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US2784347A - Electric high pressure discharge lamps - Google Patents

Electric high pressure discharge lamps Download PDF

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US2784347A
US2784347A US332481A US33248153A US2784347A US 2784347 A US2784347 A US 2784347A US 332481 A US332481 A US 332481A US 33248153 A US33248153 A US 33248153A US 2784347 A US2784347 A US 2784347A
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starting
electrodes
filament
electrode
discharge
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US332481A
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Thouret Wolfgang Emery
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CBS Corp
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Westinghouse Electric Corp
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    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01JELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J61/00Gas-discharge or vapour-discharge lamps
    • H01J61/02Details
    • H01J61/54Igniting arrangements, e.g. promoting ionisation for starting
    • H01J61/541Igniting arrangements, e.g. promoting ionisation for starting using a bimetal switch
    • H01J61/542Igniting arrangements, e.g. promoting ionisation for starting using a bimetal switch and an auxiliary electrode inside the vessel
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01JELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J61/00Gas-discharge or vapour-discharge lamps
    • H01J61/82Lamps with high-pressure unconstricted discharge having a cold pressure > 400 Torr

Definitions

  • My invention relates to electric discharge lamps with solid incandescent electrodes, the electrode leads of which are conected by incandescent wires or incandescent coiled filaments parallel to the discharge path for the purpose of starting the discharge.
  • the wires or wire coils have such dimensions that they glow brightly when the mains voltage is switched on. They ionize the discharge path by emitted electrons and thus bring about or facilitate starting of the discharge.
  • This starting arrangement has considerable fundamental importance as, other. than contact starting by means of mechanically movable electrodes, it is the only arrangement that renders possible instantaneous starting of high pressure lamps in any state of operation at standard mains voltageswithout auxiliary electrodes and without additional external electric devices. However, up to the present it could be applied inpractice only to low pressure discharge lamps and only to such types at very low voltages under 30 volts.
  • the starting wire or starting filament must have such dimensions that its resistance per unit length is at least equal to or greater than that of the discharge path after starting.
  • the starting filament must be made of a rather thin wire that burns through instantaneously if the arc discharge starts from it even only for a short moment.
  • the danger of burning through is considerably greater in high pressure lamps than in low pressure lamps because the high pressure are forms a concentrated hot spot and has a much higher energy density in its starting point.
  • the starting filament is not connected directly at both ends to the main electrode leads but: only through certain solid resistors arranged inside or outside the discharge tube. As soon as a current.
  • the resistors in series to the filament have to be so great that in each of them occurs 'a minimum voltage drop of at least 10% of the mains voltage or transformer voltage with which the lamp is operated.
  • V v The resistors can be manufactured by any method,
  • electrodes usually they will be made preferably of refractory materials with high resistivity as e. g. semi conducting refractory metal compounds.
  • the ends ofthe starting filament can be led outside by special seals'and can be connected outside through the resistors to the leads of the main electrodes.
  • the resistors will be in the bases or within the outer bulbs of the lamps preferably. 7 7
  • the electrodes have deep grooves or off-center holes parallel to the discharge axis and parallelto the starting filaments through which. the ends of the starting filament are led. .
  • the starting filaments are fastened in such way that they are enclosedpartlyor completely by the electrode bodies but dont touch the electrodes.
  • the starting filaments are electrically, .a"nd' mechanically connected only at the rear electrode endsor at the electrode leads, eventually through the above meni tioned series resistors.
  • the filaments are not stiff enough to avoid safely a contact to the-electrodes, when the lamp is shaken, they can be equipped with a core fof refractory insulating or poorly conducting material.
  • cores can consist e. g. of sintered purealu'minum oxide, zirconium oxide, or thorium oxide.
  • operating pressures from 0.5 to or very high pressures up to 100 atm. or more. They can have activated or purely metallic solid incandescent electrodes and they can be filled with pure metal vapor, pure rare gas, or any combined mixture of metalvapors and rare gases.
  • the starting arrangement can consist of one or more starting filaments parallel to the discharge path. It can also be applied to lamps with more than one pair of electrodes or more than one are.
  • Fig. 1 represents a spherical super high pressure lamp with rare gas filling of about 20 atm. suitable for operation on 110 v. D. C. or A. C. mains voltage.
  • Fig. 2 represents a tubular high pressure mercury vapor lamp. In the Fig. 1 lamp, the rating is 2000 watt at an arc voltage of about 35 v. and an operating current of about 60 amps.
  • Both relatively large electrodes E consist of pure tungsten and have off-center holes L parallel to their axis through which the ends of the starting filament Z extend freely without touching.
  • the filament contains a core of s'intered thorium oxide rod to attain the stiffness necessary to avoid electrical contact to the electrode.
  • the starting filament Z is connected to the electrode leads through both series resistors R1 and R2.
  • R1 and R2 are 3 ohms each, the filament itself has a resistance of about 16 ohms.
  • the current in the starting circuit is about 5 amps. and between the electrodes and the starting filament ends a voltage drop of 15 v. occurs.
  • the field strength between the front surfaces of the main electrodes is considerably greater than that between any parts of the starting filament.
  • the resistance per unit length of the starting filament is considerably greater than that of the are after starting.
  • the voltage between the main electrodes drops to about 35 v.
  • the current in the starting circuit decreases to about 1.5 amps. the latter being negligible compared to the arc current of about 60 amps.
  • Fig. 2 shows a mercury high pressure lamp of about 3 atm. operating pressure with tubular quartz bulb. It has 300 watts at about 120 v. are voltage and 2.6 amps. operating current.
  • the electrodes B have deep grooves N offset from the eelctrode axis and parallel thereto. Through these the starting filament is led freely without touching. The ends of the starting filament vare led outside by means of separately sealed leads for the purpose of switching olf after the starting of the main discharge. Outside of the discharge tube the two resistors R1 and R2 are in series to the starting filament, each having about 30 ohms .resistance.
  • the outer lamp circuit contains the choke-ballast D.
  • the mains voltage Ne is 220 v.
  • the starting filament has a resistance of 160 ohms.
  • the "starting circuit By contact between :1 and '2 the "starting circuit is switched on, the filament Z starts glowing and the are between the electrodes 5 results in a great drop of the electrode voltage, the glow discharge in the glow-starters cannot be maintained and extinguishes.
  • the bimetal electrodes 1 open the contacts between 2 and 1, thus switching ofi the starting circuit on both ends. It is switched on again only after the mains voltage is connected again to the main electrodes after the era has b en xt ngu sh
  • the elec rod s in the glowstarters can be arranged so that the bimetal contact touches both electrodes 2 and 3 at the same time or shortly one after the other (first 2, then 3).
  • the starting circuit is closed then only for the short moment between the extinguishing of the short-circuited glow discharge and the moment when the bimetal electrodes have cooled down enough to open the contact again.
  • the glow-starters operate automatically several times until an arc has started between the main electrodes of the lamps. If the starting circuit is to be switched off only on one end of the filament, this can be done by means of a simple .twoeelect-rode glow-starter.
  • the combination which comprises an electric highpressure gas-discharge lamp having an envelope with lamp electrodes spaced apart from one another within said envelope and adaptedto have an arc discharge maintained in a path therebetween, and a starting arrangement comprising, a double-ended starting conductor within said envelope and paralleling and adjacent to said discharge path, first and second three-element glow starters positioned exteriorly of said envelope, each of said starters having a bi-rnetal first electrode, a second electrode and a third electrode, said starter electrodes being normally spaced from one another, a first resistor electrically connected between said bi-metal electrode of said first starter and said third electrode of said second starter, said til-metal electrode of said first starter being directly electrically connected to one of said lamp electrodes, a second resistor electrically connected between said bi-rnetal electrode of said second starter and said third electrode of said first starter, said bi-metal electrade of said second starter being directly electrically connected to the other of said lamp electrodes, a third resistor electrically connected between said second electrode of said first

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Description

Filed Jan. 21, 1953 IN V EN TOR.
M7494? fay 2 M 2,784,347 ELECTRIC HIGH PRESSURE DISCHARGE LAMPS Wolfgang Emery Thouret, East Orange, N. J., "assignr to Westinghouse Electric Corporation, East Pittsburgh, Pin, a corporation of Pennsylvania Application January 21, 1953, Serial No. 332,481
1 Claim. (Cl. 315-47) My invention relates to electric discharge lamps with solid incandescent electrodes, the electrode leads of which are conected by incandescent wires or incandescent coiled filaments parallel to the discharge path for the purpose of starting the discharge. Usually the wires or wire coils have such dimensions that they glow brightly when the mains voltage is switched on. They ionize the discharge path by emitted electrons and thus bring about or facilitate starting of the discharge. This starting arrangement has considerable fundamental importance as, other. than contact starting by means of mechanically movable electrodes, it is the only arrangement that renders possible instantaneous starting of high pressure lamps in any state of operation at standard mains voltageswithout auxiliary electrodes and without additional external electric devices. However, up to the present it could be applied inpractice only to low pressure discharge lamps and only to such types at very low voltages under 30 volts.
For perfect and reliable operation of the arrangement the starting wire or starting filament must have such dimensions that its resistance per unit length is at least equal to or greater than that of the discharge path after starting. As a consequence of this condition, the starting filament must be made of a rather thin wire that burns through instantaneously if the arc discharge starts from it even only for a short moment. The danger of burning through is considerably greater in high pressure lamps than in low pressure lamps because the high pressure are forms a concentrated hot spot and has a much higher energy density in its starting point.
Several difierent means have been suggested to avoid that an are starting point is formed and stays at the starting filament because one isaware of the fact that this can result in decreasing its life or eventually in burning it through quickly also in low pressure lamps. These measures e. g. consist in having the starting coil pass closely to the main electrodes so that they are preheated by the glowing filament or the are already started at it. Thus the arc shall be influenced to jump over from the filament to the main electrode. According to another suggestion the starting coil is :conencted to the electrode leads not tightly but only loosely so that undefined contact resistances are formed that can favor the jumping of the arc from the filament to the main electrodes. All these suggested arrangements have been found unreliable for use in high pressure lamps because they are based on the start of the are at the filament and only aim to have the arc jump from the filament to the main electrodes later. It has been proven by extendedexperiments that in practice only such starting arrangements can be used inhigh pressure lamps that principally avoid starting of the are at the filament. Thus no'part of the starting filament acts as electrode during the starting procedure. The filament may be used exclusively as a means to create thermal electrons for the purpose of ionizing the main discharge path. It is the purpose of my invention torealize the above mentioned principle by several new arrangements or measures that can be used alone or simultaneously. Thus the known starting arrangement with incandescent parallel filament canbe improved so that italsoworks reliably in high pressure lamps of all kinds operating with solid incandescent electrodes at op e. g. as Wire coils arranged in the spaces behind the main; electrodes. But as there is very limited space behind the.-
crating pressures higher than 0.5 atm. and at voltages higher than v. t
' According to my invention the starting filament is not connected directly at both ends to the main electrode leads but: only through certain solid resistors arranged inside or outside the discharge tube. As soon as a current.
flows through the starting filament after the mains volt-.
age has been switched on, the voltage drops in the re-= sist ors result in the field strength along the filament being lower than that between the main electrodes before the arc has started. Thus the main discharge starts directly at the main electrodes and no intermediate are starting the voltage between the filament ends to less than one;
'half or one third of the voltage on the main electrodes before starting of the arc. But in any case the resistors in series to the filament have to be so great that in each of them occurs 'a minimum voltage drop of at least 10% of the mains voltage or transformer voltage with which the lamp is operated. V v The resistors can be manufactured by any method,
electrodes usually they will be made preferably of refractory materials with high resistivity as e. g. semi conducting refractory metal compounds. In the case of limited space within the discharge tube the ends ofthe starting filament can be led outside by special seals'and can be connected outside through the resistors to the leads of the main electrodes. In this case the resistors will be in the bases or within the outer bulbs of the lamps preferably. 7 7
According to my invention another measure for pre venting an arc starting spot'on the filament or for trans; ferring it safely and instantaneously to the main electrodes is the following: The electrodes have deep grooves or off-center holes parallel to the discharge axis and parallelto the starting filaments through which. the ends of the starting filament are led. .The starting filaments are fastened in such way that they are enclosedpartlyor completely by the electrode bodies but dont touch the electrodes. The starting filaments are electrically, .a"nd' mechanically connected only at the rear electrode endsor at the electrode leads, eventually through the above meni tioned series resistors. In case the filaments are not stiff enough to avoid safely a contact to the-electrodes, when the lamp is shaken, they can be equipped with a core fof refractory insulating or poorly conducting material. Such cores can consist e. g. of sintered purealu'minum oxide, zirconium oxide, or thorium oxide. Finally according to my invention the'starting filaments are switched off the main electrodes immediately after the'main arc has started for protecting them against burning through and securing the immediate transfer ,.'6f the arc. For this purpose usually the ends of the" starting filament must be led outside of the discharge tube'T-by means of separate seals. As switches preferably" on 1' two glow discharge bimetal-relays, well known as' 'f g starters, are used. In principle any kind of relay fiuenced by the lamp voltage or any manually spent switch can be used. In switching the starting filam nts oif the electrodes the additional advantage is won in they consume no wattage during lamp operationjand' consequently the operating efiiciency "of 'th'e'la'nipT is injured by the filaments. QThe starting arrangements imprjo've H Patented Mar. 1951.
operating pressures from 0.5 to or very high pressures up to 100 atm. or more. They can have activated or purely metallic solid incandescent electrodes and they can be filled with pure metal vapor, pure rare gas, or any combined mixture of metalvapors and rare gases.
The starting arrangement can consist of one or more starting filaments parallel to the discharge path. It can also be applied to lamps with more than one pair of electrodes or more than one are.
'The accompanying drawing shows two practical examples of high pressure lamps with starting arrangements according to my invention. Fig. 1 represents a spherical super high pressure lamp with rare gas filling of about 20 atm. suitable for operation on 110 v. D. C. or A. C. mains voltage. Fig. 2 represents a tubular high pressure mercury vapor lamp. In the Fig. 1 lamp, the rating is 2000 watt at an arc voltage of about 35 v. and an operating current of about 60 amps. Both relatively large electrodes E consist of pure tungsten and have off-center holes L parallel to their axis through which the ends of the starting filament Z extend freely without touching. The filament contains a core of s'intered thorium oxide rod to attain the stiffness necessary to avoid electrical contact to the electrode. Behind the electrodes E the starting filament Z is connected to the electrode leads through both series resistors R1 and R2. R1 and R2 are 3 ohms each, the filament itself has a resistance of about 16 ohms. Thus, when the lamp is switched on, the current in the starting circuit is about 5 amps. and between the electrodes and the starting filament ends a voltage drop of 15 v. occurs. Thus the field strength between the front surfaces of the main electrodes is considerably greater than that between any parts of the starting filament. Besides this the resistance per unit length of the starting filament is considerably greater than that of the are after starting. When the arc is started the voltage between the main electrodes drops to about 35 v., the current in the starting circuit decreases to about 1.5 amps. the latter being negligible compared to the arc current of about 60 amps.
Fig. 2 shows a mercury high pressure lamp of about 3 atm. operating pressure with tubular quartz bulb. It has 300 watts at about 120 v. are voltage and 2.6 amps. operating current. The electrodes B have deep grooves N offset from the eelctrode axis and parallel thereto. Through these the starting filament is led freely without touching. The ends of the starting filament vare led outside by means of separately sealed leads for the purpose of switching olf after the starting of the main discharge. Outside of the discharge tube the two resistors R1 and R2 are in series to the starting filament, each having about 30 ohms .resistance. The outer lamp circuit contains the choke-ballast D. The mains voltage Ne is 220 v. The starting filament has a resistance of 160 ohms.
After switching the mains voltage on, a current of about 1 amp. flows in the starting circuit and both ends of the starting filament have a potential difference of about 30 v. each with respect to the adjoiuingmain electrode. When the .arc is formed the arc voltage or electrode voltage drops to about 120 v. and this decrease is used for switching off the starting circuit on both ends by means of both glow discharges bimetal relays (glowstarter) G.
'Theseglow-starters are of special three-electrode design and work as follows: When the mains Ne is switched on, the full mains voltage is between the outer lamp con- Emotions and between the movable bimetal electrodes '1 and the fixed counter electrodes 3 of the glow-starters. For this purpose the latter are connected to the opposite lamp connections by means of the relatively great auxiliary resistors H. A glow discharge is started in the glow starters, the current of which is limited by the resistors H. This current heats the Lbimetal electrodes 1, the same approachthe electrodes 2 and make contact to them. By contact between :1 and '2 the "starting circuit is switched on, the filament Z starts glowing and the are between the electrodes 5 results in a great drop of the electrode voltage, the glow discharge in the glow-starters cannot be maintained and extinguishes. The bimetal electrodes 1 open the contacts between 2 and 1, thus switching ofi the starting circuit on both ends. It is switched on again only after the mains voltage is connected again to the main electrodes after the era has b en xt ngu sh The elec rod s in the glowstarters can be arranged so that the bimetal contact touches both electrodes 2 and 3 at the same time or shortly one after the other (first 2, then 3). The starting circuit is closed then only for the short moment between the extinguishing of the short-circuited glow discharge and the moment when the bimetal electrodes have cooled down enough to open the contact again. In this case the glow-starters operate automatically several times until an arc has started between the main electrodes of the lamps. If the starting circuit is to be switched off only on one end of the filament, this can be done by means of a simple .twoeelect-rode glow-starter.
Having thus disclosed my invention what I claim as new and desire to secure by Letters Patent of the United States is:
The combination which comprises an electric highpressure gas-discharge lamp having an envelope with lamp electrodes spaced apart from one another within said envelope and adaptedto have an arc discharge maintained in a path therebetween, and a starting arrangement comprising, a double-ended starting conductor within said envelope and paralleling and adjacent to said discharge path, first and second three-element glow starters positioned exteriorly of said envelope, each of said starters having a bi-rnetal first electrode, a second electrode and a third electrode, said starter electrodes being normally spaced from one another, a first resistor electrically connected between said bi-metal electrode of said first starter and said third electrode of said second starter, said til-metal electrode of said first starter being directly electrically connected to one of said lamp electrodes, a second resistor electrically connected between said bi-rnetal electrode of said second starter and said third electrode of said first starter, said bi-metal electrade of said second starter being directly electrically connected to the other of said lamp electrodes, a third resistor electrically connected between said second electrode of said first starter and one end of said starting conductor, a fourth resistor electrically connected between said second electrode of said second starter and the other end of said starting conductor, each of said starters being adapted to maintain a glow discharge between their first and third electrodes upon application of an operating potential thereacross, each of said himetal electrodes upon receiving heat from said glow discharges being adapted to move into contacting relationship with the said second electrode of its respective starter to place a potential across said starting conductor to cause same to heat, the breakdown potential across said lamp electrodes being lowered by the heat of said starting conductor to cause said are discharge to occur thereacross, said are discharge being of sufficiently low resistance to extinguish the glow discharges in said starters to cause each of said bi-metal electrodes to cool, each of said bi-metal electrodes upon cooling being adapted to resume their normal spaced relationship, whereby said starting conductor is electrically isolated by said starters. I
References Cited in the file of this patent UNITED STATES PATENTS 1,990,170 Dellian 'Feb. 5, 1935 2,177,105 Gustin Oct. 24 1939 2,263,171 Hays V Nov. 118, 1941 12,275,768 "Kern Mar. 10, 194 2
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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2966607A (en) * 1959-05-26 1960-12-27 Duro Test Corp High pressure short arc lamps and method of making same
DE1124603B (en) * 1959-05-15 1962-03-01 Patra Patent Treuhand High-pressure discharge lamp with a filling pressure equal to or less than 2 at
DE1132657B (en) * 1959-05-15 1962-07-05 Patra Patent Treuhand High-pressure discharge lamp with an ignition coil arranged in the discharge space parallel to the discharge
US3093769A (en) * 1959-05-15 1963-06-11 Patent Treuhand Ges Fuer Elektrische Gluehlampen Mbh Mixed-light electric lamp
US4316122A (en) * 1979-10-03 1982-02-16 Matsushita Electronics Corporation High pressure sodium vapor discharge lamp
US4431945A (en) * 1981-03-16 1984-02-14 Tokyo Shibaura Denki Kabushiki Kaisha High pressure metal vapor discharge lamp

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1990170A (en) * 1932-12-07 1935-02-05 Gen Electric Gaseous electric discharge lamp device
US2177105A (en) * 1937-07-03 1939-10-24 Westinghouse Electric & Mfg Co Vapor discharge lamp
US2263171A (en) * 1940-07-05 1941-11-18 Westinghouse Electric & Mfg Co Gaseous discharge lamp
US2275768A (en) * 1939-06-17 1942-03-10 Gen Electric Electric lamp

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1990170A (en) * 1932-12-07 1935-02-05 Gen Electric Gaseous electric discharge lamp device
US2177105A (en) * 1937-07-03 1939-10-24 Westinghouse Electric & Mfg Co Vapor discharge lamp
US2275768A (en) * 1939-06-17 1942-03-10 Gen Electric Electric lamp
US2263171A (en) * 1940-07-05 1941-11-18 Westinghouse Electric & Mfg Co Gaseous discharge lamp

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1124603B (en) * 1959-05-15 1962-03-01 Patra Patent Treuhand High-pressure discharge lamp with a filling pressure equal to or less than 2 at
DE1132657B (en) * 1959-05-15 1962-07-05 Patra Patent Treuhand High-pressure discharge lamp with an ignition coil arranged in the discharge space parallel to the discharge
US3093769A (en) * 1959-05-15 1963-06-11 Patent Treuhand Ges Fuer Elektrische Gluehlampen Mbh Mixed-light electric lamp
US2966607A (en) * 1959-05-26 1960-12-27 Duro Test Corp High pressure short arc lamps and method of making same
US4316122A (en) * 1979-10-03 1982-02-16 Matsushita Electronics Corporation High pressure sodium vapor discharge lamp
US4431945A (en) * 1981-03-16 1984-02-14 Tokyo Shibaura Denki Kabushiki Kaisha High pressure metal vapor discharge lamp

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