WO1996029471A1

WO1996029471A1 - Road studs

Info

Publication number: WO1996029471A1
Application number: PCT/GB1996/000685
Authority: WO
Inventors: Peter Kenneth Slade; Ray Parker; John Brown
Original assignee: Btm Somerford Limited
Priority date: 1995-03-22
Filing date: 1996-03-22
Publication date: 1996-09-26
Also published as: AU5151496A

Abstract

A road stud comprises a body (2) made from a transparent material. A recess (12) in the body accommodates a reflective device (14). Light (20) travelling horizontally is refracted at a light-receiving surface (10) on the body to fall on the reflective device (14) substantially normally. The light is thus reflected back to return in the direction towards the source.

Description

ROAD STUDS

This invention relates to road studs. Road studs are used on roadways for various reasons. For example they may be used to delineate traffic lanes, to indicate kerbsides or to separate motorway slip roads from the main carriageway. Invariably, road studs are provided with some form of reflective means which reflects the light from vehicle headlights back to the driver, so that the studs are visible at night. Road studs may be fixed to the carriageway by a variety of methods, but it is increasingly common for them to be secured by means of an adhesive.

Road studs are subjected to severe operating conditions; they are exposed to the weather and to impact and abrasion from vehicle wheels. Such influences can degrade the reflective qualities of the road studs. For example, it is common for the reflective means to take the form of a reflective panel provided on the body at or near the surface of the stud. These panels are prone to abrasion, reducing the reflective quality of the panel. Also, water or other liquids penetrating behind the reflective panel, or any other kind of reflector, can destroy entirely its ability to reflect light. According to the present invention there is provided a road stud for fixing to a roadway, comprising a body of light-transmitting material, the body having a light-receiving face which lies at an acute angle to the horizontal when the stud is fixed to a roadway, whereby light travelling in a generally horizontal direction and striking the light receiving face is refracted towards the roadway, a recess being formed in the body, the recess constituting or accommodating reflective means which is disposed in the path of the refracted light, whereby the light is reflected from the reflective means to emerge from the light receiving face in a direction generally towards the original light source.

An advantage of such a road stud is that the reflective means is not directly subjected to traffic and weather influences.

The body is preferably made from a clear, transparent material, which may be glass but may alternatively be a plastics material such as polycarbonate or a similar impact-resistant material. By using a material which is sufficiently strong and abrasion resistant to withstand impact from traffic, it may not be necessary to take any additional measures to avoid scratching or other damage. However, in some circumstances, the body may be provided with a scratch- resistant coating, for example by applying a coating of thin glass or by chemical or other treatment of the surface of the body. The scratch-resistant coating may be provided on only part of the surface of the body, for example over the light-receiving surface, or over the entire surface.

In an embodiment of a road stud in accordance with the present invention, the recess is in the form of a slot which is inclined to the horizontal'. The angle of inclination of the slot may be greater than that of the light-receiving face. For example, the light-receiving face may be inclined to the horizontal at an angle in the range 25° to 60° (in one specific embodiment this angle is 28°, and in another it is 40°) and the slot may be inclined at an angle in the range 60 to 75° (in the two specific examples mentioned above, these angles may be 64° and 69° respectively) . Preferably, the angle of inclination of the slot is related to the angle of inclination of the light-receiving face and the refractive index of the material of the body so that light travelling horizontally and striking the light-receiving face then travels through the material of the body in a direction which is substantially normal to the plane of the slot. In most practical embodiments, this requirement will result in the angle of inclination of the slot being 30° to 40° larger than that of the light-receiving face. Consequently, the light strikes the reflective means substantially normal to the plane of the reflective means. This provides optimum performance of the reflective means.

The body may have two parallel slots positioned in the path of the light passing through the material of the body from the same light-receiving face. Such a construction makes it possible for substantially all of the light passing through the ligh -receiving face to be reflected back to its source. The slot nearer the light-receiving face may have a smaller depth than the other slot.

The slot or slots preferably extend into the material of the body from a base surface of the stud. A base plate may be secured over the base in order to seal the interior of the slot from the surroundings, or reliance may be placed upon the adhesive used to secure the stud to the roadway to provide this sealing.

Means may be provided for reinforcing the body in the region of the slots. In one embodiment, the reflective means in the or each slot may comprise two or more reflective devices which are separated from one another by one or more webs extending from one side of the slot to the other. The web may be moulded integrally with the remainder of the body. In another embodiment, or in combination with the above measure, the reflective device may comprise one or more reflective elements in the form of a reflective panel and a rear panel which are bonded together to provide an air gap between them, with webs extending between the reflective panel and the rear panel. In both embodiments, the reflective elements may be welded or glued into the slots, or may be a push fit, or may be formed by moulding appropriate formations directly onto a surface of the or each slot. The reflective elements may have a corner-cube reflective structure which may be metallised or rely on an air gap behind the corner- cube structure.

According to another aspect of the present invention there is provided a reflective element for use on or in a road stud, the reflective element comprising a reflective panel of transparent material having a rear face from which, in use, light transmitted through the material is reflected, the reflective element also comprising a rear panel which is fixed to the reflective panel at a position spaced from the rear face of the reflective panel to provide an air gap between the reflective panel and the rear panel, the air gap being sealed from the surroundings. The air gap may be divided into cells by webs extending between the reflective panel and the rear panel. Such a reflective element may be mounted internally of a road stud body, as described above, or may be secured to an exterior surface of the road stud body, for example in a recess formed in the exterior surface. The rear face of the reflective panel may have a corner-cube structure, and may or may not be metallized. The front face of the reflective panel may have a scratch-resistant surface, provided, for example by a thin sheet of glass. For a better understanding of the present invention, and to show how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which:

Figure 1 is a perspective view of a road stud; Figure 2 is a front view of the road stud of Figure 1; Figure 3 is a partial sectional view taken on the line III-III in Figure 2;

Figure 4 corresponds to Figure 3 but shows an alternative embodiment; Figure 5 is a sectional view taken on the line V-V in Figure 3;

Figure 6 is an enlarged view, corresponding to Figure 3, but showing a modified form of reflector element; and Figure 7 is a partial cut-away view of a reflector element similar to that of Figure 6.

The road stud shown in Figure 1 comprises a body 2 made from a clear, transparent plastics material such as polycarbonate. The body has a generally oblong base 4, a top surface 6 and opposite end surfaces 8. Part of the surface of the body extending from the top surface 6 to the base 4 between the end faces 8, is flat, and serves on each side of the body as a light- receiving face 10. This light-receiving face 10 is inclined to the base 4 (i.e. the horizontal) by 28°. A slot 12 (Figure 3) extends into the body from the base 4. The slot 12 stops short of the top face 6. It extends in a direction between the end faces 8, but stops short of those end faces 8. Although Figure 3 shows only one light-receiving face 10 and one slot 12, it should be appreciated that there is a corresponding slot 12 disposed near the light-receiving face 10 on the other side of the stud, the stud being generally symmetrical about a longitudinal plane extending between the light-receiving faces 10.

The slot 12 accommodates a reflective element 14, which is shown outside the slot 12 in Figure 3 for the sake of clarity. The reflective element 14 may take various forms and may be formed from flexible or rigid material, but is represented in Figure 3 as a panel of transparent plastics material having a flat front face 16 and a rear face 18 having a corner-cube formation. This corner-cube formation is metallised with the result that light entering the panel through the face 16 is reflected back in the same direction as the incoming light, even if the incoming light does not fall normally on to the front face 16.

The reflective device 14 may be secured within the slot 12 in any suitable manner. For example, the reflective device 14 may be a firm press fit within the slot 12, or it may be retained by means of an adhesive. Alternatively, or for additional security, a closure plate or tape may be applied to the base 4 over the opening of the slot 12 to keep the reflective device 14 in place. In some circumstances, it may be desirable for the front face 16 to be bonded to the adjacent wall of the slot over its full area, to exclude air from the interface. If air is present at the interface, it may obstruct light from passing to the reflective element. For use, the road stud is secured to a road surface, for example by means of an adhesive. The road stud can, if necessary, be inset into the road surface. The stud is oriented so that one of the light-receiving faces 10 is directed towards oncoming traffic. In most applications, of course, a row of road studs will be applied to the road surface to define a traffic lane or to separate one area of carriageway from another.

By day, the light-receiving face 10 will assume the colour of the reflective device 14, and so will stand out clearly from the surrounding road surface, which is usually of a dark colour. By night, the stud will be visible to a driver because the reflective device 14 will reflect back the light from the headlights of the driver's vehicle. The way in which this happens can be seen from Figure 3. Lines 20 represent the path of light rays from the vehicle headlights. These rays are shown to be travelling horizontally, which is a close approximation to the true situation, even though the vehicle's headlights will be some distance above the top of the road stud. It will be appreciated that the region of the body 2 between the light-receiving face 10 and the reflective device 14 is not of uniform thickness (i.e. it is not parallel-faced) but is in the shape of a prism. When the light strikes the light-receiving face 10, it is refracted at the boundary between the air and the material of the body 2. The light will therefore be refracted in the direction towards the road surface, and will pass through the material of the body 2 towards the reflective device 14. By appropriate inclination of the slot 12 relatively to the horizontal, taking account of the refractive index of the material (e.g. polycarbonate) of the body 2, it can be arranged that the light will strike the reflective device 14 travelling in a direction substantially normal to the front face 16. In the particular embodiment shown in the drawings, the angle of inclination of the slot is 64°. The reflective device 14 will reflect the light back along its' previous path and, again, the light will be refracted as it emerges through the light-receiving face 10 to return in an approximately horizontal direction towards the oncoming vehicle. As a result of the corner-cube formations on the rear face 18 of the reflective device 14, the light will be returned to the oncoming vehicle, even if the incoming light strikes the light-receiving face 10 obliquely (i.e. if the stud is positioned to one side of the path of the vehicle) .

By making the body 2 of the stud from a clear, transparent material, and by providing the reflective device 14 within the body of the material, well away from the light receiving face 10, the reflective device 14 is well protected from the weather, and from the effects of vehicle tyres passing over the stud. Also, because the body is moulded in a single piece, it is possible for the light-receiving face 10 to blend smoothly into the neighbouring parts of the body 2, avoiding recesses and the like in which dirt and moisture can collect. As a result, the efficiency, being the ratio of emitted light to incident light, remains high over the life of the road stud, with very little possibility of total failure of the reflective properties of the reflective device 14.

It will be appreciated from Figure 3 that some of the incident light, represented by a band 22, strikes the lower region of the light-receiving face and is refracted to a position below the bottom edge of the reflective device 14. The effect of this is that a proportion of the light striking the light-receiving face 10 is not emitted again towards the driver of the vehicle. To avoid this problem, it is possible to provide a second slot 24, provided with a second reflective device 14, as shown in Figure 4. Although the slot 24 positioned nearer the light-receiving face 10 is of smaller depth than the other slot 12, the two reflective devices 14 can be identical to one another, since the device 14 received in the slot 12 can be positioned at the upper end of the slot 12 (nearer the top face 6) leaving the lower part of the slot 12, near the base 4, unoccupied. This configuration will enable all of the light striking the light-receiving face 10, even that striking the lower region of the face 10, to be returned towards the driver of the oncoming vehicle.

While it is possible for the slots 12 and 24 to extend substantially fully across the width of the stud, this may, in some circumstances, have the effect of weakening the body 2, so that the stud becomes vulnerable to cracking or breaking up as a result of traffic passing over it. In order to avoid this effect, it is possible for each of the slots 12 and 22 to be discontinuous, as shown in Figure 5. In this embodiment, each slot is constituted by separate chambers 12A, 12B etc. which are separated from one another by webs 26. A single reflective element 14 is then accommodated in each chamber 12A, 12B.

An alternative means for strengthening the body 2 is shown in Figure 6. In this embodiment, the reflective device comprises a panel 28 of retro- reflective material, similar to each of the devices 14 except that it has no metallisation on the rear, corner-cube, face. A rear panel 30 is secured to the panel 28 by webs 32, which are integral with the panel 30 and are bonded to the panel 28. This provides an air gap 34 between the rear face 18 of the panel 28 and the panel 30, which, because it is sealed from the exterior, avoids any moisture coming into contact with the rear face of the panel 28. The webs 32 isolate the cells 34 from one another so that, even if liquid should penetrate into one of the cells 34, it will be prevented by the webs 32 from flowing to the neighbouring cells, leaving them fully effective. Also, the webs 32 provide structural strength to the reflective device and consequently to the stud as a whole.

Light passing through the material of the body 2 from the light-receiving face 10 passes into the material of the panel 28 and is reflected back by the rear, corner-cube, face. The panel 30 may be adhesively bonded to the material of the body 2, so enhancing the rigidity and strength of the overall structure of the body 2.

As shown in Figure 7, the rear panel 30 of the reflective device 14 is divided by the webs 32, and by a surrounding wall 36, into cells which form the air gaps 34 when the rear panel 30 is bonded to the panel 28. Of course, the orientation and arrangement of the webs 32 can be varied to suit the particular circumstances. For example the webs 32 can extend horizontally as shown in Figure 6 or vertically as shown in Figure 7, or a combination of both. The webs 32 may be omitted, so that a continuous air-gap, defined by the surrounding wall 36, extends across substantially the full area of the rear face 18. A reflective device 14 as shown in Figure 6 or 7 may be used as surface mounted reflectors on road studs, as well as being used as internally-fitted reflectors as shown in the embodiments of Figures 1 to 6. It will be appreciated that the particular road stud (and its variations) represented in the drawings represents only one way in which the invention can be put into effect. Various modifications can be made, and in particular the angles of inclination of the light-receiving face 10 and of the slot 12 can be altered. For example, in another embodiment (not shown) the angle which the light-receiving face makes with the horizontal is 40°, and the corresponding angle for the slot or slots 12 is 69°.

Claims

1. A road stud for fixing to a roadway, comprising a body of light-transmitting material, the body having a light-receiving face which lies at an acute angle to the horizontal when the stud is fixed to a roadway, whereby light travelling in a generally horizontal direction and striking the light receiving face is refracted towards the roadway, a recess being formed in the body, the recess constituting or accommodating reflective means which is disposed in the path of the refracted light, whereby the light is reflected from the reflective means to emerge from the light receiving face in a direction generally towards the original light source.

2. A road stud as claimed in claim 1, in which the body is made from a clear, transparent material.

3. A road stud as claimed in claim 1 or 2, in which the body is provided with a scratch-resistant coating which extends over the light-receiving surface.

4. A road stud as claimed in claim 3, in which the scratch-resistant coating is provided over the entire surface of the body.

5. A road stud as claimed in any one of the preceding claims, in which the recess is in the form of a slot which is inclined to the horizontal.

6. A road stud as claimed in claim 5, in which the angle of inclination of the slot is greater than that of the light-receiving face.

7. A road stud as claimed in claim 6, in which the light-receiving face is inclined to the horizontal at an angle in the range 25° to 60° and the slot is inclined to the horizontal at an angle in the range 60° to 75°.

8. A road stud as claimed in claim 6 or 7, in which the angle of inclination of the slot is related to the angle of inclination of the light-receiving face and to the refractive index of the material of the body so that light travelling horizontally and striking the light-receiving face then travels through the material in a direction which is substantially normal to the plane of the slot.

9. A road stud as claimed in any one of claims 6 to 8, in which the angle of inclination of the slot is 30° to 40° larger than that of the light-receiving face.

10. A road stud as claimed in any one of claims 5 to 9, in which the slot is one of two parallel slots positioned in the path of the light passing through the material of the body from the same light-receiving face.

11. A road stud as claimed in claim 10, in which the slot nearer the light-receiving face has a smaller depth than the other slot.

12. A road stud as claimed in any one of claims 5 to 11, in which the slot or slots extend into the material of the body from a base surface of the stud.

13. A road stud as claimed in any one of claims 5 to 12, in which means is provided for reinforcing the body in the region of the slots.

14. A road stud as claimed in claim 13, in which the reflective means in the or each slot comprises two or more reflective devices which are separated from one another by one or more webs extending from one side of the slot to the other.

15. A road study as claimed in claim 13 or 14, in which the reflective device comprises one or more reflective elements each in the form of a reflective panel and a rear panel which are bonded together to provide an air gap between them, with webs extending between the reflective panel and the rear panel.

16. A reflective element for use on or in a road stud, the reflective element comprising a reflective panel of transparent material having a rear face from which, in use, light transmitted through the material is reflected, the reflective element also comprising a rear panel which is fixed to the reflective panel to provide an air gap between the reflective panel and the rear panel, the air gap being sealed from the surroundings.

17. A reflective element as claimed in claim 16, in which the air gap is divided into cells by webs extending between the reflective panel and the rear panel.

18. A road stud substantially as described herein with reference to, and as shown in, Figures 1 to 3, or Figure 4, or Figures 5 to 7 of the accompanying drawings.

19. A reflective element for a road stud substantially as described herein with reference to, and as shown in, Figures 5 to 7 of the accompanying drawings.