JP4280866B2 - Flash lamp and its electrode unit - Google Patents

Description

The present invention relates to a flash lamp used as a light source for ultraviolet sterilization using light pulses, a light source for exciting a solid laser, or an instantaneous heating device, and an electrode unit used therefor.

As a light source for ultraviolet sterilization, a low-pressure mercury lamp that efficiently emits ultraviolet light having a wavelength of 254 nm, which is effective for sterilization, and has a long lamp life is generally used. A large amount of objects to be treated cannot be sterilized in a short time, and if a high output is to be obtained, the number of lamps to be used must be increased. When the light transmittance of an object is low, or when bacteria are present at a high concentration and adhere to the surface of the object to be treated, etc., or when the bacteria generate a biofilm and lurk in it, or In the case of bacteria having a high resistance to irradiation with ultraviolet rays, such as spore bacteria covered with a thick film, there is a drawback that a sterilization effect (sterilization of 99.9999% or more) cannot be obtained.

For this reason, sterilization of foods, beverages, pharmaceuticals, etc., containers and packaging materials that are not suitable for heat sterilization is generally performed using a chemical solution. The chemical solution remaining on the surface of the product must be washed and removed, so a cleaning facility that cleans the material to be treated with aseptic water, a water supply facility that supplies and supplies the sterile water, and wastewater that contains used chemical solution There is a problem that wastewater treatment facilities and the like that are made harmless are necessary, and the facility costs and running costs increase, and at the same time, the installation space for the facilities becomes remarkably large. In recent years, the development of a non-polluting sterilization technology that does not use chemicals is awaited as the global environmental conservation movement increases.

In view of such circumstances, various sterilization techniques using flash lamps (flash discharge lamps) that emit ultraviolet rays with higher output and higher illuminance than low-pressure mercury lamps have been proposed. In this type of technology, for example, a xenon flash lamp 50 as shown in FIG. 5 is used to instantaneously irradiate high-intensity ultraviolet rays, and the lamp 50 is a light emission composed of a silica glass tube filled with a rare gas xenon gas. A pair of electrodes 52 and 53 are disposed opposite to both ends of the tube 51 (see Patent Document 1).

Japanese Utility Model Publication No. 64-19252

The xenon flash lamp 50 configured as described above is a lead connected to the rear end portions of the electrode lead rods 54 and 55 fixed to the sealing portions 56 and 57 by heat-sealing the tube end portion of the arc tube 51. When pulsed power is supplied via a wire (not shown), it is generated in the discharge space E of the arc tube 51 in which the electrodes 52 and 53 provided at the tip portions of the electrode lead rods 54 and 55 are opposed to each other. Xenon gas is excited in an instantaneous discharge plasma, and emits a short wavelength ultraviolet ray of 200 to 300 nm that exhibits a bactericidal effect.

Thus, for example, using a xenon flash lamp 50 having a distance between electrodes (emission length) of 250 mm, an outer diameter of the arc tube of 10 mm, and an inner diameter of 8 mm, a cylindrical polyethylene vial having a diameter of 20 mm and a length of 100 mm is filled. In a sterilization test for killing about 10 ⁶ black mold spores charged in 20 ml of the physiological saline, when the irradiation distance from the center of the lamp 50 to the center of the vial is 30 mm, It is confirmed that the lamp output and the number of irradiations required for the sterilization treatment of the black mold mold spores that are input are 1000J, and that the processing time is only 0.5 seconds. ing.

However, if a flash lamp is made to emit light continuously at a high load and at short intervals in order to sterilize a large amount of objects to be processed in a short period of time, the color center in the arc tube is caused by the photochemical action of the arc tube made of silica glass tube. Since this color center has an absorption wavelength of about 220 nm to 250 nm, the light output of the flash lamp is rapidly reduced because the short wavelength ultraviolet light transmission that has a bactericidal effect is lost only by lighting several hundred thousand times. This causes a problem that the lamp life is short, which is one of the major factors hindering the practical application and spread of light pulse sterilization using flash lamps. Further, since the color center generated in the arc tube is also a defect of intermolecular bond, the mechanical strength of the silica glass tube constituting the arc tube is lowered by long-term use, and the lamp may be damaged.

Accordingly, the present inventors have used other types of lamps other than flash lamps, such as high-pressure sodium lamps, in order to suppress the chemical action between the arc tube and its encapsulated material, and thus chemically stable polycrystalline alumina and single crystal alumina. Focusing on the fact that an arc tube made of an alumina tube manufactured in (1) was used, we intended to use an alumina tube as the arc tube of a flash lamp.

And since the arc tube made of alumina having a high melting point is difficult to heat-seal the tube end portion like the arc tube made of silica glass, the tip end portion for attaching the electrode to the tube end portion is difficult. A high-pressure sodium lamp in which a large-diameter metal pipe closed is inserted and the gap formed between the metal pipe and the tube end of the arc tube is hermetically sealed with a sealing glass called frit or solder glass (Non-Patent Document) 1), a flash lamp 40 as shown in FIG. 4 in which a metal pipe having a closed end is inserted into the tube end of an arc tube made of an alumina tube and the tube end is hermetically sealed. did.

The High-pressure Sodium Lamp Dr ir J.J.de Groot & ir J.A.J.M.van Vliet Macmillan education ltd 1986 Philips technical library P19, p229, p231, p251, p254

The flash lamp 40 shown in FIG. 4 manufactured by the present inventors is fixed in a tube end portion of an arc tube 41 made of an alumina tube and closed in a hole 43 formed in an end plate 42R (42L) that closes the tube end portion. A large-diameter metal pipe 46R (46L) with a closed end to which an electrode lead rod 45R (45L) provided with an electrode 44R (44L) is attached is inserted, and the metal pipe 46R (46L) and the end plate 42R ( 42L) is hermetically sealed with a sealing glass 47R (47L), and the metal pipe 46R (46L) is fixed to the end plate 42R (42L) with the sealing glass 47R (47L). The metal pipe 46R (46L) was made of refractory metal niobium, and the arc tube 41 was filled with xenon gas.

However, when the flash lamp 40 is operated, the metal pipes 46R, 46L are fixed to the end plates 42R, 42L forming the tube ends of the arc tube 41, and the sealing glass 47R, 47L is hermetically sealed. As a result, the crack grew in a short time and immediately caused no lighting due to arc tube leakage. Therefore, when the cause of the occurrence of cracks was investigated, the xenon gas enclosed in the arc tube 41 was repeatedly expanded and contracted by the continuous lighting operation of the flash lamp 40, and each time the end plates 42R and 42L were When the metal pipes 46R and 46L fixed to the pipe are compressed and deformed by receiving the expansion pressure of the xenon gas, a strong stress is generated in the fixing portion of the metal pipes 46R and 46L, and the stress is hermetically sealed by the stress. It was found that cracks occurred in the sealing glasses 47R and 47L. Further, when the flash lamp 40 is turned on at a high output, the electrodes 44R and 44L and the electrode lead bars 45R and 45L are overheated, and the metal pipes 46R and 46L are expanded by the heat, and a strong stress is applied to the fixing portion of the pipe. It was also found to occur.

The technical problem to be solved by the present invention is that even if the flash lamp is continuously operated at a high output in order to achieve practical use and spread of a light pulse sterilization or light pulse irradiation device using a flash lamp, The electrode lead bar is fixed to the tube end portion of the tube, and a crack that causes leaking of the arc tube does not occur in the seal portion that hermetically seals the fixed portion, thereby dramatically improving the lamp life.

The present invention relates to a flash lamp in which an electrode lead rod is fixed to the tube end portion of the arc tube and a sealing portion for hermetically sealing the fixed portion is formed, and the electrode lead rod expands the gas sealed in the arc tube. The damper is fixed to the tube end of the arc tube via a damper that relieves stress during lamp operation caused by the pressure, and the damper is placed on the outer periphery of the electrode lead bar so as to form an airtight space around the outer periphery. It is characterized by comprising a gas damper in which a gas is sealed inside a refractory metal tube mounted so as to form .

The flash lamp of the present invention is a lamp generated in a seal portion that hermetically seals a fixed portion of an electrode lead rod by a damper interposed between the tube end portion of the arc tube and the electrode lead rod fixed to the tube end portion. Since stress during operation is relieved and cracks that cause arc tube leakage are prevented from occurring in the seal portion, there is an effect that the lamp life is greatly improved.

In the best mode of the present invention, the electrode lead rod fixed to the tube end portion of the arc tube has an arc tube through a damper that relieves stress during lamp operation that occurs in a seal portion that hermetically seals the fixing portion. A flash lamp fixed to a tube end, wherein the damper is attached to the outer periphery of an electrode lead bar having an electrode at the tip, and the tube end of the arc tube made of an alumina tube is plugged into the tube end. The plate is fixed, and the electrode lead bar is fixed by inserting the damper mounted on the outer peripheral portion thereof into a hole formed in the end plate, and the fixing portion is hermetically sealed with sealing glass, and The damper is inactive at a pressure higher than the gas sealing pressure in the arc tube inside the refractory metal tube mounted so as to cover the outer periphery of the electrode lead rod and form an airtight space around the outer periphery. Gas sealed Those consisting of been gas damper.

The flash lamp 1 shown in FIG. 1 is provided with a pair of electrode units 3R and 3L at both ends of an arc tube 2 having an outer diameter of 10 mm and an inner diameter of 8 mm made of an alumina tube which has a good ultraviolet transmittance and hardly generates a color center. One electrode unit 3R has a cylindrical shape with an outer peripheral portion of 7 mm in diameter and a conical shape at the tip of an electrode lead rod 4R made of a tungsten rod having an outer diameter of 2.4 mm, with triated tungsten containing thorium oxide. An electrode 5R to be a formed cathode is provided, and the other electrode unit 3L is an anode formed to have a diameter of 7 mm and a length of 40 mm at the tip of an electrode lead rod 4L made of a tungsten rod having an outer diameter of 2.4 mm. An electrode 5L is provided. The distance between the electrodes 5R and 5L facing each other is 250 mm.

End plates 6R and 6L that close the tube end are fixed to the tube end of the arc tube 2, and each electrode unit 3R and 3R is connected to an electrode lead bar 4R that is fixed to the tube end of the arc tube 2. Dampers 8R and 8L are mounted on the outer periphery of the 4L to relieve stress during the lamp operation that occurs in the seal portions 7R and 7L that hermetically seal the fixed portions. The electrode lead rods 4R and 4L are arranged on the outer periphery. The dampers 8R and 8L attached to the parts are inserted into the holes 9 formed in the end plates 6R and 6L and fixed to the tube end of the arc tube 2, and the fixing part is a seal part 7R made of sealing glass. 7L is hermetically sealed. Then, in the tube of the arc tube 2 in which the tube ends to which the electrode lead rods 4R and 4L are fixed are hermetically sealed, the inside of the tube is exhausted and 40 kPa of xenon gas is sealed.

The dampers 8R and 8L are gas dampers in which a gas is sealed inside a refractory metal tube 11 mounted so as to cover the outer periphery of the electrode lead rods 4R and 4L so as to form an airtight space 10 around the outer periphery. The refractory metal tube 11 is formed of niobium, preferably niobium containing 0.5% of zirconium, to have a wall thickness of 0.2 mm and an outer diameter of 3 mm. The electrode lead rods 4R and 4L are each brazed and fixed to the outer periphery of each of the electrode lead rods 4R and 4L, and at the same time hermetically sealed to form the hermetic space 10, and a high melting point that forms the hermetic space 10. Inside the metal tube 11, the same xenon gas as the gas sealed in the tube of the arc tube 2 or other inert gas is 80 kPa, which is higher than the pressure of the gas sealed in the tube of the arc tube 2. It is filled with pressure. Note that the refractory metal tube 11 may be fixed by laser welding both ends of the tube 11 to the outer periphery of each electrode lead bar 4R, 4L.

The end plates 6R and 6L fixed to the tube end of the arc tube 2 are formed of an alumina ceramic disk having a diameter of 10 mm and a thickness of 3 mm capable of closing the tube end of the arc tube 2 having an outer diameter of 10 mm. A hole 9 having a diameter of 3.2 mm is formed at the center of the disk, into which dampers 8R and 8L made of a high melting point metal tube 11 having an outer diameter of 3 mm attached to the outer periphery of the electrode lead rods 4R and 4L can be inserted. An end plate that forms the tube end of the arc tube 2 by injecting molten sealing glass into the gap formed between the hole 9 and the dampers 8R and 8L inserted therein to cool and solidify the sealing glass. The electrode lead rods 4R and 4L are fixed to the holes 9 of the 6R and 6L via the dampers 8R and 8L, and at the same time, seal portions 7R and 7L are formed to hermetically seal the fixed portions.

FIG. 3 shows a lighting circuit used for a life test of the flash lamp 1. The lighting circuit includes a charging capacitor 13, a charging power source 14, a waveform adjusting impedance 15, a semiconductor switch 16, a simmer discharge power source 17, a simmer When a DC voltage of 2000 V is applied from the simmer discharge power source 17, the lamp breaks down and lights up. At this time, a simmer current of 100 mA flows due to the impedance 17 for controlling the simmer discharge current, and the lamp enters a flash lighting standby state. Next, a DC voltage is applied from the charging power source 14 to the capacitor 13 so that a charging energy of 2000 J is obtained. Stored (charge voltage 4000 V, capacitor capacity 250 μF). When a lighting signal is input to the semiconductor switch 16, the charge stored in the capacitor 13 flows all at once along the discharge path formed in the discharge space of the arc tube 2, and instantaneously emits high-intensity light. A pulse is emitted. Although the current is controlled by the waveform adjustment impedance 15, the peak current in this life test is 2600 A and the half-value width is 400 μs.

With this lighting circuit, the flash lamp 1 is turned on at a frequency of twice per second, and a polyethylene packaging container (depth 100 mm, bottom surface) that is continuously conveyed in the longitudinal direction of the lamp by a conveyor at a speed of 6 m / min. If a light pulse is irradiated to a diameter of 20 mm, 99.9999% of black mold spores can be sterilized. Further, when the lamp is turned on at a frequency of 6 times in 10 seconds, the xenon gas pressure in the arc tube 2 repeatedly increases and decreases rapidly from 40 kPa to 800 kPa.

Then, at the moment when the flash lamp 1 is turned on, the expansion pressure of xenon gas that rapidly expands in the discharge space of the arc tube 2 is attached to the inner surface of the arc tube 2 and the outer peripheral portions of the electrode lead rods 4R and 4L. Acting on the end plates 6R, 8L that are fixed to the end plates 6R, 6L of the arc tube 2, the dampers 8R, 8L are compressively deformed, but the wall thickness is as thin as 0.2 mm. The dampers 8R and 8L, which are gas dampers in which a gas is sealed inside the refractory metal tube 11, have elasticity to absorb the expansion pressure of the xenon gas, and therefore end with a sealing glass that forms the seal portions 7R and 7L. The portions fixed to the plates 6R and 6L are hardly deformed. Therefore, the stress generated in the seal portions 7R and 7L is relieved by the expansion pressure of the xenon gas that thermally expands during the lamp operation, and cracks are prevented from occurring in the seal portions 7R and 7L.

Even if the electrode lead bars 4R, 4L are overheated by the continuous lighting operation of the flash lamp 1, the heat is sealed in the airtight space 10 of the dampers 8R, 8L mounted on the outer periphery of the electrode lead bars 4R, 4L. Therefore, the tube 11 is not easily transmitted to the refractory metal tube 11 forming the hermetic space 10, and the tube 11 is thin, so that stress due to thermal expansion of the tube 11 is remarkably reduced. Thereby, according to the life test of the flash lamp 1 using the lighting circuit of FIG. 3, it was confirmed that stable life characteristics were exhibited even after 15 million times of lighting.

In addition, the prototype flash lamp 40 shown as a comparative example in FIG. 4 is not illuminated due to arc tube leakage due to cracks in the sealing glasses 47R and 47L even in the early lighting period. On the other hand, the probability of occurrence of arc tube leakage reaches about 50%. However, the flash lamp 1 of the present invention does not cause arc tube leak after lighting about 5 million times, and exhibits stable lighting characteristics.

The dampers 8R and 8L are formed of a thin high-melting-point metal tube 11 that is fixed to the tube end of the arc tube 2, and the tube 11 is disposed inside the arc tube 2 inside. Since the rigidity is given by sealing the gas at a pressure higher than the gas sealing pressure, the electrode lead bars 4R and 4L can be held at the predetermined mounting positions.

As described above, according to the present invention, it is possible to obtain a long-life flash lamp that is unlikely to cause arc tube leakage even when continuously lit at short intervals. There is a very good effect that it can contribute to the spread.

1 is a longitudinal sectional view showing an example of a flash lamp according to the present invention. Partial enlarged sectional view of the flash lamp shown in FIG. Diagram showing the lighting circuit of the flash lamp Longitudinal section of a prototype flash lamp shown as a comparative example Longitudinal sectional view showing a conventional flash lamp

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Flash lamp 2 Arc tube 3R Electrode unit 3L Electrode unit 4R Electrode lead rod 4L Electrode lead rod 5R Electrode 5L Electrode 6R End plate 6L End plate 7R Seal part (sealing glass)
7L seal part (sealing glass)
8R damper 8L damper 9 hole 10 airtight space 11 refractory metal tube 12 gold solder

Claims (3)

In the flash lamp in which the electrode lead rod is fixed to the tube end portion of the arc tube and the seal portion is hermetically sealed, the electrode lead rod is sealed by the expansion pressure of the gas sealed in the arc tube. It is fixed to the tube end of the arc tube through a damper that relieves stress during lamp operation, and the damper covers the outer periphery of the electrode lead bar to form an airtight space around the outer periphery. A flash lamp comprising a gas damper in which a gas is sealed inside a refractory metal tube attached to the tube . The damper is attached to the outer periphery of the electrode lead rod, and an end plate for closing the tube end is fixed to the tube end portion of the arc tube, and the electrode lead rod is attached to the outer periphery of the end plate. The flash lamp according to claim 1, wherein the flash lamp is fixed by being inserted into a hole formed in the housing. In an electrode unit for a flash lamp in which an electrode is provided at the tip of the electrode lead rod, the electrode lead rod is fixed to the outer periphery of the electrode lead rod fixed to the tube end portion of the arc tube by the expansion pressure of the gas sealed in the arc tube. A damper is attached to relieve stress during the lamp operation that occurs in the seal part that hermetically seals the fixed part, and the damper covers the outer periphery of the electrode lead rod so as to form an airtight space around the outer periphery. An electrode unit for a flash lamp , comprising a gas damper in which a gas is sealed inside a mounted refractory metal tube .

Images