Radiant energy – Radiant energy generation and sources – With radiation modifying member
Reexamination Certificate
1998-12-09
2001-12-25
Nguyen, Kiet T. (Department: 2881)
Radiant energy
Radiant energy generation and sources
With radiation modifying member
Reexamination Certificate
active
06333509
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ultraviolet electromagnetic radiation transmitter/ reflector device comprising a straight glass tube with an end-to-end bore for retaining a pressurised ionising gas, extending therethrough around an axis and defining a radiation transmitter beam.
2. Description of Related Art
It also relates to apparatuses and a process implementing such a device. The invention finds a particularly important, although non-exclusive, application in the field of photochemical treatment of materials by ultraviolet radiation with transmitter tubes containing an ionising gas at high or medium pressure, for example used in the paper industry, textiles, plastics industry, food industry, automobile industry and in the printing field, in particular for polymerization of inks or varnishes on films, for example formed by rolls of paper or cardboard
By high or medium pressure we mean absolute gas pressures greater than or equal to 2 kg/cm
2
,for example 3 kg/cm
2
for a medium pressure and greater than 5 kg/cm
2
for a high pressure, being able for example to go up to 100 kg/cm
2
.
The invention is not limited to the types of products to be treated. It can for example be used for drying of plated products, for drying of certain varnishes and adhesives, for drying of wire products extending around an axis, or for sterilization of liquid products.
Devices for production and reflection of ultraviolet radiations are already known comprising a straight transmitter tube and a straight concave reflector having a parabolic cross section or an elliptic cross section.
These devices present drawbacks. They are in fact cumbersome and require a transmitter tube completely separated from the reflector by a distance of several millimetres to enable efficient cooling by air flow between the transmitter tube and reflector.
High temperatures from 600 to 900° are in fact observed on the ultraviolet transmitter, whereas the temperature of the reflector is much lower, for example about 50° C.
The materials used are moreover different, the transmitters being made of glass and the reflectors of reflecting metal, of the aluminium type, i.e. presenting a very different thermal expansion coefficient from that of glass.
The tubes of great length of the devices of the prior art moreover present buckling with time.
In the case more particularly concerned by the invention, i.e. ultraviolet radiation transmission, known transmitters also cause formation of ozone in non-negligible quantity.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a radiation transmitter/reflector device, an apparatus and a process implementing such a device, meeting the requirements of practice better than those known before, in particular in that it proposes a compact device which is not cumbersome, able to considerably limit ozone production while maximizing the usable photochemical energy due to a structural design enabling an excellent optimization of the energy efficiency of the transmitted radiation.
For this purpose, the invention proposes in particular an ultraviolet radiation transmitter/reflector device comprising a straight glass tube with an end-to-end bore for retaining an ionising gas under high or medium pressure, extending around an axis, and defining a radiation transmitter beam, and a surface for reflecting the transmitted radiation comprising two longitudinal side wings symmetrical in relation to an axial plane of the bore, the reflecting surface being at least partially secured to the transmitter tube and presenting a transverse cross section at least partially parabolic, elliptic or straight, or then again at least partially appreciably parabolic, appreciably elliptic or appreciably straight, characterized in that the portions of reflecting surface corresponding to the side wings and presenting a transverse cross section at least partially parabolic or elliptic, or then again at least partially appreciably parabolic or appreciably elliptic, belong to a curve (parabola or ellipse) whose generating line at the peak is situated at a distance d from the axis of the bore, such that:
d=f and O<d<r+e+1 mm with
f: distance between the focal point of the parabola or ellipse and the corresponding generating line at the peak,
r: distance between the axis and the internal surface of the bore in the axial plane of the bore passing through the generating line at the peak, and
e: thickness of the tube in the axial plane, on the same side as and passing through the generating line at the peak.
Even more advantageously, both of the two end portions of the side wings present a cross section strictly in the form of a portion of parabola or ellipse or strictly straight. In the embodiments more particularly described, the present invention implements a straight transmitter tube whose geometric transmission centre is the same as the corresponding reflector focal point, also straight and of at least partially parabolic cross section (for example to treat flat surfaces), or of at least partially elliptic cross section (for example to treat curved surfaces), the generating line at the peak of the reflection curve being parallel to the axis merged with the focal line, and the end edges of the parabolic or elliptic portions being situated below the generating line of the bore, on the other side from the latter in relation to said generating line at the peak.
More precisely the medium or high pressure ultraviolet transmitters of the invention more particularly described here are tubes called “discharge tubes” comprising electrodes at very high temperature (greater than 1000° C.) called “hot electrodes”. The transmitter is therefore not provided with any filament of the infrared transmitter filament type.
The electric arc generated by the two electrodes, respectively situated on each side of the transparent tube, generates a light cylinder of constant cross section generally formed by one or more metallic iodides in plasma state, or by xenon or a mercury/xenon mixture or other gases or rare earths, each end of the cylinder being in the form of light cones whose peaks are merged with the electrodes.
The light cylinder, which can advantageously be truncated, for example flattened, as will be seen, presents a total length formed by the distance between the two electrodes, for example comprised between a few mm for short arc transmitters and more generally between 30 mm and 2500 mm, and also presents for example a cross section of the same size as, or smaller than, the internal cross section of the transparent tube which houses it.
The metallic iodide(s) can come from pure metals or alloys i.e. and e.g. a pure mercury, a pure iron, a pure gallium, an iron/cobalt (mixture), a gallium/lead (mixture), a mercury/gallium (mixture) etc.
More generally the gas(es) used can be pure (for example xenon) or in mixture form (for example mercury/xenon).
The list of mixtures of metals, rare earths and/or gases given above is naturally not restrictive.
Moreover their respective proportion is determined according to the required radiation wavelengths, in a manner known in itself.
In advantageous embodiments recourse is in addition had to one and/or the other of the following arrangements:
d=r+e;
r≦d<r+e;
d≦r;
the bore is cylindrical;
the cross section of the bore is an at least partially truncated circle, so that the radiating beam is of truncated transverse cross section;
the cross section of the bore is truncated by one or two dioptric planes perpendicular to the axial plane of the bore, in such a way that the beam is for example of appreciably rectangular shape inscribed in a cylinder (case where it is doubly truncated);
the reflecting surface is securedly united to the tube;
the external wall of the tube comprises a protruding part in the form of a cupola, hereinafter called dome, of external surface adapted to the internal wall of the bore and arranged, for example being a portion of a cylinder in the case of a cylindri
Lumpp & Consultants
Nguyen Kiet T.
Oliff & Berridg,e PLC
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