Electric gas-lighter

Details Electric gas-lighter Electric gas-lighter

1999-05-10

2002-09-10

Sircus, Brian (Department: 2836)

Electricity: electrical systems and devices

Igniting systems

For electric spark ignition

C315S2090CD

Reexamination Certificate

active

06449138

ABSTRACT:

The present invention relates to an electric gas-lighter which may be applied, for example, to the cooking range of a gas cooker.
BACKGROUND OF THE INVENTION
Cooking ranges are known which are fitted with built-in electric gas-lighters operated manually to produce sparks and light gas flames on the range.
One type of cooking range with an electric gas-lighter (
FIG. 1
) comprises metal gas burners
2
, each provided with a respective electrode
3
located to the side of the burner
2
and insulated electrically with respect to the grounded metal surface
4
supporting the burners.
When operated, the electric gas-lighter produces a spark between each electrode
3
and the respective burner
2
to light the flame of the burner supplied with gas.
FIG. 1
shows a complete circuit diagram of one known type of gas-lighter.
In addition to electrodes
3
, the gas-lighter comprises a first and a second input terminal
7
,
8
connectable to a supply line, e.g. an alternating mains line (not shown), by closing a switch (not shown); and an electric-discharge generating circuit
5
interposed between input terminals
7
,
8
and electrodes
3
, for producing the sparks on electrodes
3
.
Circuit
5
comprises a resistor
9
having a first terminal connected to input terminal
7
, and a second terminal connected to the anode of a rectifying diode
10
, the cathode of which is connected to a first node
11
.
Circuit
5
also comprises a capacitor
12
having a first terminal connected to node
11
, and a second terminal connected to a node
13
in turn connected to second input terminal
8
.
Circuit
5
also comprises a voltage discharge device
15
having a first terminal connected to node
11
, and a second terminal connected to a first terminal
16
a
of a primary winding
16
of a transformer
17
. The primary winding of transformer
17
has a second input terminal
16
b
connected to node
13
, and transformer
17
also comprises two identical secondary windings
18
, each having far more turns than primary winding
16
.
The terminals of each secondary winding
18
are connected to respective electrodes
3
.
The gas-lighter operates as follows.
When the switch (not shown) is closed to connect the gas-lighter circuit to the alternating supply line, the alternating mains voltage is rectified by diode
10
and a rectified voltage is applied to charge capacitor
12
. When the voltage at the capacitor terminals reaches a threshold value V
TH
equal to the ignition threshold value of discharger
15
, transformer
17
and capacitor
12
are connected, and capacitor
12
discharges via primary winding
16
. A discharge current I
SC
of extremely high intensity (e.g. a 150-280 A peak) is thus generated and flows through primary winding
16
, at the terminals of which a discharge voltage V
1
(e.g. of 400 V) is generated during the discharge transient (lasting a few microseconds). Discharge voltage V
1
induces, at the terminals of secondary windings
18
, a voltage V
2
much higher than V
1
(e.g. 28 kV) and which is applied to electrodes
3
. For each secondary winding
18
, voltage V
2
is sufficient to produce sparks between each electrode
3
and metal burner
2
, which is grounded.
Gas-lighters of the above type have the drawback of generating, at the output (i.e. towards the supply mains) and during the discharge transient, severe electromagnetic noise above the limits laid down by European standards (EN55014 and following).
One proposed solution to the problem is to fit the gas-lighter with an electronic filter to reduce the electromagnetic noise at the output and so obtain a low-noise gas-lighter as shown in FIG.
2
. In addition to the components described above (indicated using the same reference numbers), a low-noise gas-lighter comprises an electronic filter
20
interposed between terminals
7
,
8
and a circuit
5
a
equivalent to circuit
5
but having no resistor
9
.
Filter
20
comprises a first decoupling resistor
25
a
having a first terminal connected to terminal
7
and a second terminal connected to a node
22
communicating with the anode of diode
10
and with a first terminal of a capacitor
21
a
having a second terminal connected to a reference potential (ground). Filter
20
also comprises a second decoupling resistor
25
b
having a first terminal connected to terminal
8
and a second terminal connected to a node
23
communicating with node
13
and with a first terminal of a capacitor
21
b
having a second terminal connected to the reference potential (ground).
Capacitors
21
a
and
21
b
are thus located between respective nodes
22
and
23
and a common node
24
which is the ground.
Filter
20
defines a preferential path by which to discharge the electromagnetic energy produced during the discharge transient of capacitor
12
. More specifically, this energy is conveyed by capacitors
21
a
and
21
b
directly towards ground
24
to reduce the electromagnetic emissions emitted by the circuit towards the supply mains.
Though filter
20
indeed provides for reducing the noise level generated during operation to well below the prescribed limit, gas-lighters fitted with filters
20
are not without further drawbacks.
Though minimum per gas-lighter, the expense of providing the filter with two capacitors is far from negligible on a mass-production scale, as in the household appliance industry.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an electric gas-lighter which is highly straightforward, and which at the same time provides for eliminating the drawbacks associated with gas-lighters of the type described above.
According to the present invention, there is disclosed an electric gas lighter having a discharge generating circuit comprising input terminals connectable to a supply source and at least one output terminal for generating sparks. The gas lighter also comprises a filter for filtering electromagnetic noise. The filter consists essentially of a single capacitor having a first terminal communicating with a reference potential and a second terminal communicating with one of the input terminals through a first resistor.


REFERENCES:
patent: 3644075 (1972-02-01), Squiers
patent: 3681001 (1972-08-01), Potts
patent: 3877864 (1975-04-01), Carlson
patent: 4001638 (1977-01-01), Bauer et al.
patent: 4450499 (1984-05-01), Sorelle
patent: 4626196 (1986-12-01), Stohere, Jr.
patent: 5621278 (1997-04-01), Chambers
patent: 5862033 (1999-01-01), Geislinger et al.
patent: 6242866 (2001-06-01), Bianchi
patent: EP 0 801 267 (1997-10-01), None
patent: 1175160 (1987-07-01), None
patent: 57-99272 (1982-06-01), None
Integrated Publishing's Official Web Page, FILTERS, 1998.*
muRata, Technical Notes: Noise Suppression Principles Using EMI Filters, Dec. 2000.*
Sprague, Ceramic EMI/RFI Filters, 2000*
Syfer, Multilayer Ceramic EMI Filters, 1999.

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