WO2009141765A1 - Fluorescent lamp with electrode shield - Google Patents

Fluorescent lamp with electrode shield Download PDF

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Publication number
WO2009141765A1
WO2009141765A1 PCT/IB2009/051983 IB2009051983W WO2009141765A1 WO 2009141765 A1 WO2009141765 A1 WO 2009141765A1 IB 2009051983 W IB2009051983 W IB 2009051983W WO 2009141765 A1 WO2009141765 A1 WO 2009141765A1
Authority
WO
WIPO (PCT)
Prior art keywords
lead
electrode
wires
envelope
wire
Prior art date
Application number
PCT/IB2009/051983
Other languages
French (fr)
Inventor
Johannes T. J. Van Haastrecht
Original Assignee
Koninklijke Philips Electronics N.V.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Koninklijke Philips Electronics N.V. filed Critical Koninklijke Philips Electronics N.V.
Publication of WO2009141765A1 publication Critical patent/WO2009141765A1/en

Links

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J61/00—Gas-discharge or vapour-discharge lamps
    • H01J61/02—Details
    • H01J61/04—Electrodes; Screens; Shields
    • H01J61/06—Main electrodes
    • H01J61/067—Main electrodes for low-pressure discharge lamps
    • H01J61/0672—Main electrodes for low-pressure discharge lamps characterised by the construction of the electrode
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J61/00—Gas-discharge or vapour-discharge lamps
    • H01J61/02—Details
    • H01J61/04—Electrodes; Screens; Shields
    • H01J61/10—Shields, screens, or guides for influencing the discharge

Definitions

  • a fluorescent lamp comprising an elongated glass envelope
  • the invention is related to a fluorescent lamp comprising an elongated glass envelope and a mount structure sealing each end of said elongated envelope, each of said mount structures having a glass base, and two separated lead-in wires being embedded in said glass base and extending into said envelope where they are interconnected by an electrode, the two lead-in wires being connected with two electric contact members extending outside the mount structure for connection with the power supply of a lamp holder, and an electrode shield surrounding each electrode, said electrode shield being electro conductive Iy connected with one of the two lead-in wires.
  • a fluorescent lamp is disclosed in US-A-2005/0200257.
  • the disclosed lamp is provided with a metal electrode shield having an open top side, which top side is directed towards the other end of the elongated envelope.
  • the bottom side is also open and is directed towards the glass base of the mount structure, in which glass base the two lead-in wires are embedded.
  • the electrode shield reduces the so-called end blackening of the elongated envelope of the lamp, which end blackening is caused by the deposition of sputtered and evaporated compounds from the electrode on the cooler ends of the elongated glass envelope during operation of the lamp.
  • the electrode shield is made electrically active by connecting the electrode shield electrically with one of the lead-in wires.
  • the electrode shield may have an open bottom, but the bottom may be closed, or partially closed as is described in US-B-6741023.
  • the electrode shield may have a Faraday cage structure in order to prevent the entry or escape of an electromagnetic field, so that the portion of the electrode enclosed in the cage will not be affected by the electric field from the other electrode. Therefore, the lamp will not ignite on the portion of the electrode being enclosed by the Faraday cage.
  • the electrode shield When the electrode shield is made electrically active, i.e. the shield is electro conductive Iy connected with one of the lead-in wires, the electrode shield cooperates with the electrode during the anode phase of the electrode, whereby it receives electrons just like the electrode does. In experiments it has been found that even more than 75% of the lamp current may flow through the electrode shield during the anode phase of the electrode. On the other hand, during the cathode phase of the electrode, the flow of current through the electrode shield appeared to be relatively low.
  • the elongated fluorescent lamp can be mounted in a lamp holder in such a manner that the two ends of the lamp are engaged by the lamp holder.
  • the two electric contact members at each end of the lamp make contact with two corresponding electric contact elements of the lamp holder.
  • the lamp holder comprises control means for guiding electric power to the contact elements in order to provide the two electrodes of the lamp with an alternating voltage (potential difference) and to provide for an electric current through the electrodes, so that the electrodes are heated to a predetermined temperature.
  • the object of the invention is to provide a fluorescent lamp comprising an elongated glass envelope enclosing an electrode at each end of the envelope, wherein an electrode shield surrounds each of the electrodes, which electrode shield is electroconductively connected with one of the two lead-in wires, whereby the lifetime of the lamp is improved.
  • the two lead-in wires are connected by means of a diode bridge with the two electric contact members in such a way that the lead-in wire which is connected to the electrode shield is continuously the negative lead-in wire.
  • the negative lead-in wire is the lead-in wire having the lower voltage compared to the other lead-in wire, being the positive lead-in wire.
  • the lamp can be mounted in the lamp holder in two positions, wherein it is not predetermined which contact member of the lamp engages each of the contact elements of the lamp holder. Therefore, each contact member can be the electrically negative or the electrically positive contact member.
  • a predetermined lead-in wire will always be the negative lead-in wire, so that the electrode shield can be connected with that negative lead-in wire.
  • a diode bridge is well known. It is an arrangement of four diodes connected in a bridge circuit, that provides the same polarity of output voltage for any polarity of the input voltage.
  • the electrode shield By connecting the electrode shield with the negative lead-in wire, the electrons received by the electrode shield are guided through the electrode during the anode phase of the electrode. Thereby, the current through the electrode is increased, so that the temperature of the electrode is increased, resulting in a longer lifetime of the lamp.
  • the electrode shield can be connected to a support member being embedded in the glass base of the mount structure.
  • the electrode shield is supported by the lead-in wire to which it is electrically connected, so that no additional mounting means for the electrode shield are required.
  • Publication US-A- 2005/0200257 describes such a supporting structure.
  • the glass base of the mount structure is shaped like a dome having its concave surface outside the glass envelope, with the diode bridge being located inside said dome.
  • the invention will now be further elucidated by means of a description of an embodiment of an elongated fluorescent lamp comprising an elongated glass envelope enclosing an electrode at each end of the envelope, reference being made to the drawing comprising a diagrammatic Figure.
  • the Figure shows the end portion of the elongated fluorescent lamp in a cross sectional view.
  • the lamp comprises an elongated cylindrical glass envelope 1, and both ends of the envelope 1 are sealed by the glass base 2 of the mount structure 3.
  • the glass base 2 has the shape of a dome, and its circular edge 4 is melted to the circular edge 5 of the glass envelope 1.
  • the mount structure 3 furthermore comprises a cap 6 of electrically insulating material being connected to the edge 5 of the glass envelope 1 and the edge 4 of the glass base 2.
  • the cap 6 comprises two bar-shaped electrical contact members 7,8.
  • Electrode 9 situated between the ends of two lead-in wires 10,11, which lead-in wires 10,11 are embedded in the glass base 2 of the mount structure 3.
  • the electrode 9 is surrounded by a metal electrode shield 12, which electrode shield 12 is electro conductive Iy connected by means of a supporting member 13 with the lead-in wire 10.
  • the closed space 19 between the cap 6 and the dome-shaped glass base 2 of the mount structure 3 comprises a diode bridge 14.
  • the diode bridge 14 comprises four diodes arranged in such a manner that the polarity of its two output wires 15,16 is always the same, independent of the polarity of the two input wires 17,18 of the diode bridge 14.
  • output wire 15 is the negative output wire
  • output wire 16 is the positive output wire.
  • the two input wires 17,18 of the diode bridge 14 are connected with the two contact members 7,8 attached to the cap 6.
  • the two output wires 15,16 of the diode bridge 14 are connected with the two lead-in wires 10,11 embedded in glass base 2, so that lead-in wire 10 is continuously the negative lead-in wire during operation of the lamp.
  • the electrode 9 receives electrons from the electrode at the other end of the elongated glass envelope 1, which other electrode is at that moment in its cathode phase. Because the electrode shield 12 is electrically active, i.e. is connected with one of the lead-in wires 10, also the electrode shield 12 will receive electrons during the anode phase of the electrode 9. Because the electrode shield 12 is connected with the negative lead-in wire 10, the received electrons will flow through the electrode 9 to lead- in wire 11, and thereby increase the temperature of the electrode 9. During operation of the lamp, the two contact members 7,8 will be connected with corresponding contact elements in the lamp holder carrying the lamp.
  • each of the two contact members 7,8 are identical and rotationally symmetrically mounted in the cap 6 of the mount structure 3 of the lamp, each of the two contact members 7,8, can be connected with each of the two contact elements of the lamp holder.
  • the polarity of the contact members 7,8 during operation of the lamp is not predictable.
  • the lead-in wire 10 is always the negative lead-in wire during operation of the lamp.
  • the mount structure 3 as shown in the Figure, including the diode bridge 14, is present at both ends of the cylindrical glass envelope 1 of the lamp.
  • the described embodiment of the invention is only an example, and many other embodiments are possible within the scope of the invention.

Landscapes

  • Vessels And Coating Films For Discharge Lamps (AREA)

Abstract

A fluorescent lamp comprising an elongated glass envelope (1) and a mount structure (3) sealing each end of said elongated envelope. Each of the mount structures (3) has a glass base (2), wherein two separated lead-in wires (10,11) are embedded in said glass base (2) and extend into said envelope (1) where they are interconnected by an electrode (9). An electrode shield (12) surrounds each electrode (9), which electrode shield (12) is electroconductively connected with one (10) of the two lead-in wires (10,11). At each end of the elongated glass envelope (1), the two lead-in wires (10,11) are connected by means of a diode bridge (14) with two electric contact members (7,8) extending outside the mount structure (3), so that the lead-in wire (10) which is connected to the electrode shield (12) is continuously the negative lead-in wire.

Description

A fluorescent lamp comprising an elongated glass envelope
FLUORESCENT LAMP WITH ELECTRODE SHIELD
FIELD OF THE INVENTION
The invention is related to a fluorescent lamp comprising an elongated glass envelope and a mount structure sealing each end of said elongated envelope, each of said mount structures having a glass base, and two separated lead-in wires being embedded in said glass base and extending into said envelope where they are interconnected by an electrode, the two lead-in wires being connected with two electric contact members extending outside the mount structure for connection with the power supply of a lamp holder, and an electrode shield surrounding each electrode, said electrode shield being electro conductive Iy connected with one of the two lead-in wires. Such a fluorescent lamp is disclosed in US-A-2005/0200257. The disclosed lamp is provided with a metal electrode shield having an open top side, which top side is directed towards the other end of the elongated envelope. The bottom side is also open and is directed towards the glass base of the mount structure, in which glass base the two lead-in wires are embedded. The electrode shield reduces the so-called end blackening of the elongated envelope of the lamp, which end blackening is caused by the deposition of sputtered and evaporated compounds from the electrode on the cooler ends of the elongated glass envelope during operation of the lamp. In order to improve the functioning of the fluorescent lamp, the electrode shield is made electrically active by connecting the electrode shield electrically with one of the lead-in wires. The electrode shield may have an open bottom, but the bottom may be closed, or partially closed as is described in US-B-6741023. Furthermore, the electrode shield may have a Faraday cage structure in order to prevent the entry or escape of an electromagnetic field, so that the portion of the electrode enclosed in the cage will not be affected by the electric field from the other electrode. Therefore, the lamp will not ignite on the portion of the electrode being enclosed by the Faraday cage.
When the electrode shield is made electrically active, i.e. the shield is electro conductive Iy connected with one of the lead-in wires, the electrode shield cooperates with the electrode during the anode phase of the electrode, whereby it receives electrons just like the electrode does. In experiments it has been found that even more than 75% of the lamp current may flow through the electrode shield during the anode phase of the electrode. On the other hand, during the cathode phase of the electrode, the flow of current through the electrode shield appeared to be relatively low.
In general, the elongated fluorescent lamp can be mounted in a lamp holder in such a manner that the two ends of the lamp are engaged by the lamp holder. In the mounted state of the lamp, the two electric contact members at each end of the lamp make contact with two corresponding electric contact elements of the lamp holder. The lamp holder comprises control means for guiding electric power to the contact elements in order to provide the two electrodes of the lamp with an alternating voltage (potential difference) and to provide for an electric current through the electrodes, so that the electrodes are heated to a predetermined temperature.
The object of the invention is to provide a fluorescent lamp comprising an elongated glass envelope enclosing an electrode at each end of the envelope, wherein an electrode shield surrounds each of the electrodes, which electrode shield is electroconductively connected with one of the two lead-in wires, whereby the lifetime of the lamp is improved.
In order to achieve this object, at each end of the elongated glass envelope the two lead-in wires are connected by means of a diode bridge with the two electric contact members in such a way that the lead-in wire which is connected to the electrode shield is continuously the negative lead-in wire. The negative lead-in wire is the lead-in wire having the lower voltage compared to the other lead-in wire, being the positive lead-in wire.
In general, the lamp can be mounted in the lamp holder in two positions, wherein it is not predetermined which contact member of the lamp engages each of the contact elements of the lamp holder. Therefore, each contact member can be the electrically negative or the electrically positive contact member. By connecting the contact members by means of a diode bridge with the lead-in wires, a predetermined lead-in wire will always be the negative lead-in wire, so that the electrode shield can be connected with that negative lead-in wire.
A diode bridge is well known. It is an arrangement of four diodes connected in a bridge circuit, that provides the same polarity of output voltage for any polarity of the input voltage.
By connecting the electrode shield with the negative lead-in wire, the electrons received by the electrode shield are guided through the electrode during the anode phase of the electrode. Thereby, the current through the electrode is increased, so that the temperature of the electrode is increased, resulting in a longer lifetime of the lamp.
The electrode shield can be connected to a support member being embedded in the glass base of the mount structure. However, in a preferred embodiment, the electrode shield is supported by the lead-in wire to which it is electrically connected, so that no additional mounting means for the electrode shield are required. Publication US-A- 2005/0200257 describes such a supporting structure.
In a preferred embodiment, the glass base of the mount structure is shaped like a dome having its concave surface outside the glass envelope, with the diode bridge being located inside said dome. The result is a compact mount structure.
The invention will now be further elucidated by means of a description of an embodiment of an elongated fluorescent lamp comprising an elongated glass envelope enclosing an electrode at each end of the envelope, reference being made to the drawing comprising a diagrammatic Figure. The Figure shows the end portion of the elongated fluorescent lamp in a cross sectional view. The lamp comprises an elongated cylindrical glass envelope 1, and both ends of the envelope 1 are sealed by the glass base 2 of the mount structure 3. The glass base 2 has the shape of a dome, and its circular edge 4 is melted to the circular edge 5 of the glass envelope 1. The mount structure 3 furthermore comprises a cap 6 of electrically insulating material being connected to the edge 5 of the glass envelope 1 and the edge 4 of the glass base 2. The cap 6 comprises two bar-shaped electrical contact members 7,8.
Inside the elongated glass envelope 1 there is an electrode 9 situated between the ends of two lead-in wires 10,11, which lead-in wires 10,11 are embedded in the glass base 2 of the mount structure 3. The electrode 9 is surrounded by a metal electrode shield 12, which electrode shield 12 is electro conductive Iy connected by means of a supporting member 13 with the lead-in wire 10.
The closed space 19 between the cap 6 and the dome-shaped glass base 2 of the mount structure 3 comprises a diode bridge 14. The diode bridge 14 comprises four diodes arranged in such a manner that the polarity of its two output wires 15,16 is always the same, independent of the polarity of the two input wires 17,18 of the diode bridge 14. Here, output wire 15 is the negative output wire and output wire 16 is the positive output wire. The two input wires 17,18 of the diode bridge 14 are connected with the two contact members 7,8 attached to the cap 6. The two output wires 15,16 of the diode bridge 14 are connected with the two lead-in wires 10,11 embedded in glass base 2, so that lead-in wire 10 is continuously the negative lead-in wire during operation of the lamp.
In the anode phase of the electrode 9, the electrode 9 receives electrons from the electrode at the other end of the elongated glass envelope 1, which other electrode is at that moment in its cathode phase. Because the electrode shield 12 is electrically active, i.e. is connected with one of the lead-in wires 10, also the electrode shield 12 will receive electrons during the anode phase of the electrode 9. Because the electrode shield 12 is connected with the negative lead-in wire 10, the received electrons will flow through the electrode 9 to lead- in wire 11, and thereby increase the temperature of the electrode 9. During operation of the lamp, the two contact members 7,8 will be connected with corresponding contact elements in the lamp holder carrying the lamp. Because the two contact members 7,8 are identical and rotationally symmetrically mounted in the cap 6 of the mount structure 3 of the lamp, each of the two contact members 7,8, can be connected with each of the two contact elements of the lamp holder. Thus, the polarity of the contact members 7,8 during operation of the lamp is not predictable. However, by making use of the diode bridge 14, the lead-in wire 10 is always the negative lead-in wire during operation of the lamp.
The mount structure 3 as shown in the Figure, including the diode bridge 14, is present at both ends of the cylindrical glass envelope 1 of the lamp. The described embodiment of the invention is only an example, and many other embodiments are possible within the scope of the invention.

Claims

CLAIMS:
1. A fluorescent lamp comprising an elongated glass envelope and a mount structure sealing each end of said elongated envelope, each of said mount structures having a glass base, and two separated lead-in wires being embedded in said glass base and extending into said envelope where they are interconnected by an electrode, the two lead-in wires being connected with two electric contact members extending outside the mount structure for connection with the power supply of a lamp holder, and an electrode shield surrounding each electrode, said electrode shield being electro conductive Iy connected with one of the two lead- in wires, characterized in that, at each end of the elongated glass envelope, the two lead-in wires are connected by means of a diode bridge with the two electric contact members, so that the lead-in wire which is connected to the electrode shield is continuously the negative lead-in wire.
2. A fluorescent lamp as claimed in claim 1, characterized in that said electrode shield is supported by the lead-in wire to which it is electrically connected.
3. A fluorescent lamp as claimed in any one of the preceding claims, characterized in that the glass base of the mount structure is shaped like a dome having its concave surface outside the glass envelope, and the diode bridge is located inside said dome.
PCT/IB2009/051983 2008-05-20 2009-05-13 Fluorescent lamp with electrode shield WO2009141765A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
EP08156530.1 2008-05-20
EP08156530 2008-05-20

Publications (1)

Publication Number Publication Date
WO2009141765A1 true WO2009141765A1 (en) 2009-11-26

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ID=40910892

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/IB2009/051983 WO2009141765A1 (en) 2008-05-20 2009-05-13 Fluorescent lamp with electrode shield

Country Status (1)

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WO (1) WO2009141765A1 (en)

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DD221881A1 (en) * 1983-12-14 1985-05-02 Ilmenau Tech Hochschule AUXILIARY ELECTRODE FOR ELECTRIC GAS DISCHARGE LAMP OPERATED WITH AC VOLTAGE
US5004949A (en) * 1988-05-31 1991-04-02 North American Philips Corporation Fluorescent lamp with grounded electrode guard
US20050200257A1 (en) * 2005-06-02 2005-09-15 Osram Sylvania Inc. Fluorescent lamp with reduced end blackening and mount therefor

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DD221881A1 (en) * 1983-12-14 1985-05-02 Ilmenau Tech Hochschule AUXILIARY ELECTRODE FOR ELECTRIC GAS DISCHARGE LAMP OPERATED WITH AC VOLTAGE
US5004949A (en) * 1988-05-31 1991-04-02 North American Philips Corporation Fluorescent lamp with grounded electrode guard
US20050200257A1 (en) * 2005-06-02 2005-09-15 Osram Sylvania Inc. Fluorescent lamp with reduced end blackening and mount therefor

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