EP2313557B1

EP2313557B1 - Road stud

Info

Publication number: EP2313557B1
Application number: EP09784635.6A
Authority: EP
Inventors: David Hill; Lou Bown
Original assignee: Industrial Rubber PLC
Current assignee: Industrial Rubber PLC
Priority date: 2008-07-30
Filing date: 2009-06-30
Publication date: 2015-08-12
Anticipated expiration: 2029-06-30
Also published as: GB2493859A9; GB2462276B; EP2313557A1; GB2493859B; GB0813928D0; WO2010012974A1; GB2493859A; GB201218244D0; GB2462276A

Description

Field of the Invention

The present invention relates to road studs, and in particular to a road stud that receives a depressible insert.

Background of the Invention

Road studs are in widespread use to provide visible guidance and warnings to motorists and other road users. Such road studs typically include one or more reflectors made out of glass or plastic to reflect light from vehicle headlights. The road studs help a motorist to determine his or her position on the road during hours of darkness.
There are two main types of road stud in use in the UK. The first is generally known as a "stick on", and is normally formed from a plastic unit incorporating one or more plastic reflectors. Plastic stick-on reflectors are placed on top of the surface of the road and are attached to the road by adhesive. They are relatively cheap but also have a relatively short life-time. For example, they may become detached from the road surface by passing traffic, and/or the visibility of the reflector may become reduced, for example by dirt being deposited onto the surface of the reflector.
The other main type of road stud in use in the UK is a depressible (also sometimes referred to as a "cat's eye"). This comprises a rectangular base unit, normally made of cast iron, which holds a resilient insert. The insert is typically made of rubber, and carries one or more glass or plastic reflectors. This type of road stud is installed by drilling a hole in the road, and then bonding the road stud into location using bitumen or some other road grout.
The inserts for depressible road studs are generally provided with one or more wiper blades. When the insert is compressed, for example because a lorry has driven over the road stud, these blades are designed to wipe across the reflectors. This helps to keep the surface of the reflectors free from dirt, and hence helps to maintain high visibility.
One example of a depressible road stud is described in GB 2263298 . A road stud generally in accordance with this patent is sold commercially under the "Light Dome" trademark by Industrial Rubber plc, of Fareham, Hampshire. The insert described in this patent includes ducts to allow water that has collected in the base of the road stud to be applied to the wiper blades. The water helps to lubricate the wiping action of the blades on the reflectors, thereby reducing wear, as well as assisting with the overall cleaning process.
As noted above, the wiping action of a depressible road stud is important for maintaining the insert in a good operating condition. Accordingly, any improvement in the effectiveness of such wiping action will be of assistance in this regard.
The front and rear portions of most existing cast iron base units are hollow underneath. These hollow portions are filled with molten bitumen at the time of installation to help bond the road stud to the road surface in a process known as frogging. A plastic version of a depressible road stud is described in GB 2426540 . The underside of the base unit for this road stud is structured to avoid the need for frogging (which is a relatively time-consuming process). However, it is difficult to replicate this structure in a metal base unit due to the different manufacturing process.
BE408747 discloses a reflector for use at a cross-roads in which two roads cross one another (approximately at 90 degrees to one another). The reflector in BE408747 is in the shape of a cross, whereby each arm of the cross supports one or more reflectors, thereby enabling the device to provide reflectivity for each direction of each road at the cross-roads. BE408747 further discloses other shapes for a reflector, including a right-angled triangle and an ellipse.

Summary of the Invention

One embodiment of the invention provides a base unit for a road stud. The base unit has a recess for receiving a depressible insert and a plurality of projections extending into the recess for retaining the depressible insert therein. The recess has a shape in plan view comprising a rectangle with chamfered corners, wherein each chamfered corner comprises a single side, such that the shape comprises a total of eight sides. The base unit may be made of metal, plastic, or any other suitable material.
Having such a shape for the recess has been found to hold the insert more firmly in position, and in particular, when the insert is compressed by passing traffic, the insert suffers less distortion. This helps to ensure a better wiper action when cleaning the reflector(s) of the insert, and may also help to prolong the lifetime of the insert against splitting as well. Such a shape also maximises compatibility with existing base units.
The rectangle comprises a first pair of sides perpendicular to the intended line of sight for the base unit, and a second pair of sides perpendicular to the first pair of sides. The plurality of projections extends from said second pair of sides.
In one embodiment, the base unit is substantially circular in plan view, or at least has a greater degree of rotational symmetry than conventional base units for depressible inserts. Having a recess with eight sides in such a base unit helps to provide a better match between the shape of the recess and the overall shape of the base unit. This allows the wall(s) of the base unit defining the recess to be of more constant thickness, which helps to avoid any regions of weakness.
Another embodiment of the invention provides a depressible insert for use in combination with a base unit to form a road stud. The insert is received into a recess of the base unit and has holes for receiving projections from the base unit to retain the insert in the recess. The insert also has a shape in plan view comprising a rectangle with chamfered corners, wherein each chamfered corner comprises a single side, such that the shape comprises a total of eight sides.
The rectangle comprises a first pair of sides perpendicular to the intended line of sight for the road stud, and a second pair of sides perpendicular to the first pair of sides. The holes for receiving the projections are located in said second pair of sides. It will be appreciated that the insert will generally be shaped to correspond as closely as possible to the shape of the recess in the base unit for receiving the insert. Nevertheless, i the insert has a shape that comprises a rectangle with chamfered corners and the holes for receiving the projections are suitably located, then such an insert can also be utilised with existing base units that have a rectangular recess, in that the insert will fit into and be retained in such a base unit (although the benefit of reduced distortion will be lost).
The insert generally includes at least one reflective eye (plastic or glass) located in the insert, and one or more wiper blades for cleaning the reflective eye(s). In particular, the shape may comprise a side perpendicular to the intended line of sight for the road stud, with the wiper blade(s) then being located in and parallel to said side. As mentioned above, the shape of the insert and the base unit can be arranged as described herein to reduce distortion of the wiper blade (and hence improve cleaning) compared to existing base units.
A base unit for a road stud is disclosed herein. The base unit is made of metal, such as cast iron, and is adapted to accommodate a reflective insert (depressible or otherwise). The outer wall of the base unit comprises a groove extending horizontally around the periphery of the base unit. The groove lies below surface level when the base unit is installed into a road.
During installation, road grout such as molten bitumen flows into the groove. This provides a keying action to retain the base unit in the road, and hence removes (or lessens) the need for frogging, thereby helping to make installation quicker and cheaper.
The base unit may be substantially circular (although other shapes may also be used). A circular shape allows for easier drilling and reduced weight and cost compared to existing base units, which have an elongated shape instead (in part to provide space for frogging). The base unit may have a substantially flat underside without excavated portions. The lower wall of the groove may be defined by an outward extension of the floor of the base unit.

Brief Description of the Drawings

Various embodiments of the invention will now be described in detail by way of example only with reference to the following drawings:

Figure 1 is a view from above and to the side of a base unit for a road stud in accordance with one embodiment of the invention.
Figure 2 is a top view of the base unit of Figure 1 in accordance with one embodiment of the invention.
Figure 3 is a view from below and to the side of the base unit of Figure 1 in accordance with one embodiment of the invention.
Figure 4A is a longitudinal section from front to back through the centre of the base unit of Figure 1 in accordance with one embodiment of the invention.
Figure 4B is a side view of the base unit of Figure 1 in accordance with one embodiment of the invention.
Figure 5A is a transverse section from side to side through the centre of the base unit of Figure 1 in accordance with one embodiment of the invention.
Figure 5B is a front view of the base unit of Figure 1 in accordance with one embodiment of the invention.
Figure 6 is a view from above and to the side of a base unit for a road stud in accordance with another embodiment of the invention.
Figure 7 is a view from below and to the side of the base unit of Figure 6 in accordance with one embodiment of the invention.
Figure 8 is a top view of the base unit of Figure 6 in accordance with one embodiment of the invention.
Figure 9A is a longitudinal section from front to back through the centre of the base unit of Figure 6 in accordance with one embodiment of the invention.
Figure 9B is a transverse section from side to side through the centre of the base unit of Figure 6 in accordance with one embodiment of the invention.
Figure 10 is a view from above and to the side of a depressible insert for a road stud in accordance with one embodiment of the invention.
Figure 11 is a view from below and to the side of the depressible insert of Figure 10 in accordance with one embodiment of the invention.
Figure 12 is a longitudinal section from front to back through the centre of the depressible insert of Figure 10 in accordance with one embodiment of the invention.
Figure 13 is a top view of the depressible insert of Figure 10 in accordance with one embodiment of the invention.
Figure 14 is a bottom view of the depressible insert of Figure 10 in accordance with one embodiment of the invention.

Detailed Description

Figures 1 and 2 illustrate a cast iron base unit 100 for a road stud in accordance with one embodiment of the invention. The base unit is designed to receive a depressible insert having one or more reflectors. For convenience of explanation, the front of the base unit (as perceived by an oncoming motorist) is indicated by the location of letter A, the rear of the base unit by the letter B, and the sides by the letters C and D. It will be appreciated nevertheless that the base unit of Figures 1 and 2 is symmetric, so that alternatively B could be considered as the front and A as the rear. This symmetry supports bi-directional operations, for example if the road stud is to be fitted down a central line of a single carriage-way, in which case the insert can incorporate reflectors for both directions (forwards and backwards). In other locations, such as to demarcate lanes within one carriage-way of a motorway, the insert only needs to be provided with reflectors (or a reflector) facing in the forwards direction, i.e. towards oncoming traffic.
The main body of the base unit 100 includes side walls 101 and 102, front portion 106 and rear portion 107. When the base unit 100 is installed in the road, the top surface of front and rear portions 106 and 107 and also of side walls 101 and 102 protrudes slightly above the road surface. The portions of side walls and front/rear walls that lie above the road surface slope upwards towards the centre of the base unit, in effect acting as a ramp onto the top of the road stud.
The base unit further includes a recess 110 defined between side walls 101 and 102, which is used to receive the depressible insert. Each side wall includes a pair of projections 121A, 121B, and 122A, 122B that extend into recess 110. The projections 121, 122 are used to retain the resilient insert within recess 110. The insert is sized so that when held in recess 110, it protrudes slightly above the top surface of the base unit 100. As a result, the insert is compressed by any vehicle wheel that passes directly over the road stud, thereby activating the wiper blades within the insert to clean the reflectors (as described in GB 2263298 ).
The front portion 106 of the base unit 100 is formed with a channel 116 that slopes down towards recess 110. The channel 116 helps to provide a clear line of sight to the reflector(s) located on the insert within recess 110. In addition, the channel 116 also helps rainwater to run into recess 110, where it can collect for use in cleaning and lubricating the reflector(s) (as described in GB 2263298 ).
Base unit 100 is intended for use with an insert having two reflectors facing forwards (i.e towards the front of the base unit). The channel 116 is therefore bifurcated by ridge 126, which provides one sub-channel for each reflector. Note that ridge 126 also helps to direct rainwater to corresponding ducts in the insert that communicate with the bottom of recess 110, where rainwater can accumulate (such ducts are also described in GB 2263298 ).
The rear portion 107 of the base unit is shaped in the same manner as the front portion 106. In particular, the rear portion includes channel 117, which is bifurcated by ridge 127. It will be recognised by the skilled person that the configuration of base unit 100 as so far described corresponds generally to the shape of existing base units made of cast iron, thereby ensuring compatibility with such existing base units.
The top surface of base unit 100 is provided with an anti-skid or anti-slip pattern 120. The anti-skid pattern 120 helps to ensure that when a vehicle wheel crosses the top surface of base unit 100 protruding from the road, the wheel does not suddenly lose traction or start to skid. The particular anti-skid pattern 120 shown in Figures 1 and 2 comprises a diamond stud configuration, but the skilled person will appreciate that any suitable anti-skid configuration or texture could be used for this top surface. In addition, the anti-skid pattern 120 of Figure 2 is shown extending across only a portion of the top surface of the base unit 100. The skilled person will appreciate that in other embodiments, the anti-skid pattern(s) may be provided on all or different portions of this top surface.
As can be seen most easily in Figure 2, the recess 110 has a generally octagonal shape for receiving a depressible insert. This contrasts with the rectangular recess shape for known base units, such as described in GB 2426540 and GB 2263298 . In fact, the recess shape of Figure 2 can be considered as generally rectangular, but with bevelled or chamfered corners 161, 162, 171, 172.
The recess shape of Figure 2 has been found to provide a more secure location for the insert than a recess of conventional rectangular shape, such as described in GB 2426540 and GB 2263298 (but without changing the manufacturing tolerances). In particular, the insert suffers less distortion when a vehicle passes over the road stud. This in turn provides an improved wiper action, since the wiper blades maintain their linear profile better.
One way of viewing this improved performance is to consider the depressible action as caused by a downward displacement of the insert at the centre of the road stud. In a rectangular recess, the corners of the recess represent the portions of the recess furthest from the point of displacement. This therefore allows maximum distortion in the directions to the corners. In contrast, chamfering the corners decreases the distance in a diagonal direction from the centre of the recess outwards to the edge of the recess, thereby reducing the opportunity for distortion.
The downward displacement of the insert at the centre of the road stud can also be considered as producing a force on the insert directed radially outwards. In the corners of a conventional base unit, where the front/back and sides walls meet, no wall directly opposes the radial force outwards. Rather, the front/back and side walls act at an angle compared to the radial force outwards, and this causes distortion of the insert. In contrast, the chamfered corners 161, 162, 171 and 172 are substantially perpendicular to the outward radial force on the insert, and hence are better able to reduce the force without distortion of the insert. As mentioned above, it has been found that reducing the distortion leads to a more effective cleaning action by the wiper blades of the insert.
In general, the recess will have a pair of sides perpendicular to the line of sight for the road stud, which then determines a flat surface for locating the reflective eye(s) and wiper blade(s). The recess may also have a pair of sides perpendicular to the first pair of sides (i.e. parallel to the line of sight) for receiving the projections from the base unit. This leads to a generally rectangular recess, but with chamfered corners.
In the embodiment of Figures 1 and 2, each chamfered corner is defined by a single side which is approximately 45 degrees to the line of sight - i.e. diagonal compared with front-back axis and side axis of the base unit.
A further benefit of the octagonal shape of recess 110 in comparison with the rectangular shaped recess of conventional base units is related to the shape of the overall base unit. Thus the base units shown in GB 2426540 and GB 2263298 are generally rectangular in shape, with a relatively long axis parallel to the line of sight onto the base unit. However, the circular base unit of Figures 1 and 2 is somewhat easier to install in the road than a conventional rectangular base unit, since a rotating drill will most naturally produce a circular hole in the ground.
Locating a rectangular recess in a circular base unit can lead to the walls of the base unit being relatively narrow at locations corresponding to the corners of the recess. This in turn can weaken the overall structure of the base unit. However, by making the corners of the recess chamfered, as shown in Figures 1 and 2, this allows the walls of the corner regions 261, 262, 271, 272 of the base unit to be relatively thicker, thereby leading to a more robust base unit. In other words, by making the recess have a shape that is closer to the circular shape of the base unit, the recess walls are able to have a more constant thickness. This helps to allow the overall size of the base unit to be shrunk, while still maintaining a minimum thickness (and hence strength) for the walls of the base unit.
Figure 3 illustrates the underneath of the base unit 100 of Figures 1 and 2 in accordance with one embodiment of the invention. As can be seen, the underside 140 of base unit 100 is substantially flat or smooth. This is in contrast to conventional cast iron base units, which generally have excavated regions underneath their front and back portions which are used for frogging the base unit when it is being installed.
As best seen in Figures 4A, 4B, 5A and 5B, the base unit 100 is provided with a groove 142 that extends horizontally around the circumference of the base unit. The groove is formed between a lower rim 141 and an upper rim 143, wherein lower rim and upper rim also both extend horizontally around the circumference of the base unit. The lower rim 141 represents an outward extension of the underside 140 of the base unit. The upper rim 142 is provided at a level corresponding to the installation depth of base unit 100 into the road. In other words, the top of upper rim 142 is approximately level with the road surface, with the sloping portions of front/rear walls 106/107 and side walls 101/102 then extending above the road surface.
When base unit 100 has been installed, groove 142 sits below the road surface. During installation, groove 142 helps to key the base unit into the road, in that molten bitumen or other road grout flows into groove 142 and after setting then acts to hold down rim 141 into the ground. This keying arrangement avoids the need for frogging, and hence also avoids the need to provide regions of the base unit to accommodate such frogging. As a result, base unit 100 is more compact than a conventional base unit (for substantially the same shaped insert). This reduces the amount of material in the base unit, thereby saving both cost and weight. In addition, avoiding the need to frog base unit 100 simplifies and quickens the installation procedure.
In the particular embodiment of Figures 1-5, the groove has a height of approximately 15mm (from the top of lower rim 141 to the underside of upper rim 143) and the depth of the groove is approximately 12mm with respect to the lower rim and 6mm with respect to the upper rim. However, it will be appreciated that other embodiments may have other dimensions for the groove.
In addition, although groove 142 extends continuously around the entire periphery of base unit 100, in other embodiments groove 142 may extend around only a portion of the base unit. In addition, although groove 142 in base unit 100 has a relatively simple profile comprising just a single channel, other base units may have a more complicated groove structure comprising multiple channels, etc.
Note that although the base unit 100 shown in Figures 1-5 has both an octagonal recess 110 and a groove 142 for keying, these features may be provided independently of one another. For example, some base units may have an octagonal recess, but without a groove for keying. Such base units may rely on some other mechanism for adhering to the road, such as frogging. Conversely, some base units may have a groove for keying, but with a conventional rectangular recess 110 for receiving an insert (or any other suitably shaped recess). Furthermore, the insert for a metal base unit with a groove may not be a depressible insert, but might instead comprise a (substantially) rigid plastic reflector, for example such as described in GB 2435663 .
Figures 6 through 9 illustrate a base unit 300 in accordance with another embodiment of the invention. This embodiment is made of plastic (rather than the metal of base unit 100). Many aspects of base unit 300 are the same as base unit 100 and accordingly will not be described again. In particular, base unit 300 has an octagonal recess 110 for receiving a correspondingly shaped insert. Indeed, base unit 100 and base unit 300 are shaped and sized so that they can accommodate the same depressible insert. Accordingly, comments made above in relation to the shape of the recess 110 for base unit 100 apply also to the shape of the recess 110 for base unit 300.
Note that the floor 140 of recess 110 in base unit 300 is provided with two holes, one hole 310C under projections 121A and 121B, and the other hole 310D under projections 122A and 122B. These holes are intended to receive inserts, as described in the above-referenced GB 2426540 .
Base unit 300 does not have a circumferential groove for keying. The underside of base unit 300 is provided with ribbing 330 in an anti-frogging arrangement (as also described in the above-referenced GB 2426540 ). In addition, the side walls of base unit 300 are provided with through-holes 320 or channels connected via ribbing 330 to openings in the bottom of the base unit. When the base unit 300 is installed, road grout flows through these holes 320 to link up with the road grout underneath the base unit, thereby holding the base unit in position (as described in GB patent application 0714584.0 ). (N.B. it is generally difficult if not impossible to make the configuration of holes 320 in a metal rather than a plastic base unit).
Figures 10 and 11 illustrate a depressible insert 500 in accordance with one embodiment of the invention. The depressible insert 500 may be used, for example, to form a road stud with base units 100 and 300 of Figures 1 to 9. The depressible insert 500 is of similar overall form to the depressible insert described in GB 2263298 and has a generally rectangular shape with front and back walls 506, 507 and side walls 501, 502. Each side wall is formed with (two) holes 521A, 521B and 522A, 522B for receiving corresponding projections from a base unit (such as projections 121, 122 as shown in Figure 2). Such projections engage holes 521, 522 to retain the insert in the base unit.
The front and/or back of the insert 500 may each be provided with one or more reflectors (not shown in the Figures). Figure 10 shows an opening 550 for receiving the reflector(s). The particular embodiment of Figures 10 and 11 can house a pair of glass reflectors facing in each direction. For example, Figure 10 shows the back of the opening 550 having two separate holes, 551C and 551D, each for holding a separate reflective glass eye. The holes 551C and 551D can also be used to hold instead a single plastic eye, such as described in GB 2438203 (or any other suitable form of reflector(s)).
The bottom lip of opening 550 is provided with two ducts or channels 555C, 555D. These connect to the bottom of the recess in the base unit for holding the insert and allow rainwater to flow down into this recess. As mentioned above, this rainwater can then be used to assist the cleaning action of the wipers 590A, 590B of the depressible insert when a vehicle drives over the top 570 of the insert and compresses the insert down into its base unit. The location of wipers can also be seen in Figure 12.
As can be seen in Figures 13 and 14, the insert comprises a generally rectangular shape with chamfered corners. In particular, corners 561, 562, 571 and 572 are bevelled to give insert 500 an octagonal shape overall. It will be appreciated that this shape matches the recess shape of base units 100 and 300, and accordingly insert 500 can be used with these base units. (In fact insert 500 is also able to fit into a conventional base unit with a rectangular recess, although the gaps in the corners may cause increased distortion).
As discussed above, placing an insert having the shape shown in Figures 13 and 14 into base unit 100 or 300 reduces the distortion of the insert when a vehicle drives over the road stud. This produces an improved wiping action, in that shape of the wiper blade is better maintained through the compression, which in turn helps to keep the insert reflector(s) cleaner. In addition, reducing the distortion of the insert during compression by a passing vehicle helps to reducing splitting of the insert, and can therefore assist in prolonging the insert lifetime.
In conclusion, although a variety of embodiments have been described herein, these are provided by way of example only, and many variations and modifications on such embodiments will be apparent to the skilled person and fall within the scope of the present invention, which is defined by the appended claims.

Claims

A base unit (100) for a road stud, said base unit having a recess (110) for receiving a depressible insert (500) and a plurality of projections (121,122) extending into the recess (110) for retaining the depressible insert (500) therein, and characterised in that said recess (110) has a shape in plan view comprising a rectangle with chamfered corners (161,162,171,172), wherein each chamfered corner comprises a single side, such that the shape comprises a total of eight sides.
The base unit of claim 1, wherein said rectangle comprises a first pair of sides perpendicular to the intended line of sight for the base unit, and a second pair of sides perpendicular to the first pair of sides.
The base unit of claim 2, wherein said plurality of projections extend from said second pair of sides.
The base unit of any preceding claim, wherein said shape extends substantially the full height of the recess.
The base unit of any preceding claim, wherein said base unit is made of metal.
The base unit of any of claims 1 to 4, wherein said base unit is made of plastic.
The base unit of any preceding claim, wherein said base unit is substantially circular in plan view.
The base unit of any of claims 1 to 6, wherein said base unit has rotational symmetry of order 4 or more in plan view.
A depressible insert for use in combination with a base unit according to claim 1 to form a road stud, wherein said insert (500) is received into a recess (110) of the base unit (100), said insert having holes (521, 522) for receiving projections (121, 122) from the base unit to retain the insert in the recess, and having a shape in plan view comprising a rectangle with chamfered corners (561, 562, 571, 572), wherein each chamfered corner comprises a single side, such that the shape comprises a total of eight sides.
The insert of claim 9, further comprising at least one reflective eye located in the insert and one or more wiper blades for cleaning said at least one reflective eye, wherein said shape comprises a side perpendicular to the intended line of sight for the road stud, and said wiper blade is located in and parallel to said side.
The insert of claim 9 or 10, wherein said holes are configured to maintain compatibility with pre-existing installed base units.
A road stud comprising a base unit and the insert of any of claims 9 to 11.
The road stud of claim 12, wherein the base unit comprises the base unit of any of claims 1 to 8.