Compact lighting unit having a convoluted fluorescent lamp with integral mercury-vapor pressure-regulating means, and method of phosphor-coating the convoluted envelope for such a lamp

A fluorescent lamp having a multi-U-bent tubular envelope of convoluted configuration is combined with circuit means, a translucent protective cover and a base module to provide an efficient lamp unit of high brightness and long life that is compact enough to be used as a replacement for incandescent lamps in fixtures designed for residential and commerical lighting installations. Various spatial arrangements for including the ballast and starter components of the energizing circuit as integral parts of the compact lamp unit, despite the stringent space limitations, and also venting the cover and base module to provide convection cooling of the convoluted fluorescent lamp and the other electrical components are also disclosed. Tubulations provided on U-bent portions of the lamp envelope serve as phosphor-drainage means during lamp manufacture and are subsequently tipped off to form mercury-condensation chambers within the finished lamp that regulate the mercury-vapor pressure during lamp operation. The vapor-pressure regulating tubulations are so located relative to the vent openings in the lamp unit that they are exposed in the cool air which circulates through the lamp unit when the latter is energized and in use.

BACKGROUND OF THE INVENTION 
This invention relates to electric lamps and has particular reference to a 
compact fluorescent lamp unit that is adapted for use as a direct 
replacement for incandescent type lamps in lighting fixtures employed for 
residential and commercial illumination, and to a convoluted fluorescent 
lamp component for such a compact lamp unit. 
Fluorescent lamp units having integral circuit and base components which 
permit the unit to be screwed into and operated in the sockets of lighting 
fixtures that are designed for incandescent type lamps are generally well 
known in the art. A lamp unit of this type having a cylindrical envelope 
that contains concentric annular partitions (or which is made from tubing 
that is bent upon itself to provide a U-shaped bulb) is disclosed in U.S. 
Pat. No. 3,551,736 granted Dec. 29, 1970 to Doehner. As disclosed in FIG. 
5 and at lines 24-30, column 2 of this patent, if a tubular U-shaped bulb 
is used as the envelope it may be additionally twisted into spiral shape 
or redoubled on itself to provide a generally M-shaped envelope. A lamp 
assembly having adapter means which accommodates a conventional straight 
tubular fluorescent lamp and contains a ballast transformer that is part 
of a threaded base member which permits the lamp assembly to be screwed 
into an incandescent lamp socket is disclosed in U.S. Pat. No. 3,815,080 
granted June 4, 1974 to F. Summa. 
According to a more recent development, a screwing type fluorescent lamp 
bulb is provided with integral ballast means that is disposed in 
telescoped relationship with an envelope that defines a discharge space of 
flat toroidal shape of similar configuration. A lamp unit of this type is 
disclosed in U.S. Pat. No. 3,953,761 granted Apr. 27, 1976 to T. Giudice. 
Another fluorescent lamp assembly of this general type having a tapered 
cylindrical envelope of molded glass that defines a helical-shaped 
discharge channel and accommodates a ballast component is described in 
U.S. Pat. No. 3,899,7l2 issued Aug. 12, 1975 to H. Witting. 
An electrodeless fluorescent lamp unit of the screw-in type that is 
energized by high frequency energy produced by a self-contained 
radio-frequency oscillator and ferrite core is disclosed in U.S. Pat. No. 
3,521,120 granted July 21, 197O to J. M. Anderson. 
Electric discharge lamps having tubular envelopes which are bent into 
various shapes to provide concentrated sources of light are also generally 
well known in the art. A sodium-vapor discharge lamp of double-ended 
construction having an envelope formed from a vitreous tube that is folded 
or bent upon itself twice to provide three straight segments that are 
disposed in triangular-spaced relationship is disclosed in British Patent 
No. 854,745 published Nov. 23, 196O (FIGS. 3 and 4 embodiment). A luminous 
discharge tube designed for advertising and display purposes (or for use 
as a beacon light) and having thimble-like electrodes and an envelope 
which is formed from glass tubing bent upon itself eleven times to provide 
a corresponding number of conjoined U-shaped sections is disclosed in U.S. 
Pat. No. 1,898,615 granted Feb. 21, 1933 to Byrnes. A plug-in type 
discharge lamp having a tubular envelope that is bent upon itself three 
times to provide a multi-segment envelope which is disposed within a 
heat-conserving double-walled enclosure is disclosed in U.S. Pat. Nos. 
2,001,511 and 2,200,940 granted to Uyterhoeven et al. 
Fluorescent lamps having "three-dimensional" type envelopes that are formed 
by coupling several arcuate lamp components together or interconnecting 
several straight tubular bulbs in "bundled" configuration are also known 
in the art and are disclosed in U.S. Pat. No. 2,652,483 (Laidig et al.) 
and U.S. Pat. No. 3,501,662 (Plagge), respectively. 
The use of an exposed tubulation on the envelope of a fluorescent lamp 
which provides a "cool" chamber or region within the lamp that controls 
the mercury-vapor pressure during operation and thus prevents loss of 
light output due to excessively high vapor pressure is per se known in the 
art. Fluorescent lamps having such tubulations are disclosed in U.S. Pat. 
Nos. 3,331,977 (Wainio) and 3,511,405 (Plagge). 
SUMMARY OF THE INVENTION 
While it has long been realized in the prior art that the physical size of 
a fluorescent lamp could be decreased to provide a brighter light source 
by using partitioned or bent multi-segment tubular envelopes, lamp units 
employing such concepts were impractical from a commercial standpoint 
since they required special electrode and seal structures and/or envelopes 
that were very difficult and expensive to make on a mass production basis. 
In many cases the envelopes were also so configured that the physical 
dimensions of the lamp unit which contained integral circuit components 
and was fitted with a screw-in type base component were too large to 
permit the lamp unit to be used in lighting fixtures and sockets designed 
for incandescent lamps. Another serious shortcoming of the prior art 
screw-in type fluorescent lamp units was that, when they were made small 
enough to fit into incandescent lamp fixtures and sockets, they were 
unable to generate a sufficient amount of light to provide illumination 
comparable to that obtained without an incandescent lamp, or to produce 
such illumination without radio-frequency interference and at a level of 
efficiency that would justify the added initial expense of such lamp 
units. 
Bending the tubular envelopes of fluorescent lamps into convoluted form to 
reduce the physical size of the lamp also created a manufacturing problem 
in that it was very difficult to coat the inner surfaces of such 
convoluted envelopes with a uniform layer of phosphor. Due to the compact 
size of such fluorescent lamps, proper control of the mercury-vapor 
pressure within the operating lamp was also difficult to achieve, 
especially when the lamp was placed within a protective housing and/or 
operated at high power loadings to increase its light output to a desired 
level. 
The foregoing manufacturing problems and commercial disadvantages are 
overcome in accordance with the present invention by providing a screw-in 
type lamp unit which contains a fluorescent lamp that has a tubular 
envelope of tridimensional convoluted configuration. The envelope is of 
multi-U-bent construction and so shaped that it not only permits 
conventional stem and electrode components to be employed but physically 
accommodates circuit means and a threaded base in such a manner that the 
resulting lamp unit is small enough to be used in sockets and lighting 
fixtures designed for incandescent type lamps and produces light of an 
intensity comparable to that obtained from such incandescent lamps. The 
envelope configuration is also of such character that it provided an 
integral "cooling" chamber for mercury-vapor pressure regulation and means 
for avoiding phosphor-coating difficulties. 
Since the fluorescent lamp component employed in the new lamp unit is 
basically a conventional straight tubular fluorescent lamp that has been 
bent into convoluted form, it employs the same components and basic 
technology used to manufacture standard type fluorescent lamps and thus 
can be made at a reasonable cost and will have the excellent light output 
and efficacy, as well as the long useful life, exhibited by conventional 
fluorescent lamps now being marketed and in use. The improved fluorescent 
lamp unit provided by the present invention accordingly has the requisite 
physical compactness, light output, and high level of quality and 
performance needed to make it a practical and energy-conserving substitute 
for incandescent type lamps. 
In accordance with one embodiment, the convoluted fluorescent lamp is of 
triple-U-bent construction and the tubular leg segments of the U-shaped 
sections of the envelope are arranged in spaced quadrangular columnar 
relationship to provide a central opening that accommodates an elongated 
choke ballast and thus reduces the size of the lamp unit without 
materially decreasing its light output. In another embodiment, the ballast 
and starter components are located within the base structure to provide a 
fluorescent lamp unit that is more elongated but of smaller width 
dimension. Integral means for facilitating the phosphor-coating operation 
and subsequently defining a vapor-pressure regulating "cool" chamber for 
condensed mercury within the finished lamp is provided and comprises a 
tubulation that extends outwardly from the U-bent portion (or portions) of 
the convoluted envelope to permit rapid drainage of the phosphor paint, 
and is subsequently sealed off to form a "cooling" tip or appendage. 
Experimental fluorescent lamp units embodying the present invention and 
containing integral ballast and starter components which permit the units 
to be operated from conventional 120 volt alternating-current power 
outlets have outputs in the order of 1,000 lumens and system efficiencies 
of approximately 40 lumens per watt and are compact enough to be used in 
table lamps and similar lighting fixtures that are employed in homes and 
offices and were specifically designed for incandescent type lamps. 
Another important feature of the present invention is the use of a 
protective cover or housing which diffuses the intense light from the 
convoluted fluorescent lamp in a pleasing manner and has vent openings 
that cooperate with similar openings in the base structure to permit air 
to circulate through the lamp unit past the vapor-pressure regulating 
appendage of the envelope during operation and thus dissipate heat 
generated by the lamp and circuit components. The resulting convection 
cooling of the operating lamp unit and envelope appendage is very 
advantageous since it prevents the fluorescent lamp and integral circuit 
components from becoming overheated during operation and thus becoming 
less efficient, despite the compactness of the lamp unit. Such cooling 
also provides the option of using convoluted fluorescent lamp components 
that have higher light outputs, in the order of 2,000 lumens for example.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
While the present invention can be advantageously employed in various kinds 
of lamp units and assemblies that are suited by virtue of their small 
physical size and high brightness for lighting homes or offices, it is 
particularly adapted for use in conjunction with lamp units that have 
screw-in or bayonet type bases and employ low-pressure type discharge 
lamps such as fluorescent lamps as the light source and it has, 
accordingly, been so illustrated and will be so described. 
A compact fluorescent lamp unit 12 embodying the invention is shown in FIG. 
1 and consists of three basic components--namely, a fluorescent lamp L 
having a tubular envelope 14 of convoluted configuration which provides a 
concentrated light source of high efficacy and brightness (as hereinafter 
explained), a light-transmitting housing such as a cover C that 
protectively encloses the fluorescent lamp L, and a base structure B that 
is coupled to the sealed ends of the lamp envelope 14 and holds the 
fluorescent lamp L in assembled relationship with the cover C and the 
various integral components of a circuit which permits the lamp unit 12 to 
be operated on an alternating-current power source. 
As will be noted, in this embodiment the circuit means comprises an 
elongated ballast component 15 (that is located in the space between the 
U-bent sections of the convoluted fluorescent lamp envelope 14) and a 
conventional condenser 16 and starter 17 that are connected with the 
ballast 15 and the lamp electrodes in the usual manner. The base structure 
B has a cup-shaped portion 18 that accommodates and contains the sealed 
ends of the fluorescent lamp envelope 14 as well as the condenser 16 and 
starter 17. The base structure B is terminated by a suitable electrical 
connector component, preferably a threaded base member 20 having the usual 
insulator 21 and end contact 22. The threaded base member 20 is of a type 
that will fit the threaded sockets designed for incandescent type lamps so 
that the single-ended fluorescent lamp unit 12 can be screwed into and be 
operated in such sockets. 
As shown more particularly in FIG. 2, the envelope 14 of the fluorescent 
lamp L comprises a vitreous tube that is bent in a manner such that it has 
four substantially straight leg segments 24, 26, 27, 28 that extend in the 
same direction and are joined by three U-bent segments 29, 30, 31. The 
U-bent segments are of such curvature and so oriented that the tubular leg 
segments are disposed in quadrangular columnar array and spaced from one 
another. The leg segments and U-bent segments accordingly form three 
conjoined U-shaped envelope sections that are located in three different 
planes and define a single discharge channel of serpentine configuration 
that is terminated by leg segments 24, 26. The envelope 14 is, 
accordingly, of triple-U-bent tridimensional form and very compact. 
As shown, the U-bent segment 31 which constitutes the medial portion of the 
convoluted envelope 14 and is adjacent to the terminal leg segments 24, 26 
has a tipped-off segment 32 of a glass tubulation that is used to drain 
phosphor paint from the envelope during the phosphor-coating operation and 
ensure that the medial U-bent section is coated with a uniform layer of 
phosphor material. Insofar as the compact fluorescent lamp L operates at 
rather high loading, the tipped-off segment 32 affords an additional 
advantage in the finished lamp pursuant to the invention since it defines 
a cavity inside the envelope 14 that serves as a "cool spot" and thus 
functions as a reservoir for-condensed mercury that controls the mercury 
vapor pressure during lamp operation. The leg segments 24, 26 extend 
beyond the medial U-bent segment 31 and are hermetically sealed by 
conventional stem components 33, 34 which include the usual tungsten-coil 
electrodes 35, 36 that are coated with suitable electron-emission material 
and connected to suitable conductors such as paired lead-in wires 37, 38 
that extend through the respective stems and beyond the sealed ends of the 
envelope 14. Each of the stems have a sealed-off remnant 39, 40 of an 
exhaust tubulation which permits the convoluted phosphor-coated envelope 
14 to be evacuated and then charged with a suitable fill gas and dosed 
with mercury in accordance with standard lamp-making practice. 
If desired, non-tubulated type stems can be used and the evacuation, 
gas-filling and mercury-dosing operations can be done through the 
tubulation which extends from U-bent segment 31. 
As will be noted in FIGS. 1 and 2, the sealed legs 24, 26 of the envelope 
14 extend beyond the medial U-bent segment 31 and are disposed in 
side-by-side paired relationship on the same side of such segment. These 
are important structural features since they provide an unobstructed space 
or central opening that extends upwardly from the base structure B into 
the triple-U-bent envelope 14 between the leg segments 24, 26, 27, 28, as 
well as a smaller space below U-bend 31 adjacent the sealed ends of the 
legs 24, 26. As illustrated in FIG. 1, the provision of such spaces 
permits the elongated ballast component 15 to be placed in telescoped 
nestled relationship with the convoluted lamp envelope 14 and provides 
room for recessing the condenser 16 and starter 17 within the base 
structure B adjacent the sealed ends and beneath the medial U-bent segment 
of the envelope. The circuit components thus constitute integral parts of 
the compact lamp unit 12 and are located within its physical confines. 
Since the tubular leg segments 24, 26, 27, 28 of the triple-U-bent envelope 
14 extend in the same direction and are disposed substantially parallel to 
one another in quadrangular and columnar-spaced array, the overall 
configuration of the fluorescent lamp L is such that it is generally 
cubical or tetrahedral in character. When the lamp L is energized it thus 
constitutes a three-dimensional source of light which, while very compact, 
still has a single discharge channel that is about four times the height 
of the envelope 14 and thus permits the lamp to be operated efficiently at 
a voltage and current compatible with the electrical power supplied to 
homes and offices. 
As indicated in FIG. 1, the width dimension w.sub.1 of the lamp unit 12 is 
governed by the diameter of the circular cup-shaped portion 18 of the base 
structure B required to accommodate the cylindrical protective cover C and 
is thus only slightly larger than the width of the convoluted lamp L. The 
height dimension h.sub.1 of the lamp unit 12 is determined by the combined 
lengths of the convoluted lamp L and base structure B. Due to the 
triple-U-bent configuration of the lamp L and the interfitting of the 
envelope 14 with the circuit components and cup-shaped portion 18 of the 
base structure B, the height dimension h.sub.1 of the lamp unit 12 is 
drastically reduced. 
While the convoluted lamp envelope 14 can be made by joining three U-bent 
sections of vitreous tubing together, it is preferably formed from a 
single piece of lead glass tubing of the kind used for conventional 
fluorescent lamp bulbs. The glass tubing is bent at the proper points to 
form the U-bends and is subsequently coated with phosphor and provided 
with stem assemblies, etc., in the usual manner. The envelope 14 is 
charged with a suitable ionizable medium such as a fill gas and a measured 
dose of mercury that are introduced into the envelope through the exhaust 
tubes of the stems 33, 34 before they are tipped-off and sealed. A 
suitable fill gas is argon at a pressure below about 10 Torr, and 
preferably about 3 Torr. The mercury dosage will vary according to the 
physical size of the lamp L and the power loading at which it is operated 
but is sufficient to provide mercury vapor at a partial pressure of from 
about 6 to 10 millitorr when the lamp is operated at its rated wattage, 
and maintain, the mercury vapor pressure at this level within the lamp 
throughout its useful life. 
While any suitable phosphor (or mixture of phosphors) can be used to form 
the luminescent coating deposited on the inner surface of the convoluted 
tubular envelope 14, in lighting applications where optimum visual clarity 
and color rendition of the illuminated objects or area are required, 
phosphor coatings which contain a blend of three phosphors that emit 
visible radiations in three different selected regions of the spectrum 
(specifically, the wavelength regions of about 450 nm, 540 nm and 610 nm) 
are desirably employed to provide a so-called "prime color" fluorescent 
lamp L, pursuant to the teachings of the W. A. Thornton in the article 
entitled "Luminosity and Color-Rendering Capability of White Light", 
Journal of the Optical Society of America, Vol. 61, No. 9 (September 
1971), pages 1155-1163. As a specific example, a suitable phosphor blend 
for a triple-U-bent fluorescent lamp having such an enhanced light output 
contains manganese-activated zinc silicate phosphor, europium-activated 
strontium chlorophosphate phosphor, and europium-activated yttrium oxide 
phosphor--all of which are well known to those skilled in the art. 
Alternatively, the envelope 14 can be coated with "Cool White" or "Warm 
White" halophosphate type phosphors (or any other kind of phosphor or 
phosphor mixtures) employed in conventional fluorescent lamps. 
As shown more particularly in FIGS. 3 and 4, the compact fluorescent lamp 
unit 12 is fabricated by first inserting the elongated ballast component 
15 in nestled position within the leg segments 24, 26, 27 and 28 of the 
convoluted envelope 14 and then connecting the ballast, condenser 16 and 
starter component 17 to the insulated lead wires 37, 38 and socket 
contacts in the manner illustrated in FIG. 3 (a separate insulated 
conductor 41 being employed to connect one side of the ballast 15 with the 
shell contact of the screw base 20). The end contact 22 of the base 20 is 
connected by one of the lead wires 37 directly to one of the lamp 
electrodes so that the ballast 15 is connected in series with the 
electrodes. The condenser 16 and starter 17 are connected in the usual 
manner to start the fluorescent lamp L in preheat fashion when the lamp 
unit 12 is connected to an alternating-current power source. 
The convoluted fluorescent lamp L and its attached circuit components are 
then mounted in upstanding position within the cup-shaped end portion 18 
of the base structure B, secured to the latter by suitable means (not 
shown) such as cement or an interlocking support member that couples the 
sealed legs 24, 26 of the envelope 14 to the base structure, and the 
conductors 37 and 41 are fastened to the base contacts by soldering or the 
like. The resulting subassembly (consisting of the convoluted fluorescent 
lamp L, connected circuit components and coupled base structure B) is then 
inserted into the protective cover C until the rim of the cover is firmly 
seated within and frictionally held by (or otherwise secured to) the 
cup-shaped end 18 of the base structure B. 
Since the convoluted fluorescent lamp L and integral circuit components are 
confined within a very small space, care must be taken to prevent the 
operating lamp unit 12 from overheating since this would cause the lamp 
efficacy to decrease and could create a potential safety hazard. These 
problems are avoided in accordance with the invention by providing a 
plurality of vent apertures 42 (see FIGS. 3 and 4) that are spaced along 
the bottom wall of the cup-shaped portion 18 of the base structure B, and 
by utilizing a protective cover C which consists of a cylindrical sleeve 
having a tapered end 43 with a central opening 44, which opening (in 
conjunction with the vent apertures 42 in the base structure) permits the 
free circulation of air through the operating lamp unit 12 in chimney-like 
fashion. The resulting "convection cooling effect" dissipates heat 
generated by the fluorescent lamp L and ballast component 15 and ensures 
that they do not become too hot. 
As shown in FIG. 4, the medial U-bent segment 31 of the convoluted envelope 
14 is located almost directly above the vent apertures 42 in the 
cup-shaped portion 18 of the base structure B. The circulating current of 
cool air thus flows past the tipped-off segment 32 which depends 
downwardly from U-bent envelope segment 31 and inherently provides the 
proper operating conditions for the mercury-condensation cavity or chamber 
defined by the seal tip 32. 
In order to minimize light losses, the ballast component 15 is desirably 
covered by a sheath 45 (shown in FIGS. 3 and 4) of suitable white or 
light-colored insulating material such as a heat-resistant tape or 
plastic. Of course, a metal case can also be used as the light-reflective 
sheath instead of the tape or plastic, providing due care is taken to 
insulate the ballast from the metal case. As will be noted in FIG. 4, the 
ballast component 15 desirably comprises a so-called "finger" type choke 
ballast that has an iron core 46 which is overwound with insulated wire 47 
and encased in the light-reflective sheath 45. 
The cup-shaped support portion 18 of the base structure B can be formed 
from suitable metal such as aluminum, providing the conductors which 
connect the circuit components to the lamp electrodes are properly 
insulated to prevent short circuits. The screw-in base member 20 is 
preferably of the "medium" screw type and can be secured to the bottom 
wall of the cup-shaped support 18 with suitable fasteners, or it can be 
formed as an integral part of the cup-shaped support 18 by stamping the 
cup-shaped member and base shell from a single piece of metal (or by 
molding it from suitable plastic). 
The protective cover C can be made of glass, heat-resistant plastic or 
other suitable transparent or translucent material that will not absorb 
the light rays generated by the fluorescent lamp L. If transparent 
material is used, it may be made translucent by a white light-diffusing 
coating (or other means) to reduce glare from the bright surface of the 
triple-U-bent lamp L and to provide a more uniform and pleasing lighted 
appearance. 
The starter component 17 is of the conventional "glow lamp" type that is 
permanently wired in place. However, it could be made in the form of a 
fuse-like component and mounted within the base structure B in such a 
manner that it may be readily removed and replaced as necessary by a 
twist-lock action. The condenser 16 is of the miniature wafer type and is 
connected in the circuit in such a fashion that it eliminates or minimizes 
radio interference during lamp starting. 
ALTERNATIVE COMT LAMP UNIT EMBODIMENT (FIGS. 5-7) 
An alternative compact lamp unit 12a, shown in FIGS. 5-7, employs a ballast 
component that is "built into" the base structure B.sub.a and thus 
provides a lamp unit which is slightly longer but smaller in diameter or 
width dimension than the embodiment just described. 
As illustrated in FIGS. 5 and 6, the ballast component 15a according to 
this embodiment is of truncated cylindrical shape rather than elongated 
slender configuration and is located within a similarly shaped extension 
48 that protrudes from the bottom of the cup-shaped portion 18a of the 
base structure B.sub.a and is joined to the threaded base member 2Oa. The 
ballast 15a is again preferably of the choke type and consists of an iron 
core (not shown) and a wire winding 47a that are encased in a suitable 
sheath or covering 45a of nonconductive material (see FIG. 6). The wall of 
the cylindrical extension 48 is spaced from the ballast component 15a and 
is provided with a series of laterally extending vent openings 49 which 
permit air to circulate freely around the ballast component and through 
the base structure B.sub.a when the lamp unit 12a is energized and in use. 
As will be noted in FIG. 6, the triple-U-bent fluorescent lamp L.sub.a is 
identical to that employed in the previous embodiment except that the 
U-bent segments 29a, 3Oa, 31a have a smaller radius of curvature and thus 
reduce the spacing between the tubular leg segments 24a, 26a, 27a, 28a. 
The condenser 16a and starter 17a are connected by the insulated lead-in 
wires 38a, 37a to the ballast component 15a and lamp electrodes 35a, 36a 
and the condenser and starter components are disposed within the 
cup-shaped end 18a of the base structure B.sub.a (in the space beneath the 
medial U-bend 31a alongside the sealed legs 24a, 26a of the envelope 14a 
as in the previous embodiment). The protective cover C.sub.a is modified 
and consists of a cylindrical sleeve (of translucent or transparent 
material) that is open at both ends and is seated in and gripped by the 
circular cup-shaped portion 18a of the base structure B.sub.a. 
As indicated in FIGS. 5 and 7, the placement of the ballast component 15a 
within the base structure B.sub.a increases the overall length h.sub.2 of 
the lamp unit 12a but permits a "tighter bundling" of the tubular leg 
segments of the convoluted envelope 14a with a resultant decrease in the 
width dimension w.sub.2 of the lamp unit, compared to the corresponding 
dimensions of lamp unit 12. 
As in the previous embodiment, heat generated by the triple-U-bent 
fluorescent lamp L.sub.a and the integral circuit components is dissipated 
by convection cooling produced by the air which circulates through the 
energized unit 12a through the vent openings 42a and 49 in the base 
structure B.sub.a and out of the open end of the tubular protective cover 
C.sub.a. Such convection cooling directs a current of air from outside the 
lamp unit 12a through the base vent apertures 42a, 49 into the space 
occupied by the U-bent envelope segment 31a and "cooling" tip segment 32a 
since the latter is located in very close proximity to the apertures 42a. 
ADDITIONAL ALTERNATIVE LAMP UNIT EMBODIMENT (FIG. 8) 
From the standpoint of the consumer, it would be very advantageous 
financially to be able to remove and replace only the convoluted 
fluorescent lamp component of the lamp unit and retain the base structure, 
protective cover and circuit components as permanent parts of the lighting 
fixture in which the lamp unit is used. A lamp unit 12b which provides 
this cost advantage is shown in FIG. 8 and will now be described. 
As will be noted, the fluorescent lamp L.sub.b has the same triple-U-bent 
type tubular envelope 14b as in the previous embodiments except that the 
sealed ends of the leg segments 24b and 26b are fitted with small plug-in 
type base members 50, 52. These base members have protruding contact 
elements such as rigid pins 51, 53 that are adapted to be inserted into 
aligned receptacles of a suitable socket member (not shown) located within 
the cup-shaped portion 18b of the base structure B.sub.b. The resulting 
plug-in type electrical connection of the lamp component L.sub.b and the 
base structure B.sub.b permits the consumer to simply remove the cover 
C.sub.b and unplug and remove the lamp component (when it becomes 
inoperable or has reached the end of its useful life) and then plug in a 
new lamp component. Hence, the lamp unit 12b can be readily relamped by 
the user and the waste and added expense associated with discarding the 
entire lamp unit each time the fluorescent lamp "burns out" is avoided. 
In order to rigidify the lamp envelope 14b and permit it to be handled 
without breaking, the plug-in base members 50 and 52 are desirably secured 
to a transverse panel member 54 of suitable nonconductive material. In 
addition, this panel member can be coupled to the medial U-bent segment 
31b of the envelope by a suitable brace means such as a wire strut 56 that 
has a hooked end 57 which is slipped over and grips the medial U-bent 
segment. The panel member 54 is also desirably shaped to nestingly engage 
the cup-shaped end 18b of the base structure B.sub.b and seat against a 
part thereof in such a manner as to stabilize the fluorescent lamp L.sub.b 
in its upright assembled position relative to the base structure. 
While the sealed ends of the convoluted tubular envelope 14b have been 
provided with pin-type base members, it will be appreciated by those 
skilled in the art that other kinds of bases and electrical coupling means 
can be employed which will permit the fluorescent lamp L.sub.b to be 
easily removed from the lamp unit 12b as a separate part by the user and 
replaced by a new lamp component. 
In contrast to the previous embodiments, the starter and condenser 
components (not shown) are wired to the ballast component 15b and the 
plug-in socket means (also not shown) so that they constitute permanent 
integral parts of the base structure B.sub.b. Alternatively, the starter 
and condenser could be mounted on top of panel member 54 and connected to 
the lamp lead-in wires in an appropriate manner so that all three of these 
connected components comprise a replaceable assembly that can be unplugged 
from the lamp unit. Of course, if the starter and condenser were connected 
to the lamp leads in the proper fashion, then only two pin contacts rather 
than four would be required. 
As will also be noted in FIG. 8, the ballast component 15b is housed within 
a cylindrical extension 48b of the base structure B.sub.b so that it also 
constitutes a permanent integral part of the base structure. Vent openings 
42b and 49b in the base structure B.sub.b permit free circulation of air 
around the ballast component 15b, through the cylindrical jacket or cover 
C.sub.b past the triple-U-bent lamp L.sub.b and its vapor-pressure 
regulating tip segment 32b and then out through the open end of the cover 
(when the lamp unit 12b is burned in a base-down position). The base 
structure B.sub.b is terminated by a threaded base member 20b having 
exposed contacts so that lamp unit 12b is once again of single-ended 
construction and adapted to be screwed into an incandescent-type lamp 
socket. 
ALTERNATIVE COVER EMBODIMENTS (FIG. 9-11) 
The compact discharge lamp units of the present invention can be fitted 
with various types of protective jackets or covers in addition to those 
previously described. For example, the light-transmitting cover can be 
closed at one end by a dome that is provided with suitable vent openings 
to permit the free passage of air. A cover C.sub.c having these features 
is illustrated in FIG. 9 and consists of a light-transmitting sleeve of 
tubular or cylindrical shape that is terminated by a dome 58 having a 
plurality of circular apertures 5g that are distributed in a predetermined 
spaced pattern. 
A modified domed-end type protective cover C.sub.d that is specifically 
designed for a compact lamp unit having an upstanding elongated ballast 
component disposed in nestled relationship within the legs of a 
triple-U-bent lamp is shown in FIG. 10. As will be noted, this cover 
consists of a cylindrical sleeve that is also terminated by a domed end 60 
which, in addition to a plurality of spaced apertures 61, also has a 
central opening 62 that communicates with a longitudinally-extending 
passageway 63 which is defined by a coaxially disposed tube 64 that is 
joined to and merges with the domed end 60. The axial passageway 63 is 
located to accommodate the elongated ballast component of the lamp unit 
and is dimensioned to fit between the U-bent sections of the triple-U-bent 
envelope when the cover C.sub.d is secured to the base structure of the 
lamp unit. The passageway 63 is also slightly larger than the ballast 
component and thus serves as a "chimney" that enables air to circulate 
freely through the lamp unit from the vent openings in the base structure, 
around and along the ballast component and then through the central 
opening 62 in the domed end 60 of the cover C.sub.d. The U-bent sections 
of the convoluted envelope are disposed in the annular space between the 
coaxial tube 64 and cylindrical wall of the cover C.sub.d and are thus 
exposed to air which circulates through this space from the base structure 
of the lamp unit and through the dome apertures 61. 
Another form of domed cover C.sub.e is shown in FIG. 11 and consists of a 
light-transmitting sleeve of tubular or cylindrical configuration having a 
domed end wall 65 that is provided with a plurality of spaced 
circumferentially-extending vent openings of slot-like configuration. The 
overlying portions of the cover C.sub.d are flared outwardly and form 
louvers 67 that serve as protective shrouds or hoods for the vent 
openings. 
SPECIFIC EXAMPLES 
A better appreciation of the compactness and advantageous energy-conserving 
characteristics of the fluorescent lamp units provided by the present 
invention will be obtained from the following specific examples of two 
prototype units that have been made and tested. 
A compact fluorescent lamp unit of the type shown in FIGS. 1-4 having a 
nested "finger" type choke ballast and a medium screw-type base was made 
by bending a tubular fluorescent lamp 20 inches (50.8 cms.) long and O.69 
inch (17.5 mm.) in outside diameter into triple-U-bent configuration so 
that the overall length of the consulted lamp was approximately 51/2 
inches (14 cms.) and its width approximately 21/4 inches (5.7 cms.). The 
spacing between the medial U-bent section and sealed end legs of the 
envelope was about 7/8 inch (22.2 mm.) and the end legs were spaced about 
1/2 inch (12.7 mm.) apart. An elongated "finger" choke ballast measuring 
about 3/4".times.3/4".times.4" (19 mm..times.19 mm..times.101.6 mm) was 
inserted in nestled relationship within the three U-bent sections of the 
fluorescent lamp and connected to the lead wires and a conventional type 
"glow-lamp" starter and wafer condenser used for standard preheat type 
fluorescent lamps. 
The resulting subassembly was mounted on a 2 13/16 inch diameter (7.14 
cms.) support member of the type shown in FIGS. 1 and 3 having 1/4 inch 
(6.4 mm.) vent apertures and a medium screw-type base. A protective cover 
consisting of a frosted glass cylinder approximately 51/2 inches (14 cms.) 
long and 23/4 inches (7 cms.) in diameter having a central opening of 13/4 
inches (4.44 cms.) was slipped over the convoluted fluorescent lamp and 
seated in the cup-shaped support portion of the base structure. 
The completed fluorescent lamp unit had an overall width dimension w.sub.1 
of 2 13/16 inches (7.14 cms.) and an overall height h.sub.1 of about 7 
inches (17.8 cms.). The triple-U-bent envelope was coated with "Cool 
White" halophosphate type phosphor and the lamp unit, when operated at 120 
volts input at a current of 345 milliamperes, had an output of 1,000 
lumens and a system efficacy (that is, the fluorescent lamp component in 
combination with the choke ballast) of approximately 37 lumens per watt. 
The total power consumption of the lamp unit was approximately 27 watts 
(about 20 watts in the fluorescent lamp component and about 7 watts in the 
ballast). 
A second prototype fluorescent lamp unit made in accordance with the FIGS. 
5-7 embodiment contained a triple-U-bent fluorescent lamp which was formed 
from an envelope 20 mm. in diameter and 43.1 cms. long. The convoluted 
lamp component had an overall length of 13 cms., a width of 5.1 cms. and 
the legs of each of the U-bent sections were spaced 11 mm. apart. The lamp 
was mounted on a base structure having a cylindrical extension that housed 
a cylindrical choke ballast, the "glow-lamp" starter and the wafer 
condenser. The base structure had a circular cup-shaped end approximately 
27/8 inches (7.3 cms.) in diameter and a cylindrical open-ended cover of 
frosted glass having a diameter of about 23/4 inches (7 cms.) and an 
overall length of 51/2 inches (14 cms.) was secured to the base structure. 
The resulting lamp unit had an overall width dimension w.sub.2 of 
approximately 27/8 inches (7.3 cms.) and an overall height dimension 
h.sub.2 of approximately 81/8 inches (20.6 cms.). When the lamp unit was 
operated at 120 volts input and 345 ma, it had a light output of 
approximately 960 lumens and a system efficacy of 40 lumens per watt. 
While life tests on triple-U-bent fluorescent lamps of the type employed in 
the compact lamp units of the present invention have not been completed, 
the lamps should have useful lives in the order of 9,000 hours or so 
since, when mass-produced, they would be made with standard stem and 
electrode assemblies and utilize the wellknown phosphor coating 
compositions and other technology used to manufacture conventional 
fluorescent lamps of equivalent size (15 to 20 watt rating) that have 
nominal life ratings of such magnitude. 
In contrast, a standard 75 watt A19 type incandescent lamp produces about 
1,210 lumens at an efficacy of about 16 lumens per watt and has an average 
life (published) of only 850 hours. 
As will be apparent to those skilled in the art, the compact fluorescent 
lamp units of the present invention can employ triple-U-bent fluorescent 
lamps made from glass tubing of various diameters and lengths to provide 
lamp units having higher or lower wattage ratings and light outputs. The 
starting and/or operating circuits can also be made in the form of 
solid-state modules or components that are "built into" the base structure 
or mounted between the legs of the U-bent sections of the envelope to 
provide a new family of compact low-pressure discharge lamp units that can 
be advantageously used as cost-saving and energy-conserving replacements 
for incandescent-type lamps now employed for general lighting applications 
in homes and offices. The use of solid-state circuit means would be 
particularly advantageous in fabricating screw-in type lamp units having 
light outputs of 2,000 lumens or so since the miniaturized circuitry would 
still make it possible to keep the overall dimensions of such high-output 
lamp units within the limits required to permit the units to fit into and 
be used in table lamps and similar lighting fixtures designed for 
incandescent type lamps. 
Of course, if the ballast and other circuit components were physically 
separated from the fluorescent lamp and made part of a specially-designed 
lighting fixture (for example, if they were housed within the base of a 
table lamp or floor lamp), then step-up transformers, high-frequency 
converters and similar energizing means can be used to increase the 
efficacy of the system and make the lamp units per se even more compact 
and economical. In addition, the ballast component can be physically 
separated from both the discharge lamp unit and the lighting fixture by 
making the ballast a "pass-through" type that would be connected to and 
constitute a part of the power cord. Alternatively, such a "pass-through" 
ballast component could be made in the form of a unit that plugs directly 
into the wall socket and is connected to the lighting fixture by a power 
cord. 
PREFERRED DRAINAGE AND COOLING TIP CONFIGURATION (FIGS. 12-13) 
A convoluted triple-U-bent envelope 14c having a preferred form of open 
tubulation 32' for allowing the phosphor paint to drain from the envelope 
during the phosphor-coating operation is shown in FIG. 12. As will be 
noted, the glass tubulation 32' extends downwardly from the medial U-bent 
segment 31c (when the envelope 14c is in upstanding position as shown). 
This permits the wet paint to drain from the medial U-bent segment 31c 
along with the paint from the other two U-bent segments 29c, 30c, which 
flows along the terminal leg segments 24c, 26c and out of the open ends of 
the envelope 14c. This prevents the wet phosphor paint from collecting at 
U-bend 31c and solves the very difficult problem of depositing a uniform 
and smooth coating of phosphor 110 on the inner wall surfaces of the 
convoluted envelope 14c. 
In the case of a triple-U-bent envelope made of glass tubing having an 
outer diameter of approximately 18 mm., phosphor coatings of acceptable 
uniformity were obtained with a drainage tubulation that was about 20 mm. 
long and had an outside diameter of about 7 mm. 
After the phosphor coating dried and was lehred, the glass tubulation 32' 
was tipped off to form a "cooling" nipple or tip 32c that was from about 4 
to 10 mm in length and defined a cavity or chamber within the finished 
lamp for condensed excess mercury. To avoid possible seal problems, the 
tubulation 32' is preferably wiped clean of phosphor before it is tipped 
off. The sealed tip 32c is accordingly made of clear glass. The rest of 
the envelope 14c inner wall remains coated with the phosphor 110. 
A finished convoluted fluorescent lamp L.sub.c having a triple-U-bent 
envelope 14c with such a cooling tip 32c is shown in FIG. 13. Since the 
tip 32c is the coolest part of the lamp when the latter is operating, the 
excess mercury condenses in the tip-cavity within a few hours and the 
temperature of the tip 32c then controls the mercury-vapor pressure inside 
the lamp. Maximum lumen output occurs when the tip 32c is at a temperature 
of about 40.degree. C. Since the bulb wall temperature of a fluorescent 
lamp of this type made from 18 mm. O.D. tubing operated at about 350 ma is 
approximately 60.degree. C., the lumen efficacy is much lower without the 
cooling tip and chamber. 
As a specific example of the effectiveness and functional importance of the 
cooling tubulation in the operation of compact triple-U-bent type 
fluorescent lamps, two test lamps of such configuration were made at the 
same time and in the same fashion except that one had a cooling tubulation 
that was 9 mm: long and around 7 mm. in outside diameter and the other had 
no such tubulation. After the lamps were burned for 100 hours and 
stabilized in free air, the lamp with the cooling tubulation (and chamber) 
produced 22% more lumens than the lamp without the tubulation. 
MULTI-U-BENT FLUORESCENT LAMP EMBODIMENTS (FIGS. 14-19) 
The dual function drainage-and-cooling tubulation of the present invention 
is not limited to fluorescent lamps that have triple-U-bent types of 
envelopes but can be used with the same advantages in other types of 
compact fluorescent lamps and lamp units. 
In FIGS. 14 and 15 there is shown a compact fluorescent lamp unit 12f that 
contains a multi-U-bent fluorescent lamp Lf which embodies the invention 
and is held within a light-transmitting housing or cover Cf by a base 
module or structure Bf. As will be noted, the lamp Lf is of single-ended 
construction and has a tubular envelope 14f of convoluted configuration 
which provides a concentrated tridimensional light source that has a long 
arc path and is thus of high efficacy and brightness. The cover Cf has a 
top opening 44f and protectively encloses the lamp. The base structure Bf 
holds the lamp Lf in assembled relationship with the cover Cf and has a 
generally rectangular-shaped cup portion 18f that accommodates and is 
coupled to the sealed ends of the lamp envelope 14f. It also has an inner 
wall that extends transversely across the top of the base structure and 
serves as a panel-support member which retains the lamp Lf in its upright 
position. 
As will be noted more particularly in FIG. 15, the base structure Bf also 
has a bottom panel or wall 69 and is terminated by a suitable electrical 
connector component, preferably a bayonet-type base member 20f which 
includes the usual insulator 21f and end contacts 22f. The walls 68 and 69 
of the base structure Bf are provided with a series of spaced apertures 70 
and 71, respectively, which permit air to enter the lamp unit 12f and pass 
through the opening 44f at the top of the cover Cf. The "chimney effect" 
produced by the heat generated by the fluorescent lamp Lf (when the lamp 
unit is energized) causes air to circulate freely through the unit and 
convection cool the lamp, thus avoiding excessive operating temperatures 
and the resultant drop in light output that might occur due to the power 
loading of the lamp and its compact size. 
The cup-shaped portion 18f of the base structure Bf can be molded from 
suitable temperature-resistant plastic to provide a one-piece member that 
is fastened to the metal shell portion of the bayonet base 20f. The rim of 
the protective cover Cf is seated in a groove 72 (shown in FIG. 15) that 
is provided along the inner periphery of the cup-shaped portion 18f and, 
in accordance with this embodiment, the chamber which is defined by this 
part of the base structure Bf contains a conventional condenser 16f and 
starter component 17f that are connected to the fluorescent lamp Lf and to 
a separate ballast component (not shown) in the usual fashion to permit 
the lamp to be started and operated from an AC power supply. 
As illustrated in FIGS. 14 and 15, the envelope 14f of the fluorescent lamp 
Lf comprises a vitreous tube that is bent upon itself in such a manner 
that it has six substantially straight leg segments 73, 74, 75, 76, 77 and 
78 that extend in the same direction and are joined by five U-bent 
segments 79, 80, 81, 82 and 83. The U-bent segments are of such curvature 
and so oriented that the tubular legs are disposed in columnar array and 
spaced from one another. The leg segments and U-bent segments accordingly 
form five conjoined U-shaped envelope sections that are located in three 
different planes and define a single discharge channel of serpentine 
configuration that is terminated by the leg segments 73 and 78. The six 
straight tubular legs of the envelope 14f are disposed in two rows with 
three legs in each row and, together with the U-bends, form a pair of 
generally S-shaped sections. The convoluted fluorescent lamp Lf thus 
constitutes a compact light source that is rectangular in cross section. 
As shown in FIGS. 14 and 15, U-bent segment 82 has a tipped-off remnant 32f 
of a glass tubulation that is sealed to the envelope 14f after it has been 
bent into its convoluted form. This tubulation is used to drain phosphor 
paint from the retrobent envelope during the phosphor-coating operation 
and thus ensures that the U-bent sections are coated with a uniform layer 
of phosphor material. Another tipped-off phosphor-draining tubulation (not 
shown) can be provided on the other downwardly-extending U-bent section 
80. Since the compact fluorescent lamp Lf operates at a rather high power 
loading to attain the desired high brightness, the aforementioned 
tipped-off tubulations 32f afford an additional advantage in the finished 
lamp since they provide chambers or cavities inside the envelope 14f that 
serve as desirable "cool spots" and reservoirs for condensed mercury which 
regulate the mercury-vapor pressure during lamp operation. 
Since the pressure-regulating tips 32f are located near the bottom of the 
lamp unit 12f directly above the vent openings 70, 71 in the base 
structure Bf (as shown in FIGS. 14 and 15), a stream of cool air flows 
into the base structure and past the pressure-regulating tips when the 
unit is operated in a base-down position. This maintains the tips 32f and 
mercury reservoirs in the temperature range required for proper 
mercury-vapor pressure regulation. 
The leg segments 73 and 78 that terminate the envelope 14f and the 
discharge channel are hermetically sealed by conventional stem components 
which include the usual tungsten-coil electrodes that are coated with 
suitable electron-emission material and are connected to suitable 
conductors, such as paired lead-in wires, that extend through the 
respective stems and beyond the sealed ends of the envelope. The stem 34f 
which seals off leg segment 78 and includes the associated electrode 36f 
and lead-in wires 38f is shown in FIG. 15. Each of the stems has a 
sealed-off exhaust tubulation (not shown) which permits the convoluted 
envelope 14f to be evacuated and then charged with a suitable fill gas and 
dosed with mercury in accordance with standard lamp-making practice. If 
desired, non-tubulated type stems can be used and the evacuation, 
gas-filling and mercury-dosing operations can be done through the 
phosphor-draining tubulations 32f which are fused to and extend from the 
U-bent segments 80 and 82. 
As will be noted in FIGS. 14 and 15, the sealed ends of the terminating leg 
segments 73, 78 of the convoluted fluorescent lamp Lf are located within 
the chamber defined by the cup-shaped portion 18f of the base structure Bf 
and are secured in a suitable manner to the top wall 68 of base structure 
so that the lamp is held in upstanding position within the protective 
cover Cf. Additional support means such as a wire brace 56f can be 
provided, if desired, to hold the lamp Lf in place. As shown, the brace 
56f is anchored to the wall 68 of the base structure Bf and extends around 
and snugly grips the adjacent U-bent segments 80 and 82 of the envelope 
14.sub.f. 
The protective cover Cf can be made of glass, heat-resistant plastic or 
other suitable transparent or translucent material that will not absorb 
the light rays generated by the fluorescent lamp Lf. 
The starter component 17f is of the conventional "glow lamp" type and is 
permanently wired in place and connected in the usual manner to the lamp 
electrodes. However, the starter could be made in the form of a fuselike 
component that is mounted within the base structure Bf in such a manner 
that it may be readily removed and replaced as necessary by a "twist-lock" 
action. The condenser 16f is of the miniature wafer type and is connected 
in the lamp circuit in such a fashion that it eliminates or minimizes 
radio interference during lamp starting. 
While the convoluted lamp envelope 14f can be made by joining five separate 
U-bent sections of vitreous tubing together, it is preferably formed from 
a single piece of "soft" lead glass tubing of the kind used for 
conventional fluorescent lamp bulbs. The glass tubing is bent at the 
proper locations to form the U-bends and is subsequently coated with 
phosphor and provided with stem assemblies, evacuated, gas-filled, etc. in 
the usual manner. A suitable fill gas is argon at a pressure below about 
10 Torr, and preferably about 3 Torr. The mercury dosage will vary 
according to the physical size of the lamp and the power loading at which 
it is operated but is sufficient to provide mercury vapor at a partial 
pressure of from about 6 to 10 millitorr, when the lamp Lf is operated at 
its rated wattage, and maintain the mercury vapor pressure at this level 
within the lamp during its useful life. 
The inner surface of the convoluted tubular envelope 14f is coated with a 
suitable phosphor (or a blend of several phosphors) by flushing it with 
phosphor paint and draining the paint from the envelope through its open 
ends and the tubulations 32f (before they are tipped-off). 
Another type of compact lamp unit 12g and convoluted fluorescent lamp Lg 
which embodies the phosphor drainage and cool-tip feature of the present 
invention is shown in FIG. 16. As will be noted, the lamp unit 12g of the 
same basic type as those previously described in that it consists of a 
compact discharge lamp Lg that has a retrobent envelope 14g which is 
disposed within a vented protective cover Cg and held in operative 
relationship therewith by a base structure Bg which has a cup-shaped 
portion 18g and is terminated by a suitable connector such as a 
bayonet-typebase 20g which includes the usual insulator 21g and pair of 
end contacts 22g. In accordance with this embodiment, a ballast means 
comprising an inductor S4 and a capacitor 85 that are connected in series 
are located in separate compartments within the base structure Bg which 
are formed by a partition 86 that constitutes part of the cup-shaped 
portion 18g. The partitioned base structure Bg has a pair of support 
panels 68g and 69g that are provided with vent apertures 7Og, 71g which 
permit air to circulate freely through the composite base and lamp unit 
12g and thus provide convection cooling of the enclosed inductor 84 and 
capacitor 85 as well as the lamp Lg during operation. 
As shown in FIG. 17, the inductor 84 is connected in series with the 
capacitor 85 and one of the lamp electrodes 36g, and the latter is 
connected to the other electrode 36g through the starter component 17g. 
The electrical values of the inductor 84 and capacitor 85 are such that 
the reactance of the capacitor at the frequency of the AC power supply 
conventionally used in homes is slightly greater than the reactance of the 
inductor and thus causes the ballast to operate as a so-called "lead-type" 
circuit. This generates a voltage across the lamp Lg which is greater than 
the input or supply voltage and thus reliably starts the lamp despite its 
long arc length. This type of ballast arrangement is very compact in size, 
light in weight and has excellent operating efficiency and is thus well 
suited for use in compact fluorescent lamp units where such 
characteristics are of prime importance. 
As will be noted in FIG. 16, the starter component 17g and its connected 
noise-suppressing capacitor 16g can be located within the convolutions of 
the retrobent lamp envelope 14g or, if desired, they can also be housed 
within the partitioned base module Bg along with the ballast components. 
As in the previously-described embodiments, auxiliary support means for 
the retrobent lamp Lg is provided by a brace 56g that is anchored to the 
support wall 68g of the base structure and engages the adjacent U-bent 
section 98 of the envelope 14g. 
In contrast to the previous embodiments, the convoluted fluorescent lamp Lg 
has an envelope 14g that is of different configuration and has seven 
conjoined U-shaped sections which provide a discharge channel that is of 
greater length and thus further increases the light output of the lamp. As 
shown more clearly in FIG. 18 (which is an isometric view of the lamp 
envelope 14g immediately after it has been formed and before it is 
phosphor coated and sealed), the convoluted envelope has eight straight 
tubular leg segments 87, 88, 89, 90, 91, 92, 93 and 94 that are disposed 
in two rows that each contain four of the leg segments and are joined by 
seven U-shaped segments 95, 96, 97, 98, 99, 100 and 101. Three of the 
U-bent segments are conjoined to form a generally M-shaped section that is 
aligned with and spaced from another generally M-shaped section of the 
envelope 14g which is formed by the second set of three conjoined U-shaped 
segments. The aforesaid generally M-shaped sections of the envelope are 
disposed in spaced parallel planes and joined by the seventh U-shaped 
segment 98 which constitutes the medial portion of the vitreous tube from 
which the envelope 14i g is formed. The tubular leg segments 87 and 94 
which terminate the envelope (and the single discharge channel that is 
defined by the seven conjoined U-shaped segments) are disposed adjacent 
one another in a common plane that is spaced from and parallel to the 
plane which contains the U-shaped segment defined by U-bend 98 and the 
tubular legs 90 and 91. 
As will be noted in FIG. 16, in accordance with the present invention each 
of the downwardly extending U-bent segments 96, 9 and 100 (not shown) of 
the lamp envelope 14gare provided with protruding tips 32g of sealed-off 
vitreous tubulations which facilitate the phosphor-coating of the 
convoluted envelope and also provide "cool-spots" for mercury-vapor 
regulation within the operating fluorescent lamp, as described previously. 
Once again, the location of the cooling tips or tubulations 32g directly 
above the vent apertures 70g, 71g in the base module Bg provides a flow of 
outside air around the tubulations (and out of the open end 44g of the 
cover Cg) which decreases the if operating temperature and helps the 
tubulations control the mercury-vapor pressure in the desired manner. 
As shown in FIG. 18, the convoluted envelope 14g prior to be processed into 
a lamp is provided with glass tubulations 32' which are sealed to and 
extend downwardly from the three U-bends 96, 98 and 100 that are located 
on the same end of the envelope as the open ends of the terminal leg 
segments 87 and 94. The open ends of the tubulations 32' and those of the 
tubing from which the envelope 14g is formed are thus all oriented in the 
same direction and permit the phosphor paint to be poured into the 
convoluted envelope 14g and then drained from the lowermost U-bent 
segments 96, 98 and 100 in a carefully controlled manner so that a very 
uniform layer of phosphor 110 is deposited on the inner surfaces of the 
envelope. The tubulations 32' are of relatively large outside diameter 
(preferably around 7 mm.) to provide rapid drainage and permit 
cooling-cavities of sufficient size to be subsequently formed within the 
finished lamp when the tubulations are tipped off. 
The finished lamp Lh formed from the envelope 14h is shown in FIG. 19. As 
will be noted, the ends of the envelope are sealed by stems (one of which 
has an exhaust tube 40h) and the drainage tubulations are tipped off to 
provide clear-glass appendages 32h of controlled length (preferably from 
about 4 to 10 mm.) and three "cool" spots or chambers at spaced locations 
within the lamp. 
While the drainage-and-cooling tubulations for each of the illustrated lamp 
embodiments have been located on U-bent parts of the envelope which are 
proximate the sealed ends of the envelopes and are thus all positioned 
directly above the base vents when the lamp units are burned in a 
base-down position, one or more tipped-off tubulations can also be 
provided on the U-bends which are located on the opposite end of the 
envelope as shown in FIG. 20. These tipped-off tubulations will then be 
positioned adjacent the vent openings in the protective cover and thus be 
directly exposed to a cool air flow if the lamp unit is operated in a 
base-up position. This arrangement will thus provide a "universal 
burning-position" compact fluorescent lamp unit. Of course, the protective 
cover will be made of such length that the vapor-regulating tubulations 
will be spaced from and recessed within the cover. 
In addition, in those cases where the compact lamp units are operated at 
such high power inputs and/or under such ambient temperature conditions 
that the cooling-tubulations operate at too high a temperature to provide 
proper regulation of the mercury-vapor pressure, it is within the scope of 
the present invention to also provide an amalgam of mercury and another 
metal (such as indium, cadmium, etc.) at one or more strategic locations 
within the fluorescent lamp to assist the cooling tubulations in 
maintaining the vapor pressure under control. The amalgam can be secured 
to one or both of the stem assemblies (pursuant to the teachings of U.S. 
Pat. Nos. 3,534,212 to Evans or 4,020,378 to Morehead, the disclosures of 
which are incorporated herein by reference). The amalgam can also be 
placed within one or more of the cooling-tubulations if desired, providing 
a suitable means such as a porous diaphragm or screen component is used to 
retain the amalgam at such a location without obstructing the passage of 
the mercury vapor into and out of the tubulation. 
If slow "warm-up" and objectionable delays in reaching rated light output 
are encountered with convoluted fluorescent lamps that contain such 
auxiliary amalgam-sources for vapor pressure control, a small quantity of 
amalgam can be placed close to one of the electrodes (for example, on a 
suitable carrier which is secured to one of the lead wires pursuant to the 
teachings of U.S. Pat. No. 3,562,571 to Evans et al). The electrode will 
rapidly heat this additional amalgam source and thus relieve the "mercury 
starved" condition of the lamp which is responsible for the retarded 
stabilization of lamp operation and delayed light output.