Patent ID: 8281758
Filing Date: 2012-10-09
Classification: F01M,F02B

Abstract:
1. A single-cylinder, four-stroke cycle, spark ignition internal combustion engine for mounting on a power tool comprising: a cylinder block having a cylinder, a cylinder head, a piston mounted for reciprocation in said cylinder, said cylinder head defining an air-fuel combustion chamber; an air-fuel mixture intake port and an exhaust gas port in said cylinder head; a valve cover on said cylinder head defining a valve chamber; an intake valve and an exhaust valve mounted in said intake and exhaust port, respectively, for reciprocation between port-open and port-closed positions; a valve-actuating valve train, said valve train including at least one rocker arm and at least one valve train push rod assembly extending therefrom within said valve chamber and engaging said rocker arm; a crankshaft rotatably mounted in a crankcase, said crankshaft includes a crank portion and at least one counterweight web; a connecting rod having articulated connections at one end thereof to said piston and at an opposite end thereof to said crank portion, thereby forming a piston-connecting rod crankshaft assembly; at least one cam shaft with a cam to actuate inlet valve and a cam to actuate exhaust cam rotatably mounted in a crank shaft chamber, said at least one cam shaft being drivably connected by cam gear on it with crank gear on said crank shaft, said at least one cam shaft driven at one-half crankshaft speed; tappets which reciprocate in said cylinder block driven by said inlet cam and exhaust cam respectively; at least one push rod assembly inserted in said cylinder block, an end of push rod being connected with rocker arm in valve chamber, the opposite end of said tappets being drivably connected to said tappet whereby said push rod assembly is actuated with a reciprocating motion of tappet upon rotation of said inlet and exhaust cam, a lubrication oil reservoir formed below the crankcase; an oil pump connected drivably to said cam shaft, with said oil pump including a first and second inlet cavity with each cavity being separated by a wall in an arrangement such that the first inlet cavity is in direct communication with the oil reservoir for inhaling oil therefrom and the second inlet cavity is in direct communication with the valve chamber formed on the cylinder head for inhaling oil from the valve chamber such that oil is splashed from both the oil reservoir and the valve chamber into the crank shaft chamber to lubricate the engine parts inside the crank shaft chamber.