Note: Descriptions are shown in the official language in which they were submitted.
3~
The present inven-tlon relates generally to small
internal combustion engines of the type which might for
example be employed in snowthrowers, lawnmowers and the like,
and more particularly ,to such an enyine incorpo,ra-ting several
innovative techniques to reduce the overall cost of manu-
facture of that engine.
This is a division of copending Canadian Patent
Application Serial No, 378,146, filed May 22, 1981.
Engines of this general type are frequently vertical
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 star-ter.
Such eng~nes have been well known for a number of years and
have met with conside~able commercial success and ~hile the
present inyention w111 be described i~rl the context of such
an engine~ the i~nyenti~on is clearly applicable to other
engine des~i~gns.
Engines of the type descri~ed are not without their
problem,s and one eyer present requirement i~n the design of
such- engines is the minimization of manufacturing costs. For
exa,mple, t,he yalye train typically found in such engines
em,ploys a number o~ spur gears coupli~ng the engine crankshaft
to one, ~r m,ore cam shafts to properly ti~e the opening
and closillg of the intake and exhaust ports. ?hese spur
years a~e,~etallic and generally expens~ve to manufacture
si`nce they~requI~re accurate machining of the gear teeth.
The asse,mkly of the yalve train i~s als~ a tIme consuming
operating inyolving the simultaneous positioning of the
, valves in their seats and respective yalYe stems in their
gu;`des and the positionin~ o,f the valve lifters'in their
respect:ive guides~ as well as the engaging of generally
mab/~
complex spring biasing arrangernents, to hold these several
elements in position and bias the valves toward their
closed position. One improvement in this complicated assembly
procedure is illustrated in ~nited States Patent No.
3,556,062 assigned to the assignee of the present invention.
In that improvement patent, a single split loop or hairpin
type valve spring ~i~ases both the intake and exhaust val.ves
toward their closed position, however, that arranyement
still employs yalye lifters and the associated li~fter
guide arrangement, making assembly somewhat more difficult
than necessary, as will be apparent in the sequel.
One part;cularly annoying problem with engines of
the type described, and indeed with most internal combusti~on
engi~ne arrangements, involves the rusting out and/or falling
o~f of the engine exhaust muffler~ With engines of the
type described, mufflers form,ed of stamped sheet metal
~equir~i~ng a subse~uent cri~pin~ operation, are fastened:bo
the engine block by a pair of bolts. Dlle to mass of -the
muffler and yibration, these bolts frequently loosen, allow-
ing exhaust ga erosi~on to occur where the muffler attaches
to the block, and frequently resulti~ng in the loss of the
~uffler, .~Further, th.e stamped sheet metal muffler itself,
due to tem,perature and moi$ture buildup, eventually falls
y~i~cti~.to rusting and exhaust ~as erosion. Accordingly,
th.e~proyision:o~.a muff~e~ arrangement less subiect to rust
and erosi~n wi~th.better retention on the engine, would be
hi~hly desi~rable.
Accordin~ to the present invention~ there is pro-
vided an arrangement for biasing intake and exhaus-t poppet
- valYes toward their closed positions includi~ng a coiled wire
spring having a pair oE outwardly extending legs with each
leg connected to one of the respective valves. The central
bight portion of this coiled wire spring is anchored, such
mab/; Y
~8~ 8
as by a stud relatively fixed in a location intermediate
~the valves and passing through the coïl of the spring so
that the stud and one valve provide the fixed support
points against which the spring is flexed when the other
valve opens.
Referring now to the accompanying ~rawings:--
Fig. 1 is a perspective view of a low cost internalcombustion engine incorporating the several features of the
present invention;
Fig. 2 is a cross-sectional view of a portion of
the block of the engine of Fig. 1 showing the formation
of the muffler shell therein;
Fig. 3 is a view in elevation of one of the
like pair of apertured metal ~affle plates which occupy
the open end of the muffler shell defining cavity of Fig.
2;
Fig. 4 is a view partially in section and at a
right angle to the yiew of Fig. 2 lllustrat;'ng a pOrtIon
o~ the engine block casting including the intake and exhaust
valye seat and the integrally cast muffler shell;
Fig. 5 is a ~i~ew in section along the line
mab/ ~
1 5-5 o~ Fi~. 1 illus krating the engl.ne vAlve kr~in;
~ig 6a and 6~ illustrate the valve stem an~
ca~ ~ollower of ~ig. 5 with the section o~ the
follower in Fig, 6a bein~ along the lines 6-6 of
~ig 6b;
- Fig. 7 il~us~rates a pull rope recoil starter
disposed on tha engine of ~ig~ 1 on the si~e opposite
~he cylinaer head and spark plug;
Fig. 8 is a v~ew of the auxiliary po~er ~ke-
off ~rrangement and-a portion o the valve ~rain
as seen from ~he riyht o~ ~ig. 5j
FigO ~ is a sectional ~iew along the line
9-9 o~' ~ig.. ~
Fig. 10 is a view in cross-section al~g the
line 10-10 of Figs. 1 ~nd 5 illustr~t:ing the engine
crankshaft and recoil start ~echanism; and
~ig.- 11 is a view i~ section alony line 11-
11 0~ FigO 1 illustrating the combined cra~kcase
. brea~h~r ana filler c~p~ . . - -
Corresponding reference charac~ers in~cate
corresponding par~s throughouk the several ~iews
o.~ ~he ~r~wing~
. The exemplificat.ions set ou~ herein il~ustra~e
a preferrea embodinent o~ the invention in ~ne
25 ~orm ~hexeof and such exemplifications are n~ .
t~ ~e construed as limiting the scope of ~he disclosiure
ox the scope of the invention in any ~anner_
~eferring first to some of the broadl~ conventio~a~
features of the intexnal combustion engine 13 of
~ig~ 1, in operation a.ir is inyested throug~ air
cleaner 15 to be mixed with fuel in carbure~or
17, and ~hat ~uel air mixtu.re passing throug~ an
- inta~e conduit past the oen -ntake valve 21 o~
.
.the poppe~ or lift variety (~ig. 5) ana into cylinder
23 ~Fiy. ~ to be cor~pxessed ana ignited b~r a spar~
~rom sparkplug ~, i.nitiating the expansion or
_ g _ . . I
3~
1 power stroke oE the plston. Therea~ter, valve
21 remains closed and exhaust valve 27 (~;y. 53
opens and as the piston progresses toward cylinder
head 29, the exhaust gases are expelled from the
~ cylinder hy way of e~haust port 31 [~ig. 5) ana
the exhaust muffler 33 to the atmosohere.
Referring briefly to Fig. 10, the engine piston
is connected ~y a conventional connecting rod 35
to crankshaft 37; the lower end of which may connect
~o a mower blade in known fashi-on. The upper end
of crànkshaft 37 is connectea to a ~lywheel 39
which may have a pluralit~ of vanes 41 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 with ~eeth
on a spur gear 47, se~ectively actuable by a pull
rope to engage the keeth 45 to start the engine,
and additionally may include a permanent magnet
or othex portion of an ignition system for the
engine. Flywheel 39, as suchh ~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, ~hile
the engine ignition system is not il~ustrated,
but may ~e of the type illustrated in either U.S.
Patent 3,490,426 or 3,952,712, as well as an~ of
several other known ignition systems with the ~osses
49 and 51 of Fig~ 1 being provided to mou~ that
ignition system.
Turnin~ now to some o the non-conventional
features of the present in~ention, and xeferring
still to the drawing generall~, it should first
be notea th~t 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
su~sequent expensive machining operation required.
-- 5 --
3~
1 Thus, in FicJs. 5, 6, ~ and 9, the radial cams 51
and 53 and the s~ur dxive gears 55 and 57, along
with spur gear 59, power take-off bevel gears 61
and 63, and the pair of cam followers or shoes
5 - 65 and. 67 may all be manufactured from a plastic
material, ho~Jever, in many cases some of these
elements, such as spur gear 59, may be of a powdered
metal or other type material. In one embodiment
of the pre~ent invention~ the cams and spur drive
gears ~nd bevel gear 63 were injection mol~ed of
Dupont' s ZYTEL 70G33HSl while the Iifters 65 were
in~ection molded of Dupon-tls DELRIN 100 NC-10.
Another difference in the design philosophy
of the.present engine, as co~pared to known prior
art engines, resides in the casting of the engine
block with a number o~ auxiliary elements in~egrally
cast therewith and this in.tegral casting feature
is facilitated somewhat by locating ~he parting
plane 6g substantially higher than on prior engines.
20 . Typically, the partin~ plane for the block cas~-
ing on pxior engines is located close to the power
take-off shaft 71. Thus, the spring ~ocating stud
73, a lug 75 for anchoring one end of the pull
rope recoil starter spring, a pull rope guide 77 J
the boss 79 for mounting the pull rope recoil starier,
and the previously mentioned exhaust mu~fler shell
33 may all be cast as an integral part of the engine
block rather than fabricating each of these devices
as a separate part which must be fastened to the
- 30 block, requiring additional labor and increased
cos~s .
Delvin~ moxe deeply into the unique aspects
of ~he present invention, and referrin~ irst to
Fig. 6, the valve portion 27 may be of any conventional
poppet or lift ~alve con:Eiguration, typically having
a tapered seat portion for mating with a s;milarly
tapered seat portion 81 of the engine exhaust port
* - Trade Marks
3433
of Fi~s. ~ an~ 5. The in-take port will have a similar
tapered sea-t portion 83 Eor mating with the intake valve.
Stem portion 85 is provided with a notch 87 for engagernent
with the leg 89 of the spring, and leg 97 engages a similar
notch in the intake valve stem so that the spring biases
both valves toward their closed position. Stem end 91 which
is the end of the stem opposite the valve 27 fits snugly
within the depression 93 of the canl follower or shoe 65 and
of course the surface 95 opposite this depression in thè
shoe is the surface which rides on the surface of~radial cam
51. It will be noted that when notch 87 is engaged by the
spring leg 89, rotation of the valve about the stem axis
will be prevented.
The above described valve structure utilizing the
cam follower 93 is also disclosed and is claimed in above-
identified parent application Serial No. 37~ 6.
The exhaust valve and cam follower of Fig. 6 is
illustrated in position within the engine in Fig. 5 along
with a very similar intake Yalve 21 and cam follower or shoe
~o 67. Both valves are biased toward their closed position by
the legs 89 and 97 of the coiled wire spring engaging their
respective stem notches with the bight or helical portion
99 of this spring being held in a relatively fixed location
by the stud or boss 73. It would, of courser also be poss-
i~le to form a pocket in the engine block casting for
holding this bight portion in posi`tion. Thus, each valye
s-tem notch provides a ~ixed support for one sprin~ leg when
the other valve opens, flexing the spring. That this support
location be fixed is of course not necessary, however! since
i~ntake and exhaust valves are typi~cally not open at the same
time ! the support location is fixed relatiye to the other
valye when that other valYe opens. It should also be noted
that no valve lifter guides are employed in the
-- 7
mab/j~c,
3~
1 present engine and that the cam followers 65 and
67 are held in position solely by the valve stem
engagemen~ ~ith the depression in the follower
and the sprlng urging of the stem toward the cam
S so that the cam follower is captive between the
cam and valve stem.
Stil~ ref~rring to Fig. 5, it will be noted
that the gears 55 and 57 have a like number.of
teeth with this n~mber being twice the n~mber of
lQ 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 S9 is directly
driven by the engine crankshaft 37 ~hereby pxoviding
the desir~d opening and closing of each o~ the
lS intake an~ exhaust valves once during two revolutions
of the engine.
A bevel gear 63 engages a su~stantially smaller
bevel gear 61 on the rear 5ide of spur gear S7 r
as best seen in Figs. 8 and 9, with this substantial
disparity in bevel gear sizes, an~ the two:one
speed re~uction between gears 59 and 57 providing
the desired low speed rotation of the power ta~e-
off shaft 71, as for example will be desired to
drive th~ wheels of a power lawnmo~er. Gear 55
may be i~entical to gear 57 including the bevel
gear port~on like ~1 t if the reduction in .initial
tooling ~sts as well as the reduction in requixed
spare par~s inventory justifies this duplication,
or gear 55 may be of a more simplistic design,
since it need only drive cam 51. Of course also,
somewhat di~ferent engine conf.igurations may allow
cams 51 ~d 53 to share a common shaftO
Figs. 2, 3, 4 and 5 illustrate the integrally
cast mu~er shell of the present invention. As
perhaps ~st seen in Figs. 2l 4 and 5, an exhaust
gas passageway 31 extends from the enyine c~li.nder
13~
/
1 23 by wa~ nf the exhaust port between valve 27
and seat 81 passing into a substantially enlarged
area or cavity as deflned by the shell 33 which
forms at least a part of the muffler shell~ Within
S ~he cavity and terminating near the open end, there
is located a boss 101 also cast as an integral
portion of the engine block and having an outwardly
*acing hole 103 which may be tapped or which may
simply be a cast hole for receiving a self-tapping
or self-threading screw 105~ In either case, the
boss provides a support for the muffler baf~les
107 and 109.
As best illustrated in Figs. ~ and 3, each
ba~le comprises an ayertured meta~ plate ~or providing
a circuitous or ~ortuous exhaust path from the
cavity to the atmosphere. In Fig. 2, as illust.rated
by the a~rows, this path from exhaust p~ssageway
31, is through the apertures near the bottom of
plate 101~ ~hen upwardly between the two plates
and outwardly through the apertures ~n the upper
por~ion of plate 1070 The plates may be substantlally
iden~ica~, each having a generally centrally located
depression 111 with the attachment ~olt passing
aperture 113 within the depresslon. The plates
are positioned with their respective depressions
abutting and the remaining plate portions separated
by about t~ice the depth of the depressions and
with bolt lOS passing through the respective apertures
such as 113 and into hoss 101 to securely hold
the platés in position near the cavity open end.
As most clearly shown .in.Fig. 3, each plate
is of a gene.r~lly rectangular configuration provided
with a plurality of small exhaust gas apertures,
such as 115 and 117, with those small apertures
being concentrated in one half of the rectangular
3~
1. configuration wh.ile the other half thexeof is substantially
aperture free. When the plates are then positioned
with depression against depression-, the apertured
half of plate 107 is near the top, as illustrated
in Fig. 2, while the apertured half of plate 109
i5 near the bottom of that same Figure~
~ he combination crankcase breather mechanism
and oil fill cap 119 of Fig. 1 functions to restrict
an oil filler opening in the engi~e which communicates
~y way o~ an ~il fill tube ~enerally at 121 and
leading to the engine oil sump 123 (Fig. 10) while
pro~iding a flow path for the expulsion o~ gases
from the engine crankcase 125 (Fig. 10) and limiting
the egress ~ oil from the engine through that
flow pat~. This breather mechanism cap combinatio~
~s illustrated in cross-section in Fig. 11 and
inclu~es a screw cap portion 127, an u~pex baffle
por~ion ~29, and a lower baffle portion 131, all
fastened ~ogether to provide a circuitous path,
as-illustrated by the arrows, ~rom the cxank~ase
to the atmosphere, by way of the disc 133 of a
check valva and an oil colle~ting tray 135 ha~ing
oil retur~ arain holes, ~uch as 137, near the bottom
thereof~ .
Referr;ng to Fig. 11 in greater detail, the
oil ~ill opening may have a neck 139 with a threaded
region 141 which engages a complementaxy portion
of the screw cap 127 about the oil fill openin~.
The upper baffle poxtion 1~9 has a downwardly depending
generally cylindrical baffle 143 while the lower
baffle.portion 131 has inner 145 and outer 147
generally cylindrical baffles which are interleaved
with th ~ownwardl~ depending baffle 143. The
disc 133 of the check valve is cap~ive with a limited
amount of free movement between the upper ~ld lower
b~ffle portions. This check valve restricts the
-- 10 --
1 entrance oE air into the engine crankcase by way
of the breather mechanism ~7hile allowing the expulsion
- of gases rom ~he ~ngine crankcase by way of the
breather ~echanism. The expulsion gases pass,
as indicated by the arrows, upwardly through the
check valve and over an uppex rim of the inner
lower baf1e 145 ~nd then downwardly between the
baffle and the downwardly depending baffle l43
and beneath a lower rim or edge of baffle 143 to
~hen pass upwaxdly between the outer lower baffle
147 and the ao~mwar~ly depending baffle 143, through
a plurality of cap apertures, such as 149, 151
and -155 to the atmosphere. I.rhe inner cylindrical
baffle 145~ of course, includes a valve seat lS3
of an annular con~iguration while the downwardl~
dependlng cylindrical portion 156 of the upper
- baffle p~r~ion restricts ~he ~alve disc to move-
ment within the inner cylindrical baffle. An oil
collecting kxay of an annular configuration is
formed by the bottom portlon 1~7 which connects
the inner and outer baffles from whichr as noted
earlier, oil drains back to the engine sump by
way o~ drain holes, such as 137. It should also
be noted that the location of the cap 119 ~emote
from and sùbstantially above the engine sump oil
level 7 aids materially in the se~aration of oi.l
from the escaping gases, as those gases pass along
the oil fill tube extending from the engine crankcase
to the oil filler opening~
Referring now to Figs. 7 and 10, pulling ~he
start handle 159 causes rope 161 to unwind from
the drum ~63~ inducing rotation in that drum and
helically threaded hub 167 about the axis of the
recoil starter attaching bolt 165 and inducing
a restorative force in the starter recoil spring.
Gear 47 is attached to the hub 167 of the startex
31'1~13~3
1 mechanis~ by a helical thread arrangement so that
rotation of drum 163 causes gear 47 to move toward
the left, as viewed in Fig~ 10 and into engagement
with the ~eeth 45 of the fl~wheel with continued
S ro~a~ion of hub 163 and of gear 47 providing the
starting rotation of the flywheel. Spring clip
168 fric~ionally engages hub 167 and spans stud
75 to move the hub and startoer gear between their
axial limits. When the engine starts, gear 47
is disengaged and release of the handle 159 allows
the mechanism to rewind for the next starting operation
since ~he clock type coil spring urges the gear
47 back alony the helical thread arrangement, and
as tension of rope 161 is released, that rope is
rewound about the drum 163. The further details
o the s~arter mechanism may be as in conventionally
~mployea re~Jind starters, as illustrated in U.SO
Patent 3,375,813 for example, however, as noted
earlier, substantial economies in the manufacture
20 of the engine are realized by casting the recoil
starter attachment boss 79 as well as the spring
anchoring stud 75 and recoil starter xope guide
77 as integral portion5 of the engine block~ and
eliminat~ng all support bxackets. Another suitable
recoil s~arter is illustrate~ in U.S.~Patent 4,019,490O
~ro~ the fore~oing, it is now apparent that
a nov~l interna~ combustion engine having a unique
block casting and valve train arrangement, as well
as unique muffler and breather configurat;ons,-
has b2en disclosed meeting the objects and advantageous
features set out hereinbefore as well as others
and that modifications as to the precise configurations,
~ shapes and details may be made by those having
ordinary skill in the art without departin~ from
the spirit of the in~ention or the scope thereof
as set o~t by the claims which follo~.
- 12
