Illumination – Illuminated scale or dial – Edge illuminated modifier or light rod/pipe
Reexamination Certificate
1999-06-09
2001-02-06
O'Shea, Sandra (Department: 2875)
Illumination
Illuminated scale or dial
Edge illuminated modifier or light rod/pipe
C362S023000, C362S029000, C362S035000
Reexamination Certificate
active
06183099
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to illumination arrangements for instrument dials and more particularly to an improved illumination system for a wristwatch dial.
It is known to provide instruments such as wristwatches with a light source for illuminating the dial. The wristwatch dial may be an analog wristwatch dial having indicia or markers used in connection with hands of the watch, or the dial may comprise an electro-optic display of actuated indicia, such as a liquid crystal display. One objective in a dial illumination system has been to achieve a constant and uniform lighting for the dial. Uniform background lighting may be achieved by using a distributed uniform light source, such as an electroluminescent light source. However, in order to reduce the cost of an illumination system for a dial, concentrated light sources, such as a single incandescent bulb or a light emitting diode (LED) have also been considered. One problem with using a concentrated light source is to transfer and diffuse the light from a point source of bright light to a uniformly distributed light source for illuminating the dial. The prior art contains many examples of efforts to effect the transformation.
In addition to illumination, light may be used to achieve an aesthetic graphic presentation. In this case it must be possible to locate areas of greater or lesser brightness or different colors at different locations on the dial. Traditional constructions using edge lighting around the outside periphery of a light guide are ineffective in directing the light to the desired location.
Constructions are known for using a light guide behind a light transmissive dial, and to inject light into the light guide. The following U.S. Patents are representative of prior art constructions for illuminating dials from a concentrated light source using a light guide.
U.S. Pat. No.
INVENTOR
ISSUE DATE
TITLE
3,748,456
Brien
July 24, 1973
Illuminated
Instrument
Dials
2,140,972
Rylsky
Dec. 20, 1938
Means far
Illuminating
Dials of
Instruments
2,188,821
Rylsky
Jan. 30, 1940
Compass
2,480,393
Bossert et al.
Aug. 30, 1949
Dial Light
3,043,038
Marble
July 10, 1962
Illuminated
Dial Face
3,561,145
Shotwell
Feb. 9, 1971
Light
Distributing
Lens System
The aforementioned Marble U.S. Pat. No. 3,043,038 and Shotwell U.S. Pat. No. 3,561,145 employ light guides bounded is by substantially planar surfaces and attempt to distribute the light rays which are undergoing multiple internal reflections which are introduced from a concentrated source at the peripheral edge of the light guide. Such a construction is deficient for several reasons. For example, in the '038 patent identified above, the light entering the lens must do so at an edge and therefore, the distribution of light along the entire lens surface is less than uniform. Secondly, and as conceded in the '038 patent, there is a tremendously non-uniform illumination in the lens nearest the lamp. Hence, the '038 patent employs an opaque member that causes less than the entire dial surface to illuminate. Although this is considered by the '038 patent to be a “novel effect,” it is clear that it is less than desirable in a watch where it is desirable to illuminate the entire dial. Lastly positioning the lamp adjacent the lens is permissible in a device where space is not a priority. In watches, space is a valuable commodity that must be considered at all times.
U.S. Pat. No. 5,667,289 issued Sep. 16, 1997 to Akahane et al. describes a background lighting apparatus for a liquid crystal display, in which a nonuniform pattern of light dispersing reflective layers are applied to a light guide illuminated from the edges of the light guide. The reflective layers are arranged to increase in size as the distance from the lighted edge become greater.
It is particularly difficult to effectively and uniformly conduct light from a concentrated source to a light guide in a wristwatch disposed beneath the watch dial. Space is at a premium and the previously known constructions have not been satisfactory.
Accordingly, an improved illumination arrangement for a watch dial that overcomes the drawbacks found in the prior art while at the same time provides for a desirable and uniform distribution of illumination, is desired.
SUMMARY OF THE INVENTION
Generally speaking, in accordance with the present invention, a lightguide for illuminating a dial in a timekeeping device, such as a watch, is provided. The lightguide preferably includes an at least essentially flat portion having a bottom surface and an upper surface in facing alignment with the dial, a lightpipe integrally formed with and extending below the flat portion, the lightpipe having a foot region at one end thereof, and geometries molded into the bottom surface of the flat portion to selectively eject internally reflected light from the bottom surface of the flat portion through the upper surface, wherein the lightguide provides illumination to the dial when a concentrated light source disposed below and spaced apart from the foot region conducts light to the lightpipe. In a preferred construction, the foot region has a concave surface for channeling light to the flat portion. Furthermore, the lightpipe forms, with the flat surface, a cavity, and a conical light deflector may be disposed in the cavity to reduce the visible intensity of light emanating from the concentrated light source and conducted through the lightpipe. The edges of the lightguide may also be painted to further reduce light from exiting the edges of the lightguide. The timekeeping device may be a watch such as a wristworn watch, a stopwatch, or a pocketwatch or even a clock. In a preferred embodiment the illumination is uniform although differing illumination patterns could be created as disclosed and discussed herein.
The invention is also directed to an illumination arrangement for a timekeeping device, such a wristworn watch, stopwatch, pocketwatch or clock, and preferably comprises a lightguide as disclosed above, a dial to be illuminated disposed above the lightguide, the dial comprising a light transmissive member having a periphery substantially coextensive with that of the lightguide and having a bottom surface in facing alignment with the upper surface of the lightguide, and a concentrated light source disposed below and spaced apart from the foot region of the lightguide, wherein the lightguide provides at least essentially uniform illumination to the dial when the concentrated light source conducts light to the lightpipe. In the preferred embodiment, the concentrated light source is at least one light emitting diode, the molded geometries increase in size as the distance from the lightpipe increases and the dial may include an absorption pattern on the bottom surface thereof to reduce the visible intensity of light emanating from the concentrated light source.
Accordingly, it is an object of the present invention to achieve a desired illumination of light for a dial for a timekeeping device.
It is also an object of the present invention to achieve a uniform distribution of light using a concentrated or point light source and conducting the light to a lightguide for illuminating a dial.
Another object of the present invention is to construct a timepiece with an illumination arrangement that is relatively easy to manufacture.
Another object of the present invention is to construct a lightguide for use in the timepiece, such as a watch, that accommodates manufacturing tolerances existing among the other timepiece components.
Still another object of the present invention is to construct an improved illumination arrangement that includes features that more effectively directs the light and reduces or eliminates any “hot-spots” existing above the concentrated light source.
Yet another object of the present invention is to systematically mold geometries within the bottom surface of the lightguide to assist in creating a uniform distribution of illumination of the watch dial.
Still yet another object of the present inven
Ciervo Richard D.
Garay John L.
Kurple William M
Carmody & Torrance LLP
Negron Ismael
O'Shea Sandra
Timex Corporation
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