This invention relates to an apparatus for use in different industrial processes, like for instance curing of plastic when lining leaking pipe lines, the apparatus comprising a lamp for emitting UV-light, which is enclosed in a first glass cylinder, and the apparatus comprising an arrangement for cooling by forced air stream.

Such an apparatus is previously known by U. S. patent No. 5.423.630. In this connection a fan blows an air stream between the lamp itself and the glass cylinder.

UV-lamps of the type discharge lamps are based on the fact that light is emitted from a gas when an electric current flows through the gas. That means that a miniature lightening is created between two electrodes which are enclosed in a quartz tube which also contains inert gases and evaporated metal vapours. A coupling device controls the current through the lamp so that a constant electric arc instead of separate lightenings is obtained. The temperature of the electric arc is in the size of 4000 to 4500°C and it is the heat from the electric arc that evaporates the different basic elements being in the lamp so that they are excited. The plasma then emits light with different wave lengths, which are characteristic for the basic elements being in the lamp.

Since discharge lamps generating UV-light almost without exception are manufactured of quartz glass which melts at temperatures higher than 1100°C, the outer temperature of the lamps often is around 800 to 950°C. Thus, it is important when using UV-lamps in industrial processes to minimise the outer temperature of these ones in order to avoid that material in the proximity of the lamp is damaged or set on fire.

The apparatus according to the mentioned U. S. patent, however, is impaired by a plurality of drawbacks. Firstly, a stream of cooling air, passing the UV-lamp itself, means that its plasma is cooled down, the cooling down being in direct proportion to the amount of cooling air. This means in its turn that the light emission of the UV-lamp is strongly deteriorated, which makes the known apparatus unsuitable to use for certain purposes, for instance curing of plastic material. Thus, in order to be able to use the known apparatus, it is necessary to renounce the cooling, and therefore the UV-lamp gets a so high outer temperature that there is a great risk for fire and/or material

damages.

Another drawback with the known apparatus is that there is a great risk that an inflammable gas, being in the apparatus area, shall penetrate into the space between the UV-lamp itself and the glass cylinder and be set on fire by the hot UV-lamp.

This invention intends to eliminate the problems with known technique and to provide an apparatus, which has such a design that its outer temperature can be reduced to such a low level that the risk of a potential fire and/or damages on surrounding material is eliminated.

This has been made possible by an apparatus of the kind mentioned by way of introduction which is characterized by the combination of the following features: -The first glass cylinder is enclosed in a second glass cylinder in such a way that an annular space is created between the two glass cylinders; -The mentioned space is partly connected to an inlet for the mentioned air stream, partly connected to an outlet for the mentioned air stream.

Due to that fact the amount of cooling air through the apparatus can be multiplied without deteriorating the light emission of the plasma of the UV-lamp. When testing the new apparatus, it has appeared to be possible to bring down the temperature of the outer parts of the apparatus to 50-250°C.

Two preferred embodiments of the invention shall be described more closely below with reference to the accompanying drawings, where Fig. 1 shows an apparatus according to the first embodiment, and Fig. 2 shows an apparatus according to the second embodiment.

The first embodiment according to fig. 1 has an oblong UV-lamp 1, which is arranged inside a first glass cylinder 2, which in its turn is arranged inside a second glass cylinder 3, preferably co-axially with each other. Both end portions 4,5 of the two cylinders are connected with each other and closed, whereby there is created an annular space 6 between the two glass cylinders 2,3. This space is at the one pair 4 of end portions in connection with the surroundings via an inlet pipe 7, whereas the space at the second pair 5 of end portions is in connection with an outlet pipe 8. Of course, the inlet

and outlet pipes 7,8 can be swifted regarding the function. Through the mentioned space 6 is a forced air stream intended to stream for cooling the apparatus in order to avoid that the material in the proximity of the apparatus shall be damaged or be set on fire. As has been mentioned previously, the UV-lamp has an outer temperature of 800-900°C, but due to the mentioned cooling arrangement, the outer temperature of the apparatus can be reduced to 50-250°C without deteriorating the light emission of the plasma of the UV-lamp.

Simply practically are the two glass cylinders 2,3 suitably designed like a double-walled circular-cylinder of quartz glass, the inner cylinder-wall constituting the first glass cylinder, whereas the outer cylinder-wall constituting the other glass cylinder.

In this connection the two end portions of the glass cylinder are closed but are provided with an inlet opening and an outlet opening as has been mentioned previously.

As is apparent from fig. 1 is the UV-lamp 1, which preferably also is made of quartz glass, enclosed in the mentioned, double-walled glass cylinder 2,3. At the two end portions of the double-walled glass cylinder and within the same there is arranged a circular ceramic plate 9,10, both of which are tightened against the inside of glass cylinder by ceramic cement. Due to that fact there is formed a completely gas-tight enclosing for the UV-lamp. The great advantage with this arrangement is that no chemicals can penetrate in towards the UV-lamp and its glow-hot surface of quartz glass, and therefore the risk of fire, due to that fact, is further reduced.

In each end of the oblong UV-lamp 1 there is arranged an electrode 11,12 which gas-tightly goes through the mentioned ceramic plates 9,10 and via a ceramic plug 13, 14 is in connection with an electric cable 15,16.

As is distinctly apparent from fig. 1, the two electrodes are designed like a"S" and become in that way flexible. This has been made in order that the electrodes shall be able to take up the length expansion that the UV-lamp is exposed to and that is greater than that of the double-walled glass cylinder 2,3.

The embodiment according to fig. 2 has great similarities with that one according to fig. 1. Thus, the embodiment according to fig. 2 comprises a UV-lamp 1 which is

enclosed in a double-walled circular-cylinder 2,3 of quartz glass, which has an inlet pipe at its one end portion and an outlet pipe at its other end portion. The difference between the two embodiments is the way to enclose the UV-lamp within the double-walled glass cylinder 2,3.

According to the second embodiment the two end portions 1A and 1B of the UV- lamp have the design of a pipe, each of which pipes being gone through by an electrode and itself going through a ceramic plate 17,18, which correspond to the ceramic plates 9,10 of the first embodiment, and which in a corresponding way is connected to a ceramic plug 19,20 with an electric cable belonging to the plug. In this connection the mentioned plates are placed a small distance inside respective end portion of the glass cylinder 2,3.

In immediate connection with respective end portion of the double-walled glass cylinder 2,3 is fastened a gable 21,22, which is made of a metallic material. Between each gable and adjacent ceramic plate 17,18 there is arranged a cooling and sealing ring 23,24 of copper wool, which is cooled by the mentioned cooling air and which is sealing between the centrically arranged ceramic plug 19,20 and the inner surface of the glass cylinder 2,3. In order that the cooling and the sealing ring shall be held in place in a secure way, is between the mentioned cooling and sealing ring and respective ceramic plate arranged a cup-shaped copper washer 25,26, which accordingly cooperates with the cooling and sealing ring and which at the same time makes the sealing between the lamp and the double-walled cylinder.

The long and narrow form of the UV-lamp depends on the fact that there is a difference regarding the coefficient of the expansion of length between the electrodes of the UV-lamp and the casing, made of quartz glass, of the UV-lamp. The difference is so great that the quartz glass is burst to pieces if the temperature exceeds ca 350°C.

(This fact has validity for all lamps of this type). Therefore, the electrodes, where the casing of the UV-lamp begins to become narrower, extend in pipes of quartz glass until the electrodes have passed the ceramic end plates which accordingly function as heat- reflecting shields. First in the ends where the temperature has sunken well under 350°C,

the electrodes in the form of thin foils of molybdenum pass through the quartz glass and are contacted with the connection cables. Thereafter, the end portions of ceramic are cemented over the actual contacting means.

This apparatus is not gas-tight like the apparatus according to the first embodiment. That means that theoretically chamicals can penetrate into the hot UV- lamp and be set on fire, but due to the arrangement with a ceramic plate/a metallic sealing/a metallic gable, possible fire will not be spread outside the space of the UV- lamp. The metallic gable is cooled down by the cooling air before the same passes the double-walled cooler. Possible inflammable gas having come into the annular space between the UV-lamp itself and the double-walled cooler of quartz glass and takes fire is extinguished when the burning flame shall pass through the very narrow opening between the copper washer and the double-walled cooler of quartz glass and through the ring of copper wool.

An advantage with the second embodiment is that the double-walled glass cylinder, used as a cooler, can be maintained when exchanging the UV-lamp.

In the text has been mentioned curing of plastics. Of course it would be possible also to use the invention for curing other materials like glues, lacquers and colours.

The invention is not limited to the mentioned embodiments but can be modified within the scope of the following claims. Thus, for instance the UV-lamp could have another form than the oblong form, mentioned in the text.