U.S. patent application number 10/813202 was filed with the patent office on 2005-01-27 for intake air and carburetor heating arrangement for v-twin engines.
Invention is credited to Brower, David R., Davis, Steven T., Dopke, Russell J., Koehler, Scot A., Stenz, Gary L., Sterr, Randall E., Wetor, Clyde R..
Application Number | 20050016474 10/813202 |
Document ID | / |
Family ID | 34067971 |
Filed Date | 2005-01-27 |
United States Patent
Application |
20050016474 |
Kind Code |
A1 |
Dopke, Russell J. ; et
al. |
January 27, 2005 |
Intake air and carburetor heating arrangement for V-twin
engines
Abstract
A V-twin engine having a crankcase and a pair of cylinders
defining a V-space therebetween, wherein the V-space is
substantially enclosed, and a carburetor is positioned within the
V-space. An intake air preheating arrangement supplies heated
intake air to the carburetor, and a carburetor heating arrangement
heats the V-space and the carburetor which is positioned within the
V-space. Each of the foregoing arrangements, used separately or in
combination within one another, aids in preventing "freeze-up" of
the carburetor during running of the engine in a cold
environment.
Inventors: |
Dopke, Russell J.; (Elkhart
Lake, WI) ; Brower, David R.; (Beaver Dam, WI)
; Koehler, Scot A.; (Appleton, WI) ; Stenz, Gary
L.; (Mt. Calvary, WI) ; Wetor, Clyde R.;
(Cascade, WI) ; Davis, Steven T.; (Green Bay,
WI) ; Sterr, Randall E.; (North Fond du Lac,
WI) |
Correspondence
Address: |
BAKER & DANIELS
111 E. WAYNE STREET
SUITE 800
FORT WAYNE
IN
46802
|
Family ID: |
34067971 |
Appl. No.: |
10/813202 |
Filed: |
March 30, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60461266 |
Apr 8, 2003 |
|
|
|
Current U.S.
Class: |
123/54.4 ;
123/556 |
Current CPC
Class: |
F02M 15/02 20130101;
F02M 31/08 20130101; Y02T 10/12 20130101; F02M 35/10137 20130101;
F02B 75/221 20130101; F02B 2075/1808 20130101; Y02T 10/126
20130101; F02M 35/10196 20130101; F01N 5/02 20130101; F01N 1/00
20130101; F02M 35/10268 20130101; F02B 63/02 20130101; Y02T 10/16
20130101; F01N 2340/04 20130101; F02B 75/22 20130101; F02M 1/10
20130101; F02M 35/1017 20130101 |
Class at
Publication: |
123/054.4 ;
123/556 |
International
Class: |
F02M 031/04 |
Claims
What is claimed is:
1. An internal combustion engine, comprising: a crankcase having a
crankshaft rotatably disposed therein; a blower driven by said
crankshaft to generate an air stream; a pair of first and second
cylinders connected to said crankcase; an air intake system in
fluid communication with said cylinders; and an intake air heating
arrangement, comprising: a heater box disposed proximate said first
cylinder, an interior of said heater box in airflow communication
with said air stream; and a conduit in airflow communication with
said heater box and with said air intake system, whereby air from
said air stream is heated within said heater box and is conducted
through said conduit into said intake system of said engine.
2. The engine of claim 1, wherein said first and second cylinders
are disposed at an angle with respect to one another to define a
V-space therebetween.
3. The engine of claim 2, wherein said air intake system includes a
carburetor, said carburetor disposed within said V-space.
4. The engine of claim 3, wherein said air intake system further
includes an air cleaner, said air cleaner connected to said
carburetor and in airflow communication with said conduit.
5. The engine of claim 1, wherein said heater box is connected to
said first cylinder, said heater box disposed externally of said
V-space.
6. The engine of claim 1, further comprising a muffler in exhaust
flow communication with said first cylinder and disposed proximate
said heater box, whereby air from said air stream is heated within
said heater box by heat from said muffler.
7. The engine of claim 1, further comprising a cylinder wrap at
least partially enclosing said first cylinder, said first cylinder
and said cylinder wrap defining an air passage in airflow
communication with said heater box through which said air stream is
conducted.
8. The engine of claim 1, wherein said crankshaft is disposed
horizontally.
9. A method of heating intake air in an engine which includes a
pair of cylinders disposed at an angle with respect to one another
to define a V-space therebetween, said method comprising the steps
of: generating an air stream; conducting the air stream proximate a
hot portion of the engine to heat air within the air stream;
capturing heated air from the air stream in a heater box; and
conducting heated air from the heater box to an intake system of
the engine.
10. The method of claim 9, wherein said first conducting step
comprises conducting the air stream proximate at least one of a
cylinder and a muffler of the engine.
11. The method of claim 9, wherein said first conducting step
further includes drawing heated air into the air stream from the
vicinity of a muffler of the engine.
12. The method of claim 9, wherein said second conducting step
comprises conducting heated air from the heater box to a carburetor
disposed within said V-space.
13. An internal combustion engine, comprising: a crankcase having a
crankshaft rotatably disposed therein; a blower driven by said
crankshaft to generate an air stream; a pair of cylinders connected
to said crankcase, said cylinders disposed at an angle with respect
to one another to define a V-space therebetween, said V-space
substantially enclosed by portions of said engine; a carburetor
disposed within said V-space; and a duct assembly disposed
proximate at least one of said cylinders and in airflow
communication with said air stream and with said V-space, whereby
air in said air stream is heated within said duct assembly and is
conducted to said V-space to heat said carburetor.
14. The engine of claim 13, further comprising a muffler in exhaust
flow communication with at least one of said cylinders and disposed
proximate said duct assembly, said duct assembly further including
an inlet disposed adjacent said muffler whereby heated air from the
vicinity of said muffler is drawn by said air stream into said duct
assembly.
15. The engine of claim 13, further comprising a fuel tank disposed
proximate an upper portion of said cylinders and a shroud disposed
proximate a front side of said cylinders, said duct assembly
including a wall disposed proximate a rear side of said cylinders,
said fuel tank, shroud, and wall cooperating with one another to
substantially enclose said V-space.
16. The engine of claim 13, wherein said duct assembly includes a
cylinder wrap at least partially enclosing said at least one
cylinder, said at least one cylinder and said cylinder wrap
defining an air passage in airflow communication with said V-space
through which said air stream is conducted.
17. The engine of claim 13, wherein said crankshaft is disposed
horizontally.
18. A method of heating a carburetor of an engine having a pair of
cylinders which are disposed at an angle with respect to one
another, said method comprising the steps of: generating an air
stream; conducting the air stream proximate a hot portion of the
engine to heat air within the air stream; and conducting heated air
from the air stream into a substantially enclosed V-space defined
between the cylinders, in which the carburetor is positioned.
19. The method of claim 18, wherein said first conducting step
comprises conducting the air stream proximate at least one of a
cylinder and a muffler of the engine.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit under Title 35, U.S.C.
.sctn.119(e) of U.S. Provisional Patent Application Ser. No.
60/461,266, entitled INTAKE AIR AND CARBURETOR HEATING ARRANGEMENT
FOR V-TWIN ENGINES, filed on Apr. 8, 2003.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This invention relates to small internal combustion engines
of the type commonly used in lawn mowers, lawn and garden tractors,
snow throwers, other working implements, or in sport vehicles. In
particular, the present invention relates to heating the intake air
and the carburetors of such engines.
[0004] 2. Description of the Related Art
[0005] Small internal combustion engines typically include a
carburetor which mixes ambient atmospheric air with liquid fuel to
provide an air/fuel mixture for combustion within the engine.
Usually, the intake air is drawn from the atmosphere through an air
filter to remove dirt and other debris from the intake air before
the intake air enters the carburetor. A potential problem in such
arrangements is that when the engine is used in a cold environment,
such as in a snow thrower application, the intake air is often cold
and moist, and may include snow. The moisture in the cold intake
air may freeze and accumulate within the carburetor, causing the
carburetor to "freeze up" and inhibit good engine performance.
[0006] It is known to provide small single cylinder engines with
duct arrangements which are disposed near the engine muffler. In
operation, the duct is heated by radiant heat from the muffler
during running of the engine. Air is drawn through the duct by the
carburetor, and the air is heated before it enters the carburetor.
However, such ducts are typically formed from two or more separate
components which fit together and cooperate to define the duct, and
therefore, multiple parts are required.
[0007] A further problem in many small engines is that the
carburetor itself is often positioned in a manner in which it is
exposed to the cold environment, potentially leading to carburetor
"freeze up". For example, the carburetor may be positioned on one
side of the engine in such a manner that at least a portion of the
body of the carburetor is disposed externally of the engine
enclosure structure and is exposed to the environment.
[0008] What is needed is an intake air and/or carburetor heating
arrangement for small internal combustion engines which is an
improvement over the foregoing.
[0009] Also, intake air and/or carburetor heating arrangements
which are adapted for use with V-twin engines are not known, thus,
a further need is for an intake air and/or carburetor heating
arrangement for a V-twin engine.
SUMMARY OF THE INVENTION
[0010] The present invention provides an apparatus and method for
heating the intake air which is drawn into the carburetor of a
V-twin engine, as well as an apparatus and method for heating the
carburetor of a V-twin engine.
[0011] In a V-twin engine having a crankcase and a pair of
cylinders attached to the crankcase and defining a V-space between
the cylinders, a heater box is attached to one of the cylinders
proximate the exhaust port of the cylinder. The heater box is
connected to the air cleaner cavity of the engine via an insulated
conduit. During operation of the engine, intake air is drawn from
externally of the engine through an opening in the cylinder wrap
which surrounds the cylinder, and the air is heated as it passes
near the exhaust port of the cylinder and into the heater box.
Additionally, a portion of the cooling air from the flywheel/blower
of the engine is directed between the cylinder and the cylinder
wrap, around the exhaust port of the cylinder, and into the heater
box. The air which enters the heater box is heated within the
heater box, and then passes through the insulated conduit into the
air cleaner cavity and thereafter into the carburetor. Thus, intake
air, drawn from the foregoing two sources, is heated before it is
drawn through the carburetor and into the engine.
[0012] Additionally, a structure for heating the carburetor itself
is provided. The carburetor is disposed in the V-space between the
engine cylinders, and the V-space is substantially enclosed by the
engine shroud, fuel tank, and a wall portion of a duct structure.
Air from the flywheel of the engine passes between a cylinder wrap
and a cylinder of the engine, and through an opening in the
cylinder wrap into the duct structure. Passage of the air through
the opening in the duct structure creates a suction or "venturi
effect" with which draws an additional portion of heated air into
the duct structure from an air space between the muffler and the
cylinder wrap. The heated air passes into the V-space to warm the
V-space, thus warming the carburetor which is positioned within the
V-space.
[0013] Advantageously, the foregoing arrangement provides an
apparatus and method for heating the intake air which is drawn into
the engine to prevent "freeze-up" of the carburetor when the engine
is used in a cold environment. Additionally, the foregoing
arrangement provides an apparatus and method of heating the
carburetor itself to further prevent "freeze-up" of the carburetor,
in which warmed air is directed to a substantially enclosed V-space
between the engine cylinders in which the carburetor is
positioned.
[0014] In one form thereof, the present invention provides an
internal combustion engine, including a crankcase having a
crankshaft rotatably disposed therein; a blower driven by the
crankshaft to generate an air stream; a pair of first and second
cylinders connected to the crankcase; an air intake system in fluid
communication with the cylinders; and an intake air heating
arrangement, including a heater box disposed proximate the first
cylinder, an interior of the heater box in airflow communication
with the air stream; and a conduit in airflow communication with
the heater box and with the air intake system, whereby air from the
air stream is heated within the heater box and is conducted through
the conduit into the intake system of the engine.
[0015] In another form thereof, the present invention provides a
method of heating intake air in an engine which includes a pair of
cylinders disposed at an angle with respect to one another to
define a V-space therebetween, the method including the steps of
generating an air stream; conducting the air stream proximate a hot
portion of the engine to heat air within the air stream; capturing
heated air from the air stream in a heater box; and conducting
heated air from the heater box to an intake system of the
engine.
[0016] In another form thereof, the present invention provides an
internal combustion engine, including a crankcase having a
crankshaft rotatably disposed therein; a blower driven by the
crankshaft to generate an air stream; a pair of cylinders connected
to the crankcase, the cylinders disposed at an angle with respect
to one another to define a V-space therebetween, the V-space
substantially enclosed by portions of the engine; a carburetor
disposed within the V-space; and a duct assembly disposed proximate
at least one of the cylinders and in airflow communication with the
air stream and with the V-space, whereby air in the air stream is
heated within the duct assembly and is conducted to the V-space to
heat the carburetor.
[0017] In another form thereof, the present invention provides a
method of heating a carburetor of an engine having a pair of
cylinders which are disposed at an angle with respect to one
another, the method including the steps of generating an air
stream; conducting the air stream proximate a hot portion of the
engine to heat air within the air stream; and conducting heated air
from the air stream into a substantially enclosed V-space defined
between the cylinders, in which the carburetor is positioned.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] The above-mentioned and other features and advantages of
this invention, and the manner of attaining them, will become more
apparent and the invention itself will be better understood by
reference to the following description of embodiments of the
invention taken in conjunction with the accompanying drawings,
wherein:
[0019] FIG. 1 is a front perspective view of a horizontal
crankshaft, V-twin engine including intake air and carburetor
heating arrangements in accordance with the present invention;
[0020] FIG. 2 is a perspective cut-away view of a front portion of
the engine of FIG. 1, showing the heater box, conduit, and air
cleaner cavity of the intake air heating arrangement;
[0021] FIG. 3 is a fragmentary perspective view of an outside
portion of one of the engine cylinders, showing the exhaust port,
and the heater box of the intake air heating arrangement;
[0022] FIG. 4 is a fragmentary perspective view of an outside
portion of one of the engine cylinders, shown with the cylinder
wrap removed; and
[0023] FIG. 5 is a top schematic view of the engine of FIG. 1,
looking directly down one of the cylinders, showing the carburetor
heating arrangement in accordance with the present invention,
wherein a portion of the air cleaner cavity is shown to the left of
line L.sub.1-L.sub.1, and is disposed above the flywheel/blower of
the engine.
[0024] Corresponding reference characters indicate corresponding
parts throughout the several views. The exemplifications set out
herein illustrates preferred embodiments of the invention, and such
exemplifications are not to be construed as limiting the scope of
the invention any manner.
DETAILED DESCRIPTION
[0025] Referring first to FIG. 1, a small internal combustion
engine 20 is shown as a horizontal crankshaft V-twin engine, such
as the engine which is described in detail in U.S. patent
application Ser. No. 10/409,262, entitled INTERNAL COMBUSTION
ENGINE, filed on Apr. 8, 2003 (Attorney File Ref.: TEL0633-02),
assigned to the assignee of the present invention, the disclosure
of which is expressly incorporated herein by reference. Although
engine 20 is shown as a horizontal crankshaft V-twin engine which
may advantageously be used in a snow thrower, for example, the
carburetor and intake air heating concepts of the present invention
also could be embodied in vertical crankshaft V-twin engines.
[0026] Engine 20 generally includes crankcase 22 having a pair of
engine cylinders 24 mounted to crankcase 22 in the manner described
in the above-incorporated U.S. patent application Ser. No.
10/409,262. A horizontally disposed crankshaft 26 is rotatably
carried within crankcase 22, and is coupled to a pair of
conventional piston/connecting rod assemblies (not shown), one
corresponding to each engine cylinder. Engine 20 also includes
intake air heating arrangement 28 and carburetor heating
arrangement 30, which are discussed in detail below.
[0027] Engine cover or shroud 32 is connected to crankcase 22, and
covers at least a portion of each of crankcase 22 and cylinders 24.
Shroud 32 may be formed of metal, or from an injection molded or
vacuum-formed plastic material, for example. Cylinder wraps 34,
typically made of a relatively thin sheet metal, are also connected
to crankcase 22 and cylinders 24, and closely surround cylinders 24
for directing cooling air around cylinders 24 as discussed below.
Fuel tank 36 is mounted via brackets 38 to the upper ends of
cylinder wraps 34. Air inlet screen 40 is mounted to shroud 32, and
covers an opening in shroud 32 through which intake air is drawn
during running of engine 20 by rotation of flywheel/blower 42 (FIG.
5), which is attached to an end of crankshaft 26 which extends
externally of crankcase 22, and includes a plurality of fins 43.
Specifically, rotation of flywheel/blower 42 draws intake air
through louvers 44 in air inlet screen 40 and into an area defined
between crankcase 22 and shroud 32.
[0028] Referring to FIGS. 2 and 5, cylinders 24 are disposed at an
angle with respect to one another to define V-space 46
therebetween. Typically, cylinders 24 are disposed at a 90.degree.
angle with respect to one another. Shroud 32 closes the front side
of V-space between cylinders 24, and includes air cleaner cavity 48
which optionally includes an air cleaner element 50 therein.
Further details regarding intake air cleaner cavity 48 and air
cleaner element 50 are discussed in U.S. patent application Ser.
No. 10/408,882, entitled AIR CLEANER ASSEMBLY FOR INTERNAL
COMBUSTION ENGINES, filed on Apr. 8, 2003 (Attorney File Ref.:
TEL0681), assigned to the assignee of the present invention, the
disclosure of which is expressly incorporated herein by
reference.
[0029] In FIG. 5, engine 20 is shown from a top view, with engine
20 rotated clockwise about 45.degree. such that the left cylinder
24 in FIG. 5 is disposed vertically and the right cylinder in FIG.
5 is disposed horizontally. A portion of air cleaner cavity 48 and
air cleaner element 50 are shown to the left of line
L.sub.1-L.sub.1 of FIG. 5, which are disposed above flywheel/blower
42 and air inlet screen 40. To the right of line L.sub.1-L.sub.1 in
FIG. 5, air cleaner cavity 48 and air cleaner element 50 are
omitted and flywheel/blower 42 is shown, which is disposed beneath
air cleaner cavity 48 and air cleaner element 50, and a portion of
air inlet screen 40 is cut away to show pulley 51 of the recoil
starter assembly of engine 20.
[0030] As shown in FIG. 5, carburetor 52 is disposed within V-space
46. Carburetor 52 is connected to shroud 32 and includes carburetor
body 54 and fuel bowl 56. Throat 58 is disposed through carburetor
body 54 and includes an inlet end in communication with air cleaner
cavity 48. Choke valve 60 and throttle valve 62 are rotatably
disposed within throat 58 of carburetor 52 on opposite sides of
venturi region 64 of throat 58. Fuel bowl 56 includes a quantity of
fuel which is drawn upwardly into throat 58 during running of
engine 20 for mixing with intake air at venturi region 64. Outlet
end 66 of carburetor 52 is connected to intake manifold 68, which
includes a pair of intake pipes 70, each connected to a respective
intake port 72 of cylinders 24. Intake manifold 68, intake pipes
70, and intake ports 72 of cylinders 24 are all disposed within
V-space 46. Although engine 20 is described herein as including a
carburetor 52, the intake air heating arrangement of the present
invention could also be used to heat the intake air of an engine
which includes a fuel injection system.
[0031] Exhaust ports 74 of cylinders 24 are disposed on a side of
cylinders 24 opposite intake ports 72, and face outwardly of
V-space 46. Thus, heat from exhaust ports 74 is readily dispersed
outwardly of engine 20 to the sides of engine 20.
[0032] Referring to FIG. 2, intake air heating arrangement 28 will
now be described. Heater box 80 is connected to one of cylinders 24
proximate exhaust port 74 of the cylinder 24. Heater box 80 may be
formed of a suitable metal, such as sheet metal or stainless steel,
for example. Heater box 80 generally includes inlet 82 (FIGS. 3 and
4), and outlet 84 which is shown in FIG. 2 in the form of a
cylindrical coupling.
[0033] Air cleaner cavity 48 of shroud 32 includes an inlet opening
86 formed in a wall thereof. Inlet opening 86 may be formed as a
knock-out portion within the wall of air cleaner cavity 48, in
which the knock-out portion is removed from the wall of air cleaner
cavity 48 during assembly of engine 20 if engine 20 is to be
equipped with air heating arrangement 28. Alternatively, if engine
20 is not to be equipped with air heating arrangement 28, the
knock-out portion may be left in place. Conduit 88 includes first
end 90 connected to outlet 84 of heater box 80, and second end 92
connected to inlet opening 86 of air cleaner cavity 48 to thereby
fluidly communicate heater box 80 with air cleaner cavity 48.
Conduit 88 is made of a flexible material such as rubber, which
material is also resistant to heat transfer such that conduit 88 is
insulated, as discussed further below. Alternatively, the
construction of conduit 88 may vary. For example, conduit 88 may be
a passage integrally formed within shroud 32, or may take the form
of a separate duct piece attached to shroud 32 and defining a
passage between the duct member and shroud 32.
[0034] Referring to FIGS. 3 and 4, exhaust port 74 of cylinder 24
includes adapter 94 mounted to exhaust port 74 by suitable
fasteners. Adapter 94 includes first flange 96 mounted to exhaust
port 74 of cylinder 24, and an opposite second flange 98 to which
muffler 100 (FIGS. 1 and 5) may be attached. Cylinder wrap 34
surrounds cylinder 24 and is positioned closely adjacent cooling
fins 102 of cylinder 24. In FIG. 4, cylinder wrap 34 has been
removed for clarity. Referring to FIG. 3, cylinder wrap 34 includes
an opening 104 through which exhaust outlet adapter 94 extends,
with opening 104 having a larger diameter than exhaust outlet
adapter 94 to define a gap 106 between opening 104 and exhaust
outlet adapter 94.
[0035] As shown in FIGS. 3 and 4, the space between cylinder wrap
34 and the outer wall of cylinder 24 defines an air passage 108,
through which air is directed by the rotating of flywheel/blower 42
during running of engine 20. Air passes along arrows A.sub.1
through air passage 108, where same is heated by radiant heat from
cylinder 24 and from exhaust port 74 and adapter 94 before entering
inlet 82 of heater box 80. Additionally, as shown in FIG. 3, air is
drawn by the passage of air along arrows AI in the direction of
arrows A.sub.2 from externally of engine 20 through gap 106 between
opening 104 in cylinder wrap 34 and exhaust port adapter 94. The
air corresponding to arrows A.sub.2 is heated from exhaust port
adapter 94 and muffler 100 before entering inlet 82 of heater box
80. In this manner, heated air enters heater box 80 from the
foregoing two sources along arrows A.sub.1 and A.sub.2. Further,
heater box 80 is itself heated by conduction from cylinder 24
during running of engine 20, such that air within heater box 80 is
further heated.
[0036] Referring to FIG. 2, air within heater box 80 passes through
conduit 88 into air cleaner cavity 48. Conduit 88 is made of an
insulating material to prevent loss of heat from the air
therewithin to the outside of engine 20, such that the air within
conduit 88 retains its heat as same passes from heater box 80 into
air cleaner cavity 48. Heated air within air cleaner cavity 48 then
passes through filter element 50 (FIG. 5) to remove particulate
matter from the air. Alternatively, air cleaner cavity 48 may lack
filter element 50. The heated air thereafter passes into the inlet
end of carburetor 52, as shown in FIG. 5, for mixing with fuel at
venturi region 64 of throat 58 to provide an air/fuel mixture for
combustion within engine 20. In this manner, the intake air of
engine 20 is heated before same enters carburetor 52, preventing
"freeze-up" of carburetor 52. Also, if desired, engine 20 may
include a pair of heater boxes 80, one connected to each cylinder
24, and a pair of conduits for directing air from the heater boxes
into air cleaner cavity 48.
[0037] Referring to FIG. 5, carburetor heating arrangement 30 will
now be described. Duct assembly 120 generally includes duct 122,
wall 124, and cylinder wrap 34. Wall 124 of duct assembly 120 is
connected to both cylinders 24 to substantially enclose the rear
side of V-space 46 which is disposed opposite shroud 32.
Additionally, fuel tank 36, shown in phantom lines in FIG. 5, is
connected via brackets 38, as shown in FIG. 1, to the upper
portions of cylinders 24. In this manner, shroud 32, wall 124, and
fuel tank 36 cooperate to substantially enclose V-space 46 between
cylinders 24, such that airflow into and out of V-space 46 is
controlled in the manner set forth below.
[0038] Cylinder wrap 34 includes an outlet 126 in the form of a
section of cylinder wrap 34 which is separated from the remainder
of cylinder wrap 34, and which opens into duct 122. Duct 122
includes a first end 128 in communication with air space 130
between muffler 100 and cylinder wrap 34, and a second end 132 in
communication with V-space 46.
[0039] In operation, air is directed from flywheel/blower 42
between cylinder wrap 34 and cylinder 24 along arrows A.sub.3, and
is heated from cylinder 24 A portion of this heated air passes
through outlet 126 of cylinder wrap 34 into duct 122 along the
direction of arrow A.sub.4. The forced passage of air through
outlet 126 creates a low pressure area within duct 122 behind
outlet 126, i.e., a "venturi" effect, at first end 128 of duct 122,
thereby drawing additional heated air from air space 130 through
duct 122 along arrow A.sub.5. Heated air from air space 130
combines with the heated air passing through outlet 126 of cylinder
wrap 34, and this combined heated air passes through duct 122 along
arrow A.sub.6 to second end 132 of duct 122 and is discharged into
V-space 46. In this manner, the substantially enclosed V-space 46
is heated by a continuous input of heated air into V-space. Heating
of V-space 46 in turn heats carburetor 52, which is positioned
within V-space 46. Heating of carburetor 52 aids in preventing
"freeze-up" of carburetor 52 during running of engine 20.
[0040] After heating carburetor 52, spent heating air within
V-space 46 may exit V-space 46 by passing through openings within
V-space 46, such as gaps between fuel tank 36 and shroud 32 or
between fuel tank 36 and wall 124 of duct 122, for example.
Alternatively, a dedicated duct structure or conduit (not shown)
may be used to vent the spent heading air from V-space 46.
[0041] Advantageously therefor, intake air preheating arrangement
28, including heater box 80 and conduit 88, supplies heated intake
air to carburetor 52, and carburetor heating arrangement 30 heats
V-space 46 and carburetor 52 which is positioned within V-space.
Each of the foregoing arrangements, used separately or in
combination with one another, aids in preventing "freeze-up" of
carburetor 52 during running of engine 20 in a cold
environment.
[0042] While this invention has been described as having a
preferred design, the present invention can be further modified
within the spirit and scope of this disclosure. This application is
therefore intended to cover any variations, uses, or adaptations of
the invention using its general principles. Further, this
application is intended to cover such departures from the present
disclosure as come within known or customary practice in the art to
which this invention pertains and which fall within the limits of
the appended claims.
* * * * *