Lubrication of two-cycle engine gearbox

Claim 2

A two-cycle engine comprising an engine block including a cylinder a crankcase assembly including a crankcase, periodically communicable with said cylinder, and a gearcase, a crankshaft journaled in said crankcase assembly and extending through said crankcase and said gearcase, said crankshaft having a first gear means positioned in said gearbox; an output shaft journaled in said crankcase assembly and extending through said gear case, said output shaft having a second gear means positioned in said gearcase and meshing with said first gear means, a piston pivotally connected to said crankshaft and reciprocably movable axially within said cylinder between top dead center and bottom dead center positions to periodically pressurize said gearcase, an intake assembly connected to said crankcase for introducing thereinto a combustion mixture including lubricating oil, said intake assembly including an inlet port and a valve member movable relative to said inlet port for admitting the combustion mixture into said crankcase when the pressure iN said crankcase is less than the exterior pressure and for preventing back flow of fluid through said inlet port when the pressure in said crankcase is greater than the exterior pressure, a sump in the bottom portion of said crankcase for collecting lubricating oil separating from said combustion mixture and valve means periodically communicating said sump with said gearcase only during a period of positive pressure in said crankcase so that the lubricating oil flows from said sump into said gearcase.

Claim 3

An engine according to claim 1 including return flow passage means communicating with said gearcase and said intake assembly at a point upstream of said valve member for returning oil from said gearcase to said intake assembly.

Claim 4

An engine according to claim 2 wherein said return flow passage means includes an inlet positioned above the bottom of said gearcase so that a predetermined level of lubricating oil is maintained in said gearcase.

Claim 5

An engine according to claim 1 wherein said valve means is an elongated, axial groove which is formed in said crankshaft, which extends into said gearbox and which periodically communicates with said sump during rotation of said crankshaft.

Claim 6

An engine according to claim 2 wherein said return flow passage means includes an outlet located in the top portion of said intake assembly so that the returning lubricating oil flows downwardly into the incoming stream of combustion mixture.

Claim 7

An engine according to claim 2 wherein said return passage means includes an outlet located immediately upstream of said valve member so as to expose said return flow passage means to the reduced pressure occuring during travel of said piston toward the top dead center position.

Claim 8

A two-cycle engine comprising an engine block including a cylinder, a crankcase assembly including a crankcase, periodically communicable with said cylinder, and gearcase, a crankshaft journaled in said crankcase assembly and extending through said crankcase and said gearbox, said crankcase having a first gear means positioned in said gearbox, an output shaft journaled in said crankcase assembly and extending through said gearbox, said output shaft having a second gear means positioned in said gearcase and meshing with said first gear means, a piston pivotally connected to said crankshaft and reciprocably movable axially within said cylinder between top dead center and bottom dead center positions to periodically pressurize said crankcase, an intake assembly connected to said crankcase for introducing thereinto a combustion mixture including lubricating oil, said intake assembly including an inlet port and a valve member movable relative to said inlet port for admitting the combustion mixture into said crankcase when the pressure in said crankcase is less than the exterior pressure and for preventing back flow of fluid through said inlet port when the pressure in said crankcase is greater than the exterior pressure, a sump in the bottom of said crankcase for collecting lubricating oil separating from the combustion mixture, an elongated, axial groove which is formed in said crankshaft, which extends into said gearbox and which periodically communicates with said sump during rotation of said crankshaft only during a period of positive pressure in said crankcase so that the lubricating oil flows from said sump into said gearbox, and return flow passage means communicating with said gearbox and said intake assembly upstream of said valve member for returning oil from said gearbox to said intake assembly, said return flow passage means including an inlet position above the bottom of said gearcase so that a predetermined level of lubricating oil is maintained in said gearbox.

Claim 9

A two-cycle engine comprising an engine block including a cylinder, a crankcase assembly including a crankcase, periodically communicable with said cylinder, and gearcase, a crankshaft journaled in said crankcase assembly and extending through said crankcase and said gearbox, said crankcase having a first gear means positioned in said gearbox, an output shaft journaled in said crankcase assembly and extending through said gearbox, said output shaft having a second gear means positioned in said gearcase and meshing with said first gear means, a piston pivotally connected to said crankshaft and reciprocably movable axially within said cylinder between top dead center and bottom dead center positions to periodically pressurize said crankcase, an intake assembly connected to said crankcase for introducing thereinto a combustion mixture including lubricating oil, said intake assembly including an inlet port and a valve member movable relative to said inlet port for admitting the combustion mixture into said crankcase when the pressure in said crankcase is less than the exterior pressure and for preventing back flow of fluid through said inlet port when the pressure in said crankcase is greater than the exterior pressure, a sump in the bottom of said crankcase for collecting lubricating oil separating from the combustion mixture, an elongated, axial groove which is formed in said crankshaft, which extends into said gearbox and which periodically communicates with said sump during rotation of said crankshaft only during a period of positive pressure in said crankcase so that the lubricating oil flows from said sump into said gearbox, and return flow passage means communicating with said gearbox and said intake assembly upstream of said valve member for returning oil from said gearbox to said intake assembly, said return flow passage means including an inlet position above the bottom of said gearcase so that a predetermined level of lubricating oil is maintained in said gearbox.

Claim 10

An engine according to claim 7 wherein said return flow passage means includes an outlet located in the top portion of said intake assembly so that the returning lubricating oil flows downwardly into the incoming stream of combustion mixture.

Claim 11

An engine according to claim 7 wherein said return passage means includes an outlet located immediately upstream of said valve member so as to expose said return flow passage means to the reduced pressure occuring during travel of said piston toward the top dead center position.