Note: Descriptions are shown in the official language in which they were submitted.
5 1 3
~ 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
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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
LD 7630
-- 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
LD 7630
~ _ ,
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
LD 7630
-- 5 --
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
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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~
- 8 - LD 7630
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
LD 7630
_ 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 ~ ~
LD 7630
~ 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
LD 7630
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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
LD 7630
- 12 -
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 ~
LD 7630
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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
LD 7630
- 14 -
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
- 15 -
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
LD 7630
- 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
LD 7630
- 17 -
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 ~
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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
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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
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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.
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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
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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
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- 23 -
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
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24 -
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~ ~
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~ 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~
