TECHNICAL FIELD
[0001] The present invention relates to cooking appliances having a cooktop with gas burners
to which the gas flow and ignition of the gas flow is adjustable and assisted by a
controller having a microprocessor for control of drivers for actuating elements that
control the flow rate as well as the timing of the flow.
BACKGROUND ART
[0002] In most standard surface gas burner systems, whether used in counter cooktops or
the cooktop portion of ranges, the flame is manually adjustable from a high output
rating to a minimum output rating. The minimum output rating is the flow rate at which
a small flame can be sustained at the burner ports without nuisance extinction. For
most existing burner systems, the minimum output rating is in the range of 800 to
1500 BTU/hr.
[0003] One previously known attempt to obtain an output rating lower than most existing
burner systems was to segregate gas flows by using dual burner heads. A small simmer
head is placed in the center of a larger burner ring. This burner system is used in
conjunction with a manual valve that has two valves internally. In the simmer mode,
the outer ring is not used. The central burner provides the low output required for
simmering. One big drawback of this system is the complexity of the gas piping system.
There are two feeding pipes from the manual valve to the burner head. The burner head,
as previously discussed, is actually two heads and the manual valve is actually two
valves in one. Another disadvantage is that the central simmer head poses a performance
deficiency in that the heat from a sustained flame is concentrated in a very small
area. As a consequence, hot spots are created that may be hot enough to scorch a food
item being simmered.
[0004] Another improvement providing lower energy output, for example a Thermador XLO burner
system, provides sustainable flame control by cycling the flame on and off in order
to achieve a heat output rating lower than what can normally be achieved using only
limited range rate, controlled standard burner systems. This avoids complicated piping
and may be incorporated with a cooktop construction with a standard size burner head.
The heat is dissipated more evenly and the severity of hotspots is eliminated.
[0005] The previous system utilizes a manual valve that turns 280° counterclockwise. The
valve is on HI at the 90° mark providing maximum flow through the valve. Further rotation
reduces the gas flow to the burner as the valve is turned toward a minimum opening
permitting a low flow rate at which the flame can be sustained at the burner. The
unmodulated gas flow output is then kept constant as the valve is turned from 210°
to 280°. Between 210° and 280°, the micro controller generates a valve control signal
sequentially opening and closing a solenoid driven valve. For example, in a system
that uses a 60 second period as its time base, at 210°, the flame is turned on for
a predetermined time, e.g. 54 seconds, out of every 60 seconds. At 280°, the flame
is turned on 7 seconds, out of every 60 seconds. The on times vary linearly between
the 210° mark and the 280° mark. The signal is delivered to a solenoid driven valve
connected between the manual gas valve and the burner head. The controller determines
when to open the solenoid. The position of the manual valve is indicated to the controller
by a potentiometer that is carried on the manual valve and operable for response variation
as the user rotates the manual valve stem. The solenoid valve is powered by the electronic
controller which in turn is energized by the mains power. Accordingly, the previous
system is inoperational during a power outage because the solenoid valve is closed
when not energized.
[0006] Moreover, the multiple valve bodies require additional gas path couplings that must
be sealed and maintained throughout the useful life. Moreover, automating operation
of the previous supply valve would require such high force actuation that coils or
the like would be too large to package conveniently or to build in a reasonable cost
consumer product.
Another type of known valve control, for example, cooktop controls of certain European
manufacturers, utilize an integrated cut-off solenoid valve. The solenoid valve is
comprised of a magnetic coil and a plunger with a rubber seal at one end that is displaced
to allow or prevent the flow of gas. The solenoid is used in conjunction with a thermocouple
mounted close to the burner head that generates the power to energize the solenoid.
[0007] In operation, the valve stem or knob is pushed down and turned counterclockwise.
The pushing action pushes the solenoid plunger open and against the biasing spring
force that pushes the plunger closed. The opening of the plunger allows gas to flow
to the burner head. The gas is then ignited by an independent ignition system. The
resulting flame heats up the thermocouple which generates an output to energize the
coil and hold the plunger open. At this point, the user can stop pushing on the valve
knob and the flame should be sustained. In the case that the flame in the burner head
is extinguished, the thermocouple cools and the output generated drops until it releases
the plunger to close, stopping the gas flow. This is a cut-off feature that prevents
the escape of unignited gas. However, such a control is not a control for reducing
energy output during cooking, and does not address the problems of hotspots or low
energy flame control. Morever, such valves are physically designed to handle substantially
less operating cycles (opening and closing) than would be required in a sequencing
operation over a reasonable appliance service life, for example, tens of thousands
of cycles over many years, where the valve closing and opening cycle repeats every
minute during operation.
DESCRIPTION OF THE PRESENT INVENTION
[0008] The present invention overcomes the above-mentioned disadvantages by providing an
electronic controller and a valve with an actuator for controlling both the timing
and the flow rate of gas delivery through the valve to the burner. The cooktop control
actuator may include a driver for a valve that opens and closes the flow of gas toward
the burner and a driver which provides a range of control for the flow rate of gas
to the burner, preferably within a single valve housing package.
[0009] The cut-off solenoid valve previously known may be modified in order to, for example,
respond to an external electronic controller to pull in the plunger, control closing
and opening of the gas flow. To reduce the size and power required to operate previously
known valve structures, materials features such as wear-resistant, physical coatings
and surface hardness characteristics may be added to reduce resistance that creates
electrical losses, and thereby minimize coil size and packaging requirements. In addition,
a thermocouple provides high energy power to the coil to take over in holding the
plunger open once the plunger is open and a flame is established. Moreover, the valve
is coupled so that the electronic controller may interrupt the output from the thermocouple
to release the plunger and stop the gas flow.
[0010] The present invention provides the advantages of the existing cut-off solenoid valve,
and also the advantage of using the valve as the cycling valve for the pulsed sequence
burner operating feature. The preferred embodiment of the present invention eliminates
the need for a separate external solenoid valve and at the same time, improves the
previously known sequencing feature by adding an extra level of flame control as well
as a feedback control from the burner. Unlike the simple cut-off solenoid valve system
discussed in the previous section, the user does not need to hold down the knob while
the thermocouple heats up when a flame is first established, since the electronic
controller drives the actuator to open the valve and keeps the plunger open to allow
the flow of gas during the initial heat up of the thermocouple.
[0011] Additionally, the present invention allows the use of the burner in the event of
a power outage, whereas the existing XLO system does not. In the preferred embodiment,
if the burner flame is already generated when a power interruption occurs, the burner
will remain lit. On the other hand, if the flame is off, for example, because it is
in the off portion of a sequencing cycle, then the burner will remain unlit. If the
burner is not flaming when the power is interrupted, the knob may be pressed down
while the flame is manually lit with a match. After ignition, the knob may be pushed
down for a time, for example, a couple of seconds, until the thermocouple generates
enough energy to hold the safety valve open. At this point, the user can release the
knob and the burner should operate normally, except without the pulsed sequencing
feature. Regardless of the presence of the mains power, the system avoids gas releases
after inadvertent flame extinction.
[0012] In a preferred embodiment, a solenoid valve of the previously known type is modified
by the addition of a pickup coil. The pickup coil will be energized by the electronic
control. Once the plunger opens, the microcontroller drive signal to the pickup coil
can be reduced to a holding value. In addition, as soon as the output of the thermocouple
gets to a level high enough to energize the existing holding coil, the power to the
pickup coil is turned off. In order to release the plunger, the controller may short
out the output of the thermocouple, thus de-energizing the holding coil and releasing
the plunger to close the valve. Alternatively, the controller may provide a drive
signal to the pickup coil with a power whose magnitude is at least equivalent to that
produced by the thermocouple but opposite in polarity. The opposite power will generate
a magnetic field that will negate the magnetic field produced by the thermocouple,
thus releasing the plunger. In either event, the controller permits pulsed sequencing
of the gas flow when electrical power is available and incorporates flame shut off
capability without requiring electrical power to operate the gas burner appliance.
BRIEF DESCRIPTION OF THE DRAWING
[0013] The present invention will be more clearly understood by reference to the following
detailed description of the preferred embodiment when read in conjunction with the
accompanying drawing in which like reference characters refer to like parts throughout
the views, and in which:
FIGURE 1 is a schematic diagram of the cooktop control system according the present
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0014] Referring first to Figure 1, a cooktop is shown comprising a cooktop burner system
10 in which the cooktop panel 12 includes at least one gas burner 14. The burner 14
is coupled in fluid communication to a gas manifold 16, and a control 18 for a delivery
of gas to the manifold is described in detail below. The control 18 includes valve
actuator 22 and an electronic control module such as the microprocessor based controller
24. In addition, the control 18 includes an ignition control module 26 for operating
the ignitor 28 that is positioned adjacent to burner 14 on the cooktop panel 12.
[0015] The electronic controller 24 is adapted to control responsive elements in a valve
30 which also includes manual inputs as well known in the previous sequenced burner
of U.S. Patent 5,765,542. Preferably, the electronic controller 24 and the ignition
module 26 are housed in a single control package 32 for convenient arrangement and
interconnection with the other parts of the control 18. In addition, the valve 30
may be of various types of construction, although as schematically represented in
Figure 1, includes at least one responsive element responsive to a driver 34. The
valve is preferably carried in a single housing body 31, for example, as is accomplished
in a Sourdillon Valve Model 099, including a cut-off valve and a flow rate adjuster.
The responsive element 36 in the preferred embodiment is a pick-up coil 58, although
other electronically driven devices could also be employed. The responsive element
36 controls at least one valve actuator, for example, plunger shaft 38, for controlling
the connection between the gas supply 20 and the gas manifold 16.
[0016] In the preferred embodiment shown in Figure 1, the responsive member 36 includes
the plunger shaft 38 acting as a valve stem that carries a valve head 40 for displacement
into contact with and away from the valve seat 42. Closure of the valve head 40 against
the valve seat 42 obstructs the flow of gas input between the supply 20 and the gas
manifold 16. In addition, the valve construction shown in Figure 1 includes flow rate
adapter that varies the amount of gas that can be passed from the supply 20 to the
gas manifold 16 and into the burner 14. For example, the actuator 22 may include a
tapered valve stem with a flow control channel that controls the amount of blockage
of the flow passageway through the valve 30 from its inlet 72 to its outlet 74. Both
the valve head 40 and the valve stem control chamber are within the flow passage through
the valve body from its inlet 72 to its outlet 74. The plunger shaft 38, holding coil
52 and pick-up coil 58 are carried in a chamber sealed by cap 70. Preferably, these
parts are carried in a cartridge 76 for simple installation within the chamber. For
example, the cartridge 76 may be constructed to replace the valve components provided
with the Sourdillon valve Model 099, without otherwise changing the valve body, but
replacing the original coil actuator with both coil actuators of the preferred embodiment.
[0017] The position of the valve stem 44 is relayed by a position encoder 46, preferably
a potentiometer when a simple electrical circuit incorporating previous controls is
desired, coupled to the electronic controller 24, although other counters or devices
may be used. In the preferred embodiment, the stem is actuated by a knob 48. Nevertheless,
other types of controls such as touch sensitive switches or the like may be used as
an actuator 22 without departing from the present invention. In any event, the feedback
from the actuator 22 to the controller 24 advises the controller 24 of the flow rate
of gas to be delivered to the burner as will be discussed in detail below.
[0018] The cooktop 12 also includes a thermocouple 50 adjacent the peripheral ports of the
burner 14. The thermocouple 50 generates a current in response to the presence of
a flame at the thermocouple that is delivered to a holding coil 52 acting upon the
valve shaft 38. So long as the flame is sustained to generate heat at the burner 14,
the thermocouple 50 generates sufficient current to hold the solenoid core of the
plunger shaft 38 in a retracted position from the valve seat 42. Of course, the valve
head 40 may be resiliently biased, for example by the spring 54, toward the seat 42
to shut off the flow of gas in the event that electric power is not available to the
ignitor 28 or to the controller 18 for the gas valve. The holding coil 52 is sufficiently
large to be energized so that it overcomes the biasing force, for example, the force
of the spring 54, to displace the shaft 38 to its retracted position.
The position encoder 46 may be an analog device such as a potentiometer or a digital
device such a binary encoding counter, without departing from the present invention.
The position of the valve stem 44 determines the amount of gas within the predetermined
range of flow rates for the gas delivered to the manifold 16 for controlling the amount
of heat released at the burner 14 in the preferred embodiment. In the preferred embodiment,
the knob 48 is turned to open the valve to a wide-open position for easy ignition
by the ignitor 28. For example, the position encoder 46 may signal that actuation
of the knob 48 is to initiate flame kernel generation at the ports by the ignitor
28, for example, a sparking ignitor, as the movement of stem 44 opens the passageway
between the valve seat 42 and the gas manifold 16. At the same time, the driver 34
generates a drive signal to the pickup coil 58 and releases the valve head 40 from
the valve seat 42. Accordingly, gas input from the supply 20 may be delivered through
the valve and the manifold to the burner ports at the burner 14.
[0019] Preferably, the controller 24 drives the ignitor 28 to repeatedly generate a charge
until a flame sensor, for example, the thermocouple 50 as shown at 60, or a dedicated
ignition sensor incorporated in the ignitor as designated at 62, determines that a
flame has been generated at the adjacent ports of the burner 14. Morever, once the
thermocouple 50 has been heated to continuously generate a signal to the holding coil
52, the driver 34 of the controller 24 is switched off, while the valve head 40 remains
retracted from the valve seat 42 by the force in the holding coil 52. Alternatively,
the ignitor 28 may be an electronic spark module for ignition, for example, a hot
surface ignitor, that may or may not cycle with the flame when using the pulsed sequence
feature.
[0020] As indicated in Figure 1 at 60, a flame sensing feature of the ignitor 28 may be
directed to the electronic controller 24 so that if the burner fails to generate a
flame after a predetermined number of charges have been delivered to the ignitor 28,
the controller 24 may generate a response for example, to power the pickup coil 58
or to power the holding coil 52. For example, if the output of the thermocouple 50
gets to a level high enough to energize the existing holding coil 52, the power to
the pickup coil 58 may be turned off. In order to release the plunger, the controller
24 shorts out the output of the thermocouple 50, de-energizing the holding coil 52
and permitting the valve head 40 to close against the valve seat 42 when the electronic
controller 24 determines that a pulse sequence operation is required.
[0021] Alternatively, the controller 24 may provide a drive signal to the pickup coil 58
with a power whose magnitude is equivalent to that produced by the holding coil 52
but opposite in polarity so that an opposite force magnetic field will negate the
magnetic field produced in the coil by the current from the thermocouple 50. In either
event, the controller 24 permits pulsed sequencing of the gas flow in a well known
manner when electrical power is available. Moreover, the system provides a flame cut-off
capability in the event that ignition of gas at the burner 14 cannot be sustained
with a continuous flame. Morever, the burner 14 may be still be operated without electrical
power if the thermocouple 50 detects existence of a flame so that the holding coil
52 maintains the valve head 40 in a retracted position from the valve seat 42.
[0022] Moreover, the control of flow sequencing as well as flow rate may be further automated.
For example, a valve as used in the preferred embodiment may be modified by incorporating
a driver 66 for delivering a power signal to a displacer 68 on the stem 44 in a manner
that varies the flow rate, for example, turning the valve body 45 for variable passage
capacity where a modern user interface, such as a touch-sensitive switch panel, is
desired. Alternatively and preferably, an automated control of the flow rate could
be most conveniently be produced as responsive to an electronic controller by using
a proportional gas valve that varies the gas flow proportional to an electrical current
or voltage applied to an actuator by the controller.
[0023] Having thus described the present invention, many modifications will become apparent
to those skilled in the art to which it pertains without departing from the scope
and the spirit of the present invention as defined in the appended claims.
1. A cooktop control for a cooking appliance including a cooktop having at least one
gas burner having a plurality of ports, at least one ignitor adjacent to at least
one port on the burner; and a control for sequentially delivering gas to the burner
ports and igniting the gas at burner ports, said control comprising:
a valve and a responsive element in said valve for controlling gas flow through a
passageway coupled in fluid communication with said plurality of ports;
an ignition module for generating a drive signal to the at least one ignitor;
an electronic controller interfacing with said ignition module and coupled to a driver
for actuating said responsive element;
wherein said driver enables said responsive element to default to a status that closes
said passageway, wherein said driver comprises a pick up actuator that enables said
responsive element to initiate an open position status that opens said passageway,
and a holding actuator that enables said responsive element to maintain an open position
status;
a sensor for detecting the presence of flame at said burner port and coupled to said
holding actuator and said electronic controller; and
wherein said driver is responsive to each of said controller and said sensor to
displace said responsive element from said default status to said open position status.
2. The invention as described in claim 1 wherein said open position status comprises
a timed pulse period in a sequence of timed pulses.
3. The invention as described in claim 1 wherein said responsive member comprises a solenoid
coil.
4. The invention as described in claim 3 wherein said driver comprises a circuit delivering
electrical current to said coil.
5. An automated cooking appliance having a cooktop comprising:
a cooktop panel;
at least one burner supported for exposure at said cooktop panel and sealed to said
panel;
a gas manifold connectable to a gas supply for delivering gas to said burner;
a valve for controlling the gas flow from said supply to said manifold;
an ignitor for generating a flame at said burner;
an electronic controller including a driver for said valve and an ignition module
for driving said ignitor; and
at least one flame sensor at said burner for generating a response in said valve driver.
6. A burner control for a cooktop with at least one gas burner, and a manifold for delivering
gas to said at least one gas burner, the control comprising:
at least one valve including a responsive member for controlling displacement of head
with respect to a valve seat in fluid communication with said manifold;
an electronic control including a driver for actuating said responsive member, and
a pulsed sequence control for said driver;
a sensor for detecting the presence of flame at said burner and generating an indication;
and
a feedback signal for actuating said driver in response to said indication.
7. The invention as described in claim 6 wherein said pulsed sequence control selectively
applies said feedback signal to said driver.