Abstract: A muffler for coupling to an exhaust port of an internal combustion engine includes a housing, a first hollow body within the housing, a catalyzer within the first hollow body, and a second hollow body within the housing. The first hollow body has an inner surface defining a first chamber and an inlet adjacent the exhaust port to admit the exhaust gas into the first chamber. The exhaust gas is exothermally treated as it flows through the catalyst in the first chamber in a direction away from the engine and passes through an outlet of the first hollow body to a second chamber. The second chamber is formed by an inner surface of the second hollow body and an outer surface of the first hollow body. The treated exhaust gas flows through the second chamber in a direction toward the engine over the outer surface of the first hollow body where a thermal reaction takes place and/or further emission reduction takes place by a catalytic coating on the outer surface of the first hollow body.

Abstract: A resetting ignition switch for a portable power tool whereby movement of a choke assembly from a first, normal position to a second, choking position simultaneously and automatically moves an ignition switch from a stop to a run position to permit starting of the engine. The ignition switch, which forms a portion of an ignition circuit for the power tool, includes an integral lever which extends across a body of the power tool and relatively beneath a shaft of the choke. The shaft includes a depending arm which engages and rotates the lever as the shaft is moved longitudinally from its normal position toward its choking position. Rotation of the lever causes the ignition switch to pivotally move from the stop to the run position. The ignition switch is movably without interference from the choke assembly when the choke assembly is in its normal position.

Abstract: A muffler for a two-cycle internal combustion engine used to power lawn and garden equipment includes two mating shells and two plates, sandwiching a spark arrestor screen, are disposed between the shells to form first and second expansion chambers between each plate and the adjacent shell. The first chamber includes an opening for coupling to the exhaust port of the engine. Within one plate is stamped a first depression, a baffle within that depression, and an elongated depression separate from the first depression. In the other plate is stamped a second depression that is punched with an air passage. When mated, an attenuating tube having an entrance in the second of the two expansion chambers and an exit into the atmosphere is formed. The first and second depressions cooperate to expose a large area of the spark arrestor screen to a flow of exhaust gas from the first chamber, through the baffle and into the second chamber.

Abstract: Emission gasses from an engine exhaust pipe are collected through an inlet of a dilution tunnel which is an elongated, hollow tube. The inlet is spaced from the exhaust pipe to also admit surrounding air. Ambient air and emissions are mixed in the tunnel by a screen in the tunnel. A probe in the tunnel diverts a portion of the mixture to gas analyzers. Prior to analysis the mixture may be condensed, filtered or otherwise processed. The analysis determines a CO/CO.sub.2 ratio which is used to determine the air/fuel ratio in the engine based on characteristics of the fuel. The air/fuel mixture of the engine is then adjusted to achieve desired performance.

Abstract: A flexible line trimmer for shipping and storing in a knocked down version for reduced package sizes includes a single length of tube that is received within an extended neck portion of a motor housing. During final assembly, the tube is extended and locked into position without the need for tools.

Abstract: A flexible line trimmer is powered by a two-stroke internal combustion engine. The engine is scavenged in a uniflow fashion and has a scavenging cylinder and an exhaust cylinder connected by a common combustion chamber. Each cylinder has a piston turning one of two cantilevered crankshafts that are geared through adjacent counterweights having integrally formed teeth. The crankshafts extend in opposite directions for self-balancing. One crankshaft is coupled to a flywheel fan and other coupled to a starter. A fuel and air mixture is transferred to a common crankcase for the crankshafts through an intake port located on the exhaust cylinder. The piston of the scavenge cylinder is retarded with respect to the exhaust cylinder. An exhaust window opens prior to a scavenge window. The scavenge window closes after the exhaust window. The exhaust window is shortened to improve crankcase compression. The cylinders are joined in a siamese fashion, fabricated from a single piece, and skewed toward each other.

Abstract: An air cooled internal combustion engine for a hand-held power tool has a flywheel fan that is rotated within a fan housing. The bottom of the fan housing, which is perpendicular to the axis of rotation of the fan, includes an opening for an air duct. Ramps axe formed around the leading edges of the duct opening, either on a plate (metal or plastic) attached to the housing or integrally with the bottom wall, for deflecting solid particles entrained in the air away from the outlet. A relatively particle-free stream of pressurized air stream is diverted into the duct and delivered to an air intake box containing an air filter and carburetor.

Abstract: A flexible line trimmer with a vibration dampening support handle includes a rotary power source and a rotatable trimmer head, both of which are connected by a drive shaft enclosed in a rigid housing. A flexible line trimmer has a vibration dampening rear support handle assembly and a front control handle. The rear handle assembly is resiliently coupled to the drive shaft housing and to the power source housing.

Abstract: A portable work producing apparatus, such as a chain saw, has an engine cooled by air from a blower driven by the engine. The engine's carburetor is pressurized with clean air from the blower. The blower includes a centrifugal impeller mounted within a fan housing having a set of blades for creating a vacuum to draw air into the housing. The impeller has a second set of relatively low-profile blades underneath the impeller for creating a vacuum under the impeller that draws air in through holes defined through the hub of the impeller. The air drawn through the holes is supplied to the carburetor. A circular screen extends from the axis of the impeller over the holes. Small particles entrained in the air stream entering the housing tend to be carried by the predominant portion of the stream into the housing. The screen is positioned and of a size that the trajectories of more massive particles entering the housing that are not blown into the housing bounce off the screen.

Abstract: A line head (10) for a rotary line trimmer uses a bail (16) to clasp a single length of cutting line (18). The head has a first and second side (12, 14). The first side (12) of the head (10) has a plurality of radial ridges extending radially from a central shaft engagement hub (20). The second side has several raised portions (44, 46, 48, 50) which define a first and second channel (17, 19). The bail (16) rotates between an open position to a closed position in the first channel. The second channel (19) is dimensioned to engage the cutting line. The bail (16) has a clasp means (16c) which removably engages a lip portion (42) when the bail is in the closed position. The bail (16) also has a central portion (16b) which overlays the second channel (19) when the bail is in the closed position.