Flasher string

Details Flasher string Flasher string

2000-10-05

2002-05-28

Wong, Don (Department: 2821)

Electric lamp and discharge devices: systems

Plural series connected load devices

Christmas lights

C315S094000, C315S100000

Reexamination Certificate

active

06396219

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Related Art
The present invention relates to a lamp string, and particularly, to a flasher string having thyristor diodes coupled with respective flashers in parallel to maintain the circuit loop even when some flashers turn off.
2. Background of the Related Art
The lamp string has been widely used to produce a twinkling light for decoration or celebration of specific festivals, especially at Christmas, as shown in FIG.
1
. The lamp string of the prior arts has connecting wires
11
to connect the filaments
13
of the lamps
12
in series to form a loop, which is provided an appropriate voltage source S to turn on the lamps
12
. With reference to
FIG. 2
, the flasher is often used as a switch to turn on or off all the lamps in series so as to create a tinkling light. The flasher
21
comprises a tungsten filament
22
, a lamp filament
24
and a metal piece
23
. The tungsten filament
22
is joint to the metal piece
23
and normally contacts the lamp filament
24
, as shown in FIG.
2
A. When the flasher
21
turns on to heat the metal piece
23
by conducting current, the metal piece
23
in contact with the lamp filament
24
is thermally distorted and then escapes from the lamp filament
24
to form an open loop, as shown in
FIG. 2B
, so that the flasher
21
turns off. Sequentially, the metal piece
23
is cooled down and then returns back to contact the lamp filament
24
so that the flasher
21
turns on again. The above process repeats until the power is cut off. As a result, all the lamps connected in series with the flasher
21
can be turned on or off at a time by turning on or off the flasher
21
. Several such lamp strings with different on/off states at the same time may constitute a larger light source to produce a larger area of twinkling light. However, the sense of twinkling light is quite different from the natural star light at night because all the lamps in a specific lamp string should turn on or off simultaneously.
With reference to
FIG. 3
, another type of flasher
31
(
FIG. 3A
) with equivalent circuit in
FIG. 3B
comprises a tungsten filament
32
connected to a metal piece
33
in parallel, which is normally not in contact with a lamp filament
34
. When the flasher
31
turns on, the metal piece
33
is thermally distorted towards and then contacts the lamp filament
34
. As a result, the two lamp filaments
34
,
35
, are short circuited and all the current flows through the lamp filaments
34
,
35
and the metal piece
33
without any current flowing through the tungsten filament
32
so that the flasher
31
turns off but the current loop is still closed. A lamp string consisting of such flashers
31
may produce a more natural twinkling light source because each flasher
31
can turn on or off independently. However, the current is quite unstable because the short circuited state of the flasher may abruptly increase the current to an extreme level to burn up the lamp filaments, especially when many flashers are short circuited at the same time.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a lamp string having a plurality of flashers connected in series and a plurality of thyristor diodes, each thyristor diode connected to a respective flasher in parallel. Each flasher may turn on and off independently to produce a natural-like twinkling light without any impact on the conducting current so that the current is stable during operation.


REFERENCES:
patent: 5610479 (1997-03-01), Schmitt
patent: 5886423 (1999-03-01), Gershen et al.
patent: 6107746 (2000-08-01), Chen

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