Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates to fuel mixing devices
and more particularly to devices for producing mixtures of air
and gaseous fuel for use with internal combustion engines, either
alone or in combination with the conventional liquid fuel
carburetors.
With substantial increases in the cost of gasoline,
which is conventionally used for operating internal combustion
engines increased attention has been paid to alternative fuels
for this purpose, for example propane and natural gas which are
gaseous at atmospheric temperature and pressure conditions and can
be stored as liquids in appropriate containers. Various systems
have been proposed for converting gasoline powered internal
combustion to use such a fuel. The systems conventionally include
some form of pressure regulator vaporizer for evaporating the
liquid fuel and controlling the pressure of the resulting gas and
a mixer for mixing the gaseous fuel with air in appropriate amounts
for supply to the engine.
One known form of mixer for such a system is a fuel
injection nozzle that is inserted into a drilled and threaded bore
in the gasoline carburetor for the engine at the point of minimum
venturi diameter. In another known system, an adapter including
a venturi is mounted on top of the conventional gasoline
carburetor to supply air-fuel mixture -to its air inlet. This
latter form of mixer is in many ways more satisfactory in that
it has much greater range of applicability and does not require
the major modification of the gasoline carburetor.
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One significant problem with the adapter style of mixer
is fitting it into the limited space available in the engine
compartments of a modern car. Where the mixer is to be mounted
on top of the conventional gasoline carburetor, the space available
is usually limited to that necessary for the air cleaner. The
relatively long venturi style adapter mixer clearly cannot be
used under the circumstances. While attempts have been made to
construct equivilent mixers that are shorter, they still have a
significant height that limits their applicability. Reference is
made, for example, to Middelton et al United States Patent 2,939,775
where the venturi passage is in the form of a frusto-conical
annulus which is said to have an effective length approximating
that of a theoretically perfect linear venturi.
Other problems that are encountered with the known
systems are the contxol of the fuel flow rate to match the engine
demand and the ability to use both liquid and gaseous fuels.
According to one aspect of the present invention there
is provided a mixer for forming a mixture of air and gaseous
fuel for an internal combustion engine comprising:
an annular main body with a central outlet opening for
the mixture and a peripheral flange around the outlet opening;
an annular crown mounted on top of the main body
around the outlet opening to define with the main body an annular
fuel distribution chamber;
a fuel inlet chamber in the main body for receiving
fuel from a source thereof and passing it into the distribution
chamber tangentally thereof;
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a flat crown plate mounted above the crown and the
outlet opening define with the top of the crown a narrow,
horizontal air inlet gap; and
fuel inlet orifices in the top of the crown for
discharging fuel from the distribution chamber into the narrow gap.
With a mixer of this sort, the air flow into the mixer
is perpendicular to the flow through the carburetor rather than
coaxial with it. The mixer can be made of a sufficiently low
height that lt can be located substantially within an air cleaner of
lQ conventional dimensions. The narrow gap between the crown and
the crown plate provides a high velocity air flow across the fuel
inlet orifices that induces the fuel into the air flow in an amount
depending upon the speed of the air flow. This effect can be
angmented if the orifices discharge into the gap immediately
downstream of a steplike notch in the crown. Alternative, the
inner face of the crown may be convexly rounded and the
inlet orifices sloped inwardly toward the axis of the crown.
Furthermore, with the fuel drawn directly into the air flow
~; through the narrow gap between the crown and the crown plate, the
homogeniety of the mixture is much better than where fuel is
- supplied to the periphery or to the center of a laminar flow such
as in a venturi style mixer.
According to another aspect of the present invention
` there is provided a gaseous fuel mixer for a dual fuel
supply system for an internal combustlon engine having a
conventional liquid fuel carburetor having an air inlet,
said mixer comprising:
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an annular housing adapted to be mounted on the air
inlet of the carburetor with an annular fuel distribution chamber
of the housing surrounding the carburetor air inlet, said housing
including a gaseous fuel inlet into the annular distribution
chamber and a plurality of fuel discharge orifices for discharging
fuel from the distribution chamber in a direction away from the
carburetor inlet;
a crown plate mounted over the housing for movement
between a liquid fuel position spaced from the housing and a gaseous
fuel position adjacent the housing and forming therewith a
narrow annular gap into which the fuel discharge orifices discharge.
As is known, liquid fuels, such as gasoline, require a
considerably greater volume of air for combustion than do gaseous
fuels such as propane and natural gas. Thus, it is necessary to
provide in a dual fuel system, some arrangement for increasing the
air flow when changing the system over to operate on a liquid
fuel. With the described system, the changeover is particularly
simple and may be performed automatically. In one preferred
embodiment, two vacuum operated diaphragms are used for retracting
the crown plate from its gaseous fuel position to its liquid
fuel position.
According to a further aspect of the present invention
there is provided an apparatus for supplying a mixture of air and a
gaseous fuel to an internal combustion engine comprising an
annular fuel distribution crown, a crown plate positioned on one
side of said crown and defining therewith a narrow, annular gap,
a plurality fuel outlet orifices in the crown for discharging
fuel into the gap in a response to an air flow therethrough and
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means for supplying gaseous fuel to said crown at atmospheric
pressure in volumes dependent on the flow rate of fuel from said
orifices.
The use of a "demand" type of fuel vaporizer-regulator
with the annular fuel distribution chamber enables a reduction of
the chamber size with a consequent reduction in the overall size
and cost of the mixer. Where fuel is supplied to the mixer chamber
under pressure, a large volume chamber in the nature of a plenum
rather than a manifold is necessary to stagnate the flow of fuel
in the plenum and produce a uniform distribution throughout. A
further improvement can be obtained if the fuel is supplied
to the fuel distribution chamber so as to produce a cyclonic or
swirling effect around the chamber to ensure uniform fuel
distribution throughout.
According to a further aspect of the present invention
there is provided, in a mixer for producing a mixture of air and
gaseous fuel comprising an annular fuel distribution chamber, a
plurality of fuel outlet orifices from the chamber and a crown
plate extending over the chamber to form therewith a narrow gap
20 into which the fuel outlet orifices discharge, the improvement
comprising a stepped recess on a face of the distribution chamber
confronting the crown plate, with the fuel outlet orifices
discharging into said gap downstream of the step.
There is a flow separation at the stepped recess generat-
ing a low pressure, turbulent flow immediately downstream of the
step. The discharge of fuel from the fuel inlet orifices into this
low pressure turbulent flow improves the fuel induction and mixing
effects.
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In the accompanying drawings, which illustrate exemplary
embodiments of the present invention:
Figure 1 is a sectional view of a gaseous fuel mixer;
Figure 2 is an exploded view of the mixer of Figure l;
Figure 3 is a sectional view like Figure 1 of a mixer
for dual fuel application;
Figure 4, found on the same sheet as Figure 1, is
a sectional view through the fuel inlet chamber; and
Figure 5, also found on the same sheet as Figure 1,
is a diammetrical section of an alternative form of crown.
Referring to the drawings, and particularly to the
embodiment illustrated in Figures 1 and 2, there is illustrated
a mixer 1 for forming a mixture of air and gaseous fuel for an
internal combustion engine. The mixer has an annular main body 2
including a central cylindrical mixture outlet opening 4 surrounded
by a flange 6. The flange 6 is equipped with a crown seat 8
immediately around the upper end of outlet opening 4 for
mounting a crown as will be described in the following.
Surrounding the crown seat, the flange 6 has a frusto-
conical section 10 that slopes away from the crown seat. This isfollowed by a radial, annular, peripheral section 12 to form a
seat for an air cleaner as will be described in the following.
An inlet chamber 14 is formed on one side of the main
body, beneath the crown seat 8. As most particularly illlustrated
in Figure 4, this includes a trapezodial recess 16 open at the top
to the crown seat and two threaded bores 18 opening into the
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inlet chamber tangentially to the crown seat and sloping up-
wardly toward the open top of inlet chamber 14. These two bores
are identical. One oE them receives a fuel inlet fitting 20
connected to a gaseous fuel line 22 and the other is fitted
with a plug 24. The plug 24 and fitting 20 are interchangeable
so that the fuel line 22 can be led in rom either side of the mixer.
The main body 2 of the mixer also has a threaded bore
26 radially outside of the inlet chamber 14. This receives a
vaporexhaust fitting in the form of elbow 28 that is in use,
connected to the valve cover of the engine so that vapors generated
in the valve cover will be led into the mixer and ultimately
burned in the engine to prevent their escaping to the atmosphere.
As will be appreciated, a single main body will not be
able to fit all carburetors in use. To adapt the mixer to various
carburetor sizes, an adaptor 30 is fitted to the central outlet
opening 4. This adapter consists of a radial flange 32 with a
notch 34 along its outer periphery to receive the end of the
central outlet opening 4 of the main body 2. At the center
of the flange 32 is a cylindrical element 36 sized to fit a
given size of carburetor.
An annular crown 38 with the general shape of an
invented U in radial section is fitted to the crown seat 8
to provide an annular fuel distribution chamber 40 immediately
surrounding the central opening 4 of the main body. The
crown has a convexly curving face 42 that forms a continuation
of the inner cylindrical face of the central outlet opening
in the main body and curves outwardly to form a bell like
entry for the main body outlet opening. A stepped notch 44
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is formed in the crown at the top of the inner face 42.
Immediately inside of this stepped notch are a plurality of
fuel outlet orifices 46 oriented parallel to the axis of the
crown and extending from the distribution chamber 40 to the
base of the stepped notch 44.
A crown plate 48 is mounted above the crown 38 so as to
form a narrow annular gap 50 between the top of the crown and the
crown plate. The crown plate, crown and main body are secured
together by means of cap screws 52 passing through the crown plate,
the crown and the main body and nuts 54 fitted onto the cap
screws beneath the main body. Spacers 56 are located on the
cap screws 52 between the crown plate and the crown to maintain
the desired gap 50.
As discussed in the foregoing, the main body 2 has a
radial peripheral section 12 that forms a seat for an air cleaner
58. This cleaner is of conventional annular form with a pleated
annular filter element 60 faced on either side with a plastic seat
62. The preferred filter has a filter element of fiberglass
material since this is noncombustable and reusable.
A flat, circular cover plate 64 extends over the top of
the cleaner 58 and is secured in place by means of a threaded rod
66 threaded into the conventional fitting on the gasoline
carburetor (not shown) and a wing nut 68.
In operation, the gaseous fuel is supplied at atmospheric
pressure (0 pressure gage~ through the inlet chamber 14 to the
distribution chamber 40. The orientation of the bores 18 and the
fuel inlet fitting 20 ensures that the fuel is introduced into
the distribution chamber 40 tangentally to produce a cyclonic
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or swirling motion around the distribution chamber 40, to
ensure uniform fuel distribution within the chamber. ~ecause
-the fuel is supplied at atmospheric pressure there will be
no flow into the distribution chamber or through the fuel
orifices 46 unless there is a pressure less than atmospheric
at the outlet of each orifice 46. The desired subatmospheric
pressure is generated when the engine draws fuel through the
gap 50 between the crown plate 48 and the crown 38. As the
air flow passes the stepped notch 44, the abrupt change in
flow cross section produces a low pressure, turbulent zone
immediately at the outlet of each of the fuel orifices which
will induce the flow of fuel from the distribution chamber
40 through each orifice 46 and mix the fuel thoroughly with
all of the air entering the central mixing zone bounded by the
crown plate, crown and main body. As the engine demand increases,
the air flow through the gap 50 increases, the air pressure at
the outlets of orifices 46 decreases and fuel is drawn more rapidly
into the mixer from the distribution chamber 40.
It will be observed that the crown is recessed into the
surrounding air cleaner and ~hat the overall height of the complete
mixer unit, including air cleaner, is very little more than
the total height of the air cleaner.
Turning now to Figure 3, this Figure illustrates a
gaseous fuel mixer for a dual fuel supply system for an interal
combustion engine. This mixer differs from that of Figures 1 and
2 in that it employs cap screws 70 that do not pass through the
crown plate 48 but provide the desired gap using a specified cap
thickness of the screw head or may also retain the spacers 56,
the crown 38 and the main body 2 together. In this embodiment,
two frustoconical diaphragms 72 are mounted on the underside of
the cover plate 64 by means of respective annular retainers
74 which compress annular lips extending from the maximum
diameter ends of the frusto-conical diaphragms 72 against
the underside of cover plate 64 in an air tight manner.
Within each diaphragm 72 is a plate 76 conforming to the
inside of the smaller diameter end of the diaphragm. ~hat
end of the diaphragm is compressed between the respective
plate 76 and the top face of the crown plate by a rivet 78
passing through the crown plate, the diaphragm and the
plate.
A spiral coil spring 80 is positioned within each
diaphragm with one end bearing on the underside of the cover plate
64 and the other end bearing on the associated plate 76 so as to
bias the crown plate 48 into engagement with the spacers 56
so as normally to provide a fixed air gap 50 between the
crown and the crown plate. The conical shape of the spring allows
it to compress flat. A pair of fittings in the form of
elbows 82 are connected to the cover plate 64 to communicate
with the chambers on the insides of the respective diaphragms
72. The elbows 82 are connected to respective vacuum hoses
84 that are connected via a Y fitting 86, into a main vacuum
conduit 88. The conduit 88 contains, in series, an operated
solenoid vacuum valve 90 and a check valve 92. It is ultimately
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connected to a manifold coupling 94 so as to be exposed at
that point to manifold vacuum. A tee 96 is inserted in the
line 88 between the check valve 92 and the manifold connection
and is connected to a vacuum line 98 to a vaporizer lG0.
The vaporizer 100 is also connected to a fuel inlet line
102 which contains a solenoid operated fuel valve 104. Two coolant
lines 106 supply heated engine coolant to the vaporizer to
supply the heat of vaporization of the fuel being evaporated,
so as to maintain the temperature of the vaporizer. A fuel
outlet line 108 leads from the vaporizer to supply gaseous fuel to
the inlet chamber 14 of the main body 2. A flow regulator
110 is inserted in the line 108.
As illustrated, the mixer is mounted on a gasoline
carburetor supplied with gasoline through a line 114. Flow through
the gasoline line 114 is controlled by a solenoid operated gasoline
valve 116. The gasoline valve 116, the gaseous fuel valve 104
and the vacuum valve 90 are all connnected to a switch 118
for switching the system from liquid fuel to gaseous fuel or
vice versa. The gaseous fuel valve 104 is connected to the
switch 118 via a vacuum switch 120 operated by a vacuum in
line 98, derived by an appropriate tee fitting 122 and a
vacuum line 124.
Any "zero governor" style vaporizer may be used with
the present mixer. A vaporizer of this type supplies fuel in
response to a vacuum in the fuel outlet line 108. Fuel supply
: is prevented in the absence of a vacuum in line 98.
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The switch 118 is a five position switch. When
the switch knob is pressed, one set of contacts is closed to
open a priming valve so as to supply pressurized fuel to the
third stage of the vaporizer.
The switch knob also has four rotary positions.
One of these is for running on gaseous fuel wherein the solenoids
of vacuum valve 90 and gasoline valve 116 are not energized so
that the valves are closed, and the solenoid of gaseous fuel
valve 104 is energized and the valve open provided the
vacuum switch 120 senses a vacuum in the engine manifold.
A second position of the switch 118 is for running
on gasoline. When the switch is in that poisition, the solenoid
valve of gasoline 116 and the solenoid valve vacuum of 90
are energized to open -the associated valves. The gaseous fuel
valve 104 is not energized and the valve is closed. Opening
the gasoline valve permits the supply of gasoline to the
carburetor 112 while opening the vacuum valve 90 permits the
application of manifold vacuum to the collapsible chambers
within diaphragms 72, so that the crown plate 48 is withdrawn
to an upper position in engagement with the retainers 74 to
enable the supply of adequate combustion air to the carburetor.
The check valve 92 acts as a vacuum retainer to retain the
vacuum in the conduits 88 and 84 and the chambers of diaphragms
72 dispite any momentary loss of manifold vacuum. When closed,
the vacuum valve 90 vents conduit 88 to atmosphere.
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The remaining two posi~ions on the switch 118 are
change over positions. To change over to gasoline from gaseous
fuel operation, the switch is turned to one of these positions
where both the gasoline and gaseous fuel valve solenoids are
energized and the valves open. This enables the enyine to
operate on gaseous fuel until the carburetor float bowl is
full. At that time, the switch is turned to the gasoline
position to close the gaseous fuel valve.
To reverse this operation, the switch knob is turned
to the remaining position in which both valves are closed.
This allows the engine to run on the gasoline in the carburetor
float bowl until it is empty. At that time, the valve is turned
to the gaseous fuel position for operation. The switch knob
turns clockwise only to ensure proper operation.
The flow regulator 110 in the gaseous fuel line 108 is
a variable flow restriction in this line. It is a "fine tuning"
adjustment on the amount of gaseous fuel supplied to the mixer in
response to a given air flow into the mixer through the gap 50.
Turning to Figure 5, this illustrates an alternative form
of crown that may be employed in the mixer. This crown 126 has
an inner face 128 that is convexly curved from a vertical
orientation adjacent the central opening of the mixer main
body up to a horizontal orientation at the top of the crown
adjacent the radially outer face. There is no stepped notch
in the crown and the fuel orifices 46 slope inwardly towards
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the axis of the crown. It has been found that an angle of
27 is particularly suitable.
In either embodiment of the crown, the number and size of
the fuel orifices can be varied according to engine displacement,
athough it is preferred to provide a crown configuration that
will suit a range of engine displacements and to tune the
system using the flow regulator 110.
While specific embodiments of the invention have
been described in the foregoing, it is to be understood that
the present invention is not limited to the specific constructions
illustrated. The scope of the invention is defined in the
appended claims.
