Abstract: A bar adjustment assembly for a chain saw includes a shaft, a bar adjustment pin that is journalled for rotation relative to the shaft, and a pin alignment spring that biases the pin toward an engagement position. A void is provided for accommodating the pin it is rotated away from the engagement position by a guide bar that has been incorrectly attached.

Abstract: The cooperative operational relationship among an ignition switch, choke mechanism and air filter unit for a portable power tool are integrated in a way to improve that relationship. The ignition switch and choke mechanism are arranged in a coactive relationship wherein the ignition switch and a choke lever in the choke mechanism have engaging parts such that the ignition switch is moved to an “On” position by the choke lever when the choke lever is moved to a position where it has reduced the air flow to a carburetor. A spring engaging the ignition switch is biased for applying a force to the ignition switch in a direction toward a mounting element on which the ignition switch is mounted and away from the choke lever. In a particular embodiment, the ignition switch is mounted on the air filter unit.

Abstract: An SAS two-cycle engine has a cylinder block that has a bore with at least one scavenging port and at least one fresh air port therein. The bore extends to a crankcase. A piston of the engine is located within the bore and separates a combustion chamber of the bore from the crank area and is movable between a first position, in closest proximity to the crank area, and a second position. The air port and the piston are configured such that air may flow from the air port into the combustion chamber of the cylinder when the piston is at the first position. In one example, the scavenging port and the air port have edges that are selectively revealed upon movement of the piston. The air port includes an upper edge, which may be contoured such that only a portion of the upper edge is exposed when the piston is at the first position.

Abstract: The present invention includes a muffler for attachment to an engine that includes an inlet for receiving exhaust gases into the muffler, a catalyst assembly located within the muffler, and a fastener tube for fastening the muffler to the engine. A fastener tube cover covers the fastener tube and includes an outlet for exiting exhaust gases. The outlet includes a directional louver that directs the exiting exhaust gases. The fastener tube cover can retain a spark arrestor which maintains maximum spark particle size in the exiting exhaust gases.

Abstract: A device for a power tool that includes an internal combustion engine and a carburetor for supplying an air and fuel mixture to the engine. The carburetor includes at least one externally adjustable component. An air filter arrangement of the device is for in-taking air, filtering the air, and directing the filtered air to the carburetor. The arrangement includes a housing. A tamper-resisting portion of the device extends from the air filter arrangement housing and extends adjacent to the location of the at least one adjustable component. The tamper resisting portion includes a segment that permits access to the at least one adjustable component along a first direction and limits access to the at least one adjustable component off of the first direction.

Abstract: The cooperative operational relationship among an ignition switch, choke mechanism and air filter unit for a portable power tool are integrated in a way to improve that relationship. The ignition switch and choke mechanism are arranged in a coactive relationship wherein the ignition switch and a choke lever in the choke mechanism have engaging parts such that the ignition switch is moved to an “On” position by the choke lever when the choke lever is moved to a position where it has reduced the air flow to a carburetor. A spring engaging the ignition switch is biased for applying a force to the ignition switch in a direction toward a mounting element on which the ignition switch is mounted and away from the choke lever. In a particular embodiment, the ignition switch is mounted on the air filter unit.

Abstract: A piston channel is provided for a piston of an air scavenging internal combustion engine. The channel extends radially inward partially around a circumference of a piston body. An edge wall of the channel is sloped towards a wrist pin aperture in the piston to improve purging efficiency of a transfer duct.

Abstract: An SAS two-cycle engine has a cylinder block that has a bore with at least one scavenging port and at least one fresh air port therein. The bore extends to a crankcase. A piston of the engine is located within the bore and separates a combustion chamber of the bore from the crank area and is movable between a first position, in closest proximity to the crank area, and a second position. The air port and the piston are configured such that air may flow from the air port into the combustion chamber of the cylinder when the piston is at the first position. In one example, the scavenging port and the air port have edges that are selectively revealed upon movement of the piston. The air port includes an upper edge, which may be contoured such that only a portion of the upper edge is exposed when the piston is at the first position.

Abstract: An arrangement that provides a semi-automatic tension adjustment of an endless cutting chain on a guide bar of a chain saw as the links of the chain wear with use. A specially designed cam biases a tensioner pin to continuously force the guide bar away from the drive sprocket on the engine chassis to tension the chain. A knob on a clutch cover assembly attached to the engine chassis can be tightened to force two high friction surfaces together to lock the guide bar in a tensioned position, or loosed to release the guide bar to seek a proper tensioned position. An override lever on the face of the clutch cover assembly moves in a channel with peripheral nomenclature that indicates when the cutting chain should be replaced. The entire arrangement is self-contained and does not require any tools to function.

Abstract: An arrangement that provides a semi-automatic tension adjustment of an endless cutting chain on a guide bar of a chain saw as the links of the chain wear with use. A specially designed cam biases a tensioner pin to continuously force the guide bar away from the drive sprocket on the engine chassis to tension the chain. A knob on a clutch cover assembly attached to the engine chassis can be tightened to force two high friction surfaces together to lock the guide bar in a tensioned position, or loosed to release the guide bar to seek a proper tensioned position. An override lever on the face of the clutch cover assembly moves in a channel with peripheral nomenclature that indicates when the cutting chain should be replaced. The entire arrangement is self-contained and does not require any tools to function.