CA1192137A - Economical engine construction - Google Patents

Abstract

ABSTRACT
An improved engine construction is disclosed having a valve train including valves and corresponding valve stems for controlling the intake and exhaust ports, cams for imparting reciprocating motion to the valves by way of the valve train, and a valve spring for biasing each valve toward its closed position and the valve train into tracking relation with the cam. The only element of the valve train coupling a cam to a stem is a cam follower with a depression for receiving the corresponding stem end and a cam engaging surface opposite the depression with the cam follower being held captive intermediate the stem and cam solely by the spring biasing of the stem toward the cam and the engagement of the stem end and the depression. The spring biasing is provided by a coiled wire spring having outwardly extending legs each of which engages a corresponding stem to urge the valves toward their closed position. The bight or coiled portion of the spring is held in a relatively fixed position by a portion of the engine casting. Another feature of the engine resides in the engine block casting which includes an exhaust gas passageway extending from an engine cylinder and including near the end thereof remote from the cylinder an enlarged cavity which defines at least a part of a muffler shell. Numerous other elements may be cast integral with the engine block including a boss for attaching a pull rope recoil starter assembly along with an anchoring point for one end of the rewind spring of that starter assembly and retaining guides for the rope of the starter assembly. The locator, such as a stud for the intake and exhaust poppet valve biasing spring, may also be cast integrally with the engine block. A further feature of the engine resides in a combination crankcase breather mechanism and oil fill cap which due to its remote location from the engine crankshaft as well as the tortuous air flow path through the cap to the atmosphere minimizes the egress of oil from the engine through the breather mechanism.

Description

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 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 ~ 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 ' 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 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.

Claims (14)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. An internal combustion engine block casting including an exhaust gas passageway extending from an engine cylinder and including near the end thereof remote from the cylinder an enlarged cavity defining at least part of a muffler shell.

2. The casting of claim 1 further including a boss within the cavity terminating near an open end of the cavity and having near that open end, means for supporting muffler baffle means.

3. The casting of claim 2 further including a pair of apertured metal plates for providing a circuitous exhaust path from the cavity to the atmosphere, the metal plates comprising the muffler baffle means.

4. The casting of claim 3 wherein the metal plates are substantially identical, each having a generally centrally located depression with an attachment bolt passing aperture within the depression, the plates being positioned with their respective depressions abutting and the remaining plate portions separated by about twice the depth of a depression and with a bolt passing through the respective apertures and into the boss to securely hold the plates in position near the cavity open end.

5. The casting of claim 4 wherein the plates are of a generally rectangular configuration and are provided with a plurality of small apertures, the small apertures being concentrated in one half of the rectangular configura-tion with the other half thereof being substantially aper-ture free.

6. The casting of claim 5 wherein the circuitous path is provided in part by positioning the apertured half of one plate facing the substantially aperture free half of the other plate.

7. An internal combustion engine block casting including:
at least a portion of a muffler shell;
a boss for attaching a pull-rope recoil starter assembly;
an anchoring point for a spring of the recoil starter assembly;
a lug for a retaining guide for the rope of the recoil starter assembly; and a locator for a spring to bias both intake and exhaust valves toward their closed positions, all integrally cast therewith.

8. A combination crankcase breather mechanism and oil fill cap for restricting an oil filler opening in an internal combustion engine while providing a flow path for the expulsion of gases from the engine crankcase and limiting the egress of oil from the engine through the flow path com-prising:
a screw cap portion having threads for engaging a complementary portion about the oil filler opening;
an upper baffle portion fastened to the screw cap portion having a downwardly depending generally cylindrical baffle;
a lower baffle portion fastened to the screw cap portion having inner and outer generally concentric generally cylindrical baffles interleaved with the downwardly depending baffle; and a check valve for restricting the entrance of air into the engine crankcase by way of the breather mechanism while allowing the expulsion of gases from the engine crank-case by way of the breather mechanism, expulsion gases passing upwardly and over a rim of the inner lower baffle, downwardly between the inner lower baffle and downwardly depending baffle, beneath a rim of the downwardly depending baffle, and upwardly between the downwardly depending baffle and the outer lower baffle to the atmosphere.

9. The crankcase breather mechanism and oil fill cap of claim 8 wherein the check valve comprises a disc captive with a limited amount of free movement between the upper and lower baffle portions.

10. The crankcase breather mechanism and oil fill cap of claim 9 wherein the inner cylindrical baffle includes an annular valve seat, the disc being captive within the inner cylindrical baffle and movable therein between the valve seat and a downwardly depending disc movement limiting portion of the upper baffle portion.

11. The crankcase breather mechanism and oil fill cap of claim 8 wherein the inner and outer baffles are con-nected by a generally annular bottom of the lower baffle portion, the annular bottom. in conjuction with the inner and outer baffles forming an annular oil catching tray and including an oil drain for allowing oil accumulated in the tray to drain back into the engine crankcase.

12. A combination crankcase breather mechanism and oil fill cap for restricting an oil filler opening in an internal combustion engine while providing a flow path for the expulsion of gases from the engine crankcase and limiting the egress of oil from the engine through the flow path comprising:
a cap portion for engaging a complementary por-tion of the oil filler opening;
an upper baffle portion fastened to the cap portion and having a downwardly depending baffle;
a lower baffle portion fastened to the cap portion having first and second baffles interleaved with the down-wardly depending baffle, the first and second baffles being connected by a bottom of the lower baffle portion and forming in conjunction therewith an oil catching tray having an oil drain for allowing oil accumulated in the tray to drain back into the engine crankcase; and a check valve for restricting the entrance of air into the engine crankcase by way of the breather mech-anism while allowing the expulsion of gases from the engine crankcase by way of the breather mechanism, expulsion gases passing upwardly and over a rim of the first baffle, down-wardly between the first and the downwardly depending baffles, beneath a rim of the downwardly depending baffle, and upwardly between the downwardly depending baffle and the second baffle to the atmosphere.

13. The crankcase breather mechanism and oil fill cap of claim 12 wherein the check valve comprises a disc captive with a limited amount of free movement between the upper and lower baffle portions.

14. The crankcase breather mechanism and oil fill cap of claim 12 wherein the oil filler opening is located remote from the engine crankcase and substantially above the engine sump oil level to reduce the oil content of the gases reaching the oil filler opening, the combina-tion further including an oil fill tube extending from the oil filler opening to the engine crankcase.