Vertical three cylinder two cycle engine with single carburetor

In a two cycle internal combustion engine (80) comprising three cylinders (22, 24, 26) vertically in-line, a single intake manifold (82) services all three of the cylinders, and a single fuel delivery device (84), such as a carburetor, on the manifold delivers fuel to each of the cylinders. Location and orientation of the three reed block openings (90, 92, 94) relative to each other and relative to the throttle bore (128) provide desired fuel distribution. Manifold structure, including internal dams (142, 146) and a deflector plate (138), prevents an overly rich fuel mixture in the lower cylinder (26) at idle, and prevents an overly rich fuel mixture in the upper cylinder (22) at running speeds above idle.

BACKGROUND AND SUMMARY 
The invention relates to two cycle internal combustion engines with 
vertically in-line cylinders, and more particularly to simple and 
significantly cost-reduced fuel delivery structure therefor. 
The invention arose during development efforts directed toward two cycle 
internal combustion marine engines having three cylinders vertically 
in-line. In the prior art, each cylinder has its own carburetor which 
supplies fuel through a respective reed block into the crankcase. The 
carburetor throttles are connected to each other by throttle linkage. This 
system is costly because of the expense of three separate carburetors. 
Furthermore, tuning requires not only synchronization of all three 
carburetors through the linkage, but also three sets of adjustments, e.g. 
three separate idle mixture adjustment screws, three choke linkages, etc. 
The present invention provides a simple and effective solution to the above 
noted problems, and provides a significant cost reduction. A single intake 
manifold services all three cylinders, and a single fuel delivery device 
on the manifold delivers fuel to all of the cylinders. The invention 
eliminates the extra carburetors, the complicated linkage system, the 
extra adjustments, etc.

DETAILED DESCRIPTION 
Prior Art 
FIG. 1 schematically shows a two cycle internal combustion engine 20 having 
three cylinders 22, 24, 26, vertically in-line and drivingly rotating a 
vertical crankshaft 28. Each cylinder has its own carburetor 30, 32, 34, 
respectively, each with a float bowl 36, 38, 40, respectively, as further 
shown in FIG. 2. The carburetors are mounted to a reed plate adaptor 42 
which is mounted to the engine crankcase 44. Three reed blocks 46, 48, 50, 
one for each cylinder, are mounted to adaptor 42 and extend into the 
respective cylinder 22, 24, 26, to admit a combustible fuel mixture which 
flows through respective transfer passages (not shown) to the other end of 
the respective cylinder for ignition by the respective spark plug 52, 54, 
56. The carburetor throttles are connected to each other by throttle 
linkage 58, FIG. 2. Reed blocks 46, 48, 50 are received in respective reed 
block openings 60, 62, 64, FIG. 3, in crankcase 44. Each of the reed block 
openings has a length, as shown at arrow 68, and a width as shown at arrow 
70. Length 68 is greater than width 70. Each of the reed block openings 
extends longitudinally horizontally along the dimension of length 68. 
Present Invention 
FIG. 4 schematically shows a two cycle internal combustion engine 80 in 
accordance with the invention and uses like reference numerals from FIG. 1 
where appropriate to facilitate understanding. The engine has three 
cylinders 22, 24, 26 vertically in-line, a single manifold 82 servicing 
all three of the cylinders, and a single fuel delivery device 84 on the 
manifold delivering fuel to each of the cylinders. Fuel delivery device 84 
is a carburetor having a float bowl 86, FIG. 5, or may alternatively be a 
throttle body fuel injection device, or the like. 
Engine crankcase 88, FIGS. 6 and 7, has first, second and third reed block 
openings 90, 92, 94, one for each of respective cylinders 22, 24, 26. 
Manifold 82 covers all of the reed block openings 90, 92, 94, FIG. 8. Reed 
block opening 90 has a portion 96, FIG. 6, horizontally aligned with a 
portion 98 of reed block opening 92. Reed block opening 92 has another 
portion 100 horizontally aligned with a portion 102 of reed block opening 
94. Reed block openings 90 and 94 are vertically aligned. Reed block 
opening 92 is horizontally offset from reed block openings 90 and 94. 
Each of the reed block openings has a length, as shown at arrow 104, FIG. 
6, and a width, as shown at arrow 106. Length 104 is greater than width 
106. Each of the reed block openings extends longitudinally vertically 
along length 104 between a top end and a bottom end. The bottom end 108 of 
reed block opening 90 is lower than the top end 110 of reed block opening 
92. The bottom end 112 of reed block opening 92 is lower than the top end 
114 of reed block opening 94. The longitudinal extent of reed block 
opening 92 is parallel to the longitudinal extent of reed block opening 90 
and parallel to the longitudinal extent of reed block opening 94. The 
longitudinal extents of reed block openings 90 and 94 are colinear. Reed 
block opening 90 includes a ramp 116, FIG. 7, within crankcase 88 
directing the fuel mixture upwardly towards the center 118 of cylinder 22. 
Reed block opening 92 includes a ramp 120 within crankcase 88 directing 
the fuel mixture downwardly towards the center 122 of cylinder 24. Reed 
block opening 94 includes a ramp 124 within crankcase 88 directing the 
fuel mixture downwardly towards the center 126 of cylinder 26. 
Fuel delivery device 84 has a throttle bore 128, FIG. 5, horizontally 
aligned with portions 96 and 98, FIG. 6, of reed block openings 90 and 92. 
Throttle bore 128 has a diameter 130. Reed block openings 90 and 92 are 
horizontally spaced by a gap 132 having a width less than diameter 130 of 
throttle bore 128. The top 134 of throttle bore 128 is horizontally 
aligned with top end 110 of reed block opening 92. The bottom 136 of 
throttle bore 128 is horizontally aligned with the bottom end 108 of reed 
block opening 90. Fuel flows along a travel path from throttle bore 128 
through manifold 82 generally horizontally to portions 96 and 98 of reed 
block openings 90 and 92, respectively. The fuel travels generally 
vertically in manifold 82 to reed block opening 94. 
In one embodiment, manifold 82 includes a deflector plate 138, FIGS. 8 and 
9, blocking part of the fuel travel path from throttle bore 128 to reed 
block opening 90. Manifold 82 has an opening 140. Fuel delivery device 84 
is mounted to manifold 82 such that throttle bore 128 is aligned with 
opening 140. Deflector plate 138 extends across a portion of aligned 
throttle bore 128 and opening 140 and is horizontally aligned with portion 
96 of reed block opening 90. Fuel from device 84 strikes deflector plate 
138 and disperses rather than directly entering lower portion 96 of reed 
block opening 90, to prevent an overly rich fuel mixture in upper cylinder 
22 during running of the engine at speeds above idle. 
Manifold 82 includes a dam 142, FIG. 10, effective at engine idle and 
diverting to upper cylinder 22 a portion of the gravitationally induced 
vertical fuel flow which would otherwise drain to lower cylinder 26 during 
engine idle and cause an overly rich fuel mixture in lower cylinder 26 and 
an overly lean fuel mixture in upper cylinder 22. Fuel delivery device 84 
is mounted to manifold 82 at opening 140 in the manifold horizontally 
spaced from portions 96 and 98 of reed block openings 90 and 92. Dam 142 
is a ramp extending from manifold opening 140 to portion 96 of reed block 
opening 90 such that fuel from throttle bore 128 of device 84 drains along 
ramp 142 to portion 96 of reed block opening 90 during engine idle. 
Manifold 82 has an outer wall 144, FIGS. 8 and 9, extending downwardly from 
manifold opening 140. Another dam is provided by a second ramp 146, FIG. 
10, extending from outer wall 144 to the bottom end 112 of reed block 
opening 92, and providing a fuel drain path to reed block opening 92. 
Outer wall 144 of manifold 82 has a bulged portion 148, FIGS. 9 and 12, 
bulged outwardly away from and below manifold opening 140 and generally 
opposite reed block opening 92 to provide increased air volume. Outer wall 
144 has a tapered portion 150 tapered downwardly and inwardly from bulged 
portion 148 and generally opposite reed block opening 94 and providing 
decreasing air volume. Manifold 82 has a second opening 152, FIG. 9, above 
opening 140 and generally opposite reed block opening 90. Opening 152 has 
a fitting 154 for receiving recirculated heavy fuel ends. 
Opening 140 in outer wall 144 of manifold 82 is thus opposite and 
horizontally aligned with portions 96 and 98 of reed block openings 90 and 
92. Fuel delivery device 84 is mounted to manifold 82 and has its throttle 
bore 128 aligned with opening 140 in outer wall 144 of manifold 82. Reed 
block opening 90 provides fuel to upper cylinder 22. Reed block opening 92 
provides fuel to middle cylinder 24. Each of reed block openings 90 and 92 
has upper and lower portions. The lower portion 96 of reed block opening 
90 is horizontally aligned with upper portion 98 of reed block opening 92. 
Manifold 82 includes deflector plate 138 blocking a portion of the fuel 
flow path from throttle bore 128 of device 84 to lower portion 96 of reed 
block opening 90, such that at engine speeds above idle, fuel from device 
84 strikes deflector plate 138 and disperses rather than directly entering 
lower portion 96 of reed block opening 90, to prevent an overly rich fuel 
mixture in upper cylinder 22 during running of the engine at speeds above 
idle. Deflector plate 138 is part of outer wall 144 of manifold 82 and 
extends across a portion of opening 140 in outer wall 144. 
First, second and third reed blocks 152, 154, 156, FIG. 15, are mounted to 
a reed block adaptor 158, which is mounted between crankcase 88 and 
manifold 82. Reed blocks 152, 154, 156 are in respective reed block 
openings 90, 92, 94. Reed block adaptor 158 has an outer peripheral flange 
160 sandwiched between crankcase 88 and manifold 82. Reed block adaptor 
158 has first, second and third adaptor openings 162, 164, 166, at which 
reed blocks 152, 154, 156, respectively, are mounted to reed block adaptor 
158 by screws such as 168. Each of the adaptor openings has a length, as 
shown at arrow 170, and a width, as shown at arrow 172. Length 170 is 
greater than width 172. Each of the adaptor openings extends 
longitudinally vertically along its length between a top end and a bottom 
end. Adaptor openings 162 and 166 are vertically aligned. Adaptor opening 
164 is horizontally offset from adaptor openings 162 and 166. 
Reed block adaptor 158 further includes a raised rib 174 extending 
longitudinally parallel to the longitudinal extent of adaptor opening 164. 
Raised rib 174 has a length greater than the length of adaptor opening 
164. The longitudinal extents of adaptor openings 162 and 166 extend 
colinearly, and raised rib 174 extends longitudinally parallel to the 
longitudinal extents of adaptor openings 162 and 166. 
In the preferred embodiment, the bottom 136, FIG. 6, of throttle bore 128 
is located slightly above or horizontally level with the bottom end 108 of 
upper reed block opening 90. The middle reed block opening 92 is located 
as close as possible across gap 132 to reed block opening 90 in parallel 
relation. The middle reed block opening 92 is located low enough that the 
top end 110 of reed block opening 92 is even with the top 134 of throttle 
bore 128. The lower reed block opening 94 is located as high as possible, 
i.e. as high as the opening into the crankcase will allow. Minimum 
manifold cross sectional area deviation from the throttle bore area is 
desirable. Minimum variation in crankcase volume is also desirable. 
FIG. 16 shows an alternate embodiment, with crankcase 180, diagonal reed 
block openings 182, 184, 186, and throttle bore 188. 
It is recognized that various equivalents, alternatives and modifications 
are possible within the scope of the appended claims.