Light fixture including light pipe having contoured...

Optical waveguides – Noncyclindrical or nonplanar shaped waveguide

Reexamination Certificate

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Details

C385S901000, C362S551000

Reexamination Certificate

active

06275644

ABSTRACT:

TECHNICAL FIELD
This invention relates generally to fiber optic light pipes and, more specifically, to such light pipes configured to include mounting appendages.
INVENTION BACKGROUND
Light pipes are elongated monofilament or single fiber optic cables of relatively large diameter that are capable of transmitting light from one end to the other. Light pipes may either be “end-fire” light pipes, meaning that they are constructed to transmit light longitudinally with minimal lateral or radial light emission, or “side-fire” light pipes that are configured to both transmit light longitudinally and emit light laterally. Light pipes may include no more than a simple core of a clear plastic material, or may include one or more of a number of different claddings and coatings. End-fire light pipes may include jackets including claddings configured to prevent lateral light emissions. Side-fire light pipes may include claddings configured to encourage or diffuse such lateral emissions. These claddings may be flouropolymer tubes applied by such methods as heat shrinking the tube onto the core or inserting a core into a pre-formed cladding tube by pressure filling. Some light pipe jackets also include a clear or translucent plastic coating that surrounds and protects the cladding.
Light pipes are most commonly circular in cross section, but have also been formed in a number of other cross-sectional shapes. For example, U.S. Pat. No. 5,218,660 issued Jun. 8, 1993 to Omata discloses a light pipe having a polygonal cross-section. U.S. Pat. No. 4,734,829, issued Mar. 29, 1988 to Wu et al., discloses an arc lamp image transformer that includes a light pipe having the same arcuate cross-sectional shape as the beam of light it will transmit. U.S. Pat. Nos. 4,668,264 and 4,669,814 issued May 26, 1987 and Jun. 2, 1987, respectively, to Dyott, each disclose light pipes having a non-circular, e.g., half-circular, cross-sections each defining two transverse orthogonal axes. U.S. Pat. No. 5,221,387, issued Jun. 22, 1993 to Robbins et al. and assigned to Lumenyte International Corporation (the Lumenyte '387 patent) suggests that alternate cross-sectional light pipe shapes including squares, triangles and various fluted shapes might be used.
It is desirable to suspend or otherwise support light pipes in positions where they can transmit light from a source to a desired point and/or to illuminate a desired area. Some suspension systems disclosed in the prior art include rings or clips that encircle or partially encircle the light pipes they suspend. The rings or clips are affixed in some way to a supporting structure in a light fixture. Such suspension systems do not require modifications to the light pipes they are designed to suspend.
Other light pipe suspension systems include structures that integrally extend from some portion of a light pipe and that are configured to engage an adjacent support structure. For example, the Lumenyte '387 patent discloses a light pipe having a cross-sectional shape that includes a tangentially oriented elongated mounting protrusion included in an outer coating of the light pipe. The outer coating surrounds a cladding layer that surrounds a core of the light pipe. The protrusion extends the entire length of the light pipe and functions to aid in mounting the conduit to a backing, wall or other support structure. The mounting protrusion is extruded simultaneously with the coating in a co-extrusion process that forms the light pipe.
Another example of a light pipe suspension system that relies on an appendage extending from the light pipe is the system disclosed in U.S. patent application Ser. No. 08/767,969. The application is assigned to the assignee of the present application and discloses a light pipe having an elongated integral appendage extending radially outward from along the length of the light pipe and having a “Christmas tree”-shaped cross section. The “branches” of the tree are configured to engage opposed edges of an elongated mounting slot. Light pipes having integral appendages of this type have relatively complex cross-sectional shapes.
What is needed is a simple, cost-effective light pipe suspension system that includes a light pipe configured to mount easily to a supporting structure while being inexpensive to manufacture.
INVENTION SUMMARY
In accordance with this invention a light pipe support assembly is provided that includes an elongated light-transmissive monofilament core and an elongated laterally pinched region between elongated upper and lower lobes that allows the light pipe to be suspended between a pair of opposed inwardly-extending protrusions. The assembly comprises a support structure that includes at least one pair of the inwardly extending protrusions. The light pipe is supported on the support structure between the protrusions. The core has a generally constant cross-sectional size and shape along its length. The core includes an elongated upper lobe that integrally extends from an elongated lower lobe. The lower lobe has an arcuate lateral profile. The pinched region has a width less than the width of the upper lobe and less than the width of the lower lobe. The width of the pinched region is also slightly less that the width of a gap between the inwardly extending protrusions. The width of the gap between the protrusions is smaller than the width of the upper lobe. This allows the light pipe to be suspended from the protrusions by resting the upper lobe on the protrusions.
According to another aspect of the invention the upper lobe has an arcuate profile that facilitates an optional means of mounting the light pipe on the track by pushing the upper lobe edgewise through the gap between the protrusions or rails of the support track.
According to another aspect of the invention, the inwardly extending protrusions of the support structure are elongated parallel rails. The rails form a track for receiving the light pipe.
According to another aspect of the invention, the upper lobe is smaller than the lower lobe. By forming the upper lobe smaller, the amount material dedicated to supporting the light pipe, as opposed to transmitting light, is minimized and takes up less space above the rails.
According to another aspect of the invention, the light pipe support assembly is flexible. This flexibility allows the light pipe to be more easily transported and mounted and provides more design flexibility. Design flexibility is greater because curved sections of support track may be included. Mounting is easier because the light pipe can be more easily slid along the curved sections.
According to another aspect of the invention, the light pipe includes a jacket comprising a cladding layer. The cladding layer, which may comprise a fluoropolymer material, improves side-light dispersion. A generally transparent coating may be disposed on the cladding to protect the cladding.
According to another aspect of the present invention, the light pipe includes an elongated generally tubular jacket disposed on the core. The core may be disposed in the lower lobe and the upper lobe may comprise an elongated nub portion of the jacket.
According to another aspect of the invention a method is provided for making a light pipe support assembly comprising a support structure having a pair of opposed inwardly-extending protrusions, and a light pipe including an elongated light-transmissive mono-filament core supported on the support structure, the light pipe having a generally constant cross-sectional size and shape along a length of the light pipe, the light pipe including an elongated upper lobe integrally extending from an elongated lower lobe, the lower lobe having an arcuate lateral profile, the light pipe including an elongated laterally pinched region between the upper lobe and the lower lobe, the pinched region having a width less than the width of the upper lobe and less than the width of the lower lobe and slightly less that the width of a gap between the inwardly-extending protrusions, the width of the gap between the protrusions being smaller tha

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