GB2448615A

GB2448615A - Photovoltaic lamp for use in conjunction with a traffic road cone

Info

Publication number: GB2448615A
Application number: GB0807187A
Authority: GB
Inventors: John Leslie Pritchard
Original assignee: ACCI LITE Ltd
Current assignee: ACCI LITE Ltd
Priority date: 2007-04-18
Filing date: 2008-04-18
Publication date: 2008-10-22
Also published as: GB0707436D0; GB0807187D0

Abstract

A lamp for use in conjunction with a traffic cone is disclosed. The lamp comprises a housing that has a tubular body portion (10) and a head portion (12). The head portion is disposed on an axial end of the body portion. The body portion contains a rechargeable battery pack. The head portion contains a light-emitting device and control circuitry, and carries a photovoltaic panel (30) that is directed axially away from the body portion. Under the control of the control circuitry, the photovoltaic panel can charge the battery pack when the ambient light is in excess of a trigger threshold, and the battery pack can power the light-emitting device when the ambient light is below a threshold. The output of the photovoltaic cell is monitored to determine the ambient light level, and control operation of the lamp in response thereto.

Description

Lighting apparatus This invention relates to lighting apparatus. In

particular, it relates to lighting apparatus that can be deployed and left unattended for an extended period of time without connection to a supply of mains electricity, for example in road works or construction site.

There are many places in which lighting units are deployed to indicate a temporary Q 10 hazard. One particularly important example is in a site of road works. Traffic cones are used to delimit traffic lanes so that traffic is separated from road workers. These Q work well during daylight, but must be supplemented by lights to be effective after IC) dark.

Conventionally, the lights used on road cones use non-rechargeable batteries, which is undesirable from both an economic and an environmental point of view, and the requirement for frequent replacement of the batteries is very labour-intensive. They are also carried on a cone by means of looping a component of the lamp over the top of the cone, which makes them insecure and difficult to deploy. An example is disclosed in GB-A-2 287 271.

An aim of this invention is to provide a lamp for use in combination with a traffic cone that is a substantial improvement upon lamps that are presently available.

To this end, the invention provides a lamp for use in conjunction with a traffic cones set forth in Claim 1.

The physical disposition of a lamp embodying the invention is advantageous for mounting at the top of a traffic cone, while its electrical components allow it to operate without regular replacement of batteries.

The head portion and the body portion are most typically of circular cross-section, and are coaxial, and the head portion is typically of a greater diameter than the body portion.

The control circuitry most advai-itageously determines the ambient light level by measurement of the output of the photovoltaic panel. This avoids the need to provide a separate light sensor for this purpose. In order to avoid the need to calibrate the lamp during manufacture, it is preferable that, upon being switched on for the first time, the controller determines the ambient light level and stores that light level as the trigger threshold.

To provide a means by which the battery can be charged, an electrical connection 0 socket to which electrical power can be delivered to charge the battery pack. There Lt) 15 may also be an electrical connection socket to which an option key can be connected to switch on the lamp (which may be the same socket as the charging connector).

One of a plurality of option keys may be connected to the socket, a mode of operation of the lamp being selected by the particular key that is inserted into the socket. The modes of operation typically include steady illumination and flashing illumination.

Advantageously, the light-emitting device includes one or more light-emitting diodes.

These are particularly energy-efficient. The lamp may be configured such that a variable number of light-emitting diodes can be installed in dependence upon the amount of light that the lamp must produce for a particular function. The perceived brightness of the LED(s) can be varied using pulse-width modulation of power applied to them.

An end part of the body portion that is remote from the head portion may be tapered.

This facilitates insertion of it into a hole, as present in the top of a cone. The head portion may be tapered close to its connection with the body portion. This provides stability when the lamp is installed in a cone.

From another aspect, the invention provides, in combination, a traffic cone and a lamp according to any preceding claim, in which the traffic cone has an opening that is upwardly-directed in use, the body portion of the lamp being inserted into the opening such that the body portion rests upon the top of the cone.

The weight of the batteries within the body portion ensure that the lamp is stable when so installed.

An embodiment of the invention will now be described in detail, by way of example, and with reference to the accompanying drawings, in which: Co Figure 1 illustrates an embodiment of the invention; Figure 2 is a flowchart that illustrates operation of the embodiment of Figure 1; IC) Figure 3 is a block diagram of the functional components of the embodiment of Figure 1; and Figure 4 illustrates a second embodiment of the invention; Figures 5 and 6 are top and bottom views of a third embodiment of the invention; Figure 7 is a cross-sectional view of the embodiment of Figures 5 and 6 Figures 8 and 9 show a fourth embodiment that is a variation on the embodiment of Figures 5 to 7; and Figure 10 shows the embodiment of Figures 8 and 9 mounted upon a traffic cone.

With reference to Figure 1, an embodiment of the invention is a lamp for use in combination with a road cone.

The lamp comprises a housing that includes a stem 10 and a head 12. For use, the lamp is in the disposition shown in Figure 1, with the head uppermost, and the following description will assume that the lamp is in this disposition in its use of terms such as "up", "down", "higher", "lower", and so forth.

The stem is a cylindrical metal tube of approximately 33 mm outer diameter. This diameter is chosen such that it is a close fit within the holes that are commonly formed in the uppermost end of a moulded plastic road cone. It is approximately 250 mm in length. A lower end portion of the stem 10 is constituted by an end cap 14 that closes the lower end of the stem. An externally accessible electrical connection socket (not shown) is contained within the end cap 14. The end cap is formed to have a taper to help guide it into the top of a cone. Within the stem 10, three cylindrical rechargeable nickel/metal hydride (NiMH) batteries are contained, arranged in series. The batteries together form a 3.6V battery pack that comprises Lt) three cells of 1.2 V, giving a total energy storage capacity of 4000-4500 mAh.

The head 12 is circular in cross-section. The head 12 has a lower plastic portion 16 that tapers outwardly and upwardly from the stern 10, to a cylindrical region. The plastic portion serves as an enclosure for an electronic control system of the lamp.

Above the cylindrical region there is a cylindrical lens 20. Above the lens 20, the head 12 includes a collector 22 of circular section and diameter larger than the lens 20. Within the lens there are one or more light-emitting devices which are, in this embodiment, light-emitting diodes. The number of LEDs installed within the lamp is determined by both the required light output level and direction -this embodiment can be provided with one or more LEDs. It is also possible to install a reflective shield within the lens 20 to occlude part of the light output. For example, it is sometimes necessary to ensure that only traffic approaching the lamp from one direction can see it, so that light emerges from the lens over only a part, for example, extending 180 around the periphery of the lens.

The main components of the electronic control system will now be described with reference to Figure 2.

Within the collector 22 there is mounted a photovoltaic cell 30. The cell faces upwardly and is covered by protective transparent plastic.

The control system is operated by a programmed microcontroller 34 that incorporates non-volatile memory. When there is adequate ambient light falling on the pliotovoltaic cell 30, it provides charge current for the battery pack 40. The charge current is measured by a current monitoring stage 32, and the magnitude of the current is fed to an input of the microcontroller 34. The microcontroller 34 interprets the measurement of the current to determine the level of ambient light, and thereby determines whether the lighting unit should be on or off. It should be noted that no device is dedicated to measurement of light -the photovoltaic cell 30 serves both a source of power and as a light measurement device.

Q It is undesirable to rely upon component values or the effectiveness of the IC) 15 photovoltaic cell 30 to calibrate the control system. Therefore, a system of automatic calibration is implemented. The first time the lamp is powered, the light level (as determined by the output of the photovoltaic cell 30) is recorded and the value is stored in non-volatile memory. During subsequent operation of the lamp, the light level thus measured is used as a threshold level for switching the lamp on and off.

Thus, the light unit can be automatically calibrated. However, the microcontroller 34 is configured such that there is a difference between the level of light at which the lamp switches on and off. Thus, there is some hysteresis in a switching cycle.

Likewise, the level of ambient light is sampled over a period of, say, two minutes.

This avoids false readings that might occur, for example, if a vehicles headlamps illuminate the sensor after dark or if the sensor is fleetingly shadowed during the day.

The threshold can be set in the range of 250-1000 lux.

The voltage of the battery pack 40 is monitored by the voltage monitoring stage 36.

The microcontroller 34 uses the measured voltage to limit the charge current when the battery pack 40 is fully charged, as might happen when there is comparatively little darkness, as during the height of summer.

The connection socket can receive an option plug 42. When a user inserts a plug 42 into the socket, this is detected by the microcontroller 34, which then changes its operation accordingly. When no plug 42 is fitted, the unit is switched off, but the photovoltaic cell 30 continues to charge the battery pack 40 when adequate light is available. When an option plug is fitted, the unit is switched on. Alternative plugs are provided that cause the lamp to function in different ways. The plug is a multi-pole plug so that the different functions can be encoded by different connections within the plug. A first plug selects an operating mode to cause the lamp to flash while an alternative plug selects an operating mode to cause the lamp to stay on continuously (when the ambient light is below the threshold). It is also possible to co connect an external power supply to the socket to charge the battery pack 40.

Parameters that affect operation of the lamp can be stored in the non-volatile Q 15 memory within the microcontroller 34. These might include values at which the LED Lt) light source will turn ON or OFF, the brightness of the LED light source, and its flash rate.

Brightness of the LEDs is controlled through use of pulse-width modulation. That is, power is applied to the LEDs in pulses, and the ratio of on-time to off-time determines the perceived brightness of the LEDs, whereby the perceived brightness can be varied using software. The pulse rate for steady operation is approximately 97Hz, the perceived brightness being set by PWM (Pulse Width Modulation).

Operation of the embodiment will now be described with reference to Figure 3.

The operational sequence starts when either an option plug is connected to the socket (Step 50). The microcontroller 34 is then initialised (Step 52).

If this is the first time that the lamp has been powered on (Decision 54), then its first task is to calibrate the switching threshold at Step 56. The microcontroller measures the output voltage of the photovoltaic cell 30 and stores this measured value in non-volatile memory. Once this has been done, the system returns to Step 52, above.

If this is the not first time that the lamp has been powered on (or if the calibration step 56 has just been performed) then the lamp starts to operate. The first decision that the microcontroller 34 must make is whether it is to enter day or night operation (Decision 54) -that is, whether the ambient light is above or below the threshold that was measured in Step 56. If the ambient light exceeds the threshold, then daylight operation is assumed, and the LED(s) are turned off, in Step 62. Power from the photovoltaic cell 30 is used to charge the battery pack 40. If the ambient light is less than the threshold, then night-time operation is assumed. Co

During night-time operation, the microcontroller 34 checks, at Decision 64, the type of option plug 42 that has been inserted into the socket. According to the type of Q 15 option plug 42, the microcontroller 34 either causes the LEDs to illuminate steadily LC) (Step 68) or causes them to flash at a pre-programmed rate (Step 66) which is typically approximately 66.7 flashes per minute, nominal 250ms on, or whatever is required to meet the relevant legislatorial or regulatory standard.

During all modes of operation, the microcontroller 34 loops in two-minute periods (Step 70). At Decision 72, if an hour has passed since the microcontroller 34 was initialised, then it is re-initialised by returning to Step 52. Periodic re-initialisation ensures that the microcontroller operation has not become corrupted and the lamp continues to operate reliably. Otherwise, the microcontroller 34 loops back to Decision 58 to react to the level of ambient light.

As shown in Figure 4, an alternative embodiment of the invention has a structure that is particularly suited to providing illumination in a particular direction, rather than distributed over a wide angular range (when the lamp is viewed from above). Parts of the second embodiment that correspond to parts of the first embodiment are given a reference number that is 100 more than given to the part in the first embodiment.

In this embodiment, the lens 112 is generally planar. A central region of the lens is formed as a Fresnel region 114 that concentrates the output from the light-emitting S device(s). A region 118 surrounding the Fresnel region 116 is covered in a retroreflective material to reflect light from the headlights of passing vehicles back to their drivers. The collector 122 extends horizontally (in use) above the lens 112 to offer it some protection from rain and other falling debris.

The tapered portion of the lower part 116 of the head has a plurality of radial ribs 100 which help to retain the lamp in place on a cone and prevent it from rotating with respect to the cone. Co

Q With reference now to Figures 5 to 10, third and fourth embodiments of the invention have a squat housing, and are suitable for providing a directional light output. These two embodiments are essentially similar, varying only in the external shape of the It) 15 housing. The operational components of this embodiment are substantially the same as those of the first embodiment, so these will not be described further. Parts of the third and fourth embodiments that correspond to parts of the first embodiment are given a reference number that is 200 more than given to the part in the first embodiment.

The housing of these embodiments comprises a lower part 216, typically formed from as a moulding of opaque plastic material, and closed by a transparent upper part 222.

The general outer shape of the housing is of a cuboid with rounded corners.

Optionally, the collector 230 is angled to the horizontal.

An upwardly-tapering recess 252 is formed in the lower part 216 of the housing. A downwardly-extending cylindrical stem 210. In these embodiments, the stem 10 does not project downwardly below a lowermost surface of the lower part 216 of the housing. This allows the lamp to sit on a flat surface, as shown in Figure 8, which is convenient for storage and transportation prior to deployment.

As shown in Figure 10, when the lamp is deployed upon a cone 250, the stem 10 enters a hole in the top of the cone. The taper of the recess 252 is selected to be substantially the same as the taper of the cone, such that an upper part of the cone is retained within the recess, which acts to stabilise the deployed lamp. Co cD IC)

Claims

Claims 1. A lamp for use in conjunction with a traffic cone, the lamp

comprising a housing in which is contained a rechargeable battery pack, a light-emitting device and control circuitry, and a photovoltaic panel whereby, under the control of the control circuitry, the photovoltaic panel can charge the battery pack when the ambient light is in excess of a trigger threshold, and the battery pack can power the light-emitting device when the ambient light is below a threshold.
2. A lamp according to claim 1 in which the head portion is disposed on an C axial end of the body portion.
3. A lamp according to claim 1 in which the head portion at least partially surrounds the body portion.
4. A lamp according to claim 2 in which the head portion is shaped generally as a cuboid with rounded corners.
5. A lamp according to claim 2 or claim 3 in which the head portion has a recess into which there projects a stem.
6. A lamp according to claim 5 in which the stem is cylindrical.
7. A lamp according to claim 1 in which the head portion and the body portion are of circular cross-section, and are coaxial.
8. A lamp according to claim 7 in which the head portion is of a greater diameter than the body portion.
9. A lamp according to any preceding claim in which the control circuitry determines the ambient light level by measurement of the output of the photovoltaic panel.
10. A lamp according to any preceding claim in which, upon being switched on for the first time, the controller determines the ambient light level and stores that light level as the trigger threshold.
11. A lamp according to any preceding claim having an electrical connection socket to which electrical power can be delivered to charge the battery co pack.

C
12.A lamp according to any preceding claim having an electrical connection C socket to which an option key can be connected to switch on the lamp. LC)
13.A lamp according to claim 12, as dependent from claim 11 in which the option key can be connected to the same socket that can be used for charging the battery pack.
14. A lamp according to claim 12 or claim 13 in which one of a plurality of option keys can be connected to the socket, a mode of operation of the lamp being selected by the particular key that is inserted into the socket.
15.A lamp according to claim 14 in which the modes of operation include steady illumination and flashing illumination.
16. A lamp according to any preceding claim in which the light-emitting device includes one or more light-emitting diodes.
17. A lamp according to claim 16 in which a variable number of light-emitting diodes can be installed in dependence upon the amount of light and/or direction that the lamp must produce for a particular function.
18.A lamp according to claim 16 or claim 17 in which the perceived brightness of the LED(s) can be varied using pulse-width modulation of power applied to them.
19. A lamp according to any preceding claim in which an end part of the body portion that is remote from the head portion may be tapered.
20. A lamp according to any preceding claim in which the head portion may be tapered close to its connection with the body portion. Co
21.A lamp according to any preceding claim in which the head portion includes a lens that surrounds the light-emitting device. cD

LI)
22.A lamp according to claim 21 in which a portion of the lens is obscured such that light from the light-emitting device is occluded such that light from the light emitting devices is visible only from a restricted range of angles.
23.A lamp substantially as described herein with reference to the accompanying drawings.
24. In combination, a traffic cone and a lamp according to any preceding claim, in which the traffic cone has an opening that is upwardly-directed in use, the body portion of the lamp being inserted into the opening such that the body portion rests upon the top of the cone.