WO2006067267A1

WO2006067267A1 - Led illuminator for traffic control

Info

Publication number: WO2006067267A1
Application number: PCT/FI2005/000537
Authority: WO
Inventors: Kari Taskula; Vesa Rasinen
Original assignee: Oy Sabik Ab
Priority date: 2004-12-23
Filing date: 2005-12-19
Publication date: 2006-06-29
Also published as: EP1829011A4; FI117178B; FI20041660A0; NO338004B1; EP1829011A1; EP1829011B1; NO20073845L

Abstract

An illuminator for control lights used in traffic control, such as traffic lights, railway signal heads or line lights for waterborne traffic, in which illuminator the light source consists of one or more LEDs (2) fitted in lens holders (3) by means of which they can be connected onto a connection base (1) and which illuminator comprises optical feedback wherein one or more light-sensitive detectors (4) are arranged on the connection base (1) in connection with the LEDs used as light sources, some of the light coming from the LEDs being conveyed to said detectors, by means of which an optical feedback is formed for monitoring and/or adjusting the operation of the illuminator. The lens holders (3) are at least partly permeable to light so that light emitted laterally from the LEDs can be conveyed to the light-sensitive detectors fitted on the connection base.

Description

LED ILLUMINATOR FOR TRAFFIC CONTROL

The present invention relates to an illuminator for control lights used in traffic control, such as traffic lights, railway signal heads or line lights for waterbome traffic, said illuminator having a light source which consists of LEDs fitted on a connection base and which comprises optical feedback arranged for monitoring and control of the operation of the illuminator.

At present, illuminators based on incandescent light sources, such as incandescent lamps, are still used in the control of land and waterbome traffic. Incandescent lamps involve the problems of high energy consumption in relation to the quantity of light produced, a short service life and consequent high maintenance costs.

LEDs traditionally have a considerably lower power consumption than incandescent lamps. In addition, they have a longer service life, so they are very well applicable for use e.g. in traffic control lights. For example, patent application Fl 20002733 discloses a traffic control light in which the light source consists of LEDs fitted on a connection base. This publication describes an illuminator intended for low-power LEDs with a power rating below 1 W, and an apparatus for its control. The control apparatus disclosed in this publication utilizes optical feedback, which allows the operation of the LEDs used as light sources to be monitored and regulated, so that information is obtained in all situations about the actual operational condition of the control light. In addition, the optical feedback can be utilized in the control of the luminous intensity of the light source.

In the publication referred to, LEDs are connected onto the surface of a circuit board. The number of LEDs is typically over 10. Placed over the circuit board is a colorless or colored transparent lens dome part made of plastic, e.g. polycarbonate, and having inside it a Fresnel lens opposite to each LED. To monitor the operation of the illuminator, it is provided with optical feedback, which is used to monitor the operation of the LEDs by passing some of the light of the LED via the optical feedback to a control electronics unit, which takes care of detection and adjustment of the luminous intensity of the light source as well as level measurement and fault indication for failure and disturbance situations. For optical feedback, the circuit board is provided with light-sensitive transistors, which are arranged between the LEDs on the same side of the circuit board and which detect the light coming from the LEDs by means of reflectors mounted between the lenses. In recent times, there has been a pronounced increase in the power of LEDs. At present, high-power LEDs with a power rating above 1 W, even 10 W, are available. By using such high-power LEDs, the number of LEDs needed in traffic control lights can be significantly reduced, and the same luminous intensity that was ob- tained before with a large number of low-power LEDs can now be achieved with a smaller number of LEDs.

High-power LEDs like this are mounted on the surface of a circuit board. To obtain a better thermal conductivity, the circuit board is often made of aluminum or a ce- ramie material, but it is also often possible to use a conventional glass fiber circuit board. High-power LEDs can also be mounted directly on the surface of a cooling plate.

Each LED is provided with an external optical lens, the lens is secured to a lens holder surrounding the LED. Normally the lens holder is made of a non-transparent material, but if the lens holder is manufactured from a transparent material, then it is possible to get a sample of the light emitted by the LED. In the case of high- power LEDs, the light is directed into a very large opening angle, typically even over 100°, in the upright direction of the LED. In prior-art solutions, the lens holders completely prevent the light from being directed sideways from the LED.

The object of the present invention is to create a traffic control light expressly applicable for high-power LEDs and provided with optical feedback, so that, as in the case of Fl patent application number 20002733, information is obtained about the actual operational condition of the control light. In the solution of the invention, the lens holder is at least partly permeable to light, and light-sensitive elements are arranged on a connection base to receive expressly this laterally directed light. The details of the features of the apparatus of the invention are presented in the claims below.

The invention makes it possible to achieve a very simple and reliable monitoring arrangement expressly for high-power LEDs with a power rating above 1 W for the monitoring of traffic control lights. In addition, the optical feedback can be utilized in the regulation of the luminous intensity of the light source.

In the following, the invention will be described in detail with reference to an example and the attached drawing, wherein figures 1 and 2 present a perspective view of a LED control illuminator according to the invention, which is suited for use in traffic control lights and which incorporates optical feedback according to the invention.

Figures 1 and 2 illustrate an illuminator as used e.g. in a railway signal head, which uses a light source consisting of high-power LEDs with a power rating above 1 W. The illuminator produces a unidirectional light beam, which is directed towards the locomotive of a train approaching from afar, so that the locomotive driver can perceive the light emitted by the signal head in time and act according to the color of the light. The illuminator has a frame part with e.g. an edge flange allowing it to be fastened to signal heads, e.g. instead of illuminators with incandescent lamps. Inside the frame part it is possible to fit a transformer and other devices needed for the control of the illuminator, as well as a circular circuit board 1. The control electronics (not shown) are fitted in connection with the circuit board 1 or on a separate circuit board.

Connected to the surface of the circuit board 1 are the LEDs 2 and the lens holders 3 surrounding them. The lens holders are connected to the circuit board 1 e.g. by means of connecting studs or with glue, the LEDs are connected to the circuit board 1 typically by soldering or gluing. In this embodiment example, the number of LEDs is 18, and typically over 10, but depending on the luminous intensity required, a smaller number of LEDs can also be used. Placed over the circuit board 1 is a colorless or colored transparent lens dome part made of plastic, e.g. polycarbonate. The outer surface of the lens may be smooth and planar, so that, as the lenses form the outer surface of the illuminator, they are easy to keep clean.

To allow the operation of the illuminator to be monitored, it is provided with optical feedback, which is used to monitor the operation of the LEDs by passing some of the light of the LED 2 via the optical feedback to the control electronics, which can take care of detection and adjustment of the luminous intensity of the light source, level measurement and fault indication for failure and disturbance situations.

For optical feedback, the circuit board 1 is provided with light-sensitive transistors 4 arranged between the LEDs on the same side of the circuit board 1. The light coming sideways from the LEDs is detected by the transistors 4, whose output signals are passed to the control electronics. Thus, some of the light of the LEDs 2, coming laterally through the transparent lens holder 3 in a slightly downward oblique direc- tion, is conveyed directly, i.e. without reflectors or other guide elements, to the pho- totransistors 4 placed against the circuit board.

The phototransistors can be connected to monitor either one LED, in which case a separate phototransistor can be placed beside the LED as in Fig. 1 , or alternatively an array of LEDs, in which case a phototransistor is placed at the middle of e.g. four LEDs.

As shown in Fig. 2, inside the lens dome part there may be a plate 5 which has an aperture in the area of each LED and which is affixed to the circuit board via a screw fastening 6. The aperture plate 5 prevents light coming from outside the illuminator from reaching the phototransistor 4, so the illumination conditions outside the illuminator have no disturbing effect on the operation of the monitoring and regulating equipment of the control light. In addition, the plate protects the detectors against other harmful types of radiation (e.g. UV and IR radiation) coming from outside the illuminator. The aperture plate also ensures in a mechanical sense that the lenses will remain secured in their lens holders, and therefore impacts and vibration applied to the illuminator device can not dislocate the lenses.

It is obvious to the person skilled in the art that different embodiments of the invention are not exclusively limited to the example described above, but that they may be varied within the scope of the claims presented below. A sufficient number of phototransistors can be placed in the illuminator so that sufficiently reliable information about the operation of the illuminator is obtained.

Instead of using a transparent lens holder, it is possible to provide the lens holders e.g. with openings to direct laterally emitted light to the light-sensitive transistors.

Claims

1. An illuminator for control lights used in traffic control, such as traffic lights, railway signal heads or line lights for waterborne traffic, said illuminator having a light source which consists of one or more LEDs (2) fitted in lens holders (3) by means of which they can be connected onto a connection base (1) and further comprising optical feedback wherein one or more light-sensitive detectors (4) are arranged on the connection base (1) in connection with the LEDs used as light sources, some of the light coming from the LEDs being conveyed to said detectors, by means of which an optical feedback is formed for monitoring and/or adjusting the operation of the illuminator, characterized in that the lens holders (3) are at least partly permeable to light so that light emitted laterally from the LEDs can be conveyed to the light-sensitive detectors fitted on the connection base.

2. An illuminator according to claim 1, characterized in that the lens holders are made of a transparent plastic material at least in the direction of the light- sensitive element.

3. An illuminator according to claim 1 , characterized in that the detectors are connected onto the connection base (1) at the level of the lower part of the lens holder (3).

4. An illuminator according to claim 1 , characterized in that the light-sensitive elements have been fitted to monitor one LED, in which case a separate light- sensitive element is placed beside the LED.

5. An illuminator according to claim 1 , characterized in that the light-sensitive elements have been fitted to monitor an array of LEDs, in which case the photo- transistor is placed at the middle of or beside a number of LEDs.

6. An illuminator according to claim 1, characterized in that the illuminator comprises a lens dome part and inside it a plate (5) with an aperture opposite to each LED, said plate preventing light coming from outside the illuminator from reaching the light-sensitive elements.

7. An illuminator according to claim 1, characterized in that the LED is a high- power LED having a power rating of at least 1 W.