Abstract: A two-cycle engine, especially for a portable, manually guided implement, has a combustion chamber cylinder in which a piston reciprocates. The engine has at least one transfer channel that fluidically connects the crankcase with the combustion chamber and opens thereinto via an inlet window. The engine has an air channel that supplies essentially fuel-free gas into the cylinder via an air channel window. The piston has at least one piston window establishes a fluidic connection between the air channel window and the inlet window of the transfer channel. The piston has. The distance of the upper edge of the piston window in the direction of the longitudinal axis of the cylinder from the axis of the connecting rod eye of a connecting rod that is connected with the piston is less than the radius of a piston boss for connecting the piston with the connecting rod.

Abstract: A portable hand-guided work apparatus (1), such as a motor-driven chain saw, cutoff machine or the like, includes an internal combustion engine (2) and an air filter (10). At least one air channel (8) and an intake channel (7) are provided which fluidly connect the internal combustion engine (2) to the clean side of the air filter (10). The intake channel (7) is configured at least partially in a carburetor (9). The air channel (8) opens at an air channel opening (13, 13?, 13?) and the intake channel (7) opens at an intake opening (12) at the clean side of the air filter (10). Air channel opening (13, 13?, 13?) and intake opening (12) open spatially separate from each other at the clean side of the air filter (10).

Abstract: A two-cycle engine, especially in a portable, manually-guided implement, is provided, and has a combustion chamber that is formed in a cylinder and is delimited by a reciprocating piston, which via a connecting rod drives a crankshaft mounted in a crankcase. The engine has an inlet and an outlet, as well as at least one transfer channel that, in prescribed positions of the piston, connects the crankcase with the combustion chamber. An air channel that conveys essentially fuel-free air is, in prescribed positions of the piston, fluidically connected via a piston window with an inlet window of a transfer channel into the combustion chamber. For a good scavenging result, the flow resistance through the transfer channel in the direction of flow from the crankcase to the combustion chamber corresponds approximately to the flow resistance in the direction of flow from the combustion chamber to the crankcase.

Abstract: A two-stroke engine, (1) is disclosed which includes (I) transfer channels (15, 15?, 15?, 16, 16?, 16?) which open into the crankcase (8) and fluidly connect the crankcase (8) to the combustion chamber (3) at specific positions of the piston (4) and (ii) an intake channel (11) for supplying an air/fuel mixture into the crankcase (8) via an inlet (9) and is connected to an air filter (13). At least one air channel (12) supplies additional combustion air into at least one transfer channel (15, 15?, 15?, 16, 16?, 16?). For a good load-independent air/fuel mixture ratio, the length (a) of the intake channel (11) is up to 60% of the length (b) of the clean air path; and, length (b) is the mean channel length from the air filter (13) to the opening (19, 20) of a transfer channel (15, 16) into the crankcase (8).

Abstract: A valve drive having a rocker arm mounted on a cylinder head is provided. One end of the rocker arm is actuated by a push rod to actuate a valve stem of a poppet valve that engages the other end of the rocker arm, which is pivotably held between its ends on a support pin that extends into the cylinder head, with a spherical mounting being provided between the support pin and the rocker arm. Provided on that side of the rocker arm remote from the cylinder head is a bolt head for adjusting the bearing spacing between the rocker arm and the cylinder head for adjusting valve play. To prevent unintended adjustment of the bolt head, the latter cooperates with a rotation preventing element that has an arresting portion that engages the bolt head, and a support portion that conveys the adjustment moment away.

Abstract: A two-cycle engine is provided and has a cylinder with a combustion chamber delimited by a reciprocating piston. The engine has an inlet for fuel/air mixture, an outlet out of the combustion chamber for exhaust gas, and four transfer channels that open into the cylinder via inlet windows, and fluidically connect the crankcase with the combustion chamber as a function of the piston position. The transfer channels have a connecting portion to the crankcase, an ascending portion substantially parallel to the longitudinal axis of the cylinder, and an opening-out portion into the combustion chamber. The planes defined by that side wall of the transfer channel close to the outlet that is remote from the outlet, and by the side wall of the transfer channel remote from the outlet that is close to the outlet, intersect in a line extending on the side of the mirror plane facing the transfer channels.

Abstract: A method is provided for producing a cylinder in a two-cycle engine. The cylinder bore is first machined as a preparation for the provision of a coating. The thereby resulting window edges that surround an inlet window are then at least partially chamfered. The cylinder bore is consequently provided with the coating, which at least partially overlaps the chamfered window edge. There thereby results in the region of the window edge a location of least spacing relative to the axis of the transfer channel. The piston liner or gliding surface is finally machined to a finished dimension such that in the region of the chamfered and coated window edge or corner there is formed a coating edge having a wall spacing relative to the location of least spacing, which such wall spacing having a maximum value of 0.7 mm.

Abstract: A two-cycle engine is provided that has a cylinder in which is formed a combustion chamber delimited by a reciprocating piston that via a connecting rod drives a crankshaft rotatably mounted in a crankcase. An inlet is provided for a supply of fuel into the crankcase, and an outlet leads out of the combustion chamber. In predetermined positions of the piston the crankcase communicates with the combustion chamber via at least one transfer channel. The cover is secured to a connecting flange of the cylinder, the cover closes off the transfer channel on an outer side of a cylinder, the connecting flange is inclined relative to the longitudinal axis of the cylinder by an angle that opens in a direction toward the crankcase.

Abstract: A muffler assembly for an internal combustion engine of a portable handheld work apparatus such as a motor-driven chain saw, cutoff machine or the like includes an exhaust-gas muffler (1) which has a muffler housing (10). The muffler housing (10) is formed essentially from two half shells (24, 25) connected substantially fluid-tight to each other. The interior space of the muffler housing (10) includes at least two chambers (2, 3) which are partitioned from each other by a partition wall (4). A catalytic converter (5) is mounted in the partition wall (4). In the interior space of the muffler housing (10), an exhaust-gas inlet (6) opens which is connected to an exhaust-gas stub (9) of the cylinder (8) of the engine. The exhaust-gas muffler has an exhaust-gas outlet (7) which conducts exhaust gas from the interior space.

Abstract: A diaphragm carburetor for an internal combustion engine that operates with scavenging is provided, especially for the two-cycle engine in a manually guided implement. The carburetor has a housing in which is formed an intake channel portion in which is disposed a butterfly valve that is rotatably held via a butterfly valve shaft. The carburetor has at least one air channel that supplies additional combustion air and that is provided with an air valve that is rotatably held via an air valve shaft. The air valve is, at least in one angular range, coupled to the movement of the butterfly valve, whereby the coupling includes a butterfly valve lever that is fixedly connected with the butterfly valve shaft, and an air valve lever that is fixedly connected with the air valve shaft. Disposed on one of the levers is a driver member that at least in one angular range slides upon the other lever between an outer contact point and an inner contact point.

Abstract: A cam drive is provided for a valve control of a mixture-lubricated internal combustion engine that has a cylinder, and a cylinder head in which is disposed a poppet valve which is actuated by a pivotable rocker arm. Mounted in a cam chamber is a control cam that is driven by the crankshaft of the engine and on the cam path of which rests a drag lever that transfers the cam lift to the rocker arm. To achieve a reliable mixture lubrication, a flow guidance element is disposed in the annular chamber between the peripheral wall of the cam chamber and the maximum diameter of the path of a cam nose. The flow guidance element is provided with a flow edge that is disposed adjacent to the drag lever in the vicinity of the path diameter of the cam nose.

Abstract: A portable handheld work apparatus such as a motor-driven chain saw includes a housing (6) of a drive unit (2). The following are mounted in the housing (6): an internal combustion engine (3), a carburetor (4) for fuel metering and an air filter (5) as well as a fuel tank (8). The air filter (5) is mounted ahead of the carburetor in the flow direction of the fresh air flow. A largest possible filter action is obtained with a compact configuration in that a housing (10) of the air filter (5) lies at least partially in a space between the carburetor (4) and the fuel tank (8).

Abstract: A catalytic converter for the after-treatment of the exhaust gas from an internal combustion engine is provided. The catalytic converter has a housing having an internal space for receiving exhaust gas therethrough. Surfaces of walls of the housing facing the internal space are at least partially provided with catalytically active material in a flow path between inlet and outlet openings for exhaust gas. Hollow domes are provided on oppositely disposed walls of the housing, and extend into the internal space. The free ends of the hollow domes are provided with the outlet openings, and the free ends of those hollow domes on one of the walls extend beyond the free ends of the hollow domes of the oppositely disposed wall.

Abstract: The invention relates to a method for operating a two-stroke engine having scavenging-advance storage. The combustion chamber (3) which is configured in the cylinder (2) is supplied with an air/fuel mixture via a transfer channel (12, 15). This air/fuel mixture was drawn by induction through an inlet into the crankcase (4) during the intake phase. During the intake phase, a fuel-free fluid such as pure air is inducted via a fluid channel (17) and stored in the transfer channel. To obtain good exhaust-gas values while also having reduced fuel consumption and reliable lubrication, lambda (&lgr;) of the air/fuel mixture, which is stored in the crankcase (4), is adjusted in a range of approximately 0.2 to 0.6 in the part-load and full-load ranges of the two-stroke engine (1).

Abstract: The invention relates to an intake system (1) for the combustion air (2) of an internal combustion engine (3) in a portable handheld work apparatus (4). The intake system (19) includes a filter housing (5) having an air filter (6) for purifying the combustion air (2). The clean space (8) of the air filter (6) is fluidly connected to an outlet opening (10) of the filter housing (5). The outlet opening (10) communicates with a carburetor (7) of the engine (3). A centrifugal-force separator (13) is mounted forward of the air filter (6) for separating large amounts of dust in the inducted combustion air (2). The separator (13) is so positioned ahead of the filter housing (5) that a central core flow (14) of the separator has a lower particle density (15) and is supplied to the filter (6). A tangential flow (16) surrounds the central core flow (14) in the interior of the separator (13).

Abstract: A two-cycle engine, especially in a portable, manually-guided implement, is provided, and has a combustion chamber that is formed in a cylinder and is delimited by a reciprocating piston, which via a connecting rod drives a crankshaft mounted in a crankcase. The engine has an inlet and an outlet, as well as at least one transfer channel that, in prescribed positions of the piston, connects the crankcase with the combustion chamber. An air channel that conveys essentially fuel-free air is, in prescribed positions of the piston, fluidically connected via a piston window with an inlet window of a transfer channel into the combustion chamber. For a good scavenging result, the flow resistance through the transfer channel in the direction of flow from the crankcase to the combustion chamber corresponds approximately to the flow resistance in the direction of flow from the combustion chamber to the crankcase.

Abstract: A two-cycle engine, especially for a portable, manually guided implement, is provided and has a combustion chamber that is formed in a cylinder and that is delimited by a reciprocating piston which, via a connecting rod that is connected with the piston at a connecting rod eye, drives a crankshaft rotatably mounted in a crankcase. The engine has at least one transfer channel that fluidically connects the crankcase with the combustion chamber and that opens at one end into the combustion chamber via an inlet window. The engine has at least one air channel that supplies essentially fuel-free gas and that opens into the cylinder via an air channel window. The piston has at least one piston window that in one region of the piston position establishes a fluidic connection between the air channel window and the inlet window of the transfer channel. The piston has a piston boss for connecting the piston with the connecting rod.

Abstract: A two-cycle engine, especially for a portable, manually-guided implement such as a chain saw, cut-off machine or the like is provided. The engine has a cylinder in which is formed a combustion chamber that is delimited by a reciprocating piston. An inlet opens into the cylinder for supplying fuel/air mixture into a crankcase. The engine has an outlet for exhaust gases from the combustion chamber and at least one transfer channel, which, in prescribed positions of the piston, fluidically connects the crankcase with the combustion chamber. The engine has a clean air path that includes an air channel, a piston window and a transfer channel, whereby in prescribed positions of the piston the air channel is fluidically connected via the piston window with an inlet window of the transfer channel.

Abstract: A diaphragm carburetor for an internal combustion engine that operates with scavenging is provided, especially for the two-cycle engine in a manually guided implement. The carburetor has a housing in which is formed an intake channel portion in which is disposed a butterfly valve that is rotatably held via a butterfly valve shaft. The carburetor has at least one air channel that supplies additional combustion air and that is provided with an air valve that is rotatably held via an air valve shaft. The air valve is, at least in one angular range, coupled to the movement of the butterfly valve, whereby the coupling includes a butterfly valve lever that is fixedly connected with the butterfly valve shaft, and an air valve lever that is fixedly connected with the air valve shaft. Disposed on one of the levers is a driver member that at least in one angular range slides upon the other lever between an outer contact point and an inner contact point.

Abstract: A two-stroke engine, especially for a portable handheld work apparatus such as motor-driven chain saws, cutoff machines or the like, has a combustion chamber (3) which is configured in a cylinder (2) and is delimited by a piston (4) moving upwardly and downwardly. The two-stroke engine (1) includes transfer channels (15, 15′, 15″, 16, 16′, 16″) which open into the crankcase (8) with openings (19, 20) and fluidly connect the crankcase (8) to the combustion chamber (3) at specific positions of the piston (4). The two-stroke engine (1) includes an intake channel (11) for supplying an air/fuel mixture into the crankcase (8) via an inlet (9) and is connected to an air filter (13). At least one air channel (12) supplies additional combustion air into at least one transfer channel (15, 15′, 15″, 16, 16′, 16″).