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Patent Abstract
A fuel oil supply circuit that includes two bypass mechanisms for
burner startup including an electrical valve bypass in parallel
circuit with a mechanical valve bypass. The fuel oil supply circuit
includes an oil pump that is adapted to pressurize fuel oil and
a downstream regulating valve assembly that is adapted to regulate
pressurized fuel flow to the nozzles of the burner. A solenoid valve
controls flow of pressurized fuel oil through the regulating valve
assembly to the nozzles. The solenoid valve has a first state keeping
the regulating valve assembly closed, and a second state allowing
the regulating valve assembly to open. A diaphragm valve is fluidically
connected to the pump in parallel circuit with the regulating piston
assembly to provide an alternative bypass mechanism as a backup
for the electrical solenoid valve.
Patent Claims
What is claimed is:
1. A fuel oil supply circuit for supplying fuel oil to a nozzle
in an oil burner, comprising: an oil pump connected to a fuel supply
and adapted to provide pressurized fuel oil; a regulating valve
assembly having an inlet port receiving the pressurized fuel oil
and an outlet port connected with the nozzle, the regulating valve
assembly having open and closed positions allowing and preventing
flow of the pressurized fuel oil between inlet and outlet ports,
respectively; a solenoid valve controlling flow of pressurized fuel
oil through the regulating valve assembly, the solenoid valve having
a first state keeping the regulating valve assembly closed and a
second state allowing the regulating valve assembly to open; and
a diaphragm valve fluidically connected to the pump in parallel
circuit with the regulating piston assembly, the diaphragm valve
having a first position allowing flow of pressurized oil through
a return to the fuel supply and a second position forcing oil to
flow to the regulating valve assembly.
2. The fuel oil supply circuit of claim 1, further comprising a
fuel supply passage between the oil pump and the regulating valve
assembly further comprising a restricting valve interposed along
the fuel supply passage dividing the fuel supply passage into upstream
and downstream passages, the restricting valve adapted to provide
a pressure drop from the upstream passage to the downstream passage.
3. The fuel oil supply circuit of claim 2 wherein the downstream
passage includes a first branch to the regulating valve assembly
and a second branch to the diaphragm valve, the upstream passage
acting on the diaphragm valve opposite fluid pressure contained
in the second branch, the diaphragm valve being spring biased to
an open position in which the second branch is fluidically connected
to the return leading to the fuel supply and closing in response
to sufficient pressure in the upstream passage.
4. The fuel oil supply circuit of claim 3 wherein the regulating
valve assembly comprises a piston and a spring, the spring acting
on the piston tending to keep the regulating valve assembly closed,
the regulating valve assembly adapted to open a passage leading
to the nozzle via pressurized fuel oil acting upon a face of the
piston against the action of the spring.
5. The fuel oil supply circuit of claim 4 wherein the solenoid
valve while in the first state bypasses fuel oil through the return
to the fuel supply.
6. The fuel oil supply circuit of claim 1 wherein the solenoid
valve includes a valve element that while in the first state blocks
pressurized oil from flowing to through the outlet port and while
in the second state opens the outlet port.
7. The fuel oil supply circuit of claim 1 wherein upon startup
of the burner, the diaphragm valve closes to second position before
the solenoid valve allows the regulating valve assembly to open.
8. The fuel oil supply circuit of claim 1 wherein the diaphragm
valve closes when the pump reaches a predetermined speed, and wherein
the solenoid valve allows the regulating valve assembly to open
after a predetermined time, the regulating valve assembly staying
closed until the pump reaches the predetermined speed and the predetermined
time has elapsed.
9. The fuel oil supply circuit of claim 1 wherein the solenoid
valve includes a thermistor providing delayed activation of the
solenoid.
10. The fuel oil supply circuit of claim 1 wherein the solenoid
valve is electronically controlled by a electronic controller of
the burner.
11. A fuel oil supply circuit for supplying fuel oil to a nozzle
in a oil burner, comprising: an oil pump adapted to pressurize fuel
oil; an oil regulator regulating pressurized fuel oil from the oil
pump to the nozzle; an electrical control for the oil regulator,
the electrical control adapted to prevent pressurized fuel flow
to the nozzle upon startup of the burner and allow pressurized fuel
flow to the nozzle after startup of the burner; and a valve bypass
in parallel circuit with the oil regulator responsive to oil pressure
of the pressurized fuel oil, the bypass valve adapted to bypass
oil past the oil regulator during the start up of the burner.
12. The fuel oil supply circuit of claim 11, further comprising
a fuel supply passage between the oil pump and the regulator and
a restricting valve interposed along the fuel supply passage dividing
the fuel supply passage into upstream and downstream passages, the
restricting valve adapted to provide a pressure drop from the upstream
passage to the downstream passage, wherein the valve bypass is a
diaphragm valve having one side subjected to the upstream passage
and a second side subject to the downstream passage.
13. The fuel oil supply circuit of claim 11, wherein the diaphragm
valve has an open position at startup in which fuel oil is recirculated
to a fuel supply and a closed position preventing recirculation
of fuel oil through the diaphragm valve, wherein the diaphragm valve
includes a spring tending to keep the diaphragm valve open.
14. The fuel oil supply circuit of claim 11 wherein the electrical
control is a solenoid valve.
15. The fuel oil supply circuit of claim 14 further comprising
means for switching the solenoid valve between states after a predetermined
time at startup of the burner.
16. The fuel oil supply circuit of claim 14 wherein the oil regulator
comprises a piston and a spring, the spring acting on the piston
tending to keep the oil regulator closed, the oil regulator adapted
to open an outlet port leading to the nozzle via pressurized fuel
oil acting upon a face of the piston against the action of the spring,
the oil regulator having an excess fuel port recirculating fuel
oil to a fuel oil supply for the pump, the piston adapted to open
the excess fuel port when excess fuel oil is supplied to the oil
regulator.
17. The fuel oil supply circuit of claim 16 wherein the solenoid
valve controls fuel oil flow through a bypass port in the oil regulator,
the bypass port recirculating fuel oil to the fuel oil supply for
the pump, sufficient fuel oil flowing through the bypass port to
relieve pressure in the oil regulator and keep the piston closed
over the outlet port.
18. The fuel oil supply circuit of claim 16 wherein the solenoid
valve blocks flow through a second outlet port between said first
outlet port and the nozzle during startup of the burner, and intermediate
passage connecting the first and second outlet ports.
19. The fuel oil supply circuit of claim 11 wherein the valve bypass
closes when the pump reaches a predetermined speed, and wherein
the electrical control allows the regulating valve assembly to open
after a predetermined time, the oil regulator staying closed until
the pump reaches the predetermined speed and the predetermined time
has elapsed.
20. The fuel oil supply circuit of claim 11 wherein the electrical
control and the valve bypass each independently prevent smoking
and soot production in the combustion chamber of the burner upon
startup of the burner.
Patent Description
FIELD OF THE INVENTION
[0001] The present invention relates generally to oil burners,
and more particularly relates to valve mechanisms for controlling
oil flow upon start up and shut down of oil burners.
BACKGROUND OF THE INVENTION
[0002] Oil burner units have in the past been provided with regulating
valves interposed between the nozzles or nozzle which discharge
fuel into the combustion chamber and the fuel pump which supplies
fuel oil to the nozzles. Generally, these regulating valves open
upon delivery of a predetermined supply pressure from the pump,
regulate a substantially constant pressure flow to the burner nozzles,
and shut off the supply of fuel oil to the nozzles when the pump
is turned off upon shut down. In addition to regulating the pressure
of fuel oil delivered to the burner nozzles, these valves often
have a bypass function of diverting an excess portion of the fuel
oil pressurized and delivered by the pump back to the tank or pump
reservoir so that only a portion of the fuel oil supplied by the
pump is delivered to the nozzles.
[0003] One of the problems that has been dealt with in the past
is that transient variations in the fuel oil discharge from the
nozzles at startup and/or shutdown cause highly undesirable smoking
and soot production in the combustion chamber at these times. One
known attempt of remedying this problem has been to arrange a mechanical
valve bypass, which typically comprises a diaphragm valve (typically
in association with a cone valve) downstream of the fuel pump. For
example, mechanical valve bypass mechanisms are shown in U.S. Pat.
No. 5,692,680 to Harwath, U.S. Pat. No. 5,145,328 to Harwath, and
U.S. Pat. No. 3,566,901 to Swedberg, the entire disclosures of these
patents are hereby incorporated by reference. This mechanical valve
bypass has an open position that returns fuel oil to the tank or
pump reservoir (typically through the diaphragm valve) for moments
directly after burner startup and upon loss of pressure upon shut
down. When sufficient pressure is present, the mechanical valve
bypass closes and fuel is allowed to flow through the regulating
valve to the nozzles for combustion.
[0004] Although the mechanical valve bypass (e.g. the diaphragm
valve) has provided acceptable results with respect to reducing
most soot production and smoking in the combustion chamber, there
is still some smoking and soot production with this approach. This
is due to the fact that the blower of the burner is not fully up
to speed when the diaphragm valve closes and fuel oil is ported
to the nozzles. A good draft up the chimney is also not established
at this point. A less than desirable fuel to air ratio still exists
momentarily upon start up using the combination of the cone valve
and the diaphragm valve.
[0005] Attempts have been made to overcome the drawbacks of mechanical
valve bypass mechanisms and to provide for longer fuel oil bypass
time periods at burner start up. Specifically, according to some
fuel oil supply circuits, the mechanical valve bypasses have been
eliminated and replaced with electrical control devices such as
solenoid valves, which either block flow or bypass flow through
the regulating valves to prevent the regulating valves from opening.
This prevents flow to the burner nozzles upon startup. For example,
fuel pump units according to this fuel circuit arrangement are commercially
available from the present assignee, Suntec Industries, Inc. and
sold under SUNTEC MODEL A-7400 FUEL UNIT, SUNTEC MODEL B-8400 FUEL
UNIT and SUNTEC MODEL A-2100 FUEL UNIT. With electrical control,
it is known to provide the solenoid devices with a thermistor that
delays movement of the solenoid valve and thereby prevents the opening
of the regulator valve. Longer times periods and hence better control
can be achieved with thermistor operated solenoid valves over mechanical
valve bypasses.
[0006] It is also known to use electronic control over the solenoid
instead of thermistors to control opening of the regulating valve.
The solenoid valve can be controlled directly by the burner control.
This provides more precise or exact control over the opening and
closing of the regulating valve and thereby provides better results.
One problem that can occur with electrical solenoid valves is that
improper installation or incompatible electrical set ups can cause
failure of the solenoid to delay fuel oil flow to the nozzles upon
burner start up. Improper installation can thus cause the regulating
valve to open immediately upon burner start up and thereby result
in undesirable smoking and soot production in the combustion chamber.
BRIEF SUMMARY OF THE INVENTION
[0007] In view of the foregoing it is a primary objective of the
present invention to provide a fuel oil supply circuit for an oil
burner that more reliably prevents smoking and/or soot production
upon burner start up and/or shutdown.
[0008] In accordance with these and other objectives, the present
invention is directed toward a fuel oil supply circuit that includes
two mechanisms for preventing fuel flows to nozzles at burner startup
including an electrical control or solenoid valve in parallel circuit
with a mechanical valve bypass. The provision of two mechanisms
arranged such that one backs up the other better ensures that smoking
and soot production is maintained at acceptable levels in the burner,
even if for example, the electrical system fails or is improperly
installed.
[0009] According to disclosed embodiments of the present invention,
the fuel oil supply circuit includes an oil pump that is adapted
to pressurize fuel oil and a downstream regulating valve assembly
that is adapted to regulate pressurized fuel flow to the nozzles
of the burner. The regulating valve assembly has an inlet receiving
the pressurized fuel oil and an outlet port connected with the nozzles.
A solenoid valve controls flow of pressurized fuel oil through the
regulating valve assembly to the nozzles. The solenoid valve has
a first state keeping the regulating valve assembly closed, and
a second state allowing the regulating valve assembly to open. A
diaphragm valve is fluidically connected to the pump in parallel
circuit with the regulating piston assembly to provide a backup
for the solenoid valve. The diaphragm valve has a first position
allowing flow of pressurized oil through a return to the fuel supply
and a second position forcing oil to flow to the regulating valve
assembly.
[0010] According to one embodiment of the present invention the
solenoid valve bypasses fuel through a return passage leading back
to the fuel supply while in the first state. This causes the fuel
pressure to stay sufficiently low in the regulating valve assembly
such that the regulating valve is kept closed under the force of
a spring.
[0011] According to another embodiment of the present invention,
the solenoid valve blocks fuel flow and prevents fuel from flowing
through an outlet port of the regulating valve assembly. This keeps
the regulating valve assembly closed.
[0012] Other objectives and advantages of the invention will become
more apparent from the following detailed description when taken
in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The accompanying drawings incorporated in and forming a
part of the specification illustrate several aspects of the present
invention, and together with the description serve to explain the
principles of the invention. In the drawings:
[0014] FIG. 1A is a schematic representation of a new and improved
oil pumping system according to a first embodiment of the present
invention illustrated under normal burner operating conditions.
[0015] FIG. 1B is an enlarged view of the regulating valve assembly
and solenoid control valve shown in FIG. 1A, illustrated in a different
state at start up.
[0016] FIG. 2A is a schematic representation of a new and improved
oil pumping system according to a second embodiment of the present
invention illustrated under normal burner operating conditions.
[0017] FIG. 2B is an enlarged view of the regulating valve assembly
and solenoid control valve shown in FIG. 2A, illustrated in a different
state at start up.
[0018] While the invention will be described in connection with
certain preferred embodiments, there is no intent to limit it to
those embodiments. On the contrary, the intent is to cover all alternatives,
modifications and equivalents as included within the spirit and
scope of the invention as defined by the appended claims.
DETAILED DESCRIPTION OF THE INVENTION
[0019] As shown in the drawings for purposes of illustration, the
invention is embodied in a fuel oil supply circuit 10 of the type
used to supply fuel to the combustion chamber 11 of an oil burner
such as might be incorporated into a furnace or boiler. The circuit
10 includes a pump 15 that draws fuel oil from an oil supply such
as a tank 12 through an intake line 13.
[0020] The pump 15 includes a body or housing 16 and may be of
the crescent gear type. An inner gear 17 within the housing is attached
to a drive shaft 18 and is eccentrically disposed with respect to
an outer gear 19. A crescent-shaped member 20 is disposed between
the non-engaging portions of the teeth on the gears for the purpose
of sealing the expanding fluid chambers defined by the gears from
the contracting fluid chambers in a well known manner.
[0021] The pump shaft 18 is journaled in the housing 16 and is
sealed with respect thereto by an elastomeric sealing member which
herein is shown in the form of a lip seal 22. The lip seal 22 is
disposed within and seals off a lubrication chamber 23 in the housing.
[0022] The pump 15 may communicate with a local fuel oil supply
or reservoir 26 that receives fuel oil from the main oil supply
or tank 12. The pump 15 includes a pump inlet 25 that is connected
by an inlet passage 27 in the housing to the reservoir 26. The reservoir
26 is defined by an end cover 29 bolted to one end of the housing
16 and has an intake port 28 to which the intake line 13 is connected.
A suitable strainer 30 located within the reservoir 26 between the
intake port 28 and the pump inlet 25 serves to filter the fuel oil
as it is drawn from the tank to the pump 15. The pump 15 pressurizes
the fuel oil and outputs fuel into a supply passage 32. A bleed
valve 33 may be disposed along the supply passage 32. The supply
passage 32 ultimately delivers fuel oil to a main regulating valve
assembly 34 that serves to regulate the pressure of fuel oil and
causes fuel flow to nozzles 36 to be of a substantially constant
pressure.
[0023] Herein, the regulating valve assembly 34 is located in the
housing 16 and serves to control the fuel flow from the supply passage
32 to a nozzle passageway 38 that leads to the nozzles 36. The nozzle
passageway 38 is formed partly through a fitting 39 threaded into
the housing 16. The fitting 38 has a projection that defines a valve
seat 40 that is adapted to be closed by a hollow piston 42. The
piston 42 is slidably mounted in a pressure chamber 44 and regulates
fuel flow entering the chamber 44 through an inlet port 46. Specifically,
the piston 42 controls the flow of fuel entering the inlet port
46 to an outlet port 48 and a return port 49 that leads to a low
pressure return passage 50 back to the pump reservoir 26 (or alternatively
to the tank 12). The piston 42 includes a land 52 between ends that
regulates fuel flow to the return port 49 and return passage 50.
The return passage 50 may pass through the lubrication chamber 23
so as to lubricate the drive shaft 18 and lip seal 22. The forward
end or disc face 54 of the piston 44 is adapted to engage the valve
seat 40 and close the outlet port 48 and nozzle passageway 38. A
coil spring 56 tends to keep the piston 42 in the closed position
and seated against the valve seat 40. A spring adjustment mechanism
57 may be provided to control and adjust the biasing force exerted
by the spring 56.
[0024] A solenoid valve 58 controls opening of the regulating valve
assembly 34 upon startup and may control closing of the regulating
valve assembly 34 upon shut down. The solenoid valve 58 regulates
flow through a bypass port 60 that connects with the pressure chamber
44 of the regulating valve assembly 34. The bypass port 60 drains
to the return passage 50 leading back to the pump reservoir 26.
The solenoid valve 58 drives a movable valve element 62 between
two states that open or close an opening 63 through a valve seat
64. The valve seat 64 is situated in the bypass port 60 such that
the solenoid valve element 62 can open and close the bypass port
60. The solenoid valve 58 includes an electrical control element
66 for driving the valve element 62 with electrical lead wires 68
that may connect with the burner control (not shown) or electrical
circuit of the shaft motor (not shown) for the drive shaft 18.
[0025] The solenoid valve 58 includes an open state as shown in
FIG. 1B, wherein the fuel oil is bypassed through the bypass port
60 and return passage 50. This reduces pressure in the pressure
chamber 44 sufficiently such that the regulating valve assembly
34 is kept closed under the action of the spring 56. The solenoid
valve 58 also includes a closed state as shown in FIG. 1A in which
fuel pressure may build in the pressure chamber 44 and cause the
piston member 42 to be lifted off of its seat 40 to allow fuel to
flow through the nozzle passageway 38. While in this state shown
in FIG. 1A, any excess fuel will cause the piston 42 to slide even
further causing the return port 49 to open partially to allow excess
fuel to drain and be recycled back to the pump reservoir 26. This
allows fuel flow and pressure through the nozzle passageway 38 to
be substantially constant.
[0026] The electrical control element 66 may include a thermistor
providing a desired time delay for switching the solenoid valve
between states. Alternatively, the electronic control (not shown)
for the burner may provide the means to control activation of the
solenoid control element. In either event, a delay is typically
provided in order to provide sufficiently high pump speed and fuel
pressure; and also to allow the speed of the blower 70 (which is
driven by the same shaft 18 as the pump 15) to be sufficient to
establish a good draft up the chimney 72 of the burner.
[0027] In accordance with the invention, a second mechanical bypass
mechanism shown herein as a diaphragm valve 74 is arranged in parallel
circuit with the first bypass mechanism of the solenoid valve 58
and/or the regulating valve assembly 34. The diaphragm valve 74
causes the pump 15 to reach a high start-up rpm before the regulating
valve assembly 34 opens and causes the regulating valve assembly
34 to close after the pump 15 falls below a certain rpm upon shutdown.
The diaphragm valve 74 includes a resilient diaphragm 76 located
within a chamber and dividing the chamber into two compartments
78, 80. The resilient diaphragm 76 carries a valve member 73 within
the second compartment 80. A spring 75 biases the valve member 74
toward an open position. The valve member 73 is adapted to engage
a valve seat 77 which includes an return outlet 79 to a return passage
81 leading back to the pump reservoir 26 (or alternatively to the
tank 12). The first compartment 78 directly communicates with the
outlet pressure of the pump 15. However, the second compartment
80 is subjected to a reduced pressure along the supply passage 32
caused by a restricting valve shown herein as a cone valve 82.
[0028] The cone valve 82 provides for a pressure drop along the
supply passage 32 and thereby divides the supply passage 32 into
an upstream segment 86 and a downstream segment that is comprised
of a first branch passage 88 to the inlet port 46 of the regulating
valve assembly 34 and a second branch passage 90 to the second compartment
80 of the diaphragm valve 74.
[0029] With the foregoing arrangement, the spring 75 normally holds
the valve member 73 of the diaphragm valve 74 in an open position
with respect to the return outlet 79. When the pump 15 is started,
fuel oil from the pump 15 is supplied to the first compartment 78
of the valve 74 through the upstream segment 86 of the supply passage
32. Fuel oil is also supplied to the second compartment 80 of the
valve 74 through the cone valve 82 by way of the second downstream
branch passage 90. During start-up when the pump 15 is at relatively
low speed, the flow past the cone valve 82 is relatively low and
thus the differential between the pressure the compartments 78,
80 is insufficient to overcome the spring 75 and close the valve
member 73 with respect to the return outlet 79. As a result, fuel
delivered to the second compartment 80 flows through the return
outlet 79 and along the return passage 81 to the pump reservoir
26.
[0030] As long as the speed of the pump 15 is relatively low, the
valve member 73 of the diaphragm valve 74 remains open and prevents
a build up of pressure in the chamber 44 of the regulating valve
assembly 34 sufficiently such that the regulating valve assembly
34 remains closed. However, as the pump speed increases, the increased
flow past the cone valve 82 causes the pressure differential between
the compartments 78, 80 to increase sufficiently such that the pressure
in the first compartment 78 overcomes the combined force of the
pressure in the second compartment 80 and spring 75 to close the
valve member 75 against the seat 77 and thereby close return flow
through the return outlet 79. This allows for sufficient pressure
to build in the regulating valve assembly 34 (assuming the solenoid
valve closes) such that the regulating valve assembly 34 can open
and fuel oil can be delivered to the nozzles 36 for combustion in
the combustion chamber 11.
[0031] The diaphragm valve 74 acts as a back up for the solenoid
valve 58 and better ensures that smoking or soot production does
not occur in the combustion chamber 11. The regulating valve assembly
34 remains closed as long as either the diaphragm valve 74 remains
open or the solenoid valve 58 remains open. The regulating valve
assembly 34 opens only after the diaphragm valve 74 closes and the
solenoid valve 58 closes. Because the diaphragm valve 74 is sensitive
to pressure and hence pump speed, and the solenoid valve 58 is responsive
to electronic signals or a time delay period, different parameters
are utilized to control opening of the regulating valve assembly.
For example, if the solenoid valve 34 is hooked up incorrectly,
is stuck closed, or if the pump does not come up to sufficient speed
within the allotted delay time, the regulating valve assembly 34
will not open prematurely and cause substantial smoking and soot
production in the combustion chamber 11 due to the diaphragm valve
74. Thus, under preferred settings, the regulating valve assembly
34 will not open or deliver fuel to the nozzles 36 until a specified
pre-purge time has elapsed and the pump has reached its full speed.
[0032] Turning to FIGS. 2A and 2B, an alternative embodiment of
the present invention has been illustrated which is similar to the
first embodiment except for the configuration of the regulating
valve assembly 134 and the solenoid valve 158. Because of the similarities,
the same reference numbers have been used for like components in
FIGS. 2A and 2B, except for those components which are materially
different which have been to the extent possible referenced with
similar characters that are greater in value by 100.
[0033] In the second embodiment, the solenoid valve 158 does not
bypass flow during startup but instead selectively blocks the flow
from entering the nozzle passage 138 and thereby blocks fuel flow
to the combustion chamber 11. This embodiment includes a different
type of nozzle fitting 139 threaded into the regulating valve assembly
134. The nozzle fitting 139 includes an intermediate passage 141
connected to the pressure chamber 144 which is adapted to be closed
at one end by the piston 42 and at the other end by a valve element
162 of the solenoid valve 158. The intermediate passage 141 extends
partly through an end portion of the fitting 139 and up into a receptacle
opening 145 that receives the solenoid valve 158. A valve seat insert
147 is mounted in the receptacle opening 145 for cooperation with
the solenoid valve 158. This arrangement provides the regulating
valve assembly 134 with two separate outlet ports 148A and 148B
through which fuel oil must pass to reach the nozzle passageway
138. The piston 42 continues to be biased by the spring 56 to close
the first outlet port 148A. The solenoid valve element 162 is adapted
to close the second outlet port 148B of the regulating valve assembly
134.
[0034] In operation, as long as the diaphragm valve 74 is open
and the pump speed is below a predetermined level, the piston 42
of the regulating valve assembly 134 remains closed at the first
outlet port 148A (regardless of whether the second outlet port is
open), and hence the regulating valve assembly 134 remains closed.
Once the diaphragm valve 74 closes, the piston 42 of the regulating
valve assembly 134 is lifted off of its seat which opens the first
outlet port 148A. However, the regulating valve assembly 134 may
still remain closed and fuel is still not permitted to flow through
the nozzle passage 138 by virtue of the solenoid valve 158 blocking
the second outlet port 148B. Typically, the diaphragm valve will
close very rapidly within a couple of seconds after burner start
up and therefore the solenoid valve 158 continues to block the second
outlet port 148B and keep the regulating valve assembly closed for
several seconds thereafter even though the piston 42 is lifted off
of its seat and the assembly 134 is regulating the fuel oil pressure.
During this time, fuel may be bypassed through the excess fuel return
port 49, where it is recirculated back to the pump reservoir 26
or tank 12. With sufficient pressure lifting the piston 42 off its
seat and once the solenoid valve 158 switches states and opens as
shown in FIG. 2A, the regulating valve assembly 134 opens and allows
fuel oil to be supplied through the nozzle passageway 138 to the
nozzle 36. If insufficient pressure is present in the pressure chamber
144 to open the first outlet port 148A when the solenoid valve 158
opens the second port 148B, the regulating valve assembly 134 remains
closed. However, at this point the solenoid valve 158 having opened
the second port 148B allows the regulating valve assembly 134 to
open automatically upon sufficient pressure being generated and
received in the pressure chamber 144.
[0035] In the second embodiment, the diaphragm valve 74 is hooked
up in parallel circuit with the regulating valve assembly 134 and
operates in the same manner as in the first embodiment. Thus, the
diaphragm valve advantageously serves to back up the operation of
the solenoid valve 158. If the solenoid valve 158 is hooked up incorrectly
to open upon start up or is otherwise stuck open, most smoking and
soot production will be prevented in the combustion chamber 11 by
virtue of the flow being bypassed through the diaphragm valve 74
which keeps the first outlet port 148A of the regulating valve assembly
134 closed.
[0036] All of the references cited herein, including patents, patent
applications, and publications, are hereby incorporated in their
entireties by reference.
[0037] The foregoing description of various embodiments of the
invention has been presented for purposes of illustration and description.
It is not intended to be exhaustive or to limit the invention to
the precise embodiments disclosed. Numerous modifications or variations
are possible in light of the above teachings. The embodiments discussed
were chosen and described to provide the best illustration of the
principles of the invention and its practical application to thereby
enable one of ordinary skill in the art to utilize the invention
in various embodiments and with various modifications as are suited
to the particular use contemplated. All such modifications and variations
are within the scope of the invention as determined by the appended
claims when interpreted in accordance with the breadth to which
they are fairly, legally, and equitably entitled. |