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Патент USA US2135702

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Nov, 8, 1938.
Filed 001:. 15, 1937
Willem. E‘enb
5. Jul“
Patented Nov. 8, 1938
Willem Elenbaas, Eindhoven, Netherlands, as
signor to General Electric Company, a corpo
ration of New York
‘ Application October 15, 1937, Serial No. 169,162
In Germany November 10, 1936
3 Claims.
The present invention relates to electric gaseous
discharge devices generally, and in particular to
(Cl. 176-124)
of 2 to 5 mm. A great advantage of these lamps
devices operating with a relatively high vapor
lies in the fact that they have a favorable efli
ciency even in the smaller sizes, of for instance 40
and 75-watt consumption.
A particular object of the invention is to pro
vide an electric gaseous discharge device of high
luminous e?iciency. A further object of the in
vention is to provide a lamp of long useful life.
Still other objects and advantages of the inven
10 tion will appear from the following detailed speci
Between these two lamps there is a vast ?eld Cl
which has previously been unexplored, in which
an almost unlimited number of combinations of
dimensions, pressures, and other characteristics
of the lamps is possible. I have found, how
ever, that the e?iciency as Well as the life of 1 )
?cation or from an inspection of the accompany
.these lamps is dependent upon the particular
ing drawing.
relationship of these various characteristics. The
The invention consists in the new and novel present invention is directed to the production of
structure hereinafter set forth and claimed.
lamps within this range having the highest at
Among the illuminating devices of recent years, tainable ei?ciency and a long useful life.
the high-pressure mercury-vapor discharge tubes
In the design of any of these lamps two fac
are of great importance. The modern lamps of tors are usually ?xed at the start. Thus the
this type commonly have a cylindrical discharge wattage consumption of the lamp is a matter
bulb containing a small quantity of mercury. of arbitrary choice, and the voltage drop with
20 These bulbs are provided with solid thermionic in the burner is a substantially ?xed fraction, of 20
electrodes which are generally covered with mate
rials of a high electron emissivity (especially
earth alkali metal oxides). In order to facilitate
ignition, a quantity of rare gas is also ordinarily
25 placed in this bulb. The actual discharge bulb
is generally surrounded by a glass cover, while
the space between the discharge bulb and. the
cover is evacuated, or is ?lled with a gas (for
instance, nitrogen, rare gas, or air).
The discharge of these lamps has the character
of a high-pressure discharge. In other words, the
discharge is constricted as a result of the high
vapor pressure that is developed, so that it does
not ?ll the entire cross-section of the discharge
35 bulb. At the same time, the burning voltage of
the. order of a half or two-thirds. of the voltage
of the line on which it is intended to operate the
lamp. With these two factors settled, however,
there is still a vast number of combinations of
length. diameter and operating pressure that will
meet the predetermined conditions, but not with
the same e?iciency or useful life. I have dis
covered, however, that the maximum e?iciency,
together with a long useful life of at least 2000
hours is produced in a lamp designed to operate 03 0
with B watts energy consumption with VB volts
across the lamp itself where the internal diam
eter of the discharge envelope is made equal, in
millimeters, to
B2 0.3
the discharge is relatively high, ordinarily having
a value which is many times as great as the so
called “initial burning voltage”, that is, of the
burning voltage which occurs immediately after
40 the ignition.
The mercury-vapor pressure dur
ing operation in the lamps of the type which were
?rst developed is approximately one atmosphere.
These lamps are manufactured in different sizes,
and the power consumption is from approximately
45 150 watts to several kilowatts.
Recently, mercury-vapor discharge tubes which
operate with a much higher mercury-vapor pres
sure, that is a pressure which is generally con
siderably higher than 10 atmospheres, have also
v50 gone into extensive use. These lamps have a
diameter which is much smaller than that of
the lamps previously referred to in which the
operating vapor pressure is approximately one
atmosphere. The internal diameter of these new
55 lamps, which are made of quartz, is of the order
In addition, I have
2.3 found that a lamp having
an internal diameter which meets the foregoing
condition combined with a length as given below 40
will operate with a quiescent discharge, even
when the arc tube is vertical, thus avoiding the
turbulence and; wobbling of the arc stream which
is otherwise an undesirable characteristic of many
of the lamps operating at relatively high pres- 4',
sure. This eliminates the necessity of using
baiiles and the like to impart stability to the
arc path. While it is desirable from all these
standpoints that‘ the diameter should be close
to the value indicated by the foregoing formula, 50
I have found that satisfactory results can be at
tained with a deviation therefrom of 15 per cent,
and in some cases of even a maximum of 20 per
cent, although I prefer to keep the deviation less
than 15 per cent.
With the diameter thus determined, however,
I have dmcovered that it is essential to the at
Any usual means to facilitate the ignition,
such as a suitably connected auxiliary electrode
tainment of the desired eiilciency, stability and ‘ in the vicinity of one of the glow electrodes or
long life that the length of the discharge path a thin metal wire wound around the tube ap
should be equal, in centimeters, to
proximately at the center of the tube, is provid
ed where desired.
10 when B is again the energy consumption, in
watts, and Be the arc voltage, in volts. Although
by far the best results are attained with an arc
path of the length determined by this formula,
it has been found that deviations up to 25 per
cent can be permitted with satisfactory results.
When, in the case of a given power consump
tion and lamp voltage, the diameter and the
length of the discharge path have been deter
mined in this manner, then the other data of the
Thus with a
20 lamps are also readily calculated.
given lamp voltage and length of the discharge
path, the gradient is determined by dividing this
voltage less the cathode fall by the length of
‘ the discharge path.
Only one certain mercury
vapor pressure will give this gradient with the‘
designed diameter and power consumption. The
vapor pressure is determined by the coldest point
The lamp is intended to be connected to a 220
.volt source of commercial frequency, in series
with a choke coil 8, as shown. The power con
sumption of the tube is 250 watts and the bum
ing voltage (in the case of normal operation
after equilibrium is attained) is 120 volts. The
internal diameter of the discharge bulb agrees
with the ‘above-mentioned formula, while the
length of the discharge path is only slightly
smaller than the valve calculated by means of
the formula indicated for this length, and is
within the. limits oi! the permissible deviation.
The output of visible light of the described
lamp is 50.8 international lumens per watt, while
it the discharge path is increased to a length of
5_ cm., then the light output of this modi?ed
lamp is reduced to 49.4 international lumens per
,watt for the same power consumption (250
watts) and the same operating voltage (120
The wall thickness of the'discharge bulb was
of the discharge bulb, or in. case the quantity
calculated by means of the formula
of mercury is limited to such an extent that the
30 lamp operates with an unsaturated vapor, itis
determined by the quantity of mercury placed in .
the lamp. These values must for that reason be
selected in such a way that the required gradient and amounts to 1.3 mm. However, it is possible '
is obtained, using well known formulae.
to permit large tolerances in the value of this
The wall thickness of the discharge bulb is wall thickness.
preferably made approximately
The discharge lamp is arranged, where de
sired, in a re?ector of suitable shape. The lamp
is not cooled arti?cially; the developed heat is
dissipated by means of natural cooling. When
the lamp is to be used for the emission of ultra 40
where d is the internal diameter in mm., in or
der to withstand the internal pressure.
The above formulae apply only in those cases
in which the internal diameter is more than 7
mm., and are of particular importance for
lamps with a power consumption of more than
75 watts. They have no validity for lamps which
are cooled arti?cially, for instance, with running
The drawing shows by way of example a dis
ing from the spirit of the invention.
charge tube according to the invention.
The discharge bulb I consists of a cylindrical
quartz tube with an internal diameter of 15
mm., and contains two activated thermionic
electrodes, 2 and 3, which are arranged close to
the ends of the bulb and consist of coil-shaped
What I claim as new and desire to secure by 50
Letters Patent of the United States, is:
1. In combination, a source of electrical en
ergy, a bailasting device and a tubular mercury
vapor arc discharge device connected in series
across said source, said bailasting device limit 55
violet rays, the cover ‘I is made of a material
which permits these rays to pass.
While I have illustrated my invention by ref
erence to a particular embodiment thereof, it
is to be understood that it is not limited there 45
to, but that various omissions, substitutions and
changes, within the scope of the appended
claims, may be made therein without depart
tungsten wires which are coated with an earth
ing the potential across said discharge device to
alkali oxide. As shown, these’ electrodes are
of the type heated by the discharge. The spac
(3.0 ing of the electrodes 2 and 3 is 4 cm. The dis—
charge bulb is ?lled with argon, which at room
temperature has a pressure of the order of 10
mm. There is further placed in the bulb a
small quantity of mercury, which evaporates
Va volts when B watts energy is consumed in
completely during operation so that the lamp
operates with unsaturated vapor.
The discharge bulb is attached by means of
the current supply wires 4 and 5 to the stem
press 6 of the glass bulb ‘I which has the shape
70 of an ordinary incandescent bulb. The space
between the discharge bulb I and the bulb ‘I is
preferably ?lled with nitrogen, which at room
temperature has a pressure of approximately 50
cm. The bulb is provided with a conventional
75 screw base 8.
said device, the inside diameter of said discharge
device being equal (in millimeters) to
B: 0.:
and greater than 7 mm. and the length of the
discharge path within said device being equal
(incentimeters) to
2. In combination, a source of electrical en~
ergy, a bailasting device and a tubular mercury
vapor arc discharge device connected in series
across said source, said bailasting device limiting
the potential across said discharge device to Va
volts when 3 watts energy is consumed in said
device, the inside diameter or said discharge de
vice being equal (in millimeters) to
device, the inside diameter of said discharge de
vice being equal (in millimeters) to
B2 o.a-2o%
and greater than
2.3 7 mm. and the length of the
discharge path within said device being equal (in
centimeters) to
and greater than 7 mm. and the length of the
discharge path within said device being equal (in
centimeters) to
Ti 25%.
3. In combination, a source of electrical en
ergy, a ballasting device and a tubular mercury
vapor arc discharge device connected in series
across said source, said ballasting device limiting
the potential across said discharge device to V1;
volts when B watts energy is consumed in said
the source of said vapor within the discharge
being limited to such an amount that it is wholly
vaporized when 13 watts energy is consumed in
said device.
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