SINGLE END HALOGEN INCANDESCENT BULB
The present invention relates to an incandescent halogen bulb having a light
transmitting envelope which encloses a sealed cavity with a pinch or press seal at one end.
A coiled filament is disposed with the sealed cavity and connected with a pair of lead
5 wires. More particularly, the invention relates to a single end incandescent halogen bulb
having a filament wherein both ends of the coil are pulled out and respectively clamped to
a pair of lead wires.
Figs. 1 A -1C show a previously proposed filament arrangement wherein one end of
the coiled filament is pulled out straight and clamped to a current supply wire through a
10 flattened clamp, while at the other end of the coil is, while still coiled per se, connected to
the a second current supply wire via a standard clamp arrangement.
In the drawings:
Fig. 1 A is a side view of a previously proposed filament arrangement
Fig. IB is a front end view showing the manner in which one end of a coiled
15 portion of a filament depicted in Fig. 1A, is clamped to a supply wire.
Fig. 1C is a rear end view showing the manner in which a second end of a coiled
portion of a filament of the arrangement depicted in Fig. 1A, is clamped to a supply wire.
Fig. 2A is a side view showing an exemplary embodiment of the invention
Fig. 2B is a front end view showing the manner in which one end of a coiled
20 filament depicted in Fig. 2A, which has been pulled out, is to a supply wire.
Fig. 2C is a rear end view showing the manner in which a second end of the coiled
filament depicted in Fig. 2A, is also pulled out and clamped to a supply wire.
Fig. 3 shows the arrangement of Fig. 2A disposed in a sealed envelope.
As shown in Figs. 2A - 2C and 3, both ends of the coiled filament 100 (shown as
25 an elongate rectangle for the sake of illustration) are pulled out so as to be essentially
straight and to form first and second filament legs 102, 104. These filament legs 102, 104
have diameters which are approximately those of the wire from which the filament 100 is
formed, and are clamped to first and second current supply wires 106, 108. As shown, the
first current supply wire 106 passes through the pinch or press seal 110 formed at the
30 bottom of the hard-glass envelope 112, and enters the cavity 114 which is defined in the
envelope 112. In this embodiment, the cavity 112 is filled with a halogen compound and
an inert gas and the filament 100 is made of tungsten wire.
The second current supply wire is shorter than the first, and is arranged to terminate
in the press seal 110. The second of the filament legs 104 is arranged to extend into the
press seal 110 and to be clamped to the second current supply wire by the clamp 116.
This arrangement has the advantages that the first filament leg 102, because it is
5 pulled out straight it provides better support for the filament coil 100 than in the instance a
portion of the coiled filament is clamped in the manner shown in Fig. IB. That is to say, as
the length of filament which is clamped in the manner shown in Fig. IB, is still coiled per
se, it tends to act as a spring and can extend and contract in the manner similar to a
"slinky®" spring. With the embodiment of the invention, the first filament leg 102 material
10 length is shorter and smaller effective diameter. It expands less for the same leg length and
temperature, and moreover provides improved mechanical support for the main body of
the filament 100.
In addition, the clamp 118 which is formed at the upper end of the first current
supply wire 106, can be flattened with a force which is not applicable with the arrangement
15 shown in Figs. 1A and IB. That is to say, with this embodiment there is no fear of
crushing and breaking the filament and a clamping force can be applied which will
assuredly provide a good electrical connection.
The lower filament leg 104 is, as noted above, clamped to the second current supply
wire by a clamp 116. This clamp is, as shown in Fig. 3, buried in (sealed within) the press
20 seal 110. The portion of the lower filament leg 104A which is buried in the press 1 10
along with the clamp 116, acts as a redundant series element, supporting the end of life
action of filament leg 104A to assure passive extension of the end-of-life arcing when it
One method of producing the above arrangement comprises drawing the ends of the
25 coiled wire filament 100 out straight to form the first and second filament legs 102, 104
which have diameters which are approximately the same as diameter of the wire from
which the coiled filament is formed. This can be followed (not necessarily in the listed
order) by the steps of clamping the first filament leg 102 to a first current supply wire 106
using the clamp 118 formed at a terminal end thereof; suspending the filament 100 within
30 the cavity 112 using the first current supply wire 106; clamping the second filament leg
104 to the second current supply wire 108 using the clamp 116 formed at a terminal end
thereof; adjusting the positions of the first and second current supply wires 106, 108 with
respect to each other and the envelope 112 in which the cavity 114 is formed so that the
coiled wire filament 100 is located in a predetermined position within the cavity 114; and
sealing a portion of the second filament leg 104 and the terminal end of the second current
supply wire 108 in the press seal 110 which is formed at end of the envelope and which
5 closes one end of the cavity 114.
The disclosure of PCT publication WO 02/01601 published on January 3, 2002 is
hereby incorporated by reference thereto.
Even though the invention has been described with reference to only a limited
number of embodiments, the various modification and changes which can be made without
10 departing for the scope of the claims, which is limited only by the appended claims, will be
self-evident to the person of skill in the art which the present invention pertains.