GB2415730A

GB2415730A - Base unit for a road stud

Info

Publication number: GB2415730A
Application number: GB0510799A
Authority: GB
Inventors: Rod Ashton
Original assignee: Industrial Rubber PLC
Current assignee: Industrial Rubber PLC
Priority date: 2005-05-26
Filing date: 2005-05-26
Publication date: 2006-01-04
Anticipated expiration: 2025-05-26
Also published as: GB0510799D0; GB2415730B

Abstract

The base unit 100, for use with depressible road studs, has a substantially rectangular shape comprising front 106 and back 107 portions and opposing side walls101,102, with a cavity 110 for retaining a resilient insert located between the front portion, the back portion and the side walls, wherein the external surface of each side portion incorporates one or more recesses 131A,131B,131C,132A,132B,132C. Each recess preferably extends to the bottom of the base unit, and comprises a groove with a rounded profile or horizontal cross-section that runs vertically, in use, down the external surface of the side wall and which is arched at the top. There are preferably three recesses in each side wall that each extend vertically for at least half the height of the corresponding wall. Each recess preferably extends at least halfway into the thickness of the corresponding side wall and with the recesses being positioned so that after installation they do not extend above the road surface. The cavity is preferably positioned between the recesses with projections 121,122 projecting into the cavity from the side walls for retaining the resilient insert being positioned so that they are interspersed with the recesses.

Description

24 1 5730

ROAD STUD

Field of the Invention

The present invention relates to road studs, and in particular to an improved base unit for such a road stud.

0 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 Repressible (also sometimes referred to as a "cat's eye"). This comprises a 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. It has been suggested that the base unit for a Repressible road stud might be made of plastic, although no such plastic base units are currently in use on roads in the UK.

The inserts for Repressible 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. s

One example of a Repressible road stud is described in GB 2263298 B. A road stud generally in accordance with this patent is sold commercially under the "Light Dome" trademark by Industrial Rubber pie, 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 0 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.

The typical weight of a conventional base unit made of cast iron is approximately 5 kg.

Although the large weight of the base unit assists in retaining the stud in the road, it does mean that the base units are relatively expensive to transport around the country since they are so heavy.

In addition, it is difficult to machine lay such heavy road studs; rather, the road studs are generally laid by manual workers by hand, and their weight might potentially cause injury if dropped onto the foot of such a worker.

Summary of the Invention

Accordingly, one embodiment of the invention provides a base unit for a road stud. The base unit has a substantially rectangular shape comprising a front portion, a back portion, and 2s opposing side walls. A cavity for retaining a resilient insert is located between the front portion, the back portion, and the opposing side walls. The external surface of each side wall incorporates one or more recesses.

The provision of the recesses in the side walls helps to reduce the overall weight of the base unit (compared to a conventional base unit with continuous walls). In addition, the recesses also provide an extended contact area for keying with the bitumen or other material used to bond the base unit with the road surface, thereby providing greater adhesion of the road stud to the road. Furthermore, the recesses allow easier manipulation of the base unit, whether by hand or by machine, for example at the time of installation.

In one embodiment, each recess extends to the bottom of the base unit. This helps to s maximise the weight reduction achieved as well as providing an effective geometry for installation and bonding. The recesses are also positioned so that after installation of the base unit in a road, the recesses do not extend above the road surface. This ensures that the exposed portion of the base unit has a generally smooth profile. (Note however that in other embodiments, it may be desirable for at least some of the recesses to extend above the road surface, for example to help 0 with manipulation either during installation of the road stud, or perhaps with subsequent removal).

In one embodiment, each recess comprises a groove running vertically down the external surface of the side wall. The top of each groove may be arched, with each groove having a rounded profile or horizontal crosssection. The rounded profile and arched top for the grooves help to provide good strength despite the reduced material of the base unit.

In one embodiment, each recess extends vertically for at least half the height of the side wall, and each recess also extends at least halfway into the thickness of the corresponding side wall. Having recesses of this size ensures that a significant proportion of the weight of the side walls is removed due to the presence of the recesses.

In one embodiment of the invention, there are three recesses on each side wall. In general, the provision of three recesses provides a good widthto-depth ratio for the recesses, which aids increased keying and weight reduction, but without a significant reduction in mechanical strength.

2s For example, having a single broad recess would not provide such an increased contact area for improved keying. On the other hand, having multiple shallow recesses would not provide so much weight reduction, and having multiple deep recesses may lead to a weakness in the side walls between the recesses (and there may also be a problem with the bonding material such as bitumen accessing a deep but narrow recess).

In one embodiment, the recesses are positioned so that the cavity for receiving the resilient insert is located between the recesses. Note that the side walls in existing base units are relatively thick on either side of the cavity, thereby offering greater scope for weight reduction. (In contrast, the side walls are already rather thinner for the front and back portions of the base unit, due to excavation of the underneath of these front and back portions). The recesses may interspersed or interleaved with projections extending into the cavity from the side walls for retaining a resilient insert within the cavity. In this configuration, the projections are attached to the thickest and therefore strongest portions of the side walls (i.e. in-between recesses), which helps to retain the insert in the road stud.

The present invention also provides a road stud comprising the combination of a base unit such as described above and a resilient insert fitted into the cavity 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 plan view of a base unit for a road stud in accordance with one embodiment of the invention; Figure 2 represents a view of the base unit of Figure 1 from underneath; and Figure 3 represents a transverse section through the base unit of Figure 1.

Detailed Description

2s Figure 1 illustrates a base unit 100 for a road stud in accordance with one embodiment of the invention. The base unit is designed to receive a Repressible insert having one or more reflectors. The base unit 100 is compatible with existing base units and inserts, such as described in GB 2263298 - in other words, base unit 100 accepts inserts made for existing base units. Base unit 100 is generally made of cast iron as per existing base units, but may instead be made of any other suitable material(s), such as aluminium or some other metal alloy, a resin, a plastic, and so on.

Figure 1 shows a plan view of the base unit 100. 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 s nevertheless that the base unit of Figure 1 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 lo 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 lot and 102 protrudes slightly above the road surface.

The base unit further includes a recess or cavity 110 defined between side walls 101 and 102, which is used to receive the Repressible insert. Each side wall includes a pair of projections 121A, 121B, and 122A, 122B that extend into cavity 110. The projections 121, 122 are used to retain the resilient insert within cavity 110. The insert is sized so that when held in cavity 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 B).

The front portion 106 of the base unit 100 is formed with a channel 116 that slopes down 2s towards cavity 110. The channel 116 helps to provide a clear line of sight to the reflector(s) located on the insert within cavity 110. In addition, the channel 116 also helps rainwater to run into cavity 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. The final portion of channel 116 is therefore bifurcated by ridge 126, which provides one sub-channel s for each reflector. Note that ridge 126 also helps to direct rainwater to corresponding ducts in the insert that communicate with the bottom of cavity 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, rear portion includes channel 117, which is bifurcated by ridge 127.

As shown in Figure 2, the underside of front portion 106 is excavated to form cavity 156.

This cavity is spanned by ribbing 216, which is parallel to the longitudinal direction of the base unit 100. This ribbing 216 helps to strengthen the base unit against the impact of passing lo vehicles. There is a similar cavity 157 in the underside of rear portion 107, which is likewise protected by longitudinal ribbing 217.

It will be recognised by the skilled person that the shape of base unit 100 as so far described corresponds generally to the shape of existing base units made of cast iron. This helps IS to ensure compatibility with existing base units and resilient inserts. However, as can be seen in Figures I to 3, base unit 100 is also provided with three recesses 131A, 131B, and 131C in side wall 101, and three recesses 132A, 132B, and 132C in side wall 102. In the embodiment shown, the six recesses all have the same shape and size, and are formed as grooves running vertically down the external surface of the side walls 101, 102 - i.e. the surface of each side wall that is in contact with the road after the base unit is installed into the road. The recesses 131, 132 help to lighten the base unit. In addition, the recesses 131, 132 also provide enhanced keying to the bitumen or other material used to bond the road stud into the road, due to the increased contact area for adhesion.

2s A further benefit of recesses 131, 132 is to aid manipulation of the base unit 100, either directly by a manual worker, or automatically via a machine. For example, recesses 131, 132 could be used to allow the fingers of a mechanical device to grip and lift the base unit, such as for machine installation into the road.

As seen in Figure 2, the grooves have a semi-circular profile in a horizontal plane. This shape is maintained for the full height of the grooves 131, 132. The grooves extend all the way to the bottom of the base unit 100, where they form side indentations into the floor 160 of the base unit. The grooves then extend upwards for approximately two- thirds of the height of the base unit 100. The depth of the grooves tapers very slightly with increasing height, until the top portion of the grooves, which is arched (apse-shaped).

Note that after installation of the base unit into the road, the grooves do not extend above the surface of the road. In other words, the exposed surface of base unit 100 is the same as for a conventional base unit. This avoid the risk of anything becoming caught in the groove (such as wind-blown debris). However, in other embodiments, one or more grooves might be arranged to lo extend slightly above the road surface. This could then provide a facility for machine lifting of the base units from the road if so desired, e.g. for replacement or refurbishment.

The depth of the grooves at the bottom of each groove corresponds to approximately three-quarters of the thickness of the side walls. The total width of the three grooves for each side wall (in the longitudinal direction of the base unit) corresponds to approximately two-thirds of the total length of the central section of the side wall - i.e. approximately two-thirds of the portion of the side walls 101, 102 corresponding to recess 110, in other words, in-between front portion 106 (cavity 156) and rear portion 107 (cavity 157). It will be appreciated therefore that grooves 131, 132 excavate a substantial portion of side walls 101, 102, thereby leading to a significant weight reduction for base unit 100.

The grooves 131, 132 are separated by ridges 141, 142, representing portions of the side walls 101, 102 that retain the original thickness of the side wall. In particular, ridge 141A separates grooves 131A and 131B, ridge 14 IB separates grooves 131B and 131C, ridge 142A separates grooves 132A and 132B, and ridge 142B separates grooves 132B and 132C. The width of each ridge 141, 142 corresponds very approximately to half of the width of a groove 131, 132.

As can be seen best in Figure 1, the locations of the ridges 141, 142 on the outside of side walls 101, 102 match the locations of projections 121, 122 on the inside surface of side walls 101, 102. In other words, ridge 141A is aligned with projection 121A, ridge 141B is aligned with projection 121B, ridge 142A is aligned with projection 122A, and ridge 142B is aligned with projection 122B. It will be appreciated that in operation of a Repressible road stud, the wheels of passing vehicles may impart a force to a resilient insert to try to lift the insert from the base unit 100. This force must then be resisted by projections 121 and 122 in order to retain the insert within the base unit. The alignment of the ridges 141, 142 with corresponding projections 121, s 122 therefore ensures that the side walls have maximum thickness and strength to support the projections 121, 122 in retaining the insert within the base unit.

Although Figures 1 to 3 have illustrated one particular embodiment, it will be appreciated that in other embodiments the size, shape and/or number of recesses 131, 132 may be different 0 from those shown in Figures 1 to 3. For example, the recesses 131, 132 may not extend to the bottom of the base unit 100, and/or may have a horizontal profile that is not semi-circular - e.g. it could be V-shaped or rectangular instead. In addition, although all of the recesses 131, 132 in the illustrated embodiment have the same size and shape, in other embodiments, different recesses in the base unit may have different sizes and/or different shapes. One factor in determining the number, size and/or shape of the recesses may be compatibility with any machine used for handling the base unit, for example for laying them into a road.

Some embodiments may have more or fewer than three recesses in each side wall, for example, one, two or four recesses per side wall. Note that the size and shape of the recesses are constrained by the available space in a side wall, and may also be determined by various other considerations. For example, having one big recess (e.g. extending across all three recesses 131A, 131B and 131C from Figure 1) would not provide such an increased contact area, and so may not give such good keying as the illustrated embodiments. Alternatively, if a relatively large number of recesses were provided, then if these were as deep as those of the illustrated embodiments, they may be too narrow for a relatively viscous bonding material such as bitumen to flow into properly. In addition, the portions of the side walls 101, 102 between such multiple recesses (i.e. corresponding to ridges 141, 142) cannot be too thin in order to retain the strength of the side walls 101, 102. Conversely, if a relatively large number of shallower recesses were provided, then this would not provide such a weight saving for base unit 100, given the lesser amount of excavated material from the side walls.

It will also be noted that having three recesses in the illustrated embodiments provides two intervening ridges 141, 142, one corresponding to each projection 121, 122. However, other embodiments may have a different number of projections, or may have a different relationship between the intervening ridges (if any) and the projections. s

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 and their equivalents.

Claims

Claims 1. A base unit for a road stud, said base unit having a

substantially rectangular shape comprising a front portion, a back portion, and opposing side walls, wherein a cavity for retaining a resilient insert is located between the front portion, the back portion, and said opposing side walls, and wherein the external surface of each side wall incorporates one or more recesses.
2. The base unit of claim 1, wherein each recess extends to the bottom of the base unit.
3. The base unit of claim I or 2, wherein each recess comprises a groove running vertically down the external surface of the side wall.
4. The base unit of claim 3, wherein the top of each groove is arched.
5. The base unit of claim 3 or 4, wherein each groove has a rounded profile or horizontal cross-section.
6. The base unit of any preceding claim, wherein there are three recesses in each side wall.
7. The base unit of any preceding claim, wherein each recess extends vertically for at least half the height of the corresponding side wall.
8. The base unit of any preceding claim, wherein each recess extends at least halfway into the thickness of the corresponding side wall.
9. The base unit of any preceding claim, wherein the recesses are positioned so that after installation of the base unit into a road, the recesses do not extend above the road surface.
10. The base unit of any preceding claim, wherein the cavity is located between the recesses.

11. The base unit of any preceding claim, further comprising projections extending into said cavity from the side walls for retaining a resilient insert within the cavity, and wherein said projections are interspersed with the recesses.

s 12. A road stud comprising the base unit of any preceding claim and a resilient insert fitted into the cavity of said base unit.

13. A base unit for a road stud substantially as described herein with reference to the accompanying drawings.

Amendments to the claims Claims 1. A base unit for a road stud, said base unit having a substantially rectangular shape comprising a first end portion, a second end portion, and opposing side walls, wherein a cavity for retaining a resilient insert is located between the first end portion, the second end portion, and said opposing side walls, and wherein the external surface of each side wall incorporates two or more recesses, said base unit further comprising projections extending into said cavity from the side walls for retaining a resilient insert within the cavity, wherein said projections are interspersed lo with the recesses such that the projections arc located where the thickness of the side walls is not reduced by a recess.

2. The base unit of claim I, wherein each recess extends to the bottom of the base unit.

3. The base unit of claim 1 or 2, wherein each recess comprises a groove running down the external surface of the side wall perpendicular to the base of the unit.

4. T he base unit of claim 3, wherein the top Preach groove is arched.

5. The base unit of claim 3 or 4, wherein each groove has a rounded profile or cross-section in a plane parallel to the base of the unit.

6. The base unit of any preceding claim, wherein there are three recesses in each side wall.

7. The base unit of any preceding claim, wherein each recess extends in a direction perpendicular to the base of the unit for at least half the height of the corresponding side wall.

8. The base unit of any preceding claim, wherein each recess extends at least halfway into the thickness of the corresponding side wall.

9. The base unit of any preceding claim, wherein the recesses are positioned so that after installation oi'the base unit into a road, the recesses do not extend above the road surface. (I

: ':: 2. ': . ' ::: : '.' 10. The base unit of any preceding claim, wherein the cavity is located between the recesses.
11. A road stud comprising the base unit of any preceding claim and a resilient insert fitted into the cavity of said base unit.
12. A base unit for a road stud substantially as described herein with reference to the accompanying drawings. (3

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