UV lamp

Abstract

A gas discharge lamp and a photoionization sensor employing the same. The lamp includes a housing containing a working gas sealed within the housing and a first UV-transmitting window extending through a first longitudinal end of the housing. In a first embodiment, the lamp includes an arcuate band of elastic getter material having diametrically opposed legs that are wedged within a chamber defined by the housing. In a second embodiment, the lamp includes a second UV-transmitting window within the housing, the second UV-transmitting window being held in place against the first UV-transmitting window by an arcuate metal support band within the housing.

Description

Technical Field

[0001] The invention relates to a UV lamp. Background Art

[0002] Gas discharge lamps are used in a variety of applications to emit radiation within a defined frequency bandwidth. Such lamps are often employed in analytical chemistry instruments, particularly gas sensors based on the principle of photoionization, known as photoionization detectors (PIDs). In one common design, radiation is emitted by the lamp through capacitive excitation of a working gas retained within the lamp using a pair of excitation electrodes located radially on opposite sides of the lamp. One such gas discharge lamp is described in U.S. Patent No. 6,646,444, the contents of which are incorporated herein by reference. Alternatively, the working gas can be inductively excited. As disclosed in U.S. Patent No. 6,646,444, the preferred working gas is krypton.

[0003] To maintain proper performance of gas discharge lamps, the working gas needs to remain relatively pure. Contamination of the working gas within the lamp (e.g., residual gas remaining in the lamp during the manufacturing process or adsorbed gas gradually released into the lamp) degrades operability and performance.

[0004] Getters are often incorporated into gas discharge lamps to reduce or eliminate contaminant gases within the lamp. Getters work by chemically combining with or adsorbing the contaminant gases, thereby preventing them from interfering with the excitation and emission of the working gas.

[0005] When located between the electrodes on the lamp, the getter can interfere with ignition of the gas discharge lamp, while when located above the UV window of the lamp, the getter can interfere with the propagation of ultraviolet (UV) light. Therefore, the getter should be positioned within the lamp to avoid being located between the electrodes or above the UV window and should be fixed in such a sideways position. One technique for achieving this is disclosed in U.S. Patent 9,368,338, in which one end of a getter strip is embedded in the closed end of the lamp housing.

[0006] The technology disclosed in U.S. Patent 9368338 is a significant advancement over previous efforts, but has certain drawbacks, such as loss of control over the final shape of the lamp housing and inconsistent positioning of the getter within the lamp body. Therefore, there remains a need for alternative methods of fixedly incorporating getters into UV lamps.

[0007] The range of gaseous volatile organic compounds (VOCs) detectable by VOC gas detection sensors using photoionization is controlled by the electron volt (eV) energy emitted by the lamp. The eV rating of a lamp depends on the type of fill gas used by the lamp and the spectral filtering method used for the lamp.

[0008] A typical krypton-filled lamp used for photoionization detection purposes has an eV rating of 10.6, or simply "10.6eV." This means that the detection sensor is capable of detecting any and all VOC gases with an ionization potential of 10.6 or less.

[0009] For some applications, it's desirable to limit the range of detectable VOC gases by filtering some of the energy emitted by the lamp. One approach is to add a calcium fluoride window to the lamp. Calcium fluoride crystals are transparent to a narrower range of UV wavelengths than the standard magnesium fluoride crystal windows used on lamps. Therefore, adding a calcium fluoride window to a typical 10.6 eV UV lamp would shift its rating from 10.6 eV to 10.0 eV.

[0010] The typical method of adding a calcium fluoride window is to attach the window directly on top of the magnesium fluoride window using epoxy, cement, adhesive, etc. This method of attaching the calcium fluoride window has several disadvantages, including damage to the fragile calcium fluoride window and / or magnesium fluoride window during the attachment of the calcium fluoride window, the calcium fluoride window and / or magnesium fluoride window becoming detached from the lamp, and the risk of cleaning fluid used to clean the lamp becoming trapped between the two windows and significantly blocking UV transmission through the windows.

[0011] Therefore, there remains a need for a 10.0 eV lamp that avoids the disadvantages associated with conventional 10.0 eV lamps that have a calcium fluoride window mounted directly on top of a magnesium fluoride window, without incurring other significant disadvantages. Summary of the Invention

[0012] A first aspect of the present invention is an ultraviolet gas discharge lamp.

[0013] A first embodiment of the first aspect of the present invention is a gas discharge lamp with an enclosed getter. The lamp comprises a housing, a UV-transmitting window, a working gas, and an arcuate strip of resilient getter material. The housing, preferably glass, defines a longitudinal axis and has a chamber of defined contour having openings at longitudinal ends. The UV-transmitting window sealingly covers the opening in the housing so as to hermetically seal the chamber. The working gas is sealed within the chamber. The arcuate strip of resilient getter material is located within the chamber and has diametrically opposed longitudinally extending legs, each leg having an end proximal to the UV-transmitting window, and each leg being biased outwardly into engagement with the housing, thereby wedging the strip into the chamber.

[0014] A second embodiment of the first aspect of the present invention is a double-window gas discharge lamp. The lamp includes a housing, a first UV-transmitting window, a working gas, an arcuate metal support band, and a second UV-transmitting window. The housing (preferably glass) defines a longitudinal axis and has a chamber with a defined contour, the chamber having openings at longitudinal ends. The first UV-transmitting window is made of a first material and sealingly covers the opening in the housing so as to hermetically seal the chamber. The working gas is sealed within the chamber. The arcuate metal support band is located within the chamber and has diametrically opposed longitudinally extending legs, each leg having an end proximal to the first UV-transmitting window and offset in the longitudinal direction. The second UV-transmitting window is made of a second material different from the first material and is sandwiched within the chamber between the first UV-transmitting window and the end of the arcuate metal support band.

[0015] The ultraviolet gas discharge lamp of both embodiments may include a pair of metallic energizing electrodes positioned radially about the longitudinal axis on or within the housing.

[0016] A second aspect of the present invention is a photoionization sensor comprising the ultraviolet gas discharge lamp according to the first aspect of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is an isometric view of one embodiment of the present invention.

[0018] Figure 2 yes Figure 1 A bottom view of the present invention is shown in FIG.

[0019] Figure 3 yes Figure 1 A top view of the present invention is shown in FIG.

[0020] Figure 4 yes Figure 1 A front view of the present invention is shown in FIG.

[0021] Figure 5 yes Figure 1 A right side view of the present invention is shown in FIG.

[0022] Figure 6 yes Figure 1 A rear view of the present invention is shown in FIG.

[0023] Figure 7 yes Figure 1 A left side view of the present invention is shown in FIG.

[0024] Figure 8 yes Figure 7 The main enlarged portion of the invention shown in FIG. 1 is used to enable the depiction of the working gas at the molecular level.

[0025] Figure 9 yes Figure 1 Front view of the getter tape shown in .

[0026] Figure 10 yes Figure 1 Side view of the getter strip shown in .

[0027] Figure 11 is an isometric view of one embodiment of the present invention.

[0028] Figure 12 yes Figure 11 A bottom view of the present invention is shown in FIG.

[0029] Figure 13 yes Figure 11 A top view of the present invention is shown in FIG.

[0030] Figure 14 yes Figure 11 A front view of the present invention is shown in FIG.

[0031] Figure 15 yes Figure 11 A right side view of the present invention is shown in FIG.

[0032] Figure 16 yes Figure 11 A rear view of the present invention is shown in FIG.

[0033] Figure 17 yes Figure 11 A left side view of the present invention is shown in FIG.

[0034] Figure 18 yes Figure 11 A front view of the support belt shown in FIG.

[0035] Figure 19 yes Figure 11 Side view of the support belt shown in .

[0036] Figure 20 yes Figure 11 A side view of the second ultraviolet transmission window is shown in FIG. DETAILED DESCRIPTION

[0037] Reference Numbers

[0038] 10. Ultraviolet gas discharge lamp

[0039] 20 lamp housing

[0040] 21 First longitudinal end of the lamp housing

[0041] 22 Second longitudinal end of the lamp housing

[0042] 28 through the opening at the first longitudinal end of the lamp housing

[0043] 29 Lamp housing chamber

[0044] 30 UV rays through the window

[0045] 31 First UV transmission window

[0046] 32 Second UV light transmission window

[0047] 32c Second ultraviolet light passes through the peripheral edge of the window

[0048] 40 belts

[0049] 40′ Getter Tape

[0050] 40'' support belt

[0051] 41 The first leg of the belt

[0052] 41d The distal end of the first leg of the belt

[0053] 41t A tab formed at the distal end of the first leg of the support strap

[0054] 42 with the second leg

[0055] 42d The distal end of the second leg of the belt

[0056] 42t A tab formed at the distal end of the second leg of the support strap

[0057] 43 The curved part of the belt

[0058] 50 excitation electrodes

[0059] 51 first excitation electrode

[0060] 52 second excitation electrode

[0061] 60 working gas

[0062] x1 longitudinal axis of the housing

[0063] r radial direction from the longitudinal axis of the housing

[0064] c Circumferential direction around the longitudinal axis of the housing

[0065] structure

[0066] First embodiment

[0067] refer to Figure 1-7A first embodiment of the first aspect of the present invention is a gas discharge lamp 10, particularly an ultraviolet discharge lamp 10 suitable for use with a photoionization sensor (not shown). Lamp 10 includes a housing 20, an ultraviolet-transmissive window 30, a getter strip 40', and a working gas 60. Lamp 10 may also include a pair of metallic excitation electrodes 51 and 52 (collectively referred to as electrodes 50), radially positioned on or within housing 20 about a longitudinal axis x1 of housing 20. When attached to lamp 10, electrodes 50 are preferably attached to an outer surface of housing 20.

[0068] The housing 20 is preferably constructed of glass, defines a longitudinal axis x1 , and has a first longitudinal end 21 , a second longitudinal end 22 , and a chamber 29 having a defined contour and an opening 28 into the chamber 29 through the first longitudinal end 21 .

[0069] The UV-transmitting window 30 is made of a UV-transmitting material, typically magnesium fluoride crystal, and is sealingly attached to the housing 20 above the opening 28 to hermetically seal the chamber 29 .

[0070] refer to Figure 8 A working gas 60 (usually an inert gas, such as krypton) is sealed in the chamber 29. Hydrogen can also be used as the working gas 60.

[0071] refer to Figure 9 and 10 The getter strip 40' is formed of a resilient getter material and has a pair of diametrically opposed first and second legs 41 and 42 connected to each other at proximal ends (not numbered) by curved portions 43 and 42, and each having a distal end 41d and 42d. The getter strip 40' preferably has a contour corresponding to the contour of the chamber 29, with the spacing between the distal ends 41d and 42d of the getter strip 40' being slightly greater than the diameter of the chamber 29. Thus, the getter strip 40' is resiliently biased against the wall of the housing 20 to wedge the getter strip 40' into a fixed position within the chamber 29.

[0072] refer to Figure 1 and 4 -7, the getter strip 40 ′ is positioned in the chamber 29 , with distal ends 41 d and 42 d proximal to the UV-transmitting window 30 .

[0073] The getter strip 40' is constructed of an oxidizable metal getter material, such as titanium or a sintered getter alloy. The length of the getter strip 40' (i.e., the dimension along the getter strip 40' extending from the distal end 41d to the distal end 42d) is a length that enables the getter strip 40' to be firmly biased outwardly and wedged into the chamber 29 without interfering with the attachment of the UV-transmitting window 30 to the housing 20. Typically, a length of approximately 6 to 12 mm and a width of approximately 1 to 2 mm are effective. A thickness in the radial direction r of approximately 0.05 to 0.3 mm is a generally cost-effective range for providing the desired structural integrity to provide the getter strip 40' with the desired amount of resilience to allow the getter strip 40' to be wedged into the chamber 29.

[0074] The legs 41 and 42 of the getter strip 40 ′ and the energizing electrodes 51 and 52 are preferably evenly circumferentially spaced relative to each other about the chamber 29 to minimize any disturbance that may be imparted to the getter strip 40 ′ when the working gas 60 is energized by the electrodes 50 .

[0075] Second embodiment

[0076] refer to Figure 11-17 A second embodiment of the first aspect of the present invention is a gas discharge lamp 10, particularly an ultraviolet discharge lamp 10 suitable for use with a photoionization sensor (not shown). Lamp 10 includes a housing 20, a first ultraviolet transmission window 31, a second ultraviolet transmission window 32, a support belt 40", and a working gas 60. Lamp 10 may also include a pair of metallic excitation electrodes 51 and 52 (collectively referred to as electrodes 50), radially positioned on or within housing 20 about the longitudinal axis x1 of housing 20. When attached to lamp 10, electrodes 50 are preferably attached to the outer surface of housing 20.

[0077] The housing 20 is preferably constructed of glass, defines a longitudinal axis x1 , and has a first longitudinal end 21 , a second longitudinal end 22 , and a chamber 29 having a defined contour and an opening 28 into the chamber 29 through the first longitudinal end 21 .

[0078] The first UV-transmitting window 31 is made of a first material, typically magnesium fluoride crystal, and is sealingly attached to the housing 20 above the opening 28 to hermetically seal the chamber 29 .

[0079] refer to Figure 8 As in the first embodiment, a working gas 60 (usually an inert gas, such as krypton) is sealed in the chamber 29. Hydrogen can also be used as the working gas 60.

[0080] refer to Figure 18 and 19The arched support band 40' has a pair of diametrically opposed first and second legs 41 and 42, which are connected to each other at the proximal end (not numbered) by a bent portion 43 and each has a distal end 41d and 42d. The contour of the support band 40' preferably corresponds to the contour of the chamber 29. Like the getter band 40', the support band 40' can be made of an elastic material, and the spacing between the distal ends 41d and 42d of the support band 40' is slightly larger than the diameter of the chamber 29, so that the support band 40" is elastically biased against the wall of the shell 20 so as to wedge the support band 40' into a fixed position within the chamber 29.

[0081] refer to Figure 11 and 14 -17, the support belt 40 ″ is positioned in the chamber 29 and has distal ends 41 d and 42 d that are proximal to the first ultraviolet transmission window 31 and offset longitudinally. The distal ends 41 d and 42 d of the legs 41 and 42 are each preferably bent inwardly toward the longitudinal axis x1 of the housing 20 to produce inwardly protruding support tabs 41 t and 42 t.

[0082] The support band 40" can be made of an oxidizable metal getter material, such as titanium or a sintered getter alloy. The length of the support band 40" (i.e., the dimension extending along the band 40" from the distal end 41d to the distal end 42d) is effective to securely and fixedly hold the second UV-transmitting window 32 between the first UV-transmitting window 31 and the distal ends 41d and 42d of the arched metal support band 40. Typically, a length of approximately 6 to 12 mm and a width of 1 to 2 mm are effective. A thickness in the radial direction r of approximately 0.05 to 0.3 mm is a generally cost-effective range for providing the required structural integrity to support the second UV-transmitting window 32 in place.

[0083] Legs 41 and 42 of support belt 40 and energizing electrodes 51 and 52 are preferably evenly circumferentially spaced relative to one another about chamber 29 to minimize any disturbance that may be imparted to support belt 40 ″ when working gas 60 is energized by electrodes 50 .

[0084] Refer again Figure 11-17 The second UV-transmitting window 32 is made of a second material different from the first material, such as calcium fluoride crystal. The second UV-transmitting window 32 is sandwiched between the first UV-transmitting window 31 and the distal ends 41d and 42d of the support belt 40'' in the chamber 29. Figure 20The peripheral edge 32 c of the second UV-transmitting window 32 is preferably chamfered on both the upper and lower edges (not numbered) of the second window 32 to facilitate placement of the second window 32 in the chamber 29 through the opening 28, regardless of which side is inserted first before attaching the first UV-transmitting window 31 over the opening 28.

Claims

1. An ultraviolet gas discharge lamp comprising: (a) a housing having a longitudinal axis and a chamber having a defined contour, the chamber having openings at longitudinal ends; (b) an ultraviolet light-transmitting window covering the opening and sealed to the housing to hermetically seal the chamber; (c) a working gas sealed within the chamber; and (d) an arcuate strip of resilient getter material positioned within the chamber and having diametrically opposed longitudinally extending legs, each leg having an end proximate said UV-transmissive window and each leg biased outwardly into engagement with the housing to wedge said strip within said chamber.

2. The lamp according to claim 1, further comprising: A pair of metallic energizing electrodes are positioned on or within the housing radially about the longitudinal axis.

3. The lamp according to claim 2, wherein: The legs of the arcuate band and the energizing electrode are uniformly circumferentially spaced relative to each other around the chamber.

4. An ultraviolet gas discharge lamp comprising: (a) a housing having a longitudinal axis and a chamber having a defined contour, the chamber having openings at longitudinal ends; (b) a first ultraviolet-transmitting window composed of a first material, the first ultraviolet-transmitting window covering the opening and being sealed to the housing so as to hermetically seal the chamber; (c) a working gas sealed within the chamber; (d) an arcuate metal support strip positioned within the chamber and having diametrically opposed longitudinally extending legs, each leg having an end proximal to and longitudinally offset from the first UV-transmissive window; and (e) A second ultraviolet light transmitting window, the second ultraviolet light transmitting window being made of a second material different from the first material and being sandwiched between the first ultraviolet light transmitting window and the end of the arcuate metal support strip within the chamber.

5. The lamp according to claim 4, further comprising: A pair of metallic energizing electrodes are positioned radially about the longitudinal axis on or within the housing.

6. The lamp of claim 4, wherein: The first material is magnesium fluoride.

7. The lamp according to claim 6, wherein: The second material is calcium fluoride.

8. The lamp of claim 4, wherein: The working gas is krypton.

9. The lamp of claim 4, wherein: The arched metal support strip is the getter.

10. The lamp of claim 4, wherein: The arcuate metal support has a length extending from one end to the other and a longitudinal profile corresponding to the profile of the chamber.

11. The lamp of claim 4, wherein: The arcuate metal support band has a thickness of 0.05 to 0.3 mm in a radial direction relative to the longitudinal axis of the housing, and a width of 1 to 2 mm in a circumferential direction relative to the longitudinal axis of the housing.

12. The lamp of claim 4, wherein: The ends of the legs of the arcuate metal support strip are each bent inwardly toward the longitudinal axis of the housing to create an inwardly projecting tab operable to support the second ultraviolet-transmissive window.

13. The lamp of claim 5, wherein: The legs of the arcuate metal support band and the energized electrode are evenly circumferentially spaced relative to each other about the chamber.

14. A photoionization sensor comprising the ultraviolet gas discharge lamp according to claim 1.

15. A photoionization sensor comprising the ultraviolet gas discharge lamp according to claim 4.

16. A photoionization sensor comprising the ultraviolet gas discharge lamp according to claim 11.

17. A photoionization sensor comprising the ultraviolet gas discharge lamp according to claim 12.

18. A photoionization sensor comprising the ultraviolet gas discharge lamp according to claim 13.

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