Writable disk sign

Details Writable disk sign Writable disk sign

1999-04-20

2001-04-24

O'Shea, Sandra (Department: 2875)

Illumination

Plural light sources

With modifier

C362S812000, C362S802000, C362S259000, C362S800000, C362S249070, C362S277000, C040S546000, C040S477000, C040S479000

Reexamination Certificate

active

06220723

ABSTRACT:

This invention relates to novel means for illuminating an array of flip disks using LEDs to improve the contrast and therefore the legibility. The novel lighting design is particularly suitable for an array surrounded by its own housing, such as some vehicle's destination signs, since it allows the physically forward side of the array to approach closer to the front transparent wall or the windshield of the vehicle than many prior designs, thus widening the viewing area. The design also lends itself to retro-fitting of an array with flip disk forward facing surfaces, formerly lit by fluorescent lamps.
The following abbreviations are used herein:
LED—light emitting diode
PCB—printed circuit board
PWB—printed wiring board. This is a synonym for PCB
LED lamp is a lens combined with the LED to shape the LED radiation beam.
‘Lamp’ herein means LED lamp
Flip disks are those approximately flat disks often used in an array for conveying changeable information, which disks display contrasting visual appearances on opposite surfaces and selectively individually move between limiting positions to display selected surfaces in the forward direction.
A fluorescent component of a surface is a component which emits a radiation spectrum while stimulated by incident ultra violet radiation. Such components are well known to those ordinarily skilled in the art.
‘Forward’ is a direction from the array toward the intended viewer location and ‘backward’ is the opposite direction.
The direction from the viewing location to the forward side of the array is referred to as the intended viewing direction.
A ‘side’ refers to any other edge of the active elements (considered collectively) in an array.
A ‘group’ of LEDs is intended to include a row of LEDs but to also to include other arrangements.
The array of display elements can be generally planar, but if curved ( as in some vehicle destination signs) can still be thought of as defining a median plane.
The array is considered as viewed in the intended viewing direction and is generally of rectangular form having top, bottom and sides.
‘Contrasting surfaces’ refers to the relation of the opposed surfaces of the flip disks which give some kind of differing visual impression. Thus the opposite surfaces may be light (which may contain a fluorescent component in one variant of the invention) and dark (usually a bright yellow and a dull black). However in one aspect of the second variant of the invention the two opposite sides may have the same hue but one surface only has a fluorescent component which glows (hence ‘contrasts’ with the other) under UV radiation.
‘Intended viewing location’ is that area from which the array, as a whole is intended to be viewed. Thus the viewing location may for example be narrow, be the width of a highway or of a parking lot depending on the function of the array.
In comparison with fluorescent tubes for illuminating the disks, LEDs are solid state devices with a lifetime much longer than fluorescent tubes. LEDs require no ballasting and the power required is much less for LEDs than for fluorescent tubes of comparable intensity.
A first variant of the invention has an array of display elements contained in a housing arranged to face a viewing location. The forward surface of the disks is illuminated by LEDs emitting visible radiation backwardly onto them. The LEDs are masked from the viewer. The reflection or lack of it from the forward faces of the disks defines the appearance of the array.
Moreover recent developments in LED technology have introduced higher intensity LEDs and a broad range of color selection and radiation angle. Color selection in the first variant of the invention where the radiation is in the visible spectrum and the disk first surfaces are merely reflective is usually chosen to approach, as closely as possible the color of the first surface of the disk elements. In accord with the first aspect of the invention a plurality of LEDs extends along one side of an array and forward of the median plane, but clear of the intended viewing path from the viewing location to the array. With reflective only light sides there is preferably a row of LEDs located outside opposed boundaries of the array. The LEDs are directed and selected to illuminate the array of elements relatively evenly. The radiation cones of the LEDs are also selected for best even illumination across the array. Masking means prevent direct viewing of the LEDs by a viewer looking from the viewing location.
The array is composed of a number of disk elements rotatable about an axis approximately transverse to the ordinary viewing direction. With such disk elements one usually displays a light or dark surface when facing forward.
Such disk elements may be of several types including those pivoting on an approximate median such as those shown in U.S. Pat. No. 4,860,470 Browne or U.S. Pat. No. 4,577,427 Browne or may be edge mounted as exemplified by U.S. Pat. No. 4,528,932 Ducza et al, U.S. Pat. No. 3,916,403 Mandzu et al or may be board mounted arrays such as in U.S. Pat. No. 5,809,675.
Thus, the radiation directed from the LEDs is reflected from the disk light sides, some of it in the viewing direction, to improve the clarity and appearance of the sign for viewing. In a first variant of this invention the clarity of the array information is enhanced if the color of the LED illuminating radiation is close to that of the disk light sides.
With the first variant of the invention, it is found that particularly good results are obtained when the illumination of the display elements is by two groups or rows of LED lamps located on each of the opposite sides of the array, as viewed from the viewing location. Thus, a mask plate may be located to prevent radiation from each row or group of the LED lamps toward the viewer.
There are prior arrays in a transparent front housing, where the then forward sides of the disks are lit by fluorescent tubes. The invention may be retrofit into such housing by removing the fluorescent tubes and installing opposed rows or groups of LEDs in the casing, clear of the intended viewing lines from the viewing location. Masking plates are then provided on the housing if not already there to mask the LED lamps from the viewer.
Printed circuit boards are particularly suitable for mounting the LED lamps and the energizing conductors therefor in the first variant of the invention, LED lamps in opposed groups and preferably rows, located on mutually opposed sides of a rectangular array lend themselves to location and direction to produce relatively even illumination. In one arrangement the LEDs in an opposed row include a set which illuminates a region of elements near the nearer edge of the array and a set which illuminates a central region of the array. The interleaving of the two sets in each of the opposed rows may thus be arranged to so that one set illuminates the disk forward faces nearer that one of the opposed rows and the central areas between the side strips in a relatively even manner.
LED lamps in this arrangement have a predetermined beam cone angle. Thus, in relation to the arrangement described in the previous paragraph, those LEDs in the set used for (primarily) illuminating elements adjacent the near boundary have been found effective with the LED lamps selected to have a cone of preferably between 15° and 25° included angle, while the LED lamps used for (primarily) illuminating the middle region have, been chosen with radiation between 35° and 45° included angle.
In the second variant of the invention there is an array of flip disk elements which are each provided with opposing first and second surfaces where the first surface includes fluorescent materials in its coating. LED lamps are provided for illuminating the array on the forward facing surfaces. The radiation from the LED lamps causes the first surfaces to fluoresce. There is thus created increased contrast between the viewer-visible first and second surfaces. Fewer LEDs are usually required than with the first variant. Thus usually a row of LED lamps i

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