Abstract: A stratified scavenging two-stroke engine includes a first scavenging passage that extends from a first scavenging intake that opens to the inside of the crankcase to a first scavenging port that opens to the inside of a cylinder, and a second scavenging passage that extends from a second scavenging intake that opens to the inside of the crankcase to a second scavenging port that opens to the inside of the cylinder. The first and second passages are formed so as to communicate with each other via a communicating portion. An air passage is connected to the first passage at a position closer to the first scavenging intake than the communicating portion. A first check valve inhibits a flow from the first passage to the inside of the crankcase, and a second check valve inhibits a flow from the first passage through the air passage to the outside.

Abstract: A stratified scavenging two-stroke engine includes a first scavenging passage that extends from a first scavenging intake that opens to the inside of the crankcase to a first scavenging port that opens to the inside of a cylinder, and a second scavenging passage that extends from a second scavenging intake that opens to the inside of the crankcase to a second scavenging port that opens to the inside of the cylinder. The first and second passages are formed so as to communicate with each other via a communicating portion. An air passage is connected to the first passage at a position closer to the first scavenging intake than the communicating portion. A first check valve inhibits a flow from the first passage to the inside of the crankcase, and a second check valve inhibits a flow from the first passage through the air passage to the outside.

Abstract: A chain saw (1) includes a guide bar (5) supporting a chain (7) and attached to a main body (3). Disposed within the body is an anchor bolt (9) for securing the guide bar to the main body. Disposed within a sprocket cover (8) is a hexagonal nut (11) screwed onto the anchor bolt. Furthermore, provided coaxially with the hexagonal nut is a cylindrical element (15) having a hexagonal cavity (13) that engages the hexagonal nut and is axially movable and rotatable about the same axis as the hexagonal nut. Also provided is a lever (17) disposed at the outer end of the cylindrical element. Provided within the sprocket cover are an adjustment pin (19) engaging the guide bar, a screw stock (20) onto which the adjustment pin is threaded and which extends in the axial direction of the guide bar, a first helical gear (21) disposed at one end of the screw stock, and a second helical gear (23) meshing with the first helical gear. Further provided is a rotating element (25) coaxial with the second helical gear.

Abstract: A chain saw (1) includes a guide bar (5) supporting a chain (7) and attached to a main body (3). Disposed within the body is an anchor bolt (9) for securing the guide bar to the main body. Disposed within a sprocket cover (8) is a hexagonal nut (11) screwed onto the anchor bolt. Furthermore, provided coaxially with the hexagonal nut is a cylindrical element (15) having a hexagonal cavity (13) that engages the hexagonal nut and is axially movable and rotatable about the same axis as the hexagonal nut. Also provided is a lever (17) disposed at the outer end of the cylindrical element. Provided within the sprocket cover are an adjustment pin (19) engaging the guide bar, a screw stock (20) onto which the adjustment pin is threaded and which extends in the axial direction of the guide bar, a first helical gear (21) disposed at one end of the screw stock, and a second helical gear (23) meshing with the first helical gear. Further provided is a rotating element (25) coaxial with the second helical gear.

Abstract: A chain saw brake device that can instantly halt the rotation of a cutting chain when a motor drive switch is turned off. The chain saw brake device includes a brake band wound around a brake drum, such that by operating a hand guard and pulling the forward end of the brake band, the brake band is tightened around the brake drum, thereby stopping the cutting chain. The rear end of the brake band is fixed to a bent rod, and the bent rod is urged rearwardly by a coil spring when the drive switch is turned off, causing the brake band to tighten around the brake drum. By activating a trigger lever, the movable member, engaged with the trigger lever, is moved forwards, thereby pushing forwards the bent rod, and loosening the brake band.