U.S. patent application number 16/214190 was filed with the patent office on 2020-06-11 for gas cooktop fire prevention and alarm system.
The applicant listed for this patent is BSH Home Appliances Corporation BSH Hausgerate GmbH. Invention is credited to Garrett Bentley, Brian Silva.
Application Number | 20200182460 16/214190 |
Document ID | / |
Family ID | 69061272 |
Filed Date | 2020-06-11 |
United States Patent
Application |
20200182460 |
Kind Code |
A1 |
Bentley; Garrett ; et
al. |
June 11, 2020 |
GAS COOKTOP FIRE PREVENTION AND ALARM SYSTEM
Abstract
A home cooking appliance includes a gas surface cooking unit and
a gas cooktop fire prevention system. The gas surface cooking unit
includes a gas burner, a support surface configured to support a
cooking vessel above the gas burner, a cooktop floor below the gas
burner, and a gas supply line supplying gas to the gas burner. The
gas cooktop fire prevention system includes a solenoid valve on the
gas supply line and a gas supply cutoff unit configured to detect a
temperature of the cooktop floor and close the solenoid valve when
the detected temperature of the cooktop floor is equal to or
greater than a predetermined threshold temperature of the cooktop
floor, thereby cutting off a supply of the gas through the gas
supply line to the gas burner.
Inventors: |
Bentley; Garrett;
(Knoxville, TN) ; Silva; Brian; (Knoxville,
TN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
BSH Home Appliances Corporation
BSH Hausgerate GmbH |
Irvine
Munich |
CA |
US
DE |
|
|
Family ID: |
69061272 |
Appl. No.: |
16/214190 |
Filed: |
December 10, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F23N 2225/16 20200101;
F23N 5/242 20130101; F24C 15/2021 20130101; F24C 3/126 20130101;
G08B 17/10 20130101; F23N 2900/05005 20130101; F23N 5/102 20130101;
F23D 14/725 20130101; F24C 3/103 20130101; F24C 7/081 20130101;
F23D 14/76 20130101; F24C 15/36 20130101 |
International
Class: |
F23D 14/72 20060101
F23D014/72; F24C 15/20 20060101 F24C015/20; F24C 7/08 20060101
F24C007/08 |
Claims
1. A home cooking appliance, comprising: a gas surface cooking unit
including: a gas burner; a support surface configured to support a
cooking vessel above the gas burner; a cooktop floor below the gas
burner; and a gas supply line supplying gas to the gas burner; and
a gas cooktop fire prevention system including: a solenoid valve on
the gas supply line; and a gas supply cutoff unit configured to
detect a temperature of the cooktop floor and close the solenoid
valve when the detected temperature of the cooktop floor is equal
to or greater than a predetermined threshold temperature of the
cooktop floor, thereby cutting off a supply of the gas through the
gas supply line to the gas burner.
2. The home cooking appliance of claim 1, wherein the gas supply
cutoff unit further comprises: an alarm unit configured to provide
an alert to a user when the temperature of the cooktop floor is
equal to or greater than the predetermined threshold temperature of
the cooktop floor.
3. The home cooking appliance of claim 1, wherein the gas supply
cutoff unit includes a high temperature cutout switch (HTC switch)
underneath the cooktop floor, the high temperature cutout switch
(HTC switch) configured to interrupt a power supply to the solenoid
valve when the temperature of the cooktop floor detected by the
high temperature cutout switch (HTC switch) is equal to or greater
than the predetermined threshold temperature of the cooktop floor,
thereby closing the solenoid valve and cutting off the supply of
the gas through the gas supply line to the gas burner.
4. The home cooking appliance of claim 3, wherein the gas supply
cutoff unit further comprises: an alarm unit in communication with
the high temperature cutout switch (HTC switch), wherein the alarm
unit is configured to provide an alert to a user when the
temperature of the cooktop floor detected by the high temperature
cutout switch (HTC switch) is equal to or greater than the
predetermined threshold temperature of the cooktop floor.
5. The home cooking appliance of claim 1, wherein the gas supply
cutoff unit includes a positive temperature coefficient thermistor
(PTC thermistor) underneath the cooktop floor, the positive
temperature coefficient thermistor (PTC thermistor) configured to
interrupt a power supply to the solenoid valve when the temperature
of the cooktop floor detected by the positive temperature
coefficient thermistor (PTC thermistor) is equal to or greater than
the predetermined threshold temperature of the cooktop floor,
thereby closing the solenoid valve and cutting off the supply of
the gas through the gas supply line to the gas burner.
6. The home cooking appliance of claim 5, wherein the gas supply
cutoff unit further comprises: an alarm unit in communication with
the positive temperature coefficient thermistor (PTC thermistor),
wherein the alarm unit is configured to provide an alert to a user
when the temperature of the cooktop floor detected by the positive
temperature coefficient thermistor (PTC thermistor) is equal to or
greater than the predetermined threshold temperature of the cooktop
floor.
7. The home cooking appliance of claim 1, wherein the gas supply
cutoff unit comprises a temperature sensor configured to
continuously monitor the temperature of the cooktop floor.
8. The home cooking appliance of claim 7, wherein the gas supply
cutoff unit further comprises: a control circuit in communication
with the temperature sensor; a relay in communication with the
control circuit, the relay configured to connect a power supply to
the solenoid valve, wherein the control circuit is configured to
control the relay to interrupt the power supply to the solenoid
valve when the temperature of the cooktop floor detected by the
temperature sensor is equal to or greater than the predetermined
threshold temperature of the cooktop floor, thereby closing the
solenoid valve and cutting off the supply of the gas through the
gas supply line to the gas burner.
9. The home cooking appliance of claim 8, wherein the gas supply
cutoff unit further comprises: an alarm unit in communication with
the control circuit, wherein the control unit activates the alarm
unit to provide an alert to a user when the temperature of the
cooktop floor is equal to or greater than the predetermined
threshold temperature of the cooktop floor.
10. The home cooking appliance of claim 3, wherein the high
temperature cutout switch (HTC switch) is mounted to an underside
surface of the cooktop floor in thermal contact with the underside
surface of the cooktop floor.
11. The home cooking appliance of claim 5, wherein the positive
temperature coefficient thermistor (PTC thermistor) is mounted to
an underside surface of the cooktop floor in thermal contact with
the underside surface of the cooktop floor.
12. The home cooking appliance of claim 7, wherein the temperature
sensor is mounted to an underside surface of the cooktop floor in
thermal contact with the underside surface of the cooktop
floor.
13. The home cooking appliance of claim 1, wherein, after the
solenoid valve is closed, the gas supply cutoff unit is configured
to re-open the solenoid valve when the detected temperature of the
cooktop floor is less than the predetermined threshold temperature
of the cooktop floor, thereby reconnecting the supply of the gas
through the gas supply line to the gas burner.
14. The home cooking appliance of claim 1, wherein the gas supply
cutoff unit further comprises a reset switch configured to re-open
the solenoid valve upon being actuated by a user.
15. The home cooking appliance of claim 3, wherein, after the
solenoid valve is closed, the high temperature cutout switch (HTC
switch) reconnects the power supply to the solenoid valve when the
temperature of the cooktop floor detected by the high temperature
cutout switch (HTC switch) is less than the predetermined threshold
temperature of the cooktop floor, thereby re-opening the solenoid
valve and reconnecting the supply of the gas through the gas supply
line to the gas burner.
16. The home cooking appliance of claim 3, wherein the gas supply
cutoff unit further comprises a reset switch configured to re-set
the high temperature cutout switch (HTC switch) upon being actuated
by a user.
17. The home cooking appliance of claim 5, wherein, after the
solenoid valve is closed, the positive temperature coefficient
thermistor (PTC thermistor) reconnects the power supply to the
solenoid valve when the temperature of the cooktop floor detected
by the positive temperature coefficient thermistor (PTC thermistor)
is less than the predetermined threshold temperature of the cooktop
floor, thereby re-opening the solenoid valve and reconnecting the
supply of the gas through the gas supply line to the gas
burner.
18. The home cooking appliance of claim 5, wherein the gas supply
cutoff unit further comprises a reset switch configured to reset
the positive temperature coefficient thermistor (PTC thermistor)
upon being actuated by a user.
19. The home cooking appliance of claim 8, wherein, after the
solenoid valve is closed, the control circuit is configured to
control the relay to at least one of: automatically reconnect the
power supply to the solenoid valve when the temperature of the
cooktop floor detected by the temperature sensor is less than the
predetermined threshold temperature of the cooktop floor, and
reconnect the power supply to the solenoid valve when the
temperature of the cooktop floor detected by the temperature sensor
is less than the predetermined threshold temperature of the cooktop
floor and in response to a reset switch being actuated by a user,
thereby re-opening the solenoid valve and reconnecting the supply
of the gas through the gas supply line to the gas burner.
20. The home cooking appliance of claim 1, wherein the gas surface
cooking unit includes a second gas burner and the cooktop floor
extends below the second gas burner, and wherein the gas supply
cutoff unit includes a first gas supply cutoff sub-unit and a
second gas supply cutoff sub-unit, the first gas supply cutoff
sub-unit configured to detect the temperature of the cooktop floor
at the gas burner and the second gas supply cutoff sub-unit
configured to detect the temperature of the cooktop floor at the
second gas burner.
21. The home cooking appliance of claim 1, wherein the gas surface
cooking unit includes a second gas burner and the cooktop floor
extends below the second gas burner, and wherein the gas supply
cutoff unit is configured to detect the temperature of the cooktop
floor at a location between the gas burner and the second gas
burner and close the solenoid valve when the detected temperature
of the cooktop floor is equal to or greater than the predetermined
threshold temperature of the cooktop floor.
Description
FIELD OF THE INVENTION
[0001] The present invention is directed to a gas cooktop fire
prevention and alarm system, and more particularly, to a domestic
home cooking appliance including a cooktop having a gas cooktop
fire prevention and alarm system.
BACKGROUND OF THE INVENTION
[0002] Some modern domestic gas surface cooking units, such as a
gas range, stove, or cooktop, have one or more gas burners for
heating foodstuff in a cooking vessel, such as a pot, pan, kettle,
etc., and commonly include a support surface, such as a cooking
grate, griddle, etc., positioned over one ore more burners for
supporting the cooking vessel over a burner. Some cooking ranges or
cooktops include a top sheet or spill tray for catching spills,
overflows, etc. from the cooking vessel and for concealing other
components of the cooking unit, such as gas supply lines.
SUMMARY OF THE INVENTION
[0003] The present invention recognizes that, in some
circumstances, a temperature of the cooking vessel, or a
temperature of a cooking oil, fat, foodstuff, etc. in a cooking
vessel can approach or reach an autoignition point, which may
result in a fire event that could lead to a potentially destructive
or deadly fire, particularly in a circumstance when a cooking
vessel is left unattended or unsupervised on a gas surface cooking
unit. Currently, a typical solution for preventing a fire
associated with a cooking event is a smoke detector/alarm in the
home, which alerts a user in a home or residence upon the
occurrence of an active fire event (i.e., after an active fire
event is in progress). The present invention recognizes that a risk
of a fire event can be prevented or minimized by proactively
shutting off a flow of gas to the one or more gas burners before a
cooking vessel, or foodstuff, fat, oil, etc. in the cooking vessel,
approach or reach conditions for autoignition of common cooking
fats, oils, etc. (e.g., canola oil), which are commonly being
heated or cooked in a cooking vessel.
[0004] The present invention further recognizes that some
conventional solutions attempt to prevent a cooking vessel, oil, or
fat, etc. from approaching or reaching conditions for autoignition
before a fire event occurs by directly monitoring or detecting the
temperature of the cooking vessel to detect a pre-ignition point
using one or more obtrusive temperature sensors that project from
or extend through an opening in the cooktop floor (e.g., a spill
tray or top sheet of the cooktop), project from or extend around or
through an opening in a burner or burner cap, or project from or
extend around or through an opening in a support surface (e.g.,
cooking grate) for supporting the cooking vessel, such that a
temperature sensor is placed in direct contact with a surface of
the cooking vessel to monitor the temperature of the cooking
vessel. For example, as shown in FIG. 7, such obtrusive temperature
sensors may utilize a resistance temperature detector (RTD) 900,
such as a spring loaded resistance temperature detector (RTD), that
sticks up, protrudes from, or extends through a spill tray 106 of
the cooktop unit and directly contacts, or is forced into direct
contact with, the bottom surface of a cooking vessel 300 when the
cooking vessel is rested on the support surface to directly measure
the temperature of the cooking vessel. In other arrangements, an
obtrusive temperature sensor may stick up, protrude from, or extend
through or around the body or burner cap of the burner 102 or a
support surface (e.g., cooking grate) 104 of the cooktop unit. By
sticking up or protruding from, or extending through, the spill
tray, burner or burner cap, or support surface of the cooktop unit,
such obtrusive temperature sensors create additional places where
spilled fluids or overflows undesirably may leak into the area of
the cooktop below the cooktop floor (e.g., through an opening in
the spill tray or top sheet of the cooktop, burner, etc.), which
may result in damage to other components of the appliance. Such
obtrusive temperature sensors also result in additional surfaces
and components that need cleaning, and create additional surfaces
and areas, such as where the obtrusive temperature sensor
intersects or rests on other components of the cooktop (e.g.,
between or around the sensor and the cooktop floor), that are more
likely to catch, trap, or accumulate debris from foodstuff, spills,
etc., thereby making it more difficult for a user to clean in or
around components of the cooktop. Additionally, such obtrusive
temperature sensors are visible to a user and commonly do not match
the other components of the cooktop unit, thereby detracting from
the aesthetical appearance of the appliance to the user.
[0005] To solve these and other problems, the present invention
provides a home cooking appliance having a gas surface cooking unit
and a gas cooktop fire prevention system that can simply, easily,
and proactively prevent the autoignition of many or most common
cooking oils and fats resulting from overheating a cooking vessel
on the gas surface cooking unit before such autoignition occurs,
while at the same time providing a gas cooktop fire prevention
system that can be implemented easily and inexpensively without
costly or complex control systems, and that does not detract from
aesthetics of the appliance or hinder the cleanability of the
appliance.
[0006] In an exemplary embodiment, a home cooking appliance
includes a gas surface cooking unit and a gas cooktop fire
prevention system. The gas surface cooking unit includes a gas
burner, a support surface configured to support a cooking vessel
above the gas burner, a cooktop floor (e.g., a spill tray or top
sheet of the cooktop) below the gas burner, and a gas supply line
supplying gas to the gas burner. The gas cooktop fire prevention
system includes a solenoid valve on the gas supply line, and a gas
supply cutoff unit configured to detect a temperature of the
cooktop floor and close the solenoid valve when the detected
temperature of the cooktop floor is equal to or greater than a
predetermined threshold temperature of the cooktop floor, thereby
cutting off a supply of the gas through the gas supply line to the
gas burner. The predetermined threshold temperature of the cooktop
floor can be selected to correspond or correlate to a predetermined
temperature of a cooking vessel to be supported by the support
surface (e.g., a cooking grate) that is less than a predetermined
auto-ignition temperature of one or more types of foodstuff, fat,
oil, liquid, etc., to be heated or cooked (e.g., commonly heated or
cooked) in a cooking vessel by the gas burner.
[0007] The gas supply cutoff unit can include, for example, a high
temperature cutout switch (HTC). The High Temperature Cutout switch
(HTC) can be, for example, a thermal reset or thermal cutout such
as a bimetal switch that opens (i.e., automatically opens) and cuts
power to the solenoid valve when a predetermined temperature is
reached or exceeded. In other embodiments, the gas supply cutoff
unit can include, for example, another type of thermal switch such
as a Positive Temperature Coefficient (PTC) thermistor, which has a
"switch" temperature at which the resistance suddenly rises
rapidly, limiting the current through a circuit. When a PTC
thermistor is used in conjunction, for example, with a thermistor
relay, the PTC can be configured to cut power to the solenoid valve
at a predetermined temperature of the cooktop floor. In other
examples, the gas supply cutoff unit can utilize a temperature
sensor (e.g., resistance thermometer, resistance temperature
detector (RTD) or element, thermocouple, etc.) to continuously
monitor a temperature of the cooktop floor. In these examples, the
temperature sensor can be coupled, for example, to a control unit
or control circuit configured to activate, for example, a relay
connected to the gas line solenoid valve to cut power to the
solenoid valve at a predetermined temperature of the cooktop
floor.
[0008] For example, in one example, the gas supply cutoff unit of
the gas cooktop fire prevention system utilizes a high temperature
cutout switch (HTC) mounted underneath the cooktop floor. As the
temperature of the cooking vessel (e.g., pan temperature) rises,
radiant heat off the cooking vessel heats up the cooktop floor
below the pan. The high temperature cutout switch (HTC), or the
like, is selected such that, at a predetermined threshold
temperature of the cooktop floor, which correlates to a
predetermined temperature of the cooking vessel, the switch in the
high temperature cutout switch (HTC) will open (i.e., automatically
open) and cut power to a solenoid valve on the gas supply line,
thereby closing the solenoid valve and cutting of the supply of gas
through the gas supply line. The solenoid valve may be on a main
gas line to the entire appliance, on a gas manifold, or on a gas
line supplying gas to a specific burner of the appliance, or
multiple solenoid valves may be provided at various locations for a
plurality of gas burners. With power cut to the solenoid valve, the
gas supply to the burner is shut off, preventing or limiting
further heating of the cooking vessel, or fat, oil, etc. in the
cooking vessel, thereby limiting the temperature to below an
auto-ignition temperature of the oil, fat, etc. being heated or
cooked in the cooking vessel. In this way, the gas cooktop fire
prevention system can cut off a supply of gas to one or more gas
burners before a temperature of the cooking vessel, or foodstuff,
fat, oil, etc. in the cooking vessel, approaches or reaches
conditions for autoignition of common cooking fats, oils, etc.
(e.g., canola oil), which are commonly being heated or cooked in a
cooking vessel.
[0009] In another example, the gas cooktop fire prevention system
utilizes a temperature sensor (e.g., resistance thermometer,
resistance temperature detector (RTD) or element, thermocouple,
etc.) to continuously monitor a temperature of the cooktop floor.
In these examples, the temperature sensor can be coupled, for
example, to a control unit or control circuit configured to
activate, for example, a relay connected to the gas line solenoid
valve. At a predetermined threshold temperature of the cooktop
floor detected by the temperature sensor, the control circuit can
cause the relay to cut power to the solenoid valve on the gas
supply line. As in other examples, the solenoid valve may be on a
main gas line to the entire appliance, on a gas manifold, or on a
gas line supplying gas to a specific burner of the appliance, or
multiple solenoid valves may be provided at various locations for a
plurality of gas burners. In this way, the gas cooktop fire
prevention system can cut off a supply of gas to one or more gas
burners before a temperature of the cooking vessel, or foodstuff,
fat, oil, etc. in the cooking vessel, approaches or reaches
conditions for autoignition of common cooking fats, oils, etc.
(e.g., canola oil), which are commonly being heated or cooked in a
cooking vessel.
[0010] In some examples, the gas cooktop fire prevention system
(e.g., utilizing a high temperature cutout switch (HTC), a positive
temperature coefficient (PTC) thermistor, a temperature sensor such
as a resistance thermometer, resistance temperature detector (RTD)
or element, thermocouple, etc., or the like) can be configured to
communicate (e.g., wired or wirelessly) with an alarm unit or
"signaling" system to alert a user that there has been a high
temperature incident (e.g., an incident in which the temperature of
the cooktop floor is equal to or greater than the predetermined
threshold temperature of the cooktop floor). The alarm unit can
include, for example, one or more of an indicator light, an audible
signal, a displayed alert message, or electronic message (e.g., a
text message, app alert, email message, and/or phone call,
etc.).
[0011] In this way, the examples of the present invention can
provide a home cooking appliance having a gas surface cooking unit
and a gas cooktop fire prevention system that can simply, easily,
and proactively prevent the autoignition of many or most common
cooking oils and fats resulting from overheating a cooking vessel
on the gas surface cooking unit before such autoignition occurs,
thereby preventing or minimizing a risk of a fire event, such as in
circumstances where an unattended cooking vessel is left over a gas
burner, before it occurs. The examples of the present invention can
provide a gas cooktop fire prevention system that can be
implemented easily and inexpensively without costly or complex
control systems, and that does not detract from aesthetics of the
appliance or hinder the cleanability of the appliance. The examples
of the gas cooktop fire prevention system do not require obtrusive
temperature sensors that project from or extend through the cooktop
floor, thereby reducing the possibility of spills or debris from
undesirably passing below the cooktop floor, reducing areas where
debris can collect, and improving cleanability. Furthermore, by
being mounted under the cooktop floor, the examples of the gas
cooktop fire prevention system according to the invention can be
hidden from view by a user, thereby improving aesthetics of the
appliance.
[0012] Other features and advantages of the present invention will
become apparent to those skilled in the art upon review of the
following detailed description and drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] These and other aspects and features of embodiments of the
present invention will be better understood after a reading of the
following detailed description, together with the attached
drawings, wherein:
[0014] FIG. 1 is a front perspective view of a domestic kitchen
with a domestic home cooking appliance including a cooktop having a
gas cooktop fire prevention system according to an exemplary
embodiment of the invention;
[0015] FIG. 2 is a schematic view of a domestic home cooking
appliance including a cooktop having a gas cooktop fire prevention
system according to an exemplary embodiment of the invention;
[0016] FIG. 3 is a schematic view of a domestic home cooking
appliance including a cooktop having a gas cooktop fire prevention
system according to an exemplary embodiment of the invention;
[0017] FIG. 4 is a schematic view of a domestic home cooking
appliance including a cooktop having a gas cooktop fire prevention
system according to an exemplary embodiment of the invention;
[0018] FIG. 5 is a schematic view of a domestic home cooking
appliance including a cooktop having a gas cooktop fire prevention
system according to an exemplary embodiment of the invention;
[0019] FIG. 6 is a schematic plan view of a domestic home cooking
appliance including a cooktop having a gas cooktop fire prevention
system according to an exemplary embodiment of the invention;
and
[0020] FIG. 7 is a schematic view of a conventional domestic home
cooking appliance.
DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS OF THE
INVENTION
[0021] The present invention now is described more fully
hereinafter with reference to the accompanying drawings, in which
embodiments of the invention are shown. This invention may,
however, be embodied in many different forms and should not be
construed as limited to the embodiments set forth herein; rather,
these embodiments are provided so that this disclosure will be
thorough and complete, and will fully convey the scope of the
invention to those skilled in the art.
[0022] With reference to FIGS. 1-6, exemplary embodiments of a
domestic home cooking appliance including a gas surface cooking
unit (e.g., gas cooktop) 100 and a gas cooktop fire prevention
system 200, will now be described.
[0023] FIG. 1 illustrates an example of a domestic kitchen having a
gas surface cooking unit 100 having one or more gas burners 102 for
heating foodstuff in a cooking vessel, such as a pot, pan, kettle,
etc. The domestic gas surface cooking unit 100 can be, for example,
a surface cooking unit of a slide-in gas range (as shown in the
example illustrated in FIG. 1), a gas cooktop or rangetop (e.g.,
counter mounted, island mounted, etc. as shown in the example
illustrated in FIG. 6), a gas stove, a gas grill, etc. The domestic
gas surface cooking unit 100 includes a support surface 104, such
as a cooking grate, griddle, grill, teppanyaki grill, etc.,
positioned over one ore more burners 102 for supporting a cooking
vessel over at least one of the burners 102. The domestic gas
surface cooking unit 100 includes a cooktop floor 106 (e.g., a
fixed spill tray or top sheet, a removable spill tray or top sheet,
etc.) for catching spills, overflows, etc. from a cooking vessel
and/or for concealing other components of the cooking unit, such as
gas supply lines, electrical wiring, etc. (not visible in FIG.
1).
[0024] FIG. 2 illustrates an example of a domestic gas surface
cooking unit 100 of a home cooking appliance. In this example, the
domestic gas surface cooking unit 100 includes one or more gas
burners 102, a support surface 104 (cooking grate) configured to
support a cooking vessel 300 above a gas burner 102. In other
examples, the support surface 104 can be a griddle, grill, or
teppanyaki grill, etc. A cooktop floor 106 is disposed below the
gas burner 102. The cooktop floor 106 can extend under one or more
of the gas burners 102. A gas supply line 108 is disposed under the
cooktop floor 106 and supplies gas to the gas burner 102. In other
examples, the appliance can include a plurality of gas burners 102.
The gas burners 102 can be supplied gas via one or more gas lines
108. For example, a main gas line can supply or convey gas to a gas
manifold, which in turn supplies the gas to each respective burner,
for example through individual gas lines.
[0025] As schematically illustrated in FIG. 2, the home cooking
appliance includes a gas cooktop fire prevention system 200
including a solenoid valve 204 on the gas supply line 108, and a
gas supply cutoff unit 202 configured to detect a temperature of
the cooktop floor 106 and close the solenoid valve 204 when the
detected temperature of the cooktop floor 106 is equal to or
greater than a predetermined threshold temperature of the cooktop
floor 106, thereby cutting off a supply of the gas through the gas
supply line 108 to the gas burner 102. One or more solenoid valves
204 can be on the main gas line 108 to the entire appliance, on a
gas manifold, and/or on a gas line to a specific gas burner 102 of
the appliance.
[0026] The gas supply cutoff unit 202 can be configured to detect
the temperature of the cooktop floor 106, for example, using one or
more sensors, temperature dependent switches, etc. In an example,
the gas supply cutoff unit 202 can include, for example, a high
temperature cutout switch (HTC), which can be, for example, a
thermal reset or thermal cutout such as a bimetal switch that opens
(i.e., automatically opens) and cuts power to the solenoid valve
when a predetermined temperature is reached or exceeded. In other
embodiments, the gas supply cutoff unit 202 can include, for
example, another type of thermal switch such as a Positive
Temperature Coefficient (PTC) thermistor, which has a "switch"
temperature at which the resistance suddenly rises rapidly,
limiting the current through a circuit. When a PTC thermistor is
used in conjunction, for example, with a thermistor relay, the PTC
of the gas supply cutoff unit 202 can be configured to cut power to
the solenoid valve 204 at a predetermined temperature of the
cooktop floor 106. In other examples, the gas supply cutoff unit
202 can include a temperature sensor (e.g., resistance thermometer,
resistance temperature detector (RTD) or element, thermocouple,
etc.) to continuously monitor a temperature of the cooktop floor
106.
[0027] One or more components (e.g., temperature dependent
switch(es), sensor(s), etc.) of the gas supply cutoff unit 202 can
be mounted underneath the cooktop floor 106 and in thermal contact
with the cooktop floor 106, such as mounted directly to, or in
direct thermal contact with, an underside surface of the cooktop
floor 106. In operation, the gas supply cutoff unit 202 is
configured to interrupt (e.g., automatically interrupt) a power
supply 206 to the solenoid valve 204 in the event that a
temperature of the cooktop floor 106 detected by the one or more
sensors of the gas supply cutoff unit 202 reaches or exceeds (i.e.,
is equal to or greater than) a predetermined threshold temperature
of the cooktop floor 106, thereby closing the solenoid valve 204
and cutting off the supply of the gas through the gas supply line
108 to the gas burner 102. The predetermined threshold temperature
of the cooktop floor 106 can be selected to correspond or correlate
to a predetermined temperature of a cooking vessel 300 supported by
the support surface 104 (e.g., cooking grate) that is less than an
auto-ignition temperature of one or more types of foodstuff, oil,
liquid, etc., to be heated or cooked (e.g., commonly heated or
cooked) in a cooking vessel 300 by the gas burner 102.
[0028] As schematically illustrated in FIG. 2, some examples of the
gas supply cutoff unit 202 can includes a reset unit 207, such as a
reset switch, button, etc., configured to re-close the solenoid
valve 204 upon being actuated by a user. The reset unit 207 can be
integrally provided with another component of the gas supply cutoff
unit 202 or system 200, or in other examples, can be a separate
component. The reset unit 207 can be configured to communicate
(e.g., via wired or wireless communication, such as Bluetooth,
Wi-Fi, cellular, optical, app communication, Z-wave, etc.) with one
or more components of the gas supply cutoff unit 202 or system 200.
For example, a remote or wireless reset unit 207 can be arranged in
communication with, or integrated into, a smart home network, one
or more home systems, such as a security or monitoring system,
communication system, etc., a smartphone, a personal computer,
and/or another electronic device.
[0029] As schematically illustrated in FIG. 2, some examples of the
gas cooktop fire prevention system 200 can include an alarm unit
208 configured to provide an alert to a user when the temperature
of the cooktop floor 106 is equal to or greater than the
predetermined threshold temperature. The alarm unit 208 can
include, for example, an audible alarm device such as an audible
signal, siren, etc., a visual alarm device such as one or more
indicator lights, flashing lights, a displayed alert message, etc.,
a notification or electronic message (e.g., a text message, app
alert, email message, and/or phone call, etc.) sent to one or more
other components such as one or more remote or wireless devices, or
a combination of two or more thereof. The alarm unit 208 can be a
separate component, or in other examples, can be integrally
provided with another component, such as the gas supply cutoff unit
202. The alarm unit 208 can be configured to communicate (e.g., via
wired or wireless communication, such as Bluetooth, Wi-Fi,
cellular, optical, app communication, Z-wave, etc.) with one or
more components of the appliance, cooktop 100, or system 200, or
with one or more other devices. A remote or wireless alarm unit 208
can be arranged in communication with, or integrated into, a smart
home network, one or more home systems, such as a security or
monitoring system, communication system, etc., a smartphone, a
personal computer, and/or another electronic device in order to
alert a user.
[0030] In an example illustrated in FIG. 3, the gas cooktop fire
prevention system 200 can include a gas supply cutoff unit 202
having a high temperature cutout switch 210 positioned underneath
the cooktop floor 106 and in thermal contact with the underside of
the cooktop floor 106. The high temperature cutout switch 210 can
include, for example, a thermal switch or thermal cutout switch,
which opens when a temperature reaches or exceeds a predetermined
temperature and re-closes when the temperature drops below the
predetermined temperature. In another example, the high temperature
cutout switch 210 can include, for example, a thermal switch or
thermal cutout switch, which opens when a temperature reaches or
exceeds a predetermined temperature and requires a manual reset by
a user before the switch re-closes. The high temperature cutout
switch 210 can be mounted underneath the cooktop floor 106, such as
directly mounted to an underside surface of the cooktop floor 106,
and configured to detect the temperature of the cooktop floor 106.
The high temperature cutout switch 210 connects a power supply 206
to the solenoid valve 204. The solenoid valve 204 can be on a main
gas line or manifold to the entire appliance, or to a gas line to a
specific gas burner 102 of the appliance.
[0031] In operation, when the temperature of the high temperature
cutout switch 210 on the underside of the cooktop floor 106 reaches
or exceeds (i.e., is equal to or greater than) a predetermined
threshold temperature, the high temperature cutout switch 210
opens, thereby interrupting the power supply 206 to the solenoid
valve 204 and cutting off the flow of gas through the gas supply
line 108 to the gas burner 102. The predetermined threshold
temperature of the cooktop floor 106 can be selected to correspond
or correlate to a predetermined temperature of a cooking vessel 300
supported by the support surface 104 (cooking grate) that is less
than an auto-ignition temperature of one or more types of
foodstuff, oil, liquid, etc., to be heated or cooked (e.g., common
types of foodstuff, oil, liquid, etc. to be heated or cooked) in a
cooking vessel 300 by the gas burner 102.
[0032] In some examples, when the temperature of the high
temperature cutout switch 210 on the underside of the cooktop floor
106 is less than the predetermined threshold temperature, the high
temperature cutout switch 210 can be configured such that it
re-closes, thereby reconnecting the power supply 206 to the
solenoid valve 204 and enabling the flow of gas through the gas
supply line 108 to the gas burner 102. In other examples, the gas
supply cutoff unit 202 can include a reset unit 207, such as a
reset switch, button, etc., configured for a user to manually reset
or re-close the high temperature cutout switch 210, and thereby
re-open the solenoid valve 204. When the temperature of the high
temperature cutout switch 210 on the underside of the cooktop floor
106 is less than the predetermined threshold temperature, the reset
unit 207, such as a reset switch, button, etc., can be actuated by
a user, thereby re-opening the solenoid valve 204 by reconnecting
the power supply 206 to the solenoid valve 204 and enabling the
flow of gas through the gas supply line 108 to the gas burner 102.
As schematically illustrated in FIG. 3, some examples of the gas
cooktop fire prevention system 200 can include an alarm unit 208
configured to provide an alert to a user when the temperature of
the cooktop floor 106 is equal to or greater than the predetermined
threshold temperature.
[0033] In an example illustrated in FIG. 4, the gas cooktop fire
prevention system 200 can include a gas supply cutoff unit 202
having a positive temperature coefficient thermistor (PTC
thermistor) 211 positioned underneath the cooktop floor 106 and in
thermal contact with the underside of the cooktop floor 106, along
with a thermistor relay 213. The positive temperature coefficient
thermistor (PTC thermistor) 211 can be mounted to an underside of
the cooktop floor 106, such as directly mounted to an underside
surface of the cooktop floor 106, and configured to detect the
temperature of the cooktop floor 106. The relay 213 is configured
to electrically connect the power supply 206 to the solenoid valve
204. The solenoid valve 204 can be on the main gas line 108 to the
entire appliance, or to the specific gas burner 102 of the
appliance.
[0034] In operation, the positive temperature coefficient
thermistor (PTC thermistor) 211 is used in conjunction with the
thermistor relay 213 to interrupt the power supply 206 to the
solenoid valve 204 when a temperature of the cooktop floor 106
detected by the temperature sensor 212 is equal to or greater than
a predetermined threshold temperature of the cooktop floor 106,
thereby closing the solenoid valve 204 and cutting off the supply
of the gas through the gas supply line 108 to the gas burner 102.
Similar to other examples, the predetermined threshold temperature
of the cooktop floor 106 can be selected to correspond or correlate
to a predetermined temperature of a cooking vessel 300 supported by
the support surface 104 (cooking grate) that is less than an
auto-ignition temperature of one or more types of foodstuff, oil,
liquid, etc., to be heated or cooked (e.g., common types of
foodstuff, oil, liquid, etc. to be heated or cooked) in a cooking
vessel 300 by the gas burner 102.
[0035] In the example shown in FIG. 4, if the temperature of the
cooktop floor 106 is less than (i.e., drops below) the
predetermined threshold temperature of the cooktop floor 106, then
the gas cooktop fire prevention system 200 can be configured to
reconnect (e.g., automatically reconnect) the power supply 206 to
the solenoid valve 204, or to reconnect the power supply 206 to the
solenoid valve 204 upon actuation of a reset unit 207, such as a
reset switch, button, etc., by a user, thereby opening the solenoid
valve 204 and enabling the supply of the gas through the gas supply
line 108 to the gas burner 102. As schematically illustrated in
FIG. 4, some examples of the gas cooktop fire prevention system 200
can include an alarm unit 208 configured to provide an alert to a
user when the temperature of the cooktop floor 106 is equal to or
greater than the predetermined threshold temperature.
[0036] In an example illustrated in FIG. 5, the gas cooktop fire
prevention system 200 can include a gas supply cutoff unit 202
having a sensor 212 (i.e., one or more sensors) positioned
underneath the cooktop floor 106 and in thermal contact with the
underside of the cooktop floor 106, a control unit or control
circuit 214 in communication with the sensor 212, and a relay 216
in communication with the control circuit 214. The one or more
sensors 212 can be mounted to an underside of the cooktop floor
106, such as directly mounted to an underside surface of the
cooktop floor 106, and configured to detect the temperature of the
cooktop floor 106. In this example, the sensor 212 can be, for
example, a temperature sensor (e.g., resistance thermometer,
resistance temperature detector (RTD) or element, thermocouple,
etc.) capable of continuously monitoring the temperature of the
cooktop floor 106. The relay 216 is configured to electrically
connect the power supply 206 to the solenoid valve 204. The
solenoid valve 204 can be on the main gas line 108 to the entire
appliance, or to the specific gas burner 102 of the appliance.
[0037] In operation, the control circuit 214 is configured to
control the relay 216 to interrupt the power supply 206 to the
solenoid valve 204 when a temperature of the cooktop floor 106
detected by the temperature sensor 212 is equal to or greater than
a predetermined threshold temperature of the cooktop floor 106,
thereby closing the solenoid valve 204 and cutting off the supply
of the gas through the gas supply line 108 to the gas burner 102.
Similar to other examples, the predetermined threshold temperature
of the cooktop floor 106 can be selected to correspond or correlate
to a predetermined temperature of a cooking vessel 300 supported by
the support surface 104 (cooking grate) that is less than an
auto-ignition temperature of one or more types of foodstuff, oil,
liquid, etc., to be heated or cooked (e.g., common types of
foodstuff, oil, liquid, etc. to be heated or cooked) in a cooking
vessel 300 by the gas burner 102.
[0038] In some examples, the control circuit 214 can be configured
to control the relay 216 to reconnect (e.g., automatically
reconnect) the power supply 206 to the solenoid valve 204 when the
temperature of the cooktop floor 106 detected by the temperature
sensor 212 is less than the predetermined threshold temperature of
the cooktop floor 106, thereby opening the solenoid valve 204 and
enabling the supply of the gas through the gas supply line 108 to
the gas burner 102. In other examples, the control circuit 214 can
be configured to control the relay 216 to reconnect the power
supply 206 to the solenoid valve 204 when the temperature of the
cooktop floor 106 detected by the temperature sensor 212 is less
than the predetermined threshold temperature of the cooktop floor
106 and upon actuation of a reset unit 207, such as a reset switch,
button, etc., by a user, thereby opening the solenoid valve 204 and
enabling the supply of the gas through the gas supply line 108 to
the gas burner 102. As schematically illustrated in FIG. 5, some
examples of the gas cooktop fire prevention system 200 can include
an alarm unit 208 configured to provide an alert to a user when the
temperature of the cooktop floor 106 is equal to or greater than
the predetermined threshold temperature.
[0039] FIG. 6 illustrates an example of a home cooking appliance
having a domestic gas surface cooking unit 100 including a cooktop
floor 106 (e.g., a fixed spill tray or top sheet, a removable spill
tray or top sheet, etc.) for catching spills, overflows, etc. from
a cooking vessel and/or for concealing other components of the
cooking unit, such as gas supply lines, electrical wiring, etc.
(not visible in FIG. 1). For illustrative purposes only, FIG. 6
shows the surface cooking unit as a gas cooktop or rangetop (e.g.,
counter mounted, island mounted, etc.). However, as explained with
reference to the examples shown in FIGS. 1-5, other examples of the
surface cooking unit can include a surface cooking unit of a
slide-in gas range, gas stove, gas grill, etc.
[0040] FIG. 6 schematically illustrates a domestic gas surface
cooking unit 100 including several examples of a gas cooktop fire
prevention system 200 including one or more gas supply cutoff units
202 configured to detect a temperature of the cooktop floor 106 at
one or more locations and to close one or more solenoid valves (not
shown in FIG. 6) when the detected temperature of the cooktop floor
106 is equal to or greater than a predetermined threshold
temperature of the cooktop floor 106, thereby cutting off a supply
of the gas through a gas supply line to one or more of the gas
burners (e.g., 102, 102a, 102b, 102c, 102d). The one or more
solenoid valves can be on a main gas line to the entire appliance,
on a gas manifold, and/or on a gas line to a specific gas burner of
the appliance.
[0041] As shown by the dashed lines in FIG. 6, one or more
components (e.g., temperature sensing components, such as
temperature dependent switch(es), temperature sensor(s), etc.) of
the gas supply cutoff unit 202 can be mounted underneath the
cooktop floor 106 and in thermal contact with the cooktop floor
106, such as mounted directly to, or in direct thermal contact
with, an underside surface of the cooktop floor 106. The cooktop
floor 106 can be a top sheet, spill tray, etc. of the domestic gas
surface cooking unit 100, for example, which is exposed to radiant
heat off the cooking vessel during operation of one or more of the
gas burners (e.g., an uppermost surface of the cooktop floor, which
is below and/or adjacent to a gas burner and is exposed to and
heated by radiant heat off the cooking vessel during operation of
the gas burners). As the temperature of the cooking vessel (e.g.,
pan temperature) rises, radiant heat off the cooking vessel heats
up the cooktop floor below and/or adjacent to the cooking vessel.
The cooktop floor 106 can be a single, continuous floor extending
across a width of the domestic gas surface cooking unit 100, or the
cooktop floor 106 can be formed by two or more sections or parts
forming the floor. For example, in FIG. 6, a single, continuous
floor can extend under each of the burners 102, 102a, 102b, 102c,
102d. In an alternative example, a first cooktop floor can be
provided under the two gas burners 102 and 102a, a second cooktop
floor can be provided under gas burners 102b and 102c, and a third
cooktop floor can be provided under the gas burner 102d. Other
combinations and arrangements of the cooktop floor 106 are
possible.
[0042] In one example, a dedicated gas supply cutoff unit 202
(including the one or more components, e.g., temperature sensing
components such as temperature dependent switch(es), temperature
sensor(s), etc.) can be provided for an individual gas burner 102,
or a plurality of gas supply cutoff units 202 (e.g., gas supply
cutoff sub-units) can be provided, such as one unit 202 (e.g., gas
supply cutoff sub-unit) for each individual gas burner (e.g., 102,
102a). As exemplarily shown in FIG. 6 (left-hand side), at least
one dedicated gas supply cutoff unit 202 (e.g., gas supply cutoff
sub-unit) can be provided for each individual gas burner 102, 102a.
One or more of the dedicated gas supply cutoff units 202 (e.g., gas
supply cutoff sub-units, such as a first gas supply cutoff
sub-unit, a second gas supply cutoff sub-unit, etc.) can have one
or more components (e.g., temperature sensing components such as
temperature dependent switch(es), temperature sensor(s), etc.) of
an arrangement as shown for example in any of FIGS. 2-5, and can be
configured to close one or more solenoid valves for supplying the
gas to each of the individual burners or to a plurality of burners
at the same time (e.g., one burner, less than all of the burners,
or all of the burners).
[0043] FIG. 6 illustrates other examples in which a shared gas
supply cutoff unit 202a can be provided for more than one gas
burner. As shown in the example on the right-hand side of FIG. 6, a
shared gas supply cutoff unit 202a can be provided for gas burners
102b and 102c. In this example, the shared gas supply cutoff unit
202a can be configured to detect a temperature of the cooktop floor
106 adjacent to both of the burners 102b and 102c, and close one or
more solenoid valves when the detected temperature of the cooktop
floor 106 is equal to or greater than a predetermined threshold
temperature of the cooktop floor 106, thereby cutting off a supply
of the gas through one or more gas supply lines to the gas burners
102b and 102c. In this example, a single cooktop floor 106 extends
under/around both of the gas burners 102b and 102c such that the
shared gas supply cutoff unit 202a can detect the temperature of
the cooktop floor 106 adjacent to both of the burners 102b and 102c
at the same time. The shared gas supply cutoff unit 202a, in this
example, can have an arrangement as shown for example in any of
FIGS. 2-5 and can be configured to close one or more solenoid
valves for supplying the gas to the one or more burners. A solenoid
valve 204 can be provided for each of the burners 102b and 102c, or
one or more of the gas burners can have a shared solenoid
valve.
[0044] With reference to other examples in FIG. 6, a shared gas
supply cutoff unit 202b can be provided for gas burners 102b and
102d. In this example, the shared gas supply cutoff unit 202b can
be configured to detect a temperature of the cooktop floor 106
adjacent to both of the burners 102b and 102d, and close one or
more solenoid valves when the detected temperature of the cooktop
floor 106 is equal to or greater than a predetermined threshold
temperature of the cooktop floor 106, thereby cutting off a supply
of the gas through one or more gas supply lines to the gas burners
102b and 102d. In this example, a single cooktop floor 106 extends
under/around both of the gas burners 102b and 102d such that the
shared gas supply cutoff unit 202b can detect the temperature of
the cooktop floor 106 adjacent to both of the burners 102b and 102d
at the same time. The shared gas supply cutoff unit 202b, in this
example, can have an arrangement as shown for example in any of
FIGS. 2-5 and can be configured to close one or more solenoid
valves for supplying the gas to the one or more burners. A solenoid
valve 204 can be provided for each of the burners 102b and 102d, or
one or more of the gas burners can have a shared solenoid
valve.
[0045] With reference to other examples in FIG. 6, a shared gas
supply cutoff unit 202c can be provided for gas burners 102b, 102c,
and 102d. In this example, the shared gas supply cutoff unit 202c
can be configured to detect a temperature of the cooktop floor 106
adjacent to the burners 102b, 102c, and 102d, and close one or more
solenoid valves when the detected temperature of the cooktop floor
106 is equal to or greater than a predetermined threshold
temperature of the cooktop floor 106, thereby cutting off a supply
of the gas through one or more gas supply lines to the gas burners
102b, 102c, and 102d. In this example, a single cooktop floor 106
extends under/around the gas burners 102b, 102c, and 102d such that
the shared gas supply cutoff unit 202c can detect the temperature
of the cooktop floor 106 for all of the burners 102b, 102c, and
102d at the same time. The shared gas supply cutoff unit 202c, in
this example, can have an arrangement as shown for example in any
of FIGS. 2-5 and can be configured to close one or more solenoid
valves for supplying the gas to the one or more burners. A solenoid
valve 204 can be provided for each of the gas burners 102b, 102c,
and 102d, or one or more of the gas burners can have a shared
solenoid valve.
[0046] With reference again to other examples shown in FIG. 6, a
gas supply cutoff unit 202d similarly can be provided for gas
burners 102a, 102c, and 102d. In this example, the gas supply
cutoff unit 202d can be configured to detect a temperature of the
cooktop floor 106 adjacent to the burners 102a, 102c, and 102d, and
close one or more solenoid valves when the detected temperature of
the cooktop floor 106 is equal to or greater than a predetermined
threshold temperature of the cooktop floor 106, thereby cutting off
a supply of the gas through one or more gas supply lines to the gas
burners 102a, 102c, and 102d. In this example, a single cooktop
floor 106 extends under/around the gas burners 102a, 102c, and 102d
such that the gas supply cutoff unit 202d can detect the
temperature of the cooktop floor 106 for all of the burners 102a,
102c, and 102d at the same time. The shared gas supply cutoff unit
202d, in this example, can have an arrangement as shown for example
in any of FIGS. 2-5 and can be configured to close one or more
solenoid valves for supplying the gas to the one or more burners. A
solenoid valve 204 can be provided for each of the gas burners
102a, 102c, and 102d, or one or more of the gas burners can have a
shared solenoid valve.
[0047] The example arrangements can be provided individually or in
combination with one or more of the other examples. One of ordinary
skill in the art will recognize that other arrangements of the gas
supply cutoff unit on the cooktop floor with respect to one or more
burners also are possible within the spirit and scope of the
invention.
[0048] With reference again to FIGS. 1-6, exemplary embodiments of
the invention include a home cooking appliance comprising a gas
surface cooking unit (e.g., 100) including a gas burner (e.g., one
or more gas burners 102, 102a, 102b, 102c, 102d), a support surface
(e.g., 104) configured to support a cooking vessel (e.g., 300)
above the gas burner (e.g., one or more gas burners 102, 102a,
102b, 102c, 102d), a cooktop floor (e.g., 106) below the gas burner
(e.g., one or more gas burners 102, 102a, 102b, 102c, 102d), and a
gas supply line (e.g., one or more gas supply lines 108) supplying
gas to the gas burner (e.g., one or more gas burners 102, 102a,
102b, 102c, 102d). The gas surface cooking unit (e.g., 100)
includes a gas cooktop fire prevention system (e.g., 200) including
a solenoid valve (e.g., one or more solenoid valves 204) on the gas
supply line (e.g., one or more gas supply lines 108), and a gas
supply cutoff unit (e.g., one or more gas supply cutoff units or
sub-units 202, 202a, 202b, 202c, 202d) configured to detect a
temperature of the cooktop floor (e.g., 106) and close the solenoid
valve (e.g., one or more solenoid valves 204) when the detected
temperature of the cooktop floor (e.g., 106) is equal to or greater
than a predetermined threshold temperature of the cooktop floor
(e.g., 106), thereby cutting off a supply of the gas through the
gas supply line (e.g., one or more supply lines 108) to the gas
burner (e.g., one or more gas burners 102, 102a, 102b, 102c, 102d).
The gas supply cutoff unit (e.g., one or more gas supply cutoff
units or sub-units 202, 202a, 202b, 202c, 202d) can include, for
example, one or more of a high temperature cutout switch (e.g.,
210), a positive temperature coefficient thermistor (PTC
thermistor) (e.g., 211) and thermistor relay (e.g., 213), a
temperature sensor (e.g., 212), a control circuit (e.g., 214), and
relay (e.g., 216), among other arrangements, etc. In this way, the
examples of the present invention can provide a home cooking
appliance having a gas surface cooking unit and a gas cooktop fire
prevention system that can simply, easily, and proactively prevent
the autoignition of many or most common cooking oils and fats
resulting from overheating a cooking vessel on the gas surface
cooking unit before such autoignition occurs, while at the same
time providing a gas cooktop fire prevention system that can be
implemented easily and inexpensively without costly or complex
control systems, and that does not detract from aesthetics of the
appliance or hinder the cleanability of the appliance.
[0049] The present invention has been described herein in terms of
several preferred embodiments. However, modifications and additions
to these embodiments will become apparent to those of ordinary
skill in the art upon a reading of the foregoing description. It is
intended that all such modifications and additions comprise a part
of the present invention to the extent that they fall within the
scope of the several claims appended hereto.
* * * * *