U.S. patent number 3,825,238 [Application Number 05/302,378] was granted by the patent office on 1974-07-23 for overflow type carburettor.
This patent grant is currently assigned to Mikuni Kogyo Kabushiki Kaisha. Invention is credited to Yoshio Nishihara, Isamu Ohashi.
United States Patent |
3,825,238 |
Nishihara , et al. |
July 23, 1974 |
**Please see images for:
( Certificate of Correction ) ** |
OVERFLOW TYPE CARBURETTOR
Abstract
An overflow type carburettor provided with fuel supply valve
which closes the fuel inlet of the carburettor when the fuel supply
pressure is not applied. Further the carburettor may be provided
with a fuel channel which communicates with the lower end of the
fuel feed duct leading to the fuel spray nozzle and the bottom of
the fuel well of the fuel chamber. This carburettor is free from
leaking of fuel even when the stopcock of the fuel supply duct is
left open, and provides stabilized engine operation even when the
vehicle is driven in an extremely inclined position.
Inventors: |
Nishihara; Yoshio (Atsugi,
JA), Ohashi; Isamu (Odahara, JA) |
Assignee: |
Mikuni Kogyo Kabushiki Kaisha
(Tokyo, JA)
|
Family
ID: |
13988697 |
Appl.
No.: |
05/302,378 |
Filed: |
October 30, 1972 |
Foreign Application Priority Data
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Oct 10, 1971 [JA] |
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46-90086 |
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Current U.S.
Class: |
261/36.2;
261/DIG.50; 261/6; 261/66; 261/DIG.67; 261/72.1 |
Current CPC
Class: |
F02M
17/06 (20130101); Y10S 261/50 (20130101); Y10S
261/67 (20130101) |
Current International
Class: |
F02M
17/00 (20060101); F02M 17/06 (20060101); F02m
017/06 () |
Field of
Search: |
;261/DIG.50,36A,66,DIG.67,72 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Miles; Tim R.
Attorney, Agent or Firm: Lada, Parry, Von Gehr, Goldsmith
& Deschamps
Claims
What we claim is:
1. An overflow carburettor comprising, a fuel chamber, an overflow
drain section, an overflow partition separating said fuel chamber
and said overflow drain section, an outlet return means for excess
fuel to a fuel tank from said overflow section, an inlet means to
the fuel chamber connectable to a fuel supply pump and entering the
fuel chamber below the fuel level, a fuel supply valve at the fuel
inlet of the fuel chamber and forming part of the carburettor
structure, said valve being operable to close the fuel inlet when
fuel supply pressure from the pump is not applied.
2. The carburettor as set forth in claim 1, wherein the fuel supply
valve comprises a ball valve, and a resilient means to hold said
ball valve in a closed position.
3. The carburettor as set forth in claim 1, wherein the fuel supply
valve comprises a diaphragm valve and a resilient means to hold
said diaphragm in a closed position.
4. The carburettor as set forth in claim 1, wherein a plurality of
air vents are provided in the fuel chamber, which vents open in the
head space of the fuel chamber at spaced different positions,
whereby irrespective of the inclination of the carburettor at least
one vent is free of fuel.
5. The carburettor as set forth in claim 4, wherein there is
provided a plurality of vents spaced apart, a common duct into
which the plurality of vents join together, an air inlet into which
the duct opens, said duct opening into the air inlet in the
elevational plane containing the longitudinal center line of the
air inlet.
6. The carburettor as set forth in claim 5, wherein there is
provided a central fuel feed duct, a fuel channel communicating
with the lower end of said fuel feed duct with two or more branches
in said channel having inlet ends at opposed points in the bottom
of the fuel chamber, a valve at the end of each of said branches
which valve closes the opening of the branch when the inlet opening
of the branch is raised and exposed to a gaseous phase.
7. The carburettor as set forth in claim 6, wherein each valve is a
ball valve.
8. The carburettor as set forth in claim 7, wherein there are two
branches forming a straight channel both ends of which open at the
bottom of the fuel well.
9. The carburettor as set forth in claim 8 wherein a plurality of
air vents are provided which open in a head space of the fuel
chamber at different spaced positions.
10. The carburettor as set forth in claim 6, wherein the overflow
partition comprises a cylindrical wall surrounding the central fuel
feed duct, a horizontal partition separates the fuel chamber into
an upper section and a lower section, said horizontal partition
being provided with an annular hole surrounding the fuel duct, and
a fuel supply duct extends from the fuel inlet to supply both the
upper section and the lower section.
11. The carburettor as set forth in claim 10, wherein the fuel
channel communicates with the lower end of the fuel feed duct, two
branches of said channel communicate with the lower end of the fuel
chamber and, a ball valve is provided at the fuel chamber end of
each branch.
12. The carburettor as set forth in claim 4, wherein there is
provided a baffleboard in the fuel chamber which baffle extends
under the inlet openings of the air vents.
13. The carburettor as set forth in claim 6, wherein the
baffleboard is provided in the fuel chamber to extend under the
openings of the air vents.
Description
BACKGROUND OF THE INVENTION
This invention relates to an improvement of the overflow type
carburettor in which no float is used but the fuel level is
maintained by means of an overflow partition over which excess fuel
flows to be returned to a fuel tank or fuel pump.
The overflow type carburettor has long been known and has been
mainly used for small size internal combustion engine vehicles such
as scooters, motorcycles and small size agricultural all-purpose
tractors. But the prior art carburettors of this type are
unsatisfactory in the following points.
In the case of motor cycles, the fuel tank is usually positioned
higher than the carburettor, and fuel is freely fed by gravity to
the fuel chamber of the carburettor. Excess fuel overflows the
partition and is returned to the fuel tank by means of a
recirculating pump. A stopcock is provided in the tubing connecting
the fuel tank and the fuel chamber, and this clock must be closed
when the engine is not operated. If the cock is inadvertently left
open when the engine is not operating, the fuel may fill the fuel
chamber, flow out of the carburettor and/or penetrate into the
engine cylinders, since the circulating pump is not operated then,
either.
In the case where the fuel tank is positioned beneath the engine
and fuel is fed into the fuel chamber by a feed pump, if the
stopcock is left open when the engine is not operating, the fuel
chamber will empty since the fuel stored therein gradually returns
to the tank, and this causes trouble when operation of the engine
is started again.
The overflow type carburettors of the prior art do not provide
stabilized engine operation when the vehicle is extremely inclined.
If a vehicle is inclined more than 30.degree., the prior art
overflow carburettor usually does not work well, because the fuel
level in the fuel chamber of the carburettor falls and fuel is not
fed to the engine smoothly.
In the prior art overflow carburettor, when fuel is supplied to the
fuel chamber by means of a supply pump there is considerable flow
of fuel in the fuel chamber, which is sometimes swirling. This
stirring effect influences the fuel feed to the fuel nozzle, and
thus the feed of the fuel to be sprayed in the fuel-air mixing
chamber often fluctuates and thus smooth operation of the engine is
impaired.
As an overflow carburettor has no float in the fuel chamber, and
therefore, the fuel in the fuel chamber is shaken harder than a
float carburettor and the shaken fuel spatters and often penetrates
the air vent to clog it.
The object of this invention is to provide a novel overflow type
carburettor which is free from the above-mentioned defects and is
more versatile than the overflow carburettor of the prior art and
thus can be used for vehicles which are driven in an extremely
inclined state such as snowmobile.
SUMMARY OF THE INVENTION
In the general aspect of this invention, an overflow type
carburettor provided with a fuel supply valve which closes the fuel
inlet of the fuel chamber (fuel well) of the carburettor when no
fuel supply pressure is applied is provided. With this, the fuel
does not drain from the carburettor and the fuel chamber is never
emptied even when the engine is not operated.
In another aspect of this invention, an overflow type carburettor
in which a plurality of air vents are provided in the head space of
the fuel chamber is provided. No prior art overflow carburettor is
provided with a plurality of air vents in the fuel chamber. Said
air vents open in the head space of the fuel chamber at different
positions. Thus, communication between the head space of the fuel
chamber and the atmosphere is always maintained by some vent or
vents which are exposed to the gaseous phase in whichever direction
the carburettor is inclined.
In still another aspect of this invention, an overflow type
carburettor in which a fuel channel which communicates with the
lower end of the fuel feed duct leading to the fuel spray nozzle
and the bottom of the fuel well of the fuel chamber. The fuel
channel has two or more branches, the end of each of which forms an
opening to the fuel well provided with a valve, which closes the
opening when the fuel channel lies horizontal and closes the
opening when the carburettor is inclined and the opening is raised
high. Thus the carburettor can maintain some fuel head and
introduction of air to the fuel feed duct is prevented even if the
carburettor (vehicle) is deeply inclined.
In still another aspect of this invention, an overflow type
carburettor provided with said fuel channel which further has as
the overflow partition, a cylindrical wall surrounding the fuel
feed duct is provided. The fuel well formed by the cylindrical wall
is separated by a horizontal partition into an upper section and a
lower section, and an annular hole surrounding the fuel feed duct
is provided in the horizontal partition so that the upper section
and the lower section communicate with each other. The carburettor
is practically operable in whichever direction the vehicle may be
inclined.
In still another aspect of this invention, an overflow type
carburettor, in which a baffleboard which extends under the opening
of the air vents, is provided. This further contributes to
stabilized engine operation.
The carburettor of this invention can be easily manufactured by
those skilled in the art guided by the attached drawings, and
therefore there is no necessity to explain the manufacture
thereof.
BRIEF EXPLANATION OF THE ATTACHED DRAWINGS
FIG. 1 is a longitudinal elevational cross-sectional view of an
embodiment of the carburettor of this invention.
FIG. 2 is a traverse elevational cross-sectional view of the
carburettor of FIG. 1 along line A -- A in FIG. 1.
FIG. 3 is a plan view of the carburettor of FIG. 1, showing the
connection with the engine.
FIG. 4 is a traverse elevational cross-sectional view of the fuel
chamber of another embodiment of the carburettor of this
invention.
FIG. 5 is a cross-sectional view of another example of the fuel
supply valve used in the carburettor of this invention.
DETAILED DESCRIPTION OF THE INVENTION
A preferred embodiment of this invention is shown in FIGS. 1
through 3. In these drawings, member 1 is a fuel-air mixing
channel, 2 is a throttle valve for fuel-air mixture, 3 is a fuel
nozzle, 4 is an air inlet, 5 is a fuel-air mixing chamber, 6 is a
fuel chamber which is positioned on the underside of the fuel air
mixing chamber. The fuel chamber is separated by an overflow
partition 7 into a well or pool for fuel 8 and an overflow drain
section 9. In the fuel well 8 are provided, a fuel supply valve 10
at the bottom and a fuel feed duct 11 at the center. In the
overflow drain section 9 are provided, a drain outlet 12 at the
bottom and a baffleboard 13 at the top.
The fuel supply valve 10 may be a ball valve for example. In FIG.
1, the valve comprises a ball 16 which closes the opening of fuel
supply tubing 14 by virtue of the resilient force of a spring 15
supported by a suitable supporter 17. The valve closes the fuel
inlet when no pumping force (fuel supply pressure) is applied to
the fuel supplied. (The carburettor of this invention is used for
an engine provided with a fuel supply pump.) The valve may be
surrounded by a filter net or a flow-regulating member made of a
porous material 20.
An alternative structure of the fuel supply valve is shown in FIG.
5. This is a diaphragm valve, and this is installed between the
fuel chamber of the carburettor and the fuel supply pump. In FIG.
5, member 51 is a valve body, 52 is a diaphragm, 53 is an
atmospheric pressure chamber, 54 is a fuel chamber of the valve, 55
is a spring, 56 is a stopper attached to the diaphragm 52, 57 is a
passage communicating with the fuel supply pump, 58 is a fuel feed
duct communicating with the fuel chamber of the carburettor, and 59
is a through hole. This valve functions as follows.
When the engine is not operating, that is, when the fuel supply
pump is not working, the diaphragm 52 is pressed by the spring 55
and the stopper 56 closes the fuel passage. But when the engine is
in operation, the pressure of the fuel opens the stopper and the
fuel flows into the fuel chamber of the carburettor. It is
advantageous that a through hole 59 in the atmospheric pressure
chamber 53 is arranged so as to communicate with the engine
manifold. By this the atmospheric chamber is maintained at
sub-atmospheric pressure and this will make the diaphram more
responsive.
The fuel feed duct 11 communicates with a spray nozzle 3 at the
upper end thereof and it contains a jet orifice 18 therein. The
fuel feed duct 11 communicates with the fuel well 8 by a horizontal
fuel channel 19 which runs beneath the bottom of the fuel well 11
and opens to the well at both ends 21 and 22 thereof as shown in
FIG. 2. At the openings 21 and 22 are provided valve chambers 23
and 24, in which a free ball valve 25 or 26 is placed
respectively.
At the ceiling of the fuel chamber in the shade of the baffleboard
13, air vents 27 and 28 are provided. They penetrate through the
wall of the fuel-air mixing chamber and open in the fuel-air mixing
channel. In FIGS. 1 and 2, the two vents join together and open in
the mixing channel by a common opening 29 on the center line of the
mixing channel. But they may have independent openings.
The fuel feed duct 11 and the overflow drain outlet 12 are
positioned on the longitudinal center line and thus the carburettor
is installed in the engine so that inclination of the engine occurs
with this longitudinal center line as the axis of rotation. In the
case of a wheeled vehicle for instance, the carburettor is
installed in the engine so that this longitidunal center line is in
alignment with the longitudinal center line of the vehicle. FIG. 3
shows such an arrangement of the carburettor, a fuel tank and a
fuel supply pump. In this drawing, member 30 drawn in broken line
is an engine manifold, 31 is a fuel tank and 32 is a fuel supply
pump, 33 is a fuel supply pipe, and 34 is a fuel recirculation
duct. In FIG. 3, fuel chamber 6, overflow partition 7, fuel supply
valve 10, fuel feed duct 11, fuel channel 19, valve chambers 23 and
24, ball valves 25 and 26 are shown in broken lines, too.
A small size vehicle such as motorcycle is often titled or tipped
extremely in the direction perpendicular to the direction of the
motion of the vehicle. Especially in the case of a snowmobile, it
is often driven tippped to the side almost 90.degree. in order to
remove the snow piled thereon. The carburettor of this invention
can be used for such a vehicle that is driven in such an extremely
inclined position.
Again refer to FIG. 2, and suppose that the carburettor of this
embodiment is installed in a vehicle in the above-explained
fashion. If the vehicle is tipped to the right with respect to FIG.
2, the left side inlet 21 of the fuel channel 19 is raised high and
is exposed to the gaseous phase or the head space in an extreme
case. However, the inlet of the fuel channel is closed by the ball
valve 25 by virture of gravity, and, therefore, neither excess fuel
is supplied to the spray nozzle nor only air is fed to the nozzle,
but fuel continues to be almost normally supplied through the right
side inlet 22.
As the overflow drain outlet 12 is positioned on the axial line of
inclination and air vents are provided on both sides of the axial
line, the fuel level determined by the position of the drain outlet
12 is secured and the head space is maintained at the atmospheric
pressure whether the vehicle is inclined to the right or to the
left. That is, with this carburettor, the engine can be almost
normally operated even when the vehicle is inclined or tipped,
since fuel head is maintained at an operating level all the time,
although it may be lower or higher than the normal level as
determined when the engine is level. It will be noted that the fuel
level is lowered as the vehicle is inclined to some extent, but the
level is raised again as the inclination approaches 90.degree. and
at 90.degree. the fuel level is a little higher than at the normal
position.
If a vehicle in which the carburettor of this invention is to be
installed is a vehicle, which may be inclined not in a definite
direction, such as an agricultural vehicle, and if the carburettor
can be made on a little larger scale, it will be advantageous to
construct the fuel chamber as shown in FIG. 4.
In this embodiment, the overflow partition is not a straight wall
as 7 in FIGS. 1 and 2 but is a cylindrical wall surrounding the
fuel feed duct 11 as shown at 41 in FIG. 4. Thus the overflow drain
section is provided outside of the cylindrical overflow partition
as shown at 9 in FIG. 4. Usually a plurality of drain outlets 12
are provided in the overflow drain section 9 but they are not
necessarily positioned on the longitudinal central line. The fuel
well 8 is separated into an upper section 8" and a lower section 8'
by a horizontal partition 42 and an annular hole 43 is provided
around the fuel feed duct 11. Member 44 is a fuel supply duct
communicating with the fuel tank, and there is a small through-hole
45 open in the lower section 8' and there is another small
through-hole 46 open in the upper section 8". Of course, although
it is not shown in FIG. 4, a fuel supply valve such as shown in
FIG. 1 or FIG. 4 is provided.
In the carburettor of FIG. 4, the fuel channel 19 has more than two
branches. Thus in whichever direction a vehicle is inclined, the
ball valve that is positioned at the highest level closes the
corresponding branch of the fuel channel so as to prevent
introduction of air into the fuel duct 11.
When this carburettor is inclined, the fuel surface in the lower
section 8' of the fuel well 8 is maintained at the level determined
by the lowest edge 47 of the annular hole 43, in whichever
direction the carburettor may be inclined.
Another aspect of this invention is the provision of a baffleboard
under the air vents as shown in FIG. 1 and FIG. 2. The baffleboard
prevents penetration into the air vents of fuel spattered by
agitation of fuel caused by vibration of the engine and jolting of
the vehicle.
The arrangement of the carburettor and the fuel mixing chamber is
not limited to that represented by FIGS. 1 through 3. It is of
course possible to arrange so that the orientation of the fuel
channel 19 and air vents is perpendicular to that of the
longitudinal axis of the fuel-air mixing chamber.
Although the invention has been explained with reference to a few
specific embodiments which include many aspects of this invention
in combination, it must be understood that each aspect has an
inventive merit per se.
* * * * *