Optical: systems and elements – Lens – With support
Reexamination Certificate
1999-09-03
2001-05-29
Sugarman, Scott J. (Department: 2873)
Optical: systems and elements
Lens
With support
C359S810000, C359S811000
Reexamination Certificate
active
06239925
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an instrument cluster lens assembly having a lens attached to a base. In addition, the present invention relates to a method of manufacturing such an instrument cluster lens assembly.
BACKGROUND OF THE INVENTION
Instrument cluster lens assemblies are commonly used in vehicles to cover a group of gauges and indicators such as a fuel gauge, temperature indicator, speedometer, or tachometer. Some known instrument cluster lens assemblies have an injected molded lens that is connected to a retainer by fasteners such as screws or by ultrasonic or vibration welding.
One known type of instrument cluster lens assembly has a flat lens that is pressed against a curved surface of a retainer by ultrasonic welding apparatus and bonded to the perimeter of the retainer. However, both the retainer and the ultrasonic welding horn must be shaped to conform to the desired lens shape. Thus, each instrument cluster lens assembly must have a uniquely designed ultrasonic welding horn which greatly reduces manufacturing flexibility and increases production costs.
Moreover, ultrasonic and vibration welding require that the welding horn have direct physical contact with the lens, which produces unwanted scratching that leads to quality concerns and an increased number of parts that are rejected as scrap. In addition, ultrasonic and vibration welding require that the entire lens move relative to the retainer to create heat at a weld interface. As welds are initially created, they are also broken due to the relative movement. The scrubbing action between the parts leads to weld lines that have “hairs” along their outer edges. The hairs are visible through the lens and are aesthetically unattractive.
Further, ultrasonic and vibration welding require that the lens and retainer be produced with tighter tolerances because of the need for exact alignment between the mating surfaces of the parts, otherwise, frictional heat would not be generated. In addition, tighter tolerances are required to ensure that the lens and retainer are able to properly align with the shape of the welding horn.
Although laser welding is a known technique for joining two components together, laser welding has historically been used to join two components made from the same material. Accordingly, laser welding has not been successfully used to join a lens and retainer of an instrument cluster assembly because the lens and retainer are usually fabricated from dissimilar materials.
SUMMARY OF THE INVENTION
The present invention is directed to a lens assembly for an instrument cluster comprising a lens having a top surface and a bottom surface and including a mounting portion. A base having at least one lens receiving portion is adapted to be attached to the lens. In addition, the mounting portion of the lens is laser welded to the lens receiving portion of the base to securely connect the lens to the base thereby forming the lens assembly for an instrument cluster.
The lens and the base can be fabricated either from different materials or the same material. Preferably, the lens is generally transparent to laser light and the base is generally opaque to laser light to permit the laser welding to occur at the interface between the mounting portion of the lens and the lens receiving portion of the base. Moreover, the lens can include an acrylic material and the base can include an ABS plastic material.
Further, the lens can optionally include a removable protective film on the top surface that is transparent to laser light for protecting the lens during shipping. A similar removable protective film can be applied to the bottom surface of the lens and be peeled away just prior to assembly of the lens with the base.
The present invention further relates to a method of forming a lens assembly for an instrument cluster comprising the steps of providing a lens having a mounting portion and providing a base having a lens receiving portion. Then, aligning the mounting portion of the lens with the lens receiving portion of the base and laser welding the lens to the base for secure attachment. The laser welding step is performed using a laser having a wavelength between approximately 800 to 1100 nanometers. Preferably, the laser is a diode laser having a wavelength between approximately 800 to 960 nm. Diode lasers are compact in size, cost efficient and can utilize fiber optics to deliver the laser beam to a workpiece.
Still further, the present invention relates to a method of forming a lens assembly for an instrument cluster comprising the steps of providing a substantially planar lens made from flat sheet stock and providing a base having a non-planar lens receiving portion. Another step includes aligning the lens relative to the non-planar lens receiving portion of the base followed by pressing the lens against the base to form a generally non-planar lens. Thereafter laser welding of the non-planar lens to the base occurs for secure attachment. Thus, a non-planar lens can be made without the cost of expensive molding or forming equipment. The laser weld maintains the originally flat lens in its curved, non-planar position that corresponds to the non-planar shape of the lens receiving portion of the base.
The method according to the present invention can further include removing a protective film on a bottom surface of the lens before pressing the lens against the base. Another step includes removing a protective film on a top surface of the lens just before installing the instrument cluster lens assembly in an instrument panel.
Still further, the present invention relates to a method of forming a lens assembly for an instrument cluster comprising the steps of providing a pre-shaped, non-planar lens having a mounting portion and providing a base having a lens receiving portion. A further step includes aligning the mounting portion of the lens with the lens receiving portion of the base and laser welding the lens to the base for secure attachment.
One benefit of the present invention is that no physical contact occurs between the welding apparatus and the lens and the retainer. Thus, the present invention provides the ability to have removable protective film on the top surface of the lens to protect against scratches before, during and after the laser welding process. Additionally, a removable protective film can be provided on the bottom surface until just before laser welding takes place. Thus, the lens can be protected against scratches on both the top and bottom surfaces up to the point of the laser welding step and thereafter still be protected on the top surface. Further, laser welding can be performed from a single side of the lens assembly in contrast to the ultrasonic and vibration welding which requires welding apparatus from both sides. Therefore, less complex fixturing is used with the present invention.
Also, laser welding eliminates the unattractive weld lines having “hairs” along their edges that are inherent with ultrasonic and vibration welding. In addition, the lenses and bases can be made with greater tolerances since laser welding only needs selected mating surfaces and not necessarily an entire perimeter between the component parts. In addition, the lenses and bases can be made with greater tolerances because they do not have to precisely fit the contours of an ultrasonic welding horn.
Another important benefit that the present invention provides is flexible manufacturing. Unlike the prior art attachment techniques, the present invention can have a robot with multiple different programs that move the laser along different paths for welding different lens assembly designs. Thus, it is easier and faster using laser welding to convert a production run between different lens assembly designs. In contrast, prior art methods have unique welding horns for each lens assembly design and require ordering, producing and changing out the special shaped welding horns to convert between production runs.
Further, the present invention provides the ability to fabricate the lens and bas
Ardrey Kenneth J.
Herfurth Hans J.
Mehta Sandip R.
Key Plastics, Inc.
Rader & Fishman & Grauer, PLLC
Seyrafi Saeed
Sugarman Scott J.
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