Operator carried power tool having a four-cycle engine

A hand-held power tool to be carried by an operator while in use, comprising:

• a frame, including a handle to be carried by an operator;
• an implement cooperating with the frame and having a rotary driven input member;
• a four-stroke cycle, internal-combustion engine attached to the frame, said engine having:
• a crankshaft having an axial shaft with an output end adapted to be attached to the implement input member and an input end coupled to a parallel radially offset crankpin and a counterweight;
• a lightweight aluminum engine block having a cylindrical bore, an enclosed oil reservoir located in communication with said cylindrical bore, and a bearing located below said cylindrical bore for rotatably supporting the crankshaft;
• a piston reciprocally cooperating within the bore;
• a connecting rod including a bearing pivotally cooperating with the piston and a bearing pivotally cooperating with the crankshaft thus forming a piston-connecting rod-crankshaft assembly;
• a splasher driven by the piston-connecting rod-crankshaft assembly for intermittently engaging oil within the enclosed oil reservoir to create an oil mist to lubricate the engine block;
• a cam rotatably supported by the engine block and driven by the crankshaft at 1/2 engine speed;
• a cylinder head assembly attached to the block to define a combustion chamber in cooperation with the cylinder bore and the piston, said cylinder head assembly having overhead intake and exhaust ports, and a spark plug hole extending into the combustion chamber with an intake valve, an exhaust valve and a spark plug respectively cooperating therewith;
• a valve train operatively connecting the cam to the intake and exhaust valves;
• a valve cover attached to the cylinder head to define a valve chamber therebetween at least partially enclosing the valve train, said valve chamber being isolated from the oil reservoir and provided with an independent lubricant for the valves.

A single-cylinder, four-stroke cycle, spark-ignition, internal-combustion engine for a power tool which is carried by an operator while in use comprising:

• a cylinder block having a first housing portion defining a power cylinder and a cylinder head, a power piston mounted for reciprocation in said power cylinder, said cylinder head defining an air/fuel combustion chamber;
• an air/fuel mixture intake valve port and an exhaust gas port in said cylinder head;
• a valve chamber, intake and exhaust valves mounted in said intake and exhaust ports, 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 extending at one end thereof within said valve chamber and engaging said rocker arm;
• a second portion of said cylinder block defining a cam housing portion;
• a crankshaft rotatably mounted in said cylinder block including a crank portion and a counterweight portion;
• a connecting rod assembly having articulated connections at one end thereof to said piston and at the opposite end thereof to said crank portion;
• a cam rotatably mounted in said cam housing portion, said cam being drivably connected to said crankshaft whereby it is driven by said crankshaft at half crankshaft speed, the opposite end of said push rod operatively engaging said cam whereby said push rod is actuated with a reciprocating motion upon rotation of said cam;
• a lubrication oil reservoir, an oil mist generator element connected drivably to said crankshaft, said element agitating lubrication oil into a mist in said reservoir, said reservoir being in fluid communication with said power cylinder whereby pressure pulses are created in said mist upon reciprocating movement of said piston;
• oil mist passages extending from said reservoir to said valve chamber, said pressure pulses establishing flow of said mist through said passages;
• and
• a valve mechanism controlling the flow of said mist through said passages to and from said valve chamber whereby a continuous flow of lubricating oil is circulated through said engine.

A hand-held, portable power tool carried by an operator in use, comprising:

• a frame, including a handle positioned on said power tool permitting said power tool to be carried by an operator;
• an implement cooperating with said frame and having a rotary-driven input member;
• a four-stroke cycle, internal-combustion, spark-ignition engine attached to said frame, said engine having:
• a lightweight aluminum engine block having a cylinder bore and an oil reservoir;
• a rotary crankshaft rotatably mounted in the engine block and having an output end attached to said implement input member, an input end coupled to a radially offset crankpin and a counterweight;
• a piston mounted within said bore for reciprocation and providing an engine displacement of less than 50 cc;
• a connecting rod assembly including a first end having a bearing providing a pivotal connection with said piston, a second end of said connecting rod assembly having a bearing providing a pivotal connection with said crankpin;
• a splasher connected drivably to said crankshaft for engaging oil in said reservoir to generate an oil mist in said reservoir to lubricate the engine;
• a cam rotatably mounted in said engine block and connected drivably to said crankshaft whereby it is driven at 1/2 engine speed;
• a cylinder head assembly on said block defining a combustion chamber, said cylinder head assembly having overhead intake and exhaust ports, and a spark plug hole extending into the combustion chamber with an intake valve, an exhaust valve and a spark plug respectively cooperating therewith, said valves being disposed at substantially diametrically opposed locations in said combustion chamber thereby creating cross-flow of combustion chamber gases;
• a valve train drivably connecting said cam to said intake and exhaust valves;
• a valve cover attached to said cylinder head assembly and defining a valve chamber therebetween at least partially enclosing the valve train;
• and
• a head lubrication system including a passageway connecting said oil reservoir to said valve chamber to provide oil mist flow to said valve chamber to lubricate said valve train.

A single-cylinder, four-stroke cycle, spark-ignition, internal-combustion engine for a hand-held power tool which is adapted to be carried by an operator while in use, the engine comprising:

• a cylinder block having a first housing portion defining a power cylinder and a cylinder head, a power piston mounted for reciprocation in said power cylinder, said cylinder head defining an air/fuel combustion chamber;
• a valve chamber, intake and exhaust valves in said intake and exhaust ports, respectively, for reciprocation between port-open and port-closed positions;
• a throttle-controlled, air/fuel induction system including an air/fuel mixture intake valve port and an exhaust gas port in said cylinder head for regulating air and fuel flow to said intake valve;
• a valve-actuating valve train including at least one rocker arm and at least one valve train push rod extending at one end thereof within said valve chamber and engaging said rocker arm, a second portion of said cylinder block defining a cam housing portion;
• a crankshaft rotatably mounted in said cylinder block including a crank portion and a counterweight portion;
• a connecting rod assembly having articulated connections at one end thereof to said piston and at the opposite end thereof to said crank portion;
• a cam rotatably mounted in said cam housing portion, said cam being drivably connected to said crankshaft, the opposite end of said push rod being operatively connected to said cam whereby said push rod is actuated with a reciprocating motion upon rotation of said cam;
• a lubrication oil reservoir, an oil mist generator element connected drivably to said crankshaft, said generator element agitating lubrication oil into a mist in said reservoir, said reservoir being in fluid communication with said power cylinder whereby pressure pulses are created in said mist upon reciprocating movement of said piston;
• oil mist passages extending from said reservoir to said valve chamber, said pressure pulses establishing flow of said mist through said passages;
• and
• an oil mist valve for controlling flow of said mist through said passages to and from said valve chamber whereby a continuous flow of lubricating oil is circulated through said engine.