Electric lamp and discharge devices: systems – Periodic switch in the supply circuit – Impedance or current regulator in the supply circuit
Reexamination Certificate
2002-03-08
2004-01-20
Lee, Wilson (Department: 2821)
Electric lamp and discharge devices: systems
Periodic switch in the supply circuit
Impedance or current regulator in the supply circuit
C315S290000, C315S225000, C315S308000
Reexamination Certificate
active
06680583
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a transformer assembly for stepping up an a.c. power for application to sign lamps (cold cathode discharge tubes such as a neon tube or an argon tube) to light it and provided with protective functions against abnormalities such as non-grounding of a neutral point of a transformer casing, a connection to an a.c. power source in reverse polarities and the like.
FIG. 1
shows a conventional lighting transformer assembly with protective functions. Specifically, a transformer
11
includes a primary winding
12
, across which a first and a second input terminal
14
,
15
are connected, and a secondary winding
13
. It will be noted that a power interrupting switch
16
is connected in series between the first input terminal
14
and one end of the primary winding
12
. An a.c. power source such as a commercial power supply
17
is connected across the first and second input terminal
14
,
15
. The opposite ends of the secondary winding
13
are connected to a first and a second output terminal
18
,
19
, respectively, across which a discharge tube or tubes
21
such as neon tubes or argon tubes are connected.
The a.c. power from the source
17
is fed to the primary winding
12
, which steps it up, thus allowing a high tension a.c. power to be supplied from the secondary winding
13
to the discharge tubes
21
in order to light them.
In the event of occurrence of a ground fault on the secondary side such as a connection of the secondary winding
13
to the ground as a result of a contact of a wiring of the discharge tube
21
with a neon tower, such a ground fault is detected by an abnormality detection circuit
22
, the arrangement being such that a detection output is applied to an interrupter circuit
23
, which is effective to turn the power interrupting switch
16
off to interrupt the supply of the a.c. power to the primary winding
12
, thus preventing a continued current flow through the point of ground fault of the secondary side to cause a fire.
A duty is imposed upon transformer such as the transformer
11
mentioned above to connect a transformer casing
24
to the ground before use. If a person forgets to connect a ground terminal
15
of the casing
14
to the ground and the assembly is put to use, this is detected by the abnormality detection circuit
22
to activate the interrupter circuit
23
to turn the switch
16
off. In a similar manner, if the commercial power supply
17
is connected to the first and the second input terminal
14
,
15
in reverse polarities, this is again detected by the abnormality detection circuit
22
to turn the switch
16
off. A protective circuit
20
including the abnormality detection circuit
22
which detects the occurrence of one or more of a variety of abnormalities relating to the transformer
11
and the interrupter circuit
23
which turns the switch
16
off to interrupt the supply of the a.c. power to the transformer
11
in response thereto is contained in the transformer casing
24
. The interrupter circuit
23
has the function of maintaining the switch
16
off once it is turned off. By way of example, the switch
16
may comprise relay contacts, and a movable contact of the relay is connected to the first input terminal
14
and is arranged to be switched from a normal closed contact
16
NC
to a normally open contact
16
NO
to close a self-holding circuit for the relay. The interrupter circuit
23
is connected across the first and the second input terminal
14
,
15
to be fed from the a.c. power applied across the first and the second input terminal
14
,
15
.
A neon sign may be formed by discharge tubes
21
such as neon tubes or argon tubes, which may be flashed to achieve an advertisement effect. At this end, a flasher
10
is connected between the commercial power supply
17
and the first and the second input terminal
14
,
15
to interrupt the supply of the a.c. power to the first and the second input terminal
14
,
15
in various forms, causing the discharge tubes
21
to be flashed in various forms as a result of such interruption. A conventional arrangement for the abnormality detection circuit
22
and the interrupter circuit
23
which detect the occurrence of a ground fault and interrupts the supply of the input a.c. power is shown in
FIG. 2
, designating corresponding parts to those shown in
FIG. 1
by like reference numerals. In this example, the secondary winding
13
has a midpoint
41
which is connected to the ground terminal
25
. A pair of tertiary windings
13
t
1
,
13
t
2
which are magnetically coupled to opposite halves located on the both sides of the midpoint
41
of the secondary winding
13
form part of the abnormality detection circuit
22
. Normally, the tertiary windings
13
t
1
,
13
t
2
are juxtaposed on a magnetic core on which the secondary winding
13
is disposed between the lowermost layers thereof such that a layer of insulating material having a high withstand voltage on the order of 6000-7000 V is interposed between the tertiary windings
13
t
1
,
13
t
2
and the secondary winding
13
to provide a high electrical insulation therebetween while allowing a satisfactory magnetic coupling between the secondary winding
13
and the tertiary windings
13
t
1
,
13
t
2
.
At their one end, the tertiary windings
13
t
1
,
13
t
2
, are connected together in an inverse phase relationship so that their induced voltages cancel each other while at their other end, the tertiary windings
13
t
1
,
13
t
2
are connected to an input of a rectifying and smoothing circuit
42
, the output of which is connected through a Zener diode
46
across a parallel circuit comprising a resistor and a capacitor. The parallel circuit
47
is connected across the gate and the cathode of a triac
30
. The triac
30
is connected across the input terminals
14
,
15
through a relay drive coil
16
c,
which when energized, controls relay contacts that define the switch
16
.
Under a normal condition, voltages induced across the tertiary windings
13
t
1
,
13
t
2
are substantially equal in magnitude, but are opposite in phase, whereby an input voltage to the rectifying and smoothing circuit
42
is nearly zero. However, upon a ground fault of the sign lamps
21
or a wiring thereof, one end of the secondary windings which is associated with the ground fault will be short-circuited to the midpoint
41
, causing a substantial decrease in the induced voltage in the tertiary winding which is coupled with this secondary winding
13
to allow the full induced voltage across the other tertiary winding to be applied to the rectifying and smoothing circuit
42
. This voltage is rectified and smoothed and an increase in the rectified and smoothed output voltage turns the Zener diode
46
on, with consequence that the triac
30
is turned on to energize the relay drive coil
16
c
to open the switch
16
, thus interrupting the supply of the input a.c. power to the transformer
11
. The movable contact of the switch
26
comprising the relay contacts is thrown to the normally open position
16
NO
, whereby the holding current to the relay drive coil
16
c
flows.
A ground fault protective circuit is shown in
FIG. 3
, with corresponding parts to those shown in
FIG. 2
being designated by like reference characters as used before. Specifically, the midpoint
41
of the secondary winding
13
is connected to the ground terminal
25
through a rectifying diode
37
and a series circuit including a Zener diode
38
and a light emitting element
55
PE
of a photocoupler
55
. The midpoint
41
of the secondary winding is also connected through a resistive element
39
to the ground terminal
25
. A series circuit including the relay drive coil
16
c
and a light receiving element
55
PR
of the photocoupler
55
is connected across the input terminals
14
and
15
. It is to be noted that on the opposite sides of the midpoint
41
, the secondary winding
13
is wound in the opposite directions.
Normally, the potentials at the output terminals
18
and
19
Goshima Daiki
Matsui Yoshihiro
Nakamura Yoshihiro
Noda Makoto
Samura Tadayoshi
Connolly Bove & Lodge & Hutz LLP
Lecip Corporation
Lee Wilson
LandOfFree
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