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Патент USA US3069591

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Dec. 18, 1962
E. LEMMERS
3,069,581
LOW PRESSURE DISCl-iARGE LAMP
Filed Feb. 9, 1961
<1. .,
Invenetor:
Eugene Le mew-s
b9
é
.
His A‘T‘TOT'HGS
ilnit
i
3,6@,58l
Patented Dec. 18, 1952
1
2
LGW PRESSURE DEQHARGE LAMP
3,969,531
Eugene Lemrncrs, Cleveland Heights, Ohio, assignor to
as fluorescent lamps having higher ef?ciencies than here
tofore achieved.
A more speci?c object of the invention is to provide
General Electric Company, a corporation of New Yorlr
improved ?uorescent lamps operating at substantially the
Filed Feb. 9, 1961, Ser. No. 88,228
10 Claims. (Cl. 313—185)
same ratings and under substantially the same conditions
as the common sizes of ?uorescent lamps which have
This invention relates to low pressure electric discharge
lamps such as ?uorescent lamps comprising a pair of
thermionic electrodes sealed into opposite ends of an
elongated tube containing mercury vapor and an inert
gas for the ionizable medium. The present application
is a continuation-in-part of my copending application
Serial No. 812,235, ?led May 11, 1959, of the same title
and assignee and now abandoned.
15
In the ?uorescent lamp, the electric discharge through
a mixture of mercury vapor at a few microns pressure
and an inert gas or mixture of inert gases at a few milli
been commercially available but having higher overall
e?iciency and producing greater lumen output for the
same wattage input.
Another object of the invention is to provide improved
shielded electrode structures suitable for use in high ef
?ciency lamps according to the invention.
In accordance with the invention, I have discovered
that shields or anode plates about the thermionic elec
trodes in a low pressure discharge lamp such as a flu
orescent lamp may be correlated in design to the ?lamen
tary electrodes and particularly to the thermal inertia and
operating temperature thereof so as to achieve the de
meters pressure produces ultraviolet radiation principally
sired shielding eltect and prevention of end darkening of
at 2537 A. The ultraviolet radiation is converted by the 20 the lamp without any acceleration of damage to the
phosphor coated internally on the walls of the envelope
electrode.
into visible light which is transmitted through the glass
Preferably lamps in accordance with the invention
walls. The source of ultraviolet radiation resides in
use an inert starting gas (including mixtures of starting
the excited mercury atoms and there is an optimum
gases) at a lower ?lling pressure than has heretofore
mercury vapor pressure, usually about six microns, at 25 been commonly used and which, in the absence of suit
which the ef?ciency of conversion of electrical energy
able counter measures, would ordinarily result in short
into ultraviolet energy is a maximum. The inert start
ened cathode life resulting in greater end darkening and
ing gas, which in the past has most commonly been argon
poorer maintainance of lumen output. However in ac
at a pressure generally not less than approximately 3
cordance with the invention, such greater end darkening
millimeters, is necessary principally at starting. The 30 or poorer maintenance of lumen output is substantially
starting gas lowers the voltage required to initiate the
prevented through the use of shields about the ?lamentary
arc discharge between the electrodes and also serves to
electrodes to which are correlated the electrode thermal
protect the electrodes from destructive ion bombardment
inertia and normal operating temperature to prevent
during the starting interval.
damage to the electrodes.
It has been appreciated for a long time that it is pos
Ordinarily putting shields about a cathode as has been
sible to increase the luminous e?‘lciency, that is the ratio
done in the past (in the absence of a polarized structure
of luments output to watts input, in conventional ?uores~
where the anode shield current is caused to pass through
cent lamps such as the common 40-watt size by lower
the ?lament) causes damage to the cathode by several
ing the pressure of the inert starting gas. However, ?u
mechanisms. Usually the shields have been placed close
orescent lamps having argon gas ?lling at pressures below 40 to the cathode in order to trap sputtered and evaporated
approximately three millimeters yield progressively short
material more effectively and the general practice has
er life, greater end darkening and poorer maintenance of
been to place them so close as to produce substantial ion
lumen output as the pressure is reduced. These effects
trapping. Such ion trapping is of course equivalent to
are caused principally by more destructive positive ion
increase-d wall losses and alters the degree of ionization
bombardment of the cathodes especially at starting. In
in the sheath about the cathode. The cathode automati
the rapid-start type of lamp where the electrodes are
cally makes up this loss by adjusting to a higher cathode
heated by circulating current therethrough, cathode life
fall whereby to increase the degree of ionization. A
can readily be brought back to normal by increasing
higher cathode fall results in greater ion bombardment
the cathode area and raising the electrode temperature
with resulting shorter life. In addition, if the shield is
to a higher value whereby to achieve increased thermionic
connected to the electrode inleads as it normally is, it will
emission, in accord with the teachings of Hull Patent
carry a substantial proportion of the anode current dur
1,790,153. The drawback which has up to now defeated
such a scheme for improving the e?iciency of the ?u
orescent lamp has been that the increase in cathode heat
ing watts required to maintain cathode life augments the '
overall losses to the point where the gains in e?iciency
achieved by lowering the argon gas pressure are sub
stantially completely o?set.
ing the anode half-cycle, the proportion depending upon
the area of the shield and its position relative to the cath
ode. Current carried by the shield during the anode half
cycle is of course current which must be subtracted from
what the cathode would otherwise be carrying, with the
result that the reduced current flow through the ?lamen
tary cathode causes a reduction in cathode temperature.
The severe end darkening associated with lowered
Reduced cathode temperature normally entails a reduc
?lling gas pressure can be prevented by the use of shields
tion in electron emission and again the cathode must
about the cathodes which trap the sputtered or vaporized
make up therefor by readjusting to a higher cathode fall
electrode material before it can reach the phosphor on
in order to increase the electrode emission to the degree
the bulb wall. However it is now generally accepted
necessary to support the discharge current.
that shields, at least as used in the past, effectively shorten
In accordance with the invention, these drawbacks to
65
lamp life. This may be rather surprising in view of the
the addition of a shield are circumvented by reducing
fact that the principal purpose of the shield has been
the size or thermal mass of the cathode so as to achieve
to prevent end darkening. However I have determined
the optimum temperature despite the presence of the
that shields as ordinarily used to reduce end darkening
shields and their tendency to rob ions from the sheath
actually shortened the life of the cathode; in other words,
and to subtract current from the cathode. I have discov
the shields while hiding the damage have accelerated it.
The principal object of the invention is to provide new
and improved low pressure electric discharge lamp such
ered that by using a smaller ?lamentary cathode designed
to operate in the usual manner without shields at 50%
to 75%, and preferably at 50 to 62.5% of the normal
3,069,581
3
discharge current, proper operating conditions can be
4
of neon, for instance from 25 to 40% neon. This permits‘v
raising the wattage input into the lamp without exceeding:
remtablished at normal current, that is at 100% current,
with the use of shields. In effect, for the preferred range,
its normal current rating, Alternatively, the envelope;
the cathode is designed as regards resistance and thermal
cross section may be reduced, for instance by reducing the
diameter of the circular section envelope from a nominal
mass including its disposition to lose heat by radiation
diameter of 1%. to 1% inches. In addition the preferred
and otherwise, to achieve an emission spot temperature
lamp construction makes use of improved phosphors
in the range of 1050 to 1200° C. while providing 100%
which have been treated to reduce the rate of depreciation,
of the electron emission on the cathode half cycle and
such treatment being particularly desirable in view of the
only 0 to 25% of the electron collection on the anode
half cycle. The balance of electron collection on the 10 higher rate of ?ow of ions to the wall in the instant lamp
with resulting tendency towards more rapid depreciation
anode half cycle is made up for the most part by the
of the phosphor.
shields with possibly a minor fraction by the inleads.
The invention itself, together with further objects and
The shields or anode plates are spaced far enough away
advantages thereof, may best be understood with reference
from the cathode, a minimum of approximately 3 milli
meters, that ion trapping has a negligible effect on cath 15 to the following description, taken in conjunction with the
accompanying drawing. The novel features believed to be
ode fall.
In the usual rapid start lamp, the lamp starting voltage
characteristic of the invention are set forth in the a -
pended claims.
which sustains the discharge current is applied at the
in the drawings:
same time as the lamp ?lament voltage which produces
PEG. 1 is a partially cutaway perspective view of a
the current circulating through the ?laments to heat them. 20
One result of this situation is that a demand is set up
fluorescent lamp representative of the invention.
for electrons from the cathode immediately and before
it has reached a temperature where a copious supply
the lamp in side elevation.
can be emitted.
As a result, the discharge which nor
FIG. 2 illustrates the mount and electrode structure of
FIG. 3 illustrates the same mount and electrode struc~~
mally occurs at starting and which is frequently referred 25 ture in end view.
FIGS. 4 and 6 illustrate successive stages in making the
to as a glow discharge occurs with a high cathode fall,
cathode ?lament.
I
for instance as high as 100 volts and this heats the oath
Referring to FIG. 1, the low pressure discharge lamp 1
ode and quickly raises its temperature to the necessary
embodying the invention may correspond, in regards to its"
electron emitting level. However the high cathode fall
at starting also causes positive ion bombardment and 30 size and general con?guration, to the ordinary 40-watt
rapid start ?uorescent lamp of 48" nominal length and
sputtering of the conductors including the lead-in Wires
11/2” nominal diameter The lamp comprises an elon
and shields about the cathode. The material thus sput
gated cylindrical envelope 2 having shouldered ends to
tered or vaporized deposits on the cathode and reduces
which are secured bases 3 each provided with a pair of
its electron emissivity, in effect poisoning the cathode.
Existing rapid start lamps have been so designed that 35 insulated contact terminals or pins 4, 5. As shown at the
end of the lamp where a fragment of the envelope Wall
the damage due to this high cathode fall or glow current
has ‘been broken out, electrode mount 6 comprises a rela
at starting is insu?icient to cause less than published or
tively short stem tube 7 having its ?ared outer end 8
rated life. However when shields of large area are at
sealed peripherally into the shouldered tube end and hav
tached to the cathode mount structure they may take a
portion of the glow current at starting by emitting elec 40 ing a press @ at its inner end through which are sealed
current inlead wires 11, 12. The inward projections of
trons and thus reduce the proportion emitted by the oath
the inlead wires support the ?lamentary cathode 13 where
ode. This tends to increase the time taken by the cathode
as the outward projections are connected to the terminal
to come up to the necessary emitting temperature. This
pins 4, 5'. In addition the transverse extensions of the
phenomenon of course entails more sputtered material
produced to poison the cathodes. Thus shields of large 45 inleads support the cathode shields 14, 15. The other end
of the lamp is provided with a similar cathode and one of
area which can operate as anodes further tend to reduce
the stem flares is provided with an exhaust tube which is
cathode life due to the phenomena occurring at starting.
sealed or tipped off in the usual fashion.
In accordance with yet another feature of the invention,
The lamp contains a quantity of mercury indicated by’
these drawbacks are prevented by making the thermal
inertia of the cathode such that even with large area 50 droplet 16 exceeding in amount the quantity vaporized
during operation of the lamp. The lamp contains in ad
shields connected to the mount structure, the combined
dition a ?lling of an inert starting gas, for instance argon
effects of cathode heating resulting from ?lament heat
ing voltage, that is, from ballast cathode voltage and glow
and neon in a proportion and at a total pressure to be
current, will bring the ?lament to full emission tempera
more particularly speci?ed hereinafter. A phosphor coat
ing indicated at 17 on the inside of the envelope wall
converts the resonance radiation of the discharge through
the mercury vapor into visible light. The lamp may be
coated externally with a water repellent substance to facili~
tate starting under adverse atmospheric conditions as
ture at least as quickly as in the standard lamp. Prefer
ably the ?lament is brought up and stabilized at a tem
perature in the range of 850 to 1050° C. in a time interval
less than 1 second after the application of ?lament heat
ing voltage. Thus loss of life due to the conditions at
starting is substantially avoided and cathode life again 60 when the humidity is high.
restored to normal.
Another feature of the invention is the use of shields
or anode plates of relatively large area and consisting
of a metal such as nickel preferably, or tantalum, tung
The shields 14, 15 are eifective in reducing and substan
tially preventing the end darkening associated with low
ered inert starting gas pressure. They do this by trapping:
the vaporized or sputtered darkening material before it.
sten or molybdenum having the characteristic of forming 65 can reach the phosphor on the bulb wall. Each shield
comprises a main portion 18 which is disposed generally'
a suitable base member for a barium oxide cathode.
parallel to the ?lament i3 and transversely to the longiNickel or nickel plated iron is preferred for effectiveness
tudinal axis of the lamp, and an auxiliary portion 19 which
and low cost. This permits a lower anode voltage drop
extends approximately at right angles. This shield con-i
during the anode half-cycle and thereby raises the elli
ciency.
70 ?guration serves to more or less box in the cathode where‘
by to trap the darkening material more effectively. The
In a preferred lamp construction embodying the inven
shields are located about at the boundary of the cathode
tion, the foregoing features of the invention are combined
glow and in any case at a distance greater than approxi
with a lower inert starting gas ?lling pressure, for in
mately 3 millimeters from the emitting surface of the
stance in the range of l to 2 millimeters, and the starting
cathode. For example, in a preferred construction suit;
gas consists of a mixture of argon with a minor proportion
3,069,581
5
6
able for a 40-watt ?uorescent lamp, the distance d is 5 to 7
current on the anode half-cycle so that the cathode sup
millimeters. With this spacing, the ion trapping effect of
ports, on a full cycle average, 56 to 59% of the total dis
the shields has negligible effect on the cathode fall.
charge current.
The usual procedures are followed in making a lamp
using the cathodes of the present invention. Previous to
mounting the lamp envelope, the cathode mounts are
processed to coat the ?lamentary cathodes with activating
material such as barium, strontium, and calcium carbon~
As previously mentioned, the tendency'of the shields to
reduce the operating temperature of the cathode by sub
tracting from it a substantial portion of the discharge cur
rent during the anode half-cycle, is o?set by using a
smaller cathode which heats up more quickly and which
will be maintained at the required electron emitting tem
ates or mixtures thereof. The mounts are then sealed to
perature, for instance in the range of approximately 900 10 the ends of the glass envelope and the electrodes are ac~
to 1000° C., under the conditions encountered. I have
tivated during lamp manufacture by passing a heating
found that in general a cathode which is designed to op
current through them to reduce the carbonates to oxides.
erate in the usual manner, without shields, at a current
which is 50 to 62.5% of the normal lamp current, will
operate in the desired fashion at normal current with
shields.
The shields are preferably made of a metal which forms
a good base member for activation by barium or barium
oxide. Suitable metals are tungsten, molybdenum and
As an example of a cathode in accordance with the
invention suitable for a 40-watt ?uorescent lamp and uti
nickel; nickel-plated iron is satisfactory and is preferred
because it is cheapest. The shields of nickel-plated iron
become so—to—speak “activated” during operation, and this
lizing an overwind in accordance with the teachings of
reduces the anode fall and permits an increase of 3 to 5%
US. Fatent 2,306,925, Aicher, the following construction 20 in lamp e?iciency. The “activation” of the shields comes
may be used. Referring to KG. 4, the ?rst coiling pro
vides the overwind convolutions consisting of 0.4 mil tung
about as a result of the deposition thereon of evaporated
sten wire 21 wrapped at 290 turns per inch around a com
iZed from the cathodes. A surface which is a good elec
emission material, principally barium, sputtered or vapor
posite mandrel formed by a 1.9 mil tungsten Wire 22 and
tron emitter is also a good electron collector and as a re
a 1.5 mil molybdenum wire 23 laid alongside each other 25 sult when the shields operate as anodes during the anode
to provide a composite wire 24-. In the second coiling
half-cycle, the anode voltage drop and of course the lamp
illustrated in PEG. 5, the product 24 of the ?rst coiling is
voltage is decreased by several volts. If desired, the
wrapped at 13% turns per inch around a mandrel consist
shields may be made of screening or else of perforated
ing of a 3.5 mil molybdenum wire 25 to provide a com
‘strip in order to reduce trapping of 2537 A. radiation
posite wire 2-5. In the illustration of FIG. 5, molybdenum 30 originating from the cathode glow. The shield plates need
mandrel wire 23 has been omitted for the sake of clarity;
not necessarily be L-shaped as described and illustrated;
also in FIG. 6, both molybdenum wires 23 and 25 are
another convenient form consists in C~shaped shield seg
omitted for the same reason. In third coiling illustrated
ments whereby the shield encircles the ?lament in a circud
in FIG. 6, the product as of the second coiling is Wrapped
lar or ring-like con?guration.
around a mandrel
ccnsistirn7 of a 13.5 mil steel pin, the 35
With the shields placed in the preferred position about
cathode coil being thereafter removed from it by slipping
the cathodes, namely the outer fringes of the expanded
it off. The cathode coil or ?lament 13 may consist of ap
cathode glow, and with the inert ?lling gas pressure low
ered into the range of l to 2 millimeters, a 48" long 11/2"
extensions or legs which are clamped between the folded
diameter lamp is found to consume only about 37 watts in
inner ends of the inlead wires 11, 12. Previous to clamp 40 order to produce the same lumens output as the standard
ing between the inlead wires, the cathode convolutions
40-watt lamp while at the same time realizing an efficiency
are set by suitable heat treatment and the molybdenum
approximately 8% higher.
mandrel wires 23 and 25’ are removed by dissolving in
In the foregoing lamp which requires an input of 37
acid. Thus the ?lament 13 is a hollow or skeletal structure
watts only to produce the same lumens output as the prior
consisting of the triple-coiled overwind wire 21 ?tting
art 40-watt lamps, the wattage input may be restored to
loosely around the turns of the double-coiled mandrel wire
the 40-watt level and the total lumen output raised pro~
22. This particular ?lament is merely an example of a
portionately by decreasing the bulb diameter or by chang
proximately 18 turns of the ?nal coiling with straight
cathode meeting the requirements of the invention in
ing the inert starting gas composition. The latter may be
regards to correlation with shield design so that the cath
done in accordance with the teachings of copending appli
ode carries 50 to 62.5% of the total discharge current. 50 cation Serial No. 812,236, ?led May 11, 1959, of Kurt
Other cathode structures may readily be proportioned to
Schmidt, entitled Fluorescent Lamp Gas Filling, and as
the sarae criteria. including if desired simpler cathode
signed to the same assignee as the present invention. In
structures not using an overwind or triple coiling and using
accordance therewith, at relatively low loadings in the
for instance only double coiling.
range of 5 to 15 watts per foot, an increase in e?iciency
The shield structure comprises a pair of thin nickel 55 may be achieved by replacing up to approximately 50%
strips 14, 15, each having a width W of approximately 8
of the usual argon ?lling gas by neon in the pressure range
mm. and a total length L of approximately 21 mm. The
from 1.5 to 3 millimeters. At a pressure of approximate
short leg 1? of each stril welded to the inlead is approxi
ly 2 millimeters, the preferred proportions of neon is in
mately 6 mm. long. and the long leg 18 approximately 15
the range from 25 to 40%, the latter being preferred
mm. long. The long legs are preferably positioned par 60 where the emphasis is on maximum output, and the former
allel to the ?lament as illustrated in FIG. 3. The distance
being preferred where the emphasis is on maximum life.
D between strips is approximately 15 mm. and the overt'll
This allows an improvement in efficiency of approximately
shield structure surrounds the ?lament in a plane trans
2% over the maximum ef?ciency which may be achieved
verse to the longitudinal axis of the lamp and is generally
with pure argon at the same total pressure. For the in
box-like around the ?lament. The distance d from the 65 stant 40-watt lamp, the preferred ?lling gas mixture con
emitting surface of the ?lament to the shield strip is ap—
sists of 65% argon and 35% neon at a total pressure of
proximately 6 millimeters, a distance substantially greater
approximately 2 millimeters of mercury.
than the minimum of 3 millimeters required to reduce
It is known that reducing the ?lling pressure of the
ion trapping to the point where it has negligible e?ect on
inert starting gas or using a starting gas of low atomic
cathode fall. The total inside surface of the shield mem 70 weight such as neon in lieu of part of the argon, entails
bers 14, 15 surrounding the cathode is approximately 1/2
in.2 or 3.3 cm.2. However this is not critical and may be
varied within the principles stated, and in particular may
be inc eased substantially. With the given dimensions,
a greater rate of depreciation of the phosphor coating.
The foregoing measure increases the rate of flow of ions
to the wall which appears to be responsible for a reaction
‘occurring between the constituents of the bulb glass and
the cathode or ?lament carries from 12 to 18% of the 75 the phosphor. Among the end products of this reaction
3,069,581
8
are a phosphor surface which is mercurophilic, that is
wires sealed through said envelope, said ?lament being
one to which mercury is more attracted and becomes
proportioned in resistance and thermal mass to achieve
an electron emission spot temperature in the range of
1050 to 1200" C. with 100% emission of d.'s:harge cur
rent on the cathode half cycle and 0 to 25% eclectic-n
on the anode half cycle, and conductive shields fastened
more readily attached. The attachment of mercury to
the phosphor surface causes a reduction in lumen output
because the mercury layer is opaque to both the exciting
ultraviolet radiation and to the emitted visible light. To
reduce this deleterious effect as much as possible in the
instant lamp, the phosphor may be treated to remove the
surface metallic ions such as antimony, manganese, etc.
Also the envelope wall may be treated to remove alkali
materials therefrom whereby to make it a better insulator
and also to leave less material for reaction with the phos
to said inleads encompassing the cathode glow region
of said electrode and collecting substantially the balance
of discharge current.
2. A low pressure electric discharge lamp comprising
a vitreous envelope de?ning an elongated discharge chan
nel having a pair of electrode structures at opposite ends
cury. Another procedure which may be used is to apply
a potential to the bulb wall with such polarity that all
and containing an ionizable medium comprising mercury
vapor and an inert starting gas, each electrode structure
comprising a coiled tungsten ?lament coated with acti
the electro-positives such as sodium are moved to the
outer surface.
vating material and supported at opposite ends by inlead
wires sealed through said envelope, said ?lament being
phor surface or to serve as attachment points for mer
Comparative tests of the foregoing improved 40-watt
proportioned in resistance and thermal mass to achieve
lamp in accordance with the invention and of regular
an electron emission spot temperature in the range of
production 40-w‘att rapid start ?uorescent lamps produced 20 1050 to 1200“ C. with 100% emission on the cathode
half cycle and 0 to 25% collection on the anode half
the following results. The cathode (?lament) tem
perature of the regular lamp at nominal cathode heating
cycle, and conductive shields fastened to said inleads
generally surrounding said ?lament and encompassing
voltage (3.65 volts) stabilized at approximately 930° C.
its cathode glow region, said conductive shields con
in 1.6 seconds after inital application of voltage, and the
sisting of metal subject to activation by deposition there
temperature of the emission spot on the cathode with
on of activating material from said ?lament and being
normal discharge current (430 milliamperes) was ap
proximately 1130“ C. In the improved lamp using the
substantial in surface area whereby to collect substan
tially the balance of discharge current on the anode half
rapid heating ‘lament and the shields and a ?lling of
cycle with a low anode voltage drop.
65% argon and- 35% neon at a total pressure of 2 milli
3. A low pressure electric discharge lamp comprising
meters of mercury, the cathode (?lament) temperature 30
a vitreous envelope de?ning an elongated discharge chan
stabilized at approximately 985° C. in 0.6 second after
nel having a pair of electrode structures at opposite ends
initial application of voltage, and the temperature of
and containing an ionizable medium comprising mercury
the emission spot with normal discharge current was
approximately 1125" C.
The foregoing temperatures
vapor and an inert starting gas, each electrode structure
were measured with an optical pyrorneter focused on the 35 comprising a coiled tungsten ?lament coated with activat
ing material and supported at opposite ends by inlead
wires sealed through said envelope, said ?lament being
oxide coated surface of the electrode and include no
correction for departure from black body radiation.
Thus the improved lamp stabilizes as to cathode tempera
proportioned in resistance and thermal mass to stabilize
at a temperature in the range of 850 to 1050° C. in a
ture in one half to one third the time and has substan
tially the same emission spot temperature despite the 40 time interval less than 1 second after the application of
large area shields which operate as anodes. By compari
?lament heating voltage and to achieve in operation an
son, When the shields are merely added about the cathodes
electron emission spot temperature in ‘the range of 1050
of the regular lamp, the emission spot temperature drops
from 1130° C. to 970° C., a value too low for satis
factory life and maintenance.
The improved 40-watt lamp in accordance with the in
vention realizes an improvement in ef?ciency of 8%
over prior lamps, and for the ?rst time makes possible
an output in excess of the 3000 lumens level for an in
put of 40 watts.
By using in this lamp more e?icient
phosphors of controlled particle size for maximum bright
ness, an output of 3100 lumens at an e?iciency of 77.5
lumens per watt is achieved. Such high ef?ciency has
6:0
to 1200° C. with 100% emission of discharge current on
the cathode half cycle and 0 to 25% collection on the
anode half cycle, and conductive shields fastened to said
inleads encompassing the cathode glow region of said
electrode and collecting substantially the balance of dis
charge current.
4. A low pressure electric discharge lamp comprising
a vitreous envelope de?ning an elongated discharge chan
nel having ‘a pair of electrode structures at opposite ends
and containing an ionizable medium comprising mercury
never belore now been rcaiized in a 40-watt lamp.
vapor and an inert starting gas, each electrode structure
comprising a coiled tungsten ?lament coated with activat
While a certain speci?c embodiment of the invention
has been illustrated and described in detail, various modi
ing material and supported at opposite ends by inlead
wires sealed through said envelope, said ?lament being
?cations will readily occur to those skilled in the art
proportioned in resistance and thermal mass to stabilize
inasmuch as‘ the underlying principles may readily be
at a temperature in the range of 850 to 1050° C. in a
applied to different sizes of lamps. The elongated dis
time interval less than 1 second after the application of
charge channel may be otherwise than straight and tubu 60 ?lament heating voltage ;and to achieve in operation an
lar; for instance a channel of re-entrant cross-section
may be used, or a curved channel as in circline lamps,
or a sinuous channel as in labyrinthine panel lamps.
The appended claims are therefore intended to cover
electron emission spot temperature in the range of 1050
to 1200‘ C. with 100% emission on the cathode half
cycle and 0 to 25% collection on the anode half cycle,
and conductive shields fastened to said inleads generally
any such modi?cations coming Within the true spirit and
surrounding said ?lament and encompassing its cathode
glow region, said conductive shields consisting of metal
subject to activation by deposition thereon of activating
material from said ?lament and collecting substantially
scrpe of the invention.
What I claim as new and desire to secure by Letters
Patent of the United States is:
1. A low pressure electric discharge lamp comprising
a vitreous envelope de?ning an elongated discharge chan
nel having a pair of electrode structures at opposite ends
and containing an ionizable medium comprising mercury
the balance of discharge current on the anode half cycle.
5. A low pressure electric discharge lamp comprising
vapor and an inert starting gas, each electrode structure
a vitreous envelope de?ning an elongated discharge chan
nel having a pair of electrode structures at opposite ends
and containing an ionizable medium comprising mercury
comprising a coiled tungsten ?lament coated with activat
vapor ‘and an inert starting gas, each electrode structure
ing material and supported at opposite ends by inlead
comprising a coiled tungsten ?lament coated with activat
8,0 easm
9
10
ing material and supported at opposite ends by inlead
wires sealed through said envelope, said ?lament being
gas consisting of a mixture of argon and not over 50%
neon at a total pressure less than 3 millimeters of mercury,
each electrode structure comprising a coiled tungsten ?la
proportioned in resistance and thermal mass to stabilize
at a temperature in the range of 850 to 1050° C. in a
time interval less than 1 second after the application of
?lament heating voltage and to achieve in operation an
electron emission spot temperature in the range of 1050
to 1200° C. with 100% emission on the cathode half cycle
ment coated with activating material and supported at op
posite ends by inlead wires sealed through said envelope,
said ?lament being proportioned in resistance and thermal
mass to stabilize at a temperature in the range of 850 to
1050° C. in a time interval less than 1 second after the
application of ?lament heating voltage and to achieve an
and 0 to 25% collection on the anode half cycle, and a
pair of conductive shields fastened to said inleads gen 10 electron emission spot temperature in the range of 1050
to 1200° C. with 100% emission of discharge current on
erally surrounding said ?lament and located at a distance
the cathode half cycle and 0 to 25% collection on the
from the emission spot surface of said ?lament not less
anode half cycle, and conductive shields fastened to said
than approximately 3 millimeters and disposed at about
inleads encompassing the cathode glow region of said
the limits of the cathode glow region, said conductive
shields being substantial in surface area and consisting 15 electrode and collecting substantially the balance of dis
charge current.
of metal subject to activation by deposition thereon of
9. A low pressure electric discharge lamp comprising
activating material from said ?lament whereby to collect
an elongated vitreous envelope having a pair of electrode
substantially the balance of discharge current on the
structures at opposite ends and containing an ionizable
anode half cycle with a low anode voltage drop.
medium comprising mercury vapor and an inert starting
6. A low pressure electric discharge lamp comprising
gas consisting of a mixture of argon with appoximately
a vitreous envelope de?ning an elongated discharge chan
25 to 40% neon at a total pressure of approximately 2
nel having a pair of electrode structures at opposite ends
millimeters of mercury, each electrode structure com
and containing an ionizable medium comprising mercury
prising a coiled tungsten ?lament coated With activating
vapor and an inert starting gas, each electrode structure
comprising a multiple coiled tungsten ?lament coated 25 material and supported at opposite ends by inlead wires
sealed through said envelope, said ?lament being propor
with alkaline earth oxide activating material and sup
tioned in resistance and thermal mass to stabilize at a
ported at opposite ends by inlead wires sealed through
temperature in the range of 850 to 1050° C. in a time
said envelope, said ?lament being proportioned in re
interval less than 1 second after the application of ?lament
sistance and thermal mass to stabilize at a temperature
in the range of 850 to 1050° C. in a time interval less 30 heating voltage and to achieve an electron emission spot
temperature in the range of 1050 to 1200° C. with 100%
than 1 second after the application of ?lament heating
emission of discharge current on the cathode half cycle
voltage and to achieve under operating conditions an
and 0 to 25% collection on the anode half cycle, and con
emission spot temperature in the range of 1050 to 1200°
ductive shields fastened to said inleads encompassing the
C. with 100% emission on the cathode half cycle and 0
to 25 % collection on the anode half cycle, and a pair of 35 cathode glow region of said electrode and collecting sub
stantially the balance of discharge current.
conductive shields fastened to said inleads generally sur
10. A low pressure ?uorescent lamp comprising an
rounding said ?lament in a plane transverse to the lon
elongated vitreous envelope coated internally with a
gitudinal axis of said channel thereat and located at a
phosphor and having a pair of electrode structures at op
distance from the center of said ?lament not less than
approximately 3 millimeters and disposed at about the 40 posite ends and containing an ionizable medium compris
ing mercury vapor and an inert starting gas consisting of
limits of the cathode glow region, said conductive shields
a mixture of argon and 25 to 40% neon at a total pres
being substantial in surface area and consisting of metal
sure of approximately 2 millimeters of mercury, each
subject to activation by deposition thereon of activating
electrode structure comprising a multiple coiled tungsten
material from said ?lament whereby to collect substan
tially the balance of discharge current on the anode half 45 ?lament coated with alkaline earth oxide activating ma
terial and supported at opposite ends by inlead wires
cycle with a low anode voltage drop.
sealed through said envelope, said ?lament being propor
7. A low pressure electric discharge lamp comprising
tioned in resistance and thermal mass to stabilize at a
an elongated vitreous envelope having a pair of electrode
temperature in the range of 850 to 1050° C. in a time
structures at opposite ends and containing gas consisting
of an ionizable medium comprising mercury vapor and 50 interval less than 1 second after the applicationof ?la
ment heating voltage and to achieve in operation an elec
an inert starting mixture of argon and not over 50%
tron emission spot temperature in the range of 1050 to
neon at a total pressure less than 3 millimeters of mer
cury, each electrode structure comprising a coiled tungsten
1200° C. with 100% emission of discharge current on the
cathode half cycle and 0 to 25% collection on the anode
?lament coated with activating material and supported
at opposite ends by inlead wires sealed through said 55 half cycle, and a pair of conductive shields fastened to
said inlead generally surrounding said ?lament in a plane
envelope, said ?lament being proportioned in resistance
transverse to the longitudinal axis of said envelope and
and thermal mass to achieve an electron emission spot
located at a distance from the center of said ?lament not
temperature in the range of 1050 to 1200° C. with 100%
less than approximately 3 millimeters and disposed at
emission of discharge current on the cathode half cycle
and 0 to 25% collection on the anode half cycle, and
conductive shields fastened to said inleads encompassing
the cathode glow region of said electrode and collecting
about the limits of the cathode glow region, said con
ductive shields being substantial in surface area and hav
ing a nickel surface subject to activation by deposition
thereon of activating material from said ?lament whereby
substantially the balance of discharge current.
to collect substantially the balance of discharge current
8. A low pressure electric discharge lamp comprising
an elongated vitreous envelope having a pair of electrode 65 on the anode half cycle with a low anode voltage drop.
structures at opposite ends and containing and ionizable
No references cited7
medium comprising mercury vapor and an inert starting
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