Tricolor fluorescent lamp

• US 4,625,152 A
• Filed: 07/09/1984
• Issued: 11/25/1986
• Est. Priority Date: 07/18/1983
• Status: Expired due to Term

• Current Assignee: Asahi Matsushita Electric Works Ltd. (Panasonic Holdings Corporation)
• Original Assignee: Asahi Matsushita Electric Works Ltd. (Panasonic Holdings Corporation)
• Inventors: Nakai, Katsumasa
• Primary Examiner(s): NOT, DEFINED
• Application Number:
  US06/628,738
• Time in Patent Office: 869 Days
• Field of Search: 315/DIG. 1, 315/317, 315/323, 315/324, 315/211, 315/217, 313/610, 313/25, 313/634, 313/493
• US Class Current: 315/317
• CPC Class Codes: H01J 61/72 having a main light-emitting filling of easily vaporisable metal vapour, e.g. mercury
• CPC Class Codes: H01J 61/94 Paths producing light of different wavelengths, e.g. for simulating daylight
• CPC Class Codes: H05B 41/295 with semiconductor devices and specially adapted for lamps with preheating electrodes, e.g. for fluorescent lamps
• CPC Class Codes: H05B 41/36 Controlling
• CPC Class Codes: H05B 41/3927 by pulse width modulation H05B41/3922 takes precedence
• CPC Class Codes: Y10S 315/01 Fluorescent lamp circuits with more than two principle electrodes

Abstract

A tricolor fluorescent lamp operating on a DC power source is disclosed herein. The lamp comprises an outer envelop defining therein a sealed space in which an ionizable medium is filled at low pressure. Disposed within said outer envelop are three tubular envelops of a generally inverted U-shaped configuration which define correspondingly three separate discharge paths and which are coated with respective fluorescent substances emitting different colors. Three sequentially energized anodes are located within the sealed ends of the respective envelops and a common cathode is disposed in adjacently facing relation with the open ends of the envelops, such that the three envelops can be sequentially energized to emit the specific colors which are additively mixed in various proportions to produce a desired color as emitting from the whole lamp. Said U-shaped configuration of the tubular envelops emitting different colors results in the elongated discharge paths or increased light emitting surfaces within a limited space, providing a compact arrangement of the tricolor lamp to be well suitable for decorative illumination. Also, the bent portions of the U-shaped envelops are cooperative to provide a viewing surface on which all three color emitting sources can appear, which renders the tricolor lamp to be well adaptable for use as a picture element in a color display. Further, the sequential shifting of the discharge paths allows the common cathode to be constantly energized, preventing irregular color reproduction which would otherwise result from the interruption in energizing the cathode during the course of changing the colors to be emitted from the lamp.

Claims

1. A tricolor fluorescent lamp operating on a DC power source through at least a ballast resistor which comprises:

an outer envelop having a closed top and an open bottom;

a stem hermetically sealed to the bottom of the outer envelop for defining within the outer envelop a sealed space;

an ionizable medium including an inert gas and mercury vapor filled within said sealed space at low pressure;

three bent tubular envelops of a generally inverted U-shaped configuration disposed within said sealed space with one end of each tubular envelop being hermetically sealed to the stem and with the other end of each tubular envelop being open to define thereby three separate discharge paths within said sealed space, the substantially entire inner surfaces of the tubular envelops being coated with fluorescent substances emitting different colors;

a common cathode disposed on the stem at the position adjacent to the open ends of the tubular envelops;

three anodes disposed on the stem within the confines of the sealed ends of the respective tubular envelops for being sequentially energized such that the colors emitted from the three tubular envelops can be additively mixed in various proportions to produce a desired color; and

said tricolor tubular fluorescent lamp is further characterized in that said outer envelop is the form of an equilateral triangle prism with a closed top and an open bottom sealed by the stem of the correspondingly shaped equilateral triangle, said stem being provided at its apexes of the triangle with the respective anodes and provided at its center thereof with said common cathode so that the open ends of said tubular envelops are directed to the center of the stem with the axes of the tubular envelop being in parallel relationship with each other.

2. The tricolor fluorescent lamp as set forth in claim 1, wherein said fluorescent substances with which the tubular envelops are coated are for emitting three primary colors and have the respective maximum emission spectrum of 400-500 nm, 500-600 nm, and 600-700 nm.

3. A fluorescent lamp device operating on a DC power source which produces various colors which comprises:

a lamp having an outer envelop and a stem hermetically sealed together to define therebetween a sealed space;

an ionizable medium including an inert gas and mercury vapor filled within said sealed space at low pressure;

a plurality of bent tubular envelops of a generally inverted U-shaped configuration disposed within said discharge space with one end of each tubular envelop being hermetically sealed to the stem and with the other end of each tubular envelop being open to define thereby a plurality of separate discharge paths within said sealed space, the substantially entire inner surface of the tubular envelops being coated with fluorescent substances emitting different colors;

a common cathode disposed on the stem at the position adjacent to the open ends of the plurality of tubular envelops;

a plurality of anodes disposed on the stem within the confines of the sealed ends of the respective tubular envelops;

at least one ballast resistor inserted in the circuit between the lamp unit and the DC power source;

a switching means connected in series with said resistor and connected between the anodes and a positive side of the DC power source for repeatedly and individually energizing the anodes for predetermined time intervals such that the colors emitted from the plurality of tubular envelops can be additively mixed in various proportions to produce a desired color;

a controller for giving the predetermined time intervals of energization of each electrode of the inner bent tubular envelops to the switching means; and

preheating means for preheating the cathode only when all the anodes are deenergized.

4. The fluorescent lamp device as set forth in claim 3, wherein said ballast resistor is of a variable type.