Abstract: A work apparatus having an internal combustion engine includes a body case (100) that houses the engine and other components of the apparatus and a hood (102) that removably covers a top opening of body case (100). The hood (102) has an inclined pin (104) extending aslant downward toward one end of the hood (102) from a portion near the one end. The body case has an inclined bore (106) for receiving the inclined pin (104). A rear end portion of the hood (102) is locked to the body case (100) by a known lock means. The inclined pin (104) wears an elastic tube (112) on its outer circumference.

Abstract: Object It is intended to prevent intrusion of air-fuel mixture into an air cleaner by blow-back in an air-fuel mixture passage of a stratified-scavenging two-stroke engine. Solution The air cleaner (24) includes a guide member (30). A blow-back flow of air (20) flowing back to the air cleaner (24) through a first air opening (23A) due to blow-back of air is induced to a vicinity of a second air opening (23M) by the guide member (30). A blow-back flow of air-fuel mixture (21) occurring in an air-fuel mixture passage (2) prior to the blow-back phenomenon in an air passage (3) collides the air flow 20 moving toward the vicinity of the second air opening (23M), and retains the air-fuel mixture near the second air opening (23M).

Abstract: A vibration-absorbing coupler (30A) which is capable of suppressing the torsional vibration of the transmission shaft (7) and also capable of enhancing the durability thereof is disclosed. This vibration-absorbing coupler (30A) is featured in that the rotation of an output shaft (31) of an internal combustion engine (6) is enabled to transmit to a transmission shaft (7) through a torsion coil spring (40A) and torsional vibration of the transmission shaft (7) is enabled to be absorbed by the torsion coil spring (40A). The vibration-absorbing coupler (30A) further includes a regulator (50, 37A) for regulating the rotation of the torsion coil spring (40A) so as not to allow it to twist more than a predetermined angle.

Abstract: A cylinder bore (4) of a two-stroke internal combustion engine (1) has first scavenging ports (12) and second scavenging ports (13) inside. The first scavenging ports (12) are nearer to an exhaust port (11) of the engine (1) than the second scavenging ports (13). In each scavenging stroke, the second scavenging ports (13) are opened earlier than the first scavenging ports (12) and introduce fuel-free air (A) from the second scavenging ports (13) into a combustion chamber (6). The first scavenging ports (12) are opened later and introduce an air-fuel mixture (M) pre-compressed in a crank chamber (8) into the same combustion chamber (6). Thus, harmful substances contained in exhaust gas discharged from the engine (1) are reduced.

Abstract: A part positioner according to the present invention is used for fixing a part having a first pair of opposite portions extending along a mounting surface to the mounting surface by use of a clamping fixture. The part positioner includes a pressing member for pressing the part against the mounting surface with a clamping force of the clamping fixture. The pressing member includes a pressing portion (tapered projection) for pressing the first pair of opposite portions in opposite directions in a position apart from the clamping fixture, owing to a clamping operation of the clamping fixture.

Abstract: A trimming machine according to the present invention has a pair of blades each of which has a plurality of cutting edges along a longitudinal direction of the blades and which are reciprocated along the longitudinal direction relative to each other by a rotary power unit. The trimming machine further has a substantially cylindrical eccentric cam eccentrically rotated by the rotary power unit, and a connecting rod having an annular larger end part slidably fitted around the eccentric cam, a smaller end part pivotally attached to one of the blades, and a connecting rod axis passing through a central axis of the smaller end part and a central axis of the larger end part. The larger end part has a bearing portion for bearing load from the blade, and the bearing portion is located on the connecting rod axis when the connecting rod axis is aligned with the longitudinal direction, and is deformable along the connecting rod axis when the bearing portion is subjected to a load.

Abstract: An air cleaner is used in a two-stroke internal combustion engine to supply an air-fuel mixture passage and a fresh air passage in a carburetor with air cleaned by an air cleaner element. The air cleaner includes an air cleaner base having an air-fuel mixture opening communicating with the air-fuel mixture passage and a fresh air opening communicating with the fresh air passage, and an air guide member provided at the air-fuel mixture opening. The air guide member is configured to curve near the air-fuel mixture opening and extend from there along the air cleaner base, and has a cross section surrounded by a peripheral wall. The air guide member defines a mixture-use air extension passage for air to be added to prepare an air-fuel mixture air-fuel mixture, which extends from a first clean air intake to the air-fuel mixture opening.

Abstract: A cylinder bore (4) of a two-stroke internal combustion engine (1) has first scavenging ports (12) and second scavenging ports (13) inside. The first scavenging ports (12) are nearer to an exhaust port (11) of the engine (1) than the second scavenging ports (13). In each scavenging stroke, the second scavenging ports (13) are opened earlier than the first scavenging ports (12) and introduce fuel-free air (A) from the second scavenging ports (13) into a combustion chamber (6). The first scavenging ports (12) are opened later and introduce an air-fuel mixture (M) pre-compressed in a crank chamber (8) into the same combustion chamber (6). Thus, harmful substances contained in exhaust gas discharged from the engine (1) are reduced.

Abstract: To achieve improved cooling in a power unit, a first fan is coupled with an end of a crankshaft of an internal combustion engine to cool at least a cylinder of the internal combustion engine, and a second fan is coupled with another end of the crankshaft to cool at least the cylinder. The cylinder is cooled by the air supplied from the first fan and the second fan.

Abstract: In a stratified-scavenging two-stroke internal combustion engine, air-fuel mixture outlets (14b) and air outlets (15b) are provided on either side of a cylinder (3), and the air-fuel mixture outlets (14b) and the air outlets (15b) communicate with a crank chamber (6) via air-fuel mixture passageways (14) and air passageways (15). The crank chamber (6) is charged with air from an air-feeding port (12). An inlet port (10) is disposed on either side of the air-feeding port (12), and mixture (M) from each inlet port (10) is charged into the air-fuel mixture passageways (14) via air-fuel mixture introduction recesses (17) formed in the outer surface of a piston (2). The air outlets (15b) are positioned nearer to the exhaust port (11), while the air-fuel mixture outlets (14b) are positioned nearer to the inlet ports (10).

Abstract: A saw chain tensioning mechanism for adjusting the tension in a saw chain extending around a chain guide plate includes a threaded rod member disposed adjacent to a rear end of the chain guide plate and along the longitudinal direction of the chain guide plate, a movable member engaged with the chain guide plate and adapted to be moved along the threaded rod member by a rotation of the threaded rod member, and a driving gear integral with the threaded rod member. The tensioning mechanism includes a driving gear for rotatively driving the driving gear and an operating member for manually rotating the driving gear. Manipulating the operating member changes the longitudinal position of the chain guide plate and correspondingly causes a change in a tension of the saw chain.

Abstract: A backpack blower comprising a blower which has an air intake opening, a backpack frame which is used to support the blower on the back of a user, and a back pad that is coupled to the backpack frame and contacts the back of the user. The back pad is composed of a cushion material and has a back surface contacting the back of the user and an opposite surface. The air intake opening communicates with at least a portion of the opposite surface, so that the air intake noise of the blower can reach at least the portion of the opposite surface.

Abstract: There is provided a refuse-trapping cover for a portable working machine, which is capable of reducing the deterioration of the engine-cooling performance of the cooling fan that may be caused by the fibrous sawdust of a palm tree. The refuse-trapping cover includes a frame (40) having a plurality of open windows (40a-40j) and attached to the outer casing (20) of a chain saw (1) to thereby cover the air inlet slits (22), and a mesh member (50) integrally fixed to the frame (40) to thereby cover open windows (40a-40j). The frame (40) is constructed to have predetermined dimension and configuration, and the mesh member (50) is fixed to a predetermined location of the frame (40) to thereby provide a sufficient space (S) between the mesh member (50) and the outer casing (20) to avoid the mesh member (50) from being adsorbed onto the outer casing (20).

Abstract: An engine shut-down device, which protects a portable working machine from static electricity discharge damage, is provided. In the portable working machine, engine operation can be stopped by switching or forcing a short-circuit at a primary coil in the ignition unit of the engine. The engine shut-down device, includes a manually operable ON/OFF switch for switching or forcing the short-circuit, and an conductive ground-mounting plate that is interposed between a switch operating member and a main switch body. The ground-mounting plate is electrically grounded at a designated electric grounding portion of the engine. Static electricity accumulated in the working machine can discharge via a path running directly from the ground-mounting plate to ground avoiding harmful passage through the ignition unit.

Abstract: In a two-stroke internal combustion engine (1) using an internal cooling piston (2), the piston (2) has in-piston scavenging passages (19) defined therein by partition walls (18), and lower-end inlets (20) of the in-piston scavenging passages (19) are opened downward and narrowed in opening area by piston pin bosses (16). In-cylinder scavenging passages (14), which are opened and closed as the piston (2) moves, are supplied with an air-fuel mixture from the narrowed lower-end inlets (20) through the in-piston scavenging passages (19). Thereby, a fresh air-fuel mixture is increased in flow rate when flowing from the in-cylinder scavenging passages (14) to the combustion chamber (10), and the scavenging efficiency of the engine is improved.

Abstract: A two-stroke internal combustion engine (1) includes one pair or two pairs of scavenging passageways (31, 32) of reverse flow system where scavenging outlet ports (31b, 32b) are opened to the cylinder bore (10a); the internal combustion engine being characterized in that an external air inlet port (42, 44, 46) for introducing external air into a combustion actuating chamber (15) formed over a piston (20) is formed at a portion of the cylinder (10) which is located closer to an exhaust port than a scavenging outlet port (31b, 32b) from which an air-fuel mixture (M) is introduced into the combustion actuating chamber (15) in a descending stroke of piston, and/or the external air inlet port (42, 44, 46) is formed at a portion of the cylinder (10) which enables the external air to be introduced into the combustion actuating chamber (15) prior to introduction of the air-fuel mixture (M).

Abstract: A vibration-absorbing coupler (30A) which is capable of suppressing the torsional vibration of the transmission shaft (7) and also capable of enhancing the durability thereof is disclosed. This vibration-absorbing coupler (30A) is featured in that the rotation of an output shaft (31) of an internal combustion engine (6) is enabled to transmit to a transmission shaft (7) through a torsion coil spring (40A) and torsional vibration of the transmission shaft (7) is enabled to be absorbed by the torsion coil spring (40A). The vibration-absorbing coupler (30A) further includes a regulator (50, 37A) for regulating the rotation of the torsion coil spring (40A) so as not to allow it to twist more than a predetermined angle.

Abstract: An oil pump mechanism is incorporated in a chain saw having a centrifugal clutch and a saw chain adapted to be driven through the centrifugal clutch and activated in synchronization with the centrifugal clutch to supply a lubricating oil to the saw chain. The mechanism includes a crankshaft, a clutch shoe being mounted on the centrifugal clutch and being connected in driven relation to the crankshaft, a clutch drum disposed coaxially around the crankshaft, a worm fitted on the crankshaft by insertion in a freely rotatable manner and connected in driven relation to the clutch drum to be integrally rotated with the clutch drum, a driven gear engaged with the worm, and a movable pumping element for pumping the lubricating oil. The worm has an inner portion located opposed to the crankshaft and an outer portion including a tooth region. The inner portion is made of self-lubricating resin and the outer portion is made of wear-resistant metal.

Abstract: There is provided a method of cast molding a cylinder for an internal combustion engine by making use of an insert core, which makes it possible to rationally form the chamfered portions at the rim portion, on the cylinder bore side, of the scavenging ports, the suction port and the exhaust port with high precision and high freedom in dimension and configuration without fluctuation in size and configuration of the chamfered portion.

Abstract: A two-stroke internal combustion engine (1) includes one pair or two pairs of scavenging passageways (31, 32) of reverse flow system where scavenging outlet ports (31b, 32b) are opened to the cylinder bore (10a); the internal combustion engine being characterized in that an external air inlet port (42, 44, 46) for introducing external air into a combustion actuating chamber (15) formed over a piston (20) is formed at a portion of the cylinder (10) which is located closer to an exhaust port than a scavenging outlet port (31b, 32b) from which an air-fuel mixture (M) is introduced into the combustion actuating chamber (15) in a descending stroke of piston, and/or the external air inlet port (42, 44, 46) is formed at a portion of the cylinder (10) which enables the external air to be introduced into the combustion actuating chamber (15) prior to introduction of the air-fuel mixture (M).