ILLUMINABLE SIGN This invention relates to an illuminable sign, principally for use on vehicles and especially at the rear thereof. Especially when used in such a position, it is a requirement that the sign should, at least when illuminated, be coloured red. In some circumstances, as when the sign is used to indicate that the vehicle is special, such as one that has unusual performanceand may be designated by a legend such as "XR3i", it is desirable that it should be legible also in daylight, the sign exhibiting a bright appearance with adequate contrast between the back- ground and the legend. A degree of reflection at night of at least the background part may also be desirable as a safety feature.
In the construction of aesthetically acceptable signs of the general type to which this invention relates, it has been usual to use special materials, such as for example a coloured and transparent patterned material which has unpatterned areas shaped to correspond to the characters of a legend to be displayed. Such special materials are produced by using highly expensive moulding tools.
Cost is likely to be a major consideration, and in order to keep this within bounds, instead of using special materials and/or tools, use is made in carrying out the invention of a prismatic sheet, which is defined for the purposes of this document as a sheet of translucent or transparent material having on one or both faces an overall pattern of light refracting areas such as to cause a diffusion of light passing therethrough ki acrylic resin material may be used and a useful example is that which is intended for domestic glazing in situations such as communicating doors and shower screens where light transmission combined with an obscured image is required. This material is available in large thin sheets (about 3mm. in thickness) and in numerous patterns, and is a relatively inexpensive prismatic sheet.The form of such sheet that has been found especially suitable for use in this invention is one that has impressed on to one surface a pattern of shallow hollow contiguous pyramids, although one with raised pyramids may also be used.
According to one form of the invention an illuminable sign comprises a prismatic sheet to one face of which is applied a reflective coating except in areas representing the characters of a legend to be displayed, means for illuminabing at least the area of the legend, and a clear transparent cover sheet.
In a preferred form of the invention the margins of the characters forming the legend are clarified by superimposing an opaque mask having clearly defined edges. The mask may be produced as separate items to be secured in position over the uncoated characters of the legend on the prismatic sheet, but it is preferred to apply the mask by a technique such as screen printing on to a smooth surface of the sign.
Where the prismatic sheet has its smooth face towards the observer the mask may be applied to that face in this way. However, it has been found that a more acceptable reflective effect is obtained by applying the reflective coating to the patterned face of the sheet and having this face towards the observer.
Thus, according to a preferred form of the invention an illuminable vehicle or like sign comprises a prismatic sheet having its smooth face away from the observer, a reflective coating, fro example of sprayedaluminium or aluminium paint, applied to the patterned face of the prismatic sheet with blank uncoated areas for the characters of a legend to be displayed, a transparent coloured sheet superposed on the patterned face of the first sheet and an opaque mask applied to one of the smooth surfaces of the transparent coloured sheet and aligned with and defining the edges of each character of the legend. A screen-printed mask may be of black or dark-coloured material e.g. paint but it has been found that a pleasing effect is obtained by making the mask of white or other light coloured paint.In this case the mask is preferably applied to the outside face of the transparent sheet, since otherwise the white or other pale colour of the mask tends to be affected by the colour of the sheet.
The illuminating means for the sign of the invention may include a light box, secured to the face away from the observer, and containing one or more electric lamps for illuminating that part of the sign containing the legend.
An example of the invention is illustrated in the drawing in which:Figure 1 is a front elevation of a signaccording to the invention,Figure 2 is a section on line II-IIof Figure 1, andFigure 3 is an enlarged scrap view of thearea indicated by a circle in Figure 2.
In the drawing a sheet of clear acrylic resin 1, which is coloured red in this example and smooth on both faces, is bonded around its periphery to a backing 2 of prismatic sheet. In this example the sheet 2 is smooth on its rear face and its front face is embossed or otherwise provided with a surface pattern of contiguous shallow hollow pyramids 3. The front face is generally covered by a reflective coating 4 of aluminium paint but this is omitted in the area occupied by the characters of the legend "XR3i" as indicated at 5 in Figure 3. This may be achieved by spraying-on the coating 4 while covering the legend area with a mask which is removed when the spraying is complete.Since the area 5 is virtually non-reflective, or at least considerably less reflective that the surrounding area, the legend "XR3i" will stand out when the sign is viewed from the left side as seen inFigures 2 and 3.
Owing to the nature of the surface formed by the pyramids 3 the edges of the characters are ill defined and the effect of this is avoided by providing a permanent mask 6 on the smooth rear surface of the sheet 1. The mask 6 is registered with the legend on the sheet 2 so that the edges of the characters on the latter are completely covered, and the sign when viewed from the front exhibits the legend "XR3i" in sharp contrast with the background.
In the event that a white or light-coloured margin for the legend is preferred, an alternative mask 6a is appropriately coloured and is applied to the other face of the sheet 1 so that its colour is not modified by the colour of the sheet.
The sign is completed by a light-box 7 secured by screws to blocks 8 cemented to the rear of the sheet 2 with edges of the box located in rebates machined in the face of the sheet 2 as shown.
Each end of the box 7 is enlarged to receive a festoon type lamp 9, and the remainder is shallow and of light coloured material to reflect light from the lamps through the legend area. The lamp 9 is energisable through terminals one of which is shown at 9a.
The reflective coating 4 may be applied as a very thin layer such that, although iy serves adequately as a reflective layer, it is nevertheless sufficiently translucent to permit light from the lamps 8 to be seen directly therethrough, and in this case an area of opaque material 11 such as black paint or tape is applied to the rear face of the sheet 2 in the region of each lamp. If black or dark material is used it mar be desirable to augment the reflection of light towards the centre of the sign where the legend is situated by providing a further coating, in that region, of light reflecting material. However, where the displayed legend is large in relation to the total size of the sign it can happen that, when viewed in the dark with the internal illumination energised, too much light is emitted, especially at the margins of the legend nearest to the lamps.
This can be corrected by arranging that the obscuring layer 11 has a black or dark coloured surface.
The sign may be secured to a vehicle by further blocks (not shown) cemented to the rear face of the sheet 2.
It will be appreciated that many variations are possible within the scope of the invention. For example since the sheet 2 is of transparent material in the form in which it is usually available commercially, it is possible to place the reflective coating on the rear smooth face, while the patterned face would in this case still be towards the observer. A sharp-edged character would then be attainable by spraying or screen printing. However, a dark margin or at least a contrasting one is still desirable and this could either be incorporated on the rear face of the sheet 2, or it could be placed on either of the faces of the sheet 1.