U.S. patent application number 09/884828 was filed with the patent office on 2005-04-28 for electronic gas cooktop control with simmer system and method thereof.
Invention is credited to Olson, Allen L., Repper, Pierre P., Shute, Alan B., Shute, Christa B., Shute, Suzanne J., Zhou, Feng.
Application Number | 20050089809 09/884828 |
Document ID | / |
Family ID | 22574512 |
Filed Date | 2005-04-28 |
United States Patent
Application |
20050089809 |
Kind Code |
A9 |
Repper, Pierre P. ; et
al. |
April 28, 2005 |
ELECTRONIC GAS COOKTOP CONTROL WITH SIMMER SYSTEM AND METHOD
THEREOF
Abstract
An electronically activated gas cooktop control system,
responsive to a touch-sensitive user interface, and capable of
providing a predetermined range of cooking and simmer levels of BTU
output, has two complementary heating modes of operation A first
heating mode of operation is provided to produce a wide selection
of simmer levels of BTU output, by electronically sequencing a
solenoid-operated modulating gas valve "on" and "off", at a
predetermined level of flame. A second cooking mode of operation is
provided by electronically modulating the level of flame, through
use of a pulse-width-modulation (PWM) output signal to produce a
wide selection of cooking levels of BTU output. An igniter system
capable of insuring proper ignition of gas without generating
harmful electromagnetic interference is also provided.
Inventors: |
Repper, Pierre P.;
(Carteauguay, CA) ; Shute, Alan B.; (Stowe,
VT) ; Shute, Christa B.; (Stowe, VT) ; Shute,
Suzanne J.; (Stowe, VT) ; Olson, Allen L.;
(Craftsbury, VT) ; Zhou, Feng; (Gloucester,
CA) |
Correspondence
Address: |
JAMES MARC LEAS
37 BUTLER DRIVE
S. BURLINGTON
VT
05403
US
|
Prior
Publication: |
|
Document Identifier |
Publication Date |
|
US 0045142 A1 |
April 18, 2002 |
|
|
Family ID: |
22574512 |
Appl. No.: |
09/884828 |
Filed: |
June 18, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09884828 |
Jun 18, 2001 |
|
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PCT/US00/28624 |
Oct 16, 2000 |
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60159885 |
Oct 18, 1999 |
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Current U.S.
Class: |
431/66 |
Current CPC
Class: |
F23N 2227/42 20200101;
F23N 2231/20 20200101; F23N 2231/22 20200101; F23N 2235/16
20200101; F23N 1/005 20130101; H03K 2217/960785 20130101; F23N
2227/10 20200101; F24C 3/126 20130101; F23N 5/10 20130101; F23N
2237/10 20200101; F23N 2241/08 20200101; F23N 2237/02 20200101;
F23N 2227/36 20200101; F23N 5/203 20130101; H03K 2217/96066
20130101; H03K 17/9622 20130101 |
Class at
Publication: |
431/066 |
International
Class: |
F23N 005/00 |
Claims
What is claimed is:
1. A cooktop, comprising one or more gas bumers, one or more gas
valves, each of said valves being connected to control gas flow to
one of said gas burners, a user interface for user entry of burner
heating level for each of said one or more gas burners, a
controller operative to control each of said one or more gas valves
in accordance with said user entry entered for the corresponding
one of said one or more gas valves, one or more igniters, each of
said one or more igniters being connected to ensure ignition of the
gas delivered to said gas burners, and one or more temperature
sensors, each of said sensors connected and placed to monitor the
presence of flames at each of the said burners, the cooktop being
characterized in being adapted to operate alternatively in either
of first and second modes, said first mode having continuous flame
modulation varying continuously between predetermined lower first
and higher second heating levels, and said second mode having
intermittent flame for producing heating levels less than said
lower first heating level for simmering operation, said
intermittent flame being controlled between on and off states by
said one or more gas valves, said gas valves being controlled by a
pulse-width modulated electrical signal provided by said controller
in accordance with said user entry.
2. A cooktop as in claim 1, wherein said user interface comprises
one or more touch-sensitive pads.
3. A cooktop as in claim 1, wherein each of said gas valves
comprises a proportionally controlled solenoid-operated modulating
gas valve wherein no gas flow condition is measured in its fully
closed position.
4. A cooktop as in claim 3, wherein each of said gas valves
comprises a proportionally controlled solenoid-operated modulating
gas valve wherein maximum gas flow is measured in its fully open
position.
5. A cooktop as in claim 4, wherein each of said gas valves
comprises a proportionally controlled solenoid-operated modulating
gas valve is also capable of providing any intermediate controlled
position.
6. A cooktop as in claim 1, wherein said user interface comprises a
multiplicity of touch-sensitive pads operable to select burner
heating levels in a predetermined set of user-selectable steps.
7. A cooktop as in claim 6, wherein lowest portion of said
user-selectable steps corresponds to a flame "on/off" sequencing
mode of flow settings of gas valves.
8. A cooktop as in claim 6, wherein a highest portion of said
user-selectable steps corresponds to a continuous flame modulation
mode of flow settings of said gas valves.
9. A cooktop as in claim 6, wherein said each of said
user-selectable steps corresponds to a multiplicity of flow
settings of said gas valves in a predetermined range of flow
settings.
10. A cooktop as in claim 2, wherein said user interface further
comprises a visual interface including a display selected from the
list consisting of: a) seven-segment LED displays, b) discrete LED
displays, c) bar-graph LED displays, d) LCD displays, e) vacuum
fluorescent displays, and f) field-emission displays.
11. A cooktop as in claim 2, wherein said user interface further
comprises an audible interface including an annunciator selected
from the list consisting of: a) an external drive piezo-acoustic
element, b) a built-in drive piezo-acoustic element, c) an external
drive magnetic transducer, d) a built-in drive magnetic transducer,
e) an external drive Mylar speaker, and f) a built-in drive Mylar
speaker.
12. A cooktop as in claim 1, wherein said igniter comprises a
resistive hot-surface igniter.
13. A cooktop, comprising: a) one or more gas burners, b) one or
more gas valves, each of said valves being connected to control gas
flow to one of said gas burners, c) a user interface for user entry
of burner heating level for each of said one or more gas burners,
d) a controller operative to control each of said one or more gas
valves in accordance with said user entry entered for the
corresponding one of said one or more gas valves, e) one or more
igniters, each of said igniters being connected to ensure ignition
of the gas delivered to the said gas burners, and f) one or more
temperature sensors, each of said sensors being connected and
placed to monitor the presence of flames at each of the said
burners.
14. A cooktop as in claim 13, wherein said user interface comprises
one or more touch-sensitive pads.
15. A cooktop as in claim 13, wherein each of said gas valves
comprises a proportionally controlled solenoid-operated modulating
gas valve wherein no gas flow condition is measured in its fully
closed position.
16. A cooktop as in claim 13, wherein each of said gas valves
comprises a proportionally controlled solenoid-operated modulating
gas valve wherein maximum gas flow is measured in its fully open
position.
17. A cooktop as in either of claims 15 and 16, wherein each of
said gas valves comprises a proportionally controlled
solenoid-operated modulating gas valve is also capable of providing
any intermediate controlled position.
18. A cooktop as in claim 1, wherein said user interface comprises
a multiplicity of touch-sensitive pads operable to select burner
heating levels in a predetermined set of user-selectable steps.
19. A cooktop as in claim 18, wherein a lowest portion of said
user-selectable steps corresponds to a flame "on/off" sequencing
mode of flow settings of gas valves.
20. A cooktop as in claim 18, wherein a highest portion of said
user-selectable steps corresponds to a continuous flame modulation
mode of flow setting of gas valves.
21. A cooktop as in claim 18, wherein said each of said
user-selectable steps corresponds to a multiplicity of flow
settings of said gas valves in a predetermined range of flow
settings.
22. A cooktop as in claim 13, wherein said user interface further
comprises a visual interface including a display selected from the
list consisting of: a) seven-segment LED displays, b) discrete LED
displays, c) bar-graph LED displays, d) LCD displays, e) vacuum
fluorescent displays, and f) field-emission displays.
23. A cooktop as in claim 13, wherein said user interface further
comprises an audible interface including an annunciator selected
from the list consisting of: a) an external drive piezo-acoustic
element, b) a built-in drive piezo-acoustic element, c) an external
drive magnetic transducer, d) a built-in drive magnetic transducer,
e) an external drive Mylar speaker, and f) a built-in drive Mylar
speaker.
24. A cooktop as in claim 13, wherein said igniter comprises a
resistive hot-surface igniter.
25. A heating device, comprising: a burner; an electronic
controller for electronically controlling a first mechanism and a
second mechanism; said first electronically controlled mechanism
for controlling flow of gas to said burner capable of providing at
least two different on-levels of continuous gas flow to said
burner; and said second electronically controlled mechanism for
controlling flow of gas to said burner capable of stopping and
starting flow of gas to said burner, wherein combination of said
first mechanism and said second mechanism provides capability to
achieve a lower temperature than is achievable with just continuous
flow of gas from said first mechanism.
26. The stove as recited in claim 25, wherein said first
electronically controlled mechanism is capable of providing 30
different on-levels of gas flow.
27. The stove as recited in claim 25, wherein a flame is produced
at said burner, wherein said electronic controller is capable of
controlling said second mechanism for sequencing the flame on and
off at a predetermined level of flame.
28. The stove as recited in claim 27, wherein said controller
comprises a microcontroller, wherein sequencing the flame on and
off is controlled by said microcontroller.
29. The stove as recited in claim 28, wherein said microcontroller
further comprises a pulse width modulation output port and an A/D
converter.
30. The stove as recited in claim 27, wherein sequencing the flame
on and off is controlled by time.
31. The stove as recited in claim 27, wherein sequencing the flame
on and off is accomplished with the on level set to a medium-low
level of BTU output.
32. The stove as recited in claim 27, wherein sequencing the flame
on and off is accomplished with gas flow on for 1 second and off
for 8 seconds.
33. The stove as recited in claim 25, wherein said controller uses
pulse-width-modulation for controlling said first mechanism.
34. The stove as recited in claim 25, flier comprising an igniter,
wherein said igniter assures flame re-ignition when said second
mechanism is used,
35. The stove as recited in claim 34, wherein said igniter does not
need to be synchronized with flame on/off cycling during simmer
mode
36. The stove as recited in claim 35, wherein said igniter is
continuously powered when said second mechanism is used.
37. The stove as recited in claim 34, wherein said igniter
comprises a resistive hot-surface igniter.
38. The stove as recited in claim 37, wherein said igniter
comprises a ceramic hot-surface igniter capable of constant
re-ignition
39. The stove as recited in claim 25, further comprising a main
in-line solenoid safety valve.
40. The stove as recited in claim 25, further comprising a
plurality of bumers, wherein said device comprises one of said
first electronically controlled mechanisms and one of said second
electronically controlled mechanisms for each said burner.
41. The stove as recited in claim 25. wherein said first mechanism
comprises a variable orifice solenoid that has a plurality of
positions controlled by application of a voltage signal.
42. The stove as recited in claim 25, wherein a single gas valve
includes both said first electronically controlled mechanism and
said second electronically controlled mechanism.
43. The stove as recited in claim 25, further comprising an igniter
for igniting gas when said first electronically controlled
mechanism provides flow of gas.
44. The stove as recited in claim 43, wherein said igniter is a hot
wire igniter.
45. The stove as recited in claim 43, flier comprising an igniter
for igniting gas when said first electronically controlled
mechanism and said second electronically controlled mechanism
provides flow of gas.
46. The stove as recited in claim 45, wherein said igniter is set
to be on continuously when said second electronically controlled
mechanism is being used to stop and start flow of gas to said
burner.
47. The stove as recited in claim 43, firther comprising a circuit
to monitor ignition by sensing temperature or sensing current
flowing in said ignite:.
48. The stove as recited in claim 25, further comprising a user
interface.
49. The stove as recited in claim 48, wherein said user interface
comprises a dial control.
50. The stove as recited in claim 48, wherein said user interface
comprises touch switches.
51. The stove as recited in claim 50, wherein said touch switches
comprises a touch pad.
52. The stove as recited in claim 48, wherein said user interface
comprises a capacitive touch keyboard.
53. The stove as recited in claim 48, wherein said user interface
comprises a power key, an on key, power level control keys, and an
off key.
54. The stove as recited in claim 25, further comprising a digital
visual display of cooking level of each burner,
55. The stove as recited in claim 54, wherein said digital visual
display comprises an LED, LCD, or a vacuum fluorescent display
56. The stove as recited in claim 25, further comprising a
temperature sensor fixed to a burner base,
57. The stove as recited in claim 56, further comprising an igniter
and a circuit to detect current flowing in said igniter, when if no
currant flows in said igniter or no elevated temperature is sensed
with said temperature sensor then visual and audible alarms are
generated
58. A gas valve comprising a first electronically controlled flow
control mechanism and a second electronically controlled flow
control mechanism different from said first flow electronically
controlled flow control mechanism,wherein both said first
electronically controlled flow control mechanism and said second
electronically controlled flow control mechanism can be used
together to provide control over burner temperature.
59. A method of heating comprising the steps of electronically
energizing an igniter, electronically setting a level to a
modulating valve, and electronically setting a sequencer to provide
a selected BTU output level.
60. The method as recited in claim 59, further comprising the step
of displaying said selected level.
Description
TECHNICAL FIELD OF INVENTION
[0001] This invention relates to control of gas appliances in
general and more specifically to an electronically actuated gas
cooktop flame proportioning control with flame sequencing simmer
system.
BACKGROUND ART
[0002] While easily achieved in electric cooktops, simmer
temperatures have until now been complicated issues for gas cooking
apparatus. Conventional gas cooktops are generally operated by
using manually activated mechanical actuator knobs, with infinitely
varying settings of the flow of gas by rotating associated gas
proportional valves. Most often, adjustment of cooking level is
achieved by comparing level indicators printed on the knob, to a
fixed pointer printed on the cooktop surface, immediately
surrounding the knob. With such knobs and associated infinite
valves, it often becomes difficult for the user to precisely
re-adjust the valve to a predetermined preferred level of BTU
output and thus repeatability is rarely achieved. This effect is of
an even greater concern in simmer mode of cooking where delicate
food such as chocolate or sauces can be spoiled, if cooked at
slightly higher temperatures than those recommended. Additionally,
mechanical knobs are also usually susceptible to wear and tear and
are often vulnerable to contaminants normally present in cooking
areas, such as greases and moisture infiltration that generally
find their way through open areas, necessary for the mechanical
valve installation in the cooking surface. Spark igniters are
typically used to ensure ignition of the gas and are generally
activated upon rotation of the above-mentioned mechanical knobs.
Most often, integrated sensors, such as flame detectors, are used
to continuously monitor proper combustion of the gas. Such sensors
typically provide feedback to the spark ignition module, to ensure
re-ignition of the gas, should it fail to combust. However, very
low flames have been proven hard to detect by such sensor types and
are often a cause for spark igniters to unnecessarily generate
discharges in response to false detection incidents. Spark igniters
are also known, by those in the industry, to emit powerful
electromagnetic interference (EMI) that often disturbs electronic
equipment working in their vicinity. Microcontrollers used in
electronic controls are also known to be highly susceptible to EMI
emission, and hence generally need additional protection when used
in conjunction with spark igniter modules in gas cooking
apparatuses. Due to their large orifice size, burners that are
capable of high BTU output are usually not suitable for simmer, one
of the reasons being that smaller flames have the tendency to
self-extinguish in such conditions. Therefore, some cooktops have
been equipped with simmer burners, featuring smaller orifice
diameters and capable of delivering stable low-to-medium BTU
output. This has often had the effect of reducing the number of
available burners capable of high BTU output on a given cooking
surface. Various methods involving flame sequencing have been used
to provide gas-cooking appliances with low temperature output to
provide a simmer. Sequencing the flame on and off in a timely
fashion provides for an elegant solution to achieve very low is BTU
output from a burner also capable of high BTU output, but simmer
systems of the prior art generally involve synchronized re-ignition
of the gas following each flame on/off cycle, complicating even
further the design of simmer controls in gas cooktops. Moreover,
repeated re-ignitions of the gas during simmer mode often have the
undesirable effect of continuously generating harmful
electromagnetic interference. As mechanical valves are
traditionally used to adjust the gas flow, additional electrically
controlled "on/off" cycling solenoid valves are generally added to
provide the "on/off" sequencing of the flame in simmer mode,
contributing to higher system cost and reliability issues.
[0003] U.S. Pat. No. 4,376,626 to Rossi et al. (Device for the
control of a sequential burner of a cooking apparatus) discloses a
control device for at least one sequential burner of a cooking
apparatus, comprising in combination: a geared-down synchronous
motor and a drum which can be driven in rotation by this motor, an
electric circuit associated with this drum, comprising at least one
electric contact pressing upon the surface of the drum and at least
one electrically conductive track arranged on the drum in such
manner as to permit operation of the burner according to heating
sequences which are variable as a function of the position of the
electric contact on the drum, and means for adjusting the position
of the contact in relation to the conductive track in order that
the duration of the heating sequences of the burner may be varied
progressively and continuously.
[0004] U.S. Pat. No. 5,575,638 to Witham et al. (Stove burner
simmer control) discloses a burner control which provides a pulsed
flame sequence in response to a user's selective manipulation of an
actuator through a range of response. A microcontroller-based
control module switches both a burner igniter control and an
electric valve for gas supply to the burner in a predetermined time
sequence depending upon the actuator position within the
predetermined range. Preferably, one or more of a plurality of
burners on a single cooking top are controlled for pulsed sequence
operation, and a single actuator for each channel, preferably in a
form of a rotary knob, provides a simple user interface for
utilizing the pulsed flame sequence, preferably in a low gas flow
or simmer cooking range.
[0005] U.S. Pat. No. 6,116,230 to Clifford et al. discloses a gas
appliance comprising a burner, a conduit, a control circuit, and a
valve. The control circuit is adapted to provide a
pulse-width-modulated signal to the valve, whereby the valve
provides a substantially linear flow rate of fuel from a fuel
source to the burner. The gas appliance of Clifford et al. employs
a spark igniter.
[0006] Thus, there is a need for an electronically controlled gas
cooktop appliance capable of delivering true simmer temperatures
from gas burners that are also capable of high BTU output. There is
also a need for an electronic gas cooktop appliance that is capable
of fine, precise, and repeatable control of heating levels,
provided by a direct level-dialing control, thus providing the user
with a more precise selection of available and controllable
temperatures. There is also a need for a gas cooktop appliance
capable of assuring flame re-ignition without generating harnful
electromagnetic interference. There is equally a need for a gas
cooktop flame-sequencing simmer system integrating gas-flow
modulation and "on/off" sequencing ability into a single gas valve.
Finally, there is a need for a gas cooktop appliance integrating an
electronic user touch interface for burner activation and selection
of temperature settings.
OBJECTS OF THE INVENTION
[0007] The present invention is intended to provide practical
solutions to problems in the existing art, thus globally fulfilling
the above-mentioned needs.
[0008] A major object of the invention is a gas cooktop appliance
capable of delivering very low heat power while maintaining
capability of delivering very high BTU output, in each available
burner, and also capable of fine, precise and repeatable control
over the entire span of cooking levels. Another object of the
present invention is to provide a gas cooktop appliance with an
innovative electronic control featuring a capacitive touch user
interface, thus featuring a flat, smooth and sealed cooking
surface. Such a capacitive touch interface facilitates the
maintenance of surfaces that are generally prone to become dirty
and that are also difficult to reach. A capacitive touch interface
offers the additional benefit of eliminating the wear and tear
associated with mechanical devices and also of preventing
contaminants such as greases and moisture from reaching sensitive
components internal to the cooktop apparatus.
[0009] Another object is an electronic control capable of handling
simultaneously both modulation of the valve(s) for metering the gas
flow delivered to the burners from medium to high BTU output, and
sequencing of the flame "on" and "off" at a predetermined medium
level of flame, to provide efficient simmer temperatures. An
additional object is to provide electronic control of a gas cooktop
featuring a direct-dial keyboard-entry system and a digital visual
user interface such that repeatability and precise re-selection of
predetermined cooking levels is achieved. Yet another object is to
provide an initial gas ignition and a flame sequencing re-ignition
system that does not need to be synchronized with the flame on/off
cycling during simmer cook mode and that does not generate harmful
electromagnetic interference.
SUMMARY OF THE INVENTION
[0010] The present invention relates to the field of gas cooking
appliances in general and more specifically to a
micro-controller-based electronic controller and simmer system for
a gas cooktop appliance. In a preferred embodiment, the present
invention is presented as a gas residential cooktop with controls,
but it will be understood that the teachings of the present
invention are also applicable to industrial and commercial gas
cooktop appliances.
[0011] Among features provided by this invention are: a capacitive
touch keyboard interface, an entirely electronic control system
controlling the gas flow through modulating valves; an innovative
modulating valve activated through a pulse-width-modulation (PWM)
port, capable of infinitely controlling the flow of gas while also
providing for an "off" position, the electrical modulating valve
therefore eliminating the need for an additional in-line solenoid
valve to sequence the flame "on" and "off" during simmer operation;
and ceramic hot-surface igniter(s) controlled and monitored by the
electronic control system, capable of constant gas re-ignition
without generation of electromagnetic interference.
[0012] Natural or propane gas is selectively provided to each
individual burner, through the use of electrically actuated
modulating valves, thus eliminating the need for mechanical valves
and actuator knobs protruding through the user console and
facilitating the maintenance of such surfaces. Ignition of the gas
is monitored through temperature sensing, and ceramic hot-surface
igniters are also monitored through current sensing. Safety
features such as main in-line valve closure and de-energizing of
the igniters are supported in the event that a fault condition
occurs. Features such as visual and audible alarms are also
generated, providing the user with positive indications of serious
error conditions.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a basic block diagram of a cooktop system made in
accordance with the invention.
[0014] FIG. 2 is an example of one of many possible user
interfaces, to be used in conjunction with the present invention.
FIGS. 3a and 3b together show a flowchart of control software for a
preferred embodiment of the invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0015] FIG. 1 is a basic block diagram of a cooktop system made in
accordance with this invention. The cooktop shown in FIG. 1 has one
or more gas burner(s) 114 placed on a ceramic glass panel 109; one
electronically controlled in-line safety gas valve 112; one or more
electronically controlled in-line modulating valve(s) 113; a gas
line conduit 123 to conduct gas from the main gas supply to the
burner(s) under control through the in-line valves; a user
interface panel 110 preferably placed in registry with a
silk-screened portion of a ceramic glass panel 109; one or more
temperature sensor(s) 118; one or more hot-surface igniter(s) 117;
and a controller 111 operative to control each of the gas valves in
accordance with the user's selection entered at the user interface,
the apparatus being controlled by a suitably programmed
microcontroller 101.
[0016] The user interface panel 110, placed in registry with a
silk-screened portion of a ceramic glass panel 109, preferably
firther includes one or more visual indicator(s) 116, such as
seven-segment LED displays, discrete LED displays, bar-graph LED
displays, LCD displays, and vacuum fluorescent displays, for
displaying information 120 concerning the status of the cooktop to
the user; an audible annunciator 125 such as an external drive or
built-in drive piezo-acoustic element, magnetic transducer or Mylar
speaker, used to provide audible indication 124 that a touch key is
selected and also to provide for an audible alarm whenever a system
error is detected; and an array of capacitance sensitive keypads
115, each one having a capacitive field 119, produced, detected and
analyzed by a capacitive-keyboard decoding interface module 102,
and capable of electrically reacting to a human hand or finger 121,
placed in proximity with any one capacitive field 119 associated
with one of the capacitance sensitive keypads 115.
[0017] The microcontroller-based control 111 comprises an array of
modules, dedicated to the driving and monitoring of the various
elements of the system, controlled by the microcontroller 101.
[0018] The display elements of the visual indicators 116 are driven
by a display-power-driver module 103 preferably comprising serial
output shift registers (integrated circuits), multiple channels of
source-driver integrated circuits, multiple channels of sink-driver
integrated circuits, and may also include driver circuits using
discrete transistors.
[0019] A power module 126 consisting of discrete transistor
circuitry drives the audible interface 125. Power module may be
unnecessary if the audible interface is made with one or more
built-in drive acoustic annunciators.
[0020] A valve-power driving module includes a power relay or a
triac module 107 for driving main safety valve 112 and a Darlington
array integrated circuit or an array of discrete transistors 108
for driving the modulating valve(s) 113.
[0021] An igniter-power driving module 105 is also provided and
includes a power relay or a triac module for driving one or more
ceramic hot-surface igniter(s) 117. A current sensor module 104 is
also provided for monitoring the current flowing through the
hot-surface igniter(s) 117.
[0022] Appropriate amplification module 106 is provided to deliver
reliable temperature sensor data, at the proper voltage span, to an
analog-to-digital input port of microcontroller 101. Amplification
may not be needed for some sensors, and thus module 106 may also be
a simple voltage divider circuitry, e.g., if the temperature sensor
used is a thermistor.
[0023] A sine-to-square-wave converter input module 127 is
preferably included in the microcontroller-based control 111 to
provide the microcontroller 101 with a reliable time base for
proper timing of "on/off" flame sequencing periods, during simmer
mode. The sine-to-square wave converter input module 127 may
consist of a diode rectifying input circuitry, tapping a portion of
the conventional AC supply voltage and feeding a transistor based
circuit. That circuit, connected to a pull-up resistor, provides as
an output a square wave representative of the 50 Hz or 60 Hz signal
carried by the AC voltage supply line.
[0024] Additionally, the microcontroller-based control 111
preferably includes a capacitive-keyboard decoding interface module
102 with a serial or parallel communication interface, capable of
detecting and analyzing a user touch condition. The
capacitive-keyboard decoding module preferably includes: a
capacitive matrix decoder integrated circuit with a serial or
parallel communication interface, a portion of the ceramic glass
panel 109 (preferably silk-screened) used to provide for a user
touch interface, and an array of capacitive sensing keypads 115
placed in registry with the user touch interface portion of the
ceramic glass panel 109. Key sensitivity may be made individually
trinrnable for adaptation to key size, key shape, and key location
on the user interface keyboard. Capacitive sensing for the keyboard
interface may be done as described in U.S. Pat. No. 5,730,165 to
Philipp, the entire disclosure of which is hereby incorporated by
reference. In U.S. Pat. No. 5,730,165, a capacitive field sensor
employs a single coupling plate to detect a change in capacitance
to ground. The apparatus comprises a circuit for charging a sensing
electrode and a switching element acting to remove charge from the
sensing electrode and to transfer it to a charge detection
circuit.
[0025] A suitable capacitive-keyboard decoding interface 102 is the
model QM1, available from Quantum Research Group Ltd. of
Southampton, England and Pittsburgh, Pa, or preferably the models
QT60320 and QT 60321 Matrix Scan IC's available from that company.
The QT60320 family of Matrix Scan IC's is a family of
capacitive-keyboard decoding interfaces, based on the Philipp
invention mentioned above, utilizing dual coupling capacitive plate
sensors, disposed in a key matrix configuration.
[0026] The microcontroller-based control 11 also preferably
includes a microcontroller integrated circuit 101 having integrated
features, as per the following list:
[0027] a) a bi-directional serial communication port for
interfacing with a capacitive-keyboard decoder integrated
circuit;
[0028] b) a serial peripheral interface port for interfacing with
display interface circuitry;
[0029] c) a pulse-width-modulation (PWM) output port for
controlling gas modulating valves;
[0030] d) an input port for 60 Hz signal detection;
[0031] e) an output port for controlling a main gas solenoid safety
valve;
[0032] f) an output port for interfacing with an audible
annunciator;
[0033] g) an analog-to-digital converter input port for temperature
monitoring;
[0034] h) an output port for controlling a gas igniter module;
and
[0035] i) an analog-to-digital converter input port for monitoring
gas igniter current.
[0036] Those skilled in the art will recognize that multiple ports
of any of the types listed may be provided.
[0037] The valve portion of the system preferably includes an
in-line gas valve assembly having a single main in-line solenoid
safety valve 112, commonly found in the industry and an in-line
modulating valve 113 for each burner. One suitable modulating valve
is disclosed in U.S. Pat. No. 5,458,294 to Zachary et al., in which
a variable orifice solenoid has a plurality of positions, and the
positions are controlled by the application of a voltage signal to
the modulating valve. The entire disclosure of U.S. Pat. No.
5,458,294 to Zachary et al. is incorporated herein by reference, as
is the entire disclosure of U.S. Pat. No. 6,116,230 to Clifford et
al., mentioned above.
[0038] U.S. Pat. No. 5,458,294 discloses an apparatus for
accurately controlling gas fuel flow to a combustion device to
control gas flow to a burner of the combustion device. A variable
orifice solenoid-operated valve serves as a control element. The
valve includes a poppet having a fixed control surface at an end
received in an insert element having a variable control surface.
The poppet has a plurality of positions within the insert element,
including a full open position and a full closed position. Maximum
fuel flow is measured in the full open position and minimum fuel
flow is measured in the full closed position. Intermediate
partially open positions are adjustable by a signal of an
electronic controller connected to the solenoid valve operating as
a function of actual and desired temperature of the combustion
device. If desired, the fixed control surface can contact the
variable control surface at some point as the fixed control surface
moves into the insert, to completely seal the valve and shut off
the flow of gas to the burner means.
[0039] The flame ignition portion of the system preferably includes
a resistive hot-surface igniter 117, preferably fixed to the burner
base 128, capable of producing a temperature of 1350.degree. C. in
a time-to-design-temperature equal to or less than 3 seconds. U.S.
Pat. No. 5,892,201 to Croucher et al., discloses a ceramic igniter,
comprising: (a) a pair of electrically conductive portions, each
portion having a first end, (b) a hot zone disposed between and in
electrical connection with each of the first ends of the
electrically conductive portions, the hot zone having an electrical
path length of less than 0.5 cm, and (c) an electrically
non-conductive heat sink material contacting the hot zone. The
entire disclosure of U.S. Pat. No. 5,892,201 to Croucher et al. is
incorporated herein by reference. One suitable resistive ceramic
hot-surface igniter is the Norton Igniter model No. M-401
manufactured by Saint-Gobain Industrial Ceramics Inc. of Milford,
N.H.
[0040] Additionally, the invention provides for one or more
temperature sensor(s) 118, each one fixed to the burner base 128
and directed at the flame area of the burner to detect a flame,
thus monitoring proper ignition of the gas delivered to the burner
114 by the modulating valve(s) 113. The temperature sensor may be
of any suitable type, such as: thermistors, thermocouples, or
infrared temperature sensors.
[0041] Operation
[0042] A continuous flame modulation mode of operation, described
below, is used for the portion of the total span of gas output
levels that can be safely modulated by the modulating valve, where
the flame is continuously present and not sequenced "on" and "off"
by the controller. This continuous flame modulation mode is
associated with cooking levels ranging from medium-low to high BTU
output. Furthermore, medium-low level of flame is defined here as
being the lowest level of flame that can be safely maintained
without self-extinguishing, can be safely ignited by a ceramic
hot-surface igniter, and can be easily sensed by the flame
detector, for any particular burner orifice size.
[0043] In continuous-flame-modulation mode of operation the
microcontroller 101 first sends a signal to the power-driving
portion 107 of the controller, driving the safety valve 112 "on" to
permit the gas entering the system 122 to reach the in-line
modulating valve(s) 113, then the microcontroller 101 sends a
pulse-width-modulation signal to the power-driving portion 108 of
the controller 111 driving the modulating valve 113, to
proportionally modulate the valve opening size to the desired gas
flow level, as selected by the user and, thus, to permit the gas to
reach the burner. Hence, this mode of operation adjusts the flame
height to any desired level of BTU output ranging from medium-low
to high BTU output. Furthermore, in this particular mode of
operation, the hot-surface igniter 117 is powered only during the
first phase of the continuous-flame modulation mode of operation.
Ignition is provided and maintained from the time that the gas is
permitted to reach the burner, until a flame is detected by the
appropriate temperature sensor 118 associated with the controlled
burner. Ignition process can also be aborted if one of the
following error conditions occurs: no hot-surface igniter current
is sensed, and/or flame is not detected for a predetermined period
of time. In any of these error condition cases, the controller 111
automatically turns off the safety valve 112, the hot-surface
igniter 117, and the modulating valve 113 corresponding to the
faulty burner. Then, visual and audible signals are generated to
alert the user of the faulty condition.
[0044] Simmer mode of operation is defined here as being the mode
of operation used for the lowest portion of the total span of BTU
output levels. In simmer mode of operation, the microcontroller 101
first sends a signal to the power-driving portion 107 of the
controller, driving the safety valve 112 "on", to permit the gas
entering the system 122 to reach the in-line modulating valve(s)
113. Then, the microcontroller 101 sends a predetermined
pulse-width-modulation signal to the power-driving portion 108 of
the controller 111 driving the modulating valve 113, to
proportionally modulate the valve opening size to a predetermined
level of gas flow, and, thus, to permit the gas to reach the
burner. In simmer mode of operation, the pulse-width-modulation
(PWM) output level is set to provide a predetermined medium-low
height level of flame that can safely be maintained without
self-extinguishing, can safely be ignited by the ceramic
hot-surface igniter, and can easily be sensed by the flame
detector, for any particular burner orifice size. In that
particular mode of operation the pulse-width-modulation output,
which drives the modulating valve associated with the burner
working in simmer mode, is continuously being sequenced "on" and
"off" by the microcontroller 101 A time-based sequencer, ruled by
appropriate software program and 60 Hz detection module 127, is
activated, toggling the PWM output driving the modulating valve,
and thus turning the flame "on" and "off" in a timely fashion.
During the "off" portion of the sequencing, while no PWM signal is
provided to the modulating valve, the valve reverts to its "off"
position, sealing the opening and thus preventing the gas from
reaching the gas burner under simmer mode of operation. During the
"on" time portion of the sequencing, the PWM output is set to the
medium-low level of BTU output, providing the safest low level of
flame that can be ignited, maintained, and sensed by the
temperature sensor. The "on" and "off" periods are produced to
correspond to a desired simmer level as selected by the user. As an
example of this, for a particular output level, as selected by the
user; "on" time, when the flame is present, can be equal to 1
second, and "off" time, when the flame is not present, can be equal
to 7 seconds, to produce a 1 over 8 or 1:8 ratio of BTU output in
relation to an hypothetical constant flame produced at the same
predetermined flame height level. Additionally, during that
particular mode of operation, the hot-surface igniter 117 is
continuously powered by the igniter power module 105, and
constantly monitored by the igniter-current sensor module 104 to
provide for an instantaneous ignition process, bypassing the
time-to-design-temperature period. Furthermore, the temperature
sensor output is read during each "on" portion of the flame
sequencing activities. Ignition is thus provided and maintained
until the user selects a burner powering level other than those
provided within the span of simmer mode of operation, and can also
be aborted if one of the following error condition occurs: no
hot-surface igniter current is sensed and/or flame is not detected
during the "on" periods of the sequencing cycles. In any of these
error condition cases, the controller 111 automatically turns off
the safety valve 112, the hot-surface igniter 117, and the
modulation valve 113. Then, visual and audible signals are
generated to alert the user of the faulty condition.
[0045] Total span of BTU output can range from very low to very
high and have an infinite number of steps from which many can
operate in simmer mode of operation and many others in the
continuous flame modulation mode of operation. For example, a
particular control could arbitrarily offer 44 levels of BTU output,
from which the lowest fourteen levels could be operating in a
simmer mode of operation and the remaining 30 levels could be
modulated in a continuous flame modulation mode of operation. The
above-mentioned example is given here only as one possible
embodiment of the present invention and does not intend to
constitute a limitation to the present invention. One of ordinary
skill in the art would readily perceive that the total number of
possible cooking-level steps, as well as the portion of these steps
predetermined to work either in the simmer mode or in the
continuous flame modulation mode of operation, are readily defined
by appropriate software programming alone. Control software
programming is described next.
[0046] Control Software
[0047] FIGS. 3a and 3b together show a flowchart of control
software for a preferred embodiment of the invention, using
conventional flowchart symbols. Table I below shows the steps used
in the control software illustrated in FIGS. 3a and 3b
together.
1TABLE I Control software process steps Step Function performed 300
Start burner subroutine 301 Test: Is at least one burner active?
302 Shut safety valve OFF 303 Scan keyboard for user input 304
Test: Is a burner OFF key selected? 305 Shut igniter OFF; stop PWM
output; clear burner display 306 Go to main routine 307 Test: Is a
burner ON key selected? 308 Show "0" in selected burner display;
enter selected burner program mode 308.1 Test: Is there a burner in
program mode? 309 Test: Is a burner BTU level selected? 310 Is the
selected BTU level a simmer level? 311 Energize the hot surface
igniter, etc. (Simmer mode -- see description) 312 Energize the hot
surface igniter, etc. (Continuous flame modulation mode -- see
description) 313 Test: Is current of the selected hot surface
igniter sensed? 314 Test: Is current of the selected hot surface
igniter sensed? 315 Test: Is flame sensed at the selected burners?
315.1 Loop flame sensing for predetermined period of time 316 Test:
Is flame sensed at the selected burners? 316.1 Loop flame sensing
for predetermined period of time 317 Display appropriate error
code; sound audible alarm 318 De-energize appropriate hot surface
igniter
[0048] It can be seen in FIGS. 3a and 3b that if no burner is
activated 301, the safety valve of the gas system is turned "off"
302. As illustrated in the flow chart of FIGS. 3a and 3b, the
keyboard is periodically scanned for user input 303 and, depending
on the type of key detected as touched by the
capacitive-keyboard-decoding interface, a specific number of steps
are consequentially performed by the microcontroller as dictated by
the control software. For instance, if a burner "0ff" key is
touched 304, the microcontroller will then shut the appropriate
igniter "off" , stop the PWM output to the appropriate modulating
valve, clear the appropriate burner display 305 and finally revert
to the main routine of the control software 306. If a burner "On"
key is detected 307, the software will place the appropriate burner
in programming mode and notify the user of that condition using of
the appropriate display 308. If a burner level key is selected 309,
the software verifies 310, through the use of a software table,
whether the selected BTU level belongs to the class of BTU output
dedicated to simmer mode or to continuous-flame-modulation mode of
operation, and chooses the appropriate mode accordingly. Although
the two modes of operation adopt different behaviors 311 and 312,
in both cases current flowing through the igniters 313 and 314 and
also flame ignition 315 and 316 are monitored for proper
operation.
[0049] If no current flows through the igniters while activated
and/or no flame is sensed while gas is conducted to the burner
under control, then visual and audible alarms are generated 317,
and the faulty burner is deactivated by stopping appropriate PWM
output, shutting off the appropriate igniter and clearing the
appropriate burner display 305.
[0050] In simmer mode of operation shown by the series of actions
identified by reference numeral 311, i.e., when a simmer level of
BTU output is selected by the user, the microcontroller energizes
the hot surface igniter, energizes the main solenoid valve, outputs
a predetermined PWM level to the appropriate modulating valve, sets
the PWM output sequencer to selected BTU output level, shows the
selected burner level in the burner display and leaves the igniter
continuously "on" during the entire simmer operation.
[0051] In continuous-flame-modulation mode of operation, shown by
the series of actions identified by reference numeral 312, i.e.,
when a level of BTU output other than simmer level is selected by
the user, the microcontroller then energizes the hot surface
igniter, energizes the main solenoid valve, outputs the selected
PWM level to the appropriate modulating valve, shows the selected
burner level in the burner display and further de-energizes the hot
surface igniter once the ignition of the flame is achieved 318.
[0052] Use of the Invention
[0053] To use the invention, a user touches desired control keys on
the cooktop keyboard similar to the one illustrated in FIG. 2. For
example, the user may touch a POWER key 201 to energize the
keyboard and enable the controller. The user may then touch the ON
key 202 of a particular burner, corresponding to a particular
position on the keyboard layout, to turn a specific gas burner on.
The user may touch arrow keys 203 to raise or lower the gas power
level for the selected burner and get a visual indication of the
newly selected power level, through the visual interface 204. If a
"slider" control is provided on the keyboard layout, the user can
move a finger along the slider control to control the heat level of
a particular burner. The user may directly touch any one of the
POWER level number 205 or "L" 206 for low or "H" 207 for high. The
user may touch the "off" key 208 of a particular burner to turn it
off or touch the POWER key 201 to turn every active burner off. The
particular keyboard layout embodiment depicted in FIG. 2 is meant
to be representative of a type of touch-sensitive keyboard layout
suitable for a cooktop. Preferably, the keyboard layout should, by
the use of numerals, symbols, and other indicia, convey to the user
the various control functions available, in a manner that is as
clear and intuitive as possible. The person of ordinary skill in
the art of appliances will recognize that many variations of
keyboard layouts with correspondingly programmed functions may be
made that are suitable for various uses of gas or hybrid
gas/electric cooktops.
[0054] Industrial Applicability
[0055] The invention is useful in domestic and commercial cooking,
providing an electronically controlled gas cooktop with multiple
heating modes, including precisely controlled simmering and safety
features.
[0056] Although specific embodiments of the present invention have
been illustrated in the accompanying drawings and described in the
foregoing detailed description, it will be understood that the
invention is not limited to the particular embodiments described
herein, but is capable of numerous rearrangements, modifications,
and substitutions without departing from the scope of the
invention. One skilled in the art can easily ascertain the
essential characteristics of this invention, and without departing
from the spirit and scope thereof, can make various changes and
modifications of the invention to adapt it to various usages and
conditions.
* * * * *