Patent Grant
6856090
The present invention relates generally to incandescent halogen lamp assemblies, and more particularly to incandescent halogen lamp assemblies used in vehicle headlamp systems that are designed to reduce glare attributable to reflection from interior lamp components.
Vehicle headlamp systems have experienced many adaptations over the years, including the use of incandescent halogen lamps which result in increased light output and lower energy consumption. Unlike traditional incandescent lamps, where a filament is surrounded by an inert gas such as argon (Ar), incandescent halogen lamps envelop the filament with a gas composition that includes a gas from the halogen group. In both designs, the filament, generally tungsten (W), is supported by and connected to electric current carrying lead wires which supply the filament with current and cause it to become a glowing “white hot” according to a process commonly known as incandescence. A consequence of the incandescence process is that the filament is heated to extreme temperatures and begins to evaporate such that tungsten atoms are released into the surrounding volume. In traditional incandescent lamps, the released tungsten atoms are deposited onto a large glass bulb surrounding the filament, thereby darkening the bulb and weakening the filament. Unique to incandescent halogen lamps is the ability for the evaporated atoms to combine with the surrounding halogen gas and subsequently redeposit themselves back onto the filament, a process sometimes referred to as the halogen cycle. In this process, when the evaporated tungsten atoms are in the vicinity of a surrounding quartz envelope, they are somewhat cooled and combine with the halogen gas to form a tungsten halide molecule. This molecule then migrates back to the vicinity of the heated filament, which decomposes the molecule such that the tungsten is deposited back onto the filament and the halogen gas is released into the surrounding volume. Thus, the incandescent halogen lamp undergoes a type of recycling process, thereby increasing the life of the lamp. Moreover, the incandescent halogen lamp can be operated at a hotter temperature, thereby increasing the light emission per unit of energy. While incandescent halogen lamps improve many of the characteristics of vehicle headlamp systems, there still remains much room for further improvement.
For instance, a portion of the total light emitted from incandescent halogen lamps often reflects off of interior components of the lamp, such as the lead wires, and results in uncontrolled stray light appearing as glare to oncoming drivers. U.S. Pat. No. 4,302,698 issued Nov. 24, 1981 to Kiesel et al. discloses an incandescent halogen lamp for use in a vehicle headlamp assembly. The embodiment shown in
Addressing this concern, some designs have incorporated filaments having long leg portions and short lead wires, as will be subsequently discussed. In these designs, the filament has a long, thin leg portion that extends from its uppermost end and bends downward at approximately a 90° angle. The thin leg portion extends alongside the filament until it connects with a thicker lead wire proximate the lowermost end of the filament. Because the filament leg is substantially thinner than the shortened lead wire, it does not interfere with the light emission to the extent that a thicker lead wire running alongside the filament would. Accordingly, designs of this nature realize the benefits of utilizing an incandescent halogen lamp and reduce the amount of stray light, and hence glare, attributable to reflection off of internal lamp components. While these designs can improve the illumination performance of the lamp assembly, they can also compromise its structural integrity. The thin filament leg portion is weaker than the substantially thicker and stronger lead wires previously discussed. Consequently, these designs may have difficulty satisfying testing requirements, particularly vibrational testing.
Thus, it would be advantageous to provide an incandescent halogen lamp design that reduces glare due to reflection from interior lamp components, such as lead wires, but does not compromise the structural integrity of the lamp.
The above-noted shortcomings of prior art incandescent lamps are overcome by the present invention, which in one aspect comprises an incandescent lamp having a filament capable of emitting light, a lead wire, and an envelope. The lead wire supports the filament and at least partially forms an electrical network capable of supplying the filament with electric current. The envelope surrounds the filament and at least a portion of the lead wire. The lead wire has a flattened outer end that includes a narrow profile and a wide profile, with the flattened outer end being oriented such that the narrow profile is aligned with the direction of illumination of light emitted by the filament. This provides the advantages of providing good mechanical support for the filament while helping minimize the amount of undesirable light reflection off the support lead.
Preferably, the incandescent lamp is a halogen vehicle headlamp, and can include a second filament also supported by a lead wire having a flattened outer end, with the two filaments being connected at their other end to a third, common ground lead wire. The lamp can also be part of a complete vehicle headlamp system that includes the lamp, a reflector, and a front lens.
In accordance with another aspect of the present invention, there is provided a method for of forming the incandescent lamp. The method includes the steps of forming a first lead wire by flattening an end portion of a section of electrically-conductive wire, providing a second lead wire formed from a section of electrically-conductive wire, attaching a filament between the second lead wire and the flattened end portion of the first lead wire, and sealing the filament and at least a portion of the first and second lead wires within a glass envelope. During the assembly of these components together, the flattened end portion is oriented such that the it lies within a plane that intersects the filament. Preferably, the end portion is flattened by stamping and this stamping operation can also be used to simultaneously impart a roughened surface texture to the end portion to further reduce the amount of light reflected off the end portion. Other surface treatments such as coating can be used as well to provide a roughened surface on the flattened end portion.
Referring to
In operation, the prior art incandescent halogen lamp 10 emits visible light by selectively supplying electric current through the lead wires such that one of the two filaments are energized. This energization causes the filament to emit light which exits envelope 14 and is focused in front of the vehicle by reflector 16. As previously mentioned, it is desirable to create an incandescent halogen lamp that reduces glare caused by reflection off of internal components. Moreover, it has been found that a significant portion of the internal component glare is attributable to reflection off of the lead wires. Thus, the prior art lamp assembly seen in
Referring now to
Interior components 52 are similar to those commonly found in most incandescent halogen lamps and generally include positive lead wires 60 and 62, ground wire 64, high beam filament 66, low beam filament 68, and support bridge 70. Lead wires 60 and 62 are part of an electrical network of the vehicle headlamp system and act as positive terminals to filaments 66 and 68, respectively. Ground wire 64 is also part of the electrical network and functions as a common ground for the two filaments. Each of these three wires passes through support bridge 70, which is a disk-shaped component comprised of a high temperature material similar in nature to the envelope, and acts as a spacer and support for the wires. At the uppermost end of each of the positive lead wires 60 and 62, there is a flattened outer end section 72 and 74, respectively. These sections are formed by a flattening tool that, prior to assembly of the lamp, is used in a stamping operation to deform the end portion of the positive lead wires into a flattened shape. The surface of the flattening tool can have a textured surface so that this stamping operation can be used to simultaneously flatten the end portion and impart a roughened surface to that end portion. It is envisioned that this flattening tool could impart other non-reflective surface features onto the flattened outer ends at the time of flattening, and that the flattened outer ends can be provided with a roughened surface treatment in other ways, such as non-reflective coatings, etc. Thus, positive lead wires 60 and 62 begin as uniform lengths of wire, but are later flattened at an outer end such that the flattened sections have a narrow profile in a first direction, and a wide profile in a second direction. The views seen in
As indicated in the drawings, only a portion (such as the end portion) of the positive lead wires 60 and 62 are flattened, such that these lead wires have both a flattened portion and a non-flattened portion. The flattened portion of each lead wire 60, 62 runs alongside its associated filament with the non-flattened portions being located below the filaments where they cause little if any undesirable reflection of light coming from the filaments. The lead wires 60, 62, and 64 have a generally circular cross-sectional shape. Also, as indicated in
It should also be noted that the mass of flattened outer ends 72, 74 has not been reduced, unlike the thin leg portion 32 seen in
Filaments 66 and 68 are helical, spring-like tungsten filaments that are supported by lead wires 60 and 62, respectively, and are capable of emitting visible light when energized with sufficient electric current. Best seen in
Envelope 54 is comprised of a high temperature, transparent material and generally includes a main body portion 80, a non-transparent tip portion 82, and a base portion 84. The main body portion is generally cylindrical in shape and axially extends from base portion 84 to tip portion 82. This portion of the envelope is transparent, as light is intended to radially exit the main body portion, strike the reflector, and be redirected in front of the vehicle. In order to reduce stray light that could otherwise be transmitted out of the tip of the envelope, tip portion 82 has a non-transparent, or even reflective, coating applied to it. Therefore, the high majority of light emitted by the filaments must pass through the transparent main body portion 80 and be focused by reflector 56, a process that produces more precise and focused illumination patterns than emitting light directly out of tip portion 82. Base 84 may take on one of any number of shapes necessary to accommodate attachment to the reflector or another headlamp system component, as is commonly known in the art.
Reflector 56 is part of the greater vehicle headlamp system and is generally a reflective parabolic component having a focal point corresponding to the position of one of the filaments, preferably low beam filament 68. By positioning the low beam filament with respect to the focal point of the reflector, it is possible for the reflector to focus and redirect the impinging light rays such that they leave the reflector in an essentially parallel orientation. This reduces spreading of the illumination pattern and thereby decreases the amount of glare seen by oncoming drivers.
Operation of the present invention is best described in conjunction with the top down view of the present invention shown in FIG. 3. In use, the vehicle headlamp system selectively applies electric current to one of the two positive lead wires 60, 62 (not shown) depending on whether the high or low beams have been selected. If the high beams are chosen, electric current is supplied through lead wire 60, flattened outer end Section 72, filament 66, and ground wire 64. The current through the filament energizes the filament such that it emits visible light, as demonstrated by the light rays shown in FIG. 3. Similarly, if the low beams have been engaged, the headlamp system will send a current through lead wire 62, flattened outer end section 74, filament 68, and ground wire 64, thereby causing the filament to emit visible light. As light emanates from the filament, it radially exits the transparent main body portion 80 of the envelope and strikes reflector 56. Thus, the light rays leave the reflector in a generally parallel manner, thereby creating a tight illumination pattern and minimizing glare producing stray light.
As previously mentioned, a significant portion of the stray light commonly produced by incandescent halogen lamps is attributable to reflection off of internal components, such as the lead wires. In response to this undesirable reflection, the otherwise thick lead wires of the present invention have been flattened such that there is little obstructing surface area to interfere with light emanating from the filaments. Again referring to
It will thus be apparent that there has been provided in accordance with the present invention an incandescent halogen lamp which achieves the aims and advantages specified herein. It will, of course, be understood that that foregoing description is of a preferred exemplary embodiment of the invention and that the invention is not limited to the specific embodiment shown. Various changes and modifications will become apparent to those skilled in the art and all such changes and modifications are intended to be within the scope of the present invention.
| Number | Name | Date | Kind |
|---|---|---|---|
| 3904908 | Wolfe et al. | Sep 1975 | A |
| 4302698 | Kiesel et al. | Nov 1981 | A |
| 4492893 | Steiner et al. | Jan 1985 | A |
| 4801845 | Kiesel | Jan 1989 | A |
| 5313135 | Fletcher | May 1994 | A |
| 5856723 | Rittner | Jan 1999 | A |
| 5857764 | Tabata et al. | Jan 1999 | A |
| 5949181 | Tabata et al. | Sep 1999 | A |
| 6093999 | English et al. | Jul 2000 | A |
| Number | Date | Country | |
|---|---|---|---|
| 20030184223 A1 | Oct 2003 | US |
