GB2338309A

GB2338309A - Recognition apparatus for toughened glass

Info

Publication number: GB2338309A
Application number: GB9812724A
Authority: GB
Inventors: Neil Colin Hamilton
Original assignee: Individual
Current assignee: Individual
Priority date: 1998-06-13
Filing date: 1998-06-13
Publication date: 1999-12-15
Anticipated expiration: 2018-06-13
Also published as: GB9812724D0; GB2338309B

Abstract

Apparatus for recognising toughened glass comprising an opaque casing having a planar surface for placement on the surface of a sheet of glass to be tested. An opening 6 is formed in the planar surface in which is mounted a filter (7, fig.1) which polarises light passing therethrough. A source of white light 12 is housed within the casing and is positioned to direct emitted light through the filter (7) and onto the surface of the glass sheet on which the planar surface of the casing is placed. A transparent window 9 is formed in the casing surface opposite to the filter-containing planar surface with the window at least partially aligned with the filter (7). The arrangement is such that light from the source polarised by the filter is directed onto a sheet of glass to be tested and is reflected by the sheet surfaces back onto the filter to display images whose colours are dependent on the angles of incidence of the received reflected light rays, these images being viewable through the transparent window 9.

Description

2338309 1 RECOGNITION APPARATUS FOR TOUGHENED GLASS This invention relates

to apparatus for recognising sheets of toughened glass.

Toughened glass is a safety glass which is produced by subjecting a sheet of heated annealed glass to rapid cooling to cause high compression in the surfaces of the glass sheet and compensating tension in the sheet interior. Toughened glass has relatively high strength, exhibits greater flexibility than conventional annealed glass, and is less likely to break on impact. The properties of toughened glass depend interafla on the balance of imposed stresses being maintained.

Unlike annealed glass, if broken toughened glass shatters into a multiplicity of relatively small fragments which do not have sharp edges and which therefore are unlikely to cause injury. It is commonly employed in locations where serious injury may occur if a person -is, likely to make physical contact with a sheet of glass. It is therefore important that a sheet of toughened glass can be recognised as such.

Toughened glass can be produced by heat treating and rapid cooling of several species of annealed glass, these including clear float, sheet, polished plate and solar controlled glass.

At the present time toughened glass may be recognised by brand 2 markings or by patterns of slight iridescent discolourations when viewed in certain lighting conditions. Brand marking is by no means universal and even conventional annealed glass can display iridescent discolourations when viewed in certain lighting conditions, particularly in locations where it is subject to compressive stress, e.g. around its supported edges. Apparatus for detecting iridescent discolourations has been proposed previously, but has generally proved to be expensive to produce and cumbersome to employ.

The present invention sets out to provide hand-held apparatus which operates to provide an effective and repeatable recognition of toughened glass in sheet form.

According to the present invention in one aspect, there is provided apparatus for recognising toughened glass which comprises an opaque casing having a planar surface for placement on the surface of a sheet of glass to be tested, an opening formed in this planar surface in which is mounted a filter which polarises light passing therethrough, a source of white light housed within the casing and positioned to direct emitted light through the filter and onto the surface of the glass sheet on which the planar surface of the casing is placed, and a transparent window formed in the casing surface opposite to the filter-containing planar surface with the window at least partially aligned with the filter, whereby light from the source polarised by the filter is directed onto a sheet of glass to be tested and is reflected by the sheet surfaces back onto the filter to display images whose colours are dependent on the angles of incidence of the received reflected light rays, these images being viewable through the transparent window.

The light source may be positioned behind an internal partition of the casing, the filter spanning the partition whereby a part thereof is directly above the light source. The partition may extend to the full internal height 3 of the casing thereby effectively dividing the casing interior into separate compartments. The transparent window preferably does not span the partition, it being positioned to the side of the partition remote from the fight source. The transparent window may comprise a flat piece of plastics or glass.

The light source may comprise an elongate bulb connected in series with a dc battery housed within the casing. The battery may be rechargeable and may comprise an 8.4 volt rechargeable battery. The light source may be operated by a depressible switch connected in series with the battery.

The opening which receives the filter is preferably recessed into the planar surface of the casing with the filter positioned out of the plane of the casing surface.

In another aspect, the invention provides apparatus for recognising a sheet of toughened glass, the apparatus comprising an opaque casing which houses a source of white light connected in series with a dc battery, the casing having opposed planar surfaces in one of which is mounted a polarising filter and in the other of which is mounted a transparent window, the filter and window lying in spaced generally parallel planes which at least partially overlap and switch means to operate the source and to cause filtered polarised light waves to pass onto and through a sheet of glass in contact with the filter-carrying planar surface of the casing and to be reflected from the glass sheet surface onto the filter to produce coloured images which can be viewed through the window of the other planar surface, the colour of the images determining whether or not the glass sheet is toughened.

The invention will now be described by way of example only with reference to the accompanying diagrammatic drawings in which:- 4 Figure 1 is a plan view from above of apparatus in accordance with the invention; Figure 2 is an end view of the apparatus illustrated in Figure 1 taken in the direction of arrow A of Figure 1; Figure 3 is a side view of the apparatus illustrated in Figure 1 taken in the direction of arrow B of Figure 1; and Figures 4 and 5 are isometric views of the apparatus illustrated in Figures 1 to 3.

The illustrated apparatus comprises a casing 1 which includes a base 2, side and end walls 3, 4 respectively and a lid 5. The lid may be secured to the base by any conventional means, for example a set of screws which screw into threaded pillars positioned at the casing corners. Only the margins of the casing features are illustrated for ease of understanding and to enable items housed within the casing to be readily identified. The casing is typically produced from an opaque plastics material with the outer surfaces of the base and lid generally planar. The internal surfaces of the base and/or side and/or end walls and/or lid may be ridged or corrugated for enhanced strength.

The base 2 is formed with an opening 6 in which is mounted a polarising filter 7. The opening 6 defines a recess within the base 2 with the filter 7 protected by the walls of the recess. Thus, the filter 7 lies in a plane which is generally parallel to the planar surface of the base but remote from that planar surface. The shape of the opening and therefore the filter, is generally rectangular with the filter extending lengthwise of the casing and over approximately one-half of the length of the base 2. The filter may typically be a quarter wave length polarising filter. However, any filter which has the effect of causing light waves to vibrate in a single direction or plane may be employed.

The casing lid 5 is formed with a generally rectangular opening in which is mounted a piece of transparent material, e.g. glass or plastics. The transparent material therefore defines a window 9 through which the filter 7 can be viewed. This window 9 lies flush with the planar surface of the lid 5. The positioning of the filter 7 and the window 9 is such that they partially but not wholly overlap one with the other. As will be seen from Figure 1, the length of the window is less than that of the filter.

The interior of the casing 1 includes a partition 11 which extends over the full height of the casing. A source 12 of white light is positioned behind the partition 11. The partition is removed in Figure 5 to illustrate more fully the positions of the light source, filter and window. In the embodiment illustrated in the drawings, the source 12 comprises an elongate bulb whose filament is connected in series to the terminals of a battery 14 by wiring. Typically the battery is a nickel metal hydride rechargeable 8.4 volt battery. Other batteries could, however, be employed. In the embodiment illustrated, the battery 14 is rechargeable via a socket 15.

The partition 11 is positioned effectively to confine the light emitted by the source 12 to the casing area behind the partition. The light source 12 is operated via a depressible switch or button 16 connected in series with the terminals of the battery 14.

As will be seen from the drawings the filter 7 extends over and to both sides of the partition 11. Thus, one end 7a of the filter is in direct communication with the elongate bulb 12. The window 9, however, lies only to the side of the partition remote from the bulb. Thus, all light emitted by the source 12 leaves the casing through the end portion 7a of the filter.

In use, the planar surface of the base 2 of the casing 1 is placed on 6 the surface of a sheet of glass to be tested and the switch 15 operated to cause white light to pass from the source 12, through the filter 7 and onto and through the glass sheet under test. The filter 7 polarises the emitted white light so that the direction of vibration for all emitted light waves is the same. This light is reflected back from the sheet surfaces to create images on the surface of the polarising filter 7. These images can be viewed through the window 9, the offsetting of the window with respect to the filter enabling the images to be seen from the lid side of the casing. For untoughened glass the light from the glass sheet surfaces will be of the same colour, e.g. blue, the angles of incidence of the reflected light waves being the same. For toughened glass, however, the light is caused to be reflected back to the filter at different angles of incidence by the stress patterns induced in the glass during heating and rapid cooling. The colour of the reflected images will therefore be different from those for nontoughened annealed glass sheet and will change as the planar surface of the casing is moved over the surface of the glass sheet. These images may, for example be red, orange or other colours of the spectrum.

The elongate shape of the bulb 12 creates images as discrete lines, one line being apparent for each sheet surface. Thus, two lines are apparent for a window comprising a single sheet, four lines for a double glazed window and multiple lines for laminated sheets of glass. Other bulb shapes can, however, be employed if other image shapes are required.

It will be apparent from the foregoing that the hand-held apparatus described enables the presence of toughened glass to be readily recognised.

It will be appreciated that the foregoing is merely exemplary of apparatus in accordance with the invention and that modifications can readily be made thereto without departing from the true scope of the invention.

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Claims

Apparatus for recognising toughened glass which comprises an opaque casing having a planar surface for placement on the surface of a sheet of glass to be tested, an opening formed in this planar surface in which is mounted a filter which polarises light passing therethrough, a source of white light housed within the casing and positioned to direct emitted light thro,ugh the filter and onto the surface of the glass sheet on which the planar surface of the casing is placed, and a transparent window formed in the casing surface opposite to the filter-containing planar surface with the window at least partially aligned with the filter, whereby light from the source polarised by the filter is directed onto a sheet of glass to be tested and is reflected by the sheet surfaces back onto the filter to display images whose colours are dependent on the angles of incidence of the received reflected light rays, these images being viewable through the transparent window.
2. Apparatus as claimed in claim 1 wherein the light source is positioned behind an internal partition of the casing, the filter spanning the partition whereby a part thereof is directly above the light source.
3. Apparatus as claimed in claim 2 wherein the partition extends to the full internal height of the casing thereby effectively dividing the casing interior into separate compartments.
4. Apparatus as claimed in claim 3 wherein the transparent window is positioned to the side of the partition remote from the light source.
5. Apparatus as claimed in any one of claims 1 to 4 wherein the transparent window comprises a flat piece of plastics or glass.

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6. Apparatus as claimed in any one of claims 1 to 5 wherein the light source comprises an elongate bulb connected in series with a dc battery housed within the casing.
Apparatus as claimed in claim 6 wherein the light source is operated by a depressible switch connected in series with the battery.
8. Apparatus as claimed in any one of the preceding claims wherein the opening which receives the filter is recessed into the planar surface of the casing with the filter positioned out of the plane of the casing surf ace.
9. Apparatus for recognising a sheet of toughened glass, the apparatus comprising an opaque casing which houses a source of white light connected in series with a dc battery, the casing having opposed planar surfaces in one of which is mounted a polarising filter and in the other of which is mounted a transparent window, the filter and window lying in spaced generally parallel planes which at least partially overlap and switch means to operate the source and to cause filtered polarised light waves to pass onto and through a sheet of glass in contact with the filter-carrying planar surface of the casing and to be reflected from the glass sheet surface onto the filter to produce coloured images which can be viewed through the window of the other planar surface, the colour of the images determining whether or not the glass sheet is toughened.
10. Apparatus for recognising a sheet of toughened glass substantially as herein described and as described with reference to Figures 1 to 5 of the accompanying diagrammatic drawings.