Light guide for a telephone dial

• US 5,130,897 A
• Filed: 10/31/1991
• Issued: 07/14/1992
• Est. Priority Date: 10/31/1991
• Status: Expired due to Fees

• Current Assignee: American Telephone & Telegraph Company (AT&T, Inc.)
• Original Assignee: AT&T, Inc.
• Inventors: Kuzma, Vineeta
• Primary Examiner(s): Lazarus, Ira S.
• Assistant Examiner(s): Hagarman, Sue
• Application Number:
  US07/785,965
• Time in Patent Office: 257 Days
• Field of Search: 362/23, 362/26, 362/24, 362/27, 362/29, 362/30, 362/32, 362/86, 362/88, 362/89, 362/255, 362/326, 362/330, 362/331, 362/335, 362/800, 40/337, 40/546
• US Class Current: 362/24
• CPC Class Codes: H01H 13/023 Light-emitting indicators for multi-layer switches H01H13/83
• CPC Class Codes: H01H 2219/062 Light conductor
• CPC Class Codes: H01H 2231/022 Telephone handset
• CPC Class Codes: H04M 1/22 Illumination; Arrangements for improving the visibility of characters on dials
• CPC Class Codes: Y10S 362/80 Light emitting diode

Abstract

An improved light guide for use in illuminating a telephone dial includes apertures through which individual buttons of a telephone dial extend. These buttons are used for dialing and are illuminated by one or more light sources that are positioned within recesses in the light guide. Each recess comprises four inwardly curved walls for directing light from the light source along two paths that are substantially perpendicular to each other. Additional openings within the light guide are designed to reflect light into areas of the dial needing more illumination, and the sides of the light guide are shaped to reflect additional light into those areas. The present invention directs light so efficiently that only two sources are needed to provide uniform illumination in standard telephone dials.

Claims

1. A light guide for use in illuminating buttons of a telephone dial, the light guide comprising a generally planar structure with a plurality of apertures therein for receiving buttons that extend therethrough, the light guide further including at least one recess having an interior region for receiving a light source therein, each recess including sidewalls for surrounding the light source, at least one of the sidewalls being curved toward the interior of the recess for focusing more light in one direction than in another direction.

2. The light guide of claim 1 wherein the number of inwardly curved sidewalls in each recess is four, the sidewalls being positioned to direct light from the light source into two principal directions that are approximately perpendicular to each other.

3. The light guide of claim 1 wherein each recess extends completely through the light guide.

4. The light guide of claim 2 wherein the apertures are positioned in a rectangular array of horizontal rows and vertical columns, each recess being positional at an intersection between the rows and columns of apertures.

5. The light guide of claim 2 wherein the number of recesses is two.

6. The light guide of claim 4 further including a plurality of openings, positioned between the same columns as the recesses, for reflecting light emanating from the light source within each recess toward predetermined apertures.

7. The light guide of claim 6 wherein each opening fully extends between opposite sides of the light guide.

8. The light guide of claim 1 wherein the light guide is made from methacrylate material of optical clarity.

9. A telephone dial assembly comprising:

a circuit board having one or more light sources mounted thereon;

a plurality of button members, made from translucent material for use in dialing; and

a transparent light guide having a plurality of apertures for receiving the button members that extend upwardly through the apertures, said apertures being arranged in any array of columns and rows, the light guide further including one or more recesses for individually receiving a light source, each recess comprising sidewalls for surrounding the light source, at least one of the sidewalls being curved toward the interior of the recess for focusing more light in one direction than in another direction.

10. The dial assembly of claim 9 further including an opaque bezel mounted on the light guide, said bezel including a plurality of apertures for the button members to extend therethrough;

whereby only the light from the button members is visible.

11. The dial assembly of claim 10 further including membrane switching means, made from a flexible rubber material and comprising a plurality of generally hemispheric domes, equal in number to the number of button members, each dome being positioned beneath one of the button members and including conductive material on one side thereof for completing an electrical path during dialing.

12. The dial assembly of claim 9 wherein the guide has a generally planar appearance and further includes a plurality of shaped openings that extend between opposite sides of the light guide for the purpose of reflecting light toward predetermined buttons in the assembly.

13. The dial assembly of claim 12 wherein the light guide further includes edges that are contoured to reflect light toward predetermined buttons in the assembly.

14. The dial assembly of claim 12 wherein the light source comprises a light emitting diode, said diode being adapted to emit light principally in a single plane, said plane being coincident with the light guide.

15. An illuminated faceplate comprising a substantially planar sheet of transparent plastic having a top surface that is opaque except for a number of discrete regions which are illuminated with light from a lesser number of light sources, the faceplate further comprising:

at least one recess in the thickness of the faceplate; and

a light source fitted within each recess, said recess comprising four inwardly curved walls for directing light from the light source along two axes that are generally perpendicular to each other.

16. The illuminated faceplate of claim 15 wherein the top surface comprises a bezel, mounted on the transparent plastic.