Street furniture safety device

An electrical isolation system specifically adapted for use in street furniture (10) having an electrical supply (24) to working electrical components (20) is described. The system includes an impact sensor (22) located in use within the street furniture and a monitoring unit (30) and an electrical isolator (32) located in use remote from the street furniture. When the impact sensor is activated a signal is sent to the monitoring unit which sends a signal to the electrical isolator to disconnect the electrical supply to the working components of the street furniture. A method of providing electrical isolation in street furniture (10) having an electrical supply (24) to working electrical components (20) is also described. In the event that the street furniture is damaged, the method including the steps of: a) sensing an impact suffered by the street furniture; b) sending a signal to indicate that an impact has occurred to a monitoring unit at a location remote from the street furniture; c) the monitoring unit acting to disconnect the electrical supply to street furniture at the location remote from the street furniture.

DESCRIPTION OF INVENTION

The invention relates to a safety device for street furniture and in particular to an isolation system for use in street furniture which include an electrical supply, such as for examples a traffic signal (commonly referred to as a traffic light), street light, or illuminated sign.

Many installations of street furniture which include an electrical supply are located very close to the roadway, and thus are vulnerable to being collided with by vehicles. When such a collision occurs the street furniture itself represents a danger to the vehicles and its occupants, in that it might remain in place as a rigid structure ensuring that the vehicle suffers very significant damage or it might fall onto the vehicle. Recently laws or new practices have been introduced in many territories which require or advise that, at least in some circumstances such as on roads with a speed limit of 50 mph or higher, the street furniture collapses in some predetermined manner in order to minimise the physical danger the street furniture represents.

In addition the electrical supply itself can represent a danger to the people involved in such an accident, or those who arrive to assist those involved, or those who subsequently arrive to repair the street furniture. If the electrical supply remains connected to the damaged street furniture then live electrical wires may be open to the elements and to being touched by such people, thus leading to risk of electric shocks being inflicted on those people, and to sparks igniting spilt fuel or chemicals.

In some territories there are now also requirements to disconnect the electrical supply to the street furniture in the event of damage to it, and in general such safety cut-off systems are being included in new installations and in some cases in refurbishment of existing installations. In the United Kingdom at present the only system available to implement this requirement includes an in-line socket and connector which are held under tension and are designed to part company when the street furniture is badly damaged, thus disconnecting the electrical supply to the street furniture within the street furniture itself. However, this has two distinct disadvantages. First, plugs and sockets used in this way tend to be unreliable, and second they only work to disconnect the electrical supply in certain kinds of accidents and then only within the street furniture installation itself. This means that a live feed still exists to the base of the street furniture and this still represents a risk of electrical shock in some circumstances, in particular to those people who come to repair the street furniture.

It is an aim of the present invention to provide an alternative electrical isolation system for use in street furniture.

According to a first aspect of the present invention there is provided an electrical isolation system as set out in claim1. Further features of the electrical isolation system according to the invention are set out in dependent claims2to10.

According to a second aspect of the present invention there is provided a method of providing electrical isolation as set out in claim11. Further features of the method according to the invention are set out in dependent claims12to15.

According to a third aspect of the present invention there is provided street furniture having an electrical supply to working electrical components and including an electrical isolation system according to the first aspect of the invention and/or which operates in accordance with the method of the second aspect of the invention.

Referring first toFIGS. 1 and 2, a simple cross-roads junction having traffic signal control is illustrated in two different views. There are four traffic signals10, one at each road entry to the junction, located close to the roadway12and thus vulnerable to being collided with by vehicles. The traffic signal control for the junction includes a termination cabinet14and a control cabinet16(as in the prior art, for normal control of the traffic signal installation at the junction, and thus which will not be described further here), located at a greater distance from the road way than the traffic signals10are, and in this example back off the pedestrian pavement18in a grassed area19. It should be understood that a single cabinet may be provided in place of the two described here.

Referring now also toFIG. 3, a schematic view of the traffic signal control for the junction is illustrated. In each traffic signal10are working components20of the traffic signal, as in the prior art and thus which will not be described further here, and an impact sensor22, such as an accelerometer although any suitable kind may be used. The working components20of the traffic signal10have an electrical feed24and the impact sensor22has an applied voltage via line26. The impact sensor22is, in this case, a switch which is normally closed but which when triggered is open.

In the termination cabinet14are a monitoring unit30and a plurality of isolators32, in this case four, one for each traffic signal10. The applied voltage lines26to the impact sensors22of each traffic signal10are connected to the monitoring unit30. The electrical feed24to the working components20of each traffic signal10are each connected to an isolator32which is controlled by the monitoring unit30. Each isolator32, typically an MCCB (multi-pole circuit breaker) although any other suitable type may be used, receives an electrical feed34from the control cabinet16.

The monitoring unit30includes visual indicators (not shown) for the supply of power to each traffic signal10and for the activation of each impact sensor22, although these could be omitted. Preferably the monitoring unit30also includes visual indicators for the status of other features of the traffic signals10, such as to indicate failure of a bulb, or a software problem within the controls of the junction in the control cabinet16. The monitoring unit30is also provided with additional contacts36,38for integration into a telemetry system if provided, such that any failures noticed by the monitoring unit30, or a complete power failure at the junction, can automatically be reported to a remote control room, but these can be omitted if not required.

The electrical isolation system operates as follows. When an impact sensor22is activated, the switch opens (effectively sending a signal) and the monitoring unit30identifies that it has gone open circuit. In response the monitoring unit30disconnects the voltage to the sensor22via electrical feed26and lights the respective visual indicator. In addition the monitoring unit30provides a constant latched output to the respective isolator32resulting in disconnection of the electrical supply to the working components20of the respective traffic signal10via the supply24, and the relevant visual indicator is activated to show the disconnection. This disconnection occurs rapidly after activation of the impact sensor22, (e.g. within 400 milliseconds) although any time period which meets the relevant regulations (if any) can of course be provided for.

The latched output to the respective isolator32prevents inappropriate re-energising of the supply to the working components20of the respective traffic signal10. There is a reset switch (not shown) on the monitoring unit30for each feed to an impact sensor22. However, even if the reset switch is activated the monitoring unit30maintains the latched output to the isolator32until it receives a further signal, in this case a return voltage via line26, indicating that the sensor22has been reset or replaced. Receipt of such signal also switches off the visual indicators for activation of the sensor22and disconnection of the electrical feed24.

Hence, when an impact is sensed the electrical supply to a traffic signal10is cut off quickly at a remote location and cannot be reconnected until such time as the impact sensor22has been reset or replaced. Thus, the electrical isolation system of the invention provides a significant improvement on safety when compared with the prior art.

Alternative forms of impact sensor, such as those which actively send a signal, may of course be used in place of the switch described above. In addition alternative forms of electrical isolator may be employed.