Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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BACKGROUND O~ THE INVENTION
Field of the Invention
The invention relates to a carburetor for mixing air
and fuel prior to combustion, as used in an internal combustion
engine.
Prior A
Carburetors have been known for many years, the
common type of carburetor having a throat with a venturi and
being provided with a butterfly valve for controlling air
flow through the throat. FUQ1 is drawn by suction at the
venturi to discharge through a jet as a fine spray into the
throat. For automotive applications, usually the carburetor
has several jets and fuel delivery circuits to maintain
desired air/fueL ratios or all engine conditions. Normally
a separate choke and a rich fuel circuit is required for
9tarting, and for acceleration an accelerator pump to inject
a measured amount o fuel into the throat is commonly pro-
vided. Modern automobile carburetors are relatively complex
and are prone to blockage from dirty fuel and, with increasingly
strict air pollution standards, are known to be relatively
inefficient for atomization and mixing of the fuel.
A common fault with many modern carburetors relates
to the "flat spots" occuring when the engine accelerates and
the fuel flow transfers from ~ne fuel circuit to another, for
example from the idling circuit, into the accelerating cir-
cuit. The flat spot is known to result from the discontinuity
in the air/fuel ratios between the two circuits~ and further
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complicated structures have been devised to reduce the
effects o such flat spots.
SUMMARY OF THE INVENTION
The invention reduces some of the difficulties of
the prior art by providing a mechanically very simple car-
buretor which uses one fuel circuit for all engine conditions
and eliminates the venturi, choke and accelerator pump.
Becaùse one fuel circuit only is used, flat spot difficulties
associated with the prior art carburetors are eliminated.
Furthermore, the carburetor according to the invention is
sel-cleaning to a limited extent, is physically compact
and provides a relatively constant air/fuel ratio for most
engine conditions.
The carburetor according to the invention includes
a body having a throat deined by a side wall, a uel spray
tube extending into the throat and adapted to receive fuel
and to discharge uel into the throat, and a valve assembly
cooperating with the fuel tube. The valve assembly has a
valve axis extending across the throat, first and second
sliding gate valve members, and a complementary valve guide
means to mount the valve members for generally transverse
sliding along the valve axis between closed and wide open
positions. Each valve member has an inner portion having an
inner edge shaped to approximate to a portion of the side
wall of the throat when in the wide o~en position. The valve
members are also adapted to cooperate with each other so as
to close essentially the throat in the closed position. The
carburetor also includes a valve actuating means, a fuel
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metering means and a fuel atomizing means. The valve actuating
means coop~rates ~,~ith the valve members to move the valve
members concurrently in opposite directions between the
respective open and closed positions in re~ponse to an oper-
ator control. The fuel metering means is responsive to
valve position and meters fuel to be discharged from the
~uel spray tube. The fuel atomizing means cooperates with
the fuel spray tube so as to discharge into the throat an
acceptable fuel mixture ~or combustion for all valve positions.
The ue] atomizing means can also be used, with
suitable modiications, in a conventional carburetor with a
common valve means for controlling air flow through the
throat, for example a butter~ly valve. The fuel atomizing
means includes the fuel spray tube extending illtO the throat
and being characterized by discharge jet means extending sub-
stantially across the throat and positioned so as to be
expoged to suction resulting rom air 10wing around the
spray tube. The fuel spray tube includes a maniold
e~tending substantially across the throat and communicating
with ~e discharge jet means, and a fuel orifice positioned
mid-way across the throat to discharge metered fuel into the
maniold for distribution to the discharge jet means.
A detailed disclosure ollowing, related to drawings,
describes preferred embodiments o the invention which, however,
is capable of expression in structure other than that particularly
described and illustrated.
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DESCRIPTION OF THE DRAWIN~S
Fig. 1 is a simplified fragmented section through a por-
tion of the carburetor, portions of the carburetor
being removed to show valve actuating mechanism
and the valve members in open positions,
Fig. 2 is a simpli~ied section on Line 2-2 of Fig. 1
showing the valve members in wide open positions,
Fig. 3 is a simplified section on Line 2-2 of Fig. 1,
the valve members being shown in closed positions,
Fig. 4 is a simplified transverse section on Line 4-4 of
Fig, 1,
Fig. 5 is a simplified perspective showing valve members
separated beyond the wide open position,
0 Fig. 6 is a simpliEied perspective showing the valve
members cooperating in a partially open position,
Fig. 7 is a simplified section on Line 7-7 of Fig. 2,
the valve members and fuel metering means being
shown in half open positions,
Fig. 8 is a simplified top plan of a first alternative
carburetor, valve members thereof being shown in
half open positions,
Fig. 9 is a simplified section generally on Line 9-9 of
Fig. 8, the valve members being shown in the half
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open positions, some por~ions being removed,
Fig. 10 is a simplified section on Line 10-lO of Fig. 8,
a fuel metexing means being shown in a half open
position, some portions being removed,
Fig. 11 appearing on Sheet 3 of the drawings~ is a sim-
plified section of a second alternative carburetor~,
O Fig. 12 appearing on Sheet 3 of the drawings~ is a sim-
plified top plan of a third alternative carburetor,
some portions being removed.
DETAILED DISCLOSU~E .
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Reerring par~icularly to Figs. 1 through 3, a
carbureto~ 10 ~o~ mixing air and fuel prior to combustion in-
~0 clude8 a body 12 ha~ing a throat 13 de~ined by a cylindrical sidewall 14~ Air enters ~he carburetor ~rom an intake s~ack in the
direction of an arrow 15, in response to reduced induction pres-
sureO A fuel spray tube 16 extends across and between opposed
portions of the throat and has a fuel inlet 17 at one end to
receive fuel and a plug 19 at an opposite end and is adapted to
discharge fuel into the throat by means to be described. The
carburetor has a throat central axis 18 and a valve assembly 20
having a valve axis 21 extending across the throat on a diameter
thereof. Thus the spray tube 16 and the valve axis 21 extend
normally to the throat axis 18. The valve assembly is control-
led by valve actuating ffleans 23 coupled by a valve control link
2~ to an operator contrc~l (not shown)O
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The valve assembly includes Eirst and second sliding
gate valve members 25 and 26 and a complementary valve guide
means 27 to mount the valve members for generally transverse
sliding along the valve axis between an open position of the
5 valve shown in Fig. 2 and a closed position shown in Fig, 3u
The valve members 25 and 26 have inner portions 31 and 32
provided with concave inner edges 33 and 34 respectively, the
inner edges being disposed generally symmetrically about the
valvè axis and being shaped to approximate to a portion of
the side waLl 14 of the throat when in the wide open position3
ie. shaped to correspond to approximately one hal of the
throat sidewallO As seen in Fig. 2, when the carburetor is
open the inner edges 33 and 34 are not necessarily ~lush with
the ~hroat si.de w~ll, but can pro~ect into the throa~ ~rom the
side wall to produce turbulence in the air flow which improves
the mixing o the fuel with the air~ l~ maxi~n~m air flow
through the throat is a major consideration the inner edges 33
and 34 should retract to be fltlsh with the throat side wall in
the wide open position. The guide means 27 has oppositely
extending valve guide projections 28 and 29 to receive and
support outer portions of the valve members 25 and 26 res-
pectively in the wide open position, and to support outer
portions of the tube 16~
As best seen in Figso 4, 5 and 6, the valve member
25 has first and second portions 37 and 38 having thicknesses
35 and 36 respectively, the thickness 36 being approximately
twice the thickness 35O The first portion is a generally
rectangular slab having a pair of spaced parallel side edges
41 and 42 adapted to slide in the valve guide means 27,
and the concave inner edge 33~, The first portion 37 has a
face 43 with an axial groove 44 to accept approximately
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one-half of the fuel spray tube 16, the face having a periphery
defined in part by portions of the second portion, the edges
33, 41 and 42 and an outer edge 48 of the valve member. The
face 43 also has a pair of gear racks 46 and 47 extending
parallel to and adjacent the side edges 41 and 42 of ~he
member between spaced inner edges of the inner portion 31
and the outer edge 48.
The second portion 38 has an axially disposed
passage 45 aligned with the groove 44 in the face 43 so as
to accept the fuel spray tube 16 which passes ~hrough the
second portion to the outer edge 48. The second portion has
a convex semi-cylindrical inner wall 50 spaced outwards
from the inner edge 33 a distance 51 as measured along
the valve axis, which distance defines valve overlap. Thus
the groove 44 extends between mid-positions of the convex
inner wall 50 and the concave inner edge 33.
The second valve member 26 is generally similar to
the first valve member and has first and second portions 57
and 58 and a passage 53 in the second portion aligned w.th a
groove S5 extending across a face 56 of the first portion 57,
forming a valve overlap. The passages 45 and 53 and the
grooves 44 and 55 of the valve members are mutually aligned
for all positions of the valve members to permit free sliding
of the members along the fuel spray tube 16. The first portior,
57 has parallel side edges 59 and 60 with gear racks 61
and 62 extending parallel to and adj acent the side edges
59 and 60.
The valve members 25 and 26 are mounted in the valve
guide means 28 in opposite relationship to each other, so
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that faces 34 and 56 of the respective first portions are
posi~ioned so as to be adjacent to each other. As best seen
in Fig. 6, the concave inner edge 3~ of the first portion 57
of the valve member 26 is complementary to the conve~ inner
wall 50 of the second por~:ion 38 of the valve member 25.
Similarly, the second portion 58 of the valve member 26 has
a conve2~ inner wall 63 (shown in Figs. 1, 2 and 3) which is
complementary to the inner edge 33 o:E the valve members 25.
Because the concave inner edge and convex inner wall of one
valve member is complementary to the concave inner edge and
convex inner wall of the other valve member, when the valve
is closed, air flow through the carburetor is restricted.
The degree of restriction can be adjusted by changing equally
on each valve member the width of the valve overlap and
degree of fit of the complementary portions o~ the valve
members. When closed a relatively small amount of air can
10w around the side edges of the valve members between the
guide means and this is sufficient to provide cool air for
cool~ng the cylinder after the engine has been switched
of but is still rotating. The air flowing around the edges of
the valve member remote from the throat thus by-passes the fuel
spray tub~ and thus does not draw fuel into the engine which, in
.some cases, would otherwise tel d to initiate ignition even
when the engine has been switched off. Thus this is an
air by-pass means and the amount of air being by-passed
can be adjusted be selecting p.irticular clearances between
the valve members and guide means. It is important that
negligible air by-passes the fuel spray tube when the valve members
are open and the engine is operating as this would cause eratic
running due to undesirable variations in air/Euel ratio.
As b~est seen in Fig. ~, a pair of similar gear
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wheels 65 ancl 66 are journalled on pins 67 and 68 extending
inwards from the valve guide means 27, the gear wheels meshing
with the opposed racks 46 and 61, and 47 and 62 respectively
of the valve members, to provide a simple rack and pinion
mechanisms on each side of the fuel spray tube. The rack
and pinion mechanisms automatically couple the valve members
together so as to move equal amounts in opposite directions.
The valve members and gear wheels can be made -Erom injection
molded plastic so that lubrication problems are reduced and
the tolerances obtainable with precision injection moldings
permit economical mass production of the major components
of the valve mechanism. For a given movement of one valve
member, change in opening between the valve members is twice
that that would be obtained if only one valve member moved.
Thus the valve assembly has a particularly fast response for
a given colltrol movement when compared with a s:ingle plate valve.
Fur~hermore, the movement oE the valve members is
symmetrical relatlve to the throat for all valve positions,
which also contrasts witl~ a single plate valve.
The valve control link 24 includes a sheathed control
cable 70, such as a Bowden cable, having an outer end 71 of
the sheath thereof secured to the projection 28 of the valve
gui-le means, and an outer end 73 of an inner wire thereof
secured to the valve member 25. Inner el~ds Snot shown~
extend to an operator's throttle control,for example,
the hand grip o a motor cycle, or the accelerator pedal
linkage of an automobile. Compression s~ring means 75
enclose a portion of the fuel spray tube 16 and extend be-
tween the valve guide means and the outer edge 48 of the
member 25 to apply a closing force to the valve member tending
to move it to the closed position. The closing force is
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applied along the axis 21 and aligned with the tube 16 which
also is a guide and thus jamming tendency is reduced. The
throttle is opened by drawing the wire o~ter end 73 outwards,
thus compressing the spring means 75 ~nd moving the valve mem-
ber 25 outwards which, through the gear wheels 65 and 66 con-
currently moves the valve member 26 outwards, i.e. in the
opposite direction. Thus the gear wheels 65 and 66, the
gear racks 46, ~7, 61 and 62 and the control cable 70
serve as valve actuating mea~s cooperating with the -valve
members to move the valve members concurrently in opposite
directions between the respective open and closed positions
in response to an operator control. It is noted that the
gear wheels are rotatable means journalled for rotation
relaive to the carburetor, and alterna~ive and equivalent
valve actuating means and rotatable means are disclosed
with reference to Figs. 8 and 9.
As best seen in Figs. 1 and ~, the valve guide
means 27 includes open rectang-llar recesses 77 and 78 on
~0 oppos~te sides of the spray tube, and recess 77 having
opposed parallel walls 80 an~ 81 which restrict the valve
members against rockin~ relative to the v~lve a~is as the
val~e members move between e~treme positLons. Additional
support or the valve members is obtained by opposed inner
~aces 83 and 84 of the valve guide projections 28 (shown in
Fig. 1 only), which inner faces engage upper and lower faces
respectively of inner and outer portions o~ the v~lve members.
Similarly, inner faces 85 and 86 of the valve guide projection
29 engage upper and lower faces respectively at opposite ends
of the valve members. It can be seen that the valve members
are thus supported along the side edges thereof for all
positions o the va:lve members with additional support of
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the inner and outer portions of the valve members when in
extreme positions. This produces smooth, sliding o the
valve members along the guide means and also along the fuel
spray ~ube wi~h little tendency to jam through non-alignment.
Fi~s. ~ and 7
Referring mainly to Figo 7, the fuel spray tube 16
has a plurality of air bleed jets 91 spaced along the tube
and facing generally upstrema to inlet air flow, shown as the
arrow 15, so as to receive a portion of ram air entering the
car~uretorO The fuel tube also has a plurality of discharge
jets 93 spaced along the tube and positioned so as to be ex-
posed to suction resulting from air flowing around the spray
tube. In some condltions suction can also be generated by air
flord around the inner portions 31 and 32 of the valve members
whi~h augments suction produced by air flowing around the tube~
~he air bleed jets and discharge jets extend in rows between
opposi~e portions of the side wall of the throat and are equally
spaced, The air bleed jets are larger, spaced further apart
and fewer ln number than ~he discharge jets for reasons to be
describedO As best seen in Figo ~ the discharge jets are
positioned on the periphery of the tube at about 45 degrees to
the main direction o air flow at a position where suction is
generated as air 10ws past the tube 16. Preferably most of
the air entering the air bleed jets 91 cannot pass directly out
through the discharge jets 93 and thus the discharge jets are
non-aligned with the air bleed jets.
As best seen in Fig. 7, portions of the valve members
having the passages 45 and 53 and the grooves 44 and 55 res-
pectively partially enclose portions of the fuel spray tube
adjacent opposite portions of the throat. Thus, as the valve
assembly closes, the valve members move towards each other and
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the air bleed jets and the discharge jets adjacent opposite
portions of the throat are progressively closed by the valve
members. It is noted that as the valve member 25 Moves inwards,
the valve overlap of the member 25 closes the discharge jets
ahead o the air bleed jets. Likewise as the member 26 moves
inwards, its valve overlap closes the air bleed jets ahead of
the discharge jets.
The fuel spray tube 16 is characterized by an outer
sleeve 96 having a central bore 95 and the rows of air bleed and
discharge jets 91 and 93 respectively, and an inner tube 97 which
is a snug fi~ within the central bore 95. The inner tube 97 has
a central bore 99 for receiving uel from a fuel line (not shown)
connected ~o the ~uel inlet 17 and entering the bore in direction
o an arrow lOOo The fuel line receives fuel from a constant
lS head device such as a common float chamber or constant pressure
delivery pump (not shown). The central bore 99 has a restric-
tion 101 defining a fuel flow jet 102 which communicates with a
discharge chamber 104 on a side of the restriction remote from
the inlet 17, An inner end 98 of the tube 97 has an annular
~0 groove 106 extendlng therearound~ which defines with a portion
of the central bore 95 of the outer sleeve 96 and opposed shoul-
ders o the groove 106 an annular manifold 107 within the tube
160 The manifold 107 extends between the upstream and downstream
portions of the bore 95 and along the spray tube between extreme
outer positions of the air bleed and discharge jets and connects
the air bleed jets to the discharge jetsO A fuel orifice 109
passing through an inner wall 110 of the manifold connects the
discharge chamber 104 to a downstream portion of the manifold
and thus is disposed relative to the air bleed jet means so as
to be essentially sheltered from direct flow of air entering
the air bleed jet means. The fuel orifice 109 is on the
throat axis 18 and thus is disposed approximately mid-way
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across the throat 13 to ensure central distribution of fuel
into the m~nifold, i.e. a~. a mid-position of the manifold
to provide generally even distribution of fuel to the dis-
charge jets. Th~ls fuel passes along the bore 99, through the
fuel jet 102, into the ~ischarge chamber 10~, through the
fuel ori~ice 109 and then generally equally to opposite ends
of the manifold 107. Ram air that enters the air bleed jets
91 flows around the annular groove 106 and mixes with fuel
discharged from the fuel orifice 109. Some atomization of
the liquid fu~l may take place here, but mostly air is mixed
with fuel droplets to form a relatively rich primary air/fuel
mixture which is then drawn through the fuel discharge jets
93 to atomize in the suction adjacent the jets 93. This
subsequent atomization at the jets 93 is assisted by air
turbulence and suction resulting from air flow passing the
inner portions 31 and 32 of valve members. The air bleed
jets preerrably have a total area greater than the discharge
jetg so as to pass an aclequate volume of air to initiate
primary mixing of ~he metere~d Euel. The discharge jets
are rela~ively ~ine openings to improve atomi~ation. Thus
the air bleed jets 91, the f~lel orifice 109, the mani-fold 107
and discharge jets 93 serve as fuel atomizing means 111.
A fuel needle 112 has a tapered outer end 113
passing through the fuel flow jet 102 and an inner end 115
releasably connected to an inner end of an arm 116. The arrn
116 has an outer end fitted in an opening 118 in the valve
member 26, and a portion of the outer sleeve 96 has an
elongated slot 120 to provide clearance for the arm 116 to
pass therethrough. As can be seen, as the valve mem'~er 26
moves axially between open and closed positions in directions
shown by a double-headed arrow 122, the tapered ~nd 113 of
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the fuel needle moves axially thr~gh the fuel flow jet 102
varying degree o~ restriction of ~he fuel jet thus serving
as a fuel metering means 121. The slot 120 thus has a length
equal to at least tota~ stroke of one valve member to accom-
modate full movement of the valve member between extreme
positions. An "0" ring seal 124 encircles an inner parallel
portion of the fuel needle essentially to prevent loss of
iuel through an outer end of the discharge chamber 104.
Thus the arm 116 serves as a coupling means 125 which con-
nects the ~lel needle to an adjacent valve means so that
axial movement of the valve member is reflected by the
needle. The plug 19 has an openi~g 123 to accept a screw
driver (not shown) for engagement with a screw driver slot 126
at the inner end 115 of the needle 112 for turning the needle
in the arm 116 or axial adjustment of the needle. The needle
112 can thus be moved axially relative to the arm 116 for
"zeroing" the needle relative to the jet 102.
As best seen in Fig. 4, the needle has a flat
'portion 127 inclined to a central axis of the needle, so
that cross-sectional area of the needle varies along the
length thereo~. Thus when the needle 112 cooperates with the
jet 1~2, with a constant fuel supply pressure, the fuel
flow through the fuel jet is metered an amount dependent on
cross-sectional area of that portion of the needle which
cooperates with the jet. The tapered needle 112 thus serves
as a variable fuel flow restricter which cooperates with t'ne
fuel jet to vary degree of restriction of the f~el jet.
Because the needle is connected to the valve member 26,
relative position of the flow restricter in the jet is
dependent OIl position of the valve member, which is related
to volume of air flowing through throat. The flat portion
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127 is preferrably disposed adjacent the fuel orifice 109 so as
to provide a relatively direct route between the fuel jet and
the fuel orifice and this relative disposition can usually be
attained after rotation of the needle 112. The fuel orifice is
no smaller than the jet 102 when fully open so as not to restrict
flow from the chamber 104. It is seen that as the needle moves
in the jet 102, it would tend to clean it vf a blockage, thus
making the carburetor self-cleaning to a limited extent.
In summary, it can be seen that the carburetor has
the fuel metering means 121 and the fuel atomizing means 111
positioned within the fuel spray tube, in which the fuel
metering means is responsive to valve position to meter fuel
discharged from the fuel spray tube, and the fuel atomizing
means cooperates with the fuel spray tùbe so that as the
valve closes, volume flow o~ air entering the air bleed
o~iEices is controlled by selectively closing air bleed jets
simultaneou ly with the discharge jets, It is noted that
the air bleed ~ets communicate with the discharge jets and
a suppLy o$ metered fuel so that the metered uel and the
ram air in the maniold discharge simul~aneously through the
discharge jet means.
OPERATION
A portion of ram air entering the carburetor throat
enters the fuel spray tube through the air bleed jets 91
and passes through the mani~old 1~7 to leave the ~el
spray tube through the discharge jets 93. This portion of
air concur~ently mixes initially with metered fuel passing
through the fuel orifice 109 to form the relatively rich
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~41~029
primary air/fuel mixture in the manifold 107, which then
discharges through the discharge jets 93 for subsequent
mixing with air in the throat downstream from the spray tube
to produce a desired leaner air/fuel mixture for combustion.
It can be seen that, as the carburetor closes, air bleed and
discharge jets are closed progressively from each end of the
tube, thus proportioning ram air fed into the jets and fuel
discharged f~-om the jets in an ~mount generally proportional
to air flowing through the carburetor. Note that fuel
metering is determined primarily by position of the fuel
needle 112 in the fuel jet 102, with some adjustment being
possible by varying ram air fe~ into the mixing manifold.
ALTERNATIVES AND EQUIVALENTS
The spray tube 16 has the plurality o air bleed jets
91 and discharge jets 93 spaced along the tube between the
side wall of the carburetor throat. If required, size and
spacing of the jets can be varied to accommodate air flow
variations across the throat, or to accommodate different
air/fuel mixtures for different valve positions. Two rows
of discharge jets can be provided symmetrically on opposite
sides of the fuel spray tube so as to exposed to the suction,
and if desired can be staggered relative to each other or
even dispersion o~ fuel into the air stream.
Alternatively, the air bleed jet can be a narrow
axial slit extending along an upstream portion of the spray
tube and the discharge jet can be a similar narrow slit
extending along a portion of the fuel spray tube exposed to
suction. This would produce a continuously varying area of
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air bleed jet or discharge jet exposed LO air ~'low, contrasting
with the pluraljty of jets which is discontinuous or incremental,
The slits c~u~d ~aper to provide non-linear area characteristics
to attain desired air/fuel ratios for all valve positions.
Alternatively one ~ir bleed je~ and one fuel discharge jet
can be provided at the middle of the tube, i.e. mid-way across
the throat. This latter alternative does not have extensive
or progressive closing of jets as the valve closes, from
the wide open positions until the valve members approach
edges of the jets. All structures above are termed air bleed
jet means and discharge jet means.
The fuel atomizing means can be used also as a
substitute for the fuel jets in a conventional carburetor
having common valve means for controlling air flow through
the ~hroat, or example a butterfly valve. The atomizing
me~ns incLudes a ~uel spray tube extendlng into Lhe throat,
the tube hav:l~g discharge jet means extending sub9tantially
across the throat and poqitioned so as to be exposed to
suction resulting fram ai~ flowing around the throat. The
fue~ spray tube includes a manifold extending substantially
across the throat and communicating with ,t,he discharge jet
means, and a fuel orifice positioned mid-way across the
throat to disch~e metered fuel into the manifold for dis-
tribution to the discharge jet means. It is noted that inthis simplified arrange~e~t the air bleed jets can be
elimina~ed and thus met~ring ~ ram air or pre-mixing in the
tube to form the rich primary mixture is eliminated. In
the simplified arrangement with an alternative valve means,
the-val~e means is not coul~led to the fuel metering means and
does not cooperate wi~h the discharge jets to proportion
the exposure of discharge jets to-valve opening. Thus
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4~29
valve coupling o the metering means and jets is elimlnated
and the atomizing means provides a distribution of atomized
fuel across a diameter of the throat in which the fuel
has been previously metered by the existing jets in the car-
buretor. The existing jets re2~1ate fuel supply to the
fuel tube in an amount dependent on suction at the discharge
jets. It is noted that the Euel metering means is now remote
from the carburetor throat and the spray tube, and mostly
would still require only one uel circuit. Thus this sim-
plified alternative provides a conversion kit for an existing
common carburetor to g:ive the advantages of essentially even
diametrical distribution of atomized fuel which has been
metered in an amount dependent on throat suction.
Alternatlve valve actuating means, fuel atomizing
means and relative dispostlons of the valve members and
spray tubes are described with reference to Figs, 8 through 12
as follows.
Fl~s, 8 thro~
Referring initially to Fig. 8, an alternative car-
~buretor 130 having a thtoat 131 has an alterna~ive valve
assembly 132 actuated by an alternat-ive vnlve actuating
means 133, and an alternative fuel spray tube 134 having an
alternative fuel metering means 135. The valve assembly 132
has a valve axis 136, and first and second valve members 137
and 138 mounted in valve guide means 139 and a~apted for the
transverse sliding along the valve axis between closed and
wide open positions. The valve members and the valve guide
means are generally similar to the valve gui~e means of
Fig. 1, with diferences as follows. As seen i~ Fig. 8, a
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major difference from the carburetoî 10 of Fig. 1 relates
to the fuel spray tube 134 which extends diametrlcally across
the throat normally ~o the valve axis 136 of Fig. 8, in
contrast to the tube 16 of Figs. 2 and 3 which extends
parallel to the valve axis. The tube 134 receives fuel in
direction of an arrow 142 from a fuel supply (not shown).
Inner portions 140 and 141 of the members 137 and 138 have addi-
tional clearance 143 and 145 to receive the fuel spray tube 134
transversely so as to extend over downstream and upstream
sides of the tube respectively so as to sandwich the fuel
tube. Thus the passages 45 and 53 and grooves 44 and ~5 of
the valve ~embers 25 and 26 of Figs. 1 through 6 are eliminated.
The fuel spray tube 134 has a plurality of air bleed jets 144
and discharge jets (not shown) on the upstream and downstream
sides o~ the tube respectively, which are generally similar
to the ~ets 91 and 93 o~ the uel spray tube 16 o the car-
buretor 10. The fuel spray tube 134 cooperates with the
valve ~o~berq 137 ancl 138 so that jets adjacent opposi~e
portlons of the throat are progressively closed by the
va~v~ members as the valve assembly closes, similarly to the
structure o~ Fig, 1. The tube 134 has a manifold and a
related centrally disposed fuel orifice (neither of which
are shown) similarly to the tube 16.
The valve actuating means 133 eliminates and is a
substitute for the rack and pinion mechanism of the means
23 o Fig. 1. Referring also to Fig. 9, the means 133 has a
lever mechanism 146 which includes a lever 148 secured at a
mid-point thereof to an axle 150 which is journalled for
rotation about an axis 149 disposed diametrically to the
carburetor throat. The axis 149 is shown to be aligned with
the fuel spray tube 134 although alternative locations are
- 20 -
0(~Z9
envisaged. A pair of links 151 and 152 have inner ends 153
and 154 connected to ~)pposite ends of the lever 1~8, and outer
ends 155 and 156 journalled on pins 157 and 158 extending
transversely :from the valve members 137 and 138 as shown.
The pins 157 and :L58 extend through axial slots 161 and 162
in the valve guide means and are thus constrained to move ln
planes parallel to the valve axis. ~s can be seen in Fig. 9
rotation of the axle 150 rotates the lever 148 between its
valve open position 1~4 and its valve closed position 165
resulting in concurrent mutual sliding of the v~lve members
e~ual amounts in opposite directions. A control arm 166
secured to an outer end of the axle 150 is connected to an
operator control, for example the throttle lever, through
control link means tnot shown), with return sprin~ means
lS (also not shown) as required.
The ~uel metering means 135 is positioned remote
from the throat 131 and within one portion of the guide
means 139. As seen in Figs. 8 and 10, the means 135 includes
a tapered fuel needle 169 which cooperates with the tube 134
to meter flow through a longitudinal bore thereof as follows.
The needle has a tapered outer end 17~, and an inner end 170
threaded on to an arm 171 extending from the vaLve member
138 into a clearance slot 172 in the valve guide means.
The valve guide means has a parallel bore 175 adapted to
receive the end 173 and the fuel spray tube 134 passes through
that portion of the valve guide means an~ is pierced by the
bore 175. Thus the outer end 173 of the needle passes trans-
versely across the longitudinal bore of the fuel spray tube
to meter fuel flow therethrough. The end 170 has a screw
driver slot and the valve guide means 139 has a clearance
bore 177 to accept the screw driver for rotation of the
1~4C~(~Z9
needle for axial adjustment of the needle. As can be seen,
movement of the valve member 138 in clirection of an a~row 178
to close the valve moves the flel netdle inwards, increasing
restriction oE the fuel spray ~ube 134, thus decreasing flow
of uel through the metering means 135 in an amount pro-
portional to movement o~ ~he valve members.
Fig. 11
A second alternative carburetor ~.84 has an alter-
native valve assembLy ~85 having first and second valve members
187 and 18~ for~d from flat plates, outer edges of which are
adapted to run in valve guide means 18~ which are generally
similar to the previously described valve guide means.
The carburetor has an alternative fuel atomizing means 191
characterized by a fuel spray tube 193 extend:ing across the
throat parallel to movement of the valve members. The fuel
~pray tube has a plur.tlity o~ air bleed jets 194 and
dlscharge jets 1~5 sp~ced along the tube on upstream and
downstream sides thereof similarly to the previously
described embodiments. The tube 193 is positioned ad~acent
to and downstream of the valve members so that the valve
members close the air bleed jets a~ required. The first and
second portions o the previously described valve members
are thus eliminated, together with the passages and grooves
to accept the fuel spray tube. Valve actuating means (not
shown) such as the lever mechanism 1~6 of Fig.8, move the
valve members concurrently in opposite directions as pre-
viously described. The fuel spray tube is positioned in
turbulence produced in the air flow past the valvc members
to improve atomization and mixing of the fuel. The valve
members only restrict entry of ram air into the upstream
- 22 -
~L0400Z9
facing air bleèd jets, and provide no restriction for
discharge from the discharge jets on ~he lower surface thereof.
A fuel needle 196 cooperates with a fuel flow jet (not shown)
within the tube 193 and is threaded onto an arm 197 extending
from the valve member 187 into a clearance slot 198 in the
tube 193. Thus fuel metering is proportional to valve
opening as in the previous embodiments.
Alte~natively, the first and second valve members
can be fitted on the downstream side the fuel spray tube 193
as shown generally in broken outline at 187.1 and 188.1.
In this alternative position the air bleed jets 194 remain
unobstructed for all valve positions, and suction at some of
the discharge ~ets 195 is reduced by the valve members when
partially closed. The alternative carburetor 184 provides a
simplified structure which could have applications where
atomization is less critical.
FiR. 12
A third alternative carburetor 200 has a throat
having a side wall 201, and first and second valve members
202 and 203 supported in complementary valve guide means
205 for generally transverse sliding along a valve axis 207.
Valve actuating means (not shown) move the valve members
concurrently between wide open and closed positions, similarly
to the previously described embodiments. A fuel spray tube
210 extends from!one side of the carburetor throat half-way
across the throat, and has an inner end face 212 positioned
ad~acent a central axis 213 of the throat. The tube 210
has a longitudinal bore 215 extending inwards from the ~ace
212 and an outer end 216 adapted to be connected to a constant
~o~z9
pressure fuel supply so as to receive fuel which passes
along the bore 215 to discharge fuel into the throat.
The first valve member 202 is positioned on a side
of the throat opposite to the fuel spray tube so that when
the first valve member moves to close the carburetor it
approaches the tube 210. The valve members are shown in a
partially closed position, and the first valve member has a
clearance bore 221 to accept an inner portion of the tube 210
to permit essentially complete closure of the throat by the
valve members. ~he second valve member 203 has a clearance
passage 218 to accept the fuel spray tube as a sliding fit
therein. The member 203 is generally similar to the second
valve member 26 of Fig. 1 and thus has a first portion 217
having a groove to accept a portion of the fuel spray tube
and the clearance passage 218 is equivalent to the psssage
53 of Fig. 1. Valve overlap similarly to overlap 51 of
Fi8. S is provided as needed.
A fuel needle 220 extends from ehe first valve
member and is aligned with the longitudinal bore 215 of the
fuel spray tube so as to enter the longitudinal bore. The
fuel needle has an inner end 224 threaded in the bore 221
and a screw driver can be inserted in the bore 221 for axial
ad~ustment of the needle relative to the first valve member.
The fuel needle tapers towards an outer end 222 thereof and
thus has a cross-sectional area which varies along~the length
so as to restrict flow of fuèl discharged from the long-
itudinal bore in an amount dependent on relative pcsition of
the first valve member and the inner end of the tube. If
desired the needle can be clear of the bore in the wide
open position, thus providing no restriction to fuel flow,
-24-
~04~)02~
or alternatively the needle can be in the bore even when the
carburetor is fully open.
It can be seen that as the valve members move
apart, the fuel needle 220 is withdrawn from;ithe longitudinal
bore 215 increasing flow of fuel therefrom which discharges
from the inner end face 212 to be atomized by air flow
flowing past the end face. Thus the fuel needle 220 cooper-
ating with the bore 215 and the inner end face 212 serve as
a fuel atomiæing and fuel metering means 223, eliminating
the manifold and more complex atomizing and mixing
means of the previously described embodiments. It is noted
that fuel is discharged in the center of the throat, pro-
viding generally uniform dispersion across the throat.
A further alternative carburetor (not shown) gen-
erally similar to the carburetor 200 has fuel spray tube
secured to the second valve member so as to move therewith,
in swhich case a flexible fuel hose would be secured to the
outer end of the fuel spray tube to move therewith. In this
alternative, the fuel is discharged at a pcint which moves across
the throat, thus producing non-uniform dispersion.
This in all alternative embodiments as above, the
fuel needle cooperates with the bore of the fuel spray tube to
serve as a variable flow restrictor which cooperates with the
fuel jet to vary degree of restriction of the fuel ~et. The
flow restricter is~connected to the valve means so that
relative position of the flow restricter in the jet is related
to volume of air flowing through the carburetor throat. In
all embodiments except the last alternative, the fuèl atomizing
means discharge fuel symmetrically relative to the throat,
-25-
~09~029
and, in some cases, also distrlbutes the fuel diametrically
across the throat prior to discharge.
_26-
