Illumination – Elongated source light unit or support – Plural sources or supports therefor
Reexamination Certificate
2000-01-13
2001-08-28
Cariaso, Alan (Department: 2875)
Illumination
Elongated source light unit or support
Plural sources or supports therefor
C362S223000
Reexamination Certificate
active
06280052
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to light diffusers.
In a fluorescent lamp, phosphor crystals are coated on the inner surface of a glass envelope containing a mercury vapor. The lamp includes a cathode for generating electrons which bombard the vapor and generate ultraviolet light. The ultraviolet light causes the phosphor crystals to emit visible light in both radial and tangential directions of the glass envelope. Because it is generally desired that the light be directed to particular areas, reflectors are generally used to help direct the emitted light to the target areas.
A typical fluorescent lighting system, for example, has a housing, referred to as a troffer for supporting one or more fluorescent tubular lamps, as well the necessary wiring and electrical hardware for providing power to the lamps. The troffer generally has a box-like structure and is often used as a reflector. Light rays incident on the side and rear portions of the troffer are either absorbed or reflected by the surface. The inner surfaces of the troffer are typically painted white in order to decrease the amount of light absorbed by the surfaces.
With rising energy costs, efforts are being made to improve the optical efficiency of lighting systems. The optical efficiency represents the total amount of light directed to an area relative to the total amount of light generated by the lamp.
SUMMARY OF THE INVENTION
The invention relates to a light diffuser for efficiently directing light emitted from an elongated lamp toward an area desired to be illuminated.
In one general aspect of the invention, the light diffuser includes a curved member positioned between the lamp and the area desired to be illuminated and having a particular configuration. The curved member is generally parallel to a longitudinal axis of the lamp and is symmetric about a plane that extends through the longitudinal axis. The curved member includes a first curved portion, on one side of the plane of symmetry, extending from a first end to a second end. The first end is disposed adjacent the plane of symmetry and spaced from the lamp while the second end is disposed adjacent the lamp and spaced from the plane of symmetry. The curved member also includes a second curved portion on an opposite side of the plane of symmetry extending from a first end to a second end. The first end of the second curved portion is disposed adjacent the plane of symmetry and adjacent the first end of the first curved portion. The second end of the second curved portion is disposed adjacent the lamp and spaced from the plane of symmetry.
Because the diffuser is positioned between the lamp and the area desired to be illuminated, the lamp is hidden from view. Thus, the lighting system has an aesthetically more pleasing appearance. The diffuser increases the lighting efficiency of the lamp and diffuses light relatively uniformly in vertical and horizontal directions.
In another general aspect of the invention, a lighting system includes a first lighting unit having the diffuser described above, the lamp, and a troffer for housing the lamp, and the diffuser. The troffer includes an attachment for removably attaching the diffuser and a reflector that reflects light towards the area desired to be illuminated. The lamp is positioned between the reflector and the diffuser to direct light that would otherwise be directed elsewhere to the area desired to be illuminated, thereby increasing the overall lighting efficiency.
Embodiments of these aspects of the invention may include one or more of the following features. At least one of the first curved portion and the second curved portion of the diffuser defines a convex face oriented towards the lamp. Each of the curved portions defines a convex face oriented towards the lamp. The convex face is defined by a polynomial equation, such as a parabolic equation. The parabolic equation may define an ellipse centered off the axis of symmetry. The curved member includes a prismatic material that includes linear prisms. The curved member is formed of a material including plastic, such as a methacrylate.
The curved portions result in a diffusion efficiency that is greater than 80%, preferably. The curved portions also diffuse light relatively equally in vertical and horizontal directions. The diffuser of claim
1
wherein the directing of light is relatively uniform in all directions.
The curved member includes an attachment device for removably attaching the curved member to a troffer which houses the lamp. The attachment device includes a cavity defined by the second end of the first member. The cavity is configured to removably engage an attachment lip of the troffer. This construction allows the diffuser to be used with standard troffers that are commonly used in lighting systems.
The plane of symmetry either extends through the area desired to be illuminated or is transverse to it. The reflector is curved and defines a substantially concave face oriented towards the lamp. The shape of the reflector results in substantially uniform horizontal and vertical distribution of light from the lighting system.
In one particular embodiment, the lighting system includes a second lighting unit positioned adjacent to the first lighting system. The lighting first lighting unit is oriented such that the plane of symmetry of the first lighting unit lies along the plane of symmetry of the second lighting unit. The first end of the first portion of the first lighting unit is oriented in an opposite direction to a corresponding first end of a first portion of the second lighting unit.
In an alternative embodiment, the lighting system is oriented such that the first end of the first portion of the first unit is oriented in substantially the same direction as a corresponding first end of a first portion of the second lighting unit. The plane of symmetry of the first lighting unit lies parallel to the plane of symmetry of the second lighting unit.
In either case, the two lamps increase the total lighting in the area that is desired to be illuminated. The orientation of the two lamps also maintains the efficiency and the uniform horizontal and vertical distribution of light from the two lamps.
In yet another general aspect of the invention, a method of forming a diffuser for directing light toward an area desired to be illuminated, includes the following steps. A curved member is formed to include a first curved portion and a second curved portion, symmetric to the first curved portion about a plane of symmetry. The curved member is formed so that it is generally parallel about a longitudinal axis. The first curved portion is formed so that it extends from a first end to a second end. The first end is formed so that it is disposed adjacent the plane of symmetry while the second end is formed so that it is spaced from the plane of symmetry. The second curved portion is formed so that it extends from a first end to a second end. The first end of the second curved portion is formed so that it is disposed adjacent the plane of symmetry and adjacent the first end of the first curved portion. The second end of the second curved portion is formed so that it is spaced from the plane of symmetry.
Embodiments of the aspect of the invention may include one or more of the following. The curved portion is formed from a material including plastic (e.g. methacrylate) by extrusion. The second end of the first portion is formed to define a cavity for engaging the diffuser to a troffer by receiving a troffer attachment lip.
Other advantages and features of the invention will become apparent from the following description and the claims.
REFERENCES:
patent: 3647148 (1972-03-01), Wince
patent: 4698734 (1987-10-01), Ngai
patent: 4933820 (1990-06-01), Engel
patent: 5020252 (1991-06-01), De Boef
patent: 5075827 (1991-12-01), Smith
patent: 5746502 (1998-05-01), Huang
patent: 6024468 (2000-02-01), Kassay
Catalog Sheet, LX135 series (wraparound), Tristar Lighting.
Catalog Sheet, Wayfarer Series 88, Lightron of Cornwall, Inc., 4 pp.
Cariaso Alan
Fish & Richardson P.C.
Lightron of Cornwall Incorporated
Sawhney Hargobind S.
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