GB2462085A - Single LED traffic bollard illuminator - Google Patents

Abstract

A single high powered light emitting diode (LED) is current driven to restrict the light output to below its rated output, to reduce heat generation, and is centrally positioned in a traffic bollard D. The LED can be mounted on a standard replaceable gear tray B. The LED life is extended and produces an evenly distributed light with a 120° arc. A heatsink and a moulded lens may not therefore be required.

Description

Improvements to Traffic Bollard Illumination Traffic Bollard Illumination has progressed from internally mounted incandescent lamps, internally mounted fluorescent lamps, to subterranean fluorescent lamps, and now with subterranean Light Emitting Diodes (LED), with progressive reduction in capital, maintenance and energy costs. The means of illumination are housed on a gear tray which fits into a cast aluminium chamber fitted with a translucent flat or lens shaped weatherproof cover, the light being projected upwards into a hollow plastic bollard. In most situations repair to a traffic bollard is affected by plugging in a replacement gear tray and fitting a new lens cover and bollard moulding.

LED lamp life and efficiency is directly related to the operating temperature. The accepted way of using LED's in bollards is to provide a number of lamps, typically 6 to 12 on a gear tray, all running at their rated power consumption and rated temperature with the provision of good thermal contact between the LED and an expensive heat sink to conduct and radiate the excess heat produced to maintain the operating temperature within the LED manufacturer's limits. During routine maintenance an LED gear tray can replace trays using previous higher energy consumption light sources, but the array of LED lamps can develop uneven light spots during their life, especially when the circuitry driving the LED controls the voltage applied, not the current passing through.

This invention adopts the novel concept of running one LED of a high power capacity at, typically, only one third of its rated output. This has an immediate effect on installation cost by eliminating the need for special heat sinks; extending the life of the lamp; simplifying the circuitry to just one lamp; reducing energy cost. Using one centrally sited light source with a built in wide angled arc is a unique feature providing an even distribution of light and an opportunity to achieve the maximum light to power ratio, eliminating the need for an expensive moulded lens over the gear tray. The existing practise of an array of LED's would require expensive optics to focus the available light in this way, even more uneven pin points of light would result if these type of LED fittings were run below rated output. Typically this high powered LED running below capacity consumes lOW, compared to 36W for an array of 12 off 3W LED's running at rated capacity, with the same or improved light output meeting the stringent Highways Agency Lighting Requirements.

Furthermore many existing LED driver circuits have a voltage applied which is calculated to provide the lamp manufacturers rated power consumption, any voltage surges will be more likely to overload the lamp, eventually affecting lamp life. During the life of the lamp, particularly when running many hours at maximum rated temperatures, as lamp efficiency reduces, with substantially constant voltage the power consumption and light output falls. In this invention running the LED below its rated output accommodates voltage surges and the LED driver' circuit controls the current to achieve the calculated power consumption, typically one third of the rated power, so as lamp efficiency falls during lamp life the power consumption and light output is maintained.

The present invention provides a bright, long life, energy efficient light source running at such a low temperature that it lends itself to being totally encapsulated in a translucent resin. The principal has wide applications for lighting in other situations where adverse weather conditions apply, such as other traffic signalling applications, onshore and offshore nautical and aeronautical situations, and, more importantly, Class III hazardous operating areas, typically petrol forecourts, tunnels, tank inspections etc. A particular way of applying this invention is described with reference to the attached drawings.

Figure 1 shows the schematic positioning of the parts of the bollard.

Figure 2 shows the positioning of components on the gear tray.

In figure 1 the gear tray A is shown in a breakaway view in the base of the bollard mounted on the cast aluminium subterranean chamber B. Part of the translucent lens C is visible in this view, the whole being surmounted by D, the opaque traffic bollard body suitably marked. Illustrated in the breakaway section is the included angle of the cone of light, 1200 in this example, which is a feature of the construction of the lamp, not the lens. Light is internally projected evenly over all the area of the bollard body U. In figure 2 a plan view of the aluminium gear tray A shows the positioning of the Light Emitting Diode E, a one piece high powered LED rated at 30W but driven at lOW, between 30 and 50% of conventional energy consumption levels of other LED traffic bollard installations. Housing a multi-chip on one substrate, this is effectively a single point light source. The device is secured to the gear tray with two fixing screws, which thermal contact is adequate to dissipate the slight heat produced. The current driver F is indicated. The plug, socket and fuse assembly are not shown.