Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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D 93-1-445 -1- PATENT
El~ctrodele ~ Lamp With A Thin Shell Pow~r Applicator
1. Technical Field
The invention relatQ~ to electric lamps and
particularly to electrodele~9 high inten~ity dl charge
lamp~. More particularly the invention i3 concerned with a
power applicator for an electrodeless high inten~ity
discharge lampc
2. Background Art
Electrodeless, high inten~ity lamp~ are efficient
producers of vi~ible llght. The bright, inten~e light
emitted by electrodele~ lamp~ exceeds many common need~, ~o
the lamp~ are commonly ~caled to have relatively ~mall ~ize.
For example, a lamp powerful enough to form a Yehicle
hea~lamp might use a lamp capsule only a few millimeters in
diameter and only a few centimeter~ long. For 5uch a ~mall
capsule, the power applicator and lamp need to b~ accurately
aligned, as mi~alignment result~ in mismatch and power loss.
There i~ a similar n~ed to control the thermal flux of the
cap~ule. ~he high liyht output i~ a result of th~ hi~h
temperature o the enclosed plasma, but wi~h such a ~mall
lamp body, heat 19~s can be rapid and substantial.
In the past, power ha~ been applied to the lamp capsule
by machined metal cups, metalized ceraMic cups ~ and me~al
coils. The Applicant has found that th~ mach~ned metal cup~
conduct he8~ away from the lamp cap~ule, coollng ~h~ cap~ule
and ~hereby reducing ~he energy Pf f iciency of the lamp .
Al~o, the heat conducted into the power applicator may
detrimentally affect the power coupling to the capsule, the
mechanical ~ntegrity of the applicator, the applicator
~upport structure, and the electrical conn~ction o~ the
applicator. In particular, the Applicant has found that the
hiqh heat experienced by the machined cup~ when in clo~e
prox~mity to th~ lamp capsule cau~d the ~olid metal
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D 93-1-445 -2- PATENT
surface~ to darken, or ~pall, while the coatings of ceramic
material~ evaporated, or ~caled off. The hlgh heat al~o
caused the soldered connection hetween the applicator and
the ~icrostripline power lead to soften or melt, allowing
the applicator to shift po~ition~ in the ~older thereby
al~ering the conductivity of the connection and the power
delivery to the capsule. The high heat loss under any
condition represented a los8 of power efficiency. There i~
a need for a power coupler that minimally conduct3 heat from
the lamp capsule.
Machined metal cup type applicators al~o compri~e
electrical capacitors with unwanted alectrlcal
characteristics. The Appllcant has found the regular
metallic ~urface of a machined block ~upport~ a stray
capacitance with respect to the rest of the block's
surroundings. The stray capacitance alters the tuning
between the concave field ~haping ~urface and the lamp,
causing movament of thz lamp pla~ma, and flicker and color
irregularitie~ in the light outpu~. Without accurate
sh~ping, the lamp plasma may be displaced, and may thereby
detrimentally interact with the capYule wall, shortening
lamp life, or reducing lamp quality. There i8 a need for a
power applicator, that has reduced or no stray capacitance
to interfere with lamp operation.
Machined cups ~re also relatively heavy, thereby
requirlng heavier supports to resi~t vibration. The heavy
support~ have similar adver~e heat and capacit~ve affect~ a~
do the machined CUp8 . There ~ then a need for a small
power applicator ~hat can be inexpensively manufactured,
that may be held in po~ition accurately.
Example~ of the related art are shown in the following
U.S. patents:
U.S. patent 4,041,352 i~ ued to William H. McNeill et
al on August 9, 1977 for a starting system for an
electrodeles~ lamp shows a singled ended excitation source.
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D 93-1-445 -3- PATENT
U.S. patent 4,041~352 issued to William H. McNeill e~
al on Augu~t 9, 1977 for a ~tarting ~ystem for an
electrodele~ lamp show~ a capsule held in a cup radlator,
which is then enclo~ed by a container and mesh screen
radiator.
U.S. patent 4,266,162 is~ued ~o William H. McNeill et
al on August 9, 1977 for a starting system for an
electrodeless lamp shows a doubled ended excitation ~ource.
In claim 1 Mc~eill cite~ the termination load approach, and
in claim 5 cites the need to conkrol the electric field in
the vicinity of the lamp envelope.
U.S. 5,113,121 issued to Walter P. Lapatovich et al, on
May 12, 1392 for Electrodeless HID Lamp with Lamp Cap~ule
~hows a doubled ended cap~ule ~upported on a circuit board
structure, having two coil power applicators. In ~olumn 6,
line~ 34 et s~q. the coils are de~cribed as being o~fset
from the lamp cap~ule. By not touching the cap~ule, the
heat lo~ from tho capsule is limited.
U.S. 5,130,612 issued to i~sued as to Walter P.
Lapatovich e~ al, on July 14, 1992 for Loop Applicator for
Hi~h Frequency Electrodele~s Lamp~ ~how~ a doubled ended
capsule supported on circuit board structur~, havlng two
hairpin wire power applicators. In column 3, line~ 13 et
eq. the coils are de~cribed as belng offset from tha lamp
cap~ule. An advantags of the hairpin coll is de~cribed to
be the minimal coupling of heat conducted back to the solder
~oint~.
U.S. 5,130,612 l~ued to i ~ued a3 ~o Sco t Butler,
Walter P. Lapatovich, and Jason 80chin~ki September 1, 1992
for Electrodeless HID ~amp Coupling Strueture with Integral
Matching Network, shows a doubled ended capsule supported on
a circuit board structure, having two coil power
applicators. A matching impedance network structure is
de~cribed.
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D 93-1-445 -4- PATENT
U. S, S. N. 07/757,095 issued to Walter P. Lapatovlch,
for End Cup Applicator for High Frequency Electrodele~
Lamps disc10-~2s solid metal block applica~ors with concave
openings. The block3 are altsrnatively formed from a
metali2ed ceramic. The concavity ls offset from the lamp
capsule by from 0.1 to 10 millimeters.
Disclosure_of the Invention
An ~lectrodele~s lamp may be formed with an
electrodeles~ lamp capsule, the cap~ule having an axis, an
enclosed volume containing a mlxture of gas and chemical
dopant material excitable by radio frequency electromagnetlc
radiation to a state of luminous em~ sion, and a mechanical
support coupling, a first power appllcator, a second power
applicator, and radio frequency power connection. The lamp
capsule l~ generally positioned coaxial with ~he fir~t power
applicator ~o the enclosed volume of the lamp capsule i3
intermediate the fir~t power applicator and the 3econd pow~r
applicator. A support coupled ~o the lamp capsule may be
formed to hold the lamp capsule intermedia~e the f~r~t power
applicator and the second power applicator. The fir~t
preferred power appllcator i~ formed a~ a thin metal ~hell
having a concaYe wall ad~acent, while off~et from the lamp
cap~ule 30 as to not touch the lamp capsule, while being
approximately conformal with a portion of the exterior
surface of the lamp capaule.
Brief Deacri~tion of the Drawin~
0 FIG. 1 show~ a slde, cross sectional view, partially broken
away of a preferred embodiment of a thin sh~ll pow~r
applicator and lamp capsule.
FIG. 2 shows a ~op view of an ~lectrodeless lamp.
FIG. 3 show a front vi~w of a preform for a power
applicator with a wide tab.
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D ~3-1-445 -5- PATENT
FIG. 4 shows a front view of a preform for a power
applicator with a moderately wide tab.
FIG. 5 shows a front view of a preform fox a power
applicator with a narrow tab.
Best Mode for Carrvin~ Out the Invention
FIG. 1 shows a side~ cros~ sectional view, partially
broken away of a preferred embodiment of a thin shell power
appllcator, and lamp capsule. Like reference number~ are
used throughout the drawings and specification to designate
like or corresponding parts. The electrodeless lamp 10 may
be assembled from a lamp capsule 12, a fir~t power
applicator 26, a secvnd power applicator 58, a fir~t power
lead, a ~econd power lead~ and a support structuxe. FIG. 2
shows a top view of an electrodeless lamp 10.
Th~ lamp cap~ule 12 may be made out of quartz to have
the general form of a elongated, closed tube with a lamp
cap~ule axis 14. The lamp capsule 12 ~hereby defines an
enclosed volume 16 that may be filled with any of the well
known combinations of ga~e~ and chemical dopants u~ed in
~lectrodeless l~mps. The lamp cap3ule 12 in the region of
the enclosed volume 16 has a fir~t outside diameter 18. ~he
fir~t outside diameter 1~ typically varie~ from perhaps a~
little as 2 millimeters to a3 much a~ 10 or more
millimeter~, The pre~erred fir~t out~ide diameter 18 i~ 4.0
millimeter~, while the ad~acent wall~ are 1.0 millimeters
th~ck, giv~ng an in~ide diameter of about 2.0 millimeter~.
~he lamp capsule 12 may b~ rounded, at a fir~t end 20 to
generally have a hemispherical form. Pro~ecting axially
from one or both of the ends of the lamp cap~ule 12, the
preferred embodi~ent further includes one (or two) rod or
tubular extension(s) 22. The lamp capsule 12 may be ~upport
by the extension(s) 22. The preferred lamp cap~ule 12 has a
tubular rod extension 22 wi~h an ou~side diameter 24, les~
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D 93~1-445 -6- PATEN~
than th~ first outside diameter l~. The preferred exten~ion
22 i~ open at the end far~hest from the lamp capsule 12. ~y
way of example, the lamp cap~le 1~ iq ~hown a~ a s~raight
tube with a larger diameter middle region, saaled at each
end, with a ~maller diameter, axially aligned, tubular
extension 22 that may be used to support the lamp capsule
12.
FIG. 3 ~hows a front view of a prPform for a fir~t
power applicator 26 with a wide tab 28 with a width 30.
FIG. 4 show~ a front view of an alternative preform for a
first power applicator 32 with a modexately wide tab 34 with
a width 36. FIG. 5 shows a front view of a still further
alternative preform for a fir~t power applicator 38 with a
narrow tab 40 wlth a width 42. The first power applicator
26, 32, 38 may be made out of conductive metal1 abl~ to
withstand the high temperature of nearly 900 Cel~ius
resulting from being po~itionsd close the oparating lamp
cap~ule 12. Metal~ such as nickel, molybdenum, titanium,
and tung~ten are sugge~ted. Alternatively a high
temperature ~uper conducting ceramic, ~uch a~ a yttium-
barium-copper-oxide formed a~ a thln foil ~s thought to be
potentially useful, e~pecially for lamps with fill
chemistries requiring only low operating temperatures. In
such a ca3e, the high temperature ~uperconduc or may remain
~uperconductive.
The preferred $irst power applicator 26 is formed from
a thin nickel foil, with a concave wall 44 that i~ ~ized and
shaped to fit around an end of t~e lamp capsule 12 to be
near an axial end o the enclosed volum~ 16. The wall
thicknes~ 46 ~hould be substantially le~ than th~ width 47
of the whole power applicator 26, perhaps one tenth of the
whole applicator w~dth, to reduce capacitance, and i~
preferably about the thicknes~ of the mircostripline 64 for
minimal impedance mismatch. Nonetheless~ the first power
applicator 26 must still be thick 46 enough to mechanically
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D 93-1-445 -7- PATENT
~tand in place. The preferred wall thickness 46 of the
power applicator 26 i9 les3 than 1.0 millimeter, and more
preferably is about 0.5 millimeters thick. By limiting the
power applica~or 26's thickne~s 46, the adverse capac1tive
affect~, heat content, and thermal conductlvity of the fir~t
power applicator 26 are limited.
The fir~t power applicator 26 is preferably formed with
a concave wall 44, with the concave wall 44 facing the lamp
capsule 12's enclosed volume 16. Further, the concave wall
44 may have a similar or the same shape a~ the exterior wall
of the adjacent first end 20 of the lamp capsule 12. The
lamp capsule 12 is preferably rotationally symmetric about
the lamp cap~ule axis 14. Similarly the preferred first
power applicator 26 in the concave wall 44 region i8 al~o
rotationally symmetr$c around the fir~t power applicator
axis 48. Where the lamp capsule 12 i5 formed wlth an
approximately hemispherical first end 20, the preferred
power applicator 26 is formed with a similar heml~pherical
concave wall 44 that then ha~ a slightly larger
hemispherical appllcator d~ameter 50. The hemi~pherical
~hell then define~ an appllcator axis 48, that is preferably
parallel with, and even collinear with the lamp cap~ule axis
14. The first power applicator 26 may have a ~imilar
general form, that o~ a thin walled, hemi~pherical 3hell,
roughly conformal with shape of the exterior of the sealed
end of the lamp cap~ule 12. The preferred concave wall 44
ha~ an axial depth that i~ at lea~t a tenth of the
applicator diameter 50. The shape of the concave wall 44
forces an electrlc field concentra~ion in the vicinity of
the fir~t end 20 and in the gap between the opposing fir t
power applicator 26 and the ~econd power applicator 58.
While hemispherical form8 have been used, elliptic~l, and
hyperbolic surface~ of revolution about the lamp axis may
also be used. Even planar flat wall structures may be used,
but these are believed to be le~s efficient power coupler3.
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D 93-1-445 -8- PATENT
Where the fir3t power applicator 26 i~ concave, the end
of the lamp capsule 12 may be ins~rted in~o the concave
region of ~he first power applicator 26. The fir~t power
applicator 26 may then be po~ltioned in a clo~e, ~ymmetric,
but evenly offset relation to the first end 20 of ~he lamp
capsule 12. The stand off 52 distance is considered to be
the least axial distance from lamp capsule's fir~t end 20 to
the first power applicator 26. The preferred ~tand off 52
i5 in the range of from 0.1 to 10.0 millimeter~. The
preferred stand off 52 ls about 0.5 millimeters for lamps
with hemispherical ends, 4.0 millimeters iJI outside
diameter, and operated at about 35 watts. The applicator
diameter 50 of the concave wall 44 may then equal the first
outside diame~er 18 of the lamp capsule 12, plu3 twice the
expected stand off 52 distance, say 0.5 millimeter~, for a
total inside applicator diameter 50 of 5.0 millimeter~.
Where the lamp cap~ule 12 includes a pro~ecting tubular
extension 22, the f~rst power applicator 26 may deflne an
included through hole 54, of sufficien~ly large diameter to
allow the tubular exten~ion 22 to pass through, while
leaving ~uf f icient separation ~pace, so the tubular
extension 22 and fir~t power applicator 2~ do not touch,
particularly during lamp operation. The fir~t power
applicator 26 then does not act a3 an effective heat sink
for the lamp cap ule 12. The preferred fir~t power
applicator 26 i~ then positloned to be clo~e to the first
end 20 of the lamp cap~ule 12, les~ than a quarter wave
lengSh o~ the power to be applied, or le~. G2nerally, for
good coupl~ng of the appliad power into the lamp cap~ul0 12,
the fir~t power applicator 26 i~ positioned a3 clo~ely as
possible, but wi~hout actually touching the lamp capsule 12.
A ~tand off 52 distance between the lamp capsule 12 and the
first power applicator 26 of f;ve or less millimeters is
preferred~ from 0.5 to 1.0 mlllimeters being most preferred.
Similarly the lamp cap~ule 12 and flrst power applicator 26
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D 93-1-445 -9- PATENT
are preferably parallely aligned and even collinearly
allgned.
The concave wall 44 of the fir~t power applicator 26
may be ~upported by an elongated tab 28 having a width 30
approximately equal to the applicator diameter 50. The
length of the tab 28 may be conveniently cho~en to allow the
tab 28 to be held and connected to th~ radio frequency power
lead, ~uch as mlcrostripline 64. In one form, the tab 28
was bent to provide a solderable ba~e portion for the power
applicator. By bending the tab 28 at about 90, a stand
with a flat base 72 may be formed that i~ readily po~itioned
agains~ and then soldered to a microstripline 64. The thin
walled first power applicator 26 even w~th a wide tab 28 i9
effective in llmiting heat conduction and improving lamp
performance.
The tab 28 is inherently a heat conductor. ~y also
limiting the width of the tab 28 to less than the applicator
diameter 50, les~ heat may flow from the concave wall 44
ad~acent the lamp capsule, down the length of the tab 28 to
the radio frequ0ncy power source ~tructure, which in on~
case wa~ a circuit board. FIG. 4 shows a ~imilar power
applicator 32 wlth a tab 34 whose width 36 i~ about 70
percent of the applicator diameter 50, or in one example
about 3.5 millimeters. The narrower tab 34 resi~t~ heat
conduction bett~r than the wider tab 28. FIG. 5 show~ a
~imllar pow~r applicator 38 with a ~till narrower tab 40
whose width 42 is about 40 percent of the applicator
diameter 50, or in one example about 2.0 millimeters. The
narrower the tab width 30, 36, 4~, the less heat may be
conducted through the tab to the support for the power
applicator. The tab 28 ~34, 40) also serve~ as a radio
frequency power connection. By matchlng the tab width 30
(36, 423 to the width of the radio frequency input source,
such as the microstripline S4 width, an e~ficient el~ctrical
connection i~ made. The preferred tab width i~ fir~t
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21~86~2
D 93-1-445 -10- PA~EN~
ad~u3ted to match the width of the micro~tripline. The
preferred tab width then depends indirectly on the impedance
characteri3tics of the miorostripline, the lamp capsule, the
power frequency, and the power source.
As shown ln Fig. 2, a sQcond power applicator 58 may be
~imilarly formed and 3imilarly po~it~oned with re~pect to
the lamp capsule 12, but at the opposLte axial end, the
second end, of the lamp capsule 12. The preferred first
power applicator 26 and the second power applicator 58 are
symmetric, so the power distributed by them is even acros~
the length of the lamp capsule 12, and the enclosed volume
16. Th~ first power applicator 26, the lamp capsule 12, the
enclos~d volume 16, and the second power applicator 58 are
preferably parallely align~d, and even collinearly aligned.
The enclosed volume 16 then receives the electromagnetic
energy radiated between the first power applicator 26 and
second power appli~ator 58 evenly.
The first pow~r applicator 26 receive~ a radio
fre~uency power lnput from a first power lead, ~uch a~ a
microstripline 64, connected to a power source (not ~hown).
Applicant~ prefer a planar tran~mlssion line, as constructed
on a circuit board structure with a microstripline 64 on one
side, an insulating intermsdiate layer 66, and a conductive
plane 68 on the opposite side, the second side. The first
power applicator 26 may then be soldered to the
microstriplin2 64, while being braced by th0 circuit board
material. The second power appl~cator 58 may be slmllArly
electrically coupl~d to a ~econd m~crostripline connection,
whlle al50 being mechanically ~upported by the circuit board
material. The micro~tripline connectlons may lead back
throu~h circuit patterns, such a~ a balun~ (not ~hown) to a
power source (not hown) as is known in the art. The
preferred circuit allows power transmission to the two power
applicators with the vol~age~ in each power applicator 180
out of pha~e with the other.
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93-1-445 -11 PATENT
In a working example, the lamp cap~ule was made of
quartz, and had an outside diameter of 4.0 millime~er~, a
wall thicknes~ of 1.0 millimeters, an inside dlameter of 2
millimeter~, and an in~ide length of about 10.0 millimeters.
The enclosed volume was about 0.03 cubic centim~ter~. The
ends were closed to have approximately hemispherical ~hape~
and had a tubular rod extended axially ~rom one end. The
tubulax exten~ion had an outside diameter of 1.8
millimeters, an in~ide diameter of 1.0 millimeter~, and a
length of about 20.0 mlllimeters. The first power
applicator was formed a~ a thin, flat, elon~ated, nickel
foil rectangle. The foil was 0.25 millimeter~ (0.01 inch~
thick. One end of the rectangle was spun pr2~sed with a
hemispherical tool to form a deep dimple, or concave wall.
The cavity was 5.0 millimeters in diamet~r. An axial
through hole was drilled through the middle of the concave
wall, and had a diameter of 2.25 millimeter~, ~lightly
larger than the outside diameter of the tubular exten~ion.
At about 1.0 millimeters from the rim of the formed cavi~y,
the foil tab wa~ bent at a right angle to parallel the
cavity axl~, in the directlon away from the cavity opening.
The bent right angl~ portion o~ the foil provided a ~upport
staAd (foot), and solder point for the form~d Aemlspher$cal
ravity. ~ notched circuit board, with micro~tripline
circuitry, provided the mechanical ~upport and electrical
connection for thQ fir3t power applicator. ~ ~imilar second
power applicator, wi~h a center through hole, was formed for
the second end of the lamp capsule. The two power
applicator~ were then thin walled, and still self ~tanding.
The two power applicators were positioned ad~acent the lamp
capsule with the tubular extenYion passing through the axial
through hole. The feet of ths two fir3t power applicator~
were ~oldered to the microstripline circuitry of the circuit
board to thereby receive the power to be directed to the
lamp caps~le. ~he tab~ of the power applicator~ were formed
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D 93-1~445 -12- PATENT
to have approximately the ~ame widths and thicknesses as the
micro~tripline had. A ceramic V-block was attached to the
circult board, and a bead of silicone rubber wa~ placed in
the V of the support block. The ~ubular exten~ion wa3
placed across the V-block, and a second bead of ~ilicone
rubber was place on top of the tubular exten~1on in the V-
block. The tubular exten~ion positioned by the V-block then
collinearly aligned the enclosed cavity and the fir~t power
applicator. ~he power applicator~ recelved radio frequency
power from the ~icrostripline circuitry to thereby power the
lamp capsule. The applied power wa~ ~upplied through a
micro~tripline structure at 2.45 GHz. Similar devLces have
been operated at 915 Mhz, and still other frequencies may be
u~ed. The reduction of the metal mas3 of the power
applicator reduced the stray capacitances of the power
applicators, making the power appl~cator easier to tune to
the lamp operating impedance. The th~n foil al~o reduced
the thermal conductivity of the power applicator. While
heavier, solld metal cup applicators tended to float on a
pool of ~oft or even molten solder after contlnued
operation, le~ heat was conducted lnto the solder ~olnt by
the thi~ walled applicator~, go the hin walled applica~ors
stayed ~n place. ~he disclo~ed dimen~ion~, configurations
and embodlment~ are as example~ only~ and other ~uitable
configurations and relatlons may be us~d to implement the
inv~ntlon.
The operatlon of the lamps was also found to be more
l~othermal, than with heavy end cup structure~. For
example, oth~r field applicators u~ed with a 4 millimeter
diameter lamp and operated at 2.45 GHz showed an end to end
temperature difference of 65 to 70 Celsiu~ and a top to
bottom temperature difference of about 50 Celsius. With
the thln walled power applicators, the end to end
~emperature difference was ahout 55 Celsius and the top to
bottom difference was about 7 Cel~ius. Being more
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D 93-1-44S -13- PATENT
i~othermal contributed to the stabili~y of the discharge,
and to a more uniform lumlnance along the arc. The close to
isothermal operation give~ a better condensate distribution
and mora light output. The nearly lsothermal opera~ion 1
thought to result ~rom power being delivered to the
di~charge more uniformly.
In operation, the lamp was found to have le~s flicker
and similar distortion of the arc due to the reduced
capacitive affects. The power applicator~ did not over
heat, and did not change poYition due to ~older softening.
The lamp capsule with the thin walled power applicator wa~
found to produce 124 lumen~ per watt, while a similar lamp
capsule, with a coil type applicator was found to produce 88
lumens per watt. Thl~ amounted to a forty percen~ increase
in efficiency. The greater lumen efficiency 1~ thought to
b~ due to the improved capacltive coupling to the discharge
lamp capsule.
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