Ambient pressure lamp

An ambient pressure lamp for automobiles and related conveyances includes a parabolic reflector having an inner reflective surface, an outer surface, a base portion and an outer peripheral edge wherein the base portion includes a centrally located clearance aperture for receipt of a lamp filament socket. The reflector member is enclosed by a lens member which as a stepped inner surface and a surrounding lip portion which is sealingly attached to the outer peripheral edge of the reflector member in order to define an inner chamber wherein a lamp filament is positioned. An expandable membrane is sealingly joined around the outer surface of the reflector member and around the lamp filament socket so as to define an expansion chamber between the outer surface and the membrane. This expansion chamber is completely enclosed except for being in flow communication with the inner chamber so that as pressure increases result due to the heating of the filament and heating of the internal atmosphere within the inner chamber, the expandable membrane stretches outwardly in order to provide an increased volume so that the internal pressure within the lamp remains at an ambient level regardless of the operating status of the lamp. The lamp filament socket includes purge and fill passageways so that the inner chamber and the expansion chamber can be purged of all oxygen and moisture and filled with an inert gas mixture.

BACKGROUND OF THE INVENTION 
The present invention relates in general to vehicle headlamps and in 
particular to the type of headlamp which has a parabolic reflector and 
cover lens. 
Conventional vehicle headlamps typically include some type of filament, a 
parabolic reflector base and a molded lens sealed thereto in order to 
create an evacuated chamber. The atmosphere of this evacuated chamber 
surrounds the filament and the operational characteristics of the lamp 
(i.e., average life and candlepower) are directly influenced by the nature 
of this inner atmosphere. 
In this inner atmosphere is not evacuated to a level sufficiently below one 
atmosphere when at "room temperature," then as the filament conducts 
current and heats the interior of the evacuated chamber, the gases filling 
this chamber expand to an excessive pressure level. While one solution to 
this potential problem is to evacuate the inner chamber to a lower 
pressure level, this option is offset by the fact that some inner 
atmosphere is needed in order to provide a suitable heat conductor 
surrounding the filament. The choice between the two "solutions" becomes a 
compromise in lamp construction wherein the initial chamber atmosphere is 
evacuated to a pressure level low enough to permit expansion to an 
allowable inner pressure when the lamp is at maximum operating 
temperature. 
A related concern to that of an evacuated inner chamber is the need to void 
the interior of moisture and seal therewithin the particular gases 
selected for the interior atmosphere. The greater the pressure difference 
between the inside and outside atmospheres, the greater will be the 
demands placed upon the seal locations, and consequently, the more 
susceptible the assembly will be to leakage and thus failure. 
One means to improve upon the foregoing problems is provided by the present 
invention wherein an expandable membrane is arranged in cooperation with 
the inner chamber of the lamp in order to accommodate volumetric expansion 
during operation. The membrane serves as an interface between two 
atmospheres of equal pressure. Although there is a variety of known prior 
patents which pertain to lighting and lamps, no reference is known to 
exist which reveals any concept that is related to the expandible membrane 
concept of the present invention. 
A related aspect of the present invention pertains to the design of the 
filament and the use of a ceramic glow bar in order to increase the 
luminance and candlepower of the source. While glow bar concepts are known 
to exist, the present invention provides a design which is a practical, 
high production means of fabrication, its actual configuration, and its 
combined use with the disclosed ambient pressure lamp incorporating the 
expandable membrane. 
Listed below are various patent references which are known to the inventor 
and which disclose lamp designs and related concepts. Consequently, these 
references may be relevant to the present invention, but none of the 
references are anticipatory of the present invention nor render the 
present invention obvious. 
______________________________________ 
Pat. No. Patentee Issue Date 
______________________________________ 
1,406,645 Heany 2/14/22 
1,640,829 Heany 8/30/27 
1,749,136 Heany 3/04/30 
1,975,499 Braselton 10/02/34 
2,007,926 Braselton 7/09/35 
2,901,654 Myers 8/25/59 
4,032,809 Corth 6/28/77 
4,146,812 Gagnon 3/27/79 
3,027,481 Baber et al. 
3/27/62 
2,950,413 Jayne et al. 
8/23/60 
2,007,945 Harding, Jr. 
7/09/35 
1,623,761 Skaupy 4/05/27 
2,273,762 Reerink et al. 
2/17/42 
______________________________________ 
Heany ('645) discloses an incandescent electric lamp having a particularly 
styled filament. The filament includes a first helical coil of refractory 
metal disposed over a refractory compound. Additionally, there is a second 
coil providing an outer layer of turns disposed over a second layer of a 
refractory compound. To the extent that this particular invention pertains 
primarily to the construction and materials of the filament, it may have 
some relevancy to the present invention. Otherwise, the remainder of the 
lamp is in no way relevant. 
Heany ('829) discloses an incandescent electric lamp, and in some regard 
similar to the first Heany reference, the invention focuses almost totally 
on the construction of the filament. In particular, a large number of 
arrangements are disclosed, all relating to the disposition of a tungsten 
coil relative to a refractory compound which supports the coil and 
possesses great strength at the operating temperature and is capable of 
becoming highly incandescent at the operating temperature of the lamp. 
Heany ('136) discloses an incandescent electric lamp, again of the same 
basic idea and concepts of the earlier two Heany references. Here again, 
the invention focuses almost totally on the design and construction of the 
filament and the relationship of the tungsten coils to the refractory 
compound. 
Braselton ('499) discloses a constant illumination electric lamp wherein 
the main thrust of the invention pertains to the arrangement of the 
filament which, in this case, is disposed between two support rods and 
includes a filament coil disposed around a rod of refractory metal and 
between the two support rods. 
Braselton ('926) discloses a light-emitting unit wherein four support rods 
are provided and two coils. The two coils are arranged in a double-coil 
design such that two of the support rods support one coil and the other 
two support rods support the other coil. Both coils are disposed about a 
core of electron-emitting material in order to provide the desired 
illumination and candlepower for the light-emitting unit. Again, this 
particular invention pertains almost totally to the design and 
construction of the filament. 
Myers discloses an electric incandescent lamp of the self-contained 
reflecting type which is adapted to project a beam of light. Additionally, 
the invention pertains to improvements in lamps of this type which are 
shatter-proof and to techniques for fabricating such lamps. The lamp 
assembly includes a Mangin mirror which is secured at its periphery to one 
end of a cylindrical metal shell. The other end of the shell is enclosed 
by a transparent window plate in order to form an evacuated chamber which 
contains the light-emitting element. The shell is constructed with 
inwardly turned edges in order to form a bellows-type of configuration at 
which point it provides a glass-to-metal seal. The fact that this shell is 
formed of a durable metal eliminates any suggestion or possibility that 
the interior volume is permitted to expand outwardly by expansion of the 
shell. 
Corth discloses a coiled incandescible filament which principally comprises 
tantalum carbide and which has coiled end portions overfitting relatively 
thick tantalum carbide members. The inner surfaces of the overfitting 
coils are welded to the relatively thick members. Electrical connection 
and support for the filament is made to the relatively thick, overfitted 
members, rather than the fine, brittle filament. 
Gagnon discloses a motor vehicle headlight which includes a curved 
reflector having a lens bonded to the front thereof and a tungsten-halogen 
capsule disposed within the reflector. A filling hole extends through the 
rear of the reflector and this hole is hermetically sealed by means of a 
nonrigid sealing material. 
Baber et al. discloses in general a projection lamp and in particular to 
incandescent lamps that may be used in various devices utilizing an 
optical system in the projection of slides, motion picture films, or other 
types of transparent or semi-transparent objects. In particular, the lamp 
disclosed is intended to be acceleration and vibration-resistant and 
includes a filament in the form of a pair of semi-circular segments which 
are carried and supported by a generally cylindrical support element which 
in turn is held in position relative to the lamp by a plurality of 
rod-like supports. 
Jayne et al. discloses a filament connection for electric lamps and similar 
devices and in particular relates to the connection between the filament 
and the leading end conductors. Although the patent discloses some 
specifics regarding the filament design, the primary nature of the 
invention is the connection concepts which are disclosed. 
Harding, Jr. discloses an electric lamp with a concentrated light source 
and includes a pair of support rods holding a filament. The filament 
constitutes the primary aspect of the invention and is disclosed as 
including a cylinder of refractory material which is provided with a 
helical groove and an electron-emitting element which is made into a coil 
form and wound into the grove. 
Skaupy discloses an electric glow lamp design wherein the support element 
which is normally made of refractory material is made of transparent 
material which will convey sufficient heat to the light-giving element 
mounted thereon in order to make the element luminous, yet the body in 
which the element is mounted does not interfere materially with the 
radiation of the light-giving element thereby enabling the light-giving 
element to stand out. This particular patent reference is believed to have 
very limited applicability to the present invention. 
Reerink et al. discloses an incandescible cathode construction wherein one 
or more thin metal wires is wound around a metal core made of refractory 
material in order to form a structure in which a comparatively large mass 
and large area of a highly electron-emissive substance surrounds the core 
and is securely retained by the turns and/or layers of the thin wire. The 
purpose of this particular invention is to generate a very large emitting 
surface that can be provided on the cathode with an ample supply of 
emissive substance, which substance at the same time firmly adheres to the 
cathode. 
A concept related to the invention of an ambient pressure lamp is the 
ability to reconfigure the front lens. When there is an internal pressure 
within the lamp, a convex outer lens is preferred from the standpoint of 
overall strength. In order to fabricate this convex shape, a molded glass 
construction is typically employed; but a plastic lens cemented to a 
reflector is one option. One drawback with the use of such plastic is the 
fact that it is more susceptible to the elements of weather and to 
chemicals. Once the plastic is scratched or begins to deteriorate due to 
the chemicals, light transmission is reduced. 
One solution to this drawback is to use a lens with a flat outer surface 
and to fabricate this outer surface of a more durable material such as, 
for example, a thin overlay of glass. An inner layer of plastic can still 
be used for lens focusing, but a flat layer of glass on the outer surface 
provides the needed protection from the elements and chemicals. The fact 
that the interior of the lamp is at ambient pressure permits the use of a 
flat lens because the strength requirements for the lamp are greatly 
reduced since the internal lamp pressure of the present invention equals 
the external ambient pressure. 
SUMMARY OF THE INVENTION 
An ambient pressure lamp for automobiles and related conveyances according 
to one embodiment of the present invention comprises a reflector member 
having an inner reflective surface, an outer surface, a base portion and 
an outer peripheral edge, an enclosing cover member having an outer 
peripheral lip portion, the lip portion being assembled to the outer 
peripheral edge so as to define an inner chamber between the inner 
reflective surface and the enclosing cover member, a lamp filament, a 
filament socket assembled to the reflector member adjacent the base 
portion and cooperatively adapted for receipt of the lamp filament, and an 
expandable membrane sealingly joined around the outer surface and around 
the filament socket so as to define an expansion chamber between the outer 
surface and the expandable membrane, the expansion chamber being 
completely enclosed except for being in flow communication with the inner 
chamber. 
One object of the present invention is to provide an improved headlamp of 
lower cost. 
Related objects and advantages of the present invention will be apparent 
from the following description.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
For the purposes of promoting an understanding of the principles of the 
invention, reference will now be made to the embodiment illustrated in the 
drawings and specific language will be used to describe the same. It will 
nevertheless be understood that no limitation of the scope of the 
invention is thereby intended, such alterations and further modifications 
in the illustrated device, and such further applications of the principles 
of the invention as illustrated therein being contemplated as would 
normally occur to one skilled in the art to which the invention relates. 
Referring to FIG. 1, there is illustrated a side elevation view in full 
section of an ambient pressure lamp 20 which includes parabolic reflector 
21, lens 22, filament 23, filament socket 24 and expandable membrane 25. 
Parabolic reflector 21 includes an inner reflective surface 28, an outer 
surface 29, a base portion generally defined at 30 and an outer peripheral 
edge 31 which is circular in shape (see FIG. 7). Reflector 21 is 
constructed of cast plaster material and then surface 28 is coated with a 
high-gloss paint and thereafter aluminized. Lens 22 is generally convex in 
cross-sectional configuration having a stepped internal surface 34 and a 
substantially smooth outer surface 35. Disposed on outer surface 35 are 
three aiming nodes 36 which are provided in order to establish a flat 
reference plane for establishing the proper centering and squareness of 
the lamp. Lens 22 is molded of a polycarbonate plastic and may include 
certain surface coatings to improve abrasion resistance. 
Filament 23 is described in greater detail in FIGS. 2 and 3 and includes a 
tungsten wire 37 coiled about a non-metallic refractory core 38. The 
opposite free ends of the tungsten wire are each supported by support rods 
39 and 40 which are joined to contact prongs 41 and 42, respectively. Rods 
39 and 40 are first assembled to prongs 41 and 42 and this subassembly is 
then secured to socket 24 in a fixed position. 
Lens 22 includes an outer peripheral lip portion 45 which is configured in 
an overlapping style so as to fit over and around outer peripheral edge 31 
of the parabolic reflector 21. Lip portion 45 includes an overlapping area 
45a, an outwardly extending area 45b which provides the mounting means to 
the vehicle, and retroreflector band 45c, which is annular in shape (see 
FIG. 7). Band 45c makes use of an otherwise lost area and is particularly 
helpful to oncoming vehicles when one headlamp is out. The annular shape 
outlines the lamp and permits on-coming drivers to orient themselves 
relative to vehicles with only one lamp. Lip portion 45 and edge 31 are 
sealingly joined together by compound 46 which is placed at four locations 
around this circular interface and the assembly defines an inner chamber 
47 which constitutes the interior of lamp 20. Compound 46 provides the 
means for support of the reflector and socket by the lens. 
Filament socket 24 includes a air of in-line passageways 48 and 49 into 
which contact prongs 41 and 42 are slidably inserted. A crossing 
passageway 50 is provided for a retaining compound in order to secure the 
two contact prongs in a desired orientation. 
Although the geometry and dimensions of the parabolic reflector 21, 
filament socket 24 and filament 23 are such that these component parts 
assemble together in a very accurate and precise manner, there is still 
some variation both as to geometry and dimensions which require that the 
placement of the filament be adjustable so as to place the center of 
luminance of the filament at the focal point of the parabolic reflector. 
As can be appreciated from the FIG. 2 illustration, each contact prong has 
a reduced diameter central portion around which a retaining compound is 
injected via passageway 50 thereby locking the two contact prongs in a 
fixed location relative to the socket. Once the subassembly of rods, 
prongs and the socket is completed, there is the opportunity for 
adjustment of the filament socket 24 relative to the parabolic reflector 
as can be appreciated by the sliding receipt of the filament socket by 
clearance aperture 51 which is centrally disposed within base portion 30. 
The separation existing between clearance aperture 51 and filament socket 
24 is filled with a retaining compound 52 which is inserted through port 
53. 
Socket 24 also includes two purge and fill passageways 56 and 57. These two 
passageways are each adapted with a conical port in order to permit 
filling and evacuating with dry nitrogen via adapted nozzles. As dry 
nitrogen is added and then evacuated, oxygen and water are purged from 
inner chamber 47 (as well as chamber 60). Once all oxygen and moisture are 
removed, chamber 47 and the collapsed portion of chamber 60 are filled 
with a mixture of inert gases, such as an argon-nitrogen mixture. This 
purging and filling is accomplished by a series of filling and evacuation 
steps ultimately concluding with inner chamber 47 being filled with an 
inert gas mixture at one atmosphere. As the purge and fill nozzles are 
removed from passageways 56 and 57, a sealing compound 56a is injected 
thereby closing off the passageways and sealing closed chambers 47 and 60. 
Expandable membrane 25 is sealingly attached to and around outer peripheral 
lip portion 45 at sealing point 58 and to and around filament socket 24 at 
sealing point 59. The two sealing points may be enhanced by providing an 
O-ring groove and a tightly fitted O-ring at each location. The result of 
that construction is that outer surface 29 of parabolic reflector 21 in 
combination with expandable membrane 25 define an expansion chamber 60 
which is completely enclosed except for being in flow communication with 
inner chamber 47 via the clearance spaces left between edge 31 and lip 
portion 45 (i.e., those areas not receiving retaining compound 46). 
Consequently, when filament 23 conducts current and heats up which in turn 
increases the temperature of the atmosphere (and inert gases) within inner 
chamber 47, the volumetric expansion of the gases is accommodated by being 
permitted to flow into expansion chamber 60. This volume increase causes 
expandable membrane 25 to expand outwardly to a configuration similar to 
that illustrated by phantom line 61. Clearly, the degree of volumetric 
expansion and the extent of pressure increase directly influence the 
degree of expansion of expandable membrane 25. Membrane 25 is constructed 
of a high-density, substantially impermeable, but thin-walled elastomeric 
compound. Phantom line 61 represents what is likely the maximum degree of 
expansion based upon normal operating conditions and temperature increases 
to be expected upon the energizing of filament 23. 
Purge and fill passageway 56 communicates directly with expansion chamber 
60 while purge and fill passageway 57 communicates directly with inner 
chamber 47. In this manner, both chambers can be purged of oxygen and 
water and sufficient inert gas mixture placed within inner chamber 47 to 
position the diaphragm so as to allow for both expansion and contraction 
of the gas. The result of this construction is an arrangement wherein the 
interior atmosphere of the lamp coincides accurately to the pressure of 
the outside atmosphere. This greatly minimizes, if not completely reduces, 
any pressure differences existing between the interior portions of the 
lamp and the outside atmosphere. This pressure balance reduces sealing 
requirements and maximizes the conductive nature of the inside atmosphere. 
The result is an improved lamp which can be described as an ambient 
pressure lamp. 
Referring to FIG. 6, the general design and construction of ambient 
pressure lamp 20 is illustrated in phantom form with the one change 
illustrated in solid line form, that one change being a revised lens 
construction. Ambient pressure lamp 70 includes virtually the same 
construction as to the parabolic reflector portion, the filament, the 
filament socket and the expandable membrane. The difference between 
ambient pressure lamp 70 and the previously described ambient pressure 
lamp 20 pertains to the design and construction of lens assembly 71. Lens 
assembly 71 includes a substantially flat lens member 72 having a stepped 
inner surface 73 and a substantially flat outer surface 74. Lens assembly 
71 further includes a substantially flat glass cover plate 75 which is 
received by and securely joined to the flat outer surface 74 of lens 
member 72. 
The particular construction represented by lens assembly 71 differs from 
that disclosed in FIG. 1 in that it is substantially flat throughout its 
entirety rather than being convex in nature. Typically, automobile 
headlamps have a convex outer lens member in order to provide a 
construction of greater strength for resistance to the internal pressure 
which builds up inside of the headlamp. Due to the internal pressures 
which do build up in conventional automobile headlamps, substantially flat 
outer lens members are not employed. In order to construct the lens of 
FIG. 1 in the convex shape which is illustrated, the lens is molded of a 
plastic compound so as to enable low-cost, mass production. One problem 
associated with the use of plastic for this lens member is that it is of a 
plastic construction throughout both as to the inner stepped surface 34 as 
well as the exterior surface 35. Consequently, the lens may be acted upon 
by various road and insect chemicals as well as being weathered by its 
exposure to the elements. As these various chemicals and elements act upon 
the lens member, it becomes scratched, and deteriorates. The result is a 
loss of incident light. The improved design representated by FIG. 6 is 
that because of the ambient internal pressure and the expandable membrane, 
strength requirements are not at issue. Therefore, a substantially flat 
all glass lens assembly may be employed, and although the inner lens 
member 72 is typically still of a plastic construction, it is fronted on 
its exterior or exposed surface by the flat glass cover plate 75. 
Consequently, it is a glass member rather than plastic which is acted upon 
by the various chemicals and weather elements, thus enabling the plastic 
to remain unaffected. The result is a much more durable and lasting 
headlamp which is able to maintain light intensity and focus throughout 
its useful life. 
Another advantage provided by the use of a substantially flat lens 
assembly, and in particular the presence of a substantially flat glass 
cover plate, is that the aiming nodes previously seen in FIG. 1 at points 
36 are not required. The aimining nodes of FIG. 1 are included in order to 
provide a means for establishing a planar surface inasmuch as the lens is 
convex. If the lens is not convex but rather flat as is disclosed in FIG. 
6, then there is no need for aiming nodes in order to establish proper 
lamp centering and squareness. Since a plane of reference is already 
provided, the aiming nodes can be eliminated. Consequently, the aiming 
nodes can be and are eliminated from the embodiment of FIG. 6, and become 
a part of the aiming fixture. 
Referring to FIGS. 4 and 5, the construction and method of fabrication of 
filament 23 are disclosed in greater detail. As has been previously 
described, filament 23 includes a tungsten wire 37 and a ceramic core 38. 
While these are believed to be the preferred materials for the particular 
lamp, it is to be understood that generally a filament of this nature is 
fabricated from a refractory metal such as tungsten or a tungsten alloy 
and that the core 38 is of a refractory compound which is capable of 
withstanding extremely high heat. Suitable materials for core 38 may 
include rare oxides or a mixture of rare oxides such as zirconia or 
magnesia. As is clearly illustrated in FIG. 3, refractory core 38 is 
configured with a helix-shaped channel 78 which extends for virtually the 
full length of core 38 with a constant pitch and depth. Tungsten wire 37 
is similarly formed with a helix configuration and the coil has an outside 
diameter which is substantially coincident with the outside diameter of 
the ceramic core. In order to achieve this end result, it is necessary 
that the depth of helix channel 78 generally correspond to the diameter of 
tungsten wire 37. The free ends 79 and 80 of the coiled tungsten wire are 
provided in order to be secured to support rods 39 and 40 as illustrated 
in FIG. 2. 
In order to facilitate the assembly of the coiled tungsten wire around the 
refractory core, it is preferred to initially form the tungsten wire by a 
separate fabrication step and then threadedly insert the core into the 
coiled wire while retained in the coiling machine. Due to the small size 
of the core and the coiled wire, it is neither convenient or feasible to 
attempt to coil the tungsten wire directly around the core. A 
significantly important aspect of this assembly procedure is that the 
tungsten wire is stiff and possesses relatively high elasticity. 
Consequently, coiling the wire directly around the ceramic core would 
thereafter allow the coiled wire to spring back or out thereby increasing 
the size of the coil and precluding a coincident cylindrical relationship 
between the outer diameter of the coil and the outer diameter of the core 
as illustrated in FIG. 3. Consequently, one method of fabrication of the 
core and coil assembly is illustrated in part by FIGS. 4 and 5. 
FIG. 4 discloses a coil mandrel 81 which includes a helix-shaped channel 82 
extending throughout virtually the entire length of the mandrel. The 
outside diameter of channel 82 is smaller than the outside diameter of 
channel 78. Therefore, as the tungsten wire is tightly wound around 
mandrel 81 by placement within channel 82, it has in this restrained 
condition (see FIG. 5) a smaller diameter than its ultimate end-use size. 
Next the coiled wire is partially unwound to an expanded diameter size and 
the mandrel is withdrawn. While the coiled wire is still held in its 
expanded condition, the core is threadedly inserted. Since the unwound 
diameter of the wire is slightly larger than the outside diameter of the 
core, their threaded fit is loose. However, once the wire is released, its 
spring character and the fact of its earlier forming on the mandrel cause 
the wire to spring back tightly into channel 82 and around core 38. By 
separately coiling the segments of tungsten wire on mandrels such as 
mandrel 81 and thereafter threadedly inserting the cores into the 
individual segments of coiled tungsten wire, the entire filament 
fabrication procedure can be automated and is both reliable and low-cost. 
FIG. 7 is provided as an illustration of a front-on view of ambient 
pressure lamp 20. Due to the fact that the convex nature of lens 22 of 
FIG. 1 geometrically projects as a flat circular plate, FIG. 7 is 
representative of both ambient pressure lamp as well as ambient pressure 
lamp 70. The sole difference between these two embodiments relative to the 
illustration of FIG. 7 is that nodes 36 are provided in FIG. 7, but such 
nodes are not part of ambient pressure lamp 70. The front center portion 
of lens 22 is broken away in order to illustrate the centralized location 
and the orientation of filament 23. 
While the invention has been illustrated and described in detail in the 
drawings and foregoing description, the same is to be considered as 
illustrative and not restrictive in character, it being understood that 
only the preferred embodiment has been shown and described and that all 
changes and modifications that come within the spirit of the invention are 
desired to be protected.