U.S. patent number 3,711,236 [Application Number 05/168,095] was granted by the patent office on 1973-01-16 for gas burner control device with low pressure cutoff.
This patent grant is currently assigned to Emerson Electric Co.. Invention is credited to Howard R. Kinsella, John J. Love, Carl A. Smith, Charles D. Visos.
United States Patent |
3,711,236 |
Kinsella , et al. |
January 16, 1973 |
GAS BURNER CONTROL DEVICE WITH LOW PRESSURE CUTOFF
Abstract
A gas burner control device including a biased closed,
electromagnetically operated, fuel cutoff valve dependent upon
electrical energy generated by a pilot burner-heated thermocouple
to hold it open, and a biased open pressure responsive switch
controlling the thermocouple-cutoff valve circuit, the switch being
dependent upon a predetermined minimum gas supply pressure to close
it and hold it closed, whereby either a drop in fuel supply below a
predetermined minimum pressure or the extinguishment of the pilot
flame effects closure of the fuel cutoff valve.
Inventors: |
Kinsella; Howard R. (St. Louis
County, MO), Love; John J. (St. Louis, MO), Smith; Carl
A. (Lemay, MO), Visos; Charles D. (Manchester, MO) |
Assignee: |
Emerson Electric Co. (St.
Louis, MO)
|
Family
ID: |
22610102 |
Appl.
No.: |
05/168,095 |
Filed: |
August 2, 1971 |
Current U.S.
Class: |
431/53; 236/68D;
431/80; 431/58; 431/89 |
Current CPC
Class: |
F23Q
9/14 (20130101) |
Current International
Class: |
F23Q
9/00 (20060101); F23Q 9/14 (20060101); F23q
009/08 () |
Field of
Search: |
;431/53,52,54,55,58,78-80,89 ;236/68D,15A |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Dority, Jr.; Carroll B.
Claims
We claim:
1. In a fuel flow control device for gas burners, a body having an
inlet, an outlet, and means forming a connecting passageway, a
pilot burner, a biased closed safety cutoff valve controlling said
passageway, manual means for opening said cutoff valve,
electromagnetic means operative when energized to hold said cutoff
valve open, an energizing circuit for said electromagnetic means
including as a power source a thermocouple junction heated by said
pilot burner, and a pressure responsive switch controlling said
energizing circuit, said switch being responsive to gas pressure in
said passageway and operative to complete said energizing circuit
when the gas pressure is above a predetermined minimum and to break
said energizing circuit when the gas pressure drops below said
predetermined minimum.
2. In a fuel flow control device for gas burners, a body having a
valve chamber, an inlet and an inlet fuel passageway leading to
said valve chamber, a main burner outlet, a pilot burner outlet,
and main and pilot burner fuel passageways leading from said valve
chamber to said outlets, a manual valve in said valve chamber
controlling the flow through said main and pilot burner
passageways, a biased closed safety cutoff valve in said valve
chamber, manual means for opening said cutoff valve,
electromagnetic means for holding said cutoff valve open, an
energizing circuit for said electromagnetic means including a
thermocouple junction heated by said pilot burner, and a pressure
responsive switch controlling said energizing circuit, said switch
being responsive to gas pressure in said pilot burner fuel
passageway to complete said energizing circuit when the gas
pressure is above a predetermined minimum and to break said
energizing circuit when the pressure drops below said predetermined
minimum.
3. The fuel flow control device claimed in claim 2 in which the
manual valve is operative to selectively permit the flow of fuel
through said main and pilot burner fuel passageways.
4. The fuel flow control device claimed in claim 3 which further
includes a thermostatically actuated valve controlling said main
burner fuel passageway.
5. The fuel flow control device claimed in claim 2 in which said
safety cutoff valve is positioned upstream from said manual
valve.
6. In a burner control system, a main burner, a pilot burner, a
source of fluid fuel under pressure, thermostatic valve means for
controlling the flow of fuel to the main burner, manual valve means
for controlling the flow of fuel to both main and pilot burners, a
biased closed safety cutoff valve controlling the flow to both main
and pilot burners, manual means for opening said safety cutoff
valve, means operative in response to flame at said pilot burner to
hold said safety valve open, and pressure responsive means
operative in response to a drop in fuel supply pressure below a
predetermined minimum to render said safety cutoff valve holding
means inoperative.
7. The burner control system claimed in claim 6 which further
includes pressure regulating means and in which said fuel pressure
responsive means is responsive to the fuel pressure as regulated by
said pressure regulating means.
8. In a fuel flow control device for gas burners, a main burner and
a pilot burner for igniting the main burner, a body member, a fuel
inlet, a pilot burner outlet, and a main burner outlet in said
body, said body being further provided with a pilot fuel passageway
leading to said pilot burner outlet, a main burner fuel passageway
leading to said main burner outlet and means forming a common fuel
passageway connecting said inlet with said pilot and main burner
fuel passageways, a biased closed safety cutoff valve, a pressure
regulator and a manual valve in said common fuel passageway, manual
means for opening said cutoff valve, electromagnetic means
operative to hold said cutoff valve open when energized, a
thermocouple junction operative to energize said electromagnetic
means when heated by pilot flame, and means mounted in said body
and responsive to the fuel pressure in said pilot burner passageway
and operative to de-energize said electromagnetic means when the
pressure drops below a predetermined minimum.
9. The fuel flow control device claimed in claim 8 in which said
pressure responsive means comprises a pressure operated switch
controlling circuit connections between said thermocouple junction
and said electromagnetic means, said switch comprising a cup-like
casing, a flexible diaphragm, a pair of spaced stationary contacts,
a biasing spring, and a conductive bridging member connected to
said diaphragm, said body member having a recess formed therein and
said switch being mounted in said recess.
10. The burner control system claimed in claim 6 in which said
means operative in response to pilot flame to hold said safety
valve open comprises an electromagnetic device, a thermocouple
junction adjacent the pilot burner, and circuit connections, and in
which said pressure responsive means comprises a pressure
responsive switch controlling said circuit connections.
Description
Currently, most gas burner control devices or systems include a
pilot flame heated thermocouple providing electrical energy to hold
open a biased closed, electromagnetically operated, safety fuel
cutoff valve so that failure of pilot flame will result in loss of
electrical energy and closure of the cutoff valve. These devices or
systems also frequently include temperature responsive switches
responsive to abnormally high temperatures to break the
thermocouple cutoff valve circuit thereby to cut off fuel to the
burner to preclude a hazardous overheating condition.
A hazardous condition may also result when the fuel supply pressure
falls below that which will sustain combustion at the main burner,
or below that pressure which will sustain an adequate igniting
flame at the pilot burner but is yet sufficient to sustain the
heating or prolong the cooling of the thermocouple. Moreover, a
momentary interruption of the fuel pressure resulting in the
extinguishing of both pilot and main burner flames also presents a
hazardous condition due to the time interval required for the
thermocouple to cool sufficiently, during which, upon a
reinstatement of fuel supply pressure, fuel may flow to the main
and pilot burners in the absence of pilot flame to ignite it.
It is an object, therefore, of the present invention to provide
means in a gas burner control device to effect the immediate cutoff
of fuel to either the main burner or to both main and pilot burners
when the gas supply pressure drops below a predetermined minimum
value.
A further object is to provide a control device for gas burners
having a biased closed, electromagnetically operated, safety cutoff
valve controlling fuel flow to the main burner and an energizing
circuit therefor to hold it open including as a power source a
thermocouple heated by a pilot flame, which device includes a
pressure operated switch responsive to fuel pressure to maintain
completion of the thermocouple electromagnetic valve energizing
circuit, thereby to hold open the safety cutoff valve when gas
pressure is adequate to sustain combustion at the main burner and
to break the energizing circuit and effect instant closure of the
safety cutoff valve when gas pressure drops below that which is
adequate to reliably sustain combustion at the main burner.
A further object is to provide a control device as in the foregoing
paragraph having both main and pilot burner fuel passageways formed
therein and in which the safety fuel cutoff valve controls the flow
of fuel through both main and pilot burner fuel passageways,
whereby fuel to both main and pilot burners is instantly cut off
when the fuel supply pressure drops below a predetermined minimum
value.
A further object is to provide a control device for gas burners, as
in the foregoing paragraphs, which further includes pressure
regulating means, and in which the pressure responsive switch is
responsive to fuel pressure downstream from said pressure
regulating means.
A further object is to provide a control device for gas burners as
in the foregoing paragraphs, in which the pressure responsive
switch is responsive to the fuel pressure in the pilot burner fuel
passageway.
Further objects and advantages will appear from the following
complete description of a preferred form of the invention when read
in connection with the accompanying drawing.
The single FIGURE of the drawing is a cross-sectional view of a gas
burner control device constructed in accordance with the present
invention.
Referring to the drawing, the device comprises a body generally
indicated at 10, formed of inlet and outlet sections 16 and 28,
respectively, joined along the line 12 and connected by screws 14.
The inlet body section 16 houses a hollow tapered plug valve 18, a
dual purpose pressure regulating and safety cutoff valve 20, and an
electromagnet 22 energized by a thermocouple 24 positioned so as to
be impinged by the flame of a pilot burner 26. The outlet body
section 28 houses a thermostatically operated main valve 30 and a
clicker disc 32 to effect its snap action operation. A mounting
flange 34 having a threaded stud 36 is attached to the outlet body
section 28 by screws 38, and a rod and tube type thermostatic
actuator 40 supported in the mounting flange 34 is operative to
actuate the valve 30 through a lever 33, an axially slidable
cylindrical member 35, and the clicker disc 32.
The hollow plug valve 18 has an intermediate tapered portion seated
in a tapered bore 42 in the inlet body section 16, an upper
cylindrical flanged portion 44 loosely fitting in an upper
concentric cylindrical bore 46, and a lower cylindrical portion 48
fitting a lower concentric cylindrical bore 50. The electromagnet
22 is entered into the bore 50 through a smaller concentric bore
and is provided with a lower screw-threaded portion 54 threadedly
engaged in a screw-threaded portion of the smaller bore.
The inlet body section 16 has a horizontal inlet passage 56
intersecting the lower cylindrical bore 50, which passage is screw
threaded for receiving a gas supply conduit, and a horizontal
communicating passage 58 connecting tapered bore 42 with
concentric, cylindrical, main valve chambers 60 and 62 formed in
the outlet body section 28. The valve chamber 62 is smaller in
diameter than the valve chamber 60, whereby a shoulder forming a
valve seat 61 is provided for thermostatically operated valve 30.
The valve chamber 62 is intersected by a vertical outlet passage
64, the lower end of which is screw threaded for connection of a
fuel conduit leading to a main burner (not shown).
The hollow rotary plug valve 18 is provided with ports 66 in the
lower cylindrical portion 48 thereof, which ports register with
inlet passage 56 to provide communication at all times between the
inlet passage and the interior of the hollow plug valve. The plug
valve 18 is also provided with a main burner port 68 in the tapered
portion thereof which registers with passage 58 to complete
communication between the inlet passage 56 and valve chamber 60
when the plug valve is rotated to an "on" position. The plug valve
18 is further provided with a circumferentially elongated pilot gas
port 70 in the tapered portion thereof which registers with a
passage 72 leading from the port 70 to a screw-threaded pilot
outlet 73. A conduit 74 connects pilot outlet 73 with pilot burner
26. The circumferential extent of pilot port 70 permits maintaining
registry of the port 70 with the passage 72 to supply fuel to the
pilot burner when the plug valve 18 is either rotatably positioned
to permit flow from port 68 to the main burner or in a position to
cut off flow through port 68 to the main burner.
The lower hollow cylindrical portion 48 of plug valve 18 is
provided with a valve seat 76 at the upper end thereof with which
the dual purpose cutoff and regulating valve 20 cooperates to
control the flow through the tapered portion of the hollow plug
valve 18. The poppet-type valve 20, being constructed of
rubber-like material, is mounted on a valve stem 78, which stem
extends vertically above and below the valve 20. At its upper end
valve stem 78 is connected to the central portion of a transverse
flexible diaphragm 80. The periphery of diaphragm 80 is clamped
between the flange 44 at the upper end of hollow plug valve 18 and
the rim of a cap member 82 which forms a closure at the upper end
of the hollow plug valve. The cap member 82 is rigidly connected to
the top of plug valve 18 by suitable means (not shown). The
diaphragm 80 has a rigid cup member 84 bonded to a central portion
thereof, thereby to provide vertical space for a relatively long,
soft spring 86 which biases the valve 20 toward an open
position.
At its lower end the valve stem 78 is connected to the central
portion of a flexible diaphragm 88. The periphery of diaphragm 88
is fixed to the wall of the lower hollow cylindrical portion 48 of
the plug valve by a press-fitted bushing 89. The ports 66 in the
wall of the lower hollow cylindrical plug valve portion 48 lie
between the valve seat 76 and diaphragm 88, so that inlet gas
pressure acts downwardly on diaphragm 88, as well as upwardly
against valve 20, thereby to substantially balance the valve with
respect to inlet pressure.
A centrally perforated plate 90 fixed to the body section 16 at the
upper end of cylindrical bore 46 forms a closure, and a compression
spring 92 positioned between the plate 90 and cap member 82 biases
hollow plug valve 18 in firmly seated position in tapered bore 42.
The cap member 82 has a central perforation and circularly
arranged, upwardly extending prongs 83. An operating knob 94
extending through the central perforation in closure plate 90 is
provided with deep, axially extending, circularly arranged recesses
96 extending upward from the lower end thereof. The recesses 96
slidably receive the circularly spaced prongs 83 on the cap member
82. The knob 94 is thereby axially movable on the plug valve 18,
but rotates with the plug valve.
The operating knob 94 is provided with a retaining flange 98 at its
lower end, and an external rib 100 extending radially from the side
of the knob registers with a slot 102 in the closure plate 90 to
permit the downward vertical movement of the operating knob only
when the plug valve is rotated to a "pilot" position. The operating
knob 94 is further provided with a screw threaded axial bore 104
having a short, hollow, headless adjusting screw 106 threadedly
engaged therein and a headed screw 108 closing the upper end of the
bore. The spring 86 bears at its upper end against adjusting screw
106 and at its lower end against cup member 84, thereby biasing the
operating knob 94 upward and the central portion of diaphragm 80,
the valve stem 78, and, consequently, valve 20 and pressure
balancing diaphragm 88 downward in a valve opening direction.
Attached to the closure screw 108 is a long, small diameter,
actuating rod 110 extending downward through hollow adjusting screw
106 and the spring 86 to a point just short of engaging diaphragm
80 when the valve 20 is completely closed on its seat 76.
The electromagnet 22 has an electromagnetic winding, an iron core,
an axially movable armature (not shown) enclosed within a casing
23, and a rod 112 connected at its lower interior end to the
armature and extending exteriorly upward from the end of the
casing. The rod 112 carries a disc 114 on the upper end thereof,
and a spring 116 bearing against the upper end of casing 23 and the
lower surface of disc 114 biases the armature upward in a direction
away from the magnetic core. The actuating rod 110 is of such
length as to engage the upper end of the valve stem and diaphragm
assembly and cause valve 20 to be opened and the armature of the
electromagnet to be pressed against the iron core when the
operating knob 94 is fully depressed in a pilot position.
The electromagnetic winding within casing 23 is sufficiently
energized by electrical energy generated at the thermocouple
junction 24 through coaxial conductors 118 to hold the armature
against the iron core when the junction is heated by the flame of
the pilot burner 26. The electromagnet is shown in an energized,
retracted position, in which position the valve 20 is free to move
between open and closed positions in response to pressure variation
downstream thereof. In the absence of pilot burner flame, the
electromagnetic winding becomes de-energized and the spring 116
moves the armature away from the core and the disc 114 upward into
engagement with the lower end of valve stem 78 and the diaphragm
88, and the spring 116 has sufficient length and strength to close
the valve 20 firmly on its seat 76 thereby to cut off all fuel flow
through the device.
The rod and tube type thermostat 40 comprises a tube 41 having a
closed outer end and an inner end threadedly engaged in a
screw-threaded bore in the mounting stud 36 and a coaxial rod 43
fixed at its outer end to the closed outer end of tube 41 and at
its inner end engaging the lever 33 at an intermediate point
thereon. The tube 41 has a relatively high coefficient of thermal
expansion while the rod 43 has a relatively low coefficient so that
a change in the temperature ambient to the tube 41 effects an axial
movement of the rod 43. The lever 33 is fulcrumed at one end on the
end of an adjusting screw 120 and at its other end bears against
the outer end of cylindrical member 35. The cylindrical member 35
is slidably mounted in a bore 122 and is provided on its inner face
with an annular knife edge 124 which engages the clicker disc 32
near its periphery.
Inward pressure on cylindrical member 35 causes clicker disc 32 to
snap through a planar shape from the outwardly convex form shown to
an outwardly concave form. In this movement, the disc engages a
valve stem 31 connected to main valve 30 and opens the valve
against the spring 29. When the inward pressure on cylindrical
member 35 is released, the spring 29 initiates the return of the
clicker disc and firmly closes the valve 30.
The upper side of pressure regulator diaphragm 80 communicates with
atmosphere through a vent 81 in the cap member 82, and the lower
side of the pressure balancing diaphragm 88 communicates with
downstream pressure through passageways 126 and 127 extending from
the lower side of diaphragm 88 to the pilot passageway 72. The
lower side of diaphragm 88 is thereby in communication with
downstream pressure when only the pilot port 70 is open in pilot
position as well as when both ports 70 and 68 are open in on
position.
A cavity 128 having a circular side wall is formed in the lower
surface of the inlet body portion 16, which cavity receives a
pressure operated switch generally indicated at 130. Switch 130
comprises a rigid circular cup-shaped member 132 formed of
dielectric material, a flexible circular diaphragm member 134 also
formed of dielectric material, a pair of stationary contacts 136
and a conductive bridging element 138 which when in the position
shown in the drawing effects conduction between contacts 136. The
conductive bridging element 138 has an upwardly extending stem
portion encased in a central boss portion of flexible diaphragm 134
and therefore moves with the central portion of the diaphragm.
The cavity 128 is provided with a counterbore 140 forming an
annular shoulder 142. Peripheral portions of the cup member 132 and
diaphragm member 134 are received in the counterbore with the
peripheral portion of the diaphragm lying against shoulder 142 and
the peripheral portion of the cup member overlying the diaphragm
member. The peripheral portion of the rigid cup member is pressed
against the diaphragm member and shoulder and held firmly fixed by
staking; that is, by deforming portions of the body member adjacent
the periphery of the cavity 128, as indicated at 144, so as to
overlie the peripheral portion of the cup member.
The central portion of diaphragm 134 and bridging member 138 are
biased upward away from contacts 136 by a spring 146. The contacts
136 include hollow terminal connector portions 148 extending
downward and exteriorly of the cup member which receive and connect
thereto the ends of the interior one of the coaxial thermocouple
leads 118. The switch therefore controls the energizing circuit for
the electromagnet 22. The cavity 128 communicates with the pilot
burner fuel passageway 72 via passage 126, and the pressure
operated switch 130 is therefore responsive to supply pressure as
regulated by valve 20 when the plug valve 18 is in either pilot or
on position.
OPERATION
The elements of the device are shown in the positions they assume
when the tapered plug valve is rotated to an on position and the
pilot burner is burning, but the main burner is not burning because
the temperature of the medium being heated by the main burner is at
or near the temperature selected to be maintained and therefore
requires no more heating.
Under these conditions, when sufficient supply pressure exists, the
electromagnet 22 is energized, thereby holding the actuator rod 112
and disc 114 in retracted position. Both ports 68 and 70 in the
plug valve are open, but main valve 30 is closed. Fuel flowing to
the pilot burner 26 through inlet 56, ports 66, valve seat 76, port
70, passage 72, and conduit 74 is regulated at a pressure
preselected by adjustment of the spring 86. As the pressure on the
downstream side of valve 20 tends to increase above the preselected
pressure due to higher inlet pressure, the diaphragm 80 moves the
valve toward a closed position, and when the pressure on the
downstream side of valve 20 decreases due to lower inlet pressure,
the valve 20 is moved openward by spring 86.
A predetermined drop in temperature of the medium being heated
below that preselected to be maintained will cause the rod and tube
thermostat 40, immersed in the medium, to effect a snap action
opening of main valve 30, and fuel now flows through the main
burner outlet to the main burner where it is ignited. The fuel now
flowing to both the pilot and main burners through the upper
portion of the hollow plug valve 18, the ports 70 and 68, and
passages 72 and 58, respectively, is regulated by the single valve
20 and its operating diaphragm 80.
The effective area of pressure balancing diaphragm 88 is preferably
made such as to effect substantially the same downward force on the
valve stem 78 as the upward force applied thereto by valve 20 when
in a closed or near closed position due to inlet pressure acting on
these two elements. This provision permits the operating diaphragm
80 working between downstream pressure, the reference atmospheric
pressure, and the adjusted tension of spring 86 to closely maintain
the preselected downstream pressure. Without this provision the
downstream pressure would increase somewhat above the preselected
pressure and drop somewhat below the preselected downstream
pressure as the inlet pressure drops or increases, respectively. By
connecting the downstream side of balancing diaphragm 88 with pilot
burner passage 72, the diaphragm is rendered operative when the
plug valve 18 is in pilot position as well as in on position when
the valve 30 is open.
When the medium to which thermostat 40 is responsive is
sufficiently heated, the main valve 30 will close, thereby cutting
off fuel to the main burner. The valve 30 will thereafter continue
to open and close to cycle the main burner off and on to maintain a
temperature of the medium which may be selected by turning the
adjustable pivot screw 120.
When it is desired to terminate operation of both main and pilot
burners and cut off all fuel supply thereto, the manual knob 94 is
turned to rotate the plug valve to an off position in which both
ports 70 and 68 are out of registry with respective passages 72 and
58. When this occurs, the pilot burner will be extinguished, the
thermocouple junction 24 will cool, and the electromagnet 22 will
be de-energized. De-energization of electromagnet 22 permits spring
116 to move rod 112 upward and disc 114 into engagement with the
diaphragm 88 and the lower end of valve stem 78 and to move the
valve 20 in firm closure seating engagement with valve seat 76. The
device is now in an inoperative condition.
When subsequently it is desired to operate the pilot and main
burners, the knob 94 is first turned to pilot position. In this
position a portion of the circumferentially extending port 70
registers with pilot passage 72, but port 68 is out of registry
with passage 58. Also, in pilot position, the radial rib 100 on
knob 94 registers with the radial slot 102 in cover plate 90,
thereby to permit axial downward movement of the knob and the
actuating pin 110 carried thereby. The knob 94 is now fully
depressed manually, causing the valve 20 to be opened and disc 114
and rod 112 to be depressed and the electromagnet armature to be
pressed against its iron core or pole piece. Fuel will now flow to
pilot burner 26, which is now ignited by any suitable means. During
and after ignition of the pilot burner, the knob 94 is held in a
depressed position until sufficient time has elapsed for the pilot
burner to sufficiently heat the thermocouple 24 and effect
energization of the electromagnet. When the electromagnet is
energized, it will hold the armature against its core and therefore
the rod 112 and disc 114 in retracted position. The knob 94 may now
be released, whence it is returned to its position shown by spring
86 and then rotated to an on position wherein both ports 70 and 68
are in registry with their respective passages 72 and 58.
If the knob 94 is released prematurely before the thermocouple 24
is sufficiently heated by the pilot burner, or if insufficient
supply pressure exists in passageway 72, the knob will return to
its upper position and valve 20 will close under bias of spring
114. Also, if at any time after the thermocouple has been
sufficiently heated the pilot burner is extinguished for any reason
or if the pressure in pilot passageway 72 drops below a
predetermined minimum, the spring 116 will effect the closure of
valve 20 and cut off all flow through the device.
The illustrated device is adapted to use as a fuel flow control
device for gas-fired water heaters because of the provision of the
screw-threaded mounting stud for threaded engagement in the wall of
a water tank and because of the provision of a rod and tube type
thermostat which is well adapted to immersion in the water to be
heated. It will be understood, however, that the device will serve
just as well in connection with space heaters and that any
temperature responsive means suited to other uses, with suitable
connecting actuating mechanism, may be employed to effect the on
and off cycling of main valve 30.
* * * * *