GB2365521A

GB2365521A - Ultraviolet fluorescent tube life indicator

Info

Publication number: GB2365521A
Application number: GB0005197A
Authority: GB
Inventors: John Allen Burrows; David William Harmer
Original assignee: MORANLORD Ltd
Current assignee: MORANLORD Ltd
Priority date: 2000-03-04
Filing date: 2000-03-04
Publication date: 2002-02-20
Also published as: GB0005197D0

Abstract

A UV fluorescent tube life indicator comprises a first portion of material 3, 4 to emit a first visible radiation signal indicating the quantity of UVA radiation emitted by a UV source, and a second portion of material 5 to emit a second visible radiation signal indicating the quantity of visible radiation emitted by the source. The indicator is in the form of a disc 1, having a central core comprising the first material 3, 4 and an annular ring surrounding the core comprising the second material 5. The UV fluorescent tube 2 emits both visible and UV light. Visible light 2 is partially transmitted through the diffusing material 5 but absorbed by filter material 3; UV light is transmitted by filter material 3 and causes fluorescent layer 4 to fluoresce visible light.

Description

<Desc/Clms Page number 1> ULTRAVIOLET FLOURESCENT TUBE LIFE INDICATOR The invention relates to an indicator device for determining the effectiveness of ultraviolet flourescent tubes during their lifetime. Ultraviolet emitting lamps are widely used in electronic insect traps. These usually take the form of a flourescent tube, which comprises a phosphor which gives out energy in the ultraviolet (UV) radiation spectrum. UVA radiation is not visible to the human eye, but strongly attracts most forms of flying insects. The insects are drawn to the UV radiation and away from food products in the area thus providing a more hygienic environment for food preparation. Generally the energy is in the form of UVA radiation having a wavelength in the band -r 330nm to -- 380nm. The phosphor most commonly used has a peak output at about 365nm. In addition to the UVA radiation, such tubes generally give out additional radiation on the visible spectrum. With the most commonly used phosphors, due to the physics of the gas emissions from the phosphor, this visible radiation is generally presented as a blue light having a line spectra of around 550nm . The UVA output of ultraviolet flourescent tubes declines with use, typically falling to around 85 % of its maximum in the first 100 hours run. Further decreases in UVA output occur more gradually often diminishing to about 50% after 6000 hours. Rendering the insect trap considerably less effective. A disadvantage of UV flourescent tubes is that over time, the tube may have a greatly reduced UVA output due to this ageing process, but may still emit a fairly strong visible blue light, giving the outward appearance of a fully functioning tube.

The UVA output of such a tube may be measured in a number of ways, each

typically involving the use of some form of UV meter. Such meters are expensive and cumbersome to use and must be used repeatedly over time if the effectiveness of the flourescent tube is to be continually monitored. In accordance with the present invention, there is provided a UV fluorescent tube life indicator comprising a first portion of material which is responsive to an emitted source of UV radiation to provide a first visible radiation signal indicative of and variable with the quantity of the UV radiation being emitted by the source, and a second portion of material which is responsive to visible radiation emitted by the aforesaid source to provide a second visible radiation signal indicative of the quantity of visible radiation emitted by the source, the two signals being of similar wavelength and at least the first signal being variable in intensity with the quantity of UVA radiation emitted by the source. A device made in accordance with the present invention can provide a simple to use, relatively inexpensive indicator to continuously monitor the UVA output of an insect trap and alert the user when the UVA output falls below a level at which the insect trap may no longer function effectively . Preferably, the first portion of material is responsive to UV radiation of wavelengths between about 330nm to about 380m-n. Preferably the second portion of material is responsive to visible radiation of wavelengths between about 400 and 550nm. Optionally the first and second portions of material are selected to respond to the UV and visible radiations emit scintillations of visible light. Alternatively, the first portion of material is a laminate comprising a filter layer which attenuates visible radiation and transmits UV radiation and a fluorescent layer which fluoresces in response to UV radiation transmitted by the filter layer and the first portion of material is a diffuser material which diffuses visible radiation emitted by the source. In such embodiments, the fluorescent layer may be provided in the form of a coating on the filter layer.

Preferably the laminate is provided in circular form and the diffuser material is provided in the form of a ring around the laminate. Conveniently, the indicator is embodied in a form which further comprises a means for attachment to a fluorescent light tube. This may be in the form of a clip or an adhesive or any other suitable means. Such a device is then portable and can be reused with new tubes when `dead' tubes are replaced. Alternatively, the indicator may be incorporated into the insect trap during manufacture. Optionally, the two portions of material may be coated directly onto the flourescent tube during manufacture. As another option, the response of the first portion of material may be selected so that, when a predetermined quantity of UV radiation is emitted by the source, it provides a first visible radiation signal of substantially the same intensity as that of the second visible radiation signal. This allows the user to be alerted when the efficacy of the insect trap has fallen below a predetermined level and enables the user to maintain a certain standard of hygiene in his work area. This principle may be extended to provide an array of indicators each selected for a different predetermined quantity of UV radiation, for example, 90 %, 80 %, 70 %, 60 % and 50 % of the maximum `as new ' emitted levels. On regular visual inspection, this arrangement provides a countdown of the life of the flourescent tube and the consequent efficacy of the insect trap. Some embodiments of the invention will now be described by way of example and with reference to the following Figures, in which. Figure 1 shows a cross-sectional view of one embodiment of a UV fluorescent tube life indicator according to the present invention positioned on a UV fluorescent tube of the type used in insect traps.

Figure 2 shows a face on view of the embodiment of Figure 1.

As can be seen from the Figures, a UV fluorescent tube life indicator comprises

a small disc 1, secured on a UV fluorescent tube 2 of an insect trap. The disc 1 comprises an outer ring 5 of a diffusing material and an inner circular core having a bottom layer of filter material 3 and an upper layer of fluorescent material 4. The ring of diffusing material 5 will transmit a proportion of the visible light emitted by the fluorescent tube 1 giving a visible radiation signal of a wavelength similar to that emitted by the bare tube, typically around 550n-m, but of lower intensity. The bottom layer of filter material 3 is positioned adjacent the tube 2 and attenuates visible light emitted by the tube of similar wavelengths to that transmitted by the diffusing material but of greater intensity. The filter material also acts to UVA radiation to which flying insects are attracted, typically this radiation is of wavelengths between about 330 and 380nm. The upper layer of fluorescent material 4 fluoresces in response to the UVA radiation transmitted by the bottom layer to emit visible radiation. The intensity of the visible radiation emitted by the upper layer 4 will decay with the quantity of UVA radiation transmitted by the bottom layer 3. When sufficient UVA is passing through the tube life indicator, the core 3, 4 of the indicator will appear as a bright spot against the surrounding ring 5. As the quantity of UVA radiation emitted by the tube 1 falls, the intensity of this spot will fade and the spot will become less easily discriminated from the ring 5. Optionally the materials may be chosen such that the intensity of the signal emitted by the core becomes less than that of the signal emitted by the ring. Thus the user can, on visual inspection of the indicator device of present invention, readily determine the efficiency of his insect trap at any point in time. As the contrast between the spot and the ring 5 decreases, the user is alerted to the deterioration in performance of the insect trap and the impending need to replace the fluorescent tube.

The properties of the diffuser ring 5 and flourescent core 3,4 can be optimised such that when the UVA output of the tube is within useful limits, then the central 'spot' will appear brighter than the surrounding illuminated ring. When the UVA output declines to a predetermined threshold value, then the 'spot' will fade to the same

intensity of the ring. Further decline in the UVA output will result in the 'spot' appearing darker than the ring indicating an urgent need to replace the fluorescent bulb. The indicator as attached to the fluorescent tube by any suitable means, in this case by a plastic clip 6 extending from the disc 1 and fastenable about the circumference of the fluorescent tube 2. The device is particularly effective due to the exceptional ability of the human eye to discriminate visual images of this nature. In another embodiment (not shown), the device comprises a disc having a centre core of a first material and an outer ring of a second material. The materials respectively emit scintillations in response to UV and visible light. The centre 'spot' emits scintillations only in response to UV radiation, down-converting to a chosen colour, say red. The second material is chosen to emit scintillations in response to visible radiation and also down-converts to red. As the quantity of UV emitted by the flourescent tube falls, the scintillations of the first material fade in comparison to those of the second material. The indicator thus behaves in a similar fashion to the embodiment shown in the Figures allowing the user to assess the useable life of his insect trap by discriminating the intensities in light emitted by the spot and ring. Whilst the embodiments described refer to differences in intensities emitted by . the materials used in the indicator, it is equally possible that the materials may be chosen to emit different coloured signals which may change to similar colours, or vice versa. Other embodiments may no doubt occur to the skilled addressee without deviating from the true scope of the invention.

Claims

CLAIMS 1. A UV fluorescent tube life indicator comprising a first portion of material which is responsive to an emitted source of UV radiation to provide a first visible radiation signal indicative of and variable with the quantity of the UV radiation being emitted by the source. and a second portion of material which is responsive to visible radiation emitted by the aforesaid source to provide a second visible radiation signal indicative of the quantity of visible radiation emitted by the source, the first signal being variable with the quantity of UVA radiation emitted by the source. 2. A UV fluorescent tube life indicator as claimed in claim 1 wherein the first portion of material is responsive to UV radiation of wavelengths between about 330nm to about 380nm. 3. A UV fluorescent tube life indicator as claimed in claim 1 or claim 2 wherein the second portion of material is responsive to visible radiation of wavelengths between about 400 and 550nm. 4. A UV fluorescent tube life indicator as claimed in any preceding claim wherein the first and second portions of material respond to emit scintillations. 5. A UV fluorescent tube life indicator as claimed in any one of claims 1 to 3 wherein the first portion of material is a laminate comprising a filter layer which attenuates visible radiation and transmits UV radiation and a fluorescent layer which fluoresces in response to UV radiation transmitted by the filter layer and the first portion of material is a diffuser material which diffuses visible radiation emitted by the source. 7. A UV flourescent tube as claimed in claim 6 wherein the laminate is provided in substantially circular form and the diffuser material is provided as a ring surrounding the laminate.

<Desc/Clms Page number 7>

8. A UV fluorescent tube life indicator as claimed in any preceding claim further comprising means for attachment to a fluorescent tube. 9. A UV fluorescent tube life indicator as claimed in any preceding claim wherein the response of the first portion of material is selected so that, when a predetermined quantity of UV radiation is emitted by the source, it provides a first visible radiation signal of substantially the same intensity as that of the second visible radiation signal. 10. A UV fluorescent tube life indicator system comprising a plurality of UV fluorescent tube life indicators as claimed in 7, each UV fluorescent tube life indicator being selected for a different predetermined quantity of UV radiation. 11. A UV fluorescent tube comprising a tube life indicator as claimed in one of claims 1 to 7. 12. A UV fluorescent tube comprising a tube life indicator system as claimed in claim 8. 13. UV fluorescent tube life indicator substantially as described herein and with reference to the Figures. 14. A UV fluorescent tube life indicator system substantially as described herein and with reference to the Figures. 15. A UV fluorescent tube substantially as described herein and with reference to the Figures.