CA1281766C - Method and apparatus for position orientation of a metal halide lamp base assembly - Google Patents

Abstract

METHOD AND APPARATUS FOR POSITION ORIENTATION
OF A METAL HALIDE LAMP BASE ASSEMBLY
ABSTRACT
A method and an apparatus for position orienting a base assembly of a metal halide lamp is describe for maintaining the curved arc tube in the upward position when the lamp is inserted in a socket. Once the lamp has been fully assembled and sealed a locator structure is attached to the base shell in order to create a base assembly which will properly position the lamp when it in the socket, The welding apparatus of the present invention resistance welds the locator structure onto the base shell once the locator structure has been aligned approximately 90 degrees counterclockwise from the lip of the curved portion of the arc tube when viewed from the dome end of the lamp. The lamp resulting from the method and use of the apparatus will be more inexpensive and will not have the problems of a loose base or a cracked seal.

Description

lX81766 METHOD AND APPARATUS FOR POSITION ORIENTATION
OF A METAL HALIDE LAMP BASE ASSEMBLY
, TECHNICAL FIELD

The present invention relates in general to metal halide lamps and in particular to a method and apparatus for position orienting a metal halide lamp base with respect to a curved arc tube.

BACKGROUND

Metal halide lamps that are made with curved or arched arc tubes must be operated horizontally with the curve of the arc tube in the upward or arch uppermost 15 pos~tion (see U.S. Patent No. 3,858,078). To accomplish thls, thè base and socket must provide a means of interlocking such that when the lamp is screwed into the - socket firmly, the arc tube curve will be upward.
Presently, the socket used has a notch and the base has a pln added to it so that when the lamp is screwed into the socket, it will stop in a predetermined position.
This is in contrast to the usual screw type base that is used with prior art commercial metal halide lamps; a screw type base ls not a po~itioning base and can be used in prior art lamps sin~e the arc tubes thereof straight cylinders.
It is an object of this invention to provide a method and an apparatus for position orienting a base with respect to a curved arc tube.
In accordance with one aspect of this invention, there is provided a method for position orienting a base assembly with respect to a curved arc tube of a high intensity discharge lamp, the base assembly including a base shell having an eyelet and a locator structure attached thereto. The method comprises the steps of ~ :
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providing within the discharge lamp an arc tube support structure coplanar with the arc tube and providing means for welding the locator structure to the base shell, the welding means capable of separately receiving and supporting the lamp and the locator structure. The method further includes disposing the locator within the welding means and psoitioning the lamp within the welding means such that the base shell and the locator are in operative contact before welding. Next a light source is provided proximate to the welding means and the light beam of the light source is aligned perpendicular to both the longitudinal axis of the lamp and to the plane formed by the arc tube and the locator structure. Furthermore, a screen is provided opposite the lamp such that a shadow image of the arc tube support structure is formed thereon when the light beam passes throught the center of the neck of the lamp and impinges on the screen. Flnally, the lamp is rotated radially within the welding means until the plane formed by the arc tube and the support structure is perpendicular to the arc tube - locator plane:
Thereupon the welding means is activated to weld the locator structure to the base shell, thereby forming a base assembly that is position oriented with the curved arc tube.
In accordance with another aspect of this invention there is provided a position oriented high intensity discharge lamp comprising a light transmissive outer envelope and a curved arc tube disposed within the envelope and supported by an arc tube support structure that is coplanar with the arc tube. The lamp further includes a base assembly attached to the outer envelope, the base assembly having a base eyelet and a locator structure affixed externally thereto, the locator disposed at a predetermined distance from the base eyelet.
In accordance with yet another aspect of this invention, there is provided an apparatus for attaching ~ 7 66 a tab-type structure to the base of a high inte~sity discharge lamp. The apparatus comprises a resistance welder and a welding fixture attached to the welder including a frame, a bottom electrode disposed within the frame having an apertured surface, and means for guiding the lamp within the apparatus in contact with the frame. The apparatus further includes a back stop structure having a sur~ace positioned proximate to the guide means for minimizing the lamp movement within the apparatus and a retractable top electrode positioned above and spaced from the bottom elecrode.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 illustrates an example of a typical curve arc tube metal halide lamp base;
Flgure 2 illustrates a cross section of a known socket for a high intensity discharge lamp;
Figure 3 illustrates the top or dome end view when looking down onto a curved arc tube metal halide lamp;
Figures 4A through 4C illustrate an actual metal halide lamp containing a curved arc tube therein, a high intensity discharge lamp having the improved locator structure attached to the base and enlarged view of the improved locator structure, respectively;
Figures 5A and 5B lllustrate slde and front vlews of the welding apparatus for attaching the locator structure onto the lamp base;
Flgure 6 illustrates how the high intensity discharge lamp is posltioned ln the welding fixture of flgure 5; and Figures 7A and 7B illustrate the lamp and the fixture position with respect to a light source and screen used for aligning the lamp base with the arc tube.

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1~8~766 Re~erring now to Figures 1 and 2, which will aid in clearly illustrating any problems associated with the prior art lamp bases, figure 1 illustrates a typical lamp base 10 comprised of a base shell 12, a base eyelet 14 and a base pin 16. Figure 1 also illustrates a headed brass pin 16 which is a~fixed into and protrudes from base shell 12 in order to position the curved arc tube of a metal halide lamp. Figure 2 illustrates a cross section of a typical socket 20 made of a porcelain casing 22 that has been partially cut away such that notch 24 can be seen. To make the pin and notch arrangement workable, a given dimension of X, X being about one inch with a positive tolerance of 1/32 of an inch was established between base eyelet 14 and pin 16, ln Figure 1. Notch 24 (illustrated in Figure 2) in the socket shell 26 is located such that when base pin 16 is wlthln the dimenslons stated, eyelet 14 on base shell 12 will make contact with tab 28 in the socket. The tolerance of plus 1/32 of an inch translates into rotational tolerance of about 45 degrees of rotation or about 5t8 of an inch distance along the crest of the thread on which the pin is located The present method of pinning and attaching the base to the lamp is as follows; a hole is drilled in base shell 12 on the crest of the thread to meet the dlmenslon stated with resPect to Figure 1. A headed brass pln 16 ls then inserted into the hole with the head on the inslde of base shell 12 and se-urely soldered in place. Since the soldering discolors the brass, the use of a nickel base is necessary for good cosmetics. During the lamp sealing process, four dimples are molded into the seal to permit a threaded inner shell having tabs with corresponding dimples to be snapped in place. Once in place, base shell 12 is securel~ screwed onto the inner shell and then is staked or Pierced in three places to lock it to the inner shell.

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lZ81766 When sealing lamp~ with a curved arc tube, the tip on the arc tube is located with respect to one Q~ the dimples in the mold. In the basing process, the inner shell is selectively snapped into place such that the thread location on the inner shell corresponds to the dimple orientation accomplished during the sealing process. When the base is screwed onto the inner shell, the pin should be approximately 90 degrees counterclock-wise fro.,l the tip on the curved portion of the arc tube when viewed from the dome end of the metal halide lamp.
Figure 3 illustrates a metal halide discharge lamp 30 when viewed from the top dome end looking down onto the lamp. Lamp 30 has an outer envelope 32, a curved arc Tube 34, arc tube pressed end 36, and arc tube tip 38, a base shell 40 and a locating pin 42 slmilar to Figure 1. Figure 3 al~o illustrates a plane of the arc tube and support structure which runs along the line B-B'. A
90 degree angle ls marked between the plane of the arc tube B-B' and the plane created by the arc tube and the locatlng pin marked C-C'.
The posltion orientation or locating arrangement in the past has not been very accurate, since the base has normally been manually screwed onto the inner shell until snug then the pin location i~ checked wlth respect to plane B-B' to see if the angle between them is 90 degrees + 5 degrees. If the angle is not within this range, the base must be loosened or tightened to meet the requirement. This action allows for a certain amount of movement to meet the angular requirement, however lf the base is backed off too much from the snug position, the base will be loo~e after staking. If the base is over torqued, the lamp seal will crack. In either case, the lamp is rejected. The problems associated wlth the present pin locating methods are as follows:
possible rejections mav occur due to the loose base or cracked seal and over torquing can cause severe -'_ 1~81766 field and life problems. The present method does not lend itself well to an efficient assembly line operation and predrilling of bases and soldering pins on are time consuming and expensive. Since soldering discolors a brass base, nickel plated bases must be used for good cosmetics, therefore nickel plating is an added expense.
Since production operations are constantly changing, such as utilizing a threaded glass seal in place of dimples and an inner shell for attaching the base, the present method as described is not adaptable for use with a threaded mold lamp seal. Therefore, a need exsists for a method of position orienting a metal halide lamp base assembly with respect to the curved arc tube.
Figures 1, 2 and 3, were used to help describe some of the problems associated with the prior art methods of positioning or position orienting a base with respect to a curved arc tube. Reference will be made throughout the specification to Flgures l and 3 in order to describe the improved method and apparatus for position orienting a base with respect to a curved arc tube. With respect to Figures 4A-4C, Figure 4A illustrates a known metal halide lamp 30 in a horizontal position having a curved arc tube. Lamp 30 in Figure 4A indludes an outer envelope 32, an arc tube 34, an arc tube pressed end 36, an arc tube tip 38, a base shell 40 and an arc tube support structure 44. Figure 4B partially illustrates an improved metal halide lamp 50 and lamp neck 53 having ,~ .
~ 5 ~ 7 ~ ~2 8~7~6 a base asseubly Sl which include6 a base shell 52 and a locator structure 54 Pigure 4C illustrates an enlarged viev locator 6tructure 54 and surface 56 whic~ vill be attac~ed to base s~ell 52 upon for~ing t~e ba~e as~e~bly Sl illu6trated in ~igure ~B
According t~ one o~bodi~ent of tbe pre~ent inventio~, a ethod for po6ition orienting a base a~oubly vith rQcpect to a cur~ed arc tube of a ~igh int-~-ity discha~go laup vill be de w ribed The la~p of Pigur- 4A i6 alignod a~ ~ievod in Pigure 3 so that tbe plan- or the arc tube B-B' as ~hovn in Pigure 3 is aligu d vitb the ~tart vith the fir~t thread on the threaded uold of the glass, this align~ent being acco~pli~hed during laup cealing The laup6 6ealing, exhauct and basing are th~n coopleted, including the ba~e w lderinq operation A nevly dosignod tab-type locator 5~ ~hovn in Piguro 4C is then placed iD a ~-ldiDg apparatus 60 w~ich is illustrat-d in ~igures 5A
and 5B, W-lding apparatus 60 illustratod in ~igures SA
and 5B pro~i~es a eans ror wolding locator structure 54 to ba~e ~hell 5~ Th- volding apparatu6 is capable of s-parately recoi~ing and supporting la~p S0 and locator structure 54 As illu~trated iD Pigure ~C locator ~tructure 54 is L-shap-d in toru Pigur-s SA and SB illustrato apparatus 60 tor attaching a tab-type structure to tho ba~e Or a hig~
int-Daity discharge la~p Apparatus 60 comprisos a rs~i~taAce v-ldor 61 and velding fixture 62, attac~od to velder 61, that include~ a rra~o 63, a botto~ olectrode 64 di~po~ed within fra~e 63, having an apertured ~urface 66, and tvo guide pin~ 68 to guide a laup vithin fixture 62 poritioned on either ~ide of botto~ electrode 64. A

~ 8 -12 8~766 bac~ stop 70 i8 positioned proxi-ate to guiae pins 68 and ~ retractable top electrode 72 i~ pos~tioned above and spaced fro~ botto~ electrode 64 Aperture 66 of botto~ electrode 64 6upport~ locaeor structure 54 that i8 to be attac~ed to the la~p ba6e The locator ~tructure 54 i6 next placed in aperture 66 of bottou oloctrode 64 of apparatu6 60 La-p S0 i~
tb-~ placod betveen guide pin~ 68 witb tbe base eyelet being placed in operati~e contact ~ith bac~ 6top ~tructure 70 rixture 62 i~ ~esigned ~UCD t~at tne cro~t o~ tho throad of ~a~e ~hell 52 i6 alvay6 po~itio~od o~or botto~ ctrode 64 and aperture 66 With tho baro oyolet clo~e to bac~ ~top 70 the plane of t~- a~c tube B-B', a~ aligned in Pigure 3 i~ near to tbo corr-ct location The tolerance of plu~ 1~32 of an inch ~,04 inch-~) tran~lates into a rotational tole~ance of about 45 d-gr--~ ot rotatioD or about 5/~ of an iDCh aloDg th- cr-~t of th- thread oo ~hich tab locator ~tructur- 54 i~ to b- located, With tbe alignaent ~lluat~at-d iD Pigur- 3, the proper tab locatioD vill alvayr rall vithin that 5/8 of an incb on the threaded cr-~t The tab or locator ~tructure i~ nov dispo~ed ~ithin ~-lding apparatu~ 60 and la~p 50 is positio~ed vithin volding apparatu~ 60 6ucb tbat ba~e 6hell 52 and locator 5~ ar- in op-rati~o contact bororo volaiDg (~oe r~gu~- 6 ) .
~ -r-rring to pi9urQ 6, Pigure 6 illu~trates la~p 50 po~it~on-d vithin wolding ~ixturo 62 aDd illustrato~
lavp upport brac~ot 74 vhich ~upport~ la~p 50, that i~
~pac- rro~ l-ctrode 64 Pigure 6 al~o illu~trate~ that laup 50 har a loDgitudiDal axi~ 75 vhich vill help iD
alig~i~g locator structure 54 vith the arc tube of la~p ,,~

_ 9 _ 50 ~igure 6 al~o illu~trates that top electrode 72 i~
retractable and will co~e down on base ~hell 52 to veld locator 54 located witbin botto~ electrode 64, to base ehell 52 vhen tbe lamp has beeD properly aligned S Referring AOV to Figure~ 7A and 7B, ~igure 7A
illu~trates la~p 50 po~itioned vithin fixture 62 V~tD
re~pect to a ligbt source 76 and a target or screeD 78 tbat i~ usea for properly aligning the la~p base and tbe locator ~tructure while Pigure 7B illustrates tbe ~iev through ~ection A-A' of Pigure 7A In particular~ light ~ourc- 76 i~ located proxi~ate to fixture 62 and a lig~t b-a~ 77 e~itted rro~ eource 76 i~ aligned to be porpendicular to botb longitudinal axis 75 (eee Pigure 7B) Or la~p 50 and to tbe plane ro~ed by tbe arc tube ~nd the locator ~tructuro which ie identified as 80 in Pigur- 7A Light ~ource 76 in Piqure 7A is positioned oppo~it~ p 50 euch that light bea~ 77 pa~se~ tbrough the c-nt-r Or tbe ncc~ 53 o~ the la~p and i~pingee on ~¢r--n 78, Light b~a~ 77 ie aleo adjusted to be ~-rp-ndicular to th- plane ror~-d by tbe lower arc tube ~u~port ~tructur~ 44, as illuetrated in Pigure 7B, that i~ ~ttacb-~ to arc tube 34 (~ee Pigure 7B) ID this particular e~bodi~eot, ligbt bea~ 77 ~hinniDg througb o-c~ 53 o~ la-p 50 vill sbov 2 ~hadov lin-~ rrou lo~er eupport etructure 44 onto 6creen 78 rrO~ tb~ tvo lege Or lov-r ~upport ~4 La~p 50 i~ t~en rotated radially eith-r cloc~viJe or countercloc~vise until the tvo lege or ~upport 44 register as one ~bado~
line on w r-eo 78, At tbi~ point, tbe plane ror~ed by th- arc tub- and tbe ~upport 6tructure i~ perpendicular to the arc tube locator plan- 80 Tab or locator etructure 54 in botto~ electrode 64 i~ nov about 9o '~ - .

al76~
_ 10 _ degrees countereloc~ e ro~ arc tube tip 38 ~ ~ho~n in Pigure 3 Res~6tance ~elder 61 is nov act~vated to re~i~tance ~eld the tab or locator structure 54 to ba6e ~hell 52 thereby for~ing a ba6e asce~bly that iE
po6~tion oriented with re~pect to curved arc tube 3~
Pigur- 4B ~ho~ locator ctructure 54 velded to the bace of the la~p Therefore t~rough the u~e of the aforedeccribed ~thod, an inprovod pocition oriented h~gh intensity diccharge la-p ha~ recult-d ther~fro Such an i~proved pocition ori-nt-d di w harge lanp i~ partially illuftrated rrO~ the la~p i~ ~igure ~A and the base afce-bly Or rigure 4B The i~pro~ed ldmp co~peisec ~06t Or tho lo~ent~ o~ the la~p illu~trated in ~igure 4A
~ith ba~o asce-bly 51 of Pigure 4B The locator ctructure 54 or ba~e a~co~bly 51 ic dicpo~ed at a pr-d-t-r~ined dictance fro- the ba~e yelet ~ Locator ctructu~e- 54 al~o hac a predeter~ined rotational tol-rance radially along ba~e chell 52 The ~red-ter~lD-d ai~taDc- i~ vithin a raDge of about one inch to about 1 05 inchec and the rotational tolerance ic about 45 d-gree~ of rotation along the cre~t of t~e thr-ad of ba~e chell 52 Sh- advantagec o~ u~ing 6UCh an i~proved ~etal bal~- laup include~ th- ab~ence or ce3ection~ due to loo~e bac-~ or crac~ed ceal~ The ba~e dooc not have anr aperture~ (aue to prior art prearilling to include t~e pi~ rrOu the previouc la~p) and ~elding of tbe locator ~tructure onto the ba6e ~ill not di6color the brac- bace therefore nic~el plating of the base is an unn-ce~cary ~anufacturing ctep ~bich al~o increa~es the exp-nce of the la-p A

l~B~766 _ 11 ~ bile tbere ba~e been 6bown and de6cribed ~at are at present con~idered t~e preferred e~bodi~ent6 of tbe invention, it ~ill be obvious to those s~illed in t~e art t~at variou~ changes and ~odifications ~ay be ~ade t~erein ~ithout departiDg fro~ the scope of t~e in~eDtion as aefined by t~e appended Clain6.

Claims (18)

1). A method for position orienting a base assembly with respect to a curved arc tube of a high intensity discharge lamp, said base assembly including a base shell having an eyelet and a locator structure attached thereto, said method comprising the steps of:
providing within said discharge lamp an arc tube support structure coplanar with said arc tube;
providing means for welding said locator structure to said base shell, said welding means capable of separately receiving and supporting each of said lamp and said locator structure;
disposing said locator within said welding means and positioning said lamp within said welding means such that said base shell and said locator are in operative contact before welding;
providing a light source proximate to said welding means and aligning the light beam of said light source perpendicular to both the longitudinal axis of said lamp and to the plane formed by said arc tube and said locator structure;
providing a screen opposite said lamp such that a shadow image of said arc tube support structure is formed thereon when the light beam passes through the center of the neck of said lamp and impinges on said screen;
rotating said lamp radially within said welding means until the plane formed by said arc tube and said support structure is perpendicular to said arc tube-locator plane; and activating said welding means to weld said locator structure to said base shell, thereby forming a base assembly that is position oriented with respect to said arc tube.

2). The method according to Claim 1 wherein said locator structure is of the tab-type.

3). The method according to Claim 2 wherein said locator is L-shaped in form.

4). The method according to Claim 1 wherein said welding means comprises a welding fixture attached to a resistance welder.

5). The method according to Claim 4 wherein said welding mixture comprises a frame, a bottom electrode disposed within said frame, two guide pins to guide said lamp within said fixture positioned on either side of said bottom electrode, a back stop positioned proximate to said guide pins and a retractable top electrode positioned above and spaced from said bottom electrode.

6). The method according to Claim 5 wherein said bottom electrode has a surface with an aperture therein for holding said locator structure within said welding fixture.

7). The method according to Claim 5 wherein said welding fixture further includes a support bracket spaced from said bottom electrode, said bracket providing support for a lamp positioned within said welding fixture.

8). A position oriented high intensity discharge lamp comprising:
a light transmissive outer envelope:
a curved arc tube disposed within said envelope and supported by an arc tube support structure that is coplanar with said arc tube; and a base assembly attached to said outer envelope, said base assembly including a base shell having a base eyelet and a locator structure affixed externally thereto, said locator disposed at a predetermined distance from said base eyelet.

9). The discharge lamp according to Claim 8 wherein said locator structure has a predetermined rotational tolerance radially about said base shell.

10). The discharge lamp according to Claim 9 wherein said locator is L-shaped in form.

11). The discharge lamp according to Claim 8 wherein said locator structure is disposed about 90 degrees radially from said arc tube-support structure plane.

12). The discharge lamp according to Claim 8 wherein said locator is affixed externally to said base shell by a resistance weld.

13). The discharge lamp according to Claim 9 wherein said predetermined distance is within a range of about 1 inch to about 1.05 inches and said rotational tolerance is about 45 degrees of rotation along the crest of the thread of said base shell.

14). An apparatus for attaching a tab-type structure to the base of a high intensity discharge lamp, said apparatus comprising:
a resistance welder: and a welding fixture attached to said welder including a frame, a bottom electrode disposed within said frame, having an apertured surface means for guiding said lamp within said apparatus in contact with said frame, a back stop structure having a surface positioned proximate to said guide means for minimizing lamp movement within said apparatus and a retractable top electrode positioned above and spaced from said bottom electrode.

15). The apparatus according to Claim 14 further including a lamp support bracket spaced from said bottom electrode for supporting a lamp positioned within said apparatus.

16). The apparatus according to Claim 14 wherein said apertured surface of said bottom electrode supports said tab-type structure to be attached to said lamp base.

17). The apparatus according to Claim 14 wherein said guide means includes two guide pins to guide said lamp within said fixture, said guide pins positioned on said frame on either side of said bottom electrode.

18). The apparatus according to Claim 15 further including a light source and screen, said light source disposed adjacent said welding fixture and emitting a light beam that passes through lamp positioned within said fixture and creating a shadow image on said screen.