CA1167513A - Method of manufacturing a lamp - Google Patents
Method of manufacturing a lampInfo
- Publication number
- CA1167513A CA1167513A CA000352167A CA352167A CA1167513A CA 1167513 A CA1167513 A CA 1167513A CA 000352167 A CA000352167 A CA 000352167A CA 352167 A CA352167 A CA 352167A CA 1167513 A CA1167513 A CA 1167513A
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- lamp
- neck portion
- neck
- tube
- headstock
- Prior art date
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Abstract
METHOD OF MANUFACTURING A LAMP
ABSTRACT OF THE DISCLOSURE
A metal halide discharge lamp is manufactured on a horizontal glass blowing lathe which is indexed by a turn-table through angularly spaced work stations. Initially, a length of quartz tubing is formed into a lamp body having an enlarged bulbous midportion defining an arc chamber with tubular necks projecting in opposite directions.
Thereafter, a cathode is inserted into one neck, metal halide pellets and a globule of mercury are inserted into the arc chamber, an anode is inserted into the other neck, and hermetic seals are made between the necks and the electrodes. All of the insertions axe carried out by moving the various components through the tailstock of the lathe and into the lamp body through one of the necks, the cathode being moved tip-last through the one neck, across the arc chamber and into the other neck. A rotary seal attached to the headstock allows an inert dry gas to be flushed through the lamp body during the assembly steps for the purpose of drying the quartz and the electrodes and to prevent the halide pellets from being exposed to water vapor. Precision in determining the interelectrode yap is achieved by maintaining the initial seizure of the quartz tubing in the headstock of the lathe and referencing bulb formation and electrode insertion to the circular path described by the headstock.
ABSTRACT OF THE DISCLOSURE
A metal halide discharge lamp is manufactured on a horizontal glass blowing lathe which is indexed by a turn-table through angularly spaced work stations. Initially, a length of quartz tubing is formed into a lamp body having an enlarged bulbous midportion defining an arc chamber with tubular necks projecting in opposite directions.
Thereafter, a cathode is inserted into one neck, metal halide pellets and a globule of mercury are inserted into the arc chamber, an anode is inserted into the other neck, and hermetic seals are made between the necks and the electrodes. All of the insertions axe carried out by moving the various components through the tailstock of the lathe and into the lamp body through one of the necks, the cathode being moved tip-last through the one neck, across the arc chamber and into the other neck. A rotary seal attached to the headstock allows an inert dry gas to be flushed through the lamp body during the assembly steps for the purpose of drying the quartz and the electrodes and to prevent the halide pellets from being exposed to water vapor. Precision in determining the interelectrode yap is achieved by maintaining the initial seizure of the quartz tubing in the headstock of the lathe and referencing bulb formation and electrode insertion to the circular path described by the headstock.
Description
~ 1 - LD 7630 METHOD OF MANUFACTURING A LAMP
ack~round of the Invention This invention reIates to a method of manufacturing a double~-ended lamp; it is particularly suitable for making high pressure metal vapor discharge lamps of the type wherein the lamp body comprises an enlarged bulbous midportion with oppositely extending tubular necks. The bulbous midportion defines an arc chamber which contains an inert starting gas and a fill of vaporizable metal or metals such as mercury or a mixture of mercury and se-lected metal halides. Electrodes are hermetically seale~
; within the necks and project into the arc chamber. When ; an arc is created across the interelectrode gap and the fill is vaporized within the arc chambert light is pro-duced in known manner.
The`invention relates more particularly to the manufacture of a lamp of the type in which the fill and the starting gas are introduced into the arc chamber through one of the necks. This is in contrast to a lamp in which the electrodes are first sealed within the necks 2U and in which the fill and the starting gas are then in-troduced into the arc chamber through a lateral exhaust tube which is subsequently tipped ofE. The vestiges of the tip-off form a discontinuity which is more objec-tionable the smaller the size of the lamp.
In all discharge lamps it is necessary to have a clean arc chamber and to avoid contamination oE the fill.
5 ~ 3 Certain types O:e f.ills (e.g~, those containing me-tal halides) are very hygroscopic and react when exposed to even minute amounts of water vapor. Metal halides usual-ly are supplied in the form of pellets having a high degree of purity. To preserve this purity and insure the production of an acceptable lamp, it is necessary to protect the halides, the elec-trodes and the lamp body from water vapor and other contaminants during assembly of the components and until such time as the arc chamber has been safeIy sealed. In miniature discharge lamps, -the deleterious effects of contamination are magnified and the need for protection is all the greater.
In high pressure metal vapor lamps, the arc volt~
age drop varies proportionally to the length o the in-terelectrode'gap. ~he heating of the ends o the arcchamber is strongly influenced by the extent to which the el'ectrodes are'inserted and project into the chamber.
Such heating determines vaporization of the fill, par-ticularly the metal halides which'tend to condense in the cooler ends. Thus both the length and the location of the interelectrode gap are important and the need for precision in its determination increases as the size of the lamp is reduced Summary of the-Invention The general aim of the present invention is to pro~
vide a high speed, mass production method for manufac-turing lamps of the aforegoing general character. The invention is particularly characterized in one aspect by the unique manner in which the components of the lamp are assembled to protect against d~gradation of the fill;
in a second aspect by the manner in which the arc cham-ber i5 formed to achieve high internal purity which is preserved by the unique'manner of assembly of components occurring the'reafter; and in a third aspect by the ! f) ,~ 3 precision in determination of the i.nterelectrode gap made possible by seizing a vitreous tube in a glass lathe at the outset and maintaining such single seizure through-out subsequent formation o the lamp body and assembly of components.
One object of the invention is to load the elec-trodes and the'fill into the lamp body by a novel method which'enables the lamp body to be flushed continuously with'a dry gas for preventing contamination of the com-ponents of the lamp during the assembly operations.
Another object is to provide a lamp assembly methodwhich advantageously may be'carried out at relatively high speed on a hori~ontal glass blowing la-the immediately after the lamp body itself has been formed on the lathe, and which takes advantage of the accuracy of assembly and of the cleanliness made possible ~y a continuous operation startin~ with quartz tubing and ending in a finished lamp.
Electrode Insertion Sch'eme -In its firs~ aspect, the invention resides in a method in which'the fill and the two electrodes are in-serted into the'lamp body through'just one of the necks thereof and preferably while the lamp body is held and hermetically coupled in the chucks of the headstock and the tailstock of a horizontal glass blowing lathe. This allows a purging gas to be flushed through the lamp body by way of the'second neck. The first electrode is in-serted tip last and the second is inserted tip first, and they are both transported upstream against the gas ~low.
Continuous Flush In its second aspect, the invention provides the additional feature of forming ~he lamp body from a length of vitreous tubing which has been heated into the soften-ing range, immediately prior to inserting ~he electrodes ~7513 ~ _ , into the bulb in the unique manner previously described.While beiny heated, and also after it is formed in-to a bulb as by blowing, the tube or lamp body is flushed and such flushing removes moisture and other contaminants from the vitreous material over a higher temperature range than ~he finished lamp will encounter throughout its life. The flushing is continued of course during the insertion of the electrodes and the ~ill up to the closing off of the lamp body. This makes possible the high'degree of purity needed for a miniature metal halide - lamp.
Preci'se Determination of Gap In its third aspect, the invention realizes the high level of accuracy needed in the interelectrode gap determination. This is achieved by seizing a vitreous tube in a glass lathe'and thereafter maintaining this single sei'zure and referencing to it throughout the formation of the bulbous midportion in the tube and the insertion o the electrodes. By accurately positioning, relative to the'lathe,' first the mold into which the bulb is expanded and then the electrodes which are sub-sequently inserted into the bulb~ precision is achieved in both'the'length'of the gap and its location within the bulb.
Preferred Sequence - In a preferred sequence, a glass lathe is ~sed in forming the lamp body and is mounted on a rotary turn-table or carrousel for advance through various work stations. A length of quartz tubing is seized in the headstock o~ the lathe and such seizure is thereafter maintained while the tube is rotated and its midportion is heated into the softening range. Meanwhile the tube is flushed with inert dry yas to drive out moisture and contaminants from the'quartz. The tube is then tempo rarily pressurized and expanded into a mold which is 1 ~6751 3 precisely located relative to the circle described by the headstock of the lathe. This provides a lamp body having a bulbous midportion wi~h oppositely projecting neck portions one of which is seized in the headstock.
Flushing is resumed and one electrode-inlead assembly is inserted reversely or tip-last through the downstream neck and transported upstream throuyh the arc chamber into the ups~ream neck. The fill is then loaded through the downstream neck and deposited in the arc chamber.
'rhereafter the other eIectrode-inlead assembly is in-serted tip firs~ through the downstream neck and trans-ported up to the arc chamber. Flushing is termirlated when the downstream neck portion is closed off and there-after the electrodes are heat-sealed into their respec-tive neck portions. This sequence utilizes all threeaspects of the invention and obtains all the impor-tant advantages, nameIy a bulb of high internal purity, lamp components and fill that were at all times protected against contarnination or degradation, and precision in arc gap determination, all in a high speed mass pro-duction proce~s.
Brief _escription of the Drawings FIG. l is a cross-sectional view~ on a greatly enlarged scale, taken longitudinally through a typical lamp adapted to be manufactured by the new a~d improved method of the present invention.
FIG. 2 is a fragmentary top plan view of exemplary apparatus for carrying out the method.
FIG. 3 is an enlarged fragmentary cross-section taken substantially along the line 3-3 of FIG. 2 and shows one of the glass blowing lathes.
FIG. 4 is a fragmentary cross-section taken sub-stantially along the line 4-4 of FIG. 3.
FIG. 5 is a diagram schematically showiny the control circuit for the flushing gas 11~'7~3 EIG. 6 is a fragmentary view of the headstock and tailstock o~ the lathe illustrated in FIGS. 3 and 4 and shows the first step oE the method.
~ IGS. 7 to 14 are views similar to FIG. 6 and show additional steps of the method.
FIG. 14a is an enlarged view which shows, on an enlaryed scale, the step illustrated in FIG. 14.
FIGS. 15 to 17 are views similar to FIG 14a and show the next ~hree steps of the method.
FIGS. 18 to 22 also are views similar to FIG. 6 and show the final steps of the method.
Detailed~Description Lamp Structure A typical lamp 30 which is adapted to be manufac-tured by the process o~ the present invention is shownin FIG. 1 and is similar to one of the lamps disclosed in Cap et al Canadian application Serial No. 306,479 filed June 29, 1978 and entitled High Pressure M~tal Yapor Discharge Lamps of Improved Efficacy, that appli-cation being assigned to the same assignee as the pres-ent invention~ Briefly, such a lamp comprises an arc tube or lamp body 31 made from a piece of fused silica or quartz tubing and having a hollow bulbous midportion 32 which~defines an arc chamber 33 for containing a high pressure discharge. In this particular instance, the arc chamber is generally spherical and has a volume of less than one cubic centimeter. The arc chamber mayr however, be of various shapes (e.g., ellipsoidal or cylindrical) and may be considerably larger than that o~ the lamp 30.
Joined to and extendin~ in diametrically opposite directions from the midportion 32 of the lamp body 31 are two reduced diarneter tubular neck por-tions 34 and 35. Each neck is generally cylindrical and is of small cross-sectional area when compared with the cross-section-~ ~7~
~ 7~30-- 7 --al area of the midportion.
Elec-trode-inlead assemblies 36 and 37 are inserted into the necks 34 and 35, respectively~ The electrode 36 forms the cathode of the lamp 30 and comprises a length of molybdenum wire 38 which'projects a predetermined dis-tance out of the neck 34 and into the arc chamber 33.
coil 40 of tungsten wire is wound around the inner end portion of the molybdenum wire and terminates in a sphere which defines the tip 42 of the'eIectrode 36. Reference may b ~ ade to Canadian application Serial No. 3~?,~7~ , filed~ by Dvorak and Fridrich, Electrode for High - Pressure Metal Vapor Lamp, assigned like this application, for a more complete'description of the subject electrode.
The eIectrode 37 constitues the anode of the lamp 30 and is formed by a len~th of tungsten wire 43 received within the neck 35 and projecting a predetermined distance into the arc chamber 33. A small sphere is formed on the distal end of the'wire 43 and defines the tip 44 of the electrode 37. The space between the tips 42 and 44 of the electrodes 36 and 37 defines the arc gap.
Molybdenum inlead wires 45 and 46 extend into the outer ends of the necks 34 and 35~ respectively r and are adapted for connection to the electrical terminals o~ an outer envelope (not shown). The inlead 45 is -formed in--tegrally with'the'molybdenum wire 38 of the electrode 36 while ~he inlead 46 is suitably joined at 47 to the tungsten wire 43 of the electrode 37. The join at 47 is conveniently made by a laser butt weld per U.S. patent 4,136,298 - Hansler. Each inlead includes a relatively flat foliated portion 48 intermediate its ends which may be formed by cross-rolling or by longitudinal rollingD
Alternatively a composite inlead comprising a length of foil with a wire welded to each end may be used. The foil portion enables a hermetic seal to be established between the electrode and the neck so as to hold the ~'75~
electrode in place and to seal the arc chamber 33 from the outside atmosphbre. The seals through necks 34 and 35 are formed by heatiny and fusing the quart~ to col-lapse the internal passage through each neck and cause the quartz to wet and seal to the foil portion of the associated inlead. ' A fill or dose of ~aporizable met'al is contained within the arc chamher 33 and is adapted to vaporize and produce light in a well-known manner when an appropriate voltage is applied across the'eIectrodes 3G and 37 to create an arc between the'tips 42 and 44 thereof. Herein, the fill comprises mercury and a mixture of selected metal halides (e.g., NaI, ScI3 and ThI4) although the fill could consist of mercury alone. After the lamp 30 has been manufactured but before the lamp is first operated, the mercury exists in the arc chamber 33 in the form of a globule 51 while the halides exist in the form of one or more pellets 52.
- The lamp 30 is completed by a quantity of inert starting gas which ini.tially exist.s in the arc chamber 33 at a subatmospheric pressure of about 120 torr ab-solute. Argon is used as the starting gas in the present-lamp. Unlike many discharge lamps, the present lamp does not include a tipped-off lateral exh~ust tube ex-tending from the bulbous midportion 32.
In manufacturing a lamp 30 of the above -type, one of the difficult problems which`is encountered invol~es loading the halide dose into the arc chamber 33 withou-t contaminating the dose with water vapor or other im-purities during insertion of the dose and while sealingthe chamber. The halide pellets 52 are extremely hygro~
scopic and ~ere momentary exposure to the ambient at-mosphere may allow enough moisture to be picked up that lamp operat,ion will be deleteriously af~ected. As i.n-itially processed, the total oxygen content of the pellets ~1~)7513 _ g _ is less than fifty parts per million. In order for thelamp 30 to operate ef~ectively and reliably, it is nec-essary to preserve the high purity of the pellets by shielding them at all times from -the atmosphere and its inevitable water vapor until they are safely sealed in the arc chamber.
The present invention contemplates the provision of a high speed, mass production lamp manufacturing pro-ces~ which enables the interior of the lamp body 31 to be eEfectiveIy purged o~ water vapor and kept free of such vapor from prior to the time the halide pellets 52 -' are inserted into the arc chamber 33 until the time the arc chamber has been completely sealed and the pel]ets are protected by the starting gas therein. The in-vention is particularly characterized by the fact that purging of the lamp body 31 is effected by continuously flushing the body during a certain interval of the manu-facturing process with a dry non-reactive gas which is introduced into the body through one of the necks 34~
35 (e.g., the neck 34~. By a non-reactive gas is meant a gas that does not react deleteriously with any of the lamp or equipment parts at the temperature involved. It is most convenient to use argon because it serves also as the inert starting gas which is ~inally sealed into the arc chamber. But dry nitrogen could be used as an economy measure during the bulb forming steps~ and argon sub~tituted therefor prior to sealing in the elect~ode~
inlead assemblies. To enable the flushing gas to be in-troduced continuously through the neck 34, the pellet~
30 52 r the mercury globule 51 and both of the electrodes 36 and 37 are inserted into the lamp body 31 frorn the outer end o~ the other neck 35 with the e7ectrode 36 passing tip last through that neck, across the arc chamber 33 and into the neck 34 ~see FIGS. 14 to 17).
7 !j ~ ~
~ 10 --Glass Lathe Construction In the present instancet a horizontal glass blow-ing lathe 55 (FIGS. 3 and 4) is used in manu~acturing the lamp 30. To enable hi~h speed production of the lamps~ several identical lathes 55 preferably are car-ried on and are spaced angularly around a rotary turn-table or carrousel 56 (FIG. 2) adapted to be indexed intermittently and counterclockwise about a vertical axis 50 as to move each lathe through a series of sta-tions where successive opera-tions are performed to manu-facture the lamp. Each lathe herein is indexed to and dwells momentarily at twenty-oné stations while a lamp is being manufactured, the lathe being moved through such sta~ions as-the table 56 rotates through one-half revolution. To enable effective use of the stations, twenty-one lathes are spaced angularly around one-half of the table and thus one lathe dwells at each station each time the table is stopped. An additional twenty-one lathes (not shown) are spaced around the other half o~ the table'and move through twenty-one stations which are identical to the corxesponding stations around the first half of the table. Thus, one lamp is made when any given lathe is moved through one-half revolution by the tabl'e'and then a secona lamp is made on that same lathe when the'latter is moved throuyh an additional one-half re~olution. It should be appreciated~ however, that thé lathes and the stations may be arranged around the table in any desired manner.
To help gain a quick understanding of the manu-facturing method of the present in~ention, the construc-tion of the lath~s 55 will be described briefly before the method'itself is described. Each lathe comprises a headstock 57 and a tailstock 58 adapted to move toward and away from the headstock. The lathes are mounted in radial attitudes with the headstock located inboard near ~ ~75~ 3 -- 11 ~
the outer peripheral portion oE the turntable 56 above -the upper side thereof and secured to horizon-tal mount-ing plate 59 (FIGS. 3 and 4) fastened to the tableO The mounting plate projects outwardly from the table and also 5 serves to support the tailstock located outboard relative :
to the headstock. As shown in FIGS. 2 and 3, the mounting ;;
plate and the tailstock overhang a circular base or work bench 60 which underlies and projects outwardly fro~ the turntable 56. The work bench is stationary and supports various apparatus (to be described subsequently) used in making the lamp 30.
In many respects) the headstock 57 and the tail-stock 58 of each lathe 55 are identical. Thus, both the headstock and the tailstock include a housing 61 (FIG~ 3) having bearings 62 which support a rotatable chuck, the chucks of the headstock and the tailstock being indicated generally by the reference nu~erals 63 ana 64~ respectively.
Each chuck comprises an outer sleeve 66 journaled by the bearings 62 and receiving a collet 67 (see FIG. 6) having one end portion formed by a series of angularly spaced spring fingers 69. A sleeve 70 o:E silicone rubber is telescoped into -the collet and is adapted to engage and couple hermetically with the quartz tubing to be received in the collet.
A key (not shown) couples each collet 67 for ro-tation with its respective sleeve 66 while allowing the collet to move a~ially within the sleeve. When the col-let is retracted inwardly into the sleeve, the fingers ~9 of the collet are cammed radially inwardly ~y the end portion of the sleeve 66 to effect closing of the col-let (see FIG. 7). Axial shifting of the collet in the opposite direction enables the fingers to spring outwardly so as to open the collet~
~o shift each collet 67 inwardly and outwardly, a tubular drawbar 71 (FIG. 3) is connected to the collet 7 5 ~ 3 and is slidably received wlthin the sleeve 66. One end portion of the drawbar is journaled by the inner race of a bearing as~embly 73 whose outer race is pivotally con-nected at 7~ to the lower end portions oE a pair of up-right arms 75 disposed on opposite sides of the bearingassembly. A pin 76 extends through the arms 75 between the ends thereof and connects the arms pivotally to a plate 78 attached to the~upper side of the housing 61.
Supported on the'plate is a pneumatically operated ac-tuator 80 having a reciprocable rod 81 which is con-nected pivotally to the upper end portions of the arms 75. When the rocl 81 is extended from the position shown in FIG. 3,' the arms 75 pivo~ about the pin 76 and act through'the drawbar 71 to push the collet 67 outwardly from its sleeve'66 to enable the collet to open. The collet is cl~sed when the rod 81 o~ the actuator 80 is retracted and pivots the arrns 75 in a direction to cause the drawbar 71 to pull the collet into the sleeve 66.
The headstock 57 of each lathe 55 is fixed on the mounting plate'59 but the tailstock 58 is arranged to move toward and away from the headstock. For this purpose, the housing 61 of the tailstock is slidably supported on a pair of horizontal guide shafts 84 and 85 (FIG. 4) mounted on the'upper side of the plate 59. The guide shaf-t ~4 is formed with a toothed section 86 tFIG. 43 defining a xack which meshes with a pinion 87. The lat-ter is adapted to be rotated by the shaft of a revers-ible stepping motor 88 attached to the lower side of the housing 61 of the tailstock 58. When the motor is energized, the pinion travels along the rack and ad-vances the'tailstock toward or retracts it away from the headstock.
The'chuc~s 63 and 64 of each lathe 55 are adapted to be rotated by an electric rnotor 89 tFIG. 3) secured to the underside of the table 56 and located beneath the headstock 57. A timing belt 90 is trained around a ~ lfi~51 ~
first pulley 91 on the drive shaft of the motor and a second pulley 92 which is keyed to the guide shaft 85.
The latter is rotatably supported on the mounting plate S9 and within the'lower portions of the housings 61 and thus sexves as a jackshaEt as well as a guide shat.
Another timing belt 93 (FIG. 3) is trained around pulleys 94 and 95 secured to the shaft 85 and to the sleeve 66 of the chuck 63 of the headstock 57. Accord-ingly, the sleeve'66 and the collet 67 of the chuck 63 are rotated whenever the motor 89 is energized. To rotate'the'chuck 64 of the tailstock 58, a third timing belt 96 is trained around pulleys 97 and 98. The pul~
ley 97 is secured to the sleeve'66 of the chuck 63 while the pulley 98 is slidably supported on a non-circular portion of the shaft 85. When the'tailstock 58 is ad-vanced toward the headstock 57, a bracket 99 (FIG. 4) secured to the housing 61 of the tailstock pushes the pulley gæ along the shaft 85 in order to keep that pul-ley properly aligned with the pulley 97. The housing 61 of the tailstock pushes the pulley 98 in the opposite direction along the shaft 85 when the tailstock is re-tracted away from the headstock.
Each'lathe 55 is completed by a rotary seal 100 (FIGS. 3 to 5) which is located at ~he inboard end of the headstock 57 to enable gas to be introduced into and 10w through the chuck 63 of the headstock while ro-tating. The rotary seal herein comprises a rotating portion 101 which'is fast to and turns with drawbar 71 of chuck 63, and a fixed portion 102 supported by bxack-et 103 on turntable 56. The two portions are coupledin such manner as to establish a gas-tight seal between them while allowing rotation of the rotatable portion.
Since there are rotary seals commercially a~ailable whose construction and mode of operation are known, no details need be given here, :I ~S 75~ 3 The stationa~y portion 102 of the rotary seal 100 of e~ch lathe 55 communicates via a line 104 (FIG. 5) with a bank o three solenoid-actuated~ two-position valves 105, 106 and 107 which are connected in parallel with one another. The valves 105, 106 and 1~7 associ-ated with each lathe communicate with three manifolds 108, 109 and 110, respectively, which serve all o the lathes on the'table 56. An inert gas such as argon from a pressurized source 111 is supplied to the manifold 108 via a pressure'reducin~ valve'112 which establishes a oomparatively high'pressure'o about 8.0 psig in the manifold 108. Communication between the manifol~s 10 and 109 is established by way of a second pressure re-ducing valve 113'which'maintains the argon in the mani-fold 109 at a reIatively low pressure such as 0.1 psig.The third manifold 110 communi~ates with the manifold 109'via an adjustable metering valve 114 and also com-municates with'an adjustabIe pressure regulating valve 115 and a vacuum pump 116. The metering valve 114 and the pressure regulating valve 115 are adjusted so as to maintain the'argon in the manifold 110 at a pressure o about 120 torr absolute. Valve 106 is actuated ta allow argon gas at the low 0.1 psig pressure to 10w into the headstock collet s7eeve 70 at all inactive stations in order to prevent contamination by atmospheric moisture.
Lamp Manufacturing Method Now that the construction of the lathes 55 has been explained, the lamp manufacturing method can be 30' described in detail. To facilitate such description, the twenty-one stations at which each lathe dwells have been numbered rom 1 to 21, respectively, around the stationary base or work bench 60 shown in FIG~ 2 with station No. 1 being illustrated as being located at a six o'clock position and with station No~ 21 being located ~7~1 3 ~ D 7630 just short of a twelve o'c~ock position. Various au$o-~ated mechanisms for performing the lamp manufacturing op- -erations are located in the different stations and are positioned on the work bench. These mechanisms per se do not, however, form any part of the present invention and thus they have been shown and will be described only in such detail as is necessary to gain an understanding of the manufacturing method~
The lamp body 31 is made from an elongated piece 120 (FIG..6) of quartz tubing which is initially cyl-indrical. At station No. 1, a piece of tubing having a ;. length somewhat greater than the'length of the finished lamp 30 is loaded into the lathe'55 in station No. 1 while the tailstock 58 of that lathe is fully retracted lS from the headstock 57 as shown' in FIG. 6. Loaaing of the tube 120 may be effected by using a reciprocable pusher 121 to move'the'tube endwise through the drawbar 71 of the tailstock and into the collet 67 thereof from the outboard end of the drawbar while the collet is open (see FIGS. 2 and 6). A stack of tubes may be contained - in a magazine (not shown) in station No. 1 and may be .
released one-by-one to the pusher 'by a suitable escape-ment (not shown).
After the tube 120 has been located in the co7let 67 of the tailstock in the position shown in FIG. 6, the collet is closed by the actuator ~0 on the tailstock 5~
so as to cause the rubber sleeve 70 to grip the outboard end portion of the tube~ After the pusher 121 has been retracted out of the drawbar 71 of the tailstockJ the table S6 is indexed to advance the lathe 55 to station No. 2.
At station No. 2 tFIG. 7), motor 89 is ener~ized to rotate chuck 64 and quartz tube 120 held by it, and a flame 122 is played against the tube next to the'chuck.
At the same time a flexible finger 123, suitably in the ~7513 - 16 ~
form of a wand extending from a length of coiled spring 124, is swung into place by a pneuma-tic actuator 125 (~IG. 7) so as to touch lightly the unsuppor-tea end of tube 120. The'flame playing on the supported end of the tube is just sufficient to so~ten the quartz, and the light pressure oE the finger on the unsupported end causes the tube'to straighten out and corrects any ec~
centric or whipping movement of the unsupported end.
Next, lathe'55 is indexed to and dwells in station No. 3 (FIG. 8), and stepping motor 8~ is energized to move tailstock''S8 toward headstock 57 and cause the in-board end of the guartz'tube to enter collet 67 of the headstock. 'That collet then is closed by the actuator 80 of the headstock'and thus the tube becomes gripped by both the'headstock and the tailstock. As soon as the collet is closed,,the'argon from ma~ifold 10~ flows through the quartz tube. Meanwhile'motor 89 is energized,to ro-tate both'chucks 63 and 64, and whi~e the quartz tube 120 is rotating~ a flame 131 (FIG. ~) is played against ~0 it close to headstock 57. The heat-softening serves to relieve any stress which might have been induced in the tube as a result of being gripped by both chucks 63 and ~4, and also serves to straighten the headstock end of the tube. The seizure of tube 120 in collet 67 of headstock 57 will now be maintained until the ~ulbous midportion 32 has been formed in the tube and the elec-trodes have been positioned in it. Since the headstock is ~Eixed on the carrousel, it describes a circular arc in advancing from station ~o station.
At station No. 4 (~IG. 9), a Elame 132 is direct--ed against the center of the quartz tube as it rotates while held in both chucks 63 and 64 (see FIG. 9). At the same time, the tailstock 53 is advanced a short distance toward the headstock 57 to gather the quartz or, in other words, to force the soEtened quartz at the center of the tube to bulge outwardly and begin ~7513 formation o:E the bulbous midportion 32 of the lamp body 31.
Gathering operations identical ~o those performed at station No. 4 are carried out at each of stations Nos.
5 and 6 (not shown in detail). In each of the latter stations, the tailstock 58 is advanced inwardly an ad-ditional shoxt distance toward the headstock 57 to effect furthe~gathering of the quartz tube 120 and to cause the bulbous midportion 32 of the lamp body 31 to enlarge grad-ually~
The bulbous midportion 32 is blown into its ~inalshape when the lathe'55 dwells in station No. 7 ~FIG.
10~. For this purpose, a mold 134 on the work bench 60 is advanced automatica`lly into proximity with the par-tially formed bulbous midportion 32. The mold is ac-curately located relative to the circular arc described by the headstock to assure that the final configuration into which'the midportion 32 is b:Lown be located at a precise distance''from the headstock in which quartz tube
ack~round of the Invention This invention reIates to a method of manufacturing a double~-ended lamp; it is particularly suitable for making high pressure metal vapor discharge lamps of the type wherein the lamp body comprises an enlarged bulbous midportion with oppositely extending tubular necks. The bulbous midportion defines an arc chamber which contains an inert starting gas and a fill of vaporizable metal or metals such as mercury or a mixture of mercury and se-lected metal halides. Electrodes are hermetically seale~
; within the necks and project into the arc chamber. When ; an arc is created across the interelectrode gap and the fill is vaporized within the arc chambert light is pro-duced in known manner.
The`invention relates more particularly to the manufacture of a lamp of the type in which the fill and the starting gas are introduced into the arc chamber through one of the necks. This is in contrast to a lamp in which the electrodes are first sealed within the necks 2U and in which the fill and the starting gas are then in-troduced into the arc chamber through a lateral exhaust tube which is subsequently tipped ofE. The vestiges of the tip-off form a discontinuity which is more objec-tionable the smaller the size of the lamp.
In all discharge lamps it is necessary to have a clean arc chamber and to avoid contamination oE the fill.
5 ~ 3 Certain types O:e f.ills (e.g~, those containing me-tal halides) are very hygroscopic and react when exposed to even minute amounts of water vapor. Metal halides usual-ly are supplied in the form of pellets having a high degree of purity. To preserve this purity and insure the production of an acceptable lamp, it is necessary to protect the halides, the elec-trodes and the lamp body from water vapor and other contaminants during assembly of the components and until such time as the arc chamber has been safeIy sealed. In miniature discharge lamps, -the deleterious effects of contamination are magnified and the need for protection is all the greater.
In high pressure metal vapor lamps, the arc volt~
age drop varies proportionally to the length o the in-terelectrode'gap. ~he heating of the ends o the arcchamber is strongly influenced by the extent to which the el'ectrodes are'inserted and project into the chamber.
Such heating determines vaporization of the fill, par-ticularly the metal halides which'tend to condense in the cooler ends. Thus both the length and the location of the interelectrode gap are important and the need for precision in its determination increases as the size of the lamp is reduced Summary of the-Invention The general aim of the present invention is to pro~
vide a high speed, mass production method for manufac-turing lamps of the aforegoing general character. The invention is particularly characterized in one aspect by the unique manner in which the components of the lamp are assembled to protect against d~gradation of the fill;
in a second aspect by the manner in which the arc cham-ber i5 formed to achieve high internal purity which is preserved by the unique'manner of assembly of components occurring the'reafter; and in a third aspect by the ! f) ,~ 3 precision in determination of the i.nterelectrode gap made possible by seizing a vitreous tube in a glass lathe at the outset and maintaining such single seizure through-out subsequent formation o the lamp body and assembly of components.
One object of the invention is to load the elec-trodes and the'fill into the lamp body by a novel method which'enables the lamp body to be flushed continuously with'a dry gas for preventing contamination of the com-ponents of the lamp during the assembly operations.
Another object is to provide a lamp assembly methodwhich advantageously may be'carried out at relatively high speed on a hori~ontal glass blowing la-the immediately after the lamp body itself has been formed on the lathe, and which takes advantage of the accuracy of assembly and of the cleanliness made possible ~y a continuous operation startin~ with quartz tubing and ending in a finished lamp.
Electrode Insertion Sch'eme -In its firs~ aspect, the invention resides in a method in which'the fill and the two electrodes are in-serted into the'lamp body through'just one of the necks thereof and preferably while the lamp body is held and hermetically coupled in the chucks of the headstock and the tailstock of a horizontal glass blowing lathe. This allows a purging gas to be flushed through the lamp body by way of the'second neck. The first electrode is in-serted tip last and the second is inserted tip first, and they are both transported upstream against the gas ~low.
Continuous Flush In its second aspect, the invention provides the additional feature of forming ~he lamp body from a length of vitreous tubing which has been heated into the soften-ing range, immediately prior to inserting ~he electrodes ~7513 ~ _ , into the bulb in the unique manner previously described.While beiny heated, and also after it is formed in-to a bulb as by blowing, the tube or lamp body is flushed and such flushing removes moisture and other contaminants from the vitreous material over a higher temperature range than ~he finished lamp will encounter throughout its life. The flushing is continued of course during the insertion of the electrodes and the ~ill up to the closing off of the lamp body. This makes possible the high'degree of purity needed for a miniature metal halide - lamp.
Preci'se Determination of Gap In its third aspect, the invention realizes the high level of accuracy needed in the interelectrode gap determination. This is achieved by seizing a vitreous tube in a glass lathe'and thereafter maintaining this single sei'zure and referencing to it throughout the formation of the bulbous midportion in the tube and the insertion o the electrodes. By accurately positioning, relative to the'lathe,' first the mold into which the bulb is expanded and then the electrodes which are sub-sequently inserted into the bulb~ precision is achieved in both'the'length'of the gap and its location within the bulb.
Preferred Sequence - In a preferred sequence, a glass lathe is ~sed in forming the lamp body and is mounted on a rotary turn-table or carrousel for advance through various work stations. A length of quartz tubing is seized in the headstock o~ the lathe and such seizure is thereafter maintained while the tube is rotated and its midportion is heated into the softening range. Meanwhile the tube is flushed with inert dry yas to drive out moisture and contaminants from the'quartz. The tube is then tempo rarily pressurized and expanded into a mold which is 1 ~6751 3 precisely located relative to the circle described by the headstock of the lathe. This provides a lamp body having a bulbous midportion wi~h oppositely projecting neck portions one of which is seized in the headstock.
Flushing is resumed and one electrode-inlead assembly is inserted reversely or tip-last through the downstream neck and transported upstream throuyh the arc chamber into the ups~ream neck. The fill is then loaded through the downstream neck and deposited in the arc chamber.
'rhereafter the other eIectrode-inlead assembly is in-serted tip firs~ through the downstream neck and trans-ported up to the arc chamber. Flushing is termirlated when the downstream neck portion is closed off and there-after the electrodes are heat-sealed into their respec-tive neck portions. This sequence utilizes all threeaspects of the invention and obtains all the impor-tant advantages, nameIy a bulb of high internal purity, lamp components and fill that were at all times protected against contarnination or degradation, and precision in arc gap determination, all in a high speed mass pro-duction proce~s.
Brief _escription of the Drawings FIG. l is a cross-sectional view~ on a greatly enlarged scale, taken longitudinally through a typical lamp adapted to be manufactured by the new a~d improved method of the present invention.
FIG. 2 is a fragmentary top plan view of exemplary apparatus for carrying out the method.
FIG. 3 is an enlarged fragmentary cross-section taken substantially along the line 3-3 of FIG. 2 and shows one of the glass blowing lathes.
FIG. 4 is a fragmentary cross-section taken sub-stantially along the line 4-4 of FIG. 3.
FIG. 5 is a diagram schematically showiny the control circuit for the flushing gas 11~'7~3 EIG. 6 is a fragmentary view of the headstock and tailstock o~ the lathe illustrated in FIGS. 3 and 4 and shows the first step oE the method.
~ IGS. 7 to 14 are views similar to FIG. 6 and show additional steps of the method.
FIG. 14a is an enlarged view which shows, on an enlaryed scale, the step illustrated in FIG. 14.
FIGS. 15 to 17 are views similar to FIG 14a and show the next ~hree steps of the method.
FIGS. 18 to 22 also are views similar to FIG. 6 and show the final steps of the method.
Detailed~Description Lamp Structure A typical lamp 30 which is adapted to be manufac-tured by the process o~ the present invention is shownin FIG. 1 and is similar to one of the lamps disclosed in Cap et al Canadian application Serial No. 306,479 filed June 29, 1978 and entitled High Pressure M~tal Yapor Discharge Lamps of Improved Efficacy, that appli-cation being assigned to the same assignee as the pres-ent invention~ Briefly, such a lamp comprises an arc tube or lamp body 31 made from a piece of fused silica or quartz tubing and having a hollow bulbous midportion 32 which~defines an arc chamber 33 for containing a high pressure discharge. In this particular instance, the arc chamber is generally spherical and has a volume of less than one cubic centimeter. The arc chamber mayr however, be of various shapes (e.g., ellipsoidal or cylindrical) and may be considerably larger than that o~ the lamp 30.
Joined to and extendin~ in diametrically opposite directions from the midportion 32 of the lamp body 31 are two reduced diarneter tubular neck por-tions 34 and 35. Each neck is generally cylindrical and is of small cross-sectional area when compared with the cross-section-~ ~7~
~ 7~30-- 7 --al area of the midportion.
Elec-trode-inlead assemblies 36 and 37 are inserted into the necks 34 and 35, respectively~ The electrode 36 forms the cathode of the lamp 30 and comprises a length of molybdenum wire 38 which'projects a predetermined dis-tance out of the neck 34 and into the arc chamber 33.
coil 40 of tungsten wire is wound around the inner end portion of the molybdenum wire and terminates in a sphere which defines the tip 42 of the'eIectrode 36. Reference may b ~ ade to Canadian application Serial No. 3~?,~7~ , filed~ by Dvorak and Fridrich, Electrode for High - Pressure Metal Vapor Lamp, assigned like this application, for a more complete'description of the subject electrode.
The eIectrode 37 constitues the anode of the lamp 30 and is formed by a len~th of tungsten wire 43 received within the neck 35 and projecting a predetermined distance into the arc chamber 33. A small sphere is formed on the distal end of the'wire 43 and defines the tip 44 of the electrode 37. The space between the tips 42 and 44 of the electrodes 36 and 37 defines the arc gap.
Molybdenum inlead wires 45 and 46 extend into the outer ends of the necks 34 and 35~ respectively r and are adapted for connection to the electrical terminals o~ an outer envelope (not shown). The inlead 45 is -formed in--tegrally with'the'molybdenum wire 38 of the electrode 36 while ~he inlead 46 is suitably joined at 47 to the tungsten wire 43 of the electrode 37. The join at 47 is conveniently made by a laser butt weld per U.S. patent 4,136,298 - Hansler. Each inlead includes a relatively flat foliated portion 48 intermediate its ends which may be formed by cross-rolling or by longitudinal rollingD
Alternatively a composite inlead comprising a length of foil with a wire welded to each end may be used. The foil portion enables a hermetic seal to be established between the electrode and the neck so as to hold the ~'75~
electrode in place and to seal the arc chamber 33 from the outside atmosphbre. The seals through necks 34 and 35 are formed by heatiny and fusing the quart~ to col-lapse the internal passage through each neck and cause the quartz to wet and seal to the foil portion of the associated inlead. ' A fill or dose of ~aporizable met'al is contained within the arc chamher 33 and is adapted to vaporize and produce light in a well-known manner when an appropriate voltage is applied across the'eIectrodes 3G and 37 to create an arc between the'tips 42 and 44 thereof. Herein, the fill comprises mercury and a mixture of selected metal halides (e.g., NaI, ScI3 and ThI4) although the fill could consist of mercury alone. After the lamp 30 has been manufactured but before the lamp is first operated, the mercury exists in the arc chamber 33 in the form of a globule 51 while the halides exist in the form of one or more pellets 52.
- The lamp 30 is completed by a quantity of inert starting gas which ini.tially exist.s in the arc chamber 33 at a subatmospheric pressure of about 120 torr ab-solute. Argon is used as the starting gas in the present-lamp. Unlike many discharge lamps, the present lamp does not include a tipped-off lateral exh~ust tube ex-tending from the bulbous midportion 32.
In manufacturing a lamp 30 of the above -type, one of the difficult problems which`is encountered invol~es loading the halide dose into the arc chamber 33 withou-t contaminating the dose with water vapor or other im-purities during insertion of the dose and while sealingthe chamber. The halide pellets 52 are extremely hygro~
scopic and ~ere momentary exposure to the ambient at-mosphere may allow enough moisture to be picked up that lamp operat,ion will be deleteriously af~ected. As i.n-itially processed, the total oxygen content of the pellets ~1~)7513 _ g _ is less than fifty parts per million. In order for thelamp 30 to operate ef~ectively and reliably, it is nec-essary to preserve the high purity of the pellets by shielding them at all times from -the atmosphere and its inevitable water vapor until they are safely sealed in the arc chamber.
The present invention contemplates the provision of a high speed, mass production lamp manufacturing pro-ces~ which enables the interior of the lamp body 31 to be eEfectiveIy purged o~ water vapor and kept free of such vapor from prior to the time the halide pellets 52 -' are inserted into the arc chamber 33 until the time the arc chamber has been completely sealed and the pel]ets are protected by the starting gas therein. The in-vention is particularly characterized by the fact that purging of the lamp body 31 is effected by continuously flushing the body during a certain interval of the manu-facturing process with a dry non-reactive gas which is introduced into the body through one of the necks 34~
35 (e.g., the neck 34~. By a non-reactive gas is meant a gas that does not react deleteriously with any of the lamp or equipment parts at the temperature involved. It is most convenient to use argon because it serves also as the inert starting gas which is ~inally sealed into the arc chamber. But dry nitrogen could be used as an economy measure during the bulb forming steps~ and argon sub~tituted therefor prior to sealing in the elect~ode~
inlead assemblies. To enable the flushing gas to be in-troduced continuously through the neck 34, the pellet~
30 52 r the mercury globule 51 and both of the electrodes 36 and 37 are inserted into the lamp body 31 frorn the outer end o~ the other neck 35 with the e7ectrode 36 passing tip last through that neck, across the arc chamber 33 and into the neck 34 ~see FIGS. 14 to 17).
7 !j ~ ~
~ 10 --Glass Lathe Construction In the present instancet a horizontal glass blow-ing lathe 55 (FIGS. 3 and 4) is used in manu~acturing the lamp 30. To enable hi~h speed production of the lamps~ several identical lathes 55 preferably are car-ried on and are spaced angularly around a rotary turn-table or carrousel 56 (FIG. 2) adapted to be indexed intermittently and counterclockwise about a vertical axis 50 as to move each lathe through a series of sta-tions where successive opera-tions are performed to manu-facture the lamp. Each lathe herein is indexed to and dwells momentarily at twenty-oné stations while a lamp is being manufactured, the lathe being moved through such sta~ions as-the table 56 rotates through one-half revolution. To enable effective use of the stations, twenty-one lathes are spaced angularly around one-half of the table and thus one lathe dwells at each station each time the table is stopped. An additional twenty-one lathes (not shown) are spaced around the other half o~ the table'and move through twenty-one stations which are identical to the corxesponding stations around the first half of the table. Thus, one lamp is made when any given lathe is moved through one-half revolution by the tabl'e'and then a secona lamp is made on that same lathe when the'latter is moved throuyh an additional one-half re~olution. It should be appreciated~ however, that thé lathes and the stations may be arranged around the table in any desired manner.
To help gain a quick understanding of the manu-facturing method of the present in~ention, the construc-tion of the lath~s 55 will be described briefly before the method'itself is described. Each lathe comprises a headstock 57 and a tailstock 58 adapted to move toward and away from the headstock. The lathes are mounted in radial attitudes with the headstock located inboard near ~ ~75~ 3 -- 11 ~
the outer peripheral portion oE the turntable 56 above -the upper side thereof and secured to horizon-tal mount-ing plate 59 (FIGS. 3 and 4) fastened to the tableO The mounting plate projects outwardly from the table and also 5 serves to support the tailstock located outboard relative :
to the headstock. As shown in FIGS. 2 and 3, the mounting ;;
plate and the tailstock overhang a circular base or work bench 60 which underlies and projects outwardly fro~ the turntable 56. The work bench is stationary and supports various apparatus (to be described subsequently) used in making the lamp 30.
In many respects) the headstock 57 and the tail-stock 58 of each lathe 55 are identical. Thus, both the headstock and the tailstock include a housing 61 (FIG~ 3) having bearings 62 which support a rotatable chuck, the chucks of the headstock and the tailstock being indicated generally by the reference nu~erals 63 ana 64~ respectively.
Each chuck comprises an outer sleeve 66 journaled by the bearings 62 and receiving a collet 67 (see FIG. 6) having one end portion formed by a series of angularly spaced spring fingers 69. A sleeve 70 o:E silicone rubber is telescoped into -the collet and is adapted to engage and couple hermetically with the quartz tubing to be received in the collet.
A key (not shown) couples each collet 67 for ro-tation with its respective sleeve 66 while allowing the collet to move a~ially within the sleeve. When the col-let is retracted inwardly into the sleeve, the fingers ~9 of the collet are cammed radially inwardly ~y the end portion of the sleeve 66 to effect closing of the col-let (see FIG. 7). Axial shifting of the collet in the opposite direction enables the fingers to spring outwardly so as to open the collet~
~o shift each collet 67 inwardly and outwardly, a tubular drawbar 71 (FIG. 3) is connected to the collet 7 5 ~ 3 and is slidably received wlthin the sleeve 66. One end portion of the drawbar is journaled by the inner race of a bearing as~embly 73 whose outer race is pivotally con-nected at 7~ to the lower end portions oE a pair of up-right arms 75 disposed on opposite sides of the bearingassembly. A pin 76 extends through the arms 75 between the ends thereof and connects the arms pivotally to a plate 78 attached to the~upper side of the housing 61.
Supported on the'plate is a pneumatically operated ac-tuator 80 having a reciprocable rod 81 which is con-nected pivotally to the upper end portions of the arms 75. When the rocl 81 is extended from the position shown in FIG. 3,' the arms 75 pivo~ about the pin 76 and act through'the drawbar 71 to push the collet 67 outwardly from its sleeve'66 to enable the collet to open. The collet is cl~sed when the rod 81 o~ the actuator 80 is retracted and pivots the arrns 75 in a direction to cause the drawbar 71 to pull the collet into the sleeve 66.
The headstock 57 of each lathe 55 is fixed on the mounting plate'59 but the tailstock 58 is arranged to move toward and away from the headstock. For this purpose, the housing 61 of the tailstock is slidably supported on a pair of horizontal guide shafts 84 and 85 (FIG. 4) mounted on the'upper side of the plate 59. The guide shaf-t ~4 is formed with a toothed section 86 tFIG. 43 defining a xack which meshes with a pinion 87. The lat-ter is adapted to be rotated by the shaft of a revers-ible stepping motor 88 attached to the lower side of the housing 61 of the tailstock 58. When the motor is energized, the pinion travels along the rack and ad-vances the'tailstock toward or retracts it away from the headstock.
The'chuc~s 63 and 64 of each lathe 55 are adapted to be rotated by an electric rnotor 89 tFIG. 3) secured to the underside of the table 56 and located beneath the headstock 57. A timing belt 90 is trained around a ~ lfi~51 ~
first pulley 91 on the drive shaft of the motor and a second pulley 92 which is keyed to the guide shaft 85.
The latter is rotatably supported on the mounting plate S9 and within the'lower portions of the housings 61 and thus sexves as a jackshaEt as well as a guide shat.
Another timing belt 93 (FIG. 3) is trained around pulleys 94 and 95 secured to the shaft 85 and to the sleeve 66 of the chuck 63 of the headstock 57. Accord-ingly, the sleeve'66 and the collet 67 of the chuck 63 are rotated whenever the motor 89 is energized. To rotate'the'chuck 64 of the tailstock 58, a third timing belt 96 is trained around pulleys 97 and 98. The pul~
ley 97 is secured to the sleeve'66 of the chuck 63 while the pulley 98 is slidably supported on a non-circular portion of the shaft 85. When the'tailstock 58 is ad-vanced toward the headstock 57, a bracket 99 (FIG. 4) secured to the housing 61 of the tailstock pushes the pulley gæ along the shaft 85 in order to keep that pul-ley properly aligned with the pulley 97. The housing 61 of the tailstock pushes the pulley 98 in the opposite direction along the shaft 85 when the tailstock is re-tracted away from the headstock.
Each'lathe 55 is completed by a rotary seal 100 (FIGS. 3 to 5) which is located at ~he inboard end of the headstock 57 to enable gas to be introduced into and 10w through the chuck 63 of the headstock while ro-tating. The rotary seal herein comprises a rotating portion 101 which'is fast to and turns with drawbar 71 of chuck 63, and a fixed portion 102 supported by bxack-et 103 on turntable 56. The two portions are coupledin such manner as to establish a gas-tight seal between them while allowing rotation of the rotatable portion.
Since there are rotary seals commercially a~ailable whose construction and mode of operation are known, no details need be given here, :I ~S 75~ 3 The stationa~y portion 102 of the rotary seal 100 of e~ch lathe 55 communicates via a line 104 (FIG. 5) with a bank o three solenoid-actuated~ two-position valves 105, 106 and 107 which are connected in parallel with one another. The valves 105, 106 and 1~7 associ-ated with each lathe communicate with three manifolds 108, 109 and 110, respectively, which serve all o the lathes on the'table 56. An inert gas such as argon from a pressurized source 111 is supplied to the manifold 108 via a pressure'reducin~ valve'112 which establishes a oomparatively high'pressure'o about 8.0 psig in the manifold 108. Communication between the manifol~s 10 and 109 is established by way of a second pressure re-ducing valve 113'which'maintains the argon in the mani-fold 109 at a reIatively low pressure such as 0.1 psig.The third manifold 110 communi~ates with the manifold 109'via an adjustable metering valve 114 and also com-municates with'an adjustabIe pressure regulating valve 115 and a vacuum pump 116. The metering valve 114 and the pressure regulating valve 115 are adjusted so as to maintain the'argon in the manifold 110 at a pressure o about 120 torr absolute. Valve 106 is actuated ta allow argon gas at the low 0.1 psig pressure to 10w into the headstock collet s7eeve 70 at all inactive stations in order to prevent contamination by atmospheric moisture.
Lamp Manufacturing Method Now that the construction of the lathes 55 has been explained, the lamp manufacturing method can be 30' described in detail. To facilitate such description, the twenty-one stations at which each lathe dwells have been numbered rom 1 to 21, respectively, around the stationary base or work bench 60 shown in FIG~ 2 with station No. 1 being illustrated as being located at a six o'clock position and with station No~ 21 being located ~7~1 3 ~ D 7630 just short of a twelve o'c~ock position. Various au$o-~ated mechanisms for performing the lamp manufacturing op- -erations are located in the different stations and are positioned on the work bench. These mechanisms per se do not, however, form any part of the present invention and thus they have been shown and will be described only in such detail as is necessary to gain an understanding of the manufacturing method~
The lamp body 31 is made from an elongated piece 120 (FIG..6) of quartz tubing which is initially cyl-indrical. At station No. 1, a piece of tubing having a ;. length somewhat greater than the'length of the finished lamp 30 is loaded into the lathe'55 in station No. 1 while the tailstock 58 of that lathe is fully retracted lS from the headstock 57 as shown' in FIG. 6. Loaaing of the tube 120 may be effected by using a reciprocable pusher 121 to move'the'tube endwise through the drawbar 71 of the tailstock and into the collet 67 thereof from the outboard end of the drawbar while the collet is open (see FIGS. 2 and 6). A stack of tubes may be contained - in a magazine (not shown) in station No. 1 and may be .
released one-by-one to the pusher 'by a suitable escape-ment (not shown).
After the tube 120 has been located in the co7let 67 of the tailstock in the position shown in FIG. 6, the collet is closed by the actuator ~0 on the tailstock 5~
so as to cause the rubber sleeve 70 to grip the outboard end portion of the tube~ After the pusher 121 has been retracted out of the drawbar 71 of the tailstockJ the table S6 is indexed to advance the lathe 55 to station No. 2.
At station No. 2 tFIG. 7), motor 89 is ener~ized to rotate chuck 64 and quartz tube 120 held by it, and a flame 122 is played against the tube next to the'chuck.
At the same time a flexible finger 123, suitably in the ~7513 - 16 ~
form of a wand extending from a length of coiled spring 124, is swung into place by a pneuma-tic actuator 125 (~IG. 7) so as to touch lightly the unsuppor-tea end of tube 120. The'flame playing on the supported end of the tube is just sufficient to so~ten the quartz, and the light pressure oE the finger on the unsupported end causes the tube'to straighten out and corrects any ec~
centric or whipping movement of the unsupported end.
Next, lathe'55 is indexed to and dwells in station No. 3 (FIG. 8), and stepping motor 8~ is energized to move tailstock''S8 toward headstock 57 and cause the in-board end of the guartz'tube to enter collet 67 of the headstock. 'That collet then is closed by the actuator 80 of the headstock'and thus the tube becomes gripped by both the'headstock and the tailstock. As soon as the collet is closed,,the'argon from ma~ifold 10~ flows through the quartz tube. Meanwhile'motor 89 is energized,to ro-tate both'chucks 63 and 64, and whi~e the quartz tube 120 is rotating~ a flame 131 (FIG. ~) is played against ~0 it close to headstock 57. The heat-softening serves to relieve any stress which might have been induced in the tube as a result of being gripped by both chucks 63 and ~4, and also serves to straighten the headstock end of the tube. The seizure of tube 120 in collet 67 of headstock 57 will now be maintained until the ~ulbous midportion 32 has been formed in the tube and the elec-trodes have been positioned in it. Since the headstock is ~Eixed on the carrousel, it describes a circular arc in advancing from station ~o station.
At station No. 4 (~IG. 9), a Elame 132 is direct--ed against the center of the quartz tube as it rotates while held in both chucks 63 and 64 (see FIG. 9). At the same time, the tailstock 53 is advanced a short distance toward the headstock 57 to gather the quartz or, in other words, to force the soEtened quartz at the center of the tube to bulge outwardly and begin ~7513 formation o:E the bulbous midportion 32 of the lamp body 31.
Gathering operations identical ~o those performed at station No. 4 are carried out at each of stations Nos.
5 and 6 (not shown in detail). In each of the latter stations, the tailstock 58 is advanced inwardly an ad-ditional shoxt distance toward the headstock 57 to effect furthe~gathering of the quartz tube 120 and to cause the bulbous midportion 32 of the lamp body 31 to enlarge grad-ually~
The bulbous midportion 32 is blown into its ~inalshape when the lathe'55 dwells in station No. 7 ~FIG.
10~. For this purpose, a mold 134 on the work bench 60 is advanced automatica`lly into proximity with the par-tially formed bulbous midportion 32. The mold is ac-curately located relative to the circular arc described by the headstock to assure that the final configuration into which'the midportion 32 is b:Lown be located at a precise distance''from the headstock in which quartz tube
2~ 120 is seized. A flame 135 for heating the bulbous midportion is located generally opposite the mold which is formed w.ith'a cavity whose shape is complementary to the'desired final shape of the bulbous midportion.
While'the mold 134 is being moved into place in station No. 7, a closure in the form of a plu~ 136 (FIG.
10) is shifted into the outboard end of the drawbar 71 of the chuck 64 of the tailstock 58. The plug is sup-ported and advanced by a suitable mechanism 137 ~FIG.
2) on the work bench 60 and serves to seal off the chuck 64 and the tailstock end of the tube 120 so that the tube may be pressurized with gas for ~he purpose of expanding the bulbous midportion 32 into the cavity of the mold, Pressurization of the tube 12~ is effected by automatically opening the valve 105 (FIG. 5) to cause argon at relatively high pressure ~i.e., 8 psig~
5 1 ~
to flow from the manifold 108, through the rotary seal 100 and the chuck 63'of the headstock 57, and into the tube. The gas is introduced into the tube as it ro-tates while held by the chucks 63 and 64 and while the 5 fla~e 135 is being directed against the bulbous mid-portion 32 to soften the quartz. Accordingly, the ~uartz is blown into and is shaped by the mold 134 so as to form the bulbous midportion 32 into its Einal configuxation shown in FIG. 1. The mold 134 and the plug 136 then are retracted to permit the lathe 55 to advance to station No. 8.
At station No. 8 (see FIG. 11), the tube 120 is heated along substantially its entire length while si-multaneously being flushed with argon admitted into the chuck 63 and the'tube through the valve 105. The prior heating of the midportion during the quartz gather-ing and bulb blowing together with the present heating and flushing operation clean the tube of any contaminants over a higher temperature range'than the finished lamp will e~counter during its life. In particular, moisture is driven from the tube so that the tube will be truly ~ry when the'halide pellets 52 are subsequently intro-duced into it. As shown in FIG. 11, heating of the tube 120 is effected by a series of ~lames 138 spacea along the length o~ the tube. As an alternati~e, however, a single'flame'could he traversed along the t~be to heat the tube along substantially its entlre length. As the tube 120 is heated at station No. 8, it is rotated by the chuck 63 of the headstock 57. Also, the tailstock 58 may be opened to release the'tube (see FIG. 11~ and shifted to its retracted position during the heating and flushing operation so that moisture within the tube will eScape to atmosphere rather than being driven into the chuck 64 of the tailstock. Retraction of the tailstocX
also prevents excessive heating of the tailst~ck. ~owever 1~fi751~
- lg -the tube is not reIeased from the headstock so -that the precise positioni.ng of the bulb is maintained.
Upon being advanced to station No. 9 (FIG. 12), the tube 120 is cooled to permit subsequent re-gripping oE
the tube by the tailstock 58. Herein, cooling oE the tube is effected by directing jets of cooled nitrogen from a manifold 140 against the tube while the latter is being rotated by the headstock 57, while the tailstock is retracted, and wh'ile argon is being introduced into the tube through the'h~adstock.
At station No.'10, the tailstock 58 advances Eor-wardly and re-grips the tube 120 as shown in FIG~ 13.
Thereafter, a mechanism 141 on the work bench 60 moves inwardly toward the'outboard end of the tai.lstock to en- ~
15 able a leak test to be performed. As schematically shownl -the mechanism comprises an apertured plug 143 a.dapted to telescope'into the'outboard end oE the drawbar 71 oE the -.
tailstock, there'being a vacuum gauge 145 communicating :;
with the aperture'in the plug. Once the plug 143 has been advanced to the position shown in FIG. 13, the valve 107 ~FIG. 5) is opened to cause th~ vacuum pump 116 to draw a vacuum in the tube 120 via the manifold 110, the rotary seal 104 and the headstock 57. If the bulbou~ midportion 32 of the lamp body 31 has been proper-ly formed and is gas-tight, a high order of ~acuum will be established in the tube 120 and the reading of the vacuum gauge 145 will be below a predetermined value.
If on the other hand there is a leak in any part o~
the tube 120, the reading o the gauye indicates a de-: 30 fective tube. The gauga'may also produce a siynal which is used to efEect cancellation oE the operations thak otherwise would be perEormed on the tube a-Eter station No. 10.
A~ter the'leak test has been completed, the mecha-35 nism 141 is retracted away from the drawbar 71 of the 5 ~1 3 2~ -of the tails-tock 58 to enable the lathe S5 to ad~ance to station No. 11 where the cathode-inlead assembly 36 is inserted into the tube 120 (see FIGS, 14 and 14a). Before the mechanism 141 is retracted,,the valve 107 is closed to cut off the vacuum and the valve 105 is opened to in-itiate a flow of argon from the man:ifold 108 through the headstock 57 and into the tube 120. The flow of argon into the tube is maintained continuously until the tube is sealed and serves to keep it purged of moisture.
Importantly and in keeping with the invention, the cathode assembly 36 is inserted into the ~uartz tube 120 at station No. 11 by being moved tip-last through the chuck 64 of the tailstock 58, through that portion of the tube'that ultimately defines the neck 35 of the lamp 30,,across the arc chamber 33, and finally into that portion of the tube that ultimately def,ines the neck 34 of the lamp. Thus, the cathode assembly 36 is not loaded tip-first through'the headstock'57 and directly into the neck 34 but instead is loaded tip--last into the neck 34 after irst passing through'the tailstock 5~ and the neck 35. As a result of the cathode being loaded in this way, the rotary seal 100 can be located at and can remain attached permanently to the inboard or upstream end ~f the headstock 57 to enable the tube 120 to be flushed continuously with a dry non-reactive gas such as argon until such time as the tube is sealed.
More specifically, the cathode assembly 36 is pre-loaded into a sleeve-type holder 150 (FIG. 14a) which is automatically brought into alignment with the out-board end of the drawbar 71 of the tailstock 58 when th~lathe 55 dwells at station No. 11 (see the position of the cathode shown in phantom lines in FIG. 14~. The holder 150 is oriented such that the tip 42 o~ the cathode is d'sposed in trailin~ relationship to the in-lead 45 thereof.
7 5 ~1 3 AEter the lathe $5 stops at station ~o. 11, a pusher (not shown~ shoves the holder 150 and the pre-loaded cathode assembly 36 through the chuck 64 of the tailstock 58, through the neck 35 and into the neck 34 ~see FIG. 14a). If the tip o~ the cathode be considered the head of the cathode-assembly, the assembly may be said to be shoved feet first throuyh the lamp body~ The stroke of the pusher is controlled so as to locate tlle tip 42 of the cathode at a predetermined distance from the headstock chuck. Because the lamp body has never been released from the headstick ch~lck since the forma-tion of the bulb, the tip of the cathode is thereby auto-matically accurateIy located in the lamp body. Once the cathode assembly has been properly located, the pusher is retracted and withdraws the holder 150 from the cathode and out through the tailstock. During retraction of the hblder, a plunger lSl engages the tip 42 of the cathode -to prevent the latteî from moviny with the holder. After removal of the holder, the cathode assembly is prevent- -ed from sliding and held in a centered position in the neck 34 by virtue of the frictiona:L engagement of the inside diameter of the neck by foi:L portion 48 of the inleadv As pointed out above, argon flows continuously through quartz tube 120 during loading of the cathode assembly. Accordingly, the argon serves to dry any moisture which might be present on the assembly or ~he holder 150 and thus maintains the tube in a "clean"
condition. The flow of argon is continued during in-dexing of the lathe 55 to station No. 12.
At station No. 12, the halide pellets 52 areloaded into the arc chamber 33 (see FIG. 15). This is achieved by insertiny a tubular needle 153 throuyh the tailstock 58 and the neck 35 and by stopping the needle when its tip is near the center of the arc chamber. A
5 ~ 3 - 2~ -downwardly opening port 154 is formed in the needle near the tip thereof while a smal:ler port 155 opens out of the tip. The needle communicates with a low pressure source (not shown) o:f dry inert gas located on the work bench 60 at station No. 12.
A stream of the dry inert gas is flushed at all times through needle 153. After the needle has been positioned in the arc chamber 33, an appropriate number of halide pellets 52 are metered from a storage container (not shown) and are reIeased into the stream of gas. The stream carries the peIlets through the needle until they reach the downwardly opening port 154 and fall into the arc chamber 33. Because the pellets are discharged from the nesdle along a path extending transversely to the stream of purging gas flowing into quartz tube 120 -through the headstock 57, there is little danger o~ the pellets becoming entrained in that stream and being blown into or through the neck 35.
Following release of the halide pellets 52, the needle 153 is withdrawn from the tailstock 58 and then the lathe 55 is indexed to station No. 13 where a globule 51 of mercury is injected into the arc chamber 33 (see FIG. 16). Injection of the mercury is ef~ected in sub stantially the same way as injection of the halide pel lets S2 and .is carried out with a neeal~ 157 which i5 virtually identical to the needle 153. The needle ~57 is inserted into the tailstock 58, the mercury globule 51 is released to the gas stream in the needle and then the nesdle is retrac-ted after the mercury drops into the arc chamber 33. Flushing o~ quartz tube 120 b~ gas introduced through the headstock 57 continues during in-jection of the mercury.
The lathe 55 next is indexed to sta-tion No. 14 for insertion of the anode assembly 37 into the tube 120 (see FIG. 17). The assembly is preloaded into a holder 7 ~ :1 3 159 s:imilar to the holder 150 and is shoved through the tailstock 58 and into the neck 35 by a pusher. Urllike the cathode 36, the anode 37 is pushed tip or head first into the neck 35. The stroke of the pusher (not shown) is controlled so as to accurately locate the tip 44 of the anode relative to the headstock chuck. Since the lamp body is accurat~ly positioned relative to the head-stock chuck and the cathode tip has previously been ~c-curately located, now the length of the gap between cathode and anode tips is precisely determined. Also the gap is accurately positioned at the precise location within the arc chamber 33 called for by the lamp design. Gas con-tinues to flow into quartz tube 120 during insertion of the anode to insure against water vapor reacting with the halide pellets 52.
While the lathe 55 dwells at station No. 15, the tallstock 58 is operated to release quartæ tube 120 and is retracted ~see FIG. 18). A flame 161 then is directed against the unsupported end of the rotating tube~ The heat causes the quartz to collapse and dome over as in-dicated at 162 so as to tip off the tube and ~orm a tem-poraxy seal. ~n operation identical to that perormed at station No. 15 is pexformed by a flame 163 (see FIG.
2) at station No. 16 to insure that tip 162 is truly sealed. Durïng the tipping operation~ at sta-tions Nos.
15 and 16, argon at low pressure li.e. 9 0.1 psig) is ad-mitted into quartz tube 120 through the headstock 57 by way of manifold 109, valve 106 and rotary seal 100. The argon keeps the tube dry but its pressure is of such low magnitude that there is no danger of the gas blow-ing a hole in the newly ormed tip 162~
At station No. 17, a stream of cooled nitrogen is directed at the tip 162 through a nozzle 165 ~see FIG.
2) to cool the tip and allow subsequent re-gripping of the ~uartz tube by tailstock $8. Pressurization of the ~:~fi7513 tube with ].ow pressure argon from the manifold 109 is continued during the cooling step When the lathe 55 reaches sta-tion NoO 18, the quart~
tube 120 is re-gripped by the tailstock 5B and is .rotated by both the headstock and the tailstock (see FIG. 19).
At this station, the cathode inlead assembly 36 is her-metically sealed into the neck 34 by heating the guar-tz and causing it to collapse around the foil portion of the inlead. This may be done ~or example by a laser 167 which traverses along an appropriate length of the neck to cause the quartz to collapse around the cathbde. At the same time the bulb portion 32 of the lamp body is cooled by advancing a metal shroud 168 to partially surround it.
The shroud contains a sponge which engages the bulb and which is kept wet by water supplied by tube 169 while aspirator tube 170 removes excess water.
Just prior to sealing of the neck 34, the valve 106 is closed and the valve 107 is opened to establish communication between the vacuum pump 116 and the tube 120 by way of the manifold 110 and the rotary seal 100.
The vacuum pump draws argon from the manifold 109 into the manifold 110 via the metering valve 114 and reduces the pxessure of the argon in the tube 120 to the sub-atmospheric value of 120 torr absolute. Accordingly, the desired pressure for the starting gas of the lamp 30 is established as an incident to sealing of the neck 34, and the sub-atmospheric pressure assures the de-sired collapse of the guartz around the foil portion of the inlead.
At station No. 19, the neck 35 is seale~ to the anode 37 by a laser 171 similar to the laser 167 ~see FIG. 20) while the bulb is cooled by water cooler 172 similar to that previously descri.bed~ For some lamp si2es, it may be preferable to seal neck 35 ~irst and then neck 34; this sequence permits a closer control 1~7S~ ~
~ 25 --of the argon pressure while making the last seal.
When -the lathe 55 is indexed to station No. 20, a scoring head 173 (~'IG. 211 having a pair of scoring tools 174 is advanced into an operative position adjacent the tube 120. The tools 174 are located to score the end portions of the necks 34 and 35 beyond the sealing regions so that the end portions subsequently may be broken away to expose the inleads 45 and 46.
At station No. 21 ~see FIG. 221, the lamp 30 is removed from the lathe 55. This may be achleved by re-tracting the headstock 58 from the lamp, by gripping the lamp with an automatically operable unloading device 175 and then by retracting the tailstock from the lamp. The empty lathe then may advance to the twelve o'clock posi-tion shown in FIG. 2 to receive another quartz tube andbegin another cycle~
While'the mold 134 is being moved into place in station No. 7, a closure in the form of a plu~ 136 (FIG.
10) is shifted into the outboard end of the drawbar 71 of the chuck 64 of the tailstock 58. The plug is sup-ported and advanced by a suitable mechanism 137 ~FIG.
2) on the work bench 60 and serves to seal off the chuck 64 and the tailstock end of the tube 120 so that the tube may be pressurized with gas for ~he purpose of expanding the bulbous midportion 32 into the cavity of the mold, Pressurization of the tube 12~ is effected by automatically opening the valve 105 (FIG. 5) to cause argon at relatively high pressure ~i.e., 8 psig~
5 1 ~
to flow from the manifold 108, through the rotary seal 100 and the chuck 63'of the headstock 57, and into the tube. The gas is introduced into the tube as it ro-tates while held by the chucks 63 and 64 and while the 5 fla~e 135 is being directed against the bulbous mid-portion 32 to soften the quartz. Accordingly, the ~uartz is blown into and is shaped by the mold 134 so as to form the bulbous midportion 32 into its Einal configuxation shown in FIG. 1. The mold 134 and the plug 136 then are retracted to permit the lathe 55 to advance to station No. 8.
At station No. 8 (see FIG. 11), the tube 120 is heated along substantially its entire length while si-multaneously being flushed with argon admitted into the chuck 63 and the'tube through the valve 105. The prior heating of the midportion during the quartz gather-ing and bulb blowing together with the present heating and flushing operation clean the tube of any contaminants over a higher temperature range'than the finished lamp will e~counter during its life. In particular, moisture is driven from the tube so that the tube will be truly ~ry when the'halide pellets 52 are subsequently intro-duced into it. As shown in FIG. 11, heating of the tube 120 is effected by a series of ~lames 138 spacea along the length o~ the tube. As an alternati~e, however, a single'flame'could he traversed along the t~be to heat the tube along substantially its entlre length. As the tube 120 is heated at station No. 8, it is rotated by the chuck 63 of the headstock 57. Also, the tailstock 58 may be opened to release the'tube (see FIG. 11~ and shifted to its retracted position during the heating and flushing operation so that moisture within the tube will eScape to atmosphere rather than being driven into the chuck 64 of the tailstock. Retraction of the tailstocX
also prevents excessive heating of the tailst~ck. ~owever 1~fi751~
- lg -the tube is not reIeased from the headstock so -that the precise positioni.ng of the bulb is maintained.
Upon being advanced to station No. 9 (FIG. 12), the tube 120 is cooled to permit subsequent re-gripping oE
the tube by the tailstock 58. Herein, cooling oE the tube is effected by directing jets of cooled nitrogen from a manifold 140 against the tube while the latter is being rotated by the headstock 57, while the tailstock is retracted, and wh'ile argon is being introduced into the tube through the'h~adstock.
At station No.'10, the tailstock 58 advances Eor-wardly and re-grips the tube 120 as shown in FIG~ 13.
Thereafter, a mechanism 141 on the work bench 60 moves inwardly toward the'outboard end of the tai.lstock to en- ~
15 able a leak test to be performed. As schematically shownl -the mechanism comprises an apertured plug 143 a.dapted to telescope'into the'outboard end oE the drawbar 71 oE the -.
tailstock, there'being a vacuum gauge 145 communicating :;
with the aperture'in the plug. Once the plug 143 has been advanced to the position shown in FIG. 13, the valve 107 ~FIG. 5) is opened to cause th~ vacuum pump 116 to draw a vacuum in the tube 120 via the manifold 110, the rotary seal 104 and the headstock 57. If the bulbou~ midportion 32 of the lamp body 31 has been proper-ly formed and is gas-tight, a high order of ~acuum will be established in the tube 120 and the reading of the vacuum gauge 145 will be below a predetermined value.
If on the other hand there is a leak in any part o~
the tube 120, the reading o the gauye indicates a de-: 30 fective tube. The gauga'may also produce a siynal which is used to efEect cancellation oE the operations thak otherwise would be perEormed on the tube a-Eter station No. 10.
A~ter the'leak test has been completed, the mecha-35 nism 141 is retracted away from the drawbar 71 of the 5 ~1 3 2~ -of the tails-tock 58 to enable the lathe S5 to ad~ance to station No. 11 where the cathode-inlead assembly 36 is inserted into the tube 120 (see FIGS, 14 and 14a). Before the mechanism 141 is retracted,,the valve 107 is closed to cut off the vacuum and the valve 105 is opened to in-itiate a flow of argon from the man:ifold 108 through the headstock 57 and into the tube 120. The flow of argon into the tube is maintained continuously until the tube is sealed and serves to keep it purged of moisture.
Importantly and in keeping with the invention, the cathode assembly 36 is inserted into the ~uartz tube 120 at station No. 11 by being moved tip-last through the chuck 64 of the tailstock 58, through that portion of the tube'that ultimately defines the neck 35 of the lamp 30,,across the arc chamber 33, and finally into that portion of the tube that ultimately def,ines the neck 34 of the lamp. Thus, the cathode assembly 36 is not loaded tip-first through'the headstock'57 and directly into the neck 34 but instead is loaded tip--last into the neck 34 after irst passing through'the tailstock 5~ and the neck 35. As a result of the cathode being loaded in this way, the rotary seal 100 can be located at and can remain attached permanently to the inboard or upstream end ~f the headstock 57 to enable the tube 120 to be flushed continuously with a dry non-reactive gas such as argon until such time as the tube is sealed.
More specifically, the cathode assembly 36 is pre-loaded into a sleeve-type holder 150 (FIG. 14a) which is automatically brought into alignment with the out-board end of the drawbar 71 of the tailstock 58 when th~lathe 55 dwells at station No. 11 (see the position of the cathode shown in phantom lines in FIG. 14~. The holder 150 is oriented such that the tip 42 o~ the cathode is d'sposed in trailin~ relationship to the in-lead 45 thereof.
7 5 ~1 3 AEter the lathe $5 stops at station ~o. 11, a pusher (not shown~ shoves the holder 150 and the pre-loaded cathode assembly 36 through the chuck 64 of the tailstock 58, through the neck 35 and into the neck 34 ~see FIG. 14a). If the tip o~ the cathode be considered the head of the cathode-assembly, the assembly may be said to be shoved feet first throuyh the lamp body~ The stroke of the pusher is controlled so as to locate tlle tip 42 of the cathode at a predetermined distance from the headstock chuck. Because the lamp body has never been released from the headstick ch~lck since the forma-tion of the bulb, the tip of the cathode is thereby auto-matically accurateIy located in the lamp body. Once the cathode assembly has been properly located, the pusher is retracted and withdraws the holder 150 from the cathode and out through the tailstock. During retraction of the hblder, a plunger lSl engages the tip 42 of the cathode -to prevent the latteî from moviny with the holder. After removal of the holder, the cathode assembly is prevent- -ed from sliding and held in a centered position in the neck 34 by virtue of the frictiona:L engagement of the inside diameter of the neck by foi:L portion 48 of the inleadv As pointed out above, argon flows continuously through quartz tube 120 during loading of the cathode assembly. Accordingly, the argon serves to dry any moisture which might be present on the assembly or ~he holder 150 and thus maintains the tube in a "clean"
condition. The flow of argon is continued during in-dexing of the lathe 55 to station No. 12.
At station No. 12, the halide pellets 52 areloaded into the arc chamber 33 (see FIG. 15). This is achieved by insertiny a tubular needle 153 throuyh the tailstock 58 and the neck 35 and by stopping the needle when its tip is near the center of the arc chamber. A
5 ~ 3 - 2~ -downwardly opening port 154 is formed in the needle near the tip thereof while a smal:ler port 155 opens out of the tip. The needle communicates with a low pressure source (not shown) o:f dry inert gas located on the work bench 60 at station No. 12.
A stream of the dry inert gas is flushed at all times through needle 153. After the needle has been positioned in the arc chamber 33, an appropriate number of halide pellets 52 are metered from a storage container (not shown) and are reIeased into the stream of gas. The stream carries the peIlets through the needle until they reach the downwardly opening port 154 and fall into the arc chamber 33. Because the pellets are discharged from the nesdle along a path extending transversely to the stream of purging gas flowing into quartz tube 120 -through the headstock 57, there is little danger o~ the pellets becoming entrained in that stream and being blown into or through the neck 35.
Following release of the halide pellets 52, the needle 153 is withdrawn from the tailstock 58 and then the lathe 55 is indexed to station No. 13 where a globule 51 of mercury is injected into the arc chamber 33 (see FIG. 16). Injection of the mercury is ef~ected in sub stantially the same way as injection of the halide pel lets S2 and .is carried out with a neeal~ 157 which i5 virtually identical to the needle 153. The needle ~57 is inserted into the tailstock 58, the mercury globule 51 is released to the gas stream in the needle and then the nesdle is retrac-ted after the mercury drops into the arc chamber 33. Flushing o~ quartz tube 120 b~ gas introduced through the headstock 57 continues during in-jection of the mercury.
The lathe 55 next is indexed to sta-tion No. 14 for insertion of the anode assembly 37 into the tube 120 (see FIG. 17). The assembly is preloaded into a holder 7 ~ :1 3 159 s:imilar to the holder 150 and is shoved through the tailstock 58 and into the neck 35 by a pusher. Urllike the cathode 36, the anode 37 is pushed tip or head first into the neck 35. The stroke of the pusher (not shown) is controlled so as to accurately locate the tip 44 of the anode relative to the headstock chuck. Since the lamp body is accurat~ly positioned relative to the head-stock chuck and the cathode tip has previously been ~c-curately located, now the length of the gap between cathode and anode tips is precisely determined. Also the gap is accurately positioned at the precise location within the arc chamber 33 called for by the lamp design. Gas con-tinues to flow into quartz tube 120 during insertion of the anode to insure against water vapor reacting with the halide pellets 52.
While the lathe 55 dwells at station No. 15, the tallstock 58 is operated to release quartæ tube 120 and is retracted ~see FIG. 18). A flame 161 then is directed against the unsupported end of the rotating tube~ The heat causes the quartz to collapse and dome over as in-dicated at 162 so as to tip off the tube and ~orm a tem-poraxy seal. ~n operation identical to that perormed at station No. 15 is pexformed by a flame 163 (see FIG.
2) at station No. 16 to insure that tip 162 is truly sealed. Durïng the tipping operation~ at sta-tions Nos.
15 and 16, argon at low pressure li.e. 9 0.1 psig) is ad-mitted into quartz tube 120 through the headstock 57 by way of manifold 109, valve 106 and rotary seal 100. The argon keeps the tube dry but its pressure is of such low magnitude that there is no danger of the gas blow-ing a hole in the newly ormed tip 162~
At station No. 17, a stream of cooled nitrogen is directed at the tip 162 through a nozzle 165 ~see FIG.
2) to cool the tip and allow subsequent re-gripping of the ~uartz tube by tailstock $8. Pressurization of the ~:~fi7513 tube with ].ow pressure argon from the manifold 109 is continued during the cooling step When the lathe 55 reaches sta-tion NoO 18, the quart~
tube 120 is re-gripped by the tailstock 5B and is .rotated by both the headstock and the tailstock (see FIG. 19).
At this station, the cathode inlead assembly 36 is her-metically sealed into the neck 34 by heating the guar-tz and causing it to collapse around the foil portion of the inlead. This may be done ~or example by a laser 167 which traverses along an appropriate length of the neck to cause the quartz to collapse around the cathbde. At the same time the bulb portion 32 of the lamp body is cooled by advancing a metal shroud 168 to partially surround it.
The shroud contains a sponge which engages the bulb and which is kept wet by water supplied by tube 169 while aspirator tube 170 removes excess water.
Just prior to sealing of the neck 34, the valve 106 is closed and the valve 107 is opened to establish communication between the vacuum pump 116 and the tube 120 by way of the manifold 110 and the rotary seal 100.
The vacuum pump draws argon from the manifold 109 into the manifold 110 via the metering valve 114 and reduces the pxessure of the argon in the tube 120 to the sub-atmospheric value of 120 torr absolute. Accordingly, the desired pressure for the starting gas of the lamp 30 is established as an incident to sealing of the neck 34, and the sub-atmospheric pressure assures the de-sired collapse of the guartz around the foil portion of the inlead.
At station No. 19, the neck 35 is seale~ to the anode 37 by a laser 171 similar to the laser 167 ~see FIG. 20) while the bulb is cooled by water cooler 172 similar to that previously descri.bed~ For some lamp si2es, it may be preferable to seal neck 35 ~irst and then neck 34; this sequence permits a closer control 1~7S~ ~
~ 25 --of the argon pressure while making the last seal.
When -the lathe 55 is indexed to station No. 20, a scoring head 173 (~'IG. 211 having a pair of scoring tools 174 is advanced into an operative position adjacent the tube 120. The tools 174 are located to score the end portions of the necks 34 and 35 beyond the sealing regions so that the end portions subsequently may be broken away to expose the inleads 45 and 46.
At station No. 21 ~see FIG. 221, the lamp 30 is removed from the lathe 55. This may be achleved by re-tracting the headstock 58 from the lamp, by gripping the lamp with an automatically operable unloading device 175 and then by retracting the tailstock from the lamp. The empty lathe then may advance to the twelve o'clock posi-tion shown in FIG. 2 to receive another quartz tube andbegin another cycle~
Claims (7)
1. A method of manufacturing a lamp, said method comprising the steps of: providing a lamp body having a hollow bulbous midportion with a pair of tubular neck portions projecting in opposite directions therefrom, inserting a first electrode tip-last completely through one neck portion and into the other neck portion so that said first electrode remains supported solely by said other neck portion, inserting a second electrode tip-first into said one neck portion so that said second electrode remains supported solely by said one neck portion at a predetermined spacing from said first electrode, and then sealing said electrodes into their respective neck portions.
2. The method of claim 1, further including the step of inserting a dose of vaporizable material into said midportion preceding insertion of said second electrode.
3. The method of claim 2, wherein non-reactive dry gas is flushed through said lamp body during said inserting steps.
4. The method of claim 3, for making a lamp without resort to an exhaust tube wherein said dry gas is admitted into said body through said other neck portion and let out through said one neck portion.
5. A method of manufacturing a metal vapor lamp without resort to an exhaust tube, said method comprising the steps of: providing a lamp body having a hollow bulbous midportion with a pair of tubular neck portions projecting in opposite directions therefrom, heating said body while rotating said body about the axis of said neck portions and while flowing inert dry gas into an upstream neck portion and out the downstream neck portion, and continuing the flow of gas while:
(a) inserting a first electrode tip-last completely through said downstream neck portion and said midportion and into said upstream neck portion so that said first electrode remains supported solely by said upstream neck portion, (b) inserting a dose of vaporizable material which is solid or liquid at ambient temperature through said downstream neck portion and into said midportion, and (c) inserting a second electrode tip-first into said downstream neck portion so that said second electrode remains supported solely by said downstream neck portion at a predetermined spacing from said first electrode, the foregoing steps (a), (b) and (c) being performed in a sequence that makes (c) last, and then closing off said downstream neck portion thereby terminating the flow of said gas, cooling said midportion, supplying inert dry gas at subatmospheric pressure to said body, and heat-sealing said electrodes into their respective neck portions.
(a) inserting a first electrode tip-last completely through said downstream neck portion and said midportion and into said upstream neck portion so that said first electrode remains supported solely by said upstream neck portion, (b) inserting a dose of vaporizable material which is solid or liquid at ambient temperature through said downstream neck portion and into said midportion, and (c) inserting a second electrode tip-first into said downstream neck portion so that said second electrode remains supported solely by said downstream neck portion at a predetermined spacing from said first electrode, the foregoing steps (a), (b) and (c) being performed in a sequence that makes (c) last, and then closing off said downstream neck portion thereby terminating the flow of said gas, cooling said midportion, supplying inert dry gas at subatmospheric pressure to said body, and heat-sealing said electrodes into their respective neck portions.
6. The method of claim 5, performed with equip-ment which supports said lamp body horizontally so that when said dose inserted into said midportion is released thereinto, said dose falls along a path which is transverse to the flow of said gas.
7. The method of claim 6, wherein said lamp is a metal halide lamp, and said dose comprises metal halide and mercury.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000352167A CA1167513A (en) | 1980-05-16 | 1980-05-16 | Method of manufacturing a lamp |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000352167A CA1167513A (en) | 1980-05-16 | 1980-05-16 | Method of manufacturing a lamp |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1167513A true CA1167513A (en) | 1984-05-15 |
Family
ID=4116980
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000352167A Expired CA1167513A (en) | 1980-05-16 | 1980-05-16 | Method of manufacturing a lamp |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1167513A (en) |
-
1980
- 1980-05-16 CA CA000352167A patent/CA1167513A/en not_active Expired
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