Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J61/00—Gas-discharge or vapour-discharge lamps
  • H01J61/02—Details
  • H01J61/24—Means for obtaining or maintaining the desired pressure within the vessel
  • H01J61/26—Means for absorbing or adsorbing gas, e.g. by gettering; Means for preventing blackening of the envelope

Definitions

• the invention concerns a discharge lamp, provided with a discharge vessel surrounded, at some distance, by an outer bulb filled with gas and provided with a getter.
• a discharge lamp is known.
• An example of such a discharge lamp is a metal halide lamp.
• the outer bulb is often filled with nitrogen, the pressure of which at room temperature is selected to be in the range 250 mbar - 600 mbar.
• the getter is present in the lamp in order to remove hydrogen that comes to be in the outer bulb during lamp manufacture. If this hydrogen is not removed from the outer bulb, this hydrogen also enters the discharge vessel by diffusion through the discharge vessel wall. In this case re-ignition of the discharge lamp will be problematic.
• a discharge lamp as mentioned in the opening is characterized in accordance with the invention in that the getter comprises more than 80% by weight Zr and Co and moreover one or more elements are chosen from among the rare earth elements. It has been found that in a discharge lamp in accordance with the invention hydrogen is effectively removed from the outer bulb of the discharge lamp. It was found to be unnecessary to activate the getter, and the getter did not become so poisoned by other gases present in the outer bulb that the hydrogen gettering activity dropped significantly.
• the gas composition contains nitrogen. It has been found that the getter that is used in the outer bulb of a discharge lamp in accordance with the invention is able to effectively getter hydrogen without becoming saturated with nitrogen and without it being necessary to activate the getter.
• Discharge lamps in accordance with the invention with which good results have been obtained are metal halide lamps. It has been found that the quantity of hydrogen in the outer bulb of these lamps after a relatively low number of burning hours has fallen to virtually nil. An example of the invention will be explained in more detail with reference to a drawing.
• Figure 1 shows an example of a discharge lamp in accordance with the invention.
• the contacts 9 are secured to a lamp base 8.
• an outer bulb 4 formed from hard glass is secured that surrounds a gas-tight area filled with nitrogen.
• the filling pressure of the nitrogen at room temperature is approximately 500 mbar.
• a discharge vessel 1 is present that is formed from quartz glass and is secured to supply conductors 5. At one of the supply conductors 5, also a getter 6 is secured.
• the getter 6 is manufactured by SAES, is referred to as St 787/DF25 and comprises approximately 80% by weight Zr, 15% by weight Co and 5% by weight a mixture of rare earths elements comprising La, Nd and Ce.
• the discharge lamp is a metal halide lamp and the discharge vessel comprises 60 mbar Ar and a mixture of metal iodides.
• Reference numeral 2 refers to electrodes of the discharge lamp that are connected via current supply conductors 3 with the supply conductors 5. For a discharge lamp as shown in Figure 1 it has been found that the quantity of hydrogen present in the outer bulb after 100 hours of burning and after 200 hours of burning is less than 0.001 mol%.
• Table 1 shows the results of an experiment in which the nitrogen-sensitivities of both the St 787/DF25 getter and the PH/DF50 getter from SAES are evaluated.
• the getter PH/DF50 is a getter that is often used in discharge lamps with an outer bulb filled with nitrogen.
• the getter PH/DF50 comprises 70% by weight Zr 2 Ni, 20% by weight Ni and 10% by weight W.
• Each of the getters was placed in a nitrogen atmosphere of 1000 mbar at a temperature of 500°C for varying time intervals. Then the activity for hydrogen absorption was measured in an argon flow comprising 1 mol% hydrogen.
• the table shows the maximum hydrogen getter speed J max of the two getters after 0, 1, 19, 70 and 384 hours contact with nitrogen at 500°C.
• the table also shows how long it took before this maximum getter speed was reached: time raax , as well as the value Q of the capacity of the getter. It can be seen that the maximum hydrogen getter speed of St787/DF25 is in all cases higher than that of PH/DF50. Furthermore, it can be seen that after a relatively long exposure to the nitrogen atmosphere this maximum getter speed is reached considerably more quickly by the St787/Df25 getter than by the PH/DF50 getter. Finally, it can be seen that the capacity of the getter for hydrogen after all the measured time intervals in which the getter was in contact with a nitrogen atmosphere of 500°C, is considerably higher in the case of St787/DF25 than in the case of PH/DF50. The data in Table I therefore clearly show that St787/Df25 is a more effective hydrogen getter in a nitrogen atmosphere than PH/DF50.

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• Discharge Lamp (AREA)

Priority Applications (2)

Applications Claiming Priority (2)

Publications (2)

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ID=8180231

Family Applications (1)

Country Status (5)

Cited By (3)

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• 2002
  • 2002-04-22 WO PCT/IB2002/001424 patent/WO2002089174A2/en not_active Ceased
  • 2002-04-22 CN CNB028014928A patent/CN100550277C/zh not_active Expired - Fee Related
  • 2002-04-22 JP JP2002586376A patent/JP4024151B2/ja not_active Expired - Fee Related
  • 2002-04-22 EP EP02722622A patent/EP1386344A2/en not_active Withdrawn
  • 2002-04-30 US US10/135,343 patent/US6800998B2/en not_active Expired - Fee Related
• 2004
  • 2004-08-20 US US10/923,278 patent/US6943497B2/en not_active Expired - Fee Related

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