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Патент USA US2134439

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Oct. 25, 1938.
Filed Dec. 27, 1957
E 6€ ßoil‘yeZ, O
Patented Oct. 25, 1938
Eduard Gerardus Dorgelo, Eindhoven, Nether
lands, assignor to N. V. Philips’ Gloeilampen
fabrieken, Eindhoven, Netherlands
Application December 27, 1937, Serial No. 181,929
In Germany December 29, 1936
3 Claims.
(Cl. 17E-Mél)
The present invention, which forms a contin~ - of the ñlm can be effected during this period
without being perceptible on the screen, and
uation-in-part of my copending U. S. patent ap
plication Ser. No. 127,756, now Patent #2,130,077, thereby make the use of shutters unnecessary.
It is well known that, in shutterless apparatus,
relates to a system for periodically energizing
it is unnecessary that the light emission be re
high-pressure metal-vapor discharge tubes, par
duced to zero during the periods of 'movement
ticularly when such tubes are used as light
of the nlm. On the contrary, if the luminous
sources in motion picture apparatus.
My invention is especially useful with discharge intensity on the projection screen during move
tubes of the type described in U. S. Patents ment of the nlm falls below a given value which
#2,094,694 and #2,094,695 to Cornelis Bol et al. depends on the maximumv value of the luminous
Such tubes are particularly suited for projection intensity, a “travel ghost” of the picture is not
perceptible for physiological reasons. When the
purposes because they develop an intrinsic bril
liance up to and above 200,000 Int. candles per projection is carried out with relatively small
sq. in., and the spectrum of the emitted light variations in luminous intensity, for example, in
meets all the requirements of picture projection. comparatively small systems, a shutter may be 15
Furthermore, such tubes have the advantage provided. In such cases the device according to
that when they are properly energized, their the invention not only prolongs the life of the
light-emission -curve has dark periods of such discharge tube but also effects a certain saving
duration that the nlm can be moved during these in current.
In order that my invention may be clearly
periods without the movement being visible on
the screen, which makes a shutter unnecessary. understood and readily carried into effect, I shall
describe the same in more detail with reference
In my above-mentioned application I have de
scribed an energizing system for such tubes which to the accompanying drawing, in Which:
comprises a circuit connected across an alter
nating~current supply and having twoparallel
branches. One of these branches comprises a
preferably variable ohmic resistance and a rec
tiñer, the other branch comprises an impedance
and the discharge tube, and a condenser is con
nected in series with both these branches.
I have found, however, that the life of such
tubes depends upon the manner in which the
current passes through them, and if this current
is periodically interrupted, the life of the tube
is materially reduced. More particularly, due to`
the reduction of the ionization in the discharge
space of the tube, the starting voltage of the
tube is increased, which may result in premature
destruction of the tube. Furthermore, to main
tain a given mean intensity of illumination, it is
necessary that the tube has a higher luminous
intensity during the periods of light emission,
i. e. a larger current must be passed through
the tube. Because of the above the life of the
tube was considerably shortened.
The main object of my invention is to over
come the above diiliculties and to increase the
life of such tubes. For this purpose and in ac-_
cordance with the invention, I use in circuits of
the above type a condenser and an impedance
of such values that a current will continuously
pass through the tube.
I make the minimum value of the tube current
such that the emission of light from the tube
periodically becomes so 10W that the movement'
Figure l is a schematic circuit diagram of an
arrangement according to the invention,
Fig. 2 is a sectionalized view of the discharge
tube of Fig. l, '
Fig. 3 is a schematic circuit diagram of an
arrangement according to another embodiment
il l)
of the invention, and
Fig. 4 is a graph showing the current- and
voltage-time curves of the arrangement of Fig
ure 1 when~ the condenser and the impedance
have the values in accordance with the invention.
As shown in Figure 1, an alternating-current
source e, which may be the ordinary lighting or
power supply, or a transformer, has one terminal
l connected through a condenser C to a point 1,
and has its other terminal 2 connected to a
point 8.
Connected in parallel across points ‘l
and 8 is a. branch circuit comprising a rectifier
G and a variable resistance R, and a second
branch circuit comprising a choke coil L and
a discharge tube E. Resistance R may be con
nected between points 3 and 4, or between points 45
5 and 6 as shown in Fig. 3. In addition, the choke
coil L may be replaced by a resistance.
As the discharge tube E, I prefer to use cooled
high~pres`sure metal-vapor discharge tubes such
as described in the above-mentioned patents.
Preferably the tube should be lliquid-cooled and
have a mercury-vapor filling of high-pressure,
preferably more than 6 atmospheres, for eX
ample 150 atmospheres, and should comprise
one or more incandescible electrodes protruding 55
only slightly from a vaporizable metallic mass
which surrounds said electrodes and which con
tains mercury or amalgam. With such discharge
tubes an intrinsic brillianceof 20,000 Interna
points 1r and 8. Hence the inductance voltage
tional candles per sq. cm. and upwards, e. g.
of curve I8.
from 80,000 to 100,000 and more, can readily be
obtained, while the spectral composition of the
light fully meets the requirements to be complied
with for faultless projection. Such a tube is
10 illustrated in Figure 2 in which the reference
numeral 3| indicates a transparent envelope,
e. g. of quartz, in which are disposed two mer
thus produced at the choke can still maintain
through vtube E for a short time, a current of
decreasing intensity, indicated by portion I9-20
In the meantime rectifier G again becomes
operative at a point 2|.
At a point 22 an in
creasing voltage commences to be set up between
the points 1 and 8, and as a result, the current
through tube E vbetween points 20 and 23 de
creases more slowly than between points I9 and
20, and even increases at point 23. This above
cury electrodes 32. The tube is surrounded by -described process is then repeated periodically
a cooling jacket 33 of transparent material with a frequency equal to that of the alternating
15 through which cooling water is circulated as in
current supply.
dicated by the arrows.
If, in accordance with the invention, condenser I
The circuit arrangement operates as follows. C is given a sufliciently high capacity, it will
When terminal 2 is positive, condenser C be
periodically discharge only a comparatively small
comes charged Aby a potential which is governed amount which means that the voltage across
20 by resistance R, since rectifier G permits the cur
~the same drops only a small amount (see curve
rent to ilow in this direction. When the poten
part Il), and when choke L is given the proper
tial oi terminals I and 2 are reversed, there is inductance, it is possible to maintain the flow
consequently set up across tube E a total voltage of current through tube E until the voltage be
which is the sum of the voltage of condenser C
25 and the voltage of supply e. It follows therefore
that the circuit arrangement illustrated in Figs.
1 and 3 makes it possible »to start and to main
tain in operation discharge tubes which have a
starting-voltage higher than the highest voltage
30 of the alternating-current source.
The operation of the circuit arrangements
shown in Figs. 1 and 3 is illustrated by the graph
of Fig. 4 in which curve 9 represents the volt
age curve of the alternating-current source e.
When the supply voltage reaches a value corre
sponding to point I0 on curve S-which point
corresponds to the breakdown voltage of recti
fier G-the latter becomes operative and con
denser C cornmences to be charged. Whether
40 or not condenser C will become charged to the
highest value that can be reached, i. e. to the
maximum A. C. voltage indicated by point I2,
depends upon the capacity of condenser C and
on the value of resistance R that limits the rate
45 of flow of the charging current. In the circuit
arrangement illustrated the value of resistance
R is such that the condenser voltage, designated
by dotted curve II, approaches very closely to
the maximum voltage of the alternating-current
50 source. The condenser retains its charge, because
rectifier G does not allow passage of current in
the reverse direction. After the voltage of the
A. C. -source has reached the maximum value at
l2, it decreases so that there is set up between
the points 1 and 8 of Figs. 1 and 3, a potential
difference which is indicated diagrammatically
in Fig. 4 by the cross-hatched part.
Connected in series across points l and 8 are
the discharge tube E and the choke L. When,
60 after the device has been placed in operation,
the voltage across points 'I and 8 reaches for
the first time, at point I4, a value equal to the
breakdown voltage of the discharge tube, indi
cated by line I3 in Fig. 4, the tube 'lights up.
The iiow of current through the tube is indi
cated diagrammatic’ally by the curve I6 which
starts at a point I5. The condenser then dis
charges through the tube E as indicated by the
portion Il of curve II.
At a point I8, the potential difference between
the points 'I and 8 becomes equal to zero. How
ever, the current passing through the discharge
‘ tube is not equal to zero at this moment, because
the current in choke II lags in well-known man
75 ner with respectI to the voltage applied across
tween the points ‘I and 8 again increases and a
renewed increase in current is set up from the
point 23 onwards. Thus tube E will not become
extinguished but will be supplied with an unin
terrupted and periodically varying current. The
higher the values of the inductance of choke L
and the capacity of condenser C, the less will be
the periodical decrease of the current through
the tube.
In the above system the condenser C, the
rectiiler G and the impedance L act as a recti
fying circuit, in which C and L together form
the smoothing filter. The greater the value of
the condenser C and the impedance L, the smaller
will be the alternating current ripple on the
direct current.
When the maximum value oi’ the A. C. is
greater than the D. C. the rectiiied current will
beperiodically interrupted; but when it is smaller,
the rectified current will be uninterrupted.
In accordance with the invention the con
denser C and the impedance L are so propor
tioned that the maximum value of the alternat
ing component (curve I 6) of the rectified cur
rent will be smaller than the value of the direct
component (curve 24) of said rectified current,
i. e., so that the current through the tube E
will not be interrupted.
As a specific example, I have used the follow
ing values: Supply voltage e=500 volts; supply
frequency f=50 cycles per sec.; operating volt
age of discharge tube e=500 volts; a mean tube
current 1 or 2 amps.; capacity of condenser
C=30 nf; inductance of choke L=from 2 to 3
henries; a resistance R=about from 10 to 100
ohms. With such values, it was found that the
life of the tube was about 10 times greater than
when supplied with periodically interrupted cur
While I have described my invention in con
nection with specific examples-and applications,
I do not wish to be limited thereto but desire
the appended claims to be construed as broadly
as permissible in view of the prior art. '
What I claim is:
l. An energizing system for a high-pressure
metal-vapor discharge tube having a contracted
discharge path, comprising a source of alternat
ing current, and means between said source and
said tube for passing through said tube an un
interrupted and periodically varying operating
current. said means comprising a circuit con
nected across said supply and having two parallel
branches, a condenser in said circuit and in series
with both of said branches, ‘a rectiñer in one of
said branches, an impedance in said circuit be
tween said rectifier and one end of said'source,
and a second impedance, said second impedance
and discharge tube being connected in series
in said second branch.
2. An energizing system for a high-pressure
metal-vapor discharge tube having a contracted
discharge path, comprising a source of alternat
ing current, and a rectifying circuit connected
_ 3. An energizing system for a high-pressure
metal-vapor discharge tube having a contracted
discharge path, comprising a source of alternat
ing current, and means associated with said
source to rectify said alternating current and to
supply to said tube an uninterrupted and pe
riodically varying operating current, said means
comprising a vcircuit connected across said sup-ply and having two parallel branches, a condenser
in said circuit and in series with both oí said 10
branches, a rectiñer in one of said branches,
a variable resistance in said circuit between said
rectifier and one end of said source, and an im
across said supply and having two> parallel` pedance, said impedance and discharge tube being
branches, a condenser in 'said circuit and in connected in series in said second branch, said 15
l series with both of sai.’ branches, a rectiiier in
condenser and said impedance being propor
one of said branches, an impedance in said cir
cuit between said rectiñer and one end of said
source, and a second impedance, said second
impedance and discharge tube being connected
y in series in said second branch, said condenser
and second impedance being proportioned to
cause an uninterrupted and periodically varying
current to pass through said tube.
tioned to cause the maximum value of the alter
nating component of the reotiñed current to be
smaller than the value of direct component of
said rectiñed current.
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