Note: Descriptions are shown in the official language in which they were submitted.
The presen-t invention relates generally to small
internal combus-tion engines of the type which might Eor
example be employed in snowthrowers, lawnmowers and the like,
and more particularly to such an engine incorpora-ting
several innovative techniques to reduce the overall cost
of manufacture of that engine.
This is a division of copending ~anadian Paten-t
~pplicatio.n Serial No. 378!146, filed May 22, 1981.
Engines of this general type are frequen-tly verti-
cal crankshaft four-stroke cycle engines provided with a
powered take-off shaft for example to drive the wheels of
a self-propelled lawnmower having but a single cylinder, a
solid state ignition arrangement and a pull rope recoil
sta-ter. Such engines have been well known for a nurnber of
years and have met with considerable cornmercial success and
while the present invention will be described in the context
of such an engine, -the inyention is clearly applicable to
other engine designs.
Engines of the type described are not without
their problems and one ever present requirement in the
design of such engines is the minimization of manufacturing
costs. For example, the ~alve train typically found in
such.engines employs a number o$ spur gears coupling the
en~ine c~ankshaft to one or more cam sha~ts to properly time
the opening and clos~ ng of the intake and exhaust ports.
These sp~r gears are metalli~c and generally expensive to
manufacture since they require accurate machining of the
gear teeth. The assembly of the valve trai~n is also a
time consuming operation inYolYing the simultaneous posi-
tioning of the yalyes in their seats and respective valve
stems in their gui~des and the positioning of the yalve
lifters in their respectiye guides, as well as the engaging
of generally complex spring biasing arrangements, -to hold
~,~
rnab/~
these several elements in posi-tion and bias the valves
toward their closed position. One improvement in this
complicated assembly procedure is illustrated in United
States Patent No. 3,556,062 assigned to the assiynee of
the present invention. In -that improvement patent, a single
split loop or hairpin type valve spriny biases both -the
intake and exhaust valves toward their closed position,
however, that arrangementstill employs valve lifters and
the associated lifter guide arrangement, making assembly
somewhat more difficult than necessary, as will be
apparent in the sequel.
On particularly annoying problem with engines
of the type described, and indeed with most internal com-
bustion engine arrangements, involves the rusting out
and/or falling off of the engine exhaust muffler. With
engines of the type described, mufflers formed of stamped
sheet metal requiring a subsequent crimping operation,
are fastened to the engine block by a pair of bolts. Due
to mass of the muffler and vibration, these bol-ts frequently
loosen, allowing exhaust gas erosion to occur where the
muffler attaches to the block, and frequently resulting
in the loss of the muffler~ Further, the stamped sheet
metal muffler itself, due to temperature and moisture build-
up, eventually falls victim to rusting and exhaust gas
erosion. Accordingly, the provisi`on of a muffler arrange-
ment less subject to rust and erosion with better re-tention
on the engine~ would be h;`ghly desirable.
Among the several objects of the present inven-
tion may be noted the proyision of an internal combustion
engine ha~ing an engine block casting with at least a portion
mab/(~
of a muffler shel.l, a boss for attaching a pull rope recoil
s-tarter assembly, an anchoring point for one encl of the re-
coi:l s-tarter rewind spring, a re-tai.ning arrangement for
-the rope of the recoil starter, and a locator for a spring
to bias both intake and exhaust valves towards their closed
positions, all integrally cast therewith; the provision
of an internal combus-tion engine block casting including
an exhaust gas passageway extending from an englne cylinder
and including near the end thereof remote :Erom the cylinder,
an enlarged cavity defining at least part of a muffler shell;
the provision of a muffler arrangement which is retained in
position on the engine, which is largely indestruc-tible and
at least part of which lasts the li.fe of the engine; the
provision of a combi~ned crankcase breather and oil filler
cap which effectively separates engine oil from exiting
gases due in part to its remoteness from the engine crankcase,
and in part to the circuitous air escape path through the
cap; the provision of a combined crankcase breather and oil
filler cap with an oil collecting tray in a tortuous air
venting path having an oil drain hole in the bottom thereof;
and the provision of an internal combustion engine charac-
~erized by i-ts simplicity of construction and economy of
manufacture. These as well as other ob~ects and advantageous
features of the present invention will.be i`n part apparent
and in part poi~nted out hereinaf-ter.
Still further in general~ and in one :Eorm of
the i~nvention~ an internal combustion engine block casting
haying an exhaust ~as passageway extendi~ng from an engine
cylinder includes, near
-- 3
mab/~
the end ~hereof remote rom the cylinder, an enlarged
cavity defininc~ at leasl: part of a mu:Efler shell.
The block casting may f ur ther include a locator
for ~ spring to hias intake ~nd exhaust valves
simultaneously towara their closed positions ~long
with further protuberances ~or attaching a pull
rope recoi.l starter assembly to the engine.
Also in general, and in one form of the inventio~
a crankcase ~reather and oil fill cap has a cap
portion ~or engaging the oil filler opening on
an internal combustion engine along with upper
and lower b~ffle portions proviaing ;nterleaved
haffles defining an oil catching tray having an
oil drain for allowing oil accumulaked in ~he ~ray
to d~ain ba~k into the engine cran~case. The breather
mechanis~ may include a check valve and preferabl~
is located remo~e from the engine crankc~s~ to
reduce the oil content o gases reaching the oil
filler openingO
Fig. l is a perspective view of a low cost
interna~ combustion engine incorporating the several
~eatures of the present invention;
Fig. 2 is a cross-sectional view o~ a poxtion
of the block of the engi~e of ~ig. 1 showing the
Z5 forma~ion of the mu~fler shell therein;
Fig, 3 is a view in eleva~ion of one ~f the
li~e paix of apertured metal baffle plates which
occupy the open end of the muffler shell ~efining
cavity ~f Fig. 2;
FigO 4 is a view partially in section and
at a right angle to the view o~ FigO 2 illustrating
a portion of the engine bloe~ casting including
the intake and exhaust ~alve seat and the ;ntegrally
cast muffler shell;
Fig 5 is a view in section along the line
1 5-5 of Fig. 1 illustrat.ing the engine valve train;
~ig. 6a and 6b illustrate the valve stem and
c~m follower o~ Fig~ 5 with the section o~ the
follower in Fig. 6a being along the lines 6-6 o
Fig ~;
Fig. 7 illustra~es a pull rope recoil startex
disposed on the engine of Fig. 1 on the side opposite
the cylinder head and spark plug;
FigO 8 is a v;ew o the auxiliary power take-
of arrangement and a poXtlOn o~ the valve train
as seen fro~ the rig~t of Fig. 5;
Fig. ~ is a sectional view along the line
~3~9 o:~ ~ig. 8;
Fig. 10 is a view in cross-section along the
line 10-10 o~ Fi~s. 1 ~nd 5 illustrat-ng the engine
cranksha~ and recoil start mechanism; and
Fig. 11 is a view in section along line 11
11 o Fi~. 1 illustrating the combined crankcase
. breather and filler cap.
Corresponding reference chara~ters indica~e
corxespon~ing parts throughout the several views
of the drawing.
. The exem~ icat.ions set out herein illustrate
a preferxed embodimenk of the invention in one
~5 ~orm thexeof and such exem~lifications are not
to be construed as limiting the scope o the ~isclosure
or ~he scope o~ the invention in an~ manner.
Referring firs-t to some of the broadly con~entional
features of the internal combustion engi~e 13 of
FigO 1, in operation air is in~es~ed through air
cleaner 15 ~o be mixed with fuel in carburetor
17~ and that fuel air mixture passing through an
inta~e conaui~ past the open intake valve 21 of
.the poppet or lift var iety (Fig~ 53 and into cylinder
23 (Fig. 4) to be compressea and ignited by a spar~
fxom spar~lug 25, initiating the expans;on ox
1 power stroke of the piston. Thereafter, valve
21 remains closed and exhaust valve 27 (Fig. 5)
opens and as the piston progresses toward cylinder
head 29, the exhaust gases are expelled from the
cylinder by way o exh~ust port 3L (Fig. 5~ and
~he exhaust muffler 33 to the atmosohere.
Referring briefly to Fig~ 10, the engine piston
is connected by a conventional connecting rod 35
to crankshaft 37, the lower end b~ which ma~ connect
to a mower blade in known fashion. The upper end
of crankshaft 37 i~s connected to a flywheel 3g
which may have a plurality of vanes 4~ and 43 for
circulating air within an engine housing, not shown~
for the purposes of illustration, as well as a
toothed gear portion 45 for cooperating ~?ith te2th
on a spur gear 47, selectively actuable by a pull
rope to engage the -teeth 45 to start the e~gine,
and additionally may include a permanent magnet
ox other portion of an ignition system for the
engine. Fl~heel 39, as such~ ~ay be of the ~y~e
disclosed in U.S. Patent No. 4,278,054, issued
July 14, 1981, and assigned
to the assignee o~ the present application r while
~he engine ignition system is not il~ustrated,
but may be o the type illustrated in either U.S.
Patent 3,490,426 or 3,952,712, as well a~ any of
several other known ignition syste~s with the bosses
49 and 51 of Fig. 1 being provided to moun-~ that
ignition system.
Turning now to some of the non-conven~ional
features o~ the present invention, and referring
still to the drawing generallv, it should ~irst
be notea that a number of the engine parts are
manufactured as cast plastic parts while their
prior art counterparts, if they exist at all, are
manufactured of metal and have -the earlier mentioned
subsequent expensive mach:inin~ operation required.
3 ,~,, 3 ~ ~
1 Thus, in Fig~. 5, 6, 8 and 9, the radial cams 51
and 53 and the snur drive gears 55 and 57, alony
with spur gear 59, power ta~e-off beve~ ~ears 61
and 63, and the pair of cam followers or shoes
65 and 67 may all be manu~actured ~rom a plastic
material, ho~lever, in many cases some o~ these
elements, such as spur gear 59, may be of a powdered
metal or other type material. In one embodimen-t
of the presen~ invention, the cams and spur drive
gears and bevel gear 63 were injection molded oE
Dupont9s ZYTEL 70G33HSl while the lifters 65 were
injection molded of Dupont's DE~RIN lOO NC-lO.
Another difference in the design philosophy
of the present engine, as compared to known prior
art englnes, resides in the casting o~ the engine
block with a ~umber o~ auxiliary elements integrally
cast therewith and this integral casting feature
is facilitated somewhat by locating the parting
plane 69 substantially higher than on prior engines~
Typically, the parting plane for the block cast-
ing on prior engines is located close to the power
take-off shaft 71. Thus, the spring loca~ing stud
73, a lug 75 for anchoring one end of the pul~
rope recoil starter spring, a pull rope guide 77~
the boss 79 for mounting the pull rope recoil startert
and the previously mentioned exhaust mu~1er shell
33 may all be cast as an integral part of the engine
block rather than fabricating each of these aevices
as a separate part which must be fastened to the
3a block, requirin~ additional labor a~d increased
~osts.
Delving more deeply into the unique aspects
of the present invention, and referring firs~ to
Fig. 6~ the valve portion 27 may be of any conventional
poppet ox lift valve configuration, typically having
a tapered seat portion for mating with a similarl~
tapered seat portion 81 of the engine exhaus-t port
* - I'rade Marks
-- 7 --
~ 3t~
1 of Figs. ~ and 5. The intake port will have a
similar ~apered seat portion 83 for mating with
the intake valve. St~m por~io~ 85 is provided
with a notch.87 for engagement with the le~ 89
of the spring, and leg 97 engages a similar notch
in -~he i~ake valve stem so tha~ ~he sprin~ biases
bo~h valves toward their closed position. St m
end ~1 which is khe end of the stem opposite the
valYe 27 fiks snugly wlthin the depression ~3 of
the cam ~ollower or shoe 65 and of course ~he surface
95 opposi.te this depression in the shoe i5 the
surface which rides on the.sura~e of radial ca~
51~ It will be noted that when notch 87 is engaged
by the spri.ng leg ~9, rotation ~f the val~e about
~he stem axis will be pre~ented.
The exhaust valve and cam ollower o* ~ig.
~ is illustrated in position within ~he en~ine
in ~i~. 5 along with a very similar intake valve .
21 and cam follower or shoe 67. Both ~alves are
2Q biased toward their closed position by ~he legs
89 and 97 o~ the coiled wire spring engaginy their
~espective stem notches with the bight~ or helical
pox~ion 99 of this sprinq being held in a relatively
fixed location by the stud or boss 73. It would,
25. of course~ also be possible to form a pock~t in
the en~ine block castin~ for holding this ~ight
portion in position. Thus~ each valve ste~ notch
provides a ~ixed support for one spring leg ~hen
the other v~lve opens, fleY~ing the spring That
this supPort location be fixed is of cours-~ no~
necessa~y0 however, since intake and exha~st valves
are typically not open at the same time, ~he support
location is fixed relative to the other va1ve when
~hat other valve opens. It should al50 be~ no-ted
tha-t no valve lifter guides are employed in the
3~
presen-t engine and that -the cam followers 65 and 67 are
held in position solely by the valve s-tem engagement with
the depression in the follower and the spring urging of the
stem toward the cam so that the cam follower is captive
between the cam and valve stem.
The above-described spring arrangement for the
intake and exhaust valves is also described and claimed in
copending Canadian Patent Application Serial No.
filed ~anuary 4, 1984, which is also a division of above-
identified parent application Serial No. 37~,146.
Still referring -to Fig. 5, it will be noted that
the gears 55 and 57 have a llke number of teeth with this
number being twice the number of teeth on spur gear 59 so
that for each rotation of the spur gear 59, each of the gears
55 and 57 executes one-half revolution. The gear 59 is direc-
-tly driven by the engine crankshaft 37 thereby providing the
desired opening and closing of each of the intake and exhaust
valves once during two revolutions of the engi~ne.
A bevel gear 63 engages a substantially smaller
bevel gear 61 on the rear side of spur gear 57, as best seen
in Figs. 8 and 9, with this substantial disparity in bevel
gear sizesr and the two:one speed reduction between gears 59
and 57 proyiding the desired low speed rotation of the power
take-off shaft 71, as for example will be desire~ to driye the
wheels of a power lawnm,ow~er. Gear 55 may be identical to
gear 57 includi~ng the bevel ~ear portion like 61, if the re-
duction in ini~ti`al toolin~ costs as well as the reduction in
required spare parts ~nventory justi~ies this duplication,
or gear 55 may be of a more simplistic design, since it need
only drive cam 51. Of course also, somewhat di~fferent engine
configurations may allow cams 51 and 53 to share a common shaf-t.
Figs. 2, 3, 4 and 5 illustrate the integrally cast
muffler shell of the p,resent inYention. As perhaps best seen
i~n Figs. 2, 4 and 5, an exhaust gas passageway 31 extends
from the engine cynlinder
g _
mab/ ~
3'7
23 b~ wa~ of the exhaust port between valve 27
and seat ~1 passing into a subst~ntially enlarged
area or cavity as de-fined by the shell 33 which
orms at least a part of the muf~ler shell. Within
the cavi~y and terminating near the open end r thexe
is located a boss 101 also cask as an integral
portion of the engine block and having an outwardly
facing hole 103 which may be ~apped or which may
simply be a cast hole for receiving a self-tapping
or self-threading screw 105~ ln either case, the
boss provides a support for the muffler baffles
107 and 109.
As best illustra~ed in Figs. ~ and 3, each
baffle comprises an apertured metal plate for providing
a ~ircuitous or tortuous exhaust path from the
cavity to the atmosphere. In ~ig. 2, as illustrated
by the arrows, this path from exhaust passageway
31, is through the apertures near the bottom of
plate 101, then upwardly between ~he two plates
and ou~waral~ through the apertures in the upper
portion of plate 107. The plates may be substantially
identical, each having a generally centrally located
de~ression 111 with the attachment bolt passing
aperture 113 within the depression. The plates
are positioned with their respective depxessions
abutting and the rema.ining plate portions separated
by about twice the depth of the depressions and
with bol~ 105 passing through the respective aper~ures
such as 113 and into boss 101 to securely hold
3~ the plates in position near the cavity open end~
As most clearly shown in Fig~ 3, each plate
is of a generally rectangular configuration provided
with a plurality of small exhaust gas apextures,
such as 115 and 117, with those small apertures
being concentrated in one half of the rectangular
-- 10 --
'
1 confi~uration while the other half thereof is substantially
aperture free. When the plates are then positioned
with depression against depression 7 the apertured
half of pl~te 107 is near the top, a~ illustrated
s in Fig~ 2, while the aperturea half of plate 109
is near the bottom of that same Figure~
The combination crankcase breather m~chanlsm
and oil fill cap 119 o~ Fig. 1 functions to restrict
an oil ~iller opening in the engine which communicates
1~ ~y way of an oil ~ill tube generall~ at 121 and
~eading to the engine oil sump 123 (FigO 10~ while
pro~iding a flow path for the expulsion of gas~s
from ~he engine crankcase 125 (Fig. 10) and limitiny
the egress of oil from the engine through that
flow path. This breather mechanism cap combination
- is illustrated in cross-section in Fig~ 11 ancl
includes a ~crew cap portion 127, an upper baffle
poxtion 129, and a lower baffle portion 131, all
fastened togethe~ to provide a circuitous pa~h,
as illustxated by the arrows, from the crankcase
to ~he atmosphere, by way of the disc 133 of a
check valve and an oil collecting tray 135 having
oil return drain holes~ such as 137, near the bottom
thereof~
Referring to FigO 11 in greaEer detail, the
oil fill opening may have a neck 139 with a thread~d
region 141 which engages a complementa~y portion
of the screw cap 127 about the oil fill openin~.
The upper bafle portion 129 has a downwardl~ depenaing
generally cylindrical baffle 143 while the lower
baffle portion 131 has inner 145 and ou~er 147
generally cylindrical baffles which are interleaved
wi~h the dot~nwarclly depending baffle 143. The
disc 133 o~ the check valve is captive with a limited
amount of free movement between the upper and lowe~
ba~fle por~:ons~ This check valve restricts the
1 entrance of air into -the engine crankcase by way
of the breather mechanism while allowing the expulsion
of gases from the engine crankcase b~ w~y of the
breather mechanism. The expulsion gases pass,
as indicated by the arrows, upwardly through the
check valve and over an upper rim of the inner
lower ha~fle 145 and then dos~nwardly between the
baffle and the downwardly depending baf~le 143
and beneath a lower rim or edge of baffle 143 to
then pass upwardly be-twee~ ~he outer lower baffle
147 and the downwardly depending ba~fle 143, through
a plurality of cap apertures, such as 149, 151
and 155 to the atmosphere. The inner cylindrical
baf~le 145, of course, includes a valve seat 153
of an annular confi~uration while the downwardly
depen~ing cylinarical portion 156 of the upper
baffle portion restricts the valve di~c to move-
ment within the inner c~lindrical baf:Ele~ ~n oil
collecting tray of an annular configLIration is
formed ~y the bottom portion 157 which connects
~he inner and outer baffles from which, as noted
earlier~ oil drains back to ~he engine sump by
way o drain holes~ such as 137. It should also
.be note~ that the location of the cap 119 remote
- 25 from and substantially above the engine sump oil.
level, aids materially in the seParation o oil
- from the escaping gases, as those gases pass along
the oil fill tube exiending from the engine erankcas~
to ~he oil filler opening.
Referrin~ now to Figs. 7 and lOy pulling the
start handle 15~ causes rope 161 to unwind from
the ~rum 163, inducing rotation in that drum and
helically threaded hub 167 abouk the axis of the
recoil starter attaching bolt 165 and inducing
a restorati~e force in the starter recoil spring~
Gear 47 is attached to the hub 167 of the starter
- 12 -
1 mechanism by a helical thread arrangement so that
rotation o~ drum 163 causes gear 47 to move toward
the left, as viewed in Fig. 10 and i.nto engagement
with the teeth 45 of the fl~wheel with oontinued
S rotation of hub 163 and o~ gear 47 providing the
starting rotation of the flywheel. Spring clip
168 frictionally engages hub 167 and spans stud
75 to move ~he hub and starter ~ear be~w~n their
axial limits~ When the engine starts, gear 47
is disengaged and release of the hand~e 159 allows
~he mechanism to rewind for the next starki.ng operation
since the clock type coil spring urges the geax
47 back along the helical thread arrangement~ and
as tension of rope 161 is rel~ased, that rope is
rewound about the drum 163. The further details
of the starter mechanism may be as in conventionally
employed ret~ind starters, as illustrated in U.S.
Patent 3,375,813 for example, however, as noted
earlier, substantial economies in the manufacture
of the engine are realized by casting the recoil
s~arter a~tachment boss 79 as well as the spring
anchoring stud 75 and recoil starter rope guide
77 as integral portions of the engine block r and
eliminatîng all support brackets. Another suitable
~5 recoil starter is illustrated in U.SO.Patent 4,019,490.
Fxom the foregoing, it is now apparent thak
a novel internal combustion engine having a unique
block casting and valve train arranqement, as well
as unique muf~ler and breathex configurations,
30 -has been disclosed meeting the o~jects and advantageous
~eatures set out hereinbeore as well as others
an~ thak modifications as to the preoise confi~uratiDns~
shapes and details may be made by those having
ordinary skill in the art ~ithou-t departing ~om
the spirit of the invention or the scope thereof
as set out by the claims which follow.
- 13 -
