US3678458A

US3678458A - Directional signal having refractive indicant areas

Info

Publication number: US3678458A
Application number: US53592A
Authority: US
Inventors: Gunnar R Ljungkull; Robert H Johnson
Original assignee: Minnesota Mining and Manufacturing Co
Current assignee: 3M Co
Priority date: 1970-07-09
Filing date: 1970-07-09
Publication date: 1972-07-18
Anticipated expiration: 1989-07-18
Also published as: DE2134664A1; CA956284A; GB1365154A; JPS5219439B1

Abstract

A traffic signal, appearing from a distance as a uniformly illuminated warning light, converts into an instructional signal as viewed during the approach. The instructional area is defined by a multi-prismatic refractor.

Description

unneu states Patent Ljungkull et al. [451 July 18, 1972 [54] DIRECTIONAL SIGNAL HAVING [56] References Cited REFRACTIVE INDICANT AREAS UNITED STATES PATENTS [72] Inventors: Gunner R. LJungkull, White Bear Lake; 3 222 516 12/1965 Mlles 350/194 :33 Paul 3,543,235 '11/1970 Eikenberry et al. .....340/107 3,568,346 3/1971 Smith ..40/125 [73] Assignees Minnesota Mining and Manufacturing 2,831,284 4/1958 Thompson... ...40/l25 Company, St Paul, Mim 2,833,176 5/1958 Ossoinak ..40/125 [22] Filed: July 1970 Primary Examiner-Harold I. Pitts [21] AWL No: 53,592 Attorney-Kinney, Alexander, Sell, Steldt& Delahunt 57 ABSTRACT [52] U.S. Cl. "340/107, A tragic signal appearing from a distance as a uniformly [51] In. m q 1/100 minated warning light, converts into an instructional signal as 58 Field ofSearch ..340/110, 106, 107, 382, 383, msmcmnal ma defined 7 Clalns, 7 Drawing Figures 25 F X y DIRECTIONAL SIGNAL HAVING REFRACTIVE INDICANT AREAS This invention relates primarily to the instruction and control of vehicular and other moving traffic and to novel signal lights for use therein. One illustrative embodiment is an arrow turn signal for instructing approaching traflic to make the indicated turn; and the invention, while not in any way restricted thereto, will for convenience be described primarily in terms of a light-signal which changes in appearance from a fully lighted surface to that of an imposed illuminated arrow or other directional signal as theviewer enters the signal-controlled approach zone.

Lighted arrow displays on traffic control lights are ordinarily provided by screening or masking of background areas. The resultant restriction of lighted area makes the display difficult to see at a distance. I The present invention on the contrary provides for illumination of the full area of the viewing surface as seen at a distance, but restricts the observable area of illumination to define only the directional symbol when observed from more closely adjacent positions along the path of travel of the observer.

, The'effect described is obtained, in accordance with this invention, by directing the background rays generally toward the more distant point and refracting the directional rays toward the less distant point orpoints, while still maintaining adequate overlapping of the two or more beams.

More specifically, the signal or other device is provided with a control panel incorporating a substantially non-refracting background area and groups of one or more refracting areas defining the desired arrow or other instructional symbol. Light is directed from the background and from the refracting areas in generally cone-shaped beams each covering an angle of not more than about forty-five or preferably about thirty degrees. The axes of the two or more cones are displaced from each other, usually by a lesser angle so that the beams overlap. The device is positioned so that the primary beam is directed substantially along the line of approach, the other beam or beams then being directed to intersect said line at the beginning of, or within, the approach zone. As a result, the observer approaching a position closely adjacent the signal sees first the fully and uniformly illuminated signal surface, followed by rapid blacking out of background areas to reveal the instructional symbol as he passes from the area of the background or overlapping beams into the area of the beam from the instructional area only.

Although the device will usually show a central arrow or other instructional symbol area surrounded by an outer background area, it will be apparent that the opposite form, wherein the arrow-shaped area serves as the background, may alternatively be used.

Direction of the primary beam may be accomplished within the signal structure, e.g., by suitable use of reflectors, lenses, or other conventional elements or combinations. In a simple form of signal the light source may be located within a rounded or generally parabolic hooded reflector which directs the light forwardly and in a cone covering about 45 of arc, and the control panel is placed across the forwardly extended open end of the reflector. A more effective and particularly desirable structure, as described in U.S. Pat No. 3,457,400, comprises a source of diffuse illumination located at the focus of a condensing view lens, the spread of the beam being controlled by an aperture located at the focus. The refracting areas may be formed in the view lens itself, or preferably in a separate transparent protective control panel located forwardly of the view lens and directly adjacent thereto.

The symbol-defining refractor is conveniently constructed of colored or colorless clear transparent thermoplastic material, e.g., by a process involving hot pressing against a preformed metal mold. It will preferably take the form of a clear flat plate or pane of plastic having at the symbol-defining areas a series of narrow parallel linearly extended flat faces each at an appropriate angle with the plane of the surface of the plate. The flat faces may be in parallel planes or may be arranged in a repeating sequence of planes at varying angles to the plane of the plate surface.

In the drawing,

FIG. 1 is a representation in front elevation of a trafiic control signal assembly embodying the device of the invention,

FIG. 2 is a representation in elevation of the appearance of the go signal to a motorist within the turn zone,

FIG. 3 is an enlarged view of the control panel of the signal shown in FIG. 2,

FIG. 4 is a view in section of a segment of the control panel of FIG. 3,

FIG. 5 is a schematic illustration of a simplified directional signal in traffic control position, and

FIGS. 6 and 7 are schematic illustrations in cross-section of representative forms of trafiic control signal assemblies embodying the principles of the invention.

FIG. 1 illustrates a conventional traffic control signal assembly 10 having an upper red stop" module 11, a central amber caution" module 12, and a lower green go" module 13. A suitable regulating device, not shown, activates these several signals in the desired sequence. As seen from a distance, for example from point A in FIG. 5, each of the modules in turn displays a fully uniformly lighted disc. Upon closer approach, as at point B in FIG. 5, the appearance of the go" signal changes to that shown in FIG. 2, the viewing panel 16 showing a central green arrow 14 surrounded by a substantially unlighted outer area 15. The arrow appearance persists at least to point C, beyond which the motorist need no longer refer to the signal for directions.

FIGS. 3 and 4 illustrate the construction of the control panel 16 of the module 13. The central instructional symbol area 17 is defined by a sequence of groups of parallel elongate flat light-refracting

surfaces

18, 19, 20 arranged at progressively lesser angles with the plane of the panel 16. The remaining surface area 21 is flat and parallel with the opposite surface of the panel. The light-refracting surfaces are indicated in FIG. 3 to be horizontal and linearly parallel to the direction of the arrow, but may be at any angle required .for the particular situation. In general, the light-refracting surfaces will be most effective when disposed at the perpendicular to a plane defined by the position of the signal and the line of traffic flow approaching the signal, which in the illustration would require a slight downward slant of the lines toward the right of FIG. 3; but in ordinary practice these linearly extended refracting surfaces are found to be entirely adequate when disposed horizontally as shown in the Figure.

FIG. 5 illustrates the positioning and indicates the requirements of a signal at a traffic intersection. The light rays passing through the background areas 21 and the segments 20 form a cone 22 the axis of which is directed along the highway 23. Light passing through the segments 19 is refracted into cone 24 which will be seen to overlap cone 22 along a portion 25 while being visible along an additional segment of the highway including point B. Similarly,'light passes through the segments 18 to define a conical beam 26 which is further offset from the primary beam and is visible both at point B and point C. Points B and C are outside of the cone of light from the background areas 21.

The traffic signal assembly 60 of FIG. 6 includes an incandescent lamp 61 within a generally parabolic specular reflector 62 fitted with a forwardly extending tubular hood 63 which direct the light rays forwardly and within a cone covering about 45 degrees of are. A symbol-defining refractor 64 as herein described covers the open forward end of the hood 63. The assembly 70 of FIG. 7, following the description in U.S. Pat. No. 3,457,400, includes a lamp 71 within a smaller housing 72, a light-transmissive diffusion plate 73, a larger housing 74, and a display lens 75, the surface of the plate 73 being at the focus of the lens 75. A symbol-defining refractor 76 as herein described is disposed forwardly of the lens 75. The edges of the smaller housing 72 serve as aperture-defining edges and are substantially at the focus of the lens 75.

The arrangement of the refracting surfaces shown, i.e., in a repeating sequence and with overlapping beams, assures that the intensity of light reaching the observer remains substantially constant over the entire applicable area. Thus for example, an observer at point A of FIG. 5 will receive light from all but refractive surfaces 18, so that the apparent intensity of the arrow symbol remains at substantially the intensity of the background 21. As the observer approaches the intersection, the background light is cut off and only the arrow is visible. The intensity of the light reaching the observer from this area is diminished as he passes from point A to point B and again from point B to point C, but his distance from the signal is simultaneously rapidly diminishing, and the two effects substantially counterbalance each other so that the signal remains sharply visible.

Additional viewing area may be covered by increasing the number of refractor lines per group; and less may be required in other instances. In a presently preferred example, each group consists of five surfaces having angles with the plane of the panel of, respectively, 0, 6,,14, 22 and 29; and there are 10 such groups per inch across the instructional area. With these angularities, and with the control panel constructed of polymethyl methacrylate and applied to a signal having a 30 primary beam, the resulting deflections are 3, 7, 11 and 15. The beam projected through the last-named surfaces, i.e., with its axis at an angle of 15 to that of the primary beam, lies substantially alongside the latter.

What is claimed is as follows:

1. An instructional signal comprising source means for projecting a primary light beam along an axis and over a projection angle of not more than about forty-five degrees, and a transparent panel adjacent to said source means in position for controlling said light beam and having instructional and background areas, wherein said instructional area comprises a sequence of groups of elongate parallel refractors each said group including at least one of said refractors, said refractors causing refraction of said beam toward and beyond one side of said primary beam, and said background areas being substantially non-refracting.

2. Signal of claim 1 wherein each said group consists of at least three said refractors and wherein the refracted beam projected by at least one of said refractors lies substantially alongside said primary beam.

3. Signal of claim 2 wherein said source means comprises a condensing lens, aperture-defining means with all aperturedefining edges substantially at the focus of said lens, and lighting means for providing diffuse illumination to said lens from said focus and from the entire aperture.

4. Signal of claim 2 wherein said source means comprises a source of illumination and a hooded rounded specular reflector.

5. Signal of claim 1 for use in conjunction with the directing of traffic approaching a point closely adjacent thereto and wherein said parallel refractors are disposed substantially perpendicularly to a plane defined by said signal and the line of said approaching traffic.

6. Signal of claim 5 wherein is included a green filter, said signal being adapted for service as a go traffic signal.

7. Method of controlling traffic comprising placing adjacent the desired control point a signal comprising source means for projecting a primary light beam, having a projection angle of not more than about 45, with its axis along the line of traffic, and disposing, adjacent to said source means and in position to control said light beam, a transparent control panel having instructional and background areas, wherein said instructional area comprises a sequence of groups of elongate parallel refractors each said group including at least one of said refractors, said refractors causing refraction of said beam toward and beyond the side of said primary beam in the direction of traffic movement, and said background areas being substantially non-refracting.

Claims

3. Signal of claim 2 wherein said source means comprises a condensing lens, aperture-Defining means with all aperture-defining edges substantially at the focus of said lens, and lighting means for providing diffuse illumination to said lens from said focus and from the entire aperture.

6. Signal of claim 5 wherein is included a green filter, said signal being adapted for service as a ''''go'''' traffic signal.

7. Method of controlling traffic comprising placing adjacent the desired control point a signal comprising source means for projecting a primary light beam, having a projection angle of not more than about 45*, with its axis along the line of traffic, and disposing, adjacent to said source means and in position to control said light beam, a transparent control panel having instructional and background areas, wherein said instructional area comprises a sequence of groups of elongate parallel refractors each said group including at least one of said refractors, said refractors causing refraction of said beam toward and beyond the side of said primary beam in the direction of traffic movement, and said background areas being substantially non-refracting.