CA2103418A1

CA2103418A1 - Base for electrodeless discharge lamp

Info

Publication number: CA2103418A1
Application number: CA 2103418
Authority: CA
Inventors: Raymond A. Heindl; Mark E. Duffy; Frederick Hetzel; David J. Marks; Lawrence T. Mazza; Curtis E. Scott; Michael M. Secen
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1992-12-14
Filing date: 1993-11-18
Publication date: 1994-06-15
Also published as: DE69310704D1; JPH06318431A; ES2101247T3; EP0610628B1; EP0610628A1; DE69310704T2

Abstract

BASE FOR ELECTRODELESS DISCHARGE LAMP

ABSTRACT OF THE DISCLOSURE
A base for an electrodeless arc discharge lamp having an elongated tubular stem extending through an outer envelope pinch or press seal includes a pair of electrically non-conductive members secured in mating relation to define an upper cavity and a lower axial bore. The lamp is mounted in the base with its pinch seal secured in the cavity and its stem extending into the bore. With the base mounted in a fixture, RF energy is coupled into the lamp to excite a starting aid in the stem via a conductive bushing in the bore.

Description

21 0 3 91 1 ~

--1 ~

BASE_FOR ELECTRODEL~SS DISC~A~GE LA~P

BACKGROUND OF THE INVENTION

Field of the_Inve~tion This invention relates to an electrically non-conductive base for an electrodeless discharge lamp. ~ore particularly thi~ invention relates to an electrically non-conductive base for an electrodel~ss arc discharge lamp having an outer envelope press sealed over a tubular lamp stem containing a starting aid, wherein the base is secured, in clamshell fashion, to the press seal portion of the lamp and contains means ~or coupling RF energy to the starting aid for energizing the lamp.

Backaround oP the Disclosure High intensity electroded arc discharge lamps such as high pressure sodium lamps and m~tal halide lamps are well known and include a light-transmi~sive arc discharge chamber or tube hermetically sealed and enclosing within a pair of spaced apart electrodes and a suitable fill such as an inert starting gas and one or more ionizable metals or metal halid~s. Two of the major causes of lamp failure are sputtering o~

electrode material onto the lamp envelope and thermal and electrical stresses which result in electrode failure. More recently a new class o~ high intensity arc discharge lamps has been devsloped called electrodeless la~ps. Such lamps have a light-transmissive, electrodeless arc chamber or t~be generally shaped like a pillbox or oblate spheroid and containing a fill which comprise~ a suitable inert buffer g~s and one or more metal halides.

- , .~ . ~: -:

2~3~8 Radio frequency (RF) energy applied or coupled to the fill via capacitive or inductive coupling generates a light-emitting arc. In operation of such a lamp via inductive c~upling, the arc tube or chamber acts as a single-turn secondary coil of a transformer and is surrounded by an ~F energy excitation coil which acts as a primary coil. Various embodiments of such lamps are disclosed, for example, in U.S. Patents 4,810,938; 4,959,584; 5,039,903; 5,059,868 and 10 5/140,22~ all of which are assigned to the assignee of the present invention. The electronics required for starting and sustaining the arc discharge in : -these lamps is costly and complex and also requires the u~e of a rather large copper or aluminum inductiv~ drive coil to function as the primary coil for carrying the high frequency current required.
Hence some development has been directed toward ~:
replaceable electrodeless discharge lamps, particularly o~ the high intensity type employing one or more metal halides as the arc sustaining fill, wherein the lamp itself is physically separate from both the electronics and the inductive drive coil. -one such attempt is disclosed in U.S. 4,959,584 as a luminaire having a replaceable electrodeless, HID
metal halide arc discharge lamp wherein the arc chamber is cradled in a thermal jacket which in turn is contained within an outer envelope having a :
conventional metal screw base with a conductive lead passing through the ~ase to the vicinity of the arc tube. U.S. 5,059,868 discloses an HID electrodeless arc discharge lamp wherein the arc chamber is supported in an ou~er envelopa by means of a support .
rod which contains an electrical inlead for supplying -electricity to the arc chamber,in order to start the .. , . ~ ... ~., .. , . :. , - .: . -: - : . . - .

, . , -: . - , . ,- .;

2~0341~

arc. The arc chambar-outer cha~ber assembly terminates at one end in a conventional metal base having pin~ for securing in a socket. However, it is preferable to minimize the amount o~ metal clos~ to the drive coil, because metal (or any conductor) will pick up energy from ~he coil which will result in heating the metal and loss of system efficienay.

SUMMARY OF THE INVENTION
The present invention relates to a lamp base suitable for use with a lamp having an envelope closed off by a pinch seal at one end and a tubular stem portion ext2nding beyond the pinch seal and has been found to be useful with electrodeless arc discharge lamps, particularly a high intensity electrodeless arc discharge la~p of surh construction. A lamp base o~ this invention co~prises at least two electrically non-conductive members assembled into mating engagement and def ining a bore axially extending from one end through a portion o~ the base and terminating in an upwardly opening cavity provided in a remaining portion of the base, with the cavity in com~unication with the bore. The cavity has means for retaining the pinch seal portion of the lamp. The lamp is mounted to the base with its envelope pinch seal re~ained in the cavity and its stem extending into the bore. The bore contains an electrically conductive means for transferring RF en~rgy to the tubular portion of the lamp which extends into the bore. The base has further means for securinq the base into a suitable ~ixtur~ or luminaire. The fixture or luminaira will contain means for coupling RF energy to the lamp and to the conductive means in the,base. In most casas 2103~18 -4- : :

the fixture or luminaire contains an RF coil which surrounds the lamp in the vicinity of the arc chamber for which the base of the invention provides accurate alignment o~ the lamp with respect to the RF coilO -BRIEF DESCRIPTION OF THE DRAWING
Figure 1 is a schematic illustration of a lamp base of the invention shown assembled in l(a) with :
l(b) being a top view, l(c) illustrating means for :
securing the base in a fixture and l(d) illustrating RF energy transfer means.
Figure 2 schematically illustrates three views of one of two clamping members which form a base of the invention. ::
Figur~ 3 schematically illustrates a lamp-base assembly according to the invention and a lamp useful with the base. ::-Figures 4(a) and 4(b~ schematically illustrate one of two clamping members which form a base of the invention having different embodiments of an RF
energy transfer means.

DETAILED DESCRIPTION
The lamp base of the present invention, generally indicated at 10, is formed by a pair of opposing and cooperating shell-like, semicylindrical (other shapes could be used) m~mbers 12, 12 shown in mating engagement as seen in Figure 1 to form a hollow, cylindrical structure having a top 32 and bottom 34 and a bora 14 in which hollow, conductive metal (e.g., brass~ bushing 50 is held. Members 12, 12 are identical and mate with each other along surfaces 16, 16 to form base 10. The shell members are made of a suitable electrically non-conductive . . .

^~ LD0010405 21~3~

and heat-resistant material which includes ceramic materials and plastics such as Delrin, Teflon, poly~ulfones, liquid crystal polymers, such as Vectra A130 by Celanese Corporation, polyetherimides such as Ultem by GE and polyphenylene sulfides such as Supec by GE and Ryton by Philips. In one embodiment members 12, 12 are made of Delrin ~DuPont) and assembled by means o~ a cavity 19 and a molded-in Delrin pin 18, molded as part of each member 12, so that th~ mating half 12 contains a matching and opposing hole 19 and pin 18. A thin layer of epoxy adhesive applied to flat surfaces 16, 16 illustrated in Figure 2 providQs a permanent bond~ Other suitable means such as ultrasonic welding, thermal weldingr other adhesives, mechanical means, etc., may be employed to as~emble and secure clamping members 12, 12 to form bas~ 10. Further, although it is preferable that pins 18 be electrically non-co~ductive, they could be separate and not molded 20 as part of one or both of the members. Figure l(d) illustrates one embodiment of an ~F energy transf2r means as a brass or other suitable conductive metal bushing 50 comprising hollow cylindrical portion 52 open at one end and containing bore 54 for receiving 25 stem 64 of lamp 60 as illustrated in Figure 3(b) and ~lat disk or flange portion 56 at the other end.
Disk 56 could have a hole in it instead of being solid as shown so that the bushing 50 would be open at both ends. Figures 4(a) and 4(b) illustrate still 30 further embodiments of an RF energy transfer means, such as an electrically conductive half-bushing 80 molded into cavity 13 of member 12. Mating member 12 will have an identical half-bushing molded into it to form a bushing similar to 50 wh~n the two members are .: . . . . . ~ .

2~34:l~
-6- :

assembled into a base. Although 80 i5 shown having a half disk or flange 81, it could be merely half a cylinder without a flange. Yet another embodiment is illustrated as a conductive metal plating 82 on the surface of the cavity 13 as illustrated in Figure 4(b). Although not shown in Figure 4(b), conductive plating 82 could extend around the exterior bottom portion o~ the mem~ers in any desired configuration.
However, in yet another embodiment, the RF energy transfer means could form a part of a fixture or luminaire, so that when the base lamp assembly is inserted into the fixture or luminaire, a suitable RF
energy transfer means forming part o~ ~he fixture is inserted into the base cavity 14, and surrounds or contacts at least a portion of lamp stem 64.
As illustrated in Figure 2, bore 14, which extends through the lower portion of the base, is defined by the mating of the cavities 13 formed in both me~bers 12, 12. The upper end portions of the memb~irs beyond cavities 13 and flat surfaces 16 are formed with concavities 20 such that, when mated, the concavities define a large diameter cavity 30 in open communication with bore 14. Immediately above the floor 22 of cavity 30, the opposed edges of the concavities 20 are relieved as indicated at 26, to provide enlarg~d, diametrically opposed side openings into ca~ity 30. Member edges 38 above reliefs 26 are set back from flat surfaces 16 such that, with the members mat~d as seen in Figure l(a), diametrically opposed slots 39 are provided. The upper interior surface of cavity 30 is cylindrical as indicated at 28. While cavity 30 is illustrated as somewhat or at least partially cylindrical in this embodiment, other shapes may be useful to the practitioner.

~ LD001 0405 2~03~ 18 As seen in ~i~ure l(c), an L-shaped keyway 36 is formed in the lower portion near the ~ottom 34 of each member to receive pins or other means serving to secure base 10 in a suitable fixture or luminaire and preferably one equipped to furnish RF energy to the lamp mounted in ~he base. Other means may be employed to secure the base in a fixture or luminaire, the choice being left to the practitioner.
Turning to Figure 3, an electrodeless arc discharge lamp 60 is illustrated as comprising hermetically sealed arc chamber 62 to which is attached a hermetically sealed tubular stem portion 64 containing a ga~eous fill (not shown~ which acts as a starting aid as disclosed in U.S. Patent 5,140,227, the dis~losures of which are incorporated herein by re~erence. Arc cham~er 62 is hermetically sealed within a fused quartz outer envelope 68 closed of~ by means of a hermetic pinch seal 70 formed by pinching one end of 68 closed over tubular stem 640 Tubular stem portion 64 thus extends through pinch seal 70 with its other end closed off by the wall of arc chamber 62 as disclosed in the '227 patent. The medial portion of pinch seal 70 is generally flat . :-having sides 72 and a raised bottom ridge 74 25 protruding transverse to the longitudinal axis of the `~
lamp 60 as is shown in Figure 3(b). As seen in Figure 3(b), lamp 60 i5 shown mechanically secured or . -:~
seated in base 10 by means of cavity 30 around pinch seal 70. Stem 64 extends into bore 14 and into bore ~:~
54 of metal bushing 50. Pairs of opposed, raised ~or recessed) flats 78 are formed in the pinch seal 70 during the pinch seal moldiny process in positions -- such that, with the lamp fully seated, 2ach flat is confronted by or adjacent an edge surface 38 of the . - - ~ . . .

---` LD001 0405 2 1 (~

base. Flats 78 are molded into both sides of pinch seal 70 and also adjacent both sides o~ stem seal portion 76. I~ desired, a suitable adhesive or cement may be applied to bond or cement the four flat sur~aces 78 of the pinch seal to each of corresponding lamp base flat surfaces 38 to prevent any movement of lamp 60 within base 10.
The foregoing embodiments are intended to be illustrative, but non-limiting with respect to the practice of the inYention. Some departure from these embodiments is permissible within the SCOp2 of the invention as those skilled in the art will know and appreciate.

: - , , -.
- - - - .

.

: - =, -:- :: : : .

Claims

1. A lamp base comprising at least two electrically non-conductive members assembled into mating engagement defining a bore axially extending through a lower portion of said base and an upwardly opening cavity in an upper portion of said base, said cavity having means for retaining a lamp.

2. A base of claim 1 having means for securing said base in a fixture.

3. A base of claim 2 having electrically conductive means in said bore.

4. A base of claim 3 wherein said electrically conductive means comprises a hollow metal cylinder.

5. A base of claim 4 wherein said cylinder comprises two halves, each of which is molded into a respective one of said two members.

6. A base of claim 3 wherein said means comprises metal plated onto the surface of said bore.

7. A base of claim 2 having means for retaining a press seal portion of a lamp.

8. In combination, a lamp and a lamp base, said lamp having an elongated tubular stem extending through an outer envelope press seal and said bass comprising at least two electrically non-conductive members assembled into mating engagement defining a bore axially extending through a lower portion of said base and an upwardly opening cavity in an upper portion of said base, said cavity having means for retaining said seal of said lamp, whereby said lamp seal is secured in said base cavity and said tubular stem extends into said bore.

9. A combination of claim 8 having means for securing said base in a fixture.

10. A combination of claim 9 having electrically conductive means in said bore of said base for providing RF energy to said tubular stem of said lamp.

11. A combination of claim 10 wherein said electrically conductive means comprises a hollow metal cylinder.

12. A combination of claim 11 wherein said cylinder comprises two halves each of which is molded into a respective one of said two members.

13. A combination of claim 10 wherein said electrically conductive means comprises metal plated onto the surface of said bore.

14. A combination of claim 8 wherein said lamp comprises an electrodeless, high intensity discharge lamp.

15. A combination of claim 10 wherein said lamp comprises an electrodeless, high intensity discharge lamp.

16. The invention as defined in any of the preceding claims including any further features of novelty disclosed.