Patent Application
20100002458
1. Field of the Invention
The invention relates to electric lamps and particularly to electric lamps. More particularly the invention is concerned with automotive lamps with multiple filaments for headlamp lighting.
2. Description of the Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
Advanced forward lighting systems (AFS) for vehicles provide additional light to the turning side of a vehicle. Mechanical systems that turn the whole headlamp or the reflector to the right or left are mechanically complex and subject to wear failure. An alternative is to incorporate multiple filaments in a single incandescent lamp. By selectively illuminating supplementary filaments, the turning illumination may be provided at modest cost increase. Multiple lamps forming one beam, or multiple filaments in one lamp commonly have supports that intersect the light from the alternative source leading to glare production, suggesting a single filament on a relevant side for the supplementary light. Maintaining two lamp types, right and left, is expensive, and could lead to incorrectly installed lamps. The right and left lamps may be keyed to prevent incorrect installation, but the cost of maintaining both right and left lamp supplies is troublesome. There is then a need for an AFS incandescent type lamp with a minimum of filaments, and makes the need for both left and right supplies unnecessary.
A single automotive lamp and reflector assembly may be formed to enable an automotive headlamp providing both a low beam and advanced forward lighting features. The automotive lamp includes a light transmissive envelope defining a lamp axis extending positively in a forward direction and negatively in a rearward direction. The envelope also defines an enclosed volume. The envelope has a seal at a rear end of the envelope. A first filament is located in the enclosed volume and has a first filament axis that extends generally in the lamp axis direction. The first filament has a front leg extending at a forward end of the first filament, and a rear leg extending at a rear end of the first filament. The lamp also includes a second filament located in the enclosed volume and that extends in a second filament direction that is perpendicular to the lamp axis and in a plane parallel to but offset from the lamp axis. The second filament coil is positioned rearward of the rearward most portion of the first filament coil. The second filament has first leg extending at a left end of the second filament, and a second leg extending at a right end of the second filament. A first electrically conductive lead extending through the seal and electrically couples to and mechanically supports the front leg of the first filament. A second electrically conductive lead extends through the seal and electrically couples to and mechanically supports the rear leg of the first filament. A third electrically conductive lead may optionally be used that extends through the seal and electrically couples to and mechanically supports the left leg of the second filament. A fourth, (the third if the optional third lead is not used) electrically conductive lead extends through the seal and electrically couples to and mechanically supports the right leg of the second filament. A concave reflector is positioned generally axially rearward of the automotive lamp. The reflector has a concave reflective surface, with at least one reflective first section defining at least one first focal point located adjacent to or within the convex volume defined by the first filament. The reflective first section is optically defined to project light from the first filament in a forward direction as an automotive forward beam pattern, such as a low beam pattern. The reflector also has at least one reflective second section defining at least one second focal point located adjacent to or within the convex volume defined by the second filament. The reflective second section is optically defined to project light from the second filament in a direction that is horizontal and to a side (right or left) of the forward direction when the lamp axis is horizontal and the second filament axis is horizontal.
The lamp 12 has a second filament 34, preferably a cylindrically coiled wire, located in the enclosed volume 20 and extending in a second filament axis 36 direction that is perpendicular to the lamp axis 18 in a plane parallel to but offset from the lamp axis 18. The second filament 34 is positioned so its coiled portion is rearward of rearward most portion 32 of the coiled portion of the first filament 24. From this position, light from the second filament 24 that strikes the first reflective zones of the reflector can be directed downward into the foreground, and therefore not interfere with down the road illumination. The second filament 34 has first leg 38 extending at a left end of the second filament 34, and a second leg 40 extending at a right end of the second filament 34. In a preferred embodiment, the second filament 34 has equal axial extensions with respect to the second filament axis 36 on both sides of a vertical plane through the first filament axis 26 when the lamp axis 18 is horizontal and the second filament axis 36 is horizontal. With the second filament 34 equally extended on either side of the vertical plane through the low beam filament, the filament structure is symmetric and may be used in with either right or left side reflectors. In other words, the same purchased lamp may be installed in either a right side or left side reflector. The reflectors however need not be symmetric, and are not anticipated to be symmetric as the light control needed to the side of a vehicle adjacent the oncoming traffic is different from the light control needed to the side of a vehicle away from the oncoming traffic. The axial extension of the second filament may be varied according to how much or how little light is desired to be projected to the side. In a preferred embodiment, the lamp axis 18 is tangent to a side of the second filament 34.
The automotive lamp 12 has a first electrically conductive lead 42 extending through the seal 22 and is electrically coupled to and mechanically supports the front leg 28 of the first filament 24. In a preferred embodiment, the first electrically conductive lead 42 parallels a side of the first filament 24.
The automotive lamp 12 has a second electrically conductive lead 44 extending through the seal 22 and is electrically coupled to and mechanically supports the rear leg 30 of the first filament 24. The preferred second electrically conductive lead 44 is also electrically coupled to and mechanically supports the second leg 40 of the second filament 34. In a preferred embodiment, the whole of the second electrically conductive lead 44 is rearward of the coiled portion of the first filament 24 and is above and/or rearward of the coiled portion of the second filament 34, when the lamp axis 18 is horizontal and the second filament 34 axis is horizontal. In a less preferred embodiment, the function of the second electrically conductive lead 44 can be divided between two leads, one lead connecting the leg 30, and a second lead connecting leg 40.
The lamp 12 may have a third electrically conductive lead 46 extending through the seal 22. The third electrically conductive lead 46 is electrically coupled to and mechanically supports the first leg 38 of the second filament 34. In a preferred embodiment, the whole of the third electrically conductive lead 46 is above and rearward of the coiled portion of the first filament 24 and is above and rearward of the coiled portion of the second filament 34, when the lamp axis 18 is horizontal and the second filament 34 axis is horizontal.
The lamp capsule can be used on both right and left sides of a vehicle without rotation. This means the parasitic images are maintained in the same positions. The first filament 24 is offset from the center of the capsule (from the capsule center axis) so the ghost image from the capsule wall is above the first filament 24. The bottom side of the first filament then acts as a clean cut off. The lower projected image is inverted by the reflector 14 and appears on the top of the beam. If the second filament 34 is positioned on one side and creates the bending beam then the beam for the opposite side of the first filament 24 and requires for the opposite side requires a bulb that is rotated 180 degrees or less. This moves the ghost image to the opposite side of the first filament 24 and would create glare. The solution is to have the second filament 34 mounted above the first filament 24 and centered horizontally.
The second filament 34 is oriented transverse to the bulb axis 18. The reflector facets about the bulb are then responsible for forming the bending beam, can create a horizontal images from the second filament 34 in the beam. The result is a sharper cut-off in the beam and allows better optical control of the light from the second filament 34.
The preferred first filament is 4.6 mm long, 1.66 mm in diameter and is sufficient, despite light lost to the black topped capsule end and to the base to provide a 1000 lumens final output. The preferred second filament is symmetrically transverse to, above and behind the first filament. The preferred second filament is 3 mm long, 2 mm in diameter and provides 500 lumens. The preferred reflector is divided into two sections. Most of the reflector is used for the low beam pattern production. The area in the horizontal center of the reflector and above the bulb capsule is used for the advanced forward lighting system bending beam production. A reflector prescription for the low beam on both sides of the vehicle. Only the advanced forward lighting facets have to be design separately for each side. Previous designs required the complex right and left beam patterns throughout the reflectors' optical design. The second filament is positioned above and behind the first filament. This ensures the second filament 34 images are centered by the low beam reflector portions are below the horizon and do not create glare. This is true also for the first filament images created by the advanced forward lighting reflector facets. When the second filament is energized the low beam first filament shades the second filament with respect to the low beam reflector elements, thereby reducing glare. Any light from the second filament reaching the low beam reflector elements is projected high down the road. Similarly light reflected from (missed by) the low beam or first filament from the second filament is projected.
While there have been shown and described what are at present considered to be the preferred embodiments of the invention, it will be apparent to those skilled in the art that various changes and modifications can be made herein without departing from the scope of the invention defined by the appended claims.
