EP1948869B1

EP1948869B1 - Breakaway base for road columns

Info

Publication number: EP1948869B1
Application number: EP06812815.6A
Authority: EP
Inventors: Oddbjörn NES
Original assignee: Saferoad As
Current assignee: Saferoad As
Priority date: 2005-11-07
Filing date: 2006-11-07
Publication date: 2016-04-06
Anticipated expiration: 2026-11-07
Also published as: EP1948869A1; NO20055220D0; NO325205B1; WO2007053040A1; DK1948869T3; EP1948869A4

Description

The invention relates to a breakaway base according to the introductory part of claim 1, for road columns, particularly road columns for roads with high velocity and heavy traffic.

Background

Road columns with a breakaway base (slip base) have been known for years. The brochure "Avskjæringsledd" published by Örsta Stålindustri January 1997, describes a breakway base with two triangular dishes bolted together. The breakaway base is clamped together with three bolts, one at each corner. The dishes have open slots instead of bores. This lets the upper dish and the column slide out of the bolts upon an impact, hence the term "slip base" Between the dishes is inserted a thin (0,7 mm) galvanized intermediate sheet or dish with a hole in each corner for the bolts. This is to avoid the bolts "working" out of the slots due to vibration if the bolts are not tightened. The bolts are easily broken out of the intermediate dish due to its thinness.
Columns with such a breakaway base have functioned well, but in some cases, the columns have not been released. Due to this, the authorities in some countries have turned negative to this prior art design. The reason for not releasing may have been due to a car impacting the road column at some height above the base, e.g. at an opening, when the road column is arranged on a downward slope. The friction of the breakaway base is relatively high, thus when a car impacts at some distance from the base, the bending moment increases at the base thereby increasing the friction. The tube of the road column lacks the strength to transfer the load necessary to release the breakaway base and the road column will break at the point of impact. There is also a risk that the breakaway base will sieze due to corrosion between the dishes.
Further, US 6 540 196 B describes a breakaway base according to the preamble of claim 1.

Objects

The main object of the invention is to ensure that the breakaway base releases even when a car impacts it at some distance from the base. A further object is to provide a breakaway base which is not liable to siezing and decreasing breakaway function due to long service and weathering.

The Invention

The invention is stated in claim 1. Further features of the invention are stated in claims 2-9.
With this breakaway base, the release of the breakaway base is ensured at an impact, also when the impact is at some distance from the base, when the base is located on a downward slope.
As stated in claim 1, rollers particularly of metal are used as friction reducing elements. Multiple rollers are arranged between the dishes (foot flange and carrier plate) to reduce the friction, and the dishes having the friction reducing elements may be circular to arrange the rolls optimally along the edge, and make the dishes more resistant to bending of the edges.
The novel breakaway base may have a short straight edge for arrangement parallel to the road/direction of traffic, so that the rollers may be perpendicular to the road and enhance the effect at a collision. Tests have also been conducted with rollers arranged parallel to the road, also giving reduced friction compared to prior art breakaway bases.
Further details of the invention will appear from the examples.

Examples

The invention is described more in detail with reference to the drawings, wherein

Figure 1 shows an exploded perspective view of an embodiment of the invention,
Figure 2 show a cross section elevation view with an axial section of the socket with the breakaway base of Figure 1,
Figure 3 show a plan view of a sheet according to the invention, and
Figure 4 shows an alternative spacer sheet with roller holders.

The main elements of Figure 1 are a road column 11, a socket 12 provided for mounting on a fundament (not shown). The road column 11 is manufactured of a conical or stepwise tapered steel tube 13 with a foot flange 14 welded on the lower end of the steel tube 13 with three supporting webs 15. For short road columns for low loads, the webs is may be omitted. The flange 14 has a straight part 16 intended, in use, to be parallel to the road edge, and three notches 17 spaced 120° around the circumference. The notches 17 are intended to accommodate bolts 18 to be described in the following. The flange 14 can also be a closed dish.
The socket 12 has a base dish 19, in the illustrated embodiment quadratic, with a bore hole 20 at each corner for fastening to a fundament not shown, e.g. of concrete, with imbedded bolts. The base dish 19 carries a carrier plate 21 on a tubular collar 22, said parts being joined by welding. The carrier plate 21 of this embodiment has a mating design of notches 23 as the foot flange and a corresponding flange design. This implies having a straight edge 24. The nuts for fastening the bolts 18 are designated 25, while the nuts for fastening the base dish 19 have reference numeral 31.
Intermediate the foot flange 14 and the carrier plate 21 are embedded series of rollers 26 of steel or similar pressure resistant material. The rollers 26 are arranged in openings 28 in an intermediate or spacer sheet 27 shown in Figure 3. The rollers may have a diameter of 6 mm.
The design of the arrangement of the rollers 26 shown in Figure 3 is particularly advantageous, but other arrangements can also be used.
As an alternative to the openings 28, slots accommodating multiple rollers can be used. The intermediate sheet 27 is relatively thin, e.g. 0,7 mm, and is provided with holes 29 for the bolts 18. The purpose of the intermediate sheet 27 is twofold,: 1) to keep the position of the bolts until the sideward load on the breakaway base exceeds a certain level, tearing off the intermediate sheet, and additionally 2) to keep the rollers 26 in place.
The design of the openings 28 and thus of the arrangement of the rollers 26, is shown in Figure 3. The rollers 26 are arranged with the axis perpendicularly to the straight edge 30, which, when the intermediate sheet 27 is mounted, will be parallel to the road edge. The friction reducing elements preferably are arranged in multiple groups, e.g. three groups, distributed over the face of contact.
Figure 2 shows how the rollers 26 are clamped between the foot flange 14 and the carrier plate 21. This embodiment has an annular socket 19 with a bevelled inner edge 32 joining a central collar 33.
The number of rollers is determined by the maximum bending torque, to avoid pressing of the rollers into the dishes or the rollers being deformed. In the intermediate sheet 27, with the openings for the rollers, the rollers are fixed by wax or a glue sheet. This will make the mounting easier. Road columns with breakaway base according to the invention are normally delivered factory mounted, to ensure proper mounting and right make up torque of the bolts.
Figure 4 shows an embodiment of an intermediate sheet 34 with rectangular openings 35 in a corresponding symmetrical arrangement as in Figure 3, for rollers 36. In this case groups of four rollers 36 are inserted in cassette frames or roller holders 37 arranged in the openings 35. This makes the transport of the rollers and the mounting of the rollers in the breakaway base easier and less demanding.

Claims

Breakaway base for road columns (11), wherein a carrier plate (21) is mounted on a carrier (19) being anchored in the ground, as carrier for a foot flange (14) for the lower end of the column (11), the carrier plate (21) and the foot flange (14) being connected with at least two axially arranged fastening bolts (18) secured with nuts, wherein at least one of the foot flange (14) and the carrier plate (21) has notches (17, 23) for the bolts (18) allowing the release of the bolts (18) upon a sideway impact, and wherein an element, particularly an intermediate sheet (27) with holes (29) for the fastening bolts, is arranged to keep the bolts (18) in place under normal use, multiple friction reducing elements (26) being arranged to reduce the friction at sideway slip between the foot flange (14) and the carrier plate (21), characterized in that the friction reducing elements are rollers (26), particularly of metal.
Breakaway base according to claim 1, characterized in that the rollers (26) are arranged with their axis perpendicularly to an adjoining road edge.
Breakaway base according to any one of claims 1 to 2, characterized in that the intermediate sheet (27) has openings (28) for the friction reducing elements (26).
Breakaway base according to any one of claims 1 to 3, characterized in that the foot flange (14) and the carrier plate (21) are at least generally circular.
Breakaway base according to claim 4, characterized in that at least one of said elements (14, 21) has a straight part (16, 24) for arrangement parallel to the road edge
Breakaway base according to any one of claims 1 to 5, characterized in that the friction reducing elements are arranged in multiple groups distributed on the contact surface.
Breakaway base according to claim 3, characterized in that the intermediate sheet (27) is provided to keep the friction reducing elements during mounting.
Breakaway base according to any one of the claims 1 to 7, characterized in that it comprises roller holders (37) holding groups of rollers together during mounting and use.
Breakaway base according to claim 8, characterized in that the roller holders (37) are of frame structure, preferably with four rollers (36) in each.