Damage will be caused to the metal strands of the grid or mesh but in comparison to the damage that would be caused to the polymeric material alone this is minimal and in general will not significantly detract from the appearance or integrity of the panel. 5 In one arrangement of the present invention, the grid or the mesh may be partially embedded into the surface of the sheet of polymeric material. In an alternative arrangement, the grid or the mesh may be adhered to the surface of the sheet of polymeric material.

It has been found that in certain applications and combinations of material the adhesion of the grid or mesh to the sheet of polymeric material is not as strong as may be required. Therefore the glazing panel may include a layer of a second material, preferably a polymeric material, between the grid or mesh and the sheet of polymeric material to enhance the adhesion of the grid or mesh to the sheet of polymeric material. The selection of the material of this depends on the combination of materials used in the glazing panel and is made so that the layer bonds strongly to the grid or mesh and the material of the polymeric sheet.

The layer may be formed from any suitable polymeric material, for example where a steel grid or mesh is used the material may be polyethylene, The layer provided there to enhance the bonding of the grid or mesh to the sheet of polymeric material and preferably has a thickness in the range of 25 to 100 microns.

The grid or mesh may comprise steel strands and have a spacing between the strands in the range I mm to 1.75mm and have a diameter in the range 0.36mm to 0. 5mm, and preferably has a diameter in the range 0.4mm to 0.45mm.

The grid or mesh may be provided on one or both sides of the panel dependent on the use of the glazing.

The choice of materials for the panel will be dependent on the application to which the panel is to be put. In locations, where the panel should be transparent to allow people to see through the polymeric material of the sheet may be transparent or slightly tinted.

However, in locations where transparency is not at issue the polymeric material of the panel may be opaque.

3 In one embodiment of the present invention, the sheet is formed from polyethylene terephtalate (PET) or polycarbonate (PC). These two types of material are already used in glazing with bus and train shelters.

The metal grid or mesh being formed from metal is harder and more resistant to damage than the polymeric material forming the sheet. The thickness of the strands and the size of the mesh can have an influence on the effectiveness of the panel to resist damage. In particular, if the spaces in the grid or mesh are too large the barrier effect of the grid or mesh may not be sufficient to prevent damage to the surface of the polymeric material. Further, if the strands of the grid or mesh are too small they may not have sufficient strength to absorb or deflect any damaging blows. Additionally the smaller the mesh size, and therefore the spaces between the strands in the mesh, as well as the thicker the strands of the mesh the lower is the visibility through the panel or its transparency. Consequently, in locations where visibility through the panel is a consideration a balance will be made between the above factors.

In one arrangement of the present invention, the metal grid or mesh is a square meshed steel wire cloth. This type of interwoven steel stranded material is currently available for use in other applications and therefore provides a readily available source for one of the components of the panel.

Glazing made in accordance with the present invention will not totally prevent damage to the panel, it acts to reduce the effects of attempted damage and consequently lengthens the effective life span of the panel.

In accordance with a second aspect of the present invention there is provided a method of manufacturing glazing panels made in accordance with the first aspect of the present invention, which method comprises the steps of providing a sheet of polymeric material; providing a grid or mesh; cleaning the grid or mesh; heating the grid or mesh to a temperature in excess of the softening or melting temperature of the polymeric material but below the temperature at which the polymeric material would burn; 4 locating the grid or mesh over the sheet of polymeric material; and applying pressure to the grid or mesh to fix it to the polymeric material.

The grid or mesh is heated to a temperature slightly in excess of the melting temperature of the polymeric material so that the polymeric material surrounding the strands of the grid or mesh is heated and softened. As the pressure is applied to the grid or mesh, the softened polymeric material is displaced and the grid or mesh is located in the surface of the sheet of polymeric material. Cooling of the polymeric material and the grid or mesh allows the polymeric material to reset and as this occurs the polymeric material grips and bonds to the grid or mesh.

The level of the pressure applied to the grid or the mesh will determine the extent that the grid or the mesh is located below the general surface of the polymeric material. In a preferred arrangement of the present invention, the grid or mesh is located into the surface of the polymeric material.

The bonding of the polymeric material to the grid or mesh in this manner has other advantages that help advance the safety features of the panels. Specifically, if the polymeric sheeting of the panel is broken, the grid or mesh is likely to maintain its integrity and the bonding of the polymeric material to the grid or mesh helps to retain the arts of the broken polymeric material as part of the panel. Further, if grid or mesh is provided on both sides of the panel this will act to sandwich the polymeric material in place and retain it. Therefore, it is unlikely that broken shards of material will be present and the grid or mesh thus helps to prevent puncture injuries from someone falling on the broken panel.

The strength of the bond between the grid or mesh and the polymeric material is important to the effective working of the panel and it is therefore important that the grid or mesh is cleaned to remove grease and debris that may affect the quality of the bond. The grid or mesh can be cleaned in any suitable manner, and in one arrangement of the invention, it is envisaged that the grid or mesh will be chemically cleaned. A typical example of a suitable solvent for this cleaning is acetone.

Roughening the surface of the gird or mesh may further enhance the strength of the bond. The method of manufacturing the glazing panel may also include roughening of the surface of the material of the grid or mesh prior to cleaning of the grid or mesh for application to the sheet of polymeric material.

In one arrangement of the present invention a layer of a second material is provided between the grid and mesh and the sheet of polymeric material so as to enhance bonding of the grid or mesh to the sheet of polymeric material. The method of manufacturing a glazing panel may also include providing a layer of a second material on the sheet of polymeric material prior to locating the grid or mesh.

Heating of the grid or mesh may be carried out using any suitable method, for example by a resistance heating method where the strands of the grid or mesh are heated directly.

The invention will now be illustrated by description of certain examples with reference to the accompanying drawings, in which:

Fig 1 shows a plan view of a glazing panel made in accordance with the present invention:

Fig 2 shows a cross-sectional side view of first type of panel in accordance with Fig 1 of the drawings; and Fig 3 shows a cross-sectional side view of a second type of panel in accordance with Fig 1 of the drawings.

Referring to the drawings there are shown a couple of designs for the damage resistant glazing panels 1 made in accordance with the present invention. The panel 1 comprises a sheet 2 of polymeric material having a grid or mesh 3 fixed to at least one of the surfaces thereof In the example shown in Fig 2 of the drawings, a grid or mesh 3 is provided on both surfaces of the sheet 2 of polymeric material. In the particular example, shown in the drawing the grids or meshes 3 on both surfaces have been aligned to enhance the visual transparency of the panel 1. In the design of the panel shown in Fig 3 of the drawings, a grid or mesh 3 is provided on one surface of the sheet 2 only.

6 The way in which the panel resists damage is the same in both designs. The selection of which type of panel is used is made on the actual use to which it is to be put, and whether one or both sides of it have to be protected. As can be seen in Figs 2 and 3 of the drawings the grid(s) or mesh(es) 3 is set into the surface of the sheet 2 of polymeric material so that a proportion of the strands of the grid or mesh 3 stand proud of the surface of the sheet 2. The, or each, grid or mesh 3 thereby forms a barrier over the surface of the sheet 2 so that any damage is preferably inflicted to the material of the grid or mesh 3 and not the surface of the sheet 2.

In alternative embodiments of both of the above described glazing panels I a layer of clear polyethylene is provided between the grid or mesh 3 and the sheet 2. The layer is provided to enhance the adhesion of the grid or mesh 3 to the sheet 2.

In this way, the glazing panels I are damage-resistant. It is acknowledged that the panels I are more suited to resisting damage from slashing blows or motion than direct forward attack motion. The ability of the panel to resist this later type of damaging blow or motion is dependent on the spacing between the strands of the grid or mesh 3 protecting the particular surface of the sheet.

The choice of the grid or mesh 3 to be used in a particular panel I is affected by the usage of the panel as well as the damage limitation required. One design usage of the panels 1 is in bus and train shelters where damage-resistant glazing panels I that have a grid or mesh 3 on both sides are provided. With this usage, there is a need for the people using the shelter to be able to have a clear view through the glazing panels I so that they feel safe, and can see approaching buses or trains. The provision of the grid or mesh 3 does detract from the visual transparency of the panel 1, but if grid or mesh 3 is chosen correctly this will not be overly so. Consequently, the grid or mesh 3 used with bus and train shelters is likely to have spaces between the strands of the grid or mesh 3 larger than would be the case if damage resistance was the only consideration. This may make the panel I more susceptible to damage by direct thrusts and therefore detracts from the damage resistance aspect.

Further, the effectiveness of the panel to resist damage is also affected by the diameter of the strands of the grid or mesh 3. If the strands are not sufficiently large or strong enough to resist bending moments or provide a sufficient barrier to slashing type motion this also would detract from the effectiveness of the panel I to do its job.

7 Typically, the panel is formed from a sheet of PET or PC material and the grid or mesh 3 is a steel wire cloth having strands and spacing between the strands as given in the following table: 5 Example Wire Diameter Wire Spacing Use mm mm 1 0.4 1.336 Bus or Train Shelter 2 0.45 1.466 Bus or Train Shelter In one method of manufacturing the glazing panel I the following steps are followed:

a sheet 2 of PET having a thickness of 4mm is provided and laid out; a grid or mesh 3 as in example 2 above is provided; A the grid or mesh 3 is cleaned by submerging in a bath of acetone and vibrating in the conventional manner to remove any grim and/or grease from the grid or mesh 3; heating the grid or mesh 3 by a resistance method direct including direct passage of electrical current through the strands of the grid or mesh 3 to a temperature slightly above the melting point of the PET sheet; contacting the surface of the sheet 2 with the grid or mesh 2 and applying a pressure to push the grid or mesh into the surface of the sheet to a controlled depth.

The grid or mesh is heated to a temperature only slightly above the melting point of the polymeric material so that there is sufficient heat to soften and melt the polymeric material in the immediate vicinity of the strands of the grid or mesh but not enough to burn. Any burning of the PET would detract form the finish and appearance of the panel 1.

Contact of the grid or mesh 3 to PET heats and softens the PET so that as pressure is applied the material is forced away from the grid or mesh and the grid or mesh 3 embeds in the surface of the sheet. With cooling of the grid or mesh and the PET the material hardens and grips the strands of the PET securing the grid or mesh in place.

The above method of manufacture is adapted by inclusion of the step of providing a layer of clear polyethylene, typically 50 microns in thickness, over the sheet 2 of polymeric material prior to locating the grid or mesh over the sheet 2. In this the application of pressure on the grid causes the layer to melt prior to the material of the sheet 2 and provided an adhesive layer between the grid or 3 and the sheet 2.

The above examples are provided to illustrate how this invention works they are not intended to limit the invention and should be considered on that basis.

9

Claims

Claims

I A glazing panel which comprises a sheet of polymeric material having fixed to one or both surfaces thereof a grid or mesh of metal strands that stand proud of the surface of the sheet.
2 A glazing panel as claimed in claim I wherein the grid or the mesh is partially embedded into the surface of the sheet of polymeric material.
3 A glazing panel as claimed in claim I wherein the grid or the mesh is adhered to the 10 surface of the sheet of polymeric material.
4 A glazing panel as claimed in any one of the preceding claims wherein the glazing panel includes a layer of a second material between the grid or mesh and the sheet of polymeric material to enhance the adhesion of the grid or mesh to the sheet of polymeric 15 material.
A glazing panel as claimed in claim 4 wherein the layer of a second material is a layer of polyethylene.
6 A glazing panel as claimed in claim 4 or 5 wherein the layer has a thickness in the range of 25 to 100 microns.
7 A glazing panel as claimed in any preceding claim, wherein the grid or mesh comprises steel strands having a spacing between the strands in the range I min to 1.75mm and a diameter in the range 0.36mm to 0.5mm.
8 A glazing panel as claimed in claim 8, wherein the strands have a diameter in the range 0.4mm to 0.45mm.
9 A glazing panel as claimed in any preceding claim wherein the grid or mesh is provided on one side of the panel only.
A glazing panel as claimed in any preceding claim wherein the grid or mesh is provided on both sides of the panel. 35
11. A glazing panel as claimed in any preceding claim wherein the sheet is formed from polyethylene terephtalate (PET) or polycarbonate (PC).
12 A method of manufacturing glazing which comprises the steps of. 5 providing a sheet of polymeric material; providing a grid or mesh; cleaning the grid or mesh; heating the grid or mesh to a temperature in excess of the softening or melting temperature of the polymeric material but below the temperature at which the polymeric material would bum; locating the grid or mesh over the sheet of polymeric material; and applying pressure to the grid or mesh to fix it to the polymeric material.
13 A method of manufacturing glazing panels as claimed in claim 12 wherein the grid or mesh is cleaned in acetone.
14 A method of manufacturing glazing panels as claimed in claim 12 or 13, wherein teh method also includes roughening of the surface of the material of the grid or mesh prior to cleaning of the grid or mesh.
A method of manufacturing glazing panels as calimed in any one of claims 12 to 14, wherein the method also includes providing a layer of a second material on the sheet of polymeric material prior to locating the grid or mesh.
16 A method of manufacturing glazing panels as claimed in any one of claims 12 to 15 wherein the heating of the grid or mesh is carried out by a resistance heating method where the strands of the grid or mesh are heated directly.
17 A glazing panel as hereinbefore described with reference to Fig I or Fig 2 or Fig 3 of the drawings.
18 A method of manufacturing a glazing panel substantially as hereinbefore described with reference to the accompanying drawings.