GB2159949A - Illuminable instrument panel - Google Patents

Abstract

An illuminable panel 10 for use in a motor vehicle instrument panel, comprises a lamina moulded from a transparent synthetic plastics material, said lamina having first and second surfaces 14, 16 parallel to one another and an edge surface 18 connecting said first and second surfaces 14, 16, the first surface 14 carrying thereon a pattern 22 having translucent areas 24, 26 and 28 therein formed as indicia, and said second surface 16 being coated with at least one shaped area 32 of a metallic foil such as aluminium, positioned substantially opposite said translucent areas 24, 26, 28 on said first surface 14. The illuminable panel 10 is adapted to be mounted adjacent a light source so that the edge surface 18 and the uncoated areas 34 of the second surface thereof are illuminable by said light source, and the shaped area of metallic foil is so shaped as to ensure substantially bright, even illumination of said translucent areas 24, 26, 28 of the pattern 22 by said light source. <IMAGE>

Description

SPECIFICATION Illuminable panel This invention relates to an illuminable panel for use in a motor vehicle instrument panel, and, in particular, to an improved illuminable panel of the type which comprises a light-transmitting lamina moulded from a transparent synthetic plastics material carrying on a first surface thereof a patterned layer having transluent areas therein formed as indicia.

Many improvements have been made recently in the illumination of instrument panels for motor vehicles, based upon the extensive use of optical quality transparent synthetic plastics material such as acrylic plastics, polycarbonate and polystyrene as light guides to direct light from a light source adjacent an instrument panel so as to illuminate dial markings and other indicia on a visible surface of the instrument panel.

A problem encountered in the illumination of instrument panels by such light guides is that of ensuring an adequate, even illumination of the indicia on the instrument panel, particularly when using a light source positioned in a non-central position relative to the indicia to be illuminated. Thus, for example, the illumination of an instrument panel displaying a number of dials and other indicia with a number of point sources of light positioned beneath the visible surface of the instrument panel tends to produce uneven illumination of the dial indicia and other indicia on the panel.One procedure that has been practiced commercially to overcome this problem involves the overprinting of those areas of the instrucment panel which are more highly illuminated than the remainder of the panel with numerous layers of semi-opaque material in order to cut down the light transmission through those highly illuminated areas, and thus reduce the visible illumination of those areas sufficiently to match the light transmitted through the lowly illuminated areas of the instrument panel.

Unfortunately such a procedure tends to be both costly and time-consuming, and results in an instrument panel having a relatively low degree of overall illumination.

An illuminable panel according to the present invention, for use in a motor vehicle instrument panel, comprises a lamina moulded from a transparent synthetic plastics material, said lamina having first and second surfaces parallel to one another and an edge surface connecting said first and second surfaces, said first surface carrying thereon a patterned layer having translucent areas therein formed as indicia, said second surface being coated with at least one shaped area of a metallic foil positioned substantially opposite said translucent areas, said illuminable panel being adapted to be mounted adjacent a light source so that the edge surface and the uncoated areas of the second surface thereof are illuminable by said light source, said shaped area of metallic foil being so shaped as to ensure substantially bright, even illumination of said translucent areas of said patterned layer by said light source.

Preferably the illuminable panel is moulded from transparent acrylic plastics material.

In a preferred embodiment of the present invention, the patterned layer comprises a printed pattern of said translucent areas on an opaque background which is deposited on one surface of a translucent sheet of polycarbonate material, said translucent sheet of polycarbonate material being secured to said first surface of the lamina so as to sandwich said printed pattern between said translucent sheet and said lamina.

The metallic foil can be any suitable metallic foil displaying a very high reflectance of light incident on the foil. Suitable foils can be made of bright metallic silver, chrome, aluminium, gold or copper, and a particularly suitable foil is aluminium foil, since it is readily available commercially at reasonable cost. Such commercially available aluminium foils have a bright metallic silver appearance and reflect almost ail of the light incident upon them. It will be understood that the invention disclosed herein is not confined solely to the use of metallic foils having a silvery appearance, since it may be desirable to utilise coloured metallic foils, particularly where it is felt desirable to adjust the colour balance of the source of illumination for an instrument panel including an illuminable panel according to the present invention.

Any suitable method can be used for coating areas of the second surface of the lamina with a suitable metallic foil, but a highly suitable technique is that of a hot foil pressing technique, wherein a desired pattern of adhesively coated metallic foil is simultaneously cut-out and fused to said second surface by means of a rubber stamping member. Such a hot foil pressing technique readily lends itself to mass production assembly line operation, any changes required in the pattern of the metallic foil being obtained by changing the pattern of the rubber stamping member.

It is desirable in a illuminable panel according to the present invention to arrange to maximise the light input into the lamina of the panel when said lamina is illuminated by a light source. This can be done, in one embodiment of the invention, by providing at least one chamfered portion to the edge surface of the lamina, and, in another embodiment of the present invention, by providing integral light guide formations on uncoated portions of said second surface and said edge surface of the lamina.

The invention and how it may be performed are hereinafter particularly described with reference to the accompanying drawings, in which: Figure 1 shows a front view of an illuminable panel according to the present invention for use as a dial for a tachometer for a motor vehicle; Figure 2 shows a side view of the panel shown in Figure 1, taken along the line 2-2'; Figure 3 shows a rear view of the panel of Figure 1; Figure 4 shows a front view of an illuminable panel according to a second embodiment of the present invention, for use as a combined instrument panel for water temperature gauge, petrol gauge and oil and battery warning lights for a motor vehicle; Figure 5 shows a side view of the panel shown in Figure 4 taken along the lines 5-5'on Figure 4; and Figure 6 shows a rear view of the panel shown in Figure 4.

Turning now to Figures 1 to 3 of the accompanying drawings, these show a tachometer dial 10 according to the present invention, which tachometer dial comprises a lamina 12 moulded from acrylic plastics material, said lamina having first and second surfaces 14, 16 parallel to one another and an edge surface 18 connecting said first and second surfaces 14, 16. Secured to said first surface 14 of the lamina 12, as by adhesive, is a translucent sheet 20 of polycarbonate material carrying thereon a printed pattern 22 for the tachometer dial 10, which printed pattern 22 comprises translucent numerals 24 and a translucent area in the form of an arcuate band 26 of hatched design interrupted at regular intervals by radial translucent bars 28 representing numerical values associated with the translucent numerals 24 on the dial 10.A terminal portion 30 of the arcuate band 26 is coloured red. The remainder of the printed pattern 22, filling the remaining portion of the visible dial 10, comprises a squared pattern of intersecting thin translucent lines on a substantially black opaque background.

The printed pattern 22 is deposited on one side of the translucent sheet 20, which side of the sheet 20 is then provided with a coating of clear, pressure-sensitive adhesive. The translucent sheet 20 of polycarbonate material is then secured to said first surface 14 of the lamina 12 so as to sandwich said printed pattern 22 between the translucent sheet 20 and the lamina 12. The translucent sheet 20 is thin enough to ensure that the printed pattern 22 can be seen clearly through the translucent sheet, but is thick enough to provide an adequate protection against damage to the pattern during use of the instrument. A suitable thickness of polycarbonate material is 0.25 millimetre.

The lamina 12 of acrylic pastics material is a flat sheet of material having a thickness suitable for the adequate transmission of light through the peripheral edge surface 18 thereof. A suitable thickness for the lamina 12 is of the order of 2 millimetre. the peripheral edge surface 18 is shaped in the form of a double bevel surface, each bevel surface being at 45 degreees to the adjacent respective first and second surfaces 14, 16 of the lamina 12, so as to maximise light input to the lamina through the peripheral edge surface 18.

As can be seen in Figure 3 of the accompanying drawings, the second surface 16 of the lamina 12 carries thereon a shaped area 32 of a metallic foil secured to the second surface 16. This shaped area 32 is positioned on the second surface 16 substantially opposite the translucent numerals 24, the arcuate band 26 and the radial translucent bars 28 of the printed pattern 22 on the first surface 14. A circular area 34 of the second surface 16 remains uncoated with metallic foil. Consequently, when the tachometer dial 10 is mounted in an instrument panel of a motor vehicle and illuminated by a source of illumination beneath the instrument panel, light enters the lamina 12 through the peripheral edge surface 18 and the circular uncovered area 34 of the second surface 16.Once within the lamina 12, the light undergoes repeated reflection, backwards and forwards between the first surface 14 and the second surface 16, and, in the area of the second surface 16 coated with the shaped area 32 of metallic foil, the high reflectance of light exhibited by the metallic foil causes a high percentage of the light incident thereon to be reflected back and to exit the first surface 14 of the lamina through the translucent areas of the printed pattern 22 composed of translucent numerals 24, the arcuate band 26 and the radial translucent bars 28.

The shaped area 32 of metallic foil is shaped so as to ensure substantially bright, even illumination of these translucent areas of printed pattern 22 when the visible surface of the tachometer dial 10 is viewed.

The metallic foil forming the shaped area 32 on the second surface 16 is made from aluminium, and is fused in place upon the second surface 16 by a hot foil pressing technique which involves securing an adhesively coated aluminium foil to the second surface 16 by means of a heated rubber stamping member. During this hot foil pressing technique, the desired pattern of the shaped area 32 of metallic foil is fused to the second surface 16 of the lamina 12, and the unsecured portions of the metallic foil bordering the shaped area 32 of metallic foil is fused to the second surface 16 of the lamina 12, and the unsecured portions of the metallic foil bordering the shaped area 32 can be readily stripped away.

The tachometer dial 10 shown in Figures 1 to 3 includes a central aperture 36, through which the needle shaft of a tachometer movement passes, when the tachometer dial 10 is mounted in position on an instrument panel and the two apertures 38, 40 either side of central aperture 36 are for the fixing screws to retain the tachometer dial 10 in position upon the tachometer movement. A fourth aperture 42 in the dial 10 is provided for an end stop for the needle of the tachometer movement.

Two notches 44, 46 formed opposite one another in the peripheral edge surface 18 of the dial 10 are provided for the purpose of accurately locating the translucent sheet 20 of polycarbonate material in place upon the lamina 12 of acrylic plastics material. Lasly, there is a tab portion 48 shown in Figures 1 and 3, which extends from the peripheral edge surface 18 of lamina 12. This tab portion 48 is part of the sprue which remains after moulding the lamina 12, and is retained upon the lamina 12 as a means of handling the lamina 12 without the risk of contaminating the optical quality of the first surface 14 and the second surface 16 of the lamina 12 during the assembly procedure of covering the first surface 14 with the translucent sheet 20 of the polycarbonate material and fusing the shaped area 32 of metallic foil to the second surface 16 of the lamina 12. It will be clearly understood that this tab portion 48 is a non-essential feature of the tachometer dial 10, and can be readily removed before insertion of the tachometer dial 10 in the instrument panel in which it is to be mounted.

A second embodiment of the illuminable panel of the present invention is shown in Figures 4 to 6 of the accompanying drawings, this second embodiment being a portion of an instrument panel designed to act as a dial panel for both a fuel gauge and a water temperature gauge for a motor vehicle, in association with warning lights for oil pressure and battery of the vehicle.The illuminabie panel 50 shown in Figures 5 to 6 comprises a lamina 52 made from acrylic plastics material, having first and second surfaces 54, 56 parallel to one another and an edge surface 58 connecting said first and second surfaces 54, 56. Mounted upon said first surface 54 is a translucent sheet of polycarbonate material 60 carrying thereon a printed pattern 62 which comprises two translucent scales 64, 66 and four translucent symbols 68, 70, 72 and 74 carried upon an opaque black background which is subdivided into squares by means of thin translucent intersecting lines. Directly below the symbols 72 and 74 there are respective rectangular translucent areas 76, 78, both of which are coloured red.

Similarly, there are translucent areas 80 coloured red in both of the scales 64 and 66.

As in the tachometer dial structure shown in Figures 1 to 3, illuminable panel 50 has the translucent sheet 60 secured to the first surface 54 of lamina 52 by means of a clear, pressure-snsitive adhesive, with the printed pattern 62 sandwiched therebetween. As can be seen in Figure 6 of the accompanying drawings, the second surface 56 of the lamina 52 carries three discrete shaped ares 82, 84 and 86 of metallic foil secured to the second surface 56 in positions corresponding to the scales 64, 66 and symbols 68, 70, 72 and 74 of the printed pattern 62 on the first surface 54 of the lamina 52.

More specifically, the shaped foil area 82 is aligned with scale 66 and symbol 70, the shaped metallic foil area 84 is aligned with scale 64 and symbol 68, and the shaped metallic foil area 86 is aligned with symbols 72 and 74. The remaining portion of the second surface 56 remains uncoated.

A moulded light box 88, made from an opaque white synthetic plastics material, is secured to a lower section of lamina 52 by means of clip members 90, 92 which embrace the peripheral edge surface 58 of lamina 52, this light box 88 being positioned so as to overlie the rectangular translucent areas 76, 78 of the printed pattern 62. This light box 88 is designed to accomodate two separate point sources of light arranged to illuminate respectively rectangular areas 76, 78, these point sources of light being respective elements of an oil pressure warning system and a battery warning system of a motor vehicle in which the illuminable panel 50 is installed, said point sources of light being energised when the respective warning system is energised.As can be seen in Figure 6 of the accompanying dcawings, the light box 88 is provided with respective rectangular apertures 94, 96 which are aligned with the rectangular areas 76, 78 of printed patterns 62. There are similar rectangular-shaped apertures (not shown) formed in lamina 52, which are aligned with the apertures 94, 96 in the light box 88, to ensure that light generated in the light box 88 passes directly through the corresponding rectangular area 76, 78 of the printed patterns 62 without entering the lamina 52.

Lamina 52 also includes integral light guide formations 98, 100, 102, 104 and 106, all of which are situated on or adjacent the uncoated portion of the second surface 56 of the lamina 52, and serve to maximise light input into said lamina 52 when the illuminable panel is mounted within an instrument panel of a motor vehicle and is illuminated by one or more light sources positioned behind the instrument panel.As is the situation with the first embodiment of the invention described hereinbefore, when the illuminable panel 50 is illuminated in this fashion, light transmitted into the panel 50 through the peripheral edge surface 58, the uncoated portion of the second surface 56 and the integral light guides 98, 100, 102, 104 and 106 is reflected backwards and forwards between the first surface 54 and the second surface 56 until it reaches the shaped areas of metallic foil 82, 84 and 86. Again, the reflectance of these metallic foil covered areas is such that the light incident thereon is reflected out of the lamina 52 through the translucent areas of printed pattern 62 which constitute scales 64, 66 and symbols 68, 70, 72 and 74.The shape and size of these areas of metallic foil 82, 84 and 86 are such as to ensure substantially bright, even illumination of the aforesaid translucent areas of the printed pattern 62.

Also shown in Figures 4-6 are fixing apertures 108, 110.112 and 114 for the respective gauge movements for the fuel gauge and the temperature gauge associated with the illuminable panel 50, and locating notches 116 and 118 serving to locate the translucent sheet 60 of polycarbonate material in position upon the lamina 52.

The metallic foil used to cover areas 82, 84 and 86 of the second surface 56 of the lamina 52 is made from aluminium, the foil areas being applied to the lamina 52 in exactly the same fashion as previously described with respect to the embodiment shown in Figures 1 to 3. Of course it will be clearly understood by a man skilled in the art that metallic foils other than aluminium foils can be used within the scope of the present invention, and that the foil area can be formed by any other suitable deposition technique, such as, for example, direct chemical deposition.

The present invention provides a simple but effective modification of a transparent synthetic plastics light guide material to form an illuminable panel for use in vehicle instrumentation. The concept used is both simple yet surprisingly effective in producing illuminable panels carrying a pattern thereon which can be brightly and evenly illuminated from a combination of edge and back lighting of the panel. An illuminable panel according to the present invention can be manufactured simply and quickly, without the multiplicity of operations required in the commercial manufacture of illumin able panels of the prior art.Since the illuminable panels according to the present invention are capable of producing far better illumination of indicia carried on the first surface thereof when the second surface thereof is illuminated with a given source of light than is the case with prior art illuminable panels, such panels do not require such powerful light sources for illumination as are required with prior art illuminable panels. This, in turn, has the advantage that the power rating required for the source of illumination of the instrument panel containing illuminable panels according to the present invention can be reduced below that required for equivalent panels of the prior art construction, so decreasing the tendency for the build-up of heat to occur behind such instrument panels.

The illuminable panels of the present invention have been described specifically herein in terms of two specific embodiments of the invention. It will be understood, however, that modifications can be made to the method of construction described specifically hereinbefore, such as, for example, depositiong the printed pattern directly upon the first surface of the lamina without the covering layer of polycarbonate material. Consequently, the scope of the present invention is defined by the scope of the claims appendant hereto.

Claims (9)

1. An illuminable panel for use in a motor vehicle instrument panel, said panel comprising a lamina moulded from a transparent synthetic plastics material, said lamina having first and second surfaces parallel to one another and an edge surface connecting said first and second surfaces, said first surface carrying thereon a patterned layer having translucent areas therein formed as indicia, said second surface being coated with at least one shaped area of a metallic foil positioned substantially opposite said translucent areas, said illuminable panel being adapted to be mounted adjacent a light source so that the edge surface and the uncoated areas of the second surface thereof are illuminable by said light source, said shaped area of metallic foil being so shaped as to ensure substantially bright, even illumination of said translucent areas of said patterned layer by said light source.

2. An illuminable panel according to claim 1, in which the lamina is moulded from transparent acrylic plastics material.

3. An illuminable panel according to claim 1 or 2, in which the patterned layer comprises a printed pattern of said translucent areas on an opaque background which is deposited on one surface of a translucent sheet of polycarbonate material, said translucent sheet of polycarbonate material being secured to said first surface of the lamina so as to sandwich said printed pattern between said translucent sheet and said lamina.

4. An illuminable panel according to any one of the preced- ing claims, in which the metallic foil is formed of aluminium.

5. An illuminable panel according to any one of the preceding claims, in which the metallic foil is applied to said second surface of said lamina by means of a hot foil pressing technique.

6. An illuminable panel according to any one of the preceding claims, in which said edge surface includes at least one chamfered portion to maximise light input into said lamina when said lamina is illuminated by said light source.

7. An illuminable panel according to any one of claims 1 to 5, in which integral light guide formations are provided on uncoated portions of said second surface and said edge surface of said lamina to maximise light input into said lamina when said lamina is illuminated by said light source.

8. An illuminable panel substantially as hereinbefore particularly described, and as shown in Figures 1 to 3 of the accompanying drawings.

9. An illuminable panel substantially as hereinbefore particularly described, and as shown in Figures 4 to 6 of the accompanying drawings.