Note: Descriptions are shown in the official language in which they were submitted.
117~37~
INCANDESCENT LAMP WITH INFRARED REFLECTING
COATING AND WITH ENVELOPE MADE OF SEVERAL
1 SECTIONS AND METHOD OF ~ANUFACTURING SAME
Background of Invention
Various types of energy conserving incandescent
lamps having means, such as a coating, thereon for reflect-
ing infrared (IR) radiation back to the filament and fortransmitting visible light are known. One such lamp is
shown, for example, in U.S. Patent 4,160,929 granted
July 19, 1979 to Thorington, et al and assigned to the
same assignee.
The energy conserving incandescent lamps of
the aforesaid patent, as well as others, for various
reasons preferably place the coating on the inner surface
of envelope, although it can be placed on the outer
surface. Several coatings are shown, for example, in
the aforesaid patent 4,160,929 to Thorington, et al.
Most incandescent lamps utilizing an IR reflective-
visible energy transmissive coating operate on the same
general principle. That is, the coating is placed on an
optically curved surface, generally the envelope, and the
filament is located with respect to the envelope curved
surface so that the infrared radiation will be reflected
by the coating to impinge upon the filament and raise its
operating temperature. This reduces the amount of power
neecled to raise the filament to its operating temperature
thereby improving the operating efficiency oE the lamp. The
filament is preferably of a compact type, made as closely
resembling a point source as possible. In theory, the
filament should be optically centered with respect to the
envelope to optimize the return of the IR radiation. It is
also possible to produce a satisfactory lamp in which the
filament is deliberately placed off center of the envelope
optical axis~ While in the latter type of lamp, the
..
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1 impingement of IR energy on the filament occurs after two
or more reflections of the IR energy from the coating, the
IR reflective efficiency of the coating is sufficiently high
so that the lamp is still energy efficient. The off-center
mounting of the filament reduces manufacturing problems
associated with centering the filament.
It is preferred to apply the IR reflective coating,
sometimes called a heat mirror, to the envelope's interior
wall. This eliminates mechanical and chemical reactions of
the coating with the external environment, which are known to
cause degradation of the coating, as compared to the relatively
benign environment of inert atmosphere internal of the lamp.
Also, a coating on the inner wall avoids the heat loss
occurring when infrared radiation is partly absorbed by
the lamp envelope.
Although a coating on the interior of the envelope
is preferable, it is more difficult to deposit a homogenous
coating on the interior of a conventional envelope, of
spherical, or some other, shape than on its exterior. For
example, in a film having multi-layers, such as disclosed in
U.S. Patent 4,160,929, one method for depositing the coating,
is by radio frequency (RF) sputtering. Substantial inhomo-
geneities develope with interior wall coatings when the
targets are inserted and operated in the confined space of
a conventional spherical envelope. This is generally due
to the physical constraint of positioning and moving the
targets through the narrow opening of the neck and restriction
of the gas flow. Consequently, in such conventional envelopes
coatings are more readily laid down on the envelope outer
surface. In addition, the inner surface of a lamp of
conventional shape, has surface irregularities, such as peaks
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and valleys, wh}ch are p;oducc-d when the en~elope is m~nufdct~.red
by conventional processes. Such surface irregularities are of no
consequence in a cvnventional incandescent lamp. 'ow~ver, ~here
the IR Leflective-visible tranmissive coating is to be de?osLted
on s~cn a surface, the efficiency of IR reflc-ctivity is reduced.
Accordingly, tne present invention relates to an
incandescent laJrlp having an IR reflective-vis'ble transmissive
ccating on its interior wall in which the erl~elope is foriied of
multi-sections which are joined together and a method of making
such a lamp. The use of an envelope formed of multi-sections
permits various advantayes to be obtained. Fo{ example, the
lnterior wall of each section can more readily be processed with
a higher quality optical finish to remove surface irregularities.
This increases the IR reflectivity from the coating deposited
1~ thereon. Further, it is also easier to aeposit the coating on
the inner surface of each section since there is no constraint
with respect to, for example, the narrow neck of a conventional
incandescent lamp envelope. The multi-sectioned construction
also lends itself to novel and improved filament suppoft and
filament mount configurations which reduce energy losses associ-
ated with conventional constructions. Further, the multi-section
envelope approach also lends itself to new and novel techniques
with respect to assembling lamps and for sealing the same.
It is, therefore, an object of the present invention to
2a provlde an incarldescent lamp having an envelope of multi-sections.
A further object is to provide an incandescent lamp having
an infrared energy reflective-visible transmissive coating on the
envelope inner wall in which the envelope is of multi-sections.
An additional object is to provide a ger,erally spherical
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I or generally ellipsoidal envelope for an incandescent la~!p ~,nich is
-ade of several sections joined toge.her with the filanent mo-~nted
therein.
Yet another further object is to p:ovide an incandescent
lamp having an envelope of multi sections, in which the sections
are jo ned together by laser welding.
A further object is to provide an ir~ccndescent la,llp with
an IR reflective-visible transmissive coating on tne interior
surface of an envelope made of multi-sections.
]0 Other objects and advantages of the present invention
will become more apparent upon re-Eerence to the following speci-
fication and annexed drawings in which:
Fig. 1 is an elevational view, partly in section,
showing a prior art type incandescent lamp.
Fig. 2 is a view of a multi-section lamp in accordance
with the invention in which the envelope is of generally spherical
shape;
Fig. 3 is an incandescent lamp in which the envelope is
multi-section and is of generally ellipsoidal shape; and
2~ Figs. 4-6 are views of various forms of filament mount-
ing arrangements which can be used with multi-section envelopes;
and
Referring to Fig. 1, there is shown a prior art type of
incandescent lamp of the type under consideration. The lamp 10
2~ inciudes a generally spherical envelope 11 having thereon on the
interior wall of the envelope a coating 12 of the types previo~sly
considered with respect to U.S. Patent 4,160,929, having a
multiplicity of discrete layers.
The lamp envelope has a narrowed down neck terminating
1~'79'726
I in a base which incl~des a threaa-d ~etallic SGc~et 14 and a
conductive contact tip 16 which is insulated from the socket.
Attached to the tip 16 and socket 14 are a pair of conductive
leads 17 and 18 which pass through a stem 19 having tubulation 20
which is used to seal off the envelope. Connected to the leads
17 and 18 is a coiled-coil or triple coil type which is located
at the optical ccnter of the envelope or off of the axis. T},e
filament is prefer2bly made colT,pact, i.e. h2s a small lenoth to
diameter ratio. A reflector 25 of part spherical shape is
]0 mounted on the stem l9 to complete an overall spherical surface
for the envelope.
In operation, current is supplied to the filament 22
through the electrical contacts 14 and 16 and the leads 17 and
- 18. The current causes the fi-lament 22 to incan2esce and produce
l~ energy in both the visible light range and in the infrared range
of wavelengths . The coating 12 on the envelope ll reflects a
large portion of the IR energy back toward the filament due to
the curvature of the envelope ll and the location of the filament
22. The IR energy returned to the filament raises its operating
~0 temperature thereby improving the efficiency of the lamp since
less current is needed to raise the ilament to its operating
temperature. At the same time, the coating 12 permits a large
portion of the visible of the energy in the visible light range
produced by the filament to pass through for illumination purposes.
The~reflector 25 is also coated to reflect IR energy back toward
the filament. It is located at the base of the envelope where
visible light cannot be transmitted and it need not transmit-
visible energy.
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I As explained previously, it is preferred that the
coating 12 be placed on ~he inner surface of the envelope alti-,ough
it can be located on the outer surface. ~owever, as also explained
previously, due to the narrow neck of the envelope it is difficult
to deposit a hornogeneous coating, particularly a multi-lRyer
coating onto the envelope inner wall. ~lso, the finish of the
interior wall is not optically precise.
Fig. 2 shows an illustrative errlhodilnent of a larllp 30
according to the present invention in which the envelope 32 is of
]0 generally spherical shape. The envelope has a plurality of
sections, here shown as two, of generally hemispherical si-ape 33
and 34. i~ore than two sections can be used but an increase in
the number of sections ma~es sealing more difficult. The envelope
sections 33 and 34 are of a suitable glass material, for example,
PYREX, lime glass, optical glass, etc. The type of glass is not
critical to the invention as long as it has cost effectiveness
and also, preferably, it can be optically polished. The two
sections 33 and 34 are joined together along a seam line 35 which
defines a hermetic seal.
Located within the envelope 30 is the filament 40 which
is held by stem leads 42 and 44. A further sup?ort lead 46 of
conductive or non-conductive material is provided which is loosely
placed around the elongated filarnent 40. The ~wo leads 42 and 44
and the support wire 46 are fastened to a base 50 which is shown
in greater detail on Fig. 2A. The filament is located on the base
such that when the base is assembled to the lower section 34, the
filament will be located at the proper position. The suppor-t
wire 46 minimizes motion of the filament during shipping and also
guards against excessive sag when the filament is in the horizontal
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1 burning position. The base 50 is a circular "b~tton" of glass or
glass-co~patible material. It includes a tubulation 52 through
which the lamp can be exhausted and the tubulation tipped off in
the usual m,anner.
Tne two envelope sections 33 and 34 are formed by any
conventional glass makiny process, for exanlple, molding, vacuum
forming, blowing, etc. By forming tne enJelope of two or more
shaped pieces instead of one, it is possible to use glass fabri-
cation techniques which yield superior reflectors compared with
conventional blown bulbs, such as shown in Figure 1. For example,
the internal surface of the reflector can be finished by grinding
and polishing to produce an optical quality reflector.
The use of two or more sections to form the shaped envelope
has further advantages in that it greatly simplifies the deposition
of a uniform heat mirror coating on the inside surface since the
coating can be done by a variety of sputtering, reactive evapora-
tion or chemical vapor deposition techniques without the constriction
of plasma or restriction in gas flow characteristic of a one piece
envelope construction.
In assembling the lamp of Fig. 2 the hemispheres 33,34
are formed. The lower hemisphere 34 is processed to cut out an
opening at its bottom, or at some other loction, which conforms
to the shape of the socket 50 and into which t}-e socket 50 is
inserted and sealed by any suitable technique, for example, by
metalization and soldering of the edges, by the use of an adnesive
or by the use of frit or solder glass. Hermetically sealed into
the socket 50 are the lead wires 42 and 44 as well as the support
lead wire 46.
The two hemispherical sections 33 and 3~ are placed
26
1 rogether. Prefe~ably, before this is done, the eoges of the
hc-J-nispheres have been suitably treated, for exa}nple, by polishing,
to proviàe a smooth finish without jagged edges so that a good
seal can be formed. The seal is ~,ade by i,ietali~ation and solder-
a ing at these edses, by the use of an adhesive, ror e~ample, apolyamide or high temperature epoxy resin, or by the use of frit
or solder glass.
After the seam has been made, the cnvelope is exhausted
through the tubulation 52. If a fill gas is required ror the
lamp envelope, for example argon gas, it is inserted through the
tubulation. The tubulation is then tipped off. After this is
accomplished, the usual metal socket piece is connected, such as
by an adhesive to the envelope, and tne lamp is completed.
In assembling the base 50 to the lower section 34, the
1~ filament 40 is already precisely aligned so that when the base is
inserted into the envelope and fastened thereto, the filament
will be more or less at the optical center of the curved envelope.
As pointed out above, one of the advantages of manufactur-
ing the envelope out of several sections is that a higher optical
finish can be produced on the interior surfaces of the envelope
than is possible with a conventional envelope with neck as shown
in Fig. 1. It should be understood that internal surface irregu-
larities underneath the coating detract from the homogeniety of
the coating and the focussing effect of the reflector and thereby
2~ reduce the efficiency of the c-nvelope. It has been found that an
envelope in which the interior surface on which the coating is
laid down has been optically finished is substantially more
efficient from the point of view of reflecting IR energy than a
conventional blown envelope having surface irregularities.
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1 Fig. 3 shows a further embodiment of the invention
wherein the envelope is ellipsoidal in shape. As described
in copending application Serial No. 076,368, filed September
17, 1979, which is asslcJned to the assignee of the subject
application, an ellipsoidal envelope in which an elongated
filament is located such that the two foci of the ellipse
are along the length of the envelope will minimize end and
side abberational losses of the filament.
In Fig. 3, the envelope 60 is formed by two hemi-
ellipsoid sections 62 and 64 which are joined together on
a seam line 65 in the manner previously described. As
before, sections 62 and 64 are preferably optically finished
on the interior thereof to provide a better optical surface
before the coating 67 is deposited.
In the embodiment of Fig. 3, a different base 70
is shown which does not have a tubulation. The base 70
has two contact studs 76 and 78 sealed therein each having
a head 80 at the lower end. The lead wires 42 and 44 are
fastened for example, by spot welding, to the portion of
the respective studs 76 and 78 which extend into the
envelope. The support lead 76 is fastened only into the
glass of the base 70. Electrical contact is made for the
filament 40 through the lead wires 42 and 44 and the
respective stud connectors 80. The base 70 of Fig. 3
also can be used with the spherical shaped envelope of
Fig. 2. The base constructions 50 of Fig. 2 and 70 oE
Fig. 3 have further advantages in that the usual stem 19
of Fig. 1 is not needed~ This reduces the light and heat
loss within the envelope.
_9_
i~17~2~
I In the lamp of Fig. 3 or the ]amp of Fig. 2 ~sing the
base of Fig. 3, final assembly is accomplisrled entirely within
the machine used to seal the envelope. That is, as explained
below, the sealing is accom?lished in a port~on of the machine
a which is either a vacuurn or else is provided with the fill
~,as at tne a~propriâte pressure. This is described in yLeater
detail below.
r~ulti-piece envelope constructiorls such as shown in
Figs. 2 and 3 enables filament configurations where the support
~o leads can be eliminated or at least the removal of the obstruc-
tion of the insulated support lead if the existing current leads
are also used for support.
Referring to Fig. 4, there is shown one-half of a
section of an envelope in which a support wire 84 of non-conductive
material is strung across the e~uaiorial plane an approximately
diametrical position and fastened to the envelope. The fastening
is accomplished, for example, by adhesive or glass bonding to a
surface of the envelope part. Fig. 4A shows mechanical retention
in a groove 86 located at each end of a diametrical line with
2() each groove being covered during the final sealing process to
make the lamp leak proof.
The support wire 84 can be tensioned with a spring
member if necessary. On assembling the lalnp the support wire is
slipped into position in the vicinity of the middle of the
2a filament and lies generally perpendicular to ~he filament The
filament is mounted with conventional lead wires, such as shown
in Fig. 2. More than one support wire may be employed to support
or restrain filament movementr
Figs. 5 and 5A show further ernbodiments of the invention
which are possible with the multi-sectioned envelope construction.
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These embodiments eliminate some of the obstruction to IR reflec-
tion from the lead-ins to the filament~ In Figs. 5 and 5A, a
filarrlent is attached to current lead-ins 92,~4 which extend
across the plane separating the two p eces. The leads 92, 94 can
be exter,ded beyond the lamp to pLovide the ,ninilTium obstruction of
radiation. This is shown in Fig. 5. The leads can also be
directed alc,ng the s~rface to a convenient locat~on for a base.
This is snown in Fig. SA. The filarnc-nt arrarlgeliient of Figs. 5
and 5A may be conveniently combined with the strung wire support
as shown in Fig. 5B to obtain an energy saving lamp configuration
~ith minimum radiation obstruction for a supported filament.
Considering tr,e lamp of Fig. 2 which has the tubulation,
to complete its processing, after the sections of the envelope
have been joined together, the lamp is placed in a finishing
~5 chamber. At this time, the lamp has been sealed in, that is, the
filament and the base 50 are joined to the envelope but the
exhaust tubulation remains open.
The finishing chamber has attached to it a roughing
pump ar,d a hiyh vacuum pump, both connected through suitable
valving to provide alternate roughing and high vacuum conditions.
Valving and connections to nitrogen and suitable filled gases are
also provided along with an absolute pressure gauge for monitoring
the fill pressure of the system.
The finishing chamber is also connected to a fill gas
2~ retrieval system which is connected through a valve to a suitable
pump, for example, a two stage diaphragm pump. T}le output staye
of the pump is connected to a diaphragm gas compressor which is
in turn connected to a gas storage tank. The storage tank output
is in turn connected back to the finishing chamber. The gas
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1 storage tank is also provided with cornectior;s to allow the
continual replenishir,ent of the storage tank.
A suitable laser, for example, a carbon dioxide laser
is connected thLo~gh beam benders in a suitable conduit to a
focusing head having a lens. The laser system focusing head
previously has been aligned with the la-r,p tubulation which is
inside of the finishing chamber.
The lamps are rnoved into the fin~shing chamber where
they are rough pumped and then purnped to a high vacuum. At this
point the high vacuum valve is closed and the charnber is back-
filled with the fill gas at a desired pressure. The lamp pressure
and the chamber pressure are now e~,ual. The lamp exhaust tubu-
lation is positioned by an externally actuated latching device
- and bulb rotation is provided-by a lamp car on the inside of the
1~ chamber.
The lamp exhaust tubulation, which is of a heat sensi-
tive glass material, ls aligned with a window in the chamber
through which the laser beam can enter. The window can be, for
example, zinc selenide. The laser is actuated and the beam is
directed to the tubulation. The tubulation is heat sealed and is
now tipped off within the chamber and the fill gas at the proper
pressure. If a number of lamps are being processed at the same
time, when they a~l have been tipped off, the fill gas retrieval
system pumps out about 95% of the remain;ng fill gas to the
storage tank. The chamber is now vented back to the atmosphere
with nitrogen and the tipped off lamps are removed.
The system and process described can be used to seal
the larnps shown in Fig. 2, whether these lamps are of ellipsoidal,
-12-
7~i
1 spnerical, or of some other shape.
A modified process is useful either wi~h the tubulated
lamps of Fig. 2, in which the tubulation is sealed in the
r"anner already described or with the lamp of Fig. 3 in which no
tubulation is provided.
In both czses, it is assumed tnat the lamp is in the
finishing chamber and has been pum2ed out and then oack filled
with the fill gas at the required pressure. Thus, the environment
within the finishing chamber is the fill gas which can be the
]0 only gas which will permeate into the lamp envelope. Pumping out
is done with the two envelope sections spaced apart and open
facing each other. The equatorial region of the hemispheres have
previously been coated with a suitable joining compound, i.e.,
- epoxy, solder glass, solder, etc., or alternatively, a simple
glass to glass seal may be made.
The hemispheres are brought together in a line with
each other vertically adjacent the window through which the laser
beam enters the chamber. The lamp is then rotated and subjected
to a continuous or pulsed laser beam. The heat generated causes
the coated or uncoated sections of the equatorial region to heat
up and allows the hemispheres to be joined forming a lamp in a
fill gas atmosphere at the correct pressure and gas mixture. The
chan,ber is vented and the finished lamps are removed.
As should be apparent, novel electrical envelopes
2~ for electrical lamps having energy reflective coatings have been
provided which give rise to advantages in mounting filament,
processing, etc.
