Compact fluorescent lamp with a screw base

A compact fluorescent lamp with a screw base having a lamp with an inner tube, an outer case which is provided at one end of the lamp and includes an operating circuit section therein and has a screw base at one end of the outer case, and a molding compound having excellent insulation and good conduction of heat which is pressed and interposed into the gap between the operating circuit section and the outer case in order to transfer the heat generated in the operating circuit section to the outer case.

BACKGROUND OF THE INVENTION 
The present invention relates to a compact fluorescent lamp with a screw 
base which is to be used in place of an incandescent lamp and, more 
particularly, to a heat radiation structure which is suitable for the 
protection of circuit elements in a high frequency electronic ballast 
(including an oscillator transformer) and a transistor or a FET (Field 
Effect Transistor), and for improvement of the reliability of the circuit 
elements. 
The high frequency operating circuit section corresponding to such type of 
compact fluorescent lamp requires a sealed structure and the elements 
therein need to be highly compacted. In addition, since the operating 
circuit section is usually located above a lamp, it is subjected to the 
heat which is generated from the lamp. On the other hand, there are some 
elements, among the circuit elements contained in the compact fluorescent 
lamp, which are likely to be adversely influenced by this heat that is 
being generated. Therefore, the use of a heat radiation fin is considered 
one type of structure for effectively radiating the heat of the oscillator 
transformer, which is a heat element or source of heat in the operating 
circuit section to the atmosphere. Further, another way for improving the 
heat radiation effect is by enlarging the heat transfer area, as indicated 
in Japanese Utility Model Examined Publication No. 59-4539, by pouring the 
insulating compound into the outer case and thereby allowing the ballast 
(oscillator transformer) to come into contact with this compound, or by a 
means for enlarging the heat transfer area by molding the transformer 
using a heat hardened resin. In addition, there has been used the means 
for attaching the heat radiation fin to the transistor or FET or directly 
attaching the transistor or FET to the outer case. 
According to the above conventional techniques, although the heat radiation 
effect increases, the total lamp weight also substantially increases due 
to the pouring of the compound. In the case of molding the transformer 
with the resin, the productivity decreases and the total cost in turn 
increases. Also, the pouring of the compound results in the structure 
becoming complicated, having an increased number of parts, and results in 
a decrease of productivity. The attachment of the heat radiation fin to 
the transistor or FET results in an increase in the number of required 
parts and in a high attachment cost. On the other hand, the method whereby 
the transistor or FET is directly attached to the outer case results in a 
very complicated assembled structure. As mentioned above, the conventional 
technologies have resulted in various problems. 
SUMMARY OF THE INVENTION 
It is therefore an object of the present invention to provide a compact 
fluorescent lamp with a screw base, which is low in cost, excellent in 
productivity, light-weight, maintaining the increase in the total weight 
to be as small as possible and also be highly reliable, effectively 
reducing the temperatures of the elements by efficiently transferring the 
heat generated by the transformer and the heat generated by the transistor 
or FET to the outer case (metal casing) due to conduction of heat. 
To accomplish the above objects, a compact fluorescent lamp with a screw 
base according to the present invention comprises: a lamp having an inner 
tube; an outer case which is provided at one end of the lamp and includes 
an operating circuit section and has a screw base at one end of the outer 
case; and a molding compound having excelled insulation and good 
conduction of heat which is pressed and interposed into the gap between 
the operating circuit section and the outer case in order to transfer the 
heat generated in the operating circuit section to the outer case. 
As a result of such construction characterizing the present invention, 
namely the compression and pressure contact of the molding compound such 
as a rubber-like molding compound, the reduction of the heat radiation 
effect that results from the contraction occurring with time of the 
compound can be suppressed. As a result, the reliability of the molding 
compound can be improved. The total weight can be reduced by using the 
minimum amount of heat conductive compound that is necessary, e.g., by 
pre-shaping the compound. Further, there is no need to pour the compound 
and then wait for it to harden the compound. Consequently, the 
productivity, based on the improvements that would result by using a 
molding compound according to the present invention, would significantly 
improve.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
An embodiment of the present invention will now be described, hereinbelow, 
with reference to FIGS. 1A, 1B and 2. In these diagrams, an outer case 1 
is formed of aluminum and a high frequency operating circuit is built in 
the outer case 1. A lamp section including an inner tube 4 and an outer 
bulb 3 is provided under the operating circuit section. A screw base is 
attached to the outer case 1. A compact fluorescent lamp with the screw 
base is constituted in this manner. An oscillator transformer 5 is 
provided in the outer case 1 in close vicinity of the outer case 1. An 
insulating silicon rubber molding compound 6 having excellent conduction 
of heat is pressed in the gap between the outer case 1 and the transformer 
5. 
As a result of the improved structure, the heat generation of the 
transformer 5 is thus transferred to the outer case 1 by the molding 
compound 6, thereby enabling the elements which would otherwise be 
weakened by the heat to be protected from the heat. Thus, there is no need 
for using instead the surrounding structure which would be necessary until 
the poured compound material becomes hardened for prevention of the 
outflow of the poured compound, according to the conventional compound 
pouring structure. Thus, the structure surface according to the present 
invention, can be simplified. In addition, by using rubber-like silicon 
with the hardness rating (JIS. A) of 30 to 50 as a compound material and 
pressing it into the gap between the outer case 1 and the transformer 5, 
the reduction of the heat conduction effect due to the contraction 
occurring of the molding compound 6, as time elapses, can be suppressed. 
Miniaturization and a light weight are realized. 
Further, it is sufficient to dispose the pre-shaped molding compound 6 of 
this embodiment as illustrated in FIG. 2 on the transformer 5, leading to 
improved productivity and efficiency. 
As mentioned above, according to the embodiment, by using the molding 
compound 6, such as silicon rubber, the heat radiation increasing effect 
is obtained due to the enlargement of the heat radiation area. On the 
other hand, the amount of compound required is reduced to about 80% of the 
volume corresponding to that of the conventional example, previously 
discussed because of the improved heat conducting efficiency effect from 
the compression of the rubber, so that the light weight aspect is also 
realized. Also, the structure is simplified as compared with the 
conventional compound pouring means, so that the productivity is extremely 
improved and the cost is also reduced. 
Another embodiment of the invention will now be described with reference to 
FIGS. 3A, 3B 4A and 4B. In these diagrams, the outer case 1 is formed of 
aluminum and a high frequency operating circuit is built therein. A lamp 
section including the inner tube 4 and outer bulb 3 is provided according 
to the illustrated embodiment, under the operating circuit. The screw base 
2 is attached to the outer case 1. The compact fluorescent lamp with the 
screw base is constituted in this manner. The oscillator transformer 5 and 
a transistor or FET 7 serving as a switching element are arranged in the 
outer case 1 in close vicinity of the outer case 1. Insulating silicon gel 
molding compounds 6' and 8 having excellent conduction of heat are pressed 
into the gap between the outer case 1 and the transformer 5 and into the 
gap between the outer case 1 and the transistor or FET 7. 
With such a structure, the generated heat of the transformer 5 and 
transistor or FET 7 is transferred to the outer case 1 by the molding 
compounds 6' and 8, respectively thereby enabling the elements which are 
sensitive to the heat to be protected. 
Thus, the surrounding structure necessary until the compound is hardened 
for preventing the outflow of the compound, which structure has been 
needed in the conventional compound pouring structure, becomes 
unnecessary, thereby allowing the structure to be simplified. In addition, 
in the case of the previous embodiment of the present invention using the 
rubber with the hardness rating (JIS. A) of 30 to 50, the silicon molding 
compound must be molded in accordance with the shape of the transformer or 
transistor. But, by alternatively using gel silicon material, e.g. silicon 
rubber gel, the gel silicon material is arbitrarily deformed during 
assembly. Therefore, the pre-shaping of the molding compound is simplified 
as, for example, shown in FIG. 4A or 4B. In addition, since the gel 
compound is pressed, the reduction of the heat conduction effect resulting 
from the contraction occurring with the elapse of time and decrease in 
weight and the like can be suppressed and the small size and light weight 
are realized. Moreover, it is sufficient to just dispose or press into 
place the molding compounds 6' and 8 in the embodiment on the transformer 
5 and transistor or FET 7 during the time of assembly of the compact 
fluorescent lamp thereby resulting in improved productivity and 
efficiency. 
As described above, according to this embodiment, by using rubber like gel 
silicon molding compounds 6' and 8 which have high heat conductivity, the 
heat radiation effect is enhanced because of the enlargement of the heat 
radiation area. By using such a compound compressible material which has 
high conduction of heat characteristics, the volume of compound which is 
necessary can be reduced to 1/3 and the weight can be decreased to 2/3 as 
compared with that in the conventional example, so that a compact 
fluorescent lamp of light weight is realized. Also, according to the 
present invention, the structure is simplified as compared with that of 
the conventional compound pouring means thereby resulting in improved 
productivity and reduced cost.