Patent Application
20120098407
The present disclosure relates to an incandescent lamp, more specifically, to a filament coil structure with a different geometry. The filament coil structure finds particular application in vehicle headlamps or headlights, although it will be appreciated that selected aspects may find application in related applications encountering issues of increasing contrast of the cut-off region.
U.S. Publication No. 2006/0038471 and U.S. Pat. No. 7,456,558 disclose incandescent lamp filaments having different pitch ratios located at opposite ends of the filament in order to increase the luminance at the light/dark boundary of the low beam. The pitch ratio is represented by the following equation:
PR=h/d
Even in light of recent advances, the industry continues to lack a filament with useful geometry for achieving high luminance in the region of the light/dark boundary of the low beam vehicle headlight where good illumination is desired.
In an exemplary embodiment, a filament coil for an incandescent lamp assembly includes a helical winding extending generally along a longitudinal axis between a first end and a second end. The winding has a first pitch ratio at the first and second ends, and a different, second pitch ratio along an intermediate portion located between the first and second ends.
In one embodiment of the disclosure, a first helical pitch is less than a second helical pitch.
In still another embodiment of the disclosure, the coil has substantially the same diameter at the first and second ends, and a smaller diameter along the intermediate portion.
A method of forming a filament coil for an incandescent lamp includes supplying a helical winding having an intermediate portion located between first and second ends along a longitudinal axis. The method further includes providing a first pitch ratio at the first and second ends, and a different, second pitch ratio at the intermediate portion.
A primary benefit realized by the filament coil for an incandescent lamp is the ability to increase the maximum luminance of the vehicle headlight around a hot-spot region.
Another benefit realized by the filament coil for an incandescent lamp is the ability to increase the maximum luminance of the vehicle headlight by changing the filament geometry.
Still another benefit realized by the filament coil for an incandescent lamp is the ability to sell new competitive products in the automotive aftermarket segments with an increased luminance and without having to replace an entire headlamp assembly.
Still other features and benefits of the filament coil for an incandescent lamp will become more apparent from reading and understanding the following detailed description.
The current inventive filament coil achieves higher luminance in vehicle headlamps or headlights by changing the geometry of the coil in a manner differently compared to current technology. In one exemplary embodiment, the filament has higher pitch ratios at the ends and a lower pitch ratio in the middle or intermediate region between the ends in order to allow for an increase in luminance of the vehicle headlight. This is due to the filament having uniform interspace between two adjacent turns in the middle. Further, the filament has continuously increasing pitch or pitch ratios from the intermediate region in the direction of the two ends of the filament.
In another exemplary embodiment, the filament has an increased diameter at both ends and a smaller diameter in the middle or intermediate region between the ends in order to increase the maximum luminance of the vehicle headlight. Thus, the filament preferably has a uniform filament diameter in the middle region with a continuously increasing diameter from the middle region in the direction of the two ends of the filament. In this embodiment, either the filament pitch ratio can be varied in a similar way as the first embodiment or the filament can have a uniform spacing between two adjacent full turns. In particular, the embodiments of the present disclosure are suitable for lamps having axially or transversely aligned filaments.
First and second exemplary filament coils 100, 200 of the present disclosure are illustrated in
The filament coil 100 of the first embodiment (
The first helical pitch is less turns per inch (tpi) than the second helical pitch. The first helical pitch located at the first and second ends 104, 106 for an exemplary embodiment, for example, can be at least 45 turns per inch (tpi), and generally less than about 70 turns per inch (tpi), e.g., about 60 turns per inch (tpi). The second helical pitch located at the intermediate portion 108 for an exemplary embodiment, for example, can be at least about 50 turns per inch (tpi), and generally about 100 turns per inch (tpi), e.g., about 70 turns per inch (tpi). The exemplary filament coil 100 has substantially the same diameter D at the first and second ends 104, 106, and along the intermediate portion 108. The diameter D for an exemplary embodiment, for example, can be 1.1 mm, and generally about 1.0-1.3 mm although one skilled in the art will appreciate that other dimensions can be used without departing from the scope and intent of the present disclosure.
A side view of a filament coil 200 of the second exemplary embodiment is illustrated in
The disclosure has been described with reference to the preferred embodiments. Obviously, modifications and alterations will occur to others upon reading and understanding the preceding detailed description. It is intended that the disclosure be construed as including all such modifications and alterations.
