Patent Application
20200324003
The present invention relates to a UV steriliser assembly for disinfection purposes, particularly of a type which is capable of an optimised sterilisation effect. The assembly utilises a reflector that targets the most effective wavelengths of light for photochemical breakdown of micro-organisms or specifically remove wavelengths of light that aid in repair of micro-organisms.
In connection with the use of an ultraviolet (UV) light source for disinfection of water, surfaces and/or air it is known that micro-organisms that are deactivated by specific wavelengths of electromagnetic radiation can also undergo a ‘photo-repair’ mechanism when exposed to other wavelengths. In other words, while some wavelengths damage and destroy micro-organisms, other wavelengths can repair those same micro-organisms and encourage growth.
Therefore, especially if a broad spectrum source is used (e.g. from a medium pressure UV lamp) and to a lesser degree narrow spectrum sources (e.g. low pressure germicidal lamp, amalgam lamp or LED UV sources), the overall system efficiency is reduced because wavelengths have conflicting effects on the target organism. Such a feature makes broad spectrum sources in need of optimisation.
GB2531319 describes a UV lamp unit according to a standard industry application. Dichroic reflectors have been used for many years in order to remove heat from a substrate when running UV systems.
The present invention seeks to provide a disinfection assembly, particularly of a broad spectrum UV source type, with improved efficiency for sterilisation purposes.
In one broad aspect of the invention there is provided a UV steriliser assembly and method of constructing same according to the appended claims. The assembly is comprised of a UV source, e.g. a lamp, configured to emit ultraviolet light of a range of wavelengths and a reflector associated with the source; wherein the reflector is configured to permit transmission therethrough of identified light wavelengths in order to control/manage/regulate/restrict the wavelength of light reflected by said reflector.
According to the invention, the efficiency of the assembly for sterilisation purposes is increased by removing the wavelengths that play a part in any repair process. The light wavelengths that do fall on the media are restricted to those which actively cause micro-organism damage or have no effect. In an alternative form the identified wavelengths are those known to have the greatest destructive effect on micro-organisms.
In a preferred form the reflector includes a dichroic coating that is formulated according to its light transmission properties for known wavelengths. The reflector/coating is configured to reflect wavelengths that are either damaging or encouraging to micro-organism growth depending on the configuration in relation to the media to be disinfected/sterilised.
As mentioned in the background section above, dichroic reflectors are known to be used in connection with removing heat from a substrate. The present invention utilises a coating specifically for selective removal of UV and visible wavelengths detrimental to micro-organism deactivation in sterilisation systems. The invention is not concerned with removing infrared (heat) and is inspired by a newer understanding of how organisms photo-repair.
In practice, dichroic coatings are applied in a vacuum chamber by evaporating various metals and oxides onto a substrate to form very fine dielectric layers. Each layer is around 2 microns thick and 3 to 50 layers are applied to the surface to build up the dichroic coating.
Each alternate layer is applied with high and low refractive index materials respectively such that as light passes through the interface between them it changes its direction. The amount of direction change is also related to the wavelength of light passing through the various layers. Therefore, by the selection of the different layers and their respective thickness, a skilled person can select which wavelengths can pass through the coating and which will be reflected.
One of the most important properties of dichroic coatings is that they are particularly efficient, with up to 98% of the selected light being reflected. This property, coupled with the nature of the materials used, allows a reflector assembly to operate up to around 400° C., with good chemical inertness and little radiation absorption making them particularly suitable for use in this inventive application.
It is expected that the greatest benefits of the invention will be achieved on broad spectrum UV sources and, as such, the preferred embodiment of assembly utilises a Medium Pressure (MP) lamp, although it is conceivable that other UV sources may be employed and that, in such cases, a dichroic coating could be applied directly to the surface of the UV source.
In practice, performance of the sterilisation assembly may be optimised by a combination of a specially selected dichroic coating and appropriate addition of an element into the lamp chemistry to modify its transmission characteristics, i.e. to desirable wavelengths.
The invention can be applied to a range of lamp layouts and/or associated water sterilisation chambers.
It is usual with MP lamps that the characteristic spectrum comes predominantly from the excitation of mercury in an electric arc and the internal pressure that the lamp is allowed to achieve. It is also common practice to modify the output spectrum with the addition of other chemicals, usually in the form of metals or metal halides. In this way the output of the lamp can be more closely tuned to the specific absorption characteristics that the process requires, in order to be more effective.
This concept can also be applied to low pressure lamps but, as the operating temperature is much lower, there is less opportunity to use other materials with higher vaporisation temperatures to enhance the spectrum. The spectrum in a low pressure lamp is also of a significantly different shape due to lower operating pressure, and the UV output tends to be concentrated over narrower wavelength ranges.
As is known in the art, lamp output can also be effected by the choice of envelope material. For disinfection purposes this is usually some form of fused silica (e.g. quartz) mainly due to its high transmittance to short wave UV. The addition of doping agents to this material will block certain wavelengths from being emitted, acting as a filter. Conversely the use of highly purified material (e.g. synthetic grades) will allow transmission of shorter wavelengths that would be blocked if a lower grade is used. The invention is enhanced by selecting doping agents that block or inhibit wavelengths associated with photo-repair of microorganisms, since this compliments the coating on the reflector described hereinafter which also targets wavelengths associated with photo-repair.
As most lamps operate above a temperature that a suitable filter media applied directly to a lamp surface could remain serviceable a separate reflector is, in practice, associated with the lamp. Particularly, according to the invention, the reflector can feature a dichroic coating which has the property of being able to be selected and applied in such a way to reflect very specific identifiable wavelengths, with the rest passing through the reflector.
Once the inventive concept, of tailoring a dichroic coating to target wavelengths associated with micro-organism damage and photo-repair, is established it is possible to propose specific mechanical embodiments to carry out the invention. For example, as shown in
Alternatively,
By contrast, if the desirable wavelengths (13) are required to be reflected by the coating 11 into the process media S, then such an arrangement can be achieved by embodiments according to
Referring to
The embodiment of
It can be understood from the foregoing that, by manipulating (i.e. doping) the output characteristic of UV radiation sources combined with the use of dichroic reflectors, the effects of photo-reactivation can be reduced or eliminated in any disinfection system. This will increase system efficiency by reducing the ‘undoing’ effect from the unwanted radiation, which could be turned into a higher micro-organism deactivation rate or energy saving. Particularly, in the past wavelengths in the UV range have been assumed to be destructive and it was visible wavelength light that enabled photo-repair. The present invention recognises the discovery that some UV wavelengths are counterproductive to sterilisation procedures and proposes a novel construction to take advantage of this discovery. Visible wavelength light is also preferably removed, but the improvement of the invention is primarily in reduction of selected UV wavelengths that assist photo-repair.
As micro-organisms have varying resistance to UV treatment, the method and apparatus of the invention allows a high degree of optimisation via customisation, depending on the selected target organisms, by selecting the correct combination of lamp output and reflector characteristics.
Additionally, energy density benefits can be achieved in a suitably designed system that has the ability to focus a “tuned” UV output on to the media being treated. High energy density could also be used to increase efficiency in the UV breakdown of other non-biological chemicals (e.g. hormones or nitrates that exist in water supplies).
The invention is exemplified by a tailored dichroic coating selected to permit or inhibit UV wavelengths associated with photo repair, but it is conceivable that other treatments or techniques could be applied to the reflector to achieve equivalent results.
In principle, the general concept of the invention can be adapted for other photochemical processes. For example, provision of a coating not necessarily for the destruction of microorganisms (by removal of repairing wavelengths) but to enhance or inhibit some other quality.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1605798.6 | Apr 2016 | GB | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/GB2017/050891 | 3/30/2017 | WO | 00 |
