Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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205~447
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F-4 168(FJ)
FLUORE~SCENT LAMP
The invention relates to a fluorescent lamp, particularly a mercu~y vapor discharge
lamp, with a discharge tube, which is transparent to light and preferably of glass,
S with which the ohmic heating wire is in thermal contact.
As is wcll known, fluorescent lamps usually consis~ of an extended discharge tube
of glass, into the ends of which hot electrodes are fused. As a rule, the tube is
evacuated and filled with krypton, argon and mercury. Known fluorescent lamps
are generally operated by mains voltage. For this purpose, a choke coil and a
starter are rcquircd to fire the gas discharge. However, ~he choke and the starter
lead to additional consumption of energy or to a decrease in the efficiency, as well
~:i as to an inductivc or wattless current load on the alternating-current mains supply.
In addition, furthcr compcnsation and radio noise suppression mcasures arc re-
quircd.
- 15 ~dmittedly, fluorcsccnt lamps with an attached powcr supply, which rectifies the
altcrnating currcnt from thc mains suppl~ for dircct current operation, arc known.
Hswevcr, thc direct curren,t must be modulated to a high frequcncy and/or chopped,
in order to prcvent polarizaflon at the ends of the hot electrodcs of thc dischargc
tube; otherwise, the mercury present in ~he dischargc tube would be depositcd atonc end of ~he dischargc tube, which would then bccome useless within a few
hours.
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The problem, on whicll the invention is based, follows from this, the prohlem bein~
to avoid the disadvantages mentioned above and to provide a fluorescent lamp,
which uses current sparingly and, at the same time, is reliable in itS operation, and
to do so with only little additional circuit complcxity, it being possible, in particular,
to use conventional, commercial, standard fluorescent tubes. To solve this problem,
it is proposed, pursuant to the invention, for a fluorescent lamp with the character-
istics initially named, that a heat-insensitive filament, ~or example of glass, wire or
some other strand, be provided, which extends along the discharge tube and is
surrounded, preferably spirally by the heating wire as the inner guide core for the
latter.
When operated pursuant to the invention, the discharge tube is in constant, thermal
contact with a heatcr, which is structurally intcgrated in the fluorescent lamp and
with which the opcrating tempcrature for the dischargc gas in the tube can bc
optimized. Mercury, as dischargc gas, for example, can bc heated in ~his manncr
to a tcmperaturc, at which it is constan~ly in thc vapor or gaseous statc, its boiling
point being excecdcd. Thercforc, due to the hca~ing, it is dispcrsed over thc whole
of thc discharge tube and is not dcposited at one end of the hot electrodes of the
discharge tube, although thc hot clectrodes are subjectcd to a direct currcnt opera-
tion and the discharge tube thcrefore is polarized. A furthcr advantage, which is
achievcd with the invention, cgnsists thercin that thc discharge tube with its contents
is maintained at an opcrating tempcrature, which is optimum with rcspect to its
efficicncy; a high light yield can thus be achieYed at a relatively low opcrating
voltage or current consumption. Practical consideratians and trials have rcvealcd
that thc energy costs amount to only about 33% of those cncountered with fluores-
cent tubes, which are operated with al~crnating current w~th choke and starter.
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Advantageously, the heater is realized by an ohmic heating resi~t~nce, which con-
tacts the discharge tuhe by means of a thermal connection. This concept c~n ~e
developed further in a particularly advantageous manner owing to the fact that the
heater resistance is interposed in a current-limiting manner in the electric circuit
S of the hot electrodes of the discharge tube and, in particular, is connected in series
with the hot electrodes. In so doing, the ballast resistance, which as such is ab~o-
lutely essential for every fluorescent lamp and which serves, among other purpose,
to limit the current in the case of a direct current operation, is integrated struc-
turally with the heater and can therefore fulfill two functions, namely, on the one
hand, to selve as a ballast/current-limiting/series resistance and, on the other, to
hcat the discharge tube and its contents.
Compared to atmospheric pressure, the discharge tube generally is under a higheror lower pressure (low-pressure, high-pressure and highest pressure lamps). An
appropriate development of the invention takes this into account owing to the fact
that thc heatcr, particularly thc hcating rcsistance, is constructcd as a hcating wire,
which lies on the outer wall of the discharge tube. In order to attain a uniform,
symmetrical tcmperature distribution within the discharge tube with such an arrange-
mcnt, thc hcating wirc, pursuant to a further advantageous realization of thc
invention, is shapcd or disposcd in such a manncr, that it extcnds along helicallincs over the wholc length of the tubular discharge tube.
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In thc luminous operation of thc fluoresccnt lamp, the heating wire, which extends
on thc outer surface of the discharge tubc, can interfere optically This is coun-
tcred by a further inventive development, according to which a heat-inscnsitive
filamcnt, wire or other strand, around which the heating wire is guided in helical
fashion, is stretched from onc end of the discharge tube to the other. The filament,
205~447
at the same time, ~orms a core for the heating wire for its guidance and so stat i-
lizes the mounting of the heating wire on the outer wall of the discharge tube.
A particularly advantageous further development of the invention consists therein
that ;rhe filament and/or the discharge tube is surrounded by a transparent outer
S enclosure of plastic or glass. Particularly when the filament with the heating wire
coiled around it runs along the outside of the discharge tube, the outer enclosure
forms an appropriate insulation against external environmental effects and serves for
;¦ additional stabilization and, at the same time, for increasing the safety and reli-
ability.
On the other hand, if the heating wirc is to bc disposcd in the interior of the
discharge tube, it is particularly advisable, for insulation against the discharging gas
and, at the same time, for the mechanical stabilization and for prolonging the
service life, to surround the filament and the heating wire on it with a rigid and/or
insulating tube.
lS Duc ~o the invcntivc arrangement of thc heatcr, i~ is possihle to opcratc thc
fluorcscent lamp with direct current, dcspite the polarizssion that takcs placc at thc
same time. Consequently, it is advantagcous for thc imcntivc fluorcsccnt lamp toprovidc an altcrnating voltagc rectifier, which is couplcd with the hot clcctrodcs in
thc discharge tubc and/or thc heater, in ordcr to supply them ~ith direct current
~or dircct-current opcration, the impedances causing inductivc, rcactive or wattless
power, such as chokc coils for firing the gas discharge, are cancelled. Conscquently,
, the problcm is raised of starting the gas discharge in the discharge tube with hot
elec~rodes under a direct current voltage For this purpose, a firing network is
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provided in a further ~levelopment of the invention. This firing network i~ c(~n-
nected in series with one of the hot electrodes and consists of one or more stabi-
lizing diodes and coupling and/or smoothing capacitors; these are arranged and
designed in such a manner, that the firing network initiates the discharging process
S and can stabilize the continuous discharge operation. Furthermore, it is coupled on
the input side with the rectifier and/or the alternating voltage source. One realiza-
tion of the firing networlc, which lies within the scope of the invention, lies therein
tha~ it comprises two stabilizing diodes, which are connected in series and a capac-
itor, which is connected in parallel to these diodes, this connection in series and
parallel being connected on the input side with the rectifier output and on the
output side with one of the hot electrodes. The stabilizing diodes serve to keep the
electrical voltage of the hot electrode, which is connected in series, constant com-
pared to the opposite, other hot eleclrode, while the smoothing capacitor decreases
the residual waviness of the rectification of the alternating current network.
A particularly advantageous development of the invention to initiate the firing of
the gas discharge consists therein that the (stabilizing) diode ncarcst to thc hot
electrode is connected with its input terminal to a capacitor, which is designed as
a differentiating element and is connected on its opposite side directly with the
alternating current network. In the switching-on phase of the fluorescent lamp, this
capacitor couples the applied alternating voltage over the stabiJizing diode with the
hot elec~rode. Because of the differentiating properties of this capacitor, a current
surge is brought about in the discharge tube. This is sufficient to get the gas
diseharge going in the tube.
For realizing the rectifier, it is advisable to dispose four diodes in a bridge circuit
2S in a known manner. ~n alterna~ing current resistance is then connected in parallel
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with and at the input side of the bridge rectifier and/or one or more charging
capacitors are connected in parallel with and at the output side of the bridge
rectifier. As is well know, the charging capacitors serve to smoothen the outputvoltage of the rectifier in an integrating fashion; in addition, they have the extra-
S ordina~y a~vantage that they initially act during the switching-on phase as short-
circuiting current drains, until they are charged; during this time, the gas discharge-
firing effect of the above-mentioned, differentiating coupling capacitor can develop
without being impeded or impaired.
To achicvc an attractive appearance and ~I compact construction, a fluorescent tuhe
ballast, comprising an optional alternating voltage rectifier and/or a firing network,
is integrated structurally with particular advantage with the or in the lamp con-
nection socket, which serves for bringing about electrical contact, and, in particular,
is constructcd in one piece with this socket. The connecting socket can be provided
as a scrcw base with a standard external thread for screwing into an appropriateholder, which is conncctcd with a powcr plug; on the other hand1 a power supply
cable with plug can Icad dircctly into the screw base. An alternative possihiliq for
accammodating thc fluoresccnt tube ballast consists of disposing it structurally in thc
annular space boundcd by the inner discharge tubc and by the outer enclosurc
surroundin& this tube.
Further charactcristics, dctails and advantages of the imcntion arisc out of thcfollowing description of preferred embodiments of the invention, as well as from the
drawing, in which
Figurc 1 shows the arrangemcnt of the fluorescent tubes and thc electronic circuit
components associated with thcm,
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Figure 2 shows a further development of the invemive fluorescent tube ~rrange-
ment in a partially cut, longitudinal view,
Figure 3 shows a truncated exterior ~icw of the end of the inventive fluorescent tube and
Figure 4 shows a modified embodiment in a vicw corrcsponding to that of Figure
3.
Thc cssential parts of thc arrangcmcnt shown in Figurc 1 arc a convcntional,
commercial onc-pin basc fluorcscent tube 1 with heatcr 2, as wcll as the altcrnating
current rectifier circuit 3 and firing circuit 4. In thc cxamplc, the hcater 2 is
constructed as a helical hesting wirc and disposcd so as to lic on the outer wall
of the tube 5. llle one end of the hcating wirc k connected to thc negati~c
terminal 6, which is led dircctly ou~ of thc rcctificr circuit 3 and the othcr cnd is
connccted over a ter ninal jaw 7 with the connecting pin 8b of one of the two one-
pin bases 9. The connccting pins 8 at cach cnd of thc fluoresccnt ~ubcs or of thc
dischargc tube I change over in thc intcrior of thc lattcr into thc (not drawn) hot
clectrodcs. Thc heating wire 2 spirally surrounds a filamcnt 10, which thus forrns
an inncr guide corc of the hcating wire and is mounted on thc outcr wall at the
cnd of the fluorcscent tub~e 1 averta1 from thc tcrminal jaw 7 by mcans of an
adhcsivc joint 11 (drswn diagrammatically). Thc o~her, oppositc end of thc filament
10 is fastened within thc tcrrninal jaw 7, which in turn is fastencd by being clsmped
around thc connccting pin 8. By thesc means, thc filamcnt 10 is placed under
mechanical tension betwecn the cnds of the fluorescent tubc or thc discharge tube
1 and the filamcnt 10 can functinn as thc intcrnal guiding core for mechanical
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stabilization of the position of the heating wire coil 2.
The connecting pin 8a, which lies at the end of the fluorescent tube 1 that is
averted from the clamping jaw 7, is connected over an electrical connecting iine 12
with a positive terminal 13, which is led indirectly out of the rectifier circuit 3 ~y
way of the ~Iring circuit 4. The rectifier circuit 3 is supplied at ~he input side from
a 220 volt alternating current network, a load resistance RL being connected in
parallel to the two output terrninals of the alternating current network (such as the
phase conductor and the neutral conductor) in order to produce a defined input
voltage. The rectifier 3 comprises the four diodes D~, D2, 1:~3 and D~" which are
disposed in a known manner in a bridgc circuit. A charging capacitor CLI and
CL2 jS connected in parallel with the positive and negative outputs of this bridge
rec~ifier circuit 3, as well as with one of the output terminals of the alternating
voltage source with 220 volt.
The negative output 6 is connected dircctly vith the heatcr 2. On the other hand,
thc firing network 4 is dircctly connected in scrics with the output of the rectifier
3 with positive polarity. Thc firing network 4 has the two stabilizing diodes Ds and
D6, which are disposcd in series and wi~h which a smoothing capacitor Ca is jointly
connected-in parallel. Moreover, thc firing andl at the same time, stabilizing circuit
4 has a coupling capacitor C~, thc one terminal of which is connectcd directly with
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an output terminal of thc 22û volt alternating current source and the other terminal
of which is connectcd directly with an input of one of the stabilizing diodes D5, D6,
prefcrably with the stabilizing diode D6, which is disposed closest to the connecting
pin 8a of the fluorescent tube 1. Suitable design values for the load resistance RL
arc 100 - 680 k~, for the two charging capacitors CLI alld CL2 2.2 ~LF, for the
coupling capacitor CIY 0.082 ,~F and for the smoothing capacitor CG 0-1 ,uF. For
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the heating wire, a resistance coating of 600 Q/m has proven to be appropriate.
When the 220 volt alternating current source is switched on, the charging capacitors
CL1 and CL2 must first of all still be charged; consequently, they function initially as
short circuiting current drains. The current, flowing at the same time over the load
S resistance RL. produces a corresponding voltage drop, which is differentiated by the
coupling capacitor CK into a current surge or a current peak, which, ~y way of the
stabilizing diode D6 that is connected in series, reaches the positive terminal 13 and,
by way of the connecting line 12, the connecting pin 8a of the fluorescent tube.Thc energy, which is thus supplied to the nuorescent tube 1 or the discharge tube
1, is sufficient to fire the gas discharge process. When the charging capacitors CL~
and CL2 are largely charged at the end of their time constant, which is also affected
by the load resistance RL. the voltage drop at the load resistance RL ;S diminishcd
in such a manner, that the coupling capacitor CK loses its dctectablc effect and that
thcrefore a uniform direct voltage exists between the connecting pins 8 at thc two
lS oppositc ends of the fluorescent tube 1 and this voltage is suffciently stablc for
continuous opcration.
According to Figure 2, the arrangement shown in Figure 1, comprising the fluorcs-
ccnt tube 1! with thc heating wire 2, which is lying on the tluorcsccnt tube 1 and
is coilcd in spiral fashion around thc filamcnt 10, is surroundcd b~ an outer en-
closurc. In thc example drawn~ this outer cnclosure has the shapc of a (p~stic)
tube, which is closed off at one end with a stoppcr 15 that is prcssed into forcc fit.
A basc housing 16 with a standard external thread 17 and a contact element 18 isslipp¢d onto the other end of the outer enclosurc 14. The extcrnal thrcad 17 andthe contact element 18, which is insulated from it, serve to connect a source ofaltcrnating current, as drawn in Figure 1. Moreover, the circuit componcnts that
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are also shown in Figure 1, namely the rectifier 3 or the ~Iring circuit 4, which are
optionally mounted on a printed circuit board, are accommodated within the base
housing 16. According to Figure 3, the fluorescent lamp arrangement can be
screwed with the internal thread (not shown) by means of its base housing 16 into
S a conventional holder 19 for lamp or incandescent bulbs. A network cable 20 with
plug 21 for the connection to a conventional receptacle leads from the holder 19.
Of course, it is also within thc scope of the invention to lead the networlc cable 20
with the plug 21 directly through the base housing 16 ~o the alternating currentrectificr 3, as shown in Figure l; if this is done, the extcrnal thread 1~ and the
con~act clement 18, which together scr~e to form a closcd altcrnating current circuit,
can be omittcd.
.
Thc embodiment of Figurc 4 diffcrs from thosc of Figures 2 and 3 owing to the
fact that thc socket 16 is replaced directly by thc network plug 21, in which the
~forem tionod fluorescent lamp ballast can bo _mmodalod.
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