CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority from International Patent Application No. PCT/US 10/20508, filed on January 8, 2010; the contents of which are incorporated herein in its entirety for all purposes.

FIELD

[0002] This disclosure relates to four stroke engines, and more particularly, to ventilation of a crankcase for a four-stroke engine.

BACKGROUND

[0003] Four-stroke internal combustion engines can be used in outdoor power tools, such as line-trimmers, edgers, chain saws, blowers, and the like. Typical four-stroke internal combustion engines include a crankcase, a cylinder communicating with the crank case, and a piston configured for reciprocation within the cylinder. During the combustion process, gases leak past the piston rings and create elevated pressure in the crankcase.

SUMMARY

[0004] A system and method of ventilating the crankcase is presented to alleviate and prevent pressure buildup in the crankcase. One embodiment takes the form of a four stroke engine having a mechanical breather system. The crankshaft of the four stroke engine is supported to the engine by at least one bearing. The mechanical breather system includes a rotating member coupled to the crankshaft, a breather bearing positioned adjacent to the at least one rotating member, an air receiving chamber positioned adjacent the breather bearing and opposite from the rotating member, and a passage through a wall of the air receiving chamber. The rotating member has at least one inlet channel extending between an outer perimeter of the rotating member and an inner region of the rotating member. The breather bearing can have an inner race and an outer race. The breather bearing is configured to allow air to pass between the inner race and the outer race. Additionally, a passage formed in the wall of the air receiving chamber allows for fluid communication with an interior of the air receiving chamber and an exterior of the air receiving chamber. The mechanical breather system can also include a breather housing that can provide the air receiving chamber. A rotating member support member can be provided to position the rotating member relative to the breather housing and the breather bearing.

[0005] As the four stroke engine undergoes combustion processes, the crankshaft rotates within the crank case in conjunction with the reciprocation of the pistons. As the crankshaft rotates, the mechanical breather system coupled to the crankshaft separates the oil and air within the crankcase. The centrifugal force resulting from the rotating inlet channels of the rotating member forces oil away from the center of the rotating member, but allows the air to pass through the breather bearing of the mechanical breather system. The air passes through the breather bearing into an air receiving chamber on the opposite side of the breather bearing. The air then passes from within the air receiving chamber to exterior of the crankcase. The passage of air as described above ventilates the crankcase, thereby reducing and alleviating crankcase pressure. The air from the crankcase can be run through one or more filters for example an air filter.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006] The foregoing features of the disclosure will be more readily understood by reference to the following detailed description, taken with reference to the accompanying drawings, in which:

[0007] FIG. 1 is a cross-section of a four- stroke engine having an exemplary mechanical breather assembly in accordance with an exemplary embodiment; [0008] FIG. 2 is a cross-section of a four stroke engine having an exemplary mechanical breather assembly in accordance with an alternative exemplary embodiment;

[0009] FIG. 3 is an exploded perspective view of an exemplary mechanical breather assembly in accordance with an exemplary embodiment;

[0010] FIG. 4 is a perspective view of a exemplary breather bearing;

[0011] FIG. 5 is a front elevational view of the breather bearing illustrated in FIG. 4 in accordance with an exemplary embodiment;

[0012] FIG. 6 is an exploded perspective view of a four stroke engine having an exemplary mechanical breather assembly in accordance with an exemplary embodiment excluding the crankshaft;

[0013] FIG. 7 is an exemplary mechanical breather system shown in an exploded view with a crankshaft of a full-crank engine;

[0014] FIG. 8 is a side elevational view of the mechanical breather system illustrated in

FIG. 7;

[0015] FIG. 9 is a cross-section of a four stroke engine having an exemplary mechanical breather system in a full-crank engine;

[0016] FIG. 10 is a perspective view of a four stroke engine having an exemplary mechanical breather system in an assembled configuration;

[0017] FIG. 11 is a partial view of the four stroke engine illustrated in FIG. 10;

[0018] FIG. 12 is side view of an exemplary rocker box assembly in accordance with an exemplary embodiment; [0019] FIG. 13 is a front view of a four stroke engine having the exemplary rocker box assembly illustrated in FIG. 12;

[0020] FIG. 14 is a rear view of the four stroke engine having an exemplary rocker box assembly illustrated in FIG. 13;

[0021] FIG. 15 is a cross-section of a four-stroke engine having another exemplary mechanical breather assembly;

[0022] FIG. 16 is an assembly view of the exemplary mechanical breather assembly illustrated in FIG. 15;

[0023] FIG. 17 is an assembled view of the exemplary mechanical breather assembly illustrated in FIG. 16;

[0024] FIG. 18 is a perspective view of the rotating member, rotating member shaft and bearing illustrated in FIG. 15; and

[0025] FIG. 19 is a plan view of the rotating member, rotating member shaft and bearing illustrated in FIG. 15.

DETAILED DESCRIPTION

[0026] A mechanical breather system for a four-stroke engine configured according to the present teachings will hereinafter be described more fully with reference to the accompanying drawings in which embodiments of the mechanical breather assembly are illustrated. The breather system can, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those persons skilled in the art. In the figures and description, like reference numbers refer to like elements throughout. [0027] Four-stroke engines can build crankcase pressure resulting from the reciprocation of the pistons during the engine's combustion processes. Excess crankcase pressure buildup can affect fuel combustion. As described herein, a mechanical breather system is disclosed that provides a system to ventilate crankcase pressure. While the embodiments described herein focus on the implementation of the mechanical breather system for an outdoor power tool, other tools and machines having a four-stroke engine are also considered within the scope of this disclosure. For example, such tools and machines can include pressure cleaners, powered scooters, and powered bikes.

[0028] A four-stroke engine creates power though combustion in one or more cylinders.

The four-strokes are typically referred to as an intake stroke, compression stroke, combustion stroke and exhaust stroke. During the intake stroke, the piston moves downward from a top dead center position as a mixture of air and fuel is forced into the cylinder. In the compression stroke, the air and fuel mixture is compressed in the cylinder. A spark can be used for ignition if the four-stroke engine is a gasoline powered engine or other similar fuel mixture. In other instances, the compression coupled with some heat can cause ignition. As the fuel burns, it produces a gas forcing the piston downward again. Then, during the exhaust stroke, the combusted gases are exhausted through an exhaust valve. During the compression stroke, the rings sealing the piston can allow the gasses to enter into the crankcase. Additionally, the motion of the piston within cylinder can cause the crankcase to increase in internal pressure as the crankcase is fluidly coupled to bottom of the cylinder.

[0029] In order to more fully illustrate the present disclosure, some elements of the engine and crank case are omitted in the drawings to more fully disclose the relevant portions thereof. For example, the piston and cylinder have not been illustrated. FIG. 1 illustrates a cross-section of a four-stroke engine 100 including a crankcase 105. Additionally, a crankshaft 110 is illustrated. The crankshaft 110 rotates within the crankcase 105 as the piston (not shown) reciprocates within the cylinder. The piston can be coupled to the crankshaft via a connecting rod which is in turn coupled to the crankshaft 110. In a half-crank engine the crankshaft 110 is supported at one position by at least one bearing 120. Additionally, the rotating member 140 is driven directly by the crankshaft 110 in that an extended crank pin serves as a connecting member 125 and drives the rotating member 140. The at least one bearing can be sealed or unsealed. The bearing allows the crankshaft 110 to easily rotate.

[0030] The engine illustrated in FIGS. 1 and 2 also includes a mechanical breather system 135 that comprises a rotating member 140 coupled to the crankshaft 110, a breather bearing 145 positioned adjacent to the rotating member 140, an air receiving chamber 150 positioned on the breather bearing 145 and opposite from the rotating member 140, and a passage 165 in fluid communication with an interior of the air receiving chamber 150 and an exterior of the air receiving chamber 150. As illustrated in FIG. 1, the crankshaft 110 is received in the crankcase 105 and supported by at least one bearing 120. The crankshaft 110 also includes a counterweight 130 on a first end 115 of the crankshaft 115.

[0031] A connecting member 125 couples the crankshaft 110 to a rotating member 140.

The connecting member 125 couples the mechanical breather system 135 to the crankshaft 110. For example, the rotating member 140 can be driven directly or indirectly by the crankshaft 110. When the rotating member 140 is directly driven, the rotating member 140 can be affixed to the crankshaft 110 or driven by a connecting member 125 such as a crankpin. When the rotating member 140 is indirectly driven, another mechanism couples the rotating member 140 to the crankshaft 110 so that different speeds or direction of motion may be achieved by the rotating member 140 as compared with the crankshaft 110. As illustrated, the connecting member 125 is coupled at a first end to the counterweight 130 of the crankshaft 110. In FIG. 1, the rotating member 140 is configured to receive the second end of the connecting member 125 such that when the crankshaft 110 rotates, the connecting member 125 causes the rotating member 140 to rotate. While the connecting member 125 directly connects the crankshaft to the rotating member 140, other connecting members could be implemented whereby the angular acceleration and/or speed of the rotating member 140 can vary from the speed of the crankshaft 110. The rotating member 140 can include at least one inlet channel 310 (described in detail below in regards to FIG. 3). An inlet channel 310 as used herein refers to a pathway for fluid communication between the outer perimeter 305 of the rotating member 140 and an inner region of the rotating member 140. The inlet channel 310 can be formed by one or more vanes 311 as illustrated, further embodiments will be described below. The at least one inlet channel 310 of the rotating member 140 allows for oil to be spun outward while air passes through a breather bearing 145 positioned adjacent thereto.

[0032] The breather bearing 145 is positioned adjacent to the rotating member 140. As illustrated, the crankshaft 110 and counterweight 130 are on the same side of breather bearing 145. The crankshaft 110 and the rotating member 140 are configured such that when the crankshaft 110 rotates the rotating member 140 rotates. In one embodiment, the breather bearing 145 is mounted to an internal portion of the crankcase 105. In another embodiment, illustrated in FIGS. 1 and 2, the breather bearing 145 can also be coupled to a breather housing 155, which in turn is coupled to the crankcase 105. In the illustrated embodiment, the coupling of the breather bearing 145 to the crankcase 105 or breather housing 155 can be a press-fit, welding or other suitable mounting configurations that maintains position during use of the engine 100. The breather bearing 145 is configured to allow air to pass from one side of the breather bearing 145 to the other side of the breather bearing 145. For example, with respect to the exemplary four- stroke engine 100 illustrated in FIGS. 1-2, air will pass from the left side of the breather bearing 145 to the right side of the breather bearing 145. An example of a breather bearing 145 configured according to the present disclosure will be provided in detail hereinbelow.

[0033] In the illustrated embodiments of FIGS. 1 and 2, a rotating member support member 160 positions the rotating member 140 relative to the breather housing 155 and the breather bearing 145. An air receiving chamber 150 is positioned on the breather bearing 145 on a side of the breather bearing 145 opposite from the rotating member 140. A passage 165 is provided through a wall of the air receiving chamber 150 such that the passage 165 is in fluid communication with an interior of the air receiving chamber 150 and an exterior of the air receiving chamber 150. As illustrated in FIG. 1, the coupling of the breather housing 155 and the breather bearing 145 defines the air receiving chamber 150. The top wall of the breather housing 155 that faces outwardly with respect to the rotating member 145 and the crankshaft 110 can provide the wall for the passage 165 that is in fluid communication with the interior of the air receiving chamber 150 and the exterior of the air receiving chamber 150. As seen in FIG. 1, the interior of the air receiving chamber 150 is the area between the breather bearing 145 and the inner face of the top of the breather housing 155. The exterior of the air receiving chamber 150 can be the area on the outer face of the top of the breather housing 155 that is opposite to the inner face of the breather housing 155. In an alternative embodiment, the passage can include an exhaust stem 170, as illustrated in FIG. 2. While the air receiving chamber 150 as described above is within the breather housing 155, other embodiments of the present disclosure contemplate the inclusion of the air receiving chamber 150 within a portion of the crankcase 105 with or without the presence of a breather housing 155.

[0034] While the illustrated engine 100 in FIGS. 1 and 2 is a half-crank engine supported by one bearing 120, one of ordinary skill in the art will understand that the engine 100 can be a full-crank engine, as will be described later in this disclosure.

[0035] FIG. 3 is an exploded view of the mechanical breather system 135 for a four stroke engine. The rotating member 140 has at least one inlet channel 310 extending between an outer perimeter 305 of the rotating member 140 and an inner region of the rotating member 140. As illustrated in FIG. 3, the at least one inlet channel 310 is curved between the outer perimeter 305 of the rotating member 140 and the center of the rotating member 140. However, one of ordinary skill in the art will appreciate the at least one inlet channel 310 can extend straight and radially from the center of the rotating member towards the perimeter 305 of the rotating member 140. Additionally, while FIG. 3 illustrates a rotating member 140 having ten inlet channels 310, one of ordinary skill in the art will appreciate that the rotating member 140 can have two inlet channels, three inlet channels, seven inlet channels, thirteen inlet channels, or any number of inlet channels so long as the rotating member has at least one inlet channel 310. While the illustrated embodiment shows the at least one inlet channel 310 formed from a vane 311, one skilled in the art will appreciate that the at least one inlet channel 310 can be an aperture through the rotating member 140 or can be a groove formed in the surface of the rotating member 140. Additionally, as illustrated a plurality of vanes 311 are illustrated and thus a plurality of inlet channels 310. In the illustrated embodiment, ten vanes 311 are illustrated and are shaped with single cup shape along a single radius. In other embodiments, the vanes 311 can have multiple curvatures to encourage the flow of air in the at least one air inlet channel 310. [0036] The rotating member 140 can include a socket 325 configured to receive a second end of the connecting member 125. The socket 325 can be disposed on the face of the rotating member 140 that is opposite to the side having the at least one inlet channel 310. In other embodiments, the connecting member 125 can be coupled to the rotating member 140 through other mounting mechanisms such as a screw, bolt, threaded engagement and the like. In other embodiments, the connecting member 125 can be fixedly attached to the rotating member 140. The rotating member 140 can also include a protrusion 315 that protrudes from substantially the center of the rotating member 140. The protrusion 315 can be provided to receive the breather bearing 145. While the illustrated rotating member 140 in FIG. 3 is an impeller, one of ordinary skill in the art will appreciate that the rotating member 140 can be a rotor having inlet channels, a blower, a turbine, or any other rotating member that can have at least one inlet channel 310 in fluid communication between an outer perimeter 305 of the rotating member 140 and an inner region of the rotating member 140. As illustrated, the at least one inlet channel 310 is formed from the vanes 311 which are integral part of the rotating member 140. In other embodiments, the vanes 311 can be constructed separately and affixed to the rotating member through welding or the like.

[0037] As illustrated in FIGS. 3-5, the breather bearing 145 has an inner race 400 and an outer race 410. In at least one embodiment, including the illustrated embodiment, the breather bearing 145 can comprise at least one ball bearing. In other embodiments, other types of bearings that allow for air to pass therethough are considered within the scope of this disclosure. For example, the breather bearing 145 can comprise a needle bearing or a bushing between the inner race 400 and the outer race 410. The breather bearing 145 is be configured to allow air to pass between the inner race 400 and the outer race 410. For example, the inner race 400 and the outer race 410 of the breather bearing 145 can form a space through which air can pass. In at least one embodiment, the breather bearing 145 can be the bearing that supports the crankshaft 110 in the crankcase 105.

[0038] FIG. 4 is a perspective view and FIG. 5 is a front view of the breather bearing 145 illustrating the inner race 400, the outer race 410, and the at least one ball bearing 415. The at least one ball bearing 415 is free to move within the inner race 400 and the outer race 410 of the breather bearing 145. While the illustrated embodiments show six ball bearings 415 disposed between the inner race 400 and the outer race 410, one of ordinary skill in the art will appreciate that two ball bearings, three ball bearings, four ball bearings, or more can be disposed within the inner 400 and outer races 410 so long as the breather bearing 145 includes at least one ball bearing 415. In the embodiment illustrated in FIGS. 4-5, the ball bearings 415 can move within the area between the inner 400 and outer races 410 which can facilitate air passage between the ball bearings 415 and between the inner 400 and outer races 410. The breather bearing 145 as illustrated is an unsealed bearing thereby facilitating the passage of air between the inner race 400 and the outer race 410.

[0039] In a half-crank engine, the crankshaft 110 does not extend through the crankcase

105. In at least one embodiment, as illustrated in FIG. 3, the breather bearing 145 includes an aperture 405 through the center of the breather bearing 145 that is configured to receive the protrusion 315 of the rotating member 140. The aperture 405 and protrusion 315 are configured to couple the breather bearing 145 with the rotating member 140 such that when the crankshaft 110 rotates the rotating member 140, the breather bearing 145 will also rotate. The cooperation of the aperture 405 and protrusion 315 add further stability to rotating member 140 as it rotates. Furthermore, the protrusion 315 can also include rotating member support aperture 320 which is configured to receive the rotating member support member 160. The rotating member support member 160 can position the rotating member 140 relative to the breather housing 155 and the breather bearing 145. The rotating member support member 160 can also be rotatably coupled to the breather housing 155. The breather housing 155 is configured to receive the breather bearing 145 and to rotatably couple the rotating member 140 to the crankcase 105. The breather housing 155 includes an air receiving chamber aperture 165 through a top wall of the breather housing 155. The air receiving chamber aperture 165 can be configured to receive the exhaust stem 170, as illustrated in FIG. 3. The exhaust stem 170 provides the passage in fluid communication between the interior of the air receiving chamber 150 and the exterior of the air receiving chamber 150. While the embodiment illustrated in FIG. 3 includes an exhaust stem 170 to be inserted into the air receiving chamber aperture 165, one of ordinary skill in the art will appreciate that the air receiving chamber aperture 165 can provide the passage in fluid communication with the interior of the air receiving chamber 150 and the exterior of the air receiving chamber 150 and can also provide the passage of air from within the air receiving chamber 150 to the exterior of the crankcase 105. In an alternative embodiment, the exhaust stem 170 can be a hose, such as a rubber hose.

[0040] FIG. 6 is an exploded view of an assembled mechanical breather system 135 in accordance with the present disclosure with respect to the engine crankcase 105. In FIG. 6, the assembled mechanical breather system 135 is illustrated without the associated crankshaft of the four- stroke engine 100. In an assembled configuration, the breather bearing 145 is received within an interior of the breather housing 155 such that a surface of the breather housing 155 is adjacent to the at least one inlet channel 310 of the rotating member 140. Bolts 600 can secure the breather housing 155 to the crankcase 105, which together with the connecting member (not shown) thereby secures the mechanical breather system 135 in place during operation of the four stroke engine 100. In the assembled configuration, the exhaust stem 170 protrudes from the top of the breather housing 155 to expel the air and excess pressure from inside the crankcase 105.

[0041] In an alternative embodiment, the mechanical breather system 135 can be configured as illustrated in FIGS. 7 and 8. FIG. 7 is a perspective view, and FIG. 8 is a side view of the mechanical breather system 135 in accordance with the present disclosure for the crankshaft 110 of a full-crank engine. The embodiment illustrated in FIGS. 7 and 8 is shown without the associated crankcase of the full-crank engine. The crankshaft 700 has a first portion 705 and a second portion 710 coupled together by a crankpin 715. The crankshaft 700 is supported by at least two bearings 725, 145. A connecting rod 720 is coupled to the crankpin 715 such that when a piston (not shown) associated with the connecting rod 720 reciprocates within a cylinder (not shown) of the full-crank engine, the crankshaft 700 will rotate within the crankcase. A first counterweight 730 can be coupled to the first portion 705 of the crankshaft 700 and can be positioned adjacent to the crankpin 715. A bearing 725 can also be coupled to the first portion 705 of the crankshaft 700 such that the bearing 725 is adjacent to the first counterweight 730 on the side opposite to the crankpin 715. The bearing 725 can be coupled to the crankcase such that the crankshaft 700 is supported for rotation within the crankcase. A second counterweight 735 can be coupled to the second portion 710 of the crankshaft 700 and can be positioned the crankpin 715. In FIGS. 7 and 8, the first counterweight 730 and the second counterweight 735 are positioned on opposite ends of the crankpin 715. The mechanical breather system 135 can be mounted to the second portion 705 of the crankshaft 700 adjacent to the second counterweight 735 on the side opposite to the crankpin 715. The rotating member 140 of the mechanical breather system 135 is positioned adjacent to the second counterweight 735. As illustrated in FIG. 8, the rotating member 140 is mounted on the crankshaft 700. In the illustrated embodiment, the rotating member 140 rotates in direct correspondence to rotation of the crankshaft 700. In other embodiments, the rotating member 140 can be configured to rotate at a different rate as compared to the crankshaft 700. The breather bearing 145 is positioned adjacent to the rotating member 140 on the side having the at least one inlet channel 310 as described above. In the illustrated embodiment of FIG. 7 and 8, the breather bearing 145 is one of the at least two bearings 725, 145 supporting the crankshaft 700 to the crankcase. The at least two bearings 725, 145 can be configured to allow for fluid communication between the inner and outer races of the breather bearing 145. While the illustrated embodiment shows a breather bearing 145 and a bearing 725, one of ordinary skill in the art will appreciate that a third bearing can be used to support the crankshaft 700 to the crankcase in addition to the breather bearing 145. The second portion 710 of the crankshaft 700 can include a protruding end 740 which passes through the air receiving chamber 150 of the mechanical breather system 135. In other respects the mechanical breather 135 can be configured as described above.

[0042] FIG. 9 is a side cross-sectional view of the mechanical breather system 135 illustrated in FIG. 8 as it is assembled in a full-crank engine 900. The full-crank engine 900 can include a seal 910 for sealing the crankcase 905 and the protruding end 740 of the second portion 710 of the crankshaft 700. As illustrated, the seal 910 and the crankcase 905 can provide the air receiving chamber 150 positioned on the breather bearing 145 and opposite from the at least one inlet channel 310 of the rotating member 140. For example, the seal 910 and the crankcase 905 can form the wall of the air receiving chamber 150 on which the passage is disposed. The passage is then in fluid communication with the interior and the exterior of the air receiving chamber. In the illustrated example of FIG. 9, the passage can be space between the protruding end 740 of the crankshaft 700 and the seal of the crankcase 905. [0043] FIG. 10 is a perspective view of an exemplary four-stroke engine 100 assembled with a mechanical breather system 135 in accordance with an exemplary embodiment described herein. FIG. 11 is a partial view of the four-stroke engine 100 illustrated in FIG.10. Specifically, FIG. 11 is a front view of the breather housing 155 of the crankcase, which is coupled to the mechanical breather system 135. In FIG. 11, the exhaust stem 170 extends from the interior of the air receiving chamber and passes through the top wall of the breather housing 155 towards the exterior of the air receiving chamber to expel the air and excess pressure of the crankcase 105. Additionally, the exhaust stem 170 connects to a hose which further carries the air towards an air intake portion of the engine 100.

[0044] FIG. 12 is a side perspective view of an exemplary embodiment of an engine

1200 including a rocker box 1205 configured according to the teachings of this disclosure. FIG. 13 is a front perspective view and FIG. 14 is a rear perspective view of the engine 1200 including a rocker box 1205 as illustrated in FIG. 12. A rocker box assembly 1205 can be coupled to the four stroke engine 1200 via a push rod shaft 1210 and a valve stem shaft 1215 above the engine block 1220 of the four stroke engine 1200. The rocker box assembly 1205 includes a bottom surface 1225 to which both the push rod shaft 1210 and the valve stem shaft 1215 are coupled. The bottom surface 1225 can decline towards the push rod shaft 1210. For example, the bottom surface 1225 can decline towards the push rod shaft 1210 along the longitudinal axis 1230 of the bottom surface 1225. In an alternative embodiment, the bottom surface 1225 can decline towards the push rod shaft 1210 along the lateral axis 1235 of the bottom surface 1225. In another alternative embodiment, the bottom surface 1225 can decline towards the push rod shaft 1210 along both the lateral axis 1235 and the longitudinal axis 1230 of the bottom surface 1225. In the particular embodiment illustrated in FIG. 12, the inclination of the bottom surface 1225 is tilted at a 15 -degree angle from the push rod shaft 1210 to the valve stem shaft 1215. In alternative embodiments, the bottom surface 1225 can be inclined at a 17-degree angle, a 25-degree angle, a 30-degree angle, or any other angle not less than 15- degrees.

[0045] As seen in FIGS. 12-14, the inclination of the rocker box 1205 forms a window

1240 with the adjacent engine block 1220. The shape of the window 1240 corresponds to the inclination of the bottom surface 1225 of the rocker box assembly 1205. The window 1240 permits a larger volume of cooling air to flow across any intervening valves and ports between the rocker box assembly 1205 and the engine block 1220. Such cooling air can cool the valves and ports thereby enhancing the efficiency of the engine 1200. For example, as shown in FIGS. 12-13, the window 1240 has a trapezoidal shape. Because of the trapezoidal shape, air flows through the window 1240 similar to air flow through a nozzle. Because of the inclination of the bottom surface 1225 of the rocker box assembly 1205, the air flowing beneath the rocker box assembly 1205 can be distributed to cool more surface areas of the valves and ports between the rocker box assembly 1205 and the engine block 1220. Although FIGS. 12-13 illustrate a window 1240 having a trapezoidal shape, one of ordinary skill in the art will appreciate that the window 1240 can have any other shape, such as a window having a concave top portion, a window having a convex top portion, an ovular window, or the like so long as the shape corresponds with the inclination of the bottom surface 1225 of the rocker box assembly 1220.

[0046] A method of draining excess oil within a four stroke engine will be described in relation to the rocker box assembly 1205 illustrated in FIGS. 12-14. While the following method is described with respect to the particular embodiment illustrated in FIGS. 12-14, one of ordinary skill in the art will appreciate that the method can be applied to any embodiment including any of the components described in this disclosure. During operation of the four stroke engine 1200, pressure changes within the crankcase can draw oil up through the push rod shaft 1210 in to the rocker box assembly 1205 which can cause buildup of unwanted oil in the rocker box assembly 1205. However, in the illustrated rocker box assembly 1205, the bottom surface 1225 of the rocker box declines toward the push rod shaft 1210. As oil collects within the rocker box assembly 1205, the oil can drain down the bottom surface 1225 of the rocker box assembly 1205 towards the push rod shaft 1210. The oil can then drain down the push rod shaft 1210 and back into the crankcase. The oil drainage can lubricate the connecting rod and can keep excess oil from pooling in the top of the rocker box assembly 1205.

[0047] Another exemplary embodiment of a mechanical breather assembly according to the present disclosure is presented in FIGS. 15-19. While the mechanical breather assembly 135 as illustrated in FIGS. 15-19 is implemented on both a half-crank engine, the mechanical breather assembly 135 can be implemented on a full-crank engine. As both the half-crank and full-crank engines have been illustrated above, FIG. 15 is a cross-section view of the breather assembly 135 and its coupling to the crankshaft 110. The rotating member 140 is coupled to the crankshaft 110. A connecting member 125 directly connects the crankshaft 110 to the rotating member 140. The connecting member 125 is shown as being coupled to the counterweight 130 of the crankshaft. Additionally, the rotating member 140 can be mounted on the crankshaft 110. For example, when the engine 100 is a full-crank engine, the rotating member 140 can have a through hole and a key receiving portion so as to couple the rotating member 140 to the crankshaft 110. While the illustrated embodiment uses a connecting member 125, the present disclosure contemplates that the rotating member 140 could be coupled directly or indirectly to the crankshaft 110. For example, other connecting members could be implemented whereby the angular acceleration and/or speed of the rotating member 140 can vary from the speed of the crankshaft 110.

[0048] The rotating member 140 can be configured as described above. Namely, the rotating member 140 is configured so as to sling oil outward while allowing air to pass to the inner portion 142 of the rotating member. The rotating member 140 can include at least one inlet channel 310 (as described in regards to FIG. 3 and 16). The inlet channel 310 as used herein can refer to a pathway for fluid communication between the outer perimeter 305 of the rotating member and an inner region 142 of the rotating member 140. The inlet channel 310 can be formed by one or more vanes 311 as illustrated. Further embodiments as described herein can also be implemented.

[0049] A breather housing 155 is coupled to engine 100 so that it is adjacent to the rotating member 140. The breather housing 155 has an air receiving chamber 150 formed therein. The air receiving chamber 150 is configured to receive air from the rotating member 140. As described above, as the rotating member 140 rotates it spins oil outward and allows the blow-by air to pass to an inner region 142 of the rotating member 140. The rotating member 140 is configured to allow fluid communication of air to the air receiving chamber 150. For example, as illustrated, when the rotating member 140 has at least one inlet channel 310, the inner portion of the at least one inlet channel 310, corresponding to the inner portion 142 of the rotating member 140, is in fluid communication with the air receiving chamber 150. The inner portion 142 of the rotating member 140 is configured to allow air to pass from the at least one inlet channel 310 to the air receiving chamber 150. In the illustrated embodiments, the at least one inlet channel 310 is open so as to allow the air to flow from the at least one inlet channel 310 to the air receiving chamber 150. In other embodiments, a plate or cover can be installed on the rotating member 140 to restrict to control the air flow to the air receiving chamber 150. For example, the plate can limit where along the at least one inlet channel 310 air is allowed to flow into the air receiving chamber 150.

[0050] While the description provided below is in relation to cylindrical areas and cross- sections, the rotating member 140, air receiving chamber 150 and other components can have non-cylindrical shapes. Additionally, other ratios and relative sizes of the components can be implemented as well. In the illustrated embodiment, the rotating member has a diameter (D) that is larger than the diameter (Di) of the air receiving chamber 150. The relative ratio of the diameter (D) to diameter (Di) of the air receiving chamber 150 allows for some separation of the oil from the air via the at least one channel of the rotating member. When the at least one channel 310 is open to the air receiving chamber 150, the relative sizes of the rotating member 140 and air receiving chamber 150 allow for the required separation of oil from air so that little or no oil is passed into the air receiving chamber 150. The relative ratio of the diameter (D) as compared with diameter (Di) of the air receiving chamber can also dependent upon the diameter (Ds) of the shaft 148 so that air flow into the air chamber 150 is sufficient. For example the ratio of diameter (D) of the rotating member 150 to that the diameter (Di) of the air receiving chamber 150 can be two to one, three to one, three to two, or any other ratio. The ratio can depend upon the oil used and the size of the engine 100. Furthermore, the ratio can also depend upon the speed that the engine is designed to operate under normal conditions. While the above description is provided in relation to the diameters of the components, similar ratios of radiuses can also be made.

[0051] When the engine is a half-crank like the one illustrated, the rotating member 140 can be coupled to a to a rotating member shaft 148. The rotating member shaft 148 is coupled at a first end 147 to the rotating member 140. The second end 149 of the rotating member shaft 148 is coupled to a bearing 146. The rotating member shaft 148 can be removably coupled at both the first end 147 and the second end 149. The rotating member shaft 148 provides for stabilization when the rotating member is turned by a half-crank engine. In other embodiments, the rotating member shaft can be removed if the rotating member is substantially supported in relation to the crankshaft such with a full-crank engine and the bearing 146 can provide support for the crankshaft (not shown).

[0052] The bearing 146 can be coupled to the bearing housing 155. As shown, the bearing is located on the opposite side of the air receiving chamber 150 from the rotating member 140. The bearing 146 is coupled to adjacent to an outside wall 157 of the breather housing 155. The outside wall 157 is substantially opposite and substantially parallel to the rotating member 140. The rotating member shaft 148 traverses the air receiving chamber 150.

[0053] The air from the rotating member 140 enters the air receiving member and is expelled via passage 165. The passage provides for coupling of an exhaust stem 170 that takes the air outside of the air receiving chamber.

[0054] FIG. 16 illustrates an exploded perspective view of the mechanical breather system 135. The mechanical breather assembly includes the rotating member 140, rotating shaft 148, bearing 146, breather housing 155, and an exhaust stem 170. The rotating member 140 as illustrated includes at least one inlet channel 310 extending between an outer perimeter 305 of the rotating member 140 and an inner region of the rotating member 140. As illustrated in FIG. 16, the at least one inlet channel 310 is curved between the outer perimeter 305 of the rotating member 140 and the center of the rotating member 140. However, the at least one inlet channel

310 can extend straight and radially from the center of the rotating member towards the perimeter 305 of the rotating member 140. Additionally, while FIG. 16 illustrates a rotating member 140 having ten inlet channels 310, the rotating member 140 can have two inlet channels, three inlet channels, seven inlet channels, thirteen inlet channels, or any number of inlet channels so long as the rotating member has at least one inlet channel 310. While the illustrated embodiment shows the at least one inlet channel 310 formed from a vane 311, the at least one inlet channel 310 can be an aperture through the rotating member 140 or can be a groove formed in the surface of the rotating member 140. Additionally, as illustrated a plurality of vanes 311 are illustrated and thus a plurality of inlet channels 310. In the illustrated embodiment, ten vanes

311 are illustrated and are shaped with single cup shape along a single radius. In other embodiments, the vanes 311 can have multiple curvatures to encourage the flow of air in the at least one air inlet channel 310. Additionally, the rotating member 140 can include a socket 325 configured to receive a second end 149 of the connecting member 125. The socket 325 can be disposed on the face of the rotating member 140 that is opposite to the side having the at least one inlet channel 310. In other embodiments, the connecting member 125 can be coupled to the rotating member 140 through other mounting mechanisms such as a screw, bolt, threaded engagement and the like. In other embodiments, the connecting member 125 can be fixedly attached to the rotating member 140.

[0055] The bearing illustrated in FIG. 16 is an unsealed bearing having an inner race and an outer race. The unsealed configuration allows for passage of air between the inner race and outer race. In other embodiments, a sealed bearing can be implemented. When the sealed bearing is implemented it can also include a lubricant within the sealed bearing.

[0056] The breathing housing 155 can be formed to an integral engine cover 154. When the breather housing is formed as part of the engine cover 154, the engine cover can be coupled to the engine using removable fasteners such as bolts, screws, and pins. Additionally, a seal can be included that prevents air or other fluids from escaping the engine cavity.

[0057] Additionally, the inner portion 142 of the rotating member 140 is illustrated in

FIG. 16. As illustrated, the inner portion 142 is shown in dashed lines. As discussed above, the inner portion 142 is the portion of the rotating member 140 that can be in fluid communication with the air receiving chamber 150. The channels 310 of the rotating member can be enclosed until they reach the inner portion 142 of the rotating member 140. In other embodiments, an additional member can be included that prevents the flow of air from the rotating member 140 to the air chamber 150 until it reaches the inner portion 142 of the rotating member 140. For example, the additional member can be a plate with apertures.

[0058] FIG. 17 illustrates the assembled perspective view of the mechanical breather assembly of FIG. 16. As illustrated the bearing 146 has been coupled within the breather housing 155 and the rotating member shaft 148 has been coupled to the bearing 146. The exhaust stem 170 has been coupled to the breather housing 155 to provide for passage of air from within the bearing housing to an air intake port (not illustrated). [0059] FIG. 18 illustrates an exploded view of the rotating member 140 and bearing 146.

As illustrated the shaft 148 is coupled to an inner race of the bearing 146. As mentioned above, the bearing 146 is an unsealed bearing. In other embodiments, the bearing can be a sealed bearing.

[0060] FIG. 19 illustrates a plan view of bearing 146, rotating member shaft 148 and rotating member 140. As seen, the rotating member shaft 148 extends perpendicularly away from the rotating member 140.

[0061] Exemplary embodiments have been described hereinabove regarding mechanical breather systems for four stroke engines. The mechanical breather system 135 described herein can be used in relation to any type of four stroke engine, such as a half-crank four stroke engine, a full-crank four stroke engine, a four stroke engine for an outdoor power tool such as a blower, trimmer or the like, a small four stroke engine for a motored bike or scooter, or any other four stroke engine that requires ventilation of crankcase pressure.

[0062] INDUSTRIAL APPLICABILITY: The present disclosure finds applicability in the power tool and industrial tool industries.