Electric lamp assembly with threaded base portion

There is disclosed an electric lamp assembly with a threaded base, the assembly including a lamp envelope, a threaded base, and a light source. The electric lamp with threaded base includes portions of the threaded base positioned in concavities formed on a tubular end of the lamp envelope. No melt junction, and no glues are needed in coupling the envelope and base. The coupling is strong enough to resist decoupling by hand and grows stronger with time.

BACKGROUND OF THIS INVENTION 
1. Field of the Invention 
This invention relates to electric lamps and, more particularly, to 
electric lamps with threaded bases. 
2. Description of the Prior Art 
Tungsten halogen lamps are known in the art and have an inner capsule which 
contains the tungsten halogen apparatus, and an outer envelope which 
guards against possible non-passive fracture of the inner capsule, and 
shields the user from the high surface temperature of the inner capsule. 
The inner capsule is mounted on a frame inside the outer envelope, with 
the frame acting as an electrical connection for the inner capsule. 
Tungsten halogen lamps can produce a higher quality light, be more 
efficient, and have a longer life than ordinary filamented lamps. 
During assembly, the frame and inner capsule are inserted in the outer 
envelope, and a threaded base is screwed onto the outer envelope. The 
threaded base pinches exterior arms of the frame against an envelope neck 
to make electrical contact and hold the frame in place. To make good 
electrical contact, and to ensure the base is not subsequently unthreaded, 
the frame-to-base contact has been made by a sharp point, directed in the 
threading direction. As the base threads over the frame, the frame points 
dig progressively deeper into the base. In final position, the frame 
points are well embedded in the base, ensuring electrical contact, and are 
pointed against the unthreading of the base to prevent removal of the 
base. Because of variations in the pointed ends, the lengths of the frame 
components, molded glass dimensions and similar causes, the frame ends do 
not always contact the base equally. The frame can then be twisted in the 
outer envelope, leaving the inner capsule misaligned and presenting both a 
cosmetic problem and a mechanical problem. The misaligned inner capsule 
can knock against the outer envelope during shipment and break. The life 
of the inner capsule may also be affected by the irregular heat flow 
around the adjacent outer envelope. There is thus a need for a support 
frame that consistently centers the inner capsule in the outer envelope. 
Double envelope, tungsten halogen lamps are, in manufacture, assembled by 
hand threading the base to the lamp neck. The torque characteristic of 
lamps with pointed frame ends is not a linear force, but is an increasing, 
and perhaps, even an accelerating force. The high torque needed to thread 
the base to its final position may lead to injuries from repeated high 
stress of the assemblers' fingers, hands, or wrists. By reducing the 
diameter of the support frame wire, the support frame may be made more 
flexible, but a more flexible support frame allows greater sway in the 
assembled lamp. Greater flexibility in the support frame is also likely to 
result in a bent, or distorted support frame. There is then a need for a 
double envelope electric lamp with a low assembly torque support frame for 
the internal capsule that is unlikely to sway or be distorted. 
Standard lamps have frequently been sealed by cementing or epoxying the 
threaded metal base to the outer glass envelope. Fluid or paste glues and 
cements are not easy to work with in an assembly line operation. 
Inadequate gluing may occur, allowing the base to open, while excessive 
gluing may leave the lamps cosmetically unacceptable. Glues and cements 
are also usually relatively expensive materials. There is thus a need for 
a capsule lamp having the metal base fixed to the outer envelope without 
glue or cement. 
Small portions of the threaded base have also been peened into slots formed 
in the lamp envelope. Peening requires that the lamp be properly oriented, 
so the peenings properly complement the preformed envelope slots. 
Alignment of peening apparatus and envelope slots consumes time, and 
machinery is required to properly execute such alignment. Peening 
regularly results in broken product, where the peening strike is 
excessive. Alternatively, less peening force can yield lamps with bases 
that loosen. There is thus a need for a lamp with a mechanically sealed 
envelope and base connection that does not require alignment of peening 
apparatus and envelope slots. 
Hand assembly of lamps does not usually lead to strong mechanical couplings 
between bases and envelopes. On the other hand, a lamp envelope, being 
made of glass, necessarily is fragile, and a mechanical coupling made by a 
machine often leads to fracture of the lamp envelope, and wasted product. 
There is then a need for a machine-made mechanical coupling between the 
outer envelope of a capsule lamp and a threaded metal base, which coupling 
reduces or eliminates waste through fracturing of envelopes. 
Examples of the prior art are shown by the following U.S. patents: 
U.S. Pat. No. 3,194,625 issued to G. K. Danko on Jul. 13, 1965, for an 
Electric Lamp with Unitary Inner Envelope and Stem Assembly and 
Manufacturing Thereof, shows a threaded base lamp with an internal capsule 
integral with an outer envelope. The threaded base is cemented to the 
outer envelope. 
U.S. Pat. No. 3,243,634 issued to F. A. Mosby on Mar. 29, 1966, for an 
Electric Lamp and Support Web, shows a threaded base lamp with an internal 
capsule supported from the threaded base. The threaded base is cemented to 
the outer envelope with an epoxy. 
U.S. Pat. No. 4,657,809 issued to R. G. Blaisdell et al. on Mar. 3, 1987, 
for Electric Lamp with Self-Mounting Frame-Assembly and Method of 
Constructing Same, shows a threaded base lamp with an internal capsule. 
The internal capsule is supported on a wire frame that has spiked ends 
bent around the opening of the outer envelope. The threaded base is 
threaded to the outer envelope, causing the spiked ends to be compressed 
and pointed into the base. The spikes resist unthreading of the base from 
the outer envelope. 
U.S. Pat. No. 4,959,583 issued to Vito J. Arsens et al., on Sep. 25, 1990, 
for Reflective Lamps Having An Improved Light Source Mounting Arrangement, 
shows a threaded base lamp with an internal capsule. The threaded base is 
coupled to the outer envelope by a high temperature resistive adhesive. 
SUMMARY OF THE INVENTION 
Accordingly, an object of the present invention is to provide an electric 
lamp assembly of the tungsten halogen type, which assembly includes a 
support frame which centers the inner capsule within the outer envelope, 
which support frame is unlikely to sway or be distorted, and which 
assembly includes a threaded base portion which is mechanically sealed to 
the glass envelope without requiring glue or cement, and without 
fracturing of the glass envelope. 
With the above and other objects in view, as will hereinafter appear, a 
feature of the present invention is the provision of an electric lamp 
assembly with a threaded base portion, the assembly comprising a lamp 
envelope having a wall defining an enclosed chamber, a tubular end 
defining an opening to the enclosed chamber, and having a series of 
prominences encircling the tubular end, the prominences defining a series 
of corresponding concavities respectively intermediate respective pairs of 
prominences, the threaded base portion being coupled to the tubular end of 
the lamp envelope, the threaded base portion having thereon an end ring 
extending at least partially into the envelope tubular end concavities, 
and a light source enclosed in the lamp envelope having an electrical lead 
in contact with the threaded base. 
The above and other features of the invention, including various novel 
details of construction and combinations of parts, will now be more 
particularly described with reference to the accompanying drawings and 
pointed out in the claims. It will be understood that the particular 
devices embodying the invention are shown by way of illustration only and 
not as limitations of the invention. The principles and features of this 
invention may be employed in various and numerous embodiments without 
departing from the scope of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to FIG. 1, it will be seen that an illustrative embodiment of an 
electric lamp assembly 10 includes a lamp envelope 12 and a light source 
22 mounted within the envelope 12. 
The lamp envelope 12 may be of quartz, glass, or any other suitable light 
transmissive material. The preferred material is glass. The lamp envelope 
12 includes a wall 14 defining an enclosed chamber 16 and an opening 18 at 
a generally tubular end 20. The wall 14 preferably defines a standard 
light bulb, or an A-line bulb. The enclosed chamber 16 is sufficiently 
large to house the light source 22, such as a tungsten halogen light 
capsule, or an arc discharge capsule, and a support frame 24. 
Formed as a portion of the lamp envelope 12, extending from the enclosed 
chamber 16, and ending at the opening 18, the tubular end 20 is aligned 
along a lamp axis 26. The tubular end 20 may be provided with a constant 
or variable diameter along the axial length at any selected point along 
its axial length. The preferred tubular end 20 is provided with a circular 
cross section, and a constant or decreasing diameter as the opening 18 is 
approached from the enclosed chamber 16. 
Referring to FIGS. 3 and 4, it will be seen that circularly distributed 
around the tubular end 20 are a series of prominences 28 defining 
therebetween a series of intermediate concavities 30 (FIG. 3). The 
prominences 28 and intermediate concavities 30 are distributed around a 
collar portion 32 of the tubular end 20, in a plane normal to the axial 
cross section of the tubular end 20. The preferred prominences 28 are a 
regularly spaced series of rounded peak bumps disposed in circular fashion 
around the tubular end 20. The prominences 28 define the series of 
intermediate concavities 30. Between two sequential prominences 28 is a 
concavity 30, and adjacent a prominence 28, on either side thereof, are 
two concavities 30. 
Referring to FIG. 5, it will be seen that the concavities may be formed 
alternatively as flat planes 30' between prominences 28' giving the cross 
section of collar portion 32' something of a polygonal form. Making the 
concavities 30' flatter, or less deep, enhances the sealing contact 
between lamp envelope 12 and a threaded base, but is believed to reduce 
the resistance of the base to unthreading. 
The concavities may be indented further, as deep indentations 30" (FIG. 6), 
so that collar portion 32" has a geared, or splined form. In FIG. 6 are 
shown concavities 30" and prominences 28" with deep sinusoidal 
indentations forming a gear-like pattern. Increasing the depth of the 
cavitations 30" is thought to increase the resistance of a base to 
unthreading, but reduces the sealing contact between the lamp envelope 12 
and a threaded base. The concavities 30, 30' and 30" have sufficient depth 
34 and width 36 to receive an indented portion of an adjacent threaded 
base to be described hereinafter. A radial angle 38 of 15 or more degrees 
subtending each concavity 30 is preferred. 
In a preferred embodiment, ten or twelve prominences 28 are formed around 
the collar portion 32 of the tubular end 20, similarly forming ten or 
twelve intermediate concavities 30 with radial angles 38 of from 15 to 18 
degrees each. The preferred concavities 30 have smooth concave faces. The 
preferred prominences 28 have a peak dimension 34 that preferably is 
greater than the wall thickness 62 of the threaded base (FIG. 7). 
In the preferred embodiment, adjacent the collar portion 32, the ring of 
prominences 28 and concavities 30, on a side of the collar portion away 
from the opening 18 is a circular rib 40 (FIG. 3). Lead troughs 44 are 
molded in the tubular end 20, extending from the opening 18, across the 
tubular end 20, towards the circular rib 40, and ending adjacent the 
collar portion 32. The lead troughs 44 have a width and depth sufficient 
to receive a light source lead, or leg of the support frame 24, to be 
trapped between the lamp envelope 12 and the lamp base 60, thereby making 
a secure electrical connection to the threaded base 60. 
By way of example, the lamp envelope 12 is shown in the drawings as a 
conventional bulb with the tubular end 20 formed thereon. Formed on the 
tubular end 20 are ten rounded prominences 28 distributed equiangularly 
(36 degrees) around the collar portion 32 of the tubular end 20. 
Intermediate the prominences 28 are ten smooth surfaced concavities 30. 
The tubular end 20 is additionally molded with lead troughs 44. The lamp 
envelope 12 need not necessarily include a lead trough 44, as the light 
source lead may be soldered, pinched to, or otherwise electrically coupled 
to, the threaded base 60. 
The light source 22 may be of any selected form with two exposed electric 
leads 50, 52 (FIG. 1). The lamp envelope 12 encloses the light source 22, 
along with the support frame 24, if a frame support is used. The threaded 
base 60 seals the light source 22 in the enclosed chamber 16, and 
electrically connects to the lamp lead. By way of example, the light 
source 22 is shown as a single ended tungsten halogen capsule 54 with a 
press sealed quartz tube 56, and the two electric leads 50, 52 extending 
from the press seal. One lead 50 is connected to the support frame 24 that 
is, in turn, connected to the threaded base 60 side wall contact. The 
other lead 52 may be connected to a center contact 70 (FIG. 1). Other 
suitable light sources may be used, such as a double ended tube, a high 
intensity arc discharge source, or a low intensity source. 
The threaded base 60 is illustrated in FIG. 7. The threaded base 60 may be 
made of brass, aluminum, or other malleable and conductive metals, to have 
the general form of a cup with a threaded side wall. The tubular end 20 of 
the lamp envelope 12 slidingly receives the threaded base 60. The 
preferred threaded base 60 has an end ring 64, a base threading 66 formed 
in a side wall, an insulating ring 68, and the center contact 70. The end 
ring 64 of the threaded base 60 has an axial extension 72 sufficient to 
span at least a portion of the collar portion 32 with the ring of 
prominences 28 and concavities 30, when the lamp envelope 12 is properly 
positioned in the threaded base 60. The preferred threaded base 60 has an 
internal diameter sufficient to slidingly mate with the tubular end 20 of 
the lamp envelope 12 while entrapping a light source lead, or leg of the 
support frame 24 in a lead trough 44. The preferred end ring 64 is a right 
circular tube, having an internal diameter substantially the same as the 
external diameter of the collar member ring of peaks of the prominences 
28, and having an axial length equal or greater than the axial length of 
the ring of prominences 28 and concavities 30. The end ring 64 closely 
fits upon, and covers the ring of prominences 28 and concavities 30. 
Positioned along the exterior side wall of the threaded base 60 is the 
base threading 66, sized to fit a lamp socket. In the preferred threaded 
base 60, positioned at the end of the threaded base 60 around the axis 26 
is the insulating ring 68, and positioned at the end of the threaded base 
60 at the axis 24 is the center contact 70. The insulating ring 68 may be 
of glass, and the center contact 70 may be a metal eyelet. The insulating 
ring 68 and center contact 70 form the standard center contact, typical of 
common light bulbs. 
An electric lamp 10 with a threaded base may be assembled by performing the 
following steps. First, a glass lamp envelope 12 is molded having the 
above-mentioned envelope features. Similarly, a threaded base 60, such as 
a brass base, is made, also with the above-mentioned base features. In the 
preferred procedure, the legs of the support frame 24 are bent to form 
hooks, and one lead 50 of the light source 22 is welded to the support 
frame 24. The light source 22 and support frame 24 unit is then inserted 
in the lamp envelope 12, with the hooked support frame legs positioned in 
the lead troughs 44. The second lead 52 extends axially out of the 
enclosed chamber 16, through opening 18. The threaded base 60 is then slid 
over the second lead, so the second lead passes through the eyelet forming 
the center contact 70. The threaded base 60 is then slid over the lamp 
envelope tubular end 20, trapping the legs of the support frame 24 in the 
lead troughs 44 in contact with the threaded base 60 side wall. The 
threaded base 60 is threaded forward until the end ring 64 is aligned to 
cover the ring of prominences 28 and concavities 30 of the lamp envelope 
12. Sliding the base onto the lamp envelope 12 may cause the inside 
portions of the base threads 66 to press progressively harder against the 
legs of the support frame 24 in the lead troughs 44, thereby forming a 
hard-pinched contact between the threaded base 60 and the trapped support 
frame legs. The second lead 52 is then soldered to the eyelet forming the 
center contact 70, and any excess lead is trimmed appropriately, if 
needed. 
The lamp envelope 12, with the threaded base 60 in position, may then be 
held coaxially in a rotatable cup 74 (FIGS. 8 and 9). In FIG. 8, there is 
illustrated equipment for roller sealing an electric lamp, the equipment 
being shown prior to the sealing operation. The preferred cup 74 includes 
a rubber grip 76 to frictionally grasp the lamp envelope 12. A roller 
sealing assembly is then advanced from the position shown in FIG. 8 until 
a rotating contact 80 engages the center contact 70 of the threaded base 
60 (FIG. 9). 
As may be seen in FIG. 9, with the lamp envelope 12 and threaded base 60 
rotating in the cup 74, swing arms 82, 84 are advanced to move pressing 
wheels 86, 88 against the threaded base 60 along the end ring 64. The 
pressing wheels 86, 88 are aligned to contact diametric sides of the 
threaded base 60 and end ring 64 with sufficient pressure to press the end 
ring 64 against the lamp envelope 12 along the prominences 28, and down 
into the concavities 30. The lamp envelope 12 and threaded base 60 are 
then rotated, while pressure from the pressing wheels 86, 88 forces the 
end ring 64 against the prominences 28, and into the concavities 30. The 
end ring 64 is thereby trapped in the concavities 30 and the threaded base 
60 is sealed to the lamp envelope 12, and has high resistance to 
unthreading of the threaded base 60 from the lamp envelope 12. Epoxy need 
not be used in the lamp envelope to threaded base coupling. Tests have 
been performed that indicate the roller sealed threaded base 60 is not 
easily unthreaded from the lamp envelope 12 with ordinary human strength. 
Further, it has been found that over time a reaction occurs between the 
glass of the envelope 12 and the metal of the threaded base 60, which 
actually strengthens the bond therebetween. 
In a preferred embodiment, the lamp envelope 12 is of glass, and is 
provided with the wall 14, the enclosed chamber 16, the tubular end 20, 
and ten prominences 28 and intermediate concavities 30 formed on the 
collar portion 32. The tubular end is provided with an outside diameter of 
25.0 millimeters (0.985 inch). The concavities are about 2.235 millimeters 
(0.088 inches) wide. Adjacent the collar portion is the circular rib 40, 
about 3.2 millimeters (0.126 inch) axially wide. The lamp envelope has two 
leads troughs, diametrically positioned, each about 1.65 millimeter (0.065 
inch) wide, 0.86 millimeters (0.034 inch) deep, and 7.34 millimeters 
(0.289 inch) axially long. The threaded base is of brass, and has a 
tubular end with an end ring 27.0 millimeters in diameter (1.075 inch), an 
insulator ring 15.62 millimeters in diameter (0.615 inch), and an 
eyelet-like center contact 10.0 millimeters in diameter (0.40 inch) and 
threading. 
There is thus provided an electric lamp assembly including a support frame 
which centers the inner capsule in the outer envelope and which requires 
low assembly torque, but is unlikely to sway or be distorted in assembly. 
There is further provided a capsule lamp having a metal base fixed to an 
outer envelope by a mechanical seal not requiring the application of glue 
or cement, which mechanical seal can be rendered by machine without undue 
loss or waste through fractures of envelopes. 
It is to be understood that the present invention is by no means limited to 
the particular construction herein disclosed and/or shown in the drawings, 
but also comprises any modifications or equivalents within the scope of 
the claims.