DE JONGE ROBERT J (NL)
RATH PAULINA (NL)
VONDENHOFF NORBERT (DE)
RIEDERER XAVER (DE)
PHILIPS INTELLECTUAL PROPERTY (DE)
KRAPP HANS-DIETER (DE)
DE JONGE ROBERT J (NL)
RATH PAULINA (NL)
VONDENHOFF NORBERT (DE)
RIEDERER XAVER (DE)
WO2003060379A2 | 2003-07-24 |
EP1435643A2 | 2004-07-07 | |||
US20070120492A1 | 2007-05-31 | |||
US20060071603A1 | 2006-04-06 | |||
EP1271612A2 | 2003-01-02 | |||
DE1805750A1 | 1970-06-04 | |||
US3860903A | 1975-01-14 | |||
EP1458010A2 | 2004-09-15 |
CLAIMS:
1. Gas discharge lamp for emitting ultraviolet light, comprising a discharge vessel (12) comprising a vessel volume V at least partially filled with a gas and/or a salt for providing an illuminating atmosphere for a discharge arc, a first electrode (14) ending in the discharge vessel (12), - a second electrode (16) ending in the discharge vessel (12) and a control unit (18) electrically connectable to an electrical source and electrically connectable to the first electrode (14) and the second electrode (16) for providing the discharge arc between the first electrode (14) and the second electrode (16) due to an applied electrical power P, whereby the control unit (18) is adapted to operate the first electrode (12) and the second electrode (16) in a normal operating mode at a ratio r of the electrical power P to the vessel volume V, wherein r is 1176 W/cm 3 < r < 2647 W/cm 3 , particularly
1618 W/cm 3 < r < 2500 W/cm 3 and preferred 2059 W/cm 3 < r < 2353 W/cm 3 .
2. Gas discharge lamp according to claim 1, whereby a cooler (22) is provided for providing a forced convection to an upper part (20) of the discharge vessel (12).
3. Gas discharge lamp according to claim 1, whereby the electrodes (14, 16) comprise a diameter d and the diameter d of the electrodes (14, 16) is chosen with respect to the applied power P such that P/d 2 is 450W/mm 2 < P/d 2 < 750W/mm 2 , preferred
500W/mm 2 < P/d 2 < 700W/mm 2 and most preferred 550W/mm 2 < P/d 2 < 650W/mm 2 .
4. Gas discharge lamp according to claim 1, whereby the discharge vessel (12) is elliptical shaped in axial direction.
5. Gas discharge lamp assembly comprising a plurality of gas discharge lamps (10) according to claim 1 and at least one cooler (38, 40) for providing a forced convection to an upper part (20) of the discharge vessel (12), wherein the number of the provided gas discharge lamps (10) is lower than the number of the provided coolers (38, 40).
6. Gas discharge lamp assembly according to claim 5, whereby only one cooler (38, 40) is provided or whereby only one cooler (38) for providing a positive pressure and only one cooler (40) for providing a negative pressure are provided.
7. Gas discharge lamp assembly according to claim 5, whereby several gas discharge lamps (10) are arranged in a plane, particularly side by side.
8. Gas discharge lamp assembly according to claim 5, whereby at least one deflector element (34) is provided for guiding a forced convection flow (36) along the upper part (20) of the discharge vessel (12) in mainly horizontal direction.
9. Method for operating a gas discharge lamp (10) for emitting ultraviolet light, comprising the steps: - providing the gas discharge lamp (10), particularly according to claim 1, wherein the gas discharge lamp (10) comprises a discharge vessel (12) comprising a vessel volume V at least partially filled with a gas and/or a salt for providing an illuminating atmosphere for a discharge arc, a first electrode (14) ending in the discharge vessel (12) and a second electrode (16) ending in the discharge vessel (12), and - providing the first electrode (14) and the second electrode (16) with an electrical power P, wherein in a normal operating mode a ratio r of the electrical power P to the vessel volume V is provided, wherein r is 1176 W/cm 3 < r < 2647 W/cm 3 , particularly 1618 W/cm 3 < r < 2500 W/cm 3 , preferred 2059 W/cm 3 < r < 2353 W/cm 3 .
10. Method according to claim 9, wherein the ratio r is provided for at least 90%, particularly at least 95% and preferably at least 98% of the operating lifetime of the gas discharge lamp (10). |
Gas discharge lamp and method of operating a gas discharge lamp
FIELD OF THE INVENTION
The invention relates to the field of gas discharge lamps, by means of which ultraviolet light (UV), particularly ultraviolet A light (UVA), may be provided for instance for use in medical treatments like UVA-therapy for curing skin diseases. Particularly the invention relates to a high intensity discharge (HID) lamp, a ultra high performance (UHP) lamp and/or a micro power xenon light (MPXL) lamp. The invention further relates to a method of operating such a gas discharge lamp.
BACKGROUND OF THE INVENTION From US 6,016,031 an electrodeless high intensity discharge lamp (EHID) lamp is known, which is operated inside a discharge vessel at a power density in the range of 1000 W/cm to 9000 W/cm , so that it is possible to start in the absence of electrodes the EHID. Due to the absence of electrodes a power density in the range of 1000 W/cm 3 to 9000 W/cm is possible without melting back of the electrodes. It is known from a typical high intensity discharge (HID) lamp comprising electrodes and a discharge vessel volume of 0.034 cm 3 to operate this HID at a power of 35 W leading to a power density inside the discharge vessel of 1029 W/cm 3 . Due to this power density a deformation of the HID and a low lifetime are prevented.
There is an instant need for small gas discharge lamps providing much ultraviolet light without a significantly shortened lifetime.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a small gas discharge lamp providing more ultraviolet light without a significantly shortened lifetime as well as a method for operating a small gas discharge lamp for providing more ultraviolet light without a significantly shortened lifetime.
This object is achieved by a gas discharge lamp for emitting ultraviolet light, comprising a discharge vessel comprising a vessel volume V at least partially filled with a gas and/or a salt for providing an illuminating atmosphere for a discharge arc, a first
electrode ending in the discharge vessel, a second electrode ending in the discharge vessel and a control unit electrically connectable to an electrical source and electrically connectable to the first electrode and the second electrode for providing the discharge arc between the first electrode and the second electrode due to an applied electrical power P, whereby the control unit is adapted to operate the first electrode and the second electrode in a normal operating mode at a ratio r of the electrical power P to the vessel volume V, wherein r is 1176 W/cm 3 < r < 2647 W/cm 3 , particularly 1618 W/cm 3 < r < 2500 W/cm 3 and preferred 2059 W/cm 3 < r < 2353 W/cm 3 . This means that for instance at a given discharge vessel volume V of 0.034 cm 3 of a HID an electrical power P is provided of 4OW < P < 9OW, particularly 55 W < P < 85 W and preferred 7OW < P < 80W.
With respect to a common HID adapted for 35W, which comprises a discharge vessel volume of 0.034 cm 3 , the gas discharge lamp according to the invention is intentional provided with a too high power by the control unit in the normal operation mode as intended by the manufacturer. Measurements show that the amount of UV-A light is increased wherein the amount of UV-B light is not significantly increased. Two small gas discharge lamps according to the invention operated at 80W may replace a single large gas discharge lamp operated at 400W. Thus, it is possible to provide as much UV-A light as a larger lamp with less electrical power, less building space and less costs even in the long run. The gas discharge lamp can be used for medical treatments like UVA-therapy for treating human skin diseases like sensitive skin disorders or skin cancer. The gas discharge lamp can further be used for non-medical treatments like at sun studios. Due to the electrodes the gas discharge lamp can faster and more often be started and restarted. Particularly the gas discharge lamp starts at a much lower voltage than an electrodeless high intensity discharge lamp leading to a safer handling of the gas discharge lamp during operation. Further less electromagnetic shield protection and less electric isolation is necessary leading to reduced manufacturing costs.
Depending on the specific application of the gas discharge lamp according to the invention a significant reduction of the lifetime does not occur. The amount of passive cooling, for instance by natural convection, is sufficient to guarantee a long lifetime. If so, an additional active cooling may be provided for instance by means of a cooling fan or the like. Surprisingly a significant melting back of the electrodes do not occur. For instance the electrodes comprise a mainly circular cross section comprising a diameter d. Preferably the diameter d of the electrodes is chosen with respect to the applied power P such that P/d 2 is 450W/mm 2 < P/d 2 < 750W/mm 2 , preferred 500W/mm 2 < P/d 2 < 700W/mm 2 and
most preferred 550W/mm 2 < P/d 2 < 650W/mm 2 . Due to this design of the electrodes a melting back can be prevented.
In a preferred embodiment a cooler is provided for providing a forced convection to an upper part of the discharge vessel. Preferably the cooler is adapted to provide a positive pressure and/or a negative pressure at the upper part of the discharge vessel. The cooler may comprise at least one fan for providing a positive and/or negative pressure. The cooler is preferably adapted to safeguard a maximum Temperature T max of the discharge vessel of 700 0 C < T max < 1100 0 C, particularly 800 0 C < T max < 1000 0 C, preferably 900 0 C < T max < 950 0 C. Due to the cooled upper part of the discharge vessel a maximum temperature can be safeguarded that prevents a melting or recrystallization of the discharge vessel material. A deformation of the discharge vessel is prevented. Cooling more than the upper part of the discharge vessel is not necessary. Due to heat conduction the lower part of the discharge vessel, which is not subjected to such a high heat than the upper part of the discharge vessel, can also be cooled. Measurements shows that even the electrodes are cooled, when the upper part of the discharge vessel is cooled, so that a melting back of the electrodes is prevented. Thus, the use of electrodeless high intensity discharge lamps can be avoided.
Preferably the discharge vessel is elliptical shaped in axial direction. In comparison to a spherical discharge vessel the discharge vessel is elongated in axial direction. This leads to a greater surface of the discharge vessel increasing the amount of natural and forced convection, so that a better cooling of the discharge vessel is possible. Further more evaporated salts are positioned in the area of the discharge arc, so that a more intensive illuminating atmosphere can be provided comprising more excited salts. The illumination atmosphere may comprise an inert gas like xenon and appropriate salts like FeI and/or Hg.
The invention further relates to a gas discharge lamp assembly comprising a plurality of gas discharge lamps as previously described and at least one cooler for providing a forced convection to an upper part of the discharge vessel, wherein the number of the provided gas discharge lamps is lower than the number of the provided cooler. One cooler may cool more than one gas discharge lamp. Particularly only one cooler is provided. In the alternate only one cooler for providing a positive pressure and only one cooler for providing a negative pressure are provided. It is possible to provide a cooling stream which flows along all upper parts of the gas discharge lamps of the gas discharge assembly. This leads to an easy and cost efficient cooling of a plurality of gas discharge lamps.
Preferably several gas discharge lamps are arranged in a plane, particularly side by side. Due to this arrangement the cooling of the gas discharge lamps may be facilitated. Since two or more small gas discharge lamps according to the invention may replace a large gas discharge lamp according to the state of the art a more homogenous field of ultraviolet light sources may be provided so that the intensity of the ultraviolet light is equalized. An equalized intensity of ultraviolet light is a very important property of a gas discharge lamp assembly for use in a UVA-therapy for human skin. The risk of harming the human skin during a session of the UVA-therapy is reduced, wherein at the same time a shorter UVA-therapy session is not necessary to prevent a damage of the human skin. Thus, a UVA-therapy becomes faster and more efficient.
Particularly at least one deflector element is provided for guiding a forced convection flow along the upper part of the discharge vessel in mainly horizontal direction. Due to the deflector element the flow of a cooling stream can be adjusted as needed. Preferably at the beginning of the cooling stream a cooler for providing a positive pressure is provided and at the end of the cooling stream a cooler for providing a negative pressure is provided. A high pressure difference can be provided by the cooler, wherein the deflector elements secure a correct flowing of the cooling stream.
The invention relates further to a UV apparatus, particularly for use in a UVA- therapy for human skin, comprising a gas discharge lamp assembly as previously described. The UV apparatus may be further a pocket lamp or the like for providing ultraviolet light for instance in order to detect phosphor and/or substances which are luminous or visible mainly under ultraviolet light.
The invention relates further to a method for operating a gas discharge lamp for emitting ultraviolet light, comprising the steps of providing the gas discharge lamp, particularly as previously described, wherein the gas discharge lamp comprises a discharge vessel comprising a vessel volume V at least partially filled with a gas and/or a salt for providing an illuminating atmosphere for a discharge arc, a first electrode ending in the discharge vessel and a second electrode ending in the discharge vessel, and providing the first electrode and the second electrode with an electrical power P, wherein in a normal operating mode a ratio r of the electrical power P to the vessel volume V is provided, wherein r is 1176 W/cm 3 < r < 2647 W/cm 3 , particularly 1618 W/cm 3 < r < 2500 W/cm 3 , preferred 2059 W/cm 3 < r < 2353 W/cm 3 . Particularly the ratio r is provided for at least 90%, preferably at least 95% and most preferred at least 98% of the operating lifetime of the gas
discharge lamp. Due to this method the small gas discharge lamp can be operated such that more ultraviolet light is provided without a significantly shortened lifetime.
BRIEF DESCRIPTION OF THE DRAWINGS These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter. In the drawings:
Fig. 1 is a schematic sectional view of a gas discharge lamp and Fig. 2 is a schematic sectional view of a medical UV apparatus.
DETAILED DESCRIPTION OF EMBODIMENTS
The gas discharge lamp 10 according to the invention is in the illustrated embodiment exemplarily designed as high intensity discharge (HID) lamp. The gas discharge lamp comprises a burner 11 with an elliptical discharge vessel 12, which comprises a volume V of for example 0.034 cm 3 . The gas discharge lamp 10 comprises a first electrode 14 and a second electrode 16 which protrude into the discharge vessel 12. The discharge vessel may comprise xenon and FeI and/or Hg salts for providing an illuminating atmosphere for a discharge arc generated between the electrodes 14, 16 due to a respective high electrical power or voltage. The electrodes are connected to a control unit 18, which may be an integrated circuit of a socket for the burner 11. Due to the control unit 18 a power density is provided between the electrodes 14, 16, which is significant higher than necessary for only providing a discharge arc between the electrodes 14, 16.
An upper part 20 of the discharge vessel 12 is cooled by a cooler 22, which may be a fan or the like. The cooler 22 may provide a positive or negative pressure at the upper part 20.
The gas discharge lamp 10 can be used in a gas discharge assembly 24, which comprises a plurality of gas discharge lamps 10 (Fig. 2). The gas discharge assembly may be part of a UV apparatus 26 used in the UVA-therapy for treating sensitive skin disorders or the like. The UV apparatus comprises a bed 28 for a human. Via a distance piece 30 a head 32 is arranged above the bed 18. The bed 28 comprises the gas discharge lamp assembly 24, which comprises a plurality of gas discharge lamps 10 arranged side by side in a horizontal plane. The head 32 comprises a deflector element 34 for guiding a cooling stream 36 along the upper parts 20 of the discharge vessels 12 of the gas discharge lamps 10 in mainly horizontal
direction. The cooling stream 36 is provided in the illustrated embodiment by a first cooler 38, which provides a positive pressure, and by a second cooler 40, which provides a negative pressure, so that the cooling stream 36 is guided along the deflector element 34.
While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments. For example, it is possible to operate the invention in an embodiment wherein the UV apparatus 26 comprises only one cooler 38, 40 or wherein the cooler 38 40 are arranged mainly in a horizontal line with respect to the gas discharge lamps 10. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.