GB1583460A - Fluorescent lamp - Google Patents

Description

(54) FLUORESCENT LAMP (71) We, TOKYO SHIBAURA ELECTRIC COMPANY LIMITED, a Japanese corporation, of 72 Horikawa-cho, Saiwai-ku, Kawasaki-shi, Japan, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to a straight tube type fluorescent lamp with high efficiency.

More particularly, it relates to a straight tube type fluorescent lamp of which the efficiency is improved by reduction of power consumption.

The fluorescent lamp of straight tube type comprises a glass bulb provided on the inside with fluorescent coating and sealed with lamp bases having electrodes at both ends of the bulb. The glass bulb is filled with an amount of mercury vapor for ultraviolet radiation and a small amount of rare gas, for example, argon as lamp starting gas.

The lamp efficacy of the fluorescent lamp is defined as a ratio of light output (lumen) to lamp power (W). Improvement of the fluorescent lamp efficacy is to produce large light output for a given lamp power or to reduce lamp power for a given light output.

The applicants of the present application proposed à fluorescent lamp having a high lamp efficacy which was developed on the basis of the latter method. The fluorescent lamp had a diameter of the glass bulb of approximately 32mm and is filled with argon for rare gas. Since the bulb diameter was made small, loss of ultraviolet rays in the bulb was reduced so that a large light output was attained for a given lamp power. Further, lamp current was reduced from 435mA to 415mA so that commonly used ballasts conforming to the Japanese Industrial Standards (JIS C8108), could be used without any modification. For further details, see U.S. patent Nos. 3,438,370; 3,462,631 and 3,546,519, and British patent No. 1,162,552.

Demand for a very high efficiency fluorescent lamps has been increased recently and advent of such a high efficiency fluorescent lamps over the conventional one with 32mm of diameter has been earnestly desired.

AccQrdingly, gn object of the present invention is to provide a high efficiency fluorescent lamp of straight tube type with reduced power consumption and light output larger than that of the conventional fluorescent lamp.

Another object of the present invention is to provided fluorescent lamp of straight tube type with highly improved lamp efficacy and allowing use of the conventional parts such as ballasts.

According to the present invention, there is provided a fluorescent lamp of the straight tube type having a cylindrical glass bulb provided on the inside with a fluorescent coating, sealed with lamp bases with electrodes, at both ends of the bulb, and filled with mercury vapor and starting gas. the outer diameter of the glass bulb being 27 to 3 lmm, the starting gas being mixed rare gas consisting of krypton of 10 to 40 volume % and argon of 90 to 60 volume So, and the pressure of the mixed rare gas being 1.5 to 2.5 mmHg.

The present invention will be better understood from the folowing description taken in connection with the accompanying drawings, in which: Fig. 1 is a view, partly broken away, showing an example of a straight tube type fluorescent lamp; and Fig. 2 shows a sectional view taken along line II-II of Fig. 1.

With a view to improving the lamp efficacy, the mixed rare gas of argon and krypton is used for a starting gas, being substituted for argon gas used in the conventional lamp. It has been found that use of the mixed rare gas reduces the impedance of a fluorescent lamp, with the result that the lamp current necessarily increases and the ballast normally used in the conventional fluorescent lamp cannot endure the increased current. Experiments have shown that changing the mixing ratio of argon and krypton to increase the krypton in the mixed rare gas leads to increase of lamp current and reduction of luminous flux.

Development of a new ballast which can endure the increased current, however, is problematic in time and cost, thus making the use of a conventional ballast desirable. This is satisfied by reducing the outer diameter of the glass bulb to less than 32mm which is the one of the conventional fluorescent lamp, by which the lamp current is much the same as that of the conventional one. Excessive reduction of the outer diameter reduces area of the coating of the fluorescent substance, followed by reduction of light emission amount and luminous flux.

The experiments further have shown that the pressure of the mixed rare gas in the glass bulb has a close relation to the starting voltage and lamp life.

It has been found by the experiments that the tube diameter, the mixing ratio of krypton and argon, and the pressure of the mixed rare gas must be within the given range of the values, in order to obtain fluorescent lamps with a very high lamp efficacy by using the mixed rare gas of argon and krypton.

These three factors constitute a decisive difference of the invention from the conventional fluorescent lamp.

The construction of the fluorescent lamp of the invention is illustrated in Figs. 1 & 2. A straight glass bulb 1 is provided on the inside with fluorescent coating 2. Lamp bases 4,4 with filament electrodes 3, 3 are hermetically secured on both ends of the bulb 1. The outer diameter d of the glass bulb 1 ranges from 27 to 3 lmm, preferably 29mm. When the outer diameter d exceeds 31mm, the lamp current increases to an extent that the conventional ballast can not endure the increased lamp current. In the case of less than 27mm of the outer diameter d, the luminous flux is reduced compared to that of the conventional fluorescent lamp.

The starting gas sealed into the glass bulb 1 is the mixed rare gas of argon and krypton. The ratio of krypton in the mixed rare gas is 10 to 40 volume % and preferably 25 volume %.

When the ratio of krypton exceeds 40 volume %, lamp current increases, and then if the outer diameter d is above 29mm, the lamp current excessively increases to possibly break the conventional ballast. Further, the luminous flux is reduced for the same current. In the case of less than 10 volume % of krypton, power consumption of the lamp is not saved and more adversely wear of the electrodes 3, 3 is remarkable to shorten lamp life.

The pressure of the mixed rare gas ranges from 1.5 to 2.5 mmHg and 2.0 mmHg is preferable. When the gas pressure is above 2.5 mmHg, the starting voltage is high so that it is difficult to start the lamp particularly in winter. On the other hand, when the gas pressure is less than 1.5 mmHg. the starting voltage is low but wear of the electrodes 3,3 is considerable, thus shortening lamp life. Further, the lamp current increases to exceed the withstanding limit for current of the conventional ballast.

A lamp characteristic was measured changing the bulb outer diameterd, composition ratio of the mixed rare gas, and the sealed gas pressure. The fluorescent lamp used was 40W of rated input power and the ballast used was of the conventional one of the Japanese Industrial Standards (JIS C8108). The results of the measurement are tabulated in Table I. In the Table I fluorescent lamp numbers 1, and 18 to 20 indicate fluorescent lamps other than those of the present invention, and fluorescent lamp number 20 indicates the conventional fluorescent lamp with a diameter of approximately 32mm as mentioned above.

Table I(1) Fluorescent lamp number 1 2 3 4 5 6 7 8 9 10 Distance between lamp bases L (mm) 1,198 1,198 1,198 1,198 1,198 1,198 1,198 1,198 1,198 1,198 Distance between electrodes # (mm) 1,118 1,118 1,118 1,118 1,118 1,118 1,118 1,118 1,118 1,118 Bulb outer diameter d (mm) 29 29 29 29 29 29 29 29 29 29 Mixed rare Kr (vol.%) 5 10 10 10 20 20 20 25 25 25 gas compositions Ar (vol.%) 95 90 90 90 80 80 80 75 75 75 Gas pressure (mmHg) 2.0 1.7 2.0 2.3 1.7 2.0 2.3 1.7 2.0 2.3 Luminous flux (lumen) 3,290 3,295 3,270 3,195 3,280 3,270 3,170 3,270 3,250 3,180 Lamp current (mA) 395 407 401 394 413 409 405 415 411 405 Lamp voltage (V) 118 113 116 119 109 111 114 109 110.5 113 Lamp power (W) 39.2 38.2 38.2 38.1 38.0 38.0 37.9 37.9 37.9 37.7 Lamp efficacy (lumen/W) 83.9 86.3 85.1 83.9 86.3 86.1 84.0 86.3 85.8 83.6 Starting voltage (V) 160 160 161 161 159 160 161 159 160 161 Table I(2) Fluorescent lamp number 11 12 13 14 15 16 17 18 19 20 Distances between lamp bases L (mm) 1,198 1,198 1,198 1,198 1,198 1,198 1,198 1,198 1,198 1,198 Distance between electrodes # (mm) 1,118 1,118 1,118 1,118 1,118 1,118 1,118 1,118 1,118 1,118 Bulb outer diameter d (mm) 29 29 29 29 29 29 30 29 29 32.5 Mixed rarc Kr (vol.%) 30 30 30 40 40 40 30 45 50 gas compositions Ar (vol.%) 70 70 70 60 60 60 70 55 50 100 Gas pressure (mmHg) 1.7 2.0 2.3 1.7 2.0 2.3 2.0 2.0 2.0 2.4 Luminous flux (lumen) 3,260 3,240 3,140 3,200 3,170 3,100 3,200 3,100 3,050 3,250 Lamp current (mA) 418 412 407 427 420 415 418 423 428 415 Lamp voltage (V) 107 110 112 104 107 110 109 106 104 111 Lamp power(W) 37.8 37.7 37.4 37.3 37.2 37.0 37.8 36.9 36.4 39.8 Lamp efficacy (lumen/W) 86.0 85.9 84.0 85.8 85.2 83.8 84.6 84.0 83.8 81.7 Startingg voltage (V) 159 160 161 159 159 160 159 158 157 165 As seen from Table I, the fluorescent lamps numbered 2 to 17 of this invention are superior to the conventional one 20 in lamp power consumption and lamp efficacy. In the fluorescent lamp 1, because of a too small amount of krypton, lamp power consumption is substantially equal to that of the convention lamp 20, failing to attain the power saving objective intended.

The fluorescent lamps 18 and 19 are markedly darker than the conventional one 20, because of large reduction of the luminous flux.

Table I refers to the case of the straight tube type fluorescent lamp of rated power 40W.

The present invention is applicable for the same type lamp of rated power 20W allowing use of the same parts such as ballasts. In this case, pleasing results of power saving and high lamp efficacy may likewise be attained.

As described above, the lamp current of the fluorescent lamp of the invention is almost equal to that of the conventional one with a diameter of about 32mm. Accordingly, use of the conventional ballast is permitted. Additionally, power consumption is considerably smaller and the luminous flux is equal to or larger than that of the conventional one, thus remarkably improving lamp efficacy. Furthermore, starting of the lamp is easier compared to the conventional lamp therefore increasing the life time.

WHAT WE CLAIM IS: 1. A fluorescent lamp of the straight tube type having a glass bulb provided on the inside with a fluorescent coating, sealed with lamp bases with electrodes at both ends of the bulb, and filled with mercury vapor and starting gas; the outer diameter of said glass bulb being 27 to 31mm, said starting gas being mixed rare gas consisting of 10 to 40 volume % of krypton and of 90 to 60 volume % of argon, and the pressure of said mixed rare gas being 1.5 to 2.5 mmHg.

2. A fluorescent lamp according to claim 1, in which the outer diameter of said glass bulb is 29 mm.

3. A fluorescent lamp according to claim 1 or claim 2, in which said starting gas is mixed rare gas consisting of 25 volume % of krypton and of 75 volume % of argon.

4. A fluorescent lamp according to any of claims 1 to 3, in which the pressure of said mixed rare gas is 2.0 mmHg.

5. A fluorescent lamp according to claim 1 and substantially as hereinbefore described with reference to the accompanying drawing.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (5)

**WARNING** start of CLMS field may overlap end of DESC **. As seen from Table I, the fluorescent lamps numbered 2 to 17 of this invention are superior to the conventional one 20 in lamp power consumption and lamp efficacy. In the fluorescent lamp 1, because of a too small amount of krypton, lamp power consumption is substantially equal to that of the convention lamp 20, failing to attain the power saving objective intended. The fluorescent lamps 18 and 19 are markedly darker than the conventional one 20, because of large reduction of the luminous flux. Table I refers to the case of the straight tube type fluorescent lamp of rated power 40W. The present invention is applicable for the same type lamp of rated power 20W allowing use of the same parts such as ballasts. In this case, pleasing results of power saving and high lamp efficacy may likewise be attained. As described above, the lamp current of the fluorescent lamp of the invention is almost equal to that of the conventional one with a diameter of about 32mm. Accordingly, use of the conventional ballast is permitted. Additionally, power consumption is considerably smaller and the luminous flux is equal to or larger than that of the conventional one, thus remarkably improving lamp efficacy. Furthermore, starting of the lamp is easier compared to the conventional lamp therefore increasing the life time. WHAT WE CLAIM IS:

1. A fluorescent lamp of the straight tube type having a glass bulb provided on the inside with a fluorescent coating, sealed with lamp bases with electrodes at both ends of the bulb, and filled with mercury vapor and starting gas; the outer diameter of said glass bulb being 27 to 31mm, said starting gas being mixed rare gas consisting of 10 to 40 volume % of krypton and of 90 to 60 volume % of argon, and the pressure of said mixed rare gas being 1.5 to 2.5 mmHg.

2. A fluorescent lamp according to claim 1, in which the outer diameter of said glass bulb is 29 mm.

3. A fluorescent lamp according to claim 1 or claim 2, in which said starting gas is mixed rare gas consisting of 25 volume % of krypton and of 75 volume % of argon.

4. A fluorescent lamp according to any of claims 1 to 3, in which the pressure of said mixed rare gas is 2.0 mmHg.

5. A fluorescent lamp according to claim 1 and substantially as hereinbefore described with reference to the accompanying drawing.